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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 university 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 engineering, school of Physical sciences and engineering, 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 mechanical 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 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

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

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

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

RADIATION AND DIFFRACTION OF WATER WAVEs BY A sUBMERGED CIRCULAR CYLINDER AT FORWARD sPEED

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Journal of Hydrodynamics 1993年第4期5卷 85-96页

作者： G.X.Wu department of mechanical engineering,university college london,Torrington Place,london wc1E,7JE,U.K.

The wave radiation and diffraction by a submerged circular cylinder in deep water is analysed by the multipole expansion *** theory is based on the inviscid and linearized potential flow.

关键词： flow water wave circular cylinder

Taxol inhibits stretch-induced electrophysiological alterations in isolated rat hearts with acute myocardial infarction

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science China(Life sciences) 2010年第8期53卷 1009-1014页

作者： CAO JunXian1, FU Lu1, sUN DianJun2, XIE Rongsheng1, ZHOU Jue3 & QU Fan4 1department of Cardiology, The First Affiliated Hospital of Harbin Medical university, Harbin 150001, China 2Chinese Research Center for Endemic Disease Control, Key Laboratory of Etiological Epidemiology, Ministry of Health (23618504), Harbin Medical university, Harbin 150081, China 3Pharmacy department, king’s college london, Franklin-Wilkins Building, 150 stamford street, london, uk 4The First Affiliated Hospital, school of Medicine, Zhejiang university, Hangzhou 310003, China 1. department of Cardiology The First Affiliated Hospital of Harbin Medical University Harbin 150001 China2. Chinese Research Center for Endemic Disease Control Key Laboratory of Etiological Epidemiology Ministry of Health (23618504) Harbin Medical University Harbin 150081 China3. Pharmacy Department King’s College London Franklin-Wilkins Building 150 Stamford Street London UK4. The First Affiliated Hospital School of Medicine Zhejiang University Hangzhou 310003 China

Mechanosensitive channels have been determined to work as transducers of mechanoelectric feedback in the heart, which is associated with the generation of arrhythmias. Recent studies have investigated the role of the cytoskeleton in ion channels control. This study explored the ability of taxol to inhibit stretch-induced electrophysiological alterations in the ischemic myocardium. Thirty-two Wistar rats were randomly divided into four groups: normal control group (n=9), taxol group (n=7), myocardial infarction (MI) group (n=9), and MI+taxol group (n=7). After Langendorff perfusion, the isolated hearts were stretched for 5 s by balloon inflation to 0.2 or 0.3 mL. The effects of stretching on 90% monophasic action potential duration (MAPD90), premature ventricular beats (PVB), and ventricular tachycardia (VT) were observed for 30 s. stretching increased MAPD90 in both the normal control and MI groups, but MAPD90 increased more in the MI group for the same degree of stretch. Taxol (5 μmol L?1) had no effect on MAPD90 under baseline, unstretched conditions, but MAPD90 in the taxol group was slightly increased after stretching compared with the normal control group (P>0.05). However, taxol reduced MAPD90 in infarcted myocardium (Ps of PVB and VT in the MI group were higher than in the normal control group (both Ps in normal myocardium, but it inhibited PVB and VT in infarcted hearts (both Ps changes in MAPD and the occurrence of arrhythmias caused by mechanical stretching of the myocardium could be inhibited by taxol in isolated rat hearts during AMI, indicating the involvement of tubulin in mechanoelectric feedback in AMI.

关键词： arrhythmia microtubulin monophasic action potential stretch/mechanoelectric coupling

Tribological behavior of lubricant-impregnated porous polyimide

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Friction 2024年第4期12卷 711-725页

作者： Jinbang LI Ningning ZHOU Janet s.s.WONG school of mechanical engineering and Mechanics Ningbo UniversityNingbo 315211China Beijing Key Laboratory of Long-life Technology of Precise Rotation and Transmission Mechanisms Beijing Institute of Control EngineeringBeijing 100029China department of mechanical engineering Imperial College LondonLondon SW72AZUK

Porous materials impregnated with lubricants can be used in conditions where limited lubricant is *** this work,three porous polyimides(PPI)with different densities were ***(PAO)impregnated PPI(iPPI)discs were rubbed against steel and sapphire *** operando observations of the iPPI-sapphire contacts show that oil is released under an applied load,forming a meniscus around *** at the outlet is created at high sliding *** amount of released oil increases with increasing PPI *** moduli,E*,estimated based on the actual contact size show that trapped oil in iPPIs contributes to load *** higher speeds,tribological rehydration of the contact occurs in low density iPPI,with that E*rises with *** high density PPIs,high speeds give a constantly high E*which is limited by the viscoelastic properties of the PPI network and possibly the rate of oil *** of iPPI-steel contacts is governed by the mechanical properties of the PPI,the flow of the lubricant,and the roughness of the PPI *** low-and medium-density(highly porous,high roughness)PPIs,large amount of oil is released,and lubrication is mainly via lubricant restricted in the contact in the pores and possibly tribological *** high density(low porosity)PPI,with lower roughness,hydrodynamic lubrication is achieved which gives the lowest *** results show that polymeric porous materials for effective lubrication require the optimization of its surface roughness,stiffness,oil flow,and oil retentions.

关键词： polyimide porous material friction mechanism polymer limited lubrication