Sabemos la centralidad que la noción de estado electro-tónico tuvo en la primera formulación de las ecuaciones de Maxwell. El concepto, sin embargo, proviene de Faraday, que lo introdujo a raíz de su descubrimiento de la inducción electromagnética en 1831, y recurrió a él intermitentemente en los años siguientes. La tesis pretende trazar la evolución del concepto en la obra de Faraday.El capitulo 1 se ocupa, en primer lugar, de proporcionar algunos elementos para comprender la situación de la electricidad y el magnetismo en las dos décadas del siglo XIX previas al descubrimiento del electromagnetismo en 1820. Posteriormente se discute el descubrimiento de Oersted, y dos de los resultados más notables del impacto que dicho descubrimiento produjo la electrodinámica de Ampère y el descubrimiento de Faraday de sus rotaciones electromagnéticas. Por último se discuten los primeros intentos de detectar corrientes inducidas, en particular el de Ampère.Es conocido que el descubrimiento de las corrientes inducidas se debe a Faraday. El capítulo 2 se ocupa de dicho descubrimiento y de la primera respuesta de Faraday a las anomalías que presentaba frente a sus expectativas teóricas. El concepto de estado electro-tónico, aquí introducido, resuelve estas anomalías, explicando por qué se interrumpe la primera corriente inducida y por qué se origina una en sentido opuesto al eliminar la fuerza inductiva. En el capítulo se proporciona la fecha en que Faraday leyó en la "Royal Society" una primera versión de la memoria que expone sus primeros resultados sobre la inducción, y se propone una explicación de por qué Faraday difundió una fecha inexacta aceptada posteriormente por todos los estudiosos. Asimismo, se llama la atención sobre un error que Faraday cometió en el sentido de las corrientes inducidas el mismo día en que descubrió la inducción, error que se mantuvo durante tres meses y que es posible seguir mediante las anotaciones de su diario de investigación, cuyo examen permite identificar el momento en que Faraday corrigió su error. Esta circunstancia había sido pasada por alto hasta la fecha. El capítulo termina analizando las razones que llevaron a Faraday al "abandono", en 1832, de su estado electro-tónico. Se sugiere, sin embargo, que ya desde este mismo momento Faraday intentaba armonizar su concepto con el otro que había puesto a punto para explicar la inducción: el corte de curvas magnéticas por el conductor. Desde el punto de vista de Faraday, ambos conceptos eran necesarios para proporcionar una explicación más completa de la inducción electromagnética.El capítulo 3 aborda un tema poco estudiado previamente: la investigación de Faraday, en 1834, del fenómeno de autoinducción. Sin embargo, es aquí donde re introduce el estado electro-tónico en el contexto de la inducción electromagnética. En lo que despuéS iba a identificar como la inducción de la corriente sobre sí misma, Faraday creyó primeramente un fenómeno peculiar de inducción que presentaba indicios del estado electro-tónico abandonado públicamente dos años antes. En el capítulo se explica cómo incluso después de comprender la verdadera naturaleza del supuesto fenómeno peculiar, Faraday mantuvo el concepto de estado electro-tónico y le dotó de una dimensión causal que estaba ausente en su primera formulación.Es suficientemente conocido que Faraday es el descubridor de la acción del medio en la transmisión de la inducción electrostática, acción que veía representada por su concepto de capacidad inductiva específica y la curvatura de las líneas de fuerza inductiva estática. El capítulo 4 discute estos dos temas para facilitar la comprensión de las especulaciones de Faraday, en 1838, sobre la relación entre electricidad y magnetismo. Estas especulaciones se ocupan de dos problemas que tienen un origen común: el principio de unidad de las fuerzas. Este principio, piensa Faraday, exige, por un lado, la correspondencia de la fuerza eléctrica y magnética y, por otro, que el modo de transmisión del magnetismo sea el mismo que el de la electricidad. Para resolverlo recurre a su estado electro-tónico que aparecerá, no sin una cierta ambigüedad, como el estado estático de la fuerza magnética que debe existir para preservar la correspondencia con el estado estático de la fuerza eléctrica, y como el estado que adoptan las partículas de la materia en su transmisión de la fuerza magnética.A raíz de su descubrimiento, en 1845, de la rotación del plano de polarización de la luz por la materia sometida a la fuerza magnética, Faraday creyó encontrar de nuevo indicios de su estado electro-tónico. El capitulo 5 comienza analizando esta investigación, y posteriormente se centra en el papel del estado electrotónico en la sistematización de las ideas de Faraday sobre las líneas de fuerza magnética. Para ello se discute en detalle el artículo crucial "On the Physical Character of the Lines of Magnetic Force" (1852), donde Faraday se plantea el problema de la naturaleza física de dichas líneas. Retomando el tema de la correspondencia entre estados de la fuerza eléctrica y magnética, Faraday reflexiona sobre la naturaleza de las líneas de fuerza magnética, esforzándose en determinar si su naturaleza es estática o dinámica. En el capítulo se propone que la solución de Faraday es considerar que esas líneas tienen una naturaleza dinámica, pero con un fundamento estático que se identifica con el estado electro-tónica. Con ello el concepto de estado electro-tónico llega al punto final da su evolución en la obra de Faraday.El capítulo 6 revisa, en primer lugar, las referencias al estado electro-tónico en la historiografía anterior a la monumental biografía de Faraday que Williams publicó en 1965. Posteriormente se discuten algunos puntos dudosos en la interpretación que hace Williams del concepto de estado electro-tónico, y en las de trabajos posteriores, como los de Agassi, Berkson y Gooding. / This dissertation traces the history, in Faraday's work, of his concept of an electro-tonic state. After a first introductory chapter, chapter 2 examines Faraday's discovery of the electromagnetic induction. It is argued that Faraday made a mistake on the direction of the induced currents right on the same day of his discovery, 29 August 1831. This mistake lasted more than three months and its correction was consequential for Faraday's withdrawal of his electro-tonic state in 1832. As far as I know, Faraday's mistake has been overlooked by Faraday scholars.Chapter 3 focuses on a previously little studied topic: Faraday's study of self-induction in 1834. It is argued that here is where he introduced again his notion of an electro-tonic state, providing it with a causal dimension previously absent.Chapter 4 examines Faraday's appeal to his electro-tonic state in 1838. Two problems demanded this appeal. First of all, Faraday's strong feeling in favour of the necessary existence of a correspondence between states of the electric and magnetic force. Second one, Faraday's conviction about magnetic force being transmitted, as electric force, through the action of contiguous particles.Chapter 5 looks into the role of the electro-tonic state in Faraday's discussion of the nature of the physical lines of magnetic force in 1852. The point is made that Faraday was inclined to consider the lines as having a dynamic nature, but with a static foundation: the electro-tonic state.The last chapter discusses some points in the interpretation of Faraday's electro-tonic state put forward by scholars like Williams, Agassi, Berkson and Gooding.

The use of High-Frequency (HF) radio-wave propagation in the ionosphere remains prevalent for applications such as long-range communication, target detection and commercial broadcasting. The ionosphere presents a challenging channel for radio-wave propagation as it is a varying medium dependent on a number of external factors. Of the many adverse effects of ionospheric propagation, signal fading is one of the most difficult to eliminate due to its unpredictable nature. Increase in the knowledge of how the ionospheric channel affects the propagating signals, in particular fading of the signals, will drive the continual improvements in the reliability and performance of modern wide-bandwidth HF systems. This is the underlying motivation for the study of signal fading of HF radio-waves propagating through the ionosphere, from both the theoretical and experimental perspectives, with the focus of application to modern wide bandwidth HF systems. Furthermore, it is the main objective of this investigation to address the lacking in the current literature of a simple analytical signal fading model for wideband HF systems that relates the physics of the ionospheric irregularities to the observable propagation effects due to the irregularities, and one that is verified by experimental observations. An original approach was taken in the theoretical investigation to develop an analytical model that combines the effects of signal fading and directly relating them to the ionospheric irregularities that are causing the fading. The polarisation fading model (PFM) is a combination of geometric optics, perturbation techniques and frequency offset techniques to derive expressions for the Faraday rotation of the radio-wave propagating in the ionosphere. Using the same notation as the PFM, the amplitude fading model (AFM) extends the Complex Amplitude concept using perturbation techniques and Green’s functions solution to arrive at a set of expressions that describes the focussing and defocussing effects of the wave. The PFM and AFM, together with expressions for combining the effects of multiple propagation paths, provide a simple analytic model that completely describes the fading of the signal propagating in the ionosphere. This theoretical model was implemented into an efficient ionospheric propagation simulator (IPS) from which simulations of wide bandwidth HF signals propagating through the ionosphere can be undertaken. As an example of the type of results produced by the IPS, for a typical 1200km path in the north-south direction with the ionospheric channel under the influence of a travelling ionospheric disturbance (TID), a 10 MHz radio-wave signal in one-hop path is shown to be affected by polarisation fading with fading periods in the order of minutes, and a fading bandwidth in the order of 100 kHz. Further results generated by the IPS have shown to be consistent with the results reported elsewhere in the literature. The experimental investigation involves the study of signal fading from observations of real signals propagating in the ionosphere, a major part of which is the development of a digital compact channel probe (CCP) capable of operating in dual-polarisation mode, and the characterisation of such systems to ensure that data collected are not compromised by the non-idealities of the individual devices contained within the system. The CCP was deployed in experiments to collect transmissions of HF frequency-modulated continuouswave (FMCW) radio signals from the Jindalee Over-the-Horizon radar (OTHR) in dualpolarisation. Analyses of the collected data showed the full anatomy of fading of signals propagating in the ionosphere for both horizontal and vertical polarisations, the results of which are consistent with that from the IPS and thus verifying the validity of the theoretical model of fading. Further experimental results showed that in majority of the observations polarisation fading is present but can be masked by multi-path fading, and confirming that periods of rapid signal fading are associated with rapid changes in the ionospheric channel. From the theoretical and experimental investigations, the major achievement is the successful development of an efficient propagation simulator IPS based on the simple analytical expressions derived in the PFM and AFM theoretical models of signal fading, which has produced sensible signal fading results that are verified by experimental observations. One of the many outcomes of this investigation is that polarisation diversity has the potential to bring improvements to the quality of wide-bandwidth HF signals in a fading susceptible propagation channel. The combination of an efficient propagation simulator IPS based on theoretical signal fading model and the experimental data collection by the dual-polarisation CCP is a major step in allowing one to fully understand the different aspects of fading of signals propagating in the ionosphere, which sets a solid foundation for further research into the design of wide bandwidth HF systems and the possible fading mitigation techniques. / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2008

Thesis (M.S.)--University of North Texas, Dec., 2008. / Title from title page display. Includes bibliographical references.

Universiẗat, Diss., 1995--Paderborn.

La recherche de défauts dans les matériaux est un sujet complexe et important, en particulier lorsque la sécurité est en jeu comme dans le domaine aéronautique. Cette thèse s’inscrit dans cette problématique et s’organise en deux parties. La première partie est dédié à la détection des défaut dans les composites carbones par trois nouvelles méthodes radiofréquences permettant de détecter, en particulier, les impacts sur les peaux des composites carbones. La deuxième partie est consacrée à la détection des infiltrations d’eau dans les composites alvéolaires par une méthode multiphysique couplant une onde hydraulique non linéaire et une détection par un RADAR CW. / Detecting default inside material is a complex and important topic, particularly when the safety is at riske like for instance in the aeronautic field. This phd thesis is divided in two parts. In a first part, mainly we will present three new RF methods allowing to detect, for example, impact damages on carbon composite skins. In a second part we will present a new method aimed to detect water ingress in cellular composite. This new method is based on the interaction of a nonb-linear water wawe with a RADAR

Orientador: Maria Jose Pereira Monteiro de Almeida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Educação / Made available in DSpace on 2018-08-04T20:00:10Z (GMT). No. of bitstreams: 1 Montenegro_AnisabeldaGloriaPachecodeMacedo_M.pdf: 10253870 bytes, checksum: 3c1cff858493be431cff478c086c04f9 (MD5) Previous issue date: 2005 / Mestrado / Ensino, Avaliação e Formação de Professores / Mestre em Educação

Cette thèse présente les résultats obtenus au sein du projet BMV (Biréfringence Magnétique du Vide), dont l'objectif principal est la mesure de la biréfringence magnétique linéaire du vide. Cet effet est prédit dans le cadre de l'électrodynamique quantique mais n'a jamais été observé expérimentalement. La biréfringence attendue est de l'ordre de 10-24 pour un champ magnétique appliqué de 1 T. Sa mesure constitue donc un véritable défi expérimental. Dans un premier temps, le dispositif expérimental permettant la mesure de biréfringences magnétiques par polarimétrie est décrit. Puis les résultats concernant les mesures des biréfringences magnétiques circulaire (effet Faraday) et linéaire (effet Cotton-Mouton) de l'hélium et du xénon gazeux sont exposés. Enfin, une valeur de la biréfringence magnétique linéaire du vide est donnée. / In this work, we present the results obtained by the BMV (Biréfringence Magnétique du Vide) project, whose goal is to measure the linear magnetic birefringence of vacuum. This effect is predicted in the framework of quantum electrodynamics but it has never been observed experimentally. The expected birefringence is as small as 10-24, for an applied magnetic field of 1 T. Thus its measurement is an experimental challenge. First, we describe the experimental setup which allows magnetic birefringences measurements using a polarimetry method. Then, we present the results concerning the measurements of the circular magnetic birefringence (Faraday effect) and the linear magnetic birefringence (Cotton-Mouton effect) of helium and xenon gases. Finally we give a value for the linear magnetic birefringence of vacuum.

Commutated N-path networks have seen a resurgence in the past decade in the context of modern integrated circuits. N-path circuits have been used to implement high-quality tunable band-pass and notch filters with just switches and capacitors. Recently, nonreciprocal circuits such as circulators and isolators have also been reported as other applications of Linear Periodically-Time-Varying (LPTV) networks. In this dissertation, high performance filters and inductorless nonreciprocal components based on novel LPTV networks are introduced. We proposed a concept called Negative Transresistance (NTR) in phase-shifted N-path structures. The rejection of the conventional N-path notch filters is limited to the number of paths used; however, by using our proposed NTR concept, we were able to achieve more than 50dB rejection regardless of the number of paths. Using the same concept, we introduced the first prototype of N-path Low-Pass Filter (LPF). The resulting components can find application in blocker-tolerant systems, to select closely-spaced frequency channels, and also in the analog Baseband (BB). Nonreciprocal components such as circulators and isolators have traditionally relied on ferrites that offer nonreciprocal behavior based on Faraday Effect (by applying an external magnetic field). Recent efforts to eliminate the need for magnetic materials, despite being a huge success involve the usage of transmission lines (and/or inductors). In this dissertation, a novel concept called Nonreciprocal Transresistance (NRTR) is introduced. This led to the first ever inductorless RF isolator. Furthermore, we expanded the idea to the first inductorless circulator consisting of only switches and capacitors. The resulting isolator can find application in base stations to prevent back reflections (e.g. to protect the Power Amplifier (PA)). Also, in superconducting quantum systems, an isolator is necessary to separate the noise and reflections at the interface of different blocks. The introduced circulator can find applications in wireless communication systems as an antenna interface connecting the Transmitter (TX) and the Receiver (RX) to a shared antenna. This is crucial, especially for Full-Duplex (FD) applications where high isolation between RX and TX is necessary as they are operating at the same frequency. Finally, we enhanced the performance of the conventional N-path Band-Pass Filter (BPF). We first introduced a second-order N-path BPF with passive gain called impedance-transforming N-path filter. We then proposed a concept called rotary-clock-path in N-path filters which enables passive frequency shifting of N-path filters of any kind without the need for a separate clock frequency or active circuitries. Then by combining the impedance-transforming BPF and rotary-clock-path ideas, we implemented the first ever inductorless passive higher-order N-path BPF with voltage gain. The resulting BPFs can find applications in matching networks and also in a Surface Acoustic Wave (SAW)-less mixer-first receivers.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18781号 / 理博第4039号 / 新制||理||1581(附属図書館) / 31732 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 藤 定義, 教授 佐々 真一, 教授 早川 尚男 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19728号 / 工博第4183号 / 新制||工||1645(附属図書館) / 32764 / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 田中 勝久, 教授 平尾 一之, 教授 三浦 清貴 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM