Performance of coupled ED-tether/ion thrsuter system

Use of propulsion systems that couple electyrodynamic tethers to ion thrusters, as suggested in the literature, is discussed. The system establishes electrical contact with the ionospheric plasma, at the anodic end of the tether, by ejecting ions instead of collecting electrons; also, the ion thruster adds its thrust to the Lorentz force on the tether. In this paper, we analyze the performance of this coupled system, as measured by the ratio of mission impulse (thrust times mission duration) to the overall system mass, which includes the power subsystem mass, the tether subsystem mass, and the propellant mass consumed in the ion thruster. It is shown that a tether acting by itself, collecting electrons at its anodic end, substantially outperforms the coupled system for times longer than a characteristic time of the ion thruster, for which propellant mass equals the power subsystem mass; for shorter times performances are shown to be similar.

High Intensity Lasers Application to Advanced Materials Processing: Laser Peening and Related Processes

High Intensity Lasers Application to Advanced Materials Processing: Laser Peening and Related

Secure optical networks based on quantum key distribution and weakly trusted repeaters

Abstract—In this paper we explore how recent technologies can improve the security of optical networks. In particular, we study how to use quantum key distribution(QKD) in common optical network infrastructures and propose a method to overcome its distance limitations. QKD is the first technology offering information theoretic secretkey distribution that relies only on the fundamental principles of quantum physics. Point-to-point QKDdevices have reached a mature industrial state; however, these devices are severely limited in distance, since signals at the quantum level (e.g., single photons) are highly affected by the losses in the communication channel and intermediate devices. To overcome this limitation, intermediate nodes (i.e., repeaters) are used. Both quantum-regime and trusted, classical repeaters have been proposed in the QKD literature, but only the latter can be implemented in practice. As a novelty, we propose here a new QKD network model based on the use of not fully trusted intermediate nodes, referred to as weakly trusted repeaters. This approach forces the attacker to simultaneously break several paths to get access to the exchanged key, thus improving significantly the security of the network. We formalize the model using network codes and provide real scenarios that allow users to exchange secure keys over metropolitan optical networks using only passive components. Moreover, the theoretical framework allows one to extend these scenarios not only to accommodate more complex trust constraints, but also to consider robustness and resiliency constraints on the network.

Advances in global instability computations: from incompressible to hypersonic flow

Esta tesis constituye un gran avance en el conocimiento del estudio y análisis de inestabilidades hidrodinámicas desde un punto de vista físico y teórico, como consecuencia de haber desarrollado innovadoras técnicas para la resolución computacional eficiente y precisa de la parte principal del espectro correspondiente a los problemas de autovalores (EVP) multidimensionales que gobiernan la inestabilidad de flujos con dos o tres direcciones espaciales inhomogéneas, denominados problemas de estabilidad global lineal. En el contexto del trabajo de desarrollo de herramientas computacionales presentado en la tesis, la discretización mediante métodos de diferencias finitas estables de alto orden de los EVP bidimensionales y tridimensionales que se derivan de las ecuaciones de Navier-Stokes linealizadas sobre flujos con dos o tres direcciones espaciales inhomogéneas, ha permitido una aceleración de cuatro órdenes de magnitud en su resolución. Esta mejora de eficiencia numérica se ha conseguido gracias al hecho de que usando estos esquemas de diferencias finitas, técnicas eficientes de resolución de problemas lineales son utilizables, explotando el alto nivel de dispersión o alto número de elementos nulos en las matrices involucradas en los problemas tratados. Como más notable consecuencia cabe destacar que la resolución de EVPs multidimensionales de inestabilidad global, que hasta la fecha necesitaban de superordenadores, se ha podido realizar en ordenadores de sobremesa. Además de la solución de problemas de estabilidad global lineal, el mencionado desarrollo numérico facilitó la extensión de las ecuaciones de estabilidad parabolizadas (PSE) lineales y no lineales para analizar la inestabilidad de flujos que dependen fuertemente en dos direcciones espaciales y suavemente en la tercera con las ecuaciones de estabilidad parabolizadas tridimensionales (PSE-3D). Precisamente la capacidad de extensión del novedoso algoritmo PSE-3D para el estudio de interacciones no lineales de los modos de estabilidad, desarrollado íntegramente en esta tesis, permite la predicción de transición en flujos complejos de gran interés industrial y por lo tanto extiende el concepto clásico de PSE, el cuál ha sido empleado exitosamente durante las pasadas tres décadas en el mismo contexto para problemas de capa límite bidimensional. Típicos ejemplos de flujos incompresibles se han analizado en este trabajo sin la necesidad de recurrir a restrictivas presuposiciones usadas en el pasado. Se han estudiado problemas vorticales como es el caso de un vórtice aislado o sistemas de vórtices simulando la estela de alas, en los que la homogeneidad axial no se impone y así se puede considerar la difusión viscosa del flujo. Además, se ha estudiado el chorro giratorio turbulento, cuya inestabilidad se utiliza para mejorar las características de funcionamiento de combustores. En la tesis se abarcan adicionalmente problemas de flujos compresibles. Se presenta el estudio de inestabilidad de flujos de borde de ataque a diferentes velocidades de vuelo. También se analiza la estela formada por un elemento rugoso aislado en capa límite supersónica e hipersónica, mostrando excelentes comparaciones con resultados obtenidos mediante simulación numérica directa. Finalmente, nuevas inestabilidades se han identificado en el flujo hipersónico a Mach 7 alrededor de un cono elíptico que modela el vehículo de pruebas en vuelo HIFiRE-5. Los resultados comparan favorablemente con experimentos en vuelo, lo que subraya aún más el potencial de las metodologías de análisis de estabilidad desarrolladas en esta tesis. ABSTRACT The present thesis constitutes a step forward in advancing the frontiers of knowledge of fluid flow instability from a physical point of view, as a consequence of having been successful in developing groundbreaking methodologies for the efficient and accurate computation of the leading part of the spectrum pertinent to multi-dimensional eigenvalue problems (EVP) governing instability of flows with two or three inhomogeneous spatial directions. In the context of the numerical work presented in this thesis, the discretization of the spatial operator resulting from linearization of the Navier-Stokes equations around flows with two or three inhomogeneous spatial directions by variable-high-order stable finite-difference methods has permitted a speedup of four orders of magnitude in the solution of the corresponding two- and three-dimensional EVPs. This improvement of numerical performance has been achieved thanks to the high-sparsity level offered by the high-order finite-difference schemes employed for the discretization of the operators. This permitted use of efficient sparse linear algebra techniques without sacrificing accuracy and, consequently, solutions being obtained on typical workstations, as opposed to the previously employed supercomputers. Besides solution of the two- and three-dimensional EVPs of global linear instability, this development paved the way for the extension of the (linear and nonlinear) Parabolized Stability Equations (PSE) to analyze instability of flows which depend in a strongly-coupled inhomogeneous manner on two spatial directions and weakly on the third. Precisely the extensibility of the novel PSE-3D algorithm developed in the framework of the present thesis to study nonlinear flow instability permits transition prediction in flows of industrial interest, thus extending the classic PSE concept which has been successfully employed in the same context to boundary-layer type of flows over the last three decades. Typical examples of incompressible flows, the instability of which was analyzed in the present thesis without the need to resort to the restrictive assumptions used in the past, range from isolated vortices, and systems thereof, in which axial homogeneity is relaxed to consider viscous diffusion, as well as turbulent swirling jets, the instability of which is exploited in order to improve flame-holding properties of combustors. The instability of compressible subsonic and supersonic leading edge flows has been solved, and the wake of an isolated roughness element in a supersonic and hypersonic boundary-layer has also been analyzed with respect to its instability: excellent agreement with direct numerical simulation results has been obtained in all cases. Finally, instability analysis of Mach number 7 ow around an elliptic cone modeling the HIFiRE-5 flight test vehicle has unraveled flow instabilities near the minor-axis centerline, results comparing favorably with flight test predictions.

High data rate modulation of high power 1060-nm DBR tapered lasers with separate contacts

Direct optical modulation at 2.5 Gb/s with amplitude of more than 0.5 W has been demonstrated in single longitudinal mode distributed Bragg reflector tapered lasers emitting at 1060 nm with separated injection of the ridge waveguide and tapered sections. The modulating signal of ~110 mA peak to peak was applied to the ridge waveguide section, yielding a high modulation efficiency of ~5 W/A. The large-signal frequency response of the experimental set-up was limited by the bandwidth of the electrical amplifier rather than by the internal dynamics of the laser, indicating that higher bit rates could be achieved with improved driving electronics.

Analysis of gain-switching in two-section tapered lasers

We analyze the gain-switching dynamics of two-section tapered lasers by means of a simplified three-rate-equation model. The goal is to improve the understanding of the underlying physics and to optimize the device geometry to achieve high power short duration optical pulses.

Transformer-coupled converter for voltage modulation techniques

In high performance digital systems as well as in RF systems, voltage scaling and modulation techniques have been adopted to achieve a more efficient processing of the energy. The implementation of such techniques relies on a power supply that is capable of rapidly adjusting the system supply voltage. In this paper, a pulsewidth modulation multiphase topology with magnetic coupling is proposed for its use in voltage modulation techniques. Since the magnetic coupling in this topology is done with transformers instead of coupled inductors, the energy storage is reduced and very fast voltage changes are achieved. Advantages and drawbacks of this topology have been previously presented in the literature and in this paper, the design criteria for implementing a power supply for the envelope elimination and restoration technique in an RF system are presented along with an implementation of the power supply.

Web based interactive educational software introducing semiconductor laser dynamics: Sound Of Lasers (SOL)

In this work, educational software for intuitive understanding of the basic dynamic processes of semiconductor lasers is presented. The proposed tool is addressed to the students of optical communication courses, encouraging self consolidation of the subjects learned in lectures. The semiconductor laser model is based on the well known rate equations for the carrier density, photon density and optical phase. The direct modulation of the laser is considered with input parameters which can be selected by the user. Different options for the waveform, amplitude and frequency of thpoint. Simulation results are plotted for carrier density and output power versus time. Instantaneous frequency variations of the laser output are numerically shifted to the audible frequency range and sent to the computer loudspeakers. This results in an intuitive description of the “chirp” phenomenon due to amplitude-phase coupling, typical of directly modulated semiconductor lasers. In this way, the student can actually listen to the time resolved spectral content of the laser output. By changing the laser parameters and/or the modulation parameters,consequent variation of the laser output can be appreciated in intuitive manner. The proposed educational tool has been previously implemented by the same authors with locally executable software. In the present manuscript, we extend our previous work to a web based platform, offering improved distribution and allowing its use to the wide audience of the web.

Laser Shock Microforming of Thin Metal Sheets with Q-Switched ns Lasers

The increasing demands in MEMS fabrication are leading to new requirements in production technology. Especially the packaging and assembly require high accuracy in positioning and high reproducibility in combination with low production costs. Conventional assembly technology and mechanical adjustment methods are time consuming and expensive. Each component of the system has to be positioned and fixed. Also adjustment of the parts after joining requires additional mechanical devices that need to be accessible after joining.

Modelización de las propiedades radiativas e interacción de láseres ultraintensos con la materia

Desde el año 2004 el código ARWEN ha sido utilizado con éxito para simular y diseñar experimentos relacionados con blancos para fusión por confinamiento inercial [146], astrofísica de laboratorio [145], plasmas como amplificadores de láseres de rayos X [107] o plasmas creados por láser para la medición de espectros de transmisión. Para la realización de estas simulaciones es necesario, además de métodos de alto orden precisos y que presenten buenas propiedades conservativas, conocer ciertas propiedades de los plasmas. En el caso de la fluidodinámica y la conducción electrónica necesitaremos conocer la ecuación de estado [94, 49, 36], y para el transporte de la radiación será preciso disponer de los datos de absorción y emisión [104, 95, 40]. Hasta el año 2009 ARWEN dependía de códigos externos para la generación de estas tablas de opacidad, careciendo de control sobre los métodos empleados para su generación. Además estos códigos asumían equilibrio local termodinámico (LTE), limitando su validez a rangos de alta densidad y baja temperatura. En el marco de esta tesis se ha desarrollado el código BIGBART para la generación de tablas detalladas de opacidad y emisividad para su uso en el módulo de transporte de radiación. De esta forma el grupo dispondrá de su propia herramienta de generación de propiedades radiativas. El código desarrollado es capaz de tratar plasmas en estado fuera de equilibrio (non-LTE) mediante el modelo colisional-radiativo, extendiendo así el rango de validez de las tablas generadas. El trabajo desarrollado para implementar un código LTE/non-LTE estacionario es el siguiente Cálculo de estructura y datos atómicos. Se ha acoplado en código FAC a BIGBART, incorporando la capacidad para generar potenciales atómicos para una configuración y el cálculo de funciones de onda de electrones en orbitales ligados y libres. Aproximaciones y métodos para la obtención de tasas y secciones eficaces de procesos. Se han incluido y programado los modelos implementados en FAC para el cálculo de secciones eficaces de fotoionización, y tasas de decaimiento de emisión espontánea y autoionización. Además se ha incluido el modelo Plane-Wave Born (PWBA) para el cálculo de las secciones eficaces de ionización y excitación colisional. Modelos para la obtención de la distribución de estados iónicos dentro del plasma. Se ha programado un solver LTE basado en la ecuación de Saha-Boltzmann con efectos de ionización por presión debida a los iones adyacentes. También se ha implementado un modelo non-LTE colisionalradiativo para la resolución del sistema de ecuaciones que nos permite obtener la densidad de estados iónicos fuera de equilibrio. Modelo non-LTE RADIOM. Se ha implementado el modelo RADIOM para aproximar efectos de no-equilibrio mediante cálculos LTE a una temperatura equivalente, menor o igual que la temperatura electrónica real. Cálculo de las propiedades espectrales de absorción y emisión. Se han implementado los modelos para el cálculo de los perfiles espectrales de absorción y emisión para procesos entre niveles ligados, ligado-libre y librelibre. Aprovechando el trabajo realizado en este sentido, durante el transcurso de esta tesis se amplió el código BIGBART para tratar problemas con dependencia temporal. La extensión para tratar este tipo de problemas se orientó a la simulación numérica de la interacción de láseres ultra intensos en el rango XUV/rayos X. Para ello, además de adaptar el modelo non-LTE colisionalradiativo se incluyeron procesos adicionales asociados a la interacción de la materia con fotones altamente energéticos. También se han incluido modelos para el cálculo de las propiedades ópticas, y por ende las propiedades dieléctricas de la materia irradiada, de gran interés en algunas aplicaciones novedosas de estos láseres intensos. Debido a la naturaleza fuertemente fuera de equilibrio en la interacción de fotones de alta energía con la materia, se incluyó el tratamiento de la distribución de electrones libres fuera de equilibrio en la aproximación de Fokker-Planck, tanto para condiciones degeneradas como no degeneradas. El trabajo desarrollado en el código non-LTE con dependencia temporal es el siguiente Procesos asociados a láseres intensos XUV/rayos X. Se ha implementado el cálculo de procesos radiativos estimulados de absorción y emisión por el láser. También se han incluido procesos asociados a la creación de vacantes en capas internas electrónicas (Shake), además de doble autoionización y doble fotoionización. Cálculo de propiedades ópticas y dieléctricas en blancos sólidos. Se ha implementado un modelo para la absorción por bremsstrahlung inverso en blancos en estado sólido. Con el coeficiente de extinción debido a procesos de fotoabsorción resonante, fotoionización y bremsstrahlung inverso se obtiene el ´ındice de refracción mediante la relación de Kronig-Kramers. Electrones fuera de equilibrio. Se ha tratado la evolución de la distribución de electrones, cuando no está justificado asumir que es Maxwelliana o de Fermi-Dirac, mediante la aproximación de Fokker-Planck para la colisión entre electrones libres. En la resolución de la ecuación de Fokker-Planck se han incluido los procesos inelásticos por colisiones con iones y términos fuente por interacción con el láser y otros procesos. ABSTRACT Since 2004 the ARWEN code has been successfully used to simulate and design targets for inertial confinement fusion experiments [146], laboratory astrophysics [145], plasmas as X-ray lasers amplifiers [107] or laser created plasmas for measuring transmission spectra. To perform these simulations it is necessary, in addition to high order precise methods with good conservative properties, to know certain properties of plasmas. For fluid dynamic and electronic conduction we need to know the equation of state [94, 49, 36], and for radiation transport it will be necessary to have the data of the absorption and emission [104, 95, 40]. Until 2009 ARWEN depended on external codes to generate these opacity tables, lacking of control over the methods used for their generation. Besides, these codes assumed local thermodynamic equilibrium (LTE), limiting their validity ranges to high densities and low temperatures. As part of this thesis it has been developed the BIGBART code for generating detailed opacity and emissivity tables for use in the radiation transport module. This group will have its own tool for the generation of radiative properties. The developed code is capable of treating plasmas out of equilibrium (non-LTE) by means of a collisional-radiative model, extending the range of validity of the generated tables. The work to implement an LTE/non-LTE steady-state code is as follows Calculation of structure and atomic data. the FAC code was coupled to BIGBART, incorporating the ability to generate atomic potentials for calculating configuration wave functions for bound and free electrons. Approaches and methods for obtaining cross sections and processes rates. We have included and reprogrammed in Fortran the models implemented in FAC for calculation of photoionization cross sections and decay rates of spontaneous emission and autoionization. We also included the Plane- Wave Born (PWBA) model to calculate the cross sections of ionization and collisional excitation. Models for the obtention of the distribution of ionic states within the plasma. We programmed a LTE solver based on the Saha-Boltzmann equation with pressure ionization effects due to adjacent ions. It has also been implemented a non-LTE collisional-radiative model for solving the system of equations that allows us to obtain the density of ionic states out of equilibrium. Non-LTE RADIOM model. We have implemented the non-LTE RADIOM model to approximate non-equilibrium effects with LTE data at an equivalent temperature, lower or equal to the actual electronic temperature. Calculation of the spectral absorption and emission properties. Models have been implemented for the calculation of the spectral profiles of absorption and emission processes between bound levels, free-bound and free-free. Taking advantage of the work done in this direction throughout the course of this thesis the code BIGBART was extended to treat time-dependent problems. The extension to treat such problems is oriented to the numerical simulation of the interaction of ultra intense lasers in the XUV/X-ray range. For this range, in addition to adapting the non-LTE collisional-radiative model, additional processes associated with the interaction of matter with high energy photons. We also included models for calculation of the optical properties, and therefore the dielectric properties of the irradiated material, of great interest in some novel applications of these intense lasers. Due to the strong non-equilibrium nature of the interaction of high energy photons with matter, we included the treatment of the distribution of free electrons out of equilibrium in the Fokker-Planck approximation for both degenerate and non-degenerate conditions. The work in the non-LTE time-dependent code is as follows Processes associated with intense XUV/X-ray lasers. We have implemented the calculation of stimulated radiative processes in absorption and emission. Also we included processes associated with the creation of electronic vacancies in inner shells (Shake), double autoionization and double photoionization. Calculation of optical and dielectric properties in solid targets. We have implemented a model for inverse bremsstrahlung absorption in solid targets. With the extinction coefficient from resonant photoabsorption, photoionization and inverse bremsstrahlung the refractive index is obtained by the Kramers-Kronig relation. Electrons out of equilibrium. We treat the evolution of the electron distribution, when it is not justified to assume a Maxwellian or Fermi-Dirac distribution, by the Fokker-Planck approximation for collisions between electrons. When solving the Fokker-Planck equation we included inelastic collision processes with ions and source terms by interaction with the laser and other processes.

A swarm intelligence approach based on coupled oscillators: an application in demand side management with photovoltaic distributed generation

Esta Tesis aborda los problemas de eficiencia de las redes eléctrica desde el punto de vista del consumo. En particular, dicha eficiencia es mejorada mediante el suavizado de la curva de consumo agregado. Este objetivo de suavizado de consumo implica dos grandes mejoras en el uso de las redes eléctricas: i) a corto plazo, un mejor uso de la infraestructura existente y ii) a largo plazo, la reducción de la infraestructura necesaria para suplir las mismas necesidades energéticas. Además, esta Tesis se enfrenta a un nuevo paradigma energético, donde la presencia de generación distribuida está muy extendida en las redes eléctricas, en particular, la generación fotovoltaica (FV). Este tipo de fuente energética afecta al funcionamiento de la red, incrementando su variabilidad. Esto implica que altas tasas de penetración de electricidad de origen fotovoltaico es perjudicial para la estabilidad de la red eléctrica. Esta Tesis trata de suavizar la curva de consumo agregado considerando esta fuente energética. Por lo tanto, no sólo se mejora la eficiencia de la red eléctrica, sino que también puede ser aumentada la penetración de electricidad de origen fotovoltaico en la red. Esta propuesta conlleva grandes beneficios en los campos económicos, social y ambiental. Las acciones que influyen en el modo en que los consumidores hacen uso de la electricidad con el objetivo producir un ahorro energético o un aumento de eficiencia son llamadas Gestión de la Demanda Eléctrica (GDE). Esta Tesis propone dos algoritmos de GDE diferentes para cumplir con el objetivo de suavizado de la curva de consumo agregado. La diferencia entre ambos algoritmos de GDE reside en el marco en el cual estos tienen lugar: el marco local y el marco de red. Dependiendo de este marco de GDE, el objetivo energético y la forma en la que se alcanza este objetivo son diferentes. En el marco local, el algoritmo de GDE sólo usa información local. Este no tiene en cuenta a otros consumidores o a la curva de consumo agregado de la red eléctrica. Aunque esta afirmación pueda diferir de la definición general de GDE, esta vuelve a tomar sentido en instalaciones locales equipadas con Recursos Energéticos Distribuidos (REDs). En este caso, la GDE está enfocada en la maximización del uso de la energía local, reduciéndose la dependencia con la red. El algoritmo de GDE propuesto mejora significativamente el auto-consumo del generador FV local. Experimentos simulados y reales muestran que el auto-consumo es una importante estrategia de gestión energética, reduciendo el transporte de electricidad y alentando al usuario a controlar su comportamiento energético. Sin embargo, a pesar de todas las ventajas del aumento de auto-consumo, éstas no contribuyen al suavizado del consumo agregado. Se han estudiado los efectos de las instalaciones locales en la red eléctrica cuando el algoritmo de GDE está enfocado en el aumento del auto-consumo. Este enfoque puede tener efectos no deseados, incrementando la variabilidad en el consumo agregado en vez de reducirlo. Este efecto se produce porque el algoritmo de GDE sólo considera variables locales en el marco local. Los resultados sugieren que se requiere una coordinación entre las instalaciones. A través de esta coordinación, el consumo debe ser modificado teniendo en cuenta otros elementos de la red y buscando el suavizado del consumo agregado. En el marco de la red, el algoritmo de GDE tiene en cuenta tanto información local como de la red eléctrica. En esta Tesis se ha desarrollado un algoritmo autoorganizado para controlar el consumo de la red eléctrica de manera distribuida. El objetivo de este algoritmo es el suavizado del consumo agregado, como en las implementaciones clásicas de GDE. El enfoque distribuido significa que la GDE se realiza desde el lado de los consumidores sin seguir órdenes directas emitidas por una entidad central. Por lo tanto, esta Tesis propone una estructura de gestión paralela en lugar de una jerárquica como en las redes eléctricas clásicas. Esto implica que se requiere un mecanismo de coordinación entre instalaciones. Esta Tesis pretende minimizar la cantidad de información necesaria para esta coordinación. Para lograr este objetivo, se han utilizado dos técnicas de coordinación colectiva: osciladores acoplados e inteligencia de enjambre. La combinación de estas técnicas para llevar a cabo la coordinación de un sistema con las características de la red eléctrica es en sí mismo un enfoque novedoso. Por lo tanto, este objetivo de coordinación no es sólo una contribución en el campo de la gestión energética, sino también en el campo de los sistemas colectivos. Los resultados muestran que el algoritmo de GDE propuesto reduce la diferencia entre máximos y mínimos de la red eléctrica en proporción a la cantidad de energía controlada por el algoritmo. Por lo tanto, conforme mayor es la cantidad de energía controlada por el algoritmo, mayor es la mejora de eficiencia en la red eléctrica. Además de las ventajas resultantes del suavizado del consumo agregado, otras ventajas surgen de la solución distribuida seguida en esta Tesis. Estas ventajas se resumen en las siguientes características del algoritmo de GDE propuesto: • Robustez: en un sistema centralizado, un fallo o rotura del nodo central provoca un mal funcionamiento de todo el sistema. La gestión de una red desde un punto de vista distribuido implica que no existe un nodo de control central. Un fallo en cualquier instalación no afecta el funcionamiento global de la red. • Privacidad de datos: el uso de una topología distribuida causa de que no hay un nodo central con información sensible de todos los consumidores. Esta Tesis va más allá y el algoritmo propuesto de GDE no utiliza información específica acerca de los comportamientos de los consumidores, siendo la coordinación entre las instalaciones completamente anónimos. • Escalabilidad: el algoritmo propuesto de GDE opera con cualquier número de instalaciones. Esto implica que se permite la incorporación de nuevas instalaciones sin afectar a su funcionamiento. • Bajo coste: el algoritmo de GDE propuesto se adapta a las redes actuales sin requisitos topológicos. Además, todas las instalaciones calculan su propia gestión con un bajo requerimiento computacional. Por lo tanto, no se requiere un nodo central con un alto poder de cómputo. • Rápido despliegue: las características de escalabilidad y bajo coste de los algoritmos de GDE propuestos permiten una implementación rápida. No se requiere una planificación compleja para el despliegue de este sistema. ABSTRACT This Thesis addresses the efficiency problems of the electrical grids from the consumption point of view. In particular, such efficiency is improved by means of the aggregated consumption smoothing. This objective of consumption smoothing entails two major improvements in the use of electrical grids: i) in the short term, a better use of the existing infrastructure and ii) in long term, the reduction of the required infrastructure to supply the same energy needs. In addition, this Thesis faces a new energy paradigm, where the presence of distributed generation is widespread over the electrical grids, in particular, the Photovoltaic (PV) generation. This kind of energy source affects to the operation of the grid by increasing its variability. This implies that a high penetration rate of photovoltaic electricity is pernicious for the electrical grid stability. This Thesis seeks to smooth the aggregated consumption considering this energy source. Therefore, not only the efficiency of the electrical grid is improved, but also the penetration of photovoltaic electricity into the grid can be increased. This proposal brings great benefits in the economic, social and environmental fields. The actions that influence the way that consumers use electricity in order to achieve energy savings or higher efficiency in energy use are called Demand-Side Management (DSM). This Thesis proposes two different DSM algorithms to meet the aggregated consumption smoothing objective. The difference between both DSM algorithms lie in the framework in which they take place: the local framework and the grid framework. Depending on the DSM framework, the energy goal and the procedure to reach this goal are different. In the local framework, the DSM algorithm only uses local information. It does not take into account other consumers or the aggregated consumption of the electrical grid. Although this statement may differ from the general definition of DSM, it makes sense in local facilities equipped with Distributed Energy Resources (DERs). In this case, the DSM is focused on the maximization of the local energy use, reducing the grid dependence. The proposed DSM algorithm significantly improves the self-consumption of the local PV generator. Simulated and real experiments show that self-consumption serves as an important energy management strategy, reducing the electricity transport and encouraging the user to control his energy behavior. However, despite all the advantages of the self-consumption increase, they do not contribute to the smooth of the aggregated consumption. The effects of the local facilities on the electrical grid are studied when the DSM algorithm is focused on self-consumption maximization. This approach may have undesirable effects, increasing the variability in the aggregated consumption instead of reducing it. This effect occurs because the algorithm only considers local variables in the local framework. The results suggest that coordination between these facilities is required. Through this coordination, the consumption should be modified by taking into account other elements of the grid and seeking for an aggregated consumption smoothing. In the grid framework, the DSM algorithm takes into account both local and grid information. This Thesis develops a self-organized algorithm to manage the consumption of an electrical grid in a distributed way. The goal of this algorithm is the aggregated consumption smoothing, as the classical DSM implementations. The distributed approach means that the DSM is performed from the consumers side without following direct commands issued by a central entity. Therefore, this Thesis proposes a parallel management structure rather than a hierarchical one as in the classical electrical grids. This implies that a coordination mechanism between facilities is required. This Thesis seeks for minimizing the amount of information necessary for this coordination. To achieve this objective, two collective coordination techniques have been used: coupled oscillators and swarm intelligence. The combination of these techniques to perform the coordination of a system with the characteristics of the electric grid is itself a novel approach. Therefore, this coordination objective is not only a contribution in the energy management field, but in the collective systems too. Results show that the proposed DSM algorithm reduces the difference between the maximums and minimums of the electrical grid proportionally to the amount of energy controlled by the system. Thus, the greater the amount of energy controlled by the algorithm, the greater the improvement of the efficiency of the electrical grid. In addition to the advantages resulting from the smoothing of the aggregated consumption, other advantages arise from the distributed approach followed in this Thesis. These advantages are summarized in the following features of the proposed DSM algorithm: • Robustness: in a centralized system, a failure or breakage of the central node causes a malfunction of the whole system. The management of a grid from a distributed point of view implies that there is not a central control node. A failure in any facility does not affect the overall operation of the grid. • Data privacy: the use of a distributed topology causes that there is not a central node with sensitive information of all consumers. This Thesis goes a step further and the proposed DSM algorithm does not use specific information about the consumer behaviors, being the coordination between facilities completely anonymous. • Scalability: the proposed DSM algorithm operates with any number of facilities. This implies that it allows the incorporation of new facilities without affecting its operation. • Low cost: the proposed DSM algorithm adapts to the current grids without any topological requirements. In addition, every facility calculates its own management with low computational requirements. Thus, a central computational node with a high computational power is not required. • Quick deployment: the scalability and low cost features of the proposed DSM algorithms allow a quick deployment. A complex schedule of the deployment of this system is not required.

A coupled elastoplastic-damage constitutive model with Lode angle dependent failure criterion

A coupled elastoplastic-damage constitutive model with Lode angle dependent failure criterion for high strain and ballistic applications is presented. A Lode angle dependent function is added to the equivalent plastic strain to failure definition of the Johnson–Cook failure criterion. The weakening in the elastic law and in the Johnson–Cook-like constitutive relation implicitly introduces the Lode angle dependency in the elastoplastic behaviour. The material model is calibrated for precipitation hardened Inconel 718 nickel-base superalloy. The combination of a Lode angle dependent failure criterion with weakened constitutive equations is proven to predict fracture patterns of the mechanical tests performed and provide reliable results. Additionally, the mesh size dependency on the prediction of the fracture patterns was studied, showing that was crucial to predict such patterns

Temporally flat top pulse generation from gain switched semiconductor lasers based on a polarization interferometer with variable transfer function

We propose the use of a polarization based interferometer with variable transfer function for the generation of temporally flat top pulses from gain switched single mode semiconductor lasers. The main advantage of the presented technique is its flexibility in terms of input pulse characteristics, as pulse duration, spectral bandwidth and operating wavelength. Theoretical predictions and experimental demonstrations are presented and the proposed technique is applied to two different semiconductor laser sources emitting in the 1550 nm region. Flat top pulses are successfully obtained with input seed pulses with duration ranging from 40 ps to 100 ps.

High brightness semiconductor lasers as transmitters for space lidar systems

High brightness semiconductor lasers are potential transmitters for future space lidar systems. In the framework of the European Project BRITESPACE, we propose an all-semiconductor laser source for an Integrated Path Differential Absorption lidar system for column-averaged measurements of atmospheric CO2 in future satellite missions. The complete system architecture has to be adapted to the particular emission properties of these devices using a Random Modulated Continuous Wave approach. We present the initial experimental results of the InGaAsP/InP monolithic Master Oscillator Power Amplifiers, providing the ON and OFF wavelengths close to the selected absorption line around 1572 nm.

A new regularization method for fast and accurate propagation of roto-translationally coupled asteroids

There is a well-distinguished group of asteroids for which the roto-translational cou-pling is known to have a non-negligible e�ect in the long-term. The study of such asteroids suggests the use of specialized propagation techniques, where perturbation methods make their best. The techniques from which the special regularization method DROMO is derived, have now been extended to the attitude dynamics, with equally remarkable results in terms of speed and accuracy, thus making the combination of these algorithms specially. well-suited to deal with the propagation of bodies with strong attitude coupling.