Colombia is a privileged country with the amount of water it has, but due to the inadequate conjunction between hydric wealth and land use, we have lived in continuous tragedy, spending huge resources on ongoing reconstructions and helping the floods and landslides victims. However, floods are natural events, in many cases exacerbated by men’s actions over the territory; events to which no country is exempted, but with consequences that vary according to the characteristics of the duo people-territory and its relationships with the water bodies. This document, offers a review of the characteristics and criteria that define a river in good ecological status, and the anthropic pressures, with its impacts and effects over the water courses, deepening into the hydraulic risk, water quality and the disturbance of the natural environments. Continue presenting the “River Restoration” as a new form of river management, reasoning about the Colombian hydric problems, making emphasis on the pollution problems and disasters related to water; and suggesting solutions from the River Restoration perspective for some specific urban cases and linking this new fluvial hydraulic with the “National Police for Integral Management of the Hydric Resource”.

The present work aims to describe and analyse the influence of the reliability and maintainability of the pump systems on the overall plant availability. The study was developed into an aliphatic solvent plant situated in Colombia and owned by the state company Ecopetrol S.A. This plant is composed of six pump systems, each one of them with parallel redundancy, working in series. The first step during the process was the identification of the dominant failure modes for these pump systems according to historical maintenance information collected during the last nine years and recorded in the CMMS of the company. For these dominant failure modes a Weibull analysis was carried out in order to determine the main parameters of the failure probability distribution function and, in this way, to build a mathematical model useful for predictions of future failures. Additionally, a maintainability model was developed based on the current repair process capability of the work shop employed by the company. By employing reliability block diagrams the reliability dependencies between components, items, units, and systems were taking into account. A general model for the whole plant unit was built and several simulations were performed using Monte Carlo techniques. The simulation results were helpful to identify the more sensitive elements for the overall plant availability and suggest some maintenance and operational actions in order to reduce plant downtime and maintenance costs.

In this master thesis were characterized two highly porous media and a conduit in sandstone with special focus in the transition region between the laminar and turbulent states. As porous media were used glass beads and coarse sand of similar size, 2 and 1.9 mm respectively; for the laboratory work was used a setup where was possible to control the discharge and was measured the hydraulic head. Laminar flow ceases at Reynolds number of 0.25 in glass beads and 0.21 in coarse sand. The flow follows the same pathway between laminar and transitional, without regard if the velocity was increasing or decreasing. A conduit of 5 mm diameter was drilled in a fragment of sandstone for the experiments. The discharge and head losses through the conduit were measured. It was possible to establish two critical Reynolds values, 365 and 3060, for the state change between laminar to transitional and transitional to turbulent. A hysteretic behavior was observed when the flow switches between laminar and transitional. All the results were modeled using the Conduit Flow Process Mode 2 and compared with the experimental data. For porous media there is not a good agreement between the outputs of the model and the measured data.

The building sector plays a significant role regarding CO2 generation in the UK, accounting for 37%. Efforts have been oriented to lower the energy consumption by increasing the efficiency of conditioning systems and by integrating smart designs that lower the energy requirements. The newest storage facility from NMS was designed to use energy efficiently to provide the necessary environmental conditions to approximately 10 million items with specific climate conditions. However, the designers are interested to know how the building is performing and how the energy usage could be lowered. In this report, an assessment of this distinctive building with a dual nature of a storage facility coexisting with a research workplace is conducted. Initially, it was unforeseen how much energy had been used by each piece of equipment; given the type of data recorded, the assessment is performed in a detailed fashion to provide the figures that could help to make decisions to modify the energy usage. Additionally, even though the building was designed using efficient equipment, with air-tightness that was classified as better than typical and a good isolated envelop, opportunities were still found to improve even more its operative functions and hence to reduce the annual cost of energy and the CO2 emissions generation. The results show how to reduce the energy consumption at practically zero cost by making more flexible the temperature settings and by modifying the control strategy, resulting mainly in savings up to 35% in gas consumption. Another potential solution is provided by calculating the energy that a PV array could harvest. Two other recommendations that cannot be implemented are assessed. More elaborated strategies can be analysed and implemented when environmental-friendly buildings are designed. 

Mixing sound in headphones has always been a very attractive idea. They are portable, allow for surgical listening and are very affordable when compared to the cost of an adequately treated mixing room equipped with high-fidelity loudspeakers. The approach in this project was to design a workflow permitting to mix in surround format while monitoring through headphones. By reproducing the filtering responsible for accurate localization of sounds that occurs in the human auditory system using Binaural technology, a portable “virtual mixing studio” was designed and employed in the creation of three surround soundtracks for film material. Chapter 1 of this paper gives a description of the 5.1 surround system features and Binaural technology. Chapter 2 outlines the tools used to design a workflow allowing to produce and render a mix in 5.1 format. Chapter 3 describes the process of creating a 5.1 mix while monitoring through headphones. Chapter 4 provides a description of a listening experiment: aims, method, result, and discussion.

The results of this report indicate how niche product developments for Space Based Solar Power (SBSP) can be easily achieved using present day technology, which markets need to be addressed, which niche configurations to pursue, and which organizations have the needed competencies to proceed. Classical SBSP concepts generally call for large rigid systems to be placed in orbit to collect and transmit several GW of energy down to Earth’s commercial electricity grid, and are still faced with many problems including system complexity, development, and costs. Smaller more specific niche applications of these concepts focus on different markets with lower complexity and barriers to entry while developing technologies and infrastructure needed for the classical SBSP. Technical research was performed in order to identify potential system configurations as well as crucial competencies and technologies needed by the SBSP effort. A pair of unique technical configurations was proposed in an attempt to mitigate standard SBSP challenges such as construction, rigidity, and launch costs. A strategic evaluation tool was created to evaluate all potential system configurations in terms of risk and complexity; ideal configurations were chosen based on anticipated markets and the results from the strategic analysis. Market research was performed in order to understand and valuate the utility of different niche configurations; these included the scientific, remote, green, space to space, and military markets. Very high value segments were observed in each of these market areas with a range of $0.37 to $1.88 USD per kwh for Terrestrial applications, and a range of $380.00 to $1200.00 per kwh for space applications. Exploration of the European Carbon Trading Exchange as a source of revenue is explored due to CO2 offsets. A unique satellite product is proposed and valuated which receives energy directly from an external on orbit source. The value of restoring functionality to damaged satellites is estimated in the millions of dollars.

Modern data acquisition techniques such as Global positioning system (GPS), Radio-frequency identification (RFID) and mobile phones have resulted in the collection of huge amounts of data in the form of trajectories during the past years. Popularity of these technologies and ubiquity of mobile devices seem to indicate that the amount of spatio-temporal data will increase at accelerated rates in the future. Many previous studies have focused on efficient techniques to store and query trajectory databases. Early approaches to recovering information from this kind of data include single predicate range and nearest neighbour queries. However, they are unable to capture collective behaviour and correlations among moving objects. Recently, a new interest for querying patterns capturing ‘group’ or ‘common’ behaviours have emerged. An example of this type of pattern are moving flocks. These are defined as groups of moving objects that move together (within a predefined distance to each other) for a certain continuous period of time. Current algorithms to discover moving flock patterns report problems in scalability and the way the discovered patterns are reported. The field of frequent pattern mining has faced similar problems during the past decade, and has sought to provided efficient and scalable techniques which successfully deal with those issues. This research proposes a framework which integrates techniques for clustering, pattern mining detection, postprocessing and visualization in order to discover and analyse moving flock patterns in large trajectory datasets. The proposed framework was tested and compared with a current method (BFE algorithm). Synthetic datasets simulating trajectories generated by large number of moving objects were used to test the scalability of the framework. Real datasets from different contexts and characteristics were used to assess the performance and analyse the discovered patterns. The framework shows to be efficient, scalable and modular. This research shows that moving flock patterns can be generalized as frequent patterns and state-of-the-art algorithms for frequent pattern mining can be used to detect the moving flock patterns. This research develops preliminary visualization of the most relevant findings. Appropriate interpretation of the results demands further analysis in order to display the most relevant information.

El sistema de aumentación en tierra GBAS permite mejorar el rendimiento de cualquier sistema de navegación por satélite, o GNSS, permitiendo proveer operaciones de precisión en aproximación y aterrizaje hasta la categoría CAT I para aeronaves civiles. El equipo a bordo de la aeronave confía en la validez y exactitud de la información suministrada por la estación GBAS para así calcular sus propios Niveles de Protección (PL). Por tanto, la estación GBAS es completamente responsable de evaluar los y asegurar los niveles de integridad de la señal que recibe, en cumplimiento con los requerimientos establecidos. De lo contrario, una notificación o mensaje ha de ser enviado por la estación GBAS a las aeronaves informando de esta situación. El error de posicionamiento de satélite debido a efemérides es una falla en la cual la ver- dadera posición del satélite no se corresponde con aquella calculada por las aeronaves. Pese al hecho de que la probabilidad de tales eventos es baja, y que normalmente cuando se sucede su magnitud no es lo suficientemente considerable para tener un impacto significativo en el posicionamiento, podría ocurrir que una combinación de factores diera lugar a una amenaza real a la integridad, y a potenciales errores en el posicionamiento. Este reporte se centra en el tipo de error de orbitas B, en el cual la discordancia entre la posición emitida por satélite y la verdadera es una consecuencia directa de un error en la información contenida en las efemérides. Trabajos previos han demostrado satisfactorios resultados detectando estas fallas comparando el mensaje de efemérides recibido con respecto a un mensaje previo que ya haya sido validado, implementando una aproximación de orden cero (ZOH), de primer orden (FOH) y de segundo orden (SOH). El objetivo principal es la implementación de estas aproximaciones, comparar los resultados y elegir un candidato para el monitor de error en orbitas de satélite de tipo B, cumpliendo los requerimientos para aproximaciones y aterrizajes de precisión categoría CAT-I. El siguiente trabajo de grado presentado para optar por el título de Master en Sistemas de Navegación por Satélite en la Escuela Nacional de la Aviación Civil Francesa, ENAC, también presentado como resultado final del trabajo de practicas la Universidad Politécnica de Catalunya, UPC, bajo el marco del Master de Ciencias y Tecnologías Aeroespaciales, detalla el desarrollo e implementación practica de un monitor de orbita de satélite para ser utilizado en aproximaciones de precisión CATI.

Abstract: The synthesis of nanostructures has attracted much interest due to their advanced properties compared to their bulk material. Zinc Oxide (ZnO) has gained substantial interest in the research community due to its large exciton binding energy (60 meV). ZnO is a semiconductor with several favorable properties like a good transparency in the visible region, and a wide band gap of 3.37 eV. Those properties are already used in many emerging applications as chemical sensors, nano laser, and transistors. Due to its wurtzite crystal structure ZnO readily grows to elongated nanoparticles such as nanorods or nanowires. Elongated nanostructures are promising due to precise electron transport in one direction. Special attention has been devoted to the realization of transparent conductive oxides (TCOs) for optoelectronic devices such as solar cells and displays. The first part of this thesis is dedicated to the comparison of the synthesis of ZnO nanorods in a three-neck flask to solvothermal method. In order to investigate the effects of various reaction parameters on the structural and optical properties in the solvothermal method, different temperatures, volumes of solvent and reaction time were selected. The second part addresses the tailoring of the microstructure and electrical properties of ZnO nanorods modified with aluminum and indium, respectively. Finally, doped ZnO nanorods thin films prepared on glass substrate by drop casting method were investigated. This thesis provides first experimental work for transparent conductive zinc oxide prepared by solvothermal synthesis and highlights possibilities and boundaries for introduction of dopants in ZnO nanorods. Resumen: La síntesis de nanoestructuras ha atraído mucho interés debido a sus excelentes propiedades en comparación con su material a granel. El óxido de zinc (ZnO) ha ganado un interés sustancial en la comunidad de investigación debido a su gran energía de ligadura (60 meV). ZnO es un semiconductor con varias propiedades favorables, así como una buena transparencia en la región visible, y una amplia brecha de banda de 3,37 eV. Esas propiedades ya se utilizan en muchas aplicaciones emergentes como sensores químicos, nano láser y transistores. Debido a su estructura de cristal de wurtzita, ZnO se desarrolla fácilmente a nanopartículas alargadas como nanorods o nanocables. Las nanoestructuras alargadas son prometedoras debido al transporte preciso de electrones en una dirección. Se ha dedicado especial atención a la realización de óxidos conductores transparentes (TCO) para dispositivos optoelectrónicos como células solares y pantallas. La primera parte de esta tesis está dedicada a la comparación de la síntesis de nanorods de ZnO en un matraz de tres bocas versus un método solvotermal. Con el fin de investigar los efectos de diversos parámetros de reacción sobre las propiedades estructurales y ópticas en el método solvotermal, se seleccionaron diferentes temperaturas, volúmenes de disolvente y tiempo de reacción. La segunda parte aborda la adaptación de la microestructura y las propiedades eléctricas de los nanorods de ZnO modificadas con aluminio e indio, respectivamente. Finalmente, se investigaron las películas finas de nanorods modificadas y preparadas sobre sustrato de vidrio mediante el método de moldeo a gotas. Esta tesis proporciona el primer trabajo experimental para óxido de zinc como conductor transparente preparado por síntesis solvotérmica y resalta las posibilidades y los límites para la introducción de dopantes en nanorods de ZnO.

Recent projections estimate that the Netherlands needs circa 33 GW of offshore wind capacity in the North Sea to meet the goals of the Paris Agreement. To this end, the Dutch government has very ambitious plans to create new wind sites far from shore and integrate that power generation to the high-voltage power grid in the next years. Due to the challenges of connecting future massive amounts of offshore wind power into the grid TenneT operates it becomes urgent to investigate new alternatives for this purpose. A grid topology with transmission capacities above 1 GW connecting offshore wind farms at distances close to 100 km in a standardized, modular, and cost-efficient manner is the focus of this thesis. With eight point-to-point HVDC links in operation in Germany and more expected in near future, TenneT TSO is analysing new offshore grid connection concepts to achieve a reliable and secure operation of the infrastructure connecting wind energy both in Germany and the Netherlands. A solution is presented in this thesis report in which new wind farms are connected with 66-kV cables to a centralised platform with a connection capacity of 1050 MW. This platform will utilise HVDC technology based on VSC conversion techniques and MMC topology. It is expected that the 66-kV cables will not be connected to a single busbar through paralleled converter transformer, but that this will be done with at least three converter transformers connected to each other on the valve side but not connected on the 66-kV side. A dynamic performance study of a test network with the novel connection topology developed in PSCAD has been done. Each component of the system was studied to obtain a complete overview and understanding of the overall behaviour. All the associated control loops for the MMC terminals and wind turbines were modelled in detail. Through several simulations based on eight cases and scenarios the performance of the offshore 66-kV ac grid and the MMC-HVDC link using the control schemes of MMC converters as in a typical grid connection topology for OWFs was assessed. Proyecciones recientes estiman que los Países Bajos necesitan alrededor de 33 GW de capacidad eólica marina en el Mar del Norte para cumplir los objetivos del Acuerdo de París. Para este fin, el gobierno holandés tiene planes muy ambiciosos de crear nuevas plantas eólicas lejos de la costa e integrar esa generación de energía a la red eléctrica de alto voltaje en los próximos años. Debido a los desafíos de conectar cantidades masivas de energía eólica marina a la red que opera TenneT en el futuro, es urgente investigar nuevas alternativas para este propósito. El objetivo de esta tesis es estudiar una nueva topología de red con capacidades de transmisión por encima de 1 GW que conecte parques eólicos marinos a distancias cercanas a 100 km de manera estandarizada, modular y rentable. Con ocho enlaces HVDC punto a punto en operación en Alemania y más esperados en el futuro cercano, TenneT TSO está analizando nuevos conceptos de conexión a la red en el mar para lograr una operación confiable y segura de la infraestructura que conecta la energía eólica tanto en Alemania como en los Países Bajos. En este reporte de tesis se presenta una solución en la que los nuevos parques eólicos están conectados con cables de 66 kV a una plataforma centralizada con una capacidad de conexión de 1050 MW. Esta plataforma utilizará tecnología HVDC basada en las técnicas de conversión VSC con topología MMC. Se espera que los cables de 66 kV no se conecten a un solo punto eléctrico a través de transformadores convertidores en paralelo, sino que esto se hará con al menos tres transformadores convertidores conectados entre sí en el lado del convertidor, pero no en el lado de 66 kV. En este documento se presentan los resultados de un estudio dinámico de una red de prueba con la nueva topología de conexión desarrollada en PSCAD. Cada componente del sistema se estudió para obtener una visión general completa y una comprensión del comportamiento de toda la red. Todos los lazos de control de las estaciones convertidoras MMC y las turbinas eólicas se modelaron en detalle. A través de varias simulaciones basadas en ocho casos y escenarios se evaluó el comportamiento de la red de ac de 66 kV en alta mar y el enlace MMC-HVDC utilizando los esquemas actuales de control de los convertidores MMC de las topologías típicas de conexión de red para granjas eólicas marinas.