无线自组网移动场景中的多媒体传输性能分析与评估

随着无线网络的迅猛发展,多媒体传榆越来越受到人们的关注.本文阐述无线自组网多媒体传输存在的挑战,并对影响多媒体传输性能的各种因素进一步地分析.仿真试验验证了多媒体传输在GOP、压缩量化参教、封包长度和封包错误率的设计之间的关系,对无线自组网场景下多媒体传输协议的设计具有一定的指导作用.     

量化因子在IEEE 802. 11 b/e无线局域网视频流传输中的图像质量性能仿真研究

在NS2-MyEvalvid模型基础上分析了量化因子对传输图像质量性能的影响,并在NS2平台上通过仿真实现了基于Evalvid机制的视频流在无线局域网环境下的传输,总结归纳了编码相关参数仿真视频流在无线网络图像传输过程中的一般方法,通过改变编码的量化因子,得到了在多速率无线局域网环境(802.11b/e)下视频流传输的图像平均延迟和平均PSNR值.分析表明,802.11e在视频流传输性能上比802.11b具有更好的表现.     

MPEG压缩域多尺度镜头切变检测算法

如何在压缩域进行镜头的切变检测一直是视频自动索引和检索中的难点。提出了一种MPEG压缩域多尺度镜头切变检测算法,在GOP、slot和B帧三个尺度上对MPEG视频流进行分析。通过对相邻I帧的检测,确定一个GOP中是否存在镜头切变;通过对slot的分析,确定镜头切变在GOP中所处的区域;通过对B帧的检测,确定镜头切变发生的确切位置。     

无线多媒体传感器网络视频流区分服务多径Qos路由算法

无线多媒体传感器网络视频流传输需要提供多样性QoS保障,传统的无线传感器网络路由协议不能很好地保证多媒体视频流数据传输, 改进多径路由算法TPGF下一跳节点选择方法,提出一种适合视频流传输的区分服务多路径Qos路由算法DSMQRA。综合考虑各路径跳数与节点剩余能量情况,在源节点与汇聚节点间找到多条优化的节点不相交路径;采用区分服务机制,重点保护视频流关键帧,提高视频流传输质量。在NS2环境下与AODV、GPSR、TPGF等算法进行仿真对比分析,实验结果表明DSMQRA算法能够有效延长网络生存时间、降低丢包率、减小帧延时、图像峰值信噪比较高,更加适合无线多媒体传感器网络视频流数据传输。     

一种用于提高流媒体传输性能的标记方法

在DiffServ网络中常用的标记法由于无法区分出数据流中每一个包在应用层的重要程度,因此不能有效提高视频流的传送质量。针对MPEG特点,采用在数据源与边界路由器两次标记的策略,通过基于NS 2的仿真系统对这种新标记策略进行对比,在带宽受限的情况下能有效的提高视频流的传输质量。     

IP网络环境下基于PI控制的实时视频流连续播放控制算法

为了克服IP网络环境下网络扰动对流媒体连续播放的影响,从接收端的角度来解决流媒体连续播放问题,提出一种基于PI控制的实时视频流连续播放控制算法.该方法在接收端使用根轨迹法设计PI控制器,通过控制播放速率,调节缓冲区的长度,实现了媒体的连续播放.为了真实地反映网络传输对接收端播放的影响,本文构建了一种基于TFRC协议的实时视频流传输控制框架.NS2仿真实验表明该方法与其他方法相比,播放质量明显提高,缓冲区出现欠载和溢出的机率明显降低,视频帧端到端平均时延明显缩小,实时性能明显增强.     

基于NS2的802.11效果异常现象仿真研究

在802.11 WLAN(Wireless Local Network)中,当一些无线节点的传输速率明显低于其他节点与AP(Access Point)间的传输速率时,将会使区域内所有节点的传输性能降低,这种现象称为效果异常(Performance Anomaly),Hyogon K等人在文献[6-7]中提出用改变封包容量和竞争窗口大小的方式来解决这个问题.文章通过在NS2网络仿真环境下,设计实验拓扑,编写性能分析脚本,对效果异常现象进行仿真并验证了上述两种方案能够有效缓解该现象并保持系统传输性能稳定.     

MPEG-2传送流传输方法的研究与改进

高品质视频流媒体的传输在流媒体业务中占有很重要的地位，同时带来许多难题．以传统的恒定速率传输变比特率压缩的视频时，播放终端往往需要很大的缓存．PCR协助的恒定速率传输是一种新的恒定速率传输机制．这个方法的详细研究表明PCBR方法利用嵌入MPEG-2传送流的程序参考时钟来定期校正传送速率，是以较高传输速率为代价减少了缓存需求．因此对该方法进行了改进，通过缩小传输时间尺度来降低传送速率但没有增加额外的缓存需求，在NS通信系统仿真软件和实验平台的测试结果都表明，改进的方法能够更好服务于流媒体传输与终端回放．     

无线自组网络QoS流的准入控制和流量控制

作者曾提出一个QoS路由和准入控制机制－QDSR,并且在小规模实时视频传输实验床上实现了这些方案。虽然QDSR的准入控制只保证每个节点有足够的可用带宽给准入的所有流使用,但并不保证每个流在较小的时间尺度上得到请求的带宽。为此,作者对QDSR的准入控制机制进行了改进并增加了流量控制机制,以满足实时应用的QoS需求。在NS2仿真环境中实现了QDSR以及对QDSR的改进。仿真结果表明,改进机制改善了QDSR的视频流的传输质量,较好地提高了视频流的吞吐率和投递率,减小了数据包的端到端延迟,并且能很好地满足包括视频传输在内的多种业务的传输需要。     

基于错误传播模型的非均等视频流丢失保护

提出一种适用于丢包网络、面向图像组（GOP）层的非均等视频流丢失保护方案。利用GOP中不同帧之间的非均等显著性,将不同数量前向错误校正包分配到GOP层的不同帧中。采用帧间包交错机制将突发包丢失分散到不同帧上,提高处理突发包丢失时的鲁棒性。仿真结果表明,在不同信道丢失模式下,该方案能提高视频接收质量。     

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。     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。