A thermogravimetric study of the oxidative growth of Al2O3/Al alloy composites

The oxidation of liquid Al–Mg–Si alloys at 900–1400 °C was studied by thermogravimetric analysis (TGA). The development of a semi-protective surface layer of MgO/MgAl2O4 allows the continuous formation of an Al2O3-matrix composite containing an interpenetrating network of metal microchannels at 1000–1350 °C. An initial incubation period precedes bulk oxidation, wherein Al2O3 grows from a near-surface alloy layer by reaction of oxygen supplied by the dissolution of the surface oxides and Al supplied from a bulk alloy reservoir through the microchannel network. The typical oxidation rate during bulk growth displays an initial acceleration followed by a parabolic deceleration in a regime apparently limited by Al transport to the near-surface layer. Both regimes may be influenced by the Si content in this layer, which rises due to preferential Al and Mg oxidation. The growth rates increase with temperature to a maximum at ~1300 °C, with a nominal activation energy of 270 kJ/mole for an Al-2.85 wt. % Mg-5.4 wt. % Si alloy in O2 at furnace temperatures of 1000–1300 °C. An oscillatory rate regime observed at 1000–1075 °C resulted in a banded structure of varying Al2O3-to-metal volume fraction.

Nucleation and growth of Al2O3/metal composites by oxidation of aluminum alloys

The nucleation and growth mechanisms during high temperature oxidation of liquid Al-3% Mg and Al-3% Mg-3% Si alloys were studied with the aim of enhancing our understanding of a new composite fabrication process. The typical oxidation sequence consists of an initial event of rapid but brief oxidation, followed by an incubation period of limited oxide growth after which bulk Al2O3/Al composite forms. A duplex oxide layer, MgO (upper) and MgAl2O4 (lower), forms on the alloy surface during initial oxidation and incubation. The spinel layer remains next to the liquid alloy during bulk oxide growth and is the eventual repository for most of the magnesium in the original alloy. Metal microchannels developed during incubation continuously supply alloy through the composite to the reaction interface. During the growth process, a layered structure exists at the upper extremity of the composite, consisting of MgO at the top surface, MgAl2O4 (probably discontinuous), Al alloy, and finally the bulk Al2O3 composite containing microchannels of the alloy. The bulk oxide growth mechanism appears to involve continuous formation and dissolution of the Mg-rich oxides at the surface, diffusion of oxygen through the underlying liquid metal, and epitaxial growth of Al2O3 on the existing composite body. The roles of Mg and Si in the composite growth process are discussed.

Influence of melt pouring temperature and plate inclination on solidification and microstructure of A356 aluminum alloy produced using oblique plate

The preparation of semisolid slurry of A356 aluminum alloy using an oblique plate was investigated. A356 alloy melt undergoes partial solidification when it flows down on an oblique plate cooled from underneath by counter flowing water. It results in continuous formation of columnar dendrites on plate wall. Due to forced convection, these dendrites are sheared off into equiaxed/fragmented grains and then washed away continuously to produce semisolid slurry at plate exit. Melt pouring temperature provides required condition of solidification whereas plate inclination enables necessary shear for producing semisolid slurry of desired quality. Slurry obtained was solidified in metal mould to produce semisolid-cast billets of desired microstructure. Furthermore, semisolid-cast billets were heat treated to improve surface quality. Microstructures of both semisolid-cast and heat-treated billets were analyzed. Effects of melt pouring temperature and plate inclination on solidification and microstructure of billets produced using oblique plate were described. The investigations involved four different melt pouring temperatures (620, 625, 630 and 635 degrees C) associated with four different plate inclinations (30 degrees, 45 degrees, 60 degrees and 75 degrees). Melt pouring temperature of 625 degrees C with plate inclination of 60 degrees shows fine and globular microstructures and it is the optimum.

Amorphous W-S-N thin films: The atomic structure behind ultra-low friction

Amorphous W-S-N in the form of thin films has been identified experimentally as an ultra-low friction material, enabling easy sliding by the formation of a WS2 tribofilm. However, the atomic-level structure and bonding arrangements in amorphous W-S-N, which give such optimum conditions for WS2 formation and ultra-low friction, are not known. In this study, amorphous thin films with up to 37 at.% N are deposited, and experimental as well as state-of-the-art ab initio techniques are employed to reveal the complex structure of W-S-N at the atomic level. Excellent agreement between experimental and calculated coordination numbers and bond distances is demonstrated. Furthermore, the simulated structures are found to contain N bonded in molecular form, i.e. N-2, which is experimentally confirmed by near edge X-ray absorption fine structure and X-ray photoelectron spectroscopy analysis. Such N-2 units are located in cages in the material, where they are coordinated mainly by S atoms. Thus this ultra-low friction material is shown to be a complex amorphous network of W, S and N atoms, with easy access to W and S for continuous formation of WS2 in the contact region, and with the possibility of swift removal of excess nitrogen present as N-2 molecules. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Numerical study of solidification of A356 aluminum alloy flowing on an oblique plate with experimental validation

Molten A356 aluminum alloy flowing on an oblique plate is water cooled from underneath. The melt partially solidifies on plate wall with continuous formation of columnar dendrites. These dendrites are continuously sheared off into equiaxed/fragmented grains and carried away with the melt by producing semisolid slurry collected at plate exit. Melt pouring temperature provides required solidification whereas plate inclination enables necessary shear for producing slurry of desired solid fraction. A numerical model concerning transport equations of mass, momentum, energy and species is developed for predicting velocity, temperature, macrosegregation and solid fraction. The model uses FVM with phase change algorithm, VOF and variable viscosity. The model introduces solid phase movement with gravity effect as well. Effects of melt pouring temperature and plate inclination on hydrodynamic and thermo-solutal behaviors are studied subsequently. Slurry solid fractions at plate exit are 27%, 22%, 16%, and 10% for pouring temperatures of 620 degrees C, 625 degrees C, 630 degrees C, and 635 degrees C, respectively. And, are 27%, 25%, 22%, and 18% for plate inclinations of 30, 45, 60, and 75, respectively. Melt pouring temperature of 625 degrees C with plate inclination of 60 generates appropriate quality of slurry and is the optimum. Both numerical and experimental results are in good agreement with each other. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Entre o princípio da emancipação e o fardo da institucionalização: dilemas do projeto ético-político profissional na busca de caminhos para intervenção

O objetivo desse estudo é refletir sobre questões pertinentes aos limites e às possibilidades que permeiam o exercício profissional de assistentes sociais comprometidos com o que se convencionou chamar, no meio profissional, de Projeto Ético-Político do Serviço Social brasileiro. O que, em nossa compreensão, requer considerar os impactos da intervenção profissional em relação aos diferentes projetos societários. Para a realização desse estudo, retomamos debates que consideramos centrais para pensarmos a intervenção do assistente social, enfatizando os dilemas e pretensões postos a esse profissional, partindo dos interesses burgueses que conformaram o Projeto institucional que lhe traz requisições. Buscamos pensar a tensão presente entre esse Projeto Institucional e o referido Projeto Ético-Político, considerando as relações de oposição e poder, e possíveis negociações estabelecidas entre ambos, pois, assim, pudemos mergulhar nesse universo e avaliarmos o conceito de autonomia profissional, em busca de possibilidades interventivas pertinentes à materialização (ainda que relativa) do Projeto Ético-Político do Serviço Social brasileiro. Para enriquecer esse debate, realizamos uma pesquisa empírica que recorreu instrumentalmente a questionários e a entrevistas. O primeiro teve a finalidade de contribuir para a escolha dos profissionais a serem entrevistados e enriquecer alguns dados de análise. A entrevista foi realizada com assistentes sociais que atuam na área da saúde, empregados pelo Estado, em processo de formação continuada e que alegaram compromisso com o referido Projeto Ético-Político Profissional.

Narrativas docentes sobre processos de formação nos movimentos estudantis: tecendo diálogos sobre práticas democráticas

Este estudo tem como propostas pensar os processos formativos que acontecem nos movimentos estudantis e como as experiências vivenciadas neste espaçotempo influenciaram e influenciam práticas educacionais que busquem ser mais democráticas. Assim, neste texto, dedicar-me-ei a refletir um pouco mais sobre a noção de democracia que venho assumindo nesta pesquisa e meus caminhos formativos como pesquisadora e professora. Dialogo com Oliveira (2009) e Santos (2007) para pensar a democracia, partindo da noção de que uma sociedade seria realmente democrática quando as relações tecidas entre os diferentes conhecimentos, culturas e valores se darem de maneira horizontal, nas quais não sejam estabelecidas formas de inferiorização e marginalização entre as diferentes perspectivas de estar no mundo. Este trabalho parte da ideia de que as experiências vividas por ex-militantes/praticantes dos movimentos estudantis ajudam na promoção de subjetividades mais democráticas eo fortalecimento desta premissa se dá através das narrativas de professores/professoras que tiveram experiências nos espaçostempos dos movimentos estudantis. Assim, procuro tecer uma narrativa através do compartilhamento de diferentes experiências docentes, não como objetivo de qualificar ou quantificar o grau de democracia desenvolvida nessas práticas, mas sim, de apresentar que são múltiplas as práticas que partilham da noção de solidariedade entre os conhecimentos, valores e sentimentos, ocorrendo elas dentrofora do ambiente escolar.

Análise dos discursos dos professores de uma licenciatura em Ciências Biológicas sobre o ensino de evolução: dificuldades, limitações e abordagens promissoras

Este trabalho procura identificar e discutir aspectos da formação inicial que estejam relacionados com o ensino de evolução biológica no curso de licenciatura plena em Ciências Biológicas da Faculdade de Formação de Professores da Universidade do Estado do Rio de Janeiro. A evolução biológica é considerada tanto por vários estudiosos como por documentos oficiais de educação como um eixo unificador dentro das Ciências Biológicas que, além de interligar as diversas partes que compõem a Biologia, é imprescindível para a compreensão de diversos conceitos e processos biológicos. A coleta de dados foi realizada a partir de entrevistas semiestruturadas aplicadas a quatro docentes do curso, sendo dois responsáveis por disciplinas de conteúdo biológico específico e os outros por disciplinas relacionadas ao ensino de Ciências e Biologia. Os discursos foram analisados a partir da Análise de Conteúdo. Os resultados aqui expostos revelam que o ensino da teoria evolutiva ocupa posição de destaque na formação dos alunos da FFP-UERJ ao longo do curso, contribuindo para a construção de uma visão mais global sobre a Biologia para muitos. As principais dificuldades apontadas para a sua abordagem são a ausência de atividades interdisciplinares como trabalhos de campo; a falta de comunicação entre os docentes do curso sobre o assunto; a falta de maturidade dos alunos para compreender os processos evolutivos; a falta de materiais de apoio em determinadas áreas específicas; e o embate entre as explicações científicas e alguns pontos de vista religiosos sobre a origem da diversidade biológica. A maioria dos docentes apontou as estratégias que utilizam para superar tais empecilhos e incluir o tema em suas disciplinas. O resultado deste esforço é reconhecido por eles mesmos, ao perceber que, ao longo do curso, os alunos desenvolveram capacidade intelectual para relacionar temas de distintos campos através da perspectiva evolutiva.

O e-learning na formação contínua de professores : perceções, impacto e linhas orientadoras

Tese de doutoramento, Educação (TIC na Educação), Universidade de Lisboa, Instituto de Educação, 2015

Référentiel de compétences infirmières : soins intensifs, traumatologie

Rapport de stage présenté à la Faculté des sciences infirmières en vue de l'obtention du grade de Maître ès sciences (M.Sc.) en sciences infirmières option formation en soins infirmiers

A formação inicial dos Professores do Ensino Primário no Portugal do Século XX (1942-2000). Do modelo maternal ao modelo profissional

Pensamos com este nosso trabalho de investigação contribuir para o estudo da formação inicial dos professores do ensino primário/professores do 1º ciclo do ensino básico (1942-2000), tomando como eixo a evolução dos conceitos educação, professor, aprendizagem, sintetizados no modelo maternal, em que a professora governava a sua classe como a mãe a sua família e no modelo profissional que faz do professor um expert e insiste na sua competência, quer a nível dos saberes, quer a nível das técnicas pedagógicas. Escolhemos como referente inicial do nosso estudo o ano de 1942, data em que, pelo decreto-lei nº 32 243 de 5 de Setembro de 1942, são reabertas as Escolas do Magistério Primário em Lisboa, Porto, Coimbra e Braga. Escolhemos como referente final do nosso estudo o ano de 2000, fecho de século e milénio que, na formação inicial de professores, inseriu os primeiros professores do 1º ciclo do ensino básico com licenciatura (decreto-lei nº 115, de 19 de Setembro de 1997). No percurso da formação inicial dos professores do Ensino Primário, da reabertura das Escolas do Magistério Primário (1942), à instituição das Escolas Superiores de Educação (1986), à promulgação do Estatuto da Carreira Docente (1990), à exigência do grau de licenciatura na formação inicial dos professores do 1º ciclo (1997) questionamos: - Que conceitos de educação, professor e aprendizagem estão presentes na formação inicial realizada em Escolas do Magistério Primário e Escolas Superiores de Educação? - Que transformações sofrem estes conceitos com a adopção de novos modelos de formação inicial experimentados a partir da Revolução Portuguesa de 25 de Abril de 1974?

O Probásica e a formação de professores no Pólo de Parnamirim: política de formação profissional no Rio Grande do Norte?

This work studies the thematic of the politics of formation of teachers in the Program of Professional Qualification for Basic Education (PROBÁSICA) developed in the City of Parnamirim, Rio Grande do Norte. It has as its main objective to identify and to analyze the contribution of this politics of initial formation for the professional formation of teachers. To install the work, we will use the procedures of bibliographical research, documentary analysis, comment, structuralized interview, questionnaire-script and virtual research. In the analysis of the data, we trace a general view on PROBÁSICA while initial formation along with the continued formation, pedagogical research, collaborative research and the exercise of the teaching profession, identifying the possibilities and limits of the Program in the direction to reach the objective considered in this work. From the inquiry, we construct the institutional land scope of the program in question, also focusing, the organizational aspects of its functioning. We have to take care about the results, we evidence that PROBÁSICA is making the possible to access of the teachers in the educational service to the University, what the main aspect that consists, trying to prove eminent weak points in its systematic due to give to the organizational structure of this educational politics that does not count with curricular, institutional and financial the necessary conditions for the success of the professional formation of the teachers. The research will try to understand that the operationalization of the politics of formation in Parnamirim will be belong with it the main idea of the Educational Reformation in years of 1990, articulated to the neoliberal interests, that the responsibility for the problems of the public system of education attributed to the teachers, and that are not answered completely through the purpose of the professional formation, and ti seems that it does not define one global national politics that deals with seriousness to the questions the initial formation, permanent formation, pedagogical research, , career and conditions of work for the teachers

As ciências da educação e a prática: sentidos atribuídos por estudantes do curso de Pedagogia

This study focuses on the initial formation of the pedagogue in college, especially the formation that takes place in the Pedagogy Course. It is bound by the following question: what senses are attributed by the Pedagogy Trainees regarding the relation between the Education Science knowledge and the Pedagogic Practice knowledge developed in the Pedagogy Course of UESB, in order to build up teaching knowledge and practice? Therefore it aims to reflect on the relations between the Education Science framework and the Pedagogic Practice under the supervised classes that belong to the Pedagogy Course. It presents the implications and contextualizations concerning the pedagogue formation as a historic and cultural process, emphasizing the current moment of this formation. It is based on the idea that the senses trainees, future pedagogues, attribute to their own formation process reflect on the learning of theorical and practical knowledge that validates the process of teachers formation, especially the pedagogue formation. Accordingly, it believes that the senses attributed by the students of teachers initial formation courses regarding the Education Science knowledge and Pedagogic Practice knowledge are essential as organizers in the construction of teaching knowledge and practice while the supervised classes take place. The theorical and methodological option is based on the studies of Qualitative Epistemology by Gonzalez Rey. Empiric studies took place at the Pedagogy Course of Universidade Estadual do Sudoeste da Bahia (UESB), located in the city of Vitória da Conquista/Bahia. The students who took part in this research were six graduating ones, enrolled in the last two semesters of the referred course, stage when the supervised classes happen. The procedures used in the organization of collected information consist of analysis of documents such as the mentioned course curricular project and the students reports, besides interactive and provocative talks to the students. The results show the senses students attribute to Educational Science theorical basis to practice to Pedagogic Practice opportunity of feeling as if they were teachers and to the relation between Education Science and Pedagogic Practice opportunity of experiencing the relation between theory and practice. Besides, the theorizations students have about the relation between theory and practice in teachers formation are also presented. Consequently, it is emphasized that the supervised classes are the moments in which the trainees might understand the relations between thought and pedagogic practice, building the senses attributed to the relation between the Education Science knowledge and the ones of Pedagogic Practice as organizers in the teaching knowledge and practice. In this context, the trainees build some knowledge regarding what it means to be a teacher, which is not written or published, due to its subjective dimension, but circumscribed in their pedagogic practice while the supervised classes take place and when professional teaching practice becomes effective

As Ciências da Educação e a prática pedagógica: sentidos atribuídos por estudantes do curso de Pedagogia

This study focuses on the initial formation of the pedagogue in college, especially the formation that takes place in the Pedagogy Course. It is bound by the following question: what senses are attributed by the Pedagogy Trainees regarding the relation between the Education Science knowledge and the Pedagogic Practice knowledge developed in the Pedagogy Course of UESB, in order to build up teaching knowledge and practice? Therefore it aims to reflect on the relations between the Education Science framework and the Pedagogic Practice under the supervised classes that belong to the Pedagogy Course. It presents the implications and contextualizations concerning the pedagogue formation as a historic and cultural process, emphasizing the current moment of this formation. It is based on the idea that the senses trainees, future pedagogues, attribute to their own formation process reflect on the learning of theorical and practical knowledge that validates the process of teachers formation, especially the pedagogue formation. Accordingly, it believes that the senses attributed by the students of teachers initial formation courses regarding the Education Science knowledge and Pedagogic Practice knowledge are essential as organizers in the construction of teaching knowledge and practice while the supervised classes take place. The theorical and methodological option is based on the studies of Qualitative Epistemology by Gonzalez Rey. Empiric studies took place at the Pedagogy Course of Universidade Estadual do Sudoeste da Bahia (UESB), located in the city of Vitória da Conquista/Bahia. The students who took part in this research were six graduating ones, enrolled in the last two semesters of the referred course, stage when the supervised classes happen. The procedures used in the organization of collected information consist of analysis of documents such as the mentioned course curricular project and the students reports, besides interactive and provocative talks to the students. The results show the senses students attribute to Educational Science theorical basis to practice to Pedagogic Practice opportunity of feeling as if they were teachers and to the relation between Education Science and Pedagogic Practice opportunity of experiencing the relation between theory and practice. Besides, the theorizations students have about the relation between theory and practice in teachers formation are also presented. Consequently, it is emphasized that the supervised classes are the moments in which the trainees might understand the relations between thought and pedagogic practice, building the senses attributed to the relation between the Education Science knowledge and the ones of Pedagogic Practice as organizers in the teaching knowledge and practice. In this context, the trainees build some knowledge regarding what it means to be a teacher, which is not written or published, due to its subjective dimension, but circumscribed in their pedagogic practice while the supervised classes take place and when professional teaching practice becomes effective