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Search Results: 1 - 10 of 4324 matches for " Luciano Zunino "
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Fractal Dimension of the Cantor Moire Structures
Luciano Zunino,Mario Garavaglia
Physics , 2005,
Abstract: In a recently published paper (J. of Modern Optics 50 (9) (2003) 1477-1486) a qualitative analysis of the moire effect observed by superposing two grids containing Cantor fractal structures was presented. It was shown that the moire effect is sensible to variations in the order of growth, dimension and lacunarity of the Cantor fractal. It was also verified that self-similarity of the original fractal is inherited by the moire pattern. In this work it is shown that these Cantor moire structures are also fractals and the fractal dimension associated with them is theoretically determined and experimentally measured attending the size of rhombuses in the different orders of growth.
Modeling turbulent wave-front phase as a fractional Brownian motion: a new approach
Dario G. Perez,Luciano Zunino,Mario Garavaglia
Physics , 2004, DOI: 10.1364/JOSAA.21.001962
Abstract: This paper introduces a general and new formalism to model the turbulent wave-front phase using fractional Brownian motion processes. Moreover, it extends results to non-Kolmogorov turbulence. In particular, generalized expressions for the Strehl ratio and the angle-of-arrival variance are obtained. These are dependent on the dynamic state of the turbulence.
A fractional Brownian motion model for the turbulent refractive index in lightwave propagation
Dario G. Perez,Luciano Zunino,Mario Garavaglia
Physics , 2003, DOI: 10.1016/j.optcom.2004.08.007
Abstract: It is discussed the limitations of the widely used markovian approximation applied to model the turbulent refractive index in lightwave propagation. It is well-known the index is a passive scalar field. Thus, the actual knowledge about these quantities is used to propose an alternative stochastic process to the markovian approximation: the fractional Brownian motion. This generalizes the former introducing memory; that is, there is correlation along the propagation path.
Permutation Entropy and Its Main Biomedical and Econophysics Applications: A Review
Massimiliano Zanin,Luciano Zunino,Osvaldo A. Rosso,David Papo
Entropy , 2012, DOI: 10.3390/e14081553
Abstract: Entropy is a powerful tool for the analysis of time series, as it allows describing the probability distributions of the possible state of a system, and therefore the information encoded in it. Nevertheless, important information may be codified also in the temporal dynamics, an aspect which is not usually taken into account. The idea of calculating entropy based on permutation patterns (that is, permutations defined by the order relations among values of a time series) has received a lot of attention in the last years, especially for the understanding of complex and chaotic systems. Permutation entropy directly accounts for the temporal information contained in the time series; furthermore, it has the quality of simplicity, robustness and very low computational cost. To celebrate the tenth anniversary of the original work, here we analyze the theoretical foundations of the permutation entropy, as well as the main recent applications to the analysis of economical markets and to the understanding of biomedical systems.
Characterization of Laser Propagation Through Turbulent Media by Quantifiers Based on the Wavelet Transform
Luciano Zunino,Dario G. Perez,Osvaldo A. Rosso,Mario Garavaglia
Physics , 2003, DOI: 10.1142/S0218348X04002471
Abstract: The propagation of a laser beam through turbulent media is modeled as a fractional Brownian motion (fBm). Time series corresponding to the center position of the laser spot (coordinates x and y) after traveling across air in turbulent motion, with different strength, are analyzed by the wavelet theory. Two quantifiers are calculated, the Hurst exponent and the mean Normalized Total Wavelet Entropy. It is verified that both quantifiers gives complementary information about the turbulence state.
Experimental confirmation of long-memory correlations in star-wander data
Luciano Zunino,Damián Gulich,Gustavo Funes,Aziz Ziad
Physics , 2014,
Abstract: In this letter we have analyzed the temporal correlations of the angle-of-arrival fluctuations of stellar images. Experimentally measured data were carefully examined by implementing multifractal detrended fluctuation analysis. This algorithm is able to discriminate the presence of fractal and multifractal structures in recorded time sequences. We have confirmed that turbulence-degraded stellar wavefronts are compatible with a long-memory correlated monofractal process. This experimental result is quite significant for the accurate comprehension and modeling of the atmospheric turbulence effects on the stellar images. It can also be of great utility within the adaptive optics field.
Characterization of laser propagation through turbulent media by quantifiers based on the wavelet transform: dynamic study
Luciano Zunino,Dario G. Perez,Mario Garavaglia,Osvaldo A. Rosso
Physics , 2005, DOI: 10.1016/j.physa.2005.09.054
Abstract: We analyze, within the wavelet theory framework, the wandering over a screen of the centroid of a laser beam after it has propagated through a time-changing laboratory-generated turbulence. Following a previous work (Fractals 12 (2004) 223) two quantifiers are used, the Hurst parameter, $H$, and the Normalized Total Wavelet Entropy, $\text{NTWS}$. The temporal evolution of both quantifiers, obtained from the laser spot data stream is studied and compared. This allows us to extract information of the stochastic process associated to the turbulence dynamics.
Wavelet entropy and fractional Brownian motion time series
Dario G. Perez,Luciano Zunino,Mario Garavaglia,Osvaldo A. Rosso
Physics , 2005, DOI: 10.1016/j.physa.2005.09.060
Abstract: We study the functional link between the Hurst parameter and the Normalized Total Wavelet Entropy when analyzing fractional Brownian motion (fBm) time series--these series are synthetically generated. Both quantifiers are mainly used to identify fractional Brownian motion processes (Fractals 12 (2004) 223). The aim of this work is understand the differences in the information obtained from them, if any.
Complexity-Entropy Causality Plane as a Complexity Measure for Two-Dimensional Patterns
Haroldo V. Ribeiro, Luciano Zunino, Ervin K. Lenzi, Perseu A. Santoro, Renio S. Mendes
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0040689
Abstract: Complexity measures are essential to understand complex systems and there are numerous definitions to analyze one-dimensional data. However, extensions of these approaches to two or higher-dimensional data, such as images, are much less common. Here, we reduce this gap by applying the ideas of the permutation entropy combined with a relative entropic index. We build up a numerical procedure that can be easily implemented to evaluate the complexity of two or higher-dimensional patterns. We work out this method in different scenarios where numerical experiments and empirical data were taken into account. Specifically, we have applied the method to fractal landscapes generated numerically where we compare our measures with the Hurst exponent; liquid crystal textures where nematic-isotropic-nematic phase transitions were properly identified; 12 characteristic textures of liquid crystals where the different values show that the method can distinguish different phases; and Ising surfaces where our method identified the critical temperature and also proved to be stable.
The Quantum-Classical Transition as an Information Flow
Andres M. Kowalski,Maria T. Martin,Luciano Zunino,Angelo Plastino,Montserrat Casas
Entropy , 2010, DOI: 10.3390/e12010148
Abstract: We investigate the classical limit of the semiclassical evolution with reference to a well-known model that represents the interaction between matter and a given field. This is done by recourse to a special statistical quantifier called the “symbolic transfer entropy”. We encounter that the quantum-classical transition gets thereby described as the sign-reversal of the dominating direction of the information flow between classical and quantal variables.
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