• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 25
  • 20
  • 8
  • 5
  • 3
  • 1
  • 1
  • Tagged with
  • 75
  • 26
  • 24
  • 24
  • 21
  • 20
  • 20
  • 15
  • 13
  • 12
  • 10
  • 10
  • 10
  • 9
  • 6
  • 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.
21

Creation of a Finite Element Model andSystem Analysis for the Low and HighFrequency Cryogenic Telescopes of theSpace Mission LiteBIRD

Rittatore Texeira, Matias January 2022 (has links)
The Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection (LiteBIRD) is a Japan Aerospace Exploration Agency (JAXA)-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the early Universe, through the measurement of their imprint onto the polarization of the Cosmic Microwave Background (CMB). It is an international collaboration, with European Union (EU) operations being coordinated by France. A short study on the merits of 2-dimensional versus 3-dimensional elements in the Finite Element Model (FEM) meshing of basic plates and beams was performed as well as the analysis of two different methods of representing threaded connections in FEM models. Both these activities were in service of the creation of a FEM model of the structure of the contribution of the EU to LiteBIRD: the Medium-High-Frequency Telescope (MHFT). All analysis was done using the Siemens NX software and the Simcenter Nastran solver. This model has passed preliminary quality checks and will be used for future structural analysis intended to verify the integrity of the design, its compliance with JAXA requirements, and to perform screw dimensioning. The results of those analyses will inform possible future design changes or will support the current design. Logistical work on the project was also performed, consisting of the groundwork to initiate an Assembly, Integration and Testing (AIT) plan and an Assembly, Integration and Verification (AIV) plan. This primarily involved the creation of a Model Definition Document, which contained clear and complete descriptions of the different MHFT models to be used throughout project development. The document defines the purpose and components of the models, the dependencies between models, as well as the necessary tests to be performed on each as part of the AIT and AIV process. A list of the structure interfaces was also created, which will contribute to the development of an interface control document.
22

Development of calibration and noise characterization methods for a CMB telescope, GroundBIRD, using its commissioning observation data / CMB偏光観測望遠鏡 GroundBIRDにおけるコミッショニング観測のデータを用いた較正手法とノイズ評価手法の開発

Sueno, Yoshinori 25 March 2024 (has links)
京都大学 / 新制・課程博士 / 博士(理学) / 甲第25107号 / 理博第5014号 / 新制||理||1715(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 田島 治, 教授 中家 剛, 准教授 榎戸 輝揚 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM
23

Etude des différentes composantes de la polarisation du ciel en vue de l'observation du Fond Diffus Cosmologique avec le satellite Planck

Aumont, Jonathan 27 September 2007 (has links) (PDF)
Cette thèse est dédiée à la mesure des anisotropies du Fond Diffus Cosmologique (CMB) ainsi qu'à la caractérisation des émissions d'avant-plan. Les travaux que nous avons entrepris s'inscrivent dans le cadre de la préparation à l'analyse et à l'exploitation des données du satellite Planck.<br />L'exposé débute par une introduction à la cosmologie et au CMB. Un état des lieux des mesures cosmologiques est dressé et les expériences Archeops, WMAP et Planck sont présentées.<br />Une deuxième partie est consacrée à l'effet d'un champ magnétique primordial sur la polarisation du CMB. Nous y dérivons les spectres de puissance angulaire de cet effet et nous donnons une limite supérieure sur l'intensité actuelle de ce champ à l'aide des données de WMAP.<br />Dans une troisième partie, nous présentons les analyses effectuées à partir des mesures de l'expérience Archeops. D'une part, nous montrons le caractère gaussien des données en température à 143 GHz, contraignant ainsi le paramètre de couplage non linéaire et les résidus systématiques et d'autre part, à l'aide des données à 353 GHz, nous montrons la première mesure de l'émission diffuse polarisée de la poussière galactique à grande échelle.<br />Une quatrième partie présente une méthode de séparation de composantes permettant d'extraire les différentes contributions physiques à partir d'observations multifréquences, en température et en polarisation. Nous caractérisons ses performances sur des simulations du ciel vu par Planck.<br />Enfin, dans une dernière partie, nous nous attachons à modéliser les émissions galactiques polarisées du synchrotron et de la poussière et nous comparons ces émissions simulées aux données des expériences Archeops et WMAP.
24

Sources des aérosols en milieu urbain : cas de la ville de Paris / Aerosol composition and source apportionment in urban areas : case of Paris City Metropolitan Area

Abidi, Ehgere 18 December 2013 (has links)
La connaissance des sources des particules dans le milieu ambiant est devenue une préoccupation majeure depuis que leur impact sur la santé est avéré. Ainsi, une connaissance détaillée de la nature des fines particules (PM) et de leurs sources, devient nécessaire pour quantifier l’importance des émissions sur la masse totale en PM. Dans ce contexte, l’objectif de ce travail est de mieux connaître la composition chimique et les sources de l’aérosol organique. Les travaux réalisés s’intègrent dans le cadre du projet MEGAPOLI. Deux campagnes ont été conduites en région parisienne en été et en hiver sur deux sites urbain (LHVP) et suburbain (SIRTA). Une caractérisation chimique des PM2.5 a été effectuée. La contribution des sources primaires des PM2.5 fut calculée par modélisation CMB et les résultats furent par la suite intercomparés à ceux obtenus par les approches AMS/PMF et radiocarbone 14C. L’analyse CMB montra qu’en hiver, les principales sources contributrices sont les sources primaires, dominées par les émissions véhiculaires et la combustion de la biomasse. En été, les concentrations de PM2.5 sont gouvernées par les espèces secondaires. D’après l’approche basée sur les marqueurs organiques secondaires, le SOA biogénique traditionnel contribue faiblement à la masse de PM2.5. La comparaison des deux approches CMB et AMS-PMF a montré qu’en hiver, les différences ont été observées pour les deux sources majeures d’aérosol organique : combustion de biomasse et source véhiculaire. En été, les différences obtenues sont moins marquées. Les comparaisons des résultats de modélisation CMB avec les mesures de 14C, approche totalement indépendante, montrèrent un bon accord. / Knowing the sources of airborne fine particulate matter in ambient area became a major concern since their adverse effects on health were. Then, knowing in detail the nature and the sources of the fine particles (PM) is necessary to quantify the relative importance of the emissions on the total PM concentration. In this context, the main objective is to better know the chemical composition and the sources of the organic aerosol. This works is integrated within the MEGAPOLI framework. Two intensive campaigns were led in Paris region in summer and in winter at an urban (LHVP) and a suburban (SIRTA) sites. During the both sampling campaigns, a complete PM2.5 chemical characterization was made. The contributions of the PM2.5 primary sources were calculated by CMB modelling and the results were intercompared with those obtained by the AMS/PMF and the radiocarbon 14C approaches. The CMB analysis showed that in winter, the main contributing sources were primary, dominated by vehicular exhaust and biomass burning. In summer, the PM2.5 ambient concentrations were mainly governed by secondary species. According to the approach based on the secondary organic markers, the traditional biogenic SOA contribution to the PM2.5 mass was. The both CMB and AMS-PMF approaches comparison showed that in winter, the differences were particularly observed for both major organic aerosol sources: biomass burning and vehicular exhaust. In summer, the differences between both approaches were less visible. The comparisons of the CMB modeling approach results with the radiocarbon 14C measurements, a totally independent approach, show a very good agreement between both approaches
25

Reversed flux patches on the archeomagnetic field / Lóbulos de fluxo reverso no campo arqueomagnético

Filipe Terra Nova dos Santos 30 April 2015 (has links)
Archeomagnetic field models may provide important insights to the geodynamo. Here we investigate the existence and mobility of reversed flux patches (RFPs) in an archeomagnetic field model. We introduce topological algorithms to define, identify, and track RFPs. In addition, we explore the relations between RFPs and dipole changes and apply robustness tests to the RFPs. In contrast to previous definitions, patches that reside on the geographic equator are adequately identified based on our RFPs definition. Most RFPs exhibit a westward drift and migrate toward higher latitudes. Undulations of the magnetic equator and RFPs oppose the axial dipole moment (ADM). Filtered models show a tracking behavior similar to the nonfiltered model, and surprisingly new RFPs occasionally emerge. The advection and diffusion of RFPs have worked in unison to yield the decrease of the ADM at recent times. The absence of RFPs in the period 550-1440 A.D. is related to a low in intermediate degrees of the geomagnetic power spectrum. We thus hypothesize that the RFPs are strongly dependent on intermediate spherical harmonic degrees 4 and above. Filtered models and comparison with the GUFM1 model suggest that RFPs are robust features of the geomagentic field for the last millennia. / Modelos do campo arqueomagnético podem fornecer importantes informações sobre o geodínamo. Nesta dissertação, estudou-se a existência e a mobilidade de lóbulos de fluxo reverso (RFPs, em inglês) no campo arqueomagnético. Testes de robustez foram aplicados para diferentes modeles. Além disso, foram exploradas as relações entre RFPs e as variações do momento do dipolo axial (ADM, em inglês). Para tanto, foram desenvolvidos algoritmos topológicos para definir, identificar e mapear os RFPs em modelos do campo arqueomagnético (modelo CALS3k.4b e modelo GUFM1). O equador magnético foi usado para definir a polaridade ao invés do equador geográfico. Uma vez que cada ponto da grade de 1 grau x 1 grau de latitude/longitude é associado com um hemisfério magnético e uma polaridade (normal ou reversa), o passo seguinte é identificar os picos de lóbulos de fluxo reverso. No passo final de identificação um critério de intensidade é imposto para evitar lóbulos que possuem intensidade muito baixa. Para mapear lóbulos de fluxo reverso no tempo, foi codificado um algoritmo que calcula a distancia de cada lobulo para todos os lóbulos do próximo intervalo de tempo. Diferentemente das definições anteriores, lóbulos que residem no equador geográfico são adequadamente identificados com a nova definição de RFPs. A maioria dos RFPs exibe deriva para Oeste e mais de 75% deles migram em direção a altas latitudes. Ondulações do equador magnético e RFPs resultam de campo com momento oposto ao ADM. Modelos filtrados apresentam resultados de mapeamento semelhantes aos de modelos não-filtrados, e em alguns casos, surgem nos modelos filtrados novos RFPs. Resultados dos modelos CALS3k.4b e GUFM1 para o período de 1840 AD até 1990 AD mostram concordância para o mapeamento de lóbulos de fluxo reverso com maiores similaridades para os filtros mais fortes. Os resultados desta dissertação são compatíveis com a ideia que a advecção e a difusão de RFPs tem operado em conjunto causando o decréscimo do ADM nos últimos séculos. A ausência de RFPs no período de 550-1440 AD sendo relacionada a baixos valores nos graus intermediários do espectro de potencia. Dessa forma, sugere-se que os RFPs são fortemente dependentes dos harmônicos esféricos de graus 4 e acima. Modelos filtrados e comparações com o modelo GUFM1 sugerem que lóbulos de fluxo reverso são feições robustas do campo magnético terrestre nos últimos milênios.
26

A gest??o educacional de uma institui????o de ensino p??blica da esfera federal: o caso do Col??gio Militar de Bras??lia

Souza, Gabriela Menezes de 16 August 2017 (has links)
Submitted by Sara Ribeiro (sara.ribeiro@ucb.br) on 2018-01-19T15:31:04Z No. of bitstreams: 1 GabrielaMenezesdeSouzaTese2017.pdf: 1470084 bytes, checksum: 4eb1b2a5304d3f3ae89a8ee7cf9dfc29 (MD5) / Approved for entry into archive by Sara Ribeiro (sara.ribeiro@ucb.br) on 2018-01-19T15:31:22Z (GMT) No. of bitstreams: 1 GabrielaMenezesdeSouzaTese2017.pdf: 1470084 bytes, checksum: 4eb1b2a5304d3f3ae89a8ee7cf9dfc29 (MD5) / Made available in DSpace on 2018-01-19T15:31:22Z (GMT). No. of bitstreams: 1 GabrielaMenezesdeSouzaTese2017.pdf: 1470084 bytes, checksum: 4eb1b2a5304d3f3ae89a8ee7cf9dfc29 (MD5) Previous issue date: 2017-08-16 / This research has as general objective to identify the model of educational management employed in the CMB from the official documents that govern the teaching in the institution and from the perception of the participants of the research. This is a case study about the Military College of Bras??lia (CMB), a public institution of the federal sphere, whose main sponsor is the Brazilian Army. Participating in the research were a manager of the Directorate of Preparatory Education and Assistance (DEPA), the Teaching Director, the pedagogical advisor to the Head of the Teaching Division (DE), the Head of School Supervision and six former CMB students, as well as teachers and educational supervisors. Also analyzed were documents that deal with all activities related to the development and operation of military colleges belonging to the Military College System of Brazil (SCMB). In these normative documents, it was noticed the concern with the diverse dimensions of the school. They are texts that act as support for the activities of the manager, since they guide all the work to be developed in the college. As theoretical reference, theoretical ideas were used that deal with concepts of management of educational institutions, educational management models, educational planning concepts and models of such planning as Ribeiro (1978), L??ck (2000), Zainko (2000) ), Sander (2007), Kuenzer et all (2015), among others. After analyzing the data, it is considered that the management model adopted by the CMB follows a hierarchical structure that can be noticed in the way the analyzed documents are organized. The results show that the management model assumed by the CMB contemplates traces of a strategic planning and allows, in a limited way, the participation of the school community. We therefore consider that the management model applied by CMB is close to the multidimensional paradigm of Sander (2007), since it contemplates the different dimensions in which a school should be managed, except for the dimension of the participation of the school community. / Essa pesquisa tem como objetivo geral identificar o modelo de gest??o educacional empregado no CMB a partir dos documentos oficiais que regem o ensino na institui????o e a partir da percep????o dos participantes da pesquisa. Trata-se de um estudo de caso sobre o Col??gio Militar de Bras??lia (CMB), uma institui????o de ensino p??blico da esfera federal, cuja mantenedora ?? o Ex??rcito brasileiro. Participaram da pesquisa uma gestora da Diretoria de Educa????o Preparat??ria e Assistencial (DEPA), o Diretor de Ensino, o assessor pedag??gico do Chefe da Divis??o de Ensino (DE), o Chefe da Supervis??o Escolar e seis ex-alunos do CMB, al??m de professores e supervisoras educacionais. Tamb??m foram analisados os documentos que tratam de todas as atividades relacionadas ao desenvolvimento e funcionamento dos col??gios militares pertencentes ao Sistema Col??gio Militar do Brasil (SCMB). Nesses documentos normativos, percebeu-se a preocupa????o com as diversas dimens??es da escola. S??o textos que atuam como suporte para as atividades do gestor, visto que orientam todo o trabalho a ser desenvolvido no col??gio. Como referencial te??rico, utilizou-se as ideias de te??ricos que versam sobre conceitos de gest??o de institui????es de ensino, modelos de gest??o educacional, conceitos de planejamento educacional e modelos desses planejamentos tais como Ribeiro (1978), L??ck (2000), Zainko (2000), Sander (2007), Kuenzer et all (2015), dentre outros. Ap??s a an??lise dos dados, considera-se que o modelo de gest??o adotado pelo CMB obedece a uma estrutura hierarquizada que pode ser notada na maneira como s??o organizados os documentos analisados. Os resultados obtidos revelam que o modelo de gest??o assumido pelo CMB contempla tra??os de um planejamento estrat??gico e permite, de forma limitada, a participa????o da comunidade escolar. Consideramos, portanto, que o modelo de gest??o aplicado pelo CMB aproxima-se do paradigma multidimensional de Sander (2007), pois contempla as diversas dimens??es em que uma escola deve ser gerida exceto no que tange ?? dimens??o da participa????o da comunidade escolar.
27

Reversed flux patches on the archeomagnetic field / Lóbulos de fluxo reverso no campo arqueomagnético

Santos, Filipe Terra Nova dos 30 April 2015 (has links)
Archeomagnetic field models may provide important insights to the geodynamo. Here we investigate the existence and mobility of reversed flux patches (RFPs) in an archeomagnetic field model. We introduce topological algorithms to define, identify, and track RFPs. In addition, we explore the relations between RFPs and dipole changes and apply robustness tests to the RFPs. In contrast to previous definitions, patches that reside on the geographic equator are adequately identified based on our RFPs definition. Most RFPs exhibit a westward drift and migrate toward higher latitudes. Undulations of the magnetic equator and RFPs oppose the axial dipole moment (ADM). Filtered models show a tracking behavior similar to the nonfiltered model, and surprisingly new RFPs occasionally emerge. The advection and diffusion of RFPs have worked in unison to yield the decrease of the ADM at recent times. The absence of RFPs in the period 550-1440 A.D. is related to a low in intermediate degrees of the geomagnetic power spectrum. We thus hypothesize that the RFPs are strongly dependent on intermediate spherical harmonic degrees 4 and above. Filtered models and comparison with the GUFM1 model suggest that RFPs are robust features of the geomagentic field for the last millennia. / Modelos do campo arqueomagnético podem fornecer importantes informações sobre o geodínamo. Nesta dissertação, estudou-se a existência e a mobilidade de lóbulos de fluxo reverso (RFPs, em inglês) no campo arqueomagnético. Testes de robustez foram aplicados para diferentes modeles. Além disso, foram exploradas as relações entre RFPs e as variações do momento do dipolo axial (ADM, em inglês). Para tanto, foram desenvolvidos algoritmos topológicos para definir, identificar e mapear os RFPs em modelos do campo arqueomagnético (modelo CALS3k.4b e modelo GUFM1). O equador magnético foi usado para definir a polaridade ao invés do equador geográfico. Uma vez que cada ponto da grade de 1 grau x 1 grau de latitude/longitude é associado com um hemisfério magnético e uma polaridade (normal ou reversa), o passo seguinte é identificar os picos de lóbulos de fluxo reverso. No passo final de identificação um critério de intensidade é imposto para evitar lóbulos que possuem intensidade muito baixa. Para mapear lóbulos de fluxo reverso no tempo, foi codificado um algoritmo que calcula a distancia de cada lobulo para todos os lóbulos do próximo intervalo de tempo. Diferentemente das definições anteriores, lóbulos que residem no equador geográfico são adequadamente identificados com a nova definição de RFPs. A maioria dos RFPs exibe deriva para Oeste e mais de 75% deles migram em direção a altas latitudes. Ondulações do equador magnético e RFPs resultam de campo com momento oposto ao ADM. Modelos filtrados apresentam resultados de mapeamento semelhantes aos de modelos não-filtrados, e em alguns casos, surgem nos modelos filtrados novos RFPs. Resultados dos modelos CALS3k.4b e GUFM1 para o período de 1840 AD até 1990 AD mostram concordância para o mapeamento de lóbulos de fluxo reverso com maiores similaridades para os filtros mais fortes. Os resultados desta dissertação são compatíveis com a ideia que a advecção e a difusão de RFPs tem operado em conjunto causando o decréscimo do ADM nos últimos séculos. A ausência de RFPs no período de 550-1440 AD sendo relacionada a baixos valores nos graus intermediários do espectro de potencia. Dessa forma, sugere-se que os RFPs são fortemente dependentes dos harmônicos esféricos de graus 4 e acima. Modelos filtrados e comparações com o modelo GUFM1 sugerem que lóbulos de fluxo reverso são feições robustas do campo magnético terrestre nos últimos milênios.
28

Dynamique non-linéaire et anisotropie primordiale en cosmologie

Pitrou, Cyril 29 May 2008 (has links) (PDF)
La grande précision des mesures du fond diffus cosmologique nécessitent de comprendre avec finesse la physique sous-jacente afin d'en tirer des conclusions pertinentes sur la phase primordiale de l'univers. Dans cette thèse nous étudions la théorie des perturbations non-linéaires dans le cadre de la relativité générale. Notre but est de déterminer le transfert des perturbations de la métrique ainsi que des perturbations du contenu matériel,<br />entre la phase primordiale de l'univers et les observations réalisées<br />aujourd'hui. Nous nous plaçons tout d'abord dans l'approximation fluide afin d'appréhender les comportements généraux attendus. Ensuite nous étudions la théorie cinétique au second ordre, nécessaire pour obtenir le transfert radiatif non-linéaire, dans le but de déterminer la non-gaussianité dans le<br />fond diffus cosmologique. <br />Nous étudions également la théorie des perturbations linéaires<br />autour d'espaces anisotropes. Nous élaborons la théorie des perturbations invariantes de jauge autour d'un espace de Bianchi I, puis nous étudions les signatures observationnelles d'une phase primordiale d'inflation possédant cette symétrie.
29

Contributions à l'analyse des données dans l'expérience Archeops et à la mesure de la masse des neutrinos avec les expériences CMB

Bourrachot, Alexandre 22 September 2004 (has links) (PDF)
Les anisotropies du rayonnement fossile de l'Univers (CMB) constituent une des surces d'information les plus prometteuses sur la physique de l'Univers. C'est pourquoi de nombreuses expériences de mesure d'anisotropies se sont développées ces dernières années. Archeops est une expérience ballon de mesure des anisotropies du CMB, fruit d'une collaboration internationale pilotée par le Centre de Recherches sur les Très Basses Températures (CRTBT) du CNRS de Grenoble. Archeops est d'un point de vue technique le précurseur du futur satellite européen Planck. Dans un premier temps, je rappelle les fondements théoriques du modèle standard de la cosmologie. Je présente ensuite les caractéristiques des expériences de mesure des anisotropies du CMB et notamment celles d'Archeops. Dans un deuxième temps, j'expose mes contributions au sein de la collaboration Archeops. Mon travail comporte d'une part une partie instrumentale liée à la reconstruction du pointage, et d'autre part une partie d'analyse de données basée sur le développement d'algorithmes de destriage. Pour finir, je discute de la nature des contraintes sur la masse des neutrinos qui seront susceptibles d'être obtenus avec les données de Planck.
30

Etudes autour des anisotropies du corps noir cosmologique et des amas de galaxies

Dore, Olivier 21 December 2001 (has links) (PDF)
Le paradigme cosmologique actuel s'appuie sur l'instabilite du modele de Friedman-Lemaitre vis-a-vis des inhomogeneites de densite d'energie, pour rendre compte de la formation des grandes structures de l'Univers, telles que nous les observons. Dans ce cadre, il a ete predit, puis observe, que ces necessaires inhomogeneites impriment sur un rayonnement fossile millimetrique (CMB), par ailleurs thermalise a 3K, homogene et isotrope, d'infimes variations de temperature. Par l'observation plus precise de telles anisotropies, de nombreuses expériences presentes ou a venir, telles ARCHEOPS, TopHat, ou PLANCK, esperent tester ce paradigme avec une precision sans precedent. Toutefois, les besoins inedits de ces experiences necessitent l'invention de nouvelles methodes d'analyse de donnees CMB. En reponse a certains de ces besoins, nous avons developpe au cours de notre these, une methode multi-grille originale de fabrication rapide de cartes de ces fluctuations de temperature a partir de donnees ordonnees en temps, une methode hierarchique de mesure du spectre de puissance angulaire de ces cartes, une modelisation analytique des effets de lobe instrumental, et un test original de detection d'une composante non-Gaussienne dans la distribution statistique de ces fluctuations. Par ailleurs, regardant ces inhomogeneites bien plus tardivement dans leur evolution, nous pouvons observer, entre autres grandes structures, des amas de galaxies. A ces objets, les plus massifs gravitationnellement lies aujourd'hui, nous nous sommes interesse dans un second temps. En particulier, nous avons construit un modele analytique permettant l'inclusion d'effets de chauffage non-gravitationnel, connus par leurs consequences observationnelles importantes. Enfin, nous avons presente une methode permettant une meilleure description du contenu baryonique de ces amas au moyen d'\emph(une analyse conjointe d'observations de distorsions gravitationnelles, de l'effet Sunyaev-Zel'dovich, et de l'emission X, ces deux derniers effets originant du gaz chaud contenu dans les amas.

Page generated in 0.0204 seconds