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Constrained Bézier curves' best multi-degree reduction in the L2-norm

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Progress in Natural Science:Materials International 2005年第9期15卷 843-850页

作者： ZHANG Renjiang 1,2 ** and WANG Guojin1(1. Institute of computer Images and Graphics, Zhejiang University, Hangzhou 310027, China 2. China Institute of Metrology, Zhejiang, Hangzhou 310034, China) Institute of computer Images and Graphics Zhejiang University Hangzhou 310027 China. State Key Laboratory of CAD&CG Zhejiang University Hangzhou 310027 China. China Institute of Metrology Zhejiang Hangzhou 310034 China

In computer aided geometric design, the degree reduction of the parameter curve is a key technique in data exchange and data compression. The various existing methods of degree reduction cannot decide whether the degree reduction curve satisfying the given tolerance exists beforehand, cannot give approximation of the best multi-degree reduction, or cannot provide explicit expression and error formula of the degree reduction curve. In this paper, we propose an entirely new method, which can hurdle the above flaws completely. For a given Bézier curve of degree n, we can easily decide whether a Bézier reduction curve of degree m exists, which has equal derivatives with the given curve up to （r-1）-th and （s-1）-th orders （r,s≤m） respectively at the endpoints, so the approximating error is less than the given tolerance ε in the L2-norm. If the curve exists, the explicit expression can be given.

关键词： computer aided design Bézier curve degree reduction L2-norm tolerance.

Object-Oriented design for FDTD Visual Scientific Computing

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Journal of Systems Engineering and Electronics 2001年第3期12卷 71-75页

作者： Dong, X. Wang, W. Wang, G. Electromagnetic and Commun. Lab. Sch. of Electronic and Info. Eng. Xi'an Jiaotong University Xi'an 710049 China

A scheme for general purposed FDTD visual scientific computing software is introduced in this paper using object-oriented design (OOD) method. By abstracting the parameters of FDTD grids to an individual class and separating from the iteration procedure, the visual software can be adapted to more comprehensive computing problems. Real-time gray degree graphic and wave curve of the results can be achieved using DirectX technique. The special difference equation and data structure in dispersive medium are considered, and the peculiarity of parameters in perfectly matched layer are also discussed.

关键词： Computational methods computer aided design Data structures Difference equations Finite difference method Iterative methods Natural sciences computing Object oriented programming Parameter estimation Three dimensional computer graphics Time domain analysis

APPLICATION OF GENERAL SYSTEM CAD ON ENGINES

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Journal of Wuhan University of Technology(Materials Science) 1998年第1期13卷 54-58页

作者：蒋炎坤 Huazhong Univ. of Science Technology China College of Comminution Huazhong University of Technology Wuhan 430074 China

Using modern design theory and methods comprehensively, this paper investigates a model of parameterization of engine general plan design (PEGPD). On the basis of engineering database, parametric drawing of longitudinal and cross section of engine can be obtained from this mode. The model is significant for improving the efficiency and quality of engine general system design. (Author abstract) 6 Refs.

关键词： computer aided design diesel engine general engineering database parametric drawing

A novel algorithm for explicit optimal multi-degree reduction of triangular surfaces

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Science in China(Series F) 2008年第1期51卷 13-24页

作者： HU QianQian WANG GuoJin Institute of computer Images and Graphics State Key Laboratory of CAD & CG Zhejiang UniversityHangzhou 310027 China

This paper introduces the algebraic property of bivariate orthonormal Jacobi polynomials into geometric approximation. Based on the latest results on the transformation formulae between bivariate Bernstein polynomials and Jacobi polynomials, we naturally deduce a novel algorithm for multi-degree reduction of triangular B^zier surfaces. This algorithm possesses four characteristics： ability of error forecast, explicit expression, less time consumption, and best precision. That is, firstly, whether there exists a multi-degree reduced surface within a prescribed tolerance is judged beforehand; secondly, all the operations of multi-degree reduction are just to multiply the column vector generated by sorting the series of the control points of the original surface in lexicographic order by a matrix; thirdly, this matrix can be computed at one time and stored in an array before processing degree reduction; fourthly, the multi-degree reduced surface achieves an optimal approximation in the norm L2. Some numerical experiments are presented to validate the effectiveness of this algorithm, and to show that the algorithm is applicable to information processing of products in CAD system.

关键词： computer aided design data compression triangular Bezier surface multi-degree reduction Bernstein polynomial,Jacobi polynomial L2 norm

Study of Piezoresistive Micro Electro-Mechanical Accelerometer design Platform

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Journal of Beijing Institute of Technology 2005年第3期14卷 289-292页

作者：张菁华石庚辰 School of Mechatronics Engineering Beijing Institute of Technology Beijing100081 China School

According to the inland micro electro-mechanical system （MEMS） process technique level, a design platform of piezoresistive micro electro-mechanical accelerometer is given. This platform is much more adaptable to the inland designer compared with the current MEMS CAD software. The design flow is presented in detail, and the key techique in the platform is analyzed amply. The structure design methodology is exemplified in the design of a piezoresistive accelerometer, and the accelerometer is the optimized structure for the given performance requirements. The accelerometer is now being manufactured.

关键词： micro electro-mechanical system sensor computer aided design

Study on Modeling Technology in Digital Reactor System

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Plasma Science and Technology 2004年第5期6卷 2503-2506页

作者：刘晓平罗月童童莉莉 FDS Team Institute of Plasma Physics Chinese Academy of SciencesHefei 230031China VCC Division School of Computer&InformationHefei University of TechnologyHefei 230009China 不详

Modeling is the kernel part of a digital reactor system. As an extensible platformfor reactor conceptual design, it is very important to study modeling technology and develop somekind of tools to speed up preparation of all classical computing models. This paper introducesthe background of the project and basic conception of digital reactor. MCAM is taken as anexample for modeling and its related technologies used are given. It is an interface program forMCNP geometry model developed by FDS team (ASIPP & HUT), and designed to run on windowssystem. MCAM aims at utilizing CAD technology to facilitate creation of MCNP geometry model.There have been two ways for MCAM to utilize CAD technology: (1) Making use of user interfacetechnology in aid of generation of MCNP geometry model; (2) Making use of existing 3D CADmodel to accelerate creation of MCNP geometry model. This paper gives an overview of MCAM'smajor function. At last, several examples are given to demonstrate MCAM's various capabilities.

关键词： computer aided design auto-modeling MCNP, 3D, MCAM, cooperation digital reactor

BUILDING A UNIFIED PRODUCT MODEL WITH COMPLEX METHOD

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Chinese Journal of Aeronautics 1996年第2期9卷 111-121页

作者： Wu Zhongke Wu Junheng (CAD/CAM Research Group, School of Space Technology, Beijing Universityof Aeronautics and Astronautics, Beijing, China, 100083) CAD / CAM Research Group School of Space Technology Beijing Univ. Aero. and Astronaut. Beijing 100083 China

After undergoing wireframe modeling, surface modeling and solid modeling, a unified product model, which holds a variety of constraints in engineering, supports design process, and unifies the wire frame, surface modeling, and solid modeling,is a general tendency of modeling technology. A discussion is presented here on how tobuild a unified product model by using the complex method. The concept of complex inalgebraic topology is introduced into the model and a new B-REP representation of thenon-manifold model is given --Identification Edge Structure. Based on it, some basicoperators and high-level operators are built. The model has a rigorous mathematicalbasis, and is flexible and easy to extend, and holds the lamina face, lamina edge andlamina vertex. As a result, the variety of constraints in engineering, such as parametricconstraints, optimization methods, fuzzy constraints, artificial intelligent, etc., can beadded to the system. The model may form the kernel for the implementation of the nextgeneration CAD system --intelligent CAD system.

关键词： computer aided design models polyhedrons

RESEARCH AND REALIZATION OF MUTUAL TRIMMING OF NURBS

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Chinese Journal of Aeronautics 1997年第2期10卷 119-126页

作者： Shen Qingyun Zhou Laishui Zhou Rurong(Research Center of CAD/CAM Engineering, Nanjing University ofAeronautics and Astronautics, Nanjing, 210016, China) Res. Center of CAD/CAM Engineering Nanjing Univ. Aero. and Astronaut. Nanjing 210016 China

Since regular surface is defined by a mapping from 2-D parameter plane to 3-D space, trimming of NURBS surface is equivalent to changing a valid parameter region ofthe surface with the same mapping. In this paper, by presenting a rigid and comprehensi-ble definition of union, difference and intersection of two intersecting loops in the parame-ter region of NURBS surface, and by working out the corresponding algorithm, a rebui1d-ing algorithm of the valid parameter region of NURBS surface is obtained.

关键词： contours surfaces computer aided design parametric surface nonuniform rational B-spline

THE CAPP SYSTEM IN CIMS ENVIRONMENT

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Chinese Journal of Aeronautics 1995年第2期8卷 125-132页

作者： Fan Qijin Huang Naikang Zhang Zhenming(Faculty 1003,Northwestern Polytechnical University,Xi’an,China,710072)

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关键词： computer aided design computer aided manufacturing tools