Abstract:Conservation tillage effectively protects the environment. A no-till planter can seed on the straw mulching farmlands, and it is the most important machine in conservation tillage. In order to make sure the consistency of sowing depth, an active seeding depth control system was designed for a no-till planter. The system was consisted of piezoelectric film sensor, a signal processing circuit, a control signal generating circuit and a pneumatic drive system. When planting with a conventional row crop planter which had a plurality of row units mounted on a toolbar, it was necessary to provide a sufficient down force on each row unit to ensure that the seed trench opener was fully penetrated into the soil. Proper down force was also essential to provide proper amount of soil compaction in the side walls of the seed trench. Seeding depth primarily depended on the down force on each row unit. In order to make adjustments to the down force in real time, it was needed to measure the magnitude of the down force on an ongoing basis. The piezoelectric film sensors were used for measuring the deformation of depth limit wheel, the down force of the row unit was monitored in real time according to the deformation of the limit wheel. The piezoelectric film generated charge during rotating of the wheel. The sensor changed the charge into a voltage signal. The voltage signal was processed by low-pass filter and preamplifier circuit in order to eliminate the noise and amplifiy the filter, and then the peak-holding circuit gained the peak voltage value which was sampled by A/D conversion and sent to control signal generating circuit by the wireless transmitter. Wireless receiver received the digital signal which was compared with the present value stored in the microcontroller, if the received signal was less than the present value, the difference between the received signal and the present value formed the control signal. The pneumatic drive system was consisted of air compressors, tank, filters, electric-gas proportional valve and air spring. To provide the necessary down force, an air spring was assembled at the linkage which was mounted in the row unit to the toolbar. Compressed air was generated by the air compressor and stored in the tank, and then the compressed air was filtered to filter out dust and impurities. Pure compressed air was fed to the electric-gas proportional valve; the output of electricgas proportional valve was connected to the air spring. The output gas pressure of the electricgas proportional valve was controlled by control signal, the air spring can generate corresponding down force on the unit row. A field experiment was conducted to verify the performance of the seeding depth automatic control system, and the result showed that the seeding depth control system can provide accurate ditching depth and reliable performance of profiling. When the speed of the planter was over 8km/h, the qualified sowing depth rate of the active seeding depth control system was much better than that of the passive control system.

Abstract:The working efficiency of cotton-picking machine is always influenced by its working speed. To solve this problem, an algorithm for real-time adjusting the working speed was put forward based on fuzzy PID control technology. The walking speed regulation model was also established to achieve the optimal control of the working speed of cotton-picking machine. The algorithm combined the traditional PID control with fuzzy algorithm by acquiring the real-time parameters under the input load gradient congestion conditions, such as cotton production online. Both the fuzzy rules and reasoning method of PID were used to set online parameters and adjust the real-time working speed to achieve optimal control of operating speed. The field test was conducted by using 4MZ—5 five-line cotton-picking machine based on FPGA hardware. The testing result showed that the algorithm response speed was stable in 75s. According to the cotton volume of online production, several parameters were adjusted by using fuzzy rules under the load gradient and block boundary conditions, which ensured the stability of picking up for cotton-picking machine with the best speed and improved working efficiency. It also reduced the loss in the process of picking cotton, and effectively avoided the tube plugging failure as a result of large amount of cotton. The system showed a strong flexibility and versatility and it could be used to reduce the driver’s workload and improve the automation and information level for large equipment.

Abstract:Experiments on electro-spraying were carried out under a combined electric field based on micro-scale combustion system by using ethanol as fuel. A stable cone-jet mode was obtained. And theoretical calculation was performed based on the cone-jet mode. The distribution of electric field strength was calculated by using ellipse integral method and the relationship between Cartesian coordinates and polar coordinates. The results showed that the electric field strength produced by the ring electrode alone at the center of nozzle reached its maximum value, which was 0 V/m at the position of the center of ring electrode. It increased with the increase of cone angle when all the other conditions were kept the same. The electric field strength produced by the ring electrode could be ignored compared with that produced by the nozzle electrode due to the much bigger diameter of ring electrode and smaller electrode spacing. The distribution of electric field strength in the jet region was axis-symmetry and extremely non-uniform in the angle range φ of 0°~49.3°. The strength in the center of nozzle was very small while it was bigger around the outer side of nozzle, which enhanced the electric induction. Changing the voltage of the ring electrode put little effect on the electric field distribution in the jet region, but the electric field strength in the spraying region was greatly increased.

Abstract:In order to investigate the cavitation characteristics of centrifugal pumps under low flow rates, the cavitating flows in the centrifugal pump typed IS50—65—160 with three different bladenumber impellers were numerically simulated based on the k—ε turbulent model combined with Rayleigh—Plesset cavitation model by using the software ANSYS CFX 14.5. Meanwhile, grid independence check was carried out to verify the accuracy of calculation. The effect of blade numbers on the cavitation characteristics in the pump was firstly analyzed from the points of suction performances, torque as well as axial forces acted on impellers. The results showed that as the blade number increased from 4 to 8, the pump head increased while the variable regulation of its efficiency was quite complicated. Both the head-drop and torque-drop curves of impellers with three different blade numbers had the same shape of creeping dropping, with the corresponding break-down points occurring asynchronously. The axial forces acted on impellers almost kept constant as the amount of head dropping was 3% or higher. The vapor volume in one blade was larger than others, and finally a significantly asymmetric distribution occurred on all blades. It was firstly obtained that the creeping-drop characteristics of both pump head and torque acted on the impellers were possibly related to onset of asymmetric blade cavitation phenomenon. Moreover, this study to some extent can also provide some reference for the design of centrifugal pump in the industry in case of avoiding serious cavitation occuring at low flow rates.

Abstract:In order to research the internal flow mechanism of screw centrifugal pump, the PIV testing technology was used after the pump was improved with the transparent handling. The velocities of shaft section and radial section at different stages were obtained. The flow of each section was received and then the internal flow in screw centrifugal pump was revealed. The results showed that the perturbation of physical parameters at the whole shaft section was bigger than the one at radial section. The vortex was appeared obviously at shaft section of impeller passage and the vortex volume increased significantly in the impeller passage which was deep into volute. With the depth of the fluid flow, it caused fluid force reallocation by the spiral vane segment. At radial section, velocity was rotated along with the direction of the flow line. Simultaneously, there was a trend that fluid moved from the center to the outside due to the centrifugal force from the centrifugal section, which played an important role after the spiral section. The spiral propulsion of spiral section and the energy conversion of centrifugal section were cooperated with each other to make up the working process of screw centrifugal pump.

Abstract:In order to investigate the flow loss in guide vanes, detached eddy simulation (DES) was used to simulate the transient flow field of a multistage centrifugal pump. The obtained numerical results were compared with experimental results, and the outcome showed that mean errors of head and efficiency were less than 4%. Simulation results analyzation showed that there were three main causes of the loss, which were flow separation in return guide vane passage, circumflux in transferable channel and collision in PS side. In order to decrease the loss, return guide vanes were designed through impeller blade design methods and transferable channels were optimized. The results showed that flow separation and collision reduced when applied impeller blade design method and circumflux reduced through TZ type transferable channel, which improved pump’s efficiency by 2.4% and 1.7%, respectively. The analysis of flow fields in the coupled vanes showed that circumflux, collision and separation flow were both reduced significantly, which improved pump’s efficiency by 2.9%.

Abstract:In order to investigate the effect of adjustable outlet guide vane on hydraulic performance of axial-flow pumping system, the pumping system with seven different adjustable angles of outlet guide vane were simulated based on the RNG k—εturbulent model and Reynolds time-averaged equations. Vectorgraph of airfoil flow were analyzed under different operating conditions at different adjustable angles of guide vane. BP-ANN prediction model about effect of adjustable outlet guide vane on the hydraulic performance of axial-flow pumping system was established based on numerical results. The effectiveness of prediction model was verified by using theoretical analysis and numerical simulation. The results showed that the high-efficiency area moved to the large flow rate direction with the adjustable angle of guide vane increased along clockwise, otherwise, it moved to the small flow rate direction. The internal flow field of guide vane was improved by adjusting angle and the flow separation of tail and guide vane inlet ledge were decreased or eliminated, which would improve hydraulic efficiency of pumping system. The input model of the BP-ANN prediction model is presented and the number of middle layer is fixed by many tests. The characteristic data of 42 pumping system operating conditions are used to train the network model, and the data of the other seven pumping system operating conditions are used to test the network model. The prediction accuracy of BP-ANN model was below 1%, which can meet the requirement of practical engineering.

Abstract:To improve the performance of high specific speed centrifugal non-clogging submersible sewage pump, the 350QW 1500—16—90 sewage pump was designed by using unequal head hydraulic design method and traditional equal head hydraulic design method. Three different optimization plans were proposed and CFD software ANSYS CFX was applied to analyze the interior flow field of each plan under different conditions, the performance was predicted and the best plan was selected to test by internal flow characteristics and performance curves. It was demonstrated that using unequal head hydraulic design method can reduce the area of low pressure of impeller working face and backflow, central runner had the lowest relative velocity so that blade outlet of the pump had a uniform static pressure and velocity distribution. The predicted curve obtained by CFD technology and performance curves obtained by experiment of head and efficiency had the consistent variation. There was no saddle zone and overload phenomenon, which indicated that it satisfied the design requirements and the numerical simulation was accurate and it had guiding significance for the high specific speed sewage pump design. The absolute value of head curve slope increased with the increase of flow, the maximum efficiency point was occurred at 1699.93m3/h and maximum efficiency was 80.256%. Maximum efficiency point shifted to the large flow, where the efficiency curves changed gently, 0.9Q~1.3Q was high efficiency area which was conformed to be the operating characteristics of the sewage pump running at high flow conditions, it was helpful to improve the current situation of high energy consumption at sewage treatment for using unequal head hydraulic design method.

Abstract:The whole flow passage of Francis turbine including clearance structure such as cavity between crown and top cover, weep hole and seal passage of runner was built to study pressure distributions and velocity distributions in main passage as well as clearance flow characteristics by CFD method. Variation rules of leakage flux and static pressure in chamber head of the turbine was revealed due to different micro channel clearance widths, weep hole diameters and numbers. ICEM structured grid was used to divide the key components to analyze the seal clearance flow. The sizes of grid nodes were set up as one smaller regional area and another larger one according to the large space between the main passage and seal passage. The numerical results showed that seal widths, weep hole diameter and number had an impact on flux leakage and pressure in chamber head. According to numerical simulation results, the weep hole number was determined as 6, weep hole diameter was 40mm and seal width was 1mm. Under the rated condition, turbine installation efficiency was 86.75% with flow rate of 5109m3/h, and the clearance leakage reach 0.3% of the whole unit flow. The calculation results agreed well with the test, which showed that clearance flow calculation method could provide scientific basis for the design of Francis hydraulic turbine weep hole diameter and number, and details of seal gap structure. The results would benefit to avoiding the hydraulic vibration and ensure the secure and efficient operation of units.

Abstract:Runaway Stabilities of Pump-turbines and Its Correlations with S Characteristic Curves

Abstract:Dolphin’s special skin structure has characteristics of drag reduction, by mimicking this structure, a kind of bionic coupling functional surface which has practical engineering application value was designed. It was applied on the surface of a centrifugal pump impeller to investigate the efficiency enhancement of the pump through contrast experimental method. The experimental results showed that the pump efficiency was improved by 3% by using this kind of bionic coupling functional surface. The hardness of surface material had influence on the pump efficiency. The mechanism of efficiency enhancement of bionic coupling functional surface was the coupling deformation between elastic surface material and bionic structure on the basal material, which can decrease the drag of impeller surface, absorb some energy and effectively reduce the turbulent kinetic energy of the inlet and outlet of impeller, thus, the hydraulic loss would be decreased.

Abstract:The net water diversion of agriculture in Hetao Irrigation District was studied. Based on the data during 1982 to 2012 in Hetao Irrigation District, the characteristics of the net water diversion variability in 31 years were analyzed by using several statistic methods, such as ANOM, ANOVA, correlation analysis, time series analysis and survival analysis. In addition, the impact of annual precipitations and water-saving engineering projects was analyzed by the progress of Hetao Irrigation District developmental history. The forecasted net water diversion in Hetao Irrigation District would be about 44.5×10.8m3 in 2013, 44.18×108m3 in 2014 and 43.86×108m3 in 2015 by the time series analysis method. In current water-saving engineering project, the forecasted net water diversion would be from 35×108m3 to 55×108m3 by the survival analysis method. The net water diversion was influenced sharply by annual precipitation (more than 211.76mm, namely wet years) and water-saving engineering project. These two factors had a negative correlation with the net water diversion. Finally, the relationship between net water diversion and total investment of water-saving engineering project was discussed. The results provided an important foundation for the management of sustainable development in Hetao Irrigation District.

Abstract:In order to explore the accurate management mode of water and fertilizer supply for young apple tree in semi-arid region, the bucket cultivation experiment was conducted to study the response mechanism of physiological properties and crop water productivity of two-year-old young apple tree to different water and fertilizer treatments. The treatments consisted of four irrigation levels: 75%~85% (W1), 65%~75% (W2), 55%~65% (W3) and 45%~55% (W4) of field capacity, and three fertilization (N—P2O5—K2O) levels: 0.6—0.6—0.2 (F1), 0.4—0.4—0.2 (F2) and 0.2—0.2—0.2g/kg (F3) water-free soil. The results showed that relative and saturated water contents and SPAD value of young apple trees’ leaves all can reflect the deficit status of soil moisture. The highest and lowest proline were found in F1W4 and F3W1 treatments (that in F1W4 was increased by 440.8% compared with F3W1), and the highest and lowest malonaldehyde were found in F3W4 and F1W1 treatments (that in F3W4 was increased by 167% compared with F1W1), respectively. The highest water use efficiency of leaf (WUE) and crop water productivity (CWP) both appeared in the treatment of F2W2 of which the net photosynthetic rate Pn, transpiration rate Tr and stomatal conductance Gs were decreased by 18.8%, 29.1% and 23.2%, respectively, while WUE was increased by 14.2%, dry mass was decreased by 5.2%, water consumption was also decreased by 16.4% and CWP was increased by 13.4%. WUE can reflect the CWP to some degree and the treatment of F2W2 reached the best water and fertilizer coupling mode.

Abstract:The spatial correlation between soil water content and root distribution in non-irrigation dense-dwarf jujube plantations was analyzed in semiarid hilly loess region of China. The soil coring method was used to sample roots at different depths within the 0~1000cm soil profile under different-aged jujube plants (1, 3, 5 and 12a). The results showed that the increment of average annual root depth decreased with the increase of jujube stand age. The maximum root depth of 12-year-old jujube was 520cm and the minimum root depth was 100 cm from the tree base, which was half-way between two trees planted 2 m apart. The difference between maximum and minimum root depths of 12-year-old jujube trees was 180 cm. Lateral roots started developing intersection networks after three years of planting. Soil water fluctuation was not induced by vertical root systems of dense-dwarf jujube plants. Root depth, dry soil layer depth and annual soil water variance within top 0~200 cm soil layer increased with increase of jujube stand age. However, root-zone soil water content decreased with increase of stand age, while dry soil layer depth was slightly larger than root depth. The results can provide vital technical support for jujube cultivation especially under semiarid conditions.

Abstract:The objective of this paper is to discuss the effects of mulching methods on freezing and thawing characteristics of salinized soil and the autumn irrigation quality in cold—drought—salt irrigation district. The field freezing and thawing experiments were conducted with the mulched salinized soil in Hetao Irrigation District. The experiments included five treatments: chopped maize straw 0.9kg/m2 (F0.9), chopped maize straw 0.6kg/m2 (F0.6), whole maize straw (YZ), plastic film (DM) and no mulching (CK). The results showed that the heat transport capability of different soil layers was affected by surface mulching after autumn irrigation. Mulching affected the process of soil freezing and thawing and changed the response correlation of the soil frozen depth to the negative accumulated temperature. The soil frozen depth variability during the freezing period can be assessed and predicted by the available negative cumulative air temperature. Results revealed that all mulching treatments improved the soil water storage in the maize sowing time for following year at depth of 0~10, 0~40 and 0~120cm significantly compared with CK. The soil salinity in the surface layer (0~10cm) and plough layer (0~40cm) was drastically lower than that of CK. The salt control effect of whole maize straw YZ was superior to the other treatments. The suitable sowing date of spring maize under plastic film mulching was advanced by 7d relative to CK, while the straw mulched date was delayed by 6~7d. Mulching measures improved the maize seedling emergence rate significantly，the emergence rate of maize of YZ and F0.9 were considerably higher than F0.6 and DM. The results could be used to guide the research of autumn irrigation scheduling under mulching situations in Hetao Irrigation District.

Abstract:Reference evapotranspiration (ETo) is a major component of the hydrological cycle. Accurate assessment of evapotranspiration is needed for water resources management and irrigation scheduling. The performance ability of gene-expression programming (GEP) and radical basis function neural network (RBFNN) was investigated for modeling ETo in weather station of Du’an for a 5-year period (2008—2012). The data set was comprised of daily maximum temperature, minimum temperature，sunshine duration and relative humidity, which was employed for modeling ETo by using FAO—56 Penman—Monteith equation as reference. GEP results were compared with RBFNN and Hargreaves models, and their performances were evaluated through determination coefficient (R2) and root mean square error RMSE. Based on the comparisons, GEP was found to perform better than RBFNN and Hargreaves models. The GEP model which can replace Hargreaves model and the GEP model without relative humidity were established. Statistically, GEP is an effectual modeling tool for successfully computing reference evapotranspiration.

Abstract:Based on the theory of unsaturated soil water dynamics and characteristics of soil moisture movement under negative pressure irrigation, a moisture infiltration model was proposed. The time-varying rules of moisture infiltration at the vertical soil profile on condition of negative pressure irrigation were simulated by moisture infiltration model of HYDRUS—2D. Result showed that the relative error between simulated and measured value was 2%~4%, which was within a reasonable range. The soil moisture infiltration rules under the negative pressure irrigation can be described effectively by the model. Moisture infiltration with different soils (soil and matrix in Beijing area) and different sizes of emitters (radius varied 8, 10 and 12cm) were simulated. The simulation results indicated that emitter size was a significant influence factor for soil moisture infiltration. The initial moisture migration rate was faster with larger emitter than that with smaller emitter. Meanwhile, the delay at the beginning of infiltration was shorter with larger emitter. There was a positive correlation between infiltration rate and emitter size, and water infiltration rate increased with the increase of the radius of emitter.

Abstract:There are some research difficulties and highlights in analyzing spatial variation in recent years, such as how to choose advanced methods, how to make efficient and reasonable experimental designs, how to normalize field sampling program process, and how to select representative sampling points. In view of the above mentioned issues, a research on spatial variable of soil thermal parameters on basin scale in Jinghui Canal Irrigation District, Shaanxi Province was conducted by combining RS, GPS and GIS technology. The results showed that soil thermal capacity, thermal diffusion and thermal conductivity displayed moderate variation in the selected regional scale. Thermal diffusion and thermal conductivity displayed a stronger spatial heterogeneity than soil thermal capacity, which showed a relative weaker one. Furthermore, a strong spatial dependence was found among the above three parameters. The optimum fitting models for soil thermal capacity, thermal diffusion and thermal conductivity were exponential model, spherical model and Gaussian model, respectively. And the sample spacings of above three models were recommended to be 2.67, 3.68 and 2.76km, respectively. Meanwhile, the best sampling spacing of soil thermal parameters in this region was recommended to be 3km. A simple fitting formula for soil thermal parameters determined by basic parameters of soil physics was established based on describing the spatial variability of soil thermal parameters. It was proved to be a good applicability with R2>0.80 after verifying. It indicated that quantization analysis on complex spatial variability of soil thermal parameters could be well achieved based on the introduced method.

Abstract:In order to investigate the effect of super absorbent polymers (SAP) dosage on the carbon footprint of farmland ecological system, a field experiment was conducted to study carbon absorption, carbon emission, carbon cost, carbon efficiency and net carbon sink. The results indicated that although the application of SAP and various agricultural inputs increased farmland carbon footprint, they promoted the growth of crop and improved quality of crop dry biomass. Thus SAP and various agricultural inputs significantly improved the carbon absorption, reduced carbon cost and improved the efficiency of carbon and net carbon sink. Carbon cost of the treatment with 60kg/hm2 of SAP was the minimum, which was reduced by 25.6% compared with the control, while its carbon efficiency and net carbon sink were the maximum, which were increased by 35.3% and 30.6% than that of the control, respectively. Meanwhile, SAP could improve water use efficiency of winter wheat, the treatment with 60kg/hm2 of SAP was the best. The correlation analysis among different factors showed that positive correlations were found between water use efficiency, carbon sequestration, carbon efficiency and carbon net sink, while negative correlation was found between water use efficiency and carbon cost.

Abstract:Soil nitrogen is necessary nutrient elements for plant in agricultural ecosystem，and excessive nitrogenous fertilizer is one of the main reasons of rural surface source pollution and water eutrophication. Therefore, understanding the spatial variability of soil nitrogen is vital for agricultural production and ecological environment protection. Qionghai lake is the second largest inland plateau freshwater lake of Sichuan Province. And it is important conservation areas for drinking water and nature reserve. Presently the water quality of Qionghai lake was mesotrophic status. Excessive nitrogen from rural surface source pollution was one of the main pollution factors. In this research, 386 soil sample points were selected by using random sampling method in Qionghai Basin，and soil physical and chemical properties were analyzed. Furthermore，spatial variability of soil nitrogen in the surface layer of this region was analyzed by using the geostatistics and GIS method，and its influential factors were also analyzed by means of variance analysis and buffer analysis．The results showed that the contents of soil total nitrogen (TN) and available nitrogen (AN) were (1.85±0.51) g/kg and (138.5±47.7) mg/kg, respectively. Variable coefficients of TN and AN were 27.52% and 32.24%, respectively, which belonged to a moderate level. Geostatistical analysis suggested that the spatial autocorrelations of soil TN and AN were moderate level，and random factors played a more important role in spatial variability than structural factors．The spatial variability of soil TN and AN were anisotropic, and obvious in northeast—southwest direction. TN and AN in the area were distributed in band and patches．Regions with high soil TN and AN contents were mainly distributed in southeast suburbs of Xichang City, and decreased gradually to north, east and south. Regions with low soil TN and AN contents were mainly distributed in north lakeshore zone of Qionghai lake. Spatial variability of soil TN and AN was significantly influenced by land use types, soil parent materials, soil textures, soil pH values as well as distributions of citiy, town, river and Qionghai lake. There was no significant correlation between spatial variability of soil TN and AN contents and roads.

Abstract:Mountainous soils often contain large amounts of gravels which impact rainfall infiltration, runoff and soil erosion. The flow velocity within gravels is of great importance for research of soil erosion process in rocky mountainous areas. Dye tracer method was commonly used to measure the leading edge velocity. The gravels of about 2 cm in diameter were used to fill to a thickness of about 5cm in a flume of 4m long, 15cm wide and 50cm high. Five sensors were used to measure the electrolyte conductivity change process at 0.3, 0.6, 0.9, 1.2 and 1.5m from the solute injector under three flow rates of 3, 6 and 12L/min and three slope gradients of 4°, 8°and 12°. The peak, mean and leading edge velocities were computed before comparisons were made with those measured by using dye tracer method. The results showed that under different conditions, flow velocity was not significantly affected by discharge rate, but notably affected by slope. With the increase in slope, flow velocity increased from 0.031m/s to 0.070m/s. The peak velocities were 0.81~0.83 times of the leading edge velocity, regardless of the effect of slope and flow rate. Mean velocities were about the same as the peak velocities, which were 0.68~0.78 times of the leading edge velocities and increased with distance increasing. The ratio of mean velocity and leading edge velocity can be also used to calculate the flow velocity within gravels measured by dye tracer method. The method should be useful to understand the hydrodynamics of water flow within gravel layers.

Abstract:Studying hillslope soil erosion processes in the black soil region is of great importance to black soil conservation and national grain production security. A rainfall simulation study was conducted to examine the effects of rainfall intensity and topography (slope gradient and slope length) on hillslope soil erosion processes. The experimental treatments included two rainfall intensities (50 and 100 mm/h) of representative erosive rainfalls in the black soil region, two common slope gradients (5°and 10°) and two slope lengths (5 and 10m). Each treatment had two replications. The results showed that runoff was increased by 1.4~12.4 times and 0.1~3.1 times, respectively, when rainfall intensity or slope length was increased under different treatments. Effects of slope gradient on runoff were complex, which were affected by both rainfall intensity and slope length. Rainfall intensity, slope gradient and slope length had important effects on hillslope soil loss. Soil loss was increased by 4.2 times when rainfall intensity was increased from 50mm/h to 100mm/h, and it was increased by 04 times for increasing slope gradient from 5° to 10° and 0.5 times for increasing slope length from 5m to 10m, which indicated that rainfall intensity had the most significant effects on hillslope soil loss. When rainfall intensity, slope gradient and slope length were increased simultaneously, soil loss was increased by 18.0 times, which suggested that the comprehensive effects of three factors were much greater than those of each single factor or the combination of two factors. Runoff had the strongest correlation with rainfall intensity, followed by coupling effects of rainfall intensity—slope length and coupling effects of rainfall intensity—slope gradient—slope length. Soil loss had the strongest correlation with coupling effects of rainfall intensity—slope gradient—slope length, followed by rainfall intensity and coupling effects of rainfall intensity—slope length. According to these observed data, the empirical equations for predicting runoff and soil loss were also established.

Abstract:Studying the effects of preferential flow on the infiltration process is of great importance to increase the accuracy of measurement. An experimental device was suggested to display water movement process in the soil during infiltration. The device consisted of a disassemble soil container, a halved infiltration ring and see-through container surface made of plexiglass plate. After infiltration ring was hammered into soil inside the container, the soil inside the halved ring was cut radially into two halves with a steel plate, part of soil outside the experimental part of the container was removed and a plexiglass plate was used to cover the soil inside infiltration ring for dynamic visualization infiltration experiment. Then the infiltration process in the soil profile within the ring can be observed. The structure of the device, working principle and its application methodologies were detailed. A series of infiltration experiments were conducted to demonstrate the working procedures of the device with silt loam taken from Beijing. The exemplary soil infiltrability processes were computed based on the water supplied into the ring during the experiments. The dynamic process of wetted area in the soil profile inside the ring indicated that preferential flow not only influenced the initial infiltration process but also affected the total infiltration process. The whole infiltration process was divided into three stages based on the infiltration characteristics produced by wetting soil, which were initial infiltration stage, transitional stage and steady infiltration stage, respectively.

Abstract:The spatial distribution of soil organic matter (SOM) has intimate connection with topography, but the synergy effect of topography for SOM spatial redistribution was frequently ignored in the study of SOM by traditional geostatistics. In order to investigate the influence of different topography on the spatial distribution of SOM, the method of SOM spatial interpolation based on topographic unit was proposed. Firstly, the terrain factors such as slope, aspect, topographic wetness index and topographic position index were calculated from the digital elevation data (30m×30m). Secondly, the topographic units were precisely divided into 13 different classical types more subtly by integrating the terrain factors, which effectively avoided the traditional terrain classification method that only based on elevation data. The regions were divided, which was based on terrain classification rules formed by the distribution of terrain factors in different landforms. Thirdly, soil samples were collected in different topographic types, and the distribution of SOM for each sample set in different topographic units was generated by ordinary Kriging. Then, the corresponding results of interpolation for each sample set were segmented based on topographic unit region, and combining the result in each region, the spatial distribution of SOM based on topographic unit was obtained. Finally, verification and comparison with the accuracy of each SOM distributions were performed, which were obtained by using topography based geostatistics and traditional global geostatistics, respectively. The results of experiment for researching the SOM distribution in Zhongxiang City showed that higher accurate and efficacious spatial layout of SOM can be acquired by geostatistics based on topographic units, especially in the gently topography region, the precision was increased by 16.39%. The SOM prediction accuracy in the rest of the terrain unit was similar to the global prediction accuracy with Pearson correlation coefficient of 0.75. Using geomorphic zoning to obtain higher accuracy for spatial distribution of SOM, and the influence of topography was considered in the study of SOM geostatistics. 

Abstract:Three case study areas from north, central and south Henan Province in China were selected for applying spatial grain size method to the research of distribution patterns of surface water body diversity. On the basis of summarizing and adapting the previous research methods of surface water body diversity from related references, a new method of space distribution length index (MSHDLI) was put forward. Then all the selected information was further processed to present the effects of different grain sizes, correlativity and effects of grain size between the correlation coefficient of MSHDLI, water network density (RD) and MSHDAI (modified Shannon diversity area index), and scaling relations between the three used indices and parameter, and multiple regression analysis model at a resolution of 1km×1km. Results showed that with the increase of spatial grain size, the granularity of the response curves of MSHDLI, RD and MSHDAI belonged to drop type; MSHDLI maintained significant correlativity with RD and MSHDAI with average correlation coefficient of 0.997和0.878 (P<0.01), respectively. Effect of grain size of correlation coefficient was significantly positive correlation between MSHDLI, RD and MSHDAI. The fitting function of MSHDLI and RD was logarithmic function, MSHDLI and MSHDAI was polynomial function. Multivariate linear regression model of MSHDLI, RD and MSHDAI indices was also conducted to show that MSHDLI was the dependent variable and RD, MSHDAI were the independent variables. The fitting model showed that MSHDLI and RD, MSHDAI had linear correlationship, and the level of MSHDLI to explain the others was above 95%. To a certain extent, MSHDLI can be a good combination of the indexes of RD and MSHDAI to describe the breadth and the spatial discreteness in surface water resource distributions.

Abstract:Fractal theory was used as one of the methods to quantitatively analyze soil particle size distribution (PSD) because it can better describe soil physical properties. The single- and multi- fractal were used to analyze the features of the soil PSD, the effects of different land use types on fractal parameters and the relationship between fractal parameters and soil PSD. Results showed that soil PSD was diversity in different regions of the Loess Plateau. Soil particle size, which was measured by laser method, was mainly distributed in two power-law domains, named Dsilt and Dsand. It was needed to redefine the domain boundary of Dclay, Dsilt and Dsand. Soil particle size was distributed in range of 20~100μm which was narrow and presented obvious heterogeneity, thus it was necessary to use multi-fractal method to describe soil particle distribution characteristics. The correlation analysis indicated that Dsilt showed prominent positive correlation with content of clay and silt (P＜0.01), Dsand showed negative correlation with sand content but not prominent. Consequently, Dsilt can be used to predict the change of soil texture and soil erosion degree of different land use types. There was an extremely remarkable effect of land use types on clay, silt, sand content, Dsilt, D0, D1 and D1/D0 value (P＜0.01), and remarkable effect on Dsand (P＜0.05), which indicated that multi-fractal parameters can be the indexes to reflect effects on soil properties.

Abstract:Subsurface irrigation has been realized by burying pots, pitchers and subsurface porous pipe, but the present preparation process of porous ceramics could not meet the performance requirements of subsurface irrigation emitters. A new preparation process of clay-based porous ceramics used for subsurface irrigation with minimal cost was explored. The effects of the preparation process (shirking temperature, contents and particle size of slag in the green body) on flexural strength, linear shrinkage and open porosity of porous ceramic were discussed. Finally, the optimal preparation process of porous ceramic with high flexural strength, low linear shrinkage and elevated open porosity were selected. The results showed that the sintering temperature and the contents and particle size of slag in the green body were three key factors influencing the properties of porous ceramics. When sintering temperature was 1075℃ along with content of slag in the green body between 10% and 30%, the porous ceramics showed the best performance with maximum particle size of 0.613mm. Flexural strength of porous ceramic was 9.0~11.0MPa with open porosity of 36.8%~44.8% and the linear shrinkage was 3.8%~4.7%. Therefore, the clay-based porous ceramic could be the appropriate material for subsurface irrigation emitter.

Abstract:In recent years, high temperature steam gasification (HTSG) is a new gasification technology which utilizes super-heated, high temperature steam as gasifying agent as well as partial heat carrier. A HTSG experimental platform for generating hydrogen-rich gas from biomass was proposed. The experimental platform included a high temperature steam generating system, a downdraft gasifier, a gas purification system, a sample gas collection system and an automatic control system. The gasification performance of the downdraft gasifier was evaluated by using pine wood shavings which considered the effects of reaction temperature. The steam temperature was controlled from 600℃ to 1000℃ during experiment. The results showed that combustible gas composition over volume fraction of 77% was obtained in these experiments. The volume fraction of H2 increased and CO and CH4 decreased as the reaction temperature increased. When steam temperature was (948±4)℃, the volume fraction of H2 reached (51.83±0.12)%, the lower heating value of produced gas was 9.81MJ/m3, composition ratio of H2/CO reached 2.17 and the gas produced by high temperature steam gasification can be stable to burn, thus the gasification performance was regarded as relatively perfect. High temperature steam gasification is an effective way by using biomass such as pine wood shavings for making hydrogen rich gas, and it has the huge development potential and application space. The results could provide guidance for gasifier and engineering design of the biomass gasification.

Abstract:The deterioration risk of bale silage is relatively high because of a high surface-area to volume ratio. Therefore, the damages of plastic covers of bales should receive particular attention since it may often occur during removing or transportation process. When bales are punctured, oxygen is allowed to permeate the silage and subsequently aerobic organisms flourish and metabolize the products of fermentation, and the temperature inside the bales will rise up again. So temperature is a key indicator when the material is noticed to be “heating” since while oxygen comes into contact with the silage. In order to forecast the risks of aerobic deterioration of silage, grass bale silage and alfalfa bale silage were selected as study objects. The method which used to embed temperature sensors into the bale to measure the temperature was proposed. The self-developed multi-sensor experimental system with a specific penetration shaft and cone (V-structure) was used. While the cone penetrated into bale, the thermal-couple sensor followed the cone into the bale. If the cone arrived at the place desired, the cone would extract but the thermal sensors would stay at the place. It can put the sensors into bale without introducing air followed. Two schemes measuring temperature changes in punctured bale were designed. The temperature of planned locations in bale was monitored. It was detected that the temperature of the silage which was closer from the damaged cover rose sooner. Paired t test was done between the corresponding values from the upper and the lower within bale silage. The test results showed that two temperature rising processes of upper and lower had a significant difference. By temperature curve comparison of the same silage materials with different dry matter contents, it was found that the temperature rising of silage with higher dry matter was faster. Furthermore, to measure the temperature field inside bale, a specific penetrometer was designed. It was fixed on the platform of measurement and controlled during temperature measurement. Based on the data of temperature distribution, the temperature distribution in bale silage could be visualized in 3D map. It is a powerful tool to analyze temperature distribution around the bale silage in multi-angle.

Abstract:Infant formula milk powder is very important for infants whose mother cannot or does not want to breastfeed. There is a growing need for infant formula milk powder market in China, however, the research of basic nutrition and process technology is relative backwardness. The domestic and abroad research progresses about nutrition of infant formula milk powder were introduced by analyzing the breast milk nutrient profile, standard of formula and the development of powder composition. By comparing the dry process and wet process with their effects on powder functionality, the progresses on the process technology of infant formula milk powder were discussed. The hazard analysis was also discussed to better control the quality of infant formula milk powder. A general overview of the selection of formula composition, process technology and the direction of industrial development was provided. Strengthening the basic research on breast milk nutrition, improving the differentiation among products and developing the infant formula which was mostly close to the Chinese breast milk were the key to the future development of China’s infant milk powder.

Abstract:To determine the effect of coagulation time and temperature on coagulation process of soymilk and develop a method to online evaluate soymilk gel’s qualities nondestructively, electrical impedance spectroscopy (EIS) and rheological measurement (elastic modulus G′ and viscous modulus G″) were employed to analyze the coagulation process. Phase angle of soymilk mixture increased drastically at low frequencies and then gradually reached around zero at high frequencies in each tested time course, and 10kHz was chosen to evaluate soymilk coagulation process as an optimum frequency. Normalized volume resistivity at 10kHz initially increased sharply and then gradually approached to an equilibrium state for each temperature course. The similar tendency was observed for rheological properties during soymilk coagulation process. Electrical impedance spectroscopy measurement was useful in determination of the endpoint of soymilk coagulation process. The coagulation process of soymilk was divided into two stages which were considered as two successive first-order reactions. The activation energy values calculated by volume resistivity, elastic modulus and viscous modulus were 17.82, 112.90 and 53.72kJ/mol, respectively. The rheological properties were affected more greatly by coagulation temperature than EIS properties. Good agreements between volume resistivity and rheological properties were ascertained by the linearity of plot at all coagulation temperatures. Therefore, electrical impedance spectroscopy measurement can provide a method for determining the endpoint of soymilk coagulation process, which was also a simple, fast and realtime approach for monitoring the rheological properties of soymilk gel.

Abstract:The transfer approach and transfer probability of Aeromonas spp. under various food-handling scenarios were centralized in a two-dimensional data table by applying matrix method, which aimed at quantifying cross-contamination of Aeromonas spp. among different food-contact surfaces. Results showed that the number of Aeromonas spp. on donor and recipient surface could be calculated simultaneously, for instance, the average values of Aeromonas spp. in chilled pork before and after cross-contamination were 3.02 lg CFU/g and 1.82 lg CFU/g, respectively. Results also confirmed that proper conducts after splitting pork including cleaning contaminated boards, knives, hands and/or just changing them into clean ones before splitting Brassica chinensis could effectively reduce cross-contamination level. The study of microbial cross-contamination could be helpful for setting good hygienic practice guidelines for consumers, and it could provide a theoretical basis for assessing the potential risk of cross-contamination.

Abstract:Sorption isotherms of freeze-dried mango (variety Tainong No.1) were determined at 25℃ and the data were modeled by GAB model. A J-shaped sorption isotherm of mango was presented and the GAB monolayer moisture contents were observed to be 0.107g/g. The unfreezable and freezable water contained in freeze-dried mango was examined to develop the state diagram. The state diagram of mango was developed using glass transition line(glass transition temperature vs solids content), freezing curve(initial freezing point vs solids content) and maximal-freeze-concentration condition. Freezing points and glass transition temperature were measured by differential scanning calorimetry (DSC) as a function of water content. Freezing points were fitted according to the Clausius—Clapeyron model and the parameter E was determined as 0.071 by using non-linear optimization technique. Glass transition was fitted to Gordon—Taylor model. The constants Tgs and k were estimated as 15.7℃ and 4.42, respectively. Glass transition increased with the increase of solids content, which was due to the plasticizing effect of water in mango solids. Freezing points decreased as total solids content increased. The maximal-freeze-concentration condition was calculated to be at a solid content of 84% with characteristic temperature of end point of freezing (T′m) being -32.8℃ and characteristic glass transition temperature (T′g) being -52.9℃. These characteristics revealed that the quantities of unfreezable water were 0.16g/g indicating the amount of reactive water. The state diagram of mango can be used in evaluating the storage stability as a function of temperature and moisture content. Moreover, it can also be used to design drying and freezing processes. 

Abstract:The dehydration process of ginger slices at microwave power of 0.8, 1.2, 1.6W/g (dry basis) was researched. The moisture content, drying speed and moisture ratios at different stages were calculated. Some drying mathematical models were selected, and by fitting analysis of the moisture ratios, Wang—Singh model can be used for dehydration process of ginger slices by microwave fluidized drying. Through the technology of nuclear magnetic resonance (NMR), the flow characteristics of moisture in ginger slices drying process were studied. A conclusion could be got that the free water can be converted to some uneasy flowing bound water in a short time, the whole drying process was dominated by drying bound water, and at the final stage the bound water was decreased to a certain extent and hydration water content increased, while uneven drying hadn’t been eliminated completely in microwave fluidized drying. A theoretical basis for the process control and process optimization of ginger slices microwave drying was provided.

Abstract:In order to meet the needs of quality detection of agricultural products during logistics, a wireless electronic nose (WEN) based on GPRS for applications in the “on-the-go” environment was designed. It consisted of 5 modules which were the sensor-array with 8 MOS sensors, signal processing module, master controlling module, GPRS module and remote monitoring system. The GPRS communication performance of the WEN was tested, it was found that when data transmission cycle exceeded 400ms, three communication performance indexes of GPRS network which were the time-lag between sending and receiving, packet loss during the transit and transmission rate would meet the demands of detection simultaneously. An application aimed at fresh mangos was taken by using the present WEN, and the obtained profiles of mango aroma were clear and stable. Mango storage prediction models were built with stepwise regression method (SR) and LDA—SVM, respectively, and it was indicated that the SR model of the control group mango had a certain predictive effect only for the mangos stored for 4 and 6 days, the SR model of the experimental group and the LDA—SVM model either of the control group or the experimental group achieved satisfactory predictive effect as a whole.

Abstract:In order to study osmotolerant yeasts which are capable of causing spoilage for apple juice concentrate, the yeasts present in apple juice concentrate collected from apple juice processing plants in Shaanxi Province were isolated and purified by using osmotic YPD media. The sugar-tolerance of different yeast isolates was assayed. The colony morphology, cell morphology and physiological characteristics were studied and the phylogenetic tree based on 26S rDNA sequence analysis was constructed to determine the genetic location of isolates. Except the isolate N18 which was identified as strain of Candida tropicalis, all the other isolates belonged to Zygosaccharomyces rouxii. All the isolated strains of Z. rouxii were capable of growing in 900g/L glucose and apple juice concentrate, displaying better sugartolerance ability and greater harm to the quality of apple juice concentrate than isolate of C. tropicalis which showed sugar-tolerance of 750g/L glucose and no visible growth in apple juice concentrate. The results suggested that strains of Z. rouxii might pose a threat to the quality of apple juice concentrate, and it was needed to be controlled in the production line of apple juice concentrate．

Abstract:To explore wireless underground sensor network (WUSN) node deployment, signal transmission and the channel characteristics in the soil, the relationship among radio frequency signal propagation characteristics of AG—UG, UG—AG and UG—UG communication mode under wireless channel and node burial depth, horizontal inter-nodes distance and soil water content were studied with 240, 433 and 868MHz carrier frequency for configuring wireless underground sensor networks in the soil. The experiment demonstrated that the maximum and minimum determination coefficient R2 of 24 models for goodness of fit were 0.997 and 0.910, respectively, which was the effect of node burial depth and soil water content on RSSI and BER in AG—UG and UG—AG communication. And that maximum and minimum R2 of 12 models for goodness of fit were 0.971 and 0.866, respectively, which was the effect of horizontal inter-nodes distance and soil water content on RSSI and BER in UG—UG communication. Besides, three-dimensional surface of RSSI was built with frequency of 433MHz, which could reflect the exact wireless signal propagation characteristics in the soil environment, and the model verification experiment was conducted through SPSS software. In the AG—UG and UG—AG communication, the minimum R2 of goodness of fit was 0.954, the maximum was 0998, and root mean square error was in the range of 0.729～3.198dBm. In the UG—UG communication, the minimum R2 of goodness of fit was 0.854, the maximum was 0960, and root mean square error was in the range of 3.238～6.553dBm. Validation results showed that the model could better predict the received signal strength in different communications. The results can provide technical support for building of wireless underground sensor network system in the soil.

Abstract:To date diverse soil moisture sensors have been commercially available but all of these are at point-scales of centimeters-to-decimeters with limited volume of sensitivity (VOS). In many cases, the spatial variability of soil moisture distribution can be considerably larger than the VOS. A novel motorized dielectric PVC-tube sensor prototype was presented for horizontally scanning soil moisture content (maximum scanning length 380cm). The sensing probe was cylindrical and thus can be mobilized through the PVC tube which was horizontally embedded at a certain depth of soil layer. In order to prove its technical feasibility, two case applications associated with drip emitter tests were presented as well. The experimental results demonstrated that the applications were potential to support the model validation for simulating water migration, monitor soil water variation in root-zone accompanying plant growth, provide one-dimension data for precision irrigation and evaluate the effectiveness of irrigation equipment.

Abstract:129 loess soil samples taken from the field in Qian County of Shaanxi Province in 2014 were chosen as objects to build the inversion model between soil moisture content and spectra. The spectra and gravimetric moisture content of soil samples were measured during the process of soil air drying, and the relationship between spectra and soil moisture content was analyzed. The spectral predictive models of soil moisture content were established by using the linear regression and exponential analysis. Results showed that the biggest correlation coefficients and absorption depth bands located in 570, 1460, 1960nm and 490, 1460, 1960nm in the region of 400~1340, 1460~1790, 1960~2390nm, respectively. The linear relationship between spectral characteristic indexes and moisture content was better than the index relationship. The linear models were optimum models for predicting moisture content of loess by using characteristic band (C1980) and absorption depth (D1980 and D1480) as independent variables. The calibration and validation coefficient of determination R2 and residual prediction deviation (RPD) were higher than 0.92 and 2.5, respectively, and the root mean square error (RMSE) was less than 2.5%. These results showed that the moisture content of natural soil samples can be predicted rapidly by using spectral reflectance during the soil drying process. The study can provide a reference for real-time and rapid soil moisture content monitoring and soil moisture quantitative inversion in large area by using remote sensing technology.

Abstract:Light use efficiency is an important parameter of plant productivity model. It is an evaluation index for plant to turn the solar energy into dry matter efficiency. Taking cucumbers as the study objects, a method for light use efficiency prediction was proposed with the help of analysis technique of laser-induced chlorophyll fluorescence spectra based on the theory of support vector machine (SVM). Chlorophyll fluorescence spectra, net photosynthetic rate and photosynthetic active radiation of cucumber leaves were synchronously acquired, and the 500~800nm band of chlorophyll fluorescence spectrum was selected as study objects. Firstly, the original spectra was pretreated by SG—FDT method. Secondly, the characteristic values of pretreated spectra were extracted by using principal component analysis (PCA) method, the first ten principal components whose cumulative contribution rate was 93.49% were selected instead of the original spectral information in the study. Finally, the prediction model of light use efficiency was established through the SVM with the radial basis function. The penalty parameter C and kernel function parameter g were ultimately determined as C=0.03125, g=1 by carrying out a large number of tests, and then 60 training samples were combined to train the model. Ten testing samples were used to test the established model, and the results showed that the average error of the testing samples was 8.94%, which indicated a good predictive power.

Abstract:Aiming at the problem that the detection of aquaculture pathogens suffers from difficult isolation, time-consuming and low degree of automation, a detecting method of aquaculture pathogens concentration based on microfluidic system with magnetic isolation was proposed．A dedicated microfluidic chip with automatic sample injecting, magnetic isolation and impedance measurement was designed, and the experiment platform based on microfluidic detection system was built. The optimum impedance measurement frequency, magnetic force and target bacteria capture time in the microfluidic system were determined, and as an example of Escherichia coli O157:H7 the performance of the system was experimentally verified. Experiment results showed that compared with plate counting method the proposed method was nearly the same in detection accuracy, and the detection time was decreased from 48 h to 50 min because of no-cultivation. The microfluidic system realized rapid isolation and detection for aquaculture pathogens with increased automation in the prevention of aquaculture disease.

Abstract:Individual tire magic formula parameter is traditionally derived from expensive equipment in laboratory which needs a large number of experimental data. And then the parameter is transferred to vehicle model at a design stage to simulate the vehicle handling behavior. The main source of uncertainty in this type of models lies in the tire—road interaction due to high nonlinearity. Proper estimation of tire model parameters is important for obtaining reliable results. A vehicle dynamics system containing constant noise and non-linear model was established，and the Runge—Kuttta method was used to simulate the model. The parameters were estimated by using auxiliary particle filter through two rounds weighted processes, and the vehicle dynamic parameters such as tire lateral forces could be estimated by using the parameters estimated before. Meanwhile, the field test was done. The measurements under several standard handling maneuvers (step-steer, double-lane-change, etc.) were presented, and the results showed that the proposed algorithm improved the accuracy of standard particle filter.

Abstract:A rapid compression machine test bench was developed for studying the combustion characteristic of alternative fuel， and the compression performance tests were carried out. After analyzing the influences of the factors such as hydraulic buffer, driven pressure on properties of the rapid compression machine and improving the compression performance, compression speed of the rapid compression machine was higher than 8m/s and the compressed temperature can be controlled in the range of 650~1120K. Combustion performance tests were carried out by using DME-O2-N2 mixtures. The two-stage combustion and two-stage ignition delay time of the mixtures were observed. The two-stage and overall ignition delay times of DME-O2-N2 mixtures were studied under varied compression ratios, compressed temperatures and compressed pressures. Results showed that with the compressed temperature and compressed pressure increased, the first and overall ignition delay times of mixtures were shorten under the same initial pressure. Under a certain compressed temperature, with increasing compressed pressure, the second and overall ignition delay times of mixtures were shorten while the first stage ignition delay time was shorten slightly.

Abstract:Accurate air-fuel ratio control is the key element for fuel economy low emissions and good driveability of spark ingnition engine. In order to more accurately identify the fuel film model parameter and achieve precise control of air-fuel ratio, the film identification equation based on fuel film dynamic model was built under the consideration of model error and random error. According to recursive least squares, the parameter estimation with weighted matrix expression was got, then the weighted matrix was solved using Markov estimation and the estimated value of optimal film parameter was got consequently. An engine model was set up using GT-power, and air fuel ratio, mass injection flow engine speed and air mass flow were obtained by using sampling experiment. Parameter identification applying the proposed algorithm and the least squares were conducted at 1000~3500r/min with throttle opened from 5%~75%, respectively. Meanwhile, the identification results were compared with the calibration value. The results showed that the deposition coefficient X of fuel reduced and evaporation time constant τ of film quality increased with increase of throttle opening degree when speed was the same, and X, τ decreased as speed increasing when throttle opening degree was the same. Compared with the least squares algorithm, more accurate identification result can be got by using the proposed algorithm.

Abstract:An attitude measuring method for excavator’s manipulator based on vision measurement was proposed. Using the industrial camera to grab the perspective images of the manipulator, a saddle point detection was adopted to detect the manmade targets which was fixed on every arm of the excavator. Then the fixed geometric dimensioning between two targets was used as a constraint condition to select the saddle point in targets, and the attitude angle of the corresponding arm can be derived from the saddle point coordinates. The image detection area was reduced through anticipation of target movement and the algorithm processing speed was improved. Experiment results showed that compared with the original displacement sensor system installed on the excavator, the measured deviations of dynamic attitude angle for boom and arm were less than 1 degree and 2 degrees, respectively. The average processing time of this method for each manipulator movement frame was within 100ms. And the feasibility of this method for measuring excavator manipulator’s attitude was verified.

Abstract:In order to solve the problem of multi-objective size optimization of truss structures with stress constraints, a multi-objective optimization algorithm with multi-neighborhood was proposed. Based on the Euclidean distance between individuals, the population was divided into multi-neighborhood to form several niche populations. A number of individuals were assigned to each cell as neighborhood by the proposed algorithm. The individuals were only allowed interacting with each other within its neighborhood and generating offspring. The influence of different sizes of neighbors on the performance was analyzed through simulation experiments. The test results on 18 benchmarks revealed that the proposed algorithm outperformed some state-of-the-art algorithm in terms of covered area and diversity, which showed good uniformity and diversity. The obtained Pareto front showed good uniformity and diversity when solving the classic multi-objective optimization problem of 25-bar truss structure. The algorithm showed good performance in program design, solution space and generality and so on, which was very simple, practical and suitable for engineering practice.

Abstract:The bat algorithm was integrated into decomposition mechanism on the basis of its evaluation and a multi-objective bat algorithm based on decomposition (MOBA/D) was proposed. In order to improve the algorithm diversity, the differential evolutionary strategy was introduced into MOBA/D. The performances of MOBA/D on 14 multi-objective optimization problems were tested, which included family benchmark functions of LZ—09 and ZDT with different neighborhood scales effect on the performance of the algorithm. The result indicated that MOBA/D had the best performance with neighborhood size of 20. Compared with MOEA/D—DE and NSGA—II, the simulation results showed that MOBA/D can obtain a more uniform distribution of Pareto solution set and better convergence as well as diversity than those of state-of-the-art multi-objective metaheuristics. For further performance analysis of MOBA/D on constraint problem, the optimization design of sliding bearing was solved to demonstrate the feasibility and effectiveness. The good performance on convergence and diversity of the obtained Pareto set demonstrated that MOBA/D was suitable for engineering practice, which was an effective way for solving complex and high dimensional multi-objective optimization problems.

Abstract:As a new geometric representation and calculation system, the conformal geometric algebra has been recognized as a research hotspot in recent years. But as a new branch of algebra, the conformal geometric algebra is still in the process of development, especially its application in theory of mechanism is relatively deficient at present. The new geometric algebra method for the kinematics analysis of spatial parallel mechanisms was studied and a conformal geometric algebra method integrating geometric representation and calculation was proposed. With the origin of coordinates on the moving platform describing its position and Euler angles describing its orientation, the conformal geometric algebra expression of an arbitrary point’s location on the moving platform in the fixed coordinate system was presented. Then a method to establish kinematics equations for the kinematics analysis of spatial parallel mechanisms was proposed to conduct the forward and inverse kinematics analysis of spatial parallel mechanisms. A 4-UPU parallel mechanism was taken as an example to illustrate the proposed conformal geometric algebra method for kinematics analysis of spatial parallel mechanisms. And a numerical example was given to verify correctness and effectiveness of the proposed approach. The proposed conformal geometric algebra method was a new method for the kinematics analysis of spatial parallel mechanisms by integrating geometric representation and computation.

Abstract:For the dimension synthesis of eight-bar linkages for 4-position, a solution region synthesis method was presented. Firstly, the solution curves meeting the requirements were obtained according to the specified 4-position 4R open chain. The solution region was set up according to feasible sections of solution curves. Secondly, the linkage with defects was removed from the solution region by using defects identification method of eight-bar linkages. Finally, the feasible solution region was built and practical engineering requirements were considered and imposed. The eight-bar linkages from the feasible solution region, which met the requirements, can be picked out rapidly and accurately by designers. The problem of dimension synthesis of eight-bar linkages for 4-position was solved effectively by the solution region synthesis method and the eight-bar linkages could be widely applied in reality. The synthesis process of eight-bar linkages for 4-position was illustrated by the example.

Abstract:An efficient condensation parallel computing method for finite element structural analysis was proposed based on the sparse storage techniques and direct sparse solvers. In the proposed method, the process of condensation was converted to the process of solving a series of linear equations, and then the linear equations were solved with a direct sparse solver. It can avoid the storage and computation of many zero elements within the bandwidth in the traditional parallel computing method with variable bandwidth format condensation. Therefore, the memory space can be greatly saved and the amount of computation can be effectively reduced. Finally, the experiment of the finite element numerical simulation for an engine crankshaft was used to validate the proposed method. Test results showed that, compared with the conventional parallel computing method with variable bandwidth format condensations, the proposed parallel computing approach with sparse storage format condensation could considerably save memory space and significantly improve computational efficiency. The larger the size of each subdomain, the effect of the proposed method on aspects of saving memory space and improving computational efficiency was more obvious. The proposed method can be applied to many industrial areas such as aerospace, automobile, energy, civil and architecture to significantly improve the efficiency of engineering design and analysis.

Abstract:At present, the non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ) is used widely in researches of flexible job-shop multi-objective rescheduling problem. Because of the excessive elite reservation, the algorithm is easily precocious, thus the performance of multi-objective optimization algorithm could be improved. By analyzing the research status and insufficiency of multi-objective flexible job-shop scheduling problem (FJSP), a multi-objective FJSP optimization model was put forward, in which the makespan, processing cost and processing quality were considered. According to the above model, a modified non-dominated sorting genetic algorithm (NSGA-Ⅱ) with close relative variation was designed. In this algorithm, the chromosome mutation rate was determined after calculating the blood relationship between the two cross chromosomes. Crossover and mutation strategies of NSGA-Ⅱ were optimized, and the prematurity of population was overcome. Finally, the performance of the proposed model and algorithm was evaluated through a case study, and the results demonstrated the efficiency and feasibility of the proposed model and algorithm.

Abstract:With the aim to tackle the problem that the engineering complex curves can not be constructed by using a single curve, the continuity condition of the λ-Bézier curves of degree n with shape control parameters were investigated. The λ-Bézier curves of degree n not only inherit the outstanding properties of the corresponding classical Bézier curve of degree n, but also have a good performance on adjusting their shapes by changing shape control parameters. In the particular case where the shape control parameter equals to zero, the λ-Bézier curves degenerate to the classical Bézier curve. Firstly, the Bernstein-like basis functions of arbitrary order n were constructed by using a recursive formula from the initial basis functions, and the geometric property at the endpoints of the λ-Bézier curves were obtained, such as interpolation at the corners, the derivative at end-points and the second derivative at end-points. Secondly, based on the analysis of basis functions and terminal properties, the necessary and sufficient conditions of G1, G2 continuity and C1,C2 continuity between two adjacent λ-Bézier curves were proposed. Finally, some properties of the continuity condition for the λ-Bézier curves and applications in λ-Bézier curves design were discussed. In addition, the influence rules of the shape parameters on the complex λ-Bézier curves shape were studied.The modeling examples showed that the proposed method was effective and easy to implement, which greatly enhanced the ability to construct complex curves by using λ-Bézier curves.

Abstract:Rapid and wide application of the complex surface in modern manufacturing makes new demands of the registration techniques on complex surface. Although significant progress has been made in complex surface registration, it remains a difficult problem in some situation. For a complex part with multiple freeform surfaces, the precision of measurement points often exists different in different surface regions due to a variety of measurement methods. Meanwhile, the manufacture precision in different regions is also not the same in complex manufacture process. Problems of registration on complex surface, have become increasingly prominent and new methods are bound to be found. Robust principle was generalized to the complex surface registration in which the precision difference existed in different surface regions. A robust registration was presented based on M-estimation. The effect of low precision measured data was weakened for the registration result by M-estimation functions. But the solving efficiency of the model was low due to the highly nonlinear and piecewise of the objective function. A good initial position was easily available with current registration method, and the error functions were linearly approximated by Taylor expansion when the rotation transform was slight. A linear registration model was found and the efficiency was improved. An approximation of the rotation matrix based on the minimization of Fibonacci norm was adopted in each iteration. Both theoretical and experimental results confirmed the stabilization and efficiency.

Abstract:According to the requirement of a given parallel mechanism end actuator and to make sure that kinematics transmission performance of each branch is relatively better in optimum design of its structure parameters，local and global motion (speed), force and power distribution performance indicators were defined by using the character of dispersion, which reflected the ability of branch to share the load requirements. For a single drive branch power output, the effect of speed and force was discussed which were both variable physical quantities on power, and the movement and force coefficient were defined. The workspace of parallel mechanism was analyzed by using those parameters. Finally the 3-RPS parallel mechanism for attitude adjustment components was used as an example. And a detailed solution to the above indicators was developed. Performance atlas in the modified design space was overlaid，the structural parameters of the mechanism were optimized and the corresponding workspace was found out. The motion, force and power distribution performance indicators can be further applied to the performance analysis of other parallel mechanisms, as well as to guide optimization design of parameters. Each branch of the parallel mechanism obtained through this optimization method has good power, motion and force transmission performance. This sets the foundation for the kinematics and dynamics analysis of parallel mechanism.

Abstract:Adjustability of infeed angle is of great importance to design and use of the whole continuous flat press which is used to produce wood-based panels. Based on the capability of bending deformation of the steel, a method using bending deformation of integral infeed upper hot platen shaped as rectangular in cross section to adjust infeed angle was put forward. On the basis of analyzing curving principle of bending deformation and deducing geometrical relationship between radius of curvature and height of curving, bending strength of infeed upper hot platen was calculated by simulation and a distributed system as well as human-computer interaction control system based on fieldbus was established. Displacement gradient progressive-approximation algorithm used for hydraulic cylinders was set up and the system was applied to continuous flat press designed in China. The results showed that bending deformation of upper hot platen met requirements of bending strength, the method of adjusting infeed angle and the control algorithm could be used to achieve progressivity of displacement changing for hydraulic cylinders and dynamic adjusting of infeed angle, and the control precision could be reached by field debugging. The maximum error was 0.4mm between theoretical and practical value, and maximum horizontal difference was 0.6mm when radius of curvature was 100000mm.