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Zhiani R.,Islamic Azad University at Neyshabur
Applied Surface Science | Year: 2017

The binding properties of the adsorption of five different classes of amino acids, namely, alanine (Ala), arginine (Arg), asparagine (Asn), histidine (His) and cysteine (Cys) on the surface of the graphene (Gra) and the born-nitride (BN) nano-sheet structures were studied from molecular viewpoint using quantum mechanics methods. Density functional theory (DFT) and DFT-D3 calculations were carried out to investigate the electronic properties and the dispersion interaction of the amino acid/adsorbent complexes. Several parameters affecting the interactions between the amino acids and the adsorbent surfaces such as solvent effect, adsorption energy and separation distance were investigated. Findings show that Arg forms the most stable complexes with the graphene and the BN nano-sheet compare to the other amino acids used in this study. The observed frequency results which were related to the band gap energies were consistent with the above statement. Results exhibit that adsorption of the amino acids on the surface of the BN nano-sheet and the graphene accompanied with the release of the energy. Calculations show that there are no bonded interactions between the amino acids and adsorbent surfaces. The polarity of the BN nano-sheet provides the more affinity towards the amino acids. These results were proved by the quantum chemistry studies. © 2017 Elsevier B.V.

Mohammadi R.,Islamic Azad University at Neyshabur
Chinese Physics B | Year: 2015

The aim of the present paper is to present a numerical algorithm for the time-dependent generalized regularized long wave equation with boundary conditions. We semi-discretize the continuous problem by means of the Crank-Nicolson finite difference method in the temporal direction and exponential B-spline collocation method in the spatial direction. The method is shown to be unconditionally stable. It is shown that the method is convergent with an order of O(k2 + h2). Our scheme leads to a tri-diagonal nonlinear system. This new method has lower computational cost in comparison to the Sinc-collocation method. Finally, numerical examples demonstrate the stability and accuracy of this method. © 2015 Chinese Physical Society and IOP Publishing Ltd.

Sadatian S.D.,Islamic Azad University at Neyshabur
International Journal of Modern Physics D | Year: 2012

We have studied a DGP-inspired braneworld scenario where the idea of Lorentz invariance violation has been combined into a specifying preferred frame that embed a dynamical normal vector field to brane. We propose the Lorentz violating DGP brane models with enough parameters can explain crossing of phantom divide line. Also we have considered the model for proper cosmological evolution that is according to the observed behavior of the equation of state. In other view point, we have described a Rip singularity solution of model that occur in this model. © 2012 World Scientific Publishing Company.

Moshizi S.A.,Islamic Azad University at Neyshabur
Engineering Computations (Swansea, Wales) | Year: 2015

Purpose - The purpose of this paper is to focus on convective heat and mass transfer characteristics of Cu-water nanofluid inside a porous microchannel in the presence of a uniform magnetic field. The walls of the microchannel are subjected to constant asymmetric heat fluxes and also the first order catalytic reaction. To represent the non-equilibrium region near the surfaces, the Navier's slip condition is considered at the surfaces because of the non-Adherence of the fluid-solid interface and the microscopic roughness in microchannels. Design/methodology/approach - Employing the Brinkman model for the flow in the porous medium and the "clear fluid compatible" model as a viscous dissipation model, the conservative partial differential equations have been transformed into a system of ordinary ones via the similarity variables. Closed form exact solutions are obtained analytically based on dimensionless parameters of velocity, temperature and species concentration. Findings - Results show that the addition of Cu-nanoparticles to the fluid has a significant influence on decreasing concentration, temperature distribution at the both walls and velocity profile along the microchannel. In addition, total heat transfer in microchannel increases as nanoparticles add to the fluid. Slip parameter and Hartmann number have the decreasing effects on concentration and temperature distributions. Slip parameter leads to increase velocity profiles, while Hartmann number has an opposite trend in velocity profiles. These two parameters increase the total heat transfer rate significantly. Originality/value - In the present study, a comprehensive analytical solution has been obtained for convective heat and mass transfer characteristics of Cu-water nanofluid inside a porous microchannel in the presence of a uniform magnetic field. Finally, the effects of several parameters such as Darcy number, nanoparticle volume fraction, slip parameter, Hartmann number, Brinkman number, asymmetric heat flux parameter, Soret and Damkohler numbers on total heat transfer rate and fluid flow profiles are studied in more detail. To the best of author's knowledge, no study has been conducted to this subject and the results are original. © Emerald Group Publishing Limited.

Nobahari M.,Islamic Azad University at Neyshabur | Seyedpoor S.M.,Shomal University
Mathematical and Computer Modelling | Year: 2011

An efficient optimization procedure is proposed to detect multiple damage in structural systems. Natural frequency changes of a structure are considered as a criterion for damage presence. In order to evaluate the required natural frequencies, a finite element analysis (FEA) is utilized. A modified genetic algorithm (MGA) with two new operators (health and simulator operators) is presented to accurately detect the locations and extent of the eventual damage. An efficient correlation-based index (ECBI) as the objective function for the optimization algorithm is also introduced. The numerical results of two benchmark examples considering the measurement noise demonstrate the computational advantages of the proposed method to precisely determine the sites and the extent of multiple structural damage. © 2011 Elsevier Ltd.

Ramezanpour A.,Islamic Azad University at Neyshabur
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2016

We study the inverse problem of constructing an appropriate Hamiltonian from a physically reasonable set of orthogonal wave functions for a quantum spin system. Usually, we are given a local Hamiltonian and our goal is to characterize the relevant wave functions and energies (the spectrum) of the system. Here, we take the opposite approach; starting from a reasonable collection of orthogonal wave functions, we try to characterize the associated parent Hamiltonians, to see how the wave functions and the energy values affect the structure of the parent Hamiltonian. Specifically, we obtain (quasi) local Hamiltonians by a complete set of (multilayer) product states and a local mapping of the energy values to the wave functions. On the other hand, a complete set of tree wave functions (having a tree structure) results to nonlocal Hamiltonians and operators which flip simultaneously all the spins in a single branch of the tree graph. We observe that even for a given set of basis states, the energy spectrum can significantly change the nature of interactions in the Hamiltonian. These effects can be exploited in a quantum engineering problem optimizing an objective functional of the Hamiltonian. © 2016 American Physical Society.

Mohammadi R.,Islamic Azad University at Neyshabur
Computer Physics Communications | Year: 2014

In this study, the exponential spline scheme is implemented to find a numerical solution of the nonlinear Schrödinger equations with constant and variable coefficients. The method is based on the Crank-Nicolson formulation for time integration and exponential spline functions for space integration. The error analysis, existence, stability, uniqueness and convergence properties of the method are investigated using the energy method. We show that the method is unconditionally stable and accurate of orders O(k+kh+h2) and O(k+kh+h4). This method is tested on three examples by using the cubic nonlinear Schrödinger equation with constant and variable coefficients and the Gross-Pitaevskii equation. The computed results are compared wherever possible with those already available in the literature. The results show that the derived method is easily implemented and approximate the exact solution very well. © 2013 Elsevier B.V. All rights reserved.

Daryaei E.,Islamic Azad University at Neyshabur
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

We study the scaling limit of a planar loop-erased random walk (LERW) on the percolation cluster, with occupation probability p≥pc. We numerically demonstrate that the scaling limit of planar LERWp curves, for all p>pc, can be described by Schramm-Loewner evolution (SLE) with a single parameter κ that is close to the normal LERW in a Euclidean lattice. However, our results reveal that the LERW on critical incipient percolation clusters is compatible with SLE, but with another diffusivity coefficient κ. Several geometrical tests are applied to ascertain this. All calculations are consistent with SLEκ, where κ=1.732±0.016. This value of the diffusivity coefficient is outside the well-known duality range 2≤κ≤8. We also investigate how the winding angle of the LERWp crosses over from Euclidean to fractal geometry by gradually decreasing the value of the parameter p from 1 to pc. For finite systems, two crossover exponents and a scaling relation can be derived. This finding should, to some degree, help us understand and predict the existence of conformal invariance in disordered and fractal landscapes. © 2014 American Physical Society.

Malvandi A.,Amirkabir University of Technology | Hedayati F.,Islamic Azad University at Neyshabur | Ganji D.D.,Babol Noshirvani University of Technology
Powder Technology | Year: 2014

Unsteady two-dimensional stagnation point flow of a nanofluid over a stretching sheet is investigated numerically. In contrast to the conventional no-slip condition at the surface, Navier's slip condition has been applied. The behavior of the nanofluid was investigated for three different nanoparticles in the water-base fluid, namely copper, alumina and titania. Employing the similarity variables, the governing partial differential equations including continuity, momentum and energy have been reduced to ordinary ones and solved via Runge-Kutta-Fehlberg scheme. It was shown that a dual solution exists for negative values of the unsteadiness parameter A and, as it increases, the skin friction Cfr grows but the heat transfer rate Nur takes a decreasing trend. The results also indicated that, unlike the stretching parameter ε, increasing in the values of the slip parameter λ widen the ranges of the unsteadiness parameter A for which the solution exists. Furthermore, it was found that an increase in both ε and λ intensifies the heat transfer rate. © 2013 Elsevier B.V.

Hedayati F.,Islamic Azad University at Neyshabur | Domairry G.,Babol Noshirvani University of Technology
Powder Technology | Year: 2015

The effects of nanoparticle migration on mixed convection of titania/water nanofluid inside a vertical microchannel have been investigated numerically via Runge-Kutta-Fehlberg method. A modified two-component heterogeneous model is employed for the nanofluid in the hypothesis that the Brownian motion and the thermophoresis are the only responsible mechanisms for nanoparticle migration. Because of small dimensional structures of microchannels, a linear slip condition is considered at the boundaries, which appropriately represents the non-equilibrium region near the interface. To impose different temperature gradients, the heat flux ratio of the right to the left wall (. ε) is investigated in three different situations, namely the adiabatic right wall (. ε= 0), unequal heat fluxes at the walls (. ε<. 1) and equal heat fluxes (. ε= 1). It is revealed that the asymmetric thermal boundary condition affects the direction of nanoparticle migration and distorts the symmetry of the velocity and temperature profiles. In the rich nanoparticle concentration region, the viscosity and the local conductivity increase, which lead to a stronger conduction and a weaker convection rate. Also, it is found that splitting the total amount of heat flux on the walls unevenly, is the most efficient way to enhance the heat transfer rate in the vertical microchannels. © 2014 Elsevier B.V.

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