A simple approximation for a multistage capacitated production-inventory system

We develop a simple approximation for multistage production-inventory systems with limited production capacity and variable demands. Each production stage follows a base-stock policy for echelon inventory, constrained by production capacity and the availability of upstream inventory. Our objective is to find base-stock levels that approximately minimize holding and backorder costs. The key step in our procedure approximates the distribution of echelon inventory by a sum of exponentials; the parameters of the exponentials are chosen to match asymptotically exact expressions. The computational requirements of the method are minimal. In a test bed of 72 problems, each with five production stages, the average relative error for our approximate optimization procedure is 1.9%. © 1996 John Wiley & Sons, Inc.     

Evaluation of base-stock policies in multiechelon inventory systems with state-dependent demands part I: State-independent policies

This article analyzes a model of a multiechelon inventory system. The exogenous demands form Markov-modulated Poisson processes. That is, the demand rates are functions of an underlying Markov chain. Each location follows a base-stock policy which is independent of the state of the underlying Markov chain. We employ the exogenous transit mechanism introduced by Zipkin [7] and Svoronos and Zipkin [6]. The transit times between locations have phase-type distributions. An exact procedure to compute steady-state performance measures is presented. © 1992 John Wiley & Sons, Inc.     

Does Terrorism Increase after a Natural Disaster? An Analysis based upon Property Damage

Does an emergency such as a natural disaster lead to a surge of terrorism? This paper contributes to the emerging literature on this issue. We consider the experience of 129 countries during the period 1998–2012 to determine the effect of a natural disaster on both domestic as well as transnational terrorism. We also control for endogeneity using expenditure on health care and land area in a country as instruments. In contrast to the existing literature, we measure the extent of terrorism by the value of property damage. The results indicate that after natural disasters, (a) transnational terrorism increases with a lag, and (b) a statistically significant impact on domestic terrorism is not observed.     

The effects of information on a queue with balking and phase‐type service times

This article generalizes the models in Guo and Zipkin, who focus on exponential service times, to systems with phase‐type service times. Each arriving customer decides whether to stay or balk based on his expected waiting cost, conditional on the information provided. We show how to compute the throughput and customers' average utility in each case. We then obtain some analytical and numerical results to assess the effect of more or less information. We also show that service‐time variability degrades the system's performance. © 2008 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.