The effects of forcing and dissipation on phase transitions in thin granular layers

Recent experimental and computational studies of vibrated thin layers of identical spheres have shown transitions to ordered phases similar to those seen in equilibrium systems. Motivated by these results, we carry out simulations of hard inelastic spheres forced by homogenous white noise. We find a transition to an ordered state of the same symmetry as that seen in the experiments, but the clear phase separation observed in the vibrated system is absent. Simulations of purely elastic spheres also show no evidence for phase separation. We show that the energy injection in the vibrated system is dramatically different in the different phases, and suggest that this creates an effective surface tension not present in the equilibrium or randomly forced systems. We do find, however, that inelasticity suppresses the onset of the ordered phase with random forcing, as is observed in the vibrating system, and that the amount of the suppression is proportional to the degree of inelasticity. The suppression depends on the details of the energy injection mechanism, but is completely eliminated when inelastic collisions are replaced by uniform system-wide energy dissipation.Comment: 10 pages, 5 figure

Educación superior de calidad para el siglo XXI

Este artículo tiene como objetivo presentar de modo explícito la serie de opciones ideológicas y pedagógicas que, dentro del contexto costarricense, deben ser tenidas en cuenta por la persona encargada de tomar las decisiones, cuando intente mejorar la calidad de la educación para enfrentar los retos del siglo XX

Disorder Effects in Dirac Heterostructures

In this dissertation, we study theoretically heterostructures based on Dirac mate- rials, i.e. materials, such as graphene in which the electrons behave as massless Dirac fermions at low energies. We first examine how the presence of long-range disorder affects the electronic ground state of a double layer graphene heterostruc- ture formed by two graphene layers separated by a thin dielectric film. We then identify the necessary conditions for the formation of an interlayer exciton conden- sate in such a system. We also comment on the effect of long-range disorder on the broken symmetry ground state induced by electron-electron interactions in bilayer graphene. Then, we study the transport properties of heterostructures obtained by stacking a graphene layer on the surface of a strong three-dimensional topological insulator (TI). In particular, we determine the non-equilibrium current-induced spin density accumulation for these systems using linear response theory and taking into account the effects of long- and short-range disorder both in the limit of strong and weak tunneling between the graphene layer and the TI. Finally, using some of the theoretical approaches developed to characterize the effect of long-range disorder in Dirac materials, we study the effect of long-range inhomogeneities in first-order phase transitions. In particular, we present a theoretical model to describe the ef- fect of inhomogeneities on the relaxation dynamics of vanadium dioxide films after a photo-induced metal-insulator transition

Light trapping properties of cylindrical well diffraction gratings in solar cells: Computational calculations

Light trapping using diffraction gratings is a promising approach to increasing absorption in solar cells. In this paper, the computationally calculated absorption enhancement expected from a diffraction grating consisting of a triangular array of cylindrical wells is presented. Angle-extended polychromatic illumination is considered, and special attention is paid to absorption of sub-bandgap photons in an intermediate band solar cell. Results are compared to the absorption enhancement expected from an ideal Lambertian (randomizing) scatterer, which is considered as a baseline. It is found that for cells which absorb very weakly, the diffraction grating provides absorption enhancement above that of the ideal Lambertian scatterer over a wide wavelength range. For cells which absorb more strongly, the grating underperforms the ideal Lambertian scatterer over almost all wavelengths. Finally, the grating period, well height and well radius are optimised. Keywords: Light Trapping, Diffraction Grating, Intermediate Band Solar Cel

Aplicacion, Registro y Pagos de los Tributos en las Empresas ENLASA de la ciudad Matagalpa en el Periodo 2016

El presente Seminario de Graduación aborda el tema Tributos en las Empresas del Departamento de Matagalpa en el periodo 2016, con el objetivo de evaluar la aplicación, registro y pago de los Tributos en las empresas de la ciudad de Matagalpa en el periodo 2016. Los Tributos son de gran importancia para el desarrollo de cada país, permitiendo a los gobiernos el desarrollo de programas sociales para mejorar la calidad de vida de sus habitantes, a través del pago a tiempo de cada ciudadano de los Tributos ante el Estado. Al culminar nuestro trabajo investigativo llegamos a las siguientes conclusiones: Los Tributos aplicados en la empresa ENLASA son los siguientes: Impuesto sobre la Renta (IR), Impuesto Municipal sobre Ingresos (IMI), Impuesto de Matricula, Tasas por Servicios, las cuotas del INSS Laboral y Patronal e INATEC, el registro de los Tributos se realiza de la siguiente manera: Impuesto sobre la Renta (IR) como un Pasivo y su anticipo siendo un Activo, el Impuesto Municipal sobre Ingresos (IMI) y el Impuesto de Matricula representan Gastos de Ventas, las Tasas por Servicios como un Gasto de Administración, las Cuotas del INSS Laboral y Patronal e INATEC constituye un Gasto de Administración y se provisiona como un Pasivo, por lo anteriormente mencionado se valoró que la Empresa ENLASA aplica correctamente los Tributos, no demostrando dificultad alguna en su procedimientos de registro y pago de los mismos, cumpliendo con las Leyes Tributarias para obtener solvencia fiscal ante el Estado Palabras claves: Tributos, Aplicación, Registro, Pago, Procedimiento

In Support of Access and Inclusion: Joint Professional Development for Science and Special Educators

This article addresses the need for collaborative professional development of science and special educators to enhance access and inclusion for students with disabilities and improve science learning for all students. The purpose of the study was to examine changes in the teaching practices of science and special educators, grades 4 to 8, as they jointly completed an intense year-long professional development program designed to promote hands-on, inquiry-based science in their classrooms; expand their instructional repertoires to better serve students with disabilities and other learning problems; and facilitate communication between the groups. Quantitative and qualitative measures, including pre and post ratings of teacher classroom performance, action research projects, and teacher interviews, were used to determine changes in teacher instructional and collaborative practices

Frontend del sistema de información para la identificación de vulnerabilidad territorial

Trabajo de InvestigaciónEl sistema de información para la identificación de vulnerabilidad territorial brinda la posibilidad de conocer información detallada de las poblaciones existentes en el sistema. Estos datos almacenados tienen alguna influencia (baja, media y alta) a la hora de calcular el índice de vulnerabilidad de una zona determinada. El valor obtenido será un valor entero en una escala de 1 a 10 y a su vez se verá representado en el mapa con un color distintivo según el valor obtenido.PregradoIngeniero de Sistema