Evaluación del potencial fotovoltaico del Campus Sur de la Universidad Politécnica de Madrid

El presente proyecto engloba el estudio del potencial fotovoltaico del Campus Sur de la Universidad Politécnica de Madrid. Este estudio se divide en tres partes. En primer lugar, se calcula la productividad del campus. En segundo lugar, se diseña la disposición de los generadores fotovoltaicos en los terrenos disponibles. Como paso final, se realiza un estudio económico de distintos supuestos. Para realizar los cálculos de productividad, se utiliza IESPRO, un programa desarrollado en Matlab©, junto con una aplicación complementaria desarrollada en el mismo lenguaje. Gracias a estos dos software es posible obtener una estimación muy realista de la energía anual generada. El aprovechamiento del terreno se estudia con la ayuda del software libre Sketchup©. Gracias a esta aplicación, es posible la reconstrucción del Campus Sur en 3D. Dicha reconstrucción incluye edificaciones y vegetación, facilitando la distribución de los generadores fotovoltaicos en todas las zonas, pudiendo evitar zonas con sombreado o no aptas para la instalación, y maximizando la utilización del terreno. El conjunto de los análisis anteriores permiten determinar el rendimiento energético del Campus Sur en sus distintas configuraciones, es decir, únicamente instalando generadores fotovoltaicos en las azoteas de los edificios, o la instalación en todo el terreno disponible, el cual incluye las azoteas y los descampados. Este rendimiento energético, comparado con el consumo anual de todo el campus, permite estimar el coste financiero de llevar a cabo la instalación y su rentabilidad, todo ello detallado en el estudio económico. El estudio económico se basa en dos supuestos, el primero de ellos, únicamente tiene en cuenta la instalación en las azoteas de los edificios. El segundo estudio, incluye los descampados y las azoteas. Con estos dos estudios se puede verificar la viabilidad del proyecto, facilitando datos concretos sobre las ventajas de cada uno de ellos. ABSTRACT. The aim of this work is to study the photovoltaic potential in the South Campus of the Polytechnic University of Madrid. The work has been divided into three parts. The first one is focused on the calculus of the solar harvesting productivity of the South Campus. The second part is centered in the development of the complete photovoltaic system layout design, taking into account the available placement. In the third part, an economic study considering several different scenarios is carried out. In order to calculate the solar productivity, the MATLAB based software tool IESPRO together with a complementary application developed in MATLAB as well, have been used. These programs allow to obtain an accurate estimation of the generated annual energy. The land use is studied with the help of free software SketchUp. With this application, it is possible to rebuild the South Campus in 3D. This reconstruction includes: buildings and vegetation, facilitating the distribution of photovoltaic generators in all areas, to avoid shaded or unsuitable areas for the installation, and maximizing land use. All the above analysis allow determining the energy efficiency of the South Campus for two different configurations, i.e., installing solar photovoltaic arrays only on the roofs of the buildings, or installing solar photovoltaic arrays throughout the land available, including vacant lots and rooftops. The facilities final cost and the cost effectiveness are estimated by comparing the energy efficiency with the South Campus total consumption. This study is based on two different scenarios: the first one considers the solar arrays installation in the buildings roofs, and the second one includes in the layout the vacant lots and rooftops. These studies allow verifying the feasibility of the project, and provide specific information related to the advantages and drawbacks of each scenario.

Sistema para cambiar la geometría de un motor

En este proyecto se desarrolla un sistema electrónico para variar la geometría de un motor de un monoplaza que participa en la competición Fórmula SAE. Fórmula SAE es una competición de diseño de monoplazas para estudiantes, organizado por “Society of Automotive Enginners” (SAE). Este concurso busca la innovación tecnológica de la automoción, así como que estudiantes participen en un trabajo real, en el cual el objetivo es obtener resultados competitivos cumpliendo con una serie de requisitos. La variación de la geometría de un motor en un vehículo permite mejorar el rendimiento del monoplaza consiguiendo elevar el par de potencia del motor. Cualquier mejora en del vehículo en un ámbito de competición puede resultar determinante en el desenlace de la misma. El objetivo del proyecto es realizar esta variación mediante el control de la longitud de los tubos de admisión de aire o “runners” del motor de combustión, empleando un motor lineal paso a paso. A partir de la información obtenida por sensores de revoluciones del motor de combustión y la posición del acelerador se debe controlar la distancia de dichos tubos. Integrando este sistema en el bus CAN del vehículo para que comparta la información medida al resto de módulos. Por todo esto se realiza un estudio aclarando los aspectos generales del objetivo del trabajo, para la comprensión del proyecto a realizar, las posibilidades de realización y adquisición de conocimientos para un mejor desarrollo. Se presenta una solución basada en el control del motor lineal paso a paso mediante el microcontrolador PIC32MX795F512-L. Dispositivo del fabricante Microchip con una arquitectura de 32 bits. Este dispone de un módulo CAN integrado y distintos periféricos que se emplean en la medición de los sensores y actuación sobre el motor paso a paso empleando el driver de Texas Instruments DRV8805. Entonces el trabajo se realiza en dos líneas, una parte software de programación del control del sistema, empleando el software de Microchip MPLABX IDE y otra parte hardware de diseño de una PCB y circuitos acondicionadores para la conexión del microcontrolador, con los sensores, driver, motor paso a paso y bus CAN. El software empleado para la realización de la PCB es Orcad9.2/Layout. Para la evaluación de las medidas obtenidas por los sensores y la comprobación del bus CAN se emplea el kit de desarrollo de Microchip, MCP2515 CAN Bus Monitor Demo Board, que permite ver la información en el bus CAN e introducir tramas al mismo. ABSTRACT. This project develops an electronic system to vary the geometry of a car engine which runs the Formula SAE competition. Formula SAE is a design car competition for students, organized by "Society of Automotive Engineers" (SAE). This competition seeks technological innovation in the automotive industry and brings in students to participate in a real job, in which the objective is to obtain competitive results in compliance with certain requirements. Varying engine’s geometry in a vehicle improves car’s performance raising engine output torque. Any improvement in the vehicle in a competition field can be decisive in the outcome of it. The goal of the project is the variation by controlling the length of the air intake pipe or "runners" in a combustion engine, using a linear motor step. For these, uses the information gathered by speed sensors from the combustion engine and by the throttle position to control the distance of these tubes. This system is integrated in the vehicle CAN bus to share the information with the other modules. For all this is made a study to clarify the general aspects of the project in order to understand the activities developed inside the project, the different options available and also, to acquire knowledge for a better development of the project. The solution is based on linear stepper motor control by the microcontroller PIC32MX795F512-L. Device from manufacturer Microchip with a 32-bit architecture. This module has an integrated CAN various peripherals that are used in measuring the performance of the sensors and drives the stepper motor using Texas Instruments DRV8805 driver. Then the work is done in two lines, first, control programming software system using software MPLABX Microchip IDE and, second, hardware design of a PCB and conditioning circuits for connecting the microcontroller, with sensors, driver stepper motor and CAN bus. The software used to carry out the PCB is Orcad9.2/Layout. For the evaluation of the measurements obtained by the sensors and CAN bus checking is used Microchip development kit, MCP2515 CAN Bus Monitor Demo Board, that allows you to see the information on the CAN bus and enter new frames in the bus.

Tutoriales multimedia para sistemas de telecomunicación

Este Proyecto Fin de Carrera está destinado a la ilustración y aprendizaje del uso de varios dispositivos de los laboratorios del Departamento de Ingeniería Audiovisual y Comunicaciones, de la Escuela Universitaria de Ingeniería Técnica de Telecomunicación, de la Universidad Politécnica de Madrid, en forma de vídeos tutoriales basados en mediciones y prácticas habituales de las asignaturas del departamento para que puedan ser utilizados por los alumnos de la escuela como apoyo a las explicaciones del profesor en ocasiones puntuales. En concreto se han realizado hasta seis vídeos tutoriales en los que se explica: el diseño de un circuito impreso y la creación y fabricación de éste. Por otro lado, también se ha explicado el fenómeno del ruido de fase y cómo es el proceso de su medida, como una de las muchas características de un analizador de espectros. A modo de análisis, se ha realizado otro tutorial acerca de la modulación en FM, sus características y sus aplicaciones. Por último se ha hecho un estudio del comportamiento de un analizador de redes, exponiendo su funcionamiento y explicando su proceso de calibración. Para la realización de estos tutoriales se han utilizado diferentes aplicaciones sobre creación de vídeos multimedia, animación, producción de audio y narración. En especial se han usado: Sprint-Layout 5.0, Adobe Flash Professional CS5.5, Camtasia studio 7, Corel VideoStudio Pro X4, Loquendo TTS7 y WinPlot. Para el apartado de las grabaciones de las diferentes escenas se ha necesitado el uso de distintos instrumentos de medida del laboratorio tales como: analizador de espectros, analizador de redes, generador de señal, generador de funciones, osciloscopio y otros equipos adicionales como: cámara de vídeo y trípode del departamento. Para la composición de los diferentes tutoriales se ha comenzado creando un guion, para cada uno de ellos, estableciendo la aparición de las imágenes, vídeos, y locución. A continuación se exponen los diferentes temas en los que se han basado estos tutoriales de laboratorio, uno a uno. ABSTRACT. This Project is destined to learn the use of several devices at the laboratory of “Ingeniería Audiovisual y Comunicaciones” Department at “Escuela Universitaria de Ingeniería técnica de Telecomunicaciones” of “Universidad Politécnica de Madrid”, on the way as tutorial videos base on the subjects from this department to be used by the college students as help of the teacher’s explanations. In this project you will find up to six tutorial videos, showing: printed circuit design, printed circuit board manufacture. You can also find an explanation about the phenomenon of phase noise and how it’s its measurement process, as one of the many features of a spectrum analyzer. Another tutorial video is based on FM modulation, its features and applications. The last tutorial explains the networks analyzer functionalities and its calibration process. To carry out these tutorials different applications have been used to create multimedia videos, animation, audio production and storytelling. Such as Sprint Layout 5.0, Camtasia 7.0, Corel VideoStudio Pro X4, Adobe Flash Professional CS5.5, Loquendo TTS7 y WinPlot. About the recording side of the different scenes, several equipment have been required at the laboratory, such as spectrums analyzer, signal generator, oscilloscope, function generator, network analyzer and other additional devices, such as: a video camera with its tripod. The composition of the different tutorials has begun creating a script, for each of them, setting the times of appearance of images, video, speech and music. After this abstract, the different topics of the tutorials are showed, one by one.

An approach to a model of the visual cortex: disorders of vision

One of the most challenging problems that must be solved by any theoretical model purporting to explain the competence of the human brain for relational tasks is the one related with the analysis and representation of the internal structure in an extended spatial layout of múltiple objects. In this way, some of the problems are related with specific aims as how can we extract and represent spatial relationships among objects, how can we represent the movement of a selected object and so on. The main objective of this paper is the study of some plausible brain structures that can provide answers in these problems. Moreover, in order to achieve a more concrete knowledge, our study will be focused on the response of the retinal layers for optical information processing and how this information can be processed in the first cortex layers. The model to be reported is just a first trial and some major additions are needed to complete the whole vision process.

La arquitectura residencial en El Real Sitio de El Pardo (1885 - 1965): Orígenes, tipos y configuración del trazado urbano

Tras la denominación de Real Sitio a mediados del siglo XVIII, bajo el reinado de Fernando VI, su sucesor Carlos III procedió a la incorporación a su Patrimonio de todos los Montes y Bosques de El Pardo. Comenzó entonces el proceso de planeamiento urbano y de construcción arquitectónica que finalizó en torno al año 1800. En lo sucesivo, no sólo se mantiene el curso de la conservación y consolidación de los edificios principales, sino que se realiza obra nueva de índole civil. Algunos edificios cambiaron de propiedad y de uso hasta que tras la Guerra Civil se procedió a la mayor transformación vivida por el Real Sitio. El intervalo que aquí se trata (1885 a 1965), no ha suscitado, en los estudios sobre El Pardo, atención suficiente al no acontecer obra nueva de carácter patrimonial ni ha sido objeto de análisis el trazado y la fisonomía del centro urbano residencial del pueblo que Carlos III configuró. Sin embargo se estima relevante analizar los cambios en la actividad residencial; en primer lugar porque coexiste con la arquitectura oficial y, por tanto, se entiende necesario un análisis global del conjunto y en segundo lugar porque facilita la comprensión sobre la imagen original de carácter histórico del conjunto de finales del siglo XVIII. Este marco temporal determina tres partes principales de estudio que estructuran la presente tesis, cuyas fechas establecen los intervalos históricos clave: Actuaciones sobre el núcleo urbano consolidado (1885-1931). Cese de la actividad constructiva (1931-1939). Propuestas regeneradoras y crecimiento acelerado (1939-1965). Dentro de ellos se establecen, a su vez, dos subcapítulos diferenciados con la finalidad de explicar los sucesos que pautaron los cambios trascendentales en la historia de El Pardo. En el estudio del estado de la cuestión se observa que en El Pardo, al igual que sucede en otros Reales Sitios, se investigan los edificios destacados como el Palacio, la Casita del Príncipe, la Casa de Oficios y la Casa de Infantes desde el punto de vista de su historia pero no desde la arquitectura ni de cómo esta afecta al desarrollo del trazado y por tanto al contexto urbano. Se manifiestan determinadas carencias de tratamiento gráfico que facilitarían la comprensión histórica mediante el análisis de la forma y cómo esta ha ido variando sustancialmente. El concepto de escala y orientación reordena el estudio, no sólo de estos edificios protagonistas sino de los que se entretejen a su alrededor y componen el conjunto histórico, lo cual aporta nuevas conclusiones al estado de la cuestión que aquí compete. El principal objetivo de la tesis es, por tanto, contribuir a la dimensión patrimonial mediante el estudio de la arquitectura residencial del pueblo de El Pardo y en cómo esta ha ido conformando y consolidando el entramado urbano original en torno a edificios de la realeza y corte. Analizar aquellos edificios que perduran, los que fueron reconstruidos, rehabilitados, y apuntar acontecimientos históricos que formularon la actual fisonomía. Sistematizar y reordenar sobre la traza actual los edificios que desaparecieron, nos da las pistas sobre las modificaciones en concepto de escala arquitectónica y urbana. El estudio de las fuentes y establecer una metodología de conexión de estas, ayuda a detectar dónde no se han dirigido aún los focos de interés así como las lagunas que han quedado por explorar con el fin de responder a nuevas hipótesis, conceder conclusiones y abrir otras líneas de investigación. Como conclusiones generales, la tesis aporta documentación nueva sobre el objeto de estudio, no solicitada, digitalizada o publicada con anterioridad. En ella se analizan los procesos de configuración, consolidación y transformación en el Real Sitio mediante la sistematización de estados comparativos. Con respecto al estudio de los diferentes contextos natural y urbano la tesis analiza cómo los accidentes naturales, el desarrollo de infraestructuras y el impulso de la agronomía afectaron a El Pardo a partir del siglo XIX, y estudia los procesos de configuración, consolidación y transformación en el Real Sitio mediante la sistematización de la documentación encontrada de manera gráfica y escrita. En relación al marco patrimonial arquitectónico, la tesis analiza los procesos edificatorios históricos. Se estudian, a su vez, cambios de ocupación o uso que derivaron en reformas, ampliaciones, obras de nueva planta e incluso en derribos, así como los proyectos no materializados o que se llevaron a cabo de manera parcial. Con respecto al análisis del momento histórico, la tesis analiza las posibles afectaciones, políticas, sociales y económicas en las etapas de Monarquía, Segunda República, Guerra Civil y Posguerra. Por último, la tesis abre cuatro vías de investigación (que ya se han tratado y avanzado en parte pero que escapan a los límites de este trabajo) que pueden plantear nuevas hipótesis, reportando así respuestas sobre objetos de estudio complementarios y paralelos al presente. Estas refieren a análisis más concretos sobre El Palacio Real de El Pardo y la Casa de Oficios, el Camino Real de Madrid a El Pardo desde la Puerta de Hierro, los cuarteles, puertas y portilleras del Monte de El Pardo y los proyectos desarrollados por el arquitecto Diego Méndez en los Reales Sitios para el Patrimonio Nacional. ABSTRACT Following the Royal Site denomination being granted in the mid-18th Century, during the reign of Ferdinand VI, his successor Charles III proceeded to include all the Forests and Woodlands of El Pardo in his heritage. That then gave rise to the process of town planning and architectural construction that was completed around 1800. Thereafter, not only the process of conservation and consolidation of the main buildings has been maintained, but new civil engineering works have also been carried out. Some buildings changed ownership and use until, after the Civil War, the greatest transformation experienced by the Royal Site was undertaken. The time frame this paper concerns (1885 to 1965), has not attracted sufficient attention in studies of El Pardo due to there having been no new works with heritage status, nor has there been an analysis of the layout and external appearance of the residential centre in the town once conceived by Charles III. However, it is considered relevant to analyse the changes in residential activity, firstly, because it coexists with the official architecture and, thus, it is considered necessary to perform a global analysis of the complex and, secondly, because it facilitates a historical understanding of the original appearance of the complex at the end of the 18th Century. This time framework defines three main parts of the study that provide the structure of this thesis, the dates of which establish the key historical time frames: Actions in the consolidated town centre (1885-1931). Cessation of construction works (1931-1939). Proposals of regeneration and accelerated growth (1939-1965). Two distinct sub-chapters are also established within these, in order to explain the events that marked the transcendental changes in the history of El Pardo. When studying the subject matter, it is noted that in El Pardo, as is the case in other Royal Sites, outstanding buildings such as the Palace, the Prince's Cottage, the Trades House and the Infantes House are usually researched strictly from the point of view of their history, but not from an architectural perspective, nor analysing how that affects the development of the site layout and thus the urban area. Specific shortcomings are evident in the graphic treatment that would have otherwise facilitated a historical understanding through the analysis of the shape and the way it has gradually undergone substantial variation. The concept of scale and orientation reorganises the study, not only of these key buildings, but also of those that are woven around them and make up the historic complex, allowing entirely new conclusions concerning the subject matter analysed herein. Therefore, the main purpose of this thesis is to outline our heritage through the study of the residential architecture of the town of El Pardo and the analysis of the way the original town has been built up and consolidated around the buildings erected by royalty and the court; to analyse the buildings that still remain, those that were rebuilt, refurbished, and to note historic events that shaped its current appearance. To this end, a systematic classification and reorganisation on the current urban layout of the buildings that have disappeared will give us the key to understand changes in the concept of architectural and urban scale. Studying the sources and establishing a methodology to connect them will help us detect those areas where the focus of interest has not concentrated yet, and will also reveal the gaps that remain unexplored, in order to respond to new hypotheses, reach new conclusions and open up new lines of research. As general conclusions, this thesis provides new documentation on the subject matter that had not been requested, digitized or published before. There we find an analysis of the processes of configuration, consolidation and transformation of the Royal Site through a systematic classification of comparative states. With regard to the study of the multiple natural and urban environments, this thesis analyses the way natural features, development of infrastructures and agricultural driving forces affected El Pardo as of the 19th Century, and it studies the processes of configuration, consolidation and transformation of the Royal Site by systematically classifying the documentation found in graphic and written documents. In relation to the architectural heritage framework, this thesis analyses historical building processes. Likewise, a study is also performed on the changes in land occupation or use that led to reforms, extensions, new buildings and even to demolitions, as well as on unrealized projects, or even on those that were partially implemented. As for the analysis of the historical time period, this thesis assesses the potential political, social and economic effects of the Monarchy, Second Republic, Civil War and Post-War Periods. Finally, this thesis opens up four lines of investigation (that have already been discussed and partially advanced, but which fall beyond the scope of this work) that could pose new hypotheses, thus giving answer to other subject matters parallel and complementary to the one assessed herein. These refer to more specific analyses of El Palacio Real de El Pardo (Royal Palace of El Pardo) and the Casa de Oficios (Trades House), the Royal Highway from Madrid to El Pardo from Puerta de Hierro, the barracks, gates and entrances to estates in the Woodlands of El Pardo and the projects developed on the Royal Sites by the architect Diego Méndez for the National Heritage.

Vulnerability analysis of RC buildings with wide beams located in moderate seismicity regions

A significant number of short-to-mid height RC buildings with wide beams have been constructed in areas of moderate seismicity of Spain, mainly for housing and administrative use. The buildings have a framed structure with one-way slabs; the wide beams constitute the distinctive characteristic, their depth being equal to that of the rest of the slab, thus providing a flat lower surface, convenient for construction and the layout of facilities. Seismic behavior in the direction of the wide beams appears to be deficient because of: (i) low lateral strength, mainly because of the small effective depth of the beams, (ii) inherent low ductility of the wide beams, generated by high amount of reinforcement, (iii) the big strut compressive forces developed inside the column-beam connections due to the low height of the beams, and (iv) the fact that the wide beams are wider than the columns, meaning that the contribution of the outer zones to the resistance of the beam-column joints is unreliable because there is no torsion reinforcement. In the orthogonal direction, the behavior is worse since the only members of the slabs that contribute to the lateral resistance are the joists and the façade beams. Moreover, these buildings were designed with codes that did not include ductility requirements and required only a low lateral resistance; indeed, in many cases, seismic action was not considered at all. Consequently, the seismic capacity of these structures is not reliable. The objective of this research is to assess numerically this capability, whereas further research will aim to propose retrofit strategies. The research approach consists of: (i) selecting a number of 3-story and 6-story buildings that represent the vast majority of the existing ones and (ii) evaluating their vulnerability through three types of analyses, namely: code-type, push-over and nonlinear dynamic analysis. Given the low lateral resistance of the main frames, the cooperation of the masonry infill walls is accounted for; for each representative building, three wall densities are considered. The results of the analyses show that the buildings in question exhibit inadequate seismic behavior in most of the examined situations. In general, the relative performance is less deficient for Target Drift CP (Collapse Prevention) than for IO (Immediate Occupancy). Since these buildings are selected to be representative of the vast majority of buildings with wide beams that were constructed in Spain without accounting for any seismic consideration, our conclusions can be extrapolated to a broader scenario.

High speed railroad bridges. Conception, bases of design, typological possibilities and construction methods

Diseño conceptual de puentes de alta velocidad ferroviarios. Railroad bridges, in general, and those for high speed railways, in particular, demand very special conditions. The traffic loads are much higher than for road bridges. Loads due to braking and acceleration determine, due to their magnitude, the structural layout. Because of the speed of the vehicles there are specific dynamic effects which need to be considered. In order to ensure passenger comfort, compatible with speeds of up to 350 km/h, it is necessary to meet very demanding conditions with respect to stiffness, displacements and dynamic behavior. In this paper these conditions are briefly described and different typological possibilities to satisfy them are presented as well as the main construction methods applicable to this kind of bridges.

Aerodynamic study of a blended wing body, comparison with a conventional transport airplane.

Blended-wing-body (BWB) aircraft are being studied with interest and effort to improve economic efficiency and to overcome operational and infrastructure related problems associated to the increasing size of conventional transport airplanes. The objective of the research reported here is to assess the aerodynamic feasibility and operational efficiency of a great size, blended wing body layout, a configuration which has many advantages. To this end, the conceptual aerodynamic design process of an 800 seat BWB has been done completed with a comparison of performance and operational issues with last generation of conventional very large aircraft. The results are greatly encouraging and predict about 20 percent increase in transport productivity efficiency, without the burden of new or aggravated safety or operational problems.

Application of global numerical procedures to the analysis of shells

Examples of global solutions of the shell equations are presented, such as the ones based on the well known Levy series expansion. Also discussed are some natural extensions of the Levy method as well as the inherent limitations of these methods concerning the shell model assumptions, boundary conditions and geometric regularity. Finally, some open additional design questions are noted mainly related to the simultaneous use in analysis of these global techniques and the local methods (like the finite elements) to finding the optimal shell shape, and to determining the reinforcement layout.

Spatial divisions of society

The encounter of architecture and urbanism with parcelisation is marked with the sign of a historical debt. Parcelisation is a tremendously powerful design tool. Architecture and urban planning attest to its capacity to shape sociospatial relations across a range of scales and contexts. From Renaissance palazzi to modernist slabs, from nation-wide agrarian reforms and Haussmann’s Paris to Christopher Alexander’s new theory of urban design and Michael Webb’s Suitaloon — most of the historical revolutions and experimental projects that have shaken these fields have relied, consciously or not, on a critique and restructuration of inherited divisions of land and space. The layout of parcel patterns has a series of implications including forms of property, the divide between private and public realms, the distribution of spatial contents and uses through zoning, typological decisions and so forth. The behaviour of any urban structure depends on the tissue of plots that configures the urban fabric and many of the challenges urban design faces today —complexity, urban vitality, social equality, etc.— hinge upon the forms of land division and distribution we adopt.

Optimized design of the prestress in continuous bridge decks

In this paper a method for automatic design of the prestress in continuous bridge decks is presented. In a first step of the procedure the optimal prestressed force for a completely geometrically defined and feasible prestress layout is obtained by means of linear programming techniques. Further on, in a second step the prestress geometry and minimum force are automatically found by steepest descent optimization techniques. Finally this methodology is applied to two-span continuous bridge decks and from the obtained results some preliminary design rules can be drawn.

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.

Using pMOS Pass-Gates to Boost SRAM Performance by Exploiting Strain Effects in Sub-20-nm FinFET Technologies

Strained fin is one of the techniques used to improve the devices as their size keeps reducing in new nanoscale nodes. In this paper, we use a predictive technology of 14 nm where pMOS mobility is significantly improved when those devices are built on top of long, uncut fins, while nMOS devices present the opposite behavior due to the combination of strains. We explore the possibility of boosting circuit performance in repetitive structures where long uncut fins can be exploited to increase fin strain impact. In particular, pMOS pass-gates are used in 6T complementary SRAM cells (CSRAM) with reinforced pull-ups. Those cells are simulated under process variability and compared to the regular SRAM. We show that when layout dependent effects are considered the CSRAM design provides 10% to 40% faster access time while keeping the same area, power, and stability than a regular 6T SRAM cell. The conclusions also apply to 8T SRAM cells. The CSRAM cell also presents increased reliability in technologies whose nMOS devices have more mismatch than pMOS transistors.