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    Numerical simulation of heat transfer in mixed electroosmotic pressure-driven flow in straight microchannels

    , Article Journal of Thermal Science and Engineering Applications ; Volume 8, Issue 2 , 2016 ; 19485085 (ISSN) Shamloo, A ; Merdasi, A ; Vatankhah, P ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2016
    Abstract
    This paper investigates two-dimensional, time-independent elecroosmotic pressuredriven flow generated by a direct current electric potential with asymmetrical and symmetrical zeta potential distributions along the microchannel walls. Fluid flow through the horizontal microchannel is simulated using a numerical method. Two different cases are proposed to study the effect of electric potential on the flow field. First, negative electric potential is applied on the microchannel walls. In this case, large segments with negative electric potential are initially placed on the first half of the microchannel walls with two different arrangements. Afterward, smaller segments with negative electric... 

    Design and Simulation of a Passive Microfluidic Device for Particle Separation

    , M.Sc. Thesis Sharif University of Technology Vatankhah, Parham (Author) ; Shamloo, Amir (Supervisor)
    Abstract
    Nowadays, separation and filtration of particles has many industrial applications in biology and medicine. In this thesis, passive microfluidics are designed and simulated which are able to separate and filter particles. Although particles aer generally expected to follow laminar flow streamlines in the absence of external forces, inertial forxes van cause particles to migrate across mictochannels in an accurate and predictable manner. The effect of these forces is invedtigated, and by using previous research, a model is developed to predict these forces. First design is a microchannel with Archimedean spiral which utilizes both inertial forces and Dean flow to separate particles in the... 

    Parametric study on mixing process in an in-plane spiral micromixer utilizing chaotic advection

    , Article Analytica Chimica Acta ; Volume 1022 , 2018 , Pages 96-105 ; 00032670 (ISSN) Vatankhah, P ; Shamloo, A ; Sharif University of Technology
    2018
    Abstract
    Recent advances in the field of microfabrication have made the application of high-throughput microfluidics feasible. Mixing which is an essential part of any miniaturized standalone system remains the key challenge. This paper proposes a geometrically simple micromixer for efficient mixing for high-throughput microfluidic devices. The proposed micromixer utilizes a curved microchannel (spiral microchannel) to induce chaotic advection and enhance the mixing process. It is shown that the spiral microchannel is more efficient in comparison to a straight microchannel, mixing wise. The pressure drop in the spiral microchannel is only slightly higher than that in the straight microchannel. It is... 

    Control and Optimization of Robotic Swarm Flocking Using Naturally Inspired Methods

    , M.Sc. Thesis Sharif University of Technology Vatankhah, Ramin (Author) ; Alasty, Aria (Supervisor)
    Abstract
    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... 

    Vibration Control of Nonclassical Microbeams Using Boundary Control Theory of Partial Differential Equations

    , Ph.D. Dissertation Sharif University of Technology Vatankhah, Ramin (Author) ; Alasty, Aria (Supervisor)
    Abstract
    Nowadays, continuous systems such as strings, bars, beams and plates have become widespread in science and engineering applications. To achieve the control purposes of continuous systems, most of engineers use discretization techniques to reduce the governing partial differential equation (PDE) into a set of ordinary differential equations (ODEs). From practical point of view, this model reduction can cause many problems such as in-domain measurement and actuation and control spillover. This thesis attempts to investigate the problem of vibration control of nonclassical microscale beams using the partial differential equation control theory which eliminates spillover instabilities. To this... 

    Observer-based vibration control of non-classical microcantilevers using extended Kalman filters

    , Article Applied Mathematical Modelling ; January , 2015 ; 0307904X (ISSN) Vatankhah, R ; Karami, F ; Salarieh, H ; Sharif University of Technology
    Elsevier Inc  2015
    Abstract
    In non-classical micro-beams, the strain energy of the system is determined by the non-classical continuum mechanics. In this study, we consider a closed-loop control methodology for suppressing the vibration of non-classical microscale Euler-Bernoulli beams with nonlinear electrostatic actuation. The non-dimensional form of the governing nonlinear partial differential equation of the system is introduced and converted into a set of ordinary differential equations using the Galerkin projection method. In addition, we prove the observability of the system and we design a state estimation system using the extended Kalman filter algorithm. The effectiveness and performance of the proposed... 

    Observer-based vibration control of non-classical microcantilevers using extended Kalman filters

    , Article Applied Mathematical Modelling ; Volume 39, Issue 19 , 2015 , Pages 5986-5996 ; 0307904X (ISSN) Vatankhah, R ; Karami, F ; Salarieh, H ; Sharif University of Technology
    Elsevier Inc  2015
    Abstract
    In non-classical micro-beams, the strain energy of the system is determined by the non-classical continuum mechanics. In this study, we consider a closed-loop control methodology for suppressing the vibration of non-classical microscale Euler-Bernoulli beams with nonlinear electrostatic actuation. The non-dimensional form of the governing nonlinear partial differential equation of the system is introduced and converted into a set of ordinary differential equations using the Galerkin projection method. In addition, we prove the observability of the system and we design a state estimation system using the extended Kalman filter algorithm. The effectiveness and performance of the proposed... 

    Vibration control of vehicle suspension system using adaptive critic-based neurofuzzy controller

    , Article 2009 6th International Symposium on Mechatronics and its Applications, ISMA 2009, Sharjah, 23 March 2009 through 26 March 2009 ; 2009 ; 9781424434817 (ISBN) Vatankhah, R ; Rahaeifard, M ; Alasty, A ; Sharif University of Technology
    2009
    Abstract
    This paper presents an active suspension system for passenger cars, using adaptive critic-based neurofuzzy controller. The model is described by a system with seven degrees of freedom. The car is subjected to excitation from a rode surface and wheel unbalance. The main superiority of the proposed controller over previous analogous fuzzy logic controller designed approaches, e.g., genetic fuzzy logic controller, is its online tuning characteristic and remarkable reduced amount of computations used for parameter adaptation, which makes it desirable for real time applications. Considering the simplicity of this controller and its independence from the system model, this control method has the... 

    Performance of RC Shear Walls Strengthened by Vertical Strips of Steel Plates under Seismic Loading

    , M.Sc. Thesis Sharif University of Technology VatanKhah Rahmani, Borna (Author) ; Khaloo, Alireza (Supervisor)
    Abstract
    Even though a considerable amount of research has been conducted on composite wall system during past years, very limited research has been reported on shear walls strengthened by steel plates. In 2008, the composite shear wall, which consisted of reinforced concrete wall, retrofitted by steel plates, attached to both sides of RC walls using mechanical connectors in form of shear studs, bolts or lateral ties tested under axial load and lateral force. In this research, seismic behavior of RC shear walls strengthened by vertical strips of steel plates is going to be studied. The result will be compared with RC shear wall which fully covered by steel plates. The behavior of RC shear wall will... 

    The second strain gradient theory-based Timoshenko beam model

    , Article JVC/Journal of Vibration and Control ; Volume 23, Issue 13 , 2017 , Pages 2155-2166 ; 10775463 (ISSN) Asghari, M ; Momeni, S. A ; Vatankhah, R ; Sharif University of Technology
    SAGE Publications Inc  2017
    Abstract
    The governing equations of motion, together with the associated boundary conditions, are derived for the second strain gradient Timoshenko micro- and nano-beams. The second strain gradient theory is a highly powerful nonclassical continuum theory, capable of capturing the size effects in micro- and nano-scale structures. In case studies, the static and free-vibration behaviors of a hinged-hinged beam are investigated utilizing the presented second strain gradient theory-based Timoshenko beam model. The obtained results are compared with those of the available models in the literature, which are based on the (first) strain gradient theory, the modified couple stress theory, and the classical... 

    Exact boundary controllability of vibrating non-classical Euler-Bernoulli micro-scale beams

    , Article Journal of Mathematical Analysis and Applications ; Vol. 418, issue. 2 , 2014 , pp. 985-997 ; ISSN: 0022247X Vatankhah, R ; Najafi, A ; Salarieh, H ; Alasty, A ; Sharif University of Technology
    2014
    Abstract
    This study investigates the exact controllability problem for a vibrating non-classical Euler-Bernoulli micro-beam whose governing partial differential equation (PDE) of motion is derived based on the non-classical continuum mechanics. In this paper, it is proved that via boundary controls, it is possible to obtain exact controllability which consists of driving the vibrating system to rest in finite time. This control objective is achieved based on the PDE model of the system which causes that spillover instabilities do not occur  

    Boundary stabilization of non-classical micro-scale beams

    , Article Applied Mathematical Modelling ; Volume 37, Issue 20-21 , 2013 , Pages 8709-8724 ; 0307904X (ISSN) Vatankhah, R ; Najafi, A ; Salarieh, H ; Alasty, A ; Sharif University of Technology
    2013
    Abstract
    In this paper, the problem of boundary stabilization of a vibrating non-classical micro-scale Euler-Bernoulli beam is considered. In non-classical micro-beams, the governing Partial Differential Equation (PDE) of motion is obtained based on the non-classical continuum mechanics which introduces material length scale parameters. In this research, linear boundary control laws are constructed to stabilize the free vibration of non-classical micro-beams which its governing PDE is derived based on the modified strain gradient theory as one of the most inclusive non-classical continuum theories. Well-posedness and asymptotic stabilization of the closed loop system are investigated for both cases... 

    Adaptive critic-based neuro-fuzzy controller in multi-agents: Distributed behavioral control and path tracking

    , Article Neurocomputing ; Volume 88 , July , 2012 , Pages 24-35 ; 09252312 (ISSN) Vatankhah, R ; Etemadi, S ; Alasty, A ; Vossoughi, G ; Sharif University of Technology
    2012
    Abstract
    In this paper, we follow two control tasks in a leader following frame with undirected network and local communications. As the first goal, distributed behavioral imitation, which is necessary to fit agents with complicated motion equations in kinematic frames, is discussed. Providing real agents with behavioral controller makes them capable to act as a kinematic particle. The second goal is to design an active leading strategy for the LA to move the group on a predefined path. Both problems can be mathematically modeled in an affine form, which is the reason behind using a unique adaptive controller to solve them. The controller is based on a neuro-fuzzy structure with critic-based leaning... 

    Stabilization of a vibrating non-classical micro-cantilever using electrostatic actuation

    , Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 1824-1831 ; 10263098 (ISSN) Vatankhah, R ; Karami, F ; Salarieh, H ; Alasty, A ; Sharif University of Technology
    Sharif University of Technology  2013
    Abstract
    A closed-loop control methodology is investigated for stabilization of a vibrating non-classical micro-scale Euler-Bernoulli beam with nonlinear electrostatic actuation. The dimensionless form of governing nonlinear Partial Differential Equation (PDE) of the system is introduced. The Galerkin projection method is used to reduce the PDE of system to a set of nonlinear Ordinary Differential Equations (ODE). In non-classical micro-beams, the constitutive equations are obtained based on the non-classical continuum mechanics. In this work, proper control laws are constructed to stabilize the free vibration of non-classical micro-beams whose governing PDE is derived based on the modified strain... 

    Backstepping boundary control for unstable second-order hyperbolic PDES and trajectory tracking

    , Article Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference 2009, DETC2009, 30 August 2009 through 2 September 2009 ; Volume 4, Issue PART C , August , 2010 , Pages 1787-1792 ; 9780791849019 (ISBN) Vatankhah, R ; Sadeghian, H ; Abediny, M ; Alasty, A ; Sharif University of Technology
    2010
    Abstract
    In this paper, a problem of boundary feedback stabilization of second order hyperbolic partial differential equations (PDEs) is considered. These equations serve as a model for physical phenomena such as oscillatory systems like strings and beams. The controllers are designed using a backstepping method, which has been recently developed for parabolic PDEs. With the integral transformation and boundary feedback the unstable PDE is converted into a system which is stable in sense of Lyapunov. Then taylorian expansion is used to achieve the goal of trajectory tracking. It means design a boundary controller such that output of the system follows an arbitrary map. The designs are illustrated... 

    A geometrically nonlinear beam model based on the second strain gradient theory

    , Article International Journal of Engineering Science ; Volume 91 , June , 2015 , Pages 63-75 ; 00207225 (ISSN) Karparvarfard, S. M. H ; Asghari, M ; Vatankhah, R ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    The geometrically nonlinear governing differential equation of motion and corresponding boundary conditions of small-scale Euler-Bernoulli beams are achieved using the second strain gradient theory. This theory is a non-classical continuum theory capable of capturing the size effects. The appearance of many higher-order material constants in the formulation can certify that it appropriately assesses the behavior of extremely small-scale structures. A hinged-hinged beam is chosen as an example to lay out the nonlinear size-dependent static bending and free vibration behaviors of the derived formulation. The results of the new model are compared with the previously obtained results based on... 

    Vibration boundary control of micro-cantilever timoshenko beam using piezoelectric actuators

    , Article Scientia Iranica ; Volume 25, Issue 2B , 2018 , Pages 711-720 ; 10263098 (ISSN) Mehrvarz, A ; Salarieh, H ; Alasty, A ; Vatankhah, R ; Sharif University of Technology
    Sharif University of Technology  2018
    Abstract
    One of the methods of force/moment exertion on micro beams is utilizing piezoelectric actuators. In this paper, considering the effects of the piezoelectric actuator on asymptotic stability achievement, the boundary control problem for the vibration of a clamped-free micro-cantilever Timoshenko beam is addressed. To achieve this purpose, the dynamic equations of the beam actuated by a piezoelectric layer laminated on one side of the beam are extracted. The control law was implemented so that vibrations of the beam could be decayed. This control law was achieved based on feedback of time derivatives of boundary states of the beam. The obtained control was applied in the form of piezoelectric... 

    Formulation for Mechanical Modelling of Small-Scale Micro- and Nano- Beams and Plates for Statical and Vibrational Analysis Based on the Second Strain Gradient Theory

    , Ph.D. Dissertation Sharif University of Technology Momeni, Alireza (Author) ; Asghari, Mohsen (Supervisor) ; Vatankhah, Ramin (Co-Advisor)
    Abstract
    In this thesis, the formulation of beams and plates in the micro- and nano scales is presented based on the second strain gradient theory (SSGT) introduced by Mindlin. The SSGT is a non-classical continuum theory that includes the second-order gradients of strain tensor in its formulation and this leads to more accurate modeling for mechanical behavior of materials than the strain gradient theory. On the other hand, due to the ever-increasing use of micro- and nano-electromechanical systems, analysis of the mechanical behavior of their deformable components for design and construction is of particular importance. For this purpose, analysis of Timoshenko beams and Euler-bernoulli beams made... 

    Boundary control of anti-symmetric vibration of satellite with flexible appendages in planar motion with exponential stability

    , Article Acta Astronautica ; Volume 147 , 2018 , Pages 219-230 ; 00945765 (ISSN) Kaviani Rad, H ; Salarieh, H ; Alasty, A ; Vatankhah, R ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    In this research, we have investigated the planar maneuver of a flexible satellite with appendages anti-symmetric vibration. The hybrid governing equations are comprised of coupled partial and ordinary differential equations which are derived by employing Hamilton's principle. In this paper, control goals are the tracking desired pitch angle along with the flexible appendages vibration suppression simultaneously by using only one control torque which is applied to the central hub. The boundary control is proposed to fulfill these control aims; furthermore, this boundary control ensures that spillover instability phenomenon is eliminated, and in-domain sensors and actuators implement are... 

    Boundary control of flexible satellite vibration in planar motion

    , Article Journal of Sound and Vibration ; Volume 432 , 2018 , Pages 549-568 ; 0022460X (ISSN) Kaviani Rad, H ; Salarieh, H ; Alasty, A ; Vatankhah, R ; Sharif University of Technology
    Academic Press  2018
    Abstract
    In this paper, the planar maneuver of a flexible satellite with regard to its flexible appendages vibration has been studied. The flexible satellite translates and rotates in a plane; in addition, the flexible appendages can also vibrate in that plane. The system governing equations, which are coupled partial and ordinary differential equations, are obtained based on Hamilton's principle. Then the original system converts to three equivalent subsystems, two of which contains one partial differential equation and one ordinary differential equation along with four boundary conditions, by using change of variables. Employing control forces and one control torque which are applied to the central...