Abstract:Electrical control of tractor electro hydraulic hitch system is an important part of the tractor automated driving system. The electrohydraulic hitch control system included the linear actuator, transmission mechanism and single-chip microcomputer control unit. The control unit ECU received decision-making control command from host machine real-time, controlled the rod lifter motor to drive tractor hydraulic lifter and adjust the implements to the suitable position. PWM motor control method with the slope feedforward and PI feedback control algorithm was adopted as the main program. Slope feedforward control algorithm was used at the starting stage to make motor start smoothly. PI control algorithm was used at the steady stage to minimize the movement time of the motor and improve the position control precision of the motor. Control unit was responsible for receiving the linear actuator feedback information to decide and produce appropriate PWM signal, which adjusted the speed and the location of the hitch control system. The ECU hardware system was developed based on Cygnal C8051F040 micro-processor. The whole control software system was realized by using C language programming and its main functions included CAN communication between host computer and slave ECU, AD conversion of the motor feedback signal, the PID control and serial interface communication, etc. The deadzone threshold was set to 10 (AD), the maximum error range was ±11 (AD), which indicated that the displacement error of linear actuator was less than 0.26 mm. It conforms to the requirements of the motor control design. This system can be added onto traditional tractor to realize the accurate position control of agricultural implements.

Abstract:In order to improve the shift performance of the tractor hydraulic power-split CVT, the influence factors and the parameters matching were studied based on the method of both simulation and experiments. First of all, the model of clutch axial force and the model of transmission system were built based on the experiments on shift pressure and piston displacement. The model was proved to be correct and effective with eight groups of experimental verification under different test conditions. Then, the influence factors were divided into three groups, i.e., the external factors, the designing factors and the controllable factors, and each influence factor on shift performance was simulated and analyzed. Finally, the interactive effects among these factors on shift performance were studied and the optimal parameters were acquired. The research results showed that there was no significant effect of the pipeline volume of swash plate axial piston units on shift performance. The effect of engine speed on shift performance was influenced by the displacement of variable displacement pump. The shift performance would be improved with the increase of clutch oil charge flow and shift timing under the prerequisite of constant output speed condition. The effects of clutch oil charge pressure, load torque and inertia on shift performance were not robustness. The research is helpful to improve the dynamic characteristics of the hydraulic power-split CVT and it is useful to develop the control unit.

Abstract:Recently, ditching continuous fertilization and digging fertilization are the two main approaches for orchard fertilization in China. However, orchard ditching continuous fertilization always wastes a large proportion of fertilizer while digging fertilization manually is backbreaking work. Based on common ditching fertilizer devices, an orchard toward-target variable-rate fertilizer system was designed, which mainly included an orchard hole fertilization precision fertilizer feeder and a toward-target variable-rate fertilizer controller. Fertilizer ejecting times of ejectors with different sectional areas were obtained by using a high speed photography, and quantitative hole fertilization was realized through using grooved wheel mechanism. A new fertilizer ejecting monitoring method using a horizontal rotating fan was put forward, and a monitoring device was designed. Then the orchard hole fertilization precision fertilizer feeder was designed and developed. The toward-target variable-rate fertilizer controller was developed based on a microcontroller STC12C5A60S2, a photoelectric sensor used to detect orchard tree trunk was adopted to obtain fertilizer ejecting position, and an approach switch sensor was used to acquire speed by detecting wheel rotation. Laboratory experiments were carried out by using self-made test platform. The results showed that when the application setting was one of the 1~5 grades, the maximum error between the average amount of ejected fertilizer and theoretical amount was 10 g, with maximum variation coefficient of 4.6%; the range of average fertilizer length was 20.2~40.9 cm; the maximum and minimum fertilizer position offset errors were 5.5 cm and 0.6 cm, respectively, with average standard deviation of 4.26 cm; in each fertilizer ejecting process, the monitoring device could get the on-off signal two times at least, and the accuracy of fault alarm was 100%. Field experiments showed that the accuracy of fertilizer ejecting was 97% in selected 100 wolfberry trees. This system could control fertilizer seeder based on real-time orchard tree detection, monitor fertilizer ejecting for fault alarm, and meet the need of orchard ditching fertilization with toward-target fertilizer ejecting requirement.

Abstract:According to the characteristics of potato tissue culture seedlings and their culture environments, a picking seedling machinery which can pick seedlings out of bottle without damage in one time was designed. It included a manipulator of mother bottle and a seedling grasper. The seedling grasper was used for holding the root of potato seedlings stationarily, meanwhile the manipulator moved backward with the mother bottle. The potato seedlings and the bottle moved relatively and then most part of the seedlings’ stems were out of the bottle, which provided good basis for the next operation in the automated micropropagation. The key parameters of picking seedling machinery were analyzed. In order to find the effect of the distance between the two pairs of claws, the number of each bottle, speed of manipulator and the swing frequency of mother bottle on the result of picking seedlings, orthogonal experiments were done. The index was inclination of culture medium after picking seedlings. The result showed that the distance between the two pairs of claws exerted the greatest effect on the inclination of culture medium, and other factors such as the number of each bottle, speed of manipulator and the swing frequency of mother bottle had no significant effects. As the distance between the two pairs of claws was 26 mm, the number of potato seedlings in each bottle was 45~55, the speed of manipulator was 25 mm/s, and swing frequency of mother bottle was 2 Hz, the minimum inclination of culture medium can be obtained by using the designed seedling mechanism for potato tissue culture seedlings.

Abstract:The bale knotter is the core components of the baler. To understand the working principle of the bale knotter more deeply, more and more researchers have built varieties of the knotter test bench. But this bale knotter test bench could not get the motion state of D-bale knotter and the tension of cord synchronous in the process of straw baling, a set of D-bale knotter movement and cord tension information synchronous acquiring system in real time was set up in the existing square baler. In order to achieve the goal of synchronous acquiring information, a synchronization module was designed for synchronous trigger high-speed photography and tension sensor. In order to verify performance of the system, a test was carried out under the condition of 1 000 Hz. The object of this test was wheat straw. Four groups of tests were carried out. From the tests it can be found that the number of target images captured by the high-speed photography and the number of target data captured by tension sensor were the same, and the feature points of D-bale knotter movement and variation coefficient of peaks of cord tension corresponding to the tooth plate degree was less than 3% in different sets of the tests. From the tests it could be known that the system can get the information of D-bale knotter movement and cord tension at the same time. The motion sequence range of D-bale knotter was obtained based on the information of knotter movement and cord tension. The motion sequence was more accurate than the existed motion sequence got by other researchers. The accurate motion sequence chart of the rope disc, bill hook and knife lever were got from the motion sequence. It could help to understand the working principle of D-bale knotter more clearly. The synchronous acquiring system built the foundation of the geometrical conditions for D-bale knotter. It was very useful for the research of D-bale knotter.

Abstract:According to the limitation of traditional inverse problem of centrifugal pump blade and its optimization, the free form deformation (FFD) inverse method of centrifugal pump impeller based on load driving was proposed to design the centrifugal pump impeller. A more stable and effective deformation function was established. The centrifugal pump blade load was parameterized by using sectional spline according to the characteristic of centrifugal pump impeller load. The design of experiment was implemented in the designed variables space, and the response surface method was introduced to optimize the distribution of blade load. The three-dimensional transient turbulent flow in pump was simulated by using commercial software. The control and deformation of blade shape and analysis of blade load were implemented by Matlab code. The computation of FFD and CFD was coupled. The relationships between distribution of blade load, blade shape and its hydraulic performance were analyzed. The reasonable distribution of blade load for low specific speed pump blade was deduced. The calculation case results showed that the proposed centrifugal pump blade load optimization theory and method were rational.

Abstract:Centrifugal pump start up process is a complex transient process. Along with the rapid rise of the impeller rotating speed in a short period of time, its characteristic parameters that include head, flow, and shaft power would change rapidly, which may have a very big impact on pump body and system’s secure and stable operation. Therefore, it is very important to do research about the safety and stability of the pump during the startup process. Research of centrifugal pump is mainly concentrated in steady conditions, the application of centrifugal pump is gradually expanding, centrifugal pump will work under unsteady conditions, such as start, stop and other transient conditions, and the working conditions of pump are complicated transient process, which will make a great difference to the safe and stable operation of pump body and the system. Numerical simulation was used to study its transient characteristics during starting period, the computational domain was the entire closed test rig and the model selected was SST-SAS model. During calculating the startup time was controlled by varying the rotational acceleration of the process, then the transient characteristics of pump startup process under different startup time were studied. Combined with the experimental data, it was found that the transient head of the experiment showed good agreement with simulation, and it was also concluded that the peak of the pump head size was little affected by the startup time during the same startup rule of linear type; three-dimensional numerical simulation of the whole circuit was more accurate than the numerical simulation of the local boundary when simulated during the pump startup process; volute pressure pulsation had a great relationship with the pump startup time, and with the decrease of pump startup time, the volute tongue would produce bigger low-frequency pressure-pulse.

Abstract:The algorithm optimization of hybrid grid for centrifugal pump optimizes tetrahedral mesh and tri-prism grid separately, which will lead to low quality and efficiency. To solve this problem, a tri-prism grid quality optimization objective function balancing triangle shape and orthogonality of prismatic side was established. Besides, the effects of six different methods of solving optimal solution on the results of optimizing hybrid grids were compared. Moreover, the impact of weight coefficient on optimization was also studied and the optimization results between the algorithm and a commercial software were compared. Results showed that the optimization results and efficiency were better when the conjugate gradient method and dichotomy were combined and weight coefficient value was 0.2. With the optimization algorithm, the quality of the worst grid cell and the whole grid was increased, comparing with the commercial software. In addition, the quality of the worst grid cell with the optimization algorithm was also increased compared with the commercial software. It indicates that the optimization algorithm is better than the existing algorithms.

Abstract:Under the rotating stall condition the periodic generation and shedding of stall cells always induce the low frequency pressure fluctuation，which has severe influence on the safety and stability of pumps. In order to reveal the role of the rotating stall cells in the pressure fluctuations, a centrifugal pump impeller was chosen as the research object to investigate by numerical simulation. A number of reference locations were arranged in the entrance of the passages for recording the pressure fluctuation. A developed large eddy simulation named dynamic mixed nonlinear model (DMNM) was applied to the numerical simulation and the simulation results showed good agreement with the experimental results. The internal flow field and pressure fluctuation characteristics under different stall operation conditions were also obtained. The simulation results showed that the stall cells first occurred in the suction side of the blade, and then moved to the pressure side with continuous decay. When the rotating stall occurred, the amplitude of pressure fluctuation was much higher than that at unstalled point. The propagation of stall cells had significant effect on the pressure fluctuations in the impeller. The dominant frequency of pressure fluctuation at blades was rotating stall frequency. The maximum amplitude of pressure fluctuation was located at the leading edge of blade, and it decreased gradually along the flow direction. As the flow rate was further reduced, the amplitude of dominant frequency decreased but the stall frequency increased. This research can provide useful reference for the secure and stable operation of centrifugal pumps.

Abstract:The low frequency pressure fluctuations in axial flow pump with variable inlet guide vane were studied. The numerical method based on the RANS equations and SST k-ω turbulence model was used to simulate unsteady flow in the axial flow pump. The hexahedral meshing scheme was used for the whole computational domain, particularly with O-grid around the blades. The multiple reference frame approach was applied to solve the rotor-stator interaction problem in steady simulation and it was changed to the sliding mesh technology in unsteady simulation. The mass flow rate was adopted at the inlet section and static pressure at the outlet section. No-slip conditions were applied to the whole wall boundary. The effects of variable inlet guide vane on pump performance were firstly investigated. Then through analyzing the spectra of pressure fluctuation at different pressure survey points, the variation of low frequency pressure fluctuation by adjusting the angles of inlet guide vane was presented. The flow field in outlet guide vane under small flow condition was also presented. The results showed that the predicted results were in good agreement with the experimental data. When the angle of inlet guide vane was negative, the pump head was increased due to the prewhirl regulation, and the efficiency was basically kept unchanged at small flow rate and it was slightly increased at large flow rate. When the angle of inlet guide vane was positive, both the pump head and the efficiency were decreased, and the efficiency dropt greatly at large flow rate because of the large hydraulic loss caused by inlet guide vane. At small flow rate, the vortex in the exit guide vane can cause low frequency pressure fluctuation, which was consistent with the vortex frequency. When the axial flow pump was operated under off-design condition, the variable inlet guide vane could decrease the angle of attack at the impeller entrance and further descend the amplitude of low frequency pressure fluctuation.

Abstract:Based on the RNG k-ε turbulent model and Reynolds Navier-Stokes equation, the hydraulic performance of the bidirectional shaft tubular pump was simulated with the commercial CFD software. By comparing the hydraulic loss of each part, the results indicated that the hydraulic loss at the tail of the shaft tubular was large when the shaft tubular was used as inlet passage, and the hydraulic loss near the outlet of the vane and the bifurcation of the shaft tubular was also large when the shaft tubular was used as outlet passage. The hydraulic losses of the shaft tubular and straight passage were small when they were used as inlet passages due to the frictional head loss, but the hydraulic losses were large when they were used as outlet passages, with the effect of circulation and spread section, the flow was easy to be taken off, thus the hydraulic losses were large. The performance of the pump unit was improved compared with the original case, as the head loss was significantly reduced by adjusting the hull lines of the flow channel, and finally the hydraulic performance optimization design was finished. The efficiency of the simulation was up to 72.0% under positive condition, and it was up to 57.9% under reverse condition, the efficiency of the model test was up to 70.4% under positive condition, and it was up to 56.2% under reverse condition.

Abstract:A special impeller with forward curved blades can improve the performance of pump as turbine (PAT). From the point of turbine working condition, blade inlet angle at leading edge was determined using shockless inlet flow, while its outlet angle was designed with non-swirling outflow. The distribution rule from inlet angle at leading edge to outlet angle at trailing edge is one of the main factors in impeller design. Therefore, an investigation on the distribution rules of blade angles influencing PAT’s performance is useful. In order to investigate the effects of blade angle distributions on the performance of PAT with forward curved blades, three special impellers with different blade angle distributions were designed by using ANSYS Bladegen software. The validity of numerical simulation was first confirmed through the comparison between numerical and experimental results. The impellers with the same blade inlet, outlet angles and different blade angle distributions were numerically investigated. The performance, pressure distributions and hydraulic loss distributions within PATs were analysed. The results showed that under the optimal working condition, the differences of three PATs impeller in terms of efficiency, pressure distributions and hydraulic loss distributions were minor. Under non-optimal working conditions, when the angle distribution was linearly changed, the performance curve was more flat and the low pressure area at the outlet of the impeller was larger than those of the other two PATs. Hydraulic loss distribution analysis illustrated that the influence of blade angle distributions on impeller was larger than those of volute and draft. Linear distribution had positive influence while “S” shaped change of angle distribution had negative influence on PATs performance.

Abstract:Advances in remote sensing (RS) technology provide an effective approach for the estimation of regional evapotranspiration, crop classification and yield, which lays the foundation for the quantitative assessment of irrigation efficiency and crop water use efficiency. Relevant models and methods were reviewed, including RS-based evapotranspiration models, upscaling methods of instantaneous evapotranspiration to daily evapotranspiration, interpolation methods of available daily evapotranspiration, RS-based crop classification methods and crop yield estimation models, and assessment methods for irrigation efficiency and crop water use efficiency based on evapotranspiration and crop yield estimations. Furthermore, key issues that require further investigation were proposed, including RS-based evapotranspiration model with strong physical bases and applicable to heterogeneous land surfaces, proper interpolation method of daily evapotranspiration considering the abrupt change of soil water content due to irrigation and/or precipitation, precise estimation of irrigation water consumption in farmland evapotranspiration, RS-based crop classification model applicable to complex cropping pattern and multi-years, and operational RS-based crop yield estimation model with higher precision. With further developments of RS technology and relevant models, the quantitative assessment results of irrigation water use efficiency and crop water use efficiency will provide sound foundation for agricultural water management.

Abstract:Maize is one of the main grain crops in Northeast China. Droughts are often accompanied by low temperatures during seedling stage in the region, which often harmfully affect the establishment of the seedling. Drip irrigation under plastic film mulch is an alternative that has been applied to maize production in Northeast China in recent years for supplying complementary irrigation and increasing accumulated temperature. For better understanding of the effects of mulched drip irrigation on water and heat conditions in field and maize yield in sub-humid regions, field experiments were carried out in the sub-humid environment of Heilongjiang Province, China, during the growing seasons of maize in 2011, 2012 and 2013. In the experiments, three treatments, including mulched drip irrigation, non-mulched drip irrigation and surface irrigation were tested. The daily soil temperature was recorded manually at 08:00, 14:00, and 18:00 at 5 cm intervals within the 5~25 cm profile by geothermometers in 2012 and 2013. In addition, high-revolution soil water-heat-salt automatic systems (ECH2O) were used to continuously monitor soil water content and temperature at fixed locations of the mulched and non-mulched drip irrigation treatments within the 20~80 cm profile in 2013. Micro-lysimeters (MLS) with inner diameter of 10 cm and height of 15 cm were fabricated to measure evaporation from the soil surface during the growing season of 2013. Additionally, air temperature and humidity in canopy were measured using a Kestrel 4 000 pocket weather station during selected typical days. Plant height, leaf area index (LAI), aboveground dry matter, and nitrogen uptake were also measured during the seedling, jointing, tasseling, filling, and physiological maturity stages of maize. The results indicated that mulched drip irrigation increased the daily temperature at 5~25 cm soil depth by 2.3℃ compared with that of the non-mulched treatments. Accordingly, the accumulated soil temperature for the mulched drip irrigation treatment was about 87℃ higher than that for the non-mulched treatments during the seedling stage, which led to the highest increment of accumulated soil temperature during the whole growing season (115~150℃). Furthermore, the daily evaporation rate from the soil surface for the mulched drip irrigation treatment (0.7 mm/d) was 53% lower than that for the non-mulched drip irrigation treatment (1.5 mm/d), resulting in a higher water content in topsoil layer during the early growing season. Compared with the non-mulched drip irrigation treatment, the mulched drip irrigation produced a higher air temperature and lower air humidity in canopy at sunny days of the jointing stage, implying a greater transpiration rate for the mulched drip irrigation treatment. In terms of crop growth, the growth speed of plant height, LAI, aboveground dry matter and nitrogen uptake with the growing degree days (GDD) for the mulched drip irrigation treatment was obviously greater than those for the non-mulched drip irrigation and surface irrigation treatments during the early growing stage. At the physiological maturity stage, the aboveground dry matter averaged over the three growing seasons for the mulched drip irrigation treatment was 14% and 23% greater than that for the non-mulched drip irrigation and surface irrigation treatments, respectively. Accordingly, the nitrogen uptake for the mulched drip irrigation treatment was 16% and 28% greater than those for the non-mulched drip irrigation and surface irrigation treatments, respectively. The three-year average grain yield and water use efficiency (WUE) for the mulched drip irrigation treatment were 11% and 8% greater than those for the non-mulched drip irrigation treatment, and 21% and 18% greater than those for surface irrigation treatment, respectively. In conclusion, mulched drip irrigation produced a more favorable water-heat environment in field which promoted crop growth and improved maize yield and WUE.

Abstract:Dew is one of the important water sources for plants growing, especially in arid and semi-arid regions. However, it was seldom researched. The dew amount and its relationships with input-output of water resources in the jujube plantations in semi-arid Loess hilly-gully region were investigated during jujube growth periods in 2012 and 2013, depending on the dew intensities, canopy temperature, canopy relative humidity, sap flow, soil moisture and meteorological factors which were measured by the dielectric leaf wetness sensor (LWS), the VP-3 relative humidity/temperature sensor, thermal diffuse probe (TDP), neutron probe and meteorological station, respectively. The results showed that the dew amount increased throughout the jujube growth seasons and reached its maximum value at the fruit ripening stage. The cumulative dew amounts during jujube growth periods in 2012 and 2013 were 31.31 mm and 37.87 mm，respectively, which accounted for 6.87% and 7.90% of rain, 10.00% and 15.00% of transpiration, and 17.65% and 17.90% of evaporation at the same period, respectively. The dew amount with high frequency and strong stability had a large proportion of heavy dew in the jujube plantations in the Loess hilly-gully region. As one of the input water resources, dew significantly reduced jujube transpiration during fruit enlargement and ripening stages (P<0.05), but had no significant effect on evaporation. It is indicated that dew is an important part of water resource which affects regional water balance in the jujube plantations in semi-arid Loess hilly-gully region and it should not be ignored.

Abstract:Traditional irrigation practices caused low maize water use efficiency, yield and income of local farmers in Nile Delta of Egypt. To explore the optimal irrigation and fertilization strategies, the effects of interactions between irrigation and fertilization on leaf area index (LAI), aboveground dry matter (ADM), yield component, water use efficiency (WUE), economic yield and benefit of maize were investigated. During the field experiments in two consecutive years (2012 and 2013), there were three irrigation modes (drip irrigation, bubble irrigation and traditional furrow irrigation, irrigation rates were 80%, 70% of estimated evapotranspiration and local traditional irrigation quantity, respectively) and two fertilization types (liquid organic fertilizer and chemical fertilizer). Six treatments were arranged in a randomized complete block design, with four replicates for each treatment. The results showed that irrigation modes and fertilization types had significant effects on the LAI and ADM after the tasseling stage, with the largest LAI and ADM in the treatment applied liquid organic fertilizer with drip irrigation (OD). For the same fertilization type, bubble irrigation had higher impact on maize yield and WUE than drip irrigation, and then followed by traditional furrow irrigation. For three irrigation modes, liquid organic fertilizer increased maize yield by 18.6%～24.4% and WUE by 18.7%～23.4% compared with chemical fertilizer. The treatment applied chemical fertilizer with bubble irrigation (CB) yielded the highest average annual net benefit of 7 373 Yuan/hm2, but there was no significant difference between the treatments of CB and CF (applied chemical fertilizer with traditional furrow irrigation). In general, the combination of bubble irrigation and chemical fertilizer can be recommended as the optimal irrigation and fertilization strategy for maize production in Nile Delta, which will have a broad prospect for field irrigation in Egypt.

Abstract:In order to clarify the characteristics of photosynthesis and yield responses of summer maize to pre-sowing irrigation advancement for winter wheat, a single factor experiment of irrigation times (Sep. 30th, Sep. 25th, Sep. 20th written as I9.30, I9.25, I9.20) was conducted during 2011—2012 and no irrigation advancement treatment was taken as control (CK). The results indicated that the diurnal variation of net photosynthesis (Pn) in ear leaf of maize was different among the four treatments, CK showed a single peak curve, while the other three treatments showed bimodality. As to the averages of the diurnal variation of Pn of each treatment, I9.20 and I9.25 were higher than others and the change of leaf source capacity (LSC) of the total three near ear leaves appeared a similar pattern, i.e., I9.20 and I9.25 showed higher values. The changing of sugar content in maize stem, however, was different from that of the photosynthesis characteristics; the stem sugar content of CK was higher than those of other treatments. Grain filling was also influenced by different irrigation treatments. The I9.20 and I9.25 treatments showed larger maximum filling rates, longer active grain filling periods, and higher grain weights and grain yield. Different irrigation times had effect on the dry matter distribution as well. The amount of accumulated dry matter after anthesis of different treatments showed a trend as I9.25>I9.20>I9.30≥CK, which demonstrated that the pre-sowing irrigation advancement of winter wheat was able to improve the population photosynthetic performance, promote dry matter translocation from vegetative organs to grains after anthesis, and finally increase the grain yield of maize in Hebei Plain. The best period for irrigation advancement in this experiment was from Sep. 20th to Sep. 25th.

Abstract:In order to reveal the response of cotton to waterlogging stress, lysimeter experiments were conducted in the Irrigation and Drainage Experiments Station of Wuhan University during 2008—2011. Effects of different waterlogging forms (surface waterlogging, subsurface waterlogging and the combination of both) and different occurring growth stages (bud stage, flowering and boll setting stage or boll opening stage) on cotton morphology (leaf area index (LAI), stem diameter and plant height) and yield (seed cotton and dry matter) were discussed. Structural equation modelings (SEM) of yield and morphology characteristics related to waterlogging stress were established. Interactive relationships between these models were analyzed. The results showed that subsurface waterlogging stress inhibited the development of cotton morphology less than that of surface waterlogging stress, while the combination of surface and subsurface waterlogging stresses inhibited the growth most. Waterlogging stress occurred in bud stage, flowering and boll setting stage inhibited the development of morphology characteristics significantly (p<0.05), while the inhibiting effect at boll opening stage was not significant. LAI, followed by stem diameter and plant height, was the most sensitive morphology index to describe the response of cotton morphology to waterlogging stress. The cotton yield reduction with subsurface waterlogging stress was less than that with surface waterlogging stress, while the reduction was almost the same when surface waterlogging stress or subsurface-surface waterlogging stress was occurred. Waterlogging stress occurred at flowering and boll setting stage reduced the yield most, followed by bud stage and boll opening stage in sequence. And the inhibiting effects of waterlogging stress on seed cotton yield were more than that on dry matter yield. According to SEM analysis, waterlogging stress effects on yield were more than that on morphology characteristics, and waterlogging temporal indices (SWFDH and SEW30) were better than spatial indices (SFW and SEW30) and SFEW30 in describing waterlogging stress effects on growth and yield of cotton.

Abstract:Highland barley is the main food crop in high altitude cold region of Tibet. Effects of water deficit levels at different growth stages on the water use efficiency and yield of spring highland barley (Hordeum vulgare) were studied by barrel cultivated experiments. Experimental treatments included full irrigation treatment (two controlled lower limits on soil moisture content and straw mulching) as well as four water deficit levels (mild, moderate, severe and extreme deficits) in the whole growth period and five different growth stages, respectively, and the total treatments were 27. Experimental results showed that the harvest index, grain yield and water use efficiency of spring highland barley in the treatment with the water controlled lower limit of 75% of field capacity (FC) were greater than those of 80% FC treatment, and straw mulching treatment resulted in the largest grain yield and crop water use efficiency in all experimental treatments under full irrigation condition. Under the condition of various water deficit levels in the whole growth period, the grain yield of spring highland barley was smaller than that of full irrigation treatment, and it was decreased significantly with the increase of water deficit level. Water deficit from mild to severe levels obtained larger harvest index and crop water use efficiency, but extreme deficiency on water supply resulted in the lowest grain yield, harvest index and crop water use efficiency under various water deficit treatments in the whole growth period. The grain yield and crop water use efficiency under water deficit treatments at different growth stages of spring highland barley were basically decreased with the increase of water deficit level except the treatment with water deficit at ripening stage, and the effect of water deficit at jointing, tillering and filling stages on grain yield was greater than that at other growth stages. Straw mulching or water deficit with mild to severe levels in the whole growth period of spring highland barley can improve crop water use efficiency, and their effects in practice are deserved to be paid more attentions.

Abstract:Snow cover, as the most common upper boundary condition during freezing and thawing period in the cold region of northern China, directly affected the soil moisture distribution and movement, soil temperature and frozen depth, freezing rate, etc. In order to reveal the influence of snow on soil moisture movement, soil water and heat coupled transfer during freezing and thawing period was studied. Through field experiment, the soil moisture movement patterns of seasonal freezing-thawing black soil in Harbin were dynamically observed under the conditions of four different coverages: bare land, natural snow, compacted snow and thicken snow. The density and liquid water content of snow were measured by the Snow Fork, the liquid water content and total water content of soil were measured by time domain reflector and neutron moisture meter. From the perspectives of temporal and space change of soil moisture content, the results indicated that the thickness and density of snow can largely affect the protection of snow on soil, when only considering the subsidence of increased snow density, the greater the thickness of snow was, the better the protection was. The response of soil moisture content to temperature change and soil thawing time were delayed, the degree of delay was increased with soil depth increasing. Compared with increase of snow thickness, denser snow can protect the soil better, and the influence of temperature on soil was decreased. When winter snow was small, farmers can artificially compact it, which can strengthen the protection of soil.

Abstract:Soil water content (SWC) is of great importance to establish an appropriate irrigation scheme. The study object is 5-year-old dwarf apple trees under water storage pit irrigation method (depth 40 cm). In order to find an optimal SWC monitoring location, the distribution of apple tree fine roots (d≤2 mm) at different locations and SWCs within the root zone were studied and analyzed with regression and cluster analysis methods. The results showed that over 90% fine roots of apple tree were within 0~90 cm from the apple tree trunk in horizontal direction, while over 80% fine roots were within 0~120 cm from the apple tree trunk in vertical direction. The growth peak of fine roots was within 40~60 cm depth which accounted for over 40% of total fine roots. Meanwhile, the monitoring points were located at 90 cm away from the trunk (Dr90). SWC distribution in vertical direction of the Dr90 monitoring points was accorded with exponential function, with correlation coefficient greater than 0.8. Through sorting the SWC at six different depths in Dr90 with R type hierarchical clustering method, it showed that the soil moisture sensors in 60 cm can be used to represent the SWC condition within 0~120 cm depth. The SWC error between the simulations and observations in 2013 was within ±5%. The experimental results suggested that the profile (depth 60 cm) of SWC measured in the Dr90 was sufficient to estimate the water consumption amount under the water storage pit irrigation in the orchard.

Abstract:In order to explore the applicability of critical nitrogen dilution curve and the feasibility of nitrogen surplus evaluation for summer maize in Guanzhong Region, Shaanxi Province, two nitrogen fertilizers: urea (N 0, 80, 160 and 240 kg/hm2, 40% of N fertilizer applied as basic and 60% top dressed at bell stage) and controlled-release fertilizer (N 0, 60, 120, 180 and 240 kg/hm2, all applied as basic fertilization) were chosen to determine critical nitrogen concentration dilution curve based on field experiments in 2013 and 2014. Models of nitrogen uptake, nitrogen nutrition index and accumulative nitrogen deficit were established to diagnose nitrogen nutrition status of maize plant according to the critical nitrogen concentration. In addition, nitrogen use efficiency was compared among different nitrogen application rates treatments. The results showed that a negative power function correlation between maximum aboveground dry matter and critical nitrogen concentration was existed. Calibrations (using the data series of 2014) indicated that these models had high reliability with relative error of 0.46%~4.08%. The nitrogen nutrition index model and the accumulative nitrogen deficit model could be used to diagnose plant nitrogen status effectively and regulate nitrogen fertilizer management quantitatively. The appropriate nitrogen application rate of urea and controlled-release fertilizer for maize growth was 160~174 kg/hm2 and 120~150 kg/hm2, respectively. Compared with urea, controlled-release fertilizer could significantly increase the nitrogen use efficiency and save nitrogen amount approximately by 14% for maximum yield (urea: 10.73 t/hm2; controlled-release fertilizer: 11.01 t/hm2).The investigation is beneficial to the dynamic and precise fertilization, nitrogen management optimization and effective utilization of resources both on theoretical and technical sides.

Abstract:The critical nitrogen concentration in plant was defined as the minimum nitrogen concentration required for maximum plant above-ground biomass. By collecting and analyzing seven-site-year field experiments with various nitrogen application rates according to certain criteria, the critical nitrogen concentration dilution curve was constructed for the main winter wheat variety “Xiaoyan 22” in Guanzhong Plain. The relationship between maximum above-ground biomass and critical nitrogen concentration of winter wheat could be described by a negative power function. The nitrogen dilution curves affected by different nitrogen treatments were evaluated and compared. Results showed that increased nitrogen supply generally resulted in a greater nitrogen concentration. The winter wheat yield with zero, deficient, suitable and excess nitrogen were 4 263, 5 097, 6 023 and 6 203 kg/hm2, respectively. Nitrogen deficiency would reduce wheat yield, however, there was no significant difference between the yield of excessive and suitable nitrogen application treatments. The dilution curve was validated with independent experiment data (2010—2011) through nitrogen nutrition index (NNI), which was defined as the ratio of measured to critical nitrogen concentrations. The results showed that the NNI value with zero, deficit, suitable and excess nitrogen application treatments were 0.70, 0.89, 1.01 and 1.25, respectively. Wheat would get nutrition imbalance when nitrogen was used only as a base fertilizer and even reduce crop yield with excess nitrogen application. The suitable nitrogen application rate was 75~180 kg/hm2 (averagely 137 kg/hm2) for winter wheat in Guanzhong Plain due to the variety of soil productivity. The critical nitrogen dilution curve could be used as a diagnostic tool to detect wheat nitrogen nutrition, and it also provides a key technical approach for guiding nitrogen fertilization practices and management in wheat production in Guanzhong Plain.

Abstract:Pogostemon cablin belongs to Labiatae, with reputation in the domestic and foreign markets. The Hainan Patchouli, in addition to medicine, due to high oil content, is also used to extract volatile oil for export. To test the effects of compound application of organic and chemical fertilizers on Patchouli plants, eight treatments of compound fertilizer mixed with organic fertilizer and chemical fertilizer were set to study their influences on Patchouli growth, yield, oil, quality and soil nutrient contents. The treatments were set as organic fertilizer of 100% (100% OF), chemical fertilizer of 100% (100% CF), 75% OF+25% CF, 60% OF+40% CF, 50% OF+50% CF, 40% OF+60% CF, 25% OF+75% CF and no fertilizer as control (CK). The results showed that different fertilization treatments promoted the improvement of Patchouli yield, oil, quality and soil nutrient contents, but an significant difference was presented between different treatments. The yield and oil were the highest in 75% OF+25% CF treatment, which was 31.58% and 168.10% higher than those of CK, respectively, followed by 60% OF+30% CF and 50% OF+50% CF treatments. The growth indexes of Patchouli, such as plant height, stem diameter, number of tillers and leaf area index, and the qualities of the 12 kinds of main chemical components (β-Patchouliene, α-guaiene, exogenous squalene, α-patchoulene, δ-guaiene, nerolidol, β-elemene, caryophyllene, β-guaiene, trans-caryophyllene, pogostone, patchouli alcohol), water soluble and alcohol soluble extracts in 75% OF +25% CF treatment were the highest. Organic matter, alkali solution nitrogen, available phosphorus and potassium contents in soil were higher in 100% OF, 75% OF +25% CF， 60% OF +40% CF， and 50% OF +50% CF treatments, and 100% OF treatment got the highest values, the difference between the four treatments was not significant. Therefore, the treatment of 75% OF +25% CF could be suitable for Patchouli fertilization scheme.

Abstract:To investigate the influence of desiccation cracks on water infiltration patterns, iodine-starch staining experiments were carried out in cracked loamy clay soil. By application of the digital image processing technology and direct measurements, parameters including crack width, depth and area ratio of surface cracks were computed and employed to analyze the infiltration distribution influenced by crack geometric characteristics. The results showed that macro cracks whose width exceeded 1.25 cm could visibly accelerate water infiltration and provide obvious preferential pathways for water movement. Infiltration depths under macro cracks varied from 45 cm to 65 cm and there was no evident change in infiltration depth when the crack width increased, whereas micro cracks posed little effects on water infiltration. Water infiltration could be regarded as one dimensional semi-infinite homogeneous movement when cracks were narrow and shallow. On the contrary, deep cracks had significant impacts on infiltration, and obvious preferential features were observed around the macro cracks in soil. The results also revealed that area ratio of surface cracks was positively associated with the volume of wet soil (r=0.95), and a quantitative approach was proposed to assess the influence of soil cracks on water infiltration.

Abstract:Zero-tension lysimeters (ZTL) have been widely applied to monitor soil solution flux and solute transport through soil layers in the vadose zone to the ground water under various conditions in research areas, such as the comprehensive utilization of agricultural water and soil resources as well as soil and water environment conservations. A capillary barrier that can cause flow divergence around the system will be created between undisturbed soil and ZTL as the ZTLs are installed in the field. Meanwhile, the water can overcome the capillary barrier and enter into ZTL only when the soil water is saturated above the contact plane of soil and ZTL. Thus, the efficiency of adopting ZTL for water collection decreases correspondingly. To improve the collection efficiency of ZTL, divergence barrier was added to ZTL (ZTLd), and the factors that can affect the collection efficiency of ZTL were examined, such as soil hydraulic property, soil texture, irrigation rate, initial soil water content and height of divergence barrier, and HYDRUS model was adopted. By measuring soil water flux from seepage face in a two-dimensional model and comparing it with applied flux in a one-dimensional model at the same depth, the collection efficiency was obtained. Three soil textures including sandy loam, loam and silt were considered, and the values of van Genuchten model parameters for test soils were not changed in HYDRUS model. Moreover, irrigation rates ranged from 100 mm to 1 000 mm, and height of divergence barrier ranged from 0 cm to 70 cm. Two initial soil water contents (i.e. 0.15 and 0.35 cm3/cm3) and two soil evaporation rates (i.e. 0.2 and 0.5 cm/d) were adopted. According to the results, the collection efficiency of ZTL without divergence barrier (ZTL0) was low due to lateral diversion of water above the seepage face. As for the ZTL0 under 1 000 mm irrigation rates, the collection efficiencies were 0~11%, 5%~13% and 6%~12% in the sandy loam, loam and silt soil, respectively. Due to the fact that more water was accumulated above the seepage face, the measured soil water flux increased as the divergence barrier was installed. However, the height of divergence barrier was reduced with the increase of irrigation rates as well as the decrease of water holding ability of soil and soil evaporation rates. When the height of divergence barrier was less than 20 cm and irrigation rate reached 1 000 mm under the condition of 0.35 cm3/cm3 initial soil water content and 0.2 cm/d soil evaporation rate, the collection efficiency of ZTLd was increased to 50%. Thus, coarse-textured soils, divergence barrier, low soil evaporation rate and high irrigation rates were preferred so as to measure water flux rate accurately by ZTLd. High initial soil water content (0.35 cm3/cm3) would lead to low collection efficiency of ZTLd in sandy loam, and collection efficiency of ZTL at a certain burial depth might not be suitable for other depths. According to the assumption of the study, all simulations were based on homogeneous soil without consideration of preferential flow, thus there was no effect of size on the collection efficiency. In conclusion, the results of this research can exert significance to the improvement of ZTL.

Abstract:The virtual water flows could be seen as the spatial redistribution of water resources in virtual form, which have a significant influence on regional economy and water resources. The production, consumption, transfer of grain crops, water use and virtual water flows were calculated for different provinces of China in 2010. Then the effects of regional grain virtual water flows on regional economy and water resources were demonstrated by using water saving amount, water stress index and GDP per capita. The results showed that the volume of grain virtual water flows between different provinces of China was 113.81 Gm3 and the blue water was 44.97 Gm3. Most of the flows were from regions with relatively high water use efficiency to those with relatively low water use efficiency regions, from water-shortage regions to water-rich regions, from regions with low economic level to those with high economic level regions. As a result, about 57.89 Gm3 of water resources were saved due to regional grain virtual water flows and the value for blue water was 47.89 Gm3, the water stress index increased from 1.61 to 2.04 assuming the virtual water export was zero, and the GDP per capita decreased from 43 428 Yuan to 31 776 Yuan assuming that all of water resources used to produce the exported grain crops could be used for industrial production. The improvement of agricultural water use efficiency, the compensation for virtual water flows and the optimization of cropping pattern could be measures with great significance to alleviate the negative effects caused by regional virtual water flows of China.

Abstract:Based on the RTK GPS positioning technology, the basic physical and chemical properties and nutrient distribution of the collapsing pluvial fan were studied. Experiments with a typical collapsing pluvial fan had been made in Tongcheng County, Hubei Province. It was found that the content of alkali hydrolyzable nitrogen and available potassium were risen regularly with the increase of distance from the fan starting point and available phosphorus was increased enormously, but no prominent partial regularity increase was discovered. The study of the relationship between the nutrient contents and the main factors revealed that the main nutrient contents showed a linear distribution with the sampling elevation and the organic matter contents and a linear change with the square of clay content. The studied nutrients all shared a distinctive movement in the horizontal direction with the flood and the diffusion, and redistribution of alkali hydrolyzable nitrogen following the flood was more obvious than that of available potassium.

Abstract:To remediate the heavy metals polluted soil around a closed smelter in Shaanxi Province, 15 soil profile samples were collected in the site and analyzed for heavy metals content, including Pb, Cd, Hg, As, Cu, Cr, Zn and Ni. The pollution situation was assessed by using the ecological hazard risk assessment method, and the contaminated soil was finally remediated by in-situ replacement engineering methods. The results showed that within top 0~20 cm soil layer, Zn contents ranged from 89.80 mg/kg to 724.03 mg/kg, Cu contents varied from 28.89 mg/kg to 1 271.81 mg/kg, Hg contents changed from 0.04 mg/kg to 4.48 mg/kg，and the Pb contents were around 48.69~12 021.15 mg/kg. Cd contents in the top soil layer of 0~120 cm were above the secondary standard value of soil environment quality, while Pb, Cd, Hg, Cu and Zn contents in soil within 0~120 cm were higher than those of the Lou soil background values. The results of potential ecological risk implicated that the potential ecological risk factor for Cd ranged from 26.0 to 21 118.6, and its slight, moderate, strong, very strong and extremely strong ecological hazards frequencies were 4.3%, 15.2%, 19.6%, 15.2% and 37%, respectively. The potential ecological risk factor of Pb ranged from 0.1 to 120.2, and its slight, moderate and strong ecological hazards frequencies were 93.5%, 4.3% and 2.2%, respectively. The potential ecological risk factor of Hg ranged from 0.1 to 83.4, and its slight, moderate and strong ecological hazards frequencies were 59.3%, 39.4% and 1.3%, respectively. Elements As, Ni, Zn and Cu, all had slight ecological hazards. The soil heavy metals pollution in the study area was mainly contributed by Cd, Pb and Hg. The in-situ replacement method was proved to be an efficient method for the smelter polluted soil remediation and it could achieve satisfactory performance.

Abstract:From the point of developing a new approach for the disposal of tar derived from biomass gasification, microwave-assisted tar cracking and reforming were performed over a biomass-derived char, with toluene as a model compound of tar aromatic substances. And the reaction rules, production distribution and changes of biomass char in process of toluene cracking and reforming were studied. The results indicated that biomass char had a catalytic effect on toluene cracking, and it was approved that microwave heating could favor toluene cracking. By analyzing the results, it was observed that toluene conversion and hydrogen selectivity were directly correlated to bed temperature in cracking reaction. Toluene cracking was optimized at 750℃, and the greatest toluene conversion and hydrogen selectivity were obtained, which were 92.77% and 91.94%, respectively. Afterwards, changes in toluene conversion and hydrogen selectivity were insignificant. It was further revealed that the introduction of CO2 could reform toluene into syngas production. At 700℃, the highest conversion rate of 92.03% was reached at CO2 flow rate of 80 mL/min, accompanied by a maximal syngas yiled rate of 91.30%. And increasing CO2 flow rate decreased the ratio of H2 to CO dramatically. The lowest ratio of 0.22 was obtained at CO2 flow rate of 120 mL/mm. The introduction of CO2 also brought about a loss of carbon in biomass char. And carbon loss was maximized to 5.42% at 700℃. At the same time, the depleted carbon was further converted into additional syngas production, which provided the highest contribution of 15.40% for total syngas production. Finally, it was demonstrated that an excess of CO2 could slow down the negative effect of carbon deposition on toluene conversion.

Abstract:The emission characteristic of VOCs from biomass molding fuel combustion was studied. VOCs emission factor and the components of flue gas after combustion from four kinds of biomass shaped fuel, i.e., corn straw, wheat straw, cotton stalk and wood, were analyzed on the biomass combustion experimental platform using the sample collection-GC/MS method. The results showed that the VOCs emission factors of four kinds of biomass molding fuel were 0.447, 1.111, 0.601 and 0.104 g/kg, respectively. The VOCs emission factors of biomass molding fuel were only 50% of the powder burning straw. The main types of VOCs from wood molding fuel combustion emissions were benzene series, halogenated hydrocarbon and ketones. The main kinds of VOCs from straw molding fuel combustion emissions were halogenated hydrocarbon, ketone and benzene series. The benzene content emission factor of total straw produced by lignocellulosic biomass combustion was nearly five times higher than that of VOCs emission proportion coefficient. Biomass molding fuel combustion emitted the most of hydrocarbon and ketone with contents of 49.8% and 36.1%, respectively. The ozone generating potential (O3) of total VOCs emissions from four kinds of biomass molding fuel combustion were 4.792, 25.737, 9.598 and 4.502 g/kg, respectively. The compounds with higher ozone generating potential were benzene, ketone, olefins and halogenated hydrocarbon. The results will provide reference for industry standards built of VOCs emissions from biomass molding fuel combustion.

Abstract:The effect of recirculating the liquid fraction of digestate on the mesophilic anaerobic digestion of cattle manure was investigated using laboratory-scale continuous stirred tank reactors. The hydraulic retention time (HRT) of 40 d was employed. Recirculation was implemented after the anaerobic digestion process was stable at the organic loading rate of 3.0 g/（L?d）. However, the recirculation eventually caused the accumulation of organic and inorganic substances, which led to the inhibition of hydrolysis and methanogenesis. The daily biogas yield was decreased by 22.4% when the liquid fraction of digestate was recirculated to substitute 50% of the tap water used for feedstock dilution. The concentrations of ammonia and volatile fatty acids did not reach the inhibitory levels. However, the accumulation of refractory organics, which were more pronounced in the recycling reactors, led to the decrease of methane production. According to the results of kinetic analysis, the microbial anabolism was promoted by the recirculation. The results indicate that choosing a proper recirculation rate and adopting reasonable pretreatment measures are indispensable to avoid the negative influence caused by the accumulation of potentially harmful substances. The proposed approach will lower the amount of generated effluents, and the product of anaerobic digestion with this method will contain high solid content, which will decrease the transportation costs and the storage capacity requirements.

Abstract:Consumers demand foods which are fresh and with high nutrition and sensory quality. Therefore, processing produces minimally is necessary. In recent years, the food industry has shown increased interest in nonthermal preservation technologies. High pressure processing (HPP) is an alternative mild-technology which has become widely used to inactivate microorganisms and certain enzymes, retain the food original nutrients, and preserve the organoleptic characteristics of the produces. Moreover, HPP can induce conformational and functional changes of macromolecules which in turn can improve nutrient properties of food. Its application to the food industry has become increasingly widespread. At present, the application of HPP to crop produces processing obtained increasing attentions. Literature information on HPP application to crop produces processing was analyzed, including starch modification, protein modification, extraction, reduction of allergen, and storage extension (mold inactivation and viability prohibition). Meanwhile, the significance and prospects of HPP application to crop produces processing were discussed to guide its future development.

Abstract:In order to investigate the possibility of applying HPP in the production of soybean paste, the 〖JP3〗effects of HPP treatments (100~500 MPa, 1~20 min) and heat treatments (40, 60, 90℃, 1~20 min) on koji PPO activity were studied, which are important in forming the color of final product. The activation or inactivation kinetics of PPO following HPP treatment was also evaluated. Results showed that HPP treatment at low pressure (100~300 MPa) could activate the PPO activity with maximum relative activity of 135% at 200 MPa for 10 min. While at a higher pressure between 350 MPa and 500 MPa, koji PPO can be inactivated significantly; a larger degree of inactivation was obtained at a higher pressure with a longer pressure holding time. Moreover, the degree of inactivation could approach a maximum level with an endless pressure treatment, the maximum inactivation differed with different pressure levels, which could be expressed as 74.0%, 55.4%, 62.8%, 66.5% at 350, 400, 450, 500 MPa, respectively. Kinetic analysis indicated that the patterns of koji PPO activation or inactivation could be expressed in a different way at different pressure levels. The PPO activation pattern following HPP treatment at 100~200 MPa could be described well by a two-step first-order model with coefficient of determination (R2) higher than 0.970. The survival curves with 250~300 MPa HPP treatment followed the fractional conversion model with R2 higher than 0.994. The biphasic model was proved to be suitable to describe the kinetics of koji PPO inactivation treated by HPP between 350 MPa and 500 MPa, with R2 higher than 0.995. The results support the further investigation in shortening the fermentation time and improving the quality of final product of soybean paste by applying HPP.

Abstract:Ultrasonic probe was used for the treatment of brown rice, with two key parameters of moisture content and solid losses as indicators. The optimum cooking time of brown rice was evaluated and the optimum processing conditions of brown rice were obtained. The results indicated that ultrasonic treatment combined with heating method had no significant effect on shorten of brown rice cooking time. For the treatment of ultrasonic probe without heating, the optimum cooking time of brown rice was 30 min with the amplitude of ultrasonic probe of 8 and temperature of 50℃. For the ultrasonic probe processing with controlled temperature, the cooking time of 25 min was needed for brown rice treated with ultrasonic probe at temperature of 50℃ and the amplitude of 8. In addition, the chemical composition and nutritional quality of brown rice were little losing, the appearance, color, smell, hardness, viscosity and acceptance of brown rice were more acceptable under the condition of ultrasonic probe processing with controlled temperature than those of others. That is, ultrasonic probe combined with controlled temperature can be applied to cook high quality brown rice. Therefore, ultrasonic probe treatment provides a new train of thought for the processing of brown rice and it has broad application prospects.

Abstract:To offer a method for detecting protein content in milk, raw fresh milk and soy protein powder were used to study the influence of frequency (20~4 500 MHz), temperature (5~75℃) and soy protein mass fraction (0~3.98%) on dielectric properties (dielectric constant ε′ and dielectric loss factor ε″) with vector network analyzer and open-ended coaxial-line probe. The models describing the relationship between ε′ and ε″ with temperature and soy protein mass fraction at 40 MHz were established. The results showed that ε′ decreased with increase of frequency and temperature. ε″ had minimum values at 1 000~4 000 MHz, and it increased with the increase of temperature when frequency was below 1 000 MHz and decreased with temperature increase when frequency was above 4 000 MHz. Both ε′ and ε″ increased linearly with increase of soy protein mass fraction. Two-parameter second-order polynomials could be used to describe the relationship between ε′ and ε″ with temperature and soy protein mass fraction. The determination coefficients of developed polynomials at 27 MHz were 0.992 and 0.998, respectively. The result is helpful to understand the influence of frequency, temperature and soy protein mass fraction on dielectric properties of raw milk, and it offers a basis for developing protein content detector for milk.

Abstract:The effect of sugar content and acidity on potential maximum growth rate (μmax) and lag phase duration (λ) of Zygosaccharomyces rouxii at 25℃ was investigated. The effect of sugar content and acidity on the time for spoilage (TFS) was also analyzed under isothermal (25℃) and non-isothermal conditions. The values of μmax and λ in all sugar content and acidity combinations were obtained through fitting the growth curves by using Baranyi and Roberts model. The results showed that the determination coefficients (R2) of all fitting curves were above 0.95, which indicated that a good fitting was obtained. The effect of sugar content and acidity on μmax and λ at 25℃ and the effect of sugar content and acidity on the TFS under isothermal (25℃) and non-isothermal conditions were analyzed by using response surface (RS) method, and quadratic regression models were obtained. The results showed that R2 of each model was 0.992 1 (μmax), 0.962 5 (λ), 0.986 6 (TFS, isothermal) and 0.995 8 (TFS, non-isothermal), which effectively revealed the influence of sugar content and acidity on the growth of Z. rouxii. The influence magnitude of each factor on the growth of Z. rouxii was analyzed by comparing their standard regression coefficients. The results showed that the main limiting factor that affected Z. rouxii growth was the acidity whereas sugar content had less impact. The growth of Z. rouxii was largely inhibited at pH value of 2.3 and it was fully inhibited at pH value of 2.0. The results provide a research basis for predicting and controlling the contamination of apple juice concentrate by Z. rouxii in future.

Abstract:Alicyclobacillus spp. has recently received much attention due to its implication in the spoilage of pasteurized fruit juices, which was characterized by the production of a smoky, medicinal and antiseptic off-odor attributed to guaiacol. The species those are known to produce guaiacol are A. acidoterrestris, A. acidiphilus and A. herbarius. The effect of ε-polylysine on growth and guaicol production of these three species of Alicyclobacillus spp. was evaluated. Minimal inhibitory concentration (MIC) of ε-polylysine was determined in AAM medium by using broth dilution method. The sensitivity of Alicyclobacillus spp. to ε-polylysine was species-dependent, and MIC values ranged from 1.25 mg/mL to 5 mg/mL against vegetative cells and from 2.5 mg/mL to 5 mg/mL against the spores. Then, various concentrations of ε-polylysine were added to the model apple juice. When the dose of ε-polylysine increased to 4 MIC, Alicyclobacillus counts were reduced below 2.66 log colony forming unit (CFU)/mL, and no guaiacol was detected after 7 d incubation. The results can be very useful for better control of Alicyclobacillus-related spoilage in the fruit juice and beverage industry.

Abstract:To investigate the effect of freeze-thaw cycles (T0: fresh meat, T1: one time freeze-thaw, T2: two times freeze-thaw) on the quality of yak meat, the yak meat samples were tested for color (L*, a*, b*), myoglobin oxidation state, metmyoglobin reducing ability (MRA), thiobarbituric acid reactive substances (TBARS), thawing loss (TL), degree of protein degradation and muscle microstructure during refrigerated storage (4℃). The T0 group showed significantly decreasing trends in a* value, b* value, oxymyoglobin (OMb) content and MRA, while significantly increasing trends were observed in metmyoglobin (MetMb) content, TBARS value and TL (P<0.05). Moreover, the degradation of myosin heavy chain (200 kDa), paramyosin (97 kDa) and actin (45 kDa) were obvious during storage. With the increase of times of freeze-thaw cycles, the a* values of T1 group and T2 group were decreased by 13.42% and 20.02% than that of T0 group after 7 d of storage, and the b* values of T1 and T2 groups were decreased by 9.94% and 16.22% (P<0.05) than that of T0 group, respectively. Meanwhile, compared with that of T0 group, the OMb contents of T1 and T2 groups were decreased by 26.30% and 53.53%, the MetMb contents of T1 and T2 groups were increased by 18.03% and 45.46% (P<0.05), respectively. The TABRS and TL of T1 and T2 groups were increased by 20.55%, 30.30% and 43.71%, 121.14% (P<0.05) than those of T0 group, respectively. The degree of protein degradation of T2 group was more serious than that of T0 group and T1 group, while the muscle microstructure damage was also increased with the increase of times of freeze-thaw cycles. In conclusion, freeze-thaw process could reduce the quality of yak meat by accelerating the deterioration of meat color, lipid oxidation and protein degradation, and damaging the muscle structure. Therefore, it is meaningful to reduce temperature fluctuation in the process of transportation and storage for protecting beef quality.

Abstract:Coupled with the paralleled uniform electric field, the soft zein films with complete shape were obtained by casting. Effect of the electric field force on mechanical properties of zein film prepared for different alcohol concentrations was studied. As the tertiary structure of zein molecules was destroyed by electric field force, charged polar residues (amino groups and carboxyl groups, etc) exposed and directionally moved along the electric field lines. The stable state of micelle-like structured zein molecules was seesawed until the molecules found some new levels of equilibrium. It was demonstrated that at the initial phase, tensile strength, breaking elongation and contact angle of films were increased with the increase of the concentrations of ethanol solution, and reached the maximum value (73.41 MPa, 9.54% and 62.46°, respectively); water vapour permeability (WVP) reached the minimum value of 2.54×10-8 g?m/(m2?h?Pa). The changes of C〖FY=,1〗O and β-sheet vibrating peaks of Raman analysis indicated denaturation of protein partly. Observations under scanning electron microscope (SEM) of surface and cross section revealed that the presence of uniform electric field helped to improve the properties of zein films. In conclusion, the findings of the synergistic effect of ethanol and the paralleled uniform electric field on zein films may contribute to develop edible food packaging material with ideal surface morphology and hydrophobicity.

Abstract:China is the biggest apple juice producer in the world. High content of patulin in apple juice can cause severe food safety problem. Adsorbent resins have been applied to apple juice treatment to remove patulin due to their high adsorption abilities. However, the adsorption thermodynamics and kinetics studies of patulin separation from apple juice using adsorbent resin are still limited. The adsorption characteristics of patulin in apple juice were investigated using LSA-800B resin, with the aim to reduce the content of patulin and improve apple juice security. Results showed that the adsorption ability (qe) of the LSA-800B resin decreased with the increase of temperature. The Freundlich isotherm was found to describe the adsorption equilibrium satisfactorily (R2>0.97). Thermodynamic parameters including the changes of free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) were evaluated at 30, 40 and 50℃. The result of free energy change (ΔG<0) demonstrated that it’s a spontaneous adsorption process and involved physical adsorption. The enthalpy change ΔH<0 indicated that the adsorption was exothermal in nature. The kinetic data was best described by the pseudo first-order model. The Weber-Morris model showed that the adsorption mechanism was not limited solely by intra-particle diffusion. It is proposed that the result of this theoretical study of patulin adsorption of apple juice using LSA-800 resin can be a basis for industry control of patulin in the producing of apple juice.

Abstract:In order to obtain spatial features distribution from mixed pixels of remote sensing image and further increase accuracy of crop classification and recognition from remote sensing, a double-calculated spatial gravity model (DSGM) based on improvement of spatial attraction model was put forward and applied in research of multispectral images classification and identification in agriculture region at sub-pixel level. Law of gravity was used to describe the spatial correlation and calculate attraction between pixels. Based on the above research, the initialization algorithm of the pixel swapping model (PSM) was improved by spatial attraction model (SAM), and the optimization algorithm of PSM was improved respectively. Finally, all of the models of PSM, SAM and DSGM were applied to the sub-pixel mapping experiments of multispectral images in agricultural region and sub-pixel mapping accuracies of models were compared with each other. The study areas located in typical farming area of Huang-Huai-Hai Plain in North China, and artificial imagery in different degradation scales and GF-1 remote sensing imagery were used as the data sources in the experiment. The final results indicated that (DSGM) model could map effectively at sub-pixel level and its mapping accuracy was superior to those of PSM and SAM. Among them, in artificial image experiment, when sub-pixel degradation scale was 6, overall accuracy and kappa coefficient of DSGM were 93.90% and 0.818, respectively. Compared with K-mean classification, the DSGM model could improve overall accuracy and kappa coefficient by 3.76% and 0.254, respectively. Compared with SAM, DSGM could improve overall accuracy and kappa coefficient by 2.25% and 0.160, respectively. Compared with PSM, DSGM could improve overall accuracy and kappa coefficient by 2.45% and 0.173, respectively. In remote sensing image experiment, when sub-pixel degradation scale was 4, overall accuracy and kappa coefficient of DSGM were 83.13% and 0.742, respectively. Compared with the K-mean classification, DSGM could improve the overall accuracy and kappa coefficient by 9.50% and 0.154, respectively. Compared with SAM, DSGM could improve the overall accuracy and kappa coefficient by 5.44% and 0.088, respectively. Compared with PSM, DSGM could improve the overall accuracy and kappa coefficient by 6.39% and 0.104, respectively. It was seen that DSGM model had feasibility and applicability in sub-pixel mapping, and it could provide a new way to better surpass the limits of remote sensing image spatial resolution. DSGM could further improve accuracy of crop remote sensing classification and recognition and provide strong technical support to obtain accurate information for agricultural remote sensing.

Abstract:To address the issue of distinguishing seed maize from grain maize with remote sensing, a method of multi-temporal OLI/Landsat-8 remote sensing images combined with GeoEye-1 high-resolution texture was proposed. Utilizing the phenological phase differences of all classes from multi-temporal OLI/Landsat-8 images, the C5.0 decision tree classification algorithm was applied to the constructed EVI time-series. According to the texture difference between seed maize and grain maize, thresholds were set to identify seed maize by using GeoEye-1 high-resolution texture information. Finally, Linze County of Zhangye City in Gansu Province was taken as a study area to test the method. The results showed that the overall classification accuracy of multi-temporal OLI/Landsat-8 was 86.31% and the Kappa coefficient was 0.81, the user accuracy of maize identification was 88.39% and the mapping accuracy was 95.35%, which can meet the demand of further identification of seed maize. In contrast, when combined with texture information from high-resolution images, the user accuracy of seed maize was 86.37% and the mapping accuracy was 83.02%, which were higher than those of exclusive OLI/Landsat-8 data source. The conclusion is, this method can play a technical role in monitoring seed field over large range fast and accurately with remote sensing technology, enforcing seed market supervision and improving the authorities’ response time to the market.

Abstract:Eggs have become main sources of protein choice for Chinese consumers due to the fact that they are both inexpensive and rich in vitamins, minerals and protein. However, as a perishable product, the quality of fresh eggs deteriorates continuously during the period from their leaving the farm until final consumption or use in manufacturing. With consumers’ increasing awareness and concern for food safety, increasing attention is being given to the shelf life of eggs through the supply chain. To develop a prediction model of the shelf life of fresh eggs, two types of model were developed and tested, including a kinetic model and a back-propagation (BP) neural network model. A sample of 115 eggs was collected on the same day from the same farm layer-hen house subsequently for use in simulating quality deterioration under laboratory conditions. The experiments were conducted at constant temperatures of 5, 25 and 35℃ to cover the normal range of temperatures that can occur under real egg storage conditions and the experimental results were used to construct the kinetic and BP neural network models, and validation of model shelf-life prediction was compared with actual egg shelf life. Three layers of BP neural network were constructed with Haugh units, yolk index and temperature as the input layer parameters, 10 nodes in the hidden layer and remaining day’s duration of storage as the output layer’s parameter. It was found that the BP neural network model had a superior prediction accuracy of 95.93% compared with 90.79% of the kinetic model. Hence it can be concluded that the BP neural network model could readily be integrated as part of a quality control system setting sell or use-by-dates for consumers.

Abstract:This paper presented the design and verification of a vehicle height adjustment and attitude controller for electronically controlled air suspension. For the undesirable phenomenon such as over-charge, over-discharge and oscillation during the vehicle height adjustment process of the electronically controlled air suspension, a neural network PID control method to regulate the gas mass flow rate adaptively was proposed. According to the theory of the vehicle system dynamics and the thermodynamic theory of variable mass charge/discharge gas system, a vehicle height adjustment mathematical model for the electronically controlled air suspension was established. A BP neural network PID controller for vehicle height adjustment was designed and its actual control performance was verified by simulation. During the vehicle height adjustment process, the non-synchronous height adjustment of the four corners would result in the vehicle attitude instability phenomenon. In order to prevent the instability phenomenon, the system local control qualities were revised by fuzzy control algorithm to form the vehicle attitude fuzzy controller. Finally, the vehicle height adjustment control system was realized by D2P rapid development platform to perform vehicle bench experiments. The test results showed that the control system could regulate the vehicle height effectively and restrain the vehicle attitude change during the vehicle height adjustment process.

Abstract:Compared with traditional front-wheel-steering system, the four-wheel-steering system can improve the auto handing stability at high speed as well as the steering response at low speed. Load transfer caused by the body roll can change the tyre cornering characteristics as well as the lateral stability and the bifurcation characteristics of the 4WS vehicles. Therefore, a closed loop system dynamic model considering load transfer was established with the nonlinear coupling relationship between the body and chassis taken into account. Firstly, the existence and stability of the Hopf bifurcation were qualitatively analyzed, then it was compared with a closed loop system dynamic model, the stable region and the characteristics of the Hopf bifurcation were calculated by numerical methods. The results showed that the difference between two dynamic models was obvious. For the 3-DOF system, with the increase of preview distance, steering ratio, road adhesion coefficient and the decrease of the height of suspension roll center, the stable region of the system tended to increase. With the increase of road adhesion coefficient and the steering ratio, the amplitude of self-excited vibration of roll angle and roll angular velocity tended to decrease.

Abstract:An integrated brake system was put forward, and the dynamic model of the integrated brake system was found to set up its simulation model in computer. Based on the simulation model of the integrated brake system, simulation tests were made under three conditions of high and low adhesions with straight movement and curve movement for the ABS control performances of the integrated brake system in the small electric passenger car. The ABS control performance was described by longitudinal slip of each wheel, the brake torque of each wheel and the longitudinal acceleration of mass center. The driving stability of vehicle was described by longitudinal displacement and slip angle of mass center. The brake energy recovery performance was described by electric power consumption per kilometer. By analyzing the variables characterizing the performances of ABS control, driving stability and brake energy recovery, the research results showed that the integrated brake system with regenerative friction brake in electric vehicle was provided with good braking efficiency, favorable ABS control performance and preferable braking force distribution from front to rear wheels, as well as remarkably improved brake energy recovery rate. Depending on the above results, the suitable advices will be put forward and adopted, which would be helpful for the rapid development of the electric vehicle technology.

Abstract:In teleoperation, it is very important to ensure that task objects are not severely grasped in grasping and conveying processes. A master-slave system for a teleoperation construction robot employed an excavator with four degrees of freedom (swing, boom, arm and fork glove) as slave and two joysticks with force feedback as master was established. Since the fork glove was regarded as the hand of the robot, the control for the fork glove was the focus. A position velocity control system was previously proposed, and it was found that soft objects were severely crushed in grasping and conveying processes at slow speed. To solve this problem, a position reaction force control method, in which reaction force to the joystick was used as feedback instead of piston velocity, was proposed to improve the controllability. The position velocity control was adopted when the construction robot moving in free space and the position reaction force was introduced when reaction force generated in the grasping process. Grasping experiments were conducted using a tin and urethane foam blocks as task objects by human and control PC at slow velocity, and the experimental results confirmed the validity of the position reaction force control method during slowly grasping of a fragile or soft object. In addition, conveying experiments, which simulated transformation task in practical use by using a tire, a piece of urethane foam and a piece of sponge foam as task objects, were conducted by the position velocity and position reaction force control methods. Experimental and statistical analysis results proof that position reaction force control method is valid to safely transfer soft objects in teleoperation work and it can improve the controllability of the construction robot.

Abstract:Magnetorheological brake (MRB) is a new brake-by-wire device. It consists of rotating disk immersed in a MR fluid and enclosed in an electromagnet, where the yield stress of the fluid varies as a function of the magnetic field applied by the electromagnet. Based on Bingham model, the torque formula of disc-type MRB was presented, and the coupling relationship between its structure and magnetic circuit was analyzed. An optimization design method for the disc-type MRB was proposed based on the simulation analysis of coupling model of structure and magnetic circuit. Maximizing braking torque and minimizing brake weight were taken as optimization objectives, and the multi-objective was converted into single objective by the variable weights. An optimization procedure based on the parameterized finite element analysis of ANSYS integrated with an optimization tool was used to obtain optimal design scheme of MRB. The prototype of MRB was fabricated and tested to evaluate its performance. The experiment bench system of MRB was developed. Experimental and simulation results showed that the designed scheme of MRB can meet the braking torque requirements and the designing demands of magnetic circuit.

Abstract:A lamina emergent elevator mechanism was designed based on the principle of micro-elevator mechanism. Pseudo-rigid-body model of the elevator mechanism was established. The calculation formula of force-deflection relationship was derived based on the principle of virtual work. A lamina emergent elevator mechanism with LET hinge and LOOP hinge was designed and two kinds of elevator mechanism were studied. The bending and torsional equivalent coupled stiffness of LOOP flexible hinge which contains arc segment was studied and the calculation formula of the equivalent coupled stiffness was derived. The analysis of theoretical calculation and finite element simulation of the two designed examples showed that the theoretical calculation formula and the simulation model were correct. A physical model of the elevator mechanism based on LOOP flexible hinge was established and its function was tested. Calculation, simulation analysis and test results prove that this elevator mechanism can produce large lifting capacity with high accuracy in operating state and the slider displacement of the elevator mechanism has good input and output relationship with the rising displacement of the platform. The goal of design was reached.

Abstract:In order to realize large output angular acceleration and high working frequency of the angular vibrator, a moving component of an electromagnetic angular vibrator with a disk moving coil structure was proposed and optimally designed. First, the principle of the electromagnetic angular vibrator with a disk moving coil structure was introduced, and dynamic models of its moving component were analyzed, which showed that the output capability of angular acceleration from the angular vibrator would be improved and the working frequency range would be widened when the rotary inertia of the moving coil and the vibration table was decreased or the stiffness of the connecting shaft was increased, or the first-order torsional resonance frequency of the moving component was increased. Then, the parameters of the disk moving coil were optimally designed by particle swarm optimization (PSO) method with the goal of realizing the maximum output angular acceleration when a unit current was passed through the moving coil wire. Furthermore, in order to realize the minimum rotary inertia and the highest first-order torsional resonance frequency, the topology of the moving coil and the material combinations of the vibration table and connecting shaft were optimally designed with finite element method. Finally, the optimized moving component was applied to a prototype of the broadband electromagnetic angular vibrator. Experimental results showed that the angular vibrator could output angular acceleration as large as 2 000 rad/s2 with the maximum angular displacement of 60°, and the first-order torsional resonance frequency of the moving component for the angular vibrator could get as high as 1 100 Hz.

Abstract:To improve the performance of synchronization control of coordinated motion in the networked computer numerical control (CNC) system, a periodic communication plan which combined the point-to-point communication with the lumped-frame communication in the ring network was proposed to make the master to access the feedback messages of all axes timely. The corresponding position synchronization algorithm and motion message estimating algorithm were proposed. Meanwhile, the stability proof of the position synchronization controller designed according to the algorithms was conducted. Finally, experiment results showed that the root mean square errors (RMSE) of the position synchronization controller corresponding to the communication plan were reduced by 49.270% than those of the standard proportional-derivative (PD) controller. The results indicate that the position synchronization controller corresponding to the communication plan has good synchronization performance, which has positive meaning to further improve the performance of synchronization control in networked CNC system.

Abstract:For motion error abduction in CNC machine tools, complicated mathematical models are often needed to detect specific motion error for a specific CNC machine tool in the literature. A convenient method to simplify motion error abduction was proposed. The corner distribution on a divided error circle image generated by numerical control system was detected and the RBF neural network was combined to recognize motion error. Firstly, a new corner which indicated the distance from circle curve to circle center saltation of 16-piece divided circle was defined. The average radius and corner number of every piece of the divided circle were put into characteristic matrix to represent error circle images. In order to verify the performance of the characteristic matrix, SVM was employed to test five types of motion error circle images, which turned out to be an excellent solution with high recognition accuracy. Lastly, a RBF neural network was applied to recognize the motion errors by using the characteristic matrix as input and every motion error as output. Results show that the proposed method is of high efficiency and good accuracy for motion error abduction.

Abstract:Aiming at the difficulty to analysis the regularity of CNC machine tools’ motion precision through mathematical model, the nonlinear prediction method based on chaotic phase space reconstruction theory was proposed. The optimum delay time was evaluated by the average mutual information method and the minimum embedding dimension calculated by false nearest neighbor method. The phase space reconstruction for one-dimensional time series of the motion accuracy was implemented. The topology isomorphic state space of the original system was obtained. According to the chaotic system’s inner orderliness and regularity, the phase points’ trajectory was employed to describe motion precision’s evolution regularity in phase space. The input vector was constituted by phase points’ multi-dimensional component, and the predictive value of the motion accuracy was used as output vector. The nonlinear prediction model of CNC machine tools’ motion precision was constructed based on RBF. In order to improve the prediction accuracy and generalization ability, the algorithm of quantum-behaved particle swarm optimization was proposed to select the parameters of RBF. Global optimum value of RBF network’s center, width and connection weights were obtained. Through the prediction model, the evolution trend of CNC machine tools’ motion precision was predicted. The experiments verified that the prediction model based on chaotic phase space reconstruction can trace the evolutionary trends and regularity of the precision properly. The maximum relative error of the precision was less than 6.67%.

Abstract:Galfenol is a magnetostrictive material which can be safely operated in tension, compression and shear. The coupled modeling framework of a loaded Galfenol actuator was studied. Field and stress dependent hysteresis and saturation were modeled with the discrete energy-averaged model. The dynamic model was developed by coupling the structural model with the energy-averaged model. Coupled governing equations were obtained by employing the virtual work principle and the model was discretized with Galerkin method. Simulation results showed that the proposed model had proper accuracy to predict the response of the beam actuator. In order to analyze the characteristics when the actuator was loaded with different forces, the output characterization of the loaded Galfenol actuator was studied by using different coverage ratios of the Galfenol cantilever. Calculation results were compared with Terfenol-D and the piezoelectric ceramics. It was shown that the load capacity and the internal tension of the actuator were increased by increasing the coverage ratio of the Galfenol cantilever. With a constant load, the actuator can no longer output positive displacement when the coverage ratio was relatively small. When Galfenol was loaded with tension, simulation results showed that the internal stress distribution exceeded the yield strength of both Terfenol-D and piezoelectric ceramics. The mechanical strength of Galfenol alloy ensured the material safety when the tension was changed due to the increase of the external loads.