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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Uma origem multifractal para a turbul?ncia no meio interestelar / A multifractal origin for the turbulence in the interstellar medium

Moraes J?nior, Pedro Ricardo Vasconcelos de 13 April 2017 (has links)
Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-02-15T11:38:42Z No. of bitstreams: 1 PedroRicardoVasconcelosDeMoraesJunior_DISSERT.pdf: 2981903 bytes, checksum: d8c6074e1bcaf9fefb3aac688a2d7012 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-02-16T13:03:43Z (GMT) No. of bitstreams: 1 PedroRicardoVasconcelosDeMoraesJunior_DISSERT.pdf: 2981903 bytes, checksum: d8c6074e1bcaf9fefb3aac688a2d7012 (MD5) / Made available in DSpace on 2018-02-16T13:03:43Z (GMT). No. of bitstreams: 1 PedroRicardoVasconcelosDeMoraesJunior_DISSERT.pdf: 2981903 bytes, checksum: d8c6074e1bcaf9fefb3aac688a2d7012 (MD5) Previous issue date: 2017-04-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Nos ?ltimos anos os estudos sobre sistemas complexos vem ganhando for?a e ferramentas para poder simul?-lo e verificar seu comportamento estatisticamente. Grande parte disso se deve a muitos sistemas que passaram a se comportar de forma n?o-linear e dissipativo. Para esses casos, as geometrias convencionais como a euclidiana, n?o ? poss?vel para a proeza de explica-lo, com isso a geometria dos fractais surgiu como alternativa importante para o trato deste meio, sendo leis de escalas (pot?ncia) se aplicando muito bem para esse sistema sendo exemplificado em forma de s?ries temporais e superf?cies (geometrias bidimensionais e tridimensionais). Assim, uma variedade de m?todos foi contabilizada para esse tratamento, entre eles est?o a an?lise via expoente de Hurst e an?lise multifractal. Nosso trabalho tem como objetivo propor um novo m?todo para analisar multifractalmente imagens bidimensionais, sendo essas imagens advindas de simula??es de nuvens do meio interestelar. Primeiro passo foi gerar 12 simula??es MHD em que se diferenciavam a partir de valores de press?o e campo magn?tico, depois gerada a imagem em 2D que ? aplicado sobre elas o m?todo de tratamento multifractal MFDMA. Com a aplica??o deste m?todo ? poss?vel avaliar as imagens atrav?s de um quadro contendo os expoentes de an?lise multifractal, sendo poss?vel avaliar o comportamento de escala nas imagens e verificar o grau de complexidade, e ainda descobrir quais as fontes causadoras da multifractalidade, usando dois m?todos de an?lise multifractal que s?o embaralhamento dos dados da imagem original e substitui??o dos dados originas a partir da transformada de Fourier. Os resultados mostraram que para todas as imagens o m?todo de embaralhamento consegue destruir a fonte de multifractalidade da imagem original e ainda se comportar como um monofractal, enquanto o outro m?todo ? ineficaz, concluindo que os fatores n?o -lineares n?o est?o inclu?dos dentre as fontes e indicando como fonte de multifractalidade as correla??es de longo alcance. Outro resultado importante ? a rela??o do grau de multifractalidade ?h com a press?o. / In recent years studies on complex systems have been gaining strength and tools to be able to simulate and verify their behavior statistically.Much of this is due to many systems that have come to behave in a nonlinear and dissipative way.For these cases conventional geometries such as Euclidean is not possible for the prowess of explaining it, with this the geometry of the fractals emerged as an important alternative for the treatment of this medium,being laws of scales (power) applying very well for this system being exemplified in the form of time series and surfaces (two-dimensional and three-dimensional geometries).Thus a variety of methods were counted for this treatment, among them are the analysis via exponent of Hurst and multifractal analysis.Our work aims to propose a new method to analyze two-dimensional images multifractally, being these images coming from clouds simulations of the interstellar medium.First step was to generate 12 MHD simulations in which they differed from values of pressure and magnetic field, then generated the 2D image that is applied on them the multifractal MFDMA treatment method.With the application of this method it is possible to evaluate the images through a frame containing the exponents of multifractal analysis, being possible to evaluate the scale behavior in the images and verify the degree of complexity, and to find out which sources cause multifractality,using two methods of multifractal analysis that are shuffling the original image data and replacing the original data from the Fourier transform.The results show that for all images the shuffling method can destroy the multifractal source of the original image and still behave like a monofractal,While the other method is ineffective, concluding that nonlinear factors are not included among the sources and indicating as a source of multifractality the long-range correlations. Other important results are the relation of degree of multifractity ?h with pressure, sonic number of Mach and number of Alfv?n.

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