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    Theoretical and experimental study on the motion and shape of viscoelastic falling drops through Newtonian media

    , Article Rheologica Acta ; Volume 55, Issue 11-12 , 2016 , Pages 935-955 ; 00354511 (ISSN) Vamerzani, B. Z ; Norouzi, M ; Firoozabadi, B ; Sharif University of Technology
    Springer Verlag 
    Abstract
    In this paper, creeping motion of a viscoelastic drop falling through a Newtonian fluid is investigated experimentally and analytically. A polymeric solution of 0.08 % xanthan gum in 80:20 glycerol/water and silicon oil is implemented as the viscoelastic drop and the bulk viscous fluids, respectively. The shape and motion of falling drops are visualized using a high speed camera. The perturbation technique is employed for both interior and exterior flows, and Deborah and capillary numbers are considered as perturbation parameters up to second order. The product of Deborah and capillary numbers is also used as a perturbation parameter to apply the boundary condition on the deformation on the... 

    Dynamics of Timoshenko beams on Pasternak foundation under moving load

    , Article Mechanics Research Communications ; Volume 31, Issue 6 , 2004 , Pages 713-723 ; 00936413 (ISSN) Kargarnovin, M. H ; Younesian, D ; Sharif University of Technology
    2004
    Abstract
    The response of a Timoshenko beam with uniform cross-section and infinite length supported by a generalized Pasternak-type viscoelastic foundation subjected to an arbitrary-distributed harmonic moving load is studied in this paper. Governing equations are solved using complex Fourier transformation in conjunction with the residue and convolution integral theorems. The solution is directed to compute the deflection, bending moment and shear force distribution along the beam length. A parametric study is carried out for an elliptical load distribution and influences of the load speed and frequency on the beam responses are investigated. © 2004 Elsevier Ltd. All rights reserved  

    Relaxation constant in the folding of thin viscoelastic sheets

    , Article Physical Review Applied ; Volume 13, Issue 1 , 2020 Farain, K ; Sharif University of Technology
    American Physical Society  2020
    Abstract
    If one folds a thin viscoelastic sheet under an applied force, a line of plastic deformation is formed that shapes the sheet into an angle. This study determines parameters that define this angle and shows that, no matter how much load one applies, it is impossible to make angles less than a certain minimum angle in a definite time. Moreover, it is shown that regardless of whether the sheet is released freely afterward or kept under load, a logarithmic relaxation process follows the first deformation. The slope of this logarithm is the same in both conditions and depends neither on the applied force nor on the thickness of the sheet, which indicates that it is directly a probe of the... 

    Conceptual modeling of cardiovascular sounds

    , Article 2005 27th Annual International Conference of the Engineering in Medicine and Biology Society, IEEE-EMBS 2005, Shanghai, 1 September 2005 through 4 September 2005 ; Volume 7 VOLS , 2005 , Pages 2308-2311 ; 05891019 (ISSN); 0780387406 (ISBN); 9780780387409 (ISBN) Pouladian, M ; Tehrani Fard, A. A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2005
    Abstract
    In this paper, it is shown that the main source of mechanical energy of cardiovascular (CV) system i.e., rhythmic heart contraction is transformed to the oscillations of the CV walls and blood flow, and finally CV acoustical waves. These waves propagate through both blood flow (hemodynamical pathways) and tissues (viscoelastical pathways) toward the skin. Nonetheless, the CV walls could be assumed as the source of acoustical waves, since they act as the interface between blood flows and other tissues including skin. After obtaining the approximate accelerations of CV walls from pressure-flow (PF) models, we also needed to model the viscoelastical pathways until the skin. Some improvements on... 

    Quantitative determination of optical trapping strength and viscoelastic moduli inside living cells

    , Article Physical Biology ; Volume 10, Issue 4 , 2013 ; 14783967 (ISSN) Mas, J ; Richardson, A. C ; Reihani, S. N. S ; Oddershede, L. B ; Berg Sorensen, K ; Sharif University of Technology
    2013
    Abstract
    With the success of in vitro single-molecule force measurements obtained in recent years, the next step is to perform quantitative force measurements inside a living cell. Optical traps have proven excellent tools for manipulation, also in vivo, where they can be essentially non-invasive under correct wavelength and exposure conditions. It is a pre-requisite for in vivo quantitative force measurements that a precise and reliable force calibration of the tweezers is performed. There are well-established calibration protocols in purely viscous environments; however, as the cellular cytoplasm is viscoelastic, it would be incorrect to use a calibration procedure relying on a viscous environment.... 

    Fluid-structure interaction analysis of airflow in pulmonary alveoli during normal breathing in healthy humans

    , Article Scientia Iranica ; Volume 23, Issue 4 , 2016 , Pages 1826-1836 ; 10263098 (ISSN) Monjezi, M ; Saidi, M. S ; Sharif University of Technology
    Sharif University of Technology 
    Abstract
    In this work, the human lung alveoli are idealized by a three dimensional honeycomb like geometry and a fluid-structure analysis is performed to study the normal breathing mechanics. In contrast to previous works in which the inlet flow rate is predefined, in this model, we have applied a negative pressure on the outside surface of the alveolus which causes air to flow in and out of the alveolus. The integration of the experimental curve of breathing flow rate was used to approximate the shape of the external applied pressure. Our Fluid-Structure Interaction (FSI) model has an advantage over other literature since it addresses both the fluid dynamics and solid mechanics, simultaneously. The... 

    Application of exact continuum size-dependent theory for stability and frequency analysis of a curved cantilevered microtubule by considering viscoelastic properties

    , Article Engineering with Computers ; Volume 37, Issue 4 , 2021 , Pages 3629-3648 ; 01770667 (ISSN) Shariati, A ; Habibi, M ; Tounsi, A ; Safarpour, H ; Safa, M ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    Abstract
    The stability analysis of cantilevered curved microtubules in axons regarding various size elements and using the generalized differential quadrature method for solving equations is reported. The impacts of covering MAP Tau proteins along with cytoplasm are taken into account as the elastic medium. Curved cylindrical nanoshell considering thick wall is used to model the microtubules. The factor of length scale (l/R = 0.2) used in modified couple stress theory would result in more accuracy when it comes to comparison with experiments, while alternative theories presented in this paper provide less precise outcomes. Due to the reported precise results, at the lower value of the time-dependent... 

    Analytical solution for creeping motion of a viscoelastic drop falling through a Newtonian fluid

    , Article Korea Australia Rheology Journal ; Vol. 26, issue. 1 , 2014 , pp. 91-104 ; ISSN: 1226119X Vamerzani, B. Z ; Norouzi, M ; Firoozabadi, B ; Sharif University of Technology
    Abstract
    In this paper, an analytical solution for steady creeping motion of viscoelastic drop falling through a viscous Newtonian fluid is presented. The Oldroyd-B model is used as the constitutive equation. The analytical solutions for both interior and exterior flows are obtained using the perturbation method. Deborah number and capillary numbers are considered as the perturbation parameters. The effect of viscoelastic properties on drop shape and motion are studied in detail. The previous empirical studies indicated that unlike the Newtonian creeping drop in which the drop shape is exactly spherical, a dimpled shape appears in viscoelastic drops. It is shown that the results of the present... 

    Simulation of viscoelastic fluid flows in expansion geometry using finite volume approach

    , Article Chinese Journal of Polymer Science (English Edition) ; Volume 31, Issue 12 , November , 2013 , Pages 1599-1612 ; 02567679 (ISSN) Azizi, M ; Ahmad Ramazani, S. A ; Habib Etemadi, M ; Ehsan Shirzaei, S ; Sharif University of Technology
    2013
    Abstract
    The simulation results on viscoelastic fluid flows i sudden expansion geometry with different expansion ratios are presented. Oldroyd-B, linear Phan-Thien-Tanner (L-PTT) and Finitely Extensible Nonlinear Elastic (FENE-P) based constitutive equations were applied in two-dimensional Cartesian coordinates. The governing equations in transient and fully developed regions were solved using open source software called OpenFOAM. The flow patterns, including velocity profiles, shear stresses and first normal stress differences in some horizontal and vertical sections are illustrated. In addition, effects of the fluid type, flow dynamics and expansion ratio on the flow and vortex patterns in... 

    An analytical-numerical solution to assess the dynamic response of viscoelastic plates to a moving mass

    , Article Applied Mathematical Modelling ; Volume 54 , 2018 , Pages 670-696 ; 0307904X (ISSN) Foyouzat, M. A ; Esmaeilpour Estekanchi, H ; Mofid, M ; Sharif University of Technology
    Elsevier Inc  2018
    Abstract
    In this paper, the dynamics of a viscoelastic plate resting on a viscoelastic Winkler foundation and traversed by a moving mass is studied. The Laplace transform is employed to derive the governing equation of the problem. Thereafter, an analytical-numerical method is proposed in order to determine the dynamic response of the plate. The method is based on transforming the governing partial differential equation into a new solvable system of linear ordinary differential equations. To that extent, the proposed solution proves to be applicable to plates made of any viscoelastic material and with various boundary conditions. Moreover, the moving mass may travel at any arbitrary trajectory with... 

    Measuring viscoelastic properties of Red Blood Cell using optical tweezers

    , Article Iranian Journal of Physics Research ; Volume 19, Issue 1 , 2019 , Pages 101-108 ; 16826957 (ISSN) Seyed Reihani, S. N ; Azadbakht, A ; Mirzahossein, E ; Mottaghian, M ; Babaei, M ; Sharif University of Technology
    Isfahan University of Technology  2019
    Abstract
    Efforts have been made to study the behavior of complex materials in micrometer dimensions with various techniques. One of these methods is the use of optical tweezers for biophysical applications. Red blood cells, as the most abundant blood-forming cells, play an important role in the life of living organisms, and their unique mechanical properties are important. In this report, the study of soft materials is done using light tweezers. This work investigates micrometer particle movements in the optical trap and also, when they are connected to a red blood cell. The tweezers allow the Newtonian fluid viscosity, such as water and glycerin, to measure the mechanical properties of viscoelastic... 

    Measuring viscoelastic properties of Red Blood Cell using optical tweezers

    , Article Iranian Journal of Physics Research ; Volume 19, Issue 1 , 2019 , Pages 101-108 ; 16826957 (ISSN) Seyed Reihani, S. N ; Azadbakht, A ; Mirzahossein, E ; Mottaghian, M ; Babaei, M ; Sharif University of Technology
    Isfahan University of Technology  2019
    Abstract
    Efforts have been made to study the behavior of complex materials in micrometer dimensions with various techniques. One of these methods is the use of optical tweezers for biophysical applications. Red blood cells, as the most abundant blood-forming cells, play an important role in the life of living organisms, and their unique mechanical properties are important. In this report, the study of soft materials is done using light tweezers. This work investigates micrometer particle movements in the optical trap and also, when they are connected to a red blood cell. The tweezers allow the Newtonian fluid viscosity, such as water and glycerin, to measure the mechanical properties of viscoelastic... 

    Stochastic analysis of nonlinear viscoelastic panels under random excitation

    , Article 44th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference 2003, Norfolk, VA, 7 April 2003 through 10 April 2003 ; 2003 ; 9781624101007 (ISBN) Fazelzadeh, S. A ; Pourtakdoust, S. H ; Assadian, N ; Sharif University of Technology
    2003
    Abstract
    Stochastic behavior of viscoelastic panels in supersonic flow under random aerodynamic pressure and inplane forces is investigated. The governing equations of motion are based on the Von Karman's large deflection equation and are considered with Kelvin's model of viscoelastic structural damping. The panel under study is two dimensional and simply supported for which the first order piston theory is used to account for the unsteady aerodynamic loading. Transformation of the governing partial differential equation to a set of ordinary differential equations is performed through the Galerkin averaging technique. The statistical response moment equations are generated for two modes using the... 

    Chaotic analysis of nonlinear viscoelastic panel flutter in supersonic flow

    , Article Nonlinear Dynamics ; Volume 32, Issue 4 , 2003 , Pages 387-404 ; 0924090X (ISSN) Pourtakdoust, S. H ; Fazelzadeh, S. A ; Sharif University of Technology
    2003
    Abstract
    In this paper chaotic behavior of nonlinear viscoelastic panels in a supersonic flow is investigated. The governing equations, based on von Kàrmàn's large deflection theory of isotropic flat plates, are considered with viscoelastic structural damping of Kelvin's model included. Quasi-steady aerodynamic panel loadings are determined using piston theory. The effect of constant axial loading in the panel middle surface and static pressure differential have also been included in the governing equation. The panel nonlinear partial differential equation is transformed into a set of nonlinear ordinary differential equations through a Galerkin approach. The resulting system of equations is solved... 

    Stochastic analysis of nonlinear viscoelastic panels under random excitation

    , Article 44th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Norfolk, VA, 7 April 2003 through 10 April 2003 ; Volume 6 , 2003 , Pages 4219-4225 ; 02734508 (ISSN) Fazelzadeh, S. A ; Pourtakdoust, S. H ; Assadian, N ; Sharif University of Technology
    American Inst. Aeronautics and Astronautics Inc  2003
    Abstract
    Stochastic behavior of viscoelastic panels in supersonic flow under random aerodynamic pressure and in-plane forces is investigated. The governing equations of motion are based on the Von Karman's large deflection equation and are considered with Kelvin's model of viscoelastic structural damping. The panel under study is two dimensional and simply supported for which the first order piston theory is used to account for the unsteady aerodynamic loading. Transformation of the governing partial differential equation to a set of ordinary differential equations is performed through the Galerkin averaging technique. The statistical response moment equations are generated for two modes using the... 

    Investigating the Effect of Hemoglobin on Viscoelastic Properties of RBC

    , M.Sc. Thesis Sharif University of Technology Felekary, Arash (Author) ; Seyed Reihani, Nader (Supervisor)
    Abstract
    Red blood cells are one of the most important parts of blood and their mechanical properties are so important in some diseases. Red blood cell is mostly consisted of membrane, cell skeleton, and cytoplasm which contains hemoglobin proteins. Studying these properties separately not only could give us pieces of information about cell mechanics, but also reveals a way to predict their behavior after illnesses. Optical tweezers as a tool, which can produce and measure Piconewton to Nanonewton forces, has been interesting in red blood cell parts' studying. In this thesis, at first hemoglobin is taken out gradually by using Saponin (which is enable to make some pores in the membrane) and the... 

    Dynamics of a laminated composite beam on pasternak-viscoelastic foundation subjected to a moving oscillator

    , Article JVC/Journal of Vibration and Control ; Volume 14, Issue 6 , 2008 , Pages 807-830 ; 10775463 (ISSN) Ahmadian, M. T ; Jafari Talookolaei, R. A ; Esmailzadeh, E ; Sharif University of Technology
    2008
    Abstract
    Dynamic behavior of a laminated composite beam (LCB) supported by a generalized Pasternak-type viscoelastic foundation, subjected to a moving two-degree-of-freedom (DOFs) oscillator with a constant axial velocity is studied. Analytical solution using the Galerkin method is sought and the couplings of the bending-tension, shear-tension, and bending-twist with the Poisson effect are considered. The possible separation of the moving oscillator from LCB during the course of motion is investigated by monitoring the contact force between the oscillator and LCB. The effects of the non-rigid foundation, oscillator parameters, and the load speed on the separation are also studied. It is found that... 

    Modeling of viscoelastic solid polymers using a boundary element formulation with considering a body load

    , Article Advanced Materials Research, 7 January 2012 through 8 January 2012 ; Volume 463-464 , January , 2012 , Pages 499-504 ; 10226680 (ISSN) ; 9783037853634 (ISBN) Ashrafi, H ; Bahadori, M. R ; Shariyat, M ; Sharif University of Technology
    Abstract
    In this work, a boundary element formulation for 2D linear viscoelastic solid polymers subjected to body force of gravity has been presented. Structural analysis of solid polymers is one of the most important subjects in advanced engineering structures. From basic assumptions of the viscoelastic constitutive equations and the weighted residual techniques, a simple but effective boundary element formulation is implemented for standard linear solid (SLS) model. The SLS model provides an approximate representation of observed behavior of a real advanced polymer in its viscoelastic range. This approach avoids the use of relaxation functions and mathematical transformations, and it is able to... 

    Nonlinear dynamic analysis of a timoshenko beam resting on a viscoelastic foundation and traveled by a moving mass

    , Article Shock and Vibration ; Vol. 2014 , 2014 ; ISSN: 10709622 Mamandi, A ; Kargarnovin, M. H ; Sharif University of Technology
    Abstract
    The dynamic response of a Timoshenko beam with immovable ends resting on a nonlinear viscoelastic foundation and subjected to motion of a traveling mass moving with a constant velocity is studied. Primarily, the beam's nonlinear governing coupled PDEs of motion for the lateral and longitudinal displacements as well as the beam's cross-sectional rotation are derived using Hamilton's principle. On deriving these nonlinear coupled PDEs the stretching effect of the beam's neutral axis due to the beam's fixed end conditions in conjunction with the von-Karman strain-displacement relations is considered. To obtain the dynamic responses of the beam under the act of a moving mass, derived nonlinear... 

    An FEM approach for three - Dimensional thermoviscoelastic stress analysis of orthotropic cylinders made of polymers

    , Article Advanced Materials Research, Dubai ; Volume 685 , 2013 , Pages 295-299 ; 10226680 (ISSN) ; 9783037856765 (ISBN) Ashrafi, H ; Keshmiri, H ; Bahadori, M. R ; Shariyat, M ; Sharif University of Technology
    2013
    Abstract
    The objective of this study is to develop a general finite element formulation associated with an incremental adaptive procedure which established for thermoviscoelastic stress analysis of orthotropic cylinders made of polymers. This paper concerned with development of a numerical algorithm for the solution of the quasistatic initial/boundary value problems involving the linear viscoelastic media with thermal and mechanical deformations. The viscoelastic constitutive equations, represented in an integral form and involving relaxation functions, are transformed into an incremental algebraic relation. An incremental relaxation is then developed for the finite element formulation to deal with...