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Apoyo institucional del ICE-UPC a las dinámicas de innovación docente: Proyecto RIMA

Tue, 21 May 2013 17:25:49 GMT

Title: Apoyo institucional del ICE-UPC a las dinámicas de innovación docente: Proyecto RIMA Authors: Martínez Martínez, María del Rosario; Salán Ballesteros, Maria Núria; Adam, Araceli; Darnell, Isabel; Corral Manuel de Villena, Ignacio de; Gallego Fernández, María Isabel; Portet Cortés, Esperanza; Torra Bitlloch, Immaculada Abstract: En los últimos años, desde el Instituto de Ciencias de la Educación de la Universidad Politécnica de Cataluña (ICE - UPC), se ha incentiva do l a Innovación Docente mediante múltiples iniciativas. Desde 2007, con la creación del Proyecto RIMA (Investigación e Innovación en Metodologías de Aprendizaje - Recerca i Innovació en Metodologies d’Aprenentatge) y de su entorno virtual asociado (www.upc.ed u/rima), el apoyo a la innovación docente se completa con un proyecto coordinado, que facilita la confluencia de esfuerzos de grupos de profesorado con interés en este ámbito. En la presente comunicación y partiendo de los resultados y experiencias de los últimos años en adaptación e implantación de metodologías de innovación docente en la UPC, se realiza una reflexión sobre la acogida e incidencia de esta iniciativa en la adaptación a los nuevos planes de estudio del Espacio Europeo de E ducación Superior ( EEES), y en el planteamiento de nuevos objetivos institucionales referidos tanto al tema de la participación en innovación docente como a las nuevas metodologías y a la mejora de la calidad docente.

Novel polycarbonate-graphene nanocomposite foams prepared by CO2 dissolution

Fri, 17 May 2013 14:42:23 GMT

Title: Novel polycarbonate-graphene nanocomposite foams prepared by CO2 dissolution Authors: Gedler, Gabriel; Sousa Pais Antunes, Marcelo de; Redondo Realinho, Vera Cristina de; Velasco Perero, José Ignacio Abstract: Polycarbonate foams reinforced with 0,5 wt% of graphene were obtained by firstly melt-mixing the polycarbonate and graphene in an internal mixer, compression-moulding the melt-compounded grinded material and lastly dissolving CO2 inside a high pressure vessel. The CO2 desorption behaviour in the unfilled polycarbonate and nanocomposite was studied in terms of the CO2 saturation concentration and desorption diffusion coefficient, with the graphene-filled nanocomposite displaying a higher CO2 loss rate when compared to the neat polycarbonate. The cellular structure of the foams was found to be highly dependent on the saturation/foaming temperature, with smaller cell sizes being obtained with decreasing the temperature. Another parameter that had an important influence was the residual pressure, with higher residual pressure values resulting in foams with more uniform and regular cells. Description: Originally published as "IOP Conference Series: Materials Science and Engineering", vol. 31, no 1, 2012. DOI:10.1088/1757-899X/31/1/012008. .

Influence of foaming process on the structure-properties relationship of foamed LDPE/silica nanocomposites

Fri, 17 May 2013 13:27:52 GMT

Title: Influence of foaming process on the structure-properties relationship of foamed LDPE/silica nanocomposites Authors: Saiz Arroyo, Cristina; Rodríguez Pérez, Miguel Ángel; Velasco Perero, José Ignacio; Saja, José Antonio de Abstract: In this paper LDPE/silica nanocomposites are foamed by two different processes. First one is the pressure quench method which is based on the use of a physical blowing agent and second one is the improved compression moulding technique. As the latter process uses a chemical blowing agent, both types of foamed nanocomposites will provide very useful information about the relationship between foaming process-microstructure and macroscopic properties. Results have revealed how silica nanoparticles are able to act as nucleating sites during foaming step in both processes; however, the optimum amount of particles strongly depends on the foaming route. Thermal and mechanical properties of solid and foamed nanocomposites have been analyzed by means of thermogravimetric analysis and compression tests. Results have revealed that nanosilica particles act as effective nucleating agents, not only reducing cell size and increasing cell density but also achieving more homogeneous cellular structures. Thermal and mechanical properties are improved due to the presence of silica nanoparticles. It has been found that the improvement degree reached for samples produced using chemical blowing agents is greater than that achieved for samples produced using physical blowing agents.

Estudio de la resistencia a fatiga térmica en moldes de inyección de aluminio utilizando aceros de alta conductividad térmica

Fri, 10 May 2013 13:46:12 GMT

Title: Estudio de la resistencia a fatiga térmica en moldes de inyección de aluminio utilizando aceros de alta conductividad térmica Authors: Molas, Sílvia; Hamasaiid, Anwar; Llobet, Albert; Valls, Isaac; Casellas Padró, Daniel; Riera Colom, María Dolores Abstract: La mayoría de los mecanismos de fallo que determinan la durabilidad de un molde de inyección de aluminio a alta presión están relacionados con las solicitaciones termo-mecánicas de la superficie. En cada ciclo, la superficie de la herramienta está expuest a a elevadas variaciones de temperatura y cargas mecánicas que ocasionan la pérdida de propiedades superficiales (dureza, resistencia, etc.). La variación de las propiedades superficiales y las tensiones termo-mecánicas generadas en los ciclos de inyección inducen la aparición de grietas. A fin de retardar la aparición de estas grietas, se ha desarrollado una nueva generación de aceros de herramienta de trabajo en caliente denominados HTCS® (High Thermal Conductivity Steels) caracterizados por poseer elevados valores de difusividad térmica combinados con elevadas propiedades termo-mecánicas, comparados con los aceros de trabajo en caliente convencionales. Estas propiedades, sobre todo la difusividad térmica elevada, tienen su principal efecto en la reducción de las tensiones superficiales generadas en las herramientas debido a los gradientes térmicos durante el servicio, Esta reducción de tensiones se traduce en un aumento de la vida útil del molde de inyección. En este trabajo se evalúa el efecto de la conductividad térmica del acero de herramientas en la aparición y propagación de grietas por fatiga térmica . Para ello, se han fabricado dos moldes experimenta les de inyección de aluminio a alta presión con la misma geometría y dureza. Un molde se ha fabricado con acero de trabajo en caliente convencional (AISI Hll) y el otro molde con acero de alta conductividad térmica (HTCS®). Se ha realizado el seguimiento de la aparición y propagación de las grietas por fatiga térmica en los dos moldes durante el servicio. Para poder investigar y entender mejor la relación entre las diferencias térmicas y las tensiones superficiales generadas en los dos moldes experimenta les, se ha utilizado un modelo simple de Simulación por Elementos Finitos representativo de una sección del molde real.

Estudio comparativo del conformado en caliente de un acero microaleado usando criterios termodinámicos continuos y criterios fenomenológicos

Fri, 10 May 2013 13:22:35 GMT

Title: Estudio comparativo del conformado en caliente de un acero microaleado usando criterios termodinámicos continuos y criterios fenomenológicos Authors: Alcelay Larrión, José Ignacio; Al Omar Mesnaoui, Anas; Prado Pozuelo, José Manuel Abstract: En las últimas décadas, los mapas de procesado han sido ampliamente utilizados para diseñar, controlar y optimizar los procesos de conformado en caliente. En el presente trabajo, se presenta un estudio comparativo entre mapas de procesado elaborados usando criterios termodinámicos continuos y criterios fenomenológicos. Por ello, se llevaron a cabo ensayos de compresión en caliente en el rango de temperaturas 900 - 1150 ºC y de velocidades de deformación i: = 10-4 - 10 s-1 . El comportamiento en caliente del acero estudiado ha sido estudiado analizando las curvas de fluencia y la interacción entre el comportamiento microestructural y los parámetros de control del proceso de deformación. El estudio comparativo de los mapas de procesado muestra la diferencia entre las posiciones de los distintos dominios de deformación plástica, según el criterio de inestabilidad usado. Además, el análisis de dichos mapas indica que el acero estudiado no sufre ningún tipo de inestabilidad plástica . Sin embargo, los mapas correspondientes a la deformación ¡; = 0,6 revelan la existencia de un dominio de recristalización dinámica, considerado como el dominio más eficiente dentro de la región segura de procesado. Este dominio está centrado a 1150 ºC y 10 s·1.; In the last decades, processing maps have been widely used to design, control and optimize hot forming processes. In this paper, we present a comparative study of processing maps constructed using phenomenological and thermodynamic continuum criteria. Therefore, hot compression tests were carried out in the temperature and strain rate ranging from 900 to 1150 ºC and 10-• to 10 s-1. The hot deformation behavior of studied steel has been investigated analyzing the flow curves and the interaction between the microstructural behavior and parameters control of the deformation process. The comparative study of processing maps show the difference between the positions of plastic deformation domains predicted by the two instability criteria. The analysis of the maps indicates that the steel does not undergo any plastic instability. However, the maps corresponding to deformation E = 0,6 reveal the existence of a domain of dynamic recrystallization, considered the most efficient domain within the safe region processing. This domain is centered at 1150 ºC and 10 s-1.

Simulación de un tratamiento térmico mediante elementos finitos

Fri, 10 May 2013 13:04:34 GMT

Title: Simulación de un tratamiento térmico mediante elementos finitos Authors: Giménez, Maria; Llobet, Albert; Riera Colom, María Dolores; Prado Pozuelo, José Manuel Abstract: En la industria abundan procesos térmicos o termo-mecánicos durante los cuales se producen distorsiones difíciles de predecir y controlar. Las diferentes velocidades de enfriamiento ocasionadas a lo la rgo de la pieza durante el proceso producen una distribución de fases con volumen específico y propiedades mecánicas diferentes, que generan tensiones internas y dichas distorsiones. Incorporar la evolución microest ructura l a la simulación permitiría definir procesos industriales optimizados. El objetivo principal de este trabajo ha sido incorporar a la simulación las transformaciones de fase y las distorsiones que estas producen . Como aplicación concreta se ha simulado el tratamiento térmico de un componente real . Se ha implementado el modelo de JMAK para determinar la evolución de las transformaciones de fase gobernadas por la difusión y el modelo de Koistinen-Marburger para la transformación martensítica. Para obtener el tiempo de incubación de las transformaciones no isotérm icas y el crecimiento de las propias fases se ha utilizado la Regla de Adición. Los coeficientes de expansión térmica de cada una de las fases han sido obtenidos de la bibliografía. Estos modelos se han incorporado mediante subrutinas de usuario. Los resultados obtenidos hacen concluir que los modelos no siempre describen fielmente las transformaciones de fase . La ferrita y la perlita quedan bastante bien modelizadas, sin embargo, para la bainita, tanto el tiempo de incubación como la fracción transformada no quedan bien descritos.

Friction coefficients and wear rates of different orthodontic archwires in artificial saliva

Thu, 09 May 2013 14:46:28 GMT

Title: Friction coefficients and wear rates of different orthodontic archwires in artificial saliva Authors: Alfonso, M.V.; Espinar, Eduardo; Llamas, José María; Rupérez de Gracia, Elisa; Manero Planella, José María; Barrera, J.M; Solano, E.; Gil Mur, Francisco Javier Abstract: The aim of this paper is to analyze the influence of the nature of the orthodontic archwires on the friction coefficient and wear rate against materials used commonly as brackets (Ti–6Al–4V and 316L Stainless Steel). The mate- rials selected as orthodontic archwires were ASI304 stainless steel, NiTi, Ti, TiMo and NiTiCu. The array archwire’s materials selected presented very similar roughness but different hardness. Materials were chosen from lower and higher hardness degrees than that of the brackets. Wear tests were carried out at in artificial saliva at 37 C. Results show a linear relationship between the hardness of the materials and the friction coefficients. The material that showed lower wear rate was the ASI304 stainless steel. To prevent wear, the wire and the brackets have high hardness values and in the same order of magnitude.

Multifunctional nanocomposite foams based on polypropylene with carbon nanofillers

Thu, 09 May 2013 14:05:52 GMT

Title: Multifunctional nanocomposite foams based on polypropylene with carbon nanofillers Authors: Sousa Pais Antunes, Marcelo de; Gedler, Gabriel; Velasco Perero, José Ignacio Abstract: This work considers the preparation and characterization of polypropylene foams with variable concentrations of graphene and carbon nanofibres, focussing on the influence of the foaming process and the nanofillers on the microstructural and dynamic-mechanical- thermal properties of the foams. Great differences were found in terms of foam morphology depending on the type of foaming process, with foams prepared by physical foaming showing a vertically deformed cell structure, while chemical foams presented an isotropic-like cellular structure. The addition of graphene resulted in foams with higher cell densities and more uniform cellular structures when compared to the ones with nanofibres. All these considerations are of extreme importance, as some of the most promising applications of these polymer foams require a good electromagnetic interference shielding efficiency, which greatly depends on the developed foam morphology.

Biphasic calcium sulfate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications : in vitro study

Tue, 07 May 2013 09:56:44 GMT

Title: Biphasic calcium sulfate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications : in vitro study Authors: Vlad, María Daniela; Valle Mendoza, Luis Javier del; Poeata, I.; López López, José; Torres Cámara, Ricardo; Barraco Serra, Marc; Fernández Aguado, Enrique Abstract: In this study, the cytocompatibility of new ‘iron-modified/alpha-tricalcium phosphate (IM/α-TCP) and calcium sulfate dihydrate (CSD)’ bone cement (IM/α-TCP/CSD-BC) intended for spinal applications has been approached. The objective was to investigate by direct-contact osteoblast-like cell cultures (from 1 to 14 days) the in vitro cell adhesion, proliferation, morphology and cytoskeleton organization of MG-63 cells seeded onto the new cements. The results were as follows: (a) quantitative MTT-assay and scanning electron microscopy (SEM) showed that cell adhesion, proliferation and viability were not affected with time by the presence of iron in the cements; (b) double immunofluorescent labeling of F-actin and α-tubulin showed a dynamic interaction between the cell and its porous substrates sustaining the locomotion phenomenon on the cements’ surface, which favored the colonization, and confirming the biocompatibility of the experimental cements; (c) SEM-cell morphology and cytoskeleton observations also evidenced that MG-63 cells were able to adhere, to spread and to attain normal morphology on the new IM/α-TCP/CSD-BC which offered favorable substratum properties for osteoblast-like cells proliferation and differentiation in vitro. The results showed that these new iron-modified cement-like biomaterials have cytocompatible features of interest not only as possible spinal cancellous bone replacement biomaterial but also as bone tissue engineering scaffolds. Description: Premi del "National University Research Council" del Ministeri d'Educació i Recerca de Romania, a autors romanesos per l'impacte de la seva recerca.

Osteogenic biphasic calcium sulphate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications : in vivo study

Tue, 07 May 2013 09:39:32 GMT

Title: Osteogenic biphasic calcium sulphate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications : in vivo study Authors: Vlad, María Daniela; Sindilar, E.V.; Mariñoso, Maria Lluïsa; Poeata, I.; Torres Cámara, Ricardo; López López, José; Barraco Serra, Marc; Fernández Aguado, Enrique Abstract: In this study, the biocompatibility and the osteogenic features of a new iron-modified α-tricalcium phosphate (IM/α-TCP) and calcium sulphate dihydrate (CSD) biphasic cement (IM/α-TCP/CSD-BC) have been investigated in terms of the in vivo cement resorption, bone tissue formation and host tissue response on sheep animal model. Histological evaluation performed on undecalcified cement–bone specimens assessed the in vivo behaviour. It has been shown that the new IM/α-TCP/CSD-BC has the ability to produce firm bone binding in vivo (i.e. bioactivity). Qualitative histology proved cement biocompatibility, osteoconduction and favourable resorption, mainly through a macrophage-mediated mechanism. The results showed that the new cements have biocompatible and osteogenic features of interest as possible cancellous bone replacement biomaterial for minimally invasive spinal surgery applications. Description: Premi del "National University Research Council" del Ministeri d'Educació i Recerca de Romania, a autors romanesos per l'impacte de la seva recerca.

Estudio comparativo de la carrera académica del profesorado en las universidades públicas politécnicas españolas desde un perspectiva de género

Tue, 30 Apr 2013 10:43:15 GMT

Title: Estudio comparativo de la carrera académica del profesorado en las universidades públicas politécnicas españolas desde un perspectiva de género Authors: Marqués Calvo, M. Soledad; Salán Ballesteros, Maria Núria; Gómez, Silvia

Structure-property evaluation of trisilanolphenyl POSS®/polysulfone composites as a guide to POSS melt blending

Mon, 29 Apr 2013 16:56:24 GMT

Title: Structure-property evaluation of trisilanolphenyl POSS®/polysulfone composites as a guide to POSS melt blending Authors: Milliman, Henry; Sánchez Soto, Miguel; Arostegui, Asier; Schiraldi, David A. Abstract: A series of polysulfone/phenyl trisilanol POSS nanocomposites were produced by melt blending by twin screw batch mixing. These materials were then injec- tion molded, and their thermal, mechanical, and morpho- logical properties were tested. The tensile properties of polysulfone were moderately compromised by the addition of phenyl TPOSS, because of the formation of large ( 1 l m) voided POSS aggregates. These domains however did cause the improvement of the impact resistance of the composites as described by the mechanism of crack pinning and bow- ing. Flexural properties remained essentially unchanged, which is attributed to the formation of an aggregate free- skin layer, which formed in the injection molded parts. Thermal behavior of the composites also remained largely unchanged due to the lack of POSS-polymer interactions on the molecular/chain segment scale. Initially, it was hypothesized that a high degree of POSS-polymer interac- tions would be present in these composited based on exami- nation of their chemical structures. This however, was not the case as phase separation was clearly present. This work highlights the need for a better understanding of the predic- tion of POSS-polymer interaction.

High-resolution PLA-based composite scaffolds via 3-D printing technology

Mon, 29 Apr 2013 10:31:29 GMT

Title: High-resolution PLA-based composite scaffolds via 3-D printing technology Authors: Serra, Tiziano; Planell Estany, Josep Anton; Navarro Toro, Melba Eugenia Abstract: Fabrication of new biodegradable scaffolds that guide and stimulate tissue regeneration is still a major issue in tissue engineering approaches. Scaffolds that possess adequate biodegradability, pore size, interconnectivity, bioactivity and mechanical properties in accordance with the injured tissue are required. This work aimed to develop and characterize three-dimensional (3-D) scaffolds that fulfill the aforementioned requirements. For this, a nozzle-based rapid prototyping system was used to combine polylactic acid and a bioactive CaP glass to fabricate 3-D biodegradable scaffolds with two patterns (orthogonal and displaced double layer). Scanning electron microscopy and micro-computer tomography showed that 3-D scaffolds had completely interconnected porosity, uniform distribution of the glass particles, and a controlled and repetitive architecture. Surface properties were also assessed, showing that the incorporation of glass particles increased both the roughness and the hydrophilicity of the scaffolds. Mechanical tests indicated that compression strength is dependent on the scaffold geometry and the presence of glass. Preliminary cell response was studied with primary mesenchymal stem cells (MSC) and revealed that CaP glass improved cell adhesion. Overall, the results showed the suitability of the technique/materials combination to develop 3-D porous scaffolds and their initial biocompatibility, both being valuable characteristics for tissue engineering applications.

Modular polylactic acid microparticle-based scaffolds prepared via microfluidic emulsion/solvent displacement process: Fabrication, characterization, and in vitro mesenchymal stem cells interaction study

Mon, 29 Apr 2013 09:13:27 GMT

Title: Modular polylactic acid microparticle-based scaffolds prepared via microfluidic emulsion/solvent displacement process: Fabrication, characterization, and in vitro mesenchymal stem cells interaction study Authors: Salerno, Aurelio; Levato, R.; Mateos Timoneda, Miguel Angel; Engel López, Elisabeth; Netti, Paolo Antonio; Planell Estany, Josep Anton Abstract: The present study reports a novel approach for the design and fabrication of polylactic acid (PLA) microparticle- based scaffolds with microstructural properties suitable for bone and cartilage regeneration. Macroporous PLA scaffolds with controlled shape were fabricated by means of a semicon- tinuous process involving (1) microfluidic emulsification of a PLA/ethyl lactate solution (5% w/v) in a span 80/paraffin oil so- lution (3% v/v) followed by (2) particles coagulation/assembly in an acetone/water solution for the development of a continu- ous matrix. Porous scaffolds prepared from particles with monomodal or bimodal size distribution, overall porosity ranges from 93 to 96%, interparticles porosity from 41 to 54%, and static compression moduli from 0.3 to 1.4 MPa were man- ufactured by means of flow rate modulation of of the continu- ous phase during emulsion. The biological response of the scaffolds was assessed in vitro by using bone marrow-derived rat mesenchymal stem cells (MSCs). The results demonstrated the ability of the scaffolds to support the extensive and uni- form three-dimensional adhesion, colonization, and prolifera- tion of MSCs within the entire construct

Effect of humidity in charge formation and transport in LDPE

Thu, 18 Apr 2013 16:39:21 GMT

Title: Effect of humidity in charge formation and transport in LDPE Authors: Aragoneses Aguado, Andrés; Tamayo, Ildaberto; Lebrato, Alexander; Cañadas Lorenzo, Juan Carlos; Diego Vives, José Antonio; Arencón Osuna, David; Belana Punseti, Juan