延时信道信息下一种新的AF中继选择算法

提出单源、多中继、单目的节点的放大转发中继系统中一种新的中继选择算法.考虑源端通过反馈获得第一跳链路过时(延时)的瞬时信道状态信息,推导了中继选择方案的中断概率闭式表达,并基于该表达式,以最小化条件中断概率为目标,提出利用信道相关性信息辅助的中继选择新方案.仿真验证了新方案相比于传统方案有明显的性能增益.     

密集网络中用户接入分布式干扰协调控制方法

通过对密集网络中用户接入路由协议的分布式协调控制,提高网络的抗干扰能力和数据准确收发能力。传统方法采用路由扩频分层融合方法进行密集网络中用户接入分布式干扰协调控制,随着汇聚节点的增多受到的干扰增强,在信噪比较低的情况下网络用户进行数据通信的抗干扰性能不好。提出一种基于混合差分粒子群调度的密集网络中用户接入分布式干扰协调控制方法。首先进行了密集网络用户接入路由链路模型构建和设计,采用Internet Protocol Version 6(IPv6)互联网协议进行数据融合和信道均衡,采用混合差分进化方法对传统的粒子群算法进行改进,提高了密集网络中的路由算法的抗干扰性能,实现分布式干扰的抑制和路由链路的协调控制。仿真结果表明,采用该方法进行密集网络中用户接入的分布式干扰协调控制,有效提高了用户接入节点的连通性能和数据收发能力,提高了数据收发的准确性和网络的生存周期,抗干扰性能强,展示了较好的应用价值。     

基于稀疏重构的多用户MIMO网络联合反馈策略

为解决多用户MIMO-OFDM网络反馈链路所面临的反馈链路开销大与频谱效率低的问题,提出了一种基于稀疏重构的多用户MIMO网络联合反馈策略。该策略将压缩感知应用于多用户MIMO-OFDM网络有限反馈,首先在接收端对由信道估计得出的信道状态信息进行稀疏重构,以最大程度降低反馈链路开销,然后观测矩阵自适应地反馈到发送端,在发送端通过压缩感知重构策略重构原始信道信息,有效降低了反馈链路处理复杂度和传输的数据量。仿真结果表明,在反馈量相同的前提下,该策略的反馈开销和频谱率性能都优于传统有限反馈机制,降低了通信链路的整体开销,并一定程度上改善了网络拥塞。     

水声跳频通信系统的设计与实现

本文以工程需求开展水声跳频通信的研究,针对复杂信道特点提出一套适合于多途环境下的水声跳频通信方法,并构建了通信系统。开发数字信号处理算法,在水池实验条件下,实现了跳频编码信号的解调,恢复出基带通信信息。     

大规模MIMO系统中联合最强用户冲突解决的最大似然信道估计方案

在多小区大规模多输入多输出(MIMO)系统中,针对各小区复用相同导频序列进行信道估计存在有导频污染问题,提出了一种大规模MIMO系统中联合最强用户冲突解决的最大似然(ML)信道估计算法。该方法联合最强用户冲突解决(SUCR)算法和循环前缀的最大似然信道估计算法,先在小区用最强用户冲突解决方案减轻用户之间的竞用相同导频的干扰,减少竞争导频的用户数,提高系统的成功接入用户数数量,然后再用循环前缀的最大似然的信道估计算法,对处理后的导频序列的信道进行信道估计,以获得较为准确的信道状态信息。仿真结果表明,提出的算法对比分析传统ML算法和MMSE算法能够得到更好的归一化均方误差和系统能量效率,并且可以较明显地减轻导频污染对信道估计的影响。     

多再生中继系统中基于多播线性收发机辅助的多流多播策略

针对多再生中继系统中容量受限于中继到目的端链路的场景,提出一种多播线性收发机辅助的多流多播策略来提高系统容量.策略中,利用数据共享中继的联合传输提高中继到目的端链路容量,并在源端到中继链路进行多流多播传输以实现数据到中继的有效分发.针对源端到中继的多流多播,还设计一种多流多播收发机,有效地处理多播数据流,并抑制不同数据流间的干扰.仿真结果验证了提出的策略在中继到目的链路质量较差时对系统容量的显著增益.     

物联网传感网络路由改进设计算法研究

物联网传感网络广泛应用在环境监测和模式识别等领域,物联网传感网络的路由协议通过多跳汇聚树路由网络进行组网,随着节点数目的增多容易出现链路故障,需要进行路由修复和改进设计。提出一种基于链信息头抽取和信息源定位的物联网传感器网络路由改进设计方法。构建了物联网下传感器网络的组网和路由探测模型,采用链路信息簇头节点抽取和信息源定位方法进行链路路由信息数据聚集,采用预加重方法广播竞选簇头节点的能量损失,通过双向链路估计得到路由节点的数据传输协议,采用链路节点能量和Sink节点距离分层方法实现路由优化设计。仿真结果表明,采用该方法进行物联网传感网络的路由优化设计,提高了链路信息收发和数据传输的可靠性和吞吐量,性能优越。     

多源日志的数据挖掘方法研究

总结了安全管理系统中多源日志的数据挖掘方法的步骤、技术、类型和作用,针对海量日志的挖掘方法无法对事件进行深层关联分析的现状,分析了基于设备资产和漏洞的挖掘的方法和步骤,然后给出了基于攻击场景挖掘的思路和算法,并举例探讨了基于规则的挖掘方法,最后分别针对多目标和单主机的攻击,提出了基于事件序列的自动挖掘,给出了相应的算法.     

基于频域分段的MIMO-OFDM系统信道估计算法实现

针对目前MIMO-OFDM系统信道估计算法运算复杂度高的问题,本文着重研究低复杂度的基于导频的信道估计算法。首先,发送导频信息获得导频子载波处信道参数,然后利用插值算法来恢复出整个信道的信道参数信息,最后采用运算复杂度低的频域分段最小均方误差(SMMSE)算法,并与基于训练序列的LS和MMSE这两种基本的信道估计算法进行了比较。     

基于调和均值公平的多小区干扰协调功率分配算法

针对正交频分多址无线蜂窝系统下行链路,提出一种基于用户速率调和均值公平的多小区干扰协调功率分配算法.为了优先减轻小区边缘用户的同频干扰,把多小区功率分配问题建模为一个以用户速率调和均值公平为目标的非凸优化问题,并提出一种迭代算法求其接近最优解.该算法需要相邻的基站通过交互干扰信息进行相互协作.仿真结果表明,该算法在保证小区中心用户有较高通信速率的同时,极大提升了小区边缘用户的通信速率.     

Students' Reactions to the Introduction of Videoconferencing for Classroom Instruction

This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.     

Cooler temperatures inductive to locust outbreaks

Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.     

Exploring Multiplexity: Social Network Structures in a Computer-Supported Distance Learning Class

A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.     

Low doses of a red wine ingredient figh diabetes in mice

Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.     

The Role of Intermediating Institutions in the Diffusion of Electronic Data Interchange (EDI): How Industry Associations Intervened in Denmark, Finland, and Hong Kong

Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.     

How Electronic Publishers are Protecting Against Piracy: Doubts About Technical Systems of Protection

The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.     

Rough Justice: A Statistical Assessment of ICANN's Uniform Dispute Resolution Policy

Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP.     

Prevalence of soft neurological signs in Chinese people

Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.     

Molecular motor assembly of a biomimetic system

Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction.     

Our Own Devices: Heterotopic Communication, Discourse, and Culture in the Information Society 1

The main premise of this article is that in information societies generally, and in virtual social contexts particularly, a distinctive style of interaction to facilitate the communication of difference, heterotopic communication , has emerged. It rests on two cultural foundations: an ideological belief in the positive, socially integrating power of communication, and a prevailing ethic of instrumental rationality, subjective individualism, and strategically practiced self-interest. The former is demonstrated by the use of simulation and spectacle as sources of information; exhibitionism/voyeurism as a communicative style; and the awareness of surveillance. The latter is seen in the competitive use of knowledge as a commodity; a surface globalism masking deep parochialism; lateral as well as vertical information inequity; and the use of public versus private as strategies for engagement rather than as spaces. Those who engage in heterotopic communication resort to their 'own devices' both in the sense of personal agendas, strategies, interests, and interpretations, and in the form of the telecommunication tools that help realize them. These personal and technological devices allow individuals with the right educational and technical resources to avoid exposure to disagreement, difference, or other information that does not serve their direct purposes or reflect their particular views of the world; yet they also help convey the appearance of openness, availability, and cooperation. This style of interaction is used strategically in combination with information and communication technologies to gain social or economic advantages, but it may encourage social separatism and parochialism, inhibit the negotiation of disputes, and emphasize competing interests.