动力学修正的柔性体复合变形算法

传统柔性体变形算法存在动力学仿真不足的问题,为此,提出一种基于物理意义的复合变形算法.使用填充球模型丰富柔性体的动力学性质,解耦模型的局部变形和整体变形.柔性体外表面采用弹簧-质点模型,通过虚拟力的分层渲染,增强操作者的触觉感受.同时采用Shape Matching算法对模型的重心位置进行修正,解决由局部向全局传递形变...     

Matching perspective views of a polyhedron using circuits

We present a novel approach for finding corresponding points between two line drawings extracted from perspective views of a moving object whose surface is composed of planar polygons. In our approach, each circuit of the drawings is encoded with a boundary shape code which we call the RLCC code (run length code of convex and concave strings), then a clustering technique is used to obtain the matching result recursively. A series of measures are taken to make the algorithm tolerate considerable dissimilarities which may exist between the two drawings, such as missing lines, scale differences, rotation, perspective shape distortions, etc. Experimental results are presented.     

A virtual punching method for shape optimization of openings on curved panels using CAD-based Boolean operations

This paper aims at developing new methodologies for shape optimization of openings on three-dimensional curved panels that are used widely in aeronautical and aerospace engineering. To circumvent the difficulties associated with the hole boundary shape parameterization, a virtual punching method that exploits Boolean operations of the CAD modeler is proposed for the definition of shape design variables. Compared with the parametric mapping method developed previously, the virtual punching method is shown to be an implicit boundary representation for this specific kind of structure. Instead, the parametric mapping method is based on the explicit boundary representation.A zero-order genetic algorithm (GA) is correspondingly implemented into the design procedure of the virtual punching method to execute the optimization process for two reasons. First, it makes it possible to avoid sensitivity analysis that is relatively difficult due to the implicit boundary representation formulation and the use of an unstructured mesh. Second, the computing cost of the GA is practically affordable in shape optimization because often only a small number of design variables are involved. Numerical tests are carried out for typical examples of the stress concentration minimization around openings on the curved panels.     

基于空洞模型的地理位置路由改进算法研究

针对现有WSN中地理位置路由遇路由空洞后会产生冗余路由的问题,提出一种基于感知空洞形状的分段贪婪路由(Easy Modeling Greedy Routing,EMGR)算法。EMGR引入虚拟坐标概念,利用空洞边界探测包收集空洞边界节点信息,将其映射到虚拟坐标系中;根据空洞边界节点在虚拟坐标系的不同分布,定义凹、凸域来概括路由空洞形状;根据不同的空洞形状找到合适的中转节点,采用分段贪婪路由方式传输数据。仿真实验结果表明,相较于GPSR算法,EMGR算法产生的路由跳数减少了35%,网络能耗低,路径扩张率和网络时延小。     

Synthesis of Silhouettes and Visual Hull Reconstruction for Articulated Humans

In this paper, we propose a complete framework for improved synthesis and understanding of the human pose from a limited number of silhouette images. It combines the active image-based visual hull (IBVH) algorithm and a contour-based body part segmentation technique. We derive a simple, approximate algorithm to decide the extrinsic parameters of a virtual camera, and synthesize the turntable image collection of the person using the IBVH algorithm by actively moving the virtual camera on a properly computed circular trajectory around the person. Using the turning function distance as the silhouette similarity measurement, this approach can be used to generate the desired pose-normalized images for recognition applications. In order to overcome the inability of the visual hull (VH) method to reconstruct concave regions, we propose a contour-based human body part localization algorithm to segment the silhouette images into convex body parts. The body parts observed from the virtual view are generated separately from the corresponding body parts observed from the input views and then assembled together for a more accurate VH reconstruction. Furthermore, the obtained turntable image collection helps to improve the body part segmentation and identification process. By using the inner distance shape context (IDSC) measurement, we are able to estimate the body part locations more accurately from a synthesized view where we can localize the body part more precisely. Experiments show that the proposed algorithm can greatly improve body part segmentation and hence shape reconstruction results.      

沿参数曲面的均匀变形方法

基于参数曲面控制的物体自由变形是一项实用的技术，在已有的方法中，待变形物体被直接主控制曲面的参数空间，由于映射的非线性，导致物体变形同扭曲现象，本提出了一种基于参数曲面控制的均匀变形方法，新方法中，变形控制曲面首先以等距或局部等怕方式展开为平面，然后经由平面的线性映射，将待为形物体嵌入控制曲面的参数空间中，从而产生符合控制曲面形状的局部均匀变形，实验结果表明，本方法所产生的结果是令人满意的。     

基于L1/2正则化的三维人体姿态重构

针对从给定2D特征点的单目图像中重构对象的3D形状问题,本文在形状空间模型的基础上,结合L_1/2正则化和谱范数的性质提出一种基于L_1/2正则化的凸松弛方法,将形状空间模型的非凸求解问题通过凸松弛方法转化为凸规划问题;在采用ADMM算法对凸规划问题进行优化求解过程中,提出谱范数近端梯度算法保证解的正交性与稀疏性.利用所提的优化方法,基于形状空间模型和3D可变形状模型在卡内基梅隆大学运动捕获数据库上进行3D人体姿态重构,定性和定量对比实验结果表明本文方法均优于现有的优化方法,验证了所提方法的有效性.     

Learning visual models from shape contours using multiscaleconvex/concave structure matching

A novel approach is proposed for learning a visual model from real shape samples of the same class. The approach can directly acquire a visual model by generalizing the multiscale convex/concave structure of a class of shapes, that is, the approach is based on the concept that shape generalization is shape simplification wherein perceptually relevant features are retained. The simplification does not mean the approximation of shapes but rather the extraction of the optimum scale convex/concave structure common to shape samples of the class. The common structure is obtained by applying the multiscale convex/concave structure-matching method to all shape pairs among given shape samples of the class and by integrating the matching results. The matching method, is applicable to heavily deformed shapes and is effectively implemented with dynamic programming techniques. The approach can acquire a visual model from a few samples without any a priori knowledge of the class. The obtained model is very useful for shape recognition. Results of applying the proposed method are presented     

Geospatial analysis of terrain through optimized feature extraction and regression model with preserved convex region

In this paper, cat optimization algorithm for feature extraction in satellite image has been proposed. In cat optimization, cost function computes the pixel in the satellite image to preserve the boundary shape and avoid non-convex part of the contour of the image. However, the existing feature extraction optimization algorithm measures the distinct data framework and thematic information to insight land cover such as waterbody, urban and vegetation. The land cover is obtained from different optimized feature extraction algorithms never provide proper boundary shape and land feature. Furthermore, the proposed cat optimized algorithm distinguishes the inner, outer and extended boundary along with the land cover. The cat-optimised algorithm for low and high-resolution satellite image shows the better result of 85%, with the preserved convex region when compared with the existing feature extraction algorithm such as fuzzy and Particle Swarm Optimization (PSO).     

动态立方体纹理生成算法

CEM算法使用六张2D纹理图来构建虚拟场景中的背景环境.通常其生成的背景环境是固定不变的,不能满足某些需要背景变换场景的需求.针对这个问题,提出一个动态立方体纹理生成算法,采用映射变换的方法动态的生成立方体纹理图,实验结果表明该算法可以构建实现实时、动态的背景场景.     

An automated approach to dependability evaluation of virtual networks

Network virtualization has been pointed as a promising approach to solve Internet’s current ossification. A major challenge is the mapping of virtual networks (VNs) onto the substrate network due to its NP-hard nature, and, thus, several heuristics have been proposed aiming to achieve efficient allocations. However, the existing approaches only focus on performance, and dependability issues are usually neglected. Dependability involves metrics such as reliability and availability, which directly impact the quality of service, and a limitation is the absence of mechanisms for estimating dependability metrics in virtual networks. This paper proposes an automated approach for estimating dependability metrics in virtual network environments and a mapping algorithm based on GRASP metaheuristic. The approach is based on stochastic Petri nets (SPN) and reliability block diagrams (RBD), and a tool is also presented for automating model generation and evaluation. Experimental results demonstrate the feasibility of the proposed technique, as well as the trade-off between VN’s availability and cost.     

一种基于约束优化的虚拟网络映射方法

虚拟网络映射问题将不同的虚拟网络应用映射到相同的基础设施网络中,这是一个极具挑战性的问题.针对该问题,提出了一种基于约束优化的虚拟网络映射方法,将映射问题分解为节点映射和链路映射两个阶段,其中,前者是将虚拟节点映射到物理节点上,后者将虚拟链路映射到物理路径上,它们都是NP难问题.针对节点映射和链路映射分别提出了node-mapping算法和link-mapping算法.node-mapping算法基于贪婪算法的思想,映射时考虑了物理节点所能提供的资源数量以及物理节点间距离两个因素,该算法能够保证基础设施网络中各节点间的负载相对均衡;同时,通过采用访问控制机制,过滤一些异常的虚拟网络请求,能够有效地提高资源的使用效率.link-mapping算法基于人工智能领域中的分布式约束优化思想,其能够保证得到的解是全局最优的,即映射链路的代价最小.最后,通过模拟实验对该方法进行验证,实验结果表明该方法在求解虚拟网络映射问题时的性能良好.     

Virtual network mapping algorithm in the cloud infrastructure

Network virtualization has received considerable attention recently because a Cloud Provider (CP) that is responsible for deploying a substrate network in the cloud infrastructure uses network virtualization to support multiple Virtual Network (VN) requests over the shared substrate network. However, mapping multiple VN requests with constraints on virtual nodes and virtual links into a shared substrate network presents a significant challenge, and is considered an NP-hard problem. In this paper, we propose a heuristic mapping algorithm that handles online VN requests. The node mapping algorithm selects a substrate node for mapping that satisfies both a virtual node's resource requirement and its amount of requested bandwidth. The link mapping algorithm either maps a virtual link to the shortest substrate path that satisfies the requested bandwidth of the virtual link or uses the cut-shortest path approach to map a virtual link to multiple substrate paths that satisfy the requested bandwidth of the virtual link. The path migration algorithm migrates virtual links to different substrate paths to maximize the number of accepted VN requests in a substrate network. Simulation results show that the proposed heuristic mapping algorithm uses resources more efficiently, produces more revenue, and has better performance than existing mapping approaches.     

Novel methods for virtual network composition

Network virtualization has been proposed as a technology that aims to solve the Internet ossification. Central to the network virtualization is a virtual network composition mechanism providing an efficient mapping of virtual nodes and links onto appropriate physical resources in the network infrastructure.This paper proposes a novel backtracking heuristic algorithm for virtual network composition. Based on this algorithm, two approaches with two different objectives are presented. The first approach (Backtracking-CR) aims to compose a virtual network using the least amount of network resources, while the second (Backtracking-LB) applies load balancing for virtual network composition. Furthermore, a linear programming approach that optimizes the virtual network composition with an objective of using the least amount of network resources is presented and used to bench mark the heuristic algorithm. Simulation results show that using less network resources by applying linear programming or Backtracking-CR does not produce higher number of successfully mapped virtual networks when is compared to load balancing approach. Results also show that the proposed heuristic algorithm is scalable to large physical and virtual networks with respect to the computation time.     

基于小波技术的曲面边界光顺及简化算法

与传统造型方法相比,T 样条曲面具有曲面拼接、局部加细、数据简化等特点。基于 T 样条曲 面的非矩形拓扑结构及 B 样条小波的滤波优势,提出了一种曲面边界光顺及简化算法。与传统方法相比,该算 法基于非均匀 B 样条小波分解,对选定的曲面边界进行光顺,并利用 T 样条技术减少冗余控制点。最后,给 出具体实例以验证算法的有效性和实用性。     

Efficient optimization of common base domains for cross parameterization

Given a set of corresponding user-specified anchor points on a pair of models having similar features and topologies, the cross parameterization technique can establish a bijective mapping constrained by the anchor points. In this paper, we present an efficient algorithm to optimize the complexes and the shape of common base domains in cross parameterization for reducing the distortion of the bijective mapping. The optimization is also constrained by the anchor points. We investigate a new signature, Length-Preserved Base Domain (LPBD), for measuring the level of stretch between surface patches in cross parameterization. This new signature well balances the accuracy of measurement and the computational speed. Based on LPBD, a set of metrics are studied and compared. The best ones are employed in our domain optimization algorithm that consists of two major operators, boundary swapping and patch merging. Experimental results show that our optimization algorithm can reduce the distortion in cross parameterization efficiently.     

虚拟网映射竞争算法设计与分析

对网络虚拟化技术中的虚拟网映射问题及其研究现状进行了介绍,针对虚拟节点映射已知且物理网不支持路径分割的虚拟网映射问题,提出以物理网提供商收益最大化为目标的虚拟网映射竞争算法,并给出了算法的竞争比分析。实验表明,所提出的算法能提高物理网资源的负载均衡度和利用率,从而提高了虚拟网构建请求的接受率和物理网提供商的收益。     

网络虚拟化环境下的服务故障诊断算法

网络虚拟化环境下,底层网络的透明性造成虚拟网提供商不能诊断所有的虚拟网服务故障.为解决此问题,提出了基于映射关系的虚拟网服务故障传播模型.针对故障传播模型中故障集与症状集较大、网络环境动态和噪声大而导致的已有诊断算法误报率高、时间复杂度高的问题,基于网络虚拟化环境下症状内在相关性特点,提出了一种新的基于症状内在相关性的虚拟网服务故障诊断算法SFDoIC(service fault diagnosis algorithm based on inherent correlation among symptoms).仿真实验结果表明,SFDoIC算法能够很好地解决底层网络透明性造成的虚拟网服务故障难以定位的问题.SFDoIC算法可以有效地降低诊断算法的误报率,显著缩短诊断算法的运行时间.     

基于虚拟参考反馈整定的改进无模型自适应控制

针对一类离散时间非线性系统, 提出一种基于虚拟参考反馈整定的改进无模型自适应控制方案. 首先, 利用动态线性化方法给出非线性系统的紧格式动态线性化模型; 然后, 基于优化技术设计控制算法和伪偏导数估计算法; 最后, 设计基于虚拟参考反馈整定的伪偏导数初值和重置值的估计算法. 该控制方案设计仅依赖于被控系统的输入和输出数据, 且能保证闭环系统的稳定性和收敛性. 仿真比较结果验证了所提出方法的有效性.

     

汉字字形的凸剖分变形及合成

文中提出了一种全新的基于凸多边形变形的汉字字形自动生成方法. 通过对字体的凸剖分,把字体分解成若干个子凸多边形,并经过全局优化迭代建立两种不同字体的子凸多边形间的匹配关系,计算两匹配子凸多边形的形态和,再进行合并,则得到合成后的字体.理论上证明了此方法的正确性,讨论了不同剖分对生成字形的影响,可解决不同构字体间的合成问题,通过不同的结构元的形态变换,实现不同字体的衍生.实验证明此方法生成的汉字字形多,质量好,自动化程度高,并可用于三维字体生成.