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RISS 인기검색어
- 검색키워드
- 저자 : M. Mozaffari (검색결과 4 건)
- 무료
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M. Mozaffari,A. A. Atai,N. Mostafa 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.11
This paper presents a computationally efficient and accurate new methodology in the differential quadrature analysis of structural mechanics for flexible membranes ballooning in three dimensions under a negative air pressure differential. The differential quadrature method is employed to discretize the resulting equations in the axial direction as well as for the solution procedure. The weighting coefficients employed are not exclusive, and any accurate and efficient method such as the generalized differential quadrature method may be used to produce the methods weighting coefficients. A second-order paraboloid of revolution is assumed to describe the ballooning shape. This study asserts the accuracy, convergency, and efficiency of the methodology by solving some typical stability, straining analysis membrane problems, and comparing the results with those of the exact solutions and/or those of physical tests.
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Structural and Magnetic Properties of Mechanochemically Prepared Li Ferrite Nanoparticles
M. Haddadi,M. Mozaffari,J. Amighian 한국자기학회 2017 Journal of Magnetics Vol.22 No.2
In this work, lithium ferrite (Li0.5Fe2.5O₄) nanoparticles were prepared via mechanochemical processing and subsequent heat treatment at a relatively low (600 ℃) calcining temperature. The raw materials used were high purity Fe₂O₃ and Li₂CO₃ that were milled for between 2 and 20 h. The milled powders were then calcined at temperatures of 500 and 600 ℃ for 5 h in air. XRD results show that optimum conditions to obtain single phase lithium ferrite nanoparticles with a mean crystallite size of about 23 ㎚, using Scherrer’s formula, are 10 h milling and calcination at 600 ℃. Saturation magnetization and coercivity of the single phase Li ferrite nanoparticles are 44.6 emu/g and 100 Oe respectively, which are both smaller than those of the bulk Li ferrite. The Curie temperature of the single sample was determined by a Faraday balance, which is 578 ℃ and smaller than that of bulk Li ferrite.
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A. A. Atai,M. Mozaffari 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.3
In this paper, the differential quadrature method (DQM) was employed to study nonlinear analysis of annular isotropic membrane in which an attempt was made to explore the applicability and accuracy of DQM for nonlinear analysis of a structural membrane. For this purpose, the large deformation analyses of symmetric circular membranes were investigated. Relaxed strain energy function in conjunction with Green’s strain and perfectly flexible assumptions was utilized for modeling the nonlinear behavior of the membranes. The nonlinear governing equations were discretized at whole domain grid points, and boundary conditions were implemented exactly at boundary grid points. Comparative studies were made between approaches for different boundaries. Convergence of the methodology was demonstrated, and the results were compared with existing solutions of other methods, such as dynamic relaxation. It was shown that accurate results were obtained even when utilizing only a small number of grid points.
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Application of the energy balance method to nonlinear vibrating equations
I. Mehdipour,D.D. Ganji,M. Mozaffari 한국물리학회 2010 Current Applied Physics Vol.10 No.1
In this paper, He’s energy balance method is applied to nonlinear vibrations and oscillations. The method is applied to four nonlinear differential equations. It has indicated that by utilizing He’s energy balance method (HEBM), just one iteration leads us to high accuracy of solutions. It has illustrated that the energy balance methodology is very effective and convenient and does not require linearization or small perturbation. Contrary to the conventional methods, in energy balance method, only one iteration leads to high accuracy of the solutions. The results reveal that the energy balance method is very effective and simple. It is predicted that the energy balance method can be found wide application in engineering problems, as indicated in following examples.
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