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1
Kumar, Pawan Goldreich Peter Martin. "Excitation and damping of solar p-modes /." Diss., Pasadena, Calif. : California Institute of Technology, 1988. http://resolver.caltech.edu/CaltechETD:etd-09092008-090628.
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Bryan-Brown, Guy Peter. "Optical excitation of electromagnetic modes using grating coupling." Thesis, University of Exeter, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280664.
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Strojny, Brandan Thomas. "EXCITATION AND ANALYSIS OF CHARACTERISTIC MODES ON COMPLEX ANTENNA STRUCTURES." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1301006813.
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Wang, Feng. "Modes, Excitation and Applications of Plasmonic Nano-apertures and Nano-cavities." Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1348588159.
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Chen, Yi. "Propagation and Excitation of Electromagnetic Modes for Travelling-wave MRI Applications." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449158025.
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Lamriben, Cyril. "Transferts anisotropes d'énergie en turbulence en rotation et excitation de modes d'inertie." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00734192.
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Nous présentons une étude expérimentale de l'influence d'une rotation d'ensemble sur le déclin d'un écoulement turbulent dans une géométrie confinée. L'écoulement est généré en translatant rapidement une grille dans un récipient parallélépipédique, et nous mesurons les champs de vitesse dans un plan vertical (parallèle à l'axe de rotation) grâce à un dispositif de PIV embarqué. Nous montrons dans un premier temps qu'une partie significative de l'énergie est contenue dans un écoulement moyen reproductible, qui s'identifie à une superposition de modes d'inertie résonnants de la cuve. Le couplage possible entre cet écoulement et la turbulence suggère que la turbulence ainsi créée n'est pas en déclin libre. Nous montrons cependant qu'il est possible d'inhiber l'apparition de ces modes d'inertie en modifiant les caractéristiques géométriques de la grille. Cette nouvelle configuration permet alors de caractériser dans l'espace physique les transferts d'énergie pour une turbulence en déclin libre. L'énergie associée aux incréments de vitesse et la densité de flux d'énergie sont calculées à partir d'un grand nombre de réalisations indépendantes. Nous montrons que la rotation provoque une forte bidimensionalisation de la distribution d'énergie, et que celle-ci est contrôlée par une densité de flux d'énergie qui reste quasi-radiale, mais qui fait apparaître une dépendance angulaire marquée. Enfin, nous étudions également l'écoulement dans un cube, que nous soumettons à une libration longitudinale afin d'exciter les modes observés initialement avec le dispositif de turbulence de grille. En comparant les champs de vitesse expérimentaux aux prédictions numériques des modes inviscides, nous montrons que seul un certain nombre de modes, compatibles avec les symétries du forçage, peuvent être excités par libration. Nous caractérisons en particulier la résonance du mode de plus bas ordre compatible avec les symétries du forçage, et discutons du rôle de la viscosité.
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Elston, Stephen John. "Characterisation of ferroelectric liquid crystal layers by the excitation of optic modes." Thesis, University of Exeter, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277166.
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Al-Anbaki, Atheer Faisal Hameed. "Footfall excitation of higher modes of vibration in low-frequency building floors." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34081.
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This thesis investigates the footfall excitation of higher modes of vibration in low-frequency floor structures. This is motivated by the increased number of floors reportedly failing to meet the required occupants comfort level although being designed in accordance with the current state-of-the-art design guidelines. In particular modern, lightweight, and slender floor structures. The contribution to knowledge of this thesis can be summarised as: quantifying the signal energy of measured walking forces within and above the natural frequency cut-off proposed by the current state-of-the-art design guidelines; quantifying the contribution of higher modes of vibration to the overall response of low-frequency floors to human walking; propose measures to judge the response nature of low-frequency floors, these are the relevant change of the point stiffness and the shape of frequency response functions; proposing a frequency-domain approach that enables designers to include higher modes of vibration in the design against human-induced vibration. It was found that the signal energy of walking forces is distributed well beyond the natural frequency cut-off proposed by the current state-of-the-art design guidelines. Also, the contribution of localised, higher, modes of vibration to the overall response of ultra-lightweight floors was significant. Moreover, it was found that higher modes affect the response of floors of various construction types in one way or another. Hence, it was recommended to consider their contribution in the design of floors against human-induced vibration. Also, it was found that the higher the relative change of the point stiffness the more higher modes contribute to the overall response of floors. Finally, the frequency-domain analysis was found less expensive than time-domain analysis and could result in similarly useful information.
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Novikau, Ivan [Verfasser]. "Excitation and damping mechanisms of geodesic acoustic modes in tokamaks / Ivan Novikau." Ulm : Universität Ulm, 2020. http://d-nb.info/121694928X/34.
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Zarzuela, Fernández Ricardo. "Novel quantum phenomena and excitation modes in type-I superconductors and magnetic vortices." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/285263.
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The aim of this thesis was to study quantum phenomena and excitation modes in type-I superconductors and magnetic vortices.
The intermediate state in type-I superconductors is characterized by the gradual penetration of magnetic flux and the coexistence of normal and superconducting domains. This thermodynamic phase shows a magnetic irreversibility of topological origin, even in the case of defect-free samples. This irreversibility has been explored in disk-shaped samples made of lead (the prototype of a type-I superconductor) using a magnetic field applied perpendicularly to the disk plane, by means of the measurement
of hysteresis cycles at different temperatures, zero-field-cooled and field-cooled magnetization curves at different magnetic fields and magnetic relaxations along the descending branch of the hysteresis cycles. Non-thermal magnetic relaxations have been observed in these samples at low temperatures, which have been attributed to the tunnel effect of normal-superconductor interfaces through pinning energy barriers. A quantum model based on the Caldeira-Leggett theory for dissipative systems have been developed to explain these experimental observations. The interface is described as a 2D elastic manifold that is pinned by a planar defect. The pinning barrier can be controlled by a supercurrent that exerts a force on the interface.
The vortex state turns out to be the ground state of magnetic disks for a wide variety of thicknesses and radii. It is characterized by the curling of the magnetization in the plane of the disk, leaving virtually no magnetic ‘charges’. The very weak uncompensated magnetic moment of the disk sticks out of a small area confined to the vortex core. The low-frequency dynamics of the vortex state is characterized by the spiral-like precessional motion of the vortex core as a whole (gyrotropic mode), which can be induced by the application of an in-plane magnetic field. The presence of structural defects in these magnetic disks affects the dynamics of the vortex state, which is indicative of the elastic nature of the vortex core along the axial direction of the disk. It has been studied whether the gyrotropic mode allows spatial dispersion similar to spin waves of a finite wavelength in ferromagnets. The excitation spectrum splits into two branches, one related to the gyrotropic mode with a gap given by the gyrofrequency of the disk and the other related to the existence of an effective mass associated to the vortex core. The magnetic irreversibility of the vortex state has been also explored by means of an experimental protocol analogous to that used in the case of type-I superconductors. Non-thermal magnetic relaxations have been observed again at low temperatures, which is attributed to the tunnel effect of a segment of the vortex core line through pinning barriers. A quantum model based on the Caldeira-Leggett theory for dissipative systems have been developed to explain these experimental observations. The interface is described as a 1D elastic manifold that is pinned by a linear defect.
To conclude, the effect of the vortex state on the supercurrent of a Josephson junction has been studied in the case where the non-superconducting layer consists of a magnetic disk with the vortex as the ground state. It has been concluded that the variation of the Josephson current with tiny displacements of the vortex core can be detected experimentally.El objetivo de esta tesis ha sido estudiar fenómenos cuánticos y modos de excitación en superconductores tipo-I y vórtices magnéticos. La irreversibilidad magnética en muestras de plomo con forma de disco en el estado intermedio ha sido explorada mediante medidas de ciclos de histéresis a diferentes temperaturas, medidas de las curvas de magnetización zero-field-cooled y field-cooled a diferentes campos y relajaciones magnéticas a lo largo de la rama descendiente de los ciclos de histéresis. Se han observado relajaciones magnéticas independientes de la temperatura en estas muestras, las cuales se atribuyen al efecto túnel de las interficies normal-superconductor a través de barreras de anclaje. Un modelo de efecto túnel basado en la teoría de Caldeira-Leggett para sistemas disipativos se ha construido para explicar estas observaciones experimentales, donde la interfície se trata como una variedad 2D elástica que se ancla a defectos planares. La barrera de anclaje se puede controlar mediante la inyección de supercorriente en el sistema. El núcleo del estado vórtice muestra una naturaleza elástica a lo largo de la dirección axial de los discos magnéticos que lo presentan como estado fundamental. Se ha estudiado bajo qué condiciones el modo girótropo es compatible con una dispersión espacial semejante a las ondas de espín de longitud de onda finita presentes en un ferromagneto. El espectro de excitaciones axiales presenta dos ramas bien definidas, una asociada al modo girótropo y la otra originada por la existencia de una masa efectiva asociada al núcleo. También se ha explorado la irreversibilidad magnética del estado vórtice mediante un protocolo análogo al de los superconductores tipo-I. De nuevo se ha observado un comportamiento no térmico a bajas temperaturas en las relajaciones magnéticas, el cual es atribuido al efecto túnel de un segmento del núcleo vorticial a través de las barreras de anclaje. Un modelo de efecto túnel basado en la teoría de Caldeira-Leggett para sistemas disipativos se ha construido para explicar estas observaciones experimentales, donde el núcleo vorticial se trata como una variedad 1D elástica anclada a un defecto lineal. Por último, se ha estudiado cuál sería el efecto del estado vórtice sobre la supercorriente de una unión Josephson si como capa no superconductora se escogiera un disco magnético con este estado fundamental. Se ha concluido que la variación de la corriente Josephson con desplazamientos pequeños del núcleo vorticial es detectable experimentalmente.
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Donipudi, Raghunandan K. "Self referencing SPR sensor by simultaneous excitation of long and short range surface plasmon modes." Lexington, Ky. : [University of Kentucky Libraries], 2006. http://lib.uky.edu/ETD/ukyelen2006t00468/RaghunandanDonipudi%5FMSThesis.pdf.
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Thesis (M.S.)--University of Kentucky, 2006.Title from document title page (viewed on August 22, 2006). Document formatted into pages; contains: x, 56 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 54-55).
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Etourneau, Karine. "Etude de l'interface coeur/gaine des fibres optiques polymères par excitation de modes de galerie." Limoges, 1996. http://www.theses.fr/1996LIMO0020.
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Les procedes de fabrication des fibres optiques polymeres et leur vieillissement sont susceptibles de degrader la qualite de l'interface cur/gaine. Mon travail a consiste a elaborer des methodes d'optique guidee permettant l'etude de cette interface. L'idee de depart a ete de considerer que la puissance diffusee en raison de ces defauts le long de la fibre est proportionnelle a celle qui est guidee. Le but a alors ete d'injecter l'energie a proximite de l'interface et d'etudier sa propagation. Nous avons d'abord analyse la possibilite d'etudier l'interface en injectant, sur la face d'entree de la fibre, un mode tubulaire d'ordre azimutal eleve. Malgre une amelioration sensible du dispositif de selection modale dans une cavite laser disponible au laboratoire, le confinement de l'energie pres de la gaine n'a pas ete suffisant. Nous avons ensuite utilise les modes de galerie optiques qui permettent le confinement de l'energie a la peripherie de surfaces courbes. La vitesse de phase et le domaine occupe par ces modes ont ete determines par une theorie electromagnetique rigoureuse. Une representation par rayons lumineux et une modelisation par guide plan equivalent ont permis d'obtenir plus rapidement ces caracteristiques. L'excitation de ces modes a l'interface cur/gaine a ete realisee par prisme, apres un polissage lateral de la fibre. Les champs proche et lointain en sortie ont ete decrits en fonction des conditions d'injection. Le releve de la puissance diffusee le long de la fibre et la mesure de celle transmise, par la methode de la coupure, nous ont conduit a remettre en cause la proportionnalite prevue entre ces deux puissances. Finalement, nous avons propose des explications plausibles a cette contradiction
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Orucevic, Fedja. "Production de microtores de silice sur silicium : excitation et caractérisation de leurs modes de galerie." Paris 6, 2007. http://www.theses.fr/2007PA066642.
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Les microtores de silice sur les puces de silicium sont un nouveau type de microcavités à modes de galerie. Dans la double filiation des microsphères de silice et des microdisques de GaAs, ils en combinent les avantages, soit la très haute surtension des cavités de silice fondue (Q ~ 107 – 109), et les faibles volumes accessibles par les microcavités intégrées (V~ 100*(lambda/N)3), ce qui fait d’eux des composants idéaux pour les expériences d’électrodynamique quantique en cavité et d’optique non-linéaire. L’intégration des microtores découle de leur méthode de fabrication qui implique successivement des étapes de la lithographie et gravure de la silice et du silicium, puis la fusion au laser CO2. Cette thèse décrit successivement les modes de galerie des microcavités toriques, et la méthode de fabrication des microtores. Elle porte ensuite sur la caractérisation, l’excitation et la détection de ces modes. Elle décrit notamment une détection en onde évanescente grâce à des fibres polies selon un plan formant un grand angle avec l’axe optique, en sorte de réaliser l’accord de phase entre la microcavité et la fibre. Ceci permet de sélectionner la fluorescence émise dans les modes de galerie, au détriment de la celle émises dans les modes fuyants. De meilleures sélectivité et efficacité sont obtenues en utilisant des fibres amincies (tapers) que nous avons produites et étudiés en grand détail. Ces résultats permettent d’obtenir un couplage optimal entre les tapers et les modes des microcavités. Le spectre des modes de galerie a ainsi pu être obtenu et comparé aux prédictions théoriques.
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PANZERI, NICOLA. "NONLINEAR WAVES EXCITATION AND INTERACTION IN PURE ELECTRON PLASMAS." Doctoral thesis, Università degli Studi di Milano, 2021. http://hdl.handle.net/2434/814967.
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Nonneutral plasmas are excellent subjects for well controlled studies on basic physics problems and industrial research over a wide range of parameters. For the long-time confinement, merger and recombination of antimatter, the method of choice is some variant of the Penning-Malmberg trap, and many of the techniques for the manipulation of charged particles, such as cooling, compression, transfer, and ultimately a stable confinement in a quiescent state, are based on methods first developed by the nonneutral plasma community using electron plasmas. Another fascinating properties of nonneutral plasmas is the fluid analogy: in a cold, magnetized, nonneutral plasma, the 2D transverse dynamics equations are isomorphic to the Euler equations for an ideal 2D fluid. Hence, a pure electron plasma in a Penning-Malmberg trap evolves as an inviscid, incompressible bidimensional fluid.
The study and control of the various waves and instabilities is of great interest in physics, and it is often intertwined with non-linearity and turbulence. Experiments aimed at unveiling hidden dependencies between parameters or improve the control over non-equilibrium, unstable configurations can lead to the discover of new phenomena, and a more thorough understanding of basic plasma physics, like the excitation and interaction of different plasma modes in pure electron plasmas, is likely to be a useful tool for a range of applications.
In this thesis work, we present the results of the experiments made on two different Penning-Malmberg traps on the excitation and interaction of nonlinear waves in pure electron plasmas. On the Eltrap device, located at the University of Milan, Italy, we perform experiments on the excitation and control of high order diocotron modes via the rotating electric field technique. On the CamV device, located at the University of California, San Diego, we investigate the newly discovered phenomenon of TG waves splitting due to the interaction with a diocotron mode.
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Fraser, Michael John. "Optical Fiber Microstructures for Self-Contained Whispering Gallery Mode Excitation." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73659.
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Optical resonators, which confine light by resonant recirculation, serve as the basis for a wide variety of optical components. Though they appear in many geometric forms, the most effective of optical resonators show axial symmetry in at least one dimension. A popular variation that finds broad application is the dielectric sphere. Acclaimed for their high quality (Q) factor and small modal volume, spheres owe credit of these attractive features to their support of whispering gallery mode (WGM) resonances. The sensitivity of a resonance's frequency and Q to strain, temperature, and other parameters of the surrounding medium can be the basis for ultracompact modulators and sensors.
Physically, WGMs are special optical modes which can be understood as light rays that orbit the equator of the sphere guided by total internal reflection. Like a smooth stone can be skipped along the surface of a pond, light can be confined to the inside of a sphere by successive reflections. To best excite WGMs, the source light should initially trace a line tangent to the sphere's circumference. But incorporating a tiny sphere with such nanometric tolerances into a practical sensor structure has its challenges and the prospects for microsphere applications have suffered because of the plight of this problem.
The work in this dissertation details the fabrication and function of three new "press fit" spherical resonators. These etched fiber micro-devices were developed to meet the demand for a robust, self-integrated means of coupling light between an optical fiber and WGMs in a microsphere resonator. The etching processes have been tuned to enable secure storage of a microsphere while also providing efficient excitation and interrogation of WGMs. Furthermore, the methods have been designed to be staightforward, quick, and repeatable. Using standard etchants on common polarization-maintaining fiber with readily purchased microspheres, the press fit resonators demonstrated here can be batch-fabricated and assembled. The press fit spherical resonator offers an alignment-free and conveniently pigtailed WGM coupler that has great potential for bio-science sensing applications and studies of resonant bispheres.Ph. D.
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Li, Ran. "Molecular Characterization of Human Tissue Samples by Raman Spectroscopy with Different Laser Modes and Excitation Wavelengths." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1365419543.
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Candéla, Yves. "Microcavités de silice : Excitation par fibre des modes de galerie et fonctionnalisation par des nanocristaux de silicium." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00658670.
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Cette thèse exploite les modes de galerie de microcavités optiques, qui résultent d'un guidage par réflexion totale interne et possèdent des facteurs de qualité très élevés et de faibles volumes modaux. Ce mémoire rappelle dans un premier temps la description théorique des modes des microsphères et des microtores de silice. Leur fabrication est ensuite présentée, en soulignant les améliorations apportées au cours de la thèse, notamment la production de sphères de diamètre inférieur à 20 μm, et l'amélioration de la symétrie des tores à l'aide d'une polarisation circulaire. Nous présentons une étude détaillée de leur excitation par un coupleur fibré en insistant sur le phénomène d'interférence en ondes évanescentes qui se produit dans le gap. Ce phénomène est responsable des élargissements et déplacements des résonances dont je présente une étude poussée. Cette approche débouche sur une méthode très efficace de détermination de l'ordre radial. Par ailleurs, on observe des formes de résonance inattendues, qui résultent d'interférences entre deux modes du coupleur dans une configuration analogue à l'interféromètre de Mach-Zehnder. Nous abordons enfin la réalisation de microsources fondées sur l'émission de nanocristaux de silicium (NC Si) dans ces cavités. Les émetteurs ont des tailles contrôlées allant de 0,6 à 6 nm. Le chauffage au laser CO2 active la photoluminescence des NC Si autour de 750 nm, puis induit leur destruction partielle par coalescence. Le facteur de remplissage optique et les défauts de la matrice apparaissent comme les principaux obstacles à une amélioration significative des performances. Il a été possible de collecter l'émission de NC Si couplés à des microtores, en champs proche et lointain.
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DonlagicÌ, Denis. "Microbend sensor structure based on selective excitation and filtering of the modes in graded index optical fibres." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248635.
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Dubreuil, Nicolas. "Excitation par fibre optique et cartographie en champ proche des modes de galerie de microsphères de silice." Rennes 1, 1997. http://www.theses.fr/1997REN10161.
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Ce travail de these porte sur l'etude des modes de galerie de tres haute surtension observes dans des microspheres de silice dont le diametre varie entre 50 et 400 microns. La lumiere peut se propager le long de l'equateur dans une serie de reflexions totales internes tout en restant confinee dans un anneau dont les dimensions transverses sont de l'ordre de la longueur d'onde. Ces proprietes peuvent etre mises a profit dans des experiences fondamentales d'electrodynamique en cavite, pour obtenir des effets d'optique non-lineaire a faible seuil ou encore pour des applications interessant le domaine des telecommunications. Ce manuscrit de these decrit une nouvelle methode experimentale d'excitation des modes de galerie utilisant une fibre optique. Ce systeme presente l'avantage d'etre plus simple et plus compact que le montage d'excitation par prisme conventionnel. Nous avons illustre la possibilite d'utiliser les microspheres dans des dispositifs optoelectroniques par la fabrication d'un filtre optique tres selectif en longueur d'onde. Nous avons aussi realise des experiences de cartographie par microscopie en champ proche des modes de galerie. Ces experiences nous permettent de localiser avec precision le champ resonnant contenu dans la microsphere et de determiner les ordres d'interference des resonances. Ces informations sont essentielles pour la realisation d'experience sur le couplage d'atomes ou molecules au champ d'un mode de galerie.
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Yoshida, Kenichi. "Pair correlation and continuum coupling effects on low-frequency modes of excitation in deformed neutron-rich nuclei." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136769.
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Schoth, Mario [Verfasser], Andreas [Akademischer Betreuer] Knorr, and Thomas [Akademischer Betreuer] Renger. "Theory of excitation transfer in nanostructures influenced by vibrational modes / Mario Schoth. Gutachter: Andreas Knorr ; Thomas Renger. Betreuer: Andreas Knorr." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1067387749/34.
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El, Hami Khalil. "Excitation selective des modes de vibration d'un cantilever en utilisant les proprietes piezoelectriques et electrostrictives du coplymere p(vdf/trfe)." Besançon, 1996. http://www.theses.fr/1996BESA2062.
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Nous avons decrit une methode pour augmenter la sensibilite du capteur de force resonnant. L'excitation du cantilever avec un polymere piezoelectrique place dans des endroits sensible et precis afin de selectionner une haute frequence de resonance de vibration du cantilever. La frequence de resonance eleve est souhaitable pour augmenter la sensibilite du gradient de force ressenti entre les deux aimants. Dans l'autre partie de la these, nous nous sommes interesses a l'electrostriction du copolymere polyfluorure de vinylidene et trifluoroethylene p(vdf/trfe). En presence d'un champs electrique, le comportement mecanique du film de copolymere varie avec la temperature de recuit. Si le film est recuit avant la temperature de fusion du copolymere, nous avons observe, avant une polarisation, l'effet d'electrostriction melange avec la piezoelectricite. Si le film est recuit apres la temperature de fusion, nous avons observe uniquement l'effet electrostrictif avant toute polarisation et l'effet piezoelectrique seul apres la polarisation. La grande valeur du coefficient d'electrostriction obtenue avant la polarisation peut-etre utilise dans des applications d'actionneurs.
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Yao, Jing. "Characterization of Mechanical Properties of Thin-Film Li-Ion BatteryElectrodes from Laser Excitation and Measurements ofZero-Group Velocity Resonances." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7128.
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The mechanical properties of thin-film Li-ion battery electrodes are controlled by the micro structure of the constituent materials. In this work, a non-contact and non-destructive measurement of the mechanical properties of electrode films is performed by measurement of zero group velocity (ZGV) resonances. The ZGV Lamb wave modes of a solid bi-layer consisting of a thin metallic layer and a thin compliant coating layer are shown to be dependent on the Young's moduli, thicknesses, densities and Poisson ratios of the layers. Theoretical models are used to quantify the sensitivity of the ZGV resonances to changes in mechanical properties. Experimental ZGV resonances are excited using a pulsed infrared laser and detected using a laser interferometer. Commercial-grade battery films with different coating materials, densities and thicknesses are measured. Young's moduli of the battery electrode layers are estimated using the combination of a theoretical model and experimental results. The effect of the calendering process on the battery materials is also investigated. Results suggest that the Young's modulus of the electrode coating increases drastically after the battery films are calendered. This technique can be used to quantitatively study the mechanical properties of Li-ion battery electrodes to improve overall battery performance.
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Maury, Rémy. "Réponse d'un jet rond subsonique à une excitation fluidique stationnaire et instationnaire." Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2272.
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Ce travail tente d'analyser la réponse d'une jet axisymétrique turbulent à une excitation fluidique stationnaire et instationnaire lorsque le contenu fréquentiel et aziumutal (!,m) de la perturbation est maîtrisé. Le dispositif de contrôle utilisé est composé de 16 microjets ronds répartis sur le bord de fuite de la tuyère. L'utilisation des microjets provoque une réduction du champ acoustique rayonné (particulièrement pour le cas de contrôle stationnaire). Le champ aérodynamique est ensuite sondé grâce à des mesures fil chaud et PIV stéréoscopique résolue en temps. L'excitation instationnaire permet d'utiliser les moyennes de phase afin d'effectuer une décomposition triple du champ de vitesse. L'étude de la composante cyclique de la “réponse du jet” montre une synchronisation spatio-temporelle importante sur une grande étendue spatiale. En d'autres mots, le forçage a une grande autorité déterministe sur l'écoulement. De plus, la comparaison de la composante cyclique de la réponse du jet avec la théorie de la stabilité linéaire indique qu'il existe des ondes d'instabilité hydrodynamique au sein du jet. L'analyse du jet contrôlé par injection fluidique stationnaire montre ensuite comment l'effet du contrôle peut être expliqué par la déformation du champ moyen conduisant à la réduction du taux de croissance des ondes d'instabilité dans le jet. Cette déformation est dûe à l'introduction d'un couple de paramètre (nombre d'onde/fréquences) pour lequel le champ moyen de l'écoulement est stable. La réponse du jet étant turbulente, cela implique que les tensions de Reynolds déforment le champ moyen de manière à ce que les modes les plus instables aient des taux de croissance plus faiblesThis work investigates the response of an axisymetric turbulent jet to steady and unsteady fluidic florcing where the azimuthal wavenumber-frequency (!,m) content of the perturbation is well known. The control setup is composed of 16 round microjets azimutally distributed around the nozzle lip. Such actuation can lead to a decrease in the acoustic energy radiated by the jet (especially for the steady case). The aerodynamic fied is investigated using hotwire measurements and time-resolved stereoscopic PIV. Using the unsteady forcing, phase-averaging is possible, and this allows the implementation of a triple decomposition of the measurements. Examination of the cyclic component of the flow response shows that a non-negligible phase-locked fluctuation is obtained over a large spatial extent, in other words, the actuation has good deterministic control authority over the flow. Furthermore, comparison of the cyclic component of the flow response with Linear Stability Theory supports the idea that the jet response comprises linear hydrodynamic instability waves. Subsequent analysis of jets controlled by steady fluidic actuation shows how the control effect can be explained by a mean-flow modification that leads to the reduction of instability-wave growth rates ; the mean flow modification is argued to be due to the introduction of azimuthal wavenumber-frequency pairs to which the mean flow is stable. The response is therefore turbulent, and involves Reynolds stresses which deform the mean-field such that the most unstable modes have lower growth rates
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Hatayama, Ken. "Excitation of secondary Love and Rayleigh waves in a three-dimensional sedimentary basin evaluated by direct boundary method with normal modes." 京都大学 (Kyoto University), 1997. http://hdl.handle.net/2433/198904.
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London, Lionel. "On gravitational wave modeling: numerical relativity data analysis, the excitation of kerr quasinormal modes, and the unsupervised machine learning of waveform morphology." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53973.
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The expectation that light waves are the only way to gather information about the distant
universe dominated scientific thought, without serious alternative, until Einstein’s 1916
proposal that gravitational waves are generated by the dynamics of massive objects. Now,
after nearly a century of speculation, theoretical development, observational support, and
finally, tremendous experimental preparation, there are good reasons to believe that we will
soon directly detect gravitational waves. One of the most important of these good reasons
is the fact that matched filtering enables us to dig gravitational wave signals out of noisy
data, if we have prior information about the signal’s morphology. Thus, at the interface of
Numerical Relativity simulation, and data analysis for experiment, there is a central effort
to model likely gravitational wave signals. In this context, I present my contributions to
the modeling of Gravitational Ringdown (Kerr Quasinormal Modes). Specifically by ap-
propriately interfacing black hole perturbation theory with Numerical Relativity, I present
the first robust models for Quasinormal Mode excitation. I present the first systematic de-
scription of Quasinormal Mode overtones in simulated binary black hole mergers. I present
the first systematic description of nonlinear Quasinormal Mode excitation in simulated bi-
nary black hole mergers. Lastly, it is suggested that by analyzing the phase of black hole
Quasinormal Modes, we may learn information about the black hole’s motion with respect
to the line of sight. Moreover, I present ongoing work at the intersection of gravitational
wave modeling and machine learning. This work shows promise for the automated and near
optimal placement of Numerical Relativity simulations concurrent with the near optimal
linear modeling of gravitational output.
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Wen, Jing [Verfasser], and Bernhard [Akademischer Betreuer] Schmauss. "Excitation and Detection of Highly Confined Plasmonic Gap Modes with Subwavelength Dimensions = Anregung und Detektion hochlokalisierter plasmonischer Gap-Moden mit Subwellenlängendimensionen / Jing Wen. Betreuer: Bernhard Schmauss." Erlangen : Universitätsbibliothek der Universität Erlangen-Nürnberg, 2011. http://d-nb.info/1018308938/34.
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Jossent, Mathieu. "Développement de fibres optiques à dispersion contrôlée pour l'élaboration de lasers ultrarapides à 2 µm." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0016/document.
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L’objectif de cette thèse est d’ouvrir la voie à la démonstration de l’amplification parabolique à 2 μm en format tout fibré. La théorie sur l’amplification d’impulsions auto-similaires est d’abord présentée. Il en découle que le meilleur amplificateur tout fibré à 2 μm devra s’appuyer sur une fibre dopée aux ions Tm3+ présentant à la fois une forte dispersion normale et une grand aire effective. L’amplification parabolique ne peut pas être réalisée dans des fibres monomodes à base de silice à 2 μm du fait de la forte dispersion anormale présentée par le matériau. Afin de surmonter cette limitation, une fibre dont le mode LP02 présente à la fois une forte dispersion normale et une grande aire effective à 2 μm a été conçue et réalisée. Un convertisseur spatial de lumière dédié à la génération du mode LP02 a également été conçu et réalisé. La pureté d’excitation par ce convertisseur du mode LP02 de la fibre passive a été évaluée à 99,9% par la technique interférométrique d’imagerie spatialement et spectralement résolue. Une source d’impulsions ultrabrèves (100 fs) et accordable en longueur d’onde de 1,6 μm à 2 μm a été créée pour générer le signal de l’amplificateur. Cette source a en outre permis de mesurer la dispersion du mode LP02 de la fibre passive à la longueur d’onde de 1,95 μm, celle-ci vaut -106 ps/(nm.km) en excellent accord quantitatif avec les résultats numériques. Des modélisations numériques de l’amplificateur nonlinéaire basé sur la version active de cette fibre indiquent que des impulsions présentant une puissance crête de l’ordre du MW à 1,9 μm sont envisageables en sortie de l’amplificateur paraboliqueThe goal of this PhD thesis is to pave the way towards the demonstration of parabolic amplification at 2 μm in an all-fiber format. The physical theory on self-similar pulse amplification is first presented. The best all-fiber amplifier at 2 μm would need a special Tm-doped fiber with both high normal dispersion and large effective area. Parabolic amplification is however prohibited in silica based singlemode fiber working at 2 μm due to the large anomalous dispersion of silica. To overcome this limitation, a four-mode fiber in which the LP02 mode exhibits high normal dispersion combined with large effective area at 2 μm was designed and manufactured. A dedicated mode converter has also been designed and manufactured. Using the spatially- and spectrally-resolved imaging technique the purity of excitation of the LP02 mode in the passive fiber was evaluated to 99.9%. An ultrashort pulse (100 fs) source tunable from 1.6 μm to 2 μm was implemented to seed the amplifier. This source allowed to measure the LP02 mode dispersion of the passive fiber at the wavelength of 1.95 μm: D = -106 ps/(nm.km) in excellent quantitative agreement with the simulations. Numerical modeling of a nonlinear amplifier based on the realized active fiber shows that MW peak power class pulses centered at 1.9 μm can be obtained at the output of the parabolic amplifier
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Baboux, Florent. "Effets spin-orbite géants sur les modes collectifs de spin de puits quantiques." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-01020564.
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Cette thèse est consacrée à l'étude des effets du couplage spin-orbite dans des puits quantiques semi-conducteurs dopés (GaAs et CdMnTe), par spectroscopie Raman électronique. Dans ces structures existent des champs magnétiques intrinsèques (Dresselhaus et Rashba). Ces champs offrent des moyens attractifs pour manipuler le spin des électrons, mais contribuent aussi à la relaxation de spin via leur dépendance avec le vecteur d'onde de l'électron (mécanisme D'yakonov-Perel'). Nous montrons que pour les modes collectifs de spin de puits quantiques, le scénario destructif D'yakonov-Perel' est transformé en un scénario constructif : les interactions Coulombiennes font émerger un champ spin-orbite collectif, proportionnel au vecteur d'onde de l'excitation, et renforcé d'un facteur de plusieurs unités par rapport aux champs spin-orbite individuels. Nous mettons d'abord en évidence ces effets spin-orbite géants sur le plasmon de spin inter-sous-bande, dans des puits quantiques de GaAs. Le champ spin-orbite collectif, qui conduit à un éclatement de structure fine du spectre plasmon, est superposé à un champ magnétique extérieur et cartographié dans l'espace réciproque. Nous étudions ensuite l'onde de spin intra-sous-bande du gaz d'électrons polarisé en spin, dans des puits quantiques magnétiques dilués de CdMnTe. Le champ spin-orbite collectif se superpose ici au champ Zeeman géant du composé. Nous mesurons le facteur de renforcement du champ spin-orbite collectif. Enfin, nous déterminons la dépendance du facteur de renforcement avec la densité électronique, et démontrons la possibilité de contrôler l'amplitude du champ spin-orbite collectif à l'aide d'une grille optique.
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Chelda, Samir. "Simulation du parcours des électrons élastiques dans les matériaux et structures. Application à la spectroscopie du pic élastique multi-modes MM-EPES." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2010. http://tel.archives-ouvertes.fr/tel-00629659.
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La spectroscopie EPES (Elastic Peak Electron Spectroscopy) permet de mesurer le pourcentage he d'électrons rétrodiffusés élastiquement par la surface d'un échantillon soumis à un bombardement électronique. C'est une méthode non destructive et extrêmement sensible à la surface. L'objectif de ce travail est de modéliser le cheminement des électrons élastiques dans la matière grâce à une simulation informatique basée sur la méthode Monte Carlo. Cette simulation contribue de manière essentielle à la connaissance et à l'interprétation des résultats expérimentaux obtenus par spectroscopie EPES. Nous avons, de plus, adapté cette simulation à différentes surfaces transformées à l'échelle micrométrique et nanométrique. A l'aide d'une méthode originale, basée sur une description couche par couche du matériau, j'ai réalisé un programme informatique (MC1) rendant compte du cheminement des électrons élastiques dans les différentes couches du matériau. Le nombre d'électrons ressortant de la surface dépend de nombreux paramètres comme : la nature du matériau à étudier, l'énergie des électrons incidents, l'angle d'incidence, les angles de collection des analyseurs. De plus, je me suis intéressé à l'effet de la rugosité de la surface et j'ai démontré qu'elle joue un rôle déterminant sur l'intensité du pic élastique. Ensuite, grâce à l'association de la spectroscopie EPES et de la simulation Monte Carlo, j'ai déduit les modes de croissance de l'or sur substrat d'argent et de cuivre. Les effets de l'arrangement atomique et des pertes énergétiques de surfaces ont ensuite été étudiés. Pour cela, une deuxième simulation MC2 tenant compte de ces deux paramètres a été réalisée permettant d'étudier les surfaces à l'échelle nanométriques. Ces paramètres jusqu'alors non pris en compte dans notre simulation MC1, joue un rôle essentiel sur l'intensité élastique. Ensuite, j'ai obtenu une formulation simple et exploitable pour l'interprétation des résultats obtenus par la simulation MC2 pour un analyseur RFA. Afin de valider, les différents résultats de la simulationMC2, j'ai réalisé des surfaces de silicium nanostructurées, à l'aide de masques d'oxyde d'alumine réalisés par voie électrochimique. J'ai pu créer des nano-pores par bombardement ionique sous ultravide sur des surfaces de silicium. Afin de contrôler la morphologie de la surface, j'ai effectué de l'imagerie MEB ex-situ. La simulation Monte Carlo développée associée aux résultats EPES expérimentaux permet d'estimer la profondeur, le diamètre et la morphologie des pores sans avoir recours à d'autres techniques ex-situ.Cette simulation MC2 permet de connaître la surface étudiée à l'échelle nanométrique.
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Maatoug, Tarak. "Synthèse d'observateurs adaptatifs pour les systèmes non linéaires." Phd thesis, Université de Caen, 2009. http://tel.archives-ouvertes.fr/tel-01058802.
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Dans cette thèse, nous proposons la synthèse d'observateurs adaptatifs pour certaines classes de systèmes non linéaires multi-sorties uniformément observables. Dans un premier temps, les systèmes avec une paramétrisation linéaire sont considérés. Ensuite, les résultats obtenus ont été étendus au cas de paramétrisation non linéaire. La caractéristique principale des observateurs proposés réside dans le fait que leur gain fait intervenir une fonction de synthèse dont le choix permet d'obtenir différents types d'observateurs tels que des observateurs de type grand gain classiques ou à modes glissants. De plus, le réglage de ce gain se fait à travers le choix d'un seul paramètre scalaire. La convergence exponentielle des observateurs proposés a été établie sous une certaine condition d'excitation persistante qui a été donnée. Dans la dernière partie de la thèse, nous proposons un schéma de commande adaptative avec retour de sortie pour une classe de systèmes non linéaires commandables et uniformément observables. Les performances des observateurs proposés sont illustrées en simulation à travers des exemples académiques et des exemples réels d'application relatifs à un moteur asynchrone, un bioréacteur et un moteur à fuel.
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Cikojević, Viktor. "Ab-initio quantum Monte Carlo study of ultracold atomic mixtures." Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/672119.
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The properties of mixtures of Bose-Einstein condensates at T=0 have been investigated using quantum Monte Carlo (QMC) methods and Density Functional Theory (DFT) with the aim of understanding physics beyond the mean-field theory in Bose-Bose mixtures. In particular, quantum liquid droplets with attractive intraspecies and repulsive interspecies attraction were studied, for which we observed significant contributions beyond Lee Huang Yang (LHY) theory that affect the energy, saturation density, and surface tension. The critical atom number in droplets in free space for total number of atoms N between N=30 and N=2000 was obtained. Results of the surface tension for three values of the attractive interspecies interactions are presented. For a homogeneous system, extensive calculations of the equations of state were performed and we report the influence of finite-range effects in beyond-Bogoliubov theory. In systems interacting with a small (large) effective range, we observe repulsive (attractive) beyond-LHY contributions to the energy. For the droplets in a mixture of 39K atoms, which were observed experimentally for the first time, the calculations of equations of state were performed. Combining QMC-built functionals with DFT, the discrepancy in the estimation of critical atom number between the mean-field theory and experimental results was explained by the proper inclusion of the effective range in inter-particle interaction models. The influence of finite-range effects on breathing and quadrupole modes in 39K quantum droplets was investigated. We predicted a significant deviation in the excitation frequencies when entering a more correlated regime. Finally, the phase diagram of repulsive Bose-Bose mixtures in a spherical harmonic trap using Quantum Monte Carlo calculations was studied. Density profiles were obtained reported and we found the occurrence of three phases: separation of condensates in two blobs, fully mixed and shell-separated phase. A comparison with the Gross-Pitaevskii solutions showed a large deviation in the regime of large mass imbalance and strong interactions. We showed the universality in the density profiles with respect to the s-wave scattering length and found numerical evidence for Gross-Pitaevskii scaling present beyond the regime of applicability of Gross-Pitaevskii equations.Hemos investigado las propiedades de las mezclas de condensados de Bose-Einstein en el límite de temperatura cero. Para ello hemos usado métodos cuánticos de Monte Carlo (QMC) y la teoría del funcional de la densidad (DFT) con el objetivo de comprender la física más allá de la teoría del campo medio en las mezclas bosónicas. En particular, se estudiaron las gotas de líquido cuántico originadas con interacciones atractivas entre especies distinats y repulsivas entre especies iguales. Observamos contribuciones significativas más allá de la teoría de Lee Huang Yang (LHY) que afectan a la energía, la densidad de saturación y la tensión superficial. Calculamos el número crítico de átomos en gotitas en el espacio libre para un número total de átomos N entre N = 30 y N = 2000. Obtuvimos resultados de la tensión superficial para tres valores de las interacciones atractivas entre especies. Para un sistema homogéneo, se realizaron cálculos extensos de las ecuaciones de estado y reportamos la influencia de los efectos de rango finito en la teoría, más allá de Bogoliubov. En sistemas que interactúan con un rango efectivo pequeño (grande), observamos contribuciones repulsivas (atractivas) a la energia más allá de LHY. Para las gotitas en una mezcla de 39K átomos, que se observaron experimentalmente por primera vez en ICFO, se realizaron los cálculos de ecuaciones de estado. Combinando funciones obtenidas de QMC con DFT, explicamos la discrepancia en la estimación del número crítico de átomos, entre la teoría de campo medio y los resultados experimentales, mediante la inclusión adecuada del rango efectivo en los modelos de interacción entre partículas. Se investigó la influencia de los efectos de rango finito en los modos monopolar y cuadrupolar en gotas cuánticas de 39K. Predijimos una desviación significativa en las frecuencias de excitación al entrar en un régimen más correlacionado. Finalmente, se estudió el diagrama de fase de mezclas bosóncas repulsivas en una trampa armónica esférica utilizando cálculos de Quantum Monte Carlo. Se obtuvieron los perfiles de densidad y se probó la existencia de tres fases: separación de condensados en dos lóbulos, una fase completamente mezclada y una fase separada con capas esféricas. Una comparación con las soluciones de Gross-Pitaevskii mostró una gran desviación en el régimen de gran desequilibrio de masas e interacciones fuertes. Finalmente, mostramos la presencia de universalidad en los perfiles de densidad, con respecto a la longitud de dispersión en onda S, y encontramos evidencia numérica del factor de escala de Gross-Pitaevskii más allá del régimen de aplicabilidad de las propias ecuaciones de Gross-Pitaevskii.
Ultrahladne atomske mješavine istražene ab-initio kvantnom Monte Carlo metodom. Svojstva smjesa Bose-Einsteinovih kondenzata pri T = 0 istražena su korištenjem metoda kvantnog Monte Carla (QMC) i teorije funkcionala gustoće (DFT) s ciljem proučavanja fizike izvan teorije srednjeg polja u bozonskim mješavinama. Proučili smo kvantne kapljice s jednakim i odbojnim interakcijama između atoma istovrsne komponente te privlačnim interakcijama atoma različitih komponenti u interakciji i opazili smo značajne doprinose povrh Lee Huang Yang (LHY) teorije koji utječu na energiju, saturacijsku gustoću i površinsku napetost. Odredili smo kritični broj atoma za kapljice u slobodnom prostoru za broj atoma u kapljici N između N = 30 i N = 2000. Izračunali smo površinsku napetost za tri vrijednosti privlačnih međuatomskih interakcija. Izvršili smo opsežne proračune jednadžbi stanja iznimno rijetke tekućine bozonske mješavine i uočili utjecaj efekata konačnog dosega koji nije predviđen Bogoliubovljevom teorijom. U sustavima koji interagiraju s malim (velikim) efektivnim dosegom, opaženi su odbojni (privlačni) doprinosi koje ne predviđa LHY teorija. Izračunali smo jednadžbe stanja za kapljice bozonskih mješavina koje su po prvi put eksperimentalno uočene u smjesi 39K atoma. Kombinirajući funkcionale gustoće izgrađene pomoću kvantnog Monte Carla s DFT-om, neslaganje u procjeni kritičnog broja atoma između teorije srednjeg polja i eksperimentalnih rezultata je objašnjeno preko pravilnog uključivanja efektivnog dosega u modele međudjelovanja čestica. Istražen je utjecaj efektivnog dosega na pobuđenja kapljice 39K, i to na mod disanja i kvadrupolni mod. Dobiveni rezultati prikazuju značajno odstupanje frekvencija pobude pri ulasku u korelirani režim. Detaljno smo proučili fazni dijagram odbojnih Bose-Bose mješavina u sfernoj harmonijskoj zamci koristeći kvantne Monte Carlo račune. Dobiveni su profili gustoće koji pokazuju pojavu tri faze: separacija kondenzata u dvije nakupine, potpuno miješanje i separacije u obliku ljuske. Usporedba s riješenjima Gross-Pitaevskii jednadžbi pokazuje veliko odstupanje u režimu velike masene neravnoteže i jakih interakcija. Pokazali smo univerzalnost profila gustoće s obzirom na s-valnu duljinu raspršenja te postojanje Gross-Pitaevskii skaliranja prisutnog izvan dosega primjenjivosti Gross-Pitaevskii jednadžbi.
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Akra, Mirna. "Etude de filtres RF planaires miniatures. Amélioration de la réjection hors-bande et accordabilité." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT024/document.
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Le but de ce travail était de développer des filtres passe-bande RF dans la technologie de PCB, avec trois objectifs principaux. Le premier objectif était de développer des formules de synthèse tosimplify la procédure de conception du filtre. Le deuxième était de parvenir à un rejet wideout bande sans modifier les caractéristiques de la bande de filtrage. Le troisième objectif est de contrôler la fréquence centrale du filtre en utilisant diode varicapThe purpose of this work was to develop RF bandpass filters in PCB technology,with three main objectives. The first objective was to develop synthesis formulas tosimplify the design procedure of the filter. The second was to achieve wideout-of-band rejection without modifying the in-band filtering characteristics. Thethird objective was to control the center frequency of the filter by using varactordiode.The bandpass filter topology treated in this thesis is based on Stub-LoadedResonators (SLR). The main features of this filter topology were treated. Equivalentcircuits based on J-inverters and susceptance parameters were derived. Based onthese equivalent circuits, synthesis formulas were developed. Simulations werepresented to validate the synthesis theory. For a proof-of-concept, third orderstripline bandpass filters were designed and fabricated based on this synthesis.Analysis technique using odd- and even- mode was achieved on the SLR. Thusresonance odd- and even-mode conditions were derived. These conditions aim toeasily control the first spurious frequency. Moreover, to go further in improving theout-of-band rejection a new technique, called “U corner structure”, was developedand design rules were derived. Based on these design rules an extended out-of-bandrejection was achieved without any modification in the passband and by maintainingthe compactness of the filter. A first spurious frequency was localized at up to ninetimes the working frequency in the case of the Parallel-coupled Stub-Loadedresonator (PC-SLR) filter. Also, by applying this technique into the classicalparallel-coupled filter the first and second spurious frequencies were rejected. Toaddress the issue of tunable filters, the SLRs were correctly loaded by variablecapacitors (varactor diode). The center frequency of the PC-SLR filter was easilycontrolled by maintaining a large out-of-band rejection
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Belkadi, Nesrine. "Nouveaux MEMS C-BAR : résonateurs capacitifs à ondes élastiques de volume piégées sur substrat Silicium." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2088.
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Ces travaux de thèse décrivent l’étude et la réalisation de résonateurs MEMS (Micro-ElectroMechanical Systems) acoustiques à couplage capacitif dits C-BAR (Capacitive Bulk Acoustic Resonator). Les C-BAR exploitent les modes d’extension-compression d’épaisseur en mode fondamental à 9, 45MHz. L’élément vibrant est constitué de Si-monocristallin purement résistif et d’orientation (100). Notre but consiste à transposer au monde des MEMS a` excitation capacitive les caractéristiques de stabilité des résonateurs piézoélectriques BAW utilisés dans les sources de fréquences embarquées. Notre stratégie de développement s’est fondée sur l’exploitation de deux concepts originaux dans les domaines respectifs électrique et acoustique : l’intérêt immédiat des résonateurs MEMS-Si capacitifs tient à la disponibilité du matériau, au faible coût unitaire, à la produire à grande échelle, ainsi qu’à la robustesse. A plus longue échéance, cet intérêt tient au potentiel d’intégration avec l’électronique de commande ; Cette recherche est motivée par la nécessité d’éliminer les pertes structurelles dans les résonateurs MEMS. Grâce à l’étude de la dispersion acoustique des ondes élastiques guidées dans une plaque de Si, nous avons pu contrôler les bandes d’arrêt par modification locale des caractéristiques de la propagation afin de confiner l’énergie acoustique au centre du résonateur. Une première partie de ces travaux est consacrée à la modélisation du C-BAR. Grâce à des simulations FEM appuyées sur des calculs analytiques, nous avons défini les limites imposées aux paramètres constructifs pour l’obtention de performances satisfaisantes pour les applications visées. Nous avons notamment quantifié le nécessaire compromis entre les quantités antagonistes constituées par le k2, limité par la rigidité statique de la plaque, et le Q, limité par les constantes de dispersion des modes exploités et le facteur d’aspect de la plaque. La deuxième partie est consacrée à la micro-fabrication du C-BAR exploitant les micro techniques disponibles au sein de la Centrale MIMENTOThis PhD work describes the study and realization of capacitive Bulk Acoustic Waves MEMS resonators (C-BAR) exploiting the thicknessextensional vibration modes at 9, 45MHz of a mono-crystalline silicon plate (100). The aim of this research consists in translated to the domain of capacitive MEMS the good performances of BAW resonators for embedded frequency sources. The proposed work proposes new resonant structures bearing some originality from electric and acoustic viewpoints : capacitive full Si-MEMS have some immediate interest in the field of material availability, low cost per item, volume production and robustness, notwithstanding their know ability for electronic integration ; This research was motivated by the need to eliminate structural losses to reach the limits imposed by the material itself. With help of a study of dispersion curves, we managed a control of acoustic confinement by means of a local patterning of the surface of the vibrating element. By a proper mastering of the stop band of guided elastic waves in the structure, we can overcome the intrinsic limitations of structural MEMS. The first lock of this work is dedicated to the modeling of the C-BARs. It uses a combination of analytic and FEA calculations to frame the actual design of the resonators. This permits us to determine the limits imposed to the performances of such structures. This part especially points out the contradictory requirements of the C-BARs in terms of electromechanical coupling factor and of surtension coefficient. The second lock describes the issues of the micro-fabrication of the C-BARs at MIMENTO clean room facility
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Kika, Ondřej. "Kmitání štíhlých mostních konstrukcí." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-355606.
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Doctoral thesis called Vibrations of slender bridge structures deals with comparison of constructions’ responses at different load model of pedestrians. Specifically, in practice commonly used model, where there are the effects of pedestrians replaced by forces acting in a certain place on the bridge and other model, which takes into account the load of pedestrians moving along the deck. Calculations of responses are performed by finite element method in program ANSYS. To obtain extreme values of responses It is used parametric calculation using the program OptiSlang. At first responses on the simplified constructions are evaluated for load of two pedestrians, as well as the responses on real bridges for load of two pedestrians and four pairs of pedestrians. Responses are also evaluated in terms of pedestrian’s comfort during use structures and analyzed for what groups of pedestrians are criteria still met and for which it is necessary to consider about use of devices to reduce vibration. Possible applications and design process of the vibration dampers are shown on different configurations on the bridges.
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FRANCESCHINI, PAOLO. "NOVEL SCHEMES FOR ULTRAFAST MANIPULATION OF QUANTUM MATERIALS." Doctoral thesis, Università Cattolica del Sacro Cuore, 2022. http://hdl.handle.net/10280/111822.
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La possibilità di controllare le proprietà elettroniche on-demand su una scala di tempo ultraveloce rappresenta una delle sfide più intriganti verso la realizzazione di dispositivi fotonici ed elettronici di nuova generazione. Stimolata da questo, negli ultimi decenni la ricerca scientifica ha concentrato la propria attenzione su diverse piattaforme a stato solido. Tra tutte, nanostrutture dielettriche (e metamateriali) e materiali correlati si presentano come i più promettenti candidati per la realizzazione di dispositivi dotati di nuove funzionalità. Al di là delle caratteristiche specifiche che rendono i dielettrici più adatti ad applicazioni in fotonica e i materiali correlati ai dispositivi elettronici, entrambe le categorie manifestano nuove funzionalità se soggetti ad uno stimolo esterno sotto forma di impulsi di luce con durata più breve della scala di tempo caratteristica del rilassamento dei gradi di libertà interni al sistema. Infatti, lo stato fuori equilibrio raggiunto a seguito di una foto-eccitazione presenta proprietà elettroniche ed ottiche di gran lunga differenti da quelle all'equilibrio. Pertanto, l'obiettivo di questo lavoro di tesi consiste nello sviluppo di nuovi metodi ed approcci sperimentali in grado di indurre, misurare e controllare nuove funzionalità in materiali complessi su una scala di tempo ultraveloce.The possibility to control the electronic properties on-demand on an ultrafast time scale represents one of the most exciting challenges towards the realization of new generation photonic and electronic devices. Triggered by this, in the last decades the research activity focused its attention to different solid-state platforms. Among all, dielectric nanostructures (and metamaterials) and correlated materials represent the most promising candidate for the implementation of devices endowed by new functionalities. Apart from the specific features making dielectrics more suitable for photonic applications and correlated materials for electronic devices, both categories exhibit new functionalities if subjected to an external stimulus in the form of excitation light pulses shorter than the relaxation timescale of the internal degrees of freedom of the system. Indeed, the out-of-equilibrium state achieved upon photoexcitation exhibits electronic and optical properties highly different from those at equilibrium. Therefore, the aim of this thesis work consists in the development of new methods and experimental approaches capable to induce, measure, and control new functionalities in complex materials on an ultrafast time scale.
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NGUYEN-THI, Van-Oanh. "SPECTROSCOPIE ET STABILITE DES HYDROCARBURES AROMATIQUES POLYCYCLIQUES DANS LES CONDITIONS DU MILIEU INTERSTELLAIRE." Phd thesis, Université Paris Sud - Paris XI, 2003. http://tel.archives-ouvertes.fr/tel-00005244.
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Ce travail porte sur la dynamique intramoléculaire des Hydrocarbures Aromatiques Polycycliques soumis aux conditions du milieu interstellaire (PAH isolé rotationnellement froid mais vibrationnellement excité). Des études théoriques et expérimentales ont été menées sur leur deux voies de relaxation: émission IR ou fragmentation. Le spectre d'absorption IR a été obtenu par dynamique moléculaire couplée à une méthode semi-classique Adiabatic Switching. La dynamique a été réalisée sur une surface de potentiel semi-empirique Tight-Binding dans le but de simuler tous types de PAHs pouvant dépasser une centaine de carbones (systèmes encore inaccessibles aux expériences et aux calculs ab-inito). Une paramétrisation du potentiel adaptée aux PAHs a été développée ainsi qu'un modèle donnant la densité d'états anharmonique quantique. La simulation spectrale reproduit les grandes tendances en fonction des variables pertinentes en astrophysique: rôle de l'ionisation fort changement de l'allure du spectre et de l'intensité totale absolue), et de la température (décalage vers le rouge, élargissement et modification des intensités des bandes), effet d'anharmonicité (énergie de point zéro, fréquences), et de structure (compacité, cycle pentagonal et taille). La cinétique de fragmentation (induite par absorption séquentielle de photons) d'un hydrogène du cation fluorène (ionisation REMPI) a été étudiée à l'aide d'un jet supersonique et d'un spectromètre de masse. Cette méthode expérimentale originale a permis de déterminer la section efficace absolue d'absorption, d'analyser son atténuation avec le nombre de photons absorbés et l'évolution de la constante de dissociation dans un domaine d'énergie relativement large. Une attention particulière a été portée sur les techniques d'analyse des données. (la loi de Poisson, matrice de branchement, la loi cinétique, matrice d'évolution, simulation de la forme de signaux du spectromètre). Un ajustement libre de la variation de cette constante est proche de celui du modèle statistique PTD mais très différent à basse énergie du modèle RRK. L'énergie d'activation obtenue par ces deux modèles est compatible avec celle déduite du potentiel Tight-Binding.
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Pribac, Fred. "Octupole vibrational states in the even-mass barium isotopes." Master's thesis, 1985. http://hdl.handle.net/1885/138661.
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Kumar, Pawan. "Excitation and Damping of Solar P-Modes." Thesis, 1988. https://thesis.library.caltech.edu/3407/3/Kumar_p_1988.pdf.
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I have carried out detailed analysis of the interaction of acoustic radiation with homogeneous turbulence in order to understand the excitation of solar p-modes by turbulent convection. The most significant outcome of this investigation is the finding that, for certain types of forced turbulences, the absorption of acoustic waves is no greater than a free turbulence, whereas the emission is always enhanced by a factor M⁻², where M is the Mach number of the turbulence. Turbulent convection in the sun is an example of this kind of turbulence. This leads to the conclusion that energies in solar p-modes, due to their interaction with the convection, should be approximately equal to the thermal energy in a resonant eddy. This is found to be in good agreement with the observations. The ideas developed in the above work have been applied to explain the recently observed absorption of acoustic waves by sunspots as well. Work has also been carried out to determine the probability distribution function for the time averaged energy of stochastically excited modes. We hope to learn about the nature of the excitation and damping processes for the solar modes by comparing this theoretically determined distribution with the observations.
In an effort towards resolving the overstability question of solar p-modes, I have investigated the effectiveness of 3-mode couplings, the most plausible process for limiting the amplitudes of overstable modes. The 3-mode coupling mechanism is also a good candidate for exciting fundamental modes which are found to be linearly stable, but are observed to have energies comparable to p-modes of similar frequencies. The issue of mode stability remains inconclusive due to the unknown energies of modes with period ~3.5 minutes. However, we find the fundamental modes to be damped as a result of mode couplings and hence they require excitation by a mechanism other than the overstability.
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Jaber, Nizar. "Higher Order Modes Excitation of Micro Cantilever Beams." Thesis, 2014. http://hdl.handle.net/10754/317259.
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In this study, we present analytical and experimental investigation of electrically actuated micro cantilever based resonators. These devices are fabricated using polyimide and coated with chrome and gold layers from both sides. The cantilevers are highly curled up due to stress gradient, which is a common imperfection in surface micro machining. Using a laser Doppler vibrometer, we applied a noise signal to experimentally find the first four resonance frequencies. Then, using a data acquisition card, we swept the excitation frequency around the first four natural modes of vibrations. Theoretically, we derived a reduced order model using the Galerkin method to simulate the dynamics of the system. Extensive numerical analysis and computations were performed. The numerical analysis was able to provide good matching with experimental values of the resonance frequencies. Also, we proved the ability to excite higher order modes using partial electrodes with shapes that resemble the shape of the mode of interest. Such micro-resonators are shown to be promising for applications in mass and gas sensing.
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Chen, Tai-Lee, and 陳泰利. "Aperture-Coupling Excitation and Mode-Coupling Phenomena of Microstrip Leaky Modes." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/09419710206436045739.
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博士國立交通大學
電子工程系
87
This thesis investigates the properties and applications of the first two higher order leaky modes of the microstrip, which include efficient feeding structures, mutual coupling on microstrips, coupling effect in different leaky modes, and several antenna applications. The spectral domain analysis is employed to solve the propagation characteristics of the microstrip leaky modes throughout this study. The first part of the thesis pertains to the first higher order leaky mode (odd mode) of the microstrip line. The design procedure of the microstrip first higher order leaky-mode antenna excited by aperture-coupling method is presented. Separating the radiators from other components with the ground planes provides optimal design of both parts respectively so that the inherent broadband, high gain and frequency-scanning properties of the leaky-wave antenna can be exploited. Tilted- and broadside-beam antennas are designed in X-band. Single and dual beams arrays in K-band and a base-station antenna application for S-band are also implemented. The required elements were reduced markedly in comparison with the patch antenna for higher gain design. Versatile designs combining the merits of multilayer technology offer simplicity and efficient design for many wireless applications. In addition, the coupling effects in the coupled microstrips, which caused by the first higher order leaky mode on the microstrip, are investigated. The resonance phenomena found between the strip of the infinite coupled microstrips are owing to the inner edges of the coupled microstrips forming the resonant boundary and the leaky modes of the microstrips serving as the resonant sources. For even- and odd-symmetry of the coupled microstrips, more than one leaky mode are found in both cases, and these leaky modes couple with each other. The second part of the thesis treats the subjects of the microstrip second higher order leaky mode (even mode). Mode-coupling phenomena of the even modes on microstrip is investigated. These phenomena occur when the dispersion curve of the leaky dominant mode of the microstrip is close to those of the even higher order modes of the microstrip. Interesting patterns of the migration of mode evolution, obtained by varying the ratio of the strip width to the substrate thickness, exhibit the relationships between the even higher order modes and the leaky dominant mode. The spectral gap effect of the even higher order modes is the result of the coupling between these modes and the leaky dominant mode. Design of the even higher order leaky mode as a line source should be based on the physical implications of these phenomena. Short-end CPW and microstrip feeding method are used to excite the second higher order leaky mode. Experimentally exciting the second higher order leaky mode with and without the leaky dominant mode reveals the interference between these two leaky modes.
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LIN, CHENG-HUNG, and 林政宏. "Excitation of multivane waveguide modes by a thin axis encircling E-layer." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/21231442898720296421.
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碩士國立海洋大學
電機工程學系
90
The technology to produce high-power microwave by using the theory of the relativistic electrons spans a wide range of application to high-power microwave radar system, cyclotron resonance heating of plasma for fusion reactor, acceleration for basic research, etc. In many microwave devices, electron cyclotron tube has become the choice for microwave source over the years. And the Gyrotron is applied widely .When they are operated at the fundamental mode, a rather highly applied magnetic field is required at high frequency. Later scholars make some changes about operating the Gyrotron and named it Peniotron. It can produce higher harmonics with high power and high efficiency while enabling the lowering of the required magnetic field. At higher harmonic, because of the increasing concentration of the mode fields near the wave-guide wall and larger degree of mode competition, the operation efficiency at higher order modes lowers significantly. To overcome this problem, we may use high energy cyclotron electron beam to expand the electron Larmour radius so that the interaction with the higher mode fields can be optimized. A more effective means can be implemented by using an axis encircling electron beam generated by injecting electron beam in a cusp-magnetic field. Then we use multivane cylindrical waveguide structure which can promote higher harmonic to improve the interaction between cyclotron electron beam and higher harmonics. In this work, we have discussed an N-slotted multivane cylindrical wave-guide structure working in Gyrotron and Peniotron , and compute the modes of TE and TM. We have numerically computed the optimized parameters for number of vanes N = 8、10、12、16、24 at mode and for number of vanes N = 16、20、24、32、48 at mode operations.
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Jiue-JiaWu and 吳珏佳. "Assessment of effects of attenuation and excitation modes on ultrasonic Nakagami parameter." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/50728788739319787797.
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碩士國立成功大學
資訊工程學系
102
Statistical models, frequently adopted for describing the probability distribution function (PDF) of ultrasonic backscattered envelopes, have been utilized for tissue characterization. Due to the attenuation increase with ultrasonic frequency, the estimated statistical parameter can be affected by the broad-band attenuation in tissues and distortion of acquired echo signals. Hence, different ultrasonic frequencies and excitation signals were implemented to investigate the attenuation effect on statistical analysis of ultrasonic backscattered signals. Measurements were performed from tissue-mimicking phantoms, which were consisted of gelatin and glass beads with concentrations of 16 and 64 scatterers/mm3, using 3.5 and 7.5 MHz focus transducers. Per each experiment, a phantom was placed between the transducer and tissue-mimicking phantom for creating attenuation. Ultrasound signals were generated by exciting transducers with 1, 3, 5, and 10 cycles sinusoidal signals. The Nakagami statistical model was used to analyze the PDF of ultrasonic backscattered envelopes. This study further indicated that the attenuation could significantly vary the PDF of ultrasonic envelopes especially for the transducer was excited by monocycle sinusoidal signals. As a narrower bandwidth associated with the increase of cycles of tone burst was implemented, the attenuation effect was substantially reduced. The sinusoidal signals of 3 cycles among other excitation signals demonstrated the most appropriate performance to accommodate between attenuation effect and image resolution.
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LIN, YUAN-TANG, and 林源堂. "Nonlinear interaction of instability modes for an axisymmetric circular jet under acoustic excitation." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/26475454203617190835.
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Ho, Fei-hung, and 何飛宏. "Poincaré Gauge Theory with Coupled Even and Odd Parity Spin-0 Dynamic Connection Modes: Isotropic Bianchi Cosmologies." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/46479753624576973355.
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博士國立中央大學
物理研究所
99
We are investigating the dynamics of a new Poincaré gauge theory of gravity model,the BHN PG model which has cross coupling between the spin-0^+ and spin-0^- modes, in a situation which is simple, non-trivial, and yet may give physically interesting results that might be observable. To this end we here consider a very appropriate situation—homogeneous-isotropic cosmologies—which is relatively simple, and yet all the modes have non-trivial dynamics which reveals physically interesting and possibly observable results. More specifically we consider manifestly isotropic Bianchi class A cosmologies; for this case we find an effective Lagrangian and Hamiltonian for the dynamical system. The Lagrange equations for these models lead to a set of first order equations that are compatible with those found for the FLRW models and provide a foundation for further investigations. The constant curvature case is investigated. The first order equations are linearized and the normal modes are found. These turn out to control the asymptotic late time cosmological normal modes. Numerical evolution confirms the late time asymptotic approximation and shows the expected effects of the cross parity pseudoscalar coupling.
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Huang, Cheng-ren, and 黃正仁. "Excitation of whispering gallery modes in a microsphere by an etch-eroded fiber coupler." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/96497475695725689681.
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碩士國立中央大學
光電科學研究所
95
Microsphere resonators have attracted a lot of interest in recent years, due to ultra high quality factor and small modal volume. Numerous methods for coupling energy into the whispering gallery modes of a microsphere have been demonstrated, however most of them are limited by either low coupling efficiency or mechanical instability. In this thesis, an etch-eroded fiber coupler was investigated, and better coupling efficiency and acceptable stability was obtained. The orders of the WGMs and the quality factors can be determined by analyzing optical transmission spectra and fitting to the theoretical resonant wavelengths. Furthermore, it shows that the smaller the radius of the fiber; the higher the coupling efficiency. In this thesis, the highest coupling efficiency is obtained 42.07％, and the quality factor is ~ 25000.
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Chen, Yong-Zhi, and 陳泳智. "Excitation of fundamental whispering-gallery modes in a microsphere by a half-block coupler." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/46630769027455963367.
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碩士國立中央大學
光電科學研究所
95
A simple method for the excitation of fundamental whispering-gallery modes in a BK7 glass microsphere by a side-polished fiber half-block coupler is demonstrated. The coupler is made of the single-mode fiber (Corning SMF-28) which has an effective refractive index of 1.4682 @1550nm. The radius and refractive index of the microsphere equal to 150± 1.5 um and 1.500065 @1550 nm, respectively. The resonant modes are identified from the transmission spectrum, which indicates that the quality factor of 17000, free spectral range of 1.7 nm and coupling efficiency of 10% are obtained.
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Deepu, P. "Dynamics of Droplets Under Support, Acoustic And/Or Ambient Flow Excitation." Thesis, 2013. http://etd.iisc.ernet.in/2005/3459.
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The first step on the way to understanding the complicated dynamics of spray is to study the behavior of isolated droplets. In many industrial and natural processes such as turbulent combustion, agricultural sprays, spray cooler, falling raindrops and cloud evolution the droplet is subjected to a chaotic unsteady external flow field. The interaction between the liquid and gaseous phases results in very intricate droplet dynamics like capillary instabilities, atomization, droplet collision and coalescence and vaporization, to name a few.
In this dissertation, the focus is on shape oscillations, atomization and vaporization dynamics of pendant and sessile droplets. A droplet residing on a substrate which vibrates vertically at ultrasonic frequency will exhibit different modes of shape oscillation. The competition between capillary forces and inertia forces is basically responsible for these oscillations. However, when an acoustic force field is introduced asymmetrically around the droplet, we discover with the help of ultra high-speed imaging, a new droplet spreading phase. This new method of droplet manipulation could nd application in micro fluidics and lab-on-a-chip systems. By lading the droplet with nanoparticles, the spreading rate can be easily controlled. The spreading phase is followed by an atomization phase where surface ligaments grow to disintegrate into daughter droplets; the intensity of atomization is found to decrease with increase in fluid viscosity. The ability to control atomization characteristics of droplets by lading them with nanoparticles is a powerful technique that may be implemented in spray coolers and combustors to control the spray characteristics or combustion efficiency. Both the spreading and ligament dynamics have been theoretically simulated and the physics behind the observed trends is explained. The growth rate of the ligaments is found to be governed by Weber number modified to include the acoustic pressure level of the standing wave. The frequency of ligament breakup is found to decrease with fluid viscosity and this observation is adequately supported by a theory developed based on the evolution crater on the droplet surface.
Turning now to the pendant droplets, by decomposing the droplet shape into Legendre modes, the shape oscillations exhibited by a droplet hanging from the junction of cross-wire placed at the center of an air jet is studied. Both high-speed imaging and hot-wire anemometry are employed. The driving force of oscillation of droplets subjected to the air jet is proved to be the inherent pressure fluctuations in the jet. The effect of surface tension, viscosity and Reynolds number on the shape oscillation level has been examined. The first experimental evidence of viscous attenuation of lower frequencies in a particular mode in glycerol/water mixture is reported. A theoretical model was developed to simulate the droplet shape oscillations induced by different ambient flow fields like pulsatile flow, vortical flow and flow with broadband energy spectrum. The time of interaction of the droplet with an eddy in the flow is found to be very crucial in determining the amplitude of oscillation of the droplet. The shorter the interaction time, the higher are the chances of the droplet oscillation being pushed into resonance.
Finally, the heat transfer and droplet regression dynamics of pendant droplets in a hot air stream of various chemical compositions (like conventional fuels, alternative fuels and nanosuspensions) have been experimentally analyzed using high speed imaging. The droplet is deployed at the junction of cross-wire at the centre of a vertical air jet. A hybrid timescale has been proposed which incorporates the effects of latent heat of vaporization, saturation vapor pressure and thermal diffusivity. This timescale in essence encapsulates the different parameters that influence the droplet vaporization rate. The analysis further permitted the evaluation of the effect of various parameters such as surrounding temperature, Reynolds number, far-field vapor presence, impurity content and agglomeration dynamics (nanosuspensions) in the droplet.
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Islam, Rubaiyat. "Theory and Applications of Microstrip/Negative-refractive-index Transmission Line (MS/NRI-TL) Coupled-line Couplers." Thesis, 2011. http://hdl.handle.net/1807/31789.
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The electromagnetic coupling of a microstrip transmission line (MS-TL) to a metamaterial backward wave Negative-Refractive-Index transmission line (NRI-TL) is the primary investigation of this dissertation. The coupling of forward waves in the MS-TL to the backward waves in the NRI-TL results in the formation of complex modes, characterized by simultaneous phase progression and attenuation along the lossless lines.
Through network-theoretic considerations, we investigate the properties of these modes in the complex-frequency plane of the Laplace domain to help unravel the confusion that has existed in the literature regarding the independent excitation of a pair of conjugate complex modes. We show that it is possible to arbitrarily suppress one of the modes over a finite bandwidth and completely eliminate it at a discrete set of frequencies using proper source and load impedances. Hence we use conjugate modes with independent amplitudes in our eigenmode expansion when we analyse various coupling configurations between the two types of lines (MS/NRI-TL coupler).
We derive approximate closed-form expression for the scattering parameters of the MS/NRI-TL coupler and these are complemented by design charts that allow the synthesis of a wide range of specifications. Moreover, these expressions reveal that such couplers allow for arbitrary backward coupling levels along with very high-isolation when they are made half a guided wavelength long. The MS/NRI-TL coupler offers some interesting applications which we highlight through the design and testing of a 3-dB power splitter, a high-directivity signal monitor and a compact corporate power divider. We have included design, simulation and experimental data for the fabricated prototypes exhibiting good agreement and thereby justifying the theory that has been developed in this work to explain the coupling between a right-handed MS-TL and a left-handed NRI-TL.
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Lenk, Benjamin. "Photo-magnonics in two-dimensional antidot lattices." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-F098-8.
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