Covariance and variance evaluations of two estimators for drug–placebo difference in a trial with sequential parallel design

Chen et al. [Contemp. Clin. Trials, 32: 592–604 (2011)] heuristically proved that the covariance of two estimators is zero assuming equal correlation coefficients. In this article, the above covariance is analytically and rigorously re-derived without any strong assumption in equality between two correlation coefficients. Under rigorous analytic derivations plus assuming number of subjects continuing into Period 2 is a random variable, covariance is reconfirmed to be zero for both normal and binomial data.     

论清代诗文名家彭兆荪的骈文创作

镇洋彭兆荪是清代乾嘉间名震文坛的骈体名家，他的骈文作品主要收录在《小谟觞馆文集》4卷及《续集》2卷中。彭氏认为，骈体文的出现，乃文学史发展的必然结果；骈散异途同源，不分尊卑，而八代之文未尝衰；同时，骈文应以六朝为高标，并依此“矫厉肤庸，归诸渊雅”，使当代骈文创作走上正轨。彭氏骈文的主要特点与成就，体现在三个方面，即精熟《选》理、宏博沉丽，以散运骈、辞茂气盛和诸法兼擅、尤工议论。就文学史地位而言，在清代骈文史上，彭兆荪足称一代名家，我们应对他的骈文引起足够的重视。     

论唐代科举制对骈文普及的促进作用

中唐古文运动没有彻底改变骈文的主流文体地位,唐代仍是骈文风行的时代。唐代骈文的普及,除了骈文自身发展演变的历史惯性之外,科举制度发挥了至关重要的推动作用。唐代科举中的进士科考试以骈体诗文为重心,广大士子以骈文为必修课,科举制度遂成为骈文流行的制度保障。     

论唐太宗在骈文上的创新

唐太宗不但在政治方面开创了有名的贞观盛世,更是当时的文坛盟主,在文章方面亦颇多创新之举。他不但以实践者的身份在题材、内容、句式骈偶、用典等方面对六朝骈文旧习有所突破,并且提出了新的文风标准,其个人作品也颇有文采,这些情况均标示了唐初文学的渐变趋势,也表明了唐太宗在骈文发展史上的一席重要地位。李世民的文章题材广泛,内容充实,情感真切自然;为文骈散兼用,事典熟悉,使文章更为通脱流畅;反对六朝绮艳文风,倡导为文要庄和典丽,文章颇富文采。这些都对当时骈文乃至整个文学的发展起到了积极的推动作用。     

基于Transputer网络的直通通信技术研究

并行处理技术是提高系统处理速度的有效途径之一，而结点间的通信速度对并行处理系统性能的发挥起到关键作用。文中对并行处理系统中的通信技术进行了研究，提出了一种直通通信机制，并在基于Ｔｒａｎｓｐｕｔｅｒ的网络环境中加以实现。这种技术可以有效提高系统的通行能力     

一类刚性系统基于线性多步法的并行计算方法

针对一类分解的刚性系统,提出了一类并行组合方法.该方法将系统分割与方法分割的并行化方法相结合,采用显式线性多步方法求解非刚性子系统,采用隐式线性多步方法求解刚性子系统.讨论了方法的相容阶、收敛性和数值稳定性.数值试验结果表明,该方法对于求解分解的刚性系统是可行的.     

四维空间投影的垂直特性

本文系统地讨论了四维空间中相互垂直的几何元素的投影仍呈垂直关系的規律,当平行于某一超投影面的直线与任一直线(平面或超平面)垂直时,它们在该超投影面内的超投影仍然垂直。文章还讨论了相互垂直的两平面(或两超平面)、平面与超平面垂直时的投影规律,同时还举了几个例子以示其所得结论的应用。     

MiniCSP－R语言的操作语义

详细给出了面向对象的实时分布式语言ＭｉｎｉＣＳＰ－Ｒ的操作语义，对语句的时间限制，不确定选择给出了相应的描述方法。     

A note on closure of the ILR and DLR classes under formation of coherent systems

In this paper, we give the closure of the class of increasing likelihood ratio (ILR) life distributions under the formation of certain coherent systems with independent and identically distributed components, and particularly in k-out-of-n systems. Some possible definitions of its dual class (DLR) are discussed and results about the closure are given. Furthermore, we include examples which show that these two aging classes are not closed under formation of special coherent systems. This work has been supported by Ministerio de Ciencia y Tecnologia, Grants PB96-1105 and BFM2000-0362.     

Dispersive ordering—Some applications and examples

A basic concept for comparing spread among probability distributions is that of dispersive ordering. Let X and Y be two random variables with distribution functions F and G, respectively. Let F ⁻¹ and G ⁻¹ be their right continuous inverses (quantile functions). We say that Y is less dispersed than X (Y≤ _disp X) if G ⁻¹(β)−G ⁻¹(α)≤F ⁻¹(β)−F ⁻¹(α), for all 0<α≤β<1. This means that the difference between any two quantiles of G is smaller than the difference between the corresponding quantiles of F. A consequence of Y≤ _disp X is that |Y ₁−Y ₂| is stochastically smaller than |X ₁−X ₂| and this in turn implies var(Y)≤var(X) as well as E[|Y ₁−Y ₂|]≤E[|X ₁−X ₂|], where X ₁, X ₂ (Y ₁, Y ₂) are two independent copies of X(Y). In this review paper, we give several examples and applications of dispersive ordering in statistics. Examples include those related to order statistics, spacings, convolution of non-identically distributed random variables and epoch times of non-homogeneous Poisson processes. This work was supported in part by KOSEF through Statistical Research Center for Complex Systems at Seoul National University. Subhash Kochar is thankful to Dr. B. Khaledi for many helpful discussions.