Página 3 dos resultados de 435 itens digitais encontrados em 0.010 segundos

## ‣ Análise de multirresolução baseada em polinômio potência de Sigmóide - Wavelet

Pilastri, André Luiz
Português
Relevância na Pesquisa
37.542107%

## ‣ Análise multiescala de séries temporais do efeito da cintilação ionosférica nos sinais de satélite GPS a partir de wavelets não decimadas

Brassarote, Gabriela de Oliveira Nascimento
Tipo: Dissertação de Mestrado Formato: 84 p. : il.
Português
Relevância na Pesquisa
37.542107%

## ‣ Impacto da utilização de tecnicas de lifting explorando diferença entre ferramentas interpretada e compilada na velocidade computacional da codificação wavelet de imagens estaticas; Impact of using lifting techniques to explore the differences between interpreted and compiled tools in the computational speed of wavelet static image coding

Lucas de Oliveira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
37.542107%
O campo de análise e compressão de imagens tem recebido especial atenção da comunidade científica recentemente por abranger os principais sistemas de TV digital, comunicações via satélite e comunicações móveis. Neste contexto, as Transformadas Wavelets Discretas (TWD) surgem como uma ferramenta poderosa e suas inúmeras vantagens permitiram sua inserção em importantes padrões tais como JPEG2000, MPEG4 e MPEG7. O método lifting realiza a TWD sub-amostrando o sinal antes do processo de filtragem, implicando em rápido processamento por fazer uso das similaridades entre filtros passa-alta e passa-baixa, acelerando o cálculo dos coeficientes. Na literatura, ganhos aritméticos teóricos de diferentes proporções foram obtidos sobre o método tradicional, destacando-se os trabalhos de Daubechies e Sweldens e de Reichel. O objetivo desta pesquisa consiste em estender esta discussão de resultados teóricos quando implementados através de ferramentas, interpretada e compilada, focando no tempo de processamento necessário para a realização (decomposição e reconstrução) de diferentes imagens estáticas empregando wavelets pertencentes às famílias de Daubechies, Symlets e Biortogonais. Medidas de PSNR foram utilizadas de forma a corroborar a perfeita implementação do lifting...

## ‣ Análise de sinais de ECG com o uso de wavelets e redes neurais em FPGA; ECG signal analysis with wavelets and neural networks in FPGA

Klaus Raizer
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
37.542107%
Este trabalho apresenta a implementação de um sistema de análise de sinais de ECGs (eletrocardiogramas) embarcado em FPGA (field programmable gate array), capaz de classificar cardiopatias. A análise de ECGs é de grande importância devido a sua natureza potencialmente não-invasiva, baixo custo e alta eficiência na identificação de patologias cardíacas. Visto que um sinal de ECG pode ser composto por horas de gravação da atividade cardíaca, uma abordagem computacional para a sua análise torna-se um instrumento valioso para a redução do tempo e dos erros de diagnóstico. No presente trabalho uma série de características são extraídas dos pulsos de ECG, que foram obtidos a partir dos sinais do banco de dados MIT-BIH, através da decomposição por transformada wavelet discreta. Essas características foram então utilizadas para treinar uma Rede Neural do tipo feedforward para discernir pulsos normais de pulsos anômalos. Uma versão da rede neural foi então programada em VHDL e em seguida implementada em um Kit da Xilinx modelo Spartan 3E para a classificação pulso a pulso dos sinais de ECG. As implicações dessa arquitetura são discutidas e os resultados são apresentados; this work presents an implementation of an embedded ECG (electrocardiogram) signal analysis system using FPGA (field programmable gate array)...

## ‣ Análise do funcionamento de motores diesel utilizando wavelets; Diesel engines running analysis using wavelets

Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
37.542107%

## ‣ Esquemas de aproximação em multinível e aplicações; Multilevel approximation schemes and applications

Douglas Azevedo Castro
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Relevância na Pesquisa
37.542107%

## ‣ Wavelets and economics

Soares, M. J.; Conraria, Luís Aguiar
Fonte: International Center for Mathematics Publicador: International Center for Mathematics
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.542107%
The use of wavelet analysis is very common in a large variety of disciplines, such as signal and image processing, quantum mechanics, geophysics, medicine, biology, etc. In economics, however, wavelets are still a mysterious, but colorful, tool for time-series analysis. The pioneering work of Ramsey and Lampart [26] is unknown to the majority of economists. Among the exceptions to this rule, one can point to [4], [14], and [12]. See [6], for a recent survey of wavelet applications to economic data. Probably, wavelets are not more popular among economists, because wavelet multivariate analysis is still incipient. Recently, however, Gallegati [11] — using the maximum overlap discrete wavelet transform — and Crowley and Mayes [5] and Aguiar-Conraria and Soares [1] — using the continuous wavelet transform — showed how the cross-wavelet analysis could be fruitfully used to uncover time-frequency interactions between two economic timeseries. Still, most surely, wavelets will not become very fashionable in economics until a concept analogous to the spectral partial-coherence is developed. On this regard, the proficient reader may be interested in our most recent working-paper [2]. We present a brief and self-contained introduction to the wavelet tools used...

## ‣ Compresión de imágenes usando wavelets

Puetamán Guerrero, Gloria; Salazar Escobar, Hernán
Tipo: masterThesis; Tesis de Maestría; acceptedVersion
Português
Relevância na Pesquisa
37.542107%
Las wavelets y el análisis de multirresolución constituyen una potente herramienta para afrontar problemas fundamentales en el tratamiento de señales. Entre ellos se encuentran la reducción del ruido, la compresión de señales (de mucha importancia tanto en la transmisión de grandes cantidades de datos como en su almacenamiento) o la detección de determinados patrones o irregularidades locales en ciertos tipos de señales (electrocardiogramas, huellas digitales, vibraciones de motores, defectos de soldadura entre placas de acero, entre otras) (ver, p.e., [1], [7], [9], [11], [12], [18], [20], [23], [24], [30], [42], [47]). Esta moderna teoría ha experimentado un gran desarrollo en las dos últimas décadas mostrándose muy eficiente donde otras técnicas, como por ejemplo, la transformada rápida de Fourier no resultaban satisfactorias.; v, 95 p.; Contenido parcial: Introducción a las wavelets -- Compresión de imágenes usando wavelets -- El problema de la compresión de imágenes -- Manual del usuario y anexos.

## ‣ Multiscale Community Mining in Networks Using Spectral Graph Wavelets

Tremblay, Nicolas; Borgnat, Pierre
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.542107%
For data represented by networks, the community structure of the underlying graph is of great interest. A classical clustering problem is to uncover the overall best'' partition of nodes in communities. Here, a more elaborate description is proposed in which community structures are identified at different scales. To this end, we take advantage of the local and scale-dependent information encoded in graph wavelets. After new developments for the practical use of graph wavelets, studying proper scale boundaries and parameters and introducing scaling functions, we propose a method to mine for communities in complex networks in a scale-dependent manner. It relies on classifying nodes according to their wavelets or scaling functions, using a scale-dependent modularity function. An example on a graph benchmark having hierarchical communities shows that we estimate successfully its multiscale structure.; Comment: Proceedings of the European Signal Processing Conference (EUSIPCO 2013)

## ‣ Electromagnetic Wavelets as Hertzian Pulsed Beams in Complex Spacetime

Kaiser, Gerald
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.542107%
Electromagnetic wavelets are a family of 3x3 matrix fields W_z(x') parameterized by complex spacetime points z=x+iy with y timelike. They are translates of a \sl basic \rm wavelet W(z) holomorphic in the future-oriented union T of the forward and backward tubes. Applied to a complex polarization vector p (representing electric and magnetic dipole moments), W(z) gives an anti-selfdual solution W(z)p of Maxwell's equations derived from a selfdual Hertz potential Z(z)=-iS(z)p, where S is the \sl Synge function \rm acting as a Whittaker-like scalar Hertz potential. Resolutions of unity exist giving representations of sourceless electromagnetic fields as superpositions of wavelets. With the choice of a branch cut, S(z) splits into a difference of retarded and advanced \sl pulsed beams \rm whose limits as y\to 0 give the propagators of the wave equation. This yields a similar splitting of the wavelets and leads to their complete physical interpretation as EM pulsed beams absorbed and emitted by a \sl disk source \rm D(y) representing the branch cut. The choice of y determines the beam's orientation, collimation and duration, giving beams as sharp and pulses as short as desired. The sources are computed as spacetime distributions of electric and magnetic dipoles supported on D(y). The wavelet representation of sourceless electromagnetic fields now splits into representations with advanced and retarded sources. These representations are the electromagnetic counterpart of relativistic coherent-state representations previously derived for massive Klein-Gordon and Dirac particles.; Comment: 16 pages...

## ‣ Elliptic-cylindrical Wavelets: The Mathieu Wavelets

Lira, M. M. S.; de Oliveira, H. M.; Cintra, R. J.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.542107%
This note introduces a new family of wavelets and a multiresolution analysis, which exploits the relationship between analysing filters and Floquet's solution of Mathieu differential equations. The transfer function of both the detail and the smoothing filter is related to the solution of a Mathieu equation of odd characteristic exponent. The number of notches of these filters can be easily designed. Wavelets derived by this method have potential application in the fields of Optics and Electromagnetism.; Comment: 10 pages, 2 figures

## ‣ Construction of some types wavelets with coefficient of scaling N

Smolentsev, N. K.; Podkur, P. N.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.542107%
In this paper it is shown, that B-splines are scaling functions for any natural N. For any natural N construction of Haar wavelets, Kotelnikov-Shannon wavelets, nonorthogonal wavelets based on B-splines is given. Examples of construction of filters of N-channel decomposition of signal and filters of reconstruction based on B-splines are given; Comment: LaTeX2e, 19 pages

## ‣ Wavelets: mathematics and applications

Dremin, I. M.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.542107%
The notion of wavelets is defined. It is briefly described {\it what} are wavelets, {\it how} to use them, {\it when} we do need them, {\it why} they are preferred and {\it where} they have been applied. Then one proceeds to the multiresolution analysis and fast wavelet transform as a standard procedure for dealing with discrete wavelets. It is shown which specific features of signals (functions) can be revealed by this analysis, but can not be found by other methods (e.g., by the Fourier expansion). Finally, some examples of practical application are given (in particular, to analysis of multiparticle production}. Rigorous proofs of mathematical statements are omitted, and the reader is referred to the corresponding literature.; Comment: 16 pages, 5 figures, Latex, Phys. Atom. Nucl

## ‣ Decay properties of Riesz transforms and steerable wavelets

Ward, John Paul; Chaudhury, Kunal Narayan; Unser, Michael
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.542107%
The Riesz transform is a natural multi-dimensional extension of the Hilbert transform, and it has been the object of study for many years due to its nice mathematical properties. More recently, the Riesz transform and its variants have been used to construct complex wavelets and steerable wavelet frames in higher dimensions. The flip side of this approach, however, is that the Riesz transform of a wavelet often has slow decay. One can nevertheless overcome this problem by requiring the original wavelet to have sufficient smoothness, decay, and vanishing moments. In this paper, we derive necessary conditions in terms of these three properties that guarantee the decay of the Riesz transform and its variants, and as an application, we show how the decay of the popular Simoncelli wavelets can be improved by appropriately modifying their Fourier transforms. By applying the Riesz transform to these new wavelets, we obtain steerable frames with rapid decay.; Comment: 21 pages

## ‣ Nearly tight frames of spin wavelets on the sphere

Geller, D.; Mayeli, A.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.580688%
We show that the spin wavelets on the sphere $S^2$, which were constructed by the first author and Marinucci in an earlier article, can be chosen so as to form a nearly tight frame. These spin wavelets can be applied to the study of the polarization of cosmic microwave background radiation. For certain of these frames, there is a positive $C$ such that each frame element at scale $a^j$ is supported in a geodesic ball of radius $Ca^j$.

## ‣ Probability measures on solenoids corresponding to fractal wavelets

Baggett, Lawrence W.; Merrill, Kathy D.; Packer, Judith A.; Ramsay, Arlan B.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.580688%
The measure on generalized solenoids constructed using filters by Dutkay and Jorgensen is analyzed further by writing the solenoid as the product of a torus and a Cantor set. Using this decomposition, key differences are revealed between solenoid measures associated with classical filters in $\mathbb R^d$ and those associated with filters on inflated fractal sets. In particular, it is shown that the classical case produces atomic fiber measures, and as a result supports both suitably defined solenoid MSF wavelets and systems of imprimitivity for the corresponding wavelet representation of the generalized Baumslag-Solitar group. In contrast, the fiber measures for filters on inflated fractal spaces cannot be atomic, and thus can support neither MSF wavelets nor systems of imprimitivity.; Comment: 27 pages

## ‣ Semi-orthogonal Parseval wavelets associated to GMRAs on local fields of positive characteristics

Shukla, Niraj K.; Maury, Saurabh Chandra; Mittal, Shiva
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.542107%
In this article we establish theory of semi-orthogonal Parseval wavelets associated to generalized multiresolution analysis (GMRA) for the local field of positive characteristics (LFPC). By employing the properties of translation invariant spaces on the core space of GMRA we obtain a characterization of semi-orthogonal Parseval wavelets in terms of consistency equation for LFPC. As a consequence, we obtain a characterization of an orthonormal (multi)wavelet to be associated with an MRA in terms of multiplicity function as well as dimension function of a (multi)wavelet. Further, we provide characterizations of Parseval scaling functions, scaling sets and bandlimited wavelets together with a Shannon type multiwavelet for LFPC.; Comment: 21 pages

## ‣ Construction of Parseval wavelets from redundant filter systems

Baggett, L. W.; Jorgensen, P. E. T.; Merrill, K. D.; Packer, J. A.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.580688%
We consider wavelets in L^2(R^d) which have generalized multiresolutions. This means that the initial resolution subspace V_0 in L^2(R^d) is not singly generated. As a result, the representation of the integer lattice Z^d restricted to V_0 has a nontrivial multiplicity function. We show how the corresponding analysis and synthesis for these wavelets can be understood in terms of unitary-matrix-valued functions on a torus acting on a certain vector bundle. Specifically, we show how the wavelet functions on R^d can be constructed directly from the generalized wavelet filters.; Comment: 34 pages, AMS-LaTeX ("amsproc" document class) v2 changes minor typos in Sections 1 and 4, v3 adds a number of references on GMRA theory and wavelet multiplicity analysis; v4 adds material on pages 2, 3, 5 and 10, and two more references

## ‣ Non-equispaced B-spline wavelets

Jansen, Maarten
Tipo: Artigo de Revista Científica