Optimal base stock policies and truck capacity in a two-echelon system

With the recent trend toward just-in-time deliveries and reduction of inventories, many firms are reexamining their inventory and logistics policies. Some firms have dramatically altered their inventory, production, and shipping policies with the goal of reducing costs and improving service. Part of this restructuring may involve a specific contract with a trucking company, or it may entail establishing in-house shipping capabilities. This restructuring, however, raises new questions regarding the choice of optimal trucking capacity, shipping frequency, and inventory levels. In this study, we examine a two-level distribution system composed of a warehouse and a retailer. We assume that demand at the retailer is random. Since the warehouse has no advance notice of the size of the retailer order, inventory must be held there as well as at the retailer. We examine inventory policies at both the warehouse and the retailer, and we explicitly consider the trucking capacity, and the frequency of deliveries from the warehouse to the retailer. Both linear and concave fixed transportation costs are examined. We find the optimal base stock policies at both locations, the optimal in-house or contracted regular truck capacity, and the optimal review period (or, equivalently, delivery frequency). For the case of normally distributed demand we provide analytical results and numerical examples that yield insight into systems of this type. Some of our results are counterintuitive. For instance, we find some cases in which the optimal truck capacity decreases as the variability of demand increases. In other cases the truck capacity increases with variability of demand. © 1993 John Wiley & Sons, Inc.     

Sojourn times in G/M/1 fork‐join networks

We consider a processing network in which jobs arrive at a fork‐node according to a renewal process. Each job requires the completion of m tasks, which are instantaneously assigned by the fork‐node to m task‐processing nodes that operate like G/M/1 queueing stations. The job is completed when all of its m tasks are finished. The sojourn time (or response time) of a job in this G/M/1 fork‐join network is the total time it takes to complete the m tasks. Our main result is a closed‐form approximation of the sojourn‐time distribution of a job that arrives in equilibrium. This is obtained by the use of bounds, properties of D/M/1 and M/M/1 fork‐join networks, and exploratory simulations. Statistical tests show that our approximation distributions are good fits for the sojourn‐time distributions obtained from simulations. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

Netwar Revisited: The Fight for the Future Continues

This work continues to develop the 'netwar' concept that the authors introduced in 1993 and have expanded upon in their various RAND and other writings ever since. Deeper understanding of the nature, strengths and vulnerabilities of networks will prove useful in combating terrorism and transnational crime, but also in understanding militant social activism, both of the violently disruptive sort and that which aims at fostering the rise of a global civil society. This essay also assesses recent US performance in the terror war, and concludes by raising concerns over the possible rise of a new form of network-based fascism.     

Balancing stability and efficiency in team formation as a generalized roommate problem

The assignment of personnel to teams is a fundamental managerial function typically involving several objectives and a variety of idiosyncratic practical constraints. Despite the prevalence of this task in practice, the process is seldom approached as an optimization problem over the reported preferences of all agents. This is due in part to the underlying computational complexity that occurs when intra-team interpersonal interactions are taken into consideration, and also due to game-theoretic considerations, when those taking part in the process are self-interested agents. Variants of this fundamental decision problem arise in a number of settings, including, for example, human resources and project management, military platooning, ride sharing, data clustering, and in assigning students to group projects. In this article, we study an analytical approach to “team formation” focused on the interplay between two of the most common objectives considered in the related literature: economic efficiency (i.e., the maximization of social welfare) and game-theoretic stability (e.g., finding a core solution when one exists). With a weighted objective across these two goals, the problem is modeled as a bi-level binary optimization problem, and transformed into a single-level, exponentially sized binary integer program. We then devise a branch-cut-and-price algorithm and demonstrate its efficacy through an extensive set of simulations, with favorable comparisons to other algorithms from the literature.     

The Production and Deposition of the Guisborough Helmet

In September 1878 the British Museum received a donation of a folded metal plate which had been embossed and gilded. Restoration of the object revealed that the folded plate was in fact the outer casing of a Roman copper alloy cavalry sports type helmet which dates to the late second or third century AD. The story of what became known as the Guisborough helmet began 14 years earlier in what was then the North Riding of Yorkshire when workers employed by the Cleveland Railway Company discovered a ‘very curious plate of metal’ during road construction. It appears that the helmet was deliberately prepared for deposition and buried at a depth of c30 cm close to a stream. Examination by the authors suggests that this was a high value item that had been repaired many times. Experimental evidence suggests that the decoration alone required approximately 16 h to fashion.     

The human consequences of foreign military intervention

The empirical international conflict literature has given much recent attention to interstate armed force’s impact on human well-being. While empirical research has advanced our understanding of the phenomenon considerably, we argue that one conclusion that many studies have reached is preliminary. Some recent research contends that only full-scale war, and not force short of war, has a discernable impact on human welfare or physical quality of life (PQOL). We develop theory on one type of force short of war, large-scale foreign military intervention (FMI), and its potential effects on PQOL. Using interrupted time series and panel corrected standard error methodologies, we find that from 1960 to 2005 large-scale FMI had a statistically and substantively significant impact on the PQOL of populations in 106 developing countries. The specific effect that this type of armed force has depended in large part on the regime type of the target country.     

ON THE RELATIONSHIP BETWEEN MILITARY EXPENDITURE,THREAT, AND ECONOMIC GROWTH: A NONLINEAR APPROACH

The main objective of the paper is to decipher the military expenditure–economic growth relationship, taking the level of economic development (income) into consideration. Our findings suggest the following: (i) military expenditure has a significantly negative relationship to economic growth for the 23 countries with initial incomes (threshold variable) less than or equal to $475.93; (ii) when the threat level is heightened, economic growth (23 countries) is expected to decrease. However, military expenditure in the presence of sufficiently large threats increases growth; (iii) for the remaining 69 countries whose initial incomes (real GDP per capita in 1992 price) exceed $475.93, no significant relationship exists whether the threat variable is taken into consideration or not.     

Individual preferences and the demand for military expenditure*

Whose preferences determine the tradeoff between security and civilian output in deciding upon budget allocations to defence? This paper considers the role that consumer preferences might play in influencing military spending. We propose normative criteria to judge the economic or political efficiency of defence provision at a given time, and test them using Australian survey‐based micro‐data. Our results suggest that the political system has not delivered a simple social‐choice translation of individual preferences into collective outcomes, nor has it delivered results consistent with simple majority‐voting median preferences.     

A note on the financial condition of defense contractors

In recent years, there have been several changes in the weapon‐system acquisition market which have the potential to negatively impact the financial condition of defense contractors. This study evaluates the financial health of defense firms vis‐a‐vis nondefense firms using a fiscal distress identification model developed by E.I. Altman. We conclude that the financial condition of defense firms has deteriorated but the deterioration is the same as experienced by nondefense firms.     

Evaluating the trade‐off between military spending and investment in the United States

Using tests of a single equation model and cointegration techniques, this paper finds no evidence of a long run trade‐off, and some evidence of a short‐run trade‐off, between military spending and investment in post‐World War II United States data. The short‐run trade‐off is confined to the 1949–1971 period, and may be the result of the sharp expansion and contraction of military outlays in connection with the Korean and Vietnam Wars. In addition, cointegration techniques are used to identify a possible long‐run trade‐off between military spending and consumption.