Partitioning and balancing for the assembly of nozzle guide vanes in gas turbine engines

The gas turbine engine is used to power many different types of commercial and military aircraft. During the scheduled maintenance of these engines, many of the turbine components are replaced. Of particular importance to us is the replacement of nozzle guide vanes in the nozzle assembly section of the engine. Individual vanes are selected from inventory to make up sets, and each set must meet certain characteristics in order to be feasible. The vanes in each set must then be sequenced in order to meet additional criteria. In this article, we give heuristics for the above partitioning and sequencing problems. Empirical analyses, using actual data from a branch of the armed services and a major engine manufacturer, are used to evaluate the proposed heuristics. The results of these analyses indicate that the heuristics are effective.     

A note on the optimality conditions for the bilevel programming problem

A counterexample is given to demonstrate that previously proposed necessary conditions for the bilevel programming problem are not correct. An interpretation of the difficulty is given by appealing to a “theorem of alternative” result presented in the original work.     

Some properties of optimal control policies for entry to an M/M/1 queue

Customers served by an M/M/1 queueing system each receive a reward R but pay a holding cost of C per unit time (including service time) spent in the system. The decision of whether or not a customer joins the queue can be made on an individual basis or a social basis. The effect of increasing the arrival rate on the optimal policy parameters is examined. Some limiting results are also derived.     

Stochastic linear fractional programming with the ratio of independent Cauchy variates

In this article is studied a stochastic linear fractional programming problem, in which the parameters of both the numerator and the denominator are assumed to be mutually independent Cauchy variates. The deterministic equivalent of the problem is obtained and is shown to be a linear fractional program. A numerical example is also added for illustration.     

Estimation of the common scale parameter of two pareto distributions in censored samples

The problem of estimation of the common scale parameter of two Pareto distributions with unknown and unequal shape parameters in censored samples is considered. The uniformly minimum variance unbiased estimator (UMVUE) is given along with the UMVUE of its variance.     

An extremal problem in subconnectivity

The connectivity of a subgraph of a graph can exceed the connectivity of the graph. We call the largest of the connectivities of all subgraphs the subconnectivity. We then give the exact solution to the extremal problem of determining the maximum number of lines in a p-point graph of subconnectivity two.     

Multilateral Counter-Insurgency Networks

Postmodern terrorism presents a significant challenge to global security and law enforcement institutions. Non-state actors operating across international borders, engaged in an apparent global insurgency of extremism that transects the traditional boundaries of crime and war, pose significant challenges to both intelligence and law enforcement agencies. These networked global insurgents blend political and religious fanaticism with criminal enterprises to challenge the rule of law and pose an epochal shift in the structures and relations among states. Negotiating this epochal shift requires traditional organs of national security (the diplomatic, military and intelligence services) to forge new partnerships with police and public safety organizations at the state and local (sub-national), as well as transnational levels. Significant operational, policy and cultural challenges must be overcome to forge an effective multi-lateral global network to counter global terrorism and insurgency.     

Technical note: Traffic intensity estimation

This note examines estimation of the traffic intensity in an M/G/1 queue. We show that the ratio of sample mean service times to the sample mean interarrival times has undesirable sampling properties. To remedy this, two alternative estimators are introduced. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009