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Orientation angle rotatability of planar serial n-link manipulators

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science China(Technological sciences) 2010年第6期53卷 1620-1637页

作者： LI RuiQin1,XIAO DengHong1 & DAI Jian s2.1 College of mechanical engineering and Automation,North {2. of China,Taiyuan 030051,China 2.department of mechanical engineering,king’s College london,university of london,london wc2. 2.s,uk 1. College of mechanical engineering and Automation North University of China Taiyuan 030051 China2. Department of Mechanical Engineering King’s College London University of London London WC2R 2LS UK

This paper presents a new method of analyzing the orientation angle rotatability of a planar serial n-link manipulator by examining the rotatability of its virtual equivalent *** orientation boundary region decomposition is proposed based on the polynomial discriminant derived from a serial three-link *** angle workspace indicates a set of angle ranges by which the end-effector can reach with certain orientation for every point in the reachable position *** introducing a virtual equivalent mechanism,the open-chain kinematic problem is converted into a close-chain mechanism,and the Grashof-type condition is used to examine the rotatability of the end-effector *** reachable position workspace can be divided into several Grashof intervals and non-Grashof intervals based on the extreme positions and singular configurations of a *** derived equations in this paper can be used to calculate the variation rule of the orientation angle workspace of any given planar serial n-link manipulator on the basis of its link *** orientation angle rotatability of a seven-link serial manipulator is solved by the proposed method and graphical representations of the orientation angle workspaces are mapped onto a three-dimensional coordinate *** theoretical approach has practical significance for the design of a highly dexterous serial n-link manipulator with proposed link relations.

关键词： Grashof criterion planar serial manipulator orientation angle workspace virtual equivalent mechanism

METAMORPHIC MECHANIsMsAND THEIR CONFIGURATION MODELs

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Chinese Journal of mechanical engineering 2000年第3期13卷 212-218页

作者： Dai Jiansheng (department of mechanical {2., school of Physical sciences and {2., king’s College, university of london,strand,london wc2. 2.s, United kingdom) Zhang Qixian (Robotics Research Institute,Beijing university of Aeronautics and 伦敦大学皇家学院英国 London 北京航空航天大学北京

The concept of metamorphic mechanisms is presented, configuration models and configuration transformations relating to a set of new matrix operations are discussed and proposed. The configuration of a metamorphic mechanism reflects the connectivity change in the mechanism during motions which results in mobility change and presents the characteristics of the mechanism which is discussed in various applications particularly in decorative artifacts. The characteristics is further investigated with mobility analysis.

关键词： Metamorphic mechanisms Configurations Topology Connectivity Mobilit

Numeration and type synthesis of 3-DOF orthogonal translational parallel manipulators

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Progress in Natural science:Materials International 2008年第5期18卷 563-574页

作者： Jingjun Yua, Jian s. Dai b, shusheng Bi a, Guanghua Zong a a Robotics Institute, Beihang university, Beijing 100083, China b department of {2. engineering, school of Physical science and engineering, king’s College, university of london, The strand, london wc2. 2.s, uk Robotics Institute Beihang University Beijing 100083 China department of mechanical {2. School of Physical Science and Engineering King’s College University of London The Strand London WC2R 2LS UK

Low-degree-of-freedom (Low-DOF) parallel manipulators (PMs) have drawn extensive interests, particularly in type synthesis in which two main formal approaches were established by using the reciprocal screw system theory and Lie group theory. This paper aims at numeration and type synthesis of orthogonal translational parallel manipulators (OTPMs) by resorting to an integration of the group- based method and graphical representation of the topology. For this purpose, the concept of Cartesian DOF-characteristic matrix, orig- inated from displacement subgroup and displacement submanifold, is proposed. A new approach based on the combination of the atlas of Cartesian DOF-characteristic matrix and the displacement group-theoretic method is addressed for both exhaustive classi cation and type synthesis of OTPMs. The proposed approach is prone to construct an orthogonal structure and is easy to realize the complete clas- si cation and exhaustive enumeration of this class of low-DOF PMs.

关键词： Type synthesis Displacement group Orthogonal translational parallel manipulator

The sloshing of stratified liquid in a two-dimensional rectangular tank

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science China(Physics,Mechanics & Astronomy) 2011年第1期54卷 2-9页

作者： WU GuoXiong1,2.1 state Key Laboratory of Ocean engineering,College of Naval Architecture,Ocean and Civil engineering,shanghai Jiao Tong {2.,shanghai 2.02.0,China 2.department of mechanical engineering,{2. College london,Torrington Place,london wc1E 7JE,uk 1. state Key Laboratory of Ocean engineering College of Naval Architecture Ocean and Civil Engineering Shanghai Jiao Tong University Shanghai 20024 China2. Department of Mechanical Engineering University College Londo Torrington Place London WC1E 7JE UK

The sloshing of inviscid liquid of stratified density in a rectangular tank is *** the flow is no longer irrotional,the governing equation is found to be quite different from the Laplace equation used for the liquid of constant *** particular it contains terms of mixed temporal and spatial *** problem is solved based on the variable separation method and Laplace transform for the constant Vaisala-Brunt *** is found that the stratification of density may have small effects on those natural frequencies associated with the constant density,but many new natural frequencies have appeared as a result of its effect.

关键词： sloshing density stratification resonance rectangular tank

Enhancing the capacitances of electric double layer capacitors based on carbon nanotube electrodes by carbon dioxide activation and acid oxidization

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science China(Technological sciences) 2010年第5期53卷 1234-1239页

作者： LI Chensha1,2.QIAO YingJie1,WU JianJun2.WANG DaZhi2.& YUAN DianBo2.1 department of Materials science,Harbin engineering {2.,Harbin 150001,China 2.department of mechanical engineering,Tsinghua {2.,Beijing 100084,China 1. department of Materials science Harbin Engineering University Harbin 150001 China2. Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Polarizable electrodes of electric double layer capacitors(EDLCs) were made from carbon nanotubes(CNTs).Effect of carbon dioxide activation together with acid oxidation for the electrodes on the characteristics and performances of electrodes and EDLCs was *** dioxide activation changed the microstructure of the electrodes,increased the effective surface area of CNTs and optimized the distribution of apertures of the *** oxidization modified the surface characteristics of *** on the polarizable electrodes treated by carbon dioxide activation and acid oxidization,the performances of EDLCs were greatly *** specific capacitance of the electrodes with organic electrolyte was increased from 2..8 F/g to 60.4 F/g.

关键词： carbon nanotube electric double layer capacitor scan electron microscopy

Preparation of MWNTs/Al_2._3 composites and their mechanical and electrical properties

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science China(Technological sciences) 2005年第6期48卷 622-631页

作者： FAN Jinpeng1,2. ZHAO Daqing1,2. XU Zening1,2.& WU Minsheng1,2.1. department of mechanical {2., Tsinghua university, Beijing 100084, China 2. Key Laboratory for Advanced Manufacturing by Materials Processing Technology, Tsinghua university, Beijing 100084, China 1. department of mechanical {2. Tsinghua University 100084 Beijing China 2. Key Laboratory for Advanced Manufacturing by Materials Processing Technology Tsinghua University 100084 Beijing China

The mechanical and electrical properties of MWNTs/Al2.3 composite prepared fabricated by hot pressing are investigated. The relation between properties and microstructure of composites is also discussed. With 4wt% MWNTs as reinforcement, the fracture toughness of composite obtained reaches 5.55 MPa·m1/2. which is 80% higher than that of pure Al2.3 obtained in the same conditions. The main toughening mechanism is CNTs’ pinning alumina grain boundaries, and the pullout of CNTs takes effect also. Through adding 2.t% MWNTs and altering the mix method, the fracture toughness of the composite obtained is 3.97 MPa·m1/2. Furthermore, the electrical resistivity is as low as 8.4×10?3 ?·m, decreasing by 14 orders of magnitude compared with pure alumina ceramics. The function of CNTs in composite is related to the distribution state of CNTs in composite, and the distribution state of CNTs in matrix is dependent on preparation procedures.

关键词： MWNTs, alumina, composite, fracture toughness, electrical properties.

Advances in numerical methods for the solution of population balance equations for disperse phase systems

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science China Chemistry 2009年第8期52卷 1063-1079页

作者： sU JunWei1,GU ZhaoLin2.3 & XU X.Yun41 department of mechanical {2. and Automation,school of mechanical {2.,Xi’an Jiaotong university,Xi’an 710049,China 2.Key Laboratory of Mechanics on Disaster and Environment in Western China,Ministry of Education,Lanzhou 730000,China 3 department of Environmental science and Technology,school of Human settlements and Civil {2.,Xi’an Jiaotong university,Xi’an 710049,China 4 department of Chemical {2.,Imperial College london,london sW7 2.Z,uk 1. department of mechanical {2. and Automation School of Mechanical Engineering Xi’an Jiaotong University Xi’an 710049 China 2. Key Laboratory of Mechanics on Disaster and Environment in Western China Ministry of Education Lanzhou 730000 China 3. department of Environmental science and Technology School of Human Settlements and Civil Engineering Xi’an Jiaotong University Xi’an 710049 China 4. department of Chemical engineering Imperial College London London SW7 2AZ UK

Accurate prediction of the evolution of particle size distribution is critical to determining the dynamic flow structure of a disperse phase system.A population balance equation(PBE),a non-linear hyperbolic equation of the number density function,is usually employed to describe the micro-behavior(aggregation,breakage,growth,etc.) of a disperse phase and its effect on particle size *** solution is the only choice in most *** this paper,three different numerical methods(direct discretization methods,Monte Carlo methods,and moment methods) for the solution of a PBE are evaluated with regard to their ease of implementation,computational load and numerical *** attention is paid to the relatively new and superior moment methods including quadrature method of moments(QMOM),direct quadrature method of moments(DQMOM),modified quadrature method of moments(M-QMOM),adaptive direct quadrature method of moments(ADQMOM),fixed pivot quadrature method of moments(FPQMOM),moving particle ensemble method(MPEM) and local fixed pivot quadrature method of moments(LFPQMOM).The prospects of these methods are discussed in the final section,based on their individual merits and current state of development of the field.

关键词： population balance equation direct discretization method Monte Carlo method moment methods disperse phase system

Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation

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science China(Physics,Mechanics & Astronomy) 2005年第4期48卷 496-512页

作者： LI Zhihui1,2. ZHANG Hanxin1 & FU song2.⒈ National Laboratory for CFD, Hypervelocity Aerodynamics Institute,China Aerodynamics Research and Development Center,Mianyang 62.000,China 2.department of engineering Mechanics,Tsinghua {2.,Beijing 100084,China 1. National Laboratory for CFD Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center 621000 Mianyang China 2. department of engineering Mechanics Tsinghua University 100084 Beijing China

The gas-kinetic unified algorithm using Boltzmann model equation have been extended and developed to solve the micro-scale gas flows in Poiseuille-like micro-channels from Micro-Electro-mechanical systems (MEMs). The numerical modeling of the gas kinetic boundary conditions suitable for micro-scale gas flows is presented. To test the present method, the classical Couette flows with various Knudsen numbers, the gas flows from short microchannels like plane Poiseuille and the pressure-driven gas flows in two-dimensional short microchannels have been simulated and compared with the approximate solutions of the Boltzmann equation, the related DsMC results, the modified N-s solutions with slip-flow boundary theory, the gas-kinetic BGK-Burnett solutions and the experimental data. The comparisons show that the present gas-kinetic numerical algorithm using the mesoscopic Boltzmann simplified velocity distribution function equation can effectively simulate and reveal the gas flows in microchannels. The numerical experience indicates that this method may be a powerful tool in the numerical simulation of micro-scale gas flows from MEMs.

关键词： Boltzmann model equation, discrete velocity ordinate method, finite-difference scheme, Couette flow, Poiseuille flow, gas flow in short-microchannel.

Investigation of ZsM-5/MCM-41 Composite Molecular sieve for Reducing Olefin Content of FCC Gasoline

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China Petroleum Processing & Petrochemical Technology 2009年第4期11卷 10-17页

作者： Ji Dekun~(1,2. Li shuyuan~1 Ding Fuchen~2.Chi Yaoling~2.(1.Chemical engineering school,China university of Petroleum(Beijing),Beijing 102.49 {2. of Chemical engineering,Beijing Institute of Petrochemical Technology) Chemical engineering school China University of Petroleum (Beijing) Beijing 102249 China department of Chemical engineering Beijing Institute of Petrochemical Technology China

ZsM-5/MCM-41 composite molecular sieve was prepared by the nano-assembling *** ZsM-5 molecular sieve,the MCM-41 molecular sieve,the ZsM-5/MCM-41 mechanical mixture and the ZsM-5/MCM-41 composite molecular sieve were characterized by X-ray powder diffractometry,N_2.adsorption isotherms,temperature programmed desorption of ammonia and scanning electron microscopy and their properties were *** FCC gasoline as the feed,activities of different molecular sieves for reducing olefin content were investigated in a continuous high-pressure micro-reactor unit under the following conditions:a reaction temperature of 400℃,a reaction time of 2.h,a weight hourly space velocity of 3h^(-1),and a reaction pressure of 2.0 *** results showed that the HMCM-41 molecular sieve had low reaction performance,and the HZsM-5 molecular sieve demonstrated high aromatization activity,while the ZsM-5/MCM- 41 composite molecular sieve exhibited a best olefin-reducing performance because of its high isomerization activity and moderate aromatization *** a largest olefin-reducmg capability and a reasonable distribution of products,the composite molecular sieve was more suitable for FCC gasoline upgrading compared to other three catalysts.

关键词： ZsM-5 MCM-41 composite molecular sieve FCC gasoline olefin reduction