Some Bounds on the Distribution of Certain Quadratic Forms in Normal Random Variables

The paper derives bounds on the distribution of the quadratic forms Z = y ^H( X Γ X ^H)⁻¹ y and W = y ^H(σ² I + X Γ X ^H)⁻¹ y , where the elements of the M × 1 vector y and the M × N matrix X are independent identically distributed (i.i.d.) complex zero mean Normal variables, Γ is some N × N diagonal matrix with positive diagonal elements, I , is the identity, σ² is a constant and ^H denotes the Hermitian transpose. The bounds are convenient for numerical work and appear to be tight for small values of M . This work has applications in digital mobile radio for a specific channel where M antennas are used to receive a signal with N interferers. Some of these applications in radio communication systems are discussed.     

A NOTE ON THE INVERSE COVARIANCE MATRIX OF THE AUTOREGRESSIVE PROCESS1

The inverse covariance matrix of an autoregressive process of arbitrary order is found explicitly using the notion of the information matrix for the vector random variable, not the parameters. Any process for which a simple conditional representation exists, can be treated in the same way. The approach has merit in the teaching of statistics.     

缬沙坦对自发性高血压大鼠心肌细胞外基质重塑和氧化应激态的影响

目的研究缬沙坦对高血压诱发的心肌细胞外基质重塑和氧化应激态的影响。方法选用16w龄雄性自发性高血压大鼠(SHR)12只,随机分为2组,缬沙坦组和阴性对照组(SHR组),每组6只。另选同周龄雄性Wistar-Kyoto大鼠(WKY)6只作为正常对照组(WKY组),给药6w后测定血清Ⅲ型前胶原(PIIIP)、Ⅳ型前胶原(PIVP)、透明质酸透射(HA)、心肌羟脯氨酸和胶原蛋白含量,电镜观察心肌超微结构,同时检测血清和心肌组织活性氧(ROS)水平、超氧化酶歧化酶(SOD)活力、丙二醛(MDA)含量。结果给药6w后,缬沙坦组血清PIIIP、PIVP、HA含量、心肌羟脯氨酸和胶原蛋白含量明显低于SHR组(P<0.01);电镜显示缬沙坦组心肌与SHR组比较,肌原纤维较清晰,排列整齐,横纹清楚,间质胶原纤维无明显增生;缬沙坦组血清和心肌组织SOD活力明显高于SHR组,而ROS水平、MDA含量明显低于SHR组(P<0.01)。结论缬沙坦可改善高血压诱发的心肌细胞外基质重塑,其机制与其抗氧化应激作用有关。     

自动网络分析仪误差模型的矩阵解法

本文提出了微波自动网络分析仪误差模型的矩阵解法。与信号流图法相比,矩阵解法能较快的给出误差模型和S—参数的显式解,更适合用计算机进行数据处理,明显地提高自动网络分析仪的测试精度和速度。     

数字图书馆的建设

数字图书馆借助网络环境和高性能计算机等实现信息资源的有效利用和共享。读者可以在世界各地通过网络阅览数字图书馆中的丰富信息，可以最大限度地突破时空限制。文章介绍了数字图书馆的建设方案及其优势。     

建设广东省高校电子图书馆的思考

广东省高校电子图书馆以建立跨学科、跨专业、较完整的数字信息资源网络，发挥各高校的优势，建设特色数字资源库为目标，注重标准化建设，注重科学规划和统一管理，同时也需要各子馆转变观念，统一认识，协调发展。     

The disability divide in internet access and use

The increasing spread of the Internet holds much potential for enhancing opportunities for people with disabilities. However, scarce evidence exists to suggest that people with disabilities are, in fact, participating in these new developments. Will the spread of information technologies (IT) increase equality by offering opportunities for people with disabilities? Or will a growing reliance on IT lead to more inequality by leaving behind certain portions of the population including people with disabilities? In this paper, the authors draw on nationally representative data regarding Americans' Internet uses to (1) identify the extent to which people with disabilities are embracing use of the Internet; (2) how their use of the Internet compares with the Internet uses of the rest of the population; (3) how having a disability relates to and interacts with other social statuses (e.g. socioeconomic status, age, gender) with regard to Internet use; and (4) what explains these trends. They draw on representative data collected by the Bureau of Labor Statistics and the Census of the United States to answer these questions. It is found that people with disabilities are less likely to live in households with computers, are less likely to use computers and are less likely to be online. However, once socioeconomic background is controlled for, it is found that people with hearing disabilities and those who have limited walking ability are not less likely to be Internet users. This research enables a deeper understanding of both the use of the Internet by people with disabilities and the spread of new IT more generally.     

寻找超越时空的"在场"——试析电视谈话节目技术形态演变的内在动力

技术形态的不断演变给电视节目带来了前所未有的发展空间。通过对电视谈话节目技术形态发展脉络的梳理,认为电视技术在一个与其他技术渗透、汇聚、生成的过程中,正在不断满足人类最为原始的交流欲望———身体的在场交流。从而,得出一个推测性的结论:数字化媒介技术的出现,是满足人类实现跨越时空“在场”交流欲望的必然。随着技术日趋成熟,被现代媒介消灭的身体将会以一种新的形式被重新恢复。     

高专院校图书馆数字资源的共建共享

本文从数字资源的内涵出发,论述了现阶段我国高专院校图书馆数字资源共建共享的现状和组织原则,并提出了如何做好数字资源共建共享各项具体工作的构想。     

多电子原子中自旋和轨道相互作用能

在中心场近似下,引入有效单体自旋-轨道相互作用势代替原子中各种自旋-轨道相互作用势,再引入双张量算符表示自旋-轨道相互作用算符,把计算纳入角动量理论的框架,从而推出了自旋-轨道相互作用算符的矩阵元的普遍表示式,并应用此表示式算出了几个组态能量表示式。