Search results for "Física"
showing 10 items of 4992 documents
Multiwavelength study of accretion-powered pulsars
2010
My PhD thesis consists in a multi-frequency approach to High Mass X-ray Binaries (HMXBs), using infrared and X-ray data. On one side, my research project aimed at the identification and characterization of IR counterparts to obscured HMXBs in the Scutum and Norma inner galactic arms. The identification of optical/IR counterparts to HMXBs is a necessary step to undertake detailed studies of these systems. With data limited to the high-energy range, the understanding of their complex structure and dynamics cannot be complete. In the last years, INTEGRAL has revealed the presence of an important population of heavily absorbed HMXBs in the Scutum and Norma regions, virtually unobservable below …
New Insights into Galaxy Clusters: from Simulations to Observations
2011
The work carried out during this Thesis is framed within the field of Numerical Cosmology and focused on several broad lines intimately related which deal with the theoretical and numerical study of galaxy clusters: (i) the halo-finding problem, (ii) new improvements in cosmological simulations, and (iii) the formation and evolution of galaxy clusters. In spite of the achievements reached by Computational Cosmology in the last years, present-day hydrodynamics/N-body simulations still present important discrepancies with the observations, especially in the inner regions of massive galaxy clusters. Among these discrepancies we can cite, for instance, the breaking up of the self-similar scalin…
Asteroseismology and mass loss in Be stars. Study with CoRoT
2010
The interiors of the stars are among the most difficult parts of the Universe to observe. Essentially, asteroseismology tries to make use of the oscillations to prove the stellar interiors, which are not directly observable. The basic principles of asteroseismology are, to a certain extent, similar to those developed and employed by Earth seismologists. Asteroseismology relies on advanced mathematical descriptions of oscillations in a three-dimensional body and numerical modeling. It is therefore a prominent example of interdisciplinary science. The general aim of this work is the study of Be stars with the CoRoT space mission. Classical Be stars are B-type stars that exhibit line emission …
Espectroscopía óptica confocal aplicada al estudio de cajas cuánticas aisladas de arseniuro de indio (InAS)
2004
La nanotecnología electrónica surge como disciplina científica para dar respuesta a la demanda creciente por parte de la sociedad de dispositivos electrónicos más eficientes y de menor coste. Como su propio nombre indica, esta disciplina involucra los estudios que se llevan a cabo en la actualidad en sistemas electrónicos elementales que, aunque basados en diferentes materiales y técnicas de fabricación, tienen un nexo común en su tamaño nanométrico. En este marco, en el trabajo de tesis presentado se han investigado las propiedades ópticas y electrónicas de cajas cuánticas aisladas de Arseniuro de Indio mediante diferentes técnicas de espectroscopía óptica confocal de alta resolución espac…
Electronic structure and optical properties of III-N nanowires
2011
The term III-N nanowire (NW) will refer throughout this work to the free-standing nanowires made of group-III-nitrides semiconductors, namely InN, GaN and AlN. These nanostructures have a large length/diameter ratio, of the order of 100 (sev- eral micrometers versus tenths of nanometers). The term free-standing highlights the fact that the NWs are not embedded in another material. The improvement of the epitaxial techniques, and in particular, those based on III-N semiconductors, has lead an important part of the Solid State Physics community to concentrate the attention in the last years towards a better understanding of the physical properties of those NWs. Nanowires present several di er…
Desintegraciones hadrónicas y radiativas del leptón tau
2010
En esta Tesis se han estudiado las desintegraciones hadrónicas del leptón tau. Tras motivar que la Teoría Quiral de Resonancias era un marco adecuado para su estudio, ésta se ha aplicado en una serie de casos de interés. Con las desintegraciones 3 hemos completado el estudio de la hadronización de la corriente axial en desintegraciones a tres mesones del tau. Además, hemos calculado la anchura fuera de capa másica de la resonancia a1, que será empleada en gran número de estudios fenomenológicos posteriormente. Finalmente, hemos comprobado la corrección de nuestro tratamiento al describir con éxito los observables disponibles para estas desintegraciones. También hemos estudiado las …
Optical and radar remote sensing applied to agricultural areas in europe
2008
The global population growth, as well as the social and economic importance that the agricultural sector has in many regions of the world, makes it very important to develop methods to monitor the status of crops, to improve their management, as well as to be able to make early estimates of the agricultural production. One of the main causes of uncertainty in the production of crops is due to the weather, for example, in arid and semiarid regions of the world, periods of drought can generate big losses in agricultural production, which may result in famine. Thus, FAO, during their summit in June 2008, stressed the need to increase agricultural production as a measure to strengthen food secu…
New algorithms for atmospheric correction and retrieval of biophysical parameters in earth observation : application to ENVISAT/MERIS data
2007
An algorithm for the derivation of atmospheric and surface biophysical products from the MEdium Resolution Imaging Spectrometer Instrument (MERIS) on board ENVIronmental SATellite (ENVISAT/MERIS) Level 1b data over land has been developed. Georectified aerosol optical thickness (AOT), columnar water vapor (CWV), spectral surface reflectance and chlorophyll fluorescence (CF) maps are generated. Emphasis has been put on implementing a robust software able to provide those products on an operational manner, making no use of ancillary parameters apart from those attached to MERIS images. For this reason, it has been named Self-Contained Atmospheric Parameters Estimation from MERIS data (SCAPE-M…
Influencia de los componentes parásitos en el análisis y diseño de inversores resonantes paralelo para aplicaciones de calentamiento por inducción
1999
La aparición de nuevos dispositivos semiconductores de conmutación cada vez másrápidos y capaces junto con el uso de modernas técnicas de control ha permitido la mejora deparámetros básicos de los equipos industriales como son la fiabilidad, la seguridad y elrendimiento. En calentamiento por inducción, el uso de estos nuevos dispositivos ha permitidoademás el aumento de la potencia y frecuencia de funcionamiento con lo que se han evidenciadolos efectos perjudiciales que provocan las diversas magnitudes parásitas que aparecen en loscomponentes y conexiones de estos equipos. El presente trabajo se basa en el estudio de estosefectos y en el análisis y diseño de circuitos capaces de resolver lo…
Implementation of the ROD Crate DAQ Software for the ATLAS Tile Calorimeter and a Search for a MSSM Higgs Boson decaying into Tau pairs
2010
The ATLAS experiment of the LHC at CERN started its operation in 2009. The ROD Crate DAQ (RCD) as a part of the Trigger and Data Acquisition system (TDAQ) is responsible for the operation of the sub-‐detector specific hardware at the level of the back-‐end electronics crates. The RCD for the Tile Calorimeter is fully implemented. In first place, the specific Tile hardware and software is described in the configuration database. In second place, the various plug-‐ins for the RCD that make use of sophisticated programming techniques are characterized. The RCD performance can be evaluated in terms of global DAQ efficiency, which is over 94% for the considered period in 2010 and in terms of …