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Integro-differential IBVP versus differential IBVP: stability analysis
Branco, J. R.; Ferreira, J. A.The aim of this paper is the qualitative analysis from theoretical and numerical points of view of an integro-di erential initial boundary value problem where the reaction term presents a certain memory e ect. Stability results are established in both cases. As in certain cases the integro-di erential initial boundary value problem can be seen as a di erential initial boundary value problem, the results obtaine...
On the stability of a class of splitting methods for integro-differential equat...
Araújo, A.; Branco, J. R.; Ferreira, J. A.The classical convection-diffusion-reaction equation has the unphysical property that if a sudden change in the dependent variable is made at any point, it will be felt instantly everywhere. This phenomena violate the principle of causality. Over the years, several authors have proposed modifications in an effort to overcome the propagation speed defect. The purpose of this paper is to study, from analytical an...
Non-Fickian delay reaction-diffusion equations: theoretical and numerical study
Ferreira, J. A.; Branco, J. R.; Silva, P. daThe Fisher’s equation is established combining the Fick’s law for the flux and the mass conservation law. Assuming that the reaction term depends on the solution at some past time, a delay parameter is introduced and the delay Fisher’s equation is obtained. Modifying the Fick’s law for the flux considering a temporal memory term, integro-differential equations of Volterra type were introduced in the literature....
Characterization of magnetron co-sputtered W-doped C-based films
Silva, C. W. Moura e; Branco, J. R. T.; Cavaleiro, A.In this paper, W-doped C-based coatings were deposited on steel and silicon substrates by RF magnetron sputtering, using W and C targets, varying the cathode power applied to the W target and the substrate bias. The chemical composition was varied by placing the substrates in a row facing the C and W targets. W content in the films increased from 1 to 2 at.% over the C target to ~ 73 at.% over the W target. The...
A singular perturbation of the heat equation with memory
Branco, J. R.; Ferreira, J. A.In this paper we consider a hyperbolic equation, with a memory term in time, which can be seen as a singular perturbation of the heat equation with memory. The qualitative properties of the solutions of the initial boundary value problems associated with both equations are studied. We propose numerical methods for the hyperbolic and parabolic models and their stability properties are analysed. Finally, we inclu...
Avaliação da influência dos parâmetros de spray a plasma sobre a cristalinidade...
Silva,S. N. da; Branco,J. R. T.; Pereira,M. de M.Os parâmetros de spray a plasma influenciam na cristalinidade do recobrimento na medida em que determinadas condições de operação alteram a entalpia da tocha, produzindo variado grau de fusão das partículas do pó, além em de poder ainda causar modificações nas condições de resfriamento e solidificação. Neste trabalho, os efeitos dos principais parâmetros - corrente elétrica de ionização do plasma, proporção da ...
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