In hub-and-spoke systems, due to the changes in input parameters affecting system over time, transportation providers should make right and timely decisions about hub facilities. For this reason, multi-period location problems are especially important. This paper presents a comprehensive review of from 1990 up most recent published studies. First, we study developed models based on some charact...

BACKGROUND Catheter hub decontamination requires a thorough scrub and compliance varies. This study evaluates the effectiveness of a disinfection cap with 70% alcohol in preventing contamination/infection. METHODS A 3-phased, multifacility, quasi-experimental study of adult patients with central lines divided into P1 (baseline), when the standard scrub was used; P2, when the cap was used on a...

We present an efficient metaheuristic based on Simulated Annealing for solving the p-Median problem. These ideas are tested on the well known OR-Lib set of problems with excellent results.

Given n customers and a set F of m potential facilities, the p-median problem consists in finding a subset of F with p facilities such that the cost of serving all customers is minimized. This is a well-known NP-complete problem with important applications in location science and classification (clustering). We present a multistart hybrid heuristic that combines elements of several traditional ...

A customer is presumed to gravitate to a facility by the distance to it and the attractiveness of it. However regarding the location of the facility, the presumption is that the customer opts for the shortest route to the nearest facility. This paradox was recently solved by the introduction of the gravity p-median model. The model is yet to be implemented and tested empirically. We implemented...

This article develops several strategies for the parallelization of the metaheuristic called scatter search, which is a population-based method that constructs solutions by combining others. Three types of parallelization have been proposed to achieve either an increase of efficiency or an increase of exploration. The procedures have been coded in C using OpenMP and compared in a shared memory ...

Given a set of clients and a set of potential sites for facilities, the p-median problem consists of opening a set of p sites and assigning each client to the closest open facility to it. It can be viewed as a variation of the uncapacitated facility location problem. We propose a new formulation of this problem by a mixed integer linear problem. We show that this formulation, while it has the s...