One dimensional description of the gravitational perturbation in a Kerr background

The perturbation equation in a Kerr background is written as a coupled system of one dimensional equations for the different modes in the time domain. Numerical simulations show that the dominant mode in the gravitational response is the one corresponding to the mode of the initial perturbation, allowing us to conjecture that the coupling among the modes has a weak influence in our system of equations. We conclude that by neglecting the coupling terms it can be obtained a one dimensional harmonic equation which indeed describes with good accuracy the gravitational response from the Kerr black hole with low spin, while only few couplings are necessary to describe a high spin one. This result may help to understand the structure of test fields in a Kerr background and even to generate accurate waveforms for various cases in an efficient manner.Comment: 14 pages, 3 figure

Geometry optimization of a francis turbine for efficiency, cavitation and erosion using computational fluid dynamics

In recent years, the application of numerical computational models based on computational fluid dynamics (CFD) to industrial problems has been increasing; Today CFD is used to optimize and develop equipment and processes in many types of industry including the energy industry. The main advantage of the solutions with CFD is in the obtaining of the operating conditions and the analysis of internal and external flows, which experimentally is very difficult and expensive to achieve. This document presents the results of the research project of a master's degree in engineering with an emphasis in mechanical engineering where the geometry that minimizes the erosive wear by hard particle and cavitation for the different operating regimes maintaining the efficiency of the 10MW Francis turbine of the Amaime hydroelectric plant was obtained. To achieve this, a Simplified Virtual Laboratory (SVL) methodology was implemented, consisting of the use of Computational Fluid Dynamics and an optimization technique. First, the simulation of the current geometry of the turbine was carried out to characterize and verify, with experimental data, that the model represents the current operating conditions; this required to generate 3D CAD geometries by means of planes and reverse engineering using three-dimensional scanning of complex elements of the turbine such as blades. Second, it was required to optimize the geometry of the runner blades, guide vanes, covers and labyrinths by the combined use of factorial design of experiments, artificial neural networks (ANN) and optimization techniques by genetic algorithms.MaestríaMAGISTER EN INGENIERÍA ÉNFASIS EN INGENIERÍA MECÁNIC

Comment on "Quantum bound states with zero binding energy"

The purpose of this Comment is to show that the solutions to the zero energy Schr\"odinger equations for monomial central potentials discussed in a recently published Letter, may also be obtained from the corresponding free particle solutions in a straight forwardly way, using an algorithm previously devised by us. New solutions to the zero energy Schr\"odinger equation are also exhibited.Comment: Accepted for publication in PHISICS LETTERS

Confinement of exotic matter. I. Static solutions

We present the ${\cal E}$-boson star: A novel configuration of a boson star with an exotic matter nucleus; the exotic matter being described by a real massive scalar field with self-interaction term and kinetic term of the opposite sign. The other scalar field is canonical, so that the system is similar to the material component of the quintom cosmological scenario. Considering the static spherical symmetric case, we obtain cases where both fields are distributed as concentric spheres, and others with the remarkable feature that the canonical matter is pushed outwards and obtain a shell-like distribution of the canonical field, with a nucleus of exotic matter at the center. We present global properties of such ${\cal E}$-boson stars and stress the differences that these configuration have with respect to the usual boson stars. In particular, we obtain cases where the compactness goes beyond the Buchdahl limit.Comment: 13 pages, 14 figure

Un análisis de Flashings in the mirror de Jasper Elings

Este trabajo propone reflexionar, a partir de la obra de Net. ArtFlashings in the mirror del realizador alemán Jasper Elings, sobre las relaciones que se tejen entre la tecnología digital y la producción de nuevas subjetividades. El filósofo coreano Byung- Chul Han caracteriza a nuestra sociedad como marcada por la transparencia, en la que se produce una excesiva proliferación de imágenes que subrayan la urgencia de la sobreexposición de sí. Los sujetos se ven empujados a la compulsión de cristalizarse en imágenes digitales autorreferenciales: el mundo digital produce una inmediatez en la producción, el consumo y la reapropiación de la imagen que lleva a que en nuestra experiencia actual se desdibujen los límites entre lo privado y lo público. A partir de la articulación de conceptos provenientes del psicoanálisis, las teorías de las artes y las teorías de la comunicación, se van pensar tópicos que refieren a cómo se representa en las obras diseñadas para la Web, el impacto de Internet como fuente de extracción de materiales para la expresión artística en una poética del self que nos permite pensar los cuerpos y la miradas sobre éste, en el marco de la sociedad de la transparencia.Eje 12: Producción artística y su circulación en redes sociales y web.Facultad de Bellas Arte

Un análisis de Flashings in the mirror de Jasper Elings

Este trabajo propone reflexionar, a partir de la obra de Net. ArtFlashings in the mirror del realizador alemán Jasper Elings, sobre las relaciones que se tejen entre la tecnología digital y la producción de nuevas subjetividades. El filósofo coreano Byung- Chul Han caracteriza a nuestra sociedad como marcada por la transparencia, en la que se produce una excesiva proliferación de imágenes que subrayan la urgencia de la sobreexposición de sí. Los sujetos se ven empujados a la compulsión de cristalizarse en imágenes digitales autorreferenciales: el mundo digital produce una inmediatez en la producción, el consumo y la reapropiación de la imagen que lleva a que en nuestra experiencia actual se desdibujen los límites entre lo privado y lo público. A partir de la articulación de conceptos provenientes del psicoanálisis, las teorías de las artes y las teorías de la comunicación, se van pensar tópicos que refieren a cómo se representa en las obras diseñadas para la Web, el impacto de Internet como fuente de extracción de materiales para la expresión artística en una poética del self que nos permite pensar los cuerpos y la miradas sobre éste, en el marco de la sociedad de la transparencia.Eje 12: Producción artística y su circulación en redes sociales y web.Facultad de Bellas Arte