Abstract:In order to achieve stable operation of the free-piston engine generator, the forces status on the free-piston of the working process were analyzed. The results showed that the operation of the free-piston engine generator could be seen as a single degree of freedom damping system with forced excitations. Combining the energy conservation principle of the working process, the matching between the structure parameters and the performance parameters of free-piston engine generator was studied. Some necessary qualifications to achieve stable operation of the free-piston engine generator were obtained through coupling analysis calculation by using an energy equilibrium method. The analysis conclusion was validated on a prototype by simulation. The results showed that the movement of free-piston could reach stable operation approximately, and the coupling analysis method proposed was reasonable.

Abstract:In order to solve the matching problem, the mathematic model of starting process of free-piston engine-generator was analyzed. By simplifying the displacement and velocity of the piston, simplified expressions of driving force of linear motor was deduced. The result showed that the larger piston mass could advisably increase inertial force and decrease the minimum starting force, but reduce the maximum speed and slower the starting process. Less frictional coefficient and effective compression ratio could also reduce the starting force. With the simplified formula, the starting process of a prototype free-piston engine-generator was analyzed and the minimum starting force was achieved.

Abstract:The working process of a 1.2L low-pressure air-assisted direct injection gasoline engine was studied based on simulation. The flow of working fluid in intake port and cylinder were analyzed. The cylinder mixture concentration distribution at 20°CA between the before and after improvement of combustion chamber under different injection timings were compared. The effect of ignition timing on engine combustion process was discussed. Results show that the overall uniformity of cylinder mixture concentration distribution at 20°CA is better than the original engine, and the mixture concentration for stable ignition could be formed in the two spark plugs gap with the injection timings of 420°CA and 440°CA. With the advance of ignition timing, combustion advances gradually, the maximum cylinder pressure and the maximum pressure rise rate increase. In addition, with the delay of ignition timing, flame development duration decreases gradually, while rapid burn duration decreases at the beginning and then increases.

Abstract:Diesel engine quasi-dimensional model were corrected by test in plateau. The full-coupled working process simulation model with variable altitude adaptation on certain heavy-duty vehicle propulsion (diesel engine and auxiliary system) was set up. According to the quasi steady state flow uniformity resistance and heat transfer equations, air intaken system resistance model were established. Based on 1-D unsteady compressible fluid dynamics theory and heat transfer theory, the working model of fuel injection system was erected. Considering the effect of lubricating oil on heat transfer, the engine cooling system model was established. Auxiliary system model and the working process of the engine were coupled, that means, the boundary conditions was two-way delivered. Simulation model were verified by experiment. The results show that the power reduces by 45% and fuel consumption increases by 71% at maximum at 4500m altitude under external characteristic working condition. The heat quantity of cooling liquid in heat-flux distribution increases by 48.6%. The temperature field of piston-cylinder sleeve-cylinder head raises apparently, the peak temperature increases by 85～91K. The delivery lift of water pump drops by 3.9m at most at 3700m altitude. When the water flow grows up, the thermal load of cooling system raises.

Abstract:The effects of sparking timing on combustion process and particle emission were investigated experimentally on a gasoline direct injection engine by using combustion analyzer and DMS500 fast particulate spectrometer. Results showed that with the delay of spark timing, flame development duration decreased gradually, and rapid burning duration increased gradually. Peak value of heat release rate and cylinder mean temperature showed a gradually decrease and backward shift, which induced a slow heat release process and high cylinder temperature in expansion stroke. Also, spark timing delay led to decrease in the peak cylinder pressure. Moreover, exhaust particles from GDI engine exhibited a bimodal size distribution including nucleation mode and accumulation mode particles. As the reduce of spark advance, total particle number concentration and peak value of particle number density in nucleation mode and accumulation mode decreased gradually, and peak size of accumulation mode particles showed a decreasing trend, but spark timing exhibited a slight influence on peak size of nucleation mode particles.

Abstract:The experiment of effect of CO2 dilution on combustion characteristics of H2-CO blended fuel by using a spark-ignition engine with fixed speed was carried out. The results showed that fast burning velocity of H2 offset its lower LHV, as a result, BMEP at each equivalent ratio kept almost constant. H2 substitution also benefited for thermal efficiency, engine stability, CO and NOx exhaust emissions. Suitable dilution hardly affected BMEP and thermal efficiency, but greatly reduced NOx emission. However, excess dilution induced to partial burn, which was bad for all these parameters of BMEP, thermal efficiency and CO emission.

Abstract:In order to analyze the influence law of injection temperature on biodiesel atomization effect accurately, using self-designed high response thermocouple, the filled trough temperature variation of the soybean fatty acid methyl ester (SFAME) were measured under the rated conditions of S195 engine. In the common rail fuel injection system, the injection temperature under engine working condition was simulated. With the Malvin particle measuring instrument, the variation of droplet diameter distribution was measured under different injection temperatures. The experimental results showed that the injection temperature was 281℃ at fuel injection beginning under the stable rated conditions of S195 engine, and presented a downtrend during the injection duration. With the control of heating device of oil supply line, the Sauter mean diameter (SMD) could be decreased by increasing the injection temperature, but increase trend of SMD was slow down with the increasing injection temperature. The preheating of biodiesel before injector will increase injection temperature in the spray process later and improve the atomization effect.

Abstract:According to the characteristics of exhaust gas of diesel engine under variable conditions, a waste heat recovery system of organic Rankine cycle was designed. Under the different evaporation pressures, the effects of azeotropic mixtures and zeotropic mixtures on the performance of waste heat recovery system of organic Rankine cycle of vehicle diesel engine in variable conditions were discussed. Combined with the practical projects, the mixtures which was the most suitable for this system was chosen. The results showed that the mean value of exergy destruction rate of the ORC system using the zeotropic mixtures R415B was 38% lower than the azeotropic mixtures R508A under variable conditions. Through the comparative analysis, the zeotropic mixtures R415B was the most suitable for the waste heat recovery system of organic Rankine cycle of vehicle diesel engine under variable conditions, the maximum net power output value was about 27.60kW.

Abstract:In order to study the cavitation pattern at impeller inlet of centrifugal pump, a medium specific speed centrifugal pump was selected as an object, and a total transparent water tank was located at inlet pipeline of model pump. Based on pump product testing system and image acquisition system, the cavitation pattern at impeller inlet under three different conditions were measured on the centrifugal pump closed experimental rig. Experimental results showed that the vapors generated at suction side of blade near the leading edge at first, but the location varied with the operation condition. With the decrease of NPSHa, the vapors generated at plurality of blades. The generation, development and collapse process obviously appeared with the rotation of impeller. When the head dropped seriously, the distribution of the vapors hardly varied with the rotation of impeller, and the vapor volume fraction near impeller hub was less than that at shroud side.

Abstract:The performance of centrifugal pump with whole flow field was analyzed by using CFD technique. The blocking strategies and mesh generation on domains of the pump were presented. Numerical simulation of whole flow field model and simple model in CFX for the pump was then carried out and the reason of the difference between two models was compared. It was verified that the cavity indeed had effects on simulation results. The whole flow field model showed a higher accuracy than the simple model, and the flow pattern of two models were also different. The relationship between the sub-flowrates through front cavity and the overall performance of the pump was evaluated. The simulation results of whole flow field model and the measured results were compared. The relative errors of the head and efficiency were 0.79% and 0.9% at the normal flow rate Qd, while they were 6.24% and 9.61% at 0.2Qd. The accuracy of numerical simulation should be improved at minimal flow point.

Abstract:The effect of eccentricity and whirl frequency ratio on the internal and external characteristics of a centrifugal pump was investigated numerically and experimentally. Under a series of given rotordynamic parameters, the RNG k-ε turbulence model was applied in the simulation of whole flow field including front and back shrouds of pump. The influence of eccentricity on the external characteristics of the centrifugal pump and the impact of whirl frequency ratio on the internal flow field were analyzed. Then the distribution of the fluid-induced forces in the centrifugal pump and the effect of eccentricity and whirl frequency ratio on the fluid-induced forces in the centrifugal pump were investigated. According to the results, it could be drawn that the high efficiency area of centrifugal pump narrows as the eccentricity increases. Normal fluid force component Fn and tangential fluid force component Ft were both approximate into a quadratic function relation against the whirl frequency ratio ω/Ω, influenced by the eccentricity. The fluid-induced forces acting on the impeller were mainly generated by the internal fluid of impeller and uneven circumferential pressure distribution inside. In the centrifugal pump, when ω/Ω>0, vortexes within the impeller were less, hydraulic loss was lower and so restrained the whirling motion; when ω/Ω<0, vortexes within the impeller were more, hydraulic loss was higher and thus promoted the whirling motion.

Abstract:Slip velocity of impeller outlet for a double-blade centrifugal pump was studied with PIV technology and slip factors of six blade phases at the seven conditions were obtained. It is found that average slip factor at the six blade phases gradually decreased with the increase of flow rate. Flip factors of the double-blade centrifugal pump were calculated with Stodola formula, Weisner formula and Stechkin formula and all the results were compared with experimental values at the seven conditions. Weisner formula, whose calculation errors were the smallest, was corrected on the basis of experimental values. And a double blade impeller was redesigned to verify correct formula. The results showed that the calculation errors of corrected slip factors at the seven conditions were less than 3.5% and the maximum error was 3.23%.

Abstract:Soil dielectric property is an important physical parameter affecting the measuring accuracy and adaptation of moisture content by using FDR sensor. In order to obtain the best frequency of 7-probes FDR with length of 28mm and needle-to-needle spacing of 10mm, scattering parameters of LF-UHF wave bands (1MHz~3GHz) in four kinds of soil were measured by using VNA. Though transformation based on Logsdon model and Laird model, four soil apparent dielectric permittivities were calculated and figured in Matlab. The mechanism of soil polarization was analyzed by soil dielectric spectrum analysis. The relationship between soil dielectric property and frequency was discussed. The working frequency of 44~398MHz for FDR sensor was confirmed. Taking temperature into consideration, the ideal working frequency band was 62~110MHz in which 75MHz was the best. The soil dielectric value was only sensitive to soil moisture content under the best frequency. It was the ideal frequency for eliminating the effect of temperature and other factors on FDR sensor.

Abstract:A near infrared reflection (NIR) soil water sensor was developed for rapid measurement of soil moisture content. Light emitting diodes (LEDs), at 1940nm and 1800nm respectively, were used as measurement and reference light sources. The photodiode received the light reflected from the soil surface to produce an output electronic signal, which was related to the soil moisture content. The received signals were put into a two stage pre-amplifier, an analogue/digital (A/D) transfer, and then were displayed and stored. A certain relationship was found between the output reflected light and soil moisture content. The experiment results showed that the distance from light sensor to soil surface had some influences on the intensity of received signal. According to the sensor structure, a certain distance could be chosen to make a better intensity and stability of reflected signal. The reflectance of the two light sources decreased with increase of soil particle size. There was a strong linear correlation between the relative absorption depth and soil moisture content, and the determination coefficient was 0.863.

Abstract:Taking typical area of the Peacock River Basin as the study area, apparent electrical conductivity of soil was induced by using electromagnetic technology, and thus layered soil salinity interpreting models were built up. 3-D soil salt distribution was characterized by using 3-D ordinary Kriging method. The profile soil salt information was presented by different operation modes. The layered salinity interpreting models showed good accuracy. Soil salt distributions of different zones in this area were significantly different. Most of soil in study area belonged to moderate salinity, and some local areas were severe saline soil. Thus, the effective countermeasures should be taken to prevent and control soil salinization in this region.

Abstract:Polyacrylamide (PAM) was added to fly ash to amend sandy soil. The migration of heavy metals, such as Cr, As and Ni in soil-plant system and the influence of PAM on it were investigated, respectively. The experimental design included three PAM application rates (0, 60mg/kg and 120mg/kg) and four fly ash application rates (0, 5%, 10% and 15%). The treatment without fly ash and PAM was prepared as a control. The results showed that the addition of fly ash increased the concentrations of Cr and Ni in the surface sandy soil, while there was a decline in As concentration at high fly ash application rates (15%). The addition of PAM could stabilize a large quantity of heavy metals within topsoil to control their leaching risk as well as reduce the amounts of Cr, As and Ni absorbed by corn.

Abstract:In order to investigate the relationship between deep soil water (below 2m) vertical variation and root distribution in the nine-year-old dense jujube plantation in Loess hilly region. The soil core method and oven drying method were used to determine fine root dry weight density and soil water content. Sequential cluster analysis method was adopted to stratify the whole soil water profile into three layers, i.e. strong depletion layer (2.0~4.4m), less strong layer (4.4~5.0m) and weak depletion layer (5.0~7.0m) based on the combined analysis of soil water content and the root dry weight density. This stratification result could well reflect soil water characteristic absorbed by root. In the strong depletion layer, fine root dry weight density decreased fluctuantly with the increase of soil depth, but soil water content was low and stable. While in the less strong layer, fine root dry weight density decreased continuously, soil water content presented increasing tendency. The maximum fine root depth was 5m, there was no fine root in the weak depletion layer and soil water content increased obviously. This study determine the soil layer range of deep soil water depletion degree in densely jujube plantation. It shows that root distribution characteristic has an important effect on the deep soil water variation. 

Abstract:Over the course of one summer maize and winter wheat rotation cycle, three irrigation treatments (ground water with a quota of 52.5mm; reclaimed water with a quota of 52.5mm; reclaimed water with a quota of 105mm) were set up, and in each treatment, the soluble K+, Ca2+, Cl- and the electric conductivity (EC) leaching and migration in 0~450cm soil were studied. The results showed that the soil salinity content and EC value were in the following descending order: 380~450cm loam soil layer, 0~120cm loam soil layer, and 120~380cm sandy soil layer. Soluble K+ and Cl- in reclaimed water had a strong leaching and migration ability, and reached the 450cm depth, and the influences of reclaimed water irrigation on soluble K+ and Cl- changes were mainly in 0~450cm soil layer and 0~250cm soil layer, respectively. Soluble Ca2+ and EC reached the 380cm depth, but the influences of reclaimed water irrigation on soluble Ca2+ and EC changes were mainly in 0~120cm soil layer. The 380~450cm soil layer played a role as a block layer for soil salinity leaching, and decreased the pollution risk of soil salinity ion to groundwater. It suggested that irrigation with reclaimed water with a quota of 52.5mm, while irrigation 1 time and 4 times or less during the summer maize and winter wheat growing seasons, respectively.

Abstract:A method called “slot and hole” was proposed for preventing the soil and water loss of sloping farmland in Loess Plateau. Due to gravity load, slop surface runoff was intercepted and stored in a hole through a slot to form a soil reservoir. By applying this method, the convergence of slop runoff was avoided, and water evaporation also decreased. The loss of soil and water was thus prevented. Some skills for application of this method were pointed out. Additionally, the design standard of “slot and hole” method was proposed. Based on the principle that the corresponding standard runoff was totally stored in the hole, the reasonable layout scheme was determined, and the relationship of the diameter of the hole to the distance between two adjacent slots was obtained. Moreover, the formatting process of the hole and seepage process were simulated by employing FEM, and then the variation laws of physical and mechanical parameters of the soil around the hole were obtained. The results demonstrated that the physical and mechanical parameters of the soil around the hole varied significantly in the area of 0.4 times diameter of the hole, and the porosity and permeability coefficient of soil decreased as the dry density and deformation modulus of soil increased. The closer the area was to the hole, the smaller the porosity and permeability coefficient and the larger the dry density and deformation modulus were. After seepage analysis, the strength of the hole decreases slightly and certain deformation occurred. 

Abstract:Taking hillside orchards in Huairou district as the experimental plot, PAM and SAP were selected to apply for controlling manure pollution in this orchard. The antifouling effect of PAM on sloping field was tested by artificial rainfall experiment, and the outdoor monitoring experiment was carried out from 2010 to 2011. After applying the proposed technology, soil erosion and nutrient runoff in soil slope, also the soil water content and nutrient migration in soil profile were discussed. The results showed that PAM could reduce event mean concentration and pollution emission load of individual rainfall by 5%~8% and 16%~22%, respectively. PM treatment is the best in this experiment. Compared with control treatment PS0, chemical antifouling treatments PS1 and PS2 could promote the water content of soil root layer by 10.4% and 23.7%, increase nutrient content by 3.8% and 22.3%，reduce sediment in slope runoff by 30.7% and 61.7%，and reduce nitrate nitrogen content in slope runoff by 14.7% and 30.7%, respectively.

Abstract:Variable-rate nozzle achieves range and flow synchronous control according to the spraying shape and spray volume requirements. It has important significance on the precision irrigation. The variable nozzle with fan-shaped hole and static vane regulator was studied. Hydraulic performance, such as irrigation distribution and irrigation uniformity of variable nozzle under different pressure conditions was analyzed. Comparing with the traditional round nozzle spray domain, influence of variable vane regulator on nozzle performance and sensitivity to the working pressure were studied. The results of double factors repeated test showed that the single nozzle control area of variable precision irrigation sprinkler was reduced by 15.4% than the traditional round nozzle. The sprinkler irrigation evenness was increased by 9.5%. The sprinkler irrigation intensity was reduced by 15.7%. The range was reduced by 5.9%. The spraying domain coefficients reached to 64.0%. Combination evenness variance analysis results showed that the regulator and pressure as well as the interaction between them had significant influence. The design of the variable modifiers needs to meet the performance of nozzle under different working pressure conditions.

Abstract:Based on the model of droplet dynamics and evaporation, the simulation method of droplet flight was put forward under the wind condition. Software of simulating sprinkler water distribution was developed by Visual Basic 6.0 With the radial water distribution data of single sprinkler, the software could simulate water distribution of single sprinkler or sprinkler irrigation system and calculate combined application rate, uniformity coefficient and evaporation loss rate of sprinkler irrigation system. Taking the sprinkler 9708A as example, radial water distribution of single sprinkler and water distribution of sprinkler irrigation system with the combined spacings of 14m × 14m and 14m × 12m were simulated and compared with the measured values under the pressures of 0.20, 0.25 and 0.30MPa. The results showed that the simulated values of radial water distribution of single sprinkler had the same tendency as the measured values on the whole, the relative error between simulated and measured values of flow rate ranging from 0.83% to 8.01%, that of the uniformity coefficient (Cu) ranging from 0.44% to 7.7%, and the simulated evaporation loss rate ranging from 0.51% to 1.75%. Several cases of sprinkler water distribution with different combined spacing were compared by using the developed software and other software. The relative error of the simulated values of Cu varied from 0.11% to 2.44%.

Abstract:According to physical properties of the tar and separate requirements, a type of tar separator which is applicable to dry method of removing the tar was designed. This type of tar separator can cool and condensing the tar, at the same time separates the droplets of the tar. It can be seen from the numerical simulation results of gas flow field, the results of gas movement of heat transfer show that wall cooling has a great influence on temperature field in the cyclone separator. The temperature field also presents the characteristics that the surrounding area gradually reducing with surrounding downward flow, and the central zone rising up with centering upward flow, and the radial temperature gradually reducing in the cyclone separator. The decrease of temperature leads to the increase in gas density and the decrease in gas viscosity and the increase in the tar droplets viscosity. Wall cooling can reduce the cut size, as well as improve the separation efficiency of biomass gasification gas tar through the tar droplet separation theory and the physical analysis of tar.

Abstract:In order to improve the interfacial bonding strength of wheat straw fibers and polypropylene (PP), the wheat straw fibers were treated by combining treatment. The surfaces of fibers were pretreated by five methods, such as NaOH, soaked in acetic acid solution, hydrothermal treatment, steam explosion treatments and microwave treatment. Then, they were compounded with coupling agent treatment. The wheat straw/PP composites were prepared by melt blending and molding. The microstructure of wheat fibers after different surface treatments was observed by stereo microscope. The infrared spectroscopy of wheat straw fibers after different surface treatments was examined by Fourier transform infrared (FTIR) technology. The tribological properties of PP composites filled with different surface treated wheat straw fibers were investigated by using M-2000A abrasion testing machine. The results showed that NaOH, hydrothermal treatment and steam explosion treatments had significant impact on the chemical composition of wheat straw fiber. The tribological properties of PP composites filled with combined treated fibers excelled than that of the composites filled with coupling agent treated fibers. The main wear mechanisms of worn surfaces were abrasive wear and adhesive wear. It was found that the composites filled with hydrothermal treatment and steam explosion treatment had good tribological properties.

Abstract:Food quality safety traceability technology and its application system development are worldwide focus and hot topic. Based on the literature review, the important meaning of food quality safety traceability technology was presented. The significance, development tendency and the main characteristic were summarized from four aspects: traceability unit dividing, information collection, information transformation, and information processing. The result showed that traceable unit in food quality safety traceability technology was developed from experienced dividing to model optimization, information acquisition technology was improved from manual collection to intelligent collection, information transmission technology was changed from independent to standardized transmission, and information processing technology was changed from manual analysis to intelligent decision.

Abstract:For the existing traceability model could not express the mixing process quantitatively, the uncertain data were brought into traceability system and the model based on these uncertain data was built up. A traceability inquiry method using uncertain data was proposed. The multi-source tracing problem was solved by using basic representation and inquiry method of uncertain data. The functions of simple inquiry, node evaluation and single node abnormal deduction were achieved based on the proposed model and the solving method of multi-node abnormal deduction was presented.

Abstract:Accurate detection of agro-product quality can provide reliable basis for postharvest preservation, determining when to sell, predicting shelf-life and sorting. Laser Doppler vibrometer (LDV) technology is based on the Doppler-effect sensing the frequency shift of back scattered light from a moving surface, and has the advantages of high sensitivity, non-contact measurement, avoiding mass loading implication and so on. This technology can be used for nondestructive evaluation of agro-product quality by inspecting its vibrational properties. The development and principle of LDV technology, and its applications in nondestructive detection of agro-product quality were introduced.

Abstract:In order to explore the feasibility of hyperspectral imaging technique to estimate beef color parameters under different storage time and sampling positions, hyperspectral images of 82 representative beef samples were acquired. Color parameters, including brightness (L*), redness (a*), yellowness (b*) and saturation (C*) were also determined. Their representative spectra were obtained by selecting regions of interest (ROIs). By comparing and choosing appropriate spectral regions and pretreatment methods, optimum partial least squares (PLS) calibration models of each beef color parameters were established and evaluated, respectively. As for L*, a*, b* and C*, the correlation coefficients of calibration were 0.80, 0.91, 0.91 and 0.93, and root mean square errors of calibration were 2.23, 1.18, 0.82 and 1.12, respectively. The correlation coefficients of prediction were 0.92, 0.88, 0.87 and 0.89, and root mean square errors of prediction were 1.66, 1.45, 0.80 and 1.27, respectively. The results showed that hyperspectral imaging technique could be used to rapidly and non-destructively analyze beef color parameters under different storage time and sampling positions.

Abstract:The objective of this research was to measure firmness of‘Cuiguan’ pears on-line by using visible/near infrared spectrum, also the effect of different pretreatment methods and different points of smoothness on calibration performance were studied. The spectrometer of USB4000 was used to acquire the spectra of ‘Cuiguan’ pears at fruit moving speed of 0.5m/s, and partial least squares (PLS) was used to develop calibration. The total number of samples used was 176, and 119 samples were used as calibration set, 57 samples were used as validation set. The results indicated that it was feasible to measure firmness of ‘Cuiguan’ pears by using visible/near infrared spectrum, and wavelength range of 580~840nm was suitable for calibration. The best calibration performance was obtained when using spectra pretreated by first derivative combined with SNV, the correlation coefficient, root mean square error of calibration (RMSEC) and root mean square error of validation (RMSEP) were 0.820, 2.50N and 3.02N, respectively. For Savitzky-Golay method, the five data points obtained the best calibration, the correlation coefficient, RMSEC and RMSEP were 0.848, 2.31N and 2.85N, respectively.

Abstract:In order to achieve the fast and non-destructive detection of mini watermelon quality during growth process, the basic information collection methods for fruit measuring were analyzed quantitatively. The PLS modeling results showed that both the tissue water content and soluble solids content could obtain good results at the top position and the equator. The modeling performance had some differences with basic chemical information at different depths, but both the tissue water content and soluble solids content could got the best results in the middle information area which was under 2~3cm from the rind. The correlation coefficients of tissue water content at the top location and the equator were 0.953 and 0.924, and the RMSEP were 0.510 and 0.766, respectively. The correlation coefficients of soluble solid content at the top location and the equator were 0.952 and 0.929, and the RMSEP were 0.666 and 0.732, respectively. For the mini Jingxiu watermelon, the best foundation information area for NIR detection was the middle area.

Abstract:In order to quickly detect rice moisture content, a uniplanar capacitor probe was designed. A corresponding converting circuit was also designed for getting digital value of capacitance. The rice moisture content was converted into capacitance and digital value in turn by the capacitor probe and converting circuit. Finally, the rice moisture content was obtained by using single chip. After the calibration experiments and temperature characteristics experiments, the results showed that prediction error of moisture content was within ±0.8% at the range of rice moisture content of 8%~23%. With the temperature of 12~33℃ and rice moisture content of 12.86%, the temperature shift value was 0.2%/℃.

Abstract:Based on the theoretical analysis of flow characteristics between superheated steam and granules materials in the fluidized bed drying chamber, the fluidization experiment with superheated steam and hot air was conducted by using the dried rapeseed particles as the experimental material. A small experimental device was established. The experimental results showed that the operating velocity of superheated steam fluidized bed drying was faster than the traditional hot air fluidized bed dying under the same conditions. Under the given conditions, the critical fluidization velocity of the rapeseed particles was 1.26m/s during superheated steam fluidized bed drying.

Abstract:In order to make sure the distribution of Alicyclobacillus from apple libraries in Shaanxi province, the Alicyclobacillus in apple and air were isolated and purified by using acidified AAM medium. The cell morphology, colony morphology, growing conditions, cultural characteristics and physiological characteristics were compared with the reference strain A.acidoterrestris DSM3922T. A phylogenetic tree based on 16S rDNA sequence analysis was constructed. The genetic location of eight isolated strains was clear. The isolated strain LC-4 was basically consistent with the reference stain Alicyclobacillus acidoterrestris DSM3922 T in morphology and physiological characteristics. By 16S rDNA sequence analysis, isolated strain LC-4 shared a homology of 99% with the reference strain, so it belonged to A.acidoterrestris and the other seven strains belonged to Bacillus ginsengihuimi. The results suggested Alicyclobacillus was distributed in orchard soil, which might pose a threat to the quality of fruit juice, and needed to be controlled.

Abstract:The microbial growth kinetics model at constant temperature was built up. The effect of variable temperature on microbial growth state was found. Then the recorded variable temperatures were processed. Microbial growth kinetics model combined with Baranyi model under variable temperatures was obtained. A simulation experiment was also carried out to validate the accuracy of model. The determination coefficient was 0.956, the root mean square error was 0.165, the deviation factor was 0.994, and the accuracy factor was 1.134. The results showed that the model was adaptive to predict the growth of microbiology in the actual cold chain logistics.

Abstract:A theoretical model to evaluate total ammonia concentration in recirculating aquaculture system was established by investigating the relationship between impact factors of total ammonia. Subsequently, a system dynamics model for total ammonia in the recirculating aquaculture system was developed based on the theoretical model. The dynamics of total ammonia concentration in a culture pond during the breeding process was simulated by using STELLA simulation software. The simulation results were consistent with the measured values approximately, indicating that this model could simulate the experimental system to a certain extent and could provide suggestions on design and operation of the recirculating aquaculture system.

Abstract:Great hazards could be easily caused by high concentrations of ammonia in chick houses, which are almost inclosed and heated up with low ventilation rate. A technology of in-situ unpowered biofiltration was studied to remove ammonia gas in chick houses. Analytical parameters included inorganic nitrogen compounds, pH value, and electrical conductivity (EC) of the superficial and inner media. Results of 37d operation in synchronization with a whole circle for chick brooding showed that, in the superficial media, the maximum ammonia elimination capacity was higher than 4.03g/kg, the maximum ammonium nitrogen absorption ability achieved 1.59g/kg, the highest nitrate nitrogen content achieved 2.69g/kg, and nitrite nitrogen content was nearly 0, pH value showed a decreasing trend in the range of 8.81～7.39, and EC kept increasing with the highest increment of 2.30mS/cm. However, the contents of ammonium, nitrate and total inorganic nitrogen as well as EC in inner media were far lower than those in superficial media. It suggested that further work should be done towards optimization of media depth setting. In conclusion, in-situ unpowered biofilter exhibited high ammonia elimination capacity and could be applied for contaminated air degradation in chick houses.

Abstract:A real-time motion detection method based on stereo vision was designed in order to meet the need of precise navigation for intelligent agricultural vehicle. Multi-thread feature points detection was used to improve the efficiency of traditional SIFT algorithm. Normalized comprehensive distance algorithm (NCDA) was used to delete the error matched points. Finally, vehicle motion was calculated by the position variation of feature points in adjacent moment. Experiments showed that the average detection time spent was reduced and computing efficiency was raised up. Error matched points were successfully recognized and erased by NCDA. Measurement errors in one time were less than 0.0045m in x and z axis when the speed was 0.8m/s and image grabbing frequency was 5Hz. Measurement errors in x andzaxis were less than 0.15m when the vehicle kept moving for 10s.

Abstract:De-noising of near infrared image and nonlinear estimation of nitrogen content were carried out to cucumber leaves in greenhouse. Fruit cucumber Deitastar was chosen as the object. A CCD camera with special filters was used to collect cucumber leaves’ images in different growth time. After eliminating noise of image with wavelet transform, the images were separated based on grey theory. Correlation analysis between nitrogen content and each kind of vegetation index of cucumbers was conducted, and t tests to those coefficients of correlation were executed. The result showed that CNDVI, GNDVI, NDVI and NDGI were significantly related to nitrogen content of cucumber leaves. The correlation coefficient between CNDVI and nitrogen content of cucumber leaves reached 0.67, and the correlation coefficients between GNDVI, NDGI, NDVI and nitrogen content of cucumber leaves were all higher than 0.50. LS-SVM algorithm was used to construct estimation models between vegetation indexes and nitrogen content and CNDVI, GNDVI, NDGI and NDVI were used as the input of the model. The R2 values of calibration and validation models were 0.825 and 0.728 respectively.

Abstract:Based on the method of adaptive global threshold and markers fusion, an algorithm was proposed in order to solve the problems of over-segmentation and the under-segmentation caused by incomplete marking, which might occur concurrently during the segmentation of remote sensing building images. First, the algorithm was used in wavelet transform to generate image gradient according to the distribution and texture characteristics of buildings, and the generated gradient image was filtered through morphological reconstruction. Then, the background markers were extracted by local minimum and the building makers by adaptive global threshold. After both markers were fused, they were used to modify the weighted pixel Sobel gradient image for accurate image segmentation. The experimental results demonstrated that the algorithm could make up for a lack of the local extreme marker, and significantly inhibited both over-segmentation and the under-segmentation. As a result, the segmentation accuracy reached to 90.7%.

Abstract:The existing methods of leaf area measuring would cause certain damage to the leaf, so a measurement method of the leaf area in natural growing state was put forward. The digital camera was calibrated to get camera parameters; then leaf images at various angles in natural growing state were shot and processed by PhotoModeler software. The 3-D point cloud model of leaf was built up. The 3-D surface modeling and surface area calculating of leaf were achieved by using Matlab software. The measuring results and the calculating results with combination method of scanner and Photoshop software were compared. It showed that the accuracy of calculating results reached to 99%.

Abstract:The tree crown volume is difficult to measure and calculate because of its irregular shape. A calculating method of tree crown volume, named voxel simulation method, was presented based on 3-D laser scanning point clouds data. The main idea of this method was to use a certain size of voxel to estimate tree crown. Firstly, tree crown was cut into segments with a k step-length along tree height. For each segments, all the points were projected to a plane that perpendicular to tree height. Subsequently, the plane was divided into pixels with size of k×k. The effectiveness of each pixel depend on whether there were points projected in it. Then the effective pixels were counted and recorded as T. Finally, formula T×k×k×k was used to calculate the tree crown volume. When the k was equal to a tenth of crown diameter, the calculated crown volume was tending to stability. This algorithm did not need to consider the crown shapes of different tree species, which could reduce human’s subjective factor influence. It could be used to calculate tree crown volume based on 3-D laser scanning technology. 

Abstract:In order to improve the measuring accuracy of tree’s diameter at breast height (DBH) and decrease the working load, an algorithm for measuring tree’s DBH was proposed by combining the optical triangular method, image processing and least square fitting. The algorithm was proposed based on a series of theory analysis, and the measuring system was built up. Five trees with different diameters at breast height were measured and calculated. The testing result showed that the optical triangular method had higher accuracy, the error was less than 22mm, and the relative error was less than 5.5%.

Abstract:There has been a series of significant advances and applications in terahertz (THz) technologies which processes perspectivity, safety and spectroscopic fingerprinting ability. The unique properties of THz waves make them become tools for non-destructive detection and application in the fields of defense, industry, semiconductor, communication, biological medicine, pharmaceutical, agro-products, food and etc. Firstly, the principle and feature of THz spectroscopy and imaging techniques were introduced. Then, the non-metallic material characterization and defect inspection in foam and fiber composites were stated. The recent application of THz in agro-products and food was introduced mainly. Finally, the technology difficulties and issues of the THz technologies were analyzed, and their development prospects in the non-destructive detection field were presented.

Abstract:A comprehensive survey of the up-to-date methods and technologies for 3-D CAD model retrieval was presented. Firstly, the architecture of 3-D CAD model retrieval system was introduced, and a detailed survey on current 3-D CAD model retrieval was given from text-based retrieval, content-based retrieval and semantic-based retrieval. Then, the existing 3-D CAD model retrieval system and the application of 3-D CAD model retrieval were also introduced. Finally, some challenges and the future directions of 3-D CAD model retrieval were indicated. The proposed CAD retrieval technology provided fully retrieval support for conceptual design, detailed design, polytechnical design, and product design. It also enforced the capability of enterprise product model designing and reuse of manufacturing information.

Abstract:The rut geometric analysis is necessary for studying the interaction between the driving wheel and the loose soil. A laser scanner that consisted of a laser sensor and a 2-D traversing frame was developed to measure the digit parameters of ruts in the soil bin which were produced by the rigid wheel on loose soil. The maximum scanning area was 650mm×400mm, measurement range was 0.05～65m and scanning resolution was 0.1mm. A laser scanner with 1-D traversing frame which might be more appropriate for the measurements of rut deformation in the infield of rover was also discussed. The experimental results showed that the scanners could obtain the sections and the 3-D graphics of the surface of ruts by using contactless measuring method without disturbing the ruts. 

Abstract:Nonuniform distribution characteristics of random points generated by Monte Carlo method in the workspace of parallel manipulators were discussed. Based on the density of distribution of the multiple random variable function, the relationship between Jacobian matrix and the probability density function of workspace points generated by Monte Carlo method was deduced, and the relationship between the probability density of the output space and the manipulability of the parallel manipulator was also constructed. The manipulability of a 2-DOF 5R parallel manipulator was analyzed based on the Monte Carlo method. According to the working mode of the robot, the input space was divided into four subspaces, and the inverse singularity occurred in the boundary among different subspaces was pointed out. Simulation experiment illustrated that the Monte Carlo method could work well for manipulability analysis of parallel manipulators.

Abstract:Compliant joint is mostly applied in the field of micro-operations. Instead of traditional kinematic pairs, compliant joints were designed by using method of structural parameters to satisfy the experimental requirement, and a parallel robot with compliant joints was proposed. Combined with the control unite and OPTOTRAK measurement, the experiment system of a 3-DOF compliant parallel robot was set up for the mechanism dynamics modeling, analysis, design, planning, and control system. The experimental study of the parallel robot with compliant joints was presented, compared to that with revolute joints. Through comparative analysis, relative errors of the experimental index were controlled within the allowable range. The experimental result showed the validity of compliant joints in replacing the kinematic pairs of parallel robots.

Abstract:Traditional noise reduction method for axial piston pump by optimizing the transition area in the valve plate is based on specific structural parameters, which is of less meaning for valve plate design. The formation mechanism of the noise excitation sources of hydraulic noise and structural noise for axial piston pump was discussed. Then, aiming at elimination of the pressure overshoot in piston chamber, and control of the peak value and position of backflow into piston chamber, a forward design theory of distribution method with damping orifice and damping groove for axial piston pump was proposed. Finally, a valve plate was designed based on this design theory. The noise reduction effect of this valve plate was analyzed. Results showed that the application of this design method could reduce the flow ripple amplitude apparently and the pressure overshot could be almost eliminated. Because the structure of the damping groove was not appointed, this design theory can be used in the valve plate design of different domestic axial piston pumps.

Abstract:By using fixed/floating coordinate system and the support function method, the instantaneous 1-D linear area and interval sets were proposed. The rise motion, return motion and whole motion interval sets were put forward. The basic principles of solving the allowable selected area of the flat-faced line and the allowable value range of the cam basic radius were proposed. The analytic formulae were derived. Then the analytical criterion of the solution existence and its existing form were obtained. The class Ⅱ synthesis of disc cam mechanism with flat-faced follower in planar motion was resolved. 

Abstract:With the realization automation assembly for the tractor of driving wheel axle, the control method of fuzzy predictionwas proposed for self-locking bolt tightening assembly. According to the bolt tightening characteristic, the clamping force, torque and angle were predicted, and the self-locking bolt tightening process for the tractor of driving wheel axle assembly were controlled by using the embedded assembly controller. Moreover, the positioning device of lock blade and assist device were designed with combining the technology of fiber optical sensor detection and mechanical design. By the application of intelligent fuzzy control arithmetic, the multivariable target fuzzy intelligent control for axial pre-tightening force, self-locking bolt tightening torque and angle position of driving wheel axle were achieved. Verified by the actual production process, a self-locking bolt assembly question with the function of lock blade positioning was resolved. It had higher prediction accuracy and improved the assembling quality and efficiency. 