The rising unit cost of defence equipment — The reasons and the results

This paper constructs a conceptual model for the selection of defence equipment providing best value for money. It then shows how the unit cost of the chosen equipment increases between one generation of equipment and its successor because of developments in the perceived threat, the available technology and industrial productivity, and demonstrates that unit cost increases can arise from a logical and rational procurement policy and are not necessarily caused by technological chimeras and military vainglory. The resulting persistent rise in unit cost is unlikely to be significantly slowed by any of the counter‐measures yet proposed.

The paper then discusses the policies which nations have adopted to accommodate past increases in unit cost, and the options which confront any nation at the point when it can no longer afford to re‐equip a particular element of its armed forces.     

Life cycle costs for decision support ‐ a study of the various life cycle costs used at different levels of defence policy and management∗

Debates on many aspects of defence economics ‐ on the scale of defence expenditure, on the allocation of that expenditure to various military capabilities, and on the selection of equipment offering the best value for money ‐ are bedevilled by misunderstandings and misconceptions about the costs of defence equipment. This paper seeks to improve understanding of defence equipment costs by defining a hierarchy of defence equipment within which the direct and indirect life cycle costs of defence equipment may be allocated at different levels. Having reviewed the direct and indirect components of the life cycle cost, this paper then shows how different costing studies for different purposes require different approaches to life cycle costing, and that there is no unique life cycle cost which can be assigned to one particular item of defence equipment. There is instead a range oflife cycle costs, each of which is appropriate for a particular study, and it is important that a quoted cost of an item of defence equipment should be used only in the pertinent circumstances. The paper is written from a UK perspective and accordingly uses British nomenclature, but its principles should be relevant to defence cost studies in other nations.     

一类微分方程Poincaré分岔极限环的不存在性

利用一阶Mel'nikov函数讨论了一类广义Liénard方程Poincaré分岔极限环的不存在性,得出了若干充分条件.     

基于K均值排序方法的频域盲分离算法

针对频域盲分离算法中存在的排序不确定性问题,提出一种基于K-means算法的排序方法。该方法在排序中使用K-means算法对分离子信号进行整体排序,与传统相邻频点排序方法相比,大大提高了盲源分离的鲁棒性。仿真结果表明了该方法的有效性。     

抗战期间国民政府在黄泛区的资源整合与国家调度——以豫东地区为例

1938年6月花园口决堤后,国民政府从民族抗战大局出发,对豫东黄泛区进行了一系列的资源整合和国家调度活动,目的在于增进灾区民众的凝聚力和对敌斗争的信心.主要有:一、开展大规模的政治宣传,给灾区和难民以道德旌扬和精神抚慰;二、密切关注新黄河的水势水情,扩大以水代兵的军事价值;三、制定善后政策,规范善后活动,增进善后力度;四、采取具体措施,对难民实施直接救助和救济.这些活动未必都卓有成效,但是在当时极其艰难的斗争条件下,对于拯救灾民、聚拢人心、激发民族抗战意志、实行持久抗战所起的作用,还是应当给予应有的肯定的.     

Efficient generation of cycle time‐throughput curves through simulation and metamodeling

A cycle time‐throughput (CT‐TH) curve, which quantifies the relationship of long‐run average cycle time to throughput rate, plays an important role in strategic planning for manufacturing systems. In this paper, a nonlinear regression metamodel supported by queueing theory is developed to represent the underlying CT‐TH curve implied by a manufacturing simulation model. To estimate the model efficiently, simulation experiments are built up sequentially using a multistage procedure. Extensive numerical experiments are presented to demonstrate the effectiveness of the proposed procedure. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

Machine maintenance with workload considerations

Machine maintenance is modeled in the setting of a single‐server queue. Machine deterioration corresponds to slower service rates and failure. This leads to higher congestion and an increase in customer holding costs. The decision‐maker decides when to perform maintenance, which may be done pre‐emptively; before catastrophic failures. Similar to classic maintenance control models, the information available to the decision‐maker includes the state of the server. Unlike classic models, the information also includes the number of customers in queue. Considered are both a repair model and a replacement model. In the repair model, with random replacement times, fixed costs are assumed to be constant in the server state. In the replacement model, both constant and variable fixed costs are considered. It is shown in general that the optimal maintenance policies have switching curve structure that is monotone in the server state. However, the switching curve policies for the repair model are not always monotone in the number of customers in the queue. Numerical examples and two heuristics are also presented. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

环肋轴对称组合壳塑性极限分析的弹性模量调整有限元方法

基于轴对称截锥壳单元,以单元横截面峰值应力为等效应力,建立了弹性模量调整有限元方法,应用Fortran语言编制了有限元软件用于计算环肋轴对称组合壳的塑性极限载荷.该方法根据组合壳的应力分布情况调整轴对称壳单元和肋骨单元的弹性模量,并进行一系列的弹性迭代计算,计算收敛后即可以得到环肋轴对称组合壳的塑性极限载荷.通过对算例的计算证明:该方法具有良好的收敛性和较高的效率,计算结果与试验结果吻合较好.     

基于光流传感器的四旋翼飞行器悬停校正

由于低成本的惯性测量单元存在较大漂移,四旋翼飞行器难以稳定地悬停在固定区域,基于此,提出了一种基于光流传感器的四旋翼飞行器悬停校正方法。将光流传感器安装在四旋翼飞行器底部,利用光流信息检测四旋翼飞行器相对地面的水平移动速度,对姿态估计进行补偿,实现悬停校正。试验结果表明:该方法能够有效地提高四旋翼飞行器的悬停稳定性,从而保证飞行器能够执行战场侦察、校正射击、干扰敌人等多种军事任务。