802.11n2．0草案标准无线路由器——性能与兼容性俱佳

众所周知,现在主流的无线网络标准是802．11g,其实际传输速率仅为22Mbps左右,而1080p高清电影的码率普遍在30-50Mbps．根本无法通过802．11g无线网络流畅地在线播放1080p高清电影。另外对于企业用户来说也越来越需要具有更高传输速率和更大覆盖范围的无线网络设备,2006年市场上就已经出现采用802．11n1．0草案标准的无线路由器,     

巧用QQ旋风让视频支持手机

如果用户想将自己喜欢的影片放到移动设备上观赏,就需要先将视频转成移动设备支持的格式,这样不但要安装专门的转换软件,而且转换高清格式的时间几乎都和观看一部电影的时间差不多了,还要占用大量的机器资源,转码的同时电脑基本上干不了别的事。而"QQ旋风"推出的离线转码功能,就是来帮助解决这一问题的。     

看高清，其实很简单 LimHD 200i硬盘播放器

H264格式的高清电影由于能够以更低的码率得到更高的画质，从而使HDTV电影的容量大幅度降低，因而非常受用户欢迎。但是能够解码H.264格式的高清播放设备的缺乏，导致我们目前观看H.264格式的电影，惟有通过电脑。LimHD 200i硬盘播放器的出现，无疑为我们提供了一种非常方便的高清影片播放方式。相比其他高清播放设备，LimHD 200i硬盘播放器最大的特点就在于它不仅可以支持MPEG－2解码，     

基于无线网络环境移动流媒体码率自适应研究

基于校园无线网络环境,研究了流媒体视频码率自适应技术.利用分布式实时转码系统保证直播流视频转码的实时性,并根据校园无线网用户的特殊性,研究了首次接入视频码率选择策略,以减少码率切换次数.实验证明,这种方案在无线网络环境发生变化时,保证了视频播放的流畅性,为用户提供了友好的体验.     

高清音频全接触 带你认识高清音频

高清电影已经成为目前最火热的话题，其完美的画面表现征服了我们每一个人。但是，1080p的高清晰画面只是高清电影的一半，另一半则是声音的完美还原。BD和HDDVD高清影碟在实现画面品质提升的同时，音频鳊码更是采用了码率极高的无损压缩技术，使音频的回放品质近乎完美。因此，要完美享受高清电影，需要Full HD显示设备，高清音频解码和放大设备的完整配套。但是普通用户在观看高清电影的时候往往只注意到了高清图像的回放效果，而忽略了高清音频。本文将带领大家一起探寻被我们忽视的高清音频世界、以达到高清电影的最完美体验。     

多目标遗传优化ABC支持型切换决策机制

异构无线网络中的切换决策机制,需要综合考虑应用服务质量(quality of service,QoS)需求、服务费用、用户偏好、移动终端状态和接入网络状态等多维因素,进而实现用户和网络提供商的双赢.引入模糊数学和微观经济学知识,对影响切换决策的因素进行了刻画.在此基础上,提出了一种多目标遗传优化总最佳连接(always best connected,ABC)支持型切换决策机制,通过精英选择和个体迁移提高决策质量,基于博弈分析,寻求多终端对多接入网络的最佳切换决策方案,使用户和网络提供商效用达到或接近Nash均衡下的Pareto最优.仿真实验结果表明,该机制是可行和有效的,同现有机制相比具有更好的性能.     

基于DASH标准的码率平滑切换算法

针对现有的基于超文本传输协议的动态自适应流（DASH）码率自适应算法在无线网络环境中码率切换频繁以及平均码率偏低的问题，提出一种基于DASH标准的码率平滑切换（RSS）算法。首先，算法的带宽检测机制利用滑动窗口对历史下载速率进行取样以计算带宽偏移系数，根据带宽偏移系数的大小初步判断带宽的波动情况，并对波动较大的情况进一步确定是否存在一致性变化趋势，从而区分出带宽的持续变化和短暂抖动，同时计算出相应情况下的带宽预测值；其次，算法的码率决策模型综合考虑带宽波动情况、缓存占用和变化情况及带宽预测值等，并且分别采取快速缓冲（FB）、缓慢切换（SS）、快速上升（FR）、约束下降（LD）、稳定保持（SH）策略和休眠机制对码率选择过程进行动态控制。实验结果表明，与基于模糊逻辑的码率自适应算法以及吞吐量调节驱动的码率自适应算法相比，该算法在播放开始时能够在最短时间内将视频码率提升到最佳水平，提高视频播放过程中的平均码率，在播放过程中带宽骤变和交替性频繁波动情况下都能够很好地维持视频码率的稳定，将切换次数降到最低，从而获得良好的无线端视频体验质量。     

无线信道视频流编码与自适应传输方案

由于无线信道的时变特性和移动设备有限的能量资源,保证无线网络视频流传输的Qos是一项比较困难的任务。文章提出了一种基于无线网络的视频流自适应传输架构。这个架构不仅动态的估计了无线网络的状态进行自适应传输,而且同时执了差错控制和功率控制。通过分析网络的状态和视频流的特性来动态分配资源,提高了端到端的QoS。     

iPad视频转换 断网也能流畅看电影

New iPad大屏幕适合干什么?看高清电影是很多朋友不约而同的选择,过去总是苦于没有适合的设备来观看1080P高清视频,现在有了New iPad自然是非高清不看了。目前各大热门视频网站纷纷推出了iPad客户端应用方便iPad用户在线点播电影、电视剧、综艺节目、新闻资讯等热门视频观看,不过连接Wifi是必要条件,如果在没有网络的情况下想要用iPad看电影怎么办?那也不怕,使用专门     

移动流媒体用户QoE评估模型

HAS(HTTP Adaptive Streaming)能够实现流畅播放和视频质量的平衡,为用户提供更好的服务质量体验。大多数基于HAS的流媒体用户体验质量(Quality of Experience,QoE)模型考虑了当前系统或网络条件,但对用户所处环境的客观影响、用户心理因素的考虑较少。面向移动流媒体客户端的应用场景,从客观感知影响参数和心理效应影响参数两个方面来考虑移动端流媒体的QoE影响因素,设计用户QoE评估模型。提出移动设备抖动状态检测和用户观看位置检测方法,并将设备抖动状态、用户观看位置与流媒体服务质量相结合,再根据心理学系列位置效应来综合评估用户的质量体验情况。最后通过实验证明了所提的用户QoE模型能够提供准确有效且符合用户实际体验的QoE评估结果。     

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.