Improved minimax estimation of a normal precision matrix

Let S_{p × p} have a Wishart distribution with parameter matrix Σ and n degrees of freedom. We consider here the problem of estimating the precision matrix Σ^?1 under the loss functions L₁(σ) tr (σ) - log |σ| and L₂(σ) = tr (σ). James-Stein-type estimators have been derived for an arbitrary p. We also obtain an orthogonal invariant and a diagonal invariant minimax estimator under both loss functions. A Monte-Carlo simulation study indicates that the risk improvement of the orthogonal invariant estimators over the James-Stein type estimators, the Haff (1979) estimator, and the “testimator” given by Sinha and Ghosh (1987) is substantial.     

突厥佛教盛衰考

突厥佛教始兴于6世纪下半叶佗钵可汗统治时期,曾受到中原、印度及中亚粟特佛教的交互影响。由于佛教戒杀生、戒争斗的教义与突厥游牧射猎、尚勇好武的习俗多有抵牾,故佛教在漠北未能扎根而不久便趋于衰亡,惟中亚西突厥人因受当地佛教的影响而流行的时间较长,延至8世纪中期,后随着伊斯兰教势力的东浸而衰亡。     

中原民间美术与艺术设计发展关系研究

中原民间美术是中国民间美术和中国传统文化的重要组成部分。艺术设计在河南蓬勃发展,需要寻找其所根植的土壤。通过对民间美术和艺术设计的异同进行比较和分析,可以揭示出二者发展的关系。艺术设计和民间美术需要紧密结合,共同弘扬中原文化,发展中原经济。     

人工物技术创造过程中的隐蔽场所理论

作者借鉴系统科学研究的方法,对人工物的技术创造过程及中心法则进行比较分析,指认二者为具有逻辑相应性的同态过程,以中心法则为技术创造的同态概念模型进行分析,反应出信息要素的表达在产品使用价值构成中的关键地位,进而揭示出使用价值的生成存在一个不同于产品制造的场所——一个在以往被忽略了的隐蔽场所。     

STEIN'S METHOD AND THE BERRY-ESSÉEN THEOREM

Stein's method is used to prove the Lindeberg-Feller theorem and a generalization of the Berry-Esséen theorem. The arguments involve only manipulation of probability inequalities, and form an attractive alternative to the less direct Fourier-analytic methods which are traditionally employed.     

On uniform approximation of Poisson variates by normal ones

In this paper the accuracy of the normal approximation to the Poisson is treated from the viewpoint of direct approximation of Poisson variables by normal ones. The conclusions that are derived on the accuracy of this approximation lead (among others) to very useful results on confidence limits for the mean of a linear combination of independent Poisson variables; these latter are employed in precise determination of the composition of a mixture of radioactive isotopes by means of a scintillation counter.     

On the distribution of quadratic forms in normal random variables

This paper provides necessary and sufficient conditions for a quadratic form in singular normal random variables to be distributed as a given linear combination of independent noncentral chi-square variables. Using this result, an extension of Cochran's theorem to quadratic forms of noncentral chi-square variables is derived.     

Distribution of multivariate quadratic forms under certain covariance structures

Necessary and sufficient conditions are given for the covariance structure of all the observations in a multivariate factorial experiment under which certain multivariate quadratic forms are independent and distributed as a constant times a Wishart. It is also shown that exact multivariate test statistics can be formed for certain covariance structures of the observations when the assumption of equal covariance matrices for each normal population is relaxed. A characterization is given for the dependency structure between random vectors in which the sample mean and sample covariance matrix have certain properties.     

实施“人才强校”战略是中央民族大学争创一流的根本保证

中央民族大学要建成世界一流的民族大学,需要有一支高水平的教师队伍、高水平的管理队伍和高水平的政工队伍。同时要进行制度创新,创建一套人才辈出的良好机制。只有实施"人才强校"战略,中央民族大学争创一流才会有根本保证。     

边缘的思考，主流的文学——论鬼子小说的价值

本文从"为人生"的视角论叙鬼子小说的苦难承载的文学价值形态和真诚的写作态度,作家用悲悯的情怀叙述古老民族蜕变向现代化社会转型时期人的痛苦,人的现代文明的精神焦虑"边缘"羡慕"中心"的现代性渴慕;以陌生化的语法和陌生化的"百越境界"景象来呈现他的文学价值观.