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41.
We propose a methodology, called defender–attacker decision tree analysis, to evaluate defensive actions against terrorist attacks in a dynamic and hostile environment. Like most game‐theoretic formulations of this problem, we assume that the defenders act rationally by maximizing their expected utility or minimizing their expected costs. However, we do not assume that attackers maximize their expected utilities. Instead, we encode the defender's limited knowledge about the attacker's motivations and capabilities as a conditional probability distribution over the attacker's decisions. We apply this methodology to the problem of defending against possible terrorist attacks on commercial airplanes, using one of three weapons: infrared‐guided MANPADS (man‐portable air defense systems), laser‐guided MANPADS, or visually targeted RPGs (rocket propelled grenades). We also evaluate three countermeasures against these weapons: DIRCMs (directional infrared countermeasures), perimeter control around the airport, and hardening airplanes. The model includes deterrence effects, the effectiveness of the countermeasures, and the substitution of weapons and targets once a specific countermeasure is selected. It also includes a second stage of defensive decisions after an attack occurs. Key findings are: (1) due to the high cost of the countermeasures, not implementing countermeasures is the preferred defensive alternative for a large range of parameters; (2) if the probability of an attack and the associated consequences are large, a combination of DIRCMs and ground perimeter control are preferred over any single countermeasure. 相似文献
42.
Louise Ryan 《The Sociological review》2004,52(3):351-370
The recent increase in transnational migration among women has lead to a reappraisal of theoretical explanations of migratory movement ( Castles and Miller, 2003 ; Fortier, 2000 ; Zulauf, 2001 ). This paper reviews a number of theoretical explanations of transnational migration and then applies these theories to a qualitative study of women who migrated from Ireland to Britain in the 1930s. I explore the women's reasons for leaving Ireland and their experiences as young economic migrants in Britain in the inter‐war years. Women have made up the majority of Irish migrants to Britain for much of the twentieth century yet the dominant stereotype of the Irish migrant has been the Mick or Paddy image ( Walter, 2001 ). Through an analysis of these twelve women's narratives of migration, I explore themes such as household strategies and familial networks. I am interested in the interwoven explanations of migration as both a form of escape ( O’Carroll, 1990 ) and a rational family strategy and, hence, the ways in which women's decision to migrate can be seen as a combination of both active agency and family obligation. Drawing on the work of Phizacklea (1999 ) as well as Walter (2001 ) and Gray (1996 , 1997 ), I will analyse the ways in which family connections may transcend migration and engage with the concept of ‘transnational family’ ( Chamberlain, 1995 ). In so doing, I raise questions about the complex nature of migration and the extent to which it could be described in terms of empowerment. 相似文献
43.
Angela Shen Ryan D.S.W. Michael J. Smith D.S.W. 《Child and Adolescent Social Work Journal》1989,6(4):283-299
Families of Chinese American children with mental retardation and developmental disabilities were interviewed regarding their attitudes and coping experiences. Chinese American parents, like other American parents, reacted to the crisis with intense feelings and needs. The parents revealed a lack of knowledge and understanding of the diagnosis. Chinese belief systems about health and illness were present in the parents' concepts of causation and treatment.Hunter College School of Social Work. 相似文献
44.
45.
Codes of Conduct have enjoyed a long history as guides to human behavior. Corporate Codes of Conduct enjoy significant popularity in the U.S. and U.K. This article examines Codes in terms of their evolution (history), expectations (from possible to impossible), and enforcement (the area of greatest difficulty). The article examines trends in Corporate Codes and defines Codes as one aspect of developing corporate conscience. The article concludes with the view that useful as Codes may be, the inherent problem with Codes has been their separation over time from a moral foundation or philosophical base. 相似文献
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47.
The Lomax (Pareto II) distribution has found wide application in a variety of fields. We analyze the second-order bias of the maximum likelihood estimators of its parameters for finite sample sizes, and show that this bias is positive. We derive an analytic bias correction which reduces the percentage bias of these estimators by one or two orders of magnitude, while simultaneously reducing relative mean squared error. Our simulations show that this performance is very similar to that of a parametric bootstrap correction based on a linear bias function. Three examples with actual data illustrate the application of our bias correction. 相似文献
48.
Ryan Martin 《统计学通讯:理论与方法》2013,42(2):286-299
An empirical Bayes problem has an unknown prior to be estimated from data. The predictive recursion (PR) algorithm provides fast nonparametric estimation of mixing distributions and is ideally suited for empirical Bayes applications. This article presents a general notion of empirical Bayes asymptotic optimality, and it is shown that PR-based procedures satisfy this property under certain conditions. As an application, the problem of in-season prediction of baseball batting averages is considered. There the PR-based empirical Bayes rule performs well in terms of prediction error and ability to capture the distribution of the latent features. 相似文献
49.
Ryan T. Godwin 《统计学通讯:理论与方法》2013,42(7):1887-1901
ABSTRACTWe derive an analytic expression for the bias of the maximum likelihood estimator of the parameter in a doubly-truncated Poisson distribution, which proves highly effective as a means of bias correction. For smaller sample sizes, our method outperforms the alternative of bias correction via the parametric bootstrap. Bias is of little concern in the positive Poisson distribution, the most common form of truncation in the applied literature. Bias appears to be the most severe in the doubly-truncated Poisson distribution, when the mean of the distribution is close to the right (upper) truncation. 相似文献
50.
Ryan Martin 《统计学通讯:模拟与计算》2013,42(7):1533-1548
Estimation of finite mixture models when the mixing distribution support is unknown is an important problem. This article gives a new approach based on a marginal likelihood for the unknown support. Motivated by a Bayesian Dirichlet prior model, a computationally efficient stochastic approximation version of the marginal likelihood is proposed and large-sample theory is presented. By restricting the support to a finite grid, a simulated annealing method is employed to maximize the marginal likelihood and estimate the support. Real and simulated data examples show that this novel stochastic approximation and simulated annealing procedure compares favorably with existing methods. 相似文献