Sharif Digital Repository

In this research, a scheduling problem, minimizing the sum of weighted earliness/tardiness in a flow shop sequence-dependent group scheduling (FSDGS) problem, is investigated. In this problem, every job has a distinct due date, early penalty rate, and tardy penalty rate. This problem is typically classified in the literature as F_m | fmls,S_plk,prmu | ∑(w_j^1 E_j+ w_j^2 T_j). A mixed integer linear programming model is developed for the proposed research problem. As the problem is proved to be strongly NP-hard, only small-size problems can be solved with the mathematical model. Thus, a metaheuristic algorithm based on the Particles Swarm Optimization (PSO) algorithm is developed to solve... 

A distinct viewpoint is adopted by each centrality to analyze a network and rank its nodes. This study aims to introduce a novel centrality that ranks the nodes of a network more effectively. In this respect, a function of five centralities, namely betweenness, closeness, agent vector, degree, and Katz, is introduced to maximize the connected components of the network after ranking its nodes and deleting the first twenty ones. The proposed centrality functions better than the other mentioned centralities. Among the networks simulated to evaluate the centrality, it functions better in Erdos-Renyi and small-world networks, both of whom being based on the Poisson degree distribution, and... 

There are many linear and nonlinear programming problems with uncertain parameters and variables. These types of linear and nonlinear models are called fuzzy linear and nonlinear programming problems. Solving such problems is important, due to applications and variety of these models. Here, we first review various types of fuzzy linear programming problems based on the models or the solution methods. Next, we revise a method due to Kerre to compare two unipolar LR fuzzy numbers and present some new results on the comparison of LR fuzzy numbers. Then, we solve linear programming problems with unipolar fuzzy numbers by our proposed time varient particle swarm optimization (TV-PSO) algorithm.... 

The produced crude oil from the petroleum reservoirs usually has a value of brine (water and salt) this matter can be caused the corrosion of refinery equipment. The large part of this brine creates a stable emulsion with oil, that it couldn't be separated easily. For separation and demulsification of this emulsion, some chemical, mechanical, thermal and electrical methods can be executed. In chemical method, demulsifier materials can be added to water-in-oil emulsion. Different parameters such as properties of oil, type and concentration of demulsifiers, volume factor of water and etc., can affect the efficiency of water-in-oil emulsion separation. In this study, emulsification mechanism,... 

Determining the porosity, water saturation and permeability values in the reservoir rock, are major steps in the petroleum engineering and formation evaluation. Today in the oil industry, these parameters are obtained using Helium gas injection technique on core (Plug) samples. However, the coring operation is difficult and costly. In addition, there isn't the possibility of coring in some of wells, such as horizontal wells. In fact, the present research is the modelling of artificial neural networks to estimate permeability in one of the Iranian oil field reservoirs by using oil well logging data. In this research, MLP neural network has been used and for network training, the evolutionary... 

An important step in the early stages of an oilfield development is the accurate identification of the location of production and injection wells which has a significant impact on productivity and profitability of the reservoir. Recently, operation companies in petroleum industry focus on production optimization, recovery enhancement and cost reduction; as a result, application of non-conventional wells (NCW) or non-vertical wells have dramatically increased. Well placement optimization is a complicated task as it is a function of several contributing factors including reservoir heterogeneities and economic constraints. The complexity of this task increases when it is considered as a... 

Marine current power has been utilized in recent years as one of the most foreseeable renewable energy sources. In this study a multi-objective hydrofoil optimal design is carried out for use in marine current turbine in order to improve hydrodynamic performance due to low speed current in Qeshm channel. A particle swarm optimization code using FORTRAN is developed and coupled with XFoil software as flow solver that is based on panel method. B-spline curve is used to parameterize the hydrofoil shape and the coordinates values of the control points are designated to act as optimization parameters. Validity of flow solver examined by comparison made between computed data against experimental... 

Combined geothermal heat pump and solar collector system is a kind of load supply system for dwellings and greenhouses that operates by relying on renewable energies. The advantage of this system over conventional systems is lower power consumption. The aim of this study is to optimize the hybrid system so that in addition to reducing energy consumption and exergy destroied of the system, economically be minimized. In fact, in this study, we are dealing with an issue that should be optimize from different aspects. firstly, thermodynamic modeling for vertical ground source heat pump is done and then by considering 11 decision variables, the system is optimized by using single-objective and... 

In this research work, several guidance laws have been utilized and validated, considering the contraints on the missslie seeker angle and maximum acceleration, in order to simultaneously intercept the so-called Close-in Weapon System (CIWS) by multiple missiles. First of all, the existing guidance laws for salvo-attack are reveiwed. Then, a simulation program has been developed and validated for the misslie and CIWS as a five and two degrees of freedom systems, respectively. Optimization of the system is then carried out by the method of Particle Swarm Optimization, considering the given constraints. In the next step, for the improvement of the optimized guidance law, paramertic study has... 

Given many computing errors in current systems, a method appears necessary for predicting the nuclear parameter quickly and accurately. In this thesis, a neural network was used to predict safety in a nuclear power plant in order to develop an operating aid tool for preventive measures.First, some studies were conducted on appropriate feature selection for training neural networks. Some case studies have also been carried out on parameter prediction through soft computing in a power plant. In the next section, an expert judgment was taken into account to select DNBR (Departure from Nucleate Boiling Ratio) as a criterion for safety evaluation in the exploitation of a nuclear power plant (PWR)... 

In this study a novel, comprehensive and applicable hybrid radial basis function (RBF) neural network model optimized by particle swarm optimization (PSO) has been developed to predict MMP of pure and impure Co2 in miscible injection processes. 178 data sets from open literature used to validate and verify the proposed model. Also, slim tube test using Omani crude oil sample was carried out to confirm the model performance and its generalization Reservoir temperature, volatile to intermediate ratio and molecular weight of C5+ in the reservoir oil, composition of the Co2 and contaminants in the injected gas, considered as the input parameters. Performance of the proposed model was compared... 

In recent years passenger cars have been known as the main source of air pollution in urban areas. Despite all the research and efforts in minimizing the fuel consumption and emissions of internal combustion engines (ICE), this is merely a temporary solution. The permanent solution to overcome these disavantages is the use of electric vehicles (EV). The main downside of using electric vehicles is their short driving range. Multi-speed transmissions can be adopted to overcome this problem. Continuously variable transmissions (CVT) and infinitely variable transmissions (IVT) have been proven to enhance fuel economy in ICE vehicles and a great deal of research is being conducted to maximize... 

In recent years, simulation optimization methods have been developed to solve complicated problems that cannot be solved by mathematical programming methods. In simulation optimization methods, first the problem is modeled by simulation tools and then by applying optimization tools the optimal combination of input variables that optimizes the simulation output is determined. Although simulation optimization has attracted researchers’ attention in recent years, most of the works presented do not consider uncertainty in simulation models. This becomes our motivation in this study to develop uncertain methods in metamodel-based simulation optimization based on minimax methods that are... 

The traditional point of view on the scheduling of the healthcare systems, which is in common with the scheduling of other service and manufacturing systems, has contributed to inattention to patients’ psychological status and has given rise to many negative effects not only on them, but also on hospitals. However, this perspective has not been modified yet with respect to the features of healthcare systems, in which patients, rather that machines, are the main entities of the system. In this study, to address this draw back, a new concept, psyche-based optimization, as well as a new scheduling problem, anxiety-based scheduling of operating rooms, as the advent of this concept, have been... 

The most important sources in container terminals are berth and quay cranes. The main purpose in the container terminals is reducing delay times of vessels. This will be obtained with planning of terminal sources. This research addresses simultaneous berth and quay crane scheduling problem. A mixed integer linear mathematical model is proposed to minimize sum of completion time of vessels. Since the proposed research problem is NP-hard, two methahuristic algorithms based on Tabu Search (TS) and Particle Swarm Optimization (PSO) are presented to heuristically solve the problem. After parameter tuning, PSO and TS algorithms are compared with experimental design methods. The results indicate... 

In a solar central system plant about 40% of energy losses occurs in the heliostat field. Furtheremore, half of the investment costs for construction of the plant is related to the heliostat field. Therefore, an optimal design of the heliostat field is necessary for reduction of levelized cost of energy in solar tower power plants. In this study, in order to optimally design the heliostat field, first energy performance of the helistat field in one year is simulated. Solar power and sun’s position at each moment of the day is determined by mathematical relations. Then, loss factors in the field are modelled and heliostat field layout is designed by an algorithm. Finally, by using PSO... 

Travel time is the most significant element in choosing among different modes of transportation. In order to increase the public transportation’s utility we need to utilize some methods to reduce public transportation travel time and passenger delay. Bus system, as one of the major types of public transportation, is mainly influenced by the traffic flow more than other types of public transportation. In order to increase the bus system’s reliability we need to utilize a controlling system so that we could increase its movement discipline and reduce line’s disruption. In this research we proposed an optimization model based on bus holding strategy and the real-time data from the route. This... 

In the urban railway transportation system, large amount of power is consumed for starting the movement and acceleration. A great part of this energy is transformed to the train kinetic energy which in the case of break is reduced to zero. Thus recovering of train kinetic energy during the brake can help to reduce train energy consumption. One of the possible ways is using energy storage during the brake and using it again during acceleration. Storage can be performed in three kinds, fixed, mobile and hybrid. In this thesis, super capacitors have been investigated as fixed and mobile storages. After reviewing electrical railway transportation systems, elements of these systems have been... 

Due to the undeniable importance and applicability of both "batch processing" and "parallel machines" in service and industry, this survey strives to solve a real-world problem in which some identical parallel machine, capable of processing jobs in batches, are available. In batch processing the process of jobs starts and ends simultaneously. In real world the processing time of the batch is a function of some characteristics of the jobs in the batch. in this survey, for simplicity (as calculating the mentioned function is so difficult), we assume that the processing time of a batch equals the sum of the processing time of the jobs in the batch. we also have assumed that the capacity of a... 

One of the main concerns of automakers over last few decades was reducing fuel consumption while increasing the efficiency of vehicle. Using Continously variable transmission in vehicles could lead to reaching better performance, improving fuel consumption, reducing emissions and increasing vehicle acceleration. In this thesis types of Continously variable transmissions are introduced with focusing on steel V-belt CVT by analyzing its performance in steady and transient conditions. Unlike flat belts, V-belts moves both radial and tangential over the driver and driven pulleys resulting more complex dynamic.The dynamics of these systems in transient conditions are analyzed in two different...