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Tesis sobre el tema "Wavelet approximation"

Autor: Grafiati
Publicado: 4 de junio de 2021
Última modificación: 1 de febrero de 2022

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1

Li, Zheng. "Approximation to random process by wavelet basis". View abstract/electronic edition; access limited to Brown University users, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3318378.

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2

Martin, Richard Luis. "Wavelet approximation of GRID fields for virtual screening". Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531509.

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3

Schreiner, Michael [Verfasser]. "Wavelet Approximation by Spherical Up Functions / Michael Schreiner". Aachen : Shaker, 2004. http://d-nb.info/1170537413/34.

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4

Lee, Sang-Mook. "Wavelet-Based Multiresolution Surface Approximation from Height Fields". Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/26203.

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A height field is a set of height distance values sampled at a finite set of sample points in a two-dimensional parameter domain. A height field usually contains a lot of redundant information, much of which can be removed without a substantial degradation of its quality. A common approach to reducing the size of a height field representation is to use a piecewise polygonal surface approximation. This consists of a mesh of polygons that approximates the surfaces of the original data at a desired level of accuracy. Polygonal surface approximation of height fields has numerous applications in the fields of computer graphics and computer vision. Triangular mesh approximations are a popular means of representing three-dimensional surfaces, and multiresolution analysis (MRA) is often used to obtain compact representations of dense input data, as well as to allow surface approximations at varying spatial resolution. Multiresolution approaches, particularly those moving from coarse to fine resolutions, can often improve the computational efficiency of mesh generation as well as can provide easy control of level of details for approximations. This dissertation concerns the use of wavelet-based MRA methods to produce a triangular-mesh surface approximation from a single height field dataset. The goal of this study is to obtain a fast surface approximation for a set of height data, using a small number of approximating elements to satisfy a given error criterion. Typically, surface approximation techniques attempt to balance error of fit, number of approximating elements, and speed of computation. A novel aspect of this approach is the direct evaluation of wavelet coefficients to assess surface shape characteristics within each triangular element at a given scale. Our approach hierarchically subdivides and refines triangles as the resolution level increases.
Ph. D.
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5

Grip, Niklas. "Wavelet and gabor frames and bases : approximation, sampling and applications". Doctoral thesis, Luleå, 2002. http://epubl.luth.se/1402-1544/2002/49.

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6

Zhanlav, Tugal. "Some choices of moments of refinable function and applications". Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601316.

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We propose a recursive formula for moments of scaling function and sum rule. It is shown that some quadrature formulae has a higher degree of accuracy under proposed moment condition. On this basis we obtain higher accuracy formula for wavelet expansion coefficients which are needed to start the fast wavelet transform and estimate convergence rate of wavelet approximation and sampling of smooth functions. We also present a direct algorithm for solving refinement equation.
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7

Trisiripisal, Phichet. "Image Approximation using Triangulation". Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/33337.

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An image is a set of quantized intensity values that are sampled at a finite set of sample points on a two-dimensional plane. Images are crucial to many application areas, such as computer graphics and pattern recognition, because they discretely represent the information that the human eyes interpret. This thesis considers the use of triangular meshes for approximating intensity images. With the help of the wavelet-based analysis, triangular meshes can be efficiently constructed to approximate the image data. In this thesis, this study will focus on local image enhancement and mesh simplification operations, which try to minimize the total error of the reconstructed image as well as the number of triangles used to represent the image. The study will also present an optimal procedure for selecting triangle types used to represent the intensity image. Besides its applications to image and video compression, this triangular representation is potentially very useful for data storage and retrieval, and for processing such as image segmentation and object recognition.
Master of Science
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8

Hartmann, Christoph [Verfasser] y Stephan [Akademischer Betreuer] Dahlke. "The p-Poisson Equation: Regularity Analysis and Adaptive Wavelet Frame Approximation / Christoph Hartmann ; Betreuer: Stephan Dahlke". Marburg : Philipps-Universität Marburg, 2018. http://d-nb.info/1168380103/34.

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9

Poungponsri, Suranai. "An Approach Based On Wavelet Decomposition And Neural Network For ECG Noise Reduction". DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/101.

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Electrocardiogram (ECG) signal processing has been the subject of intense research in the past years, due to its strategic place in the detection of several cardiac pathologies. However, ECG signal is frequently corrupted with different types of noises such as 60Hz power line interference, baseline drift, electrode movement and motion artifact, etc. In this thesis, a hybrid two-stage model based on the combination of wavelet decomposition and artificial neural network is proposed for ECG noise reduction based on excellent localization features: wavelet transform and the adaptive learning ability of neural network. Results from the simulations validate the effectiveness of this proposed method. Simulation results on actual ECG signals from MIT-BIH arrhythmia database [30] show this approach yields improvement over the un-filtered signal in terms of signal-to-noise ratio (SNR).
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10

Silveira, Tiago da. "DETECÇÃO DO ESTADO DE SONOLÊNCIA VIA UM ÚNICO CANAL DE ELETROENCEFALOGRAFIA ATRAVÉS DA TRANSFORMADA WAVELET DISCRETA". Universidade Federal de Santa Maria, 2012. http://repositorio.ufsm.br/handle/1/5407.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Many fatal traffic accidents are caused by fatigued and drowsy drivers. In this context, automatic drowsiness detection devices are an alternative to minimize this issue. In this work, two new methodologies to drowsiness detection are presented, considering a signal obtained from a single electroencephalography channel: (i) drowsiness detection through best m-term approximation, applied to the wavelet expansion of the analysed signal; (ii) drowsiness detection through Mahalanobis distance with wavelet coefficients. The results of both methodologies are compared with a method which uses Mahalanobis distance and Fourier coefficients to drowsiness detection. All methodologies consider the medical evaluation of the brain signal, given by the hypnogram, as a reference.
A sonolência diurna em motoristas, principal consequência da privação de sono, tem sido a causa de diversos acidentes graves de trânsito. Neste contexto, a utilização de dispositivos que alertem o condutor ao detectar automaticamente o estado de sonolência é uma alternativa para a minimização deste problema. Neste trabalho, duas novas metodologias para a detecção automática da sonolência são apresentadas, utilizando um único canal de eletroencefalografia para a obtenção do sinal: (i) detecção da sonolência via melhor aproximação por m-termos, aplicada aos coeficientes wavelets da expansão em série do sinal; e (ii) detecção da sonolência via distância de Mahalanobis e coeficientes wavelets. Os resultados de ambas as metodologias são comparados a uma implementação utilizando distância de Mahalanobis e coeficientes de Fourier. Para todas as metodologias, utiliza-se como referência a avaliação médica do sinal cerebral, dada pelo hipnograma.
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11

Ješko, Petr. "Metody pro doplňování pixelů vně obrazu". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220070.

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The thesis deals with addition of pixels outside the image. Lists some methods for inpainting using computers and highlights the pitfalls that appear here. Examines methods for interpolation and approximation of functions in order to find the best method for extrapolating the image beyond its borders. Describes the basics of Wavelet transformation and Multiresolution analysis and briefly discusses about spatial filtering, edge detection and the algorithm OMP, falling within the sparse representation of signals. Theoretical knowledge of these areas are used in the design of several methods for adding pixels outside the image. PSNR and SSIM are used to compare achieved results. Also discussed is the development environment of MATLAB as a tool for the implementation of algorithms that practically solves the given problem.
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12

Naouai, Mohamed. "Localisation et reconstruction du réseau routier par vectorisation d'image THR et approximation des contraintes de type "NURBS"". Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00994333.

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Ce travail de thèse vise à mettre en place un système d'extraction de réseau routier en milieu urbain à partir d'image satellite à très haute résolution. Dans ce contexte, nous avons proposé deux méthodes de localisation de routes. La première approche est fondée sur la procédure de conversion de l'image vers un format vectoriel. L'originalité de cette approche réside dans l'utilisation d'une méthode géométrique pour assurer le passage vers une représentation vectorielle de l'image d'origine et la mise en place d'un formalisme logique fondé sur un ensemble de critères perceptifs permettant le filtrage de l'information inutile et l'extraction des structures linéaires. Dans la deuxième approche, nous avons proposé un algorithme fondé sur la théorie des ondelettes, il met particulièrement en évidence les deux volets multi-résolution et multi-direction. Nous proposons donc une approche de localisation des routes mettant en jeux l'information fréquentielle multi directionnelle issue de la transformée en ondelette Log-Gabor. Dans l'étape de localisation, nous avons présenté deux détecteurs de routes qui exploitent l'information radiométrique, géométrique et fréquentielle. Cependant, ces informations ne permettent pas un résultat exact et précis. Pour remédier à ce problème, un algorithme de suivi s'avère nécessaire. Nous proposons la reconstruction de réseaux routiers par des courbes NURBS. Cette approche est basée sur un ensemble de points de repères identifiés dans la phase de localisation. Elle propose un nouveau concept, que nous avons désigné par NURBSC, basé sur les contraintes géométriques des formes à approximer. Nous connectons les segments de route identifiés afin d'obtenir des tracés continus propres aux routes.
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13

Piché, Daniel Guy. "IFSM, wavelets and fractal-wavelets, three methods of approximation". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21538.pdf.

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14

Pich??, Daniel Guy. "IFSM, wavelets and fractal-wavelets, three methods of approximation". Thesis, National Library of Canada = Biblioth??que nationale du Canada, 1997. http://hdl.handle.net/10012/29.

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15

Oyet, Alwell Julius. "Robust designs for wavelet approximations of nonlinear models". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23051.pdf.

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16

Yin, Ping. "Sur une méthode numérique ondelettes / domaines fictifs lisses pour l'approximation de problèmes de Stefan". Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10013/document.

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Notre travail est consacré à la définition, l'analyse et l'implémentation de nouveaux algorithmes numériques pour l'approximation de la solution de problèmes à 2 dimensions du type problème de Stefan. Dans ce type de problèmes une équation aux dérivée partielle parabolique posée sur un ouvert omega quelconque est couplée avec une autre équation qui contrôle la frontière gamma du domaine lui même. Les difficultés classiquement associés à ce type de problèmes sont: la formulation en particulier de l'équation pour le bord du domaine, l'approximation de la solution liées à la forme quelconque du domaine, les difficultés associées à l'implication des opérateurs de trace (approximation, conditionnement), les difficultés liées aux de régularité fonds du domaine.De plus, de nombreuse situations d'intérêt physique par exemple demandent des approximations de haut degré. Notre travail s'appuie sur une formulation de type espaces de niveaux (level set) pour l'équation du domaine, et une formulation de type domaine fictif (Omega) pour l'équation initiale.Le contrôle des conditions aux limites est effectué à partir de multiplicateurs de Lagrange agissant sur une frontière (Gamma) dite de contrôle différente de frontière(gamma) du domaine (omega). L'approximation est faite à partir d'un schéma aux différences finies pour les dérivées temporelle et une discrétisation à l'aide d'ondelettes bi-dimensionelles pour l'équation initiale et une dimensionnelle pour les multiplicateurs de Lagrange. Des opérateurs de prolongement de omega à Omega sont également construits à partir d'analyse multiéchelle sur l'intervalle. Nous obtenons aussi: une formulation pour laquelle existence de la solution est démontrées, un algorithme convergent pour laquelle une estimation globale d'erreur (sur Omega) est établie, une estimation intérieure prouvant sur l'erreur à un domaine omega, overline omega subset Xi, des estimations sur les conditionnement associés a l'opérateur de trace, des algorithmes de prolongement régulier. Différentes expériences numériques en 1D ou 2D sont effectuées. Le manuscrit est organisé comme suit: Le premier chapitre rappelle la construction des analyses multirésolutions, les propriétés importantes des ondelettes et des algorithmes numériques liées à l'application d'opérateurs aux dérivées partielles. Le second chapitre donne un aperçu des méthodes de domaine fictif classiques, approchées par la méthode de Galerkin ou de Petrov-Galerkin. Nous y découvrons les limites de ces méthodes ce qui donne la direction de notre travail. Le chapitre trois présente notre nouvelle méthode de domaine fictif que l'on appelle méthode de domaine fictif lisse.L'approximation est grâce à une méthode d'ondelettes de type Petrov-Galerkin. Cette section contient l'analyse théorique et décrit la mise en œuvre numérique. Différents avantages de cette méthode sont démontrés. Le chapitre quatre introduit une technique de prolongement régulier. Nous l'appliquons à des problèmes elliptiques en 1D ou 2D.\par Le cinquième chapitre décrit quelques simulations numériques de problème de Stefan. Nous testons l'efficacité de notre méthode sur différents exemples dont le problème de Stefan à 2 phases avec conditions aux limites de Gibbs-Thomson
Our work is devoted to the definition, analysis and implementation of a new algorithms for numerical approximation of the solution of 2 dimensional Stefan problem. In this type of problem a parabolic partial differential equation defined on an openset Omega is coupled with another equation which controls the boundary gamma of the domain itself. The difficulties traditionally associated with this type of problems are: the particular formulation of equation on the boundary of domain, the approximation of the solution defined on general domain, the difficulties associated with the involvement of trace operation (approximation, conditioning), the difficulties associated with the regularity of domain. Addition, many situations of physical interest, for example,require approximations of high degree. Our work is based on aformulation of type level set for the equation on the domain, and aformulation of type fictitious domain (Omega) for the initialequation. The control of boundary conditions is carried out throughLagrange multipliers on boundary (Gamma), called control boundary, which is different with boundary (gamma) of the domain (omega). The approximation is done by a finite difference scheme for time derivative and the discretization by bi-dimensional wave letfor the initial equation and one-dimensional wave let for the Lagrange multipliers. The extension operators from omega to Omega are also constructed from multiresolution analysis on theinterval. We also obtain: a formulation for which the existence of solution is demonstrated, a convergent algorithm for which a global estimate error (on Omega) is established, interior error estimate on domain omega, overline omega subset estimates on the conditioning related to the trace operator, algorithms of smooth extension. Different numerical experiments in 1D or 2D are implemented. The work is organized as follows:The first chapter recalls theconstruction of multiresolution analysis, important properties of wavelet and numerical algorithms. The second chapter gives an outline of classical fictitious domain method, using Galerkin or Petrov-Galerkin method. We also describe the limitation of this method and point out the direction of our work.\par The third chapter presents a smooth fictitious domain method. It is coupled with Petrov-Galerkin wavelet method for elliptic equations. This section contains the theoretical analysis and numerical implementation to embody the advantages of this new method. The fourth chapter introduces a smooth extension technique. We apply it to elliptic problem with smooth fictitious domain method in 1D and 2D. The fifth chapter is the numerical simulation of the Stefan problem. The property of B-spline render us to exactly calculate the curvature on the moving boundary. We use two examples to test the efficiency of our new method. Then it is used to resolve the two-phase Stefan problem with Gibbs-Thomson boundary condition as an experimental case
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17

Meignen, Sylvain. "Problèmes d'échelle dans la segmentation par ondelettes d'images texturées". Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10241.

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Nous nous intéressons dans cette thèse à la segmentation d'images texturées à l'aide de frame d'ondelettes. Après avoir étudié les frames, en particulier les relations qui lient l'approche continue à l'approche discrète, nous nous focalisons particulièrement sur l'étude des problèmes d'échelle liés à la segmentation des macro-textures. Nous proposons des algorithmes particulièrement adaptés au traitement spécifique de ce type de textures, qui utilisent de nouvelles caractéristiques : les facteurs principaux d'une analyse en composantes principales. Des liens sont établis avec des caractéristiques plus communément utilisées. Nous montrons ensuite que la régularité Lipschitzienne des textures est un paramètre moins fiable que les facteurs principaux, aux petites échelles. Enfin, nous nous intéressons à la définition des frontières des textures, et construisons un algorithme permettant leur reconstruction partielle. La seconde partie est consacrée à l'étude d'un algorithme de décomposition multi-échelles permettant le suivi d'extrema le long des échelles. Nous regardons les applications possibles de cet algorithme à la détection des bords d'images bruitées ; puis, ces techniques de suivi d'extrema sont appliquées à la détermination du temps de réaction du muscle génioglosse, sur des enregistrements EMG.
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18

Knappett, Daniel. "Numerical solution of the stationary FPK equation using Shannon wavelets". Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367109.

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19

Shuler, Harrey Jeong. "Recovery of the local gravity field by spherical regularization wavelets approximation and its numerical implementation". Thesis, The University of Texas at Austin, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3615225.

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As an alternative to spherical harmonics in modeling the gravity field of the Earth, we built a multiresolution gravity model by employing spherical regularization wavelets in solving the inverse problem, i.e. downward propagation of the gravity signal to the Earth's surface. Scale discrete Tikhonov spherical regularization scaling function and wavelet packets were used to decompose and reconstruct the signal. We recovered the local gravity anomaly using only localized gravity measurements at the observing satellite's altitude of 300 km. When the upward continued gravity anomaly to the satellite altitude with a resolution 0.5° was used as simulated measurement inputs, our model could recover the local surface gravity anomaly at a spatial resolution of 1° with an RMS error between 1 and 10 mGal, depending on the topography of the gravity field. Our study of the effect of varying the data volume and altering the maximum degree of Legendre polynomials on the accuracy of the recovered gravity solution suggests that the short wavelength signals and the regions with high magnitude gravity gradients respond more strongly to such changes. When tested with simulated SGG measurements, i.e. the second order radial derivative of the gravity anomaly, at an altitude of 300 km with a 0.7° spatial resolution as input data, our model could obtain the gravity anomaly with an RMS error of 1 ~ 7 mGal at a surface resolution of 0.7° (< 80 km). The study of the impact of measurement noise on the recovered gravity anomaly implies that the solutions from SGG measurements are less susceptible to measurement errors than those recovered from the upward continued gravity anomaly, indicating that the SGG type mission such as GOCE would be an ideal choice for implementing our model. Our simulation results demonstrate the model's potential in determining the local gravity field at a finer scale than could be achieved through spherical harmonics, i.e. less than 100 km, with excellent performance in edge detection.

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20

Goubet, Étienne. "Contrôle non destructif par analyse supervisée d'images 3D ultrasonores". Cachan, Ecole normale supérieure, 1999. http://www.theses.fr/1999DENS0011.

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L'objet de cette thèse consiste en l'élaboration d'une chaine de traitements permettant d'extraire l'information utile de données 3d ultrasonores et de caractériser les défauts éventuellement présents dans la pièce inspectée. Cette caractérisation a été abordée pour des fissures contrôlées par un même émetteur/récepteur. Dans une première partie nous rappelons les principes du contrôle non destructif par ultrasons ainsi que les représentations classiques des données ultrasonores. La deuxième partie est consacrée à l'étude d'un modèle d'extraction de l'information d'échos présents sur les données au moyen d'une base d'ondelettes adaptée. L'utilisation d'une ondelette unique translatée dans le temps est rendue possible par un travail sur une représentation complexe des données réelles originales. Une première étape permet de détecter et de positionner les échos d'amplitude significative. Dans un deuxième temps, on effectue une régularisation spatialement cohérente des instants de détection à l'aide d'un modèle markovien. On élimine ainsi les échos dont les instants de détection ne font pas partie de surfaces d'instants régulières. Les parties suivantes traitent de la localisation et du dimensionnement des fissures. On utilise des caractéristiques extraites du faisceau ultrasonore afin de déterminer le trajet de l'onde ultrasonore du capteur à l'objet diffractant lorsque la réponse de l'écho est maximale. On met en correspondance l'instant de détection obtenu pour cet écho et le temps de parcours selon le trajet défini afin de positionner un point d'arête dans la pièce. On obtient ainsi un ensemble de points de discrétisation pour chaque arête. Dans le cadre de données 3d obtenues sur un matériau isotrope, on élimine les points d'arête extrêmes en utilisant un critère de comparaison sur les courbes échodynamiques associées aux points de détection sur les données réelles et sur des données simulées équivalentes. La localisation est abordée pour des fissures situées dans un matériau isotrope ou acier revêtu d'anisotrope.
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21

Matei, Basarab. "Methodes multiresolutions non-lineaires. Applications au traitement d'image". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2002. http://tel.archives-ouvertes.fr/tel-00002016.

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CETTE THÈSE INTRODUIT UNE CLASSE DES TRANSFORMÉS MULTI­ ÉCHELLES BIDIMENSIONNELLES ADAPTÉES AUX CONTOURS. CELLES-CI SONT DIFFÉ­RENTES DES TRANSFORMÉES EN ONDELETTES BIDIMENSIONNELLES, CAR ELLES SONT BASÉES SUR DES OPÉRATEURS NONLINÉAIRES DEPENDENTS DES DONNÉES. CES OPÉRATEURS SONT INSPIRÉS DES OPÉRATEURS D'INTERPOLATION ENO INTRODUITS PAR HARTEN ET OSHER DANS LE CONTEXTE DE LA SIMULATION NUMÉRIQUES DES ONDES DE CHOC. LE BUT EST D'INCLURE DANS LA TRANSFORMÉE UN TRAITEMENT SPECIFIC DES CONTOURS QUI, EN TENANT COMPTE DE LEURS RÉGULARITÉ GEOMETRIQUE, PERMETTRAS D'OBTENIR DES REPRÉSENTATIONS PLUS CREUSES ET DONC DES MEILLEU­RES PROPRIÉTÉS D'APPROXIMATIONS. D'UN POINT DE VUE THÉORIQUE ON S'INTERESSE À LA CONSERVATION DES MÊME PROPRIÉTÉS DE CONCENTRATION POUR LES ESPACES FONCTIONNELS CLASSIQUES (BESOV ET $BV$), ET ON S'INTERROGE AUSSI SUR LA STABILITÉ DE CES DÉ­COMPOSITIONS. CE PROBLÈME EST LOIN D'ÊTRE AUSSI SIMPLE QUE DANS LE CAS DES REPRÉ­SENTATIONS LINÉAIRES. NOUS ABORDONS DANS CETTE THÈSE CHACUNE DE CES DIFFICULTÉS, ET NOUS Y APPORTONS DES ÉLÉMENTS DE RÉPONSE, AINSI QUE DES TESTS NUMÉRIQUES VISANT À ÉVALUER CONCRÈTEMENT LES PERFORMANCES DES MÉTHODES PROPOSÉES.
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22

Phan, Anh cang. "Crack removal and hole filling on composite subdivision meshes". Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4068/document.

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Construire une surface lisse d'un objet 3D est un problème important dans de nombreuses applications graphiques. En particulier, les méthodes de subdivision permettent de passer facilement d'un maillage discret à une surface continue. Un problème général résultant de la subdivision de deux maillages initialement connectés le long d'un bord est l'apparition de fissures ou de trous entre eux. Ces fissures produisent non seulement des formes indésirables, mais induisent aussi des difficultés pour les traitements ultérieurs. Il faut donc réparer ces défauts de sorte que la surface obtenue soit lisse et puisse être subdivisée ou modifiée. Nous proposons de nouvelles méthodes pour relier deux maillages avec des résolutions différentes en utilisant une transformée en ondelettes B-splines et une approximation locale ou une interpolation locale à l'aide de fonctions de base radiales (RBF). Ces procédés génèrent un maillage de connexion où la continuité est contrôlée. La résolution du maillage est ajustable pour respecter le changement de résolution entre les zones grossières et fines. En outre, nous présentons des méthodes pour combler les trous à n-côtés, et le raffinement des maillages grâce à un schéma de subdivision adaptative. Nous avons conçu, implémenté et testé les algorithmes en MatLab pour illustrer nos méthodes et montrer des résultats expérimentaux. Ces algorithmes sont mis en oeuvre sur de nombreux modèles d'objets 3D avec des formes complexes. En outre, nous avons fourni des approches différentes pour chaque problème. Ainsi, les résultats des différentes approches sont comparés et évalués afin d'exploiter les avantages et les inconvénients de ces approches
Constructing a smooth surface of a 3D object is an important problem in many graphical applications. In particular, subdivision methods permit to pass easily from a discrete mesh to a continuous surface. A generic problem arising from subdividing two meshes initially connected along a common boundary is the occurrence of cracks or holes between them. These cracks not only produce undesired shapes, but also bring serious trouble for further mesh processing. They must be removed or filled so that the produced surface is smooth and can be further subdivided or edited. In order to remove cracks, we propose new methods for joining two meshes with different resolutions using a Lifted B-spline wavelet transform and a local approximation or radial basis function (RBF) local interpolation. These methods generate a connecting mesh where continuity is controlled from one boundary to the other and the connecting mesh can change gradually in resolution between coarse and fine areas. Additionally, we introduce methods for filling n-sided holes, and refining meshes with an adaptive subdivision scheme. We have designed, implemented, and tested the algorithms in MatLab to illustrate our proposed methods and show experimental results. These algorithms are implemented on many 3D object models with complex shapes. Additionally, we have provided some different approaches for each problem. Thus, results from the different approaches are compared and evaluated to exploit the advantages and disadvantages of these approaches
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23

Gempesaw, Daniel. "A multi-resolution discontinuous Galerkin method for rapid simulation of thermal systems". Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42775.

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Efficient, accurate numerical simulation of coupled heat transfer and fluid dynamics systems continues to be a challenge. Direct numerical simulation (DNS) packages like FLU- ENT exist and are sufficient for design and predicting flow in a static system, but in larger systems where input parameters can change rapidly, the cost of DNS increases prohibitively. Major obstacles include handling the scales of the system accurately - some applications span multiple orders of magnitude in both the spatial and temporal dimensions, making an accurate simulation very costly. There is a need for a simulation method that returns accurate results of multi-scale systems in real time. To address these challenges, the Multi- Resolution Discontinuous Galerkin (MRDG) method has been shown to have advantages over other reduced order methods. Using multi-wavelets as the local approximation space provides an inherently efficient method of data compression, while the unique features of the Discontinuous Galerkin method make it well suited to composition with wavelet theory. This research further exhibits the viability of the MRDG as a new approach to efficient, accurate thermal system simulations. The development and execution of the algorithm will be detailed, and several examples of the utility of the MRDG will be included. Comparison between the MRDG and the "vanilla" DG method will also be featured as justification of the advantages of the MRDG method.
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24

Li, Jing. "Digital Signal Characterization for Seizure Detection Using Frequency Domain Analysis". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-296861.

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Nowadays, a significant proportion of the population in the world is affected by cerebral diseases like epilepsy. In this study, frequency domain features of electroencephalography (EEG) signals were studied and analyzed, with a view being able to detect epileptic seizures more easily. The power spectrum and spectrogram were determined by using fast fourier transform (FFT) and the scalogram was found by performing continuous wavelet transform (CWT) on the testing EEG signal. In addition, two schemes, i.e. method 1 and method 2, were implemented for detecting epileptic seizures and the applicability of the two methods to electrocardiogram (ECG) signals were tested. A third method for anomaly detection in ECG signals was tested.
En signifikant del av population påverkas idag av neurala sjukdomar som epilepsi. I denna studie studerades och analyserades egenskaper inom frekvensdomänen av elektroencefalografi (EEG), med sikte på att lättare kunna upptäcka epileptiska anfall. Effektspektrumet och spektrogramet bestämdes med hjälp av en snabb fouriertransform och skalogrammet hittades genom att genomföra en kontinuerlig wavelet transform (CWT) på testsignalen från EEGsignalen. I addition till detta skapades två system, metod 1 och metod 2, som implementerades för att upptäcka epileptiska anfall. Användbarheten av dessa två metoder inom elektrokardiogramsignaler (ECG) testades. En tredje metod för anomalidetektering i ECGsignaler testades.
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25

Reis, Daniel de Brito. "Abordagem semi-paramétrica para cópulas variantes no tempo em séries temporais financeiras". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-22082017-004041/.

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Neste trabalho foram utilizadas cópulas bivariadas variantes no tempo para modelar a dependência entre séries de retornos financeiros. O objetivo deste trabalho é apresentar uma abordagem de estimação semi-paramétrica de cópulas variantes no tempo a partir de uma função de cópula paramétrica na qual o parâmetro varia no tempo. A função do parâmetro desconhecido será estimada pela aproximação de ondaleta Haar, polinômio de Taylor e Kernel. O desempenho dos três métodos de aproximação será comparado via estudos de simulação. Uma aplicação aos dados reais será apresentada para ilustrar a metodologia estudada.
In this work the bivariate Time-varying copula models have been used to model the dependence between payback. The aim of this work is to present an approach of semiparametric estimation of Time-varying copula models from a parametric copula function in which the parameter varies with the time. The function of the unknown parameter will be estimated by Haar wavelet approach, Taylor series and smoothing Kernel approximation. The measured performance of the three estimation method will be compared by simulation study. An application of the data will be presented to illustrate the studied methodology.
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26

Baril, Jérôme. "Modèles de représentation multi-résolution pour le rendu photo-réaliste de matériaux complexes". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2010. http://tel.archives-ouvertes.fr/tel-00525125.

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L'émergence des périphériques de capture numériques ont permis le dé- veloppement de l'acquisition 3D pour numériser les propriétés d'un objet réel : sa forme et son apparence. Ce processus fournit une représentation dense et précise d'objets réels et permet de s'abstraire d'un processus de simulation physique coûteux pour modéliser un objet. Ainsi, les problématiques ont évolué et portent non plus uniquement sur la modélisation des caractéristiques d'un objet réel mais sur les traitements de données issues de l'acquisition pour intégrer une copie de la réalité dans un processus de synthèse d'images. Dans ces travaux de thèse, nous proposons de nouvelles représentations pour des fonctions d'apparence issues de l'acquisition dont le but est de dénir un ensemble de modèles multi-échelles, de faible complexité en taille, capable d'être visualisé en temps réel sur le matériel graphique actuel.
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27

Scipioni, Angel. "Contribution à la théorie des ondelettes : application à la turbulence des plasmas de bord de Tokamak et à la mesure dimensionnelle de cibles". Thesis, Nancy 1, 2010. http://www.theses.fr/2010NAN10125.

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La nécessaire représentation en échelle du monde nous amène à expliquer pourquoi la théorie des ondelettes en constitue le formalisme le mieux adapté. Ses performances sont comparées à d'autres outils : la méthode des étendues normalisées (R/S) et la méthode par décomposition empirique modale (EMD).La grande diversité des bases analysantes de la théorie des ondelettes nous conduit à proposer une approche à caractère morphologique de l'analyse. L'exposé est organisé en trois parties.Le premier chapitre est dédié aux éléments constitutifs de la théorie des ondelettes. Un lien surprenant est établi entre la notion de récurrence et l'analyse en échelle (polynômes de Daubechies) via le triangle de Pascal. Une expression analytique générale des coefficients des filtres de Daubechies à partir des racines des polynômes est ensuite proposée.Le deuxième chapitre constitue le premier domaine d'application. Il concerne les plasmas de bord des réacteurs de fusion de type tokamak. Nous exposons comment, pour la première fois sur des signaux expérimentaux, le coefficient de Hurst a pu être mesuré à partir d'un estimateur des moindres carrés à ondelettes. Nous détaillons ensuite, à partir de processus de type mouvement brownien fractionnaire (fBm), la manière dont nous avons établi un modèle (de synthèse) original reproduisant parfaitement la statistique mixte fBm et fGn qui caractérise un plasma de bord. Enfin, nous explicitons les raisons nous ayant amené à constater l'absence de lien existant entre des valeurs élevées du coefficient d'Hurst et de supposées longues corrélations.Le troisième chapitre est relatif au second domaine d'application. Il a été l'occasion de mettre en évidence comment le bien-fondé d'une approche morphologique couplée à une analyse en échelle nous ont permis d'extraire l'information relative à la taille, dans un écho rétrodiffusé d'une cible immergée et insonifiée par une onde ultrasonore
The necessary scale-based representation of the world leads us to explain why the wavelet theory is the best suited formalism. Its performances are compared to other tools: R/S analysis and empirical modal decomposition method (EMD). The great diversity of analyzing bases of wavelet theory leads us to propose a morphological approach of the analysis. The study is organized into three parts. The first chapter is dedicated to the constituent elements of wavelet theory. Then we will show the surprising link existing between recurrence concept and scale analysis (Daubechies polynomials) by using Pascal's triangle. A general analytical expression of Daubechies' filter coefficients is then proposed from the polynomial roots. The second chapter is the first application domain. It involves edge plasmas of tokamak fusion reactors. We will describe how, for the first time on experimental signals, the Hurst coefficient has been measured by a wavelet-based estimator. We will detail from fbm-like processes (fractional Brownian motion), how we have established an original model perfectly reproducing fBm and fGn joint statistics that characterizes magnetized plasmas. Finally, we will point out the reasons that show the lack of link between high values of the Hurst coefficient and possible long correlations. The third chapter is dedicated to the second application domain which is relative to the backscattered echo analysis of an immersed target insonified by an ultrasonic plane wave. We will explain how a morphological approach associated to a scale analysis can extract the diameter information
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28

Tenorth, Stefanie. "Adaptive Waveletmethoden zur Approximation von Bildern". Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-B3E7-A.

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29

Lewis, James M. "The continuous wavelet transform: A discrete approximation". Thesis, 1998. http://hdl.handle.net/1911/17192.

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In this thesis, we develop an approximation to the continuous wavelet transform (CWT) which is unique in that it does not require an exact scaling relationship between the levels of the transform, but asymptotically approaches an irrational scaling ratio of 2$\sp{1/n{\sb0}}$ where $n\sb0$ is related to the number of vanishing moments of the original scaling filter. The autocorrelation sequences of the scaling and wavelet filters associated with the Daubechies family of orthonormal compactly supported wavelets are shown to converge to smooth symmetric wavelets which approximate the Deslauriers and Dubuc limiting functions. We show why this transform is superior to a conventional dyadic wavelet transform for the edge detection application, and analyze its performance in denoising applications.
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30

Hsu, Yu-Chia y 許育嘉. "Approximation of Civil Engineering Problems Using Wavelet Neural Network". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/79986624652898373911.

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碩士
國立交通大學
土木工程系
89
Forecasting engineering behavior under unforeseen circumstances is extremely difficult, accounting for why conventional forecasting methods are often inaccurate and inefficient in terms of computational time. Therefore, this study presents a novel stochastic methodology capable of approximating not only engineering behaviors but also structural engineering problems. Approximate models are developed based on the architecture similar to the Artificial Neural Network (ANN). Wavelet Transform is then used as the activation function for the “wavelon” in the Wavelet Neural Network (WNN) instead of “neuron” in the ANN. Next, the forward networks and back-propagation based learning algorithm are adopted to converge the WNNs during training. Additionally, the WNN are used to simulate the engineering behavior within a desired accuracy while depending only on input and output data of a certain engineering problem. Also presented herein are two case studies involving the use of WNNs to predict high-performance concrete (HPC) strength and identify the structural vibration during an earthquake. Simulation results indicate that the proposed model accurately estimates structural behavior to minimize the discrepancy between simulation results and real world problems. Results in this study provide a valuable reference for engineers attempting to solve approximate problems.
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31

Deng, Qi Wen y 鄧起文. "On the theory and applications of periodic wavelet approximation". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/77266494502421558664.

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32

Liu, Yi. "Exact minimax wavelet designs for discrimination /". 2004.

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33

Ehler, Martin [Verfasser]. "The construction of nonseparable wavelet Bi-frames and associated approximation schemes / vorgelegt von Martin Ehler". 2007. http://d-nb.info/986725749/34.

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34

Lindemann, Mathias. "Approximation properties of non-separable wavelet bases with isotropic scaling matrices and their relation to Besov spaces". 2005. http://elib.suub.uni-bremen.de/publications/dissertations/E-Diss1220D̲iss.pdf.

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35

Lindemann, Mathias [Verfasser]. "Approximation properties of non-separable wavelet bases with isotropic scaling matrices and their relation to Besov spaces / von Mathias Lindemann". 2005. http://d-nb.info/975529315/34.

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36

Senake, Ralalage Buddhi Wimarshana. "Identification of breathing cracks in a beam structure with entropy". 2016. http://hdl.handle.net/1993/31748.

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During vibration of engineering structures, fatigue cracks may exhibit repetitive crack open-close breathing like phenomenon. In this thesis, the concept of entropy is employed to quantify this bi-linearity/irregularity of the vibration response so as to evaluate crack severity. To increase the sensitivity of the entropy calculation to detect the damage severity, entropy is merged with wavelet transformation (WT). A cantilever beam with a breathing crack is studied to asses proposed crack identification method under two vibration conditions: sinusoidal and random excitations. Through numerical simulations and experimental testing, the breathing crack identification under sinusoidal excitation is studied first and proven to be effective. Then, the crack identification sensitivity under lower excitation frequencies is further improved by parametric optimization of sample entropy and WT. Finally, breathing crack identification under general random excitations are experimentally studied and realized using frequency response functions (FRFs) as an add-in tool with the proposed crack identification technique.
October 2016
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37

Mitchley, Michael. "Adaptive value function approximation in reinforcement learning using wavelets". Thesis, 2016. http://hdl.handle.net/10539/19298.

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A thesis submitted to the Faculty of Science, School of Computational and Applied Mathematics University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, South Africa, July 2015.
Reinforcement learning agents solve tasks by finding policies that maximise their reward over time. The policy can be found from the value function, which represents the value of each state-action pair. In continuous state spaces, the value function must be approximated. Often, this is done using a fixed linear combination of functions across all dimensions. We introduce and demonstrate the wavelet basis for reinforcement learning, a basis function scheme competitive against state of the art fixed bases. We extend two online adaptive tiling schemes to wavelet functions and show their performance improvement across standard domains. Finally we introduce the Multiscale Adaptive Wavelet Basis (MAWB), a wavelet-based adaptive basis scheme which is dimensionally scalable and insensitive to the initial level of detail. This scheme adaptively grows the basis function set by combining across dimensions, or splitting within a dimension those candidate functions which have a high estimated projection onto the Bellman error. A number of novel measures are used to find this estimate. i
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38

Chang, Yuan-Chang y 張原彰. "Approximating Nonlinear Functions via Neural Networks Based on Discrete Affine Wavelet Transformations". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/02331994373824011044.

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碩士
國立臺灣科技大學
電機工程研究所
82
Based on the discrete affine wavelet transforms, we develop a new "basis" for wavelet networks for better approximating non- smooth nonlinear functions. It is shown that the wavelet formalism supports a theoretical framework, and it is possible to perform both analysis and is of feedforward neural networks. For the purpose ofe wavelet is formulated to characterize a class (L2) of mappings so that it can be implemented by feedforward neuraltworks. Using the spatio-spectral localization properties of wavelets, we can synthesize a feedforward neural network tothe training problem to one of convex optimizationfically, we have developed the algorithm forf high-dimensional nonlinear functions. Finally, the inverted pendulum stabilizing problem is studied via the proposed wavelet neural networks in order to illustrate the usefulness of the developed theoretical framework.
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39

Shuler, Harrey Jeong. "Recovery of the logical gravity field by spherical regularization wavelets approximation and its numerical implementation". Thesis, 2009. http://hdl.handle.net/2152/24349.

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As an alternative to spherical harmonics in modeling the gravity field of the Earth, we built a multiresolution gravity model by employing spherical regularization wavelets in solving the inverse problem, i.e. downward propagation of the gravity signal to the Earth.s surface. Scale discrete Tikhonov spherical regularization scaling function and wavelet packets were used to decompose and reconstruct the signal. We recovered the local gravity anomaly using only localized gravity measurements at the observing satellite.s altitude of 300 km. When the upward continued gravity anomaly to the satellite altitude with a resolution 0.5° was used as simulated measurement inputs, our model could recover the local surface gravity anomaly at a spatial resolution of 1° with an RMS error between 1 and 10 mGal, depending on the topography of the gravity field. Our study of the effect of varying the data volume and altering the maximum degree of Legendre polynomials on the accuracy of the recovered gravity solution suggests that the short wavelength signals and the regions with high magnitude gravity gradients respond more strongly to such changes. When tested with simulated SGG measurements, i.e. the second order radial derivative of the gravity anomaly, at an altitude of 300 km with a 0.7° spatial resolution as input data, our model could obtain the gravity anomaly with an RMS error of 1 ~ 7 mGal at a surface resolution of 0.7° (< 80 km). The study of the impact of measurement noise on the recovered gravity anomaly implies that the solutions from SGG measurements are less susceptible to measurement errors than those recovered from the upward continued gravity anomaly, indicating that the SGG type mission such as GOCE would be an ideal choice for implementing our model. Our simulation results demonstrate the model.s potential in determining the local gravity field at a finer scale than could be achieved through spherical harmonics, i.e. less than 100 km, with excellent performance in edge detection.
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