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Rajabi F.,Islamic Azad University at Bandar Anzali | Ramezani S.,Guilan University
Acta Mechanica Solida Sinica | Year: 2013

A micro scale nonlinear beam model based on strain gradient elasticity is developed. Governing equations of motion and boundary conditions are obtained in a variational framework. As an example, the nonlinear vibration of microbeams is analyzed. In a beam having a thickness to length parameter ratio close to unity, the strain gradient effect on increasing the natural frequency is predominant. By increasing the beam thickness, this effect decreases and geometric nonlinearity plays the main role on increasing the natural frequency. For some specific ratios, both geometric nonlinearity and size effects have a significant role on increasing the natural frequency. © 2013 The Chinese Society of Theoretical and Applied Mechanics. Source


Ansari R.,Guilan University | Ashrafi M.A.,Guilan University | Pourashraf T.,Guilan University | Sahmani S.,Islamic Azad University at Bandar Anzali
Acta Astronautica | Year: 2015

The buckling and vibration responses of nanoplates made of functionally graded materials (FGMs) subjected to thermal loading are studied in prebuckling domain with considering the effect of surface stress. To accomplish this purpose, Gurtin-Murdoch elasticity theory is incorporated into the classical plate theory to develop a non-classical plate model including the surface effects. The material properties of FGM nanoplate are considered to be graded in the thickness direction on the basis of the power law function. Hamilton's principle is utilized to derive size-dependent governing differential equations of motion and associated boundary conditions. Selected numerical results are presented to indicate the importance of surface stress effect. It is revealed that in the presence of surface stress effect, the influence of material property gradient index on the critical thermal buckling load is more prominent for FGM nanoplates with lower length-to-thickness ratios. Also, by increasing the natural frequency of FGM nanoplate, the role of surface stress effect in the value of critical thermal buckling load is more prominent. © 2014 IAA. Published by Elsevier Ltd. All rights reserved. Source


Hamedi H.R.,University of Tabriz | Asadpour S.H.,Islamic Azad University at Bandar Anzali | Sahrai M.,University of Tabriz
Optik | Year: 2013

The linear and nonlinear response of a driven four-level Λ-type atomic system with two fold lower-levels with three driving fields is investigated. It is found that the giant Kerr nonlinearity can be achieved just by tuning the intensity of coupling fields. Maximal Kerr nonlinearity with zero linear and nonlinear absorption enters the EIT window. Also it is found that the relative phase between applied fields can change the Kerr nonlinearity behavior. © 2012 Elsevier GmbH. Source


Asadpour S.H.,Islamic Azad University at Bandar Anzali | Hamedi H.R.,University of Tabriz
Optical and Quantum Electronics | Year: 2013

A scheme for enhancement of Kerr nonlinearity with vanishing linear and nonlinear absorption in a three-level ladder-configuration n-doped semiconductor quantum well is proposed. It is shown that the Kerr nonlinearity can be controlled and even enhance by the intensity of coupling fields. Also, phase control of Kerr nonlinearity is then discussed. © 2012 Springer Science+Business Media, LLC. Source


Asadpour S.H.,Islamic Azad University at Bandar Anzali | Sahrai M.,University of Tabriz | Soltani A.,University of Tabriz | Hamedi H.R.,University of Tabriz
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2012

A novel atom configuration is proposed for a giant Kerr nonlinearity in zero linear and nonlinear probe absorption. It is shown that without coherent control field and just by quantum interference of spontaneous emission, a giant Kerr nonlinearity can be obtained. © 2011 Elsevier B.V. All rights reserved. Source

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