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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.
61

Estudo sobre determinação de elementos químicos em unhas humanas pelo método de análise por ativação com neutrôns / A study on chemical element determinations in human nails by neutron activation analysis

SANCHES, THALITA P. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:34:48Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:28Z (GMT). No. of bitstreams: 0 / As análises de unhas têm sido objeto de estudo para avaliar os níveis de elementos acumulados no organismo humano e com aplicações deste tecido na monitoração da exposição ocupacional ou ambiental, na avaliação do estado nutricional, na identificação da intoxicação por metais tóxicos e na diagnose ou prevenção de doenças. As análises de unhas apresentam vantagens devido à facilidade na coleta, estocagem e transporte das amostras bem como fornecem os níveis de elementos acumulados ao longo de um período de aproximadamente 6 meses ao contrário dos fluídos como sangue e urina. Entretanto há controvérsias sobre a aplicação dos dados de suas análises devido às dificuldades em estabelecer valores confiáveis de referência ou faixas de concentrações para uso como dados de controle. O objetivo deste trabalho foi avaliar os fatores que podem afetar nas concentrações de elementos nas unhas para posterior análise de amostras de um grupo de indivíduos aplicando o método de análise por ativação com nêutrons (NAA). As amostras de unhas das mãos e dos pés coletadas de indivíduos adultos de ambos os sexos, com idades de 18 a 71 anos e residentes na região metropolitana de São Paulo foram cortadas em pequenos fragmentos, lavadas e secas para as análises. O procedimento experimental consistiu em irradiar amostras juntamente com os padrões sintéticos de elementos por 16 h sob fluxo de nêutrons térmicos de cerca de 4,5 x 1012 n cm-2 s-1 do reator nuclear de pesquisa IEA-R1, seguido de espectrometria de raios gama para a determinação dos elementos As, Br, Ca, Co, Cr, Cs, Fe, K, La, Na, Rb, Sb, Sc, Se e Zn. No controle da qualidade analítica foram analisados os materiais de referência certificados cujos os resultados obtidos indicaram boa exatidão e precisão com erros relativos e desvios padrão relativos inferiores a 5,1 % e 11,6 % respectivamente. Os ensaios preliminares indicaram que as contribuições devido às impurezas presentes nos invólucros de plástico utilizados na irradiação assim como aquelas decorrentes da adsorção dos esmaltes nas unhas são muito baixas, podendo ser desprezadas. Nos testes de limpeza das unhas para análise foi verificado que a solução diluída de HNO3 pode provocar a dissolução das amostras. A homogeneidade da amostra preparada foi verificada pelas analises em réplicas. A comparação entre as concentrações de elementos obtidos nas unhas das mãos e dos pés indicou diferenças significativas para os elementos Br, Co e Zn (teste t, p = 0,05). As concentrações de elementos nas unhas quando comparadas em relação ao gênero, faixa etária e Índice de massa corpórea (IMC) dos indivíduos não apresentaram diferenças significativas para a maioria dos elementos determinados. A diferença significativa das concentrações de Zn das unhas das mãos foi verificada entre o gênero dos indivíduos e das concentrações de Cs entre às faixas etárias distintas. As concentrações de elementos obtidas nas unhas dos pés e das mãos apresentaram uma ampla variabilidade e para a maioria dos elementos os dados obtidos são da mesma ordem de grandeza ou dentro das faixas dos valores da literatura. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
62

Deformačně napěťová analýza femuru s distrakčním intramedulárním hřebem / Strain and stress analysis of the femur with distraction intramedullary nail

Konvalinka, Jan January 2017 (has links)
This master's thesis is focused on determination and analysis of stress and strain in femur with distraction intramedullary nail for treating leg length discrepancy with the method of distraction osteogenesis. Thesis is mainly focused on states after distraction when the callus consolidates. Problem of determining stress and strain is solved by computational modeling using FEM. Detailed description of modeling is included in this thesis, complicated 3D geometry of bone was acquired from segmentation of CT images. Computational model is solve with 4 different types of callus geometry and also material properties of callus are varied. The influence on stress and strain when the middle distal screw is not applied is also analyzed.
63

Rekonstrukce železničního tunelu / Reconstruction of the railway tunnel

Nekl, Jiří January 2013 (has links)
The diploma thesis engages in the reconstruction of railway tunnel Domasovsky that is situated at the track section Olomouc – Krnov. It illustrates the current state of the construction and the geotechnical conditons of the area of interest, it also presents the potencial solutions. The design is verified by stuructural analysis, the design documentation and technical report are also enclosed.
64

Analytical Modeling of Wood-Frame Shear Walls and Diaphragms

Judd, Johnn Paul 18 March 2005 (has links) (PDF)
Analytical models of wood-frame shear walls and diaphragms for use in monotonic, quasi-static (cyclic), and dynamic analyses are developed in this thesis. A new analytical model is developed to accurately represent connections between sheathing panels and wood framing members (sheathing-to-framing connections) in structural analysis computer programs. This new model represents sheathing–to–framing connections using an oriented pair of nonlinear springs. Unlike previous models, the new analytical model for sheathing-to-framing connections is suitable for both monotonic, cyclic, or dynamic analyses. Moreover, the new model does not need to be scaled or adjusted. The new analytical model may be implemented in a general purpose finite element program, such as ABAQUS, or in a specialized structural analysis program, such as CASHEW. The analytical responses of several shear walls and diaphragms employing this new model are validated against measured data from experimental testing. A less complex analytical model of shear walls and diaphragms, QUICK, is developed for routine use and for dynamic analysis. QUICK utilizes an equivalent single degree of freedom system that has been determined using either calibrated parameters from experimental or analytical data, or estimated sheathing-to-framing connection data. Application of the new analytical models is illustrated in two applications. In the first application, the advantages of diaphragms using glass fiber reinforced polymer (GFRP) panels in conjunction with plywood panels as sheathing (hybrid diaphragms) are presented. In the second application, the response of shear walls with improperly driven (overdriven)nails is determined along with a method to estimate strength reduction due to both the depth and the percentage of total nails overdriven.
65

"Efeito da terapia por ondas de choque na consolidação óssea após osseossíntese de fêmur com hastes bloqueadas: estudo experimental em cães (canis familiaris)" / Effect of extracorporeal shock wave therapy one bone healing after femur ostosynthesis with interlocking nails: experimental study in dogs (Canis familiaris)

Bassit, Ana Cristina Ferreira 14 September 2004 (has links)
O efeito da terapia por ondas de choque (TOC) na consolidação óssea, após osteotomias bilaterais dos fêmures e osteossínteses com hastes bloqueadas, foi estudado em 8 cães. Os fêmures direitos constituíram o grupo controle e os esquerdos, o grupo tratado, que recebeu 2000 pulsos de ondas de choque de 18 kV, energia de 5mJ (-6dB), na linha da fratura. Radiografias após 4, 8 e 12 semanas, revelaram maior proliferação periosteal no grupo tratado. Os resultados dos exames cintilográficos (razão tratado/controle), realizados na 2a, 4a, 6a, 8a, 10a e 12a semanas, foram estatisticamente superiores no grupo tratado. A TOC provocou aumento da atividade osteogênica na consolidação de fraturas agudas / The effect of extracorporeal shock wave therapy (ESWT) on bone healing, after bilateral femoral osteotomies and osteosynthesis with interlocking nails, was studied in 8 dogs. The right femurs composed the control group, and the left femurs, the treated group, which received 2000 pulses of shock wave, with 18 kV, 5 mJ (-6dB) energy on the fracture line. Radiographs after 4, 8 and 12 weeks, revealed increased periosteal proliferation in the treated group. The results (treated/control ratio) of the scintigraphic exams, performed on weeks 2, 4, 6, 8, 10 and 12, were statistically higher for the treated group. The ESWT led to increased osteogenic activity on acute fracture's bone healing.
66

Efeito do método canguru na redução do estresse crônico em gestantes, mães e bebês pré-termo através da análise do cortisol e desidroepiandrosterona em unhas / Effect of the kangaroo mother care on the reduction of chronic stress in pregnant women, mothers and preterm infants through the analysis of cortisol and dehydroepiandrosterone in fingernails

Souza, Sandra Regina de 26 January 2017 (has links)
INTRODUÇÃO: O estresse tem sido foco de interesse em diferentes áreas de estudo devido às consequências no processo saúde-doença. Destaca-se a inexistência de estudos sobre o estresse crônico no período pré e pós-natal em unhas de mulheres que tiveram parto prematuro e sua relação o método canguru (MC). OBJETIVOS: Avaliar o efeito do Método Canguru na redução do estresse psicológico materno através de escalas psicométricas e o estresse biológico crônico através dos níveis de cortisol e desidroepiandrosterona (DHEA) em unhas de mães e bebês pré-termo (PT). MÉTODO: Trata-se de estudo comparativo prospectivo. A amostra contou com 59 mães e 63 bebês, coletada num hospital com o MC implantado e em dois hospitais controle, sem o MC. Foram incluídos PT (?37 semanas), sem malformações, internados em UN; mães alfabetizadas, que tiveram contato prévio com o filho, não usuárias de drogas ou hormônios. O estresse crônico materno e do PT foi avaliado pelo Cortisol e DHEA das unhas. A primeira amostra de unhas maternas foi coletada na terceira semana de vida do PT. A segunda amostra das mães e a amostra das unhas dos PT foram coletadas três meses após parto. Para análise do cortisol e DHEA das unhas das mães foi utilizada a técnica de enzima imunoensaio e dos bebês a cromatografia líquida de alto desempenho com espectrometria de massa. As unhas foram analisadas em laboratórios especializados no Canadá. O estresse psicológico da mães foi analisado com uso das PSS-10 e PSS:NICU que foram respondidas pelas mães na semana da admissão e alta do PT. RESULTADOS: Os níveis de Cortisol e DHEA nas unhas das mães referente a gestação e puerpério não diferiu significativamente entre os grupos canguru e controle, porém, diferiu entre os tempos, sendo que, os níveis dos esteroides na gestação foi maior do que no puerpério em ambos os grupos. O estresse percebido (PSS-10) pelas mães referente a gestação (p=0,846) e puerpério (p=0,465) também não diferiu significativamente entre os dois grupos. O estresse indicado pela PSS:NICU na admissão foi moderado nos dois grupos. O maior escore foi observado na subescala alteração no papel de pais. Na alta o escore foi significativamente menor (p=0,00) no canguru do que no controle. Não houve qualquer relação entre o estresse crônico (cortisol, DHEA e razão Cort:DHEA) e o psicológico (PSS-10 na gestação e PSS:NICU no puerpério) e nem entre as duas medidas de estresse psicológico (PSS-10 e PSS:NICU na alta). O nível de cortisol foi menor nos PT submetidos ao canguru, porém, sem diferença significante (p=0,08). Diferiram significativamente a DHEA - menor no controle e a razão Cort:DHEA - menor nos PT do grupo canguru. Da análise da relação entre estresse crônico constataram-se: associação positiva entre Cort:DHEA da mãe e PT (?= 0,51canguru; ?= 0,43 controle). CONCLUSÃO: O estudo mostrou que é possível medir cortisol e DHEA em unhas de mães e de bebês PT de forma restrospectiva. Os dados sugerem que o MC pode contribuir com a regulação e redução do estresse crônico do PT e do estresse psicológico materno / INTRODUCTION: Stress has been a focus of interest in different areas of study due to the consequences in the health-disease process. We highlight the lack of studies on chronic stress in pre and postnatal period using fingernails of women who had preterm birth and its relation to the kangaroo mother care (KMC) to reduce chronic and psychological stress. OBJECTIVES: To evaluate maternal psychological stress using psicometrics tools and avaluate chronic stress of mothers and Preterm infant (PT) using the analysis of cortisol and DHEA in fingernails and analyse the implication of the kangaroo care (KMC) in reduce chronic stress. METHOD: This is a prospective comparative study. The sample were 59 mothers and 63 babies collected in a KMC\'s hospital and two controls (without the KMC). Were included PT babies (? 37 weeks), who were admitted to the NICU, those with no malformations. With regard to mothers were included that one who had saw the PT at least once and excluded those using drugs or taking hormones. Maternal and PT chronic\' stress were evaluated by fingernails\' cortisol and DHEA. The first maternal sample was collected in the third week post-delivery and the second sample in the third month after baby\'s birth. The baby\'s fingernail sample was collected in the third month of life. The enzyme immunoassay was used for analysis of mothers\' fingernails (cortisol and DHEA) and for babies\' were used high performance liquid chromatography with mass spectrometry. Fingernail\'s analysis was done in Canada. The PSS-10 and PSS: mothers filled up NICU tools on first week in NICU and at discharge of the baby from this unit. RESULTS: The cortisol and DHEA\'s level in mothers\' fingernails showed no significant difference between groups. Steroids levels in pregnancy time were higher than in puerperium in both groups (KMC and control) however, showed significant difference between times, steroids levels were higher during gestation time than the puerperium in both groups. The same occurred with the PSS-10 score (KMC\'s score referring to pregnancy (p=0,846) and puerperium (p=0,465), also had no difference was between groups. The PSS: NICU\'s stress level at admission in both groups was moderate. The highest score was showed in the subscale Parental Role. At discharge the score was significantly lower (p=0,00) in the kangaroo than in the control. There was no relationship between chronic stress (cortisol, DHEA and Cort:DHEA) and psychological stress (PSS-10 in pregnancy and PSS: NICU in the puerperium) or between the two psychological measures of stress (PSS-10 and PSS: NICU on discharge). The cortisol level was lower in PT submitted to kangaroo, however, without significant difference (p = 0.08). They differed significantly in DHEA - lower in the control and the ratio Cort:DHEA - lower in the kangaroo group. From the analysis of the relationship between chronic stress, there was a positive association between Cort: DHEA of the mother and PT (? = 0.51 kangaroo; ? = 0.43 control). CONCLUSION: The study showed that it is possible to measure cortisol and DHEA in preterm infant and mothers\' fingernails retrospectively. The data suggests that KMC can contribute to regulate and to reduce chronic stress in preterm infant and to reduce psychological mother\'s stress
67

The Asperity-deformation Model Improvements and Its Applications to Velocity Inversion

Bui, Hoa Q. 16 January 2010 (has links)
Quantifying the influence of pressure on the effective elastic rock properties is important for applications in rock physics and reservoir characterization. Here I investigate the relationship between effective pressure and seismic velocities by performing inversion on the laboratory-measured data from a suite of clastic, carbonate and igneous rocks, using different analytic and discrete inversion schemes. I explore the utility of a physical model that models a natural fracture as supported by asperities of varying heights, when an effective pressure deforms the tallest asperities, bringing the shorter ones into contact while increasing the overall fracture stiffness. Thus, the model is known as the ?asperity-deformation? (ADM) or ?bed-of-nails? (BNM) model. Existing analytic solutions include one that assumes the host rock is infinitely more rigid than the fractures, and one that takes the host-rock compliance into account. Inversion results indicate that although both solutions can fit the data to within first-order approximation, some systematic misfits exist as a result of using the rigid-host solution, whereas compliant-host inversion returns smaller and random misfits, yet out-of-range parameter estimates. These problems indicate the effects of nonlinear elastic deformation whose degree varies from rock to rock. Consequently, I extend the model to allow for the pressure dependence of the host rock, thereby physically interpreting the nonlinear behaviors of deformation. Furthermore, I apply a discrete grid-search inversion scheme that generalizes the distribution of asperity heights, thus accurately reproduces velocity profiles, significantly improves the fit and helps to visualize the distribution of asperities. I compare the analytic and numerical asperity-deformation models with the existing physical model of elliptical ?pennyshape? cracks with a pore-aspect-ratio (PAR) spectrum in terms of physical meaning and data-fitting ability. The comparison results provide a link and demonstrate the consistency between the use of the two physical models, making a better understanding of the microstructure as well as the contact mechanism and physical behaviors of rocks under pressure. ADM-based solutions, therefore, have the potential to facilitate modeling and interpretation of applications such as time-lapse seismic investigations of fractured reservoirs.
68

Efeito do método canguru na redução do estresse crônico em gestantes, mães e bebês pré-termo através da análise do cortisol e desidroepiandrosterona em unhas / Effect of the kangaroo mother care on the reduction of chronic stress in pregnant women, mothers and preterm infants through the analysis of cortisol and dehydroepiandrosterone in fingernails

Sandra Regina de Souza 26 January 2017 (has links)
INTRODUÇÃO: O estresse tem sido foco de interesse em diferentes áreas de estudo devido às consequências no processo saúde-doença. Destaca-se a inexistência de estudos sobre o estresse crônico no período pré e pós-natal em unhas de mulheres que tiveram parto prematuro e sua relação o método canguru (MC). OBJETIVOS: Avaliar o efeito do Método Canguru na redução do estresse psicológico materno através de escalas psicométricas e o estresse biológico crônico através dos níveis de cortisol e desidroepiandrosterona (DHEA) em unhas de mães e bebês pré-termo (PT). MÉTODO: Trata-se de estudo comparativo prospectivo. A amostra contou com 59 mães e 63 bebês, coletada num hospital com o MC implantado e em dois hospitais controle, sem o MC. Foram incluídos PT (?37 semanas), sem malformações, internados em UN; mães alfabetizadas, que tiveram contato prévio com o filho, não usuárias de drogas ou hormônios. O estresse crônico materno e do PT foi avaliado pelo Cortisol e DHEA das unhas. A primeira amostra de unhas maternas foi coletada na terceira semana de vida do PT. A segunda amostra das mães e a amostra das unhas dos PT foram coletadas três meses após parto. Para análise do cortisol e DHEA das unhas das mães foi utilizada a técnica de enzima imunoensaio e dos bebês a cromatografia líquida de alto desempenho com espectrometria de massa. As unhas foram analisadas em laboratórios especializados no Canadá. O estresse psicológico da mães foi analisado com uso das PSS-10 e PSS:NICU que foram respondidas pelas mães na semana da admissão e alta do PT. RESULTADOS: Os níveis de Cortisol e DHEA nas unhas das mães referente a gestação e puerpério não diferiu significativamente entre os grupos canguru e controle, porém, diferiu entre os tempos, sendo que, os níveis dos esteroides na gestação foi maior do que no puerpério em ambos os grupos. O estresse percebido (PSS-10) pelas mães referente a gestação (p=0,846) e puerpério (p=0,465) também não diferiu significativamente entre os dois grupos. O estresse indicado pela PSS:NICU na admissão foi moderado nos dois grupos. O maior escore foi observado na subescala alteração no papel de pais. Na alta o escore foi significativamente menor (p=0,00) no canguru do que no controle. Não houve qualquer relação entre o estresse crônico (cortisol, DHEA e razão Cort:DHEA) e o psicológico (PSS-10 na gestação e PSS:NICU no puerpério) e nem entre as duas medidas de estresse psicológico (PSS-10 e PSS:NICU na alta). O nível de cortisol foi menor nos PT submetidos ao canguru, porém, sem diferença significante (p=0,08). Diferiram significativamente a DHEA - menor no controle e a razão Cort:DHEA - menor nos PT do grupo canguru. Da análise da relação entre estresse crônico constataram-se: associação positiva entre Cort:DHEA da mãe e PT (?= 0,51canguru; ?= 0,43 controle). CONCLUSÃO: O estudo mostrou que é possível medir cortisol e DHEA em unhas de mães e de bebês PT de forma restrospectiva. Os dados sugerem que o MC pode contribuir com a regulação e redução do estresse crônico do PT e do estresse psicológico materno / INTRODUCTION: Stress has been a focus of interest in different areas of study due to the consequences in the health-disease process. We highlight the lack of studies on chronic stress in pre and postnatal period using fingernails of women who had preterm birth and its relation to the kangaroo mother care (KMC) to reduce chronic and psychological stress. OBJECTIVES: To evaluate maternal psychological stress using psicometrics tools and avaluate chronic stress of mothers and Preterm infant (PT) using the analysis of cortisol and DHEA in fingernails and analyse the implication of the kangaroo care (KMC) in reduce chronic stress. METHOD: This is a prospective comparative study. The sample were 59 mothers and 63 babies collected in a KMC\'s hospital and two controls (without the KMC). Were included PT babies (? 37 weeks), who were admitted to the NICU, those with no malformations. With regard to mothers were included that one who had saw the PT at least once and excluded those using drugs or taking hormones. Maternal and PT chronic\' stress were evaluated by fingernails\' cortisol and DHEA. The first maternal sample was collected in the third week post-delivery and the second sample in the third month after baby\'s birth. The baby\'s fingernail sample was collected in the third month of life. The enzyme immunoassay was used for analysis of mothers\' fingernails (cortisol and DHEA) and for babies\' were used high performance liquid chromatography with mass spectrometry. Fingernail\'s analysis was done in Canada. The PSS-10 and PSS: mothers filled up NICU tools on first week in NICU and at discharge of the baby from this unit. RESULTS: The cortisol and DHEA\'s level in mothers\' fingernails showed no significant difference between groups. Steroids levels in pregnancy time were higher than in puerperium in both groups (KMC and control) however, showed significant difference between times, steroids levels were higher during gestation time than the puerperium in both groups. The same occurred with the PSS-10 score (KMC\'s score referring to pregnancy (p=0,846) and puerperium (p=0,465), also had no difference was between groups. The PSS: NICU\'s stress level at admission in both groups was moderate. The highest score was showed in the subscale Parental Role. At discharge the score was significantly lower (p=0,00) in the kangaroo than in the control. There was no relationship between chronic stress (cortisol, DHEA and Cort:DHEA) and psychological stress (PSS-10 in pregnancy and PSS: NICU in the puerperium) or between the two psychological measures of stress (PSS-10 and PSS: NICU on discharge). The cortisol level was lower in PT submitted to kangaroo, however, without significant difference (p = 0.08). They differed significantly in DHEA - lower in the control and the ratio Cort:DHEA - lower in the kangaroo group. From the analysis of the relationship between chronic stress, there was a positive association between Cort: DHEA of the mother and PT (? = 0.51 kangaroo; ? = 0.43 control). CONCLUSION: The study showed that it is possible to measure cortisol and DHEA in preterm infant and mothers\' fingernails retrospectively. The data suggests that KMC can contribute to regulate and to reduce chronic stress in preterm infant and to reduce psychological mother\'s stress
69

"Efeito da terapia por ondas de choque na consolidação óssea após osseossíntese de fêmur com hastes bloqueadas: estudo experimental em cães (canis familiaris)" / Effect of extracorporeal shock wave therapy one bone healing after femur ostosynthesis with interlocking nails: experimental study in dogs (Canis familiaris)

Ana Cristina Ferreira Bassit 14 September 2004 (has links)
O efeito da terapia por ondas de choque (TOC) na consolidação óssea, após osteotomias bilaterais dos fêmures e osteossínteses com hastes bloqueadas, foi estudado em 8 cães. Os fêmures direitos constituíram o grupo controle e os esquerdos, o grupo tratado, que recebeu 2000 pulsos de ondas de choque de 18 kV, energia de 5mJ (-6dB), na linha da fratura. Radiografias após 4, 8 e 12 semanas, revelaram maior proliferação periosteal no grupo tratado. Os resultados dos exames cintilográficos (razão tratado/controle), realizados na 2a, 4a, 6a, 8a, 10a e 12a semanas, foram estatisticamente superiores no grupo tratado. A TOC provocou aumento da atividade osteogênica na consolidação de fraturas agudas / The effect of extracorporeal shock wave therapy (ESWT) on bone healing, after bilateral femoral osteotomies and osteosynthesis with interlocking nails, was studied in 8 dogs. The right femurs composed the control group, and the left femurs, the treated group, which received 2000 pulses of shock wave, with 18 kV, 5 mJ (-6dB) energy on the fracture line. Radiographs after 4, 8 and 12 weeks, revealed increased periosteal proliferation in the treated group. The results (treated/control ratio) of the scintigraphic exams, performed on weeks 2, 4, 6, 8, 10 and 12, were statistically higher for the treated group. The ESWT led to increased osteogenic activity on acute fracture's bone healing.
70

Study and design of new multibeam antenna architectures in Ku and Ka bands for broadband satellite applications / Étude de nouvelles architectures d'antennes multifaisceaux en bande Ka pour les télécommunications par satellite à très haut débit

Diallo, Cheikh-Dieylar 19 December 2016 (has links)
Les antennes multifaisceaux (AMFs) sont cruciales pour les applications de télécommunications par satellite modernes et futures, civiles et militaires. La partie basse du spectre électromagnétique est saturée alors que de larges bandes de fréquences sont disponibles dans la bande Ka, dans laquelle des missions à très-haut débit ont émergées au cours de la dernière décennie. La tendance consiste à réduire la taille des spots pour les couvertures multi-spots afin de diminuer le prix des satellites. Ainsi des antennes d’ouverture de plus en plus grande électriquement sont requises, induisant des ruptures technologiques majeures. Les lentilles de Luneburg insérées dans un guide d’ondes à plans parallèles (GOPP) deux plaques métalliques parallèles (PMPs) sont des solutions attractives pour illuminer les AMFs, puisqu’elles peuvent aboutir à des formateurs de faisceaux de bande et champ de visée larges, pertes et coûts faibles, et simples à concevoir, réaliser et intégrer. Les travaux de cette thèse portent sur le développement de nouvelles méthodes d’implémentation et sur la conception de AMFs à base de lentille de Luneburg. La réalisation de la lentille de Luneburg est connue pour être un défi technologique majeur. Un état de l’art des méthodes de réalisation est fourni. Ensuite, deux nouvelles méthodes sont proposées, ainsi qu’une méthode et des outils de conception. La première méthode de réalisation consiste en une matrice périodique et régulière de plots métalliques de taille inférieure à la longueur d’onde, et où la séparation du GOPP varie. La hauteur des plots et la séparation du GOPP contrôlent la valeur de l’indice de réfraction équivalente. L’antenne à 9 faisceaux tout métal conçue, fabriquée et mesurée, comporte 8314 plots et présente d’excellentes performances, notamment meilleures que sa version à séparation de plaques constante. La seconde méthode de réalisation consiste en une matrice périodique et régulière de trous circulaires de taille inférieure à la longueur d’onde réalisés sur un des deux revêtements cuivrés d’un substrat diélectrique plus une plaque métallique supérieure séparée du plan des trous par une couche d’air d’épaisseur fixe. L’antenne à 5 faisceaux conçue comporte 2696 trous et présente de très bonnes performances comparés à ces semblables dans la littérature. / Multi-beam antennas (MBAs) are crucial to modern and future, civilian and military satellite telecommunications applications. The low part of the electromagnetic spectrum is congested, while wide band of frequencies are available in the Ka-band, in which broadband missions have emerged in the last decade. The trend is reducing the size of spots in multi-beam coverage to reduce the cost of satellites, hence more electrically large antennas are needed, with major technological breakthrough as a consequence. Luneburg lenses in parallel-plate waveguide (PPW) are attractive solutions to excite MBAs, since they could lead to wide band and field-of-view, low loss and cost, easy to design, manufacture and accommodate Beam Forming Networks. This PhD deals with the development of novel implementations and the design of broadband, low loss and wide field-of-view Luneburg lens based MBAs. The implementation of the Luneburg lens is known as a major technological challenge. A state-of-the art of the implementation techniques is presented. Then two novel implementations of Luneburg lens in PPW environment are proposed, like design method, process and tools. The first implementation consists of a periodic and regular array of subwavelength vertical metal posts, where the PPW spacing is variable. The post height and PPW spacing modulate the equivalent refractive index. The all-metal 9-beams antenna designed, manufactured and measured, has 8314 posts and shows excellent performances, better than the traditional constant PPW spacing version. The second implementation consists of periodic and regular array of subwavelength circular holes etched on the copper cladding of a dielectric substrate with an air gap between the holes plane and the PPW top plate. The radius of the holes control the equivalent index. The 5-beams antenna designed has 2696 holes and shows very good performances as compared to similar devices in literature.

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