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    A stabilized piezolaminated nine-nodded shell element formulation for analyzing smart structures behaviors

    , Article Mechanics of Advanced Materials and Structures ; Volume 23, Issue 2 , 2016 , Pages 187-194 ; 15376494 (ISSN) Hosseini Kordkheili, S. A ; Salmani, H ; Afshari, S. S. G ; Sharif University of Technology
    Taylor and Francis Inc  2016
    Abstract
    An explicit hybrid stabilization method is utilized together with a reduced order integration scheme to stabilize spurious zero energy modes from the sub-integrated degenerated shell element. This stabilization is achieved after employing appropriate contravariant higher order stress modes. The relevant finite element formulation of the piezolaminated nine-nodded shell element is then derived to analyze smart structures behaviors. To show the capabilities of the presented formulation, it has been implemented in a finite element code. The developed code is used to analyze some typical problems. The results are compared with those obtained from other schemes in the literature and experiments  

    Optimization of the shaping function of a tapered piezoelectric energy harvester using tabu continuous ant colony system

    , Article Journal of Intelligent Material Systems and Structures ; Volume 30, Issue 20 , 2019 , Pages 3025-3035 ; 1045389X (ISSN) Salmani, H ; Rahimi, G. H ; Saraygord Afshari, S ; Sharif University of Technology
    SAGE Publications Ltd  2019
    Abstract
    During the past years, the development of piezoelectric energy harvesters is extensively increased for providing the required energy of sensor nodes. It has been proven that changing the beam’s cross-section along its length direction may lead to extract more power with less mass. In this article, a hybrid metaheuristic algorithm called tabu continuous ant colony system is employed to optimize the tapered piezoelectric energy harvester in a fast and course manner. The exponential and fourth-order polynomial functions are considered as shaping functions for tapering the beam’s width along its length direction. An experiment is also set up to evaluate the performance of the optimization... 

    Experimental and modelling investigations of asphaltene precipitation during pressure depletion and gas injection operations

    , Article Petroleum Science and Technology ; Vol. 32, issue. 15 , August , 2014 , pp. 1868-1875 ; ISSN: 10916466 Nakhli, H ; Alizadeh, A ; Afshari, S ; Kharrat, R ; Ghazanfari, M ; Sharif University of Technology
    Abstract
    Asphaltene precipitation problems manifest themselves in different stages of oil reservoirs production. Experimental and modeling investigations are, therefore, employed as promising tools to assist in predictions of asphaltene precipitation problems and selection of proper production facilities. This study concerns experimental and modeling investigations of asphaltene precipitation during natural production and gas injection operations for a heavy Iranian crude oil at reservoir conditions. First, with design and performance of high pressure-high temperature experiments, asphaltene precipitation behavior is comprehensively investigated; the effects of pressure and temperature are fully... 

    Hardware-in-the-loop optimization of an active vibration controller in a flexible beam structure using evolutionary algorithms

    , Article Journal of Intelligent Material Systems and Structures ; Vol. 25, issue. 10 , 2014 , p. 1211-1223 Nobahari, H ; Hosseini Kordkheili, S. A ; Afshari, S. S ; Sharif University of Technology
    Abstract
    In this study, active vibration control of a cantilevered flexible beam structure equipped with bonded piezoelectric sensor/actuators is investigated. The linear quadratic regulator technique together with an observer is adopted to design the controller as well as to provide the full-state feedback. Two different approaches are subsequently used for simultaneously integrated optimization of the controller and observer parameters. In the first approach, a linear experimental model of the system is obtained using identification techniques, and the optimization is then performed based on a computer simulation of the system. However, in the second approach, a hardware-in-the-loop optimization...