A m‐parallel crane scheduling problem with a non‐crossing constraint

In this paper, we study a m‐parallel machine scheduling problem with a non‐crossing constraint motivated by crane scheduling in ports. We decompose the problem to allow time allocations to be determined once crane assignments are known and construct a backtracking search scheme that manipulates domain reduction and pruning strategies. Simple approximation heuristics are developed, one of which guarantees solutions to be at most two times the optimum. For large‐scale problems, a simulated annealing heuristic that uses random neighborhood generation is provided. Computational experiments are conducted to test the algorithms. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007.     

Weakest‐link attacker‐defender games with multiple attack technologies

In this article, we examine a model of terrorism that focuses on the tradeoffs facing a terrorist organization that has two qualitatively different attack modes at its disposal. The terrorist organization's objective is to successfully attack at least one target. Success for the target government is defined as defending all targets from any and all attacks. In this context, we examine how terrorist entities strategically utilize an efficient but discrete attack technology — e.g., suicide attacks — when a more conventional mode of attack is available, and the optimal anti‐terrorism measures.© 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

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     

Capacitated lot‐sizing and scheduling with parallel machines,back‐orders,and setup carry‐over

We address the capacitated lot‐sizing and scheduling problem with setup times, setup carry‐over, back‐orders, and parallel machines as it appears in a semiconductor assembly facility. The problem can be formulated as an extension of the capacitated lot‐sizing problem with linked lot‐sizes (CLSPL). We present a mixed integer (MIP) formulation of the problem and a new solution procedure. The solution procedure is based on a novel “aggregate model,” which uses integer instead of binary variables. The model is embedded in a period‐by‐period heuristic and is solved to optimality or near‐optimality in each iteration using standard procedures (CPLEX). A subsequent scheduling routine loads and sequences the products on the parallel machines. Six variants of the heuristic are presented and tested in an extensive computational study. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009     

Factors that affect the optimal amount of central control in complex systems

Whereas much of the previous research in complex systems has focused on emergent properties resulting from self‐organization of the individual agents that make up the system, this article studies one vital role of central organization. In particular, four factors are conjectured to be key in determining the optimal amount of central control. To validate this hypothesis, these factors are represented as controllable parameters in a mathematical model. For different combinations of parameter values, the optimal amount of central control is found, either analytically or by computer simulation. The model is shown to provide results that match well with the level of control found across a broad spectrum of specific complex systems. This model also provides general guidelines as to how combinations of these factors affect the desirable level of control and specific guidelines for selecting and evaluating leaders. These results indicate that all of these factors, though not exhaustive, should be considered carefully when attempting to determine the amount of control that is best for a system. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

The social structure of armed groups. Reproduction and change during and after conflict

Current research on civil wars and conflict increasingly turns to the inner structure and functioning of state and non-state armed groups and their impact on aspects such as violent practice, internal cohesion and the dissolution of these groups during the conversion to peace. The first aim of this introduction is to set out the theme of this Special Issue on the social structure of armed groups and previous research within the field. The second aim is to introduce the contributions within the Special Issue, alongside possible trajectories of future research on the ‘meso-foundations’ of civil war and conflict.     

The Prickly Thorn: A Re-evaluation of Orde Wingate and the Special Night Squads

Orde Wingate’s Special Night Squads played a key role in defeating the Great Arab Revolt of 1936–1939. Wingate’s Night Squads were distinctive in their approach to counter-insurgency warfare; in addition to bringing Arab insurgents to battle, the Night Squads proved their mettle by ‘flying the flag’ and by improving cooperation between Jewish settlers and British servicemen. Nevertheless, the Night Squad’s accomplishments and legacy must be properly situated within the broader wave of tactical innovations undertaken by the British Army throughout the Rebellion.     

Insurgent Groups During Post-Conflict Transformation: The Case of Military Strongmen in Cambodia

The article discusses the experiences of a group of military strongmen during the post-conflict transformation of two Cambodian insurgent movements into a society of peace after a decades-long civil war. It explains the reasons why some of these strongmen were able to transfer their high status within the insurgency into senior positions in the incumbent government, while others became impoverished and sometimes even preferred to relapse into further conflict. Even though all of these strongmen shared a very similar life course and fought until the end of the conflict, their post-conflict fates have been very different. Central to the explanation of their behaviour during the transition is their habitus, the set of resources at their disposal and the nature of their vertical and horizontal social networks.     

The bottleneck problem with minimum quantity commitments

Given an edge‐distance graph of a set of suppliers and clients, the bottleneck problem is to assign each client to a selected supplier minimizing their maximum distance. We introduce minimum quantity commitments to balance workloads of suppliers, provide the best possible approximation algorithm, and study its generalizations and specializations. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2006