On a statistic useful in dimensionality reduction in multivariable linear stochastic system

In this paper we study the sampling properties of a test statistic which has important applications in the area of linear stochastic control systems with multi-inputs and multi-outputs. The statistic is the ratio of a partial sum of the eigenvalues of a sample covariance matrix and its trace. It turns out that using a method due to Sugiura we may derive a useful approximation for its distribution up to and including terms of order l/n, where n denotes the appropriate size. Numerical illustrations using real data are given.     

关于国有股减持的若干探讨

本文主要探讨了减持国有股的核心目的,国有股减持的比例问题,减持公司的选择原则和国有股减持与保证股市稳定的关系。     

Error reduction in density estimation under shape restrictions

For the problems of nonparametric estimation of nonincreasing and symmetric unimodal density functions with bounded supports we determine the projections of estimates onto the convex families of possible parent densities with respect to the weighted integrated squared error. We also describe the method of approximating the analogous projections onto the respective density classes satisfying some general moment conditions. The method of projections reduces the estimation errors for all possible values of observations of a given finite sample size in a uniformly optimal way and provides estimates sharing the properties of the parent densities.     

Partial least squares estimator for single-index models

The partial least squares (PLS) approach first constructs new explanatory variables, known as factors (or components), which are linear combinations of available predictor variables. A small subset of these factors is then chosen and retained for prediction. We study the performance of PLS in estimating single-index models, especially when the predictor variables exhibit high collinearity. We show that PLS estimates are consistent up to a constant of proportionality. We present three simulation studies that compare the performance of PLS in estimating single-index models with that of sliced inverse regression (SIR). In the first two studies, we find that PLS performs better than SIR when collinearity exists. In the third study, we learn that PLS performs well even when there are multiple dependent variables, the link function is non-linear and the shape of the functional form is not known.     

现代汉民族共同语的变化与方言

普通话不是孤立存在的系统.它要推广普及到各方言区的群众中去,以发挥它作为全民通用的交际工具的职能.它一旦为人们所掌握而运用于日常言语活动中,就转化为言语变体.方言以自己特有的力量和方式影响着共同语的变化.弄清其与方言的关系及变化规律,有助于澄清一些基本概念上的混乱,有助于普通话的推广.这不仅具有理论价值,更有实践意义.     

磨料射流及高分子减阻改善射流性能的实验研究

本文设计了磨料射流系统及喷嘴结构,实验研究了磨料射流切割与破碎物料的性能,确定了磨料喷嘴出口的最佳长度,对清水和磨料溶液进行了射流冲击性能比较试验;并进一步在磨料射流中加入高分子聚合物添加剂,实验证明,高分子减阻剂同样对磨料射流性能有改善.     

能量摄取、膳食构成及体育锻炼在减肥中的作用

本文论述了能量摄取、膳食构成、体育锻炼与体脂的关系以及在减肥中的作用，并通过对湖北省某高校男、女大学生超重率的调查，发现普通系无论是男生还是女生其超重率一般并不比体育系男女生高（Ｐ＞０．０５）．提出不宜以超重作为评定个体肥胖的标准。     

移频降噪理论在往复式冰箱压缩机噪声控制中的应用

通过模拟计算QD58型往复式冰箱压缩机的声学特性，指出压缩机噪声最大峰值与其内部气体共鸣音直接有关．运用移频降噪理论，改变压缩机内气体的声学固有频率，降低共鸣音．实测了空气介质下压缩机内腔安装隔板后的移频降噪数据．并用电一声类比法推导的压缩机内气体的声学固有频率对隔板各个几何参数的灵敏度公式，调整实际工作状态下隔板的几何参数，模拟计算了压缩机内部气体声学固有频率的变化．     

试谈有机化合物的氧化还原反应

本文就有机化合物的氧化还原反应作了比较系统的论述，对氧化还原反应的判别重要类型作了较详细的介绍，并引入氧化值的概念及其计算，从氧化值的改变来确定氧化还原反应以及用氧化值和氧化态解释有机物在氧化还原反应中的行为。     

与多边开发银行和发展融资有关的几个问题及其思考

在回顾过去多边开发银行在减贫与全球发展融资进程中的理论与实践的基础上,提出了对现行减贫理论及其应用现状中存在的问题。针对上述问题,阐述了多边开发银行的作用,以及发达国家与发展中国家在相关问题上的分歧,最后探讨了多边开发银行未来发展方向,并对广大发展中国家如何积极有效地参与全球发展进程,维护和争取自身利益提出了若干政策建议。