高功率微波弹倾斜起爆时对通信信号干扰抑制器设计与实验分析

针对军事对抗中高功率微波弹倾斜起爆时对通信信号的干扰在小区域内多层重叠区,抑制效果不佳的问题,提出一种可抑制高功率微波弹倾斜起爆时干扰的自适应滤波方法,并通过实验验证。首先对不同频率、不同增益的通信信号进行频率放大,使信号从噪声高功率微波弹倾斜起爆时干扰的环境中被有效提取,引入最小均方误差算法调整滤波参数,收敛信号的精度;应用最小二乘法优化滤波参数,对通信信号中的高功率微波弹倾斜起爆时干扰噪声实现抑制或者减弱。测试实验中,有效证明了该自适应滤波器实现了对通信信号的高功率微波弹倾斜起爆时干扰噪声抑制。     

室内分布系统防干扰方法研究

随着3G网络,视频技术,多媒体技术等不断的进步与发展,对网络通信的质量提出了更高的要求,通信网络的防干扰能力成为通信行业关注的热点问题,如何对提高系统的防干扰能力与通信质量,相当重要。本文通过对室内分布系统的干扰机理、类型与原因进行分析,在此基础上进行信号的杂散干扰与互调干扰的研究,通过采用隔离度的计算方法,有效的隔离了干扰,并在一些防治干扰措施的采用下,有效的提高了通信信号质量。     

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。     

网络时变信道点跟踪算法研究与仿真

提出一种基于网络信号解扩的测距码测距的时变信道点跟踪算法,设计网络线性可调滤波器,可以校正和补偿系统特征衰减,通过自适应调整网络数据信号发送滤波器和接收滤波器的权系数,使均衡器的相频特性与信道频率特性的逆向量相等,构建基于网络的信号解扩测距码频点信号模型,设计构建11级线性移位寄存器,生成网络信号测距码,计算时变信道点信号的测距码功率谱密度,经网络信号解扩的测距码时变信道点跟踪相关处理,提高解扩处理增益。仿真结果表明,该算法能使误码率最低,窄带干扰环境下,由于利用扩频伪码的离散频谱特性,对等效载噪比的影响较少,在网络远程通信和网络通信防御等领域具有较好的应用价值。     

非均匀分布多跳网络通信节点介质访问控制

在非均匀分布多跳网络中,需要对通信节点进行介质访问控制设计,提高网络通信节点的吞吐性和安全性。传统方法采用多路复用器输出端口信号检测方法进行非均匀分布多跳网络通信节点的介质访问控制,产生强烈的信道畸变,节点的通信控制性能不好。提出一种基于协同调度的混合协议激振算法的非均匀分布多跳网络通信节点介质访问控制方法。将非均匀分布多跳网络通信节点分簇模型的服务器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,构建协同调度混合协议服务器模型,求得非均匀分布多跳网络时延扩展与信道特性测量均衡后的频谱,可以有效提高信息传输的保真度。仿真结果表明,采用该算法可以有效提高对多跳网络的通信节点介质访问控制性能,提高了通信节点的吞吐性能,降低重复传输次数,保证非均匀分布多跳网络通信的安全性和保真性。     

入侵破坏后的网络信道优化通信模型研究

为了提高入侵破坏后网络信道通信性能,按照入侵破坏后网络信道的衰减特征,融合自适应比特以及功率划分方法,提出基于节点可信度子信道等效改进的网络衰减信道通信优化方法,采用基于节点可信度的信道分配方案,对关键链路优先分配信道,降低链路冲突,实现网络通信信道的初步优化,再通过子信道等效改进方法,在信道已经被入侵破坏的基础上,在传递总比特数一定时,依据发送功率最小化模型,综合分析特性相同或相近的子信道,降低已经被入侵破坏后的网络信道通信信令负荷,完成被破坏网络信道通信的再次优化。仿真结果表明,该方法可有效降低被破坏网络链路冲突率和数据丢包率,提高了衰减网络通信性能。     

噪声干扰下的传感网络敏感信号挖掘模型

传统的传感网络信号挖掘方法在噪声干扰下,以降低波动信号参与通信为代价调控网络平稳度,极大降低了网络信号传递效率,存在较大的弊端。提出一种基于改进中值滤波的神经网络敏感信号挖掘方法,分析噪声干扰下无线传感网络信号特征,采用改进中值滤波的神经网络对原始含噪敏感信号进行中值滤波,利用中值滤波抑制噪声干扰产生的敏感信号值,通过BP神经网络去除敏感信号中的噪声,采用梯度下降方法在信号权矢量空间中求取误差函数的极小值,获取使误差函数极小化的权值组合,也就是待挖掘的传感网络敏感信号最佳解,实现传感网络敏感信号的准确挖掘。实验结果表明,所提方法能更好地过滤噪声,有效挖掘出敏感信号,具有较高的鲁棒性和自适应特性。     

一种小区重叠干扰下的通信滤波器噪声抑制算法

小区域重叠干扰下的通信滤波器通信信号由于受到外界环境的干扰通常极不稳定,传统噪声抑制方法只适用于平稳信号,无法实现复杂环境下通信滤波器噪声的抑制,提出一种基于自适应非线性滤波的小区重叠干扰下通信滤波器噪声抑制算法,对小区重叠干扰下的通信信号进行预增强处理,对得到的通信信号和既定阈值进行比较,判断是否需要进行噪声抑制,为小区重叠干扰下的通信滤波器噪声抑制提供有效依据。假设小区重叠干扰喜爱通信滤波器接收信号是同步的,给出采样结果。对滤波器的估计方差和条件方差进行计算,求出背景噪声和干扰剩余之和的方差,通过自适应改变非线性变换的非线性部分的变化曲线,实现小区域重叠干扰下的通信滤波器噪声抑制。仿真实验结果表明,所提方法具有很高的噪声抑制性能。     

乘性噪声干扰下的船舶突发性故障检测挖掘方法

在船舶的突发性故障检测中,故障信号不但伴有很强的非线性,并且常伴随大量的随机噪声,乘性噪声会降低非线性故障数据之间的有效联系,淡化船舶可识别的突发特征.给船舶突发性故障检测带来较大困难.为解决此问题,提出一种基于小区域噪声消除的船舶突发故障检测挖掘算法,通过设计一种包含乘性噪声小区域内的故障确认对比方法,运用故障特征核作为船舶突发故障的标准,进行故障核距离的计算,排除乘性噪声的干扰,保证优化检测.实验表明,该方法能够较好地完成乘性噪声干扰环境下的故障检测,提高了船舶故障的检测效率.     

基于经验模态副本匹配的多径网络资源分配优化

传统方法使用基于经验模态分解的多径网络资源优化分配算法,在网络资源的交叉项时间聚集资源分配均衡性不好。提出一种基于经验模态副本匹配的多径网络资源分配算法,进行多径网络通信信道模型构建与资源分配总体设计,定义多径网络通信系统资源时变次优调节因子,采用自然对数变换的方法构建一种多分量信号动态副本相关模型,对网络资源中来自多分量信号中不同信号分量之间进行交叉作用,优化数据包通信传输信道,提高多径网络通信系统中的资源分配性能。仿真实验表明,算法能有效提高系统的资源分配效率,网络吞吐性能和资源利用率提高明显,网络分配资源得到均衡,实现安全性控制下的资源分配优化均衡,节约网络系统的通信开销,进而提高了多径网络通信性能。     

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.