Le travail présenté dans ce mémoire est une contribution au domaine de l'analyse et de l'identification du comportement dynamique des structures non linéaires. Le premier objectif est la mise au point et la comparaison de quatre techniques de calcul des Modes Normaux Non linéaires (MNNs) : l'approche de Shaw et Pierre, l'approche de Bellizzi et Bouc, l'équilibrage harmonique et la méthode de tir. La combinaison des trois dernières méthodes avec la méthode de continuation permet de détecter les points de bifurcation et de trouver les nouvelles branches de solutions. Le deuxième objectif est l'identification des paramètres caractérisant le comportement dynamique des systèmes linéaires et non linéaires à partir des réponses libres ou des réponses au bruit ambiant. Les outils présentés sur le traitement du signal réel modulé en amplitude et en fréquence par la transformation en ondelettes continue permettent d'atteindre cet objectif. Le dernier objectif est l'extension de la méthode de sous-structuration linéaire de Craig-Bampton au cas non linéaire. Lorsque l'hypothèse de couplage faible entre les sous-structures est faite, le modèle réduit de la structure globale est obtenu par assemblage de modèles réduits de sous-structures avec interfaces de couplage fixe. Ces modèles réduits sont calculés en utilisant l'approche des MNNs de Shaw et Pierre. La robustesse et l'efficacité des méthodes présentées sont étudiées au travers d'exemples numériques ainsi que de tests réels.

The goal of this research was to investigate further the role of air redistribution and continental water storage changes in the excitation of both the annual and Chandler wobbles for the period 1900-85. The annual and Chandler excitations from air redistribution have been studied by Wilson and Haubrich (1976), Wahr (1982), and Hinnov and Wilson (1985). Annual excitation from water storage was estimated by Van Hylckama (1970), Hinnov and Wilson (1985), and Chao and O'Connor (1988). Chandler wobble excitation from water storage changes has been addressed only by Hinnov and Wilson (1985). This study was undertaken as a refinement to their encouraging but preliminary results. / text

Les polaritons inter-sous-bandes sont des excitations issues du couplage fort entre la transition inter-sous-bande d'un puits quantique et un mode photonique d'une cavité micrométrique. Dans la limite de faible densité d'excitations, c'est-à-dire quand seule une infime fraction de la mer de Fermi est excitée, ces excitations sont bien décrites par un Hamiltonien effectif bosonique et quadratique. Cependant, quand le nombre d'excitations augmente, on s'attend à observer des écarts par rapport aux prédictions issues de cet Hamiltonien. Dans cette thèse nous adaptons la méthode des commutateurs pour bosons composites aux polaritons inter-sous-bandes afin étudier les effets conjoints de l'interaction de Coulomb et du principe d'exclusion de Pauli sur leur comportement à plus haute densité. Suivant une approche microscopique, nous calculons la valeur de l'interaction à deux corps entre polaritons et nous expliquons comment elle peut être encodée dans un Hamiltonien effectif bosonique et quartique. Finalement, en utilisant des paramètres réalistes, nous montrons que l'interaction entre polaritons inter-sous-bandes peut-être importante, et ce, particulièrement dans le THz. Ce résultat ouvre la voie à de futurs travaux en optique non linéaire à base de polaritons inter-sous-bandes. Les principaux résultats de ce travail sont publiés dans la référence [1].

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Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-08-13T20:10:08Z No. of bitstreams: 1 RAFAEL BEZERRA CORREIA LIMA – TESE (PPGEEI) 2016.pdf: 2251289 bytes, checksum: 6f67fd056817aec7bcfe50d4eaf21187 (MD5) / Made available in DSpace on 2018-08-13T20:10:08Z (GMT). No. of bitstreams: 1 RAFAEL BEZERRA CORREIA LIMA – TESE (PPGEEI) 2016.pdf: 2251289 bytes, checksum: 6f67fd056817aec7bcfe50d4eaf21187 (MD5) Previous issue date: 2016-09-20 / Nesse trabalho são apresentadas contribuições na área de identificação de sistemas representados em espaço de estados. É proposta uma metodologia completa para estimação de modelos que representem as principais dinâmicas de proessos industriais. O fluxo natural dos procedimentos de identificação consiste da coleta experimental dos dados, seguido pela esolha dos modelos candidatos e da utilização de um critério de ajuste que selecione o melhor modelo possível. Nesse sentido é proposta uma metodologia para estimativa de modelos em espaço de estados, utilizando excitações pulsadas. A abordagem desenvolvida combina algoritmos precisos e eficientes com experimentos rápidos, adequados a ambientes industriais. O projeto das excitações é realizado em tempo real, por meio de informações coletadas em um curto experimento inicial, baseado em uma única oscilação de uma estrutura realimentada por um relé. Esse mecanismo possibilita uma estimativa preliminar do atraso e da constante de tempo dominante do sistema. O método de identificação proposto é baseado na teoria de realizações de Kalman. É apresentada uma reformulação do problema de realizações clássico, para comportar sinais de entrada pulsados. Essa abordagem se mostra computacionalmente e cliente, assim como apresentar resultados semelhantes aos métodos de benchmark. A técnica possibilita também a estimativa de atrasos de transporte e a inserção de conhecimentos prévios por meio de um problema de otimização com restrições via LMI Linear Matrix Inequalities. Em muitos casos, somente as caraterísticas principais dos sistema são relevantes em um projeto de sistema de controle. Portanto é proposta uma técnica para obtenção de modelos de primeira ordem com atraso, a partir da redução de modelos balanceados em espaço de estados. Por fim, todas as contribuições discutidas nesse trabalho de teses não validadas em uma série de plantas experimentais em salas de laboratório. Plantas essas, projetadas e construídas com o intuito de emular o cotidiano operacional de instalações industriais reais. / This work introduces contributions related to the field of systems identification of state space models. It is proposed a complete methodology for model estimation that encompasses the main dynamics of industrial processes. The natural flux of the identification procedures rests on the the empirial colletion of data followed by the choice of candidate models and posterior use of an adjusting criteria that drafts the best model among the on tenders. In this sense, a new methodology is proposed for models estimation in state spaces using pulsed excitation signal. The developed approach combines accurate and efficient algorithms with quick experiments whose are suitable for the industrial environment. The excitation design is performed in real time by means of information colleted in a short initial experiment based in an single oscillation of a relay feedback. This mechanism allows a preliminary estimation of both delay and time on stant prevalent in the system. The identification method proposed is based on Kalman's realization theory. The thesis introduces a reformulation of the classic realization problem so it an admit pulsed input signals. This approachs how it self as computationally efficient as well as provides similar results compared to those obtained when performing the benchmark methods. More over, the techniallows the transport delay estimation and insertion of prior knowledge by means of an optimization problem with restritions via linear matrix in equalities restritions. In many cases only the characteristics of the main system are relevant in control systems design. Therefore a technique for the attainment first order models with time delay based on balanced states space models redution. Lastly all the contributions provided along the thesis are discussed and validated in a series of pilot scale plants, designed and built to emulate the operational cycle in real industrial plants.

L'intérêt de la recherche fondamentale pour les morceaux nanométriques de métaux nobles est principalement dû à la résonance localisée des plasmons de surface (LSPR) dans l'absorption optique. Différents aspects, liés à la compréhension théorique de la LSPR dans le cas de clusters de métaux nobles de taille dite intermédiaire, sont étudiés dans ce manuscrit. Afin d'avoir une vision plus large nous utilisons deux approches : l'approche électromagnétique classique et le formalisme ab initio en temps réel de la théorie de la fonctionnelle de la densité dépendant du temps (RT-TDDFT). Une comparaison systématique et détaillée de ces deux approches souligne et quantifie les limitations de l'approche électromagnétique lorsqu'elle est appliquée à des systèmes de taille quantique. Les différences entre les excitations plasmoniques collectives et celles impliquant les électrons d, ainsi que leurs interactions, sont étudiées grâce au comportement spatial des densités correspondantes. Ces densités sont obtenues en appliquant une transformée de Fourier dans l'espace à la densité obtenue par les simulations DFT utilisant une perturbation delta-kick. Dans ce manuscrit, des clusters de métaux nobles nus et protégés par des ligands sont étudiés. En particulier, motivé par de récents travaux sur les phénomènes d'émergence de plasmon, l'étude par TD-DFT de nano-alliages Au-Cu de taille tout juste inférieure à 2nm à fourni de subtiles connaissances sur les effets d'alliages sur la réponse optique de tels systèmes. / The fundamental research interest in nanometric pieces of noble metals is mainly due to the localized surface-plasmon resonance (LSPR) in the optical absorption. Different aspects related to the theoretical understanding of LSPRs in `intermediate-size' noble-metal clusters are studied in this thesis. To gain a broader perspective both the real-time \ai formalism of \td density-functional theory (RT-TDDFT) and the classical electromagnetics approach are employed. A systematic and detailed comparison of these two approaches highlights and quantifies the limitations of the electromagnetics approach when applied to quantum-sized systems. The differences between collective plasmonic excitations and the excitations involving $d$-electrons, as well as the interplay between them are explored in the spatial behaviour of the corresponding induced densities by performing the spatially resolved Fourier transform of the time-dependent induced density obtained from a RT-TDDFT simulation using a $\delta$-kick perturbation. In this thesis, both bare and ligand-protected noble-metal clusters were studied. In particular, motivated by recent experiments on plasmon emergence phenomena, the TDDFT study of Au-Cu nanoalloys in the size range just below 2~nm produced subtle insights into the general effects of alloying on the optical response of these systems.

Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2018-08-24T18:39:30Z No. of bitstreams: 2 Tese - Guilherme Colherinhas de Oliveira - 2012.pdf: 41954562 bytes, checksum: b2c7e39bdbf8d887462d338c56fcbd4f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Rejected by Luciana Ferreira (lucgeral@gmail.com), reason: Olhe a citação : Oliveira, Guilherme Colherinhas de. Estudo teórico de propriedades espectroscópicas de bases nitrogenadas e derivados de vitamina A em solução. 2012. 363 f. Tese (Doutorado em Física) - Universidade Federal de Goiás, Goiânia, 2012. on 2018-08-27T11:19:33Z (GMT) / Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2018-08-27T19:07:35Z No. of bitstreams: 2 Tese - Guilherme Colherinhas de Oliveira - 2012.pdf: 41954562 bytes, checksum: b2c7e39bdbf8d887462d338c56fcbd4f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-08-28T11:16:46Z (GMT) No. of bitstreams: 2 Tese - Guilherme Colherinhas de Oliveira - 2012.pdf: 41954562 bytes, checksum: b2c7e39bdbf8d887462d338c56fcbd4f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-08-28T11:16:46Z (GMT). No. of bitstreams: 2 Tese - Guilherme Colherinhas de Oliveira - 2012.pdf: 41954562 bytes, checksum: b2c7e39bdbf8d887462d338c56fcbd4f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2012-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / In this work we present a theoretical study for the optical absorption spectrum UV-VIS and nuclear magnetic resonance (NMR) parameters of molecules that forming the structure of the deoxyribonucleic acid (DNA): adenine, guanine, thymine and cytosine in aqueous solution and of aldehydes and carboxylic acids derivatives of vitamin A in solution of chloroform, acetonitrile, methanol and water. The Solvent effects are treated using a sequential methodology that combines Monte Carlo simulation and quantum mechanics calculations (S-MC / MQ). Effects of polarization of the reference molecules by the solvent are obtained iteratively assuring the convergence of the dipole moment in solution, with the atoms of the solvent molecules modeled by point charges. The results show that the polarization effect can give marked increases for the dipole moments of the reference molecules, especially in water, as compared with the results of gas phase. TD-DFT calculations for the vertical electronic transitions were performed with hybrid functionalities: B3LYP, PBE1PBE and BHandHLYP; and with long-range corrected functionals: CAM-B3LYP and LC-wPBE. For the isotropic magnetic shielding constants, GIAO-B3LYP results were obtained with several basis set functions: 6-311 ++ G (2d, 2p), AUG-cc-pVTZ, pcS-2, pcS-3 and AUG-pcS -2. The results obtained show the optical absorption spectrum variations between 6 and 28 nm for the nucleotide bases and between 13 and 80 nm for the derivatives of vitamin A with the functional type, whereas that for the NMR parameters of carbon atoms variations between 3 and 10 ppm with the choice of the basis set functions. However, the inclusion of the solvent polarization effects provides a reliable description for these electronic properties in solution, in comparison with available experimental results. The classical simulations were performed with the DICE program and the quantum calculations with the GAUSSIAN03 / 09 program. / Neste trabalho apresentamos um estudo teórico para o espectro de absorção óptica na região UV-VIS e para os parâmetros de ressonância magnética nuclear (NMR) das moléculas que compõe a base estrutural do ácido desoxirribonucleico (DNA): adenina, guanina, timina e citosina em solução aquosa e de aldeídos e ácidos carboxílicos derivados da vitamina A em solução de clorofórmio, acetonitrila, metanol e água. Os efeitos de solvente são tratados utilizando uma metodologia sequencial que combina simulação de Monte Carlo e cálculos de Mecânica Quântica (S-MC/MQ). Efeitos de polarização das moléculas de referência pelo solvente são obtidos iterativamente assegurando a convergência do momento de dipolo em solução, com os átomos das moléculas de solvente modelados por cargas pontuais. Os resultados mostram que o efeito da polarização pode dar aumentos substanciais para os momentos de dipolo das moléculas de referência, especialmente em água, quando comparado com os resultados de fase gasosa. Cálculos TD-DFT para as transições eletrônicas verticais foram realizados com funcionais híbridos: B3LYP, PBE1PBE e BHandHLYP; e com funcionais com correção de longo alcance: CAM-B3LYP e LC-wPBE. Para as constantes de blindagem magnética isotrópica, resultados GIAO-B3LYP foram obtidos com diferentes conjuntos de funções base: 6-311++G(2d,2p), AUG-cc-pVTZ, pcS-2, pcS-3 e AUG-pcS-2. Os resultados obtidos mostram para o espectro de absorção óptica na região do UV variações entre 6 e 28 nm para as bases nitrogenadas e na região do UV-VIS entre 13 e 80 nm para os derivados de vitamina A com o tipo de funcional, enquanto que para os parâmetros NMR de átomos de carbono variações de 3 a 10 ppm com a escolha do conjunto de funções base. Entretanto, a inclusão dos efeitos de polarização do meio fornece uma descrição realista para essas propriedades eletrônicas em solução, em comparação com resultados experimentais disponíveis. As simulações clássicas foram realizadas com o Programa DICE e os cálculos quânticos com o Programa GAUSSIAN03/09.

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L’étude des propriétés plasmoniques est un champ de recherche actuellement très actif. En particulier, la possibilité de manipuler la lumière à des échelles sub-longueur d’ondes rend ce domaine très attractif. Récemment, plusieurs études ont montré que les plasmons collectifs dans des méta-matériaux bi-dimensionnels constitués de nanoparticules métalliques se comportaient de manière similaire aux électrons dans les cristaux et partageaient certaines de leurs propriétés. Dans ce manuscrit, nous présentons une théorie unifiée permettant de décrire les propriétés de tels modes plasmoniques dans des réseaux ordonnés de géométrie arbitraires constitués de nanoparticules métalliques couplées en champ proche. En particulier, nous évaluons les taux de décroissance de ces modes ainsi que leurs décalages en fréquence afin de prédire leur observabilité expérimentale. / The study of plasmonic properties is one of the fields of research currently very active. In particular, the ability to manipulate light at subwavelength scales makes this subject very appealing. Recently, several studies have shown that collective plasmons in two-dimensional meta-materials based on metallic nanoparticles behave similarly to electrons in crystals and share some of their properties. In this manuscript, we present a unified theory for describing the properties of such modes in regular arrays of arbitrary geometries constituted by near-field coupled spherical nanoparticles. In particular, we have evaluated the linewidths of these modes as well as their frequency shifts in order to discussed their experimental observabilities.

Magnetic frustration is the underpinning theme to all of the magnetic oxide systems explored in this dissertation. The materials studied in this thesis belong to two topical families of interest in modern condensed matter physics, namely, the rare-earth titanates R2Ti2O7 and the double perovskites A2BB'O6. Chapter 1 provides the theoretical background necessary to understand the crystalline systems studied in this thesis. Chapter 2 explains the necessity of utilizing neutron scattering and x-ray experiments to tease out the key signatures which were essential to formulating the conclusions made in each study. Chapter 3 outlines the neutron scattering techniques which were employed to investigate the crystal systems. The first objective of this thesis is to understand effect of “stuffing” on the ground state anisotropy of the quantum spin liquid candidate Yb2Ti2O7 via an investigation of the crystal-field excitations in intentionally stuffed samples. The pentultimate study was performed on the monoclinic crystal systems, La2LiRuO6 and La2LiOsO6, to discern the effect of lattice distortions on the spin-orbit induced magnetic ground state of 4d3 and 5d3 double perovskites based on Ru and Os magnetic ions. The final investigation involves an inelastic neutron scattering investigation of magnetic ground states in three d2 double perovskites, Ba2CaOsO6, Ba2MgOsO6 and Ba2ZnOsO6. Here, we make the case for novel octupolar order below their respective transition temperatures T* of 50 K, 49 K and 30 K based on information provided by neutron scattering, heat capacity, muon spin relaxation and synchrotron x-ray diffraction studies. / Thesis / Doctor of Philosophy (PhD)