Efficient volume preserving approach for skeleton-based implicit surfaces

INTRODUCTIONImplicitsurfaces,especiallyskeleton basedones,arewidelyusedinmodelingsoftobjectssuchasorgans,cloudsandliquidsbecauseoftheircapabilityforgeneratingsmoothsurfacesofarbitrarygeometryandtopology(Fujitaetal.,1 990 ;Yuetal.,1 999;MurtaandMiller,1 99…     

Improvement of the termination criterion for subdivision of the rational Bézier curves

By using some elementary inequalities, authors in this paper makes further improvement for estimating the heights of Bézier curve and rational Bézier curve. And the termination criterion for subdivision of the rational Bézier curve is also improved. The conclusion of the extreme value problem is thus further confirmed.     

Improvement of the termination criterion for subdivision of the rational Bézier curves

By using some elementary inequalities, authors in this paper makes further improvement for estimating the heights of Bézier curve and rational Bézier curve. And the termination criterion for subdivision of the rational Bézier curve is also improved. The conclusion of the extreme value problem is thus further confirmed. Project supported by the National Natural Science Foundation of China (No. 60173034) and the Foundation of State Key Basic Research(973) Program (No. G1998030600), China     

一种细分格式生成极限曲面的法向量的求法

本文在Levin给出的三角域上生成极限曲面的法向量求法基础上 ,给出拟蝴蝶形细分在矩形域上生成极限曲面的情况 ,并得到了两个自由度 ,可以对法向量进行优化选取 ,这对讨论曲面的等距面有广泛的实际意义     

非对称有理细分矩阵的构造与应用

针对逼近细分法在几何造型中产生细分曲线与特征多边形改变较多的不足,在有理矩阵细分法的理论基础上。对细分矩阵加以改进,构造一个特殊非对称模式的细分矩阵．通过调整该细分矩阵中的参数使生成曲线尽可能逼近特征多边形．     

基于半边折叠的三角网格模型分片参数化与重构算法

提出了一种三角网格模型参数化与重构算法,在网格分片参数化的基础上实规了模型三角面的半正规化重构.首先,使用考虑顶点权重和边长度的半边折叠方法把网格模型分层简化到基网格,在每次折叠操作的同时使用分片参数化方法把被删除顶点动态地映射到下层网格面上;然后,把基网格进行多次平面细分,利用原始网格顶点、参数化点和细分点之间的位置关系,对细分点进行扰动完成网格重构.实验结果表明,该算法能够得到特征保持的多分辨率简化模型,使用参数化结果重构的三角网格也能够较好地还原原始模型.     

基于Geomagic Studio的细分造型技术研究

运用逆向工程专用软件可以使点云生成三角网格面,它是原始模型的线性逼近,光滑度较低。为了改善曲面的光滑度,经过对细分造型技术的研究,在分析Loop细分模式和细分模式的基础上,揭示GeomagicStudio软件中细分造型功能的原理．建立在三角网格面模型基础上的细分曲面造型技术可以改善曲面光滑度。     

旋转体侧面积与体积的计算

本文利用换元积分法和坐标变换,分别讨论了直角坐标方程、参数方程和极坐标方程表示的光滑曲线,绕任一直线旋转一周时所产生的旋转体的侧面积和体积的计算方法．     

GFFD:Generalized free-form deformation with scalar fields

INTRODUCTIONNURBSandpolygonalmeshesaretwomajorrepresentationschemesformodelingcomplex 3Dobjects.Althoughsomeeffectiveshapeeditingtoolsarenowavailableforbothofthem ,modify ingtheshapeofanobjectintuitivelyisstillte diouswork .Thisisparticularlytrueforsomesp…     

GFFD: Generalized free-form deformation with scalar fields

The novel free-form deformation(FFD) technique presented in the paper uses scalar fields defined by skeletons with arbitrary topology. The technique embeds objects into the scalar field by assigning a field value to each point of the objects. When the space of the skeleton is changed, the distribution of the scalar field changes accordingly, which implicitly defines a deformation of the space. The generality of skeletons assures that the technique can freely define deformable regions to produce a broader range of shape deformations.     

带状图像的三角剖分与细化

为了对带状图像进行快速的识别,提出了一种新的带状图像细化算法。通过对带状图像边界的近似多边形顶点集合首先进行三角化,生成三角形网格,接着把多边形外部的三角形去掉,剩余一系列保持拓扑关系的内部三角形,然后根据三角形的类型生成不同的局部骨架,最后连接生成整幅带状图像的骨架。     

Said-Ball曲线的细分算法

设实数c（0〈c〈1）将广义Said-Ball曲线r（u），0≤u≤1分为两段r[0，c]（u）=r[cu]和r[c，1]（M）=r（c＋（1-c）u），0≤u≤1.利用对偶泛函，给出用显式表示的Said-Ball曲线的细分算法（细分矩阵）。所给出的显示细分矩阵有利于曲线的生成与合并方面的研究。     

细分图的零维数

设A(G)为简单图G的邻接矩阵。图G的零维数定义为A(G)中0特征值的重数,记为η(G)。S(G)表示非平凡图G的细分图。本文讨论细分图的零维数并分别给出树、单圈图和双圈图的细分图的零维数。     

Catmull-Clark细分曲面能量精确分析方法

提出了一种新的精确计算包含奇异顶点的Catmull-Clark细分曲面能量的方法.通过把Catmull-Clark细分曲面片转化成双3次B样条曲面片,导出了任意拓扑结构的细分曲面完整的能量计算公式.该方法不需要对细分曲面进行递归细分,就能计算出细分曲面的膜能量和薄板能量,与现有方法相比,该方法能快速准确地计算出细分曲面的能量.曲面光顺实例表明,用该方法计算细分曲面能量高效可行.     

运动对骨质疏松影响的研究

在整理和分析近10年来中外文献基础上,运用文献分析法,重点对骨质疏松症的形成机制、运动对骨的影响等问题进行了综述.     

Effects of sorting on subsequent recall of unrelated items: a developmental study.

Second graders, fifth graders, and adults participated in 2 experiments designed to study the effects of sorting on subsequent recall of unrelated words. 1 group sorted the items freely, while a second group was constrained to learn the sorting schemes generated by free subjects. In the first experiment, subjects sorted until they reached a criterion of organizational stability. In Experiment 2, sorting was terminated prior to reaching a stable criterion. Recall and output clustering were reduced in Experiment 2, relative to Experiment 1, because of organizational instability. No meaningful differences were found in either experiment in the sorting schemes generated by free subjects in the 3 age groups, nor was there an effect of age of yoking partner on performance of constrained subjects. This result differed from previous research, and it was concluded that the sorting technique diminished differences in organizational behavior usually found between older and younger subjects.     

三角形网格细分法及其在曲面造型中的应用

网格细分造型技术因其计算规则简单、可以表示任意拓扑特性和几何特征的曲面等性质,受到造型技术领域中众多学者的关注,而三角形网格细分的许多算法已经成功应用于该领域。本文介绍了网格细分的相关理论,重点介绍了三角形网格细分法以及在曲面造型中的应用,为曲面造型提供了一种新的方法。     

不同经济管理模式对快递物流行业的促进作用论析

伴随全球产业链的延伸与细分,成品、半成品、大宗物品的区域、跨区域运输量成几何规模迅速膨胀,快递物流行业如雨后春笋般快速壮大,成为了新兴的朝阳产业。文章从电子商务管理、定额管理、供应链管理三个不同的经济管理模式分析各自对快递物流行业的促进作用,并针对这些管理模式的未来发展方向提出相应见解与意见,以此来优化快递物流行业的管理模式。     

Adaptive triangular mesh coarsening with centroidal Voronoi tessellations

We present a novel algorithm for adaptive triangular mesh coarsening. The algorithm has two stages. First, the input triangular mesh is refined by iteratively applying the adaptive subdivision operator that performs a so-called red-green split. Second, the refined mesh is simplified by a clustering algorithm based on centroidal Voronoi tessellations （CVTs）. The accuracy and good quality of the output triangular mesh are achieved by combining adaptive subdivision and the CVTs technique. Test results showed the mesh coarsening scheme to be robust and effective. Examples are shown that validate the method.