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Total 82 records

    Boundary Stabilization and Motion Control of Flexible Crane Systems

    , Ph.D. Dissertation Sharif University of Technology Entessari, Farshid (Author) ; Alasty, Aria (Supervisor) ; Najafi Ardekany, Ali (Supervisor)
    Abstract
    In recent years, boundary control (BC) approach for distributed parameter systems and their applications has demonstrated that it can be a well-intentioned candidate for control system design. In this approach, the main focus is on the boundary actions, where the actuators are aligned on the boundaries of the media. BC may be considered as an ideal approach, especially from applied and engineering point of view, because it deals only with actuators and sensors along the boundaries. Moreover, the problem of boundary stabilization and motion control of flexible crane systems has been one of the remarkable problems for control engineers. In this research, we contemplate the boundary control... 

    Dynamic Modeling and Adaptive Controller design for Cooperative Flexible Manipulators to Grasp and Manipulation of an Object

    , M.Sc. Thesis Sharif University of Technology Hejrati, Mahdi (Author) ; Sayyaadi, Hassan (Supervisor)
    Abstract
    In a world where energy conservation is a critical topic, cooperative flexible manipulators will play an important role. Conventional robotic manipulators have been designed to have maximum stiffness to achieve both minimum vibration and good positioning accuracy of the end-effector, which causes more power consumption and reduced efficiency. Due to the high inertia of such arms, interaction with humans or sensitive environments is hazardous. On the other hand, Flexible Link Manipulators are designed to be lightweight, using lower energy and producing higher efficiency. Unfortunately, the link's flexibility increases vibrations and decreases the accuracy of the end-effector. Since, the... 

    Identification Of Surrogate Models for Hybrid Distributed Parameters Systems Using Machine Learning Algorithms

    , M.Sc. Thesis Sharif University of Technology Taghizadeh, Mohammad Javad (Author) ; Bozorgmehry Boozarjomehry, Ramin (Supervisor)
    Abstract
    In various industries, particularly in the process industries, computational fluid dynamics (CFD) stands as the predominant method for simulating distributed systems. In these methods, discretization of system geometry and partial differential equations is necessary, resulting in a system of algebraic or ordinary differential equations, or a combination thereof. The significant computational demands arising from the extensive number of equations derived from dynamic system simulations highlight the necessity for substantial processing and computing power. The objective of this project is to reduce the computational load associated with solving these equations. It focuses on utilizing machine... 

    Optimal Sensor Location for State Estimation and Monitoring of Gas Transmission Networks

    , M.Sc. Thesis Sharif University of Technology Khaladj, Nader (Author) ; Bozorgmehry Boozarjomehry, Ramin (Supervisor)
    Abstract
    Monitoring of natural gas transmission networks, is one of the necessities for efficient, safe, and economical operation of energy supply networks. In order to efficiently control and monitor the operation of gas transmission network, various states of the network (like temperature, pressure, and flow) should be available. Among these states, some can be easily measured, and the rest should be estimated based on these measurements throughout the network. In this project, an algorithm to obtain near optimal locations of various measuring devices has been proposed. Furthermore, a method for estimation of the states of transmission network based on these measurements and Machine Learning has... 

    Nonlinear Distributed-Parameters Vibration Analysis of an AFM Microcantilever Beam in Dynamic Mode

    , Ph.D. Dissertation Sharif University of Technology Delnavaz, Aidin (Author) ; Zohoor, Hassan (Supervisor)
    Abstract
    Dynamic and vibration behavior of AFM microcantilever beam subject to the tip-sample interaction and/or contact is systematically investigated. An Euler-Bernoli microcantilever in 2D plane is considered with longitudinal and bending displacements. Inextensibility assumption and extended Hamilton’s principle is utilized to extract the single-variable integro partial equation of motion under: 1) tip-nanoparticle interactions, 2) tip-surface interactions in non-contact mode and 3) tip-surface interactions and contacts in intermittent-contact mode. Galerkin’s first mode approximation is then used to discretize the derived equations; and multiple time scales method is adopted to analyze the... 

    Wind farm layout optimization using imperialist competitive algorithm

    , Article Journal of Renewable and Sustainable Energy ; Vol. 6, Issue. 4 , July , 2014 ; ISSN: 19417012 Kiamehr, K ; Hannani, S. K ; Sharif University of Technology
    Abstract
    In this work, the wind farm layout optimization problem is dealt with using a new approach. The aim of wind farm layout optimization is to maximize the output power of a wind farm considering the wake losses. Layout optimization minimizes the wake losses regarding the location of the turbines. Three different wind scenarios with different wind direction angles, wind direction blowing probabilities, and Weibull distribution parameters are assumed. Since, the problem is nonlinear and constrained, imperialist competitive algorithm is used as a modern and powerful algorithm for continuous optimization problems. The optimization outcomes indicate that imperialist competitive algorithm yields... 

    Variation-aware server placement and task assignment for data center power minimization

    , Article Proceedings of the 2012 10th IEEE International Symposium on Parallel and Distributed Processing with Applications, ISPA 2012 ; 2012 , Pages 158-165 ; 9780769547015 (ISBN) Pahlavan, A ; Momtazpour, M ; Goudarzi, M ; Sharif University of Technology
    2012
    Abstract
    Size and number of data centers are fast growing all over the world and their increasing total power consumption is a worldwide concern. Moreover, increase in the amount of process variation in nanometer technologies and its effect on total power consumption of servers has made it inevitable to move toward variation-aware power reduction strategies. This paper formulates a variation-aware joint server placement and task assignment method using Integer Linear Programming (ILP) to minimize total power consumption of data centers. We first determine the optimum placement of servers in the data center racks based on total power consumption of each server and the data center recirculation model... 

    Utilizing network coding for file dessimination in peer-to-peer systems

    , Article 3rd International Conference on New Technologies, Mobility and Security, NTMS 2009, 20 December 2009 through 23 December 2009, Cairo ; 2009 ; 9781424462735 (ISBN) Hosseini Sohei, M ; Movaghar, A ; Sadat Bathaee, N ; Sharif University of Technology
    Abstract
    Network coding was first introduced in information theory for increasing the multicast rate in the networks with directed links. We can model many of the content distribution networks and overlay networks with such a network. Therefore, the solutions introduced in information theory can be used in these networks. In this paper, we analyze using of network coding in uncoordinated cooperative content distribution systems. Reaching the optimum performance in an uncoordinated system needs blocks of the system to be "equally important". In that case, we can retrieve the whole data without need of central controller or complex algorithms. In part of this paper, we exactly define the concept of... 

    Using genetic alghoritm for distributed generation allocation to reduce losses and improve voltage profile

    , Article 42nd International Universities Power Engineering Conference, UPEC 2007, Brighton, 4 September 2007 through 6 September 2007 ; 2007 , Pages 954-959 ; 1905593368 (ISBN); 9781905593361 (ISBN) Alinejad Beromi, Y ; Sedighizadeh, M ; Bayat, M. R ; Khodayar, M. E ; Sharif University of Technology
    2007
    Abstract
    This paper presents a method for the optimal allocation of Distributed generation in distribution systems. In this paper, our aim would be optimal distributed generation allocation for voltage profile improvement and loss reduction in distribution network. Genetic Algorithm (GA) was used as the solving tool, which referring two determined aim; the problem is defined and objective function is introduced. Considering to fitness values sensitivity in genetic algorithm process, there is needed to apply load flow for decision-making. Load flow algorithm is combined appropriately with GA, till access to acceptable results of this operation. We used MATPOWER package for load flow algorithm and... 

    Tomographical medical image reconstruction using Kalman filter technique

    , Article Proceedings - 9th IEEE International Symposium on Parallel and Distributed Processing with Applications Workshops, ISPAW 2011 - ICASE 2011, SGH 2011, GSDP 2011, 26 May 2011 through 28 May 2011 ; May , 2011 , Pages 61-65 ; 9780769544298 (ISBN) Goliaei, S ; Ghorshi, S ; Sharif University of Technology
    2011
    Abstract
    In this paper, a Kalman filter technique which is operated in time is introduced for noise reduction on CT set of projections to reconstruct medical images. The experiments were done on medical image of kidneys and the simulated projections are captured by CT scanner. Evaluation results indicated that as the number of projections increase in the collected ray sums corrupted by noise the quality of reconstructed image becomes better in terms of contrast and transparency. However, for the comparison issue, the same conditions are applied for reconstruction of medical image in frequency domain using filter back projection technique. It observes that filter back projection technique does not... 

    Thermal optimization of the continuous casting process using distributed parameter identification approach—controlling the curvature of solid-liquid interface

    , Article International Journal of Advanced Manufacturing Technology ; Volume 94, Issue 1-4 , 2018 , Pages 1101-1118 ; 02683768 (ISSN) Tavakoli, R ; Sharif University of Technology
    Springer London  2018
    Abstract
    Thermal optimization of the vertical continuous casting process is considered in the present study. The goal is to find the optimal distribution of the temperature and interfacial heat transfer coefficients corresponding to the primary and secondary cooling systems, in addition to the pulling speed, such that the solidification along the main axis of strand approaches to the unidirectional solidification mode. Unlike many thermal optimization of phase change problems in which the desirable (target) temperature, temperature gradient, or interface position are assumed to be a priori known, a desirable shape feature of the freezing interface (not its explicit position) is assumed to be known in... 

    Routing, data gathering, and neighbor discovery in delay-tolerant wireless sensor networks

    , Article 23rd IEEE International Parallel and Distributed Processing Symposium, IPDPS 2009, Rome, 23 May 2009 through 29 May 2009 ; 2009 ; 9781424437504 (ISBN) Nayebi, A ; Sarbazi Azad, H ; Karlsson, G ; IEEE Computer Society Technical Committee on Parallel Processing ; Sharif University of Technology
    2009
    Abstract
    This paper investigates a class of mobile wireless sensor networks that are not connected most of the times. The characteristics of these networks is inherited from both delay tolerate networks (DTN) and wireless sensor networks. First, delay-tolerant wireless sensor networks (DTWSN) are introduced. Then, three main problems in the design space of these networks are discussed: Routing, data gathering, and neighbor discovery. An approach is proposed for deployment of DTWSNs based on the traditional opportunistic broadcast in delay tolerant networks with on-off periods. The delay and the throughput of the routing scheme were investigated in the DTN literature. However, the energy consumption... 

    Robust stability and performance analysis of positive systems using linear programming

    , Article 24th Mediterranean Conference on Control and Automation, 21 June 2016 through 24 June 2016 ; 2016 , Pages 100-105 ; 9781467383455 (ISBN) Babazadeh, M ; Nobakhti, A ; MCA ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    Abstract
    This work presents a new necessary and sufficient condition for robust stability and robust performance of positive linear time invariant (LTI) systems with structured uncertainties. It is known that robustness analysis of LTI systems with structured uncertainties requires evaluation of structured singular value (SSV), which is known to be NP-hard. This paper shows that for positive systems, the structured singular value can be estimated efficiently using linear programming. Thus, the robustness analysis of positive systems is simplified to easily verifiable conditions that scale linearly with the dimensions of the system. This property finds great utility in analysis and synthesis of large... 

    Robust distributed control of spacecraft formation flying with adaptive network topology

    , Article Acta Astronautica ; Volume 136 , 2017 , Pages 281-296 ; 00945765 (ISSN) Shasti, B ; Alasty, A ; Assadian, N ; Sharif University of Technology
    Elsevier Ltd  2017
    Abstract
    In this study, the distributed six degree-of-freedom (6-DOF) coordinated control of spacecraft formation flying in low earth orbit (LEO) has been investigated. For this purpose, an accurate coupled translational and attitude relative dynamics model of the spacecraft with respect to the reference orbit (virtual leader) is presented by considering the most effective perturbation acceleration forces on LEO satellites, i.e. the second zonal harmonic and the atmospheric drag. Subsequently, the 6-DOF coordinated control of spacecraft in formation is studied. During the mission, the spacecraft communicate with each other through a switching network topology in which the weights of its graph... 

    Robust control of an autonomous four-wire electronically-coupled distributed generation unit

    , Article IEEE Transactions on Power Delivery ; Volume 26, Issue 1 , September , 2011 , Pages 455-466 ; 08858977 (ISSN) Karimi, H ; Yazdani, A ; Iravani, R ; Sharif University of Technology
    2011
    Abstract
    This paper proposes a control strategy for the autonomous (islanded) operation of a four-wire, electronically-coupled distributed generation (DG) unit which can feed a highly unbalanced load, e.g., due to the presence of single-phase loads. In the grid-connected mode, the power-electronic interface of the DG unit enables the exchange of real and reactive power with the distribution network, based on the conventional dq-frame current control strategy. The current control scheme is disabled subsequent to the detection of an islanding event, and the proposed controller is activated. The proposed control strategy utilizes: i) an internal oscillator to maintain the island frequency and ii) a... 

    Risk based maintenance optimization of overhead distribution networks utilizing priority based dynamic programming

    , Article 2009 IEEE Power and Energy Society General Meeting, PES '09, 26 July 2009 through 30 July 2009, Calgary, AB ; 2009 ; 9781424442416 (ISBN) Abbasi, E ; Fotuhi Firuzabad, M ; Abiri Jahromi, A ; Sharif University of Technology
    Abstract
    This paper presents a priority based dynamic programming approach for long term maintenance scheduling of overhead distribution networks. The proposed approach is based on risk management approach and utilizes the model of decoupled risk factors. Two heuristic factors are defined and utilized in order to establish a maintenance priority list and to curtail the dynamic programming search space. The proposed methodology yields a significant computational saving compare to the previously reported dynamic programming. Risk management approach enables the asset managers to consider the actual condition of electrical equipments and expected consequence of their failures. Furthermore, the decoupled... 

    Reliability worth assessment of an automatic loop restoration scheme for urban distribution networks

    , Article IEEE PES Innovative Smart Grid Technologies Conference Europe, ISGT Europe ; 2010 Kazemi, S ; Lehtonen, M ; Fotuhi-Firuzabad, M ; Sharif University of Technology
    Abstract
    Distribution automation (DA) application for fault management in the electricity distribution networks is one of the main potential remedial actions to reduce customers' outage times and hence improve service reliability. As a result, various automation schemes have been developed and introduced in different countries and by different venders. The impacts of implementing a specific automation scheme on reliability indices of a given distribution system can be different from other available automation schemes. For this reason, when comparing the available automation schemes with each other or with the other reliability improvement measures, it is necessary to perform a course of reliability... 

    Reliability worth assessment of an automatic loop restoration scheme for urban distribution networks

    , Article IEEE PES Innovative Smart Grid Technologies Conference Europe, ISGT Europe, 11 October 2010 through 13 October 2010 ; October , 2010 ; 9781424485109 (ISBN) Kazemi, S ; Lehtonen, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
    2010
    Abstract
    Distribution automation (DA) application for fault management in the electricity distribution networks is one of the main potential remedial actions to reduce customers' outage times and hence improve service reliability. As a result, various automation schemes have been developed and introduced in different countries and by different venders. The impacts of implementing a specific automation scheme on reliability indices of a given distribution system can be different from other available automation schemes. For this reason, when comparing the available automation schemes with each other or with the other reliability improvement measures, it is necessary to perform a course of reliability... 

    Reliability assessment of distribution system with distributed generation

    , Article 2008 IEEE 2nd International Power and Energy Conference, PECon 2008, Johor Baharu, 1 December 2008 through 3 December 2008 ; January , 2008 , Pages 1551-1556 ; 9781424424054 (ISBN) Jahangiri, P ; Fotuhi Firuzabad, M ; Sharif University of Technology
    2008
    Abstract
    Reliability assessment is of primary importance in designing and planning distribution systems that operate in an economical manner with minimal interruption of customer loads. Distributed generation (DG) is expected to play an increasing role in emerging power systems because they use different type of resources and technologies to serve energy to power systems. DG is expected to improve the system reliability as its backup generation. Since DG units are subject to failures as all other generation units, the random behavior of these units must be taken into account in the analysis. Existence of DG units in a distribution system will effect on restoration time of load points. In this paper,... 

    Pull-in parameters of cantilever type nanomechanical switches in presence of Casimir force

    , Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) Ramezani, A ; Alasty, A ; Akbari, J ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    In this paper, the influence of the Casimir force on two main parameters describing an instability point of cantilever type nanomechanical switches, which are the pull-in voltage and deflection are investigated by using a distributed parameter beam model. The nonlinear differential equation of the model is transformed into the integral form by using the Green's function of the cantilever beam. The integral equation is solved analytically by assuming an appropriate shape function for the beam deflection. The detachment length and the minimum initial gap of the cantilever type switches are given, which are the basic design parameters for NEMS switches. The pull-in parameters of micromechanical...