功率自激网络最近邻链缓存污染判决门限控制

功率自激网络在攻击容忍系统设计中,由于最近邻链缓存污染,导致对功率自激网络的攻击成功率较高,难以实现有限的拦截。提出采用最近邻链缓存污染判决门限控制的方法,通过自适应门限控制,提高对攻击信号的拦截概率。建立功率自激网络及缓存污染攻击系统模型,假设功率自激网络路由的内容流行度服从Zipf分布,得到入侵最近邻链缓存污染拦截在攻击容忍系统中的功率谱密度特征。采用最大似然估计进行攻击容忍系统中的HMM参数的更新,设计最近邻链缓存污染判决门限控制的方法,改进自适应判决门限控制算法,提高对攻击信号的拦截概率,达到消除缓存污染攻击的效果,实现对内容耗散网络的安全控制。仿真结果表明,该算法能有效实现了对缓存污染的拦截和冗余数据去除,缓存污染攻击拦截率,保证了功率自激网络的安全。     

基于随机共振概率密度特征阈值的入侵检测

网络入侵信号表现为一种多频非线性微弱信号,传统的随机共振检测方法受弱信号幅度和临界阈值约束,检测性能受限。提出一种采用随机共振概率密度特征确定信号检测临界阈值的方法,建立网络入侵信号自适应随机共振检测系统,把多频网络入侵信号采用EMD分解的方法分解为高频和低频信号两部分,使每个频段满足随机共振条件。采用相轨迹过零周期数相变判别算法提取随机共振概率密度特征,确定检测系统的临界阈值,实现对入侵信号的准确判别和检测。仿真实验表明,采用该算法进行网络入侵信号检测,能有效检测出多频非线性微弱入侵信号,检测概率具有明显提高,漏检和误报概率降低。     

基于鱼群信息链特征优选的域间流量监测

对内容中心网络的域间流量监测是未来互联网架构和网络安全监护的重要内容,通过域间流量监测,防止网络拥堵和不稳,提供网络性能,同时缩减网络冗余流量。传统方法中,对域间流量的预测采用双谱分析的方法进行特征提取,实现对局域网流量的预测,算法受到短时缓冲流量的非线性特征的影响,性能不好。提出一种基于鱼群信息链特征优选的域间流量预测算法,进行网络流量信号模型分析,构建流量监护数据样本驱动空间,进行鱼群信息链特征优选系统模型与数据预处理,得到域间流量为一阶空间权矩阵,域间网络流量信息数据表示为一个方阵,实现基于鱼群信息链特征优选的域间流量预测算法的改进。实验得出,采用该算法,在较低的信噪比下,仍然具有较高的预测精度,域间流量估计误差较低,性能较优。     

簇内数据相异粒度自适应阈值寻优熵融合算法

在无线传感网络簇内节点数据自适应数据压缩和分布式数据处理过程中,由于信息熵是一种基于信息表现特征的统计形式,通过熵融合可以提高数据汇总量,由于融合的上下限阈值具有不确定性,因此需要进行自适应阈值寻优,实现冗余数据过滤。提出一种基于相异粒度自适应阈值寻优的熵融合算法,对簇内二维信息熵进行最大寻优,进行簇内数据熵融合网络模型的构建,对簇内数据相异粒度自适应阈值寻优,剔除边缘异常数据,采用遗传算法进行数据布局,充分考虑了数据本身特性和网络因素,降低个体对适应度函数的灵敏度,使寻优曲线不断趋于平缓,调整粒子相异粒度之间的速度和位置,得到簇内数据的自适应阈值寻优熵融合结果。实验结果表明,该算法能实现融合阈值的自动寻优,滤除异常数据,搜寻有关信息熵的最大值,在冗余判定、数据传输延迟影响等问题研究中具有较大的应用价值。     

改进的CPU-GPU异构平台临界阈值分析方法

CPU-GPU异构平台临界阈值的精确确定是决定GPU并行程序运算性能的关键,传统的临界阈值确定方法采用Lyapunov指数算法,在系统相轨迹过零周期数变相时系统状态不稳,零极点出现漂移,导致临界阈值检测精度不高。提出一种改进的Lyapunov指数算法下的CPU-GPU异构平台临界阈值确定方法,实现对不同幅值递增步长下的系统相变阈值的计算。仿真实验表明,采用该改进算法求解CPU-GPU异构平台临界阈值,优化GPU并行驱动程序,算法复杂度更低,计算精度较高,能有效提高GPU平台并行运算加速比,高精度阈值能在短时间内被准确确定。     

网络威胁态势预测的抗体虚警概率阈值估计

对网络攻击信号检测中,需要对网络威胁态势预测的抗体虚警概率阈值估计,提高攻击信号检测性能。传统方法采用伪随机时频跳变的信息容量估计方法实现阈值估计和攻击信号检测,当攻击信号为非线性谐振信号时,检测性能不好。提出一种改进的网络威胁态势预测的抗体虚警概率阈值估计算法。构建多路复用器输入输出网络威胁态势预测算法,通过病毒信息特征预处理为免疫性分析提供信息特征数据基础。得到网络跳变向量和观测向量的标准正态阈值,将网络接收端和发送端数据的信息熵作为信道传递向量函数,在人工免疫进化过程中实现对免疫节点的抗体的虚警概率阈值估计,提高网络攻击信号的检测性能,降低网络威胁态势抗体虚警概率。仿真实验得出,该算法得到的估计结果精确,有效提高了攻击信号的检测性能,确保网络安全。     

伪随机时频跳变网络谐振信号的信息容量估计

在网络切换和数据通信中,会产生一种伪随机时频跳变网络谐振信号,需要对这种谐振信号进行信号抑制,提高网络的安全性和稳定性,对网络谐振信号的信息容量估计是实现谐振信号抑制的基础。提出一种基于人工免疫的伪随机时频跳变网络谐振信号的信息容量估计算法,首先进行伪随机时频跳变网络系统的总体设计,计算网络跳变信号在人工免疫进化过程中免疫节点的位置和尺度参数,引入自适应转发控制策略,构建数据信息链优先链路选择准则,预测信号的下一个跳变点,得到多路复用波束域约束指向形成信号容量的输出结果,通过对信号容量的准确估计,可以避免网络出现启动滞后、服务器负载、消息消耗以及颤抖等现象。实验结果表明,该算法对伪随机时频跳变网络谐振信号的信息容量估计精度高,抑制性能和检测性能较好,确保了网络系统的稳定。     

探究新一代视频编码标准H.264

新的国际视频编码标准H.264,目的在于能够比先前的标准,更好地改善编码效率以及误差鲁棒性。为了克服帧内宏块编码带来的大量比特数,H.264对原始输入信号采用空间域的帧内预测方法;帧间编码利用基于块的运动矢量做帧间预测,以减少不同的图像间的时间冗余。熵编码采用基于内容的自适应变长编码(CAVLC)和基于上下文的自适应二进制算术编码(CABAC)两种方法。为了减少块边界的块效应和防止累加的编码噪声的传播,H.264采用了去块效应滤波器。     

探究新一代视频编码标准H．264

新的国际视频编码标准H．264,目的在于能够比先前的标准,更好地改善编码效率以及误差鲁棒性。为了克服帧内宏块编码带来的大量比特数,H．264对原始输入信号采用空间域的帧内预测方法;帧间编码利用基于块的运动矢量做帧间预测,以减少不同的图像间的时间冗余。熵编码采用基于内容的自适应变长编码（CAVLC）和基于上下文的自适应二进制算术编码（CABAC）两种方法。为了减少块边界的块效应和防止累加的编码噪声的传播,H．264采用了去块效应滤波器。     

超密集网络中病毒攻击优化识别算法

超密集网络是根据汇聚节点的拓扑属性进行测度中心加权融合的网络模型,超密集网络中容易受到类似于DOS等病毒的拒绝服务攻击。由于DOS病毒特征具有频谱混迭特性,在超密集网络难以有效识别。目前采用联合特征检测方法进行病毒攻击信息的检测识别,性能随着环境干扰影响起伏较大。提出一种基于幅频响应带宽检测的病毒攻击识别算法。进行病毒攻击的数学模型构建和信号分析,然后设计格型陷波器实现攻击信号的干扰抑制和滤波,根据病毒攻击信号的检测带宽和攻击带宽,选取不同的陷波器频率参数和带宽参数,进行频谱特征混迭加权处理,提取幅频响应特征进行病毒攻击的带宽检测,实现攻击特征识别。仿真结果表明,采用该算法对超密集网络中的病毒攻击进行幅频响应特征提取,具有较好的抗干扰性能,准确检测识别概率优越于传统算法,在网络安全领域具有较好的应用价值。     

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.