Web服务器性能评测

Web服务器性能评测是一种理解Web服务器对不同负载反应能力的方法，它对Web服务器的容量规划和性能增强有很大的帮助。讨论了Web服务器性能评测的原理、方法、难点及解决方案，介绍了基于Web负载的特点、ON／OFF源模型及浏览器／服务器体系结构，开发了一个Web服务器性能评测工具－WSBench。WSBench产生渐近自相似的HTTP请求序列，从静态文档、动态文档（没有数据库存取）、动态文档（有数据库存取）及前三者根据Zipf法则的组合4个层次来评测Web服务器的性能。性能测试结果表现为每秒请求数、每秒字节数和往返时间3个指标。最后讨论了Web服务器性能问题及使用WSBench测得的指标来建议Web服务器性能增强可以采用的方法。     

TPC-W基准测试中客户端设计的关键技术

Web服务器性能测试是对服务器的综合性能测试．简要介绍了TPC-W基准测试系统的整体结构,详细论述了TPC-W基准测试系统在客户端设计中所采用的关键技术——线程内按比例访问技术．测试结果分析表明：利用线程内按比例访问技术,可以使客户端机器的资源得到充分利用,根据大量用户访问Web服务器真实行为的统计特性,进行细粒度的模拟,从而更好的对Web服务器的性能进行综舍测试．     

一种基于OSI应用层的Web群集负载平衡调序策略研究

本文总结了目前基于L7的Web群集负载平衡调度研究，分析了影响性能的主要因素，在估计Web负载时考虑了请求强度以及Web服务器自身的性能，提出了处理能力异构服务器群集的最小负载调度算法。在算法中还同时考虑了服务器在进入临界状态时性能急剧下降的因素，避免群集进入临界状态．新算法能较为准确地跟踪群集系统的负载，更好地
均衡分配负载。     

Web服务器集群请求分配和选择的性能分析

讨论并提出了 Web服务器集群的请求分配和选择控制方案 ,而且提供了这些方案的随机高级 Petri网模型 ,并强调研究这些方案及性能模型和分析方法 .为解决模型状态空间爆炸问题 ,作者提出了一种近似性能分析技术 ,可以显著地简化模型求解的复杂性 .文中的 Web服务器集群模型、请求分配和选择控制方案及近似性能分析技术可以应用于这类复杂系统的性能评价 .     

HGS:一种新的Web服务器负载生成策略

在Web服务器性能评测研究中 ,服务器负载的特性分析是一个非常重要的研究内容。准确地把握服务器负载的统计规律 ,建立负载模型是服务器性能仿真的基础。该文在详细分析Web服务器负载特性的基础上 ,建立了一个新的服务器负载层次结构模型 ,设计的层次生成策略HGS(HierarchicalGenerationStrategy)符合客户请求的基本特性 ,适用于各种Web服务器性能研究。     

基于工作量和错误日志的Web应用可靠性度量方法

Web应用环境复杂,传统基于故障测量的方法不能很好地满足系统可靠性度量的需求.充分考虑用户对系统的使用情况,从Web服务器日志中获取用户点击数、传输字节数、用户数和用户会话数,提出基于这四个指标的工作量测量法,并与传统的故障测量法结合,采用Nelson模型进行系统可靠性评估.通过实验比较工作量测量的四种方法与故障测量方法的优劣.结果验证了基于工作量测量的方法能更稳定地评估Web应用的可靠性.     

利用基于内容的缓存代理提高Web服务器性能

分布式Web服务器系统(DWSS)是提高网络服务性能的一种前沿方式。文中分析了当前几种在客户端、主机端提升Web服务性能的方法,提出了一种基于内容的缓存代理协作分布式Web服务器系统模型。该模型可以有效减少用户获得响应的时间,避免了服务器之间不必要的通信,提高了Web服务器整体的性能。     

Web服务器负载压力模型及其优化原则

分析了HTTP协议交互原理以及Web服务器对一次HTTP请求做出响应的处理机制,并建立层次化的Web服务器负载压力模型.通过对该模型的分析,提出缓解Web服务器压力的方法与原则.实验表明,这些缓解Web服务器压力的方法与原则能充分提升服务器性能,适应更大并发量的访问请求.     

利用基于内容的缓存代理提高Web服务器性能

分布式Web服务器系统(DWSS)是提高网络服务性能的一种前沿方式.文中分析了当前几种在客户端、主机端提升Web服务性能的方法,提出了一种基于内容的缓存代理协作分布式Web服务器系统模型.该模型可以有效减少用户获得响应的时间,避免了服务器之间不必要的通信,提高了Web服务器整体的性能.     

基于B/S结构的企业远程实时测控系统

介绍了一种新型的基于B／S结构的生产企业远程实时测控和数据发布方法，给出了一个由web服务器、应用服务器、实时数据库服务器、嵌入式Web服务器和ActiveX通讯插件组成的自来水厂实时监控模型，详细介绍了嵌入式Web服务器设计方案及能够提高系统实时性能的ActiveX通信插件的设计方法。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.