We study the polyhedral structure of two related core combinatorial problems: the subtree cardinalityconstrained minimal spanning tree problem and the identical customer vehicle routing problem. For each of these problems, and for a forest relaxation of the minimal spanning tree problem, we introduce a number of new valid inequalities and specify conditions for ensuring when these inequalities ...

We propose a heuristic for a class of vehicle routing problems (VRPs) with minmax objective. These include the Capacitated VRP, the Capacitated VRP with multiple use of vehicles, and the Traveling Salesman Problem with multiple use of vehicles. A tabu search based adaptive memory procedure of instances indicate that the method produces very good solutions within reasonable computing times.

The successful application of Branch and Cut methods to the TSP has drawn attention also to the polyhedral properties of the symmetric capacitated vehicle routing problem, which is the capacitated counterpart of the TSP. We investigate three classes of valid inequalities for the CVRP, multistars, pathbin inequalities and hypotours and give computational results we obtained with a Branch and Cut...

in this paper, a robust model presented is developed for hub covering flow problem in which hubs have capacity. this problem has two objective functions converting to a single-objective problem by using weighting method. firstly, the problem will be formulated in a certain case. then, by considering the demand as a non-random variable, it will be modeled by robust optimization. finally, by usin...

The Cumulative Capacitated Vehicle Routing Problem (CCVRP) is a variation of the classical Capacitated Vehicle Routing Problem in which the objective is the minimization of the sum of arrival times at customers, instead of the total routing cost. This paper presents an adaptive large neighborhood search heuristic for the CCVRP. This algorithm is applied to a set of benchmark instances and compa...

1997 ii ACKNOWLEDGEMENTS We would like mostly to thank Mr. Peter Keenan, who was as much a partner as a supervisor, for his invaluable time and erudite guidance during the summer. We must also pay tribute to our parents for their encouragement and support, not only for the duration of this dissertation, but throughout the year. ABSTRACT The Capacitated Arc Routing Problem is a NP-hard arc routi...

Recently, Chakrabarty et al. [5] initiated a systematic study of capacitated set cover problems, and considered the question of how their approximability relates to that of the uncapacitated problem on the same underlying set system. Here, we investigate this connection further and give several results, both positive and negative. In particular, we show that if the underlying set system satisfi...

It is well known that choosing a good formulation for a mixed-integer optimization model can drastically reduce its solution time with a linear-programming based branch-and-bound algorithm. Integer optimization software such as CPLEX and XPRESS-MP has progressed rapidly in recent years and implements powerful branchand-cut algorithms, combining branch-and-bound with cutting plane generation. In...