Scheduling with parallel processors and linear delay costs

This paper deals with the sequencing problem of minimizing linear delay costs with parallel identical processors. The theoretical properties of this m-machine problem are explored, and the problem of determining an optimum scheduling procedure is examined. Properties of the optimum schedule are given as well as the corresponding reductions in the number of schedules that must be evaluated in the search for an optimum. An experimental comparison of scheduling rules is reported; this indicates that although a class of effective heuristics can be identified, their relative behavior is difficult to characterize.     

THE NEXUS OF GLOBALIZATION AND NEXT-GENERATION NONPROLIFERATION

Although globalization has created opportunities for nuclear and biological proliferation dangers to take root and grow, it also has opened the door to new solutions. Original ideas and approaches are needed to develop a stronger, more flexible next-generation nonproliferation strategy that accounts for the increasingly important integration of economic, political, and technological issues. The foundation of this strategy should focus on tapping the power of market-based mechanisms, understanding how commercially driven decisions affect proliferation threats, establishing new partnerships, and forging cohesion among the current nonproliferation mechanisms. The implementation of such a strategy will require forceful leadership, a cultural shift from both policymakers and the range of stakeholders, and consensus building within the international community.     

Homophobic legislation and its impact on human security

Despite sustained opposition, legislation criminalising homosexuality persists and threatens human security in Africa in numerous ways. This paper explores the circumstances around the enactment of new anti-homosexual legislation in Nigeria and Uganda, examining five categories of insecurity faced by lesbian, gay, bisexual, and transgender (LGBT) people in the context of these laws: physical violence; extortion and blackmail; arbitrary arrest and detention; displacement from home; and loss of work.     

Outbound supply chain network design with mode selection and lead time considerations

We present a large‐scale network design model for the outbound supply chain of an automotive company that considers transportation mode selection (road vs. rail) and explicitly models the relationship between lead times and the volume of flow through the nodes of the network. We formulate the problem as a nonlinear zero‐one integer program, reformulate it to obtain a linear integer model, and develop a Lagrangian heuristic for its solution that gives near‐optimal results in reasonable time. We also present scenario analyses that examine the behavior of the supply chain under different parameter settings and the performance of the solution procedures under different experimental conditions. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

The collection depots location problem on networks

In this paper we investigate the collection depots location problem on a network. A facility needs to be located to serve a set of customers. Each service consists of a trip to the customer, collecting materials, dropping the materials at one of the available collection depots and returning to the facility to wait for the next call. Two objectives are considered: minimizing the weighted sum of distances and minimizing the maximum distance. The properties of the solutions to these problems are described. © 2002 John Wiley & Sons, Inc. Naval Research Logistics, 49: 15–24, 2002; DOI 10.1002/nav.10000     

Power approximations in the economic design of control charts

A new approximate method is proposed for the economic design of control charts based on an estimate of the power of the control chart at optimality. Multiple linear regression is employed for the derivation of the approximate formula expressing the power of the control chart as a function of the model parameters. A simple optimization procedure is then used to determine the economic design of the control chart for the predicted value of the chart's detection power. The application of the new approach is illustrated through Duncan's models for variables control charts for processes subject to single and multiple assignable causes. Evaluation of the performance of the approximate method indicates that the approximate control chart design is very close to the exact optimum while its implementation requirements are reduced.     

Monte Carlo estimation of the maximal flow distribution with discrete stochastic arc capacity levels

This article describes a highly efficient Monte Carolo sampling plan for estimating ordinates of the complementary distribution function of the maximal s-t flow in a directed network with source node s, terminal node t and whose arcs assume random capacities. Communication, electric power, transportation, and water distribution systems fit this representation. The article derives point estimates and interval estimates that hold for finite sample sizes, and shows the extent to which the proposed technique saves time, as compared to crude Monte Carlo sampling, in achieving a specified accuracy.     

Level crossing analysis of priority queues and a conservation identity for vacation models

The two purposes of this article are to illustrate the power and simplicity of level crossing analysis and to present a conservation identity for M/G/1 priority queues with server vacations. To illustrate the use of level crossing analysis we apply it to preemptive (resume) priority M/G/1 queues with single- and multiple-server vacations considered by Kella and Yechiali (1986) and to non-preemptive priority M/M/c queues considered by Kella and Yechiali (1985). The conservation identity presented here states that the ratios of mean waiting times in an M/G/1 queue with and without server vacation policies are independent of the service discipline for first come first served, shortest processing time, shortest processing time within generations and non-preemptive priority service disciplines.     

Level workforce planning for multistage transfer lines

In this article, we define two different workforce leveling objectives for serial transfer lines. Each job is to be processed on each transfer station for c time periods (e.g., hours). We assume that the number of workers needed to complete each operation of a job in precisely c periods is given. Jobs transfer forward synchronously after every production cycle (i.e., c periods). We study two leveling objectives: maximin workforce size () and min range (R). Leveling objectives produce schedules where the cumulative number of workers needed in all stations of a transfer line does not experience dramatic changes from one production cycle to the next. For and a two‐station system, we develop a fast polynomial algorithm. The range problem is known to be NP‐complete. For the two‐station system, we develop a very fast optimal algorithm that uses a tight lower bound and an efficient procedure for finding complementary Hamiltonian cycles in bipartite graphs. Via a computational experiment, we demonstrate that range schedules are superior because not only do they limit the workforce fluctuations from one production cycle to the next, but they also do so with a minor increase in the total workforce size. We extend our results to the m‐station system and develop heuristic algorithms. We find that these heuristics work poorly for min range (R), which indicates that special structural properties of the m‐station problem need to be identified before we can develop efficient algorithms. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 577–590, 2016