Designing a Multi-Objective Closed-loop Supply Chain Mathematical Model with Supplier Selection Approach and considering Discount

One of the key steps in greening supply chains is to investigate the environmental requirements and factors in supplier selection. Today supply chain networks are known as the main pillar of economic activities. To this end, in this article a multi-period, multi-product, multi-objective closed-loop supply chain problem has been investigated. Moreover, the return of defective products to the production cycle and the general and progressive simultaneous discount policy have been considered through an integer linear mathematical model. The presented model generates Pareto solutions using two proposed meta-heuristic algorithms, multi objective particle swarm optimization and non-dominated sorting genetic algorithm and combination of the two. To compare the performance of the solution methods, five criteria are defined and the numerical results show the efficiency and quality of the proposed hybrid algorithm.