Weighted kappa statistic for clustered matched-pair ordinal data

As an important extension of the regular kappa statistic, the weighted kappa statistic has been widely used to assess the agreement between two procedures for independent matched-pair ordinal data. For clustered matched-pair ordinal data, based on the delta method and sampling techniques, a non-parametric variance estimator for the weighted kappa statistic is proposed without within-cluster correlation structure or distributional assumptions. The results of an extensive Monte Carlo simulation study demonstrate that the proposed weighted kappa statistic provides consistent estimation, and the proposed variance estimator behaves reasonably well for at least a moderately large number of clusters (e.g., $K\ge 50$). Compared with the variance estimator ignoring dependence within a cluster, the proposed variance estimator performs better in maintaining the nominal coverage probability when the intra-cluster correlation is fair ($\rho \ge 0.3$), with more pronounced improvement when $\rho$ is further increased. Moreover, under the general analysis of variance setting with systematic variability between procedures and clusters being included as a component of total variation, the equivalence between weighted kappa statistic and intraclass correlation coefficient is established. To illustrate the practical application of the proposed estimator, two real medical research data examples of clustered matched-pair ordinal data are analyzed, including an agreement study to compare two methods for assessing cervical ectopy, and a physician–patients data example from the Enhancing Communication and HIV Outcomes study.     

Necessary and sufficient conditions for broadcast consensus protocols

Summary We consider consensus protocols in asynchronous distributed systems that are based on broadcast communication. We show that a necessary and sufficient condition for the existence of a deterministic consensus protocol is delivery of each broadcast message to at least (n+k+1)/2 processes in ann-process system subject tok crash failures with either eventual fair broadcasting or eventual full broadcasting. The broadcast model captures the idea of a broadcast communication medium, such as the Ethernet, in which messages, if delivered, are delivered immediately and in order but not necessarily to all processes. Louise E. Moser received the Ph.D. degree in mathematics from the University of Wisconsin, Madison, in 1970. From 1970 to 1987 she was a professor of mathematics and computer science at California State University, Hayward. In 1987 she moved to the University of California, Santa Barbara, where is currently on the faculty of the Department of Electrical and Computer Engineering. Her current research interests include parallel and distributed systems, network architectures and communication protocols, and formal methods in software engineering. P.M. Melliar-Smith received the Ph.D. degree in computer science from the University of Cambridge, Cambridge, England, in 1987. He was a senior research scientist and program director at SRI International in Menlo Park (1976–1987), senior research associate at the University of Newcastle Upon Tyne (1973–1976), and principal designer for GEC Computers Ltd. in England (1964–1973). He is currently a professor in the Department of Electrical and Computer Engineering at the University of California, Santa Barbara. His research interests include fault-tolerant distributed systems, high-speed communication networks and protocols, and formal specification and verification. Vivek Agrawala received the B.Tech. degree in chemical engineering in 1984 and the M. Tech. degree in computer technology in 1986, both from the Indian Institute of Technology, Delhi, and a Ph.D. in computer science in 1991 from the University of California, Santa Barbara. Since then he has been a Research Scientist at Siemens Corporate Research, Princeton, New Jersey. His major research interests are distributed algorithms, software design methods, and distributed systems.This research was supported by the National Science Foundation, Grant Numbers CCR-8908515 and NCR-9016361. V. Agrawala's current address is Siemens Corporate Research, 755 College Road East, Princeton, NJ 08540, USA     

Fixed-effects modeling of Cohen’s weighted kappa for bivariate multinomial data

Cohen’s kappa and weighted kappa statistics are the conventional methods that are used widely in measuring agreement for categorical responses. In this paper, we propose a general framework for the fixed-effects modeling of Cohen’s weighted kappa for bivariate multinomial data which reduces to Cohen’s weighted kappa under certain conditions and hence can be considered as a generalization of the conventional Cohen’s weighted kappa. Properties of the proposed method are investigated followed by an evaluation of the asymptotic performance through bootstrap simulation studies and two illustrative examples. Our derivation shows that the Fleiss-Cohen weights, one of the popular weight schemes for Cohen’s weighted kappa, might have some unappealing analytical properties, although these do not appear to cause an issue in application.     

蓝牙无线通信技术的应用

介绍了蓝牙无线通信技术的各种应用模式，描述了蓝牙技术在工业、信息家庭、军事上的应用及蓝牙技术的市场前景。     

一种增强的ZRTP认证机制

ZRTP本身的认证机制在一些特殊的情况下无法抵抗中间人攻击。为此,基于简单密钥协商协议(SAKA)提出一种NSAKA算法,改进ZRTP的认证机制,使用RFC4474中的SIP身份认证模型来安全传输用户预共享的秘密口令。通过分析表明,该方案可以提高ZRTP抵抗中间人攻击的能力,并弥补SAKA算法原有的安全缺陷。     

运用WTO《技术贸易壁垒协议》保护我国石化产业利益

介绍了WTO《技术贸易壁垒协议》的主要规则,指出了我国在技术标准体系存在的问题及该协议对我国石油石化行业的影响,对如何运用该协议保护我国石化产业利益提出了对策及建议。     

基于光纤以太网的集控站综合自动化系统通信方案

与几种电力系统常用的通信方式相比较，光纤通信具有不可比拟的先进性，光纤通信和以太网技术相结合，是电力系统通信方案的发展趋势。本文介绍了光纤的基本原理、基于光纤以太网的集控站网络模型，以及通讯规约的选择。     

改进的基于椭圆曲线加密的3G认证与密钥协商协议

针对第三代移动通信系统(3G)中采用的认证与密钥协商(AKA)协议存在安全漏洞和密钥管理困难等问题,采用基于椭圆曲线密码(ECC)和公钥体制协商会话密钥、对称加密算法加密消息的方法,提出了一种应用于3G业务中的改进协议.该协议不仅有效克服了AKA协议中存在的各种缺陷,避免了复杂的密钥管理难题,而且相比其他协议更简单容易,具有实际应用性.     

天然气合理利用问题探讨

合理利用天然气,是能源转型的选择方案之一。怎样做才算是合理利用天然气呢?本文根据公开资料,从天然气合理利用所应追求的目标、天然气调峰、天然气用户等三方面讨论天然气合理利用问题,供业内人士参考。     

企业动态联盟及其基于多Agent系统的构建

首先提出了动态联盟的概念,总结了动态联盟的特点。简述了多Agent系统的概念和特性,提出了多Agent系统应用于动态联盟构建的可行性。最后给出伙伴选择框架及带有时间限制的协商协议及过程。