基于链路同态解析的WSN路由选择算法

通过优化无线传感器网络(WSN)的路由选择算法,实现负载均衡,节省WSN节点的能量开销。传统的路由选择算法使用基于汇聚节点随机链路分析的路由选择算法,控制网络中节点的密度实现路由选择,算法受到外界干扰较大,性能不好。提出一种基于链路同态解析的WSN路由选择算法。设计WSN节点的能量调度算法,提取网络传输的数据多路复用器输出端口的数据,找到经过最短路径数目最多的边并将它从网络中移除,采用能量剩余度同态解析模型,把WSN的能量节点变换到链路同态解析波束域中,实现WSN路由选择算法改进,实现WSN节点的能量调度,提高WSN的负载均衡能力。仿真结果表明,该算法能优化WSN的路由选择,节点的平均能量消耗最低,提高了WSN的可靠性和生存周期。     

基于负载平衡的无线传感器网络路由算法

为了提高无线传感器网络的能量利用率和延长网络的生命周期,本文提出了基于负载平衡的无线传感器网络路由算法。首先,将网络划分成多个网格,根据网格内节点的负载情况定义网格的状态,结合网格的地理位置和网格负载状态选择路由网格;其次,根据节点剩余能量和负载大小在选择的网格内选取一个合适的节点开始数据的收发工作;最后,通过模拟实验将本文算法与GPSR算法和GEAR算法进行比较。仿真结果表明,该算法有效改善了网络的负载均衡,延长了网络的生存期,并提高了网络的吞吐量。     

基于自适应相位检波的无线网络信道优化设计

根据无线传感网络中簇头点生成过程中的多径能量特性,提出一种基于自适应均衡抵消的相位检波能量检测算法。建立无线传感器网络信号与信道系统模型,设计无线传感器网络信道自适应均衡算法,采用横行型自适应FIR滤波器进行自适应降噪滤波处理。使用相位检波方法对UWB无线传感器网络通信信道进行能量检测和优化设计。实验结果表明通过自适应相位检波能量检测方法,能最大程度上削弱无线传感网络信道慢衰落影响,降低网络功耗,提高能量检测性能和信道传输效率,实现了无线传感器网络信道优化设计。     

基于负载-功耗特征测试的WSN配网路由修复方法

为了增强无线传感网络(WSN)的自适应性,降低WSN功耗,需要进行配网路由修复。传统的路由修复算法采用能量感知模型,设置负载平衡的CTP路由协议估算剩余能量,算法没有考虑路由最大角度的负载平衡问题,路由修复性能不好。提出一种基于负载-功耗联合特征测试的WSN配网路由修复算法,设计了基于ICTP协议的WSN网络模型框架,综合考虑簇头的剩余能量及其与Sink的距离对它的生命周期的影响,进行路由选择设计,采用负载-功耗联合特征测试方法,实现WSN配网路由修复改进。实验结果表明,该算法进行WSN路由修复设计,节点剩余能量方差一直维持在最低,有效地均衡了网络负载,平衡了网络能量消耗,节点生存性较大,提高能量的有效利用率。     

高负载MANET环境下移动自适应多接口多径路由算法

移动自组织网络(MANET)是一类连接移动设备的自适应无线网络,为提高网络传输质量优化链路状态,文中以高负载MANET为背景环境,提出基于灰色区域预测的自适应多路径改进路由算法。以OLSR路由协议为基础,与卡尔曼滤波预测法相结合对链路网络连接状态实行估测,在链路失效前计算新路由,减少计算新路由耗时;估测链路时效性时对网络中灰色区域进行处理,邻居节点为灰色区域内直接判定为无效节点,确保存在稳定通信链路。基于上述稳定通信链路,以衡量链路质量为标准,采用多路径冗余传输及多路径负载均衡改进路由算法提高端到端传输可靠性;运用多路径冗余传输方式,提升端到端递交率;利用多路径负载均衡传输方式使更多节点参与转发,提高端到端吞吐量。实验证明,运用文中自适应多路径改进路由算法可有效提升网络传输质量。     

MEIL――一种高吞吐量的无线网状网路由协议

由于无线网状网具有多网卡多信道，节点移动性低等特性，使用传统的基于最短路径的移动Ad Hoc网络路由协议并不能获得良好的性能。为此本文提出了一种新的无线网状网路由协议――MEIL算法，通过引入链路干扰度，节点负载度等概念，综合考虑了无线信道的丢包率，链路干扰以及节点的负载等多种重要因素，来确定路由判据，选择链路质量好、干扰小、负载轻的路径来传输数据，有效地提高了网络吞吐量。仿真结果表明，MEIL算法比AODV路由协议和DSDV+ETX算法更适用于无线网状网，在各种业务环境下其吞吐量，时延，到达报文量等性能均具有更好的效果。     

基于修剪算法的无线传感器网络能量消耗研究

无线传感网络有大量的传感器节点组成,所以在无线传感网络中传感器节点的能量消耗是主要的能量消耗部分。基于分簇协议引起的负载不均衡现象,采用修剪技术对节点的位置、担任簇头节点的次数和剩余能量三者进行加权和分析的这种能量均衡算法,采用动态调整机制选择簇头节点。实验结果表明该算法增加传感器节点的使用时间,有效延长无线传感网络的寿命。     

无线传感器网络中一种基于遗传算法的路由算法研究

在能量采集无线传感器网络中,由于传感器具备获得能量的能力,因此传统的基于能量消耗最小化的路由算法不再有效。为此,本文提出了一种能够应用于该新型传感器网络的路由算法,该算法能够在给定的能量输入约束下,最优化无线传感器网络的路由转发性能。本文给出了该路由算法的基本原理和实施步骤,并采用仿真实验验证了该算法的可行性和有效性,最终表明本文提出的路由算法不仅能够应用于无线传感器网络,而且能够在广泛的应用场景中获得推广。     

强干扰下的无线传感器网络鲁棒性通信节点选择模型

无线传感器网络在强干扰环境下,通信节点受到干扰影响和能耗限制,导致节点之间的通信信道失衡,需要对无线传感器网络通信节点进行鲁棒性选择,提高网络通信的覆盖和均衡能力。传统方法中对无线传感器网络鲁棒性通信节点选择采用节点间互助转包轮换路由分发协议,由于邻居节点的自私性导致对节点通信的抗干扰性不强。提出一种基于自适应分层能量均衡的强干扰下的无线传感器网络鲁棒性通信节点选择模型。构建无线传感器网络的通信节点布局模型,然后进行通信节点的最优节点密度分布设计,基于自适应分层能量均衡方法实现对强干扰下的无线传感器网络鲁棒性通信节点选择模型改进。仿真实验结果表明,采用该模型进行强干扰下的无线传感器网络鲁棒性通信节点优化部署和选择,降低了数据传输丢包率和延迟,减少了计算开销,提高了网络的连通性和覆盖度,性能优越。     

基于无线传感器网络的革命遗址保护研究

为推动红色旅游,急需对原中央苏区革命遗址进行保护。提出一种部分节点移动的无线传感器网络,构建一个对革命遗址有效保护的环境监测自动化系统,给出了系统的总体结构。在路由通信方面采用贪婪地理路由协议进行路由选择,对网络拓扑变化有较好的自适应性,实现了无线传感器网络能量高效的自适应信标交换和负载均衡贪婪转发策略。仿真实验表明,该网络减少了数据分组的丢失,缓解了在高业务量情况下的拥塞程度,具有较高的实用价值和应用前景。     

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.     

To serve and promote science development via innovation

CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing.     

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.     

Tracing the origin and early radiation of birds——Paleornithologist ZHOU Zhonghe

With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants."     

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.     

Monoculture Rubber Plantations Have Negative Ef ects on Controlling Splash Erosion

<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence