variable coverage radius

Since the expansion of urban areas, demographic changes and the existing facilities have gradually been established over the past years, there is a need for them to take a re-examination and it improve in the structure of the networks if needed. This study aims to investigate the recent facilities by building a model for locating and relocating hospital facilities in a hierarchical approach. Additionally, there are some solutions for closing, changing the capacity and opening new facilities if it needs to change in the current structure of facilities. The purposes of this study consist of maximizing the demand coverage and minimizing the structure cost. This model considers the probability occurrence of disturbances and crises, such as the lack of the availability and easy access. On the other hand, coverage radius and the capacity of each hospital facility are affected on the quality and speed of responses so that this study attempts to examine the capacity levels related to facilities and their coverage radius.This means how long any facility can cover the maximum distance of the access point. It is used of the Epsilonconstraintmethod in order to solve the proposed bi-objective model. As a result, this model is implemented asa case study in Qom Hospital facilities and it is shown that the amount of the demand coverage is increased in anacceptable level.

Crisis Management includes planning and readiness to respond to the inevitable and unpredictable natural disasters. One of the aspects of crisis planning and management is the establishment of relief centers in suitable locations for responding promptly to potential victims after the disasters. In this paper, the problem locating relief centers in relief logistics is investigated in the framework of the problem of locating with the variable coverage radius model. It is assumed that the time to reach all points of the demands is not greater than a predetermined value.Since the population in need of relief (demand) is a function of the severity of the disaster and certainly is not determined before the occurrence, the proposed model is considered uncertain. In this paper, a robust two-objective mathematical planning model (minimizing logistics costs and maximizing the covered population) is developed with uncertain demand to determine the number, location, coverage, and capacity of different relief centers with different service levels. To evaluate the validity of the proposed model, one of the districts of Tehran was studied as a case study to determine the number and location of the relief centers, along with their capacity and type of service.The results in the case study show we need to construct five relief centers with appropriate distribution in the region which capable of to cover 90 percent of all potential demand points.