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531.
刘钊 《武警工程学院学报》2010,(2):52-53,58
为提高低活性粉煤灰在混凝土中的利用,依据《水泥胶砂强度检验方法》和《普通混凝土力学性能试验方法标准》,通过复掺CaO、CaSO4及防水剂、减水剂等材料对低活性粉煤灰进行了活化实验研究和混凝土性能测试研究,试验结果表明:经过活化处理后的粉煤灰重新获得了活性,提高了混凝土的强度、降低了泌水率、减小了坍落度经时的损失,从而有助于低活性粉煤灰的开发利用。 相似文献
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A defender wants to detect as quickly as possible whether some attacker is secretly conducting a project that could harm the defender. Security services, for example, need to expose a terrorist plot in time to prevent it. The attacker, in turn, schedules his activities so as to remain undiscovered as long as possible. One pressing question for the defender is: which of the project's activities to focus intelligence efforts on? We model the situation as a zero‐sum game, establish that a late‐start schedule defines a dominant attacker strategy, and describe a dynamic program that yields a Nash equilibrium for the zero‐sum game. Through an innovative use of cooperative game theory, we measure the harm reduction thanks to each activity's intelligence effort, obtain insight into what makes intelligence effort more effective, and show how to identify opportunities for further harm reduction. We use a detailed example of a nuclear weapons development project to demonstrate how a careful trade‐off between time and ease of detection can reduce the harm significantly. 相似文献
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简要介绍根据电磁辐射测量理论设计的一款电磁辐射测量仪,并在此基础上详细阐述各种抗干扰措施,包括软件和硬件相应的抗干扰设计。实验证明,该测量仪运行正常,抗干扰性能良好。 相似文献
536.
大型消防装备采购模式存在的一些问题,影响了大型消防装备全寿命期的经费使用效益,导致大型消防装备的购置费用高而效率低,装备闲置和利用率不高,装备全寿命期费用控制效果较差,必须建立大型消防装备全寿命费用管理体系,提高大型消防装备投资的效率。 相似文献
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R. Derek Trunkey 《Defence and Peace Economics》2019,30(4):454-461
The rate at which operating costs grow as aircraft age is important for setting operating budgets and for deciding when to replace aging systems. While studies using data from the 1990's typically found 1–3 percent real rates of growth in operating costs as aircraft age, studies using data from the 2000's found greater rates, for example in the 4–6 percent range. Growth in the total U.S. Air Force budget during the 2000s appears to explain much of the higher estimated annual growth rates in operating costs per flying hour beyond the growth rate intrinsic to the aging of the fleet. 相似文献
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We study the problem of designing a two‐echelon spare parts inventory system consisting of a central plant and a number of service centers each serving a set of customers with stochastic demand. Processing and storage capacities at both levels of facilities are limited. The manufacturing process is modeled as a queuing system at the plant. The goal is to optimize the base‐stock levels at both echelons, the location of service centers, and the allocation of customers to centers simultaneously, subject to service constraints. A mixed integer nonlinear programming model (MINLP) is formulated to minimize the total expected cost of the system. The problem is NP‐hard and a Lagrangian heuristic is proposed. We present computational results and discuss the trade‐off between cost and service. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009 相似文献
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There has been a dramatic increase over the past decade in the number of firms that source finished product from overseas. Although this has reduced procurement costs, it has increased supply risk; procurement lead times are longer and are often unreliable. In deciding when and how much to order, firms must consider the lead time risk and the demand risk, i.e., the accuracy of their demand forecast. To improve the accuracy of its demand forecast, a firm may update its forecast as the selling season approaches. In this article we consider both forecast updating and lead time uncertainty. We characterize the firm's optimal procurement policy, and we prove that, with multiplicative forecast revisions, the firm's optimal procurement time is independent of the demand forecast evolution but that the optimal procurement quantity is not. This leads to a number of important managerial insights into the firm's planning process. We show that the firm becomes less sensitive to lead time variability as the forecast updating process becomes more efficient. Interestingly, a forecast‐updating firm might procure earlier than a firm with no forecast updating. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009 相似文献