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241.
    
In this paper we study a capacity allocation problem for two firms, each of which has a local store and an online store. Customers may shift among the stores upon encountering a stockout. One question facing each firm is how to allocate its finite capacity (i.e., inventory) between its local and online stores. One firm's allocation affects the decision of the rival, thereby creating a strategic interaction. We consider two scenarios of a single‐product single‐period model and derive corresponding existence and stability conditions for a Nash equilibrium. We then conduct sensitivity analysis of the equilibrium solution with respect to price and cost parameters. We also prove the existence of a Nash equilibrium for a generalized model in which each firm has multiple local stores and a single online store. Finally, we extend the results to a multi‐period model in which each firm decides its total capacity and allocates this capacity between its local and online stores. A myopic solution is derived and shown to be a Nash equilibrium solution of a corresponding “sequential game.” © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006  相似文献   
242.
The individual and social optimum control policies for entry to an M/M//1 queue serving several classes of customers have been shown to be control-limit policies. The technique of policy iteration provides the social optimum policy for such a queue in a straightforward manner. In this article, the problem of finding the optimal control policy for the M/Ek/1 system is solved, thereby expanding the potential applicability of the solutions developed. The Markovian nature of the queueing system is preserved by considering the service as having k sequential phases, each with independent, identically distributed, exponential service times, through which a customer must pass to be serviced. The optimal policy derived by policy iteration for such a system is likely to be difficult to use because it requires knowledge of the number of phases rather than customers in the system when an arrival occurs. To circumvent this difficulty, a heuristic is used to find a good usable (implementable) solution. In addition, a mixed-integer program is developed which yields the optimal implementable solution when solved.  相似文献   
243.
    
This paper considers a discrete time, single item production/inventory system with random period demands. Inventory levels are reviewed periodically and managed using a base‐stock policy. Replenishment orders are placed with the production system which is capacitated in the sense that there is a single server that sequentially processes the items one at a time with stochastic unit processing times. In this setting the variability in demand determines the arrival pattern of production orders at the queue, influencing supply lead times. In addition, the inventory behavior is impacted by the correlation between demand and lead times: a large demand size corresponds to a long lead time, depleting the inventory longer. The contribution of this paper is threefold. First, we present an exact procedure based on matrix‐analytic techniques for computing the replenishment lead time distribution given an arbitrary discrete demand distribution. Second, we numerically characterize the distribution of inventory levels, and various other performance measures such as fill rate, base‐stock levels and optimal safety stocks, taking the correlation between demand and lead times into account. Third, we develop an algorithm to fit the first two moments of the demand and service time distribution to a discrete phase‐type distribution with a minimal number of phases. This provides a practical tool to analyze the effect of demand variability, as measured by its coefficient of variation, on system performance. We also show that our model is more appropriate than some existing models of capacitated systems in discrete time. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007  相似文献   
244.
    
We develop models that lend insight into how to design systems that enjoy economies of scale in their operating costs, when those systems will subsequently face disruptions from accidents, acts of nature, or an intentional attack from a well‐informed attacker. The systems are modeled as parallel M/M/1 queues, and the key question is how to allocate service capacity among the queues to make the system resilient to worst‐case disruptions. We formulate this problem as a three‐level sequential game of perfect information between a defender and a hypothetical attacker. The optimal allocation of service capacity to queues depends on the type of attack one is facing. We distinguish between deterministic incremental attacks, where some, but not all, of the capacity of each attacked queue is knocked out, and zero‐one random‐outcome (ZORO) attacks, where the outcome is random and either all capacity at an attacked queue is knocked out or none is. There are differences in the way one should design systems in the face of incremental or ZORO attacks. For incremental attacks it is best to concentrate capacity. For ZORO attacks the optimal allocation is more complex, typically, but not always, involving spreading the service capacity out somewhat among the servers. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011  相似文献   
245.
    
Technologically advanced aircraft rely on robust and responsive logistics systems to ensure a high state of operational readiness. This paper fills a critical gap in the literature for combat models by closely relating effectiveness of the logistics system to determinants of success in combat. We present a stochastic diffusion model of an aerial battle between Blue and Red forces. The number of aircraft of Blue forces aloft and ready to be aloft on combat missions is limited by the maximum number of assigned aircraft, the reliability of aircraft subsystems, and the logistic system's ability to repair and replenish those subsystems. Our parsimonious model can illustrate important trade‐offs between logistics decision variables and operational success.  相似文献   
246.
    
Though parts of Somalia appear mired in intractable conflict, both domestic and foreign trade continues. As a result amidst the conflict, corruption, and chaos Somalia's business community is a small force for peace and stability. Thus, efforts directed at enhancing the business community, possibly via the Transitional Federal Government or its successor, could play a small role in improving the situation in this strategically poised country with a very entrepreneurial population. However, such success is far from certain, and numerous other factors besides a strengthened business community would have to occur for Somalia even to begin the journey on the long road to recovery.  相似文献   
247.
The British Military Covenant can be located in and from many sources and from 2011 onwards in primary legislation. This article argues that the provision of military housing amounts to an early test of how the military covenant is understood and used by those involved in defence policy, and those in the armed forces affected by it. It finds that housing was a prominent feature of how service personnel understood how they were valued, but was not explicitly understood as a covenant issue by those personnel or the officials in charge of the Defence Estates. We locate three reasons for this: (1) the covenant has been poorly translated from aspiration into policy practice, (2) the covenant is unevenly understood across its stakeholders which has the effect of generating disappointment through misaligned expectations, (3) those engaged in the reform process surrounding the Defence Infrastructure Organisation (DIO) saw the covenant as a means to energise reform. Ultimately housing was seen as a dry and technocratic business area and thus an issue ripe for being refracted through the covenant was ultimately left outside of its remit.  相似文献   
248.
The surge in threats aided by or carried out through cyberspace has placed significant pressure on the intelligence community to adapt or leave itself open to attack. Indeed, many in both political and intelligence circles argue for access to ever greater amounts of cyber information in order to catch potential threats before they become real. By collecting all our digital information, the intelligence community argues that it is not only able to detail what people have done or are currently doing but also predict what their next move might be. However, the ethical implications are unclear and the backlash following Edward Snowden’s revelations have shown that such activities are not without controversy. This leaves the debate stuck between the important, ethical role that intelligence can play and the potential for its unrestrained use to cause undue harm. This paper will resolve this by giving greater detail to cyber-intelligence practices, highlighting the different levels of harm that the various intelligence operations can cause. The essence of this paper is not that cyber-intelligence should be banned outright, but that it can be justified given the necessary circumstances. Therefore, the paper will develop a specialised set of Just Cyber-Intelligence Principles, built on the just war tradition, to outline if and when such activities are justified.  相似文献   
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