Abstract:A dual circle tangential line-tracking control method was designed to solve the problem of linear tracking control when navigation system of 2BFQ—6 type direct-seeding combined dual purpose planter for rapeseed working near the boarders of a field. Firstly, a geometric relation formula of optimal connecting linkage was found by quantitative analysis of the far targeted line searching path. Then the method of dual circle tangential line-tracking was constructed by the geometric relation formula, which created decision-making. According to the position and orientation of the tractor, the matching control equations were selected by decision-making, and its calculations were used for tractor navigation control. Hence, a navigation system simulation model was established, which was used to achieve the purpose of optimizing model parameters and verifying the model performance. Path experiments were carried out with the navigation system of tractor. Experiments result showed that the overshoot of lateral deflection error response was less than 3%, rising time and settling time of the response were smaller than 14s and 19s, respectively. When the speed of tractor was 0~7m/s, the initial lateral deviation error of the tractor center between the target line was 7m and the initial course deviation error was 90°. When it was compared with the method of conventional pure pursuit navigation model, the dual circle tangential line-tracking control method resulted in less values of overshoot and settling time. Based on the results of path tracking experiments and field experiments, the dual circle tangential method could be applied to operation of lane-changing and turning of 2BFQ—6 type direct-seeding combined dual purpose planter for rapeseed.

Abstract:Because of two kinds of deformation with tool under general process of tillage, i.e., bending deformation with straw extrusion and shear deformation with straw shear, at loading speeds of 15~30mm/min, and also on two different positions of straw for measuring the displacement in the soil, which was horizontal and vertical with down-rotary speeds of 180~280r/min with the help of color straw labeled and arranged in lines and paralleled to the rotor axial. The original and final positions of straw tracers were drawn with Matlab software. It was found that the shape of final positions was similar to the arrangement of rotary blades attached to the rotor. The results revealed that the bending strength of wheat straw was decreased with increase of loading speed, and that of rice straw was increased at initial stage and then decreased with the increase of loading speed. It was obvious that the shear strength of rice straw was increased, and for wheat straw it was also increased at initial stage and then decreased with the increase of loading speed. The comparisons and conclusions of experiment were drawn as follows: the displacement and fluctuation of rice straw were greater compared with those of wheat straw, and the straw arrangement mode was corresponding through two types of straw distribution, the coordinate position of vertical straw and horizontal straw was symmetrically distributed on the X axis and X and Z axes, respectively. Based on these findings, the rotational speed of 230r/min can be chosen，meanwhile，adjusting the operation type and straw arrangement in the field can help to achieve a good effect of straw returning to field.

Abstract:In order to test the performance of different types of maize precision seed meters accurately and conveniently, an instrument for testing seed meter’s performance was designed. Utilizing PLC as control component, the instrument can achieve driving seed meter by servo motor, detecting falling seeds by photoelectric seed sensor, setting planting parameters and displaying detection results by touch screen. Besides, under different planting parameters (i.e., seed spacing, planting speed, and number of holes on seed plate), it can real-timely test seed meter’s seeding performance indices, such as quality of feed index, miss index, multiple index and precision index. Meanwhile, the instrument can detect the multiple and miss number of each clip in finger pick-up seed meter and make real-time animation simulation to the dropping situation of seeds. When the quantity of dropping seeds met the number set out, the instrument would stop detecting and save the results automatically. To verify the detection precision of the instrument, a comparison experiment with JPS—12 seed meter detection platform and MeterMax seed meter detector was carried out. Experimental results showed that the instrument and JPS—12 seed meter detection platform’s performance were almost the same at three speeds of 4km/h, 8km/h and 12km/h, and the quality of feed index for testing finger pick-up seed meter was differed by less than 2%. The detection precision of the instrument and MeterMax seed meter detector were much the same at nine speeds from 4km/h to 12km/h, because the results for testing finger pick-up seed meter were differed by less than 2% and the results for testing air-suction seed meter were differed by less than 0.7%. As a consequence, the instrument met requirements for testing seed meter’s performance.

Abstract:Root-cutting grafting is a new method in cucurbitaceous seedlings grafting. Compared with the traditional methods, root-cutting grafting seedling grows with stronger root, resulting in a greater production in a longer harvesting period. Recently many grafting robots can work well in grafting processing. But the lack of planting grafted seedlings automatically has become a problem in the automation of industrialized nursery process. To solve this problem, a mechanism of automatically planting root-cut grafted seedlings of cucurbitaceous was developed, which included soil hole-making unit, seedling-moving unit, seedling-planting unit and other parts. It can be added to the current grafting robot, and automatically planting seedlings grafted by the robot. The soil hole-making unit can hit a hole at the center of each cell of the seedling tray filled with soil. And the seedling-moving unit can transport the grafted seedlings from the grafting area to the planting area. The seedling-planting unit was the key part of the mechanism, which can plant the seedlings automatically. Some simulations were done with the software of Solidworks. And the simulation results showed that the velocity ratio of prismatic cylinder in the seedling-planting unit to the joint cylinder in the seedling-planting unit should be between 0.22 and 0.55. Experiments were conducted in laboratory, and the results showed that the success rate of planting seedlings was up to 92%, and the longest time of one planting was 7s. Experiment in laboratory showed that the designed planting device can work well with the current grafting robot in an automatic and efficient way.

Abstract:Apricot is a very important fruit for production and trade in Xinjiang, China. Xinjiang is the largest apricot producer in total annual production and planted area. However, the fresh apricot is very liable to become putrid and perished during storing and transporting. And the losses of apricot perished in total annual amount accounted for about 20% during transporting, marketing and storing after harvest. Thus, it is clear that fresh apricot processing, especially in the planted sites has become the most important measure and the major bottleneck for apricot industry in Xinjiang. Traditionally, fresh apricots can be processed into various special flavor apricot products, including dried apricot slices, preserved apricots，canned apricots and apricot jams, which are very favorable. One among the apricot products is the dried apricot slices, represent of the local color apricot products processed. Based on the combination theory of agricultural machinery and agronomy as well as the related basic study, this research was conducted to determine the optimal structure and design parameters of the dynamic orientation device for fresh apricots in the light of study of the physical and mechanical properties of apricot during transporting and segueing, and to develop the dynamic orientation device for fresh apricot. And self-orientation mechanism was proposed based on principle of least action principle and apricot’s physical properties. The differential speed conveying mechanism and interaction of friction with belt for fresh apricot were analyzed. The apricot’s orientation position can be adjusted by orientation belt and clamp belt during conveyance process. Structure of apricot orientation device was schemed, including clamp belt, orientation belt, slope plate, clamp gap adjustment component, belt tension adjustment components and other auxiliary components. All those components created orientation channel. The clamp gap and belt tension can be changed by adjusting the adjustment components. Line speed of clamp belt and orientation can be controlled by adjusting the current frequency of converter. Saimaiti apricot was taken as research object. Orthogonal test was designed. The test factors were speed ratio of orientation belt to clamp belt, gap between two paralleled clamp belt and size of apricot. Test indexes included orientation rate and cutting rate. Experimental results showed that the best combination level can be as follow： speed ratio of orientation belt to clamping belt was 6.52, clamp belt gap was 15mm, interval size of apricot short-axis diameter was 32.1~35.0mm. The orientation accuracy rate was 87.4% and cutting accuracy was 85.6% accordingly. The results provided a reference for dynamic orientation research which based on belt conveyance for apricot.

Abstract:The purpose of this paper was to study and modify the interaction between wiper mechanism and billhook mechanism to solve wiping failure and rigid impact problems. Firstly, load-deformation of wiper was simulated. The results indicated that the stiffness of wiper along billhook shaft direction is 801.05N/mm and the interference between wiper and billhook should be in the range from 0.38mm to 0.59mm. Furthermore, under the maximum pressure, the angles of knife that was mounted on wiper, were changed with Oxy plane, Oxz plane and Oyz plane, which were 0.659°, 0.4759° and 0.4555°, respectively, so it gives a data support for knife installing compensation. Based on rigid-flexible collision theory, a new improved design with elastic billhook shaft system was introduced. The new design used a compression spring that enables the billhook to move elastically and slightly along the shaft direction. Meanwhile, the new billhook system would not affect billhook bevel gear’s movement, since the spring keeps the gear on its original position continuously. Simulation results demonstrated that the design could reduce initial contact force between wiper and billhook by 46.3% and 83.9% at wiping and return phases, respectively. Therefore, the design can decrease impact, and it has a theoretical advantage of increasing knotting rate. Finally, a prototype of the design was produced and its feasibility was verified by actual baling experiments.

Abstract:Based on the single-stage self-priming centrifugal pump, a kind of self-priming device of multistage self-priming pump with high self-priming performance and external characteristic was proposed. Based on the positive and inverse diffuser, the backflow device was creatively designed and composed of gas-liquid separation chamber, outer shell, self-priming cover plate and gas-liquid mixture chamber. The highpressure water of finalstage pump chamber was sent to the first-stage pump chamber through the backwater device, and the gaswater was mixed repeatedly in the self-priming process. When the self-priming was completed, backflow valve in the self-priming cover plate was automatically shut off under huge pressure difference, which effectively improved the efficiency of self-priming pump. Based on the multi-objective fuzzy optimization design, the multi-objective optimization model with the maximum head of off dead point and minimum value of maximum shaft power was determined. Combined with design experience and technological needs, relevant constraints were established and solved through nonlinear extremum. Finally, the hydraulic optimization design of flow components was completed with the optimum solution. By doing the external experiments of multistage self-priming spray irrigation pump, it was concluded that the head of off dead point and maximum shaft power met the demand, which provided a new reference for optimization design of pump.

Abstract:The submersible axial-flow pump system has been more widely applied in pumping projects. Usually the existing submersible pumps used for bi-directional pumping stations are the reversible pumps, the forward and reverse pumping of which is less efficient. The flow characteristics of a new bi-directional submersible pump system combined with the submersible pumps and two-way passages together were explored. By CFX software the full-flow numerical simulation of the system was made and the system flow field was obtained. Also the system hydraulic performance was predicted. The flow characteristics of suction passage with different measures were analyzed. The velocity distribution uniformity at outlet of suction passage showed the elliptical-type flow guide cone of the passage worked the best to prevent harmful vortex, which guaranteed the flow conditions of pump operation. Using specially designed discharge-chamber with unilateral angle of 18°, the flow separation was effectively inhibited, the hydraulic losses were reduced which ensured the overall efficiency of pump systems at high level. A model test was conducted in the high-precision test-bed of hydraulic machinery. The test results showed that under the pump head of 3.11m, flow rate of 256L/s, the pump system efficiency reached 71.9%, which was above the forward or backward pumping efficiency of reversible pump system by 7 and 13 percentage points, respectively. It was evident that the vertical submerged pump system with two-way passage was suitable for bi-directional pumping station. Experimental results and predicted model performance results were consistent in high efficiency area, and the numerical calculations were well verified.

Abstract:In order to study the impeller internal flow field of the mixed-flow pump with nonuniform tip clearance, the internal flow field in mixedflow pump with two eccentricities which were 0, 0.3mm and 0.5mm was numerically simulated based on the standard RNG k—ε turbulence model and SIMPLE algorithm. Besides, the external characteristic, static pressure distribution on blade surface, tangential pressure, turbulent kinetic energy distribution and streamline distribution near the tip clearance of mixed-flow pump were compared under the conditions with or without eccentricity. The results showed that the type of numerical simulation grid and the turbulence model can accurately predict the internal flow characteristics of the mixed-flow pump. The maximum decrease of head in mixed-flow pump was 9.8%, the efficiency at the design point in mixed-flow pump was dropped by 4.3% and the high efficient point was swung to the large flow rate when eccentricity e was 0.5mm. The pressure distribution of inlet and outlet of mixedflow pump impeller was affected greatly by eccentric, and pressure distribution near the eccentric side of the blade outlet flange showed a trend which was gradient distribution along the radial and circumferential pressure distribution was greatly imbalanced. Non-uniform tip clearance seriously interfered with the end wall region flow, which led to the unsteady flow phenomenon of the leakage flow and the secondary flow in the flow field of the tip clearance was obviously increased, the turbulent kinetic energy dissipation was increased with the increase of eccentricity and hydraulic loss, which was the main factor resulting in a decline in the efficiency of mixed-flow pump. The research results had reference meaning for revealing the internal flow characteristics of impeller in mixed-flow pump with non-uniform tip clearance.

Abstract:Strong pressure fluctuation existed in semi-open centrifugal screw pump with single blade under the combined influence of asymmetric impeller structure, static and dynamic coupling effects between impeller and volute and tip clearance leakage etc., which was not conducive to the safety operation of the units. The semiopen screw centrifugal pump with blade and specific speed of 237 was taken as research object, STAR—CCM+ simulation platform was used, calculation area was partitioned with polyhedral mesh, the steady and unsteady numerical calculations of whole flow field were conducted, meanwhile, the outer characteristic was predicted and the pressure fluctuation of inlet and middle area of the blade was monitored. Results showed that the error between predicted outer characteristic and test results was very small and the trend of monitored pressure fluctuation was basically consistent with the test, but when there was a distance between monitoring points and suction surface and a large circumferential distance from the same axial height of pressure surface, the results of numerical calculation were different from the test results. It can be found from the pressure time-domain diagram of two monitoring points that pressure fluctuation span of Pre2 was larger than that of Pre1, which was due to the work capacity of blade’s middle area was better than that of inlet area. Analysis of pressure contour of monitoring points showed that when the pressure surface was close to the monitoring point, pressure reached its maximum value, and at 1/3 circumferential thickness area of the blade, pressure reached its minimum value. In addition, in the range of the lowest point to the highest point, the pressure fluctuation of two monitoring points presented three kinds of slope change under five working conditions.

Abstract:Diffuser is one of the most critical flow components in submersible well pump, its hydraulic design has an important influence on the pump performance. A typical submersible well pump was chosen as the research object to study the influence of space diffuser vane number on the performance of submersible well pump by means of numerical simulation and experimental test methods. Based on the same curve profile, the diffuser vane number was adjusted to 6, 7, 8. The calculation domain was created based on single stage pump model, which was meshed with the high density of structured grids. Grid independence analysis was processed to determine the proper meshing scheme. The numerical simulations under multi-conditions were performed based on SST k—ω turbulence and standard wall function. Through the comparisons of predicted pump performance, it is found that the pump head is increasing with the increase of vane number under small flow rates. However, too many vanes occupy more passage area, which led to blockings and more hydraulic losses under larger flow rates. The scheme of 7 diffuser vanes matches the impeller very well, its import area tallies with the impeller outlet area and less hydraulic losses. The test results that this scheme has an pump performance, both the single-stage head and efficiency are higher than the national standard, which successfully completes the expected design goal. The head and power of numerical simulation prediction are slightly higher than the test results, the predicted pump efficiency is slightly higher than the test results, but the change trend is almost same with each other. The results of this study provide basis and reference for the improvement of submersible well pump performance.

Abstract:In order to optimize the double-channel pump impeller, inner flow field of the original pump was simulated and diagnosed by introducing boundary vorticity dynamics theory. Several positive and negative BVF peak areas were observed at different locations of the original impeller, which usually relates to large pressure gratitude and flow separation. By analyzing the distribution of BVF, friction and vorticity lines on the impeller surface, the locations of the bad flow inside the impeller and their dynamic roots were found. According to diagnosis of the flow, the structural parameters affecting inner flow state of the double-channel pump impeller were adjusted to obtain the optimized double-channel pump impeller. Combined with CFD and boundary vorticity dynamics flow diagnosis method, the double-channel pump impellers, before and after optimization, were compared and analyzed. The results showed that the distribution of BVF, friction and vorticity lines on the surface of optimized impellers had been significantly improved. The peak and mean values of BVF were both decreased apparently and the uniform index was much closer to 1. The flow separation was suppressed and force distribution was improved, therefore, the head and efficiency of the pump were improved obviously. The research work proved the feasibility of applying inner flow diagnosis and optimization method based on boundary vorticity dynamics theory in the channel impeller machinery, and it also provided reference for the study of optimization design of other turbomachinery.

Abstract:In order to understand the effects of water—nitrogen coupling on nitrogen accumulation, transportation and distribution, absorption and utilization, and dynamics of nitrate accumulation in soil of dripirrigation multiple cropping oil sunflower in Shihezi area in the northern Sinkiang, based on field experiment, and combined with laboratory experiment, local early maturing variety “new No.5 hybrid oil sunflower” was taken as test materials, and a threelevel complete treatment plot experiment of two factors of water and nitrogen under drip irrigation was conducted. Results showed that nitrogen accumulations of all organs of dripirrigation multiple cropping oil sunflowers of different water—nitrogen combinations were centered by blades at earlier growth stage and by flower disc at late growth stage. Water—nitrogen combination had prominent (p<0.05) or extremely prominent (p<0.01) interaction effect on accumulation, distribution, transportation, absorption and utilization of nitrogen and production of oil sunflowers of all their organs at each growth stage. Appropriate water and nitrogen augment (pure nitrogen amount no more than 232kg/hm2, irrigation amount no more than 3000m3/hm2) can promote effective nitrogen accumulation of each organ of oil flowers and transportation and utilization of nitrogen of oil sunflowers, thus the goal of high production of oil sunflowers was realized. Water and nitrogen coupling significantly affected the nitrate accumulation in soil. With the increase of nitrogen application, the accumulation amount of nitrate in 0～80cm soil layer was increased; with the increase of irrigation water, the nitrate accumulation of 0～40cm soil layer was decreased, and that of 40～80cm soil layer was increased; after harvest, with the increase of irrigation water and nitrogen application, the relative accumulation of nitrate in 40～80cm soil layer was increased, and that of 0～40cm soil layer was decreased. Combining production of oil sunflowers and performance of plants absorbing and transporting nitrogen, the best nitrogen increase in faceplate was 2.16g/plant and yield was 3597.11kg/hm2，the best water—nitrogen combination of this experiment was irrigated with water of 3000m3/hm2 and irrigation with pure nitrogen of 232kg/hm2. 

Abstract:The difference in collapse of soil aggregate among soil wetting rates and erosion types would induce variation of hillsope erosion processes. The unique erosion characteristic of a contour ridge system may change effect of soil wetting rate on erosion processes. Simulated rainfall experiment was conducted to evaluate the characteristic of runoff, sediment yielding, and soil aggregate transport under five soil wetting rates (10mm/h, 20mm/h, 30mm/h, 60mm/h and 90mm/h) for cinnamon soil in a contour ridge system at different stages of erosion. The result showed that runoff was increased with the increase of soil wetting rate during interrill stage, but no significant difference was observed among soil wetting rates at rill stage. For sediment yield, it was enhanced gradually when soil wetting rate was increasingly shifted from 10mm/h to 90mm/h during both interrill and rill stages. Compared with 10mm/h soil wetting rate, sediment yield from 20mm/h, 30mm/h, 60mm/h and 90mm/h were significantly increased by 25.16%~115.51%, 95.02%~144.34%, 151.03%~164.49% and 249.42%~398.91%, respectively. The variation of soil wetting rate only changed process of runoff yielding at interrill stage, while it altered runoff and sediment yielding processes at rill stage. The transport of micro-aggregate, which was the chief lost size, was mainly from breakdown of 2~5mm and 0.25~0.5mm at interrill and rill stages, and critical wetting rate thresholds of 20mm/h and 10mm/h controlled the collapse of 2~5mm and 0.25~0.5mm size, respectively. The mean weight diameter for the transport of soil aggregate at different stages from large to small was in order of rill stage, undergoing wetting stage and inter-rill stage.

Abstract:In order to investigate the differences in falling-head infiltration between fresh water and saline water, one-dimensional precipitation-head water infiltration column experiments were carried out for two soils, i.e., coastal saline-alkali soil and yellow-brown soil by using either fresh water or saline water with mineralization of 1.0g/L. The results showed that higher infiltration rates were obtained for saline water than for fresh water and the wetting front advance was faster for both soils. It indicated that saline water could enhance the infiltration capacity of the two soil types. This was especially so for the yellow-brown soil because it had better structure and was more readily affected by salt in saline water. The analysis of Philip infiltration modeling showed that the model was able to describe process of both saline and fresh water falling-head infiltrations in both soil types. However, the model predictions of measured yellow-brown soil data were poorer than those of salinealkali soil data. This was caused by soil sorptivity, which was a constant in the Philip model, and it could not describe the slight decrease in infiltration capacity, which occurred with increase of infiltration duration, as accurately for the yellow-brown soil as it could for the salinealkali soil. During the redistribution processes of water and salt, the salt leaching was similar under saline and fresh water infiltration in the upper levels of salinealkali soil columns because desalting was the main process occurred in those layers. However, salt accumulation was evidently greater under saline water infiltration than that under fresh water infiltration in layers closer to the wetting front. The salt content was increased in the upper layers while it was decreased in the deeper layers of yellow-brown soil under fresh water infiltration; but it was increased in all of layers under saline water infiltration; and the top and bottom layers both had the highest levels of saltiness, because the salt was retained specifically in the top soil layers due to the damage in the soil structure and the increase in water retention capacity, while it was leached from middle layers into lower layer to some extent.

Abstract:Fertigation technology is a combination of irrigation and fertilization which could effectively improve water and fertilizer utilization ratio. It is widely used in the arid and semiarid areas. In order to explore the application effect and economic benefit of fertigation technology on wine grape, three consecutive years study of “Cabernet Sauvignon” were carried out in Helan Mountain foothill of Ningxia. By setting traditional water and fertilizer management as control (CK), drip irrigation + conventional fertilization management (DF) and fertigation technology (FI) treatments, wine grape yield, quality, cost and economic benefit were analyzed. Results showed that fertigation upfront investment was higher than that of traditional water and fertilizer management, and production increase effect was poor, but the quality and price were significantly improved and then the product price was significantly higher than that of traditional planting mode, the irrigation and pesticide use were decreased significantly. Compared with traditional water and fertilizer management, fertigation technology could save water expends by 1853 yuan/hm2 and save labor costs 9585 yuan/hm2, the average annual income reached 43128 yuan/hm2,the ratio of output to input was as high as 2.98. However, the traditional water and fertilizer management annual income was -7192 yuan/hm2, the ratio of output to input was only 0.77. Traditional water and fertilizer management had high cost and low output. Fertigation technology was low cost and high output, which could solve the low grape quality, high labor and low economic benefits problems. By setting fertigation technology on grape wine in Helan Mountain vineyard, it could significantly improve wine grape quality, save cost and increase benefit. It was suitable for widely using in arid and semi arid regions.

Abstract:Researching the effect of crop planting structure change on alteration of crop water demand and irrigation water consumption would provide basic data for irrigation water management in the period of crop growing and agricultural water resources planning. Based on the meteorological data of actual precipitation and evapotranspiration collected in Jinghuiqu Irrigation Area, the irrigation water requirement of main crops was calculated by using Penman—Monteith formula and crop coefficient method recommended by FAO, and the effective precipitations of rainy year (25%), normal precipitation year (50%) and draught year (75%) were determined through frequency calculation and fitting curve method. Then the total irrigation water requirement in typical hydrologic years was calculated according to agricultural crop planting structure data in different periods extracted from remote sensing images in Jinghuiqu Irrigation Area from 1998 to 2014. The monthly and yearly change of water demand of crop and irrigation water requirement of typical hydrologic years were analyzed. The results showed that, in Jinghuiqu Irrigation Area from 1988 to 2014, with the change of agricultural planting structure (the crop planting area was reduced by 63.5%, the orchard area was increased by more than 10.2 times, and the inhabitants area was increased by 1.63 times), the crop water demand and irrigation water requirement displayed a significant decrease. The total water demand was decreased from 780 million m3, 800 million m3 and 820 million m3 to 520 million m3, 530 million m3 and 540 million m3, and the amount of irrigation water was dropped from 290 million m3, 350 million m3 and 430 million m3 to 190 million m3, 230 million m3 and 270 million m3 in three hydrologic years, respectively. Among different planting crops, the ratio of amount of irrigation water consumption of winter wheat and summer maize was dropped from over 90% to 50%, while that of the orchard was grown from less than 5% to 50%, and that of facilitated agriculture tended to increase slightly. However, the average crop water demand of unit area of three hydrologic years from 1988 to 2005 was remained around 720mm, 700mm and 685mm, then it was decreased slightly, and later it was dropped to 700mm, 685mm and 670mm in 2014, during which period the average irrigation water requirement almost equaled to the average crop water demand of unit area. With the change of planting structure from 1988 to 2014, the total irrigation water requirement and total crop water demand of unit area in each month, apart from June, showed a significant decreasing tendency, but the average irrigation water requirement and average crop water demand of unit area were decreased in April, August and September, increased in June and remained the same in other months. It indicated that the decrease of crop water demand and irrigation water requirement was caused mainly by decrease of crop area, and slightly by change of crop structure. The result also showed that the crop irrigation water requirement after adjusted crop planting structure was more in accordance with the features of regional effective precipitation.

Abstract:Identifying the optimal flow accumulation threshold (threshold) based on digital elevation model （DEM） is a key process to define the drainage of a river basin. Due to lack of underlying surface information, it’s common to establish a quantitative calculation model for threshold relying on the watershed topography and real river network. Except topography, however, vegetation, precipitation and other underlying surface factors were also correlated with the characteristics of river network. Furthermore, the extraction of river network based on grid DEM had two different flow direction allocation strategies, i.e., the single flow algorithm and multiple flow algorithm. Since the procedure of multiple flow algorithm was complicated, the present study mainly focused on selection of threshold under single flow algorithm and lack of the research of threshold determination of multiple flow algorithm. Aim at above problem, the climate and underlying surface conditions were considered to explore the relevance between influence factors (i.e., topography, vegetation and precipitation) and threshold, and a calculation model was put forward to compute threshold based on multiple linear regression model with different algorithms in Hubei Province. The results showed that the optimal thresholds had a positive correlation with local slope, average precipitation and vegetation coverage rate. The flow accumulation threshold was increased with the increase of terrain steepness, rainfall and vegetation coverage. The calculation model of flow accumulation threshold can effectively integrate multi-source influence factors in different regions and obtain reasonable threshold. The significance level of rejecting the null hypothesis were both lower than 0.05 in different flow direction allocation strategies and the coefficients of determination (R2) were higher than 0.9. Good results of extraction can also be got by applying this method to other river basin. It meant the result of simulated river network by calculation model of flow accumulation threshold had high similarity with the real river network, it also provided rational hydrological information for agroforestry planning, agricultural disaster prediction and other industrial applications.

Abstract:Takyric solonetz is spread mainly in arid area, Northwest China. Its poor soil structure and extremely low hydraulic conductivities (Ks< 0.1 mm/d) are the key factors restricting its amelioration. The ECe(electrical conductivity of saturated paste extract), SARe (sodium adsorption ratio of saturated paste extract), and pHs (pH of saturated paste) of the native soil studied at depth of 0~30cm were 12.30dS/m, 44.12 (mmol/L)0.5 and 9.33, respectively. After deep tillage, beds (1.0m width, 0.5m height) were formed. The drip lines were placed on beds covered with plastic. Lycium barbarum L. seedlings were then planted. A three-year field experiment was conducted to determine if reclamation could be achieved while cropping Lycium barbarum L. by using drip irrigation where soil beneath the drip emitters near the plants was replaced with sand in niches that were 0.2m ground diameter and 0.2m depth. The purpose of sandfilled niche was to increase the area over which infiltration of water occured thereby reducing the application rates to values that more closely matched the saturated hydraulic conductivity of the native soil, provide a reservoir for holding the applied water before it infiltrated and avoid the adversely mechanical impact and the stirring action of applied water on soil surface. Five treatments based on soil matric potential (SMP) thresholds used to trigger drip irrigation were designed to find the optimal drip irrigation schedule, i.e., -5kPa (S1), -10kPa (S2), -15kPa (S3), -20kPa (S4) and -25kPa (S5). The results showed that significant improvement was achieved in soil infiltration capability, which was demonstrated by the increasingly enlarged wetted area beneath the drip emitter. Consequently, a desalt region (ECe< 4dS/m) was formed, and high SMP level was favorable for the saltleaching in soil. The ratio of ECe/SARe was increased significantly after planting, which indicated the changes of soil salt composition characteristics and the amelioration of soil physical properties. After planting with drip irrigation, the contents of soil available nutrients were increased sharply. Nitrate nitrogen showed a high migration with water movement, and had potential to be lost by leaching, so nitrogen fertilizer should be applied in the later period during one irrigation event to reduce the leaching of nitrogen and raise fertilizer use efficiency. While available phosphorus was distributed mainly in depth of 0~20cm under drip emitter, due to its low migration with water. After three years experiment, S1 had the lowest survival rate (56.8%), and S3 got the highest (81.1%), S2, S3 and S4 gave higher fruit yields than other treatments significantly (p<0.05), which was around 900kg/hm2, and it was close to the level in local farmland. The findings indicated that a sandfilled niche beneath the drip emitter could be adopted for the reclamation of highly saline-sodic wasteland of takyric solonetz. Considering the factors, including soil watersalt properties, soil nutrients distribution and the growth of Lycium barbarum L., an SMP of -10kPa in the first two years and -20kPa from the third year could be used to trigger drip irrigation.

Abstract:In order to find optimal pretreated wheat straw utilization on soil improvement, soil samples were collected from indoor incubation experiment of different wheat straw utilizations, seven separate indicators, including 150min of cumulative infiltration (I150), available soil water content (θ), cumulative evaporation (Ec), soil aggregate fractal dimension (FD), soil pore fractal dimension (Dp), straw decomposition rate (Rd) and total nitrogen (wTN), were chosen to evaluate the effect of different pretreated wheat straw utilizations on soil improvement (e.g., water infiltration capacity, soil moisture availability, waterholding capacity, structural stability, soil porosity, straw decomposition rate and soil total nitrogen content). The principle component analysis method was used to conduct the above mentioned seven indicators, then comprehensive improvement index of soil improvement of wheat straw utilization was established by weighted sum of different evaluation indices. Result showed that comprehensive improvement quality principle component obeyed normal distribution significantly and had good representation and objectivity, which could include 86.93% primordial quality attribute variation information, so it could be used as the overall pretreated wheat straw utilization improvement evaluation index of the seven indicators, wTN,Dp, FD and θ contributed the largest percentage (49.92%) in the first common factor, while Rd, I150 and Ec contributed the most (37.01%) in the second common factor. The treatments order of wheat straw utilization improvement was T6>T7>T3>T5>T4>T2>T1. Comprehensive soil amendment of ammoniated straw was better than that of non-ammoniated straw, comprehensive soil amendment of pulverized straw was better than that of non-pulverized straw, ammoniated straw mixed with calcium sulphate improver was better than that of mixed with aluminum sulfate improver.

Abstract:Based on the variable slopes flume experiment, adopting ultrasonic measurement technique, changes in hydraulic parameters of slope shallow flow were studied at five slopes and 21 unit width discharges from the viewpoint of hydraulic mechanism and stability characteristics. The results showed that the index mean value under test conditions of slope flow was 0.536, the fluid state was turbulent flow, and the flow pattern was specific jet. Under artificial roughness conditions, with the increase of discharge, the evolution of flow was from instability to roll wave quenching and loss stability. During this period, the surface of water flow was changed greatly. The critical flow rate of roll wave quenching was decreased with the increase of slope, and the quenching critical Reynolds number was varied from 509 to 602 and Froude number was varied from 3.29 to 7.39. The critical Reynolds number for unstable laminar flow was ranged from 778 to 961, and Froude number was ranged from 3.57 to 8.47. With the increase of flow length, the variation of wave celerity was small, but the wavelength and wave amplitude were increased, and the frequency was decreased, polymerization was occurred for roll waves along slope distance. When the unit width discharges and slope were increased, wave celerity and frequency were also increased, but the wavelength was changed little, and wave amplitude was changed in the form of single peak. The research results can provide theoretical basis for studying of soil erosion on the slope, and promote the extension of traditional hydraulics theory to overland flow. 

Abstract:The pollution level and spatial distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) in snowfall of typical city of the alpine region of China were investigated. According to different functions, nine snowfall sampling points were collected in Harbin, and concentration of PAHs was measured by GC—MS. The results demonstrated that the concentration of 16 kinds of PAHs was ranged from 33.2ng/dL to 2306.6ng/dL in Harbin snowfall, the average concentration was 1144.38ng/dL. The concentration of PAHs had obvious regional difference in different functional areas, its spatial distribution showed that the concentration in rural was 1724.1ng/dL, in commercialtraffic area was 1662.6ng/dL, in city park was 832.0ng/dL, in residence community was 528.6ng/dL and that in suburb was 33.2ng/dL, the concentration in rural and commercialtraffic area was about 50 times lager than that in suburb. Pollution sources and atmospheric diffusion conditions were the major reasons for regional difference of PAHs concentration in snowfall. It was found that the 3~4 rings PAHs content was relatively higher, which accounted for 66.8%~77.3% of total PAHs concentration. The monomer content of PAHs was also quite different, and phenanthrene (Phe) was the highest in all the monomer. In snowfall samples, the 2 ring PAHs was in strong variation, while the other ring PAHs was in moderate variation, pollution sources and physical and chemical properties might be expected to result in existence of PAHs spatial heterogeneity characteristic. Diagnostic ratio and factor analysis method were adopted to analyze the data, preliminary results showed that the source of PAHs in Harbin snowfall were coal and biofuel combustion and automobile emissions. The research results would provide reference and scientific basis for numerical simulation of secondary emission of PAHs during snow melting process, snowmelt runoff numerical simulation and formulation of environmental pollution control measures and its management policies.

Abstract:In the long-term continuous observation, observed data of global solar radiation (Rs) usually has different degrees of missing. Angstrom—Presscott (A—P) model, which was based on sunshine hours, is a widely used empirical model that has high precision. Three different parameters calibrated methods for A—P model were chosen, which were annually (M1), monthly (M2) and yearly (M3) calibrated by only one time. Radiation data from six radiation stations were used, which were Changdu, Yichang, Kunming, Ganzhou, Hangzhou and Nanning stations. Annual average Rs, annual average reference crop evapotranspiration (ET0) and parameter selection were compared by the three methods, at last, three stations were selected for interpolation accuracy evaluation. The results were as follow: t test results showed that no difference among the three methods in use of data interpolation in Changdu station, severe changes of Rs inter annual was the main reason for poor accuracy. The accuracy of M1 method for data interpolation was higher than those of other methods in Yichang and Nanning stations. When missing data were 40d and 70d, there were no difference between M1 method calibrated and measured values of Rs in calculating ET0, but when the missing data was over 20d, M2 and M3 methods showed significant difference between estimated and measured Rs, its influence on calculating ET0 was the same. Compared with the calibration method for many years, the monthly calibrated method had a little higher precision in estimating Rs, with higher precision in winter and lower precision from June to August in Ganzhou, Hangzhou, Kunming and Nanning stations. Compared with the results before 1990, the parameter a of A—P model was increased dramatically in all stations after 1990, industrial pollution led to an increased aerosol was one of main reasons. In extremely hot year, the accuracy of A—P model was lower than that in normal year, application of the model to irrigation forecast would underestimate crop water consumption, which may bring risk for decisionmaking. The results can be used in A—P model for risk assessment and improving the total radiation time series data of the interpolation precision of missing cases.

Abstract:Global solar radiation (Rs) is an important elementary datum for crop modeling and reference evapotranspiration (ETo) estimation, but only 1/20 of Chinese weather stations can observe it directly. It is a common method for estimating Rs to use empirical model based on temperature data, which are easy to get. Based on the temperatures of 20 weather stations in south of China from 1982 to 2014, parameters of six different forms of Bristow—Campbell (B—C) and Hargreaves (Harg) methods were calibrated, and the applicability of abovementioned methods and fifteen support vector machine (SVM) parameter input forms were evaluated. The results showed that SVM model was better than B—C method and Harg method as a whole. The SVM model with maximum temperature (Tmax), minimum temperature (Tmin), relative humidity (RH) and precipitation (P) as input variables had the highest precision. On average, R2 and RMSE from the twenty weather stations were 0.80 and 3.20MJ/(m2·d), respectively, even when it included precipitation data, Rs was not negative and even greater than the extraterrestrial total radiation (Ra). R2 from the twenty weather stations was 0.74 on average, and RMSE was 3.72MJ/(m2·d) when based on temperature data. Different input variables had different influences on the SVM model forecasted Rs, the input variables of Tmax and Tmin were superior to ΔT. In addition to temperature data, when the model had the relative humidity and rainfall data, it was showed that RH+P > RH > P. Among the empirical models, the B—C model’s M1 and M3, and the Harg models’ M10 and M12 were preferable, their R2 were 0.69~0.70, RMSE was about 4.0MJ/(m2·d). While the M10 and M12 had higher request to the meteorological data, which needed the data of dayly temperature and precipitation. There existed the dayly Rs overestimation or negative problems when it rained.

Abstract:The ecological security of cultivated land is related to sustainable development and food security. Evaluation on cultivated land ecological security is a significant foundation for improving the security of farmland ecosystems and sustainable use of cultivated land. The Changsha—Zhuzhou—Xiangtan (Chang—Zhu—Tan) region was chosen as study area. Fully considering the economical and social environment development of Chang—Zhu—Tan region, the original PSR model was improved according to characteristics of the study area. In the rule hierarchy of pressure, state and response, totally 17 evaluation indexes were selected in light of resource environment and social economy, and then the evaluation index system of ecological security assessment was fabricated. The index weight was determined by combination weighting approach which combined the subjective (analytic hierarchy process) with objective weighting method (entropy method). The ecological security of cultivated land in Chang—Zhu—Tan region from 2000 to 2012 was quantitatively evaluated and analyzed by the modified PSR model. The results showed that during 2000 to 2012, the comprehensive index of ecological security for cultivated land in Chang—Zhu—Tan region was gradually increased from 37.59 to 55.82, and the level of ecological security was fluctuantly increased. The pressure index showed a decreased trend with annual average of 6.86%, which was decreased from 23.37 to 4.14; fluctuate increase in state index was observed with annual average of 19.63%; the response index was increased from 4.22 to 18.12 with annual average of 27.45%. In view of security level of cultivated land ecological security, the ecological security of cultivated land in the area during 2000—2004 belonged to risk level, and that during 2005—2011 was sensitivity level, but it was risen to good level in 2012. The main factors that affecting the cultivated land ecological security in Chang—Zhu—Tan region were environmental quality index of cultivated land, the first industrial output in proportion to GDP, agricultural mechanical power of unit cultivated land, grain yield per unit of cultivated land, environmental protection investment in proportion to GDP and afforestation area of current year. Temporal and spatial variabilities of cultivated land ecological security were analyzed for every county in Chang—Zhu—Tan region. The associated suggestions to intensify protection of cultivated land, consolidate rural land, improve agricultural comprehensive production capacity, increase scientific and technological input in environmental protection and improve the quality of cultivated land, strengthen ecological construction, were proposed to increase the level of ecological security of cultivated land in Chang—Zhu—Tan region. Likewise, the local government was appealed to pay extensive attention to the cultivated land ecological security, and should take effective measures, such as working on comprehensive plan for land ecology and land use, economizing the intensivelyutilized cultivated land, realizing dynamical equilibrium of total cultivated land, strengthening protection of cultivated land in quantity and quality, improving environment around them and the level of ecological security of cultivated land. As so, the Chang—Zhu—Tan region was possible to become a comprehensive reform pilot area, as well as a national resource-saving and environment-friendly society.

Abstract:Low efficiency of resource utilization of rural solid wastes resulted in more and more serious environmental pollution in rural areas. As a significant resource approach of rural solid wastes, compost has been widely used. Compost-derived HAs as the important products of solid waste compost were confirmed to be redox recently. Whether compost-derived HAs were similar to natural HAs to be able to promote the reduction of Fe3+ mineral was unclear. The rural solid wastes compost continued 40d in an indoor composting reactor. Physical and chemical indexes changes during composting confirmed the successful rural solid waste compost. Spectra results of compostderived HAs indicated that the aromaticity, humification and content of redox functional groups of compostderived HAs were all increased during composting, which would facilitate the reduction of Fe3+ minerals. Specific UV absorbance values of compost-derived HAs demonstrated that quinones were the main redox functional groups within compost-derived HAs, which were mainly derived from the degradation of lignocellulose in compost materials in middle- and later-stage compost. Then these quinones would combine with the compost-derived HAs which would accelerate the humification of compost-derived HAs, increase their redox properties and the reduction of Fe3+ minerals and facilitate the degradation of organic contaminants in soil.

Abstract:Temperature distribution has a great influence on the efficiency of gas production for anaerobic fermentation system. Fluent is one of the most advanced software for fluid simulation. It is suitable to apply it in simulation analysis of the anaerobic reactor without stirring. Two kinds of raw materials which were water and digested slurry with TS of 12.4% were applied in two 10L anaerobic reactors to conduct anaerobic fermentation experiments. Totally 16 temperature sensors were installed at each anaerobic reactor in order to detect temperature continuously. The temperature figures indicated that two types of materials were definitely different. Therefore, applying the Fluent heat transfer simulation to digested slurry anaerobic fermentation system cannot only utilize water as physical parameter. However, the error was only 4.2% between experiment with raw material of digested slurry with TS of 12.4% and Fluent simulation, when water and Boussinesq hypothesis were simultaneously defined as physical parameters. It was also explored that setting up a virtual wall in Fluent can dramatically simplify the model calculation time, and it had the same effect with defining real wall model in Gambit. In addition, it was found that realizable k—ε model was the most suited to the anaerobic fermentation system of digested slurry with high TS. The aims of the research were to explore suitable Fluent setting and optimization method for anaerobic fermentation and provide guidance for further work. Optimizing model and improving efficiency in unsteady-state numerical analysis will be the main body of the further work. 

Abstract:Biogas yield represents a key parameter for evaluating the stability of fermentation process. In laboratory scale anaerobic fermentation experiments, the gas flow rate is generally low and the experimental period lasts long. In order to solve the problems of labor intensity and low efficiency caused by manual measurement, a system for online gas metering for low gas flow rate with high resolution and friendly interface was developed following the principle of liquid displacement. The system was designed based on the LabVIEW software. Various functions were achieved, including automatic calibration, automatic refilling the displaced liquid to compensate the loss from evaporation, real-time pressure and temperature compensation for volume, generating, displaying, storing accumulated gas production curve and data in real-time, etc. Finally, fermentation experiment was conducted to validate the system’s performance. Test results showed an average relative error of -2.30% and a maximum relative error of -3.03% compared with manual measurement, which indicated a high measurement accuracy of the system. Moreover, the results were stable even in the continuous long run for 80h, indicating a good performance at operational stability. In conclusion, the system can satisfy the need of real-time gas metering for laboratory scale anaerobic digesters, and it had great practical value.

Abstract:Alicyclobacillus spp. are non-pathogenic, thermo-acidophilic and spore-forming bacteria. Their spores can not only survive the pasteurization procedure normally applied to fruit juices and beverages, but also germinate and proliferate in acidic products. Since the first case of apple juice spoilage linked to A. acidoterrestris in 1984, Alicyclobacillus strains have recently received much attention in the pasteurized fruit juice industry. This review was intended to provide an overview on the historical background and general characteristics of the genus Alicyclobacillus. Their distribution in soil environments and juice processing facilities were described. The impact of Alicyclobacillus on fruit juice/beverage industry would be particularly discussed. The formation pathway of guaiacol was also addressed since the Alicyclobacillusrelated spoilage was characterized by the formation of a distinct medicinal or antiseptic off-odor attributed to guaiacol, which at a low level can be detected by sensory means in fruit juices. The standardized test methods and alternative detection techniques for Alicyclobacillus strains were summarized. In addition, the Alicyclobacillus control approaches aimed at different stages of juice processing, mainly in relation to fruit washing, juice sterilization and juice preservation were presented. Finally, possible directions for future research on Alicyclobacillus were proposed.

Abstract:The flavor of beer is an important means of evaluating its quality. Beer flavor is the integrated embodiment of beer smell and taste information. The aroma and taste of beer were detected by electronic nose and tongue fusion system. Principal component analysis (PCA) was respectively used for reducing the dimension of detected information, and the principal component of test data by electronic nose and tongue were extracted to fuse as the characteristic data. The classification of beer was achieved by smell and taste comprehensive information. Due to the difference in data of sensor array, the traditional K-means algorithm clustering results were depended on the selection of initial value, and it was easy to fall into local optimum. A modified K-means algorithm based on particle swarm optimization was proposed, which was based on the characteristics of fusion data. The weight coefficient was optimized in the course of operation. With the increase of iteration number, the convergence speed was adjusted, the particle search tended to be more balanced. Meanwhile, the compression factor was introduced to balance the global and local conflicts. Compared with K-means algorithm, the modified algorithm had better global convergence in experiments. It also can overcome the disadvantage which was easy to fall into the local optimum, and converge to the optimal solution. The experimental results showed that the clustering effect in five kinds of beer was obvious, and the correct rate was stable at 93.3%.

Abstract:The Shewanella separated from corruption large yellow croaker was used as research object. The growth data of Shewanella putrefaciens under different pH values, NaCl concentrations and temperatures was obtained by using viable count and optical density methods, and the Gompertz model was built. Effect of environmental factors on growth kinetic parameters was compared and analyzed. Results showed that Shewanella putrefaciens could not grow at pH value of 6.0 and NaCl concentration of 3.5% during 3~8℃. The differences of maximum specific growth rate (μmax) and generation time were not significant (p>0.05), but the differences of lag phase (λ) and the most probable density (M) were significant (p<0.05). Environmental factors had significant effect on the growth kinetic parameters.High temperature or low NaCl concentration resulted in short generation time. When temperature was 3~25℃, high temperature resulted in large μmax. The increase rate of μmax was (0.0143±0.0032)h-1/℃.When temperature was high, λ would be short. The λ was decreased at a rate of 1.5h/℃ by using viable count method, while during 8~15℃, it was decreased approximately at a speed of 2.5h/℃ by optical density method. The μmax was influenced significantly by NaCl concentration and pH value, while lag time showed no significant changes by viable count method. Using optical density method, changes of μmaxwere affected unsignificantly by NaCl concentration and pH value, while changes of λ were apparent. Thus, both of the two counting methods could judge the growth/nongrowth state of Shewanella, and the estimation errors of λ and M were increased by harsh environments when using optical density methods.

Abstract:With the purpose to investigate the relationship between spoilage and bacterial metabolism in lightly salted Mylopharyngodon piceus, Biolog GEN Ⅲ microplate was used to understand the carbon metabolism of predominant spoilage bacteria, Staphylococcus xylosus, at 5℃, 15℃, 25℃ and 33℃, respectively, and the growth curve of Staphylococcus xylosus was fitted with the modified Gompetz model. In addition, the metabolic rate was measured by using average well color development (AWCD) as indicator to describe its dynamic properties of carbon utilization. The results showed that saccharides, carboxylic acids and amino acids were utilized by Staphylococcus xylosus with degressive utilization ratio at the same temperature. Among carbon substrates, monosaccharides (e.g., glucose and mannose), disaccharides (e.g., sucrose and trehalose), polysaccharides and sugar derivatives (e.g., N-Acetyl-β-D-Mannose amine and β-Methyl-D-Glucoside), amino acids (e.g., glutamate and serine) and carboxylic acids (e.g., L-lactate) were dramatically metabolized. The lag phase of Staphylococcus xylosus was the shortest at 25℃, thus the exponential phase was reached fast. Overall, the present study focused on carbon utilization and metabolism of Staphylococcus xylosus at different temperatures to provide a theoretical basis for inhibition of microbial activity by optimizing formula and extension of shelf life of lightly salted Mylopharyngodon piceus. It was proposed that Biolog GEN Ⅲ microplate could be applied to establishment of bacterial predictive model combining simultaneous investigation on microbial activity of carbon sources utilization and metabolism.

Abstract:To improve the low quality of low-fat cheese, effects of λ-carrageenan on the physicochemical, structural and rheological characteristics of rennet milk gels made from milk of different fat contents (3.80%, 1.83% and 0.48%) were investigated. The results showed that with the addition of 0.03% λ-carrageenan, the moisture of all experimental samples was increased; the yield, protein and fat recoveries of the rennet gel made from the reduced-fat milk (1.83%) were significantly increased by 13.56%, 1.77% and 9.34%, respectively. In the low-field nuclear magnetic resonance ( LF—NMR) results, the T2 transverse relaxation time data demonstrated three distinct water populations. After the addition of λ-carrageenan, the adsorption water proportion was increased, but free water proportion was reduced. The gel time (G′=1Pa) of all the experimental groups was increased significantly after the addition of 0.03% λ-carrageenan （P<0.05), while the spontaneous whey precipitation was decreased （P<0.05). Meanwhile, the hardness, elasticity of milk gels were decreased significantly （P< 0.05). However, the addition of λ-carrageenan did not significantly affect the rheological characteristics of gel （P>0.05). Above all, there was no significant difference in the physicochemical and structural characteristics between the fullfat control and the reducedfat milk rennet gel (1.83%) after the addition of λ-carrageenan （P>0.05). In conclusion, the addition of λ-carrageenan could increase protein recovery rate of reducedfat gel while softening the texture simultaneously, which proved its great potential in improving the quality of low-fat cheese.

Abstract:Carrots contains high level of provitamin A carotenoids, especially β-carotene, which plays the function of antioxidation and scavenging free radicals in vivo. But they also have high level moisture content. This character negatively impacts the length of time that carrots can be stored. Dehydration of carrots can effectively increase storage time and retain nutrition. But in the drying process of carrots, the β-carotene degradation reaction rate would be significantly increased by destruction of tissue integrity, temperature rise, and contacting with light and oxygen, which could change the nutritional value of carrots. Carrots were dried by oxygen limited heat pump firstly, and then in vitro digestion model was used to evaluate the effect of different drying medium and oil on bioaccessibility of β-carotene in carrots during drying process. The bioaccessibility of β-carotene was measured by β-carotene release rate in supernatant by using low-speed centrifugation and β-carotene micellar rate in micelle phase by ultrafiltration. Although there was negative impact on β-carotene retention rate by drying process, there was positive impact on the bioaccessibility. Especially when CO2 was used as a drying medium, it increased the retention rate and bioaccessibility of β-carotene significantly. In addition, there was significant increase in the release rate and micellar rate of β-carotene in fresh and dried carrots when oil was added. Anyhow, there was significant increase of bioaccessibility of carrots by heat pump drying and adding oil. This may enhance the bioavailability of human beings.

Abstract:The potential of glycosidase from one selected Hanseniaspora uvarum strain to enhance aroma of Pinot Noir dry red wine was evaluated. The tolerance of glycosidase extract obtained from this isolate was assayed in winemakinglike conditions, and the activity of glycosidase was expressed by β-glucosidase. Normal harvested Pinot Noir grapes in Yangling of Shaanxi Province, China, were de-stemmed and crushed, and then the crude H. uvarum glycosidase was added to the must prior to alcohol fermentation to make dry red wine. The treatment with commercial enzyme preparation AR2000 and that without adding enzyme were set as comparisons. In April of the following year, aromatic components of wines were detected by SPME—GC—MS, and the aroma characteristics were quantified by a trained tasting panel. The results indicated that glycosidase from H. uvarum showed a relative stability at acidic pH as well as tolerance to ethanol and glucose. The enzyme treatment gave wine more complexity and greater amounts of aromatic components. The AR2000 treatment strongly encouraged the release of varietal compounds in wine, such as terpenols that presented as fruity and floral, and C6 compounds that were responsible for green trait. Additionally, the AR2000 treatment also improved alcohol and ester contents. In contrast, the treatment with H. uvarum glycosidase yielded wine with the highest level of C13 norisoprenoids and some terpenols, but lower contents of C6 and higher alcohol compounds. Finally, wine sensory analysis revealed that the treatment with H. uvarum glycosidase gave wine more complex and elegant aroma, with much temperate fruit, berry, and floral characteristics, whereas the AR2000 treatment yielded wine with prominent green characteristics. Therefore, the glycosidase of H. uvarum has the potential to improve quality of wine aroma.

Abstract:Soybean milk is a traditional plant protein beverage in China. Total solids content is an important indicator of soybean milk. However, the usually used total solids content determination methods, i.e., oven drying method, empirical method and refractometry method, had some shortcomings such as long time consuming, low precision or inconvenience. Developing a portable, quick and precise detector for measuring total solids content of soybean milk is helpful to guarantee the quality of soybean milk and soybean products. Therefore, the influence of total solids content over the range of 2.13~6.50g/(100mL) and temperature from 20℃ to 70℃ on the conductivity was investigated firstly. The results indicated that the conductivity was increased with the increase of total solids content and temperature. A binary quadratic model with determination coefficient of 0994 could be used to describe the relationship between conductivity and total solids content and temperature over the investigated ranges. Furthermore, the hardware system of a portable total solids content detector for soybean milk was developed by using the singlechip microcomputer of STC12C5A16S2 as controller, DJS—1 conductivity pole as conductivity sensor, DS18B20 as temperature sensor, and lithium cell as battery. C51 language was used to develop the software of the detector to realize data collection, treatment and display. Another batch of soybean milk samples were prepared to investigate the performance of the detector. The results indicated that when the total solids content was within the range of 2.00~8.00g/(100mL) and the temperature was within the range of 20~70℃, the measurement error of the detector was within the range of -0.52~0.37g/(100mL), the mean absolute error was 0.17g/(100mL), and the response time was less than 5s. Future research will focus on improving the accuracy of the detector. 

Abstract:Temperature is one of the key factors for maintaining the quality of fruits and vegetables during storage or transportation. Improving airflow in the container is beneficial for adjusting the temperature in a container quickly and effectively. 3-D numerical models, which combined with the theory of porosity media, were built to investigate the temperature distribution in a 40 feet container. The thermal characteristics of litchi products and the container wall were considered in the models. Totally 12 models, including different air-outlet duct velocities, porosity areas and hole locations on the air-outlet duct, were conducted to study the effects of those factors on change of air and products temperature during the cooling process in the container, by which the airflow characteristics in the container were obtained and analyzed. After comparison of the data, some results can be drawn. Improving the air velocity in air-outlet duct and the porosity area of air-outlet duct can increase the cooling speed of air, which also improved the homogeneity of temperature distribution on the products surface. The effect of porosity area on products temperature was not obvious, while products temperature was decreased faster with bigger ventilation velocity. Changing the location of holes on the air-outlet duct had little effects on the temperature decrease of air, but the decreasing amplitude was smaller after cooling process when the holes were concentrated in the middle of the air-outlet duct. A test was developed to verify the results from one of the models, and the simulated results were matched well with the test results, in which the average difference rate (MD) and the root mean square error (RMSE) were 5.05% and 5.95% for change of air temperature, respectively, while those were 14.04% and 16.48% for temperature distribution in the container, respectively. The results revealed the rules of air and products cooling in a fresh-keeping container for fruits and vegetables, which provided a certain reference for the design and optimization of fresh-keeping equipments.

Abstract:At present, the test index of air leakage is not uniform in different standards in China. Constant pressure difference method and tracer gas concentration decay method were used to test air tightness characteristic of refrigerated transport unit. The variations of air leakage were tested under conditions of different pressures (50Pa, 100Pa, 150Pa, 200Pa and 250Pa), different velocities (20km/h,40km/h,60km/h, 80km/h and 100km/h) and different agings (0, 71000km, 126000km and 175000km). The matching relationship between different parameters was analyzed. The research gave determined method of air leakage characteristic curve with experimentation and empirical formula. The test method was recommended in practical application. It showed that the leakage rate was influenced by air tightness and velocity, and the influence of aging was great. There was a maximum of 20 times difference of air leakage index in GB 29753, GB/T 5600 and GB/T 7392. Test pressures of 50Pa,100Pa and 250Pa were corresponded to velocities of 30~40km/h, 45~60km/h and 70~100km/h. And the air leakage was about 1∶2∶4 under the conditions of above constant pressure difference. After driving 100000km and 200000km, the air leakage of refrigerated transport unit was increased by 40% and 110% under 250Pa pressure difference. Combined with the actual situation, it was suggested that 250Pa as the uniform constant pressure difference condition for air leakage test standard, and a system should be established to regularly check the thermal performance of refrigerated transport unit. In addition, the air leakage of refrigerated transport unit was influenced by internal partition form, goods stacking form, temperature, etc. A comprehensive and thorough analysis was needed in the later research. 

Abstract:Fresh agricultural products and keeping live transportation in the process of cold chain requires accurate monitoring and controlling of transport micro-environmental gas concentration, thus real-time accurate monitoring and controlling all kinds of micro-environmental gas concentration is particularly important. In the longterm monitoring of gas concentration, the sensor will drift and show the phenomenon of weak stability, resulting in reduction of monitoring accuracy and low efficiency of controlling for preservation. Aiming at this problem, the design was based on wireless sensor network gas sensor for on-line calibration method, fusion techniques were used to do periodic election of logistics monitoring with distributed deployment of wireless gas sensor, measurement accuracy and stability of the leader of sensor node group were selected as a reference, dynamically calculated the change of terminal sensor drift characteristic parameters, and wireless communication technology was used to complete correction of various types of gas sensing output mapping parameters in order to calculate dynamic mapping between output signal and gas concentration. The method can realize dynamic calibration of on-line gas concentration sensing without replacing gas sensor, and output of gas sensor in the transportation was optimized as a whole to improve the accuracy of acquisition. The method was verified by low-temperature sturgeon water-free dormant keep-live transportation tests, monitoring and calibration of concentration information for the important environmental gas CO2, O2, NH3 and so on. The evaluation test was carried out by using high precision and calibrated gas concentration data recorder as standard for measurement of gas concentration for the micro environment of transportation. Experiments show that the sensor output signal for TTL level of CO2 sensor can improve the measurement accuracy by 3.28%. The precision was inferior to linear or nonlinear output functions of gas sensor;for concentration output mapping of nonlinear signal, the NH3 gas monitoring accuracy can be improved by 4.14%. The calibration method for sensor output concentration mapping for linear function of oxygen gas sensors’ calibration was the best and the monitoring precision can be improved by 4.71%. Comprehensively comparing the monitoring data of gas concentration change, this method can significantly improve the accuracy of gas monitoring, which provided basis for precise monitoring and controlling of cold chain transportation micro environment gas concentration.

Abstract:The study of effects of different crop acreage proportions, crop field shape index and crop field fragmentation on accuracy of crop classification by remote sensing provides a basis for scientific evaluation of the latter. Using GF—1 remote sensing data and based on the major crop classification results of the timeseries vegetation index, the relationship between classification accuracy of crops (including winter wheat and summer maize) and crop acreage proportion, crop field shape index as well as crop field fragmentation was studied. The research was based on 14 GF—1/WFV NDVI time series data. The timing vegetation indexbased crop classification knowledge rules were utilized on the basis of the best NDVI threshold interval of crops to be classified to complete the crops classification and make spatial distribution map. Then, totally 14 classical villages of Quzhou county were selected as sample plots, which included winter wheat—summer corn plots. The landuse ownership boundary map for the 14 classic villages was obtained according to 1∶50000 Quzhou county present landuse map, which was prepared by Quzhou County Land Resources Bureau and China Agricultural University jointly. The spatial distribution map of winter wheat—summer corn and landuse ownership boundary map among landuse survey maps were used to take image masking, and the lots and sample points of winter wheat—summer corn of each classical village region were obtained. Hence, the crop acreage proportion, crop field shape index and crop field fragmentation of winter wheat—summer corn in 14 villages were obtained, and classification accuracy, Kappa index were calculated. In addition, totally 14 groups of sample plot related data were acquired and graphs of relation between all influencing factors and classification accuracy were prepared. The results showed that the crop acreage proportion was positively correlated to classification accuracy, while the crop field fragmentation and crop field shape index were negatively correlated to classification accuracy.

Abstract:Drought is a typical complex system, and nonlinear characteristics of drought are the concentrated reflection of its complexity. Therefore, objectively understanding of complex nonlinear characteristics of drought is the key approach of assessing the effects of drought, which can provide guideline for making drought mitigation strategies. Guanzhong Plain was chosen as study area, and the kernel method was applied as a nonlinear algorithm. Based on the kernel principal component analysis (KPCA), vegetation temperature condition index (VTCI) retrieved from MODIS was projected into a highdimensional feature space for feature extraction, and then the joint distribution model of principal components with Copula function was built. Comprehensive values of VTCIs at main growth stages from 2008 to 2013 were determined by using the joint distribution model (the KPCA—Copula method). Linear regression models between the comprehensive VTCIs and wheat yields were established to assess the effect of drought on wheat yields. The results showed that the KPCA could effectively extract the nonlinear characteristics of drought, and it had better performance in dimension reduction compared with the principal component analysis (PCA). Compared with the PCA—Copula method, the determination coefficient of regression model between wheat yields and comprehensive VTCIs with KPCA—Copula method reached 0.608 (p<0.001), which indicated that the fitting degree of the model was improved, and the root mean square error (RMSE) between estimated yields and measured ones was 298.1 kg/hm2, which was about 60.1kg/hm2 lower than the RMSE by using PCA—Copula method. The comprehensive VTCIs with KPCA—Copula method were more in line with actual drought characteristics of Guanzhong Plain. These results indicated that the KPCA—Copula method could well reflect nonlinear characteristics of drought, and it had good applicability in drought impact assessment.

Abstract:In order to research the cooling effect in nature ventilation of full open-roof glass greenhouse, the CFD model was established by the k—ε turbulence and DO radiation model with high solar radiation and weak wind weather. The simulated values of the model and measured values were contrasted, and the average relative error was 2.5%. The experiment of cooling control measurements in greenhouse was carried out by using verification model. The results of experiments showed that under current natural ventilation conditions, the greenhouse gables ventilated by fanwindow and air holes of dry wet curtain. Outdoor air entered into greenhouse in horizontal direction with no upward movement velocity components. The ventilated effect of side window combined with the skylight window was poor under this condition. There was largearea air, which flowed slowly in the greenhouse. After the modification of side window structure, the airflow direction was led to generate upward velocity components when it entered into greenhouse from south gable. The ventilated effect of side window combined with skylight window was improved. The opening angle of skylight should be matched with side window, which can enhance the ventilation cooling effect. When the angle of side window was 45°, and the skylight was adjusted to 60°, the overall cooling effect of the greenhouse was better than those under other conditions which the angle of opening skylight was 45° or 75°. The overall temperature of the greenhouse was decreased from 38.4℃ to 36.9℃ and the cooling effect was improved obviously after using side window combined with roof window, when the opening angle of skylight was reasonably coordinated with side window.

Abstract:Random forest (RF) is a non-parametric technology which was firstly proposed by Leo Breiman and Cutler Adele in 2001. It was used to deal with the classification and regression problems by gathering a large number of classification tree, which can improve the prediction accuracy. It was applied in the ecological field in recent years. Predicting the spatial distribution of landslide hazard was an important way to achieve disaster prevention and mitigation. The landslide dataset of Shunchang in Fujian Province was taken as case to identify the relationship between mountain landslide occurrence and landslide factors by using RF model and logistic regression (LR) model respectively with landform, meteorological hydrology, soil and vegetation factors. The applicability of RF on landslide prediction in the southern mountain of China was tested by procedure of parameter selection and analysis of model accuracy. The result showed that the goodness of fit of RF was better than that of LR model. The prediction accuracy of RF on the landslide data was 90.8%, while the prediction accuracy of LR was 81.8%. The generalization of RF in the study area was better than that of LR model. The high risk areas and higher risk areas contained 66.05% of the total landslide, which was predicted by RF, while that of LR was 63.34%. The result of model comparison revealed that the RF model was superior to LR model on the mountain landslide prediction in the study area, thus it can be used in the landslide prediction and the division of landslide danger grade with the sample data. In addition, RF model could be applied to other relevant research.

Abstract:As one of the spatial data mining technologies, DBSCAN algorithm is a densitybased clustering algorithm. Since it can find clusters with any forms from the spatial database, DBSCAN algorithm becomes more and more popular. The optimization principle and realization process of densitybased spatial clustering algorithm were studied in detail, and the existing problems of original DBSCAN algorithm were analyzed. By avoiding repeated searches of objects in the public domain, the computation of searches on the neighborhood of core object was reduced, and the time efficiency of the algorithm was improved. After analyzing the distribution of roadside stall business in rural areas, two key parameters, i.e., Eps and MinPts, of the algorithm and the searching zone of neighborhood of core object were determined. The experiment results showed that the time efficiency of optimized algorithm was improved by approximately 33.73%. Finally, the optimized algorithm was applied to the community grid management in rural areas. By data mining of the rural area grid management system, the most frequent regions were successfully identified for roadside stall business. Using this algorithm, the hot spots of problems in rural area management can be found out in time, which uncovered the common rules hidden behind the routine business. Hence, the corresponding management can be performed to a certain region, which can provide information and auxiliary decisions for rural area management.

Abstract:Pigs’ motion data, such as daily motion duration, distance, speed, etc., are important bases for analysis of pigs’ health and performance. Manual monitoring is real-timely difficult, low accuracy, time-consuming and also easy missing for human fatigue. It can not meet the requirement of large-scale farming. Comparing with RFID (radio frequency identification technology) and sensor technology, video technology for development of animal husbandry had a profound influence without physical contact with animals. It was low cost with simple hardware deployment, which can monitor and manage large-scale farms. A scheme for pigs’ motion detection was designed based on video tracking for capturing and detecting a variety of motion information of farm pigs quickly and accurately. Firstly, color channel was selected adaptively to identify field pigs. A target segment method was provided based on characteristics of color and contour. Then each pig was fitted by an ellipse based on minimizing the cost function and tracks of pigs based on the shortest distance matching algorithm. Extraction algorithm for four motion parameters was proposed, which were displacement, velocity, acceleration and angular velocity. Finally, experiments related pigs’ motion detection, such as pigs’ daily activity, daily activity patterns and pigs daily behavior recognition, were carried out. Experimental results showed that the proposed channel selection method could identify a variety of solid colors pigs;the success rate of adhered pigs’ segmentation was 926%. The real-time video in Guangzhou Lizhi male pig farms was tested from November 21, 2015 to November 24, 2015 from 09:00 to 17:00. It showed that the characteristics of pigs daily activity, daily activity patterns and pigs daily behavior recognition could be manifested by the motion information. Therefore, this scheme was effective for pigs’ motion detection dynamically, and it provided a basic support for pigs’ health, behavior analysis and performance analysis.

Abstract:Considering energy saving and typical working condition of construction machinery, a two-level idle-speed control system based on hydraulic accumulator was proposed to ensure the quick pressure rising at inlet of working chamber of actuator when the idle speed was canceled and the actuator started a new working cycle. The mathematical model of the proposed idle speed control system was developed. The values of the two-level motor speed were obtained according to motor response and characteristics of the pump. The rules of motor speed switch between the two-level idle-speed and the normal working speed were made by detecting the pressures of joystick, pump, two chambers of actuator and accumulator. The parameters of the hydraulic accumulator which was the key component of the idle-speed control system were analyzed through simulation. The experiment was carried out on a 1.5t hydraulic excavator driven by electric power using the obtained parameters of hydraulic accumulator. The comparisons between the idle speed control system with and without hydraulic accumulator and the system without idle speed control were carried out on the testing. The test results showed that the proposed two-level idle-speed control system worked well. Compared with the system without idle-speed control, the proposed control system with hydraulic accumulator can save up to 36% energy. While compared with the idle-speed control without hydraulic accumulator, the inlet pressure of the actuator was raised more quickly and steadily in the proposed control system. This indicated that the proposed system can achieve good energy saving and control performance.

Abstract:Wiebe formula as a semi-empirical formula that calculates heat release in the zero-dimensional combustion model of diesel engine was widely used in the simulation of working process of diesel engine, the accuracy of simulation was mainly dependent on choice of parameters in the formula, but there were some blindness and poor universality in the traditional Wiebe parameters selection method. So in view of shortcoming of the selection method, the D4114B type electricitygenerating diesel engine was taken as an example, a diesel engine Wiebe formula parameters prediction method was proposed based on neural network. By experimental measurement of cylinder pressure curve, the combustion heat release rate was backward deducted, the heat release rate curve was numerically fitted, and the neural network was trained, a neural network which can be used to predict the parameters of Wiebe formula was established. Through the comparison of predicted results and experimental data, and evaluation of prediction accuracy, the accuracy and feasibility of prediction method were verified. On this basis, D4114B diesel engine dynamic simulation model was set up by using Modelica language, and the transient performance of diesel engine was simulated and researched. Finally, the simulation results of neural network input parameters were compared with experimental value, which proved the Wiebe formula parameters prediction method can be applied to the diesel engine dynamic simulation study.

Abstract:In order to investigate the spray dispersion regulation of urea solution of diesel engine SCR (selective catalytic reaction) system, a urea spray model was built up to simulate urea injection and atomization process. The correctness of the model was verified by comparing the simulation and experimental results, the influences of exhaust gas temperature, exhaust gas flow, injection rate and injector position on dispersion of urea spray were analyzed. The results indicated that with the increase of exhaust temperature, particle density of urea solution on the inner wall of exhaust pipe was gradually reduced and the volume fraction of NH3 was increased, which tended to be stable at 400℃. But with the temperature further increased, NH3 oxidation was enhanced in the exhaust pipe, so its volume fraction was decreased. With the increase of exhaust gas flow rate, the packing position of the urea solution particles on the inner wall was moved backward obviously and the volume fraction of NH3 was decreased. Because with the increase of exhaust gas flow rate, the residence time of urea solution in the exhaust pipe was decreased, which was not benefit for the decomposition of urea. With the increase of injection rate of urea solution, the density of urea solution particles and the volume fraction of NH3 were increased gradually, the packing position of the urea solution particles on the inner wall was almost unchanged. With the increase of distance between urea injector and catalyst, the thermal decomposition and hydrolysis reaction of urea became more complete and the volume fraction of NH3 was increased accordingly.

Abstract:Magnetorheological (MR) valve is a kind of smart control mechanism that using magnetorheologcial fluid as the working fluid. The advantages of regulating pressure drop and fast response time make the valve have a promising application prospects in the field of vibration attenuating system. Such as, it can be used as a bypass valve to control the MR damper, which can be formed a MR valve controlled cylinder mechanism to apply in the vehicle suspension system. A two-stage radial type MR valve with meandering fluid flow paths was developed, the fluid flow paths consisted of two annular fluid flow channels, four radial fluid flow channels and three centric pipe fluid flow channels. The working principle of the proposed MR valve was expounded in detail, and the mathematical model of pressure drop was also derived based on the Bingham model. The electromagnetic field model of the MR valve was built up by using the finite element method. The changes of pressure drop under different applied currents were analyzed, the simulation results showed that the pressure drop was 5.81MPa at applied current of 0.8A. At the same time, the experimental test rig was set up to investigate the pressure drop and response time of the proposed MR vale under different applied currents and different loading cases, the experimental results showed that the pressure drop was 5.77MPa at applied current of 0.8A, which was accorded with the simulation results. The response time was also tested, and the test results indicated that the response time was between 3ms and 7ms;the results also showed that the rising response time was shorter than the falling response time. Furthermore, the response time was independent of the loading cases, and the bigger the applied current of the excitation coil was, the faster the response time was.

Abstract:In order to improve the accuracy of NC machine tool and reduce the influence of geometric errors caused by assembly and manufacturing process, the geometric error model was established based on multi-body system theory, and a new method of identifying key elements of the geometric errors was proposed on the basis of geometric errors correlation analysis. Firstly, geometric errors model of three-axis vertical CNC machine tools was derivated by using multibody system theory and homogeneous coordinate transformation method, and correlation analysis model of the geometric error elements was established, which contained 21 geometric errors of three-axis NC machine tools. Secondly, to avoid the defects of single factor analysis, and considering the coupling effects of geometric error elements, Latin hypercube sampling method was used in the whole parameter space sampling. Finally, based on the geometric error model and correlation analysis model, spatial error was calculated by using geometric errors element which was determined by Latin cube sample. And the key geometric error elements that affected the accuracy of machine tool were analyzed. Before error compensation, the twelve-line method was applied to identify the geometric error elements for each axis based on Renishaw XL—80 laser interferometer measuring system. The comparison result of circular tests after error compensation showed that the method can effectively and quantificationally identify the key factors that affecting the precision of machine tool space and the effects of error elements of total space error, thus important theoretical foundation was provided for accuracy allocation and error compensation of machine tool reasonably.

Abstract:Because of parallel mechanism has high rigidity, high speed, high carrying capacity, and not cumulative error, etc., it has been widely used in many fields. Especially less degrees of freedom parallel mechanism has become a hot research topic. The inverse and forward position model of Tripod parallel robot was established, through kinematic analysis of the Tripod parallel robot, the degree of freedom was derived. The inverse kinematics and forward kinematics were solved by using algebraic vector method and numerical method. The condition number of Jacobian matrix was derived and the workspace was analyzed. The calculation result showed that the mechanism owned perfect isotropic properties and specious workspace. ADAMS and Matlab kinematics simulation software were used to verify the inverse and forward position model of this mechanism. The simulation results proved the correctness of the model. A model machine of Tripod parallel robot was developed and a series of experiments, such as accurate positioning, line/circle interpolation, continuous interpolation, were carried out. The results suggested that the mathematical model established for this parallel mechanism was correct. The research systemically solved the problem of theoretical analysis of Tripod parallel robot, set up the experimental prototype, and provided strong guidance for the engineering application.

Abstract:In view of the shortcomings of cable-driven and chain transmission mechanism with motor rotation direction changing frequently and large load, a novel electric-drive robot leg based on planar five-bar mechanism with dual freedoms was proposed to reduce the inertia of robot leg and enhance load capacity. Considering the close relationship between the dynamic performance of robot and the dimension parameters of planar fivebar mechanism, the kinematic and dynamic analyses of this mechanism was made, and the functional relationship between peak torque, peak angular velocity of joint motors, energy consumption in a gait period and dimension parameters were setup to get the optimal dimension parameters. In this way, a multiobjective optimization model of the dimension parameters was got. By determining the weight of the objectives based on analytic hierarchy process (AHP) method, the multi-objective optimization problem was transformed into single objective optimization problem. Then the genetic algorithm was applied to obtain the optimal solution. Finally, the virtual prototypes of robot leg before and after optimization were built via ADAMS to conduct the walking simulation test, and the comparison between simulation results and computation results was made. The motors were selected subsequently according to the optimization results, which made the robot weight decreased by 7.8%, which was beneficial to the improvement of load capacity and battery life. These results verified the correctness and validity of the proposed algorithm which can also be applicable to the selection of brushless DC motor.

Abstract:To evade predators, basilisk lizards can run across water surface with rolling pelvic to drive foot movement. Based on the mechanism of high-speed air-water interface movement, bionic water-surface vector propeller was designed according to bionic object basilisk lizards. With providing lift, thrust and moment, dimension of driving force was increased. For controlling the output of driving force, the influence of structure parameters on mechanical property was analyzed. Combined with standard k—ε turbulence function and PISO algorithm, fluid dynamics model of bionic propeller was established to calculate the mechanical properties of vector propeller with different parameters. By analyzing the changes of mechanical characteristic curve with time, it was found that threedimensional driving forces presented periodical variation. And the frequencies of driving forces were four times as much as those of rotation velocity. From comparison of the threedimensional mechanical properties, the optimal axisshape and diametershape of blade were obtained. Meanwhile, the functions between driving force and length and width of blade were derived with data fitting. By analyzing the distribution of impeller pressure and water volume, solid—liquid mutual action of impeller rotating at watersurface was presented. Finally, the experiment system of vector propeller was set up and the computed force was consistent with experiment result in general, therefore it was validated that the numerical calculation model was correct. In hydroplaning state on the surface of water, the resistance of high speed boat can be reduced and the top speed can reach 80km/h. For transforming navigation state, a new amphibious vehicle with a pair of vector propellers mounted in the rear part was presented. Hydroplaning state of amphibious vehicle with pitch angle of 10.6° was realized, and the design provided a new thought for reducing resistance and improving velocity for water-surface device.