Sharif Digital Repository

In this study, redundancy allocation problem for a system with y subsystem including k-out-of-n structure is investigated. Due to existing repairable components in each subsystem, the model consists of selecting number of repairman and redundancy level for each subsystem. The model is constructed based on Markovian process and the goal is maximization of steady-state availability under constraints such as cost, weight, and volume. In this model, two type of costs are considered; cost of employing repairmen and cost of preparing components and decision variables of the model are number of repairman and number of component in each subsystem.The model is located into integer non-linear... 

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... 

In line with advances in science and technology in the areas of robotics, artificial intelligence, computer and control, unmanned vehicles are being more utilized and focused. On the other hand, development and further advances of these vehicles is highly dependent on the level of their autonomy. Motion planning is one of the most important issues in this regard. Due to high levels of autonomy required for unmanned air vehicles (UAV), the subject of motion planning is of valuable interest in aerospace applications. The goal of the motion planning problem, that is the subject of this research, is to extract an optimal trajectory for the UAV from an initial location toward its target point... 

Optimum highway alignment problem is among the most substantial but large and complicated topics in transportation area. Infinite number of feasible solutions, numerous local optima and the constrained feature of the problem, associated with complex and mainly non-linear constrains, has put an extra effort into the problem-solving process. Moreover, the problem has a sensitive objective function to input variables. Due to the nature of the problem, conventional methods fail to find any exact solution, and so, using heuristic methods during the solving procedure is inevitable. Large-scale, complexity and sensitivity of the problem leads to a solution which is time-consuming and... 

Image steganalysis is the technique and art of detecting covert communication via images.Reduction of features dimentionality is an important issue according to accuracy and time complexity. In this thesis, GA (genetic algorithm) and PSO (Particle Swarm Optimization) are used to reduce the dimentionality of JRM, a recently proposed feature set containing 11255 features which looks high dimentional compared to other feature sets which has been reduced by evolutionary algorithms so far. So, inspite of other works done using evolutionary algorithms in this field, we use the class sepearability criterion as fitness function instead of the accuracy of the classifier. Investigating these features,... 

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... 

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... 

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... 

The idea of using groups of simple autonomous robots instead of one or limited number of very sophisticated robots is inspired by flocking behaviors of animals. Distributed control structures and artificial swarming have attracted lots of studies in robotics. There are many applications for robotic swarms in which members are very simple robots with low communication capabilities. These robots communicate only within very limited distances. In this thesis, a homogenous robotic swarm with at least two robots is assumed. Swarm robots are considered to be dimensionless with no time delay, which is a normal assumption in this field of studies. Robots move in planar space and their behaviors are... 

Hyper-redundant manipulators have large number Degrees of Freedom. Because of their redundancy, such manipulators have the advantage of obstacle avoidance, overcoming singularities and intrusion into highly constrained environments. The most challenging task in designing hyper-redundant manipulators is the synthesis of actuating mechanisms with appropriate kinematics and effective power supply. Most of previous techniques in implementing hyper-redundant robots have the disadvantages of: -Using large number of actuators, -Heavy weight due to large number of actuators, -Complexity of the control system due to need of synchronizing subsets of motors. In this thesis a novel hyper redundant... 

The competition between producers and the contracts issues between the producers and consumers of electrical energy in restructured power systems might cause on unwanted increase in power interchange beyond transmission lines capacity. If the power interchange is not well-managed, it would often cause overloads in specific path. This phenomenon is termed as lines congestion. The major goal of congestion management is to create a set of rules that ensure sufficient control over producers and consumers to maintain an acceptable level of power system security and reliability in the time of limitation of transmission network with maximizing economic market efficiency. As FACTS devices provide... 

Marine transportation is an essential aspect of global trade, as it is responsible for transporting large quantities of goods and commodities between different countries and continents. The efficient optimization of shipping routes can greatly reduce operational costs, save time, and increase the overall competitiveness of the maritime industry. One of the most critical aspects of route optimization is the selection of the most efficient path, taking into account various constraints such as fuel consumption, voyage duration, vessel speed, and port constraints. The PSO algorithm has been successfully applied to a variety of optimization problems, including the optimization of marine routes.... 

The main purpose of this thesis is to propose effective meta-heuristic algorithms for solving the scheduling problems. We consider the problems that are associated with two areas: project scheduling and shop scheduling. In project scheduling area, only the resource constrained project scheduling problem (RCPSP) is considered. For solving this problem, a hybrid particle swarm optimization (PSO) algorithm is developed. The proposed algorithm outperforms other existing PSO algorithms for the problem. However, most of the contributions of this thesis are related to the second area. The shop scheduling problems of concern include: job shop, stage shop and partial job shop. We developed two... 

Reliability and availability are one of the sensitive and significant points in each maintenance system. Due to the nature of bus system failures, that almost consist of large percentage of possibility risk factors is the systems maintenance, in this study for implementing our proposed model, the bus rapid transit garage-line1 were selected. This model is to provide solutions in strategic and operational levels in the network's garage in several sessions. The solutions include decisions about the capacity of human resources in the workshop system, determine the communication policies with suppliers of spare parts and human resources training policies by the standard scoring system, the... 

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... 

Reducing noise, vibration and damage to the vehicle's passenger compartment was always a problem that has been investigatedin many researches. Here engine mounts as connecting members between engine and chassis play a big role. Because both of engine and road vibration put on it. Many studies have been done to optimize the engine mounts. As a result, many of hydraulic engine mounts with different variety of system control. But a few researches did about optimization of location and orientation of engine mounts. Therefore this project is to provide a process to optimize the location and orientation of engine mounts. The optimization process is First the dynamic equations of dynamic system are... 

Offshore jacket platforms are one of the most motivating structures for damage detection due to their importance and productivity. In this study, the goal is to investigate the application of finite element model updating as a robust method for damage detection in this kind of structure. This method is based on minimizing a cost function which shows the difference between some features of the model and damaged real structure. Therefore, this method can be used for damage detection by comparison between updated model, which is updated by measured data from damaged structure, and the initial model which precisely shows the previous or undamaged status of the structure. The vibration features... 

The transportation and electricity industries are major emitters of greenhouse gases (GHGs). In order to reduce emissions, several strategies have been proposed, including plug-in electric vehicle (PEV) use and integration of renewable energy sources (RESs). To reduce the concern emission rate while considering economic constraints, it is important to examine different scenarios of incorporating these elements. To investigate the effectiveness of using PEVs and RES from various perspectives, this study utilizes a combined economic emission dispatch (CEED). The influence of emission and cost coefficients is examined in a sensitivity analysis. In the proposed model, two test cases containing... 

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... 

In this paper the predictive equations for collapse assessment of shear links used in eccentric braced frames are developed. An extensive database including results of over 70 cyclic tests on steel wide flange shear links is collected and the structural parameters governing the hysteresis behavior are calibrated using a simplified numerical model. The methodology of calibration is to minimize the discrepancy between the experimental hysteresis loops and the corresponding numerical results using Particle Swarm Optimization (PSO) algorithm. The objective function of PSO algorithm is minimized by iterating parameters that govern the hysteresis behavior of the numerical model. Stepwise...