Aiming at the problem that the draft-position integrated tillage depth control method with fixed comprehensive coefficient of tractor electro-hydraulic hitch system is difficult to adapt to the working environment wit...Aiming at the problem that the draft-position integrated tillage depth control method with fixed comprehensive coefficient of tractor electro-hydraulic hitch system is difficult to adapt to the working environment with large changes in soil conditions,a tractor draft-position integrated tillage depth control method with variable comprehensive coefficient was proposed.A comprehensive coefficient control scheme based on traction resistance was designed and its working principle was clarified.Aiming at the time-varying tillage depth control system,a tillage depth control algorithm based on the sliding mode control with a differential observer was designed.In order to verify the performance of the control scheme,a control system simulation model and a bench test platform were built,and the performance was compared with the draft-position integrated control method with a fixed comprehensive coefficient of 0.5.The results showed that the variable comprehensive coefficient tillage depth control method can automatically adjust the comprehensive coefficient according to the change of soil conditions,and has higher traction efficiency.In the small resistance range,it can better ensure the quality of operation;in the large resistance range,it can ensure the engine performance and protect the tractor from damage.This method is more adaptable to the complex field operation environment,which provides a reference for the research of tillage depth control method.展开更多
The spatial organization of the Chinese petrochemical industry was optimized according to the status of development of the industry employing linear programming and ArcGIS spatial analysis tools. We first identified t...The spatial organization of the Chinese petrochemical industry was optimized according to the status of development of the industry employing linear programming and ArcGIS spatial analysis tools. We first identified the indexes of the spatial organization of the petrochemical industry and established a comprehensive evaluation index system that in- cludes four major categories and 11 indicators. The weight of each index was then deter- mined by the analytical hierarchy process. Afterward, taking the 337 Chinese prefecture-level administrations as basic units and scientifically evaluating the potential comprehensive layout coefficients of the cities, 151 prefecture-level administrative units were selected as the basis for the choice of optimization sites with a linear programming model. Secondly, using the 151 prefecture-level administrative units and the maximum-coverage model, the optimal number and spatial distribution of refineries were identified for service radii of 100, 200 and 300 km. Thirdly, considering the actual distribution of China＇s refineries, general rules for the number of refinery layout points and objective values were summarized, and 52 refinery layout points were selected for China. Finally, with ArcGIS spatial analysis tools, the spatial effect of the 52 optimal refinery layout points was simulated for the service scope and socioeconomic factors respectively, and the GDP and population data for each refinery layout point were then ex- tracted within the service scope. On this basis and with estimation of the intensity of crude-oil consumption, final results were obtained for the optimal spatial organization of the Chinese refining capacity and ethylene production capacity.展开更多
This paper applies weighted least square method to estimate the three-parameter power function equation of the fatigue life curve, and uses comprehensive fatigue life coefficient to correct the equation, and at the sa...This paper applies weighted least square method to estimate the three-parameter power function equation of the fatigue life curve, and uses comprehensive fatigue life coefficient to correct the equation, and at the same time combines probability statistics method to bring out the prediction method of structure＇s three- parameter power function P-S-N curve, finally applies the prediction method to a ship＇s frame-type elevate, based on the fatigue test data of it＇s material-SA06 aluminium alloy, to obtain it＇s structure＇s three-parameter power function P-S-N curve. Compared with the conventional least square method, the presented method can give展开更多
In the case of the ski-jump type energy dissipation, the jet trajectory will be greatly affected by the air entrainment and the air resistance. It is necessary to consider those factors when estimating the trajectory ...In the case of the ski-jump type energy dissipation, the jet trajectory will be greatly affected by the air entrainment and the air resistance. It is necessary to consider those factors when estimating the trajectory of the jet flow. In this work, the effect of the air resistance on the jet trajectory is theoretically and experimentally investigated. A comprehensive resistance coefficient is proposed. To determine this coefficient, experiments of five models are conducted with the circular-shaped flip bucket placed at the point of the takeoff of ski jumps. It is shown that, this coefficient of the lower jet trajectory is only related to the approach flow Froude number, while that of the upper jet trajectory is dominated by both this Froude number and the deflection angle. Furthermore, the present methodology is validated by experimental data in this work and the maximum errors are not larger than 3.2% and 8.6% for the lower and upper jet trajectories, respectively.展开更多
Some conceptual problems were discussed in the present paper. Firstly, according to the physical meaning of effectiveness, a new expression of effectiveness was developed by using an ideal heat exchanger model and tem...Some conceptual problems were discussed in the present paper. Firstly, according to the physical meaning of effectiveness, a new expression of effectiveness was developed by using an ideal heat exchanger model and temperature histogram method, in which the non-uniform inlet temperature profile was considered. Secondly, the relation of entropy generation number to effectiveness was studied, it was pointed out that both of them could express the perfect degree of a heat exchanger to the second thermodynamic law. Finally, to describe both quantity and quality of heat transferred in a heat exchanger,a criterion named as comprehensive thermal performance coefficient (CTPE) was presented.展开更多
基金National Key Research and Development Plan of China(Grant No.2022YFD2001202)The Open Project of the State Key Laboratory of Intelligent Agricultural Power Equipment(SKLIAPE2023019)The Postgraduate Research and Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX22_0716).
文摘Aiming at the problem that the draft-position integrated tillage depth control method with fixed comprehensive coefficient of tractor electro-hydraulic hitch system is difficult to adapt to the working environment with large changes in soil conditions,a tractor draft-position integrated tillage depth control method with variable comprehensive coefficient was proposed.A comprehensive coefficient control scheme based on traction resistance was designed and its working principle was clarified.Aiming at the time-varying tillage depth control system,a tillage depth control algorithm based on the sliding mode control with a differential observer was designed.In order to verify the performance of the control scheme,a control system simulation model and a bench test platform were built,and the performance was compared with the draft-position integrated control method with a fixed comprehensive coefficient of 0.5.The results showed that the variable comprehensive coefficient tillage depth control method can automatically adjust the comprehensive coefficient according to the change of soil conditions,and has higher traction efficiency.In the small resistance range,it can better ensure the quality of operation;in the large resistance range,it can ensure the engine performance and protect the tractor from damage.This method is more adaptable to the complex field operation environment,which provides a reference for the research of tillage depth control method.
基金China Postdoctoral Science Foundation, No.2011M500375 National Natural Science Foundation of China, No.40635026 Knowledge Innovation Program of the Chinese Academy of Sciences, No.KZCXZ-YW-Q10-4
文摘The spatial organization of the Chinese petrochemical industry was optimized according to the status of development of the industry employing linear programming and ArcGIS spatial analysis tools. We first identified the indexes of the spatial organization of the petrochemical industry and established a comprehensive evaluation index system that in- cludes four major categories and 11 indicators. The weight of each index was then deter- mined by the analytical hierarchy process. Afterward, taking the 337 Chinese prefecture-level administrations as basic units and scientifically evaluating the potential comprehensive layout coefficients of the cities, 151 prefecture-level administrative units were selected as the basis for the choice of optimization sites with a linear programming model. Secondly, using the 151 prefecture-level administrative units and the maximum-coverage model, the optimal number and spatial distribution of refineries were identified for service radii of 100, 200 and 300 km. Thirdly, considering the actual distribution of China＇s refineries, general rules for the number of refinery layout points and objective values were summarized, and 52 refinery layout points were selected for China. Finally, with ArcGIS spatial analysis tools, the spatial effect of the 52 optimal refinery layout points was simulated for the service scope and socioeconomic factors respectively, and the GDP and population data for each refinery layout point were then ex- tracted within the service scope. On this basis and with estimation of the intensity of crude-oil consumption, final results were obtained for the optimal spatial organization of the Chinese refining capacity and ethylene production capacity.
文摘This paper applies weighted least square method to estimate the three-parameter power function equation of the fatigue life curve, and uses comprehensive fatigue life coefficient to correct the equation, and at the same time combines probability statistics method to bring out the prediction method of structure＇s three- parameter power function P-S-N curve, finally applies the prediction method to a ship＇s frame-type elevate, based on the fatigue test data of it＇s material-SA06 aluminium alloy, to obtain it＇s structure＇s three-parameter power function P-S-N curve. Compared with the conventional least square method, the presented method can give
基金supported by the National Natural Science Foun-dation of China(Grant No.51179056)
文摘In the case of the ski-jump type energy dissipation, the jet trajectory will be greatly affected by the air entrainment and the air resistance. It is necessary to consider those factors when estimating the trajectory of the jet flow. In this work, the effect of the air resistance on the jet trajectory is theoretically and experimentally investigated. A comprehensive resistance coefficient is proposed. To determine this coefficient, experiments of five models are conducted with the circular-shaped flip bucket placed at the point of the takeoff of ski jumps. It is shown that, this coefficient of the lower jet trajectory is only related to the approach flow Froude number, while that of the upper jet trajectory is dominated by both this Froude number and the deflection angle. Furthermore, the present methodology is validated by experimental data in this work and the maximum errors are not larger than 3.2% and 8.6% for the lower and upper jet trajectories, respectively.
文摘Some conceptual problems were discussed in the present paper. Firstly, according to the physical meaning of effectiveness, a new expression of effectiveness was developed by using an ideal heat exchanger model and temperature histogram method, in which the non-uniform inlet temperature profile was considered. Secondly, the relation of entropy generation number to effectiveness was studied, it was pointed out that both of them could express the perfect degree of a heat exchanger to the second thermodynamic law. Finally, to describe both quantity and quality of heat transferred in a heat exchanger,a criterion named as comprehensive thermal performance coefficient (CTPE) was presented.
