ELECTROMAGNETISM

Author: PALAU MASOLIVER ANA M..
Year: 2004.
University: AUTÓNOMA DE BARCELONA.
Place of defense: INSTITUT DE CIÈNCIA DE MATERIALS DE BARCELONA.
Place of preparation: ESCUELA DE POSTGRADO UNIVERSITAT AUTÒNOMA BARCELONA.

Summary: The superconducting tapes of YBCO have emerged as a very promising material for applications power and allow benefits critical current densities in the order of 1MA/cm2 to 77K under high magnetic fields (1-5T). These are made up of hundreds structure of grain boundaries low angle (FGBA) induced by the texture of flexible metal substrate on which they are placed, through pre-conditioning buffer layers. This granularity is the most important constraint to the passage of electric current and establishes the presence of two mecansmos different interacting partners on the one hand to step flow percolativa through the FGBA (critical current density associated with the grain boundaries, Jc FG) and on the other hand, the current that flows into the interiro of superconducting grains (critical current density associated with grains, Jc G). While JcG is clearly determined by the anchor of the vortices Abrikosov in grains, the dissipation associated with JcFG is still a question mark, having been theoretically predicted the existence of a new class of vortices called Abrikosov-Josephson. In this dissertation we have analyzed the response electromagnetic tapes of YBCO through superconducting magnetic cilos hysteresis and measures ac susceptibility. Based on the characteristic hysteresis cycle, we have developed a formalism that has enabled us to determine independently and simultaneously the JcFG and JcG at low magnetic field, under the model critical condition. The metodologái developed has enabled us to explore the relationship between the effects of granularity, the anchor of vortices Abrikosov and dissipation associated with the movement of the vortices Abrikosov-Josephson in FGBA and therefore has enabled us to inferiro in the physical mechanisms governing transport eléctirco of these materials. It has conducted a comprehensive study of the relationship between these various mechanisms varying parameters characteristic of the superconducting tapes as the angle between the grain boundaries, grain size, the thickness of the superconducting layer or the growth process as well as analyzing the Jc unit, with the magnetic field. The entire study has identified a plot of magnetic phases for the superconducting tapes of YBCO with different regimes of motion of vortices.

Author: SEPÚLVEDA MARTÍNEZ BORJA.
Year: 2004.
University: COMPLUTENSE DE MADRID.
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: FACULTAD DE CIENCIAS FÍSICAS.

Summary: The objectives of this dissertation are essentially two. 1. The study of a system of variable compensation phase magneto-óptico for a iterferómetro Mach-Zehnder (MZI) integrated with applications biosensoras. 2. The development of a biosensor Magneto-Óptico Resonance of Plasmón Surface (MOSPR) to improve the sensitivity and the limits on detention of sensors of plasmón surface resonance (SPR) conventional. The two objects, but based fenómienos optical different, have a common bond: both devices use sensors evanescent field of light as a principle of detección.Para achieve these objectives requires the study of phenomena magneto-ópticos in optical systems evanescent field. This study includes both theoretical aspects as experimentales.Así, the first goal has necessitated the theoretical study of the effects magneto-ópticos in wave guides, as well as theoretical study / experimental materials with effect magneto-ópticos suitable for optical integrated transport systems such as magnetic nanoparticles embedded in a matrix dieléctrica.En story to the second goal, it has been necessary, first, the theoretical study of the effects magneto-ópticos in presencis of plasmones superficiales.Dicho study has been the basis for the experimental development of a prototype sensor magneto-óptico resonance plasmón surface, which improves detection limits of conventional sensors.

Author: GRANDE SÁEZ ANA MARÍA.
Year: 2004.
University: VALLADOLID.
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The method in the Finite Difference Time Domain (FDTD) is today one of the tools of Electromagnetism Computational more employed in resolving problems in the time domain. The original wording of FDTD method given by Yee allows only simulate the propagation of electromagnetic fields on average linear isótropos and homogeneous. In recent years, media biisótropos in particular chiral media, have aroused great interest in the comunididad international science because of its potential applications. In this dissertation, develops an extension of the FDTD method for the study of the propagation of electromagnetic waves in ways biisótropos dispersive with losses. It has built a new mesh FDTD, has been described as the dispersive nature of the parameters constituent developed three possible models for the media biisotropos (non-dispersive, dispersive not complete, and dispersive complete), has been amended algorimo computational method FDTD and there has been analysis of the stability of the formulation implemented. Finally, we have conducted a series of numerical experiments that allow validate the new scheme proposed FDTD and display the main features of the propagation of electromagnetic fields in the media biisótropos (rotating optical scattering, circular dichroism and nonorthogonality of the field vectors E and H ). This extension to the FDTD method is so far the only digital technology in the domain temporary permits the simulation of the propagation of waves in the media biisótropos dispersive with losses.