Dissertations / Theses on the topic 'Feedback Rate'

[EN] This thesis deals with two characteristic problems in visual feedback robot control: 1) sensor latency; 2) providing suitable trajectories for the robot and for the measurement in the image. All the approaches presented in this work are analyzed and implemented on a 6 DOF industrial robot manipulator or/and a wheeled robot. Focusing on the sensor latency problem, this thesis proposes the use of dual-rate high order holds within the control loop of robots. In this sense, the main contributions are: - Dual-rate high order holds based on primitive functions for robot control (Chapter 3): analysis of the system performance with and without the use of this multi-rate technique from non-conventional control. In addition, as consequence of the use of dual-rate holds, this work obtains and validates multi-rate controllers, especially dual-rate PIDs. - Asynchronous dual-rate high order holds based on primitive functions with time delay compensation (Chapter 3): generalization of asynchronous dual-rate high order holds incorporating an input signal time delay compensation component, improving thus the inter-sampling estimations computed by the hold. It is provided an analysis of the properties of such dual-rate holds with time delay compensation, comparing them with estimations obtained by the equivalent dual-rate holds without this compensation, as well as their implementation and validation within the control loop of a 6 DOF industrial robot manipulator. - Multi-rate nonlinear high order holds (Chapter 4): generalization of the concept of dual-rate high order holds with nonlinear estimation models, which include information about the plant to be controlled, the controller(s) and sensor(s) used, obtained from machine learning techniques. Thus, in order to obtain such a nonlinear hold, it is described a methodology non dependent of the machine technique used, although validated using artificial neural networks. Finally, an analysis of the properties of these new holds is carried out, comparing them with their equivalents based on primitive functions, as well as their implementation and validation within the control loop of an industrial robot manipulator and a wheeled robot. With respect to the problem of providing suitable trajectories for the robot and for the measurement in the image, this thesis presents the novel reference features filtering control strategy and its generalization from a multi-rate point of view. The main contributions in this regard are: - Reference features filtering control strategy (Chapter 5): a new control strategy is proposed to enlarge significantly the solution task reachability of robot visual feedback control. The main idea is to use optimal trajectories proposed by a non-linear EKF predictor-smoother (ERTS), based on Rauch-Tung-Striebel (RTS) algorithm, as new feature references for an underlying visual feedback controller. In this work it is provided both the description of the implementation algorithm and its implementation and validation utilizing an industrial robot manipulator. - Dual-rate Reference features filtering control strategy (Chapter 5): a generalization of the reference features filtering approach from a multi-rate point of view, and a dual Kalman-smoother step based on the relation of the sensor and controller frequencies of the reference filtering control strategy is provided, reducing the computational cost of the former algorithm, as well as addressing the problem of the sensor latency. The implementation algorithms, as well as its analysis, are described.
[ES] La presente tesis propone soluciones para dos problemas característicos de los sistemas robóticos cuyo bucle de control se cierra únicamente empleando sensores de visión artificial: 1) la latencia del sensor; 2) la obtención de trayectorias factibles tanto para el robot así como para las medidas obtenidas en la imagen. Todos los métodos propuestos en este trabajo son analizados, validados e implementados utilizando brazo robot industrial de 6 grados de libertad y/o en un robot con ruedas. Atendiendo al problema de la latencia del sensor, esta tesis propone el uso de retenedores bi-frequencia de orden alto dentro de los lazos de control de robots. En este aspecto las principales contribuciones son: -Retenedores bi-frecuencia de orden alto basados en funciones primitivas dentro de lazos de control de robots (Capítulo 3): análisis del comportamiento del sistema con y sin el uso de esta técnica de control no convencional. Además, como consecuencia del empleo de los retenedores, obtención y validación de controladores multi-frequencia, concretamente de PIDs bi-frecuencia. -Retenedores bi-frecuencia asíncronos de orden alto basados en funciones primitivas con compensación de retardos (Capítulo 3): generalización de los retenedores bi-frecuencia asíncronos de orden alto incluyendo una componente de compensación del retardo en la señal de entrada, mejorando así las estimaciones inter-muestreo calculadas por el retenedor. Se proporciona un análisis de las propiedades de los retenedores con compensación del retardo, comparándolas con las obtenidas por sus predecesores sin compensación, así como su implementación y validación en un brazo robot de 6 grados de libertad. -Retenedores multi-frecuencia no lineales de orden alto (Capítulo 4): generalización del concepto de retenedor bi-frecuencia de orden alto con modelos de estimación no lineales, los cuales incluyen información tanto de la planta a controlar, como del controlador(es) y sensor(es) empleado(s), obtenida a partir de técnicas de aprendizaje. Así pues, para obtener dicho retenedor no lineal, se describe una metodología independiente de la herramienta de aprendizaje utilizada, aunque validada con el uso de redes neuronales artificiales. Finalmente se realiza un análisis de las propiedades de estos nuevos retenedores, comparándolos con sus predecesores basados en funciones primitivas, así como su implementación y validación en un brazo robot de 6 grados de libertad y en un robot móvil con ruedas. Por lo que respecta al problema de generación de trayectorias factibles para el robot y para la medida en la imagen, esta tesis propone la nueva estrategia de control basada en el filtrado de la referencia y su generalización desde el punto de vista multi-frecuencial. -Estrategia de control basada en el filtrado de la referencia (Capítulo 5): una nueva estrategia de control se propone para ampliar significativamente el espacio de soluciones de los sistemas robóticos realimentados con sensores de visión artificial. La principal idea es utilizar las trayectorias óptimas obtenidas por una trayectoria predicha por un filtro de Kalman seguido de un suavizado basado en el algoritmo Rauch-Tung-Striebel (RTS) como nuevas referencias para un controlador dado. En este trabajo se proporciona tanto la descripción del algoritmo como su implementación y validación empleando un brazo robótico industrial. -Estrategia de control bi-frecuencia basada en el filtrado de la referencia (Capítulo 5): generalización de la estrategia de control basada en filtrado de la referencia desde un punto de vista multi-frecuencial, con un filtro de Kalman multi-frecuencia y un Kalman-smoother dual basado en la relación existente entre las frecuencias del sensor y del controlador, reduciendo así el coste computacional del algoritmo y, al mismo tiempo, dando solución al problema de la latencia del sensor. La validación se realiza utilizando un barzo robot industria asi
[CAT] La present tesis proposa solucions per a dos problemes característics dels sistemes robòtics el els que el bucle de control es tanca únicament utilitzant sensors de visió artificial: 1) la latència del sensor; 2) l'obtenció de trajectòries factibles tant per al robot com per les mesures en la imatge. Tots els mètodes proposats en aquest treball son analitzats, validats e implementats utilitzant un braç robot industrial de 6 graus de llibertat i/o un robot amb rodes. Atenent al problema de la latència del sensor, esta tesis proposa l'ús de retenidors bi-freqüència d'ordre alt a dins del llaços de control de robots. Al respecte, les principals contribucions son: - Retenidors bi-freqüència d'ordre alt basats en funcions primitives a dintre dels llaços de control de robots (Capítol 3): anàlisis del comportament del sistema amb i sense l'ús d'aquesta tècnica de control no convencional. A més a més, com a conseqüència de l'ús dels retenidors, obtenció i validació de controladors multi-freqüència, concretament de PIDs bi-freqüència. - Retenidors bi-freqüència asíncrons d'ordre alt basats en funcions primitives amb compensació de retards (Capítol 3): generalització dels retenidors bi-freqüència asíncrons d'ordre alt inclouen una component de compensació del retràs en la senyal d'entrada al retenidor, millorant així les estimacions inter-mostreig calculades per el retenidor. Es proporciona un anàlisis de les propietats dels retenidors amb compensació del retràs, comparant-les amb les obtingudes per el seus predecessors sense la compensació, així com la seua implementació i validació en un braç robot industrial de 6 graus de llibertat. - Retenidors multi-freqüència no-lineals d'ordre alt (Capítol 4): generalització del concepte de retenidor bi-freqüència d'ordre alt amb models d'estimació no lineals, incloent informació tant de la planta a controlar, com del controlador(s) i sensor(s) utilitzat(s), obtenint-la a partir de tècniques d'aprenentatge. Així doncs, per obtindre el retenidor no lineal, es descriu una metodologia independent de la ferramenta d'aprenentatge utilitzada, però validada amb l'ús de rets neuronals artificials. Finalment es realitza un anàlisis de les propietats d'aquestos nous retenidors, comparant-los amb els seus predecessors basats amb funcions primitives, així com la seua implementació i validació amb un braç robot de 6 graus de llibertat i amb un robot mòbil de rodes. Per el que respecta al problema de generació de trajectòries factibles per al robot i per la mesura en la imatge, aquesta tesis proposa la nova estratègia de control basada amb el filtrat de la referència i la seua generalització des de el punt de vista multi-freqüència. - Estratègia de control basada amb el filtrat de la referència (Capítol 5): una nova estratègia de control es proposada per ampliar significativament l'espai de solucions dels sistemes robòtics realimentats amb sensors de visió artificial. La principal idea es la d'utilitzar les trajectòries optimes obtingudes per una trajectòria predita per un filtre de Kalman seguit d'un suavitzat basat en l'algoritme Rauch-Tung-Striebel (RTS) com noves referències per a un control donat. En aquest treball es proporciona tant la descripció del algoritme així com la seua implementació i validació utilitzant un braç robòtic industrial de 6 graus de llibertat. - Estratègia de control bi-freqüència basada en el filtrat (Capítol 5): generalització de l'estratègia de control basada am filtrat de la referència des de un punt de vista multi freqüència, amb un filtre de Kalman multi freqüència i un Kalman-Smoother dual basat amb la relació existent entre les freqüències del sensor i del controlador, reduint així el cost computacional de l'algoritme i, al mateix temps, donant solució al problema de la latència del sensor. L'algoritme d'implementació d'aquesta tècnica, així com la seua validaci
Solanes Galbis, JE. (2015). MULTI-RATE VISUAL FEEDBACK ROBOT CONTROL [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/57951
TESIS

Thesis (Ph. D.)--West Virginia University, 2001.
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The signal propagation delays in a high speed, wide area telecommunication network can be orders of magnitude larger than a message transmission time. This implies that the response times associated with dynamic congestion management strategies can be long relative to the characteristic times of the queue-length processes being controlled, and that such strategies may be of limited use in controlling message loss in high speed settings. We examine the interplay between signal propagation delays and efficiency of feedback-based congestion controls in the case of a very simple network model consisting of a single multiplexor serving a remote source population. We establish, using simulations of two simple approaches described in the literature, that loss performance can be very sensitive to propagation delay, and that response times can be diminished, for given propagation delays, by applying a rate-based, or cyclic, service strategy at the multiplexor output line in place or First-In, First-Out. We develop an optimization framework for the control problem, enabling the use of Markov Decision Programming to calculate the form and performance of feedback-based controllers which are optimal in terms of the trade-off achieved between forced losses at the network boundary and congestion-induced losses in the network interior. Observing that performance can be made insensitive to signal propagation delays by means of appropriate buffer dimensioning, we develop an asymptotic analysis of the buffer requirements, applicable in the limit of large values of the delay/bandwidth product.

Thesis (Ph. D.)--West Virginia University, 2008.
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Thesis (D. Ed.)--University of Oregon, 2006.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 111-116). Also available for download via the World Wide Web; free to University of Oregon users.

The emergence of very capable mobile terminals, e.g. smartphones or tablets, has dramatically increased the demand of wireless data traffic in recent years. Current growth forecasts elucidate that wireless communication standards will not be able to afford future traffic demands, thus many research efforts have been oriented towards increasing the efficiency of wireless networks. MIMO technologies, entailing the use of multiple antennas, stand as one of the candidates. This solution allows increasing not only the reliability and robustness (diversity gain), but also the efficiency of the communication (multiplexing gain or degrees of freedom (DoF)). The DoF describe the slope of channel capacity at very high signal-to-noise-ratio (SNR) regime, and for the point-to-point (P2P) channel are equal to the minimum between the number of antennas at the transmitter and the receiver. Consequently, the throughput may be scaled in a promising way. However, the DoF behavior in case of having interference is still an open problem in general. This thesis studies the DoF of interference networks. The most trivial way of tackling this problem is by means of orthogonalization, either in time, frequency or space. However, it does not allow that the scaling of DoF with the number of users. For example, if transmissions are orthogonalized in time each user is served only a fraction of time inversely proportional to the number of users. Likewise, if transmissions are orthogonalized in space, transmitters must be equipped with a large number of antennas, which is costly and not practical. For dimensionally-limited systems, the interference alignment (IA) principle proposes that instead of forcing the design to null the interference terms at the receivers, make the receiver observe them overlapped. This way the number of dimensions occupied by interference is reduced, thus allowing the allocation of more desired signals, thus symbols per user, and also relaxing the constraint on the number of required antennas. Following IA allows that "each user achieves half the cake independently of the number of users", where the cake represents the DoF of the P2P channel. At first, full channel state information was assumed to be available at the transmitter side (full CSIT), i.e. the information is acquired instantaneously, and with perfect quality. The first part of this thesis studies this case and completes the DoF characterization of the 3-user MIMO interference channel for some antenna configurations when channel coefficients are assumed constant. In practice, CSIT should be obtained from channel feedback, thus incurring delays and errors. In this context, and especially intended to scenarios with high mobility, IA concepts were extended to networks where only outdated information of the channels is available, a framework known as delayed CSIT where the channel feedback delay may be larger than the channel coherence time. This form of IA is denoted as retrospective interference alignment, since the transmission is carried out in multiple phases, and signals may be aligned along space and the different phases. The second part of the thesis deepens into the DoF of two network topologies with delayed CSIT, for which linear precoding strategies are proposed. Moreover, it is shown that the proposed strategies are better than state-of-the-art in terms of DoF-delay trade-off, which is relevant as most strategies based on delayed CSIT entail long communication delays. The concluding part of the thesis analyses how one of schemes proposed in the second part performs in terms of DoF with delayed CSIT with errors, and net DoF. This last metric describes the DoF as a function of the coherence time, and taking into account all issues related to channel acquisition at both the transmitter and receiver side: consumption of resources for channel training, for feedback transmission, and feedback waits.
La aparición de terminales móviles cada vez más potentes, e.g. smartphones o tablets, ha incrementado dramáticamente la demanda de tráfico de datos en redes inalámbricas en los últimos años. Las previsiones de crecimiento ya avisan que los estándares de comunicación actuales no serán capaces de sostener las demandas de tráfico en un futuro, por lo que se está investigando como aumentar la eficiencia de las redes inalámbricas. La tecnología MIMO, es decir, el uso de múltiples antenas, destaca como uno de los candidatos, permitiendo no sólo aumentar la fiabilidad y robustez (ganancia de diversidad), sino también la eficiencia de la comunicación (ganancia de multiplexado o grados de libertad (DoF)). Los DoF describen la pendiente de la capacidad del canal a muy alta relación señal a ruido (SNR), y para el canal punto a punto (P2P) son igual al mínimo entre el número de antenas en transmisión y recepción. Así pues, el rendimiento de la comunicación inalámbrica se escala de forma muy prometedora. Esta tesis aporta contribuciones en el conocimiento de los DoF para comunicaciones con interferencia (debido a que se sirven múltiples usuarios), cuyo comportamiento es aún un problema por resolver. La forma más trivial de abordar este problema es ortogonalizando las transmisiones, ya sea en tiempo, frecuencia o espacio. Sin embargo, no permite que los DoF escalen con el número de usuarios. Por ejemplo, si se ortogonaliza en tiempo, cada usuario se sirve sólo una fracción de tiempo inversamente proporcional a la cantidad de usuarios. Asimismo, si se ortogonaliza en espacio, se requerirán muchas antenas transmisoras, lo cual es costoso y poco práctico. La técnica de alineación de interferencia (IA) propone que en lugar de diseñar la transmisión para anular la interferencia en los receptores, estos observen todos los términos solapados. Esto permite reducir el espacio ocupado por interferencia, ensanchar el espacio de señales deseadas, pudiendo enviar más símbolos por usuario, y reducir el número de antenas requeridas. Así, IA permitió demostrar que los DoF escalan para el canal interferente con terminales equipado con una sola antena. Al principio, se suponía que los transmisores disponían de toda la información del estado del canal instantáneamente, y con calidad perfecta (CSIT completo). La primera parte de la tesis estudia este caso, y completa la caracterización de los DoF del canal interferente MIMO de 3 usuarios para ciertas configuraciones de antenas, cuando los coeficientes del canal son constantes en tiempo. En la práctica, el CSIT se debe obtener mediante reportes del canal, lo que conlleva retrasos y errores. En este contexto, y sobre todo dirigido a escenarios con alta movilidad, los conceptos de IA se extendieron al caso donde sólo está disponible información obsoleta del canal (delayed CSIT), e.g. cuando el retardo de los reportes es mayor el tiempo de coherencia del canal. Esta forma de IA se denota como retrospective IA, ya que la transmisión se lleva a cabo en múltiples fases, y las señales pueden ser alineadas a lo largo del espacio y las diferentes fases. La segunda parte de la tesis estudia los DoF de dos topologías de red con delayed CSIT, proponiendo estrategias de transmisión. Además, se demuestra que las estrategias propuestas superan el estado del arte en términos del compromiso DoF-retardo, lo que es relevante ya que la mayoría de las estrategias basadas en delayed CSIT requieren muchos usos de canal. Finalmente, la última parte de la tesis describe cómo uno de los esquemas propuestos en la segunda parte trabaja con errores, y en términos de net DOF. Este último indicador describe los DoF en función del tiempo de coherencia, y teniendo en cuenta todas las cuestiones relacionadas con la adquisición del canal, tanto en el transmisor como en el receptor: el consumo de los recursos para estimar el canal en recepción , para la transmisión de los reportes de canal, y las esperas hasta obtener los reportes.

The full autonomous control of a rotary-wing Micro Aerial Vehicle (MAV) relies on measurement inputs from sensors to allow the vehicle to maintain a constant position in a 3D environment. Monocular Visual SLAM (VSLAM) is a particularly efficient sensing method in terms of payload cost. A single camera can be used to provide a full 6-DOF pose measurement, however, this is at the cost of increased communication bandwidth and computational requirements, often resulting in low-rate and delayed feedback measurements. This thesis presents an investigation into the use of VSLAM feedback to stabilise the full 3D position of a MAV. To reach this goal, experimental work is conducted using small rotary-wing platforms in indoor environments. Platforms include the static 3-DOF Quanser and the 6-DOF AR.Drone2.0 quadrotor. Theoretical dynamic models are developed and simplified into decoupled linear sub-systems. The sensing properties of VSLAM are also experimentally identified for both static and dynamic flight scenarios. The control challenge of low-rate delayed measurements is overcome by applying discrete-time LQG control design methods. A discretisation method is detailed which can represent arbitrary delays in a discrete state-space form whilst preserving the dynamic behaviour. A method of tuning the LQG to preserve the reference tracking response is presented, making use of the discrete delayed model structure. Initially the presented control design is experimentally applied to SISO systems to assess the performance, making use of high accuracy external tracking systems. The result is then extended to the full 6-DOF helicopter where free flight is demonstrated, using VSLAM as the only pose measurement, with no additional sensors required to initialise VSLAM.

Research shows that in a system model, when the production rate is adjusted based on the number of items in queue, the nature of the model changes from an open-loop queueing system to a closed-loop feedback control system. Service-rate adjustment can be implemented in a discrete event simulation model, but the effect of this adjustment has not been thoroughly analyzed in the literature. This research considers the design of feedback signals to generate realistic simulation models of production system behavior. A series of simulation experiments is conducted to provide practical guidance for simulation modelers on how adding a service-rate adjustment feedback loop to a queueing system affects system performance.

Various roles for operators in human-machine systems have been proposed. This thesis shows that all of these views have in common the fact that operators perform best when given feedback that matches their intent. Past studies have shown that position control is superior to rate control except when operating large-workspace and/or dynamically slow manipulators and for exact tracking tasks. Operators of large-workspace and/or dynamically slow manipulators do not receive immediate position feedback. To remedy this lack of position feedback, a ghost arm overlay was displayed to operators of a dynamically slow manipulator, giving feedback that matches their intent. Operators performed several simple one- and two-dimensional tasks (point-to-point motion, tracking, path following) with three different controllers (position control with and without a ghost, rate control) to indicate how task conditions influence operator intent. Giving the operator position feedback via the ghost significantly increased performance with the position controller and made it comparable to performance with the rate control. These results were further validated by testing coordinated position control with and without a ghost arm and coordinated rate control on an excavator simulator. The results show that position control with the ghost arm is comparable, but not superior to rate control for the dynamics of our excavator example. Unlike previous work, this research compared the fuel efficiencies of different HMIs, as well as the time efficiencies. This work not only provides the design law of matching the feedback to the operator intent, but also gives a guideline for when to choose position or rate control based on the speed of the system.

This research examined three components of precision teaching; charting, timed practices, and performance aims. In the first study beginner skaters performed two roller skating skills, forward crosses and back scissors, with the aim of increasing fluency in these skills using precision teaching methods. Skaters were told to perform the skills as fast as they could during 1-min practises, aiming at a set performance aim, or goal. After each timing skaters were told how many repetitions they had performed. One group charted back scissors only and the other forward crosses only. The skaters became faster in both skills and charting did not produce faster rates. The improvement seen may have been a direct result of the performance aims. Therefore the second study, using back crosses, compared a fixed, difficult performance aim (complete 50 per minute) for one group and an easier, flexible performance aim (beat your previous sessions' high score) for a second group. After each timing skaters were told how many back crosses they had performed. Performance rates increased similarly for both groups, thus the different performance aims did not have different effects, contrary to the goal-setting literature. A third study investigated this further. Skaters performed forward crosses and back scissors during a baseline condition, where there were no performance aims or feedback. Increases in performance rates for both skills occurred. In a second condition, a performance aim higher than their number of repetitions in the previous condition was set and feedback was given for one skill only. There was an immediate increase in rate of the targeted skill for 3 of the 4 skaters, suggesting that the goal, when given with feedback, influenced the rate at which the skaters performed the skill. In the fourth study, where the effect of feedback and practice was examined more closely, soccer players dribbled a ball in and out of cones. As expected those who took part in eight to ten sessions that were told to do their best (an easy goal) and not given feedback performed this skill faster than those who completed only two sessions with the same conditions. Unexpectedly, they also performed faster than those set a performance aim of beating their previous highest score (a hard goal) and who were given feedback. Methodological issues that may have been responsible for this latter result were addressed in the fifth study. Skaters completing 10 sessions of forward crosses, with feedback and with a performance aim of completing 60 repetitions in one minute (a hard goal), became faster than skaters completing 10 sessions without feedback who were told to do their best. Skaters told to do their best, who completed only three sessions without feedback, did not get faster. These results support those in the goal-setting literature that, hard goals with feedback have more effect than being told to do your best. Overall these studies show that short, timed practices and hard performance aims, or goals, may be effective components of precision teaching while visual feedback from charting may not. Further, precision teaching methods were effective when applied to sporting skills such as those used by roller skaters and soccer players for building fluency of basic skills.

ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California
Many satellite payloads require wide-band channels for transmission of large amounts of data to users on the ground. These channels typically have substantial distortions, including bandlimiting distortions and high power amplifier (HPA) nonlinearities that cause substantial degradation of bit error rate performance compared to additive white Gaussian noise (AWGN) scenarios. An adaptive equalization algorithm has been selected as the solution to improving bit error rate performance in the presence of these channel distortions. This paper describes the design and implementation of an adaptive baseband equalizer (ABBE) utilizing the latest FPGA technology. Implementation of the design was arrived at by first constructing a high fidelity channel simulation model, which incorporates worst-case signal impairments over the entire data link. All of the modem digital signal processing functions, including multirate carrier and symbol synchronization, are modeled, in addition to the adaptive complex baseband equalizer. Different feedback and feed-forward tap combinations are considered as part of the design optimization.

Optogenetics is a set of technologies that enable optically triggered gain or loss of function in genetically specified populations of cells. Optogenetic methods have revolutionized experimental neuroscience by allowing precise excitation or inhibition of firing in specified neuronal populations embedded within complex, heterogeneous tissue. Although optogenetic tools have greatly improved our ability manipulate neural activity, they do not offer control of neural firing in the face of ongoing changes in network activity, plasticity, or sensory input. In this thesis, I develop a feedback control technology that automatically adjusts optical stimulation in real-time to precisely control network activity levels. I describe hardware and software tools, modes of optogenetic stimulation, and control algorithms required to achieve robust neural control over timescales ranging from seconds to days. I then demonstrate the scientific utility of these technologies in several experimental contexts. First, I investigate the role of connectivity in shaping the network encoding process using continuously-varying optical stimulation. I show that synaptic connectivity linearizes the neuronal response, verifying previous theoretical predictions. Next, I use long-term optogenetic feedback control to show that reductions in excitatory neurotransmission directly trigger homeostatic increases in synaptic strength. This result opposes a large body of literature on the subject and has significant implications for memory formation and maintenance. The technology presented in this thesis greatly enhances the precision with which optical stimulation can control neural activity, and allows causally related variables within neural circuits to be studied independently.

Mestrado em Engenharia de Computadores e Telemática
Anxiety disorders are the most common mental health problem in the world and it affects, on daily basis, a vast number of people all around the world. Even though there are a high number of people suffering from phobia, only a small percentage ever seeks treatment, usually sufferers avoid the source of the problem, even if it is meaning of constrains in daily and social activities. Due to the development and creation of new technologies with the focus on healthcare growing rapidly and a number of studies proving that virtual reality can be just as effective as in vivo exposure, while providing a less stressful experience, these findings can contribute to reduce the high number of people that never seeks treatment. In previous works of our group, the Veracity, virtual reality was already applied in the context of arachnophobia, an example of specific phobias as a mean to provide an exposure without any physical sensorial interaction. In this dissertation, we want to extend the system with a virtual haptic response when touching spiders. Although the use of haptic response has been used and it is being used successfully in other areas, to our knowledge this is a novelty in the relation to other works in the phobia treatment. The haptic feedback has impact in virtual spider’s level of realism/interaction, by adding the touch to the visual sensation. Through haptic feedback, while improving the realism, we aimed at maintaining the virtual experience "safe" in the phobic user perspective in comparison to in vivo exposure. In this work, we integrated the haptic feedback within the Veracity loop and evaluate the impact in the response of users to this new add-on. As in the original system we still collect physiological response of the users such as ECG, HR, Video and 3D tracking of Virtual objects that were used to compare the responses with and without haptic feedback. The preliminary evaluation of the system suggest that this approach is interesting to pursue but still need a more comprehensive evaluation to assert its usefulness and impact within the phobic users of the haptic feedback.
Os distúrbios de ansiedade são uma das doenças mentais mais comuns no mundo, afetando o quotidiano de um elevado número de pessoas. Embora exista um número significativo de pessoas que têm algum tipo de distúrbio de ansiedade, apenas uma pequena percentagem procura tratamento, preferindo simplesmente evitar a fonte da sua fobia, tendo como consequência a privação de momentos/atividades diárias. Com o rápido desenvolvimento e aparecimento de novas tecnologias, o número de soluções tecnológicas focadas em saúde tem vindo a crescer, juntamente com um número de estudos que demonstram que a realidade virtual permite resultados tão bons quanto o in vivo exposure, além de provocarem menores graus de stresse. Estes resultados podem contribuir para a redução do elevado número de pessoas que nunca chega a procurar tratamento. Um trabalho anterior do nosso grupo de investigação, o Veracity, utilizou realidade virtual no contexto da aracnofobia, um exemplo de fobia específica, de forma a proporcionar a exposição à fonte de fobia sem qualquer tipo de interação sensorial física. Com o Veracity, a interação foi realizada ao utilizar um dispositivo de reconhecimento gestual que permitia uma interação com o ambiente e aranhas, sem qualquer tipo de toque real. Nesta dissertação, quisemos acrescentar ao sistema uma resposta virtual háptica como feedback ao toque em aranhas. Apesar de o uso de respostas hápticas já ter sido usado ou estar a ser implementado com sucesso, noutras áreas, para nosso conhecimento, trata-se de uma inovação no que refere a trabalhos realizados na área do tratamento de fobias. O feedback háptico tem impacto no nível do realismo/interação das aranhas virtuais, ao adicionar o toque ao estimulo visual. Através do feedback háptico enquanto se aumentava o realismo tivemos como objetivo manter a experiência virtual segura do ponto de vista do utilizador fóbico, quando comparado com o in vivo exposure. Neste trabalho integrámos o feedback háptico dentro do loop do trabalho Veracity e avaliámos o impacto na resposta dos utilizadores, ao adicionar estas novas funcionalidades. Tal como no sistema original, continuámos a recolher as repostas fisiológicas, ECG, Frequência Cardíaca, Vídeo e Tracking 3D dos objetos virtuais, de forma a comparar as respostas dos utilizadores com, e sem respostas hápticas. Uma avaliação preliminar do sistema sugere que este método é de interesse para futuros trabalhos, apesar de necessitar de uma avaliação mais detalhada, por forma a garantir a sua utilidade e impacto do feedback háptico, entre os utilizadores fóbicos.

From a bottom-up perspective, the assessment of flow rate of stack flue gases is crucial being the very first brick of the calculation. With the concentration of pollutant, it gives access to the amount of pollutant released in the atmosphere. Nevertheless, flow rate measurement has not been well-framed and can be poorly controlled, leading to large uncertainties. The recent launch of the European Standard EN 16 911 has enlighten the lack of expertise concerning the flow rate assessment in the industry. That is why RECORD, the project sponsor, conscious of the possible lack of expertise and the possible unreliability of the measurement is willing to understand the requirements; theoretical, technical and regulatory; for a reliable pollutant emissions measurement in accordance with the EU regulation in the field of waste treatment and incineration. Thus, this study offers the theoretical, operational and regulatory keys to realize a reliable flow rate measurement. 9 methods are identified for stack flue gases flow rate measurement. For each of these methods an ID-card, based on bibliographical researches, supplier’s interviews and representatives of the industry’s feedbacks, has been built containing information required for a reliable measurement. This thesis will contribute to a report that will offers all the keys for a reliable velocity/flow rate measurement in the waste treatment (domestic waste incineration mainly but it can also be useful in every industry that releases flue gas in the atmosphere: chemistry, steel manufacture, etc.). Moreover, this study proposes an analysis of the European Standard related to flow rate measurement in the industry and enlightens the key information related to these standards for an industrial operator. Finally, in relation with the complete report published on the RECORD website, a comparison tool of the 9 technologies is created to guide the industrial in their flow rate measurement. Once the best technology has been selected thanks to the comparison tool, the ID-card gives the key to realize a reliable measurement with the selected method. Finally, the theoretical part and the standard analysis have to be used as a frame for all the technologies.

Master of Science
Department of Electrical and Computer Engineering
Dwight D. Day
Micro-hydro turbines generate power for small villages and industries in Afghanistan. They usually produce less than 100 kW of power. Currently the flow into the turbine is controlled manually and the voltage is controlled automatically with an electronic load controller. Excess power not used by the village is dumped into a community water heater. For larger sites that have a reservoir and/or large variable load throughout the day and night, the turbine needs to be fitted with an automatic flow control system to conserve water in the reservoir or deal with the variable loads. Large turbines usually use hydraulic governors that automatically adjust the flow of water into the turbine. For micro-hydro sized plants this method would be too expensive and be difficult to build and maintain locally. For this reason, a 3 phase AC induction motor will be used to move the internal flow control valve of the turbine. Because a sudden change in load is possible (30 – 40%) for micro-hydro plants, the electronic load controller will also be needed to respond to quick changes in load so that the village voltage does not exceed 220V. This report documents the process of building a test system comprising of a dynamic resistive load, microcontroller controlled resistive load, a three phase AC generator and a DC Motor. Where the dynamic resistive load represents the load of the village, the computer controlled resistive load would represent the community water heater, the three phase AC generator represents the Generator on site and the DC Motor together with its DC input voltage would emulate the turbine and its water flow respectively. The DC input voltage would be also controlled with a PWM signal through a delay loop to represent the water gate delay effects on the turbine as close as possible. With this, it would be possible to completely build and test a control system that emulates the dynamics of a water turbine generator.

Dans cette thèse, les techniques de coopération ont été étudiées pour un canal multi-accès multi-relais composé d'au moins deux sources qui communiquent avec une seule destination à l'aide d'au moins deux nœuds de relayage en mode semi-duplex. Le multiplexage par répartition dans le temps est supposé. Tout d'abord, l’algorithme d’adaptation de lien est exécuté par l'ordonnanceur centralisé. Durant la première phase de transmission, les sources transmettent chacune à leur tour leur message respectif pendant des intervalles de temps consécutifs. Dans chaque intervalle de temps dans la deuxième phase, la destination planifie un nœud pour transmettre les redondances, mettant en œuvre un protocole coopératif d'Hybrid Automatic Repeat reQuest (HARQ), où les canaux de contrôle limités bidirectionnels sont disponibles depuis les sources et les relais vers la destination. Dans la première partie de la thèse, les stratégies de sélection des nœuds centralisé sont proposées pour la deuxième phase de transmission. Les décisions d’ordonnancement sont prises en fonction de la connaissance des ensembles de sources correctement décodées par chaque noeud et ayant comme objectif de maximiser l’efficacité spectrale moyenne. L'analyse de la probabilité de coupure de l'information ainsi que les simulations Monte-Carlo (MC) sont effectués afin de valider ces stratégies. Dans la seconde partie, un algorithme d’adaptation de lien lent est proposé afin de maximiser l’efficacité spectrale moyenne sous contrainte de vérification d'une qualité de service individuelle cible pour une famille donnée de schémas de modulation et de codage, réposant sur l'information sur la distribution des canaux signalée. Les débits des sources discrets sont déterminés en utilisant l’approche "Genie-Aided" suivie d’un algorithme itératif de correction de débit. Les simulations MC montrent que l’algorithme d’adaptation de lien proposé offre des performances proches de celles de la recherche exhaustive. Dans la troisième partie, les performances de protocole HARQ à redondance incrémentale (IR) avec codage mono et multi-utilisateur, ainsi que l'HARQ de type Chase Combining avec codage mono-utilisateur sont comparées. Les simulations MC montrent que l'IR-HARQ avec codage mono-utilisateur offre le meilleur compromis entre performance et complexité pour le scénario de petit nombre de sources. Un schéma de codage pratique est proposé et validé à l'aide de simulations MC
In this thesis, cooperation techniques have been studied for Multiple Access Multiple Relay Channel, consisted of at least two sources which communicate with a single destination with the help of at least two half-duplex relaying nodes. Time Division Multiplexing is assumed. First, the link adaptation algorithm is performed at the centralised scheduler. Sources transmit in turns in consecutive time slots during the first transmission phase. In each time slot of the second phase, the destination schedules a node to transmit redundancies, implementing a cooperative Hybrid Automatic Repeat reQuest (HARQ) protocol, where bidirectional limited control channels are available from sources and relays towards the destination. In the first part of the thesis, centralized node selection strategies are proposed for the second phase. The scheduling decisions are made based on the knowledge of the correctly decoded source sets of each node, with the goal to maximize the average spectral efficiency. An information outage analysis is conducted and Monte-Carlo (MC) simulations are performed to evaluate their performance. In the second part, a slow-link adaptation algorithm is proposed which aims at maximizing the average spectral efficiency under individual QoS targets for a given modulation and coding scheme family relying on the reported Channel Distribution Information of all channels. Discrete source rates are first determined using the "Genie-Aided" assumption, which is followed by an iterative rate correction algorithm. The resulting link adaptation algorithm yields performance close to the exhaustive search approach as demonstrated by MC simulations. In the third part, performances of Incremental Redundancy (IR) HARQ with Single and Multi User encoding, as well as the Chase Combining HARQ with Single User encoding are compared. MC simulations demonstrate that IR-HARQ with Single User encoding offers the best trade-off between performance and complexity for a small number of sources in our setting. Practical coding scheme is proposed and validated using MC simulations

Le phénomène d’interférométrie par réinjection optique se produit lorsqu’une portion de la puissance optique du laser est rétrodiffusée par une cible distante puis réinjectée dans la cavité laser ce qui affecte les propriétés d’émission du laser (fréquence et puissance en particulier). Ce principe résulte alors en un capteur interférométrique compact, auto-aligné et sans contact. Des applications récentes des capteurs par réinjection optique dans les domaines de la microfluidique et de l’acoustique ont montré des résultats prometteurs et ouvert de nouveaux domaines de recherche. Pourtant, dans le cadre de ces applications, l’amplitude du signal est extrêmement faible à cause de la faible amplitude des variations de la puissance rétrodiffusée qui est mesurée. Dans cette thèse, un modèle analytique décrivant la dépendance de l’amplitude du signal issu d’une diode laser monomode au courant d’injection et à la température est développé à partir des équations d’évolution de Lang et Kobayashi. Le modèle a été développé pour toutes les méthodes connues d’acquisition du signal interférométrique par réinjection optique : par la photodiode de monitoring incluse dans le boîtier de la diode laser, par la captation de la puissance optique au moyen d’un photodétecteur externe et par l’amplification de la tension aux bornes de la diode laser elle-même. Le modèle démontre que les signaux des photodiodes et de la tension sont liés à l’efficacité externe de la diode laser, qui elle-même est fonction du courant injecté et de la température. Qui plus est, le modèle prédit une évolution très différente de l’amplitude de ces différents signaux en fonction du courant d’injection ou de la température. Un résultat remarquable, confirmé par une campagne de mesures pour ces trois types de signaux sur une large plage de courants d’injection et de températures. Ainsi ce modèle simple permet une compréhension nouvelle des stratégies de polarisation très différentes de la diode laser permettant d’obtenir une sensibilité optimale du capteur dans les différents schémas d’acquisition du signal. Par ailleurs, les relations entre la phase et l’amplitude des signaux issus des photodiodes externes et de monitoring ont été étudiées sur le plan théorique et expérimental ce qui a permis de révéler des résultats inattendus. À partir du modèle et basé sur des observations expérimentales, une étude critique a été menée sur l’impact de la combinaison des trois signaux dans la stratégie de traitement du signal afin d’améliorer la sensibilité du capteur aux réinjections optiques de faible amplitude
The optical feedback interferometry phenomenon occurs when a portion of the output optical power is back-scattered from a remote target and coupled into the laser cavity to vary the laser’s emission properties (frequency and power mostly). Thus, this scheme results in a compact, self-aligned and contact-less interferometric sensor. Recent applications of optical feedback interferometer in the domains of microfluidics or acoustics have shown promising results and open new fields of researches. However in these applications, the amplitude of the sensing signal is extremely small due to the weakness of the backscattered power changes that are measured. In this thesis, an analytical model that describes the laser injection current and temperature dependence of the optical feedback interferometry signal strength for a single-mode laser diode has been derived from the Lang and Kobayashi rate equations. The model has been developed for all the known signal acquisition methods of the optical feedback interferometry scheme: from the package included monitoring photodiode, by collection of the laser power with an external photodetector and by amplification of the variations in the laser junction voltage. The model shows that both the photodiodes and the voltage signals strengths are related to the laser slope efficiency, which itself is a function of the laser injection current and of the temperature. Moreover, the model predicts different behaviors of the photodiodes and the voltage signal strengths with the change of the laser injection current and the temperature; an important result that has been proven by conducting measurements on all three signals for a wide range of injection current and temperature. Therefore, this simple model provides important insights into the radically different biasing strategies required to achieve optimal sensor sensitivity for the different interferometric signal acquisition schemes. In addition, the phase and amplitude relationships between the external and the in-package photodiode signals have been investigated theoretically and experimentally demonstrating unexpected results. Based on our model and on experimental observations, a critical study has been performed on the impact of the combination of the three signals in the signal processing strategy in order to improve the sensor sensibility to low amplitude optical feedback

Multiple-input multiple-output (MIMO) systems have received much attention due to their multiplexing and diversity capabilities. It is possible to obtain remarkable improvement in spectral efficiency for wireless systems by using MIMO based schemes. However, sophisticated equalization and decoding structures are required for reliable communication at high rates. In this thesis, capacity achieving practical transceiver structures are proposed for MIMO wireless channels depending on the availability of channel state information at the transmitter (CSIT). First, an adaptive MIMO scheme based on the use of quantized CSIT and reduced precoding idea is proposed. With the help of a very tight analytical upper bound obtained for limited rate feedback (LRF) MIMO capacity, it is possible to construct an adaptive scheme varying the number of beamformers used according to the average SNR value. It is shown that this strategy always results in a significantly higher achievable rate than that of the schemes which does not use CSIT, if the number of transmit antennas is greater than that of receive antennas. Secondly, it is known that the use of CSIT does not bring significant improvement over capacity, when similar number of transmit and receive antennas are used
on the other hand, it reduces the complexity of demodulation at the receiver by converting the channel into noninterfering subchannels. However, it is shown in this thesis that it is still possible to achieve a performance very close to the outage probability and exploit the space-frequency diversity benefits of the wireless fading channel without compromising the receiver complexity, even if the CSIT is not used. The proposed receiver structure is based on iterative forward and backward filtering to suppress the interference both in time and space followed by a spacetime decoder. The rotation of multidimensional constellations for block fading channels and the single-carrier frequency domain equalization (SC-FDE) technique for wideband MIMO channels are studied as example applications.

To meet the exponentially increasing traffic data driven by the rapidly growing mobile subscriptions, both industry and academia are exploring the potential of a new genera- tion (5G) of wireless technologies. An important 5G goal is to achieve high data rate. Small cells with spectrum sharing and multiple-input multiple-output (MIMO) techniques are one of the most promising 5G technologies, since it enables to increase the aggregate data rate by improving the spectral efficiency, nodes density and transmission bandwidth, respectively. However, the increased interference in the densified networks will in return limit the achievable rate performance if not properly managed. The considered setup can be modeled as MIMO interference networks, which can be classified into the K-user MIMO interference channel (IC) and the K-cell MIMO interfering broadcast channel/multiple access channel (MIMO-IBC/IMAC) according to the number of mobile stations (MSs) simultaneously served by each base station (BS). The thesis considers two physical layer (PHY) resource allocation problems that deal with the interference for both models: 1) Pareto boundary computation for the achiev- able rate region in a K-user single-stream MIMO IC and 2) grouping-based interference alignment (GIA) with optimized IA-Cell assignment in a MIMO-IMAC under limited feedback. In each problem, the thesis seeks to provide a deeper understanding of the system and novel mathematical results, along with supporting numerical examples. Some of the main contributions can be summarized as follows. It is an open problem to compute the Pareto boundary of the achievable rate region for a K-user single-stream MIMO IC. The K-user single-stream MIMO IC models multiple transmitter-receiver pairs which operate over the same spectrum simultaneously. Each transmitter and each receiver is equipped with multiple antennas, and a single desired data stream is communicated in each transmitter-receiver link. The individual achievable rates of the K users form a K-dimensional achievable rate region. To find efficient operating points in the achievable rate region, the Pareto boundary computation problem, which can be formulated as a multi-objective optimization problem, needs to be solved. The thesis transforms the multi-objective optimization problem to two single-objective optimization problems–single constraint rate maximization problem and alternating rate profile optimization problem, based on the formulations of the ε-constraint optimization and the weighted Chebyshev optimization, respectively. The thesis proposes two alternating optimization algorithms to solve both single-objective optimization problems. The convergence of both algorithms is guaranteed. Also, a heuristic initialization scheme is provided for each algorithm to achieve a high-quality solution. By varying the weights in each single-objective optimization problem, numerical results show that both algorithms provide an inner bound very close to the Pareto boundary. Furthermore, the thesis also computes some key points exactly on the Pareto boundary in closed-form. A framework for interference alignment (IA) under limited feedback is proposed for a MIMO-IMAC. The MIMO-IMAC well matches the uplink scenario in cellular system, where multiple cells share their spectrum and operate simultaneously. In each cell, a BS receives the desired signals from multiple MSs within its own cell and each BS and each MS is equipped with multi-antenna. By allowing the inter-cell coordination, the thesis develops a distributed IA framework under limited feedback from three aspects: the GIA, the IA-Cell assignment and dynamic feedback bit allocation (DBA), respec- tively. Firstly, the thesis provides a complete study along with some new improvements of the GIA, which enables to compute the exact IA precoders in closed-form, based on local channel state information at the receiver (CSIR). Secondly, the concept of IA-Cell assignment is introduced and its effect on the achievable rate and degrees of freedom (DoF) performance is analyzed. Two distributed matching approaches and one centralized assignment approach are proposed to find a good IA-Cell assignment in three scenrios with different backhaul overhead. Thirdly, under limited feedback, the thesis derives an upper bound of the residual interference to noise ratio (RINR), formulates and solves a corresponding DBA problem. Finally, numerical results show that the proposed GIA with optimized IA-Cell assignment and the DBA greatly outperforms the traditional GIA algorithm.

In the present study, the differential effects of two different feedback-delivery methods (written feedback vs. written plus verbal feedback) were compared on the utility and affective reactions of the feedback providers (i.e., raters) and the recipients (i.e., ratees) toward the feedback process, and also on the job performance of the feedback recipients in a military sample. Using a quasi-experimental design, 77 supervisors (who provided feedback) and 71 subordinates (who received feedback) participated in the study. Results indicated that the feedback-delivery technique was differentially effective on the utility and affective reactions of the supervisors. Both the utility and affective reactions of the supervisors who provided written plus verbal feedback were more favorable than those of the supervisors who provided written-only feedback to their subordinates. However, neither the reactions nor the job performance of the subordinates in the two feedback conditions differed significantly from each other.

In this thesis we investigate how to improve the performance of MU-MIMO wireless system in terms of achieving Shannon capacity limit and efficient use of precious resource of radio spectrum in wireless communication. First a new suboptimal volume-based scheduling algorithm is presented, which can be applied in MU-MIMO downlink system to transmit signals concurrently to multiple users under the assumption of perfect channel information at transmitter and receiver. The volume-based scheduling algorithm utilises Block Diagonalisation precoding and Householder reduction procedure of QR factorisation. In comparison with capacity-based suboptimal scheduling algorithm, the volume-based algorithm has much reduced computational complexity with only a fraction of sum-rate capacity penalty from the upper bound of system capacity limit. In comparison with semi-orthogonal user selection suboptimal scheduling algorithm, the volume-based scheduling algorithm can be implemented with less computational complexity. Furthermore, the sum-rate capacity achieved via volume-based scheduling algorithm is higher than that achieved by SUS scheduling algorithm in the MIMO case. Then, a two-step scheduling algorithm is proposed, which can be used in the MU-MIMO system and under the assumption that channel state information is known to the receiver, but it is not known to the transmitter and the system under the feedback resource constraint. Assume that low bits codebook and high bits codebook are stored at the transmitter and receiver. The users are selected by using the low bits codebook; subsequently the BD precoding vectors for selected users are designed by employing high bits codebook. The first step of the algorithm can alleviate the load on feedback uplink channel in the MU-MIMO wireless system while the second step can aid precoding design to improve system sum-rate capacity. Next, a MU-MIMO cognitive radio (CR) wireless system has been studied. In such system, a primary wireless network and secondary wireless network coexist and the transmitters and receivers are equipped with multiple antennas. Spectrum sensing methods by which a portion of spectrum can be utilised by a secondary user when the spectrum is detected not in use by a primary user were investigated. A Free Probability Theory (FPT) spectrum sensing method that is a blind spectrum sensing method is proposed. By utilizing the asymptotic behaviour of random matrix based on FPT, the covariance matrix of transmitted signals can be estimated through a large number of observations of the received signals. The method performs better than traditional energy spectrum sensing method. We also consider cooperative spectrum sensing by using the FPT method in MU-MIMO CR system. Cooperative spectrum sensing can improve the performance of signal detection. Furthermore, with the selective cooperative spectrum sensing approach, high probability of detection can be achieved when the system is under false alarm constraint. Finally, spectrum sensing method based on the bispectrum of high-order statistics (HOS) and receive diversity in SIMO CR system is proposed. Multiple antennas on the receiver can improve received SNR value and therefore enhance spectrum sensing performance in terms of increase of system-level probability of detection. Discussions on cooperative spectrum sensing by using the spectrum sensing method based on HOS and receive diversity are presented.

This thesis consists of four essays on topics relating to the fields of international portfolio choice, trading behavior, and asset pricing. "Direct Foreign Ownership, Institutional Investors, and Firm Characteristics" analyzes portfolios of Swedish stocks held by foreign investors. The analysis reveals that foreigners tilt their portfolios to firms with certain attributes. It is also shown that the seemingly specific preferences of foreign investors are driven by the fact that they are large institutional investors, and are not linked to their national origin. "Foreigners' Trades in Risky Assets: An assessment of  Investment Behavior and Performance" analyzes foreigners' trading activities. It is shown that foreigners trade more than domestic investors. Further, they trade as non-informed trend followers in that they buy stocks that have recently done well. Nonetheless, after the liberalization of Sweden's stock market, foreigners' purchases have led to a permanent price increase and to a reduction in the cost of equity capital. "Exchange Rate Exposure, Risk Premia, and Firm Characteristics" shows that about fifty percent of Swedish listed firms are affected by exchange rate fluctuations. The sign and magnitude of exchange rate exposure are characterized across industries as well as firm attributes. The empirical analysis suggests that exposure can be eliminated through diversification, and that exchange rate risk is not priced. "Conditioning Information in Tactical Asset Allocation" examines whether investors can exploit the predictability in time-varying expected returns on Swedish stocks and bonds. It is shown that dynamic allocation strategies, based on conditioning information, significantly outperform several benchmark portfolios. This superior performance is not only statistically significant, it is economically large.
Diss. Stockholm : Handelshögsk.

This master thesis in energy optimization was made during the autumn of 2006 at Käppala wastewater treatment plant in Lidingö, Stockholm. A preceding thesis, where all electricity consumption was mapped, showed that the aeration in the biological treatment is the single largest consumer in the plant, and it is therefore of interest to reduce this cost. The oxygen control strategy used at Käppala WWTP is working well from a nutrient removal point of view, but not from an economic one. The last aerobic zones have a very low oxygen consumption during low loading periods which give rise to enhanced dissolved oxygen concentrations with excessive costs and reduced denitrification as a result. But also during periods of normal loading unnecessary high oxygen concentration are sometimes given.

By modifying the aeration control strategy three full-scale experiments have been made, with the intention to reduce the air consumption. The experiments were carried out during week 37-50 in the autumn of 2006 and showed that savings could be made.

The regular oxygen control at Käppala WWTP controls the oxygen level in the aerobic compartment with two DO-setpoints; one in the first aerobic zone and one in the last. The zones in between are controlled by an airflow fractionation depending on the oxygen level in the first and last zone. In the first strategy to be evaluated, all four zones in the aerated part were individually controlled with its own setpoint. Two different setpoint combinations were tested. By using the fact that the efficiency in the oxygen transfer rate was higher at low airflows, savings of approximately 16 % were achieved. In the second strategy tested, an ammonia-feedback control combined with a DO-feedback controlled the DO-set point in the first aerobic zone. This strategy adjusted the DO- set points to the loading variations, and this gave a decreased airflow of approximately 9 %. Finally the two strategies were combined. All zones were then controlled individually with DO-set points set by an ammonium-feedback and a DO-feedback. The strategy gave savings in the airflow of approximately 18 %. In all three trials the aerated zones were more efficiently used, and the estimated savings are 550 000 SEK/year, and with a preserved nutrient removal efficiency.

Under hösten 2006 har ett examensarbete om energieffektivisering på Käppalaverket på Lidingö utförts. Ett föregående examensarbete där all elenergiförbrukning kartlades visade att blåsmaskinerna i biosteget står för den enskilt största förbrukningen i verket och det är därför av intresse att minska denna kostnad. Syrestyrningsstrategin som används på Käppalaverket fungerar mycket bra ur reningssynpunkt, men är inte optimal ur energisynpunkt. Dels luftas de första aeroba zonerna för mycket vid låg belastning vilket ger upphov till kraftigt förhöjda syrekoncentrationer i de sista aeroba zonerna med höga luftningskostnader och risk för försämrad denitrifikation, men även under normal belastning har det visat sig att onödigt höga syrekoncentrationer ibland ges.

Tre fullskaliga optimeringsförsök har utförts, med syfte att minska luftförbrukningen med bibehållen reningsgrad. Försöken pågick från vecka 37 till 50 hösten 2006, och visade att det finns möjlighet att spara energi genom att modifiera syrestyrningsstrategin.

Den reguljära syreregleringen i Käppalaverket styr syrehalten i den aeroba bassängen mot två syrebörvärden; ett i den första luftade zonen och ett i den sista. Luftflödet till de mellanliggande zonerna styrs av luftflödesandelar beroende på syrehalten i dessa två zoner. Den första strategin som utvärderades styrde istället samtliga zoner individuellt med egna börvärden, där två olika strukturer på de satta börvärdena användes. Genom att utnyttja en högre effektivitet i syreöverföringshastigheten vid låga luftflöden uppnåddes luftflödesbesparingar på ca 16 % i första försöket.

I den andra strategin styrdes syrebörvärdet i den första luftade zonen med hjälp av två återkopplingar, en från utgående ammoniumhalt och en från syrehalten i den sista luftade zonen.

Tack vare att strategin anpassade syrebörvärdena efter belastningen av syretärande ämnen erhölls luftflödesbesparingar på ca 9 %. Slutligen kombinerades de två strategierna; samtliga zoner styrdes individuellt med börvärden satta av en ammonium-återkoppling och en syre-återkoppling. Strategin medförde luftflödesbesparingar på ca 18 %. I samtliga försök utnyttjades de luftade zonerna bättre, och besparingspotentialen uträknad från 2005 års elpriser blev som mest 550 000 SEK/år, detta med en bibehållen reningsgrad.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Em alguns problemas práticos, por exemplo, no controle de vibrações de sistemas mecânicos utilizando acelerômetros como sensores, é mais fácil obter a da derivada do vetor de estado do que o vetor de estado. Esta dissertação mostra que plantas lineares e invariantes no tempo descritas pelas matrizes {A,B,C,D}, cuja saída é a derivada do vetor de estado, são não observáveis e não estabilizáveis com realimentação da saída, quando det(A)=0. A impossibilidade de rejeição de distúrbios constantes, somados à entrada da planta quando det(A) 6= 0, realimentando-se a saída com controladores estáticos, foi também demonstrada. Adicionalmente, são propostas novas técnicas de controle para uma classe de sistemas não lineares com incertezas variantes no tempo. Condições na forma de desigualdades matriciais lineares, em inglês Linear Matrix Inequalities (LMIs), para o projeto de sistemas de controle empregando realimentação derivativa estática da derivada do vetor de estado, que ao mesmo tempo estabiliza a planta e maximiza o limite de incerteza do termo não linear, são estabelecidas com base em funções quadráticas de Lyapunov. Posteriormente estendem-se as condições de estabilidade robusta para sistemas não lineares com incertezas variantes no tempo e incertezas politópicas, que podem também representar falhas estruturais. O projeto do controlador é realizado através de condições baseadas em LMIs que, quando factíveis, podem ser resolvidas facilmente utilizando técnicas de programação convexa. Essa metodologia permite a inclusão de restrições de desempenho no projeto, como por exemplo, na taxa de decaimento e na norma de ganho dos controladores, de modo a atender às restrições do projeto. São apresentadas análises e resultados considerando o sinal de controle nulo e empregando realimentação derivativa estática do vetor de estado...
In some practical problems, for instance in the control of mechanical systems using accelerometers as sensors, it is easier to obtain the state-derivative vectors than the state vectors. This dissertation shows that (i) linear time-invariant plants given by the state-space model matrices {A,B,C,D} with output equal to the state-derivative vector are not observable and can not be stabilizable by using an output feedback if det(A) = 0 and (ii) the rejection of a constant disturbance added to the input of the aforementioned plants, considering det(A) 6= 0, and a static output feedback controller is not possible. The proposed results can be useful in the analysis and design of control systems with state-derivative feedback. Additionally, a new procedure for the control of a class of nonlinear systems with time-varying uncertainties using static statederivative feedback is proposed. Conditions based on Linear Matrix Inequalities (LMIs) for the design of robust controllers using state-derivative feedback, which simultaneously stabilizes the system and maximizes the uncertainty bound of the nonlinear term are proposed. Robust stability conditions for nonlinear systems with uncertainties and time-varying polytopic uncertainties, known as structural failures, are also presented. The controller design are based on LMIs which, when feasible, can be easily solved using convex programming techniques. This methodology allows the inclusion of performance constraints on the design, such as the decay rate and gain bounds in order to meet the design requirements. The dissertation considered cases where the control signal is equal to zero and with a state-derivative feedback. The elaboration of the theory for systems with n nonlinearities is illustrated through examples covering a single nonlinearity, with and without two polytopic uncertainties (and structural failures), and two nonlinearities... (Complete abstract click electronic access below)

Orientador: Marcelo Carvalho Minhoto Teixeira
Banca: Edvaldo Assunção
Banca: Celso Pascoli Bottura
Resumo: Em alguns problemas práticos, por exemplo, no controle de vibrações de sistemas mecânicos utilizando acelerômetros como sensores, é mais fácil obter a da derivada do vetor de estado do que o vetor de estado. Esta dissertação mostra que plantas lineares e invariantes no tempo descritas pelas matrizes {A,B,C,D}, cuja saída é a derivada do vetor de estado, são não observáveis e não estabilizáveis com realimentação da saída, quando det(A)=0. A impossibilidade de rejeição de distúrbios constantes, somados à entrada da planta quando det(A) 6= 0, realimentando-se a saída com controladores estáticos, foi também demonstrada. Adicionalmente, são propostas novas técnicas de controle para uma classe de sistemas não lineares com incertezas variantes no tempo. Condições na forma de desigualdades matriciais lineares, em inglês Linear Matrix Inequalities (LMIs), para o projeto de sistemas de controle empregando realimentação derivativa estática da derivada do vetor de estado, que ao mesmo tempo estabiliza a planta e maximiza o limite de incerteza do termo não linear, são estabelecidas com base em funções quadráticas de Lyapunov. Posteriormente estendem-se as condições de estabilidade robusta para sistemas não lineares com incertezas variantes no tempo e incertezas politópicas, que podem também representar falhas estruturais. O projeto do controlador é realizado através de condições baseadas em LMIs que, quando factíveis, podem ser resolvidas facilmente utilizando técnicas de programação convexa. Essa metodologia permite a inclusão de restrições de desempenho no projeto, como por exemplo, na taxa de decaimento e na norma de ganho dos controladores, de modo a atender às restrições do projeto. São apresentadas análises e resultados considerando o sinal de controle nulo e empregando realimentação derivativa estática do vetor de estado... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In some practical problems, for instance in the control of mechanical systems using accelerometers as sensors, it is easier to obtain the state-derivative vectors than the state vectors. This dissertation shows that (i) linear time-invariant plants given by the state-space model matrices {A,B,C,D} with output equal to the state-derivative vector are not observable and can not be stabilizable by using an output feedback if det(A) = 0 and (ii) the rejection of a constant disturbance added to the input of the aforementioned plants, considering det(A) 6= 0, and a static output feedback controller is not possible. The proposed results can be useful in the analysis and design of control systems with state-derivative feedback. Additionally, a new procedure for the control of a class of nonlinear systems with time-varying uncertainties using static statederivative feedback is proposed. Conditions based on Linear Matrix Inequalities (LMIs) for the design of robust controllers using state-derivative feedback, which simultaneously stabilizes the system and maximizes the uncertainty bound of the nonlinear term are proposed. Robust stability conditions for nonlinear systems with uncertainties and time-varying polytopic uncertainties, known as structural failures, are also presented. The controller design are based on LMIs which, when feasible, can be easily solved using convex programming techniques. This methodology allows the inclusion of performance constraints on the design, such as the decay rate and gain bounds in order to meet the design requirements. The dissertation considered cases where the control signal is equal to zero and with a state-derivative feedback. The elaboration of the theory for systems with n nonlinearities is illustrated through examples covering a single nonlinearity, with and without two polytopic uncertainties (and structural failures), and two nonlinearities... (Complete abstract click electronic access below)
Mestre

The diploma thesis focuses on the problems of electric power precipitators. Due to their current dominant position, the work concentrates on the sources of single phase transformers operating at the frequency of 50 Hz controlled by thyristors. The first part describes the electrostatic precipitator and its principle. This is followed by a brief insight into the proposal for an electrostatic precipitator. The work also explains the high voltage source that is divided into a transformer with a rectifier and into a control box with power circuits and control circuits that provide the power supplied by a transformer. The work also offers an explanation of the HV source system that operates at different conditions. The last part suggests a proposal for cooling cabinet including thyristors, for power line control box resources, for a supply line and a line to the transformer.

In Particle Accelerators, the Low-Level RF (LLRF) is the control system of the RF, and in the end, of the purpose of the machine, that is the energy transfer and acceleration of particles. It implements algorithms synchronizing the RF conveying the energy to the beam and tailoring its longitudinal parameters. For this, the LLRF uses beam-related signals whose spectral content changes during the acceleration. The increase in energy results in an increase of the beam velocity, and for circular accelerators (Synchrotrons) a decrease in revolution period. This is especially relevant for Hadron machines whose injection energy is low resulting in a significant increase of their velocity before reaching relativistic speeds. Hence, the LLRF needs to continuously tune its processing to the beam; we call this technique Beam Synchronous Processing. One important task of the LLRF is the compensation of the beam-induced voltage in the accelerating cavities (Beam Loading). In the CERN SPS the regulation bandwidth must cover 5 MHz on each side of the 200 MHz RF. With a beam revolution period around 23 µs more than a hundred revolution frequency harmonics, present in the beam signal, fall in the RF sidebands. The variation in beam velocity changes the position and spacing of the harmonics in the spectrum. The large number of harmonics and their varying positions make the algorithm reconfiguration an undesirable option. To cope with this, the early digital implementations used a system clock derived from the sweeping RF. This locks the sampling and the processing to the beam, by design. This historical solution, that is still in use in several machines, is now a limiting factor for the use of modern technologies. The Thesis presents a novel Beam Synchronous Processing Architecture, using a fixed frequency clocking, and capable of treating periodic signals with known and varying fundamental frequency. The Architecture is an alternative to the burden of reconfiguration in processing algorithms; it tunes the spectrum to the processing by resampling the input data. Two Resamplers are combined in the so-called resampling sandwich. The application algorithm requiring synchronism with the input signal is placed in the middle. The key element is a novel All-Digital Farrow-based Resampler, that accepts arbitrary resampling ratios that can be modified in real-time. The hardware uses a single fixed frequency system clock, making its implementation feasible in State-Of-the-Art FPGAs, ASICs and systems such as the new uTCA platform currently being deployed in the CERN SPS LLRF system. The input and output ports of the Resampler, and all the processing within the Architecture, are synchronous to this fixed frequency clock and accept data streams whose sampling rate can be variable and modified in real time. The Architecture has been commissioned in a LLRF uTCA crate hosting the One Turn FeedBack algorithm to control a real SPS cavity. The algorithm compensates the Beam Loading. The Architecture has demonstrated its capability to track in real-time an energy ramp with an RF frequency following a linear sawtooth pattern ramped at 2.4 MHz per second. The complete uTCA implementation has successfully passed all the functional validation and qualitative tests. The Architecture suits seamless the two technological paradigm changes adopted for the new CERN SPS LLRF system; first, the instantaneous value of the RF frequency is transmitted as a numerical word (used to set the resampling ratio), via a deterministic network, the White Rabbit. And second, the reference signal is now the fixed frequency clock recovered from this network. Both paradigms benefit from the all-digital Resampler and the Beam Synchronous Architecture that fulfil the techniques and technological needs for its implementation enabling novel LLRF algorithms and solutions.
En un Acelerador de Partículas, el Low Level RF (LLRF) es el sistema de control de la RF, e implícitamente, de la transferencia de energía y aceleración de partículas, objetivo último de la máquina. El LLRF implementa algoritmos que sincronizan la transferencia de energía de RF hacia el haz, y controla sus parámetros longitudinales. Usa señales del haz, cuyo contenido espectral se modifica con la aceleración. El incremento en energía implica un incremento en velocidad del haz que, para aceleradores circulares (Sincrotrones), resulta en un decremento del periodo de revolución. Esto es relevante en aceleradores de Hadrones, en los cuales la baja energía de inyección favorece grandes incrementos de velocidad antes de alcanzar valores relativistas. El LLRF necesita por tanto sintonizar continuamente el procesado y el haz (Beam Synchronous Processing). Una misión del LLRF es la compensación de la tensión inducida por el haz en cavidades aceleradoras (Beam Loading). En el sincrotrón SPS del CERN, el ancho de banda de regulación cubre 5 MHz a cada lado de la RF (200 MHz). Con un periodo de revolución de aproximadamente 23 µs, más de cien harmónicos de la frecuencia de revolución, presentes en la señal del haz, aparecen en las bandas alrededor de la RF. La variación en velocidad del haz cambia la posición y espaciado de estos harmónicos en el espectro. Su número y posición cambiante hacen una opción poco deseable la reconfiguración en algoritmos de control. La solución histórica es un reloj de sistema derivado de la RF, por tanto variable, que liga por diseño el muestreo y procesado al haz. Aún en uso en varias máquinas, este reloj es ahora un factor limitante para el uso de nuevas tecnologías. Esta Tesis presenta una nueva Arquitectura para Tratamiento Síncrono de Señales derivadas del Haz, mediante un reloj de sistema con frecuencia fija, que posibilita el tratamiento de señales periódicas en las que el harmónico fundamental tiene una frecuencia variable y conocida. La Arquitectura es una alternativa válida al problema de reconfiguración de algoritmos de procesado; sintoniza el espectro al procesado mediante el re-muestreo de los datos. Dos Re-muestreadores (Resamplers) son combinados en el denominada sándwich de re-muestreo. El algoritmo requiriendo sincronismo con el haz, se sitúa en medio de este sándwich. El elemento clave es un novedoso Resampler digital que acepta relaciones de re-muestreo arbitrarias y modificables en tiempo real. El hardware usa un único reloj de sistema de frecuencia fija, facilitando la implementación en FPGAs, ASICs y sistemas de última generación, como los controladores uTCA en los sistemas LLRF del SPS en el CERN. Los puertos de entrada y salida del Resampler, y todo el procesado en la Arquitectura, son síncronos a este reloj, y aceptan señales con una frecuencia de muestreo variable en tiempo real.La Arquitectura ha sido implementada en un controlador uTCA de una cavidad del SPS albergando el algoritmo One Turn FeedBack. El algoritmo compensa el Beam Loading. La Arquitectura demuestra ser viable operando sintonizada a una rampa de aceleración del haz, con una RF cuya frecuencia varia linealmente a 2.4 MHz por segundo siguiendo un patrón en diente de sierra. La implementación de la Arquitectura ha pasado toda la validación funcional y test cualitativos. La Arquitectura se adapta de manera sin igual a dos cambios de paradigma tecnológico adoptados por el LLRF del SPS; primero, la distribución del valor instantáneo de la frecuencia de RF es ahora hecho mediante una palabra digital con una red determinista, White Rabbit. Y segundo, la señal de referencia es ahora un reloj con frecuencia fija extraído de esta red. La adopción de ambos paradigmas se ve beneficiada por el uso de la Arquitectura y Resampler, que satisfacen los requerimientos técnicos y tecnológicos para la implementación de nuevos algoritmos y soluciones LLRF.
Dans le monde des Accélérateurs de Particules, le Low-Level RF (LLRF) est le système de contrôle de la RF et, in-fine, du transfert d'énergie et de l'accélération des particules. Il met en oeuvre des algorithmes synchronisant la RF transférant l'énergie au faisceau et adaptant ses paramètres longitudinaux. Pour cela, le LLRF utilise des signaux liés au faisceau dont le contenu spectral est modifié par l'accélération. L'augmentation d'énergie se traduit par une augmentation de la vitesse du faisceau, et pour les accélérateurs circulaires (Synchrotrons), une diminution de la période de révolution. Cela est particulièrement pertinent pour les machines à Hadrons dont l’énergie d’injection est faible, avec la conséquence d’une augmentation significative de leur vitesse durant l’accélération. Le LLRF doit donc ajuster en permanence son traitement au faisceau ; nous appelons cette exigence Beam Synchronous Processing. Une tâche importante du LLRF est la compensation de la tension induite par le faisceau (Beam Loading). Dans le SPS au CERN, la régulation couvre 5 MHz de chaque côté de la RF (200 MHz). Avec une période de révolution autour de 23 μs, plus d'une centaine d’harmoniques de fréquence de révolution, présentes dans le spectre du faisceau, tombent dans la bande +- 5 MHz. La variation de vitesse du faisceau modifie la position et l'espacement des harmoniques dans le spectre. Le grand nombre de raies spectrales et leur position variable font de la reconfiguration de l'algorithme une option indésirable. Les solutions digitales existantes ont donc préféré changer l’horloge d’échantillonnage : Celle-ci est verrouillée sur la RF, ce qui synchronise par conception l'échantillonnage et le traitement du faisceau. Cette solution historique, toujours en usage dans plusieurs machines, est aujourd'hui un facteur limitant pour les technologies modernes. La Thèse présente une nouvelle Architecture de traitement synchrone de faisceau, utilisant une horloge fixe, et capable de traiter des signaux périodiques de fréquence fondamentale connue et possiblement variable. L'Architecture apporte une alternative au fardeau de la reconfiguration dans les algorithmes ; il ajuste le spectre au traitement en rééchantillonnant les données d'entrée. Deux Rééchantillonneurs ont été combinés dans le sandwich de rééchantillonnage. L'algorithme d'application nécessitant un synchronisme avec le signal d'entrée est placé au milieu. L'élément clé est un nouveau Ré-échantillonneur entièrement numérique basé sur une architecture Farrow, qui accepte des taux de rééchantillonnage arbitraires pouvant également être modifiés en temps réel. L’implémentation utilise une seule horloge système à fréquence fixe, ce qui rend sa mise en œuvre possible dans les FPGA, ASIC et systèmes de pointe comme la nouvelle plate-forme uTCA actuellement déployée dans le SPS du CERN. L’entrée et la sortie du Ré-échantillonneur, et tout le traitement dans l'Architecture, sont synchrones avec cette horloge et acceptent un taux d’échantillonnage variable que peut être modifiée en temps réel. L'Architecture a été déployée dans un châssis uTCA hébergeant l'algorithme One Turn FeedBack pour contrôler une véritable cavité SPS. L'algorithme compense le Beam Loading. L'Architecture a démontré sa capacité à suivre en temps réel une rampe d'énergie avec une fréquence RF suivant une modulation en dent de scie, à 2.4 MHz par seconde. L’implémentation complète sur uTCA a passé avec succès les tests de validation fonctionnelle et qualitative. L'Architecture convient parfaitement aux deux paradigmes technologiques adoptés pour le nouveau système LLRF du SPS ; premièrement, la valeur instantanée de la fréquence RF est transmise sous forme de mot numérique (qui donnera le taux de rééchantillonnage), via un réseau déterministe, le White Rabbit. Et deuxièmement, le signal de référence est maintenant l'horloge à fréquence fixe récupérée de ce réseau. La solution présentée respecte ces deux paradigmes grâce au Réchantillonneur entièrement numérique et à l'horloge fixe.
Ciència i enginyeria de materials

Individuals born after 1980 are often immediately labeled with the term, "digital generation". This label assumes that young people are fluent, proficient, and constant users of digital media. This thesis explores digital communication behavior in the context of political communication. This thesis begins with an exploration of how age influences digital political communication, finding that while young people prefer digital media more so than older generations, they are less likely to utilize those media to communicate with government officials.  Following the age comparison, this thesis examines race, income, and education as indicators for digital political communication. This thesis utilizes secondary data analysis of surveys collected by PEW Internet & American Life Project between 2003 and 2009.  The findings herein suggest that although young people prefer digital communication in politics, the millennial generation continues to lag behind older generations in actual digital political communication behavior. Additionally, this thesis finds that young people falling into minority groups, with low-income and low-education are less likely to utilize digital political communication media than older Whites with high-income and high-education.
Master of Arts

The use of multi-rater feedback as a way to analyze perceptions within the context of job performance and leadership in the Federal Bureau of Investigation (FBI) was examined. Research in this domain is notable as this type of evaluation is now being done with regularity in the private sector and is starting to be utilized more extensively in the public sector, but is still being used to a limited extent in law enforcement. The path of this research examined differences between self-assessments and assessments of others (peers and subordinates) in dimensions of leadership as measured by the same multi-rater instrument at two points in time. This research effort made use of a multi-rater survey instrument called the "Leadership Commitments and Credibility Inventory System (LCCIS)," designed by Keilty, Goldsmith, and Company, which is used in multiple industries and was expanded to capture characteristics considered important to FBI leaders. Results showed high ratings on a five point Likert scale as indicated by mean averages of self and others. Additionally, Z scores, t tests and ANCOVA indicated that FBI supervisors did not overestimate their leadership, as indicated by (1) an overall leadership measure at time two compared to time one, (2) a greater perceptual agreement between others and self existing on second multi-rater assessments than on the initial assessments, and (3) any statistical differences of means in all measured categories at time two versus time one. Various subcategories of the assessment showed a mixture of non-statistically significant results and that subordinates and peers perceived leaders differently. Further, analysis of two unique dimensions of the LCCIS, "Manage Diversity" and "Build Public Trust" showed exceptionally high results. The implications of the present research are that leadership in the FBI, as measured by different dimensions, is strong. Yet, there is no evidence that leaders or others in this organization change their perceptions over time. These findings may point to the need for multi-rater instruments to be used in concert with personal development plans in order to improve the perception of leadership.
Ph. D.

Two topics in fading channels with a strict delay constraint and a resolution-constrained feedback link are treated in this thesis.

First, a multi-layer variable-rate single-antenna communication system with quantized feedback, where the expected rate is chosen as the performance measure, is studied under both short-term and long-term power constraints. Iterative algorithms exploiting results in the literature of parallel broadcast channels are developed to design the system parameters. A necessary and sufficient condition for single-layer coding to be optimal is derived. In contrast to the ergodic case, it is shown that a few bits of feedback information can improve the expected rate dramatically. The role of multi-layer coding, however, reduces quickly as the resolution of the feedback link increases.

The other part of the thesis deals with partial power control systems utilizing quantized feedback to minimize outage probability, with an emphasis on the diversity-multiplexing tradeoff. An index mapping with circular structure is shown to be optimal and the design is facilitated with a justified Gaussian approximation. The diversity gain as a function of the feedback resolution is analyzed. The results are then extended to characterize the entire diversity-multiplexing tradeoff curve of multiple-antenna channels with resolution-constrained feedback. Adaptive-rate communication is also studied, where the concept of minimum multiplexing gain is introduced. It is shown that the diversity gain of a system increases significantly even with coarsely quantized feedback, especially at low multiplexing gains.

L’évolution des galaxies reste assez mal comprise. La densité de formation piquant entre 1
The evolution of galaxies is something that is still not well understood. The cosmic star formation rate density peaks between 1 < z < 3. It is therefore important to investigate the high-z Universe and the mechanisms which triggers or quenches star-formation in galaxies. In this thesis I investigate the effects of AGN feedback by studying high-z radio galaxies (HzRGs). For a sample of 25 HzRGs at 1 < z < 5.2, I add new ALMA data and determine the star formation rates (SFR) by multi-wavelength spectral energy distribution fitting. The ALMA data reveals that the mm continuum emission can be complicated, with contributions from several thermal dust emission components and/or synchrotron emission. The new estimated SFRs are 7 times lower than in previous studies. We might therefore be observing the effect of the AGN suppressing the growth of the host galaxy. For one source I explore the possibilities of constraining the gas Physics of the host galaxy and the halo gas by combining MUSE and ALMA data cubes. Quiescent ionized halo gas is detected, which coincide with a molecular gas reservoir detected with ALMA in [C I]. These observations probe the complex multi-phase halo gas and show the power of multi-wavelength observations

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008.
Title from PDF title page (viewed Sept. 21, 2009). Additional advisors: Michael Crowe, Cynthia Crowley, Virginia G. Wadley, David E. Vance. Includes bibliographical references (p. 31-34).

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We present in this work the development of an α-β filter for indirect measurement in 1st order dynamic systems, derived from the known equations for the α-β filter applied to systems with a pure integer. The main α-β filter design parameters analyzed are: the variance reduction factor of the measurement noise and the total transient error for a step input. Further, we present the development of the equations for the calculation of a critically dumped filter. As example of application, we use the concepts developed for the design of an α-β filter for the indirect measurement of the oxygen up-take rate in activated sludge systems in a dissolved oxygen feedback configuration, which can be viewed as a 1st order system. Simulations and comparisons with other methods are carried out in order to illustrate the proposed formulations.
Neste trabalho, apresenta-se o desenvolvimento do filtro α-β para medição indireta em sistemas dinâmicos de 1ª ordem a partir das equações conhecidas do filtro α-β aplicados a sistemas com um integrador puro. Os principais parâmetros de projeto do filtro analisado são: o fator de redução de variância do ruído de medição e o erro total de transitório para uma entrada do tipo degrau. Além disso, apresenta-se o desenvolvimento das equações para o cálculo de um filtro criticamente amortecido. Como exemplo de aplicação, utiliza-se os conceitos desenvolvidos para o projeto de um filtro α-β para medição indireta da taxa de consumo de oxigênio em sistemas de tratamento de esgotos de lodo ativado em uma configuração de realimentação da concentração de oxigênio dissolvido, o qual pode ser considerado um sistema de 1ª ordem. Simulações e comparações com outros métodos são apresentadas de forma a ilustrar a formulação proposta.

Thesis (Ph. D.)--Florida State University, 2009.
Advisor: John Reynolds, Florida State University, College of Social Sciences and Public Policy, Dept. of Sociology. Title and description from dissertation home page (viewed on Mar. 29, 2010). Document formatted into pages; contains xi, 78 pages. Includes bibliographical references.

The prefrontal cortex (PFC) has long been thought to be the seat of social behaviours in mammals. Lesions of the orbitofrontal cortex (OFC), a subregion of the PFC, are known to cause social deficits in humans. Interestingly, social deficits are also seen in rats with OFC lesions. Rats that are deprived of peer play during development exhibit behaviour similar to OFC-ablated animals. Another subregion of the PFC, the medial prefrontal cortex (mPFC) is interconnected with the OFC. The mPFC and OFC have been shown to be reciprocally responsive to a variety of inuences, in terms of dendritic morphology. It was hypothesized that social experiences are necessary for the proper development of the OFC, and that, because of the interconnectivity, the mPFC would also be sensitive to social experience. The social condition in which juvenile rats were raised was manipulated, and the OFC and mPFC were shown to be differentially responsive to specific aspects of social experience. It was already known that OFC lesions produce specific social deficits, but the contribution of the mPFC to the production of social behaviour was unknown. To investigate the contribution of the mPFC to the performance of social behaviour, animals were given mPFC lesions, and their social play behaviour was quantified. mPFC-ablated animals had altered play patterns that were distinct from those seen in the OFC-ablated animals. It was concluded that the OFC and mPFC are differentially responsive to social stimuli during development, and that the OFC and mPFC make discrete contributions to the production of social behaviour. The results were interpreted in an evolutionary context.
x, 93 leaves : ill. ; 29 cm.