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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.
111

Misstro mot vaccination i modern kommunikation : Kvantitativ analys av Facebookgruppen "Stop Mandatory Vaccination" / Distrust of Vaccination in Modern Communication : Quantitative Analysis of the Facebook Group "Stop Mandatory Vaccination"

Sundberg, Mikael January 2019 (has links)
Syften med uppsatsen var att ta reda på hur folk som är en del av anti-vaccinationsrörelsen kommunicerar i sociala medier. Uppsatsen undersöker hur de kommunicerar i inlägg och kommentarer i en sluten grupp på Facebook. Med hjälp av ett kodschema så blev 97 inlägg analyserade och placerad i olika kategorier med olika variabler. Utifrån kodschemat blev flera tabeller skapade som visade den mest relevanta faktan. Utifrån den information, och med flera detaljerat beskriva exempel-inlägg, beskrivs den generella stämningen i gruppen och hur de talar med varandra. Resultatet blev att de kommunicerar med varandra på ett vänligt och stöttande sätt, bidrar med relevant information när det frågas efter, men med lite fientlighet visas mot de som kommer med motsatta åsikter. Gruppen var sluten, vilket innebär att bara individer som delar samma åsikter som dem är medverkande på plattformen, vilket också betyder att åsikter blir så gott som aldrig utmanade. / The purpose of this essay has been to figure out how people that are a part of the anti-vaccination movement communicate in social media. The essay explores how they communicate in posts and comments in a closed group on Facebook. With the help of a coding scheme, 97 posts became analysed and placed in different categories with different variables. A couple of tables were created from the code scheme that demonstrated the most relevant facts. From that information, and with several detailed descriptions of example posts, describes the general mode in the group and how they speak with each other. The result was that they communicate with each other in a nice and supporting way, contribute with relevant information when it was asked for, but with some hostility shown towards those who come with opposite views. The group was closed, which means that only individuals who share the same views as them are involved with the platform, which also means that opinions are almost never challenged.
112

Sociální sítě jako zdroj pro žurnalistiku v České republice / Social media as a source for journalists in Czech Republic

Žemličková, Martina January 2019 (has links)
This Diploma Thesis are focused on social media as a tool for journalists in Czech republic. It contains two main parts - theoretical and practical. In theoretical part, social media are described in general, and Facebook, Twitter and Instagram are described in more details. This part is focused mostly on current trends in social media usage. Theoretical part is also focused on journalist's source problematic, primarily in internet era, and on source's credibility and verifiability. These trends are more described for media field in USA and Czech republic. Theoretical part introduce the newest available studies in social media and journalism field. Practical part is aiming to verify or deny these trends through quantitative analysis of media content, focused on usage of citations from social media as a relevant source for articles. Quantitative analysis is supported with e-mail questioning amongst czech journalist, who complete a context to this issue with their opinion. The research shows that journalists in Czech republic use social media daily for their work and they are following their colleagues from USA, so they use citations from social media more carefully and they verify their sources more. The main reason is the fear of fake news spreading, which they perceive as the biggest thread for...
113

Análise do papel da morfologia e do uso do solo na gênese e na distribuição das feições erosivas na bacia do córrego Espraiado, São Pedro (SP) / Analysis of the role of morphology and land use in the genesis and in the distribution of erosional features in the Espraiado basin, São Pedro (SP)

Daniel, Evandro 25 September 2012 (has links)
Os fatores condicionantes antrópicos e morfométricos são determinantes na formação do escoamento pluvial, do manejo do solo e na concentração de fluxos e detritos. No município de São Pedro (SP) é notória a ocorrência desses processos, sendo classificado, segundo o mapa de erosão do Estado de São Paulo como de alta suscetibilidade. Desta forma, a bacia do córrego Espraiado, localizada neste município, foi selecionada com objetivo de analisar a gênese e a distribuição das feições erosivas a partir da influência dos parâmetros morfométricos (curvatura, declividade e hipsometria) e antrópicos numa escala evolutiva (1962, 1972, 2000 e 2006) e também numa análise integrada e quantitativa (feições erosivas, uso do solo e parâmetros morfométricos), por meio do cálculo dos seguintes índices: Concentração de Erosão (CE) e Potencial de Erosão (PE). O primeiro índice é a razão entre o número de células em cada classe afetadas pela erosão e o número total de células na bacia, enquanto o segundo índice é a razão entre o número de células em cada classe afetadas pela erosão e o número total de células na mesma classe. Nos mapas das feições erosivas, observou-se que a partir do cenário de 1962 até 2006 a área total das feições erosivas registrou uma redução, no qual a cabeceira das drenagens revelou o setor com maior ocorrência e concentração de feições. O mapa do uso do solo revelou que o aumento do percentual de mata, da área urbana consolidada e da silvicultura, e a redução do solo exposto e da pastagem tiveram um papel determinante para a diminuição das feições erosivas, embora a classe de área urbana consolidada tenha influenciado diretamente para o surgimento de novas feições e a evolução de outras. A análise integrada mostrou que a curvatura côncava, a declividade entre 20 e 40% e as classes de solo exposto e de pastagens foram as mais suscetíveis e que estão presente principalmente nas áreas das cabeceiras de drenagens, setor que está associado a solos pouco espesso. Os índices também indicaram que mesmo as áreas com a presença de curvatura convexa ou retilínea e declividades entre 0 e 15% com baixos índices de PE mas com alterações antrópicas significativas, obtiveram aumento do potencial de ocorrência de feições erosivas, assim como, as classes de uso com baixo índice de PE quando associados aos parâmetros morfométricos de alto índice, propiciaram aumento da formação de feições erosivas. / The anthropic and morphometric factors are significant in the formation of runoff, soil management and concentration flows and debris. In the São Pedro city (SP) is recognized to exist of these processes, being classified, according to the erosion map of São Paulo state as high susceptibility. Thus, the Espraiado basin, located in this city, was selected to analyze the genesis and distribution of erosional features by the influence of morphometric parameters (curvature, slope and elevation) and anthropic in the evolutionary scale (1962, 1972, 2000 and 2006) and also an integrated and quantitative analysis (erosional features, land use and morphometric parameters), by calculating the following index: Erosion Concentration (EC) and Erosion Potential (EP). The first index is the ratio of the number of cells in each class affected by the erosion areas to the total number of cells in the basin, while the second index is the ratio of the number of cells in each class affected by the areas of erosion to the total number of cells in the same class. In the erosional features maps, we observed from 1962 to 2006 scenario, that the total area of erosional features decrease, in which the head drainages revealed the sector with the highest occurrence and concentration of features. The land use map showed that the increase of the percentages of the forest, of the urban area consolidated and the forestry, and the reduction of exposed soil and pasture were the role played on the reducing the erosive features, although the class of urban area consolidated was directly influenced in the new features and developments of the others. The integrated analysis showed that the concave curvature, the slope between 20 and 40% and the classes of exposed soil and pasture were the most susceptible and are primarily in the headwaters, a sector that is associated with very thick soils. These areas of high concentration runoff flow and debris, with fragile lithology and have a PE high, is related to the presence of curvature concave, in profile and plant, and concentrated flows, as well as high slope that increases the erosive power of the flow, factors that are associated with the erosion formation. The index also indicated that even the areas with the presence of convex or straight curvatures, slopes between 0 and 15%, with low PE but with significant anthropogenic changes, obtained an increase of the potential occurrence of erosional features, as well as classes use with low PE when associated with morphometric parameters of high, caused an increase of erosional features.
114

Desenvolvimento e automatização de um método teórico para a avaliação quantitativa da seletividade de proteínas do MHC por diferentes antígenos / Development and automation of a theoretical method for quantitative evaluation of the MHC proteins of different antigens selectivity

Silva, Jackson Gois da 25 June 2004 (has links)
Realizamos neste trabalho a automatização da nova metodologia MHCalc, desenvolvida anteriormente em nosso laboratório, que teve como resultado o programa homônimo escrito em linguagem C para ambiente GNU/Linux, o qual avalia quantitativamente a seletividade de uma determinada proteína MHC. Esta avaliação quantitativa possibilita o estabelecimento de uma escala de preferência dos resíduos de ocorrência natural para cada uma das posições de interação da fenda de apresentação do MHC; por permutação destes resíduos, podem-se derivar regras de composição para peptídeos reconhecíveis em cada alelo estudado, inclusive na ausência de dados experimentais. A metodologia desenvolvida em nosso laboratório se baseia na avaliação da seletividade de cada bolsão independentemente, através da energia de interação do mesmo com cada aminoácido de ocorrência natural. O programa MHCalc utiliza o pacote de programas THORMM [Moret, 1998] de modelagem molecular para otimização geométrica das estruturas descritas, e tem como entrada unicamente um arquivo de coordenadas em formato POB contendo as coordenadas de um complexo MHC/peptídeo, tendo como saída uma tabela de dados contendo os resíduos de ocorrência natural em ordem de preferência para cada bolsão. Testamos o programa MHCalc para o complexo formado pela molécula HLA-DR1 (DRA DRB1 *01 01) e o peptídeo de Hemaglutinina, obtido no Brookhaven Protein Data Bank com a entrada 10LH, sendo este sistema escolhido por ser altamente estudado e com abundância de dados experimentais e teóricos para comparação de resultados. Até o presente momento obtivemos os dados referentes ao bolsão 1, os quais estão em pleno acordo com a literatura. / In this work we automated the new methodology MHCalc, developed previously in our laboratory, which resulted in the computational program with the same name, written in C language to GNU/Linux environment. The program MHCalc evaluates quantitatively the selectivity of a given MHC protein. This quantitative evaluation allows the establishment of a preference scale of the naturally occurring residues for each pocket of a MHC molecule. From such a study it may be derived composition rules to peptides recognizable in each allele studied, even in the absence of experimental data. The methodology developed in our laboratory is based on the selectivity evaluation of each pocket independently, through its interaction energy with each naturally occurring amino acid. The program MHCalc uses the molecular modeling package THORMM [Moret, 1998] to optimize the geometry of the structures described below, and needs as only entry the PDS like file with the coordinates of the MHC/peptide complex. The program finishes printing out a data file containing the naturally occurring residues in preference order for each pocket and the data used to order these residues. We tested the program MHCalc to the complex molecule HLA-DR1 (DRA DRB1 *01 01) with the Hemaglutinin peptide, obtained at the BrookHaven Prote in Data Bank (1 DLH entry). This system was chosen because it has been highly studied and so offers abundant experimental and theoretical data to compare our results. We obtained data referring to pocket 1 so far, which is in full agreement with the literature.
115

Interpretace výskytu ztrát míče v basketbalu mládeže v České republice / Interpretation of violations and offesive fouls in the youth basketbal

Musil, Jan January 2019 (has links)
Title: Interpretation of the occurence turnovers in youth basketbal in Czech republic. Objectives: Our goal is to assess the degree forced and unforced turnovers in basketball matches in two age categories. Our assumption is that the in the higher category, the occurrance of unforced turnovers is lower. Methods: Method of work is indirect observation of videos, analysis and creation of quantitative research on teams category U15 and U19, then a detailed analysis of the number and type of turnovers of individual categories and matches follows. Results: We found that younger category reached a larger number of unforced turnovers and forced turnovers too. Turnovers were caused primarily from the mistakes of the players.Both categories reached more forced turnovers. The possible solution is emphasis on the development of individual game performance in practice. Keywords: youth basketball, team game performance, quantitative analysis, turnovers
116

Biodiversidade de mosca-das-frutas do gênero Anastrepha (Diptera, Tephritidae) no campus Luiz de Queiroz, Piracicaba, São Paulo. / Biodiversity of anastrepha fruit flies (dip., tephritidae) on the luizde queirozcampus, Piracicaba, São Paulo.

Uramoto, Keiko 12 July 2002 (has links)
Este trabalho foi conduzido na área abrangida pelo campus Luiz de Queiroz/Universidade de São Paulo, no município de Piracicaba, Estado de São Paulo. Teve como objetivos, determinar a composição do gênero Anastrepha Schiner, sua distribuição e a análise quantitativa da população. Além disso, verificou-se a relação da flutuação populacional com variáveis bióticas e abióticas e a associação das espécies de plantas hospedeiras, estabelecidas na área, com as espécies de Anastrepha.Foram examinadas 23.263 fêmeas de Anastrepha coletadas em armadilhas McPhail e 18 espécies pertencentes a 9 grupos infragenéricos foram assinaladas. A distribuição das fêmeas por armadilha foi fortemente agregada, com 5 armadilhas (6%) capturando 50% do total de fêmeas. Apenas A. fraterculus (Wiedemann) e A. obliqua (Macquart) foram dominantes. A. fraterculus foi a espécie mais freqüente, representando 80,2% do total de fêmeas capturadas no campus e a mais constante ocorrendo em 98,04% das amostras. Em ordem decrescente de freqüência, seguiram-se A. obliqua (12,6%), A. pseudoparallela (Loew) (3,1%) e A. bistrigata Bezzi (2,1%). As demais espécies apresentaram freqüência menor que 1%. O valor elevado do índice de Simpson (0,66) e os valores baixos do índice de Shannon (0,7521) e de eqüitatividade (0,459) resultaram da alta freqüência de A. fraterculus. Um aumento no nível populacional das espécies de Anastrepha ocorreu de agosto a novembro com um pico máximo em setembro. A disponibilidade de frutos hospedeiros foi mais determinante na variação do tamanho da população das espécies mais abundantes de Anastrepha que as variáveis climáticas. Um total de 565 amostras de frutos pertencentes a 11 famílias e, pelo menos, 25 espécies botânicas foi coletado em 47 estações de capturas. Foram identificadas 10.290 fêmeas e das 18 espécies de Anastrepha capturadas em armadilhas somente 6 emergiram das amostras de frutos: A. bistrigata Bezzi, A. fraterculus (Wiedemann), A. obliqua (Macquart), A. pseudoparallela (Loew), A. serpentina (Wiedemann) e A. sororcula Zucchi. A. fraterculus foi a espécie que infestou maior diversidade de frutos. Os hospedeiros preferidos de A. obliqua foram as espécies da família Anacardiaceae. A. pseudoparallela e A. serpentina infestaram exclusivamente Passifloraceae e Sapotaceae, respectivamente. Uma nova associação de mosca-das-frutas com planta hospedeira foi constatada: A. fraterculus em Syagrus romanzoffiana (Cham.) Glassman (coquinho). Foi reportado o primeiro registro da associação de A. fraterculus em Manilkara zapota L. (sapoti) no Brasil. / This study was conducted in the Luiz de Queiroz campus of the Universidade de São Paulo, in Piracicaba, state of São Paulo. The aim of this study was to determine the number of species in the genus Anastrepha Schiner on campus, their distribution and the quantitative analysis of the population. Moreover, this study correlated populational fluctuations with biotic and abiotic factors as well as the association between host plant species and the Anastrepha species in that area. A total of 23,263 females of Anastrepha collected in MacPhail traps was examined, and 18 species belonging to nine infrageneric groups were registered. The distribution of females per trap was strongly clustered, with 5 traps (6%) capturing 50% of the total of females. Only A. fraterculus (Wiedemann) and A. obliqua (Macquart) were considered dominant species. A. fraterculus was by far the most frequent species, representing 80.2% of the total of females captured on campus, and the most constant, occurring in 98.04% of the analyzed samples. In decreasing order of frequency, A. obliqua (12.6%), A. pseudoparallela (Loew) (3.1%), and A. bistrigata Bezzi (2.1%) comprised the other major species. The remaining species showed frequency lower than 1%. The high value of the Simpson’s index (0.66) as wel as the low values of Shannon’s index (0.7521) and the equitability index (0.459) resulted from the high frequency of A. fraterculus. The populational level of Anastrepha increased from August to November with the highest peak in September. The availability of host fruit, more than climatic parameters determined most of the variation of population size in the most abundant species of Anastrepha. A total of 565 fruit samples representing at least 25 plant species from 11 families was collected in 47 capture sites. 10,290 females were identified. Of the 18 Anastrepha species captured in traps, only 6 also emerged from fruit samples: A. bistrigata Bezzi, A. fraterculus (Wiedemann), A. obliqua (Macquart), A. pseudoparallela (Loew), A. serpentina (Wiedemann) e A. sororcula Zucchi. A. fraterculus infested the greatest diversity of hosts. The preferred hosts of A. obliqua were plant species in the family Anacardiaceae. A. pseudoparallela and A. serpentina infested only species in the families Passifloraceae and Sapotaceae, respectively. A new fruit fly and host plant association was registered: A. fraterculus with Syagrus romanzoffiana (Cham.) Glassman (queen palm). The association of A. fraterculus with Manilkara zapota L. (sapodilla) was reported here for the first time in Brazil.
117

Gestão de design : uma análise quantitativa em empresas brasileiras listadas no ranking If Design

Moura, Janine Barbosa. 03 September 2009 (has links)
Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2015-03-21T00:34:54Z No. of bitstreams: 1 00000740.pdf: 1980084 bytes, checksum: 225c934ee7c428947b520fc116b828fd (MD5) / Made available in DSpace on 2015-03-21T00:34:54Z (GMT). No. of bitstreams: 1 00000740.pdf: 1980084 bytes, checksum: 225c934ee7c428947b520fc116b828fd (MD5) Previous issue date: 2009-09-03 / Nenhuma / A Gestão de Design tem recebido atenção da academia e vem sendo delineada como uma nova área de atuação em ambientes de produção, como meio para sustentar inovações, diferenciar produtos em relação à concorrência e gerar oportunidades de ganhos, contribuindo para melhorar o desempenho empresarial. A Gestão de Design explora a integração de diferentes atividades em um processo interdisciplinar que influencia a estratégia da organização, pensando e concebendo formas alternativas para gerar soluções inovadoras e sustentáveis. O objetivo desta pesquisa é analisar a Gestão de Design nas empresas brasileiras embasado em uma análise quantitativa a partir de um a população de 43 empresas brasileiras identificadas por excelência em design. Para dar suporte à pesquisa os principais aspectos que envolvem a Gestão de Design foram identificados por meio de uma revisão teórica dos conceitos associados a essa temática. A revisão permitiu elencar hipóteses a serem testadas, associadas a constructos representativos da Gestão de Design. O método utilizado foi o levantamento (survey) e os dados coletados foram submetidos a análises estatísticas, que permitiram a validação das hipóteses construídas para a população estudada. O estudo indica que as empresas que têm se destacado em design alcançaram um nível de maturidade em relação ao tema e percebem a importância da Gestão de Design para a empresa não necessariamente em função de seu porte ou tempo de mercado. / The Design Management has received attention from academia and has been outlined as a new area in production environments as a means to support innovation, differentiate products from competitors and generate revenue opportunities, contributing to improve business performance. The Design Management explores the integration of different activities in an interdisciplinary process that influences the organization's strategy, creating and developing alternative ways to generate innovative and sustainable solutions. The objective of this research is to analyze the Design Management in Brazilian companies based on aquantitative analysis from a population of 43 Brazilian companies identified for the excellence in design. To support the research the main aspects involved in the Design Management were identified through a review of theoretical concepts associated with this theme. The review helped to identify hypotheses to be tested, associated with constructs representative of Design Management. The method use dwas a survey and the data collected were subjected to statistical analysis, which allowed the validation of the hypotheses for this population. The study indicates that companies that have gained notoriety in design have achieved a level of maturity over the issue and have realized that the importance of Design Management for the company is not necessarily a function of size or time in the market.
118

Caracterização clínica, laboratorial e da composição de urólitos em felinos domésticos / Clinical, laboratory characterization and composition of uroliths in domestic felines

Gomes, Veridiane da Rosa 19 February 2018 (has links)
Submitted by Erika Demachki (erikademachki@gmail.com) on 2018-03-29T19:21:32Z No. of bitstreams: 2 Dissertação - Veridiane da Rosa Gomes - 2018.pdf: 2765105 bytes, checksum: c057139a9b5403263960909e06b08a8b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Erika Demachki (erikademachki@gmail.com) on 2018-03-29T19:23:56Z (GMT) No. of bitstreams: 2 Dissertação - Veridiane da Rosa Gomes - 2018.pdf: 2765105 bytes, checksum: c057139a9b5403263960909e06b08a8b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-03-29T19:23:56Z (GMT). No. of bitstreams: 2 Dissertação - Veridiane da Rosa Gomes - 2018.pdf: 2765105 bytes, checksum: c057139a9b5403263960909e06b08a8b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-02-19 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The dissertation is divided into two chapters, the first one is a bibliographical review about urinary lithiasis in felines and the second chapter a scientific article reporting epidemiological, clinical and laboratory characterization of urolithiasis in felines. Urinay calculi of 42 felines attended in Veterinary teaching Hospital of Federal University of Goias (HV/EVZ/UFG) and other private veterinary clinics and hospitals were assessed using chemical analysis and energy dispersive spectroscopy (EDS). The most observed mineral was struvite (38,1%), followed by ammonium urate (35,7%) and calcium oxalate (26,2%). The males were more affected (26/42), as well mixedbreed animals (36/42). Animals aged between 25 and 72 months old were the most affected (27/42). In 33 cases (78,6%) the stones were recovered of bladder. The clinical signs with most occurrence were dysuria (65,0%), hematuria (50,0%), vomiting (17,5%) and anorexia (12,5%). Of the 42 felines studied, 39 (92.8%) were neutered. Regarding feeding, 26 (61.9%) cats received dry rations exclusively, while 13 (38.1%) received dry and wet rations. Despite the higher occurrence of struvite uroliths, a significant presence of ammonium urate uroliths was observed, which highlights the importance of studies on feline disease. The urolithiasis in cats is little studied in our country and the present work is a pioneer in the analysis of calculations in felines in Brazil, mainly due to the use of techniques of quantitative analysis, such as the dispersive energy spectroscopy. / A dissertação está dividida em dois capítulos, sendo o primeiro uma revisão bibliográfica sobre a litíase urinária em felinos e o segundo capítulo um artigo científico onde objetivou-se caracterizar epidemiológica, clínica e laboratorialmente a urolitíase em felinos. Cálculos urinários de 42 gatos atendidos no Hospital Veterinário da Escola de Veterinária e Zootecnia da Universidade Federal de Goiás (HV/EVZ/UFG) e em clínicas e hospitais veterinários de diferentes regiões do país foram analisados por meio de técnica de análise química, e espectroscopia de energia dispersiva (EDS). A estruvita foi o mineral mais observado (38,1%), seguido de urato amônio (35,7%) e oxalato de cálcio (26,2%). Os machos foram mais acometidos (26/42), bem como os animais sem raça definida (36/42). Animais com idade entre 25 e 72 meses tiveram maior representação (27/42). Em 33 casos (78,6%) os cálculos foram recuperados da bexiga. Os sinais clínicos de maior ocorrência foram disúria (65,0%), hematúria (50,0%), vômito (17,5%) e anorexia (12,5%). Dos 42 felinos estudados, 39 (92,8%) eram castrados. Quanto a alimentação, 26 (61,9%) gatos recebiam exclusivamente ração seca, enquanto que 13 (38,1%) recebiam associação de ração seca e úmida. Apesar da maior ocorrência de urólitos de estruvita, foi observada significativa presença de urólitos de urato amônio o que ressalta a importância de estudos sobre a enfermidade na espécie felina. A urolitíase em gatos é pouco estudada em nosso país e o presente trabalho é pioneiro na análise de cálculos em felinos no Brasil, especialmente pelo uso de técnicas de análise quantitativa, como a espectroscopia de energia dispersiva.
119

Développement d'un dispositif de LIBS pour l'analyse quantitative en ligne des procédés de purification du silicium fondu / Development of a LIBS device for inline quantitative analysis during silicon melt purification

Patatut, Loïc 15 December 2015 (has links)
L’objectif de ce travail de thèse a été de développer et de valider une méthode d’analyse quantitative du silicium liquide par la technique LIBS (Laser Induced Breakdown Spectroscopy). Pour cela, le dispositif utilisé consiste en une mesure intrusive sur la surface de bulles gazeuses, générées au cœur du métal fondu par soufflage d’un gaz inerte au travers d’un tube. Dans un premier temps, les conditions d’acquisition du signal ont été optimisées pour permettre la répétabilité et la reproductibilité du signal LIBS en dépit des fluctuations paramétriques induites par le bullage. Dans un second temps, les paramètres expérimentaux affectant les propriétés physiques des plasmas produits ont été évalués pour maximiser la sensibilité de la mesure et réduire les limites de détection. Les deux paramètres clefs qui ont été identifiés sont la densité de puissance apportées par l’impulsion laser et la nature du gaz de bullage : l’intensité du signal et donc le nombre d’émetteurs dans les plasmas sont favorisés par les hautes énergies laser et par une atmosphère d’argon plutôt que d’hélium. Le diagnostic spectroscopique des plasmas générés en fonction de ces paramètres a permis de montrer qu’ils n’ont pas d’effet significatif sur la température des électrons, des ions et des espèces neutres. L’augmentation de masse ablatée par le laser et la modification des conditions de relaxation du plasma par le milieu ambiant sont les mécanismes majoritaires à considérer. Finalement un modèle d’analyse quantitatif a été construit dans les conditions optimisées pour les impuretés B, Al, Fe, Cu et Ti du silicium. Il permet d’atteindre des limites de détection qui vont de quelques ppmw pour les éléments B, Fe et Al jusqu’à moins de 0,5 ppmw pour le Cu et le Ti. Les concentrations prédites par LIBS présentent un très bon accord avec celles déterminées par une méthode ex-situ conventionnelle, l’ICP-OES, avec des écarts relatifs inférieurs en moyenne à 10 %. Ceci démontre l’intérêt de la technique LIBS pour contrôler in-situ et en temps réel un procédé d’élaboration du silicium photovoltaïque. / The aim of this PhD research work was to develop and to validate a quantitative method to measure the composition of molten silicon by Laser Induced Breakdown Spectroscopy (LIBS). The device used consists in an intrusive measurement on the surface of gas bubbles which are produced by blowing an inert gas through a pipe inserted into the melt. First, the signal acquisition conditions were optimized to ensure LIBS signal repeatability and reproducibility to overcome experimental fluctuations due to the bubbling. Second, the experimental parameters affecting plasma physics were evaluated to maximize the measurement sensitivity and to lower the limits of detection. The two key parameters identified are the laser power density and the ambient gas: the signal intensity and then the number of emitters inside the plasma are promoted by higher laser energy and an Ar atmosphere rather than a He one. The plasma spectroscopic diagnosis as a function of these parameters showed that they don’t have significant effect on the temperature of electrons, ions and neutral species. The only mechanisms to be considered are then the increase of the mass ablated by the laser and the modification of the plasma relaxation conditions by the ambient atmosphere. Third, calibration curves were established for B, Al, Fe, Cu and Ti impurities under the optimized conditions. Limits of detections from few ppmw for B, Fe and Al to less than 0,5 ppmw for Ti and Cu have been achieved. The predicted concentrations by LIBS are in very good agreement with the ones measured by the conventional ex-situ method, ICP-OES. The mean relative discrepancy is lower than 10 %. These results demonstrate the LIBS benefits for in-situ and in-line monitoring of photovoltaic silicon production processes.
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Quantitative analysis of multi-phase systems -steels with mixture of ferrite and austenite

Fawad, Salman Kohar January 2004 (has links)
<p>The goal of this work has been to evaluate the different experimental techniques used for quantitative analysis of multi-phase materials systems. </p><p>Powder based specimens containing two-phases, austenite and ferrite , were fabricated and quantified. The volume fraction of ferrite varied from 2 Vol% to 50 Vol%. </p><p>X ray powder diffraction (XRD) measurements were based on two peak analysis. Computer based software Topas was used for quantitative analysis, which is believed to be the most advanced in this field. XRD results were found within the absolute limit of +/- 4% of given ferrite volume fraction. Volume fraction as low as 2 Vol% was successfully detected and quantified using XRD. However, high statistical error was observed in case of low volume fraction, such as 2 Vol% and 5 Vol% ferrite volume fraction. </p><p>Magnetic balance (MB) measurements were performed to determine the volume fraction of magnetic phase, ferrite. MB results were found in good agreement with given volume fractions. As low as 2 Vol% volume fraction was detected and quantified with MB. MB results were within the absolute limit of +/- 4% of given ferrite volume fraction. </p><p>Image analysis (IA) was performed after proper sample preparation as required by electron backscatter diffraction (EBSD) mode of Scanning electron microscopy (SEM). IM results were found within the absolute limit of +/- 2 % of given ferrite volume fraction. However, high statistical error was observed in case of 2 Vol% volume fraction.</p>

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