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    Properties of Nafion Under Uniaxial Loading at Different Temperatures: A Molecular Dynamics Study

    , Article Polymer - Plastics Technology and Engineering ; Volume 54, Issue 8 , 2015 , Pages 806-813 ; 03602559 (ISSN) Ozmaian, M ; Naghdabadi, R ; Sharif University of Technology
    Taylor and Francis Inc  2015
    Nafion membrane encounters many different thermal conditions and mechanical loadings because of its wide range of applications as a proton exchange membrane (PEM). Molecular dynamics simulation of hydrated Nafion at different temperatures is carried out to investigate the alteration of the physical properties of Nafion under uniaxial loading over a wide range of temperatures. According to the simulation results, increase of the temperature reduces the yield stress. The results also show that the polymer chains ordering increases the glass transition temperature and enhances the self-diffusion coefficient of water in hydrated Nafion. Comparisons show that the elastic modulus and viscosity... 

    Nonlinear transversal vibration of an axially moving viscoelastic string on a viscoelastic guide subjected to mono-frequency excitation

    , Article Acta Mechanica ; Volume 214, Issue 3-4 , November , 2010 , Pages 357-373 ; 00015970 (ISSN) Ahmadian, M. T ; Yaghoubi Nasrabadi, V ; Mohammadi, H ; Sharif University of Technology
    In this paper, the nonlinear transversal vibration of an axially moving viscoelastic string on a viscoelastic guide subjected to a mono-frequency excitation is considered. The model of the viscoelastic guide is a parallel combination of springs and viscous dampers. The governing equation of motion is developed using Hamilton's principle. Applying the method of multiple scales to the governing partial differential equation, the solvability condition and approximate solutions are derived. Three cases, namely primary, subharmonic and superharmonic resonances are studied and appropriate analytical solutions are obtained. The effect of mean value velocity, force amplitude, guide stiffness and... 

    Mass flow rate scaling of the continuum-based equations using information preservation method

    , Article 41st AIAA Thermophysics Conference2009, Article number 2009-3746 ; 2009 ; 9781563479755 (ISBN) Roohi, E ; Darbandi, M ; Vakilipour, S ; Schneider, G. E ; Sharif University of Technology
    Kinetic theory based numerical scheme such as direct simulation Monte Carlo (DSMC) and information preservation (IP) schemes properly solve micro-nano flow problems in transition and free molecular regimes. However, the high computational cost of these methods encourages the researchers toward extending the applicability of the continuumbased equations beyond the slip flow regime. In addition to correct velocity profile, the continuum-based equations should predict accurate mass flow rate magnitude. The secondorder velocity slip models derived from the kinetic theory provide accurate velocity profiles up to Kn=0.5; however, they yield erroneous mass flow rate magnitudes because the basic... 

    Extending the Navier-stokes solutions to transition regime in two-dimensional micro- and nanochannel flows using information preservation scheme

    , Article Physics of Fluids ; Volume 21, Issue 8 , 2009 ; 10706631 (ISSN) Roohi, E ; Darbandi, M ; Sharif University of Technology
    The kinetic-theory-based numerical schemes, such as direct simulation Monte Carlo (DSMC) and information preservation (IP), can be readily used to solve transition flow regimes. However, their high computational cost still promotes the researchers to extend the Navier-Stokes (NS) equations beyond the slip flow and to the transition regime applications. Evidently, a suitable extension would accurately predict both the local velocity profiles and the mass flow rate magnitude as well as the streamwise pressure distribution. The second-order slip velocity model derived from kinetic theory can provide relatively accurate velocity profiles up to a Knudsen (Kn) number of around 0.5; however, its...