基于半正交B样条小波的任意控制顶点数曲线光顺

目前,小波分析应用于逆向工程时,对控制顶点有特殊要求,只能处理2j r个控制顶点的图形,为此提出了一种可以光顺任意控制顶点B样条曲线的小波分析新方法。在介绍B样条定义的基础上,从小波分析的定义出发,用严格的数学证明推导了任意控制顶点曲线的小波分解与重构具体算法。最后,该算法成功应用于B样条曲线的小波光顺,实例表明,该算法准确、结果稳定,效率理想。     

基于边缘曲线光顺的图像放大算法

针对常规插值方法在图像放大时图像轮廓模糊的问题,提出了一种基于边缘的图像放大算法。算法包括边缘曲线光顺和插值放大两个步骤。第1步使用能量优化方法,从离散的边缘曲线数据恢复成连续而光顺的边缘曲线,这些曲线将图像分为若干个区域;第2步基于这些光顺曲线,针对不同的区域分别进行图像插值放大计算。使用该方法得到的放大图像边缘清晰光顺,实例证明该算法产生的图像质量高于常规算法。     

Lattice Boltzmann based PDE solver on the GPU

In this paper, we propose a hardware-accelerated PDE (partial differential equation) solver based on the lattice Boltzmann model (LBM). The LBM is initially designed to solve fluid dynamics by constructing simplified microscopic kinetic models. As an explicit numerical scheme with only local operations, it has the advantage of being easy to implement and especially suitable for graphics hardware (GPU) acceleration. Beyond the Navier–Stokes equation of fluid mechanics, a typical LBM can be modified to solve the parabolic diffusion equation, which is further used to solve the elliptic Laplace and Poisson equations with a diffusion process. These PDEs are widely used in modeling and manipulating images, surfaces and volumetric data sets. Therefore, the LBM scheme can be used as an GPU-based numerical solver to provide a fast and convenient alternative to traditional implicit iterative solvers. We apply this method to several examples in volume smoothing, surface fairing and image editing, achieving outstanding performance on contemporary graphics hardware. It has the great potential to be used as a general GPU computing framework for efficiently solving PDEs in image processing, computer graphics and visualization.     

光顺B-spline曲面片的一种实用方法

重构曲面的光顺处理是逆向工程中的关键步骤，如何快速、简便、正确地光顺曲面，是曲面光顺处理问题研究的核心。本文针对B-spline方法重构曲面提出了一种光顺方法。并描述了其基本原理和光顺准则。实例表明，本文所提出的光顺方法快速、简便，是一种较为实用的光顺方法。     

基于样条函数的磁滞回线光顺处理研究

针对脉冲法在测量铁磁性材料应力状态时,磁滞回线存在奇异点的问题,提出了一种基于样条函数的磁滞回线光顺处理的方法。首先,通过分析脉冲法测量磁特性装置的组成和原理,建立了磁滞回线光顺处理的样条插值理论模型;然后,以LabVIEW软件为平台,编写了光顺处理程序模块,并嵌入了上位机后台程序;最后,对不同铁磁性材料的工件进行了对比试验,根据采集的数据,在上位机中绘制了相应的磁滞回线。试验及分析结果表明,经过样条插值处理后,该研发装置获得的磁滞回线可以在正、反向放电间隔区平滑过渡,实现了磁滞回线的光顺处理,从而为进一步研究铁磁性材料的磁特性参数奠定基础。     

基于边缘曲线光顺连续性恢复的灰度图像放大算法

灰度图像放大时，插值的平滑作用会退化图像的高频部分，致使放大图像的边缘变得模糊．本文提出了一种基于离散边缘曲线光顺连续性恢复的灰度图像放大算法，算法包括两个步骤，第一步是使用能量优化方法，根据一定的准则从离散的边缘曲线数据恢复出连续而光顺的边缘曲线；第二步是基于这些曲线对图像实施插值计算．使用本文方法得到的放大图像边缘清晰光顺．文中络出了放大实例，实验结果证明了本文方法的有效性．     

汽车覆盖件修边线展开及优化

采用二次开发工具UG/OPEN开发了无缝集成于UG NX平台的三维翻边成形性分析及修边线展开系统TUW（Trimline Unfolding Wizard）。针对UG NX曲面转换缺陷,研究了修边线噪音检测和光顺处理问题,重点分析了由于UG NX曲面转换缺陷造成的网格剖分边界失真问题,提出了修边线分段、降噪、非必要控制点过滤等方法,优化了修边线控制节点。采用局部能量法进行B样条曲线拟合,改善了修边线的光顺性。实际应用表明,光顺处理后的修边线可以达到数控加工要求,通过与实验结果比较也验证了TUW展开的修边线精度能够满足实际工艺要求。     

Automatic surface modelling of a ship hull

When defining a ship hull surface, the main objective is to obtain a faired surface or surfaces that contain some specific points of the hull, that have been selected in the design process and give the ship its hydrodynamic, stability and other properties. So, the hull surface should be a compromise between fairness and precision, and this is not and easy task. In this paper, authors present a thorough procedure for automatic modelling with a fair NURBS surface, having lists of points on the stations of the vessel as initial data. The construction of spline curves, and their application in the definition of ship lines is reviewed. Approximation of spline curves fitting the data on the stations is made, with special emphasis on the choice of parametrization, which is relevant to increase the accuracy of the splines. NURBS surfaces modelling the hull of the vessel are constructed and the fairing process adapted to maintain certain ship characteristics is described.     

有效载荷整流罩降噪性能的数值分析和优化设计研究

通过基于SAE的数值分析软件对大型运载火箭有效载荷整流罩的降噪性能进行了分析,结合已经获得的大量试验数据,确定了影响有效载荷整流罩降噪性能的关键参数,并对关键参数进行了优化设计,为有效载荷整流罩结构形式和材料的选择及降噪方案的确定奠定了理论基础和数值依据.     

Automatic Shape Control of Triangular B-Splines of Arbitrary Topology

Triangular B-splines are powerful and flexible in modeling a broader class of geometric objects defined over arbitrary, non-rectangular domains. Despite their great potential and advantages in theory, practical techniques and computational tools with triangular B-splines are less-developed. This is mainly because users have to handle a large number of irregularly distributed control points over arbitrary triangulation. In this paper, an automatic and efficient method is proposed to generate visually pleasing, high-quality triangular B-splines of arbitrary topology. The experimental results on several real datasets show that triangular B-splines are powerful and effective in both theory and practice.