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221.
We study the spatial and temporal determinants of terrorism risk in Israel, using a geocoded database of Israeli terrorist attacks from 1949 to 2004. In selecting targets, terrorists seem to respond rationally to costs and benefits: they are more likely to hit targets more accessible from their own homebases and international borders, closer to symbolic centers of government administration, and in more heavily Jewish areas. We also examine the waiting time between attacks experienced by localities. Long periods without an attack signal lower risk for most localities, but higher risk for important areas such as regional or national capitals.  相似文献   
222.
Using annual data collected from 1988 to 2015, this study provides evidence of a non-linear relationship between military spending, economic growth and other growth determinants for the South African economy. The empirical study is based on estimates of a logistic smooth transition regression (LSTR) model and our empirical results point to an inverted U-shaped relationship between military spending and economic growth for the data. Furthermore, our empirical results suggest that the current levels of military spending, as a component of total government expenditure, are too high in the South African economy and need to be transferred towards more productive non-military expenditure in order to improve the performance of economic growth and other growth determinants.  相似文献   
223.
Nonlinear initial alignment is a significant research topic for strapdown inertial navigation system(SINS).Cubature Kalman filter(CKF)is a popular tool for nonlinear initial alignment.Standard CKF assumes that the statics of the observation noise are pre-given before the filtering process.Therefore,any unpredicted outliers in observation noise will decrease the stability of the filter.In view of this problem,improved CKF method with robustness is proposed.Multiple fading factors are introduced to rescale the obser-vation noise covariance.Then the update stage of the filter can be autonomously tuned,and if there are outliers exist in the observations,the update should be less weighted.Under the Gaussian assumption of KF,the Mahalanobis distance of the innovation vector is supposed to be Chi-square distributed.Therefore a judging index based on Chi-square test is designed to detect the noise outliers,determining whether the fading tune are required.The proposed method is applied in the nonlinear alignment of SINS,and vehicle experiment proves the effective of the proposed method.  相似文献   
224.
We consider a setting in which inventory plays both promotional and service roles; that is, higher inventories not only improve service levels but also stimulate demand by serving as a promotional tool (e.g., as the result of advertising effect by the enhanced product visibility). Specifically, we study the periodic‐review inventory systems in which the demand in each period is uncertain but increases with the inventory level. We investigate the multiperiod model with normal and expediting orders in each period, that is, any shortage will be met through emergency replenishment. Such a model takes the lost sales model as a special case. For the cases without and with fixed order costs, the optimal inventory replenishment policy is shown to be of the base‐stock type and of the (s,S) type, respectively. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012  相似文献   
225.
This paper studies a periodic‐review pricing and inventory control problem for a retailer, which faces stochastic price‐sensitive demand, under quite general modeling assumptions. Any unsatisfied demand is lost, and any leftover inventory at the end of the finite selling horizon has a salvage value. The cost component for the retailer includes holding, shortage, and both variable and fixed ordering costs. The retailer's objective is to maximize its discounted expected profit over the selling horizon by dynamically deciding on the optimal pricing and replenishment policy for each period. We show that, under a mild assumption on the additive demand function, at the beginning of each period an (s,S) policy is optimal for replenishment, and the value of the optimal price depends on the inventory level after the replenishment decision has been done. Our numerical study also suggests that for a sufficiently long selling horizon, the optimal policy is almost stationary. Furthermore, the fixed ordering cost (K) plays a significant role in our modeling framework. Specifically, any increase in K results in lower s and higher S. On the other hand, the profit impact of dynamically changing the retail price, contrasted with a single fixed price throughout the selling horizon, also increases with K. We demonstrate that using the optimal policy values from a model with backordering of unmet demands as approximations in our model might result in significant profit penalty. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2006  相似文献   
226.
The paper analyzes the effects of military spending on economic growth in a small open stochastic endogenous growth model involving the supply-side and demand-side effects produced by military spending. We show that a rise in the military spending affects economic growth through four channels, including the crowding-out effect, the spin-off effect, the resource mobilization effect, and the portfolio effect. The net effect which depends on these four channels is ambiguous. Hence, we demonstrate that there exists an optimal defense burden that maximizes the economic growth rate.  相似文献   
227.
多手段综合探测巡航导弹的方法研究   总被引:5,自引:0,他引:5  
巡航导弹具有隐蔽和突然的特点 ,对巡航导弹进行有效的探测 ,是抗击巡航导弹的关键 ,综合利用各种手段 ,组成空中与地面相结合、远方和近方相结合 ,先进手段与传统手段相结合的全方位、有重点的目标探测与报知体系 ,可增大对巡航导弹的探测距离 ,提高发现概率。  相似文献   
228.
军用仿真系统中 ,专家系统作为一个决策软件包 ,满足整个软件系统运行的性能需要 ,因此研究专家系统的推理时间是必要的。专家系统的推理时间与其推理模式、知识库结构等因素有关。针对知识库结构 ,利用时间齐次马尔可夫链为专家系统知识库进行建模 ,并给出了相应的时间估计模型及其排列准则 ,从而可以研究专家系统的实时性。  相似文献   
229.
介绍了产品数据管理(PDM)的概念和基本功能,结合当前型号研制的特点和计算机信息技术应用的状况、发展,研究了型号研制产品数据管理的需求、功能及实施,为当前型号研制依靠CIMS技术实现产品数据管理提出了8条基本原则。  相似文献   
230.
由于无线传感器网络在能量消耗、内存开销和计算能力等方面的局限性,传统的网络密钥管理方法已不适用。为此提出了一种适用于无线传感器网络的密钥预分配方法——基于(t,n)-门限方案,给出了密钥分配方法,并从方案的连通性、安全性等方面进行了有效的分析,结果表明该算法在这些方面有一定的优势。  相似文献   
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