Titânio e suas ligas são materiais estruturais atrativos para várias aplicações em engenharia devido a alta resistência específica, boa resistência a corrosão e alto ponto de fusão. Em particular, o titânio grau 2 exerce um importante papel nas industrias automotivas e aeroespaciais. Entretanto, a afinidade com o oxigênio e a baixa resistência ao desgaste são fatores que limitam a aplicação destas ligas como materiais estruturais em altas temperaturas. Os tratamentos termoquímicos tem sido uma eficiente alternativa para melhorar as propriedades tribológicas e o comportamento mecânico desta classe de ligas. Neste contexto, o principal objetivo deste trabalho foi avaliar o efeito da nitretação a gás na resistência a fluência do titânio grau 2. A nitretação foi realizada a 850ºC por um período de 9 h. As amostras foram caracterizadas por medidas de dureza e rugosidade, análises metalográficas e difração de raios X. Testes de curta duração foram realizados sob carga constante a 500ºC. A nitretação gerou uma camada com Ti2N and TiN, espessura de 4,5 ?m com dureza de 1125± 82,26 HV. A nitretação aumentou em 60% a rugosidade superficial. As propriedades em fluência foram significativamente melhoradas pela nitretação. Os testes mostraram que a nitretação reduziu a taxa de fluência estacionária e aumentou o tempo de vida. Com base nos valores do expoente de tensão, o mecanismo predominante foi controlado por escalagem de discordâncias. Após a nitretação do titânio, observou-se um amento do parâmetro de tolerância ao dano. As análises fractográficas revelaram que os mecanismos de fratura foram associados à nucleação e coalescimento de microcavidades. / Titanium and its alloys are attractive structural materials for various engineering applications due to its high specific resistance, good corrosion resistance and high melting point. In particular, titanium grade 2 plays an important role in the automotive and aerospace industries. However, the affinity of titanium for oxygen and low wear resistance are factors that limit the application of titanium alloys as structural materials at high temperatures. The thermochemical treatments has been an efficient alternative for improving the tribological conditions and the mechanical behavior of these alloys. In this context, the main objective of this study was to evaluate the effect of gas nitriding on the creep resistance of titanium grade 2. The gas nitriding was performed at 850ºC during 9h. The samples were characterized using hardness and roughness measurements, metallographic analysis and Xray diffraction. Short-term creep tests were performed under constant tensile load in air at 500ºC.The nitriding treatment produced a layer compound layer of Ti2N and TiN, thickness of 4,5 µm and hardness of 1125± 82,26 HV. There was a 60% increase in the average roughness after nitriding. The creep properties of nitrided specimens were significantly improved in comparison with those of unnitrided Ti.The tests showed that the nitriding reduced the steady-state creep and increased the creep life. Based on the values of stress exponent, it was estimated that the dominant creep mechanism was controlled by dislocation climb. There was an increase in the damage tolerance after nitriding of titanium. The failure analysis revealed that the fracture mechanisms were associated with the nucleation and coalescence of microvoids.

Titânio e suas ligas são materiais estruturais atrativos para várias aplicações em engenharia devido a alta resistência específica, boa resistência a corrosão e alto ponto de fusão. Em particular, o titânio grau 2 exerce um importante papel nas industrias automotivas e aeroespaciais. Entretanto, a afinidade com o oxigênio e a baixa resistência ao desgaste são fatores que limitam a aplicação destas ligas como materiais estruturais em altas temperaturas. Os tratamentos termoquímicos tem sido uma eficiente alternativa para melhorar as propriedades tribológicas e o comportamento mecânico desta classe de ligas. Neste contexto, o principal objetivo deste trabalho foi avaliar o efeito da nitretação a gás na resistência a fluência do titânio grau 2. A nitretação foi realizada a 850ºC por um período de 9 h. As amostras foram caracterizadas por medidas de dureza e rugosidade, análises metalográficas e difração de raios X. Testes de curta duração foram realizados sob carga constante a 500ºC. A nitretação gerou uma camada com Ti2N and TiN, espessura de 4,5 ?m com dureza de 1125± 82,26 HV. A nitretação aumentou em 60% a rugosidade superficial. As propriedades em fluência foram significativamente melhoradas pela nitretação. Os testes mostraram que a nitretação reduziu a taxa de fluência estacionária e aumentou o tempo de vida. Com base nos valores do expoente de tensão, o mecanismo predominante foi controlado por escalagem de discordâncias. Após a nitretação do titânio, observou-se um amento do parâmetro de tolerância ao dano. As análises fractográficas revelaram que os mecanismos de fratura foram associados à nucleação e coalescimento de microcavidades. / Titanium and its alloys are attractive structural materials for various engineering applications due to its high specific resistance, good corrosion resistance and high melting point. In particular, titanium grade 2 plays an important role in the automotive and aerospace industries. However, the affinity of titanium for oxygen and low wear resistance are factors that limit the application of titanium alloys as structural materials at high temperatures. The thermochemical treatments has been an efficient alternative for improving the tribological conditions and the mechanical behavior of these alloys. In this context, the main objective of this study was to evaluate the effect of gas nitriding on the creep resistance of titanium grade 2. The gas nitriding was performed at 850ºC during 9h. The samples were characterized using hardness and roughness measurements, metallographic analysis and Xray diffraction. Short-term creep tests were performed under constant tensile load in air at 500ºC.The nitriding treatment produced a layer compound layer of Ti2N and TiN, thickness of 4,5 µm and hardness of 1125± 82,26 HV. There was a 60% increase in the average roughness after nitriding. The creep properties of nitrided specimens were significantly improved in comparison with those of unnitrided Ti.The tests showed that the nitriding reduced the steady-state creep and increased the creep life. Based on the values of stress exponent, it was estimated that the dominant creep mechanism was controlled by dislocation climb. There was an increase in the damage tolerance after nitriding of titanium. The failure analysis revealed that the fracture mechanisms were associated with the nucleation and coalescence of microvoids.

Titanium is thanks to its high corrosion resistance and biocompatibility widely used in medicine. Ti alloys are used due to their superior mechanical properties instead of pure Ti for load carrying components. Ti alloys are often alloyed with elements which are toxic for human body and further increase cost of Ti products. Main focus of current development is to create pure Ti with better mechanical properties. It can be done by reducing grain size by processes based on severe plastic deformation. The aim of this work is to evaluate fatigue properties as well as fatigue crack initiation and propagation mechanism of Ti grade 2 with the ultrafine grained structure. After microstructure analysis, fatigue tests with symmetrical loading were executed. Fracture surfaces of ultrafine grained Ti grade 2 were observed after fatigue tests for identification of failure mechanism. Results were compared with those for course-grained Ti grade 2.

PhDRDV / Instutute for Rural Development / The overall purpose of this study was to describe a model for the development of women in construction in the Limpopo Province of South Africa. To achieve this purpose two phases were used i.e., the two stage empirical phase that employed a mixed method research process to identify and understand the development needs of women in construction and a theory-generation phase, which consisted of 8 stages that interfaced with phase 1 The population of the study were stakeholders in the construction industry namely, women contractors who are active grade 2 (registered as such on the CIDB register of contractors) and owner-managers in the Limpopo Province of South Africa, representative of the board of the Construction Industry Development Board (CIDB), Construction Education and Training Authority (CETA), the Independent Development Trust (IDT), the Council for the Built Environment (CBE) and the South African Women in Construction (SAWIC). Qualitative data was collected through in-depth one-on-one interviews, whilst quantitative data was gathered through administering questionnaires. Six (6) stakeholders participated in the interviews and out of the targeted 167 in the CIDB register, 120 completed the questionnaires. The results of the empirical phase were subjected to the 8-step method of theory generation according to Chinn and Kramer (2011:152- 205). A conceptual framework for the model for development of rural women in construction was organized by applying the proposed elements of a practice theory according to Dickhoff, James & Wiedenbach (1968) and Barnum (1994). The theoretical evaluation of a model was done utilizing Chinn and Kramer (2011:205) criteria for evaluation of a theory. Guidelines to operationalize the theory were also described as well as recommendations and conclusion.

The purpose of this study was to examine how second graders use writing and language when they are learning to add multidigit numbers in mathematics class. Second grade students were taught addition conceptually with a focus on sharing their strategies and thought processes with each other during the mathematics lesson. Two social norms were established with students so that sharing information and asking for clarity when they did not understand would be natural and expected. Students kept a daily mathematics journal to answer the class's Problems of the Day. Patterns found in student journals indicated three stages of multidigit learning. In Stage One, students used little or no words to explain their solution, illustrations show students using counting by ones strategies. Stage Two represents students using appropriate mathematics strategies and vocabulary to explain their solutions in detail. Lastly, Stage Three consists of students solving multidigit problems with little or no word explaining their solution process and illustrations are few. Results of the study indicated that students' oral explanations of solutions to addition problems included more detail compared to students' written justification of similar problems.

Cette thèse a pour objet l'étude du comportement asymptotique des solutions des équations des fluides de grades 2 et 3. Dans le premier chapitre, on étudie les profils asymptotiques au premier ordre des solutions des équations des fluides de grade 2 en dimension 3. On démontre que les solutions des équations des fluides de grade 2 convergent vers des solutions particulières et explicites des équations de la chaleur, lorsque le temps tend vers l'infini. Ce résultat montre en particulier que les fluides de grade 2 se comportent asymptotiquement comme les fluides newtoniens régis par les équations de Navier-Stokes. Pour cette étude, on utilise les variables d'échelles (ou variables autosimilaires), et on effectue des estimations d'énergies dans divers espaces fonctionnels, en particulier dans des espaces de Sobolev à poids polynomiaux. La description des profils asymptotiques est obtenue sous des conditions de petitesse sur les données initiales de l'équation.Le second chapitre de cette thèse traite des profils asymptotiques à l'ordre 1 des solutions des équations des fluides de grade 3 en dimension 2. À l'instar des résultats du premier chapitre, on obtient ici aussi la convergence des solutions de ces équations vers des solutions explicites des équations de la chaleur. Les outils utilisés pour cette étude sont semblables à ceux utilisés pour les fluides de grade 2 en dimension 3, à savoir les variables autosimilaires et des estimations d'énergies. Dans ce cas aussi, on conclut que les fluides de grade 3 se comportent asymptotiquement comme les fluides newtoniens.Dans le dernier chapitre, on étudie l'existence d'un attracteur pour les équations des fluides de grade 3 en dimension 2 avec des conditions périodiques. On considère donc les solutions faibles de ces équations à données initiales dans l'espace de Sobolev H¹. Ces solutions faibles définissent un semi-groupe généralisé. Ensuite, on montre que les solutions à données initiales dans H² possèdent un attracteur global pour la topologie H¹. Pour ce travail, on utilise un schéma de Galerkin, des estimations a priori et une méthode de monotonie. Les principales difficultés que l'on rencontre sont liées au peu de régularité des données initiales et au fait que l'on ne sait par si les solutions des équations des fluides de grade 3 à données H¹ sont uniques.

I denna empiriska studie har användningen av transspråkande undersökts på tre olikaskolor. Transspråkande innebär i korta drag att flerspråkiga elever ges möjlighet attanvända alla sina språk i undervisningen. Studien utgår från det sociokulturellaperspektivet, och syftet med studien är att undersöka hur muntlig kommunikationrealiseras i transspråkande klassrum samt hur lärmiljön i dessa klassrum är utformade.Materialet har samlats in genom systematiska observationer i transspråkandeklassrum på tre skolor. Med stöd av ett etablerat schema för observationer av 44språkutvecklande faktorer har lärmiljöer, lärtillfällen och interaktioner studeratsunder tolv lektioner i matematik och svenska. Resultatet visar att lärmiljön i detransspråkande klassrummen var utformade med öppna planlösningar där väggarnautnyttjades för att exponera bildstöd i både svenska och matematik. Vid interaktionenmellan lärare och elev var det särskilt karaktäristiskt att läraren bemötte eleverna medderas förnamn, gick ned till deras ögonhöjd, uppmuntrande turtagande och berömdeelevernas lyssnande. Särskilt utmärkande för lärtillfällen i de transspråkandeklassrummen var att lärarna uppmuntrade användningen av flera språk blandeleverna, såväl i diskussioner som vid skriv- och läsuppgifter. Detobservationsschema som har använts i studien har tidigare inte använts vidobservation av just transspråkande.

För att ge alla elever möjlighet att läsa enskilt är det av stor vikt att den enskilda läsningen är ett inplanerat moment i undervisningen. Genom enskild läsning får eleverna möjlighet att utveckla sin läsförmåga, vilket bland annat innebär utveckling av avkodning, läsförståelse och läsflyt. Det är lärarna som ansvarar för den enskilda läsningen som sker i undervisningen och därför avser studien att bidra med kunskap om hur enskild läsning planeras, tillämpas och följs upp i undervisningen. Studien tar utgångspunkt i ett sociokulturellt perspektiv eftersom läsning sker i ett sammanhang och eleverna utvecklas efter sin förmåga. Det sociokulturella perspektivet beskriver även vikten av att använda språket som ett redskap och att utveckling sker ständigt. Syftet med studien är att bidra med kunskap om hur legitimerade lärare i årskurs 2 planerar och tillämpar enskild läsning i undervisningen för att utveckla elevers läsförmåga. En kvalitativ undersökningsmetod har använts i form av semistrukturerade intervjuer med fem lärare i årskurs 2. Intervjuerna som har genomförts transkriberades och sedan analyserades transkriberingarna utifrån en tematisk analysmetod. Resultatet visade att lärarna tillämpar enskild läsning i undervisningen, men att den inte får så mycket tid. Det framkom även att lärarnas betydelse är av stor vikt på olika sätt. Den enskilda läsningen följs upp i undervisningen med olika tester och mätmaterial samt att eleverna blir lyssnade till när de läser. Resultatet visade även att den enskilda läsningen planeras in i undervisningen men på olika sätt, det varierar i hur länge och hur många gånger i veckan eleverna får läsa. / In order to give all students the opportunity to read individually, it is of great importance that individual reading is a planned part in the classroom. Through individual reading, the students have the opportunity to develop their reading ability, which, among other things, means the development of decoding, reading comprehension and reading fluency. It is the teachers who are responsible for the individual reading that takes place in the classroom and therefore the study intends to contribute with knowledge about how individual reading is planned, applied and followed up in the classroom. The study is based on a socio-cultural perspective because reading takes place in a context and students develops according to one's ability. The socio-cultural perspective also describes the importance of using language as a tool and that development takes place constantly. The aim of the study is to contribute knowledge about how certified teachers in grade 2 plan and apply individual reading in teaching to develop students' reading ability. A qualitative research method has been used in the form of semi-structured interviews with five teachers in grade 2. The interviews that have been conducted were transcribed and then the transcriptions were analyzed based on a thematic analysis method. The result showed that the teachers apply individual reading in the classroom, but that it does not get much time. It also emerged that the importance of teachers is of great importance in different ways. The individual reading is followed up in the classroom with various tests and measuring materials and that the students are listened to when they read. The result also showed that the individual reading is planned into the teaching, but in different ways, it varies in how long and how many times a week the students are allowed to read.

Språkutveckling gynnar elevers kunskapsutveckling och framgång i skolan. Elever vars språkliga förmåga brister riskerar att få svårigheter med kunskapsutvecklingen i skolan. Lärare behöver därför kunskap om vad de kan göra för att stötta elevers språkutveckling. I denna studie undersöks förekomsten av sju språkutvecklande aktiviteter i fyra klasser inom svensk- och matematikundervisningen i årskurs 2 och 3. Lärarnas praktik dokumenteras med stöd av ett observationsschema som bygger på det brittiska observationsverktyget ”Communication Supporting Classrooms Observation Tool”. Resultatet analyseras och jämförs med avseende på skolämne och årskurs. Studien visar att de språkutvecklande aktiviteterna förekommer oftare inom svenskundervisningen men att utbudet av antal aktiviteter i matematikundervisningen är högre. Vidare visar studien att eleverna erbjuds få tillfällen att arbeta tillsammans utan att fokus istället ligger på aktiviteter som är styrda av läraren. / Language development benefits pupils’ knowledge development and progress in school. Pupils whose linguistic ability is deficient risk encountering difficulties with knowledge development in school. Teachers therefore need to know what they can do to support pupils’ language development. This study examined the occurrence of seven language development activities in four classes in Swedish and mathematics in grades 2 and 3. The practice of the teachers was documented with the support of an observation schedule based on the British “Communication Supporting Classrooms Observation Tool”. The results were analysed and compared according to school subject and grade. The study shows that language development activities occur more often in Swedish teaching but that the range of activities in mathematics teaching is wider. Moreover, the study shows that the pupils are offered few opportunities to work together, as the focus is instead on activities directed by the teacher.

The purpose of this study was to investigate how four students in grade 2 in risk for read- and write difficulties use the iPad when they read a literary digital text and to find out how the students experience reading on it. Video observations were used to get the data when the students individually read on the iPad. They read both an eBook and a book with Inläsningstjänst. (Inläsningstjänst is a program that reads the text for you while you read.) When the students read the books, they were interviewed about their experience. Socio- cultural theory in which interaction with other people and cultural tools are important for learning to take place, is the perspective used in this study. The results show that the students´ didn´t use much of the functions they had access to in the iPad while they read. That´s against the research that show that the most students feel like they get good help as they read, from the functions that are available on the digital tools. The results also show that the students experienced was that they thought that it was more fun and easier to read on an iPad, as the research review also shows. The students in my study has dissimilar experience in which way that was the best way to read, the eBook or the book with Inläsningstjänst. Some students liked the eBook best because it had big text and was easy to scroll. Other students liked the book with Inläsningstjänst best. They found it easier to concentrate when the text was read for them. / Syftet med min studie är att undersöka hur några elever som är i riskzonen för läs-och skrivsvårigheter använder iPaden då de läser en skönlitterär digital text och hur de upplever läsning av e-bok och bok från Inläsningstjänst. Studiens data har tagits fram genom videoobservationer då eleverna läste enskilt på iPaden. När eleverna läst böckerna intervjuades de om sin upplevelse. Studien utgår från ett sociokulturellt perspektiv, där interaktionen med andra och med kulturella redskap är viktiga för att lärande ska ske. Resultatet i min studie visar att eleverna utnyttjade ytterst få av de funktioner de fick tillgång till i iPaden vid läsningen vilket inte stämmer med forskningen. Forskningen visar att de flesta elever anser att de får god hjälp av de funktioner som finns på de digitala verktygen när de    läser. Resultatet visar även att eleverna upplevde att det var både roligare och lättare att läsa på iPaden, vilket även forskningsöversikten visar. Eleverna i min studie hade olika upplevelser om vilket sätt som de tyckte var bäst att läsa på av e-boken eller boken från Inläsningstjänst. Några elever tyckte att e-boken var bäst för den hade stor text och var lätt att bläddra. Några tyckte att det var bäst att läsa boken från Inläsningstjänst då de upplevde att det var lättare att koncentrera sig när texten blev uppläst.