Saeed Alinezhad; Seyyed-Mahdi Hosseini-Motalgh
Abstract
Most studies on decision making issue have supposed the problem in deterministic environment, and because uncertainty makes the decisions taken suboptimal, so in this paper we propose a credibility based fuzzy model for the Vehicle Routing Problem with Simultaneous Delivery and Pickup and Time Windows ...
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Most studies on decision making issue have supposed the problem in deterministic environment, and because uncertainty makes the decisions taken suboptimal, so in this paper we propose a credibility based fuzzy model for the Vehicle Routing Problem with Simultaneous Delivery and Pickup and Time Windows (VRPSDPTW). The dispatching cost of vehicles and customers’ time windows are supposed to be trapezoidal fuzzy numbers. We also proposed a hybrid meta-heuristic algorithm called Improved Particle Swarm Optimization (IPSO) for solving the problem. The proposed algorithm is the combination of Particle Swarm Optimization (PSO) and some removal and insertion techniques which helps to improve the searching ability and maintain diversity of solutions. Finally, to demonstrate the applicability of the proposed model in the real world we studied the distribution of dairy products among customers by a distribution company in Fars province. The computational results show that distributors can use this method to reduce operating costs of the company.
Laya Olfat; Maghsod Amiri; Ahmad Jafarian
Abstract
Cross-docking is one of the lean logistics tools that is used for uniting the shipments during the loops replacement. Cross-docking is the process of product movement form distribution centers without storage function. Vehicle routing problem in Cross-Dock external environment has much influence on cross-dock ...
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Cross-docking is one of the lean logistics tools that is used for uniting the shipments during the loops replacement. Cross-docking is the process of product movement form distribution centers without storage function. Vehicle routing problem in Cross-Dock external environment has much influence on cross-dock costs. This paper provides a model for minimizing total distance traveled by vehicles in the external environment of a cross-dock. In this paper, Vehicles routes was modeled with capacitated vehicle routing problem (CVRP) and genetic algorithm (GA) was used to solve the model. To validate responses obtained by GA, simulated annealing (SA) was used. Also, to evaluate the efficacy of two algorithms (SA & GA) in different CVRP problems in cross-dock, 10 problems with different dimensions are evaluated. The results show that in problems with smaller size GA is more efficient, whereas in large size problems SA is more efficient
