Página 1 dos resultados de 399 itens digitais encontrados em 0.020 segundos

## ‣ Algoritmos genéticos aplicados à proteção e estimação de harmônicos em sistemas elétricos de potência; Genetic algorithms applied to protection and harmonic estimation in electric power systems

Souza, Silvio Aparecido de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
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## ‣ ON THE USE OF MULTI-HARMONIC LEAST-SQUARES FITTING FOR THD ESTIMATION IN POWER QUALITY ANALYSIS

Ramos, Pedro M.; Janeiro, Fernando M.; Radil, Tomas
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
58.08758%
The quality of the supplied power by electricity utilities is regulated and of concern to the end user. Power quality disturbances include interruptions, sags, swells, transients and harmonic distortion. The instruments used to measure these disturbances have to satisfy minimum requirements set by international standards. In this paper, an analysis of multi-harmonic least-squares fitting algorithms applied to total harmonic distortion (THD) estimation is presented. The results from the different least-squares algorithms are compared with the results from the discrete Fourier transform (DFT) algorithm. The algorithms are assessed in the different testing states required by the standards.

## ‣ Harmonic Analysis of Multipath Index Time Series in GPS Stations

SOUZA,E.M.; ALVES,D.B.M.; SCHUMACHER,F.L.
Tipo: Artigo de Revista Científica Formato: text/html
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The identification of the cyclical and seasonal variations can be very important in time series. In this paper, the aim is to identify the presence of cyclical or seasonal variations in the indices of the multipath effect on continuous GPS (Global Positioning System) stations. Due to the model used to obtain these indices, there should not have cyclical variations in these series, at least due to the multipath effect. In order to identify the presence of cyclical variations in these series, correlograms and Fourier periodograms were analyzed. The Fisher test for seasonality was applied to confirm the presence of statistical significant seasonality. In addition, harmonic models were adjusted to check in which months of the year the cyclical effects are occurring in the multipath indices. The possible causes of these effects are pointed out, which will direct the upcoming investigations, as well as the analysis and correlations of other series. The importance of this analysis is mainly due to the fact that errors in the collected signals of these stations will directly influence the accuracy of the results of the whole community that directly or indirectly uses GPS data.

## ‣ Continuous incidence theory and its applications to number theory and geometry

Taylor, Krystal L. (1982 - ); Iosevich, Alex (1967 - )
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Illustrations:ill.; Number of Pages:viii, 89 leaves
Português
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Thesis (Ph. D.)--University of Rochester. Dept. of Mathematics, 2012.; The main theme of this work is the application of continuous incidence theory to various interesting problems in geometry, geometric measure theory, and analytic number theory. We first prove a fractal analog of the regular value theorem from differential geometry. Next, we use Fourier analytic methods to prove a result concerning the problem of counting integer lattice points in a neighborhood of variable coefficient families of surfaces. By studying Cartesian products of suitably large subsets of Rd restricted by a family of relations, we demonstrate a generalization of the Falconer distance problem, from geometric measure theory, to the case of a certain finite point configuration. Finally, we show that the distance set, induced by a convex centrally symmetric body B with smooth boundary and everywhere non-vanishing curvature, of a sufficiently large subset of Rd, contains an interval. The mapping properties of generalized Radon transforms, which average functions over families of curves and surfaces, are used to prove the continuous incidence theorems which provide a unifying theme throughout. Connections are made between harmonic analysis, geometric measure theory...

## ‣ Spatio-spectral analysis on the unit sphere

Khalid, Zubair
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
Português
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This thesis is focussed on the development of new signal processing techniques to analyse signals defined on the sphere. Analysis and processing of signals defined on the sphere find applications in various fields of science and engineering, such as cosmology, geophysics and medical imaging. The objective to develop new signal processing methods is served by formulating, extending and tailoring existing Euclidean domain signal processing theories in ways that they become suitable for analysis of signals defined on the sphere. The first part of this thesis develops a new type of convolution between two signals on the sphere. This is the first type of convolution on the sphere which is commutative. Two other advantages, in comparison with existing definitions in the literature, are that the new convolution admits anisotropic filters and signals and the domain of the output remains on the sphere. The spectral analysis of the convolution is provided and a fast algorithm for efficient computation of convolution output is developed. The second part of the thesis is focused on the development of signal processing techniques to analyse signals on the sphere in joint spatio-spectral~(spatial-spectral) domain. A transform analogous to short-time Fourier transform(STFT) in time-frequency analysis is formulated for signals defined on the sphere...

## ‣ Harmonic analysis on the Möbius gyrogroup

Ferreira, Milton
Tipo: Artigo de Revista Científica
Português
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In this paper we propose to develop harmonic analysis on the Poincaré ball $B_t^n$, a model of the n-dimensional real hyperbolic space. The Poincaré ball $B_t^n$ is the open ball of the Euclidean n-space $R^n$ with radius $t>0$, centered at the origin of $R^n$ and equipped with Möbius addition, thus forming a Möbius gyrogroup where Möbius addition in the ball plays the role of vector addition in $\mathbb{R}^n$. For any $t>0$ and an arbitrary parameter $\sigma \in R$ we study the $(\sigma,t)$-translation, the $( \sigma,t)$-convolution, the eigenfunctions of the $(\sigma,t)$-Laplace-Beltrami operator, the $(\sigma,t)$-Helgason Fourier transform, its inverse transform and the associated Plancherel's Theorem, which represent counterparts of standard tools, thus, enabling an effective theory of hyperbolic harmonic analysis. Moreover, when $t \rightarrow +\infty$ the resulting hyperbolic harmonic analysis on $B_t^n$ tends to the standard Euclidean harmonic analysis on $R^n$, thus unifying hyperbolic and Euclidean harmonic analysis. As an application we construct diffusive wavelets on $B_t^n$.

## ‣ Harmonic analysis on the Einstein gyrogroup

Ferreira, Milton
Tipo: Artigo de Revista Científica
Português
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In this paper we study harmonic analysis on the Einstein gyrogroup of the open ball of R$^n$, $n \in N,$ centered at the origin and with arbitrary radius $t \in R^+,$ associated to the generalised Laplace-Beltrami operator $$L_{\sigma,t} = \disp \left( 1 - \frac{\|x\|^2}{t^2} \right) \!\left( \Delta - \sum_{i,j=1}^n \frac{x_i x_j}{t^2} \frac{\partial^2}{\partial x_i \partial x_j} - \frac{\kappa}{t^2} \sum_{i=1}^n x_i \frac{\partial}{\partial x_i} + \frac{\kappa(2-\kappa)}{4t^2} \right)$$ where $\kappa=n+\sigma$ and $\sigma \in {\mathbb R}$ is an arbitrary parameter. The generalised harmonic analysis for $L_{\sigma,t}$ gives rise to the $(\sigma,t)$-translation, the $(\sigma,t)$-convolution, the $(\sigma,t)$-spherical Fourier transform, the $(\sigma,t)$-Poisson transform, the $(\sigma,t)$-Helgason Fourier transform, its inverse transform and Plancherel's Theorem. In the limit of large $t,$ $t \rightarrow +\infty,$ the resulting hyperbolic harmonic analysis tends to the standard Euclidean harmonic analysis on $R^n,$ thus unifying hyperbolic and Euclidean harmonic analysis.

## ‣ El problema de tomografía local utilizando wavelets [recurso electrónico] / Wilmar Alberto Díaz Ossa, Harold Vacca González

Díaz Ossa, Wilmar A.; Vacca González, Harold
Tipo: masterThesis; Tesis de Maestría; acceptedVersion
Português
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## ‣ Compresión de imágenes usando wavelets

Puetamán Guerrero, Gloria; Salazar Escobar, Hernán
Tipo: masterThesis; Tesis de Maestría; acceptedVersion
Português
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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.

## ‣ Horizontal Plane HRTF Reproduction Using Continuous Fourier-Bessel Functions

Zhang, Wen; Abhayapala, Thushara; Kennedy, Rodney
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Português
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This paper proposes a method to reproduce the Head Related Transfer Function (HRTF) in the horizontal auditory scene. The method is based on a separable representation which consists of a Fourier Bessel series expansion for the spectral components and a c

## ‣ Connection between the harmonic analysis on the sphere and the harmonic analysis on the one-sheeted hyperboloid: an analytic continuation viewpoint

Bros, J.; Viano, G. A.
Tipo: Artigo de Revista Científica
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In a previous paper $[$B,V-1$]$, an algebra of holomorphic perikernels'' on a complexified hyperboloid $X^{(c)}_{d-1}$ (in $\Bbb C^d)$ has been introduced; each perikernel ${\cal K}$ can be seen as the analytic continuation of a kernel ${\bf K}$ on the unit sphere $\Bbb S^{d-1}$ in an appropriate cut-domain'' , while the jump of ${\cal K}$ across the corresponding cut'' defines a Volterra kernel $K$ (in the sense of J. Faraut $\lbrack$Fa-1$\rbrack$) on the one-sheeted hyperboloid $X_{d-1}$ (in $\Bbb R^d).$ \par In the present paper, we obtain results of harmonic analysis for classes of perikernels which are invariant under the group ${\rm SO}(d,\Bbb C)$ and of moderate growth at infinity. For each perikernel ${\cal K}$ in such a class, the Fourier-Legendre coefficients of the corresponding kernel ${\bf K}$ on $\Bbb S^{d-1}$ admit a carlsonian analytic interpolation $\tilde F(\lambda)$ in a half-plane, which is the spherical Laplace transform''\ of the associated Volterra kernel $K$ on $X_{d-1}.$ Moreover, the composition law ${\cal K }= {\cal K}_1\ast^{( c)}{\cal K}_2$ for perikernels (interpreted in terms of convolutions for the

## ‣ Noncommutative Harmonic Analysis, Sampling Theory and the Duflo Map in 2+1 Quantum Gravity

Freidel, L.; Majid, S.
Tipo: Artigo de Revista Científica
Português
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We show that the $\star$-product for $U(su_2)$, group Fourier transform and effective action arising in [1] in an effective theory for the integer spin Ponzano-Regge quantum gravity model are compatible with the noncommutative bicovariant differential calculus, quantum group Fourier transform and noncommutative scalar field theory previously proposed for 2+1 Euclidean quantum gravity using quantum group methods in [2]. The two are related by a classicalisation map which we introduce. We show, however, that noncommutative spacetime has a richer structure which already sees the half-integer spin information. We argue that the anomalous extra time' dimension seen in the noncommutative geometry should be viewed as the renormalisation group flow visible in the coarse-graining in going from $SU_2$ to $SO_3$. Combining our methods we develop practical tools for noncommutative harmonic analysis for the model including radial quantum delta-functions and Gaussians, the Duflo map and elements of noncommutative sampling theory'. This allows us to understand the bandwidth limitation in 2+1 quantum gravity arising from the bounded $SU_2$ momentum and to interpret the Duflo map as noncommutative compression. Our methods also provide a generalised twist operator for the $\star$-product.; Comment: 53 pages latex...

## ‣ Aspects of Multilinear Harmonic Analysis Related to Transversality

Bennett, Jonathan
Tipo: Artigo de Revista Científica
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The purpose of this article is to survey certain aspects of multilinear harmonic analysis related to notions of transversality. Particular emphasis will be placed on the multilinear restriction theory for the euclidean Fourier transform, multilinear oscillatory integrals, multilinear geometric inequalities, multilinear Radon-like transforms, and the interplay between them.; Comment: 28 pages. Article based on a short course given at the 9th International Conference on Harmonic Analysis and Partial Differential Equations, El Escorial, 2012

## ‣ Harmonic Analysis

Tipo: Artigo de Revista Científica
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This paper describes a method of calculating the transforms, currently obtained via Fourier and reverse Fourier transforms. The method allows calculating efficiently the transforms of a signal having an arbitrary dimension of the digital representation by reducing the transform to a vector-to-circulant matrix multiplying. There is a connection between harmonic equations in rectangular and polar coordinate systems. The connection established here and used to create a very robust iterative algorithm for a conformal mapping calculation. There is also suggested a new ratio (and an efficient way of computing it) of two oscillative signals.; Comment: This new twist in harmonic analysis was primary introduced in Milwaukee's conference http://www.eit-conference.info/papers.asp

## ‣ Operators of Harmonic Analysis in Weighted Spaces with Non-standard Growth

Kokilashvili, V.; Samko, S.
Tipo: Artigo de Revista Científica
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Last years there was increasing an interest to the so called function spaces with non-standard growth, known also as variable exponent Lebesgue spaces. For weighted such spaces on homogeneous spaces, we develop a certain variant of Rubio de Francia's extrapolation theorem. This extrapolation theorem is applied to obtain the boundedness in such spaces of various operators of harmonic analysis, such as maximal and singular operators, potential operators, Fourier multipliers, dominants of partial sums of trigonometric Fourier series and others, in weighted Lebesgue spaces with variable exponent. There are also given their vector-valued analogues.; Comment: 29 pages

## ‣ Harmonic Analysis Lecture Notes

Laugesen, Richard S.
Tipo: Artigo de Revista Científica
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These notes present a first graduate course in harmonic analysis. The first part emphasizes Fourier series, since so many aspects of harmonic analysis arise already in that classical context. The Hilbert transform is treated on the circle, for example, where it is used to prove L^p convergence of Fourier series. Maximal functions and Calderon--Zygmund decompositions are treated in R^d, so that they can be applied again in the second part of the course, where the Fourier transform is studied. The final part of the course treats band limited functions, Poisson summation and uncertainty principles. Distribution functions and interpolation are covered in the Appendices. The references at the beginning of each chapter provide guidance to students who wish to delve more deeply, or roam more widely, in the subject.; Comment: 176 pages

## ‣ Harmonic analysis on quantum tori

Chen, Zeqian; Xu, Quanhua; Yin, Zhi
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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This paper is devoted to the study of harmonic analysis on quantum tori. We consider several summation methods on these tori, including the square Fej\'er means, square and circular Poisson means, and Bochner-Riesz means. We first establish the maximal inequalities for these means, then obtain the corresponding pointwise convergence theorems. In particular, we prove the noncommutative analogue of the classical Stein theorem on Bochner-Riesz means. The second part of the paper deals with Fourier multipliers on quantum tori. We prove that the completely bounded $L_p$ Fourier multipliers on a quantum torus are exactly those on the classical torus of the same dimension. Finally, we present the Littlewood-Paley theory associated with the circular Poisson semigroup on quantum tori. We show that the Hardy spaces in this setting possess the usual properties of Hardy spaces, as one can expect. These include the quantum torus analogue of Fefferman's $\mathrm{H}_1$-BMO duality theorem and interpolation theorems. Our analysis is based on the recent developments of noncommutative martingale/ergodic inequalities and Littlewood-Paley-Stein theory.

## ‣ Harmonic Analysis and Qualitative Uncertainty Principle

King, Ji
Tipo: Artigo de Revista Científica
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This paper investigates the mathematical nature of qualitative uncertainty principle (QUP), which plays an important role in mathematics, physics and engineering fields. Consider a 3-tuple (K, H1, H2) that K: H1 -> H2 is an integral operator. Suppose a signal f in H1, {\Omega}1 and {\Omega}2 are domains on which f, Kf define respectively. Does this signal f vanish if |{\Sigma}(f)|<|{\Omega}1|and|{\Sigma}(Kf)|<|{\Omega}2|? The excesses and deficiencies of integral kernel K({\omega}, t) are found to be greatly related to this general formulation of QUP. The complete point theory of integral kernel is so established to deal with the QUP. This theory addresses the density and linear independence of integral kernels. Some algebraic and geometric properties of complete points are presented. It is shown that the satisfaction of QUP depends on the existence of some complete points. By recognizing complete points of their corresponding integral kernels, the QUP with Fourier transform, Wigner-Ville distribution, Gabor transform and wavelet are studied. It is shown the QUP only holds for good behaved integral operators. An investigation of full violation of QUP shows that L2 space is large for high resolution harmonic analysis. And the invertible linear integral transforms whose kernels are complete in L2 probably lead to the satisfaction of QUP. It indicates the performance limitation of linear integral transforms in harmonic analysis. Two possible ways bypassing uncertainty principle...

## ‣ New 3D Fourier Descriptors for Genus-Zero Mesh Objects

Li, Hongdong; Hartley, Richard
Tipo: Conference paper
Português
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The 2D Fourier Descriptor is an elegant and powerful technique for 2D shape analysis. This paper intends to extend such technique to 3D. Though conceptually natural, such an extension is not trivial in that two critical problems, the spherical parametrization and invariants construction, must be solved. By using a newly developed surface parametrization method-the discrete conformal mapping (DCM) - we propose a 3D Fourier Descriptor (3D-FD) for representing and recognizing arbitrarily-complex genus-zero mesh objects. A new DCM algorithm is suggested which solves the first problem efficiently. We also derive a method to construct a truly complete set of Spherical Harmonic invariants. The 3D-FD descriptors have been tested on different complex mesh objects. Experiment results for shape representation are satisfactory.

## ‣ Comparison of artificial neural networks and harmonic analysis for sea level forecasting (Urias coastal lagoon, Mazatlán, Mexico)

Molino-Minero-Re,Erik; Cardoso-Mohedano,José Gilberto; Ruiz-Fernández,Ana Carolina; Sanchez-Cabeza,Joan-Albert
Fonte: Universidad Autónoma de Baja California, Instituto de Investigaciones Oceanológicas Publicador: Universidad Autónoma de Baja California, Instituto de Investigaciones Oceanológicas
Tipo: Artigo de Revista Científica Formato: text/html