一种Web服务器集群的可伸缩管理算法

如何根据网络任务的忙闲变化，对Web服务器进行调度管理，是Web应用中面临的新问题之一。目前，由于追求为用户提供快速及时的应答服务，越来越多的系统采用了Web服务器集群技术。文中针对Web服务器的网络任务特点，以排队论为工具，提出了一种新的Web服务器集群管理算法。该算法通过调整服务器数目来增减处理能力，实现对Web服务器集群的可伸缩管理。     

语义网中基于Web资源本体的数据中介服务

为了搜索Web资源中深层数据并对其利用,在分析利用搜索引擎获取Web资源存在问题的基础上,利用语义网和Web服务技术,提出构建Web资源本体模型实现对Web资源进行语义标识,结合服务管理代理构建数据中介服务应用模型,并以Web服务方式实现Web资源数据中介服务.通过实验验证了Web资源数据中介服务的有效性和可行性,从而实现帮助用户能在形式多样、种类繁多的海量Web资源中有效地荻取和共享Web资源数据.     

基于Web服务的个人网页资源管理组件设计

介绍了基于Web服务的个人网页资源管理组件的设计,实现了Web用户在Internet上收集网页,并将这些网页自动存储在Web服务器的个人网页存储器上,为Web用户提供个人网页的访问和管理服务。Web网站的服务提供者也可以使用该组件实现Internet增值服务。     

基于本体聚类的面向业务用户服务发现模型

现有的基于语义的服务发现机制都存在着缺陷和不足，该文提出一种面向业务用户的、基于本体聚类的Web服务发现模型，应用本体聚类算法对领域本体和Web服务进行分层管理，实现了以业务用户为中心的设计思想。     

一种基于Web单点登录系统实现

介绍了一种基于Web的单点登录实现方法,解决同一用户登录不同Web应用系统需要进行多次独立身份认证问题,详细讨论了单点登录系统中后台数据组织、存储安全性以及代理认证服务处理逻辑.同时,就服务通信安全与服务响应时间之间的矛盾问题提出了一种解决的方法.Web代理采用浏览器插件方式,截获用户第一次登录某个Web应用时的post数据,并将其存入数据库,用户在以后登录这个Web应用系统时自动提取数据库中post数据,省去了用户手动进行身份认证的过程,实现了统一身份认证.     

基于Web/Java技术的SNMP网络性能管理的研究

本文研究了简单网络管理协议和网络性能管理的有关内容。通过对简单网络管理协议(SNMP)、MIB-Ⅱ管理信息结构(SMI)的分析和使用，设计了基于Web的客户层 服务层 资源层的三层网络管理模型。采用Java Servlet实现Web服务器，C语言实现应用服务器，Java Applet作为客户端。Socket作为信息转发通道。系统采用Java Applet Servlet技术，实现了基于Web的管理方式。     

一种远程智能电源管理系统服务平台的设计与实现

针对机房海量服务器设备管理问题,提出了一种“远程网络电源管理系统平台”方案.平台由前端电源管理单元、服务平台和客户端构成.服务平台通过底层服务软件收集前端电源管理单元状态信息,传递用户控制命令.平台上层采用Web服务器和数据库系统,接收用户管理访问.为了便于管理、降低成本,客户端采用通用Web浏览器实现,用户通过Web浏览器即可远程控制服务器,随时随地监控机房,还能通过串口远程配置数据,实现真正的无人值守机房.     

基于WEB挖掘的个性化服务研究

针对用户特性向用户提供个性化服务将是web服务的发展趋势，本文从Web个性化服务的本质出发，详细地研究了实现Web个性化服务的关键技术：Web挖掘技术和信息推荐技术，并在此基础上设计了一个基于Web挖掘的个性化服务系统原型。     

基于Web统一身份认证服务的实现方案

描述了一种实现统一身份认证的方法，解决了同一用户登录不同Web应用系统需要进行多次独立身份认证问题。Web代理采用浏览器插件方式，截获用户第1次登录某个Web应用时的post数据，并将其存入数据库，用户在以后登录这个Web应用系统时自动提取数据库中post数据，省去了用户手动进行身份认证的过程，实现了统一身份认证。     

序列模式挖掘在电子商务个性化服务中的应用

分析了电子商务发展面临的问题和个性化服务的特点，提出了Web使用挖掘技术在电子商务个性化服务中的应用方法，论述了基于Web挖掘的个性化服务研究．详细阐述了其挖掘过程，最后讨论了使用序列模式和分类相结合的技术得以实现个性化服务的方法。利用这些算法得到的个性化信息可以准确把握用户兴趣模式并对Web信息资源的组织方式进行有效更新，从而提高网络信息服务效率，为用户提供“一对一”的具备自适应性的智能个性化服务。     

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。     

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.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).