The problem of transfer of radiation in a medium with polarized emission, polarized absorption and Faraday rotation of the plane of polarization is formulated. Solutions are obtained for the case of a homogeneous source. In the range of frequencies for which a medium is optically thick the degree of polarization of synchrotron radiation depends on the type of absorption process and is different for synchrotron absorption and for thermal absorption. It is therefore suggested that the low frequency polarization measurements of radio sources with curved spectra may determine whether synchrotron self -absorption or thermal absorption or another process is responsible for the low frequency curvature in spectra of certain radio sources.

Ce travail de thèse porte sur l’instabilité de Faraday qui résulte de l’oscillation verticale d’une couche de liquide. L’objectif est d’apporter une vérification expérimentale précise des résultats issus d’une analyse de stabilité linéaire. À basse fréquence, la longueur d'onde caractéristique de cette instabilité est de l'ordre des dimensions de la cellule expérimentale. Théoriquement les longueurs d'onde associées aux modes disponibles sont discrétisées selon le confinement latéral. Mathématiquement, la condition qui facilite les calculs est une condition limite pariétale sans contrainte, ce qui est irréaliste en raison des couches limites visqueuses et de l’hystérésis capillaire au point de contact du fluide avec les parois. Ici, nous présentons l'étude expérimentale d'un système de basse fréquence conçu pour se rapprocher d’une condition pariétale sans contrainte, par un choix judicieux de liquides. Le système a permis d’obtenir expérimentalement des seuils d’apparition de l’instabilité très proches des prédictions théoriques basées sur une analyse de stabilité linéaire. Les différences observées sont associées au ménisque formé par le liquide sur la paroi ainsi qu’au film liquide se formant à la paroi lors de l'excitation des ondes. Les écarts avec la théorie dû à ces imperfections semblent être fonction de la structure du mode et la périodicité des ondes. De plus, les ondes générées par le ménisque conduisent à des seuils inférieurs aux prévisions. Ceci indique une résonance mixte entre l'instabilité paramétrique et les oscillations forcées du ménisque où chaque contribution peut être contrôlée par un forçage caractérisé par deux fréquences. / This work is an inquiry into the current understanding of experimental single-mode Faraday waves, from the perspective of linear stability theory. At low frequency, the characteristic wavelength is of the order of the cell dimensions, and theoretically the wavelengths associated with the modes available for excitation are discretized by the sidewall boundary condition. Mathematically, the condition which eases manipulation is a stress-free sidewall condition, which is unrealistic due to viscous boundary layers and capillary hysteresis. We report the experimental investigation of a low frequency system designed to approximate this condition, by careful choice of the fluid liquids and thereby increasing the relative importance of the interior damping. The design has permitted close connection between the experimental thresholds and the predictions, contrasting the traditional approach of phenomenologically measuring the mode dissipation and treatment as a single degree of freedom system. Non-ideal behavior of the sidewall persists, evident by the contact meniscus and the sidewall film which is formed during wave excitation. The presence of these non-idealities is translated to trends in the deviation between the observed and predicted thresholds, depending upon the mode structure and wave periodicity. The presence of harmonically excited waves from the meniscus seems to result in observation of amplitudes consistently lower than the predictions, indicating a mixed resonance between the parametric instability and the forced meniscus oscillations. Furthermore, it is seen this interaction can be adjusted by excitation with two commensurate parametric frequencies.

No description available.

Thèse de doctorat : Chimie : Evry-Val d'Essonne : 2008. / Titre provenant de l'écran-titre.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Co-Chair: Dr. Jianmin Qu; Committee Co-Chair: Dr. Mohammed Cherkaoui; Committee Member: Dr. Christophe Giraud-Audine; Committee Member: Dr. Nico Declercq. Part of the SMARTech Electronic Thesis and Dissertation Collection.

[No abstract submitted] / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Made available in DSpace on 2016-04-28T14:16:15Z (GMT). No. of bitstreams: 1 Rodrigo Pietro Leite.pdf: 1186209 bytes, checksum: 42013de03e2921b14242622ec2ea0fbe (MD5) Previous issue date: 2012-08-24 / This research deals with experimental practices developed by Michael Faraday, held from 1836 until early 1838, focusing mainly on the experiment, which would later be known as the "Faraday cage". We analyzed the Experimental Researches in Electricity (ERE), in which are recorded reflections and experiments that were subsequently presented to the Royal Society. We also analyzed part of his correspondence and his diary, and other works. This analysis confirmed that the pillars of thought Faraday were the idea of unity of natural forces and the proposed improvement of the mind. Michael Faraday conducted several experimental tests, which helped formulate concepts fundamental to the understanding of matter. In this study focused in particular experiments relating to the load charge distribution / Esta pesquisa aborda práticas experimentais desenvolvidas por Michael Faraday, realizadas de 1836 até início de 1838, tendo como foco principal o experimento, que mais tarde seria conhecido como a Gaiola de Faraday . Analisamos o Experimental Researches in Electricity (ERE), no qual estão registrados experimentos e reflexões que posteriormente foram apresentados à Royal Society. Também analisamos parte de sua correspondência e de seu diário, além de outras obras. Tal análise reafirmou que os pilares de sustentação do pensamento de Faraday eram a ideia de unidade das forças da natureza e a proposta de aperfeiçoamento da mente. Michael Faraday realizou vários testes experimentais, que o ajudaram a formular conceitos fundamentais para o entendimento da matéria. Neste estudo focalizamos, especialmente, os experimentos relativos à distribuição de carga

A suspended ionic solution of 1-butyl-3-methylimidazolium iron tetrachloride [BMIM][FeCl4] provides a novel medium for achieving Faraday rotation under small magnetic fields at pump wavelengths of 980nm. As verified with spectrophotometry, transmission at telecommunication wavelengths makes the solution applicable across multiple applications. A cryostation was used to measure the sample up to a 340K and under field at 600mT, the ionic sample shows the necessary temperature stability and enables compact formats suitable for potential industrial applications. With a rotation of linearly polarized light of 0.04° over a 450um path length, a full 45° rotation requires only a 50.6cm path length and with only a 0.000175°/K temperature dependence. The observation of polarization effects in real time using lock-in amplifiers, and a photo-elastic modulator demonstrates the scalability, responsiveness, and stability of the ionic liquids for photonic integration. The test set up provides a convenient way to expand the research on ionic liquid Faraday rotation materials and other Faraday liquids ideally leading to a compact in-line isolator solution.

Under the conditions of quasitransverse propagation of electromagnetic waves in a magnetoionic plasma, the effect analogous to Faraday rotation in the quasilongítudinal case (which we will call Faraday pulsation) can produce a large elliptical polarization of originally linearly polarized radiation. Therefore, the presence of elliptical polarization in the radiation cannot serve as a means for distinguishing between a synchrotron mechanism with high energy electrons and any other type of emission process in radio sources in which conditions suggesting quasi - transverse propagation (large magnetic fields) may take place. The Faraday pulsation has a wavelength dependence through which it can be identified.

A millimetric droplet may bounce and self-propel on the surface of a vertically vibrating bath, where its horizontal `walking' motion is induced by repeated impacts with its accompanying Faraday wave field. This hydrodynamic pilot-wave system exhibits many features that were previously thought to be exclusive to the quantum realm, including quantized dynamics and emergent wavelike statistics. We develop a discrete-time iterative map to analyse the pilot-wave dynamics in a number of settings, employing a sophisticated fluid model to capture the intricacies of the Faraday wave evolution neglected by previous works. We first study the stability of bouncing and walking dynamics, and elucidate further features of the droplet's wave-induced added mass. We also explore the periodic and chaotic dynamics arising when the droplet is subjected to a harmonic potential, a Coriolis force, or the interaction with a seconddroplet. Finally, we modify our fluid model to account for interactions with submerged boundaries, allowing us to rationalise the pilot-wave dynamics in a circular corral.