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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
541

The Hilbert Space Of Probability Mass Functions And Applications On Probabilistic Inference

Bayramoglu, Muhammet Fatih 01 September 2011 (has links) (PDF)
The Hilbert space of probability mass functions (pmf) is introduced in this thesis. A factorization method for multivariate pmfs is proposed by using the tools provided by the Hilbert space of pmfs. The resulting factorization is special for two reasons. First, it reveals the algebraic relations between the involved random variables. Second, it determines the conditional independence relations between the random variables. Due to the first property of the resulting factorization, it can be shown that channel decoders can be employed in the solution of probabilistic inference problems other than decoding. This approach might lead to new probabilistic inference algorithms and new hardware options for the implementation of these algorithms. An example of new inference algorithms inspired by the idea of using channel decoder for other inference tasks is a multiple-input multiple-output (MIMO) detection algorithm which has a complexity of the square-root of the optimum MIMO detection algorithm. Keywords: The Hilbert space of pmfs, factorization of pmfs, probabilistic inference, MIMO detection, Markov random fields iv
542

Diagnostic de la somnolence d'un opérateur: analyse automatique de signaux physiologiques

Sharabaty, Hassan 05 December 2007 (has links) (PDF)
Depuis plusieurs années le LAAS-CNRS travaille sur la problématique de la détection de la baisse de vigilance d'un conducteur d'automobile à partir de l'analyse du mode de conduite, afin de réduire le grand nombre des accidents routiers. Dans ce contexte, nous nous sommes intéressés de dégager une mesure référante de l'hypovigilance qui permettrait, par comparaison, de valider le système de mesure embarqué associant des mesures comportementales. Cette thèse a porté sur l'analyse automatique des signaux physiologiques (EEG, EOG) permettant de caractériser la somnolence; et s'est inscrit dans le cadre du projet européen SENSATION. Ce travail s'articule en 2 parties. La première est dédiée à l'analyse des EEG et commence par une présentation de la forme d'onde des signaux à analyser et des phénomènes représentatifs de la somnolence, puis des techniques d'analyse susceptibles de répondre au problème posé : transformé de Fourier, décomposition en Ondelettes, transformation de Hilbert Huang; Pour la suite de l'étude, nous avons sélectionnée la transformation de Hilbert-Huang. La précision de cette méthode sera étudier qualitativement, avant de présenter l'algorithme développé et les premiers résultats obtenus sur des signaux réels. Les conclusions de l'analyse de la précision nous ont amené à modifier l'algorithme proposé par Huang en normalisant les composantes fournies par la transformation de Huang sur l'ensemble de la fenêtre d'analyse avant application de la transformation de Hilbert. La deuxième partie de la thèse est donc consacrée à la localisation et la caractérisation des clignements des yeux dans l'EOG. Avant de présenter l'algorithme développé, nous décrivons le signal étudié et le modèle de clignement proposé. Nous comparons ensuite, sur une base de données constituée durant des expériences menées sur un simulateur de conduite, les résultats obtenus par notre algorithme à une analyse semi-automatique. Une fois la détection des clignements validée, nous com parons le degré de somnolence déterminé après mise en place des règles utilisées par les experts à l'analyse visuelle des signaux. Le bilan du travail réalisé et les perspectives d'amélioration des résultats concluront ce travail.
543

Atrial Fibrillation Signal Analysis

Vaizurs, Raja Sarath Chandra Prasad 01 January 2011 (has links)
Atrial fibrillation (AF) is the most common type of cardiac arrhythmia encountered in clinical practice and is associated with an increased mortality and morbidity. Identification of the sources of AF has been a goal of researchers for over 20 years. Current treatment procedures such as Cardio version, Radio Frequency Ablation, and multiple drugs have reduced the incidence of AF. Nevertheless, the success rate of these treatments is only 35-40% of the AF patients as they have limited effect in maintaining the patient in normal sinus rhythm. The problem stems from the fact that there are no methods developed to analyze the electrical activity generated by the cardiac cells during AF and to detect the aberrant atrial tissue that triggers it. In clinical practice, the sources triggering AF are generally expected to be at one of the four pulmonary veins in the left atrium. Classifying the signals originated from four pulmonary veins in left atrium has been the mainstay of signal analysis in this thesis which ultimately leads to correctly locating the source triggering AF. Unlike many of the current researchers where they use ECG signals for AF signal analysis, we collect intra cardiac signals along with ECG signals for AF analysis. AF Signal collected from catheters placed inside the heart gives us a better understanding of AF characteristics compared to the ECG. . In recent years, mechanisms leading to AF induction have begun to be explored but the current state of research and diagnosis of AF is mainly about the inspection of 12 lead ECG, QRS subtraction methods, spectral analysis to find the fibrillation rate and limited to establishment of its presence or absence. The main goal of this thesis research is to develop methodology and algorithm for finding the source of AF. Pattern recognition techniques were used to classify the AF signals originated from the four pulmonary veins. The classification of AF signals recorded by a stationary intra-cardiac catheter was done based on dominant frequency, frequency distribution and normalized power. Principal Component Analysis was used to reduce the dimensionality and further, Linear Discriminant Analysis was used as a classification technique. An algorithm has been developed and tested during recorded periods of AF with promising results.
544

Contributions à l'étude algébrique et géométrique des structures et théories du premier ordre

Berthet, Jean 03 December 2010 (has links) (PDF)
La notion de T-radical d'un idéal permet à G.Cherlin de démontrer un Nullstellensatz dans les théories inductives d'anneaux. Nous proposons une analyse modèle-théorique de phénomènes connexes. En premier lieu, une réciproque de ce théorème nous conduit à une caractérisation des corps algébriquement clos, suggérant une version "positive" du travail de Cherlin, la théorie des idéaux T-radiciels. Ceux-ci se caractérisent par un théorème de représentation et sont associés à un théorème des zéros "positif". Ces résultats se généralisent à la logique du premier ordre : grâce à la notion de classe spéciale, nous développons ensuite une théorie logique des idéaux. On peut encore parler d'idéaux premiers et radiciels, relativement à une classe de structures. Dans ce cadre, le théorème de représentation est une propriété intrinsèque des classes spéciales et le théorème des zéros une propriété de préservation logique, que nous appelons "complétude géométrique" et qui entretient des rapports étroits avec la modèle-complétude positive. Les algèbres basées en groupes de P.Higgins permettent d'appliquer ces résultats aux théories modèle-complètes de corps avec opérateurs additionnels. Dans certains cas "noethériens", l'algèbre de coordonnées est un invariant algébrique des "variétés affines". Enfin, il est possible à partir d'un ensemble de formules E de généraliser les classes spéciales et autres classes de structures. Notre théorie des idéaux logiques est de plus un cas particulier du phénomène de localisation étudié par M.Coste ; dans certaines situations, un bon choix de formules permet d'identifier les types complets d'une "algèbre" à des types de localisation
545

Stochastické evoluční rovnice s multiaplikativním frakcionálním šumem / Stochastic evolution equations with multiplicative fractional noise

Šnupárková, Jana January 2012 (has links)
Title: Stochastic evolution equations with multiplicative fractional noise Author: Jana Šnupárková Departement: Department of Probability and Mathematical Statistics Supervisor: prof. RNDr. Bohdan Maslowski, DrSc. Supervisor's e-mail address: maslow@karlin.mff.cuni.cz Abstract: The fractional Gaussian noise is a formal derivative of a fractional Brownian motion with Hurst parameter H ∈ (0, 1). An explicit formula for a solution to stochastic differential equations with a multiplicative fractional Gaussian noise in a separable Hilbert space is given. The large time behaviour of the solution is studied. In addition, equations of this type with a nonlinear perturbation of a drift part are investigated in the case H > 1/2. Keywords: Fractional Brownian Motion, Stochastic Differential Equations in Hilbert Space, Explicit Formula for Solution
546

Noções de geometria projetiva / Notions of projective geometry

Portela, Antonio Edilson Cardoso January 2017 (has links)
PORTELA, Antonio Edilson Cardoso. Noções de geometria projetiva. 2017. 58 f. Dissertação (Mestrado Profissional em Matemática em Rede Nacional) - Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by Jessyca Silva (jessyca@mat.ufc.br) on 2017-09-06T17:17:00Z No. of bitstreams: 1 2017_dis_aecportela.pdf: 1065928 bytes, checksum: 468c05aa35745f3fd2761f13aa26eff1 (MD5) / Rejected by Rocilda Sales (rocilda@ufc.br), reason: Boa tarde, Estou devolvendo a Dissertação de ANTONIO EDILSON CARDOSO PORTELA, para que o mesmo realize algumas correções na formatação do trabalho. 1- SUMÁRIO ( A formatação do sumário está incorreta, primeiro, retire o último ponto final que aparece após a numeração dos capítulos e seções (Ex.: 3.1. Axioma....; deve ser corrigido para: 3.1 Axioma.....), o alinhamento dos títulos deve seguir o modelo abaixo 1 INTRODUÇÃO.....................00 2 O ESPAÇO...........................00 3 GEOMETRIA........................00 3.1 Axiomas...............................00 REFERÊNCIAS...................00 (OBS.: não altere a formatação do negrito, pois já estava correta) 2- TITULO DOS CAPÍTULOS E SEÇÕES ( retire o ponto final que aparece após o último dígito da numeração dos capítulos e seções, seguindo o modelo do sumário. Retire o recuo de parágrafo dos títulos das seções. Ex.: 3.1 Axioma.......) 3- REFERÊNCIAS ( substitua o termo REFERÊNCIAS BIBLIOGRÁFICAS apenas por REFERÊNCIAS, com fonte n 12, negrito e centralizado. Retire a numeração progressiva que aparece nos itens da referência. Atenciosamente, on 2017-09-06T17:56:50Z (GMT) / Submitted by Jessyca Silva (jessyca@mat.ufc.br) on 2017-09-11T14:48:40Z No. of bitstreams: 1 2017_dis_aecportela.pdf: 944228 bytes, checksum: 3ab4691817df04ba5d7818fd02e5095f (MD5) / Approved for entry into archive by Rocilda Sales (rocilda@ufc.br) on 2017-09-11T15:30:32Z (GMT) No. of bitstreams: 1 2017_dis_aecportela.pdf: 944228 bytes, checksum: 3ab4691817df04ba5d7818fd02e5095f (MD5) / Made available in DSpace on 2017-09-11T15:30:32Z (GMT). No. of bitstreams: 1 2017_dis_aecportela.pdf: 944228 bytes, checksum: 3ab4691817df04ba5d7818fd02e5095f (MD5) Previous issue date: 2017 / In this work, initially, some results of Linear Algebra are presented, in particular the study of the Vector Space R^n, which becomes, together with Analytical Geometry, the language used in the chapters that follow. We present a study from an axiomatic point of view, from the perspectives of Hilbert's axioms and we elaborate models of planes for the Euclidean, Elliptic and Projective Geometries. The validity of the Incidence and Order axioms for Euclidean Geometry is verified. In R^3, an approach is made to the study of the plane and the unitary sphere, highlighting the elliptical line obtained by the intersection of these sets, thus making an approach to the Elliptic Geometry. With the concepts and definitions studied in the Vector Space R^n, Three-dimensional Space and in the Euclidean and Elliptic Geometries we will approach the study of Projective Geometry, demonstrating propositions and verifying its axioms. / Neste trabalho, inicialmente, apresenta-se alguns resultados da Álgebra Linear, em especial o estudo do Espaço Vetorial R^n, que passa a ser, juntamente com a Geometria Analítica, a linguagem empregada nos capítulos que se seguem. Apresentamos um estudo de um ponto de vista axiomático, sob a ótica dos axiomas de Hilbert e elaboramos modelos de planos para as Geometrias Euclidiana, Elíptica e Projetiva. É verificada a validade dos axiomas de Incidência e Ordem para a Geometria Euclidiana. No R^3, é feita uma abordagem do estudo de plano e da esfera unitária, destacando a reta elíptica obtida pela interseção destes conjuntos, passando assim a fazer uma abordagem da Geometria Elíptica. Com os conceitos e definições estudadas no Espaço Vetorial R^n, Espaço tridimensional e nas Geometrias Euclidiana e Elíptica, abordaremos o estudo da Geometria Projetiva, demonstrando proposições e verificando os seus axiomas.
547

Groupes quantiques : actions sur des modules hilbertiens et calculs différentiels / Quantum groups : actions on Hilbert modules and differential calculi

Thibault de Chanvalon, Manon 08 December 2014 (has links)
Résumé indisponible / Résumé indisponible
548

Model-driven Time-varying Signal Analysis and its Application to Speech Processing

January 2016 (has links)
abstract: This work examines two main areas in model-based time-varying signal processing with emphasis in speech processing applications. The first area concentrates on improving speech intelligibility and on increasing the proposed methodologies application for clinical practice in speech-language pathology. The second area concentrates on signal expansions matched to physical-based models but without requiring independent basis functions; the significance of this work is demonstrated with speech vowels. A fully automated Vowel Space Area (VSA) computation method is proposed that can be applied to any type of speech. It is shown that the VSA provides an efficient and reliable measure and is correlated to speech intelligibility. A clinical tool that incorporates the automated VSA was proposed for evaluation and treatment to be used by speech language pathologists. Two exploratory studies are performed using two databases by analyzing mean formant trajectories in healthy speech for a wide range of speakers, dialects, and coarticulation contexts. It is shown that phonemes crowded in formant space can often have distinct trajectories, possibly due to accurate perception. A theory for analyzing time-varying signals models with amplitude modulation and frequency modulation is developed. Examples are provided that demonstrate other possible signal model decompositions with independent basis functions and corresponding physical interpretations. The Hilbert transform (HT) and the use of the analytic form of a signal are motivated, and a proof is provided to show that a signal can still preserve desirable mathematical properties without the use of the HT. A visualization of the Hilbert spectrum is proposed to aid in the interpretation. A signal demodulation is proposed and used to develop a modified Empirical Mode Decomposition (EMD) algorithm. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016
549

Sylvester forms and Rees algebras

Macêdo, Ricado Burity croccia 24 July 2015 (has links)
Submitted by Maike Costa (maiksebas@gmail.com) on 2016-03-31T12:43:01Z No. of bitstreams: 1 arquivo total.pdf: 1366177 bytes, checksum: 1b02d1a5ce5861390070022558e311b0 (MD5) / Made available in DSpace on 2016-03-31T12:43:01Z (GMT). No. of bitstreams: 1 arquivo total.pdf: 1366177 bytes, checksum: 1b02d1a5ce5861390070022558e311b0 (MD5) Previous issue date: 2015-07-24 / This work is about the Rees algebra of a nite colength almost complete intersection ideal generated by forms of the same degree in a polynomial ring over a eld. We deal with two situations which are quite apart from each other: in the rst the forms are monomials in an unrestricted number of variables, while the second is for general binary forms. The essential goal in both cases is to obtain the depth of the Rees algebra. It is known that for such ideals the latter is rarely Cohen{Macaulay (i.e., of maximal depth). Thus, the question remains as to how far one is from the Cohen{Macaulay case. In the case of monomials one proves under certain restriction a conjecture of Vasconcelos to the e ect that the Rees algebra is almost Cohen{ Macaulay. At the other end of the spectrum, one proposes a proof of a conjecture of Simis on general binary forms, based on work of Huckaba{Marley and on a theorem concerning the Ratli {Rush ltration. Still within this frame, one states a couple of stronger conjectures that imply Simis conjecture, along with some solid evidence. / Este trabalho versa sobre a algebra de Rees de um ideal quase intersec cão completa, de cocomprimento nito, gerado por formas de mesmo grau em um anel de polinômios sobre um corpo. Considera-se duas situa c~oes inteiramente diversas: na primeira, as formas s~ao mon^omios em um n umero qualquer de vari aveis, enquanto na segunda, s~ao formas bin arias gerais. O objetivo essencial em ambos os casos e obter a profundidade da algebra de Rees. E conhecido que tal algebra e raramente Cohen{Macaulay (isto e, de profundidade m axima). Assim, a quest~ao que permanece e qua o distante são do caso Cohen{Macaulay. No caso de monômios prova-se, mediante certa restri cão, uma conjectura de Vasconcelos no sentido de que a algébra de Rees e quase Cohen {Macaulay. No outro caso extremo, estabelece-se uma prova de uma conjectura de Simis sobre formas bin arias gerais, baseada no trabalho de Huckaba{Marley e em um teorema sobre a ltera cão de Ratli {Rush. Al em disso, apresenta-se um par de conjecturas mais fortes que implicam a conjectura de Simis, juntamente com uma evidência s olida.
550

O Décimo problema de Hilbert

Ferreira, Marcelo 27 August 2010 (has links)
In this work we present a proof that the Hilbert s Tenth Problem is unsolvable. This problem is to give a computing algorithm which will tell of a given polynomial Diophantine equation with integer coefficients whether or not it has a solution in integers. We start developing some topics of basic number theory, that will be useful at some time. In this part we prove only main results. After that, we study Diophantine equation as well as Diophantine functions. Then, we prove a serie of lemas that will be useful to proof that the exponential function is Diophantine. From there, we define the concept of recursive function and prove that a function is Diophantine if and only if it is recursive. Finally we prove the Universality Theorem. We use this last theorem to proof that the Hilbert s Problem is unsolvable. / Neste trabalho apresentamos uma demonstração da insolubilidade do Décimo Problema de Hilbert, que investiga a existência de um método para determinar se dada uma equação Diofantina qualquer podemos determinar se esta tem ou não uma solução. Começamos desenvolvendo alguns tópicos de teoria de números, que serão úteis em vários momentos, nesta parte demonstramos apenas os resultados principais. Em um segundo momento, passamos ao estudo das equações Diofantinas bem como das funções Diofantinas, que permeiam nossos resultados. Em seguida, demonstramos uma série de lemas que servem de base para mostrarmos que a função exponencial é Diofantina. A partir daı, passamos a definição do importante conceito de função recursiva e então demonstramos que uma função ser recursiva é equivalente a ser Diofantina. Finalmente, demonstramos o Teorema da Universalidade que servirá de base para a demonstração o da insolubilidade do Décimo Problema de Hilbert. / Mestre em Matemática

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