Estimating negative binomial demand for retail inventory management with unobservable lost sales

The importance of effective inventory management has greatly increased for many major retailers because of more intense competition. Retail inventory management methods often use assumptions and demand distributions that were developed for application areas other than retailing. For example, it is often assumed that unmet demand is backordered and that demand is Poisson or normally distributed. In retailing, unmet demand is often lost and unobserved. Using sales data from a major retailing chain, our analysis found that the negative binomial fit significantly better than the Poisson or the normal distribution. A parameter estimation methodology that compensates for unobserved lost sales is developed for the negative binomial distribution. The method's effectiveness is demonstrated by comparing parameter estimates from the complete data set to estimates obtained by artificially truncating the data to simulate lost sales. © 1996 John Wiley & Sons, Inc.     

A fast infiltration game on n arcs

Starting from a safe base, an Infiltrator tries to reach a sensitive zone within a given time limit without being detected by a Guard. The Infiltrator can move with speed at most u, while the Guard can only perform a restricted number of searches. A discrete variant of this zero-sum game played on a graph consisting of two vertices joined by n nonintersecting arcs is investigated. Optimal strategies and an explicit expression for its value are obtained. © 1996 John Wiley & Sons, Inc.     

Compound poisson approximation in systems reliability

The compound Poisson “local” formulation of the Stein-Chen method is applied to problems in reliability theory. Bounds for the accuracy of the approximation of the reliability by an appropriate compound Poisson distribution are derived under fairly general conditions, and are applied to consecutive-2 and connected-s systems, and the 2-dimensional consecutive-k-out-ofn system, together with a pipeline model. The approximations are usually better than the Poisson “local” approach would give. © 1996 John Wiley & Sons, Inc.     

The individual station technique for the analysis of cyclic polling systems

Polling systems are used to model a wide variety of real-world applications, for example, telecommunication and material handling systems. Consequently, there is continued interest in developing efficient algorithms to analyze the performance of polling systems. Recent interest in the optimization of these systems has brought up the need for developing very efficient techniques for analyzing their waiting times. This article presents the Individual Station technique for cyclic polling systems. The technique possesses the following features: (a) it allows the user to compute the mean waiting time at a selected station independent of the mean waiting time computations at other stations, and (b) its complexity is low and independent of the system utilization. In addition the technique provides explicit closed-form expressions for (i) the mean waiting times in a system with 3 stations, and (ii) the second moment of the waiting times in a system with 2 stations, for an exhaustive service system. © 1996 John Wiley & Sons, Inc.     

Multilinear extensions and quotients of simple games

Studied here is the problem of evaluating the formation of coalitions in cooperative games by considering its internal and external effects. Our analysis is based upon a formal theory of the quotient game and the use of multilinear extensions to compute the Shapley value and the coalitional value. When it applies to simple games, a series of interesting results is obtained. © 1996 John Wiley & Sons, Inc.     

Multi-period airline overbooking with multiple fare classes

Consider a multi-period multi-fare class airline overbooking problem that relates to a single-leg flight. Passengers may cancel their reservations at any time, including being no-shows at flight-time. Canceling passengers receive a refund that depends on their fare class, e.g., supersaver, coach, etc. At flight-time, the airline bumps passengers in excess of flight capacity and pays a penalty for so doing. A continuous state-space dynamic programming model is developed in which the state is the numbers of reservations currently on hand in each fare class. In each period, reservation requests occur in only one fare class and the fraction of reservations canceling in each class is independent of the number of reservations therein. A booking-limit policy is optimal, i.e., in each period the airline accepts reservation requests up to a booking limit if the number of initial reservations in the fare class is less than the booking limit, and declines reservation requests otherwise. The booking limits for each class depend on the numbers of reservations in the other classes. When there are two fare classes the optimal booking limits in each class decrease with the number of reservations in the other class. © 1996 John Wiley & Sons, Inc.     

Optimal number of minimal repairs before replacement of a system subject to shocks

A system is subject to shocks that arrive according to a nonhomogeneous Poisson process. As shocks occur a system has two types of failures. Type 1 failure (minor failure) is removed by a minimal repair, whereas type 2 failure (catastrophic failure) is removed by replacement. The probability of a type 2 failure is permitted to depend on the number of shocks since the last replacement. A system is replaced at the times of type 2 failure or at the nth type 1 failure, whichever comes first. The optimal policy is to select n* to minimize the expected cost per unit time for an infinite time span. A numerical example is given to illustrate the method. © 1996 John Wiley & Sons, Inc.     

Metastases: Exploring the impact of foreign fighters in conflicts abroad

This article examines the historical impact of foreign fighters and how the international community has sought to counter this threat. It argues that foreign fighters have contributed significantly to the metastasis of Salafi-jihadism over the past 30 years. They have globalized local conflicts. They have brought advanced skills to battlefields. Further, the logistics infrastructure built by foreign fighters has allowed Salafi-jihadism to expand rapidly. The challenge for security officials today is how to prevent the foreign fighters in Syria and Iraq from expanding the threat of Salafi-jihadism further. To inform this effort, this article derives lessons learned from past efforts against Arab Afghans in Bosnia (1992–1995) and Abu Musab al-Zarqawi’s foreign volunteers in Iraq (2003–2008).     

Counterinsurgency as armed reform: The political history of the Malayan Emergency

Despite the emphasis in doctrine and academia that counterinsurgency is in its essence political, these operations are all too commonly discussed and approached as primarily military endeavors. Informed by the need to refocus counterinsurgency studies, this article revisits a foundational case of the canon – the Malayan Emergency – to discuss its political (i.e., not military) unfolding. The analysis distinguishes itself by emphasizing the diplomatic processes, negotiations, and deals that gave strategic meaning to the military operations underway. In so doing, the article also generates insight on the use of leverage and elite bargains in creating new political settlements and bringing insurgent conflicts to an end.     

How long until midnight? Intelligence-policy relations and the United States response to the Israeli nuclear program, 1959–1985

Why did the United States fail to stop Israeli acquisition of nuclear weapons? Existing research argues that patrons such as the U.S. should have an easy time halting proliferation by militarily and economically vulnerable clients. Nevertheless, Israel acquired nuclear weapons with relatively little American opposition. Utilizing extensive primary source research, we argue that problematic intelligence-policy relations hindered U.S. efforts to arrest Israeli proliferation as (1) policymakers often gave mixed guidance to the intelligence community, resulting in (2) limited information on Israeli efforts that reinforced policy ambiguity. The results carry implications for understanding the dynamics of nuclear proliferation and intelligence-policy relations.