A comparison of several estimates of availability

We compare several competing estimates of the availability of a system which alternates between two states, “up” and “down,” in accordance with an alternating renewal process. Both interval and point estimators are compared under several special but representative situations. The comparison reaffirms the validity and robustness of the log-logistic jackknifed estimates. However, when the point estimates are compared from the intrinsic criterion of probability of concentration, the uniformly minimum variance estimate obtained for the Markov model performs very well.     

On the first time a separately maintained parallel system has been down for a fixed time

Consider a system consisting of n separately maintained independent components where the components alternate between intervals in which they are “up” and in which they are “down”. When the i^th component goes up [down] then, independent of the past, it remains up [down] for a random length of time, having distribution F_i[G_i], and then goes down [up]. We say that component i is failed at time t if it has been “down” at all time points s ?[t-A.t]: otherwise it is said to be working. Thus, a component is failed if it is down and has been down for the previous A time units. Assuming that all components initially start “up,” let T denote the first time they are all failed, at which point we say the system is failed. We obtain the moment-generating function of T when n = l, for general F and G, thus generalizing previous results which assumed that at least one of these distributions be exponential. In addition, we present a condition under which T is an NBU (new better than used) random variable. Finally we assume that all the up and down distributions F_i and G_i i = l,….n, are exponential, and we obtain an exact expression for E(T) for general n; in addition we obtain bounds for all higher moments of T by showing that T is NBU.     

Concept costing for defence projects: the problem and its solution

It is intrinsic to the nature of military competition that the unit acquisition costs of defence systems rise generation by generation. Traditional “bottom‐up” methods of cost‐estimating cannot meet the increasing demands for extensive studies of many options before commencing design and, while “top‐down” estimating techniques are an improvement, in particular by reducing the time required for preparing estimates, they also are inadequate to meet current requirements. A new method has been devised, therefore, further developing “top‐down” methods using Bayesian techniques to make best use of the available information, whether certain or uncertain, and its accuracy established by example.     

Toward a determination of optimal multilevel sampling plans

Traditionally continuous sampling plans have been evaluated according to relatively few criteria. These typically include the OC curve (on which AQL systems are based), the ASN, and the AOQ curve. These characteristics are all calculated under the assumption that the process is “in control” so that mathematically they are derived as long-term averages. Thus, any two plans which (long term) spend the same proportion of time on each type of sampling inspection will be identical relative to these criteria. This is true whether sampling from lots or doing unit-by-unit inspection. The goal is to first establish desirable additional criteria and then to develop methods to determine which procedure (of those which satisfy the standard criteria) is optimal relative to the new criteria. To be considered will be measures of a plan's ability to detect a sudden drop in quality (such as ARL).     

A Lanchester-type aggregated-force model of conventional ground combat

This article develops a Lanchester-type model of large-scale conventional ground combat between two opposing forces in a “sector”. It is shown that nonlinear Helmbold-type equations of warfare with operational losses may be used to represent the loss-rate curves that have been used in many aggregated-force models. These nonlinear differential equations are used to model the attrition of combat capability (as quantified by a so-called firepower index) in conjunction with a rate-of-advance equation that relates motion of the contact zone (or FEBA) between the opposing forces to the force ratio and tactical decisions of the combatants. This simplified auxiliary model is then used to develop some important insights into the dynamics of FEBA movement used in large-scale aggregated-force models. Different types of behavior for FEBA movement over time are shown to correspond to different ranges of values for the initial force ratio, for example, an attack will “stall out” for a range of initial force ratios above a specific threshold value, but it will “break out” for force ratios above a second specific threshold value. Such FEBA-movement predictions are essentially based on being able to forecast changes over time in the force ratio.     

Optimal policy for a dynamic multi-echelon inventory model

A general multiperiod multi-echelon supply system consisting of n facilities each stocking a single product is studied. At the beginning of a period each facility may order stock from an exogenous source with no delivery lag and proportional ordering costs. During the period the (random) demands at the facilities are satisfied according to a given supply policy that determines to what extent stock may be redistributed from facilities with excess stock to those experiencing shortages. There are storage, shortage, and transportation costs. An ordering policy that minimizes expected costs is sought. If the initial stock is sufficiently small and certain other conditions are fulfilled, it is optimal to order up to a certain base stock level at each facility. The special supply policy in which each facility except facility 1 passes its shortages on to a given lower numbered facility called its direct supplier is examined in some detail. Bounds on the base stock levels are obtained. It is also shown that if the demand distribution at facility j is stochastically smaller (“spread” less) than that at another facility k having the same direct supplier and if certain other conditions are fulfilled, then the optimal base stock level (“virtual” stock out probability) at j is less than (greater than) or equal to that at facility k.     

“Respect” as a personal attribute in the British Army

This article describes the results of research into the social phenomenon of “respect” as framed by junior members of the British Army, as part of a wider study into the Values and Standards of the British Army. This research was interview based, using qualitative analysis software to detect, manage, and draw conclusions from the qualitative data recorded in those interviews. The data indicated that the primary situation in which “respect” was visualised by the participants was the unit context, and that it comprised a combination of three different strands: respect for rank or “hierarchical respect,” “professional respect” for a person's military competence, and “personal respect” for an individual's character, personal behaviour, and attributes. The overall respect that an individual is given arises from the combination of these three areas. “Respect” as a concept was, in the soldiers’ characterisation, something that had to be earned (except for the “given” represented by rank) and was not stable: a person's fund of respect could go up or down in social value. Respect was also linked to trust: the more respect a person had, the more they could be trusted. Although the unit context was the primary one for discussing their framing of the concept of respect, many of the participants reported a wider dimension in which every human being deserves a basic level of respect simply for being human, and this level could not be forfeited.     

Parameter estimation for the EOQ lot-size model: Minimax and expected value choices

This article provides formulas for estimating the parameters to be used in the basic EOQ lot-size model. The analysis assumes that the true values of these parameters are unknown over known ranges and perhaps nonstationary over time. Two measures of estimator “goodness” are derived from EOQ sensitivity analysis. Formulas are given for computing the minimax choice and the minimum expected value choice for the parameter estimates using both measures of estimator “goodness”. A numerical example is included.     

Some branch-and-bound procedures for fixed-cost transportation problems

In this article we present three properties that will improve the performance of branch-and-bound algorithms for fixed-cost transportation problems. By applying Lagrangian relaxation we show that one can develop stronger up and down penalties than those traditionally used and also develop a strengthened penalty for nonbasic variables. We also show that it is possible to “look ahead” of a particular node and determine the solution at the next node without actually calculating it. We present computational evidence by comparing our developments with existing procedures.     

Requirements of an “optimizer” for computer simulations

Computer simulation has many advantages. However, one major disadvantage is that, in all too many cases, the attempt to use computer simulation to find an optimum solution to a problem rapidly degenerates into a trial-and-error process. Techniques for overcoming this disadvantage, i. e., for making optimization and computer simulation more compatible, are applicable at two points in the development of the overall computer simulation. Techniques which are used within actual construction of the mathematical models comprising the simulation will be labeled as internal methods, while those which are used after the simulation has been completely developed will be termed external methods Because external methods appear to offer the largest potential payoff, discussion is restricted to these methods, which are essentially search techniques. In addition, the development of an “Optimizer” computer program based on these techniques is suggested Although drawbacks to the use of search techniques in the computer simulation framework exist, these techniques do offer potential for “optimization.” The modification of these techniques to satisfy the requirements of an “Optimizer” is discussed.     

A note on the stochastic shortest-route problem

This paper develops an algorithm for a “shortest route” network problem in which it is desired to find the path which yields the shortest expected distance through the network. It is assumed that if a particular arc is chosen, then there is a finite probability that an adjacent arc will be traversed instead. Backward induction is used and appropriate recursion formulae are developed. A numerical example is provided.     

Alternatives for defense in the Post‐Soviet World: A guide for economists to the U.S. debate

The defense establishments of all major powers are changing to reflect changes in the foundations of national security strategy and resource allocation. The authors believe economists should play an active role in formulating these changes and offer an orientation to the U.S. debate, presenting three major alternatives: the “Base Force” (Bush Administration), Mr. Aspin's Force “C,” and the “Low” Alternative (Prof. Kaufmann and Dr. Steinbruner). These alternatives are compared using first‐order measures of capabilities, budgets and risk. Budgetary estimates are based on newly‐developed analytical tools.     

Strategic “defensivism” and post-reset blues: US–Russian nuclear arms reductions,missile defenses and minimum deterrence

US nuclear deterrence and arms control policy may be moving, by design and by inadvertence, toward a posture of strategic “defensivism”. Strategic “defensivism” emphasizes the overlapping and reinforcing impact of: (1) reductions in US, Russian and possibly other strategic nuclear forces, possibly down to the level of “minimum deterrence,” (2) deployment of improved strategic and/or theater antimissile defenses for the US, NATO allies and other partners; and (3) additional reliance on conventional military forces for some missions hitherto preferentially assigned to nuclear weapons. This article deals with the first two of these aspects only: the interaction between missile defenses and offensive force reductions in US–Russian strategy and policy. The findings are that stable deterrence as between the USA and Russia is possible at lower than New Strategic Arms Reduction Treaty levels, but reductions below 1000 deployed long-range weapons for each state, toward a true minimum deterrent posture, will require multilateral as opposed to bilateral coordination of arms limitations. Missile defenses might provide some denial capability against light attacks by states with small arsenals, but they still fall short of meaningful damage limitation as between powers capable of massive nuclear strikes.     

Power,polarity, and prudence: the ambiguities and implications of UK discourse on a multipolar international system

What do UK policymakers mean when they say that Britain’s strategic environment is returning to “multipolarity”? In realist international theory, polarity is a specific causal concept; the number of powers capable of balancing even the most capable other state(s) in the international system (“poles”) is taken to determine the system’s stability. Does the post-2017 appearance of polarity references in British security policy documents therefore reflect some unexpected UK renaissance of realist thought? Or is something else going on, as recent work by Ben Zala suggests? This article will demonstrate that, while UK official usage of the “multip–” word has indeed flourished recently, the term is actually being used in a more elastic, less bounded way than realism prescribes in order to generate other kinds of political effect. Specifically, “polarity” (and its “multi-” prefix) is used to characterise the behaviour of those major states that oppose Western-preferred international order, to elide Britain’s own relative power/status tensions, and to capture an expansive laundry-list of perceived international dangers. The article then discusses five ways in which a shift in polarity could negatively affect Britain; important consequences that merit preparatory contemplation, yet that an imprecise, catch-all understanding of “multipolarity” too readily obscures.     

光学成像侦察卫星作战效能分析

为支持航天装备体系作战效能评估,建立了光学成像侦察卫星性能指标与卫星发现目标概率和定位精度的关系以及信息处理与传递模型.以支持导弹打击大型移动目标为例,以命中目标概率为作战效能指标,建立了光学成像侦察卫星作战效能模型.对模型进行了仿真,分析了影响卫星作战效能的主要因素.仿真结果表明所建模型能够合理反映光学成像侦察卫星对作战结果的影响,可用于从顶层分析航天装备.     

How viable is international arms control for military artificial intelligence? Three lessons from nuclear weapons

Many observers anticipate “arms races” between states seeking to deploy artificial intelligence (AI) in diverse military applications, some of which raise concerns on ethical and legal grounds, or from the perspective of strategic stability or accident risk. How viable are arms control regimes for military AI? This article draws a parallel with the experience in controlling nuclear weapons, to examine the opportunities and pitfalls of efforts to prevent, channel, or contain the militarization of AI. It applies three analytical lenses to argue that (1) norm institutionalization can counter or slow proliferation; (2) organized “epistemic communities” of experts can effectively catalyze arms control; (3) many military AI applications will remain susceptible to “normal accidents,” such that assurances of “meaningful human control” are largely inadequate. I conclude that while there are key differences, understanding these lessons remains essential to those seeking to pursue or study the next chapter in global arms control.     

Toward a multi-stage information conversion model of the research and development process

Research and development activities in a business firm or government laboratory are portrayed as a multi-stage information generation and conversion process. A “basic research” phase generates opportunities, in the form of findings in a set of scientific disciplines, which are available for subsequent exploitation. It is assumed that increments to information in a subject area are stochastic, proportional to the amount of knowledge which already exists in the area, and have values which are randomly distributed. An “exploratory development” phase is viewed as a process of selecting a subset of alternative research opportunities, improving each opportunity in the direction of its applications, estimating the value of the improved opportunity and using these estimates to choose the exploratory development results to be implemented in engineering development. The “engineering development” phase makes the value of exploratory results realizable without changing value or risk. Engineering development costs are assumed to increase as value increases. If exploratory development is not successful, additional costs in engineering development must be incurred to bring the design up to a minimum desirable level. The model is intended as a step toward formulating and analyzing problems in management planning and control of the several interrelated stages of the research and development process.     

Profust故障树建模与分析

实际中普遍存在的有显著渐近失效行为的系统 ,难以用经典故障树加以分析 ,于是 ,以“模糊事件的普通概率”这一理论为基础 ,建立了Profust故障树模型 ,并进行了部分定量分析 ,该模型的最大特点是综合运用了可以得到的关于系统运行的可能性信息和概率信息     

Bringing Military Conduct out of the Shadow of Law: Towards a Holistic Understanding of Rules of Engagement

In this article, I outline a holistic approach to the military concept of “Rules of Engagement” (ROE), which complements the legal aspects of ROE with considerations of operational and political requirements for the use of military force. Drawing upon two illustrative cases from the US military experience with the use of ROE, I demonstrate that ROE for any particular military operation should be formulated to balance optimally, if not harmonize fully, the legal, operational and political concerns related to the use of force. In this task, political decision-makers and military practitioners alike are confronted with unavoidable and real-life dilemmas. How these dilemmas are handled has significant implications for how legal requirements concerning accountability and concerns for civilian lives in military combat can be preserved through ROE.     

坦克单车对抗作战效能评估

对坦克单车对抗作战的过程进行了分析,根据作战过程的特点将其分为两个阶段:抢先攻击阶段和对抗阶段.用概率的方法建立了对抗作战不同阶段的数学模型.基于建立的模型,导出了任务成功率、目标毁伤率、生存概率等作战效能度量指标的表示和计算.并对影响坦克作战结果的可能因素进行分析,可为提高坦克武器系统的作战效能提供理论依据.