共查询到19条相似文献,搜索用时 737 毫秒
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该文根据王元,方开泰[2]的近似偏差(discrepancy)的均匀性准则,定义了理想布点情况下的标准半径,定义了m 维单位子空间Cm=[0,1]中两点间的f距离和g距离,由此定义了最大空穴半径和最小空穴半径,提出了均匀性度量的密集性偏差与稀疏性偏差.给出了二维情况
下的计算结果.我们的方法计算量不大,不仅能较好地度量布点的均匀性以及布点在低维投影的均匀性,而且能指导如何调整布点使之尽可能与理想布点接近. 相似文献
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分析了均匀性度量应满足的基本条件,根据物理学的势和力的模型,提出了均匀性度量的势函数模型,该模型较好地解决了均匀性度量的可计算性、布点的均匀性调整方法等问题;而且具有均匀性度量所应该具有的所有优良性质,如旋转对称性、平移对称性、中心对称性等。最后给出了应用实例,并就低维投影的均匀性问题和势函数模型的改进作了讨论。
相似文献
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均匀试验设计是部分因子设计的主要方法之,已被广泛地应用于工业生产、系统工程、制药及其他自然科学中.各种偏差被用来度量部分因子设计的均匀性.不管使用哪种偏差,关键的问题是寻找一个精确的偏差下界,因为它可以作为衡量设计均匀性的标准.本文应用条件极值的方法得到了三水平U-设计在对称化L_(2-)偏差下的下界,该下界可作为寻找均匀设计的一个基准. 相似文献
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《中国科学:数学》2020,(5)
均匀设计自20世纪80年代被提出以来依靠其稳健和使用方便、灵活的特性而广受欢迎.为获得实验目标区域内散布均匀的设计点集,不同的均匀度量标准被相继提出,其中以从数值积分理论中发展而来的L_2-星偏差及相应的改进形式接受度最为广泛.尽管相对于最初的星偏差标准,当前广泛使用的改进偏差有更好的性质和实用性,但这些偏差仍存在一些缺点,例如,中心化偏差(centered discrepancy, CD)对于实验目标区域中心点的特殊依赖性.从各种偏差定义的本源上可以看出,对称偏差(symmetric discrepancy, SD)相较于CD有更好的几何性质, SD给实验目标区域内任何点的权重都是相同的,这在直观上更符合均匀性的要求.但受限于投影均匀性差的缺陷, SD的使用范围十分有限.本文重新研究对称偏差,分析出SD缺陷的本质,并采取加权的办法改进其投影均匀性,提出投影加权对称偏差.本文同时也研究了新偏差的相关优良性质. 相似文献
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偏差(Discrepancy)作为布点设计均匀性的一个重要度量准则,已被使用很长时间,但对它的性质还研究得很不够.该文从模平移的方面系统地研究了偏差的性质,给出了在超立方体中一个布点设计按整体、大格子、小格子各种模平移的偏差大样本性质,这些性质对于计算机试验引进有关的设计和抽样方法起着重要的作用. 相似文献
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均匀设计是部分因子设计的主要方法之一,已被广泛地应用于工业生产、系统工程、制药及其他自然科学中.各种偏差被用来度量部分因子设计的均匀性,其关键的问题是寻找一个精确的偏差下界,因为它可以作为衡量设计均匀性的标准.该文给出了4水平对称U-型设计的对称化L2-偏差的下界,以及2、3混水平和2、4混水平非对称U-型设计的对称化L2-偏差的下界. 相似文献
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中心化L2偏差已被用来作为部分因析设计均匀性的度量,并用来区分几何非同构设计.中心化L2偏差均值也被用来度量部分因析设计均匀性,这样就可以对现有最小低阶混杂设计进行水平置换,从而获得中心化L2偏差最小的均匀最小低阶混杂设计.本文里,我们针对三水平部分因析设计讨论中心化L2偏差均值的性质,给出中心化L2偏差均值与正交性准则,最小低阶矩混杂准则之间的解析关系,同时给出中心化L2偏差均值的两个下界. 相似文献
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The well-known star discrepancy is a common measure for the uniformity of point distributions. It is used, e.g., in multivariate integration, pseudo random number generation, experimental design, statistics, or computer graphics. 相似文献
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LI Hongli Department of Mathematics University of Science Technology of China Hefei China 《中国科学A辑(英文版)》2005,48(9)
In this paper,we study some packings in a cube,namely,how to pack n points in a cube so as to maximize the minimal distance.The distance is induced by the L_1-norm which is analogous to the Hamming distance in coding theory.Two constructions with reasonable parameters are obtained,by using some results from a function field including divisor class group,narrow ray class group,and so on.We also present some asymptotic results of the two packings. 相似文献
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利用格L_i(i=1,2)的性质研究了它们的卡氏积L=L_1×L_2的性质,得到了L的秩函数、Mbius函数和特征多项式,并且由L_i的几何性证明了L的几何性. 相似文献
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Choung Min Ng Seng-Huat Ong H.M. Srivastava 《Applied Mathematical Modelling》2013,37(12-13):7374-7385
Maximum likelihood (ML) estimation is a popular method for parameter estimation when modeling discrete or count observations but unfortunately it may be sensitive to outliers. Alternative robust methods like minimum Hellinger distance (MHD) have been proposed for estimation. However, in the multivariate case, the MHD method leads to computer intensive estimation especially when the joint probability density function is complicated. In this paper, a Hellinger type distance measure based on the probability generating function is proposed as a tool for quick and robust parameter estimation. The proposed method yields consistent estimators, performs well for simulated and real data, and can be computationally much faster than ML or MHD estimation. 相似文献
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In this paper, we consider the problem of finding sparse solutions for underdetermined systems of linear equations, which can be formulated as a class of L_0 norm minimization problem. By using the least absolute residual approximation, we propose a new piecewis, quadratic function to approximate the L_0 norm.Then, we develop a piecewise quadratic approximation(PQA) model where the objective function is given by the summation of a smooth non-convex component and a non-smooth convex component. To solve the(PQA) model,we present an algorithm based on the idea of the iterative thresholding algorithm and derive the convergence and the convergence rate. Finally, we carry out a series of numerical experiments to demonstrate the performance of the proposed algorithm for(PQA). We also conduct a phase diagram analysis to further show the superiority of(PQA) over L_1 and L_(1/2) regularizations. 相似文献
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We argue that the spectral theory of non-reversible Markov chains may often be more effectively cast within the framework of the naturally associated weighted-L ∞ space ${L_\infty^V}$ , instead of the usual Hilbert space L 2?=?L 2(π), where π is the invariant measure of the chain. This observation is, in part, based on the following results. A discrete-time Markov chain with values in a general state space is geometrically ergodic if and only if its transition kernel admits a spectral gap in ${L_\infty^V}$ . If the chain is reversible, the same equivalence holds with L 2 in place of ${L_\infty^V}$ . In the absence of reversibility it fails: There are (necessarily non-reversible, geometrically ergodic) chains that admit a spectral gap in ${L_\infty^V}$ but not in L 2. Moreover, if a chain admits a spectral gap in L 2, then for any ${h\in L_2}$ there exists a Lyapunov function ${V_h\in L_1}$ such that V h dominates h and the chain admits a spectral gap in ${L_\infty^{V_h}}$ . The relationship between the size of the spectral gap in ${L_\infty^V}$ or L 2, and the rate at which the chain converges to equilibrium is also briefly discussed. 相似文献
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关于伽略金方法收敛阶的估计 总被引:1,自引:0,他引:1
§1.引言设H是可分的Hilbert空间,内积为(·,·),范数为||·||.v是H的稠密子空间.于V定义另一内积[·,·]和相应的范数|·|,使v关于[·,·]具有Hilbert空间结构。假定v往H的嵌入:v|→H连续,即存在常数a>0,使 ||u||≤a|u|,uv. (1) 设L_1,L_2是由v到H的线性算子,其定义域D_(L_1),D_(L_2)是v的线性稠密子集,且D_(L_1)D_(L_2).令A=L_1+L_2(显然A的定义域D_A=D_(L_ I))。对H,我们考虑算子方程 相似文献
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Haifeng Shang 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2013,64(3):785-798
We consider existence of initial traces of nonnegative solutions for fast diffusion equation with space-dependent source and the solvability of the Cauchy problem when the initial datum is merely a function in ${L_{{\rm loc}}^1(R^N)}$ or even a Radon measure. 相似文献