The use of phase-type distributions in inventory-control models

This article investigates the use of phase-type distributions to model the demand process and the replenishment leadtimes in the standard reorder-point/order-quantity model of inventory control. Our main result is that the marginal distribution of leadtime demand has a discrete phase-type distribution with the same number of phases as the leadtime distribution, regardless of the complexity of the inter-demand times. This result leads to relatively tractable formulas for several standard performance criteria.     

Performance and properties of Q‐Statistic monitoring schemes

In this article, we study the Shewhart chart of Q statistics proposed for the detection of process mean shifts in start‐up processes and short runs. Exact expressions for the run‐length distribution of this chart are derived and evaluated using an efficient computational procedure. The procedure can be considerably faster than using direct simulation. We extend our work to analyze the practice of requiring multiple signals from the chart before responding, a practice sometimes followed with Shewhart charts. The results show that waiting to receive multiple signals severely reduces the probability of quickly detecting shifts in certain cases, and therefore may be considered a risky practice. Operational guidelines for practitioners implementing the chart are discussed. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009     

Panjwai: a tale of two COINs in Afghanistan

The US Army has two approaches to counterinsurgency operations in Afghanistan. One is hard, or combat-focused, and the other is soft, or development-focused. This study examines two US Army task forces deployed to Panjwai District, Afghanistan from 2012 to 2013. CTF 4-9 and 1-38 offer a meaningful comparison because they pursued these contrasting approaches among the same population and against the same enemy at the same time and place. The study compares each unit’s approach and finds that neither approach was successful absent the other. The article concludes by recommending further research into combining the approaches at the operational level.     

Optimal timing of switches between product sales for sports and entertainment tickets

Like airlines and hotels, sports teams and entertainment venues can benefit from revenue management efforts for their ticket sales. Teams and entertainment venues usually offer bundles of tickets early in their selling horizon and put single‐event tickets on sale at a later date; these organizations must determine the best time to offer individual tickets because both types of ticket sales consume the same fixed inventory. We model the optimal a priori timing decision for a seller with a fixed number of identical tickets to switch from selling the tickets as fixed bundles to individual tickets to maximize the revenue realized before the start of the performance season. We assume that bundle and single‐ticket customers each arrive according to independent, nonhomogeneous Markovian death processes with a linear death rate that can vary over time and that the benefit from selling a ticket in a package is higher than from selling the ticket individually. We characterize the circumstances in which it is optimal for the seller to practice mixed bundling and when the seller should only sell bundles or individual tickets, and we establish comparative statics for the optimal timing decision for the special case of constant customer arrival rates. We extend our analytical results to find the optimal time for offering two groups of tickets with high and low demand. Finally, we apply the timing model to a data set obtained from the sports industry. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

Aerial intelligence during the Algerian war

Aviation had a highly significant role in supporting French military operations in Algeria. This was particularly true of aerial reconnaissance and intelligence gathering. Initially, however, the Air Force effort was handicapped by inappropriate approaches, too few army/air liaison officers and scepticism among army officers aware of the difficulties of earlier air operations against an insurgency in Indochina (1946–54). It also lacked sufficient suitable aircraft types. Gradually, improved aircraft and photographic techniques permitted systematic and detailed aerial mapping and intelligence work, as well as rapid provision of close air support during ground battles. Better integration of air and ground forces, along with more coordinated command and control, arrived from 1959 onwards when an air force general, Maurice Challe, became inter-service commander-in-chief in Algeria. This permitted an authentic and mostly effective combined-airms and joint service approach to the locating, tracking, engagement and destruction of Algerian nationalist bands.     

The Naval Intelligence Underpinnings of Reagan's Maritime Strategy

Washington's so-called Maritime Strategy, which sought to apply US naval might against Soviet vulnerabilities on its maritime flanks, came to full fruition during the 1980s. The strategy, which witnessed a major buildup of US naval forces and aggressive exercising in seas proximate to the USSR, also explicitly targeted Moscow”s strategic missile submarines with the aim of pressuring the Kremlin during crises or the early phases of global war. Relying on a variety of interviews and newly declassified documents, the authors assert that the Maritime Strategy represents one of the rare instances in history when intelligence helped lead a nation to completely revise its concept of military operations.