A queuing model for due date control in a multiserver repair shop

This paper deals with a repair shop with multiple parallel servers, which has to carry out planned overhauls. Each overhaul consists of a large number of maintenance jobs. The overhaul process is interrupted by randomly arriving emergency jobs. To control the delivery performance of the overhauls, knowledge about the overhaul makespan distribution should be available. Using a 2‐dimensional Markov model, we derive the first and second moment of the overhaul makespan analytically for the case that the repair times of all overhaul jobs are identically and exponentially distributed. For the case of nonidentical repair time distributions, an approximation is presented. Simulation shows that the makespan distribution fitted on these moments gives an excellent approximation. © John Wiley & Sons, Inc. Naval Research Logistics 48: 281–282, 2001     

Conflict Studies and Causality: Critical Realism and the Nomothetic/Idiographic Divide in the Study of Civil War

The study of civil war has increased exponentially during the post-cold war period. This has not, however, resulted in greater levels of consensus with regard to the causes and nature of this phenomenon. In order to alleviate this situation the current article will draw on critical realist philosophy. It will argue (1) that critical realism provides conflict studies authors with a more sophisticated and coherent understanding of causality than has previously been available to them, and (2) that this understanding paves the way for an approach to social science which – rather than consistently abstracting from context – systematically engages with it.