Manufacturing flow line systems: a review of models and analytical results

The most important models and results of the manufacturing flow line literature are described. These include the major classes of models (asynchronous, synchronous, and continuous); the major features (blocking, processing times, failures and repairs); the major properties (conservation of flow, flow rate-idle time, reversibility, and others); and the relationships among different models. Exact and approximate methods for obtaining quantitative measures of performance are also reviewed. The exact methods are appropriate for small systems. The approximate methods, which are the only means available for large systems, are generally based on decomposition, and make use of the exact methods for small systems. Extensions are briefly discussed. Directions for future research are suggested.National Science Foundation (U.S.) (Grant DDM-8914277

Control Schemes in Queueing Networks

We consider open and closed queueing networks consisting of a set of controlled service centers. The controlled service center contains an exponential server, a queue of delayed customers and a control switch between them. The switch position is a function (control function) of the service center state which provides a means of controlling the service rate by admitting or not users into the server's queue. We give the stationary probability distribution for a broad class of control functions. An application of these results to the expected queue lengths and the expected waiting times in a two-server closed network is also considered.