Examinando por Autor "Alexander Ossa, E."
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Ítem Composición química y microestructura de la dentina de pacientes colombianos(2014-05-01) C. Montoya; Alexander Ossa, E.; C. Montoya; Alexander Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaLa dentina es un tejido duro que ocupa la mayor porción del diente humano. En estudios preliminares realizados en la dentina de pacientes de Estados Unidos y Colombia se han encontrado ciertasdiferencias en cuanto al tamaño y distribucionÍtem Efecto de la fotodegradación en la microestructura y composición química del asfalto(2014-05-01) Gamarra, A.; Alexander Ossa, E.; Gamarra, A.; Alexander Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaEn este estudio se ha investigado la influencia que tiene la foto-oxidación en el envejecimiento del asfalto. Al estar constituido en su mayoría por componentes orgánicos, este se ve afectado por las condiciones ambientales que causan la degradación de diÍtem Estudio de mezclas binarias Asfalto-Polímero(IMPRENTA UNIV ANTIOQUIA, 2014-01-01) Múnera, J.C.; Alexander Ossa, E.; Múnera, J.C.; Alexander Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaBitumen is a black material composed of a mixture of various natural hydrocarbons. Bitumen has been commonly used in road paving and roofing applications thanks to its hydrophobic and adhesives properties. The production of Polymer Modified Bitumens (PMB) has allowed the development of materials with better performance in comparison to pure bitumen. This work presents the effect of addition of polymer to a Colombian bitumen from its morphological, rheological and thermal properties, in order to identify different modification levels. The polymers used as modifiers were polyethylene wax (CPE), styrene butadiene styrene (SBS) and crumb rubber (CR). They were added to bitumen in proportions between 3 to 15% w/w. Both neat bitumen and PMB were characterized by penetration and softening point. Thermal and rheological characteristics were analyzed by differential scanning calorimetry (DSC) and rotational rheometry, respectively. Changes in the morphology were measured by atomic force microscopy (AFM). The experimental results showed that the CPE mixtures had the most pronounced effect on the conventional properties, achieving a 75% reduction in penetration and a 250% increase in the softening point compared to neat bitumen. The results obtained by DSC allowed identifying three glass transition temperatures (Tg) in neat bitumen. Mixtures with SBS altered Tg, showing changes on the thermal characteristics of neat bitumen. Mixtures with CPE and SBS showed the highest values of G*. The results obtained by AFM help identifying three different phases in neat bitumen and its variation with the addition of different polymer modifiers, showing considerable structural changes that led to changes in the material properties at the macroscopic level.Ítem Kaolin based ceramics obtained by Freeze casting process(UNIV VALLE, FAC INGENIERIA, 2016-01-01) Gil-Duran, S.; Alexander Ossa, E.; Gil-Duran, S.; Alexander Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaFreeze casting offers a tremendous opportunity to obtain bio-inspired synthetic materials that mimic microstructural characteristics of natural materials like bone and nacre. These natural materials display high strength and toughness; properties usually desired in synthetic engineering materials. The freeze casting process involves four basic steps. The ceramic slurry preparation consists of fine ceramic particles that are suspended in a fluid. In the current work, water based kaolin suspensions were prepared varying the volume fraction of ceramic particles. After the ceramic slurry is properly prepared, the slurry is frozen. The solidification process is often performed using directional freezing, which creates laminar pores, providing the microstructural characteristics of the final part. When a crystal is formed the frozen front moves the particles around it, allowing particles to agglomerate around the crystal, creating different types of pores. In the present study, freezing rates were varied. Subsequently, the samples have to be lyophilized in order to sublimate the frozen liquid phase. Sublimation is the transformation of a solid phase directly to the gas phase. As a result the lyophilized sample has a porous structure with a replica of the water crystals formed during freezing. As a final step, sintering of ceramics is performed. Results of the microstructural characteristics of the samples revealed that varying the volume fraction of ceramic particles and freezing rates have a direct influence on the pore characteristics, changing from circular to laminar pores.Ítem Modelación y análisis de susceptibilidad a la deformación permanente de mezclas asfálticas(Pontificia Universidad Católica de Chile, 2011-08-01) Vidal J.; Alexander Ossa, E.; Vidal J.; Alexander Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaLa deformación permanente de mezclas asfálticas del Área Metropolitana del Valle de Aburra ? Antioquia, las cuales se fabrican en nuestro medio bajo las especificaciones INVIAS (Instituto Nacional de Vías) y del Valle de AburráÍtem Natural flexible armor as an inspirationfor body armor design(Soc. for the Advancement of Material and Process Engineering, 2015-05-21) Alexander Ossa, E.; Alexander Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaAnimals have developed different strategies to protect themselves from environmental and predatory threats. One of these strategies concerns with the development of natural flexible dermal armor, usually consisting of rigid and highly mineralized units (e. g. scales or osteoderms) attached by flexible collagen fibers. These kinds of arrangements have been proven to achieve high flexibility without significant reduction in strength in comparison to monolithic structures. These are in fact features extremely valued by body armor users. This work studies the mechanical characteristics of scales and osteoderms of different animals (including mammals, reptiles and fishes), in order to compare them with other characteristics of the animal itself (like length and mobility) and characteristics of their predators like geometry and composition of their teeth and strength of bite. This comparison extends our knowledge and open new ways of understanding on how to design body armor materials and structures looking into improvements on flexibility and mobility. Copyright 2015. Used by the Society of the Advancement of Material and Process Engineering with permission.Ítem Polymer Modified Bitumen: Optimization and Selection(Elsevier Ltd, 2014-10-01) JC MUNERA; Alexander Ossa, E.; JC MUNERA; Alexander Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaPolymer modification of bitumen has been commonly performed since the 1980s in order to decrease bitumen (and pavement) susceptibility to high and low temperatures, allowing reduction in common failure mechanisms as rutting and cracking.Ítem Propiedades mecánicas del asfalto a niveles nanométricos(Corporación Para Investigación Y Desarrollo En Asfaltos En El Sector Transporte E Industrial - Corasfaltos, 2015-01-01) Alexander Ossa, E.; Múnera, J.C.; Alexander Ossa, E.; Múnera, J.C.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaEl asfalto es un material constituido por una mezcla de diversos hidrocarburos de origen natural, sus buenas propiedades aglutinantes e hidrofóbicas lo han llevado a ser ampliamente utilizado en aplicaciones que van desde la impermeabilización hasta laÍtem Selección de materiales bituminosos con base en propiedades reológicas(2014-05-01) JC MUNERA; Alexander Ossa, E.; JC MUNERA; Alexander Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaNumerosos estudios han demostrado que adicionar polímeros al asfalto para formar mezclas binarias o multicomponentes mejoran sus propiedades, logrando así obtener materiales aptos para aplicaciones en las que un asfalto crudo no desempeñaría