The unstoppable rise of photovoltaic solar energy: PV vs. PV

Photovoltaic (PV) solar energy has been growing during the last decade an explosive rate. Last year (2011) the solar cell production amounted to more than 37 GW. It is the energy technology most installed nowadays. The power generated by the 37 GW is similar to the one generated by about 7 nuclear units of 1 GW each. The solar industry is already a huge industry dominated by Asian countries led by China. It is not anymore a promise. It is just a reality.

Traditional education vs modern education. What is the impact of teaching techniques' evolution on students learning process?

The main objective of this article is to focus on the analysis of teaching techniques, ranging from the use of the blackboard and chalk in old traditional classes, using slides and overhead projectors in the eighties and use of presentation software in the nineties, to the video, electronic board and network resources nowadays. Furthermore, all the aforementioned, is viewed under the different mentalities in which the teacher conditions the student using the new teaching technique, improving soft skills but maybe leading either to encouragement or disinterest, and including the lack of educational knowledge consolidation at scientific, technology and specific levels. In the same way, we study the process of adaptation required for teachers, the differences in the processes of information transfer and education towards the student, and even the existence of teachers who are not any longer appealed by their work due which has become much simpler due to new technologies and the greater ease in the development of classes due to the criteria described on the new Grade Programs adopted by the European Higher Education Area. Moreover, it is also intended to understand the evolution of students’ profiles, from the eighties to present time, in order to understand certain attitudes, behaviours, accomplishments and acknowledgements acquired over the semesters within the degree Programs. As an Educational Innovation Group, another key question also arises. What will be the learning techniques in the future?. How these evolving matters will affect both positively and negatively on the mentality, attitude, behaviour, learning, achievement of goals and satisfaction levels of all elements involved in universities’ education? Clearly, this evolution from chalk to the electronic board, the three-dimensional view of our works and their sequence, greatly facilitates the understanding and adaptation later on to the business world, but does not answer to the unknowns regarding the knowledge and the full development of achievement’s indicators in basic skills of a degree. This is the underlying question which steers the roots of the presented research.

World fleet vs. Spanish bunkering. Its impact on ECAS areas

On December 17 came into force on community standard marine fuels. Bunker prices are expected to increase, recent statistics support this argument and the difference between the high sulphur (HS) and the low sulphur (LS) marine bunkers will be sustained. Considering also the price difference between the basis-market of Rotterdam with the rest European ports, the expected bunker prices will be higher in the Mediterranean. This paper begins with a review of the current situation in ECAS areas, highlighting the rules to be implemented shortly. The aim of the paper is known the current situation bunkering determine the estimated short term in Spain from world fleet.

Technology and characterization of GaN-HEMTs devices: high temperature and trapping effects

Los transistores de alta movilidad electrónica basados en GaN han sido objeto de una extensa investigación ya que tanto el GaN como sus aleaciones presentan unas excelentes propiedades eléctricas (alta movilidad, elevada concentración de portadores y campo eléctrico crítico alto). Aunque recientemente se han incluido en algunas aplicaciones comerciales, su expansión en el mercado está condicionada a la mejora de varios asuntos relacionados con su rendimiento y habilidad. Durante esta tesis se han abordado algunos de estos aspectos relevantes; por ejemplo, la fabricación de enhancement mode HEMTs, su funcionamiento a alta temperatura, el auto calentamiento y el atrapamiento de carga. Los HEMTs normalmente apagado o enhancement mode han atraído la atención de la comunidad científica dedicada al desarrollo de circuitos amplificadores y conmutadores de potencia, ya que su utilización disminuiría significativamente el consumo de potencia; además de requerir solamente una tensión de alimentación negativa, y reducir la complejidad del circuito y su coste. Durante esta tesis se han evaluado varias técnicas utilizadas para la fabricación de estos dispositivos: el ataque húmedo para conseguir el gate-recess en heterostructuras de InAl(Ga)N/GaN; y tratamientos basados en flúor (plasma CF4 e implantación de F) de la zona debajo de la puerta. Se han llevado a cabo ataques húmedos en heteroestructuras de InAl(Ga)N crecidas sobre sustratos de Si, SiC y zafiro. El ataque completo de la barrera se consiguió únicamente en las muestras con sustrato de Si. Por lo tanto, se puede deducir que la velocidad de ataque depende de la densidad de dislocaciones presentes en la estructura, ya que el Si presenta un peor ajuste del parámetro de red con el GaN. En relación a los tratamientos basados en flúor, se ha comprobado que es necesario realizar un recocido térmico después de la fabricación de la puerta para recuperar la heteroestructura de los daños causados durante dichos tratamientos. Además, el estudio de la evolución de la tensión umbral con el tiempo de recocido ha demostrado que en los HEMTs tratados con plasma ésta tiende a valores más negativos al aumentar el tiempo de recocido. Por el contrario, la tensión umbral de los HEMTs implantados se desplaza hacia valores más positivos, lo cual se atribuye a la introducción de iones de flúor a niveles más profundos de la heterostructura. Los transistores fabricados con plasma presentaron mejor funcionamiento en DC a temperatura ambiente que los implantados. Su estudio a alta temperatura ha revelado una reducción del funcionamiento de todos los dispositivos con la temperatura. Los valores iniciales de corriente de drenador y de transconductancia medidos a temperatura ambiente se recuperaron después del ciclo térmico, por lo que se deduce que dichos efectos térmicos son reversibles. Se han estudiado varios aspectos relacionados con el funcionamiento de los HEMTs a diferentes temperaturas. En primer lugar, se han evaluado las prestaciones de dispositivos de AlGaN/GaN sobre sustrato de Si con diferentes caps: GaN, in situ SiN e in situ SiN/GaN, desde 25 K hasta 550 K. Los transistores con in situ SiN presentaron los valores más altos de corriente drenador, transconductancia, y los valores más bajos de resistencia-ON, así como las mejores características en corte. Además, se ha confirmado que dichos dispositivos presentan gran robustez frente al estrés térmico. En segundo lugar, se ha estudiado el funcionamiento de transistores de InAlN/GaN con diferentes diseños y geometrías. Dichos dispositivos presentaron una reducción casi lineal de los parámetros en DC en el rango de temperaturas de 25°C hasta 225°C. Esto se debe principalmente a la dependencia térmica de la movilidad electrónica, y también a la reducción de la drift velocity con la temperatura. Además, los transistores con mayores longitudes de puerta mostraron una mayor reducción de su funcionamiento, lo cual se atribuye a que la drift velocity disminuye más considerablemente con la temperatura cuando el campo eléctrico es pequeño. De manera similar, al aumentar la distancia entre la puerta y el drenador, el funcionamiento del HEMT presentó una mayor reducción con la temperatura. Por lo tanto, se puede deducir que la degradación del funcionamiento de los HEMTs causada por el aumento de la temperatura depende tanto de la longitud de la puerta como de la distancia entre la puerta y el drenador. Por otra parte, la alta densidad de potencia generada en la región activa de estos transistores conlleva el auto calentamiento de los mismos por efecto Joule, lo cual puede degradar su funcionamiento y Habilidad. Durante esta tesis se ha desarrollado un simple método para la determinación de la temperatura del canal basado en medidas eléctricas. La aplicación de dicha técnica junto con la realización de simulaciones electrotérmicas han posibilitado el estudio de varios aspectos relacionados con el autocalentamiento. Por ejemplo, se han evaluado sus efectos en dispositivos sobre Si, SiC, y zafiro. Los transistores sobre SiC han mostrado menores efectos gracias a la mayor conductividad térmica del SiC, lo cual confirma el papel clave que desempeña el sustrato en el autocalentamiento. Se ha observado que la geometría del dispositivo tiene cierta influencia en dichos efectos, destacando que la distribución del calor generado en la zona del canal depende de la distancia entre la puerta y el drenador. Además, se ha demostrado que la temperatura ambiente tiene un considerable impacto en el autocalentamiento, lo que se atribuye principalmente a la dependencia térmica de la conductividad térmica de las capas y sustrato que forman la heterostructura. Por último, se han realizado numerosas medidas en pulsado para estudiar el atrapamiento de carga en HEMTs sobre sustratos de SiC con barreras de AlGaN y de InAlN. Los resultados obtenidos en los transistores con barrera de AlGaN han presentado una disminución de la corriente de drenador y de la transconductancia sin mostrar un cambio en la tensión umbral. Por lo tanto, se puede deducir que la posible localización de las trampas es la región de acceso entre la puerta y el drenador. Por el contrario, la reducción de la corriente de drenador observada en los dispositivos con barrera de InAlN llevaba asociado un cambio significativo en la tensión umbral, lo que implica la existencia de trampas situadas en la zona debajo de la puerta. Además, el significativo aumento del valor de la resistencia-ON y la degradación de la transconductancia revelan la presencia de trampas en la zona de acceso entre la puerta y el drenador. La evaluación de los efectos del atrapamiento de carga en dispositivos con diferentes geometrías ha demostrado que dichos efectos son menos notables en aquellos transistores con mayor longitud de puerta o mayor distancia entre puerta y drenador. Esta dependencia con la geometría se puede explicar considerando que la longitud y densidad de trampas de la puerta virtual son independientes de las dimensiones del dispositivo. Finalmente se puede deducir que para conseguir el diseño óptimo durante la fase de diseño no sólo hay que tener en cuenta la aplicación final sino también la influencia que tiene la geometría en los diferentes aspectos estudiados (funcionamiento a alta temperatura, autocalentamiento, y atrapamiento de carga). ABSTRACT GaN-based high electron mobility transistors have been under extensive research due to the excellent electrical properties of GaN and its related alloys (high carrier concentration, high mobility, and high critical electric field). Although these devices have been recently included in commercial applications, some performance and reliability issues need to be addressed for their expansion in the market. Some of these relevant aspects have been studied during this thesis; for instance, the fabrication of enhancement mode HEMTs, the device performance at high temperature, the self-heating and the charge trapping. Enhancement mode HEMTs have become more attractive mainly because their use leads to a significant reduction of the power consumption during the stand-by state. Moreover, they enable the fabrication of simpler power amplifier circuits and high-power switches because they allow the elimination of negativepolarity voltage supply, reducing significantly the circuit complexity and system cost. In this thesis, different techniques for the fabrication of these devices have been assessed: wet-etching for achieving the gate-recess in InAl(Ga)N/GaN devices and two different fluorine-based treatments (CF4 plasma and F implantation). Regarding the wet-etching, experiments have been carried out in InAl(Ga)N/GaN grown on different substrates: Si, sapphire, and SiC. The total recess of the barrier was achieved after 3 min of etching in devices grown on Si substrate. This suggests that the etch rate can critically depend on the dislocations present in the structure, since the Si exhibits the highest mismatch to GaN. Concerning the fluorine-based treatments, a post-gate thermal annealing was required to recover the damages caused to the structure during the fluorine-treatments. The study of the threshold voltage as a function of this annealing time has revealed that in the case of the plasma-treated devices it become more negative with the time increase. On the contrary, the threshold voltage of implanted HEMTs showed a positive shift when the annealing time was increased, which is attributed to the deep F implantation profile. Plasma-treated HEMTs have exhibited better DC performance at room temperature than the implanted devices. Their study at high temperature has revealed that their performance decreases with temperature. The initial performance measured at room temperature was recovered after the thermal cycle regardless of the fluorine treatment; therefore, the thermal effects were reversible. Thermal issues related to the device performance at different temperature have been addressed. Firstly, AlGaN/GaN HEMTs grown on Si substrate with different cap layers: GaN, in situ SiN, or in situ SiN/GaN, have been assessed from 25 K to 550 K. In situ SiN cap layer has been demonstrated to improve the device performance since HEMTs with this cap layer have exhibited the highest drain current and transconductance values, the lowest on-resistance, as well as the best off-state characteristics. Moreover, the evaluation of thermal stress impact on the device performance has confirmed the robustness of devices with in situ cap. Secondly, the high temperature performance of InAlN/GaN HEMTs with different layouts and geometries have been assessed. The devices under study have exhibited an almost linear reduction of the main DC parameters operating in a temperature range from room temperature to 225°C. This was mainly due to the thermal dependence of the electron mobility, and secondly to the drift velocity decrease with temperature. Moreover, HEMTs with large gate length values have exhibited a great reduction of the device performance. This was attributed to the greater decrease of the drift velocity for low electric fields. Similarly, the increase of the gate-to-drain distance led to a greater reduction of drain current and transconductance values. Therefore, this thermal performance degradation has been found to be dependent on both the gate length and the gate-to-drain distance. It was observed that the very high power density in the active region of these transistors leads to Joule self-heating, resulting in an increase of the device temperature, which can degrade the device performance and reliability. A simple electrical method have been developed during this work to determine the channel temperature. Furthermore, the application of this technique together with the performance of electro-thermal simulations have enabled the evaluation of different aspects related to the self-heating. For instance, the influence of the substrate have been confirmed by the study of devices grown on Si, SiC, and Sapphire. HEMTs grown on SiC substrate have been confirmed to exhibit the lowest self-heating effects thanks to its highest thermal conductivity. In addition to this, the distribution of the generated heat in the channel has been demonstrated to be dependent on the gate-to-drain distance. Besides the substrate and the geometry of the device, the ambient temperature has also been found to be relevant for the self-heating effects, mainly due to the temperature-dependent thermal conductivity of the layers and the substrate. Trapping effects have been evaluated by means of pulsed measurements in AlGaN and InAIN barrier devices. AlGaN barrier HEMTs have exhibited a de crease in drain current and transconductance without measurable threshold voltage change, suggesting the location of the traps in the gate-to-drain access region. On the contrary, InAIN barrier devices have showed a drain current associated with a positive shift of threshold voltage, which indicated that the traps were possibly located under the gate region. Moreover, a significant increase of the ON-resistance as well as a transconductance reduction were observed, revealing the presence of traps on the gate-drain access region. On the other hand, the assessment of devices with different geometries have demonstrated that the trapping effects are more noticeable in devices with either short gate length or the gate-to-drain distance. This can be attributed to the fact that the length and the trap density of the virtual gate are independent on the device geometry. Finally, it can be deduced that besides the final application requirements, the influence of the device geometry on the performance at high temperature, on the self-heating, as well as on the trapping effects need to be taken into account during the device design stage to achieve the optimal layout.

Vortex pinning vs superconducting wire network: origin of periodic oscillations induced by applied magnetic fields in superconducting films with arrays of nanomagnets

Hybrid magnetic arrays embedded in superconducting films are ideal systems to study the competition between different physical (such as the coherence length) and structural length scales such as are available in artificially produced structures. This interplay leads to oscillation in many magnetically dependent superconducting properties such as the critical currents, resistivity and magnetization. These effects are generally analyzed using two distinct models based on vortex pinning or wire network. In this work, we show that for magnetic dot arrays, as opposed to antidot (i.e. holes) arrays, vortex pinning is the main mechanism for field induced oscillations in resistance R(H), critical current Ic(H), magnetization M(H) and ac-susceptibility χ ac(H) in a broad temperature range. Due to the coherence length divergence at Tc, a crossover to wire network behaviour is experimentally found. While pinning occurs in a wide temperature range up to Tc, wire network behaviour is only present in a very narrow temperature window close to Tc. In this temperature interval, contributions from both mechanisms are operational but can be experimentally distinguished.

Application of low cost technology for the management of irrigation in organic orchards

Throughout history, humans have cyclically return to their old traditions such as the organic orchards. Nowadays, these have been integrated into the modern cities and could supply fresh vegetables to the daily food improving human health. Organic orchards grow crops without pesticides and artificial fertilizers thus, they are respectful with the environment and guarantee the food's safety . In modern society, the application of new technology is a must, in this case to obtain an efficient irrigation. In order to monitor a proper irrigation and save water and energy, soil water content probes are used to measure soil water content. Among them, capacitive probes ,monitored with a specific data logger, are typically used. Most of them, specially the data loggers, are expensive and in many cases are not used. In this work, we have applied the open hardware Arduino to build and program a low cost datalogger for the programming of irrigation in an experimental organic orchard. Results showed that the application of such as low cost technology, which is easily available in the market and easy to understand, everyone can built and program its own device helping in managing water resources in organic orchards .

Silicon PV module customization using laser technology for new BIPV applications

It is well known that lasers have helped to increase efficiency and to reduce production costs in the photovoltaic (PV) sector in the last two decades, appearing in most cases as the ideal tool to solve some of the critical bottlenecks of production both in thin film (TF) and crystalline silicon (c-Si) technologies. The accumulated experience in these fields has brought as a consequence the possibility of using laser technology to produce new Building Integrated Photovoltaics (BIPV) products with a high degree of customization. However, to produce efficiently these personalized products it is necessary the development of optimized laser processes able to transform standard products in customized items oriented to the BIPV market. In particular, the production of semitransparencies and/or freeform geometries in TF a-Si modules and standard c-Si modules is an application of great interest in this market. In this work we present results of customization of both TF a-Si modules and standard monocrystalline (m-Si) and policrystalline silicon (pc-Si) modules using laser ablation and laser cutting processes. A discussion about the laser processes parameterization to guarantee the functionality of the device is included. Finally some examples of final devices are presented with a full discussion of the process approach used in their fabrication.

Microinformática en entornos profesionales : instalación, configuración, mantenimiento y reparación

Los sistemas microinformáticos se componen principalmente de hardware y software, con el paso del tiempo el hardware se degrada, se deteriora y en ocasiones se avería. El software evoluciona, requiere un mantenimiento, de actualización y en ocasiones falla teniendo que ser reparado o reinstalado. A nivel hardware se analizan los principales componentes que integran y que son comunes en gran parte estos sistemas, tanto en equipos de sobre mesa como portátiles, independientes del sistema operativo, además de los principales periféricos, también se analizan y recomiendan algunas herramientas necesarias para realizar el montaje, mantenimiento y reparación de estos equipos. Los principales componentes hardware internos son la placa base, memoria RAM, procesador, disco duro, carcasa, fuente de alimentación y tarjeta gráfica. Los periféricos más destacados son el monitor, teclado, ratón, impresora y escáner. Se ha incluido un apartado donde se detallan los distintos tipos de BIOS y los principales parámetros de configuración. Para todos estos componentes, tanto internos como periféricos, se ha realizado un análisis de las características que ofrecen y los detalles en los que se debe prestar especial atención en el momento de seleccionar uno frente a otro. En los casos que existen diferentes tecnologías se ha hecho una comparativa entre ambas, destacando las ventajas y los inconvenientes de unas frente a otras para que sea el usuario final quien decida cual se ajusta mejor a sus necesidades en función de las prestaciones y el coste. Un ejemplo son las impresoras de inyección de tinta frente a las laser o los discos duros mecánicos en comparación con y los discos de estado sólido (SSD). Todos estos componentes están relacionados, interconectados y dependen unos de otros, se ha dedicado un capítulo exclusivamente para estudiar cómo se ensamblan estos componentes, resaltando los principales fallos que se suelen cometer o producir y se han indicado unas serie tareas de mantenimiento preventivo que se pueden realizar para prolongar la vida útil del equipo y evitar averías por mal uso. Los mantenimientos se pueden clasificar como predictivo, perfectivo, adaptativo, preventivo y correctivo. Se ha puesto el foco principalmente en dos tipos de mantenimiento, el preventivo descrito anteriormente y en el correctivo, tanto software como hardware. El mantenimiento correctivo está enfocado al análisis, localización, diagnóstico y reparación de fallos y averías hardware y software. Se describen los principales fallos que se producen en cada componente, cómo se manifiestan o qué síntomas presentan para poder realizar pruebas específicas que diagnostiquen y acoten el fallo. En los casos que es posible la reparación se detallan las instrucciones a seguir, en otro caso se recomienda la sustitución de la pieza o componente. Se ha incluido un apartado dedicado a la virtualización, una tecnología en auge que resulta muy útil para realizar pruebas de software, reduciendo tiempos y costes en las pruebas. Otro aspecto interesante de la virtualización es que se utiliza para montar diferentes servidores virtuales sobre un único servidor físico, lo cual representa un importante ahorro en hardware y costes de mantenimiento, como por ejemplo el consumo eléctrico. A nivel software se realiza un estudio detallado de los principales problemas de seguridad y vulnerabilidades a los que está expuesto un sistema microinformático enumerando y describiendo el comportamiento de los distintos tipos de elementos maliciosos que pueden infectar un equipo, las precauciones que se deben tomar para minimizar los riesgos y las utilidades que se pueden ejecutar para prevenir o limpiar un equipo en caso de infección. Los mantenimientos y asistencias técnicas, en especial las de tipo software, no siempre precisan de la atención presencial de un técnico cualificado, por ello se ha dedicado un capítulo a las herramientas de asistencia remota que se pueden utilizar en este ámbito. Se describen algunas de las más populares y utilizadas en el mercado, su funcionamiento, características y requerimientos. De esta forma el usuario puede ser atendido de una forma rápida, minimizando los tiempos de respuesta y reduciendo los costes. ABSTRACT Microcomputer systems are basically made up of pieces of hardware and software, as time pass, there’s a degradation of the hardware pieces and sometimes failures of them. The software evolves, new versions appears and requires maintenance, upgrades and sometimes also fails having to be repaired or reinstalled. The most important hardware components in a microcomputer system are analyzed in this document for a laptop or a desktop, with independency of the operating system they run. In addition to this, the main peripherals and devices are also analyzed and a recommendation about the most proper tools necessary for maintenance and repair this kind of equipment is given as well. The main internal hardware components are: motherboard, RAM memory, microprocessor, hard drive, housing box, power supply and graphics card. The most important peripherals are: monitor, keyboard, mouse, printer and scanner. A section has been also included where different types of BIOS and main settings are listed with the basic setup parameters in each case. For all these internal components and peripherals, an analysis of their features has been done. Also an indication of the details in which special attention must be payed when choosing more than one at the same time is given. In those cases where different technologies are available, a comparison among them has been done, highlighting the advantages and disadvantages of selecting one or another to guide the end user to decide which one best fits his needs in terms of performance and costs. As an example, the inkjet vs the laser printers technologies has been faced, or also the mechanical hard disks vs the new solid state drives (SSD). All these components are interconnected and are dependent one to each other, a special chapter has been included in order to study how they must be assembled, emphasizing the most often mistakes and faults that can appear during that process, indicating different tasks that can be done as preventive maintenance to enlarge the life of the equipment and to prevent damage because of a wrong use. The different maintenances can be classified as: predictive, perfective, adaptive, preventive and corrective. The main focus is on the preventive maintains, described above, and in the corrective one, in software and hardware. Corrective maintenance is focused on the analysis, localization, diagnosis and repair of hardware and software failures and breakdowns. The most typical failures that can occur are described, also how they can be detected or the specific symptoms of each one in order to apply different technics or specific tests to diagnose and delimit the failure. In those cases where the reparation is possible, instructions to do so are given, otherwise, the replacement of the component is recommended. A complete section about virtualization has also been included. Virtualization is a state of the art technology that is very useful especially for testing software purposes, reducing time and costs during the tests. Another interesting aspect of virtualization is the possibility to have different virtual servers on a single physical server, which represents a significant savings in hardware inversion and maintenance costs, such as electricity consumption. In the software area, a detailed study has been done about security problems and vulnerabilities a microcomputer system is exposed, listing and describing the behavior of different types of malicious elements that can infect a computer, the precautions to be taken to minimize the risks and the tools that can be used to prevent or clean a computer system in case of infection. The software maintenance and technical assistance not always requires the physical presence of a qualified technician to solve the possible problems, that’s why a complete chapter about the remote support tools that can be used to do so has been also included. Some of the most popular ones used in the market are described with their characteristics and requirements. Using this kind of technology, final users can be served quickly, minimizing response times and reducing costs.

Método experimental para la caracterización de las diferentes tecnologías de integración arquitectónica de la energía fotovoltaica en condiciones de funcionamiento real = Experimental method for characterization of several building integrated photovoltaic technologies under real working conditions

Hoy en día, el proceso de un proyecto sostenible persigue realizar edificios de elevadas prestaciones que son, energéticamente eficientes, saludables y económicamente viables utilizando sabiamente recursos renovables para minimizar el impacto sobre el medio ambiente reduciendo, en lo posible, la demanda de energía, lo que se ha convertido, en la última década, en una prioridad. La Directiva 2002/91/CE "Eficiencia Energética de los Edificios" (y actualizaciones posteriores) ha establecido el marco regulatorio general para el cálculo de los requerimientos energéticos mínimos. Desde esa fecha, el objetivo de cumplir con las nuevas directivas y protocolos ha conducido las políticas energéticas de los distintos países en la misma dirección, centrándose en la necesidad de aumentar la eficiencia energética en los edificios, la adopción de medidas para reducir el consumo, y el fomento de la generación de energía a través de fuentes renovables. Los edificios de energía nula o casi nula (ZEB, Zero Energy Buildings ó NZEB, Net Zero Energy Buildings) deberán convertirse en un estándar de la construcción en Europa y con el fin de equilibrar el consumo de energía, además de reducirlo al mínimo, los edificios necesariamente deberán ser autoproductores de energía. Por esta razón, la envolvente del edifico y en particular las fachadas son importantes para el logro de estos objetivos y la tecnología fotovoltaica puede tener un papel preponderante en este reto. Para promover el uso de la tecnología fotovoltaica, diferentes programas de investigación internacionales fomentan y apoyan soluciones para favorecer la integración completa de éstos sistemas como elementos arquitectónicos y constructivos, los sistemas BIPV (Building Integrated Photovoltaic), sobre todo considerando el próximo futuro hacia edificios NZEB. Se ha constatado en este estudio que todavía hay una falta de información útil disponible sobre los sistemas BIPV, a pesar de que el mercado ofrece una interesante gama de soluciones, en algunos aspectos comparables a los sistemas tradicionales de construcción. Pero por el momento, la falta estandarización y de una regulación armonizada, además de la falta de información en las hojas de datos técnicos (todavía no comparables con las mismas que están disponibles para los materiales de construcción), hacen difícil evaluar adecuadamente la conveniencia y factibilidad de utilizar los componentes BIPV como parte integrante de la envolvente del edificio. Organizaciones internacionales están trabajando para establecer las normas adecuadas y procedimientos de prueba y ensayo para comprobar la seguridad, viabilidad y fiabilidad estos sistemas. Sin embargo, hoy en día, no hay reglas específicas para la evaluación y caracterización completa de un componente fotovoltaico de integración arquitectónica de acuerdo con el Reglamento Europeo de Productos de la Construcción, CPR 305/2011. Los productos BIPV, como elementos de construcción, deben cumplir con diferentes aspectos prácticos como resistencia mecánica y la estabilidad; integridad estructural; seguridad de utilización; protección contra el clima (lluvia, nieve, viento, granizo), el fuego y el ruido, aspectos que se han convertido en requisitos esenciales, en la perspectiva de obtener productos ambientalmente sostenibles, saludables, eficientes energéticamente y económicamente asequibles. Por lo tanto, el módulo / sistema BIPV se convierte en una parte multifuncional del edificio no sólo para ser física y técnicamente "integrado", además de ser una oportunidad innovadora del diseño. Las normas IEC, de uso común en Europa para certificar módulos fotovoltaicos -IEC 61215 e IEC 61646 cualificación de diseño y homologación del tipo para módulos fotovoltaicos de uso terrestre, respectivamente para módulos fotovoltaicos de silicio cristalino y de lámina delgada- atestan únicamente la potencia del módulo fotovoltaico y dan fe de su fiabilidad por un período de tiempo definido, certificando una disminución de potencia dentro de unos límites. Existe también un estándar, en parte en desarrollo, el IEC 61853 (“Ensayos de rendimiento de módulos fotovoltaicos y evaluación energética") cuyo objetivo es la búsqueda de procedimientos y metodologías de prueba apropiados para calcular el rendimiento energético de los módulos fotovoltaicos en diferentes condiciones climáticas. Sin embargo, no existen ensayos normalizados en las condiciones específicas de la instalación (p. ej. sistemas BIPV de fachada). Eso significa que es imposible conocer las efectivas prestaciones de estos sistemas y las condiciones ambientales que se generan en el interior del edificio. La potencia nominal de pico Wp, de un módulo fotovoltaico identifica la máxima potencia eléctrica que éste puede generar bajo condiciones estándares de medida (STC: irradición 1000 W/m2, 25 °C de temperatura del módulo y distribución espectral, AM 1,5) caracterizando eléctricamente el módulo PV en condiciones específicas con el fin de poder comparar los diferentes módulos y tecnologías. El vatio pico (Wp por su abreviatura en inglés) es la medida de la potencia nominal del módulo PV y no es suficiente para evaluar el comportamiento y producción del panel en términos de vatios hora en las diferentes condiciones de operación, y tampoco permite predecir con convicción la eficiencia y el comportamiento energético de un determinado módulo en condiciones ambientales y de instalación reales. Un adecuado elemento de integración arquitectónica de fachada, por ejemplo, debería tener en cuenta propiedades térmicas y de aislamiento, factores como la transparencia para permitir ganancias solares o un buen control solar si es necesario, aspectos vinculados y dependientes en gran medida de las condiciones climáticas y del nivel de confort requerido en el edificio, lo que implica una necesidad de adaptación a cada contexto específico para obtener el mejor resultado. Sin embargo, la influencia en condiciones reales de operación de las diferentes soluciones fotovoltaicas de integración, en el consumo de energía del edificio no es fácil de evaluar. Los aspectos térmicos del interior del ambiente o de iluminación, al utilizar módulos BIPV semitransparentes por ejemplo, son aún desconocidos. Como se dijo antes, la utilización de componentes de integración arquitectónica fotovoltaicos y el uso de energía renovable ya es un hecho para producir energía limpia, pero también sería importante conocer su posible contribución para mejorar el confort y la salud de los ocupantes del edificio. Aspectos como el confort, la protección o transmisión de luz natural, el aislamiento térmico, el consumo energético o la generación de energía son aspectos que suelen considerarse independientemente, mientras que todos juntos contribuyen, sin embargo, al balance energético global del edificio. Además, la necesidad de dar prioridad a una orientación determinada del edificio, para alcanzar el mayor beneficio de la producción de energía eléctrica o térmica, en el caso de sistemas activos y pasivos, respectivamente, podría hacer estos últimos incompatibles, pero no necesariamente. Se necesita un enfoque holístico que permita arquitectos e ingenieros implementar sistemas tecnológicos que trabajen en sinergia. Se ha planteado por ello un nuevo concepto: "C-BIPV, elemento fotovoltaico consciente integrado", esto significa necesariamente conocer los efectos positivos o negativos (en términos de confort y de energía) en condiciones reales de funcionamiento e instalación. Propósito de la tesis, método y resultados Los sistemas fotovoltaicos integrados en fachada son a menudo soluciones de vidrio fácilmente integrables, ya que por lo general están hechos a medida. Estos componentes BIPV semitransparentes, integrados en el cerramiento proporcionan iluminación natural y también sombra, lo que evita el sobrecalentamiento en los momentos de excesivo calor, aunque como componente estático, asimismo evitan las posibles contribuciones pasivas de ganancias solares en los meses fríos. Además, la temperatura del módulo varía considerablemente en ciertas circunstancias influenciada por la tecnología fotovoltaica instalada, la radiación solar, el sistema de montaje, la tipología de instalación, falta de ventilación, etc. Este factor, puede suponer un aumento adicional de la carga térmica en el edificio, altamente variable y difícil de cuantificar. Se necesitan, en relación con esto, más conocimientos sobre el confort ambiental interior en los edificios que utilizan tecnologías fotovoltaicas integradas, para abrir de ese modo, una nueva perspectiva de la investigación. Con este fin, se ha diseñado, proyectado y construido una instalación de pruebas al aire libre, el BIPV Env-lab "BIPV Test Laboratory", para la caracterización integral de los diferentes módulos semitransparentes BIPV. Se han definido también el método y el protocolo de ensayos de caracterización en el contexto de un edificio y en condiciones climáticas y de funcionamiento reales. Esto ha sido posible una vez evaluado el estado de la técnica y la investigación, los aspectos que influyen en la integración arquitectónica y los diferentes tipos de integración, después de haber examinado los métodos de ensayo para los componentes de construcción y fotovoltaicos, en condiciones de operación utilizadas hasta ahora. El laboratorio de pruebas experimentales, que consiste en dos habitaciones idénticas a escala real, 1:1, ha sido equipado con sensores y todos los sistemas de monitorización gracias a los cuales es posible obtener datos fiables para evaluar las prestaciones térmicas, de iluminación y el rendimiento eléctrico de los módulos fotovoltaicos. Este laboratorio permite el estudio de tres diferentes aspectos que influencian el confort y consumo de energía del edificio: el confort térmico, lumínico, y el rendimiento energético global (demanda/producción de energía) de los módulos BIPV. Conociendo el balance de energía para cada tecnología solar fotovoltaica experimentada, es posible determinar cuál funciona mejor en cada caso específico. Se ha propuesto una metodología teórica para la evaluación de estos parámetros, definidos en esta tesis como índices o indicadores que consideran cuestiones relacionados con el bienestar, la energía y el rendimiento energético global de los componentes BIPV. Esta metodología considera y tiene en cuenta las normas reglamentarias y estándares existentes para cada aspecto, relacionándolos entre sí. Diferentes módulos BIPV de doble vidrio aislante, semitransparentes, representativos de diferentes tecnologías fotovoltaicas (tecnología de silicio monocristalino, m-Si; de capa fina en silicio amorfo unión simple, a-Si y de capa fina en diseleniuro de cobre e indio, CIS) fueron seleccionados para llevar a cabo una serie de pruebas experimentales al objeto de demostrar la validez del método de caracterización propuesto. Como resultado final, se ha desarrollado y generado el Diagrama Caracterización Integral DCI, un sistema gráfico y visual para representar los resultados y gestionar la información, una herramienta operativa útil para la toma de decisiones con respecto a las instalaciones fotovoltaicas. Este diagrama muestra todos los conceptos y parámetros estudiados en relación con los demás y ofrece visualmente toda la información cualitativa y cuantitativa sobre la eficiencia energética de los componentes BIPV, por caracterizarlos de manera integral. ABSTRACT A sustainable design process today is intended to produce high-performance buildings that are energy-efficient, healthy and economically feasible, by wisely using renewable resources to minimize the impact on the environment and to reduce, as much as possible, the energy demand. In the last decade, the reduction of energy needs in buildings has become a top priority. The Directive 2002/91/EC “Energy Performance of Buildings” (and its subsequent updates) established a general regulatory framework’s methodology for calculation of minimum energy requirements. Since then, the aim of fulfilling new directives and protocols has led the energy policies in several countries in a similar direction that is, focusing on the need of increasing energy efficiency in buildings, taking measures to reduce energy consumption, and fostering the use of renewable sources. Zero Energy Buildings or Net Zero Energy Buildings will become a standard in the European building industry and in order to balance energy consumption, buildings, in addition to reduce the end-use consumption should necessarily become selfenergy producers. For this reason, the façade system plays an important role for achieving these energy and environmental goals and Photovoltaic can play a leading role in this challenge. To promote the use of photovoltaic technology in buildings, international research programs encourage and support solutions, which favors the complete integration of photovoltaic devices as an architectural element, the so-called BIPV (Building Integrated Photovoltaic), furthermore facing to next future towards net-zero energy buildings. Therefore, the BIPV module/system becomes a multifunctional building layer, not only physically and functionally “integrated” in the building, but also used as an innovative chance for the building envelope design. It has been found in this study that there is still a lack of useful information about BIPV for architects and designers even though the market is providing more and more interesting solutions, sometimes comparable to the existing traditional building systems. However at the moment, the lack of an harmonized regulation and standardization besides to the non-accuracy in the technical BIPV datasheets (not yet comparable with the same ones available for building materials), makes difficult for a designer to properly evaluate the fesibility of this BIPV components when used as a technological system of the building skin. International organizations are working to establish the most suitable standards and test procedures to check the safety, feasibility and reliability of BIPV systems. Anyway, nowadays, there are no specific rules for a complete characterization and evaluation of a BIPV component according to the European Construction Product Regulation, CPR 305/2011. BIPV products, as building components, must comply with different practical aspects such as mechanical resistance and stability; structural integrity; safety in use; protection against weather (rain, snow, wind, hail); fire and noise: aspects that have become essential requirements in the perspective of more and more environmentally sustainable, healthy, energy efficient and economically affordable products. IEC standards, commonly used in Europe to certify PV modules (IEC 61215 and IEC 61646 respectively crystalline and thin-film ‘Terrestrial PV Modules-Design Qualification and Type Approval’), attest the feasibility and reliability of PV modules for a defined period of time with a limited power decrease. There is also a standard (IEC 61853, ‘Performance Testing and Energy Rating of Terrestrial PV Modules’) still under preparation, whose aim is finding appropriate test procedures and methodologies to calculate the energy yield of PV modules under different climate conditions. Furthermore, the lack of tests in specific conditions of installation (e.g. façade BIPV devices) means that it is difficult knowing the exact effective performance of these systems and the environmental conditions in which the building will operate. The nominal PV power at Standard Test Conditions, STC (1.000 W/m2, 25 °C temperature and AM 1.5) is usually measured in indoor laboratories, and it characterizes the PV module at specific conditions in order to be able to compare different modules and technologies on a first step. The “Watt-peak” is not enough to evaluate the panel performance in terms of Watt-hours of various modules under different operating conditions, and it gives no assurance of being able to predict the energy performance of a certain module at given environmental conditions. A proper BIPV element for façade should take into account thermal and insulation properties, factors as transparency to allow solar gains if possible or a good solar control if necessary, aspects that are linked and high dependent on climate conditions and on the level of comfort to be reached. However, the influence of different façade integrated photovoltaic solutions on the building energy consumption is not easy to assess under real operating conditions. Thermal aspects, indoor temperatures or luminance level that can be expected using building integrated PV (BIPV) modules are not well known. As said before, integrated photovoltaic BIPV components and the use of renewable energy is already a standard for green energy production, but would also be important to know the possible contribution to improve the comfort and health of building occupants. Comfort, light transmission or protection, thermal insulation or thermal/electricity power production are aspects that are usually considered alone, while all together contribute to the building global energy balance. Besides, the need to prioritize a particular building envelope orientation to harvest the most benefit from the electrical or thermal energy production, in the case of active and passive systems respectively might be not compatible, but also not necessary. A holistic approach is needed to enable architects and engineers implementing technological systems working in synergy. A new concept have been suggested: “C-BIPV, conscious integrated BIPV”. BIPV systems have to be “consciously integrated” which means that it is essential to know the positive and negative effects in terms of comfort and energy under real operating conditions. Purpose of the work, method and results The façade-integrated photovoltaic systems are often glass solutions easily integrable, as they usually are custommade. These BIPV semi-transparent components integrated as a window element provides natural lighting and shade that prevents overheating at times of excessive heat, but as static component, likewise avoid the possible solar gains contributions in the cold months. In addition, the temperature of the module varies considerably in certain circumstances influenced by the PV technology installed, solar radiation, mounting system, lack of ventilation, etc. This factor may result in additional heat input in the building highly variable and difficult to quantify. In addition, further insights into the indoor environmental comfort in buildings using integrated photovoltaic technologies are needed to open up thereby, a new research perspective. This research aims to study their behaviour through a series of experiments in order to define the real influence on comfort aspects and on global energy building consumption, as well as, electrical and thermal characteristics of these devices. The final objective was to analyze a whole set of issues that influence the global energy consumption/production in a building using BIPV modules by quantifying the global energy balance and the BIPV system real performances. Other qualitative issues to be studied were comfort aspect (thermal and lighting aspects) and the electrical behaviour of different BIPV technologies for vertical integration, aspects that influence both energy consumption and electricity production. Thus, it will be possible to obtain a comprehensive global characterization of BIPV systems. A specific design of an outdoor test facility, the BIPV Env-lab “BIPV Test Laboratory”, for the integral characterization of different BIPV semi-transparent modules was developed and built. The method and test protocol for the BIPV characterization was also defined in a real building context and weather conditions. This has been possible once assessed the state of the art and research, the aspects that influence the architectural integration and the different possibilities and types of integration for PV and after having examined the test methods for building and photovoltaic components, under operation conditions heretofore used. The test laboratory that consists in two equivalent test rooms (1:1) has a monitoring system in which reliable data of thermal, daylighting and electrical performances can be obtained for the evaluation of PV modules. The experimental set-up facility (testing room) allows studying three different aspects that affect building energy consumption and comfort issues: the thermal indoor comfort, the lighting comfort and the energy performance of BIPV modules tested under real environmental conditions. Knowing the energy balance for each experimented solar technology, it is possible to determine which one performs best. A theoretical methodology has been proposed for evaluating these parameters, as defined in this thesis as indices or indicators, which regard comfort issues, energy and the overall performance of BIPV components. This methodology considers the existing regulatory standards for each aspect, relating them to one another. A set of insulated glass BIPV modules see-through and light-through, representative of different PV technologies (mono-crystalline silicon technology, mc-Si, amorphous silicon thin film single junction, a-Si and copper indium selenide thin film technology CIS) were selected for a series of experimental tests in order to demonstrate the validity of the proposed characterization method. As result, it has been developed and generated the ICD Integral Characterization Diagram, a graphic and visual system to represent the results and manage information, a useful operational tool for decision-making regarding to photovoltaic installations. This diagram shows all concepts and parameters studied in relation to each other and visually provides access to all the results obtained during the experimental phase to make available all the qualitative and quantitative information on the energy performance of the BIPV components by characterizing them in a comprehensive way.

La implementación arquitectónica de los acristalamientos activos con agua circulante, y su contribución en edificios de consumo de energía casi nulo

La presente Tesis Doctoral evalúa la contribución de una fachada activa, constituida por acristalamientos con circulación de agua, en el rendimiento energético del edificio. Con especial énfasis en la baja afección sobre su imagen, su integración ha de favorecer la calificación del edificio con el futuro estándar de Edificio de consumo de Energía Casi Nulo (EECN). El propósito consiste en cuantificar su aportación a limitar la demanda de climatización, como solución de fachada transparente acorde a las normas de la energía del 2020. En el primer capítulo se introduce el planteamiento del problema. En el segundo capítulo se desarrollan la hipótesis y el objetivo fundamental de la investigación. Para tal fin, en el tercer capítulo, se revisa el estado del arte de la tecnología y de la investigación científica, mediante el análisis de la literatura de referencia. Se comparan patentes, prototipos, sistemas comerciales asimilables, investigaciones en curso en Universidades, y proyectos de investigación y desarrollo, sobre envolventes que incorporan acristalamientos con circulación de agua. El método experimental, expuesto en el cuarto capítulo, acomete el diseño, la fabricación y la monitorización de un prototipo expuesto, durante ciclos de ensayos, a las condiciones climáticas de Madrid. Esta fase ha permitido adquirir información precisa sobre el rendimiento del acristalamiento en cada orientación de incidencia solar, en las distintas estaciones del año. En paralelo, se aborda el desarrollo de modelos teóricos que, mediante su asimilación a soluciones multicapa caracterizadas en las herramientas de simulación EnergyPlus y IDA-ICE (IDA Indoor Climate and Energy), reproducen el efecto experimental. En el quinto capítulo se discuten los resultados experimentales y teóricos, y se analiza la respuesta del acristalamiento asociado a un determinado volumen y temperatura del agua. Se calcula la eficiencia en la captación de la radiación y, mediante la comparativa con un acristalamiento convencional, se determina la reducción de las ganancias solares y las pérdidas de energía. Se comparan el rendimiento del acristalamiento, obtenido experimentalmente, con el ofrecido por paneles solares fototérmicos disponibles en el mercado. Mediante la traslación de los resultados experimentales a casos de células de tamaño habitable, se cuantifica la afección del acristalamiento sobre el consumo en refrigeración y calefacción. Diferenciando cada caso por su composición constructiva y orientación, se extraen conclusiones sobre la reducción del gasto en climatización, en condiciones de bienestar. Posteriormente, se evalúa el ahorro de su incorporación en un recinto existente, de construcción ligera, localizado en la Escuela de Arquitectura de la Universidad Politécnica de Madrid (UPM). Mediante el planteamiento de escenarios de rehabilitación energética, se estima su compatibilidad con un sistema de climatización mediante bomba de calor y extracción geotérmica. Se describe el funcionamiento del sistema, desde la perspectiva de la operación conjunta de los acristalamientos activos e intercambio geotérmico, en nuestro clima. Mediante la parametrización de sus funciones, se estima el beneficio adicional de su integración, a partir de la mejora del rendimiento de la bomba de calor COP (Coefficient of Performance) en calefacción, y de la eficiencia EER (Energy Efficiency Ratio) en refrigeración. En el recinto de la ETSAM, se ha analizado la contribución de la fachada activa en su calificación como Edificio de Energía Casi Nula, y estudiado la rentabilidad económica del sistema. En el sexto capítulo se exponen las conclusiones de la investigación. A la fecha, el sistema supone alta inversión inicial, no obstante, genera elevada eficiencia con bajo impacto arquitectónico, reduciéndose los costes operativos, y el dimensionado de los sistemas de producción, de mayor afección sobre el edificio. Mediante la envolvente activa con suministro geotérmico no se condena la superficie de cubierta, no se ocupa volumen útil por la presencia de equipos emisores, y no se reduce la superficie o altura útil a base de reforzar los aislamientos. Tras su discusión, se considera una alternativa de valor en procesos de diseño y construcción de Edificios de Energía Casi Nulo. Se proponen líneas de futuras investigación cuyo propósito sea el conocimiento de la tecnología de los acristalamientos activos. En el último capítulo se presentan las actividades de difusión de la investigación. Adicionalmente se ha proporcionado una mejora tecnológica a las fachadas activas existentes, que ha derivado en la solicitud de una patente, actualmente en tramitación. ABSTRACT This Thesis evaluates the contribution of an active water flow glazing façade on the energy performance of buildings. Special emphasis is made on the low visual impact on its image, and the active glazing implementation has to encourage the qualification of the building with the future standard of Nearly Zero Energy Building (nZEB). The purpose is to quantify the façade system contribution to limit air conditioning demand, resulting in a transparent façade solution according to the 2020 energy legislation. An initial approach to the problem is presented in first chapter. The second chapter develops the hypothesis and the main objective of the research. To achieve this purpose, the third chapter reviews the state of the art of the technology and scientific research, through the analysis of reference literature. Patents, prototypes, assimilable commercial systems, ongoing research in other universities, and finally research and development projects incorporating active fluid flow glazing are compared. The experimental method, presented in fourth chapter, undertakes the design, manufacture and monitoring of a water flow glazing prototype exposed during test cycles to weather conditions in Madrid. This phase allowed the acquisition of accurate information on the performance of water flow glazing on each orientation of solar incidence, during different seasons. In parallel, the development of theoretical models is addressed which, through the assimilation to multilayer solutions characterized in the simulation tools EnergyPlus and IDA-Indoor Climate and Energy, reproduce the experimental effect. Fifth chapter discusses experimental and theoretical results focused to the analysis of the active glazing behavior, associated with a specific volume and water flow temperature. The efficiency on harvesting incident solar radiation is calculated, and, by comparison with a conventional glazing, the reduction of solar gains and energy losses are determined. The experimental performance of fluid flow glazing against the one offered by photothermal solar panels available on the market are compared. By translating the experimental and theoretical results to cases of full-size cells, the reduction in cooling and heating consumption achieved by active fluid glazing is quantified. The reduction of energy costs to achieve comfort conditions is calculated, differentiating each case by its whole construction composition and orientation. Subsequently, the saving of the implementation of the system on an existing lightweight construction enclosure, located in the School of Architecture at the Polytechnic University of Madrid (UPM), is then calculated. The compatibility between the active fluid flow glazing and a heat pump with geothermal heat supply system is estimated through the approach of different energy renovation scenarios. The overall system operation is described, from the perspective of active glazing and geothermal heat exchange combined operation, in our climate. By parameterization of its functions, the added benefit of its integration it is discussed, particularly from the improvement of the heat pump performance COP (Coefficient of Performance) in heating and efficiency EER (Energy Efficiency Ratio) in cooling. In the case study of the enclosure in the School of Architecture, the contribution of the active glazing façade in qualifying the enclosure as nearly Zero Energy Building has been analyzed, and the feasibility and profitability of the system are studied. The sixth chapter sets the conclusions of the investigation. To date, the system may require high initial investment; however, high efficiency with low architectural impact is generated. Operational costs are highly reduced as well as the size and complexity of the energy production systems, which normally have huge visual impact on buildings. By the active façade with geothermal supply, the deck area it is not condemned. Useful volume is not consumed by the presence of air-conditioning equipment. Useful surface and room height are not reduced by insulation reinforcement. After discussion, water flow glazing is considered a potential value alternative in nZEB design and construction processes. Finally, this chapter proposes future research lines aiming to increase the knowledge of active water flow glazing technology. The last chapter presents research dissemination activities. Additionally, a technological improvement to existing active facades has been developed, which has resulted in a patent application, currently in handling process.

Neural mechanisms underlying binocular fusion and stereopsis: Position vs. phase

The visual system utilizes binocular disparity to discriminate the relative depth of objects in space. Since the striate cortex is the first site along the central visual pathways at which signals from the left and right eyes converge onto a single neuron, encoding of binocular disparity is thought to begin in this region. There are two possible mechanisms for encoding binocular disparity through simple cells in the striate cortex: a difference in receptive field (RF) position between the two eyes (RF position disparity) and a difference in RF profile between the two eyes (RF phase disparity). Although there have been studies supporting each of the two encoding mechanisms, both mechanisms have not been examined in a single study. Therefore, the relative roles of the two mechanisms have not been determined. To address this issue, we have mapped left and right eye RFs of simple cells in the cat’s striate cortex using binary m-sequence noise, and then we have estimated RF position and phase disparities. We find that RF position disparities are generally limited to small values that are not sufficient to encode large binocular disparities. In contrast, RF phase disparities cover a wide range of binocular disparities and exhibit dependencies on orientation and spatial frequency in a manner expected for a mechanism that encodes binocular disparity. These results indicate that binocular disparity is mainly encoded through RF phase disparity. However, RF position disparity may play a significant role for cells with high spatial frequency selectivity, which are constrained to small RF phase disparities.

Filtros na rede: das relações entre discurso e tecnologia

A fim de refletirmos sobre as condições de produção na contemporaneidade, propomos discussões e análises em torno do funcionamento dos recursos de personalização de conteúdos na Internet que impõem filtros aos usuários. Para isso, mobilizamos a teoria de Análise do Discurso de linha francesa, sobretudo a partir dos trabalhos de Michel Pêcheux. Delimitamos a observação do funcionamento de tais recursos no mecanismo de busca do Google, uma vez que ele representa uma das maiores corporações na Internet e detém a maior parte do mercado de buscas. A partir dessa delimitação, selecionamos o corpus de análise oriundo da política de privacidade do buscador, de definições dadas pela empresa sobre o funcionamento de tais recursos e de relatos sobre esse funcionamento postados por usuários e disseminados na rede. Acreditamos que a análise do funcionamento dessas técnicas nos dizem sobre as condições de produção do discurso na contemporaneidade, bem como das materialidades discursivas que lhes são peculiares, compreendendo que é pela influência materialista que se chega, na Análise do Discurso, a noção de materialidade discursiva. Temos, dessa forma, contemplada uma discussão sobre história, sujeito e língua que fundamenta o funcionamento da ideologia. Ainda nesse ínterim, propomos pensar o discurso ressaltando o que concerne à memória, bem como as questões que decorrem ao considerarmos seu funcionamento perpassado pelas Tecnologias de Informação e Comunicação (TIC\'s), o que nos move a refletir sobre o discurso eletrônico e a memória metálica. Tudo isso nos mostra os efeitos discursivos dos filtros que giram em torno do controle na rede, característica que tem marcado as relações de poder no cenário atual.

MDD vs. traditional software development: a practitioner’s subjective perspective

Context: Today’s project managers have a myriad of methods to choose from for the development of software applications. However, they lack empirical data about the character of these methods in terms of usefulness, ease of use or compatibility, all of these being relevant variables to assess the developer’s intention to use them. Objective: To compare three methods, each following a different paradigm (Model-Driven, Model-Based and Code-Centric) with respect to their adoption potential by junior software developers engaged in the development of the business layer of a Web 2.0 application. Method: We have conducted a quasi-experiment with 26 graduate students of the University of Alicante. The application developed was a Social Network, which was organized around a fixed set of modules. Three of them, similar in complexity, were used for the experiment. Subjects were asked to use a different method for each module, and then to answer a questionnaire that gathered their perceptions during such use. Results: The results show that the Model-Driven method is regarded as the most useful, although it is also considered the least compatible with previous developers’ experiences. They also show that junior software developers feel comfortable with the use of models, and that they are likely to use them if the models are accompanied by a Model-Driven development environment. Conclusions: Despite their relatively low level of compatibility, Model-Driven development methods seem to show a great potential for adoption. That said, however, further experimentation is needed to make it possible to generalize the results to a different population, different methods, other languages and tools, different domains or different application sizes.

Appropriating Bimby on the Internet: Perspectives on technology mediated meals by a virtual brand community

It was Christmas day when an intriguing news piece about a kitchen technology was published in the Wall Street Journal in 2013 (Kowsmann, 2013). Immediately after, the piece went viral in the Portuguese (social) media (TV, blogs, press). It reported an odd 'obsession' of Portuguese consumers with a pricey German-made kitchen appliance - the Bimby (Figure 7.1) - during a difficult period of 'painful budget slashing in return for an international bailout'. The news piece served to unveil the irony: how come ''Western Europe's poorest country' could afford such an expensive technology 'that outsells high-end iPads [...] and is more popular on Facebook than the country's best-known rock band?' The journalistic piece advanced explanations for this technology craze: 'But the Portuguese love gadgets and seem determined, despite hard times, to maintain their tradition of regularly getting together for dinner. In this explanatory attempt, Bimby is portrayed as an intermediary that opens up the possibility for thinking about meal practices in a particular way, in this case, linking nation and meals through ideas around commensality.

The Opportunity Costs of STEM Degrees and the Unmet Needs of the Low-Skilled: Two labour market problems explained. CEPS Policy Brief No. 295, 26 June 2013

There is general consensus that to achieve employment growth, especially for vulnerable groups, it is not sufficient to simply kick-start economic growth: skills among both the high- and low-skilled population need to be improved. In particular, we argue that if the lack of graduates in science, technology, engineering and mathematics (STEM) is a true problem, it needs to be tackled via incentives and not simply via public campaigns: students are not enrolling in ‘hard-science’ subjects because the opportunity cost is very high. As far as the low-skilled population is concerned, we encourage EU and national policy-makers to invest in a more comprehensive view of this phenomenon. The ‘low-skilled’ label can hide a number of different scenarios: labour market detachment, migration, and obsolete skills that are the result of macroeconomic structural changes. For this reason lifelong learning is necessary to keep up with new technology and to shield workers from the risk of skills obsolescence and detachment from the labour market.