We study a prize-collecting version of the uncapacitated facility location problem and of the p-median problem. We say that the uncapacitated facility location polytope has the intersection property if adding the extra equation that fixes the number of opened facilities does not create any fractional extreme point. We characterize the graphs for which this polytope has the intersection property...

The Maximum static flow problem, in a single-source-single-sink network, deals with finding the maximum amount of from source to sink. Given set possible sinks, identification sink that maximizes is an important optimization problem. In this work, we consider problem when sinks have given capacities. We devise simple network transformation so algorithms uncapacitated case can be used capacitate...

This paper deals with a hub location-routing problem (HLRP) which integrates the hub location problem (HLP) and the multi-hub vehicle routing problem (MH-VRP) in parcel delivery service. The HLRP is very difficult to be solved since it is composed of two NP-hard problems, the HLP and the MH-VRP. To solve these problems simultaneously we present a novel solution framework which divides the probl...

In this paper we consider a well known class of valid inequalities for the p-median and the uncapacitated facility location polytopes, the odd cycle inequalities. It is known that their separation problem is polynomially solvable. We give a new polynomial separation algorithm based on a reduction from the original graph. Then, we define a nontrivial class of graphs, where the odd cycle inequali...

Transport networks with hub structure organise the exchange of shipments between many sources and sinks. All sources and sinks are connected to a small number of hubs which serve as transhipment points, so that only few, strongly consolidated transport relations exist. While hubs and detours lead to additional costs, the savings from bundling shipments, i.e. economies of scale, usually outweigh...

A new multi-objective intermodal hub-location-allocation problem is modeled in this paper in which both the origin and the destination hub facilities are modeled as an M/M/m queuing system. The problem is being formulated as a constrained bi-objective optimization model to minimize the total costs as well as minimizing the total system time. A small-size problem is solved on the GAMS software t...