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1

O'Dell, Ryan Andrew. "Resonant Ferromagnetic Absorption and Magnetic Characterization of Spintronic Materials". University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1533043360679487.

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2

Myers, Joshua Allen. "Nano-scale RF/Microwave Characterization of Materials' Electromagnetic Properties". Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1340883872.

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3

Ciracì, Cristian. "Study of second-harmonic generation in nonlinear nanostructured materials". Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20053.

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Au cours de ces 20 dernières années, une attention particulièrement soutenue a été donnée à l'étude et à la fabrication de matériaux nano-structurés permettant le contrôle de la lumière. Cependant, les propriétés de non-linéarité optique de ces nouveaux matériaux n'ont que très peu été explorées. Partant de ce constat, cette thèse se propose de pourvoir cette insuffisance. L'accent est mis en particulier sur le processus de génération de seconde harmonique à travers deux aspects fondamentaux: (i) le contrôle de l'émission de seconde harmonique pour des matériaux nano-structurés non-linéaires et (ii) l'augmentation de conversion dans des dispositifs photoniques intégrés. Nous présentons un nouveau phénomène de localisation non-linéaire qui a lieu dans des matériaux main-gauche et qui implique un accord de phase isotrope. Nous démontrons analytiquement le processus de localisation dans un milieu homogène main-gauche, avant de mettre en évidence un tel effet dans des cristaux photoniques non-linéaires à l'aide de simulations numériques. L'effet de localisation contra-propagative du second harmonique est utilisé pour le design d'une lentille de second-harmonique. Ce résultat théorique a été démontré numériquement pour une structure réalisable fonctionnant aux fréquences optiques. L'augmentation de génération de seconde harmonique constitue l'aspect complémentaire. En tirant parti de la forte localisation de lumière dans une chaîne de nano-tiges de dimension finie, nous montrons que, pris ensemble, le confinement transverse sub-longueur d'onde et la condition de résonance d'accord de phase contribuent de manière importante à l'augmentation de la génération de seconde harmonique. Les capacités de guidage sub-longueur d'onde de chaînes de nano-tiges sont mis en évidence en examinant leurs propriétés de propagation linéaire. Pour finir, nous nous penchons sur la condition d'accord de phase assurant l'interaction non-linéaire optimale
The past twenty years have been exceptionally rich on the study and fabrication of nanostructured materials to control light, but no much attention was given to nonlinear optical properties of these novel materials. In this context, the present thesis would partially address this gap. In particular, we focus on the second-harmonic generation process, by considering two fundamental aspects: the second-harmonic emission control by means of nanostructured nonlinear materials and the conversion enhancement in integrated photonic devices. A novel nonlinear localization phenomenon occurring in left-handed materials and involving isotropic phase-matching is presented. We analytically demonstrate the localization process in a homogenous left-handed material and by numerical simulation we show the effect for nonlinear photonic crystals. The backward second-harmonic localization effect is used to design a second-harmonic lens. This interesting theoretical result is numerically shown for a feasible structure working at optical frequencies. The second-harmonic generation enhancement is the complementary aspect. By taking advantage of the strong light localization achieved in finite size dielectric nonlinear nanorod chains, we show that sub-wavelength transversal confinement, together with the resonant phase-matching condition, adds an important property to the second-harmonic generation enhancement. A study of linear propagation properties of nanorod chain structures first evidences its sub-wavelength guiding capabilities. Finally, the phase-matching condition that assures the maximal nonlinear interaction in this kind of structure is presented
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4

Meyendorf, Robert. "Nondestructive Determination of Case Depth in Surface Hardened Steels by Combination of Electromagnetic Test Methods". University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1303834395.

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5

Parsa, Nitin. "MILLIMETER-WAVE FARADAY ROTATION FROM FERROMAGNETIC NANOWIRES AND MAGNETOELASTIC MATERIALS". University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1561468969375731.

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6

Vishal, Kumar. "Nonreciprocal magnetostatic surface wave in thin ferromagnetic film". Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1472018768.

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7

Kung, Christopher W. "Development of a time domain hybrid finite difference/finite element method for solutions to Maxwell's equations in anisotropic media". Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1238024768.

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8

Roberts, Anthony M. "Implementing a Piezoelectric Transformer for a Ferroelectric Phase Shifter Circuit". Cleveland State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=csu1337025849.

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9

Chung, Jae-Young. "Broadband Characterization Techniques for RF Materials and Engineered Composites". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1269542888.

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10

Hansen, Matthew Martin Kenneth. "Optimization of Conformal Joints in Axial Tension". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1355847865.

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11

Samuel, Paulo. "Investigating how Grade 10 Physical Science teachers help learners to make sense of concepts of electromagnetism using easily accessible materials in under-resourced schools". Thesis, Rhodes University, 2017. http://hdl.handle.net/10962/8143.

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This study sought to explore teachers’ perceptions and experiences of using easily accessible materials and how they might collaboratively develop learning and teaching support materials using easily accessible materials. The study explored three aspects. Firstly, the views, experiences and factors which influence grade 10 Physical Science teachers’ perceptions and experiences of teaching the topic of electromagnetism. Secondly, to find out what teachers can do to improve teaching and learning of electromagnetism in grade 10 Physical Science using easily accessible materials. Thirdly, to look at what enables or constrains grade 10 Physical Science teachers in under-resourced schools when dealing with electromagnetism, from using easily accessible materials. A qualitative method approach was adopted, underpinned by an interpretive paradigm but using some quantitative methods as well. Within the interpretive paradigm a case study approach was used. The study was carried out in Swakopmund and Gobabis education circuits of the Erongo and Omaheke Regions respectively. Data were collected using questionnaires, lesson observations and stimulated-recall interviews. The data obtained were validated in two ways, firstly, by triangulation from different data gathering techniques, and secondly, validation was done by member checking of the transcripts. To make meaning from the data generated, Vygotsky’s (1978) socio-cultural theory was used as a lens to analyse the data. The quantitative data generated were presented in figures, tables; whereas the qualitative data were coded inductively into descriptive texts to make meaning. It was found that teachers’s perceptions and experiences are that the topic of electromagnetism is quite challenging. Teachers reported that their learners find it difficult to comprehend phenomena associated with electromagnetism, thus making it difficult for their learners to grasp concepts associated with it. Lack of resources to do practical activities in the topic of electromagnetism was found to be a major contributing factor to teaching and learning of this topic. The use of easily accessible materials among teachers was found to be very limited. Easily accessible locally sourced materials were found to have the potential to enable grade 10 Physical Science teachers to help learners to make sense of concepts of electromagnetism in under-resourced schools. In light of the above findings, the study recommends that science teachers should make use of easily accessible materials which can minimise their dependence on standard laboratory equipment which is unaffordable anyway by most schools.
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12

Mougin, Alexandra. "Anisotropie magnétique, structure en domaines et renversement d'aimantation : déformations, couplages, champ magnétique et courant électrique comme leviers d'action". Habilitation à diriger des recherches, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00638870.

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Mes activités de recherche sont principalement axées sur le magnétisme de systèmes de basse dimensionnalité. J'ai travaillé particulièrement à préciser des interdépendances entre ordre structural, géométrie et magnétisme dans des nanosystèmes, souvent pour l'électronique de spin. Ce domaine de recherches, poussé par les applications potentielles en matière de mémoires et capteurs, est extrêmement actif et concurrentiel. Je me suis focalisée sur les relations entre les leviers d'action que sont les déformations épitaxiales, les champs magnétique ou électrique mais aussi un courant polarisé et l'aimantation, que celle-ci soit considérée du point de vue statique (anisotropie, structure en domaines) ou dynamique (renversement de l'aimantation...). Mon activité est essentiellement expérimentale et je dispose de compétences larges, allant de techniques usuelles dans nos laboratoires à d'autres plus rares (incluant l'utilisation des grands instruments comme le rayonnement synchrotron ou les réacteurs de neutrons) qui ont permis de lever certains verrous scientifiques. Si mon activité est expérimentale, ma motivation reste liée à un souci de compréhension et d'analyse quantitative des résultats obtenus ; de fait, je m'attache à développer les calculs ad-hoc lorsque l'interprétation des résultats n'est pas possible à la lumière de modèles existants. Depuis la fin de mes études universitaires en 1996, j'ai eu l'opportunité d'étudier, en recherche, des systèmes variés. Cette mobilité thématique reflète la mobilité géographique associée à mon parcours (thèse, postdoctorat et poste de chargée de recherche dans 3 laboratoires distincts) mais traduit aussi des choix de collaborations, contractuelles au besoin, ou développements que j'ai initiés au cours des dernières années en particulier. Ainsi, mon activité personnelle a été élargie vers des sujets prometteurs (matériaux multiferroïques, composés terres rares - métaux de transition, pour la dynamique d'aimantation et le transfert de spin), que je développe. Ce manuscrit tente de reproduire ce parcours...
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13

Uckert, Kyle. "High Temperature Resistivity and Hall Effect Measurements of Conductive and Semiconductive Thin Films". Ohio University Honors Tutorial College / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1276713762.

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14

Apaydin, Nil. "Novel Implementations of Coupled Microstrip Lines on Magnetic Substrates". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1373897365.

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15

Vabbilisetty, Pratima. "Fabrication and Characterization of Substrate Materials for Trace Analytical Measurements by Surface Enhanced Raman Scattering (SERS) Spectroscopy Technique". Connect to resource online, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1231794465.

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16

Ahmadi, Farzad. "Magnetic Micro- and Nanostructures for Electrical Machinery". University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1544521347564228.

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17

Bresson, Paul. "Étude des phénomènes thermiques ultrarapides dans les nanostructures plasmoniques". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST005.

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La thermoplasmonique est une branche de la plasmonique exploitant les phénomènes thermiques dans des structures métalliques. Longtemps regardées comme problématique, les pertes par effet Joule dues à l’absorption de la lumière par des nanoparticules métalliques sont maintenant considérées comme un point de départ pour de nombreuses applications : nanosources thermiques en médecine, enregistrement magnétique, catalyse chimique, thermotronique ou la conversion d’énergie.L’usage de laser femtosecondes sur des structures plasmoniques, permet de créer des nanosources thermiques confinées spatialement atteignant des températures électroniques très élevées devant la température du réseau atomique. L'absorption par un métal d'une impulsion d'énergie peut être décrite en trois étapes principales. Tout d'abord, une absorption des photons par les électrons du métal augmentant l'énergie des électrons à l'échelle de la centaine de femtosecondes avec des températures électroniques pouvant atteindre des milliers de degrés Kelvin alors que la température du réseau, elle, reste quasiment constante. Puis une deuxième étape au cours de laquelle les interactions électron-phonon transmettent l'énergie absorbée par les électrons au réseau, ce qui permet à l'énergie des électrons et du réseau d'atteindre un équilibre. Enfin, l’énergie est dissipée dans le substrat entourant le métal par conduction thermique.Il existe un grand nombre de modèles dans la littérature permettant de décrire le non-équilibre entre électrons et phonons mais cependant, une comparaison rigoureuse et quantitative avec des données expérimentales fait défaut pour valider ou invalider ces modèles. Cela a été l’objectif principal de cette étude.Afin d’étudier ces phénomènes, j’ai utilisé une expérience pompe-sonde où la pompe permet un chauffage ultra-rapide de l’échantillon ce qui provoque un changement de la permittivité dudit matériau. Le faisceau sonde permet alors de mesurer les variations dans le spectre de réflexion et de transmission, provoquées par le changement de permittivité.J’ai mis en place un code numérique permettant de modéliser l’évolution de la température dans un maillage 3D d’une structure composé d’éléments diélectriques et métalliques. Ce modèle thermique prend en compte les divers phénomènes de transport d’énergie dans un métal tel que le couplage électron-phonon, la conduction thermique électronique et des phonons et le déplacement balistique des électrons non thermalisés. Puis, via un modèle de la permittivité en fonction de la température prenant en compte les transitions interbandes et intrabandes, ce modèle a été couplé à un modèle optique permettant de simuler l’évolution des spectres optiques d’une structure en fonction de sa température afin de pouvoir confronter ce modèle numérique aux résultats expérimentaux par des ajustements des données.Ce modèle numérique a été validé sur de nombreuses expériences pompe-sonde effectuées sur des films d’or de diverses épaisseurs et des réseaux de nanostructures d’or sur verre ou sur film d’or. Nous avons pu montrer que parmi le très grand nombre de paramètres optiques et thermiques intervenant dans le modèle, toutes ces données expérimentales pouvaient être ajustées en utilisant un très petit nombre de paramètres libres, confirmant ainsi la robustesse du modèle. Enfin, ce modèle a pu être utilisé pour concevoir et optimiser des réseaux de structures permettant la mise en évidence expérimentale de la propagation de la chaleur sur des échelles de quelques centaines de nanomètre au sein d’une nanostructure d’or
Thermoplasmonics is a branch of plasmonics exploiting thermal phenomena in metallic structures. Long regarded as problematic, Joule losses due to the absorption of light by metallic nanoparticles are now considered as a starting point for many applications: thermal nanosources in medicine, magnetic recording, chemical catalysis, thermotronics or energy conversion.The use of femtosecond lasers on plasmonic structures, allows the creation of spatially confined nanosources of heat reaching very high electronic temperatures compared to the temperature of the atomic lattice. The absorption by a metal of a pulse of energy can be described in three main steps. Firstly, an absorption of photons by the electrons of the metal increases the electron energy on the scale of a hundred femtoseconds with electronic temperatures that can reach thousands of Kelvin, while the lattice temperature remains almost constant. Then, a second step, in which the electron-phonon interactions transmit the energy absorbed by the electrons to the grid, allowing the electrons and phonons to reach equilibrium. Finally, the energy is dissipated into the substrate surrounding the metal by thermal conduction.Many models exist in the literature to describe the non-equilibrium between electrons and phonons. However, a rigorous and quantitative comparison with experimental data is lacking to validate or invalidate these models. This was the main objective of this study.To study these phenomena, I used a pump-probe experiment where the pump allows an ultra-fast heating of the sample which causes a change in the permittivity of the metal. The probe beam then allows to measure the variations in the reflection and transmission spectrum, caused by the change in permittivity.I set up a numerical code allowing to model the temperature evolution in a 3D mesh of a structure composed of dielectric and metallic elements. This thermal model takes into account the various energy transport phenomena in a metal such as electron-phonon coupling, electron and phonon thermal conduction and ballistic displacement of non-thermalized electrons. Then, via a model of permittivity as a function of temperature taking into account the interband and intraband transitions, this model was coupled to an optical model to simulate the evolution of the optical spectra of a structure as a function of its temperature in order to be able to confront this numerical model with the experimental results by data fitting.This numerical model has been validated on numerous pump-probe experiments carried out on gold films of various thicknesses and gold nanostructure arrays on glass or gold film. We were able to show that, among the very large number of optical and thermal parameters involved in the model, all these experimental data could be adjusted using a very small number of free parameters, thus confirming the robustness of the model. Finally, this model was used to design and optimize samples allowing the experimental demonstration of heat propagation on scales of a few hundred nanometers within a gold nanostructure
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18

Nick, Zachary H. "Foundations for Smart Metamaterials by Liquid Metal Digital Logic and Magnetoelastic Properties Control". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587669303938667.

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19

Loreto, Renan Pires. "Proposta para realização de correntes magnéticas em gelos de spin artificiais". Universidade Federal de Viçosa, 2014. http://locus.ufv.br/handle/123456789/4272.

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Spin ice is a substance that does not have a single minimal­energy state. Even at very lower temperatures, these compounds shows a residual entropy as well as the water ice. The magnetic ordering of a spin ice resembles the position of hydrogen atoms in water ice, arranged in a tetrahedron and obeying the the ice rule. The most prominent ice spin compounds are holmium titanate and dysprosium titanate. This system is subject to geometrical frustration, when all interactions between pairs are not satisfied simultaneously. The artificial spin ice are structures that have magnetic monodomains subject to geometrical frustration generating mono pole ­ antimonopole pairs (or magnetic charges ) connected by an observable string. As the flow of electrical charges produces electric current, magnetic monopoles that can walk freely generate something like a magnetic current in these frustrated systems. In this work we manufacture and characterize structures of artificial spin ice, produced by nanolithography techniques, arranged in a rectangular unidirectional lattice and characterized by Atomic Force Microscopy (AFM) and Magnetic Force Microscopy (MFM). We note that for this particular lattice, the experimental results of ground state are consistent with the theoretical results also presented in this dissertation. Thus, these systems of artificial spin ice are a proposal for a practical use of magnetic currents caused by application of an external magnetic field. This system can be used at room temperature and its parameters, as nanoislands size and lattice spacing can be turned at will.
Gelo de spin é uma substância que não possui um único estado de mínima energia. Mesmo a temperaturas muito baixas, esses compostos apresentam uma entropia residual, assim como no gelo da água. O ordenamento magnético de um gelo de spin se assemelha a posição dos átomos de hidrogênio no gelo da água, dispostas em um tetraedro e obedecendo a chamada regra do gelo. Os gelos de spin naturais mais comuns são compostos de titanato de hólmio e titanato de disprósio. Este sistema é sujeito à frustração geométrica, quando todas as interações entre pares não são satisfeitas simultaneamente. Os gelos de spin artificiais são estruturas que possuem monodomínios magnéticos sujeitos a frustração geométrica gerando pares monopolo­antimonopolo (ou cargas magnéticas) ligados por uma string observável. Assim como o fluxo de cargas elétricas produz corrente elétrica, monopolos magnéticos podendo andar livremente, geram algo parecido com uma corrente magnética nesses sistemas frustrados. Neste trabalho fabricamos e caracterizamos estruturas de gelos de spin artificiais, produzidas por técnicas de nanolitografia, dispostas em uma rede retangular unidirecional e caracterizadas por Microscopia de Força Atômica (AFM) e Microscopia de Força Magnética (MFM). Observamos que para esta rede em particular, resultados experimentais do estado fundamental condizem com os resultados teóricos também apresentados neste trabalho. Assim, estes sistemas de gelos de spin artificiais são uma proposta para uma utilização prática de correntes magnéticas, causadas pela aplicação de um campo magnético externo. Este sistema pode ser utilizado a temperatura ambiente e seus parâmetros, como tamanho das nanoilhas e espaçamento de rede, podem ser ajustados a vontade.
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20

Murdock, Richard Craig. "RADIO FREQUENCY CONTROLLED STIMULATION OF INTRACELLULAR GOLD OR SILVER NANOPARTICLE CONJUGATES FOR USE AS POTENTIAL SENSORS OR MODULATORS OF BIOLOGICAL FUNCTION". Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1277753458.

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21

Kamanalu, Sunil S. "Proximity and Thickness Estimation of Aluminum 3003 Alloy Metal Sheets Using Multi-Frequency Eddy Current Sensor". Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1284513369.

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22

Amonson, Michael D. "Multiple Charge Carrier Species and Their Effects in Photorefractive Two-Beam Coupling in Potassium Niobate". University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1512494096366019.

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23

Yang, Yuan. "Influence of Chemical Doping on Microstructures and Superconducting Properties of MgB2 Wires and Bulk Samples". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469187563.

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24

Lalley, Nicholas M. "Composite Electromagnetic Applications and Devices". University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504878841254054.

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25

Raulet, Marie-Ange. "Contribution à la modélisation des matériaux magnétiques liés à leur environnement en génie électrique". Habilitation à diriger des recherches, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00703561.

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Les travaux de recherche présentés dans ce mémoire concernent la modélisation de lois statiques et dynamiques de matériaux dédiés à des applications de l'électrotechnique. Le titre de ce mémoire est volontairement plus général afin de montrer que ces travaux de recherche ne demandent qu'à être élargis. Les études traitées à ce jour portent sur la modélisation du comportement de matériaux magnétiques utilisés pour des dispositifs de l'électrotechnique. Une voie à venir sera de s'intéresser aux matériaux innovants et nouveaux dédiés aux applications de l'électronique de puissance et de prendre en compte les contraintes liées à leur environnement. Depuis plusieurs décennies, une course est lancée vers l'accroissement des performances technologiques et énergétiques des dispositifs du domaine du génie électrique. La miniaturisation, l'intégration, l'efficacité énergétique ou le fonctionnement avec des conditions sévères d'alimentation (formes d'onde de formes quelconques, fréquences élevées) ou de température auxquels sont soumis les convertisseurs électromagnétiques ou composants magnétiques sont autant de défis qui placent les matériaux au cœur de la conception de nouveaux prototypes. Un facteur apparu plus récemment qui résulte d'enjeux environnementaux et sociétaux tels que celui lié au développement durable vient renforcer la place occupée par les matériaux dans le domaine de l'ingénierie électrique. Concevoir des matériaux nouveaux ou innovants et les adapter au mieux au sein d'applications afin d'augmenter leurs performances est l'enjeu relevé par les ingénieurs, concepteurs, industriels et chercheurs du domaine du génie électrique. Dans cet objectif, il est important de posséder un outil d'aide à la conception de prototypes capables à représenter de façon fiable et réaliste les matériaux. Parmi les diverses approches de représentation de dispositifs électromagnétiques, la méthode basée sur du calcul de champs et celle fondée sur les Circuits Magnétiques Equivalents, constituent les méthodes les plus aptes à intégrer des lois réalistes de matériaux. Nos travaux s'inscrivent dans le cadre de ces deux approches. L'intégration d'un modèle d'hystérésis statique dans un code de calcul de champs de type éléments finis 2D a fait l'objet de nos premières activités lors de l'initiation de l'équipe matériaux du laboratoire. Nous ne détaillerons pas ces activités, seules nos contributions visant à améliorer les lois de matériaux pour leur intégration dans une modélisation par Circuit Magnétique Equivalent (CME) sont présentées dans ce mémoire. D'une façon générale, avant d'aborder l'implémentation de modèles de comportement de matériaux dans des codes de simulation de dispositifs électromagnétiques basés sur des approches diverses on doit se poser le problème de la définition de lois réalistes de matériaux. C'est dans ce cadre que se situent les activités de ce mémoire, issues du fruit d'activités de recherche personnelles ou d'équipe, ou bien de l'encadrement de travaux de thèses ou encore du résultat de collaborations industrielles. Notre cursus universitaire et notre environnement professionnel ont orienté nos activités vers des modélisations phénoménologiques des matériaux. Les modèles de lois de matériaux sur lesquels nous avons travaillés font intervenir des grandeurs macroscopiques et sont, par conséquent, transférables dans des outils de simulation employés en ingénierie ou en recherche. La modélisation du comportement des matériaux se situe à plusieurs niveaux selon les conditions de sollicitation du matériau (excitation en statique ou en dynamique) et le degré de précision réclamé pour la représentation. Nous verrons que la définition d'une loi statique précise de comportement du matériau constitue un préalable indispensable à l'élaboration d'une loi dynamique réaliste. Le premier chapitre de ce mémoire s'inscrit dans cet objectif et présente les outils que nous avons mis en place pour la représentation du comportement statique du matériau. Nos orientations ont deux visées : la première est de définir un modèle économe en paramètres, en gestion de données et temps de calcul avec l'idée sous-jacente d'une implémentation dans l'une ou l'autre approche de modélisation de dispositifs électromagnétiques ; la seconde privilégie la précision et la fiabilité du modèle. Nous verrons que concilier ces deux objectifs, constitue un réel défi. Les deuxième et troisième chapitres présentent les différentes représentations de comportement dynamique de matériaux élaborées. Nous avons volontairement scindé l'approche globale (deuxième chapitre) de l'approche aux dérivées partielles (troisième chapitre) afin de mettre en évidence la complémentarité des deux panoplies d'outils élaborées pour la représentation comportementale dynamique des matériaux. Le dernier chapitre s'intéresse à l'intégration des différents outils de représentation de matériaux mis en œuvre dans la modélisation de dispositifs électromagnétiques basée sur une approche par CME. L'apport des différents modèles de matériaux est mis en exergue au travers d'une application industrielle réelle. Pour terminer ce mémoire, nous conclurons sur les apports et les limitations des différents modèles mis en œuvre, puis nous définirons les perspectives engagées et à venir.
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26

Ning, Ding. "Analytical and Numerical Models of Multilayered Photonic Devices". University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1207712683.

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27

Silva, Leonardo de Sousa. "Efeitos de diluição química no composto intermetálico GdIn3". Pós-Graduação em Física, 2013. https://ri.ufs.br/handle/riufs/5294.

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This work proposes the development of a technique to growth of single crystals through metallic flux technique at the Sergipe State. Besides, the system YxGd1-xIn3 (0 x 0.5 to pass of 0.10 % ) has been obtained via this technique and its structural and magnetic properties are studied. X-ray diffraction results have been performed in order to verify if the desired crystalline phase was obtained. The experimental results show that it has been grown with success. The magnetic characterization is carried out through magnetic susceptibility data as function of temperature (2 x 300 K) and magnetic field (??7 H 7T). The T-dependence of the magnetization shows a suppression of the magnetic ordering temperature with increasing of the yttrium concentration. The analyses of these experimental data show that the system presents magnetic frustration which is linked to the dilution effect introduced by the yttrium ion in the gadolinium site. The magnetization data as function of magnetic field carried out at 2 K show a usual behavior of a material with antiferromagnetic ordering.
Este trabalho propôs a implementação da técnica de crescimento de monocristais via fluxo metálico, na Universidade Federal de Sergipe (UFS) campus de itabaiana. Além disso, o sistema YxGd1-xIn3 (0 < x < 0.5 a passo de 0.10 % ) foi obtido através dessa técnica e as propriedades estruturais e magnéticas foram estudadas. Medidas de difração de raios X foram realizadas com o intuito de verificar o crescimento da fase cristalina desejada. Os dados mostraram que ela foi obtida com sucesso. A caracterização magnética foi feita através de medidas de susceptibilidades magnética em função da temperatura (2 < x < 300 K) e do campo magnético (-7 < H < 7T). As medidas de magnetização em função da temperatura mostraram uma supressão da temperatura de ordenamento magnético com o aumento da concentração de ítrio. As análises desses dados mostraram que o sistema apresenta frustração magnética que está ligado ao efeito de diluição introduzido pelo íon de ítrio no sitio do gadolínio. As medidas de magnetização em função do campo magnético realizadas a 2 K mostraram um comportamento típico de um material com ordenamento antiferromagnético.
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28

Venkatasubramanian, Rajiv. "Composite Nanoparticle Materials for Electromagnetics". University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352993374.

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29

Törnqvist, Julia. "Electromagnetic Homogenization-simulations of Materials". Thesis, Uppsala universitet, Elektricitetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-395866.

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This thesis aims to determine the distribution of the relative permittivity for random mixtures of material using electromagnetic simulations. The algorithm used in the simulations is the FDTD method which solves Maxwell's equations numerically in the time-domain. The material is modeled as randomly shaped particles with radius 12 ± 10 micrometre in x- and y-direction and radius 3 ± 1 micrometre in zdirection. The scattering parameters from the transmitted and reflected electric field when a plane wave interacts with the material are measured. The relative permittivity is determined from the scattering parameters using the iterative Baker-Jarvis method. The simulations shows that both the distribution and the value of the relative permittivity is low when the particles have non conducting layers to force interruptions to prevent percolation, a conducting path between the particles. The most important result is of the kind where the simulations do not have any boundaries to prevent percolation. These simulations reflects how the relative permittivity distributes in real measurements. It is established that the value of the relative permittivity has a large distribution and also that percolation occurs because of the periodic structures.
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30

Chailloux, Thibaut. "Caractérisation et modélisation de matériaux magnétiques en hautes températures en vue d'une application au filtrage CEM". Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00703562.

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Un enjeu majeur de l'industrie aéronautique de demain est de concevoir et développer un avion " plus " électrique. En effet, sur un avion de ligne, les principaux systèmes utilisent des types d'énergies différents tels que l'énergie hydraulique ou pneumatique. La tendance actuelle est à la conversion de ces systèmes à l'énergie électrique car elle présente de nombreux avantages et permettrait des économies de masse, d'énergie, et de coûts de maintenance. Avec l'augmentation croissante des systèmes électriques dans l'avion se posent par conséquent des problèmes d'interférences et de compatibilité électromagnétique entre ces différents dispositifs. Par ailleurs ces systèmes électriques sont soumis à des conditions de travail très sévères, notamment des températures extrêmes. Dans le cadre du projet FEMINA (Filtrage Electromagnétiques et Matériaux pour l'INtégration en Aéronautique), l'objectif de notre équipe était d'étudier un filtre électrique soumis à des conditions de températures extrêmes. Ce filtre composé d'éléments passifs (condensateurs et inductances) est destiné à éliminer les interférences provoquées par le convertisseur électrique placé à proximité de la source d'énergie et de chaleur (le propulseur). Dans le cadre de mes travaux de thèse, je me suis intéressé plus particulièrement à l'effet de la température sur le comportement des inductances au travers des matériaux magnétiques qui les composent. J'ai ainsi déterminé les matériaux magnétiques que j'estimais capable de remplir leur rôle de filtrage en hautes températures, puis j'ai élaboré un modèle de comportement magnétique dynamique, tenant compte de l'effet de peau et de l'effet de la température et enfin j'ai testé ce nouveau modèle en l'incluant dans un simulateur circuit, afin de modéliser un filtre de mode commun répondant au cahier des charges de nos partenaires industriels.
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31

Sonde, Abayomi Emmanuel. "Etude et modélisation de procédés innovants de mise en compression de surfaces : Traitements de surface par cavitation et par impulsions électromagnétiques". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI015/document.

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Les procédés de traitement de surface tels que le grenaillage sont utilisés pour introduire des contraintes résiduelles de compression dans les matériaux métalliques. Cela permet de prévenir l'initiation et la propagation des fissures afin d'augmenter la durée de vie en fatigue des pièces mécaniques. Les limites et inconvénients des procédés actuels généralement utilisés pour cette fin sont connus et ont été mis en avant dans plusieurs études. Il s'agit d'une modification importante de l'état de surface (rugosité), une profondeur traitée limitée, des difficultés de mise en œuvre, etc. Aussi, de nouveaux procédés permettant d'obtenir des résultats équivalents voire meilleurs tout en évitant ces problèmes suscitent un intérêt grandissant. Le traitement de surface par cavitation (cavitation peening) et la mise en compression par impulsions électromagnétiques font partie de ces procédés innovants dont la modélisation a fait l'objet de cette thèse. Le traitement de surface par cavitation consiste à générer un jet d'eau submergé contenant des bulles de cavitation et dirigé vers la surface à traiter. La principale difficulté dans la modélisation du cavitation peening est la détermination du chargement mécanique sur la surface provenant de l'implosion des bulles de cavitation. L'effondrement des bulles peut se faire de manière sphérique ou non-sphérique suivant leur proximité de la paroi solide. Des modèles analytiques et numériques ont donc été élaborés pour étudier la dynamique des bulles et déterminer l'onde de pression due à une bulle sphérique d'une part, et la pression d'impact du micro-jet (bulle asphérique) d'autre part. Ces deux types de sollicitations ont été comparés et un modèle macroscopique pour le traitement par cavitation a été dérivé, en s'appuyant sur une simulation numérique du jet de cavitation. Une comparaison avec des résultats expérimentaux a été effectuée et a montré la pertinence du modèle proposé. En ce qui concerne le traitement par impulsions électromagnétiques, il consiste à générer un puissant champ magnétique transitoire par induction dans la pièce de matériau conducteur. Les contraintes résiduelles proviennent de la déformation plastique créée par les forces de Laplace à l'intérieur du matériau. Un modèle numérique couplant l'électromagnétisme et la mécanique des solides a été mis en place pour la simulation du procédé. Grâce à une étude d'optimisation, ce modèle a permis d'obtenir les paramètres électriques nécessaires pour arriver à mettre en compression des matériaux de type alliage de base nickel ou d'aluminium par cette méthode. Les profondeurs de la mise en compression calculées sont théoriquement par calcul plus élevées que celles obtenues avec les méthodes classiques de traitement de surface. Une étude de l'influence des différents paramètres a été faite et a montré que le procédé peut être contrôlé de manière relativement aisée en variant l'intensité et la pseudo-fréquence du courant traversant l'inducteur
Surface treatments methods like shot peening are used to introduce compressive residual stresses in metallic materials. The compressive stresses prevent the initiation and growth of cracks and hence improve the fatigue life of mechanical parts. The drawbacks and limitations of the existing processes generally used for this purpose are known and have been highlighted in many studies. These are, among others, an important surface modification (roughness), a limited compressive depth, difficulties in execution, debris and contamination problems, etc. Therefore, the interest in new surface treatment methods, which permit to obtain equivalent or even better compressive results while avoiding the previous problems, are growing. Cavitation peening and electromagnetic pulse peening are part of these innovative processes which modeling is the aim of this PhD thesis. Cavitation peening is a process of surface treatment which acts by the generation of cavitation bubbles near the workpiece surface. The modeling of this process is challenging because of the complexity of cavitation phenomenon and the main problematic point is the determination of the mechanical loading on the material due the bubbles collapse. In this thesis, an approach of modeling for cavitation peening based on the study of the dynamics of cavitation bubbles is proposed. Spherical and aspherical collapse of bubbles near a solid surface are studied by some numerical and analytical models. These two sources of loading pressures have been compared and a macroscopic model for cavitation peening have been derived by associating the numerical simulation of the cavitation jet and the localization of the cavitation zone. The comparison between the final residual stress profile calculated with the proposed model and the experimental results were satisfactory. Electromagnetic pulse peening (EMP) is a contactless process of surface treatment which could be used to introduce compressive residual stresses in conductive materials, by the generation of a high transient electromagnetic field. Laplace forces induced in the material by magnetic induction are the source of the material plastic deformation and compressive residual stresses introduction. To predict the EMP results, a numerical model have been built for the process simulation. The model, based on finite element method, coupled successfully electromagnetic and mechanical phenomena by using a sequential-coupled approach. It was proven theoretically, by the study of a reference case, that compressive residual stresses could be induced in metallic materials like nickel-based (Inconel) or aluminum alloys by the means of the present process. It was also shown by the calculations that much higher compressive depths than those of conventional peening processes could be achieved. The parametric study exhibited the influence of the maximum current intensity and frequency which affect both the compressive depth and the maximum residual stress
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32

Magda, Geoffrey. "Study of metallic architected materials under mechanical and electromagnetic loads". Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAX138.

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Des développements récents qui ont lieu dans les domaines des meta-matériaux et des couplages magnéto-mécaniques visent à la fois à améliorer des propriétés existantes ainsi que de créer de nouveaux comportements. Le but de cette thèse est d’étudier plus particulièrement les couplages entre matériaux magnétisables, courants électriques et comportements mécaniques. Tout d’abord nous détaillons le modèle multi-physique requis pour traiter ce problème. Lorsque c’est possible une résolution analytique est fournie. Néanmoins, pour traiter des géométries plus complexes une approche variationelle est fournie pour une analyse par éléments finis. Nous traitons alors deux cas concrets : un treillis partiellement magnétisable et parcouru par des courants unidirectionnels, puis un composite 2D partiellement magnétisable et conducteur. Nous en étudions le comportement sous sollicitation magnétique et mécanique ainsi que leur stabilité
Recent developments in the fields of meta-materials and magneto-mechanical couplings aim to both enhance existing properties and create new ones. The goal of this thesis is to study the interactions between magnetizable materials, electric currents, and mechanical response. First, we detail the multi-physics model required to address this issue. Whenever possible, an analytical solution is provided. To handle more complex geometries, a variational approach is employed for finite element analyses. Subsequently we examine two practical cases: a partially magnetizable mesh subjected to unidirectional currents and a partially magnetizable, conductive 2D composite. We investigate their behavior under combined magnetic and mechanical loading, as well as their stability
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33

Chazottes-Leconte, Aurélien. "Conception et fabrication d'un dispositif de mise en compression par impulsions électro magnétiques (EMP)". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1082.

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Les procédés de traitement de surface sont utilisés à l'échelle industrielle pour améliorer les performances de pièces mécaniques en introduisant des contraintes résiduelles de compression. Cette mise en compression de surface permet de limiter l'amorçage et la propagation de fissures dans le matériau. Ceci permet d'augmenter de façon significative la durée de vie en fatigue des pièces mécaniques ainsi traitées. L'utilisation de ces procédés dans l'industrie a démontré leur efficacité, mais aussi leurs limitations et inconvénients. Les défauts récurrents consistent en une profondeur traitée faible, une dégradation de l'état de surface (rugosité), des difficultés de contrôle, une contamination du matériau traité, etc. Ces défauts ont conduit à l'élaboration de nouveaux procédés innovants qui permettent de meilleures performances en évitant certains des inconvénients succinctement évoqués. Parmi ces procédés innovants, le traitement de surface par impulsion électromagnétique semble particulièrement intéressant. Ce procédé met en œuvre un puissant champ magnétique transitoire pour engendrer des forces de Laplace dans une pièce métallique et induire des contraintes résiduelles. Il n'existe que peu d'informations dans la littérature et il n'existe aucun dispositif expérimental de ce procédé. Cette thèse est dédiée à la conception et la réalisation d'un prototype de mise en compression électromagnétique. Le premier chapitre de cette thèse est un état de l'art des technologies de mise en compression et du procédé de mise en compression par impulsion électromagnétique. Ainsi, les besoins de ce procédé sont identifiés et les technologies pouvant répondre à ces besoins sont explorées. Le deuxième chapitre, après une sélection de la structure globale du dispositif, va consister aux dimensionnements des éléments du prototype EMP. Cette étude commencera avec une étude sur l'inducteur qui va être utilisé avant de continuer sur le dimensionnement du stockage d'énergie et de l'interrupteur de décharge. Afin de valider le dimensionnement des composants précédents, une simulation électromagnétique 3D du système est réalisée. L'assemblage du prototype est présenté dans le troisième chapitre ainsi qu'une première campagne d'essai sur un alliage d'aluminium. Deux types d'éprouvettes sont testées : une éprouvette fine pour vérifier visuellement la mise en compression (essai Almen) et une éprouvette massive afin d'évaluer la profondeur traitée. Une modélisation multiphysique 3D du procédé est réalisée afin de corréler ces résultats avec l'expérience. Dans un dernier chapitre, une étude exploratoire est menée sur un matériau ferromagnétique, le mumétal, pour visualiser l'influence des contraintes résiduelles sur les propriétés magnétiques de ce dernier
Penning processes are widely used in industries to apply compressive residual stresses into the most solicited part of mechanical pieces. In that way, the compressive residual stresses limit the priming and the propagation of micro-cracks in the material. This increases significantly the lifespan of the treated mechanical piece under fatigue stresses. These existing peening processes have proved their efficiency and also their limitations and weaknesses. The main recurrent defaults are a shallow depth of treatment, a degradation of the surface condition, a random control of the treatment, a material contamination, etc. These problems have led towards the development of news innovative peening processes which allow better performance avoiding some previous defaults briefly evoked. Among these news processes, the electromagnetic peening process seems especially interesting. This process uses high energy electromagnetic fields to induce Lorentz forces into a metallic piece and thus residual stresses. Actually, there is not much information about this process in the literature and no prototype was ever built. The work of this thesis is dedicated to development and realization of an electromagnetic peening prototype. The first chapter of this thesis adresses the state of the art of major peening processes actually in industrial use. Next, the electromagnetic peening process, or EMP process, is described and the electrical needs are exposed. A second state of the art is made about the technological solutions to respond to the EMP needs. The second chapter is about the conception of the EMP prototype with the electrical structure adopted in the previous chapter. The first step is about the inductor sizing to generate an electromagnetic field sufficient enough for a peening application. Next, the storage system is designed depending on the inductor parameters and finally the closing switch is created considering the electrical parameters used for the EMP process. To validate the previous results, a 3D electromagnetic simulation is done. The prototype assembly is presented in the third chapter and also the first experimental test on the EMP prototype. To begin with, an aluminium alloy with low yield strength is selected to be treated. Two different samples forms are used, a thin one, to realize a similar test to the Almen test and thick one to check the EMP depth of treatment. A 3D multiphysics simulation of these experiments is made and these numeric results are next correlated to the experimental ones. In the fourth chapter, an exploratory study is realized on the effects of the residual stresses on magnetic properties of ferromagnetic material, the mumetal
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34

CURRELI, NICOLA. "2D material-based electromagnetic devices". Doctoral thesis, Università degli Studi di Cagliari, 2020. http://hdl.handle.net/11584/284406.

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The realization of technologically-advanced components to be used in optoelectronic systems is one appealing research area in modern electronics. The electronics industry has to face several problems related to the cost of materials used in the implementation of the devices and also to pursue more sustainable growth without the use of polluting processes. To address these issues, alternative materials and processes must be developed considering the device requirements. A possible solution could be the use of two-dimensional (2D) nanomaterials due to their exceptional properties, together with pollutant-free commercially available deposition techniques. This thesis investigates the printing of specifically designed graphene- and indium selenide- based inks for the realization of antennas, supercapacitors as well as photodetectors, as fundamental units of an integrated wireless sensing system.
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35

Penfold, Justin David John. "Controlled electromagnetic rewarming of cryopreserved biological materials". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319611.

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36

Lu, Jie Ph D. Massachusetts Institute of Technology. "Novel electromagnetic radiation in Left-Handed materials". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39566.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.
Includes bibliographical references (leaves 137-141).
In this thesis, Cerenkov radiation of a moving charged particle inside a Left-Handed material (LHM) is studied through both theory and numerical simulations. A LHM is a material whose permittivity and permeability have negative real parts. In the analysis of this thesis, the general theory of Cerenkov radiation was first studied for the unbounded regions filled with LHM. The physical meanings of different Green's functions are discussed, and finally the second kind of Hankel function is determined to represent the special properties of Cerenkov radiation: forward incoming phase and backward outgoing power, which satisfies both momentum and energy conservation. The effects of the dispersion and dissipation of both permittivity and permeability are also investigated. The results show that both forward and backward radiated waves can co-exist at different frequencies. When the dissipation is reduced, the directions of forward and backward radiation are close to 900 with respect to the particle's moving direction. When the LHM is bounded, a waveguide can be formed. Depending upon the configuration and the relative dielectric constants of the surrounding normal material (we call them RHM in comparison with LHM), a surface wave can be formed.
(cont.) When a LHM is used as the filling material of a metallic waveguide, the radiation at some frequencies can be enhanced when a surface wave is excited. This enhancement can make the total radiated power in the waveguide larger than the radiation when the LHM is unbounded. Furthermore, using the same surface wave property, the decay of the radiation by a free space channel can be compensated when the channel is surrounded by a LHM. The wave of Cerenkov radiation is a TM wave. In order to have a homogeneous response, the LHM structure should have at least two dimensional isotropic negative permittivity and one dimensional negative permeability. A new LHM design was proposed in this thesis. We have demonstrated that this design shows several advantages in comparison with present published designs through reflection and transmission simulations, and TM (TE) prism simulations. For the unit cell's dimension of 5mm, a LHM band is observed between 6GHz and 7GHz for TM wave incidence. We use an antenna array to model a traveling current source, which can represent a single frequency component of a particle motion. The simulations show that our design can bend the radiation inside the structure.
(cont.) In order to observe the signal in the far field, we propose to use prism shaped LHM structures around the antenna array, by which, the difference between the angles of the forward radiation and backward radiation can be further amplified. These results can be a basis for a future experimental verification of backward radiation of the antenna arrays in a LHM. Besides, two effects of the surface wave for the effective LHM slab are also investigated. The results show that the surface wave actually determines the focusing ability of a LHM slab. When the mismatch between the slab and the surrounding area becomes small, those evanescent waves, whose wave number is less than that of the surface wave, can be amplified by the slab, and contribute to the focusing at the image plane. This property can help us easily estimate the resolution of a LHM slab when it is used as a flat lens. A unique guided wave can also exist when a LHM slab is surrounded by two RHMs, where the two RHMs can be different or the same. This guided wave has a linear function for the transverse profile of the field inside the LHM slab, which can never exist in either a RHM or a plasma dielectric waveguide.
by Jie Lu.
Ph.D.
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37

Ramesh, Prashanth. "Smart Materials for Electromagnetic and Optical Applications". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343821988.

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38

Pressl, Daniel G. (Daniel Gerd). "Investigation of electromagnetic welding". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53253.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references.
We propose several methodologies to study and optimize the electromagnetic process for Electromagnetic Forming (EMF) and Welding (EMW), thereby lowering the necessary process energy up to a factor of three and lengthening the life-time of EMW compression coils. We present a new theoretical approach to calculate a so-called critical kinetic energy to achieve a proper EMW joint, which is related to the volume of the accelerated mass and the Vicker's Hardness of the material. Using this novel approach, welding windows for several materials are presented. Studying the circuit theory, the current discharge pulse can be optimized to the needs of the EMW process, when opting for a critically damped RLC circuit. We present MultiSIM and MATLAB models that prove the proposed optimization and reflect the experimental EMW setup and parameters. Using the models, unknown parameters, such as machine inductance and resistance can be extrapolated for EMF and EMW machinery. Furthermore, the MATLAB model can calculate the optimal gap between the outer and inner workpiece for the outer workpiece to reach the maximum velocity at impact. Good correlation was found with regards to the High-Speed Videography used to study the EMF process in further detail measuring velocities between 50 m/s and 100 m/s. Studying the mechanical properties of the outer workpiece we propose an EMF-EMW setup that would decrease the strength of the outer workpiece by introducing a controlled amount of wrinkles through an EMF step with a mandrel inside the outer workpiece, followed by a lower critical energy EMW step.
(cont.) Through a failure study, accompanied by a metallurgical analysis, of an Aluminum Bronze Bitter coil we present a materials selection of other possible coil materials, as well as a new method called Electromagnetic Fatigue (EMFA) Analysis to study the crack initiation and propagation in electromagnetic high-current applications. Finally, through two sets of EMW experiments tubular lap joints that were stronger than the base material could be produced and the EMW process parameters of increased cleanliness, gap, wall thickness and a lower taper angle, for the case of our setup, showed to increase the final joint strength.
by Daniel G. Pressl.
Ph.D.
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39

Gollub, Jonah Nathan. "Characterizing artificial electromagnetic materials and their hybridization with fundamentally resonant magnetic materials". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3339169.

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Thesis (Ph. D.)--University of California, San Diego, 2008.
Title from first page of PDF file (viewed Feb. 6, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 109-115).
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40

Figueiras, Fábio Gabriel Nazário. "Study of multiferroic materials". Doctoral thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/4271.

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Doutoramento em Física
The present PhD work aims the research and development of materials that exhibit multiferroic properties, in particular having a significant interaction between ferromagnetism and ferroelectricity; either directly within an intrinsic single phase or by combining extrinsic materials, achieving the coupling of properties through mechanic phenomena of the respective magnetostriction and piezoelectricity. These hybrid properties will allow the cross modification of magnetic and electric polarization states by the application of cross external magnetic and/or electric fields, giving way to a vast area for scientific investigation and potential technological applications in a new generation of electronic devices, such as computer memories, signal processing, transducers, sensors, etc. Initial experimental work consisted in chemical synthesis of nano powders oxides by urea pyrolysis method: A series of ceramic bulk composites with potential multiferroic properties comprised: of LuMnO3 with La0.7Sr0.3MnO3 and BaTiO3 with La0.7Ba0.3MnO3; and a series based on the intrinsic multiferroic LuMn1-zO3 phase modified with of Manganese vacancies. The acquisition of a new magnetron RF sputtering deposition system, in the Physics Department of Aveiro University, contributed to the proposal of an analogous experimental study in multiferroic thin films and multilayer samples. Besides the operational debut of this equipment several technical upgrades were completed like: the design and construction of the heater electrical contacts; specific shutters and supports for the magnetrons and for the substrate holder and; the addition of mass flow controllers, which allowed the introduction of N2 or O2 active atmosphere in the chamber; and the addition of a second RF generator, enabling co-deposition of different targets. Base study of the deposition conditions and resulting thin films characteristics in different substrates was made from an extensive list of targets. Particular attention was given to thin film deposition of magnetic phases La1-xSrxMnO3, La1-xBaxMnO3 and Ni2+x-yMn1-xGa1+y alloy, from the respective targets: La0.7Sr0.3MnO3, La0.7Ba0.3MnO3; and NiGa with NiMn. Main structural characterization of samples was performed by conventional and high resolution X-Ray Diffraction (XRD); chemical composition was determined by Electron Dispersion Spectroscopy (EDS); magnetization measurements recur to a Vibrating Sample Magnetometer (VSM) prototype; and surface probing (SPM) using Magnetic-Force (MFM) and Piezo-Response (PFM) Microscopy. Results clearly show that the composite bulk samples (LuM+LSM and BTO+LBM) feat the intended quality objectives in terms of phase composition and purity, having spurious contents below 0.5 %. SEM images confirm compact grain packaging and size distribution around the 50 nm scale. Electric conductivity, magnetization intensity and magneto impedance spreading response are coherent with the relative amount of magnetic phase in the sample. The existence of coupling between the functional phases is confirmed by the Magnetoelectric effect measurements of the sample “78%LuM+22%LSM” reaching 300% of electric response for 1 T at 100 kHz; while in the “78%BTO+22%LBM” sample the structural transitions of the magnetic phase at ~350 K result in a inversion of ME coefficient the behavior. A functional Magneto-Resistance measurement system was assembled from the concept stage until the, development and operational status; it enabled to test samples from 77 to 350 K, under an applied magnetic field up to 1 Tesla with 360º horizontal rotation; this system was also designed to measure Hall effect and has the potential to be further upgraded. Under collaboration protocols established with national and international institutions, complementary courses and sample characterization studies were performed using Magneto-Resistance (MR), Magneto-Impedance (MZ) and Magneto-Electric (ME) measurements; Raman and X-ray Photoelectron Spectroscopy (XPS); SQUID and VSM magnetization; Scanning Electron Microscopy (SEM) and Rutherford Back Scattering (RBS); Scan Probe Microscopy (SPM) with Band Excitation Probe Spectroscopy (BEPS); Neutron Powder Diffraction (NPD) and Perturbed Angular Correlations (PAC). Additional collaboration in research projects outside the scope of multiferroic materials provided further experience in sample preparation and characterization techniques, namely VSM and XPS measurements were performed in cubane molecular complex compounds and enable to identify the oxidation state of the integrating cluster of Ru ions; also, XRD and EDS/SEM analysis of the acquired targets and substrates implied the devolution of some items not in conformity with the specifications. Direct cooperation with parallel research projects regarding multiferroic materials, enable the assess to supplementary samples, namely a preliminary series of nanopowder Y1-x-yCaxØyMn1O3 and of Eu0.8Y0.2MnO3, a series of micropowder composites of LuMnO3 with La0.625Sr0.375MnO3 and of BaTiO3 with hexagonal ferrites; mono and polycrystalline samples of Pr1-xCaxMnO3, La1-xSrxMnO3 and La1-xCaxMnO3.
O trabalho de doutoramento presente tem por objectivo a pesquisa e desenvolvimento de materiais que manifestem propriedades multiferróicas, em particular com uma significativa interacção entre os fenómenos de ferromagnetismo e ferroelectricidade; seja de forma intrínseca em determinados materiais singulares, ou extrínseca ao combinar materiais que apresentam respectivamente fenómenos magnetoestritivo e de piezoelectricidade e em que geralmente o acoplamento se processa mecanicamente entre as fases. Esta hibridação de propriedades permite a modificação dos estados de polarização magnética ou eléctrica por aplicação dos campos externos complementares (eléctricos e/ou magnéticos), dando origem a uma vasta área de investigação científica e potenciais aplicações tecnológicas numa nova geração de dispositivos electrónicos como memórias, processadores, transdutores, sensores, etc. O trabalho experimental inicial consistiu na síntese química de óxidos sob a forma de pós nanométricos, pelo método de pirólise da ureia; As séries de compósitos maciços com potenciais propriedades multiferróicas compreendem: LuMnO3 com La0.7Sr0.3MnO3 e BaTiO3 com La0.7Ba0.3MnO3; e uma série baseada na modificação com lacunas de Manganésio da fase multiferróica intrínseca LuMn1-zO3. A aquisição de um novo sistema de deposição por RF sputtering, no Departamento de Física da Universidade de Aveiro, contribuiu para a proposta de estudo análogo de amostras multiferróicas sob a forma de filmes finos e multicamadas. Além da estreia operacional do equipamento foram efectuadas algumas melhorias técnicas e funcionais de que se destacam: o desenho e construção das ligações eléctricas do aquecedor; de portadas, protecções e respectivos suportes para os magnetrões e para o “porta substratos”; a adição de dois controladores de fluxo de gás permitindo a introdução controlada de Árgon e de atmosfera activa de O2 ou N2 durante a deposição; e a adição de uma segunda fonte e controlador RF permitindo a co-deposição simultânea de filmes a partir de dois alvos diferentes. O estudo base sobre as condições de deposição e das características dos filmes finos resultantes em diferentes substratos foi efectuada a partir de uma extensa lista de alvos. Atenção particular foi dada à deposição de filmes finos das fases magnéticas de La1-xSrxMnO3, La1-xBaxMnO3 e da liga Ni2+x-yMn1-xGa1+y a partir dos correspondentes alvos La0.7Sr0.3MnO3; La0.7Ba0.3MnO3 e NiGa com NiMn. A caracterização estrutural das amostras foi efectuada com Difractometria por Raios-X (XRD) convencional e de elevada resolução; determinação da composição química foi essencialmente realizada por Espectroscopia de Dispersão de Electrões (EDS); medidas de magnetização foram executadas com recurso a um protótipo de Magnetometro por Vibração da Amostra (VSM) e as medidas de análise de superfície utilizaram Microscopia de Ponta (SPM) nas vertentes de piezo resposta (PFM) e de força magnética (MFM). Os resultados obtidos nos compósitos maciços (LuM+LSM e BTO+LBM) demonstram claramente que as amostras satisfazem os objectivos propostos em termos de composição pureza das fases, com eventual conteúdo em óxidos espúrios inferior a 0.5%. Imagens obtidas por SEM confirmam a compactação dos grãos e distribuição de tamanhos em torno dos 50 nm. Condutividade eléctrica, intensidade da magnetização e a dispersão da resposta em Magneto-Impedância são coerentes com a proporção relativa da fase magnética em cada amostra. A existência de um acoplamento entre as fases funcionais é evidenciada por medidas de efeito Magneto-Eléctrico na amostra “78%LuM+22%LSM” que apresenta uma resposta eléctrica de ~300% para 1 Tesla a 100 kHz; enquanto que na amostra “78%BTO+22%LBM” se assinala a transição estrutural da fase magnética a ~350 K resulta na inversão do comportamento do coeficiente ME. Um sistema de Medidas de Magneto-Resistência foi totalmente desenvolvido e montado desde a fase conceptual até ao estado operacional; permite testar amostras de 77 a 350 K em função do campo magnético até 1 Tesla, e rotação horizontal de 360º; o sistema foi também desenhado para poder efectuar medidas de efeito de Hall e permitir upgrades. Ao abrigo de protocolos de colaboração estabelecidos com diversas instituições nacionais e internacionais, foram realizados cursos de formação complementar e caracterização de amostras em técnicas como Magneto Resistência (MR), Magneto Impedância (MZ) e efeito Magneto Eléctrico (ME); Espectroscopia Raman e Fotoelectrónica de Raios-X (XPS); Magnetização via sistemas SQUID e VSM; Microscopia de Ponta em Piezo resposta (PFM) e Espectroscopia de excitação em largura de banda (BEPS); Espectroscopia de Rutherford por Retro dispersão (RBS); Difracção de Neutrões em pós (NPD) e Correlações de Perturbação Angular (PAC) Colaboração em projectos de investigação fora do âmbito dos materiais multiferróicos permitiu ampliar e versatilizar experiencia em técnicas de preparação e caracterização de amostras, nomeadamente medidas de VSM e XPS permitiram identificar os estados de oxidação dos clusters de iões de Ruténio que integram complexos moleculares utilizados em catalisadores; A certificação por XRD e SEM/EDS do conjunto dos alvos e amostragem dos substratos adquiridos implicou a devolução de alguns itens com por falta de conformidade com as especificações. Cooperação directa em projectos de investigação paralelos sobre materiais multiferróicos permitiu o acesso a amostras suplementares, nomeadamente a uma série nano pós de Y1-x-yCaxØyMn1O3 e de Eu0.8Y0.2MnO3; a series de compósitos microestruturados de LuMnO3 com La0.625Sr0.375MnO3 e de BaTiO3 com ferrites hexagonais; e a diversas amostras poli- e mono-cristalinas de Pr1-xCaxMnO3, La1-xSrxMnO3 e La1-xCaxMnO3.
FCT - SFRH/BD/25011/2005
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41

Ruff, Bradley M. "Carbon Nanotube and Nanoparticle Materials for Electromagnetics Applications". University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367925618.

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Murad, Mark Richard. "Radiation View Factors Between A Disk And The Interior Of A Class Of Axisymmetric Bodies Including Converging Diverging Rocket Nozzles". Cleveland State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1210962269.

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43

Naeem, Majid. "Theory, modelling, and applications of advanced electromagnetic materials". Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/31858.

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A multitude of recent work predicts many novel concepts based on the availability of non-natural materials; some prominent examples include transformation optics (TO) and perfect lens. The interest in this eld has grown dramatically due to spec- ulated possibility to allow for continuously varying material properties to steer the incident wave at will, such as for the TO. The posed challenges for their realisation include the limitations of numerical modelling and manufacturing techniques. A de- sign scheme has been proposed, in this thesis, for composite materials: the desired electromagnetic properties of composites can be engineered by judiciously varying the volume fraction of the inclusion-to-host materials, by manipulating the geomet- ric arrangement of inclusions, or by altering their dielectric contrast. The analysis of the homogenised response of the designed materials at macro-scale requires effective medium modelling techniques. The existing effective medium approximation tech- niques have been discussed, and their pros and cons outlined. A homogenization scheme has been introduced that is based on the interaction of the incident wave and the nanoparticles at the micro-scale, which further requires efficient electromagnetic modelling. The conventional nanoparticle modelling techniques, as well as the state of the art, have been reviewed and a dipole-moment-based method to efficiently solve modern nanoparticle-based electromagnetic problems has been outlined. The appli- cability of the proposed scheme has been demonstrated by employing it to design various EM devices. An improved permittivity extraction scheme has been proposed for the homogenization of composites. Unlike classical homogenization schemes, the extracted parameters, using the proposed technique, follow the relation between the real and imaginary parts, that is, Kramers-Kronig relations. Several random and periodic structures have been simulated for the purpose of extracting the ef- fective electromagnetic properties and interpreting the results so as to establish a connection between them.
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Hussaini, Sheena. "Integrated Magnetic Components for RF Applications". Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1431951933.

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45

Gupta, Bhaawan. "Advanced electromagnetic non-destructive testing on creep degraded high chromium ferritic steels : Characterization, Modelling and physical interpretation". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI074.

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Sous des températures et des pressions élevées constantes, les matériaux métalliques de structure subissent une dégradation mécanique par fluage qui entraîne des changements microstructuraux. Ces derniers, s'ils ne sont pas surveillés à temps, peuvent entraîner des incidents sérieux, notamment dans le domaine de la production d’énergie électrique (centrales électriques). Pour déterminer les changements microstructuraux, le matériau doit avoir une forme et une taille spécifiques pour que l'analyse des images obtenues par microscopie électronique à balayage, diffraction par rétrodiffusion d'électrons, etc. soit effectuée. Cette préparation destructive demande à extraire le matériau à tester du système, et à le modifier pour la mesure. Afin de surmonter ce problème, dans ce travail de thèse sont proposées trois techniques micro magnétiques non destructives, pour étudier l'évolution des signatures magnétiques par rapport aux niveaux de rupture auquel les matériaux sont exposés. Il est légitime de supposer que tous les changements microstructuraux qui se produisent dans le matériau vont se refléter dans les signatures magnétiques mesurées. Le matériau étudié ici est de l'acier à haute teneur en chrome très sensible au fluage et principalement utilisé dans les centrales thermiques. Certains paramètres magnétiques, tels que la coercivité, la réversibilité magnétique, sont dérivés et montrent de fortes corrélations avec la microstructure. De même, des techniques basées sur les courbes d'hystérésis et le bruit magnétique de Barkhausen sont également appliquées. Pour quantifier davantage les résultats obtenus à partir des signatures magnétiques des matériaux, le modèle de Jiles-Atherton a été adapté à la simulation des signaux de contrôle non destructif. A l’inverse, la possibilité de déterminer les paramètres du modèle à partir des seules mesures de contrôle non destructif est démontrée. Cela apporte des éléments complémentaires à l’interprétation physique des changements microstructurels. La technique de modélisation peut aider en outre à résoudre le problème de l'absence de normes dans les essais non destructifs, quel que soit le dispositif expérimental utilisé. Les paramètres sont enfin comparés pour révéler la sensibilité de chacun d’entre eux aux changements microstructuraux, et ce en fonction de chaque technique de contrôle non destructif utilisée
Under constant high temperatures and pressure, the material undergoes mechanical creep degradation which leads to microstructural changes. These microstructural changes if not monitored on time, can lead to some serious fatal accidents such as in power plants. To investigate these microstructural changes, the material has to be shaped in a certain specific shape and size to have the imaging analysis using Scanning electron microscopy, Electron backscatter diffract ion etc. which are destructive in nature and involve high equipment cost. In order to overcome this issue, this thesis work, incorporates three different non-destructive techniques, to study the evolution of magnetic signatures with respect to the level of rupture they are exposed to. It is legitimate to assume that all the microstructural changes that occur in the material can be reflected in the corresponding magnetic signatures measured. The material that has been studied here is high chromium creep degraded steel which is used in the thermal power plant. The magnetic signatures are evaluated in terms of microstructural information to draw the conclusions. Some magnetic parameters from the curves, such as coercivity, magnetic reversibility are derived which show strong correlations with the microstructure. Similarly, techniques based on Hysteresis curves, and magnetic Barkhausen Noise are also implemented. To further quantify the results obtained from the magnetic signatures of the materials, a model has been developed to derive model parameters in order to physically interpret the microstructural changes. The modelling technique will help in overcoming the issue of lack of standards in NDT, irrespective of the experimental set-up involved. The parameters are compared to reveal sensitivity based on the technique. Finally, conclusion has been drawn to check which parameters are correlated to microstructure for a particular NDT technique used
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Rafiq, Muhammad Nadeem. "Carbon Microfiber Material for Electromagnetic (Shielding) Applications". Diss., North Dakota State University, 2015. http://hdl.handle.net/10365/25293.

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Electromagnetic shielding is becoming more and more important with the abundance of wireless devices. Therefore a need has arisen for more versatile, flexible and low-cost solutions for shielding. For these requirements, carbon microfiber material has been proposed for electromagnetic shielding applications. For this purpose its shielding effectiveness has been measured and modeled in a simulation environment. A parametric simulation was conducted for the material property ?conductivity? and the results were compared to measured ones. These simulation results were also verified by the analytical solution for the shielding effectiveness and the agreement between the simulated values and analytical results demonstrated that the carbon microfiber material, though having less conductivity than the traditional metallic shields is a good candidate for electromagnetic shielding applications. Carbon microfiber not only provides comparable shielding effectiveness to a metallic shield but it can be advantageous because of its light weight, corrosion resistance and flexibility. Also, its porous nature can help with cooling of enclosed electronic circuits.
COMSATS Institute of Information Technology, Pakistan
North Dakota State University (NDSU)
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47

Sen, Saffet Gokcen. "Investigation Of Electromagnetic Wave Propagation In Double Negative Materials". Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609748/index.pdf.

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This thesis analyzes some aspects of electromagnetic wave propagation in double negative materials. Double negative materials have negative refractive indices. They are backward-wave materials. Plane waves undergo negative refraction at interfaces between double positive and double negative media. Causality principle implies these properties. High frequency plane wave scattering from a double negative infinitely long cylinder has been analyzed by using modified Watson transform, geometrical optics and Mie series. Mie series results and the modified Watson transform results have been found to be in good agreement. Hence, the physical mechanism of the scattering has been revealed.
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48

Abram, Eric Ryan. "Electromagnetic materials characterization of ferromagnetic composites at microwave frequencies". [Ames, Iowa : Iowa State University], 2007.

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49

Mackay, Tom G. "Homogenisation of linear electromagnetic materials : theoretical and numerical studies". Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368749.

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50

Youngs, Ian John. "Electrical percolation and the design of functional electromagnetic materials". Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271628.

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