Artículos FC IFIS
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- ItemA Jacobi–spectral framework for the heat equation with Dirichlet boundary conditions(2026-03-09)We developed a Jacobi–spectral framework for the heat equation in a spherical domain under axial symmetry and Dirichlet boundary conditions. The angular part of the Laplacian was realized as a Jacobi Sturm–Liouville operator on a weighted space, enabling the Jacobi transform to diagonalize the angular component and project the partial diferential equation (PDE) onto a sequence of decoupled radial problems. Each projected equation reduced to a Euler-type radial ordinary diferential equation (ODE) driven by the corresponding Jacobi coefficient of the source term. These modal equations were solved in terms of spherical-Bessel eigenfunctions and radial Green kernels, yielding explicit Duhamel-type formulas for the time-dependent coefficients and establishing convergence in the weighted space. The Legendre case recovered the classical axisymmetric model, while general Jacobi parameters provided a unified extension of this setting. A central result was the demonstration of a rigorous equivalence between the Jacobi–spectral representation and the classical separation-of-variables solution written in spherical harmonics and spherical-Bessel modes. The proposed framework clarified the angular–radial coupling in spherical geometries and connected naturally with modern Jacobi and ultraspherical spectral methods.
- ItemHydrodynamic Stydy of Lake Enriquillo in Dominican Republic(2017)This study presents an analysis of the hydrochemical characteristics of Lake Enriquillo in the southwestern region of the Dominican Republic. This lake is hypersaline and endorheic. The climatology of the region is influenced by the Caribbean Regulator Climate Centers (CRCCs). Due to the endorheic nature of the basin, evaporation plays an extremely important role in its dynamics [1]. During the study period, in November 2002, the water level of Lake Enriquillo was 42 m below sea level (BLS), and the salinity level was 104.2‰. By 2014, the water level of the lake rose to 29 m below sea level, and the salinity decreased to 23.4‰, as a result of the high cyclonic activity in the Caribbean region.
- ItemThermoluminescent response and kinetic parameters of Eu3+ -doped LiF crystals exposed to X-rays.(2017-02)In the present work pure and Eu3+-doped LiF crystals were synthesized through co-precipitation method and the effect of Eu3+ concentration on the thermoluminescent (TL) response is reported. A cubic crystalline phase was determined by XRD for all synthesized samples. The photoluminescence spectra as well as UV–vis absorbance were also analyzed and four emissions bands centered at 592 nm (5D0 → 7F1), 614 nm (5D0 → 7F2), 652 nm (5D0 → 7F3) and 698 nm (5D0 → 7F4) have been observed. The TL response to X-ray irradiation was studied for an exposition of 43 R during a total time of 52 s. The presence of Eu3+ in the samples enhanced the TL signal, due to the Eu3+ ions that are incorporated into the LiF crystalline lattice which promotes the formation of defects in the unit cell. The kinetic parameters (E, b, s) were calculated using the glow-curve shape method. Energy traps around E=1 eV and frequency factors on the order s=108 s−1 were obtained on average, regardless of the Eu3+ concentration. The host of LiF showed the higher characteristic energies and frequency factors, respectively. The 1.0 mol% Eu3+-doped sample was found to have a sensitivity 5 times greater than the host of LiF. The good TL sensitivity to X- ray exhibited by the Eu3+-doped LiF crystals synthesized in this work, suggests that this material should be further studied with respect to other characteristics before being used as a radiation dosimeter.
- ItemEffect of Synthesis temperature on morphological and luminescent properties of lithium fluoride crystals(2017-08-08)A generalization of the site-percolation problem, in which pairs of neighbor sites (site dimers) and bonds are independently and randomly occupied on a triangular lattice, has been studied by means of numerical simulations. Motivated by considerations of cluster connectivity, two distinct schemes (denoted as $S{\cap}^{}B$ and $S{\cup}^{}B$ ) have been considered. In $S{\cap}^{}B$ ($S{\cup}^{}B$ ), two points are said to be connected if a sequence of occupied sites and (or) bonds joins them. Numerical data, supplemented by analysis using finite-size scaling theory, were used to determine (i) the complete phase diagram of the system (phase boundary between the percolating and nonpercolating regions), and (ii) the values of the critical exponents (and universality) characterizing the phase transition occurring in the system.
- ItemDimer site-bond percolation on a triangular lattice(2017-02-06)A generalization of the site-percolation problem, in which pairs of neighbor sites (site dimers) and bonds are independently and randomly occupied on a triangular lattice, has been studied by means of numerical simulations. Motivated by considerations of cluster connectivity, two distinct schemes (denoted as $S{\cap}^{}B$ and $S{\cup}^{}B$ ) have been considered. In $S{\cap}^{}B$ ($S{\cup}^{}B$ ), two points are said to be connected if a sequence of occupied sites and (or) bonds joins them. Numerical data, supplemented by analysis using finite-size scaling theory, were used to determine (i) the complete phase diagram of the system (phase boundary between the percolating and nonpercolating regions), and (ii) the values of the critical exponents (and universality) characterizing the phase transition occurring in the system.