The Experts below are selected from a list of 113292 Experts worldwide ranked by ideXlab platform

P Malekzadeh - One of the best experts on this subject based on the ideXlab platform.

  • free vibration analysis of rotating functionally graded cylindrical shells in thermal environment
    Composite Structures, 2012
    Co-Authors: P Malekzadeh, Y Heydarpour
    Abstract:

    Abstract The free vibration analysis of rotating functionally graded (FG) cylindrical shells subjected to thermal environment is investigated based on the first order shear deformation theory (FSDT) of shells. The formulation includes the centrifugal and Coriolis forces due to rotation of the shell. The material properties are assumed to be temperature-dependent and graded in the thickness direction. The initial thermo-mechanical stresses are obtained by solving the thermoelastic Equilibrium Equations. The Equations of motion and the related boundary conditions are derived using Hamilton’s principle. The differential quadrature method (DQM) as an efficient and accurate numerical tool is adopted to discretize the thermoelastic Equilibrium Equations and the Equations of motion. The convergence behavior of the method is demonstrated and comparison studies with the available solutions in the literature are performed. Finally, the effects of angular velocity, Coriolis acceleration, temperature dependence of material properties, material property graded index and geometrical parameters on the frequency parameters of the FG cylindrical shells with different boundary conditions are investigated.

  • free vibration analysis of elastically supported functionally graded annular plates subjected to thermal environment
    Meccanica, 2011
    Co-Authors: P Malekzadeh, M Golbahar R Haghighi, M M Atashi
    Abstract:

    Free vibration analysis of functionally graded (FG) thin-to-moderately thick annular plates subjected to thermal environment and supported on two-parameter elastic foundation is investigated. The material properties are assumed to be temperature-dependent and graded in the thickness direction. The Equations of motion and the related boundary conditions, which include the effects of initial thermal stresses, are derived using the Hamilton’s principle based on the first order shear deformation theory (FSDT). The initial thermal stresses are obtained by solving the thermoelastic Equilibrium Equations. Differential quadrature method (DQM) as an efficient and accurate numerical tool is adopted to solve the thermoelastic Equilibrium Equations and the Equations of motion. The formulations are validated by comparing the results in the limit cases with the available solutions in the literature for isotropic and FG circular and annular plates. The effects of the temperature rise, elastic foundation coefficients, the material graded index and different geometrical parameters on the frequency parameters of the FG annular plates are investigated. The new results can be used as benchmark solutions for future researches.

  • three dimensional thermal buckling analysis of functionally graded arbitrary straight sided quadrilateral plates using differential quadrature method
    Composite Structures, 2011
    Co-Authors: P Malekzadeh
    Abstract:

    The thermal buckling analysis of functionally graded (FG) arbitrary straight-sided quadrilateral plates is presented. The material properties are assumed to be temperature-dependent and graded in the thickness direction. The thermal buckling Equilibrium Equations are based on the three-dimensional (3D) elasticity theory. The differential quadrature method as an efficient and accurate numerical tool is adopted to discretize the governing Equations. The principle of virtual work in conjunction with the geometric mapping technique is used to derive the Equilibrium Equations and the related boundary conditions. After discretizing the governing Equations, the resulting nonlinear eigenvalue system of Equations is solved by an iterative procedure. The convergence of the method is shown through different examples and its accuracy is demonstrated by comparing the obtained solutions with the existing results in literature for FG plates. Finally, the effects of temperature dependence of material properties, temperature field, volume fraction index, geometrical parameters and the boundary conditions on the thermal buckling characteristic of the FG plates of various shapes are studied.

Trujillo J Bueno - One of the best experts on this subject based on the ideXlab platform.

  • theoretical formulation of doppler redistribution in scattering polarization within the framework of the velocity space density matrix formalism
    Astronomy and Astrophysics, 2013
    Co-Authors: L Belluzzi, Landi E Deglinnocenti, Trujillo J Bueno
    Abstract:

    Within the framework of the density matrix theory for the generation and transfer of polarized radiation, velocity density matrix correlations represent an important physical aspect that, however, is often neglected in practical applications when adopting the simplifying approximation of complete redistribution on velocity. In this paper, we present an application of the non-LTE problem for polarized radiation taking such correlations into account through the velocity-space density matrix formalism. We consider a twolevel atom with infinitely sharp upper and lower levels, and we derive the corresponding statistical Equilibrium Equations, neglecting the contribution of velocity-changing collisions. Coupling such Equations with the radiative transfer Equations for polarized radiation, we derive a set of coupled Equations for the velocity-dependent source function. This set of Equations is then particularized to the case of a plane-parallel atmosphere. The Equations presented in this paper provide a complete and solid description of the physics of pure Doppler redistribution, a phenomenon generally described within the framework of the redistribution matrix formalism. The redistribution matrix corresponding to this problem (generally referred to as RI) is derived starting from the statistical Equilibrium Equations for the velocity-space density matrix and from the radiative transfer Equations for polarized radiation, thus showing the equivalence of the two approaches.

  • theoretical formulation of doppler redistribution in scattering polarization within the framework of the velocity space density matrix formalism
    arXiv: Solar and Stellar Astrophysics, 2013
    Co-Authors: L Belluzzi, Landi E Deglinnocenti, Trujillo J Bueno
    Abstract:

    Within the framework of the density matrix theory for the generation and transfer of polarized radiation, velocity density matrix correlations represent an important physical aspect that, however, is often neglected in practical applications by adopting the simplifying approximation of complete redistribution on velocity. In this paper, we present an application of the Non-LTE problem for polarized radiation taking such correlations into account through the velocity-space density matrix formalism. We consider a two-level atom with infinitely sharp upper and lower levels, and we derive the corresponding statistical Equilibrium Equations neglecting the contribution of velocity-changing collisions. Coupling such Equations with the radiative transfer Equations for polarized radiation, we derive a set of coupled Equations for the velocity-dependent source function. This set of Equations is then particularized to the case of a plane-parallel atmosphere. The Equations presented in this paper provide a complete and solid description of the physics of pure Doppler redistribution, a phenomenon generally described within the framework of the redistribution matrix formalism. The redistribution matrix corresponding to this problem (generally referred to as R_I) is derived starting from the statistical Equilibrium Equations for the velocity-space density matrix and from the radiative transfer Equations for polarized radiation, thus showing the equivalence of the two approaches.

Jia Lou - One of the best experts on this subject based on the ideXlab platform.

  • buckling and post buckling of symmetric functionally graded microplate lying on nonlinear elastic foundation based on modified couple stress theory
    International Journal of Structural Stability and Dynamics, 2018
    Co-Authors: Jia Lou
    Abstract:

    This paper is concerned with the buckling and post-buckling behaviors of a simply supported symmetric functionally graded (FG) microplate lying on a nonlinear elastic foundation. The modified couple stress theory is used to capture the size effects of the FG microplate, and the Mindlin plate theory with von Karman’s geometric nonlinearity taken into account is adopted to describe its deflection behavior. Based on these assumptions and the principle of minimum potential energy, the Equilibrium Equations of the FG microplate and associated boundary conditions are derived. By applying the Galerkin method to the Equilibrium Equations, closed-form solutions for the critical buckling load and the load–displacement relation in the post-buckling stage are obtained. Furthermore, the effects of the power law index, the material length scale parameter to thickness ratio, the stiffness of the elastic foundation, and in-plane boundary conditions on the buckling and post-buckling behaviors of the FG microplate are disc...

  • pre buckling and buckling analyses of functionally graded microshells under axial and radial loads based on the modified couple stress theory
    Composite Structures, 2016
    Co-Authors: Jia Lou
    Abstract:

    In the present paper, the pre-buckling and buckling behaviors of a simply supported functionally graded (FG) microshell under a combined action of axial and radial loads are investigated. The size effects in the mechanical behavior of the microshell are captured by using the modified couple stress theory. The first order shear deformable shell theory together with the von Karman’s geometric nonlinearity is adopted to describe its deformation behavior. Based on these assumptions and the Hamilton’s principle, the Equilibrium Equations and associated boundary conditions for the microshell are derived. By applying the Galerkin method to the Equilibrium Equations, the pre-buckling deformation is obtained. The critical buckling load is then derived with the effect of the pre-buckling deformation taken into consideration. Furthermore, the effects of the material length scale parameter to thickness ratio, the power law index and the radial load to axial load ratio on the pre-buckling and buckling behaviors of the FG microshell are discussed in detail.

Y Heydarpour - One of the best experts on this subject based on the ideXlab platform.

  • free vibration analysis of rotating functionally graded cylindrical shells in thermal environment
    Composite Structures, 2012
    Co-Authors: P Malekzadeh, Y Heydarpour
    Abstract:

    Abstract The free vibration analysis of rotating functionally graded (FG) cylindrical shells subjected to thermal environment is investigated based on the first order shear deformation theory (FSDT) of shells. The formulation includes the centrifugal and Coriolis forces due to rotation of the shell. The material properties are assumed to be temperature-dependent and graded in the thickness direction. The initial thermo-mechanical stresses are obtained by solving the thermoelastic Equilibrium Equations. The Equations of motion and the related boundary conditions are derived using Hamilton’s principle. The differential quadrature method (DQM) as an efficient and accurate numerical tool is adopted to discretize the thermoelastic Equilibrium Equations and the Equations of motion. The convergence behavior of the method is demonstrated and comparison studies with the available solutions in the literature are performed. Finally, the effects of angular velocity, Coriolis acceleration, temperature dependence of material properties, material property graded index and geometrical parameters on the frequency parameters of the FG cylindrical shells with different boundary conditions are investigated.

L Belluzzi - One of the best experts on this subject based on the ideXlab platform.

  • theoretical formulation of doppler redistribution in scattering polarization within the framework of the velocity space density matrix formalism
    Astronomy and Astrophysics, 2013
    Co-Authors: L Belluzzi, Landi E Deglinnocenti, Trujillo J Bueno
    Abstract:

    Within the framework of the density matrix theory for the generation and transfer of polarized radiation, velocity density matrix correlations represent an important physical aspect that, however, is often neglected in practical applications when adopting the simplifying approximation of complete redistribution on velocity. In this paper, we present an application of the non-LTE problem for polarized radiation taking such correlations into account through the velocity-space density matrix formalism. We consider a twolevel atom with infinitely sharp upper and lower levels, and we derive the corresponding statistical Equilibrium Equations, neglecting the contribution of velocity-changing collisions. Coupling such Equations with the radiative transfer Equations for polarized radiation, we derive a set of coupled Equations for the velocity-dependent source function. This set of Equations is then particularized to the case of a plane-parallel atmosphere. The Equations presented in this paper provide a complete and solid description of the physics of pure Doppler redistribution, a phenomenon generally described within the framework of the redistribution matrix formalism. The redistribution matrix corresponding to this problem (generally referred to as RI) is derived starting from the statistical Equilibrium Equations for the velocity-space density matrix and from the radiative transfer Equations for polarized radiation, thus showing the equivalence of the two approaches.

  • theoretical formulation of doppler redistribution in scattering polarization within the framework of the velocity space density matrix formalism
    arXiv: Solar and Stellar Astrophysics, 2013
    Co-Authors: L Belluzzi, Landi E Deglinnocenti, Trujillo J Bueno
    Abstract:

    Within the framework of the density matrix theory for the generation and transfer of polarized radiation, velocity density matrix correlations represent an important physical aspect that, however, is often neglected in practical applications by adopting the simplifying approximation of complete redistribution on velocity. In this paper, we present an application of the Non-LTE problem for polarized radiation taking such correlations into account through the velocity-space density matrix formalism. We consider a two-level atom with infinitely sharp upper and lower levels, and we derive the corresponding statistical Equilibrium Equations neglecting the contribution of velocity-changing collisions. Coupling such Equations with the radiative transfer Equations for polarized radiation, we derive a set of coupled Equations for the velocity-dependent source function. This set of Equations is then particularized to the case of a plane-parallel atmosphere. The Equations presented in this paper provide a complete and solid description of the physics of pure Doppler redistribution, a phenomenon generally described within the framework of the redistribution matrix formalism. The redistribution matrix corresponding to this problem (generally referred to as R_I) is derived starting from the statistical Equilibrium Equations for the velocity-space density matrix and from the radiative transfer Equations for polarized radiation, thus showing the equivalence of the two approaches.