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    Volume 38,2022 Issue 6
    Abstract:
    Abstract: A large amount of traditional fertilizer has been applied for the low utilization rate, even for the soil pollution during the current wide row-spacing of crop planting in the arid area of Northwest China. In this study, a layered deep fertilizing was proposed for the cotton planting mode (where the values of narrow and wide row spacing were 10 and 66cm, respectively), and the corn planting mode (where the values of narrow and wide row spacing were 40 and 60 cm, respectively). A series of field tests were performed on the layered deep application of base fertilizer in the direction of crop seed row using Beidou navigation precise positioning. The layered fertilization of cotton adopted the mode of a narrow row, two rows of seeds corresponding to one row of fertilizer, whereas, the corn used the mode of one row of seeds corresponding to one row of fertilizer. As such, the layered deep and row fertilization modes were fully combined during this time. The fertilizer application ratio of the upper and lower layers was 4:6, whereas the fertilization depths of the first and second layers were 10-13 cm, and 18-21 cm, respectively. The fertilizer applicator was composed of depth limiting walking wheel, frame, profiling monomer, fertilizer box, trenching layered fertilizer shovel, soil covering, and pressing device. The profiling monomer was designed to analyze the motion and mechanical characteristics. The profiling spring was then determined, according to the requirements for the quality of the profiling monomer. A bionic trenching shovel was developed to select the angular protrusion of the head of the male dung beetle. The contour curve fitting equation was obtained to optimize the structure and working parameters in the machine. The performance of soil penetration, trenching resistance, and soil disturbance were also evaluated for the bionic shovel. A soil tank test was conducted to obtain the best front edge angle of 65°, the disturbance to the soil was significantly reduced, compared with the traditional. The test results show that the trenching resistance and disturbance to the soil of the bionic shovel were significantly less than those of the traditional one, indicating a better performance of drag reduction. The split fertilizer box and layered fertilization components were designed for the machine. The upper and lower discharge ports of fertilizer were connected with the different discharge wheels in the fertilizer box. A controlling system was adopted for the working length of the groove wheel, in order to real-time adjust the fertilizer discharge wheel corresponding to the left and right fertilizer boxes. The field experiment of the prototype showed that the average deviation of row accuracy was 2.7 cm during layered fertilization, and the average depths of shallow and deep fertilizer were 12.44 and 20.49 cm for the six groups of fertilization shovel, respectively, where the consistency coefficients of variation were 6.12% and 4.98%, respectively. The comparative experiment of fertilization patterns presented the higher growth of plants and the better root development. The fertilizer application was reduced by 25% than before, while, the yields of cotton and corn increased by 8.9%, and 8.6%, respectively. Therefore, the deep fertilization of rows can be widely expected to achieve better performance in weight loss and efficiency.
    2022,38(6):12-21, DOI: 10.11975/j.issn.1002-6819.2022.06.002
    Abstract:
    Abstract: A corn precision seeder can determine crop performance during the whole process in Xinjiang of western China. In this study, a single driver of corn precision seeder was proposed to stabilize the planting quality under high-speed working conditions using fuzzy PID control. A functional circuit was built with the STM32F103C8T6 microcontroller as the core, according to the hardware composition and working principles of the motor-driven planting row control system. The operating speed of the planter was collected by a Hall-effect sensor, and the motor speed was fed back in real time by the high-precision photoelectric rotary encoder. A fuzzy PID with the gain adjustment was selected to make the speed control system modify the PID control parameters in real time, according to the speed deviation and deviation change rate. Therefore, the motor speed was quickly and precisely followed the operating speed. The speed control test showed that the motor presented excellent start-up characteristics with the pulse width modulation (PWM) frequency of 60 kHz. Specifically, the actual speed coefficient of variation for the motor was less than 6.29% at the motor speed of 307 to 10441 r/min, indicating higher stability and linearity. The motor speed test showed that the overshoot of the fuzzy PID speed regulation system was 0.4%, which was much lower than before, particularly when the target speed of the motor was set at 1500 r/min. The rising time and regulation time were shortened by 0.12 and 0.49 s, respectively, and the steady-state error was reduced by 0.3 percentage points. Furthermore, the accuracy and robustness of dynamic speed regulation were much higher in the fuzzy PID system than before, when the speed feedback period of the planting bed was T=1.0 s. The motor-driven planting bench test showed that there was a small difference in planting performance indexes between the two control system when the operating speed was 8 and 10 km/h. The planting qualification index of the fuzzy PID control was more than 93.04%, whereas, the reply- and miss-planting indexes were less than 5.13%, and 1.83%, respectively when the operating speed was 12 km/h. Furthermore, the average qualification index increased by 2.50 percentage points, whereas, the average replay- and miss-planting indexes decreased by 0.85 and 0.88 percentage points, respectively, compared with the traditional one. All planting performance indexes were better than before suitable for high-speed planting operations. The finding can provide a strong reference for the design of the corn high-speed precision planter.
    2022,38(6):22-33, DOI: 10.11975/j.issn.1002-6819.2022.06.003
    Abstract:
    Abstract: A seed-metering device has been widely applied with the combined positive and negative pressure in various agricultural machinery for medium and small-size seeding. However, the hole-type of seeding plate in the traditional device cannot match the seed size during filling, leading to the low carrying performance. It is a high demand for the high precision and efficiency of equipment for rapeseed seeding. In this study, a conical-hole seeding plate was proposed to increase the local population disturbance in the seed filling area, and reduce the transport resistance of the adsorbed seeds, further improving the operational performance of the precision metering device combined with the positive and negative pressure for the rapeseed in the medium-high speed sowing. The conical suction holes were also circularly distributed in the seeding plate, in order to increase the disturbance of the seed population in the seeding chamber, and the velocity of seed particles in the seed filling area near the holes. A comparison was also made on the seeding performance of the seed metering device with two types of seeding plate, such as the conical and cylindrical suction holes. The seed filling success and carrying stability were greatly improved using the seeding plate with conical suction holes, compared with the cylindrical holes, due to the low tangential resistance of the adsorbed seeds on the holes, when migrating along with the seeding plat. Discrete element simulation and quantitative analysis were implemented to compare the seeding plate with conical suction holes and cylindrical holes under the same number of holes. It was found that the average velocity of seed populations in the seeding chamber increased by 66.72% with the conical holes. Meanwhile, the velocities of seed particles in the seed filling area along the tangential, axial, and radial directions increased by 90.45%, 83.90%, and 165.60%, respectively. Specifically, the tangential resistance in the seed motion decreased by 35.60%, when the seeds were adsorbed on the holes. The bench test showed that the seed metering device with the conical-hole seeding plate greatly promoted the qualified index by 5.49%, but reduced the multiple and missing index by 68.62% and 3.79%, respectively, when the work negative pressure of the air chamber in the range of 800~4 800 Pa, and the rotating speed of seeding plate within 10~50 r/min. More importantly, the qualified, multiple and missing index reached 98.13%, 1.25%, and 0.62%, with the conical-hole seeding plate, under the working conditions of positive pressure in 200 Pa, negative pressure in 2 100 kPa, and the rotating speed of seeding plate in 25 r/min. Consequently, the conical-hole plate effectively improved the seeding performance of the precision seed-metering device without wedge churning and filling, where the holding performance of single seeding was enhanced to reduce the multiple and missing index. The conical-hole plate presented a much greater effective depth and area of seed contact than those of the cylindrical holes plate. The movement of the seed particles was facilitated to effectively implement the single seeds and holding, further to accurately take the single seed from the population and disturb the population. The findings can provide a strong reference for the structural optimization of the combined positive and negative pressure precision seed-metering device for the medium and small-size seeds and medium-high speed sowing.
    2022,38(6):34-43, DOI: 10.11975/j.issn.1002-6819.2022.06.004
    Abstract:
    Abstract: This study aims to realize the real-time planning of obstacle avoidance paths for the agricultural machinery in the field operation using Bezier curve in the dynamic recognition area. The dynamic identification area of the agricultural machinery unit was firstly constructed for the operation walking, according to the tractor length and operation width, where the radar coordinate system (X-O'-Y) was established using the installation position of LiDAR. The obstacles were then identified in the dynamic identification area. The specific steps were as follows: 1) LiDAR was used to collect the point cloud data of the obstacle in the dynamic recognition area; 2) The point cloud information was processed into the three-dimension; 3) The obstacle was used to fit the obstacle envelope cylinder, then to project into the X-O'-Y coordinate system for the envelope circle (the center and radius). Then, the conversion model was established for the coordinate system, according to the installation position of Beidou Positioning Equipment and LiDAR, in order to realize the mutual conversion of longitude and latitude coordinates under the world standard longitude and latitude coordinate system (lon-o-lat coordinate system) and rectangular coordinates under X-O'-Y coordinates. According to the position of the obstacle in the X-O'-Y coordinate system, the obstacle avoidance path was divided into the execution and regression paths. When the ordinate of the circle center of the obstacle envelope contour circle was less than 1/3 of the length of the dynamic recognition area, the obstacle avoidance regression path was planned, otherwise, the obstacle avoidance execution path was planned. Finally, the obstacle avoidance path was planned as follows. 1) The coordinate system conversion model and Beidou positioning equipment were used to convert the collected current position of agricultural machinery from the longitude and latitude coordinates in lon-o-lat coordinate system to rectangular coordinates in X-O'-Y coordinate system; 2) The selection range of obstacle avoidance path control points using the third-order Bessel curve was calculated using the current position, heading angle, center coordinates and radius of obstacle envelope circle of agricultural machinery. The path cluster satisfied the minimum turning radius. 3) Taking the minimum curvature as the goal, the optimal obstacle avoidance path was selected from the path cluster for the coordinate transformation during tractor operation. The dynamic recognition area was reconstructed to repeat the above steps for the obstacle avoidance path. A real-time planning experiment on the obstacle avoidance path was carried out to verify the planning. The experimental results show that the maximum and average curvature of the obstacle avoidance path were 0.126 and 0.054 m-1, respectively, which were reduced by 25.9% and 42.6% than before, respectively. The maximum and average lateral error in the process of path tracking were 0.12 and 0.057 m, respectively, which were reduced by 36.8% and 28.8% than before, respectively. The distance from the tractor to the outer contour of the obstacle was greater than 0.375 m. Therefore, the obstacle avoidance path fully met the minimum turning radius, where the agricultural machinery can safely, effectively, and quickly avoid the static obstacles. The finding can provide technical support for the tractor unmanned operation.
    2022,38(6):44-51, DOI: 10.11975/j.issn.1002-6819.2022.06.005
    Abstract:
    Abstract: Weed control has been the agricultural component of pest control, in order to reduce the presence of weeds on a farm. Weeds generally compete with the crops for the nutrients and water, leading to a parasitic environment for the pests and diseases, thus directly detrimental to the crop yield and quality. Herbicide application and mechanical weeding are two current means of weed control in China. However, the mechanical weeding cannot completely break the agglomeration of weed roots in the soil, whereas, the herbicides cannot evenly and fully be deposited on weeds, due to the limitations of the field environment and machine operation capacity. It is a high demand for the higher performance of weed control with less environmental pollution, according to the current national standard of "chemicals reduction and efficiency enhancement" and "weed control environment-friendly". One individual improvement in weeding machinery or chemicals cannot balance the harsh requirement of weed control in modern agriculture. Taking the maize field as the research object, the mechanical-chemical synergistic weeding strategy was proposed to determine the efficacy of weeding control during the growth period. A synergistic weeding experiment was also carried out using two mechanical weeding approaches (inter- and intra-row weeding), three chemical reduction ratios (25%, 50%, and 75%), and two chemical applications (full width and only rows). Some parameters were measured, including the conventional weeding index, such as the control efficacy, and the growth indexes of maize at the silking and mature period. The results showed that the improved mechanical weeding significantly reduced the soil compactness of the weeding area by more than 64.4% than before, indicating the loose soil in the maize field. The control efficiency of the weed plant was 83.4% under the inter-row weeding machinery after two-week treatment, which was better than that under the intra-row weeding machinery (46.7%). The weed status in the silking period of maize showed that the efficacy of the inter-row weeding with the herbicide reduction was better than that of the intra-row weeding with herbicide reduction, while, the weeding efficacy of mechanical-chemical synergistic treatment was better than that of single mechanical weeding. The leaf area and dry matter weight of maize under the mechanical-chemical synergistic weeding treatment were greater than those under the single mechanical or chemical weeding treatment. It infers that the mechanical-chemical synergistic treatment was conducive to the accumulation of plant nutrients for the better promotion of crop growth. Furthermore, the average yields of intra-row mechanical-chemical synergistic weeding treatment were 55.9% and 5.1% higher than those of single mechanical and chemical ones, respectively, while, those of inter-row one were only 29.0% and 20.4% higher. The best yield of maize was achieved under the synergistic treatment of mechanical weeding and herbicide application reduction of 25%, where the 1 000 grain weight and yield were higher than the rest. In the inter-row mechanical weeding, the 1 000 grain weight and yield were the highest under the full-width application of 75% herbicide amount and mechanical-chemical synergistic treatment. In the intra-row mechanical weeding, the grain number per ear, 1000 grain weight and yield were the highest under only the row application of 75% herbicide amount and mechanical-chemical synergistic treatment. Therefore, the mechanical weeding synergized with the chemical reduction strategy can be widely expected to reduce the number of chemical herbicides without the loss of weeding efficacy for the high yield of maize. This finding can provide a new approach for herbicide reduction and weed control in an environmentally friendly way in the maize field.
    2022,38(6):52-60, DOI: 10.11975/j.issn.1002-6819.2022.06.006
    Abstract:
    Abstract: Tubular turbines have been widely used to develop low-head hydraulic resources and tidal energy, due to their compact structure, straight flow channels, large flow capacity, and high hydraulic efficiency. However, the hydraulic vibration, fatigue damage and cracks of overflow components inevitably occur in actual operation, particularly for the low number of runner blades, the large blade area, and simple structural support. Previous studies are focused mainly on the hydraulic design and performance evaluation of tubular turbines for the prototypes using experiments or numerical simulation. Less reports remain on the free-surface fluctuations in the reservoir and the influence of water gravity on the performance of the turbine. It is a high demand to accurately reveal the internal flow state of tubular turbines for the direct causes of blade vibration and fatigue damage. Taking the tubular turbine (including the upstream and downstream reservoir areas) as the research object, a numerical simulation was performed on the internal-flow performance in a prototype machine considering the free surface and water gravity. The one-way fluid-structure coupling calculation was implemented for the stress-strain analysis of the runner blade under different operating conditions, in order to reveal the distribution along the circumferential direction during the rotation of the runner. The results were as follows. 1) The pressure in the tubular turbine increased significantly under the free surface and the water gravity, with the increase of the submerged depth. The blades experienced periodic pressure fluctuations in the process of rotation. The magnitude of pressure fluctuations on the blade surface also increased accordingly, when the submerged depth of the runner increased, as the water head decreased. Therefore, there was severe vibration on the blade surface, when the tubular turbine operated under the condition of ultra-low head. 2) There was a gradually increased deformation at different positions of the blade from the hub to the chamber of the runner along the radial direction. The maximum deformation position was located at the geometric lowest point of the blade near the shroud. There was consistent running in the direction of hydrostatic pressure and the dynamic water pressure on the blade along the entire circumferential direction, leading to the increased deformation of the blade, where the blade overcame the hydrostatic pressure with the rotation of the runner. Once the hydrostatic pressure was promoted the rotation of the blade, the dynamic water pressure on the blade surface and the hydrostatic pressure were in opposite directions, indicating a counteracting effect on the dynamic water pressure for the reduced deformation of the blade. Therefore, the maximum deformation of the blade occurred at the blade rim, when the blade was running in a horizontal position during bottom-to-top rotating from the bottom to the top of the runner chamber. 3) Since the blade of the tubular turbine was supposed as a cantilever beam structure with the fixed constraints at the hub, the stress on the blade near the shroud was relieved by a larger amount of deformation. There was no deformation of the blade near the hub, due to the fixed constraint of the pivot. As such, the maximum stress occurred at the root of the blade pivot. Therefore, the distribution of the equivalent stress on the blade increased, as the radius decreased. The water head can greatly contribute to the decrease in the submerged depth of the runner, which was reduced the hydrostatic pressure on the blade surface, where the load on the blade surface tended to decrease for the reduced maximum deformation and maximum equivalent stress on the blade at different positions of circumferential direction. The blades were prone to deformation and fatigue damage at the low operating head of the tubular turbine. The finding can provide theoretical support to the severe vibration of tubular turbines in the ultra-low head operation, particularly for the hydraulic design, operation, and maintenance of tubular turbines.
    2022,38(6):61-71, DOI: 10.11975/j.issn.1002-6819.2022.06.007
    Abstract:
    Abstract: Spatiotemporal variation of nitrate (NO3ˉ) and isotope components were investigated in the karst and non-karst sub-basins, to clarify the influence of hydrogeological conditions and underlying surface properties on the source and migration of nitrate in water. The research areas were selected as the Mudong and the Jingui sub-basin in the Qingshitan Reservoir Irrigation District of Lijiang River Basin in southwest China. Both small karst watersheds were also dominated by agricultural activity. Multiple isotopes (δD-H2O, δ18O-H2O, δ15N-NO3ˉ, and δ18O-NO3ˉ) and the Bayesian Model Stable Isotope Analysis in the R (SIAR) model were applied to compare the multiple potential nitrate sources in the water. The results indicated that the spatial and temporal variation of nitrate in water depended on the hydrogeological conditions and the associated topography, soil characteristics, and land use types of the sub-basin. Total nitrogen (TN) was mainly formed by NO3ˉ and NH4+ in the river, where the proportion of NO3 ̄ was slightly higher while decreasing along the river. TN was overwhelmingly dominated by NO3 ̄ in the shallow groundwater. Nitrification was the dominant process of NO3ˉ formation and transformation. The Jingui sub-basin included the woodland with a thicker soil layer, while the Mudong sub-basin was mainly agricultural land with the karst development and the discontinuous thin soil layer. The ranges of mean NO3ˉconcentration (0.19-15.84 mg/L), and the isotope values of δD-H2O (from -44.08‰ to -19.63‰), δ18O-H2O (from -7.24‰ to -1.55‰), δ15N-NO3ˉ (from -1.65‰ to 53.98‰), and δ18O-NO3ˉ (from 0.04‰ to 13.74‰) in the Mudong sub-basin, were all greater than those in the Jingui sub-basin. In terms of spatial distribution, the mixing of nitrogen fertilizer infiltration from the orchard of exposed karst stone mountain in the north recharge area and manure & septic waste infiltration from the village groups were not smoothly dispersed and discharged in the central tectonic basin region, resulting in the high concentration of NO3ˉ(the mean concentration range from 11.96 to 15.84 mg/L) and the high isotope value of δ15N-NO3ˉ (from 0.65‰ to 28.23‰) and δ18O-NO3ˉ (from 2.46‰ to 14.43‰) in the water of G4-G7 wells. The contributions of NO3ˉsourced from the soil nitrogen in the dry season, as well as the manure and septic waste in the wet season in the Mudong sub-basin, were less than those in the Jingui sub-basin. The reason was the low capacity of water storage in the thin soil layer that was formed by the weathering of carbonate rocks, together with the strong permeability of the shallow soil layer in the Mudong sub-basin. Consequently, spatial and temporal variations of nitrate pollution and migration in water were achieved under karst hydrogeological conditions and underlying surface properties. The finding can provide decision support for the control of agricultural non-point source pollution and the improvement of the water environment in karst and non-karst areas.
    2022,38(6):72-79, DOI: 10.11975/j.issn.1002-6819.2022.06.008
    Abstract:
    Abstract: Dripline flushing has been widely expected to control the emitter clogging in drip irrigation systems. In this study, a new type of automatic flushing valve with the exhaust function (AE flushing valve) was developed to improve the duration and water volume of flushing. Four parameters were set, including the dentation length and dentation width of the delay channel, upper cavity volume, and water pressure before flushing valve. Eighteen AE flushing valves were designed by L18 (37) orthogonal test. Four flushing valves without an exhaust device (NE flushing valve) were set as the control treatment. A hydraulic performance test was performed on the 22 3D printed AE flushing valves to verify the effect of the exhaust device. The response characteristics of AE flushing valve performance to test parameters were also investigated. The results showed that the duration, water volume, and velocity of the AE flushing valve were 18.2-67.7 s, 3 904-12 367 mL, and 0.94-1.4 m/s, respectively when the water pressure at the flushing valve inlet was 0.06-0.14 MPa. The flushing duration and water volume were positively correlated with the dentation length, dentation width, and upper cavity volume, but negatively correlated with the water pressure. The flushing velocity was positively correlated with the water pressure only. According to the significance level of 0.05, the dentation length, dentation width and upper cavity volume posed significant effects on the flushing duration and water volume. The water pressure at the flushing valve inlet presented significant effects on the flushing duration and flushing velocity. The AE flushing valve automatically discharged the air in the upper cavity to improve the flushing duration and flushing water volume, which increased by more than 83.5% and 75.4%, respectively, compared with the NE flushing valve. Considering the anti-clog performance of the delay channel inside the flushing valve, and the minimum size of the flow section of the delay channel should be less than the sensitive clogging size of the emitter of 0.6-0.7mm, the dentation length, dentation width, upper cavity volume and water pressure with the longer flushing duration and larger flushing water volume were 1.2 mm, 2.2 mm, 19.1 mL and 0.06 MPa, respectively, while the corresponding flushing duration and flushing water volume were 67.7 s and 12 194 mL, which were 2.8 and 2.7 times larger than those of NE flushing valve, and 7.4 and 7.0 times larger than those of Israel imported ones. A regression model was established for the hydraulic, structural, and operation parameters of the AE flushing valve. In three AE flushing valves different from the above 18 structural parameters, the root mean square error of measured and predicted values for the flushing duration, flushing water volume, and flushing velocity were 2.1 s, 334 mL and 0.02 m/s, respectively, and the relative error ranges from -9.4% to 8.5%. It infers that the regression equation can be used to predict the structural and operation parameters of the flushing valve. This finding can provide the basis for the development of the automatic flushing valve with the function of exhaust during irrigation.
    2022,38(6):80-88, DOI: 10.11975/j.issn.1002-6819.2022.06.009
    Abstract:
    Abstract: Winter wheat (Triticum aestivum L.) is one of the major food crops in the world. Climate warming has dominated the growth and yield of winter wheat, particularly the protein formation and content of grains. But, the effects of warming on the protein content still remain unclear so far. Taking "Ji Mai 22" as the test material, this study aims to determine the specific effects of climate warming on the winter wheat growth and development, yield, and grain protein content. Climate warming was also simulated with an infrared warming device. Field warming experiments were conducted under the No Tillage (NT), and Conventional Tillage (CT) in the North China Plain for three consecutive years (2017-2019). The results showed that the open field warming reduced the overwintering period, indicating a significant shift in the regreening period. The nutritional growth period was then prolonged for the nitrogen accumulation time in the pre-anthesis period of plants. There was an increase in the Leaf Area Index (LAI) at the regreening-anthesis period, the net photosynthetic rate at the regreening-maturity period, and the aboveground dry mass of winter wheat. 20.17% (CT) and 99.21% (NT) of nitrogen accumulation in the winter wheat stems and leaves at the anthesis period, respectively, whereas, 24.62% (CT) and 134.21% (NT) of nitrogen transfer in the stems and leaves after anthesis increased by the warming in 2019, and the contribution of nitrogen in the stems and leaves contribution to seeds increased by 2.43% (CT), and 46.10% (NT). The NT warming increased the yield, where the NT yield was on average lower than that of CT. The CT yield of warmed winter wheat decreased by 2.14% and 4.62% in 2017 and 2018, respectively, and increased by 7.05% in 2019, whereas, the NT yield increased by 5.54% (2017), 34.44% (2018), and 42.25% (2019), respectively. The winter wheat yield in 2018 was significantly lower than that in 2017 and 2019. The reason was that the excessive precipitation in spring inhibited the winter wheat growth and development, leading to less yield in 2018. The temperature greatly contributed to the protein content of winter wheat grains, with an average increase of 14.28% (CT) and 17.39% (NT) for three consecutive years, compared with the control group. Therefore, the temperature promoted the conversion of nitrogen to the grain via the physiological characteristics of winter wheat. The reduction in effective spikelets number allowed the nitrogen for more grains to enter the final effective grain number, thus significantly increasing the grain protein content at high temperatures. The soil temperature under the NT was lower than that under the CT. The soil temperature was slower to rise in early spring, which affected the greening and early growth of wheat, resulting in the lower initial values of LAI, and net photosynthetic rate of winter wheat under the NT. The NT under the warming treatment reduced the post-anthesis soil temperature, but increased the soil water content, indicating the better wheat growth under a high post-anthesis temperature environment, compared with the CT. There was no significant difference in the grain protein content between CT and NT. This finding can provide a strong reference for the effect of climate warming on the protein content of winter wheat seeds under conservation tillage.
    2022,38(6):89-95, DOI: 10.11975/j.issn.1002-6819.2022.06.010
    Abstract:
    Abstract: Gypsum can be one of the by-products of the wet Flue Gas Desulfurization (FGD) process in coal-fired power plants. FGD gypsum can also be widely expected to ameliorate the saline-alkali soil in recent years. In this study, suitable application of desulphurized gypsum to improve the yield of sunflower in saline soil of Hetao irrigation area was selected from three applications of desulphurized gypsum. A field experiment was carried out with three applications (hole, strip, and spread) of FGD gypsum in the Hetao Irrigation District of Inner Mongolia (108°11′ east longitude and 41° 02′ north latitude). The optimal application was determined for the more efficient and low-cost soil amelioration. The treatment without FGD gypsum was also used as the control. Soil samples were collected after the first season of sunflower harvest, with a depth of 100 cm and 20 cm increments at the sites of the sunflower planting strip and the center of small row spacing. An investigation was also made on the effects of different applications of FGD gypsum on the soil pH, Electrical Conductivity (EC), and water-soluble cations distribution in the soil profile. The results showed that the three applications of FGD gypsum significantly reduced the soil pH and Sodium Adsorption Ratio (SAR) in the topsoil (0-20 cm), whereas, there was an increase in the concentration of water-soluble cations and the soil EC, compared with the control. The topsoil pH and SAR in the strip application were 20% and 41% lower, while the EC and water-soluble Ca2+ concentrations were 44% and 509% higher than that in the control, respectively. The concentration of water-soluble ions decreased gradually, with the increase of soil depth. However, the concentrations of water-soluble Ca2+ increased by 47%-105% at the 80-100 cm soil layer in the FGD gypsum application. In addition, the concentrations of water-soluble Na+ at the 20-100 cm soil layer in the three FGD gypsum applications were higher than that in the control, resulting in an increase in SAR. The effects of strip and hole on the saline-alkali soil amelioration were greater than that at the center of small row spacing, while there was no significant difference between the two sampling sites in the spread treatment. The three applications of FGD gypsum significantly increased the emergence rate and yield of sunflower, where the highest yield of sunflower was obtained from the strip treatment. Therefore, the effective components under the FGD gypsum strip can be concentrated around the sunflower roots to ameliorate the saline-alkali soil in the Hetao Irrigation District of Inner Mongolia in China.
    2022,38(6):96-104, DOI: 10.11975/j.issn.1002-6819.2022.06.011
    Abstract:
    Abstract: Soil erosion has posed some serious damage on the land resources in the world. The "Grain for Green" project in 1999 has been launched to restore the vegetation on the steep slope farmlands and control the soil and water loss for a better ecological environment of the Loess Plateau in China. But, the frequent extreme rainstorms have aggravated the occurrence and development of gully erosion under global warming in recent years. The development of the gullies after the extreme rainstorm still remains unclear so far. Fortunately, the Unmanned Aerial Vehicle (UAV) data can be collected fast, accurately, and efficiently after a rainstorm. The flexible acquisition time of UAVs can be expected to serve as an effective tool for the development of gully. Taking the Wangwugou Small Watershed of Chabagou Watershed on the Loess Plateau as the research area, this study aims to investigate the formation and development of gully under a rainstorm using UAV images. A case study selected the "7·26" extreme rainfall that occurred in Northern Shaanxi of China on July 26, 2017, with a daily rainfall of 206.6 mm. The patterns of newly formed gullies were captured under the climate. An equation with the topographic parameters was established for the occurrence and development of newly formed gullies in the following three years. The results showed that: 1) There were 45 newly formed gullies during the extreme rainstorm, which were about 101 gully/km2 in total. Four types were divided, including the hill slope, terraced field, unpaved roadway, and bottom gullies. There were more gullies found on the slopping hills. The bottom and terraced field gullies presented much wider and larger in the study area. The unpaved roads, check dam farmland, and sloping farmland were more prone to the gullies. 2) In the three years after the formation of the new gullies, the development of the new gully heads was faster than that of the original, 34.48% of which were further advanced, indicating 1.32 times the original. The average gully head retreat rate of newly formed gullies was three times that of the original, up to 0.58 m/a, where the maximum speed reached 2.12 m/a. 3) The drainage area significantly promoted the development of gully heads. A critical topographic index was selected to simulate the retreat rate of gully heads. There was more severe soil erosion under extreme rainfall conditions. The source of newly formed gullies was rapidly traced within three years after the occurrence. Therefore, the appropriate management can be attached to prevent such gullies during this time. This finding can provide an essential reference to estimate the rill erosion on the different types of sloping land in the hilly area of Loess Plateau.
    2022,38(6):105-112, DOI: 10.11975/j.issn.1002-6819.2022.06.012
    Abstract:
    Abstract: Human activities commonly dominate the water source, such as moisture conditions, even for the surface subsidence, fissure zone, more severe groundwater exploitation, and complex precipitation in the semi-arid areas. This study aims to determine the variation of groundwater level and water content in the vadose zone in typical mining areas of Northern Shaanxi Province in China. The relationship between precipitation and groundwater was established by in-situ observation, statistical and wavelet analysis from the perspective of the water cycle. Some parameters were also measured, including the precipitation, groundwater table and soil moisture content in the vadose zone under the disturbance of coal mining. Particularly, the vadose zone dominated the infiltration, evapotranspiration, groundwater recharge and discharge in the water cycle. The interaction mechanism was also proposed for the response of groundwater level and water content to the changes in precipitation in both unmined areas and mining areas. The self-test system, groundwater observation wells and sensors were used to evaluate the rainfall, phreatic water level, soil moisture, and water potential in the mining areas. The soil water movement was monitored in the depths of about 10, 20, 30, 40, 50, 80, 100, and 150 cm in the unmined areas and in the depths of about 10, 20, 30, and 50 cm in the mining areas. After that, an evaluation was made on the variation of groundwater level under the disturbance of coal mining, the trend of soil moisture content with the depth, and the relationship between soil moisture content and rainfall response before and after coal mining. The results show that there was an outstanding response of groundwater level to precipitation in the unmined areas, where the absolute value of correlation coefficient reached more than 0.7. There was also a lag of about four or five months. There was no effect of small intensity of precipitation (like 50 mm) on the soil water content near the depth below 100 cm in the unmined area, but the larger precipitation (60 mm) infiltrated the depth below 100 cm. The groundwater level continued to decline, indicating the weak relationship between groundwater level and precipitation after the disturbance of coal mining for about several years. The moisture decreased with the increase of depth in the vadose zone, indicating the gentle fluctuation range of dynamic change. The soil moisture was less vulnerable to the external influence, as the farther away from the ground. There was an outstandingly different trend of soil moisture content with the rainfall at different depths, although no significant response of water content to precipitation at the same depth. In addition, the maximum soil moisture content in the mining area occurred earlier than that in the unmined area, indicating a reduced range overall. In particular, the precipitation increased significantly in July and August. The reason was that the fissures caused by coal mining shortened the precipitation time to recharge the shallow groundwater. There was no response at the depth below 50 cm to the small intensity of precipitation (like 30 mm). In general, the coal mining caused the drop in water level, resulting in the thickening of the vadose zone, whereas, the loss of water increased in the vadose zone, resulting in the rainfall infiltration of groundwater recharge decreased, further aggravating the drop of water level. Accordingly, the findings can provide theoretical support for the water cycle mechanism under coal mining.
    2022,38(6):113-121, DOI: 10.11975/j.issn.1002-6819.2022.06.013
    Abstract:
    Abstract: An accurate assessment of debris flow susceptibility is of great significance to the prevention and control of debris flow disasters in mountainous areas. In this study, Synthetic Minority Oversampling Technique (SMOTE) and multi-grained Cascade Forest (gcForest) were applied to assess the debris flow susceptibility for high accuracy. The research area was taken as the Dongchuan District, Kunming City, Yunnan Province, China, where the debris flows were prone to occur. Taking the watershed unit as the assessment unit, 15 debris flow hazard factors were preliminarily selected using multiple sources of data, such as geology, topography, and precipitation, according to the interpretation of debris flow points. The contribution rate and multicollinearity tests were performed on the initial selection factors to filter out. 13 factors were selected to build a system of disaster-predisposing factors, including the watershed lithology, average fault density, main channel bending coefficient, average river network density, land use type, average road network density, channel gradient, 24h maximum precipitation, elevation difference, melt ratio, average elevation, average slope, average NDVI. Then, the synthetic minority oversampling was used to deal with the imbalance between debris flow and non-debris flow samples, and the training data set was then constructed. At last, a multi gcForest was constructed to quantify the susceptibility of debris flow in the study area. The natural breakpoint method was selected to classify the five levels for each watershed unit, such as the very low, low, medium, high, and very high susceptibility. The prediction performance of the improved model was compared with the Back Propagation neural network (BPNN) and Random Forest (RF) models. The results show that the model accuracy was improved from 0.786 7 to 0.917 6 using the STOME oversampling technique to balance the data set, indicating the higher prediction accuracy of the model. The very low and low susceptibility areas were mainly concentrated in the eastern and western parts of the study area, whereas, the very high and high susceptibility areas of debris flow were mainly distributed on both banks of Xiaojiang River Valley and the South Bank of Jinsha River in the study area, with the most concentrated distribution in the middle and north of Tuobuka, Wulong, Tongdu Street, the north of Awang, Yinmin and the north of Shekuai, where the geological environment was fragile and the high risk. The medium susceptibility area was mainly distributed around the very high and high susceptibility areas, particularly in the upper reaches of the Xiaoqing River in Hongtudi. There were the excellent accuracy and stability in the three assessment models of debris-flow susceptibility in the mountainous areas combined with watershed units, in which the gcForest the Area under Curve (AUC) value of the Receiver-Operating Characteristic (ROC) and Accuracy (ACC) value reached 0.917 6 and 0.812 5 respectively. The AUC and ACC values of gcForest were higher than those of the BP neural network and RF model, indicating a higher performance. Correspondingly, the improved model can be used to more accurately evaluate the susceptibility of mudslides. The finding can provide a scientific basis for disaster prevention and mitigation in mountainous areas.
    2022,38(6):122-129, DOI: 10.11975/j.issn.1002-6819.2022.06.014
    Abstract:
    Abstract: Autonomous navigation can be critical to improve the quality and efficiency of orchard robots during operation. Since the identification is relatively fine, the current location of the fruit tree has posed a great challenge on the depth orientation and accuracy, resulting in some limited operations in orchards. In this study, an improved YOLOv3 algorithm was proposed for tree trunk recognition and binocular camera positioning. Firstly, the SENet attention mechanism module was integrated into the residual module in Darknet53 for a feature extraction network of YOLOv3. As such, the feature re-calibration was achieved to extract the useful feature, and compress the useless feature information, where an improved residual network SE-Res module was obtained. The stacking of residual network SE-Res modules were used several times for the improved feature extraction of the YOLOv3 model and more accurate target detection. Secondly, the K-means clustering was added into the original YOLOv3 model of anchor box information for the requirement of high precision. The updated YOLOv3 model was utilized to optimize the test frame for the more accurate inspection information, where the more accurate the test box information was set to obtain the more accurate positioning information. The images were collected by the left and right cameras of the binocular camera, respectively, and then transmitted to the improved YOLOv3 model for the tree trunk detection. The information of the inspection frame was output, including the category information, the center point coordinates of the inspection frame, and the width and height of the inspection frame. Target matching was performed on the collected images under the output detection frame. The target matching was achieved within the threshold for the difference between the area of the target inspection frame and the coordinate of the center point v axis in the left and right images for the same category information. The parallax information of the same target was obtained after successful matching. The tree trunk was then located using the triangulation of binocular camera, according to the parallax information. Experimental results show that the improved YOLOv3 model can be used to better identify and locate the fruit tree trunks, where the optimal time was 0.046 s/frame. Specifically, the average precision and recall rate were 97.54% and 91.79%, respectively, which were improved by 3.01 and 3.84 percentage points, respectively, compared with the original, while by 14.09 and 20.52 percentage points, compared with the original SSD model. The positioning accuracy of the three models in longitudinal direction was higher than that in transverse direction in the experiment. The average positioning errors of transverse direction and longitudinal direction were 0.039 and 0.266 m, respectively, and the average error ratios were 3.84% and 2.08%. Compared with the original YOLOv3, the mean value of positioning error in transverse direction and longitudinal direction were reduced by 0.140 and 0.945 m, respectively, and the error ratio was reduced by 15.44 and 14.17 percentage points, respectively. Compared with the original SSD model, the mean positioning errors of transverse direction and longitudinal direction were reduced by 0.216 and 1.456 m, respectively, and the error ratio was reduced by 21.58 and 20.43 percentage points, respectively. Therefore, the improved model can be used to identify and locate the fruit trees in the autonomous navigation of orchard robots, including the ditching fertilization, grass cutting, and pesticide spraying operations. The finding can lay a theoretical foundation to improve the efficiency for better operation quality.
    2022,38(6):130-139, DOI: 10.11975/j.issn.1002-6819.2022.06.015
    Abstract:
    Abstract: Apple has been one of the most popular cash crops for the development of the agricultural economy. Seven common diseases have posed a serious threat to the yield and quality of apples, including the Mosaic, Alternaria spot, Brown spot, Powdery mildew, Aphid, Leafminer and Spider mite pests of plant leaves. Early diagnosis and control of diseases and pests can greatly contribute to preventing the spread and reducing losses in the apple industry. However, the current lightweight models cannot accurately identify the sparse small lesions in early apple leaves. In this study, a lightweight recognition model, ALS-Net (Apple Leaf Net using channel shuffle) was proposed for the resource-constrained mobile terminals. The specific procedure was as follows: 1) Firstly, 1 881 images of diseased and healthy apple leaves were collected in Qian County, Shaanxi Province in China. Digital image processing was conducted to enhance the original images, particularly for the generalization and robustness of the model. 2) Secondly, the ALS module was constructed using depth-wise separable convolution and channel shuffle technology. The calculations and parameters of the model were significantly reduced, compared with the traditional convolution network. The channel shuffle technology fully shuffled the information between channels, and then randomly assigned it to each channel. As such, the loss of accuracy was alleviated in group convolution. The Inception structure was introduced into the model for the multi-scale feature extraction. The channel attention was selected to strengthen the disease features in the network, while suppressing the natural background. The Exponential Linear Unit (ELU) was selected as the activation function to accelerate the convergence speed of the model. 3) The knowledge distillation strategy was used to train the model, providing the soft label information that the student model cannot learn on the hard label to realize the transfer of knowledge. The accuracy of the student model was approached or exceeded the accuracy of the teacher model. DenseNet-161 with high accuracy was selected as the teacher model, and the ALS-Net was the student model. A high-performance server was utilized to train the model for the generalization of the model. The experimental results were as follows. 1) The comparative experiment showed that the accuracy of ALS-Net reached 99.43%, which was higher than that of classical CNNs, such as AlexNet and ResNet, and the size of the model was only 1.64 MB, which was lower than that of lightweight CNNs, such as MobileNetV2 and ShuffleNetV2. 2) There were two sets of ablation experiments. The first verified the effects of expanding the convolution kernel to adjust the number of blocks on the model accuracy and parameter number. The second verified the effects of Inception structure, attention module, ELU activation function, and channel shuffle on the accuracy of the model. 3) The training of knowledge distillation strategy significantly improved the recognition accuracy, further accelerating the convergence speed during training. 4) Using PyTorch Mobile, the model was deployed on HUAWEI P40 Pro 5G mobile terminal for real-time inference. The inference delay of the mobile terminal was 55 ms, fully meeting the requirements of practical application. The automatic recognition of apple leaf diseases and pests was realized on the mobile terminal. The finding can provide an insightful idea for the early diagnosis of apple leaf diseases and pests.
    2022,38(6):140-147, DOI: 10.11975/j.issn.1002-6819.2022.06.016
    Abstract:
    Abstract: Residual film pollution has posed a great threat to the agricultural environment in recent years. It is a high demand for residual film identification and coverage rate detection in cotton fields before sowing. In this study, an evaluation method of residual film coverage rate was proposed using pixel block and machine learning model, in order to effectively recognize the residual film in the cotton field before sowing by the pixel block classification. Fifty images of 1 m×1 m cotton field surface with the residual film were collected by random sampling in the cotton growing area of Kuitun, Xinjiang, China. The image with a resolution of 4 608×3 456 (Pixel) was cropped along the boundary of 1 m×1 m sampling area. After cropping, the image was resized to 1 000×1 000 (Pixel), and the brightness was corrected using normalization. The image pixel was then manually labelled, in which the residual film was labelled as 1, and the soil background was labelled as 0. Then, 45 images were randomly selected to train the models, and the rest 5 images were used to verify the final model for the evaluation of residual film coverage rate. The recognizing pixel blocks and machine learning were selected to make better use of the color and texture features of images. Each image was cut into the 10 000, 2 500 and 625 pixel blocks, according to the sizes of 10×10, 20×20 and 40×40 (Pixel), respectively. The extraction was performed on the first, second, and third order color moments of R, G and B channels, and Gray-level Co-occurrence Matrix (GLCM) of each pixel block. Meanwhile, the intensities of R, G and B channels of each pixel were extracted for comparison. The stochastic down-sampling and Synthetic Minority Oversampling Technique (SMOTE) were used to equalize the pixel block data. Principal Component Analysis was employed to extract the top 10 principal components of pixel block, in order to prevent the over-fitting for the high training speed. Consequently, 70% of the data was used for the training, and 30% was for the testing. Random Forests (RF), Xtreme Gradient Boosting (XGBoost), Support Vector Machine (SVM), and Artificial Neural Network (ANN) were used to optimize the parameters via the style search and cross validation. The residual film coverage rate was calculated to evaluate the segmentation of different sizes of pixel blocks and the machine learning models. The ANN model combined with 20×20 (pixel) blocks performed the best, with the Mean Intersection Over Union (MIOU) of 71.25%. The relative error was 0.51% in the residual film coverage rate between the prediction and actual value, and the detection time was 0.29 s. Therefore, the improved model is feasible for the accurate identification of residual film on the surface of the cotton field before sowing. This finding can provide theoretical support for the rapid detection system of residual film pollution using UAV imaging.
    2022,38(6):148-156, DOI: 10.11975/j.issn.1002-6819.2022.06.017
    Abstract:
    Abstract: The tissue culture technology of phalaenopsis has gradually matured in recent years. Seedling stem cutting has been one of the most critical steps in the process of the tissue culture industry. An automatic cutting system can greatly contribute to reducing the probability of infection for the better quality of seedlings. In this study, a cutting-point positioning system was proposed for the automatic cutting of phalaenopsis seedlings using a visual servo. The elastic cutting end was also designed using the fitting straight line for the structural characteristics of seedlings. The seedling cutting system was mainly composed of the seedling visual detection, cutting coordinate positioning, and seedling cutting execution modules. Specifically, the seedlings were firstly photographed with an industrial camera, and then the images were transmitted and saved to the core computing unit. Shuffle Net v2 - YOLOv5 model was used for the target detection of the collected images, in order to realize the accurate detection of the seedling stem, blade, and black tuber. Secondly, the saved image was identified to evaluate the feasibility of cutting performance. The image data was then extracted from the detection frame, where the image contour in the frame was extracted to fill the maximum connected region. The stem straight-line fitting with the distance correction was used to make the connected region pixels near the black tuber position closer to the cutting center. Thirdly, the cutting-point positioning was implemented to verify the resulting data using geometric profiles. Finally, the cutting coordinate was transmitted to the cutting actuator for the cutting operation. The cutting-end design fully considered the characteristics of phalaenopsis seedlings and the cutting environment of tissue culture seedlings. The structure reduced the impact force of cutting tools when performing the cutting tasks. As such, a stable and effective operation was achieved at the cutting end for the rapid replacement of sterile consumables. A user interface was also designed to cooperate with the cutting system for the phalaenopsis seedling cutting, including the display of target detection and cutting coordinates, as well as the cutting control modules. Various components of the seedling were monitored to predict the parameters of the manipulator at each joint, particularly for the end speed over the control area. A target detection experiment was conducted to compare the Faster-RCNN, YOLOv4, YOLOv5, and MobileNet v2-YOLOv5 detection models. ShuffleNet v2-YOLOv5 model presented a higher detection accuracy of 96.7%, a weight file size 1.3 MB, and an average detection time of 0.026 s, suitable for seedling image detection. In the seedling cutting test, the cutting qualified rate was higher than 86% than before, and the average cutting time per plant was less than 18 s. The finding can lay the foundation for the phalaenopsis seedling cutting system with two-arm cooperation.
    2022,38(6):157-164, DOI: 10.11975/j.issn.1002-6819.2022.06.018
    Abstract:
    Abstract: Monitoring the Crop Water Stress Index (CWSI) is of great significance for the water status and irrigation in crop production. Taking the Brassica chinensis as the test object, this study aims to measure the canopy temperature under different soil moisture conditions. Some meteorological parameters were collected, including the air temperature, relative humidity, wind speed, and photosynthetic active radiation. Meanwhile, the images of spectral reflectance were also collected for the four bands (450, 650, 808, and 940nm). Four vegetation indexes were then calculated by the canopy spectral reflectance, including the Normalized Difference Vegetation Index (NDVI), Difference Vegetation Index (DVI), Re-Difference Vegetation Index (RDVI), and Optimized Soil-Adjusted Vegetation Index (OSAVI). Support Vector Regression (SVR) was selected to construct the inversion models of the CWSI upper/lower baseline using the meteorological parameters, and the inversion models of the canopy temperature using the vegetation index. The results showed that the canopy spectral reflectance at 450 and 650 nm for the Brassica chinensis ranged from 0 to 0.1, while the relatively higher one at 808 and 940 nm ranged from 0.4 to 0.6. The reflectance at 808 and 940 nm increased outstandingly, when the Brassica chinensis was developed gradually from the vegetative to reproductive growth stage. The vegetation index reflected the growth state and vegetation coverage of the Brassica chinensis. There was a different response of vegetation indexes to the canopy temperature. The vegetation NDVI, DVI and RDVI increased, while the vegetation OSAVI decreased with the increase of the canopy temperature of the Brassica chinensis. The vegetation index under the same water treatment was slightly different in the various growth stages. Specifically, the range of the vegetation index in the reproductive growth stage was smaller than that in the vegetative growth stage. The error analysis showed that the inversion models were feasible to monitor the air temperature, relative humidity, wind speed, and photosynthetic radiation, further invert the upper/lower baseline of CWSI with the determination coefficient greater than 0.75. In the light of the error analysis of the inversion models, the vegetation index was inverted the canopy temperature of the Brassica chinensis in the vegetative and reproductive growth stage, indicating an excellent accuracy with the determination coefficient greater than 0.7. The calculated CWSI using the inversion models presented a significant correlation with the using the measurement, while the determination coefficient was equal to 0.70. And the CWSI showed the negative relationship with the stomatal conductance with the determination coefficient equal to 0.53. The meteorological parameters were used to invert the upper/lower baseline of CWSI, where the vegetation indexes were used to invert the canopy temperature. The inverted values using the SVR model shared the better fitting performance. The finding can provide a strong support for the spectral monitoring of the crop water stress index of the Brassica chinensis.
    2022,38(6):165-174, DOI: 10.11975/j.issn.1002-6819.2022.06.019
    Abstract:
    Abstract: Hetao Irrigation District (HTID) has been the largest self-flowing irrigation district with one water intake in Asia, serving an important commercial grain and oil production base in China. The annual grain production in the HTID reached 2.55 million tons in 2018, accounting for 3.9‰ of the total crop cultivation area in China. Therefore, accurate and rapid extraction of crop structure can be of great practical significance in agricultural production for the food security of the HTID. However, it is difficult to distinguish the pixels of major crops in the remote sensing images, due to the severe soil salinization, fragmented and scattered crop distribution, as well as the same crop with the different spectrum of various crops. Moreover, there are the close growth periods of major crops in the HTID, which can mix the elements in the images. In this study, Sentinel-2 high-resolution remote sensing images and the GlobeLand30 dataset were used to extract the crop planting structure of the HTID using the Google Earth Engine cloud computing platform. Nearly 1 200 sample points were filtrated using the OTSU algorithm and Google Earth visual interpretation. The features of spectra, frequently-used vegetation, red-edge vegetation, and crop texture were input into four classifiers, including the Random Forest (RF), Support Vector Machine (SVM), Naive Bayes (NB), Classification and Regression Tree (CART). The Overall Accuracy (OA) and Kappa coefficient were used to evaluate the performances of model for the extraction of crop planting structure. Firstly, the impacts of classification features and classifiers combinations on the classification accuracy were explored to identify the classifier with the highest classification accuracy. Then, the feature optimization was performed on the five irrigation sub-districts using out-of-bag error rates for each irrigation sub-district. Finally, the optimal classifier and feature combinations were achieved to derive the cropping structure of four crops in the HTID in 2018. The results show that the RF classifier presented the highest classification accuracy using all feature bands, where the average OA of the HTID (81%) was 6 percentage points and 11 percentage points higher than that of the SVM and NB classifier, respectively. The Kappa coefficient reached 0.68, which was much higher than the rest. Furthermore, the importance of feature bands filtered by the RF was ranked first for the spectral features, the second for the vegetation features, and last for the gray texture features. The indexes were calculated using red-edge bands, indicating the better performance over the other commonly-used remote sensing vegetation indices in crop recognition. In addition, the feature-optimized scheme was the combination with the highest average OA of 86% and Kappa coefficient of 0.78, while the scheme containing 25 bands of spectral, vegetation and texture features presented an OA of 85% and Kappa coefficient of 0.75. Therefore, the new sights can be offered for extracting crop spatial distribution using remote sensing cloud computing platform in complex planting structure area. The finding can provide a strong reference to adjust the agricultural production structure, and further formulate the food macro-control policies in the Hetao Irrigation District.
    2022,38(6):175-183, DOI: 10.11975/j.issn.1002-6819.2022.06.020
    Abstract:
    Abstract: Verticillium wilt has been one of the most common high-risk diseases of cotton in recent years. A huge threat can be posed to the stable production of cotton fields in Xinjiang, one of the most important commodity cotton production bases in China. However, the annual area of verticillium wilt disease in cotton fields is ever increasing and resulting in serious yield losses, due to the long-term influence of planting modes, geographical, and climate characteristics. Most traditional measurements for the yield loss present time-consuming, labor-intensive, large errors, one-sidedness. It is a high demand to accurately estimate the yield loss caused by the diseases. Fortunately, the Unmanned Aerial Vehicle (UAV) multi-spectral data can be combined with the ground survey data for the comprehensive characteristics of high accuracy. In this study, a systematic investigation was conducted to estimate the yield loss in the diseased cotton fields using the UVA multi-spectral images. An experiment was carried out in the cotton verticillium wilt disease nursery (44°31′N, 85°98′E) of Xinjiang Academy of Agricultural Sciences, Shihezi Reclamation District, Xinjiang in China in 2020. The gray desert soil was collected in the study area, with an organic matter content of 21.30 g/kg, a soil layer pH of 7.82, and electrical conductivity (EC) of 0.48 mS/cm. Taking the test variety as Xinluzao 8, the specific procedure was set: the on-demand sowing was adopted on the film, the drip irrigation under the film, (66 +10) cm wide and narrow row design, while the cotton plants were manually capped on July 5, and sprayed by drones on September 6 and September 13 Defoliant, and finally harvested by the cotton picker on October 13th. The ground monitoring points were arranged in a grid format (66 in total) from the beginning of the disease, in order to collect the disease severity data. The output was then measured in the later period. The monitoring point was taken as the center during the production measurement (cotton harvest period), and the area of the monitoring point was expanded to 6.67m2 for the yield measurement. The UAV data acquisition was consistent with the acquisition time of ground monitoring points. The correlation coefficient method was used to screen the optimal vegetation index for the diseased cotton plants, according to the UAV multi-spectral images of diseased cotton fields and ground yield loss data. The gray value standard deviation method was also used to screen the optimal band combination. As such, the comprehensive cotton field image was established, including the best band combination and DVI comprehensive image. The support vector machine radial basis kernel function classification was used to analyze the spatial distribution of the original image and the comprehensive image of the diseased cotton field, further estimate the yield loss. The results show that the best vegetation index and the best band combination were DVI (correlation coefficient |r|=0.86) and B3-B5-B8 (optimum index factor was 153.44) for the UAV multi-spectral image identification of diseased cotton fields. The comprehensive image accurately identified the spatial distribution of diseased cotton fields, where the accuracy of the bolling period was the highest (overall accuracy was 96.64%, Kappa coefficient was 95.61%). In the different disease severity (health b0, slight b1, moderate b2, serious b3, and critical b4) corresponding to the cotton field, the area ratios were 7.81%, 23.78%, 29.20%, 13.92%, and 17.43%, compared with the original image. Consequently, the comprehensive image performed the best to estimate the yield loss of diseased cotton fields. The different disease severity (b0, b1, b2, b3, and b4) corresponded to 0.00%, 22.80%, 31.32%, 49.02%, and 76.33%, respectively. It was estimated that the loss of seed cotton was 4260.01 kg, and the loss rate was 49.16%, and the loss of lint cotton was 2267.18 kg, and the loss rate was 54.51%. Compared with the estimated yield loss of cotton fields under disease stress, the actual loss rate of seed cotton in cotton fields was 6.28% higher, and the loss rate of lint cotton was 4.48% higher. The estimated value of disease-stressed cotton field yield is not significantly different from the actual harvest value of cotton field, which can accurately estimate the yield loss of diseased cotton field. Therefore, it is possible to accurately estimate the yield loss of diseased cotton fields using the integrated UAV image. The finding can provide a strong reference for the estimation of yield loss caused by similar diseases.
    2022,38(6):184-192, DOI: 10.11975/j.issn.1002-6819.2022.06.021
    Abstract:
    Abstract: Earthworm composting can serve as one type of agricultural waste treatment to combine with conventional composting with biological digestion. The earthworms can be selected to decompose the organic matter. The 'ecological interface' of earthworm composting has been utilized to optimize the earthworm culture using the large-scale breeding equipment, particularly for the harmless, reduction and recycling of agricultural wastes. However, a perfect balance needs to be gained between the short mature period of earthworms, and the large output of earthworm and earthworm dung. The separation can be the key link to harvesting the earthworm products and earthworm dung organic fertilizer. Electric stimulation can be used to separate using the instinctive reaction of earthworms with less harm. Once the electric stimulation is directly applied to the material carrier where earthworms are, the earthworms can be actively driven to leave the growing environment. There was no harm to the health of earthworms, and no secondary pollution to the environment, synergistically coupled with the breeding equipment in practice. Therefore, it is a high demand to clarify the separation process for the rapid design of the separation facility. In this study, a systematic investigation was conducted to determine the response of the separation rate of earthworms to the mode, intensity, and duration of electric stimulation, the water content of the carrier, and the material thickness. An evaluation was made to clarify the effects of electric stimulation on physiological and biochemical indexes of earthworms. The results show that electrical stimulation promoted the separation of earthworm and dung, where the intermittent electrical stimulation presented a better separation performance than the continuous. The earthworm separation rate was significantly correlated with the intensity of electrical stimulation under the intermittent mode, the circulation cycle time of power-on and power-off, as well as the times of power-on. The optimal moisture content of the material carrier was 52.6% for the earthworm growth. The smaller the material carrier thickness was, the better the earthworm separation rate was. Electrostimulation treatment had no significant effect on the contents of catalase, superoxide dismutase, acetylcholinesterase, cellulase and soluble protein in earthworms, but significantly increased the content of malondialdehyde. After 5 days of recovery domestication, the content of malondialdehyde could be restored to the level of control treatment. Consequently, the earthworm can be separated by intermittent electrical stimulation, in terms of the separation rate and the technical parameters. An optimal combination was achieved, where the intensity of electrical stimulation was 2mA, the on-off cycle time was 30 s, and the power-on time was 1s. The earthworm separation efficiency reached about 85% after 30 minutes of electrical stimulation, where the water content of the material carrier was about 50%, the material thickness was 20-25 cm, and the auxiliary 210 lx white light. The finding can provide strong support to the equipment application for the rapid and efficient separation of earthworm and earthworm dung during agricultural waste treatment
    2022,38(6):193-203, DOI: 10.11975/j.issn.1002-6819.2022.06.022
    Abstract:
    Abstract: Biogas production via anaerobic digestion (AD) can effectively utilize pig manure to produce methane instead of fossil energy. However, a large amount of lignocellulose contained in the pig manure cannot be fully decomposed during hydrolysis in the methane production during AD. Therefore, it is necessary to adopt the appropriate pretreatment for the better hydrolysis and AD performance of pig manure. It is also a high demand to consider the ecological safety index (e.g. heavy metals Cr, As, Cd, Hg, and Pb, Escherichia coli) of anaerobic digestates as agricultural organic fertilizers. A hydrothermal treatment can be widely expected to improve the biodegradability of materials, where the hemicellulose can be deconstructed to dissolve the organic matter at high temperature and pressure. Thus, it is supposed that the hydrothermal treatment of pig manure can be extended for the subsequent methane conversion. In this study, a systematic investigation was conducted to clarify the effects of hydrothermal pretreatment at different temperatures (70, 90, 120, 150, and 170 ℃) on the physicochemical properties and AD performance of pig manure, together with the ecological safety of AD digestate from pig manure. The results showed as follows. The total solid (TS) in the pig manure decreased by 1.5%-8.7%, whereas, the Soluble Chemical Oxygen Demand (SCOD) increased by 3.9%-43.6%, with the increasing hydrothermal temperature. It infers that the hydrothermal treatment enhanced the biodegradability and hydrolysis of pig manure. Nevertheless, it was easy to produce hardly degraded substances, such as organic humic acid and fulvic acid, during the hydrothermal process of pig manure. The organic humic acids and fulvic acids in the pig manure gradually increased with the increasing hydrothermal temperature. The relative content of fulvic acids increased from 37.63% to 41.97%, when the temperature increased from 150 to 170 ℃. The cumulative biogas and methane yields were 602-677 mL/g and 350-398 ml/g, respectively, in the pig manure that was pretreated at different temperatures after 30-day AD. The highest methane yield of 398±40 mL/g was obtained from the pig manure after 150 ℃ pretreatment, which significantly increased by 5.6% (P < 0.05), compared with the untreated. There was no significant enhancement in the methane production for the hydrothermal pretreatment at the rest temperatures. The reason was that the low pretreatment temperature (70 and 90 ℃) slightly increased the SCOD and hydrolysis. Maillard reaction inhibited the subsequent AD process for the less biodegrade substances at the higher temperature of 170 ℃. The contents of heavy metals Cr, As, Cd, Hg, and Pb in the pig manure digestate fully met the requirements in the national standard of Agricultural Biogas Slurry (GB/T 40750-2021). The content of Escherichia coli met the Hygienic Requirements for Harmless Disposal of Night Soil (GB 7959-2012). The content of oxytetracycline in the pig manure digestate was reduced effectively, while the enrofloxacin, sulfadiazine, and norfloxacin were lower than the detection limit. Therefore, appropriate hydrothermal pretreatment (150 ℃) of pig manure can improve the methane production performance during AD, further reducing the harmless treatment of manure and the environmental risk of AD digestate that is applied to the field.
    2022,38(6):204-212, DOI: 10.11975/j.issn.1002-6819.2022.06.023
    Abstract:
    Abstract: A thermal insulation plastic greenhouse has been widely used in China, due to the cost-saving, ease to build, and heat preservation. The original heat preservation can be maintained for the air temperature and CO2 concentration in the insulation plastic greenhouses with the large span double arch and double membrane. In this study, an active ventilation fermentation heating and supplemental gas system (AVFHSGS) was designed to control the ventilation time in the asymmetric insulation plastic greenhouse. The system included a fermentation tank (long × wide × height: 7.0 m × 2.0 m × 2.0 m), an air-permeable plate, filter, air replenishment, and sprinkler irrigation device. A field experiment was carried out, where the cow dung, wheat, corn, and tomato straw were taken as the raw materials, and the ratio of cow dung to straw was 3:1 for the active ventilation in aerobic fermentation. There was a large annual output of livestock and poultry manure, together with the straw in China, where the raw materials for biomass fermentation were cheap and accessible. Moreover, the biological oxidative fermentation was often accompanied by the generation and release of a large amount of heat and carbon dioxide. The released heat during composting was diffused into the environment in the form of waste heat, where CO2 was the raw material for photosynthesis. A high concentration of CO2 was selected to accelerate the net photosynthesis of tomato leaves and bloom, which was essential to the supplement gas fertilizer in the process of crop growth and development. An evaluation was made on the heat source and CO2 gas source for the thermal insulation plastic greenhouses, considering the temperature variation of composting fermentation in the shed, the CO2 supplement, and the diffusion of harmful gases, such as NH3, N2O, and CH4. The results showed as follows. 1) The reactor temperature in the AVFHSGS was above 50 ℃ for 30 days in total, and 55 ℃ for 17 days in total, which met the requirements of the Chinese standard for the harmless feces; 2) The air temperature increased by 1-3 ℃ at night in the experimental plastic greenhouses, indicating the better heat source, compared with the control; 3) The average CO2 concentration in the 182 m2 measurement area increased to 1 997 μmol/mol by the release of CO2 gas during composting, and the average CO2 concentration in the measurement area was 1 099 μmol/mol during the whole measurement period, the optimal concentration of CO2 increased in the tomato production was 1 000 μmol/mol, meeting the requirement of tomato concentration; 4) The concentrations of NH3, N2O, and CH4 varied from 5.7 to 18.5 μmol/mol, 1.0 to 2.4 μmol/mol and 115 to 315 μmol/mol in the test area, respectively, indicating that there was no outstanding influence or harm on the human health and crop growth. The AVFHSGS can be used as the heat source of insulated plastic greenhouse and CO2 source of crop growth.
    2022,38(6):213-220, DOI: 10.11975/j.issn.1002-6819.2022.06.024
    Abstract:
    Abstract: The traditional load distribution model of hydropower units has been confined to the "dimension explosion" in the calculation, due to the redundant constraints during operation, leading to the slow solution speed and low efficiency of the model. There are many times of units crossing the vibration zone, and a large fluctuation of unit output in the load distribution. In this study, a multi-objective multi-constraint double-layer intelligent optimization model was established for the hydropower units using the coupled dynamic programming (DP) and improved biogeography-based optimization (IBBO). The minimum water consumption in the process of load distribution was taken as the optimization objective, and the 15-minute duration was taken as the minimum load distribution period to calculate the short-term load distribution of hydropower units. A multi-constraint optimization model of the hydropower unit was constructed using the DP outer layer. The average fitness of the population was introduced into the inner layer using the IBBO. A dynamic migration model was then established from the relationship between the average fitness of the population and the individual fitness. The mixed crossover was introduced into the adaptive updating strategy of the migration operator. The unit load distribution optimization model was constructed using the unit output fluctuation constraints, according to the unit combination. Taking the data of demand load and generating head of a hydropower station on a certain day as an example, firstly, the iterative convergence times of the improved IBBO increased from 45-50 to 20 generations, and the traffic consumption was reduced by 1.28% and 1.82%, respectively, compared with the traditional IBBO and BBO, when the minimum traffic consumption was taken as the fitness function of the model. The convergence and optimization of the improved IBBO were outstandingly improved by the migration model and operator of the algorithm. Secondly, the IBBO-DP model saved 10.56% of water consumption, compared with the double-layer dynamic programming (DDP) model. The zero crossing of the vibration zone of the unit was achieved in 50 calculations on average, leading to the reduced 24 crossing of the vibration zone, compared with the DDP model. Finally, the IBBO-DP model effectively stabilized 60.24% of unit average output fluctuation amplitude, and 47.28% of unit output fluctuation ratio, compared with the DDP model, considering the constraint of unit output fluctuation. There was a great increase in the unit vibration avoidance, operation stability, and reliability in the process of load distribution of hydropower units. Consequently, the double-layer intelligent optimization model was constructed to consider the fluctuation constraint of unit output, and then a case study was used to verify the load distribution optimization of hydropower units, indicating a wide range of engineering applications for the actual operation of hydropower units. This finding can also provide a strong reference for the subsequent operation of hydro-photovoltaic complementary power generation.
    2022,38(6):221-229, DOI: 10.11975/j.issn.1002-6819.2022.06.025
    Abstract:
    Abstract: A simple structure can greatly contribute to the solar energy efficiency of the stationary photovoltaic installations in photovoltaic water pumping systems. In this study, a sun-chasing strategy was proposed to adjust the inclination of photovoltaic panels using water level. A three-point support sun-tracking device was also developed suitable for the photovoltaic water lifting system. A theoretical model was then constructed to determine the mathematical relationships with the water inlet flow in the water tank and the rotation inclination of the photovoltaic panel. An experiment was conducted to verify the key technical parameters of the floating ball drive, such as the water inlet of constant current, siphon water discharge, and the secondary water replenishment. As such, the structure, composition and operation were realized for the key components of the sun-chasing device. The result shows that the three-point support structure and the buoyancy of the floating ball were provided for the photovoltaic panel smoothly chasing the sun from the east to west, while the siphoning effect was benefit for the automatic reset of photovoltaic panels. The secondary water supply was also adjusted suitable for the various weather. The solar radiation during the whole day increased by 28.56% and 32.56% under the sunny and cloudy day, respectively, and the capacity of water pumping increased by 34.74% and 40.82%, indicating the higher performance of sun tracking than before. The secondary water-supply device was utilized to supply the continuous water for the tank of photovoltaic panels following the sun. Therefore, the multiple photovoltaic panels chasing the sun can be installed a siphon drain, a secondary water replenishment, an inlet device of constant flow, and the float drive device. Then, the multiple devices can be extended for the large-area photovoltaic power generation with the significant cost reduction and simple modification. Correspondingly, the sun-chasing device was outstandingly superior to the traditional fixed photovoltaic support, indicating higher radiation reception and water pumping. The photovoltaic water extraction and photovoltaic panels were combined to track the sun for the higher power generation efficiency of photovoltaic panels. The finding can also be extended for the application of photovoltaic panels in modern agriculture.
    2022,38(6):230-235, DOI: 10.11975/j.issn.1002-6819.2022.06.026
    Abstract:
    Abstract: Biomass has been the fourth largest energy source after coal, oil, and natural gas in the world. Densified biofuel has also drawn much attention, due to the simple preparation, high thermal efficiency, convenient storage and transportation. However, the slagging can induce the uneven heating of the grate during combustion, leading to the low heat-transfer efficiency, even some serious accidents in some cases. The additives can be an effective way to deal with slagging. But, the currently developed additives remain unclear on the anti-slagging behavior. Therefore, it is necessary to find more efficient and cheap additives for the improved anti-slagging behavior in the densified biofuel. In this study, the attapulgite clay was proposed to serve as the composite anti-slagging agent. Firstly, a series of densified biofuels were fabricated under the various doses of attapulgite clay, together with the blank control group. A proximate analysis was carried out for the high calorific values during combustion of densified biofuel. The results showed that the calorific value decreased less when the attapulgite clay addition was less than 3%. However, the ash increased rapidly with the increase of attapulgite clay addition. Secondly, the macro morphology analysis and micro morphology analysis were carried out to determine the slagging tendency of biomass ash, and the macro morphology of ash samples was collected by a high-speed camera. The results showed that the volume shrinkage of densified biofuel ash was less with the attapulgite clay addition than that without, while the SEM spectrum of biomass ash for micro morphology showed that the small ash particles were evenly distributed without agglomeration when the amount of attapulgite clay addition was more than 3%. Thirdly, the composition of biomass ash was identified by XRF and XRD, in order to clarify the anti-slagging mechanism of attapulgite clay. The organic potassium in the biomass was volatilized to the gas phase in the form of K at the temperature of 200-500 ℃ during heating. It is found that during the heating process, with a temperature of 200-500 ℃, the organic potassium in biomass was volatilized to the gas phase in the form of K, which was adsorbed by attapulgite clay. when the temperature reached 900 ℃,the release of K reached the maximum, and the XRD patterns of all ash samples at 2θ=8.57°, 12.56°, 19.59°, and 32.7° were showed no characteristic peak of attapulgite clay, indicating that the crystal structure of attapulgite clay has completely collapsed,as a result,the released K element mainly from biomass and Mg, Al and Si elements mainly from attapulgite clay formed more high melting point double salts such as KAlSiO4, KAlSi2O6 , Ca2Mg(Si2O7). Therefore, the attapulgite clay changed the migration path of the K element to reconstruct the slagging mechanism of densified biofuel ash, thereby improving the anti-slagging performence of densified biofuel. In addition, there was a relatively low cost of attapulgite clay as an anti-slagging agent for the densified biofuel. The optimal amount of attapulgite clay was 3% addition.
    2022,38(6):236-243, DOI: 10.11975/j.issn.1002-6819.2022.06.027
    Abstract:
    Abstract: Torrefaction has been one of the most significant steps to improve the biomass-based fuel quality. Rice husk has been widely used as typical agricultural biomass, due to a large annual yield in China. It is of great significance to explore the effect of dry/wet torrefaction on biomass pyrolysis and combustion reaction characteristics. In this study, the dry/wet torrefaction pretreatment of rice husk was carried out at various temperatures (200, 250, and 300 ℃; 180, 200, and 220 ℃) in the fixed bed and high-pressure reactor, where the starting temperature was room temperature, and the heating rate was 10 ℃/min. The proximate and ultimate analysis of samples was then conducted by the infrared fast coal quality analyzer (5E-MAG6700) and element analyzer (Vario MACRO), respectively. The Thermogravimetric Analyzer (TGA) was selected for the non-isothermal (room temperature to 800 ℃, 20 ℃/min) combustion of rice husk, rice husk torrefied char, and rice husk hydrochar. Moreover, the kinetics analysis of pyrolysis and combustion of samples were also conducted with the Coats?Redfern method and three common gas-solid reaction mechanism models (first-order model O1, phase boundary controlled reaction model R2 and R3). An evaluation was made on the effects of dry/wet torrefaction on the pyrolysis and combustion characteristics of rice husk. The results show that the dry/wet torrefaction increased the ash, fixed carbon, and carbon content of raw materials, while decreasing the volatile, hydrogen, and oxygen content. van Krevelen diagram displayed that the dry/wet torrefaction pretreatment behaved essentially like the process of dehydration and decarboxylation of raw materials, where the rice husk torrefied char at 300 ℃ (RT-300) was the most significant. Both pretreatments dominated the pyrolysis and combustion reaction parameters of rice husk, leading to the reduction in the pyrolysis reactivity. Dry torrefaction improved the combustion reactivity of rice husk, particularly with the temperature (200-300 ℃) rising. But the wet torrefaction slightly reduced the combustion reactivity of rice husk. The rice husk torrefied char presented a higher temperature of initial weight loss, a lower maximum rate of weight loss, the corresponding temperature and reactivity than the rice husk hydrochar during pyrolysis at 200 ℃. Moreover, the rice husk torrefied char behaved with the lower final temperature of combustion and the maximum rate of weight loss corresponding to temperature, while the higher maximum rate of weight loss and reactivity, compared with the rice husk hydrochar. Interestingly, the linear regression index of model O1 was higher than that of the other two models for the pyrolysis and combustion reactivity of rice husk, rice husk torrefied char and rice husk hydrochar (the regression indexes were all above 0.95). The dry/wet torrefaction increased the pyrolysis activation energy of rice husk, whereas, the wet torrefaction decreased the combustion activation energy. Moreover, the pre-exponential factor of the samples in the two stages increased with an outstanding linear relationship, as the activation energy increased, indicating the kinetic compensation effect between pre-exponential factor and activation energy during combustion. The rice husk torrefied char had a lower pyrolysis activation energy and a higher pre-exponential factor than the rice husk hydrochar at the pretreatment temperature of 200 ℃. In addition, the higher activation energy of combustion and the lower pre-exponential factor were achieved in the rice husk torrefied char, compared with the rice husk hydrochar.
    2022,38(6):244-253, DOI: 10.11975/j.issn.1002-6819.2022.06.028
    Abstract:
    Abstract: Energy power generation has been widely used in the field of renewable energy. Only a small part of the energy can be converted into electrical energy during photovoltaic power generation, most of which is lost in the form of thermal for the great wastes. A photovoltaic and thermoelectric sysplex can be expected to combine the thermopiles using waste heat on the surface of photovoltaic cells, in order to improve the output power of power generation. However, there is uneven heat absorption of thermopiles in the process of heating. The local shadow shading on the photovoltaic cells can cause the unstable output characteristics of temperature difference, leading to the less output power of the combined power generation system. The micro heatpipe can be equipped as the heat conduction element in the temperature control device for the even heating of the thermoelectric system in the photo-thermal combined power generation module. In this study, the simulation model and test platform were built to evaluate the performance of the micro heat-pipe element, in terms of the heat transfer and output power. A chaotic quantum behavior particle swarm optimization with the linear decreasing type, and the incremental conductance of variable step-size were used as the control strategies of photovoltaic and thermoelectric systems, respectively. Ten photovoltaic cells were connected in series in MATLAB software, in order to clarify the influence of different shading areas on the output power. The different light intensities were also set to simulate the shading of shadows. The temperature was selected as the evaluation index of the heat transfer during the light-heat conversion in the whole system. The photovoltaic cell with the power of 25 W and the thermopiles with the model of sp1848-27145 were adopted as the power generation elements of the coupling system for the test platform. The number of temperature difference plates was set as 90, according to the size of a 25 W photovoltaic cell. Every 10 plates was connected in series as a group, and then the nine groups of plates were connected in parallel. The output power of photovoltaic and thermoelectric cells was calculated to evaluate their output voltage and current. The photo-thermal sysplex was measured without/with the temperature control device when the areas of shadow shielded photovoltaic panel were 10%, 30%, and 50%. The results were achieved as follows. The micro heatpipe efficiently absorbed the heat from the photovoltaic surface for the reduced temperature of the photovoltaic cell during the power generation, due to the uneven temperature of photovoltaic cells in the shadow area. The simulation indicated that there was the smallest loss of output photovoltaic power when the area of shielding photovoltaic was 10%. The photo-thermal coupling system with a temperature control device greatly enhanced the heat absorption capacity than before. The temperature control devices were optimized to simulate the local shadow by artificial shielding at the hot and cold ends. An optimal combination was achieved, where the heat flow rate at the hot port was 0.0124 m/s when the area of photovoltaic shielding was 10%, the average output power of thermoelectric increased by 1.92% when the water velocity at the cold end was 0.0135 m/s. The average temperature difference with/without the shaded areas of the photovoltaic cell was about 274.15 K. Consequently, an approximately balanced temperature of the photovoltaic cell was realized, where the average output power of photovoltaic increased by 18.79% than before.
    2022,38(6):254-263, DOI: 10.11975/j.issn.1002-6819.2022.06.029
    Abstract:
    Abstract: Eco-compensation can be a tradeoff between the intensity of cultivated land protection and economic profits among regions, as the center of gravity of cultivated land area moves northward, like "large cultivated land county, small economic county" and "large grain county, poor financial county". The concept of "Payments for Environmental Services" was introduced in China, providing a new perspective on cultivated land protection. However, a complete system has not been established, in terms of the subject and object determination, compensation standard, procedure, funding source and supervision measures of cultivated land eco-compensation. It is very necessary to demarcate the payment/compensation zones, and then quantify the compensation standards in the cultivated land eco-compensation system, in order to better balance the relationship between the spatial transfer of cultivated land ecological carrying capacity (CLECC) and ecological equity. In this study, a differential zoning of "four quadrants" was constructed, according to the surplus and deficit of CLECC with the target of cultivated land retention in the provinces. Then, the opportunity cost was applied to evaluate the payment/compensation standard and optimal amount in total for the decision-making. The results show that: 1) According to the shadow number of cultivated land by the province in 2019, 17 and 14 provinces were characterized by the deficit and surplus zone of CLECC, respectively, indicating a spatial difference of "surplus in north and deficit in the south". About 23.21% of the ecosystem services of cultivated land were transferred from the surplus to the deficit zone. 2) The payment/compensation zone presented a spatial pattern of "strip-interspersed" from the northeast to the southwest. The full-compensation zone was mainly distributed in the provinces of cultivated land areas (8 provincial administrative regions). The reduced-compensation zone was mainly located in the central and Eastern Plains (6 provincial administrative regions). The full-payment zone was mostly located in the eastern coastal developed regions (5 provincial administrative regions). The reduced-payment zone was mainly distributed in the Loess Plateau, the Sichuan Basin, and the Qinghai-Tibet Plateau (12 provincial administrative regions). 3) The average payment/compensation standard decreased gradually from the full-payment to the full-compensation zone, indicating the optimal values of 6.13×104 yuan/hm2 in total. 4) Specifically, Heilongjiang Province received compensation of about 168.3 billion yuan at most, and Jiangxi Province received about 1.45 billion yuan at less. Zhejiang Province was paid for 215.1 billion yuan at most, and Gansu Province paid for 3.08 billion yuan at less. Lorenz Curve was selected to verify that the fiscal revenue gap between provinces was reduced by 0.06 under the cultivated land eco-compensation. The innovative system can be widely expected to stimulate the behavior of environmental protection for the sustainable development of cultivated land in the form of monetary quantity. To sum up, the cultivated land eco-compensation can be connected with the ecological compensation and cultivated land protection policies, particularly for the better interactive relationship between cultivated land eco-protectors benefiting and beneficiaries paying. The finding can provide a strong reference to improve the local cultivated land protection.
    2022,38(6):264-273, DOI: 10.11975/j.issn.1002-6819.2022.06.030
    Abstract:
    Abstract: The contradictions between land production, living, and ecological functions have gradually emerged, as industrialization and urbanization continue to advance. It is necessary to accurately allocate and coordinate the functions of land development and protection for the reasonable distribution of human activities in sustainable agriculture. This study aims to explore the spatiotemporal characteristics of trade-offs/synergies in the land use functions and the influencing factors. Taking Hangzhou City of China as an example, an attempt was made to evaluate the land production, living and ecological functions at the fine scale from 2000 to 2018 using the multi-source data and a series of geospatial models. Then, the correlation analysis was used to reveal the trade-offs/synergies of land use functions at the global and grid scales. The influencing factors of land use function trade-offs/synergies were also identified by the linear regression model. The results showed that: (1) The living function showed a trade-off relationship with the production and ecological function between 2000 and 2018, whereas the trade-off intensity of production and living functions was stronger than that of living and ecological functions. Production and ecological functions were established to determine a synergistic relationship during the study period. There was a trend of increasing first and then decreasing in the trade-off relationship between production and living functions, where the trade-offs of living and ecological functions gradually weakened. The interactive relationship between production and ecological functions was shifted from a synergistic relationship in 2000-2005 to a trade-off relationship in 2015-2018. (2) Spatially, the production-living function was dominated by strong trade-off and production-weakening trade-off, where the trade-off intensity tended to weaken from the east to the west and from the central to the periphery. The areas with a synergy state were located in the low-altitude mountain of central and western Hangzhou. The production-ecological function presented a mixed pattern of trade-off and synergy areas in space. The trade-off areas accounted for about 31%, with the weak trade-off and production-weakening trade-offs, mainly distributed in northern and eastern Hangzhou. The synergy areas occupied about 38%, with the weak synergy and simultaneous improving synergy, mainly distributed in the western and southern Hangzhou. The living-ecological function was dominated by the weak trade-off and ecology-weakening trade-off. The trade-off area accounts for 14%, where the trade-off intensity showed a trend of high in the east and low in the west, gradually decreasing from the center to the edge. The synergy relationship was dominated by weak synergy and simultaneous weakening synergy, the synergy areas accounted for 8%, mainly scattered in the outer suburbs. (3) Natural conditions and geographical location posed significant negative effects on the trade-offs/synergies in production-living and living-ecological functions, whereas there were significant positive effects on production-ecological function trade-offs/synergies. The urbanization-induced land conversion and the increase of land-use intensity further aggravated the trade-offs in land use functions. Therefore, there were different trade-offs/synergies in the land use functions at global and grid scales. The overall characteristics and local differences can be fully considered in the decision-making on land use function, according to the local conditions.
    2022,38(6):274-282, DOI: 10.11975/j.issn.1002-6819.2022.06.031
    Abstract:
    Abstract: Taking the cultivated land in the Xinbei district of Changzhou City in Jiangsu Province of China as the research object, an evaluation model was constructed for the patch-scale arable land fragmentation using the integrated functional zoning and regional clustering. Taking the cultivated land patch as the basic unit, some indicators were firstly selected, including the patch area, contiguous degree, and shape index. A spatial analysis was conducted to calculate the indicators, such as aggregation in ArcGIS 10.6. Secondly, the area weighting was used to expand the patch index to the area with the administrative village as the unit, where the Getis-Ord Gi* was further used to identify the cold and hot areas of each index for the degree of regional fragmentation. Thirdly, the research area was divided into functional zones using two-step clustering, where the administrative villages with neighboring geographical locations and similar fragmentation attributes were clustered into one zone. Finally, the Python-based Sklearn library was selected to implement the K-means clustering with the silhouette measure. The silhouette measure was introduced to determine the optimal number of clusters and the best clustering. The clustering data was then used to evaluate the degree of fragmentation of the cultivated land. The results showed that: 1) There were the insignificant area, continuous regular areas, and discrete complex zone, according to the clustering data of functional zoning. 2) The cultivated land patches were classified into three categories: Category 1, the number of patches was 17 332, the average area of patches was too small, the degree of continuity was low, the area of patch was concentrated in 0-10 000 m2, the area accounted for 21.98%, and the contiguous degree was concentrated in 1-4, mainly distributed in the central area; Category 2, the number of patches was 4 535, the complex and irregular shape of patches, the area accounts for 9.65%, the shape index was concentrated in 1.5-2.5, evenly distributed in the whole area; Category 3, the number of patches was 4 091, the patches were concentrated and regular, where the area accounted for 68.37%, the contiguous degree were concentrated in 5-10, and the shape index was concentrated in 1-1.5, mainly distributed in the peripheral area. Some consolidation suggestions were proposed, according to the fine fragmentation attributes of different categories of cultivated land. A fragmentation model of patch-scale arable land was constructed using the integrated multi-clusters and functional zoning. The index was applied for the landscape pattern indicator to the vector patch scale. There was no need to assign the weight to various indicators during clustering. The regional fragmentation degree was utilized for the specific fragmentation pattern within the region. The model can quickly, intelligently, and low-costly evaluate the fragmented cultivated land patches, which is conducive to further planning and consolidation. The model can be expected to fast, intelligently, and low-costly evaluate the finely divided farming patches for further planning and improvement. This finding can provide a strong reference to improve the evaluation of cultivated land fragmentation.
    2022,38(6):283-292, DOI: 10.11975/j.issn.1002-6819.2022.06.032
    Abstract:
    Abstract: Surface defects have posed a negative impact on the quality and yield in the process of tomato growth. A post-natal grading treatment can normally be utilized before tomato marketing. It is necessary to accurately and rapidly detect the defective tomato in the process of post-natal grading. In this study, a real-time detection was proposed for the tomato surface defects using YOLOv4 model pruning. A diffuse light box was used to improve the acquisition system. High resolution images of tomatoes were then acquired to reduce the reflection of tomato surface under the direct exposure. Parallel computing and images combination were also selected for the high speed of image processing. The input images of the YOLOv4 network were generated to stitch the RGB images collected from three continuous detection stations. In addition, the channel pruning was selected to simplify the network parameters and structure in the YOLOv4 network model. There were a complex network structure and a large number of parameters in the original YOLOv4, leading to too large calculation and low inference speed of the model. The layer pruning was also used to further compress the depth of the network model on the basis of compressing the network width, in order to improve the detection speed for the real-time detection. A non-maximum suppression with the L1 norm was proposed to remove the redundant prediction box after fine-tuning network model, thereby accurately locating the defect location in the images. The detection performance of the improved model was evaluated using the YOLOv4 training data at the pruning rates under various target detection models. The maximum Mean Average Precision (mAP) value was taken as the pruning rate, indicating the minimum model size and inference time for the requirements of real-time performance. Therefore, the channel pruning rate of the YOLOv4 network was finally set to 80%, where the obtained model was named YOLOv4P. The YOLOv3, YOLOv4, YOLOv4-tiny, YOLOv4PC, and YOLOv4P models were compared to verify the performance of the detection model for the tomato defects. The results showed that the model pruning compression technology can effectively improve the detection speed at the lowest cost of accuracy. The real-time grading system was tested on the tomato experiment data set, including the stem, calyx, and defect types. The improved YOLOv4P network reduced the model size and reasoning time by 232.40 MB and 10.11 ms, respectively, compared with the original YOLOv4 network. In conclusion, the highest mAP and the fastest detection speed were achieved to detect the tomato surface defects using the improved model. The mAP increased from 92.45% to 94.56%, fully meeting the requirements of accurate and real-time detection. The finding can also provide an efficient online detection for the tomato real-time grading system.
    2022,38(6):293-301, DOI: 10.11975/j.issn.1002-6819.2022.06.033
    Abstract:
    Abstract: The presence or absence of an embryo can pose a strong relation with the germination-rate of ginkgo seeds, together with the development status. Unfortunately, neither has been discerned via manual observation without dissection so far. In this study, a non-invasive classification of ginkgo seeds under these internal conditions was explored using deep learning on the low-field magnetic resonance (LF-MR) images. A dataset of four classes was collected, including embryo-present, embryo-absent, normal, and aperture seeds. Each of 1 200 images was sized 32×32 pixels using the LF-MR imaging of 6 000 ginkgo seeds and then categorized according to the dissection evidence. An improved Very Deep Convolutional (VGG-16) network was designed for the ginkgo seed classification (Ginkgo seed LF-MR images recognition model adapted from VGG-Net, or global view (GV)) to classify the LF-MR images, according to whether the presence or absence of embryo in the sagittal plane, or whether the seeds being normal or decayed judging from the coronal plane. The GV reused the convolutional layers of VGG-16 to replace the fully connected (FC) layers with a structural redesign, including a global average pooling layer followed by an FC layer. Compared with the VGG-16, the GV was reduced by 89%, 89%, 64%, 64%, and 45%, respectively, in the size and number of parameters, training time, training loss, and validation loss, indicating an improved accuracy in both training and validation by 2.4 and 2.5 percentage points, respectively. The classification accuracy of ginkgo seed LF-MR images reached 97.40%, and the precision, recall, and F1-score were all above 95%. The reliable detection of internal defects offered a non-invasive approach to identify those ginkgo seeds that cannot germinate. Positive experiences of redesigning and tuning deep learning networks were also gained to classify the LF-MR images, according to the internal defects of ginkgo seeds during the development of GV. At first, the super parameters of both learning rate and update period were determined to perform a transfer-learning of VGG-16 for the LF-MR images classification of ginkgo seeds. Then, a pool of eight candidate structural adaptations was built to test, branching out from the convolutional layers of VGG-16, where two candidates used the FC layers with 3 layers of 512, 512, and 4 neurons, or 2 layers of 512 and 4 neurons, another two candidates used the global convolution (g-conv) layers with 3 layers of 512, 512, and 4 kernels, or 2 layers of 512 and 4 kernels, and the rest 4 candidates adding a further global average pooling (GAP) layer in front of or behind an FC layer with 4 neurons or a g-conv layer with 4 kernels. Last, the candidate that yielded the best accuracy with the minimal size, number of parameters, and loss was equipped with three different normalizations, i.e., the local response normalization (LRN), batch normalization (BN), and group normalization (GN), further to improve the accuracy and training speed. The results show that the GAP layer followed by a single FC layer can best fuse the features passing down from the convolutional layers, compared with the multilayered FC or g-conv layers, significantly reducing the size and the number of parameters by over 89%, still with the improved accuracy. The highest accuracy was achieved at 98.02% out of the 8 fine-tuned models with the classification layer placed after GAP. Therefore, it was deemed as the GV. The GN, being not affected by the batch size, can make the validation converge more stably and further push the validation accuracy to 98.54%, when added after the convolutional modules. Since the learning rate has a great impact on the performance of the transfer learning model, it is necessary to choose a suitable initial value and a segmented constant decay strategy for the specific applications, which can effectively improve the model performance. The model proposed a novel idea for non-destructive monitoring of Ginkgo biloba seed germination and accurate prediction of germination rate after sowing.
    2022,38(6):302-311, DOI: 10.11975/j.issn.1002-6819.2022.06.034
    Abstract:
    Abstract: Soybean oil has been one of the most consumed cooking oil extracted from the seeds of the soybean. Aqueous and enzymatic processes can be widely expected for edible oil extraction in recent years. In this study, a series of numerical simulations were carried out to determine the optimum parameters for the aqueous and enzymatic oil extraction from a magnetic fluidized bed under the OpenFOAM software, in order to improve the oil quality, yield, and extraction rate of soybean. The free cellulase was also immobilized on a magnetic polymer carrier Fe3O4/SiOx-g-P (GMA) using the glutaraldehyde cross-linking protocols. The carrier was prepared using ethyl orthosilicate and 3-aminopropyl triethoxy, while, the Fe3O4 nanoparticles were modified by silane. The magnetically immobilized cellulase with the better magnetic response was obtained for the subsequent flow of magnetizing application in the fluidized bed and the separation after the reaction. Scanning electron microscopy (SEM) images showed that the rough and uneven surface of the carriers significantly increased the surface area of the magnetically immobilized cellulase for the better adsorption of the enzyme. The particle size analysis and SEM images revealed that the particle size of magnetically immobilized cellulase was outstandingly enlarged with a more uniform morphology, compared with the carrier. Correspondingly, Fourier infrared spectroscopy (FIS) verified that the magnetically immobilized cellulase was immobilized on the polymer carrier Fe3O4/SiOx-g-P (GMA). The enzymatic properties of the immobilized cellulase and the free enzyme were evaluated to determine the optimum pH (5) and temperature (60 ℃) of the immobilized cellulase, indicating that the higher heat, acid, and alkali resistance of the cellulose than before immobilization. The discrete element method (DEM) was used to construct a two-dimensional numerical model of nano-magnetase particles. The OpenFOAM software was selected to obtain the best parameters of hydroenzymatic oil extraction in a magnetic fluidized bed. An optimal combination was achieved for the magnetase with the fluidized state in the fluidized bed, the maximum reaction contact surface, and the maximum oil extraction rate, where the fluid flow rate was 0.0041m/s, and the magnetic field strength was 0.034 T. The instantaneous distribution and speed of the magnetase motion were also measured to clarify the influence of the magnetic field intensity on the magnetase motion trajectory. These optimal parameters were then applied to the circulating magnetic fluidized bed for the water-enzymatic extraction of oil. In addition, a single factor experiment was conducted to optimize the processing parameters for the oil extraction from the magnetic fluidized bed. Specific parameters were gained for the highest extraction rate of soybean oil, where the addition amount of magnetically immobilized cellulase was 1.2 mg/g, the pH value was 5, and the temperature was 55 ℃, and the reaction time was 120 min. The rate of oil extraction from the magneto-fluidized bed increased by 6.1%, compared with the conventional intermittent reaction. Magnetically immobilized cellulase was used continuously in a magnetic fluidized bed for 12 hours, where the magnetase activity remained above 80%. The finding can provide the basic theoretical support for the environmental performance of the oil process, particularly for the subsequent industrialization of enzymatic oil extraction from the magnetic fluidized bed in the vegetable oil industry.
    2022,38(6):312-318, DOI: 10.11975/j.issn.1002-6819.2022.06.035
    Abstract:
    Abstract: Low-temperature refrigeration has been commonly used for post-harvest storage and preservation of fruits. But the long-term low-temperature storage can lead to the browning peel of Huangguan pear, or even be detrimental to the fruit quality. Alternatively, ethylene can serve as an endogenous hormone to regulate plant growth and development, whether fruit ripening or the stress resistance of plants. In this study, the slow release of exogenous ethylene with different concentrations was selected to treat the Huangguan pear fruits before storage, in order to explore the effects on the peel browning and quality during the subsequent shelf life. Three ethylene concentrations were produced in the same volume of closed space: 5, 20, and 100 μL/L. The control group was taken as the Huangguan pears with the rapid cooling at 0 ℃ and without the exogenous ethylene treatment. The low-temperature treatment group was set: the Huangguan pears after harvesting was immediately treated by cooling to 0 ℃, where the temperature was kept at 30 ℃and decreased by 1 ℃ every day for 30 days. Some indicators of fruit quality were then measured, including the water content, disease incidence, soluble solids, soluble sugar, titratable acid, and ascorbic acid. The performance of postharvest exogenous ethylene treatment was evaluated on the fruit quality, in order to avoid the occurrence of browning of the fruit peel under low-temperature storage (about 0℃). The results showed that the different concentrations of exogenous ethylene treatments completely inhibited the occurrence of browning of the peel of Huangguan pear, where there were no signs of damage on the epidermis. The incidence indexes were 10% and 37.6% for the low-temperature condition treatment and the control, respectively. At the end of the shelf life (6 d), the fruit firmness of the exogenous ethylene treatment group was significantly different from that of the control group (P < 0.05). The water content of fruits in the three different concentrations of exogenous ethylene treatment groups were higher than those in the control and low temperature condition treatment (P < 0.05), which maintained the excellent taste of Huangguan pear. A low-field nuclear magnetic resonance (NMR) showed that there was a lower free water content of the 5 and 100 μL/L exogenous ethylene treatment groups, compared with the control. It infers that the low free water content reduced the incidence rate of peel browning. The exogenous ethylene treatment maintained the content of soluble solids in Huangguan pear fruit. Exogenous ethylene treatment improved the fruit quality indicators, such as the titratable acid, soluble sugar, and ascorbic acid in the Huangguan pear fruits, indicating the better sensory quality of pear fruit. Among them, the treatment was performed better at the concentration of 5 μL/L. The exogenous ethylene treatment before storage can serve as an efficient and simple technology to inhibit the browning of Huangguan pear peel for a better shelf-life quality of fruits.
    2022,38(6):319-329, DOI: 10.11975/j.issn.1002-6819.2022.06.036
    Abstract:
    Abstract: Lipase or lipase-producing lactic acid bacteria can be usually added to the cheese production process, in order to improve the sensory and flavor quality of cheese products. Taking the Xinjiang traditional cheese as the research object, this study aims to investigate the effects of lipase-producing lactic acid bacteria on the fatty acid and flavor of the cheese. Four strains of lipase-producing lactic acid bacteria (T1-5 and T1-3 are Weissella fusion, H1-6 is Lactobacillus helveticus, B2-5 is Lactobacillus plantarum) were selected in the previous stage of the experiment as a starter. Three strains were selected as the Lactic acid bacteria compounding for the yogurt cheese, according to the traditional technology. Experimental groups were: Group A T1-5 and T1-3, H1-6 (1:1:1), Group B H1-6, T1-5, B2-5 (1:1:1), Group C H1-6, T1-3, B2-5 (1:1:1), D group T1-3, T1-5, B2-5 (1:1:1); control group (group E): commercial starter. The physicochemical properties of the fermented and matured cheese were then characterized to clarify the effects of lipase-producing lactic acid bacteria on the cheese pH, titer acidity, and fat oxidation indicators. Gas chromatography (GC) was used to detect the fatty acid in the cheese, and gas chromatography-ion mobility spectrometry (GC-IMS) was used to identify the flavor substances in the cheese variety. The results showed that the pH and peroxide values of the cheeses in the four groups A, B, C, and D were significantly lower than those in the E group (control group) (P<0.05), whereas, the cheese titer values in the A and B groups were higher than those in the control E group. (P<0.05). There was no significant difference in the TBARS value between the five groups of cheese (P> 0.05). The contents of saturated fatty acid, monounsaturated fatty acid, and polyunsaturated fatty acid of the cheeses in groups A, B, C, and D were significantly higher than those in group E (P<0.05). The higher saturated fatty acids in the experimental group cheese were the meat Myristic acid (C14:0), palmitic acid (C16:0) and stearic acid (C18:0), as well as butyric acid (C4:0), caproic acid (C6:0), capric acid (C10:0) and Lauric acid (C12:0). The oleic acid (C18:1n9c) in the experimental group cheese was the main component of monounsaturated fatty acids. The linoleic acid (C18:2n6c) in the experimental group cheese was significantly higher than the control group (group E) (P<0.05). The GC-IMS and principal component analysis show that there were many types of volatile flavor compounds in group A and B cheese, indicating the high similarity. Aldehydes and esters were the main volatile flavor substances in the cheese, among which the 2-heptanone content of butyl aldehyde and butyl acetate was relatively high. There were relatively similar flavor substances in the two groups of cheeses C and E. The main volatile flavor substances in Group D were butyl acetate, 3-octanone, and heptanal, indicating a different fragrance from the others. Therefore, there were a better overall flavor and taste of A and B cheeses after the sensory evaluation, indicating the higher scores than the others. The screened lipase-producing lactic acid bacteria can be expected to serve as a starter to improve the quality of traditional Xinjiang cheese.
    2022,38(6):330-336, DOI: 10.11975/j.issn.1002-6819.2022.06.037
    Abstract:
    Abstract: Cosmic ray neutron flux measurements have emerged for the soil water content in many fields in recent years. According to the count of the cosmic ray neutrons above the ground scattered by the soil, the detection depth is very sensitive to the soil water content, atmospheric pressure, and hydrogen-containing substances on the surface. In this study, a novel approach was proposed to monitor the soil moisture using cosmic ray muons with a higher average energy (about 3GeV). The water content of the soil was inferred from the muon count of the detector. The depth of detection was improved to minimize the influence of surface environmental factors on the measurement, compared with the cosmic ray fast neutron. A CRY program was used to generate the energy and angular distributions of cosmic ray muons at sea level. A Monte-Carlo program (FLUKA) was selected to construct the soil model with the different moisture. The transportation process of cosmic ray muons in soil was simulated to determine the relationship between the muon count of the detector in the soil and the average water content of the soil above the detector. The soil was equally divided into the upper and lower layers with a total thickness of 80 cm in the model. The moisture of the upper layer of soil varied from 0.05 to 0.5 cm3/cm3, while the water content of the lower layer was maintained at 0.5 cm3/cm3. The variation of the upper layer's moisture was simulated with the FLUKA program. The results showed that the count of the detector was a linear function of the soil water content. The detection resolution of the soil moisture was inversely proportional to the square root of detecting time, which reached 0.1 and 0.05 cm3/cm3, when the detection time was 2 and 8 h, respectively, particularly with the placement depth of the detector of 80 cm. Furthermore, the situations of the water content of the upper soil varied from 0.1 to 0.5 with the placement depth of the detector (from 60 to 120 cm), and the sensitive radius of the soil model (from 5 to 8.5 m) were simulated with FLUKA, indicating that the detection resolution also varied in the detection time at various placement depths. The highest resolution accuracy (0.038 cm3/cm3) of soil water content was achieved at the placement depth of 90 cm under the same duration. Another identical detector was required on the soil surface to monitor the cosmic ray muon flux reaching the surface in practical measurements, in order to correct for the effect of atmospheric factors on the muon count of the detector placed in the soil. Correspondingly, an experiment was performed which suggested that the muon event count can be an indicator of the mass thickness, and the soil density. In summary, the cosmic ray muons can be widely expected to monitor the soil moisture with a moderate and flexible detection range without radioactive hazards.
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    May 23, 2022 , DOI:
    Abstract:
    In order to monitor the soil quality of the cultivated land in different subsidence stages of the coal mining area,and to realize the land reclamation and quality protection of the cultivated land in the mining area, three types of cultivated land in different subsidence stages around Wangzhuang Coal mine in Changzhi city, Shanxi Province were taken as examples. The images were acquired by a UAV equipped with a hyperspectral camera, and soil sample collection and indoor spectrometry were carried out in the study area. By performing four different transformations of spectral reflectance, including reciprocal, first-order differential, second-order differential and multivariate scattering correction, the correlation between the converted spectral reflectance and measured organic matter content is analyzed, and sensitive bands with higher correlation coefficient were selected. Three models of multiple linear regression (MLR) , partial least squares regression (PLSR) and BP neural network (BPNN) were used to establish a prediction model for organic matter content, and the accuracy of the prediction results of the model was evaluated. The optimal model was used to map the organic matter content in UAV aerial hyperspectral images to obtain the distribution of organic matter in cultivated land range, and the spatial differences and driving factors of organic matter in different subsidence stages of cultivated land were analyzed and discussed. The results show that : 1)The sensitive bands of organic matter content of cultivated land in coal mining subsidence area mainly focus on the bands of 400~600 nm in visible light and 800~900 nm in near infrared. The spectral curve transformed by the multivariate scattering correction has the highest correlation with the organic matter content. 2) For the spectral curve information processed by multiple scattering correction,the accuracy of the prediction model of organic matter content established by the partial least squares regression model and the bp neural network model is significantly higher than that of the multiple linear regression model, and the prediction accuracy reaches 0.863 and 0.884 respectively, which can be used for the identification of organic matter content. 3)The distribution of organic matter in cultivated land in coal mining subsidence areas shows that the distribution of soil organic matter in the undisturbed area of coal mining is relatively uniform, with an average value of 26.54 g/kg, which is in the upper middle level in general. The overall distribution of soil organic matter in the disturbed and stable subsidence area of coal mining shows great spatial heterogeneity, and the differentiation of high and low values is obvious, with a proportion from grade 1 to grade 6. The disturbed area of coal mining is between the above two. The relationship of organic matter content in mining area is as follows: cultivated land in undisturbed area of coal mining > cultivated land in disturbed area of coal mining > cultivated land in disturbed and settled area of coal mining. This is caused by surface deformation, physical and chemical properties of soil, changes in vegetation and human management before and after coal mining.
    May 23, 2022 , DOI:
    Abstract:
    In order to explore the spatial position and strategic management of paddy field planting and breeding under the requirements of industrialization development, this paper took Jiangsu province as the study area, constructed a quantitative evaluation index system from two dimensions of natural suitability and industrial dominance respectively, comprehensively evaluated the spatial priority of paddy field planting and breeding industrialization development, and put forward the policy guidance of zoning. Based on the comprehensive rating results of natural factors such as water source, soil and terrain, the area highly suitable for paddy field development accounted for 13.8% of the total paddy field in Jiangsu province, and the area moderately suitable for paddy field development accounted for 57.0%. The high value of natural suitability was mainly distributed in Lixia River area and extended to the main irrigation canal in northern Jiangsu province, and the eastern coastal plain to the south of the Yangtze River and the Tai Lake plain to the south. Based on the comprehensive rating of labor force, infrastructure, soft environment and other aspects, the results show that the industrial superiority degree in the north of Jiangsu province is high and low, and the high value of industrial superiority degree in the south of Jiangsu province is mainly distributed in the suburban counties adjacent to Shanghai and Nanjing. Based on the coupling analysis of the spatial rating results of two dimensions based on county units, the paddy field planting and breeding was divided into four types of space, and the industrialization development strategies of paddy field planting and breeding were put forward according to the directions of key development, moderate support, optimization and adjustment, and controlled development. This study can provide a reference for improving the efficiency of paddy field resource development and high quality development of paddy field planting and breeding industry.
    May 23, 2022 , DOI:
    Abstract:
    Moni toring the crop water stress index (CWSI) is of great significance for the water status and irrigation in crop production. Taking the Chinese Brassica as the test object, this study aims to measure the canopy temperature under different soil moisture conditions. Some meteorological parameters were collected, including the air temperature, relative humidity, wind speed, and photosynthetic active radiation. Meanwhile, the images of spectral reflectance were also collected for the four bands (450, 650, 808, and 940nm). Four vegetation indexes were then calculated by the canopy spectral reflectance, including the normalized difference vegetation index (NDVI), difference vegetation index (DVI), re-difference vegetation index (RDVI), and optimized soil-adjusted vegetation index (OSAVI). Support vector regression (SVR) was selected to construct the inversion models of the CWSI upper/lower baseline using the meteorological parameters, and the inversion models of the canopy temperature using the vegetation index. The results showed that the canopy spectral reflectance at 450 and 650nm for the Chinese Brassica was ranged from 0.0 to 0.1, while the relatively higher one at 808nm and 940nm was ranged from 0.4 to 0.6. The reflectance at 808nm and 940 nm increased outstandingly, when the Chinese Brassica was developed gradually from the vegetative to reproductive growth stage. The vegetation index reflected the growth state and vegetation coverage of the Chinese Brassica. There was the different response of vegetation indexes to the canopy temperature. The vegetation NDVI, DVI and RDVI increased, while the vegetation OSAVI decreased with the increasing of the canopy temperature of the Chinese Brassica. The vegetation index under the same water treatment was slightly different in the various growth stages. Specifically, the range of the vegetation index in the reproductive growth stage was smaller than that in the vegetative growth stage. The error analysis showed that the inversion models was feasible to monitor the air temperature, relative humidity, wind speed, and photosynthetic radiation, further to invert the upper/lower baseline of CWSI with the determination coefficient greater than 0.75. In the light of the error analysis of the inversion models, the vegetation index was inverted the canopy temperature of the Chinese Brassica in the vegetative and reproductive growth stage, indicating an excellent accuracy with the determination coefficient greater than 0.7. The calculated CWSI using the inversion models presented a significant correlation with that using the measurement, while the correlation coefficient equal to 0.70. And the CWSI showed the negative relationship with the stomatal conductance with the correlation coefficient equal to 0.53. The meteorological parameters were used to invert the upper/lower baseline of CWSI, where the vegetation indexes were used to invert the canopy temperature. The inverted values using the SVR model shared the better fitting performance. The finding can provide a strong support for the spectral monitoring the crop water stress index of the Chinese Brassica.
    May 18, 2022 , DOI:
    Abstract:
    It is crucial to analyze the evolution of the water cycle in the plain area by scientifically understanding the runoff generation patterns under the action of field ridges. The relationship between rainfall characteristics ~ ridge height ~ farmland runoff generation is not clear, which is the weak link in the analysis of water cycle evolution in plain areas. This study analyzed the rainfall event characterization of the Haihe Plain based on CMOPRH remote sensing precipitation data products. And the Smith & Parlange infiltration model was used as the core to construct a water flow model for farmland accumulation and simulate the rainfall~ runoff generation process in the Haihe Plain. The results are as follows: (1) The total amount of rainfall events in the Haihe Plain is mainly less than 25mm, accounting for 95% of the total rainfall events, and 96% of the rainfall events in the field within 10 hours, with the total amount of rainfall and rainfall intensity decreasing from the northeast to the northwest. (2) Under the rainfall conditions from 2008 to 2019, the average annual runoff generation of farmland under four scenarios of no ridge, 10cm ridge, 12cm ridge, and 15cm ridge were simulated. The results are 6.24 billion m3/year, 1.97 billion m3/year, 1.31 billion m3/year, and 0.5 billion m3/year, respectively. (3) Under the condition that the height of the ridge is determined, rainfall duration and rainfall intensity are the key factors affecting the runoff generation of farmland. Taking rainfall duration as the horizontal coordinate and rainfall intensity as the vertical coordinate, then classify whether rainfall is runoff generation or not by fitting an inverse proportional function curve. (4) According to the results of the three water resources evaluation periods, it is evident that the farmland yield runoff generation in the Haihe Plain decreased by 1.02 billion m3 in 2000 relative to 1979, and the farmland yield runoff generation decreased by 510 million m3 in 2016 relative to 2000. This study quantitatively analyzes the effects of rainfall characteristics and ridge height on farmland runoff generation, which is significant for analyzing the causes of surface water resource attenuation in the Haihe plain area.
    May 18, 2022 , DOI:
    Abstract:
    Exploring the spatial-temporal evolution and driving factors of cropland low-carbon utilization efficiency is of vital significance to achieve high-efficiency and low-carbon cropland utilization and agriculture green development. Based on a specific explanation of cropland low-carbon utilization and its efficiency, the paper established a cropland low-carbon utilization efficiency evaluation system and adopted the super-efficiency SBM model to evaluate the efficiency. Furthermore, the paper adopted the kernel density estimation and global differentiation index (GDI) to revealed the trend of its spatial-temporal evolution, and adopted the geographical detector model to identify its driving factors and mechanism. The results showed that: 1) the cropland low-carbon utilization efficiency in China and different regions present a time-series trend of continuous improvement, and different regions present different characteristic of time-series trend; 2) the cropland low-carbon utilization efficiency in China present a spatial pattern of " higher in the east and lower in the west, higher in the north and lower in the south " and the spatial differentiation shrank gradually; From the perspective of regional differentiation, the spatial differentiation in cropland low-carbon utilization efficiency from large to small in different regions was the central, the eastern, and the western. Specifically, the GDI of cropland low-carbon utilization efficiency in the eastern showed a "W" shaped fluctuation trend. The GDI of cropland low-carbon utilization efficiency in the central showed a "U" shaped fluctuation trend. The GDI of cropland low-carbon utilization efficiency in the western showed a continuous trend of decrease; 3) the cropland low-carbon utilization efficiency was affected by natural environmental conditions, cropland resource endowments, economic development level and agricultural production conditions. The driving force of natural environmental conditions was relatively small and unchanged basically. The driving force of cropland resource endowments greatly increased. The driving force of economic development level was greatly decreased. The driving force of agricultural production conditions decreased but was still relatively large. The driving force of various factors had obvious divergence and interaction of factors positively strengthened the single-factor driving force. Finally, the paper provides policy recommendations for improve cropland protection policies in the new era. Specifically, the policy recommendations are as follows: 1) the cropland protection policies should be promoted to transfer from quantity balance and quality balance to production capacity balance and pay more attention to the ecological function of cultivated land; 2) the typical mode of cultivated land low-carbon utilization should be explored according to local conditions in order to seek a balance between high-efficiency cultivated land utilization and low-carbon goals; 3) the low-carbon utilization of cultivated land should be promoted comprehensively in order to narrow regional differences to achieve green agricultural development.
    May 11, 2022 , DOI:
    Abstract:
    Torrefaction is a significant mean to improve biomass-based fuel quality. As a typical agricultural biomass, rice husk has a large annual yield in China, so it is of great significance to explore the effect of dry/wet torrefaction on biomass pyrolysis and combustion reaction characteristics. In this paper, the dry/wet torrefaction pretreatment of rice husk at different temperatures (200, 250 and 300 ℃; 180, 200 and 220 ℃) was carried out in fixed bed and high-pressure reactor (the starting temperature is room temperature and the heating rate is 10 ℃/min). Then proximate analysis and ultimate analysis of samples were carried out by infrared fast coal quality analyzer (5E-MAG6700) and element analyzer (Vario MACRO). Besides, the non-isothermal (room temperature-800 ℃, 20 ℃/min) combustion of rice husk, rice husk torrefied char and rice husk hydrochar was studied by thermogravimetric analyzer (TGA). Moreover, the kinetics analysis of pyrolysis and combustion processes of different samples were also conducted with Coats?Redfern method and three common gas-solid reaction mechanism models (first-order model O1, phase boundary controlled reaction model R2 and R3). The effects of dry and wet torrefaction on the pyrolysis and combustion characteristics of rice husk were compared. The results show that the dry/wet torrefaction increased the ash, fixed carbon and carbon content of raw materials, while decreased the volatile, hydrogen and oxygen content. Van Krevelen diagram displayed that dry/wet torrefaction pretreatment is essentially a process of dehydration and decarboxylation of raw materials, and the dehydration and decarboxylation of rice husk torrefied char at 300 ℃ (RT-300) was the most significant. Both pretreatment affect the pyrolysis and combustion reaction parameters of rice husk, and reduce the pyrolysis reactivity. Dry torrefaction improved the combustion reactivity of rice husk, and the reactivity improved with temperature (200-300 ℃) rising. But wet torrefaction slightly reduced the combustion reactivity of rice husk. Under the same pretreatment temperature (200 ℃), rice husk torrefied char had higher pyrolysis initial weight loss temperature, lower pyrolysis maximum weight loss rate, corresponding temperature and reactivity than rice husk hydrochar. Moreover, compared with rice husk hydrochar, rice husk torrefied char had lower combustion final temperature and maximum weight loss rate corresponding temperature, higher maximum combustion weight loss rate and reactivity. Interestingly, the linear regression index of model O1 was higher than that of the other two models for the pyrolysis and combustion reactivity of rice husk, rice husk torrefied char and rice husk hydrochar (the regression indexes are all above 0.95). Dry/wet torrefaction increased the pyrolysis activation energy of rice husk, while wet torrefaction decreased the combustion activation energy. Moreover, the pre-exponential factor (A) of the samples in the two stages increased with the increase of activation energy (E) with showing an obvious linear relationship, indicating the kinetic compensation effect between A and E during combustion. Under the same pretreatment temperature (200 ℃), rice husk torrefied char had lower pyrolysis activation energy and higher pre-exponential factor than rice husk hydrochar. In addition, compared with rice husk hydrocahr, rice husk torrefied char had higher combustion activation energy and lower pre-exponential factor surprisingly.
    May 11, 2022 , DOI:
    Abstract:
    Soil erosion seriously damages land resources, which is a global environmental problem. Gully erosion is an important manifestation of soil erosion, in recent years, frequent extreme rainstorms have aggravated the occurrence and development of gully erosion. In order to study the formation and development patterns of newly formed gullies under the condition of climate change, this paper takes the Wangwugou Small Watershed of the Chabagou Watershed on the Loess Plateau in Northern Shaanxi as the research area, and takes the “7.26” extreme rainstorm in Northern Shaanxi Province in 2017 as the main research object based on UAV images, to analyze the occurrence regularity of newly formed gullies, and discuss its development characteristics, its difference with the development of existing gullies before 2017, and its relationship with topographic parameters in the following three years. The results showed that: (1) during the “7.26” extreme rainstorm in Northern Shaanxi, there were 45 newly formed gullies in the Wangwugou Small Watershed, which are about 101 gully/km2, and they could be divided into four categories: slope surface gullies, terraced field gullies, unpaved roadway gullies and bottom gullies. The slope surface gullies were the largest, and the bottom gullies and terraced field gullies were wider and larger in area. Production roads, check dam farmland and sloping farmland are most prone to the occurring of gullies under rainstorm conditions. (2) In the three years after the formation of the new gullies, the development of the new gully heads was faster than that of the original existing gullies, and 34.48% of the heads of newly formed gully was further advanced, which was 1.32 times of the original existing gullies. The average gully head retreat distance of newly formed gullies is 3 times that of the original existing gullies, which is up to 0.58 m/a, and the maximum speed could reach 2.12 m/a. (3) The increase of the drainage area could significantly promote the development of gully heads, which is an important topographic index to simulate the retreat rate of gully heads. Under extreme rainfall conditions, the soil erosion situation is highly serious in the study area, and the source of newly formed gullies could be traced more rapidly within three years after their occurrence. Therefore, special attention and enhanced management should be attached to the prevention and control of such gullies.
    May 11, 2022 , DOI:
    Abstract:
    In order to explore the appropriate application methods of desulfurization gypsum to improve saline-alkali soil, a field trial was used in the Hetao Irrigation District of Inner Mongolia, with a control and three desulfurization gypsum application methods (hole application, strip application, and broadcast application). After a sunflower growing season, samples of 0-100 cm soil profile were collected to compare and analyze the effects of desulfurization gypsum application methods on soil pH, electrical conductivity and water-soluble base ion profile. The results showed that: compared with the control treatment, the three desulfurization gypsum application methods could significantly reduce the pH value and sodium adsorption ratio of 0-20 cm soil, significantly increase the content of water-soluble base ions, and then increase the soil electrical conductivity. The pH value and sodium adsorption of the rhizosphere soil of 0-20 cm in strip treatment were reduced by 20% and 41%, and the electrical conductivity and water-soluble Ca2+ content increased by 44% and 507%, respectively. With the increase of soil depth, the concentration of water-soluble ions basically showed a downward trend, but the concentration of water-soluble calcium ions in the rhizosphere soil of 80-100 cm treated with desulfurized gypsum increased by 47%-105% compared with the control treatment. Due to the improvement of calcium ions and the influence of surface evapotranspiration, the sodium ion concentration of the soil treated with desulfurized gypsum >20-100 cm was higher than that of the control treatment, resulting in an increase in the sodium adsorption ratio. The effect of gypsum strip application and hole application on the improvement of rhizosphere soil was significantly better than that of non-rhizosphere soil, while the effect of spreading treatment on the improvement of rhizosphere and non-rhizosphere soil was not significantly different. The three application methods of desulfurization gypsum can significantly increase the emergence rate and yield of sunflower, and the strip application has the best yield increase effect. On the whole, strip application of desulfurization gypsum can concentrate effective ingredients to improve rhizosphere soil, which can be promoted and applied in Hetao irrigation areas and similar areas.
    May 10, 2022 , DOI:
    Abstract:
    Hetao Irrigation District (HTID) has been the largest self-flowing irrigation district with one water intake in Asia, serving an important commercial grain and oil production base in China. The annual grain production in the HTID reached 2.55 million tons in 2018, accounting for 3.9‰ of the total crop cultivation area in China. Therefore, an accurate and rapid extraction of crop structure can be of great practical significance in the agricultural production for the food security of the HTID. However, it is difficult to distinguish the pixels of major crops in the remote sensing images, due to the severe soil salinization, fragmented and scattered crop distribution, as well as the same crop with the different spectrum of various crops. Moreover, there are the close growth periods of major crops in the HTID, which can mix the elements in the images. In this study, Sentinel-2 high-resolution remote sensing images and the GlobeLand30 dataset were used to extract the crop planting structure of the HTID using the Google Earth Engine cloud computing platform. Nearly 1200 sample points were filtrated using OTSU algorithm and Google Earth visual interpretation. The features of spectra, frequently-used vegetation, red-edge vegetation, and crop texture were input into four classifiers, including the Random Forest (RF), Support Vector Machine (SVM), Naive Bayes (NB), and Classification and Regression Tree (CART). The Overall Accuracy (OA) and Kappa coefficient were used to evaluate the performances of model for the extraction of crop planting structure. Firstly, the impacts of classification features and classifiers combinations on the classification accuracy were explored to identify the classifier with the highest classification accuracy. Then, the feature optimization was performed on the five irrigation sub-districts using out-of-bag error rates for each irrigation sub-district. Finally, the optimal classifier and feature combinations were achieved to derive the cropping structure of four crops in the HTID in 2018. The results show that the RF classifier presented the highest classification accuracy using all feature bands, where the average OA of the HTID (81%) was 6% and 11% higher than that of the SVM and NB classifier, respectively. The Kappa coefficient reached 0.68, which was much higher than the rest. Furthermore, the importance of feature bands filtered by the RF was ranked first for the spectral features, the second for the vegetation features, and last for the gray texture features. The indexes were calculated using red-edge bands, indicating the better performance over the other commonly-used remote sensing vegetation indices in crop recognition. In addition, the feature-optimized scheme was the combination with the highest average OA of 86% and Kappa coefficient of 0.78, while the scheme containing 25 bands of spectral, vegetation and texture features presented an OA of 85% and Kappa coefficient of 0.75. Therefore, the new sights can be offered for extracting crop spatial distribution using remote sensing cloud computing platform in complex planting structure area. The finding can provide a strong reference to adjust the agricultural production structure, further to formulate the food macro-control policies in the Hetao Irrigation District.
    May 10, 2022 , DOI:
    Abstract:
    In the present research of fruit tree identification and location, fruit tree identification has been relatively perfect, but in the fruit tree location research, most of the fruit tree depth orientation positioning, and low positioning accuracy, positioning information is incomplete and low precision, resulting in some orchard operations difficult to achieve. In this paper, an improved YOLOv3 algorithm is proposed for tree trunk recognition and binocular camera positioning. Firstly, the algorithm integrates the SENet attention mechanism module into the residual module in Darknet53, a feature extraction network of YOLOv3. SENet module can enhance the extraction of useful feature information and compress useless feature information, so as to achieve feature re-calibration. Then a new residual network module SE-Res module is obtained. YOLOv3 model largely uses stacking of residual network, so after stacking of SE-Res modules for several times, feature extraction ability of the model is improved and target detection is more accurate. Secondly, YOLOv3 model of anchor box information have already can't meet the demand of precision, so by K means clustering algorithm will original YOLOv3 model of anchor box information updated, so we can optimize the test frame information, obtain more accurate inspection information, the more accurate the test box information to obtain the more accurate positioning information. The images were collected by the left and right cameras of the binocular camera, respectively, and transmitted to the improved YOLOv3 model for tree trunk detection, and the information of the inspection frame was output, including the category information, the center point coordinates of the inspection frame, and the width and height of the inspection frame. Target matching is performed on the images collected by the left and right cameras through the output detection frame information. When the difference between the area of the target inspection frame and the coordinate of the center point v axis in the left and right images is within the threshold and the category information is the same, the target matching is considered successful. After successful matching, the parallax information of the same target is obtained. Through the parallax information, the tree trunk is located by using the triangulation principle of binocular camera. Experimental results show that this method can identify and locate fruit tree trunks well, and the average precision and recall rate of the improved YOLOv3 model are 97.54% and 91.79%, respectively, and the time is 0.046s. Compared with the original YOLOv3 model, the precision and recall rate of the improved YOLOv3 model are improved by 3.01% and 3.84%, respectively. Compared with the original SSD model, the precision and recall rate of the improved YOLOv3 model are improved by 14.09% and 20.52%. In the fruit tree positioning experiment, the average positioning errors of XL axis and ZL axis were 0.036m and 0.282m, respectively, and the average error ratios were 3.48% and 2.12%. Compared with the original YOLOv3, the positioning errors of XL axis and ZL axis are reduced by 15.76% and 13.95%, respectively. Compared with the original SSD model, the positioning errors of XL axis and ZL axis are reduced by 22.69% and 20.08%, respectively. The results show that this method can identify and locate fruit trees in orchard robot autonomous navigation, ditching fertilization, grass cutting, pesticide spraying and other operations, which lays a theoretical foundation for improving operation efficiency and ensuring operation quality.
    May 10, 2022 , DOI:
    Abstract:
    Residual film pollution has posed a great threat to the agricultural environment in recent years. It is a high demand for the residual film identification and coverage rate detection in cotton fields before sowing. In this study, an evaluation method of residual film coverage rate was proposed using pixel block and machine learning model, in order to effectively recognize the residual film in cotton field before sowing by the pixel block classification. Fifty images of 1×1 m cotton field surface with the residual film were collected by random sampling in the cotton growing area of Kuitun, Xinjiang, China. The image with the resolution of 4608×3456 Pixel was cropped along the boundary of 1×1m sampling area. After cropping, the image was resized to 1000×1000 Pixel, and the brightness was corrected using normalization. The image pixel was then manually labelled, in which the residual film was labeled as 1, and the soil background was labeled as 0. Then, 45 images were randomly selected to train the models, and the rest 5 images were used to verify the final model for the evaluation of residual film coverage rate. The recognizing pixel blocks and machine learning were selected to make better use of the color and texture features of images. Each image was cut into the 10000, 2500 and 625 pixel blocks, according to the sizes of 10×10, 20×20 and 40×40 Pixel, respectively. The extraction was performed on the first, second, and third order color moments of R, G and B channels, and Gray-level Co-occurrence Matrix (GLCM) of each pixel block. Meanwhile, the intensities of R, G and B channels of each pixel were extracted for comparison. The stochastic down-sampling and Synthetic Minority Oversampling Technique (SMOTE) were used to equalize the pixel block data. Principal Component Analysis was employed to extract the top 10 principal components of pixel block, in order to prevent the over-fitting for the high training speed. Consequently, the 70% of the data was used for the training, and 30% was for the testing. Random Forests (RF), Xtreme Gradient Boosting (XGBoost), Support Vector Machine (SVM), and Artificial Neural Network (ANN) were used to optimize the parameters via the style search and cross validation. The residual film coverage rate was calculated to evaluate the segmentation of different sizes of pixel block and the machine learning models. The ANN model combined with 20×20 pixel blocks performed the best, with the Mean Intersection Over Union (MIOU) of 71.25%. The relative error was 0.51% in the residual film coverage rate between the prediction and actual value, and the detection time was 0.29s. Therefore, the improved model is feasible for the accurate identification of residual film on the surface of cotton field before sowing. This finding can provide the theoretical support for the rapid detection system of residual film pollution using UAV imaging.
    May 07, 2022 , DOI:
    Abstract:
    [Background] Erosion gully poses a serious threat to land resources and ecological environment. The automatic extraction technology of erosion gully based on high-resolution DEM is studied for dynamic monitoring of erosion gully, which is expected to replace visual interpretation. Bidirectional Relief-shading method takes into account both extraction accuracy and efficiency, but it is only for the Loess platform/tableland landform. In other landforms, there are more false areas and missing areas in the result. [Method] To make it adapt to different landforms, this paper takes the 3.2m DEM of Wubu County, Shaanxi Province, uses the gully networks buffer filling, dilate-erode and area threshold method to eliminate the false areas and missing areas, and designs the extraction algorithm through modular programming and data partition. Finally, 10 verified watersheds are evenly selected in the county, and validation data are obtained by visual interpretation with 0.65 m image. [Result] 1) The false areas and missing areas are automatically eliminated, and the erosion gully map of Wubu County is obtained; 2) In 10 verified watersheds, the accuracy of our method is 81.1% - 86.3%, with an average of 83.8%. [Conclusion] In this paper, the gully networks buffer filling, dilate-erode and area threshold method are applied to eliminate the false areas and missing areas, so that this method can adapt to the other landform. On this basis, the algorithm and software that can realize the extraction of large-scale erosion gully are developed.
    April 28, 2022 , DOI:
    Abstract:
    Earthworm composting can serve as one type of agricultural waste treatment to combine with conventional composting with biological digestion. The earthworms can be selected to decompose the organic matter. The ‘ecological interface’ of earthworm composting has been utilized to optimize the earthworm culture using the large-scale breeding equipment, particularly for the harmless, reduction and recycling of agricultural wastes. However, a perfect balance needs to be gained between the short mature period of earthworms, and the large output of earthworm and earthworm dung. The separation can be the key link to harvesting the earthworm products and earthworm dung organic fertilizer. Electric stimulation can be used to separate using the instinctive reaction of earthworms with less harm. Once the electric stimulation is directly applied to the material carrier where earthworms are, the earthworms can be actively driven to leave the growing environment. There was no harm to the health of earthworms, and no secondary pollution to the environment, synergistically coupled with the breeding equipment in practice. Therefore, it is a high demand to clarify the separation process for the rapid design of the separation facility. In this study, a systematic investigation was conducted to determine the response of the separation rate of earthworms to the mode, intensity, and duration of electric stimulation, the water content of the carrier, and the material thickness. An evaluation was made to clarify the effects of electric stimulation on physiological and biochemical indexes of earthworms. The results show that electrical stimulation promoted the separation of earthworm and dung, where the intermittent electrical stimulation presented a better separation performance than the continuous. The earthworm separation rate was significantly correlated with the intensity of electrical stimulation under the intermittent mode, the circulation cycle time of power-on and power-off, as well as the times of power-on. The optimal moisture content of the material carrier was 52.6% for the earthworm growth. The smaller the material carrier thickness was, the better the earthworm separation rate was. Electrostimulation treatment had no significant effect on the contents of catalase, superoxide dismutase, acetylcholinesterase, cellulase and soluble protein in earthworms, but significantly increased the content of malondialdehyde. After 5 days of recovery domestication, the content of malondialdehyde could be restored to the level of control treatment. Consequently, the earthworm can be separated by intermittent electrical stimulation, in terms of the separation rate and the technical parameters. An optimal combination was achieved, where the intensity of electrical stimulation was 2mA, the on-off cycle time was 30s, and the power-on time was 1s. The earthworm separation efficiency reached about 85% after 30 minutes of electrical stimulation, where the water content of the material carrier was about 50%, the material thickness was 20~25cm, and the auxiliary 210 lx white light. The finding can provide strong support to the equipment application for the rapid and efficient separation of earthworm and earthworm dung during agricultural waste treatment.
    April 28, 2022 , DOI:
    Abstract:
    Farmland functions has undergone profound changes in the process of urbanization, It is critical to understand social and economic influencing factors of trade-off and synergy of farmland functions for balance between local economic improvements and farmland protection. Taking Huai-Hai Economic Zone as an example, this paper established the assessment system of farmland functions from the dimensions of production, society, and ecology, employed Spearman Rank Correlation to reveal the spatial and temporal variations of trade-off and synergy of farmland functions from 2000-2018. Subsequently, the driving mechanism affecting trade-off and synergy of farmland functions was quantitatively analyzed by adopting the moderating effect model. The results indicate that: (1) The farmland production function and the farmland social function generally followed a fluctuating ascending and a fluctuating downward trend, respectively. The decline of farmland ecological function was characterized by descending firstly then ascending. (2) The relationship between farmland production function and farmland ecological function among cities showed a trade-off growth trend, but the trade-off relationship within some cities gradually declined, mostly in Southern Shandong and Northern Jiangsu. The relationship between farmland production function and farmland social function among cities has changed from weak trade-off to weak synergy, and the synergy relationship within some cities gradually increased, especially in the east. The relationship between farmland ecological function and farmland social function was generated mainly through farmland production function and therefore was not measured in this study. (3) The relationship between farmland production function and farmland social function was mainly affected by the urban-rural income gap, population urbanization rate, and residents’ consumption capacity. The relationship between farmland production function and farmland ecological function was significantly influenced by residents’ consumption capacity. The effects vary according to different driving factor levels. Finally, this paper proposed some strategic suggestions to promote synergy of farmland functions in the Huai-Hai Economic Zone.
    April 28, 2022 , DOI:
    Abstract:
    Abstract:Tomato is an indispensable consumed agricultural product in the world. In the process of tomato growth, there are various defects due to the influence of many factors. Those surface defects directly provide the first impression of quality and influence consumers' purchase intention. The sales of tomato planting enterprises are further affected. In order to improve the market competitiveness of tomatoes, it is necessary to grade tomatoes according to their quality after harvesting. This study proposed a new detection method based on model pruning to realize high-throughput online detection of defective tomatoes. Firstly, the machine vision acquisition system was improved. A diffuse illumination system was used to obtain the high-quality tomato images and reduce the illumination nonuniformity. Then parallel computing and images combination were adopted to improve image processing speed. The input images of the YOLOv4 network were generated by combining RGB images at three continuous detection stations. However, a huge number of computations will be caused by the complex network structure and numerous parameters of the YOLOv4. The intensive computation will limit the inference speed of the model and affect the implementations of online detection of tomato quality. Parameters and complexity of the YOLOv4 model could be compressed and reduced by channel pruning. But only channel pruning of the model could not meet the criteria of real-time detection. To further optimize the network structure and improve the detection speed, the layer pruning method was used to further compress the depth of the network model after channel pruning of the model. In this study, the optimal channel pruning rate was determined by selecting the maximum mAP value on the premise that the inference time meets the real-time performance requirements. Therefore, the channel pruning rate of the YOLOv4 network was finally set to 80%, and the optimal detection model obtained was named YOLOv4P. Then a non-maximum suppression method based on the L1 norm was proposed to remove the redundant prediction box after fine-tuning the compressed network model and accurately identify the defect region in the combined tomato image. Besides, the effects of the different number of training images and different pruning rates on the performance of the model were discussed. In order to verify the performance of the proposed tomato defect detection model, YOLOv3, YOLOv4, YOLOv4-tiny, and YOLOv4PC were compared with YOLOv4P model. Compared with the original YOLOv4 network, the results showed that the proposed YOLOv4P network reduced the model size and inference time by 232.40 MB and 10.11 ms, respectively. The proposed method had the highest mAP and the fastest detection speed in detecting tomato surface defects. The model pruning technology could effectively decrease the inference time to ensure the accuracy of the model detection. Finally, the YOLOv4P model was deployed to the online grading and sorting system. The accuracy of online detection test was 96.4%, which met the actual engineering requirements of real-time detection of defective tomatoes, and can be applied to practical production.
    April 28, 2022 , DOI:
    Abstract:
    Presence or absence of embryo, as well as development status, both having a strong relation with the germination-rate of ginkgo seeds, unfortunately, neither can be discerned via manual observation without dissection. A non-invasive classification of ginkgo seeds on these internal conditions was explored through deep learning the low-field magnetic resonance (LF-MR) images. A dataset of four classes, including embryo-present, embryo-absent, normal, and apertured, each of 1200 images sized 32×32 pixels, was collected through the LF-MR imaging of 6000 ginkgo seeds, then selected and categorized according to dissection evidence. An improved VGG-16 convolutional network for ginkgo seed classification (Ginkgo seed LF-MR images recognition model adapted from VGG-Net, or GV) was designed to classify LF-MR images according to whether the presence or absence of embryo in sagittal plane, or whether the seeds being normal or decayed judging from coronal plane. GV reuses the convolutional layers of VGG-16 and replaces its fully connected (FC) layers with a structural redesign, including a global average pooling layer followed by a FC layer. Compared with VGG-16, GV reduces in size and number of parameters, training time, training loss, and validation loss, by respective 89%, 89%, 64%, 64%, and 45%, and improves accuracy in both training and validation by 2.4% and 2.5%, respectively. The classification accuracy of ginkgo seed LF-MR images reached 97.40%, and the precision, recall, and F1-score were all above 95%. Reliable detection of internal defects offers a non-invasive approach to identify those ginkgo seeds that cannot germinate. Positive experiences of redesign and tuning deep learning networks to classify LF-MR images according to internal defects of ginkgo seeds were also gained during the development of GV. At first, super parameters of both learning rate and update period were determined through performing a transfer-learning of VGG-16 for LF-MR images classification of ginkgo seeds. Then, a pool of eight candidate structural adaptations, branching out from the convolutional layers of VGG-16, was built and tested, including two candidates use FC layers with 3 layers of 512, 512, and 4 neurons, or 2 layers of 512 and 4 neurons, another two candidates use global convolution (g-conv) layers with 3 layers of respective 512, 512, and 4 kernels, or 2 layers of respective 512 and 4 kernels, and the rest 4 candidates adding a further global average pooling (GAP) layer in front of or behind a FC layer with 4 neurons or a g-conv layer with 4 kernels. Last, the candidate that yielded the best accuracy with minimal size, number of parameters, and loss was further equipped with 3 different normalizations, i.e., local response normalization (LRN), batch normalization (BN), and group normalization (GN) to further improve accuracy and training speed. The results showed that a GAP layer followed by a single FC layer can best fuse the features passed down from convolutional layers, compared with multilayered FC or g-conv layers, significantly reducing the size and the number of parameters by over 88%, still with improved accuracy; With the classification layer placed after GAP, the highest accuracy was achieved at 98.02% out of the 8 fine-tuned models, therefore, it was deemed as the GV; GN, being not affected by batch size, can make the validation converge more stably and further push validation accuracy to 98.54% when added after the convolutional modules; And learning rate has a great impact on the performance of the transfer learning model, it is necessary to choose a suitable initial value and use a segmented constant decay strategy for specific applications, which can effectively improve the model performance.
    April 28, 2022 , DOI:
    Abstract:
    Dripline flushing has been widely expected to controlling the emitter clogging in drip irrigation system. In this study, a new type of automatic flushing valve with auto exhaust function (AE flushing valve) was developed to improve the flushing duration and flushing water volume. Different values were set for four factors, including the dentation length and width of delay channel, upper cavity volume, and water pressure before flushing valve. Eighteen AE flushing valves were designed by L18 (37) orthogonal test. Four flushing valves without exhaust function (NE flushing valve) were set as the control. Hydraulic performance tests were conducted on the twenty-two 3D printed flushing valves to explore the effect mechanism of exhaust device to improve the hydraulic performance of flushing valve. The response characteristics of AE flushing valve performance parameters to test factors were also investigated. The results showed that the flushing duration, water volume and velocity of AE flushing valve varied 18.2~67.7 s, 3904~12 367 mL and 0.88~1.40 m/s, respectively, when the flushing valve inlet pressure was 0.06~0.14 MPa. The flushing duration and water volume were positively correlated with the dentation length, dentation width, and upper cavity volume, but negatively correlated with the water pressure. The flushing velocity was positively correlated with the water pressure only. According to the significance level of 0.05, the dentation length, dentation width and upper cavity volume posed significant effects on the flushing duration and flushing water volume, and the flushing valve inlet pressure presented significant effects on the flushing duration and flushing velocity. The AE flushing valve was automatically discharged the air in the upper cavity to improve the flushing duration and flushing water volume, which increased by more than 83.5% and 75.4%, respectively, compared with the NE flushing valve. According to previously studies, the minimum size of the flow section of delay channel should be not less than the sensitive clogging size of emitter of 0.6~0.7 mm to improve the clogging resistance of AE flushing valve itself. Thus, under the objective of the longer flushing duration and larger flushing water volume, the dentation length, dentation width, upper cavity volume and water pressure were 1.2 mm, 2.2 mm, 19.1 mL and 0.06 MPa, respectively, and the corresponding flushing duration and flushing water volume were 67.7 s and 12 194 mL, respectively. Moreover, that flushing duration and flushing water volume were 2.8 and 2.7 times larger than those of NE flushing valve, and 7.4 and 7.0 times larger than those of Israel imported flushing valves. Three regression models were established to predict the hydraulic performance of AE flushing valve based on structural and operating parameters. The root mean square error of measured and predicted values for the flushing duration, flushing water volume and flushing velocity of three new AE flushing valves under three inlet water pressure were 2.1s, 334 mL and 0.02 m/s, respectively, and the relative error ranged from -9.4% to 8.5%. It indicated that the three regression models can be used to predict the structural and operating parameters of AE flushing valve required by the practical applications and shorten the time of product development.
    April 28, 2022 , DOI:
    Abstract:
    The in-depth disclosure of the spatial poverty level in the contiguous mountainous areas of special poverty is of great scientific significance for the current analysis of the effect of poverty alleviation, the construction of the early warning mechanism for returning to poverty, and the revitalization of rural areas and even the integration of urban and rural areas after 2020. Qinling-Bashan and Wuling Mountainous Areas have a deep degree of poverty, the number of poor people is huge, is the main battlefield since the country launched poverty alleviation, in order to better consolidate the results of the attack in the later stage, studying the multi-dimensional poverty spatial characteristics of the region in the early and middle stages of poverty alleviation is conducive to explaining the delineation of concentrated contiguous special poverty areas, the causes and distribution of poverty. Based on the indicators that can characterize physical geographical characteristics, social security, economic development and location transportation in 2015, the study constructed a multidimensional poverty evaluation index system, and comprehensively measured the multidimensional poverty index and carried out poverty geographical identification by using entropy rights method and hotspot analysis. The results showed that: 1) The poverty level of townships and townships was mainly relatively poor and above, and the spatial distribution of poverty in various dimensions was significantly different, and the multidimensional poverty space showed a distribution of "north deep, south, middle and shallow" and the concentration of high-value areas was obvious, and the poverty level in the northern Qinling-Bashan Mountains was the deepest; Therefore, Qinling-Bashan Mountain Should Be More Focused on Than Wuling Mountain, Qinling-Bashan Mountain Area can provide less resources for development due to the fragile natural environment; coupled with poor traffic development, it is far from the main city of Chongqing, which is not conducive to the circulation of local elements and external resources, which has played a certain degree of obstruction to local economic and social development; and the loss of labor and talents, most local residents choose to go out to work, or pour into the main city, the west of Chongqing to work, etc., so that the degree of poverty deepens. 2) Based on the poverty measurement values under each dimension to identify the poverty factors of the evaluation unit, five large types and 16 small types of weak comprehensive constraint type, one-factor constraint type, two-factor constraint type, three-factor constraint type and strong comprehensive constraint type were divided, accounting for 27.29%, 33.42%, 21.43%, 16.33%,1.53%of the Qinling-Bashan Mountains, which were more manifested as three-factor and strong comprehensive constraints, and Wuling Mountains were more manifested as two-factor and one-dimensional constraints. The Wanzhou District, which connects the Qinling-Bashan Mountains and the Wuling Mountains, is dominated by weak comprehensive constraints, which can indicate that regional poverty is the result of comprehensive factors. According to the different types of poverty-causing factors in each region, the relevant departments can increase the infrastructure investment in the Qinling-Bashan Mountains, the introduction of leading enterprises and other measures to help the region completely get rid of poverty, and the study can provide a prerequisite scientific basis for the evaluation of poverty alleviation effects and the basic work of rural revitalization at the township scale.
    April 27, 2022 , DOI:
    Abstract:
    Lipase can improve the sensory quality and flavor quality of cheese. Lipase or lipase-producing lactic acid bacteria are usually added in the cheese production process to improve product quality. Four strains of lipase-producing lactic acid bacteria (T1-5 and T1-3 are Weissella fusion, H1-6 is Lactobacillus helveticus, B2-5 is Lactobacillus plantarum) selected in the previous stage of this experiment as starter, three strains were selected Lactic acid bacteria compounding is used to make yogurt cheese according to the traditional technology. Experimental group: Group A T1-5 and T1-3, H1-6 (1:1:1), Group B H1-6, T1-5, B2-5 (1:1:1), Group C H1-6, T1-3, B2-5 (1:1:1), D group T1-3, T1-5, B2-5 (1:1:1); control group (group E): commercial starter. After the cheese is fermented and matured, physical and chemical methods are used to analyze the effects of lipase-producing lactic acid bacteria on the cheese pH, titer acidity and fat oxidation indicators. Gas chromatography is used to detect fatty acid changes in cheese, and gas chromatography-ion mobility spectrometry is used to analyze the flavor substances in cheese. Variety. The results showed that the pH and peroxide values of the cheeses in the four groups A, B, C and D were significantly lower than those in the E group (control group) (P <0.05), and the cheese titer results in the A and B groups were higher than those in the control E group. (P <0.05); There was no significant difference in the TBARS value between the five groups of cheese (P> 0.05). The saturated fatty acid content, monounsaturated fatty acid content, and polyunsaturated fatty acid content of the cheeses in groups A, B, C, and D were significantly higher than those in group E (P <0.05); the higher saturated fatty acids in the experimental group cheese were meat Myristic acid (C14:0), palmitic acid (C16:0) and stearic acid (C18:0), as well as butyric acid (C4:0), caproic acid (C6:0), capric acid (C10:0) and Lauric acid (C12:0); oleic acid (C18:1n9c) in the experimental group cheese is the main component of monounsaturated fatty acids, accounting for more than 87% of the total monounsaturated fatty acids; linoleic acid (C18:2n6c) in the experimental group cheese is significantly higher than the control group (group E) (P <0.05). The results of GC-IMS and principal component analysis show that there are many types of volatile flavor compounds in group A and B cheese, and the similarity is high. Aldehydes and esters are the main volatile flavor substances in cheese, among which 2-heptanone the content of butyl aldehyde and butyl acetate is relatively high; the flavor substances in the two groups of cheeses C and E are relatively similar. Fragrance: Group D is different from the other 4 groups. The main volatile flavor substances are butyl acetate, 3-octanone and heptanal. Combined with sensory evaluation, the overall flavor and taste of A and B cheeses are better, and the scores are higher. The screened lipase-producing lactic acid bacteria can be used as a starter to improve the quality of traditional Xinjiang cheese.
    April 27, 2022 , DOI:
    Abstract:
    Low-temperature refrigeration is a commonly used post-harvest storage and preservation technology for Huangguan pear fruit, but long-term low-temperature storage will lead to the occurrence of browning of the peel, and even seriously affect the fruit quality and commercial value of Huangguan pear. Ethylene is an endogenous hormone that plays an important role in regulating plant growth and development. This hormone can promote fruit ripening on the one hand, and improve the ability of plants to cope with stress on the other hand. In order to avoid the occurrence of browning of the peel of Huangguan pear fruit under low temperature storage (about 0 ℃), the study used the method of slow release of ethylene to produce three different ethylene concentrations in the same volume of closed space: 5, 20 and 100 μL/L, in order to achieve the purpose of treating Huangguan pear fruits with different concentrations of exogenous ethylene before storage. The Huangguan pears treated with rapid cooling at 0 ℃ and no exogenous ethylene treatment were used as the control group. Immediately after harvesting, the temperature was kept at 30 ℃, and decreased by 1 ℃ every day for 30 days, and Huangguan pear treated by cooling to 0 ℃ was used as the low temperature condition treatment group. By comparing the water content, disease incidence, soluble solids, soluble sugar, titratable acid, ascorbic acid and other fruit quality indicators between the exogenous ethylene treatment group and the control and low temperature condition treatment, the effect of postharvest exogenous ethylene treatment on peel browning and the effect on fruit quality.The results showed that different concentrations of exogenous ethylene treatments could completely inhibit the occurrence of browning of the peel of Huangguan pear, and the epidermis showed no signs of damage. The incidence index of the low temperature condition treatment was 10%, and the incidence index of the control group was as high as 37.6%. At the end of the shelf life (6 d), the fruit firmness of the exogenous ethylene treatment group was significantly different from that of the control group (P < 0.05). The water content of fruits in the three different concentrations of exogenous ethylene treatment groups were higher than those in the control and low temperature condition treatment (P < 0.05), which maintained the good taste of Huangguan pear. Using low-field nuclear magnetic resonance technology, it was found that the free water content of the control group was the highest among the treatment groups, and the free water content of the 5 and 100 μL/L exogenous ethylene treatment groups was lower, and the lower free water content could reduce the rate of Huangguan pear Incidence of peel browning. Compared with the control and low temperature condition treatment, exogenous ethylene treatment could maintain the content of soluble solids in Huangguan pear fruit. Exogenous ethylene treatment could improve the fruit quality indicators such as titratable acid, soluble sugar and ascorbic acid in Huangguan pear fruit, and could better improve the food sensory quality of pear fruit. Among the three exogenous ethylene treatment concentrations, the effect of 5 μL/L treatment concentration was better. The research results show that exogenous ethylene treatment before storage is an efficient and simple technology that can not only inhibit the browning of Huangguan pear peel but also maintain the fruit shelf life quality.
    April 26, 2022 , DOI:
    Abstract:
    Adding citric acid to the soil can activate heavy metals in the soil, improve the bioavailability of heavy metals in the soil, and improve the remediation efficiency of hyper accumulators. Intercropping between plants can also achieve the same effect. Sedum plumbizincicola intercropping with maize is an in situ, environmentally friendly and effective way to remediate slightly cadmium-contaminated soil while producing, and the combined remediation effect of the two is better. In this study, the mechanism and effect of different citric acid addition methods in cooperation with S. plumbizincicola and maize intercropping mode on remediation of slightly Cd-contaminated paddy soil were researched through field micro-plot experiments. The experiment adopted a randomized block design, and set 3 kinds of citric acid addition methods (no addition, 1 addition (40L addition), 5 additions (single addition of 8L, once every other day, 5 additions, a total of 40L)), 3 planting modes: maize monocropping, S. plumbizincicola monocropping, S. plumbizincicola intercropping with maize, a total of 9 treatments. Each treatment area is 4m2. Citric acid is added after the corn emerges, and the amount of citric acid is 0.2mol/m2. The test area was uniformly applied for citric acid as required, and the control area was uniformly added with tap water. Samples were collected before the addition of citric acid and on the 10th, 50th, and 80th days after the addition of citric acid, respectively. The results showed that when the addition amount of citric acid was 0.2mol/m2, the effect of different citric acid addition methods were different from the strengthening and restoration of S. plumbizincicola intercropping with maize mode: Firstly, the addition of citric acid in the same planting pattern could change the form of heavy metal Cd in the soil, improve the effectiveness of Cd in soil, and significantly improve the remediation efficiency of S. plumbizincicola , and the effect of adding 5 times is the most obvious, the restoration efficiency is improved in single cropping 7.48%, and 6.59% when intercropping. Secondly, with the addition of citric acid, the content of Cd in the soil of the three citric acid intercropping treatments decreased by 11.19, 12.44 ug/kg and 13.66 ug/kg, respectively, compared with the single crop of S. plumbizincicola. The restoration efficiency of S. plumbizincicola was increased by 3.42%, 3.82% and 4.27%, respectively. At the same time, the dry matter weight of corn shoots increased, but the absorption of soil Cd by each part decreased, which achieved the effect of safe corn production. Thirdly, adding citric acid for 5 times synergistically with S. plumbizincicola and maize intercropping, the Cd accumulation in stems, leaves and roots of S. plumbizincicola reached 71.21 and 10.63 mg/kg, respectively, and the removal of Cd in S. plumbizincicola reached 18.59 mg/m2. This treatment had the best remediation effect on mildly Cd contaminated soil, and the restoration efficiency reached 10.52%. Fourthly, both citric acid and S. plumbizincicola intercropping with maize could enhance the restoration efficiency of S. plumbizincicola. contrastive analysis, compared with the citric acid addition, the remediation method of S. plumbizincicola intercropping with maize is more effective than the restoration method of adding citric acid on the restoration of mildly cadmium-contaminated soil by S. plumbizincicola, and the synergistic restoration effect of the two. Therefore, the remediation mode of citric acid combined with S. plumbizincicola and maize intercropping could enhance the remediation efficiency of S. plumbizincicola. This mode can be applied to remediation of paddy soils slightly Cd-contaminated, and realize production at the same time.
    April 26, 2022 , DOI:
    Abstract:
    Integrated territory consolidation is an important means of solving the contradiction between resources and environment, coordinates people's relationship, scientifically defining the connotation, and reasonable determination of work tasks is the core demand for land rectification in the new era. Facing the goals and needs of integrated territory consolidation in the new era, this research is based on the analytical perspective of land “spatial conflict-functional obstacles” and proposes a theoretical system of integrated territory consolidation oriented by “problem-approach-goal”, and the comprehensive remediation program of "elements transformation, boundary control, and global remediation" under the guidance of "point-line-plane" all-round remediation. Construct a integrated territory consolidation implementation mechanism oriented to explicit contradictions and hidden obstacles. With reference to relevant policies and standards, formulate a method for identification of conflicts in territorial space, including five conflict manifestations: ecological protection, basic farmland, construction land management, reserve cultivated land resources, and industrial and mining abandoned land. On the basis of the analysis of the “production-living-ecological” function and its connotation, an evaluation system of land functions is established. And the land functional obstacles are identified according to the obstacle degree model. Conflicts and obstacles are regarded as the focus of short-term and long-term remediation tasks, respectively, and a "partitions + type" model of integrated territory consolidation is formulated with the naming principle of "significant conflict + first obstacle". Integrated territory consolidation strategy and case analysis with Sichuan province as the research area. It has helped to solve real contradictions and develop short boards, excavate land potential, and support the theoretical mechanism by empirical analysis. The results are as follows: 1) There are significant spatial differences in the land conflicts in Sichuan province, and the areas with intense conflicts are mainly distributed in the eastern and southern parts of the province. The scale of land management conflict in Sichuan province is 429,297.03 hectares and the scale of land use conflict is 209,077.74 hectares; 2) Sichuan province “production-living-ecological” functional level distribution presents spatial agglomeration characteristics. The production function exhibits a distribution characteristic of “high in the middle - low in the east and west”. The living function exhibits a significant distribution characteristics of the east high and west low, The high level areas are mainly distributed in the eastern plain and hilly areas. The ecological function is generally present in the low distribution characteristics of the eastior high west, high levels are mainly located in the mountains around the Sichuan basin. The most significant obstacle factors that hinder the “production-living-ecological” function in the province are cultivated land layout, living security and ecological security.3) According to the results of land-space conflict identification and functional impairment evaluation, Sichuan province can be divided into four patitions of remediation areas: key remediation areas, urgent remediation areas, priority digging areas and moderate optimization areas, and 8 types including “layout optimization-facilities improvement-ecological protection”. Coupling types and patitions, 16 comprehensive land remediation modes can be obtained, and corresponding short-term, long-term remediation strategies are proposed, and each county will take corresponding remediation measures according to local conditions according to the results of zoning classification. The research results are conducive to deepening the theoretical research and practical cognition of Integrated territory consolidation, and provide reference and support for consolidation work and related planning at the provincial (city) scale.
    April 21, 2022 , DOI:
    Abstract:
    Rapid measurement of heavy metals concentration in soil profiles is the key to assessing soil heavy metal pollution and selecting appropriate remediation technology. In order to investigate the potential of visible and near infrared reflectance spectroscopy (VNIR) for predicting heavy metals concentration in intact soil profiles, a total of 19 complete soil profile samples with a depth of about 100±5 cm were collected in the cropland surrounding two typical mining areas in Jiangxi Province. The Cu concentration in intact soil profile samples and its reflectance spectra between 400 and 2500 nm were measured respectively. Partial least squares regression (PLSR) and three machine learning algorithms (cubist regression tree, Cubist; Gaussian process regression, GPR; support vector machine SVM) were compared to assess their ability to predict Cu concentration in intact soil profiles. In addition, the study analyzed the influences of 11 different spectral preprocessing methods (raw data, Raw; absorbance, Abs; first derivative, FD; multiplicative scatter correction, MSC; standard normal variate transformation, SNV; Gap-Segment derivatives, GS; Savitzky-Golay smoothing and derivatives, SG) and the combination of pretreatment methods (MSC+FD; Abs+FD; SNV+GS; SNV+SG) on the accuracy of Cu concentration prediction models. The determination coefficient, root mean square error and relative analysis error were used to evaluate the prediction performance of the models. The results showed that the prediction accuracy of the machine learning algorithms for the Cu concentration in the intact soil profiles was obviously higher than that of the PLSR model. Furthermore, the predictive performance of SVM was better than the other three machine learning models and the SVM model in combination with first derivative (FD) preprocessing had the highest prediction accuracy. The cross-validation results of FD-SVM showed that R2CV, RMSECV and RPDCV were respectively 0.80, 14.83 mg·kg-1 and 1.87; the independent validation results of FD-SVM showed that R2V, RMSEV, and RPDV were respectively 0.95, 7.94 mg·kg-1 and 4.34. Furthermore, the comparison results of different preprocessing methods showed that FD and SNV+GS were the two most robust preprocessing methods. FD preprocessing had the best performance in GPR and SVM models while SNV+GS had the best performance in PLSR and Cubist models. In the study, compared with the prediction models which established on soil samples after air drying, grinding and sieving, the VNIR predictive models for Cu concentration in intact soil profile samples were also reliable. This study demonstrated the ability of machine learning algorithms to predict the Cu concentration in intact soil profiles and established the optimal predictive model, providing a reference for the rapid monitoring of other heavy metal concentration and relative researches on soil heavy metal pollution.
    April 19, 2022 , DOI:
    Abstract:
    Human activity has become frequent in semi-arid areas, which causes surface subsidence, fissure zone and makes groundwater exploitation more severe, while the precipitation increases the complexity of the moisture conditions. For the variation of groundwater level and water content in vadose zone under the disturbance of coal mining in the semi-arid regions, the relationship between precipitation and groundwater was explored by in-situ observation, statistical analysis, wavelet analysis and other methods from the perspective of the water cycle. The precipitation, groundwater table and soil moisture content in vadose zone in typical mining areas of Northern Shaanxi were selected as research elements. The vadose zone plays a significant role in the water cycle and regulates infiltration, evapotranspiration, groundwater recharge and discharge and so on. And the change of groundwater level could cause a series of properties change in vadose zone. Under the disturbance of coal mining, this interaction mechanism is more complicated. In order to understand water cycle theory better, this paper analyzed the response of the groundwater level and water content to the changes of precipitation in both unmined areas and mining areas. The mining area self-test system, groundwater observation wells and sensors were used to observe rainfall, phreatic water level, soil moisture, water potential and other relevant data respectively. The observation station and sensors observed the soil water movement process in depths about 10cm, 20cm, 30cm, 40cm, 50cm, 80cm, 100cm and 150cm in unmined area and in depths about 10cm, 20cm, 30cm, 50cm in mining area. Based on the whole data, making the graph that includes the variation of groundwater level under disturbance of coal mining, the trend of soil moisture content with depth and the relationship between soil moisture content and rainfall response before and after coal mining. The results show that the response of groundwater level to precipitation is obvious in unmined areas, and the correlation coefficient can reach more than -0.7. there is also a lag about four or five months. The small intensity precipitation (like 50mm) in the unmined area has no effect on the soil water content near the depth below 100cm, but larger precipitation (60mm) can infiltrate the depth below 100cm. After the disturbance of coal mining about several years, the groundwater level continues to decline, and the relationship between groundwater level and precipitation is weak. In the vertical direction, the moisture in the vadose zone decreases with the increase of depth, and the range of dynamic change tends to be gentle. The farther away from the ground, the soil moisture is less vulnerable to external influence. The response of water content to precipitation at the same depth is not significant, but the variation trend of soil moisture content with rainfall at different depths is obviously different. In addition, the max soil moisture content in the mining area appears earlier than that in the unmined area and the overall change range is reduced. In particular, the precipitation increased significantly in July and August, and the increase of fissures caused by coal mining shortened the time for precipitation to recharge shallow groundwater. The depth below 50cm has no response to the small intensity precipitation (like 30mm). In general, the coal mining caused the drop of water level, resulting in the thickening of the vadose zone, the loss of water in the vadose zone increased, resulting in rainfall infiltration of groundwater recharge decreased, further aggravating the drop of water level. Accordingly, the findings can provide theoretical support for the study of water cycle mechanism under the influence of coal mining.
    April 18, 2022 , DOI:
    Abstract:
    Understanding the spatio-temporal characteristics of trade-offs/synergies in land use functions and their influencing factors can provide a reference for decision-making in land use function management. As industrialization and urbanization continue to advance, the contradictions between the land production, living and ecological functions have gradually emerged. How to reasonably allocate and coordinate the functions of land development and protection, and guide the reasonable distribution of human activities has become an important issue for global sustainable development. Taking Hangzhou City as an example, this paper attempted to evaluate the land production, living and ecological functions at fine scale from 2000 to 2018 by using multi-source data and a series of geospatial models. Then, the correlation analysis method was used to reveal the trade-offs/synergies of land use functions at the global and grid scales, respectively. The influencing factors of land use function trade-offs/synergies were also identified by the linear regression model. The results showed that (1) On the whole, the living function showed a trade-off relationship with production and ecological function during 2000 and 2018, and the trade-off intensity of production and living functions was stronger than that of living and ecological functions. Production and ecological functions were found to exhibit a synergistic relationship during the study period. During the different sub-periods of the study period, the trade-off relationship between production and living functions showed a trend of increasing first and then decreasing, while the trade-offs of living and ecological functions gradually weakened, the interactive relationship between production and ecological functions shifted from a synergistic relationship in 2000-2005 to a trade-off relationship in 2015-2018. (2) Spatially, the production-living function was dominated by strong trade-off and production-weakening trade-off, and the trade-off intensity tended to weaken from the east to the west and from the central to the periphery; areas with synergy state were located in the low-altitude mountains of central and western Hangzhou. The production-ecological function presented a mixed pattern of trade-off and synergy areas in space. The trade-off areas accounted for about 31%, with weak trade-off and production-weakening trade-offs, mainly distributed in the northern and eastern Hangzhou; the synergy areas occupied about 38%, with weak synergy and simultaneous improving synergy, mainly distributed in the western and southern Hangzhou. The living-ecological function was dominated by the weak trade-off and ecology-weakening trade-off. The trade-off area accounts for 14%, and the trade-off intensity showed a trend of high in the east and low in the west, gradually decreasing from the central to the edge. The synergy relationship was dominated by weak synergy and simultaneous weakening synergy, the synergy areas accounted for 8%, mainly scattered in the outer suburbs. (3) Natural conditions and geographical location had significant negative effects on the trade-offs/synergies in production-living and living-ecological functions, and had significant positive effects on production-ecological function trade-offs/synergies. The urbanization-induced land conversion and the increase of land use intensity further aggravated the trade-offs in land use functions. This study showed that the trade-offs/synergies in land use functions was different at global and grid scales, the overall characteristics and local differences should be considered in land use management decision-making to formulate appropriate policies according to local conditions.
    April 15, 2022 , DOI:
    Abstract:
    Apple is a common cash crop, which has a crucial impact on the development of the agricultural economy. Mosaic, Alternaria spot, Brown spot, Powdery mildew, Aphid, Leaf miner and Spider mite are seven common diseases and pests of apple leaves, which seriously threaten the yield and quality of apple. Early diagnosis and control of diseases and pests play a pivotal role in controlling the spread of diseases and reducing losses, which are fundamental to ensure the healthy development of the apple industry. Therefore, in order to solve the problem that the existing lightweight models can not accurately identify the sparse small lesions in early apple leaves, a lightweight recognition model ALS-Net (Apple Leaf Net using channel Shuffle) is proposed for resource constrained mobile terminals. The main works are as follows: 1) Firstly, 1,881 images of diseased and healthy apple leaves are collected in Qian County, Shaanxi Province. With the proposal of improving the generalization and robustness of the model, the original images are enhanced by digital image processing technology. 2) Secondly, the ALS module is constructed based on depthwise separable convolution and channel shuffle technology. Compared with the traditional convolution method, it significantly reduces the amount of calculations and parameters of the model. The channel shuffle technology fully shuffles the information between channels and then randomly assigns it to each channel. It alleviates the loss of accuracy in group convolution. At the same time, the Inception structure is introduced to improve the multi-scale feature extraction ability of the model. The channel attention mechanism is introduced to make the network selectively strengthen the disease features and suppress the natural background features. The ELU is selected as the activation function to accelerate the convergence speed of the model. 3) In addition, the knowledge distillation strategy is used to train the model, which provides the soft label information that the student model cannot learn on the hard label to realize the transfer of knowledge, so that the accuracy of the student model can approach or exceed the accuracy of the teacher model. DenseNet-161 with high accuracy is selected as the teacher model and ALS-Net is the student model. On the premise of keeping parameters of the model, the network recognition accuracy is further improved. This study uses the high-performance server to train the model and test the generalization of the model. Based on the experimental results, the conclusions are as follows: 1) The comparative experimental results show that the accuracy of ALS-Net can reach 99.43%, which is higher than that of classical CNNs such as AlexNet and ResNet, and the size of the model is only 1.64MB, which is lower than that of lightweight CNNs such as MobileNetV2 and ShuffleNetV2. 2) Through two sets of ablation experiments, this study verifies the effects of expanding convolution kernel and adjusting the number of blocks on model accuracy and parameter number. The second verifies the effects of Inception structure, attention module, ELU activation function and channel shuffle technology on the accuracy of the model. 3) Under the same experimental condition, the training method of knowledge distillation strategy can significantly improve the recognition accuracy and accelerate the convergence speed during training. 4) Based on PyTorch Mobile, the model is deployed on HUAWEI P40 Pro 5G mobile terminal for real-time inference. The inference delay of the mobile terminal is 55ms, which meets the requirements of practical application. This study realizes the automatic recognition of apple leaf diseases and pests on the mobile terminal, which provides a new idea for the early diagnosis of apple leaf diseases and pests.
    April 12, 2022 , DOI:
    Abstract:
    Taking the cultivated land in Xinbei district of Changzhou city as the research object, a patch-scale arable land fragmentation evaluation model was constructed to improve the evaluation method of arable land fragmentation. The evaluation model involves two parts: functional zoning and regional clustering. Firstly, taking the cultivated land patch as the basic evaluation unit, select evaluation indicators from three aspects of scale, distribution, and shape. The evaluation indicators include patch area, contiguous degree, and shape index, and use the spatial analysis methods such as aggregation in ArcGIS 10.6 to calculate the evaluation indicators. Secondly, the area weighting method is used to expand the patch index to the area with the administrative village as the unit, and Getis-Ord Gi* is further used to identify the cold and hot areas of each index , and to measure the degree of regional fragmentation. Thirdly, the research area is divided into functional zones by using two-step clustering algorithm, and administrative villages with neighboring geographical location and similar fragmentation attributes are clustered into one zone. Finally, the Python-based sklearn library implements the k-means clustering algorithm with the silhouette measure. The silhouette measure are introduced to help determine the optimal number of clusters and obtain the best clustering results. The clustering results evaluate the degree of fragmentation of the cultivated land. The results showed that: 1) According to the clustering results of functional zoning, the Xinbei district is divided into insignificant area, continuous regular area and discrete complex zone.2) The evaluation results classify the cultivated land patches of Xinbei District into three categories: Category 1, including the number of patches was 17,332, the average area of patches is too small, the degree of continuity is low, the area of patch was concentrated in 0-10000 m2, the area accounted for 21.98%, the contiguous degree was concentrated in 1-4, mainly distributed in Xinbei District central area; Category 2, including the number of patches is 4535, complex and irregular shape of patches, the area accounts for 9.65%, the shape index is concentrated in 1.5-2.5, evenly distributed in the whole area; Category 3, including the number of patches is 4091, the patches is concentrated and regular, and the area accounts for 68.37%, The contiguous degree are concentrated in 5-10, and the shape index is concentrated in 1-1.5, mainly distributed in the peripheral area; Based on the differences of fine fragmentation attributes of different categories of cultivated land, corresponding optimization pattern and consolidation suggestions are put forward. Based on functional zoning and the integration of multi-cluster algorithms, a patch-scale arable land fragmentation evaluation model is constructed. On the evaluation index, try to apply landscape pattern indicator to vector patch scale; In terms of evaluation method, clustering algorithm does not need to assign weight to various indicators, avoiding the impact of unreasonable weight setting on the results. On the evaluation results, from regional fragmentation degree to the specific fragmentation pattern within the region.The model can quickly, intelligently and low-costly evaluate the fragmented cultivated land patches, which is conducive to further planning and consolidation.The model can be fast, intelligent, low-cost evaluation of finely divided farming patches is conducive to further planning and improvement. This study provides some help for improving the evaluation method of cultivated land fragmentation.
    April 11, 2022 , DOI:
    Abstract:
    The concept of ‘Payment for ecosystem service’ provides a new perspective for cultivated land protection in China, and how to zoning and quantify scientifically is the core and key to establish cultivated land protection eco-compensation policy. Based on the concept of Ecological Carrying Capacity (ECC), this paper divided the whole country into paid area and received area, from the perspective of deficits/surplus of provincial cultivated land ECC, and achievement of provincial cultivated land quantity target. The eco-compensation standard of cultivated land protection of each province ware calculated by opportunity cost. In addition, the paid or received amount of cultivated land protection eco-compensation estimated according to the amount of deficits/surplus of provincial cultivated land ECC and per unit opportunity cost. The results show that: 1) In 2019, cultivated land ECC of China was higher in the north and lower in the south, about 28% of cultivated land ecosystem services was transfer from cultivated land ECC surplus areas to deficit areas. 2) The whole country divided into four zone. The first is the Full- received area, which covers 9 provinces located along the northern border and minority ethnic autonomous regions. The second is the Reduced-received area, which includes 6 provinces located in the the middle reaches of the Yellow River and the Yangtze River and the coastal areas of south China. The third is the Reduced-paid zone, which covers 11 provinces and stretches from north China to southwest China. The fourth is the Full-paid zone, which includes 5 provinces, mostly in the developed eastern seaboard. 3) Based on this, the eco-compensation standard for cultivated protection established to be 47500 Yuan per hectare. Heilongjiang province received the most compensation of 182 billion yuan, and Zhejiang province paid the most with 246.4 billion yuan. 4) Verified by Lorenz Curve, the fiscal revenue gap between provinces reduced by 6% through cultivated land protection eco-compensation policy. Conclusion: The paper puts forward the eco-compensation differential order zoning and standard calculation method of cultivated land protection. It may provide the main motivation for cultivated land protection, and provides scientific basis for establishing establish cultivated land protection eco-compensation policy.
    March 24, 2022 , DOI:
    Abstract:
    Acquisition of reliable multi-temporal remote sensing data with high quality is critical for accurate crop type mapping. Due to the existence of cloudy and rainy weather, satellite observations were easily affected and then generated the undesired images. Traditionally, those low-quality observations were excluded or reconstructed using temporal filters for remote sensing classification in practice. However, the temporal filtering might eliminate useful information and affect the temporal trajectory of original images, leading to uncertainty for the identification of crop types. Meanwhile, with the decrease in the spatial resolution of images, the effects of land cover mixtures within a pixel grid can be increased, which might influence the performance of temporal filters. In this study, the impacts of Savitzky-Golay (S-G) and harmonic analysis of time series (HANTS) filter methods on crop type mapping over different spatial resolutions were comprehensively investigated using the random forest classifier as well as Harmonized Landsat Sentinel-2 (HLS, 30 m) and Moderate-resolution Imaging Spectroradiometer (MODIS, 500 m) data. Specifically, we selected 6 time-series vegetation indices, i.e., NDVI, LSWI, EVI, VI-green, NDSVI and NDTI, to identify 3 main crop types (soybean, maize and rice) in Heilongjiang Province. According to the derived crop type maps, the temporal filtering had a greater impact on the spatial distribution of crop classification results in decametric spatial resolution image (HLS) than that in low spatial resolution image (MODIS). The evaluation results showed that the overall accuracy of crop type map derived by S-G and HANTS was reduced by 1.73% and 5.17% comparing to the original observations for decametric resolution images. By contrast, the overall accuracy derived by original, S-G and HANTS observations over low resolution images was 84.73%, 85.51% and 83.05%, respectively, indicating that there was no significant change in crop type mapping before and after temporal filtering. Particularly, both the intra- and inter-class differences of crop types changed after temporal filtering in decametric resolution images through the comparison of time-series vegetation indices over different crop types, introducing the different impacts on the accuracy of crop type mapping. In detail, the inter-class difference between two similar crop types may be incorrectly identified as the inherent noise by the temporal filtering method. In that case, the temporal filtering will reduce this difference and thus will decrease the accuracy of crop type mapping. For instance, the user’s accuracy of soybean and maize was reduced by 4.60% and 8.77% through the comparison between before and after the application of HANTS filter method. On the contrary, for two crop types with significant inter-difference in the time-series vegetation indices, the temporal filtering can improve the accuracy of crop type identification (e.g., the user’s accuracy of rice was improved after HANTS filter) because the intra-class difference of each crop type was further reduced comparing to the observations without filtering. In terms of crop type mapping on low resolution images (i.e., MODIS), the temporal filtering almost had no impacts on the accuracy of crop type identification, which can be primarily attributed to the larger effects of land cover mixtures in the pixel grid. This study explored the impacts of temporal filtering methods on the performance of crop type mapping over different spatial scales, which can provide theoretical references and technical supports for generating the spatial distribution of crop types in the future.
    March 22, 2022 , DOI:
    Abstract:
    In micro-nano aeration drip irrigation, the behavior characteristics of micro-bubbles in labyrinth channel were not clear, which led to the lack of scientific basis for system operations. In order to solve this problem, Particle Tracking Velocimetry technology was used to shoot videos for bubbles at five consecutive positions along the labyrinth channel under inlet pressure of 0.02, 0.06 and 0.10MPa and behavior characteristics of micro-bubbles in labyrinth channel and the influence of inlet pressure on it were analyzed. The results show that along the whole channel, the quantity of micro-bubbles decreased gradually and its maximum diameter and average diameter increased gradually. However, the average speed and average time of bubble clusters which passed the shot section showed no significant change. At the same position of the channel, the higher the inlet pressure was, the less the bubbles were; the smaller the maximum diameter of bubbles was, the shorter the average time of bubble clusters passing the channel was and the faster the average speed was. The minimum speed that the inlet pressure provided to let bubble clusters pass the channel was called “basic speed”. Basic speed increased as the inlet pressure increased. Therefore, under high inlet pressure, more gas dissolved in water while the undissolved gas existed in the form of micro-bubbles with smaller diameter and faster speed. This enabled the system to achieve better water vapor transportation effect. This research provided a theoretical reference for scientific operations of micro-nano aeration drip irrigation system.
    March 22, 2022 , DOI:
    Abstract:
    Aiming at the problem of insufficient drainage capacity of the existing solar photovoltaic subsurface pipe drainage system, and taking the solar photovoltaic subsurface pipe drainage system in Liuzhong Township, Pingluo County, Yinbei irrigation area, the drainage capacity of the current system and the feasibility of siphon auxiliary drainage are analyzed, and the siphon auxiliary drainage capacity is calculated and the improvement method of the drainage capacity is discussed through the monitoring of regional drainage, water level in the sump and drainage ditch, and groundwater level etc. The results show that the drainage capacity of the existing solar photovoltaic subsurface pipe drainage system is limited, and the drainage rate is less than or equal to 0.49mm/d, far less than the drainage rate of 1.5mm/drequired by salinization controlling in Yinbei irrigation area. At night, the water level in the sump is restored to close to the groundwater level and higher than the water level of the adjacent drainage ditch. There is a The positive water level difference between sump and ditch is more than 0.3m. For the built solar photovoltaic subsurface pipe drainage system, it is proposed to use siphon for auxiliary drainage at night that the drainage efficiency can be greatly improved by using siphon drainage at night. By selecting the appropriate siphon The diameter of the siphon is about 0.09m, and the drainage discharge at night can be equivalent to that of the solar photovoltaic pump in the daytime. For the new-built solar photovoltaic subsurface pipe drainage system, it is proposed to add a horizontal connecting pipe between the sump and the adjacent drainage ditch to realize gravity drainage at night. The research results can provide technical support for the popularization and application of solar photovoltaic subsurface pipe drainage system.
    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.
    , DOI:
    Abstract:
    In this paper, a non-contact and on-line detection system of soil moisture based on Fabry Perot interference near-infrared chip is developed to solve the problems of large number of points, high cost and destruction of cultivated layer after the probe soil moisture sensor is inserted into the soil. The hardware part of the system consists of airborne automatic detection device, electrical control box and Beidou dual antenna real-time differential positioning system. In this study, through the selection of sensors, the detection of soil water content information is realized. Through the design and packaging of the module, the internal structure of the sensor is protected from damage. By designing a lifting detection device to protect the soil moisture sensor and control the sensor to reach the soil surface for detection. By installing the ultrasonic sensor, the obstacle avoidance of the sensor and the automatic positioning of the measured height are realized. The spectral data in the range of 1750 ~ 2150mm are obtained by collecting soil samples with different water content and different types, and the partial least squares prediction model of soil surface water content is established. The determination coefficients of all prediction models are above 0.9. The curve fitting degree of the overall soil model is high, R2 reaches 0.933, which is slightly lower than that of the single soil prediction model, but the universality of the overall model is good and suitable for the prediction of most soil water content. By embedding the soil water content prediction model established based on the experiment into the original near-infrared sensing chip data acquisition software, the secondary development of the original sensor data acquisition software is realized. When measuring soil samples, the specific value of soil water and the corresponding spectral data curve can be displayed in real time on the industrial computer, so that the detection results of soil water content can be displayed more intuitively. Through the cooperation of Xinjie PLC and analog module, the distance information measured by the ultrasonic sensor is transformed into voltage information, and the closed-loop stepping motor adjusts the height of the soil moisture sensor in real time according to the change of PLC feedback signal, so as to realize the coordination between the positioning system and the detection device. Finally, through the integrated research and development of near-infrared soil moisture detection system and automatic self-propelled transplanter, the trial production of the prototype is completed. the field test results show that when the transplanter moves at the inspection speed of 0.3m/s, after the soil moisture sensor is online referenced and calibrated, it drops to the soil surface with the lifting detection mechanism for measurement. Within 5S, the moisture content value rises after the real-time display of the moisture content on the industrial computer. The measured surface soil water information is combined with the positioning information of Beidou RTK system to obtain the soil moisture content value under accurate longitude and latitude, and finally, the soil moisture content distribution map of the measured plot is generated, After the test, the sampling points are sampled, pretreated, dried and calculated to obtain the actual moisture content of the sampling points, and the relative error between the measured moisture content and the actual moisture content is calculated. It is concluded that the soil moisture content measured in the test is basically consistent with the actual soil moisture content, and the relative error of continuous detection is less than 10%. The distribution map of soil surface water content can directly match the early warning level of soil moisture, and visualize the abstract soil moisture information, so that farmers can intuitively understand the soil moisture information of the field, and provide reference basis for variable irrigation such as sprinkler irrigation and drip irrigation, so as to achieve regional water and soil adaptation and water productivity spatiotemporal pattern optimization. It has high reference value and practical significance for further creating intelligent agricultural machinery and truly realizing the "border inspection and side management" of field management.
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    2010,26(11):1-7, DOI:
    [Abstract] (32557) [HTML] (0) [PDF 0.00 Byte] (9309)
    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] (26762) [HTML] (0) [PDF 392.78 K] (6452)
    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] (21065) [HTML] (0) [PDF 0.00 Byte] (8023)
    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] (18069) [HTML] (0) [PDF 0.00 Byte] (5775)
    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] (17712) [HTML] (0) [PDF 5.12 M] (3808)
    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] (17460) [HTML] (0) [PDF 3.96 M] (5863)
    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] (17184) [HTML] (0) [PDF 361.61 K] (2605)
    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] (16924) [HTML] (0) [PDF 522.80 K] (2900)
    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(9):201-208, DOI: 10.11975/j.issn.1002-6819.2015.09.031
    [Abstract] (16679) [HTML] (0) [PDF 3.61 M] (3914)
    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(15):201-207, DOI: 10.11975/j.issn.1002-6819.2015.15.028
    [Abstract] (16648) [HTML] (0) [PDF 772.45 K] (2615)
    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(16):96-101, DOI: 10.11975/j.issn.1002-6819.2015.16.014
    [Abstract] (16445) [HTML] (0) [PDF 395.08 K] (2500)
    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] (16440) [HTML] (0) [PDF 8.13 M] (3399)
    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] (16249) [HTML] (0) [PDF 6.90 M] (3405)
    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] (16105) [HTML] (0) [PDF 6.48 M] (5272)
    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] (15996) [HTML] (0) [PDF 4.73 M] (3064)
    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(8):278-284, DOI: 10.11975/j.issn.1002-6819.2016.08.039
    [Abstract] (15963) [HTML] (0) [PDF 1.43 M] (2828)
    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(12):107-114, DOI: 10.11975/j.issn.1002-6819.2016.12.016
    [Abstract] (15962) [HTML] (0) [PDF 413.47 K] (2083)
    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.
    2016,32(5):120-125, DOI: 10.11975/j.issn.1002-6819.2016.05.017
    [Abstract] (15907) [HTML] (0) [PDF 3.29 M] (2561)
    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.
    2017,33(12):66-73, DOI: 10.11975/j.issn.1002-6819.2017.12.009
    [Abstract] (15902) [HTML] (0) [PDF 5.69 M] (3191)
    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.
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    2009,25(8):288-293, DOI:
    [Abstract] (1924) [HTML] (0) [PDF 0.00 Byte] (117620)
    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] (526) [HTML] (0) [PDF 5.55 M] (58682)
    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] (489) [HTML] (0) [PDF 8.68 M] (53415)
    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] (1329) [HTML] (0) [PDF 5.25 M] (41684)
    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] (2454) [HTML] (0) [PDF 560.68 K] (39598)
    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] (2322) [HTML] (0) [PDF 0.00 Byte] (19992)
    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] (2195) [HTML] (0) [PDF 0.00 Byte] (19958)
    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.
    2020,36(11):39-48, DOI: 10.11975/j.issn.1002-6819.2020.11.005
    [Abstract] (973) [HTML] (0) [PDF 8.24 M] (17586)
    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] (2593) [HTML] (0) [PDF 11.40 M] (17431)
    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] (741) [HTML] (0) [PDF 22.64 M] (16591)
    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.
    2021,37(1):223-232, DOI: 10.11975/j.issn.1002-6819.2021.01.027
    [Abstract] (1571) [HTML] (0) [PDF 6.54 M] (14831)
    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] (1605) [HTML] (0) [PDF 1.94 M] (14024)
    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] (1418) [HTML] (0) [PDF 4.66 M] (12794)
    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] (776) [HTML] (0) [PDF 1.77 M] (12233)
    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] (3508) [HTML] (0) [PDF 15.27 M] (12042)
    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] (743) [HTML] (0) [PDF 3.89 M] (11641)
    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.
    2008,24(8):232-235, DOI:
    [Abstract] (9388) [HTML] (0) [PDF 0.00 Byte] (11054)
    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.
    2015,31(z1):237-246, DOI: 10.3969/j.issn.1002-6819.2015.z1.028
    [Abstract] (2903) [HTML] (0) [PDF 10.15 M] (10920)
    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.
    [Abstract] (2704) [HTML] (0) [PDF 2.10 M] (9693)
    Abstract:
    Abstract: In the northern and especially northeastern areas of China, it is so quite pleasantly cool and dry in the autumn that farmers used to cure peanuts in the field for some days after digging in order to decrease the mass of the peanut plants, and more easily transport and pick up the crop. It indicated that the two-stage harvest might be more suitable to peanut production in the north and northeast areas of China. Based on the viewpoint and theory of combining machinery with agronomy, the main peanut varieties in the western of Liaoning were selected as test materials, the variances of moisture content, and mechanical properties of peanut stems and pegs accompanying the change of curing days were studied by means of an infrared moisture meter and a universal bio-material testing machine. During the test, the curing days of peanut plants in the field after digging was selected as the basic variable, and more than seven days as the time span. The moisture contents of peanut stem and peg, and the tensile strength of the peg and its nodes were measured. The change rules of moisture content of peanut plants during the curing process in the field were obtained, which showed that the change rules of three kinds of peanuts were very similar i.e. the moisture content of the peanut stem and peg dropped rapidly with the extension of curing time in the early drying time (previous two days), and then the moisture content decreased slowly. The change rules of moisture content of peanut plants change tended to be an asymptote from the third curing day, when the moisture contents of the peanut stem and peg were almost no longer dropping, and finally settled around 9%. The moisture content of the peanut peg and its two nodes ranged from 8.48% to 65.68%, and the changes of tensile strength and moisture content in the three kinds of peanuts were quite similar. In the whole curing process, the tensile strength of the peanut peg was always highest, the tensile strength of the peanut-peg node was lowest, and the tensile strength of the stem-peg node was in the middle. The tensile strength of the three key positions of the peg all changed with the moisture content. And the tensile strength of the fresh peanut plants with high moisture content were highest, the tensile strength of peanut peg and its two nodes decreased rapidly in the early curing time, and then dropped slowed until it gradually tended to a constant value. The regression equation of the tensile strength and the moisture content of the peg and its two nodes as obtained by the method of SPSS software were that the fitting coefficient of stem-peg node tensile strength was 0.9891, the fitting coefficient of peanut-peg node tensile strength was 0.9974, and the fitting coefficient of peanut peg tensile strength was 0.9966. And under the experimental condition, the optimal curing days before picking up was preliminarily determined to be 3~5d, and the corresponding moisture content of the peanut peg ranged from 10% to 20%, the tensile strength of peanut peg and stem-peg node ranged from 10N to15N, and the corresponding tensile strength of peanut-peg node ranged from 7N to 9N. The above study results could be used as important references to design a picker and thresher of peanuts and to determine the optimal picking time, as well as deeply research the mechanisms of picking up and threshing with less loss of dropping and damage.
    2006,22(2):127-131, DOI:
    Abstract:
    By analyzing the problems of traditional methods for estimating the weight of pigs, the authors discuss a new method which applies computer vision technology to pig production. The projected image area of pigs when viewed directly from above was computed. The pig weights were estimated by the linear regression of the pig real areas. The results show that a strong relationship exists between pig weight and the projected area of the pig after removing the sections of head and tail in images. The correlation coefficient is 0.94. By comparing with the measured weights, the relative error is less than 2.8%. The experiment indicates that this hands-off method has great significance in scientific management of the pigs, which does not require large labor and material resources, and also avoid the loss in production resulted from stress.
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    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(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.
    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.
    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.
    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.
    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(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.
    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.
    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.
    2007,23(5):81-87, DOI:
    Abstract:
    The study on the driving forces of rural residential land can instruct the consolidation of rural residential area, which is an important part of the study of inner law of rural residential area evolvement. Taking the Beijing mountainous area as study area, the driving forces of rural residential area change was analyzed based on GIS and SPSS using the logistic regression model by view of spatial coherence. The result indicate that the change of rural residential area is controlled by its former distribution and droved by the exterior driving forces under the interior driving forces context such as natural factors and location comprehensively. The change of rural residential area is a process that selecting the preferable location integrating the influence of the nature, local accessiblity and social-economy. The developing orientation of its driving forces is made to probe into the suitable consolidation modes in different localities, which will help to strengthen the management of rural residential area during the construction of new socialist countryside.
    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.
    2005,21(7):168-174, DOI:
    Abstract:
    The importance of and the need to secure food safety and facilitate international trade through establishing a traceability system for domestic animals and livestock products were discussed, and the essential components and characteristics of domestic animal traceability system were also introduced in this paper. Several animal identification technologies including information and network technology were compared and summarized. The history of implementation and evolution of legislative regulation of traceability systems in developed countries were reviewed; the main issues which hamper the implementation of traceability system were discussed. A pilot project of a Chinese traceability system, in which new technologies were developed, was also proposed. The trends and direction for the development of traceability system was highlighted, and findings of this paper could provide a basis for establishing a national traceability system for domestic animals and livestock products which is feasible to the situation of China.
    2006,22(2):27-32, DOI:
    Abstract:
    Field experiments were conducted at Luancheng Station, Chinese Academy of Sciences in different precipitation years. The impacts of water supplied conditions on root distribution, yield and water utilization efficiency(WUE) of winter wheat under different irrigation treatments were analyzed in order to supply a basis for optimum irrigation mode which could increase the yield and improve water utilization efficiency. The results indicated that most roots were concentrated in the upper 80 cm soil layer, and the density of roots declined exponentially downward with the increase of the soil layer depth. Considering water consumption in different soil layers, and the relationships among yield, water utilization efficiency and total water consumption, the optimal irrigation mode in North China plain was put forward, i.e., no irrigation in rain-full years, one time irrigation at jointing stage in normal years and two times at jointing stage and booting stage in dry years with the suitable water quota of 60 to 75 mm each time, which not only increased the winter wheat yield, but also benefited to using the deep soil water and improving the water utilization efficiency.
    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.
    2000,16(3):24-27, DOI:
    Abstract:
    Crop Regulated Deficit Irrigation (RDI),based on the crop-water relations,is an irrigation technique with high yield and water use efficiency. The beneficial effect of moderate water deficit was analyzed using the data of field experiments in Shaanxi,Gansu and Xinjiang. It showed that RDI should be applied at the early growth stage. The degree of water deficit can reach 45%~50% of field capacity,which has no bad effect on crop yield and can increase crop water use efficiency obviously. And some problems of RDI were also disscussed.
    2004,20(1):288-292, DOI:
    Abstract:
    The excrements from livestock and poultry have become the major source of nonpoint pollution in the rural areas of China. Hence, the annual amount of excretion has increasingly attracted people's attention. Based on the investigation of the livestock and poultry breeding husbandry in Chongqing and referred to home and abroad other researches, the approaches and parameters of estimation of annual quantity of total excretion was defined. On the basis of the data in 2001, the annual amount of excretion from the main livestock and poultry such as cattle, sheep, pig and goose, etc., and the pollutants from those excrements such as organic matter, nitrogen, phosphorus, potassium, etc. are estimated, which aims to quantize the excretion pollutants. The result of the estimation is as follows: in 2001, the gross of excretion from livestock and poultry in Chongqing is 74 210 000 tons. And in the excretion, there is organic matter 8 060 000 tons, nitrogen 425 000 tons, phosphorus214 800 tons and potassium 449 500 tons. This research can be applied both in the industrial and agricultural layout and the environmental pollution control of Chongqing.
    2005,21(7):20-24, DOI:
    Abstract:
    In order to research the impacts of minimum tillage and no-tillage on crop yield, crop water use efficiency and soil NO-3-N content under the condition of winter wheat/relays summer maize cultivation and irrigation field, five tillage systems were adopted in Longkou city, Shandong Province. The five tillage systems were as follows: conventional tillage without straw turnover , conventional tillage with straw turnover, rotary tillage with straw turnover, serrated disk harrow tillage with straw turnover, no-tillage with straw cover. The soil moisture content was measured by oven drying method. The soil NO-3-N content was measured by continued flow analysis extraction. Results showed that minimum tillage especially rotary tillage with straw returned could increase soil water content, water use efficiency and crop yield in a whole year, NO-3-N content in 0~60 cm layer of soil and decrease the leaching loss of NO-3-N in soil. Preliminary studies showed that rotary tillage with straw turnover could be adopted in this region, while no-tillage with straw cover returned was not suitable.
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