Sharif Digital Repository

Facility location decisions play a prominent role in strategic planning of many firms, companies and governmental organizations. Since in many real-world facility location problems, the data are subject to uncertainty, in this thesis, we consider the P-center problem under uncertainty of demand nodes. Using Bertsimas and Sim approach, we modeled the problem as a linear optimization model. Furthermore, we develop a tabu search algorithm to solve the problem. Finally we designed some experiments to adjust the parameters of tabu search algorithm. We presented the numerical result accordingly  

In facility location problem with uncertain data, some model parameters such as demand or transportation time are not known in advance and in many cases, no historical information exists to derive their probability distribution functions. In this situation, robust optimization is a prevalent approach. In this study, to apply robust optimization in our model, first we review its concepts and methods. Then, a mathematical model for a new facility location problem, as well as its robust counterpart is developed. Furthermore, we also develop a model for simultaneous decision making regarding facility location problem and sequencing. In this model, it is also assumed the process times are... 

According to the wide range of applications and numerous implementations, wireless networks are considered as a prominent means of providing data services, and have attracted the attention of many researches in recent years. Performance enhancement of these networks can be very beneficial to industry and wireless data service providers. Manipulation of relays, have been always considered as a proper means for improvement of network performance measures throughput and outage probability.In order to design relay networks efficiently, one should address two following problems: 1- determining transmission policy, and 2- relay location. In this research work, having in mind the optimality of... 

This thesis investigates the expertise ranking problem. Recently, the expertise ranking problem has attracted lots of attention in Information Retrieval community. The broad usages of expert ranking algorithms in commercial search engines indicate its importance and usability. Expertise ranking problem is concerned with finding people who are knowledgeable in a given topic. The main research questions in this thesis are related to three important questions related to expert ranking problem. The first question is what the sources of evidences are and how we can infer expertise of a person on a given topic. The second question is concerned with the modeling of information related to each... 

The Dynamic Maximal Covering Location Problem (DMCLP), is one of the classes of Facility Location Problem (FLP) with a wide raneg of applications in real-life situations. In order to solve this problem, this research presents a sufficient greedy heuristic algorithm, which is capable of solving the DMCLP in large scales of 2500 demand nodes and potential facilities of 200 in 5 periods in a negligible computation time in comparison to those with exact algorithms such as branch and cut. Furthermore, in this research DMCLP is also modified to reach reach a more realistic model. In this new model, a cost behaviour is defined according to the number of facilities located. Subsequently, the new... 

In the competitive facility location problem, two service providers fight over winning consumers by establishing a series of well-located facilities on the line. The consumers seek their required services from the facility which is closest to them. The order in which service providers locate and build their facilities is as follows: the first service provider establishes k facilities after which the second service provider locates another k facilities and this goes on for m rounds. The payoff of each service provider equals the number of consumers that choose that provider’s facilities to seek service from. In this dissertation, we address different types of this problem and try to analyze... 

In this study, a mathematical model for health-care facility location in two level and multi-services has been described. The facilities has two levels of clinic and hospital that has inclusive hierarchy property. In clinics, only outpatient services delivered. But, in hospitals in addition to handle outpatient services, inpatient services and emergency services are provided. In this research, we practice on queuing theory in order to consider the serious uncertainties in the health service, for instance, random demand and random service time, and by the help of which the criteria for considering the service level is calculated. Then by using applicable change variable and service level... 

This thesis studies a multi-product location-routing-inventory problem in which location-allocation, inventory and routing decisions are to be taken in a three-level supply chain including suppliers, depots and customers. Each product for each depot could be supplied by more than one supplier and each supplier has a limited supplying capacity per period. Products are distributed from depots to customers by a homogeneous fleet of vehicles. Backlogging is allowable for each customer on the condition of not exceeding a fraction of customer’s demand. A mixed-integer programming formulation is presented to describe the problem then a new hybrid heuristic algorithm based on the simulated annealing... 

Abstract The problem of competetive facility location can be defined as follows: There are a number of customers in the form of points in space, and two players arrange a number of facilities in the form of points in space, given some limitations, respectively. Each customer’s connection to each facility has a cost for the customer and an advantage for the facility, and each customer wants to be connected to at most one of the facilities which has the lowest cost for him. The goal is to find the strategy of placing the facilities and determining the cost which the facility receives from the customer, in such a way that the player’s profit is maximised.In this thesis, we first sought to... 

In this research, we propose a formulated approach to locate and allocate two level of a three-level closed-loop supply chain consist of a number of capable points production facilities, redistribution centers and customer clusters for multiple products in multiple time periods. Also, we consider environmental aspects in this supply chain network by taking into account an objective function, aside from cost objective function, in the template of emitted carbon dioxide. In this research for the first time we consider vehicles’ emitted CO2 different in each period which is a result of gradual depreciation of vehicles. In the end for the sake of validating model’s performance we developed few... 

Facility location decisions are critical elements in strategic planning processes for a wide range of private and public firms. High costs associated with facility location and construction make facility location or relocation projects long-term investments. One of the most popular models among facility location models is the covering problem. This is due to its application in real life, especially for service and emergency facilities. Set covering problem (SCP) and the maximal covering location problem (MCLP) are two categories of the covering models. The presented model in this study is based on the maximal covering location problemwhile considering some real¬ life constraintssuch as... 

In this thesis, an inventory- location model considering capacity constraints and coverage radius is described in which the capacity is determined based on the maximum accumulation inventory. This model, through minimizing the sum of the fixed facility location costs, transportation costs and safety stock and working inventory costs, concurrently, determines warehouse location, assignment of retailers to warehouses, shipment sizes from the plant to warehouses, working inventory and safety stock levels at the warehouses. This problem can be formulated as a nonlinear mixed integer program in which the objective function is neither concave nor convex. Lagrangian relaxation is incorporated for... 

In this study a mathematical model has been presented for multi depots, continuous location-routing problem with inventory restrictions. In this problem, a three-echelon supply chain was assumed and a factory which is producing one product and with unlimited capacity is on the first echelon of supply chain. In the second echelon of supply chain, several distribution centers distribute products. In the third echelon, there is a set of customers who are scattered in different geographical locations. Location of customers is pre-specified, but distribution centers should be located. In this problem, location of distribution centers will be determined in a continuous space. As the leader of this... 

This thesis studies a probabilistic bi-objective location-routing problem that considers multi-product, multi-period system with direct shipment and split delivery which is a case study in SAIPA Group. This model also considers location, allocation and routing decisions in three-level supply chain including factories, distribution centers and customers. Each product for each DC can be supplied by more than one supplier in each period of time, and each factory has a limited capacity. As shortage isn’t allowable, all of the customer’s demand should be satisfied in each period of time. Since customer’s demand could be more than vehicle’s capacity, each customer could be visited more than once... 

One of the primary concerns on many traditional capacitated facility location-network design problems is to consider costs of transportation and establishing of facilities in one single objective function. Considering a single objective in these problems may lead to misleading solutions due to the fact that the transportation costs should be considered in a short-term period of time, and therefore, the higher cost of establishing the facilities may unfairly dilute the role of the transportation cost. In this thesis, we introduce the capacitated facility location-network design problem with two separate objective functions. Moreover, in this problem, it is assumed that for connecting two...