Teacher education by volunteering in learning communities

El trabajo presentado forma parte del proyecto I+D+I “Ecologías del aprendizaje en contextos múltiples: análisis de proyectos de educación expandida y conformación de ciudadanía” financiado por MIMECO, España.El artículo presenta parte de los resultados de investigación sobre el trabajo del voluntariado en centros educativos que son comunidades de aprendizaje como una forma de avanzar en procesos de formación docente diferentes a los vigentes.Universidad de Málaga. Campus de la Excelencia Internacional Andalucía Tech

Circumnuclear structure and kinematics in the active galaxy NGC 6951

A study is presented of the central structure and kinematics of the galaxy NGC 6951, by means of broad band B'IJK images and high resolution high dispersion longslit spectroscopy, together with archival HST WFPC2 V and NICMOS2 J and H images. We find that there is evidence of two modes of star formation, in bursts and continuously. The equivalent width of the CaII triplet absorption lines show that, in the metal rich central region, the continuum is dominated by a population of red supergiants. The gaseous and stellar kinematics along three slit position angles, suggest the existence of a hierarchy of disks within disks, whose dynamics are decoupled at the two ILRs, that we find at 180 pc and at 1100 pc. This is supported by the structure seen in the high resolution HST images. The nucleus is spatially resolved within a radius of 1.5 arcsec, just inside the innermost ILR. Outside the iILR, the stellar CaT velocity profile is resolved into two components, associated with the bar and the disk. Several results indicate that this is a dynamically old system. It is thus possible that a nuclear bar has existed in NGC 6951 that drove the gas towards the nucleus, as in the bars within bars scenario, but that this bar has already dissolved by the gas accumulated within the circumnuclear region. We discuss the possibility that the kinematical component inside the iILR could be due to a nuclear outflow produced by the combined effects of SN and SN remnants, or to a nuclear disk, as in the disk within disk scenario that we propose for the fueling of the AGN in NGC 6951.Comment: 14 pages, 16 figures. Accepted for publication in Astronomy and Astrophysics. High resolution images in http://www.iaa.es/~eperez/research/degas.htm

Vibrational spectra of light and heavy water with application to neutron cross section calculations

The design of nuclear reactors and neutron moderators require a good representation of the interaction of low energy (E < 1 eV) neutrons with hydrogen and deuterium containing materials. These models are based on the dynamics of the material, represented by its vibrational spectrum. In this paper, we show calculations of the frequency spectrum for light and heavy water at room temperature using two flexible point charge potentials: SPC-MPG and TIP4P/2005f. The results are compared with experimental measurements, with emphasis on inelastic neutron scattering data. Finally, the resulting spectra are applied to calculation of neutron scattering cross sections for these materials, which were found to be a significant improvement over library data.Fil: Marquez Damian, Jose Ignacio. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Malaspina, David Cesar. Northwestern University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Granada, Jose Rolando. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Atomic scale Monte-Carlo simulations of neutron diffraction experiments on stoichiometric uranium dioxide up to 1664 K

The neutron transport in nuclear fuels depends on the crystalline structure of materials when neutron energies lie below a few eV. For that purpose, the theoretical formalism that describes the neutron elastic and inelastic scatterings by crystals has been implemented in the CINEL processing tool in order to provide temperature-dependent neutron cross sections usable by the Monte-Carlo code TRIPOLI4®. The performances of the Monte-Carlo calculations are illustrated with the analysis of neutron powder diffraction data on UO2 measured up to 1664 K with the D4 and D20 diffractometers of the Institute Laue–Langevin (Grenoble, France). The comparison of the experimental and simulated pair distribution functions confirms the unusual decrease of the U–O atomic distances with increasing temperature when an ideal fluorite structure (Fm3̄m space group) with harmonic atomic vibrations is assumed over the full temperature range. The flexibility of the CINEL code allowed to explore disorder or anharmonic oxygen vibrations in the Fm3̄m space group by using either a four-site model with a relaxation term or a structure factor equation with a non-zero anharmonic third-cumulant coefficient. As none of these models succeeded to improve the agreement with the experiments, recent works that propose other local crystalline symmetries for UO2 at elevated temperatures were investigated with the CINEL code. The case of the Pa3̄ symmetry is briefly discussed in this paper.Fil: Xu, S.. Commissariat à l'énergie atomique et aux énergies alternatives. Institut de REcherche sur les Systèmes Nucléaires pour la production d’Energie bas carbone; FranciaFil: Noguere, G.. Commissariat à l'énergie atomique et aux énergies alternatives. Institut de REcherche sur les Systèmes Nucléaires pour la production d’Energie bas carbone; FranciaFil: Desgranges, L.. Commissariat à l'énergie atomique et aux énergies alternatives. Institut de REcherche sur les Systèmes Nucléaires pour la production d’Energie bas carbone; FranciaFil: Marquez Damian, Jose Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentin

Computing optimal shortcuts for networks

We augment a plane Euclidean network with a segment or shortcut to minimize the largest distance between any two points along the edges of the resulting network. In this continuous setting, the problem of computing distances and placing a shortcut is much harder as all points on the network, instead of only the vertices, must be taken into account. Our main result for general networks states that it is always possible to determine in polynomial time whether the network has an optimal shortcut and compute one in case of existence. We also improve this general method for networks that are paths, restricted to using two types of shortcuts: those of any fixed direction and shortcuts that intersect the path only on its endpoints.Peer ReviewedPostprint (published version

Computing optimal shortcuts for networks

We study augmenting a plane Euclidean network with a segment, called shortcut, to minimize the largest distance between any two points along the edges of the resulting network. Questions of this type have received considerable attention recently, mostly for discrete variants of the problem. We study a fully continuous setting, where all points on the network and the inserted segment must be taken into account. We present the first results on the computation of optimal shortcuts for general networks in this model, together with several results for networks that are paths, restricted to two types of shortcuts: shortcuts with a fixed orientation and simple shortcuts.Peer ReviewedPostprint (published version

La desigualdad en el acceso al mercado de trabajo para residentes en espacios urbanos informales del Área Metropolitana de Buenos Aires (1974-2014)

Production of INCASI Project H2020-MSCA-RISE-2015 GA 69100

Development of neutronic models for fusion-fission hybrid reactors

Los reactores híbridos fusión-fisión (HFF) constituyen una alternativa interesante para la generación de energía en gran escala sin emisión de gases de efecto invernadero y para la eliminación de residuos de alta actividad producidos por los reactores de fisión. Los HHF potencian las ventajas relativas de la fusión y fisión y minimizan sus desventajas. La fusión produce muchos neutrones pero relativamente poca energía mientras que la fisión produce mucha energía pero necesita un flujo constante de neutrones para sostenerse. El diseño básico de un HFF consiste de un reactor de fusión, que proporciona un flujo constante de neutrones, rodeado por un manto subcrítico de material físil. El presente proyecto apunta a desarrollar la capacidad de calcular la neutrónica de un reactor híbrido fusión-fisión, tomando de partida la fuente de neutrones de un reactor nuclear de fusión tipo Tokamak. El proyecto se desarrolla en colaboración entre la Sección Fusión Nuclear y Física de Plasmas y el Departamento Física de Neutrones de la Comisión Nacional de Energía Atómica.Fusion-fission hybrid (FFH) reactors are an interesting alternative for the generation of electricity without the emission of greenhouse gases, and for the transmutation of spent nuclear fuel produced in fission reactors. FFHs multiply the advantage of separate fusion and fission reactors and minimize their disadvantages. Fusion naturally produces neutrons and a relatively low amount of energy, whereas fission produces more energy per reaction but requires a constant flux of neutrons. The basic design of a FFH consists on a fusion reactor surrounded by a subcritical blanket of fissile material.The present project aims to develop models for the neutronic calculation of fusion-fission hybrid reactors, taking as a start point the neutron source produced from a Tokamak-type fusion reactor. The project is a collaboration between the Neutron Physics Department and the Nuclear Fusion and Plasma Physics Section of the National Atomic Energy Commission

New evaluation of thermal neutron scattering libraries for light and heavy water

In order to improve the design and safety of thermal nuclear reactors and for verification of criticality safety conditions on systems with significant amount of fissile materials and water, it is necessary to perform high-precision neutron transport calculations and estimate uncertainties of the results. These calculations are based on neutron interaction data distributed in evaluated nuclear data libraries. To improve the evaluations of thermal scattering sub-libraries, we developed a set of thermal neutron scattering cross sections (scattering kernels) for hydrogen bound in light water, and deuterium and oxygen bound in heavy water, in the ENDF-6 format from room temperature up to the critical temperatures of molecular liquids. The new evaluations were generated and processable with NJOY99 and also with NJOY-2012 with minor modifications (updates), and with the new version of NJOY-2016. The new TSL libraries are based on molecular dynamics simulations with GROMACS and recent experimental data, and result in an improvement of the calculation of single neutron scattering quantities. In this work, we discuss the importance of taking into account self-diffusion in liquids to accurately describe the neutron scattering at low neutron energies (quasi-elastic peak problem). To improve modeling of heavy water, it is important to take into account temperature-dependent static structure factors and apply Sköld approximation to the coherent inelastic components of the scattering matrix. The usage of the new set of scattering matrices and cross-sections improves the calculation of thermal critical systems moderated and/or reflected with light/heavy water obtained from the International Criticality Safety Benchmark Evaluation Project (ICSBEP) handbook. For example, the use of the new thermal scattering library for heavy water, combined with the ROSFOND-2010 evaluation of the cross sections for deuterium, results in an improvement of the C/E ratio in 48 out of 65 international benchmark cases calculated with the Monte Carlo code MCNP5, in comparison with the existing library based on the ENDF/B-VII.0 evaluation

Desarrollo de una aplicación móvil implementando el método ABC para la gestión de inventarios de la empresa Aquarius Consulting S.A.C.

La siguiente investigación presenta el desarrollo de una aplicación móvil implementando el método ABC para la gestión de inventarios de la empresa Aquarius Consulting S.A.C. El inicio de esta investigación comienza con la observación de los procesos en la gestión de inventarios, determinando que carece de una planificación y control eficiente, ello se ve reflejado en el déficit al momento de realizar el inventario de artículos y los costos adicionales que generan afectando a la empresa. Por lo tanto, la investigación tiene por finalidad desarrollar una aplicación móvil que mejore determinados procesos en la gestión de inventarios. La metodología de la investigación empleada sigue un diseño experimental. Asimismo, se utiliza el tipo de investigación aplicada con un enfoque cuantitativo y de nivel explicativo. Además, para el desarrollo de la solución se emplea la metodología XP y el desarrollo de la aplicación móvil se realiza en la plataforma Android Studio empleando el lenguaje de programación Java y los principios de Clean Architecture. Por último, para la realización del pretest se utilizó la guía de observación como instrumento para la recolección de datos de los procesos en el inventario, luego de implementar la aplicación se procedió a la realización del postest recolectando los datos usando nuevamente la guía de observación. En los resultados, se obtuvo una mejora favorable de 4.08% en la planificación respecto al pretest; sobre el control, una mejora de 27.35% sobre los resultados del pretest; sobre las existencias de productos la mejora fue del 20.57% sobre los datos del pretest y el costo de mantenimiento se redujo en un 14.61%.Campus Lima Centr