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    Volume 38,2022 Issue 19
    Abstract:
    Autonomous agricultural vehicle (AAV) is believed to play a significant role in smart agriculture. In future periods, AAV will still be dominated by fuel engines, and the transmission technology will be upgraded from manual shifting to power shifting or CVT (Continuously Variable Transmission) simultaneously for which to improve the power and economy. In response to the demand of AAV, this study devotes to developing an autonomous driving and operation system based on ROS (Robot Operating System) and CVT tractor. The proposed system includes safety, planning, control and CAN bus communication modules. To do that, we integrated and deployed hardware on CVT tractor, designed a CAN bus protocol and implemented data structure for communication between ROS and CAN bus. A close-range anti-collision capability of the tractor is realized based on radar, and a lateral controller based on PID algorithm is adopted. To further validation, a corn sowing experiment was carried out in Miyun District, Beijing, with a total operating area of 2.4 hectares. This research takes DF2204 CVT tractor as the test platform according to the working requirements of autonomous tractors. We also designed the hardware platform of AAV, which was divided into computing layer, sensing layer and actuation layer. Based on the idea of modularization and hierarchy, a software architecture that meets the job requirements was developed with ROS as the middleware, which includes localization, planning, control, CAN communication, and safety modules. And a CAN bus protocol to meet the needs of vehicle control was developed. According to the control characteristics and operation requirements of the CVT tractor, a lateral control module and a longitudinal velocity control module were designed. We counted 22 straight working paths with a total working time of 5 943 s (excluding supplemental seeds and fertilizers), of which the total working time of the straight working stage was 4 037 s and the time of the U-turn stage was 1 906 s, approximately 32% of the total working time. The efficiency of our system was 1.33 ha/h, in contrast, the efficiency of the human was 1.26 ha/h which means the efficiency of unmanned operation was 5.6% higher than manual operation. Experimental result shows that the communication node could meet the communication requirements of 50 Hz. The average load of the whole machine was 80.4% and the operating time was 1.7 h., The target speed was set to 3 km/h when the tractor turns around, while the harrow was stopped and the seeder was lifted. The engine load was lower when the tractor makes a U-turn, and the torque percentage fluctuates between 10%-30%. After several seconds the engine load continued to increase, and the torque output percentage remained above 80%, with a maximum value of 94%. The engine and transmission will perform a torque reserve in order to meet the instantaneous torque demand (such as increased resistance, climbing, etc.). When the engine revs is higher than the revs corresponding to the torque peak, the increased load will cause the engine to overload, thereby reducing the revs and ego velocity, so as to output more torque. The average lateral error is 2.96 cm and the navigation error was 11.69 cm. The velocity RMSE is 0.98 km/h and MAE was 0.68 km/h. The steering angle RMSE was 1.91°, and MAE was 1.47°. This research shows that the tractor based on wire control technology and CVT tractor can fit the needs of autonomous agricultural vehicles, and the control and planning modules can meet sowing operations. This research could provide a reference for the unmanned upgrading of CVT tractors, and improve the intelligent level and operation efficiency of agricultural machinery.
    2022,38(19):10-22, DOI: 10.11975/j.issn.1002-6819.2022.19.002
    Abstract:
    Conservation tillage is widely used for the wheat and maize in a dry land. However, the blockage of planters and the low quality of no-tillage sowing have posed a great challenge on to the rice-wheat rotation in the middle and lower reaches of the Yangtze River, due to the heavy soil viscosity, strong root toughness, and a large amount of straw. It is difficult for one-time tillage to meet the requirements of the seedbed. The secondary operations on the soil and stubble of the seedbed also need to improve the soil fluidity of the seedbed for the less blockage of small row spacing crops when sowing, particularly for the effective separation of seed fertilizer and the quality of sowing. In this study, a biaxial stubble stubble-breaking no-tillage device was designed for the rice stubble field using the EDEM-ADAMS platform, according to the milling, impact, crushing, and throwing. A kinematic analysis was made to obtain the trajectories of the rotary and crushing blade shafts. The discrete element model of "the stubble breaking and ditching device-straw-soil" was established by the EDEM software. The optimal parameters of the stubble breaking and ditching device were optimized by an orthogonal experiment, together with the crushing device. The length parameters of the blade were also determined by the single single-factor test. An optimal combination of working parameters was obtained by the quadratic regression orthogonal rotation test and response surface method. Among them, the rotation speed of the rotary and crushing blade shaft, and the horizontal and vertical distance of the two axes were selected as influencing factors, while the number of bond fractures and power consumption were the experimental indexes. Accordingly, a field test was carried out using the prototype. The optimal parameters of the machine were achieved as follows. 30 rotary blades were selected in the double helix arrangement of the stubble stubble-breaking device, where the rotation speed of the blade shaft was 286 r/min. 32 L-type and 8 straight blades in the double helix arrangement were used in the crushing device, where the tool axis speed was 605 r/min. The biaxial horizontal and vertical distances were 548, and 168 mm, respectively, under the maximum number of bonding fractures and the minimum power. The simulation was verified with the above optimal parameters. It was found that the number of bonding fractures was 2 985, and the operating power was 2.65 kW, with the relative errors of 4.39 %, and 2.71 %, respectively. A field experiment was then conducted on the rice stubble field in Hubei Province of China. The excellent passability of the machine was achieved, where the straw coverage was 0.93 kg/m2, the average cutting rate of rice straw was 95.09%, and the average cutting rate of rice root stubble was 95.16%. The average seedling emergence rate was 95.29 % in the field, fully meeting the agronomic requirements of rice stubble fields. Thus, this finding can provide a strong reference for the biaxial rotary tillage device suitable for the stubble difficult to crush and the high soil viscosity during no-tillage sowing.
    2022,38(19):23-32, DOI: 10.11975/j.issn.1002-6819.2022.19.003
    Abstract:
    Hydraulic mechanical continuously variable transmission (HMCVT) has the advantages of low impact, high efficiency and high power, which could suit the requirements of continuously variable transmission for high-power vehicles such as tractors and engineering vehicles. During the HMCVT phase change, the power needs to be transferred from current clutch to target clutch. In this process, the torque of the quantitative motor reverses, which reverses the pressure on the high and low sides of the hydraulic components, resulting in the reverse power of the hydraulic circuit. as a result of which the rotational speed of hydraulic component changes abruptly, causing the fluctuation of output speed as well as vibrations and noises.Aiming at these problems in the process of power shift, a torque handover mechanism of HMCVT clutch under the condition of theoretical shifting segments is proposed based on the dynamic model of HMCVT power shift. For example, HMCVT shifts from HM2 to HM3. When the double clutches of the current range and target range overlapping,torque handover process is divided into two stages for discussion: hydraulic system positive power stage and hydraulic system negative power stage. When the ideal shift timing comes, clutch C3 would be operated. hydraulic system comes to positive power stage, the increase of C3 torque reduces C2 torque and motor torque until the positive power of hydraulic circuit becomes zero when the motor torque decreases to zero. At this stage, the torque transfer characteristics of clutch depend on C3 torque. When clutch C2 is detached, the reduction of C2 torque increases C3 torque, so that the motor torque changes from zero to negative, and the hydraulic circuit power transfers negative power from zero. At this stage, the torque transfer characteristics of the clutch depend on C2 torque. So, a piecewise-continuous function is established with torque change rate and torque change acceleration as parameters to optimize the torque handover trajectory of the two stages. The clutch controller is designed based on the terminal sliding mode control method. The torque tracking control is realized by tracking the oil pressure. The correctness of the torque transfer mechanism and the effectiveness of the controller are verified by simulation and experiment. The simulation and test results show that the clutch torque transfer mechanism is consistent with the theoretical analysis in the process of load changing, and controlling the clutch torque according to the torque transfer mechanism can realize the smooth switching of the segment. The terminal sliding mode controller can realize the tracking control of clutch oil pressure, so as to realize torque control. When the input shaft is 1 000 r/min and the load is 700 N·m, the terminal sliding mode controller is used to control the clutch for segment change. The fluctuation range of output shaft speed is (-20.6-7.4 r/min), the fluctuation range of output shaft torque torque is (-117.4-107.9 N·m), the maximum impact during the segment change is -6.16 m/s3, the maximum sliding friction work of the segment change clutch is 508.45 J, and there is no power interruption during the segment change. This research can provide a reference for the control of HMCVT shifting.
    2022,38(19):33-41, DOI: 10.11975/j.issn.1002-6819.2022.19.004
    Abstract:
    An accurate identification of a continuously variable transmission (CVT) system can greatly contribute to the tractor power device and the control strategy, particularly to the energy saving and emission reduction for the power improvement. This study aims to improve the accuracy of the theoretical model, due to the variation of the characteristics for the common continuously variable speed system with the working conditions. Taking hydrostatic transmission (HST) and hydro-mechanical continuously variable transmission (HMCVT) as the research objects, the speed regulation and efficiency characteristics of the hydraulic transmission system were determined under the working conditions (including engine speed, output load torque, and displacement ratio). The full-factor test was adopted to comprehensively analyze the hydraulic transmission system characteristics. Among them, the engine speed, output load torque, and displacement ratio were set at the 3-, 11-, and 5-levels, respectively. The samples of hydraulic transmission system characteristics were obtained by the bench test (including the test sample data of speed regulation characteristics and efficiency characteristics). The test bench was mainly composed of the variable pump, constant motor, diesel engine, wet clutch, several groups of gear devices and transmission shafts, as well as the speed torque sensors and the load device. Before that, the basic performance of the test bench was tested by the variable pump displacement ratio adjustment test (Test 1) and wet clutch test (Test 2). The influence degree of working conditions was compared using the partial least squares (PLS) method. Furthermore, the parameter identification and model correction of the hydraulic transmission system characteristics were proposed to combine the original theoretical model with the improved simulated annealing (I-SA). The simulated annealing was used as the inner cycle to construct the outer cycle. The disturbance number of the simulated annealing was improved to introduce an adaptive variation function. The results show that the speed regulation characteristics were closely related to the displacement ratio, depending mainly on the load torque, according to the bench test data from the hydraulic transmission system. PLS analysis showed that the influence degrees of the engine speed and output load torque (absolute value) were 0.36 and 0.92, respectively. The revised characteristics model of hydraulic transmission system speed regulation was the optimal combination of the original theoretical model and the first-order linear model of load torque. The accuracy of the revised model was significantly improved (34.41%) than before. The efficiency characteristics were mainly related to the displacement ratio and load torque, according to the bench test data of efficiency characteristics for the hydraulic transmission system. Among them, the influence degrees (absolute value) of the engine speed, output load torque, and displacement ratio were 0.05, 0.71, and 0.26, respectively. There was the limited accuracy of the original 6-parameter theoretical model (the mean absolute percentage error about 4.76%, and R2 about 0.70) after parameter identification, indicating the different overall change from the actual measurement. By contrast, the new semi-empirical modified model can be expected to effectively modify the original theoretical model. The mean absolute percentage error of the newly-developed 5-parameter semi-empirical modified model was improved by 47.48% than before, where the R2 was 0.93 (improved by 32.86%). The characterization of the new model was highly consistent with the actual measured values. Specifically, there was a large value in the conditions of large displacement and large load, indicating a divergent decline in the conditions of medium or small displacement and load, i.e., the gradually increased decline. Therefore, the I-SA algorithm can be expected to effectively serve as the engineering practice by introducing the outer cycle and the adaptive change of disturbance number. The reasonable design and control strategy can then be achieved in the correct speed regulation and efficiency characteristics model for the better performance of the tractor CVT system.
    2022,38(19):42-50, DOI: 10.11975/j.issn.1002-6819.2022.19.005
    Abstract:
    This study aims to implement a more efficient and stable numerical simulation of the hydraulic transient in a complex pumping station system. A finite volume method (FVM) Godunov scheme was established to simulate the simple pipeline and complex pumping station system. The FVM was then introduced to discretize the mathematical models, while the Riemann solver was selected to solve the discrete flux. The MUSCL-Hancock method was utilized to reconstruct the numerical data at the interface of control volumes. The higher numerical accuracy and stability were realized in the Godunov scheme, compared with the frequently-used method of characteristics. Meanwhile, the MINMOD slope limiter was used to avoid false oscillation. The boundary processing of the dual virtual unit was then presented for the second-order accuracy of both the computational region and the boundary, particularly for the simpler computation. The simulation of the improved model was in good agreement with the exact solution and the classical examples. The sensitivity analysis was also performed on the Courant and grid number. Furthermore, a more accurate, stable, and efficient performance was achieved in the second-order Godunov scheme, compared with the method of characteristics. More importantly, there was more outstanding attenuation with the decrease of the Courant number for a simple pipeline system. The computation time of the second-order Godunov scheme was 0.017 s at the same accuracy, compared with the method of characteristics (0.227 s). Consequently, a more stable and efficient performance was achieved in the second-order Godunov scheme. In the actual pumping system with the multiple-characteristics pipe structure, the second-order Godunov scheme required only a slight reduction in the Courant numbers, indicating the simple and convenient way for high numerical accuracy. Once the method of characteristics was used to calculate the hydraulic transition of the pumping station, the Courant number in the pipeline was less than 1 at the same length or wave velocity of the pipeline. By contrast, the Courant number was 0.72-0.76 in this case, indicating a very different simulation from the actual. Therefore, it is necessary to adjust the local pipeline length or wave velocity for the condition that the Courant number was 1. The tedious operation can lead to calculation errors, due to the change in pipeline characteristics. The accuracy can be improved but with less computational efficiency, if the wave velocity remained unchanged to increase the number of computational grids. In the method of characteristics, the number of grids can properly improve the accuracy of the calculation but with the doubled computation time, when the Courant number was less than 1. In the second-order Godunov scheme, there was little effect of grid number on the accuracy of the calculation but with the longer calculation time, whether the Courant number was equal to or less than 1. Therefore, a finer grid was preferred in the method of characteristics for the same accuracy requirements, when the Courant number was less than 1 in the transient process of the simulated pump system. Therefore, the second-order Godunov scheme can accurately simulate the process lines of rotational speed, discharge, and outlet pressure parameters during the hydraulic transient of the pump system. Anyway, the second-order Godunov scheme can be expected to effectively improve the efficiency, stability, and accuracy of hydraulic transient simulation of traditional pumping station systems.
    2022,38(19):51-59, DOI: 10.11975/j.issn.1002-6819.2022.19.006
    Abstract:
    Allium chinese is one type of the small underground bulb crops, mainly distributed among the hilly and mountainous areas in southern China. The growing place is normally characterized by the complex and changeable terrain with the high soil viscosity. Therefore, some difficulties can be posed as the mechanized harvesting of Allium chinense, such as the high requirements for separating fruit and soil, the great difficulty in separating, and terrain adaptability. In this study, a fruit soil separation technology was developed for the "rod and sieve type vibration separation + roller pushing type multistage separation". A walking device with high chassis crawler was adopted to place the working parts, such as the adjustable digging device, the rod and sieve type vibration separation device, and the roller pushing types multistage separation device between the two crawlers. The size of the machine was reduced suitable for the small plot harvesting operation under complex terrain. The excellent working performance was achieved in the digging shovel in the middle of the crawler. The strong stability of excavation depth was promoted in the fruit-soil separation of the less excavation depth. The rod and sieve type vibration separation device was realized the first step of conveying and separation by vibrating and impacting the clods. There were different linear speeds at the root and end of the vibrating rod. Specifically, the large clods were used to turn over the clods, and then cause the clods to be longitudinally sheared and damaged. Excellent conditions were created for the subsequent separation of fruit and soil. The clod was crushed and fell back to the field, as the fruit holding space was changed to form the adjacent rollers during the operation of the Roller pushing type multistage separation device. The fixed soil pressure rod of soil crushing was used to squeeze the clods into the fruit holding space, in order to achieve the efficient crushing of the soil block for the better fruit and soil separation. As such, the large clods were avoided to transport on the surface of the roller group without entering the fruit holding space. Each device in the working process was analyzed using theoretical calculation and simulation. The key parameters were obtained, such as the position and depth of the adjustable digging device, the amplitude and crank speed of the rod and sieve type vibration device, as well as the size and position of the roller. The Allium chinense harvester was finally developed, including the adjustable digging, the rod and sieve type vibration, and the roller pushing type multistage separation device. The field excavation test were designed to verify the performance of each device and the complete machine. It was found that there was the stable actual digging depth of the machine, where the rate of missed digging was 0.31%, the rate of buried fruit was 3.20%, the total rate of damaged fruit was 5.87%, and the effective harvest rate was 93.23%. Therefore, the stable performance was achieved in the reasonable structure design and layout of the whole machine. The improved harvester can fully meet the demand for the mechanized harvesting of Allium chinense under the current hilly and mountainous conditions.
    2022,38(19):60-68, DOI: 10.11975/j.issn.1002-6819.2022.19.007
    Abstract:
    Net enclosure aquaculture is one of the most important ways for farming fish and economic animals. Among them, nets, piles, ropes and iron chains can be used to delineate a certain water column in the shallow seas. More than 10 net enclosure facilities have been built across the country from the Shandong to Guangdong Province in China in recent years. However, only a few studies have been focused on the hydrodynamic performance of net enclosure aquaculture and emerging marine aquaculture facilities. The net enclosure facilities are still in the early stages. It is also lacking under the extreme ocean load resistance of aquaculture engineering structures. In addition, there is no such structural design theory or standard specifications for the net enclosure design and installation, particularly on the safety assessment. In this study, a net enclosure aquaculture facility was numerically investigated using the lumped mass model. A Newton's second-law-based motion equation was then solved using Euler's method. Finally, the MATLAB platform was used to visualize the calculations. The results showed that the maximum force of ropes was found in the second horizontal rope and the third horizontal rope under the still water level. Furthermore, the maximum forces of ropes were 2 011.8, 1 986.0, 1 797.8, 1 277.2, and 1 122.6 N in the wave-current directions of 0°, 10°, 40°, 60°, and 80°, respectively, when the wave and current were 4 m, and 1.0 m/s, respectively. Similarly, the maximum forces of net twine were 458.75, 410.89, 311.41, 223.06, and 221.61 N, respectively. The force on the netting was tilted to the right (incident direction), as the incident angle was changed gradually. As such, the force on the right side of the rope was much greater than that left side. The maximum force on the right side of the horizontal rope was 27.04% higher than that on the left side at the wave-current incident direction of 10°. Moreover, the maximum forces on the right side were 42.44%, 86.01% and 92.15% higher than that on the left side in the wave-current incident direction of 40°, 60? and 80°, respectively. The maximum displacement of the net decreased greatly, as the incident angles increased and the maximum positions of the net moved to the left. The force of the net significantly increased with the waves. The load of the entire net was mainly from the top half of the net. The main force of the net twines was distributed in the six areas that were divided by the first three horizontal ropes and the two vertical ropes. The maximum force on the net twines occurs at the position on both sides above the second horizontal rope under the water surface. The force of net twines on the right side of the rope was greater than that on the left side, with the change of the incident direction. The maximum force decreased rapidly at the incident angle of 40°-80° under the combined wave-current conditions. The maximum force of joint points appeared at positions 1, 2, 3, and 4. The numerical simulation was then performed on the net of the seam-edge type net enclosure aquaculture facility in use. The force distribution and deformation were achieved in the seam-edge type net enclosure. The finding can provide the theoretical basis for the design, installation, and reinforcement of aquaculture facilities. In addition, it was necessary to focus on the inspection and reinforcement after the event of extremely bad weather.
    2022,38(19):69-77, DOI: 10.11975/j.issn.1002-6819.2022.19.008
    Abstract:
    Lateral inflow forebay is inevitably utilized to connect the diversion and inlet passage in water transport engineering, because of geographical and construction constraints. However, the flow in the lateral inlet forebay is very easy to generate undesirable flow patterns (such as the flow separation and backflow) leading to vibration and low operating efficiency. In this study, the geometric parameters were optimized for the lateral inlet forebay of the pump sump using Computational Fluid Dynamics (CFD) and Response Surface Method (RSM), in order to improve the flow pattern for the high efficiency of the pump unit. Firstly, the parametric design was realized for the lateral inflow forebay of the pump sump using the 3D modeling software NX 10.0. There were the specified parameters associated with the Workbench, such as the diffusion angle α, slope β, and turning angle γ of the lateral inlet forebay. Secondly, the typical Box-Behnke Design (BBD) was selected to determine the three factors and three levels test. 17 groups of test schemes were obtained to simulate the flow field of the lateral inlet structure under the Fluent platform. Thirdly, the optimization target was selected as the uniformity of velocity distribution at the horn tube outlet section. The second-order polynomial regression equation was utilized to establish the regression equation of velocity distribution uniformity at the horn tube outlet section and geometric parameters, namely the diffusion angle α, slope β, and turning angle γ of the lateral inlet forebay. Subsequently, the significance of the regression equation was evaluated by the analysis of variance. As such, the regression equation reflected the relationship between the response values and factors. The maximum uniformity of velocity distribution at the outlet section was selected as the response target to determine the optimal parameter combination. Finally, the internal flow characteristics of the optimal lateral inlet structure were compared with the original model, including the uniformity of velocity distribution and the velocity-weighted average drift angle. Results indicate that there was a significant influence of the diffusion angle α, slope β, and turning angle γ on the velocity distribution uniformity at the horn tube outlet section. Among them, the most significant was the turning angle γ, whereas, the less significant was the slope β. Furthermore, there was no significance of the slope β, and the turning angle γ on the coupling effect of velocity distribution uniformity at the outlet section. By contrast, the diffusion angle and turning angle posed the most significance on the coupled uniformity of velocity distribution at the outlet section, in terms of the interaction between the diffusion angle α, and slope β. Moreover, there was the greatest influence of the interaction between the diffusion angle α and the turning angle γ. But, the least influence was found in the interaction between the diffusion angle α and the slope β. An optimal uniformity of the velocity distribution was achieved at the horn tube outlet section under the lateral inlet forebay with the diffusion angle α of 10°-13°, the slope β of 8°-9°, and the turning angle γ of 74°-75°. Compared with the original model, the cross-sectional velocity distribution uniformity of the optimized lateral inlet structure under design water level increased by 23.41 percentage points at least, and the velocity-weighted average drift angle increased by 13.95°, similarly, under low water level, the cross-sectional velocity distribution uniformity of the optimized lateral inlet structure increased by 18.30 percentage points at least, and the velocity-weighted average drift angle increased by 14.79°. More importantly, there was no deflected flow and large-area reflux in the channel. These findings can provide the positive significance to promote an optimal design of the lateral inlet structure of the pump sump.
    2022,38(19):78-86, DOI: 10.11975/j.issn.1002-6819.2022.19.009
    Abstract:
    Water consumption components can greatly contribute to crop yield and water resource utilization efficiency in arid regions. The Loess Plateau is located in the semi-arid climate region, which is an important dryland grain-producing area in China. Among them, the precipitation resource is the main agricultural water source in the crop fields. Winter wheat is one of the main grain crops in the dryland farming area in the Loess Plateau. Because of the uneven distribution of precipitation in time and space, drought occurs frequently in the main growing season, resulting in the low and unstable production level of winter wheat. This study aims to analyze the characteristics of water consumption components for winter wheat, in order to investigate the effects on the Leaf Area Index (LAI), yield, and Water Use Efficiency (WUE). The observation data of winter wheat was collected from 1981 to 2020 in the Xifeng State Agrometeorological Experimental Station in Gansu Province of China. The results showed that the average water consumption was 315 mm in the winter wheat fields over the past 40 years. The soil water was first converted from the precipitation during the growing season, accounting for 69.4%, and then consumed the soil water storage in the fallow period, accounting for 30.6%. The interannual precipitation greatly dominated the water consumption of winter wheat fields. Among them, the beginning of grow-flowering was the main supply period of soil water storage in the summer fallow period. As the years went by, the LAI, dry matter mass, yield, and WUE all showed an increasing trend. There was a power function relationship between the water consumption of winter wheat fields and the maximum LAI. The LAI was closely related to the interannual precipitation in the growth periods. However, the varieties had no significant effect on the LAI, but a significant effect was found on the dry matter mass. Dry matter mass accumulation and distribution were significantly correlated with the soil moisture before sowing, precipitation and water consumption during growth periods. The contribution rate of pre-anthesis dry matter transport to panicle mass was negatively correlated with the water consumption, whereas the contribution rate of post-anthesis dry matter accumulation to panicle mass was positively correlated with the water consumption. Both of them had a high correlation with the precipitation during growth periods. At the same time, there was a quadratic function model between the water consumption and yield of winter wheat. The high yield with the increase in water consumption over the recent 10 years was significantly higher than that over the previous 30 years, particularly with the emergence of excellent varieties. The average WUE was 11.04 kg/(hm2·mm) over the past 40 years, with the highest and lowest values in the 2010s and 2000s, respectively. Dry matter mass, yield, and WUE increased significantly in recent 10 years. One reason was the emergence of a series of drought-resistant and high-yield varieties, such as Longyu. Another was the increase in precipitation in the growth periods. The findings can provide a theoretical basis for the efficient utilization of water resources in the Loess Plateau and the sustainable development of dry farming.
    2022,38(19):87-93, DOI: 10.11975/j.issn.1002-6819.2022.19.010
    Abstract:
    Graphene is a new type of carbon nanomaterial with a broad application prospect in modern agriculture in recent years. Most studies have reported that the effect of graphene on the plant growth is closely related to the amount of added graphene. An appropriate concentration can promote the growth of plants, especially the growth of plant roots, and ultimately increase the biomass of plants. However, the high amount of graphene can inhibit the growth of plants. Therefore, it is very necessary to clarify the influence of graphene on the growth and quality of various crops with the great economic value of roots, in order to explore the application potential and value. Taking the radish (a popular fleshy root vegetable crop) as the research object, this study aims to reveal the influence of graphene soaking and treatment on the growth and quality of some root-utilizing crops. A scientific basis was also provided for the graphene application in the high-efficiency and high-quality cultivation of radish. Four concentrations of graphene (0, 20, 40, and 100 mg/L) were used to treat the radish seeds and irrigate soil. An analysis was then made on the effects on the radish seed germination and field planting. In the seed germination experiment, the germination rate of radish seeds was counted to measure the bacon length, in order to characterize the effect of graphene on the radish seed germination. In the field planting experiment, the effect of graphene on the radish growth was evaluated to measure the plant height, leaf number, leaf fresh weight, and leaf length. Some photosynthetic parameters were measured to calculate the leaf Water Use Efficiency (WUE), leaf nitrogen content, fleshy root yield and weight, soluble sugar and vitamin A content, further to comprehensively evaluate the effect of graphene on the radish yield and quality. The results showed that the concentration of graphene in the range of 20-100 mg/L was greatly promoted the germination of radish seeds, where the 40 mg/L graphene presented the most significant effect. Furthermore, the growth of radish plants was significantly improved, when the concentrations of graphene were 20 and 40 mg/L in the field experiment. There was an increase in the chlorophyll content, enhanced photosynthesis, and the leaf WUE. Among them, the WUE referred to the light and function that produced by the unit transpiration water consumption of leaves. The higher WUE value indicated the stronger drought resistance of plants. Specifically, there was the higher WUE of radish leaves that treated with 20 and 40 mg/L graphene, whereas the lower with the 100 mg/L graphene, compared with the control. All graphene treatments were promoted the absorption of N by plants in the main growth and development stage of radish. A leading role of N component was found in the plant life activities, crop yield, and quality, particularly in many important organic compounds, such as the enzymes and protein, nucleic acids, vitamins, alkaloids, and plant hormones. Therefore, the graphene was applied to increase the yield of radish fleshy roots by 3.6%-13.8%. There was also an increase in the contents of soluble sugar and vitamin A. The soluble sugar was the direct product of plant photosynthesis for the normal physiological activities and functions of cells in the plant carbon metabolism. The main process was dominated by the plant growth and development, yield and quality. Vitamin A was also closely related to the plant growth and cell division. Consequently, the graphene with the appropriate concentration can be expected to promote the radish seed germination and plant growth. As such, the absorption of nutrients can also be improved in the radish plant for the high yield and quality. Anyway, the graphene has great an application potential in the high-efficiency and high-quality cultivation of radish in agricultural production.
    2022,38(19):94-101, DOI: 10.11975/j.issn.1002-6819.2022.19.011
    Abstract:
    Sand media filters are often among the common filter modes in micro-irrigation system due to its excellent fouling capacity. The sand filter intercepts impurity particles mainly through the filter layer pores. The pore structure of filter layers directly affects the effect of particle deposition and transport during filtration .The objective of this work was to to master the internal pore structure characteristics of sand filter layers composed of different granular filter media. Taking ordinary Quartz Sand(QS1), Sea Sand(SS2), ASM Modified Glass(MG3) and Glass Beads(GB4) with selected grain size1.0~1.18 mm as research objective, this study employs the advanced CT scanning technique to construct the three-dimensional(3D) structure of four filter layers. In combination with image analysis software VGStudio MAX, Image J, et al, the pore structure parameters such as porosity, pore size distribution, pore roundness value and flatness ratio of four filter layers were obtained by processing different filter layer CT slices. In order to investigate the complexity of different layer pore structure, the box-counting fractal dimensions of pore structures were calculated with fractal theory. The research results showed that the apparent porosity range of the four filter layers were 39.7%-44.6% (QS1), 38.5-42.3%(SS2), 40.7%-45.6%(MG3), 34.8%-38.7%(GB4) and the volume porosities were 42.2%, 41.2%, 44.1%, 36.6% respectively. The pore size intervals were 75-960, 80-760, 70-1 050, 85-930 μm and the difference was not significant. The calculated pore roundness value ranges were 1.59-1.78, 1.35-1.54, 1.65-2.03, 1.20-1.36, the pore flatness ranges were 2.62-2.75, 2.05-2.20, 3.04-3.21, 1.94-2.04, the fractal dimensions Db of the four filter layers were 1.621, 1.566, 1.661 and 1.446, respectively. This study quantitatively characterized the pore structure characteristics of the filter layer, and obtained the differences of meso-pore structure of different granular filter media. The apparent porosities of the top filter layers were more higher than that of the bottom layers along the depth of the filter. The pore size distribution law was that small pores (<75 μm) accounted for the majority for all the four granular media and the pore shapes were mainly narrow and long type. With the media particle angularity increase, the distribution of the apparent porosity was more dispersed and the volume porosity was higher, the proportion of macro-pores increased accordingly and the maximum value reached 17.24% for MG3. The tendency of pore shape parameters deviation from sphericity was more obvious. The fractal box-counting dimension, which represented the complexity of pore structure, increased with the media angularity accordingly, and fractal dimension was negatively correlated with apparent porosity. The quantitative analysis of filter layers pore structure can overcome the shortage of traditional model experiment and provide a foundation for the subsequent study of particle deposition and migration in the filter layers.
    2022,38(19):102-109, DOI: 10.11975/j.issn.1002-6819.2022.19.012
    Abstract:
    Environment conditions have been the most important influencing factors on the rice quality. It is a high demand to determine the positive or negative influences of the climate and weather on the rice quality, in order to effectively improve the added value and market competitiveness of rice. In this study, an evaluation model of rice climatic quality was established to provide the theoretical basis and technical support for the evaluation of the climatic influences on in Anhui Province of China. The key period and optimum temperature were clarified for the formation of rice climatic quality. Then, the rice climatic quality and comprehensive meteorological condition index were constructed using the rice quality data from the regional trials of three sites in the Hefei, Chuzhou, and Fengtai City in Anhui Province of China. Taking the mid-season indica and japonica rice as research objects, the daily meteorological observation data was collected from 2008 to 2018. The weighted summation and computer numerical simulation were carried out to preprocess the rough data. Finally, an evaluation model was established for the climatic quality of rice using regression analysis. The optimal model was then validated using the rice quality data from the sowing experiment by the stages in 2008. The results showed that the six indexes of climatic quality were achieved, including the percentage of head rice, chalkiness, transparency, alkali spreading value, gel consistency, and amylose content. The comprehensive index of meteorological conditions was obtained after the numerical simulation of three elements (average temperature, radiation, and diurnal temperature range). The key periods and optimum temperatures of climatic quality formation were 33 and 36 days after the date of full heading stage, while 24.8℃ and 23.0℃ for the mid-season indica rice and mid-season japonica rice, respectively. Four grades were divided into the "Extra excellent", "Excellent", "Good", and "General" for the climatic quality of the mid-season indica and japonica rice. Therefore, the climatic quality index larger than 3.40 was matched with the "Extra excellent" grade of indica rice. The "Excellent" grade was matched between 3.09 and 3.40, while the "Good" grade was in the range between 2.73 and 3.09. At last, the climatic quality index smaller than 2.73 was matched with the "General" grade of indica rice. Similarly, the climatic quality index for the japonica larger than 3.36 was matched with the "Extra excellent" grade. Specifically, the ranges between 3.08 and 3.36, 2.68 and 3.08, and smaller than 2.68 were matched with the "Excellent", "Good", and "General" grades, respectively. The model validation showed that the 80% accuracy of climatic quality was achieved in the mid-season indica and japonica rice. The climatic quality grade was mainly one grade lower than the actual one. The difference between the climatic and the actual quality of rice was attributed to the different evaluation indices and impact factors. Therefore, the climatic quality of rice can be expected to serve as an excellent indicator of the actual quality. In summary, the climatic quality of rice can be evaluated by meteorological factors, such as the average temperature, radiation, and diurnal temperature range during the rice growth period. The improved evaluation model can also be used to evaluate the climatic quality of mid-season indica and japonica rice.
    2022,38(19):110-121, DOI: 10.11975/j.issn.1002-6819.2022.19.013
    Abstract:
    Apples are produced in the large quantities each year, particularly for as the largest economic fruit in China. It is highly required for the rapid picking within the harvesting period. Therefore, the automatic apple picking is essential to the apple harvesting in intensive farming. An accurate and rapid identification of fruit can be fundamental for the automatic picking. However, some environmental factors surrounding the fruit can pose a great interference in the fruit identification under the natural, complex, and variable backgrounds, such as the light intensity, occlusion, and overlap of the fruit. In this study, an apple recognition was proposed using two-level segmentation and region-marked Hough transform. Experimental results show that the robust and practical performance was achieved for the apple recognition under different illumination, branch and leaf occlusion, as well as the fruit overlap. Specific steps were as follows. Firstly, the front camera (NikonD90) of the information acquisition robot was used to capture from 600-800 mm away from the fruit tree under the conditions of nature natural light and backlight, respectively. The brightness adaptive correction algorithm was then used to correct the brightness of apple images with the uneven distribution of surface brightness, in order to enhance the image details. The Cr component images of YCbCr color space were extracted as the preprocessing samples to combine with the feature of the color of the apple. Secondly, the improved Otsu algorithm was utilized to obtain the binary image of the apple target for the initial segmentation, in order to accurately extract the contour of the target fruit under different growth states (mainly including single and double fruits with the overlap and occlusion). A morphological open-close reconstruction filter was also introduced to the Otsu algorithm to remove the background noise. The traversal range of the gray level was reduced to shorten the complexity and running time of the algorithm for the high segmentation rate. Thirdly, the watershed algorithm was combined to perform the secondary segmentation of the segmented fruit region using distance transformation. The conglutinated and overlapping apples were separated to effectively extract the apple target contour. Finally, the gradient Hough circle transformation was selected to identify the number of apples. But the algorithm traveled through the whole image for the computational complexity, time time-consuming, and easy to produce the false identification. Therefore, the minimum circumscribed rectangle outside the contour was set as the effective area for the gradient Hough circle transform in the effective area, particularly for the recognition speed and accuracy. The experimental results show that: 1) The improved Otsu algorithm was achieved in the higher segmentation accuracy of fruit targets, especially with the less segmentation time. The improved algorithm was also filled the tiny holes in the apple to suppress the noise in the background branches and leaves, further to more clearly segment the target region more than before. The average segmentation time was 1.458 s, which was 0.643 and 1.060 s shorter than the Otsu and K-means algorithm before the improvement. In the adhesion of partial apple regions in the binary images, a watershed segmentation with the distance transformation was used for the quadratic segmentation to effectively separate the sticky apples for the full apple target boundary. 2) The gradient Hough circle transform was used to recognize the 200 apple images under different lighting conditions, where the recognition accuracy was 90.75% in the nature natural light and 89.79% in the backlight, which were improved by 15.03% and 16.41%, respectively, compared with the traditional. The average recognition time was 0.665 and 0.693 s, which was 0.664 and 0.643 s shorter than before. Therefore, the proposed algorithm can meet the requirements of apple-picking robots, in terms of recognition speed and accuracy. The findings can provide a strong reference for the fast recognition of spherical fruits, such as apples.
    2022,38(19):122-130, DOI: 10.11975/j.issn.1002-6819.2022.19.014
    Abstract:
    Banana has been one of the major fruits in the production and consumption in China. But, the banana harvesting is a high labor consuming activity with the low efficiency and large fruit damage. This study aims to improve the operation efficiency and quality of the banana in the picking robot. An accurate and rapid recognition was also proposed to locate the fruit axis at the bottom of banana using the YOLOv5 algorithm. Specifically, a coordinate attention (CA) mechanism was fused into the backbone network. The Concentrated-Comprehensive Convolution Block (C3) feature extraction module was fused with the CA attention mechanism module to form the C3CA module, in order to enhance the extraction of the banana feature information. The original Complete Intersection over Union (CIoU) of loss function was replaced with the Efficient Intersection over Union (EIoU). As such, the convergence of the model was speeded up to reduce the loss value. After that, the anchor point was determined for the test to improve the regression formula of prediction target box. The camera coordinate system of the point was transformed to deal with the three-dimensional coordinates. D435i depth camera was then used to locate the fruit axis at the bottom of banana. The original YOLOv5, Faster R-CNN, and improved YOLOv5 model were trained to verify the model. The accuracy of the improved model increased by 2.8 percentage points, the recall rate reached 100%, and the average accuracy value increased by 0.17 percentage points, compared with the original. There were the 52.96 percentage points higher precision, 17.91 percentage points higher recall, and 21.26 percentage points higher average precision value, compared with the Faster R-CNN model. The size of the improved model was reduced by 1.06MB, compared with the original. The field test was conducted on July 1, 2022 in Dongguan Fruit and Vegetable Research Institute, Guangdong Province, China. A test was realized for the random real-time location of the fruit axis at the bottom of banana in the field environment. The original YOLOv5, Faster R-CNN, and improved YOLOv5 model were used to recognize and localize the single and double plants in the range of 1.0-2.5m. Each model was tested for 10 times. The estimated and real values were recorded to calculate the mean error, the mean error ratio, and the mean value. The original YOLOv5, Faster R-CNN, and improved YOLOv5 model all performed better to identify the banana in the field of view within the localization range and the estimated values. Among them, the mean errors were 0.085, 0.168, and 0.063m, respectively, while the mean error ratios were 4.165%, 8.046%, and 2.992%, respectively. The mean values of error and error ratio in the improved model were reduced by 0.105m, and 5.054%, respectively, during the original training, compared with the Faster R-CNN model. By contrast, the error and error ratio of the improved YOLOv5 model were reduced by 0.022m and 1.173%, respectively, compared with the original. In addition, the measurement error greater than 0.2m in the test was a locating error. Only test 6 showed the locating errors with the low error rate in the improved YOLOv5 model. The locating errors were found in tests 3 and 4 of the original, while the Faster R-CNN model showed the localization errors in the tests of 1, 4 and 8. Together with the ideal localization, the lower error and higher dimensional accuracy, the improved YOLOv5 model was conducive to the migration application and rapid recognition of bananas in the complex environments. In this case, the vision module of banana picking robot can meet the requirements for the axial locating of the undertaking mechanism at the bottom of banana fruit in the field environment.
    2022,38(19):131-142, DOI: 10.11975/j.issn.1002-6819.2022.19.015
    Abstract:
    Apple harvesting is a highly seasonal and labor-intensive activity in modern agriculture. Fortunately, a harvesting robot is of great significance to improve the productivity and quality of apples, further alleviating the labor shortage in orchards. Among them, the detection model of the harvesting robot is also required to accurately and rapidly detect the target apples in the complex and changing orchard environment. It is a high demand for the small size to be deployed in the embedded device. This study aims to improve the speed and comprehensive performance of apple detection in a complex orchard environment. A Lightweight apple detection YOLOX-Tiny Network (Lad-YXNet) model was proposed to reduce the size of the original model. Some images of "Yanfu" and "Micui" apples were obtained during the apple harvest season in 2021. The images were uniformly clipped to the 1024×1024 pixels. As such, 1 200 images were selected to make the dataset, including the fruits with shaded branches and leaves, fruit clusters, varying degrees of illumination, blurred motion, and high density. This model was then used to optimize the topology of the single-stage detection network YOLOX-Tiny. Two lightweight visual attention modules were added to the model, including Efficient Channel Attention (ECA), and Shuffle Attention (SA). The Shuffle attention and double convolution layer (SDCLayer) was constructed to extract the background and fruit features. Swish and Leaky Rectified Linear Unit (Leaky-ReLU) was identified as the activation functions for the backbone and feature fusion network. A series of ablation experiments were carried out to evaluate the effectiveness of Mosaic enhancement in the model training. The average precision of the Lad-YXNet model decreased by 0.89 percent and 3.81 percent, respectively, after removing random image flipping and random image length width distortion. The F1-socre also decreased by 0.91 percent and 1.95 percent, respectively, where the precision decreased by 2.21 percent and 2.99 percent, respectively. There was a similar regularity of the YOLOX-Tiny model. After removing the image random combination, the average precision of the Lad-YXNet and the YOLOX-Tiny model decreased by 0.56 percent and 0.07 percent, the F1-socre decreased by 0.68 percent and 1.15 percent, as well as the recall rate decreased by 2.35 percent and 4.49 percent, respectively. The results showed that the random distortion of image length and width greatly contributed to the performance of model detection. But the random color gamut transformation of the image decreased the performance of model detection, due to the change of apple color in the training set. Two specific tests were conducted to explore the effectiveness of visual attention mechanisms in convolution networks. Specifically, one was to remove the visual attention modules from the Lad-YXNet, and another was to exchange the position of visual attention modules from the Lad-YXNet. Compared with the Lad-YXNet, the precision of the improved model to exchange the position of the visual attention modules only increased by 0.04 percent, while the recall, F1-socre, and average precision decreased by 0.78 percent, 0.39 percent, and 0.13 percent, respectively. The precision, recall, F1-socre, and average precision of the models without the attention module were reduced by 1.15 percent, 0.64 percent, 0.89 percent, and 0.46 percent, respectively, compared with the Lad-YXNet. Consequently, the SA and ECA enhanced the ability of the Lad-YXNet to extract the apple features, in order to improve the comprehensive detection accuracy of the model. The main feature maps of Lad-YXNet's backbone, feature fusion, and detection network were extracted by the feature visualization technology. A systematic investigation was made to determine the process of detecting apples with the Lad-YXNet in the complex natural environment, particularly from the point of feature extraction. As such, improved interpretability was achieved in the apple detection with the Lad-YXNet model. The Lad-YXNet was trained to be an average accuracy of 94.88% in the test set, which was 3.10 percent, 2.02 percent, 2.00 percent, and 0.51 percent higher than SSD, YOLOV4-Tiny, YOLOV5-Lite, and YOLOX-Tiny models, respectively. The detection time of an image was achieved in 10.06 ms with a model size of 16.6 MB, which was 20.03% and 18.23% less than YOLOX-Tiny, respectively. Therefore, the Lad-YXNet was well balanced with the size, precision, and speed of the apple detection model. The finding can provide a theoretical basis to accurately and quickly detect the apples for the harvesting robot in the complex orchard environment.
    2022,38(19):143-152, DOI: 10.11975/j.issn.1002-6819.2022.19.016
    Abstract:
    Deep learning has gradually been one of the most important technologies in the field of agriculture in recent years. However, the problems of labeling quality and cost of training samples for supervised deep learning have become the bottleneck of restricting the development of technology. In order to reduce the cost of deep model training and ensure that the model can have high image segmentation accuracy, in this study, a model named Bounding-box Mask Deep Convolutional Neural Network (BM-DCNN) was proposed to realize automatic training and segmentation for maize plant. First of all, using DJI's Genie 4-RTK drone to collect top images of maize seedlings. The flight uses an automatic take-off planned route, and the entire route covers the entire test field. Second of all, using the open source labeling tool called Labelme to label top images of maize seedlings. The top images of the original maize seedling plants need to be labeled twice. In this study, we used bounding boxes as the basic shapes for weakly supervised labels, and pixels within the bounding boxes area were marked as foreground(i.e. the possible effective pixels of a maize plant). Pixels outside the bounding boxes were marked as background. Finally, the information of bounding boxes was used to generate primary pseudo-labels on the images, and the RGB color model of the images was converted to the HSV(Hue-Saturation-Value) color model, and the full connection condition random field(DenceCRF) was used to eliminate the influence of plant shadow and the image noise on the pseudo-labels accuracy in the images. The pseudo-labels were trained on the optimized YoLact model instead of the ground truth labels. The optimized model can be used for the instance segmentation of the plants at the maize seedling stage. We designed an experiment for verification and testing of BM-DCNN. By comparing the similarity between pseudo-labels mask and ground truth, it found that the mean intersection over union (mIoU) was 81.83% and mean cosine similarity (mcos(ɑ)) was 86.14%, which was higher than the accuracy of pseudo-labels generated by Grabcut(the mIoU was 40.49% and mean cosine similarity was 61.84%). For the maize seedling image (top view), the time cost of three manual annotation methods was calculated, with bounding box labels of 2.5 min/sheet, scirbbles labels of 15.8 min/sheet, and pixel-level labels of 32.4 min/sheet. Considering that the ground truth labels had an error in the handing of maize plant details, the pseudo-labels at the accuracy can be used for deep convolutional neural network training. By comparing the accuracy of instance segmentation between BM-DCNN and fully supervised instance segmentation model, when the IoU value of the BM-DCNN was greater than 0.7(AP70), the instance segmentation accuracy corresponding to the BM-DCNN model was higher than that of the supervised model. The average accuracy of the two backbone networks of the BM-DCNN model were 67.57% and 75.37%, respectively, which were close to the supervised instance segmentation results under the same conditions (67.95% and 78.52%, respectively), and the higher average accuracy can reach 99.44% of the supervised segmentation results. Therefore, For the instance segmentation task of the maize seedling plants images(top view), the instance segmentation effect of BM-DCNN can almost achieve the segmentation effect of the supervised instance segmentation model under the same conditions. It can be seen that in the large-area operation scenario of the UAV, it was feasible to use the bounding box labels of the images to replace the ground truth labels to complete the training of deep learning model, which greatly reduced the time cost of manual labeling of the samples, and provided theoretical support for the rapid realization of the application scenarios, such as the number of plants at the seedling stage of maize and the calculation of canopy coverage.
    2022,38(19):153-161, DOI: 10.11975/j.issn.1002-6819.2022.19.017
    Abstract:
    Farmland waste has been one of the most important influencing factors on the soil environment. It is very necessary to realize an intelligent and efficient picking of farmland wastes, particularly for the high accuracy and efficiency of recognition with the simple models under complex field environments. In this study, a lightweight detection was proposed for the farmland waste under the actual field situation of the equipment using the improved yolov5s, according to the target detection and edge computing. More importantly, Artificial Intelligence (AI) was promoted in the field of smart agriculture. Firstly, some images of common wastes were collected under the complex actual field environment in the farmland. The data enhancement was then performed on the image data for the large-scale farmland wastes datasets without the over-fitting during model training. Secondly, the network unit of the classification network ShuffleNetv2 was selected to reconstruct the feature extraction network of yolov5s. The calculation and parameter amount of the model were significantly reduced to improve the running speed for the cost saving in the chip cache space. Thirdly, the convolution kernel expansion and activation function optimization were performed on the introduced lightweight network unit module, in order to effectively restore the detection accuracy of the model with less amount of model computation and parameters. Finally, the efficient intersection over union (EIoU) bounding box was introduced to reduce the target positioning error of the model in the complex environment. The reason was that there were many interference factors in the process of motion detection under the complex field environment, thus easily leading to the positioning accuracy of the target in the image. In the case of the aspect ratio for the predicted and the real frame in the loss function of complete intersection over union (CIoU), the loss item was divided into the difference between the height/width of the predicted frame and the minimum bounding frame. At the same time, the difference was gradually reduced to speed up the convergence speed and regression accuracy using the proper iteration. The experimental results show that the detection accuracy of the improved model reached 90.9% with a detection speed of 74ms/frame. Higher detection accuracy and speed of the improved model were achieved to better balance the calculation and parameter amount, compared with the current target detection of SSD and yolov3. A tradeoff was made on the performance requirements of edge computing devices for accuracy and speed. The mobile terminal was selected to verify the application of the improved model. The models before and after the improvement were deployed on the two edge computing devices (JetsonTX1 and Raspberry4B). Compared with the original, the detection speed of the improved model increased by at least 20% on the edge computing devices, indicating an excellent detection performance. The finding can provide a lightweight solution to the detection tasks of field wastes.
    2022,38(19):162-171, DOI: 10.11975/j.issn.1002-6819.2022.19.018
    Abstract:
    Navigation path recognition has been widely regarded as one of the most important sub-tasks of intelligent agricultural equipment. An intelligent tracked vehicle can also be expected to realize the automatic navigation on the road between the tea garden ridges. However, there are still some challenges on the navigation path recognition between tea ridges using deep learning models, such as the low accuracy, real-time performance, and model interpretability. In this research, a new Unet-ResNet34 model was proposed to accurately and rapidly recognize the navigation path between the tea ridges using semantic segmentation. The midpoints of the navigation path were then generated using the navigation path extracted from the model. Finally, the multi-segment cubic B-spline curve equation was used to fit the midpoints, in order to generate the navigation line between the tea garden ridges. The Image Labeler toolbox in the Matlab 2019 platform was selected to label the navigation path in the collected images for the navigation path dataset. A navigation path dataset was then obtained consisting of 1824 images. Among them, 1568 and 256 images in the dataset were randomly selected for the training and the validation set, respectively. Under different illumination and weed conditions, the Mean Intersection over Union (MIoU) was utilized as the accuracy indicator of the Unet-ResNet34 model, which was 91.89% for the tea road segmentation. The navigation path segmentation mask was also used to generate the navigation information and keypoints for the path fitting. Furthermore, the multi-segment cubic B-spline curve equation was selected to calculate the navigation line of the tea road between ridges using the midpoints as the control points. Additionally, the navigation line was selected to further calculate the pixel and distance error. The mean difference between the predicted pixel and distance error of tea navigation paths were 8.2 pixels and 0.022 m, respectively. As such, the width of the tea navigation path was achieved about 1 m, where the ratio was 2.2 % between the average distance error and the width of the tea navigation path. In terms of real-time performance and the number of parameters, the inference speed of the Unet-ResNet34 model was 1.24 times higher than that of the Unet. The number of parameters of the Unet-ResNet34 model was 83.27% of that of original Unet model. The inference speed was 36.8 frames per second to process the RGB image with a size of 960 x 544. A visualization method of gradient weighted class activation mapping (Grad-CAM) was used to visually represent the final extraction feature of the improved models. More importantly, the special features were highlighted on the navigation path between the tea inter-ridges in the optimized Unet-ResNet34 structure, while retaining only the most crucial feature extractors. The speed of the tracked vehicle in the tea was mostly 0~1 m/s, particularly with the 0.179s average processing time of a single tea inter-ridge image. In summary, the improved model can be fully realized the real-time and accurate navigation path recognition of tea ridges. The finding can also provide the technical and theoretical support to the intelligent agricultural equipment in the tea environment.
    2022,38(19):172-179, DOI: 10.11975/j.issn.1002-6819.2022.19.019
    Abstract:
    Hat-shaped steel members are widely used in solar greenhouses, due to their low cost, fast construction, and high material efficiency. This study aims to determine the ultimate bearing capacity of a solar greenhouse with the hat-shaped steel under snow loads. The typical solar greenhouse with an 8m span and 3.8 m ridge height was selected as the research object. The finite element method (FEM) under ANSYS software was used to analyze the instability mechanism and failure modal of the structure under snow loads (uniform and non-uniform snow loads). An investigation was made to clarify the effects of the longitudinal tie bars, initial geometric imperfections, and sectional dimensions on the ultimate bearing capacity of the structure under non-uniform snow loads. Both the material and geometrical nonlinearity were considered in the finite element model. A bilinear kinematic hardening model was adopted for the steel with a yield strength of 235 MPa, Young's modulus of 206 GPa, and Poisson's ratio of 0.3. The geometrical nonlinearity was activated using the 'NLGEOM' option. To consider the local buckling, the greenhouse skeletons were then modeled with the Shell181 element suitable for the large strains and rotations. Fixed hinge supports were used for both ends of the skeleton. An arc-length method was utilized to trace the nonlinear load-displacement curve, in order to calculate the ultimate bearing capacity of the structure under snow loads. The ultimate bearing capacity of the solar greenhouse with the hat-shaped steel was slightly higher than that of the hollow rectangular section under the same conditions of net section area, upper flange width, web depth, and wall thickness. The solar greenhouse was more sensitive to the non-uniform snow loads, compared with the uniform ones. The ultimate bearing capacity of the hat-shaped steel solar greenhouse under non-uniform snow loads was about 28% of that under uniform snow loads. Therefore, some suggestions were presented for the non-uniform snow loads in the design stage of the solar greenhouse structure. The roof ridge and north roof end were dangerous sections under non-uniform snow loads, which firstly entered the full section yield state. The longitudinal tie bars were expected to effectively improve the ultimate bearing capacity of the greenhouse structure. The ultimate bearing capacity of the structure with the longitudinal tie bars was about 1.25 times that without tie bars. The ultimate bearing capacity was only reduced by 2%, when the initial geometric imperfections amplitude increased from 5 to 20 mm. It infers that the solar greenhouse was not sensitive to the initial geometric imperfection. The cross-section size of a hat-shaped steel was recommended that the ratio of the upper flange width to the lip width, the upper flange width to the lower flange width, and the web depth to the lower flange width were about 4.17, 3.33, and 4.67, respectively, while, the ratio of the web depth to the lip width, and the lower flange width to lip width were less than 9.25 and 1.7, respectively. These findings can provide a strong reference for the solar greenhouse with the open cold-formed thin-walled steel under snow loads.
    2022,38(19):180-189, DOI: 10.11975/j.issn.1002-6819.2022.19.020
    Abstract:
    Pig-farm wastewater is characterized by high suspended solids, organic matter, and ammonia nitrogen content. It is very difficult to treat, due mainly to the complex composition of the pig manure and feed residues. Fortunately, the straw with a large specific surface area can be expected to serve as the better retention and adsorption for the suspended solids and nutrients. For example, nitrogen content decrease can be greatly contributed to the subsequent resource utilization of pig-farm wastewater. However, it is still a new challenge for the efficient reutilization of straw filter residues. Alternatively, aerobic composting can be used to produce the organic fertilizer for better soil fertility and structure, due to the easy operation, short reaction period, better reduction, cost saving, and environmentally friendly. It is a promising way to simultaneously dispose of straw filter residues and pig manure in an intensive pig farm. Compared with the dry straw, the filtered straw is easily decomposed to participate in the composting process, where the high porosity can facilitate to absorb the water and swells. Meanwhile, the composting process is accompanied by the emissions of greenhouse gases and stenches, such as methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O), and ammonia (NH3), due to the complex composition of pig manure. Moreover, the composting microorganisms can quickly utilize the ammonium nitrogen that is adsorbed by the straw in the process of filtration. But the ammonium nitrogen is also easily volatilized to produce the NH3 for secondary pollution, leading to the reduced quality of compost due to nitrogen loss. However, it is still unclear on the relevant composting characteristics of the straw filter residues mixed with the pig manure. This study aims to filter the pig farm wastewater through maize straw and then systematically investigate the aerobic composting of straw filter residues and pig manure, the conversion of carbon and nitrogen during composting, as well as the emission of harmful gases. The results showed that the optimal conditions for the maize straw filtering the pig farm wastewater were as follows. The bulk density and height of the maize straw filter layer were 0.15 g/cm3 and 40 cm, respectively, whereas, the inner diameter of the filter column was 9 cm. The removal rates of total nitrogen (TN), total suspended solids (TSS), and chemical oxygen demand (COD) in the pig farm wastewater were 22.80%, 51.60%, and 76.81%, respectively, under the optimum conditions. Furthermore, the higher the initial ratio of the carbon to nitrogen (C/N) was, the better the composting was, the more the total organic carbon (TOC) loss was, and the less the TN loss was, when the initial C/N, ambient temperature, moisture content, and ventilation rate were 20-35, 22.32-32.05 ℃, 65%, and 0.2 m3/h, respectively. The harmful gas emissions mainly occurred in the early stage of composting. At the initial C/N of 35, the highest composting temperature reached 65.96 ℃ and the high-temperature period (>50℃) was maintained for 21 days. Among them, the maintenance time above 60 ℃ was up to 12 days. The seed germination index (GI), the loss ratio of TOC and TN after composting of 36 d reached 81.03%, 57.73%, and 10.08%, respectively. Although the emissions of CH4 and CO2 increased, there was a significant decrease in the emissions of NH3 and N2O, as well as the nitrogen loss during composting. The potential greenhouse effect was 137.53 kg/t (in CO2 equivalent) for the three greenhouse gases of CH4, CO2, and N2O. Therefore, the local anaerobic reaction can be avoided to reduce the generation of CH4 under high C/N conditions. The findings can provide the favorable support for the resource utilization of the straw filter residues and the emission reduction of harmful gases in the aerobic composting process of straw filter residues and pig manure.
    2022,38(19):190-201, DOI: 10.11975/j.issn.1002-6819.2022.19.021
    Abstract:
    Food waste is ever increasing in rural areas in recent years, particularly with the rapid economic development and population growth. If disposed of improperly, severe pollution can pose a great threat to the rural living environment. Fortunately, aerobic composting has been widely applied for food waste treatment, due to the high harmlessness and resource utilization rate. It is worth noting that food waste with high salinity can limit the application of aerobic composting. Among them, humification is one of the most important processes in the application of compost. However, only a few studies focused on the effect of salt content on aerobic compost humification. It is still lacking in the influencing mechanisms from the perspective of microbial community structure evolution. Taking food waste as the main raw material, and the maize stover as an auxiliary material, this study aims to explore the influences of salt content on the basic maturity index, organic matter composition, and dynamic change of humus substances during the composting process. The succession of microbial community was combined with the correlation statistical analysis, in order to reveal the microbial action about the effect of salt content on the mature process of food waste aerobic composting. Specifically, the food waste and maize stover were mixed well at the ratio of 4:1, where the initial moisture content was adjusted to about 63%. A composting experiment was carried out in the 60 L composting reactors for 45 days. A total of four experimental treatments were set with the addition of 0%, 0.5%, 1.0%, and 1.5% salt. Among them, the treatment without salt was the control group. The results showed that the temperature, C/N, and organic matter composition of four treatments fully met the requirements of maturity during aerobic composting. However, the salt addition greatly increased the electrical conductivity of the reactor. Particularly, the thermophilic period was shortened to 13 days at the proportion of salt addition of 1.5%. But, the seed growth was inhibited with the seed germination index reducing to 65.5%. Compared with the control treatment without salt, the degradation rate of organic matter was reduced by 6.5%, indicating the restricted humification process. The high throughput sequencing showed that the addition of 1.5% salt inhibited the activities of Thermobifida, Saccharomonospora, Aspergillus, and Trichosporon. In addition, a correlation analysis showed that the high salinity reduced the biodegradation of organic matter, such as total sugar and lignocellulose, thereby limiting the subsequent formation of humus substances. Thus, restricted improvement was found in the humification effect during food waste and maize stover composting. These findings can provide theoretical support for salt regulation in the application of aerobic composting in food wastes.
    2022,38(19):202-211, DOI: 10.11975/j.issn.1002-6819.2022.19.022
    Abstract:
    Sea cucumber is an important species cultivated in seawater ponds in Liaoning and Shandong provinces of China in the past 30 years. However, the current conventional techniques for improving pond water quality, such as water exchange by spring tides (WEST) and submerged aerator (SA), are not very ideal. The ponds can still form thermohaloclines in February and June, and a large number of macroalgae will be produced in summer and autumn. Jet Water Mixer (JWM) is a new water quality control device for sea cucumber pond. In order to explore the effect and mechanism of water quality improvement of sea cucumber breeding pond by JWM, we measured the annual changes of water quality and the changes of bacterial flora and function in spring and autumn by 16SrRNA high-throughput sequencing technology under the three water quality control methods. Nine adjacent ponds of the same size and shape were selected for the experiment. Three ponds with JWM were used as the experimental group, and the other six ponds were used as the control group, among which 3 ponds were used as SA control group and 3 ponds were used as WEST control group. The results showed that the contents of NH4+-N, NO2--N and NO3--N in the pond water with JWM were decreased, and the contents of O2, PO43--P, TN, TP, chlorophyll and suspended matter were increased, But except that the content of chlorophyll in the pond water with JWM was significantly higher than that in the control pond, there was no significant difference in other water quality indexes. The effect of water quality regulation on the composition of dominant bacterial groups in pond water showed that the higher the classification level, the smaller the effect, while the lower the classification level, the greater the effect. The composition of the top 10 dominant phyla and the top 3 dominant classes in the pond water with JWM were basically the same as that in the control ponds. The first and second dominant phyla are Proteobacteria and Bacteroidetes. The first three dominant classes were Alphaproteobacteria, Gammaproteobacteria, and Flavobacteria, but the composition of the dominant genus varied greatly in different ponds. Lefse analysis showed that JWM significantly increased the abundance of Firmicutes-Bacilli-Lactobacillales in the pond water (LDA SCORE > 4), and t-test showed that WEST significantly increased the abundance of Alteromonadaceae and SA significantly increased the abundance of Glaclecola in the pond water. FAPRTAX analysis showed that the main functional bacteria in each pond were chemoheterotrophy, aerobic chemoheterotrophy, sulfur oxidation, sulfur respiration, nitrate reduction, fermentation and plant pathogens. There was no significant difference in the annual mean abundance of the same functional bacteria among the ponds, but at the late stage of the experiment, there were large difference in the abundance of some functional bacteria between ponds. JWM increased the abundance of fermentation and plant pathogen bacteria and decreased the abundance of nitrate reduction bacteria. SA increased the abundance of nitrate reduction bacteria and decreased the abundance of plant pathogenic bacteria. The α-diversity of microbiota was the highest in the water of pond with JWM, and the lowest in that of pond with SA. The main environmental factors affecting the structure of bacterial flora were the contents of TP, NH4+-N and NO2--N in pond water. In conclusion, JWM significantly increased the abundance of Lactobacillales and plant pathogenic bacteria, and increased the α-diversity of bacterial flora in pond water. The former inhibited the growth of macroalgae, while the latter was beneficial to water quality stability.
    2022,38(19):212-218, DOI: 10.11975/j.issn.1002-6819.2022.19.023
    Abstract:
    Fish seed is one of the primary input materials for the large-scale production in aquaculture industry. In this review, a systematic summary was firstly made on the artificial fish breeding, hatchery, and larval rearing using Recirculating Aquaculture System (RAS). It is much easier to keep the environment much more convenient for the parent fish to mate and spawn in the RAS, compared with traditional. Specifically, the flounder, grouper, and butterfish can successfully lay spawn in the RAS. Among them, the previous studies reported the culture density of 0.01-4.5 kg/m3, system recirculation rate of 9-76%/h, and water discharged 0.7-3%/day. In terms of the fish eggs hatching, three kinds of incubator were mainly used for the different kind of eggs. Mcdonald-type hatching jar was used for the trout, sturgeon, and seabass, all of which eggs were suspended in water. California-type incubation troughs and vertical incubators were mainly used for the salmon and catfish, of which eggs were be stationary. Similar to the Mcdonald-type hatching jar, the funnel type incubators were used for the fresh water fish, such as the big head, grass, and koi carp. Furthermore, the different requirements of the system to grow out have been summarized to evaluate the influence of the live feed, microorganism, tank size, and light condition on the fish larval rearing. Secondly, the overview has been provided for the fish breeding and seed production in China. The current large-scale artificial fish breeding and seed production were practiced either in the outdoor ponds, net cages or the flow through various systems. Most of the seed production facilities were outdated, where the control of water quality was depended only on the climate and water resources. More importantly, the production efficiency and quality of fish seed were much lower and unstable at present, leading to the less development of aquaculture. Therefore, it is very necessary to upgrade the fish breeding and seed production technology. Recirculating aquaculture can be a promising kind of land-based industrialized aquaculture, due mainly to the high production, high efficiency, strong reproducibility, and environment friendly. Because of the high controllable water quality, recirculating aquaculture can fully meet the harsh requirements for the fish breeding and seed production. Hence, a plenty of practices on the fish breeding and seed production using RAS have been carried out with the different species all over the world. Thirdly, three research fields can be developed to promote the practice of RAS in the fish breeding and seed production in the future. 1) It is essential for the biological response of parent fish, eggs, and larval to the RAS environment stressors in the system design and seed production. 2) The control technology of environment and water quality can be developed in the scientific system configuration for different fish species. 3) The corresponding intelligent equipment can also developed during this time, such as, the screening for the parent fish using the computer vision, automatic counting for the eggs and larval, as well as the smart feeder for the live food.
    2022,38(19):219-226, DOI: 10.11975/j.issn.1002-6819.2022.19.024
    Abstract:
    Soil Cadmium (Cd) has posed a great threat to ecological security and human health in recent years. The exposure under the direct oral ingestion of contaminated soils has been the main contributor of Cd to the human body. The immobilization is an advisable technology to reduce the activity and bioavailability of Cd for the remediation of the Cd-contaminated soil. However, several challenges still remain for conventional immobilizing agents, such as the limited and weak immobilization mechanism, low efficiency and stability. Fortunately, layered double hydroxides (LDHs) can be a new promising type of functional material with great adsorption capability on heavy metals. But, only a few studies were focused on the application of soil remediation, regardless of the potential application to the health risk of soil Cd. In this comparative study, two conventional immobilizing agents (Ca(OH)2 and Ca(H2PO4)2) and one promising LDH (hydrocalumite, CaAl-Cl LDH) were used to remediate the soils with Cd contamination. Four typical soils (red soil, brown soil, cinnamon soil, and black soil) were collected from the cities of Fuzhou, Beijing, Nanjing, and Gongzhuling in China, and then artificially contaminated to the Cd concentration of 180 mg/kg. Subsequently, the three immobilizing agents were applied on the land under the pre-determined optimal patterns. Specifically, the mass ratios of Cd to the immobilizing agent were 1:100, 1:500, and 1:1000, respectively. A comprehensive analysis was also made to determine the effects on the specific soil physicochemical property (soil pH), Cd fractionation (ecological risk), and oral bioaccessibility of soil Cd (health risk) after three-month immobilization. The relevant mechanisms were further explored. Note that there was no evaluation of the health risk of soil Cd using the total concentration of Cd in the soil, due to the overestimation. Furthermore, the Cd bioaccessibility was utilized from the advanced in vitro test, where a PBET model was modified referring to the IVG model. An accurate simulation was then achieved in the digestion processes in the human gastrointestinal tract. Results showed that the soil pH increased greatly after the CaAl-Cl LDH remediation, further facilitating the Cd immobilization. In terms of Cd fractionation in soil, the Ca(OH)2, Ca(H2PO4)2, and CaAl-Cl LDH all significantly reduced the mobility factor of soil Cd (i.e., the proportion of exchangeable and carbonates-bound Cd fractions to the total Cd), with an average decrease of 16.1%, 56.9%, and 29.2%, respectively. As such, better capabilities were obtained to reduce the crop uptake of soil Cd and the ecological risk to the ambient environment. More importantly, the CaAl-Cl LDH more effectively reduced the oral bioaccessibility and the health risk of soil Cd, compared with the rest. The average decrease was 19.2% in the gastric phase, which was 3.11 and 1.99 times those of Ca(OH)2 and Ca(H2PO4)2, respectively. Besides, the decrease was 33.0% in the small intestinal phase, which was 5.99 and 2.72 times those of the conventional. A series of mechanisms were also proposed for the Cd immobilization, including surface complexation, interlayer anion exchange-adsorption, dissolution-precipitation, and isomorphous substitution. Therefore, the CaAl-Cl LDH demonstrated great potential to immobilize the soil Cd in a super-stable manner. It is also highly expected for wide application in real cases. Anyway, the finding can provide a scientific basis and valuable reference for the development, improvement, and selection of the immobilization agents/technologies, in order to better remediate the Cd-contaminated soils.
    2022,38(19):227-236, DOI: 10.11975/j.issn.1002-6819.2022.19.025
    Abstract:
    Biomass pyrolysis can generate tar and gas products with high industrial value. But the nitrogen (N) element in the biomass can inevitably migrate to the products along with the pyrolysis process, thus possibly polluting the environment. Focusing on the overall goal of preparing clean energy from biomass resources, this study systematically analyzes nitrogen migration and conversion mechanism during biomass pyrolysis, focusing on the research progress of the generation and conversion mechanism of gas nitrogen, tar nitrogen and char nitrogen. The NOx precursors can be the HCN and NH3 in the biomass pyrolysis gas. Specifically, the NH3 comes from the amino acids that are released from the amino acid pyrolysis and hydrolysis of HCN on the surface of char, while the HCN is from the secondary cracking of primary pyrolysis products, such as nitrile and N-containing heterocycle. The N-containing substances in the pyrolysis oil include the N-containing heterocycles, nitrile, and amide. Furthermore, the N-containing heterocycles can be produced by the fragmentation of some amino acids and by dehydration condensation between the amino acids. The nitrile is derived from the de-H2 reaction of amino acid molecules and the de-H2O reaction of amides. The substitution reactions can also be used to form amides from NH3 and carboxyl groups. More importantly, the biomass varies greatly in the different pyrolysis characteristics and products, due to the composition during the reaction. The higher heating rates can promote tar cracking for higher NOx precursor production during biomass pyrolysis, while the lower heating rates can contribute to tar production for better quality. The pyrolysis temperature and atmospheres of biomass can pose a large effect on the yield and composition of the pyrolysis products. The pyrolysis in the O2 and H2O atmosphere can enhance the conversion of HCN to NH3, while the pyrolysis in the CO2 atmosphere can reduce the production of NOx precursors. In terms of the pyrolysis pressure, the gas-N residence time can facilitate the reaction path of the secondary pyrolysis for the migration path of nitrogen. The larger particle sizes of the biomass can increase the NOx precursors but less the tar production, whereas, the smaller particle sizes can promote the N fixation in the char. The catalysts can reduce the pyrolysis time and the temperature for the N migration and conversion during biomass pyrolysis. The mineral elements (such as K, Ca, and Fe) in the biomass can promote the conversion of nitrogenous substances in the coke into the HCN. By contrast, the metal oxides (such as Fe2O3, Co3O4, and NiO) can be used to enhance the production of Tar-N, where Co3O4 has the best performance. The KOH can reduce the types of hydrocarbon compounds in the pyrolysis oil, but for less NH3 and HCN production. The current NOx treatments are the catalytic, plasma, microbial, absorption, and adsorption methods. All tail-end treatments cannot reduce the emission of pollutants with low efficiency and high energy consumption. Anyway, the N migration and transformation mechanism in the pyrolysis of biomass can reduce the emission of N-containing pollutants at the source during the pyrolysis process.
    2022,38(19):237-248, DOI: 10.11975/j.issn.1002-6819.2022.19.026
    Abstract:
    The "Three line" of land spatial planning and the spatial characteristics of cultivated land quality can greatly contribute to the spatial layout optimization of cultivated land protection and food security. In this study, an improved local spatial autocorrelation model was proposed to optimize the spatial layout of arable land protection using "Three line" delineation of territorial spatial planning and spatial autocorrelation attributes of arable land quality. The ecological environment served as the "fourth dimension" of the spatial correlation analysis of cultivated land quality. A plan was also presented to improve the spatial layout of cultivated land protection. The spatial autocorrelation correlation was then simulated for the natural quality, utilization management, economic value, and ecological environment index of cultivated land in the "Three line" from the plot scale. There was a positive influence on the geographical evolution of agricultural ecological landscape patterns, food safety, and farmland pollution control. The specific procedures were as follows. Firstly, some indexes were estimated to obtain the three-line delineation of land spatial planning, including the natural quality, utilization management, economic value, and ecological environment index. The plot data was collected from 1073 soil monitoring stations in the Gaochun District, Nanjing City, Jiangsu Province of China. Secondly, the spatial correlation of each indicator was analyzed using the spatial error model of the enhanced spatial weights. Finally, a new strategy was proposed to optimize the spatial layout of cultivated land, according to the geographical association findings of permanent basic farmland, urban development boundary, and the quality of inland blocks of ecological protection red line. The results indicated: 1) Much more high-quality cultivated land was concentrated in the west and dispersed in the east, in terms of the geographical distribution of cultivated land quality. Low-quality agricultural land was more prevalent in the eastern part than in the western. The ecological environment, economic value, utilization management, and natural quality index all demonstrated the "west high, east low" features of geographical distribution. 2) Each cultivated land quality index presented a positive geographic correlation, according to the spatial autocorrelation analysis of the cultivated land quality index. Both positive and negative correlation types were quite compatible with the spatial distribution of high and low-quality cultivated land. The natural quality, utilization management, economic value, and ecological environment index all presented the Moran's I values of 0.79, 0.92, 0.89, and 0.77, respectively, all of which were the spatial aggregation features. The indexes were ranked in descending order of the Utilization Management, Economic Value, Natural Quality, and Ecological Environment Index. 3) The cultivated land was divided into 14 second-level categories and four first-level categories using the spatial correlation of the cultivated land quality, including the permanent basic farmland protection, urban development buffer, ecological environment protection, and comprehensive adjustment zone. Both the permanent basic cropland and the grade rose by 0.94 hm2. The best quality was found in the permanent basic farmland protection zone. There was a significantly positive spatial dispersion impact of each quality measure for the cultivated land protection to forbid non-agricultural building. The urban development buffer zone was the best place for urban growth, due to the low quality of the farmed land and the significant geographical benefit. The ecological environmental protection zone was utilized to carry out ecological protection in the field. An ecological red line protection grid was constructed for the outstanding ecological circumstances, especially with a relatively visible deficit in the overall quality.
    2022,38(19):249-258, DOI: 10.11975/j.issn.1002-6819.2022.19.027
    Abstract:
    Ecological protection and restoration of territorial space can be one of the most important schemes to maintain the national patterns of ecological security. It is a high demand to scientifically zone and manage the key areas for the protection and restoration, particularly for the regional ecosystem function and sustainable development. Taking Shanghang County in Fujian Province of China as a typical study area, this study aims to construct a multi-dimensional ecosystem measurement framework of "Ecosystem Importance-Ecosystem Fragility-Ecosystem service value" using an integrated ecosystem integrity, system, and benefits. Multi-dimensional characteristics of the regional ecosystem were then analyzed to determine the relationship of trade-offs and synergy between the measure factors. At last, the spatial clustering method (Grouping analysis) was used to delineate the ecological protection and restoration space. The zoning management and control strategies were also proposed using the spatial heterogeneity and ecosystem structure characteristics of each zone. The results showed that: 1) There was the strong spatial heterogeneity in the ecosystem, indicating a spatial differentiation ecosystem pattern with the high importance, low fragility, and high service value. 2) There were the synergistic and tradeoff relationships among all ecosystem measure factors. All synergistic relationships were found in the comprehensive importance, fragility, and service value. As such, the high overlap was triggered between the ecosystem conservation and restoration areas. 3) An optimal number of clusters was determined as six, according to the CONTAG and COHESION indexes with different number of clusters. There were also the strongest cohesion degree and connectivity among groups, which were conducive to the stable and healthy development of the ecosystem. Six zonings were divided into: the III-I-V (Importance level III- Fragility level I-Value V), III-III-V (Importance level III- Fragility level III-Value V), III-II-V (Importance level III- Fragility level II-Value V), III-III-IV (Importance level III- Fragility level III-Value IV), II-III-I(Importance level II- Fragility level III-Value I), and IV-I-I (Importance level IV- Fragility level I-Value I). Among them, the zoning of III-I-V and III-II-V shared the large areas with the ecosystem functional bases for the regional development. The outstanding spatial heterogeneity was found in the composition of land cover types in each zoning. Particularly, the forest, shrub, cropland, and garden were the dominant land cover types. 4) A targeted and differentiated management was proposed for the environmental protection and restoration measures, according to the spatial distribution and internal structure of each zoning. After that, the study area was further divided into the ecological protection area (Ecological conservation, green development, and moderate development area), and ecological restoration area (ecological restoration, protection and restoration coordinated development area). Furthermore, the multi-dimensional ecosystem measurement "I-F-V" can be expected to identify the important ecosystems, the damaged areas of ecosystems, and integrate ecosystem services benefits. An emphasis was also made on the coordination of ecosystem protection and restoration costs, together with the development opportunities, when considering the integrity and systematism of ecosystems. Therefore, an effective assessment was achieved in the resilience and sustainability of ecosystems and economic activities, as well as the human well-being they support. Some recommendations can be also widely used in the ecosystem measurement, the ecological conservation and restoration. The findings can provide the insightful ideas and practical reference for the decision making on the protection, restoration, and ecological security pattern of territorial space.
    2022,38(19):259-268, DOI: 10.11975/j.issn.1002-6819.2022.19.028
    Abstract:
    Huaihai Economic Zone with a reclamation rate of about 70% is one of the main grain-producing areas in China. It is very necessary to grasp the spatiotemporal variation of the carbon storage for the carbon sink source areas of cultivated land. The driving factors can be used to ensure national food security for agricultural guidance in the achievement of China's "Dual carbon" goals. In this study, the carbon storage of cultivated land soil was calculated using the soil type carbon density of the Huaihai Economic Zone. The net ecosystem productivity (NEP) model was also established to calculate the carbon sequestration of cultivated land vegetation. At the same time, the ArcGIS and Geo-Detector software were selected to study the spatiotemporal evolution characteristics of cultivated land carbon storage, the "carbon" attribute of cultivated land and the driving factors in Huaihai Economic Zone from 2005 to 2020. The results showed that: 1) The soil carbon storage values of cultivated land were 6.028 2×108, 6.055 4×108, 5.927 8×108, and 5.888 9×108 t in the four years from 2005 to 2020, respectively. The land type transfer decreased by 1.393×107 t, indicating a spatial distribution of "high in the east and low in the west". 2) The carbon sequestration of cultivated land vegetation in the four years from 2005 to 2020 was 2.706 7×108, 2.727 0×108, 2.882 3×108, and 2.802 1×108 t, indicating changing trend of "first increasing and then decreasing" with 2015 as the inflection point. The NEP showed a spatial distribution feature of "high in the southeast, low in the northwest". The middle high-value area was extended to the southwest with time. 3) The overall Moran's I of the total carbon storage in the cultivated land were 0.19, 0.19, 0.16, and 0.14 from 2005 to 2020, respectively. There was a downward trend in the spatial distribution and concentration. Specifically, the number of "high-high" type areas also gradually decreased, mainly shifting to the insignificant and "low-high" outlier areas. 4) There were 32 carbon sink areas of cultivated land in the study area, where 21 medium-strength carbon sink areas were mainly distributed in the west, and five high-strength carbon sink areas were concentrated in the northeast. 5) The main factors were traffic accessibility, grain production, NDVI, elevation, slope, and aspect. The secondary factor was population, among the factors driving the spatiotemporal differentiation of cultivated land carbon storage. Therefore, the carbon source counties of cultivated land can take farmland protection and management measures in the carbon sink area, in order to reduce the loss of carbon storage of cultivated land. As such, the quality of cultivated land can be maintained for the carbon sink in the cultivated land ecosystem in the process of farmland protection in the future.
    2022,38(19):269-276, DOI: 10.11975/j.issn.1002-6819.2022.19.029
    Abstract:
    Plant-based meat products have been the popular food at present, in order to prevent processed meat from cardiovascular disease and cancer today. The pre-emulsification technique can often be used to prepare an oil-in-water emulsion, before introducing the fat/oil into a meat product. Compared with the direct oil addition, the ability to bind water and oil can allow for the better dispersion of oil into the meat batter. Recently, several studies have also reported that the particle size of the pre-emulsified oil can influence the textural properties and gel formation of the sausage. However, few studies have reported the effects of droplet size and emulsifier in the pre-emulsion on the rheological and textural properties of vegetarian sausage. Therefore, the aim of this work was to apply the pre-emulsification for the processing of vegetarian sausages with Textured Fibril Soy Protein (TFSP). An investigation was made to clarify the effects of oils pre-emulsified on the rheological properties, texture, and microstructure of TFSP vegetarian sausages using different protein emulsifiers and homogenization conditions. The results show that the apparent viscosity of both Soybean Protein Isolate (SPI) and Sodium Caseinate (SC) emulsions increased gradually, as the pressure homogenization increased from 0 to 30 MPa. The particle size d3,2 of SPI emulsions ranged from 24.80 to 0.39 μm, and the particle size d3,2 of SC emulsions ranged from 12.37 to 0.12 μm. The temperature and frequency sweep of the TFSP vegetarian meat batter demonstrated all the vegetarian meat batters formed an emulsion gel with viscoelasticity after cooking. The higher the homogenization pressure of the pre-emulsion was, the higher the storage modulus (G′) of the vegetarian meat batter was. In the Warner-Bratzler (WB) shear test and texture properties (Texture Profile Analysis, TPA), it was found that the breaking force and TPA (Hardness, Springiness, Cohesiveness, Chewiness) of TFSP vegetarian sausages increased with the decrease of the particle size d3,2 of the pre-emulsion. The microstructures of different emulsions and TFSP vegetarian sausages were characterized by Confocal Laser Scanning Microscopy (CLSM). It was found that the coalescence of emulsion droplets occurred in the TFSP vegetarian sausages after cooking, when the SC emulsions were prepared at the pressure of 0-20 MPa. However, the TFSP vegetarian sausages prepared by the SPI emulsions showed a strong ability to resist the coalescence of emulsion droplets after cooking. Therefore, the shear force and textural properties of TFSP vegetarian sausage can be effectively improved, when the pressure was more than 20 MPa during the pre-emulsification of plant oils using the SPI. The finding can provide a strong reference for the development and application of the oil pre-emulsification process in vegetarian products.
    2022,38(19):277-284, DOI: 10.11975/j.issn.1002-6819.2022.19.030
    Abstract:
    Low glycemic index (GI) food can be very necessary to alleviate the ever-increasing prevalence of diabetes, particularly for the high-quality living standards and health care services. Among them, the starch-lipid complexes can serve as a new type of resistant starch for excellent anti-digestive properties in recent years. High amylose corn starch (HACS) is considered an ideal raw material for the preparation of starch-lipid complexes, due mainly to the high amylose content. Meantime, the twin-screw extrusion has been successfully applied to fabricate the starch-lipid complexes. It is a high demand to enhance the preparation efficiency of starch-lipid complexes for scale production in anti-digestive food. The purpose of this study was to optimize the extrusion process for better structure and physicochemical properties of HACS-lipid complexes using single-factor and orthogonal experiments. Among them, the complex index (CI) was selected as the indicator. The high-amylose corn starch and flax oil were used as the material to prepare the complexes using twin-screw extrusion. The process parameters were adjusted separately, including the mass ratio, feed moisture, barrel temperature, and screw speed. The extruded complex was dried at 40 ℃ in an oven for 10 h, and then ground and passed through an 80-mesh sieve. The highest CI reached 85.63%, when the optimal parameters were 0.24 of flax oil-to-starch ratio, 40% of feed moisture, 125 °C of barrel temperature, and 150 r/min of screw speed. Fourier transform infrared spectroscopy (FTIR) pattern found the new peaks at 2850 and 1743 cm-1 in the extruded starch-lipid complex, corresponding to the C-H and C=O vibration absorption peak of lipid molecules in the complex. Moreover, the C=O vibration absorption peak of the extruded complex was shifted to the lower wavenumber, compared with the control. It infers that the lipid molecules combined with the starch were at the actions of shearing, friction force, and heat moisture during extrusion. Specifically, the extrusion first broke the hydrogen bonds of starch molecules to expose the hydrophobic helical cavity, where the lipid molecules were entered under hydrophobic interaction. The morphologies showed that the complexation induced the stacking and aggregation of starch granules. The V-type crystalline X-ray diffraction (XRD) pattern was found in the extruded complex, indicating the feasible preparation of the complexes after twin-screw extrusion. Compared with the control and HACS, there was a higher gelatinization enthalpy in the extruded complex, indicating that more energy was required to gelatinize the complex. By contrast, the extruded complex demonstrated a lower apparent viscosity, storage modulus, and loss modulus, compared with the control. Additionally, there was the highest total amount of slowly digestible starch (SDS) and resistant starch (RS) in the extruded complex among all samples, indicating the better anti-digestible properties of the complex. It can be concluded that the extrusion can promote the effective complexation between the starch and fax oil, thus altering the structure and physicochemical properties of corn starch. Therefore, the starch-lipid complex prepared by twin-screw extrusion can be expected to serve as a potential material for low GI food production.
    2022,38(19):285-294, DOI: 10.11975/j.issn.1002-6819.2022.19.031
    Abstract:
    Wheat Gluten Protein (WGP) prepared by gluten through hydration build a great and compact network structure, which has great viscoelasticity, extensibility and film formability. However, the structure is easy to break after heating due to low stability and water-holding capacity. In this research, a blended system was established to contain the vegetable protein, hydrophilic colloid, and coagulating gelatinase using the wheat gluten, Soy Isolated Protein (SPI), Methylcellulose (MC), and Glutamine Transaminase (TG). It is vital to investigate the effects and relationship between above components of the physicochemical properties, gel properties and structure in the blended adhesion system. The results showed that the SPI, MC and TG were added step by step to WGP and the disulfide bond content in the mixed system decreased by 81.03%, increased by 248.50% and 0.70%, the free sulfhydryl group content increased by 68.79%, 28.90% and 20.44%. Meanwhile, the surface hydrophobicity increased by 5.33%, decreased by 6.85%, and increased by 17.17%, decreased by molecule weight of glutenin component increased gradually with the gradual addition of WGP into the mixed system. The water holding capacity increased by 5.07%, 2.91%, and 2.79%, and the gel strength increased by 104.14%, 24.66%, and 3.52%. When it comes to the molecular weight, SPI could perturb the WGP network structure, and the less soluble parts of SPI intersect with WGP leading to the disappearance of some subunits. The MC was added to strengthen the cross-linking between proteins, further producing increasing aggregates for the molecular weight, but the TG enzymes dispersed the large aggregates into the uniform small aggregates. During the progressive addition of the three fractions, the tangles of molecular chains in the gel system increased with the degree of gelation, and the storage modulus and loss modulus rise gradually. The TG enzyme was added to prevent the transforming of α-helix structure into β-turn and irregular coil structure, leading to the increase in the α-helix and β-sheet content. The intermolecular entanglement points of the gel in the blend bonding system promoted stronger gel property. This showed that the addition of SPI partially destructed the network structure of WGP, but the MC and TG enzymes would promote the aggregation degree and strength of protein gel. The gel structure was formed by SPI bind to the WGP covalent, disulfide bonds, and hydrophobic interactions. The MC was added to cause the double protein water loss aggregation through hydrogen bonding. The TG enzyme was further induced to promote the crosslinking between SPI and WGP to make the skeleton network structure closely. The SEM observation indicated that the SPI was embedded in the WGP network skeleton, forming a new architecture as half network and half filling. With the addition of MC and TG enzymes in turn, on the basis of a large number of cross-linked filamentous structures, local continuous membrane structures were formed to cover the particles by Soybean Drawing Protein (SDP). It showed that the SDP particles were completely and tightly wrapped in the gluten SPI-MC-TG enzyme blend adhesive system. The SDP based meatloaf was made using this bonding system, and four raw materials were added to the rehydrated SDP in turn, which showed that the hardness, cohesion, chewiness, and elasticity of the meatloaf were improved. Therefore, it is an effective way to establish the gluten based blending adhesive system for better quality meat products, particularly with the SDP as the main raw material.
    2022,38(19):295-302, DOI: 10.11975/j.issn.1002-6819.2022.19.032
    Abstract:
    Pectin polysaccharides can be closely related to various physiological functions, particularly for the resistance to obesity, diabetes, and cardiovascular diseases. Therefore, pectin polysaccharides can be often used in gel foods, due to their excellent gelation property, water solubility, and low viscosity. Among them, there is up to 30% of soybean hull pectin polysaccharide (SHPP) in the soybean hull byproducts, more than three million tons of which are produced every year in China. This study aims to improve the utilization efficiency of soybean byproducts for the better application of SHPP in gel foods. A salt-assisted hydrothermal method was also applied to extract the SHPP from soybean hulls. Physicochemical properties of SHPP were characterized, including the extraction yield, composition, size distribution, and viscosity. Then, the soybean curd (one of the soy protein-based gel foods) was applied as a case study. Segregative phase separation was investigated under various concentrations (0-2.0%) of SHPP in these mixed systems. A correlation analysis was implemented on the microphase behavior and the macro-properties (e.g., rheological behavior, mechanical properties, water holding capacity, and sensory evaluation). Besides, the commonly-used commercial citrus pectin (CP) was used as a control in foods. The results showed that the extraction yield of SHPP was up to 17.95% ± 0.21%. The obtained SHPP mainly consisted of pectin, with a galacturonic acid content of 42.13% ± 2.05%. The mean size of SHPP dispersion was determined as (210.3±2.9) nm and the polydispersity index (PDI) was 0.466 ± 0.037. The extracted SHPP was better dispersed in water, due to the hydrophilic property and low shear viscosity. There was no microphase separation, when the 0-0.5% SHPP was added to prepare the soybean curd. The obtained soybean curds were pretty white in a better appearance, particularly with the viscoelastic network and excellent water holding capacity. Furthermore, the leaking water was visible around the soybean curd, as the SHPP concentration increased up to 1.0%. A significant (P<0.05) reduction was found in the viscoelasticity and water-holding capacity. The outstanding phase separation was observed when the addition of SHPP was up to 1.5%. There was a disordered microstructure with the enlarged pore of the network in the soybean curd, resulting in weak gel strength and low water holding capacity (46.2%±3.2%). Therefore, the optimal addition concentration of SHPP was 0.5% for the preparation of the soybean curd. A comparison was also made on the soybean curd that was prepared with the optimal CP concentration of 0.1%. The better texture properties and sensory scores were achieved in the color, texture, flavor, taste, and acceptability of the soybean curd prepared with 0.5% SHPP, compared with the 0.1% CP. Therefore, the SHPP can be expected to serve as a bioactive substance with various physiological functions in protein-based gel foods. The finding is conducive to the recycling of soybean byproducts in the whole bean food.
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      2022,38(18):1-10, DOI: 10.11975/j.issn.1002-6819.2022.18.001
      Abstract:
      Abstract: Plant protection spraying has been the main way to prevent crops from pests and diseases at present. However, the average utilization rate of pesticides is only 20% to 30% in manual sprayers and large-capacity rain spraying, particularly with water consumption of 600~1200L/hm2. The current pesticide spraying cannot fully meet the requirement of intensive agriculture in recent years. Among them, a large number of droplets with small particle sizes are susceptible to drifting by ambient wind. In this study, the mesh atomization of droplets was applied to reduce the wind drift for the high utilization rate of pesticides in the process of plant protection spraying. A systematic optimization was also made to investigate the secondary atomization characteristics of the droplets and the deposition effect of the droplets after the spray hits the mesh. The experimental variables were set as the pore size and the distance between the nozzle and the mesh. Phase Doppler Anemometry (PDA) was used to measure the velocity and particle size distribution of droplets after secondary atomization. A high-speed camera was selected to capture the spray angle. A 0.5 g/L methyl orange aqueous solution was prepared as a spray solution. The water-sensitive and filter tests were carried out to determine the droplet coverage and deposition amount, in order to evaluate the droplet deposition characteristics of the mesh atomization. The test results showed that: 1) the mesh effectively reduced the speed of the droplets. The average velocities of the measurement points were 1.80, 2.02, and 1.67 m/s under the mesh with pore sizes of 461, 350, and 227 μm, respectively. There were 23.40%, 13.90%, and 29.00% lower than those without the mesh (2.35 m/s). 2) The mesh reduced the particle size of the droplets. The maximum average particle sizes of the measurement points were 155.0, 165.6, and 173.3μm under the mesh with the pore size of 461, 350, and 227 μm, respectively, which were 19.5%, 14%, and 10% lower than those without the mesh (192.5 μm). 3) The spray angle of the droplet was varied in the pore size of the mesh and the distance between the nozzle and the mesh. Specifically, the maximum spray angle was 84.178° for the secondary atomized droplets at the pore size of 461 μm and the 10cm distance between the nozzle and the mesh, which was 20.365° larger than that without the mesh. 4) There was a great influence of pore size on the uniformity and penetration of the droplet deposition. The coefficient of variation of the deposition rate was between 33.51% and 88.08% at the sampling point of the mesh with the pore size of 350 and 227 μm, respectively, indicating similar deposition uniformity. By contrast, the maximum coefficient of variation of the deposition rate was 162.98% at the sampling points in each mesh layer with a pore size of 461 μm, indicating relatively less deposition uniformity. The better penetration of droplets was achieved in the mesh with the pore size of 350 μm, where the coefficient of variation of deposition between layers was between 0.8 % and 10.08 %. The better deposition was obtained in the mesh with the pore size of 461 μm in this case, compared with the pore size of 461 and 227 μm. There was no significant effect of the distance between the nozzle and the grid on the droplet coverage and deposition volume. In terms of the grids and large spraying droplets, the average droplet drift in the non-target area was 7.58 % of the deposition in the target area, indicating better performance after optimization. This finding can provide a strong reference to select the spraying and mesh parameters for the combination of plant protection UAV spray and mesh atomization.
      2022,38(18):11-20, DOI: 10.11975/j.issn.1002-6819.2022.18.002
      Abstract:
      Abstract: Spray drift has been one of the major diffuse pollution sources for fertilizers and pesticides in intensive agriculture. Non-target drift loss of pesticides has posed a great risk to the ecological environment in recent years. It is a high demand to improve the utilization rate of pesticides for the reduction of spray drift in an orchard. In this study, a hanging-type, flexible, and targeted spray device was developed to promote the efficiency of spraying with less mechanical damage to the fruit branches and leaves. The spraying device included ultrasonic target detection, a main controller, speed measurement, and a solenoid valve control module. As the core of coordination, the main controller was responsible for the data transmission with the other three modules. A Dongfanghong MS-304 tractor was taken as the carrying platform, with overall dimensions (length × width × height) of 3.6 m × 1.5 m × 1.6 m. A three-point suspension mechanism was also used to carry the spray frame on the rear side of the tractor. The spray frame mainly included a load-bearing frame, a lifting guide rail, a lifting frame, a first-level spread arm, a second-level spread arm, a hanging spray rod, and an inverted Y-shaped nozzle bracket. Among them, the spray arm was folded twice, including the lifting frame, the first-level spread arm, and the second-level spread arm. A double cross universal joint was used for the flexible connection between the hanging spray boom and the spray arm, and a flexible spray hose was between the hanging spray end and the spray head for the flexible spraying. As such, the flexible and bendable spray hose was utilized to reduce the mechanical damage to the irregular branches and leaves. Different address codes were assigned in various modules, due to a large amount of data processing. The data conflicts were avoided to first match the address codes of the main controller as-received data. Three ultrasonic ranging sensors (TCF40-16TR1) were installed on the left and right sides of the tractor, particularly in the upper, middle, and lower order along the vertical direction. The horizontal distance was 4.1m between the ultrasonic sensor holder and the spray rack, in order to detect the target at each height. In addition, a sleeve was designed to strengthen the ultrasonic energy of the sensors in the central axis of the beam, in order to reduce the detection range under the same detection distance for better directionality of the spraying. Different levels of spray nozzles were prevented to trigger the spray ahead of time, due to the driving forward of the tractor. Specifically, the Hall sensor was utilized to detect the magnetic field strength on the tractor rim for the real-time running speed of the tractor. 14 solenoid valves were selected to control the sprinklers, four of which the inverted Y-type sprinkler brackets were controlled by one solenoid valve, and each of the rest was controlled by a solenoid valve individually. A target spray test was performed on the orange trees with a planting spacing of 4.0 m, tree height of 1.6 m, and crown diameter of 1.4 m. Two factors and three levels of orthogonal experiment were designed for the test. The first factor was the travel speed with the three levels of 0.5, 1.0, and 1.5 m/s, and the second factor was the spray pressure with the three levels of 0.4, 0.5, and 0.6 MPa. A full factorial experimental design was also performed as follows. Prior to the test, 10 sampling points were evenly arranged on the upper, middle, and lower planes on the crown of each orange tree. The droplet labeling was also arranged at the sampling points to receive the medicinal solution. The allura red staining solution was then prepared. The tractor throttle was fixed, according to the factors of the spray test and the horizontal relationship. The speed of the tractor was stabilized at the speed required for the test after debugging. The pressure was also adjusted to the required. Finally, an anemometer was used to measure the wind speed of the surrounding environment. The tractor started to travel and spray when the outdoor wind speed was less than 0.2 m/s. The spraying was automatically stopped when the tractor completely passed all the orange trees. The test results show that: 1) the average droplet adhesion rates were 84.7%, 91.7%, and 88.9% at the spray pressures of 0.4, 0.5, and 0.6 MPa, respectively, when the tractor traveled at a speed of 0.5 m/s. There was no outstanding effect of spray pressure on the droplet adhesion rate at this speed. A lower spray pressure was then selected to reduce the loss of medicinal solution. 2) Once the driving speed of the tractor was 1.0 m/s, the average droplet adhesion rates of 0.4, 0.5 and 0.6 MPa were 64.2%, 70.3%, and 75.8%, respectively. The higher the spray pressure was, the higher the droplet adhesion rate was. Therefore, a higher spray pressure was selected to improve the droplet adhesion rate in this case. 3) The average droplet adhesion rate was less than 50% at the speed of 1.5 m/s, indicating the serious spray drift unsuitable for the spraying. Decreasing spraying was observed at the droplet adhesion rate in the upper, middle, and lower layers of the canopy when the spray pressure was the same. Consequently, the greater the speed of the tractor was, the more outstanding the decreasing trend was. Furthermore, the droplet adhesion rate of the leaf back was much lower than that on the leaf front, temporarily unsuitable for spraying with high requirements. It is then necessary to adjust the nozzle angle on the hanging spray bar for a higher droplet adhesion rate on the leaf back in the future.
      2022,38(18):21-30, DOI: 10.11975/j.issn.1002-6819.2022.18.003
      Abstract:
      Abstract: Target spraying can improve the utilization rate of the liquid for less environmental pollution, compared with traditional spraying. There are technical requirements for stable and reliable recognition, as well as accurate nozzle position solving in the spraying system. This research aims to develop and evaluate the accurate position-solving and error correction of nozzles for targeted spraying using a pre-designed field robot. The high accuracy of target spraying was achieved by plant protection machinery in unstructured field environments. The field robot of target spraying was mainly composed of electromagnetic nozzle, suspension, walking chassis, walking and, target spraying control system, as well as the global navigation satellite system. An Unmanned Aerial Vehicle (UAV) was used to collect the field information for the prescription map with the target spraying operation task. Specifically, the memory card was inserted with the prescription map information into the main board of the target spraying control system, and then to guide the robot for the target spraying. The robot was combined with the positioning and orientation data to solve the coordinates of each nozzle in real time during operation. Among them, the structural parameters of the robot were compared with the prescription diagram, in order to control the movement of the nozzle for target spraying. As such, the on-target spraying operation was implemented during the robot walking in a complex field. The position of the spray nozzles was solved to consider the errors originated from the production, installation, and movement of the components. The cumulative effect of error transmission between moving part was evaluated for each part of the error, compared with the robot kinematics. Among them, the end-to-end coupling error was transformed and described uniformly, and then decomposed and quantified at the end of the error transfer. The final coupling error was equivalently decomposed into the decomposition errors in six directions, including translation errors in three directions, and rotation errors around three axes. The error values were derived within the range of suspension motion under a combination of field measurements and theoretical calculations using Gaussian machine learning. The auto-regression learner established the correspondence between the length of the electric cylinder on the suspension and each error, thus enabling the prediction of the errors and the correction of the nozzle error solution model. The mean correction on the nozzle position of the solution model fully met the requirements of large field operations, compared with the commonly-used one. Finally, the corrected model of the nozzle position solution was deployed to the edge end. Leveling ground and field trials were conducted to verify the model. The results indicated that the accurate estimation of the robot's structural parameters was achieved using the Gaussian regression modelling. The average deviations were 4.3 and 1.3 mm for the relative height and relative distance between the nozzle and the positioning point, respectively. The mean plane error of the nozzle position solution was 8.5 mm. The longer the response distance of the nozzle from the target center was, the higher the target spraying accuracy and the better performance of the system were. The longer the response distance of the nozzle from the target center was, the higher the target spraying accuracy and the better the stability of the system were. Furthermore, 94.4%, 96.6%, and 99.4% of the samples were sprayed to the target with an accuracy ≤30 mm at 0, 15, and 30 cm target guidance distance, and the coefficients of variation were 0.010, 0.017, and 0.010, respectively, when the field travel speed was 1 m/s. Higher accuracy was achieved in the nozzle position solution and operational stability. The accurate calculation and correction of the nozzle position can be used for the precise control of the ground robot end-effector in the air-ground cooperative robot system.
      2022,38(18):31-39, DOI: 10.11975/j.issn.1002-6819.2022.18.004
      Abstract:
      Abstract: Precise target spraying can be widely used to detect the target information for the on-demand operation using sensors and variable actuators. An effective way can prevent the excessive spraying from the environmental pollution of food safety caused by the traditional continuous spraying, particularly for the high pesticide utilization. Nevertheless, there is the a serious fluctuation of pipeline pressure at present, due to the repeated opening and closing of different numbers of nozzles in the process of target spraying. A great threat has been posed to the droplet size, deposition distribution, and service life of the spraying system. In this study, a test platform was designed to investigate the influence of the reflux ratio on the pipeline pressure fluctuation in the target spraying system. A simulation model of target spraying pressure fluctuation was established using AMESim software. A test was also carried out to verify the model. The initial pressure of the system was set as 0.2-0.4 MPa, and the reflux ratio as 0-0.9 in the simulation. The number of closed nozzles was accounted for the a large proportion of 1/5-4/5, indicating the more serious fluctuation of pipeline pressure. The reflux ratio was 0 at the initial pressure of 0.2 MPa. Once the 4/5 proportion nozzles were closed, the pressure of the pipeline system rose from 0.2 to 5.15 MPa, indicating a 2 400% fluctuation rate. The more significant ratio was obtained in the number of closed nozzles to the pressure fluctuation at the large initial working pressure of the system. The return pipeline was effectively reduced the pressure fluctuation of the target spraying system. Specifically, the greater the return ratio was, the more significant the elimination effect was. The maximum pressure fluctuation rate was 64.53% caused by the closure of some nozzles, when the initial pressure of the system was 0.2 MPa and the return ratio reached 0.6. Therefore, the reflux ratio was recommended to be less than 0.6, in terms of the utilization rate of the pump. Once the initial pressure values of the system were 0.3 and 0.4 MPa, the reflux ratios were recommended to be less than 0.7, and 0.8, respectively. Finally, an optimal combination of target proportion and reflux ratio was achieved, according to the requirements for the tolerance of the pressure fluctuation in the target spraying system. When the initial pressure of the system was 0.2 MPa, the combination of the proportion of the target and the optimal reflux ratio were 1/5 and 0.5-0.6, 2/5 and 0.4-0.5, 3/5 and 0.2-0.3, or 4/5 and 0-0.1, respectively. When the initial pressure of the system was 0.3 MPa, the relationship groups between the proportion of the spraying target and the optimal reflux ratio were 1/5 and 0.6-0.7, 2/5 and 0.5-0.6, 3/5 and 0.2-0.4, or 4/5 and 0-0.1, respectively. When the initial pressure of the system was 0.4 MPa, the relationship groups between the proportion of the spraying target and the optimal reflux ratio interval were 1/5 and 0.7-0.8, 2/5 and 0.6-0.7, 3/5 and 0.4-0.5, or 4/5 and 0-0.3, respectively. This finding can provide a strong reference to optimize the precision target operation for the technical variables and working parameters in the plant protection spraying.
      2022,38(18):40-50, DOI: 10.11975/j.issn.1002-6819.2022.18.005
      Abstract:
      Abstract: Spray technology of plant protection unmanned aviation vehicle (UAV) is the highly efficient pesticide application in agricultural aviation, particularly for the zero growth of pesticides. The number, application area and scope of plant protection UAVs are ever increasing in China in the past 10 years. The application performance has also attracted much attention in recent years. Taking the DJI T30 plant protection UAV as the research object, this study aims to investigate the effect of rotor wind field of plant protection UAV and adjuvant on the droplet retention on the rice plant. The pure water, 1% Maifei, and 0.5% Maitu Target adjuvant formulation were taken as the spray formulation. The aviation wind tunnel and particle image velocimetry (PIV) were utilized to measure the spray flow field under the action of the rotor wind field of UAV. Some parameters were evaluated, including the dynamic surface tension, viscosity, and density in the formulations, as well as the dynamic contact angle of droplets on the surface of rice leaves. A quantitative analysis was made to clarify the effect of the rotor wind field on the droplets movement velocity and the retention of droplet on rice, the influence of adjuvant on formulation properties, the nozzle atomization performance, the droplet wetting and spreading performance on the rice leaves. A prediction model of droplet retention on the rice plant was established in the field of plant protection UAV spray technology, especially combining with the droplet interception and the droplet impact model. A field validation test was then conducted to verify the model. The results showed that the adjuvant formulation posed a significant effect on the droplet size, the formulation properties, the nozzle atomization performance, the wetting and spreading performance of the droplets on the surface of rice leaves, as well as the retention of the droplets on the rice plants. The surface tension values of 1% Maifei and 0.5% Maitu Target adjuvant formulations were reduced by 46.81%, and 62.21%, respectively, compared with water. The static contact angle of the droplets on the rice leaves was reduced by 27.74%, and 46.37%, respectively. By contrast, the retention on the per hectare rice increased by 798.93%, and 1 052.19%, respectively. The droplet size increased by at about 9.3%. There was a significant effect of UAV rotor wind field on the droplet movement velocity and the droplet retention on the rice. The droplet movement velocity increased significantly, after the rotor system was turned on and more quickly reached the stable velocity. When the UAV rotor speed increased from 0 to 1 000 r/min and then to 1 800 r/min, the droplet movement velocity increased by 366.67%, and 64.29% in turn. Compared with the droplet retention on the rice when the rotor system was turn off, the droplet retention of 1% Maifei and 0.5% Maitu Target adjuvant formulation decreased by 26.78%, and 29.75%, respectively, after the rotor system turn on. The accuracies of the retention model were 48.59%, 79.07%, and 79.29%, respectively, in order to predict the retention of the three solutions on the rice plants.
      2022,38(18):51-61, DOI: 10.11975/j.issn.1002-6819.2022.18.006
      Abstract:
      Abstract: Unmanned aerial vehicles (UAVs) have been widely used in rice direct seeding in recent years, due to the flexibility and high efficiency suitable for the terrain. Among them, UAV broadcast sowing has been one of the most UAV rice direct seeding, particularly with better seeding uniformity and work efficiency, compared with manual seeding. The broadcast sowing device can also be divided into the centrifugal disc and pneumatic types in China at present. However, the UAV broadcast sowing is easily affected by the rotor wind field, leading to uneven seeding. At the same time, the effect of seeding in the rows and holes can also result in air permeability and occurrence of diseases during the growth of rice in field management. In this study, a control system was designed for the rice shot seeding device in a flight controller order, in order to improve the uniformity and the accuracy of the seeding rate during UAV rice direct seeding. A UAV ground station function was also established to develop the experimental prototype. A closed-loop control was realized in the speed of the stepping motor using the Proportion Integral Derivative (PID). The calibration was then conducted to evaluate the excitation force of the vibration motor and the speed of the friction wheel motor. Finally, the seeding control program was designed to control the whole process of rice shot seeding using a Finite State Machine. The control functions included operation route planning, seeding rate calibration, parameter setting, seed remaining quantity display, and automatic seeding, in order to more easily realize the automatic operation of rice direct seeding. Taking three-fold pelleted rice seeds as the seeding objects, the seeding performance of the prototype was verified from three aspects: the accuracy of the seeding rate, the row effect, and seeding uniformity. The results showed that the average relative error of the seeding rate was less than 4% when the prototype flew at the speed of 1.0-2.5 m/s under the simulation. An excellent performance was achieved in the dynamic adjustment for the seeding control system, particularly with the relatively accurate seeding rate. Specifically, the average probability of seeds was 75.18% within the seed row width of 15 cm, when the prototype was seeding at the height of 2.0 m. By contrast, the average probability of seeds was higher than 80% within the seed row width of 12 cm, when the prototype seeding at the height of 1.0 and 1.5 m, indicating the better performance of the seeding row. Correspondingly, the working height of 1.5 m was preferred, in terms of safety. The average Coefficient of Variation (CV) of seeding uniformity was 20.51%-35.52% when the prototype worked at the height of 1.5 m with a speed of 0.5-2.0 m/s, and the seeding rate of three-fold pelleted rice seed of 90-150 kg/hm2 (corresponding to the seeding rate of naked seeds was 22.5-37.5 kg/hm2). It infers that the working speed greatly contributed to the seeding uniformity. Two field experiments were carried out, according to the preferred seeding parameters, where the relative errors of the seeding rate were 2.47% and 4.12%, respectively, the seeding uniformity CV values were 22.17% and 21.82%, respectively, and the seed breakage rates were 0.34% and 0.18%, respectively. The seeding control system fully met the control accuracy requirements of UAV rice direct seeding, according to the standard Technical specification of quality evaluation for the aerial broadcast seeder by remote control (standard NY/T 3881-2021). This finding can provide a strong reference for the UAV rice direct seeding.
      2022,38(18):62-71, DOI: 10.11975/j.issn.1002-6819.2022.18.007
      Abstract:
      Abstract: Sugarcane Cutting Quality (SCQ) has been one of the most important limiting factors in a sugarcane harvester. The sugarcane ratoons can be broken to reduce the budding rate, thus leading to the sugarcane yield decrease in the subsequent year. It is an extremely serious threat to the sugarcane yield for cost-saving planting. This study aims to investigate the effects of axial blade disk vibration and cutting parameters on the cutting quality of sugarcane harvesters. A series of cutting tests were performed on a self-developed test platform of a sugarcane harvester. The SCQ evaluating indexes were selected as the number of sugarcane cracks, the crack thickness, the crack depth, and the number of sugarcanes with broken ratoons. Then, the Comprehensive sugarcane Cutting Quality Evaluating Value (CCQEV) was calculated with the four parameters through the improved entropy as the test index. A regressive equation was established using single-factor tests, the orthogonal test, and the quadratic regressive orthogonal rotary combination test. The axial blade disk vibration was characterized by the vibration amplitude, frequency, and rotation velocity of the blade disk, together with the moving velocity of the sugarcane harvester, the blade installing angle, and their interactions on the SCQ. The results showed that there were strong linear negative relationships between the SCQ and the axial blade disk vibration amplitude, the SCQ and the axial blade disk vibration frequency. The significance coefficients of the axial blade disk vibration amplitude and frequency were 0.002 and 0.035, respectively. There were significant effects on the SCQ. By contrast, the significance coefficients of the sugarcane harvester moving velocity, the blade disk rotation velocity, and the blade disk installing angle were greater than 0.05, indicating no significant effect on the SCQ. The significance coefficients were 0.045 and 0.036 for the interaction of the axial blade disk vibration amplitude and frequency, as well as that of the axial blade disk vibration amplitude and the blade disk rotation velocity, respectively, indicating the significant effects on the SCQ. The significance coefficients of other interactions were greater than 0.05, indicating no significant effect on the SCQ. The significance levels were ranked in the descending order of the axial blade disk vibration amplitude > frequency > the sugarcane harvester moving velocity > the blade disk rotation velocity > the blade disk installing angle. There was a specific interaction between the axial blade disk vibration amplitude and frequency and that between the axial blade disk vibration amplitude and the blade disk rotation velocity. The greater the axial blade disk vibration amplitude and frequency were, the greater the CCQEV was, and the worse the SCQ was. The greater the axial blade disk vibration amplitude and the blade disk rotation velocity were, the greater the CCQEV was, and the worse the SCQ was. Moreover, a high-speed camera was used to capture the sugarcane-cutting process. Several times of cutting rather than one time were implemented in the sugarcane harvester, due to the axial blade disk vibration. There was an outstanding height difference between the cut-in points. The significance levels of the axial blade disk vibration amplitude and frequency were higher than those of the rest. There was also some effect of the interaction between the axial blade disk vibration amplitude and frequency on the SCQ. Therefore, an analysis was made to clarify the influencing mechanisms of the axial blade disk vibration amplitude and frequency as well as their interaction with the SCQ from the angle of the multi-cutting process. The vibration amplitude of sugarcane harvesters decreased to improve the natural frequencies of the body frame, whereas, the cutting system of sugarcane harvesters increased to avoid the resonance phenomenon. This finding can provide a strong reference for the higher SCQ in sugarcane harvesters.
      2022,38(18):72-80, DOI: 10.11975/j.issn.1002-6819.2022.18.008
      Abstract:
      Abstract: Damper throttle-slices of the cab relies generally on the finite element (FE) method for the stress characteristic analysis. It is still a lack of an analytical algorithm for the engineering application. This study aims to construct the analytical algorithm, the program interface of the stress characteristic analysis, the verification, and the thickness split design of throttle-slices of the cab for agricultural vehicles. The stress analytical formula was deduced using the stress influence coefficient. Then, a simple and practical analytical algorithm was proposed for the stress characteristic of the damper throttle-slices under the interval uniformly distributed pressure for cabs. The parameters were considered, such as the interval uniformly distributed pressure, the number of pieces, the thickness, the valve port radius, the upper gasket radius, and the lower gasket radius. The FE simulation and the theoretical analysis show that the analytical stress values of each slice at different radius positions under the working pressure were close to the simulation values for the circumferential stress, radial stress, and composite stress. Moreover, the relative deviations were all within 1.5%. The stress influence coefficient was obtained under the section uniform pressure. There were the same radial, circumferential, and composite stress influence coefficients of each slice, particularly independent of the slice thickness and section uniform pressure. Among them, the maximum influence coefficient occurred at the radius rd of the lower gasket. The stress analytical formulae revealed that the greater the thickness of each slice was, the greater the radial, circumferential, and composite stress values were. The analytical algorithm was used to establish the rapid stress check, the split design of the thickness, and the optimization design. The effectiveness of the analytical algorithm was further verified by the case study and the damper test. The throttle-slice fracture occurred before the number of tests reached 50000 times in the damper equipped with the original single slice. The damper that was assembled with the designed superimposed throttle-slices worked normally after more than 1.0 million times. Moreover, there was no slice fracture, indicating the effective thickness split of superposition slices in the damper. The algorithm effectively avoided many FEM limitations. There was the internal physical relationship between the structural parameters and the stress of the superimposed throttle-slices, the influence of the structural parameters on the stress, the rapid check of the stress intensity of the throttle-slices, and the disassembly design of the throttle-slices. The finding can provide a more practical and convenient effective tool for the relevant engineering and technical personnel.
      2022,38(18):81-91, DOI: 10.11975/j.issn.1002-6819.2022.18.009
      Abstract:
      Abstract: A seed metering device is closely related to the sowing quantity and crop yield in the planting process. Various detection methods have been used to improve the seeding performance for corn, and soybean precision seeding in recent years, such as photoelectric sensor detection, high-speed photography, and capacitance sensing. However, it is difficult to accurately count the high-frequency seed flow in the process of high-speed wheat sowing. In this study, a set of multi-channel parallel detection device was designed for the wheat seed flow with thin-surface light refraction. A "LED lamp beads + narrow slots" method was also proposed to generate the thin-surface light layer, in order to combine the convex lens refraction for the large effective detection area. According to the physical characteristics of wheat seeds, the seed stream shunt structure and the thin-surface LED narrow slot size were designed to determine the convex lens focal length and the key parameters of the sensing components. The multi-channel parallel detection and sensing were utilized to develop a multi-channel signal synchronous acquisition system for the multi-channel parallel detection device of the wheat seed flow with thin-surface light refraction. The seeding accuracy rate and frequency test was conducted to improve the detection accuracy. Among them, the error rule of the detection device was analyzed to construct the accuracy compensation model. The bench test showed that the normal seeding frequency range was 52.10~321.55Hz in the field, and the detection accuracy was not less than 96.68%, when the rotation speed of the seed metering device was 80~180r/min. The comparison test showed that high reliability was achieved with a detection accuracy of not less than 96.64%, when the seeding frequency was not more than 32.75Hz. The detection accuracy rate of the single-channel detection device decreased significantly in the frequency range of 49.40~320.75Hz during seed metering in the field, with the increase of seeding frequency. There was a stable detection accuracy rate of the multi-channel parallel detection device. Specifically, the minimum detection accuracy rates were 26.67%, and 96.53%, respectively, for single and multi-channel parallel detection devices. It infers that the multi-channel parallel detection improved the detection accuracy rate of wheat seeds after shunting. The field sowing test showed that the normal seeding frequency in the field was 67.65~323.95Hz at the operating speed of 2~9km/h, and the detection accuracy was higher than 95.28% in the detection device. Consequently, the detection device can be expected to detect the seeding frequency of the seeding device, the seeding amount of each channel, and the total seeding amount in real time. There was no influence of mechanical vibration, strong light, and soil dust on the detection device in the normal field wheat sowing. The detection device can provide effective support to accurately detect the high-frequency seed flow for the missed seeding detection and reseeding in high-speed wheat sowing.
      2022,38(18):92-102, DOI: 10.11975/j.issn.1002-6819.2022.18.010
      Abstract:
      Abstract: Rill erosion has been widely recognized as one of the most important forms of soil erosion on hillslopes. A crucial impact of rill erosion can be also posed on other erosion processes in downslope areas (e.g. gully head retreat). Morphological parameters of rills can provide useful indicators for the initiation and development of rill erosion. Previous studies have investigated the rill morphology in the erosion-deposition processes of hillslopes. However, those experiments were mainly taken in the laboratory. The physiochemical properties of backfill soil used in laboratory experiments are rather different from those of the natural soil in the field. The representative experiments were largely confined to the field erosion processes. It is necessary to explore the rill morphology associated with the erosion processes in the field. In this study, a series of field scouring experiments were conducted to determine the morphological development of rills under the hillslope erosion in the hilly and gully Loess Plateau. Five erosion plots were established on a natural slope of a small catchment (i.e. Xindiangou catchment), particularly with the input flow of hillslopes of 25, 40, 55, 70, and 85 L/min. Terrestrial Laser Scanning (TLS) was employed to acquire the ultra-high terrain information prior to the test. The various morphological parameters of rills were then derived, including the geometric indicators (length, width, and depth of cross sections), derived indicators (the ratio of width to depth, rill density, rill cleavage, and average rill depth), fractal dimension, bifurcation ratio, and geomorphic information entropy. A systematic investigation was also made to determine the effects of indicative morphological parameters on the cumulative erosion and deposition mass, as well as the sediment yield in the hillslope erosion. Results showed that: 1) The width and depth of the cross-sectional rills, the average rill depth and rill cleavage increased as the experiment progressed under all the flow conditions. The width-depth ratio was greatly varied in the input flow rate. The rills were primarily wide and shallow under the low flow condition (25 L/min), while narrow and deep under the moderately low (40 L/min) and high flow (85 L/min) conditions. There was a great change between the narrow-deep and wide-shallow manner under the moderate (55 L/min) and moderately-high (70 L/min) flow conditions. 2) The fractal dimension of rills was found to change slightly under the low flow condition, whereas, there was a considerable change under the rest of the input flow condition. The bifurcation ratio of rills increased under the moderate flow condition, while decreasing under the rest flow condition. Furthermore, the geomorphic information entropy varied significantly under the different flow conditions. However, there was the same change trend of geomorphological information entropy and sediment yield, indicating the dynamic changes of soil erosion. 3) The average rill length, the average depth of cross sections, and the derived average rill depth served as better indicators for the cumulative deposition mass, erosion mass, and sediment yield under the moderately low flow condition. The derived average rill depth was also for the cumulative erosion mass and cumulative sediment yield under the low flow condition. The average width of cross sections, average depth of cross sections, and derived average rill depth better indicated the cumulative erosion mass under the moderately high flow condition. In addition, there was a less significant relationship between the rill morphological parameters and cumulative erosion mass, deposition mass, and sediment yield, as the input flow increased. The finding can provide a strong reference to enhance the current understanding of the processes and mechanisms of hillslope erosion.
      2022,38(18):103-112, DOI: 10.11975/j.issn.1002-6819.2022.18.011
      Abstract:
      Abstract: Domestic wastewater is characterized by a single and stable source, good biodegradability, and low salinity, but high chemical oxygen demand (COD) in densely populated areas, such as campuses and communities. Therefore, there is a great potential to reuse, due to the low cost of treatment. A sustainable water recycling system can be expected to effectively alleviate the seasonal drought and water shortage with high quality in South China. However, accumulative irrigation with low-salinity reclaimed wastewater can cause a change in soil structure and hydraulic properties, and then result in irreversible damage to the soil. This study aims to explore the effects of low-salinity reclaimed wastewater irrigation on the hydraulic properties and microstructures in subtropical red soil. The campus's domestic wastewater was also treated for irrigation. Two irrigation modes were applied, including continuous reclaimed wastewater irrigation (WW), and alternating reclaimed wastewater and distilled water irrigation (AWW). In addition, the distilled water continuous irrigation was set as the control treatment (CK). An outdoor simulated soil column test was carried out to determine the soil salinity and sodicity, while the microstructure and hydraulic properties were under the irrigation modes. The interaction mechanism was proposed between the soil salinization, structure, and hydraulic properties. The results showed that: 1) Low-salinity reclaimed wastewater irrigation led to the decrease of water holding capacity and hydraulic conductivity of the red soil. Specifically, the water holding capacity under the WW treatment was higher than that under the AWW treatment, whereas, the unsaturated hydraulic conductivities were on the contrary. There was a small difference in water diffusivities under the two low-salinity reclaimed wastewater irrigation modes. 2) The low-salinity reclaimed wastewater decreased the field water holding capacity and wilting coefficient of the red soil, compared with the CK treatment. The available water increased by about 6.33% under the WW treatment, but decreased by 27.85% under the AWW treatment. 3) The low-salinity reclaimed wastewater increased the proportion of macropores. The proportion of effective pores and micropores increased by 1.3% and 5.0%, respectively under the WW treatment, and decreased by 4.3% and 1.1%, respectively under the AWW treatment. 4) Low-salinity reclaimed wastewater irrigation significantly increased the electrical conductivity (EC) value and Na+ concentration of the red soil (P<0.05), but significantly decreased the cation exchangeable capacity (CEC) (P<0.05), compared with the CK treatment. The soil exchangeable sodium percentage (ESP) and sodium adsorption ratio (SAR) under the AWW treatment were significantly higher by 142.4% and 120.3%, respectively (P<0.05) than that of the WW treatment, resulting in stronger clay dispersion. The soil particle morphology was also confirmed by scanning an electron microscope. 5) Principal component and Pearson correlation analysis were used to analyze the interaction between the soil structure, hydraulic properties, as well as soil salinity and sodicity. The field water holding capacity, wilting coefficient, available water, the proportion of effective pores, and micropores were significantly negatively correlated with the exchangeable Na+, ESP, and SAR, but significantly positively correlated with the CEC. The water with good quality (rainwater) can be involved in the process of low-salinity reclaimed wastewater irrigation, due to the high rainfall variability in subtropical regions, thus intensifying the destruction of reclaimed wastewater on the red soil. Therefore, much attention should be paid to monitoring the soil SAR, ESP, reclaimed water quality, and irrigation mode. The findings can provide a strong reference to formulate the reclaimed wastewater irrigation schedules in subtropical red soil areas.
      2022,38(18):113-121, DOI: 10.11975/j.issn.1002-6819.2022.18.012
      Abstract:
      Abstract: Aggregate structure and stability are related to a series of soil processes. However, it is still lacking in the microstructure and aggregate stability for the different types of zonal soil aggregates. In order to explore the changes of aggregate stability and pore structure for the different types of zonal soil aggregates and their relationship, this study aims to explore aggregate stability and its relevance to the pore structure characteristics in the different types of zonal soil. Five types of typical soils (Black, Brown, Cinnamon, Yellow-cinnamon, and Red soil) were selected as the research objects using geogenesis. The soil samples were collected separately from the Hailun (Heilongjiang), Shenyang (Liaoning), Luoyang (Henan), Xiangyang (Hubei), Changsha (Hunan), and Haikou (Hainan), according to the latitudinal direction zonality of soil distribution. The pore structure and MWD of aggregates were quantified using the CT scanning, wet sieving, and Le Bissonnais method..The results indicated that the water stability of aggregates was affected by the soil type and soil depth, and the values from low to high were Yellow-cinnamon soil, Cinnamon soil, Brown soil, Black soil and Red soil. The eluvial horizon in the Red soil was the highest (1.49 mm), and the parent material horizon in Yellow-cinnamon soil was the lowest (0.19 mm). The average mass diameter of the aggregates measured by LB method was ranked as MWDsw (slow wetting) >MWDws (shaking) >MWDfw (fast wetting), indicating that the dissipation and external mechanical failure were the main fragmentation mechanisms of aggregates. The resistance of soil aggregates to dissipation and fragmentation gradually decreased and then increased from north to south. Significant differences were found in the aggregate microstructure of different soil types. The porosity of the five zonal soil aggregates with different equivalent diameters showed a U-shaped variation from north to south, and the degree of variation decreased with the increase of soil depth. The total porosity and pore number were the highest for the Black soil aggregates (13.04%, 5143) and the lowest for the Yellow-cinnamon soil aggregates (5.61%, 1585). The pore sizes in most aggregates were observed to be 30-<75 μm. However, the pores larger than 100 μm were dominated in the Yellow-cinnamon soil, which was connected with the original particle arrangement and the low content of cementing material in the soil. The aggregate pore morphology was dominated by elongated pores with a few regular and irregular pores. The elongated pores decreased first and then increased from north to south. By contrast, an opposite trend was found in the irregular and regular pores. The aggregates stability showed significant positive correlations with the total porosity, total pore numbers, elongated porosity, <30, 30-75, 75-100, and >100 μm porosity, while inversely correlated with the regular and irregular porosity (P<0.01). Partial least squares regression (PLSR) showed that the water stability of aggregates was significantly correlated with the regular porosity,,mean pore shape factor, 75-100 μm porosity, and elongated porosity. The regular porosity, elongated porosity, 75-100 μm porosity and >100 μm porosity were proved to be the main controlling factors of MWDfw, MWDws and MWDsw. These results will help to deepen the understanding of the relationship between soil aggregates and pore characteristics, and better reveal the mechanism of soil processes.
      2022,38(18):122-129, DOI: 10.11975/j.issn.1002-6819.2022.18.013
      Abstract:
      Abstract: Spatial distribution of cultivated soil texture is generally crucial to the precision management of agriculture and farmland protection in black soil areas. Remote sensing technology can be an effective way to rapidly acquire the spatial distribution of soil texture. Taking the You Yi Farm in Heilongjiang Province of China as the study area, this study aims to evaluate the best time window for the remote sensing inversion of soil texture in the cultivated land. 25 Sentinel-2 images were selected in the study area from 2019 to 2021. The band and spectral index of each image were input into the random forest model, in order to establish a remote sensing inversion model of soil texture. A comparison was made on the model accuracy of soil texture inversion from the images in different periods. The most suitable image was determined for the remote sensing inversion of soil texture. The spatial distribution of soil texture was obtained to evaluate the accuracy of soil texture inversion from the Sentinel-2 multi-spectral images on different dates. The results showed that: 1) From the visible light to short wave infrared 1 (1 565-1 655nm) spectral reflectance increased with the increase of wavelength, from the short wave infrared 1 to short wave infrared 2 (2 100-2 280nm) spectral reflectance decreased significantly. The spectral reflectance decreased with the increase of silt and clay content, whereas there was an increase with the increase of sand content. 2) There was the maximum accuracy of inversion model in the silt and sand on May 7, 2020 (the coefficient of determination (R2) of silt was 0.785 in 25 Sentinel-2 images, and Root Mean Square Error (RMSE) was 6.697%; the R2 of sand was 0.776, and RMSE was 8.296 %). The maximum accuracy was also achieved in the clay inversion model on May 3, 2019 (R2=0.776, RMSE=1.6%). 3) The appropriate time of satellite images was selected as an important impact on soil texture inversion. The best time window was from late April to mid-May in the study area. The time window and good-quality spectral data were obtained to develop a stable spectral model for the spatial distribution of soil texture. 4) Different inversion accuracy of soil texture were obtained using the 25 Sentinel-2 images from 2019 to 2021. This data was attributed to the soil water content and straw mulching. 5) The silt and clay particles were distributed more in the northeast, north, and south, and less in the middle and southwest of the study area. There was the opposite trend of the sand, especially the generally high sand content in the middle of the study area. Therefore, the high-precision remote sensing inversion model was achieved in the soil texture. The finding can provide the key technologies for regional soil texture mapping and farmland protection in the black soil areas.
      2022,38(18):130-137, DOI: 10.11975/j.issn.1002-6819.2022.18.014
      Abstract:
      Abstract: Soil organic matter (SOM) is the carrier of soil organic carbon in the crop system. This component of soil solid matter is one of the core elements to evaluate soil fertility quality in agriculture and land management. An accurate and efficient acquisition of SOM content can greatly contribute to the quality grading of cultivated land. High-resolution remote sensing and google earth engine (GEE) can serve as the computing platform for the efficient inversion of SOM. Much effort has been made on the SOM prediction model and the spatial distribution map. However, it is still lacking in the appropriate satellite data sources and prediction algorithms to accurately predict the SOM content in specific regions. In this study, the accurate SOC content was predicted in the cultivated land using GEE and machine learning. The Sentinel-2A MSI and the Landsat8 OLI data were collected in the Gaocheng District, Shijiazhuang City, Hebei Province, China. The main data sources were also combined with the Sentinel-1 SAR, ECMWF/ERA5 meteorological, and USGS/SRTMGL1_003 elevation data. The variable feature sets of the spectral band were constructed, including the vegetable index (NDVI, RI, EVI, SATVI, and BI), radar feature (Sentinel-1 VV, and Sentinel-1 VH), terrain feature (slope, aspect, and elevation), and climate feature (annual precipitation, and average annual temperature). Six and five models were constructed using the Sentinel-2 and Landsat8 variable datasets, respectively. Random Forest (RF), Gradient Boosting Decision Tree (GBDT), and Support Vector Machine (SVM) were utilized to predict the SOM on the GEE platform. The predictive performances of three machine learning methods were determined for a high-precision spatial distribution map for the SOM inversion. The accuracy of the prediction model was then evaluated using the determination coefficient (R2) and the root mean square error (RMSE). The results show that: (1) the R2 and RMSE values of the model using the Sentinel-2A were better than those using the Landsat8. The Sentinel-2A model performed better than the Landsat8 model in the predicting SOM content. The best performance (R2=0.759, RMSE=2.852 g/kg) was achieved in the omnivariate model of Sentinel-2A under the GBDT. (2) The maximum improvement of 9.752% was obtained in model A-1 with the red edge band, compared with model A-0. This difference was attributed to the inclusion of four red edge bands (B5, B6, B7, and B8A) in model A-1. The addition of red edge bands greatly improved the prediction accuracy of the model, particularly with the effective spectral information for the SOM inversion. (3) The red edge band, vegetable index, Sentinel-1A radar features, terrain factors, and climate variables greatly contributed to the prediction accuracy of SOM from the perspective of different variable feature combinations. (4) The GBDT was better applied to the SOM prediction in the study area. The resultant SOM map was used to accurately characterize the SOM spatial distribution. The test data was verified for high accuracy, each group of which was an excellent consistency in the image, indicating the reliable SOM inversion. Therefore, the Sentinel-2A MSI data presented outstanding advantages over the Landsat8 OLI, due to the higher spectral and spatial resolutions. The combination of GBDT, Sentinel-2A, and GEE can be an effective way to predict the SOM map. Each prediction factor can also provide valuable information for the prediction of SOM content.
      2022,38(18):138-146, DOI: 10.11975/j.issn.1002-6819.2022.18.015
      Abstract:
      Abstract: The coastal reclamation area of Jiangsu, China is characterized by its flat topography and concentrated rainfall under the monsoon climatic condition. The farmland soils reclaimed from the coastal mudflats have high initial salt content, poor structure and low organic matter content. Improving the soil quality to increase land productivity is very important to ensure agricultural production of the reclamation area. Construction of subsurface drainage system can speed up soil water movement, thus achieve the soil desalination goal more quickly at the initial stages of land reclamation, and later protect crops from excessive water stress during the growing period. But the effect of subsurface drainage on soil organic matter accumulation in the reclamation area remains unclear, the carbon sequestration effect of agricultural measures such as crop rotation and straw returning in subsurface drained fields needs to be explored. Based on the meteorological, soil and crop information of a subsurface drainage experimental base near Dongtai, Jiangsu, China, this study examined the effect of crop rotation and straw returning method on the accumulation process of soil organic carbon (SOC) in subsurface drained fields through combined use of the field hydrological model-DRAINMOD and soil organic carbon model-DNDC (Denitrification-Decomposition Model). The simulation results showed that for the coastal reclamation areas that has shallow groundwater depth, the DNDC model better predicted the accumulation process of soil organic carbon based on the DRAINMOD predicted water table under subsurface drainage. Taking the measured current soil organic carbon content of the study area (2.95 g/kg) as the initial value, continued 32 year simulations of different crop rotations by the DNDC showed that, winter wheat and corn rotation combined with full return of straw/stalks to the field significantly increased the soil organic carbon content to 17.85 g/kg; adding alfalfa as a green manure to the rotation produced good carbon sequestration effect due to the increased proportion of activated carbon, the soil organic carbon content was increased to 16.12 g/kg. These results indicate that crop rotations have good carbon sequestration effect, which can gradually build up the soil organic carbon pool in the infertile soil. The simulation results also showed that, comparing with the conventional drainage system of less intensive open ditches in the study area, the subsurface drainage system can lower the field water table more rapidly, and the simulated farmland SOC accumulation is greater due to the increased biomass (or higher crop yields) under better soil drainage condition. In the rainy season of wet years, more frequent water table fluctuations under the subsurface drainage resulted in alternation of soil drying and wetting condition, leading to intensive soil respiration that caused some SOC losses. To avoid the adverse effect of intensive soil respiration on soil carbon loss due to excessive drainage, controlled drainage may be adopted to lower field drainage intensity according to crop drainage requirement. Findings from this research may provide reference to soil quality improvement in the study area and the similar regions for agricultural carbon neutralization.
      2022,38(18):147-155, DOI: 10.11975/j.issn.1002-6819.2022.18.016
      Abstract:
      Abstract: Soil water content is one of the essential indicators for crop growth. The main source of soil water is then the rainfall in the rainfed agricultural region. Among them, tillage management is one of the important factors for the distribution of rainfall above and below ground, which is closely related to the dynamics of soil water content. However, it is still unclear in the response of soil water content to rainfall events under different tillage management. The objective of this study is to determine the effect of tillage management on the response characteristics of soil water content to rainfall events on Mollisol. The long-standing tillage experiment was carried out in the spring of 2011 at the Lishu Experiment Station of China Agricultural University (43°16′ N, 124°26′ E), located in Lishu, Jilin Province, China. The time-domain reflectometer (TDR) probes were installed in the soil depths of 2.5, 5, 10, 20, 30, 40, and 50 cm under no-tillage (NT), and conventional tillage (CT) treatments, in order to monitor the dynamics of soil water content. Some parameters were used to quantify the dynamic response of soil water content under NT and CT to rainfall events, including the accumulated soil water content increment (ASWI), the ratio of accumulated soil water content increment between adjacent soil layers (RSWI), the maximum (Smax) and mean (Smean) rate or the slope of a soil water content curve under rainfall events, the difference of the soil water content response time between two adjacent soil layers (DRTlayer), the difference of the soil water content response time and rainfall onset time (DRTrainfall), and the duration of soil water response to rainfall events (DUR). According to the rainfall duration and intensity, 24 rainfall events were divided into three categories with the K-means clustering: the rainfall events Ⅰ with the large rainfall (25.53 mm) and long rainfall duration (15.92 h), the rainfall events Ⅱ with the small rainfall (5.42 mm) and long rainfall duration (2.00 h), and the rainfall events Ⅲ with the large rainfall (19.22 mm), short rainfall duration (4.92 h) and heavy rainfall intensity (0.29 mm min-1). The results indicated that: 1) The ASWI of NT was significantly lower than that of CT under 0-2.5, 2.5-5, and 5-10 cm soil layer, due to the lower soil water content of CT in the surface layer. 2) The ASWI of CT decreased with the increase of soil depth, while remaining stable under the NT. 3) The RSWI of NT was over 100% under the most rainfall conditions, whereas less than 100% under the CT. The values of Smax and Smean of NT were generally higher than those of CT. Moreover, there was a high frequency of negative abnormal values and average values of DRTlayer under the NT management at the high rainfall intensity. It infers that the activities of preferential flow were greater under the NT management. Therefore, the soil water content under the NT presented a stronger response to extreme rainfall. Furthermore, there was no significant influence of soil bulk density on the soil water infiltration, due to the well-developed biological pores network. Therefore, the rainfall can be percolated into the soil, as the extreme rainfall continued, which was beneficial to reduce surface runoff and soil erosion.
      2022,38(18):156-166, DOI: 10.11975/j.issn.1002-6819.2022.18.017
      Abstract:
      Abstract: Efficient utilization of water and soil resources has been critical under the changing environmental conditions in the arid oasis. It is very necessary to understand the temporal and spatial evolution of crop planting structure and crop water demand satisfaction degree (i.e. the ratio of supplied water amount to water demand) for the efficient use of water and soil resources and sustainable development of agriculture in the arid Manas River Basin, including the largest typically agricultural oasis in Xinjiang of western China. In this study, a classification model was established for the surface features via the remote sensing inversion using the Google Earth Engine (GEE) cloud computing platform, together with the coupled Simple Non-Iterative Clustering super pixel image segmentation and Random Forest classifier. The classification model was verified using a regional survey at the fixing sampling positions with the GPS. Then, the model was applied to the crop planting structure in the Manas River Basin over the past 20 years from 2000 to 2020. The Penman-Monteith formula was used to calculate the effective precipitation in the irrigation schedule from the regional survey and the water demand of the main crop (drip-irrigated cotton under film mulch). A systematic investigation was made to explore the effect of the crop planting structure on the irrigation water supply and water demand satisfaction degree for the drip-irrigated cotton under film mulch. Results showed that the new remote sensing inversion model was reliable for the surface feature classification in the Manas River Basin, with an annual average overall accuracy of 90%. The planting crop of the basin was dominated by drip-irrigated and film-mulched cotton, accounting for more than 80% of the total planting area in all the last 21 years, and mainly distributed in the midstream and downstream regions, where the climate and hydrological conditions were more suitable for the cotton growth. Beneficial from the water-saving and salinization-alleviating characteristics of drip irrigation under the film mulch, a lot of mildly- and moderately- or even severely-salinized wastelands were continuously reclaimed into the cotton fields, resulting in an increased rate of about 101 km2 yr-1 in the area. There was an ever-increasing prominent contradiction between the expansion of cotton fields and the limited supply of irrigation water resources, particularly with a significant declining trend in the water demand satisfaction degree for cotton. The irrigation amount and water demand satisfaction degree in downstream were generally lower than those in the midstream, due to the low irrigation and drainage conditions, especially when the crop was in the peak water demand during the summer irrigation period. The average water demand satisfaction degree decreased even to less than 53% over the entire basin in the whole irrigation period by 2020. It is a high demand to optimize the crop planting structure in the arid Manas River Basin.
      2022,38(18):167-175, DOI: 10.11975/j.issn.1002-6819.2022.18.018
      Abstract:
      Abstract: Net Primary Productivity (NPP) of vegetation is considered one of the main indicators for the carbon fixation capacity of ecosystems in the carbon cycle, particularly for the adaptability of ecosystems to climate change. Among them, the typical phenological factors are the key components of the ecosystem functions in many biological processes, including the Start of the Growing Season (SOS), End of the Growing Season (EOS), and Length of the Growing Season (LOS). However, it is still lacking in the relative importance of phenological and climatic factors to the NPP. The contribution of phenological factors (SOS, EOS, and LOS) to the interannual change of NPP has not been well quantified, due to the complex ecosystem. Therefore, this study aims to extract the phenological information of vegetation using a Cardiovascular-Ames-Stanford Approach (CASA) model, in order to examine the characteristics of spatial and temporal changes of NPP. The Normalized Vegetation Index (NDVI) was used from the MODIS data in Beijing from 2001 to 2020. The interaction between meteorological factors, phenological changes, and NPP was then explored using linear regression, trend analysis, and structural equation modeling. The results show that the SOS was gradually advanced by 0.53 each year on average from 2001 to 2020 over more than 70% of the regions, whereas, the EOS was gradually postponed by an average of 0.51 days per year over more than 90% of the regions. The NPP vegetation increased significantly from 2001 to 2020 (P < 0.05), where the growth rate was greater in the last 10 years than that in the first 10 years. The average annual NPP value was greater in the northern region than that in the southern. There was a strong correlation between the phenological factors (SOS, and LOS) and NPP (P<0.05). The pixel-by-pixel analysis also found that the SOS, LOS, and NPP were significantly correlated in the areas with more than 75% vegetation coverage. The NPP was also significantly affected by the advance of SOS and extension of LOS (P<0.05). The NPP increased by 3.74 g/m2 for every single day advance of SOS, while by 2.56 g/m2 for every single day extension of LOS. There was no significant effect of the EOS delay in autumn on the NPP. A coupling effect of phenology and climatic factors varied with the season. There was a greater indirect effect of climate through changing phenology (SOS and EOS) on the NPP in spring and autumn, compared with the direct. By contrast, the NPP was more directly affected by climatic factors, temperature, and rainfall in summer. In conclusion, the spring phenological change was an important driving factor for the interannual variation in the NPP. Furthermore, the annual NPP increased to the phenological advance. The findings can also provide an important supplement to determine the vegetation productivity response to the climate change in urban areas.
      2022,38(18):176-183, DOI: 10.11975/j.issn.1002-6819.2022.18.019
      Abstract:
      Abstract: Field-road trajectory segmentation (FRTS) is one of the important tasks of agricultural machinery. A sequence of field-road segments of a trajectory can be automatically divided for the big data in precision agriculture. The parameter of the FRTS model can also determine the segmentation accuracy and precision. However, the traditional parameter selection cannot obtain the superior solution, limiting the segmentation performance of the model. Therefore, this study aims to investigate the performance improvement of the FRTS model from the perspective of parameter optimization. Two aspects were mainly contained as follows. Firstly, the metaheuristic algorithms were used to determine the parameter configuration of the model. The classification accuracy was considered as an objective to transform the parameter into a single-objective optimization. Specifically, the parameter structure of the model was abstracted as the searched individual of the optimization. The reasonable fitness function was set, according to the metrics of FRTS evaluation. Then, the fitness was used to evaluate the search of the individual in the solution space. The location of the searched individual was also continuously adjusted, according to the calculation rules of the optimization. As such, the global optimal parameter structure was achieved to converge. Secondly, a multiplex oscillation slime mould algorithm (MOSMA) was proposed to realize the parameter optimization with the nonlinear characteristics and multiple locally optimal solutions. A dynamic guidance strategy was also established to adaptively change the individual movement for the better exploitation capability of the model, according to the search process of the population. Then, a strategy (called multivariate oscillation) was proposed to improve the segmentation performance and exploration capability of the model. Different search paths were utilized to produce multiple oscillations before the individual moves, and the priori rule was then to evaluate the qualities of paths. As such, the path with the highest quality was selected to move. The synergy of the two strategies enhanced the optimization capability of the model. Dynamic guidance and a multiplex oscillation strategy enhanced the oscillation contraction patterns of the slime mould and the process of the cytoplasm flows, thereby improving the optimization performance of the model. The experiments were also performed on real agricultural trajectory datasets with different sampling frequencies. A comparison was then made with the grid search (GS) and particle swarm optimization (PSO) to validate the effectiveness of the model. The experiment results show that the new optimization effectively improved the accuracy and performance of the FRTS model using direction distribution (BDFRTS). The average accuracy of the MOSMA-BDFRTS on the high-density trajectory data increased by 25.20% and 28.03%, compared with the GS-BDFRTS and PSO-BDFRTS. The MOSMA-BDFRTS was achieved in the more competitive performance on the low-density trajectory data. The average accuracy of segmentation was also improved by 17.68% and 14.08 %. Among them, the segmentation accuracy of the best-performing trajectory sample was improved from 44.26% to 89.58%, whereas, the worst-performing trajectory sample was improved from 93.6% to 96.43%. A generalized parameter optimization solution was achieved for the FRTS models, which can be applied directly to the other types of models. The finding can also provide a strong reference for the movement trajectory segmentation in agricultural machinery.
      2022,38(18):184-194, DOI: 10.11975/j.issn.1002-6819.2022.18.020
      Abstract:
      Abstract: Pine Wilt Disease (PWD), a devastating pine tree disease, has caused a serious impact on the national biosecurity, ecological security, and forestry economy. In this study, a systematic review of the research progress was made on the history of remote sensing monitoring of PWD in recent years under the object level classification of remote sensing monitoring using the literature retrieved and screened by the Web of Science (WoS) and China National Knowledge Infrastructure (CNKI). Some suggestions and outlooks were also proposed for the existing problems, which could provide reference for the technical reference and auxiliary decision-making on forestry. It was found that: 1) About 70% of the literature was published in the research field after 2017. It infers that the remote sensing monitoring of pine wood nematode has been a research hotspot in the past five years. 2) From the viewpoint of the carrier platform, the satellite, airborne, and ground datasets accounted for 17.1%, 75.6%, and 7.3% of the research data on the remote sensing monitoring of PWD, respectively. Particularly, there was the vast majority of airborne data represented by unmanned aerial vehicles (UAV). From the viewpoint of data spectral type, 44%, 34.1%, 17.1%, and 4.9% of the studies used RGB, multispectral, hyperspectral, and LIDAR data, respectively. Therefore, the RGB and multispectral datasets were dominated in the remote sensing monitoring of PWD. 3) Single plants were mainly used as the granularity of remote sensing monitoring of PWD. The diseased trees were classified into the two, three, four, five, and six categories, accounting for 53%, 23%, 15%, 6%, and 3%, respectively. There were diverse category systems with vague relationships between them. 4) Machine learning and deep learning dominated the remote sensing monitoring of PWD. Furthermore, machine learning and deep learning shared their own advantages and fail to replace each other. Furthermore, the aerospace remote sensing survey with the UAV and satellite sensors as the data sources greatly improved the efficiency of PWD epidemic increment control and stock abatement work. However, the following challenges remained: 1) A single data source cannot fully meet the harsh requirement of large-scale and fine-grained monitoring in recent years. 2) Disorganized disease classification systems led to the irregularity and specification of data for machine learning and deep learning. 3) It is still lacking in long-term series monitoring with the high-time resolution. Finally, three recommendations were proposed for the future real-time and intelligent remote sensing monitoring of PWD: 1) To explore the satellite and aerial data fusion for the large-scale and fine-grained disease monitoring; 2) To clarify the disease monitoring category system, and then to construct the relevant spectral library and sample library datasets; 3) To develop the high-frequency and long-time series remote sensing monitoring products for a general release mechanism for the PWD.
      2022,38(18):195-203, DOI: 10.11975/j.issn.1002-6819.2022.18.021
      Abstract:
      Abstract: Detection of fruit images has been one of the most important steps for automatic picking robots. There are many factors that make strawberry detection difficult in an orchard, such as the complex background, fruit occlusion, and small target fruit. In this study, an improved detection model with the YOLOv4-Tiny was proposed to rapidly and accurately recognize the strawberries in the greenhouse for the high detection accuracy of small targets in an orchard. Firstly, the GhostNet lightweight network was adopted to replace the backbone CSPDarkNet53-tiny for the feature extraction, which significantly reduced the parameters and computation of the model. Convolution Block Attention Module (CBAM) with the spatial information was embedded into the Ghost Bottleneck module instead of the original Squeeze-and-Excitation (SE) attention, in order to improve the feature extraction capability. Secondly, the Spatial Pyramid Pooling (SPP) module was introduced in the neck network structure, and then to carry out the maximum pooling operation with three pooling kernels (5×5, 9×9, 13×13). Feature Pyramid Network (FPN) structure was adopted to improve the detection accuracy of small target strawberries. Finally, the Efficient Intersection over Union Loss (EIoU Loss) was used to separate the influence factors of aspect ratio, and then calculate the length and width of the target frame and anchor box. As such, the convergence speed was faster with higher regression accuracy than before. The original data set was collected, consisting of 841 strawberry images with a complex background in the greenhouse. Data enhancement was carried out for the training, the verification, and the test set, in order to improve the generalization ability of the model. The experimental results showed that the average accuracy of the improved YOLOv4-Tiny model in the test set was 92.62%, which was 5.77 percentage points higher than the original one. The average detection time of each image was 5.63ms, and the final model size was only 4.68MB. The average accuracies of the improved model were 9.11, 4.80, 2.26, 1.22, and 1.91 percentage points higher, while the F1 scores were 0.08, 0.05, 0.03, 0.01, and 0.03 higher than those of the SSD, CenterNet, YOLOv3, YOLOv4, and YOLOv5s target detection networks. The improved YOLOv4-Tiny model was much smaller than the SSD, CenterNet, YOLOv3, YOLOv4, where the network structure size was only 1/3 of YOLOv5s. The average detection speed of each image was only 5.63ms, which was reduced by 5.57, 7.14, 9.20, 15.99, and 2.16ms, respectively. Therefore, the improved YOLOv4-Tiny model can fully meet the requirements of high precision and real-time detection of strawberry fruits under the background of the orchard in the greenhouse. The finding can provide an effective way for the accurate detection of strawberry fruits in a complex environment using picking robots.
      2022,38(18):204-211, DOI: 10.11975/j.issn.1002-6819.2022.18.022
      Abstract:
      Abstract: Bagged citrus has triggered a dramatic decrease in the texture details, due to the shape evolution from round to stripping during processing. A great challenge has also been posed in citrus object detection, depending mainly on the number of labeled samples. In this study, an accurate and rapid detection method was proposed for the bagged citrus based on the Teacher-student model with a Strip Pooling Module (SPM)-YOLOv5 algorithm. The images of bagged citrus were collected in the Paidengte Agricultural Science and Technology Demonstration Park, Bishan District, Chongqing of China. The data set of bagged citrus was generated by the image cleaning, enhancement, and labelling tags. Firstly, the stripe attention module was added to the backbone network of YOLOv5. Much attention of the model was drawn to the striped bagged citrus and branches, in order to reduce the average pooling focus on a large number of unrelated areas. Besides, the SPM was integrated into the backbone network of YOLOv5. Among them, the horizontal and vertical pooling were focused on the encoding remote context along the horizontal or vertical spatial dimensions. The SPM was also used to solve the overlapping of each spatial position in the feature map. Specifically, the global horizontal and vertical information was encoded to balance the own weight for the feature modification, in order to effectively expand the receptive field of the backbone network. As such, the SPM was different from the global pooling that only focused on one area. The striped pooling was utilized to easily realize the characteristics of discrete distribution in the horizontal and vertical pooling for a long time. The stripe kernel was used for the feature extraction in the horizontal and vertical directions, in order to capture more local details in the stripe pooling. In doing so, the strip pooling was different from the traditional space pooling that depended on the square core. At the same time, the Teacher-student model was semi-supervised to calculate the consistency loss for the unlabeled samples. Two stages were mainly composed of the model. The first stage was Burn-In. The effective pseudo tags were generated for the teacher model to be well initialized. Therefore, the teacher model was then initialized with the labeled samples. The second stage was mutual learning between the teachers and students. The model was trained using the labeled and unlabeled samples. The robustness of the model was enhanced to reduce the consistency loss in the training process. The target detection was performed on the unlabeled samples, in order to improve the performance of the model and reduce the dependence on labeled samples. The experimental results demonstrated that the average precision of SPM-YOLOv5 for the bagged citrus and branch detection was 77.4% and 53.5%, respectively, which was 7.5% and 7.6% higher than that of YOLOv5. The precision and recall rate of bagged citrus detection reached 94% and 76.2%, respectively. More importantly, the precision of SPM-YOLOv5 based on the Teacher-student model reached 82.6% under the condition of occlusion and overlapping. Meanwhile, the best detection was achieved in 1500 unlabeled and 500 labeled samples. Therefore, the SPM-YOLOv5 based on the Teacher-student model can be expected to detect bagged citrus with higher accuracy and faster speed than before.
      2022,38(18):212-221, DOI: 10.11975/j.issn.1002-6819.2022.18.023
      Abstract:
      Abstract: Environmental quality of swine gestation barns can bring a significant impact on the fertility of breeding sows. Therefore, it is crucial to accurately evaluate the environmental quality and then timely trim the conditions, particularly for high breeding efficiency under less environmental stress. In this study, an environmental quality evaluation model of swine gestation barns was proposed using the Simulated Annealing-Particle Swarm Optimization-Least Absolute Shrinkage and Selection Operator-Back Propagation (SA-PSO-LASSO-BP) neural network (NN). Firstly, nine parameters were identified using the Chinese National Criteria. A data collection system was then established to collect the environmental data. Secondly, a Kalman filter and a batch estimation adaptive weighted fusion algorithm were introduced to fuse the multi-node environmental data, in order to remove the errors and redundant data from the data collection. Thirdly, a least absolute shrinkage and selection operator (LASSO) regression model was selected for the feature selection. There were four feature factors that were closely related to environmental quality, including temperature, relative humidity, NH3 concentration, and CO2 concentration. Meanwhile, the structural parameters were optimized in the BP-NN , where the number of hidden layer nodes was determined to be 11. Finally, the initial weights and threshold values of the BP NN were optimized by the SA-PSO for the ultimate evaluation model. A comparison was made on the several NNs to verify the evaluation performance of the SA-PSO-LASSO-BP NN, including the BP, LASSO-BP, Genetic Algorithm-LASSO-BP (GA-LASSO-BP), Sparrow Search Algorithm-LASSO-BP (SSA-LASSO-BP), and the PSO-LASSO-BP NN. The training results proved that the convergence accuracy and rate of the SA-PSO-LASSO-BP network were significantly improved by the feature selection with the LASSO regression model. The number of iterations and the network errors of the LASSO-BP NN decreased by 29.9% and 17.78%, respectively, compared with the BP NN. In terms of feature selection, the SA-PSO algorithm implemented by the SA-PSO-LASSO-BP NN was utilized to optimize the initial weights and thresholds of the network, in order to further improve the convergence accuracy and rate of the model. Compared with the PSO-LASSO-BP NN, the number of iterations, running time, and network error were reduced by 54.43%, 17.24%, and 8.33%, respectively. The validation test indicated that the best performance of the model was achieved, with the coefficient of determination (R2) of 0.918, an overall accuracy of 95.85%, the Mean Absolute Error (MAE) of 0.037, and the Root Mean Squared Error (RMSE) of 0.176. Consequently, the SA-PSO-LASSO-BP NN model can better fit the nonlinear relationship between complex environmental factors and environmental quality. The finding can serve as a strong reference for the environmental quality evaluation of swine gestation barns.
      2022,38(18):222-228, DOI: 10.11975/j.issn.1002-6819.2022.18.024
      Abstract:
      Abstract: Interfacial photothermal evaporation is expected to resolve the water shortage, inconvenient water intake, and low water quality in most rural areas. However, the high material cost, complex preparation process, and low evaporation rate of the solar absorber are restricting the development of this novel technique. It has been reported that adjusting the water supply rate on the light-absorbing surface is an important approach to developing an efficient and continuous interfacial photothermal evaporator. In this work, the naturally evolved, porous, and photothermal material of pinus sylvestris was prepared with simple preparation, strong hydrophilicity, and evaporation rate close to the theoretical limit using a one-step hydrothermal method. Subsequently, the solar-driven interfacial water evaporation experiments were conducted to clarify the effects of carbonization degree and water supply height of the photothermal material on the interfacial evaporation performance. The surface temperature and evaporation reduction were considered at the different carbonization temperatures (100, 125, 150, 175, and 200℃), carbonization time (2, 4, 6, 8, 10, and 12 h), and the heights of the photothermal material (5, 10, and 15 mm). The underlying mechanism was then determined using the microstructure, element distribution, capillary water transport, and heat transfer. Importantly, the enhanced interfacial water evaporation was enabled by the carbonized wood. The results showed that the original pore structure of the log was retained with the rough surface formed by carbon microspheres after the mild carbonization process. There was a 2.3 ℃ temperature rise of the evaporation surface, particularly beneficial to the increase of light absorption. Moreover, the proportion of the C-H/C-C bond in the log (51.5%) was higher than that of the C-O-C/C-OH bond (37.7%), whereas, the proportion of the C-H/C-C bond (37.8%) in the carbonized wood was lower than those. It infers that the carbonization process greatly contributed to the log with more hydrophilic groups. This was because the parts of hydrophobic lignin and hemicellulose were removed during carbonization. Therefore, the climbing height of water in the carbonized wood increased from 4.2 to 22.3 mm during the climbing time (120 s). By contrast, the rising heights of water were 3.1 and 9.0 mm in the log and carbonized wood, respectively, indicating the weak capacity of transverse water transport. The data also agreed well with the classical Lucas-Washburn imbibition model. The steady-state evaporation rate of the carbonized wood-based evaporator increased by 130% and 28%, respectively, compared with the water- and log-configured evaporators. The maximum evaporation rate reached 1.24 kg/(m2?h) at the temperature of 200 ℃ after 8 h carbonization. It was noted that the excessive carbonization formed a bright and smooth surface, leading to the reflection loss of incident light with the reduced surface temperature of the evaporator. As a result, the evaporation rate dropped significantly. More importantly, the sidewall height of the material reduced the average temperature of the evaporation surface, resulting in the reduction of radiative and convective heat losses from the evaporator to the surroundings, thus improving the evaporation rate. Once the sidewall height was 15 mm, the evaporation rate reached 1.48 kg/(m2?h), and the corresponding solar-to-vapor conversion efficiency was 66.2%. This finding can also provide an important reference for the utilization of agricultural and forestry wastes, particularly for the heat-moisture balance during solar-driven interfacial water evaporation.
      2022,38(18):229-236, DOI: 10.11975/j.issn.1002-6819.2022.18.025
      Abstract:
      Abstract: Infrared thermography is a promising technology for crop water status assessment. Effective information can be acquired for the timely formulation of regulated deficit irrigation strategies. However, it is very necessary to optimize the assessment under field conditions, especially under variable environmental conditions (daily and seasonal). Besides, simplicity and robustness are the basis of thermography applicability in the field. In this study, the optimal thermal indicator and the best acquisition were proposed for the monitoring daily period using thermal infrared imaging. The trial was carried out in the solar greenhouse of the National field scientific observation and research station on efficient water use of oasis agriculture in Wuwei from May to September 2021. The tomato plants (Fenxi 5) were selected as the research object. Two irrigation treatments were set: W1-full irrigation (control); W2-deficit irrigation (50% of the control). Firstly, three groups of dry and wet reference planes were selected to calculate the thermal indicators, including the red fabric, green fabric, and artificial spray medium. Subsequently, the performance was evaluated on the four common thermal indicators (Crop Water Stress Index ? CWSI, Relative Stomatal Conductance Index ? IG, leaf temperature ? Tleaf, and the difference between Tleaf and surrounding air ? ΔTleaf-air) in the plant water status diagnosis. Finally, the optimal daily period of thermal imagery acquisition was determined for the tomato plants. The results showed that there were significant correlations of the normalized indices (CWSI and IG) with the plant physiological indicators, such as stomatal conductance (gs), photosynthetic rate (An), and leaf water potential. The leaf temperature Tleaf was also used in a stable planting environment to determine whether the plant was dehydrated or not. There were no significant correlations between the ΔTleaf-air and the physiological indicators of tomato plants under two water treatments. The correlations between the CWSI and IG obtained by the red fabric as the reference plane with the gs, An, and leaf water potential were the most significant among the three groups of reference planes, where the determination coefficients were 0.687, 0.698, 0.669 and 0.707, 0.661, 0.663 respectively. By contrast, the thermal indicators obtained by the green fabric as the reference plane showed a weaker correlation with the gs, An, and leaf water potential, where the determination coefficients were 0.631, 0.655, 0.615, and 0.652, 0.634, 0.638 respectively. The CWSI and IG obtained by the spraying medium artificially were achieved in the lowest determination coefficients with the leaf physiological indicators, which were 0.628, 0.643, 0.609, 0.631, 0.624, and 0.586, respectively. Among the three groups of reference plane acquisition, Twet and Tdry obtained by the red fabric were least affected by the reflection of ambient light. There was no permanent damage to the physiological characteristics of tomato leaves, thereby much easier to distinguish and extract from the thermal imagery. Therefore, the red fabric achieved a great performance to select the reference plane. In addition, the CWSI and IG were most significantly correlated with gs, An and leaf water potential during 12:00-14:00 under both irrigation treatments. Different mathematical functions were obtained to estimate the leaf gas exchange using the best-performing thermal indicators. Therefore, the water status of the plant was effectively determined using thermal infrared imaging.
      2022,38(18):237-245, DOI: 10.11975/j.issn.1002-6819.2022.18.026
      Abstract:
      Abstract: Mushroom residue (MR) is one of the most abundant edible fungus residues in China. In this study, an efficient and feasible way was proposed for the resource utilization of edible fungus residues. Transition metals were also employed to treat the MR. An investigation was made to clarify the effects of transition metal concentration (0-5mmol/g), transition metal anions (Cl-, NO3, and SO42-), and transition metal types (Fe, Zn, and Mn) on the thermal behavior of MR. The surface functional groups, pH values, proximate and ultimate analysis were then utilized to evaluate the physicochemical properties of the biochars. The potential application as an adsorbent was treated to simulate the methyl orange-contaminated wastewater. Thermogravimetric analysis showed that the main pyrolysis zone of MR was 197.83-418.22℃, and the maximum weight loss rate occurred at 351.40 ℃ with the maximum weight loss rate of -8.71%/min. The transition metals greatly contributed to the main pyrolysis region of MR shifting to a lower temperature zone, where the temperature was reduced to the maximum weight loss rate. This was highly dependent on the type of transition metal anion, concentration, and type of transition metal. Particularly, the one pre-treated with 5 mmol/g FeCl3 (MR-FeCl3-5) showed a significant effect on the decrease of the pyrolysis zone among all samples. The main pyrolysis range of MR-FeCl3-5 was 130.93-335.00℃ and the maximum weight loss rate emerged at 201.63℃ with a maximum weight loss rate of -2.28%/min. Similarly, the activation energy of MR was 34.04kJ/mol. There was also a great reduction with the introduction of transition metals. Among them, the MR-FeCl3-5 presented the lowest activation energy of 5.41 kJ/mol. The FT-IR results reveal that the biochar prepared from the MR without the transition metal treatment under 400 ℃ (MR-FeCl3-0-400C) shared the abundant surface functional groups, such as -OH, C-H, C=O, C-O, and C=C. The introduction of transition metals generally resulted in the decrease of oxygen-containing functional groups (C-O, and C=O) and the enhancement of C=C functional groups in the biochars. Ash content, fixed carbon, and volatile matter of MR-FeCl3-0-400C were 17.91%, 35.85%, and 44.44%, respectively, under the proximate analysis. The transition metals caused an increase in the ash content and fixed carbon, where there was a decreasing trend of volatile matter for the biochars. Therefore, the presence of transition metals effectively promoted the degradation of the organic composition in the MR (hemicellulose, cellulose, and lignin). Moreover, there was a decrease in the C and H of the biochars derived from transition metal-treated MR after ultimate analysis, compared with MR-FeCl3-0-400C. The pH value of MR-FeCl3-0-400C was 8.68, which was attributable to the high content of intrinsic ash in the MR. A severe decrease of the biochars was achieved in the treatment of FeCl3 and Fe2(SO4)3. By contrast, the biochar treated by Fe(NO3)3 showed a pH value close to the MR-FeCl3-0-400C. A superior adsorption performance of MR-FeCl3-5-400C was obtained for the methyl orange, compared with the MR-FeCl3-0-400C and the rest of the biochars. The theoretical maximum adsorption capacity (35.21 mg/g) was calculated from the Langmiur adsorption isotherm model, which was comparable with most of the carbon-based adsorbents. Anyway, the transition metals can be expected to convert the edible fungus residues into high value-added carbon materials, such as biochar. The finding can be a feasible way for the resource utilization of edible fungus residues.
      2022,38(18):246-254, DOI: 10.11975/j.issn.1002-6819.2022.18.027
      Abstract:
      Abstract: Shortage and matching dislocation of water resources and energy can pose a serious risk to the growth rate of food production. Particularly, water, energy and food are the indispensable resources in the human life and development. In this study, the Lorentz curve and Gini coefficient were used to evaluate the matching degree between the water-grain and energy-grain in the Yellow River Basin. Cobb-Douglas function was also applied for the grain growth damping model, in order to calculate the restriction degree of water resources and energy on the grain production. The results show that: 1) The Gini index of water resources and energy to the grain decreased first and then increased, the matching degree of which was more reasonable in the lower reaches of the Yellow River than that of the upper and middle reaches. In 2019, the Gini index values of water resources to grain in the Yellow River and the upper, middle and lower reaches were 0.365, 0.379, 0.336, and 0.122, respectively, while the Gini index values of energy to grain were 0.194, 0.218, 0.206, and 0.118, respectively, indicating the high matching in the lower reaches. The water resources and energy in the upper and middle reaches were generally matched with the grain. 2) The damping coefficient of water resources to grain production was fluctuated greatly, where the variation range of damping coefficient was 0.005~0.032. Besides, the damping effect of water resources on the grain growth basically presented a six-year cycle with a decrease-increase-decrease situation. By contrast, there was a steady increase in the damping effect of energy on the grain, the energy damping coefficient increased rapidly after 2015. Under the constraints of water resources and energy in 2019, the annual grain output growth was reduced by 0.76%, and 5.28%, respectively, compared with the previous year. 3) There was a certain degree of agglomeration in the damping effect of water resources and energy. The damping coefficient of water resources presented the pattern of small in the West and large in the East. A medium and high constraint state was obtained in the energy damping effect, which was concentrated in the eastern and lower reaches of the upper reaches, whereas, the low constraint state was concentrated in the middle reaches of the Yellow River. In addition, there was the typical spatial agglomeration in the damping coefficient of water resources and energy. The H(High)-H(High) agglomeration area of water resources damping effect was mainly distributed in the lower reaches of the Yellow River, whereas, the L(Low)-L(Low) agglomeration area of energy damping effect was distributed in the northern part of the middle reaches. The finding can provide a strong reference for the stable growth of grain and the effective allocation of resources in the Yellow River Basin.
      2022,38(18):255-263, DOI: 10.11975/j.issn.1002-6819.2022.18.028
      Abstract:
      Abstract: "Grain for Green" program has been implemented in the Loess Plateau of China since 1999, in order to control excessive soil erosion and sediment production. There is a profound impact on the vegetation cover and land use structure in recent years. It is a high demand to analyze the potential of vegetation restoration, plantation suitability areas, and land use change for regional ecosystem restoration planning and ecological protection. Taking the Beiluo River Basin as an example, this work aims to clarify the potential of vegetation restoration, vegetation suitability area, and land use change in various geomorphological areas using the dataset of climate, geography, vegetation cover, and land use. The "similar habitat" was also introduced for the statistical and geographical spatial analysis. Results showed that: 1) The spatial distribution of vegetation cover varied significantly in the study area in 2020. The vegetation cover of the earth-rock mountain area was the highest at 88.8%, followed by the gully area at 84.1%, and the terrace plain area and hilly-gully area at 68.9% and 61.9%, respectively. A spatial distribution pattern of vegetation restoration potential was obtained with the "high in the northwest and low in the southeast", particularly in the hilly-gully area in the upper reaches. The maximum recoverable vegetation cover of the hilly-gully area was 71.1%, where still 9.2% potential for the vegetation cover and the vegetation of 36.4% of the area continued to improve in the next 20-30 years. By contrast, the area with the vegetation to be improved accounted for about 11.5% of the earth-rock mountain area. The maximum recovery potential was achieved in the vegetation cover in the gully and terrace plain areas after 20 years of restoration. Therefore, there was no room to improve in the future. 2) The current land use types were dominated by cropland, forestland and grassland. The land use predictions showed that the land use change was mainly concentrated in the hilly-gully area in the next 20-30 years. The cropland decreased by 47.4% in the hilly-gully area, compared with 2020. The forestland and grassland increased by 0.7% and 15.8%, respectively. Since the cropland decreased by 23.0%, the forestland and grassland increased by 0.2% and 36.0%, respectively, in the earth-rock mountain area. Conversely, there was only a slight change in the future land use in the gully and terrace plain area. 3) The scenarios simulation was conducted to determine the plantation's suitability using the principle of "Matching Tree Species with Site". The suitable planting area in the gully and terrace plain area was 279.16 and 233.73 km2, respectively. A large area of returned cropland in the hilly-gully area was suitable for the natural restoration. There was relatively sporadic suitability for the planting area in the hilly-gully and earth-rock mountain areas. It implied that the hilly-gully area was the key area for future ecological restoration, which was the hotspot for ecological protection and high-quality development in the Yellow River Basin. Considering the limited rainfall and water carrying capacity, the ecological measures of "adaptation to local conditions" were proposed to avoid soil drying for future vegetation restoration in the Loess Plateau.
      2022,38(18):264-273, DOI: 10.11975/j.issn.1002-6819.2022.18.029
      Abstract:
      Abstract: A precise object is the premise to orderly implement the homestead remediation of the whole land. Taking the administrative village as the unit, this study aims to investigate the confirmed homestead consolidation using "potential constraint- probability choice. The coefficient correction and multi-factor comprehensive evaluation were adopted to obtain the potential scale of homestead right confirmation consolidation. The economic, social, transportation, and land factors were comprehensively evaluated at the village level using multi-source survey data, such as land, homestead right confirmation, as well as social and economic survey. Taking the plot-scale homestead land as the basic renovation unit, the systematic evaluation was combined with the upper guidance, status driven, and willingness obstruction. The priority of the renovation unit was then selected from the consolidation probability of each land parcel with the right confirmation. The results showed that: (1) the gross average correlation coefficient was 0.580 1 for the homestead-construction land in the Maogudui town. A total of 56.25% of the potential theory of regulation was realized in the 208.32 hm2 confirmed homestead with the potential reality regulation of 117.17 hm2. Correspondingly, there was the decrease in the 24.24% current area of confirmed homestead. The spatial distribution of real remediation potential was generally obtained under the influence of location advantage and future land demand. The larger the potential was, the farther it was from the market town. (2) The probability of housing land consolidation was the main judgment criterion for the priority. The total area of homestead was lower with the high consolidation probability, in terms of the confirmed homestead area corresponding to different probability intervals. However, the priority of renovation with the high and low probability was determined to preserve or renovate the homestead. An optimal selection was then made, according to the specific village conditions. (3) The iterative selection of consolidation units was carried out in the different villages using the potential constraints of various villages. A total of 4 512 consolidation units were selected with a consolidation area of 117.79 hm2. The consolidation probability was greater than 0.5 in the selected units. Among them, the remediation units greater than 0.65 were a total area of 85.13hm2, accounting for 72.27% of the target area. Therefore, the connectedness of spatial distribution in the regulated units, the priority of the hollowing and the non-central village area were beneficial to enhance the management efficiency and the cultivated land scale for the optimization of cultivated land resource. At the same time, the priority renovation of non-central villages was conducive to the planning objectives in the development of focused villages. In conclusion, the land-scale consolidation simulation can directly take the homestead land as the basic unit, corresponding to the owner of land tenure under the Spatial Planning of National Land. The finding can provide the specific and accurate decision-making reference to implement the comprehensive land consolidation in the planning period.
      2022,38(18):274-283, DOI: 10.11975/j.issn.1002-6819.2022.18.030
      Abstract:
      Abstract: Heat pump drying (HPD) is especially suitable for the drying of aquatic products, owing to the mild conditions and high energy efficiency. However, the low drying temperature can result in a long drying time for the quality degradation in aquatic products processing. This study aims to enhance the drying efficiency of scallop adductors and quality attributes of dried products, particularly for better HPD application. The scallop adductors were firstly pretreated with ultrasonic (US) pulses. Then, three kinds of edible coating were selected, including sodium alginate (SA), low-methoxy pectin (LMP), and gum ghatti (GG). Subsequently, the HPD was carried out for the samples with different coating pretreatment. The pretreatment without coating (i.e., merely pretreated with US) was set as the control group (CK). Finally, an investigation was made to determine the effects of three kinds of edible coating pretreatment on the drying kinetics and quality attributes of scallop adductors during US-assisted HPD. The low-field nuclear magnetic resonance (LF-NMR) was utilized to monitor the drying process of scallop adductors. The univariate linear (UL) and partial least squares regression (PLSR) models were employed to correlate the LF-NMR parameters with the moisture content (MC) and water activity (aw). The effective moisture diffusivity (Deff) of scallop adductors increased with the edible coating pretreatment in the range of 1.32%-8.41%, compared with the CK. The SA and GG pretreatment slowed down the migration rate of immobilized water towards bound water. As such, the flow of free water increased during drying, thus enhancing the drying efficiency of scallop adductors. More importantly, the SA and GG pretreatment increased the hardness, elasticity, cohesion, and chewiness of dried scallop adductors, whereas, decreased the rehydration ratio, shrinkage rate, and total color difference of dried products. There was a decrease in the hardness and total color difference of LMP pretreated samples. In summary, the US-SA was the most suitable pretreatment for the US-assisted HPD of scallop adductors. There was a significant (P<0.05) correlation between the LF-NMR transverse relaxation time (T2) and most quality attributes of dried scallop adductors. The end point of drying was determined in the LF-NMR spectra of samples, indicating the main peak of transverse relaxation time T2 <10 ms and only one peak. The UL model showed that the MC and aw were significantly (P<0.05) positively correlated with the peak area of immobilized water and total peak area, but negatively (P<0.05) correlated with the peak area of bound water. The PLSR model revealed that the regression model with four LF-NMR parameters as the variables accurately predicted the MC and aw of scallop adductors during HPD. This finding can provide a novel non-thermal pretreatment for the drying of scallop adductors, particularly with the enhanced drying efficiency and quality attributes of the dried products. Furthermore, the LF-NMR technology can also provide the theoretical basis and practical reference for the rapid and non-destructive monitoring of scallop adductors during US-assisted HPD.
      2022,38(18):284-292, DOI: 10.11975/j.issn.1002-6819.2022.18.031
      Abstract:
      Abstract: Berry fruits are very popular food products for their high nutritional value and unique flavor. But, the juiciness and thin skin of berries cannot be suitable for long-term storage and transportation. Therefore, berry fruits are often processed into dried products or solid powders, in order to minimize the transportation cost for the long shelf life. Among them, freeze-drying (FD) can be used for high-quality products at low temperatures under a nearly oxygen-free environment. However, the long drying time and high energy consumption of FD cannot fully meet the large-scale application in recent years. It is necessary to simultaneously consider the typical coupling mass and heat transfer for the enhancement of FD. In the present work, the technical idea of "freeze-drying of unsaturated porous media with microwave heating assisted by wave-absorbing material" was proposed to apply the berry processing. Much effort was also made to establish a high-efficient and low-cost FD. The blueberry fruits were taken as the research objects of berry fruits during experiments. The eutectic temperature of blueberry puree was measured (-20.42 ℃) as the reference of pre-freezing temperature. Quartz and silicon carbide (SiC) were also used as wave-absorbing materials in the supporting samples for comparison. Unfoamed and foamed frozen samples were prepared with the same initial mass and moisture content. Whey protein isolates and pectin were used as the forming agent and stabilizer. Conventional and wave-absorbing material-assisted microwave FD experiments of blueberry puree were conducted in a lab-scale multifunctional microwave freeze-dryer. Color, total monomeric anthocyanin (TMA), and total phenolic content (TPC) were selected as the indexes to evaluate the quality of freeze-dried products. Results showed that the FD process was enhanced by the single factor of either forming treatment or wave-absorbing material-assisted microwave heating. The foamed sample saved 39.1% freeze-drying time at the radiation temperature of 30 ℃ and 15 Pa chamber pressure with the quartz pad, compared with the unfoamed one. In the case of the same operating conditions with the SiC pad, the microwave FD time of unfoamed sample was shortened by 23.9% at the microwave power of 2 W, and by 39.1% at 4 W, compared with the conventional. The performances of SiC assisted microwave heating were enhanced by 14.3% at 2 W and 25.0% at 4 W for the foamed material, respectively. The microwave FD of foamed material assisted by wave-absorbing material was realized by the simultaneous enhancement of mass and heat transfer, indicating the greatly accelerated FD rate. The microwave FD time of foamed sample was reduced by 47.8% at 2 W and by 54.3% at 4 W, compared with the conventional FD of unfoamed sample. There were no significant differences in colors. TMA and TPC contents of microwave freeze-dried products were comparable with those of conventional ones. The retentions of TMA and TPC in all freeze-dried products were more than 80% and 75%, respectively. The SEM images of dried products revealed that the substrate of the foamed material was porous and tenuous, which was conducive to water vapor migration and bound water desorption. There was no influence of microwave heating on the pore structure of either unfoamed or foamed material. Wave-absorbing material-assisted microwave FD of foamed material can largely decrease the drying time for the process economy. There was almost the same quality of products between the microwave and conventional FD. The finding can provide promising guidance for efficient FD in the food processing industry.
      2022,38(18):293-301, DOI: 10.11975/j.issn.1002-6819.2022.18.032
      Abstract:
      Abstract: Peanut sprout (longevity sprout) is one kind of favored food and therapy, due to its crisp taste and unique flavor. The energy, protein, and crude fat content of peanut buds after germination is significantly higher than that of various vegetables. There is a great increase in the content of vitamins, potassium, magnesium minerals, and various amino acids and trace elements required by the human body, especially the content of resveratrol, a polyphenol with important bioactive functions. Among them, resveratrol (chemically known as 3, 4', 5-astragalotriphenol) has the broad-spectrum antibacterial activity as the "plant antitoxin" in recent years. But, there are only a few reports on the effects of peanut bud resveratrol on Salmonella typhimurium. This study was focused on the isolation and purification technique of resveratrol from peanut buds, together with its antibacterial properties. The resins were screened with excellent adsorption and desorption properties for the peanut bud resveratrol compounds, in order to construct the isolation and purification process. The antibacterial efficacy was evaluated to improve the comprehensive utilization of peanut resources. A comparison was made to determine the effects of 16 types of macroporous resins on the separation and purification of arachidonic resveratrol compounds using static adsorption-desorption tests. The LSA-40 was selected as the best adsorption resin for the saturation and plateau in 110 and 90min of static adsorption, respectively. The dynamic adsorption-desorption conditions were optimized as follows. The loading concentration was 120.00 μg/mL, the flow rate was 1.00 mL/min, the pH value was 4.2, and the optimum ratio of loading volume to resin was 8.00 mL/g. The desorption conditions were the 80% ethanol solution, a pH value of 6.6, and a flow rate of 1.00 mL/min. Ultraviolet (UV) spectral analysis showed that the absorption peaks of the purified arachidonic resveratrol and the control were basically the same under the optimized process conditions, where the purity was calculated to be 84.0%. Fourier infrared spectroscopy and ultra-performance liquid chromatography-tandem mass spectrometry were used to identify the components of the purified samples. It was found that the main components of the purified products were resveratrol and the derivatives. The inhibition effect of the purified product on Salmonella typhimurium was evaluated by multiplicative dilution, inhibition growth curve, and cell membrane permeability. The minimum inhibitory concentration of resveratrol-purified product on Salmonella typhimurium was 250 μg/mL. In addition, Salmonella typhimurium treated with resveratrol purification presented a prolonged lag period and a decreased growth rate in the logarithmic phase at the MIC concentration. The cell membrane permeability significantly increased (P < 0.01), according to the growth curve and the protein content of cell contents. The integrity of the cell wall was damaged causing the serious leakage of intracellular proteins, eventually leading to the death of Salmonella typhimurium. This finding can provide some theoretical reference for the comprehensive utilization of peanut resources in natural antibacterial agents.
      2022,38(18):302-307, DOI: 10.11975/j.issn.1002-6819.2022.18.033
      Abstract:
      Abstract: Silage is a type of storage fodder from green foliage crops to reduce the cost of feed and environmental pollution. The silage can be preserved by fermentation to the point of acidification. Among them, microbial growth can dominate in the silage quality. Especially, the proliferation of harmful microorganisms has also posed a great threat to crop resources, and ruminantia production, such as clostridium, acetic acid bacteria, and yeast. However, the commonly-used plate counting and turbidimetry for microbial growth in the laboratory cannot accurately characterize the growth state of silage microorganisms in time, due to tedious steps, time-consuming, and slow response rate. This study aims to effectively monitor the growth of silage microorganisms (lactic acid bacteria, acetic acid bacteria, and clostridium butyricum) separating from the silage as the indicator strains. A systematic investigation was made for the three-dimensional fluorescence spectra, the number of microbial colonies, and the absorption of 105 samples at the seven growth time points (0, 2, 4, 8, 12, 24 and 48 h). The chemometrics analysis and spectroscopic techniques were combined for the rapid screening of microbial growth. Parallel factor analysis was applied to resolve the three-dimensional fluorescence data. Back Propagation (BP) neural network was also used in the material quantitative analysis in the field of machine learning, due to its powerful nonlinear ability. The three-dimensional Synchronous Fluorescence Spectra (SFS) showed that there were two strong fluorescence peaks at about 225 and 275 nm, respectively. The main fluorescence peaks were the microbial endogenous tyrosine and tryptophan. The fluorescence intensity increased gradually with the increasing culture time, where the position of the fluorescence peak shifted the red. Meanwhile, the width of the fluorescence peak increased significantly. The parallel factor analysis showed that there was a significant difference in fluorescence information, where the characteristic wavelength Δλ was 50 nm with six components. In addition to the two characteristic peaks, there were two weak fluorescence peaks at 310-360 and 370-390 nm. The two wave peaks at 340 and 380 nm were the microbial metabolism products or acids. There was a positive correlation between the intensity of natural fluorescence peak at 380 nm during culture time. Outstandingly, there was more information on fluorescence components in the two-dimensional fluorescence spectra from the parallel factor analysis. In terms of two-dimensional spectral data, the number of microbial colonies, and the absorbance were taken as the input or the output values of the BP neural network model, respectively. The modeling was constructed for the microbial growth of different detection. The experimental results showed that the correlation coefficients of the two models were close to 1.0, and the mean square error (MSE) was all very small. A very reliable model was achieved in the neural network with a high fitting ability. Therefore, the three-dimensional fluorescence spectroscopy combined with the chemometrics was feasible to monitor the microbial growth in the silage. The finding can also provide a new technical approach for the rapid determination of the fermentation silage stage.
      2022,38(18):308-315, DOI: 10.11975/j.issn.1002-6819.2022.18.034
      Abstract:
      Abstract: Layer strains can be a particular preference for female chickens over males with respect to economic value. One-day-old male chicks are normally slaughtered once hatched in the incubation factories, leading to a huge waste of poultry resources, as well as raising serious concerns for animal welfare. It is since day 7 of incubation that the chicken embryo starts to feel pain. Thus, accurate identification can be used for the removal of the male eggs at the early stage of incubation, in order to effectively save cost and conform to the ethics for animal welfare. Generally, incubation is a complicated process concerning the inner biochemical activity and outer morphology evaluation, for example, the shape of the chicken embryo and the vessels. However, only a single information source was used, such as spectra or machine vision images, thus performing weakly in the recognition accuracy. This study aims to more accurately detect the gender of the chicken embryo at the early stage of incubation. A non-destructive decision fusion was proposed using both images and spectra using Random Forests (RF) and Dempster-Shafer (D-S) theory of evidence. A detection system was constructed to sample the transmission spectra and machine vision images of 566 chicken eggs. Day 4 of incubation was selected as the best detection time, while, the laying style of eggs was determined as placed horizontally. Machine vision images of the chicken embryo were treated via image processing, including morphological operations, and the Otsu algorithm. Then, the eleven texture features of the chicken embryo were extracted and scaled using grey level co-occurrence matrix, grey histogram statistics, and fractal dimension. The preprocessing method of spectra was determined as the scaling after the experiment. Four spectral features were extracted from the preprocessed spectra via Competitive Adaptive Reweighted Sampling (CARS). After that, two detection models were established using visual features and RF spectral. Five-fold cross-validation was then applied in the task of grid searching to optimize the two models. The machine vision model reached 78.00% accuracy with optimized parameters, while the spectral model was 82.67% accuracy for the test set. Furthermore, the feature fusion model was also constructed using texture and spectral features. The recognition accuracy of the test set only achieved 62.33% accuracy, indicating the mixed redundant information in the features. Finally, the decision fusion model was built via the D-S theory of evidence. The basic probability assignment functions were obtained from the optimal RF models of images and spectra. Then, the decision fusion model was established using the fusion principle and threshold of the D-S theory of evidence. Consequently, the fusion model reached 88.00% accuracy, particularly with 90.00% and 86.25% accuracy for the female and male eggs. Besides, 2.843 s was used for the D-S model to detect each egg. Anyway, the decision fusion can be expected to realize the gender detection of the chicken embryo at the early stage with a higher accuracy than before. The finding can provide a potential solution to the commercial application in the poultry industry.
      2022,38(18):316-325, DOI: 10.11975/j.issn.1002-6819.2022.18.035
      Abstract:
      Abstract: Sweet potato is a kind of vegetable and grain crop which is grown world-wide, and it is also the second largest potato crop in China. During the harvest and storage process, sweet potato is damaged by machinery and susceptible to pathogenic microorganisms, resulting in great economic losses caused by the deterioration of sweet potato. Therefore, callus pretreatment of potato crops before storage has become the main methods to reduce the storage loss of potato crops. To improve the existing problem of traditional callus treatment (35 ℃ heated in storage condition for more than 2 d), such as high energy consumption, low efficiency, instability, in sweet potato callus formation technology, the purpose of this research was to study the effects of different heat shock treatments on the formation of sweet potato root callus healing, the sweet potatoes were treated with High Temperature Short Time Callus (HTSTC) at 55-70 ℃ lasting 10-20 min with hot air by self-designed high-temperature-short-time healing equipment. After the callus healing was completed at (13±1)℃ for 7 d, the appearance color, the thickness of the phelloderm layer, the content of lignin and the mass loss rate of sweet potato were measured, and the suberin deposition was observed under a microscope. The results showed that after callus heat shock treatment at 65 ℃ for 15 min, the lignin accumulation and suberin deposition were the best among HTSTC groups. The HTSTC treatment under 65 ℃ for 15 min groups showed a stronger blue fluorescence intensity and lager blue fluorescence region than other HTSTC groups, which was similar to the fluorescence intensity of traditional callus treatment. On the other hand, the lignin content and cork layer thickness of 65 ℃ for 15 min HTSTC groups were 12.27% and 19.41% higher than those sweet potatoes under traditional 35 ℃ healing for 2 d callus treatment. The traditional callus method would lead to a serious mass loss problem by dehydration and respiration acceleration. Compared with traditional callus method, the mass loss of 65 ℃ for 15 min HTSTC treatment group was only (3.78 ± 0.34)%, which could effectively reduce the mass loss of damaged sweet potatoes. In addition, the optimal HTSTC treated sweet potato could increase the L* and reduce partial browning better compared with traditional callus treatment on sweet potatoes. It was found that the callus color of the 65 ℃ heat for 15 min was gray green without obvious browning, which was an acceptable appearance for consumers. In order to verify the experimental results, the HTSTC treatment temperature and time were optimized and calculated by response surface design method. Through response surface simulation optimization, the optimal heat shock treatment condition is at 67.01 ℃ for 12.69 min, which was very close to the actual experimental parameter of 65 ℃ for 15 min. The R2 of cork layer thickness, mass loss rate, and lignin content in response surface were 0.999, 0.998, and 0.997 respectively. In conclusion, the experimental results are very close to the response surface optimization results. The 65 ℃ heat for 15 min HTSTC treatment could not only achieve better result of calls formation than traditional callus treatment, but also ensure the lowest mass loss rate and maintain the best appearance quality, which could become a new scientific method for rapid, efficient, energy saving, and quality assurance callus treatment of postharvest sweet potato and other root crops.
      2022,38(18):326-332, DOI: 10.11975/j.issn.1002-6819.2022.18.036
      Abstract:
      Abstract: Blanching treatment is often used to reduce the difficulty of peeling Citrus reticulata reticulata Blanco before the real peeling process. However, the mechanism of Citrus reticulata blanching is still unclear, particularly for the relevant theoretical support in the actual processing. It is a high demand to clarify the effect of the peeling process in the special way of blanching treatment. This study aims to determine the effect of blanching treatment on the mechanical characteristics, tissue structure, and the peeling performance of Citrus reticulata reticulata Blanco peel. A test platform of Citrus reticulata peel separation was used to evaluate the peeling performance of Citrus reticulata under different blanching times. The tensile test was also carried out to evaluate the mechanical characteristics of blanched Citrus reticulata peel. The ultra-depth of field microscope and electron microscope (EM) were utilized to characterize the pericarp microstructure, white layer, and flesh structure based on the Ray CT tomography. The size of the exocarp of the Citrus reticulata was observed after blanching treatment. Therefore, the influencing mechanism was then established for the blanching treatment on the peel ability of Citrus reticulata. The experimental results showed that the blanching time posed a significantly vital and crucial effect on the maximum tensile force, the separation displacement, the peel breaking strength, and the porosity between the peel and pulp during Citrus reticulata peel separation (P<0.01). There was a positively correlated relationship between the separation displacement and the breaking strength. A negatively correlated relationship was found between the maximum tensile force and the porosity between peel and pulp. The peeled surface increasingly tended to be wrinkled, rough, and coarse with the increase of blanching time in the experiment. The pectin compounds on the peel cross section were slowly dissolved, whereas, the parenchyma cells and vascular bundle tissues totally collapsed and disappeared forward a single step. There was a gradual increase in the porosity between the peel and pulp. The peel-breaking strength changed accordingly, which first increased and then decreased. As a result, the minimum tension during peeling was reduced, where the separation displacement first increased and then decreased, the same as the peel-breaking strength. Once the blanching time equaled to 3 min, the maximum tensile force reached the minimum of 1.59N, which was reduced by 42.8%, compared with the control. The separation displacement also reached the maximum of 41.81mm, which increased by 19.6%, compared with the control. The overall peeling effect was the best at that time. But after the blanching time was more than 3 min, the peel with soft foam to break cannot be easy for the peeling. This study provides a theoretical reference for improving the difficulty of peeling Citrus reticulata reticulata Blanco and enriching the mechanism of blanching peeling.
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    November 23, 2022 , DOI:
    Abstract:
    As the basic geomorphological unit of the loess hilly gully area, the slope and gouge system is also the main source area of eroded sediment on the Loess Plateau. As the main measures for slope erosion control, vegetation and terraces play an important role in soil erosion control and ecological restoration, and quantitative assessment of the regulatory effect of forest grass and terraces on slope fine trench erosion and multi-measure collaborative allocation are of great significance for soil erosion control and ecological protection of the Loess Plateau. Based on the previous research on soil erosion and slope trench erosion, in order to reveal the synergistic regulation effect of vegetation and terraced land pattern and configuration on fine trench erosion in slope and trench system, this paper uses artificial simulation rainfall, combined with 3D laser scanning technology, to quantitatively analyze the regulatory effect of different measures on fine trench erosion from the slope surface sand production rate and slope micro-terrain change as a whole, and quantitatively analyze the characteristics of single furrow morphological changes such as the change characteristics of the development process of fine furrow length and the change characteristics of fine furrow width and depth ratio from the single furrow morphology. The development process of fine furrow network was also analyzed, and parameters including but not limited to fine furrow erosion amount, fine furrow area, and fine furrow erosion proportion were quantitatively calculated, and the influence of different slope and ditch treatment measures on the characteristic parameters related to fine furrow erosion was expounded from multiple angles, and finally the synergistic effect of different measures on the erosion amount, area and density of fine trench was quantitatively calculated and analyzed for the synergistic effect between multiple measures. The effects of four slope measures: uphill vegetation (measure A), downhill vegetation (measure B), terraces (measure C), and terraces + vegetation (measure D) on the occurrence and evolution of fine furrow erosion were analyzed. The results showed that: 1) Under the same vegetation coverage, the maximum length of the downhill vegetation furrow was reduced by 96.5cm compared with that of the uphill vegetation furrow (including the maximum ditch length of the uphill position reached 238.8cm and the maximum ditch length in the downslope position reached 142.3cm)2) In the first rainfall, the maximum sand yield rate reached more than 3500g/min, and the maximum sand yield in the second rainfall was only more than 1100g/min. The sand yield rate of the second rainfall was 1/3-1/2 of the sand yield of the first rainfall during each production time; 3) The development rate of fine furrow length under each measure was > as measure A (6.55cm/min) > measure C (5.71cm/min) > measure B (3.60cm/min). Measure D (2.69cm/min) 4) The simultaneous arrangement of terraces and vegetation (measure D) had a better regulatory effect on fine trench erosion than a single measure (measures B and C), and the terraces and vegetation had a synergistic effect on the erosion amount, area and density of fine trench on the erosion index of fine trench (7.71%, 13.76% and 7.52%, respectively). Based on the above research methods and related conclusions, this study provides a relatively new perspective in the prevention and control of soil erosion in the hilly area of the Loess Plateau, that is, when setting up actual engineering measures, the differences in the influence of the same measures on the erosion of fine ditches at different positions in the slope and ditch system and the impact of multiple measures and the synergistic effect between multiple measures can be properly considered, and the configuration of soil erosion control programs can be continuously optimized to maximize the benefits of each treatment measure. This study can provide a certain scientific reference for the allocation of slope and ditch treatment measures and the erosion control of fine ditches on the Loess Plateau.
    November 23, 2022 , DOI:
    Abstract:
    Abstract: Brackish water irrigation is an effective way to alleviate the shortage of fresh water resources in arid areas. To explore the salt accumulation of cotton mulched drip irrigation with different salinity and its impact on crop growth, this paper carried out two-year test pits of mulched drip irrigation with different gradient salinity. A total of 6 treatments were set up, with the salinity of 1 g/L(CK); 2 g/L(A); 3 g/L(B); 4 g/L(C); 5 g/L(D); 6 g/L(E). The salt accumulation characteristics of different soil layers during the cotton growth period were analyzed. Based on the data of local meteorology, soil, crop, management, and irrigation system, the AquaCrop model of drip irrigation of cotton under water source film with different salinity was constructed. The results show that: 1) the salt accumulation reaches the peak in the 40 ~ 60 cm soil layer, and the salt accumulation in the 80 ~ 100cm soil layer is less. At the end of two years, the salt accumulation of 40 ~ 60 cm soil layer of cotton under drip irrigation with water source film with different salinity was 44.29%、42.68%、43.40%、34.92%、35.69%、39.32%. 2) The mineralization degree is 3 g/L, and the growth indexes and cotton yield reach the maximum. Compared with CK, the growth indexes and yield of 4 g/L are unaffected. The suitable irrigation water source for cotton is between 3 g/L and 4 g/L. 3) By constructing the AquaCrop model, the R2 between simulated and measured values of canopy coverage and aboveground dry matter mass is greater than 0.9497, RMSE is less than 18.15, NRMSE is less than 24.1 and d is less than 0.968. The simulation effect is good. The relative error between the simulated value and the measured value of cotton yield is no more than 9.28%. The AquaCrop model can better simulate the dynamic changes of canopy coverage, biomass, and yield during the growth and development of cotton mulched drip irrigation with different salinity and can be used for yield prediction and optimal management. The research results can provide a fundamental basis for the sustainable utilization of mulched drip irrigation technology with salt water resources in arid areas.
    November 23, 2022 , DOI:
    Abstract:
    Brackish water irrigation destroys the soil structure, changes the water and fertilizer retention capacity, and threatens crop growth and food security in Xinjiang Province. Based on this background, this study focused on the typical sandy loam soil in agricultural regions of Xinjiang and used common ions including Na+, Ca2+, Cl- to treat the soil with solutions under different SAR and salinity concentrations to explore the effects of salt adsorption ratio (SAR) and concentration on physical properties of typical sandy loam in Xinjiang Province. Soil aggregates were measured according to LB method, which were quickly wetted by solutions at 6 SAR levels (40, 30, 20, 15, 10, 5 (mmol/L)1/2) and 8 salinity concentration levels (200, 150, 100, 50, 20, 10, 5, 2 mmol/L). Soil water characteristic curve (SWCC) was measured using high-speed refrigerated centrifuge at 4 SAR levels (40, 30, 20, 5 (mmol/L)1/2) and 3 salinity concentration levels (200, 100, 20 mmol/L). Soil shrinkage during soil dehydration was recorded with vernier caliper at each centrifuge speed to investigate how SAR and salinity concentration influenced soil shrinkage. The results showed that the stability of soil aggregates was negatively correlated with SAR and salinity concentration. However, the influence of salinity concentration was not significant. When SAR was lower than 30 (mmol/L)1/2, the stability of soil aggregates remained constant. The above result indicated that when the SAR in the irrigation water is at a low level and the salinity concentration is lower than 200 mmol/L (approximately 19.1 g/L), it can be considered that the soil structure is not damaged. Besides, SAR influenced SWCC of typical sandy loam in Xinjiang Province, which depended on the salinity concentration. SAR showed negative effect on soil shrinkage, while the maximum soil shrinkage increased and then decreased with the increase of the salinity concentration, which was related to the SAR of the saturated solution. Those results can provide a theoretical basis for the rational selection of brackish water for irrigation with different salt composition and concentration to protect the soil structure of farmland. What’s more, this study discussed the short-term effects of salinity and SAR on the sandy loam soil aggregate structure and soil water retention curve in Xinjiang Province. Long-term effects of salinity and SAR on soil physical properties remain to be further explored in the future.
    November 23, 2022 , DOI:
    Abstract:
    The electrical conductivity (EC) and cation concentration in soil solution are important indicators to assess the stability of soil structure. Sodium adsorption ratio (SAR) is used to quantify the impact of soil alkalinity and Na+ concentration on soil structural stability. SAR only considers the dispersion of Na+ on soil particles and the same promotion effect of Ca2+ and Mg2+ on soil flocculation. In areas with high concentration of K+ and Mg2+, the effect results of water quality on soil structure assessed by SAR deviate from the actual situation. A new water quality assessment index which called as 'cation ratio of soil structural stability' (CROSS) comprehensively takes into account the complex effects of Na+, K+, Ca2+ and Mg2+ on soil infiltration, and quantifies the extent of different cations on soil dispersion or flocculation. Researchers quantified Na+, K+, Ca2+, Mg2+ on the stability of soil structure, determined the relative dispersion power of K+ versus Na+, relative flocculation power of Mg2+ versus Ca2+, and adjusted the concentration coefficients to constantly modify the CROSS equation. CROSS compensates for the effects of SAR not considering K+ and improves the accuracy of the coefficients, can serve as the surrogate index of SAR for assessing water quality. This paper (1) analyzes the influence of K+ and Mg2+ on soil structure, discusses the rationality of CROSS replacing SAR for water quality assessment. Although the effect of K+ on soil dispersion is not as capable as Na+, irrigation water with high concentration of K+ can reduce soil saturated water conductivity, eliminates large soil pores and causes dispersion of soil particles. The dispersion effect of Mg2+ on soil is more capable than Ca2+, and the accumulation of Mg2+ in soil increases the risk of soil salinization; (2) evaluates 73 water samples collected from the Hetao Irrigation District by SAR and CROSS, respectively, the classification results are quite different. The effect of irrigation water on soil infiltration performance is not only related to EC, but also the proportion of cation concentration. Therefore, although the irrigation water with high EC value, the high cation concentration of K+, Ca2+ and Mg2+ will neutralize the negative effect of Na+ on soil infiltration, and the irrigation water will not cause potential infiltration harm. Irrigation water with low EC value, if provided with high Na+ concentration, may also bring potential harm to soil infiltration performance. For irrigation water with high cation concentration ratio of Na+/K+, Na+/Ca2+ and Na+/Mg2+, the classification results of degree of influence on infiltration rate through SAR and CROSS are not different, the higher the ratio, the more serious the impact on soil infiltration performance. It is recommended that the effect of cations in irrigation water on soil infiltration properties be assessed by EC and CROSS. CROSSf, CROSSd and CROSSopt are three different calculation formulas of CROSS, CROSSf, CROSSd and CROSSopt have different applicability in the Hetao Irrigation District, it is suggested to evaluate the irrigation water quality of the Hetao Irrigation District by EC and CROSSd or CROSSopt. On this basis, by analyzing the salt and cation concentration of soil in Hetao Irrigation District, determined the range of EC and CROSS of underground brackish water suitable for irrigation, evaluated the optimal water samples adapted to geological conditions in Hetao Irrigation District, under the premise of slight reducing infiltration rate, irrigation water suitable for Hetao Irrigation District can be selected with appropriate salt and cation concentration, in this study, we found that brackish water with higher EC and lower CROSS was most conductive to the stability of soil structure. However, the classification evaluation method suggested in this paper still needs to be corrected by infiltration tests. This assessment method comprehensively considers the influence of salt and cation concentration on soil infiltration performance, provides theoretical support for the long-term efficient utilization of brackish water.
    November 23, 2022 , DOI:
    Abstract:
    The challenge of agricultural non-point source pollution (ANSP) has been attached widespread attention in the world due to the massive application of fertilizers and pesticides in the field. It is of great significance to develop ecological restoration technologies to mitigate ANSP. Ecological ditch can function as a farmland drainage ditch and a constructed wetland, which has become a research hotspot to mitigate ANSP in recent years. Most previous studies focused on the dissipation mechanisms of nitrogen (N) and phosphorus (P), and the information about pesticides removal in the ecological ditch was limit. Meanwhile, single factor analysis was generally employed instead of multiple factors analysis, while the dissipation mechanisms of ecological ditch were influenced by the interaction of multiple factors. This paper reviewed the dissipation mechanisms of ANSP, including sediment sorption and plant resistance, plant/microorganism absorption, and plant/microorganism degradation. A literature survey of peer-reviewed papers related to the field experiments of ecological ditches was performed using the ISI Web of Science and CNKI databases from 2001 to 2022. The search criteria are including:(i) Field experiment;(ii) Ecological ditch or drainage ditch;(iii) ANSP. Based on the literature survey, a total of 559 groups of field experimental data was analyzed to explore the removal rates of total nitrogen (RTN), ammonia nitrogen ( ), nitrate nitrogen ( ), total phosphorus (RTP), orthophosphate ( ) and pesticides (RPes). Four main influencing factors were taken into account, e.g., initial contaminant concentration (C0), hydraulic retention time (HRT), plant species (PS) and plant biomass (BM). Other influencing factors, such as temperature, hydraulic load, rainfall, and alternate wetting and drying, were also discussed. Both single and multiple factors analyses were investigated in this study by using the correlation analysis and multiple linear regression model (MLR), respectively. The results indicated that both RTN and RTP increased as the C0, HRT and BM increased (P<0.01), while PS had no significant correlation with RTN and RTP. That was because that the sorption and uptake processes were stimulated by larger C0, HRT and BM in the ecological ditch, and the resuspension process was also inhibited by larger HRT and BM. The MLR analysis showed good statistical results with R2=0.80 for RTN and R2=0.92 for RTP, respectively. Both C0 and BM showed a positive correlation with RTN and RTP (p<0.05), which reconfirmed that the larger C0 and BM would bring about larger removal rates of nutrients. It was noted that the contribution ratio of C0 was larger than BM in the MLR equations for RTN and RTP. It might be due to larger concentration gradient in the ecological ditch, which promoted the diffusion of nutrients from overlying water to pore water in sediment and provided more favorable absorption conditions for sediment microorganisms and plants. For pesticides, the results of single factor analysis indicated that the RPes declined as the C0 raised, which was mainly because the toxicity inhibition effect of pesticides on degrading microorganisms and plants, which weakened the metabolic activity of microorganisms and the absorption effect of plants. The RPes raised as the HRT raised, which was mainly because the longer microbial reaction would enhance the pesticide removal rate. Besides, the MLR equation for RPes showed reliable statistical parameters in the training set with a R2=0.56. The RPes in MLR was negatively correlated with C0 and positively correlated with HRT, which were consistent with single factor analysis. According to the results of this review, it is necessary to supplement the experimental research on the interaction of multiple factors in the future research. It is also of significance to investigate other hydrologic and environmental factors on the removal efficiencies of ecological ditches. Future research are also needed to explore the effects of pesticide structures and microbiological mechanism on the pesticide removal in ecological ditches.
    November 21, 2022 , DOI:
    Abstract:
    Potential production benefits can be expected to easily quantify for the variable rate irrigation (VRI) over the conventional uniform rate irrigation (URI) systems in a given field. An e?ective VRI management can greatly contribute to the investment in the systems. In this study, a field test was conducted from October 2017 to September 2018 during the growing seasons of winter wheat and summer maize in Zhuozhou (39.45 °N and 115.85 °E), Hebei Province, China. The mean annual temperature and precipitation were 11.6°C, and 563 mm, respectively, particularly with more than 70% probability between July and September. The VRI system was set as a center pivot with three-span 140 m long with an overhang. Variable-rate water was applied along the lateral and travel direction. A control system was also used to control the duty cycle of a solenoid valve ahead of each sprinkler, and the travel speed of the center pivot. One 1.64-ha quadrant irrigated by the VRI system was delineated into four management zones (zones 1 to 4) with the available soil water holding capacity (AWC). Among them, two conventional sprinkler URI strategies (U1 and U2 treatments), and two VRI strategies (V1 and V2 treatments) were arranged in the four sub-zones for each management zone. The mean soil water contents were daily measured to determine the irrigation date in the treatments of U1, V1 and V2 in zone 1 with the lowest AWC values. Furthermore, the average soil water content was approximately represented at 0-0.4 m depths. Particularly, the mean soil water contents were measured for the four management zones in the U2 treatment. The irrigation was triggered when the measured soil water content dropped close to 66% and 70% of the field capacity for the winter wheat and summer maize, respectively. The same application was adopted for the two URI treatments. Specifically, the 20 and 30 mm depths were set before and after the booting stage for the winter wheat, respectively, whereas, the 20 mm depths were for the summer maize. The application depth was equal to the consumption of soil water calculated from the upper limit value and the measured soil water content for the V1 treatments. In the V2 treatments of winter wheat, 84%, 99%, and 68% of the rate in zone 1 were recommended for zones 2, 3, and 4, respectively, where the deliver depth for zone 1 was the same as the URI treatments. The V2 treatments of summer maize were also combined with the V1 treatments and the rain forecast. The applied water decreased by 0, 20%, and 40% for the light (less than 10 mm), moderate (between 10 and 25 mm), and heavy rain (more than 25 mm), respectively, according to the forecast report from the National Meteorological Center of China Meteorological Administration. There were some positive effects of VRI strategies on water-saving, yield, and WUE, spatial distribution of plant height, and leaf area index (LAI). Results showed that the VRI strategy was an optimal way of irrigation management, according to the upper limit value and the meteorological forecast rainfall level. Compared with the URI, the irrigation amount of the optimal VRI strategy was reduced by 36%, and 40%, while the WUE values increased by 12%, and 29% for the winter wheat and summer maize, respectively. Except for the significant difference between the VRI and URI strategies in the values of WUE for the summer maize, there was no significant difference in the yield for the winter wheat and summer maize, respectively. Besides, no significant effect was found on the spatial distribution of plant height, LAI, yield and WUE. Therefore, the irrigation prescription maps can be expected to serve as the VRI management, according to the soil water content and meteorological forecast about rainfall, particularly more suitable for both the semi-arid and semi-humid climates.
    November 21, 2022 , DOI:
    Abstract:
    With the enhancement of people's living standards and health care awareness, the increasing prevalence of diabetes has attracted people's widespread attention. Thus, it is very necessary and meaningful to promote low glycemic index (GI) foods. As a new type of resistant starch, starch-lipid complexes have been shown to exhibit good anti-digestive properties in recent years. High amylose corn starch (HACS) is considered as an ideal raw material for the preparation of starch-lipid complexes due to its high amylose content. Meantime, twin-screw extrusion technology has been successfully applied in the preparation of starch-lipid complexes. In order to enhance the preparation efficiency of starch-lipid complexes and expand the application of these complexes in anti-digestive foods, the high-amylose corn starch and flax oil was used as the material to prepare complexes using twin-screw extrusion in this study. The purpose of this study was to optimize the preparation process using single factor and orthogonal optimization experiments, and the complex index (CI) was selected as the indicator. In addition, the structure and physicochemical properties of the complex was investigated. The process parameters were adjusted separately, including the mass ratio, feed moisture, barrel temperature and screw speed. The extruded complex was dried at 40 ℃ in an oven for 10 h, and then ground and passed through an 80-mesh sieve. The highest CI was reached to 85.63% when the optimal parameters were 0.24 of flax oil-to-starch ratio, 40% of feed moisture, 125 °C of barrel temperature, and 150 r/min of screw speed. Fourier transform infrared spectroscopy (FTIR) pattern emerged new peaks at 2850 cm-1 and 1745 cm-1 in the extruded starch-lipid complex, corresponding to C-H and C=O vibration absorption peak of lipid molecules in the complex. Moreover, the C=O vibration absorption peak of extruded complex shifted to lower wavenumber compared to the control mixture. These results indicated that the lipid molecules combined with starch at the actions of shearing force, friction force and heat-moisture effect of extrusion. This may be due to extrusion broke the hydrogen bonds of starch molecules and exposed the hydrophobic helical cavity, and then the lipid molecules entered the hydrophobic helical cavity of starch molecules through hydrophobic interaction. The morphological showed that the complexation induced the stacking and aggregation of starch granules. The results of X-ray diffraction (XRD) suggested that the extruded complex possessed V-type crystalline pattern, demonstrating that preparation of the complexes by twin-screw extrusion was feasible. Compared with the control mixture and HACS the extruded complex had the higher gelatinization enthalpy, indicating that more energy was required to gelatinize the complex. While the extruded complex had the lower apparent viscosity, storage modulus and loss modulus compared to the control mixture. Additionally, the total amount of slow digestible starch (SDS) and resistant starch (RS) in extruded complex was he highest among all samples, which demonstrated that the complex exhibited better anti-digestible properties. According to above results, it can be concluded that extrusion promoted the effective complexation between starch and fax oil, thus altering the structure and physicochemical properties of corn starch. Therefore, the starch-lipid complex prepared by twin-screw extrusion technology can be expected to serve as a potential material to produce low GI foods in the future.
    November 21, 2022 , DOI:
    Abstract:
    Pectin polysaccharides is related to various physiological functions, e.g., preventing obesity, diabetes and cardiovascular diseases, etc. It is often used in gel foods because of its excellent gelation property, water solubility and low viscosity. In China, more than three million tons of soybean hull byproduct is produced every year. It contains up to 30% of soybean hull pectin polysaccharide (SHPP). In order to improve the utilization efficiency of soybean byproduct and explore the application of SHPP in gel foods, salt-assisted hydrothermal method was applied to extract SHPP from soybean hulls in this study. Physicochemical properties (e.g., extraction yield, composition, size distribution and viscosity) of SHPP were characterized. Then, soybean curd which is one of soy protein-based gel foods was applied as a mode. Varied amounts (0~2.0%) of SHPP was added and segregative phase separation was investigated in these mixed systems. Correlation of their microphase behavior and the macro-properties (e.g., rheological behavior, mechanical properties, water holding capacity and sensory evaluation) were analyzed in detail. Besides, citrus pectin (CP), a commercial pectin that is commonly involved in foods, was used as a control. Based on the results, it was found that extraction yield of SHPP was up to 17.95% ± 0.21%. The obtained SHPP was mainly consisted by pectin, with galacturonic acid content of 42.13% ± 2.05%. Mean size of SHPP dispersion was determined as (210.3 ± 2.9) nm and polydispersity index (PDI) was 0.466 ± 0.037. The extracted SHPP was well dispersed in water due to its hydrophilic property and low shear viscosity. When 0~0.5% SHPP was added to prepare soybean curd, microphase separation did not occur in this situation. The obtained soybean curds were pretty white and in good appearance, with viscoelastic network and excellent water holding capacity (> 93%). Increasing SHPP concentration to 1.0%, leaking water was visible around the soybean curd. Both of the viscoelasticity and water holding capacity were significantly (P<0.05) reduced. When the addition of SHPP was up to 1.5%, obvious phase separation was observed. Microstructure of the obtained soybean curd become disordered and pore of the network enlarged, resulting in weak gel strength and poor water holding capacity (46.2% ± 3.2%). Therefore, the ideal addition concentration of SHPP to prepare soybean curd was 0.5%. Soybean curd which prepared with the optimal CP concentration of 0.1% was set as a comparison. Results showed that texture properties and sensory scores related to color, texture, flavor, taste and acceptability of the soybean curd prepared with 0.5% SHPP were better than that with 0.1% CP. This suggests that SHPP is more suitable for the preparation of protein-based gel foods. It can serve as a bioactive substance and provide various physiological functions in foods. Most importantly, the exploitation of SHPP is conducive to the recycle of soybean byproducts and the development of whole bean food.
    November 21, 2022 , DOI:
    Abstract:
    Gluten forms wheat gluten protein (WGP) through hydration to build a fine and compact network structure, which has great viscoelasticity, extensibility and film formability. However, this structure has low stability and water-holding capacity to break after heating. In this research, wheat gluten, soy isolated protein (SPI), methylcellulose (MC) and glutamine transaminage (TG) were selected to study to establish the blend system, which contain the vegetable protein, hydrophilic colloid and coagulating gelatinase. It is vital to investigate the effects and relationship of each component on the physicochemical properties, gel properties and structure of the blended adhesion system. The SPI, MC and TG were added step by step to WGP and compared. The results showed that the disulfide bond content in the mixed system decreased by 81.03%, increased by 248.50% and 0.69%, the free mercapto group content increased by 68.79%, 6.85% and 17.16%. The mdecreased by 43.45% and 25.69%, the surface hydrophobicity increased by 5.33%, decreased by olecular weight of high molecular weight glutenin component increased gradually with the gradual addition of WGP into the mixed system. The water holding capacity increased by 5.25%, 2.91%, 2.79%, and the gel strength increased by 104.14%, 24.66%, 3.52%. When it comes to the molecular weight, SPI could perturb the WGP network structure, and the less soluble parts of SPI intersect with WGP leading to the disappearance of some subunits. The addition of MC strengthened the cross-linking between proteins to produce aggregates increasing the molecular weight, and TG enzymes dispersed the large aggregates into uniform small aggregates.With the progressive addition of the three fractions, the tangles of molecular chains in the gel system increased with the degree of gelation, and the storage modulus and loss modulus rised gradually. The addition of TG enzyme prevented the transforming of α-helix structure into β-turn and nonregular coil structure gradually, which induced the increasing of α-helix and β-sheet content. It could be seen that the intermolecular entanglement points of the gel of the blend bonding system increased with stronger gel property. This showed that the addition of SPI partially destructed the network structure of WGP , but MC and TG enzymes would promote the aggregation degree and gel strength of protein. The structural gels formed by SPI bind to WGP through covalent, disulfide bonds and hydrophobic interactions. The addition of MC would cause double protein water loss aggregation through hydrogen bonding. TG enzyme would further induce to promote the crosslinking between SPI and WGP to make the skeleton network structure closely. The SEM observation indicated that SPI was embedded in the WGP network skeleton, forming a new architecture form of half network and half filling. With the addition of MC and TG enzymes in turn, on the basis of forming a large number of cross-linked filamentous structures, local continuous membrane structures were formed to cover the particles by soybean drawing protein (SDP). It showed that SDP particles were completely and tightly wrapped in gluten SPI-MC-TG enzyme blend adhesive system. The SDP based meatloaf was made by using this bonding system, and four raw materials were added to the rehydrated SDP in turn, which showed that the hardness, cohesion, chewiness and elasticity of the meatloaf were improved. Therefore, it is an effective method to establish the gluten based blending adhesive system to improve the quality of meat products with SDP as the main raw material.
    November 21, 2022 , DOI:
    Abstract:
    Today, most consumers avoid eating meat because eating processed meat often leads to cardiovascular disease and cancer, so more and more people are interested in plant-based meat products. Pre-emulsification technique, which is the preparation of an oil-in-water emulsion before introducing fat/oil to a meat product. Compared to direct oil addition, this technique increases the ability to bind water and oil and allows for better dispersion of oil into the meat batter. Recently several studies have also reported that the particle size of the pre-emulsified oil can influence the textural properties and gel formation of the sausage. However, few studies have reported effects of droplet size and emulsifier used in the pre-emulsion on the rheological and textural properties of vegetarian sausage. Therefore, the aim of this work was to apply the pre-emulsification process to the processing of vegetarian sausages with Textured Fibril Soy Protein (TFSP). The effects of oils pre-emulsified on the rheological properties, texture and microstructure of TFSP vegetarian sausages were investigated by using different protein emulsifiers and regulating the homogenization conditions. It was found that the apparent viscosity of both Soybean Protein Isolate (SPI) and Sodium Caseinate (SC) emulsions increased gradually as the pressure homogenization increased from 0 to 30 MPa. The particle size d3,2 of SPI emulsions ranged from 24.80 to 0.39 μm and the particle size d3,2 of SC emulsions ranged from 12.37 to 0.12 μm. The results of the temperature sweep and frequency sweep of the TFSP vegetarian meat batter showed that all the vegetarian meat batters formed an emulsion gel with viscoelasticity after cooking, and the higher the homogenization pressure of the pre-emulsion, the higher the storage modulus (G′) of the vegetarian meat batter. In the Warner–Bratzler (WB) shear test and Texture Profile Analysis (TPA), it was found that the breaking force and TPA (Hardness, Springiness, Cohesiveness, Chewiness) of TFSP vegetarian sausages increased with decreasing the particle size d3,2 of the pre-emulsion. The microstructures of different emulsions and TFSP vegetarian sausages were observed and analyzed by Confocal Laser Scanning Microscopy (CLSM). It was found that coalescence of emulsion droplets occurred in TFSP vegetarian sausages after cooking when SC emulsions were prepared at pressure of 0-20 MPa. However, the TFSP vegetarian sausages prepared by SPI emulsions showed a strong ability to resist the coalescence of emulsion droplets after cooking. Therefore, the shear force and textural properties of TFSP vegetarian sausage can be effectively improved when the pressure is more than 20 MPa during the pre-emulsification of plant oils using SPI. The results of this study provide a reference for the development and application of oil pre-emulsification process in vegetarian products.
    November 21, 2022 , DOI:
    Abstract:
    Ecological protection and restoration of territorial space is an important guarantee for maintaining national ecological security patterns, and scientific zoning and manage the key areas for protection and restoration is of great significance to maintain regional ecosystem function and sustainable development. Taking Shanghang County in Fujian Province as a typical study area case, this study constructed a multi-dimensional ecosystem measurement framework of "Ecosystem Importance - Ecosystem Fragility - Ecosystem service value" based on integrating ecosystem integrity, systematisms, and ecological benefits. And then, we analyzed the multi-dimensional characteristics of the regional ecosystem and the relationship of trade-offs and synergy between measure factors. At last, spatial clustering method (Grouping analysis) was used to delineate the ecological protection and restoration space, and the zoning management and control strategies were proposed based on the spatial heterogeneity and ecosystem structure characteristics of each zone. The results showed that: 1) The ecosystem has strong spatial heterogeneity, showing a spatial differentiation ecosystem pattern with high importance, low fragility, and high service value in Shanghang County. 2) There were synergistic and tradeoff relationships among all ecosystem measure factors in study area. The relationship of comprehensive importance, fragility and service value are all synergistic, which may lead to high overlap between ecosystem conservation and restoration areas. 3) According to the results of CONTAG and COHESION index with different number of clusters, 6 was determined as the optimal number of clusters, indicating that the cohesion degree and connectivity among groups in the study area were the strongest, which was conducive to the stable and healthy development of the ecosystem. The study area can be divided into six zoning: III-I-V(Importance level III- Fragility level I-Value V), III-III-V(Importance level III- Fragility level III-Value V), III-II-V(Importance level III- Fragility level II-Value V), III-III-IV(Importance level III- Fragility level III-Value IV), II-III-I(Importance level II- Fragility level III-Value I) and IV-I-I(Importance level IV- Fragility level I-Value I), the zoning of III-I-V and III-II-V have large areas and are the ecosystem functional bases for regional development. The composition of land cover types in each zoning has obvious spatial heterogeneity and the forest, shrub, cropland, and garden were the dominant land cover types. 4) According to the characteristics and spatial distribution and internal structure of each zoning, we proposed targeted and differentiated ecological and economic management policies and environmental protection and restoration measures. The study area was further divided into ecological protection area (Ecological conservation area, green development area, Moderate development area) and ecological restoration area (Ecological restoration area, Protection and restoration coordinated development area) according to the ecological protection and restoration measures. The multi-dimensional ecosystem measurement "I-F-V" aims to identify important ecosystems, damaged areas of ecosystems and integrate ecosystem services benefits. While considering the integrity and systematisms of ecosystems, it also emphasizes the coordination of ecosystem protection and restoration costs and development opportunities. It effectively assesses the resilience and sustainability of ecosystems and the economic activities and human well-being they support, which can be widely used in ecosystem measurement and ecological conservation and restoration research and practice. The research results would provide scientific and comprehensive research ideas and practical reference for regional planning and construction of territorial space protection and restoration planning and construction, ecological security pattern maintenance.
    November 16, 2022 , DOI:
    Abstract:
    Water, energy and food are indispensable resources in terms of human life and development, the shortage and matching dislocation of water resources and energy can hinder the growth rate of food production to a certain extent. In this paper, Lorentz curve and Gini coefficient are used to evaluate the matching degree between water-grain and energy-grain in the Yellow River Basin. Based on Cobb-Douglas function, the grain growth damping model is applied, and the restriction degree of water resources and energy on grain production in the Yellow River Basin is calculated. The results show that: 1) The Gini index of water resources and energy to grain in the Yellow River Basin has decreased first and then increased, and the matching degree of which in the lower reaches of the Yellow River is more reasonable than that of the upper and middle reaches. In 2019, the Gini index values of water resources to grain in the Yellow River Basin and the upper, middle and lower reaches were 0.365, 0.379, 0.336 and 0.122 respectively, while the Gini index values of energy to grain were 0.194, 0.218, 0.206 and 0.118 respectively, it indicated that the matching degree of water resources and energy to grain show high matching status in the lower reaches. The water resources and energy in the upper and middle reaches are generally matched with grain. 2) The damping coefficient of water resources to grain production fluctuates greatly in the Yellow River Basin, and the variation range of damping coefficient is 0.005~0.032. Besides, the damping effect of water resources on grain growth basically presents a 6-year cycle with a decrease-increase-decrease situation. While the damping effect of energy on grain shows a steady increase situation, and the energy damping coefficient increased rapidly after 2015. Under the constraints of water resources and energy in 2019, the annual grain output growth in the Yellow River Basin reduced by 0.76% and 5.28% respectively compared with the previous year. 3) The damping effect of water resources and energy has a certain degree of agglomeration, the damping coefficient of water resources in the Yellow River Basin presents the situation of small in the West and large in the East. The energy damping effect presents a medium and high constraint state, which is concentrated in the eastern and lower reaches of the upper reaches, and the low constraint state is concentrated in the middle reaches of the Yellow River. In addition, the damping coefficient of water resources and energy in the Yellow River Basin has typical spatial agglomeration characteristics. The H(High)-H(High) agglomeration area of water resources damping effect is mainly distributed in the lower reaches of the Yellow River, the L(Low)-L(Low) agglomeration area of energy damping effect is distributed in the northern part of the middle reaches. It is hoped that this study can have a certain reference basis for the stable growth of grain and the effective allocation of resources in the Yellow River Basin.
    November 16, 2022 , DOI:
    Abstract:
    Abstract: The "third line" of land spatial planning and the spatial characteristics of cultivated land quality serve as the foundation for the spatial layout optimization of cultivated land protection, which is essential for improving the quality of cultivated land and ensuring food security. In this study, which used the enhanced local spatial autocorrelation model, the ecological environment served as the "fourth dimension" of the spatial correlation analysis framework of cultivated land quality. After simulating the spatial autocorrelation correlation results of the natural quality index, utilization management index, economic value index, and ecological environment index of cultivated land in the "third line" from the plot scale, a plan for improving the spatial layout of protecting cultivated land was presented. The findings of this study have important repercussions for the geographical evolution of agricultural ecological landscape patterns, food safety, and farmland pollution control. The specific procedure were: First, this study estimated the natural quality index, utilization management index, economic value index, and ecological environment index in plots using data from 1073 soil monitoring stations in the Gaochun District and the outcomes of the three-line delineation of land spatial planning. Second, this study analyzes the spatial correlation of each indicator using the spatial error model of the enhanced spatial weights. Finally, based on the geographical association findings of permanent basic farmland, urban development boundary, and the quality of inland blocks of ecological protection red line, this study suggests a strategy for the spatial layout optimization of cultivated land. The results indicated: 1) The Gaochun District has much more high-quality cultivated land concentrated in the west and dispersed in the east when it comes to the geographical distribution of cultivated land quality. Poor-quality agricultural land is more prevalent in Gaochun's eastern part than in its western region. The ecological environment index, economic value index, utilization management index, and natural quality index all demonstrated the "west high, east low" features of geographical distribution. 2) Each cultivated land quality index has a positive geographic correlation when looking at spatial autocorrelation analysis of the cultivated land quality index, and both positive and negative correlation types are quite compatible with the spatial distribution of high and poor quality cultivated land. The natural quality index, utilization management index, economic value index, and ecological environment index all have Moran's I values of 0.79, 0.92, 0.89, and 0.77, respectively, and all of them clearly exhibit spatial aggregation features. The ones that are graded from large to small geographically are the Utilization Management Index, Economic Value Index, Natural Quality Index, and Ecological Environment Index. 3) The cultivated land in Gaochun District was divided into 14 second-level categories and four first-level categories based on the results of the spatial correlation of the quality of the cultivated land, including permanent basic farmland protection zone, urban development buffer zone, ecological environment protection zone, and comprehensive adjustment zone. Both the permanent basic cropland and the grade rose by 0.94 hm2. The permanent basic farmland protection zone’s quality is the best among them, and each quality measure has a significant positive spatial dispersion impact, which should form the basis of cultivated land protection to forbid non-agricultural building. The urban development buffer zone is the best place for urban growth since the quality of the farmed land is low and the geographical benefit is significant. The ecological environmental protection zone should energetically carry out ecological protection works in the fields in order to construct an ecological red line protection grid, despite having a relatively visible deficit in terms of overall quality but having outstanding ecological circumstances. The following proposals are made for public policy: 1)Arable land ecological safety should be incorporated into the framework of arable land quality while preserving arable land quantity. 2)The government should build as soon as feasible a three-in-one mechanism to protect arable land in terms of quantity, quality, and ecology. 3)The government should establish a social support system for preserving arable land and increase public understanding of its significance. 4) The government should support regulatory agencies for the preservation of the ecological integrity and quality of arable land as well as the growth of regional cooperative economic organizations.
    November 08, 2022 , DOI:
    Abstract:
    Peanut sprout is a kind of food with both food and therapy produced by peanut germination, also known as longevity sprout. It has crisp taste and unique flavor, and is favored by consumers. It has been found that after sprouting, the energy, protein and crude fat content of peanut buds is significantly higher than that of various vegetables, and the content of vitamins, potassium, magnesium and other minerals as well as various amino acids and trace elements required by human body increases significantly, especially the content of resveratrol, a polyphenol with important bioactive functions, will increase rapidly. In recent years, it has received wide attention from scholars at home and abroad, and it has been found by a large number of studies that resveratrol has broad-spectrum antibacterial activity, but there are few reports on the effects of peanut bud resveratrol on Salmonella typhimurium. This paper focuses on the isolation and purification technique of resveratrol from peanut buds and its antibacterial properties. The objectives of this study were to screen resins with good adsorption and desorption properties for peanut bud resveratrol compounds, to establish their isolation and purification process, to evaluate their antibacterial efficacy, and to improve the comprehensive utilization value of peanuts. In this study, we compared the effects of 16 different types of macroporous resins on the separation and purification of arachidonic resveratrol compounds through static adsorption-desorption tests, and selected LSA-40 as the best adsorption resin type, which can reach saturation in 110 min of static adsorption and plateau in 90 min of static desorption; optimized its dynamic adsorption-desorption conditions, and came up with the following adsorption conditions: the upper sample concentration The dynamic adsorption-desorption conditions were optimized, and the following conditions were obtained: the loading concentration was 120.00 μg/mL, the rate was 1.00 mL/min, the pH value was 4.2, and the loading volume was 8.00 mL/g; the desorption conditions were: 80% ethanol solution, pH value was 6.6, and the flow rate was 1.00 mL/min; under the optimized process conditions, the absorption peaks of the purified arachidonic resveratrol and the control were basically the same by UV spectral analysis, and the purity was calculated to be 84.0%; fourier infrared spectroscopy and high performance liquid chromatography tandem mass spectrometry were used to identify and analyze the components of the purified samples, and it was found that the main components of the purified products were resveratrol and its derivatives.; the inhibition effect of the purified product on Salmonella typhimurium was evaluated by multiplicative dilution method, inhibition growth curve and change of cell membrane permeability, and the results showed that the minimum inhibitory concentration of arachidonic resveratrol purified product on Salmonella typhimurium was 250 μg/mL, at which the cell membrane permeability could be significantly increased (P < 0.01), and the integrity of cell wall was damaged, causing serious leakage of intracellular proteins, which eventually led to death of Salmonella typhimurium. This study can provide some theoretical reference for the comprehensive and deep utilization of peanut resources and the development of natural antibacterial agents.
    November 04, 2022 , DOI:
    Abstract:
    Aggregate stability (MWD), as an important soil structural unit, play a vital role in soil water, air and nutrient transport and soil erosion. Up to date, some limitations in the systematic research on the microstructure and aggregate stability for different types of zonal soil aggregates still exist. In order to explore the aggregate stability and their relevance to pore structure characteristics in different types of zonal soil, five types of typical soils (Black soil, Brown soil, Cinnamon soil, Yellow-cinnamon soil and Red soil) were selected as the research objects based on geogenesis. The soil samples were collected separately from Hailun (Heilongjiang), Shenyang (Liaoning), Luoyang (Henan), Xiangyang (Hubei), Changsha (Hunan), and Haikou (Hainan) according to the latitudinal direction zonality of soil distribution in this study. Combined with CT scanning, wet sieving and LB method, the pore structure and MWD of aggregate were quantified. The results indicated that the water stability of aggregates was affected by soil type and soil depth with the order of Yellow-cinnamon soil < Cinnamon soil < Brown soil < Black soil < Red soil, the eluvial horizon in Red soil was the highest (1.49 mm), and the parent material horizon in Yellow-cinnamon soil was the lowest (0.19 mm). The aggregate stability under three treatments showed slow wetting (SW) > shaking (WS) > fast wetting (FW), indicating that dissipation and external mechanical failure were the main fragmentation mechanisms of aggregates. From north to south, the resistance of soil aggregates to dissipation and fragmentation gradually decreased and then increased, and the effect of dissipation on the degree of fragmentation of soil aggregates was higher than that of mechanical damage. Significant differences were found in the aggregate microstructure of different soil types. The porosity of different effective pore diameters inside soil aggregates showed a U-shaped pattern of change from north to south, which gradually weakened with the increase in soil profile depth. Total porosity and pore number were the highest for Black soil aggregates (13.04%, 5143) and lowest for Yellow-cinnamon soil aggregates (5.61%, 1585). The porosity of different equivalent diameters decreased first and increased from north to south. The pore sizes in most aggregates were observed to be 30-75 μm, however, the pores larger than 100μm were dominant in the Yellow-cinnamon soil, which was connected with the original particle arrangement and the low content of cementing material in the soil. The aggregate pore morphology was dominated by elongated pores with few regular pores and irregular pores. From north to south, the elongated pores decreased first and then increased, while an opposite trend were found in the irregular pores and regular pores. The aggregates stability showed significant positive correlations with total porosity, total pore numbers, elongated porosity, <30 μm porosity, 30-75 μm porosity, 75-100 μm porosity and >100 μm porosity, and inversely correlated with regular porosity and irregular porosity (p<0.01). The relationship between pore parameters and aggregate stability were then analyzed using the method of partial least squares regression (PLSR). According to PLSR, the regular pores, mean pore shape factor, 75-100 μm porosity and elongated pores had significant effects on water stability of aggregates, and elongated pores showed as a positive effect. 75-100 μm porosity, >100 μm porosity, elongated pores, and regular pores were the main pore characteristic factors controlling the aggregate stability under the LB method. 75-100 μm porosity, >100 μm porosity and elongated pores were identified as the primary factors controlling the air content, water entrance, and failure stress of interior aggregates, which can reduce the rate of air saturation in the aggregates and decrease the pore expansion pressure, thus improving the stability of aggregates. These results improve the understanding of pore characteristics and aggregate stability, which provide a new way to explain the mechanism of soil processes.
    November 03, 2022 , DOI:
    Abstract:
    Rill erosion has been widely acknowledged as an important form of soil erosion on hillslopes, given that rill erosion does not dominate hillslope erosion but also exert a crucial impact on other erosion processes on downslope areas (e.g. gully head retreat). Morphological parameters of rills provide a useful indicator for understanding the initiation and development of rills. Previous studies have investigated the changes of rill morphology and its relation with the erosion-deposition processes of hillslopes. However, those studies were mainly undertaken through laboratory experiments. The physiochemical properties of backfill soil used in the laboratory experiments were rather different from those of natural soil in the field, thereby largely constraining the representativeness of those experiments for field erosion processes. Further studies were needed to explore the rill morphology and its association with erosion processes in the field. In this study, field scouring experiments were conducted to fulfill the above need on five erosion plots established on a natural slope of a small catchment (i.e. Xindiangou catchment) in the hilly and gully Loess Plateau, with the input flow of hillslopes being 25, 40, 55, 70, 85 L/min. Terrestrial laser scanning (TLS) was employed to acquire the ultra-high terrain information prior to the experiments and after each of the experiments. The achieved terrain information was then used to derive various morphological parameters of rills, including geometric indicators (length, width of cross sections, depth of cross sections), derived indicators (the ratio of width to depth, rill density, rill cleavage, average rill depth), fractal dimension, bifurcation ratio and geomorphic information entropy etc. The changes of these morphological parameters during the experiments were examined, while their relation with cumulative erosion mass, cumulative deposition mass and cumulative sediment yield was investigated respectively to determine the indicative morphological parameters for hillslope erosion processes. Results showed that: (1) The width and depth of cross sections of rills as well as average rill depth and rill cleavage increased as the experiment progressed under all the flow condition. The changes of width-depth ratio were related to the input flow rate. The rills were primarily wide and shallow under the low flow condition (25 L/min), and mainly narrow and deep under the moderately low (40 L/min) and high flow (85 L/min) condition, while their development changed between the narrow-deep manner and the wide-shallow manner under the moderate (55 L/min) and moderately-high (70 L/min) flow condition.(2) As the scouring experiments progressed, the fractal dimension of rills was found to change slightly under the low flow condition while it changed considerably under other input flow condition. The bifurcation ratio of rills increased during the experiments under the moderate flow condition, while it decreased under other flow condition. The change of geomorphic information entropy varied under different flow condition. However, the change trend of geomorphological information entropy and sediment yield is basically the same, which can better reflect the dynamic changes of soil erosion. (3) The average rill length, average depth of cross sections and the derived average rill depth were able to indicate the cumulative deposition mass, erosion mass and sediment yield under the moderately low flow condition. The derived average rill depth was also able to reflect the cumulative erosion mass and cumulative sediment yield under the low flow condition. The average width of cross sections, average depth of cross sections and derived average rill depth were able to indicate the cumulative erosion mass under the moderately high flow condition. In addition, the relationship between rill morphological parameters and cumulative erosion mass, deposition mass and sediment yield tended to become less significant as the input flow increased. Our study enhanced current understanding on the processes and mechanisms of hillslope erosion.
    October 31, 2022 , DOI:
    Abstract:
    The precise determination of the remediation object is the premise of advancing the homestead remediation orderly, and is also the key to the implementation of the whole land comprehensive remediation. Based on multi-source data such as land survey, homestead right confirmation survey and social and economic survey, this paper takes the administrative village as the unit, comprehensively considers economic, social, transportation, and land factors, and adopts coefficient correction method and multi-factor comprehensive evaluation method to obtain the potential scale of homestead right confirmation consolidation at the village level. Taking the plot scale homestead plot spot as the basic renovation unit, combining the comprehensive evaluation of upper guidance, status driven, and willingness obstruction, the consolidation probability of each land parcel with the right confirmation was obtained as the criterion for the priority selection of the renovation unit. The results showed that: (1) gross average homestead-construction land correlation coefficient of Maogudui town is 0.5801. Confirmed homestead potential with the theory of regulation 208.32 hm2, potential reality regulation 117.17 hm2, a total of 56.25% of the potential theory of regulation can be realized. It can reduce the 24.24% current area of confirmed homestead. Under the influence of location advantage and future land demand, the spatial distribution of realistic remediation potential generally shows that the larger the potential is, the farther it is from the market town. (2) The probability of housing land consolidation is the judgment criterion for choosing the priority of housing consolidation. From the perspective of the area of confirmed homestead corresponding to different probability intervals, the total area of homestead with high consolidation probability is lower. However, whether to preserve or renovate should follow the logic of priority of renovation with high probability and low probability of renovation of homestead, and the specific choice should be made according to village differences. (3) Based on the potential constraints of different villages, the iterative selection of consolidation units was carried out in different villages. A total of 4512 consolidation units were selected, with a consolidation area of 117.79hm2. The consolidation probability of all the selected units was greater than 0.5. Among them, the remediation units greater than 0.65 can achieve a total area of 85.13hm2, accounting for 72.27% of the target area. The spatial distribution characteristics of the regulated units showed the connectedness of the regulated units, the priority of the hollowing area, and the priority of the non-central village area, which is beneficial to enhance management efficiency, forming the cultivated land scale shall, realize the cultivated land resource optimization. At the same time, the priority renovation of non-central villages is conducive to responding to the planning objectives and realizing the development of focused villages. Research conclusion: Guided by the results of Spatial Planning of National Land, this paper takes homestead land as the basic unit to conduct land-scale consolidation simulation, which can directly correspond to the owner of land tenure. The consolidation simulation results can provide specific and accurate decision-making reference for the implementation of comprehensive land consolidation in a certain planning period.
    October 27, 2022 , DOI:
    Abstract:
    Wheat stripe rust and wheat yellow dwarf have posed a great threat to the yield and quality of wheat. Early identification of these two diseases has important implications for the prevention and control of wheat diseases. Drought, nutrient deficiency and bacterial disease can lead to chlorosis and yellowing of plant leaves. These phenotypic symptoms are similar to infected leaves of wheat stripe rust and wheat yellow dwarf. In addition, the infected leaves of these two diseases are similar to healthy leaves because of indistinct phenotypic symptoms in the early stage of diseases. It is difficult to quickly and accurately distinguish them by existing identification methods. In this study, an improved Faster Regions with CNN Features (Faster-RCNN) disease identification method was proposed. There are two improvement strategies in our proposed method. Firstly, in order to enhance the fine feature extraction capability of the entire network and reduce the number of model parameters, three 3×3 grouping convolutions and down-sampling delay were employed to optimize the Deep Residual Neural Network (ResNet-50), which was designed as the backbone feature extraction network. Secondly, ROI Align was employed instead of ROI pooling to reduce the feature error problem caused by double quantization. It is helpful to solve the difficult problem of distinguishing subtle differences. Meanwhile transfer learning was employed to improve the training speed of the model and data augmentation was utilized to reduce over-fitting problems, which can further enhance recognition performance and generalization ability of our method. Experiments were carried out on a self-built data set of disease leaf images covering more than 200 wheat varieties showing different resistance and susceptibility to diseases while covering various symptoms at different disease stages. Performance indicators such as loss function convergence curve and mean mean precision (mAP) were selected to evaluate the effectiveness of the improved strategy. The experimental results showed that the mAP of the improved Faster-RCNN identification method proposed in this paper was 9.26% higher than the SSD, 7.64% higher than the YOLO, and 14.97% higher than the Faster-RCNN. The mAP of our proposed method reached 98.74% for wheat stripe rust, wheat yellow dwarf, healthy wheat and wheat with other etiolation symptoms. Moreover, in order to predict the diseases as early as possible, the early identification of disease infection was strengthened in this study. Our dataset contains 683 and 630 mild symptom photos of these two diseases respectively. The mAP for mild and severe symptom identification of these two diseases reached 91.06% by utilizing our proposed method. In addition, the value of the loss function decreased faster, as well as model performed better overall. Finally, In order to implement the deployment and application of our proposed method, the intelligent recognition system of wheat disease was developed, and WeChat applet was used to identify wheat diseases in the field. Under the condition of maximum concurrent access of 100, the average return delay was 5.024 seconds, and the success rate of recognition return was 97.85%, and the average accuracy of the recognition of two kinds of wheat diseases and their subdivision was 93.56%. The system can effectively meet the practical application requirements and be employed to guide the scientific prevention and control of diseases.
    October 25, 2022 , DOI:
    Abstract:
    During the storage process of blueberries, changes in water content directly affect their edible quality. The relaxation spectrum information and proton density image information of blueberries stored at 0, 8, and 23 ℃ for 0, 3, 6, 9, and 12 days were collected by low-field nuclear magnetic resonance and imaging technology. Then the changes and migration of water content in blueberries were analyzed under different temperature storage conditions. The experimental results showed that the relaxation time and the peak area of the relaxation spectrum could effectively estimate the moisture content and migration changes of blueberries during storage, and the temperature was sensitive to the moisture content changes. With the prolongation of storage time, the vacuolar water content A23 and the total water content A2 showed the same trend of change, showing an overall significant downward trend. During the storage of blueberries at 0 ℃ and 8 ℃ for 12 days, the relaxation time shifted to the right with the prolongation of storage time and the cell wall water content A21 did not change significantly, while the cytoplasmic water content A22 showed a slight increasing trend. When the blueberries were stored at 23 ℃ for 9 days, they rotted and the cell wall water and cytoplasmic water increased rapidly. Especially after stored for 12 days, the vacuolar water decreased sharply and transformed into cytoplasmic water and cell wall water. Compared with the storage at 23 ℃, the internal water migration in low temperature storage was slow and the loss was less. While exploring changes in moisture, the changes in gray value, pseudo-color value, shape and water loss rate during storage of blueberries were also analyzed. The results were confirmed that blueberries at low temperature could be stored for at least 12 days, and the shelf life of blueberries was about one week at room temperature. For the gray value of blueberries, it decreased slowly at 0 ℃ and 8 ℃ until 12 d, and the decline loss values were all within 17.00% of the gray value at 0 d,while it began to cliff-like on the 6th day at 23 ℃. The shape of blueberries stored at 0 ℃ and 8 ℃ for 12 days remained relatively intact and the water distribution was relatively uniform. However, after 9 days of storage at 23 ℃, blueberries rotted, resulting in deformation of shape and irregular distribution of water. The water loss rates of blueberries stored at different temperatures for 12 days were 23.68% (0 ℃), 34.39% (8 ℃), 36.74% (23 ℃), respectively, and the value at 0 ℃ and 8 ℃ continued to rise, while it decreased at 23 ℃ on the 9th day due to rot, so there was no rule to follow. The test results can provide theoretical support and data reference for the storage and preservation of blueberries at different temperatures.
    October 25, 2022 , DOI:
    Abstract:
    In order to understand the changes of physiological and biochemical indexes of high oil soybeans during storage, high oil soybeans from Henan and Inner Mongolia were selected as the research object. After adjusting to different moisture (13.00 ± 0.20% and 15.00 ± 0.20%), they were stored in closed storage at 25 ℃ and 35 ℃ for 180 days respectively. Samples were taken every 30 days to determine and analyze their physiological and biochemical indexes, and the change trend of electrical conductivity and malondialdehyde were dynamically analyzed. The results showed that cat activity, POD activity and PPO activity of two kinds of high oil soybeans with different initial moisture content decreased, while electrical conductivity and malondialdehyde content increased with the extension of storage time at different temperatures. The variation range of biochemical indexes of Henan soybean with relatively high fat content at different temperatures is higher than that of Inner Mongolia soybean. The results of correlation analysis showed that the storage time had a significant or extremely significant correlation with the physical and chemical indexes of soybeans from the two producing areas. Among them, it had a strong correlation with the activities of malondialdehyde and PPO, with coefficients of 0.81 and -0.90 respectively. The correlation coefficients between storage temperature and the electrical conductivity of soybeans from Henan and Inner Mongolia were 0.66 and 0.61 respectively. The electrical conductivity and malondialdehyde of high oil soybean at different storage temperatures accord with the zero order kinetic model, and the two indexes belong to the energy required reaction during storage( Δ G > 0)。 The conductivity and zero order kinetic activation energy of malondialdehyde of Henan soybean with high crude fat content are higher than that of Inner Mongolia soybean, and the higher the initial moisture content, the greater the kinetic coefficient and the smaller the activation energy, the easier it is to lead to the change of conductivity and malondialdehyde. The zero order kinetic reaction coefficient increases with the increase of temperature, indicating that the higher the temperature, the greater the impact on the index.
    October 20, 2022 , DOI:
    Abstract:
    Improper irrigation and nitrogen (N) application has caused severe N losses and imbalance in nitrogen budget of spring wheat growing field in the irrigation district of middle and upper reaches of Yellow River, Northwest China. Thus, aiming at determining the rational irrigation and N fertilization strategy for sustainable production of spring wheat and nitrogen pollutants mitigation in this area, a field experiment was carried out in 2019-2021 to investigate the effects of irrigation and N application on soil N losses, crops N uptake and soil N budget. Three irrigation levels (I450, I315 and I180 with the number representing the irrigation depth, mm) and three N fertilization levels (N340, N250 and N170 with the number representing the N application rate, kg N ha-1) were considered in the experiment. The results showed that the fertilizer N was the main source of field N input, followed by irrigation water, atmospheric deposition, and non-bio fixation, while crops N uptake accounts for the largest proportion of soil N output, followed by NO3--N leaching, NH3 volatilization and N2O emissions. For N input, its value decreased with reducing irrigation depth and N application. For soil N output, reducing irrigation water and N application amount could significantly decrease soil total N losses, but lower irrigation water and N application would result in the reduction in wheat N uptake. The N1 treatment could result in soil N surplus, and the N3 treatment with about 50% decrease of N application amount resulted in soil N deficit. Control treatment, i.e., I1N1 resulted in the highest soil N losses, and its N losses accounts for up to 23-41% of soil N output. The NO3--N leaching and NH3 volatilization accounts for 95% of total N losses. Compared to the control treatment, the I2N2 treatment could reduce N losses by 30% without affecting crops N uptake. Meanwhile, the soil N of this treatment was in a state of slight deficit, and the soil N deficit was only 28-50 kg N ha-1. This value accounts for 11-20% of the total N application amount. If 4-8 t ha-1 season-1 wheat straw was returned to the field after harvest, the N balance of the wheat field soil could be maintained. Thus, it is evident that the soil N losses from the spring wheat farmlands in the upper Yellow River basin, Northwest China can be effectively mitigated and the soil N balance can be achieved through improved irrigation and N application management and combined with appropriate straw returning.
    March 14, 2022 , DOI:
    Abstract:
    Abstract:Planting area of fruit trees in Xinjiang accounts for about 13% of the national planting area, which is the main fruit trees producing area in China. With the help of suitable climate condition and resource advantages, the four prefectures of Southern Xinjiang around the Tarim River Basin have become the main producing area of Xinjiang specialty fruit (e.g. walnut, jujube, apricot, fragrant pear and apple). The fruit planting area here accounts for more than 80% of the total fruit planting area in Xinjiang. Real-time and accurate acquisition of fruit tree type and area information under the pattern of forest and crops interplanting is significance to improve the quality and efficiency of specialty fruit industry in southern Xinjiang. It will be conducive to improvement local farmers’ income, stabilize the achievement of poverty alleviation and promote rural revitalization. This study is to take the continuous area of forest and crops interplanting in Hotan Oasis of southern Xinjiang as an example. It proposes a method for extracting the structure information of fruit trees that integrates high-resolution remote sensing image data with abundant texture and spectral characteristics and medium-resolution sensing image data with multi-temporal characteristics. Firstly, it used object-oriented methods to extract high-precision boundary of fruit trees parcel based on GF-2 (PMS) image data. The classification rules of GF-2 image data are divided into winter (February) and summer-autumn (July-September). By analyzing Normalized Difference Vegetation Index (NDVI), spectral characteristics and texture feature information between target objects and other ground objects, it identified the correspondence between feature information and ground objects, and the classification of four plots was obtained by gradually eliminating non-target ground categories. Then, it constructed NDVI time series products based on multi-temporal Sentinel-2 image data, and established a decision tree model based on the characteristics of phenology to extract interplanting walnut orchard, pure walnut orchard, jujube orchard and grape orchard. The NDVI time series of fruit trees was analyzed, and it found that NDVI time series curve had many peaks and troughs in one year. The peak would represent the flourishing period of fruit trees growth, and the trough reflected the orchard management (such as irrigation and pruning branches). Although the NDVI timing series of pure walnut, interplanting walnut, jujubes and grapes are rarely staggered and overlapping, there are still obvious and different time windows. These differences contribute to the fruit trees classification. Finally, the multi-phase orchard classification results were overlay the high-resolution of fruit trees parcel to obtain the distribution of fruit crops in Hotan Oasis. The research results show that the area of major fruit was 4.29×105 hm2 here, with 3.31×105 hm2 of walnut orchard (including interplanting and pure walnut), 8.29×104 hm2 of jujube and 1.40×104 hm2 of grapes.The area of interplanting walnuts accounts for 63.8% of total fruit area,followed by jujube (19.38%) and grapes (3.3%). The user accuracy and overall classification accuracy are both exceed 90%, and the Kappa coefficient is 0.95 which would meet the accuracy requirements of agroforestry classification at the county and city level. Compared with the forestry survey results in 2019, the relative accuracy of walnuts jujube and grapes based on remote sensing extraction results was 62.1%, 97.8%, and 85.2%, respectively. The results show that the area of jujube and grape based on remote sensing extraction is close to the forestry survey datas. The walnut planting areas in Hotan area are mainly distributed in the upper reaches of Yurunkax River and Karakax River with suitable soil and water conditions. The jujube trees are mostly distributed in the downstream oasis desert ecotone and the grapes are mostly distributed in the sandy desert of lower reaches of Karakax River,. This method could provide valuable reference for the research of fruit tree type extraction under the pattern of forest and crops intercropping.
    May 12, 2021 , DOI:
    Abstract:
    Wolfberry (Lycium barbarum) is a traditional Chinese medicinal and edible plant. It contains a variety of functional ingredients and has various functional activities such as anti-aging, immune regulation and anti-atherosclerosis. Hubei hybrid wolfberry is a researcher who induced and doubled Ningxia wolfberry, and then crossed it with the local wild wolfberry in Hubei, and was later introduced to Jianshi County, Enshi Prefecture. It has become one of the important industries in the local poverty alleviation. Compared with Ningxia wolfberry, Hubei hybrid wolfberry has a higher moisture content. The previous study found that it is not suitable for processing into traditional dried wolfberry products. It is urgent to develop new processed wolfberry products to improve the conversion rate of Hubei hybrid wolfberry and the economic benefits of the industry. Using lactic acid bacteria to ferment characteristic fruits can not only give the product a unique flavor, but also transform or increase the types and content of active substances in it, and improve the nutritional value and health benefits of the product. However, there are few reports on the effects of different lactic acid bacteria fermentation on the nutritional quality of wolfberry juice. Therefore, this study used Hubei hybrid wolfberry as raw material and used 6 kinds of lactic acid bacteria (Lactobacillus plantarum, Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus casei and Lactobacillus fermentum) for fermentation. The physicochemical properties, main active components and antioxidant activity in vitro of wolfberry juice before and after fermentation were studied. And establish a method to comprehensively evaluate the quality of fermented wolfberry juice using principal component analysis, in order to select the most suitable lactic acid bacteria strain for wolfberry juice fermentation. The results showed that the 6 kinds of lactic acid bacteria could grow well in wolfberry juice, which the viable count can reach above 10.0 Lg CFU/mL. After fermentation, the total sugar and reducing sugar content in the juice is significantly reduced (P <0.05). Lactobacillus plantarum and Streptococcus thermophilus has better acid production capacity, and the total acid content had 6.74 g/kg and 6.07 g/kg. Compared with unfermented wolfberry juice, the total phenol content in wolfberry juice fermented by Lactobacillus plantarum, Streptococcus thermophilus, Lactobacillus rhamnosus and Lactobacillus fermentum increased by 13.76% to 28.07%, while there was no significant difference in the content of total phenols in goji juice fermented by Lactobacillus acidophilus and Lactobacillus casei (P>0.05). And the total flavonoids content increased by 55.80% to 161.97% after fermentation. The antioxidant activities of fermented wolfberry juice were also significantly improved (P<0.05). Correlation analysis results show that the increase in antioxidant activity is significantly related to the content of total phenols and total flavonoids. Based on principal component analysis, three principal components were extracted, covering three levels of fermentability, nutritional quality, and functionality. They comprehensively reflect the quality of fermented wolfberry juice. The cumulative variance contribution rate is 82.344%. The comprehensive score ranking shows that the quality of wolfberry juice fermented by Lactobacillus plantarum and Lactobacillus fermentum is better, and they are suitable as a starter for developing high-value green processed beverages of wolfberry.
    May 12, 2021 , DOI:
    Abstract:
    Abstract: Solar greenhouse has been widely used in China, and improving the heat storage and release ability of the rear wall of solar greenhouse has always been a research hotspot. The application of PCM in solar greenhouse wall can effectively improve the heat storage and release performance of the wall. Three PCM walls were studied in this experiment. First we tested three kinds of phase change materials in laboratory ability of heat accumulation of single block cement module. The heat storage per unit volume of F1 cement module increased from 6.4℃ to 35℃ is 92.6MJ/m3; the temperature of F2 cement module increased from 7.6℃ to 35℃,the heat storage per unit volume is 102.1MJ/m3; the temperature of F3 cement module increased from 8.3℃ to 32°C,The heat storage per unit volume is 95.1MJ/m3. The temperature of F1 cement module decreases from 35℃ to 5.4℃ and the heat release per unit volume is 75.8MJ/m3; the temperature of F2 cement module decreases from 35℃ to 5.9℃ and the heat release per unit volume is 92.5MJ/m3; the temperature of F3 cement module decreases from 32℃. The heat release per unit volume to 7.8°C is 84.2MJ/m3. Under sunny conditions in winter, the heat storage per unit area of the 0.08mF1 wall is 4469.0kJ/m2; the heat release per unit area is 2343.2kJ/m2; the heat storage per unit area of the 0.08m thick F2 wall is 4571.0kJ/m2. The heat quantity is 3214.6kJ/m2; the heat storage per unit area of 0.08mF3 wall is 4830.7kJ/m2, and the heat output per unit area is 3960.9kJ/m2. Compare with the heat storage and release performance of other wall materials. The heat storage per unit area of the 0.6m thick soil wall is 3357.2kJ/m2, and the heat release per unit area is 811.7kJ/m2. When the wall thickness is only about 14% of the soil wall, the heat storage performance of F1, F2 and F3 is better than 0.6m soil wall, the gap is obvious, 0.08m F1, F2, F3 phase change material cement module unit The area heat storage is 1.3 times, 1.4 times and 1.4 times that of the 0.6m soil wall; the heat release performance gap is even greater. The 0.08m F1, F2, F3 phase change material cement module emits 2.9 heat per unit area of 0.6m soil. 2.9 times, 4.0 times and 4.9 times the wall. The 0.48m red brick wall stores 5490 KJ of heat per unit area during the day and 2140kJ/m2 of heat per unit area. The three types of heat output per unit area also have huge advantages. Therefore, we applied the phase change material cement module to the solar greenhouse on a large scale. The total area accounts for about half of the wall area. The results show that the phase change material wall absorbs a large amount of excess heat inside the greenhouse during the day on a sunny day in summer. F1 The wall absorbs a total of 35614.8KJ of heat, the F2 wall absorbs a total of 72788.4kJ, and the F3 wall absorbs a total of 57153.6kJ; the three absorb a total of 165556.8kJ and emit 72718.8kJ at night; summer is cloudy, the F1 wall totals Absorb heat 1,2589.2KJ, F2 wall absorbs a total of 24310.8kJ, F3 wall absorbs a total of 22338.0kJ; the three absorb a total of 5,9238.0kJ, and emit 37809 kJ at night; on sunny days in winter, the phase change material wall absorbs during the day Heat, the three absorb heat 203158.2kJ and release a lot of heat at night, F1 wall releases a total of 36442.8KJ heat, F2 wall releases a total of 49993.2kJ heat, F3 wall releases a total of 51333kJ kJ of heat, and releases heat at night 137769kJ; On cloudy days in winter, the phase change material wall absorbs heat during the day. The three absorb heat 117,069kJ and release a large amount of heat at night. The F1 wall releases a total of 1,7035.2KJ, the F2 wall releases a total of 37260kJ, and the F3 wall releases a total of 37260kJ. The heat is 49542kJ kJ, and the heat is 103837.2kJ at night.Applying phase change materials to sunlight greenhouses, with the aid of natural ventilation measures in summer, can absorb a lot of heat, effectively reduce the temperature peak of the greenhouse, and release a lot of heat in winter to increase the night temperature of the greenhouse. This also provides new ideas and solutions for improving the greenhouse environment and regulating temperature.
    February 24, 2021 , DOI:
    Abstract:
    In order to explore the pyrolysis characteristics and synergy of single and mixed samples of corn stalks and municipal sludge, based on thermogravimetric analysis, at different heating rates (10℃/min,、20℃/min, and 30℃/min), the Corn stalks, municipal sludge and their mixed samples (mass ratio 9:1, 3:7, 5:5, 7:3, 1:9) were used for thermogravimetric test, and Coats-Redfern integration method was used to study kinetic characteristics . The results show that the difference in pyrolysis characteristics of corn stalks and municipal sludge is large, the residual rate differs by 18.57 percentage points, the comprehensive pyrolysis index differs by 35.73×10-05, and the activation energy E differs by 35.31kJ/mol~46.88kJ/mol. With the content of municipal sludge from 10% to 90%, the initial pyrolysis temperature decreased from 360.3℃ to 440.3℃, the main pyrolysis interval of mixed samples became longer from 277.7~360.3℃, and shifted to the high temperature zone. The residual rate increased from 33.69% to 45.83%, the maximum weight loss rate decreased from 7.88%·min-1 to 3.11%·min-1, and the comprehensive pyrolysis index decreased from 8.5×10-05 to 1.7×10-05. It shows that the municipal sludge improves the pyrolysis starting temperature of mixed samples, but at the same time it also widens the pyrolysis interval, increases the residual rate, slows the weight loss rate, and decreases the comprehensive pyrolysis index. The comprehensive pyrolysis index (D) of mixed samples is lower than the corresponding theoretical value to varying degrees, indicating that the co-pyrolysis of the two has an inhibitory effect. The activation energy required for the individual pyrolysis process of corn stalks is greater than the activation energy required for the individual pyrolysis process of municipal sludge. The activation energy E of corn stalks and municipal sludge under different heating rates showed that increasing the heating rate increased the activation energy of the low temperature section and the high temperature section to different degrees. As the proportion of municipal sludge increased from 10% to 90%, the pyrolysis activation energy decreased from 66.01~46.16kJ/mol to 44.47~17.04kJ/mol. The research provides theoretical basis and technical support for the effective utilization of corn stalks and municipal sludge.
    January 26, 2021 , DOI:
    Abstract:
    In order to realize the real-time on-line detection of grain protein content and record the sampling geographical location information during combine combine-harvester harvest grain, an in-line detection system of grain protein content based on the principle of near-infrared spectroscopy was developed, which was mainly composed of near-infrared spectral sensor module, spiral sampling and conveying mechanism, control module, GPS/Beidou positioning module, industrial display integrator, etc. When the grain combine-harvester near-infrared spectral protein content in-line detection system was working, when the grain discharged by the combine-harvester grain outlet was through the spiral sampling and conveying mechanism, the stepper motor of the sampling mechanism was controlled by the controller according to the detection rate requirements and intermittent grain transmission, the controller system also controls the near-infrared spectral sensor to sample the spectral when the stepper motor stops turning, and the data such as the grain near-infrared spectrum and the positioning signal of GPS/Beidou positioning module were transmitted to host computer by RS485. The control and data processing analysis software of near-infrared sensor and sampling mechanism was compiled, and the grain protein, sampling location information, etc. were displayed and saved in real time after the grain protein prediction model. In order to verify the performance of grain protein content prediction model and online detection system, indoor calibration and field system dynamic testing were carried out, and the decision coefficient of wheat protein content prediction model was 0.865, the absolute error range was -0.96 to 1.22, and the relative error range was -7.30% to 9.53%, the root mean square error of prediction(RMSEP) was 0.638, the decision coefficient of the rice protein content prediction model was 0.853, the absolute error range was -0.60 to 1.00, the relative error range was -8.47% to 9.71%, and the RMSEP was 0.516. The results of the system dynamic field test shows that the maximum relative error of wheat protein content was -6.69%, the maximum error of rice protein content was -8.02%, the system was not significantly affected by sampling and analysis interval, and the system stability and detection accuracy meet the need of grain protein online detection in the field, which provides a scientific basis for precision agricultural operation.
    January 26, 2021 , DOI:
    Abstract:
    The aim of this study was toevaluate the effect of fermentation conditions on the cumulative esterase activity of Oenococcus oeni(O.oeni) autochthonous strains in Hexi Corridor region, and influences in the aromaticesters of Chardonnay dry white wine during the malolactic fermentation(MLF). Two O.oeni autochthonousstrains GF-2, ZX-1 were identified and preserved by Gansu Key LabViticulture and Enology and one commercial strain VP41 were used to test strains. The esterase activity of different carbon chain length substrates (C2, C4, C6) were detected in the simulated wine during MLF process.To analyze and compare the effects and characteristics of different fermentation conditions (initial pH value, ethanol concentration, SO2addition and fermentation temperature) on the production of esterase by the O.oenistrains. The modification effect of the tested strains on the aroma quality of Chardonnay dry white wine was studied by microvinification experiment. The esterase activities of O.oeni autochthonousstrains were significantly higher than that of commercial strainVP41under different pH values, and the maximum esterase activity of ZX-1 was about 63.42% higher than that of VP41. When the concentration of ethanol was 8%, all the tested strains produced the maximum esterase activity, and theO.oeni autochthonous strain hadstronger esterase producing ability. Underthedifferent SO2additions, the cumulative esterase activities of two O.oeni autochthonous strains were significantly higher than that of VP41 (P<0.05), and the esterase activity of GF-2 was significantly higher than that of strain VP41 at 18 ℃ and 22 ℃ (P<0.05) .Results of compound fermentation showed that the total esterase activity originatedfrom ZX-1 was the highest, followed by GF-2and VP41.Although the major and secondary factors affecting the esterase activity of each strain were different, the optimum conditions for esterase production of all tested strains were ethanol concentration 12%, pH 3.6, SO2addition 30 mg/L and fermentation temperature 22 ℃. The highest esterase activity of ZX-1 was 620.973 mU/mL,which indicatedthat ZX-1 had strong adaptability towine habitat.The analysis of microvinification of chardonnay dry white wine showed that six esters (amyl acetate, heptyl acetate, ethyl 3-hydroxybutyrate, ethyl myristate, ethyl trans-2-hexenoate and ethyl trans-4-decenoate) were identifiedin the wine samples after MLF, and two aromaticesters (isoamyl lactate and octylformate) were onlydetected in the wine samples fermented by O.oeni autochthonous strains. Compared with commercial strain VP41, thewines fermented by autochthonousstrains GF-2 and ZX-1 have rich variety aroma and good fragrancepersistence. Both O.oeni autochthonous and commercial strains can successfully complete MLF, especially ZX-1 has strong esterase production capability and is significantly affected by fermentation conditions, which can effectively improve the content of fruit and floral aroma compoundsin Chardonnay dry white wine, significantly enhance the regional microbial terroir characteristics of wines. The O.oeni autochthonous strain ZX-1 is more suitable to be used as MLF starter of dry white wine in Hexi Corridor of Gansu Province.
    November 04, 2020 , DOI:
    Abstract:
    The use of recycled manure solids (RMS) as dairy bedding material has become a promising technology with the merits of sustainable manure management and cost saving for purchasing traditional bedding. However, cow dung contains certain amounts of pathogenic bacteria, thus the use of RMS would increase the risk of direct contact of pathogens with cows’ udder. Such serious problem has undermined the use of RMS as dairy bedding material. Drum fermentation for the bedding production has many advantages (i.e. high temperature, short time), thereby it is getting more and more attention. The objective of this study was to investigate the stability and biological safety of RMS production process using drum fermentation in different seasons, and to clarify the factors affecting the growth of pathogenic bacteria in the dairy cows’mastitis. The drum-type RMS producing system employed was composed of a two-stage solid-liquid separator, a horizontal-rotation drum fermentation tank, as well as feeding and discharging components. The automatic control system monitored equipment operation and temperature changes in real time. The drum temperature was obtained by the temperature sensors installed on the inner wall of the drum including inlet, center, and outlet. Samplings were performed from the inlet, 1/3, 2/3, and outlet of the drum. The plate culture method was used to detect the main mastitis pathogenic bacteria (i.e., Eschrichia coli, Staphylococcus aureus, Streptococcus, and Klebsiella) at different positions within the drum during the summer and winter. At the same time, the physical and chemical properties (water content, pH, total carbon, total nitrogen, ash, particle size distribution, roller temperature) of RMS were also tested. Additionally, the main factors affecting the growth of mastitis pathogens was investigated via Pearson correlation analysis.The results indicated that the fermentation temperature during the production process was stable and maintained above 65 oC both in summer and winter, and the final moisture content at the drum outlet was less than 45%. In both seasons, the particle size distribution at different positions of the roller was mainly concentrated at 0.5 mm to 2.0 mm. With the fermentation process, the large particle size gradually converted to small and medium particle size. The number of mastitis pathogens in summer and winter was highest at the drum inlet, and gradually decreased at higher fermentation temperature. At 1/3 of the drum, the number of major mastitis pathogens was significantly reduced. Streptococcus. and Klebsiella. were not detected at the drum outlet in both seasons. However, the number of Eschrichia coli and Staphylococcus aureus at the outlet of the drum in summer was about 3 lgcfu/g higher than that in winter. It may be related to the moisture content of the cow dung at the inlet of the drum. Therefore, the moisture content of the inlet of the drum should be strictly controlled between 50% and 65%. Using the Pearson correlation analysis, it was found that the major factor affecting main mastitis pathogen was drum temperature, followed by total carbon. From the security point of view, RMS should be used immediately after production to avoid environmental impacts. The results found in this study can provide deep insight for the application of drum fermentation technology to produce safer RMS.
    October 21, 2020 , DOI:
    Abstract:
    To promote the development, automation, and standardization of Chinese cuisine, it is necessary to carry out a systematic and in-depth study so as to obtain the inherent principles of heat transfer and the corresponding quality changes during the cooking process. Chinese stir-frying is one of the most distinctive and widely used cooking method, and numerical simulation is the only way to study the heat transfer process of food particles during the Chinese stir-frying. In order to study the mechanism of heat and mass transfer and the changes of maturity and quality of food particles during the Chinese cuisine process, a heat and mass transfer model including multiphase coupling phase transition and shrinkage was developed to simulate the Chinese stir-frying process of food hygroscopic porous medium based on the porous media theory, Fourier's law, Newton's cooling law, and Darcy's law. The non-equilibrium evaporation formulation, shrinkage formulation, energy, momentum and mass conservations of water, and gas governing equations were considered in this model and it was finally solved using finite element method. The temperature history, moisture content, and volumetric shrinkage rate of the Chinese stir-fried pork loin were used as comparations to validate the model accuracy. The results indicated that the accuracy and robust properties of this model was greatly increased after considering the shrinking process. To reveal the mechanisms of heat and mass transfer inside food particle, water evaporation rate of particle surface, volumetric shrinkage rate, pressure variations, moisture content and temperature distributions were all simulated for Chinese stir-frying process. The simulation results showed that the water loss, which was induced by strong convection heat transfer, was the main reason for shrinkage. The moisture loss rate and volumetric shrinkage rate were increased by the surface evaporation rate, and the particle internal pressure was affected by volumetric shrinkage.Since the volumetric shrinkage rate was similar to water loss rate, the moisture content and shrinkage were associated as an important indicator for evaluating cooking quality of food particles. Additionally, the heat transfer efficiency of particles was greatly enhanced by shrinkage because of the increasing surface area to volume ratio. The shrinkage could be used to improve the overall moisture content of food particles if evaluated from the perspective of cooking quality optimization. Combined with the maturity value theory, the effect of controlling methods of “Huohou” on the maturity and quality of food particle were further explored in this study. The simulation results indicated that the increase of the efficiency of heat and mass transfer and internal heating rate, and the decrease of average moisture content were mainly affected by the finer cutting technique of food particles, the higher preheat oil temperature, and the more vigorous stirring operations. The food particles could reach its maturity values before the average moisture content rapidly decreased under the appropriate “Huohou” controlling. Thus, the average time of food particles reaching cooking maturity termination was significantly decreased. “Huohou” controlling exhibited a significant (P <0.01) effect on the cooking quality and could bring significant advantages for obtaining food particles with better cooking quality.
    September 15, 2020 , DOI:
    Abstract:
    Technology of straw bale combustion is one of the effective ways to realize the clean utilization of agricultural residue, which has aroused widespread concern. In this paper, the latest research progress of straw bale combustion was reviewed, the reaction principle and combustion characteristics of straw bale combustion were described, the generation and emission of particulate matter in the process of straw bale combustion were analyzed, such as NOx, CO and particle. And the research progress of straw bale combustion types, principles and characteristics were systematically summarized. According to the technical characteristics and heating scale, we divided straw bale combustion into two types, one was continuous bale combustion, which can realize continuous feeding and ash cleaning in the combustion process, maintain a stable combustion state in the combustion chamber, and was suitable for the central heating area with large heating area, that mainly included cigar-bale combustion and reciprocating grate combustion. The other was sequential batch combustion technology, which had advantages in small floor area, simple and convenient operation, usually used for small heating mechanism, and it included forward combustion technology and reverse combustion technology. Based on the global literature search, the research hotspot, institutions and development trend of straw bale combustion were analyzed. The running cost of straw baled heating was evaluated. It was found that the straw bale combustion has the characteristics of simple heating process and low operation cost. The operation cost was 19.8 yuan/m2, which was suitable for the industrialization promotion of clean heating in villages and towns. Straw bale combustion technology had gradually attracted the attention of scientific researchers. Developed countries in Europe had made some progress in the field of straw bale combustion, such as combustion mechanism, boiler structure, reduction of flue gas emission, etc. And at present, the research of combustion technology had focused on flue gas emission reduction and environmental impact assessment. The existing straw bale combustion technology still has some problems, such as insufficient combustion, unclear generation mechanism of flue gas pollutants, higher NOx and particle emission. It was suggested that we should pay more attention on research of pollutant emission characteristics, and it is encouraged to reduce the generation of flue gas pollutants from the source.
    August 05, 2020 , DOI:
    Abstract:
    National policies promote the rapid development of electric vehicles, agricultural vehicles are becoming more and more electric. In general, when the battery is used as a power supply, a lot of heat will be generated. In addition to the more complex working conditions of agricultural vehicles and the compact layout of battery packs, it is inevitable to cause the thermal accumulation of batteries, resulting in the battery temperature exceeding the optimal operating temperature range and damaging the battery. At this time, an appropriate thermal management strategy is needed to control the battery temperature and make it work within a reasonable temperature range. Therefore, based on the principle of phase change heat transfer and pump-free circulation, a power battery thermal management system with cooling or heating functions is presented. Taking ternary lithium batteries as the research object, the two-way working modes of thermal management system were tested under cooling or heating conditions. Under the cooling condition,The cooling capacity of the two thermal management systems under natural convection cooling and forced convection cooling conditions was studied when the initial temperature of the battery box was 40, 50, 60 and 70 ℃. And for the thermal management system two, the influence of the inclination angle on its heat dissipation and temperature uniformity was studied. Under the heating conditions, the heating capacity of two thermal management systems was studied, and then for the thermal management system two, the initial temperature of different batteries and the heat exchange uniformity of the thermal management system two were studied. The results show that the system can realize the operation switching management of cooling and heating two-way modes based on high or low temperatures. In other words, the switch of thermal management can be realized by controlling the opening and closing of the valve at the right temperature. The test results show that, under the cooling condition, thermal management system two provides better heat transfer, It can also be interpreted as the heat dissipation capacity of the heat exchanger plate with four vertical tubes is stronger than that of the single serpentine tube, compared with natural convection, forced convection on the condenser side can increase the heat transfer power of system 1 by 10% ~ 44.2%, and system 2 by 20% ~ 48.6%; when the temperature of the battery box is 60℃, the maximum temperature difference of the heat exchange plate of the natural convection heat dissipation system is less than 2℃, and the maximum temperature difference of the heat exchange plate of the forced convection heat dissipation system is less than 1℃; at an initial battery temperature of 25°C and a discharge rate of 1C, 2C, and 3C, forced convection heat dissipation at the end of discharge can reduce the average temperature of the battery box by 2.1, 3.9, and 4.7°C, respectively. Under the heating condition, the power of the battery box in many groups of experiments is consistent. Considering the tilting effect of the heat exchanger plate in the vehicle driving, it is restricted by the flow distribution of the working fluid, and the temperature uniformity is better than the heating condition in the heat dissipation condition.
    April 17, 2020 , DOI:
    Abstract:
    The mechanical properties of gypsum board was low, and cannot be used as load-bearing materials in construction. Plant fibers can be employed as the reinforcement to increase the mechanical properties of the gypsum board, but the improvement increment on the mechanical properties was limited because of the addition of gypsum retarders during the preparation of general particle-gypsum composites. The gypsum retarder solution deteriorated the morphology of gypsum crystals, and the gypsum crystals became shorter and wider, and then the overlapping area decreased among them. The general particle-gypsum composites still cannot be used in structural application. In order to increase the mechanical properties of the particle-gypsum composite, a two-step preparation process including pre-forming molding and moisture-curing was proposed in this study. The particle-gypsum composites with different MUF content and the particle/gypsum ratio was prepared, and the physical and mechanical properties was tested. The effects of melamine-urea-formaldehyde (MUF) content and the particle/gypsum ratio on mechanical properties of the particle-gypsum composites were analyzed by one-factor experiment. The results in the present study were compared with the requirements in three product standards and that in the reported literatures. The test results showed there was a positive relationship between the MUF content and the mechanical properties of the particle-gypsum composites, and the particle/gypsum ratio had a slight impact. The mechanical properties of the particle-gypsum composites with 15% and higher MUF content met the requirements of Standard LY/T 1598 (2011), and the values, except longitudinal modulus of rupture, were in accordance with the requirements of Standard LY/T 1580 (2010) when MUF content was 21% and above. The mechanical properties of the particle-gypsum composites reached E5.0-F16.0 grade according to the Standard GB/T 35216 (2017), when 33% and higher MUF content was used. The curves of bending load with deformation of gypsum boards exhibited linear elastic behavior due to the brittleness of gypsum crystals. All particle-gypsum composites in bending tests exhibited obvious non-linear behavior before the maximum load was reached, and the failure was ductile. The strengths of the composites in the present study were all higher than that in the reported literatures. Therefore, the particle-gypsum composites can be used as structural boards in construction. Based on the combination of mechanical properties and costs, the performance of the particle-gypsum composites with 33% MUF content and a particle/gypsum ratio of 0.30 were better, and the internal bond strength, modulus of rupture, modulus of elasticity, displacement ductility coefficient and 24 h thickness swelling of the particle-gypsum composite were 1.28 MPa, 16.5 MPa, 7350 MPa, 1.64 and 1.23%, respectively. After the new preparation process was employed, the mechanical properties of the particle-gypsum composites were increased greatly due to the increase of the strength of the gypsum continuous phase and the obvious improvement of the interfacial bonding strength between the particle reinforcement and the gypsum continuous phase. The microscopic images by Scanning Electron Microscope indicated that gypsum crystals in particle-gypsum composites were slender, when the new preparation process was employed. The gypsum crystals interlaced among them, and the contact area of the gypsum crystals was increased greatly with the increase of MUF content. Therefore, the gypsum continuous phase was strengthened. The amount of the gypsum on the surface of the wood particles was significantly increased with the increase of MUF content due to the bonding performance of MUF resin.
    March 25, 2020 , DOI:
    Abstract:
    In order to make full use of solar energy and improve the energy efficiency of solar heat pump system, an energy storage solar heat pump water heating system with inserted oscillating heat pipe is proposed, which integrates solar collector, energy storage tank and oscillating heat pipe together reasonably and effectively. The system can store solar energy with the phase change materials (PCM) filled in solar collector, transfer heat efficiently by oscillating heat pipe and switch operation mode according to solar radiation, and can realize the maximum utilization of solar energy in different seasons. In summer, enough heat is transferred or stored during the day to release at night by PCM in solar collector, which is directly used to heat the circulating water through the oscillating heat pipe heat exchanger. In winter, the heat transferred or stored during the day to release at night by PCM in solar collector is low, and the heat is transferred to the heat pump evaporator by the oscillating heat pipe heat exchanger to improve the evaporation temperature of the heat pump, and thus the overall performance of the system is improved. A test rig has also been established for the performance measurement of energy storage solar heat pump water heating system with inserted oscillating heat pipe. Paraffin is chose as phase change material of the system under the consideration of capacity, phase change temperature and latent heat of phase change. Experimental study has been carried out for two years under winter conditions in Nanjing, one year for the test rig without PCMs and another year with PCMs. Under similar environmental conditions (solar radiation intensity, fluctuation and ambient temperature), the variations of the instantaneous collecting efficiency, average collecting efficiency, COP (coefficient of performance) and water temperature of the system filling or not filling PCM with the fluctuation of solar radiation are compared and studied. The comparison and experimental results show that in winter daytime under similar solar radiation intensity, fluctuation and ambient temperature, the instantaneous collecting efficiency fluctuation with PCM is 61.5% less than that of the system without PCM, which can overcome can overcome the instantaneous influence of the fluctuation of solar radiation intensity on the system. And the average collecting efficiency with PCM is 25% higher than that of the system without PCM. At winter night, under similar operation conditions, COP of the system filled with PCM is over 3.0, which is nearly twice as high as that of the system without PCM, and make water temperature reach 50℃ in a shorter time, shortening the time by more than 20%. The results can provide theoretical basis for the popularization and application of solar energy heat pump system.
    October 16, 2019 , DOI:
    Abstract:
    Column chromatography is based on the difference of physicochemical properties of each component in the mixture. The mixture is separated and purified after multiple distributions by using the different distribution coefficients of each component in the stationary phase and mobile phase. The starch was hydrolyzed by amylase after retrogradation under high pressure and humidity. The hydrogen bond of retrograde starch was opened in alkali solution to dissolve the retrograde starch, and the solution was adjusted to neutral next. Amylose with narrow molecular weight distribution was obtained by adding n-butanol to the precipitate. While, amylopectin with narrow molecular weight distribution was prepared by adding ethanol to the supernatant. In order to narrow the molecular weight distribution of amylose and amylopectin in sweet potato furtherly, column chromatography was used to separate them respectively. The results show that the artificial zeolite with 1-3 mm particle size is suitable for the separation of amylopectin, while artificial zeolite with 4-6 mm for amylose. After separated by column chromatography, the yields of both amylose and amylopectin were more than 2.4% respectively. In the course of separation, amylose with higher DP adsorbed on the macrozeolite surface. It was eluted out from the mixture first for the weaker adsorption force. Amylose with lower DP entered into the small holes of macrozeolite, and was eluted out subsequently for the stronger adsorption force. When separated by small zeolite column chromatography, the amylopectin components of F1b with small molecular weight and high homogeneity were eluted out first. While, amylopectin components F2b with large molecular weight and low homogeneity were eluted out first, indicating that the branching degree of amylopectin also played a certain role in the separation of starch components by zeolite column chromatography. X-ray diffraction showed that there were strong peaks of amylose components at the diffraction angles (2??? of 18.9°, 23.4°, 27.2°, 29.3°, 32.3°, 33.8°. There were obvious peaks of amylopectin components at around 21.6°, 22.9°, 23.9°, 26.5°, 27.1°, 29.3°, 34.1°, 35.8°, 39.5°. The molecular weight distribution index (PDI) of sweet potato amylose was close to 1.0 at the same time. Sweet potato amylopectin with extreme narrow molecular weight distribution can be prepared by artificial zeolite column chromatography. These kinds of starch exhibits X-ray diffraction peaks similar to metal salts, which can be used as materials to study the spatial structure of starch macromolecule in depth. Micrographs showed that amylose was composed of many linear molecules and presents typical linear “wicker-like” morphology, while amylopectin showed “branch-like” shape. The results provide a simple and efficient method for the preparing of amylose and amylopectin with extreme narrow molecular weight distribution. It brings about favorable conditions for further exploring morphological changes of starch macromolecules during aggregation progress.
    October 16, 2019 , DOI:
    Abstract:
    Vinegar plays an important role in our daily diet. Solid-state fermentation of vinegar using reactors has several advantages over the traditional methods, which include shorter fermentation process, and good controlled working environment. In order to fully understand the dynamic changes of main components and flavor compounds during the solid-state fermentation of vinegar in rotary drum reactor, samples were taken throughout the fermentation process. Alcohol, total acid, reducing sugar, amino nitrogen, organic acid and volatile flavor in the process of vinegar fermentation were studied by high performance liquid chromatography, solid-phase microextraction, and gas chromatography-mass spectrometry. Meanwhile, principal component analysis was carried out to explore the difference of volatile flavor in vinegar at different fermentation stages. The results showed that the fermentation process can be divided into three stages: starch saccharification, alcohol fermentation, and oxidation of ethanol to acetic acid. The alcohol content increased rapidly within 0-4 days of fermentation, then decreased gradually to zero until the end of fermentation. The total acid content showed a sharp increase tendency first, followed by a slight increase at the late stage of fermentation. The reducing sugar content decreased rapidly at first, then gradually increased during acetic acid fermentation, and finally gradually decreased. The amino nitrogen increased rapidly at first, followed by a gradual decrease at the end of fermentation. Seven organic acids were detected in our research, including acetic acid, lactic acid, oxalic acid, succinic acid, tartaric acid, citric acid, and malic acid. Among them, acetic acid and lactic acid were the main organic acids in the whole fermentation process. The lactic acid content increased rapidly first, and became the dominant organic acid in the alcohol fermentation stage. Then it showed a gradual decrease until the end of fermentation. For acetic acid, a gradual increase tendency was observed during the whole fermentation process, which accounted for 64.87% of all the organic acids contents. Compared with those, the content of other organic acids was less, and the variation during fermentation was relatively small. These organic acids were also crucial for the formation of characteristic taste of vinegar. A total of 64 flavor volatile substances were detected, including 25 esters, 12 alcohols, 6 acids, 5 phenols, 5 aldehydes, 6 ketones and 5 heterocyclic compounds. The principal component analysis results showed that the most dominant ones responsible for volatile flavor in the early, middle, and later stage of fermentation were alcohols, esters and aldehydes, and acids, respectively. Other volatile compounds, such as aldehydes, phenols, ketones, heterocycle, were present in small amounts during vinegar fermentation based on the reactor. However, they also play a vital role in the formation of special flavor for vinegar. This is the first report to study the dynamic changes of vinegar quality during fermentation process based on a reactor. The results would enhance our understanding of the fermentation property of rotary drum solid-state fermentation vinegar reactor, which may be helpful for the improvement and effective management of reactor to promote its industrial application.
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    2010,26(11):1-7, DOI:
    [Abstract] (32898) [HTML] (0) [PDF 0.00 Byte] (9680)
    Abstract:
    The problems and challenges for agricultural water management are markedly different from 50 years ago. To meet the increasing global demand for food, new challenges have been coming: increasing farmers’ income, boosting rural economy, reducing poverty, adapting climate change and protecting the ecological environment, under the conditions of the scare water resources. Therefore, the improvement of strategies and countermeasures relevant to the development of agricultural water management is nessary starting from the thinking of interdisciplinary and various sectors. The strategies include that developing water-saving agriculture, maintaining the service functions of the ecological system, increasing investment in irrigation, promoting rain-fed agriculture, improving and increasing water productivity, reducing poor population, preventing and alleviating the degradation of land and water environmental quality, reducing the risk in waste water irrigation, and strengthening policy and institution building. The efforts in improving agricultural water management and increasing agricultural productivity depend on the rational selection of the above strategies and the benefit tradeoffs.
    2013,29(14):203-209, DOI: 10.3969/j.issn.1002-6819.2013.14.026
    [Abstract] (26943) [HTML] (0) [PDF 392.78 K] (6753)
    Abstract:
    Abstract: The arable land per capita among the rural migrants located in the Three Gorges Reservoirs Area is only about 386.7 m2. The contradiction between people and their land is severe. After the impoundment of the Three Gorges Project, the water flow and the self-purification ability of the Yangtze River got slowed and declined which resulted in an overmuch growth of the green algae in main tributaries of the Yangtze River. Besides, to meet the electricity generation need in the dry winter or spring, and to prevent the deluge in the rainy summer, the Three Gorges Reservoir impound in the winter and spring, disembogue in the summer. Owing to this, the hydro-fluctuation belt along the river always outcrop into land in the hot and humid rainy summer, hence the hydro-fluctuation belt fail to intercept, absorb and filtrate the agricultural surface source pollution, which cause the increased pollution in the Yangtze River. The contradiction of the economic development and the environmental protection is severe.This research considered the Three Gorges Reservoir Area, the hydro-fluctuation area and the ecological barriers area as an entirety, and combined the specialty agriculture industries, such as: citrus, livestock and fishing industry with the newly developed agricultural technologies, like the orange residue self-drying and high temperature fermentation under aerobic environment technology along with its dedicated organic fertilizers, the biogas slurry pipeline irrigation fertilization integrated device, citrus nutrition diagnosis testing fertilization technology and the new variety of submergence-tolerant pasture, on the basis of the principles of ecological agriculture and recycling economy. A recycling agriculture ecosystems demonstration area was built in the Dachang town, Wushan county, the hinterland of the Three Groges. Relying on the greening the Yangtze River citrus belt project, the hydro-fluctuation belt management project and forced removal of the cage fish culture facilities along the river project, we build three ecological economic zones which are reservoir bank citrus plantations, hydro-fluctuation belt wetland pastures and natural fishery around the reservoir bank to develop specialty industry economy.In this project we integrated "pig-biogas-fruit-residue-feed", "fruit-residue-fertilizer", "livestock-biogas-fruit-grass" and water cycle, developing a new four-chain crossed recycling economy networking mode, and an anti-season hydro-fluctuation area ecologically recycling agriculture progression mode. By using the farming manure as the fertilizer and the irrigation water of the citrus, and using the waste of citrus processing or hydro-fluctuation belt pasture as the feedings of the livestock, we established a system that using the waste of the previous level as the production resource in current level. Due to this system we set up a citrus, pigs, grazing livestock, Yangtze fish and other specialty industrial that industrial symbiosis, coupling elements, the overall recycling and comprehensive utilization of industrial ecological chain in the very area. Also by building biogas project, citrus barrier forest, cut flood engineering, wetland pastures and fishery as 5-layer intercept network, we can block, absorb and digest the area source pollution. With this project we are able to increase the vegetation coverage of the reservoir bank, the income of the migrants and protect the environment of the Three Gorges Reservoirs Area.The established specialty recycling agriculture ecological demonstration area in Dachang Lake, Wushan county will cover the core area of 135 hm2. The 2 km long hydro-fluctuation area will be fully covered by the pasture and the cover ratio of the forest will be over 80 percent. The whole area will be fully covered by plants, and those wastes like farming excrement, waste straw, citrus residue will be completely reutilized and achieve the accomplishment of zero emission. Besides, the citrus yield in the demonstration area will be about 30 tons each hectare and the yield of pasture will be about 33 tons each hectare, which means that the output value per hectare will be over 150,000 Yuan. This area is showing the possibility that increasing the migrants' income and purifying the Yangtze River synchronously.
    2007,23(5):150-153, DOI:
    [Abstract] (21213) [HTML] (0) [PDF 0.00 Byte] (8283)
    Abstract:
    Apple storage quality properties(including hardness, moisture, soluble solid, total acid) were estimated through the mechanical properties of apple(including the maximum of compression, the yield force, the elastic modulus). An artificial neural network model of storage quality properties was built by the optimization algorithm of L-M(levernberg marquardt) BP neural network. The mechanical properties and the apple storage quality properties measured in the experiment were adopted as input and output to establish the BP neural network. The simulated results show that this neural network make a good estimation of apple storage quality properties through mechanical properties. When tested by five groups of Non-sample data, the relative error between the estimation of this model and the measured value is below 5%, which meets the accuracy requirement of apple storage quality properties in engineering application.
    2007,23(2):1-5, DOI:
    [Abstract] (18186) [HTML] (0) [PDF 0.00 Byte] (6020)
    Abstract:
    In the research of the soil erosion and soil losses, the runoff velocity of slope is an indispensable hydrodynamic parameter in the runoff computation and the soil erosion forecast. There is still no special instrument which is widely used to measure runoff velocity. It is very significant to construct a fast measurement instrument on runoff velocity. On the basis of correlation theory, the runoff velocity measurement system was established based on virtual instrument LabVIEW. The system uses the conductance sensor to acquire signal. Effect of the space between conductance sensors on the measurement system and the runoff velocity under five sediment concentrations were studied. Results indicate that the suitable sediment concentration scope of the measurement system is 0~250 kg/m3 and the greatest relative error of the system is 4.5%. While taking the flow velocity measured by the dye tracer technique as standard value to correct the correlation velocity, the greatest relative error of the proved velocity reduces to 3.81%.
    2016,32(1):46-53, DOI: 10.11975/j.issn.1002-6819.2016.01.006
    [Abstract] (17857) [HTML] (0) [PDF 5.12 M] (4118)
    Abstract:
    The application of the path tracking technology on agricultural vehicle makes the robot replace farmers for field operation, and the accuracy, production efficiency and dependability about farming automation are improved effectively.Meanwhile the labor time, labor intensity of drivers and the production cost are saved.The path tracking of agricultural vehicle was studied in an operating condition, and a variety of sensors were installed on the car features of the external environment.Then it generated a four-element in state space by the target path which was given for controling the agricultural vehicles to track the target path automaticly according to the theory of optimal navigation control.The location method of GPS/INS was selected, the navigation system was developed, and the experiment was finished in 2014.According to the needs of automatic walking positioning system, a variety of sensors has been chosen, including the inertial sensor, angle sensor and GPS sensor.Then the serial program was writen to collect the signal from the sensors and calibrate them.In order to meet the requirements of vehicle navigation system, the positioning system with low cost and high precision was developed.The hardware of the system consisted of two GPS modules, two Zigbee wireless transmission modules and an inertial sensor.The data from the sensors are filtered and fused, and finally accurate, reliable vehicle position data was got.The tracking controller based on preview control was designed to obtain the future values and target values of the vehicle.With the target path and its curvature, the feed forward control value was got.There was an error between the current state and the state of vehicle target path that was needed to use LQR for elimination.The performance of the path following controller was simulated by Matlab, then the maximum lateral error was 0.16 m and 0.27 m at the speed of 0.5 m/s and 1 m/s respectively.The results showed that the control method was feasible.The steering control system was designed based on steer-by-wire(SBW) after the study of vehicle navigation control principle.SBW removed out mechanical connection between steering wheel and steering front wheel.It used motors to control front wheel angle and simulated force characteristic.Compared with traditional steering system, SBW had characteristics of ideal steering ratio and active steering control according to vehicle state parameters, and improved safety of driving and handling stability.The strategy of BLDCM was designed in order to make actual front angle follow the desired angle better.PID control and sliding mode variable structure control were applied in strategy of BLDCM and the result of simulation showed that sliding mode variable structure control was better than PID control.This paper designed the electronic control unit of SBW based on chip of MC9S12XET256, mainly including peripheral circuit of MCU, CAN communication circuit, drive circuit of BLDCM, power circuit, signal acquisition and processing circuit, current sampling circuit of motor.Based on the requirement of joint simulation, we designed a bench test for control strategy and hardware, software of ECU in 2015.The results of test bench showed that angle correction was similar with the result of simulation and sliding mode variable structure control was better than PID control in following front angle.Finally, the vehicle steering control test and the vehicle path tracking control test were carried out based on vehicle test platform, which was built personally.The vehicle path tracking system was based on the Windows platform, using Microsoft Visual Studio as the development environment.The integrated navigation system was validated and the test data showed that the integrated navigation system had a high positioning accuracy and the steering system had a reliable tracking performance.The final navigation and positioning accuracy of integrated navigation system was around 0.1 m to 0.5 m and the response speed of the whole system was about 0.1s .The results proved that the system could meet the requirements of agricultural vehicle path tracking control system.
    2019,35(18):143-150, DOI: 10.11975/j.issn.1002-6819.2019.18.018
    [Abstract] (17594) [HTML] (0) [PDF 3.96 M] (6146)
    Abstract:
    Rosa roxburghii is widely distributed in warm temperate zone and subtropical zone, mainly in Guizhou, Yunnan, Sichuan and other places in China. Panxian and Longli are the most abundant the most varieties and the highest yield Rosa roxburghii resources in Guizhou. The harvesting of Rosa roxburghii fruit is the most time-consuming and labor-consuming work in Rosa roxburghii production, and its labor input accounts for 50%-70% of the production process. Hand-picking of Rosa roxburghii fruit is of high cost, high labor intensity and low picking efficiency. In recent years, convolutional neural network has been widely used in target recognition and detection. However, there is no relevant literature on the application of neural network in Rosa roxburghii fruit recognition. In this paper, in order to realize rapid and accurate identification of Rosa roxburghii fruits in natural environment, according to the characteristics of Rosa roxburghii fruits, the structure and parameters of VGG16, VGG_CNN_M1024 and ZF network models under the framework of Faster RCNN were optimized by comparing them. The convolutional neural network adopted bilinear interpolation method and selected alternating optimization training method of Faster RCNN. ROI Pooling in convolutional neural network is improved to ROI Align regional feature aggregation. Finally, VGG16 network model is selected to make the target rectangular box in the detection result more accurate. 6 540 (80%) of 8 175 samples were selected randomly as training validation set (trainval), the remaining 20% as test set, 80% as training set, the remaining 20% as validation set, and the remaining 300 samples that were not trained were used to test the final model. The recognition accuracy of the network model for 11 Rosa roxburghii fruits was 94.00%, 90.85%, 83.74%, 98.55%, 96.42%, 98.43%, 89.18%, 90.61%, 100.00%, 88.47% and 90.91%, respectively. The average recognition accuracy was 92.01%. The results showed that the recognition model trained by the improved algorithm had the lowest recall rate of 81.40%, the highest recall rate of 96.93%, the lowest accuracy rate of 85.63%, the highest 95.53%, and the lowest F1 value of 87.50%, the highest 94.99%. Faster RCNN (VGG16 network) has high recognition accuracy for Rosa roxburghii fruit, reaching 95.16%. The recognition speed of single fruit is faster, and the average recognition time of each Rosa roxburghii fruit is about 0.2 seconds. The average time has some advantages, which is 0.07 s faster than the methods of Fu Longsheng. In this paper, a Faster RCNN Rosa roxburghii fruit recognition network model based on improved VGG16 is proposed, which is suitable for Rosa roxburghii fruit recognition model training. The algorithm proposed in this paper has good recognition effect for Rosa roxburghii fruit under weak and strong illumination conditions, and is suitable for effective recognition and detection of Rosa roxburghii fruit in complex rural environment. This paper is the first study on the depth extraction of Rosa roxburghii fruit image features by using convolution neural network. This research has high recognition rate and good real-time performance under natural conditions, and can meet the requirements of automatic identification and positioning picking of Rosa roxburghii fruit. It lays a certain foundation for intelligent identification and picking of Rosa roxburghii fruit, and opens a new journey for the research of automatic picking technology of Rosa roxburghii fruit.
    2016,32(9):130-135, DOI: 10.11975/j.issn.1002-6819.2016.09.018
    [Abstract] (17322) [HTML] (0) [PDF 361.61 K] (2897)
    Abstract:
    Abstract: To assess the effects of different straw return modes on the content of soil organic carbon and the fraction of soil active carbon, we investigated 4 different straw return modes, non-straw return (CK), direct straw return (CS), straw return after mushroom cultivation (CMS), and straw return after livestock digestion (CGS) using field plot experiment. The results showed that different straw return modes all increased the content of soil organic carbon, but the increases in soil organic carbon content by different straw return modes did not exhibit significant difference (P>0.05). The increases in soil organic carbon content were found in the order of CGS > CMS > CS > CK. In comparison to CK mode, the contents of soil organic carbon with CS, CMS and CGS modes increased by 9.0%, 23.9% and 26.7%, respectively. In addition, different straw return modes all improved the content of soil active carbon. Under different straw return modes, the contents of dissolved organic carbon (DOC) were in the order of CS > CMS > CGS > CK, and significant differences were observed among different return modes (P<0.01). Compared to CK mode, the contents of DOC in the treatments of CS, CMS and CGS increased by 64.6%, 29.4% and 8.9%, respectively. The contents of microbial biomass carbon (MBC) followed the order of CMS > CGS > CS > CK, and their differences were significant (P<0.05). The contents of MBC in the treatments of CS, CMS and CGS increased by 28.9%, 84.7%, and 59.3%, respectively, compared to the CK treatment. Similarly, the contents of soil easily oxidizable carbon (EOC) were in the order of CMS > CS > CGS > CK, and their differences were significant (P<0.01). Compared to CK mode, the contents of EOC in the treatments of CS, CMS and CGS increased by 24.1%, 55.7%and 9.3%, respectively. Straw return modes also significantly affected the fraction of soil active carbon in the soil total organic carbon (TOC) and changed the quality of soil organic carbon. Under different straw return modes, the ratios of DOC/TOC, MBC/TOC and EOC/TOC were in the orders of CS > CMS > CK > CGS, CMS > CGS > CS > CK and CMS > CS > CK > CGS, respectively. From the perspective of improving soil quality, CMS is the recommended mode, which has the greatest ratios of MBC/TOC and EOC/TOC, as well as a higher soil carbon effectiveness that facilitates the carbon utilization by the microorganisms, thus benefiting the growth of crops. On the other hand, from the perspective of soil carbon sequestration, CGS is the recommended mode, which has the lowest fraction of DOC/TOC and the highest content of soil organic carbon, thus facilitating the carbon sequestration. The results of the study can provide the basic data for the rational and efficient utilization of straw, as well as the improvement of the quality of agricultural soil carbon pool.
    2015,31(16):78-85, DOI: 10.11975/j.issn.1002-6819.2015.16.012
    [Abstract] (17047) [HTML] (0) [PDF 522.80 K] (3115)
    Abstract:
    A typical dynamic characteristic of horizontal axis wind turbine shows up under yaw condition. Prediction accuracy is low for momentum-blade element theory and related engineering prediction model. In order to improve the prediction accuracy of dynamic load characteristics, the whole wind turbine models, based on the experiment about MEXICO (model experiments in controlled conditions) rotor in 2006, are established by three-dimensional software called Pro/E. under different yaw conditions, i.e. yaw angle of 0, 15, 30 and 45 degree. ICEM CFD (integrated computer engineering and manufacturing code for computational fluid dynamics) is applied to grid division. The rotating domain containing rotor part is meshed into hexahedral grids, and the static domain containing part of wheel hub, tower and outflow field is meshed into tetrahedral grids. When the grid size of the first layer of blade surface is set as 5×10-6 m to ensure the first dimensionless size near the wall Y+<0.5 on the wall, the 2 numbers of grids are determined by the error of axial load on the airfoil in the 60% section of blades, which respectively are 6 572 451 and 2 961 385. The aerodynamic performance of models under rated condition is simulated by ANSYS CFX with the turbulence model of SST (shear stress transport), high resolution is chosen as advection scheme, and transient rotor stator as the domain interface method. The results are converted into data, processed and analyzed by MATLAB. Finally the following conclusions are drawn. The distributions of pressure coefficients along the airfoil chord in different blade sections calculated by CFD method are in good agreement with the experimental measurements, and the error on the suction surface of airfoil is mainly caused by stall separation occurring on the pressure surface of airfoil. With the increasing of yaw angle, the pressure coefficients of the suction side are increasing and the location of minimum pressure coefficient moves to airfoil trailing edge slightly. For the pressure side, the pressure coefficients increase at first and then decrease, and the location of maximum pressure coefficient moves to airfoil leading edge slightly. The axial load coefficients and tangential load coefficients of blades first decrease and then increase and then decrease again with the increase of the azimuthal angle. With the increase of the yaw angle, the axial and tangential load coefficients are both reduced. When the yaw angle is within 30°, the relative error of axial load coefficients is in the range of ±5% and the relative error of tangential load coefficients is in the range of ±15%. CFD method is higher than BEM (blade element momentum) method in forecasting accuracy of dynamic load calculation. Under yaw condition, the hysteresis characteristic of airfoil lift and drag in blade root is more remarkable than blade tip, while the variation range of the angle of attack in blade root is much less than that in blade tip. This characteristic must be considered when BEM method is used to predict wind turbine performance. For axial inflow condition, CFD method can well predict the average speed, but restricted by turbulence model and the wake model, CFD calculation did not show the velocity characteristics of rotating vortex shedding from wind turbine impeller under yaw condition. The study provides a data support to build up the forecast model on the engineering and provides the basis for wind turbine design under yaw condition.
    2015,31(15):201-207, DOI: 10.11975/j.issn.1002-6819.2015.15.028
    [Abstract] (16783) [HTML] (0) [PDF 772.45 K] (2811)
    Abstract:
    Abstract: At present, large quantities of straws are burned in field in China, which not only wastes a renewable resource, but also causes serious air pollution. Anaerobic digestion of straws is an alternative method that may produce a clean fuel for energy generation. Currently, more research on impact of digestion for quality content of total solid of manure or mixed materials for the fermentation substrate has been studied, but research is limited in continuous stirred tank reactor for a single type of feedstock. Although the characteristics of anaerobic digestion and properties of gas production at the process of continuous stirred tank reactor and semi- continuous feeding mode has been examined for crushed straw and silage straw as the fermentation substrate, but the operation parameters of such system has not been determined. Thus, in order to obtain the corresponding relationship between solid matter retention time for substrate and the characteristics of gas production, a comparative study to determine biogas production in batch fermentation and semi-continuous fermentation process was carried out under medium temperature conditions with rice straw as feedstock. The effect of quality content of total solid in the batch and continuous biogas fermentation of straws was studied. The volume of gas production rate and the rate of raw material gas production were used as characteristic indicators in order to obtain parameter on optimum quality content of total solid and solid matter retention time for biogas plant with straws. The results showed that fermentation concentration of single straw type used for anaerobic fermentation raw material influenced the gas volume rate under the condition of batch fermentation. With the increase of total solid concentration, the volume of gas production rate was increased in batch fermentation process, but the trend of the increase was gradually decreasing. The volume of gas production rate was improved under condition of intermittent stirred compared with static batch fermentation. Especially, the improving effect was more obvious for the group of high-concentration of TS. However, the volume of gas production rate was more improved for the group of high-concentration of TS under semi-continuous feed conditions, but with the solid matter retention time (SRT) shortened, the rate of raw material gas production with every treatment was gradually decreased. Considering the characteristics of gas production and engineering applications, it was recommended that the concentration of batch fermentation should not exceed 8% for pure straw. For semi-continuous fermentation, if the straw composition in total solids content was 8%, SRT was designed as 20 days (the volume of gas production rate of 1.00 m3/(m3·d)). If the total solids content was 6%, SRT was designed as 15 days (the volume of gas production rate of 0.75 m3/(m3·d). The operating parameters provided an operational reference for biogas plant only with straw.
    2015,31(9):201-208, DOI: 10.11975/j.issn.1002-6819.2015.09.031
    [Abstract] (16753) [HTML] (0) [PDF 3.61 M] (4169)
    Abstract:
    Abstract: As one of the most effective cooling method, the fan-pad evaporative cooling system has been widely used to provide a suitable growth environment for greenhouse crops. An optimization method of the fan-pad cooling system based on computational fluid dynamics (CFD) was proposed to improve the cooling performance inside the greenhouse in summer. The Reynolds-averaged Navier-Stokes equations were solved using finite volume method (FVM). Due to the remarkable effect of gravitation on the microclimate distribution inside the greenhouse, the Boussinesq hypothesis was taken into account. The standard k-ε turbulent model was selected to predict the distribution of air flow. Solar ray tracing was applied to load the solar radiation model, while the discrete ordinate model was selected for considering the effect of thermal radiation. Crops in the greenhouse were regarded as the porous medium, which was governed by the Darcy-Forcheimier equation in the CFD model. A three-dimension greenhouse model was developed to simulate the microclimate distribution and air circulation inside the greenhouse adopting fan-pad cooling system. The verification experiment was conducted in a Venlo-type greenhouse in the campus of Zhejiang University of Technology (30°14′N, 120°09′E) from 12:30 to 13:30 on July 23, 2012. Thirteen observation points of T1-T10 and TH1-TH3 were set up in the experimental greenhouse to validate the simulated air temperature and velocity. The errors between simulated and measured air temperature at the observation points varied from 0.7 to 2℃, and the errors of air velocity were less than 0.13 m/s. Compared with the measured values, the absolute mean errors of simulated temperature and air velocity were less than 4% and 6% respectively. It proved that the CFD method is reliable to estimate the distribution of air velocity and temperature in the greenhouse. The validated CFD model was then used to further analyze the cooling performance of different greenhouse cases in terms of the greenhouse lengths, the evaporative pad areas and the greenhouse ventilation rates. The indoor environment with the temperature of below 30℃ and the velocity of below 1 m/s was suitable for crop growth, and this condition was used as a criterion for optimal design. Based on the orthogonal test method, greenhouse cases with different greenhouse lengths, evaporative pad areas and air velocities of fans were classified and simulated to analyze their relations. The simulations illustrated that the greenhouse ventilation rate of 153.1 m3/(m2·h) and the minimum pad area of 6 m2 can meet the cooling requirement in a Venlo-type greenhouse with 24 m length and 9.6 m width. In contrast with greenhouse of 70 m length, the maximum pad area of 13.5 m2 had to be configured, because the greenhouse with smaller evaporative pad need combine with the fan's velocity of more than 105 m3/(m2·h). According to the relations among greenhouse length, evaporative pad area and fan's velocity resulted from CFD analysis; the fitted results could be achieved to design the fan-pad evaporative cooling system in the greenhouse in eastern China. The fitting optimization showed good agreement with the previous corresponding research results, which demonstrated that CFD technique was rational and reliable to design the fan-pad evaporative cooling system in the greenhouse.
    2015,31(16):96-101, DOI: 10.11975/j.issn.1002-6819.2015.16.014
    [Abstract] (16572) [HTML] (0) [PDF 395.08 K] (2702)
    Abstract:
    High-speed solenoid valve (HSV) is the key component of electronic control fuel injection system for diesel engine. Improving the dynamic response speed of HSV will be able to achieve higher injection precision and more flexible fuel injection law, thus reducing gas emissions of diesel engine and improving its fuel economy. However, HSV is the complex coupling system of electric field, magnetic field, mechanical movement and flow field, and the interactions of multiple parameters exist between the fields for HSV. To improve the dynamic response speed of HSV is a complex optimization problem of multiple physical field and multiple parameters. A zero-dimensional approximation coupling model of HSV can be developed instead of the CAE (computer aided education) models or physical experiments, which conduces to achieve the efficient prediction and global optimization of performances. So the approximation model method was employed in this paper. First, the structure and principle of HSV for electronic unit pump of diesel engine were presented. Second, the three-dimensional (3D) finite element model of HSV was developed to calculate the electromagnetic force, and its accuracy was verified by means of the comparison with experimental data. Third, 3 major methods of experimental design, i.e. central composite faced-centered design (CCF), central composite inscribed design (CCI) and optimal latin hypercube design (OLH), and 3 typical approximation methods, i.e. quadratic polynomial response surface model (RSM), Kriging model (KR) and radial basis function model (RBF) were introduced. Fourth, 6 key parameters including 2 field coupling parameters, i.e. working air gap and drive current, and 4 structure parameters, i.e. coil turns, side pole radius, thickness and radius of armature were determined for establishing the approximate models. Next, 6 groups of sample points were designed, whose response values of electromagnetic forces were obtained by the 3D finite element model of HSV. Four of the groups were designed with different sizes by the OLH, and the other 2 groups were designed by the CCF and CCI. Then, 18 groups of electromagnetic force approximation models were developed by combining the 6 groups of experimental design with the 3 typical approximation methods introduced. To compare the accuracy of approximation models, 3 kinds of evaluation indices were introduced. They were multiple correlation coefficient, average absolute error and root mean square error respectively. In the end, the effects of different sample point sizes, experimental design methods and approximate methods on the accuracy of electromagnetic force approximation models were analyzed in detail. It is concluded that the accuracy of approximate model doesn't increase monotonically with the increase of the set size of sample points, and too many sample points maybe leads to the decrease of the accuracy of approximate model; the OLH has good adaptability with the KR and RBF, and can be given priority for developing approximation models. In addition, the best solution for establishing electromagnetic force approximation model of HSV is the combination of the KR and OLH, whose size of sample points is 1.5 times of the minimum sample points required by the quadratic polynomial response surface model. Its multiple correlation coefficient, average absolute error and root mean square error are 0.97, 0.06 and 0.09 respectively. It provides a theoretical guidance for the establishment of the zero-dimensional approximation coupling model and the optimization of HSV.
    2015,31(18):34-40, DOI: 10.11975/j.issn.1002-6819.2015.18.006
    [Abstract] (16512) [HTML] (0) [PDF 8.13 M] (3638)
    Abstract:
    Abstract: In China, corn harvest gradually tends to mechanization, and corn threshing is the most important section in the process of corn harvest, which is directly affecting the damage level of corn seed. Manual threshing often chips away a row of corn ear with an awl firstly, and then it's easy to thresh other kernels. Based on this, some agricultural experts put forward a process of "pre-dispersion and post-threshing". Besides, the study found that after the long-term evolution, beak has not only excellent ability to insert into corn kernels, but also strong ability of dispersing kernels with low damage. To explore the movement law of corn ear kernels and low damage in the discrete process of corn ear, this paper had an experimental study on the beak to peck the corn kernel using the discrete test system with high-speed photography. The variety of experimental corn was Zhengdan 958 and the common domestic chicken was selected for testing. Self-made corn discrete test system was used in this experiment. The whole system consisted of mechanical data acquisition system and high-speed photography system. Due to the randomness of chicken pecking corn, firstly, the high-speed camera was fixed to the bracket, and then the best angle was selected to shoot at the beginning of discrete process. The shooting in the test was mainly from the ahead, the side and the back side of the test equipment with the shooting angle of 45°. The sensors were installed on the fixture to measure the forces in 3 directions respectively. Through observing the photos, we found that the closer the kernel was from beak, the larger the horizontal component of thrust was, the more obvious the movement was, and the easier kernel was to disperse from ear; on the contrary, the further the kernel was from beak, the smaller the horizontal component of thrust was, and the more difficult kernel was to disperse from ear. The kernels followed the "arrangement law" to deliver forces, whose range was approximate to a "tower", and the movement of kernel separated from corn ear was similar to oblique throwing movement. According to the data measured, the maximum force on the corn ear was in x direction, second in y direction, and the force in z direction was the minimum. The resultant force of x and y direction had a great influence on the number of the kernels separated from the corn ear. The results of verification test were that the average discrete rate was 67.53% and the damage rate was 0.16%, which showed that the beak had a significant effect on dispersing corn ear, and the damage rate was low. The study will provide a bionic thought on designing corn threshing system with low damage.
    2017,33(7):164-170, DOI: 10.11975/j.issn.1002-6819.2017.07.021
    [Abstract] (16380) [HTML] (0) [PDF 6.90 M] (3699)
    Abstract:
    Abstract: Planting area and spatial distribution information of crops are vital for guiding agricultural production, taking effective management measurements, and monitoring crop growth conditions. Numerous crop classification algorithms have been developed with rapid development of different remote sensing data. However, distinguishing of corn and soybean cropping areas still remains a difficult challenge due to their similar growth calendar and spectral characteristics. In this study, we tried to identify corn and soybean cropping area using random forest (RF) classifier which has been proved to be an effective method in land cover classification based on multi-temporal GF-1 WFV (wide field of view) imagery. We selected Nenjiang County, Heilongjiang Province in China as the study area which was called the Town of Soybean. Seven GF-1 WFV time-series images (April 14th, May 20th, June 26th, July 16th, August 26th, September 4th, and September 29th), from which the key growth stages could be extracted and the effects of clouds could be avoided, were chosen to classify main crops. First, we conducted atmospheric and geometric corrections on multi-temporal GF-1 imagery. In order to improve the accuracy of distinguishing corn and soybean cropping area, the parameters of RF classifier were input, which included normalized difference vegetation index (NDVI), wide dynamic range vegetation index (WDRVI), enhanced vegetation index (EVI), and normalized difference water index (NDWI), and hundreds of field sample points were collected in the field survey. Also, it’s necessary to evaluate the importance of different combination of these indices. The results showed that the combination of NDVI, WDRVI and NDWI achieved the best accuracy with the producer accuracy of 91.14% for soybean and 91.49% for corn, and with the user accuracy of 82.76% for soybean and 93.48% for corn. Then, the support vector machine (SVM) and maximum likelihood (ML) supervised classifiers were also used to map corn and soybean cropping areas; the classification results from the SVM and ML methods were compared with that from the RF approach with the Nenjiang Farm as the case study. The comparisons showed that the crop classification from the RF classifier had the higher accuracy than the others. Our results indicated that GF-1 data had particular advantages in mapping cropping area with its higher spatial and temporal resolutions, and could provide more effective remote sensing data during crop growth season. The temporal changes of main crops showed the best classifying date was September 29th when soybean has been harvested but corn hasn’t, and their vegetation indices showed the maximum difference. The multi-temporal imagery contributed to the separation of different spectral feature curves of different crops in the growth stages when crops had similar temporal variation profiles, which helped to decrease the omission and commission errors of the resultant mapping. The results also showed that the extracted spectral information of water and construction land was very different from vegetation and could be easily masked. Comparing the SVM and ML classifiers with RF classifier, the results suggested that RF classifier could successfully distinguish corn and soybean, and its overall accuracy reached up to 84.82%. This study provides important reference for crop mapping in other agricultural regions.
    2015,31(20):268-273, DOI: 10.11975/j.issn.1002-6819.2015.20.037
    [Abstract] (16188) [HTML] (0) [PDF 6.48 M] (5542)
    Abstract:
    Abstract: For detecting the quality of pork, traditional optical equipment has high accuracy, whereas heavy weight, large size and high price make it difficult to use widely. The purpose of this research was to develop a portable optical device for detecting pork quality based on visible/near infrared spectroscopy and embedded system. This paper mainly explained the models building and the development of application software. Firstly, a compact and flexible system was made. Halogen lamp is as light source. To adapt to various complex environments, its hand-held probe can form black room on the surface of pork. Micro spectrometer (USB4000) receives and measures reflected light. ARM (advanced RISC machines) processor controls all parts in device and analyzes spectrum data. Based on Linux embedded operation system, liquid crystal display (LCD) touch screen interfaces with users. The whole weight of 3.5 kg makes it convenient for users. Secondly, collect the spectrum reflected from pork samples and build the partial least squares regression (PLSR) model. Before these, spectrometer parameters should be set, so that it works under the best conditions. Integration time of USB4000 was set to 7 ms, pixel boxcar width zero. Thus the reflection intensity of standard white plate was about 80% of spectrometer scale span. During experiment, after acquiring white and black spectrum data, detection probe was put on the surface of pork samples. Spectrum data in the wavelength range from 400 to 1 000 nm were collected from the surfaces of 39 pork samples, 29 spectra of which were as calibration, while others as validation. The acquired spectrum data were then processed by standard normalized variables (SNV) and Savitzky-Golay filter (S-G) to eliminate the spectra noise. After collecting the spectrum data, reference pH values of pork samples were immediately tested by pH meter (METTLER TOLEDO FE20, Switzerland), and color parameters (L*, a*, b*) were measured by precision colorimeter (HP-200, Shanghai, China). The partial least squares regression (PLSR) was applied to establish the prediction models. Experiment results showed that prediction correlation coefficients of pH value, L*, a* and b* were 0.94, 0.98, 0.95 and 0.85, and standard deviations of pH value, L*, a* and b* were 0.17, 1.19, 0.42 and 0.61, respectively. Thirdly, application software was designed and developed for detecting the quality of pork. It consisted of spectrometer control unit, spectrum data acquisition unit, spectrum analysis unit, and displaying and saving unit for prediction result of pork quality. Particularly, in spectrometer control unit, all parameters of USB4000 were set as the same as those when building the PLSR models. The coefficients matrixes of models were loaded into pork quality detection software in spectrum analysis unit. After debugged, the application program detecting the quality of pork was cross-compiled, and downloaded into the device. Finally, the accuracy of models were tested. The reflect spectra of external 41 pork samples were collected and analyzed with the device. At the same time, the real values of these samples' pH, L*, a* and b* were measured. For the pH value, the prediction model could give satisfactory results with the correlation coefficient (Rv) of 0.88 and the standard error of prediction (SEP) of 0.19. For the color L*, a* and b*, the prediction models could gain prediction results with the Rv of 0.90, 0.97 and 0.97, and the SEP of 1.77, 1.17 and 0.63, respectively. In conclusion, the field application results indicate that this portable device can satisfy the requirements of meat quality detection with high accuracy and good performance.
    2014,30(8):257-264, DOI: 10.3969/j.issn.1002-6819.2014.08.030
    [Abstract] (16060) [HTML] (0) [PDF 4.73 M] (3317)
    Abstract:
    Abstract: During aqueous processing of peanuts for simultaneous oil extraction and protein recovery, large amounts of emulsion could be formed and after enzymatic demulsification, substantial amounts of oil would be recovered while stubborn emulsions still remain. The destabilization of the stubborn emulsion is the key to improve the total free oil yield. Before its utilization and further destabilization, studying the characterization of the stubborn emulsion, especially its surface protein, which may play an essential role in emulsion stabilization, was necessary. The surface protein was extracted and its electrophoresis property, hydrophobicity, emulsifying activity, as well as emulsifying stability were studied. Confocal laser scanning microscopy (CLSM) was used to investigate its microstructure. It was found that, though the protein from the emulsion surface had similar subunits (60, 41, 38.5, 37.5, and 18 kDa) with that from aqueous phase, its hydrophobicity and emulsion activity was significantly higher. This could be attributed to the synergistic effect of temperature and pH during the alkaline extraction, which led to the unfolding of some large peanut protein molecules containing hydrophobic basic arachins. This, consequently, caused the exposure of more hydrophobic groups and enhanced the hydrophobic and emulsifying properties of the protein. Thus emulsion formation was promoted. After enzymatic treatment, the protein in the emulsion was hydrolyzed into short peptides and no subunits with molecular weight higher than 20 kDa had been detected in Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). However, in non-reducing PAGE, except for the conarachin band of 60 kDa, protein from the stubborn emulsion surface showed similar bands with that from the emulsion surface and aqueous phase. This indicated that the hydrolyzed protein could still gather on the stubborn emulsion surface and contributed to its stability. Due to the hydrolysis of protein molecules, the hydrophobic property and emulsifying activity of protein from stubborn emulsion was lower than that from an untreated emulsion surface. CLSM observation showed that stubborn emulsion had less oil droplets and that their size was lower, while the surface protein concentration (Γ) was higher, as compared with untreated emulsion. This explained the high stability of stubborn emulsion, though its surface protein has lower surface activity. To demulsify the stubborn emulsion, various treatments, including ultrasound, freeze-thaw, heating, extreme pH value, phase inversion, or ethanol addition were attempted. Free oil was obtained after centrifugation and total free oil yield was calculated thereafter. The microstructure of the stubborn emulsion after different treatments was also observed with CLSM. Results show that freeze-thaw and ethanol addition could remarkably aggregate the oil droplets in stubborn emulsion, especially after 50% ethanol addition, most oil droplets were combined and 90% of the oil in stubborn emulsion could be recovered. Under this condition, the total free oil yield could be increased to 93% from 88% in the overall process.
    2016,32(12):107-114, DOI: 10.11975/j.issn.1002-6819.2016.12.016
    [Abstract] (16028) [HTML] (0) [PDF 413.47 K] (2306)
    Abstract:
    Abstract: Rapid population growth and economy development has led to increasing reliance on water resources. It is even aggravated for agricultural irrigation systems where more water is necessary to support the increasing population. In this study, an interval-parameter two-stage Fuzzy-stochastic optimization model was developed for dispatching the underground and surface water systems for different crops in Hong Xinglong irrigation of China under the conditions of uncertainty and complexity. In the model, the maximal system benefit was regarded as the objective function and 3 methods of probability density function, discrete intervals and fuzzy sets were introduced into the two-stage linear programming framework to resolve uncertain issues. The model allocated a predefined water to crops in the first stage, according to benefit and punishment for water shortage condition to adjust the water supply in the second stage, making the system reach the balance of systems benefit and the risk of punishment, the process of water allocation for multiple corps was simulated, meanwhile, the allocation of water from various sources was optimized. Because inflows water was of obvious probability characteristics in irrigation area, the model took into account of the random of inflow, and assumed that the probability of occurrence for high, middle and low levels were 0.2, 0.6 and 0.2. Since the quantity of stream flows, water requirement of crop and available water supply were uncertain, and uncertainties might also exist in system benefits and costs, the uncertain parameters of above-mentioned were described by interval variables. The available water in the irrigation area was represented by fuzzy sets based on credibility theory. The different probabilities, discrete interval number and fuzzy sets together were used to build the irrigation multi-water resource, multi-crop water distribution model. The model was solved by the method of linear programming, the optimal distribution scheme of water was achieved and the maximum benefit was 1 355.144×106-2 371.792×106 RMB. It could reflect not only uncertainties in water resources system, but also provide an effective linkage between conflicting economic benefits and the associated penalties attributed to the violation of the predefined water distribution target. Meanwhile, the results were presented in the forms of interval number, proving a more broad decision space for decision makers. Moreover, the results indicated that farmer planted a large number of high-yield and high water consumption of crops such as rice and corn in irrigation area and single planting structure would lead to the risk of the decrease of crop production in dry year, the model was valuable for supporting the adjustment or justification of the existing irrigation patterns and identify a desired water allocation plan for agricultural irrigation under uncertainty. Compared with the other traditional two-stage model, this model had advantages: 1) it considered uncertain factors as much as possible, made the model more close to actual condition; 2) The model effectively relieved groundwater pressure of water supply by utilizing surface water and groundwater; 3) The model results would suggest managers reducing planting area of high water consumption crops; 4) Water resources management by system benefit would stimulate employee enthusiasm; and 5) The model data was relatively easy to access.
    2017,33(12):66-73, DOI: 10.11975/j.issn.1002-6819.2017.12.009
    [Abstract] (16017) [HTML] (0) [PDF 5.69 M] (3537)
    Abstract:
    Abstract: The droplet quality of hydrodynamic ultrasonic atomization nozzle is better than the ordinary two-phase nozzle. And the atomization amount is larger than the piezoelectric atomization nozzle. High-quality droplet and high atomization amount are both required in the field of aeroponics. Therefore, it is necessary to develop a hydrodynamic ultrasonic atomizing nozzle suitable for large-scale aeroponics. Based on the basic principle of the Hartmann resonator, in this study, the mechanism of ultrasonic vibration of resonant cavity and the atomization mechanism of resonant cavity supersonic nozzle were analyzed theoretically. The Hartmann low-frequency ultrasonic atomization nozzle with stepped resonator and adjustable structural parameters was designed, including the Laval tube, the stepped tube, and conical shield. The influence of the structural parameters on the resonant state of the resonator was studied by means of CFD software transient numerical simulation. In order to make the spraying angle controllable, active flow control was used in the atomizing area, namely, adding a conical shield at the exit of the nozzle. The oscillation characteristics of the stepped resonance tube were further studied parametrically by numerical simulation methods. Numerical simulation of three kinds of atomizing nozzles including cylindrical tube, stepped tube and stepped tube with conical shield was carried out. The parameters which were studied were as follows: the distance between Laval outlet and inlet of stepped tube, depth ratio of the second stepped hole and the first stepped hole, conical cover, diameter ratio of the second stepped hole and the first stepped hole. Numerical simulation results showed that: (1) If the depth ratio of the stepped tube exceeded 2, its resonance frequency reached 1.6 to 1.7 times of the cylindrical one under the same working parameters; (2) The conical shield can make the pressure oscillation amplitude in the cavity bigger; and (3) The diameter ratio of the stepped resonator had a great influence on the resonant state of the resonator. The variation of diameter ratio of the stepped resonator changed the resonant mode of the stepped resonator from one mode to another. It also can make the resonance phenomenon disappear. As such, the key dimensions of the stepped resonator were determined accordingly. And an optimal diameter ratio was selected for trial production. And the optimal distance between Laval tube outlet and the resonant inlet 5.5 mm were selected as the initial structural parameter values of the spray test. The droplet size of three kinds of atomizing nozzles was tested and the test of droplet size was carried out with distance between Laval tube outlet and the resonant inlet, depth ratio of the second stepped hole and the first stepped hole, and other factors as variables. Moreover, its atomization properties were tested contrastively under different conditions. Research results showed that: (1) Start-up properties of oscillation can be optimized due to the main frequency unaffected by the conical shield;(2) The diameter ratio of stepped resonance tube was a quite sensitive parameter influencing the resonance state. The variation of diameter ratio can make the resonance mode change from 'jet regurgitant mode' to 'jet scream mode' or make the oscillation disappear; (3) Atomization properties of Hartmann atomization nozzle with a stepped resonance tube was better than those of Hartmann atomization nozzle with a cylindrical one; (4) If the air supply pressure was low, the droplet size was more sensitive with the pressure after adding a conical shield, while the gap of the average droplet size between the nozzle with stepped tube and that with traditional tube was not obvious under the condition of high air supply pressure. The distance between the Laval tube exit and the resonance tube was another sensitive parameter influencing the droplet size. An optimal distance, where the minimum droplet size can be acquired, was 6.5 mm. The droplet diameter increased gradually no matter the distance was bigger or smaller than the optimal distance. However, the droplet diameter varied slightly with the distance near the optimal point.
    2016,32(8):278-284, DOI: 10.11975/j.issn.1002-6819.2016.08.039
    [Abstract] (16001) [HTML] (0) [PDF 1.43 M] (3056)
    Abstract:
    Abstract: At present, trawl fishing as a traditional method is widely used in shellfish harvesting at home and abroad. However, using this method to catch the scallops has many disadvantages, such as huge energy consumption, high labor intensity, and poor fishing efficiency, which have become the key questions to restrict the sustainable development of marine fishing industry. Therefore, it's very worth researching alternative scallop fishing equipment to meet the requirements of green development. The offshore scallop capture equipment is made up of platform deck, floating body and mooring, which is a kind of floating offshore engineering structure. This equipment occupies multiple functions, such as fishing, sorting, refining, storage and so on. Winch motors (ground net machine and anchor winch), cargo winch, generator unit, scallop separator, working cabin, accommodation and diesel generator were installed on the platform, and solar power as the source of power. In addition, to keep the scallops fresh and achieve the purpose of saving space, 2 shellfish purification storage networks were also set below the platform. Compared with the trawl fishing, it would substantially reduce energy consumption, realize precision fishing, raise fishing efficiency, and decrease the cost of purification. In this paper, based on the comparative methods, the technologic and economic parameters and the economic assessment indices were selected for the establishment of the technical and economic evaluation model, which was to investigate the economy of offshore scallops capture working platform. Firstly, the platform trawling engine power, the platform span, the hauls of platform anchored one time, the lateral movement time of platform anchored one time, the trawling speed of platform and the total construction cost of platform were selected as the technologic and economic parameters. Secondly, the capture fuel consumption per unit area, the unit cost of fishing and the capture efficiency were selected as the economic assessment indices. Next, the technical and economic evaluation model was established according to the technologic and economic parameters and the economic assessment indices. At last, based on this model, the economic calculation of fishing methods including fishing vessels and scallops capture working platform was carried out by using the comparative method. The results showed that when the platform trawling engine power was 400-470 kW, the platform span was 0.5-3.0 km, the lateral movement time of platform anchored one time was less than 2 h, the trawling speed of platform was beyond 1.4 kn, the total construction cost of platform was less than 27.5 million yuan, the scallops capture working platform project had more advantages over the fishing method of fishing vessels. Meanwhile, from these data, it was concluded that the haul of platform anchored one time was not very sensitive to the effect of scallops capture working platform project. The offshore scallops capture working platform conformed the policy of energy saving and emission reduction that was in line with the national "Twelfth Five-Year Plan". By further experimental verification, the analysis model and method can provide the economic theory reference for the fundamental changes in fisheries production mode in China.
    2016,32(5):120-125, DOI: 10.11975/j.issn.1002-6819.2016.05.017
    [Abstract] (15992) [HTML] (0) [PDF 3.29 M] (2823)
    Abstract:
    Abstract: Yanqi Basin is one of the most important oasis agricultural areas of Xinjiang. But the ecological environment of Yanqi Basin is fragile, which depends on groundwater resources greatly. To study the spatial-temporal evolution of total dissolved solids (TDS) of groundwater is of great significance to groundwater exploitation in arid areas with fragile ecological system seriously affected by human. In order to identify the groundwater pollution status in the plain area of Yanqi Basin, 42 groundwater samples was collected in 2014. TDS and concentration of anion and cationic of the 42 groundwater samples were tested. T test was used based on the observed data of groundwater in the different periods of the plain area to determine the variability of TDS. The relationships between TDS and macro anion, macro cation, pH were analyzed with SPSS software. The results showed that TDS of groundwater was mainly affected by SO42-, Cl-, K++Na+, Mg2+ and Ca2+. And the TDS were highly correlated with Cl- and K++Na+. The correlation between the TDS and macro anion was highest, followed by Cl-, SO42-and HCO3-; the correlation between the TDS and macro cation was also high, followed by K++Na+, Ca2+ and Mg2+. Zone map of TDS was drewn by the MAPGIS software. In the temporal scale, the average of TDS of groundwater was increased then decreased and increased again from 1983 to 2014, and the average value was 305.0, 1773.1 and 589.44 mg/L in 1983, 1999 and 2014, respectively. In the spatial scale, the TDS of groundwater evolved horizontally from piedmont to the plain area. The TDS of groundwater increased from upstream to downstream. Influenced by topography and hydrogeology conditions, the main hydrogeochemistry action changed from strong runoff to slow evaporation gradually. Area of groundwater with TDS<1 g/L showed an increasing trend but a decreasing trend from 1999 to 2014, which was consistent with downtrend of the mean value of TDS from 1999 to 2014 increased from 2011.7 to 2229.3 km2. There were 2 main reasons causing that change of groundwater TDS: 1) The groundwater table dropped from 4.98 to 7.34 m from 2000 to 2014, which prompted the solid phase calcium and magnesium soluble salts, insoluble salts and exchangeable calcium and magnesium in the soil and the lower layer sediments transferred to the groundwater; Meanwhile the increase of the groundwater table in the plain area led to high solutes concentration; 2) Urbanization had the great influence on the groundwater system. It changed the original land use patterns, and then the groundwater circulation system. And with the development of urbanization, industrial and domestic waste water increased year by year and could infiltrate into aquifer. The discharge of living and industrial waste water led to groundwater pollution, which was consistent with the dominant role of Cl- and SO42- in TDS. The study provide valuable information for understanding the condition of underground in Xinjiang.
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    2009,25(8):288-293, DOI:
    [Abstract] (2109) [HTML] (0) [PDF 0.00 Byte] (117904)
    Abstract:
    In order to study the feasibility of microwave-assisted foam mat drying method for the dehydration blackcurrant pulp, a reasonable foaming additive formula was determined and the microwave-assisted foam mat drying characteristics of blackcurrant pulp were analyzed. The concentration of glyceryl monostearate (GMS) and soy protein isolated (SPI) with food grade, selected as the foaming additive, had obvious effects on the foaming properties of blackcurrant pulp. A reasonable foaming additive formula for the blackcurrant pulp with optimum expansion and high stability was developed that the 6% GMS and 3% g SPI as foam inducers and the 10 mL carboxylic methyl cellulose (CMC) with concentration of 0.5% as foam stabilizer, accompanying with the stirring time of 6 min. The experimental results of microwave assisted foam mat drying method showed that the drying intensity of foamed blackcurrant pulp increase with the increase of initial microwave intensity and the decrease of thickness of material layer. Contrasting the microwave with conventional hot air as the heat source for the foam mat drying of blackcurrant pulp, the qualities of dried blackcurrant product in terms of drying rate, color and appearance dried by microwave method are superior to that dried by the hot air. The parameters including the initial microwave intensity of 14.0 W/g and thickness of material layer of 5 mm are recommended for the continuous microwave belt dryer to dry the foamed blackcurrant pulp. Therefore, microwave assisted foam mat drying is suitable for the dehydration processing of blackcurrant pulp.
    2021,37(12):20-27, DOI: 10.11975/j.issn.1002-6819.2021.12.003
    [Abstract] (647) [HTML] (0) [PDF 5.55 M] (59027)
    Abstract:
    Abstract: Vibration has been an ever-increasing demand for the operational stability of centrifugal pumps in recent years, especially in most large pumps in modern industry. The internal flows are generally dominated by the characteristics of operation stability and vibration of centrifugal pumps. Nevertheless, the blade and volute structures are dramatically detrimental to the internal flows. The radial force is one of the most significant factors to affect the operation stability, and the pressure pulsation inside the volute, particularly in the tongue areas. A double-volute structure is selected normally to reduce the radial force in commonly-used large pumps, instead of a single-volute structure. But the specific structures are still required to be optimized, such as the arrangement of the rib start point. In this study, a three-dimensional unsteady dynamic was proposed to clarify the influences of rib start point on the hydraulic performance, radial force, and pressure fluctuation in the volute of a large double-volute double-suction pump. The variation of fluctuation amplitude and frequency of radial forces were considered at the different rib start points. Meanwhile, the radial forces of the double-volute pump at various flow rates were also compared with those of the single-volute pump. The experiments of pump performance (head, efficiency, and power) were performed on the large-scale pump platform in KaiQuan Factory in Shanghai of China. The numerical data agreed well with the experiments, same as the grid independence check. The results indicated that the hydraulic efficiency at the design points decreased about 4%-5% in the double-volute structure, compared with the single-volute structure. Periodic variation of radial force was detected in the test, where the blade passing frequency was dominated during a blade revolution. The angle of radial force was also changed periodically. The rib start point significantly determined the radial force, where the minimum appeared when the rib started from 190° and 200°, whereas, the maximum appeared when the rib started from 212°. Seven monitoring points were located in the tongue areas to collect the pressure fluctuations. It was found that all the mean, peak, and fluctuation values at the points behind the tongue were much less than those in the front of the tongue under the different rib structures, only 25%-50% of the corresponding value of points in the front of the tongue. The pressure fluctuations of points in front of the tongue were dominated by the blade passing frequency, whereas, those points behind the tongue were dominated by the double blade passing frequency. More importantly, the pressure fluctuation of points declined dramatically, when the rib start point moved backwards, indicating a cause of double blade passing frequency. Thus, the rib start point should be placed at 200° from the tongue point in the flow direction, where the maximum efficiency and the minimum radial force can be achieved, particularly considering the coupled interaction of hydraulic performance and radial force. The finding can greatly contribute to the hydraulic improvement and structure optimization in large centrifugal pumps. Key words: pumps; experiments; rib location; double-volute pump; radial force; pressure fluctuation
    2021,37(19):7-17, DOI: 10.11975/j.issn.1002-6819.2021.19.002
    [Abstract] (654) [HTML] (0) [PDF 8.68 M] (53758)
    Abstract:
    The fuel efficiency of the engine is only 15%-35% while the tractor is working in the field, and the exhaust energy accounts for 38%-45% of the energy released by the fuel. The recovery and reuse of exhaust heat energy could help improve fuel efficiency and reduce emissions. Studies have shown that the exhaust waste heat energy based on the Organic Rankine Cycle (ORC) is the highest. The evaporator is a key component of the ORC system, analyzing its thermal performance under limited space conditions of the tractor could provide a theoretical basis for the optimal design of evaporator parameters, thereby effectively improving the utilization of exhaust heat. This study according to the actual size of the tractor, a plate-fin evaporator was trial-produced to recover diesel exhaust waste heat. A numerical model of convective heat transfer between evaporator exhaust and working fluid based on moving boundary method was established and was verified the validity by combining with bench test data, the thermal performance of the evaporator under full operating conditions of the diesel engine was quantitatively analyzed; meanwhile in order to improve the heat transfer and scope of application of the evaporator, CFD simulation and BP neural network methods were used to further analyze the heat transfer characteristics of the evaporator under off-design conditions, the structure and working fluid parameters were optimized. The results showed that: 1) the evaporator had better thermal performance under medium and high speed load conditions, and the heat transfer reached a maximum of 69.89 kW under 4 000 r/min full load conditions, and the heat transfer of the evaporator would be unstable under medium and low speed load conditions due to the lower exhaust heat capacity flow rate, heat transfer coefficient, and a larger working fluid mass flow rate, resulting in the flow was difficult to ensure that the working fluid was transformed into superheated steam, so that the heat transfer in the two-phase zone and the superheat zone was zero within the evaporator. 2) in order to improve the distribution and turbulence of the fluid in the flow channel, increasing the pipe chamfer and adopting the corrugated fin shape to promote forced heat exchange, the CFD simulation showed the entire high-temperature area moved forward to the inlet of the nozzle to make the flow channel utilization rate higher and heat transfer more. With the optimized structure of the evaporator, the working fluid had a higher degree of overheating under the condition of the same overall size, the maximum heat transfer increased by 5.2%, the heat transfer area increased by 0.19 m2, and the volume only increased by 0.002 m3. 3) combined with the BP neural network algorithm, the evaporator flow channel length, working fluid flow and inlet temperature were optimized parameters, and the thermal performance of the evaporator under off-design working conditions was further analyzed, and the parameter range under the medium and low speed load conditions is determined. Thus, the selection range of the working fluid flow rate at different speeds was proposed, which effectively improving the thermal performance of the evaporator under low-to-medium speed load conditions, and providing a reference for the selection of the transmission ratio of the booster pump and the output speed of the diesel engine and the selection of the transmission device. For example, when 1 500 r/min was under a medium and high load, the flow rate could be changed from 0.03 kg/s to 0.08 kg/s and the maximum heat transfer up to 19.46 kW; at the same time, the transmission ratio could be set to 0.78-1.88 at 1 500 r/min. The results of the study are of great significance and present the fluid flow and heat transfer characteristics of the evaporator, which provide a reference for the actual use of the evaporator in tractors and matching with diesel engine operating conditions.
    2021,37(1):68-76, DOI: 10.11975/j.issn.1002-6819.2021.01.009
    [Abstract] (1602) [HTML] (0) [PDF 5.45 M] (42099)
    Abstract:
    Citrus fruit, one of the most important economic crops, is playing an important role in the industrial development of modern agriculture in rural China. However, the management mode of most orchards in China is currently undeveloped and extensive, particularly with high dependence on labor force, as well as insufficient scientific and technological support. In recent years, the Unmanned Aerial Vehicle (UAV) monitoring technology has become a significant way to quickly extract the structural parameters in the growth of field crops at the park scale, due to its flexibility, low cost, and high resolution imaging. This study aims to construct a monitoring system for the citrus canopy structure and nutrition information using the UAV digital and multi-spectral remote sensing, to get he with the single tree segmentation. The UAV digital images and watershed algorithm were used to segment the structural dataset of citrus canopy, and then the canopy height model of citrus trees was established to extract the plant height using digital surface module. Structural parameters were also calculated, such as the number of citrus trees, and canopy projection area at the park scale. In addition, the UAV multispectral images were used to obtain eight common vegetation indexes, thereby to predict the nitrogen content of canopy in the citrus trees. The whole subset analysis was used to screen the sensitive vegetation index for the nitrogen content of canopy in the citrus trees. The inversion model of canopy nitrogen was constructed using the multiple linear regression. The remote sensing mapping was carried out to estimate the nitrogen content of citrus canopy in park scale. The results showed that: 1) Since the planting density of fruit trees was low in the experimental area, there was a certain distance between trees that can be clearly distinguished. The watershed image processing was selected to segment the single tree of height model for a citrus canopy. The overall identification accuracy, recall rate, and average F value of the fruit trees were above 93%, 95%, and 96.52%, respectively, indicating that the model was well suitable to monitor the number of fruit trees in the park. 2) The canopy structure parameters of individual fruit trees were obtained in the individual tree segmentation. There was a strong correlation between the plant height of citrus trees extracted by the canopy height model and the measured value, where the R2=0.87, and RMSE=31.9 cm. 3) Using the watershed segmentation, the extracted projection area of crown width per plant achieved a high correlation with the artificial sketching area. The coefficient of determination was more than 0.93 in most cases, except that of orchard A lower than 0.78 in December. Meanwhile, the extraction accuracy of the model depended greatly on the single tree segmentation. 4) In full subset analysis, the sensitive vegetation indexes were selected to determine the nitrogen content of citrus canopy, including the Normalized Difference Vegetation Index (NDVI), Green Normalized Difference Vegetation Index (GNDVI), and Structure Insensitive Pigment Index (SIPI), where the R2 and RMSE of the model were 0.82 and 0.22%, respectively. The data demonstrated that the nitrogen content of most fruit trees in orchard B was in the suitable range, while there was excessive application of nitrogen fertilizer in orchard A. Therefore, the UAV technology can greatly contribute to extract the physical and chemical parameters of citrus canopy, further to improve the level of accurate management of citrus on the large-scale orchard.
    2013,29(19):88-97, DOI: 10.3969/j.issn.1002-6819.2013.19.011
    [Abstract] (2618) [HTML] (0) [PDF 560.68 K] (39858)
    Abstract:
    Abstract: Aiming at the main problem that existed in estimating the crop water requirement through multiplying the crop coefficients of main crops determined in the early 1990s by ET0 calculated using the Penman-Monteith equation, the reasons for crop coefficients which need to be revised were analyzed. There is a significant difference in ET0 calculated by using the modified Penman equation and by Penman-Monteith equation, which affects overwintering crops with a longer growth period of greater than summer crops with a shorter growth period. The result showed that the monthly ET0 and ETrad calculated by using Penman-Monteith equation were higher than that by modified Penman equation, and the difference between radiation terms was the main reason that caused the difference between the calculation results by using two equations based on the meteorological data of 18 stations in Henan province. The difference of monthly ET0 and ETrad calculated by two equations in autumn and winter was higher than in spring and summer. The effect of aerodynamic term on ET0 was related to wind speed, and the reason that the effect of aerodynamic term on ET0 is higher than the radiation term maybe caused by high wind speed. Except for the relative humidity, average temperature and sunshine hours, radiation term was affected by the elevation of stations, as for the stations with a higher elevation, the impact of elevation on Penman-Monteith equation was greater than that on modified Penman equation. Using the sensitivity analysis method to evaluate the effect of average air temperature, relative humidity and sunshine hours on ETrad showed that Penman-Monteith equation was better than modified Penman model in calculating ETrad. The ETrad calculated through Penman-Monteith equation was little influenced by seasons and stations, and had a high stability. The results from 18 stations showed that the effect of average temperature on ETrad was the minimal, the impact of relative humidity in January, November and December on ETrad was larger, and the influence of sunshine hours from February to October on ETrad was also greater. Therefore, ET0 in Henan Province was calculated by Penman-Monteith equation instead of modified Penman equation, crop coefficients must be corrected, otherwise it caused the estimated values of crop water requirement to be higher, and its impact on overwintering crops with a longer growing period was greater than that on summer crops with a shorter growth period. Finally, according to the relationship between two difference methods of estimating ET0, the correction method of crop coefficient based on Penman-Monteith equation was proposed. This study has an important significance in improving the estimation precision of crop water requirement.
    2011,27(3):254-259, DOI:
    [Abstract] (2408) [HTML] (0) [PDF 0.00 Byte] (20269)
    Abstract:
    In order to study the related technology for preparing biodiesel by transesterification of cottonseed oil using solid based catalyst, with supported solid base Na3PO4/MgO as catalyst and biodiesel conversion rate as index, the optimum conditions for catalyst preparation were analyzed by single-factor and orthogonal experiments. The catalyst was characterized by methods of XRD, SEM and TG. Furthermore, the transesterification conditions from cottonseed oil to biodiesel were investigated using solid base catalyst. It was obtained that the optimum conditions for catalyst preparation were: 32% of Na3PO4 dosage on MgO, 600℃ of roasting temperature, 3 h of roasting time and 70℃ of blending temperature. Catalytic activity was related to Na3PO4 crystalline phase. The optimal conditions of transesterification with optimized catalyst were: 2.5 h of reaction time, 70℃ of reaction temperature, 15:1 of mass ratio of methanol to oil, 5% of quality ratio of catalyst to oil.
    2011,27(3):242-247, DOI:
    [Abstract] (2263) [HTML] (0) [PDF 0.00 Byte] (20250)
    Abstract:
    The technique for producing a kind of bio-degraded mulch from the straw fiber was studied. It is an alternative to plastic mulch with the same price and weed control, reducing evaporation functions. Rice straw fiber was the main material, and KP (wood fiber) as well as environment-friendly additives such as wet strength agent, rosin and bauxite were added. A central composite rotary orthogonal experimental design of RSM, with five factors and five levels for each factor was employed. Conventional paper producing technology was adopted, and pulp degree, mixture ratio, grammage, wet strength agent and conditioning agents were the input variables, dry tension strength, wet tension strength, sizing value were the response functions. The optimal technical parameters were obtained, the grammage value, conditioning agents content, wet strength agent content, mixture ratio and pulp degree were 90 g/m2, 0.2%, 0.8%, less than 68% and more than 45°SR respectively. Under the condition, dry tension strength of the sample mulch was higher than 30 N, the wet tension stress was higher than 10 N, and the sizing value was higher than 100 s. The sample of mulch made from rice straw fiber could meet the need of mechanical performance for laying field.
    2019,35(2):25-32, DOI: 10.11975/j.issn.1002-6819.2019.02.004
    [Abstract] (1240) [HTML] (0) [PDF 5.26 M] (18007)
    Abstract:
    The double vane pump is a special type of flow vane centrifugal pump. It adopts a design with less blades, which leads to a disadvantage that the performance of the double vane pump is inferior to that of the multi-blade pump at the same specific velocity. Its stability is 3%-8% lower than of a vane centrifugal pump.Therefore, it is necessary to improve the work efficiency by optimizing the hydraulic design. This article took a double-passage sewage pump model 80QW50-15-4 as the research object. The optimization objective was to design the head and efficiency of the flow point. ANSYS CFX(computational fluid dynamics x) was used to perform numerical simulation to obtain performance data. According to the two-dimensional hydraulic drawing of the initial model pump, the three-dimensional modeling software Pro/Engineer5.0 was used to simulate the water body of the impeller and the volute and to perform mesh division and irrelevance verification. The model pump was subjected to numerical simulation and experiment of clear water medium, and the performance curve was obtained and compared. The error analysis showed that the maximum error of head and efficiency was 3.9% and 1.7%, which meant that the performance prediction model established by this method had high accuracy. Partial initial model impeller structure parameters were selected for performance impact analysis. The Plackett-Burman screening test was used to determine the blade wrap angle, blade outlet angle and impeller outlet width were significant factors affecting head and efficiency of design flow. According to Fang Kaitai's unified design table, training samples of RBF(radial basis function) neural network were arranged, so as to establish important structural parameters and performance prediction models, and generated 5 groups of structural parameters random for neural network testing and error analysis. The head and efficiency performance prediction model trained by radial basis neural network was introduced into the particle swarm optimization algorithm as the fitness evaluation model of particle swarm optimization algorithm. The Pareto optimal solution set of head and efficiency was obtained, and the optimal head and efficiency were selected. In addition, this paper also studied the performance and internal flow field differences of the initial individual, the optimal individual of head and the optimal individual of efficiency when transporting different media. It was known from the performance curve that the performance of individuals was improved when transporting different media. The reason for the performance improvement was revealed by the internal flow field distribution map. In order to verify the practicability of the optimization results, a clear water test was performed on the optimal head and the most efficient individual to obtain a performance curve and compared with the performance curve of the initial individual. Among them, the experimental head of the optimal head at the design flow point increased by 0.96 m than the initial individual, the increase rate reached 5.5%, the efficiency increased by 1.6 percentage point; the efficiency of the best individual increased by 10.11 percentage point, the head decreased slightly but met the design requirements. The test proved that the optimization effect was obvious. This optimization method improves the hydraulic characteristics of impeller and the performance of double vane pump.
    2020,36(11):39-48, DOI: 10.11975/j.issn.1002-6819.2020.11.005
    [Abstract] (1130) [HTML] (0) [PDF 8.24 M] (17879)
    Abstract:
    Abstract: Accroding to literatures and preliminary tests, the structure of cheaning device of longtitudinal axial flow grain combine harvester had a significant impact on wind speed distribution of upper sieve surface and cleaning effects of the device. In this paper, the RG60 type single longitudinal axial flow grain combine harvester developed by LOVOL Heavy Industry Co. Ltd. was tested in Xichang, Si Chuan Province. In order to analyze the wind speed distribution on the upper sieve surface, 45 measuring points were set up, the measurement results showed that the wind speed on upper sieve surface was uneven, the speed at front air outlet of fan installation, forth and fifth column from left of tail sieve were greater than else, the maximum wind speed was 8.6 m/s which was smaller than floating speed of grain, the wind speed on sieves of 3 and 4 row, 6 and 7 row was 5.8 and 5.9 m/s respectively, the speed on middle sieve surface was the smallest. The wind speed on the right side was greater than that of the left side. In the middle and right of upper sieve surface, there was less accumulation of grain mixture, while there was more accumulation in the left, the distribution of grain mixture was uneven which was not conducive to separation of grain and impurities. In order to solve the problem that wind speed distribution was uneven on upper sieve surface, the force and speed of grain mixture in cleaning device were analyzed. According to the structure of cleaning device, because the right side of centrifugal fan was equipped with power input pulley so the air inlet resistance value was higher than left side, and the dynamic pressure was smaller. In addition, the large transverse width of vibrating sieve lead to uneven distribution of wind speed on upper sieve surface, resulting in more grain mixture on left side of tail sieve. In order to further analyze tje distribution of wind speed in cleaing device and optimize its structure, the simulation was carried out in Hyper Works. The results of wind speed on upper sieve showed that the test results of wind speed change trend of each measuring point were consistent with the simulation results, with an average deviation of 0.293 m/s, which indicated that the simulation can reflect wind speed distribution of the internal flow field of cleaning device. The maximum wind speed at the front of upper sieve surface was 10.024 m/s, the left side in lateral wind speed of upper sieve surface in cleaning area was much smaller than that of the right side. The maximum wind speed at the rear of upper sieve surface was about 8.02 m/s which was less than that of the suspension speed of materials. The wind speed in middle of tail sieve was high which was bad for separation of grain mixture. The wind speed of fourth column from left on front air outlet was 8.184 m/s while it at third column from left and middle of tail sieve was 8.411 m/s, and the speed on sieves of 6 and 7 row, 8 and 9 row were the smallest, this trendy was same as the test results. In longitudinal section X=650 mm of upper sieve surface, the wind direction was gradually to right in the process of blowing to upper sieve surface, and the maximum wind speed is 17.077 m/s. In cross section Z=-450 mm, the range of wind speed was from 6.5 to 10 m/s, the turbulence in wind field in middle of upper sieve surface may result in less effect separation of grain mixture. The reason for this phenomenon was the right side of centrifugal fan was equipped with a power input pulley, which made the direction of air flow generated by fan deviate. Therefore, the structure of cleaning device was improved to eliminate this phenomenon. The simulation experiment was carried out when the wind shield rotated 10°, 20°, 30°, 40° and 50° counterclockwise, respectively. The results of optimization simulation showed that internal flow field was evenly distributed when wind shield rotated 30° counterclockwise. the wind speed of upper sieve left side gradually decreased while right side gradually increased with increase of counterclockwise rotation angle of wind shield, the wind speed in middle of tail sieve was the highest which was within the range of [8.231, 10.289] m/s, about 2 m/s higher than that before the improvement, the phenomenon of uneven distribution of wind speed on sieve surface and large difference on left and right sides was improved. The optimized harvester test results showed that third column from left in front air outlet and sieves of 11 and 12 row, the wind speed increased by 1.9 and 2.8 m/s respectively, and its distribution at left and right sides of rear of tail sieve was the most uniform. the wind speed in middle of front air outlet on upper sieve (third column from left) was the maximum as 8.7 m/s, it in sieves 11 and 12 row was 6.3 m/s, the lowest was 5.0 m/s in tail sieve. The wind speed along left side and right side of upper sieve surface were gradually decreased, and the overall wind speed distribution was uniform The loss rate of wheat and the impurity rate was 0.89% and 0.37% respectively, the loss rate of rice and impurity was 1.85% and 0.51% respectively, the cleaning performance and uniformity of the wind flow field distribution of the cleaning decice was improved. The research results provide a reference for the design and parameter optimization of the cleaning device of single longitudinal axial flow harvester.
    2014,30(3):205-214, DOI: 10.3969/j.issn.1002-6819.2014.03.027
    [Abstract] (2713) [HTML] (0) [PDF 11.40 M] (17708)
    Abstract:
    Abstract: Rural residential areas are an extensive dispersion with localized concentrations, and the area of land utilization per capita is large in Dazhu village in Hechuan of Chongqing. Inefficient utilization of rural residential areas is an adverse process all over China during the urban-rural transitional period, especially in traditional agricultural areas. The space reconstruction of a rural residential area could be a breakthrough in the rational utilization of land resources, advancing new countryside construction, restructuring village space, and promoting urban-rural integration and development.This paper used the symbiotic theory to establish a rural residential restructuring symbiotic system. The system included rural residential areas as a symbiotic unit, and the policy environment and the village-domain environment as symbiotic environment. Due to the mutual functional differences of symbiotic units, village spatial reconstruction should consider a mutually beneficial symbiotic relationship between the units, namely the mutualism mode. The research analyzed a rural residential restructuring symbiotic system, and made clear the restructuring principles and procedure needed to build the space reconstruction strategy of a rural settlement. The thesis selected the demonstration village of the whole village advancement-Dazhu village in Hechuan of Chongqing as the object of empirical study. It built three kinds of functional groups-productivity-oriented, service-oriented, and living-oriented groups, a space representation of which was already presented in the village, and formed the layout of 'one axis and three groups' at the the village scale.The results showed that: first, adopting the rural residential restructuring symbiotic system analysis accords with the reality of Dazhu village to restructure village space. It further showed that the symbiotic theory has strong applicability to space reconstruction of a rural settlement. Secondly, the results of the empirical study showed that the space reconstruction of a rural settlement, which is based on the symbiotic strategy, can both ensure the inter-operability of a rural settlement and respect the principal position of farmers. It realizes 'shared resources, co-constructed environment' and exploits environmental advantages in the village domain. It can also improve the utilization efficiency of rural residential areas. Through the study of the demonstration village, the paper provides a scientific basis for formulating village space reconstruction and a new approach to the whole village advancement in a hilly area and the beautiful village construction. Due to the fact that the factors which influence rural residential restructuring are very complex, the regional social, economic, and environmental development strategies and resource endowment conditions which are expected to be considered comprehensively, need to be studied further. Different types of household willingness and future livelihoods also require deeper study.
    2021,37(16):127-135, DOI: 10.11975/j.issn.1002-6819.2021.16.016
    [Abstract] (1000) [HTML] (0) [PDF 22.64 M] (16995)
    Abstract:
    Abstract: Automatic fruit recognition is one of the most important steps in fruit picking robots. In this study, a novel fruit recognition was proposed using improved YOLOv3, in order to identify the fruit quickly and accurately for the picking robot in the complex environment of the orchard (different light, occlusion, adhesion, large field of view, bagging, whether the fruit was mature or not). The specific procedure was as follows. 1) 4000 Apple images were captured under the complex environment via the orchard shooting and Internet collection. After labeling with LabelImg software, 3200 images were randomly selected as training set, 400 as verification set, and 400 as a test set. Mosaic data enhancement was also embedded in the model to improve the input images for the better generalization ability and robustness of model. 2) The network model was also improved. First, the residual module in the DarkNet53 network was combined with the CSPNet to reduce the amount of network calculation, while maintaining the detection accuracy. Second, the SPP module was added to the detection network of the original YOLOv3 model, further to fuse the global and local characteristics of fruits, in order to enhance the recall rate of model to the minimal fruit target. Third, a soft NMS was used to replace the traditional for better recognition ability of model, particularly for the overlapping fruits. Forth, the joint loss function using Focal and CIoU Loss was used to optimize the model for higher accuracy of recognition. 3) The model was finally trained in the deep learning environment of a server, thereby analyzing the training process after the dataset production and network construction. Optimal weights and parameters were achieved, according to the loss curve and various performance indexes of verification set. The results showed that the best performance was achieved, when training to the 109th epoch, where the obtained weight in this round was taken as the final model weight, precision was 94.1%, recall was 90.6%, F1 was 92.3%, mean average precision was 96.1%. Then, the test set is used to test the optimal model. The experimental results show that the Mean Average Precision value reached 96.3%, which is higher than 92.5% of the original model; F1 value reached 91.8%, higher than 88.0% of the original model; The average detection speed of video stream under GPU is 27.8 frame/s, which is higher than 22.2 frame/s of the original model. Furthermore, it was found that the best comprehensive performance was achieved to verify the effectiveness of the improvement compared with four advanced detection of Faster RCNN, RetinaNet, YOLOv5 and CenterNet. A comparison experiment was conducted under different fruit numbers and various lighting environments, further to verify the effectiveness and feasibility of the improved model. Correspondingly, the detection performance of model was significantly better for small target apples and severely occluded overlapping apples, compared with the improved YOLOv3 model, indicating the high effectiveness. In addition, the target detection using deep learning was robust to illumination, where the illumination change presented little impact on the detection performance. Consequently, the excellent detection, robustness and real-time performance can widely be expected to serve as an important support for accurate fruit recognition in complex environment.
    2018,34(19):266-275, DOI: 10.11975/j.issn.1002-6819.2018.19.034
    [Abstract] (1345) [HTML] (0) [PDF 3.39 M] (16921)
    Abstract:
    Abstract: Human activities within the Nature Reserves are considered a threat to the endangered species. This study takes the land cover/land use as the representative of human activities within the Nabanhe National Nature Reserve. As optical remote sensing images are frequently contaminated by cloud and frog, which will restrict its practicality in monitoring human activities in Nabanhe National Nature Reserve, this study aimed to fuse the multi-resources of optical remote sensing images to build a high spatio-temporal resolution data (30 m daily surface reflectance) for the year 2000, 2004, 2010 and 2015 using the ESTARFM (Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model). The fused data was assessed during the data fusing procedure, and in a correlation of greater than 0.8 (with P<0.01) with the reference image for each period of time. The fused data was then used to generate the time-series NDVI (Normalized Difference Vegetation Index), which would be used to differentiate each of the 5 land covers (namely natural forest, rubber trees, water, farmland and built-up area) to be classified. Previous to the extraction of the time-series features, denoising of the time-series NDVI was conducted using the double S-G (Savitzky-Golay) filter. 6 features were generated using the denoised NDVI time-series data, and used to classify the 5 land covers above. The Random Forest classifier was used during the classification, and the RF classifier was trained using the reference samples that were selected from high spatial resolution Google Earth images. The overall accuracies of the final classification results were greater than 86.88%, with Kappa values greater than 0.817?6 (the overall classification accuracies for the year 2000, 2004, 2010 and 2015 were 88.13%, 86.88%, 89.38% and 90.63% respectively, and the corresponding Kappa values were 0.834?0, 0.817?6, 0.853?3 and 0.871?1, respectively). This accuracy guaranteed the availability of the classification results in monitoring human activities in Nabanhe National Nature Reserve. The land cover/land use changing trend was analyzed based on the classification results for each period of time, of which the results were as follows: from 2000 to 2004, water area increased mainly due to the conversion of farmland and built-up area, which occupied 0.06% and 0.01% respectively of the entire area of the Nabanhe National Nature Reserve. Farmland area increased, and the increased area was mainly from natural forest and rubber trees. Built-up area increased, and the increased area was from natural forest and farmland. The area of the increased rubber trees is the largest, and the increased rubber trees occupied natural forest and farmland. The only decreased land cover/land use was the natural forest during this period of time. From 2004 to 2010, water areas increased mainly due to the conversion of natural forest and rubber trees, because there was a hydropower station built during this period of time. Increased farmland area was mainly from forest, while increased built-up area was mainly from farmland. Rubber area was increasing due to the conversion of forest, the area of which was decreasing constantly during this period of time. From 2010 to 2015, increased water occupied farmland and the forest was changed to farmland with the largest area (96.47% of all land converted to farmland was forest). Expanded built-up area was from rubber farmland (occupied 76.92% of all land changed to built-up). It was during this time that the farmland changed the most, it was 5.29% of the area of the Nabanhe National Nature Reserve. Obvious land use changing trend corresponding to terrain was found from 2000 to 2015. Built-up distribution changed less, but the corresponding area increased. The rubber was distributed in areas with slopes ranging from 0 to 36 degrees, and it was first expanded from 0 to 12 degrees, and then to 24 degrees and now is distributed to near 36 degrees. The expansion of rubber is pushing the rubber planting to the limit in the Nabanhe National Nature Reserve. Same changing trend was found to the farmland from 2000 to 2015. Both of these land covers are expanding to steeper terrain and larger areas in the Nabanhe National Nature Reserve. The method provided by this study may support the governmental departments in monitoring human activities within Nature Reserves.
    2021,37(1):223-232, DOI: 10.11975/j.issn.1002-6819.2021.01.027
    [Abstract] (1771) [HTML] (0) [PDF 6.54 M] (15157)
    Abstract:
    An improved Convolutional Neural Network (CNN) was proposed to solve the time-consuming and inefficient detection for the surface defect on the Hami melon in recent years. The Hami melons were purchased from 103 Regiment, 6th Agricultural Division, the Xinjiang Production and Construction Corps, China. A total of 200 images of normal Hami melons were taken by a camera in a black box. 100 images of Hami melons were collected with the various surface defects, such as mildew, sunburn and crack. Since it is difficult to collect samples with three defect types, the data enhancement technique was used to expand the dataset. A total of 10 000 sample images were obtained, and then divided into a training and test dataset, according to the proportion of 4:1. A VGG-like model was improved by adding a convolutional layer and a pooling layer at the beginning. As such, the improved VGG-like model included three convolutional layers, three max-pooling layers, a flatten layer, and two fully-connected layers. The softmax classifier was used in the last fully-connected layer. The Rectified Linear Unit (ReLU) function was chosen as the activation function. The Stochastic Gradient Descent (SGD) was chosen as the optimizer. The improved VGG-like model was used to identify four-class defect samples. The optimal hyperparameters in the CNN models were determined via the performance under the different learning rates and epochs. In all established CNN models, the test data showed that the AlexNet model outperformed other VGG-16 models, with the learning rate of 0.001 and the epochs of 500. Moreover, the AlexNet model can achieve the best performance with the accuracy of 99.69% and 96.62% in the training and test dataset, respectively. Three image processing techniques were compared to evaluate the preprocessing impact, including the Principal Components Analysis (PCA), Singular Value Decomposition (SVD), and binarization. The results indicated that the preprocessing provided a better detection performance on the various surface features of Hami melon in image preprocessing. The improved VGG-like model was the optimal to detect four-class defect on the Hami melon surface, indicating the learning rate of 0.001 and the epochs of 500. The prediction accuracy of improved VGG-like model in test set reached 97.14%. A visualization technique was used to analyze the features of convolutional layers, particularly on feature extraction in a CNN model. The visualization results showed that the defect features became more and more obvious with the increase of the convolutional layers. The defect features were the clearest in the captured images by the last convolutional layer. In addition, the convolutional features with the input as the preprocessing images were clearer than before. Finally, the improved VGG-like model was verified by the developed software on the plateform of PyQt5. The developed software functions included Open Camera, Read Image, Image Processing (Gray, PCA, SVD and Binarization), and Image Identification. The detection time of a single image was less than 0.7 s. In each type, 50 images were captured under the same environment. A total of 200 test images were collected. The test results showed that none of normal samples was predicted as defect samples. Only 8 crack Hami melons was incorrectly identified, due mainly to the unobvious feature. The average prediction accuracy of 200 samples was 93.5%. The improved VGG-like model with the preprocessing can be expected to apply for the detection of defects on the Hami melon surface, and other on-line nondestructive detection in the future.
    2013,29(23):268-275, DOI: 10.3969/j.issn.1002-6819.2013.23.037
    [Abstract] (1683) [HTML] (0) [PDF 1.94 M] (14274)
    Abstract:
    Abstract: Clarity of juice is an important factor regarding the quality of the juice as it fetches consumer attention for the product in the market. Clarification is a key step in the processing of fruit juice and is most often achieved through micro filtration, enzymatic treatment, or by using common clarifying aids like chitosan, gelatin, bentonite, silica sol, polyvinyl pyrrolidine, or a combination of these compounds. Chitosan (poly-b(1-4)N-acetyl-glucosamine) being poly-cationic in nature, nontoxic, and biodegradable, has been found to be an effective coagulating agent in aiding the removing pectin and other carbohydrates which are present in the juice. The clarification of ponkan juice by means of chitosan was studied in this paper. In order to obtain the optimal reaction conditions of clarification of ponkan juice by commercially inexpensive chitosan, the process conditions of clarification with chitosan on ponkan juice were optimized by a Box-Behnken center-united experiment design. Taking juice clarification as a dependent variable, the models were obtained by using a response surface analysis of the three factors of chitosan concentration, chitosan treated temperature, and the chitosan treated time based on a single factor experiments. The results indicated that the interaction effect of chitosan concentration and chitosan treated temperature, chitosan concentration, and chitosan treated time on the juice clarification achieved a very significant level. The influencing factors had a complicated relationship with each other. Among these factors, chitosan treated time、chitosan concentration, and the chitosan treated temperature ranked in order. The results from the Box-Behnken center-united experiment showed that the optimum technological condition for clarification of ponkan juice was adding 0.8 g/L chitosan at 59°C for 71 min and its clarification of the ponkan juice was up to 97.8%. The experiment indicated that there was a good fit between the predicted and the experimental values. The mathematical model was also very accurate. Comparing with the original ponkan juice, the contents of soluble solids, vitamin C, and titratable acidity were almost the same after clarification. Removing the pectin, total phenolics, and proteins improved the non-biological stability of the ponkan juice, because of the phenomenon of flocculating with chitosan. According to the non-biological stability tests, the results of stability tests of protein, potassium hydrogen tartaric acid, iron, copper, and oxidation showed negative, and indicated that the non-biological stability of ponkan juice were strengthened by chitosan to a certain extent.This article could provide a theoretical basis for clarifying ponkan juice in manufacture. According to the optimal technological condition of the experiment, clarification of 1 L juice only costs 0.15 yuan. The popularization and application of this technology will bring great economic benefits for the industrial production of juice.
    2021,37(1):213-222, DOI: 10.11975/j.issn.1002-6819.2021.01.026
    [Abstract] (1594) [HTML] (0) [PDF 4.66 M] (13144)
    Abstract:
    Ginger is widely cultivated in temperate zone, tropical and subtropics. China is the largest ginger producer and exporter in the world. Sowing seeds can be the second step in the ginger production, after the soil preparation is ready. It is necessary to lay the ginger flat in the trench, and keep the shoots in the same direction when sowing, in order to ensure that the shoots can emerge in the same direction under the requirement of avoiding light in the production. All the shoots emerge towards the south in an east-west trench, whereas those towards the west in a north-south trench. Therefore, shoots recognition has become a type of key technology to ensure the same direction of shoots, and then realize automatic and accurate sowing. In this study, a feasible way was proposed to realize the rapid recognition and accurate determination of ginger shoots using deep learning. Firstly, the dataset of ginger images was established, including image acquisition, enhancement, and labeling. Secondly, in training a small sample dataset, the data was augmented using online data enhancement to increase the diversity of images, and address the lack of generalization capability. The Mosaic method was used to enrich the background of ginger shoots training without introducing non-informative pixels. Thirdly, the position of ginger shoots regression bounding box directly determined the specific position of shoots, thus DioU (Distance Intersection over Union) bounding box regression loss function was introduced instead of the traditional loss function of IOU, in order to improve the regression effect of regression bounding box. Fourthly, in order to improve the convergence rate of model, the K-means clustering using the IoU measurement was used to derive 9 anchor boxes after linear scaling, indicating more in line with the shoots size. In addition, the Darknet-53 model pre-trained on the ImageNet data set was used for transfer learning, aiming to reduce the training time of model. Finally, after the identification of shoots were completed using the YOLO v3 network, in order to facilitate the selection of the strongest shoot, the area of the prediction bounding box was used as the basis for selection, and only the prediction bounding box with a larger area was retained. A Cartesian coordinate system was established with the center of the image as the origin, and the orientation of shoots was discriminated by calculating the azimuth of the center of prediction bounding box. The average precision and F1 were used to evaluate the performance of ginger shoots recognition model. In test, the IoU threshold and the confidence threshold were analyzed to obtain the best detection effect, while the improved strategies were verified one by one. After training and testing, the detection index was the best, when the IoU threshold was 0.6, and the confidence threshold was 0.001. The average precision and F1 measure reached 98.2% and 94.9% in the shoot recognition model, respectively, where the detection speed was 112 frames/s for a single 416×416 pixels image on the GPU. Compared with the original YOLOv3, the average precision and F1 measure increased by 1.5% and 4.4%, respectively. The recognition model of ginger shoots can be used to achieve significantly excellent recognition, providing a sound theoretical basis to realize automatic and precise ginger sowing.
    2019,35(23):135-141, DOI: 10.11975/j.issn.1002-6819.2019.23.017
    [Abstract] (892) [HTML] (0) [PDF 1.77 M] (12464)
    Abstract:
    The Loess Plateau in China is one of the most severely eroded regions of the world. Since the implementation of "Grain for Green" ecological restoration project, biological soil crusts (biocrusts) were widely distributed in this region, which significantly affected surface runoff. Numerous studies have explored the effect of biocrusts on runoff. However, the conclusions were still widely different. In the Loess Plateau region, rainfall is mostly concentrated in June to September, and the rainfall duration is not fixed, which may affect the runoff characteristics of biocrustal slopes. This study investigated characteristics of runoff from biocrustal slope in different rainfall durations in the Loess Plateau region by using artificial simulated rainfall experiment. The experiment was conducted in the revegetated grassland of northern Shaanxi Provence, China. The experiment site was about 80 m×20 m, and the slope gradient was approximately 15°. The biocrust types were mainly moss crust and moss cyanobacteria mixed crust in this site and their average coverage was 79.2%. The dimensions of the experimental plots were 10 m×2.1 m (length×width).Canopy of higher plants in the plots was removed with scissors. According to the range of local biocrust coverage, two treatments were set: 1) slopes with undisturbed biocrust as a high coverage biocrust (the average biocrust coverage were 79.2%); 2) the slopes with removal of a part of the biocrusts by shovels, which simulated the low biocrust cover situation (the average biocrust coverage were 43.6%). Meanwhile, ploughing plots were set as the control group. The rainfall intensity was set as 90mm/h and the duration was1 hour. The results showed that the initial runoff time of biocrust slope was significantly reduced compared to the bare soil slope. The initial runoff yield time of bare soil was 1.59-3.04 times that of the biocrust slopes. There was a significant negative correlation between biocrust coverage and initial runoff generation time; Conclusion of the influence of biocrusts on runoff yield was contradictory during the first 15 min and 60 min. For 90 mm/h rainfall intensity, runoff from biocrust slope increased by 75.42% compared to bare soil when the rainfall duration was the 15 min. While, runoff from biocrust slope was decreased by 52.42% compared to the bare soil when the rainfall lasted to 60 min; the infiltration rate of soil moisture was affected by biocrusts. The infiltration rate of bare soil slope with 60 min rainfall was 34.30% lower than that with 15 min. The infiltration rate of high coverage biocrust slope with 60 min rainfall was only 6.38% lower than that with 15 min, which may cause the difference of runoff yield between bare soil slope and biocrust slope; the effect of biocrust on slope infiltration and runoff is closely related to rainfall duration. Different periods of rainfall are likely to lead to inconsistent conclusions. Therefore, the duration of rainfall experiment considering the factors of biocrust should be no less than 45 min. The study provides scientific evidences for explaining the differences in the effect of biocrusts on infiltration and runoff, and further clarifies the hydrological effect of biocrusts in arid and semi-arid areas.
    2016,32(17):127-135, DOI: 10.11975/j.issn.1002-6819.2016.17.018
    [Abstract] (3620) [HTML] (0) [PDF 15.27 M] (12321)
    Abstract:
    Abstract: Remote sensing technology is a major method to obtain spatial distribution and quantity of winter wheat area, and classification method suitable for business operation is a key technology target of annual winter wheat remote sensing monitoring. Aimed at the conditions and demands of winter wheat background survey business operation in agriculture information service, this paper has proposed a weighted NDVI index (WWAI) based on normal difference vegetation index (NDVI) time sequence. By taking the extraction of 2013-2014 winter wheat area of Anping County, Hebei Province as an example, the algorithm is realized by using GF-1/WFV (wide field view) data. The main idea of the algorithm is to amplify the difference between winter wheat land type and other ground object types by establishing a winter wheat area index based on time sequence images, and to differentiate winter wheat land type from the others and thus to obtain the crop area of winter wheat by automated threshold value setting method. The algorithm includes the following 5 parts: acquisition of winter wheat time sequence images, sample points setting based on grid, establishment of winter wheat area index, identifying winter wheat area index estimation threshold value by iteration, and accuracy validation. Acquisition of images is based on the identification of growth time of winter wheat, and the principle is to ensure to get one GF-1/WFV cloudless image each month. Growth period of winter wheat in Anping County is from October 1st to June 30th of the next year, including 9 growing stages, i.e. seeding, germinating, tillering, overwintering, reviving, jointing, head sprouting, milking maturity and maturity. One GF-1/WFV cloudless image is selected in the middle 10 days of each month, and a total of 9 images are selected for pre-processing and NDVI calculation. Meanwhile, the study area is divided into a certain number of grids, and each grid is further divided into 2×2 sub-grids. The ground object types of central points in upper left and lower right grid are identified by visual interpretation, expert knowledge and field investigation. In this paper, a total of 10×10 equal interval grids with the average grid size of 4.1 km × 4.0 km, as well as 400 sub-grids with the size of 2.05 km × 2.0 km are obtained. The average NDVI values of winter wheat and other ground objects on all upper left centers of this period are calculated. If the winter wheat NDVI is higher than that of other ground objects, the weight of the images of the period is set to 1, and otherwise, set to -1. The winter wheat area index images can be obtained by using the weighted average of NDVI images of all time phases. After obtaining winter wheat area index, it is also necessary to set appropriate threshold value for winter wheat area extraction. The paper takes the visual interpretation classification results of lower right grid points as the basis for threshold value extraction. The specific method is to divide winter wheat area index from small to large with certain intervals, and then to make dimidiate extraction of winter wheat area indices of the lower right centers by taking each divided value as the extraction threshold value. By comparing with the visual interpretation result, the result with the highest accuracy is taken as the optimal winter wheat area index extraction threshold value, which is identified to be approximately 1 600 with self-adaptation approach finally. In all grids, accuracy validation is conducted by taking the 10 plots with equal probability. Accuracy validation results show that the overall classification accuracy has reached 94.4%, with Kappa coefficient of 0.88. The area extraction accuracy of this method is about 1.7% higher than that of conventional method based on NDVI time sequence images. By establishing winter wheat area index, this paper turns a complicated multiple-parameter problem into a single-parameter problem with clearly defined agricultural significance. This method is featured with high automatic degree and stable classification results, and it has been widely applied in the crop area remote sensing monitoring practices in China.
    2020,36(23):171-180, DOI: 10.11975/j.issn.1002-6819.2020.23.020
    [Abstract] (882) [HTML] (0) [PDF 3.89 M] (11926)
    Abstract:
    Aiming at the problems of low efficiency of manual grading and inaccurate mechanical grading of peanut pods, a convolutional neural network peanut pod grades image recognition method based on transfer learning was proposed. By using the operations of the flip, rotation, translation, contrast transformation, and brightness transformation, the obtained five grades (first-grade pod, second-grade pod, third-grade pod, fourth-grade abnormal pod, and fifth-grade damaged pod) of peanut pod images were expanded and preprocessed, thus the peanut pod grades image data set was established. The 60% of data was randomly selected as the training set, 20% of data was randomly selected as the validation set, and the remaining 20% as the test set. The performance of peanut pod image classification based on the GoogLeNet, ResNet18, and AlexNet was compared and analyzed. The peanut pod grades recognition model was improved by transferring the AlexNet convolution layers. The local response normalization was replaced by batch normalization, and the activation function was placed in different positions before and after the batch normalization layer, so that four different recognition-training models were designed, including the PA-I model, PA-II model, PA-III model, and PA-IV model. The transfer learning contrast experiments and the hyperparameter optimization experiments of the learning rate carried out for the four improved AlexNet models proposed above. The effects of the unsaturated activation function (ReLU) and improved unsaturated activation function (LReLU) on the performance of the model were studied. The experimental results showed that the training time of the AlexNet model was the least on the basis of satisfying the test accuracy and the learning rate of transfer learning based on the improved AlexNet model was a very important hyperparameter that needed to be optimized. If the learning rate is chosen too high, the model training oscillates seriously and even can’t train normally; if the learning rate too small, the model training slow. An appropriate learning rate can speed up the training and improve the recognition ability of the model. When the learning rate was updated automatically, the model with batch normalization had better performance than local response normalization, which could make the model get higher accuracy and lower loss value. When the coefficient of activation function LReLU was 0.000 1, the performance of the LReLU used in the model was equivalent to that of the ReLU used in the model, therefore LReLU had no substantial impact on the training results of the model. The addition of batch normalization and reduction of parameters in the model reduced 220 s training time and improved the model’s performance. The classification accuracy of the proposed peanut pod grades recognition model for the first-grade pod, second-grade pod, third-grade pod, fourth-grade abnormal pod, and fifth-grade damaged pod was 93.57%, 97.14%, 99.29%, 87.14%, and 100% respectively and the average classification accuracy reached 95.43%, and F1-scores achieved 96.32%, 97.49%, 99.64%, 92.42%, and 94.50% respectively. The model proposed in this study had high classification accuracy for peanut pod grades and could provide a reference for the precise classification of other agricultural products.
    2015,31(z1):237-246, DOI: 10.3969/j.issn.1002-6819.2015.z1.028
    [Abstract] (3039) [HTML] (0) [PDF 10.15 M] (11412)
    Abstract:
    Abstract: The Internet of Things (IoT) technology, based on the perception, is developing rapidly and permeating into every walk of life. IoT of agriculture, including animal husbandry, has been showing a status of rapid development and is urgent in keeping pace with other industries. In this study, livestock coding specification and identification technology, remote monitoring technology of livestock farm environments and animal behaviors, and precise sow feeding equipment and digital network management platform of farms were reviewed to expound the application effects and limitations of IoT in animal husbandry. We found that at the perceptual layer, the international standards for livestock identification mainly included the ISO TC 23/SC 19, which set rules for radio frequency identification (RFID) for livestock management, and it was functionally divided into ISO 11784, ISO 11785 and ISO 14223. The Chinese standards for livestock identification were described in three levels: national standard specifications, local standards, and corporate standards. For example, the three different standards are Ministry of Agriculture Legislation No.67, local standard of identification in Shanghai (DB31/T341-2005), and Xinjiang (DB 65/ T3209-2011), and internal encoding specification of Beidahuang Agriculture Co., Ltd and Yiliyuan Co., Ltd. At the transport layer, the environment parameters of livestock farms like temperature, humidity, illumination intensity, ammonia concentration, and carbon dioxide concentration etc., and animal behavior parameters like body weight and body temperature would be perceived by different sensors and then the data from environment parameters and individual animal behavior data mentioned above would be remotely transferred through a wireless public network (2G/3G/4G). The video data and huge production process data were transferred into internet network databases by wired networks. At the data application layer, the typical application examples were shown below. Firstly, remote monitoring, data collection, and transmission of breeding environment parameters or animal production data were realized by using an intellectual mobile terminal to analyze and give early warning of the collected data. Then, the system will selectively turn on or off the remote intelligent environmental control equipment (draught fan, light, heater, and water pump etc.) based on the analysis results. The second example was the construction of a cloud-computing platform of cow-breeding farms and pig-breeding farms-that is, production data of hundreds or thousands farms were collected by network databases and data was cloud-stored as well as cloud-analyzed in the form of formal meta data, and the platform would give farmers warning information based on the analysis of production and breeding database by data mining technology. The third example was the development and application of automatic electro-mechanical feeding control systems of lactating sows, which was composed of electro-mechanical systems, wireless network technology, mobile SQL Lite network database, electronic data interchange, and feed intake prediction models of lactating sow nutrient requirements. This paper also analyzed the deficiencies of animal husbandry's IoT in technology, product, application, related policies, and people's cognitive from microcosmic to macrocosmic aspects, and suggestions were given based on the above deficiencies. Above all, the modernization development of animal husbandry needs the support of the IoT and IoT in turn is urged to accumulate its positive energy and promote itself better through applications in the different technological fields.
    2008,24(8):232-235, DOI:
    [Abstract] (9531) [HTML] (0) [PDF 0.00 Byte] (11262)
    Abstract:
    The adsorption-desorption characteristics of phosphate by five common substrates (savageness Zeolite, Haydite, Soil, Vermiculite and Gravel) used in soil treatment systems were illustrated in laboratory. The results indicate that phosphorus adsorption capacities of various substrates in the descending order are vermiculite and soil(1.38 mg/g and 1.24 mg/g), then haydite and zeolite(1.12 mg/g and 1.18 mg/g), and then gravel(0.90 mg/g). The five substrates all reach adsorption equilibrium after twelve hours’ shaking time, and the adsorption capacity increases as the original phosphorus concentration in the liquid increases. The results indicate that phosphorus desorption efficiencies of various substrates in the descending order are gravel, soil, zeolite, vermiculite and haydite. Considering the phosphorus adsorption capacities and desorption rates of five substrates in the research, vermiculite is one sound substrate in the soil treatment system for phosphorus removal.
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    2002,18(3):87-91, DOI:
    Abstract:
    Straw is an important biological resource in agriculture, and China is one of the most abundant countries for straw production in the world. This paper introduces the output and distribution of straw in China and discusses its utilization as the raw material in industry, livestock forage in animal husbandry, fertilizer and energy on farms and households in rural areas. This paper also indicates that great progress was made in integrated utilization based on a number of new technologies, marketing, and support from the Chinese government.
    1999,15(1):1-8, DOI:
    Abstract:
    This paper summarizes the research target of recent precision agriculture and its technical ideas and discusses the direction of technical innovations for the supporting technologies. Some proposals for the applied research in the country are presented. Recent research on precision agriculture in the world is still concentrated on precision farming for crop production. The translation of the phrase “precision agriculture” into Chinese shall be implicated in the Site Specific Crop Management. Following the rapid application of information technology to the agricultural sector, the ideas for precision management of agricultural resources and production would be expanded into all fields of agricultural system, such as precision facilities horticulture, precision raising, precision processing to keep high productivity, high efficiency, low cost and less environmental pollution as well as with high value added technology,etc. Then a real precision agriculture system will be established to support overall sustainable agriculture development based on the new information and biological technology revolution.
    1999,15(3):33-38, DOI:
    Abstract:
    Ninety eight observing points by a square of 10m×10m were made in a wheat field approximate 1 hm2. Soil samplers were obtained from each point under two layers of 0~20 cm and 80~100cm with different soil moisture and different time. Ammonia、NO3-N、Olsen-P in the soils of 0~20 cm and 80~100 cm, organic matter and total-N in surface soil (0~20 cm) were measured. The geostatistics theory was applied to analyze the data, the results indicated that both NH-N in bottom soil and organic matter in surface soil showed a normal distribution, others with a lognormal distribution. The rational sample number was determined within a given precision at a known confidence level. Semivariance analysis gave that those nutrients were correlated in a given spatial range. The Kriging method was applied to calculate the unobserved points and generate the contour map. Preliminary analysis was made for the spatial dynamic variability of those nutrients in different time. These results shows some merit in increasing nitrogen use efficient and precision agriculture.
    2003,19(3):1-4, DOI:
    Abstract:
    Conservation tillage (CT) has been shown as a wind and water erosion reduction technology from many years, research in developed countries. This program mainly evaluates the suitability of CT to China and what kinds of technology and machinery should be adopted. From 1991, China Agricultural University cooperated with Shanxi Agricultural Mechanization Bureau and so on, commenced systematic CT experiments combined agronomy and mechanization research together. It has been proved that the CT can not only reduce the wind and water erosion, but also increase the crop yield, after 10 years' experiment. Through improvement of CT operations and development of small size CT equipment, the conserration tillage technology with Chinese characteristics is basically formed, which can realize CT in small piece of land with small CT equipment, and can gain higher yield from poor soil. Therefore, it can meet the requirements of protecting environment and increasing farmers' incomes. The study shows that, due to different natural conditions, cropping systems and economical levels, different CT technological systems should be adopted in different regions.
    2002,18(1):1-5, DOI:
    Abstract:
    This paper presents the elementary concept and the developing history of land consolidation and stresses the significance of vigorously promoting land consolidation in China. Meanwhile, it outlines the overall strategy of land consolidation in China and clarifies the primary principles in the course of land consolidation. Some serious issues and problems faced in the current operation of land consolidation in China, which need to be solved in priority, are also stressed in this paper.
    2003,19(2):210-213, DOI:
    Abstract:
    Analysis on land consolidation benefits is an important part of the study on the land consolidation theory and practice. It can improve land consolidation theory and guide land consolidation practice to an analysis on its on economic, environment and social development. Though the aims and content of land consolidation are different in different countries, the practice showed that it could increase production and income, protect and improve the environment and provide farmers with fine living conditions. So the comprehensive benefits of land consolidation are the aggregation of economic, environmental, social and landscape benefits. The economic benefits of land consolidation are the effect of the practice upon the national economy and the farmers of land consolidation areas. The environmental benefits of land consolidation are the effect of the practice upon the structure and function of natural ecosystem and the environment. The social benefits of land consolidation are the effect of the practice upon the rural environment, and social economy, as well as the reasonable use of natural resources. The landscape benefits of land consolidation is the effect of the practice upon the rural landscape.
    2005,21(8):169-173, DOI:
    Abstract:
    The status quo of agricultural residues was analyzed. As pollutants have four characteristics of huge quantities, bad qualities, low price and excessive danger. As resources have four application practices, namely, biomass energy, fertilizer, feed and biomaterial. The analysis shows that the potential as fertilizer and energy is huge. However, there are some limited factors and technical bottleneck in the future. In combination with socioeconomic developmental objectives, the developing strategy and strategical emphases for the resources of agricultural residues were presented. The direction is to develop Eco-Agriculture and Cyc-Economy, which depend on the policy guidance, technical support and investment to promote agricultural residues used as resource in the future.
    2002,18(1):22-26, DOI:
    Abstract:
    Aquasorb is a kind of sodium polymer with characteristic of absorbing and storing water. There are many types and varieties in commercial market. The purpose of this study is to determine the chemical features of sodium polymer and its effect on soil improving, and to analyze the influence on crop yield and fertilizer use efficiency in farming field. The result showed that and electronic conductivity (EC) were increased but not so high when the concentration of sodium polymer was raised. pH value was almost not affected. Ions with two positive charges, such as [Ca2+] and [Mg2+] have a negative impact on drinking water characteristic of sodium polymer markedly, which is stronger than that of one positive or negative charge, such as Na+ and H2PO4-. It does not influence the drinking water of sodium polymer for different concentrations of urea. When soil is added with sodium polymer, the water holding capacity is raised, the aggregate of the soil is increased, this feature on sandy soil is more remarkable than that on clay soil, especially when there is 0.005% to 0.01% sodium polymer in soil. The test indicated that over 90% water holding by the sodium polymer can be used by plant. Based on the current results, it can be concluded that there are four aspects for action of sodium polymer, (1)conserving water by itself, (2)raising water holding by improving soil structure, (3)enhancing growth of plant and raising fertilizer use efficiency, (4)and reducing soil evaporation. The field test result showed that using sodium polymer by hole method at 15 kg/hm2, the yields of corn and potato were increased by 22% and 16%, and the ratios of investment to benefit were 1∶3.5 and 1∶4.2, respectively. When sodium polymer was mixed with urea or with urea and phosphorus fertilizer, the urea and phosphorus fertilizer use efficiencies were increased by 18.7% and 27.1%, respectively.
    2004,20(5):1-5, DOI:
    Abstract:
    Concepts and bounds of terms of biomass, biomass resources and biomass industry were defined in this paper. Developmental potential of biomass resources in China was analyzed. Aiming at the problems of agriculture, farmers and rural development at present and national requirement of energy and environment securities in the next 10 to 15 years, four developmental trends of biomass industry in China and the world, including biomass power, ethanol, biodiesel, biopolymers and dedicated energy crops and trees were discussed. A developmental pattern of bioenorgy of modern biomass industry with agriculture and forestry was briefly introduced. It is significant for development of biomass industry to settle the problem of farms and accelerate the agricultural industrilization and rural development.
    2009,25(12):211-217, DOI:
    Abstract:
    There are some problems such as statistics lacking, unsuitability of the ratio of main product output to that of by-product of the crops in the estimation of straw resources. The paper chooses the revised ratio of main product output to that of by-product of crops and estimates the quantity of straw resource comprehensively and systematically. The estimation results show that the total straw yield in China has a generally increasing trend with the improvement of agricultural comprehensive production capacity, and China is the biggest country in straw resources that its total output of straw resources in 2005 reached 841 831 200 t, which the straw of food crops was the main source. It has a great potential for rice husk, corncob, bagasse to develop new energy.
    2008,24(12):291-296, DOI:
    Abstract:
    According to document analysis and field survey, various evaluating indices of crop straw resource were used to finish the research and evaluation on main crop straw in China. The results showed that the theoretical resource amount of the 5 main crop straws was 433 million tons in China, including 176 million tons for the energy utilization. The resource could be distributed as ‘two-high and two-low’ that per capita amount of the resource was ‘high in north and low in south’ and per planting area of the resource was ‘high in east and low in west’. According to the resource distributing characteristics in each region. The whole country was divided into main developing area (Northeast, Meng-Xin and North region), proper developing area (Southwest, middle-lower Yangtze River and South region) and limited developing area (Loess Plateau and Qinghai-Tibet region). Different developing measures should be used in each region.
    2007,23(9):276-282, DOI:
    Abstract:
    Development trends of biomass energy in the future were analyzed on the basis of comprehensive evaluation of biomass energy resources, industry development and policy environment in China. Biomass resources are rich in China. Biomass energy industry begans to take shape: biogas industry was basically formed, fuel ethanol throughput reached 1.02 million tons per year, the technology that fuel ethanol was produced by use of non-food crops such as sweet sorghum stalks was developed and demonstration project of direct furl-fired generation with straw began to connect to power grid. Macro-policy environment to promote the development of biomass energy industry gradually formed. Therefore, the conclusions were concluded that development emphasis of biomass energy industry in the future in China would focus on biogas and biogas power generation, liquid fuels, biomass solid pellet fuel and biomass power generation; policies for the development of biomass energy industry would be further improved; the technology level would be further improved. There will be more large-scale enterprises to participate in this industry; it is sure that biomass energy industry will become a new growth point of Chinese national economy.
    1999,15(2):74-78, DOI:
    Abstract:
    Water retaining properties of water retaining BP agent manufactured in USA and its effect on soil and crops were studied. The results obtained were as follows: There were strong absorbretaining properties with BP,absorbing capacity in distilled water is 38.7 mL/g, there was a large change of imbibition in the range of 0~0.1 % solution concentration, the imbibition of 0.1 % solution concentration is 63 % in distilled water, the amount of available water absorbed is over 2/3; soil water physical characterictics were improved and water retention power increases as BP is added to soil; in the range of 0.01~1.5 MPa soil water potential, there were obvious increases in sand soil and heavy loam soil compared with that of light loam and middle loam soil; when BP is added to soil saturated hydraulic conductivity will decrease, soil evaporation properties have no obvious change, especially in sand soil; sand soil wheat pot experiment with BP added to soil showed that there were obvious increases in the weight of wheat root, root length and ratio of root and shoot, the nutrition condition of root system was better, and the wheat growth was improved.
    2004,20(1):13-15, DOI:
    Abstract:
    China has already joined the WTO. Standardization of agricultural production is necessary, but the draggling plant protection machinery and its application techniques are not assorted with this situation, the problems are such as low efficiently using, residue of pest, contaminated environment, toxics, etc.. Plant protection machinery is very different with the other agricultural machinery, its quality and application techniques level affect safety of products. In last 1970s, the plant protection machinery was lined in special type gricultural machinery in developed countries, they had special institution and management. After joining the WTO, the plant protection machinery must be tested according to CCC-Standards in China, but until now there is no best way to improve its draggling actuality. The existing problems of machinery and its application techniques were discussed, and the methods to solve those problems were presented.
    2006,22(11):269-272, DOI:
    Abstract:
    Increasing temperature and keeping soil moisture effect of mulching plastic film have brought a positive and important progress in agricultural productivity, and also the residue of mulching plastic film in the field has already become a negative factor that affected agricultural environment, which destroyed soil structure and harmed growth of crop. Based on results of domestic study on this issue, the authors comprehensively analyzed the application situation of mulching plastic film in agriculture, and the distribution characteristics as well as the influencing factors, the harm ways of the residue of mulching plastic film. According to the actual situation, the techniques of preventing and controlling measures for residue pollution of mulching plastic film were put forward.
    2002,18(4):155-158, DOI:
    Abstract:
    A novel method for measuring individual leaf area of vegetables was developed using digital image processing techniques and scanner. Meanwhile, the measured data from digital image analysis was compared with the values from grid-counting method, leaf-copy and weighing method, instrumental scanning method, etc. The results show that there are close relationships between digital image processing method and the other traditional methods. Relative low variation in measured data was the dominant advantage of image processing method. It can be concluded that digital image analysis technique is suitable to measure leaf area of vegetable in combination with “Maximum length×width”ruler method through correlation and the calibration coefficients for rape (Brassica napus L) and water spinach (Ipomoea aquatica Forsk) were 0.792 and 0.818, respectively.
    2003,19(2):39-44, DOI:
    Abstract:
    With the help of GPS and GIS, spatial variability of soil property was measured and analyzed by using statistics and geo-statistics, which was tested in a 13.3 hm2 field of winter wheat. Sixty three sampling points were collected on a 50 m grid in soil surface (0~20 cm) of the field, and the points were oriented by GPS receipt machine. The soil property included total N, available N, organic matter, available P, available K, bulk density, the moisture content and electrical conductivity, which were studied using spatial distribution maps and semi-variograms that can explicitly express the random and structural of soil property. The research result showed that all soil spatial characters are normal distribution; bulk density exhibited weak spatial variability, and others exhibited moderate spatial variability; the soil organic matter, total-N, available N, available K and electricity conductivity have exhibited strong spatial correlation, and soil bulk density, available P and the moisture content have exhibited moderate spatial variability, and the range of soil properties correlation distance was 246.8~426.8 m. All these results can serve as a basis for precision fertilization, precision irrigation and precision management in farm.
    2002,18(1):165-168, DOI:
    Abstract:
    The research development of recent agricultural land evaluation in China was reviewed. The two method systems, ideological bases and practical significance raised respectively in newly formulated National Rules of Classification and Gradation of Agricultural Land and Rules of Soil Fertility Gradation of Cultivated Land were analyzed and compared. The classification and gradation evaluation of agricultural land developed from such low level researches on natural soil condition investigation for estimating yield, soil nature and basic soil fertility, etc. to management and evaluation of resource value integrated with land and human being. The existing two evaluation methods of agricultural land in China are the gradation system of soil fertility of cultivated land formulated by Minstry of Agriculture and the classification and gradation evaluation system of agriculturall and drafted by Ministry of Land and Resources. There exist differences between the two systems in analyses of evaluation indexes, objective levels of achievement application and links of front and back operation. Currently, the classification and gradation evaluation of agricultural land have been implemented across China, whose method system perfection is of great practical significance.
    2002,18(2):49-52, DOI:
    Abstract:
    Study was carried out on Fluvo aquic soil of low fertility coming from Huanghe River plain for 14 years. The results show that the long term returning straw to soil changes soil properties. Soil organic matter, soil porosity, availible N,Zn,Fe,Mn and enzyme are all positively related to the amount of straw applied remarkably, while soil specific weight is negatively correlative. These indexes are affected by climate, plant growth seasons and soil texture, etc. The result of combination use of straw and fertilizer is better.
    2000,16(5):26-30, DOI:
    Abstract:
    Crop coefficient is the basic parameter for determining crop water requirement. In this paper, two methods proposed by FAO are described. One is time averaged crop coefficient(Kc) approach, which is a simple and useful method. The other is dual crop coefficient approach with more complicated computations but more accurate results. Both approaches were validated with experimental results at Xiongxian Experimental Station, Hebei Province. The results showed that the Kc values calculated by FAO methods are close to that as estimated from experiment data. Both methods are valid to use for determination of crop coefficients on the North China Plain if there are no on site experiment data available.
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