Resampling technique applied to statistics of microsegregation characterization

Characterization of chemical heterogeneities at the dendrite scale is of practical importance for understanding phase transformation either during solidification or during subsequent solid-state treatment. Spot analysis with electron probe is definitely well-suited to investigate such heterogeneities at the micron scale that is relevant for most solidified products. However, very few has been done about the statistics of experimental solute distributions gained from such analyses when they are now more and more used for validating simulation data. There are two main sources generating discrepancies between estimated and actual solute distributions in an alloy: i) data sampling with a limited number of measurements to keep analysis within a reasonable time length; and ii) uncertainty linked to the measurement process, namely the physical noise that accompanies X-ray emission. Focusing on the first of these sources, a few 2-D composition images have been generated by phase field modelling of a Mg-Al alloy. These images were then used to obtain "true" solute distributions to which to compare coarse grid analyses as generally performed with a microanalyser. Resampling, i.e. generating several distributions by grid analyses with limited number of picked-up values, was then used to get statistics of estimates of solute distribution. The discussion of the present results deals first with estimating the average solute content and then focuses on the distribution in the primary phase

Discussion on “Stable eutectoid transformation in nodular cast iron: modeling and validation”

The Minerals, Metals & Materials Society and ASM International 2017 Given that cast irons are multicomponent alloys, the decomposition of the high temperature austenite into ferrite and graphite happens within a finite temperature range and not at an invariant point, as often described schematically. Only a few models explicitly consider the existence of such an austenite–ferrite–graphite range: the contribution under discussion,[1]those that inspired it[2,3] and one previous study from the present author.[4]For kinetics reasons, this latter work explained that ferrite could not grow within the equilibrium three-phase field under continuous cooling; this is in contradiction with the other three reports. The aim of this discussion is first to recall the experimental evidence about ferrite formation during eutectoid transformation of cast iron and then to provide an explanation as to why ferrite starts forming upon cooling only when the temperature of the material is below the equilibrium three-phase field range, as observed experimentally

Compressive sensing adaptation for polynomial chaos expansions

Basis adaptation in Homogeneous Chaos spaces rely on a suitable rotation of the underlying Gaussian germ. Several rotations have been proposed in the literature resulting in adaptations with different convergence properties. In this paper we present a new adaptation mechanism that builds on compressive sensing algorithms, resulting in a reduced polynomial chaos approximation with optimal sparsity. The developed adaptation algorithm consists of a two-step optimization procedure that computes the optimal coefficients and the input projection matrix of a low dimensional chaos expansion with respect to an optimally rotated basis. We demonstrate the attractive features of our algorithm through several numerical examples including the application on Large-Eddy Simulation (LES) calculations of turbulent combustion in a HIFiRE scramjet engine.Comment: Submitted to Journal of Computational Physic

Hacia el uso autónomo y estratégico de los conocimientos adquiridos: del saber decir al saber hacer en la enseñanza de la Economía del Sector Público. Una secuencia de clases destinadas al aprendizaje constructivo

Los Planes de Estudio vigentes en la FCEyS-UNMDP enuncian que la formación universitaria debe propender a desarrollar la solidaridad y el compromiso, la actitud reflexiva y la crítica racional. La descripción de los perfiles profesionales sostiene que los graduados deben ser capaces de participar en el nivel político de la definición de objetivos socioeconómicos, aunque ello no se observa en la práctica, puesto que los egresados suelen no poseer los instrumentos y herramientas necesarios a tal fin. En este punto, identificamos una tensión entre la teoría enseñada y la práctica implementada. El trabajo describe una secuencia de clases propuesta para la cursada 2013 de la asignatura "Administración del Estado y Políticas Públicas" de la FCEyS-UNMDP, describiendo en profundidad las estrategias de enseñanza y actividades desarrolladas. La secuencia constituye un aporte hacia el aprendizaje constructivo que retroalimentó el Plan de Trabajo Docente 2014 de la asignatura, a fines de avanzar en la consolidación del trabajo grupal -presencial y fuera del aula- mediante el uso de herramientas colaborativas que fortalecen la expresión de las opiniones, el debate y la argumentación, en la convicción de que nuestra labor permite la formación de ciudadanos y profesionales que tienen y tendrán responsabilidades sociales y cívicas.Fil: Franco, N. Graciela. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina.Fil: Lacaze, María Victoria. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina.Fil: Nuñez Fioramonti, Gustavo Christian. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina

¿Conflicto o neutralidad? El rol del Estado en la formación del economista: paradigmas y pragmatismos

Las instituciones universitarias ponen de manifiesto, en los currícula, la concepción del tipo de hombre, de ciudadano, de científico y de profesional que quieren formar. El presente trabajo reflexiona acerca de la estructura curricular de la carrera de Licenciado en Economía que se dicta en la FCEyS-UNMDP. Guió la investigación el siguiente interrogante: ¿qué contenidos enseñamos a nuestros estudiantes a lo largo de su carrera, en relación al Estado como actor social que cumple diversas funciones en una economía de mercado? Pensando al currículo como portavoz de una función social, pero a la vez como la expresión formal y material de un proyecto que, a la luz de nuestras experiencias, propone ciertas secuencias de abordaje de contenidos, dieron forma al trabajo otras inquietudes vinculadas al cumplimiento del principio de gradualidad en la formación, al rol del currículo oculto y a la necesidad de explicitarnos qué contenidos, valores, habilidades, aptitudes, formas de pensar y resolver problemas de la profesión transmitimos a nuestros estudiantes. Dado que la disciplina y la profesión tienen lógicas fuertemente distintas, el trabajo propone explorar el sentido de la formación, dando significado a nuestras prácticas docentes, contrastando nuestro currículo en acción con las competencias que queremos tengan nuestros graduados.Fil: Lacaze, María Victoria. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina.Fil: Franco, N. Graciela. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina.Fil: Nuñez Fioramonti, Gustavo Christian. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina

Effect of various dopant elements on primary graphite growth

Five spheroidal graphite cast irons were investigated, a usual ferritic grade and four pearlitic alloys containing Cu and doped with Sb, Sn and Ti. These alloys were remelted in a graphite crucible, leading to volatilization of the magnesium added for spheroidization and to carbon saturation of the liquid. The alloys were then cooled down and maintained at a temperature above the eutectic temperature. During this step, primary graphite could develop showing various features depending on the doping elements added. The largest effects were that of Ti which greatly reduces graphite nucleation and growth, and that of Sb which leads to rounded agglomerates instead of lamellar graphite. The samples have been investigated with secondary ion mass spectrometry to enlighten distribution of elements in primary graphite. SIMS analysis showed almost even distribution of elements, including Mg and Al (from the inoculant) in the ferritic grade, while uneven distribution was evident in all doped alloys. Investigations are going on to clarify if the uneven distribution is associated with structural defects in the graphite precipitates

Study of the microstructure resulting from brazed aluminium materials used in heat exchangers

Re-solidification of AA4343 cladding after brazing as well as the related precipitation in the modified AA3003 core material have been investigated. Analysis of the re-solidified material showed that partial dissolution of the core alloy occurs in both the brazing joints and away of them. Far from the brazing joints, the dissolution is, however, limited and diffusion of silicon from the liquid into the core material leads to solid-state precipitation in the so-called “band of dense precipitates” (BDP). On the contrary, the dissolution is enhanced in the brazing joint to such an extent that no BDP could be observed. The intermetallic phases present in the resolidified areas as well as in the core material have been analyzed and found to be mainly cubic alpha-Al(Mn,Fe)Si. These results were then compared to predictions made with available phase diagram information