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Sandra Martínez

Publications and source records attributed to Sandra Martínez.

4 recordsLinked to original sources
arXiv2018

Superresolution method for data deconvolution by superposition of point sources

In this work we present a new algorithm for data deconvolution that allows the retrieval of the target function with super-resolution with a simple approach that after a precis e measurement of the instrument response function (IRF), the measured data are fit by a superposition of point sources (SUPPOSe) of equal intensity. In this manner only the positions of the sources need to be determined by an algorithm that minimizes the norm of the difference between the measured data and the convolution of the superposed point sources with the IRF. An upper bound for the uncertainty in the position of the sources was derived and two very different experimental situations were used for the test (an optical spectrum and fluorescent microscopy images) showing excellent reconstructions and agreement with the predicted uncertainties, achieving λ/10 resolution for the microscope and a fivefold improvement in the spectral resolution for the spectrometer. The method also provides a way to determine the optimum number of sources to be used for the fit.

cs.CV↗
arXiv2018

Finite element approximation for the fractional eigenvalue problem

The purpose of this work is to study a finite element method for finding solutions to the eigenvalue problem for the fractional Laplacian. We prove that the discrete eigenvalue problem converges to the continuous one and we show the order of such convergence. Finally, we perform some numerical experiments and compare our results with previous work by other authors.

math.NA↗
arXiv2009

A Free boundary problem for the $p(x)$- Laplacian

We consider the optimization problem of minimizing $\int_Ω|\nabla u|^{p(x)}+ λχ_{\{u>0\}} dx$ in the class of functions $W^{1,p(\cdot)}(Ω)$ with $u-ϕ_0\in W_0^{1,p(\cdot)}(Ω)$, for a given $ϕ_0\geq 0$ and bounded. $W^{1,p(\cdot)}(Ω)$ is the class of weakly differentiable functions with $\int_Ω|\nabla u|^{p(x)} dx<\infty$. We prove that every solution $u$ is locally Lipschitz continuous, that it is a solution to a free boundary problem and that the free boundary, $Ω\cap\partial\{u>0\}$, is a regular surface.

math.AP↗