In this study, two mathematical models have been developed for assigning emergency vehicles, namely ambulances, to geographical areas. The first model, which is based on the assignment problem, ambulance transfer (moving ambulances) between locations has not considered. As can improve system efficiency by decreasing response time as well operational cost, we consider in second transportation pr...

Reliable location routing problem considers a location problem and a vehicle routing problem in order to select the optimal location of facilities and at the same time the optimal routes for vehicles considering the unexpected failure for facilities in which, all facilities may fail with a probability. In this paper, a bi-objective mathematical model has been developed to minimize the total cos...

Model building is a fragile and complex process especially in the context of real cases. Each real case problem has its own characteristics with new concepts and conditions. A correct model should have some essential characteristics such as: being compatible with real conditions, being of sufficient accuracy, being logically traceable and etc. This paper discusses how to build an efficient mode...

A three-level relief chain including a number of suppliers in fixed locations, candidate distribution centers and affected areas at certain points are considered. A mixed integer nonlinear programming model is proposed for open transportation location routing problem by considering split delivery of demand. To solve a realistic problem, foregoing parameters are considered as fuzzy in our propos...

This paper investigates a multi-period multi-product stochastic inventory problem in which cash-constrained online retailer can leverage order-based loans provided by some Chinese e-commerce platforms to speed up its cash recovery for deferred revenue. Sample average approximation (SAA) and moment-matching scenario tree are adopted solve this multi-stage with the objective of maximising retaile...

in this study the location routing problem with fuzzy parameters is taken into account, this problem involves determining the location of the depots and routing of the vehicles in order to serve the customers. in this study a location routing problem with fuzzy travel times and due dates is considered and two objective models are proposed. the considered objectives are minimizing the total cost...

k-median and k-center are two well-known problems in facility location which play an important role in operation research, management science, clustering and computational geometry. To the best of our knowledge, although these problems have lots of applications, they have never been studied together simultaneously as a multi objective optimization problem. Multi-objective optimization has been ...

Hazardous waste management incorporates collection, separation, treatment, recycling and disposal of hazardous wastes. In this paper, a new multi-objective mixed integer model is presented for hazardous waste collection problem. The model aims to minimize transportation and construction costs, and environmental and population risks in hazardous waste management systems. This model is applied in...