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。     

海杂波统计特性分析及海面动目标检测

利用IPIX雷达回波数据分析了海杂波的统计特性.并利用LFM信号在分数阶Fourier域良好的能量聚集性,提出基于分数阶Fourier变换的海面动目标检测方法.此方法能较好的聚集动目标回波能量,而对海杂波回波的能量聚集不明显,可以较好的检测出动目标.最后采用实测海杂波数据做了仿真分析,证实了此方法的有效性.     

复杂进化网络的ipsweep攻击信号自校正分离

ipsweep攻击信号广泛存在于复杂进化网络系统中,对其实现自校正分离,进行攻击信号准确检测。传统算法采用PSO辨别树算法进行复杂进化网络的ipsweep攻击自校正分离算法设计,存在自适应差和检测性能不好的问题。提出一种基于Dopplerlet变换匹配投影ipsweep攻击自校正分离算法。提取攻击信号传播路径的随机概率密度特征,计算自校正分离属性的信息熵的预测值,提取信号在Dopplerle空间中相干点积功率累积尺度坐标,得到ipsweep攻击信号的自校正分离模型改进设计。仿真结果表明,该算法能有效提高对ipsweep攻击信号检测性能,传统算法的检测概率为63%,而该算法的检测概率为92%,检测性能提升明显,且能有效实现对ipsweep攻击信号Dopplerle空间谱检测。     

改进的混响数据分段Itakura距离估计算法

在主动探测自导系统设计中,混响数据分段Itakura距离的准确估计是实现自导系统测距,提高目标信号检测性能的基础,且Itakura距离可以评价对混响数据的局部平稳性。当前的混响数据Itakura距离估计算法采用基于局部高斯色噪声混响估计模型,当相邻数据段与需检测信号脉宽一致时,距离估计精度不好。提出一种基于Rayleigh分布分段副本相关检测的混响数据Itakura距离算法,构建混响数据包络模型实现对混响包络概率分布特征的准确描述,采用基于频率选择性衰落的自适应噪声抵消算法对混响数据包络模型进行简化,对混响数据进行Rayleigh分布下的概率密度特征分割,设计分段副本相关检测器,计算该组数据中相邻数据段之间Itakura距离,实现目标Itakura测距。实验结果表明,改进算法对Itakura距离估计精度较高,局部平稳性影响较小。在精确探测制导等领域具有很好应用价值。     

引入合同变换矩阵的网络攻击信号盲分离算法

对网络攻击信号进行盲分离,实现对攻击信号的准确有效检测。传统的网络攻击信号检测算法使用时频分析方法,提取非平稳群攻击信号的时频特征,实现信号检测,但算法把网络入侵检测正确率作为约束目标函数进行同步最优特征子集求解,复杂度较高,提出一种引入合同变换矩阵的网络攻击信号盲分离算法。采用时频分析Viterbi算法,得到信号谱的平均频率等于瞬时频率的时间平均,根据合同变换矩阵,对攻击信号进行离散数据解析化处理,构建网络攻击信号的解析模型,得到网络统计信号在多复变边界条件下的时频特征,实现盲分离算法改进。仿真实验表明,该算法能有效实现对网络攻击信号的盲分离,盲分离结果能准确反映网络攻击信号的内部特征,提高了对网络攻击信号的检测能力,对攻击信号的检测性能有所提高,保证了网络安全。     

模糊伸缩约束控制下柴油机油液铁谱检测设计

船舶柴油机的油液铁谱分析是实现故障诊断的重要方法。基于油液铁谱分析的船舶柴油机故障的传统检测方法是采用超声波固-液界面检测算法,导致柴油机故障信号出现环绕波齐次衰减,故障诊断效果不好。提出一种基于模糊伸缩约束控制柴油机油液铁谱分析的故障诊断方法,基于DSP设计船舶柴油机油液铁谱制谱仪和铁谱故障检测硬件系统,采用ADSP-BF537设计油液铁谱分析的电源,选用ADM706SAR芯片设计电路复位。算法设计中,构建油液铁谱分析能量模糊规则方程,设定模糊伸缩约束控制条件补偿油液铁谱分析模型的不确定性,实现对故障的准确定位和检测。实验结果表明,采用该方法进行柴油机故障信号油液铁谱分析和故障诊断,故障亮点定位准确,具有多故障状态监测应答的性能,故障准确发现概率提高显著。     

强干扰多载波雷达信号幅度检测算法

在强干扰环境下对多载波雷达信号的幅度检测是实现空中目标打击的关键技术。传统方法中,对雷达信号的幅度检测采用时频耦合算法,如果信号和背景噪声有很强干扰和多载波特征时,检测性能不好。提出一种基于分数阶Fourier时频耦合的信号幅度检测算法。构建强干扰环境,描述雷达信号的宽度和深度等特征量,对多载波雷达信号进行分数阶Fourier变换,对目标回波的尺度和时延进行估计,求解相位模糊数搜索结合解,得到雷达信号参数相位补偿结果,根据雷达信号特征量聚点塑造特征量模型运算雷达信号的特征量聚点,获取高特征量聚集区域,通过后置的高阶累积量切片,使信号的累积量增大,而噪声被抑制提高了检测精度。仿真实验表明,算法的检测概率较高,幅度检测能很好地跟踪信号幅度的变化。     

小波尺度投影多普勒容限提升制导算法改进

在航行器制导系统设计中,多普勒容限是系统设计的重要波形参数,多普勒宽容性有利于提高目标检测性能和减少设备复杂性。传统的设计方案采用双曲调频小波的自小波变换进行多普勒容限提升,当双曲调频小波出现时间尺度耦合时,产生相似结构包络平移,检测性能无法满足制导系统设计需求。提出一种改进的基于连续小波变换尺度投影算法的多普勒容限提升算法,进行制导系统设计改进,设计目标回波的宽带模型,根据选择性衰落失真模拟接收信号,构建双曲调频小波制导检测器,降低算法复杂度。实验结果表明,该算法能提升多普勒的宽容性,有效完成低信噪比下的弱信号检测,提高航行设备的制导性能,满足现有航行器制导系统的战术要求。     

基于污点数据聚类的攻击调频信号虚警预估计

对网络攻击信号的线性调频建模和虚警门限预估计,是实现网络攻击信号检测的基础。传统方法采用路由数据交换的阵列信号聚类方法进行信号建模和虚警门限估计,由于攻击信号具有多波束自相似特征,导致虚警门限的预测精度不高。提出一种基于污点数据双模聚类的攻击调频信号虚警预估计算法,采用频率调制规律设计网络攻击信号模型,对攻击信号进行双线性核相位加权,得到脉冲压缩后的攻击信号二次调频信号输出。在双模聚类的时频平面内实现对信号检测能量的聚集,以改善信号分量聚集的尖峰,实现了对攻击调频信号的时间点与频率点的重组排列和特征分布估计,达到对虚警门限准确估计的目的。实验结果表明,该算法能有效估计攻击调频信号的虚警门限,对网络攻击信号的虚警门限的预估计精度达到98.5%,提高了对攻击信号的参数估计和信号检测能力,提高检测概率,优越性明显。     

异质网间通信信道单谱脉冲响应频率估计

提出一种基于Hough变换的单谱特征分析的异质网通信信道脉冲响应频率估计算法。采用正交频率复用OFDM训练起始帧,加入多径分量的相位偏移进行相位偏转修正,构建了信道模型与脉冲响应信号模型。频率估计中采用Hough变换把信号空间中的直线的检测问题转换为参数空间中对点的检测问题,计算多普勒单谱脉冲响应信号的约束经验模态值,实现Hough变换单谱脉冲信号检测和脉冲响应频率估计算法改进。仿真实验表明,该算法能准确估计出异质网间通信脉冲响应信号的频率值,精度较传统方法高,在最小的迭代步数下实现算法收敛,误码率为0,性能较优。     

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.     

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.     

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.     

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.     

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."     

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.     

The Information Environment and Universal Service

This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment.     

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.