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Structure and kinematic analysis of a novel 2-DOF translational parallel robot

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Progress in Natural science:Materials International 2007年第10期17卷 1213-1219页

作者： Chen Tao1, Wu Chao2 and Liu Xinjun2(1. School of Application science and technology, Harbin university of science and technology, Harbin 150080, china 2. department of Precision Instruments, tsinghua university, Beijing 100084, china) School of Application science and technology Harbin University of Science and Technology Harbin 150080 China department of Precision Instruments Tsinghua University Beijing 100084 China

This paper addresses the analysis of a novel parallel robot with 2 translational degrees of freedom (DOFs). The robot can position a rigid body in a plane with constant orientation. The kinematic structure of the robot is first described in detail. Some kinematic problems, such as the inverse and forward kinematics, velocity, and singularity are then analyzed. The working and assembly modes are discussed. Since it is the most important index to design a robot, the workspace of the robot is studied systematically in this paper. Based on the analysis of reachable workspace and singularity, a kind of workspace concept characterizing the region that the end-effector of the robot can reach in practice is defined. The results of this paper will be very useful for the design and application of the robot.

关键词： parallel robot degree of freedom kinematics workspace.

Series-based approximate approach of optimal tracking control for nonlinear systems with time-delay

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Progress in Natural science:Materials International 2008年第12期18卷 1571-1576页

作者： Gongyou Tang~a Mingqu Fan~(a,b) a college of information science and Engineering,Ocean {3. of china,Qingdao 266100,china b college of information and Engineering,Shandong {3. of science and technology,Jinan 25003.,china college of information science and Engineering Ocean University of China Qingdao 266100 China college of information and Engineering Shandong University of Science and Technology Jinan 250031 China

The optimal output tracking control (OTC) problem for nonlinear systems with time-delay is *** a series-based approx- imate approach,the original OTC problem is transformed into iteration solving linear two-point boundary value problems without time- *** OTC law obtained consists of analytical linear feedback and feedforward terms and a nonlinear compensation term with an infinite series of the adjoint *** truncating a finite sum of the adjoint vector series,an approximate optimal tracking control law is obtained.A reduced-order reference input observer is constructed to make the feedforward term physically *** exam- ples are used to test the validity of the series-based approximate approach.

关键词： Nonlinear systems Time-delay Tracking control Optimal control Observer

Fabrication of Grain-oriented (Bi,Pb)_2Sr_2Ca_2Cu_3._x Superconducting Tapes Using Magnetic Field and Vibration Technique

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Journal of Materials science & technology 1998年第1期14卷 86-88页

作者： Yanwei MA and Xianjin WANG (Dept. of Metal Forming, university of science and technology Beijing, Beijing 100083.{3.)Zutang WANG (tsinghua university, Beijing 100084,{3.) Dept. of Metal Forming University of Science and Technology Beijing Beijing 100083 China tsinghua university Beijing 100084 China

Highly textured (Bi,Pb)2Sr2Ca2Cu3.x superconducting tapes have been fabricated by means of magnetic-field and vibration technique. This method is an effective way of improving the degree of grain alignment and density of oxide core in tapes after heat treatment and pressing *** of above 20% was increased than that without treatment.

关键词： Bi,Pb Pb Sr Fabrication of Grain-oriented x Superconducting Tapes Using Magnetic Field and Vibration Technique Ca Cu

REACTION MECHANISM OF BENZOPHENONE-PHOTOINITIATED CROSSLINKING OF POLYETHYLENE

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Chinese Journal of Polymer science 2002年第4期20卷 291-307页

作者： Bao-jun Qu State Key Laboratory of Fire science and department of Polymer science and Engineering {3. of science and technology of china Hefei 23.026 china university of science and technology of{3. State Key Laboratory of Fire Science and Department of Polymer Science and Engineering Hefei 230026

The radical intermediates, the crosslink microstructures, and the reaction mechanism of benzophenone (BP)-photoinitiated crosslinking of low-density polyethylene (LDPE) and model compounds (MD) have been reviewed in detail. The spin-trapping electron spin resonance (ESR) spectra obtained from the LDPE/BP systems with spin-trap agents show that two kinds of polymer radical intermediates are mainly formed: tertiary carbon and secondary carbon radicals. The spin-trapping ESR studies of MD/BP systems give further evidence that photocrosslinking reactions of PE predominantly take place a sites of tertiary carbon, secondary carbon, and especially allylic carbon when available. The high resolution C-13.NMR spectra obtained from LDPE and MD systems show that the crosslink microstructures have H- and Y-type links and that their concentrations are of the same order. The fluorescence, ESR, C-13.and H-1-NMR spectra from the PE and MD systems demonstrate that the main photoreduction product of BP (PPB) is benzpinacol formed by the recombination of two diphenylhydroxymethyl (K-.) radical intermediates. Two new PPB products: an isomer of benzpinacol with quinoid structure, 1-phenylhydroxymethylene-4-diphenylhydroxymethyl-2,5-cyclobexadiene and three kinds of alpha-alkyl-benzhydrols have been detected and identified. These results provide new experimental evidence for elucidating the reaction mechanism in the BP-photoinitiated crosslinking of polyethylene.

关键词： photocrosslinking mechanism polymer radical intermediates crosslink microstructures photolytic products of benzophenone polyethylene model compound

Generalized gradient projection neural networks for nonsmooth optimization problems

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science china(information sciences) 2010年第5期53卷 990-1005页

作者： LI GuoCheng 1 , SONG ShiJi 2 ? & WU Cheng 2 1 department of Mathematics, Beijing information science and {3. university, Beijing 100192, china 2 department of Automation, tsinghua university, Beijing 100084, china department of Mathematics Beijing Information Science and Technology University Beijing China department of Automation Tsinghua University Beijing China

Generalized gradient projection neural network models are proposed to solve nonsmooth convex and nonconvex nonlinear programming problems over a closed convex subset of R n . By using Clarke’s generalized gradient, the neural network modeled by a differential inclusion is developed, and its dynamical behavior and optimization capabilities both for convex and nonconvex problems are rigorously analyzed in the framework of nonsmooth analysis and the differential inclusion theory. First for nonconvex optimization problems, the quasi convergence results similar to those achieved by previous work are proved. For convex optimization problems, the global convergence results are proved, i.e. any trajectory of the neural network converges to an asymptotically stable equilibrium point, which is an optimal solution of the primal problem whenever it exists. This result remains valid even if the initial condition is chosen outside the feasible set. In addition, an asymptotic control result involving a Tykhonov like regularization shows that any trajectory of the revised neural network can be forced to converge toward a particular optimal solution of the primal problem. Finally, two simulation optimization algorithms for solving the optimization and control problems are designed respectively, and three typical simulation experiments are illustrated to present the accuracy and efficiency of theoretical convergence results of this paper.

关键词： nonsmooth optimization problem generalized gradient projection networks differential inclu sions convergence

Influence of mesoscale topography on vortex intensity

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Progress in Natural science:Materials International 2008年第1期18卷 71-78页

作者： Zhexian Luo*,Yun Gao Remote Sensing college,Nanjing university of information {3. and technology,Najing 210044,china Remote Sensing college Nanjing University of Information Science and Technology Najing 210044 China

The effect of mesoscale topography on multi-vortex self-organization is investigated numerically in this paper using a barotropic prim- itive equation model with topographic *** the initial field there are one DeMaria major vortex with the maximum wind radius rm of 80 km at the center of the computational domain,and four meso-b vortices in the vicinity of rm to the east of the major vortex center. When there is no topography present,the initial vortices self-organize into a quasi-final state flow pattern,i.e.a quasi-axisymmetric vor- tex whose intensity is close to that of the initial major ***,when a mesoscale topography is incorporated,the spatial scale of the quasi-final state vortex reduces,and the relative vorticity at the center of the vortex and the local maximum wind speed remarkably *** possible mechanism for the enhancement of the quasi-final state vortex might be that the negative relative vorticity lump, generated above the mesoscale topography because of the constraint of absolute vorticity conservation,squeezes the center of positive vorticity towards the mountain slope area,and thus reduces the spatial range of the major ***,because the total kinetic energy is basically conservative,the squeezing directly leads to the concentration of the energy in a smaller area,*** strengthening of the vortex.

关键词： Mesoscale topography Vortex Self-organization Intensity change

SUPERSATURATED DESIGN WITH MORE THAN TWO LEVELS

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Chinese Annals of Mathematics,Series B 2001年第2期22卷 183-194页

作者： LU XUAN SUN YIZHOU department of Mathematical science, tsinghua university, Beijing {3., china. department of Mathematical science Tsinghua Univeristy Beijing 100084 China

Supersaturated designs are useful in screening experiments. This paper discusses the topic of multi-level supersaturated design. Two quantities, E(d2) and Df, are proposed to evaluate the optimality of supersaturated designs. A lower bound of E(d2) is obtained with a necessary condition for achieving it. Some E(d2)-optimal supersaturated designs of 3. 4, and 5 levels are given.

关键词： D-efficiency Screening experiment Fractional factorial design Orthogonality

A note on the crossed product R(A, α) associated with PSL_2(R)

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science china Mathematics 2008年第11期51卷 2081-2088页

作者： WU WenMing 1 School of Mathematical and computer science, Chongqing Normal university, Chongqing 400047,{3. 2 department of Mathematical science, tsinghua university, Beijing 100084,{3. School of Mathematical and computer science Chongqing Normal University Chongqing China department of Mathematical science Tsinghua University Beijing China

Given the hyperbolic measure dxdy/y2 on the upper half plane H, the rational actions of PSL2(R) on H induces a continuous unitary representation α of this group on the Hilbert space L2(H, dxdy/y2). Supposing that A = {Mf : f ∈ L∞(H, dxdy/y2)}, we show that the crossed product R(A,α) is of type I. In fact, the crossed product R(A,α) is *-isomorphic to the von Neumann algebra B(L2(P,ν))■LK, where LK is the abelian group von Neumann algebra generated by the left regular representation of K.

关键词： crossed product rational actions PSL2(R) von Neumann algebras

Quasi-physical global optimization method for solving the equal circle packing problem

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science china(information sciences) 2011年第7期54卷 1333-1339页

作者： HUANG WenQi & YE Tao School of computer science and technology,Huazhong {3. of science and technology,Wuhan 43.074,china School of computer science and technology Huazhong University of Science and Technology Wuhan China

The equal circle packing problem is a well-known challenge in *** is also a natural,clear and fair test system for global *** paper presents a quasi-physical global optimization algorithm for solving the equal circle packing *** algorithm simulates two kinds of movements of N elastic disks: smooth movement driven by elastic pressures and violent movement driven by strong repulsive forces and attractive *** smooth movement makes the disks reach a locally optimal configuration,while the violent movement makes them jump out of the local optimum trap and reach a more promising *** algorithm is tested on the widely studied instances of N = 1,2,...,*** find better packings than the reported best-known ones on 3. instances and reproduce the best-known results on the remaining 113.instances.

关键词： equal circle packing global optimization quasi-physical method heuristic