Algorithmic and approximation analyses of the shorter queue model

A system of two parallel queues where the arrivals from a single stream of customers join the shorter queue is considered. Arrivals form a homogeneous Poisson stream and the service times in each of the two queues are independent exponential variates. By treating one of the queues as bounded, the steady-state probability vector for the system can be expressed in a modified matrix-geometric form and can be computed efficiently. Computational procedures for the sojourn time distribution and characteristics of the departure stream are developed. Some numerical results are presented, and based on these results an efficient approximation scheme for the model is developed which can be readily extended to systems with more than two parallel queues.     

A decision support system for the procurement of military equipment

The use of life-cycle costs in procurement is limited by the accuracy of cost estimates and assessments of availability risks under the conditions generating costs. Critical to these problems are the needs and responses of equipment to maintenance and repair. Using transition probabilities to define the relationships between serviceability and maintenance and repairs, this article develops a comprehensive decision support system for military procurement. It uses a dynamic programming model to determine the least-cost set of maintenance and repair decisions, where adjustments are included for warranty conditions, time value of money, the opportunity costs of equipment failure, and the end-of-cycle salvage values or disposal costs. The system allows users to define working and failed states, create their own rules or indicators of availability from estimates of state probabilities and establish thresholds of risk acceptability.     

Visibility probabilities on line segments in three-dimensional spaces subject to random poisson fields of obscuring spheres

The methodology of determining simultaneous visibility probabilities and points on line segments is extended to problems of three-dimensional spaces, with Poisson random fields of obscuring spheres. Required functions are derived analytically and a numerical example is given for a special case of a standard Poisson field, with uniform distribution of sphere diameters.     

Approximating nonstationary two-priority non-preemptive queueing systems

An approximation for analyzing transient and nonstationary two-priority non-preemptive queueing systems is presented. This system has a three-dimensional state space, and through use of state-space partitioning in conjunction with use of conditional surrogate distributions with constant parameters an approximation is designed. Regardless of system capacity K, the approximation requires the numerical solution of only ten differential equations, compared to the K² + K+1 Kolmogorov-forward equations required for the classic solution. Time-dependent approximations of the mean number of entities of type i and of the probability of a type-i entity being in service are obtained. Empirical test results over a wide range of systems indicate the approximation is quite accurate.     

“No boots on the ground”: the effectiveness of US drones against Al Qaeda in the Arabian Peninsula

The number of US drone strikes against Al Qaeda in the Arabian Peninsula (AQAP) in Yemen has increased significantly since 2010, but received limited academic attention. This article examines the effectiveness of this drone campaign using an existing theoretical framework. Crucially, we contribute to the framework by adding a fourth intervening variable, namely target correspondence. Through a single case study, it is found that drones have only enjoyed limited success in degrading AQAP's hierarchical structure, qualified human resources and access to key material resources, and in some cases – owing to our target correspondence analysis – this limited success has come at a price. It is found that drones have temporarily disrupted AQAP by successfully eliminating senior leaders involved in coordinating and overseeing external operations. Overall, AQAP's ability to hit Western targets remains significant.     

Analysis of an Alternative Military Healthcare Benefit Design

Abstract

The Military Compensation and Retirement Modernization Commission was established by the Congress in 2013 to perform a systematic review of military compensation to address rising costs and other trends. Their recommendation for reforming the TRICARE health care program was sweeping, and differed greatly from earlier proposals that focused on increasing beneficiary cost shares. Specifically, the commission proposed overhauling the current benefit delivery model and replacing it with a premium-based insurance model offering a menu of DoD-sponsored private health plans. The analysis presented here is based on work that supported the commission by estimating the budgetary impact of its proposed reforms. Results indicate that movement towards the premium-based model would produce an annual budgetary cost savings in the $2 billion to $4 billion range, with a best savings estimate of $3.2 billion.     

Deterrence Beyond Downunder: Australia and US Security Guarantees since 1955

ABSTRACT

From 1944 to 1973 Australia attempted to acquire atomic weaponry. This ambition was driven by the desire to contribute to defending British interests in Asia, fears of invasion by China, Indonesia, and Japan, great-power war, and the belief that nuclear weapons were merely bigger and better conventional weapons, that they would proliferate, and that US security assurances lacked credibility. Although the pursuit of the bomb was eventually abandoned, this was not the result of US assurances. Rather, geopolitical changes in Australia’s environment meant that a major attack on the continent was unlikely to occur outside the context of a confrontation between the US, China, and the Soviet Union. This article argues that Australia may soon have to rethink its policies towards US extended deterrence and instead focus on developing its own deterrent.     

Tipping the scales: short-term interventions and counterinsurgency

Particularly in African operations, United Nations (UN) peacekeeping forces have faced significant problems in restoring stability. In at least a few situations, unilateral national military interventions have been launched in the same countries. In the cases of Sierra Leone and Côte d’Ivoire, the British and French interventions respectively played a significant role in re-establishing stability. Lessons from these operations suggest that if effective coordination and liaison channels are established, such hybrid unilateral-UN missions can in fact be more successful than “pure” peace operations.