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Kielbassa, Janice. "Mathematical modelling of temperature effects on the life-history traits and the population dynamics of bullhead (Cottus gobio)." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10181.
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La température de l'eau joue un rôle majeur dans le cycle de vie des poissons. Dans un contexte de changement climatique global, le réchauffement peut avoir un impact fort sur la croissance, la fécondité et la survie. L'enjeu de cette thèse est la modélisation mathématique de l'influence de la température sur les traits d'histoire de vie d'une population de chabot (Cottus gobio) afin de faire de la prédiction à la fois au niveau individuel et populationnel. Les données expérimentales qui permettront de calibrer les modèles sont issues du bassin de la Drôme (France) et plus particulièrement du sous-bassin du Bez. Dans une première étape, il s'agit de développer un modèle de rétrocalcul qui peut être utilisé pour calculer les longueurs individuelles des chabots aux âges précédents à partir des données mesurées à la capture. Il s'agit, dans un deuxième temps, de développer un modèle de croissance dépendant de la température de l'eau qui sert à prédire la longueur moyenne des chabots à un âge donné. Enfin, il s'agit de passer de l'échelle de l'individu à celle de la population en prenant en compte tous les traits d'histoire de vie et leurs dépendances vis-à-vis de la température. Plus précisément, un modèle matriciel de type Leslie, à la fois dépendant du temps et de la température, structuré en classe d'âges est développé et utilisé pour prédire la dynamique de population sous différents scénario du réchauffement climatiqueWater temperature plays a key role in the life cycle of fish. Therefore, increasing temperatures due to the expected climate change may have a strong impact on growth, fecundity and survival. The goal of this thesis is to model the impact of temperature on the life-history traits of a bullhead population (Cottus gobio) in order to make predictions both at individual and at population level. The models developed here are calibrated on experimental field data from a population living in the Bez River network (Drôme, France). First, a new back-calculation model is derived that can be used to compute individual fish body lengths at earlier ages from capture data. Next, a growth model is proposed that incorporates the water temperature and can be used to predict the mean length at a given age and temperature. Finally, the population is modelled as a whole by linking all life-history traits to temperature. For this purpose, a spatialised time- and temperature-dependent Leslie matrix model structured in age classes was used to predict the population dynamics under different temperature scenarios
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Robert, Christian P. "Résultats nouveaux sur les estimateurs à rétrecisseurs scalaires et matriciels." Rouen, 1987. http://www.theses.fr/1987ROUES029.
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Dans le cadre du modèle statistique linéaire, cette thèse apporte certaines améliorations à la théorie des estimateurs à rétrécisseur à l'aide de techniques d'intégration par parties généralisée. Elle élargit tout d'abord les champs d'application de cette théorie (lois à symétrie sphérique, fonctions de rétrécissement de plusieurs variables, non nécessairement continues, opérateurs vectoriels de rétrécissement quelconques, estimateurs "bimatriciels",. . . ). Nous proposons également des méthodes de sélection parmi les classes d'estimateurs à rétrécisseur (condition nécessaire d'admissibilité, conditions suffisantes de domination par des estimateurs appartenant à des classes données,. . . ), montrant en particulier l'intérêt des estimateurs à rétrécisseur matriciel dans les situations de multicolinéarité
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Aubry, Lise Myriam. "Influence du recrutement sur les variations des paramètres démographiques avec l'âge et la vitesse de sénescence chez la mouette tridactyle, Rissa tridactyla." Toulouse 3, 2009. http://thesesups.ups-tlse.fr/1581/.
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J'ai utilisé une étude de 30 ans portant sur une espèce d'oiseau marin longévif (la mouette tridactyle) afin d'étudier les compromis évolutifs entre recrutement, reproduction, et survie. Mes résultats indiquent que l'âge à la première reproduction et la sélection de l'habitat sont intimement liés, et que l'âge au recrutement influence également les trajectoires de survie et de reproduction. D'autres sources d'hétérogénéité observée (investissement reproducteur) et non-observée ('frailty') agissent également sur la survie et la reproduction au cours de la vie. Les recrues d'âge intermédiaire (âge = 5) maintiennent un succès reproducteur élevé au cours de la vie et minimisent le déclin des chances de survie avec l'âge par rapport aux autres recrues. Même si les mesures de fitness individuelles indiquent que le recrutement précoce est la plus avantageuse des stratégies, les coûts associés au différé du recrutement semblent minimesI used a 30-year study of long-lived seabirds (black-legged Kittiwakes) that breed in Brittany to study the evolution of trade-offs between early-life breeding decisions, future reproduction, and survival. I first found that recruitment age and habitat selection were intimately linked. Recruitment age further influenced breeding success and survival trajectories. Furthermore, sources of observed (reproductive covariates, experience) and unobserved heterogeneity (frailty) explained substantial amounts of variability in breeding success and survival. Overall, intermediate age recruits (age 5) seemed to maintain high breeding success over life and minimized senescence in survival compared to other recruits. Even though individual fitness showed that earlier recruitment was the most beneficial recruitment strategy, the costs associated to delayed recruitment seemed minimal
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FRANTZ, REMY. "Processeurs optiques d'algebre lineaire : etude de synthese, description fonctionnelle et simulation numerique d'une maquette de coprocesseur." Université Louis Pasteur (Strasbourg) (1971-2008), 1989. http://www.theses.fr/1989STR13030.
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Description du fonctionnement d'un processeur vectoriel optique et etablissement de son modele physique. Par simulation numerique, les limites de son fonctionnement sont analysees et ses performances determinees
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Hadjou, Belaid Asma. "Démographie et réponses adaptatives des populations végétales aux changements environnementaux." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG034/document.
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La région méditerranéenne, hot-spot de biodiversité avec un fort taux d'endémisme, est classée parmi les zones les plus touchées par le changement climatique. La conservation des espèces nécessite de comprendre finement leur démographie face à ces changements, mais aussi leur capacité à s’adapter à ces nouvelles conditions. Au cours de cette thèse, deux espèces végétales rares méditerranéennes ont été étudiées, Centaurea corymbosa et Brassica insularis, en utilisant des modèles mathématiques récents pour analyser des suivis démographiques de long-terme (22 ans et 18 ans). Dans la première partie de cette thèse, des modèles de projection matriciels ont été construits afin d’analyser la variation spatio-temporelle des taux d’accroissement des populations de C. corymbosa. Cela a permis d'identifier les facteurs climatiques clefs qui impactent les taux d’accroissement des populations, et plus finement, les paramètres de survie, de floraison et de fécondité. Une analyse de viabilité des populations a été réalisée sous différents scénarios climatiques. Dans un second temps, une analyse de la capacité des populations de C. corymbosa à répondre à ces changements climatiques a été effectuée avec un modèle de projection intégral. Les changements des traits d’histoire de vie au cours du temps ont montré que la stratégie de floraison observée répond aux variations climatiques en suivant la même direction que la stratégie optimale. Ceci montre que les populations sont capables de s’adapter au changement climatique. Enfin, des modèles de capture-recapture (CR) ont été construits afin de déterminer l’influence de la faible détectabilité des individus sur l’estimation des paramètres démographiques chez B. insularis. Les probabilités de survie estimées par l’approche classique sont inférieures à celles estimées par les modèles CR. Les paramètres estimés par les deux approches sont en général très corrélés, à l'exception d'une population montrant des problèmes d'identification des individus. L'ensemble de cette thèse est replacé dans le cadre de la biologie de la conservation des espèces végétales, notamment en suggérant de prendre en compte leur capacité de réponse au changement climatiqueMediterranean region is a biodiversity hot-spot with a high endemism rate and is classified among the areas most sensitive to climate change. Deep understanding of demography and evolution following these changes is a necessity for species conservation. During this thesis, two rare Mediterranean plant species have been studied, Centaurea corymbosa and Brassica insularis, using recent mathematical models to analyse long term demographic datasets (22 and 18 years). In the first part of this thesis, matrix projection models have been used to analyse spatio-temporal variation in population growth rate in C. corymbosa. Major climatic parameters that impact population growth rate and survival, flowering and fecundity have been identified. A population viability analysis has been performed under various climatic scenarios. In a second part, an analysis of the population ability of C. corymbosa to response to these climatic changes has been performed using integral projection models. Temporal variation of life-history traits showed that the realized flowering strategy varied with climatic conditions following the same direction than the optimal flowering strategy. It can thus be concluded that the studied populations can adapt to climatic changes. Finally, capture-recapture models have been applied on the Brassica insularis dataset to analyse the effect of plant detectability on demographic parameter estimations. Survival probabilities obtained with the classical approach are lower than the ones estimated using the CR models. However, the parameters estimated using both methods are highly correlated, except for one population where individual identification is problematic. Results of this thesis are linked to some considerations in conservation biology of plants, particularly in link to their ability to respond to climatic changes
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Lazo, Matheus Jatkoske. "O ansatz do produto matricial: uma nova abordagem para modelos exatamente solúveis." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-01042014-173851/.
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Neste trabalho mostramos que uma grande variedade de modelos exatamente solúveis através do ansatz de Bethe coordenadas podem também ser resolvidos através de um ansatz do produto matricial. Estes modelos são descritos no caso unidimensional por cadeias quânticas, e por matrizes de transferência no caso de sistemas clássicos bi-dimensionais. Diferentemente do ansatz de Bethe, em que as auto-funções do modelo são escritas como uma combinação de ondas planas, no nosso ansatz do produto matricial elas são dadas por produtos de matrizes, onde as matrizes obedecem a uma álgebra associativa apropriada. Estas relações algébricas são obtidas impondo-se que as auto-funções escritas em termos do ansatz satisfaçam à equação de auto-valor do operador Hamiltoniano ou da matriz de transferência. A consistência das relações de comutatividade entre os elementos da álgebra implicam na exata integrabilidade do modelo. Além disso, o ansatz que propomos permite uma formulação simples e unificada para vários Hamiltonianos quânticos exatamente solúveis. Apresentamos nesta tese a formulação do nosso ansatz do produto matricial para uma grande família de redes quânticas, como os modelos anisotrópico de Heisenberg, Fateev-Zamolodchikov, Izergin-Korepin, Sutherland, t-J, Hubbard etc. Mais ainda, formulamos nosso ansatz para processos estocásticos de partículas com tamanhos e classes diferentes difundindo assimetricamente na rede. Por fim, com o objetivo de dar suporte a nossa conjectura de que todos os modelos exatamente solúveis através do ansatz de Bethe coordenadas, associados a Hamiltonianos quânticos unidimensionais ou matrizes de transferência bidimensionais, também podem ser resolvidos através de um ansatz do produto matricial, apresentamos a formulação do nosso ansatz para a matriz de transferência do modelo de seis-vértices com condição de contorno toroidalIn this work we show that a large family of exactly solved models through the coordinate Bethe ansatz can also be solved through a matrix product ansatz. The models are described in the one dimensional case by quantum Hamiltonians, and by transfer matrices in the case of two dimensional classical models. Differently from the Bethe ansatz, where the model\'s eigenfunctions are described by a plane wave combination, in our matrix product ansatz they are given by a matrix product, where the matrices obey a suitable associative algebra. Theses algebraic relations are obtained by imposing that the eigenfunctions described in terms of the ansatz satisfy the eigenvalue equation for the associated Hamiltonian or transfer matrix. The consistency of the commutativity relations among the elements of the algebra implies the exact integrability of the model. Furthermore, the matrix product ansatz we propose allows an unified and simple formulation for the solution of several exact integrable quantum Hamiltonians. We present on this thesis the formulation of our matrix product ansatz for a huge family of quantum chains such as the anisotropic Heisenberg model, Fateev-Zarnolodchikov model, Izergin-Korepin model, Sutherland model, t- J model, Hubbard model, etc. Moreover, we formulated our ansatz for stochastic process of particles with different sizes and classes diffusing asymmetrically on the lattice. Finally, in order to support our conjecture that all exactly solved models through the coordinate Bethe ansatz, associated to unidimensional quantum Hamiltonians or two-dimensional transfer matrices, can also be solved through a matrix product ansatz, we present the formulation of our ansatz, for the transfer matrix of the six-vertex model with toroidal boundary condition
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Koffi, Kouamé Fulgence. "Impact du feu sur la démographie des Graminées de savane (Lamto, Côte d’Ivoire)." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS161.
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La thèse vise à combler un déficit de connaissance sur la démographie des Poacées pérennes dans une savane humide (Lamto). L’impact de 4 traitements de feu (le feu précoce, le feu de mi-saison, le feu tardif et l’absence de feu) sur la démographie des Poacées pérennes dominantes a été étudié entre 2015 et 2018 sur des sous-parcelles de 5×5 m et 5x10 m. des modèles matriciels à cinq classes de circonférence ont été utilisés. Des réponses différenciées entre espèces ont été observées. La circonférence des touffes, varie entre 3 cm et 156 cm. La fragmentation, la rétrogression et la fécondité augmentent avec la circonférence alors que la mortalité et la croissance des touffes diminuent. Le feu tardif cause plus de mort, rétrogression et fragmentation tandis que le feu de mi-saison favorise plus de croissance et moins de rétrogression. Toutes les espèces ont présenté un taux de croissance λ < 1 en feu tardif et en absence du feu chaque année. Le feu de mi-saison est favorable à la croissance d’H. diplandra (λ = 1.02). La croissance d’A. canaliculatus a été plus favorisée par les feux précoce et de mi-saison (λ = 1.15 et λ = 1.04 respectivement). Enfin, A. canaliculatus et H. diplandra ont les mêmes âges et vivent plus longtemps sous feu précoce (87 à 103 ans). En absence du feu, A. canaliculatus peut atteindre jusqu’à 126 ans. Globalement, les espèces de Poacées pérennes diffèrent par leurs paramètres démographiques et leur réaction aux différents régimes de feu. La circonférence des touffes est un paramètre déterminant dans l’étude de la démographie de ces Poacées. Le feu de mi-saison parait être le plus favorable pour le maintien de la diversité des Poacées à LamtoThe thesis aims to fill a lake of knowledge on the demography of perennial grasses in a humid savanna (Lamto). The impact of 4 fire treatments (early fire, mid-season fire, late fire and no fire) on the demography of the dominant perennial grasses was studied between 2015 and 2018 on sub-plots of 5 × 5 m and 5 × 10 m. Matrix models with 5 classes of circumference were used. Different responses of the species were observed. The circumference of the tussocks, varies between 3 cm and 156 cm. Fragmentation, retrogression, and fecundity increase with circumference as mortality and tussock growth decrease. Late fire causes more death, retrogression and fragmentation while mid-season fire promotes more growth and less retrogression. All species showed a growth rate λ <1 in late fire and no fire each year. The mid-season fire is advantageous to the growth of H. diplandra (λ = 1.02). The growth of A. canaliculatus was favored by early and mid-season fires (λ = 1.15 and λ = 1.04 respectively). Finally, A. canaliculatus and H. diplandra have the same ages and live longer under early fire (87 to 103 years). In the no fire, A. canaliculatus can reach 126 years. Overall, perennial grass species differ in their demographic parameters and their response to different fire regimes. The circumference of the tussocks is a determining parameter in the study of the demography of these grasses. The mid-season fire seems to be the most favorable for maintaining the diversity of the grasses at Lamto
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Sioud, Khaled. "Simulation par éléments finis sur micro-ordinateur de la réponse dynamique des structures coques en régime linéaire et non linéaire." Nancy 1, 1991. http://www.theses.fr/1991NAN10127.
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Ce travail a pour objectif le développement sur micro-ordinateur des logiciels de simulation par éléments finis de problèmes généraux de mécanique des structures rencontrés en dynamique linéaire, modes réels et complexes , et non linéaire en formulations plaques et coques. La démarche poursuivie au cours de ce travail repose sur les étapes suivantes: étude détaillée des diverses méthodes de calculs des valeurs et vecteurs propres de matrices symétriques et non symétriques, accélération de ces méthodes par la mise en œuvre d'algorithmes permettant d'améliorer la convergence de la méthode des itérations de sous-espace accélérée par Tchebychev, mise en œuvre d'algorithmes permettant l'analyse dynamique, en comportement non linéaire géométrique et matériel, des plaques et coques, validation du code sur des exemples de complexité diverse, comparaison de nos résultats avec ceux d'autres codes
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Morel, Florent Rétif Jean-Marie. "Commandes directes appliquées à une machine synchrone à aimants permanents alimentée par un onduleur triphasé à deux niveaux ou par un convertisseur matriciel triphasé." Villeurbanne : Doc'INSA, 2008. http://docinsa.insa-lyon.fr/these/pont.php?id=morel.
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Sitel, Azzedine. "Méthodes de mesure des matrices acoustiques des discontinuités à un ou deux ports en présence des modes élevés." Compiègne, 2005. http://www.theses.fr/2005COMP1603.
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Cette étude présente la mise en oeuvre dans le cas d'un champ acoustique multimodal des méthodes expérimentales pour la caractérisation d'une discontinuité à deux ports par mesure de sa matrice de diffusion et de transmission ainsi que sa dissipation acoustique, et d'une discontinuité à un port par mesure de sa matrice de réflexion. La méthode proposée est appliquée à la mesure de la matrice de diffusion d'un tronçon droit sans discontinuités et d'un tronçon réactif. Les matrices de réflexion et de transmission sont mesurées pour un tronçon droit couplé avec une terminaison ouverte du conduit. Avec le surdimensionnement sur le nombre des charges, les coefficients expérimentaux de la matrice de diffusion mesurés pour le tronçon droit montrent un très bon accord avec la théorie, sauf, à l'approche des fréquences de coupure des modes. Pour le tronçon réactif, une très bonne concordance entre l'expérience et la théorie est notée pour les coefficients de diffusion associés aux ondes incidentes du côté de la source. En revanche, pour les bandes de fréquences où le tronçon filtre un des modes, la méthode des charges ne peut être utilisée pour mesurer les coefficients de diffusion associés aux ondes incidentes du côté de la charge. Pour caractériser complètement un tronçon non symétrique, un essai supplémentaire après son inversion est donc nécessaire. Pour les matrices de transmission et de réflexion, le surdimensionnement sur le nombre des configurations de la source apporte une grande amélioration sur les résultats. D'un autre côté, et afin d'estimer la sensibilité des différentes méthodes aux imprécisions de mesure, une méthode de simulation analytique de l'expérience est développéeThis study presents the development of experimental methods to characterise a two-port discontinuity by measurement of its scattering and transmission matrices and its power dissipation, and a one-port discontinuity by measurement of its reflection matrix in higher order modes propagation conditions. This method is applied to the measurement of a scattering matrix of a straight cylindrical duct and a reactive chamber. Reflection and transmission matrices are measured for an open end coupled with a straight duct. With the use of the overdetermination on the number of loads, a good agreement was found between analytical and experimental scattering-matrix coefficients measured for the straight duct except near of eut-off frequencies. The test with the reactive type muffler shows that the load method fails in determining the coefficients associated to the wave coming in the discontinuity from the open side because modes are filtered by the reactive chamber. To characterise completely an asymmetrical section, an additionnel test after its inversion is therefore necessary. Results of transmission and reflection matrices shows that the overdetermination procedure on the number of source configurations improves the results. Ln another side, and in order to estimite the sensitivity of various methods to measurement errors, an analytical procedure of simulation of the experience is developed
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Béguer, Mélanie. "Réponses d'une population aux forçages environnementaux et anthropiques : le suivi à long terme de la crevette Palaemon Longirostris de l'Estuaire de la Gironde (1979-2007)." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13884/document.
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La population de la crevette blanche Palaemon longirostris, espèce résidente des estuaires faisant l’objet d’une pêche traditionnelle, est soumise à des forçages environnementaux (fluctuations naturelles du milieu, modifications du régime hydro-climatique de l’estuaire en lien avec le changement climatique) et anthropiques importants (aspiration dans les circuits du CNPE -Centre Nucléaire de production d’Electricité du Blayais-, pêche ciblée, pollutions etc.). Dans ce contexte et sur la base d’un suivi mensuel, réalisé depuis 1979, complété par des échantillonnages en 2007, cette thèse montre que cette population répond fortement aux changements environnementaux abiotiques et anthropiques. Ainsi, d’importantes fluctuations spatio-temporelles des abondances sont mises en évidence à diverses échelles temporelles, spatiales et biologiques. L’analyse de la série à long terme montre des fortes oscillations interannuelles régulières (période 5/10 ans) en partie liées aux facteurs environnementaux et aux variations du recrutement. Une diminution de l’abondance globale, ainsi qu’un déplacement vers l’amont de cette population, sont également constatés. Ce déclin est attribué aux fortes variations et nombreuses modifications des traits de vie de l’espèce –reproduction, -croissance, -mortalité, démontrées au cours de l’étude. La présence de déformations de l’exosquelette, étudiée aussi via un élevage de plusieurs mois, révèle par ailleurs, de forts impacts négatifs à l’échelle individuelle (mortalité). De plus, des simulations réalisées à partir d’un modèle matriciel de dynamique de population élaboré durant l’étude, montrent la synergie des pressions anthropiques par prélèvements (CNPE, pêche) et des forçages environnementaux, ainsi que l’importance des processus de déplacement dans le fonctionnement de cette population. Cette étude démontre finalement l’intérêt que revêt cette population et plus largement les populations de crevettes estuariennes, pour l’étude du fonctionnement et du diagnostic de l’état des écosystèmes estuariens. De nouvelles métriques originales sont proposées, lesquelles ouvrent vers la voie vers de nouveaux indicateursThe white shrimp, Palaemon longirostris, is an estuarine species and an important fishing resource. This species therefore encounters an important environmental forcing (natural fluctuations of the environment, modifications of the hydro-climatic regime of the estuary associated with the climate change) and an anthropological forcing (drawing up by the circuits of the CNPE - Nuclear center of electricity production of Blayais-, targeted fishing, pollutions etc.). In this context and on the basis of a monthly survey in place since 1979 and completed in 2007, this study shows that this population is strongly influenced by environmental and anthropological changes. Important spatio-temporal variations in the shrimp abundance are highlighted at different temporal, spatial and biological scales. A long-term analysis underlines strong regular interannual oscillations (5/10-year period) partially linked with environmental factors and recruitment variations. A decrease in the global abundance and a movement of this population towards the upstream part of the estuary are also displayed. In this study, the decline is attributed to strong variations and numerous modifications in the life history traits of the species - reproduction, - growth, - mortality. The presence of exoskeletal deformities, alternatively studied via a rearing of several months, reveals strong negative impacts at the individual scale (mortality). Furthermore, simulations based on a population-matrix model, developed during the study, show the synergy of the anthropological pressure by capture (CNPE, fishing) and the environmental forcing, as well as the importance of movement processes in the population dynamics. This study finally demonstrates the interest of this population, and more widely of the estuarine shrimp populations, in the understanding of the functioning and the diagnosis of the estuarine ecosystem state. New original metrics are proposed, opening the way towards new indicators
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Pradhan, Sunny. "Toeplitz matrices for the long-range Kitaev model." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18018/.
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In questa tesi discuteremo delle fasi topologiche di una catena quantistica unidimensionale con accoppiamento superconduttivo, nota anche come catena di Kitaev, insieme a un paio di estensioni di essa: una con accoppiamento a lungo raggio e una con accoppiamento ai bordi della catena.
Queste fasi verranno investigate con l'aiuto della teoria delle matrici di Toeplitz, che semplifica sia la risoluzione dello spettro che delle funzioni di correlazione.
Inoltre, all'interno della teoria delle matrici di Toeplitz identificheremo un winding number particolare, che potrà essere usato come strumento per rilevare fasi topologiche e edge state non massivi.
Sulla base di questa identificazione, insieme ad alcune analisi numeriche eseguite sulla catena di Kitaev a lungo-raggio, proporremo una congettura sulla comparsa di edge state massivi, che verrà usata poi per spiegare una transizione di fase senza chiusura del gap che avviene nella catena di Kitaev a lungo raggio.
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Antal, Judit. "Fit indices for the Rasch model." Columbus, OH : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1054222470.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xiii, 102 p.: ill (some col.). Includes abstract and vita. Advisor: Ayres G.D'Costa, College of Education. Includes bibliographical references (p. 97-102).
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Fogliarini, Filha Cláudia Brum de Oliveira. "USO DE APLICATIVOS COMPUTACIONAIS E PRODUTO MATRICIAL: DUAS PROPOSTAS DE APLICAÇÃO." Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/10947.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThis work presents two educational proposals, directed to the high school, of matrix product aplication. The first proposal is made on geometric transformations (reflection, rotation, scale, shearing) with images of letters of the alphabet. It is divided into two parts: in the first, students need to make the product of matrices and the construction of the images, while in the second GeoGebra software is used to assist in the calculation and construction of the figures. The second proposal is about the projection of population growth through Leslie Model, using the Octave software as calculation tool. Before each proposal is provided the theory that supports geometric transformations as well the Leslie Model and several examples to clarify these definitions.
Este trabalho apresenta duas propostas didáticas, direcionadas ao Ensino Médio, de aplicação do produto matricial. A primeira proposta é feita sobre transformações geométricas (reflexão, rotação, escala, cisalhamento) com a imagem de letras do nosso alfabeto. Ela está dividida em duas partes: na primeira, os alunos devem fazer o produto de matrizes e a construção das imagens à mão, enquanto na segunda é utilizado o programa GeoGebra para auxiliar nos cálculos e na construção das figuras. A segunda proposta é feita sobre projeção de crescimento populacional através do Modelo de Leslie, sendo utilizado o programa Octave como ferramenta de cálculo. Antes de cada proposta, é oferecida a teoria que fundamenta tanto as transformações geométricas quanto o Modelo de Leslie, e vários exemplos são usados para esclarecer essas definições.
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Benigni, Lucas. "Dynamics of eigenvectors of random matrices and eigenvalues of nonlinear models of matrices." Thesis, Sorbonne Paris Cité, 2019. http://www.theses.fr/2019USPCC003/document.
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Cette thèse est constituée de deux parties indépendantes. La première partie concerne l'étude des vecteurs propres de matrices aléatoires de type Wigner. Dans un premier temps, nous étudions la distribution des vecteurs propres de matrices de Wigner déformées, elles consistent en une perturbation d'une matrice de Wigner par une matrice diagonale déterministe. Si les deux matrices sont du même ordre de grandeur, il a été prouvé que les vecteurs propres se délocalisent complètement et les valeurs propres rentrent dans la classe d'universalité de Wigner-Dyson-Mehta. Nous étudions ici une phase intermédiaire où la perturbation déterministe domine l'aléa: les vecteurs propres ne sont pas totalement délocalisés alors que les valeurs propres restent universelles. Les entrées des vecteurs propres sont asymptotiquement gaussiennes avec une variance qui les localise dans une partie explicite du spectre. De plus, leur masse est concentrée autour de cette variance dans le sens d'une unique ergodicité quantique. Ensuite, nous étudions des corrélations de différents vecteur propres. Pour se faire, une nouvelle observable sur les moments de vecteurs propres du mouvement brownien de Dyson est étudiée. Elle suit une équation parabolique close qui est un pendant fermionique du flot des moments de vecteurs propres de Bourgade-Yau. En combinant l'étude de ces deux observables, il est possible d'analyser certaines corrélations.La deuxième partie concerne l'étude de la distribution des valeurs propres de modèles non-linéaires de matrices aléatoires. Ces modèles apparaissent dans l'étude de réseaux de neurones aléatoires et correspondent à une version non-linéaire de matrice de covariance dans le sens où une fonction non-linéaire, appelée fonction d'activation, est appliquée entrée par entrée sur la matrice. La distribution des valeurs propres convergent vers une distribution déterministe caractérisée par une équation auto-consistante de degré 4 sur sa transformée de Stieltjes. La distribution ne dépend de la fonction que sur deux paramètres explicites et pour certains choix de paramètres nous retrouvons la distribution de Marchenko-Pastur qui reste stable après passage sous plusieurs couches du réseau de neuronesThis thesis consists in two independent parts. The first part pertains to the study of eigenvectors of random matrices of Wigner-type. Firstly, we analyze the distribution of eigenvectors of deformed Wigner matrices which consist in a perturbation of a Wigner matrix by a deterministic diagonal matrix. If the two matrices are of the same order of magnitude, it was proved that eigenvectors are completely delocalized and eigenvalues belongs to the Wigner-Dyson-Mehta universality class. We study here an intermediary phase where the deterministic perturbation dominates the randomness of the Wigner matrix : eigenvectors are not completely delocalized but eigenvalues are still universal. The eigenvector entries are asymptotically Gaussian with a variance which localize them onto an explicit part of the spectrum. Moreover, their mass is concentrated around their variance in a sense of a quantum unique ergodicity property. Then, we consider correlations of different eigenvectors. To do so, we exhibit a new observable on eigenvector moments of the Dyson Brownian motion. It follows a closed parabolic equation which is a fermionic counterpart of the Bourgade-Yau eigenvector moment flow. By combining the study of these two observables, it becomes possible to study some eigenvector correlations.The second part concerns the study of eigenvalue distribution of nonlinear models of random matrices. These models appear in the study of random neural networks and correspond to a nonlinear version of sample covariance matrices in the sense that a nonlinear function, called the activation function, is applied entrywise to the matrix. The empirical eigenvalue distribution converges to a deterministic distribution characterized by a self-consistent equation of degree 4 followed by its Stieltjes transform. The distribution depends on the function only through two explicit parameters. For a specific choice of these parameters, we recover the Marchenko-Pastur distribution which stays stable after going through several layers of the network
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Lin, Pei-Wei. "A robust model for estimating freeway dynamic origin-destination matrices." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3619.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Includes bibliographical references (p. 123-130). Also available online via the Digital Repository at the University of Maryland website (https://drum.umd.edu/).
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Pörn, Sebastian, and Arvid Rönnblom. "Assesing counterparty risk classification using transition matrices : Comparing models' predictive ability." Thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-136667.
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An important part when managing credit risk is to assess the probability of default of different counterparties. Increases and decreases in such probabil- ities are central components in the assessment, and this is where transition matrices become useful. These matrices are commonly used tools when as- sessing counterparty credit risk, and contain the probability of default, as well as the probability to migrate between different predefined rating classifica- tions. These rating classifications are used to reflect the risk taken towards different counterparties. Therefore, it is important for financial institutions to develop accurate transition matrix models to manage predicted changes in credit risk exposure. This is because counterparty creditworthiness and prob- ability of default indirectly affect expected loss and the capital requirement of held capital. This thesis will analyze how two specific models perform when used for generating transition matrices. These models will be tested to investigate their performance when predicting rating transitions, including probability of default.En viktig del vid hanteringen av kreditrisk är att bedöma sannolikheten för fallissemang för olika motparter. Ökningar och minskningar i dessa sanno- likheter är centrala komponenter i bedömningen, och det är här migrations- matriser blir användbara. Dessa matriser är vanligt förekommande verktyg vid bedömning av kreditrisk mot olika motparter och innehåller sannolikheten för fallissemang samt sannolikheten att migrera mellan olika fördefinierade be- tygsklassificeringar. Dessa betygsklassificeringar används för att återspegla den risk som tas mot olika motparter. Det är därför viktigt för finansinstitut att utveckla träffsäkra migrationsmatris modeller för att hantera förväntade förändringar i kreditriskexponering. Detta beror på att kreditvärdigheten hos motparter samt sannolikheten för fallissemang indirekt påverkar expected loss och kapitalkrav. Detta examensarbete kommer att analysera hur två specifika modeller presterar när de används för att generera migrationsmatriser. Dessa mod- eller kommer att testas för att undersöka hur de presterar när de används för att förutsäga övergångar inom betygsklassificering, inklusive sannolikheten för fallissemang.
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Rossetto, Carlos Ricardo. "Um modelo matricial para determinação de custos no processo produtivo-soja." reponame:Repositório Institucional da UFSC, 1990. http://repositorio.ufsc.br/xmlui/handle/123456789/75708.
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Os métodos atualmente existentes para alocação dos custos em lavouras agrícolas abrangem uma análise macroeconômica deixando nosso agricultor carente de informações no que tange a seu processo agrícola específico. A atuação dos mesmos se restringe basicamente à obtenção dos lucros totais, oferecendo poucas informações adicionais ao processo decisório. O presente trabalho visa desenvolver um modelo baseado em planilha eletrônica que, através de sua implantação em computadores, permite sanar as deficiências dos modelos atuais definindo, com mais clareza, a alocação de todos os cursos do produtivo permitindo um aumento considerável de subsídios e informações no processo decisório. Posteriormente, é feita uma aplicação prática do modelo proposto, objetivando verificar sua aplicabilidade. Tal aplicação foi feita em uma lavoura de soja específica, buscando analisar os resultados com o método atualmente existente, a fim de efetuar comparações e destacar as vantagens do modelo proposto. Finalmente, são apresentadas as conclusões obtidas em função do desenvolvimento e da aplicação do modelo proposto.
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Brito, Pizarro Camila Fernanda. "Teoría de matrices aleatorias aplicada al análisis estadístico de un modelo de factores." Tesis, Universidad de Chile, 2016. http://repositorio.uchile.cl/handle/2250/140486.
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Magíster en Ciencias de la Ingeniería, Mención Matemáticas Aplicadas.
Ingeniera Civil MatemáticaLas matrices aleatorias y su reciente teoría están jugando un papel fundamental como herramienta estadística en áreas tales como finanzas, meteorología y procesamiento de señales e imágenes. Algunas de las aplicaciones que han adquirido mayor desarrollo se encuentran en el sector financiero y en el área de las comunicaciones inalámbricas. El desafío planteado en este trabajo de tesis consiste en realizar un análisis estadístico basado en la teoría de matrices aleatorias referido a un modelo de factores. A través de la experimentación computacional, se pretende alcanzar dos metas. La primera de ellas consiste en contrastar dos versiones de un mismo test de hipótesis, las cuales se definen a partir de estadísticos provenientes de dos de las más conocidas familias gaussianas de matrices aleatorias: GUE y GOE. Esta comparación surge del hecho de que la familia GOE es menos estudiada en las aplicaciones de matrices aleatorias a considerar, de modo que se busca ampliar el conocimiento que de ella se tiene. Para hacer efectivo el contraste entre ambas versiones, estas se implementan para luego analizarlas en términos de sus comportamientos frente a errores y aciertos. Así, se logra probar empíricamente que no existe diferencia alguna entre ellas, por lo que la versión GOE del test es la que asume el protagonismo. Alcanzada la meta anterior, la segunda consiste en dar utilidad al test en su versión GOE, mediante el desarrollo de un procedimiento que lo aplica iteradas veces para estimar el número de factores de una muestra sujeta al modelo de factores. Posteriormente, el procedimiento es sometido a una serie de pruebas empíricas que buscan validarlo como método de estimación del número de factores. Finalmente, es preciso mencionar que, si bien, este trabajo posee un carácter fundamentalmente experimental, no se aparta del estudio, análisis y manejo abstracto de la teoría de matrices aleatorias que se requieren necesariamente para llevarlo a cabo.
Este trabajo ha sido parcialmente financiado por Núcleo Milenio: "Modelos estocásticos de sistemas complejos y desordenados"
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Kim, Myung Geun. "Models for the covariance matrices of several groups /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487758680162533.
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Ataide, Wendy Fonseca. "Modelagem do potencial matricial na frente de umedecimento." Universidade Federal de Viçosa, 2005. http://www.locus.ufv.br/handle/123456789/9744.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Infiltração é o processo pelo qual a água passa da superfície para o interior do solo, sendo dependente da carga hidráulica na superfície, do teor de água inicial, da textura, da estrutura, da condutividade hidráulica e da porosidade do solo. Diversos modelos se propõem a estimar este processo, dentre os quais se destaca o de Green-Ampt modificado por Mein e Larson (GAML), baseado numa análise física do processo. Embora seja bastante utilizado, este modelo apresenta como desvantagem a dificuldade de obtenção de seus parâmetros de entrada, principalmente do potencial matricial na frente de umedecimento ( ψ m ). Assim sendo, este trabalho teve como objetivos: obter as variáveis necessárias à estimativa do potencial matricial na frente de umedecimento, utilizando-se para tal o modelo de Green-Ampt modificado por Mein e Larson, e estabelecer modelo matemático que relacione o potencial matricial na frente de umedecimento com as características físicas e a condutividade hidráulica do solo saturado, para sua aplicação no modelo de Green-Ampt modificado por Mein e Larson. Foram utilizadas três classes de solos (Latossolo Vermelho - Amarelo – LVA; Latossolo Vermelho – LV; e Argissolo Vermelho – PV). Estes solos foram secos ao ar, destorroados e peneirados em peneira de malha 10 mm, sendo posteriormente acondicionados em colunas de PVC de 200 mm de diâmetro e 800 mm de altura, de modo que a densidade do solo ficasse próxima daquela observada em campo. Na lateral das colunas, foram instaladas horizontalmente sondas de TDR para a determinação do teor de água e para o acompanhamento da frente de umedecimento. Aplicou-se água sobre a superfície das colunas sob taxa constante, por meio de um simulador de chuvas, sendo que o excesso escoado superficialmente foi conduzido para uma caixa de coleta na qual foi instalado um medidor de nível denominado Thalimedes. O volume infiltrado foi determinado por diferença entre o volume precipitado e o escoado. Após a realização dos testes, foram coletadas amostras de solo para determinação da granulometria, densidade do solo, porosidade, macroporosidade e microporosidade. Foram determinados, ainda, os teores volumétricos de água na zona de transmissão e no início do processo e a condutividade hidráulica do solo saturado. O potencial matricial foi calculado por intermédio de um rearranjo no modelo de GAML, considerando a taxa de infiltração estável (Tie) como representativa da condutividade hidráulica do solo saturado e o teor volumétrico de água na zona de transmissão em lugar do teor volumétrico de água correspondente à saturação. De posse dos valores de ψ m e das características do solo, foram ajustados modelos de regressão, sendo a escolha do melhor modelo feita por meio dos coeficientes de determinação (R 2 ), pela significância dos parâmetros no modelo, pelo menor número de variáveis envolvidas e pela facilidade de obtenção dessas variáveis (características do solo). Os valores de condutividade hidráulica do solo saturado, de porcentagem de silte e de macroporosidade foram significativos em todos os modelos nos quais foram utilizados. A Tie não foi significativa em nenhum dos modelos. Todas as equações obtidas utilizando-se a porcentagem de silte em combinação com outras variáveis apresentaram bons resultados na modelagem do ψ m , sendo que, os melhores resultados foram obtidos para o modelo que relaciona o ψ m com a porosidade, a condutividade hidráulica do solo saturado e a porcentagem de silte.
Infiltration is the process by which water passes through the soil surface down to the soil, being dependent on hydraulic load in the surface, on the antecedent moisture, on texture, structure, soil hydraulic conductivity and soil porosity. Several models aim to estimate this process, among which the Green-Ampt modified by Mein and Larson (GAML) model is based on a physical analysis of the process. Although it is frequently used, this model has a limitation for obtaining input parameters, such as the potential head at the wetting front ( ψ m ). This work aimed to obtain the ψ m for GAML model for soils typical of tropical areas, using three classes of soils (Red-Yellow Oxisol, Red Ultisol and Red Oxisol). These soils were air-dried, ground and sieved through 10 mm mesh sieve, placed in PVC columns of 200 mm diameter and 800 mm height, so that the soil density was similar to the field. In the lateral of the columns, horizontal TDR probes were installed for the moisture determination and for the monitoring of the wetting front. The water was applied to the surface of the columns at a constant rate by means of a rain simulator device and the excess drained superficially, was collected and measured in a box using a “Thalimedes” device. The infiltrated volume was calculated by the difference among the precipitate volume and the runoff. After the tests, soil samples were collected for determination of the texture, soil density, porosity, macroporosity, microporosity, volumetric moisture (before and after the tests) and soil hydraulic conductivity. The pressure head at the wetting front was calculated through an adjustment in the GAML model, considering the rate of stable infiltration (Tie) as representative of the hydraulic conductivity, and the transmission zone moisture instead of the moisture saturation. Once having the ψ m values and soil characteristics, regression models were adjusted, choosing the best fit by R 2 , significance of parameters, less number of variables and easy of obtaining soil variables. The soil hydraulic conductivity values, percentage of silt and macroporosity were all significant for all equations. Tie was not significant in none of the equations. All the obtained equations using the amount of silt in combination with another variable showed good results in the ψ m modeling. The best fitted equation was the one which related the ψ m with the porosity, the soil hydraulic conductivity and the percentage of silt.
Dissertação importada do Alexandria
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Druet, Thomas. "Reactions involving exotic nuclei in a discretized-continuum model." Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209367.
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The structure of exotic nuclei is one of the main interests in current nuclear physics. Exotic nuclei present unusual properties, such as a low breakup energy, a short lifetime and/or a halo structure. Because of their short lifetimes, they can not be studied by usual spectroscopic techniques. Indeed, targets of such nuclei are impossible to build. But since the availability of radioactive beams, nuclear reactions have provided possibilities of exploring nuclei far from stability.The investigation of exotic nuclei has been recently reactivated by the development of intense radioactive nuclear beams. As firstly observed for the deuteron, and then for other exotic projectiles such as $^6$He and $^{11}$Be, the internal structures of the interacting nuclei can have a significant effect on the elastic cross sections. Due to their low binding energy, the projectile dissociation process, leaving the target in its ground state, highly affects elastic cross sections but also other measurements such as transfer and fusion reactions. Accurate reaction theories are therefore needed. The coupled discretized-continuum channel (CDCC) method is one of those theories and assumes a projectile made of N clusters (usually N=2 or 3) impinging on a target which is structureless. The N+1-body Schrödinger equation is approximately solved by expanding the total wave function over the bound and continuum states of the projectile. These latter take into account the dissociation events and are approximately described by a truncated set of square-integrable wave functions. There are two available methods for discretizing the continuum, the pseudostate method where the projectile Hamiltonian is diagonalized within a finite basis of square-integrable functions, or the bin method where exact scattering wave functions of the projectile are averaged over bins in a finite region of space. In both cases, the N+1-body Schrödinger equation is replaced by a set of coupled-channel differential equations, which provides the physical quantities such as the collision matrix. In principle, the CDCC method can be very close to the exact N+1-body wave function and is adapted to low as well as to high energy reactions. However, its main interest consists in the low-energy domain.
In the present work, we propose a new approach to solve the CDCC equations. This method is based on the R-matrix theory associated with a Lagrange mesh basis. We will show that the combination of both approaches provides a fast and accurate technique to solve the CDCC equations, even for large systems, where traditional methods meet convergence problems. Before investigating collisions with exotic projectiles, we restrict ourselves to the simplest nucleus, the deuteron. Then we make a step towards a more complicated system, the $^6$Li which is a well known stable nucleus. We apply the CDCC method to the d + $^{58}$Ni and $^6$Li + $^{40}$Ca elastic scattering and breakup. These systems are considered in the literature as test cases. They have been investigated by several authors who showed the importance of the breakup channels in the elastic cross sections.
After having validated the present version of the CDCC method, we focus on $^{11}$Be, a typical example of a halo nucleus, with low binding energy and large quadrupole moment. Elastic, inelastic and breakup cross sections are computed in the CDCC formalism, at energies near the Coulomb barrier, where continuum effects in the scattering of exotic nuclei, and more specifically on the $^{11}$Be + $^{64}$Zn scattering, are observed. We show that converged cross sections need high angular momenta as well as large excitation energies in the wave functions of the projectile.
A Borromean nucleus is made of three constituents which are weakly linked together, but where each pair of those three constituents does not form a bound system. The name "Borromean" comes from the Borromean rings where, if any one of three rings is removed, the remaining two become unbound. Collisions with $^6$He and $^9$Be Borromean projectiles are studied in the present work. Again we compare our method with the $^6$He + $^{208}$Pb and $^6$He + $^{12}$C benchmark calculations. Afterwards, the convergence against the parameters of the description of the $^9$Be projectile is tested for the elastic cross section. The sensitivity to the technique employed to remove the forbidden states and also the sensitivity to the collision energy are investigated.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Hyde, Scott Kohler. "Robust Methods for Multivariate Linear Models with Spectral Models for Scatter Matrices." Thesis, Montana State University, 2004. http://etd.lib.montana.edu/etd/2004/hyde/HydeS0804.pdf.
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The main goal of this dissertation is to present extensions to the robust estimation of multivariate location and scatter. These extensions include the estimation of structured scatter matrices embedded in a multivariate fixed effects model. Two different kinds of robust estimators are investigated. The first is based on Maronna's M-estimators of multivariate location and scatter (Maronna 1976). The second is a multivariate extension of the S-estimators introduced by Rousseeuw and Yohai (1984). In addition, asymptotic distributions of the estimators are derived from an estimating function approach. The sandwich estimator of the asymptotic variance is given, coupled with second order corrections to the bias of the estimators. Two different data sets are used to illustrate the techniques of the dissertation. A comparison of the new algorithms to Ruppert's SURREAL algorithm is made for each example. Models are fit to illustrate the flexibility of the new estimators. In addition, the sandwich estimate of the asymptotic variance is given for the examples. Simulations are performed evaluating the effectiveness of the estimators.
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Fung, Russell. "Trajectory calculation in an electrostatic positron beam using a reformulated extended charge density model /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20567017.
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Nzabanita, Joseph. "Bilinear and Trilinear Regression Models with Structured Covariance Matrices." Doctoral thesis, Linköpings universitet, Matematisk statistik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-118089.
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This thesis focuses on the problem of estimating parameters in bilinear and trilinear regression models in which random errors are normally distributed. In these models the covariance matrix has a Kronecker product structure and some factor matrices may be linearly structured. The interest of considering various structures for the covariance matrices in different statistical models is partly driven by the idea that altering the covariance structure of a parametric model alters the variances of the model’s estimated mean parameters. Firstly, the extended growth curve model with a linearly structured covariance matrix is considered. The main theme is to find explicit estimators for the mean and for the linearly structured covariance matrix. We show how to decompose the residual space, the orthogonal complement to the mean space, into appropriate orthogonal subspaces and how to derive explicit estimators of the covariance matrix from the sum of squared residuals obtained by projecting observations on those subspaces. Also an explicit estimator of the mean is derived and some properties of the proposed estimators are studied. Secondly, we study a bilinear regression model with matrix normally distributed random errors. For those models, the dispersion matrix follows a Kronecker product structure and it can be used, for example, to model data with spatio-temporal relationships. The aim is to estimate the parameters of the model when, in addition, one covariance matrix is assumed to be linearly structured. On the basis of n independent observations from a matrix normal distribution, estimating equations, a flip-flop relation, are established. At last, the models based on normally distributed random third order tensors are studied. These models are useful in analyzing 3-dimensional data arrays. In some studies the analysis is done using the tensor normal model, where the focus is on the estimation of the variance-covariance matrix which has a Kronecker structure. Little attention is paid to the structure of the mean, however, there is a potential to improve the analysis by assuming a structured mean. We formally introduce a 2-fold growth curve model by assuming a trilinear structure for the mean in the tensor normal model and propose an estimation algorithm for parameters. Also some extensions are discussed.
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Kalaitzis, Alfredo. "Learning with structured covariance matrices in linear Gaussian models." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4038/.
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We study structured covariance matrices in a Gaussian setting for a variety of data analysis scenarios. Despite its simplistic nature, we argue for the broad applicability of the Gaussian family through its second order statistics. We focus on three types of common structures in the machine learning literature: covariance functions, low-rank and sparse inverse covariances. Our contributions boil down to combin- ing these structures and designing algorithms for maximum-likelihood or MAP fitting: for instance, we use covariance functions in Gaus- sian processes to encode the temporal structure in a gene-expression time-series, with any residual structure generating iid noise. More generally, for a low-rank residual structure (correlated residuals) we introduce the residual component analysis framework: based on a generalised eigenvalue problem, it decomposes the residual low-rank term given a partial explanation of the covariance. In this example the explained covariance would be an RBF kernel, but it can be any positive-definite matrix. Another example is the low-rank plus sparse- inverse composition for structure learning of GMRFs in the presence of confounding latent variables. We also study RCA as a novel link between classical low-rank methods and modern probabilistic counter- parts: the geometry of oblique projections shows how PCA, CCA and linear discriminant analysis reduce to RCA. Also inter-battery factor analysis, a precursor of multi-view learning, is reduced to an itera- tive application of RCA. Finally, we touch on structured precisions of matrix-normal models based on the Cartesian factorisation of graphs, with appealing properties for regression problems and interpretabil- ity. In all cases, experimental results and simulations demonstrate the performance of the different methods proposed.
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Terreaux, Eugénie. "Théorie des Matrices Aléatoires pour l'Imagerie Hyperspectrale." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC091/document.
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La finesse de la résolution spectrale et spatiale des images hyperspectrales en font des données de très grande dimension. C'est également le cas d'autres types de données, où leur taille tend à augmenter pour de plus en plus d'applications. La complexité des données provenant de l'hétérogénéité spectrale et spatiale, de la non gaussianité du bruit et des processus physiques sous-jacents, renforcent la richesse des informations présentes sur une image hyperspectrale. Exploiter ces informations demande alors des outils statistiques adaptés aux grandes données mais aussi à leur nature non gaussienne. Des méthodes reposant sur la théorie des matrices aléatoires, théorie adaptée aux données de grande dimension, et reposant sur la robustesse, adaptée aux données non gaussiennes, sont ainsi proposées dans cette thèse, pour des applications à l'imagerie hyperspectrale. Cette thèse propose d'améliorer deux aspects du traitement des images hyperspectrales : l'estimation du nombre d'endmembers ou de l'ordre du modèle et le problème du démélange spectral. En ce qui concerne l'estimation du nombre d'endmembers, trois nouveaux algorithmes adaptés au modèle choisi sont proposés, le dernier présentant de meilleures performances que les deux autres, en raison de sa plus grande robustesse.Une application au domaine de la finance est également proposée. Pour le démélange spectral, trois méthodes sont proposées, qui tiennent comptent des diff érentes particularités possibles des images hyperspectrales. Cette thèse a permis de montrer que la théorie des matrices aléatoires présente un grand intérêt pour le traitement des images hyperspectrales. Les méthodes développées peuvent également s'appliquer à d'autres domaines nécessitant le traitement de données de grandes dimensionsHyperspectral imaging generates large data due to the spectral and spatial high resolution, as it is the case for more and more other kinds of applications. For hyperspectral imaging, the data complexity comes from the spectral and spatial heterogeneity, the non-gaussianity of the noise and other physical processes. Nevertheless, this complexity enhances the wealth of collected informations, that need to be processed with adapted methods. Random matrix theory and robust processes are here suggested for hyperspectral imaging application: the random matrix theory is adapted to large data and the robustness enables to better take into account the non-gaussianity of the data. This thesis aims to enhance the model order selection on a hyperspectral image and the unmixing problem. As the model order selection is concerned, three new algorithms are developped, and the last one, more robust, gives better performances. One financial application is also presented. As for the unmixing problem, three methods that take into account the peculierities of hyperspectral imaging are suggested. The random matrix theory is of great interest for hyperspectral image processing, as demonstrated in this thesis. Differents methods developped here can be applied to other field of signal processing requiring the processing of large data
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Lindström, Agnes, and Frida Persson. "Estimation of Hourly Origin Destination Trip Matrices for a Model of Norrköping." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-150135.
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During the last century, the number of car users has increased as an effect of the increasing population growth. To manage the environmental and infrastructural challenges that comes with a more congested traffic network, traffic planning has become of higher importance to analyze the current traffic state and to predict future capacity challenges and effects of investments. These analysis and evaluations are commonly performed in different traffic analysis tools, where updated and realistic traffic demand needs to be provided to ensure reasonable results. In this thesis, a macroscopic model of Norrköping municipality constructed in the traffic demand modelling software Visum and a daily Origin-Destination(OD)-matrix is considered. The goal of this thesis is to produce a method that modify the current daily demand matrix into hourly demand matrices, called hourly target matrices, that represents a typical weekday. The goal is also to implement and evaluate the OD-estimation algorithm Simultaneous Perturbation Stochastic Approximation (SPSA) to obtain updated and valid demand matrices for the network model of Norrköping. The method of dividing the daily demand matrix into hourly target matrices is based on the paper by Spiess %26 Suter (1990). The method makes use of the available daily trip purpose matrices combined with hourly link flow observations from 96 links in a multiple linear regression model to obtain 24 hourly demand matrices. The resulting matrices are compared with the link flow observations and has different levels of R^2-fit, the maximum fit is 85.79 % and the minimum fit is 55.89 %. The average R^2-value is 72 %. The OD-estimation based on SPSA is performed on the AM and PM peak hours. The algorithm is implemented in Python scripts that are called from Visum where the traffic assignments is calculated. The result is an increase in R^2-value since the link flow difference between estimated and observed link flow is decreased. In total, the estimated link flows are improved by 7.4 % in the AM peak hour and 15.6 % in the PM peak hour. The total absolute change in OD-demand is 3 871 trips for AM peak hour and 6 452 trips for the PM peak hour. The estimated OD-matrices are evaluated by qualitatively visualizing the difference in heat maps and in the quantitative measure structural similarity index. The result is no major structural change from the hourly target matrices which verifies that the information used when the target matrices is produced still is considered. The total demand increased in both hours, with 505 respectively 2 431 trips and flows in some OD-pairs has a very high percental change. This was restricted by adding a penalty term to the SPSA-algorithm on the PM peak hour. The result of penalized SPSA is a much less increase of total demand as well as less percental change of the OD-flows. Though, this to a cost of not decreasing the link flow difference in the same magnitude.
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Minor, Bill. "Density matrix renormalization group study of the enhanced hole-hopping model of high temperature superconductivity /." *McMaster only, 1996.
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Lahnovych, Carrie. "Analysis and computation of a quadratic matrix polynomial with Schur-products and applications to the Barboy-Tenne model /." Online version of thesis, 2010. http://ritdml.rit.edu/handle/1850/12207.
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Nzabanita, Joseph. "Estimation in Multivariate Linear Models with Linearly Structured Covariance Matrices." Licentiate thesis, Linköpings universitet, Matematiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-78845.
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This thesis focuses on the problem of estimating parameters in multivariate linear models where particularly the mean has a bilinear structure and the covariance matrix has a linear structure. Most of techniques in statistical modeling rely on the assumption that data were generated from the normal distribution. Whereas real data may not be exactly normal, the normal distributions serve as a useful approximation to the true distribution. The modeling of normally distributed data relies heavily on the estimation of the mean and the covariance matrix. The interest of considering various structures for the covariance matrices in different statistical models is partly driven by the idea that altering the covariance structure of a parametric model alters the variances of the model’s estimated mean parameters. The extended growth curve model with two terms and a linearly structured covariance matrix is considered. In general there is no problem to estimate the covariance matrix when it is completely unknown. However, problems arise when one has to take into account that there exists a structure generated by a few number of parameters. An estimation procedure that handles linear structured covariance matrices is proposed. The idea is first to estimate the covariance matrix when it should be used to define an inner product in a regression space and thereafter reestimate it when it should be interpreted as a dispersion matrix. This idea is exploited by decomposing the residual space, the orthogonal complement to the design space, into three orthogonal subspaces. Studying residuals obtained from projections of observations on these subspaces yields explicit consistent estimators of the covariance matrix. An explicit consistent estimator of the mean is also proposed and numerical examples are given. The models based on normally distributed random matrix are also studied in this thesis. For these models, the dispersion matrix has the so called Kronecker product structure and they can be used for example to model data with spatio-temporal relationships. The aim is to estimate the parameters of the model when, in addition, one covariance matrix is assumed to be linearly structured. On the basis of n independent observations from a matrix normal distribution, estimation equations in a flip-flop relation are presented and numerical examples are given.
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Silveira, Andrea Pereira. "Atributos de historia de vida, estrutura e dinÃmica populacional de Ãrvore sob clima tropical sazonalmente seco." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8591.
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FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgicoA estacionalidade e a estocasticidade pluviomÃtrica sÃo os principais reguladores da estrutura e da dinÃmica das populaÃÃes em vegetaÃÃes tropicais sazonais secas. Essa estocasticidade, no entanto, pode resultar em ambientes heterogÃneos tanto em relaÃÃo à disponibilidade hÃdrica como em relaÃÃo à disponibilidade vertical e horizontal de luz. Na vegetaÃÃo decÃdua espinhosa do semiÃrido brasileiro (caatinga), uma das espÃcies lenhosas mais abundantes à Cordia oncocalyx, Ãrvore endÃmica e explorada por extrativismo devido ao valor madeireiro, energÃtico, forrageiro, medicinal e paisagÃstico. Para entender como Ãrvores da caatinga respondem à sazonalidade e estocasticidade pluviomÃtrica foram analisados, ao longo de dois anos, a estrutura e a dinÃmica populacional de C. oncocalyx na RPPN Serra das Almas, CrateÃs-CearÃ. Foram determinados: i) estÃdios ontogenÃticos, modelo arquitetural e relaÃÃo altura-diÃmetro; ii) fenodinÃmica; iii) padrÃo espacial; iv) taxas de natalidade, mortalidade, recrutamento e crescimento biomÃtrico. ParÃmetros de estrutura e de dinÃmica foram correlacionados com precipitaÃÃo, umidade do solo, temperatura e disponibilidade vertical e horizontal de luz. A estrutura de C. oncocalyx se assemelha a das espÃcies tolerantes à sombra de florestas pluviais por concentrar a maior densidade nos estÃdios iniciais, mas difere porque forma banco de infantes ao invÃs de banco de plÃntulas. A disponibiliade vertical de luz, com apenas 4.7% atingindo o solo, e a arquitetura PrÃvost indicam a luz como fator limitante para os estÃdios iniciais. Contudo, o coeficiente alomÃtrico diferiu dos modelos de similaridade geomÃtrica, similaridade elÃstica e estresse constante. O crescimento contÃnuo em diÃmetro, mesmo apÃs os indivÃduos atingirem altura mÃxima, aponta a baixa densidade de Ãrvores e as restriÃÃes hÃdricas como as principais forÃas impulsionadoras da alometria, as quais podem limitar o crescimento em altura mas nÃo em diÃmetro. As fenofases vegetativas e reprodutivas respondem similarmente aos pulsos de chuva, com ajustes na Ãpoca, duraÃÃo e intensidade, correlacionadas com variaÃÃes na precipitaÃÃo e umidade do solo, excluÃdo o fotoperÃodo como gatilho. Menor sincronia, separaÃÃo temporal de fenofases e estoque de frutos no banco do solo, foram estratÃgias de distribuiÃÃo de risco apresentadas pela populaÃÃo. A modificaÃÃo da agregaÃÃo em semente e plÃntula para aleatoriedade em infante, e a dissociaÃÃo dos reprodutivos e sementes em relaÃÃo aos estÃdios juvenil e imaturo, indicam que a mortalidade dependente de densidade atua na estruturaÃÃo espacial da populaÃÃo. Entretanto, a retomada da agregaÃÃo nos estÃdios juvenil, virgem e reprodutivo indica que a estocasticidade pluviomÃtrica pode gerar a distribuiÃÃo agregada desses estÃdios. A natalidade e o recrutamento ocorrem na estaÃÃo chuvosa, mas a mortalidade registrada apenas em plÃntula e infante se dà ao longo do ano com pico nos meses secos. O crescimento em altura e diÃmetro mostrou decrÃscimo ou estagnaÃÃo na seca e acrÃscimo na chuva. Juvenil apresentou maior crescimento em altura em Ãreas com dossel mais aberto (rs=0.24). A taxa de incremento populacional (ʎ) foi de 1,0336 e a maior sensibilidade foi na transiÃÃo de infante para juvenil. DominÃncia local e tendÃncia de aumento populacional sÃo explicadas pela formaÃÃo de dois bancos, sementes e infantes, os quais garantem um estoque para recomposiÃÃo populacional mesmo em anos de seca.
The rainfall seasonality and stochasticity are the main regulators of structure and population dynamics in seasonally dry tropical vegetations. This stochasticity, however, can result in heterogeneous environments both in relation to water availability as in the availability of vertical and horizontal light. In deciduous thorny woodland vegetation of semiarid northeastern Brazil (caatinga), one of the most abundant woody species is Cordia oncocalyx, endemic tree and explored through extractivism due to its timber, energetic, foraging, medicinal, and scenic value. To understand how the caatinga trees respond to rainfall seasonality and stochasticity were analyzed, over two years, the structure and population dynamics of C. oncocalyx in Serra das Almas RPPN, CrateÃs-CearÃ. Were determined: i) ontogenetic stages, architectural model and height-diameter relationship, ii) phenodynamics, iii) spatial pattern, iv) birth, mortality, recruitment and growth biometric rates. Parameters of structure and dynamics were correlated with rainfall, soil humidity, temperature and vertical and horizontal light availability. The structure of C. oncocalyx resembles that of shade-tolerant species of tropical rainforest to concentrate the highest density in the early stages, but differs because it forms the bank of infant rather than a seedling bank. The availability of vertical light, with only 4.7% reaching the ground, and PrÃvost architecture indicate light as a limiting factor in the early stages. Nevertheless, the allometric coefficient differ from geometric similarity, elastic similarity and constant stress models. The uninterrupted growth in diameter, even after individuals reach the maximum height, indicates the low density of trees and water restrictions as the main driving strenght of allometry, which may limit the growth in height, but not in diameter. Both the vegetative and reproductive phenophases respond similarly to variations in rain pulses, with adjustments in time, duration, and intensity, which were correlated with variations in rainfall and soil humidity, excluding photoperiod as a trigger. Lower synchrony, temporal separation of phenophases, and storage of fruits on the ground were risk-spreading strategies used by the population in the dry year. The change of aggregation in seeds and seedlings for randomness in the infant, and the decoupling of reproductive and seeds in relation to juvenile and immature stages, may indicate that the density-dependent mortality operates in the spatial structure of the population. However, the resumption of aggregation in juvenile, virginile and reproductive stages indicates that rainfall stochasticity creates the aggregate distribution of these stages. The dynamics of birth and recruitment occur in the rainy season, but recorded mortality only in seedling and infant occurs throughout the year with a peak in the dry months. The height and diameter growth showed decline or stagnation in the drought and increase in the rainfall. Juveniles showed greater growth in height in areas with more open canopy (rs = 0.24). The rate of population increase (ʎ) was 1.0336 and the highest sensitivity was in the transition from infant to juvenile. Local dominance and population growth tendency are explained by the formation of two banks, seeds and infants, which ensure a stock for recomposition even in drought years.
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Marx, Brian D. "Ill-conditioned information matrices and the generalized linear model: an asymptotically biased estimation approach." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53584.
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In the regression framework of the generalized linear model (Nelder and Wedderburn (1972)), interative maximum likelihood parameter estimation is employed via the method of scoring. This iterative procedure involves a key matrix, the information matrix. Ill-conditioning of the information matrix can be responsible for making many desirable properties of the parameter estimates unattainable. Some asymptotically biased alternatives to maximum likelihood estimation are put forth which alleviate the detrimental effects of near singular information. Notions of ridge estimation (Hoerl and Kennard (1970a) and Schaefer (1979)), principal component estimation (Webster et al. (1974) and Schaefer (1986)), and Stein estimation (Stein (1960)) are extended into a regression setting utilizing any one of an entire class of response distributions.Ph. D.
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Back, Sung-Yong. "A shear-flexible finite element model for lateral torsional buckling analysis of thin-walled open beams." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/20999.
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Scholz, Timothy Theodore. "Density matrix theory of diatomic molecules." Title page, contents and summary only, 1989. http://web4.library.adelaide.edu.au/theses/09SM/09sms368.pdf.
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馮德操 and Russell Fung. "Trajectory calculation in an electrostatic positron beam using a reformulated extended charge density model." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31220836.
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Noiry, Nathan. "Matrices aléatoires et graphes aléatoires." Thesis, Paris 10, 2020. http://www.theses.fr/2020PA100059.
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Cette thèse se compose de plusieurs travaux ayant trait à la théorie des matrices aléatoires et à la théorie des graphes aléatoires. Dans le contexte des matrices aléatoires, un premier travail porte sur l'étude spectrale des matrices de Wishart dont la taille tend vers l'infini et dont les moments des coefficients explosent. Dans ce cadre, nous calculons un développement asymptotique de la limite des mesures spectrales empiriques au voisinage de la loi de Marchenko-Pastur. Dans un second travail, nous nous sommes intéressés aux modèles matriciels déformés. Nous démontrons que l'étude des mesures spectrales dans la direction des vecteurs propres des matrices de perturbation apporte de nombreuses informations sur le spectre de ces modèles, notamment sur les coordonnées des vecteurs propres. Enfin, dans un troisième travail, nous exploitons un outil classique de la théorie des matrices aléatoires -- la transformée de Stieltjes -- afin d'identifier une classe soluble de processus de renouvellement. Les deux autres contributions de cette thèse concernent la géométrie des modèles de configuration, (multi)-graphes aléatoires dont la suite des degrés est décidée à l'avance. Dans le régime sur-critique, nous nous sommes intéressés à l'analyse de l'algorithme de parcours en profondeur et à l'une de ses variantes, alternant entre parcours en profondeur et parcours en largeur. Nous démontrons qu'après une mise à l'échelle adéquate, les processus de contour associés à ces algorithmes convergent vers des profils déterministes, établissant en particulier l'existence de chemins simples de longueur linéaire, et l'existence de cycles de longueur linéaire ne possédant pas de raccourci à courte portéeThis thesis consists of several works related to the theory of random matrices and the theory of random graphs. In the context of random matrices, a first work concerns the spectrum of Wishart matrices whose size tends to infinity and whose entries have exploding moments. In this setting, we compute an asymptotic expansion of the limit of the empirical spectral measures in the vicinity of the Marchenko-Pastur law. In a second work, we were interested in deformed matrix models. We prove that the study of spectral measures in the direction of the eigenvectors of the perturbation matrices brings a lot of information on the spectrum of these models, in particular on the coordinates of the eigenvectors. Finally, in a third work, we exploit a classical tool of random matrix theory -- the Stieltjes transform -- in order to identify a solvable class of renewal processes.The two other contributions of this thesis concern the geometry of configuration models, which are (multi)-random graphs whose sequence of degrees is fixed. In the supercritical regime, we study the depth first search algorithm and one of its variants, which alternates between depth first and breadth first search. We prove the convergence of the renormalized contour processes associated with these algorithms to deterministic profiles, establishing in particular the existence of simple paths of linear length, and the existence of cycles of linear length without shortcut at short range
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Brugger, Stefan. "Synthesis and characterization of novel stationary phases for model and catalytic reactions in interphases and new polysiloxane matrices Synthese und Charakterisierung von neuartigen Stationärphasen für Modell- und katalytische Reaktionen in Interphasen und neuer Polysiloxan-Matrices /." [S.l. : s.n.], 2001. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9273565.
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Acosta, De la Cruz Pedro Raúl. "Modelo matricial para la construcción del diagrama de hasse de un conjunto parcialmente ordenado." Universidad Peruana de Ciencias Aplicadas (UPC), 2017. http://hdl.handle.net/10757/624351.
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El trabajo de investigación tuvo como objetivo el diseño de un modelo matricial para la construcción del diagrama de Hasse de un Conjunto Parcialmente Ordenado (CPO), que permita su implementación en un lenguaje de programación. Para lograrlo se utilizó la teoría de Relaciones de Orden Parcial, sus propiedades; matrices booleanas, sus operaciones. Este trabajo permitió determinar el diagrama de Hasse de Relaciones de Orden Parcial sin importar la cantidad de elementos del CPO, y lo más importante, permitió automatizar el modelo.The research work was aimed at the design of a matrix model for the construction of the Hasse diagram of a Partially Ordained Set (CPO), which allows its implementation in a programming language. To achieve this, we used the theory of partial order relations, their properties; Boolean matrices, their operations. This work allowed to determine the Hasse diagram of Partial Order Relations regardless of the number of elements of the CPO, and most importantly, allowed to automate the model.
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Cottereau, Régis. "Probalilistic models of impedance matrices : application to dynamic soil-structure interaction." Châtenay-Malabry, Ecole centrale de Paris, 2006. http://www.theses.fr/2006ECAP1034.
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Dans de nombreux domaines d’application, comme en génie civil ou en aéronautique, les ingénieurs sont confrontés a des problèmes de dimensionnement de structures en contact avec un domaine non-borné. Pour ces problèmes, seule la structure intéresse réellement les ingénieurs, et le domaine extérieur n’a d’importance que par sa raideur équivalente, en statique, ou sa matrice d’impédance, en dynamique. Par ailleurs, les domaines infinis considérés dans ces applications sont souvent mal connus ou complexes à modéliser. Cela entraîne des erreurs et incertitudes pour les estimations faites sur la structure, qui peuvent être en partie prises en compte par des approches probabilistes. On propose donc dans cette thèse un modèle probabiliste des matrices d'impédance, qui généralise l'approche non-paramétrique proposée récemment par Soize pour les prédictions des vibrations de structures aléatoires. La construction de ce modèle probabiliste nécessité tout d'abord la construction d'un modèle déterministe approché, dit à variables cachées, des matrices d'impédance suivant leurs propriétés de base, dont, notamment, la causalité. Ce modèle doit être identifié à partir de calculs numériques ou de mesures, et la procédure d'identification est également developpée dans le cadre de la thèse. Deux applications sont proposées. Le modèle non-paramétrique de matrice d'impédance est d'abord comparé, sur un cas simple d'interaction dynamique sol-structure, à un modèle paramétrique pour illustrer les principales différences entre les approches. Ensuite, un cas plus industriel de dimensionnement sismique permet d'envisager l'utilisation pratique du modèle probabiliste non-paramétriqueIn many application fields, as in civil engineering or aeronautics, engineers have to deal with design problems where the structure is coupled to an unbounded domain. For these problems, only the structure is of interest, and the behavior of the exterior domain is taken into account through its equivalent stiffness, in statics, or its impedance matrix, in dynamics. The models for the unbounded domains considered in these applications are usually coarse and the information available on their properties scarse and polluted. This leads to errors in the estimation of the behavior of the structure, which may partially be taken into account by using probabilistic approaches. We present, in this Ph. D. Thesis a probabilistic model of impedance matrices, which generalizes the nonparametric approaches introduced recently by Soize for the predictions of vibrations in random structures. The construction of this probabilistic model first requires the construction of a deterministic model, so-called hidden variables model, that verifies the basic properties of impedance matrices, among which the causality. The hidden variables model has to be identified from numerical results or experimental measures, and the identification procedure is also developed in this thesis. Two applications are presented. Our nonparametric model of the impedance matrix is first compared to a parametric model, on a classical problem in dynamic soil-structure interaction, to illustrate the main differences between the two approaches. Then, it is used in a more industrial seismic design problem, to show the practical application of the nonparamatric probabilistic model of impedance matrices
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Bécan, Guillaume. "Metamodels and feature models : complementary approaches to formalize product comparison matrices." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S116/document.
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Les Matrices de Comparaison de Produits (MCP) sont largement répandues sur le web. Elles fournissent une représentation simple des caractéristiques d'un ensemble de produits. Cependant, le manque de formalisation et la grande diversité des MCP rendent difficile le développement de logiciels pour traiter ces matrices. Dans cette thèse, nous développons deux approches complémentaires pour la formalisation de MCP. La première consiste en une description précise de la structure et la sémantique d'une MCP sous la forme d'un meta-modèle. Nous proposons aussi une transformation automatique d'une MCP vers un modèle de MCP conforme au meta-modèle. La seconde approche consiste à synthétiser des modèles de caractéristiques attribués à partir d'une classe de MCP. Grâce nos contributions, nous proposons une approche générique et extensible pour la formalisation et l'exploitation de MCPProduct Comparison Matrices (PCMs) abound on the Web. They provide a simple representation of the characteristics of a set of products. However, the lack of formalization and the large diversity of PCMs challenges the development of software for processing these matrices. In this thesis, we develop two complementary approaches for the formalisation of PCMs. The first one consists in a precise description of the structure and semantics of PCMs in the form of a metamodel. We also propose an automated transformation from PCMs to PCM models conformant to the metamodel. The second one consists in synthesizing attributed feature models from a class of PCMs. With our contributions, we propose a generic and extensible approach for the formalization and exploitation of PCMs
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Zheng, Xing. "Statistics of impedance and scattering matrices in microwave chaotic cavities the random coupling model /." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2920.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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梁旭亮 and Yuk-leong Daniel Leung. "Studies on collision detection using ellipsoidal bounding volumes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31224763.
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梁万珍 and Wanzhen Liang. "Localized-denisty-matrix method and its application to nano-size systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242042.
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Gomes, Wagner Oliveira. "Gestão de projetos : proposta de modelo para implantação em organização hibrida com estrutura matricial leve." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264254.
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Orientador: Olivio NovaskiDissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Subramaniam, C. "Chemorhelogical Modeling Of Amine-Cured Multifunctional Epoxy Resin Systems Used As Matrices In Aerospace Composites." Thesis, Indian Institute of Science, 1994. http://hdl.handle.net/2005/127.
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High performance multifunctional epoxy resin systems are becoming increasingly important as matrix materials for the advanced composites used in aerospace, electronics, automotive and other industries. In a composite based on epoxy resin systems, a three-dimensional network of the matrix is formed around the reinforcing fibre as a result of the chemical reaction between the resin and the curing agent. This chemical process, known as curing, is an important event to he considered in the production of composite components made up of these resin systems. Two process parameters namely viscosity and chemical conversion are of paramount significance in the production of composite materials Curing studies of the resin systems based on these two parameters, would therefore assume great importance in deciding the performance reliability of the end product.
The objectives of the present investigation are
1. to study the cure kinetics of three thermoset resin systems, viz.,
i) epoxy novolac (EPIT)/ diamino diphenyl methane{DDM), ii) trigylcidyl para- ammo phenol (TGPAP)/toluene diamine (TDA) and iii) tetraglycidyl diamino diphenyl methane (TGDDM)/pyridine diamine(PDA) using the cure kinetic models based on chemical conversion (α), Theological conversion (β) and viscosity.
2.to develop a correlation between a and viscosity (η) and modify an existing autocatalytic model based on α, to the viscosity domain and
3.to investigate the cure behaviour of these systems in terms of the TTT cure diagram and its associated models.
EPN/DDM, TGPAP/PDA and TGDDM/PDA resin systems were chosen for the studies to represent a range of functionalities, The cure was monitored using differential scanning calorimetry (DSC), fourier transform infrared (FTIR) and dynamic mechanical analysis (DMA) techniques by following the changes in enthalpy, functional groups and rheology, respectively.
The kinetic parameters namely, order of reaction and activation energy were estimated from dynamic DSC data using the methods of Freeman-Carroll and Ellerstein using nth rate expression. Barton, Kissinger and Osawa methods were employed to find out the activation energy from the peak/equal conversion at different heating rates. Isothermal DSC data were also analyzed using nth order model and it was observed that the data could be fitted satisfactorily only for higher temperatures The results obtained from the analysis of both dynamic and isothermal DSC data using nth order model clearly indicate that this model is inadequate for describing the cure behavior. The isothermal DSC data was analyzed by the autocatalytic models of Hone and Kamal Good correlation was observed with Hum and Kamal models up to 60-70%, 25% and 45% conversions for EPN/DDM, TGPAP/TDA and TCDDM/PDA systems respectively. However, the parameters m and n in Kamal model were found to be temperature dependent for EPN/DDM and TCPAP/TDA systems. The limited applicability of the autocatalytic models IK attributed to the counter-effect offered by the intra-molecular bonding taking place.
The primary amine and epoxy groups conversions obtained from FTIR were analyzed using autocatalytic model and the kinetic parameters were calculated. The reactivity ratio of the primary amine and the secondary amine with epoxy was found to be dependent on temperature in agreement with the recent findings reported m the literature.
The existing models that relate the cure kinetics and the rheological changes, are dual Arrhenius nth order model and autocatalytic model The nth order kinetic model was used to evaluate the kinetic parameters using the viscosity data at different cure temperatures under isothermal conditions As the storage modulus, G' is proportional to the chemical cross links and becomes significant only after the g<4 point, it was used to follow the changes in conversion known as rheoconversion after the gel point The rheoconversion was found by normalizing the G' data with G1^, the storage modulus of the fully cured resin It was used to study the cuie kinetics using an autocatalytic model The kinetic parameters such as rate constant, acceptation and retardation parameters were evaluated and that temperature dependence was established.
While the existing models relate viscosity and conversion only up to gel point the new proposed model, termed VISCON model takes into account the changes up to vitrification. The relation so developed is used to modify the autocatalytic cure model based on chemical conversion. The parameters appearing in this model were evaluated using Levenberg-Marquardt error minimization algorithm. The kinetic parameters obtained are comparable with the values estimated using the DSC data.
All the models cited above represent the microkinetic aspects. The models based on the information of TTT cure diagrams, however, represent the macrokinetic aspects of the cure, as they are based on the cure stages such as gelation and vitrification TTT diagram relates the cure characteristics like cure temperature, cure time, Ta and, indirectly, chemical conversion Hence the ultimate properties of the composite could he predicted and established with the help of the models based on TTT cure diagrams The changes in the storage modulus, G1 and loss modulus, G", were followed to identify the gel and vitrification points of the resin systems at different cure temperatures Gel point and vitrification point were used to generate gelation and vitrification hues in the construction of TTT cure diagrams for EPN/DDM, TGPAP/TDA and TGDDM/PDA resin systems Theoretical TTT diagrams were generated and IBO-T, contours were established using the TTT diagram-based models The cure schedule for the resin systems investigated could be determined from the TTT diagram and the respective rheological data.
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BILLEY, ESTELLE. "Systemes integrables avec matrice r dynamique : le modele de calogero-moser." Paris 6, 1996. http://www.theses.fr/1996PA066478.
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Cette these est consacree a l'etude d'une generalisation a spin du modele de calogero-moser du point de vue du formalisme de la matrice r. Dans une premiere partie, la matrice r classique du modele est calculee. Le resultat permet, dans le cas du modele hyperbolique, de mettre en evidence une hierarchie de charges conservees qui forme un yangien ; la construction d'une algebre d'observables incluant le yangien est egalement presentee. Dans une seconde partie, le modele classique est resolu par les methodes de geometrie algebrique qui reposent sur la reecriture des equations du mouvement sous la forme d'un systeme lineaire d'equations aux derivees partielles. Dans une troisieme partie, le formalisme de la matrice r est utilise pour quantifier le modele. La matrice r quantique est dynamique et verifie une generalisation de l'equation de yang-baxter. Cette structure permet de construire un ensemble d'operateurs qui commutent. Les modeles obtenus sont differents selon les representations du groupe quantique choisies
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BRITO, DIEGO SIEBRA DE. "FORECASTING LARGE REALIZED COVARIANCE MATRICES: THE BENEFITS OF FACTOR MODELS AND SHRINKAGE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=35140@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROEste trabalho propõe um modelo de previsão de matrizes de covariância realizada de altíssima dimensão, com aplicação para os componentes do índice S e P 500. Para lidar com o altíssimo número de parâmetros (maldição da dimensionalidade), propõe-se a decomposição da matriz de covariância de retornos por meio do uso de um modelo de fatores padrão (e.g. tamanho, valor, investimento) e uso de restrições setoriais na matriz de covariância residual. O modelo restrito é estimado usando uma especificação de vetores auto regressivos heterogêneos (VHAR) estimados com LASSO (Least Absolute Shrinkage and Selection Operator). O uso da metodologia proposta melhora a precisão de previsão em relação a benchmarks padrões e leva a melhores estimativas de portfólios de menor variância.
We propose a model to forecast very large realized covariance matrices of returns, applying it to the constituents of the S and P 500 on a daily basis. To deal with the curse of dimensionality, we decompose the return covariance matrix using standard firm-level factors (e.g. size, value, profitability) and use sectoral restrictions in the residual covariance matrix. This restricted model is then estimated using Vector Heterogeneous Autoregressive (VHAR) models estimated with the Least Absolute Shrinkage and Selection Operator (LASSO). Our methodology improves forecasting precision relative to standard benchmarks and leads to better estimates of the minimum variance portfolios.
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MEYER, HENDRIK. "Approches numeriques pour des modeles de physique statistique. I. Diagrammes de phase de modeles a spins. Ii. Theorie de matrices aleatoires et integrabilite." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10239.
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Cette these etudie les diagrammes de phase et l'integrabilite de differents modeles de physique statistique classique et quantique. Plusieurs methodes numeriques sont employees ; en particulier, un critere fonctionnel pour decider de l'integrabilite est presente. Le document est organise en deux parties independantes qui sont fortement reliees par les modeles etudies. La premiere partie applique la simulation de monte carlo a des modeles a spins classiques, non integrables, pour confronter des resultats de simulation a des propositions analytiques, obtenues recemment par l'etude des relations d'inverses et du groupe de symetries de ces modeles. Nous determinons ainsi les diagrammes de phase d'un modele de potts chiral a six etats sur reseau carre et du modele de potts standard a trois etats sur reseau triangulaire avec interactions a deux et trois spins. La deuxieme partie etudie l'integrabilite de differents modeles en physique statistique. Par des methodes de la theorie des matrices aleatoires nous analysons les proprietes statistiques du spectre d'un operateur decrivant le modele (le hamiltonien ou une matrice de transfert). En utilisant les symetries connues de celui-ci, on peut operer une decomposition en sous-espaces stables de cet operateur. Nous developpons la methode par l'etude systematique d'une chaine quantique de hubbard avec un terme d'echange. Par la suite, nous l'appliquons pour la premiere fois aux matrices de transfert de modeles classiques (modele d'ising 2d, 3d, modele de potts, modele a huit vertex asymetrique)
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Singh, Kumaresh. "Efficient Computational Tools for Variational Data Assimilation and Information Content Estimation." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/39125.
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The overall goals of this dissertation are to advance the field of chemical data assimilation, and to develop efficient computational tools that allow the atmospheric science community benefit from state of the art assimilation methodologies. Data assimilation is the procedure to combine data from observations with model predictions to obtain a more accurate representation of the state of the atmosphere.
As models become more complex, determining the relationships between pollutants and their sources and sinks becomes computationally more challenging. The construction of an adjoint model ( capable of efficiently computing sensitivities of a few model outputs with respect to many input parameters ) is a difficult, labor intensive, and error prone task. This work develops adjoint systems for two of the most widely used chemical transport models: Harvardâ s GEOS-Chem global model and for Environmental Protection Agencyâ s regional CMAQ regional air quality model. Both GEOS-Chem and CMAQ adjoint models are now used by the atmospheric science community to perform sensitivity analysis and data assimilation studies.
Despite the continuous increase in capabilities, models remain imperfect and models alone cannot provide accurate long term forecasts. Observations of the atmospheric composition are now routinely taken from sondes, ground stations, aircraft, and satellites, etc. This work develops three and four dimensional variational data assimilation capabilities for GEOS-Chem and CMAQ which allow to estimate chemical states that best fit the observed reality.
Most data assimilation systems to date use diagonal approximations of the background covariance matrix which ignore error correlations and may lead to inaccurate estimates. This dissertation develops computationally efficient representations of covariance matrices that allow to capture spatial error correlations in data assimilation.
Not all observations used in data assimilation are of equal importance. Erroneous and redundant observations not only affect the quality of an estimate but also add unnecessary computational expense to the assimilation system. This work proposes techniques to quantify the information content of observations used in assimilation; information-theoretic metrics are used.
The four dimensional variational approach to data assimilation provides accurate estimates but requires an adjoint construction, and uses considerable computational resources. This work studies versions of the four dimensional variational methods (Quasi 4D-Var) that use approximate gradients and are less expensive to develop and run.
Variational and Kalman filter approaches are both used in data assimilation, but their relative merits and disadvantages in the context of chemical data assimilation have not been assessed. This work provides a careful comparison on a chemical assimilation problem with real data sets. The assimilation experiments performed here demonstrate for the first time the benefit of using satellite data to improve estimates of tropospheric ozone.Ph. D.