Flexible Strategies for Disk Scheduling in Multimedia Presentation Servers

Multimedia presentations (e.g., lectures, digital libraries) normally include discrete media objects such as text and images along with continuous media objects such as video and audio. Objects composing a multimedia presentation need to be delivered based on the temporal relationships specified by the author(s). Hence, even discrete media objects (that do not normally have any real-time characteristics) have temporal constraints on their presentations. Composition of multimedia presentations may be light (without any accompanying video or large multimedia data) or heavy (accompanied by video for the entire presentation duration). The varying nature of the composition of multimedia presentations provides some flexibility for scheduling their retrieval. In this paper, we present a min-max skip round disk scheduling strategy that can admit multimedia presentations in a flexible manner depending on their composition. We also outline strategies for storage of multimedia presentations on an array of disks as well as on multi-zone recording disks.Emilda Sindhu received the B.Tech degree in Electrical & Electronics from University of Calicut, India, in 1995 and the M.S. degree in Computer Science in 2003 from National University of Singapore. This paper comprises part of her master thesis work. She is presently employed as Senior Research Officer at the A-star Institute of High Performance Computing (IHPC), Singapore. Her current research interests include distributed computing particulary Grid computing. She is involved in the development of tools and components for distributed computing applications.Lillykutty Jacob obtained her B.Sc (Engg.) degree in electronics and communication from the Kerala University, India, in 1983, M.Tech. degree in electrical engineering (communication) from the Indian Institute of Technology at Madras in 1985, and PhD degree in electrical communication engineering from the Indian Institute of Science, in 1993. She was with the department of computer science, Korea Advanced Institute of Science and Technology, S. Korea, during 1996–97, for post doctoral research, and with the department of Computer Science, National University of Singapore, during 1998–2003, as a visiting faculty. Since 1985 she has been with the National Institute of Technology at Calicut, India, where she is currently a professor. Her research interests include wireless networks, QoS issues, and performance analysis.Ovidiu Daescu received the B.S. in computer science and automation from the Technical Military Academy, Bucharest, Romania, in 1991, and the M.S. and Ph.D. degrees from the University of Notre Dame, in 1997 and 2000. He is currently an Assistant Professor in the Department of Computer Science, University of Texas at Dallas. His research interests are in algorithm design, computational geometry and geometric optimization.B. Prabhakaran is currently with the Department of Computer Science, University of Texas at Dallas. Dr. B. Prabhakaran has been working in the area of multimedia systems: multimedia databases, authoring & presentation, resource management, and scalable web-based multimedia presentation servers. He has published several research papers in prestigious conferences and journals in this area.Dr. Prabhakaran received the NSF CAREER Award FY 2003 for his proposal on Animation Databases. Dr. Prabhakaran has served as an Associate Chair of the ACM Multimedia2003 (November 2003, California), ACM MM 2000 (November 2000, Los Angeles), and ACM Multimedia99 conference (Florida, November 1999). He has served as guest-editor (special issue on Multimedia Authoring and Presentation) for ACM Multimedia Systems journal. He is also serving on the editorial board of Multimedia Tools and Applications journal, Kluwer Academic Publishers. He has also served as program committee member on several multimedia conferences and workshops. Dr. Prabhakaran has presented tutorials in several conferences on topics such as network resource management, adaptive multimedia presentations, and scalable multimedia servers.B. Prabhakaran has served as a visiting research faculty with the Department of Computer Science, University of Maryland, College Park. He also served as a faculty in the Department of Computer Science, National University of Singapore as well as in the Indian Institute of Technology, Madras, India.     

面向实时感知性能的分布式交互仿真实体迁移技术

分布式交互仿真中的实体需要实时感知周围的实体和环境信息,当仿真系统中“实体一主机”对应关系固定不变时,由于系统内通信关系和可用资源的动态变动,往往导致信息传输延迟超过QoS要求．首先提出了实体对环境的实时感知性能的评价指标,通过分析信息传输延迟的组成,得出了利用实体迁移以提高实体实时感知性能的方法．深入研究了此时实体迁移请求的提出、不同迁移请求的协调和迁移请求的处理等问题,并在HLA／RTI下进行了可行性测试．     

Web服务器群的QoS确保及其接纳控制研究

WWW访问的爆炸性发展正是Internet成功的重要原因，然而目前的Web服务器却缺乏相应的QoS机制，导致在过载时造成巨大的经济损失。一个提供多类服务的多服务器Web平台的服务质量确保体系被提出来，它以服务响应延迟为核心度量标准，将同一类服务抽象为一台虚拟服务器，并以该度量黏合起系统的各个组件．同时据此提出了一个动态自适应的服务接纳算法(DASAC)．测试表明，即使经历严重的过载与业务突发，也能保证用户感知的服务质量．     

视频服务器中多网络I/O的调度与接纳控制

在视频服务器中,由于网络I/O带宽比磁盘I/O带宽相对丰富而未得到研究者的重视,但当服务达到一定的规模、网络输出成为瓶颈时,在多网络I/O情况下,网络输出的量化计算则不可避免.着重探讨了视频服务器在多网络I/O并行输出的情况下,如何进行最大输出调度的问题,给出了3个调度算法及相应的接纳计算公式,特别是一个带缓冲的优化调度模型.实验结果显示,调度模型及规划性能是优越而有效的.该项工作对视频服务器的调度设计、资源的有效配置具有指导作用.     

利用句法信息改进交互式机器翻译

在很多领域中,全自动机器翻译的译文质量还无法达到令人满意的程度。要想获得正确无误的译文,往往需要翻译人员对自动翻译系统的输出进行后处理。在交互式机器翻译的框架内,翻译系统和译员协同工作,译员确认系统提供的译文中的最长正确前缀,系统据此对译文后缀进行预测,共同完成翻译任务。该文利用基于短语的翻译模型,建立了交互式机器翻译系统,并结合交互式机器翻译的特点,利用句法层面的子树信息来指导翻译假设的扩展。实验表明,该方法可以有效地减少人机交互次数。     

采用轮询机制提高Linux系统的网络性能

目前,Linux操作系统被广泛应用在网络数据包收发系统中。这是因为,Linux采用中断机制来响应外部事件,保证了系统能够合理高效地利用CPU资源。但是,在高负荷网络环境下,大量的CPU资源将会被频繁到达的网卡中断占用,导致系统遭遇性能瓶颈,出现接收活锁1。为了避免在高负荷网络环境下系统性能下降,该文采用轮询机制处理网络数据的收发,而在低负荷网络环境中,仍然采用原有的中断机制。     

蚁群算法的改进策略

蚁群算法是模拟蚂蚁活动规律而提出的一种元启发式优化算法,研究表明其具有很多优点,在解决优化问题时表现出很好特性,但也存在一些缺陷。因此,许多学者提出了许多改进算法。该文对算法的改进策略进行研究,形成结论,为算法进一步发展提供参考。     

无线网络时变带宽业务的准入控制性能分析

无线蜂窝网络的通话准入控制方法与通话的 Qo S以及无线信道的利用率密切相关 .使用 Markov过程得出了业务带宽需求时变状况下系统性能 (通话的切换掉线概率、并发掉线概率、阻塞概率以及信道利用率 )的理论模型 .通过数值结果分析了系统负载、用户的移动、通话的持续时间对系统性能的影响     

软件性能工程方法在交互式软件开发中的应用

在诸多交互式软件系统中,包括软件开发工具及基于万维网的工具,性能问题是至关重要的.然而在软件开发过程中,性能问题并未得到足够的重视.主要目的是展示一种有效方法, 使得经过细致设计后交互式软件有满意的性能.展示如何应用软件性能工程方法于交互式软件工具开发中,特别注重在设计阶段的性能估算及其在决定实现方案时之效果.除了源于软件性能工程的严格的量化估算方法,提出性能亦可半量化或非量化方法进行有效而经济的估算. 基于结果的描述,最终建议为源于软件性能工程方法学中苛求采用系统环境参数进行细化定量性能估算未必是惟一手段.演示了在软件工具开发早期阶段中一种用以评估性能的基于分析和实验的有效综合途经.希望能反映出了良好的实验计算机科学之本质.     

Using Character Motives to Drive Plot Resolution in Interactive Stories

One of the most important parts of a story is its ending. This is the point in which all open questions and conflicts in the narrative must be resolved. This article presents a dynamic, motive-driven resolution method for interactive stories. In the type of stories supported by this method the user participates as one of the characters and influences dynamically the development of the plot. The rest of the cast consists of discrete computer characters. The resolution method takes into account the motives of the user character to decide on: (i) the outcome of all character actions and (ii) the presentation sequence for these outcomes. The decision process is based on the current story context. In addition, it addresses the need to avoid ambiguities, to preserve consistency and to create suspense during the end. This method has been implemented and tested in DEFACTO, an EU research program for the generation of a framework for interactive story design.     

Reliability Parameters to Improve Combination Strategies in Multi-Expert Systems

Recognition systems based on a combination of different experts have been widely investigated in the recent past. General criteria for improving the performance of such systems are based on estimating the reliability associated with the decision of each expert, so as to suitably weight its response in the combination phase. According to the methods proposed to-date, when the expert assigns a sample to a class, the reliability of such a decision is estimated on the basis of the recognition rate obtained by the expert on the chosen class during the training phase. As a consequence, the same reliability value is associated with every decision attributing a sample to a same class, even though it seems reasonable to take into account its dependence on the quality of the specific sample. We propose a method for estimating the reliability of each single recognition act of an expert on the basis of information directly derived from its output. In this way, the reliability value of a decision is more properly estimated, thus allowing a more precise weighting during the combination phase. The definition of the reliability parameters for widely used classification paradigms is discussed, together with the combining rules employing them for weighting the expert opinions. The results obtained by combining four experts in order to recognise handwritten numerals from a standard character database are presented. Comparison with classical combining rules is also reported, and the advantages of the proposed approach outlined. Received: 3 August 1997?Received in revised form: 24 November 1998?Accepted: 11 December 1998     

面向交互式决策的情感计算与学习方法及其在过程控制工程中的应用

当今大量的工业过程控制工程问题, 如控制性能评价等的多目标决策问题通过人机交互得到解决. 然而, 在使用传统的交互式进化计算方法求解多目标决策问题时, 表现为局部搜索能力不强和过度依赖决策人员的主观意图. 本文提出一种新的情感计算方法和人机交互学习机制的解决方案. 提出一类基于刺激响应的情感计算模型(STAM), 并给出了情感空间和人的主观偏好之间的定量关系. 此外, 基于遗传算法框架, 建立情感交互学习策略, 旨在决策过程中逐步掌握人员的主观偏好, 降低人的疲劳程度, 使决策更加客观和科学. 附录A和B分别展示了情感学习算法的复杂度和收敛性分析. 为验证所提方法的正确性, 以测试函数及单回路反馈控制的PID参数整定问题进行研究, 得到了满意的结果, 验证了所提方法的可靠性与有效性.     

Using a Visual Attention Model to Improve Gaze Tracking Systems in Interactive 3D Applications

This paper introduces the use of a visual attention model to improve the accuracy of gaze tracking systems. Visual attention models simulate the selective attention part of the human visual system. For instance, in a bottom‐up approach, a saliency map is defined for the image and gives an attention weight to every pixel of the image as a function of its colour, edge or intensity. Our algorithm uses an uncertainty window, defined by the gaze tracker accuracy, and located around the gaze point given by the tracker. Then, using a visual attention model, it searches for the most salient points, or objects, located inside this uncertainty window, and determines a novel, and hopefully, better gaze point. This combination of a gaze tracker together with a visual attention model is considered as the main contribution of the paper. We demonstrate the promising results of our method by presenting two experiments conducted in two different contexts: (1) a free exploration of a visually rich 3D virtual environment without a specific task, and (2) a video game based on gaze tracking involving a selection task. Our approach can be used to improve real‐time gaze tracking systems in many interactive 3D applications such as video games or virtual reality applications. The use of a visual attention model can be adapted to any gaze tracker and the visual attention model can also be adapted to the application in which it is used.     

LTE系统中提高TCP性能的资源调度算法研究

LTE可以提供真正无处不在基于IP的移动宽带业务,但随着承载网的IP化,网络拥塞、丢包、抖动、延时等质量问题将影响到LTE业务层的QoS质量.作为LTE无线资源管理的核心,研究并设计一个良好的资源调度算法是提高数据业务的性能和终端用户的体验是一个亟待解决的重要任务.本文通过借鉴LTE对VoIP数据分组的半持续调度算法的思想,提出了一种LTE的无线资源调度的改进方案.方案将TCP确认包映射到具有更高优先级的空闲逻辑信道,从而降低了ACK包在无线信道中发生丢弃和拥塞的概率,避免了TCP拥塞控制机制的频繁开启.仿真结果表明,本文提出的TCP确认包映射转换方案在RTT时延、吞吐量等方面均有一定的提升,具有一定的稳定性和性能优势.     

如何在数据库工程中优化SQL SERVER数据库性能

本文主要将数据库结构设计、行为设计与实际工程应用相结合,从非范式、索引技术、查询语句以及存储过程等几个方面分析了如何在工程实践中优化数据库性能。     

小型无线网络中一种提高系统实时性的数据提交方式

在由一台PC机和多台单片机利用无线模块进行通讯的小型无线通讯网络中,采用怎样的通讯协议,PC怎样向单片机发送命令和数据,尤其是单片机怎样向PC提交数据对网络的实时性将产生直接的影响。作者结合在项目开发中取得的经验,对提高小型无线网络的实时性这一问题进行了比较深刻的探讨和研究。     

An alternative to language learner dependence on L2 caption‐reading input for comprehension of sitcoms in a multimedia learning environment

Most second/foreign language (L2) learners have difficulty understanding listening input because of its implicit and ephemeral nature, and they typically have better reading comprehension than listening comprehension skills. This study examines the effects of using an interactive advance‐organizer activity on the DVD video comprehension of L2 learners to provide an alternative to the scenario of L2 learners experiencing sensory overload in a multimedia learning environment that presents pictures, printed words and speech words. A total of 95 intermediate university‐level L2 learners with an average TOEIC (Test of English for International Communication) score of 565 were placed in four conditions for an English‐language DVD viewing task, including an advance‐organizer group, a captions group, a captions plus advance‐organizer group, and a control group. The study concludes that using advance organizers as an instructional strategy facilitated participant listening comprehension and reduced participant dependence on L2 caption‐reading input by 50% for initial comprehension. Participants also held a positive attitude towards an interactive advance‐organizer activity. The details concerning the role of L2 captions in multimedia listening are also discussed. The findings provide insight into teaching listening to L2 learners who learn most of their L2 in a more reading‐dependent classroom setting and typically have enhanced L2 literacy skills.