Some comments on the optimal assembly problem

It is shown that two recent results of Baxter and Harche [1] on monotone and balanced optimal assemblies hold only under conditions that are more restrictive than those originally proposed by the authors. We describe such additional conditions, illustrate why they are needed, and establish their sufficiency. We also consider a recent result by Malon [11] and demonstrate that, while the result itself is correct, its two proofs were incomplete. A complete proof of an extension of the result is then suggested. © 1995 John Wiley & Sons, Inc.     

An historical review of US defense strategy from Vietnam to operation Iraqi freedom

Facing nearly half a billion dollars in spending cuts over the next five years, US defense planners and strategists must simultaneously rebuild a war-weary Army weakened from over a decade of war, build new sea and air capabilities for the Pacific theater, and reduce manpower, procurement, and contractor budgets while promoting innovation. The US defense department is embarking on what may be the most sweeping period of defense transformation in recent memory. This article reviews the history of American defense transformation, focusing on an important but largely overlooked period of military innovation that began in the shadow of Vietnam and ended with troops fighting through blinding sandstorms at night on the road to Baghdad. The multifaceted transformation strategy conceived in the 1970s paved the way for a military revolution in the 1990s and enabled unprecedented battlefield adaptation in the 2000s. After reviewing the revolutionary changes that led to American dominance in conventional warfare in the 1990s, the article examines US transformation policies in the 2000s to inform defense strategy and planning efforts in the 2010s.     

Diffusion approximation to the G/G/R machine repair problem with warm standby spares

The G/G/R machine repair problem with M operating machines, S warm standby spares, and R repairmen is studied as a diffusion process. The steady-state equations are formulated as diffusion equations subject to two reflecting barriers. The approximate diffusion parameters of the diffusion equations are obtained (1) under the assumption that the input characteristics of the problem are defined only by their first two moments rather than their probability distribution function, (2) under the assumption of heavy traffic approximation, that is, when queues of failed machines in the repair stage are almost always nonempty, and (3) using well-known asymptotic results from renewal theory. Expressions for the probability density functions of the number of failed machines in the system are obtained. A study of the derived approximate results, compared to some of the exact results, suggests that the diffusion approach provides a useful method for solving complex machine-repair problems.     

An application of yield management for Internet Service Providers

In this paper we study strategies for better utilizing the network capacity of Internet Service Providers (ISPs) when they are faced with stochastic and dynamic arrivals and departures of customers attempting to log‐on or log‐off, respectively. We propose a method in which, depending on the number of modems available, and the arrival and departure rates of different classes of customers, a decision is made whether to accept or reject a log‐on request. The problem is formulated as a continuous time Markov Decision Process for which optimal policies can be readily derived using techniques such as value iteration. This decision maximizes the discounted value to ISPs while improving service levels for higher class customers. The methodology is similar to yield management techniques successfully used in airlines, hotels, etc. However, there are sufficient differences, such as no predefined time horizon or reservations, that make this model interesting to pursue and challenging. This work was completed in collaboration with one of the largest ISPs in Connecticut. The problem is topical, and approaches such as those proposed here are sought by users. © 2001 John Wiley & Sons, Inc., Naval Research Logistics 48:348–362, 2001     

Anarchy’s anatomy: Two-tiered security systems and Libya’s civil wars

ABSTRACT

No issue deserves more scrutiny than the mechanisms whereby popular unrest unleashes civil wars. We argue that one institution – two-tiered security systems – is particularly pernicious in terms of the accompanying civil war risk. These systems’ defining characteristic is the juxtaposition of small communally stacked units that protect regimes from internal adversaries with larger regular armed forces that deter external opponents. These systems aggravate civil war risks because stacked security units lack the size to repress widespread dissent, but inhibit rapid regime change through coup d’état. Regular militaries, meanwhile, fracture when ordered to employ force against populations from which they were recruited.