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261.
舰船尾流的声学特性由分布在尾流中气泡的声学特性决定.气泡的声学特性表现在对不同频率入射声波的反射和散射作用,主要由气泡的谐振频率决定.有限元分析中模态分析可以分析振动结构,得到物体结构的谐振频率.根据尾流中气泡的声学特性,建立气泡声学特性结构模型,用模态分析方法确定气泡的谐振频率以验证模型的正确性,将有限元方法引入分析舰艇尾流的声学特性中. 相似文献
262.
We consider the effects of cueing in a cooperative search mission that involves several autonomous agents. Two scenarios are discussed: one in which the search is conducted by a number of identical search‐and‐engage vehicles and one where these vehicles are assisted by a search‐only (reconnaissance) asset. The cooperation between the autonomous agents is facilitated via cueing, i.e., the information transmitted to the agents by a searcher that has just detected a target. The effect of cueing on the target detection probability is derived from first principles using a Markov chain analysis. In particular, it is demonstrated that the benefit of cueing on the system's effectiveness is bounded. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006 相似文献
263.
We consider the problem of safely and swiftly navigating through a spatial arrangement of potential hazard detections in which each detection has associated with it a probability that the detection is indeed a true hazard. When in close proximity to a detection, we assume the ability—for a cost—to determine whether or not the hazard is real. Our approach to this problem involves a new object, the random disambiguation path (RDP), which is a curve‐valued random variable parametrized by a binary tree with particular properties. We prove an admissibility result showing that there is positive probability that the use of an RDP reduces the expected traversal length compared to the conventional shortest zero‐risk path, and we introduce a practically computable additive‐constant approximation to the optimal RDP. The theoretical considerations are complemented by simulation and example. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005 相似文献
264.
In the aftermath of the tragic events of 11 September 2001, numerous changes have been made to aviation security policy and operations throughout the nation's airports. The allocation and utilization of checked baggage screening devices is a critical component in aviation security systems. This paper formulates problems that model multiple sets of flights originating from multiple stations (e.g., airports, terminals), where the objective is to optimize a baggage screening performance measure subject to a finite amount of resources. These measures include uncovered flight segments (UFS) and uncovered passenger segments (UPS). Three types of multiple station security problems are identified and their computational complexity is established. The problems are illustrated on two examples that use data extracted from the Official Airline Guide. The examples indicate that the problems can provide widely varying solutions based on the type of performance measure used and the restrictions imposed by the security device allocations. Moreover, the examples suggest that the allocations based on the UFS measure also provide reasonable solutions with respect to the UPS measure; however, the reverse may not be the case. This suggests that the UFS measure may provide more robust screening device allocations. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2005. 相似文献
265.
本文针对导弹攻防对抗仿真的特殊需求,讨论了分布表现环境中的若干问题,提出了基于表现模型的、支持层次化表现的系统设计方案。 相似文献
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268.
Moment estimators for the parameters of the Weibull distribution are considered in the context of analysis of field data. The data available are aggregated, with individual failure times not recorded. In this case, the complexity of the likelihood function argues against the use of maximum-likelihood estimation, particularly for relatively large sets of data, and moment estimators are a reasonable alternative. In this article, we derive the asymptotic covariance matrix of the moment estimators, and provide listings for BASIC computer programs which generate tables useful for calculation of the estimates as well as for estimating the asymptotic covariance matrix using aggregated data. 相似文献
269.
Charles E. Antoniak 《海军后勤学研究》1976,23(2):283-295
This paper discusses a possible measure of effectiveness for information sensing equipment, such as radar or sonar, based on its ability to provide information. It is shown that such a measure is particularly appropriate for situations where a sequence of similar limited engagements may occur, as on antisubmarine patrol, for example. In this case the measure expresses the expected rate of gain per engagement of the relative resources of the participants. Rates are calculated for the optimal and certain simpler, but suboptimal, strategies. The measure is illustrated by an exact analysis of a gambling problem and a qualitative treatment of an anti-missile missile allocation problem. 相似文献
270.
Alan E. Gelfand 《海军后勤学研究》1976,23(3):513-523
The purpose of this research is to examine several types of procedures for attribute sampling inspection-the widely used Military Standard 105D plans [8], the lesser known Double Zero plans as developed by Ellis [4] and the Narrow Limit gaging plans of Ott and Mundel [9]. Each of the procedures is described with an effort made to illuminate their more subtle features. Then the plans are compared, whence it is revealed that (i) Narrow Limit gaging plans have a serious weakness in comparison to the others and (ii) Double Zero plans tend to be essentially conservative, but that sufficiently tight Military Standard 105D plans can be selected to achieve comparable performance in all ways. 相似文献