条件接收系统中解扰器的设计与实现

介绍数字视频广播（Digital Video Broadcasting，DVB）条件接收系统的系统结构，详细分析了条件接收系统的工作原理，并给出条件接收系统的解扰器工作流程及实现方案。     

基于UDP/IP单向数据广播的加扰认证解决方案

条件接收系统是实施收费数据广播业务平台中的重要组成部分，为了实现基于DVB单向传输网络下的条件接收系统中授权问题，提出引入智能密码钥匙（USBkey）作为单向数据传输的终端用户身份认证及权限接收工具，提供一种采用对称密码体制和非对称密码体制结合安全认证方案，以实现单向传输过程中的高安全性和实时性需要。该方案在央视数据广播的条件接收系统中得以成功的实施。     

DVB通用接口的关键技术及实现方法

本文首先介绍了DVB条件接收系统的发展现状以及基本原理，然后针对机卡分离的DVB—CI通用接口技术和通用接口协议栈作了详细的阐述，对其接口从应用层到底层的协议特性和功能进行了分析和研究，并提出了通用接口的软件设计方法，实现数字电视条件接收功能，指明了DVB通用接口在条件接收系统中的作用重要性和广阔的应用前景。     

基于双重分组的密钥分配算法

实现数字电视授权管理的关键是条件接收，而条件接收的核心环节则是密钥的分配算法。本文在单一分组算法的基础上，提出了基于节目分组和用户分组的双重分组算法。与无分组或单一分组算法相比，该方案能够减少密钥传输的带宽消耗；而且，当单个用户加入或者退出授权时，只需要处理该用户的小组密钥而不影响其他小组，从而降低了系统开销，提高了系统灵活性。     

可下载条件接收系统安全性协议综述

可下载条件接收系统(DCAS)是一种双向认证授权体系,条件接收(CA)算法和密钥可以动态下载.随着互联网和数字电视为代表的数字化内容越来越丰富,条件接收系统(CAS)不断向可下载的条件接收系统(DCAS)转变已是大势所趋.本文回顾总结了主要的DCAS技术发展并对中国的DCAS发展趋势进行了展望.     

SOPCA 条件接收系统的设计与应用

数字电视条件接收系统是广泛电视信息安全的关键环节，目前国内实用的系统均为国外公司的产品，不利于国家信息安全的管理。在现有DVB（Digital Video Broadcasting)标准的基础上，提出了SOPCA （Software Platform of Connecting Appliance)条件接收系统，实现了节目传输流加扰、节目管理、用户管理、分层加密机制和IC卡控制等关键技术，完成了在自主知识产权的SOPCA嵌入式操作系统和硬件平台上的原型机应用。经过总体结构和具体性能的综合分析比较，在功能上优于其它同类系统，最后对系统功能的进一步完善进行了探讨。     

CA条件接受系统

详细论述了CA条件接受系统的原理以及关键技术，并针对实际情况给出了在数字电视系统中条件接收的实现方法。     

DVB-C条件接收系统中基于公共接口技术的机卡分离的设计与实现

本文首先介绍有线数字广播电视(DVB-C)条件接收系统的原理和相关标准，以及实现条件接收相关技术特点。然后，从运营商、用户和机项盒制造商以及CA厂家的角度出发，实现技术的选择性和竞争性，采用公共接口技术，给出了一种机卡分离方案的设计与实现。     

对客户端主动认证的条件接收系统的探讨

探讨一种基于客户端主动认证的条件接收系统。系统可以降低CA系统的处理负荷,提高网络带宽利用率,增大系统容量,同时可以支持多种业务。首先简要介绍现有条件接收系统,并指出其弊端,然后对基于客户端主动认证的条件接收系统及其关键技术进行论证,最后对系统的性能作简要分析。     

基于空分RAKE接收机的超宽带信号多径性能分析

超宽带信号由于良好的抗多径能力而适用于室内等密集多径场所的高速无线接入。该文研究的就是超宽带信号的多径信道中具体的性能指标，即在一定的信噪比条件和接收机条件下，超宽带系统传输的误码率。文中采用分空RAKE接收机，以最大组合比方式进行接收，在此基础上假设接收信号服从瑞利分布或莱斯分布，推导出了基于接收信号信噪比的不同超宽带多径信号波形及不同天线阵元数量时的误码率计算公式。之后，通过仿真对AWGN信道和多径信道的接收性能、不同UWB波形的接收性能等进行了比较，得出一些重要的具体结论。     

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.