千兆位以太网技术及应用

千兆位以太网技术以其速度快，带宽大且兼容性好，具有比传统标准以太网更强大的功能，是目前计算机高速网络的一个较新的领域，在对千兆位以太网体系结构分析的基础上，着重讨论了千兆以太网的技术特点，针对实现千兆位以太网的几个关键性技术进行了论述，并介绍了快速以太网向千兆位以太网升级的途径。     

有关千兆位以太网的常见问题

一、千兆位以太网技术 1.什么是千兆位以太网技术?它和10/100Mbps以太网有什么联系? 千兆位以太网是对取得巨大成功的10Mbps和100Mbps802.3以太网标准的一个扩展。千兆位以太网提供了1000Mbps的原始数据带宽,同时和现有的7000多万个以太     

千兆以太网何以倍受市场青睐

千兆以太网具有完善的标准、良好的兼容性和很好的性能价格比，随着越来越多的网络新技术应用于千兆以太网，给千兆以太网带来了蓬勃的发展机会，我们已进入千兆以太网的平民时代。本文就千兆位以太网的特点、标准和升级方法以及未来发展新动向作一些简要的探讨。     

3Com千兆以太市场稳执牛耳

在千兆位以太网联合会宣布IEEE802.3z(千兆位以太网)定案标准的当天,3Com公司宣布,3Com所有的千兆位以太网产品均符合这个业界标准,它们组成了业内最全面的10/100/1000Mbps网络升级系统。 按照3Com公司售出的千兆以太网产品SuperStack Ⅱ Switch 3900、SuperStack Ⅱ Switch 9300、SuperStack Ⅱhub 1000SX和CoreBuilder 3500千兆位以太网模块统计,3Com公司1998年第2季度售出的千兆位以太网端口达1万个。 3Com公司以太网园区解决方案总监     

为千兆位铺“路” 布线和设备基础结构必须到位才可获得最高速度

对于面临带宽限制的网络经理来说,升级到千兆位以太网比其它技术具有显著优势,因为千兆位以太网的协议和包格式以是以传统以太网标准为基础。因此,网络经理从10/100Mbps以太网的故障排除过程中所获得的经验将能很好地帮助他们应付千兆位以太网。另外,千兆位以太网保留了其早期产品的帧格式、全双工操作和流量控制方法,从而消除了在不同类型以太网信息流之间进行转换的要求。不过,将一个网络升级至千兆位以太网也并非毫无困难。为充分实现千兆位以太网的优势,应当对布线基础结构和网络通信模式加以特别注意。     

千兆位以太网需要怎样的布线系统?

随着信息时代的高速发展,人们对于网络及其布线设施的日益发展,开始眼花缭乱。市场上新近出现的千兆位以太网更是人们关注和议论的热点。笔者在参阅了千兆位以太网联盟:千兆位以太网白皮书及对这个问题的思考后作以下阐述,希望同行专家们本着学术争鸣的态度,各抒己见,拨冗指正。 一、千兆位以太网 现今社会随着复杂和实时计算机应用的日益增长,高速网络应用也在层出不穷。千兆位以太网则是其中的佼佼者。千兆位以太网可以使用简单的以太网机制,为网络提供超过1000Mbps的传输速率。它允许     

千兆位以太网—带刺的玫瑰

千兆以太网在网络人士的期盼与祈祷声中呱呱坠地,不长的时间便在业界煽起了千兆位以太网的热浪,人们对千兆位以太网寄予了厚望。但是,走出业界对千兆位的这种狂热,冷静思考,却发现:     

千兆标准呼之欲出,ATM成熟有佳,在你的网络升级计划书中——谁是首选

按原定计划,IEEE将在本月对千兆位以太网标准进行新一轮的投票。在千兆位以太网标准正式出台以前,Cisco、Intei、HP、Bay、Compaq等著名厂商纷纷推出千兆位以太网产品和解决方案,Fore公司也生怕落伍,宣布将在千兆位以太网标准发布之后推出产品,同时千兆位以太网交换设备的每端口价格一降再降。Cisco首席科学家Bruce Nelson博士用4个字来描绘千兆位以太网——多(带宽)、快(速度)、好(性能)、省(资金)。到底是采用ATM还是千兆位以太网?用户在升级原有网络时都应该从技术、应用、资金等多个方面权衡,不妨周到考虑。     

将千兆进行到底

光纤中使用千兆位以太网已经成为标准做法,而最近又出现了将千兆位以太网用于第5类UTP电缆、在铜线上传输的1000Base-T千兆位以太网,这使得千兆的普及迅速加快了脚步。与此同时,企业用户也已经看到了在网络骨干和数据中心使用千兆位速度的好处。 本文力求为您提供一些关于千兆位以太网的重要信息,其中包括如何使您所在企业的网络受益于标准千兆位以太网的实施方案,并给出了一些部署的例子。     

驶上千兆路需要换新车

尽管千兆位以太网还是一种不成熟的技术,但许多公司还是对它在速度和灵活性方面的潜力表现出兴趣。然而网络管理员可能没有注意到,如果要想全面实现千兆位以太网的优点,可能需要整个网络的升级。第一件要做的事情就是5类电缆,因为目前的千兆位以太网规范只定义了在光纤上的传输。虽然已经有了在铜线上传输千兆位以太网     

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.