计算网格QoS-aware作业调度的建模与性能评价

为了提高计算网格的服务质量(QoS),研究了包含多层调度器的分级分布式网格体系结构中的QoS-aware作业调度问题,提出了一种将计算网格本地调度器作业选择中所使用的作业优先级与全局调度器的作业分配策略相结合的QoS-aware作业调度综合控制策略.建立了一个具有2层调度器的计算网格的随机高级Petri网(SHLPN)模型,并且进行模型精化设计以降低模型求解的复杂性.使用基于SHLPN的性能分析技术进行系统性能评价.数值结果显示QoS-aware作业调度策略能够为高优先级的作业提供较QoS-unaware作业调度策略更好的QoS保证.     

关于简单线性恶化问题的平行机排序的一个全多项式逼近算法

In this paper, a parallel machine scheduling problem was considered , where the processing time of a job is a simple linear function of its starting time. The objective is to minimize makespan. A fully polynomial time approximation scheme for the problem of scheduling n deteriorating jobs on two identical machines was worked out. Furthermore, the result was generalized to the case of a fixed number of machines.     

优先级置顶算法在FlexRay线控转向系统中的应用研究

为解决FlexRay线控转向系统中常见的死锁问题,采用优先级置顶算法进行多任务动态调度。首先,分析FlexRay线控转向系统多任务动态调度过程中的死锁问题|然后深入研究优先级置顶算法防止死锁问题的原理|最后搭建双通道多冗余的FlexRay线控转向系统,进行重要系统参数配置。运行结果表明,未使用优先级置顶算法的FlexRay线控转向系统出现了死锁现象,使用优先级置顶算法进行动态任务调度之后,系统可正常运行,证明了算法有效性。     

Children’s Participation in a Virtual Epidemic in the Science Classroom: Making Connections to Natural Infectious Diseases

This study investigated students’ understanding of a virtual infectious disease in relation to their understanding of natural infectious diseases. Two sixth-grade classrooms of students between the ages of 10 and 12 (46 students) took part in a participatory simulation of a virtual infectious disease, which was integrated into their science curriculum. The results from our analyses reveal that students perceived the simulation as similar to a natural infectious disease and that the immersive components of the simulation afforded students the opportunity to discuss their understandings of natural disease and to compare them to their experiences with the virtual disease. We found that while the virtual disease capitalized on students’ knowledge of natural infectious disease through virtual symptoms, these symptoms may have led students to think of its transfer more as an observable or mechanical event rather than as a biological process. These findings provide helpful indicators to science educators and educational designers interested in creating and integrating online simulations within classroom environments to further students’ conceptual understanding.     

预防性周期维护下考虑可中断工件的再制造单机调度(英文)

研究预防性周期维护策略下再制造系统中可中断和不可中断2类工件的单机调度问题.以最小化完工时间为目标,提出了LPT-LS算法,该算法首先按LPT(longest processing time)规则安排不可中断工件,然后按LS(list scheduling)规则安排可中断工件.并根据可中断工件的总加工时间(记为S2)分3种情况证明了该算法的最坏情况比,结论如下:当S2大于按LPT规则安排不可中断工件后机器的空闲时间时,最坏情况比为1;当S2介于分别按LPT规则和OPT(最优排序)规则安排不可中断工件后机器的空闲时间之间时,最坏情况比小于2;当S2小于按OPT规则安排不可中断工件后机器的空闲时间时,最坏情况比小于2.最后通过算例验证了结论的正确性.     

To Block or Not To Block: That's Not the Question

Abstract

The block schedule emerged in the late 1980s as one structuring practice that allowed educators to address several problems associated with the traditional high school schedule. Among its posited advantages is the opportunity for teachers to engage students in active teaching strategies that require more time than the traditional schedule allows. Research on the use of teaching strategies in traditional and block schedule high schools is limited. Similarities and differences in survey responses of more than 2,000 teachers working in traditional- and block-schedule schools were described and analyzed in this study. In general, few differences were evident in opinions about level of use, appropriateness, and training for a variety of instruction approaches.     

基于数字校园平台多媒体网络管理系统的设计与实现

数字校园平台为各种应用系统提供了数据共享、应用访问以及统一的访问接口.探讨了基于数字校园平台多媒体网络管理系统的设计.将基于数字校园平台的一卡通系统、教务排课系统与传统的多媒体控制系统进行无缝对接,构建“控制、管理、服务、拓展”全方位的多媒体网络管理系统.系统的应用提升了教学过程的科学化管理水平.     

一种无线Mesh网络业务调度算法

无线Mesh网络技术是近年来无线通信领域研究的热点。文章详细分析Mesh模式的三种调度机制以及国内外的研究现状,针对当前分布式调度算法中存在的缺陷提出一种冲突避免的协同分布式调度算法———TDSCH。     

A QoS-aware scheduling algorithm for combined-input-crosspoint-queued switch

In this paper, we study the quality of service requirement and guaranteed-rate scheduling problem for combined-input-crosspoint-queued (CICQ) switches. Using crosspoint buffers between input queues and output ports, the input and output scheduling can be decoupled in CICQ switches. Here we propose a new guaranteed-rate scheduling algorithm which is divided seperately into input and output scheduling. Simulation results show that our algorithm can perform better than existing scheduling schemes in both packet loss and jitter control.     

Libraries in Second Life: Linking Collections,Clients, and Communities in a Virtual World

The multi-user virtual environment Second Life has drawn attention from many librarians who established virtual libraries and information spaces there. Even as interest in Second Life diminishes, it is worthwhile to look at how libraries in Second Life were established and what models they followed. This study examines the purposes, users, collections, and community integration of Second Life libraries. Researchers identified over 75 libraries in Second Life through the professional literature and search results within Second Life. Using this sample, they identified seven general categories of libraries and discuss examples of each. Some Second Life library spaces help to set a scene and contribute to the ethos of a larger space. Other Second Life libraries connect physical libraries with virtual communities. Still others serve communities that exist only in virtual spaces, supporting common interests or role-playing scenarios. Finally, some Second Life libraries expand understandings of what a virtual library might be, whether through imaginative architecture or unusual collections. Second Life libraries offer collections of resources tailored to the needs of individual communities and make them available in different formats. They also offer social and educational programs, much as physical libraries do. Whatever the future of Second Life, the libraries that have been established there raise important questions for future virtual library work.