Encontrados 28 documentos, a visualizar página 1 de 3
Stationary quasivariational inequalities with gradient constraint and nonhomoge...
Azevedo, Assis; Miranda, Fernando; Santos, LisaPublicado em "From particle systems to partial differential equations. Part 2. (Springer proceedings in mathematics & statistics, vol. 75). ISBN 978-3-642-54270-1 ; We study existence of solution of stationary uasivariational inequalities with gradient constraint and nonhomogeneous boundary condition of Neumann or Dirichlet type. Through two different approaches, one making use of a fixed point theorem and th...
Modified quaternion Newton methods
Falcão, M. I.; Miranda, FernandoWe revisit the quaternion Newton method for computing roots of a class of quaternion valued functions and propose modified algorithms for finding multiple roots of simple polynomials. We illustrate the performance of these new methods by presenting several numerical experiments.
Optimal Cut-Off Value for Homeostasis Model Assessment (HOMA) Index of Insulin-...
Timóteo, Ana Teresa; Serviço de Cardiologia. Hospital de Santa Marta. Lisboa PortugalIntroduction: Insulin resistance is the pathophysiological key to explain metabolic syndrome. Although clearly useful, the Homeostasis Model Assessment index (an insulin resistance measurement) hasn’t been systematically applied in clinical practice. One of the main reasons is the discrepancy in cut-off values reported in different populations. We sought to evaluate in a Portuguese population the ideal cut-off ...
Variational and quasivariational inequalities with first order constraint
Azevedo, Assis; Miranda, Fernando; Santos, LisaWe study the existence of solutions of stationary variational and quasivariational inequalities with curl constraint, Neumann type boundary condition and a p-curl type operator. These problems are studied in bounded, not necessarily simply connected domains, with a special geometry, and the functional framework is the space of divergence-free functions with curl in $\boldsymbol L^p$ and null tangential or no...
Effect of viscosity of a liquid membrane containing oleyl alcohol on the pertra...
Blahušiak, M.; Marták, J.; Miranda, Fernando; Schlosser, Š.; Teixeira, J. A.Solvent formulation is important in the optimization of the mass-transfer through supported liquid membranes (SLM) in pertraction and membrane extraction. Oleyl alcohol (OA) is frequently used as the solvent or diluent in the extraction of carboxylic acids. A disadvantage of OA is its relatively high viscosity of 28.32 mPa s at 25°C. This can be decreased by the application of a less viscous OA diluent, e.g. do...
Importância da pesca lúdica e desportiva no Nordeste Transmontano
Miranda, Fernando; Teixeira, AmilcarNo ano de 2012, foi feita uma caraterização da pesca lúdica e desportiva do Nordeste Transmontano, baseada num universo de 120 inquéritos realizados a pescadores entrevistados maioritariamente nas bacias hidrográficas dos rios Sabor e Tua. Foram obtidas informações relevantes, como o perfil, preferência pelo tipo de massa hídrica, frequências de viagens, motivação, gastos despendidos, interesse em competições, ...
On a p-curl system arising in electromagnetism
Miranda, Fernando; Rodrigues, José Francisco; Santos, LisaWe prove existence of solution of a $p$-curl type evolutionary system arising in electromagnetism with a power nonlinearity of order $p$, $1<p<\infty$, assuming natural tangential boundary conditions. We consider also the asymptotic behaviour in the power obtaining, when $p$ tends to infinity, a variational inequality with a curl constraint. We also discuss the existence, uniqueness and continuous dependence o...
A nonlinear hyperbolic Maxwell system using measure-valued functions
Miranda, Fernando; Santos, LisaWe consider a modified antenna's problem with power-type constitutive laws. This consists in a new nonlinear hyperbolic system that extends a Duvaut-Lions model. Using the Galerkin approximation, properties of the natural functional spaces, and exploring the $L^p$-$L^{p'}$ duality, we prove the existence of solutions, in a generalized sense, passing to the limit in a family of approximated problems and using me...
A class of electromagnetic p-curl systems : blow-up and finite time extinction
Antontsev, Stanislav; Miranda, Fernando; Santos, LisaWe study a class of $p$-curl systems arising in electromagnetism, for $\frac65 < p < \infty$, with nonlinear source or sink terms. Denoting by $\boldsymbol h$ the magnetic field, the source terms considered are of the form $\boldsymbol h\left(\int_\Omega; \boldsymbol h; ^2\right)^{\frac{\sigma-2}{2}}$, with $\sigma\geq1$. Existence of local or global solutions is proved depending on values of $\sigma$ and $p$....
Multiplicador de Lagrange num problema com restrição não constante no gradiente
Azevedo, Assis; Miranda, Fernando; Santos, LisaProva-se a existência de solução, num sentido generalizado, de um problema com um multiplicador de Lagrange, para uma restrição arbitrária no gradiente e condição de Dirichlet homogénea na fronteira. Prova-se ainda a equivalência deste problema com a correspondente inequação variacional elíptica. A abordagem utilizada para provar o resultado de existência baseia-se na utilização de soluções de uma família aprox...
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