Abstract:In order to improve the precision of path tracking, a self-tuning model control method for farm machine navigation was presented. The thought of the two-level control was induced to design the navigation controller. As the first level controller, the nonlinear kinematics model and feedback linearization theory were used to design the control law, and counting formula of the system controlling quantity was given. In order to solve the imprecision problem of the nonlinear kinematics and improve the stability of the navigation system, a second level controller was needed. As the second level controller, the fuzzy controller used the fuzzy control method to adjust system control quantity of model controller online and adaptively. The results of the path tracking experiment for the agricultural machine showed that the control method kept the advantages of model controller for tracking the straight and solved the problems of model controller in a curved path tracking. When it ran at the speed of 1.0m/s, the maximum lateral deviation of straight path tracking was less than 0.0649m, the maximum lateral deviation of curved path traced was less than 0.1857m.

Abstract:A pear orchard scene segmentation based on conditional random fields (CRFs) was proposed. The CRFs modeled posterior probabilities directly, and had an ability to fuse context information of images. Therefore, it was a suitable method to solve images segmentation of the pear orchard scene whose structures are often very complicated. Firstly, labeled images of the pear orchard scene were segmented into superpixels, and feature vectors of the superpixels and their corresponding labels were integrated into a label database as training samples. Secondly, unlabeled images of the pear orchard scene were also segmented into the superpixels, and their features and spatial relationships between these unlabeled superpixels were modeled by using the CRFs. Moreover, parameters of the CRFs model were obtained by taking the label database as the training samples. Finally, labels of the unlabeled superpixels were inferred through the maximum posterior marginal (MPM) algorithm. The experimental results showed that the proposed algorithm could provide more accurate segmentation results of the pear orchard scene compared with the mutual K-nearest neighbor method (MKNN). 

Abstract:In order to accurately segment diseases and insect pests on crop leaves, a Gaussian mixture model (GMM) based texture difference expression method and an accurate segmentation approach based on improved distance regularized level set evolution (DRLSE) were proposed. Considering that crop leaf generally has a certain texture feature, GMM was used to characterize the leaves texture feature, and improved DRLSE which took full advantage of texture difference information between objects and background, was employed to get the accurate contour of diseases and insect pests. Firstly, the texture feature of leaf sampling area was modeled by using GMM. Secondly, the texture difference between the pixels in the diseases and insect pests’ area and the sampling area was calculated, and the texture difference image was obtained at the same time. Thirdly, the initial contour for DRLSE was obtained by Otsu and morphologic post processing. Finally, the contour of diseases and insect pests was evolved accurately with texture difference guided DRLSE. The experimental results show that the diseases and pest contour can be obtained accurately with the introduced method and also can provide the basis for the subsequent identification and prevention of crop diseases and pests.

Abstract:Identification and sorting technology of egg embryo in biological vaccines production with the method of multi-information fusion was researched. The regularity cognition was obtained by the researches on image features, degradation of temperature and variations of transmittance of different types of egg embryo, which indicated that there were many thick radial blood vessels in living egg embryo image and few thin fractured blood vessels in weak egg embryo image, no blood vessels in dead egg embryo image and obvious black blocks features in polluted egg embryo image were found. The rates of temperature decay of living embryo, weak embryo, polluted embryo and dead embryo increased successively, and the transmittance of living embryo decreased gradually with hatching time increase while the variation of the transmittance of other egg embryo were comparatively lesser. The BP neural network model was established to do the egg embryo condition identification based on the information fusion of images, temperature and transmittance. Finally, 80 eggs were randomly selected to collect the information of images, temperature and transmittance to do the verifying experiment, the eggs were hatched six days and taken out from the 37.8℃ incubator and placed under normal room temperature for ten minutes. The result indicated that the identification accuracy of the system was 96.25%, which was increased by 6.25%, 13.75% and 8.75%, respectively, compared with that only using image, temperature or transparency sensors. 

Abstract:In order to improve the sprinkler application rate and kinetic energy distribution of fixed spray plate sprinkler, a dynamic water pressure based sprinkler test platform was built. A Nelson D3000 nozzle was selected and then the water application rate and kinetic energy distribution in radial direction were tested under both dynamic water pressure in trigonometric type and constant pressure. The results showed that the test platform could well meet the demands of dynamic water pressure. The wetness area of Nelson D3000 nozzle in radial direction increased from 0.85~1.36m to 2.55~4.42m. The maximum value of sprinkler application rate was reduced by 67.6%~78.4%, and the maximum value of energy density flux was reduced by 52.9%~71.6%. Both the sprinkler application rate and kinetic energy distribution of Nelson D3000 nozzle were effectively improved.

Abstract:To adjust the elevation angle of sprinkler and reduce the effect of wind on water distribution, a set of adjustment device which fixed on the original structure of the sprinkler was developed. The adjustment device consisted of support bar, limited rod, flexible metallic hose, internal thread hollow shaft sleeve, set screw and adjusting screw. Four elevation angles of sprinkler nozzle (13°, 18°, 23°and 30°) could be adjusted and fixed respectively. To evaluate the hydraulic performance of the sprinkler with adjustment device, a series of indoor experiments were conducted. The results showed that the characteristics of single sprinkler with adjustment device changed evidently at different elevation angles. When elevation angles of the sprinkler were 23° and 30°, the combinatorial uniformity coefficients were larger than that at 13° and 18°, so it was more practicable in combinatorial sprinkler irrigation. Under different working pressures of 0.20, 0.25 and 0.30MPa, the average sprinkler irrigation intensity increased with decrease of sprinkler elevation angle. Distribution of sprinkler water in the spraying end was more uniform at elevation angle of 23° than that at other angles in which the distribution of sprinkler water changed greatly and average sprinkler irrigation intensity increased accordingly. So decrease of elevation angle could reduce the effect of wind on water distribution effectively. On the other hand, because of the drastic variation of distribution of sprinkler water, the elevation angle of the sprinkler could not be too small. The rotation deviation of the adjustment device of sprinkler was less than ±10%. The test results indicated that it reached the indexes of JB/T 7867—1997.

Abstract:Based on computational fluid dynamic (CFD) and particle image velocimetry (PIV) technology, factor analysis method was used to study the effect of bottom clearance of flare on the flow characteristics of pumping system, and the occurred location change of submerges vortex and the submerged vortex core trajectory were analyzed emphatically. The results show that the occurred location of submerges vortex change along with the change of bottom clearance of flare, and the occurred location of submerges vortex along with the change of operating condition in the same bottom clearance of flare. With the decrease of bottom clearance, the velocity gradient varies greatly in the zone of the flare bottom. The bottom clearance h=0.8D was strongly suggested and the anti-submerged vortex device should be taken for this kind of box-type inlet passage. The velocity distribution contour of test section by PIV was similar to that by CFD, and the trajectory of submerged vortex by CFD was similar to that by PIV. It was also proved that the measured results showed great agreement with the calculated ones.

Abstract:A centrifugal pump with specific speed of 74 was studied. Hydraulic performance test was done firstly, and the result showed that the head changed little with the flow reduced when flow was less than 18m3/h. In order to research the flow instabilities under the above H—Q curve, PIV technique was adopted to discover the onset and development rule of unstable vortex within the impeller. The results showed that the flow was separated at 0.6QBEP, developed at 0.4QBEP and spread almost the whole impeller passage at 0.1QBEP. In addition, flow in the passage near the tongue was the most unstable, and the vortex was also occurred in this passage firstly by comparing with rest of passages. With the flow rate decreasing, the vortex on the pressure side was increased and converged to a large-size vortex which spread to the outlet of passage and moved to the centre area of the passage in the end.

Abstract:In order to analyze the internal flow characteristics of a double volute centrifugal pump, the CFD software CFX was applied to simulate the unsteady flow among different working conditions based on standard k—ε turbulence model and standard no slip mesh model. The pressure fluctuation characteristics under different working conditions on flow channels both in the impeller and the volute were obtained. The results showed that pressure pulsation of each monitoring point was relatively large and uniform under the condition of low flow rate. Pressure fluctuation near the edge of impeller outlet was 5~8 times stronger than that in other region of the impeller. In the case of rotating 30 steps (90°) and 90 steps (270°) during four working conditions, the value of pressure reached to maximum. Pressure fluctuation in the inner flow passage was stronger than that in the outer flow passage of the double volute, and it reached to maximum in the tongue of the double volute. The pressure fluctuation decreased firstly and then increased near the tongue and outlet of volute in the large flow rate due to a certain back-flow. It can be concluded from fast Fourier transform that the frequency of the impeller and its multiples were main frequencies of pressure fluctuation which presented a decreasing tendency.

Abstract:In order to clarify the cavitation near the clearance outlet, firstly, the detailed dependence checks were done to ensure the calculation accuracy. Based on these, the unsteady calculations including cavitation were done and the cavitation near the clearance outlet under NPSHr condition was predicted. Results showed that the static pressure presented a periodical non-uniform distribution with frequency of 2.27 times of the rotation frequency due to the rotation effects near the wear-ring. The cavitation occurred at the low-pressure region which located at the circle whose center was the center of the inlet pipe and the radius was slightly smaller than the intersection radius of the inlet pipe and the wear-ring outlet. The pressure pulsation near the wear-ring outlet was influenced by the impeller rotation and cavitation, it had two kinds of frequency, the first one was the blade passing frequency and it’s multiple, the second one was caused due to the periodic changes of cavitation and the frequency was an integral multiple of cavitation frequency. The conclusion was helpful to get a better understanding of the cavitation characteristics in the centrifugal pump near the wear-ring clearance.

Abstract:To test the effects of compound application of organic and chemical fertilizers on tea plants, five treatments of compound fertilizer mixed with organic vinegar residue fertilizer and chemical fertilizer were set to study their influence on tea growth, yield and quality, and soil nutrient as well. The treatments were set as organic fertilizer of 100% (100% O), chemical fertilizer of 100% (100% C), 70% O+30% C, 50% O+50% C, 30% O+70% C and no fertilizer as control (CK). The result showed that all the fertilization treatments contributed to tea yield and quality and soil nutrient contents, but the effects varied with different treatments. The treatment of 70% O+30% C was the most significant in yield increase, which was 276.91%, the treatment of 30% O+70% C was the second and the treatment of 50% O+50% C was in the middle; the growth indexes such as the length of new shoot, leaf area, 100 bud weight and bud density, and the quality indexes such as tea polyphenols, amino acid, caffeine and water extract were also the highest when the treatment of 70% O+30% C was applied. The more organic fertilizer was applied, the more alkali-hydro nitrogen, available phosphorus and available potassium were increased in the soil of tea fields, and the treatment of 100% O ranked the first place and the treatment of 70% O+30% C took the second place, between which there was no significant difference. Comprehensive analysis showed that the treatment of 70% O+30% C was optimal and worthy of application in tea fields.

Abstract:Carbon and water fluxes of cotton field with plastic mulched drip irrigation were measured using an eddy covariance (EC) technique in 2009, 2010, 2012 and 2013 at Wulanwusu experimental station, which was a representatively agricultural oasis in northern Xinjiang. The diurnal pattern of mean monthly gross primary production (GPP) and net ecosystem exchange (NEE) showed an obviously sinusoidal dynamic from June to September, whilst that of ecosystem respiration (Res) stayed low and stable between daytime and nighttime. The response of daytime hourly GPP to net solar radiation (Rnet) could be expressed by a rectangular hyperbolic function. The variations of maximal assimilation rate (A) were followed changes in LAI, and the peak value occurred in July. The seasonal variations of GPP and NEE were close to the cotton phenology, and they almost reached the peak value in July. However, seasonal variations of Res didn’t follow that of LAI, and the maximum value occurred nearly one month earlier than that of LAI. Seasonal NEE showed a carbon sink from squaring to harvest period, whilst it indicated a carbon source before the squaring time as well as after the harvest time. The cumulative GPP averaged 816.2gC/m2 during the growing season (from April to October), and more than half of GPP was partitioned into NEE (meanly -478.6gC/m2).

Abstract:In order to investigate the dynamic relationship of cotton between leaf area index (LAI) and accumulated total production of thermal effectiveness and photosynthetically active radiation (TEP), plot experiments were conducted with Shiza2 cultivar and Xinluzao43 cultivar and four nitrogen levels were imposed. The dynamic changes of LAI and TEP of the whole growth period in four nitrogen levels were quantificationally analyzed according to normalization process, and relative LAI (RLAI) and relative TEP (RTEP) were dynamically simulated using the Curve Expert. The results indicated that eight analog models showed a better fitting effect and the rational function model which had strong biological significance and a high determination coefficient (R2=0.895) can be more accurate to describe the cotton LAI dynamic correlation than others. The model was checked out with five nitrogen levels from field tests and three different ecological points separated with the high-yield field trials, the verification results showed that the confidence α were 0.169, 0.077, 0.171; determination coefficient R2 were 0.948, 0.964, 0.971; consistency coefficient CC were 0.987, 0.991, 0.989; relative error RE were 6.493%, 4.371%, 7.540%; root mean square error RMSE were 0.188, 0.143 and 0.227m2/m2. The results indicated that the RLAI dynamic model based RTEP description can accurately reflect the dynamic changes in the cotton groups. Further analysis of the effect of regulation and control of cotton groups LAI characteristics parameters of different nitrogen levels showed that the nitrogen usage amount affected the whole groups LAI dynamic regulation, especially the mean LAI; maximum LAI and ratio of the two characteristic parameters. It could be important indicators of improving the cotton leaf blade photosynthetic characteristics and the production.

Abstract:A greenhouse muskmelon variety was grown under mulched drip irrigation to investigate the effects of different water and nitrogen levels on nitrogen nutrient absorption, distribution and yield of greenhouse muskmelon, soil NO-3N distribution and accumulation, which can provide theoretical basis for high water-fertilizer use efficiency and the optimal regulation and control of greenhouse muskmelon. Muskmelon plants were subjected to three irrigation levels and three nitrogen levels, and totally were 9 treatments. Treatments were completely arranged according to randomization. Results showed that the above-ground dry matter accumulation and amounts of N accumulation were obtained in the treatment of W2N2 and the content of soil NO-3N was the highest in 0~15cm soil layer after the muskmelon harvest and the content of soil NO-3N decreased with the increase of soil depth. The accumulation of 0~60cm soil NO-3N increased with the increase of nitrogen rate and decreased with the increase of irrigation amount. The yield of muskmelon increased with the increase of irrigation amount and nitrogen rate except for the treatment of W3 and N3. It was concluded that the irrigation level W2 and nitrogen level N2 could be recommended as the best combination of water and nitrogen which can improve muskmelon yield in the production of muskmelon under drip irrigation with plastic film mulched in the experimental area.

Abstract:With the large application of agricultural plastic film, the residual of plastic film was continuously increased in soil during the last few decades. The application of biodegradable film could solve the environmental pollution because of its totally degradable property. Agricultural film was specially required in arid and cold region, so it was very important to study and get the suitable degradable film for sustainable agricultural development. Five treatments including plastic film, biodegradable film (thickness 0.012mm), biodegradable film (thickness 0.008mm), liquid film and no film (CK) were used to compare the effects of different types of film on soil temperature, soil water potential, crop growth and yield. The results showed that there were no significant differences between plastic film and biodegradable film treatments during early crop growing period (June and July), whereas the soil temperature in 0~20cm soil layer for the treatments of biodegradable film was a little lower than plastic film treatment because of film’s degradation, especially for the treatment of biodegradable film of thickness 0.008mm during the end of crop growth. However, the soil temperatures of liquid film and no film treatments were obviously lower than plastic film treatment. The results for soil water potential among different treatments were similar, and it was very close between plastic film and biodegradable film treatments, but the maximum soil water potential was shown in 0~20cm soil layer during the end of September, and there was significant difference between plastic film and biodegradable film treatments (p<0.05). No significant differences were found between plastic film and biodegradable film treatments for the crop height, leaf area index (LAI), dry matter of leaf, stem, flower dish and yield. However, both of these two treatments were clearly better than liquid film and no film treatments. Thus, it was feasible to replace plastic film with biodegradable film for mulching in arid and cold region.

Abstract:Accurate estimation of reference evapotranspiration (ETo) is the basis of irrigation water management. When weather data is lacking or only temperature data is available, ETo has to be estimated with limited weather data. An attempt was made to estimate daily ETo by using temperature-based and radiation-based methods, i.e., Penman—Monteith temperature method (PMT), corrected PMT method (PMTcor), HG equation, modified HG (HG—M1, HG—M2), Thornthwaite equation and Irmak equation, corrected Irmak equation (Irmakcor), McGuinness Bordne equation (M—B). These equations were evaluated against the PM model in Xinxiang. When using the PMT method to estimate ETo, the adjustment of Tmin for estimating Tdew was adopted, when using the Irmak equation, the multiple linear regression was adopted to modify this equation. Results showed that the performance of PMT, PMT-cor, HG, Irmak and Irmak-cor methods were similar, which got the best ETo estimation with coefficient of regression (b) and determination (R2) around 1.0, relative error RE＜20%, index of agreement d＞0.95, five models fitted the standard of good model. Crosscomparison of the five good models showed that Irmak-cor equation was the best method which had the highest accuracy in all models with b=1.00, R2=0.98, RMSE=0.17mm/d, RE=7%, d=1.00; secondly, the Irmak equation, with b=1.03，R2=0.95, RMSE=0.31mm/d, RE=12%, d=0.99. The precision of five models was in turn as Irmak-cor, Irmak, PMT-cor, PMT and HG equation. When considering the precision of the formula, the Irmak-cor equation was the best-suited equation for estimating ETo among the methods, but it was likely more appropriate to use HG equation, due to it was easy to compute and no requirements of temperature adjustment.

Abstract:Better understanding of soil fertility and nutrient balance in soil-crop systems is important for rational fertilization, refining agricultural management practices and improving utilization efficiency of water, soil and fertilizer resources. Traditional statistics, geostatistics combined with GIS technology were used to evaluate the spatial and temporal variability of soil organic matter (OM), available nitrogen (AN), available phosphorus (AP) and available potassium (AK) in Weibei rainfed highland from the 1980s to 2010—2012 based on the data from the second national soil survey and the cultivated land productivity investigation and quality evaluation project. Meanwhile, the current situation of fertilization and nutrient balance in main cropping systems was analyzed based on the information from household surveys of the national soil testing and fertilizer recommendation project during 2010 to 2012. The results indicated that the current average contents of OM, AN, AP and AK in soil were 12.9g/kg, 59.4mg/kg, 15.4mg/kg and 164.2mg/kg, respectively. Compared with 1980s, the OM, AN and AP contents in soil have been increased by 22.0%, 37.9% and 129.8%, respectively, and AK was kept stable. Compared with the rational fertilizer application rates, the ratios of households using excessive nitrogen (N) inputs in wheat, maize and apple were 89%, 69% and 74%, and the ratios for phosphorus (P) were 75%, 49% and 52%, respectively. The ratios of households using insufficient potassium (K) inputs in wheat and maize were much higher, which were 76% and 67%, respectively. Meanwhile, the ratios of households using excessive and insufficient K inputs in apple were 40% and 48%, respectively. Significant surpluses of N and P in wheat, maize and apple cropping systems were observed, with an average of 116, 111 and 655kg/hm2 for N, 88, 56 and 357kg/hm2 for P, respectively. N and P practical surplus rates were much higher than their permissible surplus rates, indicating that N and P surpluses in this area were greatly exceeded their rational ranges. K was in deficit in wheat and maize cropping systems, with an average deficit of 73 and 93kg/hm2, respectively, which were both within their permissible scopes. K was in surplus in apple cropping system, with an average of 283kg/hm2, which was 145 percentage points higher than its permissible surplus rate. From the perspective of food safety and environmental protection, inputs of N and P in this area should be reduced. By contrast, input of K should be increased to maintain high and stable cereal crop yields.

Abstract:In order to investigate the effect of land reclamation time and soil bulk density on soil hydraulic parameters, a study combined laboratory experiments with theoretical analysis was conducted to examine the changes of soil saturated hydraulic conductivity, soil water characteristic curve, and diffusivity with two different bulk densities of four reclamation soils. Results showed that the land reclamation time had significant effects on soil particle component, soil structure, sodium salt content, and so on. Soil saturated hydraulic conductivity decreased with the increase of land reclamation time, while water-holding capacity and soil moisture diffusivity increased with the increase of land reclamation time. Soil saturated hydraulic conductivity, diffusivity and soil water content under the same suction force decreased with the increase of bulk density. With increasing reclamation time, the influences of soil bulk density change on soil hydraulic parameters became more obvious.

Abstract:Heqing basin is a typical dam agriculture area in Yunnan province in Southwest China, which was selected as the study area. 114 soil samples (0~10cm) were collected in metal cylinders (diameter 5cm; length 5cm), and soil bulk density (SBD) and soil water content (SWC) were measured gravimetrically. The classical statistical analysis methods of ordinary Kriging (OK) and ordinary Cokriging (OCK) were used to study the spatial variability of soil bulk density. Results showed that the values of soil bulk density ranged from 0.74g/cm3 to 1.60g/cm3, with an average of 1.25g/cm3. The low value of soil bulk density distributed in north and south regions in the study area, while the high value distributed in mid-east region, which were influenced by soil type, texture and land use in the dam area. Soil bulk density was highly correlated with soil water content and the correlation coefficient between them was -0.686. The spatial variability of soil bulk density was studied using OCK method with soil water content as auxiliary variable, and the prediction accuracy was enhanced by 36.61%.

Abstract:Since the stable isotope composition was widely used as tracers in the process of pollutant migration and transformation, stable isotope analyses of carbon and nitrogen in paddy field sampled from Nanjing irrigation area were studied. The results showed that delta C13 values of particulate organic matter (POM) were between -31.5‰～-24.3‰, with an average value of -27.7‰. The stable carbon and nitrogen characters of particulate organic matter (POM) varied greatly in different sites. The isotopic signatures of both POM and zooplankton remained sufficiently distinct from each other throughout the period of study. Delta C13 values of particulate organic matter and zooplankton showed some seasonal variation, reflecting higher values during spring and summer than autumn and winter. But delta N15 values were more constant except the last sampling. The spatial and temporal variations of delta C13 values were similar between zooplankton and POM, which meaned that POM may be the main resource of zooplankton. The minimum delta N15 value of POM was 3.1‰ and nitrogen fixation could be ignored in the study area. This study was the first to quantify such a seasonal switch in zooplankton and particulate organic matter in paddy field.

Abstract:As the starting point to the research of water-salt transport rules under the condition of film hole furrow irrigation, water-salt distribution under brackish water film hole furrow irrigation was studied systematically by experimental observation and numerical simulation. Infiltration of film hole furrow irrigation under the condition of laboratory test was simulated with HYDRUS—3D model. Using HYDRUS—3D model to simulate the infiltration of film hole furrow irrigation was a method with relatively higher reliability. Simulation scenarios with three holed ratios and four irrigation water amount levels were designed on this basis. The water-salt transport rules of different simulation scenarios were explored, so as to provide reference for the design of film hole furrow irrigation. Simulation results showed that when irrigation amount changed from 450m3/hm2 to 900m3/hm2, the soil salt in 0～40cm soil depth could be restrained in a short time, and the salt rejection rate of 3%, 6% and 9% holed ratios were all above 46%, which could provide good environment for the growth of peanuts. Under the condition of film hole furrow irrigation, irrigation amount should not be less than 300m3/hm2 for achieving the effects of economizing water and reducing salt content. The research results could both provide theoretical and technical basis for popularization and application of brackish water film hole furrow irrigation technology and provide reasonable soil secondary salinization prevention measures as well as scientific basis for water management in the field.

Abstract:The water flow velocity over hillslope is an important hydraulic parameter. A series of comparative flume experiments were conducted to study the flow velocity with pulse boundary model method and dye tracer method, along both the frozen slopes and non-frozen slopes. The flume used in the experiments was 3.8m long, 0.2m wide, and 0.08m high, with soil taken from Koxkar Glacier basin in Akesu, Xinjiang Automous Region. The experimental soil was packed evenly into the flume to a bulk density of 1.0g/cm3 and a thickness of 5cm. The packed soil was saturated before frozen prior to each experiment. The experiments involved three flow rates (12, 24 and 48L/min) and three slope gradients (5°, 10° and 15°). The velocities measured by pulse boundary model method increased exponentially with distance from the solution injection location, before becoming steady. The distances for measuring flow velocity with pulse boundary model method on the frozen slope were calculated from the relationship of velocity and distance. The calculated results showed that the minimum distances for measured velocity with an error less than 5% were 1.7~2.7m and those for an error less than 10% were 1.4~2.1m from the injector under the given flow rates and slope gradients. The velocities, over frozen slopes, measured by the pulse boundary model method under the given experimental conditions ranged from 0.45m/s to 0.98m/s, increased with slope gradients and flow rates, which were 1.43 times of those over non-frozen slopes. The velocities over frozen slopes, as measured by the dye tracer method were 3%~20% higher than those measured by the pulse boundary model method under different slope gradients and flow rates. Those over non-frozen slopes measured by the dye tracer method were 6%~35% higher than those measured by the pulse boundary model method. The result is useful and important to understand the hydraulic dynamic process of frozen soil erosion.

Abstract:Raindrop-impact-induced erosion as the beginning of soil erosion had significant impact on the whole erosion process. In order to systematically understand the effect of rainfall characteristics on splash characteristics of Beijing, artificial rainfall experiment was conducted. Rainfall intensity, rainfall kinetic energy and duration of raining time were chosen to analyze the splash regulation. The characteristics of splash distance and fragment size distribution were also tested. The results of rainfall caused splash erosion indicated that during the splash erosion process, the quantity of splashed soil particles in down slope had a significantly larger amount than that of the up slope, while the quantity of up slope was the smallest of all the four directions. The amount of total splashed particles and net splashed particles were all positively related to rainfall intensity. Quantity of splashed soil particles was significantly positively correlated to rainfall intensity and rainfall kinetic energy, respectively. The quantity of splashed soil particles was exponentially increased with rainfall intensity. And a linear function could show the relationship between quantity of splashed soil particles and rainfall kinetic energy. The rate of total splashed soil particles decreased exponentially with duration of raining time. The splashed fragments distributed mainly in 0~10cm of the study plot, which accounted 45.4%~57.75% of the total splash erosion, while that in 50~60cm of the plot was less than 1.75%. The quantity of splashed particles was exponentially decreased with splash distance. The splashed fragment size distribution showed that fragments smaller than 2mm were transported by raindrop impacts. The mass percentage of splashed soil particles with size of 0.02~0.05mm and 0.05~0.2mm was similar to that of the texted soil. The content of fragments with size less than 0.02mm was higher than that of texted soil, while the content of fragments with size of 0.2~2mm was lower. The mass percentage of particles with size of 0.05~0.2mm was the most, while the mass percentage of particles with size less than 0.002mm and size of 0.05~0.2mm were the least. Theoretically，the quantity of splashed soil particles with certain fragment size distribution of soil reached the peak. The percentage of splashed soil particles with size less than 0.05mm increased with rainfall intensity, and then almost kept the same. The percentage of splashed soil particles with size of 0.05~0.2mm was negatively correlated with rainfall intensity. The percentage of splashed soil particles with size of 0.2~2mm increased with rainfall intensity. Splashed fragment size distribution kept the same when rainfall intensity was large enough. The amount of five kinds of splashed soil particles were all exponentially decreased with splash distance with high correlationship respectively, which was the same as that of total amount of splashed soil particles. Mean size distribution decreased with splash distance under the same rainfall intensity. Mean size distribution was significantly higher under 121.4mm/h rainfall intensity than other three rainfall intensities. The changing rate of mean size distribution was large in 0~30cm from the study plot, and the changing rate decreased as the splash distance increased.

Abstract:There is a significant spatial imbalance in the water resources distribution in China and the study on it is very important for the sustainable use of natural resources and rational distribution of agricultural structure. A typical research area in central Henan Province is selected for a correlative analysis about surface water distribution characteristic between the traditional indices (water perimeter, water area and drainage density) and the new water spatial distribution diversity methodology. Results show that there is a significant positive relationship among these four indices with the average coefficient of determination (R2) of 0.89 when the regional water is predominated by rivers or such linear surface water types, and in this situation each of these indices is suitable. However, when the regional water is predominated by rivers, lakes, reservoirs and such complex surface water types, the newest index ‘water spatial distribution diversity’ performs better and should be chosen in describing the water spatial distribution characteristic.

Abstract:Based on two-step anaerobic fermentation process, this study compares the degradation feature of rice straw and the methane production potential of hydrolyzate under the conditions of dilute acid and dilute alkali pretreatment. In the HCl mass fraction range of 0.5%～2.5%（60℃）, the hydrolyzates in the tests of 1.0% and 1.5% obtained higher COD mass concentration. During dilute acid hydrolysis, the hemicellulose fraction decreased significantly, and the glucose concentration was low. In the NaOH mass fraction of 0.5%～4.0%, the hydrolysis of rice straw was weak in the tests of 0.5% and 1.0%, while the hydrolysis efficiency in the tests of 2.0% and 3.0% was high. When the mass fraction of NaOH was higher than 2.0%, cellulose, hemicellulose and lignin all decreased, and degradation rate of lignin was the highest. The tests of acid and alkali could achieve good hydrolysis efficiency at weight-in-volume ratio of 7.5%. Used the hydrolyzate from acid and alkali pretreatment for acid and alkali pretreatment for methane production, the average gas production of unit COD mass were 631～906mL/g from HCl hydrolyzate tests and 340～373mL/g from NaOH hydrolyzate tests in five feeding periods. The biogas production rate of unit mass was less affected by concentration of feeding, and mainly affected by different methods of hydrolysis of acid and alkali. The types of anaerobic fermentation were different in the acid and alkali tests, and the process of generating volatile acid was more sufficient in the tests of acid hydrolyzates.

Abstract:In order to study the influences of different durations of ozone aeration on the nitrogen content and form transformation in anaerobic sludge, the experiment was conducted with self-designed apparatus, with six different durations of ozone aeration, 0, 10, 20, 30,40, 50min, respectively, sampling and measuring content of nitrogen in different forms. The results showed that different durations of ozone aeration remarkably affected the nitrogen content in different forms in wastewater system. Specifically, the content of total nitrogen, Kjeldahl nitrogen, soluble Kjeldahl nitrogen, ammonium nitrogen, nitrite nitrogen, particulate organic nitrogen and particulate total nitrogen, showed significant decline trend with magnitudes of 124.76, 232.51, 11.45, 191.28, 4.35, 221.06 and 286.06mg/L （P<0.05), respectively. By the contrary, the content of soluble total nitrogen, nitrate nitrogen and dissolved organic nitrogen showed upward trend, which were increased by 161.29, 29.42 and 179.83mg/L at the end of 50min（P<0.05), respectively.

Abstract:The substituted groups in lignin can influence the pyrolysis characteristics. Density functional theory (DFT) was employed to calculate the bond dissociation energies (BDEs) of the Cβ—O bonds in 18 lignin model compounds with β—O—4 linkages. The model compounds were grouped and compared to discuss the effects of hydroxyl and methoxyl groups at different positions on the BDEs. The interactions between different groups were also studied. The results indicated that there was minor influence of the hydroxyl group at Cα. The hydroxyl group at Cγ hardly affected the BDE when there was no methoxyl group at R3. However, when there was methoxyl group at R3, hydrogen bond would be formed between the hydroxyl group at Cγ and the methoxyl group at R2, and thus the spatial structure of the model compound would be strengthened and the BDE was increased. The methoxyl groups at R3 and R4 can reduce the BDEs. The methoxyl group at R3 can obviously reduce the BDEs when there was no hydroxyl group at Cγ. However, the reducing effect was weakened when there was hydroxyl group at Cγ, because the hydrogen bond between the methoxyl group at R3 and hydroxyl group at Cγ would strengthen the ether bond. The methoxyl group at R4 was not influenced by the hydroxyl group at Cγ, and thus the reducing effect on the BDE was stable. The methoxyl group at R1 and R2 had minor effects on the BDE, and moreover, it did not participate in the interactions with other functional groups.

Abstract:The dynamic of rice moisture content during hot air and microwave drying was measured and analyzed. The dynamic property of protein, amylose content and germination ratio of rice were analyzed by near infrared detection and germination observation. Furthermore, the influence of drying method on rice quality was measured by glass transition temperature which was got from the analysis of TG/DSC. Results showed that the fitting accuracy of logarithmic model was higher than exponential model during the process of rice dehydration by both drying methods, and the difference in protein and starch content of dried rice was not significant. However, there were significant differences in protein content between fresh and dried rice by hot air drying. The germination ratio of rice dried by hot air and microwave was much higher than fresh ones, which was 0.93±0.03, 0.77±0.02 and 0.65±0.19, respectively. As the rice moisture content decreased, the mass loss and heat flux of dried rice showed different changing trend and the glass transition temperature decreased as well. All of them had effect on the quality of dried rice. The results could be a reference for improving efficiency and quality during the process of grain drying.

Abstract:Enzymatic browning was mainly associated with polyphenol oxidases which were able to act with phenolic compounds in the presence of molecular oxygen and decreased the commercial quality, organoleptic acceptance and nutritional value of the product. Membrane-bound polyphenol oxidase (mPPO) in Fuji apple (Malus domestica Borkh. cv. Red Fuji) was purified by using temperature-induced phase partitioning technique, ammonium sulfate fractional precipitation and DEAE Sepharose Fast Flow ion exchange column chromatography, and analyzed by using tandem mass spectrometry (LC—MS/MS). The best conditions for isolation and purification were ultrasonic extraction for 10min, 50%~80% saturation of ammonium sulfate precipitation, and gradient elution with 0.1mol/L NaCl. The mPPO was purified by 64.30 folds with a high specific activity (387032.97U/mg). The Native—PAGE and SDS—PAGE were single bands for mPPO and the purified mPPO was a dimmer of a subunit with a molecular weight of 67kDa. The results by mass spectrometry analysis and comparison in protein database showed that the purified protein was a polyphenol oxidase.

Abstract:In order to evaluate the potential risk of Alicyclobacillus contamination in Shaanxi kiwi fruit production line, six strains of Alicyclobacillus isolated from the production line were studied. The contaminant production capacity of six strains and four corresponding standard strains was evaluated, including detection of contaminant production using GC—MS and heat resistance through drawing thermal death curves, and its biodiversity was analyzed, including analysis of carbon source spectrum by API tests and detection of its DNA hybridizations from renaturation rates. The results showed that no 2,6-dibromophenol and 2,6-dichlorophenol were detected, and the guaiacol production of six isolated strains was between 10.56μg/L and 34.74μg/L which was significantly higher than the common sensory detection threshold values in juices, D90℃ values of strains were 27.1~34.2 min and the z values were 12.14~13.66℃ in kiwi fruit juice, with the heat resistance of the three strains of A. acidoterrestris generally being higher than the data of former reports. There were 7~22 different results of API tests between the isolated strains and the data from published articles or their corresponding standard strains. The hybridizations between the isolated strains and their corresponding standard strains were between 74.75% and 104.79%. These results suggested that the isolated strains possessed potential contaminant production capacity and biodiversity to a certain extent which needed to be controlled.

Abstract:An effective organics solution phase change materials (PCMs) with high phase enthalpy change and low onset temperature was developed, which can be applied to store and preserve several kinds of agricultural produces with different optimal storage temperature. Glycine, lysine, sorbitol, proline and glucose were preselected and determined with the differential scanning calorimetry (DSC), and glycine solution was chosen as the main energy storage materials due to its highest phase enthalpy change among these five materials under the same onset temperature. To achieve a lower onset temperature, glycine was matched with 0.1mol/L glycerol solution and 0.1% sodium benzoate was added to extent self-life of PCMs and super-absorbent polymers (SAP) as matrix. The final formula of the organics solution PCMs was 0.4~0.8mol/L glycine, 0.1mol/L glycerol, 0.1% sodium benzoate and water with 0.75%~0.81% SAP as matrix. A series of this organics solution PCMs could be prepared with the change of the concentration of glycine solution, whose phase enthalpy change was 296.4~305.9J/g and onset temperature was -7.3~-5℃. Furthermore, there was almost no supercooling and phase separation phenomenon and it was safe and practical.

Abstract:In order to optimize the extraction of total polyphenols from Terminalia chebula Retz. (TCR), the extraction technology of total polyphenols from TCR were optimized by using ultrasound assisted extraction with constant temperature and three-frequency (UAE—CT & TF). The reasons for high efficiency of this extraction technology were analyzed by comparative experiments and scanning electron microscope (SEM). The dynamic equation of diffusion for the total polyphenols was determined and verified based on the first Fick theory. Results showed that the optimal parameters of extracting technology were as follows, the concentration of ethanol was 60%, ultrasound frequency was 80kHz, ultrasound power was 180W and extracting temperature was 70℃. The extraction efficiency of UAE—CT & TF dramaticlly exceeded that of water bath oscillator extraction (WBE) (P＜0.001). The microcosmic structures of powders of raw material after being extracted by UAE—CT & TF were seriously destroyed from the analysis of SEM. The dynamic equation of diffusion for the total polyphenols extraction of TCR was determined based on the first Fick theory and ultrasound extraction dynamics. The verification experiment showed the logarithms of extraction time and power were all positively proportional to the concentrations of TCR total polyphenols. The technology of UAE—CT & TF was proved as a technology with high efficiency for extracting TCR total polyphenols.

Abstract:Castanea henryi starches were treated by enzyme and heat-moisture and the effects of enzyme dosage and reaction time on their physicochemical properties were studied. The results demonstrated that crystal types of enzyme and heat-moisture treated starches belonged to type A, which were low expected glycemic index (pGI) foods because of most pGI below 55%. By analysis in vitro digestion dynamics, scanning electron microscope (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and high performance anion-exchange chromatography with pulsed ampere detection (HPAEC—PAD), the resistant starch (RS) content, molecular chain average degree of polymerization (DP), relative crystallinity and melting enthalpy of enzyme and heat-moisture treated starches along with the change of enzyme dosage and debranching time were characterized by three phases. Especially in the second phase, namely the enzyme dosage with 50~60U/g and the reaction time within 12~16h, the RS content, relative crystallinity and melting enthalpy were maximum due to the molecular chain of DP value suitable to reaggregate to form stable crystalline structure.

Abstract:To improve the content of ascorbic acid of fresh apple juice, apples of ‘Ralls’ and ‘Fuji’ juice were prepared after cold stress, and then some important quality indexes were measured. Contents of total ascorbic acid, AA and DHA of ‘Ralls’ and ‘Fuji’ reached maximum values after 20h and 8h of cold treatment at (-7±0.5)℃, respectively. Compared with the apples without cold treatment, contents of total ascorbic acid, AA and DHA of ‘Ralls’ and ‘Fuji’ were increased about 26.65%，28.93%，18.26% and 15.78%，17.33%，11.30%, respectively, and the contents of soluble solid, soluble sugar and malic acid were declined about 8.21%, 13.04%, 7.27% and 11.46%, 14.14%, 7.14%, respectively. Fresh juice was prepared at room temperature within 30min after cold treatment at (-7±0.5)℃. Compared with the juice of apples without cold treatment, contents of total ascorbic acid, AA and DHA of ‘Ralls’ and ‘Fuji’ were increased about 31.26%, 35.40%, 20.54% and 18.05%, 20.46%, 13.33%, respectively, and contents of soluble sugar, malic acid and sugar-acid ratio were declined about 12.03%, 7.54%, 5.92% and 14.53%, 10.00%, 5.04%, respectively; aroma substance was increased by 6 and 5 kinds, and its contents increased about 2.03% and 8.02%, respectively. The results indicated that cold stress could be considered as an effective measure to improve the contents of ascorbic acid for fresh apple juice.

Abstract:The Hall effect in a flowing electrolyte demonstrates the impact of a perpendicular magnetic field on positive and negative ion moving path in a velocity field, of which the essence is the application of Lorentz force in solution fluid. Potato slices were treated under a perpendicular magnetic field with impregnation solution fluid containing different concentration of calcium chloride, zinc gluconate and ascorbic acid. The results showed that a center magnetic flux density of 1500Gs promoted the permeation of the target solute, and higher velocity of flowing electrolyte declined the effect of penetration for charged ions. The quality of potato slice was significantly improved at 0.05m/s velocity treatment. In contrast, the quality of the control group was not changed. This method can also be used to achieve the fortification of minerals, keep crispness and prevent browning of other agricultural products.

Abstract:Scanning electron microscopy (SEM), texture profile analysis (TPA) and dynamic rheology technique were applied to investigate the effect of traditional bittern and different water in oil (W/O) emulsion coagulants on the rheological properties and microstructure of cold-set SPI gels. Rheological tests suggested that the development of the mechanical moduli (G′) of these SPI gels was highly dependent on the release rate of magnesium salts from W/O emulsions. The values of G′in all cold-set SPI gels gradually increased with the extension of time and W/O emulsion coagulants prolonged the solidification time of cold-set SPI gels in comparison with traditional bittern coagulant. This could be attributed to the controlled-release properties of W/O emulsion coagulants. In addition, cold-set SPI gel prepared with W/O emulsion coagulant containing WPI exhibited a longer solidification time and a lower value of G′than W/O emulsions without WPI. Cold-set SPI gels induced by W/O emulsion coagulants had better microstructure than that of traditional bittern coagulant as shown by SEM results, which elucidated that W/O emulsion coagulants could obviously decrease the strength of cold-set SPI gels and produce protein gels with smaller pores and more homogeneous network structure.

Abstract:Remote sensing technology can cost-effectively access a wide range of real-time land surface spatial information, and provides an effective way for resource surveys, environmental monitoring and disaster prediction. With the help of remote sensing technology, geo-information can be acquired quickly, accurately, efficiently and comprehensively. Undoubtedly, remote sensing will play an increasingly important role in the fields of geosciences, agricultural sciences, and so on. In particular civil resources satellite was launched in the 1970s, which was applied in agriculture and benefited first. Moreover, significant developments were registered in some key fields along with the advancement of high resolution remote sensing. The combination of their high temporal frequency with extended geographical coverage makes them particularly useful for time series crop growth monitoring, crop types subdivision, and acquisition of field precision agriculture. The fact is of note that the new challenges followed as a result of the dispersion and spatial-temporal variability in agricultural production. An overview of the history and theoretical background of agricultural remote sensing technology was introduced. And then four aspects of yield estimation, agricultural resources survey, agricultural disaster monitoring and precision agriculture management were presented. Remotely sensed data from existing platforms and the ground observation network technology which can provide an important data source for supporting agriculture were expected. On the other hand, new generation remote sensing platform of low altitude unmanned aerial vehicle (UAV) should be promoted. Although progress has been made, current methods and techniques still bear potential to further explore multi-sensors, spectral data, surface characteristic parameters and existing crop model. The combination of multi-sensor data and assimilation will enhance the perspectives of using remotely sensed data for agriculture.

Abstract:Hyperspectral remote sensing is an important technique to fulfill real-time monitoring for crop growth status based on its superior performance in acquiring vegetation canopy information rapidly and non-destructively. The objective of this study was to establish the best simulating accuracy and adaptability of wheat fraction of absorbed photosynthetically active radiation (FPAR) estimation model based on wheat canopy hyperspectral reflectance with different nitrogen or phosphorus application rate treatments, and to improve the forecast precision of the FPAR estimation model at different growth stages of dryland wheat on the Loess Plateau. The experiments were carried out during 2009—2014 at Northwest A&F University, Yangling, China. Different winter wheat (Triticum aestivum L.) varieties with stronge or weak drought resistance were chosen for the treatments in different years, nitrogen and phosphorus treatments included five nitrogen fertilizer application rates (0, 75, 150, 225 and 300kg/hm2 pure nitrogen, expressed as N) and four phosphorus application rates (0, 60, 120 and 180kg/hm2P2O5,expressed as P), the FPAR and canopy hyperspectral reflectance of different varieties and fertilizer treatments were monitored at jointing, booting,heading, grain filling and maturity stage, respectively. Then FPAR monitoring models at different growth stages of winter wheat were constructed by using correlation analysis, regression analysis and other methods. The results showed that the FPAR of wheat increased with nitrogen and phosphorus application rate increasing in different growth stages, there were significant differences among test cultivars. A good correlation relationship was presented between FPAR and canopy spectral reflectance at 670, 850 and 960nm, and the sensitive band of the FPAR occurred mostly within visible and near-infrared spectrum. The correlations between soil adjusted vegetation index (SAVI), red edge normalized difference vegetation index (NDVI705), enhanced vegetation index (EVI), difference vegetation index (DVI) and ratio vegetation index (RVI) to FPAR were significant, and the range of correlation coefficient was 0.818~0.942 at jointing, booting, heading, filling and maturity stages. Monitoring models based on SAVI, NDVI70, EVI, RVI and RVI produced better estimation for FPAR at different growth stages, and the determination coefficients (R2) were 0.854, 0.888, 0.811, 0.844 and 0.911, and the standard errors (SE) were 0.054, 0.032, 0.044, 0.047 and 0.044, accordingly. Meanwhile, comparing the predicted value with measured value to verify reliability and applicability of monitoring model, result showed that the relative errors (RE) between measured value and predicted value were 14.1%, 17.4%, 12.8%, 18.8%, 10.7%, and the root mean square errors (RMSE) were 0.139, 0.146, 0.136, 0.158, 0.130, respectively. Therefore, it was suggested the vegetation indices of SAVI, NDVI705, EVI, RVI and RVI was the most suitable model for monitoring winter wheat FPAR at jointing, booting, heading, filling and maturity stages, respectively, and there was higher prediction precision with different vegetation indices in monitoring FPAR of winter wheat at different growth stages, and different N and P rates. These conclusions had important implications for the large areas FPAR monitoring of winter wheat in the Loess Plateau. Meanwhile, there was a higher prediction accuracy of monitoring model based on the different vegetation indices at different growth stages.

Abstract:Farmland roads and ditches are the majority of land consolidation project and construction of a high standard of basic farmland, which can be monitored by the high spatial resolution remote sensing. An approach of automatic linear project feature extraction with WorldView—2 high-resolution image based on Canny edge detection algorithm was presented, which was designed especially for field roads and ditches detection in the farmland. Firstly, based on the Canny edge binary images, single-pixel gap was connected by matching one of eight masks summarized. Secondly, the suspect linear feature was identified by Euclidean distance judgment. Each pixel of enhanced images was scanned with the seed growth method. Thirdly, each line was joined into the intact linear project feature with a lower length threshold. Fourthly, redundant features were deleted with a higher length threshold. The steps listed above were divided into two directions including vertical direction and horizontal direction and the final results were formed by combining results from the two directions. Experiments were designed in the land consolidation area of Dalad Banner, Inner Mongolia. The accuracy assessment was presented, the precision was above 95% and the correctness in the simple conditions was above 95%, which also met the basic needs of land consolidation project monitoring. Based on Canny edge detection, the algorithm of this paper can be realized in a fast and efficient way. All the procedures of this algorithm were realized automatically by adjusting operators without requiring artificial interpretation.

Abstract:The purpose of this paper is to develop a method for automatically detecting vocalizations of laying hens from a large amount of original data. First, the original sound data were cut into 1 sec of length clips by using sound analysis software. Then, 130 clips including calls of Hy-Line Brown laying hens and 132 fan noise fragments were selected. Finally, an algorithm was developed for automatically identifying vocalization of laying hens and fan noise based on the discrepancies of 2 kinds of sounds’ power spectral density in 1000~1500Hz. The results showed that a 95% overall correct classification ratio was achieved and 93.3% of the vocalizations of laying hens were correctly identified. This approach can improve the efficiency during sound analysis and reduce the storage and transmission of useless sound.

Abstract:The Boost/Buck converter was introduced into the energy-harvesting circuit to coordinate dynamic performance and energy-harvesting performance of energyharvesting suspension system. The non-linear mathematical model of DC—DC converter was described by the summation of steady-state components and disturbance components. Considering the mapping capability of neural network and anti-interference of FIR filter，adaptive off-line neural network inverse controller was designed. The controller was composed of off-line neural network inverse controller and adaptive controller. The off-line neural network inverse controller was used to provide steady control input with steady components of DC—DC converter as training samples, while the adaptive controller was used to provide compensation dynamic control generated by parameter variations and uncertain interference. On this basis, the converter sample was made and the rapid control prototyping experiment was performed to validate the performance of the controller. To meet the suspension vibration isolation performance and harvest vibration energy to a large degree, the suspension control parameters was decided. And a linear motor was tested to obtain its characteristic parameters. Simulations were applied to a two-degree of freedom energy-harvesting suspension. The results showed that the linear motor can produce the desired electromagnetic damping force with the proposed controller and improve vehicle comfort. It also indicated that self-powered control with energy harvested from suspension was attainable.

Abstract:According to the principle of suspension constrained minimization, an interconnected hydraulic torsion-elimination suspension system was put forward. Firstly, the structure and principle of the system was introduced, the interconnected hydraulic torsion elimination suspension system was set up in the AMESim and the vehicle dynamic model was established with Matlab/Simulink. Co-simulation based on Matlab/Simulink and AMESim was carried out to analyze the dynamic performance of interconnected hydraulic torsion-elimination suspension system. The principle prototype of interconnected hydraulic torsion-elimination suspension system was designed and its bench test was performed. Simulation and experimental results were basically identical. The results showed that compared with the traditional passive suspension, interconnected hydraulic torsion-elimination suspension can effectively inhibit the body vibration, control the body posture and coordinate the vehicle riding comfort and safety, improve vehicle passing ability in extreme condition, eliminate part of the body torsion load and perform the real time control of vehicle steering characteristics.

Abstract:The drive unit and vehicle frame of traditional automated guided vehicle (AGV) and tractor-trailer were rigid coupling. Being different form the traditional machines, the drive unit and vehicle frame of AGV with sneak traction were flexible connection and the drive unit was used to drive the vehicle frame. To solve the problem of vehicle frame trajectory, a kinematic model was built to study the relationship between position posture of vehicle frame and the tracking path. According to geometric parameters of vehicle frame and central angle and radius of circular arc path, position posture of vehicle frame in world coordinate system was deduced. To solve the problem of AGV load driving, a dynamic model of AGV frame was built. The condition ignoring the effects of lateral force was calculated and the angular acceleration of the frame was deduced. Position posture tests proved that the kinematics model of AGV frame was correct. The results of dynamic property tests proved that the driving stability of AGV with this structure was excellent. The study results can provide the basis for improving the control performance of control system.

Abstract:Individual parameters of vehicle dynamic systems were traditionally derived from expensive component indoor laboratory tests as a result of an identification procedure. These parameters were then transferred to vehicle models used at a design stage to simulate the vehicle handling behavior and the cost of measurement was high. At the same time，acquiring the vehicle’s driving status and parameters had important significance for the process controlling of the vehicle. Normally, the status and parameter of the test vehicle needed to be estimated together, which were then transferred to vehicle models and used at a design stage to simulate the vehicle handling behavior. A vehicle dynamics system containing constant noise and non-linear model was established，Runge—Kutta method was used to simulate the model. The extended Kalman filter algorithm was used as the importance density function to update particles in particle filter, with which the local state estimated values and parameters can be calculated. The simulation results showed that the proposed algorithm improved the accuracy of standard particle filter.

Abstract:In order to improve the vehicle anti-slip performance, an acceleration slip regulation strategy based on extremum seeking control with sliding mode was proposed. Extremum seeking control with sliding mode was used as a self-optimizing way to find the extreme point of tire force-slip rate curve. In this condition, the tire slip ratio near the optimal slip ratio can be controlled without having to estimate the road surface friction coefficient or establishing the ideal reference model to improve the vehicle dynamic performance and directional stability. Moreover, a validated full vehicle simulation model was built in Matlab/Simulink. And the controller based on extremum seeking control with sliding mode was carefully designed. Finally, simulation results showed that during acceleration the vehicle can quickly reach the optimal slip ratio which corresponded to the real-time road conditions with the proposed control strategy. It implied that the proposed control strategy can improve vehicle dynamic performance.

Abstract:Pneumatic ejector is an important vacuum source for agricultural automation. During the application of pneumatic ejector, the increasing back pressure may cause the suction ability to get worse intensely and the normal operation of the system will be greatly influenced. Regarding the ejectors used in pneumatic systems, the air flow was analyzed with finite volume method based on ejector inner mechanical structural parameters. The changes of pressure distribution and suction flow velocity were studied when the back pressure was variable. Based on the theoretical analysis, an experimental apparatus was set up and the suction mass flow rate was measured as the back pressure increased. The relationship between back pressure and suction mass flow rate was obtained. Judging from both of theoretical analysis and experimental result, the suction flowrate characteristics remained unchanged at first and then got worse intensely as the back pressure increased. A method was proposed to prevent reverse flow by estimating back pressure, which was an effective complementary approach for ejector systematic design. When designing a pneumatic ejector system, the back pressure range where the ejector worked normally should be derived both from theoretical calculation and experimental test. Reverse flow could be prevented if the back pressure was controlled within normal range, thus the optimum performance would be achieved.

Abstract:The flow degradation of gear pump was induced by the contaminant particles entrained in the fluid within the power shift steering transmission (PSST). On the basis of the degradation mechanisms of gear pumps, the mathematic model for the broken process of contaminants was proposed through the investigation of contaminants entrained into the leakage path in the clearance between the gear ends and the end plates. Within the model, both the values for the particle broken constant and the leakage rate were determined. Thereafter, the degradation model for gear pump was derived for the inference on the relationship of the contaminant mass with wear parameter. In addition, the effects of the contaminant level and the construction parameters were also analyzed. Results showed that the contaminant wear, including the process of particle broken and wear debris generation, can be well interpreted by the degradation model. Meanwhile, the prediction method of contaminant sensitivity for gear pumps was provided by the model, which was valuable and practical for the improvement of hydraulic and lubricated system in PSST.

Abstract:The pumping performance of valve-less piezoelectric mainly depends on the flow resistance difference between forward and reverse directions, so testing flow resistance is particularly important. Flow resistance testing device of valve-less piezoelectric pump was designed which can realize automatic or semi automatic water supply function and the measured flow range was wide. The device can be easily used to analyze and research flow action law. Hemisphere-segment valve was taken as study object and the resistance coefficient formula was derived. Flow resistances were tested respectively by traditional and novel test devices and theoretical pump flow were calculated. The deviations between theoretical and experimental flow rates were 34.38% and 117.33%, respectively. The results showed that the accuracy of flow resistance test was greatly improved by the flow resistance testing device of valve-less piezoelectric pump, which can test and analyze flow resistance, calculate pump theoretical flow and predict experimental flow.

Abstract:2D electrohydraulic high-speed on-off valve was a two-stage valve，which had a spool with two dimensional motions, a rotary electromagnet drove the spool to rotate by a set of lever-fork and achieve pilot function, and pressure difference pushed the spool to open or close quickly. The form of three circumferential uniformly distributed 52 blades was adopted by the rotor of rotary electromagnet. The output torque of rotary electromagnet was multiplied by five times, the rotor inertia was reduced by lever-fork and the dynamic characteristics of 2D high-speed on-off valve were improved. To test the dynamic characteristics of 2D high-speed on-off valve driven by double torsion pendulum wheel and rotary electromagnet，two experimental programs of the valve were designed. The digital simulation and experimental results were quite coincide, which showed that the dynamic characteristics of 2D high-speed on-off valve were very quick; when the system pressure was 28MPa and the valve of 6mm diameter with spool driven by rotary electromagnet, the dynamic response time was about 18ms, spool displacement was 0.8mm and the flow rate was 60L/min.

Abstract:In order to improve the performance of hydraulic braking system, the influencing factors of vehicle braking performance and system principle of mine dump truck were analyzed. Results indicated that the shorter the action time, the smaller the braking distance under certain conditions of maximum braking deceleration and initial braking speed. The simplified model of hydraulic brake system was established, and characteristic analysis was made toward its key component brake pedal valve. The simulation model was built by AMESim to study the influence of brake performance with parameter variation. Conclusion showed that braking system response speed and pressure building time were impacted by several parameters such as accumulator volume, charging pressure and brake pipe length. The methods of decreasing brake action time by residual pressure control were proposed. Correctness of the simulation analysis was verified by experiment results which showed that the action time of brake was reduced and braking distance was shortened with this method. Braking performance was improved greatly, which provided theoretical basis for the design and optimization of similar products.

Abstract:The performance of servovalve driven by giant magnetostrictive actuator is seriously affected by temperature rising. In order to reduce the error from temperature rising, a giant magnetostrictive actuator applied in servovalve was presented and its working principle was introduced. The output displacement error of actuator from rising of temperature was controlled by cooling and compensating. In order to analyze the influence of heat on the accuracy of giant magnetostrictive actuator, heat transfer model was deduced from the theory of heat conduction and transversal heat transfer, the steady-state temperature on giant magnetostrictive rod and shell were given, and the simulation results were verified by numerical simulation. The results showed that when the velocity of oil surrounding giant magnetostrictive rod was more than 0.1m/s at control current of 1A, temperature of giant magnetostrictive rod and shell was about 20.3℃, the difference in temperature can be limited below 0.2℃, and temperature rise of giant magnetostrictive actuator was small. The displacement error from heat was derived based on the model described the temperature on giant magnetostrictive rod and shell. The simulation results showed that when the velocity of oil surrounding giant magnetostrictive rod was more than 0.1m/s, the output displacement from heat was less than 0.1μm.

Abstract:Precision and precision retaining ability are core indicators of performance of high precision machine tool. Guide pair works as the core part of feed system of machine tool and it decides the machining quality and precision of workpieces. Slide guide is one kind of the most frequently used guide pair of machine tool. It is a typical sliding friction system and definitely wear is the primary factor to cause the precision attenuation of the slide guide. The slide guide of machine tool feeds stochastically in its working process, which leads to the complicated wear behavior of the guide surface. Based on statistical theory, an analytical model of precision retaining ability of slide guide was constructed with analysis of the wear characteristics and accuracy attenuation of slide guide under working conditions. The quantitative relationships between precision retaining ability and its influencing factors, i.e., working condition parameters, running parameters, material property and wear coefficient were described by the model. A test bench of precision retaining ability of slide guides was developed. Bench tests of precision retaining ability with the slide guide samples were conducted to validate the theoretical model. The maximal relative error of experimental results and calculated results were 22%. It indicated that the calculated results fit with the experimental results and the model of precision retaining ability was reasonable. The model can predict the accuracy life of slide guide and it also can provide references for the tribology design and precision retaining design for slide guide.

Abstract:Support vector regression (SVR) is an effective tool for machine error modeling. To improve the predicted performance of SVR model, the core vector regression (CVR) algorithm which is suitable for resolving the training of large-scale sample data was introduced into thermal error modeling for CNC machine tool. Principal components were firstly extracted from the sample set using the feature extraction of partial least squares (PLS) algorithm to construct the feature set, which would reduce the number of state variables without information loss by dimension reduction, data de-noising and eliminating the correlative between variables. Then improved particle swam optimization (IPSO) was applied for determining the parameters of CVR to get the optimal performance of the thermal error model, and the proposed combined method was called PLS—IPSO—CVR. Experimental results showed that the training speed of PLS—IPSO—CVR model was much faster and it produced fewer support vectors on very large sample data in comparison with SVR and BP neural network. Thus the feasibility and effectiveness of this combined modeling method was verified.

Abstract:Pseudo-rigid-body model is an important way to analyze kinematic and dynamic performance of compliant mechanisms and synthesize. The beam-flexible hinge combined mechanism is essential flexible fragment. A compliant mechanism was designed by using flexible fragments to replace rigid members of pseudo-rigid model. Traditionally pseudorigidbody model did not consider the effect of geometrical nonlinearity and deformation of the beam, so there was error between pseudo-rigid-body model of LEMs and the actual. In order to reduce the error, the impact of geometric nonlinearity was considered and corrected pseudo-rigid-body model was proposed, and in order to determine the applicability of pseudo-rigid-body model, the concept of pseudo-rigid factor was put forward. Flexible fragment can directly replace the rigid member when pseudo-rigid factor was in a certain range, and then the compliant mechanism can be obtained. Finally, the LEMs were optimally designed based on pseudo-rigid factor for cell engineering by ant colony optimization algorithm for continuous space.

Abstract:Based on analysis of the reason of nodal diameter transverse vibration of thin type circular saw in sawing the stone, it was found out that the wave of the wavy deformation of traveling wave on the saw edge led to the additional axial force of sawing force. The mathematical model of axial additional force was deduced by traveling wave theory in a rotating coordinate system with the same rotational speed as the diamond circular saw, and then the transverse vibration model of diamond saw blade was built by using the thin plate theory of elastic mechanics. The model was pretreated by using complex analysis theory and some proper mathematical methods. The solving algorithm for transverse vibration model and the simulation program were designed based on the Newmark method. In order to verify the validity of the model, a transverse vibration monitoring experiment was completed in the stone producing spot. The transverse vibration of two positions of the diamond saw blade was measured under different process parameters. The error between simulation result and experimental result was less than 13%, therefore, the correctness of the model was verified. The established transverse vibration model could provide theoretical support for optimization of saw blade structure, design of sawing machine tool, noise reduction in sawing process and improvement of the machining surface quality.