We focus on the D-optimal design of screening experiments involving main-effects regression models, especially with large numbers of factors and observations. We propose a new selection strategy for the coordinate-exchange algorithm based on an orthogonality measure of the design. Computational...

In this paper we defi?ne a new problem, the aim of which is to fi?nd a set of k dissimilar alternative solutions for a vehicle routing problem (VRP) on a single instance. ?This problem has several practical applications in the cash-in-transit sector and in the transportation of hazardous...

In the multi-depot ring star problem (MDRSP) a set of customers has to be connected to a set of given depots by ring stars. Such a ring star is a cycle graph, also called a ring, with some additional nodes assigned to its nodes by single star edges. Optional Steiner nodes can be used in the...

A ring tree is a tree graph with an optional additional edge that closes a unique cycle. Such a cycle is called a ring and the nodes on it are called ring nodes. The capacitated ring tree problem (CRTP) asks for a network of minimal overall edge cost that connects given customers to a depot by...

In this paper we present a heuristic framework that is based on mathematical programming to solve network design problems. Our techniques combine local branching with locally exact refinements. In an iterative strategy an existing solution is refined by solving restricted mixed integer programs...