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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. of cad & cg, zhejiang university, hangzhou 31.027, china state key {2. of Modern Optical Instrumentation, zhejiang university, hangzhou 310058, china) state key {2. of cad & cg Zhejiang University Hangzhou 310027 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.

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 31.027,{2. state key laboratory of cad&cg, zhejiang university, hangzhou 31.027,{2. Institute of Images and Graphics Zhejiang University Hangzhou 310027 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.

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 31.027,{2. (email: tanzy@math.zju. *** heyong@math.zju.***) 2. state key laboratory of cad & cg, zhejiang university, hangzhou 31.027,{2. Department of Mathematics Zhejiang University state key {2. of cad & cg Zhejiang University

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

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. of cad&cg,zhejiang university,hangzhou 31.027,china Department of Mathematics and state key {2. 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

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 31.027,{2. 2. Department of Mathematics, zhejiang Forestry university, hangzhou 311300,{2. 3. state key laboratory of cad & cg, zhejiang university, hangzhou 31.027,{2.) Department of Mathematics Zhejiang University Hangzhou 310027 China Department of Mathematics Zhejiang Forestry University Hangzhou 311300 China state key {2. 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

Electro-mechanical response of functionally graded beams with imperfectly integrated surface piezoelectric layers

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Science china(Physics,Mechanics & Astronomy) 2006年第5期49卷 513-525页

作者： YAN Wei1 & CHEN Weiqiu1,2.1. Department of Civil Engineering, zhejiang university, hangzhou 31.027,{2. 2. state key Lab of cad & cg, zhejiang university, hangzhou 31.027,{2. Department of Civil Engineering Zhejiang University Hangzhou China state key Lab of {2. & cg Zhejiang University Hangzhou China

The time-dependent behavior of a simply-supported functionally graded beam bonded with piezoelectric sensors and actuators is studied using the state-space method. The creep behavior of bonding adhesives between piezoelectric layers and beam is characterized by a Kelvin-Voigt viscoelastic model, which is practical in a high temperature circumstance. Both the host elastic functionally graded beam and the piezoelectric layers are orthotropic and in a state of plane stress, with the former being inhomogeneous along the thickness direction. A laminate model is employed to approximate the host beam. Moreover, the coupling effect between the elastic deformation and electric field in piezoelectric layers is considered. Results indicate that the viscoelastic property of interfacial adhesives has a significant effect on the function of bonded actuators and sensors with time elapsing.

关键词： functionally graded beam piezoelectric layers Kelvin-Voigt model state-space method

维普期刊数据库

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. of cad&cg, zhejiang university, hangzhou 31.027, china) state key {2. of cad&cg Zhejiang University Hangzhou 310027 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.

Copy-and-paste operation of planar polygonal shapes

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Progress in Natural Science:Materials International 2007年第7期17卷 859-866页

作者： Yang Wenwu Feng Jieqing Huang Shengsheng Jin Xiaogang(state key {2. of cad&cg,zhejiang university,hangzhou 31.027,china) state key {2. of cad&cg Zhejiang University Hangzhou 310027 China

A 2. polygonal shape copy-and-paste method is proposed which is based on a multiple planar shapes blending algorithm. First sub-shapes are specified and selected,which correspond to user-defined visual features on the input *** they are copied and pasted with contribution weights to generate new shapes via a modified intrinsic 2. shape blending *** can edit the generated shape intuitively and interactively by adjusting the contribution *** proposed method fills the gap in the object modeling method- ology based on the copy-and-paste *** the static 2. copy-and-paste operation,the proposed method can also be applied to 2. metamorphosis among multiple planar shapes.

关键词： copy-and-paste 2. shape blending metamorphosis

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. 31.027,china 2.state key laboratory of cad&cg,zhejiang university,{2. 31.027,china) Institute of Computer Images and Graphics Zhejiang University Hangzhou 310027 China state key {2. of cad&cg Zhejiang University Hangzhou 310027 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