Computing point-set surfaces with controlled spatial variation of residuals

This paper presents an accurate method for computing point-set surfaces from input data that can suppress the noise effect in the resulting point-set surface. This is accomplished by controlling spatial variation of residual errors between the input data and the resulting point-set surface and offsetting any systematic bias. More specifically, this method first reduces random noise of input data based on spatial autocorrelation statistics: the statistics Z via Moran’s I. The bandwidth of the surface is adjusted until the surface reaches desired value of the statistics Z corresponding to a given significance level. The method then compensates for potential systematic bias of the resultant surface by offsetting along computed normal vectors. Computational experiments on various point sets demonstrate that the method leads to an accurate surface with controlled spatial variation of residuals and reduced systematic bias.     

分布式制造环境下制造资源信息收集系统

简要介绍了系统的开发平台.NET,提出了一个基于分布式Web服务的信息收集系统,详细描述了位于资源收集中心的Web服务和制造资源提供者所具有的Web客户端应用程序的工作原理和实现方法。系统采用多层的分布式程序结构设计,为资源中心的再利用和资源提供者的软件环境部署提供了方便。系统在VS.NET环境下使用VB.Net语言开发实现。     

"虚拟制造"重振武汉制造业

虚拟制造模式为企业和地区经济带来了又一次跨越式发展的契机。本文分析了武汉市制造业的现状、优势和不足,结合虚拟制造理论,从政府和企业两个角度阐述了如何利用虚拟制造的思想重振武汉制造业。     

层次化软件构造

该文针对面向对象和可视化开发环境中出现的常见问题,结合软件系统开发的实践经验,参照计算机网络中的层次参考模型,提出了层次化软件构造的思想。同时结合实现软件复用的构件技术,将软件系统的组成构件划分为物理操作层构件、公共服务层构件、特定领域层构件和用户界面层构件4个层次。文章最后结合软件开发项目的具体应用,说明了层次化软件构造的有效性和实用性。     

Induced rational parametrisations of special curves

Rational parametrisation of curves and surfaces is a defacto industry standard for computer graphics and shape representation. While it is well known that rational parametrisations of the conic sections exist, and their explicit forms are used in geometric modeling (Hoschek and Lasser, 1993), other classical curves for which rational parametrisations may be determined have received less attention in the literature. This paper presents an elegant method for the explicit computation of rational parametrisations for many 'special' or famous curves. The technique 'induces' a parametrisation of a 'higher' or 'target' curve from a 'primitive' or 'source' curve for which rational parametrisations are known - e.g., the straight line and the conic sections. A number of examples and modeling applications are given.     

嵌入式系统串口通信分层结构设计与实现

介绍了以STC89C54RD+为核心具有ISP(在线可编程)特性的嵌入式系统中,PC机与该系统串口全双工通信的实现。给出了串口通信协议,提出了嵌入式系统中串口通信程序的分层结构设计的框架,及在KeilC51中实现该软件的方法。该方法有利于提高程序的封装性和模块化程度,同时也增强了串口数据收发处理的并发性和实时性。     

An Operator Approach to Tangent Vector Field Processing

In this paper, we introduce a novel coordinate‐free method for manipulating and analyzing vector fields on discrete surfaces. Unlike the commonly used representations of a vector field as an assignment of vectors to the faces of the mesh, or as real values on edges, we argue that vector fields can also be naturally viewed as operators whose domain and range are functions defined on the mesh. Although this point of view is common in differential geometry it has so far not been adopted in geometry processing applications. We recall the theoretical properties of vector fields represented as operators, and show that composition of vector fields with other functional operators is natural in this setup. This leads to the characterization of vector field properties through commutativity with other operators such as the Laplace‐Beltrami and symmetry operators, as well as to a straight‐forward definition of differential properties such as the Lie derivative. Finally, we demonstrate a range of applications, such as Killing vector field design, symmetric vector field estimation and joint design on multiple surfaces.     

生产系统的计算机仿真研究

生产系统在设计与运行过程中面临着诸多的问题需要解决,计算机仿真技术作为一种有效验证生产系统设计合理性和辅助生产管理决策的手段,近年来在我国得到了越来越广泛的关注。该文系统总结了计算机仿真技术对生产系统的重要作用,利用Ithink5.0软件建立了简单生产过程的计算机仿真模型并进行了分析。     

Optimal part orientation in Rapid Manufacturing process for achieving geometric tolerances

Rapid Manufacturing (RM) processes have evolved from the Rapid Prototyping (RP) paradigm and are increasingly being used to manufacture parts, tools and dies in addition to prototypes. The advantages of RP methods to produce complex shapes without the use of specialized tooling can naturally be extended to RM processes. For RM to be accepted as a mainstream manufacturing process, parts created by RM have to consistently satisfy critical geometric tolerances specifications for various features of the part. This paper investigates the relation between cylindricity tolerance, one of the key form tolerances, and part build orientation in layered manufacturing. The effect of build orientation on cylindricity error is analyzed by three methods: first by a simple analytic method, second by simulating the manufactured surface using a CAD (Computer Aided Design) file of the part and third by using an STL (Stereolithography) file. The mathematical relationship between cylindricity error and part orientation in a RM process is modeled and critical feasible regions for cylinder build orientation are calculated. A graphical technique for calculating the optimal build orientation for a part with multiple cylindrical features is also developed and presented in this paper. This method is tested and validated with the help of a test case and the results are provided in the paper.     

An optimal parallel algorithm for triangulating a set of points in the plane

This paper presents an optimal parallel algorithm for triangulating an arbitrary set ofn points in the plane. The algorithm runs inO(logn) time usingO(n) space andO(_n) processors on a Concurrent-Read, Exclusive-Write Parallel RAM model (CREW PRAM). The parallel lower bound on triangulation is (logn) time so the best possible linear speedup has been achieved. A parallel divide-and-conquer technique of subdividing a problem into subproblems is employed.     

Computing Extremal Quasiconformal Maps

Conformal maps are widely used in geometry processing applications. They are smooth, preserve angles, and are locally injective by construction. However, conformal maps do not allow for boundary positions to be prescribed. A natural extension to the space of conformal maps is the richer space of quasiconformal maps of bounded conformal distortion. Extremal quasiconformal maps, that is, maps minimizing the maximal conformal distortion, have a number of appealing properties making them a suitable candidate for geometry processing tasks. Similarly to conformal maps, they are guaranteed to be locally bijective; unlike conformal maps however, extremal quasiconformal maps have sufficient flexibility to allow for solution of boundary value problems. Moreover, in practically relevant cases, these solutions are guaranteed to exist, are unique and have an explicit characterization. We present an algorithm for computing piecewise linear approximations of extremal quasiconformal maps for genus‐zero surfaces with boundaries, based on Teichmüller's characterization of the dilatation of extremal maps using holomorphic quadratic differentials. We demonstrate that the algorithm closely approximates the maps when an explicit solution is available and exhibits good convergence properties for a variety of boundary conditions.     

A Multiscale Approach to Optimal Transport

In this paper, we propose an improvement of an algorithm of Aurenhammer, Hoffmann and Aronov to find a least square matching between a probability density and finite set of sites with mass constraints, in the Euclidean plane. Our algorithm exploits the multiscale nature of this optimal transport problem. We iteratively simplify the target using Lloyd's algorithm, and use the solution of the simplified problem as a rough initial solution to the more complex one. This approach allows for fast estimation of distances between measures related to optimal transport (known as Earth‐mover or Wasserstein distances). We also discuss the implementation of these algorithms, and compare the original one to its multiscale counterpart.     

一种组件的层次化信息交互模型

借用在Internet中使用的层次化软件结构的思想,提出了一个基于层次化信息模型的信息互操作的模型。讨论了其各个层次的功能和关系,提出每一个层次中应该包含的一些主要的特性,比如二元关系、基础类型、具体化、排序和n-维关系等。最后指出相关工作并总结。     

层结构在RoboCup仿真球队中的应用

机器人足球世界杯赛是一个国际性的研究和教育组织,是人工智能和机器人学的重要研究领域之一。该文在简要介绍几种常见智能体系体结构的基础上,重点对目前采用较多的层结构进行了探讨,并结合一些典型仿真球队的智能体结构,描述了层结构的具体应用。     

面向分层模型的树形计分标准通用组件设计

树形计分规则是一种常见结构,但相关文献多着重于算法优化或特定开发及应用环境耦合紧密的解决方案。本文从框架设计角度出发,设计针对树形计分规则管理的,面向分层模型的通用组件,解决开发环境和应用环境依赖性问题,以得到良好的框架复用性。文中分析了分层模型的接口设计和通用组件的继承性设计,及两种设计如何良好集成的问题。     

层次视频多播中的自适应公平带宽分配

为解决层次视频多播传输中带宽分配的公平性问题,建立了适合的网络模型,并以有限状态机的形式给出了接收端会话基于自适应公平原则的状态转化过程。确定了一些重要参数的计算公式并将网络带宽的变化归一化为权重问题,降低了模型的复杂度。     

Learning Layered Motion Segmentations of Video

We present an unsupervised approach for learning a layered representation of a scene from a video for motion segmentation. Our method is applicable to any video containing piecewise parametric motion. The learnt model is a composition of layers, which consist of one or more segments. The shape of each segment is represented using a binary matte and its appearance is given by the rgb value for each point belonging to the matte. Included in the model are the effects of image projection, lighting, and motion blur. Furthermore, spatial continuity is explicitly modeled resulting in contiguous segments. Unlike previous approaches, our method does not use reference frame(s) for initialization. The two main contributions of our method are: (i) A novel algorithm for obtaining the initial estimate of the model by dividing the scene into rigidly moving components using efficient loopy belief propagation; and (ii) Refining the initial estimate using α β-swap and α-expansion algorithms, which guarantee a strong local minima. Results are presented on several classes of objects with different types of camera motion, e.g. videos of a human walking shot with static or translating cameras. We compare our method with the state of the art and demonstrate significant improvements.     

Computing sparse permanents faster

Bax and Franklin (2002) gave a randomized algorithm for exactly computing the permanent of any n×n zero-one matrix in expected time exp[−Ω(n1/3/(2lnn))]n². Building on their work, we show that for any constant C>0 there is a constant ?>0 such that the permanent of any n×n (real or complex) matrix with at most Cn nonzero entries can be computed in deterministic time n(2−?) and space O(n). This improves on the Ω(n²) runtime of Ryser's algorithm for computing the permanent of an arbitrary real or complex matrix.     

分层协作入侵检测系统研究

互联网在给广大互联网用户提供方便的同时也更加方便了黑客在不同地点、不同时刻发起对远程网络或主机的攻击。针对这些分布式攻击模式,该文提出并论述了一个基于Agent的分布式入侵检测系统的框架及其实现。引入这种分层协作IDS的主要目的是为了克服单一的主机入侵检测系统以及网络入侵检测系统的某些缺陷。在分布式网络环境中,不同的系统主体在各自安全域中执行彼此的独立安全策略;同时,这些系统主体通过相互协作构成上一级安全域。系统框架参考目前流行的通用入侵检测框架CIDF构建,通过经过扩展的CISL实现不同组件间的通讯及协作。