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    Dynamic diversity enhancement in particle swarm optimization (DDEPSO) algorithm for preventing from premature convergence

    , Article Procedia Computer Science ; Volume 24 , 2013 , Pages 54-65 ; ISSN: 18770509 Nezami, O. M ; Bahrampour, A ; Jamshidlou, P ; Sharif University of Technology
    2013
    Abstract
    The problem of early convergence in the Particle Swarm Optimization (PSO) algorithm often causes the search process to be trapped in a local optimum. This problem often occurs when the diversity of the swarm decreases and the swarm cannot escape from a local optimal. In this paper, a novel dynamic diversity enhancement particle swarm optimization (DDEPSO) algorithm is introduced. In this variant of PSO, we periodically replace some of the swarm's particles by artificial ones, which are generated based on the history of the search process, in order to enhance the diversity of the swarm and promote the exploration ability of the algorithm. Afterwards, we update the velocity of the artificial... 

    Optimization of the K-Out-of-N Systems using Particle Swarm Optimization Method

    , M.Sc. Thesis Sharif University of Technology Yahyatabar Arabi, Ali Asghar (Author) ; Eshraghniaye Jahromi, Abdolhamid (Supervisor)
    Abstract
    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... 

    An evolutionary decoding method for HMM-based continuous speech recognition systems using particle swarm optimization

    , Article Pattern Analysis and Applications ; Vol. 17, issue. 2 , 2014 , pp. 327-339 Najkar, N ; Razzazi, F ; Sameti, H ; Sharif University of Technology
    Abstract
    The main recognition procedure in modern HMM-based continuous speech recognition systems is Viterbi algorithm. Viterbi algorithm finds out the best acoustic sequence according to input speech in the search space using dynamic programming. In this paper, dynamic programming is replaced by a search method which is based on particle swarm optimization. The major idea is focused on generating initial population of particles as the speech segmentation vectors. The particles try to achieve the best segmentation by an updating method during iterations. In this paper, a new method of particles representation and recognition process is introduced which is consistent with the nature of continuous... 

    A Model for optimizing railway alignment considering bridge costs, tunnel costs, and transition curves

    , Article Urban Rail Transit ; Volume 5, Issue 4 , 2019 , Pages 207-224 ; 21996687 (ISSN) Ghoreishi, B ; Shafahi, Y ; Hashemian, S. E ; Sharif University of Technology
    Springer  2019
    Abstract
    Owing to wide-ranging searches (there are various alignments between two points) as well as complex and nonlinear cost functions and a variety of geometric constraints, the problem of optimal railway alignment is classified as a complex problem. Thus, choosing an alignment between two points is usually done based on a limited number of alignments designed by experts. In recent years, the study of railway alignment optimization has shown the importance of optimization and the introduction of various algorithms and their usefulness in solving different problems. It is expected that applying meta-heuristic optimization algorithms such as methods based on swarm intelligence can lead to better... 

    Suppression of torsional vibrations in drilling systems by using the optimization-based adaptive back-stepping controller

    , Article International Journal of Mechanics and Control ; Volume 20, Issue 1 , 2019 , Pages 105-110 ; 15908844 (ISSN) Tashakori, S ; Fakhar, M ; Sharif University of Technology
    Levrotto and Bella  2019
    Abstract
    Stick-slip oscillations are one of the main sources of system failure and bit damage in a rotary drilling system. Thus, suppressing such vibrations is of great importance. There are different modelling approaches demonstrating drill string dynamics, among which lumped parameter models are more common in control studies due to faster computations. Since the system dynamic includes uncertain terms, in this paper an adaptive back-stepping controller is proposed. To tune controller gains, particle swarm optimization algorithm has been employed which guarantees a better control performance. The simulation results demonstrate the feasibility of the designed controller. The results have been also... 

    Color quantization with clustering by F-PSO-GA

    , Article Proceedings - 2010 IEEE International Conference on Intelligent Computing and Intelligent Systems, ICIS 2010, 29 October 2010 through 31 October 2010 ; Volume 3 , 2010 , Pages 233-238 ; 9781424465835 (ISBN) Alamdar, F ; Bahmani, Z ; Haratizadeh, S ; Sharif University of Technology
    Abstract
    Color quantization is a technique for processing and reduction colors in image. The purposes of color quantization are displaying images on limited hardware, reduction use of storage media and accelerating image sending time. In this paper a hybrid algorithm of GA and Particle Swarm Optimization algorithms with FCM algorithm is proposed. Finally, some of color quantization algorithms are reviewed and compared with proposed algorithm. The results demonstrate Superior performance of proposed algorithm in comparison with other color quantization algorithms  

    A New Metaheuristic Algorithm Based on Particle Swarm Optimization for Discrete Time Resource Trade-off Problem

    , M.Sc. Thesis Sharif University of Technology Esfandeh, Tolou (Author) ; Kianfar, Farhad (Supervisor)
    Abstract
    In this research, a new metaheuristic algorithm is developed for solving the Discrete Time- Resource Trade off Problem in the field of project scheduling.In this problem ,a project contains activities interrelated by finish-start type precedence constraints and each has a specified work content and can be performed in different combinations of duration and resource requirement.Since the problem is NP-hard , the Particle Swarm Optimization is adopted due to minimization of the makespan subject to precedence relations and a single renewable resource. Basically PSO is used to solve continous problems and discrete problems have just begun to be solved by the discrete PSO.In proposed method,a... 

    Total fuel reduction via formation flights: a new approach to air-corridor path optimization

    , Article AIAA AVIATION 2014 -14th AIAA Aviation Technology, Integration, and Operations Conference ; 2014 Asadi, F ; Malaek, S. M. B ; Sharif University of Technology
    Abstract
    This paper presents a new approach to better utilize international air-corridors for formation flights. Using Particle Swarm Optimization, we show how different long-range flights can be brought together to form a formation. The idea serves both to increase international air-corridor capacities together and to decrease fuel consumption up to 8-10%. Case studies show that there are many places which such an approach could effectively be implemented to help cope with increase in fuel price as well as the demand for aerial transport of passengers and goods  

    GPH: A group-based partitioning scheme for reducing total power consumption of parallel buses

    , Article Microprocessors and Microsystems ; Volume 35, Issue 1 , 2011 , Pages 68-80 ; 01419331 (ISSN) Kamal, M ; Koohi, S ; Hessabi, S ; Sharif University of Technology
    2011
    Abstract
    Two main sources for power dissipation in parallel buses are data transitions on each wire and coupling between adjacent wires. So far, many techniques have been proposed for reducing the self and coupling powers. Most of these methods utilize one (or more) control bit(s) to manage the behavior of data transitions on the parallel bus. In this paper, we propose a new coding scheme, referred to as GPH, to reduce power dissipation of these control bits. GPH coding scheme employs partitioned Bus Invert and Odd Even Bus-Invert coding techniques. This method benefits from Particle Swarm Optimization (PSO) algorithm to efficiently partition the bus. In order to reduce self and coupling powers of... 

    A novel partitioned encoding scheme for reducing total power consumption of parallel bus

    , Article 13th International Computer Society of Iran Computer Conference on Advances in Computer Science and Engineering, CSICC 2008, Kish Island, 9 March 2008 through 11 March 2008 ; Volume 6 CCIS , 2008 , Pages 90-97 ; 18650929 (ISSN); 3540899847 (ISBN); 9783540899846 (ISBN) Kamal, M ; Koohi, S ; Hessabi, S ; Sharif University of Technology
    2008
    Abstract
    Two main sources for power dissipation in parallel buses are data transitions on each wire and coupling between adjacent wires. There are many techniques for reducing the transition and coupling powers. These methods utilize extra control bits to manage the behavior of data transitions on parallel bus. In this paper, we propose a new coding scheme which tries to reduce power dissipation of control bits. The proposed method employs partitioned Bus Invert and Odd Even Bus Invert coding techniques. This method benefits from Particle Swarm Optimization (PSO) algorithm to efficiently partition the bus. In order to reduce transition and coupling power of control bits, it finds partitions with... 

    Adaptive neuro-fuzzy inference system based automatic generation control

    , Article Electric Power Systems Research ; Volume 78, Issue 7 , 2008 , Pages 1230-1239 ; 03787796 (ISSN) Hosseini, S. H ; Etemadi, A. H ; Sharif University of Technology
    2008
    Abstract
    Fixed gain controllers for automatic generation control are designed at nominal operating conditions and fail to provide best control performance over a wide range of operating conditions. So, to keep system performance near its optimum, it is desirable to track the operating conditions and use updated parameters to compute control gains. A control scheme based on artificial neuro-fuzzy inference system (ANFIS), which is trained by the results of off-line studies obtained using particle swarm optimization, is proposed in this paper to optimize and update control gains in real-time according to load variations. Also, frequency relaxation is implemented using ANFIS. The efficiency of the... 

    Proposing a Method for Ranking Nodes in Complex Networks

    , M.Sc. Thesis Sharif University of Technology Esnaashari, Marzieh (Author) ; Mahlooji, Hashem (Supervisor) ; Safaei Semnani, Farshad (Co-Supervisor)
    Abstract
    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... 

    Numerical Optimization and Parametric Study of Cooperative Salvo Attack Using Particle Swarm Optimization Algorithm

    , M.Sc. Thesis Sharif University of Technology Shahadati, Mohammad (Author) ; Saghafi, Fariborz (Supervisor)
    Abstract
    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... 

    Parallel Machines with Batch Processing

    , M.Sc. Thesis Sharif University of Technology Chaghazardy, Delaram (Author) ; Salmasi, Nasser (Supervisor)
    Abstract
    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... 

    A Heuristic Method to Estimate Time-Dendent Origin-Destination Matrix Based on Fuzzy Theory

    , M.Sc. Thesis Sharif University of Technology Khavarian, Khashayar (Author) ; Shafahi, Yusef (Supervisor)
    Abstract
    One of the most important required data in order to consult transportation studies is the amount of trip demand between different zones in the study region. Trip demand is usually presented in form of a table. Due to dependence of the demand on time, it gets classified in two categories: Static and Time dependent. In Time dependent problems, which the scope of this research is, trip demand is affected by network condition and the amount of traffic supply in short periods of time, e.g. 15 minutes. Using Traffic count and prior trip demand table in order to estimate the time dependent Trip demand is among the newest methods of travel demand estimation. In this research despite of older studies... 

    Performance Analysis and Geometry Optimization of Metal Belt Based CVT

    , M.Sc. Thesis Sharif University of Technology Bakhshi Khaniki, Hossein (Author) ; Zohoor, Hassan (Supervisor) ; Sohrabpour, Saeed (Co-Advisor)
    Abstract
    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... 

    Design and Simulation of an Intelligent Power Management Strategy and a Gearshifting Pattern for Parallel Hybrid Electric Vehicles

    , M.Sc. Thesis Sharif University of Technology Sadeghian, Nasser (Author) ; Saadat Foumani, Mahmoud (Supervisor) ; Salarieh, Hassan (Supervisor)
    Abstract
    A well-designed Control Strategy (CS) in Hybrid Electric Vehicles (HEVs), as the manager of energy flow, reduces the fuel consumption and/or air pollution, while keeps an eye for prolonging the components lifetime. In this regard, the present thesis provides a new CS for parallel HEVs, based on emotional learning. It is noteworthy that the controller consists of a Takagi-Sugeno-Kang (TSK) fuzzy system and a critic. The driver’s torque command, State of Charge (SOC) error, Internal Combustion Engine (ICE) brake torque error and its time derivative constitute the controller inputs, while the output is the ICE torque command. The critic produces two stress signals based on HEV’s battery and ICE... 

    Geometrical Optimization of Traction Infinitely Variable Transmission for Minimizing of Rollers Deformation

    , M.Sc. Thesis Sharif University of Technology Afzali, Abolfazl (Author) ; Zohoor, Hasan (Supervisor)
    Abstract
    With intensified concerns of rising fuel vehicles that reduce fossil fuel globally and also prescript strict rules by standard institutes, vehicle manufacturers try to find a way for reducing the fuel of their products. One these methods use a continuously variable transmission (CVT) instead of manual and automatic gearboxes. Various CVT’s have been proposed in recent year.
    One of the proposed systems is traction infinitely variable transmission (TIVT) that is type of traction drive continuously variable transmission and has been presented in 2007. Research on this system showed that average efficiency is about 96% that is high efficiency. Completed research in 2011 showed that despite... 

    Scheduling on Parallel Machines with Preemption and Transportation Delays using a Particle Swarm Optimization (PSO)-Based Algorithm

    , M.Sc. Thesis Sharif University of Technology Shams, Hesam (Author) ; Shadrokh, Shahram (Supervisor)
    Abstract
    This research deals with the problem of scheduling independent preemptive jobs on identical parallel machines, to minimize the total completion time (makespan). The transportation of an interrupted job from a machine to another machine requires considering a constant transportation delay i.e., Pm|prmp(delay)| Cmax. This delay is called transportation delay. We propose a Mixed Integer Linear Programming formulation for the research problem in case of two machines i.e., P2|prmp(delay)| Cmax. Since the research problem is shown to be NP-hard, a particle swarm optimization (PSO) algorithm is applied to solve the problem approximately. Based on the frequency of using local search procedure, three... 

    Intra-Operative Registration of Non-Rigid Tissue for Image-Guided Surgery

    , M.Sc. Thesis Sharif University of Technology Amiri, Hakimeh (Author) ; Kasaei, Shohreh (Supervisor)
    Abstract
    Image Registration is a fundamental task in numerous applications in medical image processing and is defined as the process of determining the correspondence of between images collected at different times or using different imaging modalities. This correspondence can be used for aligning images so that the pair can be directly compared, combined or analyzed. Image-guided surgery systems use registration for establishing an accurate relation between preoperative and intraoperative image space. There have been several methods for rigid registration which are not easily applicable for soft tissues. Indeed, nonrigid deformation of soft tissues will endanger the accuracy of rigid methods, so it...