Adaptive random search for continuous simulation optimization

We present, analyze, and compare three random search methods for solving stochastic optimization problems with uncountable feasible regions. Our adaptive search with resampling (ASR) approach is a framework for designing provably convergent algorithms that are adaptive and may consequently involve local search. The deterministic and stochastic shrinking ball (DSB and SSB) approaches are also convergent, but they are based on pure random search with the only difference being the estimator of the optimal solution [the DSB method was originally proposed and analyzed by Baumert and Smith]. The three methods use different techniques to reduce the effects of noise in the estimated objective function values. Our ASR method achieves this goal through resampling of already sampled points, whereas the DSB and SSB approaches address it by averaging observations in balls that shrink with time. We present conditions under which the three methods are convergent, both in probability and almost surely, and provide a limited computational study aimed at comparing the methods. Although further investigation is needed, our numerical results suggest that the ASR approach is promising, especially for difficult problems where the probability of identifying good solutions using pure random search is small. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

Dynamic evacuation routes for personnel on a naval ship

We propose a dynamic escape route system for emergency evacuation of a naval ship. The system employs signals that adapt to the causative contingency and the crew's physical distribution about the ship. A mixed‐integer nonlinear programming model, with underlying network structure, optimizes the evacuation process. The network's nodes represent compartments, closures (e.g., doors and hatches) and intersections, while arcs represent various types of passageways. The objective function integrates two potentially conflicting factors: average evacuation time and the watertight and airtight integrity of the ship after evacuation. A heuristic solves the model approximately using a sequence of mixed‐integer linear approximating problems. Using data for a Spanish frigate, with standard static routes specified by the ship's designers, computational tests show that the dynamic system can reduce average evacuation times, nearly 23%, and can improve a combined measure of ship integrity by up to 50%. In addition, plausible design changes to the frigate yield further, substantial improvements. Published 2008 Wiley Periodicals, Inc. Naval Research Logistics 2008     

The Ethnic Russian as an Enemy of Islam: Frame Analysis of the Kavkaz Center News Agency (2001–2004)

Abstract

Typically, when analysing contemporary Russian–Chechen conflicts, the relegation of the nationalist struggle to a secondary role by the religious battle waged by the North Caucasus insurgency is pinpointed as one of the fundamental differences between the First and Second War in Chechnya. This article discusses how it was reflected in one of the most important media of the Chechen Islamist insurgency: the Kavkaz Center. To this end, 2859 English language news items posted on the website during 2001–04 were reviewed using media frame analysis.     

Discrete stochastic optimization using variants of the stochastic ruler method

We present two random search methods for solving discrete stochastic optimization problems. Both of these methods are variants of the stochastic ruler algorithm. They differ from our earlier modification of the stochastic ruler algorithm in that they use different approaches for estimating the optimal solution. Our new methods are guaranteed to converge almost surely to the set of global optimal solutions under mild conditions. We discuss under what conditions these new methods are expected to converge faster than the modified stochastic ruler algorithm. We also discuss how these methods can be used for solving discrete optimization problems when the values of the objective function are estimated using either transient or steady‐state simulation. Finally, we present numerical results that compare the performance of our new methods with that of the modified stochastic ruler algorithm when applied to solve buffer allocation problems. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005.     

Averaging frameworks for simulation optimization with applications to simulated annealing

We present two frameworks for designing random search methods for discrete simulation optimization. One of our frameworks is very broad (in that it includes many random search methods), whereas the other one considers a special class of random search methods called point‐based methods, that move iteratively between points within the feasible region. Our frameworks involve averaging, in that all decisions that require estimates of the objective function values at various feasible solutions are based on the averages of all observations collected at these solutions so far. Also, the methods are adaptive in that they can use information gathered in previous iterations to decide how simulation effort is expended in the current iteration. We show that the methods within our frameworks are almost surely globally convergent under mild conditions. Thus, the generality of our frameworks and associated convergence guarantees makes the frameworks useful to algorithm developers wishing to design efficient and rigorous procedures for simulation optimization. We also present two variants of the simulated annealing (SA) algorithm and provide their convergence analysis as example application of our point‐based framework. Finally, we provide numerical results that demonstrate the empirical effectiveness of averaging and adaptivity in the context of SA. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

A Criterion for Settling Inconsistencies in Clausewitz’s On War

On War’s unfinished state has been a source of difficulties for interpretation for 180 years. By establishing a hierarchy of revision among the parts, we propose a criterion that can bring any part of On War in line with the most advanced stage of Clausewitz’s thinking. We exemplify the utility, illustrate the underpinnings and appreciate the potential of this criterion. We argue that the criterion offers the prospect of a shared, coherent, fully consistent and faithful rendering of Clausewitz’s theory of war.     

Sweden and the issue of NATO membership: exploring a public opinion paradox

The past decade has seen substantial shifts in Swedish security policy and major change in the domestic debate about NATO. For the first time, all of the right-of-centre “alliance parties” are calling for a full NATO membership, and popular support for NATO has increased. Yet public opinion contains ambiguities and paradoxes that complicate the picture. At the same time as support for NATO has increased, the public is overwhelmingly for continued military non-alignment. Drawing on previous research, longitudinal data from national surveys, and other sources on defence and security issues, this article aims to increase our understanding of the development and change in Swedish public opinion on NATO. A key argument is that Erving Goffman’s theatre metaphor, combined with neo-institutional decoupling theory, to a large degree can help understand the public opinion paradox.     

The FARC’s militaristic blueprint

This article intends to explain the outstanding sequence of success and failure exhibited by the FARC, the main Colombian guerrilla since the 1980s. It claims that such sequence is unintelligible unless the adoption by the FARC of a militaristic organizational blueprint at its 1982 7^th Conference is taken into account. By building itself like an army, the FARC could boost its combat capacity, maintain its structural integrity, and develop powerful mechanisms that held the whole structure together. At the same time, the militarization of the FARC also entailed significant risks and costs like political isolation and high personnel turnover. After describing the militaristic blueprint, the article compares the FARC with other irregular forces that operated in the Colombian context – a comparison which is important to understand the specificity of the FARC trajectory, as well as the benefits and costs involved in it. The analysis highlights the critical role of organizational dimensions in the explanation of civil war outcomes, and suggests that at least for some problems organizational dynamics should be observed at a low level of granularity.     

New product introduction against a predator: A bilevel mixed‐integer programming approach

We consider a scenario with two firms determining which products to develop and introduce to the market. In this problem, there exists a finite set of potential products and market segments. Each market segment has a preference list of products and will buy its most preferred product among those available. The firms play a Stackelberg game in which the leader firm first introduces a set of products, and the follower responds with its own set of products. The leader's goal is to maximize its profit subject to a product introduction budget, assuming that the follower will attempt to minimize the leader's profit using a budget of its own. We formulate this problem as a multistage integer program amenable to decomposition techniques. Using this formulation, we develop three variations of an exact mathematical programming method for solving the multistage problem, along with a family of heuristic procedures for estimating the follower solution. The efficacy of our approaches is demonstrated on randomly generated test instances. This article contributes to the operations research literature a multistage algorithm that directly addresses difficulties posed by degeneracy, and contributes to the product variety literature an exact optimization algorithm for a novel competitive product introduction problem. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009