Dissertations / Theses on the topic 'Comples media'

Les principales techniques de microscopie de fluorescence sont fondamentalement limitées pour imager en profondeur par la diffusion de la lumière qui atténue exponentiellement la quantité de photons balistiques utilisés pour imager avec la profondeur. Les techniques de microscopie non linéaire permettent néanmoins de dépasser le millimètre dans le meilleur des cas, in vivo. Elles restent fondamentalement limitée par deux effets : par la réduction de la fluorescence émise au focus à cause de la décroissance exponentielle des photons balistiques mais aussi par l’augmentation de la fluorescence hors focus. Cependant, il a été démontré que l’utilisation, en amont du milieu, de modulateurs spatiaux de lumière associée à des techniques de façonnage de front d’onde permet de compenser partiellement la diffusion de la lumière en refocalisant les photons diffusés. Néanmoins, mettre en pratique la correction de la diffusion pour l’imagerie in vivo nécessite l’utilisation conjointe de modulateurs de lumière rapides, de détecteurs rapides et d’une électronique rapide afin de corriger le front d’onde dans le temps de stabilité du milieu biologique. Nous avons donc développé, au cours de cette thèse, deux systèmes de façonnage du front d’onde rapides ; l’un basé sur une technologie MEMS et l’autre sur des déflecteurs acousto-optiques couplés à un laser à bas taux de répétition. Nous avons étudié les performances (gain de focalisation, vitesse) de ces deux systèmes pour focaliser à travers des milieux diffusants dynamiques. Nous avons démontré qu’à travers des milieux présentant des séquences de diffusion avec des stabilités très variées le focus obtenu est plus stable qu’attendu. Dans un deuxième temps, nous avons couplé un système de façonnage du front d’onde à un microscope non linéaire pour compenser en épi-détection la diffusion et donc améliorer les images obtenues en profondeur. Cette étude ouvre une voie originale pour l’imagerie biphotonique en très grande profondeur
Fluorescence microscopy cannot image very deep due to multiple light scattering which decreases exponentially the amount of ballistic photons used for image recovery. In the best case, non-linear microscopy can image around one millimeter in depth in vivo. It remains fundamentally limited by two effects: by the reduction of the fluorescence emitted at the focus because of the exponential decay of the ballistic photons, and by the increase of out of focus fluorescence. Recently, wavefront shaping techniques combined with spatial light modulators have enabled to partially compensate scattering and therefore focus scattered photons inside or through a complex media. Yet, applying these techniques to in vivo imaging requires the use of fast spatial light modulators, fast detectors, and fast electronics able to compensate for the short stability time of biological tissues. In this thesis, we have developed two fast wavefront shaping systems; one based on a MEMS technology and the other on acousto-optical deflectors time locked on the output laser pulses of a regenerative amplifier. We then studied the performances (enhancement, speed) of such systems to focus through dynamic scattering media. We have shown that, through media presenting scattering sequences with a very large time stability distribution, the focus obtained can be more stable than expected. In a second serie of experiments, we coupled a wavefront shaping system to a nonlinear microscope to compensate scattering in epi-detection and thus improve the images obtained in depth (resolution and signal level). This study provides an original way for two-photon imaging at unprecedented depth

[EN] Nature is nonlinear. The linear description of physical phenomena is useful for explain observations with the simplest mathematical models, but they are only accurate for a limited range of input values. In the case of intense acoustics waves, linear models obviate a wide range of physical phenomena that are necessary for accurately describe such high-amplitude waves, indispensable for explain other exotic acoustic waves and mandatory for developing new applied techniques based on nonlinear processes. In this Thesis we study the interactions between nonlinearity and other basic wave phenomena such as non-classical attenuation, anisotropic dispersion and periodicity, and diffraction in specific configurations. First, we present intense strain waves in a chain of cations coupled by realistic interatomic potentials. Here, the nonlinear ionic interactions and lattice dispersion lead to the formation of supersonic kinks. These intrinsically-nonlinear localized dislocations travel long distances without changing its properties and explain the formation of dark traces in mica crystals. Then, we analyze nonlinear wave processes in a system composed of multilayered acoustic media. The rich nonlinear dynamics of this system is characterized by its strong dispersion. Here, harmonic generation processes and the relation with its band structure are presented, showing that the nonlinear processes can be enhanced, strongly minimized or simply modified by tuning the layer parameters. In this way, we show how the dynamics of intense monochromatic waves and acoustic solitons can be controlled by artificial layered materials. In a second part, we include diffraction and analyze four types of singular beams. First, we study nonlinear beams in two dimensional sonic crystals. In this system, the inclusion of anisotropic dispersion is tuned for obtain simultaneous self-collimation for fundamental and second harmonic beams. The conditions for optimal second harmonic generation are presented. Secondly, we present limited diffraction beam generation using equispaced axisymmetric diffraction gratings. The obtained beams are truncated version of zero-th order Bessel beams. Third, the grating spacing can be modified to achieve focusing, where the generated nonlinear beams presents high gain, around 30 dB, with a focal width which is between the diffraction limit and the sub-wavelength regime, but with its characteristic high amplitude side lobes strongly reduced. Finally, we observe that waves diffracted by spiral-shaped gratings generate high-order Bessel beams, conforming nonlinear acoustic vortex. The conditions to obtain arbitrary-order Bessel beams by these passive elements are presented. Finally, the interplay of nonlinearity and attenuation in biological media is studied in the context of medical ultrasound. First, a numerical method is developed. The method solves the constitutive relations for nonlinear acoustics and the frequency power law attenuation of biological media is modeled as a sum of relaxation processes. A new technique for reducing numerical dispersion based on artificial relaxation is included. Second, this method is used to study the harmonic balance as a function of the power law, showing the role of weak dispersion and its impact on the efficiency of the harmonic generation in soft-tissues. Finally, the study concerns the nonlinear behavior of acoustic radiation forces in frequency power law attenuation media. We present how the interplay between nonlinearity and the specific frequency power law of biological media can modify the value for acoustic radiation forces. The relation of the nonlinear acoustic radiation force with thermal effects are also discussed. The broad range of nonlinear processes analyzed in this Thesis contributes to understanding the behavior of intense acoustic waves traveling trough complex media, while its implications for enhancing existent applied acoustics techniques are presented.
[ES] La Naturaleza es no lineal. La descripción lineal de los fenómenos físicos es de gran utilidad para explicar nuestras observaciones con modelos matemáticos simples, pero éstos sólo son precisos en un limitado rango de validez. En el caso de onda acústica de alta intensidad, los modelos lineales obvian un amplio rango de fenómenos físicos que son necesarios para describir con precisión las ondas de gran amplitud, pero además son necesarios para explicar otros procesos más exóticos e indispensables para desarrollar nuevas aplicaciones basadas en propagación no lineal. En esta Tesis, estudiamos las interacciones entre no linealidad y otros procesos complejos como atenuación no-clásica, dispersión anisotrópica y periodicidad, y difracción en configuraciones específicas. En primer lugar, presentamos ondas de deformación en una cadena de cationes acoplados por potenciales realísticas. Aquí, las interacciones no lineales entre iones, producen la conformación de kinks supersónicos. Estas dislocaciones localizadas intrínsecamente no lineales viajan por la red largas distancias sin variar sus propiedades, y pueden explicar la formación de trazas en minerales como la mica. Aumentando la escala del problema, estudiamos los procesos acústicos no lineales en medios multicapa. La rica dinámica de estos medios está caracterizada por la fuerte dispersión debido a la periodicidad del sistema. Aquí, estudiamos los procesos de generación de harmónicos, mostrando como modificando la estructura podemos potenciar, minimizar, o simplemente modificar artificialmente la transferencia de energía entre las componentes espectrales, y de esta manera controlar la dinámica de las ondas y solitones en el interior de la estructura. En la segunda parte, incluimos difracción y analizamos cuatro tipos de haces singulares. En primer lugar, analizamos haces ultrasónicos no lineales en cristales de sonido bidimensionales. En este sistema, las propiedades de anisotropía del medio son ajustadas para obtener la auto-colimación simultánea del primer y segundo harmónico. Así, se obtiene la propagación no difractiva para las dos componentes. En segundo lugar, presentamos haces de difracción limitada empleando rejillas de difracción axisimétricas. Por último, demostramos la generación de haces de Bessel de orden superior mediante estructuras en espiral. En la última parte, estudiamos la competición entre no linealidad y la atenuación y dispersión observable en medios biológicos en el contexto de las aplicaciones de biomédicas de los ultrasonidos. En primer lugar desarrollamos un nuevo método computacional para la dependencia frecuencial en forma de ley de potencia de la absorción característica de los tejidos. Este método en dominio temporal es usado posteriormente para revisar los procesos básicos no lineales prestando especial interés en el paper de la dispersión del tejido. Por último, la resolución de las ecuaciones constitutivas nos permite abordar la descripción no lineal de la fuerza de radiación acústica producida en tejidos biológicos, y las implicaciones existentes con la deposición de energía y transferencia de momento para ondas ultrasónicas de alta intensidad. El amplio abanico de procesos no lineales analizados en esta tesis contribuye a una mejor comprensión de la dinámica de las ondas acústicas de alta intensidad en medios complejos, donde las implicaciones existentes en cuanto a la mejora de sus aplicaciones prácticas son puestas de manifiesto.
[CAT] La Naturalesa és no lineal. La descripció lineal dels fenòmens físics és de gran utilitat per a explicar les nostres observacions amb models matemàtics simples, però aquests sol són precisos en un limitat rang de validesa. En el cas d'ona acústica d'alta intensitat, els models lineals obvien un ampli rang de fenòmens físics que són necessaris per a descriure amb precisió les ones de gran amplitud, però a més són necessaris per a explicar altres processos més exòtics i indispensables per a desenvolupar noves aplicacions basades en propagació no lineal. En aquesta Tesi, estudiem les interaccions entre no-linealitat i altres processos complexos com atenuació no-clàssica, dispersió anisotròpica i periodicitat, i difracció en configuracions específiques. En primer lloc, presentem ones de deformació en una cadena de cations acoblats per potencials realistes. Ací, les interaccions no lineals entre ions, produeixen la conformació de kinks supersònics. Aquestes dislocacions localitzades intrínsecament no lineals viatgen per la xarxa llargues distàncies sense variar les seues propietats, i poden explicar la formació de traces en minerals com la mica. Augmentant l'escala del problema, estudiem els processos acústics no lineals en mitjans multicapa. La rica dinàmica d'aquests mitjans es caracteritza per la forta dispersió a causa de la periodicitat del sistema. Ací, estudiem els processos de generació d'harmònics, mostrant com modificant l'estructura podem potenciar, minimitzar, o simplement modificar artificialment la transferència d'energia entre les components espectrals, i d'aquesta manera controlar la dinàmica de les ones i solitons a l'interior de l'estructura. En la segona part, incloem difracció i analitzem quatre tipus de feixos singulars. En primer lloc, analitzem feixos ultrasònics no lineals en cristalls de so bidimensionals. En aquest sistema, les propietats d'anisotropia del medi són ajustades per a obtenir l'acte-col·limació simultània del primer i segon harmònic. Així, s'obté la propagació no difractiva per a les dues components. En segon lloc, presentem feixos de difracció limitada emprant reixetes de difracció axisimètriques. Per últim, vam demostrar la generació de feixos de Bessel d'ordre superior mitjançant estructures en espiral. En l'última part, estudiem la competició entre no linealitat i l'atenuació i dispersió observable en medis biològics en el context de les aplicacions biomèdiques dels ultrasons. En primer lloc desenvolupem un nou mètode computacional per a la dependència freqüencial en forma de llei de potència de l'absorció característica dels teixits biològics. Aquest mètode en domini temporal és usat posteriorment per a revisar els processos bàsics no lineals prestant especial interés en el paper de la dispersió del teixit. Per últim, la resolució de les equacions constitutives ens permet abordar la descripció no lineal de la força de radiació acústica produïda en teixits biològics, i les implicacions existents amb la deposició d'energia i transferència de moment per a ones ultrasòniques d'alta intensitat. L'ampli ventall de processos no lineals analitzats en aquesta tesi contribueix a una millor comprensió de la dinàmica de les ones acústiques d'alta intensitat en medis complexos, on les implicacions existents quant a la millora de les seues aplicacions practiques són posades de manifest.
Jiménez González, N. (2015). Nonlinear Acoustic Waves in Complex Media [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/53237
TESIS
Premiado

The dynamical evolution of an ultrawideband electromagnetic pulse as it propagates through a temporally dispersive and attenuative medium is a classical problem in electromagnetic wave theory with considerable practical importance dating back to seminal works conducted in 1914. With the use of modern asymptotic theory and numerical techniques, propagation of canonical pulses into complex (attenuative and dispersive) media have been analyzed and recently extended to nonlinear materials. The materials of interest for this research are modeled after realistic biological tissues. The mathematically rigorous and more accurate physical model of electromagnetic energy transfer into the biological materials modeled will be used as input to the FitzHugh-Nagumo circuit equivalent model for an excitable neuron. This detailed analysis will provide a new point of view to working groups and standardization committees in the eld of non-ionizing radiation safety that is based on so-called athermal effects.

Le but de cette thèse était de créer des modèles pour deux applications qui apparaissent couramment en chimie séparative, à savoir la séparation solide-liquide et la séparation liquide-liquide. L'avantage de la modélisation est manifeste dans les deux cas. L'étude fondamentale des propriétés des ions et de leur solvatation dans les milieux complexes, en tenant compte de façon simplifié des différents effets mis en jeu, nous a permis de construire un cadre qui utile aussi bien aux chimistes en laboratoire qu’aux ingénieurs lors de la conception des procédés. Nous avons adapté cette stratégie sur deux systèmes différents, qui peuvent tous deux être considérés comme complexes. Le premier système modèle pour étudier la séparation solide-liquide était des nanotubes de TiO2 dispersés dans une solution aqueuse. Ce système a été étudié au moyen de la Théorie de la Fonctionnelle de la Densité Classique couplée à une méthode de régulation de charge, au sein de l'ensemble Grand-Canonique. La méthode s'est avérée efficace pour établir la description complète des propriétés de charge des nanotubes de TiO2. Dans ce cas, nous nous sommes intéressés à obtenir la description de l'ion à l'intérieur des nanotubes chargés sous l'influence du champ électrique (créé par les nanotubes). Les calculs ont prédit des effets tels que la différence de charge de surface entre la surface externe et la surface interne, ou la violation de l'électroneutralité à l'intérieur des nanotubes. Il a été démontré que le modèle était en accord avec les données expérimentales. De plus, la méthode peut être utilisée directement pour prédire diverses techniques de titrage. Une simple généralisation de l'approche proposée permettra d'étudier l'efficacité d'adsorption réelle du procédé de séparation solide-liquide. Le second système modèle concerne l'étude du procédé d'extraction liquide-liquide et il comprend trois parties distinctes. Les trois parties ont été consacrées aux cas des extractants non ioniques, puis acides (échangeurs d'ions), et enfin aux mélanges synergiques d'extractants. Un modèle simple de thermodynamique statistique, dans lequel nous avons incorporé certains des concepts bien établis en chimie colloïdale, a fourni une approche de type matière molle pour calculer le processus à l'échelle de l'ingénieur. Nous avons développé une approche classique d'équilibres simples pour une compréhension plus large et plus intuitive de la formation des agrégats polydisperses dans l'extraction liquide-liquide. La principale conclusion présentée est que l’on doit proposer un nouveau paradigme pour la chimie : à l'équilibre, de nombreux agrégats de composition très différente mais similaires en énergie libre, coexistent. Avec la polydispersité obtenue, nous avons ainsi proposé un outil pour étudier un comportement plus "global" de l'extraction liquide-liquide. Cela nous a poussés à passer des considérations classiques d'isothermes d'extraction à celles plus précises des " cartes " d’extraction. Un grand soin a été apporté à l'étude de la synergie puisqu'il s'agit d'une important question depuis 60 ans dans la communauté scientifique et industrielle de la séparation. A notre connaissance, la première rationalisation quantitative de la synergie d’extraction a été proposée dans le cadre de cette thèse. Les effets sous-jacents des contrôles enthalpique et entropique sur la structuration des phases organiques ont été découplés et étudiés en détail. Nous espérons que cette thèse a démontré l'importance de la modélisation mésoscopique sur des exemples pratiques utilisés à la fois par les chimistes et les ingénieurs
The object of this thesis was to create models for two applications which readily appear in separation chemistry, namely the solid-liquid and the liquid-liquid extractions. The benefit of modelling in both cases is twofold. Studying the fundamental properties of ions and their solvation properties in the complex media, and simplifying the expression for important effects, enables us to construct the framework which can be used by both chemists in the laboratory, as well as the chemical engineers in the process design. For two applications we adapted two different systems, both of which can be considered as complex. The model system to study the solid-liquid separation were TiO$_{mathrm{2}}$ nanotubes dispersed in the aqueous solution. This system was studied by the means of Classical Density Functional Theory coupled with the charge regulation method, within the Grand-canonical ensemble. Indeed, the method proved to be successful in establishing the full description of the charge properties of TiO$_{mathrm{2}}$ nanotubes. In this case, we were interested in obtaining the description of ion inside the charged nanotubes under influence by the electric field (exhibited by nanotubes). Calculations predicted effects such as the difference in surface charge between the outer and the inner surface, or the violation of electroneutrality inside the nanotubes. It was demonstrated that the model was in the agreement with the experimental data. Moreover, the method can be directly used to predict titration for various techniques. A simple generalization of the proposed approach can be used to study the actual adsorption efficiency of the solid-liquid separation process. The model system to study the liquid-liquid extraction process included three distinct parts. The three parts were devoted to the cases on non-ionic, acidic ion exchangers, and finally the synergistic mixtures of extractants. Simple bulk statistical thermodynamics model, in which we incorporated some of the well-established concepts in colloidal chemistry provided a soft-matter approach for the calculation of actual engineering-scale processes. Were have expanded a classical simple equilibria approach to broader, more intuitive polydisperse aggregates formation that underlines the liquid-liquid extraction. The key finding can be presented as a current opinion or newly-proposed paradigm: at equilibrium, many aggregates completely different in composition but similar in free energy coexist. With obtained polydispersity, we were equipped with a tool to study a more 'global' behavior of liquid-liquid extraction. This urged us to pass our considerations of historical extraction isotherms to extraction 'maps'. Great care was devoted to the study of synergy since it is a 60-year old ongoing question in the separation industrial and science community. To our best knowledge, the first quantitative rationalization total synergistic extraction was proposed within this thesis. Underlying effects of enthalpy and entropy control on the organic phase structuring were decoupled and studied in detail. Hopefully, this thesis demonstrated the importance of mesoscopic modelling to assist both chemists and chemical engineers in practical examples

I was born the only American in my West Indian, Guyanese family. My culture played a large part in how I was brought up, and in turn, shaped the person and artist I have become. In my work, I like for my viewers to get a personal feel for what it is like to be West Indian American. My work is a cultural record of people, places, and things. I capture small, special moments because I know that they will never be recreated. My camera’s viewfinder has always been filtered through my eye as a child of immigrant parents. I use photography as my first step in creating and recording ordinary, everyday things. Photographs are captured where I feel most American eyes would by-pass or overlook their importance. However, my work must also involve my hand. Therefore, through my mark making, whether I am drawing, painting, collaging, stitching or using software, I add and subtract from my original photos. By manipulating my images, I change and emphasize a single, fleeting moment into something permanent and significant.

Redes são representações poderosas para muitos sistemas complexos, onde vértices representam elementos do sistema e arestas representam conexões entre eles. Redes Complexas podem ser definidas como grafos de grande escala que possuem distribuição não trivial de conexões. Um tópico importante em redes complexas é a detecção de comunidades. Embora a detecção de comunidades tenha revelado bons resultados na análise de agrupamento de dados com grupos de diversos formatos, existem ainda algumas dificuldades na representação em rede de um conjunto de dados. Outro tópico recente é a caracterização de simplicidade em redes complexas. Existem poucos trabalhos nessa área, no entanto, o tema tem muita relevância, pois permite analisar a simplicidade da estrutura de conexões de uma região de vértices, ou de toda a rede. Além disso, mediante a análise de simplicidade de redes dinâmicas no tempo, é possível conhecer como vem se comportando a evolução da rede em termos de simplicidade. Considerando a rede como um sistema dinâmico de agentes acoplados, foi proposto neste trabalho uma medida de distância baseada no tempo de consenso na presença de um líder em uma rede acoplada. Utilizando essa medida de distância, foi proposto um método de detecção de comunidades para análise de agrupamento de dados, e um método de análise de simplicidade em redes complexas. Além disso, foi proposto uma técnica de construção de redes esparsas para agrupamento de dados. Os métodos têm sido testados com dados artificiais e reais, obtendo resultados promissores
Networks are powerful representations for many complex systems, where nodes represent elements of the system and edges represent connections between them. Complex networks can be defined as graphs with no trivial distribution of connections. An important topic in complex networks is the community detection. Although the community detection have reported good results in the data clustering analysis with groups of different formats, there are still some dificulties in the representation of a data set as a network. Another recent topic is the characterization of simplicity in complex networks. There are few studies reported in this area, however, the topic has much relevance, since it allows analyzing the simplicity of the structure of connections between nodes of a region or connections of the entire network. Moreover, by analyzing simplicity of dynamic networks in time, it is possible to know the behavior in the network evolution in terms of simplicity. Considering the network as a coupled dynamic system of agents, we proposed a distance measure based on the consensus time in the presence of a leader in a coupled network. Using this distance measure, we proposed a method for detecting communities to analyze data clustering, and a method for simplicity analysis in complex networks. Furthermore, we propose a technique to build sparse networks for data clustering. The methods have been tested with artificial and real data, obtaining promising results

La connaissance du comportement hydrodynamique et du transfert de matière de la bulle est importante car elle fournira des indications pour la sélection des conditions de fonctionnement et la conception du réacteur dans de tels processus. Cette thèse a réalisé une étude expérimentale pour les bulles d’air isolées en ascension dans diverses solutions de polymères (Breox, Polyacrylamide (PAAm) and Xanthan gum) qui peuvent simuler les propriétés des eaux usées. Les travaux sont divisés en trois parties: Tout d’abord, en dressant l’état de l'art sur les techniques de visualisation pour le transfert de matière, trois techniques ont été testées pour les bulles d’air (diamètre équivalent ≈ 1 mm) en ascension dans l'eau, notamment la fluorescence induite par plan laser (PLIF, fluorophore: résorufine fluorescente), la PLIF avec inhibition (fluorophore: complexe de ruthénium) et techniques colorimétriques (colorant: résorufine rose), respectivement. Par la suite, sur la base des images capturées par une caméra haute vitesse, le comportement hydrodynamique des bulles d'air (diamètres équivalents: 0,7 à 7 mm) s'élevant dans les solutions de polymères (PAAm et Xanthan) a été étudiée, notamment la vitesse, la trajectoire et la forme de la bulle. Enfin, appliquant la technique PLIF-I, les phénomènes de transfert de matière et de diffusion dans le sillage de bulles d'air (diamètre équivalent 1 ≈ mm) dans différentes solutions aqueuses de polymères (PAAm et Breox) ont été étudiés
The knowledge on the hydrodynamic property and mass transfer of bubbles is important since it will give guidelines for selecting the operation condition and for reactor design in such processes. For this purpose, this PhD manuscript has implemented an experimental investigation of single air bubbles rising in various polymer solutions (Breox, Polyacrylamide (PAAm) and Xanthan gum) which can simulate the property of the sewage. The works can divided into three parts: Firstly, with a review of the current visualization techniques for mass transfer, three techniques have been tested for air bubble (equivalent diameter ≈ 1 mm) rising in water including traditional Planar Laser Induced Fluorescent (PLIF, dye: fluorescent resorufin), Fluorescent quenching technique (PLIF with Inhibition, dye: ruthenium complex) and colorimetric techniques (dye: pink resorufin), respectively. Secondly, based on images captured by a high speed camera, the hydrodynamics of the bubble single air bubbles (equivalent diameters: 0.7-7 mm) rising in the polymer solutions (PAAm and Xanthan) have been investigated including the bubble velocity, trajectory and bubble shape. Finally, based on PLIF-I technique, the mass transfer and diffusion phenomena in the wake of single air bubbles (equivalent diameter ≈ 1 mm) rising in various aqueous polymer solutions (PAAm and Breox) are investigated

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 171-183).
Hydrodynamic interactions of fluids and fibers are encountered in many applications, from filtration processes to the development of novel materials such as nanofluids and nanocomposites, and even in biological systems such as transport of fluids in plants and tissues. It is therefore, valuable from both a scientific and engineering perspective, to understand and be able to predict the behavior of such systems. In this thesis, hydrodynamic effects arising from the presence of fibers in fluid flows are studied in two different scenarios: i) Newtonian and non-Newtonian fluids flowing through fixed arrays of fibers (fibrous media), and ii) fibers suspended in fluids and the rheological changes resulting from the fiber-fluid hydrodynamic interactions. First, the flow of Newtonian fluids through and at the interface of fibrous porous media is studied. The primary objective of this part of the thesis was the design and development of a microfluidic device incorporating fixed beds of carbon nanotubes for filtration of specific biomarkers from biological fluid samples. Therefore, the focus is centered on defining and evaluating an interception efficiency, which provides a measure of the fraction of fluid streamlines that intercept a porous collector. It is shown through numerical simulations, that in general, the effects of geometrical confinement as well as fluid inertia and porosity (as captured by the Reynolds number and Darcy number respectively) on the flow interception efficiency are interdependent; however, for most practical cases it is possible to decouple these effects (e.g. at Darcy numbers < 10-4). For the specific case of fibrous collectors consisting of carbon nanotubes, experimental studies are conducted to investigate the convection and diffusion of dilute polymer solutions through cylindrical paths of vertically aligned carbon nanotubes. The experiments demonstrate the ability to systematically control the thickness and uniformity of adsorbed polymers on the carbon nanotubes through variation in the geometrical confinement of the fibrous array. The studies of flow transverse to fibers are also extended to the case of non-Newtonian fluids. Emphasis is placed on theoretical development of general mobility functions for complex fluids flowing through fibrous media. This is one of the major contributions of this thesis, which yields generalized laws for predicting the pressure drop that an array of fibers induces on the steady flow of fluids with a yield-stress and a rate-dependent viscosity. The resulting formulation can be applied to various geometrical arrangements and a wide range of porosities. Based on this model, we construct a unified dimensionless criterion in the form of a modified Bingham number (or dimensionless yield stress) rescaled with a suitable porosity function, which incorporates all the rheological and pore-scale parameters that are required to determine the dominant viscoplastic regime. Finally, suspensions of fibers in a Newtonian liquid matrix are studied. In this case the fibers are allowed to be flexible and move within the suspending media in addition to having attractive potentials with each other. These degrees of freedom give the resulting fiber suspensions striking features such as viscoelasticity and ability to form a percolated gel network at volume fractions as low as ~ 3% for the system of interest, which consists of an aqueous suspension of nanocrystalline cellulose fibers (length 200nm, aspect ratio 20). The changes in the rheological behavior of these dispersed fibrous systems are investigated as the volume fraction of nanofibers are varied. Finally, the correlative technique of differential dynamic microscopy (DDM) is implemented to study the collective fiber dynamics and we demonstrate that this method can be used as a complementary technique to provide microrheological insight that extends the ability to rheologically characterize the steady and transient viscoelastic properties of complex heterogeneous fluids.
by Setareh Shahsavari.
Ph. D.

Les microalgues autotrophes sont une source prometteuse de biomasse pour des applications aussi variées que l'extraction de molécules, l'alimentation animale et humaine, la production énergétique ou la décontamination environnementale. La production de masse est donc en forte augmentation dans le monde. Cependant, les techniques actuelles pour caractériser l'état physiologique des cellules algales au cours de la croissance sont coûteuses en main d'œuvre et en temps, souvent basées sur du matériel de mesure générique répondant mal au cahier des charges. Elles sont inadaptées à la mesure en ligne.De nouveaux outils doivent donc être développés pour optimiser le pilotage des procédés de culture, en effectuant des mesures rapides de l'état physico-chimique des cellules. La spectroscopie visible (VIS) et proche infrarouge (NIR) se présente comme une solution pratique. De plus des travaux antérieurs ont démontrés que les propriétés spectrales d'absorption et de diffusion des cellules d'algues dans le domaine VIS-NIR sont très corrélées à leur caractéristiques chimiques (pigments) et physiques (tailles, densité des cellules). Les densités de cellules considérées en cultures denses sont très élevées (10^6-10^9 cellules/mL), rendant inévitables les phénomènes de multidiffusion. Cependant ces derniers ont été identifiés comme gênants pour l'extraction de données à partir des spectres mesurés, car ils rendent l'hypothèse de validité de la loi de Beer Lambert fausse. Dans cette thèse nous nous intéressons à l'extraction de données sur la physiologie des cellules algales à partir de mesures spectrales effectuées sur des échantillons denses, non-dilués, directement issus du milieu de culture. Notre approche se décline en plusieurs axes, correspondants aux différentes échelles de description du problème. D'abord, l'échelle de l'échantillon algal global est considérée. Nous en définissons les propriétés spectrales apparentes, et analysons le problème pratique de leur mesure. Nous avons utilisé un montage à double sphères d'intégration et développé un protocole de mesure complet, que nous décrivons. Ensuite, les propriétés spectrales linéaires intrinsèques au milieu algal sont abordées, et nous cherchons à les reliées aux propriétés apparentes de l'échantillon. Pour cela nous utilisons le formalisme de l'équation de transfert radiatif (ETR) donnant une modélisation rigoureuse des phénomènes de multidiffusion à l'œuvre dans les milieux turbides. En pratique, résoudre l'ETR ne peut se faire que par une approximation ou la simulation. Dans nos travaux nous examinons la méthode Adding-Doubling et son inverse, utilisées avec succès par d'autres équipes sur des échantillons turbides de tissus biologiques. En troisième lieu, l'échelle de description de la cellule d'algue individuelle est abordée. AlgaSim, un programme de simulation basé sur la théorie de Mie étendue, a été développé au cours de cette thèse pour modéliser les spectres d'absorption et de diffusion d'une cellule algale décrite par ses paramètres physiologiques, tels que la taille et le poids sec, les proportions des différents matériaux cellulaires, la quantité et la composition des pigments. Ainsi, les liens entre propriétés physiques et chimiques de la cellule et ses propriétés spectrales sont étudiés. Enfin, une méthode complète est proposée pour articuler toutes les échelles de description précédemment examinées. Les liens entre propriétés intrinsèques du milieu algal et les propriétés optiques individuelles des cellules sont cherchés. Les paradigmes développés aux différentes échelles sont ensuite mis bout à bout pour relier la description physiologique des cellules d'algue aux propriétés spectrales apparentes mesurées sur un échantillon donné. La méthode est testée sur des échantillons algaux réels. Les premiers résultats sont prometteurs, démontrant le potentiel opérationnel de la spectroscopie VIS-NIR pour le suivi de procédés de culture dense de microalgues
Autotrophic microalgae are seen as a promising source of biomass for various applications such as chemicals extraction, animal and human food, energy production and environment cleaning. Consequently, the global mass production of microalgae has largely increased over the last decade. However, the current techniques used for the characterization of the algal cells all along the growth process require time-consuming sample preparation, a large amount of costly, standard instrumentation and cannot usually be performed in situ.New tools are needed to optimize the monitoring of the cultivation process by providing a faster measurement of the microalgal cells physical and chemical states. For this purpose, utilizing visible (VIS) and near infrared (NIR) spectroscopy is looked as a promising solution. Moreover, previous studies demonstrated that the spectral absorption and scattering properties of microalgal suspensions in the VIS-NIR domain depend heavily on the chemical characteristics (pigments) and physical characteristics of the cells (size, density of the cells). In a context of cultivation process, cell density in the culture medium is very high (10^6-10^9 cell/mL) which makes the multi-scattering phenomena significant. However, recent studies have showed that the data extraction from spectroscopic measurements performed on turbid samples is highly complicated by the influence of the scattering phenomena on the spectra, making the classical processing methods based on the assumption of Beer law irrelevant. This thesis addresses the issue of retrieving information about the physiological state of microalgal cells from spectral measurements performed on non-diluted, dense bulk culture media. For this purpose, our approach includes successive guidelines, corresponding to different scales of description. First, the scale of the bulk algal aliquot is considered: the apparent spectral properties are defined, and the practical issue of measuring them with an adapted setup is investigated. In particular, a double-integrating sphere setup, as well as a complete measurement protocol are implemented. Second, the intrinsic linear spectral properties of the dense algal medium are defined, and the links between the intrinsic and apparent spectral properties are investigated. The formalism of the radiative transport equation (RTE) is used for this purpose, as it rigorously models the physical phenomena due to multiple scattering. Solving the RTE must be implemented in practice with an approximation or simulation method. In this work, we investigate in particular the Adding-Doubling method and its inverse, which have been proved to be adapted to the case of highly turbid organic tissues and materials. Third, the scale of an individual algal cell is considered. In this thesis we have developed a simulation program called AlgaSim based of the extended Mie theory, which makes it possible to simulate the spectral absorption and scattering properties of an algal cell described by its physiological characteristics, such as its mean size and dry weight, proportions of different cell materials and pigment quantity and composition. The links between the chemical and physical properties of an algal cell and its spectral properties are thus investigated.Finally, a complete method is proposed to link all the scales of description. In particular, the links between the intrinsic spectral properties of an algal medium and the individual properties of the constitutive cells are considered. By organizing all the paradigms previously investigated, it is possible to implement a complete model linking the physiological description of the constitutive algal cells to the apparent spectral properties measured on a dense culture sample. The method and its inverse are tested on real algal samples. They show promising primary results, proving the operational potential of VIS-NIR spectroscopy for the monitoring of dense algal cultures

The rock pore space in many subsurface settings is saturated with water and one or more immiscible fluid phases; examples include non-aqueous-phase liquids (NAPLs) in contaminated aquifers, supercritical CO2 during sequestration in deep saline aquifers, the vadose zone, and hydrocarbon reservoirs. Self-potential (SP) methods have been proposed to monitor multiphase flow in such settings. However, to properly interpret and model these data requires an understanding of the saturation dependence of the streaming potential. This study presents a methodology to determine the saturation dependence of the streaming potential coupling coefficient and streaming current charge density in unsteady-state drainage and imbibition experiments and applies the method to published experimental data. Unsteady-state experiments do not yield representative values of coupling coefficient and streaming current density (or other transport properties such as relative permeability and electrical conductivity) at partial saturation because water saturation within the sample is not uniform. An interpretation method is required to determine the saturation dependence of coupling coefficient and streaming current density within a representative elementary volume with uniform saturation. The method makes no assumptions about the pore-space geometry. We also applied pore network models that can capture the distribution of fluids and electrical charge in real complex porous media to investigate and quantify streaming potential signals during multiphase flow at the pore level. The network modelling results were tested against the interpreted data and experimental data of Estaillades carbonate and St. Bees sandstone, which provided reliable pore-scale explanations of the experimental observations. The results presented here can be used to help interpret SP measurements obtained in partially-saturated subsurface settings.

Les méthodes utilisant des particules ont été largement utilisées pour modéliser les problèmes de transport dans les sols poreux, les aquifères et les réservoirs. Ils réduisent ou évitent certains desproblèmes des méthodes eulériennes, par exemple instabilités, diffusion artificielle excessive, bilan massique et / ou oscillations pouvant conduire à des concentrations négatives. Cette thèsedéveloppe de nouvelles méthodes de particules lagrangiennes pour modéliser les phénomènes d'écoulement et de transport dans des milieux poreux complexes avec des hétérogénéités. Pour ce faire, cette thèse passe d'abord en revue les processus stochastiques et leurs relations avec l'équation (EDP) macroscopique d'Advection-Diffusion ADE. Cette mise en revue permet de trouver les conditions nécessaires à un processus stochastique pour que sa densité de probabilité vérifie l’équation EDP de Fokker-Planck et donc l’ADE. Cependant, l’une de ces conditions est la différentiabilité des coefficients de transport. Il est donc difficile de traiter les discontinuités et les hétérogénéités, en particulier la diffusion et la porosité discontinues. Dans la littérature sur les marches aléatoires de particules, les méthodes précédentes utilisées pour traiter ce problème de discontinuité nécessitaient de petits pas de temps afin de converger vers la solution attendue. Ces restrictions sur le pas de temps conduisent à des algorithmes inefficaces. Dans cette étude, nous proposons une nouvelle approche sans restrictions sur la taille des pas de temps. L’algorithme RWPT (Random Walk Particle Tracking) proposé ici est discret en temps et continu en espace (sans grille). Le nouvel algorithme RWPT est basé sur un pas de temps adaptatif « Stop&Go », combiné à des schémas de réflexion partielle/réfraction, et étendu à trois nouveaux concepts : particules de masse négative ; particules de masse adaptative ; et particules à tête chercheuse ("homing"). Les algorithmes en domaines infinis ont ensuite été généralisés au cas de domaines finis ou semi-infinis. Les conditions aux limites de Dirichlet (concentrations) sont particulièrement difficiles à mettre en œuvre dans les méthodes particulaires. Ainsi, cette thèse propose-t-elle différentes méthodes de mise en œuvre des conditions de Dirichlet avec l'algorithme RWPT utilisé pour traiter les discontinuités. Pour tester les nouveaux schémas RWPT Stop&Go, nous développons des solutions analytiques et semi-analytiques pour la diffusion en présence de multiples interfaces (milieu multicouche discontinu) dans des domaines infinis, semi-infinis et finis avec des conditions limites de Dirichlet. Les résultats montrent que les schémas RWPT Stop&Go proposés correspondent extrêmement bien aux solutions semi-analytiques, même pour des contrastes très forts des coefficients de diffusion et porosités, y compris au voisinage des interfaces. Ensuite, la méthode RWPT est appliquée pour étudier les processus de diffusion à différentes échelles dans des supports composites (systèmes grains/pores 2D). Une condition de flux nul est appliquée localement aux interfaces grain/pore. Au niveau macroscopique, la diffusion se produit dans un milieu homogène avec des paramètres macro-échelle (porosité et coefficients de diffusion effectifs) induits par des méthodes de montée d’échelle à l'aide des moments spatiaux d’ordre 2. L'algorithme RWPT est ensuite appliqué à des géométries plus complexes de grains et pores. Tout d’abord, différentes configurations ou structures micro-échelle sont choisies afin d'obtenir des milieux composites isotropes ayant différentes porosités. Puis, en choisissant des micro-structures allongées, des effets d’anisotropies apparaissent au niveau macroscopique. Les différentes méthodes proposées dans cette thèse pourraient être utilisées pour différents problèmes, chacune ayant ses inconvénients et ses avantages. Les schémas proposés semblent prometteurs dans la perspective d’extensions vers des géométries 3D plus complexes
Particle methods have been extensively used for modeling transport problems in porous soils, aquifers, and reservoirs. They reduce or avoid some of the problems of Eulerian methods, e.g. instabilities, excessive artificial diffusion, mass balance, and/or oscillations that could lead to negative concentrations. This thesis develops a new class of gridless Lagrangian particle methods for modeling flow and transport phenomena in complex porous media with heterogeneities and discontinuities. Firstly, stochastic processes are reviewed, in relation to particle positions X(t) and to the corresponding macroscopic Advection-Diffusion Equation (ADE). This review leads to the conditions required for the Probability Density Function (PDF) of X(t) to satisfy the Fokker-Planck equation (and the ADE). However, one of these conditions is the differentiability of transport coefficients: therefore, discontinuities are difficult to treat, particularly discontinuous diffusion D(x) and porosity q(x). In the literature on particle Random Walks, the methods used to handle discontinuous diffusion required excessively small time steps. These restrictions on the time step lead to inefficient algorithms. In this study, we propose a novel approach without restrictions on time step size. The novel RWPT (Random Walk Particle Tracking) algorithms proposed here are discrete in time and continuous in space (gridless). They are based on an adaptive “Stop&Go” time-stepping, combined with partial reflection/refraction schemes, and extended with three new concepts: negative mass particles; adaptive mass particles; and “homing” particles. To test the new Stop&Go RWPT schemes in infinite domains, we develop analytical and semi-analyticalsolutions for diffusion in the presence of multiple interfaces (discontinuous multi-layered medium) in infinite domains. The results show that the proposed Stop&Go RWPT schemes (with adaptive, negative, or homing particles) fit extremely well the semi-analytical solutions, even for very high contrasts for transport properties even in the neighborhood of the interfaces. The schemes provide a correct diffusive solution in only a few macro-steps (macroscopic time steps), with a precision that depends only on the number of particles, and not on the macro-step. The algorithms are then, extended from infinite to semi-infinite and finite domains. Dirichlet conditions are particularly difficult to implement in particle methods. Thus, in this thesis we propose different methods on how to implement Dirichlet boundary conditions with the “discontinuous” RWPT algorithm. This study proposes an algorithm to solve diffusion equations semi-analytically in heterogeneous semi-infinite and finite domains with Dirichlet boundary conditions. The RWPT Dirichlet methods are then checked analytically and verified for various configurations. Finally, the RWPT method is applied for studying diffusion at different scales in 2D composite media (grain/pore systems). A zero-flux condition is assumed locally at the grain/pore interfaces. At the macro-scale, diffusion occurs in an equivalent effective homogeneous medium with macroscopic parameters (porosity and effective diffusion coefficients) obtained from the temporal evolution of second order moments. The RWPT algorithm is then applied to more complex geometries of grains and pores. Different configurations or structures at the micro-scale level will be chosen in order to obtain composite isotropic media at the macro-scale level with different porosities. Then, by choosing elongated micro-structures, anisotropy effects emerge at the macroscopic level. Effective macro-scale properties (porosities, effective diffusion tensors, tortuosities) are calculated using the second order moment. The different methods proposed in this thesis can be used for different problems, since each has its drawbacks and advantages. The schemes proposed seem promising with a view to extensions towards more complex 3D geometries

A strictly stable high order finite difference (HOFD) scheme for the scalar wave equation with discontinuous coefficients corresponding to inhomogeneity in the underlying media is constructed using summation - by - parts (SBP) operators. The domain of the equation is allowed to be complex in the sense that it can not be smoothly mapped from the unit square. The inhomogeneous media and complex geometries are handled by treating the problem in a domain decomposition setting. For each sub-domain there is a smooth one to one mapping from the unit square and its underlying media is smooth. The sub-domains are then coupled together with a penalty method, the simultaneous approximation term (SAT) method. Finally the scheme is extended to be able to handle local grid refinement, a feature quite new in the context of the SBP - SAT methodology. Accuracy and convergence properties are verified in numerical computations in 2 dimensions.

Les matériaux à structures complexes (anisotropes, multicouches et hétérogènes comme poreux) sont de plus en plus utilisés dans de nombreuses applications (ex. automobile,aéronautique, industrie chimique, génie civil et biomédical), notamment en raison de leur amélioration des propriétés mécaniques et physiques. L’identification des propriétés thermophysiques de ces matériaux devient un enjeu incontournable dans plusieurs applications afin de prédire correctement l’évolution de la température au sein de ces structures et d’assurer le contrôle et la modélisation des transferts de chaleur au cours des processus. Dans ce contexte,l’identification des propriétés thermophysiques de tels matériaux, suscitent depuis de nombreuses années une préoccupation importante et croissante. La principale caractéristique de cette thèse concerne la mise en œuvre d’une méthode d’identification directe et simultanée des diffusivités thermiques de matériaux monocouches ou multicouches à l’aide d’un modèle3D transitoire analytique et d’une expérience unique et non intrusive. La méthode proposée est d’abord validée sur un matériau monocouche opaque et isotrope, puis appliquée et vérifiée sur un matériau orthotrope. La méthode d’identification est basée sur l’expérience bien connue de la méthode flash, qui utilise l’évolution de la température sur la face avant ou arrière de l’échantillon, enregistrée via une caméra infrarouge, pour identifier les paramètres inconnus. Compte tenu de la complexité et de la non-linéarité du problème inverse, un algorithme d’optimisation hybride couplant un algorithme stochastique (Optimisation par essaims particulaires) et un déterministe (de type gradient), a été choisi. L’estimation repose sur la minimisation de l’écart entre les mesures et la réponse d’un modèle semi-analytique inspiré de l’approche des quadripôles thermiques qui prédit l’évolution de la température sur la face avant ou la face arrière. L’excitation thermique, générée par un laser CO2, est représentée par un flux de chaleur localisé imposé qui peut être de type Dirac ou créneau. Les estimations sont comparées aux valeurs trouvées dans la littérature et aux résultats obtenus en utilisant d’autres méthodes bien établies. Enfin, quelques améliorations de la méthode sont étudiées, en termes de temps de calcul et de précision, avec une optimisation des conditions expérimentales241RÉSUMÉ(durée et intensité des créneaux, face de mesure. . . ). La méthode est ensuite généralisée aux matériaux multicouches, puis appliquée expérimentalement à un matériau bicouche. Cette stratégie, qui peut être considérée comme une tâche difficile, est motivée par l’impossibilité,dans certains cas, de séparer les 2 couches, en particulier pour les revêtements déposés sur des substrats, qui sera la dernière application investiguée dans ce travail. Une analyse de sensibilité est souvent effectuée afin de tester la faisabilité de l’estimation et de la comparaison,pour les matériaux à deux couches et multicouches, de plusieurs configurations possibles en termes de faces d’excitation/de mesures. La pré-évaluation des méthodes d’identification et les études paramétriques sont effectuées à l’aide de données synthétiques bruitées et obtenues à l’aide du modèle ou d’un code numérique d’éléments finis (pseudo-expérience) afin de vérifier la faisabilité et la robustesse des approches. L’une des caractéristiques les plus distinctes de cette approche est que l’estimation peut être réalisée, et avec succès, sans aucune connaissance préalable de la forme ou de l’intensité de l’excitation. En effet, outre l’estimation simultanée des diffusivités thermiques, la méthode peut prédire la quantité de chaleur absorbée parle matériau ainsi que la distribution spatiale de l’excitation thermique
Advanced materials with complex structures (anisotropic, multilayers and heterogeneous like porous) are increasingly used in many applications, (e.g. automotive, aeronautics, chemical industry, civil and biomedical engineering) due to their advantages, in terms of mechanical and physical properties enhancements. Estimating thermophysical properties of such materials becomes a crucial issue in several applications in order to correctly predict temperature evolution inside these structures and to ensure the control and the modelling of heat transfers through the processes. In this context, the identification of such materials thermophysical properties, has taken from many years, a significant and increasing concern. The main feature of this thesis relies on the devolvement of a direct and simultaneous identification method of the thermal diffusivities of monolayer or multilayer materials using an analytical 3D transient model and a unique and non-intrusive experiment. The proposed method is firstly validated on an isotropic opaque monolayermaterial, then applied and verified on an orthotropic one. The identificationmethod is based on the well-known flash-method experiment whose temperature evolution on the front or rear face on the sample, recorded via an IR camera, is used to identify the unknown parameters. Considering the complexity, and the non-linearity of the inverse problem, a hybrid optimization algorithm combining a stochastic algorithm (Particles Swarm Optimization) and a deterministic one (gradient based), has been chosen. This minimization procedure is applied to fit the observation to the output of a pseudo- analytical model inspired from the thermal quadrupoles approach that predicts the temperature evolution on the front or rear face. The thermal excitation, generated by a CO2 laser, is mimicked by an imposed localized heat flux that may be of Dirac or pulse type. The estimations are compared with values from literature and results obtain from well-established methods. Finally, some improvement of the method are investigated, in terms of time consumption and accuracy, with an optimization of the experiment design (pulse time and intensity, measurement face). The method is then generalised to multi-layer materials, then applied experimentally to a two-layer material. This strategy, which can be considered as a challenging task, is motivated by the impossibility, in some cases, to separate the 2 layers, especially for coatings deposited on substrates which is the last application investigated in this work. A sensitivity analysis is often conducted in order to test the feasibility of the estimation and compare, for two-layer and multilayers materials, several possible configurations in terms of excitation/measurements faces. Pre-evaluation of the overall identification methods and parametric studies are performed using synthetic noisy data generated using the model or a numerical finite element code(pseudo-experiment) to verify the approaches feasibility and robustness. One of the most distinctive features of our approach is that the estimation may be successfully achieved without any a priori knowledge about the shape or the intensity of the excitation. Indeed, besides the simultaneous estimation of the thermal diffusivities, the method predicts the total amount of heat absorbed by the material as well as the space shape of the thermal excitation

Mercados financeiros são sistemas complexos com estrutura e comportamento extremamente dependentes das interrelações entre os seus componentes. Em particular, a teoria de redes tem contribuído para caracterizar e compreender o comportamento e as interdependências entre vários componentes do mercado financeiro, em especial, o mercado de ações. Pesquisas nessa área indicam que a estrutura de rede gerada do mercado pode conter informações úteis para um melhor entendimento do mercado como um todo e até mesmo prever a ocorrência de eventos extremos, como, por exemplo, uma crise financeira. Em geral, os estudos consideram apenas dependências lineares entre os objetos da rede baseados no coeficiente de correlação linear de Pearson, e nesse sentido, a proposta deste projeto é a aplicação de conceitos e métodos de teoria de redes e de teoria da informação para caracterizar e explorar o efeito de dependências não lineares na estrutura de rede do mercado brasileiro de ações. Para tal, a informação mútua foi usada como medida de dependência não linear para gerar a estrutura de redes que foi comparada com a obtida a partir da correlação linear de Pearson. Por fim, investigou-se como a estrutura da rede e suas métricas poderiam ajudar a caracterizar e a entender o comportamento dos mercados financeiros, analisando-se dois períodos, o primeiro sob gestão da Presidente Dilma Rousseff, com um retorno do índice de ações de -42%, e o segundo sob gestão do Presidente Michel Temer, com um retorno deste índice de 50%. Para tal fim, foram utilizados dados de alta frequência, sendo uma cotação a cada 15 minutos. Em suma, concluiu-se que os retornos dos ativos no segundo período parecem ter maior dependência não-linear quando comparados aos retornos do período anterior. A rede para este período é a que se mostra mais arriscada em termos de estrutura de \'transmissão de volatilidades\', tanto pela análise do coeficiente de robustez da rede, quanto pela estimativa do parâmetro da lei de potência. Encontrou-se evidência da relação entre estrutura das redes e desempenho das ações. Além disso, vimos a grande importância do setor financeiro nas redes. Finalmente, tecemos comentários quanto a aplicação destas redes para diversos fins.
This paper has the purpose to apply concepts and methods from network and information theory to characterize and to explore the role of nonlinear dependencies over the Brazilian network stock market structure. In particular, the minimum spanning tree network structure generated from the mutual information as a measure of nonlinear dependence was compared with the one obtained by Pearson\'s correlation coefficient. We analyzed two periods, the first under the management of President Dilma Rousseff, with an index return of -42%, and the second one, under the management of President Michel Temer, with an index return of 50%. For this purpose, high frequency data of fifteen minutes interval was used. Our analysis suggest that the assets returns of Temer\'s presidential term seem to have greater nonlinear dependence when compared to the returns of the previous period. Also, the network\'s robustness coefficient and power law parameter suggests that the network for the second period is the most risky in terms of volatility transmission structure. Also, we find evidence of network structure and stock performance relationship. Finally, we have also seen the great importance of financial sector within Brazilian\'s stock network

Made available in DSpace on 2016-04-27T16:59:03Z (GMT). No. of bitstreams: 1 Carlos Nely Clementino de Oliveira.pdf: 5513336 bytes, checksum: 0a24134db1e22f94d6aac26a73b16538 (MD5) Previous issue date: 2010-05-03
For quite a long time the issue of Complex Numbers has been seen as a minor or unnecessary object of interest and study to be taught in High School. Some teachers and therefore their students believe that applications of such numbers will only be a matter of interest in more advanced courses, in college, or in the area of exact sciences. Weren´t this subject still constant content in the program of entrance university exams, it would have probably been already removed from the curriculum. We believe that it is possible, despite this situation, to explore graphic aspects related to complex numbers, since the operations with these numbers are related to rotation, translation, symmetry, extension and reduction in the Argand-Gauss plane. These are the reasons which have led us to the proposal of this paper, namely, investigating whether a didactic sequence exploring the graphic aspects of complex numbers would make their learning more meaningful. The main theoretical reference points were Registers of Semiotic Representation of Raymond Duval and Theory of Didactic Situations of Guy Brousseau, which permeate the methodology of Didactic Engineering. Our research has shown us, on the one hand, motivated students who started elaborating surmises related to possible results in the complex plane and who wanted to learn more and, on the other hand, the lack of articulation among geometry, complex numbers and vectors in their academic life. After overcoming the initial difficulties of making the conversions of the algebraic register into a graph, the research has shown that the students began to make correct inferences about the results on the changes in the complex plane and mostly displayed that there are possibilities of rescuing a meaningful teaching of complex numbers, provided that the articulation among the different registers of these numbers representation is encouraged. Although the application to the solution of problems in plane geometry has not been completely successful, the possibility of these applications is potential and it should be better explored
O assunto Números Complexos tem sido, já faz algum tempo, objeto visto como desnecessário de ser ensinado no Ensino Médio. Alguns professores e consequentemente seus alunos acreditam que aplicações desses números só serão vistas em cursos mais avançados, nas faculdades, na área de ciências exatas. Não fosse ainda conteúdo constante nos programas de vestibulares, provavelmente tal assunto já teria sido eliminado do currículo. Acreditamos ser possível, não obstante essa situação, explorar aspectos gráficos relacionados aos números complexos, uma vez que as operações com esses números estão relacionadas a rotações, translações, simetrias, ampliações e reduções no plano de Argand-Gauss. Essas são as razões que nos levaram à proposta desse trabalho, a saber, investigar se uma sequência didática explorando os aspectos gráficos dos números complexos tornaria o seu aprendizado mais significativo. Os principais referenciais teóricos foram os Registros de Representação Semiótica, de Raymond Duval e a Teoria das Situações Didáticas, de Guy Brousseau, que permearam a metodologia da Engenharia Didática. Nosso trabalho nos mostrou, por um lado, estudantes motivados que começaram a elaborar conjecturas a respeito de possíveis resultados no plano complexo e que queriam se aprofundar no assunto e, por outro, a falta de articulação entre geometria, números complexos e vetores, na vida acadêmica desses estudantes. Superadas as dificuldades iniciais de se efetuarem as conversões do registro algébrico para o gráfico, a pesquisa mostrou que os alunos passaram a fazer inferências corretas sobre os resultados de transformações no plano complexo e mostrou, sobretudo, que há possibilidades de se resgatar um ensino significativo para os números complexos, desde que se promova a articulação entre os diferentes registros de representação desses números. Embora a aplicação à resolução de problemas de geometria plana não tenha sido completamente exitosa, a possibilidade dessas aplicações é latente e deveria ser melhor explorada

O processo de fusão completa foi investigado para a reação ANTPOT. 18 O + ANTPOT 10 B dentro do intervalo de energia de bombardeio 29,0 Mev The 18 O + 10 B within the bombarding energy range of 29,0 Mev < E LAB < 72,0 Mev, covering the 5° angular range. For this purpose, a high resolution position sensitive ionization chamber has been developed and constructed. Experimental results compared to model predictions and experimental systematics found in the literature allows to reject compound nucleus limitation to the fusion cross section up to energies as high as five times the coulomb barrier. Statistical model fits to the residues elementary distributions reveal a quite difuse partial fusion cross section in the angular momentum space. Systematic analysis of fusion barrier height (VB) and radius for neighbouring nuclei point out the importance of the nuclear matter diffuseness in the competition between the fusion and quasi-direct process. Calculations within this framework were performed.

This thesis has analyzed some aspects of stochastic flow and transport in geologic media with a random stationary and statistically isotropic hydraulic conductivity field. Explicit expressions for cross-covariances between velocity and head, and velocity and log conductivity as well as covariances of velocity under steady state uniform mean three-dimensional flow with an exponential log conductivity covariance are derived to first order and their structure is examined. An exact early time solution due to Batchelor for the mean concentration is compared with other existing stochastic solutions and its range of validity is determined for the case of an instantaneous point source. This early time solution is simpler and more general than any other stochastic transport solution at early time. A Monte Carlo simulation scheme is developed to study the ensemble behavior of solute particles traveling in such a field. The thesis concludes with a concentration estimation scheme conditioning on site measurements.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.
Includes bibliographical references (p. 93-94).
In this thesis, I present and examine the fundamental limitations involved in Radio Frequency Identification (RFID) as well as provide a means to improve reader-tag communication in ultra high frequency RFID systems. The ultimate goal in an RFID system is to maximize the communication link between the reader and the tags while, at the same time, minimizing the effect of product material, geometry and orientation. Reader-tag communication has improved significantly over the past five years, however, tag operations continue to be extremely sensitive to their environment. Ultra high frequencies present unique problems in transmission, generation and circuit design that; are not encountered at lower frequencies. Based on the fundamental constraints on these passive RFID systems, such as electromagnetics, power limitations and government regulations, I analyzed electromagnetic propagation through materials as applied to RFID tagged cases and pallets. Applying the electromagnetic concept of conductive parallel plates to enhance electromagnetic power to RFID tagged cases and pallets, I suggest an alternative to the current pallet structure.
by Uttara P. Marti.
M.Eng.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.
Vita.
Includes bibliographical references (p. 227-242).
Numerical methods are developed to study various applications in electromagnetic wave propagation and scattering. Analytical methods are used where possible to enhance the efficiency, accuracy, and applicability of the numerical methods. Electromagnetic induction (EMI) sensing is a popular technique to detect and discriminate buried unexploded ordnance (UXO). Time domain EMI sensing uses a transient primary magnetic field to induce currents within the UXO. These currents induce a secondary field that is measured and used to determine characteristics of the UXO. It is shown that the EMI response is difficult to calculate in early time when the skin depth is small. A new numerical method is developed to obtain an accurate and fast solution of the early time EMI response. The method is combined with the finite element method to provide the entire time domain response. The results are compared with analytical solutions and experimental data, and excellent agreement is obtained. A fast Method of Moments is presented to calculate electromagnetic wave scattering from layered one dimensional rough surfaces. To facilitate the solution, the Forward Backward method with Spectral Acceleration is applied. As an example, a dielectric layer on a perfect electric conductor surface is studied. First, the numerical results are compared with the analytical solution for layered flat surfaces to partly validate the formulation. Second, the accuracy, efficiency, and convergence of the method are studied for various rough surfaces and layer permittivities. The Finite Difference Time Domain (FDTD) method is used to study metamaterials exhibiting both negative permittivity and permeability in certain frequency bands.
(cont.) The structure under study is the well-known periodic arrangement of rods and split-ring resonators, previously used in experimental setups. For the first time, the numerical results of this work show that fields propagating inside the metamaterial with a forward power direction exhibit a backward phase velocity and negative index of refraction. A new metamaterial design is presented that is less lossy than previous designs. The effects of numerical dispersion in the FDTD method are investigated for layered, anisotropic media. The numerical dispersion relation is derived for diagonally anisotropic media. The analysis is applied to minimize the numerical dispersion error of Huygens' plane wave sources in layered, uniaxial media. For usual discretization sizes, a typical reduction of the scattered field error on the order of 30 dB is demonstrated. The new FDTD method is then used to study the Angular Correlation Function (ACF) of the scattered fields from continuous random media with and without a target object present. The ACF is shown to be as much as 10 dB greater when a target object is present for situations where the target is undetectable by examination of the radar cross section only.
by Christopher D. Moss.
Ph.D.

In this thesis we investigate designer disordered complex media for photonics and phononics applications. Initially we focus on the photonic properties and we analyse hyperuniform disordered structures (HUDS) using numerical simulations. Photonic HUDS are a new class of photonic solids, which display large, isotropic photonic band gaps (PBG) comparable in size to the ones found in photonic crystals (PC). We review their complex interference properties, including the origin of PBGs and potential applications. HUDS combine advantages of both isotropy due to disorder (absence of long-range order) and controlled scattering properties from uniform local topology due to hyperuniformity (constrained disorder). The existence of large band gaps in HUDS contradicts the long-standing intuition that Bragg scattering and long-range translational order is required in PBG formation, and demonstrates that interactions between Mie-like local resonances and multiple scattering can induce on their own PBGs. The discussion is extended to finite height effects of planar architectures such as pseudo-band-gaps in photonic slabs as well as the vertical confinement in the presence of disorder. The particular case of a silicon-on-insulator compatible hyperuniform disordered network structure is considered for TE polarised light. We address technologically realisable designs of HUDS including localisation of light in point-defect-like optical cavities and the guiding of light in free-form PC waveguide analogues. Using finite-difference time domain and band structure computer simulations, we show that it is possible to construct optical cavities in planar hyperuniform disordered solids with isotropic band gaps that efficiently confine TE polarised radiation. We thus demonstrate that HUDS are a promising general-purpose design platform for integrated optical micro-circuitry. After analysing HUDS for photonic applications we investigate them in the context of elastic waves towards phononics applications. We demonstrate the first phononic band gaps (PnBG) for HUDS. We find that PnBGs in phononic HUDS can confine and guide elastic waves similar to photonic HUDS for EM radiation.

The Huaca 20 site is a component of the Maranga Complex, located four kilometers to the south of the Rímac River, in the lower Rímac Valley. e archaeological excavations carried out in this site since the late 1990’s have uncovered a complex occupation that started during the Early Intermediate Period associated with Middle Lima artifacts, this occupation continued until a temporary abandonment during the Middle Horizon with a later occupation during the Late Intermediate Period, when the site was a funerary platform. is article shows the results of ongoing studies focused on the Middle Horizon occupation of Huaca 20. e last excavations at this site indicate that during the Middle Horizon, Huaca 20 was no longer domestic compound of Maranga but became an area composed of more dierentiated sectorswhich included domestic/productive, funerary, and administrative sectors. is latter would have served as a connection between Huaca 20 and the monumental structure of Huaca Potosí Alto.
El sitio arqueológico Huaca 20 se encuentra al interior del Complejo Maranga, a cuatro kilómetros al sur del río Rímac. Las excavaciones llevadas a cabo desde nales de la década de 1990, han develado un sitio con un proceso de ocupación complejo, que se inicia en el Periodo Intermedio Temprano con evidencias de materiales del estilo Lima Medio, que continúa durante el Horizonte Medio cuando es abandonado, para luego ser reutilizado durante el Periodo Intermedio Tardío como un montículo funerario.El presente trabajo pretende mostrar los avances de una investigación aún en curso, que plantea nuevas hipótesis sobre la utilización del espacio en Huaca 20. Los datos recopilados en las últimas excavaciones nos indican que, para iniciosdel Horizonte Medio, habría pasado de ser un sitio con características netamente domésticas a estar dividido en zonas con usos diferenciados. Dentro de estas zonas se registró un área de uso doméstico/productivo, dos áreas de uso funerario, y un área de uso administrativo. Esta última, según las evidencias, habría servido de nexo entre las actividades llevadas a cabo en la Huaca Potosí Alto y en el área doméstica de Huaca 20.

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2006.
Includes bibliographical references (leaves 75-76).
A complex stochastic process involving human behaviors or human group behaviors is computationally hard to model with a hidden Markov process. This is because the state space of such behaviors is often a Cartesian product of a large number of constituent probability spaces, and is exponentially large. A sample for those stochastic processes is normally composed of a large collection of heterogeneous constituent samples. How to combine those heterogeneous constituent samples in a consistent and stable way is another difficulty for the hidden Markov process modeling. A latent structure influence process models human behaviors and human group behaviors by emulating the work of a team of experts. In such a team, each expert concentrates on one constituent probability space, investigates one type of constituent samples, and/or employ one type of technique. An expert improves his work by considering the results from the other experts, instead of the raw data for them. Compared with the hidden Markov process, the latent structure influence process is more expressive, more stable to outliers, and less likely to overfit. It can be used to study the interaction of over 100 persons and get good results.
(cont.) This thesis is organized in the following way. Chapter 0 reviews the notation and the background concepts necessary to develop this thesis. Chapter 1 describes the intuition behind the latent structure influence process and the situations where it outperforms the other dynamic models. In Chapter 2, we give inference algorithms based on two different interpretations of the influence model. Chapter 3 applies the influence algorithms to various toy data sets and real-world data sets. We hope our demonstrations of the influence modeling could serve as templates for the readers to develop other applications. In Chapter 4, we conclude with the rationale and other considerations for influence modeling.
by Wen Dong.
S.M.

In the late eighties, a new class of materials, known as photonic crystals (PCs), emerged enabling the propagation and generation of light to be potentially manipulated with unprecedented control. PCs consist of a periodic modulation of dielectric constant in one, two, or three dimensions, which can result in the formation of directional or omni-directional photonic band gaps (PBGs), spectral regions where light propagation is forbidden, and more remarkably, novel dispersion characteristics. Since PC properties scale with the dimension of the wavelength of interest, significant technological constraints must be fully addressed to manufacture 3D PBG materials for optical or infrared applications such as displays, lightning, and communications. PCs enable the unraveling of unique optical phenomena such as PBGs, spontaneous emission rate manipulation, sub-wavelength focusing, and superprism effects. This research focuses on the feasibility to achieve omni-directional PBGs in synthetic opal-based 3D PCs through precise nanoscale control to the original dielectric architecture. In particular, the optical response to the conformal deposition of dielectric layers using atomic layer deposition (ALD) within the porous template is strongly emphasized. Geometrical models were developed to faithfully model the manipulation of the synthetic opal architecture by ALD and then used in electromagnetic algorithms to predict the resulting optical properties. From these results, this research presents and investigates a scheme used to greatly enhance and adjust the PBG width and position, as well as simultaneously reducing the dielectric contrast threshold at which the PBG forms. This Thesis demonstrates that the unique opal architectures offered by ALD not only supports the formation of larger PBGs with high index materials; but also enables the use of optically transparent materials with reduced refractive index. Additionally, slight alteration of these structures facilitates the incorporation of non-linear (NL) electro-optical (EO) material for dynamic tuning capabilities and potentially offers a pathway for fabricating multi-functional photonic devices. Finally, low-temperature ALD was investigated as a means to manipulate band gaps and dispersion effects in 2D PC silicon slab waveguides and 3D organic biologically-derived templates. The results indicate the unique ability of ALD to achieve composite structures with desirable (large PBGs) or novel (slow light) optical properties.

This dissertation builds on Wenner's (Wenner, L.A. (1989). Media, Sports and Society: The Research Agenda. In L. A. Wenner (Ed.), Media, Sports and Society (pp. 13-48). Newbury Park, CA: SAGE Publications Inc.) claims about how the culture of sport is changed as it is mediated by examining the mediation of sport through four digital sports games produced by Electronic Arts--Fight Night Round 2, Tiger Woods PGA Tour 2004, MVP Baseball 2005, and John Madden Football 2005. Following the example of digital game scholars, I employ a multi-level method of textual analysis in engaging the representation and gameplay of these respective titles. The dissertation uses three case studies to tease out the ideological implications of these games as they position their users. The fourth case study examines how the digital sports game audience responds to the ideologies and positioning identified in the textual analysis sections. In responding to the broader optimism of new media theorists, I argue for a consideration of the specific context of the digital sports game as a way into measuring the validity of their positions. In looking at the mediation of the body in Fight Night Round 2, golf and its attendant culture in Tiger Woods PGA Tour 2004, the ubiquitous quantification of MVP Baseball 2005, and audience responses to John Madden Football 2005, I argue that the potential freedom certain strands of new media theory proclaim is constrained by the ideologies resident in the texts examined here and the ways in which these digital sports games position their users. As such, scrutinizing these specific new media contexts reveals we should ultimately be cautious about the degree to which they offer the kinds of progressive freedoms advocated by celebratory new media scholarship.

Dans cette recherche, un modèle de propagation d'ondes de choc sur grandes distances sur un environnement urbain est construit et validé. L'approche consiste à utiliser l'Equation Parabolique Nonlinéaire (NPE) comme base. Ce modèle est ensuite étendu afin de prendre en compte d'autres effets relatifs à la propagation du son en milieu extérieur (surfaces non planes, couches poreuses, etc.). La NPE est résolue en utilisant la méthode des différences finies et donne des résultats en accord avec d'autres méthodes numériques. Ce modèle déterministe est ensuite utilisé comme base pour la construction d'un modèle stochastique de propagation sur environnements urbains. La Théorie de l'Information et le Principe du Maximum d'Entropie permettent la construction d'un modèle probabiliste d'incertitudes intégrant la variabilité du système dans la NPE. Des résultats de référence sont obtenus grâce à une méthode exacte et permettent ainsi de valider les développements théoriques et l'approche utilisée

We present an accelerated numerical solver for the scalar wave equation using one and two GPUs. We consider complex geometry and study accuracy when performing the computation in both single and double precision. The method uses a high-order accurate approximation of the derivatives using summation-by-parts operators.  The boundary conditions are imposed using the simultaneous approximation term technique for Dirichlet type boundary conditions. We develop a novel implementation of the discretization and perform experiments in one dimension with a discontinuity and in two dimensions for a simple embedded geometry. Numerical experiments show that the rate of convergence is as expected using double precision but levels-out for single precision. The performance of the solver when implemented using the GPU shows that runtime is significantly decreased using one graphics card. We then describe a strategy for further increasing performance using two graphics cards.

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2005.
Includes bibliographical references (p. 125-136).
The study of complex social systems has traditionally been an arduous process, involving extensive surveys, interviews, ethnographic studies, or analysis of online behavior. Today, however, it is possible to use the unprecedented amount of information generated by pervasive mobile phones to provide insights into the dynamics of both individual and group behavior. Information such as continuous proximity, location, communication and activity data, has been gathered from the phones of 100 human subjects at MIT. Systematic measurements from these 100 people over the course of eight months has generated one of the largest datasets of continuous human behavior ever collected, representing over 300,000 hours of daily activity. In this thesis we describe how this data can be used to uncover regular rules and structure in behavior of both individuals and organizations, infer relationships between subjects, verify self- report survey data, and study social network dynamics. By combining theoretical models with rich and systematic measurements, we show it is possible to gain insight into the underlying behavior of complex social systems.
by Nathan Norfleet Eagle.
Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2000.
Includes bibliographical references (leaves 194-204).
Real-world systems that have characteristic input-output patterns but don't provide access to their internal states are as numerous as they are difficult to model. This dissertation introduces a modeling language for estimating and emulating the behavior of such systems given time series data. As a benchmark test, a digital violin is designed from observing the performance of an instrument. Cluster-weighted modeling (CWM), a mixture density estimator around local models, is presented as a framework for function approximation and for the prediction and characterization of nonlinear time series. The general model architecture and estimation algorithm are presented and extended to system characterization tools such as estimator uncertainty, predictor uncertainty and the correlation dimension of the data set. Furthermore a real-time implementation, a Hidden-Markov architecture, and function approximation under constraints are derived within the framework. CWM is then applied in the context of different problems and data sets, leading to architectures such as cluster-weighted classification, cluster-weighted estimation, and cluster-weighted sampling. Each application relies on a specific data representation, specific pre and post-processing algorithms, and a specific hybrid of CWM. The third part of this thesis introduces data-driven modeling of acoustic instruments, a novel technique for audio synthesis. CWM is applied along with new sensor technology and various audio representations to estimate models of violin-family instruments. The approach is demonstrated by synthesizing highly accurate violin sounds given off-line input data as well as cello sounds given real-time input data from a cello player.
by Bernd Schoner.
Ph.D.

Cette thèse traite de la détection et de la localisation de sources autour de la faille de San Jacinto. Son but était de détecter des sources dans la croute superficielle, sur des profondeurs de l'ordre de quelques kilomètres. Ces sources ont une faible énergie et émettent principalement dans les hautes fréquences. Les sources à la surface autour et sur le réseau possèdent les mêmes caractéristiques et sont aussi étudiées afin de pouvoir les séparer des évènements en profondeur.Une méthode basée sur le traitement d'antenne, le Match Field Processing (MFP), est utilisée pour détecter et localiser de faibles évènements à faible profondeur et à la surface. Le MFP est appliqué a des données mesurées grâce a un réseau dense de capteurs une composante déployés sur une zone de 600mx600m sur la faille de San Jacinto. La méthode a d'abord été testée sur un ensemble d'évènements à la surface et en profondeur. Nous appliquons ensuite la technique sur 26 jours de données, afin de déterminer si des évènements sont présents en proche surface. Pour cela, seules la position en surface de la source et la vitesse apparente des ondes émises sont utilisés comme paramètres d'inversion. L'utilisation de ces trois paramètres permet de réaliser une première étude à moindre coût de calcul. Cependant cette première inversion ne permet pas de conclure sur la présence de sources en proche surface. L'information sur la position de la source en profondeur est nécessaire. Les résultats de localisations qui incluent la profondeur comme paramètre étant peu concluants lorsque le modèle classique de vitesse homogène est utilisé, nous étudions ensuite différentes stratégies pour améliorer la résolution en profondeur sans augmenter le coût de calcul
The focus of this thesis is the detection and localization of weak sources on the San Jacinto Fault Zone. The primary targets of interest are sources in the shallow crust, with depth down to a few kilometers. For sources at these depths high frequency content and low energy are expected. Surface sources present on and around the array site are also studied in order to discriminate them from weak seismic sources at depth.We rely on a methodology based on array processing to detect and localize shallow and weak seismic events in the fault zone complex environment. We use Match field Processing on data recorded from a dense array of 1108 vertical component geophones in a 600m x 600m area on the Clark branch of the San Jacinto Fault. We first test the method on a set of chosen events at depth and at the surface. Source epicentral positions and associated apparent velocities are then inverted for surface and seismic sources for 26 days, with the intention of determining if shallow sources are present. Inverting only for these three parameters is less expensive in terms of computational cost and is suitable for a first approach. However, this first inversion leaves us unable to conclude on the presence of shallow sources. As the resolution at depth is insufficient when all three source coordinates are inverted with a classical homogeneous velocity model, we finally investigate strategies to improve resolution at depth without increasing computational cost

O estudo de caminhadas aleatórias em meios desordenados e um assunto bastante explorado e pode modelar uma grande variedade de problemas, como por exemplo, problemas de transporte (difusão). O estudo de caminhadas determinísticas em meios desordenados é um assunto pouco explorado. Em uma paisagem composta de N sítios distribuídos aleatoriamente no espaço, um caminhante ("turista") visita estes sítios seguindo a seguinte regra determinística: ir para o sítio vizinho mais próximo que não tenha sido visitado nos últimos passos. De cada sítio inicial, a trajetória obtida com esta dinâmica determinística apresenta inicialmente um tempo de transiente t, onde novos sítios são visitados, e no final um atrator de período p, onde os mesmos sítios são sempre revisitados. Apesar da simplicidade do modelo, a dinâmica e complexa e os resultados não são triviais. Para dimensionalidades d = 2, a distribuição de atratores de período p, obtida numericamente, pode ser descrita por uma lei de potência com um corte exponencial. Os modelos de ligações aleatórias simétricas (que representa o limite de alta dimensionalidade d = 1 do modelo proposto) e assimétricas indicam que o corte exponencial se torna menos importante à medida que N aumenta. O expoente da lei de potência independe da memória tau, sendo portanto uma distribuição robusta. A dinâmica do turista pode ser aplicada a problemas mais abstratos, onde apenas relações de ordem entre vizinhos são dados. O estudo (por amostragem) da estrutura de um dicionário de sinônimos e um exemplo que foi considerado. Mostrou-se que as palavras podem ser embebidas em um espaço Euclidiano de baixa dimensionalidade.Este resultado concorda com um recente estudo exaustivo realizado e questiona o modelo de análise semântica latente. Com a finalidade de entender a transição entre uma caminhada determinística e uma caminhada aleatória, generalizou-se o problema com memória nula designando uma distribuição de probabilidades para o turista visitar os diversos sítios. Esta distribuição e parametrizada por uma variável externa T (temperatura) de modo que para T = 0 têm-se a caminhada do turista como caso limite e para T tendendo para infinito todos os sítios são visitados com igual probabilidade. Resultados analíticos (d = 1) e numéricos mostram a existência de uma região bem delimitada de transição entre os regimes não-ergódico (baixa temperatura) e ergódico (alta temperatura). Uma analogia é estabelecida com o modelo de vidros de Bouchaud. A eficiência da caminhada com relação aos novos sítios visitados, foi estudada e ela e máxima na borda da aleatoriedade, ou seja, ao redor da temperatura de transição.
The study of random walks in disordered media is one well-developed subject and it can model a great variety of problems, for instance, problems of transport (diffusion). The study of deterministic walks in disordered media is a subject not too explored. In a landscape composed of N sites randomly distributed in of, a walker ("tourist") visits these sites following the deterministic rule: going to the nearest site that has not been visited in the last tau steps. From each initial site, the trajectory, obtained with this deterministic dynamics, presents initially a time transient t, where new sites are visited, and, in the end, a p-period attractor, where the same sites are always revisited. In spite of the simplicity of the model, the dynamics is complex and the results are not trivial. For dimensionalities d = 2, the distribution of p-period obtained numerically can be described by a power law with an exponential cut. The models of symmetrical random connections (that represents the limit of high dimensionality d = 1 of the proposed model) and asymmetrical random connections indicate that the exponential cut turns out to be less important as N increases. The exponent law of the power law does not depend on the memory tau, being therefore a robust distribution. The tourist dynamics can be applied to more abstract problems, where just relationships of neighbor order are given. The study (by sampling) of the structure of a dictionary of synonyms has been considered. It has been shown that the words can be embedded in an Euclidean space of low dimensionality. This result agrees with a recent exhaustive study accomplished and it challenges the model of latent semantic analysis. With the purpose of understanding the transition between a deterministic and a random walk a generalization of the problem, with null memory has been performed by designating a distribution of probabilities for the tourist to visit the several sites. This distribution has the external variable T (temperature) as a parameter so that, when T = 0 it has the tourist walk as a limiting case and for T tending to infinity all of the sites are visited ith equal probability. Analytical numerical results (d = 1) show the existence of well delimited transition between non-ergodic (low temperature) and ergodic (high temperature) regime. An analogy is established Bouchaud glass model. The walk efficiency, regarding the new visited sites to trajectory length, has been studied and it is maximum at the edge of stochasticity, in other words, around the temperature of transition.

Segundo a Organização Mundial de Saúde (OMS), mais de um bilhão de pessoas estão infectadas com uma ou mais doenças tropicais endêmicas encontradas especialmente entre as populações pobres da África, Ásia e América Latina. Nos últimos 25 anos, apenas 1% de todos os medicamentos desenvolvidos no mundo foram destinados ao tratamento de doenças tropicais, como a doença de Chagas. A doença de Chagas é causada por um protozoário intracelular, o Trypanosoma cruzi, e atualmente apenas dois compostos tem sido empregados para tratamento etiológico da doença de Chagas: nifurtimox e benznidazol. Entretanto, ambos os compostos apresentam considerável toxicidade sistêmica. Nesse contexto, o objetivo do presente trabalho foi desenvolver complexos híbridos de rutênio, com potencial atividade tripanocida, que possam atuar com maior eficácia em sítios biológicos específicos do Trypanosoma cruzi e com reduzida toxicidade sistêmica. Para tal efeito, moléculas com conhecida atividade microbicida como derivados aminoglicosídeos, óxido nítrico e benznidazol foram coordenados a complexos de rutênio originando as espécies Ru(desoxiestreptamina), Ru(neamina), cis-[Ru(bpy)2(Bz)(NO)](PF6)3 e cis-[Ru(NO2)(bpy)2(Bz)]PF6. Os complexos foram caracterizados por espectroscopia de absorção no UV-vis e FTIR, espectrometria de massa, análise elementar, voltametria cíclica e voltametria de pulso diferencial. Nossos estudos sugerem que os complexos Ru(desoxiestreptamina), Ru(neamina), cis-[Ru(bpy)2(Bz)(NO)](PF6)3 e cis-[Ru(NO2)(bpy)2(Bz)]PF6 apresentam propriedades químicas que suportam o sucesso da coordenação dos ligantes ao íon metálico rutênio(II) ou (III). Dentre todos os compostos estudados, cis-[Ru(NO2)(bpy)2(Bz)]PF6, apresentou maior potência tripanocida desprovida de citotoxicidade, a julgar pelos estudos in vitro. IC50 foi ao redor de 0,24 ?mol.L-1, o que é 47 vezes menor do que a droga comumente usada em tratamento de Doença de Chagas. Isto determinou avaliação in vivo, no que foi observado aumento da sobrevida dos animais infectados com tripomastigotas, para 60 dias. Os estudos desenvolvidos com complexos de rutênio no presente trabalho reafirmam o sucesso na obtenção de tais complexos inicialmente propostos, implementando importantes informações e perspectivas no que diz respeito a complexos nitrosilos de rutênio e seus potenciais terapêuticos na doença de Chagas.
Ru(bpy)2(Bz)(NO)](PF6)3 and cis-[Ru(NO2)(bpy)2(Bz)]PF6 complexes. The compounds were characterized by UV-vis absorption spectroscopy, FTIR, mass spectrometry, elemental analysis, and cyclic voltammetry and differential pulse voltammogram. The chemical characterization presented in this work gave evidencie that support the coordination of biological ligand in ruthenium ion such as in Ru(desoxiestreptamina), Ru(neamina), cis-[Ru(bpy)2(Bz)(NO)](PF6)3 and cis-[Ru(NO2)(bpy)2(Bz)]PF6 complexes. Subsequently, in vitro and in vivo studies have been conducted evaluating the cytotoxicity and trypanocidal activity of the ligands and ruthenium complexes. In vitro analysis suggested us that ruthenium complexes are greatly effective against T. cruzi. Among all complexes synthesized cis-[Ru(NO2)(bpy)2(Bz)]PF6 showed higher in vitro trypanocidal activity, which has determined the in vivo assays with this compound. IC50 was around 0,24 ?mol.L-1, which is 47 times less than usual drugs used in Chagas diseases treatment. This was performed using animals infected with T. cruzi in trypomastigote form, animal survivals until 60 days. The studies developed for ruthenium complexes reaffirm the success in obtaining of the complexes originally proposed, implementing important information and perspectives regarding the nitrosyl ruthenium complex and its therapeutic potential in Chagas disease.

Utiliser des milieux nanostructurés pour confiner la lumière permet d'augmenter l'interaction entre un émetteur et le rayonnement électromagnétique. Dans cette thèse, nous utilisons un formalisme classique (présenté au Chap. 1) pour décrire cette interaction dans différents contextes, qui peuvent être regroupés en deux parties (respectivement Parties II et III).
Dans un premier temps, nous étudions l'apparition de modes localisés en champ proche de structures complexes. Nous nous intéressons à deux différents types de structures: des nanoantennes d'or et des films d'or désordonnés. Nos résultats nous permettent de discerner les modes radiatifs et non-radiatifs. Nous introduisons le concept de Cross Density Of States (CDOS) pour décrire quantitativement la cohérence spatiale intrinsèque associée à la structure modale d'un milieu complexe. Nous démontrons ainsi une réduction de l'extention spatiale des modes au voisinage de la percolation électrique des films d'or désordonnés.
Nous nous intéressons ensuite à des milieux fortement diffusants. En éclairant de telles structures par une source cohérente, on obtient une figure d'intensité complexe appelée speckle. Nous utilisons une méthode diagrammatique pour démontrer une corrélation négative entre les figures de speckle réfléchie et transmise à travers une tranche dans le régime mésoscopique. Nous nous intéressons ensuite à la corrélation C0, qui apparait lorsque la source est enfouie dans le milieu. Nous proposons une démonstration générale de l'égalité entre la corrélation C0 et les fluctuations normalisées de la LDOS, et soulignons le rôle fondamental des interactions de champ proche. Finalement, nous observons numériquement le régime de couplage fort entre un diffuseur résonnant et un mode localisé d'Anderson au sein d'un milieu désordonné 2D.