Solving the minimum vertex floodlight problem with hybrid metaheuristics

In this paper we propose four approximation algorithms (metaheuristic based), for the Minimum Vertex Floodlight Set problem. Urrutia et al. [9] solved the combinatorial problem, although it is strongly believed that the algorithmic problem is NP-hard. We conclude that, on average, the minimum number of vertex floodlights needed to illuminate a orthogonal polygon with n vertices is n/4,29.

An Ant Colony System adaptation to deal with accessibility issues after a disaster

One of the main problems relief teams face after a natural or man-made disaster is how to plan rural road repair work tasks to take maximum advantage of the limited available financial and human resources. Previous research focused on speeding up repair work or on selecting the location of health centers to minimize transport times for injured citizens. In spite of the good results, this research does not take into account another key factor: survivor accessibility to resources. In this paper we account for the accessibility issue, that is, we maximize the number of survivors that reach the nearest regional center (cities where economic and social activity is concentrated) in a minimum time by planning which rural roads should be repaired given the available financial and human resources. This is a combinatorial problem since the number of connections between cities and regional centers grows exponentially with the problem size, and exact methods are no good for achieving an optimum solution. In order to solve the problem we propose using an Ant Colony System adaptation, which is based on ants? foraging behavior. Ants stochastically build minimal paths to regional centers and decide if damaged roads are repaired on the basis of pheromone levels, accessibility heuristic information and the available budget. The proposed algorithm is illustrated by means of an example regarding the 2010 Haiti earthquake, and its performance is compared with another metaheuristic, GRASP.

Análisis de la eficiencia de los sistemas de colonias de hormigas para problemas de accesibilidad

A pesar de los avances en materia de predicción, los desastres naturales siguen teniendo consecuencias devastadoras. Entre los principales problemas a los que se enfrentan los equipos de ayuda y rescate después de un desastre natural o provocado por el hombre se encuentra la planificación de las tareas de reparación de carreteras para conseguir la máxima ventaja de los limitados recursos económicos y humanos. En la presente Tesis Fin de Máster se intenta dar solución al problema de la accesibilidad, es decir, maximizar el número de supervivientes que consiguen alcanzar el centro regional más cercano en un tiempo mínimo mediante la planificación de qué carreteras rurales deberían ser reparadas dados unos recursos económicos y humanos limitados. Como se puede observar, es un problema combinatorio ya que el número de planes de reparación y conexiones entre las ciudades y los centros regionales crece de forma exponencial con el tamaño del problema. Para la resolución del problema se comienza analizando una adaptación básica de los sistemas de colonias de hormigas propuesta por otro autor y se proponen múltiples mejoras sobre la misma. Posteriormente, se propone una nueva adaptación más avanzada de los sistemas de colonias de hormiga al problema, el ACS con doble hormiga. Este sistema hace uso de dos tipos distintos de hormigas, la exploradora y la trabajadora, para resolver simultáneamente el problema de encontrar los caminos más rápidos desde cada ciudad a su centro regional más cercano (exploradora), y el de obtener el plan óptimo de reparación que maximice la accesibilidad de la red (trabajadora). El algoritmo propuesto se ilustra por medio de un ejemplo de gran tamaño que simula el desastre natural ocurrido en Haití, y su rendimiento es comparado con la combinación de dos metaheurísticas, GRASP y VNS.---ABSTRACT---In spite of the advances in forecasting, natural disaster continue to ocasionate devastating consequences. One of the main problems relief teams face after a natural or man-made disaster is how to plan rural road repair work to take maximum advantage of the limited available financial and human resources. In this Master´s Final Project we account for the accesability issue, that is, to maximize the number of survivors that reach the nearest regional center in a minimum time by planning whic rural roads should be repaired given the limited financial and human resources. This is a combinatorial problem since the number of possible repairing solutions and connections between cities and regional centers grows exponentially with the size of the problem. In order to solve the problem, we analyze the basic ant colony system adaptation proposed by another author and point out multiple improvements on it. Then, we propose a novel and more advance adaptation of the ant colony systems to the problem, the double- ant ACS. This system makes use of two diferent type of ants, the explorer and the worker, to simultaneously solve the problem of finding the shorthest paths from each city to their nearest regional center (explorer), and the problem of identifying the optimal repairing plan that maximize the network accesability (worker). The proposed algorithm is illustrated by means of a big size example that simulates the natural disaster occurred in Haiti, and its performance is compared with a combination of two metaheuristics, GRASP and VNS.

Desarrollo de un Procedimiento Basado en Algoritmos de Optimización para el Dimensionado de Absorbedores Puntuales Aplicados a la Conversión de Energía Undimotriz

La energía transportada por el oleaje a través de los océanos (energía undimotriz) se enmarca dentro de las denominadas energías oceánicas. Su aprovechamiento para generar energía eléctrica (o ser aprovechada de alguna otra forma) es una idea reflejada ya hace más de dos siglos en una patente (1799). Desde entonces, y con especial intensidad desde los años 70, ha venido despertando el interés de instituciones ligadas al I+D+i y empresas del sector energético y tecnológico, debido principalmente a la magnitud del recurso disponible. Actualmente se puede considerar al sector en un estado precomercial, con un amplio rango de dispositivos y tecnologías en diferente grado de desarrollo en los que ninguno destaca sobre los otros (ni ha demostrado su viabilidad económica), y sin que se aprecie una tendencia a converger un único dispositivo (o un número reducido de ellos). El recurso energético que se está tratando de aprovechar, pese a compartir la característica de no-controlabilidad con otras fuentes de energía renovable como la eólica o la solar, presenta una variabilidad adicional. De esta manera, diferentes localizaciones, pese a poder presentar recursos de contenido energético similar, presentan oleajes de características muy diferentes en términos de alturas y periodos de oleaje, y en la dispersión estadística de estos valores. Esta variabilidad en el oleaje hace que cobre especial relevancia la adecuación de los dispositivos de aprovechamiento de energía undimotriz (WEC: Wave Energy Converter) a su localización, de cara a mejorar su viabilidad económica. Parece razonable suponer que, en un futuro, el proceso de diseño de un parque de generación undimotriz implique un rediseño (en base a una tecnología conocida) para cada proyecto de implantación en una nueva localización. El objetivo de esta tesis es plantear un procedimiento de dimensionado de una tecnología de aprovechamiento de la energía undimotriz concreta: los absorbedores puntuales. Dicha metodología de diseño se plantea como un problema de optimización matemático, el cual se resuelve utilizando un algoritmo de optimización bioinspirado: evolución diferencial. Este planteamiento permite automatizar la fase previa de dimensionado implementando la metodología en un código de programación. El proceso de diseño de un WEC es un problema de ingería complejo, por lo que no considera factible el planteamiento de un diseño completo mediante un único procedimiento de optimización matemático. En vez de eso, se platea el proceso de diseño en diferentes etapas, de manera que la metodología desarrollada en esta tesis se utilice para obtener las dimensiones básicas de una solución de referencia de WEC, la cual será utilizada como punto de partida para continuar con las etapas posteriores del proceso de diseño. La metodología de dimensionado previo presentada en esta tesis parte de unas condiciones de contorno de diseño definidas previamente, tales como: localización, características del sistema de generación de energía eléctrica (PTO: Power Take-Off), estrategia de extracción de energía eléctrica y concepto concreto de WEC). Utilizando un algoritmo de evolución diferencial multi-objetivo se obtiene un conjunto de soluciones factibles (de acuerdo con una ciertas restricciones técnicas y dimensionales) y óptimas (de acuerdo con una serie de funciones objetivo de pseudo-coste y pseudo-beneficio). Dicho conjunto de soluciones o dimensiones de WEC es utilizado como caso de referencia en las posteriores etapas de diseño. En el documento de la tesis se presentan dos versiones de dicha metodología con dos modelos diferentes de evaluación de las soluciones candidatas. Por un lado, se presenta un modelo en el dominio de la frecuencia que presenta importantes simplificaciones en cuanto al tratamiento del recurso del oleaje. Este procedimiento presenta una menor carga computacional pero una mayor incertidumbre en los resultados, la cual puede traducirse en trabajo adicional en las etapas posteriores del proceso de diseño. Sin embargo, el uso de esta metodología resulta conveniente para realizar análisis paramétricos previos de las condiciones de contorno, tales como la localización seleccionada. Por otro lado, la segunda metodología propuesta utiliza modelos en el domino estocástico, lo que aumenta la carga computacional, pero permite obtener resultados con menos incertidumbre e información estadística muy útil para el proceso de diseño. Por este motivo, esta metodología es más adecuada para su uso en un proceso de dimensionado completo de un WEC. La metodología desarrollada durante la tesis ha sido utilizada en un proyecto industrial de evaluación energética preliminar de una planta de energía undimotriz. En dicho proceso de evaluación, el método de dimensionado previo fue utilizado en una primera etapa, de cara a obtener un conjunto de soluciones factibles de acuerdo con una serie de restricciones técnicas básicas. La selección y refinamiento de la geometría de la solución geométrica de WEC propuesta fue realizada a posteriori (por otros participantes del proyecto) utilizando un modelo detallado en el dominio del tiempo y un modelo de evaluación económica del dispositivo. El uso de esta metodología puede ayudar a reducir las iteraciones manuales y a mejorar los resultados obtenidos en estas últimas etapas del proyecto. ABSTRACT The energy transported by ocean waves (wave energy) is framed within the so-called oceanic energies. Its use to generate electric energy (or desalinate ocean water, etc.) is an idea expressed first time in a patent two centuries ago (1799). Ever since, but specially since the 1970’s, this energy has become interesting for R&D institutions and companies related with the technological and energetic sectors mainly because of the magnitude of available energy. Nowadays the development of this technology can be considered to be in a pre-commercial stage, with a wide range of devices and technologies developed to different degrees but with none standing out nor economically viable. Nor do these technologies seem ready to converge to a single device (or a reduce number of devices). The energy resource to be exploited shares its non-controllability with other renewable energy sources such as wind and solar. However, wave energy presents an additional short-term variability due to its oscillatory nature. Thus, different locations may show waves with similar energy content but different characteristics such as wave height or wave period. This variability in ocean waves makes it very important that the devices for harnessing wave energy (WEC: Wave Energy Converter) fit closely to the characteristics of their location in order to improve their economic viability. It seems reasonable to assume that, in the future, the process of designing a wave power plant will involve a re-design (based on a well-known technology) for each implementation project in any new location. The objective of this PhD thesis is to propose a dimensioning method for a specific wave-energy-harnessing technology: point absorbers. This design methodology is presented as a mathematical optimization problem solved by using an optimization bio-inspired algorithm: differential evolution. This approach allows automating the preliminary dimensioning stage by implementing the methodology in programmed code. The design process of a WEC is a complex engineering problem, so the complete design is not feasible using a single mathematical optimization procedure. Instead, the design process is proposed in different stages, so the methodology developed in this thesis is used for the basic dimensions of a reference solution of the WEC, which would be used as a starting point for the later stages of the design process. The preliminary dimensioning methodology presented in this thesis starts from some previously defined boundary conditions such as: location, power take-off (PTO) characteristic, strategy of energy extraction and specific WEC technology. Using a differential multi-objective evolutionary algorithm produces a set of feasible solutions (according to certain technical and dimensional constraints) and optimal solutions (according to a set of pseudo-cost and pseudo-benefit objective functions). This set of solutions or WEC dimensions are used as a reference case in subsequent stages of design. In the document of this thesis, two versions of this methodology with two different models of evaluation of candidate solutions are presented. On the one hand, a model in the frequency domain that has significant simplifications in the treatment of the wave resource is presented. This method implies a lower computational load but increased uncertainty in the results, which may lead to additional work in the later stages of the design process. However, use of this methodology is useful in order to perform previous parametric analysis of boundary conditions such as the selected location. On the other hand, the second method uses stochastic models, increasing the computational load, but providing results with smaller uncertainty and very useful statistical information for the design process. Therefore, this method is more suitable to be used in a detail design process for full dimensioning of the WEC. The methodology developed throughout the thesis has been used in an industrial project for preliminary energetic assessment of a wave energy power plant. In this assessment process, the method of previous dimensioning was used in the first stage, in order to obtain a set of feasible solutions according to a set of basic technical constraints. The geometry of the WEC was refined and selected subsequently (by other project participants) using a detailed model in the time domain and a model of economic evaluation of the device. Using this methodology can help to reduce the number of design iterations and to improve the results obtained in the last stages of the project.

Modelling wake effects in large wind farms in complex terrain: the problem, the methods and the issues

Computational fluid dynamic (CFD) methods are used in this paper to predict the power production from entire wind farms in complex terrain and to shed some light into the wake flow patterns. Two full three-dimensional Navier–Stokes solvers for incompressible fluid flow, employing k − ϵ and k − ω turbulence closures, are used. The wind turbines are modeled as momentum absorbers by means of their thrust coefficient through the actuator disk approach. Alternative methods for estimating the reference wind speed in the calculation of the thrust are tested. The work presented in this paper is part of the work being undertaken within the UpWind Integrated Project that aims to develop the design tools for next generation of large wind turbines. In this part of UpWind, the performance of wind farm and wake models is being examined in complex terrain environment where there are few pre-existing relevant measurements. The focus of the work being carried out is to evaluate the performance of CFD models in large wind farm applications in complex terrain and to examine the development of the wakes in a complex terrain environment.

A model for evaluation of generic competences in engineering: application to the problem. Solving competence at the technical University of Madrid.

The competence evaluation promoted by the European High Education Area entails a very important methodological change that requires guiding support to help teachers carry out this new and complex task. In this regard, the Technical University of Madrid (UPM, by its Spanish acronym) has financed a series of coordinated projects with a two-fold objective: a) To develop a model for teaching and evaluating core competences that is useful and easily applicable to its different degrees, and b) to provide support to teachers by creating an area within the Website for Educational Innovation where they can search for information on the model corresponding to each core competence approved by UPM. Information available on each competence includes its definition, the formulation of indicators providing evidence on the level of acquisition, the recommended teaching and evaluation methodology, examples of evaluation rules for the different levels of competence acquisition, and descriptions of best practices. These best practices correspond to pilot tests applied to several of the academic subjects conducted at UPM in order to validate the model. This work describes the general procedure that was used and presents the model developed specifically for the problem-solving competence. Some of the pilot experiences are also summarised and their results analysed

A model for evaluation of generic competences in engineering: application to the problem-solving competence at UPM.

The competence evaluation promoted by the European High Education Area entails a very important methodological change that requires guiding support to help teachers carry out this new and complex task. In this regard, the Technical University of Madrid (UPM, by its Spanish acronym) has financed a series of coordinated projects with a two-fold objective: a) To develop a model for teaching and evaluating core competences that is useful and easily applicable to its different degrees, and b) to provide support to teachers by creating an area within the Website for Educational Innovation where they can search for information on the model corresponding to each core competence approved by UPM. Information available on each competence includes its definition, the formulation of indicators providing evidence on the level of acquisition, the recommended teaching and evaluation methodology, examples of evaluation rules for the different levels of competence acquisition, and descriptions of best practices. These best practices correspond to pilot tests applied to several of the academic subjects conducted at UPM in order to validate the model. This work describes the general procedure that was used and presents the model developed specifically for the problem-solving competence. Some of the pilot experiences are also summarised and their results analysed

Preprocessing and analyzing genetic data with complex networks: An application to Obstructive Nephropathy

Many diseases have a genetic origin, and a great effort is being made to detect the genes that are responsible for their insurgence. One of the most promising techniques is the analysis of genetic information through the use of complex networks theory. Yet, a practical problem of this approach is its computational cost, which scales as the square of the number of features included in the initial dataset. In this paper, we propose the use of an iterative feature selection strategy to identify reduced subsets of relevant features, and show an application to the analysis of congenital Obstructive Nephropathy. Results demonstrate that, besides achieving a drastic reduction of the computational cost, the topologies of the obtained networks still hold all the relevant information, and are thus able to fully characterize the severity of the disease.

Phase transition in the countdown problem

We present a combinatorial decision problem, inspired by the celebrated quiz show called Countdown, that involves the computation of a given target number T from a set of k randomly chosen integers along with a set of arithmetic operations. We find that the probability of winning the game evidences a threshold phenomenon that can be understood in the terms of an algorithmic phase transition as a function of the set size k. Numerical simulations show that such probability sharply transitions from zero to one at some critical value of the control parameter, hence separating the algorithm's parameter space in different phases. We also find that the system is maximally efficient close to the critical point. We derive analytical expressions that match the numerical results for finite size and permit us to extrapolate the behavior in the thermodynamic limit.

Improved heuristic drift elimination with magnetically-aided dominant directions (MiHDE) for pedestrian navigation in complex buildings

The main problem of pedestrian dead-reckoning (PDR) using only a body-attached inertial measurement unit is the accumulation of heading errors. The heading provided by magnetometers in indoor buildings is in general not reliable and therefore it is commonly not used. Recently, a new method was proposed called heuristic drift elimination (HDE) that minimises the heading error when navigating in buildings. It assumes that the majority of buildings have their corridors parallel to each other, or they intersect at right angles, and consequently most of the time the person walks along a straight path with a heading constrained to one of the four possible directions. In this article we study the performance of HDE-based methods in complex buildings, i.e. with pathways also oriented at 45°, long curved corridors, and wide areas where non-oriented motion is possible. We explain how the performance of the original HDE method can be deteriorated in complex buildings, and also, how severe errors can appear in the case of false matches with the building's dominant directions. Although magnetic compassing indoors has a chaotic behaviour, in this article we analyse large data-sets in order to study the potential use that magnetic compassing has to estimate the absolute yaw angle of a walking person. Apart from these analysis, this article also proposes an improved HDE method called Magnetically-aided Improved Heuristic Drift Elimination (MiHDE), that is implemented over a PDR framework that uses foot-mounted inertial navigation with an extended Kalman filter (EKF). The EKF is fed with the MiHDE-estimated orientation error, gyro bias corrections, as well as the confidence over that corrections. We experimentally evaluated the performance of the proposed MiHDE-based PDR method, comparing it with the original HDE implementation. Results show that both methods perform very well in ideal orthogonal narrow-corridor buildings, and MiHDE outperforms HDE for non-ideal trajectories (e.g. curved paths) and also makes it robust against potential false dominant direction matchings.

Development of a method of assessment of the problem-solving competence at the technical University of Madrid.

The competence evaluation promoted by the European High Education Area entails a very important methodological change that requires guiding support to help lecturers carry out this new and complex task. In this regard, the Technical University of Madrid (UPM, by its Spanish acronym) has financed a series of coordinated projects with the objective of developing a model for teaching and evaluating core competences and providing support to lecturers. This paper deals with the problem-solving competence. The first step has been to elaborate a guide for teachers to provide a homogeneous way to asses this competence. This guide considers several levels of acquisition of the competence and provides the rubrics to be applied for each one. The guide has been subsequently validated with several pilot experiences. In this paper we will explain the problem-solving assessment guide for teachers and will show the pilot experiences that has been carried out. We will finally justify the validity of the method to assess the problem-solving competence.

A combined algorithm for analyzing structural controllability and observability of complex networks

In this paper a combined algorithm for analyzing structural controllability and observability of complex networks is presented. The algorithm addresses the two fundamental properties to guarantee structural controllability of a system: the absence of dilations and the accessibility of all nodes. The first problem is reformulated as a Maximum Matching search and it is addressed via the Hopcroft- Karp algorithm; the second problem is solved via a new wiring algorithm. Both algorithms can be combined to efficiently determine the number of required controllers and observers as well as the new required connections in order to guarantee controllability and observability in real complex networks. An application to a Twitter social network with over 100,000 nodes illustrates the proposed algorithms.

Wind tunnel analysis of the flow topology over complex topographies

El principal objetivo de este trabajo es aportar conocimiento para contestar la pregunta: ¿hasta que punto los ensayos en túnel aerodinámico pueden contribuir a determinar las características que afectan la respuesta dinámica de los aerogeneradores operando en terreno complejo?. Esta pregunta no es nueva, de hecho, el debate en la comunidad científica comenzó en el primer tercio del siglo pasado y aún está intensamente vivo. El método generalmente aceptado para enfrentar el mencionado problema consiste en analizar un caso de estudio determinado en el cual se aplican tanto ensayos a escala real como análisis computacionales y ensayos en túnel aerodinámico. Esto no es ni fácil ni barato. Esta es la razón por la cual desde el experimento de Askervein en 1988, los modelizadores del flujo atmosférico tuvieron que esperar hasta 2007 a que el experimento de Bolund fuese puesto en marcha con un despliegue de medios técnicos equivalentes (teniendo en cuenta la evolución de las tecnologías de sensores y computación). El problema contempla tantos aspectos que ambas experiencias fueron restringidas a condiciones de atmósfera neutra con efectos de Coriolis despreciables con objeto de reducir la complejidad. Este es el contexto en el que se ha desarrollado la presente tesis doctoral. La topología del flujo sobre la isla de Bolund ha sido estudiada mediante la reproducción del experimento de Bolund en los túneles aerodinámicos A9 y ACLA16 del IDR. Dos modelos de la isla de Bolund fueron fabricados a dos escalas, 1:230 y 1:115. El flujo de entrada en el túnel aerodinámico simulando la capa límite sin perturbar correspondía a régimen de transición (transitionally rough regime) y fue usado como situación de referencia. El modelo a escala 1:230 fue ensayado en el túnel A9 para determinar la presión sobre su superficie. La distribución del coeficiente de presión sobre la isla proporcionó una visualización y estimación de una región de desprendimiento sobre el pequeño acantilado situado al frente de la misma. Las medidas de presión instantánea con suficiente grado de resolución temporal pusieron de manifiesto la no estacionariedad en la región de desprendimiento. El modelo a escala 1:115 fue ensayado utilizando hilo caliente de tres componentes y un sistema de velocimetría por imágenes de partículas de dos componentes. El flujo fue caracterizado por el ratio de aceleración, el incremento normalizado de energía cinética turbulenta y los ángulos de inclinación y desviación horizontal. Los resultados a lo largo de la dirección 270°y alturas de 2 m y 5 m presentaron una gran similitud con los resultados a escala real del experimento de Bolund. Los perfiles verticales en las localizaciones de las torres meteorológicas mostraron un acuerdo significativo con los resultados a escala real. El análisis de los esfuerzos de Reynolds y el análisis espectral en las localizaciones de los mástiles meteorológicos presentaron niveles de acuerdo variados en ciertas posiciones, mientras que en otras presentaron claras diferencias. El mapeo horizontal del flujo, para una dirección de viento de 270°, permitió caracterizar el comportamiento de la burbuja intermitente de recirculación sobre el pequeño acantilado existente al frente de la isla así como de la región de relajación y de la capa de cortadura en la región corriente abajo de Bolund. Se realizaron medidas de velocidad con alta resolución espacial en planos perpendiculares a la dirección del flujo sin perturbar. Estas medidas permitieron detectar y caracterizar una estructura de flujo similar a un torbellino longitudinal con regiones con altos gradientes de velocidad y alta intensidad de turbulencia. Esta estructura de flujo es, sin duda, un reto para los modelos computacionales y puede considerarse un factor de riesgo para la operación de los aerogeneradores. Se obtuvieron y analizaron distribuciones espaciales de los esfuerzos de Reynolds mediante 3CHW y PIV. Este tipo de parámetros no constituyen parte de los resultados habituales en los ensayos en túnel sobre topografías y son muy útiles para los modelizadores que utilizan simulación de grades torbellinos (LES). Se proporciona una interpretación de los resultados obtenidos en el túnel aerodinámico en términos de utilidad para los diseñadores de parques eólicos. La evolución y variación de los parámetros del flujo a lo largo de líneas, planos y superficies han permitido identificar como estas propiedades del flujo podrían afectar la localización de los aerogeneradores y a la clasificación de emplazamientos. Los resultados presentados sugieren, bajo ciertas condiciones, la robustez de los ensayos en túnel para estudiar la topología sobre terreno complejo y su comparabilidad con otras técnicas de simulación, especialmente considerando el nivel de acuerdo del conjunto de resultados presentados con los resultados a escala real. De forma adicional, algunos de los parámetros del flujo obtenidos de las medidas en túnel son difícilmente determinables en ensayos a escala real o por medios computacionales, considerado el estado del arte. Este trabajo fue realizado como parte de las actividades subvencionadas por la Comisión Europea como dentro del proyecto FP7-PEOPLE-ITN-2008WAUDIT (Wind Resource Assessment Audit and Standardization) dentro de la FP7 Marie-Curie Initial Training Network y por el Ministerio Español de Economía y Competitividad dentro del proyecto ENE2012-36473, TURCO (Determinación en túnel aerodinámico de la distribución espacial de parámetros estadísticos de la turbulencia atmosférica sobre topografías complejas) del Plan Nacional de Investigación (Subprograma de investigación fundamental no orientada 2012). El informe se ha organizado en siete capítulos y un conjunto de anexos. En el primer capítulo se introduce el problema. En el capítulo dos se describen los medios experimentales utilizados. Seguidamente, en el capítulo tres, se analizan en detalle las condiciones de referencia del principal túnel aerodinámico utilizado en esta investigación. En el capítulo tres se presentan resultados de ensayos de presión superficial sobre un modelo de la isla. Los principales resultados del experimento de Bolund se reproducen en el capítulo cinco. En el capítulo seis se identifican diferentes estructuras del flujo sobre la isla y, finalmente, en el capitulo siete, se recogen las conclusiones y una propuesta de lineas de trabajo futuras. ABSTRACT The main objective of this work is to contribute to answer the question: to which extend can the wind tunnel testing contribute to determine the flow characteristics that affect the dynamic response of wind turbines operating in highly complex terrains?. This question is not new, indeed, the debate in the scientific community was opened in the first third of the past century and it is still intensely alive. The accepted approach to face this problem consists in analysing a given case study where full-scale tests, computational modelling and wind tunnel testing are applied to the same topography. This is neither easy nor cheap. This is is the reason why since the Askervein experience in 1988, the atmospheric flow modellers community had to wait till 2007 when the Bolund experiment was setup with a deployment of technical means equivalent (considering the evolution of the sensor and computing techniques). The problem is so manifold that both experiences were restricted to neutral conditions without Coriolis effects in order to reduce the complexity. This is the framework in which this PhD has been carried out. The flow topology over the Bolund Island has been studied by replicating the Bolund experiment in the IDR A9 and ACLA16 wind tunnels. Two mock-ups of the Bolund island were manufactured at two scales of 1:230 and 1:115. The in-flow in the empty wind tunnel simulating the incoming atmospheric boundary layer was in the transitionally rough regime and used as a reference case. The 1:230 model was tested in the A9 wind tunnel to measure surface pressure. The mapping of the pressure coefficient across the island gave a visualisation and estimation of a detachment region on the top of the escarpment in front of the island. Time resolved instantaneous pressure measurements illustrated the non-steadiness in the detachment region. The 1:115 model was tested using 3C hot-wires(HW) and 2C Particle Image Velocimetry(PIV). Measurements at met masts M3, M6, M7 and M8 and along Line 270°were taken to replicate the result of the Bolund experiment. The flow was characterised by the speed-up ratio, normalised increment of the turbulent kinetic energy, inclination angle and turning angle. Results along line 270°at heights of 2 m and 5 m compared very well with the full-scale results of the Bolund experiment. Vertical profiles at the met masts showed a significant agreement with the full-scale results. The analysis of the Reynolds stresses and the spectral analysis at the met mast locations gave a varied level of agreement at some locations while clear mismatch at others. The horizontal mapping of the flow field, for a 270°wind direction, allowed to characterise the behaviour of the intermittent recirculation bubble on top of the front escarpment followed by a relaxation region and the presence of a shear layer in the lee side of the island. Further detailed velocity measurements were taken at cross-flow planes over the island to study the flow structures on the island. A longitudinal vortex-like structure with high mean velocity gradients and high turbulent kinetic energy was characterised on the escarpment and evolving downstream. This flow structure is a challenge to the numerical models while posing a threat to wind farm designers when siting wind turbines. Spatial distribution of Reynold stresses were presented from 3C HW and PIV measurements. These values are not common results from usual wind tunnel measurements and very useful for modellers using large eddy simulation (LES). An interpretation of the wind tunnel results in terms of usefulness to wind farm designers is given. Evolution and variation of the flow parameters along measurement lines, planes and surfaces indicated how the flow field could affect wind turbine siting. Different flow properties were presented so compare the level of agreement to full-scale results and how this affected when characterising the site wind classes. The results presented suggest, under certain conditions, the robustness of the wind tunnel testing for studying flow topology over complex terrain and its capability to compare to other modelling techniques especially from the level of agreement between the different data sets presented. Additionally, some flow parameters obtained from wind tunnel measurements would have been quite difficult to be measured at full-scale or by computational means considering the state of the art. This work was carried out as a part of the activities supported by the EC as part of the FP7- PEOPLE-ITN-2008 WAUDIT project (Wind Resource Assessment Audit and Standardization) within the FP7 Marie-Curie Initial Training Network and by the Spanish Ministerio de Economía y Competitividad, within the framework of the ENE2012-36473, TURCO project (Determination of the Spatial Distribution of Statistic Parameters of Flow Turbulence over Complex Topographies in Wind Tunnel) belonging to the Spanish National Program of Research (Subprograma de investigación fundamental no orientada 2012). The report is organised in seven chapters and a collection of annexes. In chapter one, the problem is introduced. In chapter two the experimental setup is described. Following, in chapter three, the inflow conditions of the main wind tunnel used in this piece of research are analysed in detail. In chapter three, preliminary pressure tests results on a model of the island are presented. The main results from the Bolund experiment are replicated in chapter five. In chapter six, an identification of specific flow strutures over the island is presented and, finally, in chapter seven, conclusions and lines for future works related to the presented one are included.

Development of a method of assessment of the problem-solving competency at the Technical University of Madrid

The competence evaluation promoted by the European High Education Area entails a very important methodological change that requires guiding support to help lecturers carry out this new and complex task. In this regard, the Technical University of Madrid (UPM, by its Spanish acronym) has financed a series of coordinated projects with the objective of developing a model for teaching and evaluating core competences and providing support to lecturers. This paper deals with the problem solving competence. The first step has been to elaborate a guide for teachers to provide an homogeneous way to asses this competence. This guide considers several levels of acquisition of the competence and provided the rubrics to be applied for each one. The guide has been subsequently validated with several pilot experiences. In this paper we will explain the problem-solving assessment guide for teachers and will show the pilot experiences that has been carried out. We will finally justify the validity of the method to assess the problem solving competence.

Vortex-induced vibrations on bridges : the interaction mechanism in complex sections and a new proposed semi-empirical model

El presente trabajo de investigación se ocupa del estudio de las vibraciones verticales inducidas por vórtices (VIV) en aquellos puentes que, por sus características geométricas y propiedades dinámicas, muestran cierta sensibilidad este tipo de fenómeno aeroelástico. El objeto principal es el análisis del mecanismo de interacción viento-estructura sobre secciones no fuseladas de geometría simple, con objeto de realizar una adecuada caracterización del problema y poder abordar posteriormente el análisis de otras secciones de geometría más compleja, representativas de los principales elementos estructurales de los puentes, como arcos, tableros, torres y pilas. Este aspecto es fundamental durante la fase de diseño del puente, donde deberán tenerse en cuenta también una serie de detalles que pueden influir significativamente su sensibilidad ante problemas aerodinámicos, como la morfología y dimensiones principales de la sección transversal del tablero, la disposición de barreras de seguridad y barreras cortaviento, o las riostras que unen diferentes elementos estructurales. La configuración de dos elementos en tándem o la construcción de un puente en las inmediaciones de otro existente son otros aspectos a considerar respecto a la sensibilidad frente a efectos aeroelásticos. El estudio se ha llevado a cabo principalmente mediante la implementación de simulaciones numéricas que reproducen la interacción entre la corriente de aire y secciones representativas de modelos estructurales, a partir de un código CFD basado en el método de las partículas de vórtices (VPM), siguiendo por tanto un esquema Lagrangiano. Los resultados han sido validados con datos experimentales existentes, valores procedentes de ensayos en túnel de viento y registros reales a partir de diferentes casos de estudio: Alconétar (2006), Niterói (1980), Trans- Tokyo Bay (1995) y Volgogrado (2010). Finalmente, se propone un modelo semi-empírico para la estimación del rango de velocidades críticas y amplitudes de oscilación basado en la utilización de las derivadas de flameo de Scanlan, y la densidad espectral de las fuerzas aerodinámicas en el dominio de la frecuencia. The present research work concerns the study of vertical vortex-induced vibrations (VIV) in bridges which show certain sensitivity to this type of aeroelastic phenomenon. It focuses on the analysis of the wind-structure interaction mechanism on bluff sections, with the objective of making a good characterisation of the problem and subsequently addressing the analysis of sections with a complex geometry, which are representative of the bridge structural elements, such as arches, decks, towers and piers. This issue is of relative importance during the bridge design phase, since minor details of the aforementioned elements can significantly influence its sensitivity to aerodynamic problems. The shape and main dimensions of the deck cross section, the addition of safety barriers and windshields, the presence of braces to enhance the structure mechanical properties, the utilisation of cross sections in tandem arrangement, or the erection of a new bridge in the vicinity of another existing one are some of the aspects to be considered regarding the sensitivity to the aeroelastic effects. The study has been carried out mainly through the implementation of numerical simulations that reproduces the interaction between the airflow and the representative cross section of a structural bridge model, by the use of a CFD code based on the vortex particle method (VPM), thus following a Lagrangian scheme. The results have been validated with existing experimental data, values from wind tunnel tests and full scale observations from the different case studies: Alconétar (2006), Niterói (1980), Trans-Tokyo Bay (1995) and Volgograd (2010). Finally, a new semi-empirical model is proposed for the estimation of the critical wind velocity ranges and oscillation amplitudes based on the use of the Scanlan’s flutter derivatives and the power spectral density of aerodynamic force time history in the frequency domain.