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1.
Finding spatial regularity in images is important in military applications (e.g., finding rows of landmines), texture analysis, and other areas. We give an optimal Θ(n2) algorithm for finding all maximal equally-spaced collinear subsets within a pointset in Ed. We also generalize this method to yield an optimal Θ(n3) algorithm for determining all maximal regular coplanar lattices.  相似文献   

2.
In this paper, we proposed an efficient algorithm, called PCP-Miner (Pointset Closed Pattern Miner), for mining frequent closed patterns from a pointset database, where a pointset contains a set of points. Our proposed algorithm consists of two phases. First, we find all frequent patterns of length two in the database. Second, for each pattern found in the first phase, we recursively generate frequent closed patterns by a frequent pattern tree in a depth-first search manner. Since the PCP-Miner does not generate unnecessary candidates, it is more efficient and scalable than the modified Apriori, SASMiner and MaxGeo. The experimental results show that the PCP-Miner algorithm outperforms the comparing algorithms by more than one order of magnitude.  相似文献   

3.
基于有序简单多边形的平面点集凸包快速求取算法   总被引:32,自引:1,他引:32  
凸包问题是计算几何的基本问题之一,在许多领域均有应用。传统平面点集凸包算法和简单多边形凸包算法平行发展,互不相干。本文将改进的简单多边形凸包算法应用于平面点集凸包问题中,提出了新的点集凸包算法。该算法首先淘汰掉明显不位于凸包上的点,然后对剩余点集排序,再将点集按照一定顺序串联成有序简单多边形,最后利用前瞻回溯方法搜索多边形凸包,从而得到点集的凸包。本文算法不仅达到了O的理论时间复杂度下限,而且算法  相似文献   

4.
Denoising is a common, yet critical operation in geometry processing aiming at recovering high-fidelity models of piecewise-smooth objects from noise-corrupted pointsets. Despite a sizable literature on the topic, there is a dearth of approaches capable of processing very noisy and outlier-ridden input pointsets for which no normal estimates and no assumptions on the underlying geometric features or noise type are provided. In this paper, we propose a new robust-statistics approach to denoising pointsets based on line processes to offer robustness to noise and outliers while preserving sharp features possibly present in the data. While the use of robust statistics in denoising is hardly new, most approaches rely on prescribed filtering using data-independent blending expressions based on the spatial and normal closeness of samples. Instead, our approach deduces a geometric denoising strategy through robust and regularized tangent plane fitting of the initial pointset, obtained numerically via alternating minimizations for efficiency and reliability. Key to our variational approach is the use of line processes to identify inliers vs. outliers, as well as the presence of sharp features. We demonstrate that our method can denoise sampled piecewise-smooth surfaces for levels of noise and outliers at which previous works fall short.  相似文献   

5.
Tracking graphs are a well established tool in topological analysis to visualize the evolution of components and their properties over time, i.e., when components appear, disappear, merge, and split. However, tracking graphs are limited to a single level threshold and the graphs may vary substantially even under small changes to the threshold. To examine the evolution of features for varying levels, users have to compare multiple tracking graphs without a direct visual link between them. We propose a novel, interactive, nested graph visualization based on the fact that the tracked superlevel set components for different levels are related to each other through their nesting hierarchy. This approach allows us to set multiple tracking graphs in context to each other and enables users to effectively follow the evolution of components for different levels simultaneously. We demonstrate the effectiveness of our approach on datasets from finite pointset methods, computational fluid dynamics, and cosmology simulations.  相似文献   

6.
在涉及计算机寻优等许多工程领域,都需要使用多元函数的最优化。线搜索是多元函数的最优化中已知搜索方向求最优步长的关键技术。为了提出一种高效的线搜索算法,对线搜索进行详细研究,提出一种新的线搜索寻优方法--类康托法。主要方法是去除了Fibonacci法中两个试探点必须保留一个的限制,每次把搜索区间三等分,根据试探点的导数值,来决定去除哪两个子区间。通过理论和实例的证明,结果发现类康托法比0.618法和Fibonacci法更高效,计算速度更快。其中最重要的结论是类康托法为这两种方法收敛速度的高阶无穷小。特别是在精度要求很高的时候,类康托法比这两种算法具有更明显的优势。此外,该方法具有较强的适用性,不但能用于凸函数,也能用于凹函数。  相似文献   

7.
改进型GMSM建模方法及其应用   总被引:4,自引:0,他引:4  
刘伟  田树苞 《自动化学报》1993,19(4):468-471
本文提出了一种改进的GMSM建模方法。该方法以二元插值多项式作为各层的部分描述式,利用ISM方法进行输入变量预处理,简化了原方法的整体结构。建模结果表明:改进方法对建立一般复杂过程的数学模型是有效的。  相似文献   

8.
针对气动PLC自动生产线中供料单元,在一次供料过程时,上电后却无法运作,通过观察其故障现象,分析其故障原因,提出设定故障检查次序,综合利用假设验证法、替换法、经验法和测量法等故障诊断方法,排除设备的故障,继而通过实践证明合理设定故障检查次序对设备故障排除的重要性.  相似文献   

9.
PID调节器自整定的PM法及其公式推导   总被引:32,自引:1,他引:31  
本文提出了一种只基于给定相位裕度的自整定方法,并推导出一套相应的自整定公式。对PM法,临界比例度法,理想继电特性法作了比较性研究。研究结果说明,PM法优于Z-N法和Astrom法。该法现已用于“玻纤拉丝漏板的智能温度控制仪“的科研项目中,并取得了满意的控制效果。  相似文献   

10.
本文针对PLC控制的电动机在正反转时发生故障,通过观察故障现象和分析其故障原因,提出设定故障检查次序,综合利用假设验证法、替换法、对比法和测量法等故障诊断方法,排除设备的故障,通过实践证明合理设定故障检查次序对设备故障排除的重要性.  相似文献   

11.
介绍了目前测试巷道围岩松动圈的不同方法及其测试原理,讨论和分析了不同测试方法的优缺点及适用范围。通过对比可以看出,声波测试法技术成熟、方法简单,但在软岩层中很难适用;多点位移计和多点应力计法可以实时监测巷道围岩的位移或应力变化,但其测试精度有限;地震波法测试精度高,但设备昂贵且安装复杂;地质雷达法不需钻孔,是一种无损测试方法,但测试成本较高;电阻率法对仪器测量精度要求较高,且对电极布置也有较高的技术要求;钻孔摄像法的图像清晰度受限于钻孔内恶劣的环境条件及摄像头的像素。因此,每一种测试方法都有其局限性,实际应用时应充分考虑巷道围岩的性质,选用适宜的方法以便准确测定巷道松动圈大小。  相似文献   

12.
RKNd方法是一类新的数值积分方法。在相同级数条件下,RKNd方法可达到的最高代数阶比传统的Runge—Kutta方法以及Runge—Kutt—Nystrom方法均高,而且具有更高的计算效率。将RKNd方法引入电力系统暂态稳定性数值计算。以IEEEl45节点电力系统为例,通过数值实验将新方法与电力系统分析中常用的传统数值计算方法进行了对比分析。数值实验结果表明,RKNd方法在计算精度和计算效率等方面均具有明显的优势,N而更适合于电力系统暂态稳定性及相似问题的数值计算。  相似文献   

13.
时滞系统的控制在自动化领域具有重要意义。在剖析时滞系统控制的Smith预估法的本质的基础上,提出利用具有强大噪声抑制能力的"跟踪微分器"来实现"相位超前"、"相位滞后"等功能,从而解决时滞系统控制问题的新办法,其中包括把时滞算子近似成单位1的无视时滞法;把时滞算子近似成一阶惯性环节的提高阶次法;模仿Simith预估法把相位超前的虚拟输出当作被控量来进行无时滞对象控制的输出超前法;及引入虚似控制量的输入超前法等。相应的仿真研究表明,这些新方法都能控制好大时滞系统的控制问题,时滞大小已不再成为"难控"和"易控"的标准。  相似文献   

14.
对传统大M法进行改进,若计算检验数的表达式中含有M则只计算含有M的部分,从而简化计算,迭代过程中当人工变量由基变量变为非基变量时,直接去掉人工变量部分的表格然后继续计算,从而再一次降低计算量。借鉴两阶段法的优点进一步给出了无需给出大M的迭代算法,此法不会破坏目标函数的一致性,而且可以避免传统大M法在利用计算机求解时由于M值的选取不当所导致的计算错误。  相似文献   

15.
针对目前电梯门控制装置的缺陷,提出了一种基于图像识别技术的电梯门控方法,用于在电梯轿厢门区范围内实时检测运动物体.由于门区范围存在动态变化的复杂背景,图像识别易受光线干扰,该方法通过Otsu阈值分割法实现图像二值化处理,采用帧间差分法识别门区间运动物体.提出了统计的双阈值法解决门位置误差带来的问题,并提出了改进的电梯门控方法.实验结果表明:上述方法在电梯门区图像识别过程中取得了良好的效果,为改进的电梯门控方法的实现提供了可靠的保障.  相似文献   

16.
该文介绍了三种测量噪声系数的方法:增益法,Y因子法和冷源法。重点介绍了当我们做精确测量时Y因子法的不足和冷源法的突破以及给出了这两种方法的实际测试例子。  相似文献   

17.
In this paper, we provide a framework of combinations of collocation method (CM) with the finite-element method (FEM). The key idea is to link the Galerkin method to the least squares method which is then approximated by integration approximation, and led to the CM. The new important uniformly V0h-elliptic inequality is proved. Interestingly, the integration approximation plays a role only in satisfying the uniformly V0h-elliptic inequality. For the combinations of the finite-element and collocation methods (FEM-CM), the optimal convergence rates can be achieved. The advantage of the CM is to formulate easily linear algebraic equations, where the associated matrices are positive definite but nonsymmetric. We may also solve the algebraic equations of FEM and the collocation equations directly by the least squares method, thus, to greatly improve numerical stability. Numerical experiments are also carried for Poisson's problem to support the analysis. Note that the analysis in this paper is distinct from the existing literature, and it covers a large class of the CM using various admissible functions, such as the radial basis functions, the Sinc functions, etc.  相似文献   

18.
In this article, we give the acceleration of the block successive overrelaxation (SOR) method for solving the rank-deficient least-squares problem. Santos and Silva proposed the two-block SOR method and the three-block SOR method. Here, we consider the acceleration of the two-block SOR method and the three-block SOR method using the Chebyshev polynomial and derive what we term the C-2-block SOR method and the C-3-block SOR method. The advantage of our methods is that we can get good results with very small iteration number. The comparison between the C-2-block method and the C-3-block method is presented. Finally, numerical examples are given.  相似文献   

19.
膜结构找形分析中的混合法   总被引:1,自引:0,他引:1  
在膜结构设计过程中一个很重要也是不可或缺的过程就是找形分析.常用的找形方法有力密度法、动力松弛法和非线性有限元法.力密度法原理简单但找形结果往往不能满足精度要求;非线性有限元法结果精度高但存在确定初始坐标问题和非线性系统的收敛问题.针对力密度法和非线性有限元法的不足,在综合以上两种方法后得到了混合法对膜结构进行找形,并在Matlab和Ansys中编写了相应的程序模拟实现了混合法找形.结合两个实际工程说明了混合法找形可以应用于大型复杂柔性体系的找形,同时证明了混合法找形的先进性和可行性.  相似文献   

20.
为了消除软件需求中存在的不完整性、二义性和不一致性,可以用形式化方法描述软件需求;但是,形式化描述需要很强的专业知识,这样严重阻碍其广泛应用。为了使形式化描述简单、易行,提出了一种从UML试图转化为B形式化需求的一种新的实现方法,该方法通过在实际的项目中应用,取得了一定的效果。  相似文献   

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