Measuring information in right-censored models

The theory of majorization is used to develop measures of information in the randomly right-censored model when the lifetime and censoring variables are discrete. Majorization also enables us to prove some basic theorems about the measures in a simple and unified fashion. These measures include Shannon's information as a special case. The measures are inadequate in the continuous case and some alternative measures, based on the variance of the lifetime random variable, are proposed.     

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

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     

Strength in Numbers: The Labour Government and the Size of the Polaris Force

Previous historical accounts have simplified the Labour government's decision to commission a four-boat strategic nuclear deterrent, or ‘Polaris force’, in early 1965. Utilising previously classified sources, this article shows that a number of key strategic concerns led the decision-making process. Nevertheless, broader economic and diplomatic considerations were also important in determining the size of the Polaris force. A tremendous balance of payments deficit and ongoing debates regarding levels of conventional and nuclear involvement in NATO certainly influenced the government's final decision. Moreover, competing strategic and economic interests resulted in continued debate throughout the decision-making process.     

The multidimensional nature of the Boko Haram conflict

ABSTRACT

The debate concerning the Nigerian terrorist Boko Haram is typically simplified across two false dichotomies. First, it is treated as either a local conflict in northeast Nigeria with its epicentre in Borno State or part of a broader conflict in Northwest Africa (and beyond), encompassing northern Cameroon, southern Chad, Niger, and reaching into Libya and Mali. The second dichotomy concerns whether it is animated by local material conditions on the ground, or is part of a broader anti-West jihad. The Boko Haram insurgency is not that simple. It is, rather, a multidimensional conflict and can change overtime.