Abstract:The movement and deposition of the diesel particles have important effect on the particle sampling measurement, the operation of the exhaust gas recirculation system and the trapping of the particles. The forces imposed on the emission particles of diesel engine and the deposition characteristics of the emission particles of diesel engine in the turbulent flow channel were investigated under different conditions by using the force modes and the particle random trajectory mode established. The results showed that the Stokes drag force, Brownian force, Saffman lift force, thermophoresis force, gravitation force, and buoyancy force imposed on the emission particles had strong relations with the dimension of the particles and the distance of the particles far from the wall. The main driving forces for the depositing of the emission particles were different under different conditions. The forces, the flow inlet velocity and temperature and the channel dimensions affected the deposition of the emission particles in the turbulent flow channel.

Abstract:In order to explore the mechanism of fuel droplet impacting on a wetted surface in a small-size combustor of diesel engine, experiments and numerical simulation were carried out. High speed camera was used to observe the phenomenon of spreading, liquid sheet formation, breakup and splashing during droplet impact. The results showed that the spreading factor and velocity were closely related to impact velocity. The higher impact velocity droplet had a larger spreading factor, and the intial spreading velocity was the largest, which could be increased by increasing impact velocity. The numerical simulation was developed using volume of fluid method including heat transfer and contact resistance. The mechanism of droplet fluid and heat transfer as well as breakup during impact were obtained according to analysis of results. The numerical results also showed that the pressure gradient inside liquid was the main factor resulting in droplet spreading, liquid sheet formation, breakup and splashing. The capillary wave resulted in the shrink at the neck of the liquid sheet and breakup and splash from the liquid sheet.

Abstract:A robust nonlinear control approach for modern diesel engine operating under low temperature combustion and conventional compressor ignition combustion modes is described. A nonlinear state space model of intake system is established based on the ideal gas equation and the law of mass conversation. The intake pressure, exhaust pressure and composition of inducted flow are chosen as the system outputs, which have key influence on in-cylinder combustion, and the corresponding controller is designed by the method of integral sliding mode. Smooth switching of combustion modes is achieved by tracking the key engine air-path operating variables to control the in-cylinder conditions indirectly. At last, the effects of the controller were evaluated by co-simulations using GT-Power and Matlab/Simulink and rapid control prototype respectively. The result unveiled that compared with the PI algorithm the innovative control algorithm had significant merits such as good tracking performance, fast response, strong anti-interference and robustness and so on.

Abstract:The safety and reliability of electric vehicle depend on the performance of vehicular energy storage system. The test bench composed by DC motor and flywheel was proposed to test the performance of energy storage system. This paper mainly focuses on an improved test bench. The tracking precision of speed control system was affected by the improved test bench. The model and current problems of the test bench were presented. The structure improvement method of the test bench was improved according to the theory of multi-shaft transmission system. The improved test bench was modeled by using state-space equation method. The efficiency and ratio control of continuously variable transmission (CVT) were analyzed. The dSPACE-based hardware-in-the loop (HIL) test bench was built and improved in the lab. Experimental results showed that the tracking precision of speed control system was improved with new test bench. It provides technology support for the performance testing of hybrid energy storage system.

Abstract:Based on the requirement of CF700 tractor cab suspension parameters, the elastic force and damping force model of hydro-pneumatic spring was established using fluid mechanics theory. The key parameters of hydro-pneumatic spring were calculated, and the damping adjustable hydro-pneumatic spring was designed. The effect of the excitation, throttle valve size and check valve size on the output force were studied by experiments. Test result is shown that the damping force can be in a large range of adjustment. The throttle valve size had influence on output force of both compression and rebound stroke, while the check valve size just had influence on the output force of compression stroke, and the throttle valve size had more obvious influence on the output force. The effectiveness of design ideas and methods were verified, and the research base of tractor cab hydro-pneumatic suspension was provided.

Abstract:There are many unexpected events when a rover is moving on a planet surface, and subsidence is one of the most fatal events which could result in the invalidation of the rover. It is very important to research subsidence prediction and intervention measures when encountering unpredictable excessive subsidence. Function relationship between wheel and soil is linearized to establish simple drawbar pull equation for subsidence estimation. “Yutu” lunar rover is taken as an example for revising equation by means of wheel soil-bin test and subsidence estimation function used to estimate subsidence online. Error between the calculation of the drawbar pull model and the measurement in soil bin test is less than 9%. The proposed model can be used to warn before the rover sinking, and provide the sinkage data for the earth-based simulation of breaking away from sink after the rover sinking. This method can also be used for rapid subsidence estimation when wheeled machinery performs various operations on the sand, beaches and other soft ground.

Abstract:The specific power has often been used in evaluating the influence of water droplet impact on soil surface. A Nelson R3000 rotating spray-plate sprinkler was selected and the drop size, drop velocity were tested under 100,150 and 200kPa by 2DVD.The relationship between drop kinetic energy and drop size, kinetic energy applied per unit drop volume and distances along the sprinkler, specific power and distances along the sprinkler were analyzed. Results indicated that there were proportional relation between the kinetic energy and drop size, and the maximum value of drop kinetic energy from test location increased with the distances along the sprinkler increased. At the same location from the sprinkler, the maximum and average values of drop kinetic energy decreased with the increase of working pressure. The kinetic energy per unit volume increased with the distances along the sprinkler increased, and the change between kinetic energy per unit volume and distances along the sprinkler met exponential function. At the same location from the sprinkler, the kinetic energy per unit volume decreased with the increase of working pressure. At the test location between 0~6m along the sprinklers, the specific power values were less than 0.02W/m2 and the differences were small when operating pressure values were set at 100, 150, 200kPa. At the test location from 6m to the end of the sprinklers, the maximum values of the specific power were 0.1172, 0.0827 and 0.0522W/m2, and the value of the specific power decreased with the increase of working pressure.

Abstract:Emitter clogging caused by simultaneous irrigation and fertilization (fertigation) has negative influence on the normal operation of drip irrigation systems. This study was carried out to determine the effects of fertigation amount and irrigation amount on labyrinth emitter clogging. Additionally, sediments in the labyrinth passage were analyzed by field emission scanning electron microscope (FESEM) to determine their composition. Results indicated that average discharge of the emitters decreased between 1.51% and 14.16% with the increase of the irrigation or fertigation amount after operating the drip irrigation system for 21 weeks. Statistical analysis showed that fertigation amount significantly affected emitter average discharge (P<0.01). Dissection of the clogged emitters revealed that the sediments located in the front labyrinth passage comprised primarily of sealing tape, insoluble fertilizer particles, and white powdery chemical precipitation. The chemical precipitation was found to be constituted of carbon, oxygen, phosphorus, calcium, magnesium, and other minerals. Consequently, emitter clogging was mainly caused by the combined effect of physical and chemical clogging.

Abstract:In the water-saving irrigation, the characteristics of sprinklered raindrops is an important standard of nozzles hydraulic performance. The paraments which can reflect the characteristics of raindrops mainly contain drop diameter, drop size distribution, drop velocity and raindrop kinetic energy, in all of this parameters, the raindrop diameter is the basis of other parameters studies. This paper makes accurate measurements of drop view, drop size distribution, equi-volumetric diameter and vertical velocity of raindrops by using 2D-video-distrometer. It also analyses the trend on raindrop equi-volumetric diameter affected by nozzle size and working stress, and establishes a model based on the relationship of raindrop equi-volumetric diameter and the vertical velocity. The results show that the equi-volumetric diameter of artificial rainfall sprinklers raindrop is ranged from 0 to 3mm and when the working pressure increased, the equi-volumetric diameter of raindrops decreased as the sprinklers size is not changed; on the contrary, when the working pressure is changeless, the equi-volumetric diameter of raindrops increased as the sprinklers size increased. According to the relationship model of equi-volumetric diameter versus vertical velocity of raindrops, it can get of good prediction of the vertical velocity which may provide a fundamental basis for kinetic energy calculation and establishing the mathematical models of erosion forecasting.

Abstract:On the basis of SPAD model for nutrition diagnosis of nitrogen fertilization, we determined the optimal nitrogen rate at the different growth stages of cotton with drip irrigation under mulch. Combining with relevant research at a single irrigation time and acreage of round irrigated area, we definited the fertilizer time of different specifications fertilizer disc. The capacity of the device with combined application of nitrogen fertilizer was determined by comparing with distribution and application of combined fertilizer at unit time. The results showed that the rate of fertilization per unit time for the device was related to water yield from any single well and nitrogen fertilizer in the whole cotton growth period, and the device were unable to meet the needs of topdressing when it used fertilizer disc of sizes with 100g, 200g and 300g. Furthermore, fertilizer disc of sizes with 400g and 500g could only meet topdressing nitrogen level of cotton under condition of the specific water yield from a single well. And according to our research described above, we explored the approach to optimize and improve device.

Abstract:Through stream breaking by stream interrupter installed in the rotary sprinkler, close-in water will be increased and the water distribution will be enhanced. The rotary stream interrupter rotates intermittently under the stream impact, which leads to improve the water uniformity, and at the same time, almost does not reduce the throw distance. The structural size of the diffuser fixed in the stream interrupter plays an important role to the hydraulic performance of the sprinkler. The shortest performance radius R and the affected area angle α produced by the diffuser are put forward as the optimizing indexes in the orthogonal experiment. The key sizes, such as the diffuser width a, the diffuser length interrupting in the stream h and the distance from the outlet nozzle to the diffuser c, are presented as factors. By testing the hydraulic performance influenced by the factors, the relationships among the factors and the performance radius and the affected area angle are obtained, and the optimum structural sizes of the diffuser are also brought forward. The radical water distribution of a rotaty sprinkler is composed of the distributions without the diffuser and with the diffuser by the definite spraying frequency. According to above meationed law and the concept that the ideal shape of the final water distribution is triangle, the method to calculate the shortest performance radius in the affected area is first built up. 

Abstract:A reversed running centrifugal pump can work as a hydraulic turbine. In order to improve the operating performance of pump as turbine (PAT), a special impeller with forward curved blades was designed and experimented. By using the constant velocity moment theory, the calculation expressions of volute constant within spiral volute were developed and the velocity moment before impeller was acquired. Impeller with forward curved blades was designed and manufactured. Its inlet angle at leading edge was determined by using shockless inlet flow while its outlet angle was designed on whirl free outlet flow. Performance test of PAT with designed forward curved blades impeller and conventional back swept blades impeller was performed. The comparison between designed forward curved blades and conventional back curved blades shows that the best efficiency is increased by 13.22%. Compared with original PAT performance curves, the efficiency curve of PAT with forward swept blades is more flat. The efficiecy variation of PAT with forward curved blades is only within 1.5% between 0.9QBEP (flow rate of best efficiency point)and 1.2QBEP operating range. Therefore, the high efficiency operating range of impeller with forward swept blades is wider than conventional back swept impeller.

Abstract:A differential velocity vane pump driven by Fourier noncircular gear was designed and the blades of pump were equipped the check valves in the same direction of rotation. Through the establishment of non-circular gears Fourier model and instantaneous flow models and design of the simulation software, we analyzed the influence of the three typical parameters on the shape of the section curve, the flow rate, displacement, pump structure and single or double pump, check valve on the blades to the pulsation rate. Dual pumps in parallel driven by the Fourier non-circular gear were compared with that driven by the eccentric gear to reduce pulsation rate 10.3%. And the installation of the check valve can solve the problem that the liquid trapped in closed chamber.

Abstract:Mechanism of flow instability in a centrifugal pump was studied by using the energy gradient theory. Numerical simulation was performed for the three-dimensional turbulent flow field in the centrifugal pump. The whole flow parameters in the centrifugal pump at different flow rate conditions were obtained from the simulation. The distributions of the energy gradient function K at various flow rates were calculated by using the data of the numerical simulation. According to the energy gradient method, the area with larger value of K caused instability and high turbulence intensity. The results show that instability was easier to be excited near impeller outlet area and volute tongue. In addition, as the flow rate was reduced, the unstable areas moved from the outlet to the inlet of the impeller.

Abstract:3D inverse design method was applied to configure the runner geometry of a middle-high head pump-turbine, in which design parameters were given according to pump operation and iterative calculations conducted from turbine direction. Model tests were performed to measure performances of developed runner under different operating modes and points. Test results show that the highest efficiency under pump mode is 91.34%, and highest efficiency under turbine mode is 88.5%. Internal flow analyses based on viscous full passage computations show that water pass through the passage smoothly with smaller loss under pump mode, while rather serious incidence loss exists at runner inlet and large low pressure area exists at suction side under turbine mode.

Abstract:With the aim to improve the hydraulic performance of liquid-ring pump, the three dimensional transient gas-liquid flow in liquid-ring pump was simulated by using the volume of fluid (VOF) method. The streamline, the distribution of velocity, press and the volume fraction were investigated. The secondary flow in pump was analyzed. The free interface of gas and liquid phase in pump was traced, and the relation between the shape of the free interface and the hydraulic performance of the pump was analyzed. The experimental research was carried out. The numerical results and the experimental results show good agreement. The numerical method of VOF is suitable for simulating the gas-liquid flow in liquid-ring pump. The free interface could be traced exactly and the hydraulic performance could be evaluated with enough accuracy, which pave the way for hydraulic optimization of liquid-ring pump.

Abstract:D-bale knotter is one of the key parts of square baler, which influences the efficiency and quality of baler. Based on reverse engineering, D-bale knotter was reconstituted and the accuracy of working surfaces was analyzed. The results showed that more than 90% domain for all the working surfaces can achieve the precise level above. Reconstruction parts of D-bale knotter were assembled and then simulated by using the software Solidworks. The angular velocity and displacement data of twine holder, bill hook, wiping arm, and driving dentate disc were obtained and the movement relationships of these parts were further analyzed. This study will provide basic data for the optimization of D-bale knotter.

Abstract:Present orchard spray equipment is much larger, and both power and pesticide consumption are much higher. To overcome the above deficiency, an orchard symmetric swing mist spraying system was developed. To expand the diameter of mist spraying, a planar-spatial hybrid mechanism was designed firstly by analyzing the configuration of driving point and fulcrum, and degree of freedom. The planar-spatial hybrid mechanism was driven by a DC motor, which consisted of a symmetrical double crank mechanism and different multi-degree joints at driving points and fulcrums to realize spatial swing motion of the two mist sprayers. To simplify the manipulation and avoid the backflow of pesticide, a MCU control system was designed to realize one-button start/stop operation of the complex action process of the symmetric swing mist spraying system. According to the orchard’s specification, the structural parameters, including the length of the crank, the height of crank center, height of fulcrum, distance of crank center and distance of fulcrum, were determined by nonlinear programming that took the minimization of machine size and the effective covering of canopy by mist spray as objective and constraint conditions, respectively. And then to achieve the highest efficiency of mist spraying under the constraints of both rate and uniformity of mist spraying, the optimal traveling speed of the machine and rotation speed of the crank were determined. This spraying system can guarantee the effective coverage of crowns within height of 1500~4300mm and 5500mm width with 400mm radius mini mist sprayer, and guarantee the uniformity and quantity for spray of mist spraying on both sides of the trees, whose working efficiency can reach 2.33~2.67hm2/h. It is an energy-saving, pesticide-saving and miniature mobile orchard spraying system and will be a better selection in the future for pest control in orchards.

Abstract:From 2011 to 2012, a series of field experiments were conducted in Donghai county, Huaibei region of Jiangsu Province under typical annual rice-wheat cropping rotation system. Two conventional japonica varieties, Zhendao 11 and Yongyou 8, and two hybrid japonica varieties, Yongyou 1640 and Yongyou 2640, were grown under three mechanical transplanting methods, bowl-seedling, blanket-seedling, and direct-seeding mechanical-transplanting, to determine the diversity of seedling quality, growth duration, photosynthetic production, accumulated temperature and illumination hours, yield components, and grain quality. Results showed that the seedling quality of bowl0seedling of the mechanical transplanting rice was significantly better than that of blanket-seedling mechanical transplanting rice. Compared with bowl-seedling of the mechanical transplanting rice, each growth period were postponed in blanket-seedling mechanical transplanting rice and direct-seedling mechanical transplanting rice, and whole growth period was shorted about 8~10d and 20~22d, respectively. Accumulated temperature and illumination hours of whole growth period and different growth stages were lower, and then led significantly lower crop growth rate and net assimilation rate in mid-to-late growth period. The yield of bowl-seedling mechanical transplanted rice was the highest and the yield of direct-seeding mechanical transplanted rice was the lowest. Yield components of bowl-seedling mechanical transplanted rice had the characteristics of significantly less number of panicle per unit area, significantly higher spikelets per panicle and kilo-grains weigh, and bowl-seedling mechanical transplanted method significantly increased grain yield by 10.2% and 23.4% than blanket-seedling and direct-seeding mechanical-transplanting method in hybrid rice, respectively, and by 5.6% and 19.3% in conventional rice, respectively. Moreover, grain quality of bowl-seedling mechanical transplanted rice was the best. Studies indicate that bowl-seedling mechanical transplanted method is a priority selection in Huaibei area.

Abstract:In order to accurately describe the transport mode of soil moisture in arid areas, based on previous studies, the model parameters and specific boundary conditions were determined according to the actual situation of Shihezi Reclamation, and a two-phase mass and heat flow transfer model including water and air was established fit for this vadose zone-saturated zone, thereby simulating the dynamic changes of soil moisture, soil temperature. The measured soil temperature, soil moisture were used to test models. The results showed that the simulated soil temperature and moisture could well reflect variation of measured values. Accuracy assessment indicators showed that the simulation accuracy of each soil layers was high. Simulated results of the model considering the impact of air were closer to the measured results. For the day rainfall of 9.7mm, infiltration depth could affect soil moisture of about 20cm depth for coupling model, and up to about 30cm depth for a single model. The average evaporation rate of the model considering air in the rain day was 7.7% more than the result of the model without considering air. In the day right after the rainfall event, the results without considering the effect of air pressure caused evaporation rate 3.19% lower than the results considering air effect. Calculating the total evaporation during the simulation period, the results of the two models were very close. But based on the results of water balance analysis of the two models, comparing calculated evaporation and simulated evaporation, the results of the model considering air influence were considered reliable.

Abstract:Soil dry layer has occurred widely in artificial economic forest in Loess region, which constrained vegetation restoration and reconstruction. In order to investigate deep soil depletion （below 2m） in densely planted jujube (Ziziphus jujube Mill.) orchard, soil coring method (Luoyang shovel) was used to get soil water content from surface to the maximum fine rooting depth at 0.2m soil interval. The results showed that root water uptake had a tendency to extend gradually deep, deep soil water depletion was 0, 29.6, 149.9 and 155.7mm in 2, 4, 9 and 12 year-old jujube plantation, deep soil water supply was 203.7, 167.7, 35.5 and 29.7mm, respectively, annual deep soil water depletion accounted for 0,2.3%,5.1% and 3.9% of annual soil water supply. There was almost no available water in 2~4m soil layer when the jujube plantation developed for 9 years. Jujube water requirement could not be met by the existing rainfall and drip irrigation amount. Soil dry layer extent and depth can be evaluated more accurately with the maximum rainfall infiltration depth and maximum fine rooting depth as upper and lower boundaries. Soil water content could be increased through water catchment, water conservation and water supplement, which played an important role in alleviating jujube plantation deep soil drying.

Abstract:In order to reveal the influence of decreasing range of freezing air temperature (DRFT) and soil texture on soil temperature variation and soil moisture migration with shallow groundwater, three freezing schemes, less DRFT, medium DRFT and larger DRFT, were conducted with the groundwater level depth of 87.5cm, and the temperature and moisture content of sandy loam and silty clay loam were monitored. The results showed that the surface temperature of sandy loam was lower than that of silty clay loam freezing by less DRFT, medium DRFT and larger DRFT about 0.88℃, 2.06℃ and 2.81℃, and soil profile temperature reached steady decreasing stage in 31d, 33d and 37d respectively. Soil moisture of sandy loam mainly gathered at the depth of 10cm to 30cm and that of silty clay loam gathered at the depth of 10cm to 40cm. Soil moisture of sandy loam at the depth of 0cm to 10cm freezing by less DRFT was higher than that freezing by medium DRFT and larger DRFT about 1.5% and 7.3%, while it was 2.3% and 2.7% respectively for silty clay loam. 

Abstract:Choosing Harbin as the study area, a city of typical cold climate, through the field experiment in winter (from 2013—11—01 to 2014—04—30), we measured soil temperature in the depth of 3cm, 5cm,8cm,10cm,15cm,20cm,40cm,60cm,100cm, and 140cm with four control groups (bare land, 5cm thickness of straw mulch, 10cm thickness of straw mulch, 15cm thickness of straw mulch), and air temperature and solar total radiation under different control group. The statistical analysis results show that the straw mulch can prevent heat transfer in two directions, and its dominance varies with the outer environment. Under a certain depth the soil temperature is determined by the interaction between soil thermal conductivity and straw mulching conditions. The temperature of bare land has the biggest change rate, followed by the 5cm thickness of straw mulch and the 15cm thickness of straw mulch, and the last is the 10cm thickness of straw mulch, which means that the influence of straw mulching on soil temperature does not increase monotonously with the increase of the thickness of the straw.

Abstract:The design of an automatic water runoff monitoring field was outlined. It consisted of six runoff plots and a rainfall simulator, which was generally used to study erosive processes in sloping fields. A German-made surface runoff measuring device (Umwelt-Gerate-Technik GmbH, UGT) was used in this runoff field, which effectively improved sampling efficiency and reduced human error through automatic sampling and recording. The effect of straw cover on runoff processes and sediment yield on sloping fields was investigated using this runoff monitoring field. The results demonstrated that the straw cover could significantly decrease the rates of runoff and sediment deposition, and delay the onset of surface runoff and reduce the total amount of soil loss by 54.5%~63.8%. Maximum retention of plant residues as soil cover can effectively avoid sharp increases in runoff and limit water scouring effects. It is significant for alleviating soil erosion in sloping fields.

Abstract:Kinetic energy from rainfall is one of the most active factors impacting soil chemicals transport in runoff and the chemicals transport by rainfall splash is usually the first step. Effects of raindrop kinetic energy on the transport of soluble chemicals and sediment to runoff and infiltration into a clay red soil were quantified. The runoff, chemical and sediment transfer were investigated in small soil beds for five kinetic energy of raindrops obtained by varying heights of fall (0, 0.7,1.0, 2.5 and 4.0m), using a drip-type simulator. Runoff lag time, water content in surface and depth of water infiltration decreased linearly with increasing of the droplet energy flux (DE). The relationships of total runoff(TR), sediment yield(SY) and DE were described by power and logarithmic functions, respectively. The bromide transport in surface runoff was best described by a power decay model with the decay coefficients related to rainfall energy. The concentration of dissolved phosphorus in runoff increased linearly with time and the relation between the amount of total phosphorus (TP) loss to runoff and DE was an exponential function. The vertical transport of bromide and phosphorus within the soil matrix was strongly dependent upon the raindrop impact. 

Abstract:In order to understand the effects of irrigation amount on fruit quality and yield and to investigate the efficient mode of water supply of peach tree in semi-arid area field, two-year experiments were conducted to study the response of water demand signal (sap flow velocity, net photosynthetic rate Pn, transpiration rate Tr, stomatal conductance Gs), yield and fruit quality of four years peach tree to the different irrigation amount treatments (I1:100%ETc, I2:75%ETc, I3:50%ETc, I4:25%ETc, ETc is crop evapotranspiration) under mobile rain shelter in two consecutive seasons (2010—2011). The two-year results showed that the number of fruit per hectare were both performance for I1＞I2＞I3＞I4 and the yield per hectare are both characterized by I1≈I2＞I3＞I4. Compared with I1, I2 didn’t have lower sap flow velocity and had higher water use efficiency (WUE) which was improved by 6.2% and 7.7% without reduction on the Pn and yield significantly, while I3 and I4 reduced yield by 9.2%, 21.4% and 16.9%, 42.5% respectively in 2010 and 2011, even if it had the low transpiration rate and high WUE. Meanwhile, irrigation had extremely significant effects (P＜0.01) on peach mouthfeel, vitamin C, sugar/acid, single fruit weight and yield so that I2 was improved by 2.2%, 4.5%, 24.4%, 28.8%, -2.3% and 5.9%, 3.2%, 26.5%, 9.3%, 0.4% respectively compared with I1, and significant effects (P＜0,05) on fruit number, color, firmness and titratable acid so that I2 was improved by -24,1%,85.7%, 22.1%, 12.1% and -8.1%, 40%, 28.8%, -2.7% respectively compared with I1. It had little impact on fruit moisture content and deficit irrigation (I2, I3 and I4) all improved the fruit quality of peach. The research also showed that there were high correlative relationships between peach yield, net photosynthetic rate and soil water content in two-year experiments. Under the condition of experiment, the highest yield, higher water benefit and better fruit quality of peach tree can be obtained with irrigation of 75% ETc.

Abstract:The object of this study was to explore the high quality and yield cultivation mode for maize in the north drought region. The impacts of different straw mulching modes in different growth stages on maize root-shoot ratio, root temporal and spatial distribution, surface biomass, yield and water use efficiency were analyzed through field contrast experiments from 2012 to 2013.There were a conventional tillage and four straw mulching modes in the experiments, which were surface tillage with straw mulching, no-tillage with straw mulching on furrow, no-tillage with stubble mulching, and no-tillage with straw mulching on ridge and furrow. SPSS statistics software was adopted to conduct significance analysis for data of jointing stage and harvesting stage respectively. The results showed that different straw mulching farming modes had significant effect on the control and support in root, root-shoot ratio and earth surface biomass, obvious effect in the early jointing stage. In addition, no-tillage with straw mulching on ridge and furrow was inferior to conventional tillage. But the other four kinds mulching models were better than comparison for 1.56%~5.48% in growth of earth surface biomass, higher than comparison for 15.10%~32.36% in root weight density, and higher than comparison CK for 10.38%~32.74% in root-shoot ratio. The yield and utilization efficiency of water were respectively higher than comparison for 10.38%~32.74% and 4.22%~12.31%. Surface tillage with straw mulching was an ideal cultivation method for cold and arid regions of North China, which had significantly advantages in growth of root formation, yield increase and water availability. 

Abstract:Since the soil temperature in closed greenhouses is relatively constant and less influenced by external environment, the ditch cultivation method in closed greenhouses is adopted to conduct tests in this research. Moreover, water is supplied according to the transpiration to create suitable conditions for crops. The differences among the environmental factors of different ditches with various depth and their influences on transpiration rate, yield of Chinese cabbage as well as water productivity are researched. The results show that in high temperature condition the temperature values in 0.7m and 0.9m (the depth of the ditch) are reduced obviously compared with CKi (Check treatment in greenhouse), and the maximum temperature difference is larger than 20℃. The humidity is maintained between 25% and 75%, which is suitable for the growth of crops. The water productivity for each treatment are: 0.9m＞0.7m＞0.5.m＞0.25m＞CKi＞CKo. In high temperature, ditches with the depths of 0.7m and 0.9m are more suitable for the growth of Chinese cabbage. Therefore, ditch cultivation method can solve the high temperature and high humidity problems of closed greenhouse. Meanwhile, it can improve the crop water productivity.

Abstract:In order to alleviate the soil drying of the jujube forest in semiarid loess area, we took the gradient control on jujube tree specifications by pruning, using the TDP tree rod liquid flow monitoring system to monitor the jujube tree transpiration and CNC100 neutron moisture meter to monitor soil moisture. It was found that the pruning on jujube had a significant influence on the transpiration and water consumption at different time scales through the research for two consecutive years. Pruning can significantly reduce the tree transpiration in flowering period of fruit and fruit enlargement period of jujube, and reduce the consumption of soil moisture. Compared with the control treatments, the tree transpiration with mild, moderate and severe pruning of the whole growth period decreased by 31.7%, 52.0% and 68.6%, respectively. The relationship between tree transpiration and specifications were analyzed by linear and nonlinear analysis method, and then a mathematical model of natural precipitation and trim production target was built. The suitable target yield for the sustainable management of jujube forest in northern Shaanxi was 1.2×104kg/hm2, and the tree index for water-saving trim regulation was the crown and the new length. The new mode was formed that the production of jujube was determined by soil moisture and jujube specifications were determined by production.

Abstract:By studying the characteristics of microbial number, nitrification and denitrification rates and respiration rate of rhizosphere soil of Brassica chinensis L. grown under the different concentration of lead (Pb) environments, the effect of lead on the ecological safety of plant rhizosphere micro-ecosystem was revealed. The results showed that the all numbers of bacteria, fungi and actinomycetes first increased and then decreased with increase of Pb concentration, and the peak value occurred in the environment with soil Pb concentration of 300mg/kg, 300mg/kg and 600mg/kg, respectively. The Pb tolerance of microbe was fungi > actinomycetes > bacteria under the Pb stress environments. The all numbers of nitrifying and denitrifying bacteria in the rhizosphere, soil nitrification and denitrification rate, and soil respiration rate also first increased and then decreased with increase of Pb concentration, and peak values of all above parameters occurred in the environment with soil Pb concentration of 300mg/kg. Nitrification rate and number of nitrifying (R2=0.6847), denitrification rate and number of denitrifying bacteria (R2=0.8511), and respiration rate and the total number of microbe (R2=06843) were all correlated significantly and positively. In conclusion, only when the soil Pb concentrations reaches or exceeds 1200mg/kg, significant microbial community structural and functional degradation of B. Chinensis rhizosphere micro ecosystem will occur.

Abstract:A recommended nitrogen topdressing model was built up using normalized difference vegetation index (NDVI) of cotton canopy, which was obtained by active GreenSeeker sensor for diagnosing the nitrogen nutrition in cotton plant, and the precise management of nitrogen nutrition for cotton by topdressing was realized. The field test data treated with different nitrogen fertilizer levels in 2011 and 2012 were obtained, and the quantitative correlations between NDVI and fertilizer rate as well as NDVI and yield of cotton were established. Combining with the nitrogen fertilizer effect function, the best nitrogen application rate was calculated, and the nitrogenous fertilizer recommendation model based on spectra was established and verified by field test data of 2013. The results suggested that NDVI of cotton canopy increased with the increase of nitrogen fertilizer level, and then stopped increasing when nitrogen fertilizer was up to a certain level. The NDVI of cotton canopy presented a liner increasing trend with nitrogen fertilizer rate increasing in four growth stages, full bud, flowering, full boll and early wadding stages, and the corresponding thresholds of NDVI were 0.695, 0.833, 0.881 and 0.809, respectively, when the total application rate of nitrogen fertilizer was 294.7kg/hm2 during the whole growth period of cotton. In addition, as NDVI decreased by 0.001 from the thresholds, the amounts of applied nitrogen fertilizer were 0.24, 0.91, 1,11 and 0.16kg/hm2 at four different stages, respectively. Field experiment illustrated that the nitrogenous fertilizer recommendation model could reduce the fertilizer application rate under guaranteeing the cotton yield.

Abstract:Soil organic carbon (SOC) in Beijing was taken as target variable and four different sampling densities were designed to investigate the structural changes of the variogram and uncertainty of spatial prediction with the study scale changes. The results showed that the mass ratio of SOC was macroscopically related to terrain factor and low sampling density data were the most optimal for use in fitting the trend values. As sampling density increasing, the variogram distribution of SOC mass ratio and its residuals flattened out gradually. The random variation was growing strongly, and the structural variation and uncertainty of spatial prediction decreased gradually. In addition, the range of variogram might also affect the uncertainty of spatial prediction. Increasing sampling density and regression Kriging method aided by terrain factors can improve the prediction accuracy of mass ratio of SOC. Therefore, soil monitoring and management introducing auxiliary variable can cut the number of sampling points to some extent without reducing prediction accuracy.

Abstract:This paper mainly studied the photo-hydrogen production capability of using enzymatic hydrolysate to four different energy grasses, king grass, witchgrass, grassiness and alfalfa, as substrates. The cumulative hydrogen production and hydrogen production rate were taken as the indexes to contrast photo-hydrogen production capability of different energy grasses. Then modified Gompertz equation was used to perform regression analysis of hydrogen production process, and the technical feasibility using energy grasses as raw materials for photo-hydrogen production was verified. The results showed that among these four energy grasses, the hydrogen producing capability of alfalfa was the best followed closely by king grass, and the hydrogen producing capabilities of witchgrass and grassiness were feeblish, in the circumstances of 30% inoculum size, 30℃, 2000lx illuminance, 120h of fermentation time. The cumulative hydrogen production of king grass, witchgrass, grassiness and alfalfa was respectively 75.3, 27.2, 26.1, and 81.6mL. The maximal hydrogen production rate was 7.83, 3.5, 4.33, and 14.75mL/(h?L) respectively.

Abstract:An L9（33） of orthogonal experiment on batch anaerobic digestions was conducted in order to investigate the effects to biogas production characteristics by adding biochar in anaerobic digestion of chicken manure under the mesospheric condition (35±1)℃. The effects of the three factors including biochar concentration, inoculums concentration and biochar thickness on biogas production characteristics were determined. The optimal combination of these three factors was achieved. The results showed that the factors affect biogas production from highest to lowest were biochar concentration (very significant), biochar thickness (not significant), and inoculums concentration (not significant). The effect of thickness of biochar to methane contents achieved a very significant level.

Abstract:The vapors directly catalyzed from vacuum pyrolysis of rape straw was investigated over HZSM—5 in a two-stage fixed-bed reactor to determine the effects of operating parameters on the product yields, including catalyzing temperature, biomass to catalyst mass ratio, and catalyst Si/Al ratio. The optimization of the oil phase yield was further conducted by employing response surface methodology (RSM). The statistical analysis showed that the operating parameters significantly affected the product yields. The optimal conditions for the maximum oil phase yield were obtained at catalyzing temperature of 491.0℃, biomass to catalyst mass ratio of 0.301, and catalyst Si/Al ratio of 53. Confirmation runs gave 9.80% of oil phase yield compared with 9.90% of predicated value. The upgraded bio-oil consisted of separable oil and aqueous phases. The H/C molar ratio, pH value and higher heat value (HHV) of the oil phase were 1.518, 5.15 and 33.80MJ/kg, respectively. It showed that the oil phase had a higher yield and the qualities, which can be used as an engine fuel. The H/C molar ratio and HHV of the aqueous phase (dry basis) were 1.269 and 29.69MJ/kg, respectively. The aqueous phase also had a high fuel value. 

Abstract:Taking advantage of research results about cooperative control of flow field and temperature field, the cooperative of velocity field and pressure field were further investigated by setting up indispensable parameters of heat transfer medium in refrigerated road transport carriage, according with start points of energy conservation synergistic equation and turbulent kinetic energy equation. Considering temperature distribution homogeneity as evaluation objective, the simulation distribution condition of three fields in longitudinal cross sections was qualitatively analyzed and experimentally verified. The heat transfer and pressure drop performance were fulfilled using numerical simulation analysis and comparison method for inlet orifice with three different shapes as circle holes, elliptic or regular hexagon. The test data of inside temperature in refrigerated transport carriage in fully loaded process showed that the highest temperature in cross sections with width direction dropped from 2.53℃ to 1.27℃, and the standard deviation amplitude of temperature values dropped from 0.642℃ to 0.332℃, respectively. The results also demonstrated that the flow resistance of elliptic air inlet orifice was smaller than other two shapes, and the consumption power of refrigeration motor-pump was fewer. The temperature distribution was more stable and homogeneity, and velocity field, temperature gradient field and pressure gradient field had favorable harmonious degree.

Abstract:In experiment, glycosides in Meili young wine from Yangling were extracted, and then wild yeast glycosidase was added. Varietal aroma compounds were collected and enriched after the catalytic hydrolysis, and detected by GC—MS. The catalytic effects of the almond β glycosidase reference, Aspergillus niger pectinase, and La Fort Pectinase were compared with the wild yeast glycosidase in the experiment. The results showed that free volatiles released by almond β glycosidase were the most abundant with high concentrations, while the followings were those released by A. niger pectinase and wild yeast, Rhodotorula mucilaginosa glycosidase. In the released compounds, terpenols and norisoprenoids showed lower concentrations, but they gave the wine with fruity and floral fragrance. Three kinds of trace esters of phenolic acids brought more complex aroma to the wine. However, aliphatic compounds and volatile phenols displayed higher concentrations, which led wine on to off flavor. Therefore, the glycosidase of wild yeast R. mucilaginosa with medium catalytic ability has the potentiality to the application for wine aroma enhancement.

Abstract:Fresh shrimp (Penaeus monodon) was treated by either high pressure processing (HPP) or heat for comparison. The changes of water states and distribution were detected by low field nuclear magnetic resonance (LF-NMR). Relaxation times T2 and distribution areas were calculated and compared to investigate the treatment effects on shrimp samples. Pressure levels of HPP ranged from 100MPa to 600MPa, and pressure holding time was set as constant, i.e. 10min. The initial temperature of pressure transient medium was 25℃, while 40, 60 and 90℃ were selected and the treatments time was set as 10min during heat treatments. For both HPP and heat treatments, treatment conditions of untreated control samples were at 0.1MPa and 25℃. Experimental results showed that both HPP and heat treatment could alter, to some extent, relaxation times T2 and relative contents of different states of water in shrimp samples. A kind of bound water with high capacity of combining with macromolecules in meat was induced when samples were treated at pressures in excess of 100MPa or at temperatures in excess of 60℃, with relaxation time located between 0.1ms and 1ms. The content of combined water in meat, which was highly related to product water holding capacity, was significantly influenced by heat treatment but not by pressure. The content of combined water decreased significantly with the temperature rising. The changes of combined water content after HPP and heat treatments suggested that HPP was a superior method for producing fresh shrimp to retain the water holding capacity than heat treatment.

Abstract:The one-dimensional mass transfer and heat transfer mathematical models were developed by taking mango cells as a basic unit for the effective prediction and process control of osmo-dehydrofreezing. The mass balance equations for the diffusion of different species were established separately for the intracellular and extracellular volumes taking into account the transfer through the cellular membrane and the plasmodesma. Moreover, the model also considered bulk flow of different species in the extracellular volumes. The thermal balance equations for modeling the subsequent freezing step were developed, which included the phase change phenomena. The numerical solutions were solved by a finite difference method with Matlab programs. A good agreement was obtained between the simulated and experimental results including water loss and solid gain during osmotic dehydration and temperature profile during freezing, and the relative error was controlled in 15%, which proved that this model was practical. Numerical results could describe the distribution of water and sucrose in the intracellular and extracellular volumes of mangoes during osmotic dehydration and show the change of temperature at different time during freezing.

Abstract:In order to minimize the great influence of the distance between fiber-optics probe and sample surface point on prediction results in livestock products quality and safety detection, the spectral change rules with change distances, and proposed a calibration method for the collected spectra were analyzed. Pork tenderness was investigated, and the calibration result of the proposed method was verified. First, VIS/NIR spectral data of pork (longissimusdorsi muscle) was collected by a fixed probe with the changing distance between 4 and 18mm. Then, the spectral data collected under each condition were preprocessed by the same method and PLSR prediction models were established. The correlation coefficient and root meansquare error of validation set were 0.82 and 5.82N respectively with unadjusted probe. Between 380nm and 1050nm, all the fitting coefficients obtained were higher than 0.999 with root mean square errors in the range of 0.0187~0.2422 when the spectral data at the distance of 4~18mm were calibrated to 13mm by fifth-order polynomial fitting. The correlation coefficient and root mean standard error for pork tenderness prediction were in the range of 0.83~0.90 and 4.80~5.75N respectively when the distance was at 4~17mm, by using the fitted spectral data and the best prediction model.The results show that the proposed method can overcome the influence of different distances on pork quality prediction by calibrating the spectral data.

Abstract:Agriculture is one of the most important and popular fields of remote sensing applications. The purpose of this paper is to review the advances of research and application in remote sensing for agriculture in the world. The review includes following six main aspects: cropland radiative transfer mechanism and remote sensing inversion of crop parameters, remote sensing classification and identification of crops, cropland nutrient and variable fertilization techniques, crop yield and quality perdition, agricultural disaster monitoring and forecasting, and spatial decision making support system for agricultural remote sensing monitoring. Finally, the key directions needed more attention and technical breakthrough are figured out according to the current status and trends of agricultural remote sensing techniques.

Abstract:The peak-climbing algorithm in two aspects histogram compression and the two merging based on class when it is applied to high-resolution image segmentation to achieve the tree crown extraction improved peak-climbing algorithm was simulation with programing on Matlab. In order to verify the reliability of the peak-climbing algorithm on high-resolution image tree crown segmentation, QuickBird image to extract individual tree crown and analyze the precision of its area. The study result that the test sample accuracy could more than 85% using the improved and no much differences comparing with the visual interpretation. Thus this improved peak climbing algorithm meets the application requirements

Abstract:Based on MODIS-NDVI data, taking Shaanxi and Gansu provinces as examples, the correlation between different grades of winter wheat growth and main meteorological factors at 7 different phenophases were explored. Firstly, the development stage of winter wheat was divided into 7 different stages. Then the growth condition of winter wheat from sowing to maturity stages from 2011—2012 were assessed based on MODIS-NDVI data. Furthermore, the lag correlation between different grades of winter wheat growth in each phenophase and the meteorological factors with corresponding phenophases (temperature, precipitation and sunshine), which taken from 32 meteorological stations distributed within Shaanxi and Gansu provinces, were analyzed by using correlation analysis and GIS spatial analysis methods. The results showed that the winter wheat growth varied across time and space in the study area. And no matter what grades of winter wheat growth, the correlation coefficients between winter wheat growth condition and accumulated precipitation were higher than synchronous precipitation and pre-phenophase precipitation in terms of the average value in 7 phenophases, which showed the accumulated precipitation during the whole growing season had greater influence on winter wheat growth than synchronous precipitation and pre-phenophase precipitation. The influences of temperature on winter wheat were different according to different grades of winter wheat growth. In terms of sunshine, no matter what grades of winter wheat growth, the correlation coefficients between winter wheat growth condition and accumulated sunshine were highest in terms of the average value in 7 phenophases. The study also showed that winter wheat with better and worse growth condition were more sensitive to precipitation, whereas winter wheat with normal growth condition were largely influenced by temperature in the whole.

Abstract:A new algorithm of crown volume based on a square grid method was presented, which was low in cost and high in efficiency and precision, and the normal errors in manual measurement of parameters can be reduced, such as total height, crown width, crown projected area, and so on. While the traditional assessments were not sufficient to provide accurate parameters owing to the irregular crown shapes, and three-dimensional laser was too expensive and fussy to afford. A numerical analysis of the proposed algorithm was presented, along with a design procedure and experimental results. Comparison of obtained results from classical methods and three-dimensional laser measurement was made. The point cloud data were acquired by non-prism total station and a coordinate grid of canopy surface was built, and then the crown volume can be computed with a square grid based method. Analysis of the parameters had been made with satisfactory precise and the results showed that the relative error of square grid method was 4.13% and the average accuracy was 95.75%. There was no significant difference between calculation value and actual measurement for crown volume under confidence level of 0.05. Moreover, compared to the traditional manual measurement, only one-third of time was consumed by square grid method, which costed 2% of those by three-dimensional laser scanning, therefore, the expenditure was extremely reduced and efficiency was increased. 

Abstract:In order to investigate the distribution feature of surface texture, 168 images of Hami melon samples from two different varieties in two kinds of ripeness were acquired. The algebra operations were conducted in terms of R, G, B components, and the gray images were obtained to implement the background segmentation. Then, the images were decomposed by dual-tree complex wavelet transform(DT—CWT) to obtain high frequency sub-images. Following the neighborhood operation, the extraction results were derived from selecting the optimal thresholds by iterative method. Finally, the methods of gray-scale differential statistics and texture frequency analysis were used to analyze the texture feature, support vector machine(SVM) was employed to build a model for texture classification. Results of computer simulation indicated that more continuous and complete images were obtained when DT—CWT and image neighborhood operation were employed to extract texture. There were significant differences among texture eigenvalues of four types of Hami melons, and the accuracy rate of classification was 89.3%. In addition, periodic characteristic was not found from the appearance texture.

Abstract:Characteristics extraction method of rice panicle images was proposed to solve the traditional measurement problems, such as inefficiency, worse repeatability, obtaining multi-parameters difficultly. There was significant correlation between primary branch length and spikelet number obtaining by manual measurement. Consequently, rice panicle was spread out and images were captured. Image characteristics were extracted using some image processing operations, including area, primary branch length, and panicle skeleton. Experimental result showed that the correlation coefficients were up to 0.90 between image characteristics and spikelet number, and the average predicting error of the model was 7.90%. Consequently, characteristics extraction method of rice panicle images was effective and feasible. The area and primary branch length can be perfect expression and substitute for spikelet number.

Abstract:In order to decrease the data transmission frequency of the sensor nodes in greenhouse WSN system, a method based on two-level prediction was presented. Firstly, Letts’ criterion was imported to detect the sequence of outliers and the calculation method of sliding recursive sequence variance was proposed to facilitate real-time calculation of the nodes. Secondly, a piecewise linear regression equation combined with weighted adaptive algorithm was established to form two-level prediction models in sensor node and server. When forecasting error exceeded the set threshold, the sensor nodes uploaded the actual collection value. At other times, the server automatically triggered the linear regression prediction model to fill the partial data. At the same time, a variable error threshold determination method based on parabola was presented according to the characteristics of the automatic control of facility environment. The tests proved that the first order linear regression model approximated the raw data curve in prescriptive error threshold and the number of sending data of WSN sensor nodes could be reduced 93% by using two-level prediction algorithm （error threshold is 0.9）.

Abstract:A model predictive control of air temperature in greenhouse based on unsteady CFD model was proposed. Considering the air temperature in greenhouse as the research object and CFD model as a virtual greenhouse environment, the input/output time series data of the system were provided by the unsteady CFD numerical simulation instead of the real physical experiment data. Then the CFD model was converted into system control model based on the data by system identification. The roof ventilation cooling process was controlled by MBPC method based on CFD model. The results showed that the average control error and the standard control error were 2.65℃ and 3.27℃, respectively. The indoor temperature was controlled smoothly and effectively under the allowed range of crop growth. System identification and control algorithm combine with the CFD model improved the efficiency of controller design. This design technique can enrich the technology in greenhouse control system．

Abstract:Design principles were investigated from a view of synergetics and meta rules for mechanical design and analyses were generated by introducing order parameters. Same order parameters can be used to produce different mechanisms according to specific behavior specification, and an order parameter can be used repetitively to produce the profile of a mechanism. The concept of design robots (D-Robots) was proposed to execute the repetitive operation of order parameters. Order parameters were used as action rules of D-Robots. By introducing the concept of order parameters, the process of synthesis and analysis of different mechanisms can be described in same order parameters. By introducing the concept of D-Robots, the synthesis and analysis procedure can be formulated as a generic template. Combining order parameters and D-Robots, the synthesis and analysis of mechanisms are automated. The order parameters and D-Robots were tested by mechanism synthesis and analysis. A D-Robot template for the mechanism synthesis and analysis is constructed. As case study, a D-Robot for cam mechanism design and analysis was developed and programmed. The output of the D-Robot includes generating the cam profile, kinematic analyses, the cam center and area, the bill of material, the balance weight, the speed fluctuation calculation, an animation and a report. This paper distinguishes with current research methods in generalizing meta rules to produce structures based on behavior specification rather than doing this by establishing equations for each type of mechanisms.

Abstract:Three degrees of freedom parallel manipulator 3-PUS-UP with a properly constrained passive limb was taken as the research objective. Inverse kinematics solution equations were formulated with closed vector method, and a Jacobian matrix of parallel driving part was obtained considering the influences of driving chains, constraint chain and parasitic motion of moving platform. Further, a Jacobian matrix of UP limb of serial part was acquired by adopting the D—H method. Combining the relation between the driving equations with constraint equations, a complete Jacobian matrix of the 3-PUS-UP parallel manipulator was constructed and verified by simulation analysis on the basis of the previous kinematical model. Simultaneously, kinematic dexterity and stiffness were introduced to evaluate the kinematic performance, and distribution atlas of the kinematic dexterity and stiffness in the workspace were drawn and researched. The optimum regions of the kinematic dexterity in the reachable workspace were defined and calculated. The research results show that this 3-PUS-UP parallel manipulator has good kinematic dexterity and stiffness performance.

Abstract:Aiming at the lunar soil drill-sampling task, the bedding protection performances of two coring methods, hard tube coring and soft sack coring, are analyzed based on discrete element model. A curved surface slope method is proposed to describe the bedding information of the lunar soil sample. It can directly reflect the deformation of each layer of lunar soil sample distributed with drilling depth by curvefitted surface, and quantitatively illustrate the boundary between the slightly perturbed part and bedding damage part in each layer, and also the trend and degree of the bedding failure. Analysis results show that the soft sack can significantly protect the sample bedding information. The hard tube coring method destroys the bedding of outside sample seriously, and damages more layers, while there is no obvious difference in the scope that is slightly perturbed from the soft sack coring. Additionally, in both work conditions, the bedding information of surface regolith is damaged severely, which indicates that the lunar regolith on the surface has great follow-up property.

Abstract:Based on the photoelectric principle, an accurate method to measure the deep hole straightness is built according to the changing rule of the output voltage. The changing rule of the actual hole center is analyzed when the photodetector has translational and rotational movements. Based on the least squares principle，the relationship between the deep hole straightness and the output voltage is deduced, which provides the theoretical foundation for deep hole straightness photoelectric measurement. According to the photoelectric measurement theory, a self-positioning, real-time display device of deep hole straightness measurement deviation is designed, which can effectively achieve automatic and non-destructive detection of deep hole straightness measurement.