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Konečné prvky v elektromagnetismu kompatibilní s De Rhamovým diagramem
Rybář, Vojtěch ; Doležel, Ivo (advisor) ; Vejchodský, Tomáš (referee)
Title: Finite elements for electromagnetics compatible with de Rham di- agram Author: Vojtěch Rybář Department: Department of Numerical Mathematics Supervisor: prof. Ing. Ivo Doležel, CSc. Abstract: The present work is devoted to the lowest-order finite elements for solving time-harmonic Maxwell's equations in two dimensions. Suc- cessful approximation of these equations requires the finite element spaces to be compatible with the de Rham diagram. However, the most often used basis functions (the Whitney functions) do not comply with this diagram. Therefore, we construct compatible bases and study their prop- erties. Since the construction is not unique, we investigate the influence of the particular choice on the conditioning of the corresponding finite element matrices. Finally, we utilize the special structure of the stiffness matrices, propose a few iterative schemes, and compare their convergence. Keywords: Maxwell's equations, edge finite element, de Rham diagram, finite element basis 1
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Spectral methods for reaction-diffusion systems
Rybář, Vojtěch
Although spectral methods proved to be numerical methods that can significantly speed up the computation of solutions of systems of reaction-diffusion equations, finite difference and finite element methods still prevail as the most widespread methods. This contribution offers comparison of the performance of the Fourier spectral method with finite element method for reaction-diffusion system modeling the generation of pigment patterns on the coat of the leopard.
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On the number of stationary patterns in reaction-diffusion systems
Rybář, Vojtěch ; Vejchodský, Tomáš
We study systems of two nonlinear reaction-diffusion partial differential equations undergoing diffusion driven instability. Such systems may have spatially inhomogeneous stationary solutions called Turing patterns. These solutions are typically non-unique and it is not clear how many of them exists. Since there are no analytical results available, we look for the number of distinct stationary solutions numerically. As a typical example, we investigate the reaction-diffusion systém designed to model coat patterns in leopard and jaguar.
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Irregularity of turing patterns in the Thomas model with a unilateral term
Rybář, Vojtěch ; Vejchodský, Tomáš
In this contribution we add a unilateral term to the Thomas model and investigate the resulting Turing patterns. We show that the unilateral term yields nonsymmetric and irregular patterns. This contrasts with the approximately symmetric and regular patterns of the classical Thomas model. In addition, the unilateral term yields Turing patterns even for smaller ratio of diffusion constants. These conclusions accord with the recent findings about the influence of the unilateral term in a model for mammalian coat patterns. This indicates that the observed effects of the unilateral term are general and apply to a variety of systems.
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