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Orientation angle rotatability of planar serial n-link manipulators

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 university of China,Taiyuan 030051,China 2 department of mechanical engineering,king’s college london,university of london,london wc2r 2ls,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

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Crank conditions and rotatability of 3-rrr planar parallel mechanisms

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science China(Technological sciences) 2009年第12期52卷 3601-3612页

作者： LI ruiQin 1 &DAI Jian s 2 1 college of mechanical engineering and Automation,North university of China,Taiyuan 030051,China 2 department of mechanical engineering,king’s college london,university of london,wc2r 2ls,uk college of mechanical engineering and Automation North University of China Taiyuan 030051 China department of mechanical engineering King’s College London University of London WC2R 2LS London UK

This paper investigates the rotatability of planar parallel mechanisms by revealing the crank conditions that relate to link *** paper extends the theorem of assemblability and the rotatability criterion and applies these criteria to parallel mechanisms in investigating the crank conditions of a parallel mechanism,leading to classification of three types of crank existing conditions including three-crank’s,six-crank’s and nine-crank’s of 3-rrr planar parallel *** results are summarized as constraint conditions in relation with link parameters with a concluding table and case studies.

关键词： crank rotatability planar parallel mechanism

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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 engineering, school of Physical sciences and engineering, king’s college, university of london,strand,london wc2r 2ls, 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

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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 mechanical engineering, school of Physical science and engineering, king’s college, university of london, The strand, london wc2r 2ls, uk robotics Institute Beihang University Beijing 100083 China department of mechanical engineering 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

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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 university,shanghai 200240,China 2 department of mechanical engineering,university 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

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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 engineering 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 1. department of mechanical engineering 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

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sECOND-OrDEr TrANsIENT sTANDING WAVEs IN A rECTANGULAr TANK

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Journal of Hydrodynamics 1995年第2期7卷 67-75页

作者： Wu G. X.(department of mechanical engineering ,Uniersity college london, Torrington Place,london wc1E 7JE,U. K.) Univ of college london London United Kingdom

Analytical solution are derived based on the Fourier series for the three dimensional transient free surface problem in a rectangular tank. The analysis is based on the stokes Perturbation and the second order result ... 详细信息

关键词： rectangular tank transient standing wave analytical solution

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Influence of modulation ratio on structure and properties of nanoscale ZrB_2/ZrAlN multilayered coatings

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science China(Technological sciences) 2010年第3期53卷 772-775页

作者： LI DeJun 1,KANG YuanBin 1,DONG Lei 1,DENG XiangYun 1,LIU Hao 2 &sUN XueLiang 2 1college of Physics and Electronic Information science,Tianjin Normal university,Tianjin 300387,China 2 department of mechanical&Materials engineering,university of Western Ontario,london ON,Canada 1. college of Physics and Electronic Information science Tianjin Normal University Tianjin 300387 China2. Department of Mechanical & Materials Engineering University of Western Ontario London ON Canada

ZrB2/ZrAlN multilayered coatings with various modulation ratios(t ZrB2:t ZrAlN)and constant modulation periods were prepared by magnetron sputtering system at room ***,XrD,surface profiler and nano-indenter were employed to investigate the influences of tZ rB 2:tZrAlNon the microstructure and mechanical properties of the *** interfaces and nanoscale multilayered modulation were confirmed by *** multilayer with modulation period of 40 nm and ratio of 3:1 displayed the highest hardness(36.4 GPa)and critical fracture load(76.477 mN)with lower *** polycrystalline structure and multilayered modulate structure were directly responsible for the enhanced mechanical properties.

关键词： ZrB2/ZrAlN multilayered coating magnetron sputtering modulation ratio nanoscale

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Non-Point Pollution from Crop Production: Global, regional and National Issues

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Pedosphere 2005年第4期15卷 499-508页

作者： D. NOrsE department of Geography University College London 4 Taviton Street London WC1H 0BT (UK)

China is now the world’s largest producer and user of industrial fertilizers and manures. Consequently China plays a substantial role in global N cycle dynamics and in man’s disruption of the nitrogen cycle though there are still significant uncertainties about the size and importance of emission and leaching rates. A major cause of China’s global role is the overuse of nitrogen fertilizers, which is most serious with intensive vegetable production where application rates can be up to 50% greater than crop needs, but is also a problem with wheat, rice and maize. China’s overuse of nitrogen fertiliser over the past 10-20 years has resulted in non-point source (NPs) pollution from crop production becoming a major cause of water pollution, and the situation is projected to get worse. In contrast, water pollution from point sources such as intensive livestock production and urban or industrial development is being brought more under control. The consequences for air pollution are equally serious. Emissions of nitrous oxide from fertilizers and manures may be so large that China could be responsible for 25-30% of global emissions of this damaging greenhouse gas and of the global warming resulting from it. The main national and local issues relate particularly to low fertilizer use efficiency and the losses of ammonia and NOx that lead to acid precipitation, and leaching and run-off losses that result in high nitrate levels in groundwater and eutrophication of rivers and lakes. The reasons why farmers overuse nitrogen fertilizer are complex and not fully understood. They involve agro-climate differences between provinces and counties, farming systems and farm income structures. Although there is a wide range of institutional and technological improvements that can greatly reduce this overuse rapid progress in reducing NPs is unlikely.

关键词： China fertilizer use global change nitrous oxide non-point source pollution

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Microstructure and formation mechanism of twins of laths of austenite with high nitrogen

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science China(Technological sciences) 2007年第6期50卷 755-764页

作者： WU CuiLan1,2 & LUO ChengPing2 1 Center for High resolution Electron Microscopy, college of Materials science and engineering, Hunan university, Changsha 410082, China 2 college of mechanical engineering, south China university of Technology, Guangzhou 510641, China 1. Center for High resolution Electron Microscopy College of Materials Science and Engineering Hunan University Changsha 410082 China 2. college of mechanical engineering South China University of Technology Guangzhou 510641 China

The microstructure of composite diffusion layer of the nitrided and chromized 0.2% carbon steel is investigated using TEM and EDs. It is found that laths of austenite with high nitrogen (γ N) precipitate from α-ferrite matrix in the deeper zone of the diffusion layer. These γ N laths are all twins, with their {111} twinning planes parallel to the lath axis, thus forming a characteristic "back-to-back" morphology. There are two types of γN lath. The first is a genuinely {111} twin, and γ N and α keep the accurate K-s relationship, and each γ N and α form a sharp and smooth γ N/α inter- face of {335}γN//{341}α, namely habit plane {335}fcc. The second is a pseudo-twin, with micro-twins {111} or faults formed within the two twin components. Localized lattice deformation (relaxation) seems to have occurred at the interfaces of the second type of γ N due to the formation of micro-twins or faults within the twin components. These micro-twins or faults make the orientation relationship (Or) between each of the γN and the α-matrix deviate from the accurate K-s Or, and the Or between two γ N twin components deviate from the genuine {111} twin relation- ship. In addition, the γ N/α interface of the second type of γ N is not as sharp or smooth as that of the first one.

关键词： austenite containing nitrogen, twins, steel 20, nitriding, composite chromizing

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