集群系统的I/O流透明性问题

该文着重研究了在集群（Ｃｌｕｓｔｅｒ）中的Ｉ／Ｏ流管理问题,目的在于提供一个透明的Ｉ／Ｏ流环境,以改善集群诉用户界面。在研究传统的解决流透明性方案的基础上,提出了一种新的方案,并结合实践,阐述了实现Ｉ／Ｏ流透明性的方法。     

VOD服务器中共享I/O流的关键技术

VOD服务器的I/O带宽是影响VOD系统性能的关键因素。如何通过使多个用户请求共享一个I/O流,减少对I/O带宽的要求是VOD研究领域中的研究热点之一。文章对VOD服务器中共享I/O流的基本技术Batching、AdaptivePiggybacking、Bridging和Chaining进行了全面的讨论,并对当前的研究现状进行介绍。     

两条PCI多流并发I/O结点实现技术研究

当微处理器速度快速提高的同时,受限于机电等因素的Ｉ／Ｏ性能却难以同步增长,因而许多应用程序如天气预报,石油地震数据分析等在ＭＰＰ上运行时文伯Ｉ／Ｏ总是瓶颈。为了提高Ｉ／Ｏ性能,提出两条ＰＣＩ总线多流并发Ｉ／ＯＮ设计实现方案。     

Ethersim: a simulator for application-level performance modeling of wireless and mobile ATM networks

The paper describes Ethersim, a simulation tool to model and study the performance of multimedia-oriented integrated service ATM networks with mobile hosts and wireless links. The key motivation behind Ethersim is to study the application-level impact of host mobility and wireless channels. Ethersim has a discrete event based simulator core and incorporates models of user applications and transport, network and MAC layer protocols. It provides the capability to specify a cellular wireless ATM network topology and host mobility patterns. The software architecture of Ethersim employs five special entities: an air module, a map, a mover, mobile hosts, and basestations. We also present case-studies of using Ethersim to model and study the interaction of transport layer, connection rerouting protocol, and radio characteristics in the SWAN [P. Agrawal, A. Asthana, M. Cravatts, E. Hyden, P. Krzyzanowski, P. Mishra, B. Narendran, M. Srivastava, J. Trotter, SWAN: A Mobile Multimedia Wireless Network, in: IEEE Personal Commun. Mag., April 1996] mobile and wireless ATM based multimedia network.     

VBR视频流磁盘I/O的平滑调度算法

文章将带宽平滑技术引入磁盘 I/ O调度 ,基于现已取得的研究成果 ,考虑磁盘 I/ O存取特性 ,提出一个针对VBR视频检索的整数块平滑调度算法 .算法所得的结果被证明是优化的 ,实验结果显示该算法在磁盘空间和磁盘 I/ O的带宽利用方面有很好的性能     

无压缩数字播放系统中媒体流的多线程存取控制策略

电视台无压缩数字播放系统除了实现系统自动化功能之外，至关重要的一点就是要保证播出的质量，即在无压缩视频流播出时不掉帧、无黑场、按帧切换等等．本文提出了一种多线程并行直接I／O(multithread parallel direct IO-MPDIO、存取控制策略，并详细描述了它的设计与实现．测试结果表明，该策略很好地满足了系统的性能指标．     

GESTALT: a framework for redesign of educational software

Abstract Design of educational multimedia rarely starts from scratch, but rather by attempting to reuse existing software. Although redesign has been an issue in research on evaluation and on learning objects, how it should be carried out in a principled way has remained relatively unexplored. Furthermore, understanding how empirical research on information and communication technologies (ICT) should feed back into redesign remains difficult. The present paper addresses these problems from the viewpoint of carrying out pedagogical expert evaluations, in the absence of empirical studies of target learners, in order to generate recommendations for redesign. Firstly, redesign proposals should be based on a coherent reconstruction of pedagogical foundations of educational ICT (software, documentation). Secondly, redesign proposals should result from dialogue between stakeholders, such as future users, pedagogical experts, software designers, and deciders. To these ends, we propose a framework, called GESTALT ( G oals, ( E ) S i T uations, A ctions, L earners, T ools), as a 'boundary object' for dialogical redesign. Within an activity theory approach, GESTALT is based on analysis of available tools, the actions they support, the characteristics of learners who perform actions, and pedagogical goals that could be achieved in specific situations. An illustrative GESTALT analysis of educational software is provided, principally from the viewpoint of pedagogical experts. Finally, the strengths and limits of GESTALT are discussed.     

流媒体服务器存储子系统高性能I／O接口的研究与实现

本文在分析流媒体应用特征的基础上，结合嵌入式系统的特点，提出了一种基于嵌入式Linux系统的流媒体服务器存储子系统高性能I／O接口的解决方案，在内存管理、DMA控制以及文件系统方面进行了设计和优化，并对该系统作了性能测试和分析。     

GSPress:一个GML流压缩器

GML已成为地理数据存储和交换的标准.在实际应用中,GML数据通常以数据流的形式在网络上传输.由于GML文档含有大量重复标签和高精度浮点数,使得GML文档通常比较大.因此如何有效地压缩GML数据流来减少网络传输的代价就显得越来越重要.本文提出一种GML数据流压缩算法,它只需扫描GML文档一次,将GML文档的结构和数据分离后分别进行压缩.对GML文档中的结构部分采用自适应方法进行压缩;对坐标数据则利用增量压缩的方法压缩.实验结果表明GSPress是一种高效的GML流压缩算法.     

C及C＋＋输入输出机制的讨论——从库函数到流

讨论了ＡＮＳＩＣ实现数据输入输出的特点，并且介绍了Ｃ＋＋如何用流的方法实现数据的输入输出，事实证明，后者各方面的特性都优于前者。     

Ergonomic redesign and evaluation of a clamping tool handle

The handle of a commercial bar clamp was redesigned using ergonomic principles and then compared with an original clamp. Ten male and ten female students participated in simulated clamping tasks under various conditions, including different clamping heights, clamping methods, and handle-gripping methods, with respect to the dependent variables of clamping and handle-squeezing forces. The results showed that the redesigned clamp produced larger clamping force with lower handle-squeezing forces than the original clamp. As expected, males exerted more force than females in both clamping and squeezing forces. A pistol grip method was superior to an upside-down handle-gripping method. Two-handed operation was recommended for this type of clamp by simultaneously pulling the trigger and sliding the bar in order to initially tighten around objects. This study shows that the application of ergonomic guidelines increases the efficiency and usability of manual handtools.     

Ergonomics evaluation and redesign of a hospital meal cart

The ergonomic, design and other problems of a conventional hospital meal cart were evaluated with a view to redesign a hospital meal cart by incorporating ergonomic principles and data. The operators encountered difficulty in setting the cart in motion, seeing over the cart, turning the cart and stopping the cart while in motion. The operators expressed postural discomfort in the shoulder, neck, back, lower back, knee and leg, and ankle and foot. The cart with meal trays and food was found to exceed the acceptable initial turning push force requirement of 5th percentile females. Recommendations were made for proper placement of cart handles and handle diameter, provision of large-diameter cart wheel made of hard rubber tire, reduction of cart height, use of plastic material for cart construction, provision of emergency brake, provision of individually (electrically) heated plates for soup and main meal, provision of thick air-tight transparent plastic doors, and reduction of the meal tray size. Several recommendations were adopted by the manufacturer in the new model.     

Analysis and redesign of a military orders processing system

A study was conducted which analyzed the army orders processing system at the Massachusetts Army National Guard. Timely processing of these orders was essential since they initiated active duty status. This status officially obligated a civilian into a military position. Orders processing behaved as a queuing system with batch arrivals and preemptive service. Given randomness of the arrival and service processes, insufficient clerk manpower caused the orders to be delayed in a queue. The analysis of this system was conducted using computer simulation modeling. The model was designed to schedule clerks so that total processing time was minimized and critical delays were avoided. The evaluation of different manpower alternative included varying the number and arrangement of the processing clerks. Ultimately, the entire orders processing system was redesigned. This article discusses the National Guard's response to the results and recommendations determined through simulation modeling.     

一种新颖的移动流媒体代理服务器设计

通过对移动流媒体技术为中心的移动流媒体系统相关的研究,设计实现无线局域网中的一个热点,为移动终端用户提供流媒体接入服务代理服务器。     

Digital redesign of observer-based output-feedback tracking controllers: enhancement

Digital redesign for observer-based output-feedback tracking controller with time-varying references is developed. The improvements have been done by more precisely approximating the reference and considering the state matching of the estimation error in a plant dynamics for a large sampling period, and by using the delta-operated discrete-time modelling for an extremely small sampling period.     

Snap-on-handles for a non-powered hacksaw: An ergonomics evaluation,redesign and testing

In this study, we investigated how experienced and inexperienced subjects handle a box when it could be approached from any of its sides. Subjects moved a box (11 kg) either to a high (HS) or a low surface (LS). Wrist movements and grip force were synchronised and recorded, respectively, by electrogoniometers and an instrumented box. All subjects adopted a lateral-and-bottom grip, with parts of the hands simultaneously placed on the side and bottom of the box. This grip allowed the 50th percentile of wrist movements to be within safe limits, particularly in the sagittal plane. Low force was associated with lowering the box to LS and equally distributed but greater force when lifting to HS. Larger ulnar deviation was recorded when the box was lifted to HS. Only peak of wrist extension differentiated experienced from inexperienced subjects, with experienced presenting larger wrist extension. Alternative box designs are suggested to improve handling in real settings. PRACTITIONER SUMMARY: Understanding worker preferences for box lifting behaviour can contribute to the development of new designs that facilitate the adoption of more efficient postures while reducing the risk of upper-limb musculoskeletal disorders and promoting safer manual material handling.     

Snap-on-handles for a non-powered hacksaw: an ergonomics evaluation, redesign and testing

Based on the ergonomics evaluation of existing non-powered hacksaws with original/horizontal and conventional/market handles, ergonomically designed hacksaw handles are proposed. To accommodate the entire male and female populations, the hand dimensions are categorized into three groups: small, medium and large. The proposed handles give special emphasis to hand size, length, cross-section dimension and curvature. The three-sized handles for both the preferred (rear) and non-preferred (front) hands are interchangeable to suit the individual hand size. Thus, the concept of 'snap-on-handles' with a fixed hacksaw (blade) can be promoted. The ergonomically designed hacksaw handles were tested/compared with original/horizontal and conventional/market hacksaw handles, in terms of performance or productivity (depth of cut), muscular effort or strain (EMG) and subjective scores (acceptance/comfort). The experimental results conclusively proved that the ergonomically designed hacksaw handles were significantly better than the other handles in terms of the stated criteria. The performance or productivity improvements of the ergonomically designed handles were about 25 and 148%, when compared with the conventional/market and original/horizontal handles, respectively. Furthermore, when the ergonomically designed handle was not matched with the proper or appropriate hand size, there was a significant reduction in performance or productivity, increase in muscular effort and decrease in subjective scores of acceptance/comfort.     

Stream mining: a novel architecture for ensemble-based classification

Mining data streams has become an important and challenging task for a wide range of applications. In these scenarios, data tend to arrive in multiple, rapid and time-varying streams, thus constraining data mining algorithms to look at data only once. Maintaining an accurate model, e.g. a classifier, while the stream goes by requires a smart way of keeping track of the data already passed away. Such a synthetic structure has to serve two purposes: distilling the most of information out of past data and allowing a fast reaction to concept drifting, i.e. to the change of the data trend that necessarily affects the model. The paper outlines novel data structures and algorithms to tackle the above problem, when the model mined out of the data is a classifier. The introduced model and the overall ensemble architecture are presented in details, even considering how the approach can be extended for treating numerical attributes. A large part of the paper discusses the experiments and the comparisons with several existing systems. The comparisons show that the performance of our system in general, and in particular with respect to the reaction to concept drifting, is at the top level.