Scheduling with job-dependent learning effects and multiple rate-modifying activities

We consider a scheduling problem with job-dependent learning effects and multiple rate-modifying activities. The learning effects manifest such that the processing time of a job is a decreasing function of its position in a sequence. By job-dependent learning effects, we mean that the learning of the jobs is different. A rate-modifying activity is an activity that changes the production rate of a machine. So the actual processing time of a job in our problem is a variable, which depends not only on its position in a sequence but also on whether it is scheduled before or after a rate-modifying activity. We assume that each machine may have multiple rate-modifying activities. The objective is to minimize the total completion time. We show that all the cases of the problem are polynomially solvable.