jobs are held before machine 1 and launched only when
they can be sequentially processed by all m machines without delays at any of the
machines. It is noteworthy that zero-buffer and no-wait flowshop problems are
equivalent for the two-machine problem when set-up times are included in processing
times. For separable set-up times, however, there are two cases in the zero-buffer
problem. In the first case, the set-up of the next job on machine 1 is not allowed until
the current job releases machine 1. In the second case, the set-up for the next job on
machine 1 can start as soon as machine 1 completes its processing of the current job.
The first case seems to be more practical. Notice that the zero-buffer in the first
case is equivalent to the no-wait problem (Aldowaisan and Allahverdi 1988,