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Comparison of photovoltaic devices based on MEH-PPV with various molecular weights

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Chinese Science Bulletin 2004年第21期49卷 2259-2261页

作者： KANG Bonan1,2. WANG Liduo1, YANG Yong1 & QIU Yong1 1. key laboratory of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Department of Chemistry, {2. Univer- sity, beijing 100084, china 2. state key laboratory on Integrated optoelectronics, Jilin university Region, Changchun 13002., china key laboratory of Organic Optoelectronics & Molecular Engineering of Ministry of Education Department of Chemistry Tsinghua University Beijing 100084 China

Polymer photovoltaic devices based on poly (2. methoxy-5-(2. -ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH- PPV) with three weight-average molecular weights (Mw) have been fabricated with the device structure of ITO/PEDOT/ MEH-PPV/Ca/Ag, and the effect of the molecular weight on photovoltaic properties has been investigated. The experi- mental results show that the high molecular weight of MEH- PPV leads to low series resistance (Rs) and high short-circuit current. The low molecular weight of MEH-PPV leads to high shunt resistance (Rsh) and high open-circuit voltage. When the molecular weight is 6×105, the highest power con- version efficiency was observed.

关键词： MEHPPV 分子量光电器件载流子迁移率串联电阻并联电阻聚(2.甲氧基-5-(2.-乙基-乙氧基)-1,4-亚苯基乙烯撑)

Study on simulation and experiment of array micro Faraday cup ion detector for FAIMS

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Science china(Technological Sciences) 2010年第12期53卷 3225-3231页

作者： TANG Fei, WANG XiaoHao, ZHANG Liang & YAN ZiLin state key {2. of Precision Measurement Technology and Instruments, Department of Precision Instruments and Mechanology, tsinghua university, beijing 100084, china 1. state key {2. of Precision Measurement Technology and Instruments Department of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China

An array micro Faraday cup ion detector for FAIMS (High-field Asymmetric Waveform Ion Mobility Spectrometry) was introduced, with which the size of the FAIMS system was reduced. With simple structure, good stability, low noise, large measurements range, this detector can work under the condition of atmospheric pressure. The array micro Faraday cup was composed of gate electrode, sensitive electrode and shielding electrode. The sensitive electrode was made of tens of crossing silicon columns with diameter of 2.0 μm. It was fabricated through typical MEMS technology, which was compatible completely with plane FAIMS. It was shown from FLUENT simulation result that the resistance to gas motion was low and the flow field distribution was helpful for full absorption of the ion in this array design. Through electricity simulation, the method to reduce interference on the detection signal of the micro Faraday cup was given out. Connecting with KEITHLEY 2.7 ampere meter, the noise level of the array micro Faraday cup was lower than 0.5 pA. The output signal of the acetone sample measured by experiment was about 2.0 pA. Through contrast experiment, the design parameter of the micro Faraday cup was obtained primarily. This array micro Faraday cup can meet the requirements of the FAIMS system.

关键词： FAIMS MEMS Faraday cup ion detector low current

The refined theory of deep rectangular beams based on general solutions of elasticity

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Science china(Physics,Mechanics & Astronomy) 2006年第3期49卷 291-303页

作者： GAO Yang1 & WANG Minzhong2.1. College of Science, china Agricultural university, {2. 100083, china 2. state key laboratory for Turbulence and Complex Systems and Department of Mechanics and Engi- neering Science, Peking university, {2. 100871, china College of Science China Agricultural University Beijing 100083 China state key {2. for Turbulence Complex Systems Department of Mechanics Engineering Science Peking University Beijing 100871 China

The problem of deducing one-dimensional theory from two-dimensional the- ory for a homogeneous isotropic beam is investigated. Based on elasticity theory, the re- fined theory of rectangular beams is derived by using Papkovich-Neuber solution and Lur’e method without ad hoc assumptions. It is shown that the displacements and stresses of the beam can be represented by the angle of rotation and the deflection of the neutral surface. Based on the refined beam theory, the exact equations for the beam without transverse surface loadings are derived and consist of two governing differential equations: the fourth-order equation and the transcendental equation. The approximate equations for the beam under transverse loadings are derived directly from the refined beam theory and are almost the same as the governing equations of Timoshenko beam theory. In two ex- amples, it is shown that the new theory provides better results than Levinson’s beam the- ory when compared with those obtained from the linear theory of elasticity.

关键词： deep rectangular beams,the refined theory,Papkovich-Neuber solution,Lur'e method,governing equation

Performance analysis of uplink MIMO MC-CDMA systems based on linear zero-forcing V-BLAST algorithm

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Science in china(Series F) 2008年第9期51卷 1305-1318页

作者： YANG Wei1,2.& YANG Wei1 1 state key {2. of Rail Traffic Control and safety,beijing Jiaotong university,beijing 100044,china 2.National Mobile Communications Research {2.,Southeast university,Nanjing 2.0096,china 1. state key {2. of Rail Traffic Control and safety Beijing Jiaotong University Beijing 100044 China 2. National Mobile Communications Research laboratory Southeast University Nanjing 210096 China

A structure was proposed for multiple-input-multiple-output multicarrier code divi- sion multiple access （MIMO MC-CDMA） uplink transmission system. Linear zero- forcing V-BLAST （ZF V-BLAST） algorithm and maximum ratio combining （MRC） scheme was applied to the receivers. The average bit error rate （BER） expression was derived on condition that the number of receive antennas was larger than that of transmit antennas and it was verified by simulations. Numerical results show that the number of transmit and receive antennas, as well as the number of sub- carriers, all exert significant effects on the BER performance. The space diversity and frequency diversity show different abilities to improve the BER performance. The MIMO MC-CDMA system based on linear ZF V-BLAST algorithm is capable of achieving better BER performance than that of the conventional MC-CDMA system by reducing the number of transmit antennas or increasing the number of receive antennas.

关键词： bit error rate(BER) multiple-input-multiple-output(MIMO) multicarrier code division multiple access(MC-CDMA) zero-forcing(ZF)

THE GLOBAL ARTIFICIAL BOUNDARY CONDITIONS FOR NUMERICAL SIMULATIONS OF THE 3D FLOW AROUND A SUBMERGED BODY

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Journal of Computational Mathematics 2003年第4期21卷 435-450页

作者： Hou-de Han Xin Wen (Department of Mathematical Sciences, tsinghua university, beijing 100084,{2.) Department of Mathematical Sciences Tsinghua University Beijing 100084 China

We consider the numerical approximations of the three-dimensional steady potential flow around a body moving in a liquid of finite constant depth at constant speed and distance below a free surface in a channel. One vertical side is introduced as the upstream artificial boundary and two vertical sides are introduced as the downstream artificial boundaries. On the artificial boundaries, a sequence of high-order global artificial boundary conditions are given. Then the original problem is reduced to a problem defined on a finite computational domain, which is equivalent to a variational problem. After solving the variational problem by the finite element method, we obtain the numerical approximation of the original problem. The numerical examples show that the artificial boundary conditions given in this paper are very effective.

关键词： Ship wave Potential flow Global artificial boundary condition Finite element method.

Numerical exploration of new features on three-dimensional transition of a cylinder wake

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Science china Mathematics 2004年第z1期47卷 69-80页

作者： LING Guocan, XIONG Jun & ZHU Keqinstate key {2. of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, beijing 100080, china Department of Engineering Mechanics, tsinghua university, beijing 100084, china Chinese Acad Sci Inst Mech State Key Lab Nonlinear Mech Beijing 100080 Peoples R China Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

The three-dimensional transition of the wake flow behind a circular cylinder is studied in detail by direct numerical simulations using 3D incompressible N-S equations for Reynolds number ranging from 2.0 to 300. New features and vortex dynamics of the 3D transition of the wake are found and investigated. At Re = 2.0, the flow pattern is characterized by mode A instability. However, the spanwise characteristic length of the cylinder determines the transition features. Particularly for the specific spanwise characteristic length linear stable mode may dominate the wake in place of mode A and determine the spanwise phase difference of the primary vortices shedding. At Re = 2.0 and 300 it is found that the streamwise vortices evolve into a new type of mode "dual vortex pair mode" downstream. The streamwise vortex structures switch among mode A, mode B and dual vortex pair mode from near wake to downstream wake. At Re = 2.0, an independent low frequency fm in addition to the vortex shedding frequency fs is identified. Frequency coupling between fm and fs occurs. These result in the irregularity of the temporal signals and become a key feature in the transition of the wake. Based on the formation analysis of the streamwise vorticity in the vicinity of cylinder, it is suggested that mode A is caused by the emergence of the spanwise velocity due to three dimensionality of the incoming flow past the cylinder. energy distribution on various wave numbers and the frequency variation in the wake are also described.

关键词： cylinder, wake, 3D transition, Fourier-spectral-spectral-element method, direct numerical simulation (DNS).

Effect of Heat Treatment on High Temperature Stress Rupture Strength of Brazing Seam for Nickel-base Superalloy

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Journal of university of Science and Technology beijing 2001年第2期8卷 123-125页

作者： Junying Zhang, Zhongtai Zhang, Jisheng Sun, Xiaofang Liu, Wei Tian (state key {2. of New Ceramics and Fine Processing, Department of Materials Science and Engineering, tsinghua university, beijing 100084, china) (beijing Institute of Aeronautical Tsing Hua Univ Dept Mat Sci & Engn State Key Lab New Ceram & Fine Proc Beijing 100084 Peoples R China Inst Aeronaut Mat Beijing 100095 Peoples R China Univ Sci & Technol beijing Mat Sci & Engn Sch Beijing 100083 Peoples R China

In order to enhance the high-temperature stress rupture strength of brazing seam by heat treatment, it was diffusion treated, then solution heat treated, and finally aging treated. The microstructure of brazing seam especially morphology of gamma ' phase and boride was observed and the strength of brazing seam was measured in this process. The results show that heat treatment can enhance high-temperature stress rupture strength by improving the microstructure of brazing seam. The strength of brazing seam after solution heat treatment decreases in comparison with that only after diffusion treatment while aging treatment after solution heat treatment increases the strength of brazing seam.

关键词： wide-gap brazing high temperature stress rupture strength microstructure nickel-base superalloy

Estimation methods of eco-environmental water requirements: Case study

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Science china Earth Sciences 2005年第8期48卷 1280-1292页

作者： YANG Zhifeng1,2. CUI Baoshan1 & LIU Jingling 1. School of Environment, beijing Normal university, beijing 100875, china 2. state key Joint laboratory of Environmental Simulation and Pollution Control, beijing 100875, china 1. School of Environment Beijing Normal University 100875 Beijing China 2. state key Joint {2. of Environmental Simulation and Pollution Control 100875 Beijing China

Supplying water to the ecological environment with certain quantity and quality is significant for the protection of diversity and the realization of sustainable development. The conception and connotation of eco-environmental water requirements, including the definition of the conception, the composition and characteristics of eco-environmental water requirements, are evaluated in this paper. The classification and estimation methods of eco-environmental water requirements are then proposed. On the basis of the study on the Huang-Huai-Hai Area, the present water use, the minimum and suitable water requirement are estimated and the cor-responding water shortage is also calculated. According to the interrelated programs, the eco-environmental water requirements in the coming years (2.10, 2.30, 2.50) are estimated. The result indicates that the minimum and suitable eco-environmental water requirements fluc-tuate with the differences of function setting and the referential standard of water resources, and so as the water shortage. Moreover, the study indicates that the minimum eco-environmental water requirement of the study area ranges from 2.84×1010m3 to 1.02.1011m3, the suitable water requirement ranges from 6.45×1010m3 to 1.78×1011m3, the water shortage ranges from 9.1×109m3 to 2.16×1010m3 under the minimum water requirement, and it is from 3.07×1010m3 to 7.53×1010m3 under the suitable water requirement. According to the different values of the water shortage, the water priority can be allocated. The ranges of the eco-environmental water re-quirements in the three coming years (2.10, 2.30, 2.50) are 4.49×1010m3?1.73×1011m3, 5.99×10m3?2.09×1011m3, and 7.44×1010m3?2.52.1011m3, respectively.

关键词： eco-environmental water requirements, assessment methods, Huang-Huai-Hai area.

Propagation characteristics of converted refracted wave and its application in static correction of converted wave

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Science china Earth Sciences 2008年第S2期51卷 226-232页

作者： LIU Yang1,2.& WEI XiuCheng3 1 state key {2. of Petroleum Resource and Prospecting,china university of Petroleum,beijing 102.49,china 2.CNPC Geophysical Exploration key {2.,china university of Petroleum,beijing 102.49,china 3 Exploration and Production Research Institute,SINOPEC,beijing 100083,china china Univ Petr State Key Lab Petr Resource & Prospecting Beijing 102249 Peoples R China china Univ Petr CNPC Geophys Explorat Key Lab Beijing 102249 Peoples R China SINOPEC Explorat & Prod Res Inst Beijing 100083 Peoples R China

Three-component seismic exploration through P-wave source and three-component geophone is an effective technique used in complicated reservoir exploration. In three-component seismic exploration data processing,one of the difficulties is static correction of converted wave. This paper analyzes propagation characteristics of non-converted and converted refracted waves,and discovers a favor-able condition for the formation of converted refracted wave,i.e. the velocity of overlaying medium S wave is much lower than that of underlying medium S wave. In addition,the paper proposes the static correction method of converted wave based on PPS converted refracted wave,and processes the real three-component seismic data with better results of static correction of converted wave.

关键词： PPS converted refracted wave converted wave static correction