Charge-transport simulations in organic semiconductors

In this thesis we have extended the methods for microscopic charge-transport simulations for organic semiconductors. In these materials the weak intermolecular interactions lead to spatially localized charge carriers, and the charge transport occurs as an activated hopping process between diabatic states. In addition to weak electronic couplings between these states, different electrostatic environments in the organic material lead to a broadening of the density of states for the charge energies which limits carrier mobilities.rnThe contributions to the method development includern(i) the derivation of a bimolecular charge-transfer rate,rn(ii) the efficient evaluation of intermolecular (outer-sphere) reorganization energies,rn(iii) the investigation of effects of conformational disorder on intramolecular reorganization energies or internal site energiesrnand (iv) the inclusion of self-consistent polarization interactions for calculation of charge energies.These methods were applied to study charge transport in amorphous phases of small molecules used in the emission layer of organic light emitting diodes (OLED).rnWhen bulky substituents are attached to an aromatic core in order to adjust energy levels or prevent crystallization, a small amount of delocalization of the frontier orbital to the substituents can increase electronic couplings between neighboring molecules. This leads to improved charge-transfer rates and, hence, larger charge-mobility. We therefore suggest using the mesomeric effect (as opposed to the inductive effect) when attaching substituents to aromatic cores, which is necessary for example in deep blue OLEDs, where the energy levels of a host molecule have to be adjusted to those of the emitter.rnFurthermore, the energy landscape for charges in an amorphous phase cannot be predicted by mesoscopic models because they approximate the realistic morphology by a lattice and represent molecular charge distributions in a multipole expansion. The microscopic approach shows that a polarization-induced stabilization of a molecule in its charged and neutral states can lead to large shifts, broadening, and traps in the distribution of charge energies. These results are especially important for multi-component systems (the emission layer of an OLED or the donor-acceptor interface of an organic solar cell), if the change in polarizability upon charging (or excitation in case of energy transport) is different for the components. Thus, the polarizability change upon charging or excitation should be added to the set of molecular parameters essential for understanding charge and energy transport in organic semiconductors.rnWe also studied charge transport in self-assembled systems, where intermolecular packing motives induced by side chains can increase electronic couplings between molecules. This leads to larger charge mobility, which is essential to improve devices such as organic field effect transistors, where low carrier mobilities limit the switching frequency.rnHowever, it is not sufficient to match the average local molecular order induced by the sidernchains (such as the pitch angle between consecutive molecules in a discotic mesophase) with maxima of the electronic couplings.rnIt is also important to make the corresponding distributions as narrow as possible compared to the window determined by the closest minima of thernelectronic couplings. This is especially important in one-dimensional systems, where charge transport is limited by the smallest electronic couplings.rnThe immediate implication for compound design is that the side chains should assist the self-assemblingrnprocess not only via soft entropic interactions, but also via stronger specific interactions, such as hydrogen bonding.rnrnrnrn

Tropfenbasierte Multiphasen – Mikroreaktionstechnologie in organisch-chemischer Synthese

In der vorliegenden Doktorarbeit werden neue, mikrofluidische Verfahren, zur Durchführung chemischer Reaktionen in mehrphasigen Systemen präsentiert. rnDas Einschließen von Reaktionspartnern in einzelne Segmente, deren Volumina im Bereich von Mikro- bis Femtoliter liegen und die dadurch erzeugten enormen, spezifischen Oberflächen, ermöglichen Massentransportprozesse über die Phasengrenzfläche zwischen einzelnen Segmenten, drastisch zu intensivieren. Aufgrund geringer räumlicher Ausdehnungen einzelner Kompartimente und durch vorherrschende, zirkulierende Strömungen in den einzelnen Abschnitten, sind Diffusions- und Konvektionsprozesse in diesen rasch, sodass an der Grenzfläche gebildete, reaktive Intermediate in sehr kurzen Zeitintervallen umgesetzt werden können. rnrn

Spike-based decision learning of nash equilibria in two-player games

Humans and animals face decision tasks in an uncertain multi-agent environment where an agent's strategy may change in time due to the co-adaptation of others strategies. The neuronal substrate and the computational algorithms underlying such adaptive decision making, however, is largely unknown. We propose a population coding model of spiking neurons with a policy gradient procedure that successfully acquires optimal strategies for classical game-theoretical tasks. The suggested population reinforcement learning reproduces data from human behavioral experiments for the blackjack and the inspector game. It performs optimally according to a pure (deterministic) and mixed (stochastic) Nash equilibrium, respectively. In contrast, temporal-difference(TD)-learning, covariance-learning, and basic reinforcement learning fail to perform optimally for the stochastic strategy. Spike-based population reinforcement learning, shown to follow the stochastic reward gradient, is therefore a viable candidate to explain automated decision learning of a Nash equilibrium in two-player games.

Incremental Dynamic Updates with First-class Contexts

Highly available software systems occasionally need to be updated while avoiding downtime. Dynamic software updates reduce down-time, but still require the system to reach a quiescent state in which a global update can be performed. This can be difficult for multi-threaded systems. We present a novel approach to dynamic updates using first-class contexts, called Theseus. First-class contexts make global updates unnecessary: existing threads run to termination in an old context, while new threads start in a new, updated context; consistency between contexts is ensured with the help of bidirectional transformations. We show that for multi-threaded systems with coherent memory, first-class contexts offer a practical and flexible approach to dynamic updates, with acceptable overhead.

Adult Pleomorphic Rhabdomyosarcoma: A Multicentre Retrospective Study.

BACKGROUND Pleomorphic rhabdomyosarcoma (RMS) is a rare sub-type of RMS. Optimal treatment remains undefined. PATIENTS AND METHODS Between 1995 and 2014, 45 patients were diagnosed and treated in three tertiary sarcoma Centers (United Kingdom, Switzerland and Germany). Treatment characteristics and outcomes were analyzed. RESULTS The median age at diagnosis was 71.5 years (range=28.4-92.8 years). Median survival for those with localised (n=32, 71.1%) and metastatic disease (n=13, 28.9%) were 12.8 months (95% confidence interval=8.2-34.4) and 7.1 months (95% confidence interval=3.8-11.3) respectively. The relapse rate was 53.8% (four local and 10 distant relapses). In total, 14 (31.1%) patients received first line palliative chemotherapy including multi-agent paediatric chemotherapy schedules (n=3), ifosfamide-doxorubicin (n=4) and single-agent doxorubicin (n=7). Response to chemotherapy was poor (one partial remission with vincristine-actinomycin D-cyclophosphamide and six cases with stable disease). Median progression-free survival was 2.3 (range=1.2-7.3) months. CONCLUSION Pleomorphic RMS is an aggressive neoplasm mainly affecting older patients, associated with a high relapse rate, a poor and short-lived response to standard chemotherapy and an overall poor prognosis for both localised and metastatic disease.

A Multiagent system model which suggests solutions to fuzzy incidents in the field of telecommunications

This article presents the model of a multi-agent system (SMAF), which objectives are the input of fuzzy incidents as the human experts express them with different severities degrees and the further search and suggestion of solutions. The solutions will be later confirm or not by the users. This model was designed, implemented and tested in the telecommunications field, with heterogeneous agents in a cooperative model. In the design, different abstract levels where considered, according to the agents? objectives, their ways to carry it out and the environment in which they act. Each agent is modeled with different spectrum of the knowledge base

Efectos dinámicos laterales en vehículos y puentes ferroviarios sometidos a la acción de vientos transversales

En las últimas décadas el aumento de la velocidad y la disminución del peso de los vehículos ferroviarios de alta velocidad ha provocado que aumente su riesgo de vuelco. Además, las exigencias de los trazados de las líneas exige en ocasiones la construcción de viaductos muy altos situados en zonas expuestas a fuertes vientos. Esta combinación puede poner en peligro la seguridad de la circulación. En esta tesis doctoral se estudian los efectos dinámicos que aparecen en los vehículos ferroviarios cuando circulan sobre viaductos en presencia de vientos transversales. Para ello se han desarrollado e implementado una serie de modelos numéricos que permiten estudiar estos efectos de una forma realista y general. Los modelos desarrollados permiten analizar la interacción dinámica tridimensional tren-estructura, formulada mediante coordenadas absolutas en un sistema de referencia inercial, en un contexto de elementos _nitos no lineales. Mediante estos modelos se pueden estudiar de forma realista casos extremos como el vuelco o descarrilamiento de los vehículos. Han sido implementados en Abaqus, utilizando sus capacidades para resolver sistemas multi-cuerpo para el vehículo y elementos finitos para la estructura. La interacción entre el vehículo y la estructura se establece a través del contacto entre rueda y carril. Para ello, se han desarrollado una restricción, que permite establecer la relación cinemática entre el eje ferroviario y la vía, teniendo en cuenta los posibles defectos geométricos de la vía; y un modelo de contacto rueda-carril para establecer la interacción entre el vehículo y la estructura. Las principales características del modelo de contacto son: considera la geometría real de ambos cuerpos de forma tridimensional; permite resolver situaciones en las que el contacto entre rueda y carril se da en más de una zona a la vez; y permite utilizar distintas formulaciones para el cálculo de la tensión tangencial entre ambos cuerpos. Además, se ha desarrollado una metodología para determinar, a partir de formulaciones estocásticas, las historias temporales de cargas aerodinámicas debidas al viento turbulento en estructuras grandes y con pilas altas y flexibles. Esta metodología tiene cuenta la variabilidad espacial de la velocidad de viento, considerando la correlación entre los distintos puntos; considera las componentes de la velocidad del viento en tres dimensiones; y permite el cálculo de la velocidad de viento incidente sobre los vehículos que atraviesan la estructura. La metodología desarrollada en este trabajo ha sido implementada, validada y se ha aplicado a un caso concreto en el que se ha estudiado la respuesta de un tren de alta velocidad, similar al Siemens Velaro, circulando sobre el viaducto del río Ulla en presencia viento cruzado. En este estudio se ha analizado la seguridad y el confort de la circulación y la respuesta dinámica de la estructura cuando el tren cruza el viaducto. During the last decades the increase of the speed and the reduction of the weight of high-speed railway vehicles has led to a rise of the overturn risk. In addition, the design requests of the railway lines require some times the construction of very tall viaducts in strong wind areas. This combination may endanger the traffic safety. In this doctoral thesis the dynamic effects that appear in the railway vehicles when crossing viaducts under strong winds are studied. For this purpose it has been developed and implemented numerical models for studying these effects in a realistic and general way. The developed models allow to analyze the train-structure three-dimensional dynamic interaction, that is formulated by using absolute coordinates in an inertial reference frame within a non-linear finite element framework. By means of these models it is possible to study in a realistic way extreme situations such vehicle overturn or derailment. They have been implemented for Abaqus, by using its capabilities for solving multi-body systems for the vehicle and finite elements for the structure. The interaction between the vehicle and the structure is established through the wheel-rail contact. For this purpose, a constraint has been developed. It allows to establish the kinematic relationship between the railway wheelset and the track, taking into account the track irregularities. In addition, a wheel-rail contact model for establishing the interaction of the vehicle and the structure has been developed. The main features of the contact model are: it considers the real geometry During the last decades the increase of the speed and the reduction of the weight of high-peed railway vehicles has led to a rise of the overturn risk. In addition, the design requests of the railway lines require some times the construction of very tall viaducts in strong wind areas. This combination may endanger the traffic safety. In this doctoral thesis the dynamic effects that appear in the railway vehicles when crossing viaducts under strong winds are studied. For this purpose it has been developed and implemented numerical models for studying these effects in a realistic and general way. The developed models allow to analyze the train-structure three-dimensional dynamic interaction, that is formulated by using absolute coordinates in an inertial reference frame within a non-linear finite element framework. By means of these models it is possible to study in a realistic way extreme situations such vehicle overturn or derailment. They have been implemented for Abaqus, by using its capabilities for solving multi-body systems for the vehicle and finite elements for the structure. The interaction between the vehicle and the structure is established through the wheel-rail contact. For this purpose, a constraint has been developed. It allows to establish the kinematic relationship between the railway wheelset and the track, taking into account the track irregularities. In addition, a wheel-rail contact model for establishing the interaction of the vehicle and the structure has been developed. The main features of the contact model are: it considers the real geometry

Detection and Tracking of Dynamic Objects. A MultiRobot approach to Critical Infrastructures Surveillance.

Despite that Critical Infrastructures (CIs) security and surveillance are a growing concern for many countries and companies, Multi Robot Systems (MRSs) have not been yet broadly used in this type of facilities. This dissertation presents a novel study of the challenges arisen by the implementation of this type of systems and proposes solutions to specific problems. First, a comprehensive analysis of different types of CIs has been carried out, emphasizing the influence of the different characteristics of the facilities in the design of a security and surveillance MRS. One of the most important needs for the surveillance of a CI is the detection of intruders. From a technical point of view this problem can be abstracted as equivalent to the Detection and Tracking of Mobile Objects (DATMO). This dissertation proposes algorithms to solve this specific problem in a CI environment. Using 3D range images of the environment as input data, two detection algorithms for ground robots have been developed. These detection algorithms provide a list of moving objects in the robot detection area. Direct image differentiation and computer vision techniques are used when the robot is static. Alternatively, multi-layer ground reconstructions are compared to detect the dynamic objects when the robot is moving. Since CIs usually spread over large areas, it is very useful to incorporate aerial vehicles in the surveillance MRS. Therefore, a moving object detection algorithm for aerial vehicles has been also developed. This algorithm compares the real optical flow obtained from a down-face oriented camera with an artificial optical flow computed using a RANSAC based homography matrix. Two tracking algorithms have been developed to follow the moving objects trajectories. These algorithms can efficiently handle occlusions and crossings, as well as exchange information among robots. The multirobot tracking can be applied to any type of communication structure: centralized, decentralized or a combination of both. Even more, the developed tracking algorithms are independent of the detection algorithms and could be potentially used with other detection procedures or even with static sensors, such as cameras. In addition, using the 3D point clouds available to the robots, a relative localization algorithm has been developed to improve the position estimation of a given robot with observations from other robots. All the developed algorithms have been extensively tested in different simulated CIs using the Webots robotics simulator. Furthermore, the algorithms have also been validated with real robots operating in real scenarios. In conclusion, this dissertation presents a multirobot approach to Critical Infrastructure Surveillance, mainly focusing on Detecting and Tracking Dynamic Objects.

An introduction to swarm robotics

Swarm robotics is a field of multi-robotics in which large number of robots are coordinated in a distributed and decentralised way. It is based on the use of local rules, and simple robots compared to the complexity of the task to achieve, and inspired by social insects. Large number of simple robots can perform complex tasks in a more efficient way than a single robot, giving robustness and flexibility to the group. In this article, an overview of swarm robotics is given, describing its main properties and characteristics and comparing it to general multi-robotic systems. A review of different research works and experimental results, together with a discussion of the future swarm robotics in real world applications completes this work.

Adapting mode switches into the hierarchical scheduling

Mode switches are used to partition the system’s behavior into different modes to reduce the complexity of large embedded systems. Such systems operate in multiple modes in which each one corresponds to a specific application scenario; these are called Multi-Mode Systems (MMS). A different piece of software is normally executed for each mode. At any given time, the system can be in one of the predefined modes and then be switched to another as a result of a certain condition. A mode switch mechanism (or mode change protocol) is used to shift the system from one mode to another at run-time. In this thesis we have used a hierarchical scheduling framework to implement a multi-mode system called Multi-Mode Hierarchical Scheduling Framework (MMHSF). A two-level Hierarchical Scheduling Framework (HSF) has already been implemented in an open source real-time operating system, FreeRTOS, to support temporal isolation among real-time components. The main contribution of this thesis is the extension of the HSF featuring a multimode feature with an emphasis on making minimal changes in the underlying operating system (FreeRTOS) and its HSF implementation. Our implementation uses fixed-priority preemptive scheduling at both local and global scheduling levels and idling periodic servers. It also now supports different modes of the system which can be switched at run-time. Each subsystem and task exhibit different timing attributes according to mode, and upon a Mode Change Request (MCR) the task-set and timing interfaces of the entire system (including subsystems and tasks) undergo a change. A Mode Change Protocol specifies precisely how the system-mode will be changed. However, an application may not only need to change a mode but also a different mode change protocol semantic. For example, the mode change from normal to shutdown can allow all the tasks to be completed before the mode itself is changed, while changing a mode from normal to emergency may require aborting all tasks instantly. In our work, both the system mode and the mode change protocol can be changed at run-time. We have implemented three different mode change protocols to switch from one mode to another: the Suspend/resume protocol, the Abort protocol, and the Complete protocol. These protocols increase the flexibility of the system, allowing users to select the way they want to switch to a new mode. The implementation of MMHSF is tested and evaluated on an AVR-based 32 bit board EVK1100 with an AVR32UC3A0512 micro-controller. We have tested the behavior of each system mode and for each mode change protocol. We also provide the results for the performance measures of all mode change protocols in the thesis. RESUMEN Los conmutadores de modo son usados para particionar el comportamiento del sistema en diferentes modos, reduciendo así la complejidad de grandes sistemas empotrados. Estos sistemas tienen multiples modos de operación, cada uno de ellos correspondiente a distintos escenarios y para distintas aplicaciones; son llamados Sistemas Multimodales (o en inglés “Multi-Mode Systems” o MMS). Normalmente cada modo ejecuta una parte de código distinto. En un momento dado el sistema, que está en un modo concreto, puede ser cambiado a otro modo distinto como resultado de alguna condicion impuesta previamente. Los mecanismos de cambio de modo (o protocolos de cambio de modo) son usados para mover el sistema de un modo a otro durante el tiempo de ejecución. En este trabajo se ha usado un modelo de sistema operativo para implementar un sistema multimodo llamado MMHSF, siglas en inglés correspondientes a (Multi-Mode Hierarchical Scheduling Framework). Este sistema está basado en el HSF (Hierarchical Scheduling Framework), un modelo de sistema operativo con jerarquía de dos niveles, implementado en un sistema operativo en tiempo real de libre distribución llamado FreeRTOS, capaz de permitir el aislamiento temporal entre componentes. La principal contribución de este trabajo es la ampliación del HSF convirtiendolo en un sistema multimodo realizando los cambios mínimos necesarios sobre el sistema operativo FreeRTOS y la implementación ya existente del HSF. Esta implementación usa un sistema de planificación de prioridad fija para ambos niveles de jerarquía, ocupando el tiempo entre tareas con un “modo reposo”. Además el sistema es capaz de cambiar de un modo a otro en tiempo de ejecución. Cada subsistema y tarea son capaces de tener distintos atributos de tiempo (prioridad, periodo y tiempo de ejecución) en función del modo. Bajo una demanda de cambio de modo (Mode Change Request MCR) se puede variar el set de tareas en ejecución, así como los atributos de los servidores y las tareas. Un protocolo de cambio de modo espeficica precisamente cómo será cambiado el sistema de un modo a otro. Sin embargo una aplicación puede requerir no solo un cambio de modo, sino que lo haga de una forma especifica. Por ejemplo, el cambio de modo de “normal” a “apagado” puede permitir a las tareas en ejecución ser finalizadas antes de que se complete la transición, pero sin embargo el cambio de “normal” a “emergencia” puede requerir abortar todas las tareas instantaneamente. En este trabajo ambas características, tanto el modo como el protocolo de cambio, pueden ser cambiadas en tiempo de ejecución, pero deben ser previamente definidas por el desarrollador. Han sido definidos tres protocolos de cambios: el protocolo “suspender/continuar”, protocolo “abortar” y el protocolo “completar”. Estos protocolos incrementan la flexibilidad del sistema, permitiendo al usuario seleccionar de que forma quieren cambiar hacia el nuevo modo. La implementación del MMHSF ha sido testada y evaluada en una placa AVR EVK1100, con un micro-controlador AVR32UC3A0. Se ha comprobado el comportamiento de los distintos modos para los distintos protocolos, definidos previamente. Como resultado se proporcionan las medidades de rendimiento de los distintos protocolos de cambio de modo.

MAIA: an event-based modular architecture for intelligent agents

Online services are no longer isolated. The release of public APIs and technologies such as web hooks are allowing users and developers to access their information easily. Intelligent agents could use this information to provide a better user experience across services, connecting services with smart automatic. behaviours or actions. However, agent platforms are not prepared to easily add external sources such as web services, which hinders the usage of agents in the so-called Evented or Live Web. As a solution, this paper introduces an event-based architecture for agent systems, in accordance with the new tendencies in web programming. In particular, it is focused on personal agents that interact with several web services. With this architecture, called MAIA, connecting to new web services does not involve any modification in the platform.

Simulación eficiente de mecanismos flexibles mediante formulaciones topológicas

El objetivo de esta Tesis es presentar un método eficiente para la evaluación de sistemas multi-cuerpo con elementos flexibles con pequeñas deformaciones, basado en métodos topológicos para la simulación de sistemas tan complejos como los que se utilizan en la práctica y en tiempo real o próximo al real. Se ha puesto un especial énfasis en la resolución eficiente de aquellos aspectos que conllevan mayor coste computacional, tales como la evaluación de las ecuaciones dinámicas y el cálculo de los términos de inercia. Las ecuaciones dinámicas se establecen en función de las variables independientes del sistema, y la integración de las mismas se realiza mediante formulaciones implícitas de index-3. Esta Tesis se articula en seis Capítulos. En el Capítulo 1 se realiza una revisión bibliográfica de la simulación de sistemas flexibles y los métodos más relevantes de integración de las ecuaciones diferenciales del movimiento. Asimismo, se presentan los objetivos de esta Tesis. En el Capítulo 2 se presenta un método semi-recursivo para la evaluación de las ecuaciones de los sistemas multi-cuerpo con elementos flexibles basado en formulaciones topológicas y síntesis modal. Esta Tesis determina la posición de cada punto del cuerpo flexible en función de un sistema de referencia flotante que se mueve con dicho cuerpo y de las amplitudes de ciertos modos de deformación calculados a partir de un mallado obtenido mediante el Método de Elementos Finitos. Se presta especial atención en las condiciones de contorno que se han de tener en cuenta a la hora de establecer las variables que definen la deformación del cuerpo flexible. El Capítulo 3 se centra en la evaluación de los términos de inercia de los sistemas flexibles que generalmente conllevan un alto coste computacional. Se presenta un método que permite el cálculo de dichos términos basado en el uso de 24 matrices constantes que pueden ser calculadas previamente al proceso de integración. Estas matrices permiten evaluar la matriz de masas y el vector de fuerzas de inercia dependientes de la velocidad sin que sea necesario evaluar la posición deformada de todos los puntos del cuerpo flexible. Se realiza un análisis pormenorizado de dichas matrices con el objetivo de optimizar su cálculo estableciendo aproximaciones que permitan reducir el número de dichos términos y optimizar aún más su evaluación. Se analizan dos posibles simplificaciones: la primera utiliza una discretización no-consistente basada en elementos finitos en los que se definen únicamente los desplazamientos axiales de los nodos; en la segunda propuesta se hace uso de una matriz de masas concentradas (Lumped Mass). Basándose en la formulación presentada, el Capítulo 4 aborda la integración eficiente de las ecuaciones dinámicas. Se presenta un método iterativo para la integración con fórmulas de index-3 basado en la proyección de las ecuaciones dinámicas según las variables independientes del sistema multi-cuerpo. El cálculo del residuo del sistema de ecuaciones no lineales que se ha de resolver de modo iterativo se realiza mediante un proceso recursivo muy eficiente que aprovecha la estructura topológica del sistema. Se analizan tres formas de evaluar la matriz tangente del citado sistema no lineal: evaluación aproximada, numérica y recursiva. El método de integración presentado permite el uso de distintas fórmulas. En esta Tesis se analizan la Regla Trapezoidal, la fórmula BDF de segundo orden y un método híbrido TR-BDF2. Para este último caso se presenta un algoritmo de paso variable. En el Capítulo 5 plantea la implementación del método propuesto en un programa general de simulación de mecanismos que permita la resolución de cualquier sistema multi-cuerpo definiéndolo mediante un fichero de datos. La implementación de este programa se ha realizado tanto en C++ como en Java. Se muestran los resultados de las formulaciones presentadas en esta Tesis mediante la simulación de cuatro ejemplos de distinta complejidad. Mediante análisis concretos se comparan la formulación presentada con otras existentes. También se analiza el efecto del lenguaje de programación utilizado en la implementación y los efectos de las posibles simplificaciones planteadas. Por último, el Capítulo 6 resume las principales conclusiones alcanzadas en la Tesis y las futuras líneas de investigación que con ella se abren. ABSTRACT This Thesis presents an efficient method for solving the forward dynamics of a multi-body sys-tem formed by rigid and flexible bodies with small strains for real-time simulation of real-life models. It is based on topological formulations. The presented work focuses on the efficient solution of the most time-consuming tasks of the simulation process, such as the numerical integration of the motion differential equations and in particular the evaluation of the inertia terms corresponding to the flexible bodies. The dynamic equations are formulated in terms of independent variables of the muti-body system, and they are integrated by means of implicit index-3 formulae. The Thesis is arranged in six chapters. Chapter 1 presents a review of the most relevant and recent contributions related to the modelization of flexible multi-body systems and the integration of the corresponding dynamic equations. The main objectives of the Thesis are also presented in detail. Chapter 2 presents a semi-recursive method for solving the equations of a multi-body system with flexible bodies based on topological formulations and modal synthesis. This Thesis uses the floating frame approach and the modal amplitudes to define the position of any point at the flexible body. These modal deformed shapes are obtained by means of the Finite Element Method. Particular attention has been taken to the boundary conditions used to define the deformation of the flexible bodies. Chapter 3 focuses on the evaluation of the inertia terms, which is usually a very time-consuming task. A new method based on the use of 24 constant matrices is presented. These matrices are evaluated during the set-up step, before the integration process. They allow the calculation of the inertia terms in terms of the position and orientation of the local coordinate system and the deformation variables, and there is no need to evaluate the position and velocities of all the nodes of the FEM mesh. A deep analysis of the inertia terms is performed in order to optimize the evaluation process, reducing both the terms used and the number of arithmetic operations. Two possible simplifications are presented: the first one uses a non-consistent approach in order to define the inertia terms respect to the Cartesian coordinates of the FEM mesh, rejecting those corresponding to the angular rotations; the second approach makes use of lumped mass matrices. Based on the previously presented formulation, Chapter 4 is focused on the numerical integration of the motion differential equations. A new predictor-corrector method based on index-3 formulae and on the use of multi-body independent variables is presented. The evaluation of the dynamic equations in a new time step needs the solution of a set on nonlinear equations by a Newton-Raphson iterative process. The computation of the corresponding residual vector is performed efficiently by taking advantage of the system’s topological structure. Three methods to compute the tangent matrix are presented: an approximated evaluation that considers only the most relevant terms, a numerical approach based on finite differences and a recursive method that uses the topological structure. The method presented for integrating the dynamic equations can use a variety of integration formulae. This Thesis analyses the use of the trapezoidal rule, the 2nd order BDF formula and the hybrid TR-BDF2 method. A variable-time step strategy is presented for the last one. Chapter 5 describes the implementation of the proposed method in a general purpose pro-gram for solving any multibody defined by a data file. This program is implemented both in C++ and Java. Four examples are used to check the validity of the formulation and to compare this method with other methods commonly used to solve the dynamic equations of multi-body systems containing flexible bodies. The efficiency of the programming methodology used and the effect of the possible simplifications proposed are also analyzed. Chapter 6 summarizes the main Conclusions obtained in this Thesis and the new lines of research that have been opened.

Contribución a las arquitecturas flexibles para la multiconferencia web adaptable a la demanda

Los sistemas de videoconferencia y colaboración en tiempo real para múltiples usuarios permiten a sus usuarios comunicarse por medio de vídeo, audio y datos. Históricamente estos han sido sistemas caros de obtener y de mantener. El paso de las décadas ha limado estos problemas acercado el mundo de comunicación en tiempo real a un grupo mucho más amplio, llegando a usarse en diversos ámbitos como la educación o la medicina. En este sentido, el último gran salto evolutivo al que hemos asistido ha sido la transición de este tipo de aplicaciones hacia la Web. Varias tecnologías han permitido este viaje hacia el navegador. Las Aplicaciones Ricas de Internet (RIAs), que permiten crear aplicaciones Web interactivas huyendo del clásico esquema de petición y respuesta y llevando funcionalidades propias de las aplicaciones nativas a la Web. Por otro lado, la computación en la nube o Cloud Computing, con su modelo de pago por uso de recursos virtualizados, ha llevado a la creación de servicios que se adaptan mejor a la demanda, han habilitado este viaje hacia el navegador. No obstante, como cada cambio, este salto presenta una serie de retos para los sistemas de videoconferencia establecidos. Esta tesis doctoral propone un conjunto de arquitecturas, mecanismos y algoritmos para adaptar los sistemas de multiconferencia al entorno Web, teniendo en cuenta que este es accedido desde dispositivos diferentes y mediante redes de acceso variadas. Para ello se comienza por el estudio de los requisitos que debe cumplir un sistema de videoconferencia en la Web. Como resultado se diseña, implementa y desarrolla un servicio de videoconferencia que permite la colaboración avanzada entre múltiples usuarios mediante vídeo, audio y compartición de escritorio. Posteriormente, se plantea un sistema de comunicación entre una aplicación nativa y Web, proponiendo técnicas de adaptación entre los dos entornos que permiten la conversación de manera transparente para los usuarios. Estos sistemas permiten facilitar la transición hacia tecnologías Web. Como siguiente paso, se identificaron los principales problemas que existen para la comunicación multiusuario en dispositivos de tamaño reducido (teléfonos inteligentes) utilizando redes de acceso heterogéneas. Se propone un mecanismo, combinación de transcodificación y algoritmos de adaptación de calidad para superar estas limitaciones y permitir a los usuarios de este tipo de dispositivos participar en igualdad de condiciones. La aparición de WebRTC como tecnología disruptiva en este entorno, permitiendo nuevas posibilidades de comunicación en navegadores, motiva la segunda iteración de esta tesis. Aquí se presenta un nuevo esquema de adaptación a la demanda para servidores de videoconferencia diseñado para las necesidades del entorno Web y para aprovechar las características de Cloud Computing. Finalmente, esta tesis repasa las conclusiones obtenidas como fruto del trabajo llevado a cabo, reflejando la evolución de la videoconferencia Web desde sus inicios hasta nuestros días. ABSTRACT Multiuser Videoconferencing and real-time collaboration systems allow users to communicate using video, audio and data streams. These systems have been historically expensive to obtain and maintain. Over the last few decades, technological breakthroughs have mitigated those costs and popularized real time video communication, allowing its use in environments such as education or health. The last big evolutionary leap forward has been the transition of these types of applications towards theWeb. Several technologies have allowed this journey to theWeb browser. Firstly, Rich Internet Applications (RIAs) enable the creation of dynamic Web pages that defy the classical request-response interaction and provide an experience similar to their native counterparts. On the other hand, Cloud Computing brings the leasing of virtualized hardware resources in a pay-peruse model and, with it, better scalability in resource-demanding services. However, as with every change, this evolution imposes a set of challenges on existing videoconferencing solutions. This dissertation proposes a set of architectures, mechanisms and algorithms that aim to adapt multi-conferencing systems to the Web platform, taking into account the variety of devices and access networks that come with it. To this end, this thesis starts with a study concerning the requirements that must be met by new Web videoconferencing systems. The result of this study is the design, development and implementation of a new videoconferencing services that provides advanced collaboration to its user by providing video and audio communication as well as desktop sharing. After this, a new communication system between Web and native applications is presented. This system proposes adaptation mechanisms to bridge the two worlds providing a seamless integration transparent to users who can now access the powerful native application via an easy Web interface. The next step is to identify the main challenges posed by multi-conferencing on small devices (smartphones) with heterogeneous access networks. This dissertation proposes a mechanism that combines transcoding and adaptive quality algorithms to overcome those limitations. A second iteration in this dissertation is motivated by WebRTC. WebRTC appears as a disrupting technology by enabling new real-time communication possibilities in browsers. A new mechanism for flexible videoconferencing server scalability is presented. This mechanism aims to address the strong scalability requirements in the Web environment by taking advantage of Cloud Computing. Finally, the dissertation discusses the results obtained throughout the study, capturing the evolution of Web videoconferencing systems.

Making Autonomies Matter: Sub-State Actor Accommodation in the Nordic Council and the Nordic Council of Ministers - An Analysis of the Institutional Framework for Accommodating the Faroe Islands, Greenland and Åland within ‘Norden’. EDAP Paper 03/2014

Sovereign powers are not absolute but exercised in varying areas and to varying degrees by sub-state, state and supra-state entities. The upward dispersion of power to international organisations carries implications for the sub-state level, while sub-state governance poses demands as to the conduct of governance at the international level. It is well recognised that sub-state entities, such as federal states and autonomies, may have the (restricted) capacity to enter into international relations. But what capacities do international organisations have to accommodate autonomies in their institutional frameworks? This paper shall present a case study of one such framework, namely Nordic co-operation and the accommodation of the Nordic autonomies, the Faroe Islands, Greenland and Åland, within its institutional framework. Within ‘Norden’, the position of autonomies has been scrutinised and adapted on several occasions, in the late 1960s, early 1980s and in the mid-2000s. The accommodation of the autonomies has been discussed in light of evident implications of statehood and international legal personality and the institutional arrangements eventually carved serve well to illustrate the challenges and opportunities international organisations face in the attempt to accommodate multi-level systems.

A Survey Study Examining Teachers’ Perceptions in Teaching Refugee and Immigrant Students

Thesis (Ph.D.)--University of Washington, 2016-06