A model for critical crack size estimation in fatigue failure of gun barrels

With repeated firing, fatigue cracks are produced in a gun barrel, and the barrel is no longer useful when a crack reaches a critical size. The initial crack size and the critical crack size, as well as the number of firings producing the critical crack size, may be considered as random variables. Assuming a proportional damage model for crack growth, a method for estimating the critical crack size distribution is presented. From these results, an estimate of the barrel life, or the residual barrel life once a crack of a given size is measured, can be obtained.     

Gittins-index heuristics for research planning

The classical work of Gittins, which resulted in the celebrated index result, had applications to research planning as an important part of its motivation. However, research planning problems often have features that are not accommodated within Gittins's original framework. These include precedence constraints on the task set, influence between tasks, stopping or investment options and routes to success in which some tasks do not feature. We consider three classes of Markovian decision models for research planning, each of which has all of these features. Gittins-index heuristics are proposed and are assessed both analytically and computationally. They perform impressively. © 1995 John Wiley & Sons, Inc.     

The simple multiserver loss system with time-varying intensities

For the loss system with time-varying intensities and a finite number of identical servers we derive formulas for the expected number of refused customers in a given time interval and for the expected number of servers busy at a given time instant. © 1994 John Wiley & Sons, Inc.     

Optimizing the US Navy's combat logistics force

We study how changes to the composition and employment of the US Navy combat logistic force (CLF) influence our ability to supply our navy worldwide. The CLF consists of about 30 special transport ships that carry ship and aircraft fuel, ordnance, dry stores, and food, and deliver these to client combatant ships underway, making it possible for our naval forces to operate at sea for extended periods. We have modeled CLF operations to evaluate a number of transforming initiatives that simplify its operation while supporting an even larger number of client ships for a greater variety of missions. Our input is an employment schedule for navy battle groups of ships operating worldwide, extending over a planning horizon of 90–180 days. We show how we use optimization to advise how to sustain these ships. We have used this model to evaluate new CLF ship designs, advise what number of ships in a new ship class would be needed, test concepts for forward at‐sea logistics bases in lieu of conventional ports, demonstrate the effects of changes to operating policy, and generally try to show whether and how the CLF can support planned naval operations. Published 2008 Wiley Periodicals, Inc. Naval Research Logistics 2008     

Probability inequalities via negative dependence for random variables conditioned on order statistics

Distributions are studied which arise by considering independent and identically distributed random variables conditioned on events involving order statistics. It is shown that these distributions are negatively dependent in a very strong sense. Furthermore, bounds are found on the distribution functions. The conditioning events considered occur naturally in reliability theory as the time to system failure for k-out-of-n systems. An application to systems formed with “second-hand” components is given.     

Modeling the performance of a scanning radio communications sensor

A model which allows the prediction of long-term average report rates against an array of radio emitters by a scanning sensor is presented. The model is based on Markov renewal theory.     

Decapitation,disruption, and unintended consequences in counterterrorism: lessons from Islamist terror networks in Spain

This study examines the unintended consequences of decapitation strategies. Two Islamist terror networks in Spain have been used to critically evaluate theories of leadership removal guided by large-N cross-sectional research. Arguably, current models neglect to include relational variables that constitute the foundation for policies of network disruption. Spanish terror networks are mapped out over a 10-year period (1995–2004) to demonstrate the importance of network variables. Policies meant to disrupt militant networks can generate unintended consequences, as was the case with Spain’s Operation Dátil following the 9/11 attacks on the Twin Towers and the Pentagon in the United States. The Madrid train bombing network developed in the vacant political space following the counterterrorism operation that targeted radical Islamists in Spain.     

‘A Sledgehammer to Crack a Nut’? Naval Gunfire Support During the Malayan Emergency

The utility of naval gunfire support (NGS) during the Malayan Emergency has been the subject of significant scrutiny. While the limitations of NGS were demonstrated in Malaya, it also has proven to be extremely useful under certain circumstances. The circumstances in which NGS has proven effective during earlier and later insurgencies have generally reflected those of the Malayan Emergency. Recent operations in Afghanistan and Iraq have been less conducive to the application of maritime power, but they did not denote the end of the naval role or the potential usefulness of NGS in counterinsurgency operations. NGS is an unheralded capability, but, aside from the historical significance, it remains relevant in the contemporary era under the right conditions.     

Building Legitimacy: Interactional Dynamics and the Popular Evaluation of the Kurdistan Workers’ Party (PKK) in Turkey

Abstract

Previous research has identified a variety of general mechanisms to explain how insurgents build legitimacy. Yet, there is often a gap between these mechanisms and the interactional dynamics of insurgencies. This article attempts to bridge this gap through a theoretically informed analysis of the Kurdistan Workers’ Party’s (PKK) insurgency in Turkey. I show how the PKK’s efforts to cultivate legitimacy, Turkey’s counterinsurgency strategies, and civilian perceptions of the PKK, all mutually influenced one another. Based on this analysis, I argue that the mechanisms that produce popular legitimacy coevolve with insurgents’ behaviors, states’ interventions, and civilians’ perceptions.