The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Maria Elena Valcher - One of the best experts on this subject based on the ideXlab platform.
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CDC - Zero patterns and dominant modes of the state evolutions of autonomous continuous-time positive systems
2007 46th IEEE Conference on Decision and Control, 2007Co-Authors: Paolo Santesso, Maria Elena ValcherAbstract:In this paper, the zero pattern properties and the asymptotic evolution of the trajectories of an autonomous continuous-time positive system are investigated. To this end, a normal form for the Exponential of a Metzler Matrix is provided, and the concept of "echelon basis" is introduced. By making use of these two ingredients, the dominant mode of each single block appearing in the normal form of the Exponential Matrix is determined. As a result, the zero pattern as well as the dominant mode of every state evolution, depending on the zero pattern of the initial state, can be easily inferred.
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On the zero pattern properties and asymptotic behavior of continuous-time positive system trajectories
Linear Algebra and its Applications, 2007Co-Authors: Paolo Santesso, Maria Elena ValcherAbstract:Abstract In this paper, the zero pattern properties and the asymptotic evolution of the trajectories of a continuous-time positive system are investigated. To this end, we need to introduce some new tools and to derive some new results, within the broad research area of nonnegative Matrix theory, which enable use to explore the zero pattern and the elementary modes of the Exponential of a Metzler Matrix. Specifically, a normal form for the Exponential of a Metzler Matrix is provided, and the concept of echelon basis (consisting of eigenvectors and generalized eigenvectors of the Metzler Matrix) is introduced. By making use of these two ingredients, a detailed result about the dominant mode of each single block appearing in the normal form of the Exponential Matrix is provided. This allows to obtain a “modal decomposition” of the Exponential Matrix, emphasizing the column dominant modes. As a result, the zero pattern as well as the asymptotic behavior of every free state evolution, depending on the zero pattern of the initial state, can be easily determined.
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Zero patterns and dominant modes of the state evolutions of autonomous continuous-time positive systems
2007 46th IEEE Conference on Decision and Control, 2007Co-Authors: Paolo Santesso, Maria Elena ValcherAbstract:In this paper, the zero pattern properties and the asymptotic evolution of the trajectories of an autonomous continuous-time positive system are investigated. To this end, a normal form for the Exponential of a Metzler Matrix is provided, and the concept of "echelon basis" is introduced. By making use of these two ingredients, the dominant mode of each single block appearing in the normal form of the Exponential Matrix is determined. As a result, the zero pattern as well as the dominant mode of every state evolution, depending on the zero pattern of the initial state, can be easily inferred.
N.g. Alexopoulos - One of the best experts on this subject based on the ideXlab platform.
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Surface wave modes of printed circuits on ferrite substrates
IEEE Transactions on Microwave Theory and Techniques, 1992Co-Authors: H.-y. Yang, J.a. Castaneda, N.g. AlexopoulosAbstract:Surface waves due to a current source on a grounded ferrite slab are investigated. Electromagnetic fields of the structure are in terms of a continuous plane wave spectrum. The spectrum of each field component is obtained numerically through the Exponential-Matrix method. The surface waves of the structure are extracted from the continuous spectrum by using the residue theorem and the method of steepest descent. Two types of surface waves are found and their properties are described. The surface wave modes found include dynamic surface wave modes which are closely related to the surface waves of a grounded dielectric slab, and magnetostatic surface wave modes which are related to the solution of Laplace's equation for the magnetic potential.
H.-y. Yang - One of the best experts on this subject based on the ideXlab platform.
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Surface wave modes of printed circuits on ferrite substrates
IEEE Transactions on Microwave Theory and Techniques, 1992Co-Authors: H.-y. Yang, J.a. Castaneda, N.g. AlexopoulosAbstract:Surface waves due to a current source on a grounded ferrite slab are investigated. Electromagnetic fields of the structure are in terms of a continuous plane wave spectrum. The spectrum of each field component is obtained numerically through the Exponential-Matrix method. The surface waves of the structure are extracted from the continuous spectrum by using the residue theorem and the method of steepest descent. Two types of surface waves are found and their properties are described. The surface wave modes found include dynamic surface wave modes which are closely related to the surface waves of a grounded dielectric slab, and magnetostatic surface wave modes which are related to the solution of Laplace's equation for the magnetic potential.
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Basic properties of microstrip circuit elements on nonreciprocal substrate-superstrate structures
IEEE International Digest on Microwave Symposium, 1990Co-Authors: I.y. Hsia, H.-y. Yang, N.g. AlexopoulosAbstract:A spectral domain-Exponential Matrix method is developed for evaluating the dyadic Green's function for generalized anisotropic substrate-superstrate structures. The method of moments is used to obtain the basic dispersive characteristics of microstrip and inverted microstrip circuits elements on such structures. Results are presented for the propagation constant and characteristic impedance of microstrip elements on generalized anisotropic layers. The investigation of microstrip properties on a biased ferrite-semiconductor interface is emphasized. The model accounts for arbitrarily oriented DC-bias magnetic fields. The phenomenon of forward and backward wave propagation on this type of nonreciprocal structure is highlighted.
Paolo Santesso - One of the best experts on this subject based on the ideXlab platform.
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CDC - Zero patterns and dominant modes of the state evolutions of autonomous continuous-time positive systems
2007 46th IEEE Conference on Decision and Control, 2007Co-Authors: Paolo Santesso, Maria Elena ValcherAbstract:In this paper, the zero pattern properties and the asymptotic evolution of the trajectories of an autonomous continuous-time positive system are investigated. To this end, a normal form for the Exponential of a Metzler Matrix is provided, and the concept of "echelon basis" is introduced. By making use of these two ingredients, the dominant mode of each single block appearing in the normal form of the Exponential Matrix is determined. As a result, the zero pattern as well as the dominant mode of every state evolution, depending on the zero pattern of the initial state, can be easily inferred.
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On the zero pattern properties and asymptotic behavior of continuous-time positive system trajectories
Linear Algebra and its Applications, 2007Co-Authors: Paolo Santesso, Maria Elena ValcherAbstract:Abstract In this paper, the zero pattern properties and the asymptotic evolution of the trajectories of a continuous-time positive system are investigated. To this end, we need to introduce some new tools and to derive some new results, within the broad research area of nonnegative Matrix theory, which enable use to explore the zero pattern and the elementary modes of the Exponential of a Metzler Matrix. Specifically, a normal form for the Exponential of a Metzler Matrix is provided, and the concept of echelon basis (consisting of eigenvectors and generalized eigenvectors of the Metzler Matrix) is introduced. By making use of these two ingredients, a detailed result about the dominant mode of each single block appearing in the normal form of the Exponential Matrix is provided. This allows to obtain a “modal decomposition” of the Exponential Matrix, emphasizing the column dominant modes. As a result, the zero pattern as well as the asymptotic behavior of every free state evolution, depending on the zero pattern of the initial state, can be easily determined.
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Zero patterns and dominant modes of the state evolutions of autonomous continuous-time positive systems
2007 46th IEEE Conference on Decision and Control, 2007Co-Authors: Paolo Santesso, Maria Elena ValcherAbstract:In this paper, the zero pattern properties and the asymptotic evolution of the trajectories of an autonomous continuous-time positive system are investigated. To this end, a normal form for the Exponential of a Metzler Matrix is provided, and the concept of "echelon basis" is introduced. By making use of these two ingredients, the dominant mode of each single block appearing in the normal form of the Exponential Matrix is determined. As a result, the zero pattern as well as the dominant mode of every state evolution, depending on the zero pattern of the initial state, can be easily inferred.
Salvatore Brischetto - One of the best experts on this subject based on the ideXlab platform.
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Convergence investigation for the Exponential Matrix and mathematical layers in the static analysis of multilayered composite structures
Journal of Composites Science, 2017Co-Authors: Salvatore Brischetto, Roberto TorreAbstract:The exact three-dimensional analysis of a large group of geometries is accomplished here using the same formulation written in orthogonal mixed curvilinear coordinates. This solution is valid for plates, cylindrical shells, cylinders and spherical shells. It does not need specialized equations for each proposed geometry. It makes use of a formulation that is valid for spherical shells and automatically degenerates in the simpler geometries. Second order differential equations are reduced of an order redoubling the number of variables, and then they are solved via the Exponential Matrix method. Coefficients of equations vary through the thickness when shells are considered. M mathematical layers must be introduced into each physical layer to approximate the curvature. The correlation between M and the order of expansion N for the Exponential Matrix is analyzed in this paper in order to find their opportune combined values to obtain the exact results. As their effects may depend on different parameters, several geometries, lamination sequences, thickness ratios and imposed half-wave numbers are taken into consideration.
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Exponential Matrix method for the solution of exact 3D equilibrium equations for free vibrations of functionally graded plates and shells
Journal of Sandwich Structures and Materials, 2017Co-Authors: Salvatore BrischettoAbstract:The present paper analyzes the convergence of the Exponential Matrix method in the solution of three-dimensional equilibrium equations for the free vibration analysis of functionally graded materia...
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convergence analysis of the Exponential Matrix method for the solution of 3d equilibrium equations for free vibration analysis of plates and shells
Composites Part B-engineering, 2016Co-Authors: Salvatore BrischettoAbstract:Abstract The three-dimensional equilibrium dynamic equations written in general curvilinear orthogonal coordinates allow the free vibration analysis of one-layered and multilayered plates and shells. The system of second order differential equations is transformed into a system of first order differential equations. Such a system is exactly solved using the Exponential Matrix method which is calculated by means of an expansion with a very fast convergence ratio. In the case of plate geometries, the differential equations have constant coefficients. The differential equations have variable coefficients in the case of shell geometries because of the curvature terms which depend on the thickness coordinate z. In shell cases, several mathematical layers must be introduced to approximate the curvature terms and to obtain differential equations with constant coefficients. The present work investigates the convergence of the proposed method related to the order N used for the expansion of the Exponential Matrix and to the number of mathematical layers M used for the solution of shell equations. Both N and M values are analyzed for different geometries, thickness ratios, materials, lamination sequences, imposed half-wave numbers, frequency orders and vibration modes.
