OPNET仿真技术在网络规划设计中的应用

网络仿真是一种利用数学建模和统计分析的方法模拟网络行为,从而获取特定的网络特性参数的技术.网络仿真作以其独有的方法为网络规划设计提供客观、可靠的定量依据,从而缩短网络建设周期,提高网络建设中决策的科学性,降低网络建设的投资风险.本文介绍了一种强有力的网络仿真工具-OPNET,分析了其主要特点、三层建模机制以及仿真方法和步骤,最后通过一个实例来讨论了OPNET技术在具体网络规划和设计中的应用.     

层次型IPv4网络QoS算法

网络服务质量Qo S在层次型网络中要求更高.从OSI参考模型的第二层与第三层出发,分析了传统的Qo S体系结构和三种Qo S模型的工作原理、优缺点以及网络应用环境.设计了将Int Serv与Diff Serv模型相结合的互补算法来保证层次型网络的服务质量.仿真结果表明,此模型能够从传输延迟、丢包率、延时抖动和网络吞吐量等多个方面提升网络的Qo S.     

新型广义径向基函数神经网络结构研究

提出了一种新型的广义径向基函数(RBF)神经网络,并研究了该网络的学习方法.不同于传统三层结构的RBF网络,广义RBF网络增加了基函数输出加权层,并在输出层采用超曲面去逼近任意的非线性曲面.实例仿真结果表明,与传统的RBF网络相比,该网络具有良好的逼近性能,收敛速度快,可逼近任意多变量非线性函数.     

第三层交换技术在园区网上的应用与实现

随着可网管的三层交换机的广泛应用，分层的概念已成为组建网络时应遵循的一个规律和原则。根据这个原则，网络应划分成以下三层：核心层、汇聚层和访问层。文章针对某企业园区网存在的速率瓶颈问题，详细讨论了基于第三层交换技术的主干网络拓扑结构，并提出升级改进方案，最后用网络仿真软件BOSON NETSIM对第三层交换进行了仿真实现。     

基于OPNET的移动WiMAX网络仿真

结合OPNET和IEEE 802.16e协议,采用OPNET的三层建模机制、基于包的通信机制和离散事件驱动机制首次完成对移动WiMAX网络系统级建模.建模内容划分为无线通信网络建模,IEEE 802.16e协议建模,统计信息建模三部分.通过仿真获得了移动WiMAX网络在轻负载情况下的时延性能.     

基于组态的网络虚拟实验平台的研究

在分析现场实验和用户需求的基础上,提出了新的基于组态的虚拟实验平台系统.该系统以界面控制层、底层运算层、后台数据库三层结构对仿真实验进行支撑,模块的思想贯穿于界面控制层和底层运算层;同时依托网络的浏览器/服务器模式,让虚拟实验系统实现远程操作.以现场喷管实验在该平台上的虚拟化为例,进一步阐述了该平台系统的应用方法.结论:通过模块化仿真,同时利用数据库技术和网络技术,该虚拟实验平台能够达到现场实验与用户的要求,具备良好的通用性.     

基于自定义数据包的网络业务流建模

采用OPNET Modeler仿真软件,分析企业的网络业务背景和OPNET Modeler的三层建模机制,自定义数据包产生模块和数据包处理模块,并在此基础上建立某企业的进层-节点-网络三层模型,同时对模型进行网络吞吐量及链路利用率的统计量收集。     

基于Boson NetSim的交换路由实验仿真

基于Boson Netsim仿真软件,提出二层交换和三层路由的综合实验方案。设计了模拟拓扑结构图,分析了VLAN,路由协议RIP和802.1Q的配置命令。对虚拟网络进行了仿真测试,实现了虚拟网络的通信。结果表明所组建的网络是可行的。     

两层复杂网络的特性及其抗毁性分析

构建并分析两层复杂网络的特性及其抗毁性.试图寻找两层复杂网络中具有较优抗毁性网络模型的层间链接方式和层内链接方式.基于不同的层内(层间)链接算法构建三类两层复杂网络模型并对其拓扑指标进行分析;基于最大剩余连通分支粒度分析三类复杂网络的抗毁性;通过数值仿真刻画出了具有较优抗毁性的网络拓扑结构及其特性.结果显示:当层间链接概率pn趋于10-3时,三类两层复杂网络的度分布特性均保持单层复杂网络的特性;层间链接概率pn趋于10-1时,无标度算法生成的两层复杂网络逐渐失去无标度性;蓄意攻击和随机攻击策略之下,随机算法构建的两层复杂网络具有较优抗毁性;蓄意攻击策略之下,通过无标度算法和小世界算法构建的两层复杂网络的抗毁性与层间链接概率成正比.     

OPNET软件平台下悬浮式弹载通信干扰机的仿真实现

以压制扫频式干扰为基础,设计并实现OPNET软件平台下悬浮式弹载通信干扰机的进程-节点-网络等三层子模型.详细说明各仿真参数的含义,并依托特定仿真场景进行验证.结果表明干扰机仿真模型是可行的,相关结论能够为弹载通信干扰性能研究提供参考.     

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.