The Experts below are selected from a list of 47166 Experts worldwide ranked by ideXlab platform
Taehwan Kim - One of the best experts on this subject based on the ideXlab platform.
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low complexity sorted qr decomposition for mimo systems based on pairwise column symmetrization
Wireless Communications and Networking Conference, 2014Co-Authors: Taehwan KimAbstract:This paper presents a low-complexity preProcessing algorithm for multiple-input multiple-output communication systems. The proposed algorithm performs the sorted QR decomposition through orthogonalizations based on the modified Gram-Schmidt Process, rearranging the column vectors of a real-valued MIMO channel matrix in such a way that the symmetry between the vectors is maintained. By using the symmetry, the computations required for orthogonalizing one of the two adjacent vectors can be eliminated effectively, which significantly reduces the computational complexity. The reduction rate of the computational complexity by the proposed algorithm is 50% for any MIMO configuration.
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low complexity sorted qr decomposition for mimo systems based on pairwise column symmetrization
IEEE Transactions on Wireless Communications, 2014Co-Authors: Taehwan KimAbstract:QR decomposition (QRD) is a preProcessing technique for detecting symbols in multiple-input and multiple-output (MIMO) systems, but the computational complexity is prohibitively high when the systems incorporate a large number of antennas. This paper presents a low-complexity sorted QRD (SQRD) algorithm for MIMO systems. The proposed algorithm performs SQRD through orthogonalizations based on the modified Gram-Schmidt Process, rearranging the column vectors of a real-valued MIMO channel matrix in such a way that the symmetry between the vectors is maintained. By using the symmetry, the computations required for orthogonalizing one of the two adjacent vectors can be eliminated effectively, which significantly reduces the computational complexity. Theoretical analyses show that the proposed algorithm reduces the computational complexity required for SQRD by 50% for any MIMO configurations, when compared to the conventional algorithm. In addition, the memory requirement to store resultant matrices is 50% of that in the conventional one.
Y Kiani - One of the best experts on this subject based on the ideXlab platform.
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rectangular and skew shear buckling of fg cnt reinforced composite skew plates using ritz method
Aerospace Science and Technology, 2018Co-Authors: Y Kiani, M MirzaeiAbstract:Abstract Present research deals with the shear buckling behaviour of composite skew plates reinforced with aligned single walled carbon nanotubes (CNTs). Distribution of CNTs across the thickness of the skew plate are assumed to be uniform or functionally graded. Two different types of shear loads are considered. The case of rectangular shear which produces pure shear and the case of skew shear which results in a combined uniform shear and uniaxial tension/compression. Suitable for moderately thick plates, first order shear deformation plate theory is used to estimate the displacement field of the plate. The equivalent properties of the composite media are obtained by means of the refined rule of mixtures approach which contains efficiency parameters to capture the size dependent properties of the CNTs. With the aid of the Hamilton principle, transformation of the orthogonal coordinate system to an oblique one and the conventional Ritz method whose shape functions are constructed according to the Gram–Schmidt Process, the stability equations of the plate are established and solved for two different types of loading, namely rectangular and skew shear loads. As shown, through introduction of a proper functionally graded pattern, i.e., FG-X pattern, the buckling load of the plate may be increased, significantly.
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analysis of fg cnt reinforced composite conical panel subjected to moving load using ritz method
Thin-walled Structures, 2017Co-Authors: Y KianiAbstract:Abstract Forced vibration response of a conical panel subjected to the action of a moving load is investigated in the current research. Panel is made from a carbon nanotube (CNT) reinforced composite where the CNTs as reinforcements are distributed either uniformly or functionally graded across the panel thickness. Panel is formulated using the first order shear deformation shell theory and the Donnell kinematic assumptions. It is subjected to a moving load whose path and velocity are both arbitrary. The properties of the composite media are estimated according to a refined rule of mixtures approach. The governing equations of motion of the shell are obtained according to the Ritz method where the shape functions are obtained according to the Gram-Schmidt Process. The developed equations with the aid of Ritz method are transformed into time-dependent ordinary differential equations whose solution is traced in time by means of the Newmark time marching scheme. Numerical results are provided to explore the influences of semi-vertex and opening angles of the cone, geometrical parameters and also CNT characteristics of the shell. It is shown that, dynamic deflection of the shell decreases significantly with the introduction of FG-X pattern of CNTs. Furthermore, enrichment of the matrix with more CNTs alleviates the dynamic deflection of the conical shell.
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free vibration of fg cnt reinforced composite spherical shell panels using gram schmidt shape functions
Composite Structures, 2017Co-Authors: Y KianiAbstract:Abstract Free vibration characteristics of carbon nanotube reinforced composite spherical panels are studied in the present research. First order shear deformation shell theory and the Sanders kinematics are considered as the basic assumptions. Distribution of carbon nanotubes (CNTs) across the panel thickness may be uniform or functionally graded. Equivalent properties of the media are estimated according to a modified rule of mixtures approach which consists efficiency parameters to capture the size dependency of the properties. Using Hamilton’s principle and the conventional Ritz formulation, the matrix representation of the equations associated with the free vibration motion is obtained. Shape functions of the Ritz method are obtained according to the Gram-Schmidt Process. The resulting eigenvalue problem is solved to obtain the frequencies as well as mode-shapes of the spherical panel reinforced with CNTs. Convergence and comparison studies are provided to assure the effectiveness and accuracy of the proposed method. Afterwards, parametric studies are given to explore the effects of volume fraction of CNTs, distribution pattern of CNT, boundary conditions and geometric characteristics of the panel. It is shown that, enrichment of the polymeric matrix with more CNT results in higher frequencies. Furthermore, graded pattern of CNT is an influential factor on frequencies.
R Lal - One of the best experts on this subject based on the ideXlab platform.
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boundary characteristic orthogonal polynomials in the study of transverse vibrations of nonhomogeneous rectangular plates with bilinear thickness variation
Shock and Vibration, 2012Co-Authors: R Lal, Y KumarAbstract:The free transverse vibrations of thin nonhomogeneous rectangular plates of variable thickness have been studied using boundary characteristic orthogonal polynomials in the Rayleigh-Ritz method. Gram-Schmidt Process has been used to generate these orthogonal polynomials in two variables. The thickness variation is bidirectional and is the cartesian product of linear variations along two concurrent edges of the plate. The nonhomogeneity of the plate is assumed to arise due to linear variations in Young's modulus and density of the plate material with the in-plane coordinates. Numerical results have been computed for four different combinations of clamped, simply supported and free edges. Effect of the nonhomogeneity and thickness variation with varying values of aspect ratio on the natural frequencies of vibration is illustrated for the first three modes of vibration. Three dimensional mode shapes for all the four boundary conditions have been presented. A comparison of results with those available in the literature has been made.
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Characteristic orthogonal polynomials in the study of transverse vibrations of nonhomogeneous rectangular orthotropic plates of bilinearly varying thickness
Meccanica, 2012Co-Authors: R Lal, Kumar YajuvindraAbstract:Effect of nonhomogeneity on the vibrational characteristics of thin orthotropic rectangular plates of bilinearly varying thickness has been studied using boundary characteristic orthogonal polynomials in the Rayleigh-Ritz method. The thickness variation is taken as the Cartesian product of linear variations along two concurrent edges of the plate. The orthogonal polynomials in two variables are generated using the Gram-Schmidt Process. The nonhomogeneity of the plate material is assumed to arise due to linear variations in Young’s moduli, shear modulus and density of the plate with the in-plane coordinates. Numerical results have been computed for four different combinations of clamped, simply supported and free edges. Effect of thickness variation together with varying values of aspect ratio and nonhomogeneity on the natural frequencies is illustrated for the first three modes of vibration. Three dimensional mode shapes have been presented. Comparison has been made with the known results.
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transverse vibrations of nonhomogeneous rectangular plates of uniform thickness using boundary characteristic orthogonal polynomials
2010Co-Authors: R Lal, Y KumarAbstract:Analysis and numerical results for the free transverse vibrations of uniform nonhomogeneous rectangular plates have been presented using boundary characteristic orthogonal polynomials in the Rayleigh-Ritz method on the basis of classical plate theory for four different combinations of clamped, simply supported and free edges. Gram-Schmidt Process has been used to generate these orthogonal polynomials satisfying essential boundary conditions. The nonhomogeneity of the plate is assumed to arise due to linear variations in Young’s modulus and density of the plate material with the space coordinates. Effect of the nonhomogeneity with varying values of aspect ratio on natural frequencies is illustrated for the first three modes of vibration. Three dimensional mode shapes have been presented for all the four boundary conditions. A comparison of results with those available in the literature shows a close agreement.
Zhaoye Qin - One of the best experts on this subject based on the ideXlab platform.
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a unified solution for vibration analysis of laminated functionally graded shallow shells reinforced by graphene with general boundary conditions
International Journal of Mechanical Sciences, 2020Co-Authors: Zhaoye Qin, Shengnan Zhao, Xuejia Pang, Babak Safaei, Fulei ChuAbstract:Abstract In this paper, a unified method is developed to analyze free vibrations of laminated functionally graded shallow shells reinforced by graphene platelets (GPLs) under arbitrary boundary conditions is proposed. General equations are obtained by the first-order shear deformation theory (FSDT) together with artificial spring technique. By adopting orthogonal polynomials via a Gram–Schmidt Process to expand shell displacement fields, Rayleigh–Ritz method is applied in deriving the equations of motion for functionally graded GPL reinforced composite (FG-GPLRC) shallow shells. The accuracy of proposed method is verified through comparing the present results with those from literature. free vibration behaviors of FG-GPLRC shallow shells are studied. The effects of boundary conditions, GPL weight fractions, layer number, and geometric parameters on natural frequencies are investigated. Parametric studies show that variation trends of the natural frequencies of FG-GPLRC shallow shells along with GPL layer number, weight fraction, and geometric properties are similar under different boundary conditions in most cases. However, the frequency values and variation rates are highly dependent on the stiffness values of boundary springs.
Kumar Yajuvindra - One of the best experts on this subject based on the ideXlab platform.
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Characteristic orthogonal polynomials in the study of transverse vibrations of nonhomogeneous rectangular orthotropic plates of bilinearly varying thickness
Meccanica, 2012Co-Authors: R Lal, Kumar YajuvindraAbstract:Effect of nonhomogeneity on the vibrational characteristics of thin orthotropic rectangular plates of bilinearly varying thickness has been studied using boundary characteristic orthogonal polynomials in the Rayleigh-Ritz method. The thickness variation is taken as the Cartesian product of linear variations along two concurrent edges of the plate. The orthogonal polynomials in two variables are generated using the Gram-Schmidt Process. The nonhomogeneity of the plate material is assumed to arise due to linear variations in Young’s moduli, shear modulus and density of the plate with the in-plane coordinates. Numerical results have been computed for four different combinations of clamped, simply supported and free edges. Effect of thickness variation together with varying values of aspect ratio and nonhomogeneity on the natural frequencies is illustrated for the first three modes of vibration. Three dimensional mode shapes have been presented. Comparison has been made with the known results.
