WSN中一种改进的三维DV-Hop节点定位算法

本文在研究传统的DV-Hop3D算法基础上提出了一种新无线传感器网络定位算法。新算法在算法的第一阶段设置了跳数阈值参数以减小通信开销,并且在算法的第二阶段用可选择的平均跳距代替固定的平均跳距来计算未知节点到锚节点的距离,最后用Matlab7.1进行了仿真。仿真结果表明,该改进算法可明显提高节点定位精度,并且能有效降低网络通信量。     

基于RSSI加权的三维质心定位算法

节点定位是无线传感器网络中的关键技术之一,本文针对三维地形定位存在较大误差的问题,提出了一种将接收信号强度RSSI测量方法与加权质心定位相结合的算法。该算法的权值是用点到平面的距离作为其计算的一部分来代替传统加权质心算法中点到点的距离从而达到提高定位精度的目的。仿真表明,该算法定位精度比传统的加权质心定位精度有提高。     

无线传感器网络质心定位算法仿真研究

质心定位算法是无线传感器网络中一种经典的无需测距的定位算法。系统分析了锚节点个数、节点通信半径以及网络中节点总数对该算法定位性能的影响,并进行了仿真。通过对仿真结果的分析,在100m×100m的无线传感器网络区域内,当锚节点个数为总节点个数的10％时,针对不同的总节点个数,存在最优的节点通信半径,可以使节点定位率达到95％以上,同时具有较小的节点定位误差。     

一种改进的投影聚类融合算法研究

目前提出的大多数聚类融合算法在策略选择上未能同时兼顾聚类成员的多样性及质量,而且对高维数据的聚类结果均不理想,针对以上问题,本文提出一种改进的投影聚类融合算法,该算法主要在以往经典的投影聚类算法的基础上进行了改进,将投影聚类与分形维数结合,可对高维数据集进行降维聚类处理;而且该算法将选出最优参照成员,并设计出合理的选择策略,对部分优质成员进行选择,以得到一个更加准确的最终结果。高维数据聚类仿真实验结果表明,本文提出的改进的投影聚类融合算法与其他经典数据聚类融合算法相比,提高了聚类的有效性,大大提高了数据融合性能。     

一个无需知道节点间距离的无线传感器网络定位方法

目前无线传感器网络中,大多数定位算法需要节点间的距离信息,这些方法有很多弊端.提出一种不需要节点间距离的定位方法,可以避免上述弊端.该方法只需要2个锚节点,且锚节点的位置任意.仿真结果显示该方法有较好的性能.     

基于节点接收信号强度比值的加权质心定位算法

无线传感器网络的定位技术可分为两类:基于测距和基于非测距两种。许多学者对质心算法存在的不足提出了一些有效的改进算法。本文提出的一种基于节点接收信号强度比值的加权质心定位算法,利用待定位节点接收到的节点接收信号强度求出加权比例因子,进一步对质心坐标进行加权处理,并且与其它两种算法进行比较,文中所提出的基于节点接收信号强度比值的改进算法优于其它两种算法,有效减少了定位误差,提高了定位精度。     

非密集分布下传感网络节点选择优化算法研究

提出一种混沌差分进化和动态逃逸粒子群的节点选择优化算法,通过混沌序列的均匀遍历特性和差分进化算法的高效全局搜索能力,对传感网络中的节点能量进行分类搜索,采用Logistics混沌映射对节点进行优化分区处理,将混沌扰动量融入节点能量分区过程中,获取最佳能量节点,利用动态逃逸粒子群方法,运算无线传感网络最佳能量节点的最优位置,实现网络节点覆盖优化。仿真结果说明,所提算法可增强无线传感网络最优节点的聚类性能,具有更好的无线传感器网络动态节点选择性能,并且收敛速度快,运算耗时少。     

物联网环境下传感器路由探测算法

在物联网环境下无线传感器路由节点的准确探测实现节点的定位识别,将在传感器节点的故障监测和目标识别等领域具有较好的应用价值。传统的传感器路由探测算法采用源结点追踪定位方法实现传感器路由探测,当源节点受到外界电磁场干扰时,路由探测准确性不好。提出一种基于最短路径搜索的物联网环境下无线传感器路由探测算法。构建了物联网环境下的传感器网络分布结构模型,进行传感器路由信息的量化分析,采用最短路径搜索方法进行路由传输信息的跟踪探测,采用线性阵列结构部署路由节点,能实现路由节点探测和定位的最短路径搜索。仿真结果表明,采用该算法进行物联网环境下传感器路由探测提高了传感器节点的生存概率,路由探测能量消耗较小,路由节点定位准确,提高了目标节点的识别和监测能力。     

一种改进的DV-HOP算法在WSN中的定位研究

如何能够更好的提高节点定位一直都是WSN研究的重点,本文在DV-HOP定位算法的基础上,从误差精度,锚节点稳定度和反向学习选择-最小二乘估计来对节点定位的3个方面进行改进。首先在定位误差精度中引入混沌优化算法,其次在锚节点处理中引入稳定度概念,最后在未知节点定位中引入反向学习和最小二乘估计。改进后的算法在通信半径和拓扑结构两个方面进行了仿真实验,实验表明,本文算法能够有效的减少计算带来的定位误差,提高定位精度。     

基于RSSI优化的模型参数改进室内定位算法

定位技术在无线传感器网络中越来越引起人们的重视。针对传统基于RSSI测距的室内定位算法中,RSSI值易受环境影响、最小区域传播损耗模型参数不精确的问题,提出了一种RSSI值优化处理、模型参数进行改进的定位算法。该算法先用高斯模型对节点收到的所有RSSI值进行加权处理,然后根据RSSI值对传统最小区域损耗模型参数进行了改进,最后通过选出的三个锚节点,讨论了三圆相交于一点、一个区域的二种不同情况,并用区域质心算法得到了估计位置。实验结果表明:经过RSSI优化处理的模型参数改进定位算法,优化了测距值,使三边-区域质心定位算法的定位误差维持在1.0～1.6m,提高了定位的稳定性和精确度。     

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.     

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.     

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     

Chinese Scientists Use Earth Observation Technologies to Study and Protect Wild Camels

<正>Chinese scientists plan to apply Earth Observation technologies to protect the critically endangered wild camels(Camelus ferus).With the help of remote sensing,satellite positioning,geographical information system and wireless sensors networks,they will be able to access the distribution and population of the wild camels and protect their habitats.The project will be carried out by the International Research Center for Wild Camel Conservation,which was jointly established earlier this year by the Institute of Remote Sensing and Digital Earth(RADI)of the Chinese     

More than Skin Deep – Understand Skin Biology by Means of Dermatogenomics

<正>The Paul Gerson Unna Research Group on Dermatogenomics was founded in October 2012 at the Partner Institute for Computational Biology.The ultimate goal of the group is to understand the biology of skin and skin appendages.