Improving flexibility and efficiency by adding parallelism to genetic algorithms

In this paper we develop a study on several types of parallel genetic algorithms (PGAs). Our motivation is to bring some uniformity to the proposal, comparison, and knowledge exchange among the traditionally opposite kinds of serial and parallel GAs. We comparatively analyze the properties of steady-state, generational, and cellular genetic algorithms. Afterwards, this study is extended to consider a distributed model consisting in a ring of GA islands. The analyzed features are the time complexity, selection pressure, schema processing rates, efficacy in finding an optimum, efficiency, speedup, and resistance to scalability. Besides that, we briefly discuss how the migration policy affects the search. Also, some of the search properties of cellular GAs are investigated. The selected benchmark is a representative subset of problems containing real world difficulties. We often conclude that parallel GAs are numerically better and faster than equivalent sequential GAs. Our aim is to shed some light on the advantages and drawbacks of various sequential and parallel GAs to help researchers using them in the very diverse application fields of the evolutionary computation.     

并行编程模式及分析

讨论了主从模型、单控制流多数据流、分治策略、数据流水线、投机策略、混合模型六种并行编程模型的结构和工作方式、性能及特点,分析统计了大量应用程序。指出了并行程序设计中,并行编程模式的选择直接影响了并行程序的正确性和效率,而主从模型和单控制流多数据流在整体性能上最优,程序执行效率也最好,是两种最常用的并行编程模型。     

基于并行遗传算法的去相关多用户检测器

通过将码分多址通信系统中的最佳多用户检测视为组合优化问题,利用遗传算法能全局寻优的优势,提出了一种基于并行遗传算法的去相关多用户检测器。理论分析和仿真表明:该多用户检测器无论是抗多址干扰的能力还是抗远近效应的能力都明显优于传统的检测器和去相关多用户检测器;由于采用了基于“联姻”策略的并行遗传算法,使这种多用户检测器更易于实时应用和硬件实现。     

量子阱光电子开关器件(一)

量子阱半导体结构可使诸如光调制器和开关等光电子器件做得更小、更快、效率更高。它所具有的逻辑特性使其在并行高速互连的电子集成电路的集成度上具有良好的潜力。光电子器件能采用波导,也能采用二维并行阵列制作。其集成规模可达2048个单元,可工作的光逻辑和存贮器件的阵列得以实现及运行,所有单元都可由自由空间光(free-space optics)进行外部并行访问。本文概述了量子阱器件的运行机理及其发展前景。     

知识产权保护立法中的"灰色区域"--对平行进口合法性问题的探讨

本文将从平行进口问题产生的理论根源、各国的立法比较及我国的立法对策等方面对平行进口的合法性问题进行探讨     

对专利产品的“平行进口”法律探析

国际公约、国际条约以及我国《专利法》对专利产品的“平行进口”问题尚未作出明确的规定，而这一问题关系到专利权人和社会公众之间利益的平衡，必须认真对待。我国应依据“专利权的国内穷竭”理论，借鉴国外的立法、司法实践经验，结合自己的具体情况，采取相应的对策：不在《专利法》中对专利产品的“平行进口”问题作出明确的规定；以我方利益为出发点，采用灵活折中的策略，处理合同中没有明确规定的专利产品的“平行进口”问题。     

李商隐古文思想内蕴及对其骈文写作之影响

晚唐时期,古文式微,骈文复兴。以古文起家的李商隐拜骈文大家令狐楚为师,转以骈文济世。但李商隐心存古文道义,其古文创作既受韩愈古文思想精髓的熏染,又有独立清醒的文道观念和文体意识。李商隐古文存世篇目虽不多,但涉及文体种类丰富,以议论、抒情和记人叙事为主的文字各有特点,议论文字笔锋犀利,抒情篇章笔势流畅,记人叙事笔法简约。受古文观念影响,他的骈文既远追六朝骈文华美文体本质,又融入古文雅颂正声,以情动人,与晚唐诸家骈文相比,别具一格。     

Dynamic reliability models with conditional proportional hazards

A dynamic approach to the stochastic modelling of reliability systems is further explored. This modelling approach is particularly appropriate for load-sharing, software reliability, and multivariate failure-time models, where component failure characteristics are affected by their degree of use, amount of load, or extent of stresses experienced. This approach incorporates the intuitive notion that when a set of components in a coherent system fail at a certain time, there is a jump from one structure function to another which governs the residual lifetimes of the remaining functioning components, and since the component lifetimes are intrinsically affected by the structure function which they constitute, then at such a failure time there should also be a jump in the stochastic structure of the lifetimes of the remaining components. For such dynamically-modelled systems, the stochastic characteristics of their jump times are studied. These properties of the jump times allow us to obtain the properties of the lifetime of the system. In particular, for a Markov dynamic model, specific expressions for the exact distribution functions of the jump times are obtained for a general coherent system, a parallel system, and a series-parallel system. We derive a new family of distribution functions which describes the distributions of the jump times for a dynamically-modelled system.     

舶来与本土化:澳大利亚殖民主义时期哥特式小说研究

在英美文学界,自从20世纪80年代以来,随着文化研究的发展,哥特式文学得到了热烈的讨论和研究。然而,由于白人历史不够悠久,澳大利亚长期以来被认为缺乏哥特式小说滋生的古堡文化,因而,哥特式小说在澳大利亚的新发展也未引起学术界的广泛重视。考察哥特式小说在澳大利亚殖民主义时期进行移植的可能性并且梳理哥特式小说在澳大利亚的本土化新发展,既可以拓宽澳大利亚文学研究的视野,也可以丰富哥特式文学研究。     

The competing risks analysis for parallel and series systems using Type-II progressive censoring

Abstract

Recently, the study of the lifetime of systems in reliability and survival analysis in the presence of several causes of failure (competing risks) has attracted attention in the literature. In this paper, series and parallel systems with exponential lifetime for each item of the system are considered. Several causes of failure independently affect lifetime distributions and observations of failure times of the systems are considered under progressive Type-II censored scheme. For series systems, the maximum likelihood estimates of parameters are computed and confidence intervals for parameters of the model are obtained using Fisher information matrix. For parallel systems, the generalized EM algorithm which uses the Newton-Raphson algorithm inside the EM algorithm is used to compute the maximum likelihood estimates of parameters. Also, the standard errors of the maximum likelihood estimates are computed by using the supplemented EM algorithm. The simulation study confirms the good performance of the introduced approach.