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Ítem Computational characterization of the wave propagation behavior of multi-stable periodic cellular materials(Elsevier Limited, 2019-01-01) Valencia, Camilo Andres; Restrepo D.; Mankame N.D.; Zavattieri P.D.; Gomez, Juan David; Mecánica AplicadaIn this work, we present a computational analysis of the planar wave propagation behavior of a one-dimensional periodic multi-stable cellular material. Wave propagation in these materials is interesting because they combine the ability of periodic cellular materials to exhibit stop and pass bands with the ability to dissipate energy through cell-level elastic instabilities. Here, we use Bloch periodic boundary conditions to compute the dispersion curves and introduce a new approach for computing wide band directionality plots. Also, we deconstruct the wave propagation behavior of this material to identify the contributions from its various structural elements by progressively building the unit cell, structural element by element, from a simple, homogeneous, isotropic primitive. Direct integration time domain analyses of a representative volume element at a few salient frequencies in the stop and pass bands are used to confirm the existence of partial band gaps in the response of the cellular material. Insights gained from the above analyses are then used to explore modifications of the unit cell that allow the user to tune the band gaps in the response of the material. We show that this material behaves like a locally resonant material that exhibits low frequency band gaps for small amplitude planar waves. Moreover, modulating the geometry or material of the central bar in the unit cell provides a path to adjust the position of the band gaps in the material response. Also, our results show that the material exhibits highly anisotropic wave propagation behavior that stems from the anisotropy in its mechanical structure. Notably, we found that unlike other multi-stable cellular materials reported in the literature, in the system studied in this work, the configurational changes in the unit cell corresponding to its different stable phases do not significantly alter the wave propagation behavior of the material. © 2019Ítem Efecto de las Bajas Concentraciones de Nitratos y Fosfatos sobre la Acumulación de Astaxantina en Haematococcus pluvialis UTEX 2505(Centro de Informacion Tecnologica, 2019-01-01) Miranda A.M.; Ossa E.A.; Vargas G.J.; Sáez A.A.; Universidad EAFIT. Departamento de Ciencias; Ciencias Biológicas y Bioprocesos (CIBIOP)In this study, the effect of the concentration of nitrogen and phosphorus on the accumulation of Astaxanthin in Haematococcus pluvialis UTEX 2505 was evaluated using a factorial 3 2 design. The dependent variables were cell growth, Astaxanthin production, lipid profile and Young's modulus of the cell membrane. It was found that cellular productivity increases when nitrogen levels were high, in contrast to low concentrations of nitrogen and phosphorus that showed a positive effect on Astaxanthin production. The stress generated by the source of nutrients decreases the rigidity of the cellular wall in the microalgae. As a conclusion, to obtain higher concentrations of Astaxanthin it is necessary to limit the nitrogen and phosphorus levels. © 2019 Centro de Informacion Tecnologica. All Rights Reserved.Ítem Efecto de las Bajas Concentraciones de Nitratos y Fosfatos sobre la Acumulación de Astaxantina en Haematococcus pluvialis UTEX 2505(Centro de Informacion Tecnologica, 2019-01-01) Miranda A.M.; Ossa E.A.; Vargas G.J.; Sáez A.A.; Miranda A.M.; Ossa E.A.; Vargas G.J.; Sáez A.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaIn this study, the effect of the concentration of nitrogen and phosphorus on the accumulation of Astaxanthin in Haematococcus pluvialis UTEX 2505 was evaluated using a factorial 3 2 design. The dependent variables were cell growth, Astaxanthin production, lipid profile and Young's modulus of the cell membrane. It was found that cellular productivity increases when nitrogen levels were high, in contrast to low concentrations of nitrogen and phosphorus that showed a positive effect on Astaxanthin production. The stress generated by the source of nutrients decreases the rigidity of the cellular wall in the microalgae. As a conclusion, to obtain higher concentrations of Astaxanthin it is necessary to limit the nitrogen and phosphorus levels. © 2019 Centro de Informacion Tecnologica. All Rights Reserved.Ítem FE-simulations with a simplified model for open-cell porous materials: A Kelvin cell approach(IOS Press, 2019-01-01) Montoya-Zapata D.; Cortés C.; Ruiz-Salguero O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn in-silico estimation of mechanical properties of open (Kelvin) cell porous materials, the geometrical model is intractable due to the large number of finite elements generated. Such a limitation impedes the study of reasonable domains. VoXel or Boundary representations of the porous domain result in FEA data sets which do not pass the stage of mesh generation, even for very modest domains. Our method to overcome such limitations partially replaces geometrical minutiae with kinematical constraints imposed on cylindrical bars (i.e. Truss model). Our implemented method uses node position equality constraints augmented with rotation constraints at the joints. Such a method significantly reduces the computational expense of the model, allowing the study of domains of 103 Kelvin cells. The results of the tests executed show the accuracy and efficiency of the Truss model in the estimation of Young's modulus and Poisson's ratio when compared with current procedures. The method allows application for materials which depart from Kelvin Cell uniformity, since the Truss model admits general configurations. As the simulation is made possible by the Truss model, new challenges appear, such as the application to anisotropic materials and the automatic generation of the Truss model from actual foam scans (e.g. tomographies). © 2019 - IOS Press and the authors. All rights reserved.Ítem Influence of epoxy resin as encapsulation material of silicon photovoltaic cells on maximum current(EDP Sciences, 2017-01-01) Acevedo-Gómez, D.; Velásquez-López, A.; Osorio-Gómez, G.; Mejía-Gutiérrez, R.This work presents an analysis about how the performance of silicon photovoltaic cells is influenced by the use of epoxy resin as encapsulation material with flat roughness. The effect of encapsulation on current at maximum power of mono-crystalline cell was tested indoor in a solar simulator bench at 1000 w/m and AM1.5G. The results show that implementation of flat roughness layer onto cell surface reduces the maximum current inducing on average 2.7% less power with respect to a cell before any encapsulation. The losses of power and, in consequence, the less production of energy are explained by resin light absorption, reflection and partially neutralization of non-reflective coating. © The Authors, published by EDP Sciences, 2017.Ítem ParaVoxel: A domain decomposition based fixed grid preprocessor(WORLD SCIENTIFIC PUBL CO PTE LTD, 2015-06-01) Garcia, M.J.; Duque, J.; Henao, M.; Boulanger, P.; Mecánica AplicadaIn this paper, a parallel cartesian fixed grid mesh generator for structural and fluid dynamics problems is presented. The method uses the boundary representation of a body and produces a set of equal sized cells which are classified in three different types according to its location with respect to the body. Cells are inside, outside or intersecting the boundary of the body. This classification is made by knowing the number of nodes of a cell that are inside body. That process is accomplished very efficiently as the nodes can be classified in batch. Once boundary cells are identified, its geometry is approximated by the convex hull of the nodes inside the body and the intersection points of the boundary against the cell edges. This paper presents the basics of the Fixed Grid Meshing algorithm, followed by some domain decomposition modifications and the data structures required for its parallel implementation. A set of examples and a brief discussion on the possibility of applying this algorithm together with other approaches is presented. © 2015 World Scientific Publishing Company.