A deterministic inventory model for reparable items

A reparable inventory system has two distinct inventories within it—the inventory of items ready-for-issue and the inventory of carcasses available for repair. A reparable item is usually rebuilt upon failure, but the scrap rate in the repair process is generally positive. Consequently, new items must be procured from time to time to replace those item: which were scrapped. The ready-for-issue inventory has two input sources—procurement and repair, This paper develops a deterministic inbentory model for the reparable inventory system, and determines the optimal procurement and repair quantities.     

Expected waiting time rankings in extended machine-repair models

The present paper studies the relative magnitudes of expected waiting times in extended machine-repair models, when processing times are of two Erlang types. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 864–870, 1999     

The impact of exponential smoothing forecasts on the bullwhip effect

An important phenomenon often observed in supply chain management, known as the bullwhip effect, implies that demand variability increases as one moves up the supply chain, i.e., as one moves away from customer demand. In this paper we quantify this effect for simple, two‐stage, supply chains consisting of a single retailer and a single manufacturer. We demonstrate that the use of an exponential smoothing forecast by the retailer can cause the bullwhip effect and contrast these results with the increase in variability due to the use of a moving average forecast. We consider two types of demand processes, a correlated demand process and a demand process with a linear trend. We then discuss several important managerial insights that can be drawn from this research. © 2000 John Wiley & Sons, Inc. Naval Research Logistics 47: 269–286, 2000     

On scheduling with ready-times,due-dates and vacations

A single machine sequencing problem is considered in which there are ready-time and due-date constraints on jobs and vacation constraints on the machine. Each vacation has fixed starting and finish time and no preemption is allowed for the jobs. The objective is to minimize maximum lateness. An intriguing feature of this formulation is that it allows sequencing in disconnected time windows. A relaxation of the problem is obtained by modeling the vacations as a set of jobs with flexible ready-times and artificial due-dates and a branch and bound algorithm is developed for the problem. In the algorithm, the search is not only guided by the bounds but also by a careful manipulation of the artificial due-dates. Consequently; while searching in the relaxed solution space, solutions of the original problem are implicitly enumerated. Computational results indicate that the algorithm can satisfactorily solve problems with multiple vacations.     

Strength in Numbers: The Labour Government and the Size of the Polaris Force

Previous historical accounts have simplified the Labour government's decision to commission a four-boat strategic nuclear deterrent, or ‘Polaris force’, in early 1965. Utilising previously classified sources, this article shows that a number of key strategic concerns led the decision-making process. Nevertheless, broader economic and diplomatic considerations were also important in determining the size of the Polaris force. A tremendous balance of payments deficit and ongoing debates regarding levels of conventional and nuclear involvement in NATO certainly influenced the government's final decision. Moreover, competing strategic and economic interests resulted in continued debate throughout the decision-making process.     

Communications intelligence and the battle for convoy OG 71, 15–23 August 1941

In 1941, the British instituted a comprehensive system of convoys in the Atlantic. One of the first convoys, OG 71, while sailing between Britain and Gibraltar, was shadowed by German aircraft and attacked by U‐boats. In the ensuing August battle, while no U‐boats were sunk, the British lost, out of a convoy consisting of 22 vessels, two escorts and eight merchant ships. The German victory was not complete owing to the inability of the German aircraft and U‐boats to cooperate successfully as well as the failure of the U‐boats to fight the battle effectively and aggressively. The British also made many mistakes during the defence of Convoy OG 71. The surface escorts made many errors of tactics; as for the British aircraft, owing to an inability to cooperate with the surface forces, they became almost totally ineffective. One bright spot for the British during the battle, however, was communications intelligence. The battle saw the first use of high frequency direction finders and on several occasions skillful use was made of information obtained from enemy radio transmissions. In fact important lessons were learned by the British from such use of communications intelligence which would pave the way for a more effective implementation of such information in future convoy battles.     

Jonathan Boff Winning and Losing on the Western Front. The British Third Army and the Defeat of Germany in 1918.

Building indigenous armies in Asia with military advisory and aid programs has been a mission of the United States Army for over 100 years. Creation of an indigenous army was an early goal of American occupation policy in Korea, but little support and resources were assigned. Between 1946 and 1948, a minute American advisory effort partially trained and equipped a Korean Army cadre of 25,000 men. The unceasing efforts of a talented American advisor, Captain James Hausman, made success possible. He dominated the small advisory group, was given carte blanche to implement his ideas, and left indelible changes on what became the South Korean Army.