Abstract:In order to promote the performance of the electromagnetic-hydraulic hybrid brake system when sudden stop occurs, a kind of hybrid system which adapts electromagnetic and hydraulic braking system was developed; it built a hydraulic mathematical model and a mathematical model of electromagnetic brake system which is different in low speed and high speed. Based on the force analysis of the 1/4 vehicle model, a sliding mode controller has been designed and hardware in loop experiment platform has also been constructed. The experiment which simulates on asphalt and ice road was made to compare with the commercial ABS at the same conditions. The results indicate that the hybrid brake system has more rapid responds time, more stable slip ratio controlling ability and less brake time than traditional hydraulic brake system. And at the same time, due to the electromagnetic braking system, the system’s abrasion and the braking heat fading or thermal failure is falling.

Abstract:Force and moment measurement accuracy of the tire test rig directly affects the accuracy of the tire data. A new type of tire test rig developed by research team was analyzed. Based on multi body dynamics theory, the mechanism of the attitude control of the test rig was analyzed and equation solver of force and moment of the test rig was derived. The accuracy of equation solver was verified by abaqus which is finite element software. Then the test rig which had been designed and processed was calibrated. The results showed that forces in three directions were in good agreement with the calibration, while moments were not particularly desirable. A reasonable assumption was made that the space bias of hard point at the hinged of six power cylinder of tire test rig was existed. Then the identification and optimization of spatial coordinates were made. The results showed that the optimized forces and moments in three directions were in good agreement with the calibration. Force accuracy was higher than 0.75% and torque precision can reach about 1%. Results proved that hinged misalignment assumptions were reasonable, also indicated the potential of this new test rig on the test accuracy.

Abstract:Motion differential equation of hydro-pneumatic suspension is established to describe the vibration characteristics for a certain type of construction vehicles. The output force was deduced from the suspension parameters. Based on the suspension characteristics of multi-phase medium, fractional calculus theory was introduced, and its fractional Bagley-Torvik equation was set up. The numerical computation by low-pass filter of Oustaloup algorithm was performed. The numerical solution of nonlinear fractional equation was obtained to investigate the vibration characteristics of the suspension fractional system. By the build of equal-ratio test platform and simulation model, the fractional, integer order model simulation and experimental data were compared. When the fractional-order is 0.9, it better describes the motion characteristics of suspension system. The experiments show that the experimental data can fit the fractional order system model well, thereby prove the model on hydro pneumatic suspension system.

Abstract:A visualization experimental apparatus with high speed controlled flash photography techniques was developed to investigate the flow in the hole of diesel injection nozzles and the spray construction near orifice. The experiments were performed with the transparent actual nozzles for diesel,gasoline,ethanol diesel fuel and biodiesel. The results indicate that the cavitation films could be observed in the hole for all fuels. The initial cavitation was appeared earlier and the cavitation intensity was stronger for the fuel which had lower viscosity and higher saturated vapor pressure. There was larger spray cone angle with stronger cavitation intensity. After the jet was finished, the gas backflow phenomenon could be observed in the hole and the initial bubble would be produced. And the initial bubble size could increase with the reduction of fuel surface tension. The flow status in the pressure chamber and hole was greatly affected by the movement of needle.

Abstract:Clutch friction work and vehicle jerk were synthesized to evaluate the shift process performance of dry dual clutch transmission (DCT). The entire shift process was analyzed and divided into 4 sections by the key points which were found based on the synthesized criterion. A control algorithm including proper control methods in every respective section was designed to achieve optimization of the entire process. Especially, the micro-slip control method was applied in the torque swap section and the discrete dynamic programming method was applied in the speed regulation section. At last, the algorithm was applied in the experimental vehicle and the experiment result showed the effectiveness in improving shift performance of DCT. Compared with the traditional control algorithm, the results prove that the new algorithm can decrease vehicle jerk during the entire shift process without producing more clutch friction work.

Abstract:A CPF numerical model was proposed with experimental verification. The paper introduced PM (particulate matter) catalytic regeneration percentage (α) as a criterion of CPF catalytic efficiency, investigated the influences of inlet conditions on catalytic efficiency, and selected the catalyst loading based on certain catalytic efficiency range. In addition, the effects of three kinds of channel shape, wall permeability and soot permeability on the pressure drop of CPF, the frequency of active regeneration and the maximum regeneration temperature were investigated. The results show that during certain temperature range, the increases in initial soot quantity and NO/NO2 volume proportion enhance the catalytic efficiency; the active regeneration frequency drops under the condition of hexagon channel, high wall permeability and high soot permeability; the maximum active regeneration temperature is low under the condition of square channel, high wall permeability and low soot permeability.

Abstract:Experiments were carried out on a turbo-charged, inter-cooled, heavy duty truck’s 6 cylinder diesel engine; ethanol-water blends (the volume fraction of water is 30%) were injected to the retrofitted intake pipe to realize diesel/ethanol water blends compound combustion. The combustion characteristics and economic efficiency at several kinds of speeds and loads with different high diesel substitution rates (0%, 30%, 40%, 50% and 60%) were investigated in steady working condition. The results show that, compared with normal combustion mode, the diesel/ethanol-water blends compound combustion lead to the ignition timing delay, maximum rate of heat release and in cylinder pressure peak rise, combustion duration shorten. When the engine work in low speed, the equivalent specific fuel consumption most decreases by 13%, and the effective thermal efficiency most increases by 8.3%; in high speed, the equivalent specific fuel consumption remains approximately constant, and the fuel economy can even be deteriorated slightly when the diesel substitution rates are more than 30%. The results can be used to guide the application of diesel/ethanol compound combustion in engine.

Abstract:The theoretical analysis and numerical simulation method were used to study the influence of inlet guide vane on the hydraulic performance of axial-flow pumping system. The inlet guide vane was designed based on design requirements. The three-dimensional internal flow of axial flow pumping system was simulated in different installation angles of inlet guide vane. Overall performance curves of axial-flow pumping system with adjusted inlet guide vane were obtained and the multiple non-liner regression prediction mathematical models of the hydraulic performance were established based on the results of numerical simulation and velocity triangle analysis. Compared with the pumping system without inlet guide vane, the hydraulic performance of pumping system with inlet guide vane changes little in the high efficiency area and small flow rate condition, but the efficiency of pumping system drops greatly because the hydraulic loss of inlet guide vane increases greatly in the large flow rate condition. With the increase of positive installation angle of inlet guide vane, the high efficiency operating condition is offset to small flow rate and the whole efficiency curves of pumping system would drop. While, with the decrease of negative installation angle, the high efficiency of pumping system increases firstly then decreases. The flow rate doesn’t change in the high efficiency operating condition of different negative installation angles.

Abstract:The effects of tip gap size on the unsteady flow characteristics in an axial flow pump at design flow rate were investigated using large eddy simulation with sliding mesh technique. Five configurations with different tip gap sizes were considered, and the tip leakage vortexes and pressure pulsations of near tip zone on the blades were studied in detail. The results indicate that as the tip clearance increased from 0.001D2 to 0.003D2, the head and efficiency of the pump reduce by 6.2% and 5.6%, respectively. When the tip gap is larger than 0.001D2, the dominant tip-leakage vortex extend to the pressure side of adjacent blade and the secondary tip leakage vortexes formed in the tip-gap region. Affected by the tip leakage vortex, the amplitude of the pressure pulsation of the monitoring point PP6 (on the pressure side and near the middle of the blade tip edge) increases with the tip gap size. For different tip clearance configurations, the rotating frequency (fr) dominates the pressure pulsations of near tip zone on suction side of the blades, while the dominant frequency of near tip region on the pressure side changes with the tip-gap size.

Abstract:The filter based model (FBM), which was introduced into CFX by user defined subroutine, and a homogeneous cavitation model was used to calculate cavitating flow of the axial-flow pump at different conditions. The effect of a maximum density ratio between liquid and vapor in the cavitation model on cavitation characteristic simulation was investigated. The results compared with experimental data show that the FBM based on RNG k-εmodel can predict the external characteristic of axial flow pump well. The critical NPSHs predicted by the true density ratio 43197 at three different conditions (Q=320, 392, 480m3/h) are closer to experimental values than the default 1000 and the relative errors are 1.93%, 4.73% and 8.09% respectively. With the increasing of maximum density ratio, the calculated vapor area, vapor volume fraction and the range of tip leakage vortex increase as well. This may be the cause of different predicted critical NPSHs.

Abstract:In order to further study the hydraulic performance of flow passage components for S –shaped shaft extension tubular pumping system, the whole flow passage of pumping system were simulated based on the CFD technology under multiple operating conditions. The inner flow pattern and hydraulic performance of flow passage components were analyzed. Focusing on details of flow field, the flow characteristics in the impeller and guide vane were analyzed under three different operating conditions (the small flow rate condition KQ=0.368, the best efficiency condition KQ=0.490 and the large flow rate condition KQ=0.613). The static pressure of pressure surface near shroud is larger, and the static pressure of suction surface near hub is larger than that near shroud. With the increase of spanwise location value, the differential pressure between pressure surface and suction surface increases gradually. The static pressure of guide vane surface increases from inlet section to outlet section at KQ=0.490. With the decrease of flow, the recycling circulation ratio CH decreases firstly then increases, and the minimum ratio CH was 0.031 at KQ=0.490. The accuracy and effectiveness of numerical results were verified by the physical model test. The test results show that when the flow coefficient KQ=0.443 and the head coefficient KH=0.828, the highest efficiency of pumping system is 83.55% at the blade angle -2°.

Abstract:In order to understand the characteristic of the gas-liquid two-phase flow in siphon pipe, based on the homogeneous model in multiphase flow theory of ANSYS CFX software and RNG kεturbulence model, the process of gas-liquid flow for a siphon outlet pipe in pumping station was simulated. Results of simulation showed that the air sacs are easily generated on the shell of siphon pipe when the gas mixed into the water and it has an extremely adverse influence with the siphon finish. Meanwhile, flow rate of the incoming flow is the main factor impacting the siphoning time. At last, the relations between the siphoning time and flow rate for hydraulic driving gas and mixing gas-water processes, according with the power function relationship, were given.

Abstract:In order to study the cavitating flow at different stages of cavitation in the pump casing of a centrifugal pump, the topology blocking and structured mesh generation strategies was proposed on the domain of the pump. Taking full account of the near wall region mesh quality, steady and unsteady cavitation simulation of the centrifugal pump has been proceed using the SST k-ω turbulence model combining with Rayleigh-Plesset cavitation model. Unsteady flow of the pump chamber and the force endured by the impeller were obtained under three NPSHa. The results show that cavitation increases the amplitude of pressure pulsation in pump casing sharply. Due to the presence of the wear rings, amplitude of pressure pulsation at front side chamber is greater than back side chamber. Broadband pulsation frequency increase with the cavitation intensifies, especially at axis frequency. Intensification cavitation not only affects the flow pattern of the pump chamber, but also increases the radial and axial forces acting on the impeller.

Abstract:With the aim to meet the demand of a low-specific speed centrifugal pump for the high efficiency and non-overload characteristics at several specific operation points, a series of optimization were done on a model pump TS65-40-160. An impeller was designed based on the non-overload theory, and by analyzing the inner flow distribution in CFD and verify experiments, several improvements were taken to meet the complicated requirements. After several design improvements and experiments, an optimized scheme was obtained, whose head are slightly higher than the given indexes in the shut-off, designed and maximum flow rate points, and the maximum unit efficiency is increased by nearly 14%, and the pump efficiency also meet the national standard requirement, and the shaft power has the non-overload trend, and the power value at 48m3/h is within the motor power. Through many results comparisons from CFD and experiment, a conclusion is drawn that the simulation error is small and it can meet the requirement for model optimization.

Abstract:Because of unreasonable design of double-volute splitter in ES250-370 double-suction pump, its shaft was bent which lead to wear and tear of the seal. According to the basic principle of double-volute pump design, three different double-volute splitter schemes were put forward; the reason of radical force and the problem of original double-volute were analyzed. Based on the RNG k-εturbulent model provided by CFX software and Simple algorithm, double-volute splitters from three different improved schemes were simulated. Static pressure distribution of different volutes were obtained, the axial stress and radical force of the pump were calculated as well. Steady numerical simulation and experimental results show that, compared to the original splitter, the rated point efficiency of No.3 splitter is increased by 7%, and radical force is balanced effectively and the axis stress is the minimum, while keeping the hydraulic performance. So No.3 is the best design of the three options. Splitter starts from the fourth cross section of double-suction pump and ends with eighth cross section, and it meets the logarithmic curve equipment. A method of designing the splitter for double-volute centrifugal pumps was provided for the pump designer.

Abstract:In order to acquire the main structure parameters impacting on performance of vortex pump and optimize the performance of the vortex pump, the orthogonal testing method was introduced. Impeller outer diameter D2, blade number Z, width of blade b2, impeller outlet blade angle β2 and impeller inlet blade angle β1 were chosen to be the main factors. So 16 sets of programs with 16 type of impellers were designed according to L16（45）orthogonal table. Optimum value range of each factor was preliminarily obtained through range analysis. Quadratic orthogonal test was conducted to investigate the effects of main factors and acquire the primary and secondary factors of the design parameters on the vortex pump, and an optimization scheme for further design was obtained. The internal flow field and experimental results of optimization scheme were compared with the original model, and it showed that pump inlet produced two back-flows with different degree; the back-flow loss of optimal model was less than that of the original model; the efficiency and the head of optimal model are both higher than those of the original model 4.2 percentage points and 10m, respectively. The improved efficiency and head can meet the design requirements. The orthogonal testing method has some feasibility to the performance optimization of vortex pump.

Abstract:With the aim to explore the influence of plant additive on soil water holding capacity, the soil-water characteristic curves under different soil bulk density, different plant additives and different additive proportions were measured, and the influences of plant additive on the soil water-holding capacity under the conditions mentioned above were analyzed. Then, the soil-water characteristic curves were fitted by using the models of RETC software，and the parameters of the models and the model suitability were determined. The results show that under the same soil water suction, the soil water contents of the treatments with plant additive are higher than that of pure soil; the treatment with 3% maize leaf plant additive has better water conservation capability than the treatment with 3% maize-cob, but the treatments with 1% plant additive have little difference. In the low suction stage, the mixing plant additive reduces the proportion of large pores in the soil; while at the higher suction stage, the plant additive increases the small pores proportion of soil, thereby improves the soil water-holding capacity. The analysis results of model suitability with models of RETC software show that the optimal model of unsaturated hydraulic conductivity is fitting Mualem model. The optimal models of the treatments with 1.35g/cm3 and 1.40g/cm3 soil bulk density are VGM(m,1/n) and VGM(m,n), respectively, with 1% and 3% maize leaf additive, while those are BCM and GM(m,1/n), respectively, with 1% and 3% maize-cob additive.

Abstract:Based on the soil column breakthrough experiment in laboratory, four treatments (desulfurization gypsum with none or one or three leaching times; no desulfurization gypsun with none leaching time) were set up. With the analysis of relationship among these three ions: NH+4, Ca2+, Na+ and the hydraulic conductivity (HC), the effects of the leaching times and flue gas desulfurization gypsum on ammonium nitrogen transport in solonetz were investigated. The results showed that the suppression of the adsorption of ammonium was occurred in the solonetz combined with desulfurization gypsum without leaching. But with the leaching times increasing before penetration, the slope of the breakthrough curve reduced and the adsorption enhanced. In the view of controlling water and salt, promoting the adsorption of fertilizer, inhibition of soil secondary salinization, it was inappropriate to put the ammonium fertilizer together with desulfurization gypsum in solonetz at the same time. It suggested that the solonetz mixed with desulfurization gypsum should be leached two times, which are autumn irrigation and spring irrigation, with the leaching amount of 662.7m3/hm2. On the basis of ensuring the reclamation effect, this leaching way can decrease the amount of autumn irrigation and distribute the limited freshwater resources reasonably in the area.

Abstract:Standard precipitation index (SPI) was used to analyze the annual and growing season precipitation conditions from 1957 to 2012 based on the precipitation data of meteorological station in Wuqi County. The correlation analysis was used between the SPI and the soil water layer thickness of the microtopographies during 2008—2012. The results showed that the precipitation fluctuation was larger from 1957 to 1986 than that from 1987 to 2012. The extreme and severe drought years appeared in 1957—1986, but those did not appear during 1987—2012; there was positive correlation between the SPI of growing season and the change value of soil water layer thickness of microtopographies. The SPI of growing season had the lower correlation degree (R2<0.8) with the gentle slope and sink hole of steep slope, but the R2 lay between 0.8 and 0.9 with gully, platform and ephemeral gully. The SPI of growing season had the larger correlation degree (R2>0.9) with scarp, sunny uniform slope and half sunny uniform slope; and the difference among the change value of soil water layer thickness in the all monitoring points was significant in the growing season, and the mean soil water layer thickness of gentle slope, sink hole and platform was larger than those of other monitoring points.

Abstract:In order to explore the change characteristics of soil shear strength, change characteristics and influence factors of soil shear strength were studied during maize growing period based on the method of field investigation and laboratory. The result showed that in the 0～5cm soil layer, soil shear strength increased gradually with the maize growth period and reached the maximum in mature period. However, soil shear strength increased first and then decreased with the maize growth period in the 5～10cm and 10～15cm soil layers, and soil shear strength reached the maximum in tasseling period. Soil shear strength showed the higher values in the different maize growing periods. The reinforcing effects of the shear strength in the first three soil layers were the better, and the reinforcing rates were the highest in tasseling period of maize. There existed linear function between soil shear strength and the soil moisture, and there were significant positive linear correlations between soil shear strength and soil bulk density, root amount, root length, root volume. At the same time, there were significant positive correlations between the reinforcing values of the shear strength and increasing value of 0~1mm root length. Soil shear strength enhanced gradually with the maize growth period, and soil water content, bulk density and maize root had a great influence on soil shear strength. So, it had significant importance for soil erosion control to select the maize variety with 0~1mm root ,and applied soil and water conservation measures to increase soil water content and bulk density.

Abstract:Field experiments were conducted in the test station of Dry-land Farming Institute of Hebei Academy of Agricultural and Forestry Sciences during 2011—2012. Three summer maize cultivars, Xundan 20, Zhengdan 958 and Xianyu 335, were used as experimental materials. The measurements were taken on irrigation by three stages (Sep.20, Sep.25, Sep.30). The main results showed that compared with CK, different irrigation treatments during late milk period had increased the soil moisture by 2.92%~14.14% in 0~100cm layer at harvest. The evapotranspiration amounts of maize were ranged within 380.67~434.91mm, and different treatments from small to large were I9 25, I920, I930 and CK. Different treatments also had effects on the dry matter distribution. The treatments of CK and I930 increased amount of assimilate storage in vegetative parts before silking to grains. I920 and I925 treatments, however, increased amount of assimilate storage in vegetative after silking to grains. Grain yield of I920 and I925 treatments were higher than those of other treatments. Water use efficiency for grain yield was range within 21.94~26.53kg/m3, water use efficiency for grain yield of I925, I 920 and I930 treatments were most obviously lower than that by CK treatment. This shows that at optimum irrigation time after milking, grain yield increases although water use efficiency for grain yield decreases. In comprehensive consideration of cultivating technique of high yield and efficiency for unified wheat and maize, the best time for irrigation was on 20~25 September.

Abstract:In order to investigate the law of ammonia volatilization and nitrogen infiltration in the process of biogas slurry application, the influence rules of different application rate and depth of biogas slurry on the ammonia volatilization of the soil surface and the infiltration of total nitrogen, ammonia nitrogen and nitrate nitrogen in vertical soil profile were explored systematically by soil column experiments at room temperature. The experimental results showed that the total ammonia volatilization of the soil surface and the duration of volatilization were all positively correlated with biogas slurry application rate. The moisture content, total nitrogen and ammonia nitrogen in vertical soil profile were mainly distributed in topsoil. But the nitrate nitrogen had migrated to deep layer soil with the water infiltration of biogas slurry. The total ammonia volatilization of the soil surface decreased with the increase of biogas slurry application depth when the biogas slurry was used as basic fertilizer. The ammonia volatilization rate of biogas slurry could be effectively reduced when the biogas slurry application depth was ten centimeters. And the peaks of total nitrogen, ammonia nitrogen and nitrate nitrogen in vertical soil profile were all positively correlated with biogas slurry application depth.

Abstract:The application of bioaugmentation techniques in anaerobic fermentation was reviewed in term of mechanisms, effects and influencing factors of the bioaugmentation process. It reveals that bioaugmentation has positive effects on anaerobic fermentation, such as in feedstock pretreatment, anaerobic digestion processes start up and biogas produce. However, most of the existing researches were conducted in laboratory scale and batch assays. The focal point of bioaugmentation process is the survival and activity of functional microorganisms in the fermentation system. There are still a series of problems that need to be solved to increase the success of bioaugmentation strategies widely using in actual engineering, such as revealing the interrelationship of the inoculated microbial culture and existing microflora, developing stable and adaptable functional microbial agents, seeking better ways of bioaugmentation performance, establishing evaluation criteria of the bioaugmentation effects.

Abstract:The tolerance of Fusarium oxysporum on formic acid, acetic acid, furfural, vanillin and catechol, which are hydrolysis inhibitor, during ethanol fermentation process was investigated by shake flask method. The results showed that the order of sensitivity to various inhibitors for Fusarium oxysporum was formic acid, acetic acid, vanillin, catechol and furfural during ethanol fermentation. The production of ethanol was similar with that of the control when the acid concentration was 0.6g/L at pH value 6.5 of acetic acid and pH value 7.5 of formic acid, respectively. Low concentrations of formic acid and acetic acid promoted cell growth, but high concentrations inhibited cell growth. And the inhibitory effect of vanillin, catechol and furfural on cell growth was stronger than that of the formic acid and acetic acid. The tolerance of Fusarium oxysporum for a single inhibitor was stronger than that for mixed inhibitor. The ethanol production was 78% of the control when the concentrations of formic acid, acetic acid, vanillin and catechol were 0.05g/L, respectively. 

Abstract:Fermentation temperature is instable in the northern winter which is the bottleneck of biogas system. In order to solve this problem, a heating equipment which was a hot water heater with heat pipe with gas heating used for biogas system was developed. The distance of the heating side with heat pipe from gas stove hole, flow rate of the burning gas and average water temperature were chosen as experimental parameters. The conditions of this processing technology were optimized by the index of thermal efficiency of hot heater. The result showed that the thermal efficiency of the hot water heater reached the maximum value of 63.47% when the distance of the heating side with heat pipe from gas stove hole was 21.5cm, the flow rate of the liquefied petroleum gas was 1.01kg/h and the average water temperature was 35~45℃.

Abstract:In order to determine the interaction rule of fat, starch and protein in the process of anaerobic fermentation, the influence of different mixing ratios on the characteristics of methanogenesis and degradation was investigated using mixture design under mesophilic condition. The results revealed that when fat, starch, and protein was used as substrate separately, the methanogenesis performances were inhibited in different degrees, and the mean biochemical methane potentials (BMP) were 345.36, 59.80 and 135.87mL/g, respectively, which accordingly accounted for 34%, 14% and 26% of theoretical methane production. At the same time, the degradation property was affected apparently. However, the synergistic effects on methanogenesis and degradation were obvious while the three components were mixed as substrates. The regression models between the organic ingredients mixing ratios and BMP and volatile solid (VS) degradation rate were established, furthermore, the parameter optimization was carried out. The optimization result was that as the ratio of fat, starch and protein was 36∶30∶33, BMP and VS degradation rate were maximum. Experimental verification showed that BMP and VS degradation rate were 451.36mL/g and 79.62% respectively at optimal ratio.

Abstract:With the aim to investigate the influences of blade number on the self-starting performance of vertical axis wind turbine with self-adapting wind speed (VAWT-SWS), a prototype which could change the number of blades (2,3,4) was designed. Through the wind tunnel experiment the static torque coefficient curve with azimuth angle at a wind speed of 3m/s was obtained, and compared experiments were done on Darrieus straight-bladed wind turbine with the same parameters. Then the load of VAWT-SWS was released, and rotation speed curve of VAWT-SWS changing with time at 3m/s was gotten. The experimental results showed that the self-starting performance of VAWT-SWS was superior to that of Darrieus straight-bladed wind turbine; the increase of blade number could improve the static self-starting performance of VAWT-SWS, but degraded the dynamic self-starting performance.

Abstract:In order to analyze the moisture distribution of rough rice with high moisture content within counter flow drying layer and achieve the dynamic tracking of drying process and its control, based on the moisture diffusion model of drying process and the mass conservation equation of deep bed drying process, grain moisture variation in counter flow drying process was analyzed, and the moisture distribution in grain layer and the analytic expression of drying rate were deduced. Experiments indicate that 50℃ hot air still has drying capacity after penetrating a 0.5m thick refluxed zone when the ratio of air flux to grain mass is 4. The deviation of grain moisture from discharge hopper between mathematical explanations and experimental results was within ±0.5%, and it confirmed the reliability of the analytical model.

Abstract:With the aim to explore the gelling rules, the stability and the textural properties of inulin under acidic conditions, and the effect of pH value on the gelatin were studied at different concentrations of inulin. The experimental results show that the gelling ability decreases and the gelling time increases with the decrease of pH value. The volumetric gel index increases with inulin content increase and decreases with pH value decrease. When pH value decreases to 1，gelatin can’t be formed even the concentration of inulin solution is high as 60%. The water retention of gelatin increases with the increase of inulin content and the increase extent becomes weak as pH value decreases. The water retention of 60% gelatin increases by 9.4%, 5.75% and 5.47% compared with that of 40% gelatin at pH value 7, 5 and 3, respectively. The higher the inulin content is, the stabler the stability of gelatin to pH value is. The acid hydrolysis rates of 40% inulin gelatin are 1.35 and 2.97 times higher than that of 50% and 60% gelatins when the pH value equals 3 and the hydrolysis time is 24h. Texture profile analysis shows that pH value has positive correlations with the hardness, strength, adhesiveness, cohesiveness and gumminess of gelatin. Differential scanning calorimetry analysis shows that the freezable water content of 50% gelatin increases to the maximum, 26.0%, when pH value decreases from 7.0 to 3.0.

Abstract:With the aim to solve the accurate rate short of reflection imaging technology to simultaneously detecting internal and external defects of potatoes, a nondestructive test technology based on transmission imaging and machine vision technology was proposed. It is concluded that the combination of hill climbing method and region growing method is the optimal image segmentation method for transmission and reflection images of potato by studying image preprocessing methods. Partial least squares-support vector machine (PLS-SVM) method was employed to establish the potato defects recognition model for transmission and reflection images of potato. In the potato internal defects detection, the classifying correct rates of the transmission and the reflection imaging technology are 96.30% and 59.26% respectively; in the potato external defects detection, the classifying correct rates are 94.20% and 89.86% respectively; in the simultaneous potato internal and external defects detection, the classifying correct rates are 95.83% and 81.25% respectively. The research results show that the transmission method is better than the reflection method in detecting potato internal and external defects alone, or in detecting the internal and external defects simultaneously.

Abstract:The apple CT gray scale images scanned by CT were transformed by Fourier transform, and 16 parameters were extracted from each frequency domain after transformation. Combined with the soluble solid, the titrable acidity, the pH value and the moisture content of apple, the principal components regression (PCR) and the partial least squares regression (PLSR) were employed to establish the prediction models of apples’ internal quality. In the PCR, the first ten principal components were chosen with contribution rate reaching 99%. The models show good prediction results by the F criterion with all the P values lower than 0.05. In the PLSR, each content model has the lowest sum of squared errors when the number of latent variables is 12, which indicated a good prediction result. The results show that the models built by PCR have higher predictive ability than that of PLS method in the matter of errors.

Abstract:In order to reveal the temporal and spatial variation on vegetation coverage and provide evidence for ecological environment construction on the upper Anning River, the temporal and spatial variation on vegetation coverage, during 1999—2010, on the upper Anning River was extracted and analyzed based on two periods of remote sensing images (TM in 1999, ETM+ in 2010), which was based on RS and GIS technology. Meanwhile, combined with Aster DEM data, the vegetation distribution and its variation characteristics in different altitude and slope regions were also analyzed. The results showed that the vegetation coverage condition in study area overall was good. And the area of vegetation coverage (fc) above 0.5 was more than 60%. Besides, a trend emerged during 11 years in the study area that vegetation cover overall increased. The area of first grade vegetation coverage (fc≥0.7), second grade vegetation coverage (0.5≤fc<0.7) and third grade vegetation coverage (0.3≤fc<0.5) increased by 1.24%, 4.36% and 2.28%, respectively. However, the area of fourth grade vegetation coverage (0.1≤fc<0.3) and fifth grade vegetation coverage (fc<0.1) reduced by 25.72% and 12.28%, respectively. Low vegetation coverage was mainly distributed in relatively low altitude areas. With the increase of altitude, vegetation cover increased firstly and then decreased. Variation on vegetation coverage that low vegetation coverage was transformed into high vegetation cover degree was obvious in regions below 3000m, especially lower than 2500m. With influenced less by human activity, vegetation cover above 3000m seemed to hold relatively little change. High vegetation cover was mainly located in high slope regions, while low vegetation cover was mainly located in relatively moderate slope regions. An obvious variation on vegetation coverage was concentrated in regions with slope range from 25° to 45°, regions below 25° ranked secondly. While no obvious change of vegetation cover in regions with slope above 45° appeared, with less influenced by human activity. Under hydrothermal condition，the vegetation coverage on aspect is sunny slope (135°~225°)> half sunny slope (45°~135°)> half shady slope (225°~315°)> shady slope (0°~45°, 315°~360°); the vegetation coverage increased in each aspect from 1999 to 2010, and sunny slope increased significantly while no obvious increase on shady slope.

Abstract:Taking Wang Ye Dian Forestry Farm as the study area, forest volumes of sample plots were obtained as the true value through field investigation. At the same time, the images of satellite ZiYuan 3(ZY-3) were processed, and corresponding band spectra value, combination value of spectra and topographic information of the sample volumes were obtained. Through multiple regression analysis, broad leaved forest and coniferous forest volume estimation models were established. The experimental results show that the correlation coefficient of broad leaved forest volume estimation model was 0.815, and that of coniferous forest was 0.761. There was a strong correlation between the spectra value, combination of spectra, topographic factors of ZY-3 and the forest volume. The model prediction accuracy was verified, and accuracies of broad leaved forest and coniferous forest models were 85.3% and 91.9%, respectively. The study suggests that the use of ZY-3 images for the forest volume estimation has good application prospect.

Abstract:The use of unmanned helicopters (UH) and other aviation aircraft for supplementary pollination in hybrid rice is one of the most important ways to solve the mechanization of the hybrid rice seed production. In order to conduct multi-point, multi-direction, mobile, and real-time measurement for wind field parameters on rice canopy which formed by UHs rotor airflow, a wireless wind speed sensor network system (WWSSN) was developed, and relevant reliability analysis and tests were also presented. The WWSSN consists of three modules, several wireless wind speed sensors (WWSS), the flight global position system (FGPS), and the intelligent control focus node (ICFN). The test results showed that the average relative error of wind speed measuring is not more than 3.52%, the absolute maximum error is 0.2m/s, and no significant difference among each WWSS to reliably and accurately measure the wind velocity field corresponding values, the coefficient of variation is not greater than 4.41%. The fixing brackets can help to install the WWSS in paddy field, and the topological structure between ICFN and WWSSs is a star topology, it is easily to realize multi-point, multi-direction, mobile, and real-time measurement for wind field parameters on rice canopy which formed by UHs rotor airflow. In addition, the FGPS based on high accuracy RTK GPS can also provide the pose information, which is helpful to the comprehensive analysis of the influencing factors in supplementary pollination using UH. It is indicated that the presented WWSSN can provide reliable and accurate wind field parameters measurement on rice canopy which formed by UHs rotor airflow. It can be used as an effective tool for the operation parameters optimization for supplementary pollination in hybrid rice breeding using UHs.

Abstract:In order to improve the accuracy, efficiency and automatic degree of existing acquisition techniques of animal’s conformation, based on two depth cameras, a real time system which can reconstruct the animal for body measurement, an automatic ball target based method for the extrinsic calibration of reconstruction system which is based on RANSAC were put forward. The extrinsic parameters can be used for registering point clouds acquired synchronously from depth camera in real time. And then, interactive measuring method which is optimized in picking mode for body measurement was used to get shape traits of animal. Xtion PRO was chosen as data acquisition equipment, and taking the pig specimen as an example, point clouds data acquired from high precision laser scanner was applied to evaluation of the system. The results show that the ball-target-based method can get the extrinsic parameters of depth camera automatically; the average error of registered data is less than 7.50mm; the speed of reconstructing the whole pig can reach in excess of 15f/s; body measurement error is less than 4%. So the system can be applied to body measurements in agricultural field.

Abstract:For the standard particle swarm optimization algorithm is easy to appear slow convergence speed, emerge premature convergence and fall into local minimum point in the later evolution, a kind of localization algorithm based on cross particle swarm optimization for wireless sensor networks was presented to solve these problems. The approach mainly included three stages: sink node selection, measure distances amendment and unknown sensor node localization. By referring to the crossover operation of genetic algorithm idea, cross particle swarm optimization algorithm could increase the diversity of particles and reduce the distance measure error and the influence of anchor node number on localization result. The simulation experiment result showed that the stability and localization accuracy of the method proposed are better than those of the standard particle swarm optimization algorithm. Under the condition of same measure error and the equal number of anchor nodes, the new method was compared with the shuffled frog leaping algorithm. And the compared results are as follows: the maximum of localization errors are 1.3378m and 1.7473m, respectively; the minimum of localization errors are 0.2583 m and 0.5615m, respectively; the average localization errors are 0.6512m and 10447m, respectively. Results indicate that the method proposed is suitable for agriculture wireless sensor network localization.

Abstract:In order to solve the problem of low prediction accuracy and bad robustness of the traditional forecasting methods in water quality, this paper put forward the prediction model for pH value of aquaculture water quality based on the principal component analysis (PCA) and least squares support vector machine (LSSVM), which the hyper-parameters is optimized by modified cultural artificial fish-swarm algorithm(MCAFA). The dimension of aquiculture ecologic environmental data was reduced by principal component analysis; double evolutionary mechanism of cultural algorithm for reference was applied and LSSVM was taken as an artificial fish; belief space was used to guide the shoal evolution step size, global search direction and Cauchy mutation to improve the diversity of the artificial fish swarm; so the optimal hyper-parameters nonlinear pH value prediction model was automatically obtained. Based on the prediction model, the water quality on-line monitoring was predicted for a high-density aquaculture pond from September 1, 2011 to September 4, 2011 in Yixing city, Jiangsu province. Experimental results show that the PCA-MCAFA-LSSVM prediction model has good prediction effect than the ant colony algorithm LSSVM and genetic algorithm LSSVM. The absolute error of the 93.05% test samples is less than 8%, and the max absolute error is only 1161%; the root mean square error, average absolute relative error and the running time are 0.0474, 0.0041 and 4.367s respectively, which are better than those from the other models. It is obvious that PCA-MCAFA-LSSVM prediction model has low computational complexity and high forecast accuracy. It can provide the decision basis for the water quality controlling in the high density eriocheir sinensis culture.

Abstract:Stem water storage varies with a daily cycle. However, none of sensor techniques can meet the noninvasive measurement of herbaceous plant stem water storage. A method of using a sap flow rate sensor to observe stem water storage dynamics for herbaceous plants was proposed. The preliminary experiment was conducted with a potted sunflower. The sunflower stem internal water recharging/discharging and its switching time could be obtained by the outputs of a sap flow sensor and an electronic scale. The observation of sunflower stem diameter variations further validated the effectiveness of the method. At the same time, the micro meteorological factors could be collected and the results showed that the micro meteorological factors had a great impact on stem water storage dynamic changes. Compared with other methods, the measurement system is simple, easy to operate and non destructive. Even though only sunflower samples were investigated, the method can be also applied to other herbaceous plants.

Abstract:This paper presented a physical representation for quantitatively simulating the motion of plant leaves, such as wilting and curling. The wilting motion is associated with the contraction and stretching of the plant cells. Fact based, our method modeled the physical morphological changes of the plant cells for describing the wilting motion of leaves. Firstly, a voxel mesh constructed based on 3D leaf model was used to simulate the cell structure of plant leaves. Then, the mass spring structure was applied to express the forces between cells .Finally, The Euler-Lagrange equation was utilized to model the movement process and solved by implicit newmark integration method to get the 3D positions of the voxel mesh. The movement trails of wilted leaf tip in the geometric space were used for data validation. The angular difference between measured motion direction and experimental results was 19°, and the distance between them ranged from 0.68cm to 3.0cm. The experimental data show that movement trails of wilted leaf tip that the method simulated is closed to the real wilted leaf; secondly, evaluating this method from the visual aspects, the algorithm also can realistically simulate the deformation process of plant leaf wilting.

Abstract:Based on time domain transmissometry (TDT), measurement device for shrub stem water content was designed. This device consists of high frequency signal source, coaxial transmission lines, winding probe and phase comparison circuit. Propagation velocity of high frequency electromagnetic wave varies in different medium, and the propagation phase also changes. The dielectric constant of wet shrubs mainly depends on its moisture content. By measuring phase difference between the coaxial cable A and the winding stem probe B, the moisture content in shrubs was obtained. Absorbent cotton stick was choice to simulate shrubs with different moisture content. And the influence of the phase difference from frequency of high frequency signal source and the structure of the probe was studied. Experimental results show that under the conditions of 60cm probe length, 50MHz and 100MHz signal source frequency, the phase difference between the coaxial cable A and the winding stem probe B is monotonic with the change of water content, and there exists a good correlation between phase difference and moisture content.

Abstract:Position-posture control system of six-legged walking robot has the characteristics: tight coupling, redundancy, nonlinearity. An inverse velocity kinematics model of six legged walking robot was constructed through research on inverse velocity kinematics of single leg. Then the control on position and posture of six-legged walking robot was decoupled to two closed-loops control, the position and the posture closed-loop control, based on the inverse velocity kinematics. The proportional control strategy was employed to implement the closed-loop control on the position posture of six-legged walking robot. Finally, a co-simulation on the closed-loop control on the position-posture of six-legged walking robot was carried out by using MATLAB and ADAMS, and the results verify that the method of closed-loop control on the position-posture of six-legged walking robot is correct.

Abstract:In order to improve the direct drive robot (DDR)’s trajectory tracking accuracy, a hybrid controller consisting of an adaptive sub controller and a PD sub controller was proposed. Firstly, the dynamical uncertainty of the robot was investigated while the uncertainty friction in the robot joints was modeled and the kinematics equation of the robot manipulator was derived. Then, a two close loops control system with position and speed feedback was built for the robot, and an adaptive controller being capable of identifying the uncertainties of the robot’s manipulator was employed so as to compensate the control error brought from the robot’s dynamic uncertainty. Moreover, a PD controller was embedded in the hybrid controller so as to improve the robot’s tracking accuracy. With the aim to guarantee the stability of the system, an adaptive law was presented. Finally, simulations have been accomplished to validate the feasibility of the controller. The results show that the position error and speed tracking error of the robot are limited to -0.02°~0.03° and ±0.005rad/s, which means that hybrid controller can make the robots track the desired trajectory with higher precision, and it exists widely application prospect.

Abstract:The researches on dynamic modeling, characteristic analysis, control strategy design and dynamic performance analysis for the parallel robot with compliant joints, which had the property of large range motion, were carried out. Based on pseudo rigid body model, the characteristics of compliant joints were investigated and system model with large deformation compliant joints was set up. The dynamic equation was obtained based on Lagrange method. A reaching law sliding mode control strategy was designed to eliminate the vibration and the unmodelled dynamics caused by compliant joints and the model error made by inertia parameter perturbation. And the stability of control strategy was verified. Simulation results showed that dynamic model and control strategy were effective.

Abstract:Limited motion range and easily happened rotation axis drift are the main disadvantages of traditional flexible joint of parallel robot. In order to promote the performance of flexure joint, a new design of open thin-walled flexure joint was proposed. According to the range of motion of 3RRR parallel robot, the geometry of joint was calculated by using the motion range of joint and the required joint stiffness as design parameters. And the structure strength of joint was analyzed via ANSYS. Torsion is the deformation mode of the open thin-walled flexure joint. The advantages of 36 degrees motion range and fixed rotation axis are presented in this joint. The practical joint is made of 65Mn spring steel according to the designed joint geometry. The contrast experiments between leaf spring and open thin-walled flexure joints were carried out on a three DOF parallel robot experiment platform. The results show the designed open thin walled flexure joint can accomplish trajectory tracking missions and the maximum relative error is 6。05%. Its superiority over the leaf spring joint is presented by the results.

Abstract:Aiming at the fluid-structure interaction vibration of the valve core-stem system in a single-type control valve, a dynamic simulation model of this system was built with consideration of a valve positioner. The predictor-corrector method was given for solving response of the valve core-stem system. The vibration response of the systems was analyzed by ANSYS software under the conditions of fixed and varying opening as well as flow-opening and flow-closing. The research results show that, for fixed opening, the valve core steady displacement offset and the fluid imbalance force increase with the increase of the pressure difference and the decrease of the opening; the transient time of the valve core dynamic displacement is shortened with the increase of the pressure difference, and the valve core dynamic displacement response amplitude under flow-opening is greater than that under flow-closing. For reducing the opening, the transient time of the valve core dynamic displacement is shorter than that under flow-closing, and the greater the pressure difference, the shorter the time, while under flow-opening it is opposite; for increasing the opening, the relation between the transient time and the pressure difference is contrary to that under reducing the opening.

Abstract:The flow characteristics of super-high pressure pneumatic fueling valve, a critical component of the fueling system, were detailed investigated by experimental way. The problems of large driving power need，slow response and high pressure gas leakage of super-high pressure pneumatic fueling valve, were solved by using pneumatic lever rule and self-acting sealing structure. A two-stage valve that used a pilot solenoid valve, moderate pressure and low flux, to control a high pressure and large flow-rate poppet valve is developed. A test apparatus with the affiliated measurement system for testing the flow characteristics of the pneumatic fueling valve orifice were introduced. A simplified model of the flow channel of fueling valve for different valve lift was obtained. Experimental study on the flow characteristics of the pneumatic fueling valve with different orifice throttling area was carried out under the condition that the pressure is higher than 10MPa. The results show that the back pressure growth rate of tank and the lift of valve rod have great influences on the flow characteristic of valve orifice. When valve lift is relative taller, the gas channel could be simplified as two-stage orifices in series, the flow characteristics are in accordance with that of ideal converging nozzle, and the critical pressure ratio is 0.5. When valve lift is relatively lower, the gas channel can be simplified as three-stage orifices in series, shows different flow characteristics, and the critical pressure ratio is 0.3. Increasing the valve lift and the injecting pressure is the most effective solution to enhance both the transient mass flow-rate and the discharge coefficient.

Abstract:The balanced two-ring axial piston pump has a different characteristic of flow ripple because of its improved structure. The flow rippleis analyzed when the numbers of the piston inside and outside are even or odd. And its instantaneous flow’s curves are drawn by Matlab, based on the different parameters. The results show that when the numbers of the piston inside and outside are unequal even or unequal odd, the instantaneous flow inside and outside will counteract, and the flow ripple will reduce. When the numbers of the piston inside and outside are equal even or equal odd, the instantaneous flow inside and outside will overlap, and the flow ripple will remain unchanged. When the numbers of the piston inside and outside are equal and the piston inside and outside are arranged in cross, the pump has the minimum flow ripple, the ripple period is half of that of ordinary axial piston pump, and the pump’s structure is more compact.

Abstract:Electrical runout (ERO) reflects the heterogeneity of electromagnetic characteristics on surface of shaft. On-site measurement can inspect whether the ERO satisfies the processing and the machine operating requirements. It is very important for controlling the product quality and ensuring the working property. An on-site measurement technology of ERO on shaft based on eddy current was presented. Firstly, the working principle of eddy current sensor and the distribution of eddy were introduced. Then, a finite element analytical model for measuring ERO was developed. Finally, an on-site measurement system was set up to measure the ERO of air compressor main shaft. The results verify the validity of measurement system.

Abstract:A new geometric model of quartic generalized Bézier surfaces with multiple shape parameters was constructed by using a class of quartic generalized Bernstein basis functions. The proposed quartic generalized Bézier surfaces inherit the outstanding properties of conventional Bézier Surfaces, have a good performance on adjusting their shapes by changing shape control parameters, and have quartic Bézier surfaces as their special cases. Some basic properties of the surfaces were analyzed, and the constructions of some special surfaces degenerated from the generalized surfaces were discussed. With the aim to tackle the problem that the engineering complex surfaces can not be constructed by a single surface, the continuity conditions of quartic generalized Bézier surfaces with shape parameter were investigated. Based on the analysis of the basis functions, the conditions of G1 and G2 continuity between two adjacent quartic generalized Bézier surfaces and the detail process to blend the two surfaces were proposed. In addition, some applications of the quartic generalized Bézier surfaces in geometric modeling were discussed. The modeling examples show that the proposed method is effective and easy to implement and has extensive applications in constructing engineering complex surface.

Abstract:The anisotropic mechanical properties of crystal surface of single crystal germanium, (100), (110) and (111) were studied, through nano indentation experiments. According to the load displacement curves of nano indentation processes and the theory of Oliver-Pharr, the elastic modulus and the hardness of the materials were investigated. The experimental results show that obvious plastic deformation occurred in single crystal germanium in the process of nano indentation and the plasticity of Ge（110）is the best, Ge（100）is worse than Ge（111), and the Ge（111）is the worst. And the hardness and the elastic modulus have similar change trend. When the indentation depth is shallow, significant fluctuations appeared on the hardness and the elastic modulus, affected by the surface effect. And because the atomic density of each crystal surface and the interplanar spacings are quite different, single-crystal germanium exhibits stable anisotropy, and the hardness and the elastic modulus rank from high to low as follows: (111) crystal plane, (110) crystal plane, (100) crystal plane. As the indentation depth increases, the hardness and the elastic modulus gradually stabilize, and the order from high to low are (110) crystal plane, (100) crystal plane, (111) crystal plane.

Abstract:Since conventional direct acting electro hydraulic proportional directional valve has the limitation of small flow, and two stage electro hydraulic proportional directional valve has the limitation of complex structure, a large flow and simple structure 2D electro hydraulic proportional directional valve with position feedback was proposed. The valve coaxially consists of 2D directional valve, elastic pressure torsion coupling and the proportional electromagnet. The elastic pressure torsion coupling changes the linear movement of proportional electromagnet armature into the rotation of the spool movement, at the same time, amplifying the thrust of proportional electromagnet. Based on the operational principle of the elastic pressure torsion coupling, the mathematical model was established and the analytic equations of axial force, torque, rotation angle and deflection were deduced. Then the finite element simulation of static characteristics was performed on the platform of ANSYS Workbench 13. The analytic solutions and the simulated results are in a close agreement with the experimental results. The results indicate that with 55N input of the proportional electromagnet, through the elastic pressure torsion coupling switching, the valve has 12N·m torque output, and the linearity of the force input and the torque output is good; the spool displacement and the input displacement of elastic pressure torsion coupling are very consistent. The application of elastic pressure torsion coupling to the 2D electro hydraulic proportional direction valve is feasible.

Abstract:The ionized air assisted cutting is a cutting method, in which the ionized air is jetted to the cutting zone to achieve a lubricating and cooling effect. Friction and wear tests together with cutting tests of 304 stainless steel were conducted in the atmospheres of air, air jet, ionized air jet and nitrogen plasma jet, respectively. The results prove that the ionized air jet has a favorable cooling and lubricating performance. The friction coefficient decreases by about 46% compared with dry friction. The cutting force and the flank wear decrease by about 24% and 69%, respectively, compared with the dry cutting. The adhesive wear and the build up edge also decrease significantly, and the friction and wear performance and the machinability of 304 stainless steel are remarkably raised.

Abstract:Bone remodeling is the process of ongoing replacement of old bone by new. The remodeling process is achieved by bone-resorbing osteoclasts and bone-forming osteoblasts. In terrestrial vertebrates, activities of these two types of cells are strictly balanced and adapt the shape of bone to mechanical stress. A simple bone remodeling model by coupling the bone formation and resorption based on Turing reaction-diffusion system weighed by local mechanical stress was proposed. This model was coupled with finite element method by using the element adding and removing process, and a new bionic topology optimization model was established. The major idea of this approach is to consider the continuum structure to be optimized as a piece of bone, and the process of finding the optimum topology of a structure was equivalent to the bone remodeling process. Uniform distribution of strain-energy density as a guideline updated the material distribution, until equilibrium was reached and then the optimal topology structure was obtained. The effectiveness of the present method is demonstrated by some numerical examples.