Autonomous University of the Caribbean
Barranquilla, Colombia
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Toledo M.,Federico Santa María Technical University | Utria K.,Autonomous University of the Caribbean | Saveliev A.V.,North Carolina State University
Energy and Fuels | Year: 2014

Ultrarich filtration combustion of ethane is studied in a porous medium composed of alumina spheres with the aim to achieve optimized conversion to hydrogen and syngas. Temperature, velocities, and chemical products of the combustion waves are recorded experimentally in a range of equivalence ratios φ from stoichiometry (φ = 1) to φ = 2.5. Experimental and numerical results are reported for 3.5 mm diameter alumina spheres; an oxygen content of the oxidizer is varied from 21 to 30%. Two temperature models based on GRI-MECH 3.0 and San Diego-MECH demonstrated good agreement with the experimental results. The maximum hydrogen concentration of 19.3% was recorded at φ = 2.5 and a 30% oxygen content in the oxidizer. © 2014 American Chemical Society.

Archibold A.R.,University of South Florida | Archibold A.R.,Autonomous University of the Caribbean | Rahman M.M.,University of South Florida | Goswami D.Y.,University of South Florida | Stefanakos E.K.,University of South Florida
Applied Thermal Engineering | Year: 2014

A numerical model of heat transfer and fluid flow during melting of a phase change material (PCM) inside a closed and uniformly heated spherical shell has been developed to investigate the thermal performance of the system. The control volume discretization technique has been used to solve the conservation equations for mass, momentum, and energy along with the enthalpy-porosity method to track the melting front. The study focused on PCMs with a melting temperature in the range of operation of concentrated solar thermal power (CSP) generation. A comprehensive analysis has been performed in order to determine the influence of the Grashof, Stefan and Prandtl numbers on the melting dynamics of capsules with various diameters (20, 30, 40, and 50 mm). Also the effects of the shell material and initial temperature of the system on the thermal performance have been analyzed. Correlations have been proposed for the melt fraction and average Nusselt number as a function of the main dimensionless parameters that characterized this problem. In order to support the validity of the developed model, the predicted results of a validation case are compared with the experimental results reported by Tan [1] and are found to be in good agreement. © 2013 Elsevier Ltd. All rights reserved.

Gamarra Acosta M.R.,Autonomous University of the Caribbean | Velez Diaz J.C.,Universidad del Norte, Colombia | Schettini Castro N.,Universidad del Norte, Colombia
Corrosion Science | Year: 2014

This article presents an image-processing model for detection of rust zones using digital images of metals. The input image, containing a wide range of possible rusted textures, is simulated with Perlin Noise, which allows simulating extreme corrosion conditions, without waiting for these conditions to occur. Probabilistic descriptors are determined by means of discriminant analysis using Fisher indexes. A Bayesian classifier is used to identify rusted regions. Additionally, performance tests under different noise conditions and texture variations, generated with Perlin Noise, are presented. © 2014 Elsevier Ltd.

Ibanez M.H.S.,Autonomous University of the Caribbean
Astrophysical Journal | Year: 2016

The Ertel theorem on the vorticity along the flow of adiabatic fluids is generalized for non-adiabatic flows. Several limiting cases are analyzed and the results are applied to flows behind different hydrodynamics fronts, particularly to thermal fronts (heat and cooling fronts). An important conclusion of the present analysis is that vorticity is inherent in the condensation's (or hot spots) formation by thermal instabilities in plasma flows. Implications for several astrophysical plasmas are outlined. © 2016. The American Astronomical Society. All rights reserved.

Araya R.,Federico Santa María Technical University | Araus K.,Federico Santa María Technical University | Utria K.,Autonomous University of the Caribbean | Toledo M.,Federico Santa María Technical University
International Journal of Hydrogen Energy | Year: 2014

The effect of adding steam during filtration combustion of natural gas-air mixtures was studied with the aim to evaluate the optimization of hydrogen production. Temperature, velocity, chemical products of combustion waves, and conversion from fuel to H2 and CO were evaluated in the range of equivalence ratio (φ) from stoichiometric (φ = 1.0) to φ = 3.0 and steam content in the mixture from 0% to 39%, at filtration velocities from 12 to 25 cm/s. Numerical simulation was carried out using GRI-MECH 3.0. Results suggest that H2 and CO concentrations, dominant for rich and ultrarich combustion, are products from partial oxidation and steam natural gas reforming processes. Experimental and numerical results show that hydrogen yield increase with an increase of steam content in the natural gas-air mixtures. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Archibold A.R.,University of South Florida | Archibold A.R.,Autonomous University of the Caribbean | Gonzalez-Aguilar J.,IMDEA Madrid Institute for Advanced Studies | Rahman M.M.,University of South Florida | And 3 more authors.
Applied Energy | Year: 2014

A two dimensional axisymmetric model of the heat transfer and fluid flow during the melting process inside a spherical latent heat thermal storage capsule is analyzed. A void space was provided within the capsule to take into account the volumetric expansion of the PCM. The mathematical model was solved using the finite-volume method, and the enthalpy-porosity formulation was employed to solve the energy equations in both the liquid and solid regions of the PCM. The effects of the Grashof and Stefan numbers on the thermal performance of the capsules of various diameters (20, 30, 40 and 50mm) have been investigated. It was found that increasing the Grashof number from 1.32×104 to 2. 06×105 enhances the heat transfer. Also for a constant Grashof number (9.09×104) the PCM melts at a faster rate when the Stefan number increases from 0.077 to 0.097. Finally, appropriate dimensionless variables based on a combination of the Fourier, Grashof and Stefan numbers are introduced in order to obtain a generalized correlation for the liquid mass fraction and the Nusselt number during melting of sodium nitrate. © 2013 Elsevier Ltd.

Mikulan E.P.,University of Buenos Aires | Mikulan E.P.,Diego Portales University | Reynaldo L.,University of Buenos Aires | Ibanez A.,University of Buenos Aires | And 3 more authors.
Frontiers in Human Neuroscience | Year: 2014

Emerging theories on embodied cognition have caused high expectations, ambitious promises, and strong controversies. Several criticisms have been explained elsewhere (Mahon and Caramazza, 2008; Cardona et al., 2014) and will not be discussed further here. In this paper, we will focus on a specific explanatory strategy frequently assessed by the radical embodied cognition approaches: the use of homuncular explanations for the explicit (or implicit) attribution of causal roles in the comprehension of language understanding. We first present this criticism regarding a prototypical example: the mirror neuron system (MNS) (Rizzolatti and Craighero, 2004; Iacoboni and Dapretto, 2006) in the field of language understanding and then extend our conclusions to other programs of embodied cognition. Here we discuss the radical claims that propose the MNS as the putative mechanism for multiple cognitive and social psychology constructs (e.g., Gallese, 2008; Cattaneo and Rizzolatti, 2009; Iacoboni, 2009) and the critical role of the MNS in language understanding (Heyes, 2010a; Hickok, 2013). © 2014 Mikulan, Reynaldo and Ibáñez.

Pattern recognition performance depends on variations during extraction, selection and classification stages. This paper presents an approach to feature selection by using genetic algorithms with regard to digital image recognition and quality control. Error rate and kappa coefficient were used for evaluating the genetic algorithm approach Neural networks were used for classification, involving the features selected by the genetic algorithms. The neural network approach was compared to a K-nearest neighbor classifier. The proposed approach performed better than the other methods.

Archibold A.R.,University of South Florida | Archibold A.R.,Autonomous University of the Caribbean | Rahman M.M.,University of South Florida | Yogi Goswami D.,University of South Florida | Stefanakos E.K.,University of South Florida
Applied Energy | Year: 2015

The influence of radiation heat transfer during the phase change process of a storage material has been numerically analyzed in this study. Emphasis has been placed on the thermal characterization of a single constituent storage module rather than an entire storage system, in order to precisely capture the energy exchange contributions of all the fundamental heat transfer mechanisms during the melting of a phase change material (PCM) with tailored optical properties. The equations describing the conservation of mass, momentum and energy have been solved by using the control volume discretization approach, while the radiative transfer equation (RTE) was solved by the discrete ordinate method (DOM). The enthalpy-porosity method was used to track the PCM liquid/solid interface during the process. A parametric analysis has been performed in order to ascertain the effects of the optical thickness and the Planck, Grashof and Stefan numbers on the melting rate, as well as the total and radiative heat transfer rates at the inner surface of the shell. The results show that the presence of thermal radiation enhances the melting process. Correlations for the melt fraction and modified Nusselt number are developed for application in the design process of packed bed heat exchangers for latent heat thermal energy storage. © 2014 Elsevier Ltd.

Unfried-Silgado J.,Metals Characterization and Processing Laboratory | Unfried-Silgado J.,University of Campinas | Unfried-Silgado J.,Autonomous University of the Caribbean | Ramirez A.J.,Metals Characterization and Processing Laboratory
Metals and Materials International | Year: 2014

In part II of this work is evaluated the as-welded microstructure of Ni-Cr-Fe alloys, which were selected and modeled in part I. Detailed characterization of primary and secondary precipitates, subgrain and grain structures, partitioning, and grain boundary morphology were developed. Microstructural characterization was carried out using optical microscopy, SEM, TEM, EBSD, and XEDS techniques. These results were analyzed and compared to modeling results displaying a good agreement. The Hf additions produced the highest waviness of grain boundaries, which were related to distribution of Hf-rich carbonitrides. Experimental evidences about Mo distribution into crystal lattice have provided information about its possible role in ductility-dip cracking (DDC). Characterization results of studied alloys were analyzed and linked to their DDC resistance data aiming to establish relationships between as-welded microstructure and hot deformation performance. Wavy grain boundaries, primary carbides distribution, and strengthened crystal lattice are metallurgical characteristics related to high DDC resistance. © 2014 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

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