Finalized PhD theses

Número de entradas: 74

Atmospheric Tomography Using Satellite Radio Signals

Estado: defended (04/02/2000)
Estudiante: Alejandro Flores
Supervisada por: Antonio Rius Jordán
Universidad: Universitat Politècnica de Catalunya

The Global Navigation Satellite Systems (GPS and GLONASS) have become a basic tool to obtain geodetic measurements of the Earth and a source of data for the atmospheric analysis. Since these systems provide a global, dense and permanent coverage with precise and accurate data, the radio signals they…
Estado: defended (04/02/2000)
Estudiante: Alejandro Flores
Supervisada por: Antonio Rius Jordán
Universidad: Universitat Politècnica de Catalunya

The Global Navigation Satellite Systems (GPS and GLONASS) have become a basic tool to obtain geodetic measurements of the Earth and a source of data for the atmospheric analysis. Since these systems provide a global, dense and permanent coverage with precise and accurate data, the radio signals they transmit can be used for the spatio-temporal representation of the atmosphere. GPS receivers technology has evolved at a surprising pace: nowadays they have sufficient measurement quality as to be used in geodetic studies, together with other techniques such as the Very Long Base Interferometry (VLBI), and in atmospheric studies whose results can be input into meteorological analysis. In the thesis "Atmospheric Tomography Using Satellite Radio Signals" we have focused on the use of GPS system due to the better quality and quantity of references and tools for the data processing. This notwithstanding, we have proven the possibility to broaden the concept to include any other radio signal transmitting satellite system as an atmospheric sounder. The thesis has been divided into two main areas: GPS data processing to extract the information related to the atmospheric parameters under study, and the implementation of tomographic techniques to the solution of the inverse problem. In particular, tomography has been applied to the ionosphere and to the neutral atmosphere. In both cases, results have a socio-economic impact: a) monitoring the ionosphere is essential for radio transmissions across it because of the perturbations it may produce on the signal, and b) estimating water vapour content in the troposphere is highly useful for meteorological and climate forecast For the ionospheric tomography we initally only used the data from the global IGS network. Vertical resolution was afterwards improved using the occultation data of the GPS/MET experiment. The improvement, however, was limited to the region where these data existed. Finally, we used altimeter data from the TOPEX/POSEIDON satellite to improve the maps and to prove the radar altimeter calibration capability of the tomographic technique. The application to the troposphere was possible after the improvement and refinement of both the GPS data processing and the tomographic inversion. The first results were obtained using the experimental data from the permanent network in Kilauea, Hawaii. The particular geometry of the receivers in this local network made it highly suited for these initial results, which proved the possibility of obtaining spatio-temporal representations of the troposphere using GPS data. The data analysis of the REGINA campaign, which took place at the Onsala Space Observatory, provided the description of a complex meteorological phenomenon using only GPS data tropospheric tomography. We verified the results with a direct comparison with radiosonde data. Concluding, we have demonstrated the capabilities of atmospheric tomography using satellite radio signals, with particular emphasis on the GPS signals.

The motion sensing problem in spherical Gravitational Wave detectors

Estado: defended (08/04/1999)
Estudiante: Maria Angeles Serrano Moral
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

Not available
Estado: defended (08/04/1999)
Estudiante: Maria Angeles Serrano Moral
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

Not available

Cosmological perturbation theory and the spherical collapse model

Estado: defended (30/06/1998)
Estudiante: Pablo Fosalba Vela
Supervisada por: Enrique Gaztañaga ; Emilio Elizalde
Universidad: Universitat de Barcelona

We present a simple and intuitive approximation for solving perturbation theory (PT) of small cosmic fluctuations. We consider only the spherically symmetric or monopole contribution to the PT integrals, which yields the exact result for tree-graphs (i.e. at leading order). We find that the non-linear…
Estado: defended (30/06/1998)
Estudiante: Pablo Fosalba Vela
Supervisada por: Enrique Gaztañaga ; Emilio Elizalde
Universidad: Universitat de Barcelona

We present a simple and intuitive approximation for solving perturbation theory (PT) of small cosmic fluctuations. We consider only the spherically symmetric or monopole contribution to the PT integrals, which yields the exact result for tree-graphs (i.e. at leading order). We find that the non-linear evolution in Lagrangian space is then given by a simple local transformation over the initial conditions, although it is not local in Euler space. This transformation is found to be described the spherical collapse (SC) dynamics, as it is the exact solution in the shearless (and therefore local) approximation in Lagrangian space. Taking advantage of this property, it is straightforward to derive the one-point cumulants, for both the unsmoothed and smoothed density fields to arbitrary order in the perturbative regime. To leading order this reproduces, and provides with a simple explanation for, the exact results obtained by Bernardeau (1992, 1994). We then show that the SC model leads to accurate estimates for the next corrective terms when compared to the results derived in the exact perturbation theory making use of the loop calculations (Scoccimarro & Frieman 1996). The agreement is within a few per cent for the hierarchical ratios $S_J$. We compare our analytic results to N-body simulations, which turn out to be in very good agreement up to scales where $\sigma \approx 1$. A similar treatment is presented to estimate higher order corrections in the Zel'dovich approximation. These results represent a powerful and readily usable tool to produce analytical predictions to describe the gravitational clustering of large scale structure in the weakly non-linear regime.

Search for monochromatic GW signals in data from the antenna EXPLORER

Estado: defended (17/04/1998)
Estudiante: Miquel Montero Torralbo
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

This Thesis is about the design and development of various filtering strategies for the analysis of data generated by a resonant bar gravitational wave (GW) antenna, with the goal to assess the presence (or absence) therein of long-duration monochromatic GW signals, as well as the eventual amplitude…
Estado: defended (17/04/1998)
Estudiante: Miquel Montero Torralbo
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

This Thesis is about the design and development of various filtering strategies for the analysis of data generated by a resonant bar gravitational wave (GW) antenna, with the goal to assess the presence (or absence) therein of long-duration monochromatic GW signals, as well as the eventual amplitude and frequency of the signals, within the sensitivity band of the detector. Such signals are most likely generated in the fast rotation of slightly asymmetric spinning stars. We develop practical procedures, together with a study of their statistical properties, which provide us with useful information on the performance of each technique. The selection of candidate events is then established according to threshold-crossing probabilities, based on the Neyman­-Pearson criterion. In particular, it is shown that this approach, based on phase estimation, presents a better signal-to-noise ratio than does pure spectral analysis, the most common approach. The methodology is applied and validated with data from the real GW detector EXPLORER, kindly provided by the Frascati (near Rome) Group, who designed, built and run the detector.

Spherical GW detectors

Estado: defended (17/03/1997)
Estudiante: Jose Antonio Ortega Ruiz
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

Shortly available
Estado: defended (17/03/1997)
Estudiante: Jose Antonio Ortega Ruiz
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

Shortly available

Thermonuclear burning on top of accreting white dwarfs

Estado: defended (22/07/1996)
Estudiante: José, J.
Supervisada por: Margarita Hernanz
Universidad: Universitat de Barcelona

To be introduced shortly
Estado: defended (22/07/1996)
Estudiante: José, J.
Supervisada por: Margarita Hernanz
Universidad: Universitat de Barcelona

To be introduced shortly

Structure and evolution of stars in the low main sequence

Estado: defended (01/02/1994)
Estudiante: Aparicio, J. M.
Supervisada por: Jordi Isern Vilaboy
Universidad: Universitat de Barcelona

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Estado: defended (01/02/1994)
Estudiante: Aparicio, J. M.
Supervisada por: Jordi Isern Vilaboy
Universidad: Universitat de Barcelona

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Calibraciones Ionosféricas en geodesia Espacial mediante el uso de datos GPS

Estado: defended (01/03/1993)
Estudiante: Ester sardón Pérez
Supervisada por: Antonio Rius Jordán
Universidad: Universidad Complutense de Madrid

Calibraciones Ionosféricas en geodesia Espacial mediante el uso de datos GPS
Estado: defended (01/03/1993)
Estudiante: Ester sardón Pérez
Supervisada por: Antonio Rius Jordán
Universidad: Universidad Complutense de Madrid

Calibraciones Ionosféricas en geodesia Espacial mediante el uso de datos GPS

Estudio de movimientos relativos en Europa mediante una red de radiointerferometría geodésica

Estado: defended (01/11/1992)
Estudiante: Nestor Zarraoa López
Supervisada por: Antonio Rius Jordán
Universidad: Universidad Complutense de Madrid

Estudio de movimientos relativos en Europa mediante una red de radiointerferometría geodésica
Estado: defended (01/11/1992)
Estudiante: Nestor Zarraoa López
Supervisada por: Antonio Rius Jordán
Universidad: Universidad Complutense de Madrid

Estudio de movimientos relativos en Europa mediante una red de radiointerferometría geodésica

Nucleosintesis y curvas de luz de las supernovas de tipo Ia

Estado: defended (01/02/1991)
Estudiante: Bravo, E.
Supervisada por: Jordi Isern Vilaboy
Universidad: Universitat de Barcelona

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Estado: defended (01/02/1991)
Estudiante: Bravo, E.
Supervisada por: Jordi Isern Vilaboy
Universidad: Universitat de Barcelona

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Institute of Space Sciences (IEEC-CSIC)

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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya