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241.
We consider a distribution system consisting of a central warehouse and a group of retailers facing independent stochastic demand. The retailers replenish from the warehouse, and the warehouse from an outside supplier with ample supply. Time is continuous. Most previous studies on inventory control policies for this system have considered stock‐based batch‐ordering policies. We develop a time‐based joint‐replenishment policy in this study. Let the warehouse set up a basic replenishment interval. The retailers are replenished through the warehouse in intervals that are integer multiples of the basic replenishment interval. No inventory is carried at the warehouse. We provide an exact evaluation of the long‐term average system costs under the assumption that stock can be balanced among the retailers. The structural properties of the inventory system are characterized. We show that, although it is well known that stock‐based inventory control policies dominate time‐based inventory control policies at a single facility, this dominance does not hold for distribution systems with multiple retailers and stochastic demand. This is because the latter can provide a more efficient mechanism to streamline inventory flow and pool retailer demand, even though the former may be able to use more updated stock information to optimize system performance. The findings of the study provide insights about the key factors that drive the performance of a multiechelon inventory control system. © 2013 Wiley Periodicals, Inc. Naval Research Logistics 60: 637–651, 2013 相似文献
242.
This article studies a firm that procures a product from a supplier. The quality of each product unit is measured by a continuous variable that follows a normal distribution and is correlated within a batch. The firm conducts an inspection and pays the supplier only if the product batch passes the inspection. The inspection not only serves the purpose of preventing a bad batch from reaching customers but also offers the supplier an incentive to improve product quality. The firm determines the acceptance sampling plan, and the supplier determines the quality effort level in either a simultaneous game or a Stackelberg leadership game, in which both parties share inspection cost and recall loss caused by low product quality. In the simultaneous game, we identify the Nash equilibrium form, provide sufficient conditions that guarantee the existence of a pure strategy Nash equilibrium, and find parameter settings under which the decentralized and centralized supply chains achieve the same outcome. By numerical experiments, we show that the firm's acceptance sampling plan and the supplier's quality effort level are sensitive to both the recall loss sharing ratio and the game format (i.e., the precommitment assumption of the inspection policy). © 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013 相似文献
243.
George Dimitriu 《Small Wars & Insurgencies》2013,24(3):429-458
Rarely has a military commitment led to such intense discussion in the Netherlands as the Task Force Uruzgan (TFU) mission in Afghanistan. In February 2010, the Netherlands' coalition government even collapsed after the two largest parties failed to agree on the withdrawal of Dutch troops from Afghanistan later this year. This article deals first of all with the difficult discussion over the Afghanistan mission of the TFU. The authors then subject three ISAF operations to close scrutiny. The authors provide some suggestions to help understand better this pivotal point in the execution of the whole operation and thus give a fuller picture of the Dutch counterinsurgency approach in Uruzgan. 相似文献
244.
Thomas-Durell Young 《战略研究杂志》2013,36(7):1031-1057
By any objective measure, defense institutions in Central and Eastern Europe have all but universally been incapable of producing viable defense plans that are based on objective costing and operational planning data. This situation exists in spite the provision of considerable Western advice and assistance, let alone reporting to and receiving assessments by NATO’s International Staff under Partnership for Peace, as well as via the integrated defense planning and reporting systems. An explanation for this systematic failure across European post-Communist defense institutions can be found in the continued slow development of an over-arching policy framework which directs and approves all activities of the armed forces, as well as the de-centralization of financial decision-making down to capability providers. The essay ends with an examination of the adverse effects of the early introduction of planning programming, budgeting system (PPBS), have had on the development of effective policy and planning capabilities within these defense institutions. 相似文献
245.
Unlike treaties dealing with nuclear and chemical weapons, the Biological Weapons Convention still lacks formal verification measures, 31 years after entering into force. Here we propose a global export-import monitoring system of biological dual-use items as an additional measure for a web of biological arms controls that could complement traditional export controls. We suggest that such a measure may help to guide consultation or verification processes in the biological area. 相似文献
246.
Curtis H. Martin 《The Nonproliferation Review》2013,20(1):61-88
Scholarly and popular literature in the recent past has framed nonproliferation diplomacy toward both Iran and North Korea as an example of “good cop/bad cop,” a social-psychological strategy borrowed from law enforcement to describe a process for forcing a confession by subjecting a target to stressful emotional contrast. This article examines those two cases, roughly covering the period since 2003, when the most recent attempts to deal with the Iranian and North Korean proliferation threats began, in light of criteria for employment of the good cop/bad cop strategy. There is some evidence that within the framework of the six-party talks with North Korea and within the framework of the EU-3-U.S. diplomacy toward Iran, the players seeking nonproliferation have adopted good cop/bad cop roles to that end. The article concludes, however, that while there are similarities to the interrogation room technique, the complexity of the international political environment as compared to the interrogation room has prevented the states involved from successfully adopting or effectively exploiting good and bad cop roles. Substantial and exploitable differences of interest among them, and the availability of alternative “escape routes” for the target state, raise serious questions about the applicability of the good cop/bad cop strategy to these two nonproliferation cases, and even about its applicability in future nonproliferation challenges. 相似文献
247.
为了提高无人机自主飞行、自主攻击的能力,设计一种整体式的无人机综合火力/飞行控制系统(IFFC系统),并对激光制导炸弹模态下的系统进行数字仿真.系统基于Winsock的TCP/IP协议的C/S模式,在服务器上完成无人机火控解算、火飞耦合器设计,在客户端设计基于PID算法的飞行控制模块.火控系统根据飞行状态和目标信息实时计算炸弹可达区域,瞄准距离误差经过火飞耦合器形成航向和俯仰控制命令反馈给飞控系统,驱动载机消.除瞄准误差,实现闭环控制.实验结果表明,无人机的瞄准速度和攻击精度都有所提高,为进一步开展自主式UAV的研究打下基础. 相似文献
248.
The effects of magnesium/polytetrafluoroethylene (Mg/PTFE) pyrotechnic compositions on the coupled flow field and reignition mechanism are important aspects governing the performance and range of base bleed projectiles (BBPs).Owing to a decrease in pressure and temperature when the BBP leaves the muzzle,rapid depressurization occurs,which extinguishes the base bleed propellant.The Mg/PTFE py-rotechnic composition pressed in the igniter of the base bleed unit (BBU) provides additional energy to the BBU via a chemical reaction.Thus,the extinguished base bleed propellant is reignited under the effect of high-temperature combustion gas jets from the igniter.In this study,a numerical analysis is conducted to evaluate the effects of PTFE and Mg granularity as well as Mg/PTFE pyrotechnic compo-sitions.Owing to the rapid depressurization,the temperature and pressure was found to decrease for different Mg/PTFE pyrotechnic compositions.However,the depressurization time increased as the PTFE granularity increased,the Mg granularity decreased,and the Mg content increased.When the pressure in the combustion chamber of the BBU decreased to the atmospheric pressure,the combustion gas jets from the igniter expand upstream (rather than downstream).However,these combustion gas jets exhibit different axial and radial expansion characteristics depending on the pyrotechnic compositions used.The results show that the reignition delay time,td,of the base bleed propellant was 377.608,94.27,387.243,523.966,and 221.094 ms for cases A-E,respectively.Therefore,it was concluded that the Mg/PTFE pyrotechnic composition of case B was the most beneficial for the reignition of the base bleed propellant,with the earliest addition of energy and mass to the BBP. 相似文献
249.
以具有欠驱动关节的水平两自由度机械臂为研究对象,研究当驱动关节达到指定位置后,以幅值和频率可调的驱动关节角速度信号为控制输入量来控制欠驱动关节的位置。用平均法对欠驱动机械臂的拉格朗日动力学模型进行了简化,并基于简化后的模型给出了闭环非线性反馈控制律。仿真结果表明,所设计的闭环非线性反馈控制率能够使任意初始位置的欠驱动关节趋近其指定位置。 相似文献
250.