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RISS 인기검색어
- 검색키워드
- 저자 : Esmaeilzadeh Khadem, S. (검색결과 3 건)
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Radial breathing mode frequencies of carbon nanotubes for determination of their diameters
Sedigheh Basirjafari,Siamak Esmaeilzadeh Khadem,Rasoul Malekfar 한국물리학회 2013 Current Applied Physics Vol.13 No.3
In this paper, exact formulas are obtained for the radial breathing mode (RBM) frequencies of triple-walled carbon nanotubes (TWCNTs) using symbolic package in MAPLE software. For this purpose, TWCNT is considered as triple concentric elastic thin cylindrical shells, which are coupled through van der Waals (vdW) forces between two adjacent tubes. LennardeJones potential is used to calculate the vdW forces between adjacent tubes. Then, explicit formulas for RBM frequencies of single-walled (SW), and doublewalled (DW) CNTs have been deduced from TWCNT formulas that show an excellent agreement with the available experimental results and the other theoretical model results. The advantage of this analytical approach is that the elastic shell model considers all degrees of freedom in the vibrational analysis of CNTs. To demonstrate the accuracy of this work, the RBM frequencies of different multi-walled carbon nanotubes (MWCNTs) are compared with the available experimental or atomistic results with relative errors of less than 1.5%. To illustrate the application of this approach, the diameters of DWCNTs are obtained from their RBM frequencies which show an excellent agreement with the available experimental results. Also, this approach can be used to determine the diameters of the TWCNTs and MWCNTs. The influence of changing the geometrical and mechanical parameters of a TWCNT on its RBM frequencies has been investigated, too.
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Eipakchi, H.R.,Rahimi, G.H.,Esmaeilzadeh Khadem, S. Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.16 No.6
In this paper a thick cylindrical shell with varying thickness which is subjected to static non-uniform internal pressure is analyzed. At first, equilibrium equations of the shell have been derived by the energy principle and by considering the first order theory of Mirsky-Herrmann which includes transverse shear deformation. Then the governing equations which are, a system of differential equations with varying coefficients have been solved analytically with the boundary layer technique of the perturbation theory. In spite of complexity of modeling the conditions near the boundaries, the method of this paper is very capable of providing a closed form solution even near the boundaries. Displacement predictions are in a good agreement with the calculated finite elements and other analytical results. The convergence of solution is very fast and the amount of calculations is less than the Frobenius method.
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Stability analysis of a parametrically excited functionally graded piezoelectric, MEM system
Saber Azizi,Mohammad-Reza Ghazavi,Siamak Esmaeilzadeh Khadem,Jie Yang,Ghader Rezazadeh 한국물리학회 2012 Current Applied Physics Vol.12 No.2
In this paper the mechanical behavior of a parametrically actuated functionally graded piezoelectric (FGP) clampedeclamped micro-beam is investigated. The micro-beam is supposed to be a composite material with silicon and piezoelectric base. The mechanical properties of the structure, including elasticity modulus, density, and piezoelectricity coefficient are supposed to vary along the height of the micro-beam with an exponential functionality. It is supposed that the FGP clampedeclamped microbeam is actuated with a combination of direct and alternative electric potential difference. Application of DC and AC actuation voltage leads in a constant and a time-varying axial force. The governing differential equation of the motion is derived using Hamiltonian principle and discretized using expansion theorem with the corresponding shape functions of a clampedeclamped beam. The discretized system is governed by Mathieu equation which’s stability is investigated using Floquet theory for single degree of freedom systems and verified using multiple time scales of perturbation technique.
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