Sharif Digital Repository

Nowadays, fast growth in industrial transformation and urbanization pushes the management of hazardous waste into a crisis for all markets. In this study, a multi-objective mathematical model is introduced to address a new version of the hazardous waste location-routing problem. As another multi-objective optimization model in this research area, the objective functions are minimizing the total costs, the overall risk associated with sending the hazardous waste, and the site risk related to the population in a given distance around the facilities. With regards to the literature and as far as the authors know, this is the first attempt to consider both risks of transportation and population... 

Vehicle routing problem is one of the complex and NP-hard problems, which plays a crucial role in this hectic world regarding people's lifestyle. Nowadays, many people provide their stuff online, so a logistic problem has been outstripped for companies to reduce their transportation costs. In this article, a novel approach has been introduced, which can solve the multi-depot vehicle routing problem in shorter time. By using clustering and decomposing the main problem into smaller ones, solution time has been dropped dramatically. In addition, this approach obtains a reasonable cost, which can be considered as fuel consumption, distance, or so forth. This method could reduce the solution time... 

A heuristic approach is proposed to solve a real Periodic Vehicle Routing Problem (PVRP) that aims at extending the market share with the minimum transportation cost. In PVRP, vehicles are assigned to routes in different workdays to satisfy the frequency of visiting customers. The objective is to determine the scheduling and routing policies of the vehicles to minimise the fleet size and to maximise the selling benefits. The vehicle capacity and the trip time are the main constraints. The proposed approach is verified by real data and obtained results imply a significant improvement as compared to the current status  

We are concerned with a capacitated location-multi allocation-routing problem in a road network with flexible travel times. It is assumed that all links are two-way and capacities of the server nodes and arcs for accepting of population are limited. The aim of our work is to find numbers and locations of server nodes, allocation of the existing population in existing demand nodes on the network to the servers and the allocation of existing population in each node to different routes to determine the decided server for each member so that total transportation time is minimized. Here, two basic concepts are considered: multi allocation and flexible travel times. The concept of multi allocation... 

Recently, with the expansion of environmental issues and raising of customers' awareness, companies are experiencing huge pressure from shareholders and the government for greater compatibility with their environment. Companies and industry owners must implement green operations in their daily activities to be able to keep up with the competitive atmosphere of the environment. One of the most important operations to be implemented is cooperating with green suppliers. In this study, a multi-objective mathematical model is proposed to select suppliers and allocate optimal orders to them in a two-echelon supply chain, including supply and distribution echelons. The proposed model focuses on the... 

We provide a mixed-integer nonlinear programming (MINLP) model for a location-allocation-routing problem in a transportation network with links carrying the travel times among the nodes in the network. The travel time between two nodes is considered to be intelligent, that is, since the travelling population in a link can affect the travel time, here we consider the impact of the travelling population on the travel time of the link. This way, depending on how the population is distributed in the network, the travel times of the links may change. The problem is to find an optimal locations of server node(s), allocation of existing demand nodes in the network to the server(s) and allocation of... 

The growing rate of population and technological advancement have led to an increase in natural resource consumption, which has caused irreparable damage to the environment. The implementation of green supply chain management is one of the most effective ways to deal with environmental degradation. Therefore, in this paper, a bi-objective mixed integer linear programming model is developed to design a green supply chain network. In the proposed model, the possibility of customer storage, being faced with shortage, locating of distribution centres, green vehicle routing problem, split delivery, multi-depot vehicle routing problem (VRP), capacitated VRP, and uncertainty in demands will be... 

In recent years, the number and severity of natural disasters occurring in various regions of the world have increased dramatically incurring heavy financial and human losses. Therefore, decision-makers have been concerned with ways of providing relief to reduce the losses. Here, we present a multi-objective bi-level model for disaster location-routing problem that provides the needed supplies through multiple suppliers, considering the supply risk. Moreover, to reduce the risk and increase efficiency, special attention is given to people's help for supplying goods having high priority and low risk. At the first level of the model, the cost and time objectives are considered, and at the... 

Estimating Origin-Destination matrix, named O-D matrix or ODM, is an important issue in transportation planning. Due to need to survey movements on the network, estimating ODM is usually considered as a high-cost measure in transportation planning. In this research work, a two-stage procedure, including solving routing problem and minimizing the difference between observed and estimated traffic volumes on the network, has been developed to estimate the O-D matrix elements. At the first stage, routing problem is solved to determine paths while in the second stage an absolute error function has been defined to determine the number of trips from each origin to destination pairs. The procedure... 

We study a location-allocation-routing problem for distribution of the injured in a disaster response scenario, considering a three-type transportation network with separate links. A circle-based approach to estimate the impacts of the disaster is presented. After formulating relations for computing the percentage of the injured, the destruction percentage and the damage-dependent travel times, the problem is formulated as an integer nonlinear program. We utilize a genetic algorithm and a discrete version of the imperialist competitive algorithm for solving large problems. An empirical study focused on earthquakes in Tabriz, Iran, illustrates applicability of the proposed model and... 

In the traditional agri-fresh food supply chain (AFSC), geographically dispersed small farmers transport their products individually to the market for sale. This leads to a higher transportation cost, which is the primary cause of farmers’ low profitability. This paper formulates a traditional product movement problem in AFSC. First, the aggregate product movement model is combined with the vehicle routing model to redesign an existing AFSC (the ETKA Company; the most extensive domestic agri-fresh food supply chain in Iran) based on the available data. For the four-echelon, multi-period supply chain under investigation, a mixed integer linear programming (MILP) model is developed for the...