__Abstract__:
**On the Repairman Problem with Controlled Servers and Switch-over Costs**

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This paper considers a maintenance system in which the queue size at the repair facility c
an be controlled by changing the repair time distribution. The production line consists of a f
inite number of identical and independent machines working in parallel; they are subject to fa
ilure with an exponential time-to-failure distribution. Each breakdown is repaired at a single
server repair facility using one of two possible repair time distributions whose choice is ba
sed on the number of machines waiting to be repaired. The cost structure includes a holding co
st, a repair cost, and a fixed switch-over cost when the repair time distribution is changed f
rom one distribution to the other. The control problem is represented by a semi-Markov decisio
n model in which the decision epochs are the repair completion epochs. The optimality criterio
n to be considered is the long-run average cost per unit time. A policy-iteration algorithm is
used to compute the optimal stationary policy within a class of two-parameter policies. Numer
ical results are reported using an exponential distribution for the repair time.
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