虚拟油泥造型方法

对虚拟油泥造型系统中的刮削、填补和刮削并填补三种造型方法进行了研究,介绍了其实现方法.首先根据造型工具的形状和运动状态,实时构造扫描体表面模型并离散为压缩体素模型,然后与虚拟油泥模型进行布尔运算,从而实现刮、削、扫等操作.该方法成功应用于虚拟油泥造型系统,效果良好.     

NURBS体的DEXEL化与布尔运算

NURBS曲面与NURBS体造型技术是目前复杂体造型的重要工具,但复杂体之间的布尔运算求交困难。将NURBS曲面围成的体与NURBS体体素化(VOXEL化)为由一系列平面凸四边形或三角形表示的体,通过DEXEL射线组群与四边形或三角形求交,实现NURBS体的DEXEL化。在同一DEXEL模型空间实现复杂NURBS体之间的布尔运算,所有运算是线性的。该方法可推广到在逆向工程中生成的由三角面表示的体。在Java2.0与Java3D环境下编程实现并验证了该算法,给出了一个机械零件设计实例。     

基于遗传算法和微粒群算法的群体动画造型平台

动漫制作经常需要大量的个体模型。为了解决群体造型的效率性和仿真度问题,提出了基于遗传算法和微粒群算法的群体造型方法——NGP算法,利用该算法实现由一个复杂模型生成复杂模型群体的过程。遗传算法适用于同一类群体的造型,对每种部件应用这种方法形成各种各样的部件库;微粒群算法适用于对复杂模型的部件进行组合,采用这种方法对各部件进行组合优化,以形成模型群体。实现了基于NGP算法的群体动画造型平台。实验结果表明,平台生成的群体仿真度高,且生成过程效率高。     

三角网格模型体素特征分割

针对现有机械制造领域网格模型分割结果缺少工程含义的现状,提出了一种三角网格模型体素特征分割方法。首先在对三角网格模型分割的基础上,对由网格分割得到的每个子网格进行曲面类型识别,然后在基本体素及典型结构显著特征表示的基础上,把识别出的曲面集合与基本体素及典型结构进行匹配,从而将分割结果分类为自由曲面、基本体素和复杂体素,实现具有工程含义的体素特征分割。该方法可以降低模型重构的难度,加快模型重构的速度。     

汽车离合器盖构型特征向CSG体素的映射

本文作者在现有实体造型器ＡＭＥ的基础上，建立了相应的零件模型，论述了构型特征向ＣＳＧ体素映射的方法与过程，并进行了有关讨论。     

一个平面多面体实体造型系统

本文介绍一个可在微机上运行的平面多面体实体造型系统，提出了体素离散化的方法和实现实体造型及消隐输出的算法，最后给出造型消除输出实例．     

基于构造基面的扫描体素构造方法

本文在分析机械零件造型中面作用的基础上，提出一个基于构造基面的扫描体素构造方法，讨论了构造基面的检取和显示，介绍了基于构造基面的扫描体Ｂ－ｒｅｐ模型的构造过程。     

基于单元分解的实体构造几何技术(CDCSG)——一种构造实体模型的新方法

本文提出了一种构造实体模型的新方法,CELL DECOMPOSED CONSTRUCTIVE SOLID GEOMETRY,简称为CDCSG。这种新方法较之常用的CSG加边界表达的方法有两点主要区别:第一,在CDCSG中边界表示是用来描述各基本体素的几何信息和拓扑信息而不是用来描述整体模型的。因此它没有给出显式的模型总体边界表示。第二,与CSG树不同,在CDCSG系统中建立结构二叉树(CDCSG树)时,只使用了“粘合”和“钻孔”两种简化了的布尔算子。这一造型方法和目前通用的CSG加边界表达的造型方法相比有下列明显的优点:在基于CSG加边界表达的造型系统中,有关体素间的联系信息是用显式描述的,这时要修改一个模型(增加,删除或改变与模型有关的基本体素)是很困难且代价相当高的(如果不是不可能的话),而在CDCSG造型系统中这种修改却非常容易实现;在基于边界表达的造型系统中,为了执行构造CSG树时的布尔运算,必须整个模型同时存在于计算机内存。这样就造成了复杂模型数据量大和计算机内存有限的矛盾。CDCSG方法的另一个优点是可以设计出一种动态存储管理系统。在这个系统中,每个基本体素和修改后的体素均可独立存取和调用;因而,我们能够只将使用最频繁的基本体素存于高速存储区而将大多数的数据存于低速存储区。这样就可以克服上述矛盾,为开发一个     

快速有效的半自动组织分割技术

针对医学可视化和虚拟内窥镜技术中的组织分割问题，提出边界模型和局部特征结构相结合的半自动解决方法，通过给定的特定体素点，结合边界模型找出特定组织的内部、外部体素，对边界体素计算汉森矩阵的特征值并按其特征结构进行分割．该方法只需要计算边界体素汉森矩阵的特征值，能够快速、有效地实现单一组织的分割．     

基于压缩体素模型的快速成型直接切片算法*

基于STL文件模型的间接分层切片算法存在缺乏拓扑信息, 面误差诊断修复困难等问题,结合压缩表示形式的体素模型特点,提出了一种新的基于压缩体素模型直接切片分层优化算法.该算法利用Dexel模型记录的Dexel射线和物体交点所表达的物体表面点位置,通过设定分层平面厚度等参数获得截面轮廓数据,生成可直接适用于快速成型系统的共用层接口CLI文件.该算法在虚拟油泥造型系统中得到了应用,实验结果表明算法稳定、分层效果良好.     

双迹线造型法

本文提出了双迹线造型方法,这个方法用母线沿着两条轨迹线变形生成几何体的外形,它能满足范围很广一类器皿物体的造型要求,文中还讨论了光照模型,表面加花处理,该法已用于陶瓷产品的造型设计。     

A new k-groups neural network

A novel neural-network model called GROUPSTRON is proposed to identify the k groups' elements from a data set. Based on both the divide-and-conquer principle and the coarse-and-fine competition, GROUPSTRON divides the identification process into k rounds and then sequentially identifies each group's elements from the data set. All the elements in the first group are larger than those in the second group and this relationship holds for the successive groups. The proof that GROUPSTRON converges to the correct state in every situation is also given. Moreover, the convergence rates of GROUPSTRON for three special data distributions are deduced. Finally, simulation results are given to demonstrate the effectiveness and design philosophy of GROUPSTRON.     

基于群论的柏拉图立体着色方案三维模型构造

提出用柏拉图立体的空间旋转群来完成柏拉图立体着色方案三维模型构造的思想,解决与对称性直接相关的着色方案三维模型的构造问题;提出一种柏拉图立体旋转群群元新的分类方法;提出群元抽象对称性、局部色数和饱和色数3个新概念;提出对抽象对象进行抽象着色方案的构造,然后再将抽象着色方案映射到具体的轮换上,最后映射到三维模型空间去的构造方法,设计了实现该方法的算法,并用Visual C++6.0和Direct 3D实现了算法及三维模型可视化.软件运行结果验证了所提出的方法及算法的正确性.     

Recursive computation of matrix elements in the numerical renormalization group

The numerical renormalization group is an efficient method to diagonalize model Hamiltonians describing correlated orbitals coupled to conduction states. While only the resulting eigenvalues are needed to calculate the thermodynamical properties for such models, matrix elements of Fermi operators must be evaluated before excitation and transport properties can be computed. The traditional procedure to calculate matrix elements is typically as expensive as the diagonalization of the model Hamiltonian. Here, we present a substantially faster alternative that demands much less memory, yields equally accurate matrix elements and is easier to code.     

Identifying affect elements based on a conceptual model of affect: A case study on a smartphone

The concept of affect has been considered as a requisite for the success of a product in the market. However, ‘affect’ is an ill-defined concept. This study developed a new conceptual model to explain the fundamental concept of affect. Based on this model, a systematic procedure of affect element identification was proposed using a literature review, a focus group interview, an internet survey and statistical analyses. Affect elements of smartphones were classified into two parts: appearance and applications. The results of this study are expected to help developers understand the nature of affect. The systematic approach proposed in the study can be applied with minor modifications to identify affect elements of other smart products.Relevance to industryThis study proposed a conceptual model of affect and identified affect elements of smartphones. The list of affect elements will be helpful for developing and evaluating smartphones including diverse types of smart products.     

Deriving the priority weights from hesitant multiplicative preference relations in group decision making

In this paper, we investigate the deviation of the priority weights from hesitant multiplicative preference relations (HMPRs) in group decision-making environments. As basic elements of HMPRs, hesitant multiplicative elements (HMEs) usually have different numbers of possible values. To correctly compute or compare HMEs, there are two principles to normalize them, i.e., the α-normalization and the β-normalization. Based on the α-normalization, we develop a new goal programming model to derive the priority weights from HMPRs in group decision-making environments. Based on the β-normalization, a consistent HMPR and an acceptably consistent HMPR are defined, and their desired properties are studied. A convex combination method is then developed to obtain interval weights from an acceptably consistent HMPR. This approach is further extended to group decision-making situations in which the experts evaluate their preferences as several HMPRs. Finally, some numerical examples are provided to illustrate the validity and applicability of the proposed models.     

A numerical study of plasticity models and finite element types

The available experimental results for the cyclic loading of a simply supported circular plate using a rigid circular punch is utilized to compare the numerical results obtained from computations performed using the four most popular work hardening plasticity models, namely, the isotropic, kinematic, mechanical sublayer and the Mroz models. The mechanical sublayer model appears to be the most efficient in this group. Using the mechanical sublayer model the computational efficiencies of the 3, 4 and 8-node finite elements are studied. The 8-node element emerges as the most suitable element type for the present problem.     

Classes of conjugate elements of the unitriangular group

The paper examines the classes of conjugate elements of the unitriangular group. It is shown that for sufficiently large n the problem of describing the classes of conjugate elements of the group G includes the problem of unitriangular similarity of pairs of matrices. Effective algorithms are constructed for enumeration of classes of conjugate elements and their elements. Representatives of the classes of conjugate elements of the group G with n9 are obtained by computer.Translated from Kibernetika, No. 1, pp. 40–48, January–February, 1990.     

Inverse Procedural Modeling by Automatic Generation of L‐systems

We present an important step towards the solution of the problem of inverse procedural modeling by generating parametric context‐free L‐systems that represent an input 2D model. The L‐system rules efficiently code the regular structures and the parameters represent the properties of the structure transformations. The algorithm takes as input a 2D vector image that is composed of atomic elements, such as curves and poly‐lines. Similar elements are recognized and assigned terminal symbols of an L‐system alphabet. The terminal symbols' position and orientation are pair‐wise compared and the transformations are stored as points in multiple 4D transformation spaces. By careful analysis of the clusters in the transformation spaces, we detect sequences of elements and code them as L‐system rules. The coded elements are then removed from the clusters, the clusters are updated, and then the analysis attempts to code groups of elements in (hierarchies) the same way. The analysis ends with a single group of elements that is coded as an L‐system axiom. We recognize and code branching sequences of linearly translated, scaled, and rotated elements and their hierarchies. The L‐system not only represents the input image, but it can also be used for various editing operations. By changing the L‐system parameters, the image can be randomized, symmetrized, and groups of elements and regular structures can be edited. By changing the terminal and non‐terminal symbols, elements or groups of elements can be replaced.     

A process oriented simulation model specification and documentation language

We present a language for specifying and documenting discrete event simulation models, designed to facilitate communication during model design, implementation and maintenance. The systems from which models are developed are viewed as collections of communicating elements. Each element is specified separately in a module consisting of attributes, axioms and a scenario. The model's specification consists of each model element's specification and some systemwide attributes and axioms. Synchronization among model elements (model dynamics) is specified within the model elements rather than globally. Each language control structure has a monitor associated with it. Appropriate changes are made in the model's state in response to a monitor's sensing an attribute change. The language contains a library of specifications for common simulation model entities such as the priority queue. The syntax and semantics of the language are presented through examples. Examples of a library specification and a model specification are included.