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The General Machining Process Simulator GMPS

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Journal of Systems Engineering and Electronics 1994年第3期5卷 73-79页

作者： Xiao Tianyuan, Yang Gang & Li Xin (Department of automation, tsinghua university, beijing, china, 100084) Department of automation Tsinghua University Beijing China 100084

Automated manufacturing system is characterized by flexibility. It aims at producing a variety of products with virtually no time loses to change over from one part to the next. In this paper, the Machining Process Simulator GMPS is introduced, which can be used as a supported environment for machining process. It can be executed off-line or on-line in manufacturing systems in order to predict the collisions of tool with machined workpieces, fixtures or pallets. First, the functional model of GMPS is described, then adopted critical techniques in the simulator are introduced. Finally, an application of GMPS in CIMS ERC of china is presented.

关键词： Machining process simulator Modeling Front End DNC NC code translator 3D animation detecting collision.

Process data compression based on recursive identification of nonuniformly sampled systems

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控制理论与应用（英文版） 2012年第2期10卷 166-175页

作者： Boyi NI, Deyun XIAO Department of automation, tsinghua university, beijing 100084, china Department of automation Tsinghua University Beijing China

A recursive identification method is proposed to obtain continuous-time state-space models in systems with nonuniformly sampled （NUS） data. Due to the nonuniform sampling feature, the time interval from one recursion step to the next varies and the parameter is always updated partially at each step. Furthermore, this identification method is applied to form a combined data compression method in NUS processes. The data to be compressed are first classified with respect to a series of potentially existing （possibly time-varying） models, and then modeled by the NUS identification method. The model parameters are stored instead of the identification output data, which makes the first compression. Subsequently, as the second step, the conventional swinging door trending method is carried out on the data from the first step. Numeric results from simulation as well as practical data are given, showing the effectiveness of the proposed identification method and fold increase of compression ratio achieved by the combined data compression method.

关键词： Nonuniformly sampled system Recursive identification Data compression Swinging door trending

HIGH ACCURACY NUMERICAL METHOD OF THIN-FILM PROBLEMS IN MICROMAGNETICS

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Journal of Computational Mathematics 2003年第1期21卷 33-40页

作者： Zhongyi Huang (Deft, of Mathematical Sciences, tsinghua university, beijing, 100084, china) Dept. of Mathematical Sciences Tsinghua University 北京 100084

In this paper, a new high accuracy numerical method for the thin-film problems of micron and submicron size ferromagnetic elements is proposed. For the computation of stray field, we use the finite element method(FEM) by introducing a semi-discrete artificial boundary condition [1, 2]. In our numerical experiments about the domain patterns and their movement, we can see that the results are accordant to that of experiments and other numerical methods. Our method are very convenient to deal with arbitrary shape of thin films such as a polygon with high accuracy.

关键词： Thin-film Micromagnetics stray field Semi-discrete artificial boundary condition.

SOME PROPERTIES OF LSQR FOR LARGE SPARSE LINEAR LEAST SQUARES PROBLEMS

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Journal of Systems Science & Complexity 2010年第4期23卷 815-821页

作者： Zhongxiao JIA Department of Mathematical Sciences,tsinghua university,beijing 100084,china. Department of Mathematical Sciences Tsinghua University

It is well-known that many Krylov solvers for linear systems,eigenvalue problems,andsingular value decomposition problems have very simple and elegant formulas for residual *** not only allow us to further understand the methods theoretically but also can be usedas cheap stopping criteria without forming approximate solutions and residuals at each step beforeconvergence takes *** for large sparse linear least squares problems is based on the Lanczosbidiagonalization process and is a Krylov ***,there has not yet been an analogouslyelegant formula for residual *** paper derives such kind of *** addition,the authorgets some other properties of LSQR and its mathematically equivalent CGLS.

关键词： CGLS krylov subspace lanczos bidiagonalization least squares lsqr normal equations.

FL-FN-MOGA Based Traffic Signal Control

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Journal of Systems Engineering and Electronics 2003年第3期14卷 14-23页

作者： Wei Wu & Zhang Yi Department of automation, tsinghua university, beijing 100084, P. R. china Department of automation Tsinghua University Beijing 100084 P. R. China

In this paper, a traffic signal control method based on fuzzy logic (FL), fuzzy-neuro (FN) and multi-objective genetic algorithms (MOGA) for an isolated four-approach intersection with through and left-turning movements is presented. This method has an adaptive signal timing ability, and can make adjustments to signal timing in response to observed *** 'urgency degree' term, which can describe the different user's demand for green time is used in decision-making by which strategy of signal timing can be determined. Using a fuzzy logic controller, we can determine whether to extend or terminate the current signal phase and select the sequences of phases. In this paper, a method based on fuzzy-neuro can be used to predict traffic parameters used in fuzzy logic controller. The feasibility of using a multi-objective genetic algorithm ( MOGA) to find a group of optimizing sets of parameters for fuzzy logic controller depending on different objects is also demonstrated. Simulation results show that the proposed methed is effecfive to adjust the signal timing in response to changing traffic conditions on a real-time basis, and the controller can produce lower vehicle delays and percentage of stopped vehicles than a traffic-actuated controller.

关键词： Traffic signal control Fuzzy logic Fuzzy-neuro Multi-objective genetic algorithms.

THE NAGUMO EQUATION ON SELF-SIMILAR FRACTAL SETS

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Chinese Annals of Mathematics,Series B 2002年第4期23卷 519-530页

作者： HU JIAXINDepartment of Mathematics, tsinghua university, beijing 100084, china. Department of Mathematics Tsinghua University Beijing 100084 China

The Nagumo equation ut = △u+ bu(u-a)(1-u), t＞0is investigated with initial data and zero Neumann boundary conditions on post-critically finite (p.c.f.) self-similar fractals that have regular harmonic structures and satisfy the separation condition. Such a nonlinear diffusion equation has no travelling wave solutions because of the 'pathological' property of the fractal. However, it is shown that a global Holder continuous solution in spatial variables exists on the fractal considered. The Sobolev-type inequality plays a crucial role, which holds on such a class of p.c.f self-similar fractals. The heat kernel has an eigenfunction expansion and is well-defined due to a Weyl's formula. The large time asymptotic behavior of the solution is discussed, and the solution tends exponentially to the equilibrium state of the Nagumo equation as time tends to infinity if b is small.

关键词： Fractal set Spectral dimension Sobolev-type inequality Strong (Weak) solution

Closed and endoreversible chemical oscillation

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Chinese Journal of Chemistry 1994年第3期12卷 199-205页

作者： LI, Ru-ShengDepartment of Chemistry, tsinghua university, beijing 100084, china Department of Chemistry Tsinghua University Beijing 100084 China

Based on a simple nonideal chemical reaction model, the closed system with reversible nonideal reactions and illumination is shown to be able to exhibit sustained oscillation. The essential points in the occurrence of such oscillations are the nonideality of reacting media, which gives rise to multiple chemical equilibria, and the energy flow through illumination and heat conduction, which gives rise to spontaneous transitions repeatedly between the multiple equilibrium states. During the oscillation, reacting media undergo only reversible chemical transformation and all irreversibilities are restricted to the coupling of the system to external world. This oscillation provides an example of the so-called endoreversible machine and a possible way to convert radiation energy of the light directly into mechanical energy.

关键词： Chemical oscillation closed system nonideality endoreversible machine illumination.

An overview of computational photography

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Science china(Information Sciences) 2012年第6期55卷 1229-1248页

作者： SUO JinLi,JI XiangYang & DAI QiongHai Department of automation,tsinghua university,beijing 100084,china 1. Department of automation Tsinghua University Beijing 100084 China

Computational photography is an emerging multidisciplinary *** the last two decades,it has integrated studies across computer vision,computer graphics,signal processing,applied optics and related *** are exploring new ways to break through the limitations of traditional digital imaging for the benefit of photographers,vision and graphics researchers,and image processing *** to much effort in various associated fields,the large variety of issues related to these new methods of photography are described and discussed extensively in this *** give the reader the full picture of the voluminous literature related to computational photography,this paper briefly reviews the wide range of topics in this new field,covering a number of different aspects,including:(i) the various elements of computational imaging systems and new sampling and reconstruction mechanisms;(ii) the different image properties which benefit from computational photography,*** of field,dynamic range;and(iii) the sampling subspaces of visual scenes in the real *** on this systematic review of the previous and ongoing work in this field,we also discuss some open issues and potential new directions in computational *** paper aims to help the reader get to know this new field,including its history,ultimate goals,hot topics,research methodologies,and future directions,and thus build a foundation for further research and related developments.

关键词： computational photography computational imaging plenoptic function light field

TEXTURE DETERMINATION OF THIN FILM ZrO_2 BY ELECTRON DIFFRACTION

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Acta Metallurgica Sinica(English Letters) 1993年第12期6卷 472-473页

作者： WANG Yinghua tsinghua university,beijing,china Department of Materials Science and Engineering,tsinghua university,beijing 100084,china tsinghua Univ Beijing China

A method for semi-quantitative determination of thin film texture using electron diffrac- tion is *** texture state of a zirconia thin film with a cubic structure has been determined in this way and is presented as an... 详细信息

关键词： texture thin film electron diffraction ZrO_2