عنوان مقاله [English]
In distribution networks of goods and services, identifying hub locations and determining annular routes connecting the hubs to satellite centers, ( i.e. Location-Routing problems) is one of the most important issues of strategic and operational decision making problems. In Irans current postal distibution network, in most cases, dispatching is done directly; with no major hubs for management of packages. Accordingly, given the significance of time and cost in Irans postal network, this study is dedicated to modeling the problem of locating hubs, routing, and comparing the results with the currently existing methodologies. Location-Routing problems are commonly investigated by researchers through two approaches: either modeling, or solving models. In this paper, however, both approaches will be studied. In this study, a new model is developed and then implement on Irans postal network. In the new model, in order to estimate reliability measure, the distance between cities nominated as ptential hubs and also the volume of the packages dispatched from origins and destinations are taken into considerations. In the next step, these reliability measures are utilized in determining the exact hub locations as well as in allocating satellite centers, which function as non-hubs, to those hub locations. Moreover, a new solution method is presented by employing an iterative two-step metaheuristics. Results are then reported and evaluated to illustrate the strengths of the modelling approach and the solution method used. The models are solved using Varaible Neigborhood Search (VNS) and Simulated Annealing (SA). To demonstrate the strength of these rough methods, the results of accurate model solutions are utilized as well. In this way, the innovations of this research , in terms of both modeling and solution methods, are depicted. Genrally, by using the proposed model, firstly the hub-locations are selected. Then, proper annular routes for each hub can be determined. Prudence of the results is a testament that the proposed model and recommended solution algorithm are capable of effective organizition of Irans postal network.