This paper reviews some of the most intriguing results and questions related to Lagrangean
relaxation. It recalls essential properties of the Lagrangean relaxation and of the …

The train timetabling problem aims at determining a periodic timetable for a set of trains that
does not violate track capacities and satisfies some operational constraints. In particular, we …

We present a new local optimizer called SOP-3-exchange for the sequential ordering
problem that extends a local search for the traveling salesman problem to handle multiple …

We study the problem of freight transportation in railway networks, where both passenger
and freight trains are run. While the passenger trains have a prescribed timetable that …

In order to increase the order picking efficiency, e-commerce retailers have started to
implement order picking systems where mobile robots carry inventory pods to pick stations …

The train timetabling problem (TTP) aims at determining an optimal timetable for a set of
trains which does not violate track capacities and satisfies some operational constraints. In …

This paper describes an algorithm for minimizing the non-productive time or 'airtime'for
milling by optimally connecting different toolpath segments. This problem is formulated as a …

In this article we consider a variant of the classical asymmetric traveling salesman problem
(ATSP), namely the ATSP in which precedence constraints require that certain nodes must …

In paint shops in the automotive industry, a change of colours between two consecutive cars
causes sequence-dependent set-up costs. Often, selectivity banks are used as storage and …

Ant colony system is a well known metaheuristic framework, and many efficient algorithms
for different combinatorial optimization problems have been derived from this general …