Sharif Digital Repository

The multi-facility location-allocation problem is concerned with locating m facilities in the Euclidian plane and allocating n customers to them at minimum total cost. In this work, we focus on a probabilistic version of the problem, in which the locations of the customers and their arrivals are probabilistically distributed. We first formulate the problem as a continuous location-allocation problem. Then, we give an approximated discrete model in which facilities can be located on a set of candidate points. The proposed model has two objective functions which can be calculated only through simulation. Considering the NP-hard nature of the problem and the functions’ unique properties, we use... 

Increasing the fuel cost and concerns about pollutions have facilitated the use of renewable energies. Wind power as a renewable energy has been considered as a good representative for conventional resources of electrical energy. The biggest obstacles for efficient use of the wind energy are changeability and uncontrollability in wind farm generation and to be far from the demand center. Also, conventional approaches cannot be applied to analyze the effects of this energy on power system. With increment in the penetration of the wind energy in power system, the necessity of considering its effects, especially large scale wind farm, in transmission expansion planning (TEP) studies is... 

Optimization methodologies with an emphasis on turbomachinery applications are of great interest. In the present study, a framework is proposed for the multi-objective optimization of a compressor blade using a coupled approximator and optimizer modules, as a mean for lowering the vast computational costs. The proposed framework consists of three main units: a CFD solver, an approximator unit, and an optimizer module. In this regard, a multi-layer perceptron artificial neural network is used as the approximator module while a multi-objective genetic algorithm, the non-dominated sorting genetic algorithm-NSGA II, is employed as the optimizer unit of the framework. In addition, a commercial... 

A common decision in project management is the selection of contractors to simultaneously optimize three objectives of the project’s triangle. This issue becomes more important if there is more monetary value involved or there is limited number of capable contractors. In project planning, there is numerous choices for tasks; each with specific time, cost and quality. There is no trade-off problem, if one of the choices has the best time, cost, and quality, simultaneously. However, as these criteria do not generally work in a unique direction, it makes the selection decision difficult. A contractor who performs the projects on time may have higher cost and lower quality. Given that there is a... 

Given the increased competition in supply chains and enlargement of their scale along with increasingly significant role of distribution systems, design and optimization of novel systems with comprehensive approaches in a timely manner has become important more than ever. One of such modern, efficient systems is cross docking in which the distribution network is omitted and thus operations are carried out faster and the productivity is increased. In this system, processes like packaging is done in cross docking and the goods and products are directly sent to customers. This study investigates a long-term and a short-term approach to the design of in two distinct problems. In the first... 

Most construction projects contain activities repeated in project units or locations with definite consequence. These kinds of projects are called repetitive projects. One of the fundamental objectives of planning and scheduling of repetitive projects is using resources optimally and without interruption, a concept known as continuous workflow. Traditional planning and scheduling methods like Critical Path Method (CPM) are criticized for their disability to produce a reliable workflow. Ignoring the concept of workflow in project schedule causes time and cost overrun that arise from additional waiting times and also increase the risk of accessibility to resources on time. Therefore in this... 

In recent years, economic globalization and resource globalization as two key factors have driven organizations to adjust their processes to survive in the competitive environments. Also, customers have been provided with high-quality products, lower cost, product customization and quick delivery. Moreover, globalization has let suppliers to geographically distribute across the globe, and for accomplishing the final product resources need to be gathered. Distributed infrastructure enables organizations to decrease delivery time and increase flexibility but leads to higher investment costs and lower efficiency of the system. For responding to existing issues Cloud manufacturing has been... 

In this study we addressed the problem of separated waste management. Investigating the literature on location routing problem, reverse logistics, waste management, and countries’ performance in the field, we proposed a novel method for gathering household waste that inspired from prosperous metropolises and took into account the particular situations of developing countries. As a matter of fact, the proposed method is an extension of location routing problem; it’s a bi-echelon network of facilities and multi-compartment vehicles connected via reverse cross docks. The problem is formulated using a mixed-integer linear model with 3 economic, social, and environmental functions; with respect...