共查询到19条相似文献,搜索用时 203 毫秒
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随着结构力学领域待解决问题复杂程度不断提高,多尺度构件的高质量网格生成对于其数值模拟的计算精度起着至关重要的作用。本文提出一种基于特征识别的网格自动生成技术方法,该方法将多尺度构件的不同量级尺度几何特征识别出来,根据其不同尺度尺寸设置相关区域的网格尺寸值,利用Delaunay三角化算法和前沿推进法生成能够反映不同尺度几何特征的网格单元,再对小尺度区域周围进行加密处理,最后通过几何指数控制函数将不同尺度网格过渡连接起来,形成多尺度构件的整体网格划分模型。通过2个几何模型的测试表明该方法生成的整体网格质量好,不同尺度区域网格过渡合理,自动化程度较高。 相似文献
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在边折叠网格简化算法的基础上,提出一种多尺度非均匀渐进网格简化算法。该算法不仅简化速度快,而且克服了传统算法在简化模型中网格分布均匀、无法突出模型重要特征的不足之处。该算法在模型的折叠、拐角、凹凸等表达特征的地方,采用的三角形网格面积较小、数量较多;而在平坦等不突出模型特征区域的三角形网格面积较大、数量较少。在简化程度较大的情况下仍然能够保持原始网格的几何特征和视觉特征。由于采用了渐进式多尺度的编码方式,再通过流式传输技术,就可以使采用这种算法生成的模型文件高效、方便地以渐进方式在网络上进行传输。 相似文献
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提出了基于可形变网格模型跟踪标记线的算法.通过网格模型的节点对标记线网格节点进行直接的跟踪,并将贪婪优化算法应用于模型能量极小化过程,提高了算法的速度.对多序列心脏收缩期核磁共振图像的实验表明,在保证标记线跟踪准确性的同时,文中算法大大提高了跟踪的速度. 相似文献
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适用于遮挡问题的目标跟踪算法 总被引:2,自引:0,他引:2
提出一种基于网格模型的目标跟踪算法.该算法首先进行遮挡区域检测,然后进行网格结点的运动估计和网格更新过程完成目标的多帧跟踪.改进的遮挡区域检测算法有效地提高了检测准确度,从而确保遮挡区域的准确跟踪;网格结点的运动估计是通过特征窗口运动补偿匹配完成,可以有效地克服块效应.实验证明,该算法解决了二维运动估计时网格模型在遮挡区域存在的问题,并可以有效地进行目标准确跟踪. 相似文献
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基于细节的自适应网格简化 总被引:9,自引:2,他引:9
从模型中保留的几何细节出发,提出一种自适应的三角网格简化算法.该算法首先比较顶点与其相邻点之间的欧氏距离是否超过预先设定的简化尺度,删除小于该尺度的相邻点,再对删除造成的空洞作局部三角剖分.此算法的特点是用细节度参数控制简化模型的整体精度,并且简化的尺度可以根据模型表面的细节情况作自适应调整,自动在细节丰富的区域变小而在细节稀疏的区域变大.通过两组应用实例可以看到,文中算法在有效地降低数据量的同时很好地保持了模型的视觉特征. 相似文献
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在以离散网格为基础的某些数值模拟中,网格间的数据依赖关系可以抽象为有向图.如何剖分这些有向图成多个子图,将各子图对应的数值模拟任务映射到不同的处理机,是该类数值模拟并行计算的基础.剖分算法中,需要综合考虑连通性、并行度、负载平衡、通信开销四个目标.文章在传统有向图剖分算法的基础上,提出了一个权衡这四个目标的有向图多目标剖分区域分解算法.应用于二维非结构网格上的柱对称中子输运并行计算中,通量扫描并行算法在该区域剖分算法上获得的并行效率比原来的无向图区域剖分算法高50%以上. 相似文献
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In this article, an efficient sub‐gridding finite‐difference time‐domain is developed for the simulation of multiscaled electromagnetic problems. The proposed technique is based on using the Huygens surfaces for interfacing electromagnetic fields between different grids. The use of the Object Oriented Programming for modeling FDTD simulations facilitates the imbrication of multiple sub‐grids. That heightens the spatial ratio without affecting the accuracy and stability of the sub‐gridding technique. Spatiotemporal interpolation is used to evaluate the electromagnetic fields in Huygens surface location among the coarse grid. Results of numerical experiments prove that the use of imbricated sub‐grids and spatiotemporal interpolation in the Huygens sub‐gridding is more efficient than the use of a single sub‐grid with only spatial interpolation. 相似文献
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Convex dynamic programming for hybrid systems 总被引:1,自引:0,他引:1
A classical linear programming approach to optimization of flow or transportation in a discrete graph is extended to hybrid systems. The problem is finite dimensional if the state space is discrete and finite, but becomes infinite dimensional for a continuous or hybrid state space. It is shown how strict lower bounds on the optimal loss function can be computed by gridding the continuous state space and restricting the linear program to a finite-dimensional subspace. Upper bounds can be obtained by evaluation of the corresponding control laws. 相似文献
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针对基于位置服务中用户位置信息易泄露用户个人隐私的问题,利用Geohash编码优化网格化Casper模型,提出了基于Geohash的位置隐私保护算法G-Casper。该算法采用自底向上的机制,对目标位置的Geohash编码进行字符串模糊查询来确定组成匿名区域的[k-1]个近邻,在扩大扫描区域时,对请求用户所在网格以及周边网格跨域扫描,然后再进行层级的递归,同时使用[Lmax]和[Lmin]两个参数来控制匿名区域范围,最终通过剪枝算法删除冗余网格并随机发送一个候选网格区域代替用户原本位置,达到[k]-匿名的效果。实验结果表明,该算法能够更好地提高位置服务的质量和匿名区域的成功率,并且减少了查询时间和所需储存空间。 相似文献
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手工兵棋电子化过程中一个重要的方面就是兵棋地图的数字化,而兵棋地图数字化的基础工作就是地图网格化以及网格定位。在兵棋系统中,为了减小误差,一般采用六角网格覆盖原始地图的方法来实现地图的网格化。在实际推演过程中,作战地图覆盖范围一般很大,那么怎样提高网格化以及网格定位效率就成了地图数字化过程中必须考虑的问题。文章描述了一种效率很高的六边形网格绘制算法,并提出了基于元启发式方法的快速地图网格定位算法,它的时间以及空间复杂都仅有O(1),能够很好的满足兵棋系统中超大地图数字化的要求。 相似文献
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Continuous scatterplots 总被引:1,自引:0,他引:1
Bachthaler S Weiskopf D 《IEEE transactions on visualization and computer graphics》2008,14(6):1428-1435
Scatterplots are well established means of visualizing discrete data values with two data variables as a collection of discrete points. We aim at generalizing the concept of scatterplots to the visualization of spatially continuous input data by a continuous and dense plot. An example of a continuous input field is data defined on an n-D spatial grid with respective interpolation or reconstruction of in-between values. We propose a rigorous, accurate, and generic mathematical model of continuous scatterplots that considers an arbitrary density defined on an input field on an n-D domain and that maps this density to m-D scatterplots. Special cases are derived from this generic model and discussed in detail: scatterplots where the n-D spatial domain and the m-D data attribute domain have identical dimension, 1-D scatterplots as a way to define continuous histograms, and 2-D scatterplots of data on 3-D spatial grids. We show how continuous histograms are related to traditional discrete histograms and to the histograms of isosurface statistics. Based on the mathematical model of continuous scatterplots, respective visualization algorithms are derived, in particular for 2-D scatterplots of data from 3-D tetrahedral grids. For several visualization tasks, we show the applicability of continuous scatterplots. Since continuous scatterplots do not only sample data at grid points but interpolate data values within cells, a dense and complete visualization of the data set is achieved that scales well with increasing data set size. Especially for irregular grids with varying cell size, improved results are obtained when compared to conventional scatterplots. Therefore, continuous scatterplots are a suitable extension of a statistics visualization technique to be applied to typical data from scientific computation. 相似文献
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Yukiko Kenmochi Lilian Buzer Akihiro Sugimoto Ikuko Shimizu Université Paris-Est Laboratoire d Informatique de l Institut Gaspard-Monge UMR CNRS ASI-ESIEE Cité Descartes BP Noisy-le-Grand Cedex France National Institute of Informatics Chiyoda Tokyo - Japan Department of Computer Information Communication Sciences Tokyo University of Agriculture Technology -- Naka-cho Koganedai Tokyo - Japan 《国际自动化与计算杂志》2008,5(3):246-256
This paper presents a method for segmenting a 3D point cloud into planar surfaces using recently obtained discretegeometry results. In discrete geometry, a discrete plane is defined as a set of grid points lying between two parallel planes with a small distance, called thickness. In contrast to the continuous case, there exist a finite number of local geometric patterns (LGPs) appearing on discrete planes. Moreover, such an LGP does not possess the unique normal vector but a set of normal vectors. By using those LGP properties, we first reject non-linear points from a point cloud, and then classify non-rejected points whose LGPs have common normal vectors into a planar-surface-point set. From each segmented point set, we also estimate the values of parameters of a discrete plane by minimizing its thickness. 相似文献
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This paper presents a new local search for solving the continuous p-median problem in the plane. The basic idea is to first find a good starting solution by overlaying the area containing the set of demand points with a grid and solving heuristically the location problem on this grid. The solution is then used as an initial point for running an improved version of Cooper's well-known alternating local search. 相似文献
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针对以k-means为代表的分割聚类算法初始参数的很难选取这一难题,提出基于网格质心运动的初始化算法。划分网格后,定义网格的质量,利用物质质心运动理论,提取样本的聚类中心,并由此确定样本分类数k。实验表明,该算法可以有效地提取初始聚类中心,消除噪声点,可以提高后续聚类分析的效果和效率。 相似文献