Abstract:The optimal control methods and techniques of greenhouse environment can effectively improve the production conditions of greenhouse crops and utilization efficiency of light energy resources, so as to realize the production of high yield, high efficiency and high quality. In order to make full use of domestic and international research results in greenhouse environmental control, and promote Chinese development in greenhouse area, the recent research progress of greenhouse environment control methods was summarized from five aspects based on set point, intelligent algorithms, multi-objective optimization, multi-factors coupling and crop growth information. It was considered that the major scientific problems should be solved in the future, which involved efficient control mechanism of light/temperature/nutrition coupling, high-throughput detecting method of plant phenotype. In this way, the key technologies in greenhouse can be broken through, such as information perception, internet of things, wisdom management and control, etc. A technology system of intelligent measurement and control with Chinese characteristics in greenhouse would be formed.

Abstract:The intelligent inspection robots can complete the inspection task efficiently and reliably, and reduce the labor intensity of staff. Accurate and stable navigation positioning is the basis for inspection tasks of inspection robots. A navigation system based on light detection and ranging (LiDAR) was developed to achieve mapping, path planning and navigation positioning of the robot in both indoor and outdoor environments. The navigation system was composed of remote monitoring platform and inspection robot. The remote monitoring platform can issue inspection tasks, monitor robot status, query and store detection data, while the inspection robot can conduct navigation and positioning autonomously, traverse detection point, complete data acquisition and other inspection tasks. The platform and inspection robot exchanged remote data through wireless network. To build the 2D environment map, the information from LiDAR and encoder was combined by using a robust Gmapping algorithm. Based on the information of the map and detection points, the branch-and-bound algorithm was applied to search the optimal inspection route in order to reduce inspection time and energy consumption. Adaptive Monte Carlo localization (AMCL) algorithm was used to estimate the position and posture of the robot. The navigation and positioning was achieved by combining the position, posture and the inspection route calculated previously. Robot driver control was completed based on classic PID algorithm with the input of lateral deviation and heading deviation. The robot was equipped with RGB camera and IR camera, and targets can be detected more efficiently using the fusion information of visible and infrared images. In order to verify the accuracy of the navigation system, the indoor navigation positioning experiment was carried out in this research. With the speed of 1m/s, the mean absolute error (MAE) of the position and heading deviation was less than 5cm and 1.1° and the standard deviation (SD) was less than 5cm and 1.5°, which can meet the requirements of inspection navigation and positioning.

Abstract:In order to solve the problem that vertex and bottom points of the crop are difficult to be identified in height measurement of crop by using the visual method, a crop height measurement system based on laser vision was designed. The improved triangulation model, which was designed according to the character of crop height measurement, was used to describe the mathematical model of the system. The model parameters of the crop height measurement system included three parts, which were the parameters of camera, the equation of light plane and camera installation parameter. The model parameters were calibrated by a novel checkerboard method. In the process of the system parameters calibration, the checkerboard must be placed on the parallel plane of the corresponding horizontal plane where the bottom point of the crop was on at least once，to establish the ground coordinate system. Furthermore, the system identified the crop apex by projecting the laser onto the crop. The results of measurement in crop plant height of 558.00~1843.30mm showed that the absolute error was no more than 28.30mm and the relative error was no more than 2.17%. Furthermore, the restrictive conditions of the system and suggestions for engineering implementation were given. This system can achieve real-time measurement automatically with a high precision and it had good practical value.

Abstract:In order to improve the field efficiency and reduce the operation cost, a research was conducted on the path planning method for the sprayer UAV in the field with 3D terrain. Firstly, aiming at building a 3D environment model, the grid method was selected to divide the field into small grids with the initialized properties. Secondly, the UAV was ordered to move from the current grid to the adjacent one with the highest probability. And therefore a coverage path which moved from one extreme of the field to the other in direction parallel to the crop rows alternately and turned at the boundary was identified. Thirdly, a mathematical model was established, of which the objective was to obtain the optimal return points with the minimum time in the non-spraying mode. Once the gravitational search algorithm was applied to solve the model, the planned path with return points would be outputted automatically by the proposed method. Furthermore, the proposed method was compared with the method for 2D terrain in a 700m×100m field, of which the result showed that there was deviation between the positions of the return points calculated by the different methods. And the same field was taken to test the performance of the proposed method, in which the proposed method was compared with simple path plan method and unplanned path respectively. Results showed that the advantages of the proposed method at the distance of the round trips was reduced by 23% and 90%, while the non-spraying time was reduced by 7% and 54%, respectively. After that, the proposed method was applied to a real field with 3D terrain. And the distance of the round trips and the non-spraying time were reduced by 11% and 5%, respectively in the experiment. Finally, the research result indicated that the proposed method was a reasonable, feasible and useful alternative to produce paths with less time for the sprayer UAV.

Abstract:Inspired by the efficient mining of soil function of the oriental mole cricket claws, crushing soil covering device was put forward to improve the performance of the broken soil. The toe claws of the oriental mole cricket forefoot and toe high angle, toe distance and lateral wedge angle were measured, on the basis of this, the bionic soil crushing disc was designed. The crushing type bionic soil covering device consisted of discs of big and small, bending flange, fixed frame, rotating pair, damping spring and suspension frame. The covering soil device was designed for double row seed groove, which can be used to cover the soil of two sides of soybean grooves. Ansys and Ls-Dyna softwares were used to simulate and analyze the designed components. Through the simulation analysis of the crushing bionic soil covering device, the soil broken process was simulated actually and intuitively. The cutting force and equivalent stress distribution of soil and lateral displacement of soil were obtained. Through the analysis of equivalent stress of broken soil, the equivalent stress was greater than the shear strength of the dry soil which ensured the broken effect on the dry soil. Field test results showed that the crushing bionic soil covering device completed the function requirements of soil covering, and had strong soil fragmentation and the crushing rate was 92.2%, the average thickness of covering soil was 2.4cm, and the average seed spacing was 10.1cm.

Abstract:On the base of corn insert plot hill-drop planter, in the light of sowing performance of passive duckbill opening is greatly affected by the fluctuation of ground level, a strong row-strong open metering device was designed, which is mainly composed of conjugate cam, strong platoon-strong open metering device. The sowing process of forward speed compensation device of corn insert plot hill-drop planter was analyzed to determine the key sowing time points. The displacement calculation of two kinds of movements of connecting rod and fetching seed wheel and opening forcibly of duckbill were carried out emphatically. According to the calculation results with reverse calculation method, the main cam profile of the conjugate cam was determined. A uniform rotation wheel can improve the rate of movement of the cam follower, and the motion law of cam follower was determined by calculation. And test results showed that transmission of forced sowing and forced opening for corn direct seeding machine was stable, which can complete picking and seeding corn, and duckbills when metering did not clip soil, and film hole was small, and there were no problem that duckbills pick film, tear film, etc. The hole rate of corn insert plot hill-drop planter was 1.8%, cavity and seed number of qualified rate was 95.3% and planting under film depth pass rate was 88.1%, thus the design of strong seeding corn-strong opening duckbill of insert plot hill-drop planter met the design requirements and agronomic techniques of corn planting.

Abstract:In order to further improve the quality of hole metering，aiming at hilling and blocking problems of touching parts soil sowing in the process, combined with the requirements of precision seeding technology and the use of four bar kinematic principle, a kind of dry type rotary pricking hole seeding method was put forward, its variety can be applied to different working environments with diverse mode. Selecting the core motion parameters by establishing the mathematical model and the structure of tie points VB visual programming platform and the design of key components of the concave wheel and the return spring was optimized. The principal axis speed and the spring wire diameter were selected as experiment factors, with qualified index and coefficient of variation of test indexes as two orthogonal revolving combination test, the data processing was done by using Design-Expert 10.0.3 software and selecting the optimal working parameters. Through field verification test, under the condition that the spindle speed was 27r/min and the line diameter of the spring was 1.5mm, the operation qualification index of the seeder was 92.1%, the variation coefficient was 2.5%, and the blockage rate was 0. The results showed that the mechanism can meet the requirements of operation technology of precision seeding at the same time, and further improve the reliability and uniformity of soil particle spacing. The optimization of pricking hole seeder for dry rotary provided a theoretical basis and technical reference for improvement.

Abstract:In the process of maize grain direct harvest, the threshing cylinder speed should be matched with the feed rate of combine harvester, so that the best effect of the operation can be achieved. In order to obtain the optimal ranges of the threshing cylinder speed of maize combine harvester at different feed rates, a longitudinal axial flow maize threshing and separating device was designed and developed, whose components and parts can be changed easily. It was also convenient to adjust the structure parameters and working parameters. The threshing cylinder speed and the feed rate were selected as the influence factors, and the maize kernel damaged rate and un-threshed rate were selected as the performance indexes in the experiments. The test results showed that with the increase of threshing cylinder speed, the maize kernel damaged rate was increased and the un-threshed rate was decreased. At the same threshing cylinder speed, with the increase of the feed rate, the maize kernel damaged rate and the un-threshed rate were increased slightly. Through the bench tests, regression analysis and single variable solution, the optimal ranges of the cylinder speed at different feed rates of the threshing and separating device were determined. The optimal range of cylinder speed was 254~486r/min at the feed rate of 8kg/s. The optimal range of cylinder speed was 278~466r/min at the feed rate of 10kg/s. The optimal range of cylinder speed was 313~445r/min at the feed rate of 12kg/s. Under all the conditions above, the maize kernel damaged rate was less than 5%, and the un-threshed rate was less than 2%, which reached the requirements of the national standards. The research result of the threshing and separating device provided reference for design of maize grain harvester, and the research on adaptive model of the feed rate and threshing cylinder speed.

Abstract:Traditional rake mulching film recycling machine had the problem of difficulty in unloading and packing film, poor continuity of the work. In order to solve such problems, a kind of chain rake type mulching film recycling machine which can realize continuous raking film, collecting film, transporting film, shaking off soil and unloading film was designed. The recycling machine mainly composed of frame, membrane shovel, chain rake, collecting box and so on. In order to optimize the performance of the film recovery machine, first of all, the single factor test and response surface optimization experiment were carried out on structural parameters and working parameters in soil tank laboratory. Through experimental study in soil tank, the quadratic regression equation of mulching film recycling rate, unloading film rate and quality of the soil in the film were obtained. The optimal parameters were as follows: the spacing between rake teeth assembly was 300mm, the number of rake tooth in single rake was 5, the depth of rake tooth inserting soil was 84.41mm, film recycling machine forward speed was 2.542km/h, and the speed of the chain rake was 0.417m/s. Finally, through field experiments, the performance indicators of this type of mulching film recycling machine were as such: mulching film recycling rate was 90.2%, unloading film rate was 88.1%, and the entrained soil weight was 0.41kg/m. Field experiments show that the chain rake type mulching film recycling machine can meet production requirements.

Abstract:According to poor mechanical performance such as passing and leveling difficult in hilly areas, the terrain adaptive and dynamic leveling agricultural chassis for hilly area was designed. Four groups of leveling suspension’s cantilever angle can be precisely adjusted, so the chassis can not only have the capability to adjust its own configuration to accommodate to the terrain with which it interacted and contacted, but also can locomote continuously along the ground curve of terrain surface as far as possible, moreover, it also can realize the body leveling control through the suspension’s cantilever angle adjustment. The design scheme can resolve the two problems during the chassis locomotion on the uneven ground. During the terrain adaptive locomotion, the tilt sensor can measure the inclination angle of the chassis body in real time, so the instantaneous cantilever angle adjustment value of each suspension can be calculated. And the dynamic compensation leveling of the chassis can be realized by adjusting the cantilever angle of each suspension accurately. Three-dimensional model was established by using 3D modeling software referring to Dongfanghong 500 tractor, and the model was imported into dynamic analysis software ADAMS for simulation analysis. By analyzing the simulation process, the chassis can achieve dynamic leveling control so well that the accuracy of both roll angle and pitch angle just was within 0.5°. A small scale prototype was developed and tested in the soil bin, and the chassis can perform dynamic leveling control so well that the accuracy of both roll angle and pitch angle just was within 1° during terrain adaptive locomotion with multi DOF. The simulation, experiments in the soil bin or on the natural ground can verify the theoretical analysis and calculation results, and provide reference for the application of terrain adaptive and dynamic leveling agricultural chassis in the hilly area.

Abstract:A fitting curve subsoiler was designed aiming at the problems of large soil disturbance and large tillage resistance caused by subsoiler in sub-soiling site preparation work in Northeast China. The discrete element (EDEM) software was used to simulate the movement of the tip of a subsoiler in the soil. Through calculating, the fitting curve and fitting equation were obtained from the trajectory of soil particles above the tip of shovel. After summarizing, the method of line element design was used to optimize the alignment to acquire the curve of shovel handle shape, meanwhile, to design the edge, lip and penetration angle were cut. Then the interaction effect test of shovel handle and shovel tip were used to prove the feasibility and rationality of the design. The contrast test of soil trough showed a fitting curve subsoiler can effectively reduce the soil disturbance and tillage resistance. Compared with polygonal subsoiler, the fitting curve subsoiler made the soil disturbance reduced by 53.6%, tillage resistance reduced by 36.23%. Compared with circular subsoiler, it made the soil disturbance reduced by 66.18% and the tillage resistance reduced by 29.18%. Compared the fitting curve subsoiler with the polygonal subsoiler with field experiment, it was showed that using the fitting curve subsoiler made the soil return area increased by 81.03%. Compared with circular subsoiler, the fitting curve subsoiler made the soil return area increased by 146.95%. Both the soil trough experiment and the field experiment verified that the fitting curve subsoiler can make the soil disturbance smaller and tillage resistance smaller, which met the requirements of sub-soiling operation.

Abstract:Rice bud seeds exhibit different physical properties from other crop seeds as high moisture content and large length difference of rice buds. Therefore, it is essential to calibrate the main discrete elements contact parameters of rice bud seeds with different moisture contents, and reduce the simulation system error that caused by inaccurate parameters of rice bud seeds. Three main contact parameters were calibrated, including coefficient of static friction between bud seeds and stainless plate (X1), coefficient of static friction between bud seeds (X2) and coefficient of rolling friction between bud seeds (X3), through experimental determination combined with simulation test of rice bud seeds friction angle. Two dynamic repose angles α and β and slipping friction angle γ were formed with three devices, and measured with the software InSight Explorer based on image processing technology. Then through discrete element simulation test of bud seeds frictions with EDEM, the ternary regression equation between the three coefficients X1, X2 and X3 and the three friction angles was established. The experimental results of the three frictions were the correction index, and the regression equation was numerically solved to obtain the three main content parameters. The verification test of the calibration parameters showed that the relative error between simulation and experiment results of the bud seeds friction angles with different moisture contents was less than 2.75%. So the discrete element model of rice bud seeds and the actual particle material reflected the same friction characteristics, and the regression model satisfied the calibration requirements for bud seeds parameters with different moisture contents. Furthermore, the relative error of the other variety rice bud seeds was less than 5.54%, which indicated that the calibrated discrete element model and contact parameters of the bud seeds can be applied to the dynamic simulation of the precision sowing device.

Abstract:In order to study the effects of different biological pesticides samples on the droplet characteristics with different types and size hydraulic nozzles, a particle/droplet laser image analysis system and a portable spray pattern analyzing system were used to investigate the spray droplet characteristics of biological pesticides with hydraulic nozzles. Spray parameters included the spray droplet size distributions and spray pattern widths. Seven different spray samples (water and six types of biological pesticides manufactured by Bioworks Inc.) were tested with two Teejet flat fan nozzles (XR8004 and XR11004) and two Teejet hollow cone nozzles (TXA8002 and TXVK8004) under laboratory conditions. Droplet size distribution was evaluated at the same and different spray pressures separately and the same spray height. In addition, the spray pattern width was determined at the same spray pressure and the same spray height. The results showed that there was no significant difference between the droplet size of the liquid biological pesticide after mixing with water in a certain proportion and the droplet size of water, and the droplet size of the liquid biological pesticides was higher than that of the powdery biological pesticide mixture with water. The droplet size of biological pesticide sprayed was decreased as the spray pressure increase for the same nozzle;the droplet size distribution uniformity was decreased as the increase of the nozzle flow rate, and the larger the spray flow rate was, the more dispersed the particle size was. The spray pattern width was increased as the increase of the spray angle, and different biological pesticide samples had little effect on the spray pattern width. Therefore, proper selection of nozzle types, spray pressure and flow rate was necessary for discharging particular biological products to achieve optional spray application efficiency and effectiveness.

Abstract:In order to study the applicability of the similarity law under the condition of gas-liquid two-phase flow in centrifugal pumps，the NKG65-50-140 direct-type single-stage and single-suction centrifugal pump was chosen，based on experimental and numerical simulation to study. Firstly，the performance tests of model pump under the condition of three different speeds and different inlet gas volume fractions（IGVF）were carried out at open test rig of gas-liquid two-phase flow. And then numerical simulation used the water and air as the working medium，based on the Eulerian-Eulerian inhomogeneous model，the flow condition and gas distribution were got in the impeller at different speeds and IGVF. The comparisons between the experimental and simulated results showed that the IGVF had a significant effect on the similarity law of gas-liquid two-phase flow because the IGVF affected the energy exchange capacity between impeller and liquid. For the same flow coefficient, the greater of IGVF was，the worse of the applicability to the similarity law was. With the decrease of rotational speeds，the gas distribution was moving from the tip of impeller blade to the middle of the impeller channel and the volute-tongue，which would plug the flow more easily especially when the IGVF was more than 0.03. Finally，the reliability of mathematical model and calculation methods under low IGVF was confirmed by comparing the experimental results with simulated results，which had a significant theoretical guidance for pump design.

Abstract:The pressure pulsation is one of the main causes of vibration and noise in axial flow pump, in order to study the mechanism of pressure fluctuation induced by vortex, several pressure pulsation monitoring points were stalled at the bottom of the pump sump, the horn mouth, the impeller inlet and outlet, the outlet of the guide vane. The flow rate of 1.2Qd (1.2Qd=38.4L/s) was selected. The dynamic process of vortex generation and disappearance was measured by an advanced high-speed camera, and the microscopic variation of the vortex was observed. The results showed that the vortex tube below the horn position and low position, the maximum amplitude of pressure fluctuation at the bottom of the vortex tube, the Cp value was about 1.8~2 times of the non center point of pressure fluctuation of Cp value, at the center of tube, the pressure pulsation frequency of the vortex occurred at 1 time of the impeller rotation frequency. The pressure fluctuation at the impeller inlet and the pressure fluctuation at the impeller were synchronized at 1 time of the impeller frequency, and the pressure pulsation frequency was 1 time of the frequency of impeller. The detailed structure of the vortex changes was clearly observed by high-speed cameras. On the whole, the maximum amplitude of pressure fluctuation was at the inlet of impeller, and the maximum amplitude of pressure fluctuation occurred at the center of the vortex belt. The Cp value of the pressure fluctuation at the center of the vortex belt was about 1.8~2 times of the Cp value of the pressure fluctuation at the non center point. Getting through the water inlet swirl from generation to the collapse process and the influence of pressure fluctuation, can provide a theoretical basis for the pumping station project of vortex elimination measures.

Abstract:In order to suppress the free-surface air-entraining vortex in pump sumps, the three-dimensional unsteady vortex flow in a pump sump was calculated by computational fluid dynamics (CFD) method. The dynamic process of the free-surface air-entraining vortex was simulated. And an experimental model was conducted to verify the CFD method. In this experimental model, a circular plate device was placed between the free surface and the inlet of the bell-mouth to suppress the air entrainment. Furthermore, a parameter called helicity density was adopted to reveal the mechanism of air-entrainment and its suppression. The results showed that the numerical method used in this study can predict the dynamic process of air-entrainment for the free-surface vortex accurately. The helicity density played a very important role in the formation of air entrainment. When the dimple appeared on the free surface, a helicity density tube was formed around the inlet of the bell-mouth. As air entered into water, the other helicity density tube was formed under the free surface. When the two helicity density tubes were connected with each other, the air-core from the free-surface to the inlet of the bell-mouth was formed. This meant that the mechanism of air-entrainment for the free-surface vortex was the connection of the helicity density tubes which provided a passage for air to pass through. Moreover, the circular plate with enough dimension can successfully suppress the air-entrainment through cutting off the helicity density tubes.

Abstract:With the aim to enhance the capability of predicting cavitating flows for Schnerr-Sauer model, a developed cavitation model was proposed based on an improved spherical bubble dynamic model and the homogeneous flow assumption. In particular, the terms of the second derivative of bubble radius and surface tension were also considered in the simplified Rayleigh-Plesset equation to give more reliable physical model for bubble shrink and growth. Unsteady and turbulent cavitating flows over a two-dimensional Clark-Y hydrofoil were calculated by using the proposed model and Schnerr-Sauer model in which a modified filter-based model was adopted for the turbulence modeling. The cavity shape evolution and the characteristics of hydrodynamic coefficient at different cavitation numbers were obtained from simulations. Comparing with available experimental data in the literature, for quasi-static sheet cavitation, the length of the sheet cavity as predicted by the proposed model almost remained unchanged and noticeable vapor-liquid interface was captured at the rear of the sheet cavity as well, which agreed better with the experiment description. For the periodic cloud cavitation, the cavitation area predicted by the proposed model was larger than that of the Schnerr-Sauer model, which was induced by the non-condensable gas and turbulence fluctuation considered in the proposed model. Moreover, the transient lift coefficient predicted by the proposed model agreed better with the experimental data and the proposed model had better capability than the Schnerr-Sauer model to predict some detailed features of the cyclic cavity evolutions in cloud cavitation. The overall results proved the reliability and accuracy of the improved cavitation model in cavitating flow simulations over a hydrofoil.

Abstract:With the development of precision agriculture, the demand on rapidly obtaining the area and geographical distribution of greenhouses, plastic-mulched landcover is increased. However, using the interpretation method for satellite remote sensing images to process unmanned aerial vehicle (UAV) images is not ideal, due to the complex feature extraction, low recognition accuracy, long processing time and so on. To circumvent this issue, a UAV aerial monitoring method was proposed based on deep learning for greenhouses and plastic-mulched landcover monitoring. The six-rotor UAV equipped with Sony NEX-5k camera captured aerial photographs in the Wangyefu town of Chifeng City. The 558 UAV images were orthographically corrected and stitched. The five fully convolutional network (FCN) variants, i.e. the FCN-32s, FCN-16s, FCN-8s, FCN-4s and FCN-2s models were built by multi-scale fusion. The modes were trained end-to-end by the stochastic gradient descent algorithm with momentum. The features were extracted and learned from the photographs automatically. The FCN models were compared with two economic softwares, i.e. the pixel-based classification method of ENVI and the object-oriented classification method of eCognition. The results showed that the FCN-4s was the best model on the identification of greenhouses and plastic-mulched landcover. The average overall accuracy of test area was 97%, while that of pixel-based classification method and the object-oriented classification method was 74.1% and 81.78%, respectively. The average runtime of the FCN-4s was 16.85s, which was 0.06% and 5.62% of those of pixel-based classification method and the object-oriented classification method, respectively. The proposed method demonstrated high recognition accuracy and fast speed, which can meet the demand on UAV monitoring of facilities agriculture.

Abstract:Irrigation district canal system with modern water-saving irrigation technology has a significant impact on rational distribution of water and the safety of water supply. However，the resolution of the commonly used remote sensing image of irrigation area is not high, which brings difficulties to the extraction and mapping of the drainage system. The high-precision ortho-image, elevation and slope data collected by UAVs were taken together as data sources. Features with strong canal discriminative ability were obtained from them to construct a training set. The classification system was trained via the support vector machine to segment canals from images. Then, the extraction results were denoised, connected and optimized, and the canal extraction of UAV high resolution multi-source data was realized. The results showed that the canal extraction method can identify the branch canal in the irrigation area. Meanwhile，competitive performance was achieved in the continuity of the canal, the bucket and the part of canal system. The precision was up to 89.35%. The extraction error was mainly caused by the deposition of canopy mud in the lower canal system which made the terrain features not easy to be recognized. In conclusion, the method proposed provided a new solution for the extraction of irrigation and drainage canal and can be applied to the actual agricultural production.

Abstract:Over the last decade point cloud derived from laser scanner has become the mainstream of the individual tree canopy extraction research. However, the high cost of airborne laser scanning acquisition makes it unsuitable for repeated surveys and small-scale forest mappings. Individual tree canopy was extracted from unmanned aerial vehicle images matching point cloud, aiming to provide a cost-effective method which can complement or even partly replace LiDAR forest mapping in small area. Choosing young Osmanthus and Podocarpus trees growing in a nursery as the study objects, the method was tested in two samples of images matching point cloud. An inexpensive commercial off-the-shelter drone with built-in camera was used to acquire overlapping nadir-viewing images. These images were then used to generate dense point cloud in photogrammetry software. After preprocessing, canopy height model was firstly built from the point cloud;a local maximum filter was applied to detect the canopy positions and marked as the seed points;then the initial area of regional growth can be formed from these seeds;in an iterative calculation process of all image matching points were classified. The canopy contours extracted by the algorithm were inputted into ArcGIS to obtain canopy contour vectors, and were validated by comparing with the manually drawn individual tree crown polygon (reference crown). The F score of segmentation results was higher than 89%, and the errors of individual tree crown diameter extraction results were less than 0.14m (root mean square error) in both sample plots.

Abstract:Leaf area index (LAI) is an important biophysical parameter for assessing of agroecosystems, which is widely used in various applications. The ground-based hyperspectral remote sensing technique is known to be inexpensive but effective for monitoring of the LAI of crop canopies. During the past twenty years period, hyperspectral technique has been adopted increasingly for plant LAI evaluation, which demands unique technique procedures compared with the conventional multispectral dataset, such as dimension reduction and denoising. Thus, identifying of the optimal bandwidths as well as effective wavelengths (sensitive wavelengths) is of great importance for improving the accuracy of crop LAI assessment based on the hyperspectral remote sensing data. As one of the most important oil crop in China, with a cultivated area of 7.5 million hectares and a production of about 14.4 million tons of seeds. Accurate and real-time assessment of spatial and temporal variations of crop LAI is particularly important. The objectives were to identify the optimal bandwidths and their effective wavelengths which were best suited for characterizing the winter oilseed rape biophysical variables. Five nitrogen field experiments involving different ecological sites, cultivars and planting patterns were carried out over three consecutive growing years (2013—2016) in Hubei, China. The in-site canopy hyperspectral reflectance dataset of winter oilseed rape were obtained over a wavelength region from 400nm to 1350nm (the visible and nearinfrared region), and quantitative correlations between LAI and their hyperspectra were analyzed. Moreover, a partial least square (PLS) regression model for LAI prediction was employed with different bandwidths (narrow and broad band spectral variables) canopy raw spectral reflectance (R) and its transformation technique: the first derivative reflectance (FDR). The prediction accuracy of the optimal bandwidths were determined by comparing coefficient of determination (R2), root mean square error (RMSE) and relative percent deviation (RPD) between the observed and predicted LAI values for both the calibration(cal) and validation(val) datasets. The results indicated that the values of LAI had a similar range in both the calibration dataset and the validation dataset and provided high variable coefficient values, indicating that the data partitioning was reasonable and could avoid unbiased evaluation. Compared with the R-PLS model for LAI estimation, the FDR-PLS model yielded higher retrieval accuracy for LAI prediction, and the optimal bandwidth was 20nm. The R2val, RMSEval and RPDval between the observations and predictions were 0.779, 0.414 and 2.004, respectively. The VIP scores of the FDR-PLS model with a full hyperspectral region (400~1350nm) were applied to select the effective wavelengths and decrease the high dimensionality of the canopy spectral reflectance data. Five wavelengths centered at 759nm, 847nm, 921nm, 1002nm and 1129nm were selected as sensitive wavelengths for monitoring the LAI status. The newly-developed FDR-PLS models for LAI prediction (R2val was 0.715, RMSEval was 0.486 and RPDval was 1.707) provided accurate estimations based on the field experiment validations using the effective wavelengths. The analytical thinking could provide an inventive thought thread of plant spectral wavelength selection for crop LAI prediction, and it also could provide a theoretical foundation for wavelength settings of broadband multispectral imaging spectrometer and monitoring potential applications of remote sensing data.

Abstract:Soil available phosphorus (AP) is supposed to be an important nutrient constituent for the growth and development of crops. Hyperspectral analysis has proven to be a rapid and effective means for quantitatively predicting soil AP, which has a good prospect benefit from the narrow bandwidth and the high resolution. However, the existence of multicollinearity and redundant considerably leads to overfitting of the regression model and decrease of the generalization ability. A total of 145 lime concretion black soil samples collected from the Northern Anhui Plain, China, were used as research objects to investigate the prediction performance of the back-propagation neural network (BPNN) based on the partial least square regression (PLS-R) algorithm. The PLS-R was applied to conduct dimensionality reduction and feature selection on the soil visible and near infrared hyperspectral data ranging from 400~1000nm with 339 wavelengths. Five latent variables (LVs) were obtained by the leave one out crossvalidation, and nine optimal wavelengths were selected by the variable importance in projection (VIP) scores. The BPNN regression models were built with the input of the five latent variables (LVs-BPNN), the nine optimal wavelengths (VIPs-BPNN), and the whole wavelengths (Ws-BPNN), respectively. The ratio of performance to deviation (MRPD) and the ratio of the interpretable sum squared deviation to the real sum squared deviation (MSSR/SST) were selected to evaluate the prediction accuracy and explanatory power of different regression models, respectively. As a result, the prediction accuracies of three BPNN models outperformed the PLS-R model significantly;the VIPs-BPNN model achieved similar performance (MRPD was 2.05, MSSR/SST was 0.79) as the Ws-BPNN model (MRPD was 2.09, MSSR/SST was 0.85) of the validation set, while the MRPD was decreased obviously from 10.27 (Ws-BPNN) to 2.66 (VIPs-BPNN) of the calibration set;the LVs-BPNN model gained the highest prediction accuracy as MRPD was 2.29 of the validation set, even though the MSSR/SST was slightly decreased to 0.76. The results illustrated that the PLS-BPNN models could significantly reduce the degree of overfitting and improve the generalization ability;moreover, the LVs-BPNN model could improve the accuracy of predicting soil AP.

Abstract:To get the soil moisture of the large scale rapidly and the best monitoring depth in bare soil by UAV multispectral remote sensing technology, the clay loam soil was prepared into two different depths (5cm and 10cm) and the soil moisture ranged from 3% to 30% of the different samples. The UAV was equipped with a Micro-MCA multispectral camera to monitor the soil samples at 3 p.m. for three consecutive days. The soil spectral reflectance values of six bands (490nm, 550nm, 680nm, 720nm, 800nm and 900nm) were collected. The surface moisture content (about 1cm) and overall moisture content of soil samples of two different depths were also measured. The regression models between soil moisture and the reflectance of different bands were established by the regression methods of partial least squares regression, stepwise regression and ridge regression. Quantitative relationship was analyzed of the regression modes and the methods. The results showed that the three regression models had statistical significance (P<0.001) for predicting soil moisture content. The accuracy evaluation of the model through the validation set showed that the stepwise regression model had good prediction ability (R2 were 0.775, 0.764, 0.798 and 0.694, RMSE were 0.028, 0.042, 0.037 and 0.038 and RPD were 2.22, 2.04, 2.20 and 1.75), followed by ridge regression method and partial least squares method. The regression models of the surface soil had good inversion effect in monitoring depth. The inversion effect was decreased as the increase of monitoring depth. The relationship between the soil moisture and the wavelength of 720nm, 680nm and 550nm band was better among the six bands. The results showed that the best regression method was stepwise regression method, and the best monitoring depth was the surface layer (about 1cm) of the soil samples. The research result can provide reference for the rapid monitoring of soil moisture in the area by using multispectral remote sensing of UAVs, and promote the further development of precision agriculture.

Abstract:Complex ecological network is a hotspot in the study of regional eco-environmental sustainability in recent years. The remote sensing image in 2016, DEM data and so on in Dengkou County were used as research material. The concept of ecological Coulomb force was proposed and based on the force-directed algorithm, a multi-scenario simulation model of ecological network was constructed. Furthermore, combining the minimum cumulative resistance surface model, totally 11 scenarios were set up to study the evolution of the present ecological network. The results were shown as follows: based on the current situation of ecological protection mode, the cumulative ecological resistance surface showed that the wolf mountain piedmont and the northeastern margin of the Ulan Buh Desert had great ecological resistance. In contrast, there were significantly more areas with large cumulative ecological resistance values under the economic development model. With (1.0, 0) to (0, 1.0) model conversion, ecological source grid patches gradually disappeared, the skeleton corridor was gradually broken. In the (0, 1.0) mode, the ecological network had been greatly destroyed. Under the present condition, large-scale land economic development would cause great damage to the ecological network. However, in the (0.9, 0.1) mode, although the destruction occurred on the edge of the desert, the ecological network inside the sample circle was expanded. Under the existing natural resources, there was still room for economic development in Dengkou County, but the space was limited. The multi-scenario simulation model proposed was suitable for the evolution analysis of ecological networks.

Abstract:It has always been a hot topic on using hyperspectral data to analyze in-depth crop heavy metal pollution. Some methods were put forward for qualitatively analyzing copper ion (Cu2+) and lead ion (Pb2+) pollution, discriminating the kinds of pollution elements and diagnosing their pollution degrees combined with the feature extraction methods of the higher-order spectral estimation and the gray gradient co-occurrence matrix (GGCM) based on derivative spectral data of the corn leaves stressed by different Cu2+ and Pb2+ concentrations. Firstly, the spectral data of the corn leaves were collected and the Cu2+, Pb2+ contents in the leaves were measured, which the potted corns were cultivated and stressed by different Cu2+ or Pb2+ concentrations. Then, the bisp_rts and bisp_qs matrixes and their bi-spectral 3D graphs were obtained by the bi-spectral estimation (BSE) of differential spectral data sequences of various corn leaves that the BSE was carried out by using the ARMA model parameter method of higher order spectral estimation, so that a corn leaf was analyzed visually and qualitatively to have been polluted or not by Cu2+ and Pb2+, and the kind of the pollution element could be discriminated to be Cu2+ or Pb2+. Finally, the GGCMs were constructed which were corresponded to the bisp_rts or bisp_qs matrixes, the Cu2+ and Pb2+ pollution degrees of corn leaves could be diagnosed by extracting the texture parameter eigenvalues of each GGCM. The experimental results showed that it can not only qualitatively analyze whether the old (O), middle (M) and new (N) leaves of corn were polluted by Cu2+ and Pb2+, but also correctly discriminate the O and M leaves were polluted by which one of the tow element based on the higher-order spectral estimation;the un-uniformities of gray distribution (T1) and energy (T2) eigenvalues of the bisp_rts matrix could reflect the changes of Pb2+ content in O and M leaves, so the T1 and T2 might well diagnose the pollution degree of Pb2+ in O and M leaves, and the small gradient advantage (T3) eigenvalue of the bisp_qs matrix could reflect the changes of Cu2+ content in O and M leaves, so the T3 might well diagnose the pollution degree of Cu2+ in O and M leaves.

Abstract:In traditional forest resources survey, it was hard to get tree structure parameters due to its different shapes and complex structures. Totally six stand trees were selected as a sample data in the campus of Beijing Forestry University. By using ground-based laser scanner as a tool to acquire single tree scanning point cloud data, the canopy gap fraction was calculated based on Lambert azimuthal equal area projection and stereographic projection;tree crown volume and surface area were extracted by two methods: irregular surface projection and voxel method by using cloud point data. The results showed that the average relative error of two methods for gap fraction was 0.03, and the extraction result using stereographic projection was smaller than that using Lambert azimuthal equal area projection;the relative error of crown volume of two kinds of extraction methods was 5.32%~12.43%, the average relative error was 9.29%, the relative error of the extracted crown surface area was 1.40%~5.21%, the average relative error was 3.33%. The difference between the results of the two methods were not very significant, therefore, the extraction of gap fraction, crown volume and surface area based on the use of the point cloud data can provide a more reliable data support for 3D green quantity, calculation of trees biomass, photosynthetic ability etc.

Abstract:Laser point cloud data contain detailed and high precision information, which is widely applied to forest evolution and plant reconstruction. In order to improve the accuracy and photorealistic in tree 3D reconstruction, a 3D reconstruction method based on point cloud was proposed. Firstly, the Kinect 2.0 was used for acquiring double face point cloud data of tree, and there were four plastic balls which were artificial markers near the tree. In the process of registration, artificial marker method and iterative closest point (ICP) algorithm were combined to merge point cloud data together accurately. Then, the complete point cloud data of tree can be obtained. Secondly, the improved space colonization algorithm was used with growth angle constraint to generate the 3D skeleton of tree, and then thickness of tree was estimated according to pipeline model, and the trunk was generated by generalized cylinder. Finally, leaves which were modeled based on point cloud data were added to branches according to phyllotaxis. Reconstruction experiment was performed by using magnolia, maple and limit tree data, which was provided by Visual Computing Research Center of Shenzhen Institutes of Advanced Technology (VCC). The reconstruction results showed that the proposed method can simulate 3D morphological structure of tree realistically and it showed the topological structure of trees well. Reconstructed tree models were plausible to the real-world trees and reconstruction error was less than 6.5%. Meanwhile，the proposed algorithm could be applied to the researches of three-dimensional modeling of virtual trees, virtual pruning experiment and tree topological structure analysis.

Abstract:In order to realize the real-time monitoring of ecosystem parameters in the forest with little mobile phone signal, a real-time forest microclimate monitoring system was designed based on Beidou satellite short message communication, Internet of things and cloud storage technologies. The system was composed of microclimate monitoring station, cloud server and software. The forest atmosphere, soil, sunlight and plant parameters can be real timely monitored. The system had functions such as cloud storage, dynamic query, report generation and data analysis. The calculation of forest fire weather index was smoothed and the factor of the litter layer soil humidity was supplemented to realize the forecast of the forest fire weather grade, which was used for the early warning of the local forest fire. Through the continuous experiments at Beijing Jiufeng national forest park from March to May 2017, three forest microclimate stations can obtain 11 kinds of microclimate data stably and reliably, and the success ratios of data transmission through Beidou satellite were 98.57%, 99.43% and 99.59%, respectively, successfully realizing long-term real-time monitoring. The communication fee using Beidou satellite short message communication was lower than that using Iridium SBD communication service. Since 2016, this system had been widely used for the forestry big data acquisition and analysis in Beijing, Inner Mongolia, Hebei and Henan provinces.

Abstract:In the plain area, the fragmentation of the cultivated land unit is an important factor affecting the mechanical harvesting efficiency of wheat. Taking Dingzhou City in Hebei Province as an example, the fragmentation characteristics of cultivated land unit and the quantitative evaluation of mechanical harvesting efficiency of wheat were analyzed, and then the scenario mechanical harvesting efficiency of cultivated land unit after land merger was analyzed. It was found that the cultivated land unit in plain area was small and scattered，the plot was long and narrow, the ratio of length to width range was relatively large, which was not suitable for large-scale agricultural development work. The mechanical harvesting efficiency of cultivated land area affected the total work efficiency and work efficiency was increased with the increase of areas of arable land and land consolidation, the total operating efficiency can reach 0.4301s/m2 in theory, and the efficiency can reach 0.3049s/m2. When the cultivation unit of land area reached 8500m2, the mechanical harvesting efficiency of wheat would get into full play. The total operation time and pure working time would be reduced by 38.64% and 43.11% after parcel union, respectively. The plain area should be carried out cultivation unit of land ownership adjustment and land circulation on a large scale, the contiguous area of cultivated land reached a certain scale, which can effectively improve the mechanical harvesting efficiency of wheat, and reduce the unloading time and other time. The research can provide theoretical support for land consolidation in plain area.

Abstract:Since International Association of Hydrological Science (IAHS) initiated the prediction in ungauged basin (PUB) programe, the regionalization has become a common method for identifying hydrological model parameters in ungauged basins. However, some problems exist in the regionalization method, which was commonly used for parameter identification of hydrological model in ungauged basins, such as different relationships between rainfall and runoff in similar basin, unobvious correlation between hydrological model parameters and basin characteristics, and difficult to select a reference basin in wide range of data-deficient areas, etc. It is significant to study the method of calibrating hydrological model by using the data outside the stream flow. A method was presented to calibrate the parameters of grid-based Sacramento (GSAC) model by using evapotranspiration (ET) data from global land data assimilation system (GLDAS). Firstly, a spatiotemporal-grid corresponding relationship between GLDAS ET and ET simulated by GSAC model was established. Secondly, a evaluation index based on Nash-Sutcliffe efficiency coefficient was constructed to measure the fitting effect between GLDAS ET and ET simulated by GSAC model on 0.25° grid. Finally, validation of GSAC model was carried out based on the GLDAS ET. The results of application in the Hulan River Basin indicated that GLDAS ET can better simulate the actual ET of the Hulan River Basin so that provided a useful input data for calibrating parameters of GSAC;the runoff Nash-Sutcliffe efficiency coefficient of GSAC model calibrated by GLDAS ET were 0.81 and 0.77 in the calibration and validation periods, respectively, and the results were similar to the corresponding values of GSAC model calibrated by runoff data.

Abstract:Crop model is constructed on the field scale. There are simulated errors due to the up-scaling when it is applied from filed scale to larger scale. Regional applications of crop model are becoming universal methodologies to explore the interactions between crop, climate and management in agriculture systems to provide policy and decision making for food production. A spatial resolution should be determined before using crop model to simulate yield in the regional scale. There is a dilemma in considering the spatial resolution. A high spatial resolution simulation needs more hardware resource and expensive computing cost while a coarse resolution simulation would result in loss of spatial detail of variability. Therefore, exploring the uncertainties of regional simulation of crop model due to different spatial resolutions is essential to application of crop model in large scale. A WOFOST regional simulation platform was constructed at different spatial resolutions to quantify the simulation errors by spatial resolution of model force data. Five spatial resolution meteorological data (5km, 10km, 25km and 50km) were interpolated by the thin plate smoothing spline method which was provided by the software ANUSPLIN. The corresponding resolution soil parameters were extracted from a fine resolution soil database by spatial aggregation. Spatial management and crop cultivar parameters were calculated from observed agro-meteorological sites and then extended to different resolutions by Thiessen polygon method. The simulated yields were compared at different resolutions and statistical yields, and it was found that the average value of anthesis, maturity date, total above ground production and yield at potential yield level and water limited level did not have significant difference. However, there were more extreme values in the high resolution. Each simulation of four resolutions can perform the spatial distribution of crop development. Compared with the regional statistical yields, simulated water limited yield at different resolutions contributed to the variation of statistical yields by 75.4%~85.4%. The correlation analysis between potential yield and water-limited yield and climate factor indicated that the irradiation in the growing stage contributed to 16.6%~29.6% of variability of potential yield, the precipitation in the growing stage contributed to 13.3%~17.8% of variability of water-limited yield. The data storage capacity and computing cost at high resolution, i.e. 5km was a hundred times more than coarse resolution, i.e. 50km. The results provided theoretical and scientific basis for regional application, especially for selecting suitable spatial resolution for regional simulation.

Abstract:Based on the farmland distribution maps of Naolihe River Basin in 1990 and 2013, the influences of paddy farmland and cultivation activity on temporal and spatial variation of water cycle process were analyzed quantitatively, combining with TOPMODEL model based on LBM method. Results showed that TOPMODEL model based on LBM method could simulate well the rainfall runoff process of Naolihe River Basin, and it had a high applicability on the investigated river basin. The area of forest land, grassland and construction land was not changed much, which contributed little to the change of land structure, while unused farmland and dry farmland were partly converted to paddy farmland, contributing obviously to the change of land structure. The presence of paddy farmland resulted in the increase of total evapotranspiration, decrease of the water deficit in root zone, decrease of water deficit in the unsaturated zone, decrease of surface water, and increase of underground water from May to October. Evapotranspiration was increased by 8.9%, water deficit in the root area was decreased by 10.5%, and surface water was decreased by 43%. Paddy farmland showed different effects on hydrological variables when rice was in different growth stages. It had great influence on evapotranspiration, water deficit in root zone and water deficit in unsaturated zone when rice was in tillering stage. The influence of paddy farmland irrigation on different water cycle processes was diminished in the sequence of SBAR, RZ, E, water quantity in inlet of root zone, water quantity in outlet of root zone, and RG, among which the differences of water quantity between irrigation and non-irrigation were almost the same for the inlet and outlet of root zone.

Abstract:Based on the ecosystem classification and ecological parameter data, the structure and dominant services, including sediment retention and water supply, of grassland ecosystem in Northern Shaanxi Province from 2000 to 2010, which was a key period to the Grain to Green Program, were evaluated by using the integrated valuation of ecosystem services and tradeoffs (InVEST ) model. The impacts of human activities on the ecological construction of grassland area and its ecosystem service function were clarified. The results indicated that the area of grassland ecosystem in the loess gully region of Yan’an and Yulin Cities was increased significantly, especially in steppe and scrub-grass, which showed a greening trend of the low-cover vegetation to medium-cover vegetation. During the study periods, the function of sediment retention for each types of grassland was improved and the steppe was the major contributor for sediment retention, followed by scrub-grass and sparse grass. As to the water supply, each types of grassland exhibited the tendency of decreasing firstly and then increasing. The restoration of sparse grass in north of the Great Wall of Northern Shaanxi had great value to the construction of energy and chemical industry base, and the maintenance of urban ecological security as well as the sustainable development of farming and animal husbandry. The results provided scientific basis of the major ecological construction, the sustainable development of agriculture and animal husbandry in grassland ecosystem.

Abstract:Aiming at the low efficiency of water and fertilizer in winter wheat which caused non-point source pollution in North China Plain, the objective of this experiment was to study the effects of drip fertigation on winter wheat growth, grain yield, water consumption, water use efficiency and nutrient distribution, and provide scientific basis and technical support for the application and extension of drip fertigation. Field experiments were conducted in 2013—2014, 2014—2015 and 2015—2016 three successive winter wheat growing seasons. Under drip fertigation, the fertilizer amount of fertigation was 70% of local fertilizer amount, and the soil matric potential at 0.2m depth for winter wheat was controlled higher than -40kPa. Results showed that under drip fertigation in winter wheat growing seasons in North China Plain, the average yield of winter wheat in 2013—2014, 2014—2015 and 2015—2016 was 7120.5kg/hm2, which was increased by 18.7%. The thousand kernel weight of winter wheat was increased by 4.3g averagely. The average water consumption was 387.9mm. Precipitation was the highest proportion of total water consumption, accounting for 52% in sowing to jointing stage, irrigation was the highest proportion (78%) in jointing to heading stage, while the soil water depletion was the highest (54%) in heading to harvest stage. In three winter wheat growing seasons, the percentage of different water sources in total water consumption showed that irrigation amount was the largest proportion (49%), the soil water consumption and precipitation accounted for 25% and 24%, the groundwater supplementary amount was the lowest, only 2%. Under drip fertigation, water use efficiency and irrigation water use efficiency for winter wheat was 1.8kg/m3 and 3.9kg/m3, which were increased by 38% and 95%, respectively compared with surface irrigation. The nutrient mainly distributed in 0~40cm layers with high nutrient efficiency and low nutrient leaching. In North China Plain, when the fertilizer amount of fertigation was 70% of local fertilizer amount with losscontrol fertilizer as basal fertilizer and drip irrigation, the grain yield was increased by 18.7% with better spike grain number and thousand kernel weight. Meanwhile, drip irrigation can save water by 36% and save fertilizer by 30%, improve irrigation water use efficiency by 95% and increase water use efficiency by 38%.

Abstract:A critical nitrogen concentration in plant above-ground biomass, which is defined as the minimum nitrogen concentration required for maximum plant growth, can be found at any time in the growth cycle. To determine the critical nitrogen (N) concentration dilution curve with different nitrogen levels for drip-irrigation cotton in the Manas County of Xinjiang. Field experiments were carried out with cultivars of Xinluzao 45 and five nitrogen rates (0kg/hm2, 120kg/hm2, 240kg/hm2, 360kg/hm2, and 480kg/hm2) were applied. Results showed that N concentration in above-ground biomass was declined with accumulated physiological development time after emergence. The relationship between the above-ground biomass and critical N concentration can be described by the power equation (Nc=3.91W-0.24max), with a=3.91 and b=0.24. The relationship between the correlation coefficient was 0.906. Through the root mean square error (RMSE) to verify this model, validation results showed that the model had a good simulation performance. Based on the critical N concentration model, the model of nitrogen nutrition index (NNI) was developed. According to the NNI under critical N concentrations, it was concluded that 240~360kg/hm2 could be used as the optimum N application rate of drip-irrigation cotton in Xinjiang.

Abstract:The black soil region in Northeast China is rich in soil fertility, good in soil properties, and suitable for crop growth. However, the problem of soil erosion in sloping farmland seriously threatened the regional ecological environment and national food security. To discover the influences of the optimal amount and duration of biochar supply on water saving and yield increasing in slopping farmland of the region, the two years experiments were conducted based on runoff plot in 2015 and 2016. Five treatments were set according to different amounts of biochar, which were 0t/hm2(C0), 25t/hm2(C25), 50t/hm2(C50), 75t/hm2(C75) and 100t/hm2(C100), and the same amount of biochar for each treatment was supplied continuously in the next year. The results showed that biochar made the soil bulk density decreased, and the soil porosity and organic carbon density were increased sharply with the increase of biochar in two years. The field capacity was increased with the increase of biochar in 2015 while which was first increased and then decreased in 2016, and the best one was the treatment of C50. At the same time, the three-phase and generalized soil structure index (GSSI) were the most reasonable in C50 compared with others. The annual runoff in three degrees sloping farmland both were decreased in the two experiment years, and the annual runoff coefficient was decreased most, which was in the treatment of C75 (by 15.44%) in 2015 and C50 (by 17.27%) in 2016. The addition of biochar also could increase the soil water accumulation amount and decrease the rate and magnitude with time after rainfall. The highest yield of soybean was respectively C75 (27.16%) in 2015 and C50 (28.17%) in 2016. Compared the results in 2015 and 2016, the water use efficiency of soybean was increased by 27.67% with 50t/hm2 biochar supply for two years compared with the control treatment, and the effect of water saving and yield increasing of the treatment was the best one.

Abstract:Soil mulch is one of the important agricultural measures, in order to inquiry the mechanism and characteristics of the mulching hindrance effect on heat exchange between atmosphere and soil. There were four treatments of bare land, natural snowfall mulching, 5cm straw with natural snow fall mulching and 10cm straw with natural snow mulching in winter field trial period (2016.11.1—2017.4.30), the total soil water content, liquid water content and temperature at the soil depths of 10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm and 100cm under the four treatments were determined, the heat capacity, phase change heat and heat quantity of freezing-thawing soil were calculated, and then the effects of different mulching treatments on heat spatial distribution and transfer efficiency in freezing-thawing soil were analyzed. The result showed that the depth of 30cm soil heat exchange was accounted for relatively large, the heat quantity was accounted for up to 54.57%~81.17% in different trial periods. In the freezing period, the soil heat transfers of four treatments showed the heat dissipation overall trend, and in the thawing period, the soil heat transfers of four treatments showed the heat absorption overall trend. The effects of the natural snowfall mulching, straw mulching of 5cm and 10cm on the heat transfer rate were 17%, 8% and 17%, respectively. The time periods of no soil heat change were long with proportions of 29.17%, 39.41%, 43.33% and 50.88%, respectively under different treatments. The study had practical significance for the spring soil moisture conservation.

Abstract:Snow is a unique environmental factor in the seasonal snow-covered area. The snow parameter inversion using remote sensing data has great significance on the researches of regional soil moisture forecast, hydrology, climate, etc. The problem of great error exists in the binary classification method commonly used in snow retrieval research. According to the unique geographical environment and the surface type in the black soil region of Songnen Plain, the MODIS images were chosen as data source, and the OLI images were regarded as “true value”data. Then the linear regression relation model between snow cover fraction from MODIS and NDSI was established in black soil region of Songnen Plain. The results showed that the adaptability of the MOD10A1FSC data was weak in the study area. The FSC data was 80.21% which had a big difference compared with the snow cover fraction of OLI images (87.71%) at the same time phase. The correlation coefficient between the FSC data and OLI images was only 0.58. The snow cover fraction of the inversion model built in the study was 85.28% which was close to that of OLI images at the same time phase. The correlation coefficient between the snow cover fraction of the inversion model and OLI images was 0.66. In addition, compared with the MOD10A1FSC data, the error statistics results, including root mean square error and mean absolute error of the inversion model were decreased significantly. The estimation model of snow cover fraction based on sub-pixel improved the monitoring accuracy of snow cover in black soil region of Songnen Plain to a certain extent, which can better satisfy the reality requirement to the current snow retrieval research. The research result provided a scientific basis for the soil moisture forecast in spring and agricultural cultivation in this region.

Abstract:The rheological properties of liquid phase could directly affect the treatment effect of organic wastewater and municipal sludge in the anaerobic digester. In order to evaluate the flowability of non-Newtonian liquid phase in the reactor, and provide useful suggestions for the choice of the suitable mathematical models (two-phase flow model, multiphase turbulence model, and interphase force model), the gas-liquid two-phase flow of gas mixing in anaerobic digester was studied by numerical simulation. Hydromechanical behaviors, such as velocity field, flow field, dynamic viscosity, etc., of non-Newtonian liquid phase in the anaerobic digester at different flows were discussed. In addition, the effects of multiphase model, interphase force and multiphase turbulence model on the liquid phase velocity were further analyzed. The results showed that an increase in gas flow at the inlet did not significantly affect the flow field form and vortex distribution, but could effectively reduce maximum dynamic viscosity of liquid phase, improve the flowability of the liquid phase in anaerobic digester, especially influence the dynamic viscosity of the liquid phase around the bottom of the anaerobic digester. When the inlet flows were 2.05mL/s and 5.3mL/s, Euler-Euler two fluid model (E-E) and Euler-Euler two fluid model coupled population balance model (E-E-PBM) had very similar simulated liquid velocity to experimental value, and had better simulated velocity than Euler-Lagrange (E-L) model;standard k-ε model, renormalization group k-ε model (RNG k-ε) had better simulated velocity than realizable k-ε model. The simulated velocity matched the experimental value very well when the interphase force was lift force and drag force, respectively.

Abstract:Boiler flue gas has become an important source of atmospheric pollution, biomass fuel boiler was applied widely. However, the biomass boiler flue gas purification technology and equipment was shortage. In order to further reduce the pollution of biomass flue gas emissions, a multiple flue gas purification device with dust removal, desulphurization and waste heat utilization was developed. Flue gas dust removal using cyclone separation and atomized spray method, flue gas desulfurization using alkaline water washing and atomized spray desulphurization, waste heat utilization using high, low pressure multistage flue gas heat transfer utilization. The structure design, system calculation and running performance of this biomass flue gas purification device were also studied. The study showed that the flue gas purification device showed a stable operation characteristic and high purification efficiency, which gas temperature, SO2 content, dust content, SO2 removal rate, dust removal rate and other operating parameters were stable during the continuous operation. The result showed that the outlet gas temperature was (62 ± 3)℃, SO2 concentration 4.2mg/m3, and dust content of 4.6mg/m3. The mean SO2 and dust removal rate add up to 70.6% and 90.57% respectively. The multiple flue gas purification device had good operating stability and high dust removal, desulfurization efficiency.

Abstract:In order to judge the accuracy of sensor data in greenhouse environment measurement and control system, a sensor fault identification method was proposed based on the comparison of node information. This method based on the principal component analysis (PCA) was to achieve the sensor system fault detection through the monitoring statistics T2 and SPE changes. When the system detected the fault, the different sensor fault identification by using the comparison of node information based on temporal and spatial characteristics were realized, and to compare the effects with different methods, node information was made a comparison based on temporal scale, spatial scale and temporal-spatial scale, for multi-sensor fault identification. Verification results showed that the sensor fault detection method based on PCA can effectively realize the preliminary detection of the sensor system, and the sensor fault identification method based on the comparison of node information took the time and spatial scale into consideration, which can effectively achieve the specific fault sensor positioning. The value of the sensor nodes fault data average CDR was 98.37%, and the average FAR was 1.72%. Compared with the traditional method for sensor fault identification, the CDR increased by 22.067 percentage points and the FAR reduced by 15.762 percentage points, and it was found that the fault recognition method mentioned can effectively guarantee the efficiency of fault diagnosis improve the accuracy of fault diagnosis, and reduce the false alarm rate with reliability and accuracy.

Abstract:Precision seeding put forward higher requirements for the seed quality. However, existing grading methods of seeds are destructive and unsuitable for sorting seeds based on internal characteristics, and a classification method based on the seed vitality is required. An algorithm of image acquisition and characteristics identification and classification of tomato seeds was proposed based on hyperspectral technique and image processing technology. Totally 170 grains of tomato seeds were randomly selected as the research object, and the ratio of calibration set and validation set was about 3∶1. Images of tomato seeds were collected by hyperspectral acquisition system which was composed of high performance lighting CCD camera, line scanning spectrometer, oriel instruments, image acquisition card and computer. The resolution of the camera and range of spectrometer were respectively 1376 pixels×1040 pixels and 400~1100nm. An average spectrum of interest region of each seed could be obtained. Then the results of seed vigor were obtained from the standard germination test. And the characteristic wavelengths of tomato seed vigor were acquired by successive projections algorithm (SPA), including 535nm, 577nm, 595nm, 654nm, 684nm, 713nm, 744nm, 768nm, 809nm and 840nm. The images under above characteristic wavelengths were preprocessed by bilateral filtering, Ostu and morphological transformation to gain the seed eigenvalues including area, circularity and average gray. The classification thresholds were calculated according to the eigenvalues and vitality results of the calibration set based on statistical regularity, and prediction analysis of validation set was carried out. The results showed that both of average of area and gray had significant difference between viable seeds and non-viable seeds, while the difference of circularity between viable seeds and non-viable seeds was insignificant. Classification accuracy of calibration and validation sets was above 85% in eight characteristics wavelengths. And 713nm gave the best result, the accuracy of the calibration and validation set were 93.75% and 90.48%, respectively. The results provided a new method for rapid nondestructive grading of tomato seeds, and lay the foundation for the development of tomato seed grading equipment based on seed vitality.

Abstract:Agar is a hydrophilic polysaccharide. As a common stabilizer of food, agar can improve the viscosity and texture of yoghurt. Moreover, agar can help to prevent the whey separation and improve the quality of yoghurt. The effect of different agar concentrations (0.025%~0.5%) on the microrheological properties and gel kinetics of acid-induced milk protein gel was investigated. Results showed that the elasticity index (EI) trend of agar-skim milk samples was similar with skim milk sample. So there was no significant effect of agar concentration on skim milk acid-induced gel in the fermentation stage. Macroscopic viscosity index (MVI) of agar-skim milk mixed system was higher than skim milk system significantly before the formation of gel network (P<0.05). But there was no significant difference between them after the gel formation (P≥0.05). Mesh size of all samples was decreased sharply with the fermentation process. In the cooling stage, EI of samples was increased in the agar concentration, while MVI had no significant difference (P≥0.05). It can be concluded that adding agar can increase the gel strength of the yoghurt, but it had no significant effect on the fermentation process. The suitable agar concentration in yoghurt was determined by analyzing the kinetic equation of agar-skim milk acid gel formation process. In conclusion, this research revealed microrheological properties of agar-yoghurt gels through microrheological method and gelation kinetics. The results can provide the reference and theoretical basis for the application of agar in the enterprises of yoghurt. This research also can help to promote the development of yogurt industry.

Abstract:In order to visualize the spatial distribution of potato dry matter, the internal dry matter content of potato was studied by using visible/near-infrared hyperspectral imaging (HSI) and a detection model of dry matter of potato was established. The reflectance spectra of sliced potatoes which were extracted from the regions of interest of HIS were performed with different pretreatments. The standard normal variable (SNV) combined with Savitzky-Golay smoothing (SG) and the first derivative (SNV-SG-FD) was the optimal pretreatment. Based on optimal pretreatment, competitive adaptive reweighted sampling (CARS) combined with successive projections algorithm (SPA) was used to select variables of the spectrum and obtained 22 variables. Three regression models based on principal component regression (PCR), support vector regression (SVMR) and partial least squares regression (PLSR) were established. The best performance was achieved by PLSR model, its determination coefficient (R2P), root mean square error for prediction and relative percent difference were 0.849, 0.878% and 2.312, respectively. The PLSR model based on 22 variables was superior to the full-spectrum model. An imaging processing algorithm was developed to transfer each pixel in potato dry matter content with the SNV-SG-FD-CARS-SPA-PLSR model. The imaging showed the distribution of dry matter within the potatoes. It showed that the potato dry matter was mainly distributed between the inner pith and vascular bundle and the inner pith had the lowest dry matter content. It was gradually increased from the inner pulp to the outer. Dry matter content was 12.16% in inner pith and the outer layer reached up to 24.62%. The results show that the visible near infrared hyperspectral imaging is a useful tool for rapidly and effectively visualizing detecting spatial distribution of potato dry matter.

Abstract:Structural changes of soybean protein-phosphatidylcholine complex under ultrasonic treatment and high pressure homogenization by Raman spectroscopy were analyzed. Ultrasonic treatment and high pressure homogenization treatment both were found increased the content of α-helix and random coil structure, but decreased the β-structure of soybean protein. The interaction of soybean protein and phosphatidylcholine significantly decreased the protein α-helix structure by transforming it into random coil and β-sheet structures. Under ultrasonic treatment and high pressure homogenization, the protein α-helix structure of soybean protein-phosphatidylcholine complex was lower than that of the high speed dispersion treatment complex, while the content of β-folded structure and random coil structure were higher. Tryptophan and tyrosine residues of soybean protein tended to expose with ultrasound and high pressure homogenization, which promoted the hydrophobic interaction between soybean protein and phosphatidylcholine. The interaction sites were located in soybean protein hydrophobic amino acid side chain and phosphatidylcholine lipid hydrophobic chain, the hydrophobic interaction was the main force of soybean-phosphatidylcholine interaction. Under the condition of ultrasonic treatment and high pressure homogenization, the structure of disulfide bond of soybean protein was not changed significantly, and the gauche-gauche-trans conformational vibration mode was remained. The interaction of soybean protein phosphatidylcholine did not change the structure of disulfide bond.

Abstract:In order to adapt to the multivariate environment of soil condition, a control algorithm based on soil specific resistance for force-position mixed control was explored. By building fuzzy PID control strategy, soil specific resistance B was introduced to simulate soil environment, and Matlab was used to analyze the specific resistance of different soils. Based on the system overshoot, stability time and change of tillage depth, combined with practical experience, the relationship between weight coefficient and soil specific resistance was discussed, and the control algorithm of weight coefficient was designed by the relationship. The method was compared with the method with fixed coefficient of 0.5, and the field tests were carried out. The experimental results showed that the method of variable weight force-position mixed control using this control algorithm can take advantage of position adjustment in the soil with smaller resistance, so as to ensure the depth of tillage;in the soil with larger resistance, the advantages of force adjustment can be taken to ensure the performance of the engine. The method can realize the automatic judgment and setting of the weight coefficient in the area where the soil specific resistance changed greatly, and laied the foundation for the more accurate control of the system, which can also have implications for researchers in the field.

Abstract:When electric tractor working on heavy load model, such as plowing and rotary tillage, the peak power with high frequency of the working condition has more randomness. Energy systems of the electric tractor, which consists of single type of electric power source, e.g. batteries, may not effectively match the required power of dynamic load characteristic. Aimed at these problems, the electric tractor energy system and the management strategy were researched by the way based on the power spectral density of tractor load. By the analyses of electric drive train power flow, power spectral density of potential flow variables of tractor load and frequency characteristic in discharge process of common electric source, the feasibility of the way to separate the power flows with low frequency and high frequency via synergic electric power supply system was discussed. By mathematically building the constraint modelling of the endurance performance, power property, maximum using weight of tractor, steady and dynamic characteristic of load, the design method of energy systems with synergic electric power supply system in electric tractor was proposed. After that, the 18.5kW electric tractor energy system which was assembled by the parallel connection between batteries and super capacitors via DC-DC converter was designed. For the elimination of peak power with high frequency of battery and the direction control of the super capacitor power flow, the double DC-DC converter control strategy based on logic control was generated. For the requirement of time-frequency analysis, the power distribution controller of the management strategy was designed by using two-channel filter bank with Haar wavelet. By constructing the mutual spectral density function between Gaussian white noise and working load of the tractor on plowing and rotary tillage, the load-time wave used in the simulation was established. The simulation ran on the platform that the simulation model of tractor plowing and rotary tillage unit built on AVL CRUISE dynamically combined with the management strategy simulation model on Matlab/Simulink. And it can be found that the management strategy based on power spectral density can limit the frequency of the power flow transiting electric power the batteries of synergic electric power supply system on the fundamental frequency of working load. Under the plowing condition, the frequency of battery electric power was cut off at 2Hz. And under the rotary tillage condition, the frequency of battery electric power was cut off at 7Hz. The amplitudes of electric power flow conformed to positive skew distribution. The remainder of required power was provided by super capacitance. And the amplitudes of remaining electric power flow accorded with standard normal distribution. The research proposed can offer theory reference and technology support to other researchers whose working field would be related to electric tractor and energy management.

Abstract:Redundantly actuated parallel manipulator demands higher actuation coordination than the non-redundantly actuated one, thanks to its degree of actuation exceeding its degree of freedom. To improve the actuation coordination of redundantly actuated parallel manipulator, a novel model-based driving force synchronous control method with neural network was proposed. With 6PUS+UPU parallel manipulator as object, dynamic model was derived based on virtual work principle. To improve the actuation coordination of redundantly actuated parallel manipulator, a novel driving force synchronous control method was proposed on basis of force-position hybrid actuation. The synchronous control method was based on the driving force error of actuated joints and driving force adjustment was calculated by the synchronous controller. The synchronous controller was designed with neural network. What’s more, the learning law of neural network controller was derived with manipulator’s dynamic model to improve the learning efficiency. Model simulation and prototype experiment were carried out, and a performance comparison analysis with traditional force-position hybrid actuation method was made to verify the proposed control method. Comparison analysis revealed that, comparing with the traditional force-position hybrid actuation method, driving force synchronous control with neural network proposed could effectively improve the actuation coordination of redundantly actuated parallel manipulator. The results revealed that the synchronous control method reduced the driving force errors of whole manipulator by properly magnifying the control error of force actuated joint.

Abstract:In order to solve the compatibility problem occurred during the iteration for the dynamics of a spatial rigid-flexible parallel robot, a nonlinear solution approach was proposed based on a transient kinematic correction method. The nonlinear forward and inverse dynamics of a spatial 3-RRRU parallel robot with flexible links were constructed based on both natural coordinate formulation (NCF) and absolute nodal coordinate formulation (ANCF). The derived models took into account the shear deformation and could describe large deformation for each beam. The transient kinematic correction methods were developed for the both dynamics based on NCF and kinematic model of the robot. The strategy for stable causal solution was also presented based on the aspects such as system energy of the dynamic system. The simulation results showed that the solution precision of inverse dynamics was 10-6 and the compatible error of constraints was 10-8, which met the requirements for engineering applications and could effectively improve the overall convergent performance for the dynamic system. A trajectory tracking experiment was carried out based on a prescribed circular trajectory. Compared with the control strategy on rigid dynamic model, the maximum tracking error and roundness error based on the provided control strategy were decreased by 0.372mm and 1.46mm, respectively. The calculated principal strains of the typical points on the flexible links were at the same levels and variation trends as the measured strains on them. The validity of the developed method was thus verified.

Abstract:A pneumatic bionic hexapod robot employing independent-developed multidirectional bending pneumatic joints was presented. The configuration of hexapod robot was similar to the spider, and the flexible joints of legs of robot were driven by the deformation at different air pressures. By investigating the characteristics of leg movement of robot, the gait of the hexapod robot was planned based on the tripod gait, including the straight walking gait and the turning gait. In addition, the simulation and experiments on walking gait of robot were done, respectively. The kinematics model of hexapod robot was set up according to the mechanism of joint deformation, and the relation between the center mass of robot and foot positions was got. The step, rotation angle and speed of hexapod robot were analyzed, which were verified by the experiments subsequently. The kinematics experiments of hexapod robot were completed and the workspace of the foot was studied on 3D motion capture system. Meanwhile, the movement performances of the hexapod robot on different loads were investigated with each stride frequency under different pressures. The experiments showed that the hexapod robot can stride forward, move horizontally or make a turn with the movement of each leg cooperated in harmony by controlling the pressure control system in accordance with the gait planned. The maximum speed of hexapod robot was 100mm/s, and the load capacity was 0.5kg. The research result laid the foundation for the application of pneumatic bionic hexapod robot in the complex agricultural environment.

Abstract:A nonsingular fast terminal sliding mode adaptive controller based on RBF neural network was proposed for trajectory tracking control of multi degree of freedom manipulator with slow convergence speed and low tracking precision. Firstly, the nonsingular fast terminal sliding mode hypersurface was adopted in the control scheme and the continuous terminal attractor was introduced into the switch control, which made the system converge to the equilibrium point in a finite time. Secondly, the adaptive RBF neural network was used to approximate the unknown nonlinear dynamics of the system, the adaptive compensation mechanism of approximation error and adaptive law of weights of neural networks were designed to realize the model free control. The global asymptotic stability and finite time convergence of the closed-loop system were proved by Lyapunov theory. Finally, the control method was applied to Denso serial manipulator for experimental verification, the effect of transmission delay on the experimental results was analyzed and the solution was proposed. The simulation and experimental results demonstrated that the proposed control method can improve the convergence speed and the tracking accuracy of the system effectively, and enhance the robustness of the external disturbance. At the same time, it can weaken the chattering of the system and enhance the real-time control.

Abstract:With the development of science and technology, there is an urgent need to develop micrometer positioning technology in the fields of the precision manufacturing. The traditional electromagnetic motors are difficult to meet this demand as they are characterized by high speed and low torque. Piezoelectric actuator uses piezoelectric ceramics as transducers, and utilizes the inverse piezoelectric effect of piezoelectric ceramics to convert the electrical energy to the mechanical energy, which can masterly utilize certain structural forms to transfer motions and motive forces. In addition, due to the compact structure of piezoelectric actuator, the rotor inertia is small, and fast in response to braking, the load can be directly driven, and has good controllability for positioning and speed, therefore, piezoelectric actuator is widely used in equipment drive and control with high performance for precision manufacturing. For the selected piezoelectric positioning stage system using friction drive, an approximate time-domain mathematical model was established according to its physical mechanism. The parameters were identified by the open-loop experiment with the least squares method. The model output of the pulse width signal and the triangular wave signal were consistent with that of the actual system. Then, according to the form of the model, inverse system compensation plus sliding mode variable structure control scheme was designed. The stability of the control algorithm and its control parameters were discussed. The PI control method and the control algorithm proposed were used to track the same signal. The results showed that the control precision of the control algorithm used was much better than that of the PI control method, the maximum tracking error by using the proposed control algorithm was 0.01095mm. So it had good practical value in the drive and control of precision instruments and equipment.

Abstract:Hysteresis and power consumption characteristics of Fe-Ga alloy is the basis of working efficiency study of magnetostrictive transducers. Based on hall effect and Faraday's law of electromagnetic induction, a set of automatic testing system for magnetic properties of magnetostrictive materials was designed. By using the automatic testing system, the magnetic hysteresis curve of Fe-Ga rod alloy was tested and analyzed under different magnetic field frequencies and magnetic induction intensities. And coercive force and remanence were increased when the magnetic field frequency and magnetic induction intensity were increased respectively. By the hysteresis curve of the same magnetic induction intensity under different magnetic field frequencies, electromagnetic losses and energy storage medium were calculated. Simultaneously, electromagnetic losses were separated into three main parts of hysteresis, eddy current and residual loss. It was found that when magnetic induction intensity was 1725mT and magnetic field frequency was increased from 30Hz to 70Hz, electromagnetic loss and energy storage medium were increased by 3.24 times and 1.96 times respectively as well as hysteresis, eddy current and residual losses which were separated by electromagnetic loss respectively were increased by 1.33 times, 5.26 times and 7.35 times. The proportion of hysteresis loss was fallen from 56.87% to 31.31%, the proportion of eddy current loss was risen from 32.98% to 48.69%, and the proportion of residual loss remain unchanged. For the high-frequency working conditions of Fe-Ga gallon transducer, the treatment of slicing Fe-Ga rod alloy was made to reduce the eddy current loss and improve the efficiency of Fe-Ga gallon transducer.

Abstract:Due to “the resistance wall of wave making”, the velocity of amphibious platform which sail in the state of drainage navigation with large square factor cannot be improved. For reducing resistance to improve velocity, the water-surface vector propeller of variable angle was presented based on imitating the basilisk lizard. The new mode of providing vector driving forces was realized by controlling blade angle and rotation velocity, and the new thought for improving the velocity of the platform was provided by increasing the output of lift and moment. Then, combined with the algorithm of PISO and transient analysis of two phase flow, the dynamic fluid model of propeller was set up to analyze the influence of movement and structure parameters on the driving properties. Finally, the results of numerical calculation were validated by tests. The results were shown as follows: when the blade angle was increased from 0° to 90°，the angle of driving force was increased from -6.85° to 51.95° in continuous, and when the blade angle was in the interval of [40°, 60°], the driving forces can be provided in balance. The pressure of blade was increased with the increase of the spoke length, the lift was linear with the spoke length, and the thrust and moment were quadratic functions to spoke length. The output of driving forces was increased with the increase of rotation velocity, the frequency was four times of the rotation velocity at high and low velocities, but the frequency was two times of the rotation velocity at the velocity of 5r/s due to the low recovery ability. The lift was decreased with the increase of the width and diameter of the hub. The results provided a basis for controlling the driving output of the propeller and the sail of the platform.