OPER1021 Lecture Notes - Lecture 12: The Queue, Unit Load, Standard Deviation
28 Feb 2017
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Stable process (i. e. stable throughput: inflow rate (r) = outflow rate (r) Throughput may not equal capacity due to external factors (i. e. demand: if inflow rate >= capacity, throughput (r) = capacity, if inflow rate < c\capacity, throughput (r) = inflow rate. Excess processing capacity (i. e. capacity cushion) to protect against surges in demand: particularly important for service operations because you cannot inventory service offerings. Safety capacity = capacity inflow rate: * when inflow rate < capacity. If inflow rate and capacity rate constant, queues will build up if and only if the inflow rate is greater than capacity. If there is variability in the inflow rate or capacity, queues will develop even if there is safety capacity: when high inflow coincides with low capacity, queues build up. Capacity varies with changes in: the number of resources, processing time (i. e. unit load) Variability in arrival rate means that there is variability in time between flow unit arrivals (i. e. interarrival time)
