Jose Ibañez - Academia.edu (original) (raw)

Papers by Jose Ibañez

The Astrophysical Journal, 1997

Page 1. THE ASTROPHYSICAL JOURNAL, 476 : 221»231, 1997 February 10 1997. The American Astronomica... more Page 1. THE ASTROPHYSICAL JOURNAL, 476 : 221»231, 1997 February 10 1997. The American Astronomical Society. All rights reserved. Printed in USA ( NUMERICAL M3 ] 1N GENERAL RELATIVISTIC HYDRODYNAMICS ...

The Astrophysical Journal, 1988

The Astrophysical Journal, 2000

We have studied the relativistic beamed outflow proposed to occur in the collapsar model of gamma... more We have studied the relativistic beamed outflow proposed to occur in the collapsar model of gamma-ray bursts. A jet forms as a consequence of an assumed energy deposition of ∼ 10 50 − 10 51 erg/s within a 30 • cone around the rotation axis of the progenitor star. The generated jet flow is strongly beamed ( < ∼ few degrees) and reaches the surface of the stellar progenitor (r ≈ 3 10 10 cm) intact. At break-out the maximum Lorentz factor of the jet flow is about 33. Simulations have been performed with the GENESIS multi-dimensional relativistic hydrodynamic code.

The Astrophysical Journal, 1998

Page 1. THE ASTROPHYSICAL JOURNAL, 499 : 221»226, 1998 May 20 1998. The American Astronomical Soc... more Page 1. THE ASTROPHYSICAL JOURNAL, 499 : 221»226, 1998 May 20 1998. The American Astronomical Society. All rights reserved. Printed in USA ( SUBPARSEC POLARIMETRIC RADIO OBSERVATIONS OF 3C 120: A ...

The Astrophysical Journal, 2006

We present a general procedure to solve numerically the general relativistic magnetohydrodynamics... more We present a general procedure to solve numerically the general relativistic magnetohydrodynamics (GRMHD) equations within the framework of the 3 + 1 formalism. The work reported here extends our previous investigation in general relativistic hydrodynamics where magnetic fields were not considered. The GRMHD equations are written in conservative form to exploit their hyperbolic character in the solution procedure. All theoretical ingredients necessary to build up highresolution shock-capturing schemes based on the solution of local Riemann problems (i.e. Godunovtype schemes) are described. In particular, we use a renormalized set of regular eigenvectors of the flux Jacobians of the relativistic magnetohydrodynamics equations. In addition, the paper describes a procedure based on the equivalence principle of general relativity that allows the use of Riemann solvers designed for special relativistic magnetohydrodynamics in GRMHD. Our formulation and numerical methodology are assessed by performing various test simulations recently considered by different authors. These include magnetized shock tubes, spherical accretion onto a Schwarzschild black hole, equatorial accretion onto a Kerr black hole, and magnetized thick accretion disks around a black hole prone to the magnetorotational instability.

Journal of Fluid Mechanics, 2005

We discuss the procedure for the exact solution of the Riemann problem in special relativistic ma... more We discuss the procedure for the exact solution of the Riemann problem in special relativistic magnetohydrodynamics (MHD). We consider both initial states leading to a set of only three waves analogous to the ones in relativistic hydrodynamics, as well as generic initial states leading to the full set of seven MHD waves. Because of its generality, the solution presented here could serve as an important test for those numerical codes solving the MHD equations in relativistic regimes. † Recall that a systems of m quasi-linear partial differential equations is said to be hyperbolic if the matrix of coefficients has m real eigenvalues; furthermore, the system is said to be totally or strictly hyperbolic if the eigenvalues are real and also all distinct.

Journal of Computational Physics, 1990

The Glaister (1988) approximate Riemann solver for solving the Euler gasdynamic equations in one ... more The Glaister (1988) approximate Riemann solver for solving the Euler gasdynamic equations in one dimension has been implemented in a Lagrangian hydrodynamical code and applied to spherically symmetric stellar collapse. This method is found to allow the efficient treatment of strong shocks generated by stellar collapse. By comparison with Godunov&amp;#39;s Riemann solver, Glaister&amp;#39;s is 20 percent less time-consuming.

Astrophysics and Space Science, 1987

We have solved the relativistic equations for the radial oscillations of warm cores in neutron st... more We have solved the relativistic equations for the radial oscillations of warm cores in neutron stars by assuming a given law for the interior distribution of temperature-the resulting from the condition of relativistic thermal equilibrium-and focussed on the properties of the fundamental modes.

Astrophysics and Space Science, 1990

We have derived the equations which govern the linear nonadiabatic general-relativistic radial os... more We have derived the equations which govern the linear nonadiabatic general-relativistic radial oscillations. The perturbation produces a heat flux that is coupled with the geometry, through the Einstein field equations of a stellar configuration. The classical limit is recovered. The stability conditions are examined by means of a simplified one-zone model.

The Astrophysical Journal Supplement Series, 2010

We obtain renormalized sets of right and left eigenvectors of the flux vector Jacobians of the re... more We obtain renormalized sets of right and left eigenvectors of the flux vector Jacobians of the relativistic MHD equations, which are regular and span a complete basis in any physical state including degenerate ones. The renormalization procedure relies on the characterization of the degeneracy types in terms of the normal and tangential components of the magnetic field to the wavefront in the fluid rest frame. Proper expressions of the renormalized eigenvectors in conserved variables are obtained through the corresponding matrix transformations. Our work completes previous analysis that present different sets of right eigenvectors for non-degenerate and degenerate states, and can be seen as a relativistic generalization of earlier work performed in classical MHD. Based on the full wave decomposition (FWD) provided by the the renormalized set of eigenvectors in conserved variables, we have also developed a linearized (Roe-type) Riemann solver. Extensive testing against one-and twodimensional standard numerical problems allows us to conclude that our solver is very robust. When compared with a family of simpler solvers that avoid the knowledge of the full characteristic structure of the equations in the computation of the numerical fluxes, our solver turns out to be less diffusive than HLL and HLLC, and comparable in accuracy to the HLLD solver. The amount of operations needed by the FWD solver makes it less efficient computationally than those of the HLL family in one-dimensional problems. However its relative efficiency increases in multidimensional simulations.

We present a general and practical procedure to solve the general relativistic hydrodynamic equat... more We present a general and practical procedure to solve the general relativistic hydrodynamic equations by using any of the special relativistic Riemann solvers recently developed for describing the evolution of special relativistic flows. Our proposal relies on a local change of coordinates in terms of which the spacetime metric is locally Minkowskian and permits accurate numerical calculations of general relativistic hydrodynamics problems using the numerical tools developed for the special relativistic case with negligible computational cost. The feasibility of the method has been confirmed by a number of numerical experiments.

The Journal of Physical Chemistry, 1995

The biionic potential of charged membranes has been studied theoretically. A closed, analytical s... more The biionic potential of charged membranes has been studied theoretically. A closed, analytical solution to the Nernst-Planck equations describing the multiionic transport through the charged membrane and the diffusion boundary layers has been obtained. Several limiting expressions, corresponding to negligible diffusion boundary layer effects, low bathing solution concentration, and low fixed charge concentration, have been discussed, and the experimental conditions which ensure their validity have been analyzed. The results from the model have been finally compared to recent experimental data corresponding to membranes with high charge density, and the influence of the boundary layers has been found to be significant.

ChemInform, 1991

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Spectrochimica Acta Part B: Atomic Spectroscopy, 2010

The importance of thin films in modern high technology products, such as semiconductors, requires... more The importance of thin films in modern high technology products, such as semiconductors, requires fast and non-destructive analysis. A methodology to determine the thickness of single layers with benchtop energy dispersive X-ray fluorescence (EDXRF) instrumentation is described and tested following analytical validation criteria. The experimental work was carried out on gallium nitride thin films epitaxially grown on sapphire substrate. The results of samples with layers in the range from 400 to 1000 nm exhibit a good correlation with the layer thickness determined by optical reflectance. Spectral data obtained using thin layered samples indicate the possibility to precisely evaluate layer thickness from 5 nm, with a low relative standard deviation (RSD b 2%) of the results. In view of the limits of optical reflectance for very thin layer determination, EDXRF analysis offers the potential for the thickness determination of such kind of samples.

Progress in Organic Coatings, 2007

... de la Rosa b , A. Alatorre b , J. Ibañez c , L. Godinez a , S. Gutierrez b and P. Herrasti d ... more ... de la Rosa b , A. Alatorre b , J. Ibañez c , L. Godinez a , S. Gutierrez b and P. Herrasti d , Corresponding Author Contact Information , E-mail The Corresponding Author. a Electrochemistry Department, Centro de investigación y desarrollo tecnológico en electroquímica sc, Pedro ...

Materials Research Bulletin, 1990

By means of X-ray diffraction, electron diffraction and scanning electron microscopy, we have obs... more By means of X-ray diffraction, electron diffraction and scanning electron microscopy, we have observed that for low Pb/Bi ratios lead incorporates into the structure of the so-called 80 K and Ii0 K Bi-superconductors, which normally coexist. However,the 2223 superconducting phase, which shows zero resistance at a temperature as high as 110.7 K , becomes predominant as the sintering time increases.

Materials Letters, 2007

... [5] HF Taylor, Cement. [6] In: C. Peter Hewlett, Editor, Lea's Chemistry of Cement and C... more ... [5] HF Taylor, Cement. [6] In: C. Peter Hewlett, Editor, Lea's Chemistry of Cement and Concrete, Elsevier, Oxford (2004). [7] Second International Symposium on Nanotechnology in Construction, edited by YR De Miguel, A. Porro, PJM Bartos, RILEM, Bagneux (in press). ...

Journal of the American Ceramic Society, 2007

Fly Ash Belite cement (FABC) pastes with and without nanosilica additions have been prepared and ... more Fly Ash Belite cement (FABC) pastes with and without nanosilica additions have been prepared and maintained in sulfate solutions (Na 2 SO 4 0.5 M) for 180 days. The mechanical performance and the changes in microstructure have been monitored at 28, 90 and 180 days by compressive strength, X-ray diffraction (XRD) and 29 Si MAS NMR measurements. We have found that, unexpectedly, and contrary to what happens in Ordinary Portland Cements (OPC), the addition of nanosilica particles induces an initial fall in the compressive strength of the samples. Only in samples maintained for long time (180 days), do the nanosilica addition improve the mechanical properties. Our XRD and 29 Si NMR experiments have revealed that although the nanosilica additions trigger the consumption of Belite phases, this is not always accompanied by formation of longer Calcium-Silicate-Hydrate (C-S-H) gel

Energy & Fuels, 2000

The interest in selective non-catalytic reduction (SNCR) applications has motivated the study of ... more The interest in selective non-catalytic reduction (SNCR) applications has motivated the study of a number of possible configurations for NO x reduction. Among those, the use of urea as selective non-catalytic agent appears to be interesting. 1,2 Urea seems to be suitable because of handling and storage reasons, compared to other selective NO x reduction agents such as ammonia. A number of investigations have been carried out concerning the use of urea in the SNCR process during the past years, both experimentally on different scales, 2-4 and from a kinetic modeling point of view. 3,5 While the effectiveness in the process is well demonstrated experimentally through the different investigations, the kinetic modeling of the process presented some uncertainties mainly due to the behavior of urea under high temperature conditions. Urea has been traditionally considered to be decomposed into NH 3 and HNCO at high temperatures, 6,7 even though other decomposition paths have been proposed. 5,8 The agreement between experiments and calculations using those different mechanisms for urea decomposition is reasonably good, but a reliable determination of urea thermal decomposition was needed. Recent experimental results have appeared concerning the measurement of the reaction rate for the thermal urea decomposition reaction under conditions applicable to SNCR conditions. 9