Fabrication and creep properties of eutectic-composition Al2O3/YAG/YSZ sintered composites

Three-phase alumina/YAG/yttria-stabilized cubic zirconia (YSZ) composites were fabricated by a solid-state reaction route starting from commercial powders of Al2O3, Y2O3 and monoclinic ZrO2. The final phases Al2O3, YAG and YSZ were obtained after calcination of the powder mixtures at 1400 °C. Dense bulk composites were obtained after sintering, with a homogeneous microstructure of fine and equiaxed grains with sizes of 1 μm. Compressive mechanical tests were performed at 1300–1450 °C in air at constant load and at constant initial strain rate. A brittle-to-ductile transition was found with increasing temperature. Grain boundary sliding is the main deformation mechanism in the ductile regime, characterized by a stress exponent of 2 and by the absence of dislocation activity and changes in grain morphology. Alumina seems to be the rate-controlling phase owing to the improvement in creep resistance by the presence of yttrium and zirconium of the other two phases.Ministerio de Ciencia e Innovación MAT2009-13979-C03-0

Empirical analysis of the dynamics of remediation between television and the Internet in Spain: the discourses of users

Introducción: Este trabajo se centra en analizar las posibilidades y ámbitos de participación ciudadana en la esfera pública que se desprenden de las dinámicas de remediación entre televisión e internet, particularmente en lo que respecta a las tendencias de expansión y convergencia entre ambos medios. En el escenario actual, la pugna entre televisión e internet se pone de manifiesto en el consumo de los receptores, así como en sus discursos. Objetivo: Conocer la percepción que tienen los receptores en España de la televisión, ya sea en su formato tradicional o por medio de otros cauces y prácticas, así como identificar sus patrones de consumo y determinar en qué medida dichos receptores conocen y utilizan las segundas pantallas y los medios interactivos, o participan en las mismos. Metodología: Siguiendo una metodología cualitativa, basada en 4 grupos de discusión y 2 entrevistas individuales realizadas en España, se ha recabado un amplio espectro de opiniones de un total de 26 sujetos. Resultados y conclusiones: Salvo en los sujetos de mayor edad (más de 65 años), prevalecen las dinámicas de expansión sobre las de convergencia, es decir, los sujetos han añadido otros soportes al consumo de televisión en formato tradicional (especialmente internet y, en concreto, web social 2.0), hasta el punto de sustituirlo parcial o casi totalmente en algunos casos. Sin embargo, o bien desconocen o bien no suelen hacer uso de los mecanismos de participación e interacción que incorporan las transmisiones televisivas.This article analyses the possibilities for citizen participation that have emerged in the public sphere as a result of the remediation dynamics between television and the Internet, particularly regarding the expansion and convergence trends that are taking place in both media. In the current landscape, the rivalry between television and the Internet becomes evident in users’ consumption habits and discourses. Objectives: The article has two objectives: to identify Spanish people’s perception and consumption of television, in its traditional and modern formats and platforms, and to establish the extent to what Spanish people know about and use second screens and other interactive media. Methods: The study is based on a qualitative approach that involves four focus groups and two individual interviews. The opinions of a total of 26 people were taken into account in the study. Results and conclusions: With the exception of people over 65 years of age, expansion dynamics prevail over convergence dynamics among Spanish people. In other words, people have incorporated new platforms and devices (specially the Internet and the social web 2.0) to their consumption of traditional television, to the point that some people have substituted partially and even totally the traditional consumption format. However, people either do not know or do not use the interaction and participation mechanisms that broadcast television has incorporate

Cell dynamics in microfluidic devices under heterogeneous chemotaxis and growth conditions: a mathematical study

As motivated by studies of cellular motility driven by spatiotemporal chemotactic gradients in microdevices, we develop a framework for constructing approximate analytical solutions for the location, speed and cellular densities for cell chemotaxis waves in heterogeneous fields of chemoattractant from the underlying partial differential equation models. In particular, such chemotactic waves are not in general translationally invariant travelling waves, but possess a spatial variation that evolves in time, and may even may oscillate back and forth in time, according to the details of the chemotactic gradients. The analytical framework exploits the observation that unbiased cellular diffusive flux is typically small compared to chemotactic fluxes and is first developed and validated for a range of exemplar scenarios. The framework is subsequently applied to more complex models considering the full dynamics of the chemoattractant and how this may be driven and controlled within a microdevice by considering a range of boundary conditions. In particular, even though solutions cannot be constructed in all cases, a wide variety of scenarios can be considered analytically, firstly providing global insight into the important mechanisms and features of cell motility in complex spatiotemporal fields of chemoattractant. Such analytical solutions also provide a means of rapid evaluation of model predictions, with the prospect of application in computationally demanding investigations relating theoretical models and experimental observation, such as Bayesian parameter estimation.Comment: 32 pages, 11 figure

A Mathematical Modelling Study of Chemotactic Dynamics in Cell Cultures: The Impact of Spatio-temporal Heterogeneity

As motivated by studies of cellular motility driven by spatiotemporal chemotactic gradients in microdevices, we develop a framework for constructing approximate analytical solutions for the location, speed and cellular densities for cell chemotaxis waves in heterogeneous fields of chemoattractant from the underlying partial differential equation models. In particular, such chemotactic waves are not in general translationally invariant travelling waves, but possess a spatial variation that evolves in time, and may even oscillate back and forth in time, according to the details of the chemotactic gradients. The analytical framework exploits the observation that unbiased cellular diffusive flux is typically small compared to chemotactic fluxes and is first developed and validated for a range of exemplar scenarios. The framework is subsequently applied to more complex models considering the chemoattractant dynamics under more general settings, potentially including those of relevance for representing pathophysiology scenarios in microdevice studies. In particular, even though solutions cannot be constructed in all cases, a wide variety of scenarios can be considered analytically, firstly providing global insight into the important mechanisms and features of cell motility in complex spatiotemporal fields of chemoattractant. Such analytical solutions also provide a means of rapid evaluation of model predictions, with the prospect of application in computationally demanding investigations relating theoretical models and experimental observation, such as Bayesian parameter estimation

Discursos sobre participación ciudadana y confianza/desconfianza respecto a la televisión pública en España

En el actual contexto político y social caracterizado por la noción de cambio social, los discursos que emanan de la sociedad española están ineludiblemente marcados, de modo explícito, por una demanda fuerte de participación ciudadana en la esfera pública vía medios de comunicación, y, en un nivel implícito, por una cierta sospecha hacia aquellos medios y el ejercicio de sus funciones. A nivel teórico este trabajo se contextualiza en las dinámicas de remediación entre televisión e Internet (Bolter y Grusin, 2015), así como en los datos de recientes encuestas sobre uso y percepción de televisión y otros medios. Se aplica una metodología cualitativa basada en 4 grupos de discusión y 2 entrevistas individuales realizadas en distintos puntos y contextos sociales de España a fin de recabar un amplio espectro de opiniones de un total de 26 sujetos receptores de televisión pública española. Se realiza un análisis semiótico (formal y de contenido) de los discursos centrados en la televisión pública (organización, soportes, formatos, forma de sus mensajes y dinámicas de relación), con la cual establecen actitudes de crédito o descrédito, confianza o desconfianza. Los sujetos mantienen una actitud de sospecha con respecto a los agentes y estructuras de los medios de comunicación. La verdad se perfila como un objetivo casi inalcanzable cuya consecución conlleva el despliegue de estrategias de cotejo de información procedente de medios tradicionales y remediados

ADQPCI: Data Acquisition Board for Educational purposes

En este trabajo se presenta una de las placas de adquisición de datos que se ha desarrollado con fines docentes para su utilización en prácticas relacionadas con sistemas en tiempo real e informática industrial y se plantean algunas de las ventajas e inconvenientes frente a la utilización de placas comerciales. A lo largo del trabajo se detalla el diseño del hardware, en el que se ha priorizado la facilidad de programación, siendo ésta una de las ventajas frente a las placas comerciales. En estas prácticas es fundamental que el alumno tome conciencia de la importancia de la interfaz hardware-software, si se quiere conseguir un sistema fiable y que explote al máximo las características del hardware. Con el desarrollo de una placa de adquisición de datos se consigue un sistema que el alumno puede utilizar en varias asignaturas de su titulación que están relacionadas con el desarrollo y programación de sistemas empotrados.In this work a data acquisition board developed for educational use in subjects related to real-time systems and industrial computing, is presented. The main advantages and disadvantages of using these boards versus the use of commercial boards are discussed. The hardware design described along this work emphasizes the facility of programming the board, which is one of the main advantages versus the commercial boards. In these practices it is essential that student comprehend the importance of the hardware-software interface in order to obtain a reliable system which exploits in a maximum way the characteristics of the hardware. The development of a data acquisition board allows to obtain a system that the students can use in several course during his university career which are related to the development and programming of embedded system

Hall-Petch strengthening of the constrained metallic binder in WC-Co cemented carbides: Experimental assessment by means of massive nanoindentation and statistical analysis

WC–Co cemented carbides are geometrically complex composites constituted for two interpenetrating networks of the constitutive ceramic and metal phases. Accordingly, assessment of microstructural effects on the local mechanical properties of each phase is a challenging task, especially for the metallic binder. In this work, it is attempted by combining massive nanoindentation, statistical analysis, and implementation of a thin film model for deconvolution of the intrinsic hardness and flow stress of the metallic phase. Plotting of yield stress values as a function of the binder mean free path results in a Hall-Petch strengthening relationship with a slope (ky) of 0.98 MPa m1/2. This value points out the effectiveness of WC–Co phase boundaries as strong obstacles to slip propagation; and thus, for toughening of the brittle phase (WC) by means of crack-bridging ductile (Co) reinforcement.Peer ReviewedPostprint (author's final draft