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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.
721

Εύρεση γεωμετρικών χαρακτηριστικών ερυθρών αιμοσφαιρίων από εικόνες σκεδασμένου φωτός

Τρικοίλης, Ιωάννης 20 September 2010 (has links)
Στην παρούσα διπλωματική εργασία θα γίνει μελέτη και εφαρμογή μεθόδων επίλυσης του προβλήματος αναγνώρισης γεωμετρικών χαρακτηριστικών ανθρώπινων ερυθρών αιμοσφαιρίων από προσομοιωμένες εικόνες σκέδασης ΗΜ ακτινοβολίας ενός He-Ne laser 632.8 μm. Στο πρώτο κεφάλαιο γίνεται μια εισαγωγή στις ιδιότητες και τα χαρακτηριστικά του ερυθροκυττάρου καθώς, επίσης, παρουσιάζονται διάφορες ανωμαλίες των ερυθροκυττάρων και οι μέχρι στιγμής χρησιμοποιούμενοι τρόποι ανίχνευσής των. Στο δεύτερο κεφάλαιο της εργασίας γίνεται μια εισαγωγή στις ιδιότητες της ΗΜ ακτινοβολίας, περιγράφεται το φαινόμενο της σκέδασης και παρουσιάζεται το ευθύ πρόβλημα σκέδασης ΗΜ ακτινοβολίας ανθρώπινων ερυθροκυττάρων. Το τρίτο κεφάλαιο αποτελείται από δύο μέρη. Στο πρώτο μέρος γίνεται εκτενής ανάλυση της θεωρίας των τεχνητών νευρωνικών δικτύων και περιγράφονται τα νευρωνικά δίκτυα ακτινικών συναρτήσεων RBF. Στη συνέχεια, αναφέρονται οι μέθοδοι εξαγωγής παραμέτρων και, πιο συγκεκριμένα, δίνεται το θεωρητικό και μαθηματικό υπόβαθρο των μεθόδων που χρησιμοποιήθηκαν οι οποίες είναι ο αλογόριθμος Singular Value Decomposition (SVD), o Angular Radial μετασχηματισμός (ART) και φίλτρα Gabor. Στο δεύτερο μέρος περιγράφεται η επίλυση του αντίστροφου προβλήματος σκέδασης. Παρουσιάζεται η μεθοδολογία της διαδικασίας επίλυσης όπου εφαρμόστηκαν ο αλογόριθμος συμπίεσης εικόνας SVD, o περιγραφέας σχήματος ART και ο περιγραφέας υφής με φίλτρα Gabor για την εύρεση των γεωμετρικών χαρακτηριστικών και νευρωνικό δίκτυο ακτινικών συναρτήσεων RBF για την ταξινόμηση των ερυθροκυττάρων. Στο τέταρτο και τελευταίο κεφάλαιο γίνεται δοκιμή και αξιολόγηση της μεθόδου και συνοψίζονται τα αποτελέσματα και τα συμπεράσματα που εξήχθησαν κατά τη διάρκεια της εκπόνησης αυτής της διπλωματικής. / In this thesis we study and implement methods of estimating the geometrical features of the human red blood cell from a set of simulated light scattering images produced by a He-Ne laser beam at 632.8 μm. Ιn first chapter an introduction to the properties and the characteristics of red blood cells are presented. Furthermore, we describe various abnormalities of erythrocytes and the until now used ways of detection. In second chapter the properties of electromagnetic radiation and the light scattering problem of EM radiation from human erythrocytes are presented. The third chapter consists of two parts. In first part we analyse the theory of neural networks and we describe the radial basis function neural network. Then, we describe the theoritical and mathematical background of the methods that we use for feature extraction which are Singular Value Decomposition (SVD), Angular Radial Transform and Gabor filters. In second part the solution of the inverse problem of light scattering is described. We present the methodology of the solution process in which we implement a Singular Value Decomposition approach, a shape descriptor with Angular Radial Transform and a homogenous texture descriptor which uses Gabor filters for the estimation of the geometrical characteristics and a RBF neural network for the classification of the erythrocytes. In the forth and last chapter the described methods are evaluated and we summarise the experimental results and conclusions that were extracted from this thesis.
722

Dynamics of few-cluster systems.

Lekala, Mantile Leslie 30 November 2004 (has links)
The three-body bound state problem is considered using configuration-space Faddeev equations within the framework of the total-angular-momentum representation. Different three-body systems are considered, the main concern of the investigation being the i) calculation of binding energies for weakly bounded trimers, ii) handling of systems with a plethora of states, iii) importance of three-body forces in trimers, and iv) the development of a numerical technique for reliably handling three-dimensional integrodifferential equations. In this respect we considered the three-body nuclear problem, the 4He trimer, and the Ozone (16 0 3 3) system. In practice, we solve the three-dimensional equations using the orthogonal collocation method with triquintic Hermite splines. The resulting eigenvalue equation is handled using the explicitly Restarted Arnoldi Method in conjunction with the Chebyshev polynomials to improve convergence. To further facilitate convergence, the grid knots are distributed quadratically, such that there are more grid points in regions where the potential is stronger. The so-called tensor-trick technique is also employed to handle the large matrices involved. The computation of the many and dense states for the Ozone case is best implemented using the global minimization program PANMIN based on the well known MERLIN optimization program. Stable results comparable to those of other methods were obtained for both nucleonic and molecular systems considered. / Physics / D.Phil. (Physics)
723

Electromagnetic processes in few-body systems

Rampho, Gaotsiwe Joel 11 1900 (has links)
Electromagnetic processes induced by electron scattering off few-nucleon systems are theoretically investigated in the non-relativistic formalism. Non-relativistic one-body nuclear current operators are used with a parametrization of nucleon electromagnetic form factors based on recent experimental nucleon scattering data. Electromagnetic form factors of three-nucleon and four-nucleon systems are calculated from elastic electron-nucleus scattering information. Nuclear response functions used in the determination of differential cross sections for inclusive and exclusive quasi-elastic electron-nucleon scattering from the 4He nucleus are also calculated. Final-state interactions in the quasi-elastic nucleon knockout process are explicitly taken into account using the Glauber approximation. The sensitivity of the response functions to the final-state interactions is investigated. The Antisymmetrized Molecular Dynamics approach with angular momentum and parity projection is employed to construct ground state wave functions for the nuclei. A reduced form of the realistic Argonne V18 nucleon-nucleon potential is used to describe nuclear Hamiltonian. A convenient numerical technique of approximating expectation values of nuclear Hamiltonian operators is employed. The constructed wave functions are used to calculate ground-state energies, root-mean-square radii and magnetic dipole moments of selected light nuclei. The theoretical predictions of the nuclear properties for the selected nuclei give a satisfactory description of experimental values. The Glauber approximation is combined with the Antisymmetrized Molecular Dynamics to generate wave functions for scattering states in quasi-elastic scattering processes. The wave functions are then used to study proton knockout reactions in the 4He nucleus. The theoretical predictions of the model reproduce experimental observation quite well. / Physics / Ph D. (Physics)
724

Desigualdade socioeconômica e obesidade abdominal: uma apreciação crítica e pragmática em epidemiologia. / Socioeconomic inequality and abdominal obesity: a critical and pragmatic assessment in epidemiology.

Ronaldo Fernandes Santos Alves 14 March 2014 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Esta dissertação buscou uma apreciação crítica e pragmática da relação entre desigualdade socioeconômica e obesidade abdominal, em resposta a proposição internacional de monitoramento das desigualdades em saúde e a escassez de estudos desta natureza relativos à obesidade abdominal. Dois artigos foram elaborados a fim de estimar o grau de desigualdade educacional na ocorrência de obesidade abdominal e revisar os estudos de associação entre posição socioeconômica e obesidade abdominal. O primeiro artigo utilizou o índice angular de desigualdade e o índice relativo de desigualdade em dados seccionais de 3.117 participantes da linha de base do Estudo Pró-Saúde, 1999-2001, e o segundo artigo abarcou os resultados de estudos conduzidos em população adulta no Brasil. Os índices de desigualdade resumiram a tendência monotônica e inversa observada entre escolaridade e obesidade abdominal na população feminina, proporcionando estimativas quantitativas desta desigualdade (artigo 1). Em concordância, observou-se que a associação entre indicadores de posição socioeconômica e obesidade abdominal foi majoritariamente inversa entre as mulheres, principalmente com relação à escolaridade, e estatisticamente não significativa entre os homens (artigo 2). Tal cenário epidemiológico evidencia que a obesidade abdominal tem afetado desproporcionalmente as mulheres de posição socioeconômica mais baixa e que a desigualdade de gênero na prevalência de obesidade abdominal tende a aumentar com menor posição socioeconômica. Em suma, a presente dissertação visou à produção de conhecimento epidemiológico relevante ao enfrentamento das desigualdades em saúde, com o objetivo premente de subsidiar políticas públicas de fato realizáveis e individualmente aceitáveis. / This dissertation sought to a critical and pragmatic assessment of the relationship between socioeconomic inequality and abdominal obesity in response to international proposition of health inequalities monitoring and to lack of studies of this nature relating to abdominal obesity. Two articles were prepared to -estimate the level of educational inequality in the occurrence of abdominal obesity, and review the association studies between socioeconomic position and abdominal obesity. The first article used the slope index of inequality and the relative index of inequality in the sectional data of 3.117 participants in the baseline of the Pró-Saúde Study, 1999-2001; and the second article encompassed the results of the studies conducted in the adult population in Brazil. The inequality indexes summarized strictly monotonic and inverse trend between educational achievement and abdominal obesity in the female population, providing quantitative estimates of this inequality (Article 1). Accordingly, we found that the association between socioeconomic position indicators and abdominal obesity was mostly reversed among women, especially regarding education, and statistically not significant among men (Article 2). This epidemiological scenario shows that abdominal obesity has disproportionately affected women of the lower socioeconomic position, and gender inequality in the prevalence of abdominal obesity tends to increase with lower socioeconomic position. In short, this dissertation aimed at the production of relevant epidemiological knowledge to addressing health inequalities, with the targeted of subsidize public policies feasible and individually acceptable.
725

Análise de resíduos em modelos de regressão von Mises. / Analysis of residues in von Mises regression models.

LEAL, Grayci-Mary Gonçalves. 10 July 2018 (has links)
Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-07-10T16:48:23Z No. of bitstreams: 1 GRAYCI-MARY GONÇALVES LEAL - DISSERTAÇÃO PPGMAT 2006..pdf: 956853 bytes, checksum: 4fd52ea4cb6e8e47a91cfe0b76a5c4bb (MD5) / Made available in DSpace on 2018-07-10T16:48:23Z (GMT). No. of bitstreams: 1 GRAYCI-MARY GONÇALVES LEAL - DISSERTAÇÃO PPGMAT 2006..pdf: 956853 bytes, checksum: 4fd52ea4cb6e8e47a91cfe0b76a5c4bb (MD5) Previous issue date: 2006-04 / Capes / Dados envolvendo medidas angulares estão presentes nas mais diversas áreas do conhecimento. Para analisá-los é necessário utilizar uma teoria estatística específica e apropriada, diferente da que utilizamos para dados lineares. Particularmente, quando o interesse for formular, ajustar e fazer diagnósticos em modelos de regressão, uma vez que, neste contexto, a natureza da variável deve ser considerada. Neste trabalho, utilizamos os modelos de regressão von Mises para investigar a associação tipo circular-linear e apresentamos dois resíduos padronizados que foram obtidos a partir da componente da função desvio e cujas distribuições de probabilidades podem ser aproximadas pela distribuição normal padrão, definida para dados lineares. / Datainvolvingangulararepresentinthemostdiverseareasofscience. Toanalyze them is necessary to introduce an appropriate theory and to study specific and appropriate statistics as well, different from that we use for linear data. When the interest is to formulate, to adjust and to make diagnostics on regression models, the nature of the variables must be considered. In this work, we use the von Mises regression models to investigate the circular-linear association and discuss two standardized residuals defined from the component of the deviance function whose probability distributions can be approximated by the normal standard distribution defined for linear data.
726

Estudo de reacoes fotonucleares junto ao limiar para o Np-237, com radiacao gama de captura de neutrons termicos

GERALDO, LUIZ P. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:30:52Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:14Z (GMT). No. of bitstreams: 1 01486.pdf: 7771652 bytes, checksum: b85a21fcba108c94836bcdfd32ea7d21 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
727

Investigação de parâmetros hiperfinos dos óxidos semicondutores SnOsub(2) e TiOsub(2) puros e dopados com metais de transição 3d pela espectroscopia de correlação angular gama-gama perturbada / Investigation of hyperfine parameters in pure and 3d transition metal doped SnOsub(2) e TiOsub(2) by means of perturbed gamma-gamma angular correlation spectroscopy

SCHELL, JULIANA 09 June 2015 (has links)
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-06-09T18:22:48Z No. of bitstreams: 0 / Made available in DSpace on 2015-06-09T18:22:49Z (GMT). No. of bitstreams: 0 / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
728

Desigualdade socioeconômica e obesidade abdominal: uma apreciação crítica e pragmática em epidemiologia. / Socioeconomic inequality and abdominal obesity: a critical and pragmatic assessment in epidemiology.

Ronaldo Fernandes Santos Alves 14 March 2014 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Esta dissertação buscou uma apreciação crítica e pragmática da relação entre desigualdade socioeconômica e obesidade abdominal, em resposta a proposição internacional de monitoramento das desigualdades em saúde e a escassez de estudos desta natureza relativos à obesidade abdominal. Dois artigos foram elaborados a fim de estimar o grau de desigualdade educacional na ocorrência de obesidade abdominal e revisar os estudos de associação entre posição socioeconômica e obesidade abdominal. O primeiro artigo utilizou o índice angular de desigualdade e o índice relativo de desigualdade em dados seccionais de 3.117 participantes da linha de base do Estudo Pró-Saúde, 1999-2001, e o segundo artigo abarcou os resultados de estudos conduzidos em população adulta no Brasil. Os índices de desigualdade resumiram a tendência monotônica e inversa observada entre escolaridade e obesidade abdominal na população feminina, proporcionando estimativas quantitativas desta desigualdade (artigo 1). Em concordância, observou-se que a associação entre indicadores de posição socioeconômica e obesidade abdominal foi majoritariamente inversa entre as mulheres, principalmente com relação à escolaridade, e estatisticamente não significativa entre os homens (artigo 2). Tal cenário epidemiológico evidencia que a obesidade abdominal tem afetado desproporcionalmente as mulheres de posição socioeconômica mais baixa e que a desigualdade de gênero na prevalência de obesidade abdominal tende a aumentar com menor posição socioeconômica. Em suma, a presente dissertação visou à produção de conhecimento epidemiológico relevante ao enfrentamento das desigualdades em saúde, com o objetivo premente de subsidiar políticas públicas de fato realizáveis e individualmente aceitáveis. / This dissertation sought to a critical and pragmatic assessment of the relationship between socioeconomic inequality and abdominal obesity in response to international proposition of health inequalities monitoring and to lack of studies of this nature relating to abdominal obesity. Two articles were prepared to -estimate the level of educational inequality in the occurrence of abdominal obesity, and review the association studies between socioeconomic position and abdominal obesity. The first article used the slope index of inequality and the relative index of inequality in the sectional data of 3.117 participants in the baseline of the Pró-Saúde Study, 1999-2001; and the second article encompassed the results of the studies conducted in the adult population in Brazil. The inequality indexes summarized strictly monotonic and inverse trend between educational achievement and abdominal obesity in the female population, providing quantitative estimates of this inequality (Article 1). Accordingly, we found that the association between socioeconomic position indicators and abdominal obesity was mostly reversed among women, especially regarding education, and statistically not significant among men (Article 2). This epidemiological scenario shows that abdominal obesity has disproportionately affected women of the lower socioeconomic position, and gender inequality in the prevalence of abdominal obesity tends to increase with lower socioeconomic position. In short, this dissertation aimed at the production of relevant epidemiological knowledge to addressing health inequalities, with the targeted of subsidize public policies feasible and individually acceptable.
729

Modélisation et méthodes numériques pour l'étude du transport de particules dans un plasma chaud / Modelling and numerical methods for the study of particle transport in a hot plasma

Guisset, Sébastien 23 September 2016 (has links)
Les modèles aux moments angulaires constituent des descriptions intermédiaires entre les modèles cinétiques et les modèles fluides. Dans ce manuscrit, les modèles aux moments angulaires basés sur un principe de minimisation d'entropie sont étudiés pour des applications en physique des plasmas. Ce mémoire se découpe en trois parties. La première est une contribution à la modélisation en physique des plasmas à travers le formalisme des modèles aux moments angulaires. Dans celle-ci, le domaine de validité de ces modèles est étudié en régimes non-collisionels. Il est également montré que les opérateurs de collisions proposés pour le modèle M1 permettent de retrouver des coefficients de transport plasma précis. La deuxième partie de ce document concerne la dérivation de méthodes numériques pour l'étude du transport de particules en temps long. Dans ce cadre, des schémas numériques appropriés pour le modèle M1, préservant l'asymptotique, sont construits et validés numériquement. La troisième partie représente un premier pas significatif vers la modélisation multi-espèces. Ici, le modèle aux moments angulaire M1, construit dans un référentiel mobile, est appliqué à la dynamique des gaz raréfiés. Les propriétés de ce modèle sont détaillées, un schéma numérique est proposé et une validation numérique est menée. / Angular moments models represent alternative descriptions situated in between the kinetic and the fluid models. In this work, angular moments models based on an entropy minimisation principle are considered for plasma physics applications. This manuscript is organised in three parts. The first one is a contribution to plasma physics modelling within the formalism of angular moments models. The validity domain of angular moments models in collisionless regimes is studied. It is also shown that the collisional operators proposed for the M1 angular moments model enable to recover accurate plasma transport coefficients. The second part of this document deals with the derivation of numerical methods for the long timescales particle transport. Appropriate asymptotic-preserving numerical schemes are designed for the M1 angular moments model and numerical validations are performed. The third part represents a first important step toward multi-species modelling. The M1 angular moments model in a moving frame is introduced and applied to rarefied gas dynamics. The model properties are highlighted, a numerical scheme is proposed and a numerical validation is carried out.
730

Observations extragalactiques avec optique adaptative : polarisation dans les noyaux actifs de Galaxie et étude des super amas d'étoiles / Extragalactic Observations with Adaptive Optics : Polarisation in Active Galactic Nuclei and study of Super Star Clusters

Grosset, Lucas 15 September 2017 (has links)
Malgré l’existence de modèles précis, notre connaissance des structures à petite échelle des galaxies est toujours limitée par le manque de preuves observationnelles. Les progrès instrumentaux ont permis d’atteindre une haute résolution angulaire à l’aide des nouvelles générations de télescopes, mais celle-ci est restreinte à un faible nombre de cibles extragalactiques à causes des besoins de l’Optique Adaptative (OA). En effet, afin de permettre une mesure efficace du front d’onde, l’OA requiert une source brillante et ponctuelle proche de la cible scientifique, typiquement en dessous de 30 . La partie principale de cette thèse porte sur l’analyse de la dizaine de parsecs centrale des Galaxies à Noyaux Actifs (NAG) à l’aide de différentes techniques observationnelles et numériques. Nous avons dans ce contexte développé un code de transfert radiatif nous permettant d’analyser les données polarimétriques. La seconde partie de ce travail est dédiée à l’analyse d’images en proche infrarouges de galaxies à flambée d’étoiles afin de contraindre les paramètres décrivant les super amas stellaires, jeunes cocons de poussière très massifs abritant une formation d’étoiles très soutenue, à l’aide de données obtenues avec l’instrument CANARY, démonstrateur de nouvelles technologies d’OA. / Despite having strong theoretical models, the current limitation in our understanding of the small-scale structures of galaxies is linked to the lack of observational evidences. Many powerful telescopes and instruments have been developed in the last decades, however one of these strongest tools, namely Adaptive Optics (AO), can only be used on a very limited number of targets. Indeed, for AO to be efficient, a bright star is required close to the scientific target, typically under 30 . This is mandatory for the AO systems to be able to measure the atmospheric turbulence and this condition is rarely satisfied for extended extragalactic targets such as galaxies. The main part of this thesis work consisted in going deeper in the analysis of the inner tens of parsecs of Active Nuclei (AGN) by combining different techniques to obtain and to interpret new data. In this context, we developed a new radiative transfer code to analyse the polarimetric data. A second part of my work was dedicated to a high angular resolution study of Super Star Clusters (SSC) in a new system, thanks to data obtained with the AO demonstrator CANARY instrument.

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