Texte remanié et actualisé de: Diss.--Philosophische Fakultät--Universität zu Köln, 1991. / Notes bibliogr. Index.

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Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-01-21T10:18:45Z No. of bitstreams: 0 / Made available in DSpace on 2015-01-21T10:18:45Z (GMT). No. of bitstreams: 0 / Reatores PWR empregam, como combustível nuclear, pastilhas de UO2 acondicionadas em tubos de ligas de zircônio, chamados de encamisamento. Na sua fabricação são gerados cavacos de usinagem que não podem ser descartados, pois a reciclagem deste material é estratégica quanto aos aspectos de tecnologia nuclear, econômicos e ambientais. As ligas nucleares têm altíssimo custo e não são produzidas no Brasil, sendo importadas para a fabricação do combustível nuclear. Neste trabalho são abordados dois métodos para reciclar os cavacos de Zircaloy. No primeiro, os cavacos foram fundidos utilizando um forno elétrico a arco para obter lingotes. O segundo usa a técnica da metalurgia do pó, onde os cavacos foram submetidos à hidretação e o pó resultante foi moído e isostaticamente prensado e, a seguir, sinterizado a vácuo. A composição química, as fases presentes e a dureza no material foram determinadas. Os lingotes foram tratados termicamente e laminados, sendo que as microestruturas foram caracterizadas por microscopia óptica e eletrônica de varredura. Os resultados para ambos os métodos mostraram que a composição do Zircaloy reciclado cumpre as especificações químicas e apresentaram microestrutura adequada para uso nuclear. Os bons resultados do método de metalurgia do pó sugerem a possibilidade de produzir pequenas peças, como as tampas do encamisamento - end-caps, usando a sinterização no formato quase final (near net shape). / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

The primary purpose of this study was to determine whether external conditions, in the form of an e-learning tool, impact the learning motivation of adult learners in a distance education environment. This study also tested the use of Voice-over-PowerPoint™ technology as a suitable medium to deliver motivational instruction as supplementary content to the course curriculum. This empirical study was conducted over a period of approximately two months on a sample of 57 adult learners who were enrolled for a distance education course for non-degree purposes at a tertiary education institution. Quantitative research methods were applied and data was collected using two motivation measuring surveys: (1) The Course Interest Survey, and (2) The Instructional Materials Motivation Survey, which were both developed by Keller. Motivational strategies were designed for the chosen educational technology, Voice-over-PowerPoint™ (VoP) videos, using Keller's Attention, Relevance, Confidence and Satisfaction (ARCS) model of motivation. These strategies were then delivered via the learner management system for learners to use at their convenience. This research suggests that overall, learner motivation can be affected by external conditions (VoP videos), and further supports the ARCS model. Furthermore, the use of VoP videos as a viable medium for delivering motivational strategies in a distance learning environment was validated. / Mini Dissertation (MCom)--University of Pretoria, 2016. / Taxation / MCom / Unrestricted

Informed parent advocates are essential to planning the educational outcomes of their children with special needs in the K through 12 public school system. However, inappropriate instructional techniques used in advocacy training may reduce trainees' learning outcomes by adding complexity and increasing cognitive load. This study examined whether using worked examples to break down complex problems into component parts to build long term schema could lower cognitive load and thus improve learning outcomes for parent advocacy trainees. Based on cognitive load theory, this 2 x 3 factorial design study examined the efficacy of noninteractive video lessons for parent trainees using worked examples to reduce extraneous cognitive load. Research questions explored the relationships between the independent variables of using worked examples and parents' perceived class relevance on the dependent variable, change in cognitive load of parent trainees, as well as the interaction between training type and perceived class relevance. Two groups of 65 adults in advocacy training (N = 130) participated in a video lesson in either the worked examples or nonworked examples format as part of their advocacy training. The NASA Task Load Index and the Perceived Class Relevance Survey instruments were used to measure cognitive load of trainees and perceptions of training relevance. Key findings included a significant main effect between the use of worked examples and change in cognitive load and significant interaction effects with the perception of class relevance. Training was developed for advocacy trainers in the use of worked examples for learners new to a domain. Implications for social change include improved learning outcomes for parents who must learn IEP terminology in beginning classes to effectively advocate for their children.

This dissertation investigated relevant issues among undergraduate students at two institutions and how these issues could be incorporated into an introductory personal health course. By illustrating how these issues can attract student attention, relevancy, confidence, and satisfaction, educators can make these introductory personal health courses more responsive, thereby increasing student motivation to learn. This study used a qualitative research design. Focus groups and interviews were conducted in order to gain insight into issues students felt were relevant to their lives, their satisfaction with their personal health course, and how these courses could be updated in terms of content and delivery. The ARCS Model of Motivation was used as a theoretical framework for development of questions as well as to organize emergent themes. This model has been shown to increase student motivation to learn, and the current study aimed to expand this to include health courses, which could lead to an increase in adopting healthier or risk-reductive behaviors. After five focus groups and two interviews, data saturation was met, and analysis was conducted. Findings indicate a strong desire among undergraduate students for a larger focus of content to include mental health issues (e.g., stress, time management, pressure, and healthy coping mechanisms), physical health issues, and harm reductive issues surrounding the areas of sexual health and alcohol and substance use. Additionally, students reported better recall and a preference for active learning over a more didactic method of instruction. By understanding relevant issues facing college students and incorporating those within an introductory personal health course, educators can enhance the responsiveness of these courses by illustrating relevancy of topics and teaching students how they can confidently learn to adopt healthy behaviors and practice harm reduction. This is particularly useful among undergraduate students as they are in a time of transition and emerging adulthood and are willing to learn and establish new patterns of behaviors. If educators can balance what they as experts want students to know and what students say are relevant to their lives and what they want to know, these introductory personal health courses could be an effective tool for increasing overall health and wellness of students.

The topological aspects of superconductivity on doped Weyl semimetals are investigated. / Topological phases of matter have sparked significant experimental and theoretical interest due to the topologically robust edge modes they host, as well as their classification through rich mathematics. An interesting example of a topological phase in three dimensions, the Weyl semimetal, can exhibit topological ordering through the existence of Fermi arcs on the surfaces of the material. For the doped Weyl semimetal, we investigate possible resulting Weyl superconducting states --- both the inter-Fermi surface pairing state following Li and Haldane, and the intra-Fermi surface pairing state following Burkov --- in this thesis, and study their topological properties by computing the gapless Weyl-Majorana edge modes they host. The results obtained in Ref. \cite{LH} for the inter-Fermi surface superconducting state are reproduced, and the bulk and edge properties of the intra-Fermi surface pairing superconducting state are studied in detail. / Thesis / Master of Science (MSc) / In this thesis, we study an interesting class of topological materials called the Weyl semimetal as well as its associated superconducting phases. A description of the Fermi arcs on Weyl semimetals are given, and the topological properties of the inter-Fermi surface and intra-Fermi surface pairing states are studied in detail.

La pompe de gavage ou pompe à carburant est un organe auxiliaire nécessaire au bon fonctionnement d’un véhicule. Elle permet d’acheminer le carburant du réservoir vers les systèmes d’injections du moteur. Cette pompe, constituée d’un moteur électrique entraînant une turbine, permet la mise en mouvement du carburant. Le passage du courant est assuré entre le stator et le rotor par le biais du contact frottant entre deux balais fixes et un collecteur tournant en composite graphite/polymère, immergé en milieu carburant. Ces travaux ont pour but de contribuer à la compréhension de ce contact glissant électrifié immergé. Un tribomètre spécifique a été développé afin de tester différents couples de matériaux balais-collecteur dans des conditions mécaniques, électriques et physico-chimiques variées, tout en mesurant l’usure, l’effort de frottement et la résistance électrique du double contact. De nouvelles nuances de matériaux carbonés s’adaptant aux contraintes chimiques des nouveaux biocarburants présents sur le marché automobile ont été testées et ont mis en évidence différents comportements tribologiques. L’usure observée est principalement due au passage du courant sous forme d’arcs électriques modifiant ainsi la topographie des surfaces. Deux endommagements distincts sont visibles : le cratère et la bosse dont les volumes augmentent avec l’énergie développée par l’arc et sont reliés à la présence subsurfacique de polymère. A partir de ces conclusions expérimentales, un modèle phénoménologique du comportement à l’usure a été proposé. Il permet d’apporter une aide à la compréhension des mécanismes complexes et nombreux, présents dans le frottement des balais et du collecteur. / The fuel pump, an automotive part, is used to transfer the fuel from the tank to the engine injection systems. This pump consists of an electric motor driving a turbine: this induces the fuel flow. The current flow is realized between the stator and the rotor thanks to the friction of two fixed brushes against a slip ring. All elements are made of graphite/polymer composites and are immersed into fuel. The aim of this work is to contribute to the understanding of immersed electrical sliding contacts. A specific tribometer was developed in order to mimic the fuel pump. It allows simultaneous measurement of friction forces, wear and electrical contact resistance for various mechanical, electrical and physicochemical conditions. New carbonaceous materials, specifically designed for new biofuel, exhibited different tribological behaviour. The wear observed is mainly due to the current flow, electrical arcs in particular, which modifies the surface topography. Two kinds of damage were depicted: craters and bumps whose volume increases with the arc-produced energy as a function of the presence of polymer at the vicinity of the surface. Issued from these experimental results, a phenomenological model of the wear behaviour was proposed. It brings new insights into the complex and numerous mechanisms occurring during the friction of the brushes and commutator.