A heuristic algorithm for determining replacement policies in k-out-of-n systems

The authors study a discrete-time, infinite-horizon, dynamic programming model for the replacement of components in a binary k-out-of-n failure system. (The system fails when k or more of its n components fail.) Costs are incurred when the system fails and when failed components are replaced. The objective is to minimize the long-run expected average undiscounted cost per period. A companion article develops a branch-and-bound algorithm for computing optimal policies. Extensive computational experiments find it effective for k to be small or near n; however, difficulties are encountered when n ≥ 30 and 10 ≤ k ≤ n − 4. This article presents a simple, intuitive heuristic rule for determining a replacement policy whose memory storage and computation time requirements are O(n − k) and O(n(n − k) + k), respectively. This heuristic is based on a plausible formula for ranking components in order of their usefulness. The authors provide sufficient conditions for it to be optimal and undertake computational experiments that suggest that it handles parallel systems (k = n) effectively and, further, that its effectiveness increases as k moves away from n. In our test problems, the mean relative errors are under 5% when n ≤ 100 and under 2% when k ≤ n − 3 and n ≤ 50. © 1997 John Wiley & Sons, Inc. Naval Research Logistics 44, 273–286, 1997.     

Leaderless Global Jihadism: The Paradox of Discriminate Violence

Jihadist violence is typically associated with being particularly indiscriminate. Often, as in variations of the ‘new terrorism’ thesis, this characteristic is proposed to correspond in some way to its other attributes such as its globalised, decentralised and ‘postmodern’ religious nature. Recent work appears to give more substance to such claims, by claiming to show a relationship between indiscriminate violence and decentralised group organisation. However, in this paper we show, based on an analysis of jihadist targeting in Western Europe and America from 2001 to 2013, that targeting choices by jihadists unconnected to organised militant groups have in fact been consistently more, rather than less discriminate in their targeting choices than their better-integrated peers. Drawing on this finding, as well as a broader reading of jihadist targeting discourses, we argue for a more complex understanding of the relationship between radicalisation, extremist ideology, decentralisation, and targeting choice.     

Military Expenditures and Natural Resources: Evidence from Rentier States in the Middle East and North Africa

It has been argued that the discovery of a new natural resource greatly increases the risk of conflict. This research aims to study the effect of natural resources on military spending, using the data from rentier states in the Middle East and North Africa (MENA) countries from 1987 to 2012. In considering the ‘resource curse,’ the types of natural resources matter. Our empirical results demonstrate that the ‘resource curse’ arising from the abundance of certain natural resources, particularly oil and forest resources, leads to increases in military spending. In contrast, the rent from coal and natural gas has a negative impact on military spending, while the rent from minerals has no impact on military spending, controlling for GDP growth and per capita income.     

Preemptive parallel‐machine scheduling with a common server to minimize makespan

We consider parallel‐machine scheduling with a common server and job preemption to minimize the makespan. While the non‐preemptive version of the problem is strongly NP‐hard, the complexity status of the preemptive version has remained open. We show that the preemptive version is NP‐hard even if there is a fixed number of machines. We give a pseudo‐polynomial time algorithm to solve the case with two machines. We show that the case with an arbitrary number of machines is unary NP‐hard, analyze the performance ratios of some natural heuristic algorithms, and present several solvable special cases. © 2017 Wiley Periodicals, Inc. Naval Research Logistics 64: 388–398, 2017     

Scheduling combat logistics force replenishments at sea for the US Navy

The Replenishment at Sea Planner (RASP) is saving the U.S. Navy millions of dollars a year by reducing fuel consumption of its Combat Logistics Force (CLF). CLF shuttle supply ships deploy from ports to rendezvous with underway U.S. combatants and those of coalition partners. The overwhelming commodity transferred is fuel, ship‐to‐ship by hoses, while other important packaged goods and spare parts are high‐lined, or helicoptered between ships. The U.S. Navy is organized in large areas of responsibility called numbered fleets, and within each of these a scheduler must promulgate a daily forecast of CLF shuttle operations. The operational planning horizon extends out several weeks, or as far into the future as we can forecast demand. We solve RASP with integer linear optimization and a purpose‐built heuristic. RASP plans Replenishment‐at‐Sea (RAS) events with 4‐hour (Navy watch) time fidelity. For five years, RASP has served two purposes: (1) it helps schedulers generate a daily schedule and animates it using Google Earth, and (2) it automates reports command‐to‐ship messages that are essential to keep this complex logistics system operating.     

Eight Lost Years? Nixon,Ford, Kissinger and the Non-Proliferation Regime, 1969–1977

The years following the signature of the Nuclear Non-Proliferation Treaty (NPT) of 1968 have generally been seen as a period of neglect in US non-proliferation policy. While joining recent scholarship questioning this, the article also shows that the policies that emerged from the Nixon–Ford years were the product of a broad range of factors that constrained both the United States’ ability and willingness to build an effective non-proliferation regime. These included the Nixon administration’s initial skepticism regarding the NPT, as well as the global dispersion of power away from the US, combined with the continued importance of anti-Soviet containment.     

The role and capabilities of major weapon systems transferred between 1950 and 2010: Empirical examinations of an arms transfer data set

Arms transfers provide exporters an avenue to provide security to other states while gaining economic benefits. Arms transfers provide importers an avenue to gain security without having to rely on alliances. Past research uses aggregate measures of the monetary or security value of major weapon system transfers without accounting for strategic differences in possible use in interstate and civil conflict. This article presents a data set on interstate transfers of major weapon systems between 1950 and 2010 building upon Stockholm Peach Research Institute’s Arms Trade Register with several improvements. First, it disaggregates land weapons and air weapons into categories reflecting their strategic capabilities. Second, model level characteristics (e.g. age, speed, and range) are drawn from Jane’s Defence sources. Additionally, the data set covers a larger range of time and states than previous data sets categorizing arms. To demonstrate the usefulness, this article first presents summary statistics of the data set and then replicates an earlier test to show that the effect of human rights and regime types on United States transfers differs across the categories of arms compared to alternative measures of arms transfers.     

‘Outside their expertise’: The implications of Field Manual 3-24 for the professional military education of non-commissioned officers

Within the framework of classical theory, the joint US Army-Marine field manual Counterinsurgency (FM 3-24) described an ambitious set of skills required for success against guerrillas. But if counterinsurgency, as FM 3-24 describes it, is ‘the graduate level of warfare’, then these two military services have been for years systematically failing to train their talent in the appropriate fields. In today's small wars, NCOs serve as modern-day Mounties, and consequently require at least a modest undergraduate education in armed good governance.