Abstract:Crop type identification and mapping products are required for the monitoring of crop growth, risk stress, crop yield and other parameters, as well as the planting structure adjustment, decision analysis of supply and demand, arable land resource security and ecological effect assessment. Remote sensing data have become the most important data source for crop type mapping, and the emerging digital technology also provides a series of new approaches. However, with the advent of smart agriculture era, new demands are placed on crop type mapping with higher spatial and temporal resolution, higher product accuracy and more automated. The object was to provide a review of technology trends, key issues and demand gaps of crop type mapping based on remote sensing. It was concentrated on the main problems and main research work from the three perspectives of small-scale crop type fine identification, large-scale crop type automated mapping and crop type mapping mode change. It was highlighted that crop type mapping products needed more precise, near real-time and higher accuracy on the small scale, mainly using super-high spatialresolution image data, such as one meter or less. Furthermore, it still faced significant challenges to improve crop type mapping accuracy, such as more than 95%, for extracting high accuracy crop phenotypes information to meet application needs. On the large-scale crop type mapping, it needed to be more automated and meet the reliable accuracy, such as around 90%. High spatial and temporal resolution image data were mainly used, such as 2~5d and 10~30m, and also the issues of how to deal with the storage management and analysis were faced when it came to big data, to develop the classification method in a robust manner over the large scale, and to fine a scientific and efficient ground true sample acquisition approach. It was also presented that the pattern of crop type mapping would also shift from confirming monitoring to early prediction and specific crop detection. Moreover, five prospects were proposed from the perspectives of strengthening scientific research and accelerating application, which provided some ideas for the development of remote sensing crop type identification and mapping products that met the different needs of smart agriculture and smart land.

Abstract:In factory-like planting pattern of Portabella mushrooms, aiming to provide working parameters for mushroom picking robot, mushroom bed images were collected into the industrial personal computer (IPC) to measure in situ by structured light 3D camera-SR300. For complex background of plenty of hyphae in mushroom bed, the dynamic threshold was calculated adaptively by the mode of depth data of soil surface combined to at least 20mm of stipe height, and the binary image of mushroom caps were extracted from mushroom bed background. For adhesion and quasi-circular mushrooms, the centric coordinates and radius were detected roughly based on the 2-1 cyclo-Hough transform, and then the boundaries of mushrooms were tracked, denoised and interpolated to segment adhesion mushrooms and fit a single mushroom exactly. And the three-dimensional coordinates of the centric and the boundary points of a single mushroom were calculated. By the coordinate system calibration of camera, the measurement accuracy in site was verified by using a ceramic disk. The location, diameter and deviation-lean angle of a single mushroom were calculated in world coordinate system of the camera. Field test results showed that the maximum diameter error of a mushroom was 5.57mm, the maximum lean angle error of a mushroom was 6.3°. The mean run time of a video frame was 206ms, and the mean run time of a single mushroom was 44ms, which can meet the scene requirement of the mushroom picking robot.

Abstract:Feature extraction and similarity measurement are two key problems of crop pest recognition based on image processing. The leaves of wheat powdery mildew were treated as the research objects, and an algorithm of wheat leaf disease severity recognition based on elliptical metric learning was proposed. Firstly, a method of moving window maximum (MWM) feature extraction was presented in the algorithm. The HSV color features and LBP texture features were extracted by using the sliding window method from the segmented lesion images. The maximum value of each dimension feature on the same horizontal sliding window was taken as the feature of this horizontal bar. The MWM feature representation method can effectively reduce the influence of curvature, tilt and different shooting angles of wheat leaves on the recognition rate. Then, an elliptical metric with better distinguishability for sample data was introduced, and the elliptic metric matrix was defined based on the log-likelihood ratio of Gaussian distributions on the intrapersonal sample and the extrapersonal sample. In order to maintain the maximal classification information, the feature subspace learning and elliptic metric learning were performed simultaneously. Finally, to recognize the severity of diseases, the elliptic metric was used to calculate the distance between the eigenvectors. The results of comparison experiments showed that the recognition rate of wheat powdery mildew severity was 100%, which was better than 88.33% for SVM method and 90% for BP neural network method. The research result can provide valuable help for the intelligent recognition of crop disease severity.

Abstract:Straw returning is one of the most important measures for increasing fertility. But straw returning has not been widely popularized at present. It needs to be supervised and tested. However, manual detection of straw coverage is time-consuming, laborious, low accuracy and difficult to store information. In order to solve these problems, a straw coverage detection method was proposed based on image segmentation. Considering the precision of traditional image segmentation method was not high, and the computation was complex for multi-threshold segmentation, the search mechanism of gray wolf (GWO) algorithm and differential evolution (DE) algorithm were combined, and a multi-threshold automatic segmentation method was proposed based on image, DE-GWO algorithm for field straw mulching detection. Firstly, the straw mulching image collected in the field was preprocessed, and the adaptive Tsallis entropy was used as the objective function of the algorithm to evaluate the efficiency of image segmentation. Secondly, the number of segmentation thresholds was selected according to the complexity of the image, and the multi-threshold image was segmented by DE-GWO algorithm. The proportion of the images after the segmentation was calculated by the gray degree level. Finally, the straw mulching rate in the image and the actual geographic area were converted according to the shooting height and the wide angle of the camera. The experimental results showed that the straw mulching rate in the field and the actual measurement error were less than 8%, and the DE-GWO algorithm was more accurate than the improved particle swarm optimization (PSO) and gray wolf algorithm (GWO). Compared with manual measurement, the average consumption time was reduced by more than 1500 times. In addition, a set of software system for detection of straw coverage based on DE-GWO algorithm was developed, which provided the basis of algorithm and software support for the real-time detection of the monitoring system.

Abstract:The pneumatic style straw deep burying and returning machine enjoys comprehensive functions in the aspect of stubble breaking, straw picking and crushing, ditching and crushing, inter-row deep loosening, deep-buried straw, soil covering, and finally buries the straw below 20cm between rows and at the same time constructs the furrow loose and ridge compaction plough layer structure. According to the technical requirements of reasonable tillage construction, the pneumatic conveying device was designed. The main structural parameters of the conveying device were as follows: the cross section of the conveying pipe was 0.2m×0.2m square pipe;the impeller diameter was 0.55m;the width of impeller was 0.17m; the inlet diameter was 0.26m;the width of fan shell was 0.2m;the outer diameter of screw blade was 0.25m;the diameter of the screw shaft was 0.09m;the screw pitch was 0.2m;the thickness of the screw blade was 0.003m;and the clearance between the outer diameter and the inner surface of the conveying pipe was 0.005m. According to the test of suspended velocity for corn, the suspended velocity of upper, middle and lower parts of 10cm corn stalk was 10.4m/s, 12.3m/s and 12.7m/s, respectively, with an average of 11.9m/s. The test results and simulation error was 7%. On the basis of gas-solid coupling theory, the CFD-DEM method was used to simulate the two-phase flow of gas-solid in the conveyor. When the angle was 30°and rotation speed was 1800r/min, the minimum velocity of straw in the conveying pipeline was 5.21m/s. And the corresponding velocity of air flow was 17~27m/s. At the outlet, the velocity of straw reached 6.06m/s, and 2~27m/s at the air flow rate. The number of straw inside the fan was 24 at 1.2s, and then it had the most effective delivery. The results of field experiment showed that the optimum combination of performance parameters of pneumatic conveyor was as follows: blade bending angle was 30°, straw coverage was 1.2kg/m2, fan speed was 1800r/min and the qualified rate of deep-buried was 93.2%. The research had effectively improved the deep-buried quality and also can provide reference on further study on performance improvement of pneumatic straw deep burying and returning machine as well as the promotion of agriculture mechanization level. 

Abstract:A mechanical and ecological tillage pattern (MET) which combined ploughing, rotary tillage of seeding strip, no-tillage and subsoiling in four years for a cycle was designed. To study the short-term effects of the pattern on physical and chemical characteristics of soil and groups yields in arid area, the positing experiment of four years in wheatcorn two cropping area was carried on and with continuous no-tillage (CNT) and conventional tillage (CCT) for comparison. The experiment results showed that the MET improved the quality of soil structure and soil fertility significantly, prevented soil harden, and the ecological and fertile soil effects were remarkable. It increased the aggregate content in 0 ~ 30cm soil layer significantly and improved soil structure stability, and the average aggregate content of water stability was 8.2% and 30.4% higher than those of the CNT and CCT, respectively. It reduced the bulk density of soil in 0 ~ 30cm soil layer effectively, its average bulk density was 0.089g/cm3 and 0.125g/cm3 smaller than those of the CNT and CCT. It increased the content of total nitrogen, rapid available phosphorus and rapid available potassium in 0 ~ 30cm soil layer as well, but there were no significant impacts on the content of available nitrogen. It added the content of organic carbon, the organic carbon content in MET was 0.36g/kg and 0.61g/kg higher than those in CNT and CCT, respectively, and the organic carbon concentration distribution was balanced between the layers of 0~10cm,10~20cm and 20~30cm.However, the CNT only added the organic carbon content in 0~10cm soil layer and the CCT only increased the organic carbon content in 10~20cm soil layer. The MET increased wheat yields significantly by increasing the average wheat tillering, effective spike and grain number per spike, the wheat yields of MET was 14% and 14.9% higher than those of CNT and CCT, respectively. The tillage methods before wheat sowing had after effects to a certain extent on corn, the MET and the CNT improved the corn yields by increasing the effective ear of corn and grain number per spike, the corn yields of the MET and CNT were 7.4% and 3.7% higher than that of CCT, respectively, but there was no significant difference between them.

Abstract:In order to achieve precision seeding of low sowing quantity of wheat and improve the accuracy of precision seeding of wheat, a kind of cone diversion type horizontal plate wheat precision seed-metering device was proposed. The design and theoretical analysis of key parameters were carried out. Single factor test on the effects of the guide bar form, number of holes, cone disc speed and cone disc angle on seed-filling performance were studied by EDEM discrete element software, and then the parameters were determined. On this basis, the multiple quadratic regression rotation orthogonal combination test was carried out with cone speed, seed-layer thickness and length of hole, and then the test data was analyzed by Design-Expert 8.0.6 software. The regression model and the influence of factors on the index were obtained. The influence relation of factors on the single rate was determined and the order of importance was the cone disc speed, length of hole and seed-layer thickness in turn. The order of importance of the qualified rate was the cone disc speed, seed-layer thickness and length of hole in turn. Interaction between the length of a hole and the seed-layer thickness, cone disc speed and seed-layer thickness cannot be ignored. Based on the regression model, the parameters were optimized and the seed metering device under the optimized parameter combination was tested for seed-metering performance. The results showed that the qualified seed-metering rate, the leakage rate and single rate was 90.13%, 9.87% and 49.50%, raspectively, and the test results matched the simulation optimization results. The reliability of the simulation optimization result was verified. The performance comparison tests with the original cone seed-metering device showed that the designed cone diversion type horizontal plate wheat precision seed-metering device was better than the original cone disc seed-metering device in both metering performance and breakage index. The qualified rate was increased by 3.4 percentage points, 2.1 percentage points and 1.9 percentage points at 3km/h, 4km/h and 5km/h, respectively, and the damage rate was decreased by 0.2 percentage point at 3km/h. The designed cone diversion type horizontal plate wheat precision seed-metering device can effectively improve seed filling performance and qualification index and reduce sowing quantity and breakage rate. The research results provided a reference for the design of wheat precision seeder used in wide seedling strip.

Abstract:In order to solve the problems such as poor adaptability, small supporting power, high ground clearance, large turning radius, poor pass-ability, etc. of the orchard operating machinery, combined with the orchard cultivation mode and agronomic requirements, a multifunctional dynamic chassis for orchard was designed. The structure and working principle of the multifunctional dynamic chassis for orchard were expounded, and the traveling power system and rear power output system and the three double-acting hydraulic quick-connecting output ports were designed. The theoretical of the steering performance, stability performance and crossing performance of the whole machine were analyzed theoretically. The finite element analysis of the frame was carried out to show that the maximum total deformation of the frame was 5.08mm in the middle beam part, the maximum equivalent elastic strain of the frame was 0.0035 and the maximum equivalent stress of the frame was 390.52MPa at the hinge joint between the axle and the frame under the condition of full load four-wheel landing. The maximum total deformation was 20.74mm at the side beam of the frame, the maximum equivalent elastic strain of the frame was 0.0058 and the maximum equivalent stress of the frame was 805.46MPa at the hinge joint between the axle and the frame under the condition of full load three-wheel landing. Field experiments were carried out in the orchard. The experiment results showed that the speed of multifunctional chassis for orchard was 0~35km/h, field working speed was 1~6km/h, minimum turning radius was 2m, maximum climbing angle was 24°and maximum crossing height was 235mm. Multifunctional chassis was able to connect a variety of agricultural tools as a multi-purpose machine, which can meet the requirements of field production management operations in the orchard and improve the mechanized production management level of the orchard. The research result provided theoretical and experimental basis for the research of general-purpose dynamic chassis for orchard, and provided a basis for the improvement and lightweight design of the subsequent chassis.

Abstract:Dynamics characteristics and relative tests on a type of rotary seedling pick-up mechanism of planetary gear train with combined gear transmission of incomplete eccentric circle gear and non-circular gears were studied. Based on the force analysis of each moving component in the seedling pick-up mechanism with the dynamic static analysis method and dynamics equations sequence-solution method, the dynamics mathematical model of the mechanism was built, and the dynamics analysis software was developed to solve the model to obtain the force variation law of different positions, including the chain, rotary centers and mesh points of gears and bearing of the mechanism. The virtual prototype of the mechanism was set up and its physical prototype was manufactured to conduct dynamics simulation analysis and bench tests on the mechanism, respectively. The relationship between the bearing reaction force and the rotation angle of the planetary carrier was obtained when the mechanism was rotated at 60r/min.The variation law of bearing reaction force under theoretical analysis, dynamics simulation and bench test of the seedling pick-up mechanism were basically consistent, which verified reliability of the dynamics model and correctness of dynamics analysis of the seedling pick-up mechanism. By contrast to the original seedling pick-up mechanism, it can be obtained that the maximum amplitude and variance of bearing reaction force in the y direction of the seedling pick-up mechanism were reduced from 155N and 1171N2 to 77N and 553N2, which were decreased by 50.3% and 52.7%, respectively, indicating that the mechanism had better dynamics performance than the original mechanism.

Abstract:With the goal of improving the performance of planetary gear train transplanting mechanism, the direct connection between convexity of pitch curve and the ideal transplanting trajectory was established. A method was proposed to abstract the parameters of a planetary gear train with noncircular gears based on the convexity of non-circular gear pitch curve index. Firstly, a global reference coordinate system was established based on the transplanting trajectory;next, the planetary gear train was simplified to a two-link, two degrees of freedom, and open loop chain mechanism with two revolute joints (a 2R mechanism), and a mechanism motion solving model was established based on ideal transplanting trajectory. According to the conversion relation between transmission ratio curve and non-circular gear pitch curve, the non-circular gear pitch curve convexity judgment index was put forward. The range of the transplanting mechanism with planetary gear train central position, namely the analytic domain was established. According to the kinematics principle, the ideal transplanting trajectory was replayed by a two-link, two degrees of freedom and open loop chain mechanism. The transmission ratio of gear train was calculated, and the calculation and distribution model of transmission ratio was established. The parameters of transplanting mechanism were calculated, such as the length of links, length ratio of link, and non-circular gear pitch curve convexity judgment index. The parameter information diagram of transplanting mechanism with a given transplanting trajectory was drawn. According to the requirements of transplanting agronomy, the engineering practical solution was preferred in the information map. And the blindness of adjusting non-circular gear pitch curve was avoided. The method was used to calculate and analyze several common transplanting trajectories. The eagle-nosed transplanting trajectories were chosen to design the transplanting mechanism with planetary gear train. Simulation analysis showed that the simulation trajectory and the test trajectory were basically the same as the given ideal trajectory. The correctness of the calculation model and the feasibility of the design mechanism were verified.

Abstract:The cutting frequency of the vertical cutter in the traditional rape combined harvester at different speeds keeps constant. It will cause the large re-cutting or leakage zone and lead to the increase of cutting header loss. At the same time, the work performance will be unstable. A double vertical cutter follow-up control device driven by two stepper motors was designed. And the influence of different advancing speeds on the cutting area and the cut off area of vertical cutting was analyzed. Considering the influence of rapeseed maturity and other factors, the best theoretical matching relationship between advancing speed and cutting frequency for vertical cutter was obtained. Then, the servo control system was designed for cutting frequency of vertical cutter based on S7-1200PLC. By detecting the forward speed signal of the machine and controlling the stepper motor according to the best theoretical matching relation, the follow-up control for vertical cutter frequency was realized. The comparison test of the harvested rapeseed after one week of applying the dehydrating agent showed that the total loss rate of the rapeseed header using the vertical cutter frequency follow-up control system was decreased by 36.15%~41.16%, and the loss rate of the vertical cutting knife was decreased by 40.84%~48.20%. When the characteristics of rapeseed and the harvesting conditions of the machine were changed, the magnitude of total loss rate of header and the loss rate of vertical cutter may be changed, but the downward trend was consistent, and more working conditions were needed for comparative analysis.

Abstract:Piezoelectric films were used as sensor sensitive materials. A grain cleaning loss rate monitoring device suitable for corn harvesting was designed. The impact sensor, signal processing circuit and mounting device were designed, and the corresponding processing algorithm was used to collect the impact signal. Firstly, under different experimental conditions of impact angle and height, the impact signal acquisition experiments of different sizes of corn kernels and impurities were carried out. The main characteristics of impact signal were also extracted. Secondly, the support vector machine was used for multi-classification. The model was trained by the support vector machine multi-classification algorithm and real-time classification was implemented on the monitoring device. And the classification model was validated by using different corn varieties and moisture content. Then, under the conditions of different fan speeds and cleaning screen opening degrees, the relationship between the number of grains detected by the sensor and the total loss during the test time was obtained. And the real-time cleaning loss rate was calculated according to the grain flow value. Finally, the monitoring device was mounted on a 4YL-8 combine harvester and field trials were conducted. The results showed that the average relative error of the monitoring device compared with manual detection was 12.98%, which can provide feedback for the control of the harvester.

Abstract:Plastic-film mulching has improved crop production of cotton greatly in Northwest China. With the use of plastic film year by year, the problem of pollution has become increasingly apparent. Film mulching has many advantages, such as water storage and weed control, but overmuch residual plastic film fragments influenced the physical property of agricultural soil. Aiming at the pollution problem, the new national standard of plastic film was published. On the basis of the new national standard of weathering film, a collecting and removing device for the residual plastic film recovery machine was designed as the integrity of weathering film. By testing the mechanical properties of the weatherproof film and force of the residual film when collecting, the results showed that the film would not be broken during the collecting process. The key working parts were designed and analyzed, while the length and the arrangement of the nail and the film collecting parts were determined by plotting trajectory of end of collecting nail in soil based on the software of Matlab. Through the single factor experiment on the relationship between distance of chains and residual film collecting rate and straw removing rate, the optimal value of the chains spacing was obtained. The stress analysis of ground roller, collecting and removing device was carried out during the movement process, and the performance of the machine was tested. The field experiment results showed that the recovery rate of residual film was 89.54% when the forward speed of the residual film recovery machine was between 4.0km/h and 4.4km/h, indicating that the collecting device can meet the requirements of residual plastic film collection.

Abstract:The droplet sizes are different at different positions in the spray field of flat-fan nozzle which are widely used in agriculture. It shows like the U-shaped distribution, that is, the droplet diameters of the middle droplet are smaller and the droplet diameters of both sides are larger, which results in the differences of the droplet depositional behavior on the targets at different points of the same height in the horizontal direction, leading to different control effects. The droplet sizes of the impinging nozzle were obtained according to the test system for atomizing performance of nozzles. Experiments were conducted on droplet distribution characteristics in spray field of the impinging nozzle with the exit diameter of 1mm and the groove angle of 30°. The nozzle was a new nozzle based on the coupling of jet and impinging jets. It was found that the droplet diameters of the middle droplet were uniform and the droplet diameters of both sides were smaller. For instance, when the spraying pressure was 0.4MPa, the droplet diameters of the middle droplet were 265~268μm and the droplet diameters of both sides were 250~252μm on the test surface at height of 300mm. The new nozzle was beneficial to solve the insufficiency of uneven droplet size distribution of boom sprayers in field operation. The characteristics of the new nozzle were analyzed theoretically and the three times of atomization (disturbance, impact and oscillating) in the cracking-zone was considered as the fundamental cause of these characteristics. Meanwhile, the droplet distribution uniformity of spray field was quantified by the radial nonuniformity index (RNI). It proved that the radial nonuniformity index can reflect the overall non-uniformity of spray field. The value of radial nonuniformity index was varied in a small range (0.47~0.51) when the pressure was in the range of 0.6~0.7MPa, showing that the spray field of the impinging nozzle had good droplet uniform distribution. The impinging nozzle provided a beneficial technological support for the development of intelligent precision spraying machine for plant protection.

Abstract:Soil tillage is an important operation to create a better soil condition for crop growing. However, larger draught forces exist in the tillage operation so that it is urgent to need some methods to solve these problems. Mole rat has the outstanding digging performance, and its multi-claw combination would inspire the development of new efficient tillage implements. The mathematical model of the multi-claw combination was established, and bionic soil-cutting blades were designed for investigating the effects of the bionic structural elements (m and n), soil moisture content and rake angle on the draught force. By the quadratic regression orthogonal test, it was found that the soil moisture content and rake angle had more significant effects on the draught force. Optimal combination with the least draught force was m=5 and n=1.75. Through the comparison test of the draught force between conventional and bionic soil-cutting blades at the rake angle of 10° to 90° and the soil moisture content of 10% to 30%, the bionic structural elements had no significant effects on the critical rake angle of blades, but soil moisture content had a significant effect on that. Particularly, the bionic blade showed the best cutting performance. When the soil moisture content was 10%, 20% and 30%, the draught force of the bionic blade was decreased by 11.48% to 39.16%, 17.81% to 28.00% and 11.19% to 33.26%, respectively. Moreover, the bionic blade had better soil cutting performance at the soil moisture content of 10%~20%.

Abstract:The object was to solve the problems of large tree height measurement errors in forest resources surveys, difficulties in measuring tree heights in complex forest stands, and measurement of the height of tilted stands, etc., and surveying, forest measurement, electronic information technology, sensor technology and image processing technology were focused on. Based on this, a handheld precision standing tree height measurement device was developed. The device consisted of a central processing unit, a laser range finder, a high-definition camera, a high-precision gyro sensor, a liquid crystal display, a memory and the like, and a laser-ranging sensor was used to obtain a distance between the measuring device and the root of tree, and the device was acquired at the same time. The elevation angle information was used to determine the position of the treetop after the image center was used to obtain the second elevation angle information, and the measurement tree height was solved by the distance information and the angle information. The equipment was used to measure the trunk inclination angle of the tree trunk. For the dry-bending trees, edge detection algorithm was used to identify the edges of the image trunk contour. Contour extraction method was used to extract edge points of the trunk contour, and coordinate information of the discrete points on the edge of the trunk was obtained to perform linear fitting. The slope of the straight line was converted to the angle of the trunk, and the angle compensation algorithm was used to complete the measurement of growth of trees with long slopes and standing trees. The test results showed that the tree height measurement accuracy can reach 98.04%, and the inclined standing wood measurement accuracy was 96.89%, which can meet the accuracy requirements of the national forest resource survey. The measuring method of tree height measurement device and the measuring method of high growth and volume of the inclined standing timber can provide new ideas for the research of forestry equipment.

Abstract:The geometric model of a 50-inch agricultural axial fan was established by a 3D laser scanner. The experimentally verified numerical model was used to study the influence of length of shroud of agricultural axial fan on the internal and external characteristics of fan. Keeping the inlet position of the shroud, the rounded corner radius and the diffusion angle were unchanged, and defining the ratio of length of shroud to axial width of tip as K. The value of K was chosen as 0.50, 0.78, 0.90, 1.0, 1.1, 1.2, 1.5 and 2.0. Totally seven different imported static pressure operating points were chosen for numerical simulation. The results showed that during the process of increasing the K from 0.50 to 1.0, the air volume and energy efficiency ratio of fan were obviously improved. When K was from 1.0 to 1.1, the fan air volume and energy efficiency ratio were the highest, which was about 10% higher than those of the prototype fan with K=0.78. When the K was from 1.1 to 2.0, the air volume was slightly decreased. The energy efficiency ratio was decreased significantly. Using the Q criterion to identify the vortex structure in the tip and outer frame regions, it was found that with the growth of K, the tip leakage vortex underwent three processes of division, attenuation and redevelopment. When K was 1.0 it can effectively inhibit the development of tip leakage vortex and minimize the strength of tip vortex. The lengthening of the shroud can significantly reduce the outer frame vortex.

Abstract:According to the complexity of traditional hydraulic performance optimization design of centrifugal pump, the hybrid surrogate model method which is the combination of proper orthogonal decomposition and radial basis function was proposed for the flow reconstitution of centrifugal pump impeller. The blade of low specific speed centrifugal pump was parameterized by cubic Bezier curve, and the experiment samples can be designed by introducing small perturbation of control parameters which included wrap angle, inlet and outlet blade angles. The snapshot set consisted of the control parameter for blade shape and the flow field data. According to the geometric similarity of the impeller flow passage and the mesh deformation technology, the flow field data of the similar position were interpolated. The snapshot set can be decomposed as linear combination of orthogonal basis by using proper orthogonal decomposition. The orthogonal basis coefficients for the objective blade were fitted by using radial basis function. The flow field data of the objective impeller were reconstructed. In the calculation case for the type of MH48-12.5 centrifugal pump, the flow field in impeller was reconstructed. The root-mean-square error for pressure prediction was 0.84%, and the velocity prediction error was within 0.5m/s. The computation time for the flow field prediction was less than 1/240 of the CFD. POD base modal analysis was carried out on the sample set. The base modal characteristic of flow field and its energy distribution were analyzed.

Abstract:Centrifugal pumps are widely used to deliver liquid media in agriculture, pharmacy, industry, etc. Compared with the case delivering pure liquid such as water, centrifugal pumps not only have lower efficiency but also are subject to severe vibration, noise and erosion when delivering cavity two-phase flow. In order to further improve the cavitation performance of low specific rotation centrifugal pump, a method of making the blade slotted to control cavitation in a centrifugal pump was proposed. The slotted impeller blade near the inlet of centrifugal pump was studied. According to the flow characteristics of cavitation in centrifugal pump and the cavitation dynamics model of Kubota cavitation model, the SST k-ω model was used to simulate and analyze the two-phase flow in a centrifugal pump under the same working conditions. The simulation results showed that after the blade surface was slotted, the head of the centrifugal pump was increased, and the head of the centrifugal pump was increased by 12.8% at the design point, and the efficiency was increased by 4.2%. The slotted blade can effectively prevent the low pressure region from expanding outward, change the pressure distribution and inhibit the cavitation in every stage of the centrifugal pump. The slotted blade can optimize the flow field structure, increase the pressure in the flow channel and reduce the volume fraction of the cavitation. The cavitation volume of centrifugal pump impeller in every stage of cavitation was smaller than that of impeller without slot when the blade was slotted. In the stage of cavitation development, the volume of slotted space-time bubble continued to decay.

Abstract:In order to obtain the pressure pulsation characteristics of the model of one axial flow pump unit named Paihekou station under different cavitation conditions, the monitoring points of pressure were set near the impeller inlet, the impeller outlet and the vane outlet, the test was conducted by applying a dynamic pressure sensor system under four different head conditions with three different cavitation conditions of no cavitation, critical cavitation (pump efficiency decreased by 1%), deep cavitation (pump efficiency decreased by 3%). The test results showed that the pressure pulsation curve at the inlet of the wheel was a smooth and approximate sine curve, and the amplitude of the pressure fluctuation curve at the outlet of the impeller was the largest and showed obvious second harmonic characteristics in a rotating cycle under the high head condition without cavitation. The time domain characteristics of pressure pulsation of vane outlet were similar to that of impeller inlet. The results of FFT showed that the main frequency of each monitoring point under different working conditions was the integral frequency doubling of the blade passing frequency. With the deepening of cavitation, harmonic frequency near the main frequency of each monitoring point was gradually moved to the low frequency section. The vane outlet and impeller inlet were less affected by the blade passing frequency and showed similar frequency characteristics.

Abstract:Farming convenience degree (FCD) is an important feature of cultivated land. In order to accurately characterize all requirements of modern agriculture for FCD, the definition and its meaning of FCD were introduced. Then, a systematic and comprehensive evaluation model was constructed and applied in a project area of Dingzhou City in Hebei Province. The results showed that the newly defined FCD put farming efficiency on an importance place, which consisted of field work efficiency and traffic efficiency. Three key indexes were thoroughly studied, including connective degree, field road accessibility and farming distance. Their meaning and acquisition method offered the foundation to obtain FCD accurately. The evaluation results showed that the FCD condition of farmland in the study area was good overall. Based on the comprehensive evaluation score, the farm units were divided into four levels. Among that, totally 82.41% of all farmland area was at the level of very convenient or more convenient. These kinds of units mainly had the feature of convergent distribution and large average land area, and also distributed in the area close to roads. It was the appropriate area for developing high-efficiency agriculture and spreading mechanized farming. On the contrary, it was difficult to exert scale benefit and mechanical tillage for farmland of the grades like general convenient and not convenient, because of their small units and scattered distribution. The research can provide technical support and method reference for the project selection and performance evaluation for well-facilitated farmland as well as the evaluation of cultivated land quality.

Abstract:The image segmentation of target plant plays an important role in the automation of plant target detection and variable spray. The application of a single two-dimensional feature to object orientation, tracing and other occasions cannot meet the requirements of modern agriculture. However, in the segmentation of the three dimensional characteristics of plants, the traditional supervoxel clustering segmentation has the problem of high segmentation rate and poor real-time performance of plant. To solve this problem, a super voxel segmentation method was proposed, which fused saliency maps. Firstly, the color and depth maps of target plant were acquired in real time by using Kinect V2, and the RGB (RGB color model) color space images were converted into CIELab (CIELab color model) color space images. The eigenvalues of each pixel were calculated, and then the color feature map was obtained. After obtaining three feature graphs, fusion color feature graph, luminance feature graph and direction feature graph were used to construct a significant feature graph, and then the saliency map and the depth map were synchronously aligned to obtain the significant point cloud. The octree grid was used to initialize point cloud, and the grid point cloud was obtained, which satisfied the probability density threshold through Mean-Shift algorithm, and taking the maximum probability density point as the seed point，based on the Euclidean distance between points and CIELab similarity criterion as regional growth, the super voxels were generated. Finally, the locally convex connected patches (LCCP) algorithm was used to cluster the salient point cloud. The experimental results showed that the improved supervoxels based on salient point cloud-locally convex connected patches (SSV-LCCP) algorithm method can greatly improve the accuracy and rapidity of the target foreground segmentation, and effectively overcome the background noise and outliers.

Abstract:The red turpentine beetle (RTB) is a major forestry invasive insect that damages the coniferous species of pine trees in northern China. Therefore, the monitoring of RTB plays an important role in forestry pest controlling. However, traditional trap-based monitoring depends on human experts to manually recognize and count pests, which prohibits the modern RTB monitoring. To automatically recognize and count RTB captured by pheromone traps, a RGB camera was integrated in traditional cup trap to capture in-trap images and build the bark beetles dataset. The default boxes of Faster R-CNN object detection model based on deep learning were optimized by the K-means clustering algorithm. The optimized Faster R-CNN models were trained end to end by the GPU server, which enabled the in-trap detection of RTB with unconstrained postures. The models were evaluated by two metrics: the object oriented quantitative metric and the trap oriented qualitative metric. The experiments demonstrated that the optimized models outperformed the original Faster R-CNN model in terms of both metrics. The area under the curve (AUC) of precision-recall plot for object and trap on difficult test sets were increased by 4.33% and 3.28%, respectively. The AUC for object and trap on all test sets reached 0.9350 and 0.9722, respectively. The detection speed of the model was 1.6s per image. The optimized models outperformed the SSD, Faster R-CNN object detection models in terms of accuracy, which was robust to pose variance, bark interference, alcohol volatilization, etc. The proposed method distinguished and counted RTBs from the six species of scolytidae insects attracted by the pheromone lure, which could reduce the human cost of pest monitoring and forecasting.

Abstract:Existing nursery inventory methods require people hand-counting, which is very labor consuming and not efficient. Using unmanned aerial vehicle (UAV) to facilitate counting the number of nursery-grown plants automatically with high accuracy provides an alternative to inventory management. The segmentation of individual plants in UAV images is the crucial step to achieve the plants counting task, which is challenging because of variations in illumination changes under natural conditions, the size difference between individual plants, the complicated background of the ground weeds and overlapping of adjacent plants. A spruce image segmentation algorithm based on fully convolutional networks (FCN) was proposed. Images were collected by using DIJ PHANTOM 4 in Inner Mongolia, in which 470 labeled spruce images with 300 images as training set, 170 images as test set, and 90 Pinus sylvestris images labeled as additional test set for comparing test results. To design FCN for accurate spruces segmentation, VGG16 was chosen as a basic network with the shared weights and the decreasing learning rate to improve the accuracy under Tensorflow framework. The results on the test set showed that FCN algorithm achieved effective spruces segmentation in spite of illumination changes, the size difference between individuals, the complicated background and the overlapping problem, with pixel accuracy (PA) of 0.86, mean pixel accuracy (MPA) of 0.86, mean intersection over union (MIoU) of 0.75 and frequency weighted intersection over union (FWIoU) of 0.76 at an average speed of 85 millisecond per image. Compared with K-means clustering segmentation algorithm and HSV threshold segmentation algorithm, the MIoU value of FCN algorithm was 0.10 and 0.38 higher, respectively. All of the test results showed that the proposed FCN algorithm provided an effective pipeline for plants segmentation.

Abstract:Considering the shortcomings of contact thermometer, such as low precision, poor real-time performance and cross-infection, a body temperature implantable sensor of cow was developed to realize the intelligent detection of cow body temperature signal by using wireless sensor network. PT1000 was used as temperature measuring probe, and the analog-to-digital converter ADS1256 and control chip MSP430 were used to filter the acquisition voltage and improve the accuracy. The 433M wireless signal module was used in conjunction with the ZigBee network to design the collar node, as a relay node that transmitted cow body temperature data from body to outside. In details, the 433M wireless signal was transmitted from cow to collar node, then the 2.4GHz ZigBee network was used from collar node to remote monitoring center, which worked more stable and reliable, realizing high-precision real-time monitoring of temperature. The sensor accuracy, stability, reaction speed, transmission performance and system packet loss rate were tested, respectively. The results showed that the designed sensor temperature measurement error was less than 0.05℃, the maximum fluctuation of 12h temperature measurement was 0.02℃, which was stable within 15s. The information can be effectively transmitted to the collar node by using implantable sensor RF. Inside one cattle farm, the packet loss rate of the whole system was no more than 1.2%, providing important data for cow estrous prediction and disease prevention. Vaginal temperature could become a good indicator for predicting not only the onset of calving, but also the necessity of assistance. The research result can also be a reference for other animals’ temperature detection.

Abstract:Tens of thousands of question and answer data have been increased per second in the internet agricultural technology extension community, these massive data have features of recessive part of speech, emotion and unwanted vectors, and how to implement data aggregation and data block reduction is the difficult problem in this field. An analytical model for the extraction of emotional polarity in agricultural question and answer based on convolutional neural network was proposed, the training set was transformed into a 256-dimensional word vector by using the Skip-gram model after segmenting the dataset with agricultural word segmentation dictionary. The convolution neural network after batch-normalization specification was used to train the dataset, and the neural network model parameters used to identify the part of speech emotional similarities in the agricultural technology promotion community question and answer were obtained. The experimental results showed that the method could accurately identify redundant queues in the test sample set, and by comparing with the other four text classification methods, there were also obvious advantages in each index, the accuracy of the semantic feature extraction for the test set was up to 82.7%.

Abstract:Decision on optimal selection of interconnected river system network schemes is an analysis process which combines deterministic evaluation index and evaluation criteria with uncertain evaluation factors and their weight changes. The evaluation indexes involved include resource criteria, economic criteria, social criteria, environmental criteria, engineering criteria and so on. Intermediary transition of these evaluation indexes leads to uncertainty in the results of different multi-attribute decision-making methods. How to evaluate the stability of these decision-making methods is worth studying. According to the theorem of the unity of opposites of variable sets, the principle and method of variable sets for optimal selection of interconnected river system network schemes were proposed, and the sensitivity analysis method of variable sets decision results based on cloud model was proposed. Taking Xinanjiang (S1), Fuchunjiang (S2) and Taihu-Fuchunjiang (S3) water diversion projects in northern Zhejiang Province as examples, the ranking of the three schemes was evaluated and analyzed in terms of comprehensive evaluation and different criteria evaluation, and the robustness of the evaluation results of variable model under change of single index and multiple index weights was analyzed. The main conclusions were as follows: using the rand feature values and relative difference degrees to analyze the results of multi-criteria comprehensive evaluation, it was indicated that S3 was superior to S1 and S2;variable model (α=1, p=1) and (α=2, p=1) comprehensive evaluation of the scheme ranking stability was better from the index sensitivity analysis. It can be seen from the weight sensitivity analysis that the ranking of the comprehensive evaluation schemes, especially S2 and S3, of the four kinds of variable models with different parameter combinations was easily affected by the change of index weight. According to the analysis of index sensitivity and index weight sensitivity combined with the comprehensive evaluation and the evaluation of different criteria, the evaluation results were affected by the index system to some extent, which indicated that it was needed to make specific analysis on the research objects to choose the appropriate evaluation method.

Abstract:In order to study the temporal-spatial distribution of solar radiation (Rs) in Northwest China, daily Rs of 16 stations in Northwest China from 1961 to 2015 were calculated by ?ngstr?m-Prescott (A-P) model, and cloud model was used to describe the temporal-spatial distribution of Rs in Northwest China. To obtain the best parameters calibrated method and assess its adaptability, Northwest China was divided into four areas. Ⅰ area included northern Xinjiang, middle and west section of Hexi Corridor of Gansu, central and northern Ningxia, western Inner Mongolia. Ⅱ area included southern Xinjiang. Ⅲ area included Qinghai. Ⅳ area included southeast Gansu, southern Ningxia, Guanzhong and northern Shaanxi. Daily climatic data radiation (Rs) and sunshine hour (n) of 16 stations from 1995 to 2015 were used to calibrate A-P model parameters, and four different parameters calibrated methods for A-P model were used, including monthly (M1), seasonally (M2), bi-annualy (M3) and annually (M4), in which high precision and simple calculation method for each area was finally selected to calculate Rs. The results showed that the fitting results of four parameters calibrated methods conformed the measured values well both in daily and monthly scales. RMSE and nRMSE of four parameters calibrated methods changed little. The values of t statistic showed that there was no difference among the three methods (M1, M2 and M3) in use of data calculation in Ⅰ area and Ⅲ area, no difference between the two methods (M1 and M3) in use of data calculation in Ⅱ area, no difference between the two methods (M1 and M2) in use of data calculation in Ⅳ area. When cloud model was used to analyze the temporal-spatial distribution characteristics of Rs in Northwest China, as a consequence, there was good homogeneity but poor stability of Rs in Ⅰ area in the time. There was good homogeneity and stability of Rs in Ⅱ area and Ⅲ area in the time. There was poor homogeneity and stability of Rs in Ⅳ area in the time. Besides, spatial distribution of Rs in Northwest China was uneven. Rs of the four seasons in Ⅲ area (Qinghai Province) was larger than those of other areas. In general, the homogeneity and stability of Rs in the space was worse than that in the time. The results can be used to construct a complete Rs time series in Northwest China and provide a scientific reference for the study of temporal-spatial distribution characteristics of Rs in Northwest China.

Abstract:Drought is an extreme climate event with long duration of slow development, and the impact of climate change on drought is particularly significant, drought has become a global problem in a changing climate. Assessing the impact of climate change on the drought characteristics of Yunnan Province is particularly important. The drought conditions in Yunnan Province were analyzed by using the multi-time scale standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI). The seasonal variation of two indexes and the characteristics of drought in the region were analyzed by using non-exceedance probability and runs theory, respectively. The results showed that the non-exceedance probability of SPEI (1) below and equal to -1.0 in the winter of 1961—1995 was 5.2%, and it was increased to 18.4% from 2066 to 2100;the non-exceedance probability of SPEI (6) below and equal to -1.0 was increased from 4.4% to 21.4%, SPEI (24) was increased from 7.0% to 25.7%. It was showed that due to climate change, serious droughts may occur in the future, and the medium and long-term droughts were more serious than shortterm droughts. Severe droughts caused by climate change during the winter and summer periods from 1961 to 1995 and from 2066 to 2100, and the severity of medium and long-term droughts was particularly strong during winter and summer. SPI and SPEI time series were applied to the runs theory and it was found that the drought intensity determined by SPEI (1) from 1961 to 1995 was 28.3, which reached 60.9 by 2066 to 2100, indicating that the climate changes had exacerbated the future drought. The results were instructive and practical for drought prediction and assessment in Yunnan Province, as well as its risk management and application decisions. At the same time, it can provide a scientific reference for the future dry farming ecological management and drought evolution prediction.

Abstract:Sand layer is a common covering material on the surface of earth. The sample can provide more information for geological analysis in the area. Sand particles were carried by water and wind easily. Therefore, the shallow sample obtained by traditional cutting ring method would lose some important characters. For the high fluidity and low cohesive of sand, the traditional cutting ring sample method cannot collect the samples from the length greater than 20cm with continuous layers information. A new sample drilling technology with flexible tube mechanism was proposed to resolve this problem. It was composed by flexible tube which was fixed in the auger. The sample drilling technology had ability to increase coring length and protect layers. The contact principle and disturbance between the coring drill and sand were analyzed. Based on the simulation results analysis, the reasons for the failure of continuous sampling were revealed. An experimental bench was built to test the difference between the traditional cutting ring and flexible tube drilling method on sampling rate. The results showed that the coring rate was decreased by 10.4% and increased by 16.4% to the flexible tube and traditional cutting ring, respectively. The sampling rate and efficiency of flexible tube were much higher and less adverse the sequence of sand layers. The coring rate of flexible tube was increased from 13.08% to 84.08%.

Abstract:Coastal areas in eastern China have a large amount of reclaimed land and slight saline water resources. In order to exploit the reasonable and sustainable utilization of them, a pot experiment was carried out to investigate the characteristics of soil salinity, photosynthesis parameters, oxidation parameters, antioxidant enzymes activities, growth, yield and water use efficiency of summer maize (Zea mays L.) subjected to three alternate sequences (i.e., BFF: in which maize was irrigated with saline water at the seedling stage and fresh water at other stages;FBF: in which saline water was irrigated at the jointing stage and fresh water at other stages;FFB: in which plants were watered with saline water at the reproductive stage and fresh water at other stages) with three levels (i.e., 1 was 1g/L NaCl;3 was 3g/L NaCl;5 was 5g/L NaCl). The result showed that under the same salinity of saline water irrigation, the descending order of soil salt content distribution in upper layer was FBF，FFB and BFF. Net photosynthetic rate (Pn) and stomatal conductance (Gs) of summer maize leaves under slight saline water irrigation were decreased compared with that under fresh water irrigation throughout the whole growth period (CK). Under the same salinity irrigation, the descending order of Pn and Gs was FFB, BFF and FBF. Intercellular carbon dioxide concentration (Ci) was decreased due to stomatal limitation, but with the increase of irrigation water salinity, non-stomatal limitation caused Ci to increase in 5g/L treatment. FBF5 had a maximum increase of 19.44% at 81d and FFB5 had a minimum increase of 1.38% at 108d. Hydrogen peroxide and malondialdehyde (MDA) in maize leaves under saline irrigation was higher than those under freshwater irrigation. At the same time, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were also increased. However, limitation of the activities of POD and CAT was observed in FBF5 treatment, but it was still higher than those of CK by 37.67% and 13.71%. Compared with CK, alternate irrigation with fresh and slight saline water inhibited the growth and production of maize, resulting in the reduction of plant height, leaf area, growth, yield and water use efficiency. In addition, these adverse effects were more evident in BFF and FBF, because the salt resistance of summer maize was not fully developed and it was more sensitive to salt stress caused by brackish water irrigation. Maize suffered from the most deleterious impact due to saline irrigation during the jointing stage, leading to the most loss of growth and yield. It was confirmed that although maize became more tolerance as crops developing, enhanced crop evapotranspiration also caused more intense salt stress at the jointing stage. Its increasing salt resistance was still insufficient to overcome the corresponding salt stress. In all alternate sequences，the order of water use efficiency (WUE) of summer maize from high to low was FBF，BFF and FFB. As the degree of salinity was increased, the WUE of FBF5 was the lowest, which was decreased by 38.04% compared with that of CK. Based on the analysis of the experimental results, 1g/L and 3g/L salinity water irrigation can be applied at the seedling stage with negligent negative impacts on maize production, and higher salinity irrigation can be used at the reproductive stage, while freshwater irrigation was more appropriate during the jointing stage.

Abstract:In order to reveal the absorption and utilization of topdressing to maize under different irrigation schemes, 15N tracer technology was used based on field test data, the ratio of absorption and utilization to topdressing was analyzed and the distribution of fertilizer nitrogen in the upper parts of maize under different irrigation schemes, and the residue in the soil and final loss rate of nitrogen after harvest were studied. The results showed that 8.14%~13.21% of total nitrogen accumulation in maize aboveground parts came from topdressing under different irrigation schemes, there was a significant difference between the treatments (P<0.05). Among them, topdressing nitrogen accumulation in the grain accounted for 47.90%~74.40% of the total topdressing accumulation. The nitrogen recovery rate of top dressing was 19.16%~64.72% under different treatments, and the recovery rate of grain topdressing was 11.29%~47.17%. The proportion of topdressing nitrogen in different organs was different, the distribution of 47.95%~74.40% was in grain, 10.50%~27.73% was in leaves, 3.02%~9.48% was in stem, 5.22%~15.53% was in spike axis, and only 0.53%~2.35% was in coating. In the early stage of maize growth, the irrigation amount was too large and the water shortage in the later period would have a negative effect on the absorption of nitrogen in the plant and the redistribution of nitrogen to the grain. At the same time, the amount of single irrigation was too large, resulting in the leaching loss of nitrogen, waste of resources and pollution of environment. After harvest, there were 8.81%~24.89% topdressing nitrogen residue in the soil. With the decrease of irrigation frequency and increase of single irrigation amount, the nitrogen residue rate of topdressing was decreased gradually. Considering yield and fertilizer utilization ratio, the irrigation scheme which met the requirements of water saving, high yield and high efficiency in this area was 800m3/hm2 of irrigation quota and four times of irrigation (seedling, jointing, tasselling and filling), the results can provide theoretical support and data reference for maize production in Northeast China.

Abstract:In order to explore the effects of biochar on improvement of soil water-retaining capacity and water utilization of flowering Chinese cabbage, based on the field experiment, the effects of four treatments, including no fertilizer (CK), mere organic fertilizer (MC0, 110t/hm2), combination of organic fertilizer and a small amount of biochar (MC1, 110t/hm2+8.5t/hm2) and combination organic fertilizer and a large amount of biochar (MC2, 110t/hm2+17t/hm2) on soil moisture dynamic, yield, quality as well as water use efficiency of flowering Chinese cabbage were studied. As the result shown, organic fertilizer combined with biochar could significantly increase the water content in 0～20cm soil layer and increase water reserve in 0～70cm soil layer, the average water content of whole growth period of MC1 and MC2 was increased by 4.7% and 8.6% （P<0.05) and the amount of water reserve in 0～70cm soil layer was increased by 12.3% and 3.4%, respectively, compared with MC0. The water content in 0～20cm soil layer under the treatment CK was changed drastically (10.5%～31.2%) and MC1 was changed relatively unnoticeable (15.4%～30.4%). MC1 apparently promoted the growth of flowering Chinese cabbage and improved the quality of vegetable sprouts compared with treatment MC0, MC2 and CK. The plant height, number of leaves, leaf area circumambient of MC1 all reached the highest. The biomass and yield of MC1 were increased by 36.7% and 59.1%, respectively, however the content of nitrate was decreased by 20.0%～44.3%, compared with CM0. Compared with CM2, MC0 and CK, MC1 annual water consumption was decreased by 3.6%, 6.8% and 13.7% （P<0.05), the yield water use efficiency was increased by 49.8%, 75.7% and 2264.8% （P<0.05), biomass water use efficiency was increased by 45.4%, 46.6% and 720.1% （P<0.05), respectively. Compared with MC0, the yield and water use efficiency of MC2 were significantly increased, but they were significantly lower than that of MC1. The research result can provide a theoretical basis for the rational formulation of fertilization system for organic vegetables in the arid region of Northwest China.

Abstract:Radiation use efficiency (RUE) is critical for improving crop yield. The object was to explore the influence of limited irrigation and nitrogen rates on the canopy light interception rate, RUE and yield of maize under border irrigation in salinization irrigation district and realize the efficient utilization of water and nitrogen. A field experiment was conducted in Hetao Irrigation District (HID). The experiment referred to the local conventional irrigation and nitrogen amounts in HID, which had three irrigation amounts (W1, 150mm;W2, 225mm;and W3, 300mm, which was the local conventional irrigation amount) and three nitrogen amounts (N1, 172.5kg/hm2;N2, 258.8kg/hm2;and N3, 345kg/hm2, which was the local conventional nitrogen application amount), meanwhile, interactive experiments were carried out. The leaf area index (LAI), leaf inclination angle (MFIA), photosynthetic active radiation and biomass of maize were measured at the tasseling-filling stage, and soil water and salt contents and the final yield were also measured at the same time. To investigate the mechanism of maize yields in salinization farmland, the correlation analysis and path analysis methods were used. Main conclusions were as follows: the light interception rate (F) of maize was significantly affected by irrigation at the tasseling-filling stage in salinization farmland. At the same nitrogen application rate, the F of W3 and W2 levels were higher than that of W1 level, but the difference of F between W2 and W3 was not significant;the RUE of maize was significantly （P<0.05) affected by irrigation, nitrogen and interaction effects in salinization farmland. Especially, at grain filling stage, RUE was increased with the increase of irrigation and nitrogen rates, but the promotion of RUE had inhibition growth effect when excessive irrigation or nitrogen application was conducted. The RUE of maize was significantly improved with the moderate reduction of irrigation and nitrogen application rate;maize yields were significantly （P<0.05) affected by irrigation and nitrogen in salinization farmland. Moderately reducing irrigation volume and nitrogen rate had no significant effect on maize yields. The yield of W2N2 treatment was 4.01% and 3.91% higher than those of W3N3 and W3N2 treatments （P>0.05), respectively;correlation analysis showed that the yield was positively correlated with LAI, leaf area duration (LAD) and the light interception rate (F) during filling stage. Path analysis showed that LAI had the greatest effect on yield mainly through LAD and F. The RUE had the greatest direct contribution to yield and biomass accumulation, LAI, LAD and F contributed indirectly to yield through RUE;compared with the rest of treatments, the conditions of soil water and salt were obviously improved by W2N2 treatment at the late growth stage of maize in salinization farmland, which was beneficial to promote the development of canopy and increase photosynthetic productivity. The W2N2 treatment with small MFIA and large LAI was beneficial to enhance the light interception rate and area of photosynthesis during the late growth stage. Especially, at late grain filling stage, the LAI and LAD of W2N2 treatment were 7.15%~42.24% and 5.95%~37.60% higher than the rest of treatments, respectively, the decreasing rate of LAI was 37.35% and 53.49% lower than those of W3N3 and W3N2 treatments, respectively, which can construct proper canopy structure, keep high photosynthetic performance and increase biomass accumulation. Thus, W2N2 treatment was beneficial to the improvement of RUE. The RUE of W2N2 treatment was 18.61%~66.93% higher than those of the rest of treatments. Finally, W2N2 treatment achieved the highest yield. In conclusion, the W2N2 treatment had the advantages of saving water and nitrogen, high yield and RUE, as a water and nitrogen management mode, it was very suitable for maize planting in salinization farmland in HID.

Abstract:Soil moisture was closely linked to plant photosynthesis rate and plant productivity. Water stress was important factors for photosynthetic depression and yield decrease. However, the key limiting step and underlying mechanism was highly uncertain. The resistance distribution along the pathway of CO2 transport from the atmosphere surrounding the leaf to the site of carboxylation inside the chloroplast stroma of tomato under different soil water content gradients was explored. Soil moisture was maintained by a standardized gravimetric approach. Stomatal and mesophyll conductance were estimated from simultaneous measurement of leaf gas exchange and chlorophyll fluorescence. The results showed that the photosynthesis rate (Pn), rubisco carboxylation capacity (Vc,max), maximum electron transport capacity (Jmax) and carboxylation efficiency (CE) were increased with the increase of soil moisture, which showed as“S” curves and can be described in logistic models. Stomatal conductance, mesophyll conductance and the total conductance for CO2 transport were decreased with water stress. The proportions of stomatal and mesophyll conductance limitations imposed on photosynthetic depression were increased with soil water stress, which were the dominant limiting factors;in contrast to stomatal and mesophyll limitation, biochemical limitations were increased with the increase of soil moisture and performed as predominant limiting factors when soil moisture was sufficient. Stomatal conductance showed positive linear relationship with leaf water potential, which was declined with soil water stress;mesophyll conductance showed negative linear relationship with leaf mass area, which was increased with soil water stress. The research result demonstrated that stomatal and mesophyll resistance for CO2 uptake were key limiting step for photosynthesis rate. The greatest resistance of stomata under water stress was determined by the turgor loss of guard cells while the mesophyll conductance was determined by the leaf anatomical structure.

Abstract:Aiming to understand eco-hydrological processes and boost water use efficiency in rainfed agroecosystem, a field experiment was conducted in non-mulched (CK) and mulched (PM) maize fields of eastern Loess Plateau to continuously monitor water and energy flux in the maize fields under CK and PM. Based on the monitoring results, diurnal and seasonal variations of water and energy flux as well as energy partitioning were investigated. The results indicated that energy fluxes presented typical diurnal and seasonal variations during the entire growing seasons. Net radiation (Rn) was dominated by latent heat flux (λET) during maize growing seasons while sensible heat flux (H) was the predominant component of Rn during non-growing seasons. Compared with the energy flux before rainfall, λET was increased significantly while H and soil heat flux (G) was decreased after rainfall in development stage, however, in late stage, the changes in soil water content resulted by rainfall did not increase λET significantly for the both treatments, which indicated seasonal distribution of rainfall had significant influence on energy budget of maize fields. Rn was the primary factor affecting λET, followed by average air temperature and vapor pressure deficit, wind speed and relative humidity had relatively minor influence on λET.

Abstract:In order to further reveal infiltration mechanism of intermittent infiltration of layered soil under surge irrigation, through the analysis of experimental data and theoretical research, Brook-Corey and Green-Ampt (BC-GA) improved infiltration model of layered soil under intermittent infiltration of surge irrigation was built. Relationship between water suction and wetting depth of intermittent wetting front of layered soil was built, which showed that the suction value Sf was decreased with the increase of wetting depth zf. Soil saturated hydraulic conductivity, retained moisture content, intake suction value, water conductivity coefficient, shape coefficient and depth change in the sand layer were proved to be the main influence parameters of migration distance of layered soil under intermittent infiltration. When the number of cycles was increased, the saturated hydraulic conductivity of the upper soil was decreased, saturated water moisture content was reduced and the suction was increased. Only the intake suction value in the sand layer was increased with the increase of cycle number. Calculation of intermittent infiltration characteristics and wetting front migration characteristics of sandy soil with different burial depths based on BC-GA model pointed out that the cumulative infiltration amount under the same sand layer depth was decreased and the wetting front migration distance under the same sand layer depth was increased. The cumulative infiltration volume and the wetting front was increased under the same water supply period. When the water supply period reached the maximum, the buried depth of the sand layer would reduce the cumulative infiltration amount and the wetting front migration distance. The research result could lay a scientific foundation for further development of surge irrigation technology.

Abstract:Saline-alkali land is an important reserve land resource in China. Real-time and accurate acquisition of soil information is important for the classification and evaluation of soil salinization to prevent its degradation and realize agriculture sustainable development. Selecting different soil salt crusts in northern Ningxia Yinchuan as the study objects, based on soil science and geostatistics methods, and taking the spectra data of different soil salt crusts and measured soil salinization parameters in 0~5cm layer of laboratory as the source of information, the characteristics of spectra reflectance of different salt crusts were analyzed, the sensitive spectral wavelengths or index to pH value, EC and salt ions in crust layer were selected, and then the soil salinization monitoring models were established and confirmed. Results showed that the spectral reflectance of white alkali crust was the highest among different soil saline crusts;the reflectance of equine caustic crust was next, and the reflectance of black alkali crust was the lowest. The main salt crust types in the study region could be classified by the spectral reflectance of the field. The highest correlation coefficients between the transformations of smoothing reflectance through the first order differential, the first derivate differential of logarithmic reciprocal of reflectance, continuum removal, the first derivative of continuum removal and salinity parameters were significantly improved than the transformation of smoothing reflectance gradually. The best transformation method of reflectance about soil pH value, EC, CO2-3 and Mg2+ were the first derivative of continuum removal;the best transformation method of reflectance about soil SO2-4, Ca2+, K+ were first derivate differential of logarithmic reciprocal of reflectance;the best transformation method of reflectance about soil HCO-3, Cl- nd Na+ were the first order differential. There was the strongest correlation between the first derivative of continuum removal and salinity parameters. On the whole from different salinity parameters, the sensitive wavelength was 450nm, 470nm and 485nm in blue region;501nm and 575nm in green region;680nm in red region;there were many sensitive wavelengths in infrared region. The highest correlation coefficients between pH value, EC, CO2-3, HCO-3, Cl-, SO2-4, Ca2+, Mg2+, K+ and Na+ and nine salinity indexes was S1 (Salinity index), S3 (Salinity index), SCI (Soil curst index), S3, SI3 (Salinity index 3), S2 (Salinity index), SCI, S2 (Salinity index), SI3 and S3, respectively. Except for CO2-3, the models were suitable for predicting the content of soil pH value, EC, and other salinity parameters, and there was the highest R2 about Na+ n this region. The study would provide some beneficial references for regional soil salinity classification and prediction.

Abstract:Biomass tar is produced as a by-product in the pyrolysis process of biomass, which is difficult to remove and harm to human health. The physical and chemical properties of pyrolysis tar were analyzed and it was fond that it had a high calorific value. After combustion, it can provide heat source for pyrolysis equipment and realize energy recycling. Aiming at the problems of poor atomization effect and unstable direct combustion of pyrolysis oil, a secondary atomizing nozzle was designed. And a mixed combustion process of biomass pyrolysis tar and pyrolysis gas was proposed. And a certain amount of pyrolysis gas was used as a combustion supporting agent to provide a stable flame for the combustion of the pyrolysis tar. And a test system for pyrolysis oil combustion was developed. The burning test of tar showed that the burning quantity of tar in the burner was 20~55kg/h, which met the design requirement. And when the atomizing air pressure was 0.6MPa, the pyrolysis oil pressure was 0.2~0.4MPa, the gas pressure was 0.3~0.5kPa, the burner was burned stably and the flame was bright. Through the analysis and test of the flue gas analyzer, it was fond that the content of CO and NOx in the combustion flue gas was high, which showed that the primary combustion in the combustor did not achieve the ideal combustion effect. Therefore, it was suggested that the next step was to improve the combustion chamber and reduce CO and NOx emissions by secondary air distribution combustion of the burned flue gas.

Abstract:Hydrothermal bio-char (ht-biochar) produced from hydrothermal carbonization at different temperatures (200℃, 240℃, 280℃, 320℃ and 360℃) were used as material. Chemical composition, kinetic parameters, combustion index were applied in evaluating the combustion characteristics of ht-biochar.The effects of hydrothermal temperature on the combustion characteristics were also studied. It can be concluded that with the temperature increasing from 200℃ to 360℃, the weight ratio of fixed carbon to volatiles in ht-biochar was increased from 0.34 to 1.2, accompanying with the decrease of O/C (mol/mol) and H/C (mol/mol) from 0.5 and 1.17 to 0.07 and 0.67, respectively. The increase of temperature deepened the coalification degree of ht-biochar. When the hydrothermal temperature was amounted to 320℃, the chemical composition of ht-biochar resembled that of bitumite. At elevated temperature, combustion index Z of ht-biochar was decreased from 3.49×10-2 to 6.64×10-3， indicating that the increase of temperature reduced the combustion activity, which could be confirmed by the variation of chemical composition and calculation results of kinetic parameters. This proved that dimensionless combustion index Z could be used to rate the combustion characteristics accurately.

Abstract:Harvest maturity is a key factor affecting apple storage performance. Thus, in order to achieve batch harvesting and suitable picking maturity of apple, rapid and non-destructive discrimination model was studied based on visible/near infrared spectral technology. Apple samples were classified into three maturity levels (mid-ripe, ripe and over-ripe) according to different fruit development times after flowering. Spectral information of all samples was acquired by using the visible/near-infrared spectral system with a wavelength range from 200nm to 1100nm in the laboratory, and spectral differences of samples at different mature stages were analyzed. It was found that the spectral reflectance of the mid-ripe samples was significantly higher than that of the ripe and over-ripe samples. However, the spectral bands behind the ripe and over-ripe samples had similar spectral characteristics, resulting in overlapping. Then, after the preprocessing of SG and multivariate scatter correction method, a method using callback arithmetic operator named twice-detect was used to detect outlier sample for different quality parameters. Among them, five outlier samplers of the soluble solids content, two outlier samples of firmness and no outlier sampler in color factor were removed. Finally, the remaining 235 samples were participated in the modeling analysis. The characteristic variables of soluble solids, firmness and the parameters of L*, C*, h*, a andb were extracted by the random algorithm which can be modeled with a small number of variables. A maturity index coupling internal quality named simplified internal quality index (SIQI) and another maturity index coupling with factor analysis named factor quality index (FQI) were applied to evaluate the maturity of apple. Using the characteristic variable as input, the partial least squares prediction model of SIQI index and FQI index was established. The prediction correlation coefficient of SIQI index was 0.938, and the root mean square error was 0.216. Similarly, the prediction correlation coefficient of FQI index was 0.917 and the root mean square error was 1.152. Therefore, it was feasible to use spectral information to predict the maturity evaluation index of coupled multiple indexes. At the same time, the classification model using spectral information was directly established by the extreme learning machine (ELM) algorithm and the support vector regression (SVR) algorithm. By comparing the results of the four classification models, it was found that the classification results based on SIQI index combined with SVR algorithm were the best, which was better than the direct classification model. The classification accuracy was 85.71%. The results stated that the classification of apple harvest maturity can be achieved by using visible/near-infrared spectroscopy information and the maturity evaluation index coupling with related internal quality indicators. The research result can provide a theoretical reference for the development of nondestructive testing equipment for subsequent apple harvesting maturity.

Abstract:Feed conditioner is a key component in the pellet mill, and conditioning is a very process during the pelleting and extrusion. To explore the movement rule and bonding state of materials in feed conditioner, the working process of small axial conditioner was simulated and optimized based on the CFD-DEM gas-solid coupling mathematical model. The method of establishing the coupling model was as follows: the structure model of the conditioner was built by the 3D software Pro/E, and the grid of the model was meshed by the software Gambit. The RNG k-ε turbulence model in the software Fluent was used as the fluid model. Afterwards, the discrete element model of wet stick feed materials was established by the software EDEM, and then the boundary parameters and coupling parameters of coupling models were set to be the basis of simulation. The blade installation angle, speed of conditioner and filling rate were selected as the influencing factors, and the output result was selected as evaluating indicator, thus the performance optimization experiments were carried out under the quadratic orthogonal rotation design. Based on the software regression analysis of Design-Expert 8.0.6 and response surface analysis method, the relationship between the three influencing factors and evaluating indicator was established. The results of the study showed that speed regulator and filling rate had an extremely significant effect on the evaluating indicator (P<0.01), and blade installation angle had a significant effect on the evaluating indicator (P<0.05). The output result of raw materials was selected as the chosen target;by using response surface method, the optimal aggregative index could be obtained under the condition that the blade installation angle was 38.49°, speed of conditioner was 182.2r/min, and filling rate was 58.4%. In this case, the output result of raw materials was 13.1g/s. Therefore, the conditioner had good practicability in the process of conditioning feed raw materials;the research provided references for performance improvement of feed conditioner and the parameters optimization of processing technology.

Abstract:In order to study the law of internal water migration in the process of potato chip heat pump drying, the changes of transverse relaxation time T2 and peak area A2x were analyzed by low-field NMR technique, and a dynamic model was established for different states of moisture change in the drying process. The results showed that in the process of heat pump drying, increasing the hot air temperature can significantly increase the drying rate and accelerate the migration rate of bound water, immobilized water and free water. In the drying process, the free and bound water was changed before the immobilized water, and the free water content was remained basically the same for the first 90min, and then dropped rapidly. The proportions of the immobilized and bound water both showed a rise and then decrease. In the trend, after the free water was removed, the immobilized water and the bound water successively reached a maximum value, and as the drying proceeding, the flowing water was gradually removed, and then the bound water started to be removed until the drying was completed. The heat pump drying process of potato slices belonged to internal diffusion control, and the effective water diffusion coefficient was ranged from 5.228×10-8m2/s to 1.434×10-7m2/s. A dynamic model was established for the changes of moisture content and its content in different stages of potato slice drying with time. The coefficient of determination of all models was greater than 0.98, which was a good predictor of the law of moisture migration of potato slices in different states during the drying process.

Abstract:The traditional particle swarm optimization (PSO) algorithm has some shortcomings such as low convergence precision, stagnant search and so on, which lead to the low precision of robot path planning. In order to improve the precision of path planning, the traditional particle swarm optimization algorithm was improved. Firstly, the inertia weight factor and acceleration factor were adjusted adaptively by the trigonometric function in each stage of the algorithm operation, so that the parameters in the algorithm were optimized in each stage of the algorithm operation, and the search ability of the algorithm was improved. Secondly, the hen equation and chick equation of chicken swarm algorithm were introduced to perturb the search stagnation particles, and the global optimal solution was used in the introduced equation to make the disturbed particle approach the global optimal solution. Finally, through two sets of comparative experiments of function optimization and path planning, it was proved that the improved algorithm had the advantages of high searching precision and good robustness.

Abstract:Aiming to improve the trajectory tracking robust stability of agricultural vehicles, a path tracking control method was proposed based on the linear predictive model. Through the proposed method, the path tracking problem can be divided into two problems: the trajectory planning problem and the trajectory tracking optimization problem with speed and steering angle constraints. Firstly, a dynamic model of the agricultural vehicle was established and discretized to deduce the system error model, based on which the prediction model was obtained for the controller. Then the Lyapunov function was introduced to validate the convergence and robust of the controller. Secondly, an objective function based on system variables and control inputs was coined. And the constraints of system state variables and control inputs were taken into consideration. The optimal control system was transformed into an optimization problem. Finally, the interior point method was brought forward to solve the optimization problem. The Matlab simulation results validated the road tracking ability of the tested road with enough robust performance. When front wheel disturbance was not more than 15° and tracking disturbance in lateral direction was not more than 1.5m, the controller can quickly adjust the vehicle to the reference track. Meanwhile, the corresponding experiments were conducted. It was showed that the maximum lateral tracking deviation was 10.57cm and the mean was 8.49cm with forward speed of 2m/s. During circular sections or after injecting the disturbance, the deviation was significantly increased and the maximum lateral deviation was 23.89cm, but the effective tracking can still be achieved. It can be concluded that the controller can satisfy the requirements of the precision and robustness of agricultural vehicles when the speed was less than 2m/s.

Abstract:It can be seen from the literature that the existing control methods for the control of DC-DC Buck converters are mostly based on the pure state feedback. When the disturbances are large, the gains of the controllers are usually required to be tuned large enough so as to suppress the adverse effects of disturbances, while the large gains usually affect the dynamic and steady-state performance of the closed-loop systems. To tackle this problem, a composite control scheme was proposed by combining the terminal sliding mode and disturbance observer techniques to further improve the dynamic and steady-state performance of Buck converter’s control system. First of all, taking the external disturbance, system uncertainties and parameter perturbations into account, the average state model of DC-DC Buck converters should be firstly built. On this basis, a sliding mode controller by virtue of the non-singular terminal sliding mode control technique was designed for the Buck converter such that the fundamental voltage regulation can be implemented. Finally, by applying the disturbance observer technique, a nonlinear disturbance observer was constructed to estimate the unknown disturbance, and the estimated value as the feedforward term plus the state feedback constitute the composite controller, which can further improve the performance of the closed-loop system. Simulation and experimentation results verified the effectiveness of the proposed method.

Abstract:According to the design theory for parallel mechanisms (PMs) based on position and orientation characteristic (POC) equation and the principle for coupling degree reduction, a novel 3T1R PM with lower coupling degree was proposed. Firstly, the structure coupling-reducing optimization design for a kind of 3T1R PM was performed, whose POC and degree of freedom were unchanged with lower coupling degree (κ1=1 and κ2=0).Moreover, the topological structure and the decoupling characteristic were analyzed and the results showed the motion of the mechanism was partially decoupled. Secondly, the positive and inverse analytic solutions were analyzed, and the singularity analysis was also performed based on Jacobian matrix, from which two singularity-free workspace regions were obtained. Finally, the workspace and rotation capability were also analyzed, which showed that workspace and rotation capability of the coupling reduction PM were enhanced compared with that of the original PM under the same structural parameters. The results showed that the coupling reduction mechanism had good motion-decoupling property, simple mechanical structure, large workspace and remarkable consistent rotational capacity in full workspace, and avoided the shortcomings of bad rotational capacity and strong coupling, which made it a promising prospect in the application of industry.

Abstract:In order to solve the problem that the existing hydraulic motor is easy to be damaged due to unbalanced radial force, a couple force-type radial piston motor was designed based on the idea of double stators. The radial force balance of motor output shaft was not affected by the lateral force, and the torque was output through the force couple. The inner and outer motors were formed in one shell of the motor, and three kinds of torque and rotational speed can be output through different flow distribution modes. The structural characteristics and working principle of the motor were introduced, and the relationship between curve of guide rail and pulsation of motor torque and rotational speed were analyzed through the analysis of instantaneous torque of motor, the condition that torque and rotational speed of the motor without pulsating was obtained, and the law of angle distribution of guide rail curve when the torque ripple was zero was obtained. A motor test bench was built to test and measure the output characteristics of the motor. When the inner motor worked alone, the output torque was low and the rotation speed was high;when the outer motor worked alone, the torque was high and the rotation speed was low;when the inner and outer motors worked together, the maximum torque and minimum rotation speed were output. The motor prototype was processed and tested, and the output characteristics of the motor under three working modes were tested. The results showed that the torque pulsation was related to the sum of velocities of plungers in the oil inlet section. If the sum of the velocities was constant, there was no torque-speed pulsation in theory.

Abstract:Since the single pump controlled asymmetric cylinder closed circuit demands extra flow compensating unit and its velocity fluctuates during the changes of load directions, an innovative double pump controlled asymmetric cylinder closed circuit system and its control strategy were proposed. The cylinder was directly controlled by double variable speed pumps driven by a servo motor and a low-pressure hydraulic accumulator was adopted as the tank. The operating principles of the single pump and double pump controlled cylinder closed circuit under a four-quadrant operation were analyzed. The mechanical model of the front attachment of a micro-excavator was built, as well as the pump controlled cylinder closed circuit system and the velocity feed-forward open loop and closed loop control strategies. Furthermore, the built hydraulic system of the double pump controlled cylinder was partially validated. The simulation was performed by using this partially validated model, a velocity reference for the stick cylinder and a zero load for the bucket of the front attachment. After the analyses and comparisons of the operating behavior and energy consumption, the results magnified that compared with the single pump controlled cylinder system, although the energy efficiency of the proposed double pump controlled cylinder system was decreased by 4 percentage points, the velocity fluctuation problem caused by the four-quadrant operation was eliminated and the maximum position error of running 0.8m was only 4mm. Therefore, the proposed system and its control strategies were effective and feasible for the four-quadrant operation of the asymmetric cylinder.

Abstract:A structure optimization method of machine tool weak part based on mapping model between structure and whole machine performance was proposed. In this method, firstly the structure weak component was determined by the dynamic and static characteristics analysis of machine tools. Secondly, the structure-performance mapping modeling method based on elliptical basis function (EBF) neural network, whose extended constant was selected adaptively, was proposed. In this section, the elliptical basis function neural networks was modified and improved, and the EBF modeling method based on self-adaptive extended constant was proposed. The self-organizing selection of expansion coefficients was used to determine the reasonable participation and overlap of different elliptic basis functions, and it can avoid all elliptical basis functions from too flatting or too slant effectively, which may affect the accuracy of EBF modeling. Then, the structure-performance mapping model based on improved elliptic basis function neural network was structured. Also the validity and correctness of the mapped model was verified based on the sample data: the correlation coefficients between actual values and calculation results from mapped model were all above 0.995. Thirdly, on the above basis, according to the physical mapping relation between structure and static/dynamic performance of the whole machine tool, considering the effect of boundary constraint of the whole assembly, by taking dynamic and static performances as evaluation, and choosing the structure of weak component as the optimization object, based on multi-objective optimization algorithm, the optimization of weak structure part and the whole dynamic performance of machine tool were realized finally. After optimization, the center point deformation of tool was reduced by 12.8%, the mass of structure part was reduced by 9.7%, while the first order natural frequency of the whole machine tool was increased by 6.9%.