Redundant spares allocation to reduce reliability costs

The problem considered here is the optimal selection of the inventory of spares for a system built from two kinds of modules, the larger of which can be connected so it performs the role of the smaller one. The optimal inventory is the least costly one which achieves a specified probability that the spares will not be exhausted over the design lifetime. For some costs and failure rates it is most economical to use the larger module for both roles, due to the resulting increase in flexibility in the deployment of a single type of spare module. Both analytical and simulation methods have been used to study this problem.     

MIDDLE EAST NONPROLIFERATION

The Middle East is a crucial region for the global nonproliferation regime. In 2010, the state parties to the Treaty on the Non-Proliferation of Nuclear Weapons proposed a conference on a Middle East Weapons of Mass Destruction-Free Zone. The nuclear weapon-free zone model, on which this idea builds, has achieved important results in other regions, but faces especially stark challenges in the Middle East. However, the attempt to apply the boldly imaginative zone approach to the Middle East holds promise for building a more inclusive dialogue on nonproliferation and regional security.     

RELIABLE ENERGY SUPPLY AND NONPROLIFERATION

The phenomenon of global warming has led to a revival of the prospects for increased nuclear energy production worldwide, yet such increased production carries with it the increased risk of proliferation. To mitigate this risk, various multinational arrangements have been proposed to provide reliable supply of nuclear fuel while at the same time discouraging the construction of national plants for nuclear enrichment and reprocessing. This article provides a brief history of some of these proposals and concludes that the likelihood of success for such schemes as effective tools for nonproliferation is not high at this time. A proposal from the World Council on Renewable Energy to expand the understanding of supplier obligations under Article IV of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) to include the development of non-nuclear energy technologies for NPT parties in good standing is potentially a much better nonproliferation tool. Such an approach tracks the ideas contained in Title V of the Nuclear Non-Proliferation Act of 1978, which has recently received revived congressional interest.     

Assessing military reform in Indonesia

This article seeks to assess the magnitude of military reform in Indonesia and its impact in establishing greater levels of professionalism within the armed forces. To this end, the authors will offer some reflections on the studies of civil-military relations and military transformation for inculcating a higher degree of military professionalism; analyse to what extent the process of military reform in Indonesia has reshaped the institutional role of the armed forces; and discern three major strategic gaps in Indonesia's military reform, namely the “legal loopholes and regulation vacuum,” the “shortcomings of democratic civilian control,” and the “defence-economic gap.” This article asserts that military professionalism will grow more substantially depending on the ability of civilian elites to exercise effective control over the military and the capacity of the government to transform the military establishment keeping pace with strategic challenges and operational requirements.     

Confidence bounds and propagation of uncertainties in system availability and reliability computations

This paper develops bounds on the uncertainties in system availabilities or reliabilities which have been computed from structural (series, parallel, etc.) relations among uncertain subsystem availabilities or reliabilities. It is assumed that the highly available (reliable) subsystems have been tested or simulated to determine their unavailabilities (unreliabilities) to within some small percentages of uncertainty. It is shown that series, parallel and r out of n structures which are nominally highly available will have unavailability uncertainties whose percentages errors are of the same order as the subsystem uncertainties. Thus overall system analysis errors, even for large systems, are of the same order of magnitude as the uncertainties in the component probabilities. Both systematic (bias type) uncertainties and independent random uncertainties are considered.     

Optimal replacement of parts having observable correlated stages of deterioration

A single component system is assumed to progress through a finite number of increasingly bad levels of deterioration. The system with level i (0 ≤ i ≤ n) starts in state 0 when new, and is definitely replaced upon reaching the worthless state n. It is assumed that the transition times are directly monitored and the admissible class of strategies allows substitution of a new component only at such transition times. The durations in various deterioration levels are dependent random variables with exponential marginal distributions and a particularly convenient joint distribution. Strategies are chosen to maximize the average rewards per unit time. For some reward functions (with the reward rate depending on the state and the duration in this state) the knowledge of previous state duration provides useful information about the rate of deterioration.     

The dynamic lot size model with quantity discount: Counterexamples and correction

Federgruen and Lee ([3]) proposed an optimal algorithm for the single-item dynamic lot size model with all-unit discount. In this note we show that their algorithm fails to find the optimal solution for some special cases. We also provide a modification to the algorithm to handle them. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 419–422, 1998