Web集群服务器的分离式调度策略

主要用排队论方法讨论了Web集群整体性能与请求调度策略之间的关系，所获得的结论是：在Web集群非过载情况下，一部分后端服务器仅处理静态请求而另一部分后端服务器仅处理动态请求的分离式调度策略要好于所有后端服务器既处理静态请求又处理动态请求的混合式调度策略。用SPECweb99测试工具所做的实际测试更进一步证明：当负载参数为120个连接时，采用分离式调度策略的Web集群服务器可完成63个连接，而采用混合式调度策略的Web集群服务器仅能完成36个连接，性能提高了22.5%。     

Web服务系统的性能分析与测试

总结了衡量Web服务性能的重要评价指标,并以Web Server性能测试工具－－SPECweb99为例阐述了测试原理和测试方法。通过性能分析模型和测试实例系统地分析了负载情况、服务器处理能力（着重于动态请求内容的处理方式）、网络带宽等关键因素对Web服务系统性能的影响。这些结论对于提高和改善Web服务性能具有较强的指导意义。     

SPECweb99—Web服务器性能测试工具

阐述了Web服务器性能测试工具－SPECweb99的工作原理、安装配置及测试方法,并结合测试实例就如何解决使用SPECweb99对Web服务器性能进行测试时可能遇到的问题进行了总结。     

AB:一种简单的性能测试工具

Web及其应用程序的普及使得Web服务器的性能测试变得越来越重要,现有的性能测试工具林林总总,数量很多,不同的性能测试工具都有其优缺点,应根据实际情况挑选最适合的工具.Apache自带的性能测试工具AB,功能虽然不多,但非常实用,使用也很简单.文章阐述了性能测试工具AB的特点、安装及测试方法,并结合测试实例分析了它的测试结果及遇到的一些问题.     

WebMark:一个Web服务器性能测试工具

Web及其应用程序的普及使得Web服务器的性能测试变得越来越重要,而现有的测试工具都具有一定的适应性限制.总结了Web服务器性能测试的指标和原则,提出了一个更加合理的测试指标--加权响应时间.介绍了一个Web服务器性能测试工具WebMark.它用事件驱动的方式管理异步I/O,通过修改Client的TCP/IP协议栈来模拟Internet环境.使用它对Apache进行了全面测试,证明了研制WebMark这样一个功能强大的测试工具是十分必要的.     

一种提高Web服务性能的方法

首先阐述了Web服务器性能的定义，然后从Web服务器性能的几个关键问题入手，从应用负载，服务器软件和服务器硬件3个层面上详细讨论了如何解决这些关键问题，通过对比目前流行的测试工具，选择了合适的应用负载，采用探索式方法优化服务器软件的配置参数，从而减少了测试次数，通过屏蔽各种HTTP请求找出影响性能的瓶颈－对动态请求CAD GET的处理，针对该种请求，调整其在动态请求中所占的比例分析其对不同大小的文件在响应速度上的影响，最后优化相应的代码，将这一方案应用到曙光3000超级服务器上并使用SPECweb99作为Benchmark测出实验数据，对比改进前的结果，可以明显看到Web服务器的性能提高了一倍。     

Web系统性能测试及优化

讨论了Web系统的性能测试方法和测试工具。并在一个Web系统的实例中指明了如何运用这些工具和方法进行测试以及对测试结果的分析。最后提出了对Web系统性能进行优化的方法。     

基于用户会话的Web应用性能测试方法的研究

近年来,Web应用成为互联网时代基础设施中最重要的组成部分。随着互联网技术的不断进步以及使用用户数量的不断增长,Web应用也越发变得复杂。为了保证Web应用性能测试的有效性和真实性,提出一种利用服务器日志中的用户会话信息、结合经过序列匹配算法改进的层次凝聚算法来自动产生Web应用性能测试脚本的方法。提出的方法通过从服务器日志中提取出用户会话信息,分析用户真实的访问模式,通过聚类算法将同类型的用户访问模式进行聚集,自动产生相应的测试请求序列,生成测试集。相比于传统的基于录制/回访的测试方法,基于用户会话的性能测试方法通过对用户会话进行聚类分析,还原实际的用户访问模式,减少了设计测试用例时的人工参与,保证了测试结果的有效性和真实性。     

Web服务器的过载模拟和性能测量

本文对典型Web服务器的过载机理进行了分析,并采用事件驱动和异步I/O技术设计和实现了一种高效Web服务器负载生成器aLoad,而且使用它对Apache Web服务器进行了过载模拟、性能测量和分析。通过对比实验表明,aLoad可产生大大高于传统性能评测工具的并发负载。     

基于异构双极信息的模糊查询研究

研制自动化的Web服务脆弱性测试工具对基于Web服务的软件工程有重大影响,并能提高软件的安全性和可靠性,是当前软件行业一个有意义的研究课题。针对广泛使用的Web服务,设计和实现了一个测试Web服务脆弱性的原型系统WSVTS (Web Service Vulnerability Testing System)。根据SOAP消息参数的个数和类型,实现了两种基于SOAP消息变异的Web服务脆弱性测试方法,分别是最坏差异输入变异方法(The Worst-input Mutation Approach)和杂乱数据变异方法(Fuzz Data-input Mutation Approach)。测试系统融合这两种测试方法,实现了两种测试用例生成算法,分别是最远邻测试用例生成算法TCFN(Test Cases generation based on Farthest Neighbor)和杂乱数据输入变异算法FDMA(Fuzz Data-input Mutation Algorithm),然后,将算法产生的测试用例作用于SOAP请求消息,从客户端观察应答消息,来分析Web服务的脆弱性。     

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.