From electric circuit theory view, a system model of series hybrid electric vehicle was built which uses engine-generator and battery pack as its on-board energy source in this paper. Based on the analysis for the con...From electric circuit theory view, a system model of series hybrid electric vehicle was built which uses engine-generator and battery pack as its on-board energy source in this paper. Based on the analysis for the constant power work mode and constant bus voltage work mode of engine-generator, a third work mode was put forward which combined the advantages of constant power and constant bus voltage work modes. The new work mode is reasonable to keep the battery in good working conditions and to extend its life. Also the working conditions of engine can be bettered to get low pollution and high efficiency.展开更多
The paper analyzes the practical use of management mode of small-scale farmland irrigation works in China,and studies various problems existing in the present management mode.It puts forward a mode named Water-consume...The paper analyzes the practical use of management mode of small-scale farmland irrigation works in China,and studies various problems existing in the present management mode.It puts forward a mode named Water-consumer Association which is the most practical one at present.It points out some rules which must be mastered in solving problems appearing in using this mode.展开更多
The FY-2C meteorological satellite had been working well for 8 years as of October 19, 2012. Though the satellite was originally designed to work for 3 years, it still operates steadily. As the nation's first oper...The FY-2C meteorological satellite had been working well for 8 years as of October 19, 2012. Though the satellite was originally designed to work for 3 years, it still operates steadily. As the nation's first operational first-generation geo- stationary meteorological satellite, FY-2C works together with the following satellites FY-2D, FY-2E and FY-2F, in a operational mode of two operational plus two backup ones. FY-2C, FY-2D and FY-2E were the second batch satellites of FY-2 series展开更多
The relatively high stress probably leads to generation of a fractured or even instable area around a working coalface. Also, the generated weak area often evolves into an easy-infiltrating field of water/gas to great...The relatively high stress probably leads to generation of a fractured or even instable area around a working coalface. Also, the generated weak area often evolves into an easy-infiltrating field of water/gas to greatly increase probability of accident occurrence. To reveal the distribution of high stress around working faces, we put forward the mode-I-crack compression model. In this model, the goaf following a working face is regarded as a mode-I crack in an infinite plate, and the self-gravity of overlaying strata is transformed into an uniform pressure applied normal to the upper edge of the model crack. Solving this problem is based on the Westergaard complex stress function. For comparison, the software RFPA-2D is also employed to simulate the same mining problem, and furthermore extendedly to calculate the stress interference induced by the simultaneous advances of two different working faces. The results show that, the area close to a working face or the goaf tail has the maximum stress, and the stress is distributed directly proportional to the square root of the advance and inversely proportional to the square root of the distance to the working face. The simultaneous advances of two neighboring working faces in different horizontals can lead to extremely high resultant stress in an interference area.展开更多
Wireless Sensor Network(WSN)is a cornerstone of Internet of Things(IoT)and has rich application scenarios.In this work,we consider a heterogeneous WSN whose sensor nodes have a diversity in their Residual Energy(RE).I...Wireless Sensor Network(WSN)is a cornerstone of Internet of Things(IoT)and has rich application scenarios.In this work,we consider a heterogeneous WSN whose sensor nodes have a diversity in their Residual Energy(RE).In this work,to protect the sensor nodes with low RE,we investigate dynamic working modes for sensor nodes which are determined by their RE and an introduced energy threshold.Besides,we employ an Unmanned Aerial Vehicle(UAV)to collect the stored data from the heterogeneous WSN.We aim to jointly optimize the cluster head selection,energy threshold and sensor nodes’working mode to minimize the weighted sum of energy con-sumption from the WSN and UAV,subject to the data collection rate constraint.To this end,we propose an efficient search method to search for an optimal energy threshold,and develop a penalty-based successive convex approximation algorithm to select the cluster heads.Then we present a low-complexity iterative approach to solve the joint optimization problem and discuss the implementation procedure.Numerical results justify that our proposed approach is able to reduce the energy consumption of the sensor nodes with low RE significantly and also saves energy for the whole WSN.展开更多
文摘From electric circuit theory view, a system model of series hybrid electric vehicle was built which uses engine-generator and battery pack as its on-board energy source in this paper. Based on the analysis for the constant power work mode and constant bus voltage work mode of engine-generator, a third work mode was put forward which combined the advantages of constant power and constant bus voltage work modes. The new work mode is reasonable to keep the battery in good working conditions and to extend its life. Also the working conditions of engine can be bettered to get low pollution and high efficiency.
基金Supported by Provincial Water Conservancy Research and Technology Promotion Project:Research on Key Technical Problems of Farmland Water Conservancy Projects in Shandong Province(SDSLKY201401)
文摘The paper analyzes the practical use of management mode of small-scale farmland irrigation works in China,and studies various problems existing in the present management mode.It puts forward a mode named Water-consumer Association which is the most practical one at present.It points out some rules which must be mastered in solving problems appearing in using this mode.
文摘The FY-2C meteorological satellite had been working well for 8 years as of October 19, 2012. Though the satellite was originally designed to work for 3 years, it still operates steadily. As the nation's first operational first-generation geo- stationary meteorological satellite, FY-2C works together with the following satellites FY-2D, FY-2E and FY-2F, in a operational mode of two operational plus two backup ones. FY-2C, FY-2D and FY-2E were the second batch satellites of FY-2 series
基金Projects 50774083 and 40811120546 supported by the National Natural Science Foundation of ChinaNCET-07-0803 by the Program for New Century Ex-cellent Talents in University 2005CB221502 by the National Basic Research Program of China
文摘The relatively high stress probably leads to generation of a fractured or even instable area around a working coalface. Also, the generated weak area often evolves into an easy-infiltrating field of water/gas to greatly increase probability of accident occurrence. To reveal the distribution of high stress around working faces, we put forward the mode-I-crack compression model. In this model, the goaf following a working face is regarded as a mode-I crack in an infinite plate, and the self-gravity of overlaying strata is transformed into an uniform pressure applied normal to the upper edge of the model crack. Solving this problem is based on the Westergaard complex stress function. For comparison, the software RFPA-2D is also employed to simulate the same mining problem, and furthermore extendedly to calculate the stress interference induced by the simultaneous advances of two different working faces. The results show that, the area close to a working face or the goaf tail has the maximum stress, and the stress is distributed directly proportional to the square root of the advance and inversely proportional to the square root of the distance to the working face. The simultaneous advances of two neighboring working faces in different horizontals can lead to extremely high resultant stress in an interference area.
基金supported in part by the National Nature Science Foundation of China under Grant 62001168in part by the Foundation and Application Research Grant of Guangzhou under Grant 202102020515.
文摘Wireless Sensor Network(WSN)is a cornerstone of Internet of Things(IoT)and has rich application scenarios.In this work,we consider a heterogeneous WSN whose sensor nodes have a diversity in their Residual Energy(RE).In this work,to protect the sensor nodes with low RE,we investigate dynamic working modes for sensor nodes which are determined by their RE and an introduced energy threshold.Besides,we employ an Unmanned Aerial Vehicle(UAV)to collect the stored data from the heterogeneous WSN.We aim to jointly optimize the cluster head selection,energy threshold and sensor nodes’working mode to minimize the weighted sum of energy con-sumption from the WSN and UAV,subject to the data collection rate constraint.To this end,we propose an efficient search method to search for an optimal energy threshold,and develop a penalty-based successive convex approximation algorithm to select the cluster heads.Then we present a low-complexity iterative approach to solve the joint optimization problem and discuss the implementation procedure.Numerical results justify that our proposed approach is able to reduce the energy consumption of the sensor nodes with low RE significantly and also saves energy for the whole WSN.
