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Thresholds of geographic environmental elements in sediment yield of drainage basins

science china Earth sciences 2005年第2期48卷 230-240页

作者： CHEN Hao, ZHOU Jinxing, CAI Qiangguo, LU Zhongchen & LI Zhongyan institute of Geographic sciences and Natural Resources Research, Chinese Academy of sciences, beijing 100101, china institute of Forestry science, Chinese Academy of Forestry science, beijing 100091, china Research Center for Eco-Environment sciences, Chinese Academy of sciences, beijing 100085, china computing institute of science and engineering, north china electric power university, beijing 102206, china institute of Geographic sciences and Natural Resources Research Chinese Academy of Sciences Beijing China institute of Forestry science Chinese Academy of Forestry Science Beijing China Research Center for Eco-Environment sciences Chinese Academy of Sciences Beijing China computing institute of science and engineering North China Electric Power University Beijing China

Threshold of environmental elements in drainage basin sediment yield refers to, under effect of climate, underlying surface and human activity, a turning point of abrupt changes in drainage sediment yield related to environmental element characteristics. Previous studies on threshold of sediment yield of relevant drainage basins were mainly concentrated on impact of natural zones with a few researches on impact of other environmental elements. Particularly studies on compound environmental element threshold in drainage basin sediment yield remain blank today. Studies indicate that sediment yield in drainage basins is affected by compound interactions and complex actions. Based on single element analysis, the present paper gives quantitatively compound threshold of environmental elements affecting sediment yield of the drainage basin between Hekouzhen and Tongguan in the middle Yellow River by the method of multi-variant, polynomial formula regression analysis.

关键词： middle Yellow River, environmental element, sediment, sediment delivery mudule, threshold.

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Numerical simulation of ski-jump jet motion using lattice Boltzmann method

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science china(Technological sciences) 2011年第S1期54卷 72-75页

作者： ZHANG Hua 1 &ZHANG XiaoDong 2 1 School of Renewable Energy,north china electric power university,beijing 102206,china 2 School of Energy power and Mechanical engineering,north china electric power university,beijing 102206,china School of Renewable Energy North China Electric Power University Beijing China School of Energy power and Mechanical engineering North China Electric Power University Beijing China

Based on the lattice Boltzmann method,a lattice Boltzmann(LB) model of the ski-jump jet two-phase flow is developed first and the corresponding boundary conditions are studied.A simple case study of a droplet horizontal movement calculation is carried out to test and verify the model,where level set method is used to track and reconstruct the moving droplet free surface. Then,we numerically simulate a two dimensional flow field of the ski-jump jet with the LB model,derive the moving surface and velocity vector field of the jet *** simulation results are very consistent with the physical *** effectiveness and reliability of the model are demonstrated by the numerical examples.

关键词： ski-jump jet droplet lattice Boltzmann method interface numerical simulation

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INFLUENCES ON COUPLED LATERAL AND TORSION VIBRATION BEHAVIOR OF RUB-IMPACT ROTOR BY ROTOR-TO-STATOR CLEARANCE

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Chinese Journal of Mechanical engineering 2004年第2期17卷 210-214页

作者： Gu Yujiong He Chengbing Yang Kun Zhang Jianqiang Department of power engineering,north china electric power university,beijing 102206, china 华北电力大学（北京）北京 102206

With the establishment of the nonlinear coupled lateral and torsion vibrationequations of rub-impact Jeffcott rotor and through numerical simulations, the influences on lateraland torsion vibration behavior by rotor-to-stator clearance are analyzed, which prove that there isstrong impact on coupled lateral and torsion vibration behavior. Smaller the clearance is, morecomplex the motion of rotor is. When the clearance is larger, the frequency spectrum of rub-impactrotor is mainly composed of 1/2X, 1/3X and 1/4X components. With the decrease of clearance,quasi-periodic and chaotic motions will be present. Under different clearances, the bifurcationdiagrams of lateral and torsion vibrations can be divided into rub-free zone, rub-light zone andthree complex motion zones in which the motion trend of lateral vibration is similar to that of thetorsion vibration. Compared with the lateral vibration, the torsion vibration is of more motionforms and more abundant frequency components in amplitude spectrum.

关键词： Rub-impact rotor Rotor-to-stator clearance Coupled lateral and torsionvibrations

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Mission planning of the flying robot for powerline inspection

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Progress in Natural science:Materials International 2009年第10期19卷 1357-1363页

作者： Chang’an Liu,Lei Wang,Chunyang Liu School of Computer science and Technology,north china electric power university,beijing 102206,china School of Computer science and Technology North China Electric Power University Beijing 102206 China

Mission planning is an important step in the powerline inspection flying *** deal with the tasks of powerline flying robots,a flying robot mission-planning system is established based on the unmanned mini-helicopter model described in this *** can deter-mine the best checking order,the optimal space path and the best flight *** objective function and the constraints are described by establishing the mathematical model,and the mission-planning system is decomposed by using the tiered ***-agent technology is chosen to solve the mission-planning ***,simulation is conducted to verify that the mission-planning system is feasible and efficient.

关键词： powerline inspection flying robot Mission planning Multi-agent technology

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An ecological hydraulic radius approach to estimate the instream ecological water requirement

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Progress in Natural science:Materials International 2007年第3期17卷 320-327页

作者： LIU Changming and MEN Baohui ( Key Laboratory of Water Cycle and Related Land Surface Process, institute of Geographical sciences and Natural Resources Research, Chinese Academy of sciences, beijing 100101, china Key Laboratory of Water and Sediment sciences, Ministry of Education & Water sciences College, beijing Normal university, beijing 100875, china Department of Hydraulic and Hydropower engineering, north china electric power university, beijing 102206, china) Key Laboratory of Water Cycle and Related Land Surface Process Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China. Key Laboratory of Water and Sediment sciences Ministry of Education & Water Sciences College Beijing Normal University Beijing 100875 China. Department of Hydraulic and Hydropower engineering North China Electric Power University Beijing 102206 China

This essay defines the concepts of ecological flow velocity as well as ecological hydraulic radius (EHR) and proposes an ecological hydraulic radius approach (EHRA) which considers both the watercourse information (including hydraulic radius, roughness coefficient and hydraulic gradient) and the required stream velocity necessary for maintenance of certain ecological functions all together. The key parameter of EHRA is to fix the watercourse cross-sectional flow area corresponding to EHR, by which the relation between parabola shaped cross-sectional flow area and hydraulic radius is deduced. The EHRA not only meets the requirement of flow velocity for adequate fish spawning migration, but also is applicable to the ecological flows in regard with other ecological issues (such as the calculation of the instream flow requirements for transporting sediment and for pollution self-purification, etc.). This essay has illuminated the computational process taking the estimation of ecological water requirement of Zhuba Hydrologyical Station watercourse in Niqu branch of the Yalong River as an example. Additionally, we compare EHRA with Tennant approach. The result shows that the Zhuba Hydrological Station ecological water requirement calculated by EHRA lies between the minimum and favorable ecological water requirement calculated by the Tennant approach. This is due to the fact that the ecological flow velocity (such as the fish spawning migration flow velocity) was taken into consideration, producing results applicable to the practical situation.

关键词： ecological flow flow velocity cross-sectional flow area ecological hydraulic radius (HER) instreamecological water requirement.

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Measures against the adverse impact of natural wind on air-cooled condensers in power plant

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science china(Technological sciences) 2010年第5期53卷 1320-1327页

作者： YANG LiJun,DU XiaoZe & YANG YongPing Key Laboratory of Condition Monitoring and Control for power Plant Equipment of Ministry of Education of china,north china electric power university,beijing 102206,china Key Laboratory of Condition Monitoring and Control for power Plant Equipment of Ministry of Education of china North China Electric Power University

The natural wind plays disadvantageous roles in the operation of air-cooled steam condensers in power *** is of use to take various measures against the adverse effect of wind for the performance improvement of air-cooled *** on representative 2×600 MW direct air-cooled power plant,three ways that can arrange and optimize the flow field of cooling air thus enhance the heat transfer of air-cooled condensers were *** physical and mathematical models of air-cooled condensers with various flow leading measures were presented and the flow and temperature fields of cooling air were obtained by CFD *** back pressures of turbine were calculated for different measures on the basis of the heat transfer model of air-cooled *** results show that the performance of air-cooled condensers is improved thus the back pressure of turbine is lowered to some extent by taking measures against the adverse impact of natural wind.

关键词： air-cooled condenser wind speed and direction flow and heat transfer back pressure power plant

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Current distribution and stability of LTS/HTS hybrid superconducting conductors

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science china(Technological sciences) 2010年第7期53卷 2000-2007页

作者： GUAN XiaoJin1,2, WANG YinShun1 & ZHOU WeiWei3 1 Key Laboratory of HV and EMC beijing, north china electric power university, beijing 102206, china 2 Department of Physics, Baoding university, Baoding 071000, china 3 institute of electrical engineering, Chinese Academy of sciences, beijing 100190, china Key Laboratory of HV and EMC beijing North China Electric Power University Beijing China Department of Physics Baoding University Baoding China institute of electrical engineering Chinese Academy of Sciences Beijing China

Current distribution and stability of a hybrid LTS/HTS superconductor, consisting of multifilamentary NbTi/Cu and Bi2223/Ag tapes, were numerically analyzed according to power-law models. The results showed that most of current passed through the LTS and the current increased in the HTS with temperature rise when the transport current was below the critical current of the hybrid conductor. The quench propagation velocity of the hybrid conductor was smaller but its minimum quench energy was larger than those of LTS conductors, indicating that the stability of the hybrid superconducting conductor was effectively improved and a high engineering current density was simultaneously achieved. Finally, a hybrid sample, made by soldering Bi2223/Ag tape onto NbTi/Cu conductor, was prepared and tested successfully at helium temperature. The experimental results qualitatively agreed with the simulated ones.

关键词： distribution hybrid conductor minimum quench energy quench propagation velocity n value stability

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Reduced analysis and confirmatory research on co-adaptability theoretical solution to conflicting events in construction engineering projects

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science china(Technological sciences) 2010年第2期53卷 480-485页

作者： HOU XueLiang1 , LU Mei2 & WANG Kai3 1 School of Business Administration, north china electric power university, beijing 102206, china 2 Department of Construction Management, Tsinghua university, beijing 100084, china 3 College of Management, beijing Jiaotong university, beijing 100084, china School of Business Administration North China Electric Power University Beijing China Department of Construction Management Tsinghua University Beijing China College of Management Beijing Jiaotong University Beijing China

The co-adaptability theoretical solution to conflicting events in construction engineering projects has three problems. First, the transformation of constraint conditions of theoretical solution is very difficult in practical engineering applications; second, some coefficients are difficult to be determined; third, there are overfull circular arithmetic operations involved in it. To resolve these problems, a new method to reduce the theoretical solution complications is proposed. By analyzing the operating mechanism of theoretical solution model, redundancies in the theoretical solution can be eliminated, and the ISM mapping with the co-adaptability solution can be set up. Based on this approach, a procedure to solve practical conflicting events in construction projects is established by replacing characteristic variables with mathematic variables. The research results show that the procedure can replace the co-adaptability theoretical solution effectively and solve practical conflicting events in construction projects.

关键词： construction project conflict theoretical solution reduced analysis ISM confirmatory research

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Analysis of leakage current in GaAs micro-solar cell arrays

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science china(Technological sciences) 2010年第5期53卷 1240-1246页

作者： WANG YanShuo1,CHEN NuoFu1,2,3,ZHANG XingWang1,BAI YiMing1,WANG Yu1,HUANG TianMao1,ZHANG Han1 & SHI HuiWei1 1 Key Laboratory of Semiconductor Materials science,institute of Semiconductors,Chinese Academy of sciences,PO Box 912,beijing 100083,china 2 School of Renewable Energy engineering,north china electric power university,beijing 102206,china 3 National Laboratory of Micro-Gravity,institute of Mechanics,Chinese Academy of sciences,beijing 100080,china Key Laboratory of Semiconductor Materials science Institute of Semiconductors Chinese Academy of Sciences Beijing China School of Renewable Energy engineering North China Electric Power University Beijing China National Laboratory of Micro-Gravity Institute of Mechanics Chinese Academy of Sciences Beijing China

The output characteristics of micro-solar cell arrays are analyzed on the basis of a modified model in which the shunt resistance between cell lines results in current *** modification mainly consists of adding a shunt resistor network to the traditional *** obtained results agree well with the reported experimental *** calculation results demonstrate that leakage current in substrate affects seriously the performance of GaAs micro-solar cell *** performance of arrays can be improved by reducing the number of cells per *** addition,at a certain level of integration,an appropriate space occupancy rate of the single cell is recommended for ensuring high open circuit voltages,and it is more appropriate to set the rates at 80%-90% through the calculation.

关键词： micro-solar cell MEMS(micro-electromechanical systems) leakage current

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Some invariant properties of ordered information systems under homomorphism

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science china(Information sciences) 2010年第9期53卷 1816-1825页

作者： WANG ChangZhong1*,CHEN DeGang2 & HU QingHua3 1Department of Mathematics,Bohai university,Jinzhou 121000,china 2Department of Mathematics and Physics,north china electric power university,beijing 102206,china 3power engineering,Harbin institute of Technology,Harbin 150001,china Department of Mathematics Bohai University Jinzhou China Department of Mathematics and Physics North China Electric Power University Beijing China power engineering Harbin Institute of Technology Harbin China

In this paper,some properties of ordered information systems under homomorphism are *** concept of a consistent function with respect to dominance relations is first introduced and its properties are ***,some main invariant properties of dominance relations under relation mappings are *** is proven that attribute reductions in the original ordered information system and its image system are equivalent under the condition of *** means of the results,we can get the smaller image system that has the same reducts as a given massive ordered information system.

关键词： consistent function dominance relation ordered information system homomorphism reduction

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