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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

Tsallis Entropy Based Velocity Distribution in Open Channel Flows

Luo, Hao 2009 December 1900 (has links)
The Tsallis entropy is applied to derive both 1-D and 2-D velocity distributions in an open channel cross section. These distributions contain a parameter m through which the Tsallis entropy becomes a generalization of the Shannon entropy. Different m parameter values are examined to determine the best value for describing the velocity distribution.Two Lagrangian parameters that are involved in the final form of 1-D velocity distribution equation are determined from observations of mean velocity and the maximum velocity at the water surface. For channels which are not wide and where the maximum velocity does not occur at the water surface, a 2-D velocity distribution is more appropriate. The Tsallis entropy is applied to derive 2-D velocity distributions. A new parameter M is introduced which represents the hydraulic characteristics of the channel. The derived velocity distributions are verified using both field data and experimental data. The advantages are found by comparing with Parandtl-von Karman, power law and Chiu’s velocity distributions.
2

Métodos de análise de imagens aplicados à caracterização tecidual, perfusão miocárdica e inervação autonômica em MRI e SPECT no contexto da doença de Chagas / Methods of image analysis applied to tissue characterization, myocardial perfusion and autonomic innervation in MRI and SPECT in the context of Chagas disease.

Barizon, Gustavo Canavaci 22 May 2015 (has links)
A doença de Chagas possui uma importante relevância clínica, sendo uma das principais causas de mortalidade e morbidade na América Latina. As relações entre a lesão tecidual miocárdica e os defeitos na inervação autonômica na doença de Chagas são pouco conhecidas. Este trabalho descreve o desenvolvimento e aplicação de métodos de segmentação, corregistro e análise de imagens capazes de prover uma análise integrada das lesões teciduais através do imageamento de ressonância magnética (MRI), perfusão miocárdica e inervação autonômica, disponíveis através da tomografia de emissão de fótons (SPECT). O método proposto é baseado na segmentação e corregistro entre as imagens MRI e imagens SPECT usando 99mTc-MIBI e 123I-MIBG. Para realizar a segmentação do miocárdio, foi utilizada a técnica de Contorno Ativo Geodésico. A segmentação de fibrose em imagens MRI foi realizada com base na maximização da entropia de Tsallis. O corregistro não-rígido foi realizado através do método B-Spline. Os resultados de quantificação indicam correlações entre a presença de fibrose, desnervação e isquemia, além de mostrar a presença de regiões de miocárdio vivo, isquêmico e desnervado. Assim, a ferramenta desenvolvida fornece uma análise integrada de informação, permitindo uma melhor compreensão da relação entre o dano ao tecido do miocárdio e defeitos de inervação autonômica causadas pela doença de Chagas. / Chagas disease is of major clinical relevance, and a major cause of morbidity and mortality in Latin America. The relations between the myocardial tissue damage, myocardial perfusion and defects in autonomic innervations are poorly understood. This study proposes the development and application of image analysis methods capable of providing an integrated visualization and analysis of tissue injuries through enhanced magnetic resonance imaging (MRI), autonomic innervations and myocardial perfusion, available through photon emission tomography (SPECT). The proposed method is based on segmentation and registration between MRI images and SPECT images using 99mTc-MIBI and 123I-MIBG. To perform the segmentation of myocardium, we used Geodesic Active Contour. Fibrosis segmentation in MRI images was performed based on the algorithm of maximum Tsallis entropy. Nonrigid registrations was performed based on B-Spline method. The quantification results showed correlations between the presence of fibrosis, denervation and ischemia, as well as showing the regarded presence of regions of healthy myocardium, ischemic and denervated. Thus, the developed tool provides an integrated analysis of information contributing to a better understanding of the relationship between myocardial tissue damage and autonomic innervations injuries caused by Chagas disease.
3

Métodos de análise de imagens aplicados à caracterização tecidual, perfusão miocárdica e inervação autonômica em MRI e SPECT no contexto da doença de Chagas / Methods of image analysis applied to tissue characterization, myocardial perfusion and autonomic innervation in MRI and SPECT in the context of Chagas disease.

Gustavo Canavaci Barizon 22 May 2015 (has links)
A doença de Chagas possui uma importante relevância clínica, sendo uma das principais causas de mortalidade e morbidade na América Latina. As relações entre a lesão tecidual miocárdica e os defeitos na inervação autonômica na doença de Chagas são pouco conhecidas. Este trabalho descreve o desenvolvimento e aplicação de métodos de segmentação, corregistro e análise de imagens capazes de prover uma análise integrada das lesões teciduais através do imageamento de ressonância magnética (MRI), perfusão miocárdica e inervação autonômica, disponíveis através da tomografia de emissão de fótons (SPECT). O método proposto é baseado na segmentação e corregistro entre as imagens MRI e imagens SPECT usando 99mTc-MIBI e 123I-MIBG. Para realizar a segmentação do miocárdio, foi utilizada a técnica de Contorno Ativo Geodésico. A segmentação de fibrose em imagens MRI foi realizada com base na maximização da entropia de Tsallis. O corregistro não-rígido foi realizado através do método B-Spline. Os resultados de quantificação indicam correlações entre a presença de fibrose, desnervação e isquemia, além de mostrar a presença de regiões de miocárdio vivo, isquêmico e desnervado. Assim, a ferramenta desenvolvida fornece uma análise integrada de informação, permitindo uma melhor compreensão da relação entre o dano ao tecido do miocárdio e defeitos de inervação autonômica causadas pela doença de Chagas. / Chagas disease is of major clinical relevance, and a major cause of morbidity and mortality in Latin America. The relations between the myocardial tissue damage, myocardial perfusion and defects in autonomic innervations are poorly understood. This study proposes the development and application of image analysis methods capable of providing an integrated visualization and analysis of tissue injuries through enhanced magnetic resonance imaging (MRI), autonomic innervations and myocardial perfusion, available through photon emission tomography (SPECT). The proposed method is based on segmentation and registration between MRI images and SPECT images using 99mTc-MIBI and 123I-MIBG. To perform the segmentation of myocardium, we used Geodesic Active Contour. Fibrosis segmentation in MRI images was performed based on the algorithm of maximum Tsallis entropy. Nonrigid registrations was performed based on B-Spline method. The quantification results showed correlations between the presence of fibrosis, denervation and ischemia, as well as showing the regarded presence of regions of healthy myocardium, ischemic and denervated. Thus, the developed tool provides an integrated analysis of information contributing to a better understanding of the relationship between myocardial tissue damage and autonomic innervations injuries caused by Chagas disease.
4

Termoestatística do Movimento Superamortecido de Partículas Interagentes / Thermostatistics of Overdamped Motion of Interacting Particles

Silva, George Frederick Tavares da January 2013 (has links)
SILVA, George Frederick Tavares da. Termoestatística do Movimento Superamortecido de Partículas Interagentes. 2013. 129 f. Tese (Doutorado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2013. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-05-05T16:50:05Z No. of bitstreams: 1 2013_tese_gftsilva.pdf: 4464784 bytes, checksum: c215b7122d3e38256ec6c8231ceb3bc9 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2015-05-07T16:59:18Z (GMT) No. of bitstreams: 1 2013_tese_gftsilva.pdf: 4464784 bytes, checksum: c215b7122d3e38256ec6c8231ceb3bc9 (MD5) / Made available in DSpace on 2015-05-07T16:59:18Z (GMT). No. of bitstreams: 1 2013_tese_gftsilva.pdf: 4464784 bytes, checksum: c215b7122d3e38256ec6c8231ceb3bc9 (MD5) Previous issue date: 2013 / The Fokker-Planck equations of nonlinear - EFPNL are differential equations able to describe macroscopic physical and chemical systems that have some type of anomalous diffusion. Examples of applications of scientific and technological importance, we may cite the case of transport in porous media, the growth dynamics of surfaces, diffusion of polymerlike breakable micelles and the dynamics of interacting vortices in type II superconductors. For the latter, it is known that the vortex motion causes power dissipation, and the interaction between them can be represented by a modified Bessel function type. Therefore, in order to model vortices in superconductors, we study the overdamped motion of interacting particles in contact with a thermal reservoir at temperature T, using the same type of interaction for vortices. We show, by means of the nonlinear Fokker-Planck equations formalism, that there is an association of the system under study, in the temperature limit T = 0, with the generalized Tsallis statistics. To prove this direct relation, we use the well-known H theorem and its generalizations, which allows an unambiguous relationship between the generalized entropy function with EFPNL. We show that even for relatively high temperatures, the system should be better represented by the Boltzmann-Gibbs standard statistical, since the distribution function of particles in the steady state, has the form of a Gaussian. In addition to the analytical results for the distribution function, numerical results for overdamped motion of interacting particles were obtained by molecular dynamics with the addition of white noise (additive) thus confirming the theoretical results. / As equações não lineares de Fokker-Planck - EFPNL são equações diferenciais capazes de descrever macroscopicamente sistemas físicos e químicos que apresentam algum tipo de difusão anômala. Como exemplos de aplicações de importância científica e tecnológica, podemos citar o processo de transporte em meios porosos, a dinâmica de crescimento de superfícies, difusão de polímeros do tipo micelas quebráveis e dinâmica de vórtices em supercondutores do tipo II. Para este último, sabe-se que o movimento de vórtices causa dissipação de energia, e a interação entre eles pode ser representada por uma função do tipo Bessel modificada. Portanto, no sentido de modelar vórtices em supercondutores, estudamos o movimento de partículas interagentes em regime de superamortecimento e em contato com um reservatório térmico a temperatura T, utilizando esse mesmo tipo de interação para vórtices. Mostramos então, por meio do formalismo das equações não lineares de Fokker-Planck, que há uma associação do sistema em estudo, no limite de temperatura T=0, com a estatística generalizada de Tsallis. Para comprovar essa relação direta utilizamos o conhecido teorema H e suas generalizações, o qual permite uma relação entre o funcional entrópico generalizado com uma família de EFPNL. Mostramos ainda que para temperaturas relativamente altas, o sistema deve ser melhor representado pela estatística padrão de Boltzmann-Gibbs, pois a função distribuição de partículas, no estado estacionário, tem a forma de uma gaussiana. Além dos resultados analíticos para a função distribuição, resultados numéricos foram obtidos para o movimento superamortecido de partículas interagentes por meio de Dinâmica Molecular com a inclusão de um ruído branco (aditivo), confirmando assim os resultados teóricos.
5

Estudo do fluxo de neutrino solar com o c?digo evolutivo de Toulouse - Geneva

Silva, Flavio Maux Vianna da 24 April 2014 (has links)
Made available in DSpace on 2015-03-03T15:15:30Z (GMT). No. of bitstreams: 1 FlavioMVS_DISSERT.pdf: 786675 bytes, checksum: 15c59d932af3a41769e781bb08d4e3e9 (MD5) Previous issue date: 2014-04-24 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The study of solar neutrinos is very important to a better comprehension of the set of nuclear reactions that occurs inside the Sun and in solar type stars. The ux of neutrinos provides a better comprehension of the stellar structure as a whole. In this dissertation we study the ux of neutrinos in a solar model, addressing the neutrino oscillation, analyzing with the intention of determining and verify the distribution from a statistical point of view, since this ux depends on the particles intrinsic velocity distributions in stellar plasma. The main tool for this analysis was the Toulouse-Geneva Stellar Evolution Code, or TGEC, which allow us to obtain the neutrino ux values per reaction and per layer inside the Sun, allowing us to compare the observational results for the neutrino ux detected on experiments based on Cl37 (Homestake), Ga71 (SAGE, Gallex/GNO) and water (SNO). Our results show the nal distribution for neutrino ux as a function of the depth using the coordinates of mass and radius. The dissertation also shows that the equations for this ux are present in TGEC. / O estudo do neutrino solar ? muito importante para uma melhor compreens?o sobre o conjunto de rea??es nucleares que ocorrem no interior do Sol e nas estrelas do tipo solar. O fluxo de neutrino tamb?m proporciona uma melhor compreens?o da estrutura estelar como um todo. Nesta disserta??o, estudamos o fluxo de neutrinos em um modelo Solar, abordando a oscila??o de neutrinos, analisando com intuito de determinar e verificar a distribui??o do fluxo do ponto de vista estat?stico, uma vez que este fluxo depende das distribui??es intr?nsecas de velocidades das part?culas no plasma estelar. A principal ferramenta desta analise foi o c?digo de evolu??o estelar Toulouse-Geneva (Stellar Evolution Code, ou TGEC), o qual permite-nos obter os valores do fluxo de neutrino por rea??o e por camada no interior do Sol, e assim podemos comparar com os resultados observacionais para o fluxo de neutrino detectado a partir de experimentos com base no Cl37 (Homestake), Ga71 (SAGE, Gallex/GNO) e agua (SNO). Nosso resultado mostra a distribui??o final para o fluxo de neutrinos em fun??o da profundidade em coordenadas de massa e raio. A referida disserta??o apresenta ainda as equa??es relacionadas com este fluxo que est?o presentes no TGEC
6

Inversion d'un système par krigeage : application à la synthèse des catalyseurs à haut débit

Bettinger, Régis 22 October 2009 (has links) (PDF)
Ce travail concerne la modélisation du processus de synthèse (construction) de supports de catalyseurs obtenus par réaction silice-alumine. La synthèse est caractérisée par 5 variables d'entrée et 2 variables de sortie (la surface spécifique et le volume mesoporeux du support de catalyseur). Chaque combinaison des valeurs de sortie ayant une application potentielle, on voudrait savoir en synthétiser le plus grand nombre, c'est-a-dire connaitre les variables d'entrée permettant de construire un catalyseur ayant une surface et un volume donnes quelconques. Les limites atteignables des deux sorties du système sont inconnues. Ne disposant pas de suffisamment d'essais pour pouvoir espérer construire un modèle fiable sur l'ensemble du domaine de variation des variables d'entrée, nous choisissons une approche par plans d'expérience séquentiels avec modélisation par krigeage, permettant d'éviter une trop grande dispersion des variables d'entrée tout en assurant une exploration du domaine accessible pour les variables de sortie. Les essais sont choisis séquentiellement en se servant de l'information apportée par les essais précédents et traitée par le modèle de krigeage. Cette façon de procéder est a priori plus efficace que celle consistant a utiliser un plan d'expériences fixe au départ et comprenant la totalité des essais disponibles. Des critères d'ajout séquentiel de points d'expérimentation (définissant les valeurs des variables d'entrée) sont proposes, qui favorisent une forte dispersion des sorties correspondantes et prennent en compte les incertitudes associées aux prédictions par krigeage. Enfin, les critères retenus, l'un à base de distance et l'autre à base d'entropie, sont testes sur des données simulées afin de vérifier la bonne répartition finale des valeurs des réponses. Des rappels sur la modélisation par processus gaussien, la régression/interpolation par krigeage et ses liens avec les méthodes de type splines et SVM, ainsi que la planification d'expériences sont présentes en essayant de concilier rigueur et clarté.
7

ENTROPY OF ELECTROENCEPHALOGRAM (EEG) SIGNALS CHANGES WITH SLEEP STATE

Mathew, Blesy Anu 01 January 2006 (has links)
We hypothesized that temporal features of EEG are altered in sleep apnea subjects comparedto normal subjects. The initial aim was to develop a measure to discriminate sleep stages innormals. The longer-term goal was to apply these methods to identify differences in EEGactivity in sleep apnea subjects from normals. We analyzed the C3A2 EEG and anelectrooculogram (EOG) recorded from 9 normal adults awake and in rapid eye movement(REM) and non-REM sleep. The EEG signals were filtered to remove EOG contamination. Twomeasures of the irregularity of EEG signals, Sample Entropy (SpEn) and Tsallis Entropy, wereevaluated for their ability to discriminate sleep stages. SpEn changes with sleep state, beinglargest in Wake. Stage 3/4 had the smallest SpEn (0.57??0.11) normalized to Wake values,followed by Stage 2 (0.72??0.09), REM (0.75??0.1) and Stage 1 (0.89??0.05). This pattern wasconsistent in all the polysomnogram records analyzed. Similar pattern was observed in leadO1A2 as well. We conclude that SpEn may be useful as part of a montage for assessing sleepstate. We analyzed data from sleep apnea subjects having obstructive and central apnea eventsand have made some preliminary observations; the SpEn values were more similar across sleepstages and also high correlation with oxygen saturation was observed.
8

Métodos estatísticos para classificação de massas em mamografias

Alcântara, Rafaela Souza 14 December 2015 (has links)
Submitted by Diogo Barreiros (diogo.barreiros@ufba.br) on 2017-06-02T17:34:16Z No. of bitstreams: 1 template-msc.pdf: 7779839 bytes, checksum: 3727636ba3903e44e4de17aefcf68481 (MD5) / Approved for entry into archive by Uillis de Assis Santos (uillis.assis@ufba.br) on 2017-06-07T18:25:00Z (GMT) No. of bitstreams: 1 template-msc.pdf: 7779839 bytes, checksum: 3727636ba3903e44e4de17aefcf68481 (MD5) / Made available in DSpace on 2017-06-07T18:25:00Z (GMT). No. of bitstreams: 1 template-msc.pdf: 7779839 bytes, checksum: 3727636ba3903e44e4de17aefcf68481 (MD5) / O câncer de mama é considerado a segunda neoplasia responsável por mais mortes em mulheres no mundo. Para a prevenção e redução desse número, a mamografia de screening é o exame mais utilizado para detecção de nódulos em estágios iniciais. A partir desse exame, o radiologista pode analisar as anomalias e a partir disso desenvolver um diagnóstico. Para aumentar a acurácia dos resultados obtidos a partir das imagens de mamografia, estão sendo desenvolvidos softwares de auxílio à diagnóstico computer-aided diagnosis capazes de automatizar o processo de análise da imagem e extrair informações relevantes para a classificação dos nódulos presentes nos exames. Esse trabalho apresenta duas novas metodologias para extração de features e classificação de massas e não-massas,s a partir da Entropia de Tsallis extraídas através da matriz de co-ocorrência (GLCM) e através da matriz de valores singulares (SVD) da imagem de mamografia, alcançando uma acurácia máxima de 91.3% / Breast cancer has been considered the second neoplasia responsible for women’s death in the last few years. To prevent and to reduce these statistics, screening mammography has been used as the most important exam to detect nodules on initial stages. From this exam, the radiologist can analyze anomalies and to provide some diagnostic. To improve the results accuracy rate from mammography images, computer-aided diagnosis softwares have been developed with the ability to automate the image analyses processing and to extract relevant information for mass classifications on screening exams. This work presents two new methodologies for feature extraction for mass and non-mass classification, based on Tsallis entropy calculated from gray level cooccurrence matrix (GLCM) and from singular value decomposition (SVD), reaching the best accuracy rate of 91.3%.
9

Region of Interest Based Compression of Grayscale Images

Budihal Prasad, Adhokshaja Achar 01 January 2015 (has links)
Image compression based on Region of Interest (ROI) has been one of the hot topics of interest in image processing. There is not a single widely accepted method for detecting the ROI automatically form an image. To reduce the transmission bandwidth and storage space requirements of gray scale images, an algorithm is suggested for detecting the ROI automatically based on Tsallis entropy method. Tsallis entropy method is used to segment the image into two segments, the ROI and the background. These two segments can then be compressed at different rates, to avoid losing information in the ROI while achieving a good compression. Different approaches of compression based on wavelets and use of various compression methods are also discussed.
10

Entropické modely datového provozu / Entropic models of data traffic

Blažek, Petr January 2015 (has links)
This thesis solves possibility of using entropy for anomaly detection in data communication and especially for security attacks. The main advantage of using entropy is ability to identify unknown attacks because entropy detects changes in network traffic but not the content as existing methods. In this work was tested the suitability of different models entropy (Shannon, Renyi, Tsallis). Also been tested the effect of Renyi and Tsallis parameter on resulting entropy. From the resulting values, I found that all tested entropy achieve good result in the identification of anomalies in network traffic.

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