计算机网络可用性研究

网络可用性是网络性能评价的一个重要指标,基于网络可用性参考模型,重点探讨了三种生存机制下网路可用性的计算方法,并利用可用性参考模型对两个网络拓扑图的三种生存机制下的端端可用性进行计算,最后给出了实验结果.     

Web引文可引证性的分析

通过对2000到2003年期刊论文中的Web引文记录的统计分析，提出了引文有效率、年衰减指数和有效性半衰期等指标。基于这些指标，我们对Web资源是否适合学术引用进行了探讨，并得出结论是：在目前这种互联网环境下，鉴于网络的动态性和不稳定性，Web资源的可查证性是有问题的。同时我们还看到，由于网站发布成本下降，Web信息趋于更加不稳定，其可查证性也随之降低。     

Web引文的可查证性分析

本文以图书情报学科 6种有代表性的核心期刊为样本 ,从中随机抽取了 30 0篇web引文 ,从可获得性、语种、来源网站三个不同的角度研究了其可查证性。此外 ,还简要介绍了国外在这方面所作的研究     

Why Can’t Students Get the Sources They Need? Results from a Real Electronic Resources Availability Study

Availability studies are used to estimate the proportion of items in a library collection that are available to users, and the proportion of items in a library collection that are unavailable to users as a result of system and/or human errors. Sanjeet Mann of the Armacost Library at the University of Redlands used a series of availability studies to more accurately understand and troubleshoot the e-resources access errors that keep undergraduate students at the university from obtaining the full text of electronic resources. In this presentation, Mann shared the details of his process, his results, and the implications of those results for improving local search systems as well as a conceptual model of e-resource availability errors based on the results of his research.     

The impact of chronic carbohydrate manipulation on mucosal immunity in elite endurance athletes

Carbohydrate (CHO) availability could alter mucosal immune responses to exercise. This study compared the effect of three dietary approaches to CHO availability on resting and post-exercise s-IgA levels. Elite race walkers (n = 26) adhered to a high CHO diet (HCHO), periodised CHO availability (PCHO) or a low CHO/high fat diet (LCHF) for 3 weeks while completing an intensified training program. HCHO and PCHO groups consumed 8.0–8.5 g.kg^?1 CHO daily, with timing of ingestion manipulated to alter CHO availability around key training sessions. The LCHF diet comprised 80% fat and restricted CHO to < 50 g.day^?1. A race walk test protocol (19 km females, 25 km males) was completed at baseline, after adaptation, and following CHO restoration. On each occasion, saliva samples were obtained pre- and post-exercise to quantify s-IgA levels. Resting s-IgA secretion rate substantially increased ~ two-fold post-intervention in all groups (HCHO: 2.2 ± 2.2, PCHO: 2.8 ± 3.2, LCHF: 1.6 ± 1.6; fold-change± 95% confidence limits), however, no substantial differences between dietary treatments were evident. Post-exercise, substantial 20–130% increases in s-IgA concentration and 43–64% reductions in flow rate occurred in all dietary treatments, with trivial differences evident between groups. It appears that high volume training overrides any effect of manipulating CHO availability on mucosal immunity in elite athletes.     

生态系统可利用性视角下的商业模式启动机制——基于京东的扎根探索研究

如何利用已建构的商业生态系统,高效开启焦点企业的商业模式,是理论界和实业界的重要议题。本文从商业生态系统的“可利用性”角度出发,在识别生态功能/属性基础上,匹配焦点企业的生态位角色及策略,以探究新商业模式的开启机制,并以京东为例开展扎根理论研究。研究发现：处于商业生态系统中心的焦点企业,通常面临“动机缺失”“能力缺乏”与“主体缺位”等商业模式启动挑战。焦点企业（生态主）应该利用生态系统的功能属性（展示主场、学习俱乐部、引力磁场）,定位“愿景展示者”“知识协调者”和“服务主导者”角色,匹配“共赢”“赋能”“吸引”的生态圈策略。本文旨在为新经济背景下新商业模式的开启提供借鉴,同时为商业生态系统与商业模式启动的过程机理提供理论依据。     

修如旧模型中储存系统备件量的计算及其置信区间

研究了在修如旧可修系统模型下,对相同储存条件下同时开始储存的N个系统,给出了在预定储存期T0 内使N个系统正常的概率不小于P0 时所需备件数M的计算公式.特别,针对储存寿命服从威布尔分布的系统,利用枢轴量,给出了前述备件数M的置信区间 ;并基于系统寿命试验的完全样本数据,给出系统可靠度和系统可用度Fiducial分布的计算方法,进而得出备件量M的置信区间的计算方法.     

对Web Service可伸缩性的研究

探讨了Web Service涉及的可伸缩性问题,包括扩展策略、服务器群集的维护、维持系统的高可用性、与第三方服务的协调等,提出实现可伸缩性的一些基本思路。     

一种基于云计算的高可用性集群设计与实现

针对云环境下虚拟机运行在单节点中易导致单节点故障的问题.提出一种基于云计算的高可用性集群方案,根据虚拟机在云计算环境中的运行情况和云环境在实际工程中的应用,制定出高可用性集群,通过对磁盘的镜像和磁盘的共享实现存储的高可用性,通过集群管理软件对虚拟机资源进行自动化管理,提高虚拟机资源的可用性.通过此高可用性集群,可达到将计划内及计划外宕机时间减少到最少,其次减少恢复一个失败虚拟机的时间,在最短的时间内恢复虚拟机的运行.实验结果表明在该集群环境下,可确保虚拟机提供具有高度可用性的服务.     

基于开源虚拟化的高可用服务器架构

提出一个基于开源操作系统CentOS 5.5及开源虚拟化软件KVM的高可用系统架构,说明其工作机制和实现方法,同时介绍在深圳大学图书馆的应用案例。