Yu Zhenhuan , Liu Shunan , Zhang Na , Li Wanlin
2014, 45(1):1-7. DOI: 10.6041/j.issn.1000-1298.2014.01.001
Abstract:The electromagnetism(EM)-fluid and fluid-structure interaction (FSI) modeling and solving method of shock absorber were studied. Adina software was used to establish accurate structure finite element mesh model and the finite element mesh model of EM-flow field based on EM-fluid and FSI method. Post-processing module of adina software was used for solving analysis. The velocity characteristics, indicator diagram, magnetic field distribution characteristics, core area fluid pressure field and velocity field characteristics of shock absorbers were obtained under the state of MR damper non-controlling and energized condition. The results show that under the high-speed impact of the shock absorber MR fluid and the core area fluid pressure field are changed significantly. According to the magnetic field distribution characteristics, self-designed mono tube MR damper structure can enlarge damping force adjustment range. The EM-CFD and FSI model is closed to the physical reality because of the consideration of turbulent flow of MR fluid; so the simulation results are in good agreement with the experimental results.
Zhu Yuan , Wu Sibei , Wu Zhihong , Lu Ke
2014, 45(1):8-13. DOI: 10.6041/j.issn.1000-1298.2014.01.002
Abstract:A precise torque closed-loop control method based on torque estimator for interior permanent magnet synchronous motor (IPMSM) was presented to improve the torque precision. MRAI (Model Reference Adaptive Identification) method of the IPMSM, which is based on the theory of Popov stability, was derived and analyzed. In order to improve the response speed of the system, the method of pole placement is was proposed and adopted. The effect of the adaptive model’s control parameters on MRAI’s system response speed was researched. The validation and theoretical analysis were carried out in this study. The simulation and experimental results show that the permanent magnet flux and the stator resistance could be identified accurately; the actual torque can be estimated by torque observer according to the result of parameter identification. So base on this and the torque command, the torque closed-loop control system was built the torque command. Therefore, the torque control precision of the driving system could be improved even the permanent magnet flux is changed, at the same time, the driving performance of EV is fulfilled and guaranteed.
Lai Xiaoliang , Guan Cheng , Xiao Yang , Zhong Guangxu
2014, 45(1):14-20. DOI: 10.6041/j.issn.1000-1298.2014.01.003
Abstract:By analysis on the principle and structure of the parallel hydraulic hybrid excavator, an improved hydraulic hybrid scheme was proposed which uses a two-way hydraulic motor to replace the hydraulic secondary regulation pump and controls the assistant power loop by switching valve in different states. After modeling the new system with Simulink software, the parameters of the components and control method were determined. The double speed points control strategy was test on the improved parallel hydraulic hybrid excavator. The engine speed and the output torque of the assistant hydraulic power system were adjusted by an engine speed PID control method integrated with the load forecasting. The simulation and experiment results showed that the control method could effectively improve the engine speed fluctuation in the hydraulic hybrid system, and make the speed stable near the target speed, so energy-saving increases by 14%.
Lin Tianliang , Ye Yueying , Liu Qiang
2014, 45(1):21-26. DOI: 10.6041/j.issn.1000-1298.2014.01.004
Abstract:To improve the efficiency of driving system applied in hybrid or electric hydraulic excavators, a parameter matching method was developed to optimize the system which is adopting the pump controlled technology with energy recovery technology.Structure and working condition were analyzed as well. Then, considering the saving the space of energy accumulator when installed, flux matching of the cylinder when boom goes up asymmetrically and extending the working life of the energy accumulator, parameter matching of the low energy density of the accumulator, motor, generator etc. for the energy-saving system proposed was discussed. The matching results were analyzed using the model built in AMEsim software. The results show that the close loop energy-saving can be around 55% because there is no throttling loss and the potential energy of the boom can be regenerated. Not only can the excavator boom be controlled without valve but also the energy recycles under the negative pressure condition for excavator.
Chen Hanyu , Zuo Chengji , Wang Zuofeng , Wang Duidui
2014, 45(1):27-33. DOI: 10.6041/j.issn.1000-1298.2014.01.005
Abstract:In order to break through the “NOx-Soot” trade-off curve bound of the diesel engine, a new diesel engine combustion mode in the O2/CO2 environment is proposed. The pressure, temperature fields distribution of the cylinder and the power performance of the engine were simulated by AVL-FIRE software. The influence of various parameters on the engine combustion characteristics were analyzed, so the optimal O2/CO2 mole percent was obtained. Finally, the visualization research of combustion process in cylinder was carried out on the optical engine test bench. The simulation results indicate that when the injection advance angle is unchanged, fuel can’t be ignited or burnt as O2 is below 50%, and the mole percent that 65% O2 and 35% CO2 is the optimum in this scheme;when the injection advance angle is changed, the scheme that 50% O2 and 50% CO2 is the optimum. The visualization tests show that the average temperature in cylinder is lower at the maximum pressure rise rate and the maximum heat release rate, nevertheless the average temperature in cylinder is slightly higher at the peak pressure in the O2/CO2 environment compared to that in the normal intake environment. The diffusion combustion speed during the main combustion period approximately increases by 37.6% in the O2/CO2 environment compared with that in the normal intake environment.
Wang Ling , Wang Xin , Liu Jian , Wang Shumao
2014, 45(1):34-39. DOI: 10.6041/j.issn.1000-1298.2014.01.006
Abstract:With the features of wide distribution, adverse environment and large numbers of agricultural machinery in our country, it could cause a lot of manpower and material consumption to use technologists to follow-up and detect agricultural machinery for long-term, and it is low level of automation. Also there are some problems such like high cost, poor accuracy in acquisition and energy-wasting in the traditional online monitoring methods. Thus, a remote monitoring system for a group of agricultural machinery was established. Remote data acquisition integrated with GSM and GPS technology and engineering signal receiver were consisted in the hardware device; and the features such like automatic monitoring of operating status, harvesting areas and geographic information, and data uploads actively were implemented. Flexible remote data monitoring centre based on LabWindows/CVI was developed using a shared set of parameters architecture, and specific measurement and control software aiming at different kinds of agricultural machinery group and different tasks could be efficiently developed by users. The goals of real-time displaying of uploaded data, saving data, accurate positioning of geography information and following of running track were realized by monitoring center. Combined with a Microsoft Access database management system, dynamic combination and centralized group management of agricultural machinery were realized. Through a field test, it shows that the requirements of on-site real-time data transmission and accuracy data collection of agricultural machinery are implemented by the system. By the shared set of parameters of architecture, the efficiency of software development for object-oriented measurement and control system is greatly improved.
Li Jingbin , Chen Bingqi , Liu Yang
2014, 45(1):40-45. DOI: 10.6041/j.issn.1000-1298.2014.01.007
Abstract:An image algorithm to detect the navigation route and the filed end while the cotton plastic film mulch planter was working in the field was studied. The method of Daubechies wavelet transform was used to smooth and filter the image of the cotton sowing operation under the natural environment. The trough of the vertical cumulative histogram in the image processing region was detected in the first frame image. Based on this, the candidate points were detected scanning from the bottom row of the image to the top by using the method of detecting the trough of the local window cumulative histogram. For other frame images, the candidate points were detected segment by segment by the association between the navigation route of the current frame and that of the previous frame. Then the navigation route was fitted based on the passing a known point Hough transform (PKPHT). The experiments showed that the algorithm could quickly and accurately detect the navigation route and the field end while the cotton plastic film mulch sowing work. The average processing time of each frame was 72.02ms, which could meet the actual sowing work requirement of the film mulch planter.
Cong Jinling , Yu Jiajia , Cao Xiuying , Liao Yitao , Liao Qingxi
2014, 45(1):46-52. DOI: 10.6041/j.issn.1000-1298.2014.01.008
Abstract:To improve the use efficiency of seeder,a pneumatic precision metering device for rapeseed and wheat was designed in view of the adjacency of sowing time of rape and wheat in Yangtze river valley,and a new kind of structure of wheat seeding plate with seed guiding strips inlaid was presented. The working principle,main structure and performance parameters of the pneumatic metering seeder were analyzed and determined; experimental study on the relationships between main performance indices and rotating speed of seeding plate,negative pressure in sucking chamber and positive pressure in releasing chamber were carried out. The test indicated that the device works well with both rapeseed and wheat seed; the wheat seeding plate inlaid with guiding strips enhances wheat quality index by 27.31% and reduces missing index by 25.86%; for precision sowing rapeseed,when the rotating speed of seeding plate is 18r/min,negative pressure, positive pressure,the quality index and the missing index 〖JP3〗are -2200Pa, 400Pa, 90.02% and 2.59%, respectively; for precision sowing wheat seed, when the rotating speed of seeding plate is 15r/min,negative pressure,the quality index of single row and the missing index are -2300Pa, 90.62% and 2.96%, respectively. And the test in field indicated that the device is provided with highmetering accurateness and meets agronomic requirement of planting rapeseed and wheat.
Li Ping , Liao Qingxi , Li Lei , Han Cairui , Huang Peng , Li Haitong
2014, 45(1):53-58. DOI: 10.6041/j.issn.1000-1298.2014.01.009
Abstract:For the problem of the high lose rate of rapeseed with different mature degree by the combine harvester and its short period of harvest, 4SY-1.8 rape windrower was designed ,and a new kind of combined stem conveyer, which integrates the stem convey both in longitudinal and transversal directions, was presented.The overall structure and the working principle of the main parts of a rape windrower were analyzed and the parameters of key components were confirmed such as the reel, the cutting device, the conveyer and vertical roller etc. The field test indicated that rape windrower could harvest mechanical direct-seeding rape and manual direct-seeding rape. When the windrower harvests mechanical direct-seeding rape, the upper windrowing angle and the lower angle of rape stalks are 23.6° and 17.1° respectively, and the difference between both angles is less than 10°, at the same time, the root difference is less than 0.12m. When the windrower harvests manual direct-seeding rape, the upper windrowing angle of rape stalk was is less than 5°while the lower was is less than 2°, and the difference between both angles is less than 5°, furthermore, difference between the rape root is less than 0.1m. This study indicates that swath quality could meet the requirements of the harvesting quality standards and the agronomic requirement.
Liu Jizhan , Xu Xiuqiong , Li Pingping
2014, 45(1):59-64. DOI: 10.6041/j.issn.1000-1298.2014.01.010
Abstract:With the aim to verify the feasibility of cutting peduncles with laser beam in harvesting robot, several laser drilling and cutting experiments of cucumber peduncles were conducted with a 30W fiber-coupled semiconductor laser in view of different factors. It was found that the laser focusing spot with heat power density of only 0.75W/mm2 could drill through a cucumber peduncle, and a successful drilling could be achieved even if diameter of peduncles, defocusing distance, or incident angle of laser beam changed within a large range. However, 23.73~28.13s was necessary to cut a cucumber peduncle when pointing a 14.94W semiconductor laser beam vertically without any defocus at the peduncle surface. It is not an ideal vaporizing but a burning process to cut peduncles attributed to the much worse beam quality of semiconductor laser, and it is believed that a Nd:YAG or fiber laser can achieve high speed cutting of peduncles, which can supply 102~103 times higher heat power density of focusing spot.
Lü Jidong , Zhao Dean , Ji Wei
2014, 45(1):65-72. DOI: 10.6041/j.issn.1000-1298.2014.01.011
Abstract:In order to lessen picking time of apple harvesting robot,the fast tracing recognition method of target fruit for apple harvesting robot was researched. Firstly, the first collected image was segmented by the OTSU dynamic threshold segmentation method based on R-G color feature, and the picking target fruit was determined based on the principle of the nearest to image center. Next, the target fruit in the follow images were traced and recognized with the improved fast mean-residual normalized product correlation template matching algorithm while the region of image process idea was smaller frame-by-frame continuously according to the correlated information between the acquired images. At last, the comparative tests, which took into account of different threshold segmentation methods, different matching recognition by gray value, brightness and contrast, and the recognition time with the new and old methods, were done, and results from experiments indicated that the method used is viable, decreases by 36%.
Zhang Desheng , Wang Chuan , Shi Weidong , Pan Dazhi , Zhang Guangjian
2014, 45(1):73-78. DOI: 10.6041/j.issn.1000-1298.2014.01.012
Abstract:In order to put forward the impeller cutting law of double channel pump, two kinds of double channel pumps with the specific speed of 77 and 122 were selected as research objects. The impeller was cut as five times respectively and the performance experiments of double channel pumps were conducted. By investigating the change law between the performance parameters and the impeller diameter at optimal point and dead point, the corresponding value range and equation of cutting index were obtained. Results show that the flow rate, head, shaft power and efficiency reduce with the decrease of the impeller diameter. However, as the increase of impeller cutting percentage, the change law and the reducing amplitude of performance parameters at optimal point are different, and head and shaft power obviously decrease with the decreasing of the impeller diameter at dead point. The cutting index number of double channel pump at dead point can be viewed independent of the specific speed while the change of the cutting index number is obvious with the change of the specific speed at the optimum and common points. The predicted value of the cutting law according to the impeller cutting law established agrees with the experimental value well.
Pei Ji , Wang Wenjie , Yuan Shouqi , Meng Fan , Chen Jia
2014, 45(1):79-83,88. DOI: 10.6041/j.issn.1000-1298.2014.01.013
Abstract:To decrease the flow unsteadiness in pump hydraulic design procedure as much as possible, the inner flow unsteadiness intensity and distribution should be understood. For analyzing the unsteady flow phenomenon in low-specific speed centrifugal pump, CFD software was employed to simulate the 3-D unsteady fluid flow in the pump, and meanwhile the time-averaged unsteadiness intensity coefficients were defined based on velocity triangle in order to directly depict the flow unsteadiness. By analyzing the distributions of the intensity coefficients in the low-specific speed pump, the results show that stronger flow unsteadiness can be found near blade suction side, and in the wake flow area the flow varies with time strongly. In addition, strong flow unsteadiness is also significant in the discharge tube and the area near impeller outlet of the volute.
Zhang Renhui , Guo Miao , Yang Junhu , Liu Yi , Li Rennian
2014, 45(1):84-88. DOI: 10.6041/j.issn.1000-1298.2014.01.014
Abstract:A new inverse method for centrifugal pump blade based on free-form deformation, which is used to parametric control of the pump blade shape, was proposed. The blade was implanted to a trivariate control volume which is equally subdivided by control lattices. The control volume can be deformed by moving the control lattices in it, thereupon the object is deformed. The parametric method for the blade shape according to the distribution of the blade load was proposed, and the lattices deformation function was constructed. The deformation of the lattices was implemented according to the three dimensional turbulent flow solve in pump and the desired load distribution of blade. At last, the blade shape was controlled by the physical parameters. The calculation case shows that the proposed inverse method based on FFD method is rational.
Chang Shuping , Shi Yanfeng , Zhou Chen , Ding Jiangming
2014, 45(1):89-93. DOI: 10.6041/j.issn.1000-1298.2014.01.015
Abstract:In order to improve controllability of mixed-flow pump performances during the design process, effects of exit circulation distribution on design of mixed-flow pump impeller were researched. Based on three-dimensional inverse design theory, the meridional derivative of circulation Vur was chosen for the control parameter of blade loading distributions. Three impellers were designed, whose exit circulations were respectively averaged-loaded, rising-loaded and falling-loaded. The RANS equations embedded with SST turbulence model were solved by using multiple-reference-frame model to simulate flow field of the three pumps. The pump efficiency and cavitation, total pressure and meridional velocity at the impeller exit were compared and analyzed. The results show that the rising-loaded pump has the highest efficiency but the worst cavitation performance, and performances of the falling-loaded pump are just on the contrary. The three-dimensional inverse design theory with adjustable exit circulations can effectively adjust the work abilities at different blade heights. Both the total pressure and meridional velocity at the rising-loaded impeller exit the rapidest increasing velocity with the radius rising.
Wei Zhengying , Yuan Weijing , Zhou Xing , Zhao Guangxi
2014, 45(1):94-101,107. DOI: 10.6041/j.issn.1000-1298.2014.01.016
Abstract:With superior hydraulic performance, the pressure compensating emitter (PCE) has extensive application in mountain and hill regions where the hydraulic pressure in irrigation systems often changes greatly. Because of the complicate structure, PCE design mechanism is still not clear. There’s a big difficulty in developing new types of PCE products even with high cost, which also makes it almost impossible to popularize PCE in China. The application and research status of PCE in both China and foreign countries was overviewed in order to supply a clear understanding to the readers. An improved development route for PCE was proposed on the base of combining several advanced techniques including numerical simulation, rapid prototyping (RP) and visualization experiment. Then the key problems involved in this route were discussed. And problems proposed in some early papers were solved. For the compensating mechanism is the key problem in PCE design and development, through part work of our team, it was pointed out that numerical simulation with fluid-structure interaction method, which provides us with pressure and velocity distribution, was an effective way to solve this problem.
Xu Jinghui , Ma Xiaoyi , Sally D Logsdon , Robert Horton
2014, 45(1):102-107. DOI: 10.6041/j.issn.1000-1298.2014.01.017
Abstract:The soil dielectric spectrum are related to the soil physical properties, and those are affected by the structure of the probe too. In order to determine how the probe structure influence the soil dielectric spectrum measurement, the two kinds of soils were measured at four water content level by 10mm and 14mm spacing needle at 28mm probe length, 28mm and 45mm length needle at 10mm spacing. It has been confirmed that the probe spacing has no effect on the soil dielectric spectrum measurement above 31.2MHz by comparing the dielectric spectrums, and the length of the probe can affect the real or imaginary part of the soil dielectric spectrum in the range of 0.001~3GHz. The research shows that the spacing of needle is not the key factor to the soil dielectric property measurement within a certain spacing, and the length of the probe has a greater influence on the soil dielectric property measurement. The smaller of the probe length, the larger of the dielectric relaxation frequency. Therefore, the probe length is the important factor that affect soil dielectric measurements. The FDR probe should be shorter, it is good to improve the measurement accuracy and environmental adaptation.
Nie Weibo , Fei Liangjun , Ma Xiaoyi
2014, 45(1):108-114. DOI: 10.6041/j.issn.1000-1298.2014.01.018
Abstract:Based on the furrow irrigation which was conducted in Yangling District with the clay loam and sandy loam, effects of different combinations of soil infiltration characteristics and Manning roughness on the water advance trajectory and irrigation performance were analyzed. The results show that the spatial variability of soil infiltration characteristics has a great effect on the water advance trajectory and irrigation performance. When optimizing the design of the furrow irrigation, the spatial variability of soil infiltration characteristics must be taken into consideration. However, the spatial variability of Manning roughness affects slightly on the water advance trajectory and irrigation performance. When optimizing the design of the furrow irrigation, the average value of Manning roughness can be used in various irrigation ditches. Based on the above results and verified field experiments, the results show that the average relative error between the measured and simulated values of the water advance trajectory is 7.28%, and the application efficiency, distribution uniformity and storage efficiency between the measured and simulated values are 5.74%, 6.18% and 4.07%, respectively.
Gao Guanglei , Ding Guodong , Zhao Yuanyuan , Feng Wei , Bao Yanfeng , Liu Ziwei
2014, 45(1):115-120. DOI: 10.6041/j.issn.1000-1298.2014.01.019
Abstract:To reveal the effects of biological soil crusts (BSCs) on soil particle size characteristics in Mu Us Sandland, soil samples under algae, lichens, and mosses crusts as well as the uncovered sandland were selected in Yanchi research station. Soil particle size distributions were identified by using laser diffraction technique. Particle size parameters were subsequently calculated including average particle size, standard deviation, skewness, kurtosis and fractal dimension. The results indicate that the majority soil particle size is occupied by sand particles approximately accounting for 80%~95% of the total volume; accordingly clay and silt particles contents are much less; soil particle size distributions in different sites are comparatively centralized that resulted in poor sorting, very positive skewness as well as sharp or very sharp kurtosis; the fractal dimension of soil increases progressively across the successional stages of BSCs in range of 2.15~ 2.30. In short, as affected by BSCs, clay and silt particles continue to increase leading to constantly particle distribution optimization, and soil particle size distribution inclines to uniform and symmetric pattern. Therefore, BSCs are beneficial to soil improvement and development, but rather slowly.
Wang Lishu , Yue Linlin , Tang Zejun , Zhang Xin
2014, 45(1):121-128. DOI: 10.6041/j.issn.1000-1298.2014.01.020
Abstract:Shiyang River Basin is located in the east of Hexi Corridor in the Gansu Province. It is one of the most serious water shortage and ecological vulnerable regions. Finding out the relationship between groundwater and natural conditions and human activities has important practical significance to research and solve the water resource utilization and ecological problems. Regression analysis method was used to study the influence of the basin climate change and agricultural production and development to the groundwater level in Shiyang River Basin. The results indicate that rainfall and evaporation have a small impact on groundwater in the long run. The influence coefficient of rainfall and evaporation on the groundwater level in Wuwei region was below 0.004, meanwhile the influence coefficient was below 0.001 in Minqin region. However,runoff and change of grain yield are the primary causes of decline in groundwater level. The coefficients of runoff impact on the groundwater level in Wuwei and Minqi region were 1.381 and 6.008. At last, through the least squares regression model, an equation was determined, which describes the relationship between groundwater level and runoff, total output. The model has higher simulation accuracy after verification. Wuwei average groundwater level forecast to fall 0.945m per year, while 0.919m per year in Minqin in the future.
Lü Yue , Wu Pute , Chen Xiaoli , Wang Yubao , Zhao Xining
2014, 45(1):129-136,142. DOI: 10.6041/j.issn.1000-1298.2014.01.021
Abstract:The nutrient uptake, photosynthesis and yield of different separation methods were measured to analyze resource competition from above-and below-ground interaction. The treatments included no shoot or root separation (T1), shoot and root separation (T2), root separation (T3), shoot separation (T4), sole maize (T5) and soybean (T6). The land equivalent ratios of grain yield and biomass were 1.23 and 1.20 for T1, 0.97 and 0.91 for T2, 1.01 and 1.02 for T3, 1.10 and 1.08 for T4, respectively. Competiveness of maize relative to soybean was 0.79 for T1, -0.08 for T2, 0.14 for T3 and 0.39 for T4, respectively. The nutrient competitive ratios of maize relative to soybean were 1.63, 1.92 and 1.50 for T1; 1.05, 1.03 and 1.06 for T2; 1.28, 1.32 and 1.27 for T3; 1.47, 1.43 and 1.36 for T4, respectively. Except the jointing stage, the Pn, Tr, Gs and Ci of maize were the highest for T1; and the values for T4 were the second; and the values for T2 and T3 were remarkable lower than that for T1. Except the branching stage, the parameters of soybean were the lowest for T1, and the values for T2 and T3 were significantly higher than that for T1. In summary, as for maize/soybean intercropping advantages, the interactions of above- and below-ground parts was greater than that under the action of a single factor, and there was greater role from below-ground part than above-ground part.
Gou Mangmang , Qu Zhongyi , Yang Xiao , Zhang Dongliang
2014, 45(1):137-142. DOI: 10.6041/j.issn.1000-1298.2014.01.022
Abstract:Study on modified sandy loam soil and increased tomato yield by using biochar was conducted through the pot experiment. There were five installed treatments that sandy loam soil (CK), per kilogram sandy loam soil plus 10g of biochar(C10), per kilogram sandy loam soil plus 20g biochar(C20), per kilogram sandy loam soil plus 40g of biochar(C40) ,and per kilogram sandy loam soil plus 60g of biochar(C60).Results show that biochar can improve soil fertility and the effect of higher biochar application is remarkable. Compared with CK, the content of organic matter in treatment C60 increased by 560%. In treatments C60 and C40, both available N increases by 290% and 150% respectively; both available P increases by 410% and 290%, and both available K increases by 290% and 150% respectively. Soil water content in treatment C60 is 170% higher than CK. Using biochar can effectively improve tomato yield. Comparing with CK treatment, tomato yield increases 98% and 170% in treatments C60 and C40, respectively, and the largest increase is in treatment C40.Through correlation analysis, water and fertilizer are important factors affecting tomato yield, and correlation is more than 80%. In order to make full use of existing resources, reduce the use of chemical fertilizers, save water resources, improve agricultural land, water and ecological environment, application of biochar technology is a new idea.
Shi Huixian , Lü Tao , Zhu Hongguang , Fan Min , Xu Kai , Ma Jieqiong
2014, 45(1):143-149,167. DOI: 10.6041/j.issn.1000-1298.2014.01.023
Abstract:In recent years, solar assisted heat pump based heating system has been widely applied in the buildings and greenhouses, but it is little applied and researched in biogas projects. Exergy analysis of solar assisted heat pump based heating system of biogas project was conducted, and the weak links were found in the energy-using process; system status parameters were obtained by solving variable nonlinear optimization problem with Matlab; specific measures and methods of improving system exergy efficiency were proposed and validation experiments were done ;the effect of individual status parameters and equipment performance parameters on system exergy efficiency was also studied. The results showed that optimized system exergy efficiency can increase from 18.44% to 28.99%. The status parameter(storage tank temperature tv) and performance parameters(pump system CCOP(year) and collector efficiency ηcol) have a great influence on system exergy efficiency. The system exergy efficiency can increase by 0.58% with the temperature increasing by 1℃, increase by 5.94% with the CCOP (year) increasing by one unit of value, increase by 0.045% with the collector efficiency ηcol increasing by one percentage point.
Wang Guijin , Yuan Hongyou , Guo Daliang , Zhou Zhaoqiu , Yin Xiuli , Wu Chuangzhi
2014, 45(1):150-154. DOI: 10.6041/j.issn.1000-1298.2014.01.024
Abstract:The steam gasification of wheat straw black liquor char (BLC) was studied in a laboratory-scale tube furnace at temperature from 750℃ to 900℃. The impacts of temperature and causticizing agent TiO2 on characteristics of gas and solid product during gasification process were investigated. Influence of TiO2 on weight loss characteristics of BLC was also studied by thermo gravimetric analyzer at temperature 850℃.Results showed that at temperature from 750℃ to 900℃, with TiO2 addition, the relative concentration of CO2 increases by about 5% while the relative concentration of H2 decreases by about 5% in gas product, at the same time the gas heating value reduces by about 7%; however, carbon conversion rate increases by about 10% without melting of char in the gasification process;temperature has no significant effect on the composition of the solid product. Furthermore, TiO2 changes the partition of Na and Si in char. TiO2 not only reacts with Na2CO3 to form Na2O〖DK〗·nTiO2, but also combines with Na2SiO3 to generate Na2TiSiO5.
Li Lianhua , Sun Yongming , Kong Xiaoying , Yuan Zhenhong , Zhen Feng , Li Dong
2014, 45(1):155-161. DOI: 10.6041/j.issn.1000-1298.2014.01.025
Abstract:The effects of growth stages on the physico-chemical properties and anaerobic digestion performance of Pennisetum hybrid were studied in batch mesophilic experiments. The results indicated that the content of C,TS, VS and lignin increase over time at different growth stages. The dry matter yield per hectare firstly increases then declines, with the highest dry matter of 15.01t/hm2. Biogas production performance of Pennisetum hybrid firstly increases and then deceases, and the maximum biogas yield is obtained when Pennisetum hybrid is harvested at 60d growth stage, which are 0.68L biogas/g VS and 0.37L methane/g VS. Based on the biomass yield per hectare and biogas production of Pennisetum hybrid, the area specific biogas yields of 848.07~6279.73m3/hm2 can be achieved from 〖JP2〗the Pennisetum hybrid harvested at different growth stage, the corresponding energy production of 165.49~〖JP〗292.66GJ per year. Biogas production from Pennisetum hybrid suggests that the energy grass is a potential material for anaerobic digestion.
Song Li , Su Meng , Wang Ruizhe , Lin Lihua , Tian Rui
2014, 45(1):162-167. DOI: 10.6041/j.issn.1000-1298.2014.01.026
Abstract:The energy conversion device with flexible blades was taken as the research object; in the closed experimentation section of the low speed wind tunnel, velocity field of curved blade boundary layer was tested by PIV measure technology; when camber of the blades was changed, the rule of flow separation and vortex motion on the boundary layer were obtained. The experimental results showed that the bending deformation of blades in the front layer can reduce accumulation and diffusion low-energy fluid on the boundary layer, and it is helpful to reduce the lift loss of the blades due to flow separation; but for the rear layer, flow instability will increase because the dynamic stall vortex near boundary layer extends due to the bending deformation of blades.The flow field analysis of the curved blades can guide material selection and the design of flexible blades, and provide experimental reference for improvement of the energy conversion efficiency and working stability.
Zhu Songming , Su Guangming , Wang Chunfang , Zhan Yao , Hu Feifei , Yu Yong
2014, 45(1):168-177. DOI: 10.6041/j.issn.1000-1298.2014.01.027
Abstract:The advantages of high pressure (HP) technology have been widely accepted by researchers in domestic and overseas in recent years. However, research and development on HP processing of aquatic products didn’t attract much attention in last century as compared to that of fruit and vegetable products. Since entering the new century, more and more research work has been done focusing on HP processing of aquatic products. Literature information on HPP of aquatic products was analyzed, including pasteurization, preservation, HP freezing and thawing, shellfish shucking, compound extraction and functional modification. The significance, applications and prospect of these research achievements were introduced and discussed. The main research fields for future development on HP processing of aquatic products were explored and presented.
Hu Feifei , Zhu Rui , Yang Nan , Yu Yong , He Jinsong , Zhu Songming
2014, 45(1):178-183,190. DOI: 10.6041/j.issn.1000-1298.2014.01.028
Abstract:The effect of pulse mode high-pressure on E.coli in fresh carrot juice was studied. Destruction kinetics of E.coli was investigated after pulse mode high-pressure treatment (300~600MPa, 1~4pulses). Enumeration was carried out in brain-heart infusion agar and violet-red bile agar to differentiate between surviving cells with and without injury. Results showed that with an increase in either pressure or pulse, both injured and killed cells increase significantly. At more than 400MPa, the increase of pulse, rather than pressure,makes the sterilization effect better. Two pressure pulses at 500MPa or a pressure pulse at 600MPa destroys the entire population (107.8cfu/mL) of E.coli in carrot juice. And on both BHIA and VRBA, pulse mode high-pressure destruction of E.coli in carrot juice follows first-order kinetics under experimental conditions. Modeling analysis showed that, for lethal effect, every 3.95, 1.76 and 0.83 pulses result in a decimal change of E.coli for 300, 350 and 400MPa, respectively; for injured effect, every 1.68, 1.26 and 0.48 pulses result in a decimal change of E.coli for 300, 350 and 400MPa, respectively. To achieve a same sterilization effect, when the pressure pulse decreases an order of magnitude the pressure has to increase by 229MPa and 206MPa, for BHIA and VRBA, respectively.
Qu Guiqin , Wang Pan , Li Jinlong , Yin Lijun
2014, 45(1):184-190. DOI: 10.6041/j.issn.1000-1298.2014.01.029
Abstract:Layer-by-layer technology (LBL) and enzymatic cross-linking technology were used to make modified β-carotene emulsion. Two kinds of modified β-carotene emulsion were prepared by using whey protein isolate as emulsifier, and then 0.15% sugar beet pectin was added to cover the surface of particles under the action of electrostatic adsorption and enzymatic cross-linking. The results showed that compared with original emulsions, particle size of modified emulsions increases; however, the bioavailability of β-carotene in modified emulsions is obviously lower than that in original emulsion, and it suggests that β-carotene in modified emulsions, especially in emulsion modified through enzymatic cross-linking, has sustained-release function.
Sun Zhichang , Feng Xiaoqin , Han Ling , Zhao Huiping , Yu Qunli
2014, 45(1):191-196,202. DOI: 10.6041/j.issn.1000-1298.2014.01.030
Abstract:Totally 24 Gannan yak were slaughtered at 0~4℃, wind speed 0.5m/s conditions to aging , then the shear force, MFI and apoptotic enzymes activity were determined during postmortem aging. Results from this research show that the shear force values of TB, ML and SM decrease by 35.6%, 27.4%, 33.5%, and the MFI values increase by 69.7%,65.7 %,63.0%. This investigation also indicated that TB and SM at 1d postmortem aging caspase-3 activity reach the highest value (P<0.001), while ML at 10h postmortem aging caspase-3 activity reaches the highest value; caspase-8 activity reaches the highest value activity (P<0.001) at 5h postmortem aging, and the caspase-8 activity of TB and SM reach highest value earlier than ML; at 5h postmortem aging, caspase-9 activity is significantly higher than that at 0.5h postmortem aging(P<0.001), at the same time caspase-9 activity reaches the highest value in ML and SM muscles, while the caspase-9 activity of TB reaches the highest value at 10h postmortem aging, it is 2.39 times than its initial value; the caspase-3 and caspase-8 activity is related to shear force and MFI significantly (P<0.01), while caspase-3, caspase-8 and caspase-9 activity show significant correlation with each other (P<0.05).
Dong Qingli , Yao Yuan , Zhao Yong , Chen Hao
2014, 45(1):197-202. DOI: 10.6041/j.issn.1000-1298.2014.01.031
Abstract:An automated turbidimetric system, Bioscreen C, was used to monitor the growth of Pseudomonas aeruginosa, which was separated from spoilage pork at a range of temperature (25~40℃), pH (5.0~7.5) and mass concentration of sodium lactate (0~0.035g/mL). The cardinal parameters model (CPM) was built on the basis of nonlinear least squares method using fminsearch function of Matlab software, and CPM represented the lag time of P.aeruginosa growth as a function of temperature, pH value and sodium lactate mass concentration. The CPM is able to determine the cardinal parameters Tmin, Topt, Tmax, Pmin, Popt, Pmax and the minimum inhibitory concentration of sodium lactate, respectively. This model was validated with ten random data within above ranges. The results showed that the growth parameters are predicted well by CPM with R2=0.9291, Bf=1.0975, Af=1.3936, and E= 1.5989, respectively. The validation parameters are 0.8546, 1.1225 and 1.2117 for R2, Bf and Af, respectively.
Jiang Hui , Deng Weimin , Chen Xiaoqing
2014, 45(1):203-208. DOI: 10.6041/j.issn.1000-1298.2014.01.032
Abstract:Pearson correlation coefficient was used to choose some physicochemical indexes of grape which have strong correlation with those of wine and multi factor regression equations was established to determine their quantitative relations by the stepwise regression. Each physicochemical index of wine has a specific linear relationship with several physicochemical indexes of corresponding grape or just only one. At the same time, the multi-kernel support vector machine was carried out to classify the wine samples. The results from the multi-kernel support vector machine are approximately consistent with those from the artificial with an accuracy of 91.89%. Results from this study show that the physicochemical indexes of grape and wine can determine the taste evaluation of wine well.
Wang Zhouli , Wu Xiaohong , Yue Tianli , Zhang Nan , Guo Caixia , Yuan Yahong
2014, 45(1):209-213,221. DOI: 10.6041/j.issn.1000-1298.2014.01.033
Abstract:In order to improve the clarity and stability of cider, membrane ultra-filtration technology was used for clarification. Box-Behnken response surface methodology (RSM) was adopted to study effect of the key parameters pressure, temperature and feeding velocity on membrane flux. The results indicate that the order of three factors effects on membrane flux are as follow: temperature, pressure, feeding velocity. The optimal levels for cider clearing were obtained, including pressure of 0.7MPa, temperature of 24℃, feeding velocity of 5.6mL/min. Under optimized conditions, the luminousness of cider is 98.72%, the membrane flux is 14.38L/(m2〖DK〗·h), and the flavor and quality of cider are satisfactory.
Shi Qilong , Zhao Ya , Ma Zhanqiang
2014, 45(1):214-221. DOI: 10.6041/j.issn.1000-1298.2014.01.034
Abstract:Moisture sorption isotherms of pure yacon powder (YP) and yacon powder with maltodextrin addition (YP-MD) (total solids ratio of yacon〖DK〗∶maltodextrin=1∶1) were determined at different temperatures (15, 25 and 35℃) by static gravimetric method. The best model for describing yacon adsorption characteristic was determined through seven models fitting analyses. Thermodynamic properties, namely net isosteric heat of sorption, differential entropy, enthalpy-entropy compensation and spreading pressure, were determined from sorption isotherm data of yacon. The effect of maltodextrin (MD) on the sorption characteristics and thermodynamic properties were also discussed. The results show that the sorption behaviour of yacon follows a type Ⅲ isotherm; GAB model is the best fit one for describing yacon adsorption characteristic for both YP and YP-MD. Equilibrium moisture content of YP and YP-MD increases with water activity (aw). Addition of MD decreases the monolayer moisture content (M0) of yacon. When temperature ranges from 15℃ to 35℃, the M0 of YP and YP-MD ranges from 15.04% to 9.04%, 8.80% to 5.91%, respectively. The net isosteric heat of sorption (qst) and differential entropy (Sd) decreases with the increasing of moisture contents. The qst of YP and YP-MD decreases from 67.44kJ/mol to 62.23kJ/mol, and 66.17kJ/mol to 62.12kJ/mol as the moisture content increases from 6.33% to 75.29%. The value of Sd of YP is always higher than that of YP-MD. The spreading pressure of YP and YP-MD increases with increasing aw, and decreases with increasing temperature. The value of spreading pressure of YP is always higher than that of YP-MD at fixed aw and temperature. Through this study, a conclusion can be drawn at last that the driving force of moisture sorption for PY and PY-MD is entropy.
Xu Fengying , Chen Zhen , Li Changyou , Liao Jianyuan
2014, 45(1):222-227,235. DOI: 10.6041/j.issn.1000-1298.2014.01.035
Abstract:The uniformity dynamic of moisture content of litchi fruit during infrared drying was measured and fitting analyzed. Besides, the dynamic differences of the shell porosity and its fractal dimension of litchi during infrared drying were compared using Image-Pro and SPSS software. Furthermore, the change of the color of shell surface color of litchi during fractal dimension was also measured. The results show that the moisture content change of each litchi fruit is uneven during infrared drying. For relatively small litchi, the moisture content decreases quickly during initial drying; later on, the moisture content changes slowly, and during the last drying the difference among individual drying rates becomes significant. The fruit shell porosity significantly changes with the reduction of moisture content, and its mean value decreases from 0.519 to 0.381, to 0.276, and then to 0.184; but the fractal dimension of the pore increases from 1.486 to 1.674, to 1.708, and then to 1.800. The DL and Db values of shell surface color change significantly at the beginning, however, they change slowly during the following drying. Results from this study could provide a reference for the uniformity research of other multilayer-structure fruits and vegetables in infrared drying.
Weng Weibing , Fang Dianjun , Li Qiang , Cao Miaolong , Wu Jian
2014, 45(1):228-235. DOI: 10.6041/j.issn.1000-1298.2014.01.036
Abstract:Evaluating indicator for temperature distributions homogeneity was developed through optimization using orthogonal experiment. The influences of rotation speed of air refrigerating machine fan, porosity of flow equalization board and vertical space between frames on temperature distribution were analyzed. The simulation results show that the higher the fan rotation speed is, the better the temperature distribution homogeneity is, although the highest temperature in carriage is basically unchanged; the smaller the porosity is, the better temperature distribution homogeneity is; and the highest temperature in carriage is lowest when the porosity is 0.1; the smaller the frame vertical spacing is, the lower the highest temperature in carriage is and the better temperature distributions homogeneity is. For the “peak area” in temperature distribution, the carriage structure was new designed based on field-coordination principle and the temperature distributions homogeneity can be controlled by adjusting the gas curtain fan’s direction in right air-returning outlet.
Liu Xiangge , Huang Jianxi , Qin Jun , Wang Pengxin , Xu Tongren
2014, 45(1):236-245. DOI: 10.6041/j.issn.1000-1298.2014.01.037
Abstract:A land surface temperature data assimilation scheme was developed on weak-constraint viarational method and simple land surface model,which is mainly used to improve the estimation of the turbulent heat fluxes by assimilating geostationary operational environmental satellite (GOES) retrieved land surface temperature (LST). A variational data assimilation scheme was developed based on the weak-constraint concept. It can estimate both state variables and model unspecified parameters together, which is depend on the building of the cost function. The objective of the variational method is to minimize the cost function to seek the most optimal control variables and accurately estimate sensible heat and latent heat. The GOES LST is compared with the ground measured LST, and the root mean square error (RMSE) was taken as the observation error. The scheme was tested and validated based on measurements in two mainly observation sites of Ameriflux. Results indicate that data assimilation method improves the estimation of surface temperature, sensible heat flux and latent heat flux. The RMSE of estimated LST is around to 1K in both sites. Meantime, the average RMSE of estimated sensible heat and latent heat dropped to 22W/m2 and 26W/m2 respectively. It is a promising way to improve the estimation of turbulent heat fluxes by assimilating GOES LST into land surface model.
Sun Li , Wang Fei , Li Baoguo , Chen Xiwei
2014, 45(1):246-252. DOI: 10.6041/j.issn.1000-1298.2014.01.038
Abstract:For the complexity of land surface and the climatic variation, the result of drought monitoring maybe couldn’t give us satisfaction only by using the single remote sensing index. A new solution of the problem was put forward. An integrated linear weighted drought monitoring index (IMDI) was suggested, which is incorporated with remote sensing index (TVDI)constructed by EOS/MODIS data and meteorological factor, named percent of precipitation departure (PPAI). Two periods had been selected to monitor drought in Wuling Mountain area including mid- and the late April in 2011. By comparing with soil moisture in 10cm depth from the observatories around the same area in 2010 and 2011, together with contrasting the correlations with SPI, IMDI and TVDI were confirmed to be able to monitor drought distribution in such a large and complicated area and IMDI is superior to TVDI. However, drought monitored by SPI may be more serious than that of actual situation.
Zhao Yandong , Rong Fei , Liu Shengbo , Martin Kraft , Qi Jiandong
2014, 45(1):253-258,245. DOI: 10.6041/j.issn.1000-1298.2014.01.039
Abstract:Wilting is one of life features of plants responding to drought stress. Early identification of plant wilting is of importance for effective use of water in crop production. For this purpose, a laser scanner based on the principle of triangulation project was used to obtain 3D images of plants and the DC component of 2DFT was extracted as a wilting index. Four species, including zucchini, gourd, pumpkin and okra, were tested. The experimental results demonstrated that this index could identify the early wilting for each species and has a good linear correlation with the wilting degrees (R2>0.82). In addition, the statistical models of multiple linear regression, which relates the wilting index to DVPD and the solar effective radiation, was proposed; and it can be used as the qualitative index of plant water deficit stress degree.
2014, 45(1):259-265. DOI: 10.6041/j.issn.1000-1298.2014.01.040
Abstract:Focusing on the problem about traditional farming methods which cannot meet the increasing scale of aquaculture, and combining RFID technology and the internet of things technology with the processes of aquatic breeding, an aquatic intelligent breeding solution was proposed. Firstly, the basic processes of aquatic breeding and the aquatic farming environment were analyzed, and then the environmental factors affecting aquatic growth were obtained, at the same time the best environment for aquatic products high-density breeding was given; at last, an aquatic intelligent breeding solution based on RFID and internet of things was proposed. Field tests were also conducted. Results show that the accuracy of closed-loop control response speed and other performances of this system satisfies actual needs of this project, and temperature error, dissolved oxygen error and pH error are ±0.5℃, ±0.3mg/L, ±0.3, respectively, and the data transmission accuracy of the system is up to 98%.
Wen Changji , Wang Shengsheng , Zhao Xin , Wang Min , Ma Li , Liu Yiting
2014, 45(1):266-274. DOI: 10.6041/j.issn.1000-1298.2014.01.041
Abstract:Information acquisition of the cow behavior modes and regulars are very important. It is one of judgments for the manual intervention in a particular period. There is certain limitation in the way of obtaining information by using external sensors. So, firstly a modified spatial-temporal local binary pattern for feature presentation was proposed. Secondly through building a visual dictionary, the cow sow-behavior were recognized on the test video. Finally, the basic rule of cow sow-behavior was studied through the statistics occurrence frequency of specific behaviors. For verifying the efficiency of the proposed method, different experimental settings were tested for recognizing the typical sow-activities such as walking, side-lying and look-backing. One was tested on 90 groups of videos under given visual angles and the other on 30 groups of videos under the random perspective ; the experiment results show that the average accuracy is 94.6% and 88.3%, respectively. The other side, a thirteen-hours video before and after delivery was using to sow-activity recognition and frequency count. The experiment results show that the average occurrence frequencies of look-backing and side-lying are 30 and 21.2, respectively. The occurrence frequencies of above two kinds of behaviors are former-low to after-high. Before delivery, the frequency of look-backing reaches to maximum 8.8 and side-lying reduces to 2.2. The results show that this method proposed reveals the basic principle of cow sow-behavior.
Guo Wenchuan , Zhou Chaochao , Han Wenting
2014, 45(1):275-280. DOI: 10.6041/j.issn.1000-1298.2014.01.042
Abstract:Based on Android mobile phone platform, a rapid and non-destructive method for measuring area of plant leaves was developed. After snapping the images which contained reference object with known area and plant leaf whose area would be measured, through image graying, smoothing, binarizing, geometric correcting and connected components labeling, the area of plant leaf could be obtained according to the values of pixels of reference object and plant leaf. Functionality and interface of the system were designed with programming techniques based on Android. Geometric correction method was provided for image tilt distortion problem. Many leaves of several plants, such as clover, hibiscus, wintersweet, maple, ginkgo and sakura were used as the object for experiment. Results showed that the system can effectively measure plant leaf area and is not restricted by leaf shape; the relative error of measured area is range from -2.9% to 2.7%.
Chen Hong , Xia Qing , Zuo Ting , Tan Hequn , Bian Yinbing
2014, 45(1):281-287. DOI: 10.6041/j.issn.1000-1298.2014.01.043
Abstract:In order to grade of shiitake mushroom, grading system of a shiitake mushroom with the practical corresponding algorithm was developed based on machine vision. According to length of stem, shape sorting of shiitake mushroom, and method of area, identification algorithm based on curve reconstruction was presented. With shiitake mushroom as a case study, the boundary is tracked and the curvature is calculated by tracking the boundary, and then the concave-convex quality of boundary can be distinguished with the curvature, then the possible shiitake mushroom region is found and the actual position of the shiitake mushroom can be found with the class radius of curve. Linear interpolation of edge curve of the shiitake mushroom handle removed region is performed under polar coordinate, and the shape of pileus is reconstructed, then nine shape parameters and one parameter of size are distracted based on the curve reconstructed. The shape parameters are reduced to 3 with principal component analysis. The minimum distance classifier can be constructed as the sorting model with the 3 main shape parameters as input. Considering with the identification of stem of shiitake mushroom, the final identification of the shiitake is determined on both of the shape and the size classification. Experiments shows that the accuracy of stem identification is 91.4%, and the accuracy of shape sorting can be greatly improved by identification of stem of shiitake mushroom; the precision ratio of shiitake mushroom shape grading is 95.6%,while the accuracy of shiitake mushroom grading can reach to 92.2%.
Tang Yiping , Xia Shaojie , Feng Yijun , Chen Xinfeng , Zhu Zhiliang , Li Chenrong
2014, 45(1):288-292,280. DOI: 10.6041/j.issn.1000-1298.2014.01.044
Abstract:An imaging apparatus of monocular multi-view was designed by putting a symmetric bucket cavity, which was made by 4 planar mirrors, in front of the camera. An image of the pear surface from different perspectives could be obtained by this device; then, a variety of views which present pearl quality could be obtained by image processing. Finally the quality of the pearl could be determined by feature fusion. Experimental results show that the image captured of pearl entire surface could be obtained in a unified color system by the proposed device. Besides, the device accomplishes pearl online detecting and grading according to the quality indicator such as size, shape, luster, blemish and color.
Dou Yuchao , Yao Jiantao , Gao Sihui , Han Xing , Liu Xiaofei , Zhao Yongsheng
2014, 45(1):293-300. DOI: 10.6041/j.issn.1000-1298.2014.01.045
Abstract:The redundant actuation can reduce the instantaneous maximum driving force of the parallel mechanism and improve the carrying capacity effectively. However, the driving force coordination misallocation or the redundant driving force control error is over, not only can the above-mentioned functions not be realized, but even cause overlarge internal force leading to mechanism damage. Therefore, the 6UPS〖CD*2〗UPU parallel robot with redundant actuation is taken as an example, and the velocity and acceleration of the driving links, constraint link and moving platform were analyzed. Partial velocity and partial angular velocity were introduced to establish the system dynamic equation using Kane equation. The target of minimizing the instantaneous maximum driving force was proposed and the weighted least square method was used to distribute the driving force; driving force of each leg was obtained by numerical calculation under the condition of given trace. The mode that combination of DSP controller and motion controller was used to improve the real-time of driving force coordinate distribution, and then control of the redudant driving force was realized. The experimental results show that the instantaneous maximum driving force is obviously decreased, and the driving force distribution becomes more balanced under the influence of the redudant driving force. Consequently, the method and the strategy proposed are effective.
2014, 45(1):301-305. DOI: 10.6041/j.issn.1000-1298.2014.01.046
Abstract:An optimum strategy for driving force distribution, which can hold preload in the robot,was presented. First, an approach for the kinematic and dynamic analysis of redundant planar parallel robot was proposed. In this method, theory of screws was used to deduce the Jacobian matrix, and the Newton-Euler equation was used to calculate wrench of pivot points, and the principle of virtual work was sued to formulate the dynamic equation of motion. Then, the driving forces of 3-RRR and 4-RRR were optimized based on force optimization, respectively and the peak of driving force for 4-RRR is lower than that for 3-RRR. In the end, the internal preload and driving forces of the 4-RRR were optimized based on the power optimization and the variations rules of the driving forces and internal preload were obtained.
Hu Junfeng , Xu Guiyang , Hao Yazhou
2014, 45(1):306-312. DOI: 10.6041/j.issn.1000-1298.2014.01.047
Abstract:In order to achieve the precise motion of a compound bridge-type micro-platform, an optimization model based on its dynamic characteristics was presented and the optimization design of structure parameters was carried out. The kinematic, stiffness and strength characteristics of the platform were derived by using the virtual work principle. The pseudo-rigid-body method and Lagrange equation were applied to establish the dynamic model. All proposed model is based on the structural parameters as the independent variables in the closed form, and it can provide the theoretical model for the optimization design. By comparing the theoretical model and FEA, the results show that the errors are within 6.0%~9.3%, which illustrates the proposed feature models are correct and precise. According to the closed-form natural frequency and amplification ratio, the sensitivity of this model with respect to structural parameters was analyzed, and then the design variables were chosen, which have greater impact on the dynamic properties of the platform. At last, the optimal model was proposed as the maximum natural frequency and amplification factor for the objective and the hinge strength, input stiffness, and geometric dimensions for constraints. The results show that higher natural frequency and more amplification factor are obtained from the optimum platform.So the proposed optimum platform can meet the design requirement.
Gui Zhongdong , Ding Fan , Yuan Ye , Li Youce , Liu Shuo , Man Zaipeng
2014, 45(1):313-320,300. DOI: 10.6041/j.issn.1000-1298.2014.01.048
Abstract:A novel electro-hydraulic servo hub machine loading test bench for controllable pitch propeller (CPP) was presented. Thrust, rotational resistance, centrifugal force and rotary vane torque generated by CPP in water at different pitch, rotational speed and speed can be imitated through a multi-channel electric hydraulic force (torque) servo control system. The servo control system could apply static, dynamic, pulsating load or variable load according to a loading spectrum to the hub. A vertical structure was utilized for the loading system, with a massive disk as the foundation bed. The loaded hub was installed upside-down in the center of the disc. Finite element analysis for the key parts of test bench was conducted, as well as the frequency response analysis of electro-hydraulic servo loading system. The experiments demonstrated that the loading test bench could meet the variety of load requirements.
Yuan Shihao , Yin Chenbo , Ye Yi , Liu Shihao
2014, 45(1):321-327. DOI: 10.6041/j.issn.1000-1298.2014.01.049
Abstract:Relative to circular throttling port, partial pressure throttling groove is significant for releasing pressure drop contraction in throttling port, and decreasing cavitation probability. For typical non-circumferential throttling ports U groove and V groove, their flow abilities(hydraulic diameters) were studied, and it was observed that for U groove, the flow ability is limited under a larger opening, as actual flow ability is depend on minor hydraulic diameter and it is a fixed value; for V groove, hydraulic diameters has a good linear relationship with port opening that means V groove has a wider flow range than U groove does, in other words, V groove is easier to obtain stable smaller flow rate; based on classic cavitation index, new-form cavitation index calculation formula, which is applicable to partial pressure throttling port,was deduced, and the cavitation indexes of U groove and V groove were calculated respectively, and it was found that whether U or V groove, for different flow directions cavitation indexes are different; when fluid flows from the larger section A1 to section A2 cavitation index near section A2 is remarkly larger than that when fluid reversal. At last, this phenomena was theoretically explained.
Bao Zhiyan , Ji Shiming , Ruan Shufeng
2014, 45(1):328-334,340. DOI: 10.6041/j.issn.1000-1298.2014.01.050
Abstract:The characteristics of swarm evolutionary mechanism were analyzed, and a corresponding product configuration model was proposed. In order to select appropriate queen and male bees, a selection operator was established via similarity evaluation technique. A crossover operator was established to inherit useful components through components traversal, and a mutation operator was also established so as to configure individualized components based on the topological sort algorithm of constraint directed graph. The method of fitness evaluation was put forward by using estimated elements. The strategy and method were effective in an instance of the product called bridge crane.
Cao Junhui , Fu Wenzhi , Li Mingzhe , Liu Chunguo , Su Shizhong , Pham D T
2014, 45(1):335-340. DOI: 10.6041/j.issn.1000-1298.2014.01.051
Abstract:A new flexible forming technique for thermoplastic polymer: multi-point thermoforming (MPTF) was developed. Polycarbonate (PC) is a typical thermoplastic polymer exhibiting many properties ideally. The material parameters of PC according to Mooney-Rivlin hyperelastic constitutive model were determined based on the high temperature tensile test data. The commercial software Abaqus was utilized to simulate the MPTF process of PC sheet. A series of numerical simulation results show that the best combination of forming temperature and forming pressure for PC sheet are 160℃ and 10kPa, respectively. MPTF experiments were carried out under the processing parameters which were determined by numerical simulations and the simulation results were validated by comparing them with the experimental results. The spherical and saddle-shape parts formed by MPTF were measured using a 3D sensing system and the measured data were compared with the target shape to analysis the accuracy of MPTF. The comparison results show that the formed parts have good accuracy.
Zhang Pengfei , Zhang Deyuan , Chen Huawei
2014, 45(1):341-345. DOI: 10.6041/j.issn.1000-1298.2014.01.052
Abstract:Nepenthes’ pitchers are marvelous leaves working as insect traps which is mainly caused by the inner surfaces. While the wettability of the inner pitcher surface is still a lack of in-depth research. Through various measuremtns of the contact angle of Nepenths’ pitcher surfaces, it was found that the slippery zone is hydrophobic with the maximum contact angle (150±2)° and the digestive zone is hydrophilic with the minimum contact angle (16±2)°, and there exists an obvious wettability dividing line between slippery zone and digestive zone. Micro- and nanoscale hierarchical structures are present on the slippery zone, while a microscale hierarchical structure is present on the digestive zone. The effect of the material composition and microstructure of the inner surfaces on wettability were analysed through chemical treatment and bio-replication. The results show that hydrophobic of the slippery zone is mainly caused by the wax on pitcher surface and hydrophilic of the digestive zone may be caused by some kinds of hydrophilic materials. The large span of wettability between slippery zone and digestive zone is depend on both its chemical composition and its surface morphology. This research may provide a reference for the design of slippery surfaces.
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