网络财务的优势、困惑及对策

在网络技术飞速发展的今天,网络财务有着较传统财务不可比拟的优势,但同时也存在着不少困惑,有待人们在探索中采取一定的对策予以解决.     

PERT时间参数的算法及工期费用的优化

建立了PERT时间参数计算的数学模型,即工期-费用优化的精确模型,给出了数值计算的实例.在PERT技术中运用对偶理论,为敏度分析创造了必要条件.     

A simple way to obtain the spectral decomposition of variance components models for balanced data

By means of an example it is shown how eigenvalues and eigenvectors of variance components models can be obtained straightforwardly when balanced data are available. Simple asymptotically efficient estimators of the variance components are presented.     

过度商品化引发的生态问题研究

资本主义生产和生活方式是形成全球生态危机和灾难的根本原因。资本将人类的财富生产转化为了商品生产,由于资本家对商品中剩余价值的贪婪,刺激其生产方式和科学技术过度商品化,其结果虽然提高了资本主义社会从大自然获取生产和生活资料的能力,但在资本主义制度下,这种能力不断扩张为对大自然的疯狂掠夺、消耗和破坏,致使资本主义生产方式和科学技术异化为人与自然、人与人、人与社会、社会与自然的对抗,从而引发生态危机和灾难。     

The 'improved' brown and forsythe test for mean equality: some things can't be fixed

Mehrotra (1997) presented an ‘;improved’ Brown and Forsythe (1974) statistic which is designed to provide a valid test of mean equality in independent groups designs when variances are heterogeneous. In particular, the usual Brown and Fosythe procedure was modified by using a Satterthwaite approximation for numerator degrees of freedom instead of the usual value of number of groups minus one. Mehrotra then, through Monte Carlo methods, demonstrated that the ‘improved’ method resulted in a robust test of significance in cases where the usual Brown and Forsythe method did not. Accordingly, this ‘improved’ procedure was recommended. We show that under conditions likely to be encountered in applied settings, that is, conditions involving heterogeneous variances as well as nonnormal data, the ‘improved’ Brown and Forsythe procedure results in depressed or inflated rates of Type I error in unbalanced designs. Previous findings indicate, however, that one can obtain a robust test by adopting a heteroscedastic statistic with the robust estimators, rather than the usual least squares estimators, and further improvement can be expected when critical significance values are obtained through bootstrapping methods.     

一类n阶非线性微分方程多点边值问题解的存在性

利用Leray-Schauder度理论建立了n阶非线性微分方程y(n)=f(x,y,y′,…,y(n-1)),n≥3,满足多点边界条件yn-1(0)-hyn-2(0)=0,y(i)(ηi)=0,i=0,1,…,n-3,y(n-1)(1)+ky(n-2)(1)=0.的多点边值问题的解存在性的几个充分条件,并给出了应用举例.     

发展可持续农业的几个问题

本文就发展可持续农业中的几个问题进行了讨论。提出发展可持续农业要以系统科学理论为指导，必须落实到区域，应切实抓好人口控制这一基础性工作；特别强调了林业的天然屏障作用和技术创新的意义；给出了有关指标体系和规划办法等。这对创建和发展可持续农业大有稗益。     

A new special class of peb designs

A new class of partially efficiency-balanced designs is introduced from a practical point of view. This new design includes all equireplicated incomplete block designs available in literature as special cases. The fundamental properties of the design are clarified with relation to other block designs.     

Robust test for means when population variances are unequal

We consider the problem of testing the equality of two population means when the population variances are not necessarily equal. We propose a Welch-type statistic, say T^* _c, based on Tiku!s ‘1967, 1980’ modified maximum likelihood estimators, and show that this statistic is robust to symmetric and moderately skew distributions. We investigate the power properties of the statistic T^* _c; T^* _c clearly seems to be more powerful than Yuen's ‘1974’ Welch-type robust statistic based on the trimmed sample means and the matching sample variances. We show that the analogous statistics based on the ‘adaptive’ robust estimators give misleading Type I errors. We generalize the results to testing linear contrasts among k population means