全IP的有线无线一体化接入与认证技术

本文介绍了未来全IP化的网络,提出了基于IPv6协议的有线无线一体化接入和认证系统。这种接入网络可同时为有线用户和无线用户提供IP网络接入服务,能够进行认证和计费,能够支持IP漫游和移动。采用IPv6协议保证了为每个终端分配一个全局IP地址。满足未来基于IP的、端到端的通信需要。并对有线无线一体化接入和以太网接入认证技术进行了分析。     

基于uClinux的蓝牙无线网络接入实现

蓝牙无线技术和网络接入技术的集成是蓝牙技术中有广阔前景的应用方向，把蓝牙无线的低功耗、低成本和方便快捷的优点与网络接入结合在一起将推动家庭宽带用户的市场快速发展。研究了在uclinux操作系统下蓝牙无线网络接入设备的实现，描述了蓝牙协议栈，分析了蓝牙无线接入的原理，并考虑了在具体实现中所要注意的问题。     

无线CORBA中间件的系统结构分析与研究

随着无线技术的快速发展,移动网络中的分布式计算也日趋重要。无线CORBA针对解决无线接入和终端移动这两个关键问题,系统地展现、归纳和评述了无线CORBA的总体系统结构、原理与规范,分析了移动IOR、GIOP隧道协议和越区切换管理等无线CORBA中间件体系的核心支撑技术,给出了实现终端GTP通信处理的系统级设计解决方案,指出了存在的问题和进一步的研究方向。这些工作对移动分布式系统的研究和实践具有一定的参考价值。     

无线Ad Hoc网络关键技术研究

首先介绍无线Ad Hoc网络的路由协议、接入技术、移动终端定位、电源管理、移动性管理QoS保障、网络管理和安全等关键技术；接下来，介绍了目前国内外所取得的研究进展；最后给出今后在无线Ad Hoc网络的路由协议和网络管理方面的研究方向。     

基于群组移动模型的OLSR协议性能仿真与评估

在研究移动自组网移动模型和无线路由协议的基础上,选取移动自组网中具有代表性的参考点群移动模型,基于ns2网络模拟平台,以参考点群组移动模型生成移动场景文件,应用层使用cbr数据流量,对OLSR无线路由协议在不同参数条件下的性能进行了模拟测试。通过对测试结果数据的详细分析,总结得出了OLSR无线路由协议在参考点群移动模型下端到端时延、报文交付率和路由负载三个方面的特点。为进一步研究移动自组网下基于OLSR协议的各种应用提供参考。     

Ad—Hoe网络中TDMA接入的无线网卡设计

随着Ad—Hoc网络的发展和应用，TDMA接入方式逐渐成为Ad—Hoe网络MAC协议研究的热点。根据TDMA接入方式的特点，讨论Ad—Hoe网络中TDMA接入方式无线网卡的设计思路，提出Ad—Hoe网络无线网卡的设计方案，开发出一种适应性强、性能优良的新型无线网卡。该无线网卡可以构建多个节点的Ad—Hoc网络，实现TDMA固定接入方式和多种改进接入方式，能够满足实际应用的多种需要。     

Ad-Hoc网络中TDMA接入的无线网卡设计

随着Ad-Hoc网络的发展和应用,TDMA接入方式逐渐成为Ad-Hoc网络MAC协议研究的热点.根据TDMA接入方式的特点,讨论Ad-Hoc网络中TDMA接入方式无线网卡的设计思路,提出Ad-Hoc网络无线网卡的设计方案,开发出一种适应性强、性能优良的新型无线网卡.该无线网卡可以构建多个节点的Ad-Hoc网络,实现TDMA固定接入方式和多种改进接入方式,能够满足实际应用的多种需要.     

基于短信服务的移动VPN应用系统

文中给出了一个基于移动公网短信增值服务的无线接入VPN应用系统的解决方案，文中介绍了该解决方案的整体架构，描述了通过短信服务实现VPN应用系统无线接入的实现原理，绘出该方案应用层自定义协议“ADTP”的结构和协议基本数据元定义，对其数据通信安全和移动终端接入论证的实现策略做了相应说明。     

一种基于Java技术的WSP模拟实现及其在通信中的应用

文章简述了WAP体系结构以及WSP协议特点,给出了一个实现无线应用的移动终端模拟软件的体系结构,论证了使用Java技术开发移动终端模拟软件的可行性,最后提出了一种设计和实现WSP协议方法,为无线应用(WML网络浏览、彩信收发等)提供基于会话的数据传输服务,研制的模拟软件能很好地测试WAP网关的性能。     

多路径DSR和AODV路由协议性能研究

在支持移动节点和自组织网络的路由协议中,最典型的单径路由协议是DSR和AODV协议,对它们进行扩展分别得到相应的多径路由协议。通过仿真比较分析这2种多径路由协议在混合无线Mesh网络和移动AdHoc网络中的性能。结果显示,混合无线Mesh网络中的这2种多径路由协议具有分组传输率高、端到端的平均延时和路由开销小等优点。以DSR协议为基础扩展得到的多径路由协议,在高度动态的网络环境中,性能得到了改善,能广泛应用于移动性强的环境中。     

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).