3Þ The term α is an “improvement factor” which allows for a variable effect of maintenance on the aging of a workstation. When α¼0 the effect of maintenance is to return the workstation to a state of “good-as-new” and when α¼1 maintenance has no effect and the workstation remains in a state of “bad-as-old”. Note that the maintenance action at the end of period t partially lowers the rate of occurrence of failure of workstation i, as shown in Fig. 1. Furthermore, the maintenance action takes TPMi to be done and a maintenance cost Mi is incurred at the end of that period.