论旅行社业现有分工体系的重新构建

长期以来,中国旅行社业的经营一直采取以人为市场分割为特征的水平分工体系,各旅行社除了在目标市场方面有所不同之外,在业务上并无批发、零售的主营差异,从而导致了整个行业市场的混乱。相比之下,欧美国家旅游市场上的批发经营商、零售代理商层次分明,以专业化分工为特征的垂直分工体系,有效地克服了因缺乏分工而导致的业务交叉覆盖、混乱竞争等弊端,使得整个旅行社行业的经营协调有序。从理论上来说,垂直分工体系的确是一种理想的、有助于规范市场秩序的专业化分工体系。在我国旅行社业界,垂直分工体系如能得以实现,将会有效地规范各类旅行社的市场行为。     

On the Limitations of Redundancies in the Improvement of System Reliability

Some program managers share a common belief that adding a redundant component to a system reduces the probability of failure by half. This is true only if the failures of the redundant components are independent events, which is rarely the case. For example, the redundant components may be subjected to the same external loads. There is, however, in general a decrease in the failure probability of the system. Nonetheless, the redundant element comes at a cost, even if it is less than that of developing the first one when both are based on the same design. Identical parts save the most in terms of design costs, but are subjected to common failure modes from possible design errors that limit the effectiveness of the redundancy. In the development of critical systems, managers thus need to decide if the costs of a parallel system are justified by the increase in the system's reliability. NASA, for example, has used redundant spacecraft to increase the chances of mission success, which worked well in the cases of the Viking and Voyager missions. These two successes, however, do not guarantee future ones. We present here a risk analysis framework accounting for dependencies to support the decision to launch at the same time a twin mission of identical spacecraft, given incremental costs and risk-reduction benefits of the second one. We illustrate this analytical approach with the case of the Mars Exploration Rovers launched by NASA in 2003, for which we had performed this assessment in 2001.     

量子阱光电子开关器件(二)

量子阱半导体器件是一种基于量子电子学原理的新型光电子器件。它具有体积小、速度快、功耗低等优点,并且由于它能够与逻辑电路元件混合集成,在解决高复杂度集成电路的高速互连方面具有巨大的实际应用价值。基于这一原理实现的光调制器和开关等光电子器件,可以制成波导,也可制成二堆并行阵列器件。目前,光逻辑和存贮器件阵列的集成规模已达2048个单元,其中所有的单元都可利用自由空间光(free-space optics)进行外部访问。本文概述了量子阱半导体器件的运行机理及其发展前景。     

论指数函数及其四则运算的并行算法

本文用指数函数建立双曲函数的并行串行最新算法     

A genetic algorithm tutorial

This tutorial covers the canonical genetic algorithm as well as more experimental forms of genetic algorithms, including parallel island models and parallel cellular genetic algorithms. The tutorial also illustrates genetic search by hyperplane sampling. The theoretical foundations of genetic algorithms are reviewed, include the schema theorem as well as recently developed exact models of the canonical genetic algorithm.     

分层总线式群集系统设计

给出了一种基于通信效率和群集度比(T_e/I_l)构建有限层总线式松耦合并行系统的一般模型,并详细描述下一个6×6群系统的设计思想和实现过程,工作结果将指导这类系统的集成。     

Identifiability of distributions under competing risks and complementary risks model

Let X₁,X₂,…,X_p be p random variables with cdf's F₁(x),F₂(x),…,F_p(x)respectively. Let U = min(X₁,X₂,…,X_p) and V = max(X₁,X₂,…,X_p).In this paper we study the problem of uniquely determining and estimating the marginal distributions F₁,F₂,…,F_p given the distribution of U or of V.

First the problem of competing and complementary risks are introduced with examples and the corresponding identification problems are considered when the X₁'s are independently distributed and U(V) is identified, as well as the case when U(V) is not identified. The case when the X₁'s are dependent is considered next. Finally the problem of estimation is considered.     

Some characterization results for parallel systems with two heterogeneous exponential components

In this paper, we study ordering properties of lifetimes of parallel systems with two independent heterogeneous exponential components in terms of the likelihood ratio order (reversed hazard rate order) and the hazard rate order (stochastic order). We establish, among others, that the weakly majorization order between two hazard rate vectors is equivalent to the likelihood ratio order (reversed hazard rate order) between lifetimes of two parallel systems, and that the p-larger order between two hazard rate vectors is equivalent to the hazard rate order (stochastic order) between lifetimes of two parallel systems. Moreover, we extend the results to the proportional hazard rate models. The results derived here strengthen and generalize some of the results known in the literature.     

On the right spread ordering of parallel systems with two heterogeneous components

This article discusses the variability ordering of lifetimes of parallel systems with two independent heterogeneous exponential components in terms of the right spread order. It is proved, among others, that the reciprocal majorization order between the two hazard rate vectors implies the right spread order between the lifetimes of two parallel systems. The result is then extended to the proportional hazard rate model as well. The results established here extend and enrich those known in the literature.