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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.
11

Etude des amas de galaxies avec l'expérience PLANCK, via l'effet Sunyaev-Zel'dovich / The Sunyaev-Zel'dovich effect from galaxy clusters with the PLANCK satellite

Hurier, Guillaume 10 December 2012 (has links)
Cette thèse se focalise sur l'étude des amas de galaxies, via l'effet Sunyaev-Zel'dovich (tSZ), qui consiste en l'interaction de ces même amas avec le fond diffus cosmologique. Pour ce faire j'ai utilisé les données expérimentale de l'instrument HFI du satellite PLANCK. Cette thèse ce découpe en trois parties majeures, (1) L'analyse et le traitement des données en temps, des données brut jusqu'au cartes du ciel, ce focalisant tout particulièrement sur les effets systématiques. (2) Le développement de méthode de séparation de sources, permettant la construction de cartes par émission astrophysique (tout particulièrement l'effet Sunyaev-Zel-dovich) à partir de données multi-fréquences. (3) L'analyse physique des cartes d'effet Sunyaev-Zel'dovich, produit par le gaz d'électron chaud présent dans les amas de galaxies. Ce travail permet la mise en place de contrainte, sur le profile de pression des amas de galaxies, sur la présence de filaments de matière entre des système binaire d'amas de galaxies, ainsi que la mise en évidence du spectre de puissance de l'effet tSZ. / This work is focusing on the study of the thermal Sunyaev-Zel'dovich (tSZ) effect produced by the gaz of hot electrons present in galaxy clusters. This effect consist on the interaction between the Cosmic Microwave Background (CMB) and galaxiy clusters. For this purpuse I used the data from the High Frequency Instrument (HFI) of the PLANCK satellite. This work can be divided in three main parts : (1) The study of systématics effects present in the Time Ordered Data and in the construction of the sky maps. (2) The devellopement of new components seperation methods for the tSZ effect in the context of multi-frequencies observations. (3) The physical analysis of the tSZ effect providing constraints on the galaxy clusters properties. This work allow to put some constraints on the galaxy clusters pressure profile, on the WHIM components present in the inter-clusters medium between binary system of galaxy clusters and on the detection of the tSZ power spectrum with PLANCK.
12

Caractérisation des effets systématiques de l'instrument Planck/HFI, propagation et impact sur les données scientifiques / Characterization of the systematic effects on the Planck/HFI instrument, propagation and impact on science data

Sauvé, Alexandre 05 December 2016 (has links)
Planck est un satellite de l'ESA lancé en 2009, qui avais pour mission de faire une carte de très grande précision du rayonnement fossile de l'Univers, afin de mieux comprendre comment il s'est formé. Cet objectif ambitieux nécessite un niveau de maîtrise extrême des effets instrumentaux. Cependant en cours de mission il s'est avéré que le composant responsable de la numérisation des données scientifiques introduisait un bisais important qui compromettait l'exploitation scientifique des données de l'instrument Planck/HFI. Ce travail décris comment ce biais a été compris et corrigé avec succès. Une analyse très poussée a été conduite sur les détecteurs du satellite, la chaine cryogénique embarquée et le composant de numérisation lui même. Ce qui a nécessité une méthodologie spécifique afin de télécharger les données nécessaire depuis le satellite avant sa fin de mission et son décommissionnement. / Planck is an ESA spacecraft launched in 2009, its mission goal was to map with an exquisite precision the first light of Universe, to help understanding how it has formed. This ambitious objective requires a very high level of control on the instrumental effects. During the mission, it has been found that the component responsible of the digitization of scientific data introduced an unexpectedly high bias effect, preventing full exploitation of data from the Planck/HFI instrument. The present work relates how this bias effect was understood and successfully corrected for. A very deep analysis of the spacecraft detectors, the cryogenic chain, and the digitization component has been performed, which required a specific methodology to gather data from the spacecraft before the end of the mission and its decommissioning.
13

Constraining the Temperature Evolution of the Cosmic Microwave Background Using the Sunyaev Zel’dovich Effect with SPT-3G

Korman, Milo 27 January 2023 (has links)
No description available.
14

Multi-mode receiver systems for cosmic microwave background B-mode polarisation experiments

Legg, Stephen January 2018 (has links)
A measurement of the primordial B-mode polarisation of the Cosmic Microwave Background would provide direct evidence of inflation in the early universe. The extremely weak nature of the B-mode signal necessitates an instrument with a high sensitivity and precise control over systematic effects. Multi-mode antenna feed horns offer higher sensitivity than their single-mode counterparts, however their behaviour is much more complex. The Short Wavelength Instrument for the Polarisation Explorer (SWIPE) onboard the Large Scale Polarisation Explorer (LSPE) is one instrument planning to implement multi-mode feed horns. SWIPE will attempt to detect the primordial B-mode at large angular scales, measuring the sky in three bands at 140, 220 and 240 GHz. A single on-axis High-Density PolyEthylene (HDPE) lens and polarisation-splitting wire grid combine to focus the radiation from the sky onto two focal planes of multi-mode horns feeding bolometric detectors. A large diameter rotating metal-mesh half-wave plate allows both polarisations to be measured by the same pixel, therefore bypassing many detector systematics. Simulations are performed to predict the sky beam for two key pixels: closest to and furthest from the centre of the focal plane. For the 140 GHz channel the cross-polarisation is predicted, and the optimum location at which to place the telescope’s focus behind the horn aperture to maximise gain and optimise beam shape is investigated. A measurement of the multi-mode horn is performed using a room-temperature bolometer. An investigation is also conducted to assess to what extent the same measurements can be performed using a coherent measurement system such as a vector network analyser. A working coherent measurement technique is devised, however it is limited to horns carrying only the first 3 modes.
15

Air-quality modeling and source-apportionment of fine particulate matter: implications and applications in time-series health studies

Marmur, Amit 27 September 2006 (has links)
Fine particulate matter (PM2.5) has been associated with adverse effects on human health, but whether specific components of PM2.5 are responsible for specific health effects is still under investigation. The complex chemical composition of PM2.5 and issues such as multi-component interactions, spatial variability and sampling/instrument error further complicates this analysis. A complementary approach to examining species-specific associations is to assess associations between health outcomes and sources contributing to PM2.5, which can provide critical information to regulators to tighten controls on sources that contribute most to adverse health effects and allows for better multi-pollutant epidemiologic analyses, as the number of source-categories is typically far less than the number of PM2.5 species. This study develops and evaluates various air quality modeling approaches for determining daily source contributions to ambient PM2.5. Results from long-term air quality simulations using an emissions-based model (Models-3/CMAQ - Community Multiscale Air-Quality model) were evaluated in terms of the model's ability to simulate short-term (e.g., daily) variability in concentrations of PM2.5 components. To examine source-specific health outcomes, an extended PM2.5 source-apportionment model, CMB-LGO (Chemical Mass Balance incorporating the Lipschitz Global Optimizer) was developed and compared with results based on other approaches such as CMB, PMF (Positive Matrix Factorization), and Models-3/CMAQ in terms of simulating the daily variability of source impacts. Based on findings from spatial and temporal analyses of tracer concentrations and source impacts, PM2.5 source-apportionment results from CMB-LGO and PMF were applied in a health-study for the Atlanta area. Despite methodological differences and uncertainties in the apportionment process, good agreement was observed between the CMB-LGO and PMF based risk ratios, indicating to the usefulness of applying apportionment methods in health studies.
16

Characterization and Improvement Strategies of Mobile Source Air Quality Monitoring Station¡V Using Kungkuan Station of Miaoli as An Example

Chen, Chang-Jeong 17 February 2005 (has links)
ABSTRACT It is important to improve ambient air quality by reducing the emission from mobile sources. In order to investigate the characteristics of mobile sources, the statistic of traffic flow and the measurement of suspended particles were conducted in the Gonguan air quality monitoring station of Miaoli County in this investigation. Through chemical mass balance (CMB) receptor model and backward trajectory model, the location and contribution of emission sources were further identified. Accordingly, the improvement strategies for mobile sources were further proposed to improve local ambient air quality. In order to know the traffic flow variability of motor vehicles, passenger cars, motorcycle, heavy-duty diesel trucks, and buses were recorded every 15 minutes by a video camera for both weekend and weekdays. In the meantime, TSP and PM10 were simultaneously collected with high-volume samplers. The metallic content and water-soluble ionic species of particulate matter were analyzed with an inductively coupled plasma-atomic emission spectrophotometer (ICP- AES) and an ionic chromatography (IC). Chemical composition of suspended particles was then be used for source apportionment with the CMB model. Finally, the improvement strategies for mobile source management were further proposed through the correlation of traffic flow and vehicle emission rate. The results showed that the PM10/TSP ratios of suspended particles collected at the rooftop of a four-floor building was higher than those sampled at the air quality monitoring station for all quarters except the third quarter. PM>10 is the main factor for the concentration difference of suspended particles sampled on the rooftop of the building as well as at the monitoring station. Results from traffic flow records showed that passenger cars were the major source contributing greatly to the traffic flow, while no significant variation of buses was observed in the traffic flow. The linear regression of PM>10 concentration and vehicles for different wind directions (i.e. northwest, southwest and northeast) was undertaken. The results showed that, when the winds were blown from the northwest and southwest, the determination coefficients (R2) of the regression were 0.1226 (passenger cars), 0.4821 (motorcycles), 0.1014 (heavy-duty trucks), 0.3113 (buses), and 0.1919 (total traffic flow) respectively. It was 0.6140 (passenger cars), 0.6227 (motorcycles), 0.7761 (heavy-duty trucks), 0.2111 (buses), and 0.6309 (total traffic flow), respectively, for the northeast winds. It concluded that the traffic flow has significant influence on the concentration of suspended particle at the downwind sites. Among the vehicles, heavy-duty trucks played a key role. Consequently, reducing truck flow has to be paid more attention for the improvement of ambient air quality. During the sampling period, Ca, Fe, and Al were the most abundant metals of suspended particles, while Mg, K, Zn, and Cu ranked the second. Besides, the metallic contents of suspended particles sampled at the rooftop were generally lower than those collected at the monitoring station. It suggested that street dusts had major contribution to Gonguan air quality monitoring station. Among the water-soluble ionic species, sulfate (SO42-), nitrate (NO3-), and ammonium (NH4+) were major anions, converting mainly from SO2, NOx, and NH3. The results showed that the metallic contents in the second quarter were higher than that in the fourth quarter. However, an opposite trend was observed for anions. The Back Trajectory Model and CMB were applied to analyze the suspended particle. The results showed that the seasonal variation of air pollutants was also affected by the monsoon. Though air pollutants emitted from the nearby waste incinerators and industrial districts could be transported to the sampling site, resulting in unavoidable influence on suspended particles, tail gas and fugitive dusts emitted from vehicles were the most important sources contributed to the ambient air quality. The results indicated that motor vehicles were the major source of ambient suspended particles on the road sites. Therefore, the reduction of traffic emission should be the first step of the improvement strategies for ambient air quality. Especially, the emission of road dusts resulting from the drive-through of heavy-duty trucks should be paid more attention. This study proposed two strategies for improving ambient air quality: one for raising the road serving level and the other for reducing vehicles on road at the traffic crowd section. After the road serving level was improved, the TSP, NOx, CO and THC were respectively decreased about 41, 5,765, 316, and 62 g/day. The concentration of TSP, NOx, CO, and THC was respectively decreased about 95.66 £gg/m3, 38.59 ppb, 1.93 ppm, and 1.90 ppm. After carrying out special vehicle on the road control strategy, TSP, NOx, CO, and THC could be respectively decreased about 2,136, 19,291, 169,843, and 3181g/day. The concentrations of TSP, NOx, CO, and THC were respectively decreased about 96.03 £gg/m3, 52.25 ppb, 2.05ppm and 1.69ppm.. Thus, ambient air quality can be effectively improved if the heavy-duty trucks can be controlled during the rush hour. Furthermore, a substitute road for heavy-duty trucks is another option for the improvement of ambient air quality.
17

Source contributions of suspended particles using Air Quality Model and Receptor Model

Wang, Wen-Cheng 21 December 2008 (has links)
Air quality of the Kao-Ping airshed has been the worst of all airsheds which are divided into seven groups by districts in Taiwan. The percentage of annual bad air quality (Pollution Standard Index, PSI > 100) in the Kao-Ping airshed (6.65−13.56%) was twice than it in the Yun-Chia-Nan airshed (2.58−6.98%) during the past decade (1998−2007). Oil refineries, petrol/plastic industries, power plants, and iron/steel/metal plants are the major industries in the Kaohsiung metropolitan area. Due to intensive industrial and traffic activities, the Kao-Ping area has the poorest air quality in Taiwan − either increased ground-level concentrations of particulate matter (PM) or ozone (O3) associated with unfavorable meteorological conditions − particularly between late fall and mid-spring The temporal and spatial characterization of suspended particles in the Kao-Ping area was analyzed by using TAPM (air quality model) and CMB (receptor model) to understand the contributions of the major emission sources. Estimations using the TAPM model suggest that point-source emissions were the predominant contributors (about 49.1%) to PM10 concentrations at Hsiung-Kong industrial site in Kaohsiung City, followed by area sources (approximately 35.0%) and neighboring transport (7.8%). Because Ping-Tung City (urban) and Chao-Chou town (rural) are located downwind of Kaohsiung City when north or northeasterly winds prevail, the two sites also experience severe pollution events despite the lack of industrial sources; neighboring transport contributed roughly 39.1% to PM10 concentrations at Ping-Tung and 48.7% at Chao-Chou. Results of CMB (chemical mass balance) modeling show that the main contributors to PM2.5 mass are vehicle exhaust (gasoline vehicle emission: 43% and diesel vehicle emission: 17% at Hsiung-Kong; gasoline vehicle emission: 45% and diesel vehicle emission: 19% at Ping-Tung; gasoline vehicle emission: 12% and diesel vehicle emission: 29% at Chao-Chou). And the main contribution to PM2.5-10 mass is the paved road emission (Hsiung-Kong: 40%; Ping-Tung: 48%; Chao-Chou: 50%). It is recommended that air quality model is an appropriate tool to large area and receptor model is more suitable to specific point to identify emission sources by the results in this study.
18

Análise sistêmico-funcional de gêneros argumentativos

Serra, Gláucia Cristina Maia Réga 07 December 2017 (has links)
Dissertação (mestrado)—Universidade de Brasília, Instituto de Letras, Departamento de Linguística, Português e Línguas Clássicas, Programa de Pós-Graduação em Linguística, 2017. / Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2018-04-04T17:05:13Z No. of bitstreams: 1 2017_GláuciaCristinaMaiaRégaSerra.pdf: 2808713 bytes, checksum: 6d0eafec8021c048677cf443558b7efa (MD5) / Approved for entry into archive by Raquel Viana (raquelviana@bce.unb.br) on 2018-04-10T18:53:07Z (GMT) No. of bitstreams: 1 2017_GláuciaCristinaMaiaRégaSerra.pdf: 2808713 bytes, checksum: 6d0eafec8021c048677cf443558b7efa (MD5) / Made available in DSpace on 2018-04-10T18:53:07Z (GMT). No. of bitstreams: 1 2017_GláuciaCristinaMaiaRégaSerra.pdf: 2808713 bytes, checksum: 6d0eafec8021c048677cf443558b7efa (MD5) Previous issue date: 2018-04-10 / Este estudo tem como objetivo analisar textos argumentativos utilizados em aulas, exercícios e provas do Ensino Médio do Colégio Militar de Brasília, a fim de identificar e descrever as configurações dos gêneros presentes nesse corpus, bem como as características léxicogramaticais que auxiliam essa configuração. Esta pesquisa toma como base os pressupostos teórico-metodológicos da Linguística Sistêmico-Funcional (HALLIDAY, 1978, 1994; HALLIDAY e MATTHIESSEN, 2004, 2014) e a perspectiva de gênero da Escola de Sydney (MARTIN e ROSE 2008, 2012). e As categorias gramaticais das Metafunções: Ideacional, as representações do mundo físico e da consciência; Interpessoal, a representação das relações estabelecidas entre autor e leitor; e Textual, a forma de organização das informações em texto, foram investigadas no intuito de se compreender de que forma esses elementos podem auxiliar o processo argumentativo. Analisou-se, também, a presença de nominalização nos textos como recurso argumentativo. Após as análises, pode-se constatar o uso da 1ª pessoa na metade dos textos e o uso frequente dos processos relacionais, conferindo subjetividade aos textos, o que se confirma com os estudos feitos quanto à modalização e a modulação. Além disso, a nominalização se manifesta como recurso eficaz no processo argumentativo, por meio do empacotamento de ideias, do apagamento do agente e da densidade que cria nos textos. Com base nas análises do corpus, composto de textos da Família dos Argumentos, nomenclatura segundo a Escola de Sydney, verificou-se a predominância de textos do gênero Exposição, que discute apenas um ponto de vista no texto. A divisão dos textos em etapas e fases revelou a predominância de fases declarativas, responsáveis pelo início da maioria das etapas e pelo estabelecimento dos tópicos frasais. Constatou-se também que esse tipo de análise é um recurso importante para que os alunos, que geralmente apresentam dificuldades no processo ensino e aprendizagem do texto argumentativo, possam não só compreender o processo de construção desse texto, mas também sejam capazes de produzi-lo de forma mais eficaz. / This study aims to analyze argumentative texts used in classes, exercises and tests of the High School of Military College of Brasília, in order to identify and describe the configurations of the genres present in this corpus, as well as the lexical-grammatical characteristics that help this configuration. The theoretical and methodological frameworks of the Theory of Genres from Sydney School (MARTIN and ROSE, 2008, 2012) and Systemic Functional Linguistics (HALLIDAY, 1978, 1994; HALLIDAY and MATTHIESSEN, 2004, 2014) guide this research. The grammatical categories of Metafunctions: Ideational, representations of the physical world and consciousness; Interpersonal, representation of the relationships established between author and reader; and Textual, how information is organized in text, were investigated in order to understand how these elements can aid the argumentative process. It was also analyzed the presence of nominalization in the texts as an argumentative resource. After the analyzes, the use of the first person in almost 50% of the texts and the frequence of the relational processes could be verified, conferring subjectivity to the texts, which is confirmed by the studies made on modalization and modulation. In addition, nominalization appears as an effective resource in the argumentative process, by the packing of ideas, the erasing of the agent and the density it creates in texts. Based on the analysis of the corpus, composed of texts of the Family of Arguments, nomenclature according to the Sydney School, there was the predominance of texts of the genre Exposition, which discusses only one point of view in the text. The division of the texts into stages and phases showed the predominance of declarative phases, responsible for the beginning of most stages and the establishment of phrasal topics. This type of analysis is an important resource so that students, who usually present difficulties in the teaching and learning process of the argumentative text, can not only understand the construction of this text, but also be able to produce it more effectively.
19

Modelling and experimental study of millimetre wave refractive systems

Ozturk, Fahri January 2014 (has links)
Astronomical instruments dedicated to the study of Cosmic Microwave Background polarization are in need of optics with very low systematic effects such as beam shape and cross-polarization in an optical configuration. With the demand for millimetre wave larger focal planes comprising thousands of pixels, these systematic effects have to be minimal across the whole focal surface. In order to reach the instrument requirements such as resolution, cross-polarization and beam ellipticity, new optical configurations with well-understood components have to be studied. Refractive configurations are of great importance amongst the potential candidates. The aim is to bring the required technology to the same level of maturity that has been achieved with well-understood existing ones. This thesis is focused on the study of such optical components for the W-band spectral domain. Using optical modelling with various software packages, combined with the manufacture and accurate experimental characterization of some prototype components, a better understanding of their performance has been reached. To do so, several test set-ups have been developed. Thanks to these new results, full Radio-Frequency refractive systems can be more reliably conceived.
20

Searching the Cosmos: Ripples from Avant-Garde Cosmological Probes

Montero Camacho, Paulo 02 October 2019 (has links)
No description available.

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