Edge-to-edge matching and its applications - Part II. Application to Mg-Al, Mg-Y and Mg-Mn alloys

A model for the crystallography and morphology of diffusion-controlled phase transformations - edge-to-edge matching - has been used to predict the orientation relationships (OR) and habit planes of precipitates Mg17Al12 in Mg-Al alloy, Mg24Y5 in Mg-Y alloy and alpha-Mn in Mg-Mn alloy. Based on the crystal structures and lattice parameters only, the model predicts that the possible ORs between Mg17Al12 and Mg matrix are the near Burgers OR, the Potter OR, the Gjonnes-Ostmoe OR and the Crawley OR. In the Mg-Y alloy, the OR between Mg24Y5 precipitates and the Mg matrix is predicted to be the Burgers OR only. The model also predicts that there are no reproducible ORs between alpha-Mn and Mg in the Mg-Mn alloy. Combining the edge-to-edge matching model and W. Zhang's Deltag approach, the habit plane and side facets of the precipitate for each OR can be determined. All the predicted ORs and the corresponding habit planes in Mg-Al and Mg-Y alloys agree very well with the experimental results. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Catalytic effects of subsurface carbon in the chemisorption of hydrogen on a Mg(0001) surface: an ab-initio study

Ab initio density functional theory (DFT) calculations are performed to explore possible catalytic effects on the dissociative chemisorption of hydrogen on a Mg(0001) surface when carbon is incorporated into Mg materials. The computational results imply that a C atom located initially on a Mg(0001) surface can migrate into the subsurface and occupy an fcc interstitial site, with charge transfer to the C atom from neighboring Mg atoms. The effect of subsurface C on the dissociation of H-2 on the Mg(0001) surface is found to be relatively marginal: a perfect sublayer of interstitial C is calculated to lower the barrier by 0.16 eV compared with that on a pure Mg(0001) surface. Further calculations reveal, however, that sublayer C may have a significant effect in enhancing the diffusion of atomic hydrogen into the sublayers through fcc channels. This contributes new physical understanding toward rationalizing the experimentally observed improvement in absorption kinetics of H2 when graphite or single walled carbon nanotubes (SWCNT) are introduced into the Mg powder during ball milling.

Edge-to-edge matching - The fundamentals

The basis of the present authors' edge-to-edge matching model for understanding the crystallography of partially coherent precipitates is the minimization of the energy of the interface between the two phases. For relatively simple crystal structures, this energy minimization occurs when close-packed, or relatively close-packed, rows of atoms match across the interface. Hence, the fundamental principle behind edge-to-edge matching is that the directions in each phase that correspond to the edges of the planes that meet in the interface should be close-packed, or relatively close-packed, rows of atoms. A few of the recently reported examples of what is termed edge-to-edge matching appear to ignore this fundamental principle. By comparing theoretical predictions with available experimental data, this article will explore the validity of this critical atom-row coincidence condition, in situations where the two phases have simple crystal Structures and in those where the precipitate has a more complex structure.

Application of wear resistant coatings by the brush plating technique

The development of cobalt molybdenum and cobalt tungsten brush plating electrolytes is described. Their optimum compositions and operating conditions for commercial applications have been determined. The effects of composition, pH, applied voltage, stylus speed and pressure upon deposit composition and efficiency have been investigated. Transmission and Scanning Electron Microscopy have been employed to study the cobalt alloy deposits produced. Evaluation of the wear resistant properties of the cobalt alloys developed in this work was carried out in the laboratory using a pin and disc technique and a simulated hot forging test, and by industrial trials involving the "on site" plating of hot forging dies and cold pressing tools. It was concluded that the electrolytes developed in tl1is work enabled cobalt alloys containing 6% Mo or 8% W to be deposited at 17-20V. Brush plated cobalt deposits possessed a mixed CPU and FCC crystallographic structure at room temperature. The application of 13µm of either of the cobalt alloys resulted in improved wear performance in both pin and disc and simulated hot forging tests. The results of the industrial trials indicated that by the use of these alloys, the life of hot forging dies may be increased by 20-100%. A commercial forging organisation is using electrolytes developed in this work to coat dies prior to forging nimonic alloys. Reductions in forging temperature and improved forging qualities have been reported. Cold pressing tools coated with the alloys showed a reduced tendency to "pick-up" and scoring of the pressed panels. Reports of a reduced need for lubrication of panels before pressing have also been received.

Strengthening mechanisms in nanostructured copper/304 stainless steel multilayers

Nanostructured Cu/304 stainless steel (SS) multilayers were prepared by magnetron sputtering. 304SS has a face-centered-cubic (fcc) structure in bulk. However, in the Cu/304SS multilayers, the 304SS layers exhibit the fcc structure for layer thickness of =5 nm in epitaxy with the neighboring fcc Cu. For 304SS layer thickness larger than 5 nm, body-centered-cubic (bcc) 304SS grains grow on top of the initial 5 nm fcc SS with the Kurdjumov-Sachs orientation relationship between bcc and fcc SS grains. The maximum hardness of Cu/304SS multilayers is about 5.5 GPa (factor of two enhancement compared to rule-of-mixtures hardness) at a layer thickness of 5 nm. Below 5 nm, hardness decreases with decreasing layer thickness. The peak hardness of fcc/fcc Cu/304SS multilayer is greater than that of Cu/Ni, even though the lattice-parameter mismatch between Cu and Ni is five times greater than that between Cu and 304SS. This result may primarily be attributed to the higher interface barrier stress for single-dislocation transmission across the {111} twinned interfaces in Cu/304SS as compared to the {100} interfaces in Cu/Ni.

The development of an online neonatal intensive care unit family education

Background: British Columbia’s Fraser Health Authority (FHA) neonatal intensive care units (NICUs) value family centered care (FCC). Nevertheless, there is limited evidence that FCC is actually incorporated into practice, as well as some concern that FHA NICU education is inaccessible, inconsistent, or disorganized. Purpose: The mission of this project is to support the principles of FCC throughout the development of an FHA online NICU family education guide by reflecting upon the needs of families throughout their NICU journey. Methods: A needs assessment was initially completed and included literature reviews, consultations, and an environmental scan. This data informed development of an online NICU family education guide which plots current education materials along key stages of the NICU journey: prenatal, admission, early days, growing and developing, discharge and at home. For the purposes of this practicum, only the prenatal stage was fully developed and will serve as a template for other stages following a formative evaluation. A pamphlet and revised FHA Neonatal Checkpoint will also be developed to augment teaching by health care professionals. Implementation and evaluation plans were adapted from the Center for Disease Control Framework for Program Evaluation in Public Health. Results: The needs assessment validates and directs the development, implementation, and evaluation of the online guide illustrating an FCC approach. The online guide centralizes and organizes education by selecting education topics that relate to each stage of the NICU journey. This family-directed design enables families’ access to consistent and reliable information and offers them an opportunity to learn at their own pace. Conclusion: The process of creating, implementing, and evaluating an online family education program for FHA NICUs elucidates the intricacies and the advantages of integrating FCC into NICU practice.

O PIBID - Programa Institucional de Bolsas de Iniciação à Docência e a crise das Licenciaturas: o caso de um Curso de Pedagogia a Distância

Tendo em vista a atual crise das licenciaturas, especialmente em termos da pouca atratividade que a formação para a docência vem apresentando em nosso contexto educacional e, considerando, ainda, as críticas sobre a fragilidade da formação inicial de professores ocorrer na modalidade a distância (no caso, o curso de Pedagogia), o PIBID - Programa Institucional de Bolsas de Iniciação à Docência surge como uma política de incentivo e valorização do magistério com o propósito de contribuir para uma formação mais sólida e articulada em termos da relação teoria-prática, especialmente pela proximidade que favorece aos alunos bolsistas, com o cotidiano escolar – este é o foco desta investigação que teve por objetivos: refletir sobre o histórico da formação docente em interface com a desvalorização do magistério que, consequentemente, levou à crise das licenciaturas e, a partir disso, analisar a proposição do PIBID como uma política pública para o enfrentamento desta crise; analisar as representações de bolsistas do PIBID, de um curso de Pedagogia a distância, sobre a experiência que estão tendo, e se ela contribui, no caso dos licenciandos, para o fortalecimento da escolha pela carreira docente; verificar as contribuições do programa para a formação dos licenciandos, dos supervisores (professores das escolas públicas parceiras) e do coordenador de área e se este oportuniza uma complementação na preparação para o exercício da docência. A pesquisa realizou uma revisão da literatura sobre a crise das licenciaturas e o contexto do aparecimento do PIBID, bem como sobre a formação de professores ocorrer na modalidade a distância, tendo como referencial teórico autores como Libâneo (1998), Gatti e Barreto (2009), Bahia e Duran (2011), Scheibe (2006), Sommer (2010), FCC (2009), Tardif (2005). Realizou, também, uma pesquisa de campo que teve como sujeitos sete bolsistas do PIBID de um curso de Pedagogia a distância (de uma instituição de ensino superior, particular, de São Paulo), sendo: quatro licenciandas, duas supervisoras e uma coordenadora de área do subprojeto. Foram aplicados dois instrumentos para a coleta de dados: um questionário para o delineamento do perfil dos sujeitos e a realização de entrevistas de aprofundamento. As reflexões realizadas a partir da revisão da literatura e das análises dos dados coletados junto aos sujeitos indicam que: em relação à proposição da formação inicial de professores a distância, esta denota maiores críticas, diferentemente da formação continuada de professores a distância, que apresenta uma maior aceitabilidade; em relação ao PIBID, os estudos vêm apontando a positividade das diversas experiências que vêm se desenvolvendo no território nacional e que denotam um trabalho articulado entre teoria e prática, bem como no resgate da identidade docente, com uma ênfase na valorização, inserção e permanência dos licenciandos nos seus cursos; as representações dos sujeitos investigados sobre a experiência que estão tendo com o PIBID apontam para: o reconhecimento de que o Programa garante, efetivamente, a reflexão e vivência entre a teoria e prática; a contribuição para a aquisição de maior segurança na relação com os alunos das escolas parceiras e também no desenvolvimento das atividades práticas; a certeza e/ou convicção de que realmente querem ser professoras.

THE MICROSTRUCTURES OF ZR-EXCEL ALLOY: EFFECTS OF HEAVY ION IRRADIATION, PLASTIC DEFORMATION, THERMAL TREATMENT AND IN-SITU HEATING

Zr-Excel alloy (Zr-3.5Sn-0.8Nb-0.8Mo) is a dual phase (α + β) alloy in the as-received pressure tube condition. It has been proposed to be the pressure tube candidate material for the Generation-IV CANDU-Supercritical Water Reactor (CANDU-SCWR). In this dissertation, the effects of heavy ion irradiation, deformation and heat treatment on the microstructures of the alloy were investigated to enable us to have a better understanding of the potential in-reactor performance of this alloy. In-situ heavy ion (1 MeV) irradiation was performed to study the nucleation and evolution of dislocation loops in both α- and β-Zr. Small and dense type dislocation loops form under irradiation between 80 and 450 °C. The number density tends to saturate at ~ 0.1 dpa. Compared with the α-Zr, the defect yield is much lower in β-Zr. The stabilities of the metastable phases (β-Zr and ω-Zr) and the thermal-dynamically equilibrium phase, fcc Zr(Mo, Nb)2, under irradiation were also studied at different temperatures. Chemi-STEM elemental mapping was carried out to study the elemental redistribution caused by irradiation. The stability of these phases and the elemental redistribution are strongly dependent on irradiation temperature. In-situ time-of-flight neutron diffraction tensile and compressive tests were carried out at different temperatures to monitor lattice strain evolutions of individual grain families during these tests. The β-Zr is the strengthening phase in this alloy in the as-received plate material. Load is transferred to the β-Zr after yielding of the α-Zr grains. The temperature dependence of static strain aging and the yielding sequence of the individual grain families were discussed. Strong tensile/compressive asymmetry was observed in the {0002} grain family at room temperature. The microstructures of the sample deformed at 400 °C and the samples only subjected to heat treatment at the same temperature were characterized with TEM. Concentration of β phase stabilizers in the β grain and the morphology of β grain have significant effect on the stability of β- and ω-Zr under thermal treatment. Applied stress/strain enhances the decomposition of isothermal ω phase but suppresses α precipitation inside the β grains at high temperature. An α → ω/ZrO phase transformation was observed in the thin foils of Zr-Excel alloy and pure Zr during in-situ heating at 700 °C in TEM.

Topics in equilibrium and nonequilibrium thermodynamics: computing crystalline free energies and engineering Maxwell’s demon.

This dissertation covers two separate topics in statistical physics. The first part of the dissertation focuses on computational methods of obtaining the free energies (or partition functions) of crystalline solids. We describe a method to compute the Helmholtz free energy of a crystalline solid by direct evaluation of the partition function. In the many-dimensional conformation space of all possible arrangements of N particles inside a periodic box, the energy landscape consists of localized islands corresponding to different solid phases. Calculating the partition function for a specific phase involves integrating over the corresponding island. Introducing a natural order parameter that quantifies the net displacement of particles from lattices sites, we write the partition function in terms of a one-dimensional integral along the order parameter, and evaluate this integral using umbrella sampling. We validate the method by computing free energies of both face-centered cubic (FCC) and hexagonal close-packed (HCP) hard sphere crystals with a precision of $10^{-5}k_BT$ per particle. In developing the numerical method, we find several scaling properties of crystalline solids in the thermodynamic limit. Using these scaling properties, we derive an explicit asymptotic formula for the free energy per particle in the thermodynamic limit. In addition, we describe several changes of coordinates that can be used to separate internal degrees of freedom from external, translational degrees of freedom. The second part of the dissertation focuses on engineering idealized physical devices that work as Maxwell's demon. We describe two autonomous mechanical devices that extract energy from a single heat bath and convert it into work, while writing information onto memory registers. Additionally, both devices can operate as Landauer's eraser, namely they can erase information from a memory register, while energy is dissipated into the heat bath. The phase diagrams and the efficiencies of the two models are solved and analyzed. These two models provide concrete physical illustrations of the thermodynamic consequences of information processing.

Base de Datos “I&D” Primera Experiencia con el Software Microisis, Versión 3.0 Multiusuario -Versión de Prueba-

La normalización facilita la comunicación y permite el intercambio de información con cualquier institución nacional o internacional. Este objetivo es posible a través de los formatos de comunicación para intercambio de información automatizada como CEPAL, MARC., FCC.La Escuela de Bibliotecología, Documentación e Información de la Universidad Nacional utiliza el software MICROISIS en red para la enseñanza. Las bases de datos que se diseñan utilizan el formato MARC y para la descripción bibliográfica las RCAA2.Se presenta la experiencia con la base de datos “I&D” sobre desarrollo rural, presentando la Tabla de Definición de Campos, la hoja de trabajo, el formato de despliegue y Tabla de selección de Campos.

Desenvolvimento e otimização de um filme biodegradável à base de proteína do tremoço (Lupinus angustifolius)

Dissertação de Mestrado, Biologia Molecular e Microbiana, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

A regulação diante da evolução da essencialidade do serviço público : a reclassificação da banda larga como serviço de telecomunicações nos Estados Unidos

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Direito, Programa de Pós-Graduação em Direito, 2016.

La educación intercultural bilingüe en la educación superior Argentina: identidades juveniles, diversidad cultural y políticas públicas

info:eu-repo/semantics/publishedVersion

El efecto de la definición regulatoria de banda ancha sobre la difusión y la competencia del mercado de servicios de Internet fijo en Colombia

A partir de la dinámica evolutiva de la economía de las Tecnologías de la Información y las Comunicaciones y el establecimiento de estándares mínimos de velocidad en distintos contextos regulatorios a nivel mundial, en particular en Colombia, en el presente artículo se presentan diversas aproximaciones empíricas para evaluar los efectos reales que conlleva el establecimiento de definiciones de servicios de banda ancha en el mercado de Internet fijo. Con base en los datos disponibles para Colombia sobre los planes de servicios de Internet fijo ofrecidos durante el periodo 2006-2012, se estima para los segmentos residencial y corporativo el proceso de difusión logístico modificado y el modelo de interacción estratégica para identificar los impactos generados sobre la masificación del servicio a nivel municipal y sobre las decisiones estratégicas que adoptan los operadores, respectivamente. Respecto a los resultados, se encuentra, por una parte, que las dos medidas regulatorias establecidas en Colombia en 2008 y 2010 presentan efectos significativos y positivos sobre el desplazamiento y el crecimiento de los procesos de difusión a nivel municipal. Por otra parte, se observa sustituibilidad estratégica en las decisiones de oferta de velocidad de descarga por parte de los operadores corporativos mientras que, a partir del análisis de distanciamiento de la velocidad ofrecida respecto al estándar mínimo de banda ancha, se demuestra que los proveedores de servicios residenciales tienden a agrupar sus decisiones de velocidad alrededor de los niveles establecidos por regulación.