Monte Carlo simulation of recrystallization

A Monte Carlo computer simulation technique, in which a continuum system is modeled employing a discrete lattice, has been applied to the problem of recrystallization. Primary recrystallization is modeled under conditions where the degree of stored energy is varied and nucleation occurs homogeneously (without regard for position in the microstructure). The nucleation rate is chosen as site saturated. Temporal evolution of the simulated microstructures is analyzed to provide the time dependence of the recrystallized volume fraction and grain sizes. The recrystallized volume fraction shows sigmoidal variations with time. The data are approximately fit by the Johnson-Mehl-Avrami equation with the expected exponents, however significant deviations are observed for both small and large recrystallized volume fractions. Under constant rate nucleation conditions, the propensity for irregular grain shapes is decreased and the density of two sided grains increases

An oscillator circuit to produce a radio-frequency discharge and application to metastable helium saturated absorption spectroscopy

We present an rf gas discharge apparatus which provides an atomic frequency reference for laser manipulation of metastable helium. We discuss the biasing and operation of a Colpitts oscillator in which the discharge coil is part of the oscillator circuit. Radiofrequency radiation is reduced by placing the entire oscillator in a metal enclosure.Comment: 9 pages, 5 figure

Modelo de ISING en 3-d. aplicación a sensores magnéticos

El modelo de Ising es un problema de física estadística que tiene solución exacta en dos dimensiones, para el caso de tres dimensiones es preciso utilizar procedimientos de simulación. En este trabajo se ha utilizado un método de Monte Carlo para estudiar el comportamiento del sistema en distintas situaciones, siendo de especial interés el estudio del paso por la transición de fase a la temperatura crítica (Temperatura de Curie, Tc). Se ha estudiado la cinética de los dominios magnéticos, considerando la estructura de los dominios desde el punto de vista de la energía, y en consecuencia, hemos tenido en cuenta la energía de canje que tiende a mantener alineados los espines de los electrones en los materiales ferromagnéticos. Este término contribuye a hacer mayor el espesor de la pared, por la tendencia a que los espines de los átomos vecinos se mantengan alineados. Se ha considerado el ferromagnetismo desde el punto de vista cuántico y basado en las propiedades de simetría de las funciones de onda de los electrones, que se manifiestan en variaciones de la energía electrostática de un sistema en función de la orientación de sus espines. Se han estudiado los efectos de histéresis que resultan al aplicar un campo magnético externo a la red y la orientación de los espines de la misma a lo largo de su evolución. Para la determinación de las propiedades de los materiales ferromagnéticos se utiliza el ciclo de histéresis aunque algunas de las propiedades magnéticas, como la dirección de anisotropía, no pueden ser deducidas directamente de esta manera. Se utilizan distintos métodos para la determinación de la anisotropía de las muestras. El acoplamiento entre la magnetización en zonas próximas a la superficie y la magnetización en zonas internas de la muestra puede ser utilizado para obtener un ciclo de histéresis, que permita obtener sensores magnéticos adaptados a las medidas que se quieran realizar. Mediante el control del campo coercitivo y la susceptibilidad se abre una línea de investigación para el desarrollo de sensores magnético

Distance Multimedia Degree Studies. The Application of Multimedia Technology to Multimedia Studies

This paper describes the set of courses that make up the distance multimedia degree studies offered by the UPC in conjunction with the UOC. These courses are designed to meet the increasing demand for continued education by integrating the advances in information technologies currently arising from new paradigms in distance learning. The study plan has been specially designed and is fully interdisciplinary. The plan draws on three areas of knowledge: creation and design of the programme content, marketing and management of multimedia production, and computer and communications technology. The educational model seeks a balance between practical activities, similar to those students are likely to undertake in the workplace, and theory−based reading tasks aimed at furthering and consolidating their grasp of the concepts involved. The model is structured around three elements: self−access material, virtual activities, and real activities. The self−access materials and the assessment system give the student continued feedback on their progress. The average age of the students is 32'3 years (range 19−55). Most are men (77%), and 60% are pursuing university studies for the first time. A key element of the distance multimedia studies is the involvement of the teachers in the preparation of the multimedia teaching materials. This role means that they must be trained in materials design and must use models of specific contents. The activities of the course tutor and the general tutor combine a proactive attitude with rapid response to the questions that arise as part of the Distance Multimedia Degree.This paper describes the set of courses that make up the distance multimedia degree studies offered by the UPC in conjunction with the UOC. These courses are designed to meet the increasing demand for continued education by integrating the advances in information technologies currently arising from new paradigms in distance learning. The study plan has been specially designed and is fully interdisciplinary. The plan draws on three areas of knowledge: creation and design of the programme content, marketing and management of multimedia production, and computer and communications technology. The educational model seeks a balance between practical activities, similar to those students are likely to undertake in the workplace, and theory−based reading tasks aimed at furthering and consolidating their grasp of the concepts involved. The model is structured around three elements: self−access material, virtual activities, and real activities. The self−access materials and the assessment system give the student continued feedback on their progress. The average age of the students is 32'3 years (range 19−55). Most are men (77%), and 60% are pursuing university studies for the first time. A key element of the distance multimedia studies is the involvement of the teachers in the preparation of the multimedia teaching materials. This role means that they must be trained in materials design and must use models of specific contents. The activities of the course tutor and the general tutor combine a proactive attitude with rapid response to the questions that arise as part of the Distance Multimedia Degree

Estudio de las concentraciones y mecanismos de desplazamiento de radón y descendientes en recintos cerrados

La importancia de la medida de concentración de radón en recintos cerrados radica en que la dosis debida a su presencia en el ambiente representa aproximadamente el 50% de la dosis total de la radiación de origen natural recibida por la población, estando presente tanto en espacios abiertos, como en el interior de edificios. Se han desarrollado numerosos estudios encaminados a determinar el riesgo radiológico por unidad de exposición Para alcanzar este fin se han puesto a punto diversas técnicas que permiten analizar, tanto en una instalación de laboratorio como en espacios habitados, el factor de equilibrio, la fracción libre y el espectro dimensional de descendientes del radón en estado libre. Por otra parte, si tenemos en cuenta los mecanismos de desplazamiento del 222 Rn sabemos que éste se difunde a través de las grietas del terreno y de los materiales de construcción. Por lo tanto, tendremos que en recintos cerrados el mecanismo difusivo es el más significativo, siendo en este caso determinante la longitud de difusión desintegrarse

Histomorfologia funcional do intestino do pirarucu, Arapaima gigas (Cuvier, 1829).

Este trabalho avaliou a histomorfologia do intestino de juvenis de pirarucu, visando elucidar a dinâmica de absorção e aproveitamento de nutrientes pela espécie e subsidiar futuras pesquisas abrangendo sua nutrição e saúde.Organizado por: Sílvio Ricardo Maurano; AQUACIÊNCIA 2012

Researches is health of Pirarucu, Arapaima gigas: partnership between EMBRAPA-SEBRAE.

Aiming to deepen the scientific knowledge on health aspects of pirarucu, and attempting to improve the fingerlings survival rates a partnership was signed between SEBRAE and EMBRAPA, in collaboration with the UFT

MAD@VLT: Deep into the Madding Crowd of Omega Centauri

We present deep and accurate Near-Infrared (NIR) photometry of the Galactic Globular Cluster (GC) Omega Cen. Data were collected using the Multi-Conjugate Adaptive Optics Demonstrator (MAD) on VLT (ESO). The unprecedented quality of the images provided the opportunity to perform accurate photometry in the central crowded regions. Preliminary results indicate that the spread in age among the different stellar populations in Omega Cen is limited.Comment: 6 pages, 3 figures, to appear in the Springer Astrophysics and Space Science Proceedings, "Science with the VLT in the ELT era", ed. A. Moorwoo