MDCent:一种高可扩展、高吞吐量的模块间互连结构

近年来,提出的以服务器为中心的新型数据中心网络互连结构部分程度地解决了传统树型结构面临的性能瓶颈和可扩展性难题,同时出现了以集装箱为基本模块构建超大规模的数据中心.然而,如何设计模块之间的互连结构,确保数据中心网络具有高可扩展性、模块之间具有高带宽是一个非常具有挑战性的问题.以BCube为代表的新型数据中心网络,能够将数千台服务器互连在一个集装箱内,且对各种典型流量模式提供较高的带宽.提出了一种常量度数的模块之间的互连结构MDCent.MDCent基于BCube结构进行模块内服务器互连,利用模块内大量未被使用的上行端口,在各个模块保持常量度数的情况下,能够保证模块之间具有高可扩展性,同时模块之间具有较高的带宽.     

BCube在2-限制连通度下的容错路由算法

BCube是具有良好性能的数据中心网络。相比传统的树形数据中心网络,BCube在扩展和容错性能方面都表现出很大的优势。目前,对于BCube的研究可以归结为对其逻辑图BC_n,k(广义超立方体的一种特例)的研究,其中交换机被视为透明设备。在实际应用中,随着网络规模的不断增加,顶点发生故障已经成为一种常态。因此,研究网络的容错路由很有意义。目前,有不少关于BC_n,k容错路由的研究,但其2-限制连通度下的容错路由目前还没有被研究。在提出容错路由算法之前,首先证明了BC_n,k的2-限制连通度为3(k+1)(n-1)-2n,其中k≥3且n≥3。然后在此基础上提出了一个时间复杂度为O(κ(BC_n,k)³)的容错路由算法,其中κ(BC_n,k)=(k+1)(n-1)是BC_n,k的连通度。该算法可以在故障顶点个数小于3(k+1)(n-1)-2n且每个无故障顶点至少有两个无故障邻居时找到任意两个不同的无故障顶点之间的一条无故障路径。     

数据中心网络可靠组播的研究

通过分析数据中心网络特征和云计算应用需求,提出一种适合数据中心网络的可靠组播机制R2M。针对云计算应用同时强调数据完整性和传输实时性的要求,R2M充分利用数据中心网络服务器间存在多路径的特点,通过组织多棵不相交组播树并行传输数据,并在相邻节点间采用P2P技术建立跨树的恢复关系,实现恢复路径与组播传输路径完全隔离。选择最邻近节点重传数据和较小的路径差错相关性使得R2M能够快速恢复丢失的数据包。基于BCube的仿真实验结果显示R2M具有高可靠性和较小的恢复延迟。     

一种以服务器为通信节点的数据中心网络设计

根据虚拟网络在数据中心(Data Centers)网络的发展和研究现状,提出了一种基于工业电信网络圆柱型结构的数据中心网络架构。深入阐述了数据中心虚拟网络的结构、网络特性、路由策略以及构建成本等,着重分析了静态路由策略以及基于容错机制的路由算法设计与实现。利用常用TCP/IP协议构建网络内部传输模型,测试数据中心网络的传输性能、路由查询速率以及静态路由策略工作效率并进行分析,同时仿真测试了网络的负载平衡及其容错性。     

基于SDN的数据中心网络路由与调度

随着计算机技术的不断发展,云计算也变得越来越普及,应用在人们生活的各个角落,这就为网络数据中心带来了新的发展契机,但任何一个行业,机遇和挑战都是并存的,数据中心现有的网络构架存在着诸多的缺陷,在程序运行的过程中各种问题也随之凸显出来;另外,路由协议和调度策略也有不足之处,这些都制约着云计算技术的发展.面对这种现状,基于SDN的数据中心网络路由与调度的研究就很有必要.     

基于骨干网的数据中心网络服务规划设计

数据中心是云计算的核心,而当前基于电交换器、传统多级交换网络、集中放置与管理的数据中心架构无法满足未来云服务对高性能数据中心在可生存性、高可用性与设计灵活性等方面的要求。以网络可生存性和最小化网络代价为目标,针对数据中心的放置、服务路由及保护进行联合优化设计。首先通过设计ILP获取最优解。该ILP集成了p-cycle、服务量备份以及快速重路由等思想,分别针对单个链路或单个服务器损坏进行快速保护。然后进一步给出一种启发式算法,该算法包含数据中心的放置及服务路由和快速保护两大步骤。ILP和启发式两种方法最终都通过广泛的仿真实验进行了验证。     

数据中心网络路由研究进展

随着云计算的迅速发展,运营商对数据中心的需求与日俱增.作为数据中心网络的关键技术,路由负责在数据中心内部以及数据中心之间为流量选路,为不同服务质量要求的流量提供差异化的路由转发服务.当数据中心规模比较大时,由于应用不可预估的通信流量以及数据中心网络的拓扑特点,传统因特网路由方法不能提供令人满意的高吞吐率和资源利用率,网...     

基于软件定义数据中心网络的节能路由算法

由于数据中心网络是云计算和下一代网络技术的平台和基础设施,日益增长的网络数据在满足用户需求的同时,也大幅增加了数据中心的能耗。许多针对数据中心网络的节能策略被提出,多数采用硬件与软件相结合的策略来完成节能模型的设计。为了进一步降低能耗,从网络负载均衡和节能路由设计的角度提出了一种新的节能路由算法,其基本思想是首先对负载均衡进行量化分析,然后提出带宽限定的负载均衡与节能相结合的节能路由算法,充分考虑到网络整体的可达性和可靠性。该算法为数据中心节能提供了一种新的视角。通过与传统的节能路由作比较,验证了该算法能够在保证较高网络可靠性的同时能耗较低。通过对实验数据的分析和解释得到了若干有益的结论,为进一步的研究工作奠定了基础。     

面向流数据处理的数据中心网络拓扑研究

作为网络服务的底层硬件平台,数据中心的网络拓扑结构及工作机制对于上层的应用服务的性能具有决定性的作用。传统数据中心采用的树形分层结构已经难以满足新一代网络服务的需求,特别是在数据流的应用上传统的网络结构更加无法适用。因此,提出一种针对流数据处理的新型模块化数据中心拓扑构建方式并设计以服务器为中心的路由算法。该方案采用低造价的商业级交换机构建数据中心网络,在降低构建造价的同时提高网络的吞吐量及容错性能。实验表明,所提出的拓扑结构及路由算法在流数据处理上的网络吞吐量表现优于传统的树形结构并且具有更好的容错性能。     

云计算技术研究现状综述

"云应用"使用大规模的数据中心以及功能强劲的服务器来运行网络应用程序与网络服务。任何一个用户通过合适的互联网接入设备以及一个标准的浏览器都能够访问一个云计算应用程序。当前,工业界已经有很多公司聚集在云计算这样一个新型计算概念下面,分别提出了自己针对云计算的理解,用不同的技术来实现上述目标。     

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.