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.     

WB-1型长效汽车防冻液的研制

研制了WB-1型汽车发动机防冻液,讨论了缓蚀剂的选择与复配关系及稳定剂和添加剂的选用,确定了乙二醇型防冻液的组成,并对防冻液的各项性能进行了测试.结果表明,WB-1型防冻液各项技术指标均达到美国ASTM D3306-94标准.     

SrBPO5:Ce3 的光谱特性

运用高温固相法,在空气中合成了SrBPO5:Ce3 荧光体,通过研究SrBPO5:Ce3 的光谱特性,发现激发光谱随Ce3 的掺入量增加而红移,据此认为Ce3 在进入格位时有两种电荷补偿方式,发射光谱则随Ce3 的掺入量增加而增强.     

论企业结构调整中的机制创新

企业结构调整是企业推进技术进步、培育新的增长点、增强企业活力、提高企业核心竞争能力的根本性措施.在企业结构调整中,不仅要调整企业要素的构成,还必须加强企业运行机制的建设,只有转变经营观念,抓好机制创新与深化改革、机制创新与加强企业管理、机制创新与培育新的增长点的结合,才能把企业结构调整与机制创新有机地融合起来,使企业处于良好的循环状态,企业才会具有旺盛的生命力.     

On the incidence–prevalence relation and length‐biased sampling

For many diseases, logistic constraints render large incidence studies difficult to carry out. This becomes a drawback, particularly when a new study is needed each time the incidence rate is investigated in a new population. By carrying out a prevalent cohort study with follow‐up it is possible to estimate the incidence rate if it is constant. The authors derive the maximum likelihood estimator (MLE) of the overall incidence rate, λ, as well as age‐specific incidence rates, by exploiting the epidemiologic relationship, (prevalence odds) = (incidence rate) × (mean duration) (P/[1 ? P] = λ × µ). The authors establish the asymptotic distributions of the MLEs and provide approximate confidence intervals for the parameters. Moreover, the MLE of λ is asymptotically most efficient and is the natural estimator obtained by substituting the marginal maximum likelihood estimators for P and µ into P/[1 ? P] = λ × µ. Following‐up the subjects allows the authors to develop these widely applicable procedures. The authors apply their methods to data collected as part of the Canadian Study of Health and Ageing to estimate the incidence rate of dementia amongst elderly Canadians. The Canadian Journal of Statistics © 2009 Statistical Society of Canada     

Parental Work Schedules and Children's Cognitive Trajectories

Previous work has shown an association between mothers' nonstandard work schedules and children's well-being. We built on this research by examining the relationship between parental shift work and children's reading and math trajectories from age 5/6 to 13/14. Using data (N=7,105) from the National Longitudinal Survey of Youth and growth curve modeling, we found that children's math and reading trajectories were related to parents' type of nonstandard shifts (i.e., evening, night, or variable). We found that having a mother who worked more years at a night shift was associated with lower reading scores, having a mother work more years at evening or night shifts was associated with reduced math trajectories, and having a father work more years at an evening shift was associated with reduced math scores. Mediation tests suggest that eating meals together, parental knowledge about children's whereabouts, and certain after-school activities might help explain these results.     

科技英语疑问句的信息功能探析

句子的功能所实现的交际任务是传递信息。根据话语信息传递和语言交际功能理论原则,通过甄选科技英语相关例证作为分析语料,从英语的科技文体视角探析了疑问句在科技英语信息推进中的五大作用,同时指出了解这些相关作用的必要性。     

《水浒传》“灵官殿”小考——兼及《水浒传》成书时间问题

《水浒传》第十三回和第十四回都写到了刘唐醉卧灵官殿,这应是灵官信仰在民间较为普遍所致。有关灵官之名及其事迹、信仰的记载都大量出现于明永乐年间之后,因此,关于灵官殿的细节应视为推断《水浒传》成书时间的重要参考依据。     

Bayesian inference for dynamic social network data

We consider a continuous-time model for the evolution of social networks. A social network is here conceived as a (di-) graph on a set of vertices, representing actors, and the changes of interest are creation and disappearance over time of (arcs) edges in the graph. Hence we model a collection of random edge indicators that are not, in general, independent. We explicitly model the interdependencies between edge indicators that arise from interaction between social entities. A Markov chain is defined in terms of an embedded chain with holding times and transition probabilities. Data are observed at fixed points in time and hence we are not able to observe the embedded chain directly. Introducing a prior distribution for the parameters we may implement an MCMC algorithm for exploring the posterior distribution of the parameters by simulating the evolution of the embedded process between observations.     

娄底市城区经营性健身场馆构成现状分析

采用文献资料、问卷调查和实地访谈法,对娄底市城区经营性健身场馆的现状进行了调查研究,结果表明:娄底市城区健身服务场馆在数量上有了快速的增长,但经营形式比较单一,收费标准与同类城市相比偏高,健身指导员队伍质量较低,体育消费人群较集中,指出娄底市城区经营性健身服务场馆应在产业结构和布局,经营管理和市场定位等方面提高.