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81.
Research and development activities in a business firm or government laboratory are portrayed as a multi-stage information generation and conversion process. A “basic research” phase generates opportunities, in the form of findings in a set of scientific disciplines, which are available for subsequent exploitation. It is assumed that increments to information in a subject area are stochastic, proportional to the amount of knowledge which already exists in the area, and have values which are randomly distributed. An “exploratory development” phase is viewed as a process of selecting a subset of alternative research opportunities, improving each opportunity in the direction of its applications, estimating the value of the improved opportunity and using these estimates to choose the exploratory development results to be implemented in engineering development. The “engineering development” phase makes the value of exploratory results realizable without changing value or risk. Engineering development costs are assumed to increase as value increases. If exploratory development is not successful, additional costs in engineering development must be incurred to bring the design up to a minimum desirable level. The model is intended as a step toward formulating and analyzing problems in management planning and control of the several interrelated stages of the research and development process.  相似文献   
82.
A major challenge in making supply meet demand is to coordinate transshipments across the supply chain to reduce costs and increase service levels in the face of demand fluctuations, short lead times, warehouse limitations, and transportation and inventory costs. In particular, transshipment through crossdocks, where just‐in‐time objectives prevail, requires precise scheduling between suppliers, crossdocks, and customers. In this work, we study the transshipment problem with supplier and customer time windows where flow is constrained by transportation schedules and warehouse capacities. Transportation is provided by fixed or flexible schedules and lot‐sizing is dealt with through multiple shipments. We develop polynomial‐time algorithms or, otherwise, provide the complexity of the problems studied. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005  相似文献   
83.
Conventional wisdom seems to hold that under Barack Obama, the US ballistic missile defence programme has been pushed aside to allow for a refreshed domestic and international agenda. Proponents point to Obama's campaign thinking and rhetoric, the ballistic missile defence (BMD) budget cuts, the decision to end the Third Site in Europe, and the reset relations with Russia through the New Strategic Arms Reduction Treaty (New START) as evidence that the programme has undergone a significant period of change, retraction and rationalisation. This article argues instead that BMD has not fallen from prominence and that there is a change in focus rather than retraction of its strategic goal. Consequently, BMD continues to grow in importance as a component of US national security strategy.  相似文献   
84.
From the Barents and the Baltic Sea in the north, through Central Europe and the Balkans, to the Black Sea in the south a range of new subregional groups and cooperation processes have emerged in Europe during the 1990s. Compared to NATO and the European Union, these new subregional groups have received little attention. Their ‘indirect approach’ to security, however, plays an important role in overcoming the legacy of the Cold War, reducing the risks of military conflict and addressing non‐military security challenges. As NATO and the EU expand eastwards, subregionalism is assuming growing importance as a means of avoiding new ‘dividing lines’ in Europe. After the wars in Bosnia and Kosovo, subregionalism is also gaining importance as a means of building cooperation in South‐Eastern Europe. The challenge for the future is to give more substance and depth to Europe's new subregional cooperation frameworks.  相似文献   
85.
Politicians, political pundits, and others focus a lot of attention on the political militias in Iraq, usually blaming them for their destabilising effect on the country and insisting that they disband. This study examines the impact that the militias in Iraq have on the Iraqi government's ability to consolidate control over its territory by first explaining how militias rose to prominence in Iraq during the power vacuum created by Saddam Hussein's ousting, then analysing the many ways militias adversely impact the security situation. The study then examines the other side of the argument – that is, why militias enjoy so much support in Iraq among their constituencies, and why they may actually be necessary to achieve stability in Iraq in the short term.  相似文献   
86.
We consider the problem of placing sensors across some area of interest. The sensors must be placed so that they cover a fixed set of targets in the region, and should be deployed in a manner that allows sensors to communicate with one another. In particular, there exists a measure of communication effectiveness for each sensor pair, which is determined by a concave function of distance between the sensors. Complicating the sensor location problem are uncertainties related to sensor placement, for example, as caused by drifting due to air or water currents to which the sensors may be subjected. Our problem thus seeks to maximize a metric regarding intrasensor communication effectiveness, subject to the condition that all targets must be covered by some sensor, where sensor drift occurs according to a robust (worst‐case) mechanism. We formulate an approximation approach and develop a cutting‐plane algorithm to solve this problem, comparing the effectiveness of two different classes of inequalities. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 582–594, 2015  相似文献   
87.
88.
Acceptance sampling is often used to monitor the quality of raw materials and components when product testing is destructive, time-consuming, or expensive. In this paper we consider the effect of a buyer-imposed acceptance sampling policy on the optimal batch size and optimal quality level delivered by an expected cost minimizing supplier. We define quality as the supplier's process capability, i.e., the probability that a unit conforms to all product specifications, and we assume that unit cost is an increasing function of the quality level. We also assume that the supplier faces a known and constant “pass-through” cost, i.e., a fixed cost per defective unit passed on to the buyer. We show that the acceptance sampling plan has a significant impact on the supplier's optimal quality level, and we derive the conditions under which zero defects (100% conformance) is the policy that minimizes the supplier's expected annual cost. © 1997 John Wiley & Sons, Inc. Naval Research Logistics 44: 515–530, 1997  相似文献   
89.
This article generalizes the classical periodical replacement model with minimal repair by considering the effect of the overhaul, which is assumed to be able to rejuvenate the system. The generalization is based on the notion of the virtual age of a system introduced by Kijima, Morimura, and Suzuki [“Periodical Replacement Problem without Assuming Minimal Repair,” European Journal of Operational Research, 37 , 194–203 (1988)]. © 1995 John Wiley & Sons, Inc.  相似文献   
90.
Harvard professor Samuel P. Huntington has frequently been considered a Vietnam War hawk. His observation that ‘forced-draft urbanization’ might help the United States win the war has come to define his engagement in contemporary strategic debates. This essay argues that both Huntington’s academic work and his private policy advice to the U.S. Government in fact urged a political settlement to the conflict. It argues that in spite of this, Huntington refused to break publicly with the U.S. policy because of his wider concern over what he saw as a crisis of authority in the U.S. foreign policy and governing institutions in the era.  相似文献   
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