Abstract:Screening is one of the critical processes of grain harvesting. The performance of the combine harvester is directly affected by the operating quality of the screening device. The performance of the screening devices can meet the basic requirements of grain harvesting. However, the development of screening technology was affected by some factors, for example, the diversity of agricultural materials, the complexity of the operating environment, and the requirements for agricultural machinery of having the capability of high-speed operation, which resulted in the increase of the throughput and the irregular change of the moisture content. And the difficulty of high-quality-efficient screening would be increased. Screen structure and its driving mechanism were the critical parts of the screening device. The motion of particles on the screen, such as slipping, being thrown upwards, static, and so on, was affected by the shape of the screen, the configuration of the screen hole, the screen material, and other factors. And the performance of the screening device would be affected. The driving mechanism of the screen could achieve the multi-dimensional motion of the screen. The reasonable motion of the screen could accomplish the rapid dispersion of the materials on the screen for penetrating the screen holes efficiently. And the screening efficiency of the device could be improved. The screening technology’s key idea was to solve the contradiction among the screening efficiency, loss percentage of grains, and the impurity percentage of grains. In other words, the grains should penetrate the screen holes efficiently, and the materials other than grains should not penetrate the screen holes but discharge from the device. The purpose of screening was to recover of the full-value grains to ensure the economic value of the grains. These problems were considered, such as particles blocking screen holes, low screening efficiency of devices in a high-throughput, poor fluidity of particles, and wet particles adhering to the screen surface. The research status of screening devices applying to grain was investigated based on the screen’s structure and its driving mechanism. The reference and supplement of grain screening technology, and the efficient and intelligent development of screening devices were discussed. A reference was provided for the research of the grain screening technology and the design of the innovative device in China.

Abstract:Aiming at the low precision and efficiency of the fruit identification and harvesting motion of existing harvesting robots, the hand-eye coordination planning with deep visual servo for harvesting robot was carried out. A small lifting harvesting robot with deep visual servo of RealSense-in-hand was developed, which was composed of the autonomous vehicle, lifting bin, electric fork lifter, grip-cut integrated end-effector, and 3-freedom manipulator. The workspace and posture analysis of fruit picking and placing was performed, and the coordinate transformation model of hand-eye coordination was established for the eye-in-hand mode. Based on the depth visual servo of RealSense-in-hand, the far-to-close hand-eye coordination strategy was proposed for the harvesting robot. The canopy detection from a distance, sub-region division and location, close-range fruit accurate identification and positioning were effectively combined, so that the step-by-step visual guidance of the manipulator was realized. According to the parameters of RealSense and the manipulator, the segmented motion planning between far-to-close key points based on depth vision was completed. It was shown in the hand-eye coordinated harvesting test that, the average positioning accuracy of the end-effector in the X, Y and Z directions was 3.51mm, 2.79mm and 3.35mm, respectively. The average time consuming was 19.24s, which included the motion time of the manipulator from the initial position to picking position (12.04s), the fruit recognition and computing time (3.82s), and the fruit placing time (7.2s). The time of manipulator motion accounted for 80.2% of the whole cycle. Both the robot structure and the hand-eye coordination strategy based on depth visual servo of RealSense-in-hand can meet the needs of fruit harvesting operation.

Abstract:In order to realize the nondestructive picking of slender fruits and vegetables, a soft pneumatic gripper with aeration and spiral motion was proposed. Based on the finite element static simulation analysis of the gripper, the interaction effect of each factor on the spiral characteristics of the soft pneumatic gripper was studied by using the three-factor and three-level central combination design and response surface analysis method. The quadratic regression model was established with the spiral diameter and pitch of the soft pneumatic grip as the response values, and the determining coefficients of the model were 0.9987 and 0.9351, respectively. The order of significance of the influence of each factor on the spiral diameter and pitch was as follows: wall thickness, cavity width and cavity angle. The simulation diameter of the soft pneumatic gripper was 35mm, and the simulation pitch [50mm,150mm] was taken as the objective function to optimize each influencing factor. The optimal design results were 2.51mm of wall thickness, 30.52° of chamber angle and 11.91mm of chamber height. The results of experiment and simulation showed that the error of screw diameter and pitch was less than 5%. The grasping force of the soft pneumatic gripper was measured under different air pressures, and the results showed that the soft pneumatic gripper had the maximum grasping force of 3.37N at 0.13MPa. Finally, the effectiveness of the soft pneumatic gripper was demonstrated by grasping slender fruits and vegetables of different sizes and softness. Finally, the cucumber was picked as the object, and the cucumber was successfully captured and the stem was broken in 3.6s.

Abstract:Data quality issues are the bottleneck hindering the development of agricultural machinery big data platforms. The existing data cleaning algorithms are not suitable for large-scale, multi-source heterogeneous, high-dimensional, and strong spatiotemporal correlation of agricultural machinery real-time streaming data. To this end, the source and characteristics of the abnormal data of agricultural machinery in complex environments were analyzed, the detection and correction technology of abnormal data was studied, and an online cleaning method for agricultural machinery operation data based on sliding window mechanism was proposed. The method determined abnormal data based on the principle of variance constraint; generated preliminary candidate data based on the principle of minimum change; based on the time correlation of data, the final repair value was obtained through AR and ARX model optimization; relying on the Flink distributed computing platform, it was suitable for large data throughput and high concurrency of agricultural machinery. The validity of the algorithm was verified based on the agricultural machinery operation data of a certain province. The results showed that when the amount of data reached 1×10 5 and the proportion of abnormal data was 5%, the abnormal recognition rate of the algorithm reached 0.94, and the root mean square error was smaller than that of the existing cleaning algorithm. The experiment was designed based on the Box-Behnken method, and the regression model was obtained through response surface analysis to study the influence of algorithm parameters on the root mean square error and time. The hybrid genetic algorithm based on binary coding optimized the parameters, and the optimized parameter combination can make the root mean square error of the algorithm reach 0.16 and the running time reach 0.13s. The data cleaning method can provide high-quality data support for the real-time processing of the agricultural machinery big data platform.

Abstract:Aiming at the problems of no-tillage maize planting in drip irrigation area, the drip irrigation tape in narrow row is easy to entangle with straw, which affects the trafficability of no-till planter. The straw partition cleaning method suitable for no-tillage wide-narrow row in drip irrigation area was put forward, and the device for cleaning straw in sowing strip was designed, which adopted longitudinal dislocation arrangement straw cleaning mechanism to clean up straw in sowing strip. Based on the theoretical analysis of the interaction law between the key components and straw, key influencing factors and value ranges were determined. Based on the EDEM discrete element simulation technology, the working speed, soil contacting depth and the longitudinal spacing were selected as the influencing factors, and straw cleaning rate was selected as the response value for three factors and three levels sub-regression orthogonal test design. The regression equations to describe the relationships between the factors and straw cleaning rate were established by using the regression analysis and response surface analysis with the software Design-Expert 10.0.7. The optimum combination of the selected parameters was obtained, and the field test verification was also conducted. The results showed that the significant effects of working speed, the longitudinal spacing and soil contacting depth on cleaning rate were in a decreasing order. While the working speed was at 9km/h, the longitudinal spacing was 1100mm and soil contacting depth was 45mm, straw cleaning rate of the device was 87.61%, which was 1.8 percentage points lower than the theoretical value of model optimization. The cleaning width of sowing strip was ranged from 508.0mm to 540.4mm.

Abstract:Aiming at the problems of high missed weeding rate and low weeding rate between plants in paddy fields, and the existing weeding device cannot determine the position of the seedlings and led to the high seedling damage rate, an arc-tooth type automatic seedling avoided weeding device was designed to remove weeds between plants during paddy field cultivation, which was based on the idea of controlling the intermittent opening and closing movement of the weeding execution component. According to the growth status of rice plants in the weeding period of intertillage, the symmetrical weeding teeth used to remove weeds between plants were designed through theoretical analysis, and the main structural parameters of arc-shaped weeding teeth were determined. The automatic control system for avoiding seedlings was designed through the synergy of photoelectric sensors and electric linear actuators. When the weeding device needed to perform the action of avoiding seedlings, the control system controlled the arc-shaped weeding teeth to open a certain distance according to the real-time monitoring of the forward speed to avoid the seedlings. A virtual experiment was carried out based on the dynamic simulation software LS-DYNA. In the experiment, the soil disturbance rate within 0~40mm below the ground surface was used as the evaluation index, and the working depth of the arc-shaped weeding tooth of the device was determined to be 32mm, and at this time, the soil disturbance rate reached the maximum value, which was 90.02%. The operating performance of the inter-plant weeding device and automatic seedling avoidance control system was verified through field experiment. When the forward speed was 0.5~0.9m/s, the average weeding rate of the device was 86.51% and the average seedling damage rate was 0.20%. The performance of weeding and seedling avoidance was stable, and the operation quality can meet the agronomic requirements of paddy field weeding and the operation requirements of “avoiding seedlings and weeding” between plants.

Abstract:In order to ensure the operation efficiency of lateral deep fertilization in paddy field and improve the fertilization uniformity of lateral deep fertilization device, combined with the agronomic requirements of lateral deep fertilization of rice in cold region, a disc ejection type lateral deep fertilization device was designed, its working principle was expounded, and the key components, disc ejection type fertilizer discharger and air delivery system, were analyzed. Kinematics model of fertilizer discharging process was established, and the rotating speed of fertilizer discharge disc was an important factor affecting fertilization performance. The best work of fertilizer discharging disc was 10~60r/min by EDEM virtual simulation test. The fertilization performance experiment of lateral deep fertilization device was carried out. The results showed that the consistency of discharge amount and stability of fertilization met the national operation standard of fertilization machinery. Taking the effective working length of fertilizer tank as a factor, the average value of fertilization amount, coefficient of variation of fertilization uniformity and total fertilization amount as indicators, the single factor experiment was carried out. The results showed that when the density of fertilizer was 1.15g/cm3 and the effective working length of fertilizer tank was adjusted between 5mm and 20mm, the total fertilization amount was varied from 137kg/hm2 to 921kg/hm2, and the coefficient of variation of fertilization uniformity of lateral deep fertilization device was ranged from 5.96% to 12.77%. Compared with the straight-grooved wheel type and the inclined-grooved wheel type side-deep fertilization device, it was concluded that the disc ejection type side-deep fertilization device effectively improved the uniformity of fertilization, and there was no fertilizer crushing phenomenon in long-term operation under the premise of meeting the requirements of fertilization amount. Four special fertilizers with different densities were selected to verify the fertilizer adjustment performance of the fertilizer application device. The experimental results showed that the designed device had good adaptability to commonly used special fertilizers, and the obtained curves of effective working length of fertilizer tank and total fertilizer application with density of 0.85~1.40g/cm3 can be directly applied to field operations, which had important reference value for debugging and application of machines and tools and actual production operations.

Abstract:The seed metering device for rapeseed was the core working part of rape mechanized seeding technology. The performance of seed metering device for rapeseed directly determined the quality of rape seeding. One of the trends to achieve intelligent sowing is to obtain sowing information through real-time detection of rape seed flow and control the sowing volume accordingly. The electronic control seed metering device that used motor speed as the control target had the problem of unstable seeding quantity in real time under complex working conditions. This problem has made it difficult for the seed metering device to achieve the agronomy requirements of sowing quantity. A seed metering device which can perform feedback control based on real-time sowing information was designed to solve this problem. The seed metering device for rapeseed consisted of a screw tube seed rowing mechanism, a detection and control module, a small grain size seed sensing module and a drive module. In order to orderly pass all seeds through the sensing area of the small grain size seed sensing module, the structure of the seed guide tube was designed. This seed guide tube can match the sensor module. It can effectively reduce loss sowing. The seed metering device for rapeseed was tested for rotation speed-seeding frequency measurement and seeding accuracy rate. A seeding quantity compensation model was constructed based on the result of test. This model reduced sowing detection errors. The seed metering device for rapeseed was tested for rotation speed-seeding quantity measurement and seeding accuracy rate. A seeding quantity compensation model was constructed based on the result of test. This model reduced sowing detection errors. A seed metering device control system was designed by using the small grain size seed sensing module to complete real-time seeding information detection, and it used the detected information as input to the control system. The control module calculated based on the set seeding information and the forward speed information measured by the hall speed measurement module. The control module converted the difference between the theoretical seeding frequency and the actual seeding frequency measured in real time by the small grain size seed sensing module into the speed difference as the controller input. The control module decided on the corresponding duty cycle. The bench test showed that the seeding quantity detection accuracy of the seed metering device for rapeseed detection was higher than 98.75% in the range of 10.1~60.4Hz seeding frequency. The coefficient of variation of seeding quantity stability of seed metering device for rapeseed was less than 1.16% at different rotation speeds. The field test results showed that the error rate of sowing quantity was less than 2.55% and the coefficient of variation of seeding quantity stability of seed metering device for rapeseed was less than 0.98% at different forward speeds of the tractor. This seed metering device for rapeseed provided technical support for precision sowing in small plots.

Abstract:Aiming at the problems of small size, light weight and pityriasis in millet seed sowing and seed-metering device, such as hole blocking, poor seed uniformity and low seed filling rate at high rotating speed of seed-metering plate, a combined type of positive and negative air pressure and hole wheel seed sowing and seed-metering device was designed according to the agronomic requirements of millet seed sowing. The parameters of key parts of seed sorter were designed and calculated, and the mechanical model of seed in the flow field and filling area was established through theoretical analysis. It was found that the main factors affecting the airflow force on seeds were the diameter of suction hole and the vacuum degree inside the type hole. The vacuum degree required by seed sorter during seed filling was 1.13~3.21kPa. Through single factor test, it was determined that the optimal hole of the seed metering device was cylindrical conical composite hole, and the optimal hole diameter was 1mm, and it was verified that the pass rate of the hole metering device under the condition of negative pressure at high speed was significantly higher than that without negative pressure. In order to get the best performance parameters of the metering device, with hole type wheel speed, vacuum degree, and suction diameter as the test factors, percent of pass, replanting rate, sowing rate as the evaluation index, the three factors five levels quadratic orthogonal rotation combination test was taken, and multi-objective optimization method was used, and the best parameter combination was determined as follows: when the suction diameter was 1.04mm, the vacuum degree was 2.10kPa, hole type wheel speed was 22.46r/min, the percent of pass was 93.14%, the replanting rate was 3.48%, the leakage rate was 3.38%. The verification results were basically consistent with the optimized results. In order to investigate the actual sowing performance of seed metering device, field seeding experiments were carried out. The field test results showed that the pass rate was 88.2%, the replanting rate was 4.9%, and the leakage rate was 6.9%. All the indexes met the requirements of hill seeding agronomy of millet.

Abstract:Aiming at the problems such as high seed damage rate and the requirement about seed grading pre-treatment of the mechanical Panax notoginseng seedling seeding device, a kind of air suction roller sowing seed device was designed by using the working principle of negative pressure seed suction, brush rolling and clean seed, and positive pressure throwing seeds. Through the mechanical analysis of the filling stage, the clearing stage, the carrying stage and the sowing stage, the main structural parameters of the seed-arrangement were studied and the main influencing factors of the performance of the seed-arrangement were analyzed. In combination with single factor test results, vacuum degree, drill speed, filling indoor seed quality as test factors, taking the qualified index, the missed seeding index, and seeding replant index as test indexes, three factors five levels quadratic orthogonal rotating test was carried out, to establish the regression equation between the test indexes and test factors, using the Design-Expert 10.0 software, by using the response surface method, all the factors affecting the filling performance of primary and secondary sequences were analyzed as follows: working speed of the seeder, degree of vacuum, and seed quality. Through parameter optimization, it was concluded that the optimal combination of parameters was as follows: the working speed of the seeder was 0.18m/s, the vacuum degree was 9.6kPa and the seed quality of the filling chamber was 1.2kg. At this time, the qualified index was 95.6%, the seeding replant index was 0.4% and the missed seeding index was 4.0%, which can meet the agronomic requirements of Panax notoginseng sowing.

Abstract:In order to solve the problem of the seeding quality descend caused by the poor performance of the dibbler, a secondary seed feeding mechanism was added between the seed taking plate and the duck’s beak. The purpose was to improve the seeding performance by planning the seed movement path, reducing the height of seed point, and reducing the phenomenon of missing and replaying. On the basis of the air suction roller type dibbler, the installation position, seed path contour, entrance and exit structural parameters of the secondary seed feeding mechanism were designed and analyzed. The trajectory, velocity and seeding performance of seeds were discussed by discrete element method. The causes of the phenomenon of missing and replaying were clarified. And the evaluation index of seeding performance of secondary seed feeding mechanism was determined as follows: qualified index, missing index and replaying index. Three factors quadratic rotation orthogonal combination test was carried out to study the influence of installation angle, operating speed and inner seed channel height on seeding performance. The results showed that the installation angle had a great influence on the seeding performance, the height of inner seeding channel had the least influence on the pass index. When the installation angle was 10.95°, the operating speed was 3.29km/h, and the height of inner seed channel was 16.68mm, the qualified index was 98.40%, the missing index was 0.85%, and the replaying index was 0.75%. Field experiments were carried out, the qualified index of the dibbler with the optimized secondary seed feeding mechanism was 98.06%, which was 2.21 percentage points higher than that of ordinary dibbler.

Abstract:Focusing on the problems of tearing and folding，when mulching straw fiber film for tobacco through using plastic-film mulching machines on ridge，a tobacco mulching device on the ridge with wheat straw fiber film cultivation was designed. The mulching straw fiber film process was analyzed to establish the mathematical model of mulching straw fiber film on the ridge with correction coefficient and the main factors affecting tearing of straw fiber film was proposed，when mulching straw fiber film. The structural parameter range of the key components was analyzed and confirmed and the structural parameter ranges were got, aiming at the guide roller of side of film and the device pressing side of film and mulching and pressing soil on the side of film etc.Three factors three levels orthogonal test was used，the distance between the roller of flattening film and the roller pressing side of film，the inclination angle of the guide roller of side of film and working speed were selected as test factors.The outspread degree and rate split by film-covering drill of light-struck film were taken as evaluation indexes.The results showed that the working speed and the distance between the roller of flattening film and the roller pressing side of film had an significant effect on rate split by film-covering drill of light-struck film (0.01＜P＜0.05). The effect of the inclination angle of the guide roller of side of film on the outspread degree was extremely significant (P＜0.01)．The results of verification test were as follows：the working speed was 3.6km/s, the distance between the roller of flattening film and the roller pressing side of film came to be 120cm, the inclination angle of guide roller of side of film reached 30°，such outspread degree was 97.4%，and rate split by film-covering drill of light-struck film was 12.6mm/m2. The device mulching wheat straw fiber film can achieve agricultural need and mechanization of film mulching machine on the ridge for tobacco cultivation.

Abstract:Aiming at the problems of low mechanization degree, low harvest efficiency and high harvest damage rate of Panax notoginseng in greenhouse, a self-propelled greenhouse Panax notoginseng harvest machine with hydraulic power transmission system and 380V three-phase power source was designed, which can complete the harvest of Panax notoginseng, root soil separation and other tasks, its key components were studied. Based on agronomic requirements, the whole machine structure and crawler chassis were designed, and the kinematics model was established. The linear motion characteristics of the complete machine were studied using RecurDyn. The single-side traction power was about 1357N, and the center of mass fluctuation was stable. By establishing the kinematic model of the root-soil mixture, the optimal structural parameters of the excavation were determined. The hydraulic control design was divided into three parts: walking, driving, and lifting. FluidSIM and GX Developer were used to design the local operating system and remote-control system software, respectively. The field test results showed that the hydraulic control system and the mechanical part worked well under the conditions of excavation. Under different control modes, the harvest machine can complete the functions of straight line, turning, lifting, and lifting chain rotation, etc. The straight-line travel was stable, the travel offset was 0.49%, and the forward and backward velocities of the hydraulic cylinder were 0.22m/s, respectively, which were basically consistent with the simulation results. The average yield loss rate was 1.48%, and the average root injury rate was 1.77%. There was no obvious root embedding phenomenon, which met the evaluation index of Panax notoginseng harvest machine.

Abstract:In order to study the influence of various factors on the forage crops conditioning performance and improve the quality of forage crops after harvest, a toothed roller conditioning test bench with adjustable space between conditioning rollers was designed. The test bench was mainly composed of conditioning roller, gap adjusting mechanism, quick changing mechanism of conditioning roller and measurement and control system, etc. The measurement and control system can collect the torque and speed information between the fixed roller and the transmission shaft in real time, and then calculate the energy consumption of the test bed. In order to test the performance of the conditioning test bench, taking the rotate speed of the fixed roller, the feeding rate of the per unit working length of the conditioning rollers and the gap of the conditioning rollers as the experimental factors, the unit energy consumption, the stem breakage rate and the grain breakage rate as the target values, a three-factor three-level response surface test with the Box-Behnken test method was carried out using forage crops. By the analysis of the test data, the quadratic regression models of the unit energy consumption, the stem breakage rate and the grain breakage rate were established, respectively, the optimal solution of the working parameters of the forage crops conditioning test bench were achieved, that was, the rotate speed of the fixed roller was 1157r/min, and the feeding rate of the per unit working length of the conditioning rollers was 10.84kg/(m〖DK〗·s), and the gap of conditioning rollers was 2.6mm. Meanwhile, the optimal solutions of the conditioning qualities of the forage crops under the optimal working parameters conditions were achieved, respectively, that was, the unit energy consumption was 2347.44J/kg, the stem breakage rate was 95.66%, and the grain breakage rate was 95.19%. Subsequently, the working parameters of the forage crops conditioning test bench were set as the optimal solution parameters of the models listed above, the confirmation tests with the forage crops were carried out. The results showed that the measurement values of the conditioning quality parameters of the forage crops under the optimal working parameters conditions were consistent with the optimization results, that was, the unit energy consumption, the stem breakage rate and the grain breakage rate of the forage crops were respectively 2377.53J/kg, 95.62% and 95.02%, the relative errors between the solution optimization values of the models and the measured values of the confirmation tests were less than 1%. The research results provided data reference and technical support for the design of forage crop conditioning machinery and the selection of working parameters.

Abstract:One of the critical barriers for small rubbing filament machine is the great varies of material sizes especially in the feeding direction, which makes it difficult to process the local baled straw by the same device. A small and adjustable bale-breaking and rubbing filament machine was developed and tested to improve baled straw filamentous performance. The machine integrated bale-breaking and feeding device, cutting and shredding device, rubbing and filamentous device and sieving and discharge device. The structure and working principles of the machine were introduced, and the force of the straw in each device was analyzed, on which key devices and components were designed. Meanwhile, the ratio speed of each aixs were matched by the analysis of the transmission system. Effects of motor output speed (X1), screen hole diameter (X2) and feeding gap (X3) on the productivity of standardized unit power (YE) and the percentage of filamentous straw (YH) were explored. Three-dimensional quadratic regression orthogonal rotation central combination experiment method combined with response surface method was used to conduct experiments and explore the interaction effects of influence factors on indicators. A regression model of influence factors and evaluation indicators was established through the analysis of variance. The significant factors affecting YE were ordered of X1, X3, X2, and the significant factors affecting YH were ordered of X2, X1, X3. In the interaction of factors, X1X2 had an extremely significant impact on YE1, and a significant impact on YH1 and YH2; X1X3 had an extremely significant impact on YE1 and a significant impact on YE2; X2X3 had an extremely significant effect on YE1 and YE2. The optimal structure and working parameters combination were determined to be 1353r/min and 1072r/min for x1, 47mm and 46mm for x2, and 12cm and 35cm for x3, respectively for the whole-plant and the square-bale maize straw. Verification experiments demonstrated that the actual values for the whole-plant and square-bale maize straw of YE and YH were 99.34kg/(kW·h), 113.56kg/(kW·h), 98.86% and 98.30%, respectively. The small and adjustable bale-breaking and rubbing filament machine operation developed was effective for improving productivity and filamentous performance in the baled straw rubbing. It met the design requirements for the grain size of the comprehensive utilization of straws. Overall, the study laid the foundation for the development of the small multi-purpose straw rubbing filament machine.

Abstract:Bagging is an important link from harvesting to transportation and storage of potatoes. To solve the problems of low efficiency and high damage rate of existing potato bagging machines, a new infusion, bag support and fixed weight bagging structure was designed, an efficient and low damage roller-type infusion potato fixed weight bagging machine was developed, and mechanical analysis of key components of the machine and kinematic analysis of key motion processes were conducted, and the main factors affecting the damage and bagging efficiency were identified as inflow bin door angle, conveying speed and loading volume. A quadratic regression orthogonal rotating combination test was conducted with the inflow bin door angle, conveying speed and loading volume as the test factors, and the breakage rate, injury rate and single-port bagging efficiency as the test indicators, and the test results were analyzed by ANOVA with Design-Expert 8.0.6 to determine the main order of the factors affecting the test indicators and to fit the test data. The test factors were analyzed by visually discerning the optimization region through response surface analysis, and the influence law of the test factors on the test indexes was analyzed. Using Design-Expert 8.0.6 optimization module and combining with the actual working situation to determine the optimal values of each factor, a test bench verification test was conducted on this basis, and the test results showed that when the inflow bin door angle was 45°, the conveying speed was 0.35m/s, and the loading volume was 27t/h, the breakage rate was 1.8%, the injury rate was 1.4%, and the single-port bagging efficiency was 12.4t/h, this parameter under the roller type guide flow potato fixed weight bagging machine breakage rate and injury rate was lower, and the bagging efficiency was higher.

Abstract:A low specific speed centrifugal pump was selected as the research object, and a method of suppressing cavitation was proposed by arranging rough zone on the suction surface of the blade leading edge. The modified SST k-ω turbulence model and Kubota cavitation model was applied to carry out cavitation numerical simulation on the whole flow area of the centrifugal pump. By comparing the flow field structure, turbulent kinetic energy distribution, velocity vector, cavitation volume change and pressure fluctuation of monitoring points in centrifugal pump impeller with and without rough zone structure under different cavitation numbers, the performance and cavitation suppression effect of rough zone structure on centrifugal pump were analyzed. The research results showed that the rough zone structure had little effect on the head and efficiency loss of the centrifugal pump, and it also did not have a great impact on the operation of the centrifugal pump. After the rough zone was arranged, the flow field distribution in the impeller was improved, the vortex intensity was weakened, and the flow became more stable. The rough zone structure effectively suppressed the initial formation of cavitation bubbles, reduced the energy dissipation caused by turbulence in the initial stage, and also had a certain inhibitory effect on the volume of the cavitation in the stage that cavitation bubbles had a great impact on the head of the centrifugal pump. Under different cavitation numbers, the rough zone structure had little effect on the main frequency pressure amplitude at the impeller inlet, the outer edge of the impeller and the volute separation tongue, and produced varying degrees of disturbance to the pressure pulsation behind the rough zone structure and close to the structure. The structure had certain reference significance for practical engineering applications.

Abstract:The three-dimensional velocity field measurement system V3V was used to measure the flow field under the bell mouth of vertical axial-flow pump. The velocity gradient, vortex intensity and vortex kinetic energy in the vortex region during the evolution of floor-attached vortex were analyzed. The experimental results showed that the formation process of the floor-attached vortex was accompanied by the constant changes of velocity gradient, vortex intensity and vortex kinetic energy. The velocity gradient, vortex strength and kinetic energy of vortex in the vortex region was firstly increased with time and reached the maximum, and then maintained for 0.4s, and then decreased rapidly. The duration of the formation and development of the floor-attached vortex was longer than that of the collapse and disappearance of the vortex. The vortex intensity was changed in different stages and positions reflected the characteristics of vortices in the evolution of vortices. The intensity of the floor-attached vortex was firstly increased with time, then maintained for a period of time, and then decreased rapidly. In the initial stage of vortex development, the vortex intensity was gradually decreased with the increase of the height from the bottom of the pump sump, after the floor-attached vortex entered the maintenance stage, the floor-attached vortex satisfied the vortex intensity conservation law; affected by the complex environment in the bell, the vortex was firstly collapsed and disappeared from the impeller inlet, and the floor-attached vortex intensity was gradually decreased from up to down. The research provided theoretical guidance for the optimal design of the pump sump.

Abstract:Desert steppe is the most arid type of grassland. As the transition between grassland and desert, desert steppe constitutes the fragile zone of ecological environment, and it is also the early warning area of climate change and ecosystem evolution. Using unmanned aerial vehicle (UAV) hyperspectral remote sensing technology to extract grassland vegetation types more quickly and accurately is of great significance to the monitoring of grassland ecological security and the rational development of grassland animal husbandry. The HEX-6 eight rotor UAV was utilized, on which the Pika XC2 hyperspectral imager (spectral wavelength: 400~1000nm, spectral resolution: 1.3nm) was mounted to collect remote sensing images of desert steppe in Inner Mongolia, China. The hyperspectral images with a spatial resolution of 2.1cm were obtained by the UAV flying at a height of 30m from the ground. Spectral difference was enhanced by spectral continuum removal transformation and vegetation indices were constructed by the spectra after continuum removal transformation. The step by step band selection method was used to select vegetation feature bands for reducing data dimension. A random forest classification model with 24 variables, including spectral features, vegetation features, terrain features and texture features was constructed and compared with support vector machine (SVM), K-nearest neighbor (KNN) and maximum likelihood classification (MLC). The random forest classification algorithm (SBS_RF) proposed had the best classification effect among the four classification methods. The overall classification accuracy was 91.06%, which was 7.9, 15.61 and 18.33 percentage points higher than that of SVM, KNN and MLC, respectively. Kappa coefficient was 0.90, which was 0.13, 0.23 and 0.26 higher than that of SVM, KNN and MLC, respectively. The results showed that the combination of UAV hyperspectral remote sensing and SBS_RF algorithm provided a technical means for rapid investigation of desert grassland vegetation types and quantitative indicators for grassland ecological monitoring and animal husbandry management.

Abstract:Due to human over-exploitation and utilization in recent years, the landscape types of Tibet’s alpine mountains have been severely damaged. The landscape pattern index can effectively evaluate the evolution of landscape types on the time scale. Therefore, an object-oriented classification method was used to determine landscape types, and the diversity index, dominance index, uniformity index and aggregation index were selected as indicators to evaluate and analyze the ecological sensitivity of the study area. The grand canyon was selected as the study area, and the object-oriented classification method was used to algorithmically classify the Tibetan artificial disturbance zone. Finally, a total of 1761 patches of ten types of landscapes were obtained, of which the woodland landscape and grassland landscape with the largest areas, respectively were 48.84% and 22.68%, and the proportion of snow/glacier landscape was 17.39%. From the landscape index, the landscape diversity index in the study area was 1.374, the dominance index 0.982, the evenness index 0.597, and the polymerization index 97.374. The grand canyon research area had high diversity, the single landscape had a relatively low dominance, and the distribution of different landscape spaces was better. In general, the landscape in this area was dominated by virgin forests, alpine meadows and glaciers, with less disturbance of human activities, and was mainly concentrated in the conversion of farmland and grasslands in the valley. Based on the weighted analysis of the ecological sensitivity of the grand canyon study area, the six types of impact factors were combined. The ecological sensitivity was mainly concentrated in moderate and highly sensitive areas, with a total of 95.71%. Moderately sensitive areas were concentrated in low-altitude and low-slope areas around river valleys, and the land was mainly waters, grasslands and shrubs. Highly sensitive areas were concentrated in high-altitude areas of the mountains, with steep slopes. The landscape was dominated by woodland landscapes and glaciers/ice landscapes.

Abstract:To study the temporal and spatial evolution law and driving force mechanism of navel orange orchard land, and formulate sustainable land use policy and maintain a good balance between economic development and ecological environment protection in the Three Gorges Reservoir area, Fengjie County of Chongqing, the main production area of navel orange, was selected as the research area, the temporal and spatial evolution pattern of navel orange orchard in Fengjie County from 2000 to 2019 was explored by using multi-source data such as geographical national conditions data and remote sensing images. On the basis of natural and socio-economic categories, policy category was introduced, totally 26 potential factors of pixel and township scales were selected, and then the random forest regression method was used to quantitatively analyze the relative importance of driving factors of land use change in navel orange orchard, and the marginal effects of main factors were also analyzed. The results showed that the navel orange orchard in Fengjie County was expanded rapidly from 2000 to 2019, with an overall scale increase of 150% and an average annual growth of 7.5%. They were mainly distributed along the Yangtze River, Meixi River, Daxi River, Caotang River, Zhuyi River and other main water systems in a zonal distribution, and gradually expanded along the river valley direction. The relative importance of the following driving factors ranked in the top nine were as follows: distance from water source, distance from urban area, soil pH value at pixel scale, and average slope, average elevation, special fund for poverty alleviation of navel orange industry, special fund for modern agricultural citrus industry, science and technology project fund of navel orange industry at township scale and aspect. The contribution of policy factors in the expansion of navel orange orchard was significant, which indicated that more appropriate policies were needed to be formulated to guide the healthy development of navel orange industry. The marginal dependence of navel orange orchard expansion on the main driving factors was strong, and there were differences among different spatial levels. On the whole, the expansion of navel orange orchards tended to occur in areas with average slope of 15°~25°, average elevation of 200~450m, distance from water source less than 3km, soil pH value of 5.5~7.6, financial support and good location conditions. The relative importance of the driving factors of land use/cover change (LUCC) in navel orange orchard was quantitatively analyzed, the driving mechanism of navel orange orchard expansion was explained, and effective technical reference for formulating land use policies was provided to guide the sustainable development of navel orange industry.

Abstract:A two-dimensional method for the detection of copper-lead stress in maize leaves based on hyperspectrum was proposed. Multi-order red-edged copper-lead sensitivity index (RECLSI) cluster of maize leaves was constructed by using the spectral values of the red edge position and two wavelengths in the 0.1~2.0 fractional order derivative (FOD) spectrum. The correlation coefficient between index and stress type in each cluster was calculated. The copper-lead identification features (CLIF) were constructed with the maximum and minimum correlation coefficients. The stress identification boundary (SIB) was established when clustering related to stress type appeared in the two-dimensional distribution of CLIF, enabling copper-lead stress identification. It was found that the maximum and minimum values of the correlation coefficient between the index and the stress type in each RECLSI cluster showed a trend of firstly rising and then falling, or firstly falling and then rising with the increase of FOD spectrum order. The poles appeared in the RECLSI clusters corresponding to the 1.3 order and 1.4 order FOD spectra, respectively. The two-dimensional CLIF distribution of 0.7~1.5 order FOD spectra showed clustering in relation to the type of stress, and the identification of copper-lead stresses could achieve different degrees according to CLIF-SIB. In the test set, the identification effect of CLIF-SIB in 1.2 order FOD spectrum was the best, with the accuracy (A) of 100%, and the 0.9 order, 1.0 order and 1.3 order FOD spectra corresponded to value of A of more than 90%. In the verification set, the identification effect of CLIF-SIB in 1.4 order FOD spectrum was the best, A was 87.5%, and the A was 81.25% at the 1.2 order FOD spectrum. The CLIF-SIB maize leaf copper-lead stress discrimination method based on FOD spectrum can effectively discriminate the stress types and it was stable.

Abstract:To improve the precision of crop yield estimation by integrating the remote sensing data into the crop model, two methods were applied, the four-dimensional variational (4DVAR) and the ensemble Kalman filter (EnKF), to assimilate the leaf area index (LAI) and the soil moisture (θ) derived from Sentinel multi-source data with the CERES-Wheat model. The two algorithms were assessed on the performance of assimilation of LAI and θ and estimated the yield of winter wheat across three counties located in the south of Shanxi Province in China. It was found that both assimilation algorithms can combine the advantages of remote sensing observations and crop model simulations. Compared with the crop model simulation values, the accuracy of assimilated LAI and θ were improved. Compared with EnKF, the 4DVAR algorithm can reduce the RMSEs of the assimilated LAI and θ by 0.1490m2/m2 and 0.0091cm3/cm3, respectively. And 4DVAR-LAI could accurately identify the phenological period of winter wheat according to the remote sensing observations, which was more consistent with the growth and development of the actual phenological period of winter wheat. Therefore, 4DVAR showed a better performance in the assimilation of Sentinel multi-source data with CERES-Wheat model. The accuracy of the yield estimation model based on assimilated LAI and θ by 4DVAR (RMSE was 449.77kg/hm2, MRE was 7.85%) was higher than the yield accuracy based on simulated values by the CERES-Wheat model (RMSE was 641.55kg/hm2, MRE was 10.23%). The 4DVAR assimilation algorithm effectively improved the yield estimation accuracy of winter wheat at a regional scale.

Abstract:In order to ensure the quality of seedlings and provide healthy and robust seedlings to meet the needs of large-scale and standardization of modern rapeseed industry, a 21d temperature stress experiment of rapeseed seedling was carried out. The aim was to study the identification of robust seedlings of rape under temperature stress using hyperspectral imaging technology. Firstly, the sensitive bands of temperature stress were extracted by spectral reflectance and continuous wavelet transform. And then the continuous projection algorithm and continuous wavelet transform-stepwise discriminant analysis were respectively used to extract characteristic wavelengths from sensitive bands of temperature stress. The waveband features and spectral features of rapeseed seedlings were analyzed with time. A total of seven features were selected, including the curve area at band MA and tangent eigenvalue tanθ of 554~714nm, the reflectance value at 1213nm and 1567nm, wavelet feature w(9, 967), w(13, 1213) and w(7, 1567) to establish a multi-feature fusion Fisher discriminant model. The results showed that the average classification accuracy of the model was 88.68%, and the best detection accuracy reached 95.56% at the three-leaf stage, which could better distinguish the temperature stressed rape seedlings and provide a reference for the rapid detection of robust rape seedlings based on hyperspectral technology.

Abstract:Realizing identification and counting of vegetable pests captured by yellow plates under complex conditions in the field is an essential prerequisite for targeted prevention and treatment pests and diseases of crop. Because of the small size, the large number and uneven distribution of pests trapped by yellow plates, it brings a great challenge to both manual and machine identification of pests. The current mainstream machine learning model Faster R-CNN was introduced to identify and count the main pests such as diamondback moth, striped flea beetle and bemisia tabaci on the yellow plates. It also proposed a modified Faster R-CNN pest detection algorithm (Mobile terminal pest Faster R-CNN, MPF R-CNN) based on Faster R-CNN. This algorithm combined ResNet101 network with FPN network as a feature extraction network and designed a variety of different size anchor pairs in the RPN network to judge the foreground and background of features. This algorithm also adopted ROIAlign instead of ROIPooling for feature mapping and a dual loss function for algorithm parameter control. The experimental analysis of 2440 sample images showed that the average accuracy of MPF R-CNN in the detection of bemisia tabaci, striped flea beetle, diamondback moth and other large pests (body length greater than 5mm) in the realistic and complex natural environment were 87.84%, 86.94%, 87.42% and 86.38%, respectively. The average accuracy in the low density of 0~480 on 35cm×25cm yellow plate was 93.41%, and the mean accuracy in the case of the medium density of 480~960 was 89.76%. There was no significant difference between the detection accuracy in sunny and rainy days in medium and low density and the determination coefficient between the counting result of this algorithm and the insect count was 0.9255. Simultaneously, the average recognition time of the algorithm was 1.7s when it was put into the Mi 7 mobile terminal system with the architecture of “WeChat applet + cloud storage server + algorithm server” for application test. The results showed that the present algorithm can support the current portable applications in terms of accuracy and speed and can provide technical support for the rapid mobile monitoring and identification of vegetable pests, which had a good promotion prospect.

Abstract:In recent years, deep learning has gradually developed in flower recognition research, which has a positive impact on the growth management and fruit production of orchard fruit trees. In order to tackle the problem that the densely gathered litchi flowers cannot be recognized by instance segmentation method in natural environment, a deep semantic segmentation network was proposed to recognize and segment flowers and leaves pixels. Firstly, pictures of litchi flowers were shoot in the experimental orchard in the flowering stage, which were taken to make pixel-level images, and then were used for data augmentation. Then a backbone network of 34 layers based on ResNet was built, in which dense features were connected layers by layers and in order to exploit the useful information, attention blocks were also added into the networks. A dense features connection method meant each layer was connected to every other layer in a feed-forward fashion, different from that features were only from the last consecutive layer. Attention block was a mechanism of propagating information useful for the specific task and suppress the useless one. Finally, a full convolution layer was added for image pixel prediction. The average intersection union ratio of the proposed model was 0.734, and the pixel recognition accuracy reached 87%. In summary, with good robustness and high recognition accuracy, the proposed deep semantic segmentation model can solve the problem of litchi flower recognition and segmentation, and provide visual support for intelligent flower thinning.

Abstract:In order to solve the problems in the process of feeding and management of meat rabbits, such as stress caused by manual weighing and difficulty in process of collecting weight information, a method of image segmentation and weight estimation based on deep convolution neural network was proposed, which can realize the contactless weighing of rabbits. A rabbit instance segmentation network based on Mask R-CNN was constructed. The residual network ResNet101 was used as the backbone network, and COCO dataset was used for migration learning to improve the training efficiency and obtain the segmentation results of unrestricted meat rabbits in the fence. Then the pixel area of each sample mask was extracted, and curvature and body length were introduced to modify the weight relationship between each sample and the corresponding weight. Projection area, curvature, body length and age as input parameters and body weight as output parameters, a six neuron weight estimation neural network was constructed to test the rabbit instance segmentation network and weight estimation neural network, the results showed that when IoU was 0.5∶0.95, the classification accuracy of rabbit segmentation network was 94.5%, and the pixel segmentation accuracy was 95.1%. The fitting correlation coefficient R of weight estimation neural network was 0.99391, MSE was 0.0336, and the mean weight error was 123g. The model had a good prediction effect on meat rabbits of different ages and different postures.

Abstract:Aiming at the problems that the subject feature and sentence vector in the traditional entity relationship extraction method are difficult to effectively integrate, and the existing BIO annotation strategy is difficult to effectively deal with the overlapping relationships, a joint extraction of entity relationship of poultry disease diagnosis and treatment text (JEER_PD) based on BERT and dual-pointer was proposed. JEER_PD used the dual-pointer labeling (DPL) strategy to establish two pointer labelers at the head and tail, marking the beginning and ending positions of all entities at once; introduced the conditional layer normalization (CLN) network layer to strengthen the connection between the subject extraction task and the object relationship joint extraction task; and used the probability balance strategy (PBS) to combat the imbalance of positive and negative labels to accelerate the model convergence.The experimental results showed that the accuracy, recall and F1 value of JEER_PD were 97.69%, 97.59% and 97.64%, respectively, and the three indicators were significantly improved compared with that of the existing methods, which proved that JEER_PD can quickly and accurately extract the entity relationship triples in the complex knowledge text of the diagnosis and treatment of poultry diseases.

Abstract:Based of a long-term tillage experiment from 2011 to 2017 in Henan Province, the RZWQM2 model was calibrated and validated. Effects of no-tillage on soil water storage at the depth of 0~100cm, nitrogen accumulation in aboveground and root, crop yield and nitrogen use efficiency of winter wheat in different precipitation patterns were analyzed. The simulated results showed that the nitrogen accumulation in aboveground and root and crop yield of winter wheat in different precipitation patterns were decreased successively in the order of wet year, normal year, and dry year. Compared with conventional tillage, the average soil water storage at the depth of 0~100cm under no-tillage was significantly increased by 11.3%, 12.9% and 16.9% in dry, normal and wet year at the whole growing stages of winter wheat, respectively. The aboveground nitrogen accumulation in dry year and root nitrogen accumulation from heading to harvest stage in normal year under no-tillage were both increased by 2.5% and 3.1% compared with conventional tillage, respectively. The nitrogen use efficiency under no-tillage was increased by 26.7%, 8.7% and 6.0% in dry, normal and wet precipitation patterns respectively compared with conventional tillage. However, compared with conventional tillage, N fertilizer using efficiency was increased by 11.7% in dry year, and decreased by 1.7% in wet year.

Abstract:In response to the problem of excessive nitrogen application and low nitrogen use efficiency in summer maize farmland in Guanzhong, Shaanxi, a two-year field trial was set up in Yangling, Shaanxi in 2018 and 2019. Five levels of nitrogen application (conventional nitrogen application N1 (300kg/hm2), 100% slow-release nitrogen fertilizer N2 (300kg/hm2), 65% slow-release nitrogen fertilizer N3 (195kg/hm2), 30% slow-release nitrogen fertilizer N4 (90kg/hm2) and no nitrogen (N0) were set, in which phosphate and potassium fertilizers were applied according to uniform standards, with no fertilizer CK as the control, the effects of different slow-release nitrogen fertilizer application rates on the dry matter accumulation, nitrogen accumulation uptake, soil nitrate nitrogen distribution and accumulation, yield and nitrogen utilization efficiency of summer maize were studied. Explanation of results: the application of nitrogen fertilizer can significantly increase the dry matter accumulation, nitrogen uptake and yield of summer maize. Compared with the local conventional nitrogen application (N1 treatment), the above-ground dry matter accumulation and nitrogen accumulation, nitrogen absorption efficiency, nitrogen partial productivity, yield and other indicators of N2 and N3 treatments were all increased significantly. Two-year trial, there was no significant difference between N2 treatment and N3 treatment in dry matter accumulation, cumulative nitrogen uptake, and yield. However, the partial productivity of nitrogen fertilizer of N3 treatment was increased by 54.61% and 56.25% compared with that of N2, and the agronomic utilization rate of nitrogen was increased by 35.24% and 61.48%, the nitrogen transfer rate of vegetative organs was increased by 17.34% and 18.10%, respectively. Reduced application of slow-release nitrogen fertilizer can significantly reduce the residual nitrate nitrogen in the 0~200cm soil layer, and increase the proportion of nitrate nitrogen in the 0~40cm soil layer. The highest proportion of nitrate nitrogen in the 0~40cm soil layer was N3 treatment compared with other nitrogen application treatments, and it was increased by 6.82%~118.60%. Under the condition that both high yield and high nitrogen use efficiency and low nitrogen loss can be satisfied, the application rate of pure nitrogen of slow-release nitrogen fertilizer of 195kg/hm2 was the best fertilization method in this area.

Abstract:In order to reveal the nitrogen uptake and utilization of rice roots under water and biochar management, field plot experiment and 15N tracer micro plot were used. Two irrigation modes (dry-shallow-wet irrigation and conventional flooding irrigation) and four straw biochar application levels (0t/hm2, 2.5t/hm2, 12.5t/hm2 and 25t/hm2) were set up. The effects of straw biochar on the morphological and physiological characteristics of rice roots, and the absorption and utilization of fertilizer and soil nitrogen by roots under dry-shallow-wet irrigation were studied. The results showed that the application of straw biochar changed the morphological and physiological characteristics of rice roots, and the appropriate amount of straw biochar increased the main root length, root volume, root fresh weight, root active absorption area, root bleeding velocity and root activity, optimized the root-shoot ratio, which was conducive to nitrogen absorption; the uptake of fertilizer-15N and soil nitrogen by rice roots under dry-shallow-wet irrigation mode was also improved. There was a significant positive correlation with root bleeding and root activity (P < 0.01), a significant positive correlation with active absorption area (P < 0.05), and a significant negative correlation with root-shoot ratio (P<0.05). The changes of root morphological and physiological characteristics in dry-shallow-wet irrigation mode promoted the uptake of fertilizer-15N and soil nitrogen by rice roots, and improved rice yield and nitrogen use efficiency. Compared with the treatment without straw biochar, the economic yield, nitrogen absorption and utilization efficiency, agronomic utilization efficiency and partial productivity of nitrogen fertilizer in the treatment of dry-shallow-wet irrigation with 12.5t/hm2 straw biochar were increased by 13.05%, 30.54%, 11.67% and 13.05%, respectively. The results can provide theoretical basis and technical support for the application of straw biochar in paddy field in cold and black soil region.

Abstract:The low water and fertility retention capacity of paddy soils in the semiarid area of Western Liaoning is one of the important obstacles restricting water conservation and high yield in this area. In order to study the water-saving and fertilizer-reducing effects of clinoptilolite in water-saving irrigated paddy fields and clarify the relationship between the process parameters of nitrogen accumulation and rice yields, field experiments were conducted in semiarid areas of Western Liaoning in 2019 and 2020. Conventional flooding irrigation treatment was taken as control, and alternate wet-dry irrigation with application of clinoptilolite, alternate wet-dry irrigation with application of clinoptilolite and 1/4 less nitrogen treatment, alternate wet-dry irrigation with application of clinoptilolite and 1/4 less phosphorus treatment, alternate wet-dry irrigation with application of clinoptilolite and local organic fertilizer instead of quick-acting fertilizer treatment,were designed to monitor rice water consumption, dry matter, nitrogen uptake, etc. Results showed that compared with conventional flooding irrigation, clinoptilolite coupled with alternate wet-dry irrigation significantly saved irrigation water by 4.8% to 11.4%, increased water productivity by 6.2% to 15.5%, reduced phosphate fertilizer by 25%, and increased rice grain yield up to 9.7%. The rice water consumption presented that it was firstly increased and then decreased, and the plant nitrogen requirement conformed to the Richards’s growth function. The principal component analysis showed that the three important parameters affecting the highrice yield were the nitrogen accumulation amount, nitrogen accumulation duration and stablity of nitrogen accumulation process. The significant increase in rice yield for “alternate wet-dry irrigation with application of clinoptilolite and 1/4 less phosphorus” treatment, and “alternate wet-dry irrigation with application of clinoptilolite” treatment was due to the increased nitrogen accumulation in leaves, and then increased the dry matter accumulation and the nitrogen accumulation in rice panicles. In summary,alternate wet-dry irrigation with application of clinoptilolite and 1/4 less phosphorus treatment, and alternate wet-dry irrigation with application of clinoptilolite treatment had characters of both high nitrogen accumulation amount and duration, and stable nitrogen accumulation process, which became the important ways to save irrigation water and increase production efficiency in apaddy field of the semi-arid area of Western Liaoning.

Abstract:Aiming to analyze crop nitrogen uptake, nitrogen utilize efficiency, soil ammonia-oxidizing mushroom and nitrogen concentration in surface water based on a fertilization field experiment to select an environmentally friendly nitrogen application practice in the area along Yangtze River. Five treatments were designed, including non fertilization (CK), traditional fertilization (NPK, 225kg/hm2), equivalent nitrogen (CRF1), reducing 15% nitrogen (CRF2), and reducing 25% nitrogen (CRF3) by controlled release mixing fertilizer. Results showed that there was no significant difference in the rice yield except for CRF2 among NPK, CRF1 and CRF2 treatments. Compared with NPK treatment, the values of crop nitrogen uptake, nitrogen utilize efficiency and direct economic benefit under CRF2 treatment were increased by 7.4%, 10.7%, 43.4% and 27.2%, respectively. Ammonia-oxidizing archaea (AOA) accounted for between 73.5% and 88.4% was the dominate mushroom in the paddy soil. Compared with NPK treatment, the ratios of AOA accounted for ammonia-oxidizing mushroom under CRF1, CRF2 and CRF3 treatments were significantly (p<0.05) increased by 13.6%, 9.9% and 6.0%, respectively. It was indicated that the intensity of soil ammonia-oxidizing process could be reduced. Compared with NPK treatment, the concentrations of total, dissolved and particulate nitrogen in surface water under CRF2 treatment were significantly decreased by 13.2%, 10.6% and 33.7%, respectively. The corresponding values under CRF3 treatment were 24.9%, 22.9% and 40.6%, respectively. In conclusion, our findings indicated that controlled release mixing fertilizer application, especially for reducing 15% nitrogen (190kg/hm2), was a prefer nitrogen management practice for maintaining rice yield, decreasing intensity of soil ammonia-oxidizing process, improving nitrogen efficiency and reducing the risk of agricultural non-point nitrogen pollution. Therefore, the practice should be recommended in the single cropping rice region down the Yangtze River.

Abstract:Insufficient irrigation water resources and excessive input of nitrogen fertilizer are very common in agricultural production in North China Plain. In order to deal with these problems, a field trial with winter wheat as test material was conducted in the lysimeters in 2018—2019. Under three irrigation levels of W1 (60%ETc(reference crop water requirement), 300mm), W2 (75%ETc, 370mm) and W3 〖JP3〗(ETc, 495mm), and three nitrogen levels of N1 (180kg/hm2), N2 (255kg/hm2) and N3 (330kg/hm2), the effects of irrigation-fertilization methods on soil water and nitrogen distribution, photosynthetic characteristics and light response curve parameters of winter wheat flag leaf function period and wheat grain yield were examined. The results showed that W2N2 treatment can maintain wheat growth demand and improve water and nitrogen use efficiency, which increased soil water storage by 41.12mm and decreased soil nitrate leaching by 15.87%, compared with that of W3N3 treatment. The interaction of water and nitrogen had a significant effect on the photosynthetic characteristics of wheat flag leaves. The Pn, Tr and Gs of W2 and W3 treatments was significantly higher than that of W1 treatment, but there was no significant difference between them, and N treatment had the same response. According to the result of yield test, W2N2 had the largest yield, with significant difference than other treatments. In addition, there was a significant relationship between yield and photosynthetic characteristics, light response curve parameters, which indicated that the improvement of photosynthetic characteristics caused by water and nitrogen was conducive to the accumulation of photosynthetic products, and then increased the yield. Under the conditions of this experiment, W2 treatment (irrigated 370mm in overwintering period, 75%ETc）combined with N2 treatment (with nitrogen application rate of 255kg/hm2) can not only maintain high photosynthetic characteristics and crop yield, but also improve the utilization of soil water storage and reduce the risk of nitrate leaching, realizing the water-saving and nitrogen reduction production of winter wheat in the North China Plain.

Abstract:Farmland soil is the foundation of national food security, and the management and protection of soil health is crucial to achieve sustainable development goals. Based on the theory of functional soil management, selected evaluation indicators for the five functions of primary productivity, provision and cycling of nutrients, provision of functional and intrinsic biodiversity, water purification and regulation, and carbon sequestration and regulation, by identifying paddy land, irrigated land and dry land for different soils. The relationship between the supply and demand of functions was identified, a soil function supply and demand discriminant matrix was constructed, and the heavy metal pollution threat factors were overlied, the farmland soil health was evaluated, and the spatial mapping of evaluation indicator—soil function/threat—soil health was realized. A study on the applicability of the evaluation method was carried out in Wen County, Henan Province. The results showed that the spatial pattern of the supply and demand of the five soil functions in Wen County basically showed a trend of gradually increasing from south to north, with Qingfengling as the boundary, the supply and demand of soil functions in the central and northern regions were in surplus, while the supply and demand in the southern region were in an imbalanced state. Staggered distribution of soil health grades, the sub-health area accounted for the largest proportion, accounting for 44.4%. Healthy soil was scattered in Huangzhuang Town, Fantian Town, Wude Town, and Xiangyun Town. Soil texture, soil structure, soil nutrients, soil biological activity and heavy metal pollution threat were the main factors for the spatial differentiation of soil health. This research can enrich the soil health evaluation method system theoretically, and promote the sustainable utilization and management of farmland resources in practice.

Abstract:Aiming at the problem of high energy consumption of artificial light source in plant factory, the study on improving the energy utilization rate of lettuce and reducing the energy consumption of light source was carried out through alternating light supply mode. Lettuce was grown in the fully artificial light plant factory, where adjustable red and blue LED panels were used as the sole light source for lettuce growth. In the experiment of alternating irradiation mode of red and blue light, the alternating interval in alternating treatments was 5min, 10min, 15min, 30min and 60min, respectively. The simultaneous RB light was regarded as the control, and also pure red R and pure blue B were set for comparison. The results showed that, the fresh weight, LUE and EUE of lettuce in all alternating light treatments were improved by respectively 18.6%~53.6%, 34.3%~78.6% and 34.6%~79.4% compared with the control. The highest fresh weight, LUE and EUE were all detected under 30min treatment, which were respectively 115.50g, 5.84% and 1.92%. R/B(30m) significantly improved the net photosynthetic rate, water use efficiency, Ψo, RC/CSo, PⅠabs, ABS/CS, TRo/CS and ETo/CS, as well as the specific activity of PSⅡ in lettuce leaves. Lettuce biomass were the highest under monochromatic red light, while LUE and EUE were significantly lower than that under R/B(30m). PⅠabs was the highest under pure blue light, while LUE and EUE were the lowest or not significantly different with the lowest value. The content of carotenoids in lettuce under R/B(5m) was significantly higher than that in other treatments. High alternating frequency of red and blue light better stimulated the synthesis and accumulation of carotenoids in leaves, which was beneficial for the protection of photosynthetic organs.

Abstract:Artificial feeding and orientational sorting of postharvest cabbage are inefficient, labor-intensive and high-cost. Aiming at above problems, and combined with the commercial handling technology and moment of inertia of postharvest cabbage, a monomer sorting and orientational conveying device for postharvest cabbage was developed. Firstly, Turnover and unloading of postharvest cabbages in a spatially stacked state were realized by using a cylinder. Then, the postharvest cabbages were discharged in a single layer under the action of single-layer feeding roller and curved buffer track. And monomer sorting was realized under the guidance of the limit roller and the variable pitch conveyor roller. Finally, single postharvest cabbage in stable space formed by four tapered rollers was directionally conveyed based on moment of inertia. The structure design of the key mechanisms, such as turnover and unloading mechanism, monolayer feeding and buffer mechanism, monomer sorting mechanism with variable pitch, orientational conveying mechanism with tapered roller, was carried out. And the prototype of the monomer sorting and orientational conveying device for postharvest cabbage was trial produced. Taking “Zhonggan 15” cabbage as test material, the orthogonal test was carried out with running speed of unloading cylinder, revolving speed of single-layer feeding roller, revolving speed of variable pitch conveyor roller and line speed of conveying chain as the test factors, and the success rate of monomer sorting and the success rate of orientation as the test indexes. The results showed that the optimal parameters of running speed of unloading cylinder, revolving speed of single-layer feeding roller, revolving speed of variable pitch conveyor roller and line speed of conveying chain were 10mm/s, 50r/min, 30r/min and 300mm/s, respectively. Under the condition of the optimal parameter combination, the average success rate of monomer sorting was (96.50±2.54)%, the average success rate of orientation was (95.17±3.28)%, and the single-channel operation efficiency was about 1004kg/h, which met the operation requirements of subsequent links such as root trimming, detecting and grading. The research results provided a reference for further research and development of multi-channel high-throughput monomer sorting and orientational conveying device, and the mechanization operation of commercial handling for postharvest cabbage.

Abstract:At present, the detection of soybean seed coat crack mainly depends on visual inspection, which has low detection efficiency and large error, a method for automatic identification of soybean seed coat cracks based on near infrared spectroscopy and machine learning was proposed. The near infrared spectra of 150 soybean samples (75 cracked and 75 normal) were collected by FT-NIR spectrometer. The original spectra, standard normal variable (SNV), multiple scatter correction (MSC), the first derivative and the second derivative with SG smoothing were used to process the obtained spectra. Then partial least squares discriminant analysis (PLS-DA), k-nearest neighbor (KNN), support vector machine (SVM), random forest (RF), stochastic gradient boosting (SGB) and extreme gradient boosting (XGBoost) were used to establish soybean seed coat crack identification models. The effects of different spectral preprocessing methods on the classification results of the six machine learning methods were compared and analyzed. Under the appropriate spectral preprocessing conditions, the accuracy of validation set of six different machine learning algorithms was not less than 80.00%. PLS-DA had the best classification result, and the optimal accuracy rate of validation set reached 90.00%; the next was XGBoost, the optimal accuracy rate of validation set reached 86.67%, followed by SVM, KNN, SGB and RF. The results showed that near infrared spectroscopy combined with machine learning was feasible to identify soybean seed coat cracks, and PLS-DA was the best method to identify soybean seed coat cracks under the original spectral conditions. The research result can provide a method for automatic identification of soybean seed coat cracks.

Abstract:To improve the credibility and efficiency of quality traceability based on blockchain, some studies were reportedand explainedthe overall designs of combining hazard analysis and critical control points (HACCP) and blockchain technology. However, there is still a lack of operational technical solutions in documented research on the combined use of the two.To make up for the above shortage, a quality traceability model based on HACCP was constructed by using blockchain technology. This critical control points (CCP) in the HACCP specification was extracted for raw oyster processing as the monitoring data points of the traceability system, obtaining the to-be-recorded data structure that can truly reflect the product quality. A highly scalable standard smart contract was designed based on this data structure. Smart contracts for each key control point were then derived. What this achieved was the on-chain data monitoring as well as automatic data quality judgment of the whole raw oyster processing process. It also discussed how a highly robust deployment model was implemented with the reference to a permissioned chain platform Hyperledger Fabric. The whole process of data on-chain was explained from a theoretical perspective. Lastly, the traceability system prototype of the model was implemented. Function and performance tests on the implemented system were conducted. In function tests, the system ensured the traceability and credibility of the quality traceability data by the reading of product history records. The automatic judgment and real-time control of product quality were achieved at the same time. In performance tests, the system average transaction success rate reached up to 377, the transaction success rate was 99.96% and the average delay was 0.5s when the total transaction volume reached 2000, which met the business needs of the quality traceability of the raw oyster processing process. The research result can provide a new reference for the traceability of aquatic product quality or quality safety risks.

Abstract:To improve the navigation path tracking controlling performance of small crawler tractors which are widely used in traditional orchards, a navigation path tracking control method based on the virtual radar model was developed. Drew on the human experience of driving, referred to the principle of radar scanning and the idea of image recognition, the virtual radar model was constructed to generate the virtual radar map. The virtual radar map was used to describe the position relationship between the vehicle and the path, and the corresponding driving operation instructions were generated by the deep neural network classification. The typical U-shaped path of orchard operation was taken as an example to carry out simulation and real vehicle test, and the simulation results showed that the proposed method can accurately achieve the navigation path tracking control; orchard test results revealed that when the vehicle speed was 0.36m/s and 0.75m/s, maximum lateral error of path tracking was 0.150m and 0.191m, the average lateral error was 0.031m and 0.051m, the standard error was 0.025m and 0.036m, respectively; compared with the designed fuzzy control method, the maximum lateral error was reduced by 15.73% and 36.33%, the average lateral error was reduced by 27.91% and 19.05%, and the standard error was reduced by 21.88% and 28.00%, respectively. The results demonstrated that the navigation path tracking control method based on the virtual radar model presented high path tracking accuracy and driving stability, which met the actual operational needs of orchards. It provided a way of thinking to solve the navigation path tracking control problem.

Abstract:In order to improve the large travel stiffness in direction Z and the comprehensive performance of the hybrid robot, a five degree-of-freedom (DOF)hybrid robot 3-RHUR/PUS+PP was proposed, which was composed of a 3-DOF parallel head with a following sliding barrel in series double slideways. Firstly, the forward and inverse position solutions were given based on the nonlinear constrained equations. Considering the parallel mechanism and the series mechanism, the forward and inverse kinematics mapping relationships of the hybrid robot were established based on the screw theory, which provided the basis for the research on the overall performance of hybrid robots.The stiffness of the direction without DOF was infinity, because the hybrid robot was lower-mobility hybrid mechanism.Its direction stiffness was discussed by the flexibility model of the hybrid robot. Secondly, taking into account the rotational ability, force transmission performance, speed performance and stiffness performance of the 3-RHUR/PUS+PP hybrid robot, the hybrid robot was optimized with multiple objectives on the basis of the linear weighted method.The optimization algorithm combining optimal Latin hypercube sampling (OptLHS) and interpolation was proposed, which shortened the time required to optimize the calculation and obtainedthe optimal parameters of the robot. Finally, according to the optimization result, the preferred robot parameters were obtained, and its rotational ability, speed performance and stiffness performance were studied.

Abstract:In order to calculate the friction torque of double-nut ball screw more accurately, based on the load distribution models, the influence of lead error on load distribution was analyzed. The calculation results showed that lead error directly led to uneven load distribution of ball screw and if ignoring the screw, nut elastic deformation and other errors, the axial deformation of each ball was linearly distributed. Only to calculate the axial deformation of the first ball and the lead error between balls, the total deformation of balls, preload and friction torque of ball screw can be calculated. And when the thickness of gasket was constant, the axial offset of nuts raceway curvature center and the axial offset of curvature center of screw raceway contacting the first ball to the two nuts midplane can be determined by numerical fitting of lead error and friction. Based on these, the relationship model between friction torque and lead error of double-nut ball screw was proposed. To verify the model, the lead error of screws with different accuracy levels was measured, and each screw was assembled with the same nut, gasket and balls to form a ball screw pair, and the friction torque was measured. The test results showed that the relative error between friction torque value calculated by previous model and test value was 11.75%~54.69%, while the relative error between friction torque value calculated by the model and test value was 0~8.79%. The relative error was obviously small, which indicated that the model can more accurately predict the influence of lead error on ball screw friction torque. The problem that ball screw led error and ball load distribution was not considered when calculating the friction torque of ball screw was solved, and the validity of the model was verified.

Abstract:Microchannel heat exchanger is widely used in agriculture due to compact structure and high efficiency. However, the minification of size can lead to the increase in flow resistance of the system, pressure drop and energy consumption, and finally cause lower economic efficiency. Previous work has proved that ultrasound can be applied to microchannel heat exchanger to improve its heat transfer performance, but the effect of ultrasound on flow boiling pressure drop is not clear. To investigate the effect of ultrasound on flow boiling pressure drop characteristics in microchannels, a microchannel experiment section with an ultrasonic transducer was designed. Using the refrigerant R141b as the experimental working fluid, the flow boiling experiment was conducted in rectangular microchannels with the cross-section of each single channel being 2mm×2mm to study the pressure drop characteristics of refrigerant R141b in microchannels under the action of ultrasound and a high-speed digital video camera was used to visualize the flow boiling in the microchannels. The pressure of the system was set as 152kPa, the heat flux density ranged from 10.01kW/m2 to 23.30kW/m2, mass flow rate ranged from 29.67kg/(m2·s) to 177.96kg/(m2·s), the applied ultrasonic power ranged from 12.5W to 50W and frequency ranged from 23kHz to 40kHz. The results showed that the proportions of the pressure drop components of the microchannels with or without ultrasound were approximately the same and the friction pressure drop accounted for the largest proportion, followed by gravity pressure drop and acceleration pressure drop, with the proportion of inlet and outlet pressure drop being the smallest. The ultrasound applied at the inlet of microchannels had a slight reduction effect on the flow boiling pressure drop of the microchannels. When the mass flow rate was 118.64kg/(m2·s) and the heat flux density was 17.03kW/m2, the application of 50W and 40kHz ultrasound could reduce the two-phase frictional pressure drop per unit length by 12.70%. When the mass flow rate was 118.64kg/(m2·s) and the heat flow density was 18.56kW/m2, the frictional pressure drop per unit length of two phases was increased by 36.15% with 50W ultrasound compared with 12.5W ultrasound, and the frictional pressure drop per unit length was decreased by 23.85% with 40kHz ultrasound compared with 23kHz ultrasound. The influence of ultrasonic parameters on the friction pressure drop per unit length was weaker at higher heat flux. In order to reduce the flow boiling pressure drop in microchannel, ultrasonic wave with relatively lower power and higher frequency would yield better results. The ultrasound affected the pressure drop of two-phase region mainly by changing the bubble dynamics. The visualization results showed that ultrasonic wave can affect the number and size of bubbles and flow pattern in the channel. In the bubble flow stage, acoustic cavitation and acoustic streaming could promote the formation of bubbles and increase the frequency of bubble detachment. In the intense boiling stage, the increase of gas-liquid interface would hinder the propagation of ultrasound and weaken acoustic cavitation. The research result can provide a reference for the application of ultrasound in microchannel heat exchanger.