基于构造过程的参数化特征造型方法

分析了形状特征的结构,给出了相应的数据结构。对于在基于特征的设计过程中特征间的合成关系进行了分析,给出了二叉树的存储方法。可在此基础上实现基于构造过程的参数化特征造型。     

基于参数化零部件的自动装配设计

介绍在参数化零部件库的基础上实施装配设计的参数化。在设计者对装配尺寸或零部件的参数作出个性后,可自动进行装配图调整,达到零部件参数化和装配设计参数化的统一,实现自动设计。     

基于构造过程的船舶节点参数化设计

本文通过对船舶节点和节点设计方法的考察,应用基于构造过程的约束求解方法建立一种使设计人员利用交互手段选择有关模型操作建立船舶新节点类型的参数化设计方法。     

参数化系统设计

该文结合工程实际,根据参数化设计理论设计开发出参数化系统,提出了支持参数化设计的数据结构,参数化设计中的参数等级划分的概念及参数化图形分级降解、递归处理的方法,解决了系统开发过程中的一些问题,并对传统的参数化系统设计方案做了改进。     

基于Web的网络拓扑图自动构造的研究与实现

文中针对目前网络拓扑发展应用局限于网管工作站的不足,提出了一种基于Web的网络拓扑图的自动构造方法,使网络管理员能够通过浏览器了解网络的拓扑情况,并为其它基于Web的网管应用的进一步开发打下了基础。     

自动生成参数化同步系统的符号化模型

验证具有任意进程个数的并发系统是一个重要的具有挑战性的课题。那些包含任意多个类似的有限状态进程的并发系统出现在一些领域中，如硬件设计、通信协议和高速缓存一致性协议。当验证进程数目较大的问题时，传统的有限状态验证技术遭受状态爆炸问题。为了解决这个问题，提出了一些不同的技术来推理无限家族，如互模拟关系、定理证明和网络语法、抽象解释和搜索技术。尽管在一般情况下，验证参数化并发系统是不可判定的，但对于一些包含相同的有限状态进程的子系统，已     

参数化特征造型技术研究

参数化技术通过规则或代数方程的形式定义了尺寸或要素之间的约束关系，实现对已建模型的动态修改，大大提高了设计的自动化程度；作为解决ＣＡＤ／ＣＡＰＰ／ＣＡＭ集成接口问题的特征造型技术，将参数化的思想与方法吸收进来，并有机结合，产生了先进的参数化特征设计方法，成为现代ＣＡＤ领域的重要研究方向。本文详细介绍了一个参数化特征造型系统中参数化特征技术的具体应用与实现方法     

参数曲线的最优参数化

利用有理重新参数化的自由度求解参数曲线的最优参数化问题,提出一种度量曲线的参数速度与弧长参数化接近程度的方法.利用该方法求得的最优参数化在曲线的重新参数化曲线族中,参数速度偏离单位速度的最大值达到最小.最后,通过计算实例对该方法与其他算法得到的最优参数化的参数速度进行了比较.     

A topology-preserving optimization algorithm for polycube mapping

We present an effective optimization framework to compute polycube mapping. Composed of a set of small cubes, a polycube well approximates the geometry of the free-form model yet possesses great regularity; therefore, it can serve as a nice parametric domain for free-form shape modeling and analysis. Generally, the more cubes are used to construct the polycube, the better the shape can be approximated and parameterized with less distortion. However, corner points of a polycube domain are singularities of this parametric representation, so a polycube domain having too many corners is undesirable. We develop an iterative algorithm to seek for the optimal polycube domain and mapping, with the constraint on using a restricted number of cubes (therefore restricted number of corner points). We also use our polycube mapping framework to compute an optimal common polycube domain for multiple objects simultaneously for lowly distorted consistent parameterization.     

Differentials-Based Segmentation and Parameterization for Point-Sampled Surfaces

Efficient parameterization of point-sampled surfaces is a fundamental problem in the field of digital geometry processing. In order to parameterize a given point-sampled surface for minimal distance distortion, a differentialslbased segmentation and parameterization approach is proposed in this paper. Our approach partitions the point-sampled geometry based on two criteria： variation of Euclidean distance between sample points, and angular difference between surface differential directions. According to the analysis of normal curvatures for some specified directions, a new projection approach is adopted to estimate the local surface differentials. Then a k-means clustering （k-MC） algorithm is used for partitioning the model into a set of charts based on the estimated local surface attributes. Finally, each chart is parameterized with a statistical method -- multidimensional scaling （MDS） approach, and the parameterization results of all charts form an atlas for compact storage.     

Para-Graph: Graph-Based Parameterization of Triangle Meshes with Arbitrary Genus

This paper describes a novel approach to the parameterization of triangle meshes representing 2‐manifolds with an arbitrary genus. A topology‐based decomposition of the shape is computed and used to segment the shape into primitives, which define a chart decomposition of the mesh. Then, each chart is parameterized using an extension of the barycentric coordinates method. The charts are all 0‐genus and can be of three types only, depending on the number of boundary components. The chart decomposition and the parameterization are used to define a shape graph where each node represents one primitive and the arcs code the adjacency relationships between the primitives. Conical and cylindrical primitives are coded together with their skeletal lines that are computed from and aligned with their parameterization. The application of the parameterization approach to remeshing guarantees that extraordinary vertices are localized only where two patches share a boundary and they are not scattered on the whole surface.     

Automatic pose-independent 3D garment fitting

Given a virtual garment model on a reference human model, we propose an automated 3D garment fitting system that fits the garment model to a target human model. The proposed method can transfer garment models between human models without any user guidance even when the reference and target human models have different poses. Our goal is not to resize or deform the original garment model according to the target human model but to yield realistic fitting results of the given garment on the target human models. Using pose-independent segmentation and cloth simulation, we achieve realistic and automatic fitting results in reasonable running time. Our method can replace the time-consuming manual fitting process that is necessary for many applications that use virtual garments, such as games, animations, CAD tools and online clothing stores.     

Stretch-Minimizing Volumetric Parameterization

Not many methods for parameterization guarantee bijectivity or local injectivity, which is essential for foldover-free mappings. Stretch-minimizing parameterization which is widely used for surface par...     

Segmentation of High Spatial Resolution Remotely Sensed Data Using Watershed with Self-adaptive Parameterization

Segmentation of high spatial resolution remotely sensed image is the important foundation of Object\|Based Image Analysis(OBIA), most of the image segmentation algorithms involve the problem of parameter setting. Self\|adaptive Parameterization is one of the key factors that affect the efficiency and effectiveness of remote sensing image segmentation. Considering that traditional watershed segmentation algorithm is susceptible to noise and the segmentation scale parameter is difficult to be self\|adaptively chosen,this paper propose a scale self\|adaptive method in watershed segmentation. After median filtering in primary image, this paper uses spatial statistical method to realize the self\|adaptive setting of watershed segmentation parameters, and then segments the high spatial resolution remote sensing image. This study uses IKONOS and Quickbird multispectral images as experimental data to testify the validity of the method proposed by this paper. The homogeneity within the segmentation parcels and the heterogeneity between thesegmentation parcels are used to build up a synthetic evaluation model to quantitatively evaluate the segmentation results by the proposed method by comparing with different parameter sequences segmentation results. The comparison result show that the proposed method perform well in high spatial resolution image segmentation. As result, the method proposed in this paper not only improves the accuracy of image segmentation to a certain extent, but also raises the automation of the segmentation parameter selection, which provides a new way for image segmentation and the research of parameterization in the future.     

Construction of Endpoint Constrained Cubic Rational Curve with Chord-Length Parameterization

This paper discusses the problem that constructing a curve to satisfy the given endpoint constraints and chord-length parameters. Based on the research of Lu, the curve construction method for the entire tangent angles region （α0, α1）∈（-r, r）×（-r, r） is given. Firstly, to ensure the weights are always positive, the three characteristics of cubic rational Bezier curve is proved, then the segment construction idea for the other tangent angles are presented in view of the three characteristics. The curve constructed with the new method satisfies the endpoint constraint and chord-length parameters, it＇s G1 continuous in every segment curve, and the shapes of the curve are well.     

Parameterization and applications of Catmull–Rom curves

The behavior of Catmull–Rom curves heavily depends on the choice of parameter values at the control points. We analyze a class of parameterizations ranging from uniform to chordal parameterization and show that, within this class, curves with centripetal parameterization contain properties that no other curves in this family possess. Researchers have previously indicated that centripetal parameterization produces visually favorable curves compared to uniform and chordal parameterizations. However, the mathematical reasons behind this behavior have been ambiguous. In this paper we prove that, for cubic Catmull–Rom curves, centripetal parameterization is the only parameterization in this family that guarantees that the curves do not form cusps or self-intersections within curve segments. Furthermore, we provide a formulation that bounds the distance of the curve to the control polygon and explain how globally intersection-free Catmull–Rom curves can be generated using these properties. Finally, we discuss two example applications of Catmull–Rom curves and show how the choice of parameterization makes a significant difference in each of these applications.     

基于Agent的文本分类系统

信息检索的一个核心问题是自动文本分类。基于分类体系的文本分类需要全文抽取主题词、计算权重,再根据分类体系对文献进行分类。文中构建一种基于Agent技术的文本自动分类系统,仅需要对文档头进行信息处理就可以进行快速文本分类,有效地减少了文本分类过程中的时间和空间的消耗。     

控制系统故障树自动建造方法的研究

在对建树过程进行规范化描述的基础上,阐述了控制系统中反馈、前馈、分流和汇流等复杂结构在多状态故障树自动建造中的识别及处理算法.在此基础上形成的专家系统软件,可直接利用已有部件模型库,按指定顶事件状态自动生成故障树,节约了人力和时间,对FTA技术的推广有一定促进作用.