SOJOURN TIMES IN NON-HOMOGENEOUS QBD PROCESSES WITH PROCESSOR SHARING

We study sojourn times of customers in a processor sharing queue with a service rate that varies over time, depending on the number of customers and on the state of a random environment. An explicit expression is derived for the Laplace–Stieltjes transform of the sojourn time conditional on the state upon arrival and the amount of work brought into the system. Particular attention is paid to the conditional mean sojourn time of a customer as a function of his required amount of work, and we establish the existence of an asymptote as the amount of work tends to infinity. The method of random time change is then extended to include the possibility of a varying service rate. By means of this method, we explain the well-established proportionality between the conditional mean sojourn time and required amount of work in processor sharing queues without random environment. Based on numerical experiments, we propose an approximation for the conditional mean sojourn time. Although first presented for exponentially distributed service requirements, the analysis is shown to extend to phase-type services. The service discipline of discriminatory processor sharing is also shown to fall within the framework.     

A case–control study relating railroad worker mortality to diesel exhaust exposure using a threshold regression model

A case–control study of lung cancer mortality in U.S. railroad workers in jobs with and without diesel exhaust exposure is reanalyzed using a new threshold regression methodology. The study included 1256 workers who died of lung cancer and 2385 controls who died primarily of circulatory system diseases. Diesel exhaust exposure was assessed using railroad job history from the US Railroad Retirement Board and an industrial hygiene survey. Smoking habits were available from next-of-kin and potential asbestos exposure was assessed by job history review. The new analysis reassesses lung cancer mortality and examines circulatory system disease mortality. Jobs with regular exposure to diesel exhaust had a survival pattern characterized by an initial delay in mortality, followed by a rapid deterioration of health prior to death. The pattern is seen in subjects dying of lung cancer, circulatory system diseases, and other causes. The unique pattern is illustrated using a new type of Kaplan–Meier survival plot in which the time scale represents a measure of disease progression rather than calendar time. The disease progression scale accounts for a healthy-worker effect when describing the effects of cumulative exposures on mortality.     

三大优良作风是我党不断前进的重要法宝

理论联系实际、密切联系群众、批评与自我批评三大作风是我党在长期的革命实践中的显著标志和政治优势,也是我们党领导人民群众从胜利走向胜利的显著标志和政治优势.在新形势下,三大优良作风并没有过时,仍然是我党不断前进的重要法宝.     

浅析当前国际环境和国际政治斗争给大学生带来的影响

本文概述了当前的国际环境和国际政治斗争的新变化 ,分析了国际环境和国际政治斗争给大学生带来的影响 ;对新形势下 ,高等学校如何抵制和防范西方敌对势力的渗透和颠覆进行了初步的探讨。     

“C程序设计”教学方法探索与思考

C语言之所以能存在和发展,具有旺盛的生命力,并作为广泛使用的教学语言,是有其不同于或优于其他语言的特点决定的。这些特点主要是语言简洁、紧凑,使用方便、灵活,运算符和数据结构丰富,可移植性好和硬件控制能力高,表达和运算能力强等特点,有广泛的应用领域,虽然目前有在C语言     

卡文迪许实验室为何成为诺贝尔科学奖的"孵化器"

英国剑桥大学卡文迪许实验室,被誉为诺贝尔科学奖的"孵化器".选拔优异的学术权威和异质学者、创设良好的硬件和软件环境条件、把握机遇条件等是其取得成功的三大法宝.借鉴卡文迪许实验室发展经验,探讨大学学术生态环境对科学研究的巨大作用具有重要的现实意义.     

明清时期广东山区的陂塘水利与生态环境

叙述了明清山区陂塘水利与生态环境之间的关系。陂塘水利改善了山区的农业环境,提高了土地的价值。而日益严重的水土流失使河道和陂塘淤塞,废弃的河道、陂圳、山塘又被占垦为田。同时,陂塘水利的发展与航运矛盾,减弱了陂塘水利的功能。溪流河道上层级而设的陂坝使径流流速减慢,沙泥停蓄。而河床渐高又使河水漫溢,也影响了对水力资源的运用。人们针对当时陂塘水利出现的情况,提出了一些治理的措施。     

论实践“以人为本”的基本原则

"以人为本"是科学发展观的实质和核心,如何践行"以人为本"是理论研究和实际工作的一个重要课题.实践"以人为本"就要以人的现实需要作为出发点,以充分发挥人的作用为准则,以人的全面发展为目标.     

准确把握理论联系实际思想原则的科学内涵

理论联系实际是马克思主义一贯坚持的思想原则 ,对于它的科学内涵应该有正确的理解和把握。毛泽东在《整顿党的作风》等著作中对这个问题有过明确的论述 ,为我们指出了方向。理论联系实际并非不要理论 ,而是在理论与实际相联系的基础上作出合乎实际需要的理论性创造     

基于元学习的企业核心能力形成机理

动态环境下,企业需要建立元学习系统才能不断开发核心能力。"信息转移与恢复"、"实验"、"动态惯例"、"环境审视"、"标杆瞄准"等五个学习子系统在企业核心能力形成中发挥着各自的作用,而由五个子系统整合而成的元学习系统,产生了企业的动态核心能力。