基于SIP的无线网络移动性管理研究

为了使移动设备能在无线IP网络中无缝漫游，无线IP网络必须要能提供有效的移动性管理来支持终端的移动性。基于SIP提出了一种新的应用层移动性管理方案，和已有的移动性管理方案相比，它既支持实时业务的快速切换，减少了切换时的延迟和丢包．也支持非实时业务，而且实现和部署起来比较简单方便。     

MIP与SIP融合的无线网络移动性管理方案

目前,无线Internet移动性管理主流方案之一是采用移动IP(MIP)以及初始会话协议(SIP).其中移动IP是无线Internet实现各种移动业务的关键技术,而SIP是提供和实现IP业务的重要协议.文章根据MIP与SIP的综合应用提出了一种MIP/SIP融合的移动性管理方案,它优化了注册过程,减少了移动节点的信令开销,并引入了平滑切换机制来减少切换过程中的丢包率,从而很大程度上提高了网络的性能.     

移动IP移动性管理技术综述*

融合型全IP网络已经成为网络发展的大趋势,采用移动IP解决无线IP网络中的移动性管理成为一种必然。移动IP v6作为网络层移动性管理的核心技术,其相关移动IP扩展技术是移动IP关于移动性管理的重要内容,但必须有更优化的微移动性管理协议处理本地移动性,层次型的移动性管理结构被大家所认同。分层移动性管理的策略对网络中位置代理的位置和层次进行规划,但是增加相应的管理机制引入切换管理愈加重要。     

基于多协议层联合优化的移动性管理技术

针对下一代网络的通用移动性,从多协议层联合优化的角度提出一种可以有效融合多业务的通用移动性管理方案。该方案以网络层移动性支持协议（Mobile IP）及其微移动管理协议为基础,并在此基础上融合会话初始协议（SIP）,将网络层移动性管理与应用层移动性管理进行联合优化设计,同时考虑链路层的切换,减少功能性和信令数据信息的重复。     

MG-HMIP协议模型的实现及应用

由于无线局域网(WLAN)IEEE802.11协议不能解决移动节点的三层漫游问题,介绍了WLAN与移动IP结合的解决方案。由于上述方案存在切换延时长、不支持微移动性等缺陷,研究了分层移动IP技术,并对分层移动IP进行了改进,提出了一个多GFA分层移动IP(MG-HMIP)模型,并详细介绍了MG-HMIP模型的注册机制和MN选择GFA的机制。最后,给出了MG-HMIP与WLAN结合的模型。这个改进的方案不仅解决了WLAN与传统的MobileIP结合所存在的切换延时长、频繁切换等问题,而且增强了分层移动IP的网络健壮性。     

下一代网络IPv6的移动切换优化策略

IP移动性是IPv6标准的一部分。由于移动终端的移动性特征,当移动终端发生切换时,保持正在进行的通信,是IPv6支持移动性的一个关键因素。本文研究在IPv6中优化移动节点的移动切换管理,提出分级切换和快速切换机制来优化IPv6网络中的移动切换管理。     

MG—HMIP协议模型的实现及应用

由于无线局域网（WLAN）IEEE802．11协议不能解决移动节点的三层漫游问题，介绍了WLAN与移动IP结合的解决方案。由于上述方案存在切换延时长、不支持微移动性等缺陷，研究了分层移动IP技术，并对分层移动IP进行了改进，提出了一个多GFA分层移动IP（MG—HMIP）模型，并详细介绍了MG—HMIP模型的注册机制和MN选择GFA的机制。最后，给出了MG—HMIP与WLAN结合的模型。这个改进的方案不仅解决了WLAN与传统的Mobile IP结合所存在的切换延时长、频繁切换等问题，而且增强了分层移动IP的网络健壮性。     

基于SIP的移动性管理

几个无线技术论坛,比如3GPP2,已经决定采用SIP作为移动因特网会话管理的信令协议,很显然SIP将成为移动因特网协议结构中不可分割的一部分。详细描述了怎样使用SIP对终端和个人移动性的支持。移动IP虽然使得移动性对更高层是透明的,但是它也带来了三角路由和隧道管理等问题,而SIP在应用层对移动性进行管理,对于实时通信来说,这种方案更加有效。     

微移动协议下全IP无线网络的移动性管理研究

改善移动节点通信质量的移动性管理最有效的方式是IP微移动．它的核心是切换管理．分析微IP协议和IP网络的不足之处．对全IP无线网络的移动性管理最关心的问题进行详细阐述,介绍一种目前主流的区域移动性管理协议PMIPv6．并分析其域内切换移动性管理机制。提出一种优化的基于网络的区域移动性管理域内切换管理方法．并与已形成IETF标准的切换管理方法进行性能分析比较．证明该方法可以有效地减少切换时延和位置更新信令代价．     

GPRS和移动IP中移动管理研究

1 引言因特网与移动通信结合而诞生的无线因特网,己成为当今全球信息产业的热点。它使人们能在移动中从因特网上获取丰富的多媒体信息资源,享受到各式各样的个性化服务,从而引发工作和生活模式的巨大变革。在无线因特网的构成中,无线蜂窝网络扮演着极为重要的角色。当前,无线蜂窝网络正处于快速发展演变阶段,如何提供灵活和低廉的因特网数据接入服务将是第三代乃至第四代移动通信系统面临的主要任务。在无线蜂窝网络的体系结构中,移动管理起着关键作用。移动IP提供了一种简单、扩展性强的全球移动方案,但是缺乏对快速移动切换、实时位置跟踪、安全验证和分布式策略管理等功能的支持。另一方面,通用分组无线业务GPRS(Gen-     

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。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

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.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.