Hot-pressing process modeling for medium density fiberboard (MDF)

In this paper we present a numerical solution for the mathematical modeling of the hot-pressing process applied to medium density fiberboard. The model is based in the work of Humphrey[82], Humphrey and Bolton[89] and Carvalho and Costa[98], with some modifications and extensions in order to take into account mainly the convective effects on the phase change term and also a conservative numerical treatment of the resulting system of partial differential equations.Comment: LaTeX, 11 figures. Added references. Fixed some errors. To appear in International Journal of Mathematics and Mathematical Sciences, http://jam.hindawi.co

A Coupling Strategy for a Chimera Method Applied to Thermal Conduction Optimization Problems

The main idea of the Chimera method is to generate independent meshes for the objects present in a computational domain and to couple them by a coupling strategy in order to obtain a unique solution of the system. The method has appealing characteristics that are convenient for applications like simplified mesh generation, moving components, local refinement and optimization. The optimization process is a straightforward application where several objects, each one with its respective mesh, can be moved around without the need to remesh the whole computational domain. Then, different optimization techniques can be used to find the optimum configuration of the system in terms of an objective function. In a previous work (B. Storti et al., “A chimera method based on Dirichlet-Dirichlet coupling and pasting penalization operators”, Mecánica Computacional, vol. XXXIV, 2016), we have presented and validated a Chimera scheme in the finite element context for structured meshes, and we have proven that it has a good convergence rate solving the system iteratively with BiCGStab (BiConjugate Gradient Stabilized method). In the present work, we improve the Chimera method to solve thermal conduction problems on overlapping unstructured meshes and then we test it in several optimization cases. A Dirichlet-Dirichlet coupling imposes the continuity of the unknown on overlapping subdomains and to transfer these values between the multiples domains, a third order interpolation method is used in conjunction with a "pasting" penalization operator. Several numerical examples are also shown in order to validate the proposed interpolation method. Finally a variety of optimization problems are solved under the pyOpt framework, either using gradient-free or gradient based optimizers, running in the CIMEC cluster Seshat (http://www.cimec.org.ar/c3/seshat/equipos.php), where every evaluation test of the objective function is compute on each core. Seshat is a 69 nodes cluster, which has an Infiniband network and a computing power of almost 7 TFLOPS.Publicado en: Mecánica Computacional vol. XXXV, no. 28.Facultad de Ingenierí

Coplanar back contacts for thin silicon solar cells

The type of coplanar back contact solar cell described was constructed with interdigitated n(+) and p(+) type regions on the back of the cell, such that both contacts are made on the back with no metallization grid on the front. This cell construction has several potential advantages over conventional cells for space use namely, convenience of interconnects, lower operating temperatures and higher efficiency due to the elimination of grid shadowing. However, the processing is more complex, and the cell is inherently more radiation sensitive. The latter problem can be reduced substantially by making the cells very thin (approximately 50 micrometers). Two types of interdigitated back contact cells are possible, the types being dependent on the character of the front surface. The front surface field cell has a front surface region that is of the same conductivity type as the bulk but is more heavily doped. This creates an electric field at the surface which repels the minority carriers. The tandem junction cell has a front surface region of a conductivity type that is opposite to that of the bulk. The junction thus created floats to open circuit voltage on illumination and injects carriers into the bulk which then can be collected at the rear junction. For space use, the front surface field cell is potentially more radiation resistant than the tandem junction cell because the flow of minority carriers (electrons) into the bulk will be less sensitive to the production of recombination centers, particularly in the space charge region at the front surface

Modelización del flujo invíscido alrededor de la pala de un aerogenerador mediante el método de los paneles

Se describe la formulación de un modelo computacional para determinar, bajo condiciones invíscidas, el flujo tridimensional alrededor de la pala de una turbina eólica de eje horizontal. Dicho modelo se basa en la representación mediante paneles de una pala rígida, delgada, torsionada y de envergadura finita. A estos paneles se asocian hilos vorticosos rectos, que conforman el sistema ligado a la pala, y un sistema de hilos vorticosos libres, que presentan trayectorias helicoidales de radios no constantes, que determinan una estela de configuración fija. Las velocidades inducidas por el sistema vorticoso completo son calculadas por la aplicación de la ley de Biot-Savart. Se presenta la metodología seguida para el cálculo de las distribuciones de circulación, velocidades inducidas y resultantes y cargas aerodinámicas a lo largo de la envergadura y cuerda de una pala de geometría definida, bajo una determinada condición de viento y rotación uniformes, sin la consideración de los efectos de interferencia.This work describes the formulation of a computational model to detemine, under inviscid conditions, the tri-dimensional flow field around the blade of an horizontal-axis wind turbine. The model is based upon a panel representation of a rigid, thin and twisted blade of finite span.The distribution of circulation is originated by a system of straight bound vortices associated to the blade and a system of free vortex filaments, having helical paths with non-constant radii, that generates a prescribed fixed wake. The velocities induced by that vortex system are calculated by the Biot-Savart law. The methodology followed in order to calculate the span and chordwise distributions of circulation, induced velocities and aerodynamic loads is presented for a blade whose geometry and working conditions are defined, without considering the interference effects.Peer Reviewe

Modelización del flujo invíscido alrededor de la pala de un aerogenerador mediante el método de los paneles

Se describe la formulación de un modelo computacional para determinar, bajo condiciones invíscidas, el flujo tridimensional alrededor de la pala de una turbina eólica de eje horizontal. Dicho modelo se basa en la representación mediante paneles de una pala rígida, delgada, torsionada y de envergadura finita. A estos paneles se asocian hilos vorticosos rectos, que conforman el sistema ligado a la pala, y un sistema de hilos vorticosos libres, que presentan trayectorias helicoidales de radios no constantes, que determinan una estela de configuración fija. Las velocidades inducidas por el sistema vorticoso completo son calculadas por la aplicación de la ley de Biot-Savart. Se presenta la metodología seguida para el cálculo de las distribuciones de circulación, velocidades inducidas y resultantes y cargas aerodinámicas a lo largo de la envergadura y cuerda de una pala de geometría definida, bajo una determinada condición de viento y rotación uniformes, sin la consideración de los efectos de interferencia.This work describes the formulation of a computational model to detemine, under inviscid conditions, the tri-dimensional flow field around the blade of an horizontal-axis wind turbine. The model is based upon a panel representation of a rigid, thin and twisted blade of finite span.The distribution of circulation is originated by a system of straight bound vortices associated to the blade and a system of free vortex filaments, having helical paths with non-constant radii, that generates a prescribed fixed wake. The velocities induced by that vortex system are calculated by the Biot-Savart law. The methodology followed in order to calculate the span and chordwise distributions of circulation, induced velocities and aerodynamic loads is presented for a blade whose geometry and working conditions are defined, without considering the interference effects.Peer Reviewe

Deformation Sequence and Paleofluids in Carbonate Buckle Folds Under Transpression (Pag Anticline, External Dinarides, Croatia)

Contractional deformation structures at the front of transpressional orogens display complex three-dimensional geometries deviating from the interpretative templates commonly applied in thrust belts. Accordingly, detailed constraints on deformation patterns and associated paleofluid circulation are desirable, especially for fracture geometry and permeability predictive purposes. The Pag anticline, which is located in the Dinaric fold and thrust belt, provides an appropriate field site for studying fold- and fault-related deformation structures in a transpressive setting. We performed a multiscale structural analysis together with petrographic and stable isotope characterization of the deformation-related calcite cements. Structural mapping suggests that the Pag anticline is a detachment fold developed mainly by buckling, since large-scale thrust faults are absent. Fold tightening in a transpressive setting produced a complex deformational structure including two sets of N-S right-lateral and E-W left-lateral late-stage strike-slip fault sets trending oblique to the NW-SE fold axis. The pre-folding deformation pattern includes incipient normal faults likely related to the forebulge stage, veins and stylolites coherent with NE-SW layer parallel shortening contraction in a strike-slip regime, and metric to decametric scale conjugate thrusts coherent with layer parallel shortening in a compressive regime. Buckle folding preceded propagation of a series of accommodation structures during fold tightening. Petrographic and isotopic data indicate meteoric alteration of the Cretaceous platform carbonates in the prefolding stage, likely due to forebulge subaerial exposure. Layer parallel shortening and early syn-folding veins involved formational fluids resulting from mixed marine and meteoric fluids during folding at shallow burial conditions. Eventually, meteoric fluid infiltrated again along strike-slip faults, acting as cross-formational conduits in the postfolding stage

Functionalized lactic acid macromonomers polycondensation

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