Abstract:Rapeseed is an important oil plant in China. Precision seeding technology is an important method to decrease the costs and increase the efficiency of mechanical and scale operation for rapeseed and is also the important and difficult research point for rapeseed full mechanization. The planting status and main seeding equipments of rapeseed at home and abroad were concluded. The research status and development tendency for the key seeding technologies including precision seeding, seedbed preparation and intelligent seeding, were analyzed. Precision seeding technology, as the basic and key aspect for precision seeding, included one-row and centralized seeding technologies, according to different structure and principle of seeding device. The factor to affect the stability of seeding depth and furrow depth for rapeseed planting and the method to ensure the seeding depth, furrow depth and seedbed surface flatness were studied. The intelligent technologies for rapeseed sowing were consisted of technology of loss sowing detection and variable reseeding, automatic navigation and variable sowing. Moreover, the conclusion and prospection for the planting characteristics and development trend were provided from following three aspects: firstly, the precision seeding technology had the performance with high speed, wide work breadth, high efficiency and precision seeding; secondly, the technology to control the seeding depth, the tillage technology to reduce resistance and adherence were the research focus for improving rapeseed seedling rate and protecting seedlings from waterlogging; thirdly, combined agricultural machinery, agronomy and information technology is benefit to population structure and yield. Technologies of loss sowing detection and variable reseeding, automatic navigation and variable sowing promote the intelligent level of rapeseed planter and improve the intelligent development for rapeseed sowing.

Abstract:For the problem that the traditional angle sensor’s complex mechanical structure and prone to failure and the gyro bias cause the error accumulates over time in automatic driving system, a wheel turning angle measurement system based on double GNSS antennas and single gyro was proposed. The system’s sensors mainly included two GNSS antennas and a MEMS gyro. The double GNSS antennas were mounted on both side of the vehicle and provided the speed, attitude angle, latitude and longitude of the vehicle. The single MEMS gyro was mounted on the wheel and the angular rate was measured. An algorithm used the above data was designed to integrate the angular rate to obtain the steering angle. In order to solve the problem that the error accumulates over time, a Kalman filter based on the vehicle dynamics model was designed to calibrate the error of integration of the gyro data. At the same time, the lever-arm compensation algorithm was used to solve the speed error caused by lever-arm. The straight line experiment was carried out to verify the effectiveness of the system and the curve line experiment was carried out to verify the effectiveness of the lever-arm compensation algorithm. Compared the steering angle of the proposed system with the Hall effect angular sensor, the average error of the straight line experiment was -0.064°and the error variance was 0.309°and the cure line experiment’s mean error was 0.299°and the error variance was 1.009°. The result of the experiments showed that this system could replace the traditional angle sensor and it was easy to install and overhaul.

Abstract:In order to recognize potato typical insect pests accurately and quickly, a new feature extraction and recognition method based on wavelet and space domain was proposed. The processing object in the method was the segmented image of insect pests separated from complex background by the twodimensional Otsu method and morphological method. Aiming at the processing object, totally 12 invariant texture features of high frequency covariance matrix eigenvalues and low frequency lower order moments (HELM) were extracted from the high frequency images in the horizontal, vertical and diagonal directions, forming a Gaussian space model, and from low frequency image decomposed by sym8 wavelet function. Meanwhile, 4 Hu moments with invariant shape features were extracted from the binary image of the processing object. As thus, 16 pest features were put into support vector machine (SVM), and the results of insect pest classification could be obtained. For SVM classifier, the One-vs-One voting strategy was adopted, and the parameters, including radial basis kernel function parameter, error cost coefficient and relaxation coefficient were set to 0.0125, 60 and 0.001, respectively. By the classification of 8 kinds of pests, on the one hand, using the same SVM method, the test results showed the effectiveness of proposed HELM feature extraction. Texture features in wavelet domain were traditionally related to single scale low frequency lower order moments (SLM), including the mean, variance and the third order moment of low frequency image, multiscale low frequency lower order moments (MLM), multiscale high frequency lower order moments and low frequency lower order moments (HMLM), and LBP features for the low frequency image. Texture features in space domain were traditionally related to LBP, PCA and features based on gray-level co-occurrence matrix (GLCM). Compared with SVM recognition rates of the traditional texture features in wavelet domain and space domain, it was found that the proposed HELM feature had a higher recognition rate which were increased by at least 17 percentage points. In addition, the proposed HELM feature had moderate run time of 11.7 s containing from features extraction of 210 pest images to SVM classification of 8 kinds of typical pests. On the other hand, using the same HELM features and Hu moments, the test results showed the effectiveness of the proposed SVM recognition. For artificial neural network (ANN), three layers BP network structure was constructed and the sigmoid transfer function of hidden layer was selected. For Bayes classifier, Gaussian window function was used for estimating probability density. Compared with ANN run time, containing from the train for 105 pest images to the test for 105 pest images, the run time of the proposed SVM was 0.481s, nearly 2s less than ANN. Meanwhile, compared with ANN and Bayes recognition rates, the proposed SVM recognition rate was 97.5% , increasing at least 6 percentage points.

Abstract:In the study of crop nutrition diagnosis based on machine vision, it is usually necessary to collect leaf samples and quantitatively determine their nutrient content under laboratory conditions. However, due to the overlapping of leaves, the leaf samples cannot be clearly reflected in the canopy image. In order to solve this problem, it is needed to use image analysis technology to effectively extract the leaves in the crop canopy image and according to the processing results to collect laboratory test samples. Based on the complex background extraction, gradient graph calculation, wavelet transform, marker selection and watershed segmentation, the leaf segmentation of tomato canopy multispectral image was realized. Firstly, four kinds of complex background elimination algorithms were compared. It was found that the threshold segmentation based on normalized difference vegetation index (NDVI) was accurate when the enhancement factor was 1.3, which was suitable under various lighting conditions, and the space-time complexity was low. Secondly, in the aspect of gradient graph calculation, the morphological gradient of near-infrared (NIR) band image can eliminate the texture of the leaves caused by veins, light and so on while keeping the target edge. Then, markers of leaves were selected according to wavelet transform that used the low-frequency coefficient of 4-level db4 wavelet decomposition and H-maxima transform with threshold of 18. Finally, the results of wavelet transform watershed segmentation and mathematical morphology watershed segmentation were superimposed, and it was found that the average segmentation error rate of tomato canopy leaves was 21% for complex background and different light intensities, which provided some technical support for the analysis of tomato leaf nutrient content detection.

Abstract:Green tea has the largest consumption in China, and needle-shaped green tea is a typical type of green tea. The appearance of green tea is the key sensory evaluation index of green tea. However, it is hard to realize an accurate, objective and quantitative evaluation of green tea through manual evaluation on the characteristics as the color, stripe, tenderness and uniformity, etc. Based on internal and external factors such as quality forming process and visual morphology of tea, an intelligent sensory evaluation method of the appearance quality of tea was established. Firstly, collecting the process parameters of tea products and image characteristics of made tea, totally 17 process parameters, nine color features and six texture features were selected, conducting correlation analysis with expert sensory evaluation, and screening out remarkably correlated characteristic variables. In order to obtain an efficient evaluation model, based on process parameters and image characteristic parameters respectively, multiple quantitative evaluation models were established for needle-shaped green tea appearance senses by using three multivariate correction methods such as partial least squares (PLS), extreme learning machine (ELM) and strong predictor integration algorithm (ELM-AdaBoost). The comparison of the results showed that the ELM-AdaBoost model based on image characteristics had the best performance (RPD was more than 2). Its predictive performance was superior to other models, with smaller RMSEP (0.874), Bias (-0.148), SEP (0.226), and CV (0.018) values of the prediction set, respectively. Meanwhile, non-linear model had better predictive performance than linear model, which can better represent the analytic relationship between process parameters, image information and sensory scores, and modeling faster (0.014~0.281s). AdaBoost method, which was a hybrid integrated algorithm, can further promote the accuracy and generalization capability of the model. The above conclusions indicated that it was feasible to evaluate the quality of appearance of needle green tea based on machine vision and process. This study provided an effective technical method and idea for developing tea sensory quality evaluation methods, and laid theoretical basis and data supports on the development of expert process strategy supporting systems of tea quality, which had a broad industry prospect in tea processing, trading and refined blend technology.

Abstract:Crop disease is one of the most important influencing factors for agricultural high yield and high quality. Accurate classification of diseases is a key and basic step for early disease monitoring, diagnostics and prevention. The optimal individual classifier design is currently the common limitation in most crop disease recognition methods based images. To improve the accuracy and stability of disease identification, a disease recognition method of cucumber leaf images via dynamic ensemble learning was proposed. The approach consisted of three major stages. Firstly, totally 75-dimension color features of leaf image were extracted with image block processing. Secondly, a disagreement approach was used to measure the diversity among 10 classifiers of neural networks with an ensemble technique, where the classifiers were ordered according to the diversity. Finally, with the confidence of classifiers, a classifier subset was dynamically selected and integrated to identify the images of crop leaf diseases. To verify the effectiveness of the proposed method, classification experiments were performed on images of four kinds of cucumber leaf tissues, including 512 samples composed of powdery milder, downy mildew, gray mold and normal leaf. The experimental results showed that the recognition error rate of the proposed method was 3.32%, compared with those of BP neural network, SVM, Bagging and AdaBoost methods, it was reduced by 1.37 percentage point, 1.56 percentage point, 1.76 percentage point and 0.78 percentage point, respectively. The proposed method identified the diseases accurately from cucumber leaf images. Moreover, the method was feasible and effective, and it can also be utilized and modified for the classification of other crop diseases.

Abstract:For the traditional no-tillage planter, the straw and stubble could be cut or removed in the operation, so there was still high quality of performance requirements for cutting components, large power consumption, dust pollution and twining of straw and other issues. A kind of hill-mechanisms of no-tillage seeding was studied, which could penetrate the obstacles and then the hole was formed without any special treatment to the covering of surface. The key mechanism consisted of a duckbill type of roller seeding device and a passive roller driven by its own duckbill, both of which were in internal tangential relationship. The straw was rolled into a thin layer by the rotating drum, and then the duckbill reached and passed through the thin layer of straw to form a hole and accomplish seeding. Based on the kinematics analysis, the mathematical model among the drive angle (φ) of the duckbill, the power angle (α) of the duckbill, the angular velocity (ω0) of duckbill type of roller seeding device and the angular velocity (ω1) of the drum was established. According to the seeding condition that the spacing must be integral multiple of 100mm, the Matlab (matrix laboratory) image processing module was used to analyze the equation of the models, and the structure and work requirements were chosen as the constraints, the speed fluctuation of rotating drum was selected as the main measure index and the compact condition of structure as the auxiliary measure index, thus optimized to obtain the optimal combination of the parameters: the radius of the duckbill wheel seeding device was 200mm, the radius of the rotating roller was 400mm, the power angle of the duckbill (α) was 23°, and the initial driving angle (φ) was 31°, then the number of driving holes of the rotating drum was calculated as 23, the size of which was 84mm×32mm by the method of further geometric analysis. Using CATIA to do digital prototype motion simulation, the practical situation and the change rule of angular velocity when the rotating drum under the action of the duckbill were analyzed, therefore the theoretical analysis was verified. The prototype test showed that the passive roller type of no-till planter hill-mechanism could meet the design requirements, it was simple and reliable in working process and it was also an effective technical choice for no-tillage seeding.

Abstract:In order to study the spray flow filed characteristic of large-scale plant protection unmanned aerial vehicle (UAV), based on the spray system of FR-200 large-scale plant protection UAV, the simulation platform of depositing spray droplets without plant canopy was established. The SST k-ω turbulence model and the DPM discrete phase model were adopted to simulate the deposition process of UAV spray droplets. By means of numerical Fluent simulation software, the flight speed, spray boom relative position and spraying angle impact on the spray flow field were studied，field test was done to verify the results of simulation. The vertical velocity distribution of FR-200 UAV downwash flow field was unsymmetrical. The UAV speed had linear relationships with both the droplet swarm anti-drift coefficient and deposition, the total amount of the target droplets deposition density were 4.208μL/cm2 when flying speed was 3m/s, the total amount of the target droplets deposition density were 1.766μL/cm2 when flying speed was 5m/s. The anti-drift coefficient was 87.5%, 93.0% and 96.4% at sampling plane height of 0m, 0.5m and 1.0m when flying speed was 4m/s, respectively. With the increase of sample surface height, the anti-drift performance of droplets was promoted. The drift phenomenon of nozzles was serious which was installed on both sides of the spray boom. The nozzles were affected by the trailing vortex which caused the droplets drift. The rotor downwash flow increased spray droplets initial kinetic energy, the spray droplets acceleration was caused by gravity and downwash flow. The dispersion of number 5 nozzle spray droplets was increased due to the blocking effect, and it was hard to reach the sample surface due to the vertical kinetic energy attenuation of droplets. The smaller the spraying angle was, the stronger the droplets total anti-drift performance became.

Abstract:As the scale of agricultural production gradually expands, agriculture is developing forward to mechanization and intelligent direction. At present the main ways of domestic thinning are artificial thinning and chemical control thinning. Artificial thinning has the disadvantages of low efficiency and high labor intensity. Chemical control thinning makes seedling emergence come out not evenly, and people have to fill the gaps manually. Mechanical thinning can improve the working efficiency and bring great economic benefits with even seedling. The swing motion thinning robot was designed for the first thinning of seedlings and the kinematics model was established for the optimal to simulate the moving path. Then the virtual orthogonal experiment was done by different optimal edge lengths, different angles between optimal edge and optimal handle, different optimal handle lengths and different distances between optimal handle and center of crop-row. The prediction model of weeding rate and wounded seedling rate were analyzed by taking the coverage rate and the inbreaking rate as evaluation indexes. Based on the calculation, the best parameters in combination were as follows: distance between optimal handle and center of crop-row of 55mm, optimal edge length of 75mm, optimal handle length of 130mm, angle between optimal edge and optimal handle of 65°.The experiment result verified that the simulation and orthogonal experiment were accurate and efficient with good operation effectiveness of the prototype, and the weeding rate reached 89.4%, yet the wounded seedling rate was only 7.2%.

Abstract:A straw chopper cum spreader was developed to deal with the problems of unadjustable chopped straw spreading uniformity and width. The machine which was mainly composed of a curved shell, transmission system, eight guide vanes, a deflector, a guide vane regulating device, a running gear, a hood and a straw chopping device can realize the function of crop straw chopping and chopped straw spreading. The front casing of the shell was a logarithmic spiral line surface, and the equation of the front casing was built. The comparison between curved type shell and break line type shell was made by using Fluent software, the results of which showed that the curved type shell could improve the flowability of straw in the shell. A row of stationary blades was mounted to support the chopping process of the combined flails, which could help to reduce length of the chopped straw. The distance between the stationary blade and combined flail was determined according to the chopping quality. The fan-shaped blades which were mounted on both side of the roller increased the fluid flow rate, and improved the straw feeding ability. The guide vane can guide the flow of chopped straw at the outlet of the shell, which improved the spreading uniformity of the chopped straw. The guide vane regulating device can control the spreading width, velocity and uniformity of the chopped straw by adjusting the guide vanes position on the deflector. The structural parameters of the guide vane regulating device were determined according to the features of mechanisms. Field experiment results showed that with the forward speed of 1.8m/s, straw moisture of 78.4%, and PTO rotation speed of 540r/min in the unharvested cornfield, the machine could achieve a qualification rate of straw chopping of 90.01%, spreading width of 2223.3mm, average stubble height of 62.0mm, and spreading unevenness of 22.95%. The performance indexes of the machine satisfied the agronomic requirements of returning straw onto soil surface. The research can provide some references for the design of new chopper with good straw chopping and spreading ability.

Abstract:Parallel vibrating screen could be widely used due to multi-dimensional vibration, which was conducive to efficient screening of particle materials. In order to improve the parallel screening performance, firstly, the three-dimensional parallel vibrating screen with different initial phases model was proposed and the kinematics analysis was carried out. The single factor simulation experiment of initial phase was carried out by EDEM software, then, the simulation results were verified by bench test and the multi-factor orthogonal test was carried out to analyze the influence of each factor on the performance index and get a better combination of factors. The results showed that the experimental results were in good agreement with the simulation results under the same conditions. When the other conditions were constant, as the initial phase angle in X direction was increased, the sieving grain was increased first and then decreased, and the impurity content was higher when the initial phase in X direction was 45°. When the initial phase of in Z direction was 90°, the sieving grain was the lowest, the impurity content was increased first and then decreased with the increase of initial phase in Z direction. The sieving grain was higher when the initial phase were 30° and 60°, the impurity content in the whole sieving time was lower than other levels at 60° and the difference was obvious. The orthogonal test showed that the primary and secondary order of the factors affecting the screening efficiency was X amplitude, Y amplitude, Z initial phase, X initial phase, Y initial phase and Z amplitude. The primary and secondary order of the factors affecting the dirt percentage was Z amplitude, Y amplitude, X amplitude, X initial phase, Z initial phase and Y initial phase. The efficiency of three-dimensional vibration was improved by 62.02% and the inclusion rate was reduced by 53.85% when using the best combination of parameters.

Abstract:In view of the problem that the driver frequently turns round to observe and manually operate the baler during the process of straw-bundling and bale-unloading of minitype round baler, an automatic manipulation and alarming device was developed. The device mainly consisted of three travel switches as a singlechip, an operation mechanism driven by electric cylinder and a buzzer. By analyzing the working process of straw-bundling and bale-unloading, three travel switches were used to detect whether straw was filled with bale chamber, straw-bundling motion finished and the bale fell to the ground from bale chamber. The control flow of straw-bundling and bale-unloading was designed, and the control parameters of straw-bundling time and bale-unloading time were determined. Simulation tests of indoor working condition showed that the single chip could process the trigger signal of three travel switches to make electric cylinder stretch out and draw back, and the hydraulic valve handle was driven by the operation mechanism to realize automatic bale-unloading. The buzzer made different rhythm of the alarm sound during the process of straw-bundling and bale-unloading to effectively detect spurious triggering of travel switches and parts fault, which improved the reliability of the system. The pick-up and baling tests of prototype baler showed that the device may improve the working efficiency of minitype round baler by 22.5% to 32.2%, and the success rate of straw-bundling and bale-unloading may reach 100%.

Abstract:Aiming to probe new principle and parts of soybean seed thresher and solve the conflict between high seed damage and no-threshed rate during threshing, a new soybean seed thresher with tangential-axial flow double-roller was designed based on the new threshing principle and structure. From the overall structure, the threshing device was designed, which was composed of a couple of primary and secondary threshing rollers with different diameters, lengths, concave screen and transmission system. The double rollers of the thresher were configured by tangential-axial flow form. Compared with the traditional threshing ways with single threshing, the new soybean thresher was combined several threshing principles and two rollers with two kinds of threshing parts, the secondary threshing roller consisted of spike teeth was used as pre-thresh of soybean plants, and the primary threshing roller consisted of bow-spike teeth, which threshed and separated most of the plants in the axial threshing space. The double-roller operated with different linear velocities which realized the ordered feeding and fast grabbing of soybean plants. In order to check and find the optimal structure and parameters of the soybean seed thresher, performance test of the thresher was conducted under the condition that the moisture content of soybean seed was 17%~19%, the moisture content of soybean straw was 12%~15% and the straw-grain ratio was 1.275. Three parameters, including feeding quantity, rotating speed of double-roller and concave clearance were selected as input variables and the damage rate and un-threshed rate as output parameter. Meanwhile, a drastic orthogonal rotary regressive experimental design was employed to develop the second order polynomial regression models, which explained the relationship between the input and output parameters, and then the main parameters of the thresher was optimized through Design-Expert 8.0 software. Experimental results showed that feeding quantify, rotating speed of double-roller and concave clearance had an effect on the damage rate and un-threshed rate, and the rotating speed of double-roller was the most important influence element among the three. Optimization analysis indicated that the most optimum combination was the feeding quantity of 0.44kg/s, the rotating speed of double-roller of 489r/min and the concave clearance of 25.06mm, and the damage rate was 1.18% and the un-threshed rate was 0.65%. Compared with the traditional soybean threshing machine, it can make the damage rate and un-threshed rate decreased by 0.22 percentage points and 0.38 percentage points, respectively.

Abstract:Centrifugal pumps are widely used to deliver liquid media in agriculture, pharmacy, industry, petrochemical industry, etc. Compared with the case delivering pure liquid such as water, centrifugal pumps not only have lower efficiency but also are subject to severe vibration, noise and erosion when delivering cavity two-phase flow, leading to the deterioration of flow field and even the shortage of service life. The cavitation flow in centrifugal pump performs strong instabilities, thus a method of a tiny obstacle fitted on the blade surface was proposed to suppress the cavitation development on a ns=32 model pump. The unsteady cavitation flow varied with cavitation number in centrifugal pump was simulated by modified SST k-ω turbulence model combined with Kubota cavitation model. The results showed that the head of centrifugal pump with obstacle was decreased within 5% at various flow rate and within 3% at design point, the efficiency was decreased within 3% at various flow rate and 1.2% at design point, the head with obstacle was great improved when cavitation flow developed. The obstacle can enhance the turbulent kinetic energy near the blade wall and reset the absolute pressure distribution, which can suppress the cavitation at different stages in centrifugal pump. The obstacle can optimize the flow structure and degrade the vortex intensity near the suction side of blade especially the area close to the tongue. The obstacle can decrease the cavity volume at varied cavitation number and the cavity volume keep attenuating when cavitation developed. The obstacle can cause small magnitude of the disturbance on the pressure frequency spectrum. The effects of cavitation suppression were optimal when the bubbles reached close to the obstacle.

Abstract:With the wide use of vane centrifugal pump, it is urgent to discuss and study its stable operation and internal unsteady flow mechanism and other related issues in depth. The vaned diffuser is an important flow passage component in rotating machines and is widely used in turbines, compressors and pumps. The vaned diffuser applied to the multistage centrifugal pump can convert kinetic energy of liquid to pressure energy, and reduce radial force imposed on impeller in a single centrifugal pump. However, the internal flow in the centrifugal pump with vaned diffuser can be extremely complexity, which will impact the performance and stable operation of the centrifugal pump. From the SST k-ω turbulence model, numerical analysis of the unsteady flow field inside the centrifugal pump was carried out by using numerical software ANSYS-CFX and experimental method. The pressure pulsation characteristics and unsteady flow field distribution of the centrifugal pump were studied by experimental method. The results showed that the pressure pulsation at the inlet of the guide vane was higher than that at the outlet of the guide vane, and the pulsation strength of the volute was smaller than that at the exit. Impeller pressure distribution was mainly affected by the rotor-stator interaction. The pressure distribution in the guide vane was affected by both rotor-stator interaction and asymmetric geometry of the spiral case;the static pressure of the suction surface near the outlet of the impeller was larger than that of the pressure surface due to the impeller exit wake flow. Because of the influence of the vane leading edge and the trailing edge of the impeller, the pressure distribution at the vane inlet of the guide vane was very complicated and the regularity was poor.

Abstract:The object is to improve the hydraulic performance of the axial-flow pump and find out the main geometric parameters that affect the performance of axial-flow pump. Based on the L9(34) orthogonal experiment, number of blades, airfoil seating angle, hub ratio, the distance between the blade and guide vane were selected as test factors, and each experimental factor corresponded to three levels. Using orthogonal test method, the head, efficiency, shaft power and pressure pulsation were taken as the evaluation indexes. According to the results of intuitive analysis and range analysis, the best experimental scheme was determined by comprehensive frequency analysis. The results showed that hub ratio had the greatest influence on the four test evaluation indexes and the distance between blade and guide vane had the least effect. Under the optimum test plan, the flow regime was better, the whirlpool on the back of guide vane almost disappeared and the streamline on the blade surface distributed evenly. After optimization, the high pressure area of the blade surface disappeared basically, and the pressure distribution was more uniform, and the optimization effect was better. Compared with the original model，the optimized model of axial-flow pump in the flow and head satisfied requirement for module at the same time, under the new design flow, efficiency was increased from 74.33% to 78.59%, which was increased by 5.7%;shaft power was decreased from 20.54kW to 20.29kW, which was fallen by 1.21%;pressure pulsation coefficient absolute value was decreased from 0.344 to 0.310, which was reduced by 11%. Four evaluation indexes were achieved and the optimized model of axial-flow pump had a wide range of efficient area and the feasibility of comprehensive frequency analysis method in multi-objective orthogonal optimization was verified.

Abstract:Maize is widely planted in China and even in the world. Nitrogen is an essential nutrient for the growth and development of maize, which has a significant impact on maize yield. In order to provide a non-destructive and rapid detection method for nitrogen content of maize leaves, the relationship between the color characteristics and nitrogen content of maize leaves was analyzed, and a nitrogen content detection software for maize leaves was developed based on Android platform. The image containing the measured maize leaf and the calibration color block group (red, green, blue, white, black and grey) were obtained. In order to reduce the distortion caused by the external illumination and other factors, the image color was corrected by the calibration color block. After the image segmentation, image smoothing, and color feature information extraction, the relationship between the color features and the nitrogen content of the maize leaves was analyzed. The experimental results showed that the linear relationship between the green standard value and the nitrogen content was the best. Besides, Java programming language and OpenCV were applied to realize image acquisition, image processing and results viewing based on Android platform. The validation results indicated that the absolute error of the method for the nitrogen content of maize leaves was between -0.40% and 0.35%, and the root mean square error was 0.20%. The time from image collection to giving results was less than 10s. The proposed nitrogen detection method had the advantages of rapidity, economy and portability, and can be used for real-time detection on nitrogen content of maize leaves.

Abstract:Apple nitrogen status is a key indicator for evaluating quality of apple fruits. In order to estimate total nitrogen content of apple leaves (LNC), a way was proposed to monitor LNC which extracted spectral characteristics parameters from hyperspectral reflectance in the visible and near infrared regions. Hyperspectral monitoring of LNC was realized by using empirical regression analysis. Results showed that the correlation between spectral parameters and leaf nitrogen content was good in whole growth period, the best spectral parameters were Kge and S△ABC, respectively, the correlation coefficient was 0.85, the correlation between spectral parameters and leaf nitrogen content was bad, and a lot of spectral parameters were highly uncorrelated. Modeling results showed that the best model in the slope of the spectral characteristic curve was Kge of Fuji apple, the determination coefficient was 0.76, the root mean square error was 0.28, the relative error was zero, the best model in spectral characteristic curve area was S△ABC and S△BCD of gala apple, the determination coefficient was all 0.76, the root mean square error was all 0.30, the relative error was all 0.01%and zero;the best model in area ratio vegetation index was S△CDE /S△BCD and S△CDE /S△BCD of Fuji apple and S△DEF/S△ABC of Gala apple, the determination coefficient was 0.74, the root mean square error was all 0.35, the relative error was 0.01% and 0.02%, the best model in area normalized vegetation index was (S△CDE-S△BCD)/(S△CDE+S△BCD) in the whole growth period and (S△CDE-S△ABC/(S△CDE+S△ABC) of Gala apple, the determination coefficient was all 0.73, the root mean square error was 0.36 and 0.31, and the relative error was zero and -0.01%. The best verification results was area ratio vegetation index S△CDE/S△ABC, the determination coefficient, the root mean square error and the relative error was 0.47, 0.34 and -3.78% in the whole growth period, respectively. The determination coefficient, the root mean square error and the relative error was 0.37, 0.34, 3.00% and 0.40, 0.38, 3.70% in Fuji and Gala apple varieties, respectively. The other spectral characteristic parameters were significantly correlated with the LNC except spectral characteristic area variable S△EFG and normalized area vegetation index (S△CDE-S△FGH)/(S△CDE+S△FGH), in which spectral characteristic curve slope Kge and Kgprv, spectral characteristic area S△ABC and S△BCD, area ratio vegetation index S△CDE/S△ABC, S△CDE/S△BCD and S△DEF/S△ABC,normalized area vegetation index (S△CDE-S△ABC)/(S△CDE+S△ABC), (S△CDE-S△BCD)/(S△CDE+S△BCD) and (S△DEF-S△ABC)/(S△DEF+S△ABC) can describe preferably dynamic changes of LNC and these characteristic parameters were feasible for prediction of LNC of apples. By the precision evaluation of estimation models, the algorithm model constructed by S△CDE/S△ABC, S△CDE/S△FGH and (S△CDE-S△ABC)/(S△CDE+S△ABC) was proved to be the best model for estimation of LNC of apples. The results showed that the characteristics of the hyperspectral curve can provide a new reference for monitoring nitrogen nutrition.

Abstract:Aiming to study the effect of segmentation scale on object based segmentation and classification of forest gap through fusion of aerial orthophoto (DOM) and LiDAR data, the typical natural secondary forest in Maoershan Experimental Forest Farm Donglin Industry Zone of northeastern China was selected as the experimental area. The DOM and airborne LiDAR were used for multiscale segmentation and object-oriented forest gap classification. In the process of image segmentation, three segmentation schemes (segmentation of DOM, segmentation of LiDAR data and segmentation of a fusion of DOM and LiDAR data) were adopted. For each segmentation scheme, 10 segmentation scales were set, then based on the segmentation results, spectral and height features extracted from DOM and LiDAR data were used for object-oriented forest gap classification with the support vector machine (SVM) classifier. The results showed that the classification accuracies of three segmentation and classification schemes showed a decline trend with the increase of scale, which was opposite with trend of ED3 (Modified). Based on the LiDAR data at scale parameter of 10, the best segmentation result was got. At all scale (10~100), the classification accuracy based on LiDAR segmentation and classification was higher than that based on two other data segmentation and classification schemes, and had the more obvious advantage than using only DOM. Based on scheme of LiDAR data segmentation and classification at scale parameter of 10, the highest classification accuracy was got with Kappa coefficient of 80%. The classification accuracies of three segmentation and classification schemes at the optimal scale were significantly higher than these at other scales. The segmentation scale had important effect on the object-oriented forest gaps classification.

Abstract:Accurately obtaining the building information in the hollow village areas is important for hollow village renovation and research. With the rapid development of remote sensing technology, remote sensing image resolution has been greatly improved and the ground targets can be obtained from high-resolution remote sensing image. But the traditional methods based on low-level hand-engineered features or mid-level features have great limitation in complex environment, especially in hollow village areas. So it needs to use high-level features to express. Convolution neural network (CNN) has become one of the important methods of ground object recognition and detection. Based on CNN, a novel automatic building detection method was proposed. Firstly, a multi-scale saliency computation was employed to extract building areas and a sliding windows approach was applied to generate candidate regions. And then a CNN was applied to classify the regions. In order to verify the validity of this method, the high resolution remote sensing image of typical hollow village was selected to construct the building sample library. Finally, the model for building interpretation was experimentally studied based on the sample library. The results showed that multi-scale saliency can effectively get the main target, weaken the impact of other unrelated targets, and reduce data redundancy. The CNN can automatically learn the high level feature, and the classification accuracy (ACC) of this method can reach 97.6%. So the proposed method can be used to detect building and it had high practical value to hollow village research and renovation.

Abstract:Based on the remote sensing image data of 2005, 2010 and 2015, the spatial distribution of urban land surface temperature was studied by using the IB algorithm in the study area of Haidian District, Beijing. The data assimilation algorithm EnKF-3DVar and CA/Markov model integration were used to simulate the urban surface temperature in Haidian District by assimilating the spatial distribution data of the annual mean ozone concentration. The results showed that the urban surface temperature in Haidian District showed a downward trend in the past 10 years, and then showed a rising trend. But its overall showed a downward trend. The average temperature in 2015 was 31.1393℃. The prediction model of EnKF-3DVar can significantly improve the simulation precision of the model, and the Kappa coefficient of the predicted data in 2015 was 0.8216. Under the model of urban park green space, the urban surface temperature showed a decreasing trend. In the absence of urban green space park, urban surface temperature had a clear trend of expansion. The maximum temperature reached 56.1423℃, and the urban ecological green space had a great influence on the spatial distribution of urban surface temperature. Rational layout of urban green space was of great significance. The urban green space had a very large effect on the land surface temperature. In the process of urban green space construction, the construction of the green space network should be strengthened, and in the area of high land surface temperature in Haidian District, a large green plate should be built. The research result can provide technical support for the current and future urban green space planning and regional surface temperature mitigation.

Abstract:In order to investigate the stability of soil structure and the distribution characteristics of organic carbon in different soil depths (0~10cm, 10~20cm,…, 90~100cm) under long-term conventional tillage and no-tillage conditions, mixed soil samples and undisturbed soil samples collected from no-tillage and conventional tillage treatments were designed to measure soil structure and soil organic carbon content. The results indicated that with the increase of soil depth, the contents of aggregates with diameter of 0.5~2.0mm and greater than 2.0mm were gradually decreased, while other particle agglomerates were increased. No-tillage treatment could improve the large aggregates (greater than 0.5mm) content, and significantly improve the stability of soil structure, the effect of depth was more than 60cm. With the increase of soil depth, soil organic carbon and active organic carbon content were increased firstly and then decreased, and then trended to be stable. Soil carbon and active organic carbon of no-tillage treatment in 0~80cm soil layer were higher than that of conventional tillage. With the increase of soil depth, soil aggregates organic carbon content was decreased, while organic carbon content of large aggregates was higher than other size aggregates. No-tillage was more conducive to increase soil organic carbon content of different size aggregates under 0~40cm soil depth. With the decrease of soil aggregates, soil active organic carbon content was decreased. Compared with conventional tillage, except 0.053~0.250mm size aggregate, no-tillage increased active organic carbon content in 0~20cm soil layer of various aggregates. With the increase of soil depth, the contribution rate of organic carbon to soil total organic carbon in different size fractions showed the trend of decreasing first, then increasing and then decreasing. In different aggregates, contribution rate of organic carbon of aggregates with diameter greater than 2.0mm and less than 0.053mm in the 0~100cm soil layer was lower than those of other size aggregates. In 0~20cm, 30~40cm and 90~100cm soil layers, accumulation contribution rate of different aggregates organic carbon of no-tillage treatment was higher than that of conventional tillage.

Abstract:Judgement of crop water requirement just by soil water content is not competent, which is closely related with crop yields and water use efficiency. Corn water consumption and yield in response to mulching method (M1: fully mulched and M2: partially mulched), and irrigation amounts (I1 and I2) under variable drip irrigation lateral spacings (A1: 1m and A2: 0.5m) were investigated over two growing seasons in the Hetao Irrigation District under arid growing conditions. Results showed that evapotranspiration (ET) in partially mulched treatments were higher than that in treatments with full mulch cover under low irrigation frequency. However, the yields and water use efficiency (WUE) were lower under partial mulched treatments compared with full mulch. Closer lateral spacing had no effect on ET under low irrigation frequency, but yield was increased with high irrigation amount under low irrigation frequency. The yield response factor (ky) of the crop water production function(CWPF) was sensitive to mulching method and it was lower in partially mulched treatments than in fully mulched treatments under low irrigation frequency. Under high irrigation frequency, ky was sensitive to irrigation amounts, mulching methods and lateral spacing. The CWPF along with WUE and crop yield can aid in the selection of optimal irrigation and mulching management. Considering ky, yield, WUE and costs, partial mulch with 1m lateral spacing under high irrigation amount and full mulch with 0.5m lateral spacing with low irrigation amount was optimal under high irrigation frequency while either 1m or 0.5m lateral spacing under partial mulch with low irrigation amount was optimal under low irrigation frequency, respectively. This study can guide irrigation application for maize in the Hetao Irrigation District.

Abstract:The technology of film mulched drip irrigation（FMDI is applied widely to cotton cultivation in Xinjiang, China. Resulted from its characteristics of high ratio and small amount of irrigation, a problem of shallow roots and weak adversity resistance is often found in practice and thus would limit further development of FMDI. Since the irrigation water is supplied deeper in the root zone, the subsurface drip irrigation (SDI) is easily to be considered as an alternative to solve the problem. To avoid probable damage from mechanical farming and prolong the application duration, the irrigation tape in a traditional SDI system is usually buried in deeper root zone (e.g. beneath 35cm from the soil surface), which might be extremely inconvenient for seedling irrigation and management maintenance of the irrigation system. In fact, with the technological progress and cost reduction for manufacturing the irrigation tape, the practical use of disposable drip irrigation tape is becoming more and more popular. The objective was to explore the reasonable depth of disposable drip irrigation tape in SDI by using numerical simulation method. The HYDRUS-2D/3D software was used to simulate the dynamics of soil water and salt, and a field experiment was conducted in Manasi County of Xinjiang autonomous region to validate the numerical model and selected hydraulic parameters. Simulated and observed soil water content distributions were in good agreement with the maximum mean absolute error (Me) and root mean square error (Rm) of 0.034cm3/cm3 and 0.040cm3/cm3, the minimum correlation coefficient (R) of 0.8 and Nash-Sutcliffe efficiency coefficient (Ns) of 0.34~0.62, respectively, between them. Correspondingly for soil salinity distributions, the values of maximum Me and Rm were 3.31g/kg and 4.24g/kg, the minimum R was 0.6 and Ns were -0.06~0.38, respectively, which was also in acceptable range. Then the transport processes of soil water and salt under SDI with different burying depths H (5cm, 15cm and 30cm, respectively) for irrigation tape were simulated by using the validated numerical model and hydraulic parameters. The results showed that salt was gradually driven away from the tape by irrigation water, with soil salinity decreased around the tape but increased near the wetting front. While the increase of H resulted in decrease of evaporation loss, the shallow soil layers near surface would be more and more difficult to be wetted by irrigation water. Synthesizing the factors such as recycling convenience of disposable tape, water requirement for cotton seedling, desalination demand of root zone and water use efficiency for desalination, local disposable tape of SDI was recommended to set at about 15cm, a moderate depth from the soil surface.

Abstract:In recent years, there has been a substantial change for groundwater dynamic change in northern of China, and the level of groundwater in many cities overall decline. The West Liao river plain area in Tongliao City, Inner Mongolia, is a typical ecotone between agriculture and animal husbandry, and the major water source of it is groundwater. Therefore, it is significant to study the groundwater dynamic state and its causes for reasonable exploitation and utilization of water resources and ecological environment management. The Horqin District of Tongliao City was selected as the research area. Based on the relationship between dynamic variation of groundwater, precipitation and groundwater exploitation,by using the comparison method of regression analysis, M-K mutation testing, accumulative anomaly method and accumulation slope change rate, the rate of different impact contribution for the vary of groundwater dynamic was quantitatively separated, and the driving factors also were quantitatively analyzed. The results showed that there was a significant upward trend for the groundwater depth over the years. Besides, precipitation showed clear hysteresis phenomenon for groundwater dynamic changes, and the delay period was three years. The abrupt change year of groundwater and precipitation in the study area is 1998. The contribution of climate change to the dynamic variation of groundwater in the study area was 24.5%, and the contribution of human activities to the dynamic variation of groundwater was 75.5%. The change of groundwater dynamic state was mainly caused by the human activity. The results of this research would have important practical significance for rational exploitation and utilization of water resources and ecological environment management.

Abstract:The reasonable ratio of water and fertilizer for maize planting has been an important subject in agricultural research. However, previous studies only pay more attention to the one of the factors of yield, water use efficiency and photosynthetic rate, etc. to make the scheme of water and fertilizer coupling. The purpose was to reveal the coupling effects of fertilizer and water on photosynthetic rate, yield and WUE. A scheme of water and fertilizer combination was made based on the multi-objective genetic algorithm (MOGA), aiming to achieve an overall optimization of the above three factors. The D-416 saturation optimum design with 16 treatments and three replicates was used in the experiment. There were four levels of irrigation amount (400.0m3/hm2, 473.7m3/hm2， 604.1m3/hm2 and 700.0m3/hm2), five levels of N supply (180.0kg/hm2, 198.3kg/hm2, 225.0kg/hm2, 251.7kg/hm2 and 270.0kg/hm2), and five levels for both of P2O5 and K2O (60.0kg/hm2, 72.2kg/hm2, 90.0kg/hm2, 107.8kg/hm2 and 120.0kg/hm2). The design of each block was 10.4m×10m with 702 plants and 23cm in spacing. Maize variety of Longdan 9 was selected to seed on April 25, 2016. P2O5 and K2O were supplied as base fertilizer before seeding. Half of N was used as base fertilizer and the remaining half was applied at elongation stage. Each treatment was irrigated respectively at elongation stage and tasseling stage with the same amount of water. The photosynthetic rate of the fourth leaf from the top to the bottom of maize was measured by the LI-6400 (LI-COR Biosciences Company, USA) during 09:00—11:00 on August 9, 2016. The yields for each block were recorded on September 21, 2016. The regression model of N, P2O5, K2O and irrigation water amount on maize photosynthesis rate was established by four-factor quadric regression analysis, and the coefficient of determination was 0.99. Sorting from large to small, the effect of various factors on the photosynthesis rate of maize was irrigation water amount, N, K2O and P2O5. The photosynthetic rate appeared the trend of increasing first and then declining with the increase of each factor. Coupling effects between irrigation water amount and N, P2O5 and K2O, irrigation water amount and K2O were significant while the coupling effects between the rest factors were not significant. The medium irrigation and medium fertilizer were favorable for maize photosynthesis. Increasing yield was beneficial to improve WUE. A multi-objective optimization model of photosynthetic rate, yield and WUE of maize was established. The genetic algorithm was used to optimize this model. The most suitable combination of irrigation water amount and fertilizer was as follows: irrigation amount was 700m3/hm2, and the fertilizer was 270kg/hm2 of N, 60.26kg/hm2 of P2O5, 60.02kg/hm2 of K2O and the corresponding optimum maize photosynthetic rate, yield and WUE were 13.54μmol/(m2·s), 24520.10kg/hm2 and 5.14kg/m3, respectively. The results had a guiding role in maize production.

Abstract:Filtration is essential to the efficient operation of drip irrigation systems and screen filter is the most common types of filter used in drip irrigation systems. The screen of filter could be clogged by sand particles which cannot pass through the filter mesh pore in the process of filtering. The clogging experiment was carried out to analyze the process and reason of screen clogging, and obtain some parameters of calculating the pressure drop of screen filter after being clogged. According to experimental results, the clogging reason was analyzed by the medium clogging and filtration cake clogging, respectively. The sizes of sand particles in inner layer of filtration cake were large and the sizes in the outer layer were small and uniform. With the large size of mesh pore, the time of screen clogging was short and the screen was easy to be clogged. Under the same size of mesh pore, the time of screen clogging would be shortened with large sand concentration. Based on Darcy’s law and actual parameters of screen, the relationship between pressure drop of screen and the mesh pore, mesh thickness, mesh porosity, filtration cake thickness, filtration cake porosity was developed theoretically. According to the actual data of the filtration mesh and cake, the pressure drops between the internal and external surfaces of screen were calculated with the mesh pore sizes of 430μm, 280μm and 200μm, respectively. The results indicated that the pressure drops were increased with the increase of flow rate, mesh thickness and filtration cake thickness. The pressure drops also were increased with the decrease of mesh pore and cake porosity. The calculated results of pressure drop were compared with the measured values, which indicated that the predicted pressure drop for each filtration level showed a good correlation with the measured pressure drop of filter screen, and the results can reflect the clogging law of screen.

Abstract:Gravel mulching technology, as one of the most important field management techniques, has been long applied by farmers in dry areas to decrease water evaporation and maintain soil temperature, which can also improve crop production in the arid and semi-arid regions. Studying on the influences of gravel mulching on soil water and temperature as well as ecosystem CO2 emissions will play an important role in assessing farmland ecological effects of gravel mulching. A winter wheat field experiment over two-year periods was carried out and annual CO2 emission was monitored with a static opaque chamber and chromatography method, and the net ecosystem exchange and harvest index were calculated. In the experiment, four field treatments were applied, including CK (control with no mulching), WCK (supplementary irrigation with no mulching), GM (gravel mulching with no irrigation), and WGM (gravel mulching with supplementary irrigation). Compared with the control treatments, the gravel mulching treatments can significantly increase the soil temperature and moisture, for specific performance, WGM was the largest, and followed by GM. Consequently, gravel mulching exerted greater effect on soil water and temperature. Seasonal dynamics of CO2 emissions generally followed the change of soil temperature with high peaks of CO2 fluxes from April to June in both years, whereas CO2 fluxes went conversely with soil water content change over the two years. Statistical analysis also showed that soil temperature and soil moisture had significant interactions on CO2 emissions at P<0.05 level. By the correlation matrix and principal component analyses, the distribution of CO2 emissions was the closest with the two control treatments (CK and WCK), and the farthest with the two gravel mulch treatments (GM and WGM). The gravel mulching practice, particularly the WGM treatment, can significantly influence the distribution of winter wheat growth parameters such as yield, harvest index, net ecosystem exchange and so on. The above mentioned results indicated that the gravel mulching technology had the potential to increase winter wheat yield, promote net ecosystem exchange and reduce CO2 emissions from ecosystem. All in all, gravel mulching combined with supplemental irrigation in the key growth stages could effectively improve soil hydro-thermal conditions, and reduce CO2 emissions from farmland ecosystems.

Abstract:The research of composite load-deformation relationship of soil under vertical and lateral loads is the difficulty in vehicle terramechanics field now. The lateral load causing slide sinkage was put forward by some scholars in the past but the numerical relationship between lateral load and slide sinkage was not clear yet. The deformation law of soil under vertical and lateral loads was analyzed on the base of finite element theory. Firstly, the soil stress-strain characteristics was analyzed and the modified drucker-prager cap model was chosen as the constitutive model of soil considering the soil elastic behavior, yield criterion, hardening law, flow rule and failure criterion. Then the load-deformation relationship of soil under vertical load was analyzed in the way of relationship between plate sinkage and pressure by the plate-sinkage test. Finally, the composite load-deformation relationship of soil under vertical and lateral load was analyzed considering the lateral load influence by the shear test on the base of load-deformation relationship of soil under vertical load. The lateral load could cause the increase of sinkage in the vertical direction, divided the total sinkage into static load sinkage and slide sinkage, it can be found that the lateral load can cause the slide sinkage and there was a linear relationship between shear displacement and the slide sinkage. The influence factors to the value of slide sinkage were analyzed and the major factors that affected the value of sinkage were vertical load and soil plastic parameters such as soil cohesion and frication angel, the soil elastic parameters such as elastic modulus and passion ratio had little effect on the value of sinkage. The linear relationship between shear displacement and slide sinkage of soil was clearly put forward and it can be used to calculate the soil bearing characteristics more accurately in vehicle terramechanics and other research fields involved soil deformation.

Abstract:Wastewater irrigation was adopted in irrigation district in southeastern suburb of Beijing from 1950s to 2003, the main source of wastewater was industrial and domestic wastewater from Beijing. Reclaimed water was used for irrigation since 2003 in the irrigation district. To investigate the residual levels of polycyclic aromatic hydrocarbons (PAHs) in topsoil and crops in the irrigation district, totally 31 samples of soil and 38 samples of crops were collected, and the concentrations of 16 US EPA (United States Environmental Protection Agency) priority PAHs were determined by gas chromatography equipped with a mass spectrometry detector (GC-MS) in 2015. Results showed that the PAHs in topsoil in the district were ranged from 113.5μg/kg to 449.8μg/kg, with a mean value of 258.5μg/kg. And 80% of the collected soil samples were slightly polluted by PAHs. The sums of 10 PAHs were 83~307μg/kg, which were lower than the standard of Netherlands (the intervention value was 40mg/kg). The average value of bap toxic equivalence quantity (TEQBap) for 10 PAHs in topsoil was 19.0μg/kg, which was lower than the standard of Netherland (33.0μg/kg), indicating that there was no remarkable potential ecological risk. The concentrations of winter wheat grain, summer maize grain and vegetables were 368.7~389.9μg/kg, 87.7~113.5μg/kg and 51.8~291.8μg/kg, respectively. Benzo(g,h,i)perylene was the dominant component in winter wheat grain and summer maize grain, which accounted for 36.6%~41.6% of the 16 PAHs concentrations. For vegetables, the highest individual PAH was phenanthrene, which represented 24.0% of the 16 PAHs. The concentrations of benzo(a)pyrene in cereal grains were lower than the Chinese standard limits of 5μg/kg in food. The high temperature combustion was the major pollution source for PAHs in topsoil and cereal grains, while the mixed sources of fossil fuel combustion and oil source were the pollution source for PAHs in vegetables. The carcinogenic risk of adult and child caused by PAHs were 4.02×10-5 and 1.76×10-5, respectively;the non-carcinogenic hazard index of PAHs for adult and child were 2.72×10-2 and 4.78×10-2, respectively;all of them were lower than the threshold values. Dietary intake was the major route of human exposure, which accounted for 98.39%~99.64% of carcinogenic risk and 99.8%~99.9% of non-carcinogenic hazard index, respectively. The carcinogenic risk caused by benz（a）pyrene and dibenzo（a,h）anthracene were relatively higher, which accounted for 42.89%~46.72% and 22.15%~26.36% of the total carcinogenic risk, respectively. The non-carcinogenic hazard index of benzo(g,h,i)perylene and phenanthrene were relatively higher, which accounted for 44.28%~46.28% and 29.14%~29.60% of the total non-carcinogenic hazard index, respectively.

Abstract:The grid-based Sacramento (GSAC) model divides a basin into discrete areas using grids. Conventionally, it is difficult to achieve the grid parameter for runoff module of GSAC model. With an aim to solve this problem, a method for estimating the runoff parameters of GSAC model using the soil property data of harmonized world soil database (HWSD) was proposed, in which the physical and chemical characteristics of each soil layer were given on the basis of the division of topsoil (0~30cm) and subsoil (30~100cm). Firstly, the percentages of sand and clay content and texture classification in topsoil (T-layer) and subsoil (S-layer) of HWSD were extracted. And the data was used to estimate the soil water constants such as wilting point, field capacity and saturated water content in each grid. Secondly, the upper layer thickness of GSAC model was adjusted using wilting point, field capacity and tension water capacity of T-layer, and a climatic index defined as ratio of mean annual precipitation to potential evapotranspiration. In each grid, the soil water constants of T-layer and S-layer were converted into those in the upper layer and lower layer of GSAC model by upper layer thickness. Finally, runoff parameters in each grid were estimated using the upper layer thickness and the converted soil water constants of GSAC model. Meanwhile, totally 12 adjustment coefficients were used to adjust the runoff parameters, and all the adjustment coefficients were determined by the GSAC model via the free search (FS) algorithm. The results of model application in the Hulan River Basin indicated that it was feasible to estimate runoff parameters of GSAC model using HWSD soil property data;the better runoff simulation results were obtained by GSAC model using the adjusted runoff parameters;and Nash efficiency coefficients (NSEC) were 0.81 and 0.83 of the calibration phase and verification phase, respectively.

Abstract:In order to improve the availability and accuracy of online monitoring data of water resources, it is very important to detect and correct the outliers of monitoring data. The water resources monitoring data are non-linear and non-stationary time series data, the outlier detection method of the conventional time series did not take into account the convexity and concavity of time series. A combining median and ensemble empirical mode decomposition (EEMD) method was presented for outlier detection. Firstly, the outliers were preliminarily detected by the median method. And then the remaining data were decomposed by EEMD. The overall trend of most of the data can be fitted by superimposing the low-frequency components, but not affected by outlier, and the outlier can be detected effectively according to the deviation rate. Then, according to change of convexity and concavity of time series data after outlier detection, the method of piecewise curve fitting was used to correct the outliers. Finally, taking the daily water intake data of H1 waterworks as an example, the results showed that the method of combining median and EEMD can detect outliers effectively. The data obtained after correction can truly reflect the actual situation of water intake of waterworks. It can also provide more reliable data for subsequent analysis.

Abstract:The effect of relieving heat stress of cows was verified by three kinds of average spraying droplet diameter (SDD) (0.829mm,0.947mm and 1.127mm) through field test. In the test, the body surface temperature of dairy cow was collected by thermal imager;the respiratory rate and physiological index of rectal temperature were measured at the same time. Based on this, the theory of enthalpy difference of Merkel was used to calculate the heat transfer of spraying cooling. The results showed that during the process of spraying, for three kinds of SDD (0.829mm,0.947mm and 1.127mm), the average reductions of temperature were 0.7℃, 1.1℃ and 0.9℃ in the region of neck;in the region of abdominal, the average reductions of temperature were 0.7℃,1.4℃ and 1.5℃, respectively;and the average respiratory rates were decreased by 0.6, 4.2 and 2.1 times per minute, respectively. After spraying, for three kinds of SDD, the average reductions of temperature were 0.2℃, 0.4℃ and 0.6℃ in the region of neck;in the region of abdominal, the average reductions of temperature were 0.1℃, 0.5℃ and 0.6℃, respectively, and the average respiratory rates were decreased by -0.4, 1.4 and 1.2 times per minute, respectively. The rectal temperature was controlled within the stable range before and after spraying. The average rectal temperatures under SDD of 0.947mm and 1.127mm were lower than that under SDD of 0.829mm. Under three kinds of SDD, the heat exchanges of cows in unit time were 417.4W, 469.9W and 430.4W, respectively, which showed that heat exchange reached the maximum under SDD of 0.947mm. In summary, the SDD of 0.947mm was more suitable for the cooling of dairy cows in summer.

Abstract:The quality of the environment could directly affect the production performance of pigs. Especially for weaned pigs, they have just undergone weaned stress and are very sensitive to external environment change. In order to evaluate the environmental conditions in the weaned pigs building in typical East China, and provide useful suggestions for pig barn structure design and the environment improvement, based on computational fluid dynamics (CFD) method, a three-dimensional steady state simulation was conducted on air speed, temperature, relative humidity and particle concentration distribution of a weaned pig building with negative pressure ventilation system and manure pit system. It was known from the CFD results that CFD could be a useful tool in analyzing the indoor environment in livestock house. When air was input to the pig house during winter days, the wind speeds in the region where pig was fed at z=0.2m could maintain within 0~0.2m/s, and most of them were below 0.1m/s. Also, the relative humidity remained at about 60%~70%. Its temperature was maintained within 26~34℃. In addition, the PM2.5, PM10 and TSP concentrations were kept in 0~0.1mg/m3, 0~0.7mg/m3 and 0~1.0mg/m3, respectively,in most area of pig house, which could meet the requirements of weaned pigs in winter according to environmental parameters and environmental management for intensive pig farms. Yet, at entrance of the units and some corners, there was still potential for optimization.

Abstract:The solar greenhouse can effectively reduce the heat loss under the outdoor condition at low temperature by covering insulation materials. Based on the previous study of design and experiment of the rear fixed type rolling shutter device in solar greenhouse, in order to study the influence of rolling shutter opening on the temperature change in solar greenhouse, aimed at the insulation pads, the typical “Liaoshen Ⅳ” solar greenhouse structure was simplified. The result suggested that the indoor temperature of solar greenhouse can be affected by the rolling shutter opening, which changed the covering area of insulation materials and heat dissipation rate of solar greenhouse. There was a linear proportional relationship between indoor temperature of solar greenhouse and rolling shutter opening. And then this theory was verified by CFD-Fluent. The following conclusion was drawn: covering the shutter can effectively reduce the heat loss and maintain appropriate indoor temperature and its uniformity for solar greenhouse. Under ideal conditions, the rolling shutter opening would change the covering area of insulation materials and lead to the differences of heat dissipation rate for solar greenhouse, at last, lead to the regional difference of inner temperature. And the relationship between changes of inner temperature and the value of rolling shutter opening was almost linear. The study intuitively reflected the relationship between indoor temperature and roller shutter opening of solar greenhouse, and provided a theoretical basis for further strengthening the precision control of rolling shutter machines, besides it would provide effective reference for greenhouse production practice in China, and it had an important theoretical and practical significance.

Abstract:With the aim to improve the separation efficiency of hydraulic vortex separator (HDVS) in recirculating biofloc technology (RBFT) system, three HDVSs with different structural parameters were studied by using numerical method of computational fluid dynamics (CFD). The simulations of the solid-liquid phase flow in HDVSs were conducted based on an Eulerian-Eulerian multi-phase turbulence 3-D model combined with the kinetic theory of granular flow, which specifically analyzed the velocity contours, vector contours, streamlines of liquid phase, inner and outlet distribution characters of solid phase. The simulation results showed that with the increase of α, the velocity field below the inlet part and surrounding area of the sleeve had small difference at the inlet velocity of 0.36m/s. But the difference of results of inner region of sleeve was stark and the turbulence was enhanced in this regions. In addition, some swirls occurred in the inner zone of the sleeve, which added energy waste and had negative effect on the flocs separation. The separation efficiency of HDVS had a negative correlation with the increase of α. When α was 1.5, the removal efficiency was 27%, which was more effective than 17% (α was 2.0). But when α was increased from 2.0 to 2.5, the HDVSs almost had the same solid phase volume fraction at the outlet and the separation efficiencies only had a small change. To validate the accuracy of simulation results, the simulation values and experimental data were compared. The good agreement of the flow velocity and change law of the separation efficiency proves that the mentioned two fluid model (TFM) can be used to optimize the structure of HDVS.

Abstract:Alcoholysis liquefaction synthesis of levulinate esters from crop residues has attracted extensive attentions in recent years. However, the natural dense structures of biomass have become a key obstacle to the efficient use of straw for levulinate production. Ball milling is a new way of mechanical pretreatment which can effectively damage the recalcitrance of biomass and promote the availability in conversion and utilization. Ball milling can increase the production of ethyl levulinate significantly.Sulfuric acid, phosphoric acid, p-toluene sulfonic acid, Al2(SO4)3 have been applied for the conversion of biomass to ethyl levulinate. The results showed that the stronger the acidity of the catalyst was, the better the catalytic effect was under the same H+ concentration. Sulfuric acid was found to be highly active compared with other three catalysts under identical reaction conditions. And the acidity strength in sequence was sulfuric acid, p-toluene sulfonic acid, Al2(SO4)3 and phosphoric acid. The milling time had the most obvious effect on the yield of ethyl levulinate. Elevated miling time can contribute to the enhancement of reaction rate and conversion efficiency. However, the effect of filling rate and volume ratio of the spheroids on the yield of ethyl levulinate was not significant. Furthermore, based on the yield of ethyl levulinate, the optimal ball milling process was as follows: non-catalyst ball milling, 60min of the milling time, 35% of the filling rate, 2 of the volume ratio of spheroids, under this ball-milled condition,the yield of ethyl levulinate was increased from 20.08%(unmilled sample) to 33.34% (milled sample). The research result can provide some references for the production of ethyl levulinate from mechano-catalysis grinding of biomass.

Abstract:In order to realize fast, nondestructive and real-time detection of nutrition components (fat and protein) for pork, a portable nondestructive detection device based on near infrared reflectance spectra was designed and developed. The hardware part included spectrum acquisition unit, light source unit and control unit. The corresponding detection software was developed to realize the effective acquisition and real-time analysis of the sample spectrum information. In order to establish a stable and reliable forecasting model, the research focused on the effects of band selection, different sample grouping methods and variables selection methods on the models. Based on visible/short wavelength near infrared (Vis/SWNIR), long wavelength near-infrared (LWNIR) and Vis/SWNIR-LWNIR, all the samples were divided by random selection (RS) method, Kennard-Stone (KS) algorithm and sample set partitioning based on joint X-Y distances (SPXY) algorithm, and then partial least square prediction models for fat and protein content were built, respectively. The results showed that the best prediction models for fat and protein were built based on Vis/SWNIR-LWNIR by using SPXY algorithm. On the basis of the best model for each parameter, comparative analysis of competitive adaptive weighted algorithm, Random Frog algorithm and uninformative variable elimination-successive projection algorithm were employed to screen variables. The results showed that the simplified model based on competitive adaptive weighting algorithm was the best with correlation coefficients in the prediction set of 0.9505 and 0.9510 for fat and protein, respectively. The results indicated that the designed portable detection device based on near infrared reflectance spectroscopy was able to realize fast, nondestructive and real-time detection of fat and protein content for fresh meat and had certain application potential and market prospects.

Abstract:With the development of social economy and growth of people’s living standand, the demond of fruit quality is ever increasing. Quality detection and grading of postharvest fruit is an integral part of commoditization processing, which is also an effective way to achieve high price with good quality. Visible/NIR spectroscopy with the advantages of rapid, nondestructive and being on-line analyzing, has been widely used in agriculture. In the actual application of visible/NIR spectroscopy for on-line detection of fruit internal quality, multi-channels measurement often exists, in which the prediction model is not universal among multi channels due to different spectrometers or their different manufacture precisions. Calibration model transfer is a key problem in visible/NIR spectral quantitative analysis. Comparative analysis of some calibration model transfer methods, such as direct standardization (DS), piecewise direct standardization (PDS), slope/bias (S/B) between two different visible/NIR spectrometers (master and slave spectrometers, model QE65000 and QE65Pro, Ocean Optics, Inc., USA) in the sugar content on-line detection of crown pears was carried out at conveyor speed of 0.5m/s. The results showed that the prediction values by DS algorithm and DS algorithm based on the mean spectra subtraction correction (MSSC-DS) were relatively good with low root mean square error of prediction (RMSEP) of less than 0.5°Brix, which can satisfy the industry application. And pre-processing method of MSSC can improve the prediction accuracy of calibration model transfer by eliminating and mitigating the differences between the spectra acquired on master and slave spectrometers. However, the best prediction result on salve instrument after calibration model transfer (RMSEP was 0.453°Brix) was still inferior to that predicted by the model developed directly using slave data (RMSEP was 0.381°Brix). Thus, in the actual application, appropriate modeling selection should be considered from the cost and the accuracy of classification.

Abstract:Greengage acidity detection is very important in refining and deeply processing greengage. However, traditional greengage acidity detection methods based on physicochemical analysis are destructive, time-consuming and not detective online. The fast and non-destructive method based on hyperspectral imaging system was proposed to predict greengage acidity. Hyperspectral images of 487 greengage specimens between wavelengths of 550nm and 1000nm were captured. Three spectral dimensional reduction methods such as successive projection algorithm (SPA), genetic algorithm (GA) and SPA combined with GA (SPA+GA) were explored after spectrum relative reflectivity was calibrated and the images were filtered in six different ways. The featured wavelengths of the spectrum were extracted which reflected the internal acidity information of greengage. Partial least squares (PLS) prediction model was built between wavelength, and pH value and prediction precision were compared among different methods of filters and dimensionality reductions. The results showed that the model smoothly filtered by Savitzky-Golay (S-G) had the highest prediction accuracy. The model smoothly filtered by five points and then dimensionally reduced by both SPA and GA can reduce its complexity and improve its prediction accuracy compared with the ones only using SPA or GA. The root mean square error of prediction set was 0.0706, and the correlation coefficient of prediction set was 0.7925. This model based on the selected wavelength was practical to predict the greengage acidity, which would lay the foundation for further developing actual greengage multispectral image system.

Abstract:A non-destructive method for on-line determining the internal comprehensive quality of Huping jujube fruit was investigated based on visible/near-infrared reflection spectrum. Moisture content, soluble solid content, firmness, soluble protein content and vitamin C content were respectively used as internal indexes to assess the quality of Huping jujube at full ripe stage. Competitive adaptive reweighted sampling (CARS) was applied to select sensitive wavelengths. Models of the least squares-support vector machines (LS-SVM) were built based on the sensitive wavelengths respectively. The model of firmness showed that the correlation coefficient of prediction was 0.9452 and root mean square error of prediction was 41.6849. The other four models obtained the better results with the correlation coefficient of each prediction over 0.9230 and root mean square error of each prediction from 0.2674 to 3.7792. Then, the correlation was analyzed between the quality indexes. The results indicated that an extremely significant or a significant correlation was revealed between any two indexes in the P<0.01 or P<0.05 levels. Therefore, factor analysis was carried out on five internal quality index of fresh jujube to develop the internal comprehensive quality index, and the CARS-LS-SVM model of this index was established. The results indicated that the correlation coefficient of prediction was 0.9241 and root mean square error of prediction was 6.0635. This research showed that the established CARS-LS-SVM model was effective to realize evaluation of the internal comprehensive quality on fresh jujube. This research provided theoretical basis for on-line, rapid and non-destructive detection on internal comprehensive quality of fresh jujube.

Abstract:In order to study the antioxidative stability of wheat peptide in the processing of manufacturing and gastrointestinal digestion, effects of temperature, pH value, food raw materials and adjuncts, metal ions and simulated gastrointestinal digestion on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, superoxide radical anion (O-2·) scavenging activity and hydroxyl radical (·OH) scavenging activity of wheat peptide were determined. The results showed that antioxidant activity of wheat peptide exhibited better thermal stability, while its antioxidant activity was significantly declined under the alkaline condition;NaCl, glucose and citric acid were beneficial to improve the antioxidant activity of wheat peptide and the synergistic effects were increased obviously with higher concentrations, while sucrose, potassium sorbate and sodium benzoate had little effect on antioxidant activity of wheat peptide;K+, Ca2+ and Mg2+ had no obvious effect on antioxidant activity of wheat peptide, while Zn2+ and Cu2+ could play certain enhancement role in the antioxidant activity of wheat peptide;artificial gastric juice digesting solely was helpful to improve antioxidant activity of wheat peptide, while artificial intestinal juice digesting solely resulted in the obvious decline of antioxidant activity of wheat peptide, moreover, artificial gastric juice and artificial intestinal juice digesting step by step caused certain decline of antioxidant activity of wheat peptide. However, wheat peptide could still maintain high antioxidant activity. It indicated that antioxidant activity of wheat peptide was affected by the manufacturing and gastrointestinal digestion of wheat peptide. Therefore, reasonable optimized processing conditions were critical for maintenance of the antioxidative stability of wheat peptide.

Abstract:Mulberry is rich in polyphenols with characteristics of nutritional qualities and bioactive phytonutrients. However, the capacity and health benefit potential are limited due to their weak stability during processing and preservation. Spray drying encapsulation was well-established and widely utilized for protecting bioactive substances such as polyphenols. However, undesirable phenomena such as stickiness on the drier chamber wall arose during spray drying of sugar-rich solution such as fruit juice. Furthermore, powder recovery was decreased owing to stickiness issue during spray drying. Therefore, effect of different total solid ratios of whey protein isolate (WPI) and maltodextrin (MD) in the feed solution on physical and chemical properties of spray dried mulberry juice powders was investigated. The results showed that the powder recovery of spray dried mulberry juice powders was significantly increased when MD in the feed solution was replaced by small amount of WPI. The reason can be attributed to the high surface activity and excellent film-forming properties of WPI. The moisture content of spray dried mulberry juice powders was increased with the increase of WPI mass fraction in the feed solution. However, water activity, bulk density, particle size, water solubility index and glass transition temperature were decreased with the increase of WPI mass fraction in the feed solution. The hygroscopicity of mulberry juice powders was not significantly influenced by WPI/MD ratio in the feed solution. The color parameters of spray dried mulberry juice powders such as L, b and ΔE were increased with the increase of WPI mass fraction in the feed solution. Whereas, opposite behavior was observed for parameter a. The total phenol content and DPPH scavenging capacity of spray dried mulberry juice powders were decreased with the increase of WPI mass fraction in the feed solution.

Abstract:Collichthys lucidus is an important raw material for surimi production. Well known as one of the effective cold sterilization methods, electron irradiation has been widely used in industrial food preservation, as well as in food quality improvement, food safety, and other allied fields in many countries. Some studies indicated that electron irradiation can change the conformation of surimi proteins, leading to protein denaturation, aggregation and gelation. Thus the quality of surimi gel will be improved by using electron beam irradiation pre-treatment. The purpose was to investigate the influence of electron beam irradiation on the smell of surimi gel. Using gas chromatography-mass spectrometry (GC-MS) and relatively odor activity value (ROAV), the effect of different electron beam dose on the volatile flavor components of Collichthys lucidus surimi gel was studied. The sensory evaluation in association with electronic nose was applied to confirm the optimal dose, which can effectively maintain the original flavor of surimi gel. The results showed that the fish smell of gel derived from surimi irradiated was slightly reduced, and a little bit of irradiation odor was presented in high-dose group (≥7kGy). Compared with the control and irradiation groups, the difference of linear discriminant analysis (LDA) by electronic nose was obvious. The overlap of LDA between groups of 3kGy and 5kGy showed these two groups had similar odor characteristics, so did groups of 7kGy and 9kGy. After dealing with different irradiation doses, the species of volatile flavor compound and the relative contents of hydrocarbons, aldehydes and ketones from surimi gel were increased. Decanal, 1-octen-3-ol, 3-methyl-butanal and 2,3-octanedione were the key odor compounds of surimi gel. There was little influence of electron beam irradiation with low-dose (less than or equal to 5kGy) on the key and modify odor compounds of surimi gel. When the irradiation dose was more than 7kGy, (Z)-2-nonenal, (Z)-2-decene aldehyde, 2-hexenal in the surimi gel became important flavor components, the contribution to the flavor of ethyl acetate and 2-ethyl-furan was significantly reduced, it was likely to be the leading cause of the irradiation odor. In conclusion, 3～5kGy of electron beam irradiation dose, the original flavor of Collichthys lucidus surimi gel can be effectively maintained, but high dose (more than or equal to 7kGy) of irradiation would cause the generation of special off-odor. The results can provide some theoretical basis for using electron beam irradiation pre-treatment to improve the quality of surimi gel.

Abstract:The objective was to evaluate the interaction between ultrasonic treatment soybean protein isolate and chitosan, and the structural properties of the complexes. The interaction was studied by UV-Vis absorption and fluorescence spectroscopy. The relationships between structure changes and functional properties of soybean protein-chitosan complexes through SDS-PAGE, dynamic light scattering particle size analysis, surface charge and turbidity measurement were investigated. The results showed that with the increase of ultrasonic power, the maximum absorption peak of UV-Vis absorption spectrum was gradually increased and occurred red-shifted;the fluorescence intensity was firstly decreased and then increased. The intensity of the endogenous fluorescence was the highest at 600W. Ultrasonic treatment affected soybean protein isolate subunit composition and mainly promoted the interaction between 7S subunits and chitosan. The particle size of the complex was firstly decreased and then increased. The charge potential of the complexes was larger under 300～500W than those under others. The turbidity was also decreased, which was beneficial to homogeneous distribution and stability of the solution. The results showed that the formation of the complex was relatively stable at low power, but the interaction between soy protein isolate and chitosan was affected by the insoluble aggregation and rearrangement of the protein after high power ultrasonic treatment. The interaction of different complexes affected the microenvironment of amino acid residues, the tertiary structure and molecular flexibility of soybean protein isolate, and then impacted the structure and functional properties of the complexes.

Abstract:The method of mechanical stirring to separate egg membrane from eggshell has the advantages of high separating efficiency, bulk processing and no pollution to the environment. Fluent 6.3 was used to explore the effects of different stirring rotational velocities, particle diameter sizes and solid-liquid ratios on the flow field characteristics of the particle suspension state, solid holdup distribution, solid-phase velocity and stirring power consumption. Simulation results showed that the scope of particle accumulation at the bottom would be decreased while the solid-liquid ratio was decreased and the solid-liquid ratio should be reduced properly. Particles accumulation was decreased while stirring rotational velocity was increased, but power consumption would be increased dramatically, in order to ensure most particles suspension and reduce power consumption, the stirring rotational velocity should be set as 300~350r/min in experiment. Enlarging particles diameter size can reduce particle accumulation at bottom, lower particles suspension height, and increase the moving resistance of particles along the axial direction in the flow field, so the particles size of 1.5~2.5mm can be chosen for eggshell separation experiment. Therefore, appropriate conditions were obtained for the experiment of separating membrane from eggshell according to the simulation results. Moreover, quadratic orthogonal rotary combination experiments were carried out with factors of stirring rotational velocity, stirring time, solid-iquid ratio and separating medium temperature. The experimental data was optimized and analyzed by Design-Expert 8.0.6. The regression model between the experiment index and the factors was obtained. Meanwhile, the response surfaces were established between membrane recovery and experiment factors in order to obtain the relationship intuitively. The experiment result showed that the importance of stirring rotational velocity to egg membrane recovery was the most, and then the stirring time, separation medium temperature and solid-liquid ratio. The interaction between stirring time and stirring rotational velocity to separation effect was the most significant. Optimization results showed that the membrane recovery rate reached 88.58% while the stirring time was 18.57min, stirring rotational velocity was 337.68r/min, solid-liquid ratio was 0.07g/mL, and the separation medium temperature was 20℃, and the separation effect of egg membrane from eggshell was perfect. Conclusions of numerical simulation and experiment would improve the membrane recovery and utilization of discarded eggshell, and provide a reference for the solid-liquid two-phase flow and related study.

Abstract:A transparent nozzle was designed to replace the sac and orifice of the original injector. Visualization experimental apparatus with a long distance microscope together with an ultrahigh speed CCD camera was employed to study the cavitation characteristic in the nozzle and the initial spray structure in the near nozzle region by photography technique with the help of backlighting. High spatial and temporal resolutions allowed a detailed observation of the very emergence of fuel from the nozzle orifice to the outside of nozzle. The experimental results showed that the residual fuel and initial bubbles were trapped in the injector hole after the end of injection, which had an important effect on the initial spray structure of the next injection. The cavitation was related to the needle lift and the injection pressure, and it was found that higher injection pressure led to earlier cavitation inception. Moreover, the types of free cavitation, cloud cavitation and string cavitation were also observed. In addition, based on the large eddy simulation (LES) and volume of fluid (VOF) multiphase flow model, the evolution of the initial bubble in the injection hole and the formation of the initial spray structure were simulated. The computational domain and settings mimicked the experimental injector internal geometry and experimental operating conditions. The initial bubbles inside the injector influenced the spray structure and could be a source of the observed deviation between experimental and numerical results. But the experimental results were basically consistent with the simulation results.

Abstract:A preliminary experimental investigation of a free piston expander-linear generator (FPE-LG) prototype was presented. The aim of developing this FPE-LG prototype was to applied it in a small scale organic Rankine cycle (ORC) system for vehicle waste heat recovery, which can convert the thermodynamic energy of working fluid into electric energy. Technical feasibility of prototype using a newly developed valve train was verified. The phase matching of different cam plates, free-piston motion characteristics, as well as the power output of FPE-LG was identified based on the compressed air test bench. Experimental results showed that FPE-LG can run stably under the condition of high inlet pressure. The cycle-to-cycle variations of velocity at the reference position and the cycle-to-cycle variations of displacement at top dead center and bottom dead center can be ignored. The peak velocity of free-piston was close to 1.2m/s when the intake pressure was 0.2MPa and working frequency was 2.5Hz. The valve timing and intake pressure had an important influence on the motion characteristics of free-piston and power output of linear generator. Decreasing the exhaust duration angle or increasing the intake duration angle can improve the stability, symmetry of free piston, reduce cycle-to-cycle variation of free-piston motion and improve the power output obviously when other parameters were constant. The maximum peak power output was about 19.0W when inlet pressure was 0.19MPa and working frequency was 2.5Hz.

Abstract:A novel 5-degree-of-freedom (5-DOF) hybrid serial-parallel manipulator was proposed, the 2RPU/UPR parallel mechanism (PM) was the parallel part of this manipulator;and it was a kind of parallel mechanism with two continuous rotational axes, which had one translational DOF and two rotational DOFs (2R1T). The kinematics of this manipulator with high degree of modularity was quite simple, which made it easy to implement trajectory planning, parameter calibration and motion control. Firstly, to establish the inverse dynamic model of this 5-DOF hybrid manipulator, the 3×3 velocity Jacobian square matrix, between the moving platform and the independence movement parameters, was obtained. Secondly, the centroid velocity mapping matrix from the moving platform to each limb was established. Especially, the kinematics models of the UPR and RPU limbs were gotten. And the dynamic model of the 2RPU/UPR PM was obtained by use of the virtual work principle. Thirdly, the force analysis of the tilting head with single DOF was finished by means of D’ Alembert principle. Then, the inverse dynamic model of the 5-DOF hybrid manipulator was solved by combining the virtual work principle and the D’ Alembert principle. At last, the dynamic numerical simulations were performed through Matlab software and ADAMS software, the results showed that the dynamic model of this 5-DOF hybrid manipulator was correct, which provided a new idea for establishing the dynamic model of this type hybrid manipulator.

Abstract:A type of 3-DOF flexible pneumatic actuator (FPA) employing elongation pneumatic artificial muscles was developed. It was mainly composed by three pneumatic artificial muscles symmetrically distributed in parallel and three artificial muscles were fixed 120° each other in space. The pneumatic artificial muscle was a closed cavity formed by the rubber tube and the end covers, and the outer side of it was thin sheet restraint rings set compacted. The elastic skeletons were added among the artificial muscles to improve the rigidity and stability of FPA. Specially, the driving device of FPA was just the body of the actuator. The FPA has the advantages of small volume, light weight and multiple degrees of freedom, and it can axially elongate and bend in any direction by controlling the input gas pressure of different artificial muscles. According to the force and torque analysis, the nonlinear theoretical model was developed to simultaneously describe the elongation, bending direction and bending angle of the FPA. Further, the theoretical model was verified by experiments, and then the deforming properties of FPA were obtained under different ventilation modes. The results showed that the FPA was in arc shape approximately when it was bent;it had high flexibility to elongate in axial direction or bend in any direction which had the similarity to the biological muscles in the body flexibility, movement and driving ability. In summary, this type of FPA can be as flexible fingers or flexible joints applied to fruit and vegetable picking manipulator or agricultural robot.

Abstract:Industrial robots are widely used in the fields of handling, stacking and machining due to their advantages of large workspace, compact structure and good flexibility, but the stiffness of the robot is relatively weak due to the series structure. In addition, the external load of the robot is fully shared by servo motors which increase the driving power and energy consumption of the robot arm, especially for the big and small arms. In order to increase the robot stiffness and reduce the driving power of the robot arm, a robot structure with a novel robot arm was presented. A parallelogram structure with diagonal driven was adopted for robot big and small arms. The diagonal electric cylinders driven by ball screws using double nuts with preload to eliminate the reverse backlash, and the anti-backlash method was applied to the rotary base and the robot wrist to eliminate the transmission backlash. By using the parallel quadrilateral frame to balance the external bending moment, the driving power and the energy consumption of the mechanical arm were reduced in principle. The energy consumption of the novel robot and the corresponding industrial robot were compared under the same external load, and the simulation results showed that the driving power of the big arm can be reduced from 20% to 80% compared with the industrial robot and the small arm was equal to the industrial robot when only the external gravity load was applied. Moreover, the power consumption of the driving motor was not required when only external bending moment was applied. Finally, based on the strain energy and Castigliano’s theorem, combining with the robot arms stiffness results using finite element analysis (FEA), the integral robot stiffness was calculated and the results showed that the overall stiffness of the robot was better than that of industrial robots, which made it beneficial to improve the load capacity in the operations of handling, stacking and so on.

Abstract:Magnetorheological valve is one of the basic ways to apply and accommodate the MR fluid into most of hydraulic applications. A novel magnetic isolation radial MR valve which the magnetic flux was guided into the annular gap was proposed by changing the material properties of the typical single radial type MR valve. Compared with the magnetic field lines distributed only in the radial flow path of the non-magnetic radial MR valve, the magnetic isolation radial MR valve increased the effective annular region of the valve by changing magnetic field structure and without having to increase the valve dimension. The finite element method (FEM) was used to investigate the effects of magnetic field structure on pressure drop change in the non-magnetic and magnetic isolation radial MR valves under the same geometry conditions and the same flow path. The experimental test rig was set up to validate the simulation results, the simulation and experimental results showed that the pressure drop of the magnetic isolation radial MR valve can be increased by changing the material properties to twist and weave the magnetic flux into unexposed region to the magnetic field, which was superior to that of non-magnetic radial MR valve. In addition, due to the annular flow path was affected by the magnetic field, the magnetic isolation radial MR valve had greater rise response time.

Abstract:In order to solve the problem that the widely used hydraulic driving system only can output one characteristic, a theory of proportional type multi-pump and multi-speed motor driving system was presented based on proportional type of multi-pump and multi-speed motor. Multi-pump can output multi flows, to work in different pressures without a reducing valve, and multi-speed motor can output multi speeds and torques. Two proportional type multi-pump and multi-speed motor driving systems were designed based on describing the structure and working principle of the multi-pump and multi-speed motor, and the features of the two new driving system were introduced, the output characteristics of the two driving system in different working ways were analyzed theoretically, the effects of the displacement coefficient on the driving system were also discussed. The outputting speeds and torques of the new hydraulic driving system in different working ways were obtained through expanding the output characteristic of this system. The experimental platform of proportional type multi-pump and multi-speed motor driving system was built. The result showed that this driving system can output multi speeds and torques through controlling the working ways of the multi-pump and multi-speed motor, and each level of speeds and torques was related to the displacement coefficient. The research on the proportional type multi-pump and multi-speed motor driving system established a basis for its design and application.