Abstract:In order to measure the crop geometrical feature real-timely in the complex background, interactive software system and hardware system were designed. Based on the Matlab image process technology, crops geometrical feature calculation models and the idea of human-computer interaction and classification calculation, the software system were designed. The whole measuring process was divided into four steps, which were image acquisition, RGB color feature acquisition, crops region separation from the background and crops geometrical feature calculation. A human-computer interactive software interface was designed, which consisted of menu bar, operation button, image display window and measurement value display window, and it could control each measuring step. RGB color eigenvalues of different crops were obtained by using discrete sample point interactive selection method and region interactive selection method, then the crops region was separated from background efficiently by using screening method based on RGB color eigenvalue difference of each pixel. The software system built classified color database for some kinds of crops according to the environmental condition and crops feature, so pertinence and efficiency for extracting crops region were improved, and real-time measurement was realized. Image was rectified to enhance measurement precision. Corresponding relationships between the actual sizes represented by unit pixel and different object distances were determined previously in order to calculate the actual crops geometrical feature values in real time, so it was not needed to set reference object to calculate the actual size represented by unit pixel when the system was used. The software system built calculation models for several crops geometrical features, including volume, area, and length calculation models of revolving and non-revolving body. The crops volume and projective area regressive model was explored, which provided a new idea for calculating the volume of the crops with non-revolving feature. The objectives of classification design were to expand the measuring types of crops, make the calculation process convenient and enhance the calculation speed of the system. The hardware system consisted of high-performance PC core component, industrial touch screen with a rapid responding speed, industrial camera which had the function of automatic focusing in a fixed focal length and adjustable support. High-capacity lithium battery supplied power for the hardware system. The whole system was 29.8 cm×19.9 cm×6 cm in size, and it was easy to manipulate the system, thus the system could be used as a portable device. For the purpose of installing the device on machine, the adjustable camera support was designed, which was made up of electric dividing plate, stepper motor and S7-200 PLC, and industrial camera shooting direction could be controlled by PLC. The measuring accuracy and real-time feature of system were verified, and the result showed that the measuring error was 4%～8%，and the average processing time was 1.63 s (without the time to construct the color feature database). The system could accomplish the measurement of crops geometrical feature with relatively high speed and calculating accuracy in real time. The system could be used in the field of crops geometrical feature measurement.

Abstract:A vision-based fruit-vegetable picking robot helps to improve picking efficiency by making full use of the information by which the target of harvest can be recognized and located. For harvesting robots, it is important and difficult to calculate and locate the picking point from the recognized main fruit bearing branch of litchi. Hence, calculation of picking point and its stereo match become the research focuses. To meet the needs of picking the whole litchi cluster for litchi picking robot, a scheme of combined algorithms of Harris and improved SIFT to compute picking point of litchi and achieve its stereo matching was proposed. Firstly, corner extraction from the main fruit bearing branch of litchi was carried out by Harris method, and the whole identified area of litchi fruits was taken as a big fruit, the feature information on “centroid” and the maximal vertical coordinate vertex of the MBR (Minimum bounding rectangle) of the big fruit (denoted by Y ) were then attained. Then, taking each Harris corner whose vertical coordinates were bigger than Y as the center of circle, all possible circles were computed and the center of circle whose circle area was the maximum was chosen as the pixel coordinate of picking point in original collected litchi image. Furthermore, the computed picking point was described with a characteristic vector of SIFT with 128 dimensions, and its binocular stereo matching based on cosine distance similarity of SIFT was also proposed. Theoretical analysis and experimental results show that the proposed scheme can satisfy the need of vision of litchi picking robot with successful matching rate of 89.55%, which means that the scheme can improve the computation precision of picking point from main fruit-bearing branch with complex construction.

Abstract:Aimed at plugging problem of baling intact rice straw by the domestic small and midsize steel-roll round baler, baling process was studied by the self-made steel-roll round baler (diameter of bale was 500 mm). The forming process of rotary straw core was essentially the process of inwinding and continuous accumulation of rice straw in baling chamber by analysis using high-speed camera. Large traction, which was produced by the rotary straw core on the subsequent feeding rice straw, was beneficial to eliminate baling plugging. Test results showed that the formation of rotary straw core mainly depended on the friction of the steel rolls on rice straw and the sustained driving force of the subsequent feeding rice straw, and the main influencing factors were analyzed. The main influencing factors were as follows: friction effect of the steel roll on rice straw, linear velocity of spring-finger and feeding quantity of rice straw. The dry mass of rotary straw core was decided as the evaluation index, and the Design-Expert software was used to optimize the level of each factor. The contributing rate of each factor on the dry mass of rotary straw core was as follows: friction effect of the steel roll on rice straw, linear velocity of spring-finger, feeding quantity of rice straw. When the parameters of sliding friction coefficient between steel and rice straw was 0.65, the linear velocity of spring-finger was 2.23 m/s and the feeding quantity of rice straw was 1.5 kg/s, the dry mass of rotary straw core was 1.58 kg. The research results can be used to support innovative design and parameters optimization of steel-roll round baler.

Abstract:In order to further improve the operation effect and stability of transplanter with chute, the guiding seedling mechanism was chosen as the research object, indoor mixed level uniform design experiment was done under the condition that the length of the connecting rod, initial phase angle of crank and velocity of the 2ZDJ-2 seedling transplanter were made as the experiment factors and lodging rate was made as the experiment indicator. Multivariate non-linear regression model between experiment factors and indicator was built by making statistical analysis of the experiment result, and the influence rule of factorial effect on experiment indicator was analyzed. Optimized solution of experiment factor combination was done within the scope of experiment data by using Matlab software, and repeated verification experiment of optimal factors combination was done. Experiment result showed that the guiding mechanism worked well when the initial phase angle of crank was 70°, the length of the connecting rod was 356 mm, and the velocity was 280 mm/s, under this condition, the erectness percentage was up to 95.5%, and the mechanism worked smoothly.

Abstract:For no full analysis on the theories of three planting bars of transplanting mechanism and reducing the row spacing applicable range by increasing the quantity of planting bars, a non-uniform rotation three planting bars of transplanting mechanism was proposed. The kinematics analysis model was built based on its working principle, and the effects of transplanting parameters on non-uniform rotational speed were studied. The theoretical analysis was received that the non-uniform rotational speed had no effects on the static trajectory of planting hoe, taking seedling angle, pushing seedling angle and trajectory height. Eccentricity ratio and initial phase angle of the elliptic gears had great effects on the velocity with axis y at the point of taking seedling, the speed of taking seedling points with axis y reached the largest when the phase angle was 0°. The transplanting hole was increased with the increase of eccentricity ratio, the initial phase angle had relatively complex effects on the transplanting hole, which would get large with the increase of initial phase angle between 0°~90°, and get small with the increase of initial phase angle between 90°~180°. The effects of speed of transplanting bars and the movement times of seedling box on the damaged seedling rate and stripping-slicing homogeneities were tested in laboratory, the results indicated that the damaged seedling ratio was increased with the increase of revolving speed and the impact was significant, but the movement times had no significant impact on it. The movement times had significant impact on the stripping-slicing homogeneity, which was significantly higher than the matched group when the movement times was 18, the difference between the stripping-slicing homogeneities when the movement times equaled to 21 and 24 and the two contrast transplanting bars was little, but the revolving speed had effect on it and the impact was non-significant. Field contrast test indicated that the planting quality of the non-uniform rotation three planting bars was superior to that of the matched group, the damaged seedling rate was increased with the increase of work speed, the laid seedling hill rate and the floating seedling rate were also increased with the increase of work speed, but the impacts were non-significant, and the work speed had no effect on the missing planting hill rate.

Abstract:At present, acquisition of soil compaction for sowing line surface needs people to get into the field again after the operation of agricultural machinery, which is labor intensive, time consuming and belongs to non-real-time measurements. A soil compaction acquisition system for sowing line surface was designed based on ZigBee technology. A linear displacement transducer was used as measuring sensor to measure expansion amount of wheel spoke of press wheel in the system, and CC2530 was chosen as main control chip to realize module control and data wireless transmission. The main control chip CC2530 and the sensor were connected at child node to collect and store the measurement data of the sensor. The measured data of the sensor were sent to the main node. The main node received data from the child node and vehicle speed sensor, and the soil compaction measurement was realized based on mathematical model. The mathematical model was established based on the relationship between expansion amount of wheel spoke of press wheel and soil compaction to realize data acquisition of soil compaction. Field test was conducted to validate the system’s performance, which showed an average relative error of 6.3% and maximum relative error of 13.3%. The system can realize real-time acquisition and wireless transmission of soil compaction information for sowing line surface, which can provide technical support for real-time adjustment of pressure.

Abstract:A simple and easily adaptable analytical approach was developed for the hydraulic design of micro-irrigation paired tapered laterals laid on uniformly sloping grounds based on the definition position locations where the same average emitter pressure head existed in the uphill and downhill laterals. Analytical expressions of the best manifold position, inlet working pressure head, coefficient of variation by hydraulic variation and the 〖JP2〗limited length of the paired tapered laterals were separately developed by using the energy gradient line method. Three tables showed the values used in estimating the design parameters of the best manifold position, inlet working pressure head and coefficient of variation by hydraulic variation, respectively, for the common diameter ratio, 〖JP〗pressure loss ratio and velocity exponent. When the length, diameter and designed emitter flow were given, the best manifold position and other parameters of the paired tapered laterals could be directly designed without using iterative methods. When the diameters, designed emitter flow and water application uniformity criterion were provided, the limited length, the best manifold position and remaining parameters of the paired tapered laterals could be easily determined by Excel Equation-Solver in Microsoft Excel. When the length, designed emitter flow and water application uniformity criterion were provided, the design diameter, the best manifold position and the remaining parameters of the paired tapered laterals could also be easily determined in Microsoft Excel by the iterative technique. Three numerical design examples covering various conditions indicated that the proposed approach could produce accurate results for practical purposes.

Abstract:The research on simulation of water distribution of fixed spray plate sprinkler was limited. Experiments were conducted to test the droplet velocity and angle of the Nelson D3000 spray plate sprinkler under different working pressures and different nozzle diameters by using droplets photography technology. Empirical relationship was built and jet velocity and angle were related to working pressures and nozzle diameters. Based on this, a three-dimensional numerical model was developed to describe the water-drop trajectories of individual drops after their releases from the nozzle. The model was solved by multistage Runge-Kutta algorithm and output data included droplet size distribution, water distribution, kinetic energy distribution and water evaporation loss of the sprinkler. A custom computer software script was developed by using Eclipse software to implement the method to engineering case study. Hydraulic characteristics of the Nelson D3000 spray plate sprinkler under different working conditions were simulated by using the software. Single sprinkler data were used to calculate the overlapping uniformity of moving sprinkler irrigation system with different spray sprinkler spacings. Results showed that the simulated droplets distribution and water application were correlated well with the experiment data. The relative error between simulated and measured values of Christiansen uniformity was ranged from 0.04%~ 14.77%, and the software can provide technical guidance for optimal design of linear-move sprinkler machines.

Abstract:Irrigation system with center-pivot sprinkling system is considered as a system with the highest degree of automation so far. The uniformity in field is one of the important indicators to characterize performance of the center-pivot irrigation system. The off-design working condition was a common phenomenon in actual operation management. Taking Herman-Hein uniformity coefficient ( C UH ) and distribution uniformity coefficient ( D U ) as the evaluation indicators, the influence of off-design working conditions and configuration on uniformity was analyzed by field test. The results showed that C UH was reduced by 12.91%, D U was reduced by 6.35% with low pressure sprinkler D3000, and C UH was reduced by 10.50%, D U was reduced by 2.39% with low pressure sprinkler R3000 when moving speed was changed from 30% to 100%. When the inlet pressure of the center-pivot irrigation system was reduced from designed value of 0.16 MPa to 0.08 MPa, C UH was reduced by 14.04%, D U was reduced by 15.09% with D3000, and C UH was reduced by 13.37%, D U was reduced by 15.61% with R3000. When the end water spray gun was open, C UH was 〖JP〗reduced by 10.27%, D U was reduced by 14.13% with D3000, and C UH was reduced by 20.78%, D U was reduced by 23.15% with R3000. Without pressure regulator under the condition of flat ground, when inlet pressures were 0.12, 0.16, 0.20 MPa , C UH values of the center-pivot irrigation system with D3000 were reduced by 1.23%, 1.82% and 6.51%, D U values were reduced by 29.61%, 14.87% and 12.52%, and C UH values were reduced by 9.26%, 15.00% and 17.19%, D U values were reduced by 40.05%, 32.45% and 29.76% with R3000, respectively.

Abstract:In order to investigate the round jet fragmentation mechanism of impact sprinkler, the primary breakup process of impact sprinkler round jet was simulated by using geometry reconstruction interface tracking method based on VOF multiphase flow model provided by Fluent, and the primary breakup length and crusher droplet diameter were obtained under different low pressure conditions from 200~ 600 kPa. The results were compared with the high speed camera technology, and relative error between numerical simulation and experiment results of the breakup length and primary crushing droplet diameter was analyzed. The results showed that the primary breakup shapes included continuous, transitional and fragmental sections. Nozzle diameter and the inlet pressure were the main factors affecting droplet diameter and breakup length. Primary crushing droplet diameter and the nozzle diameter d （ d >5 mm）had a good correlation ( D =1.634 d , R 2 =0.912), the relative error of droplet diameter between simulation and experiment was 23.92%. The fitted relationship between Weber number ( We ) and breakup length L could predict the sprinkler breakup length under low pressure conditions. As the increase of Weber number, the breakup length increased. The results had a good significance on the theory of water round jet spray dispersion and irrigation uniformity improvement.

Abstract:The unsteady numerical simulations were carried out to investigate the transient flow features of a centrifugal pump system at startup and valve-opening processes. The scale-adaptive simulation (SAS) based on SST turbulence model was used in the simulation. The computational domain was the entire closed double-suction centrifugal pump test rig. The transient head of the pump, the pressure pulsation on the casing and the radial force on the impeller were focused on. The results showed that the predicted transient head of the pump in startup processes agreed well with the experimental data. Compared with the steady-state calculations, the transient valve-opening simulation produced a pump head which was more close to the experimental data. The transient flow rate increased significantly with the increase of valve-opening time, while valve-opening speed almost did not affect the transient head. During the valve-opening process, the pressure pulsation on the volute changed cyclically, the dominant frequency equaled to the blade passing frequency. In addition, the most dramatic change in pressure pulsation amplitude was found in the region near the tongue. The radial force on the impeller decreased with the increase of the valve opening size, and it changed with the blade passing frequency.

Abstract:With the aim to study the mechanical properties of the mixed-flow pump impeller rotor under the fluid-structure interaction, the flow field and impeller structure response in the mixed-flow pump were cooperatively solved based on the bidirectional synchronization solving method. The Reynolds-averaged Navier-Stokes equations and k-ε turbulent model were used for the simulation of the flow field, while the elastic structural dynamics equations were used for the structural dynamic response. The influence before and after fluid-structure interaction on the flow field in the mixed-flow pump was studied by comparison of pressure fluctuation and external characteristic changes at different monitoring points between flow channels. Meanwhile, the deformation of blade and the dynamic stress distribution on blade were analyzed based on the bidirectional fluid-structure interaction. The results showed that fluid-structure interaction had greater influence on the pressure pulsation amplitude at the vane outlet. After the coupled interaction, the amplitude of the head and power fluctuation were increased while the efficiency was decreased. The largest deformation location of blade occurred at the back side near to the rim of impeller with the maximum deformation of 0.062 7 mm. The maximum equivalent stress was detected on the back side nearby the outlet of the hub with the maximum equivalent stress of about 19.85 MPa. The coupling dynamic stress of the sample point was changed periodically and the amplitude value of the dynamic stress on the rim and the hub had a difference by 10 3 magnitudes, which meant that fatigue damage was easier to happen in the hub region. The results of the research provide reference basis for the structure design and reliability analysis of the mixed-flow pump.

Abstract:This research was taken on probing the internal flow pattern of relative velocity flow field in the back-swept double blades centrifugal pump. Firstly, different turbulence models, including k-ε , SST and DES were used to do unsteady numerical simulation on the particle image velocimetry (PIV) test pump whose specific speed was 70. Secondly, PIV test was done on the pump and the relative velocity flow field distribution in the impeller was got. The results showed that numerical simulation results of k-ε turbulence model were more consistent with PIV test results. By analyzing the distribution of relative velocity of the impeller whose specific speed was 70 under different flow rate conditions ( Q/Q d was 0.6, 1.0, 1.6), the variation of axial vortexes and low-speed zones in the impeller was found out. When Q/Q d was 0.6 and 0.8, there were low-speed zones and axial vortexes were opposite to rotation directions of impeller in the middle zone of channels nearby the pressure surface of the blades, and with the increase of flow rate, low-speed zones and axial vortexes decreased. Then k-ε turbulence model was used to do numerical simulation on the pump whose specific speed was 157, the results showed that the variation law of the relative velocity flow field distribution in the impeller was similar with that of PIV test pump. To explain the phenomenon, the theory of limited number blades in the centrifugal pump internal flow was introduced, which revealed the fundamental reason for the existence and development of the low-speed zones and vortexes. The research results have an important reference value for the further research of the internal flow pattern of protrusive type twisted blades centrifugal pump.

Abstract:In order to improve the hydraulic and structural performances of the double-channel pump, the uniform test design, fluid-structure interaction calculation, combination of artificial neural network and multi-objective genetic optimization method were applied. The inlet diameter, inlet width, tongue angle and diffusion length were selected as optimization variables, which were then used to produce 50 tests by using the method of uniform test design. The efficiency and maximum stress, attained through fluid-structure interaction in a volute at the design condition, were chosen as the optimization goals and then were applied to get the approximate function by BP neural network training. Special multi-objective genetic optimization strategy was designed to solve the function and search the optimized results which are called the Pareto frontiers of geometry parameters of the volute. During the process of searching the Pareto frontiers, the efficiencies, heads and stresses were chosen as constrains to get the final two optimizations. The results showed that compared with the original case, pressure diffusion effects of the optimized cases were improved obviously, backflow phenomena was reduced, and the efficiencies of cases opt1 and opt2 were increased, while the maximum stresses and the mean vibration velocities of opt1 and opt2 were depressed. The results indicated that the proposed multi-objective and multidisciplinary optimization method can obviously improve the hydraulic and structural performances of double channel pump, meanwhile, it has some reference value for optimization researches on other turbomachineries.

Abstract:In order to reduce fish mortality during passage through the large and medium-sized pumping station and maintain the balance of the ecological system, a blade strike model applied to axial-flow pump was analyzed to predict the fish passage capacity of the original pump, including blade strike probability, strike mortality and fish mortality. The theoretical fish mortality of the original pump was only 68% at the design flow point. Thus, a fish-friendly pump was designed based on the original pump to reduce fish mortality and keep hydraulic performance acceptable. Furthermore, three optimization plans were done by reducing the number of blades to two, using the streamline method of nonlinear circulation distribution to design the inlet and outlet blade angles, increasing the chord length of the blade airfoil, optimizing the profile of the leading edge to spiral and thickening the leading edge. The comparison of the three optimization plans showed that the fish mortality of plans 1 and 2 was reduced by 49% on average and that of plan 3 which was better for fish to pass through the pump was reduced by 52%. Meanwhile, the flow through the pump was simulated with ANSYS-CFX, and the numerical results such as head and efficiency were compared with the experimental results to analyze the hydraulic performance. To be specific, the head of all the plans met the operating requirements at the design flow point and the efficiency of plan 2 which corrected the inlet blade angle of plan 1 was 3% lower than that of the original pump at the design flow point, while the efficiency of plan 3 which was better for fish was 5% lower. It was noted that the fish-friendly pump was effective to reduce fish mortality even with the efficiency dropping by 5%, and it can provide a basis for axial-flow pump design of agricultural irrigation works.

Abstract:Improving the efficiency of pump is necessary for energy conservation, which also has very important significance on creating resource-saving society. When the working condition deviated from the designed condition, the flow direction at impeller outlet did not match well with the flow direction at guide inlet, which led to the efficiency drop of axial-flow pump. The inlet part of guide was changed with conventional guide, so as to improve the efficiency of axial-flow pump under off-design conditions and to broaden the high efficiency area. Firstly, the guide was divided into three parts: inlet, middle and outlet parts of guide. Based on numerical simulation and model experiment, the influence of different inlet parts of guide on the hydraulic performance of axial-flow pump was studied. The results showed that the inlet angle of guide affected the flow regime and hydraulic loss in the guide vane, which further affected the hydraulic performance of axial-flow pump. By rotating clockwise with appropriate angle under the original inlet angle of guide, the high efficiency area can be significantly broadened and the efficiency under low head and large flow-rate condition can be increased.

Abstract:With the increasing shortage of fresh water resources, reasonable exploitation and utilization of brackish water have become an important way to alleviate the contradiction between water supply and demand. Irrigation with brackish water which contains a lot of salt will affect crop growth and soil quality; therefore, taking effective measures to control the status of soil water and salt has become the basis for the safe use of brackish water. A detailed review of research development on brackish water irrigation was done, including the transport characteristics of soil water and salt with brackish water irrigation, brackish water infiltration mathematical function and soil water and salt transport model, the method of brackish water irrigation, the influence on crop growth and advances in soil water and salt regulation methods. And the scientific and technological problems on the safe use of brackish water combined with the core issues of interest were put forward in order to provide some guidances for further understanding the mechanism of effects of brackish water irrigation on soil quality and crop growth and establishing the reasonable types for using brackish water to irrigate the farmland.

Abstract:Heilongjiang Province is one of the most important commodity grain bases in China. Because the territory of Heilongjiang Province is very vast, and the natural conditions and management mode are different, the diversity of irrigation water use efficiency in different regions in Heilongjiang Province is very remarkable. In 2013, the average irrigation water use efficiency in Heilongjiang Province was only 53%, which was lower than the average level in China. Therefore, in order to study the problems of low irrigation water use efficiency in Heilongjiang Province, the spatial distribution and influencing factors of irrigation water use efficiency index system were analyzed according to the geo-statistics theory by using GIS technology. The results showed that for the variation coefficients of all the variables, the intact rate of irrigation engineering was the biggest, and the evapotranspiration was the smallest. The field water use efficiency had the greatest influence; its positive spatial autocorrelation range was 145 km. And the positive spatial autocorrelation range of irrigation water use efficiency was 124 km; the water conveyance efficiency was mainly affected by random factors, its scale of positive spatial autocorrelation was 73 km. The Kriging maps showed that the three indexes had high values in Daqing, Harbin, Suihua Cities and their vicinities. The influence of natural factors was less than that of human factors on irrigation water use efficiency. There were negative correlations respectively between rainfall and irrigation water use efficiency, field water use efficiency. Improving the proportion of irrigation water saving area and the intact rate of irrigation engineering had significant driving to field water use efficiency and the water conveyance efficiency. The study results had important significance to the improvement of water saving in different regions in Heilongjiang Province.

Abstract:The messages of crop water deficit, soil moisture and field meteorology are the fundamental data to meet the needs of water saving, good quality and high yield in modern field irrigation management. Above all, it is very important to obtain these data at the same step in real time. A field monitoring system in real-time was presented which could support the data of crop canopy temperature, environment message and soil moisture at 1 h interval. It was powered by solar panel and controlled with a microprocessor to manage the data collection and storage.The configured sensors included infrared temperature, air temperature and humidity, soil water content, soil water potential and temperature. The infrared temperature sensor was installed at the end of the cantilever arm fitted on the upright stainless steel rod. It had a 45° inclination angle of the cantilever arm to scan the temperature of underlying surface. Each time, it collected multiple spot at 36° interval above the crop canopy and went back to the original location. Therefore, the average value of the canopy temperature would be more precise than that of the single detection. The rapid locking device could adjust the cantilever arm and sensors to the suitable position following the stainless steel rod, according to the need in different crop growth seasons. After the analysis of the monitoring data, all of these could describe the refined crop actual circumstance in the field and they can be used in irrigation decision-making and irrigation management. Moreover, how to separate reasonably the surface temperature occurred from infrared data scanned and determine the dependable threshold values of irrigation decision-making indexes, are the key points in the next step.

Abstract:As the standard method for estimating reference crop evapotranspiration (ETo), FAO Penman- Monteith (FAO-PM) model incorporates both the thermodynamic aspect and the aerodynamic aspect of evapotranspiration. The model needs complete agricultural meteorological data to estimate ETo, which is considered to be a difficult task in many locations of Hexi Corridor. Meanwhile, the accuracy of the temperature-based models is insufficient. In order to solve these problems, a monthly ETo estimation model (DC-BP-NN) was proposed, which integrated air-temperature, divide and conquer (DC) method and back propagation neural network (BP-NN) with the structure of FAO-PM model. The model consisted of two BP-NN models: the radiation BP-NN model and the aerodynamic BP-NN model. In the experiments, the data was from Jiuquan Weather Station in Hexi Corridor. The reference standard was obtained by FAO-PM model. The results showed that DC-BP-NN model was superior to the other six ETo estimation models, including Blaney-Criddle model, Hargreaves-Samani model, two improved Hargreaves-Samani models, BP-NN model and BP-NN1 model (BP-NN model was based on air temperature and monthly ordinal number), with average root mean square error of 5.99 mm/month, mean bias error of 0.99 mm/month, mean absolute percentage error of 7.18% and determination coefficient of 0.988 6. Therefore, the DC-BP-NN model can be used for estimating monthly ETo in Hexi Corridor with insufficient meteorological data.

Abstract:Accurate prediction of three-dimensional (3D) spatial distribution of soil salinity can provide a scientific basis for land use planning and improvement of salt-affected soil. An area of about 70 hm 2 of saline and alkaline land in Xinjiang was taken as the study area, and a total of 1 386 data of soil salt content was obtained from different soil layers (0~200 cm) at 126 sampling sites by the method combining the electromagnetic induction technique with soil sampler. The spatial interpolation of soil salinity was made with 3D-inverse distance weighting (3D-IDW) method and the effects of vertical expanding multiples and searching points amount on the interpolation results were explored. The results indicated that it had higher average salt content and larger variations in soil layer of 0~140 cm depth than those in 140~200 cm soil depth. The average soil salt content in 0~140 cm soil layer was in the range of 1.84~2.11 g/kg, while it was 1.74~1.79 g/kg in 140~200 cm soil layer. The statistical characteristics (mean, standard deviation and coefficient of variation, etc.) of soil salinity decreased as soil depths increased. The root mean square error (RMSE) decreased with the increase of vertical expanding multiples, but it increased with the increasing amount of searching points, and the RMSE varied from 0.1 g/kg to 0.4 g/kg. When the vertical size was expanded by 300 folds and searching point was six, the optimal 3D spatial distribution map of soil salinity was obtained by the 3D-IDW method, and the results showed that the spatial distribution of soil salinity agreed well with the observed values. The soil salt content in most of the study area was less than 2.5 g/kg, and the areas close to the north and south boundaries belonged to non-salinized soil with relatively low soil salt content, while the heavy-salinized soil was mainly distributed in the central and south of the study area with soil salt content over 4 g/kg. About 80% of the study area belonged to non- and light-salinized soils, and only 20% of the study area belonged to moderate and heavy salinity soils. The main factors influencing the distribution of soil salinity were irrigation, local terrain, clay layers depths, groundwater depth and its degree of mineralization. When the difference of sampling interval in different directions was very large, it would be crucial to choose suitable expanding multiples and amount of searching points to improve the prediction accuracy of the 3D-IDW method.

Abstract:The three-dimensional (3D) spatial distribution characteristics of farmlands’ soil organic matter and total nitrogen were revealed in Xinzheng City, and the related technical methods and train of thought were provided. The methods of 3D Kriging interpolation and 3D inverse distance weighted interpolation were comprehensively used to simulate the 3D spatial distribution characteristics of soil organic matter and total nitrogen content in different depths, and their prediction accuracies were compared by using the cross validation method. The results showed that soil organic matter and total nitrogen had significantly different spatial distribution difference along the different soil depths (0~20 cm，20~40 cm，40~60 cm), the mean range of soil organic matter content in three depths varied from 11.31 g/kg to 15.48 g/kg, and the mean range of soil total nitrogen content was 0.48~0.79 g/kg, and both of them were decreased with the increase of soil depth. The amount of information that 3D spatial distribution of soil organic matter and total nitrogen expressed was more abundant, which was able to directly show the distribution information of the nutrient content in soil arbitrary section. The prediction accuracy of interpolation results of organic matter obtained through 3D Kriging method was higher than that obtained through inverse distance weighting method, and the result of total nitrogen was the same. 3D Kriging interpolation method could more veritably reflect the 3D spatial distribution characteristics of soil nutrients.

Abstract:The coupling effects of different water and fertilizer combinations on seed cotton yield, water use efficiency and net benefits under drip fertigation were studied in the field of Shihezi during the growing seasons in 2012 and 2013. Multivariate quadratic regression and normalization as well as three different target combinations were used and the optimal water and fertilizer combination that maximized the multi-objective benefits was explored. There were five N-P 2 O 5 -K 2 O fertilizer application rates (150- 60-30, 200-80-40, 250-100-50, 300-120-60, 350-140-70 kg/hm 2 ; denoted as F 150 , F 200 , F 250 , F 300 and F 350 , respectively) and three irrigation levels (W 1 : 60%ET C ; W 2 : 80%ET C ; W 3 : 100%ET C ; ET C represents crop evapotranspiration). The results showed that the coupling of water and fertilizer had significant effects on seed cotton yield, water use efficiency and net benefits. The treatment with low irrigation level (60%ET C ) significantly inhibited seed cotton yield and net benefits, while the treatment with high irrigation level (100%ET C ) significantly increased seed cotton yield and net benefits, but caused lower water use efficiency than that of the treatment with low irrigation level. The combination of irrigation with 100%ET C and fertilizer application rate of 300-120-60 kg/hm 2 (N-P 2 O 5-K 2O) in 2012 produced the highest seed cotton yield, but it did not increase the net benefits. Instead, the combination of irrigation with 100%ET C and fertilizer application rate of 250-100- 50 kg/hm 2 (N- P 2 O 5 - K 2O) produced the highest net benefits in 2012 and 2013. The quadratic regression analysis showed that the multiplication combination exhibited much smaller differences in water and fertilizer inputs in 2012 and 2013 than other combinations. The combination of irrigation with 92%ET C and fertilizer application rate of 278-111-56 kg/hm 2 (N-P 2 O 5 -K 2 O) in 2012, and the combination of irrigation with 90%ET C and fertilizer application rate of 268-107-53 kg/hm 2 (N-P 2 O 5 -K 2 O) in 2013 could maximize the overall multi-objective benefits of seed cotton yield, water use efficiency and net benefits. The results can provide new ideas for the multi-objective management of water and fertilizer in cotton fields under drip fertigation.

Abstract:In order to explore the accurate management mode of water and fertilizer supplies for young apple tree in semi-arid area field, the bucket cultivation experiment, including four levels of irrigation as 75%~85% (W 1), 65%~75% (W 2), 55%~65% (W 3) and 45%~55% (W 4) of field capacity, and three levels of fertilization (N-P 2O 5 -K 2O) as 30-30-10 g/plant (F 1), 20-20-10 g/plant (F 2) and 10-10-10 g/plant (F 3), was conducted to study the effects of water and fertilizer coupling on yield, fruit quality and water and fertilizer use efficiency of three-year old young apple tree. The results showed that controlled water and fertilizer can effectively regulate the plant and leaf area growth during bud flowering to new growth period; the highest and lowest yields were obtained by F 1W 1 and F 3W 4 treatments, respectively (compared with F 3W 4, yield of F 1W 1 was increased by 139.1%), and the determination coefficient between yield and dry mass was 0.908 5. Increasing irrigation depth could improve apple color index but it would reduce the shape index, deficit irrigation and increased fertilizer application rates both could improve apple firmness. Increased fertilizer application rates could improve the vitamin C content of apple under mild deficit irrigation treatment (F 2); irrigation depth had no significant effect on soluble solids content and soluble sugar content, but increased fertilizer application rates could improve both of them; increased irrigation depth could reduce titratable acid and improve the sugar acid ratio, but fertilization rate had no significant effect on them. High irrigation depth and low fertilization rate could get high partial factor productivity (PFP), but the maximum water use efficiency (WUE) could not be got by F 1W 1 treatment. The maximum WUE was appeared in F 2W 2 treatment with yield decreased by 7.5%, water consumption decreased by 16.7% and WUE increased by 11.2% compared with F 1W 1 treatment. Thus, F 2W 2 treatment was the best water and fertilizer application combination for the young apple tree and it reached the best water and fertilizer coupling mode.

Abstract:Plastic film mulching is an efficient agronomic method to increase yield and improve water use efficiency in arid and semi-arid regions. However, with the overuse of traditional refractory plastic film, the residual of plastic film was constantly increasing in the soil during the last recent decades, which had led to some negative impacts, such as environmental pollution and land degeneration. In order to maintain the function and reduce the negative impacts of traditional refractory plastic film, some degradable films were obligatory to take place of it. Several studies had demonstrated that biodegradable film could apply to maize and cotton cultivation instead of traditional plastic film, but few of them were dedicated to studying whether biodegradable film was suitable for winter oilseed rape ( Brassica napus L.), which is the most important oil crop in China. Three treatments, including plastic film (PM), biodegradable film (JM) and no film (CK), were conducted to systematically analyze and compare the effects of different types of film on soil temperature at 5 cm and 25 cm depths, soil water capacity in 0~100 cm depth, crop growth, root morphology characteristics, yield, quality and water use efficiency of winter oilseed rape in two growing seasons (2012—2013 and 2013—2014). The results showed that the effects of improving soil temperature and conserving soil moisture of JM were similar to PM and significantly better than those of CK （ P ＜0.05) before 150 DAS (days after sowing), but the effects were significantly lower than those of PM after 150 DAS because of the degradation of degradable film. No significant differences were found between PM and JM in plant height, leaf area index, shoot dry matter weight at different growth stages and taproot diameter of different soil depths at maturity stage （ P ＞0.05), but they were all significantly better than those of CK （ P ＜0.05). And the same characteristic was found in branch numbers, pod numbers and seed numbers of main raceme and branch raceme. Compared with PM, JM could better promote taproot to extend to deep soil layer, and effectively increase lateral root mass density in soil layer of 20~30 cm. No significant difference was found between PM and JM in saving water and increasing yield （ P ＞0.05), and yield and water use efficiency of two types of film were significantly higher than those of CK in two years （ P ＜0.05). When treated with PM and JM, the yields of winter oilseed rape were increased by 45.91% and 37.02%, respectively, and the water use efficiencies were increased by 81.68% and 53.86%, respectively. JM could also reduce erucic acid and glucosinolate content, which were harmful to human health, compared with PM. Then, from the perspective of application effects, biodegradable film could be applied to winter oilseed rape cultivation instead of traditional refractory plastic film.

Abstract:Two-year (2013 and 2014) field experiment was carried out to increase rainfall utilization efficiency and improve soil water availability for crops in arid area. A total of five treatments (CK: ridge-furrow planting without mulching over both ridge and furrow; M1: ridge-furrow planting with transparent film mulching over ridge only; M2: ridge-furrow planting with corn straw mulching over furrow only; M3: ridge-furrow planting with transparent film mulching over ridge and corn straw mulching over furrow; M4: ridge-furrow planting with black film mulching over ridge and corn straw mulching over furrow) were chosen to investigate the effects of different rainwater harvesting patterns on soil hydrothermal regimes, yield and water use efficiency of summer maize. The results showed that rainwater harvesting treatments could improve soil water storage, soil moisture content and compensation degree of soil water storage deficit significantly （ P <0.05). The treatments with mulching over both ridge and furrow (M3 and M4) were superior to the treatments with mulching either over ridge or over furrow (M1 and M2). And treatment M4 was better than treatment M3. Compared with transparent film mulching over ridge, black film mulching over ridge could reduce the temperature under film （ P <0.05 ). In contrast to no mulching over furrow, corn straw mulching over furrow could optimize the heat condition around roots. With improved soil water and temperature conditions, the treatment of ridge-furrow planting with black film mulching over ridge and corn straw mulching over furrow (M4) could increase yield and water use efficiency of summer maize to a great extent. Compared with CK, the average yield and water use efficiency of M4 in 2013 and 2014 were increased by 30.90% and 57.49%, respectively. In conclusion, treatment M4 was the appropriate rainwater harvesting pattern for summer maize cultivation in Guanzhong Region, Shaanxi Province. The results could provide valuable information for selecting efficient rainwater harvesting pattern in semi-arid regions of China.

Abstract:The effects of combining organic fertilizer with chemical fertilizer on cotton field N 2O emission flux, emission characteristic and total amount of N 2O emission were investigated by using the static chamber-gas chromatograph method under plastic-mulched drip irrigation. The four-year field experiment consisted of four treatments, including CK, CF, 60%CF+OF and 60%CF+BF (without fertilization as CK, total chemical fertilizer as CF, organic fertilizer as OF and bio-organic fertilizer as BF). The results showed that N 2O emissions with fertilizer supply were significantly higher than that without fertilizer treatment during the growing season of cotton. The order of N 2O emission on the third or fourth days after fertilization was: CF > 60%CF+OF > 60%CF+BF > CK, and a significant difference existed between treatments ( P <0.01) during each fertigation schedule with drip irrigation system. However, treatments with organic fertilizer combined with chemical fertilizer increased N 2O emission compared with chemical fertilizer treatments on the seven or eighth days after fertigation. In addition, when all irrigation and fertilization schedules were finished, higher N 2O emission flux was always observed with treatments supplied with organic fertilizer in contrast to that with chemical fertilizer application. The highest amount of total N 2O emission in the cotton growing season was found in CF treatment. Compared with CF, the treatments of 60%CF+OF and 60%CF+BF decreased N 2O emission by 3.75% and 8.37%, respectively. It was found that N 2O emission factor (EF) was also decreased by 1.39% with 60%CF+OF treatment and by 73.8% with 60%CF+BF treatment. Meanwhile, path analysis showed that N 2O emission was more closely related to soil NO - 3-N content than to NH + 4-N content.

Abstract:Biochar of peanut shells and corn stalks was prepared in the shaftless-screw-conveying continuous pyrolysis reactor at 300, 400, 500℃. Measurements of proximate analysis and calorific value were carried out to obtain the composition and calorific value of biochar. Experiment on the adsorption property of methylene blue and iodine of biochar was carried out, and the respective correlations between absorption properties and RGB, grey value were explored. Results showed that with the increased carbonization temperature, the volatile content was reduced, the fixed carbon and ash content and the calorific value of biochar were increased. Methylene blue adsorption value and iodine adsorption value of biochar made at low pyrolysis temperature were larger than those at high pyrolysis temperature. It meant that adsorption characteristics of biochar at low pyrolysis temperature were better. With the increase of pyrolysis temperature, adsorption value and RGB value of biochar were declined. There was a strong positive correlation between adsorption characteristics and RGB value, and the correlation coefficient was ranged from 0.582 to 0.944. Analogously, the correlation coefficient of adsorption characteristic value and grey value was ranged from 0.685 to 0.977, which indicated that they also had strong positive correlation. A quick detecting method of carbonization level and adsorption properties of biochar was proposed.

Abstract:Stripping combined with struvite precipitation (MAP) was used to treat the liquid digestate. The results showed that the best process parameters for stripping of the digestate from mesophilic digestion were as follows: the pH value was 10, stripping time was 8 h, gas-liquid ratio was 2 400, and filler was added. The removal rate of ammonia in the digestate was about 90%. The pH value of the digestate after stripping was about 9.2 and it was suitable for MAP precipitation method. The pH value regulation was not necessary, so it can save the cost of dosage. The removal rate of ammonia nitrogen and total phosphorus were 95% and 80%, respectively, after MAP precipitation treatment. The removal rates of COD and SS were 40% and 32%, respectively. The pH value of the effluent after MAP precipitation was about 8.3, which can meet the requirements of biochemical treatment. Meanwhile, C/N ratio of the effluent was greatly improved, which was increased from 0.7 to 10, and it was conducive to further treatment of the follow-up biochemical system. The process not only makes the digestate be processed, but also can recover the nutrients.

Abstract:In order to explore the feasibility of using electronic nose substitute for physicochemical indexes to detect the quality information change of fruit, the physicochemical indexes identification method and electronic nose identification method were used for litchi samplings, which were in six different maturing stages (p1, p2, p3, p4, p5 and p6). The physicochemical indexes sampling results showed that fruit diameter, kernel diameter and fruit weight were increased as the fruit matured continuously. During stages of p1—p4, the green and yellow of fruits were continuously deepening, the brightness degree was continuously increasing. During stages of p4—p6, the brightness degree of fruit was increased at first and then decreased, the color was obviously gone red, the yellow was first deepened and then became shallow. After extracting the feature values, the principal component analysis (PCA), linear discriminant analysis (LDA), back propagation neural network (BPNN), simple correlation analysis (SCA) and canonical correlation analysis (CCA) were used for data process. Both results of physicochemical indexes identification method combined with PCA and LDA showed that litchi’s maturing stage can be well identified, and both of their accuracies were 100%. But the distance between stages of p1, p2 and p3 were close when using PCA for analysis, which may be confused in practical classification and identification. However, litchi’s maturing stage cannot be identified when using electronic nose combined with PCA or LDA for identification. When using electronic nose combined with BPNN for classification, the accuracies of train set and test set were 100% and 92%, respectively. SCA results showed that physicochemical indexes had significant correlation with electronic nose sensors’ response except L * value during litchi’s maturing process. CCA results showed that there was significant correlation between the whole physicochemical index set and the whole electronic nose sensors’ response set. Part of physicochemical indexes had significant correlation with the whole electronic nose sensors’ response set. The results proved the feasibility of using physicochemical index identification method and electronic nose identification method for detection of quality information change of fruit. It also provided reference for using electronic nose substitute for physicochemical indexes to detect the quality information change of fruit.

Abstract:The objectives of this study were to analyze and identify volatile flavour compounds in dry-cured yak and beef by electronic nose and solid phase microextraction/gas chromatography-olfactometry-mass spectrometry (SPME/GC-O-MS). The results obtained from the electronic nose data showed that there were significant differences in flavour characteristics of dry-cured yak and beef ( p <0.05). A total of 54 volatile compounds were identified. Totally 42 and 50 volatile compounds were detected in dry-cured yak and beef, respectively. Only 38 volatile compounds detected in dry-cured yak and beef included hydrocarbons (12), aldehydes (7), alcohols (8), ketones (3), furans (2), esters (1) and others (5). Among these compounds, there were significant differences in content of 13 compounds ( p <0.05). Hydrocarbons were the major compounds in dry-cured yak, and aldehydes were the most abundant volatile compounds in dry-cured beef. Indane, hexadecane, acetic acid ethyl acetate, 2-ethylhexyl ester were detected only in dry-cured yak. 3-methyl -butanal, (E)-2-octenal, (E)-2-nonenal, 4-ethyl-benzaldehyde, 3-methyl-1-butanol, (E)-2-decen-1-ol, (E)-2-octen-1-ol, 1-nonanol, phenylethyl alcohol, acetic acid ethenyl ester, hexanoic acid ethyl ester were detected only in dry-cured beef. Lipid oxidation, Strecker degradation of amino acids and microbial metabolism played an important role in the formation of flavour in dry-cured yak and beef. The results could provide a theoretical basis for flavor quality evaluation, flavor control technology and standardization products of dry-cured yak and beef.

Abstract:The drying process is one of the most important processes in food engineering. Infrared radiation drying is a process of non-steady-state heat and mass transfer, with the change of material moisture migration and quality characteristics. Heat and moisture transfers in fruits and vegetables during drying are complex processes, and knowledge of the moisture profile is fundamentally important for industrial processes. A better understanding of the mechanism of moisture transfer would help to improve product quality and the efficiency of drying process for fruits and vegetables. Low field nuclear magnetic resonance （LF-NMR） has the technique advantages of nondestructive and non-invasive, which can be used to study the variation, distribution and flow of different phases state moisture in fruits and vegetables. The study of regularity of moisture migration was the foundation for optimizing drying parameters. With the radiation temperature of 60℃ and the thickness of the carrot slices of 5 mm, the tests of infrared drying were made. The spectra of transverse relaxation time T 2 were analyzed by using the method of low field magnetic resonance spectroscopy （LF-MRS） to explore the moisture transfer characteristics of carrot slices dried by infrared radiation （IR）. The results showed that in comparison with hot air drying, the values of transverse relaxation time T 2 of free water and semi-bound water from the process of infrared radiation drying were much greater, and the decay rate of the peak area A 0 from the process of infrared radiation drying was also faster, which meant that the drying rate and moisture gradient were much higher. The fitting equations of the peak area A 0 versus drying time was obtained with attenuation trend for carrot slices dried by infrared radiation and hot air. The results could lay a solid foundation for the further study on refinement drying and the drying technique optimizing for carrot slices.

Abstract:A single cell growth image system was used to study the growth of Pseudomonas aeruginosa single cells. A stochastic modeling process was applied to connect the growth of P. aeruginosa single cells and cell populations, which made it possible to simulate the growth of P. aeruginosa . The lag time and specific growth rate distributions with different inoculum sizes were obtained as a result of the simulation’s repetitive executions which were further introduced into the reduced Baranyi model for establishing an individual-based model. Then a stochastic growth process of P. aeruginosa was conducted by using Monte Carlo simulation. Results showed that a negative relationship existed between lag time and inoculum size. As the inoculum size increased from 1 cell to 100 cells, the lag time decreased from 2.91 h to 2.55 h at 25℃ and from 1.49 h to 0.99 h at 35℃. The coefficient of variation decreased from 29.90% to 2.96% at 25℃ and from 22.53% to 4.64% at 35℃. The specific growth rate was more affective to the temperature changes which increased from 0.70 lnCFU/h at 25℃ to 1.00 lnCFU/h at 35℃. Meanwhile, the stochastic growth of P. aeruginosa with different inoculum sizes demonstrated that the growth of P. aeruginosa showed a determinate tendency as inoculum sizes increasing, in spite of the stochastic growth property of bacterial single cells. Compared with the traditional determinate predictive modelling, studying bacterial population growth from stochastic single cell dynamics opened the door for applications in risk assessment and prediction of shelf life.

Abstract:The effects of malondialdehyde on bovine mitochondrial microstructure and metmyoglobin reduction ability were evaluated by measuring membrane permeability, malondialdehyde binding capacity, microstructure, electron transport chain-mediated metmyoglobin reduction and NADH-dependent metmyoglobin reductase activity. Compared with control groups, mitochondria incubated with malondialdehyde were increased significantly ( P <0.05) from membrane permeability and fluorescence intensity. As a result, mitochondria were swollen, mitochondrial cristae were partially disappeared and some of which were slightly vacuolated. Mitochondria incubated with malondialdehyde at pH value of 7.4 (storage condition) had a greater membrane permeability and higher fluorescence intensity ( P <0.05) than those of at pH value of 5.6 (physiological condition), which indicated that malondialdehyde reacted with mitochondrial membrane more easily under physiological condition, resulting in more serious injury to membrane. Succinate promoted the electron transport chain-mediated metmyoglobin reduction, the relative metmyoglobin contents were decreased by 21.70% and 12.87% ( P <0.05) at pH values of 5.6 and 7.4 compared with control groups (without succinate), respectively. Nevertheless, mitochondrial electron transport chain-mediated metmyoglobin reduction was inhibited when incubated with malondialdehyde, the reduction amounts of metmyoglobin were decreased by 15.68% and 3.83% ( P <0.05) at pH values of 5.6 and 7.4 compared with control groups (without malondialdehyde), respectively. In addition, NADH-dependent metmyoglobin reductase activity was also inhibited by malondialdehyde, which was decreased by 48.97% and 47.80% ( P <0.05) respectively when incubated with malondialdehyde at pH values of 5.6 and 7.4. In conclusion, malondialdehyde could injure the microstructure of mitochondria and inhibit the mitochondria mediated metmyoglobin reduction, which was disadvantageous to color stability of fresh beef. Therefore, it is meaningful to reduce lipid oxidation and maintain mitochondrial respiratory function for protecting color stability during storage.

Abstract:In order to accurately and easily determine the canopy moisture content of winter wheat during wintering period, methods of image processing and feature application based on visible light image were researched. According to the illumination invariance and color constancy principle, the combinational algorithm of homomorphic filtering and multi-scale Retinex was proposed for illumination enhancement processing to eliminate the adverse effects of natural light condition. Totally 39 initial image features which belonged to color, texture and morphology were extracted and investigated, remarkable features selection was conducted by correlation analysis and hypothesis testing. Partial least squares regression was then adopted to establish the water content detection model of canopy. Test results for two winter wheat varieties of “Huai-mai 30” and “Yan-nong 19” showed that the mean relative error and variance of the proposed method were 1.290% and 1.053, respectively, which had no obvious differences between the two varieties, and the detection errors were slightly large in sunny days and noon. The results indicated that the proposed method had high detection accuracy and good adaptability. The key issues of the field image enhancement and image feature selection were studied, and the results are helpful to improve the practicability of crop moisture detection based on the computer vision technology under the background of agricultural internet of things. Meanwhile, the canopy moisture content detection model of winter wheat during wintering period which was established based on this method has good performance, and it can provide effective technical support for winter wheat freeze-proofing and drought resistant decision.

Abstract:Forest plays an important role in the terrestrial ecosystem. Acquirement of tree height has vital significances in global ecology analysis, environmental protection, national economic construction and other related fields. In the past decades, polarimetric interferometric synthetic aperture radar (PolInSAR) has been widely treated as an advanced microwave remote sensing technique to extract vegetation information of the earth surface. However, the existing methods for tree height inversion suffer seriously from the deviations of coherence estimation, especially in the case of high-resolution SAR images. In order to improve the accuracy of tree height estimation with single-baseline PolInSAR, a new tree height extraction algorithm with improved coherence estimation based on nonlocal sample selection was proposed. The optimized interferogram was firstly acquired from four pairs of quad polarimetric SAR images with the proposed algorithm, and then the independent identical distribution samples were selected which were adopted to estimate accurate coherence, and at last the classical three-stage height inversion processing procedures were employed to obtain the vegetation height. In the experiment, multiple pairs of PolInSAR data were simulated through the PolSARPro software designed by European Space Agency (ESA). From the experiments, it can be concluded that the proposed algorithm has the capacity to maintain the boundary information effectively and the accuracy of tree height estimation was increased by nearly 5%.

Abstract:The development of precision agriculture demands high accuracy and efficiency of cultivated land information extraction. Due to the low spatial resolution of satellite remote sensing images, it is difficult to identify cultivated land of small areal extent in critical regions, which requires image data of high spatial resolution for specific or general cases. Simultaneously, unmanned aerial vehicle (UAV) has been increasingly used for natural resource applications in recent years as a result of their great availabilities, the miniaturization of sensors, and the ability to deploy UAV relatively quickly and repeatedly at low altitudes. But most UAV images lack spectral information and cultivated land information extraction which usually leads to an unsatisfactory result. Based on this, a novel cultivated land information extraction method based on transfer learning (TLCLE) was proposed. Firstly, linear features (roads and ridges, etc.) were rejected based on deep convolutional neural network (DCNN). Secondly, feature extraction method learned from DCNN was used for extracting cultivated land information by introducing transfer learning mechanism. Finally, cultivated land information extraction results were completed by the TLCLE method and eCognition software for cultivated land information extraction (ECLE). The experimental results show that TLCLE can obtain equivalent accuracy to ECLE, and it outperforms ECLE in terms of guaranteeing the integrity and continuity of cultivated land information.

Abstract:The diffuse reflection and diffuse transmission spectra of 491 cocoon samples were collected and compared for male and female discrimination. Maya2000pro NIR spectrometer was used in this experiment. Subsequently, diffuse transmission spectra within 450~1050 nm was approached by the mean center and the first order derivative pretreatment. Finally, partial least squares discriminant analysis (PLSDA) was used to make a predictive analysis for the three species of cocoon samples. As a result, the diffuse transmission spectra were better to reflect the characteristics of the components inside the chrysalis, compared with the diffuse reflective spectra. The diffuse transmission spectra could distinguish male and female well respectively for three species (sensitivity of 89.796%, specificity of 92.424% and accuracy of 90.854% for variety Shidong A〖DK〗·Hua 3xC〖DK〗·7532; and sensitivity of 96.250%, specificity of 94.253% and accuracy of 95.210% for variety Huazhong 2〖DK〗·Hua 3xC〖DK〗·7532; sensitivity of 97.260%, specificity of 91.954% and accuracy of 94.375%for variety 9〖DK〗·Fu x7〖DK〗·Xiang ). The identification results of all samples mixed together were also good with sensitivity of 94.024%, specificity of 92.917% and accuracy of 93.483%.

Abstract:In order to improve high-speed emergency steering stability of the vehicles equipped with electromagnetic clutch-electronical controlled hydraulic power steering (E-ECHPS), the feedback tracking linear reference model control strategy was proposed based on differential geometry. First of all, the nonlinear dynamics models were established, including vehicle dynamics model, tire model, steering system model and ESC model, and the correctness of the model was verified by road test and bench test. And on this basis, the affine nonlinear system state equations were deduced. Considering the nonlinearity of tires, hydraulic system and ESC, then the differential geometry theory was applied to implement precise linearization of nonlinear system, and the input and output pseudo linear systems were gained. Because the vehicle state is usually stable when vehicle is under the linear operation condition. The linear reference model with steering system under consideration was built. To achieve tracking of ideal vehicle state, the feedback tracking controller was constructed. Finally, the step steering simulation and single lane changing simulation with steering torque as input signal were carried out under controllable and uncontrollable conditions respectively. The results show that feedback tracking control strategy can improve the stability of the vehicle equipped with E-ECHPS under high-speed emergency steering condition. It provides the basis for E-ECHPS control strategy design.

Abstract:A finite frequency linear parameter-varying (LPV) controller design approach with look-ahead preview measurements was presented, and the proposed approach was applied to a multi-objective control problem of vehicle active suspension systems with time-varying velocity. Firstly, the Padé approximant method was used to deal with the preview information, so as to get the augmented system of active suspension with velocity information in the form of state-space equation. Secondly, the time-varying velocity was described by a polytope with finite vertices. As human body is fairly sensitive to the car body vertical acceleration within 4~8 Hz, and road disturbance happens only within the finite frequency domain range, the traditional H ∞ method over the infinite frequency range can not result in the optimum control plan obviously. The H ∞ norm of the car body acceleration was used as the performance optimization index to make it acquire the optimum energy gain attenuation within the concerned frequency band. In addition, the time-domain constraint conditions were guaranteed as well. The controller, whose gain matrix depended on the measurement information of the velocity, was designed in the form of linear matrix inequality (LMI). Finally, a numerical example was used to verify the reliability of the method, simulation results illustrated the usefulness and advantages of the proposed method and the designed controller can achieve better comfort than the traditional entire frequency-domain control approach and ensure that hard constraints are satisfied.

Abstract:The objective of this research was to supply theoretical bases for design and optimization of stiffness and damping parameters of active suspension system based on LQG control. Taking linear and nonlinear half car models with 4-degrees of freedom (DOF) as research examples respectively, influences of the above two parameters on active suspension system were analyzed through theoretical derivation and numerical simulation. Theoretical derivation about the linear model showed that the Ricatti Equation’s solution of the active suspension system based on LQG had nothing to do with stiffness and damping parameters. Result came as that the time domain response of the active suspension system had nothing to do with stiffness and damping parameters. Numerical simulation about the linear model revealed that each integral force made up with stiffness force, damping one and active control one were independent of the other and invariable when stiffness and damping parameters were changed, and the global damping characteristics of the active control obviously became negative from positive with its parallel damping parameter increasing. As for the nonlinear car model in general, three steps, including linearizing the control system, designing LQG controller for the linearized control system, and de-linearizing in control implement, were executed to achieve the LQG controller for the nonlinear active suspension system. The design process showed that the integral forces were not influenced by stiffness and damping parameters, because their force actions were counteracted in the above linearizing and de-linearizing steps. Thus, the above results about the linear active suspension system were also true when the active suspension system was with nonlinear stiffness and damping characteristics.

Abstract:In order to solve the negative effect of random disturbance on the height switching, the air suspension vehicle height adjustment system model was established with the air spring model. A neural network PID adaptive height adjustment controller was designed based on single neuron self tuning gain algorithm. To test performance of the controller, vehicle height control model was set up by Matlab/Simulink, and a real vehicle test platform was built with main equipment of Yaxing YBL6891 passenger car of air suspension, independently developed controller, inductance height sensor, assembled solenoid valve, debug system of electronic-controlled air suspension. Simulation and test were done in a continuous process of firstly increased and then decreased height. The simulation results showed that the height adjustment, pitch angle and lateral dip angle of PID controlled system had some strong oscillation, and the vibration phenomenon was obviously relieved in the control of the adaptive neural network PID controller. The improved height control system was relatively stable, and the control precision was improved. Vehicle test results showed that the open loop control system reached the target height with multiple oscillations. It was obvious that the control effect was not satisfactory over charge and discharge phenomenon, and the reaction time was time delay obviously. The system was stable to the target position after inflating 20 s and deflating 20 s separately. The response of the designed height controller was significantly accelerated, and stable to the target control position after inflating 5 s and deflating 3 s separately. The oscillation was significantly reduced, which was not obvious over charge and discharge. The designed controller meets the vehicle height switching.

Abstract:With energy supplies intense increasingly and environmental protection being concerned in particularly, electric vehicle gained great development in recent years with the characteristics of low exhaust emission, low noise and independent of petroleum. For electric vehicle, the onboard battery capacity is limited. Therefore, the technology of energy utilization improvement has become the research focus. An improved A * algorithm based energy optimal path planning method for electric vehicle was proposed and verified. Energy consumption cost function was built with consideration of the energy loss and recuperation along the path. New heuristic estimated energy cost function was designed to improve A * algorithm. The heuristic estimated energy cost function was proved to be admissible and consistent, which can ensure the optimality of the improved A * algorithm. According to the range anxiety problem, a feasible energy optimal path planning method was proposed with consideration of the state of charge battery, the positions and altitudes of the charging stations and destination. Simulation experiments showed that the proposed method can find the energy optimal path between the origin and the destination. When the battery energy was low, the proposed path planning method can find the feasible energy optimal path with a charging station to reduce range anxiety, which verified the rationality and feasibility of the proposed method.

Abstract:As for the special application environment of underground tunnels, an auto\|driving technique of unmanned underground scraper was proposed based on optimal trajectory tracking. The core of this method is acquiring horizontal position deviation, course angle deviation through vehicle\|sensor while the scraper is under auto\|driving in the tunnels, with deviation information being mixed to realize the tendency to zero of deviation by adjusting fore and post splice angle of scraper through real\|time control. A navigation coordinate has been set for controlling while the scraper is ready for auto\|driving firstly. Then the principle of the controlling algorithm was introduced. How to calculate the horizontal position deviation and course angle deviation was explored in detail with the laser measurement system mounted on the top of the scraper’s cab. The deviation was fused integration for the controlling data. The step of real\|time controlling algorithm was executed in order to realize unmanned driving of underground scraper with steering systematical movements controlled by output controlling voltage of the valve. Simulation test on the algorithm was carried out combined with practical application. To further verify the feasibility of the algorithm, the method was applied to the real auto\|driving control of two\|cubic diesel scraper. The experimental result shows that this control algorithm based on deviation fusion can realize the auto\|driving of scraper. The auto\|driving control system can be adjusted easily and quickly as the control system owns fast tracking speed and realizes balance between fast and smooth without great overshoot and oscillation.

Abstract:To realize the rigid dynamics modeling of a novel 4-UPS (universal joints-prismatic pairs-spherical joints)-RPU (revolution joints-prismatic pairs-universal joints) spatial 4-degree of freedom redundant actuation parallel mechanism, the Lagrange method was adopted. Firstly, the expression of kinetic energy and potential energy of 4-UPS-RPU redundant actuation parallel mechanism were educed, and the equivalent generalized force of non conservative force was analyzed. Secondly, the dynamics model of 4-UPS-RPU redundant actuation parallel mechanism was established by the Lagrange method, which was the foundation of the solution of driving force and dynamic analysis. Finally, the driving forces of 4-UPS-RPU spatial 4-degree of freedom redundant actuation parallel mechanism were solved by theoretical calculation and virtual simulation combined with examples, respectively. The numerical results obtained by solving the dynamics model of the 4-UPS-RPU parallel mechanism by Matlab were in agreement well with the virtual simulation results by ADAMS. The results can provide theoretical basis for dynamic optimization design and control of 4-UPS-RPU parallel mechanism, and also suggest a way of thinking about rigid body dynamics modeling for other redundant actuation spatial parallel mechanism.

Abstract:The parallel mechanism composition theory and the design method for topology structure of the parallel mechanisms were studied based on the basic kinematic chain (BKC) units. Firstly, a new expression for the parallel mechanism composition theory based on BKC was proposed, which had clear physical meaning. Secondly, according to the composition theory and the formula for calculating the value of the coupling degree k , 53 kinds of BKC with coupling degree k =0~3, the basic loop v =1~5, as well as their analytical expressions were presented. It was found that there were six mostly common types of basic BKCs and these basic BKCs can constitute 40 kinds of BKC topology structure which are the basic unit of parallel mechanism. A concept of virtual POC set of BKC topology structure was proposed and 40 kinds of BKC topology structures were classified according to 13 kinds of virtual POC sets with the coupling degree k , which provided the composition unit, i.e., building block of a parallel mechanism, for designing the topology structure of parallel mechanisms. Finally, a general and practical method for topology structure design of parallel mechanism was presented with BKC as the composition units, and meeting the position and orientation characteristics (POC) set as the design goal. Three examples were illustrated. The method had only three steps and no need to synthesize the branch chains and their topology structures between the base and the moving platform. Compared with the existing four main methods for type synthesis, this new method has better usability and universality.

Abstract:In order to solve the problem of kinematics modeling of parallel mechanism with sub closed-chains (PMHSC), definition of the mechanism was made. The concept of general screw was derived by discussing the motion relationship of planar four-bar linkage, and its inner connection with instantaneous equivalent screw of so-called general kinematic pair was explained. Based on the concept, the relative velocity and acceleration of any two bars in a sub closed-chain with multi-DOF were obtained, and the result was arranged to the form by using general screw. Combining the new screw representation of sub closed-chain with conventional screw form of relative motion of two rigid bodies that connected directly with a joint, the first and second order influence coefficients of single kinematic serial limb with sub closed-chain were obtained, the discussion was conducted from the serial with one sub closed-chain to multi ones. It revealed that the elements corresponding to the sub closed-chain contained the general screw, especially in the second order influence coefficient matrix, which was consisted of two parts, no longer the lie bracket form of two screws as usual. Furthermore, the universal formula that depicted the mapping from general input velocity and acceleration to screw velocity and acceleration of terminal body of PMHSC was derived. Simulation verification was conducted by using two parallel mechanisms. The first one was 6-(PRRR) US type that had planar PRRR closed loop in each leg, it’s a 1-DOF sub closed-chain; and the second one was 5-UPS/(RPRRR) RS type which had a 2-DOF sub closed-chain in the special limb. The results prove that the method discussed is correct.

Abstract:The docking mechanical design and automatic generation of dynamics for a novel reconfigurable robot was studied. A novel unit module of the mobile modular reconfigurable robot (M 2 rBot) with twelve connection ways was firstly presented, which would enable the multiple-module robot to revolute with multi-directional rotational degree of freedom. The unit module was cubic structure with one active and three passive connection surfaces with compact structure and flexible motion. By using a new type of transmission groove with a sine acceleration curve and a pin-hole connection, the docking mechanism design was also accomplished. The mathematical transformation description table for describing the double modules’ space pose transformation (DMSPT) was then established, and the forward kinematics equations of the multi-branched chain robot were automatically derived. The dynamic equations of the M 2 rBot were also automatically generated in two steps by using geometrical formulations and the recursive Newton-Euler method, which was based on the global matrix description. And the algorithm of automatic generation of motion equations was also given based on DMSPT. Finally, taking the six-module configuration with two branches as an example, the calculation and simulation analyses of automatical generation of motion equation demonstrated the feasibility and validity of the proposed method. The simulation results will be directly used in the design of the adaptive controller applied to the different configurations for the multi-branched chain robot.

Abstract:The dynamics coupling problem for the self designed “3 parallels∪2 series” mixed type NC machine tool was studied based on the kinematics and force rule of mechanism in order to ensure that the machine can have good dynamics characteristics and high quality of parts during the process of machining complex surface. A method based on Kane and Lagrange was put forward. A whole dynamics coupling model of serial and parallel mechanism was established and the coupling factors were determined. The process of machining complex part and the force of machine tool were dynamically simulated. The simulation results showed that the established dynamics model was credible and reliable, and in accordance with dynamics rules of the force and kinematics relations. The experiment was made to cut complex surface parts and the machine tool run smoothly with fast speed. There was no large singular position and coupling error. The surface roughness results showed the kinematics accuracy of the machine tool and interference fringe proved the force uniform of machine tool. As there was no singular coupled vibration and collision, it was proved that the theoretical analysis was correct. The method and process can solve dynamics coupling problem actively, real-timely and effectively of 3PTT-2R NC machine tool, and lay a foundation for accurate control of NC machine tools.

Abstract:High speeds and acceleration create high reactive forces between the moving mass and the stationary bodies of the ball screw feed drive system and excite the structure which causes undesired vibrations. Therefore, it is necessary to have an accurate dynamic model of the feed drive system for machine design and controller tuning. An optimized dynamic modelling and simulation method of a ball screw feed drive was presented based on the lumped mass model. The mass and the rigidity of the ball screw feed drive basis were considered in this new model and the calculation method of the equivalent parameters was optimized. Simulative and experimental examinations were conducted based on an X -axial ball screw feed drive system on a MAG machining center and the presented method was proved to be accurate because of the same eigenfrequency number and the limited error (less than 5%) between the simulated and measured eigenfrequencies of the ball screw feed drive system. Based on this model the vibration characteristic of a ball screw feed drive system was studied. The simulation results showed that the natural frequency change caused by the nut position change affected the stability of the servo system, and the backlash of feed drive system encouraged the components to produce high-frequency vibration and made the servo system unstable.

Abstract:The structural optimization design of axial permanent magnet coupling (APMC) was investigated. Firstly, based on the linear layer model, the mathematical optimization model of APMC was established. The key structural parameters (air gap and thickness of copper disc) of the established model were selected as the design variables. And the lowest cost, the maximum output torque and the minimum eddy current loss were chosen as the optimization goals. Secondly, the chaotic search and self-tuning weights were introduced into the cuckoo search algorithm, and an improved cuckoo search algorithm was proposed. In addition, multi-objective problem was converted into single one by using fuzzy theory, which was solved by using improved cuckoo search algorithm. Finally, the curve of eddy loss along with rotation speed and the curve of output torque along with slip were drawn by using ANSYS simulation, respectively, and the performances of improved APMC were verified. An experimental platform was built to test the prototype, of which the output torque and efficiency under different working conditions were tested. The results showed that the proposed method was superior to the other methods, making the cost and eddy current loss decrease by 9% and 10%, respectively, and the output torque increase by 15%. The expected results were derived, which indicated that the proposed optimization method had high precision and strong engineering practicability. The method provides a feasible preliminary design for axial permanent magnet coupling, and can be applied to the field of other electromagnetic devices.

Abstract:Organic Rankine cycle (ORC) is a promising approach to utilize the low grade heat sources. For basic organic Rankine cycle (B-ORC), working fluid circulating pump is one of the main components with low efficiency and suffering cavitation problem. To improve the situation, organic Rankine cycle with booster pump (BP-ORC) was proposed, and an experimental setup was constructed. A stainless steel magnetic drive pump was used as booster pump which was installed between circulating pump and reservoir. Dichlorotrifluoroethane (R123) was selected as working fluid, and a scroll expander was used to produce shaft work. At the heat source temperature of 140℃, comparative experiment was organized to compare the stabilization and effectiveness between B-ORC and BP-ORC. The results showed that booster pump can overcome the cavitation of circulating pump effectively, resolve the deviation of working fluid mass flow rate obviously, and reduce the scale of oscillation of mass flow rate at the same time. The intension of oscillation was reduced from ±22 kg/h to ±2.1 kg/h. The maximum shaft power of expander was raised from 2.11 kW to 2.35 kW when the frequency of circulating pump was 7 Hz. The power consumption of booster pump was about 0.3 kW. Net thermal efficiency was raised from 5.78% to 6.16% when the booster pump consuming power was ignored, while it was fallen to 5.27% when the booster pump consuming power was considered. The results identified that the reasonable selection of booster pump is necessary.

Abstract:The calculation models of flow and combustion were established for a segmental catalytic micro channel incorporated with detailed hydrogen-oxygen gas-phase and surface reaction mechanisms. The aim of the study was to realize the effects of surface catalyze reaction on gas-phase reaction at different flow velocities, equivalence ratios and channel heights. The results showed that the surface catalytic reaction strengthened gas phase reaction in the downstream of catalytic segment along with the increase of inlet flow velocity. The heat released from surface reaction resulted in a temperature gap between the inner up and down walls, and this temperature gap was increased with the increase of inlet flow velocity in the domain of the front 2 mm, but it vanished gradually because of the dominant gas-phase reaction in the downstream. Due to the competition of OH radical between two reactions, a fit equivalence ratio about 1 contributed to enhancing the gas phase reaction. On the contrary, surface reaction obviously restrained the gas phase reaction when the fit equivalence ratio was too small or big. It restrained gas reaction in the domain of catalyze surface and increased the outer wall’s temperature when keeping a constant mass flow rate and a lower height channel. But it had little influence on surface reaction.