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维普期刊数据库

Inverse minimum spanning tree problem and reverse shortest-path problem with discrete values

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Progress in Natural Science:Materials International 2006年第6期16卷 649-655页

作者： LIU Longcheng and HE Yong (Department of Mathematics, zhejiang university, hangzhou 31002.,{2. state key laboratory of cad & cg, zhejiang university, hangzhou 31002.,{2.) [a]Department of Mathematics Zhejiang University Hangzhou China [b]state key {2.oratory of cad & cg Zhejiang University Hangzhou China

In this paper, we consider two network improvement problems with given discrete values: the inverse minimum spanning tree problem and the reverse shortest-path problem, where the decrements of the weight of the edges are given discrete values. First, for the three models of the inverse minimum spanning tree problem (the sum-type, the bottleneck-type and the constrained bottleneck-type), we present their respective strongly polynomial algorithms. Then, we show that the reverse shortest-path problem is strongly NP-complete.

关键词： minimum spanning tree shortest-path problem inverse problem reverse problem computational complexity.

Ordinal scheduling problem and its asymptotically optimal algorithms on parallel machine system

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Science in china(Series F) 2004年第2期47卷 161-169页

作者： TAN Zhiyi1,2.& HE Yong1 1. Department of Mathematics, zhejiang university, hangzhou 31002.,{2. (email: tanzy@math.zju. *** heyong@math.zju.***) 2. state key laboratory of cad & cg, zhejiang university, hangzhou 31002.,{2. 1. Department of Mathematics Zhejiang University 310027 Hangzhou China 2. state key {2.oratory of cad & cg Zhejiang University 310027 Hangzhou China

Focusing on the ordinal scheduling problem on a parallel machine system, we discuss the background of ordinal scheduling and the motivation of ordinal algorithms. In addition, for the ordinal scheduling problem on identical parallel machines with the objective to maximize the minimum machine load, we then give two asymptotically optimal algorithm classes which have worst-case ratios very close to the upper bound of the problem for any given m. These results greatly improve the results proposed by He Yong and Tan Zhiyi in 2.02.

关键词： scheduling design and analysis of algorithm worst-case ratio.

维普期刊数据库

Online uniform machine covering with the known largest size

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Progress in Natural Science:Materials International 2007年第11期17卷 1271-1278页

作者： Cao Shunjuan1,2.and Tan Zhiyi1,3(1. Department of Mathematics, zhejiang university, hangzhou 31002.,{2. 2. Department of Mathematics, zhejiang Forestry university, hangzhou 311300,{2. 3. state key laboratory of cad & cg, zhejiang university, hangzhou 31002.,{2.) Department of Mathematics Zhejiang University Hangzhou 310027 China Department of Mathematics Zhejiang Forestry University Hangzhou 311300 China state key {2.oratory of cad & cg Zhejiang University Hangzhou 310027 China

This paper investigates the semi-online scheduling problem with the known largest size on two uniform machines. The objective is to maximize the minimum machine completion time. Both lower bounds and algorithms are given. Algorithms are optimal for the majority values of s≥1, where s is the speed ratio of the two machines. The largest gap between the competitive ratio and the lower bound is about 0.064. Moreover, the overall competitive ratio 2.matches the overall lower bound.

关键词： scheduling and covering uniform machine design and analysis of algorithm online competitive ratio

Multiple products of B-splines used in cad system

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Progress in Natural Science:Materials International 2006年第4期16卷 425-430页

作者： XU Huixia and WANG Guojin Institute of Images and Graphics, zhejiang university, hangzhou 31002.,{2. state key laboratory of cad&cg, zhejiang university, hangzhou 31002.,{2. [a]Institution of Images and Graphics Zhejiang University Hangzhou China [b]state key {2.oratary of cad cg Zhejiang University Hangzhou China

The function upgrade of computer aided design (cad) system requested that the multiple product of B-spline functions should be represented as a linear combination of some suitable (usually higher-degree) B-splines. In this paper, we apply the theory of spline space and discrete B-splines to deduce the representation of the coefficients of all terms of the linear combination, which can be directly applied to software coding in system development.

关键词： computer aided design (cad) NURBS Marsden’s identity.

Acquisition of time-varying 3D foot shapes from video

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Science china(Information Sciences) 2011年第11期54卷 2256-2268页

作者： GAO Fei,WANG Qing,GENG WeiDong & PAN YunHe state key {2. of cad & cg,zhejiang university,hangzhou 31002.,china 1. state key {2. of cad & cg Zhejiang University Hangzhou 310027 China

The 3D scanning of time-varying objects based on multi-view geometry has been a hot topic in computer vision in recent *** paper presents an active approach to acquiring 3D shapes of moving foot from multi-view video sequences based on the explicit marker points woven in *** reference 3D model of foot is firstly recovered from the starting frames in the multi-view video clips,and then the markers in each view are traced as a whole based on a continuous motion vector field built from the reference 3D *** missing vertices in the candidate 3D model caused by self-occlusion,non-uniform illumination and random noises are reliably estimated and reconstructed in 3D space by minimizing the changes of differential features in 3D geometry of the reference *** experimental results show that our method can robustly recover the 3D model of foot in complex background even if there is a relatively large movement between the adjacent frames,with an acceptable accuracy of the resulting 3D model.

关键词： time-varying shapes 3D foot modeling feature tracking multi-view geometry

Joint segmentation and motion estimation of left ventricle with an anisotropic biomechanical model

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Progress in Natural Science:Materials International 2007年第02期17卷 226-229页

作者： ZHUANG Ling, LIU Huafeng, BAO Hujun ( state key {2.oratory of cad & cg, zhejiang university, hangzhou 31002., china state key {2.oratory of Modern Optical Instrumentation, zhejiang university, hangzhou 310058, china) [a]state key {2.oratory of cad&cg Zhejinang University Hangzhou China [b]state key {2.oratory of Modern Optical Instrumentation Zhejiang University Hangzhou China

Accurate estimation of shape and motion variability of the heart has important clinical implications for heart disease diagnosis. In this paper, we describe a framework which performs simultaneous segmentation and motion analysis of the left ventricle from 3D cardiac images. The left ventricle is formulated as an anisotropic linear elastic body represented by a set of tetrahedrons constructed from sampling nodes. The elastic body is evolved by both internal force and external force, and the external force imposed on each node is an integration of edginess measure, shape coherence measure, prior distributions of the myocardial tissues and temporal driven measure. The displacement field and the segmentation result are simultaneously solved at the equilibrium state between the internal energy and the external energy. The experiment with 3D canine MR images illustrated its abilities and benefits.

关键词： left ventricle motion simultaneous estimation deformable model image segmentation.

A new method for designing a developable surface utilizing the surface pencil through a given curve

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Progress in Natural Science:Materials International 2008年第1期18卷 105-110页

作者： Hongyan Zhao,Guojin Wang* Department of Mathematics and state key {2.oratory of cad&cg,zhejiang university,hangzhou 31002.,china Department of Mathematics and state key {2.oratory of cad&cg Zhejiang University Hangzhou 310027 China

This paper proposes a new method for designing a developable surface by constructing a surface pencil passing through a given curve, which is quite in accord with the practice in industry design and *** utilizing the Frenet trihedron frame,we derive the necessary and suffcient conditions to construct a developable surface through a given *** the requirements in shoemak- ing and garment-manufacture industries,we also study the special case of specifying the given curve as a *** given geodesic can be classified into three types corresponding to each type of developable *** also present the polynomial representation of the developable *** algorithm is convenient and effcient for applications in engineering.

关键词： cad/CAM Developable surface Geodesic Frenet frame

Hodograph computation and bound estimation for rational B-spline curves

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Progress in Natural Science:Materials International 2007年第8期17卷 988-992页

作者： Xu Huixia~(1,2. Wang Guojin~(1,2.*) (1.Institute of Computer Images and Graphics,zhejiang university,{2. 31002.,china 2.state key laboratory of cad&cg,zhejiang university,{2. 31002.,china) [a]Institute of Computer Images and Graphics Zhejiang University Hangzhou China [b]state key {2.oratory of cad&cg Zhejiang University Hangzhou China

It is necessary to compute the derivative end estimate the bound of rational B-spline curves in design system,which has not been studied to *** improve the function of computer aided design (cad) system,end to enhance the efficiency of different algo- rithms of rational B-spline curves,the representation of scaled hodograph and bound of derivative magnitude of uniform planar rational B- spline curves are derived by applying Dir function,which indicates the direction of Cartesian vector between homogeneous points,discrete B-spline theory end the formula of translating the product into a summation of B-spline *** an application of the result above, upper bound of parametric distance between any two points in a uniform planar rational B-spline curve is further presented.

关键词： computer aided design (cad) rational B-spline discrete B-spline hodograph bound of derivative distance between two points

Parameterization for fitting triangular mesh

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Progress in Natural Science:Materials International 2006年第11期16卷 1214-1221页

作者： LIN Hongwei**, WANG Guojin, LIU Ligang and BAO Hujun(state key {2.oratory of cad&cg, zhejiang university, hangzhou 31002., china) [a]state key {2.oratory of cad &cg Zhejiang University Hangzhou China

In recent years, with the development of 3D data acquisition equipments, the study on reverse engineering has become more and more important. However, the existing methods for parameterization can hardly ensure that the parametric domain is rectangular, and the parametric curve grid is regular. In order to overcome these limitations, we present a novel method for parameterization of triangular meshes in this paper. The basic idea is twofold: first, because the isotherms in the steady temperature do not intersect with each other, and are distributed uniformly, no singularity (fold-over) exists in the parameterization; second, a 3D harmonic equation is solved by the finite element method to obtain the steady temperature field on a 2. triangular mesh surface with four boundaries. Therefore, our proposed method avoids the embarrassment that it is impossible to solve the 2. quasi-harmonic equation on the 2. triangular mesh without the parametric values at mesh vertices. Furthermore, the isotherms on the temperature field are taken as a set of iso-parametric curves on the triangular mesh surface. The other set of iso-parametric curves can be obtained by connecting the points with the same chord-length on the isotherms sequentially. The obtained parametric curve grid is regular, and distributed uniformly, and can map the triangular mesh surface to the unit square domain with boundaries of mesh surface to boundaries of parametric domain, which ensures that the triangular mesh surface or point cloud can be fitted with the NURBS surface.

关键词： parameterization regular parametric curve grid mesh fitting reverse engineering.