Examinando por Materia "Hydrogen"
Mostrando 1 - 6 de 6
Resultados por página
Opciones de ordenación
Ítem Desarrollo de un electrodo bioinspirado para generación de Hidrógeno(Universidad EAFIT, 2024) Carmona Saldarriaga, Laura; Ossa Henao, Edgar AlexanderÍtem Interfibril hydrogen bonding improves the strain-rate response of natural armour(Royal Society Publishing, 2019-01-01) Arola D.; Ghods S.; Son C.; Murcia S.; Ossa E.A.; Arola D.; Ghods S.; Son C.; Murcia S.; Ossa E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaFish scales are laminated composites that consist of plies of unidirectional collagen fibrils with twisted-plywood stacking arrangement. Owing to their composition, the toughness of scales is dependent on the intermolecular bonding within and between the collagen fibrils. Adjusting the extent of this bonding with an appropriate stimulus has implications for the design of next-generation bioinspired flexible armours. In this investigation, scales were exposed to environments of water or a polar solvent (i.e. ethanol) to influence the extent of intermolecular bonding, and their mechanical behaviour was evaluated in uniaxial tension and transverse puncture. Results showed that the resistance to failure of the scales increased with loading rate in both tension and puncture and that the polar solvent treatment increased both the strength and toughness through interpeptide bonding; the largest increase occurred in the puncture resistance of scales from the tail region (a factor of nearly 7). The increase in strength and damage tolerance with stronger intermolecular bonding is uncommon for structural materials and is a unique characteristic of the low mineral content. Scales from regions of the body with higher mineral content underwent less strengthening, which is most likely the result of interference posed by the mineral crystals to intermolecular bonding. Overall, the results showed that flexible bioinspired composite materials for puncture resistance should enrol constituents and complementary processing that capitalize on interfibril bonds. © 2019 The Author(s) Published by the Royal Society. All rights reserved.Ítem Multifactorial optimization of the decolorisation parameters of wastewaters resulting from dyeing flowers.(IWA PUBLISHING, 2009-01-01) Gil Pavas, Edison; Angel Gomez-Garcia, Miguel; Gil Pavas, Edison; Angel Gomez-Garcia, Miguel; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)This work deals with the treatment of the wastewaters resulting from the process of dyeing flowers. In some local cases for growing flowers near to Medellin (Colombia), wastewater color was found to be one of the main problems in meeting local effluent standards. Wastewaters were treated by photodegradation process (which includes photocatalysis) to achieve the degradation of dyes mixture and organic matter in the wastewater. A multifactorial experimental design was proposed, including as experimental factors the following variables: pH, and the concentration of both catalyst (TiO(2)) and hydrogen peroxide (H(2)O(2)). According to the obtained results, at the optimized variables values, it is possible to reach a 99% reduction of dyes, a 76.9% of mineralization (TOC) and a final biodegradability of 0.834. Kinetic analysis allows proposing a pseudo first order reaction for the reduction, the mineralization, and the biodegradation processes.Ítem Simulación de una planta de producción de Acetaldehído en estado estacionario con estudio de rentabilidad(Universidad EAFIT, 2014) Cardona Palacio, Luis Fernando; Giraldo Agudelo, Juliana; Acosta Maya, Diego AndrésEn respuesta a la necesidad de producir químicos con biomasa como materia prima y a generar fuentes renovables de energía, se realizó un estudio de la rentabilidad a doce años de un proceso productor de acetaldehído por deshidrogenación de etanol anhidro al 98.41% mol-g/mol-g, 25.00 ºC y 101.32 kPa, a partir de una simulación en estado estacionario en Aspen Hysys ® V8.4 -- En la que se utilizó un reactor de lecho empacado con catalizador cromita de cobre a unas condiciones de reacción de 285.00 ºC y 451.26 kPa, obteniéndose 14663.65 kg/h de acetaldehído al 99.36% mol-g/mol-g a 945.40 kPa y 10.03 ºC como producto principal y 771.06 kg/h de hidrógeno al 99.34% mol-g/mol-g a 13828.82 kPa y 25.00 ºC como subproducto -- La conversión en el reactor fue de 99.95% -- Los rendimientos para el acetaldehído y el hidrógeno fueron de 99.28% y 99.76%, respectivamente -- La rentabilidad de la planta dependió significativamente del costo del etanol anhidro, al adquirirse a un precio de 0.48 USD/kg la planta fue rentable, con un valor presente neto de 9,506,968 USD/kg y una TIR de 42%, mientras que cuando el precio de compra fue 0.9 USD/kg la planta no fue rentable y se tuvo una pérdida de 70,708,370 USDÍtem Structural characterization of the (methanol)4 potential energy surface(AMER CHEMICAL SOC, 2009-09-24) David, Jorge; Guerra, Doris; Restrepo, Albeiro; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)In this paper, we report the geometries and properties of the structural isomers obtained from a random walk of the potential energy surface (PES) of the methanol tetramer. Thirty-three structures were obtained after B3LYP/6-31+g* optimization of 94 candidate structures generated from a stochastic search of the PM3 conformational space. The random search was carried out using a recently proposed modified Metropolis acceptance test in the simulated annealing (SA) procedure. Corrections for the basis set superposition error (BSSE) show improvements on the binding energies of the clusters in an average of approximately 2.0 kcal/mol, while geometries are predicted to be less sensitive to BSSE corrections. MP2/aug-cc-pvdz calculations on representative structures did not change the geometries but predicted better binding energies. Highly correlated CCSD(T) energies were calculated on the B3LYP and MP2 stationary points and used to establish relative stabilities. We report several new conformations and group the structures into six distinct geometrical motifs. Only the cyclic tetramers with four primary hydrogen bonds in the same plane are predicted to have significant populations. Secondary hydrogen bonds, those for which the donated proton comes from an alkyl group, lead to a rich conformational space.Ítem Structural studies of the water pentamer(ELSEVIER SCIENCE BV, 2011-05-09) Ramirez, Frank; Hadad, C. Z.; Guerra, Doris; David, Jorge; Restrepo, Albeiro; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)A computational study of the water pentamer gas phase conformational space is reported in this Letter. Forty-four stationary points distributed among 12 structural patterns were located at the MP2/6-311++G(d,p) level. At least 5 geometrical motifs (25 structures) are predicted within 3 kcal/mol of the most stable conformation at the CCSD(T)/aug-cc-pVTZ//MP2/6-311++G(d,p) level. We show evidence that dipole-dipole interactions are at play in stabilizing the clusters. Electron densities and their Laplacians at the hydrogen bond critical points were found to be linearly correlated with relative energies for all clusters. Logarithmic relationships were found for the [req, ?(rc)] and [req,?2?( rc)] pairs in all hydrogen bonds. © 2011 Elsevier B.V. All rights reserved.