基于Richards模型的数据中心骨干网络带宽分配策略

针对数据中心间骨干网络中存在大量突发性强的小流而难以实时跟随流量变化对其进行带宽分配的问题,提出了基于Richards种群生长模型的数据中心骨干网络带宽分配策略(RBA)。该策略采用闭环反馈控制系统实时分配带宽,以基于Richards曲线设计链路的反馈控制因子作为此系统的反馈量,可对突发流量做出平滑响应,并根据时延敏感性的不同,采用不同的异速生长参数得到不同的流量速率增长曲线,以满足时延敏感流量的QoS需求。在Mininet平台上进行了实验仿真并与典型的带宽分配策略进行了对比,结果表明RBA不但可对突发流量提供较高的带宽分配效率,还确保了各流对带宽资源竞争的公平性。     

自适应门限的EPON 动态带宽分配实现

EPON(Ethernet passive optical network)是解决宽带接入中瓶颈问题的关键技术.为了实现EPON中共享上行带宽的公平和有效分配,以及不同分类业务的QoS保证,提出了基于门限的动态带宽分配算法.该算法根据ONU(optical network unit)的带宽请求和门限值授权分配带宽,实现了3种基于反馈控制理论的自适应调整门限方法并分析了其优缺点.模拟实验结果表明,与其他算法相比,该算法能够减少平均包时延,提高网络吞吐量.     

多业务流量预测动态带宽分配方法

静态带宽资源分配方法或基于业务分类的动态带宽分配方法等很难适应业务流特性,无法保证各级业务的服务质量。设计了流量预测及带宽分配模型,给出了流量预测计算方法,提出多业务流量预测动态带宽分配方法（MSTPDBA）,该方法基于业务预测流量的大小进行可用带宽的重新分配。仿真实验证明了MSTPDBA的有效性,能控制不同业务的时延,并提高了系统带宽资源的利用率。     

一种用于无线传感网络的支持QoS的PD-DWDBA算法及其优化

DBA算法大多是基于单波长情况而制定的，为了研究多波长的情况，提出基于预测的多波长动态带宽分配算法(PD-DWDBA)。考虑到网络中不同类型业务对网络时延和带宽的要求存在差别，对不同优先级的业务采取不同的分配方案，提出支持QoS的PD-DWDBA。以first-fit策略将带宽先分配给具备高优先级业务，确保高优先级业务获得所需带宽；利用WF-DBA策略对剩余各低优先级业务实施分配，利用BP网络模型完成各优先级业务的预测，实现带宽的分配功能。依次以丢包率、包延时、带宽利用率指标分析BP网络预测对网络性能提升的效果，实验结果证实网络服务水平显著提升。     

基于角色控制的天基网带宽分配方法

针对天基综合信息网（SBN）稳定性比较差的缺点,提出一种基于角色控制的动态带宽分配算法（RCBA）,基站将服务连接的带宽请求按照优先级分类,在设定预留带宽的基础上允许抢占带宽。仿真实验表明,相比传统带宽分配算法,RCBA算法降低了时延,减少了丢包率,较好地满足了天基网的应用需求。     

多重链路时延优化动态可用带宽分配算法

为了优化多重链路多业务环境下的时延,首先分析了带宽分配及链路中数据传输时延计算方法,提出一种时延优化的动态可用带宽分配算法(DODBA)。该算法基于不同优先级业务的时延比较实现了剩余可用带宽的重新分配。仿真实验证明了DODBA的有效性,能控制各链路不同业务的时延,并提高了系统带宽资源的利用率。DODBA可用于解决大型宽带网络接入控制中的实际问题。     

基于自相似排队模型的星上交换输入缓存分配算法

针对空间信息网络的自相似分组业务流、星上交换节点的有限缓存资源,提出一种基于自相似排队模型的星上交换输入缓存分配算法。构建了基于VOQ的空间信息网络星上Crossbar交换节点模型,依据空间信息网络业务流的自相似性,通过建立虚通道自相似排队模型,估算出各个虚通道的缓存溢出概率,再根据其溢出概率采用贪婪算法来实现缓存资源的优化分配。仿真分析了在自相似分组业务流下优化分配算法和均匀分配算法的性能。结果表明,在相同缓存开销下,优化分配算法可以有效降低分组的平均时延;在同等分组平均时延下,分组业务流自相似程度为0.8和0.6时,可分别节省缓存开销约25%和17.4%。     

流媒体服务器比例带宽分配的改进算法

结合比例带宽分配与转码技术,提出了基于转码的流媒体服务器比例带宽分配算法.该算法将服务器分配与调度资源的过程细分为一系列充分小的时间片,在每一个时间片里,服务器根据已有的资源分配与预测的带宽需求情况进行综合分析,动态地给每一个请求分配带宽.建立的数学模型表明了该策略能保证所有请求都能在不同的负载下获得最佳的带宽分配.仿真实验结果表明,该策略不仅可以充分利用系统资源,而且还能保证不同优先级请求之间资源的公平分配.     

IEEE 802.16网状网络中基于队列的带宽分配

IEEE 802.16网状网络中分布式调度的建立时间对时延敏感类业务影响较大。针对该问题,使用基于令牌分发的循环轮转服务机制向邻居节点请求或授予带宽,预测调度控制消息发送间隔内到达的数据包量,据此完成三次握手过程,保证业务流公平带宽分配并减小数据包因为三次握手过程造成的队列缓冲时延。NS2仿真实验验证了该算法的有效性。     

基于用户带宽的网络流量仿真的研究

ON/OFF模型虽然可以生成具有自相似和长相关特性的网络流量,但是不能够模拟用户带宽变化对网络流量的影响。因此,以ON/OFF模型为理论依据,提出一个新的网络流量仿真模型。该仿真模型以用户数据传输请求作为数据源,以用户网络带宽决定用户传输速度,并且可以根据网络流量动态的调整用户带宽。实验结果表明,该网络流量仿真模型能够较好地反映真实的网络流量,并且通过调整用户的数据传输请求和动态地分配用户的网络带宽,有助于模拟用户带宽变化对网络流量的影响,能够为用户的网络带宽服务提供预测手段和管理依据。     

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.