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Coherent Systems (coherent + system)

Distribution by Scientific Domains
Mathematics and Statistics57%

Selected Abstracts

A branch and bound algorithm for computing optimal replacement policies in consecutive k -out-of- n -systems

NAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 3 2002
James Flynn
Abstract This paper presents a branch and bound algorithm for computing optimal replacement policies in a discrete-time, infinite-horizon, dynamic programming model of a binary coherent system with n statistically independent components, and then specializes the algorithm to consecutive k -out-of- n systems. The objective is to minimize the long-run expected average undiscounted cost per period. (Costs arise when the system fails and when failed components are replaced.) An earlier paper established the optimality of following a critical component policy (CCP), i.e., a policy specified by a critical component set and the rule: Replace a component if and only if it is failed and in the critical component set. Computing an optimal CCP is a optimization problem with n binary variables and a nonlinear objective function. Our branch and bound algorithm for solving this problem has memory storage requirement O(n) for consecutive k -out-of- n systems. Extensive computational experiments on such systems involving over 350,000 test problems with n ranging from 10 to 150 find this algorithm to be effective when n , 40 or k is near n. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 288,302, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10017 [source]

Increasingly distant from life: problem setting in the organization of home care

NURSING PHILOSOPHY, Issue 1 2008
Christine Ceci PhD
Abstract, The analysis undertaken in this paper explores the significance of a central finding from a recent field study of home care case management practice: a notable feature of case management work is the preparation of an orderly, ordered space where care may be offered. However, out of their encounters with an almost endless variety of situations, out of people's diverse narratives of need, case managers seem able to pick out only limited range of recognized needs to which to respond and demonstrate a series of responses themselves equally limited. Though this observation suggests a kind of efficiency that is currently highly valued within healthcare systems, it also underlines the system's inability to engage difference and variability in a meaningful way. This inability or limitation in effectively engaging difference is conceptualized here as, in some sense, a problem, and the nature of this problem is explored through the rhetorical process of problem setting. The central question becomes how might we develop and deploy an orderly and coherent system of care without essentializing people's experiences, without treating these experiences reductively, without, in a Foucaultian frame of reference, allowing what can be understood as similarity or resemblance among clients and situations to be folded back into sameness? As we encounter complexity, variability and difference in practice, how should we treat it? [source]

A Framework for Understanding State Balanced Budget Requirement Systems: Reexamining Distinctive Features and an Operational Definition

PUBLIC BUDGETING AND FINANCE, Issue 3 2006
YILIN HOU
Studies of state fiscal and budgetary policies often use balanced budget requirements (BBRs) as explanatory variables. While current measures laid the crucial groundwork for a basic understanding of state BBRs, their lack of comprehensiveness threatens the validity of empirical work. Based on comprehensive legal research, this article offers a framework for analyzing state requirements: each state's BBRs form a coherent system for achieving budget balance through budget cycles; a fully developed BBR system offers a three-line construct against imbalance; and the more complete, developed, and explicit a BBR system is, the more stringent it will be in achieving budgetary balance. [source]

On the application and extension of system signatures in engineering reliability

NAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 4 2008
Jorge Navarro
Abstract Following a review of the basic ideas in structural reliability, including signature-based representation and preservation theorems for systems whose components have independent and identically distributed (i.i.d.) lifetimes, extensions that apply to the comparison of coherent systems of different sizes, and stochastic mixtures of them, are obtained. It is then shown that these results may be extended to vectors of exchangeable random lifetimes. In particular, for arbitrary systems of sizes m < n with exchangeable component lifetimes, it is shown that the distribution of an m -component system's lifetime can be written as a mixture of the distributions of k -out-of- n systems. When the system has n components, the vector of coefficients in this mixture representation is precisely the signature of the system defined in Samaniego, IEEE Trans Reliabil R,34 (1985) 69,72. These mixture representations are then used to obtain new stochastic ordering properties for coherent or mixed systems of different sizes. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008 [source]

Some stochastic comparisons of conditional coherent systems

APPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 6 2008
Xiaohu Li
Abstract This paper investigates coherent systems with independent and identical components. Stochastic comparison on the residual life and the inactivity time of two systems with stochastically ordered signatures is conducted. Copyright © 2008 John Wiley & Sons, Ltd. [source]

The Global Absence of Child and Adolescent Mental Health Policy

CHILD AND ADOLESCENT MENTAL HEALTH, Issue 3 2004
Jess P. Shatkin
Background:, Few policies designed specifically to support child and adolescent mental health exist worldwide. The absence of policy is a barrier to the development of coherent systems of mental healthcare for children and adolescents. Method:, This study collected data on existing policies from international databases, WHO headquarters in Geneva, Switzerland, and in consultation with experts in child and adolescent psychiatry from around the world. A set of criteria for ranking the adequacy of these policies was developed. Results:, Though no single country was found to have a mental health policy strictly pertaining to children and adolescents alone, 35 countries (corresponding to 18% of countries worldwide) were found to have identifiable mental health policies, which may have some beneficial impact on children and adolescents. Though little has been achieved worldwide in this area, there has been a significant degree of movement towards policy development in the past 10 years. The policies identified vary greatly in terms of their provisions for delivering services, initiating research, training professionals, and educating the public. Conclusions:, The development of mental health policies is feasible and would substantially aid in the expansion of service systems, the institutionalisation of culturally relevant data gathering, and the facilitation of funding. [source]