The network design problem with relays (NDPR) is defined on an undirected graph G = (V, E, K), where V = {1, … , n} is a vertex set, E = {(i, j) : i, j ∈ V, i j} is an edge set. The set K = {(o(k), d(k))} is a set of communication pairs (or commodities): o(k) ∈ V and d(k) ∈ V denote the...

We describe a method to find low cost employee shift schedules that guarantee that the fraction of customers who wait less than a specified time (the service level) is always at or above a specified minimum. Most previous approaches used a two-step procedure: (1) determine period-by-period...

The problem of finding a maximin Latin hypercube design in two dimensions can be described as positioning n non-attacking rooks on an n x n chessboard such that the minimal distance between pairs of rooks is maximized.Maximin Latin hypercube designs are important for the approximation and...

We study two different lot-sizing problems with time windows that have been proposed recently. For the case of production time windows, in which each client specific order must be produced within a given time interval, we derive tight extended formulations for both the constant capacity and...

We consider a multi-item lot-sizing problem in which there are demands, and unit production and storage costs. In addition production of any mix of items is measured in batches of fixed size, and there is a fixed set-up cost per batch in each period. Suppose that the unit production costs are...