Power conversion systems are becoming fundamental with the increasing power generation from renewable energy sources due to global warming and energy security concerns. In particular, wind energy systems require advance power converter devices to be able to supply power to the electric network or remote isolated areas in an effective way. A practical approach to these devices is required to fully comprehend their principles of operation and how they are integrated with the expanding renewable electricity production. This thesis describes the design and construction process of an inverter and a DC-DC converter, part of the AC-DC-AC link required to connect a laboratory model of a variable speed wind power system to the grid or to an isolated load.

Fernando Vallejo escribe la biografía de uno de los mejores poetas del país. Viaje alucinado por la Bogotá de fines del siglo XIX tras los pasos del poeta José Asunción Silva. Una insólita biografía que renueva el género.

Fernando Vallejo escribe la biografía de uno de los mejores poetas del país. Viaje alucinado por la Bogotá de fines del siglo XIX tras los pasos del poeta José Asunción Silva. Una insólita biografía que renueva el género.

El objetivo principal de la presente tesis doctoral es la determinación de los HCG e HAP asociados a las partículas, emitidos por un motor diésel utilizando diversos combustibles de origen renovable. A partir de este objetivo general se definen varios objetivos específicos: La puesta a punto de un método efectivo para la identificación y cuantificación de los HCG individuales en los gases de escape del motor diésel. Este procedimiento debe incluir la metodología de muestreo, extracción, concentración y análisis, garantizando la conservación de los analitos objetivo. El desarrollo y validación de una metodología novedosa de especiación de los HAP asociados a las partículas. Esta técnica debe utilizar una combinación de extracción térmica y microextracción en fase sólida, de modo que se eliminen los inconvenientes de la extracción con disolventes tradicional y se incremente la selectividad y repetitividad del método.

The FreshWaterMill project is a transfer of Environmentally Sound Technology (EST) from The Netherlands to Colombia that involves several Dutch companies, the Delft University of Technology and Coralina (corporation for sustainable development of the Archipelago San Andrés, Providence and Saint Kathleen). The installation place is Johnny Cay, a small islet 1.5 km northeast from San Andrés, Colombia, uninhabited and exclusive for touristic use (Van Tonningen, 2014). The technology is a wind powered reverse osmosis (RO) system that can fulfil the drinkable water and electricity demands of the Cay. This way can be alleviated the sanitary conditions resulting from unsustainable touristic practices. Moreover, this project is seen as a promoter of sustainable development in the Archipelago (Coralina, 2006), and as a potential solution to provide electricity and water to rural and remote areas of low utility coverage but abundant wind power. There are no environmental or social impact analyses that validate the sustainable character of the technology transfer. Moreover, although it is intended to improve the livelihood of target users their opinions are not reflected in the project plans. This situation resembles those factors that describe the trend to failure of technology transfers. Therefore this research made an integral assessment of the project as a Socio-Technical System (STS) to provide useful findings and recommendations that could lead it away from such trend. The Functions of Innovation Systems (FIS) framework (Van Alphen, 2008) was chosen for a systems approach analysis. Through this was found that poor planning, insufficient financial resources and ineffective communication channels are the most relevant barriers for a successful implementation of the FreshWaterMill. The most relevant drivers are the suitability of the place for a wind/RO system, the planning of a local educational center, a remarkable advocacy for Renewable Energy Technologies (RETs) in the Archipelago and the existence of local human capital and R&D on RE. Five conditions for self-organization were derived from the PAR (Participatory Action Research) methodology to explore the likeliness of self-organization for bottom-up management. Through this methodology was shown that the difficult relationship between the corporation and the touristic service providers, their lack of group cohesion, managerial and operational capacities, ignorance and/or misuse of instruments for self-organization, make unfeasible for this group to address the barriers and support the drivers of the project. Relevant conditions from the context not covered by the previous methodologies were also included. These reflected that the advocacy for RETs is counteracted by the fragmentation between institutional actors and their lack of managerial skills on technology topics, which makes them rely on national and international assistance to achieve a technological transition. The regular interaction that Johnny Cay workers will have with the windmill, the affinity of the life plan of young adults to the project objectives and the likeliness of this group to make economic contributions urges the need for a participatory approach. The socio-cultural crisis of the Archipelago supports this recommendation. However, the difficulty of institutional entities to understand and assume the roles that require a participatory approach and the path dependency on top-down regulation makes it a complex challenge. A participatory approach for the FreshWaterMill is indirectly supported by the management plan of the Natural Regional Park Johnny Cay and the Community and institutional participation board. Additional to the commitment of the corporation to assume an enabling role, the process needs a mediator so the touristic service.

As it has been proved in several researches carried out by different authors, riverine floods and the scour induced by these are one of the main causes of bridge collapse. More specifically, local scour causes a loss in the lateral resistance of bridge foundation, thus potentially increasing the seismic vulnerability of a bridge system. The present study assesses the combination of scour and earthquake effects for a bridge located in a road network crossing valleys in the Pyrenees Mountain range (France). The bridge spans over a river stream of trapezoidal cross-section, which is more able to capture actual physical behaviours than the rectangular section generally used for similar studies. The bridge consists in a continuous RC deck supported by two multi-column piers. Making use of the OpenSees software, a 3D finite-element model of the bridge is built and subjected to a suite of 312 ground motions (i.e., non-linear time history analyses). Fragility curves are developed for this multi-hazard case study, considering specific levels of damage that might be of interest, as well a comparison between fragility characteristics obtained in the absence and presence of scour. In order to fully study the potentially detrimental effects of scour on the dynamic behavior of the considered bridge, it is considered different scour combinations in the non-linear time-history analyses, such as: • Equal scour depth in all columns. • Same scour depth in the columns of the same pier. • Same scour depth in columns of different piers. • Scour depth concentrated in just one column of the bridge This study demonstrates the ability of a given numerical model to account for various hazard loadings and failure mechanisms, thus providing support to decision making regarding bridge management and monitoring.

Abstract: The Environmental Control System (ECS) allows the control of the environment within the cabin and flight deck for pilot and passenger comfort, and protects them from adverse weather conditions. This study presents a Matlab-Simulink® model developed to calculate the shaft power and ventilation required by the ECS during different flight conditions. The ECS model includes two blocks. The first block determines the requirements of the ECS by means of the analysis of thermal loads presented inside the helicopter. The second block computes the ECS air-conditioning pack of the helicopter (for cooling, heating and demisting). Two different ambient and flight conditions are simulated to find the power consumption of the air-conditioning pack once a comfortable cabin environment has been achieved. It is concluded that by using this model, the changes in the comfort level can be predicted in real time in order to intelligently reduce the ECS overall power consumption in a helicopter by choosing among five different ECS configurations the most appropriated, thus maintain the thermal comfort of the pilot and the passengers. Resumen: El Sistema de Control Ambiental (ECS por sus siglas en inglés) permite el control del ambiente dentro de la cabina y la consola de control del helicóptero, proporcionando confort y protección a los pilotos y pasajeros en condiciones climáticas adversas. Este estudio presenta un modelo en Matlab-Simulink® aplicable a diversas condiciones de vuelo para calcular la potencia mecánica y la ventilación requerida por el ECS. El modelo ECS incluye dos bloques. El primer bloque determina los requerimientos del ECS por medio del análisis de cargas térmicas presentadas en el interior del helicóptero. El segundo bloque computa el sistema de acondicionamiento de aire del ECS dentro de un helicoptero (para refrigeración, calefacción y desempañado). Dos condiciones diferentes de ambiente y de vuelo son simuladas para encontrar el consumo de potencia del sistema de acondicionamiento de aire una vez alcanzado un ambiente de cabina confortable. Se concluye que por medio de este modelo, los patrones de cambio próximos en el nivel de confort se pueden predecir en tiempo real con el fin de reducir de forma inteligente el consumo general de energía del ECS en un helicóptero al seleccionar entre 5 configuraciones la más apropiada, y asi mantener el confort térmico del piloto y los pasajeros.

Abstract: Different contract types means different incentives, burdens and relationships. The contract type responsibilities and price should be in accordance with the project needs and organization capacities, not knowing this could entail less project profitability and chances of success. It is necessary to understand the alternatives and how they behave, in order to develop the right strategies to avoid overruns and improve the project quality. The goal of this thesis is to develop a decision analysis model for contract type selection. This model will become a useful tool for contractor and client preferences in an easy and effective way. Decision analysis is a powerful tool that will help us to bring clarity of thought in this process; during this thesis it is described what is a project, its phases, activities and the components that understand it, in the same way it is presented the contract management life cycle. This model attempts to link and evaluate the contract types, differentiators, and the client and contractor preferences in order to quantify the costs and benefits of each type, which could be the best option. One priority of this thesis is to understand the synergetic relationship between contract type, contract management, project management and contract price, in order to take the best decision, increasing the probability to achieve a successful project execution. As application example, a contract type selection for the EPCI (Engineering, Procurement, Construction & Installation) of a topside for a semisubmersible platform is presented.Resumen: Diferentes tipos de contrato significa diferentes incentivos, cargas y relaciones. Las responsabilidades y el precio del tipo de contrato deben estar de acuerdo con las necesidades del proyecto y las capacidades de la organización, sin saber que esto podría implicar una menor rentabilidad del proyecto y posibilidades de éxito. Es necesario comprender las alternativas y la forma en que se comportan, a fin de desarrollar las estrategias correctas para evitar los excesos y mejorar la calidad del proyecto. El objetivo de esta tesis es desarrollar un modelo de análisis de decisión para la selección del tipo de contrato. Este modelo se convertirá en una herramienta útil para las preferencias de los contratistas y clientes de una manera fácil y efectiva. El análisis de decisiones es una herramienta poderosa que nos ayudará a tener claridad de pensamiento en este proceso; Durante esta tesis se describe qué es un proyecto, sus fases, actividades y los componentes que lo comprenden, de la misma manera que se presenta el ciclo de vida de gestión de contratos. Este modelo intenta vincular y evaluar los tipos de contrato, los diferenciadores y las preferencias del cliente y del contratista para cuantificar los costos y beneficios de cada tipo, lo que podría ser la mejor opción. Una de las prioridades de esta tesis es comprender la relación sinérgica entre el tipo de contrato, la gestión de contratos, la gestión de proyectos y el precio del contrato, para tomar la mejor decisión, aumentando la probabilidad de lograr una ejecución exitosa del proyecto. Como ejemplo de aplicación, se presenta una selección de tipo de contrato para el EPCI (Ingeniería, Aprovisionamiento, Construcción e Instalación) de un topside para una plataforma semisumergible.

Este libro trata sobre quién gana con el sistema eléctrico. A través de un relato periodístico se aborda la situación del sector y su influencia en la ciudadanía. Se analizan en profundidad todas las causas que han llevado a esta situación de oligopolio casi perfecto, de inestabilidad regulatoria y de dependencia energética y se recogen algunas alternativas para un nuevo modelo más acorde a las necesidades de los ciudadanos.

Este compendio de casos de estudio tiene como finalidad apoyar el curso teórico de termodinámica II que se imparte a los estudiantes de Ingeniería Mecánica de la Universidad del Norte. Los contenidos han surgido de la experiencia de los autores en le laboratorio virtual de termodinámica, por ello se hace especial énfasis en el uso de software de simulación ASPENHYSYS para realizar cálculos de forma rápida y centrarse en el análisis de la información obtenida.