The random order service G/M/m queue

The waiting time in the random order service G/M/m queue is studied. For the Laplace transform we obtain a simpler representation than previously available. For the moments, an explicit recursive algorithm is given and carried out numrically for some cases. This gives rise to the conjecture that the waiting-time distributio can be approximated by the one for M/M/m after a suitable change of scale.     

Assessment of hazardous-inspection policies

Inspection procedures may at times pose a hazard to the system being monitored. In this article, a simple hazardous-inspection model is considered. The character of the optimal ongoing inspection policy (for inspections subsequent to the first) is reviewed, and the possible forms of the optimal initiation policy are established. Efficient computational procedures are developed for calculating optimal policies. Some discussion is included of the counterintuitive nature of some of the results.     

A note on the influence of missing operations on scheduling problems

This paper attempts to resolve the existing confusion concerning missing operations. Scheduling problems are classified in two groups: (i) null-continuous (NC)—comprising the problems where an optimal schedule remains optimal on replacement of arbitrarily small processing times (existing operations) with zeros (missing operations); (ii) null-discontinuous (NDC)—comprising those problems which are not null-continuous.     

Resequencing with parallel queues to minimize the maximum number of items in the overflow area

This article treats an elementary optimization problem, where an inbound stream of successive items is to be resequenced with the help of multiple parallel queues in order to restore an intended target sequence. Whenever early items block the one item to be currently released into the target sequence, they are withdrawn from their queue and intermediately stored in an overflow area until their actual release is reached. We aim to minimize the maximum number of items simultaneously stored in the overflow area during the complete resequencing process. We met this problem in industry practice at a large German automobile producer, who has to resequence containers with car seats prior to the assembly process. We formalize the resulting resequencing problem and provide suited exact and heuristic solution algorithms. In our computational study, we also address managerial aspects such as how to properly avoid the negative effects of sequence alterations. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 401–415, 2016     

The cyber conceptual framework for developing military doctrine

Militaries rely on secure communications. Despite the permeation of cyber-systems throughout the operational environment, there is little readily available doctrine on cyber-warfare. Doctrine that does exist has not been coherently integrated. This paper introduces a Cyber Conceptual Framework, consisting of five questions pertinent to the future use of cyberspace. The authors enunciate a definition of cyberspace, expand on existing military doctrine to reject the conceptualisation of cyberspace as a domain, define cyber-conflict, define cyber-attack and describe the four components and five levels of a cyber-attack. This work develops a common framework from available doctrine and a lexicon for future discussion.     

Scheduling on a single machine with a single breakdown to minimize stochastically the number of tardy jobs

Jobs with known processing times and due dates have to be processed on a machine which is subject to a single breakdown. The moment of breakdown and the repair time are independent random variables. Two cases are distinguished with reference to the processing time preempted by the breakdown (no other preemptions are allowed): (i) resumption without time losses and (ii) restart from the beginning. Under certain compatible conditions, we find the policies which minimize stochastically the number of tardy jobs.