Problems with unit execution time tasks and two identical parallel processors have received a great deal of attention in scheduling theory. In contrast to the conventional models, where each task requires only one processor, we consider a situation when a task may require both processors...

Chains of operations have to be scheduled on a single machine such that a minimum delay is set between any two operations linked by a precedence relation. Three sub-problems are shown to be solved in polynomial time. First, we consider the problem of minimizing the makespan when all the...

In this note, we prove ??-completeness of the following problem: Given a set of trams of different types, which are stacked on sidings in their depot and an order in which trams of specified types are supposed to leave. Is there an assignment of trams to departure times without any shunting...