We consider the PH/PH/c retrial queues with PH-retrial time. Approximation formulae for the distribution of the number of customers in service facility, sojourn time distribution and the mean number of customers in orbit are presented. We provide an approximation for GI/G/c retrial queue with general retrial time by approximating the general distribution with phase type distribution. Some numerical results are presented.
This article introduces a simulation study relating to the dynamic operating algorithm for the painted body storage (PBS) in an automotive factory. The manufacturing process in the trim shop of an automotive factory is a typical example of the mixed-model assembly production. In the paint shop, which comes before the trim shop, same-colored bodies are grouped together to reduce the changeover cost. Therefore, the PBS is located between the paint shop and the trim shop to allow for the rescheduling of the input sequence of cars to the assembly line. In this article, a case study on PBS in an automotive factory is presented. The storage/retrieval algorithms are suggested, and the proposed system is verified using simulation models. A sensitivity analysis for operating factors is also carried out.
In this paper, we discussed a problem for improving the throughput of a crankshaft manufacturing line in an automotive factory in which the budget for purchasing new machines and installing additional buffers is limited. We also considered the constraint of available space for both of machine and buffer. Although this problem seems like a kind of buffer allocation problem, it is different from buffer allocation problem because additional machines are also considered. Thus, it is not easy to calculate the throughput by mathematical model, and therefore simulation model was developed using ARENA ® for estimating throughput. To determine the investment plan, a modified Arrow Assignment Rule under some constraints was suggested and it was applied to the real case.
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