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Ljung, Björn. "Korrigering för slumpfel och metodeffekter i sambandsanalys av enkätdata med SQP 2.0." Thesis, Uppsala universitet, Statistiska institutionen, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-198883.
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Sambandsanalys av surveydata kompliceras av förekomsten av slumpfel och metodeffekter i de avgivna svaren. Dessa felkällor kan leda till betydande över- eller underskattning av sambanden mellan undersökta variabler, och riskerar att leda till felaktiga slutsatser. En sedan länge känd metod för att estimera och kontrollera för slumpfel och metodeffekter i enkätdata är den så kallade Multitrait Multimethod-metoden (MTMM). Nackdelen med MTMM-metoden är att den kräver att varje fråga som ska analyseras ställs minst tre gånger i samma enkät, vilket gör att ansatsen i praktiken oftast inte är möjlig att tillämpa. Sedan 2012 finns dock ett verktyg, SQP 2.0, som gör det möjligt att skatta slumpfel och metodeffekter i enkätdata utan att genomföra MTMM-experiment. Den här uppsatsen utvärderar prediktionerna från SQP 2.0 på en enkät om arbetslivsrelaterade frågor besvarad av svenska och brittiska respondenter. Programvarans prediktioner jämförs med resultat från MTMM-experiment, och effekten på sambandsanalysen av att tillämpa SQP-programvarans prediktioner av slumpfel och metodeffekter studeras. Slutsatserna från studien är att SQP 2.0 ger predicerade värden för slumpfel och metod-effekter som ligger nära de MTMM-estimerade i de flesta fall, men att betydande avvikelser också förekommer. Vidare konstateras att korrigering för slumpfel och metodeffekter har en betydande effekt på absolutvärdet av korrelationerna mellan variabler under de studerande förhållandena: korrelationerna i det studerade fallet ökar kraftigt efter justering. Korrelationernas relativa storlek förändras i mindre utsträckning, men för en enkät med mer varierade frågetyper kan också dessa påverkas kraftigt.Correlation analysis of survey data is complicated by the presence of random errors and method effects in the answers given. These factors can lead to significant over- or underestimation of the correlations between variables. A well-established method for estimating and controlling for random error and method effects in survey data is the Multitrait-Multimethod (MTMM) approach. The disadvantage of this method is that it requires that each survey item to be analysed is asked multiple times in the same survey, making the approach hard to use in many practical situations. Since 2012 there is a tool available, SQP 2.0, to predict random errors and method effects in survey data without performing MTMM experiments. This paper evaluates the use of predictions from the SQP 2.0 software on the correlation analysis of a survey of work related matters answered by Swedish and British respondents. The software's predictions are compared with results from MTMM experiments, and the effect on the correlations of applying the SQP software's predictions of random errors and method effects are studied. The conclusion of the study is that SQP 2.0 gives predicted values for random error and method effects that are close to the MTMM-estimates in most cases, but that considerable deviations also occur. It is further concluded that controlling for random error and method effects has a significant effect on the absolute values of the correlations between variables in the studied cases: the correlations in the study increase substantially after adjustment. The relative sizes of the correlations between variables change to a lesser extent, but a questionnaire with more varied question types may have lead to different results in this respect.
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Jones, Catherine Toni, and n/a. "Biggs's 3P Model of Learning: The Role of Personal Characteristics and Environmental Influences on Approaches to Learning." Griffith University. School of Applied Psychology, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030304.092316.
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The aim of this research programme was to examine the 3P model of learning (Biggs, 1987a, 1999). The first stage necessarily involved an examination of the Study Process Questionnaire (SPQ) (Biggs, 1987a), an instrument developed to measure the process component of the model. The structure of the SPQ was examined utilising exploratory and confirmatory factor analysis of undergraduate responses (n= 260). The results indicated the higher-order factor structure of deep-achieving and surface-achieving-motive provided the most reliability and a better model fit than either the subscales or scales of the SPQ. The construct validity of the two constructs deep and surface was assessed next using a multitrait-multimethod matrix (MTMM) constructed from the three measures of the self-report questionnaire, interview ratings and written assessments from first-year students (n = 50). The results indicated good convergent validity between the deep scale of the SPQ and the interview ratings on the deep scale, between the deep scale on the SPQ and the written assessment ratings, and between the interview ratings and written assessment ratings. The results indicated good convergent validity between the surface scale on the SPQ and the interview ratings on the surface scale, but not between the surface scale on the SPQ and the written assessment ratings, and between the interview ratings and written assessment ratings. The discriminant validity between deep and surface was good for the SPQ, but not for either the interview or the written assessment. The findings indicate the deep and surface scales of the SPQ adequately measure the underlying deep and surface constructs. The retest reliability of the SPQ was then examined utilising Spearmans Rho to assess the rank-order correlations with a sample of third-year students (n=87). Over a period of three months there were significant correlations for the surface motive, surface strategy, deep strategy, achieving motive and achieving strategy subscales of the SPQ, suggesting good reliability for these subscales. The results at the scale level of the SPQ result in similar conclusions. There was a moderate significant correlation for the surface, deep and achieving scales of the SPQ, suggesting the scales have good reliability over a period of three months. There was also a moderate significant correlation for the surface-achieving-motive and deep-achieving scales over a period of three months. The stability of SPQ scores was also assessed utilising a series of one-way repeated measures MANOVAs with a sample of third-year undergraduates (n = 64). The results suggest some change occurs in self-reported use of approaches to learning between the first and third-years of an undergraduate degree programme. The role of the teaching-learning environment was next examined. Utilising a within-subjects design, undergraduate students (n=48) concurrently enrolled in traditional (viz. lecture and tutorial) and non-traditional (viz. workshops and group projects) subjects completed the SPQ to describe their approaches to learning in each subject. A series of 2x2 repeated measures MANOVAs were undertaken. The results indicated students were likely to change their approach to learning based on their perceptions of the learning environment (traditional or non-traditional subject). However, those students identified as predominantly surface learners significantly increased their deep scale scores in the non-traditional subject when compared to deep learners. The next study examined a range of personality (locus of control, sensing function, thinking function, intelligence) and demographic variables (age, gender, year of study) to assess which were good predictors of deep and surface approaches to learning. A series of regression analyses identified age, sensing function and locus of control as significant predictors of the surface, surface-achieving-motive, and deep approaches to learning. Locus of control was found to be a significant predictor of the deep-achieving approach to learning. The final study examined the 3P model of learning. Based on the results of earlier studies in the research programme the situational component of the presage factors was not included. The model was examined using structural equation modelling (n= 394). Two initial models were tested using both the three (deep, surface, achieving) and two (surface-achieving-motive and deep-achieving) process factor models. The three process factor model provided the better model fit. The results suggest deep and surface approaches to learning do not mediate between personal characteristics and learning outcomes (i.e. GPA). The results of this series of studies suggest the need for further research into the SPQ and the 3P model of learning. The implications of the research programme are also discussed.
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Jones, Catherine Toni. "Biggs's 3P Model of Learning: The Role of Personal Characteristics and Environmental Influences on Approaches to Learning." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/366357.
Full textAbstract:
The aim of this research programme was to examine the 3P model of learning (Biggs, 1987a, 1999). The first stage necessarily involved an examination of the Study Process Questionnaire (SPQ) (Biggs, 1987a), an instrument developed to measure the process component of the model. The structure of the SPQ was examined utilising exploratory and confirmatory factor analysis of undergraduate responses (n= 260). The results indicated the higher-order factor structure of deep-achieving and surface-achieving-motive provided the most reliability and a better model fit than either the subscales or scales of the SPQ. The construct validity of the two constructs deep and surface was assessed next using a multitrait-multimethod matrix (MTMM) constructed from the three measures of the self-report questionnaire, interview ratings and written assessments from first-year students (n = 50). The results indicated good convergent validity between the deep scale of the SPQ and the interview ratings on the deep scale, between the deep scale on the SPQ and the written assessment ratings, and between the interview ratings and written assessment ratings. The results indicated good convergent validity between the surface scale on the SPQ and the interview ratings on the surface scale, but not between the surface scale on the SPQ and the written assessment ratings, and between the interview ratings and written assessment ratings. The discriminant validity between deep and surface was good for the SPQ, but not for either the interview or the written assessment. The findings indicate the deep and surface scales of the SPQ adequately measure the underlying deep and surface constructs. The retest reliability of the SPQ was then examined utilising Spearman’s Rho to assess the rank-order correlations with a sample of third-year students (n=87). Over a period of three months there were significant correlations for the surface motive, surface strategy, deep strategy, achieving motive and achieving strategy subscales of the SPQ, suggesting good reliability for these subscales. The results at the scale level of the SPQ result in similar conclusions. There was a moderate significant correlation for the surface, deep and achieving scales of the SPQ, suggesting the scales have good reliability over a period of three months. There was also a moderate significant correlation for the surface-achieving-motive and deep-achieving scales over a period of three months. The stability of SPQ scores was also assessed utilising a series of one-way repeated measures MANOVA’s with a sample of third-year undergraduates (n = 64). The results suggest some change occurs in self-reported use of approaches to learning between the first and third-years of an undergraduate degree programme. The role of the teaching-learning environment was next examined. Utilising a within-subjects design, undergraduate students (n=48) concurrently enrolled in traditional (viz. lecture and tutorial) and non-traditional (viz. workshops and group projects) subjects completed the SPQ to describe their approaches to learning in each subject. A series of 2x2 repeated measures MANOVA’s were undertaken. The results indicated students were likely to change their approach to learning based on their perceptions of the learning environment (traditional or non-traditional subject). However, those students identified as predominantly surface learners significantly increased their deep scale scores in the non-traditional subject when compared to deep learners. The next study examined a range of personality (locus of control, sensing function, thinking function, intelligence) and demographic variables (age, gender, year of study) to assess which were good predictors of deep and surface approaches to learning. A series of regression analyses identified age, sensing function and locus of control as significant predictors of the surface, surface-achieving-motive, and deep approaches to learning. Locus of control was found to be a significant predictor of the deep-achieving approach to learning. The final study examined the 3P model of learning. Based on the results of earlier studies in the research programme the situational component of the presage factors was not included. The model was examined using structural equation modelling (n= 394). Two initial models were tested using both the three (deep, surface, achieving) and two (surface-achieving-motive and deep-achieving) process factor models. The three process factor model provided the better model fit. The results suggest deep and surface approaches to learning do not mediate between personal characteristics and learning outcomes (i.e. GPA). The results of this series of studies suggest the need for further research into the SPQ and the 3P model of learning. The implications of the research programme are also discussed.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Applied Psychology
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Jain, Rinku. "Insights into the roles of metals in biology: biochemical and structural characterization of two bacterial and one archaeak metallo-enzyme." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1154819208.
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Danay, Erik. "Predictors of performance." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2011. http://dx.doi.org/10.18452/16303.
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Präsentiert werden drei Studien zum Thema Prädiktion von Leistung. In Studie 1 wurde die Prädiktion von Studienerfolg nicht nur mit Persönlichkeitsmaßen auf Facettenebene sowohl von Fremd- als auch Selbst-Ratings untersucht, sondern auch der Einfluss von faking auf die Kriteriumsvalidität. Ergebnisse zeigten, dass Fremd- über Selbst-Ratings und Intelligenz hinaus Studienerfolg prädizieren. Auch wurde gezeigt, dass Faking die Kriteriumsvaliditäten auf Facettenebene in unterschiedlicher Weise beeinflusst. Studie 2 untersuchte den Einfluss der unterschiedlichen Abstraktionsebene von Prädiktor und Kriterium auf die Kriteriumsvalidität. Dazu wurden Leistungsmotivationsskalen sowohl in einer Mathe-spezifischen Formulierung als auch in einer globalen Formulierung Schülern vorgegeben. Diese Skalen dienten dann als Prädiktoren für Noten in Mathe, Physik und Deutsch. Ergebnisse einer Varianzzerlegung mit MTMM zeigten, dass die Mathe-spezifischen Skalen durchgehend ein Plus an Varianz enthalten, welches unabhängig ist von der Varianz aufgrund der einzelnen Motivationskonstrukte. Folglich messen domänen-spezifische Skalen entweder ein engeres Konstrukt von Leistungsmotivation oder, eher, ein zusätzliches Konstrukt. Das Korrelationsmuster der domänen-spezifischen Varianz mit den drei untersuchten Noten legt nahe, dass es sich bei diesem zusätzlichen Konstrukt um Selbstkonzept handelt. Studie 3 untersuchte die Konstruktvalidität der Big 5 und möglicher higher-order factors nach Kontrolle von möglichen Biases innerhalb des CTCM-1 Ansatzes mit Selbst- und Fremdratings. Ergebnisse zeigten, dass bias-bereinigte Big 5 Maße die Annahme eines higher-order factors wenig plausibel machen. Darüber hinaus konnte ein solcher potentieller Faktor nicht theoriekonform die positive Eigenschaft Intelligenz prädizieren. Insgesamt verdeutlicht dies die Problematik des Einflusses von unterschiedlichen Quellen und Verzerrungen auf die Kriteriumsvalidität von häufig eingesetzten Persönlichkeitsmaßen.Presented are 3 studies about the prediction of performance. Study 1 analyzes the prediction of academic performance by use of self-ratings, other-ratings and faked-ratings of personality measures not only on domain level but also on facet level. Result showed that other-ratings yield incremental validity above and beyond self-ratings and intelligence. Moreover, against prior findings for domain-level, faking does influence criterion validity on facet-level, with the influence not being uniform in direction. Study 2 analyzed the influence of different levels of abstraction of predictor and criterion in the realm of achievement motivation. For that, various achievement motivation scales were administered both in a global and a math-specific wording. These scales later on served as predictor for grades in math, physics and German. By modeling this data in a MTMM model different sources of variance could be disentangled. Results showed that math-specific scales are the better predictors. More so, these domain-specific scales have uniformly an increase in variance regardless of the positive or negative valence of the various achievement motivation scales. This leads to the conclusion that math-domain-specific scales either measure a narrower construct or, more probable, they tap an additional construct. This is backed by the uniform positive additional variance. Moreover, test-criterion correlation-pattern between the math-domain-specific variance and the three different grades makes it plausible that the additional construct tapped in these scales is self-concept. Study 3 analyzed the construct-validity of personality’s Big 5 and their possible higher order factor after controlling for singular rater biases using a newly developed CTCM-1 approach. Results showed that these bias free Big 5 make the assumption of one higher order factor implausible. Moreover, such a factor would not uniformly predict intelligence as is claimed by advocates of this factor.
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Saguet, Pierre. "Analyse des milieux guides la méthode MTLM." Grenoble : ANRT, 1985. http://catalogue.bnf.fr/ark:/12148/cb37595152s.
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Oliveira, Solon Pereira de. "Aplicação do metodo MTM em linha de montagem de trocadores de calor veicular." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264212.
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Orientador: Anselmo Eduardo DinizDissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-06T20:02:45Z (GMT). No. of bitstreams: 1 Oliveira_SolonPereirade_M.pdf: 5699180 bytes, checksum: 067ac02eef0cae10532e8027dc26ebc5 (MD5) Previous issue date: 2006
Resumo: Nesse trabalho procurou-se aplicar o método MTM AI ou método básico para otimizar e balancear os postos de trabalhos dedicados ao módulo de arrefecimento do veículo de passeio, carro que a montadora está lançando em 2005 para competir com os rivais no seu próprio mercado. Os postos de trabalhos foram filmados para registrar os métodos (o método determina o tempo) empregados atualmente e para servir de base para as análises MTM AI onde foi aplicada a otimização dos métodos. Após esse levantamento os dados são introduzidos no software Ticon 2.1, para geração de relatórios e triagem dos mo~entos que agregam / não agregam valor, juntamente com avaliação da necessidade e dificuldade dos movimentos aplicados. Após a análise foi feita uma proposta para substituir ou facilitar os movimentos que geraram os maiores TMU's (Unidade de Medida de Tempo) sugerindo novos movimentos, novas distâncias um novo método em relação ao movimento original, assim como o balanceamento dos postos de trabalho otimizando o tempo de ciclo dos operadores da célula sem aumentar o ciclo de processo
Abstract: In this work it was looked to apply method MTM AI or basic method to optimize and to balance the work station dedicated to the cooling module of Vehicle. The Car Assembly Company is launching this ear in Oct 2005 to compete with the Japanese rivals in its proper market. The work station had been tilmed to register the methods (the method determines the time) employed currently and to serve as base for MTM AI analyses where the optimization ofthe methods was applied. After this survey the data were introdueed in software Tieon 2,1, for generation of reports and selection of the movements that add/do not add value, together with evaluation ofthe necessity and difficulty of the applied movements. After the analysis was made a proposal to substitute or to facilitate the movements that had generated the highest TMUs (Unit of Measure of Time) suggesting new movements, new distances a new method in relation to the original movement, as well as the balaneing of the work station optimizing the time of cycle of the operators of the cell without increasing the process eyele
Mestrado
Planejamento e Gestão Estrategica da Manufatura
Mestre Profissional em Engenharia Mecanica
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Gerbeth, Gunter, and Sven Eckert. "International Workshop on Measuring Techniques for Liquid Metal Flows (MTLM), Rossendorf, 11.-13.10.99, Proceedings: International Workshop on Measuring Techniques for Liquid Metal Flows (MTLM), Rossendorf, 11.-13.10.99, Proceedings." Forschungszentrum Rossendorf, 1999. https://hzdr.qucosa.de/id/qucosa%3A21841.
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The International Workshop on "Measuring Techniques in Liquid Metal Flows" (MTLM Workshop) was organised in frame of the Dresden "Innovationskolleg Magnetofluiddynamik". The subject of the MTLM Workshop was limited to methods to determine physical flow quantities such as velocity, pressure, void fraction, inclusion properties, crystallisation fronts etc. The present proceedings contain abstracts and viewgraphs of the oral presentations. During the last decades numerical simulations have become an important tool in industry and research to study the structure of flows and the properties of heat and mass transfer. However, in case of liquid metal flows there exists a significant problem to validate the codes with experimental data due to the lack of available measuring techniques. Due to the material properties (opaque, hot, chemical aggressive) the measurement of flow quantities is much more delicate in liquid metals compared to ordinary water flows. The generalisation of results obtained by means of water models to real liquid metal flows has often to be considered as difficult due to the problems to meet the actual values of non-dimensional flow parameters (Re, Pr, Gr, Ha, etc.). Moreover, a strong need has to be noted to make measuring techniques available to monitor and to control flow processes in real industrial facilities.
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Buresh, Megan, Shawna Morgan, and Carrie Sepp. "Implementation of Medication Therapy Management (MTM) in Community Pharmacies." The University of Arizona, 2008. http://hdl.handle.net/10150/624309.
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Class of 2008 AbstractObjectives: The purpose of this study was to identify how community pharmacies have integrated medication therapy management (MTM) programs into their workflow and specifically determine the changes that were made in order to deliver such services. Methods: This was a descriptive study on the implementation of MTM programs in community pharmacies. Pharmacy managers associated with Cardinal Health, Medicine Shoppe International, United Drugs, the Iowa Pharmacy Association (IPA) and 10 additional selected pharmacists were invited to take an online survey regarding MTM program implementation in their pharmacy. Exclusion criteria were those pharmacists that did not provide any MTM services from January 2006 through December 2007. The primary dependent variables included time spent training, time to complete clinical pharmacy program sessions, scheduling and implementing clinical pharmacy sessions, staffing, and cost for additional equipment. Data analysis included percents and frequencies for categorical variables addressed in the internet survey. Results: Pharmacists that participated in this survey were mostly male (82%) and had been practicing for greater than 10 years. Only 3 out of 17 participants were female and all were a part of the group practicing for less than 10 years. The majority of participants in both groups completed 0-2 MTM sessions per week (p=0.65). In order to complete these sessions, the hiring of additional staff was not required (82%) nor was the purchase of additional equipment (70%). Conclusions: The implementation of MTM programs in community pharmacies requires little to no additional time or money. With this data, more pharmacists should be inclined to provide MTM sessions.
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Zhao, Yanzhu. "Metal-transfer-molding (MTM) technique for micromachined RF components." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24750.
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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Mark G. Allen; Committee Member: J. Stevenson Kenney; Committee Member: Joy Laskar; Committee Member: Oliver Brand; Committee Member: Peter Hesketh.
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Almeida, Denis Leandro Monteiro de. "Análise da aplicação do método MTM em empresas de manufatura." Florianópolis, SC, 2008. http://repositorio.ufsc.br/xmlui/handle/123456789/91658.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia MecânicaMade available in DSpace on 2012-10-24T01:14:40Z (GMT). No. of bitstreams: 1 258712.pdf: 2979639 bytes, checksum: a2bec697b30a461c36a2f3c63acc3690 (MD5)
Com a competitividade cada vez mais acirrada entre as empresas, o aumento da produtividade tem se tornado obrigatório. Contudo, deve-se pensar em alternativas que permitam o aumento da produtividade sem sobrecarregar os recursos utilizados evitando assim, falhas dos equipamentos e problemas de saúde dos operadores. Para o aumento da produtividade, este trabalho propõe a utilização da metodologia MTM - Methods Time Measurement cuja tradução apropriada em português é Medição do Tempo de Métodos. Este trabalho analisará a aplicação desta metodologia em empresas de manufatura considerando os desenvolvimentos atuais das tabelas de tempos, os quais são pouco conhecidos pelas empresas brasileiras. A metodologia MTM, no entanto, não será aqui tratada de maneira isolada, mas sim em combinação com outras técnicas e ferramentas. Esta análise será realizada de maneira teórica, com o uso da revisão bibliográfica, e de maneira prática, por meio de estudos de casos de aplicações da metodologia MTM em empresas. A revisão bibliográfica discutirá questões sobre a avaliação de tempos, em especial através da metodologia MTM enquanto que no campo prático serão detalhados os métodos e resultados obtidos através da aplicação desta metodologia em duas empresas do ramo automobilístico e uma empresa da linha branca. Conclui-se que a metodologia MTM é uma ferramenta útil para o planejamento e organização dos métodos de trabalhos dos operadores e que combinada com outros métodos aplicados pelas empresas pode gerar ganhos significativos de produtividade. With the raising competition among companies, the productivity increase has become mandatory. However, alternatives to increase productivity should be considered in a way that the productivity increase does not cause resource overload, avoiding equipment failures and workers health problems. For a sustainable productivity increase, this paper proposes the use of the MTM - Time Measurement Methods methodology. This work will evaluate the use of the MTM in manufacturing industries considering the current development of MTM time tables that are barely known by Brazilian companies. The MTM methodology, however, will not be analyzed here in an isolated way, but in combination with other techniques and tools. This analysis will be carried out in a theoretical way, through literature review, and in a practical way, held through study cases of the MTM methodology application in companies. The literature review discusses issues about time evaluation focusing the MTM methodology while in the practice field details are given about the methods and results obtained through the application of this methodology in two automobilist companies and a household devices company. This dissertation concludes that the MTM methodology is a useful tool to plan and organize the methods of the operators activities and that combined with other applied methods it can generate a significant productivity increase.
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Gerbeth, Gunter, and Sven Eckert. "International Workshop on Measuring Techniques for Liquid Metal Flows (MTLM), Rossendorf, 11.-13.10.99, Proceedings." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-30159.
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The International Workshop on "Measuring Techniques in Liquid Metal Flows" (MTLM Workshop) was organised in frame of the Dresden "Innovationskolleg Magnetofluiddynamik". The subject of the MTLM Workshop was limited to methods to determine physical flow quantities such as velocity, pressure, void fraction, inclusion properties, crystallisation fronts etc. The present proceedings contain abstracts and viewgraphs of the oral presentations. During the last decades numerical simulations have become an important tool in industry and research to study the structure of flows and the properties of heat and mass transfer. However, in case of liquid metal flows there exists a significant problem to validate the codes with experimental data due to the lack of available measuring techniques. Due to the material properties (opaque, hot, chemical aggressive) the measurement of flow quantities is much more delicate in liquid metals compared to ordinary water flows. The generalisation of results obtained by means of water models to real liquid metal flows has often to be considered as difficult due to the problems to meet the actual values of non-dimensional flow parameters (Re, Pr, Gr, Ha, etc.). Moreover, a strong need has to be noted to make measuring techniques available to monitor and to control flow processes in real industrial facilities.
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Trippe, David Matthew. "An evaluation of the construct validity of situational judgment tests." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/35795.
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Situational judgment tests are analogous to earlier forms of "high fidelity" simulations such that an ostensible paradox emerges in the consistent finding of criterion-referenced validity but almost complete lack of construct validity evidence. The present study evaluates the extent to which SJT's can demonstrate convergent and discriminant validity by analyzing a SJT from a multitrait-multimethod perspective. A series of hierarchically nested confirmatory factor models were tested. Results indicate that the SJT demonstrates convergent and discriminant validity but also contains non-trivial amounts of construct-irrelevant method variance. Wide variability in the content and validation methods of SJT's are discussed as the reason previous attempts to find construct validity have failed.Master of Science
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Reis, Diogo Oliveira. "Trabalho standard: MTM e ergonomia: normalização de operadores logísticos Milk Run." Master's thesis, Universidade de Aveiro, 2010. http://hdl.handle.net/10773/4523.
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Kwoun, Sun Jong Lec Ryszard. "A multiresonance thickness-shear mode (MTSM) sensor for monitoring the formation of biological thin films /." Philadelphia, Pa. : Drexel University, 2006. http://hdl.handle.net/1860/1161.
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Dretvik, Sandbakk Katrine. "Syntese og karakterisering av katalysatorer for vannelektrolyse. : Effekt av bærestrukturer og synteseforhold på den katalytiske aktiviteten." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16306.
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I denne masteroppgaven ble det syntetisert iridiumbaserte katalysatorer på en bærerstruktur for oksygenutviklingsreaksjonen i en PEM vannelektrolysør, ved hjelp av en polyolmetode. Katalysatorpulverne ble karakterisert ved hjelp av både elektrokjemiske (syklisk voltammetri, polarisasjon og impedans), og fysiske metoder (SEM, TEM, BET, EDS, and XPS). I tillegg ble det konstruert en apparatur for måling av elektronisk ledningsevne, og denne ble benyttet for å sammenlikne den elektroniske ledningsevnen til to ulike bærermaterialer, antimondopet tinnoksid (ATO) og wolframoksid (WO3).Målet for arbeidet var å studere effekten som bruk av bærermaterialer og ulike synteseforhold har på de elektrokatalytiske egenskapene til iridiumbaserte katalysatorer på bærere.Resultatene fra dette arbeidet viser at av de to valgte bærermaterialene så har ATO de mest egnede egenskapene for bruk som bærermateriale i et elektrodesystem, i det at den elektroniske ledningsevnen var mye høyere og det spesifikke overflatearealet var større enn hos WO3. Karakterisering av de syntetiserte katalysatorene på ATO viser elektrokatalytiske egenskaper som er på samme nivå som, eller bedre enn, andre katalysatorer laget til samme formål. Forandringer gjort på synteseforholdene (pH og konsentrasjon av materialer) virket ikke å ha noen effekt av betydning på verken morfologi, partikkelstørrelse eller den katalytiske aktiviteten til katalysatorene.
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Davidsen, Jens Erik. "Formation of Silicon Carbide in the Silicomanganese Process." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16308.
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As the silicon content in a silicomanganese alloy increase, silicon carbide becomes the stable carbon phase. Little work is published on the formation of silicon carbide in the SiMn process. This thesis examines the formation of SiC through the reaction between slag, metal and coke. The goal of the thesis has been to determine where and how SiC is formed in the silicomanganese process. Focus has been given to formation through liquid-solid reactions.The investigation was carried out by heating metal and slag together with coke. XRD analysis of SiC formed in the process, as well as wettability testing of slag and metal toward SiC and graphite substrates were also examined. The raw materials consisted of two industrial SiMn alloys, named Metal 1 and 2 in the thesis. These had 19 and 28 wt.% Si, respectively. Two slags, Slag 1 and 2, were used in combination with the metal. SiC was found to form on the coke particle through reaction with both slag and metal. The formation was fastest through the metal phase and the effect of increasing silicon content in the metal was evident. A temperature increase from 1600 C to 1650 C resulted in less SiC formed on the coke particle surface for Metal 1, but gave more SiC at the surface of the coke particle for Metal 2. The decrease in SiC on the coke particle for Metal 1 is likely to be caused by a decreased driving force, as the coexistence point of C and SiC increases with increasing temperature. For Metal 2 the relative distance is smaller, making the effect neglectable. The formation of SiC occurs at the surface of the coke particle. The metal samples indicate that carbon diffuses through the SiC layer to react with silicon in the alloy. Formation through the slag is likely to go through the reduction of SiO2 to Si, before reacting to form SiC. The XRD analysis determined beta-SiC to be the dominant phase formed through both slag and metal. alpha-SiC was found in one of the industrial slag samples, indicating temperatures higher than 1700 C. The wettability testing showed both slag and metal to be non wetting toward the SiC substrate. All angles were stable with increasing temperatures. Both slags were found to be non wetting toward graphite. The wetting angle of Slag 2 was stable with increasing temperature. Slag 1 showed decreasing wetting angle with temperature, before an abrupt change back to an angle larger than the initial angle. The sudden change is likely to be caused by a reaction product, possibly SiC, forming between the substrate and slag.
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Pedersen, Jonas Hovde. "In situ strekkforsøk med EBSD karakterisering av HSLA-stål ved romtemperatur og -60 °C." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16316.
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Denne oppgaven har tatt for seg et 420 MPa HSLA stål. Stålet ble sveisesimulertfor å oppnå mikrostruktur tilsvarende grovkornet og interkritisk grovkornetHAZ. Interkritisk grovkornet HAZ ble oppnådd ved en tosyklus sveisesimuleringhvor materialet ble varmet opp til 1350 °C og avkjølt med Δτ8-5 = 15s og deretter gjenoppvarmet til 780 °C og avkjølt med Δτ 6-4 = 17s. Grovkornet HAZ ble oppnådd ved ensyklus sveisesimulering hvor materialet ble varmet opp til 1350 °C og avkjølt med Δτ 8-5 = 15s.Et eksempel på EBSD teknikken er vist ved en sammenligning av sekundærelektronbilde, fasekart og Image Quality kart. Sekundærelektronbilde og EBSD skannet er fra nøyaktig det samme område. På denne måten blir det demonstrert at EBSD teknikken er et verdifullt verktøy for å skille ulike stålfaser fra hverandre.Det ble så fortatt en grunnleggende EBSD karakterisering av de to sveisesyklusene. Fire skann med et totalareal på 150 µm x 150 µm ble gjort på hver av de to prøvene. Det ble konkludert med at den største forskjellen var øyer av restaustenitt som i gjennomsnitt utgjorde 2,45 % av det skannede område på tosyklus sveisesimulert prøve. I ensyklus sveisesimulert prøve var disse øyene så godt som fraværende.For tosyklus sveisesimulert stål ble det også gjennomført in situ strekktesting med påfølgende EBSD karakterisering ved -60 °C og romtemperatur. En spesiallaget kaldfinger ble videreutvilket for å kjøle ned prøven til -60 °C, da det ikke lykkes å nå -60 °C slik den opprinnelig var konstruert. EBSD karakterisering ble foretatt uten deformasjon og ved 1 %, 2 %, 3 % og 4 % forlengelse av stålet. En sammenligning av resultatene ved -60 °C og romtemperatur ble gjort. Det ble konkludert med at øyer av restaustenitt transformeres til martensitt som følge av plastisk deformasjon i større grad ved -60 °C enn ved romtemperatur som følge av høyere termodynamiske drivkrefter.Ved in situ undersøkelser må strekkbord og kaldfinger monteres i mikroskopet, dette fører til at det tar mye lengre tid å pumpe vakuum enn ved normale omstendigheter. Det tar 50 minutter å pumpe 2,5 x 10-6 mBar vakuum i tomt prøvekammer. Tilsvarende vakuum ved in situ undersøkelser tar over 5 timer å pumpe, grunnet større overflate inne i mikroskopet. Til slutt ble det gjennomført en sammenligning ved bruk av 1° og 2° Θ steglengde ved indisering av EBSD rådata. Indisering med 1° Θ steglengde ga 1,5% austenitt, mens 2° Θ steglengde ga kun 0,9% austenitt. Konklusjonen var at 2° Θ steglengde ikke oppdager de minste kornene på grunn av for grov omregning i Hough transformasjonen.
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Enstad, Anne-Jorunn. "EBSD-karakterisering av et HSLA-stål under in situ varmebehandling." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16317.
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Ved sveising av HSLA-stål (High Strength Low Alloy) designet for lavtemperatur applikasjoner kan det dannes lokale sprø soner som martensitt/austenitt-faser (MA-faser). Det er derfor ønskelig å karakterisere austenitten som dannes ved tosykel sveising for å gi økt kunnskap om endringene som oppstår i mikrostrukturen.Denne masteroppgaven tar for seg karakterisering av et 420 MPa HSLA-stål ved in situ varmebehandling opp til tofaseområdet for austenitt og ferritt i kombinasjon med diffraksjon av tilbakespredte elektroner (Electron Backscatter Diffraction - EBSD). Målet med oppgaven var da å karakterisere endringer som oppstår i mikrostrukturen til stålet under in situ oppvarming i mikroskopet. Oppvarmingen ble utført ved å videreutvikle et tidligere varmebord. Stålprøvene ble ènsykel sveisesimulert til 1350 °C og avkjølt med Δt8/5. Den in situ varmebehandlingen tilsvarte da den andre sveisesykelen i en tosykel sveisesimulering. Ved prøvepreparering ble prøvene elektropolert med to ulike elektrolytter; Struers A2 og AC2. I oppgaven ble det benyttet offline-EBSD da det var nødvendig med høy skannehastighet slik at tiden for hvert EBSD-skann ble så liten som mulig.For å nå tofaseområdet til HSLA-stålet var det nødvendig å varme opp til en prøvetemperatur på over 740 °C. Da ovnen har en maksimaltemperatur på 800 °C ble det benyttet en vakuumkompatibel platinamaling mellom prøven og ovnen i varmebordet for å øke varmeledningen. Temperaturforskjellen mellom prøven og ovnen ble da reduseres helt ned til 10 °C. Det ble varmet opp til prøvetemperaturer på 750 °C, 760 °C, 770 °C, 780 °C og 790 °C. Det var nødvendig å vente i 10 minutter etter å ha nådd ønsket prøvetemperatur før det ble kjørt EBSD på grunn av termisk ekspansjon av prøven.Austenitten som ble dannet under oppvarming vokste frem langs korngrenser og hadde en orienteringssammenheng med BCC-matriksen rundt som oppfyller Kurdjomov-Sachs. Det ble observert at austenitten som dannes gradvis forsvant igjen ved økende holdetid ved høy temperatur som følge av avdamping av karbon fra prøveoverflaten. Ved oppvarming viste det seg at det ble dannet en mye større andel austenitt i prøver elektropolert med Struers AC2 enn den med Struers A2. Det ble da konstruert fasediagram for tofaseområdet til stålet på bakgrunn av andel dannet austenitt ved oppvarming. Disse viste at prøver elektropolert med Struers A2 gav mest korrekt andel austenitt.
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Salvesen, Trine Viveke. "Kimdanning av sprøbrudd i et 420 MPa arktisk stål." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16319.
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Sveising fører til endret mikrostruktur i deler av stålet. I kombinasjon med lave temperaturer oppstår nye forutsetninger for brudd.I denne masteroppgava ble det sett på initiering av sprøbrudd i et sveisesimulert 420 MPa HSLA-stål fra Nippon Steel. Dette ble gjort ved å studere mikrostrukturen og bruddflata til seks sveisesimulerte prøver etter bruddmekanisk trepunktsbøying med utmattingskjerv. I tillegg ble det videre undersøkt en mulig MA-fase som tidligere ble funnet i et initieringspunkt på ei prøve med interkritisk grovkornet HAZ.To prøver hadde simulert grovkornet HAZ og fire prøver var forsøkt rendyrket martensitt- og bainittstruktur. Acikulær ferritt ble her sett på som en del av bainittstrukturen. Alle prøvene ble varmet opp til 1350 ◦C og hadde avkjølingstid, ∆τ8/5, på 5, 15 og 22,5 sekunder for derved å simulere henholdsvis martensittstruktur, grovkornet HAZ og bainittstruktur. Prøvene ble brukket ved −60 ◦C.Det var forventet at økt andel bainittstruktur i prøvene ville føre til lavere seighet og dermed lavere CTOD-verdier. Martensittstrukturen var noe selvanløpt og dermed mer duktil. Imidlertid var ikke sammenhengen mellom andel bainittstruktur og initiering av sprøbrudd så klar som forventet og det var mange observasjoner som svekket styrken i sammenhengen.På alle seks bruddprøvene ble alle mulige initieringspunkt langs og foran sprekkspissen kartlagt ved bruk av SEM. Det ble funnet dobbelt så mange initieringspunkt på prøvene med avkjølingstid lik 5 sekunder som de med avkjølingstid lik 15 og 22,5 sekunder. Imidlertid lå mange av disse sværtnær hverandre og mange var låst av duktil bruddvekst.Etter undersøkelse i SEM ble de fire rendyrkede bruddprøvene nitaletsa og undersøkt på ny. Det ble observert karbider i, eller rett ved, 61% av initieringspunktene, flest i prøvene med avkjølingstid lik 22,5 sekunder. Dette viser at initieringen kan være knyttet til karbider og dermed bainittstruktur.Mikrostrukturen til de ulike prøvene ble studert i lysmikroskop. Prøvene med martensittstruktur inneholdt også områder med bainittstruktur. Det var forventet at disse prøvene skulle få høyest CTOD-verdier på grunn av duktil martensitt, men det var ikke tilfellet. De lave CTOD-verdiene kan ha vært grunnet initiering i bainittstrukturen.Det var ingen klar tendens på hva slags beliggenhet initieringspunktene hadde i forhold til prøvenes mikrostruktur eller CTOD-verdi. På alle prøvene ble det observert initiering foran sprekkspiss. Disse initieringene ga mest bruddvekst, bortsett fra i de to rendyrkede prøvene med lavest CTOD-verdi.Det ble gjort tre slipesteg inn i prøvene med grovkorna HAZ for å undersøke mikrostrukturfordelingen langs bruddkantene ved bruk av lysmikroskop. Andelen martensitt og bainitt langs hele bruddkanten ble estimert ved å vurdere mikrostrukturen i hvert punkt som var relevant i et rutenett. Det var ingen markant forskjell i fordelingen av mikrostruktur langs bruddkanten i forhold til CTOD-verdi.Mikrosondeundersøkelser av og rundt en forhøyning i et initieringspunkt på ei prøve med interkritisk grovkornet HAZ indikerte at det kunne være en MA-fase. Desverre forsvant forhøyningen da den skulle kuttes ut ved hjelp av FIB for å undersøkes i TEM.
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Buberg, Tor Arne. "Case Hardening of Hardox 450 Steel for Increased Ballistic Strength." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16326.
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AbstractSteel alloys are the material that is most used in protective constructions today. The reason is the overall good properties of steels, with its high strength and hardness, high ductility, high formability and relatively low cost compared to other materials. Even though armour steels are affordable, work is done to limit expenses from production or come up with new and less expensive alloys.Case hardening is a technique for production of steel with a very hard and durable surface while still maintaining a tough and ductile core. Case hardened products have hard, durable and fatigue resistant surfaces and tough and durable cores. Case hardening is typically applied to machine parts that are exposed to heavy wear and high loads such as gears, bearings, screws and nuts, shafts, etcIn 2010, Lou et al. managed to significantly increase the penetration resistance of a low-cost steel (NVE36) by case hardening. Encouraged by this, Hans Magne Thorseth wrote his master’s thesis “Optimalisering av stål i beskyttelseskonstruksjoner” in 2010. His attempt to improve the ballistic strength of Hardox 450 steel by case hardening did not have the desired results. The ballistic limit velocity was reduced from approximately 800 m/s for the original Hardox 450 to approximately 770 m/s for the case hardened steel. The probable reasons for the reduction of the ballistic limit velocity was a too low carbon content increase from the carburizing and thus a too low hardness increase, in addition to deterioration of the metal core properties from the heat treatment. The objective of this master’s thesis was to improve the case hardening process used by Hans Magne Thorseth in his master’s thesis.The improvement work was divided into two parts, a preliminary project work and this master thesis. The project was carried out in the autumn of 2010, and the aim was to find the optimum case hardening process to produce steel with improved ballistic properties. This involved testing of different carburizing potentials to increase the surface carbon content of the metal and to find carburizing heat treatments that would retain the core properties of the carburized steel. Based on the results from the preliminary project it seemed possible to produce case hardened steel with surface hardness over 1000 HV, but a slight reduction of core hardness was difficult to avoid.The present master’s thesis was written during the spring of 2011. The key results from the preliminary project work were used to determine a range of case hardening courses. A total of 11 case hardening courses were tested, of which six courses employed carbon potential of 0.9% and five courses employed a carbon potential of 1.1%. Different hardening courses were tested, including direct hardening, a modified single hardening process and traditional and modified versions of double and triple hardening. Before the case hardening the plates were sandblasted to remove a corrosion-resistant primer that was applied to the plates. The primer was believed to limit the diffusion of carbon into the steel. In the preliminary project the primer was ground away and grinding was the preferred solution in this work as well, however, due to capacity issues sandblasting was employed.The ballistic limit velocity of the case hardened and the original Hardox 450 target plates were calculated from results obtained by ballistic experiments. The ballistic limit velocities of the case hardened samples, with approximately 787 m/s as the highest, were lower than that of the original Hardox 450, being approximately 800 m/s.Surface hardness measurements of the steel revealed a poor effect from the carburization, the hardest surface was measured at 735 HV. This could be explained by a probable surface decarburization of the original Hardox 450, which was discovered by microstructure examinations and hardness measurements. In contrary to in the preliminary project where this layer was ground away, the sandblasting did not remove the decarburized layer. Due to this, the case hardening did not have the desired effect on the steel surface, resulting in a too low surface hardness.The core hardness proved difficult to retain, the highest core hardness value obtained was below 460 HV, compared to the original Hardox 450 with core hardness of 475 HV. This could be another reason for the lower ballistic limit velocity of the carburized steel plates. However, the original Hardox 450 did not have the highest cross-sectional hardness integral value, so the ballistic properties probably also depend to some degree on ductility. A main reason for the superior ballistic limit velocity of the original Hardox 450 was therefore believed to be related to cracking of the rear side of the case hardened target plates during projectile penetration. The cracking seemed to be a result of the harder, and thus more brittle, outer surface layer.
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Jørgensen, Håkon Trygve Strøm. "Oxidation of silicon in aqueous media." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16333.
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Silicon is used in the production of various ceramic products. As the solar industry is advancing, the need for reusable crucibles for the casting of solar grade silicon has arisen. One idea is to produce silicon nitride crucibles by slip casting. During slip casting, silicon powder is mixed with water at high alkaline conditions to ensure good dispersion of the powder and a stabilized slip. This may lead to oxidation of the silicon and the evolution of hydrogen gas. The hydrogen evolution introduces porosity in the final product, thereby ruining the mechanical properties. Gaining knowledge on how to inhibit the oxidation of silicon in slurries would therefore prove valuable for producing defect-free silicon based ceramics.In this thesis the main objective is to gain knowledge about the oxidation of silicon in aqueous media, emphasizing on the formation of oxides with respect to initiation point, initiation time and characterizing of the oxide. Silicon powder and coarse silicon particles delivered by Elkem was oxidized in a purpose built apparatus. The effects on the powder and the coarse particles were examined by the several techniques, including among other: SEM, Colorimetry, HR ICP-MS and LECO. The mechanical properties of oxidized single crystal and polycrystalline silicon were also investigated, using nanoindentation.The most important results, indicates that the oxidation of silicon results in formation of silica and hydrogen gas evolution. Firstly silicic acid is formed until the solubility limit is reached. Further oxidation leads to silicic acid condensing to form; colloidal silica which adsorbs on the silicon particles and dispersed colloidal silica in the suspension. The oxide layer formation on the coarse silicon particles were studied and confirmed using SEM. The oxide is the result of silicic acid condensing to form silica and adsorbing on to the surface of the silicon. Initiation points for the oxidation were not found. A more controlled oxidation is needed and the study of the oxide layer must be performed with high resolution techniques like Atomic Force Microscopy and/or Auger Electron Spectroscopy.There were some problems related to reproducing the results with respect to the hydrogen evolution from the silicon powder. Storage of the powder seemed to be a key factor as the powder behaved differently from one week to another. Storage in a desiccator for two weeks lead to earlier and more intense hydrogen evolution. Any reasonable cause for this was not found, and is subject for further investigations. The initiation time for hydrogen evolution was therefore difficult to determine, as it is dependent on unknown parameters.Nanoindentation was found to be a useful technique for studying the mechanical properties of oxidized silicon. The results indicated that the single crystal samples were homogeneous with respect to mechanical properties, as each of the indents of the respective samples produced more or less the same value. The E-modulus for the oxidized single crystal sample was about 10 GPa lower than for the unoxidized sample, the hardness was not affected. The results for the polycrystalline sample is more difficult to interpret, but nanoindentation indicates that the oxidized sample is not as homogeneous as the single crystal particles with respect to mechanical properties. The hardness was equal to the single crystal samples, and the E-modulus was close to that of the unoxidized single crystal sample.
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Ottesen, Petter. "Processing and Characterisation of Diatoms for Light Harvesting Materials in Solar Cells." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16334.
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By applying a texture to the front surface of solar cells, less light may be reflected and the incoming light may be given a longer path length inside the solar cell causing a better light absorbance for the solar cell. The textured layer is today made by etching with an acidic etch with a large part hydrogen fluoride. In the future a more environmental approach for creating textured solar cells may be favoured. There are many ways of creating textured surfaces, one of them are by imprinting the surface by a template, and remove the template when the process is completed.In this project the diatom species Coscinodiscus walesii and an undefined Coscinodiscus species were cleaned and processed for investigation. The work done can be divided into four tasks. The first was characterisation and investigation of the pore structure. The second were manufacturing and characterisation of gold for use as templates. The third were deposition and characterisation of thin films of silicon and silicon nitride on diatom frustules. The last part were to make structures are very similar to solar cells with diatom frustules incorporated into them.The diatom frustules were characterised by SEM and the pore structure were cut through with FIB to characterise the structure. There were structural differences between the two species. The Coscinodiscus walesii was grown in a cultivation chamber, and lacked the circular inner pore structure which the undefined Coscinodiscus species had. This was the only real difference between the two species.On the cultivated species were deposited a gold film, which a small rectangle were lifted off by a tungsten needle in FIB. The small rectangle were characterised with the SEM-column in a dual beam FIB. Pore structures down to 40 nm were replicated by the gold film lifted off the frustule. By depositing a relatively thick film of gold on a glass substrate covered with diatom frustules and dissolving the glass substrate and diatom frustules with hydrogen fluoride, a template were made with a replication of the diatom frustule pore structure.Silicon and silicon nitride were deposited on diatom frustules and characterised with FIB to investigate how those materials followed the frustule topography. A good conformity of films made of those materials was confirmed, and 4 different samples which were similar to solar cells were manufactured and characterised by light microscopy, SEM and FIB. Two samples were made to be similar to crystalline silicon solar cells. One had dried frustules on top of a silicon surface and the entire surface of the sample were coated with silicon nitride, a blue colour were observed in the entire surface and the silicon nitride had also been deposited on the diatom frustules. For the other sample similar to crystalline silicon solar cells another layer were deposited between the frustule and the silicon substrate. The double silicon layer made the sample surface yellow, the diatom frustules did not get darker due to a layer above and a layer beneath them. Only in some places where the frustules had loosened from the sample the sample were blue as the silicon nitride layer were the same as a single layer of silicon nitride. For the last two samples, thin film solar cell structures based on amorphous silicon deposited with PECVD were made. A sample there a aluminum coating were deposited on a glass substrate and diatom frustules were dried on top of the aluminum coating, afterwards a 5 µm thick film of amorphous silicon were deposited. SEM images showed that the film were distributed even across a diatom frustule and a light microscopy investigation showed that light were spread when it hit the diatom frustules, hence creating a longer mean path through the solar cell.
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Jørstad, Steinar. "Reduction of Pelletized Tyssedal Ilmenite and the Effect of Changing Gas Composition and Flow, Pellet Size and Pre Oxidation Condition." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16338.
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This master thesis is based on reduction experiments of pelletized Tyssedal ilmenite. The focus is set on the effect of changing parameters such as gas composition, gas flow, pellet size and pre-oxidation condition. The results are interpret regarding values of conversion, degree of metalization, XRF-analysis and microstructure images. Based on these results the aim was to find out how these parameters influenced reduction. Another goal was to reveal what hampered reduction inside both grains and pellets and caused the two stage reduction behaviour. EPMA was used to examine pellets and grains and to look for explanation for the slow reduction. XRD-analysis was decisive for explaining the importance of optimum pre-oxidation for the subsequent reduction. Pre-oxidized and green pellets with a size fraction of 8-10 mm were heated in a thermogravimetric analyzer. Ar was used during heating and cooling. Reduction occurred at 930-940 °C, with either CO, H2 or both for up to 45 minutes. Gas flows used were 4.8, 7 and 9 Nl/min. In total 18 experiments were carried out. Weight before and after reduction was measured, calculations of degree of metalization, XRF- and XRD-analysis was done. Microstructure images, point analysis, line scan and mapping were obtained by EPMA. Highest final values of conversion, c. 0.9, were obtained for pre-oxidized pellets from 2011 reduced with H2. Maximum degree of metalization, 94-99 % were obtained after reduction of pre-oxidized pellets from 2010. Final value of conversion and degree of metalization were 0.23 and c. 24 % higher for pre-oxidized pellets from 2010 than from 2011. Only green pellets from 2011 was harder to reduce with CO. Reducibility was not increased with the pre-oxidation conditions at ETI Tyssedal in January 2011. In spite of that the pre-oxidized pellets from 2010 and 2011 are made in the same manner and from the same raw material they react differently during reduction. This should be kept in mind when comparing results from different sources. Reduction of pre-oxidized pellets occurred in two distinct linear stages separated by a clear bend. A normal behaviour with steadily decreasing oxygen removal rate was observed with green pellets. An increased flow of CO from 7 Nl/min to 9 Nl/min resulted in decreased reduction. Examination by EPMA confirmed the presence of the barrier effect and higher amount of oxygen 0.6-1.0 mm from the surface. This indicates hampered reduction in grains and pellets. This combined with slow migration of CO/CO2 in the pellets can partly explain the unusual reduction behaviour. Pre-oxidized pellets from 2010 contains higher amount of the easily reducible M3O5, and less M2O3 compared to pre-oxidized pellets from 2011. The less reducible M3O4 was also found in the pre-oxidized pellets from 2011, making them harder to reduce.
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Reiten, Mads. "Numerisk modellering av tilbakeglødingsoppførsel i utvalgte aluminiumslegeringer." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16339.
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I denne rapporten er det tatt for seg modellering av mykningsreaksjoner etter deformasjon for AA1200- og AA3103-legeringer. Grunnleggende teori rundt mykningsreaksjonene for disse legeringene er presentert. Det er hentet inn eksperimentelle data for sammenlikning av modellerte data, og resultatene er presentert i form av grafer for flytspenning og tabeller for rekrystallisert kornstørrelse. Det er brukt to matematiske modeller som bakgrunn for simuleringene. Den ene, Alsoft, dekker mikrostrukturelle endringer, og den andre, Presipal, dekker presipitering under varmebehandling.Resultatene for flytspenninger viser at simulering av varmebehandlingsforløp for AA1200-legeringer gjøres enkelt ved hjelp av Alsoft på grunn av fravær av presipitering som har innvirkning på varmebehandlingsforløpet. Simulering for AA3103-legeringer er mer krevende på grunn av den bremsende kraften som utøves på rekrystalliserte kim og rekrystalliserte korn som vokser på grunn av samtidig presipitering under varmebehandling. Her viser resultatene at en direkte kobling av modellene Alsoft og Presipal gir akseptabel tilpasning mellom eksperimentelle data og simulerte data for flytspenninger.Modellering av kornstørrelser viser, ved en sammenlikning med eksperimentelle resultater, at modellen har endel utfordringer med hensyn til dette. Verken størrelser eller trend er i alle tilfeller realistiske. Dette kan skyldes usikkerhet i parametere som brukes.Konklusjonen av arbeidet er at modellene i seg selv fungerer, men det kreves endel arbeid rundt fastsetting av parametere for at disse skal være anvendelige. Per dags dato blir det mye synsing for at resultatene skal vise akseptable avvik i forhold til eksperimentelle data.
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Egtvedt, Solveig. "Thermally Sprayed Aluminum (TSA) with Cathodic Protection as Corrosion Protection for Steel in Natural Seawater : Characterization of Properties on TSA and Calcareous Deposit." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16340.
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Cathodic protection is an effective corrosion protection for structures submerged in seawater. In addition to applying the current need to lower the metal below the protection potential, a resulting increase in interfacial pH leads to precipitation of calcareous deposit. This deposited layer act as a barrier against oxygen diffusion on the surface, hence lowering the current demand of the structure. However, this layer will also hinder the thermal conductivity, and is therefore unwanted at the surface of heat exchangers.There are several factors influencing the precipitation of calcareous deposit. This includes potential, current, pH, seawater chemistry, flow rate etc. These factors have been thoroughly investigated for many years, but mostly with steel as substrate material. Specimens of steel coated with thermal sprayed aluminum (AlMg5) and aluminum plates of alloys AA5082, AA1050 and Al99.99 were exposed to seawater for 5-6 weeks, polarized to -1050 mV vs Ag/AgCl. The current demand was constantly recorded using KorrosjonsLogger©. Results from introductory experiments are also included. The unsealed TSA specimens had the highest current demand, but were also exposed to a higher seawater temperature than the other specimens, which has influenced the results. The sealed TSA specimens had a current demand around 10 mA/m2 after 6 weeks, which is 10 times lower than usually found on steel specimens. For the aluminum plates the trend showed that the higher alloying elements, the higher current density.The explanation for the low current demand compared to steel is that the cathodic area for aluminum is the intermetallic particles that are cathodic to the matrix, while for steel the whole surface act as a cathodic site. In addition, mechanisms during cathodic protection of aluminum lead to an isolation of the cathodic particle, hence continuously lowering the current demand.After exposure, the specimens were investigated in SEM and the composition on the surface was found using EDS. The SEM images showed a furry surface on the TSA specimen, but no familiar structure of calcareous deposit, which has been seen on steel specimens. For the aluminum plates, the intermetallic particles had been “dug out”, showing a pit between the particle and matrix. A typical structure of calcareous deposit was not seen here either. However, the EDS analysis showed an increase in both Mg and Ca content. The Mg/Ca ratio varied over the surface, with the highest ratio and content for the intermetallic particles for the aluminum plates and at the peaks of the surface at the TSA specimens. The Mg/Ca ratios found were much higher than found on steel.Both the SEM images and EDS analysis confirms the theory that there will precipitate less calcareous deposit on TSA surfaces compared to steel. Further studies will show whether the small content found will have an influence on the thermal conductivity.
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Belland, Eirik. "Alternating Current Corrosion of Carbon Steel." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16342.
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The objective was to investigate if the established theory concerning corrosion calculations and electrochemical behavior of carbon is valid when steel is exposed to AC in an electrolyte consisting of 3,5 wt% NaCl and distilled water. The experimental work was divided in two main parts. The first part concerned corrosion testing, including weight loss measurements in stagnant conditions in combination with linear polarization resistance experiments. AC-current densities investigated was 0-, 50-, 75-, 100-, 150-, 220- and 500 A/m2. Polarization curves were produced on two weight loss samples, one exposed to 150 A/m2 and the other exposed to 220 A/m2, at the end of the weight loss experiments.From the corrosion testing it was found that the estimated corrosion current densities (icorr) from the weight loss experiments on samples exposed to AC-current densities below 500 A/m2, was in an approximate accordance with the icorr values estimated from LPR. At 500 A/m2 the measured corrosion rates and corresponding corrosion currents were slightly higher than the remainder. The higher corrosion rate measured from the samples exposed to 500 A/m2 is suggested related to a non-faradaic corrosion contribution. The suggested mechanism is a facilitation of grain boundary corrosion at high AC-current densities leading to the loss of grains. This being a non-faradaic corrosion contribution it is not possible to measure with LPR or polarization curves. The constant B [mV] from the Stern-Geary equation was estimated on basis of LPR measurements. The constant displayed a decreasing trend with increasing AC-current densities. This was explained by the lowering of anodic and cathodic tafel slopes with increasing AC-current densities. The polarization resistance (Rp’ - [Ω∙m2]) also showed a decreasing trend with increased AC-current densities. This was explained by the increased current response in the LPR measurements with increasing AC-current densities.The second part was intended to elucidate the effect of AC on electrochemical behavior of the carbon steel through producing polarization curves at different AC-current densities using a rotating electrode experimental setup. Alterations in corrosion current densities, cathodic tafel slopes, limiting current density of oxygen reduction and corrosion potentials on steel without AC and at current densities of 100-, 150-, 220- and 500 A/m2 are investigated during the electrochemical testing.  From the rotating electrode experiments no significant change in corrosion current was found with increasing AC-current densities. The potential range, in which limiting current of oxygen reduction (ilim) appeared, decreased with increasing AC-current densities. This decrease in ilim also affected the corrosion potentials (Ecorr). A decrease in the potential range of ilim leads to a more cathodic Ecorr. A particular observation was found at AC-current densities of 150 A/m2 were the effect of ilim seemed absent. The samples exposed to this AC-current density also attained the most cathodic corrosion potentials at approximately -850mVSCE which was between 200-400mV lower than the samples exposed to the remaining AC-current densities. Cathodic tafel slopes showed a decreasing trend with increasing AC-current density. Anodic rafel slopes were considered absent due to pitting above Ecorr.Pictures of the weight loss samples were captured in the SEM. It was found that the formation of pits occurred on all weight loss samples exposed to AC. On the samples without induced AC no sign of pitting was observed. Hence it was found that the corrosion attacks attained a more local character when AC-current was induced in the steel samples.
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Lauvdal, Steinar. "Experimental Studies of Cold Roll Bonded Aluminum Alloys." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16347.
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This master’s thesis is based on experimental studies of the parameters influencing cold roll bonding (CRB) of the aluminum alloys AA1200 and AA3103,in the work hardened and annealed condition. The effect on the bond strength from the preparations parameters as degreasing agent, scratch brushing and exposure time for oxide growth is investigated in comparison to former studies. Further the effect of rolling speed and effect from contributing factors from the different testing methods is discussed. Three different methods for testing the bond strength are used. One of them was established during this study and was named Tensile Bond Strength Test (TBST). A final investigation of the fracture surfaces and bond interface in a scanning electron microscope (SEM) was carried out to analyze the bond mechanism and distribution of fractured oxides.The TBST is testing the direct bond strength with no peel or shear forces involved. It also only requires a fraction of the sample material for testing and any roll bonded sample is applicable for this test. These are the huge advantages with the test method. The test method is however still naive, and suffers from a series of challenges. The current test ranged is from 4MPa to 40MPa, but with potential for a large range expansion. Further are bond damaging effects, caused by the machining, reducing the accuracy of the measurements and compromising “grooving”; a measure taken for increasing the test range above 40MPa.The strain rate at which the samples were tested, showed to have strong influence on the measured bond strength. Much higher than the effect of any work hardening on either of the alloys. The preparation prior to roll bonding including an only 90s exposure time to air, ensures a very thin oxide layer and bonding at reductions down at 22.3%. Ductile “stretch lips” was found on the fracture surface, and run in direction normal to the rolling direction. The fraction of bonded surface area did not seem to follow the percent of reduction during roll bonding, which indicates a thinning of the oxide layer.
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Holm, Thomas. "Synthesis and characterisation of the nanostructured magnesium-lanthanum-nickel alloys for Ni-metal hydride battery applications." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18466.
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Affordable price, high abundance of magnesium and high densities of hydrogenin the Mg-based hydrides attract interest to these hydrides tailored for hydrogenand energy storage applications. Ternary La-Mg-Ni hydrogen storage alloys withcomposition La3-xMgxNi9 (x = 0.8-1.2) form a new class of the materials for thenegative electrodes in Ni-Metal Hydride (MH) batteries. The electrochemical dischargecapacity of such alloys reaches 400 mAh/g which is 25 % greater than thatof the commercial AB5-type based electrodes, 315 mAh/g. The La3-xMgxNi9alloys crystallize with trigonal PuNi3 type of crystal structure. Magnesium replaceslanthanum to form the hybrid LaNi5 + Laves phase structures and favorablychanges the thermodynamics of the metal-hydrogen interactions allowingimproved performance of the advanced metal hydride battery electrodes.Differences in melting temperatures of lanthanum, nickel and easily evaporatingmagnesium and a complexity of the phase equilibria in the La-Mg-Ni systemcause difficulties in synthesis of the battery electrode alloys with controlled Mgcontent and a desired phase-structural composition.In present work a La2MgNi9 alloy was in focus. Its successful synthesis hasbeen achieved from the alloy melts containing 0-30 % of overstoichiometric Mgas compared to La2MgNi9 by use of Rapid Solidification performed at variousquenching rates, with a copper wheel rotation speed of 3.1, 10.5 and 20.9 m/s.They were analyzed by synchrotron X-ray diffraction (SR XRD) including in situstudies in hydrogen gas performed at Swiss-Norwegian Beam Lines at ESRF,Grenoble, and by Scanning Electron Microscopy (SEM) with electron probemicroanalysis (EPMA). Pressure-Composition-Temperature isotherms, hydrogenabsorption-desorption cycling and measurements of the electrochemical chargedischargeperformances were employed to characterize hydrogenation behaviorsof the studied alloys. These studies showed that the melt spinning of the alloycontaining 30 % weight excess of Mg quenched using wheel spin speed of 400 RPMallowed obtaining the most homogeneous sample with the optimal microstructureand phase-structural composition corresponding to the formation of La2MgNi9with the highest yield.Variations in magnesium content and selection of optimal conditions for the RapidSolidification process provide complementary possibilities in improving propertiesof the studied La-Mg-Ni alloys as hydrogen storage and battery electrodematerials and provide a possibility to upscale production of the battery alloys.This work was performed at Institute for Energy Technology and at Departmentof Materials Science and Engineering, NTNU.
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Sømme, Astri. "Secondary Hardening in Two Supermartensitic Stainless Steels." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18535.
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Since the late nineties weldable supermartensitic stainless steels (SMSS) has been used in subsea flowlines, and more than 400 km is installed. Hydrogen related problems in the weld fabrication stage or hydrogen induced stress cracking (HISC) due to hydrogen embrittlement under cathodic protection have been reported and testing to better understand the behavior of these materials is of interest. The present work is focusing on the effect of double heat cycles on carbide precipitation and secondary hardening in two high grade SMSS, one alloyed with Ti and one not (0.007% Ti). The experimental work included heat treatment of both steels in single and double cycles in both oven and in induction heating weld simulator. All specimens were heated to 1000 degrees celsius for 30 min to austenize the material and air cooled before simulating second heat cycles of 1-60 min in the temperature range 500-600 degrees celsius. The microstructures resulting from the heat treatments were characterized by standard metallographic techniques, hardness testing and transmission electron microscopy (TEM). The results from hardness testing show a secondary hardening effect in both steels for all temperatures tested, with a maximum for samples treated at 550 degrees celsius. For all samples there was also a significant drop in hardness from the hardness of the single cycle sample to the 1 min tempered double cycle samples. From investigation in TEM it was found that, in the steel alloyed with titanium TiC precipitate during tempering and in the steel not alloyed with titanium Cr23C6 precipitate during tempering at 550. The difference in secondary hardening found is explained by the difference in carbide precipitation mechanism. In the steel alloyed with titanium a higher secondary hardening effect was found. No carbide precipitation was found in the single cycle heat treated state of the steels.
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Sølvberg, Erlend. "Effekt av høyt silisiuminnhold i stål." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18875.
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Det har i dette arbeidet blitt undersøkt hvilke effekter relativt store mengder silisium har på egenskaper i stål. To ulike deler i stål, tinder og fjærer, som jordbruksselskapet Kverneland Group ASA produserer, har blitt undersøkt nærmere. Felles for tinder og fjærer er at de er utsatt for store mekaniske belastninger og trenger derfor høy styrke. Begge må tåle sykliske belastninger og de krever derfor stor utmattingsmotstand slik at de ikke går til brudd for tidlig.Tindelegeringen som ble studert var 33S17B og de fire fjærlegeringene var 46Si7, 55Si7, 50CrV4 og 35M13B. Felles for tinder og fjærer var at både tindelegeringen, 33S17B, og to av fjærlegeringene, 46Si7 og 55Si7, hadde et høyt silisiuminnhold på henholdsvis 1,6 %, 1,6 % og 2,0 wt.%.Hovedmålet med denne oppgaven har vært å finne ut hvilken effekt det relativt høye silisiuminnholdet i 33S17B, 46Si7 og 55Si7 hadde. For 33S17B var det interessant å se i hvilken grad silisium påvirket senterseigringene i godset. For fjærlegeringene ble de med høyt silisiuminnhold, 46Si7 og 55Si7, sammenlignet med legeringsalternativene med langt lavere silisiuminnhold, 50CrV4 og 35M13B. I løpet av dette arbeidet har kjemiske analyser og varmbehandling av tindelegeringen 33S17B blitt utført. De varmebehandlede mikrostrukturene har blitt studert i lysmikroskop og mikrohardhetsmålinger ble utført. Videre ble de fire fjærlegeringene 46Si7, 55Si7, 50CrV4 og 35M13B varmebehandlet og anløpt på ulike måter. Prøver av legeringene ble studert i lysmikroskop, hardhetsmålinger ble gjort på både mikro- og makronivå og strekkforsøk ble utført. Det høye silisiuminnholdet i 33S17B, 46Si7 og 55Si7 førte til at ferritt var en stabil fase ved relativt høye glødetemperaturer. Ved et lavere silisiuminnhold ville ikke ferritt, men kun austenitt, vært stabil for de samme glødetemperaturene.I 33S17B forekom blant annet silisium som senterseigringer i leveringsmaterialet. Konsentrasjonsforskjellen mellom seigringen og legeringens gjennomsnitt var på omtrent 1 wt.%. Dette førte til at seigringene inneholdt forekomester av ferritt etter bråkjøling fra så høye temperaturer som minst 1000 °C. Varmebehandling ved 1050 °C gjorde at seigringsferritten ble austenittisert og omdannet til martensitt ved bråkjøling.For fjærlegeringene 46Si7 og 55Si7 førte det høye silisiuminnholdet til relativt kraftig avkulling ved en herdetemperatur på 900 °C. Ettersom overflaten ble avkullet i løpet av varmebehandlingen gjorde det høye silisiuminnholdet at austenitten ikke lenger var stabil ved glødetemperaturen. Den karbonfattige austenitten i overflaten ble omvandlet til ferritt ved glødetemperaturen. Etter bråkjøling forble ferritten uforandret.Som for legering 33S17B førte også en høyere herdetemperatur til at 46Si7 og 55Si7 ble fullstendig austenittisert i forkant av bråkjølingen. Det ble funnet at 46Si7 og 55Si7 bør bråkjøles fra henholdsvis 950 °C og 1000 °C for å unngå et ferrittsjikt i overflaten.Legeringene 50CrV4 og 35M13B hadde et langt lavere silisiuminnhold og hadde derfor ikke et ferrittsjikt på overflaten. Ved å bråkjøle 50CrV4 fra 900 °C oppnådde legeringen den høyeste overflatehardheten blant samtlige avkullingsprøver. Dette viste at 50CrV4 er legeringen med den antatt høyeste utmattingsmotstanden. Det ble imidlertidig påvist mulig korngrenseoksidasjon i overflaten på 50CrV4 etter noen av varmebehandlingene, noe som i så fall vil svekke utmattingsmotstanden.Legering 35M13B bør austenittiseres og bråkjøles fra en temperatur ikke høyere enn 900 °C for å oppnå en høyest mulig hardhet på overflaten. Strekkforsøkene viste at 35M13B var legeringen med størst arbeidsherding.
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Gurrik, Stian. "Performance of supported catalysts for water electrolysis." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18880.
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The most active catalyst for oxygen evolution in PEM water electrolysis is ruthenium oxide. Its major drawback as a commercial catalyst is its poor stability. In a mixed oxide with iridium, ruthenium becomes more stable. However, it would be favorable to find a less expensive substitute to iridium. In this work, the dissolution potential and lifetime of mixed oxides containing ruthenium and tantalum are investigated. In order to effectively determine what effects tantalum and particle size have on stability, only a small amount of tantalum is used, and the catalysts are supported by antimony doped tin oxide, ATO. This leads to a very small particle size, and makes it possible to investigate small amounts of catalyst where little new surface is made available during degradation.Catalysts were prepared with the normal polyol method by reducing RuCl3 and TaCl5 in ethylene glycol, EG, before the metal particles were deposited on the ATO support. The catalysts were investigated electrochemically with cyclic and linear voltammetry. Furthermore, the lifetime of four catalysts were determined by chronoamperometry at 1.455V vs. RHE. The compositions and loading of catalyst on the support were determined by energy dispersive x-ray spectroscopy (EDS) and the particle sizes were measured with transmission electron microscopy (TEM).In one synthesis, the reduction time and temperature were increased from 3 hours at 170◦C to 4 hours at 190◦C in order to increase the reduction rate. While this had no effect on the Ta composition, the catalyst got a fraction of amorphous phase not found in any of the other catalysts. The amorphous Ru0.9Ta0.1O2 particles had the largest particle size and the highest stability of the ones investigated. 10wt% water was added to the synthesis of an ATO-RuO2 catalyst in order to increase the particle size, but no significant effect was observed. Larger RuO2 particles and amorphous Ru0.9Ta0.1O2 particles were obtained by collecting them as unsupported catalysts.The addition of tantalum has a negative effect on the catalytic activity. When Ta is present, the dissolution potential of Ru at around 1.45V is slightly increased, but the degradation rate is increased above 1.49V. A large particle size in RuO2 has a significant positive effect on stability.
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Frydendahl, Jan Gaute. "ARB-valsede laminatkompositter av AA3103 og Cu." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18885.
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Laminatkompositter av plater av AA3103 aluminium + copper, samt AA3103 + C24000 messing, har blitt laget ved å anvende en prosess for akkumulert valsesveising (ARB). To forskjellige kobber/aluminium-stabler ble utsatt for 6 sykluser ARB ved en valsetemperatur på 350°C, og beholdt en kontinuerlig lagstruktur gjennom hele prosessen. Den relativt lave graden av kaldbearbeiding gjorde imidlertid at styrken økte lite eller ingenting med økende antall passeringer. 3 andre paralleller med originalstabler ble lagd av kobber, ikke-anløpt messing, og anløpt messing, der hver plate ble stablet mellom to aluminiumsplater som var betraktelig kaldvalset. Den første passeringen ARB foregikk ved 350°C, mens de påfølgende passeringene skjedde ved romtemperatur (CARB). Hver prøve som ble laget i løpet av denne prosessen ble kritisk oppsprukket, langs midten av plata, langsmed valseretningen, i løpet av den 5. passeringen ARB. I tilleg så hadde store, akkumulerte tøyninger forårsaket betydelig sprekkvekst langs kantene av laminatplatene.Etter passeringene før kritisk sprekkvekst oppstod, viste de kaldvalsede prøvene økende styrke med økende antall passeringer gjennom valsen, helt til det punktet hvor kobber/messing-lagene hadde sprukket opp og ble diskontinuerlige. De oppsprukne lagene bidro lite til styrke i både strekk- og bøyetester, samt at disse materialene gav prøver med innbyrdes større avvik mellom prøver tatt fra forskjellige steder på samme plate. Tidligere forskningsarbeid har funnet at forskjeller i plastisk flyt kan forårsake instabiliteter ved grenseflatene, og at dette fører til necking av lagene til det hardeste materialet. I løpet av arbeidet utført i denne rapporten, ble forholdet mellom lagtykkelsen til de ulike materialene balansert for å motarbeide denne effekten. I tillegg så viste de fremstilte prøvene en hittil oversett instabilitetsmekanisme: skjærdeformasjon. Skjærbånd ble observert i kobberlagene under EBSD-undersøkelser, og antatt korresponderende bølgelignende deformasjonsmønstre, som forplantet seg på tvers av lag, ble observert i lysmikroskop.Videre ARB-passeringer med de utforskede materialene vil ikke være mulig uten noen form for varmebehandling eller anløping mellom enkelte passeringer, siden det vil bli nødvendig å løse opp spenninger i de svært arbeidsherdede materialene.
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Sande, Gunnar. "Softening Behaviour of Selected Commercially Pure Aluminium Model Alloys." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18897.
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A characterization of the softening behaviour of four different commercially pure aluminium alloys has been carried out. The work is related to the MOREAL project (Modelling towards value-added recycling friendly aluminium alloys), where the main goal is to quantify the effect of the elements in recyclable aluminium alloys on microstructure and mechanical properties during thermo-mechanical processing. Typical elements are iron (Fe), silicon (Si) and manganese (Mn), and the alloys studied in this work contain Fe and Si with different amount and ratio: alloy A1 with 0.15 wt% Fe and 0.05 wt% Si; alloy A2 with 0.15 wt% Fe and 0.15 wt% Si; alloy B1 with 0.5 wt% Fe and 0.05 wt% Si and alloy B2 with 0.5 wt% Fe and 0.15 wt% Si.The as-cast material of all four alloys were homogenized at 600 °C for 24 hours followed by a cooling sequence to 450 °C, implying a total dwell time of 160 hours. The alloys were then cold rolled to a strain of 2.6 and isothermally annealed at temperatures from 275 °C to 375 °C, and the physical and mechanical properties were followed with electrical conductivity and hardness measurements. The microstructure and texture has been investigated with electron backscattering diffraction (EBSD) in scanning electron microscope (SEM), optical light microscopy and orientation distribution functions (ODF) from X-ray diffraction. Alloy A1 and A2 where fully recrystallzed after 10 000 seconds when isothermally annealed at 300 °C. Alloy B1 and B2 are slightly faster to reach the fully recrystallized state than alloy A1 and A2. The decrease in mechanical properties during softening was nearly linear on a logarithmic time scale, especially for alloy B1 and B2, with the onset of recrystallization difficult to seperate from the recovery. Electrical conductivity measurements showed that there was minimal concurrent precipitation. Images of the microstructure of the samples annealed at 275 °C show a long recovery phase followed by recrystallization. Particle stimulated nucleation (PSN) sites seems to be an important nucleation mechanism as it is found that the initial grain size have little effect on the softening kinetics, indicating that nucleation on old grain boundaries is of little importance. The recrystallization texture is weak with the typical Cube orientation slightly rotated around the normal direction. The recrystallized grain size was found to be smaller in alloy B1 and B2 (16-20 μm) than in alloy A1 and A2 (21-27 μm), most likely due to more PSN sites in these alloys. The grain growth that followed after recrystallization was found to be slightly larger for alloy A1 and A2 than alloy B1 and B2, most likely due to the effect from solute drag.
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Bjartnes, Erik. "Oxygen evolution on La1-xSrxCoO3 Pellet-Electrodes in alkaline Solution : Charge Carrier density dependence of electrocatalytic activity." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18901.
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Alkaline water electrolysis need a catalyst with low overpotential and high current densitiy for oxygen evolution in order to be a commercial viable hydrogen source in the future. Finding and establishing a correlation between electrocatalytic activity and charge carrier density will help towards finding an optimum catalyst for this purpose. Such comparisons have been made using theoretical values for charge carrier density, but the aim of this work is to use charge carrier data from experimental values.Five powders of La<sub>1-x</sub>Sr<sub>x</sub>CoO<sub>3</sub> (with compositions x = 0, 0.25, 0.5, 0.75, 1) were synthesized by solid-state synthesis and sintered to pellets. The pellet surfaces were investigated in alkaline solution (pH = 13) by cyclic voltammetry, polarization and impedance measurements. Polariza- tion curves with Tafel lines and Mott-Schottky plots were established. The powders and pellet surfaces were investigated by XRD, SEM, EDS, AFM and light microscope.The polarization curves revealed a volcanic behavior with an increase in catalytic activity from x = 0 up to x = 0.75 and then decreasing. The charge carrier density increased with increasing strontium doping. The resulting comparison gave figure 34. Surface investigation revealed much porosity. Because of corrosion, the surface area increased with measuring, and finding the real surface area and the roughness proved to be problematic.A volcanic behavior of the charge carrier density and electrocatalytic activity relationship were observed. Finding roughness factor values by measuring double layer capacitance measured by the cyclic voltammetry method and dividing by the nominal capacitance for a flat surface proved to be unsuccessful. Better synthesis and sintering procedures of pellets are needed to increase the density of the samples in order to decrease the roughness and the effect of corrosion.
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Iversen, Torunn Hjulstad. "Intragranular Chromium Nitride Precipitates in Duplex and Superduplex Stainless Steel." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18904.
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Intragranular chromium nitrides is a phenomenon with detrimental effects on material properties in superduplex stainless steels which have not received much attention. Precipitation of nitrides occurs when the ferritic phase becomes supersaturated with nitrogen and there is insufficient time during cooling for diffusion of nitrogen into austenite. Heat treatment was carried out at between 1060◦C and 1160◦C to study the materials susceptibility to nitride precipitation with varying heat treatment temperature, nitrogen content and microstructure. Microhardness tests and Charpy v-notch tests were also carried out to investigate the nitrides effect on material properties. No standard method of quantification of nitrides exist. A method of quantifying the precipitation based on area fraction of nitrides was therefore introduced. The results show an increased amount of nitride precipitation with increased heat treatment temperature. A coarse microstructure with a large austenite spacing was found to promote higher fractions of nitride precipitation while nitrogen content was found to affect the amount of precipitation in less extent. The intragranular nitrides cause precipitation hardening in the ferrite and the precipitation was found to be at its most severe in the center of the ferritic regions, with precipitation free zones close to the phase boundaries. The microhardness of the phase was affected accordingly, with increasing hardness towards the center. Charpy v-notch test results show that nitride precipitation causes an embrittlement of the steel while intragranular secondary austenite improves the impact toughness of the material as it shortens the dif- fusion distance of nitrogen, decreasing the materials susceptibility to intragranular nitride precipitation.
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Mathisen, Martin Borlaug. "In-Situ Tensile Testing Combined with EBSD Analysis of Ti-6Al-4V Samples from Components Fabricated by Additive Layer Manufacture." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18905.
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ALM-based production of Titanium components shows great promise in supplying cost-effective products within industries such as energy, chemical processing and aerospace. In common for all is high quality demands. This necessitates extensive research into the intricacies of this production process. Complex microstructures comprised of columnar remnants of directionally solidified β-Titanium, with interior inhabited by colonies of finer α-plate structures were found in samples produced by layered plasma welding of alloy Ti-6Al-4V. Utilising the powerful characterisation tool of in-situ tensile tests combined with EBSD analysis allowed qualitative correlation between microstructural features and deformation characteristics. Non-uniform deformation occurs due to a strong variation of strain response between colonies. Prismatic and basal slip systems are active, with the prismatic systems contributing to the most severe deformation through coarse, widely spaced slip bands. Certain colonies behave as microstructural units, with easy slip transmission across the entire colony. Other colonies show significant deformation mismatch, with local build up of strain gradients and stress concentration. Segmentation occurs due to the growth morphology imposed by the columnar grains. Tensile tests perpendicular to columnar structures reveal strong deformation localization. Connections are made between the peculiarities of the production process and the observed microstructure and deformation mechanisms.
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Hansen, Kristoffer Werner. "Phase Transformation Study of X70 Steel by EBSD during In Situ Heating and Quenching." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18909.
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Arctic steels, like the API X70 steel explored in this master thesis, are developed to withstand very low temperatures, with a ductile/brittle transition temperature below −60◦C. However, during welding, brittle phases like martensite-austenite (M-A) islands may form in the heat affected zone (HAZ). In this master thesis in situ heat treatment and quenching experiments have been combined with electron backscatter diffraction (EBSD) inside a field emission scanning electron microscope in order to simulate a second weld cycle simulation. In conjunction with this a quenching device has been designed with respect to an existing hot stage.Inside the SEM, it was found difficult to recreate the characteristic microstructure of API X70 steel from a traditional second cycle thermal weld simulation. This was probably due to the slow heating rate and the excessive high temperature holding time. The developed quenching device was based on gas quenching and produced a steel sample cooling time from 600◦C to 400◦C, ∆t6/4, of approximately 6.5 seconds in every experiment. As a result of the gas quenching substantial amounts of oxide contamination, covered the sample surface following the experiments. This contamination layer produced artifacts, such as unreasonable amounts of austenite in the EBSD phase maps.Despite the quenching, islands of austenite (FCC) observed at elevated temperatures transformed into a low strain BCC structure. Some austenite islands showed a memory- effect during phase transformation, while others adapted the orientation of the surround- ing structure. No retained austenite was observed in the API X70 steel after the in situ gas quenching, probably due to insufficient cooling rates.
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Bilsbak, Audun. "Mikrostruktur og mekaniske egenskaper for skrueekstrudert aluminium : Karakterisering av skrueekstrudert aluminium etter ulike rensmetoder av råmaterialet." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18910.
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Det er aktuelt å bruke restaluminium fra produksjonsindustrien som råmaterialet til skrueekstrudering. Restaluminiumet inneholder forurensinger som blant annet skjæreolje. Dette arbeidet har fokusert på ulike rensemetoder av råmaterialet som skal skrueekstruderes og kvaliteten på ekstrudatene. Råmaterialet ble systematisk forurenset med en olje fra maskineringsindustrien og behandlet på fire ulike måter før ekstrudering, hhv. ubehandlet, vannrenset, acetonrenset og termisk renset. Mikrostruktur og mekaniske egenskaper ble undersøkt, og det var en klar sammenheng mellom kvalitet og innhold av olje i ekstrudatene. Høyere innhold av olje førte til økt spredning i strekkresultater, redusert bruddforlengelse, økt gassutvikling og delaminering. Termisk rensing gir et ekstrudat av høy kvalitet, som viser svært gode resultater med lav spredning i mekaniske egenskaper, høy styrke og god duktilitet.
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Vangskåsen, Jørund. "Metal-producing Mechanisms in the Carbothermic Silicon Process." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18911.
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The mechanisms in the carbothermic production of silicon have been examined in this report. Through the investigation of a pilot scale furnace as well as five small scale induction furnace experiments, a better understanding of this comlex process has been obtained. Especially the silicon producing reactions and mechanisms have been studied.Samples of all raw material as they travelled downwards in the pilot scale furnace was investigated along with samples from the induction furncace. SiO gas formed in the hot zone (2000 °C) travelled upwards and deposited as a condensate mixture of SiO2 and Si. In the pilot scale furnace this condensate went back down with raw material as the furnace was stoked or the raw materials slowly melted. The condensate decomposed as the temperatures increased; silicon accumulated and escaped from the SiO2-matrix in the condensate.A typical experiment conducted in the induction furnace had a specic power consumption of roughly 62 MWh per ton silicon produced, far more than normal industrial power consumption of 11-13 MWh per ton Si produced. Mass balance demonstrated that just over half of the silicon produced were left in the silicon pool in the bottom of the crucible. The other mere half had to end as silicon droplets in the condensate deposited in the upper portion of the crucible.The main silicon producing reaction is: SiO(g) + SiC(s) = 2Si(s,l) + CO(g), but the findings in this thesis have shown that the perspiration of silicon from the condensate is very important. A significant contribution to the total amount of silicon produced can therefore come from the following reaction: 2SiO(g) = SiO2(s,l)+ Si(s,l)Compression tests have been made on the agglomerate caused by the deposits of condensate (SiO2+Si). The compression strength varied from 115 to 396 MPa. Samples exposed to temperatures above 1670 °C had the lowest strenght, while those exposed to lower temperatures were the strongest.
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Krogstad, Hedda Nordby. "Deposition of Thin Film Electrolyte by Pulsed Laser Deposition (PLD) for micro-SOFC Development." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19017.
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Optimalization of PLD deposition of YSZ for micr-SOFC electrolyte applications by varying deposition pressure and target-substrate distance.Substrate used was Si-based chips and wafers (large area PLD), and the substrate temperature was held at 600. Dense films were obtained at 20 mTorr.
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Larsen, Thomas. "Stål i beskyttelseskonstruksjoner : Introduksjon av Al2O3 til stålmatriks for økt penetrasjonsmotstand." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19048.
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Lette våpen som håndvåpen, rifler og granater står for de fleste dødsfall i moderne konflikter, og behovet for robuste materialer til vern mot slike våpen er stort. Denne rapporten har tatt sikte på å avdekke hvilken effekt introduksjon av aluminafliser til en stålmatriks har på de ballistiske egenskapene, i hvor stor grad beskyttelsesevnen er redusert ved et skudd nummer 2 i samme flis og om treff mellom flisene vil gi redusert beskyttelse. For å avdekke dette ble det støpt inn 12 mm tykke fliser av alumina i den ferrittisk-martensittiske støpelegeringen S165M, med spalteavstander mellom flisen på 0, 3 og 10 mm. Det ble utført ballistiske tester med 7,62 mm AP og 12,7 mm AP ammunisjon, samt gjort undersøkelser av mikrostruktur og penetrasjonsområdet i etterkant av forsøkene. Ballistiske forsøk viste ingen klar forbedring av penetrasjonsmotstanden ved innstøping av aluminafliser. Årsaken til manglende forbedring skyldes i hovedsak oppsprekking av keramet under støping, grunnet termisk sjokk. Reduksjon i ballistisk grense ved skudd nummer 2 i samme flis var ca. 6 %. På grunn av manglende fylling av de 3 mm brede spaltene under støping, gav skudd i spaltene ingen klare resultater.
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Strandheim, Espen Oldeide. "AC Induced Corrosion of Carbon Steel in 3.5wt% NaCl Electrolyte." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19589.
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This paper deals with alternating current (AC) corrosion of low alloy carbon steel in 3.5 wt% NaCl electrolyte. Accelerated corrosion rates have been reported when exposed to AC and the corrosion mechanism is not well understood. Electrical heating of subsea pipelines, applied to avoid hydrate formation and waxing of multiphase hydrocarbon well streams has made this topic increasingly relevant in recent years. To study the effect of AC on corrosion rates, weight loss experiments under a wide range of experimental conditions were performed. Results show that AC strongly influence corrosion kinetics of the system studied. Once AC is applied, a drop in corrosion potential and the formation of a passive iron oxide surface layer is observed. This layer is porous and believed to be the result of a rapid surface alkalization. Pitting corrosion is observed for all applied AC densities at open circuit. Weight loss- and LPR measurements conform well and the use of this technique in the presence of AC is on this basis considered valid. Corrosion rates increase as applied level of AC is increased and an approximately linear relationship has been established between iAC and icorr.
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Torstensen, Andreas. "AC corrosion on cathodically protected steel." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19590.
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This report deals with the effect of alternating current on cathodically protected steel. AC corrosion has become relevant in the offshore industry due to the introduction of the direct electric heating system (DEH). The principle with DEH is to prevent wax solidification inside pipelines by heating them up with alternating current. This can give rise to AC corrosion.DC current densities, AC current densities and DC potential have been measured for steel samples under cathodic protection with applied AC voltage. Weight loss measurements were done of both steel and sacrificial anode samples after the experiments. There have also been focused on the corrosion kinetics of AlZnIn by plotting polarization curves and potential measurements over time with applied AC current.The weight loss measurements have shown that carbon steel is protected against AC corrosion for AC current densities lower than 1300 A/m^{2}. All steel samples had corrosion rate lower than 0,1 mm/year up to this value. SEM investigation showed that no pitting corrosion occurred at any of the steel surfaces. The corrosion rate of AlZnIn increased with increasing AC current density up to 300 - 500 A/m^{2}. At higher AC current density, the sacrificial anodes became passive which resulted in decreased protection current and corrosion rate. Polarization curves of AlZnIn have also shown large resistance when AC is introduced which is probably due to surface coverings.Study of the surface morphology of AlZnIn have shown that more localized corrosion occurs with increasing AC current. At 500 A/m^{2} pitting corrosion occurred at the whole surface and the pits became deeper with increasing AC. This resulted in decreased efficiency of the sacrificial anode and consequently reduced DC current density and corrosion rate of the sacrificial anode.Potential and current measurements have shown that the galvanic potential of steel and AlZnIn became more electropositive with increasing AC current density. It is believed that this is due to more localized corrosion with increasing AC voltage and consequently lowering of the anode/cathode ratio. This will force the potential to more anodic values. The initial DC current density increased with increasing AC voltage for all samples but the passivation of sacrificial anode resulted in high reduction rate with time. Polarization curves of AlZnIn showed that the corrosion potential decreased and the corrosion current increased when AC was introduced. Within the samples exposed to AC there were no significant difference in corrosion potential and corrosion current. The polarization curves of all samples that were exposed to AC were characterized by high ohmic resistance which was due to hydrogen evolution and formation of corrosion products at the surface.
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Bastiko, Arya Priambodo. "Mekaniske egenskaper til beleggsystemer for offshore vindturbin." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18702.
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De seneste årene er det oppdaget slitasjeskade på offshorevindturbinenes fortøyningsplass, hvor båter kommer inntil for på og avlastning av drift og vedlikeholdspersonell. Hensikten med denne oppgaven er å se på beleggenes egenskaper i forhold til slitasje og å få en forståelse av hvorfor slitasjeskade oppstår ved fortøyning mellom båt og vindturbin. Beleggene som er valgt ut til testing, er beleggsystemer som i dag brukes på offshorerelaterte strukturer, som oljeplattformer og vindturbiner De mekaniske egenskapene til beleggene ble undersøkt ved hjelp av vickers mikrohardhetsmåler, ruhetsmåler, slitasjeapparat og strekkapparat. • Polyester inneholder glasspartikler og fikk påvist høyest massetap, glasspartiklene kan ha falt av under slitasje og bidratt til skade på beleggoverflaten. • I slitasjetesten ble det funnet at gummi heftet på beleggenes overflate. Den avsatte gummien kan derfor ha virket som et beskyttende lag. • Det ble funnet at lang herdetid øker slitasjeegenskapene til belegget. • For epoksybeleggene og varmforsinket stål var slagfastheten bedre enn for de andre beleggene, dette skyldes god heft mellom lagene. Testene i denne oppgaven viser at det er ulike årsaker til at skade oppstår i belegg på grunn av fender. Det er funnet at glasspartikler, høy ruhet, dårlig heft mellom strøkene og kort herdetid kan ha vært årsaken til skade på belegg på grunn av fender. Et Epoksy belegg er funnet til å være det som vil være best egnet til å brukes på fender- rør.
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Brennhaugen, David Dominikus Eide. "Thermal Dependence of Shear Banding in Zr70Ni16Cu6Al8 Bulk Metallic Glasses." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27347.
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Zr70Ni16Cu6Al8 bulk metallic glass samples were cast and prepared for tensiletesting. Tensile tests were done at temperatures 77 K, 150 K and 295K, over a range of effective strain rates between 10−5 and 10−1/s in order toassess the dependence of plastic deformation through shear band sliding onthe aforementioned factors.A strong temperature dependence was found, with maximum shear bandsliding distance at 150 K. The sliding distance was also found to increasewith lowered strain rates. The temperature dependence is likely to stemfrom increased heat dissipation suppressing a decrease in viscosity, while thestrain rate dependence stems from a decrease in energy supply rate.Shear bands appeared at higher stresses at lower temperatures, resultingin larger elastic domains and higher ultimate tensile stresses. A mechanismwhere heat dissipation suppresses the formation of shear bands at low stresseswas proposed.v
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Raess, Matthieu. "Deciphering the functional and molecular differences between MTM1 and MTMR2 to better understand two neuromuscular diseases." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAJ088.
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MTM1 et MTMR2 sont 2 phosphatases de phosphoinositides appartenant à la famille des myotubularines, conservée pendant l’évolution. Bien qu’étant très similaires, des mutations dans MTM1 entraînent la sévère myopathie XLCNM alors que les mutations dans MTMR2 entraînent la neuropathie CMT4B. On ne comprend pas encore les bases moléculaires de cette spécificité de tissu, et il n’existe aucun traitement spécifique pour ces maladies. J’ai tout d’abord caractérisé l’activité des 2 isoformes endogènes de MTMR2, nommés MTMR2-L et MTMR2-S. J’ai démontré que la différence fonctionnelle entre MTM1 et MTMR2 s’explique principalement par l’extension N-terminale de MTMR2, et que l’isoforme MTMR2-S dépourvu de cette extension entraîne les mêmes phénotypes que MTM1. Ensuite, grâce à l’injection d’AAV dans les souris Mtm1 KO, j’ai démontré que l’expression exogène des isoformes de MTMR2, et surtout de MTMR2-S, améliore grandement l’atrophie musculaire, la force musculaire et les marqueurs histologiques de ces souris myopathiques. Ces résultats révèlent une première base moléculaire expliquant les spécificités fonctionnelles de MTM1 et MTMR2, et montrent que MTMR2 est une cible thérapeutique potentielle pour la myopathie XLCNMMTM1 and MTMR2 are 2 phosphatases of phosphoinositides that belong to the myotubularin family conserved through evolution. Despite their high level of similarity, mutations in MTM1 lead to the severe XLCNM myopathy while mutations in MTMR2 lead to the CMT4B neuropathy. The molecular bases for the surprising tissue-specific functions of these ubiquitously expressed proteins was unclear. Moreover, there is no specific therapy for these diseases.I first characterized the activity of the two naturally occurring isoforms of MTMR2, that we named MTMR2-L (long) and MTMR2-S (short). I found that the functional differences between MTM1 and MTMR2 reside mostly in the N-terminal extension of MTMR2-L, and that the endogenous MTMR2-S isoform lacking this N-terminal extension behaves similarly as MTM1. Then, using the myopathic Mtm1 KO mouse and AAV-mediated expression, I showed that exogenous expression of MTMR2 isoforms, and specifically of MTMR2-S, strongly improved the muscle atrophy, muscle force and the histological hallmarks of the myopathic mice. These data reveal a first molecular basis for the functional specificities of MTM1 and MTMR2, and highlight MTMR2 as a therapeutic target for XLCNM myopathy
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Ergezen, Ertan Lec Ryszard. "A multi-resonance thickness-shear mode (MTSM) measurement technique for quantitative characterization of biological interfacial processes /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3198.
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Wright, David A. "Detection of hydrocarbons and their movement in a reservoir using time-lapse multichannel transient electromagnetic (MTEM) data." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/11615.
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Using two time-lapse surveys over an underground gas storage reservoir in St. Illiers la Ville, in France, I demonstrate the potential for multichannel transient electromagnetic (MTEM) data to detect the presence and movement of hydrocarbons in the earth through a new approach to the acquisition and processing of the data. I introduce a new pre-processing methodology for noise reduction and deconvolution of the system response to recover the impulse response of the earth. The thesis is divided into three parts: overview of electromagnetic methods, modelling, and processing of MTEM data. I carried out a comprehensive review of all electromagnetic (EM) methods in relation to hydrocarbon exploration. Of all these, the MTEM method provides the best resolution, detectability and spatial coverage of resistive targets. In the MTEM method a transient current is injected into the ground through a grounded dipole source and measurements of induced voltages at many receiver sites form the data for analysis. 1-D modelling indicates that the in-line component of the electric field is most sensitive to a buried resistor. The response of the cross-line component is about two orders of magnitude smaller, while the magnetic field is not sensitive to the resistor at all. Modelling the St. Illiers la Ville data shows that the response of the reservoir occurs between about 3 and 15ms, and at offsets greater than about 750m. I modelled in-line electric field data to test the application of a resistivity analysis using a seismic refraction analogy. The analysis was applied after transforming the data to a wave-like non-diffusive domain in log-time. The results indicate that the approach works only for a two-layer model and breaks down if the resistive layer is thin, typically less than a few hundred metres. The new MTEM data processing methodology includes improved noise reduction through the application of a dip filter, and deconvolution for the system response each time the source is fired. This enables the impulse response of the earth to be recovered. Processing of two MTEM datasets from St Iliers la Ville reveals both the presence of the gas in the reservoir and the movement of the gas between the two surveys.
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Sugai, Miguel. "Avaliação do uso do MTM (Methods-Time Measurement) em uma empresa metal-mecanica." [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264278.
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Orientador: Olivio NovaskiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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