Efficient complementary sequences-based architectures and their application to ranging measurements

Premio Extraordinario de Doctorado de la UAH en 2015En las últimas décadas, los sistemas de medición de distancias se han beneficiado de los avances en el área de las comunicaciones inalámbricas. En los sistemas basados en CDMA (Code-Division Multiple-Access), las propiedades de correlación de las secuencias empleadas juegan un papel fundamental en el desarrollo de dispositivos de medición de altas prestaciones. Debido a las sumas ideales de correlaciones aperiódicas, los conjuntos de secuencias complementarias, CSS (Complementary Sets of Sequences), son ampliamente utilizados en sistemas CDMA. En ellos, es deseable el uso de arquitecturas eficientes que permitan generar y correlar CSS del mayor número de secuencias y longitudes posibles. Por el término eficiente se hace referencia a aquellas arquitecturas que requieren menos operaciones por muestra de entrada que con una arquitectura directa. Esta tesis contribuye al desarrollo de arquitecturas eficientes de generación/correlación de CSS y derivadas, como son las secuencias LS (Loosely Synchronized) y GPC (Generalized Pairwise Complementary), que permitan aumentar el número de longitudes y/o de secuencias disponibles. Las contribuciones de la tesis pueden dividirse en dos bloques: En primer lugar, las arquitecturas eficientes de generación/correlación para CSS binarios, derivadas en trabajos previos, son generalizadas al alfabeto multinivel (secuencias con valores reales) mediante el uso de matrices de Hadamard multinivel. Este planteamiento tiene dos ventajas: por un lado el aumento del número de longitudes que pueden generarse/correlarse y la eliminación de las limitaciones de las arquitecturas previas en el número de secuencias en el conjunto. Por otro lado, bajo ciertas condiciones, los parámetros de las arquitecturas generalizadas pueden ajustarse para generar/correlar eficientemente CSS binarios de mayor número de longitudes que con las arquitecturas eficientes previas. En segundo lugar, las arquitecturas propuestas son usadas para el desarrollo de nuevos algoritmos de generación/correlación de secuencias derivadas de CSS que reducen el número de operaciones por muestra de entrada. Finalmente, se presenta la aplicación de las secuencias estudiadas en un nuevo sistema de posicionamiento local basado en Ultra-Wideband y en un sistema de posicionamiento local basado en ultrasonidos

Analysis of nonlinear and non-smooth dynamics of a self-oscillating series resonant inverter

In this paper, the dynamics of a dc-ac resonant self-oscillating LC series inverter is analyzed from the point of view of piecewise smooth dynamical systems. Our system is defined by two symmetric configurations and its bifurcation analysis can be given in a one dimensional param- eter space, thus finding a non smooth transition between two strongly different dynamics. The oscillating regime, which is the one useful for applications and involves a repetitive switching action between those configurations, is given whenever their open loop equilibrium is a fo- cus. Otherwise, the only attractors are equilibrium points of node type whose stable manifolds preclude the appearance of oscillations.Postprint (author's final draft

Multichannel detection of acoustic emissions and localization of the source by using a hybrid programming system

The detection of acoustic emissions with multiple channels and different kind of sensors (ultrasound electronic sensors and optical fiber sensors) is presented. The source localization based on the times of arrival is also carried out and different strategies for solving the location equations are compared. The most efficient strategy in terms of computational and complexity costs versus performance has been selected and the error propagation is analyzed. The errors of the acoustic emission source location (localization process) are evaluated from the errors of the times of arrival (detection process). For that, a hybrid programming architecture is proposed. It is formed by a virtual instrumentation system for the acquisition and the detection of multiple acoustic channels and an algorithms-oriented programming system for the implementation of the localization techniques (back-propagation and multiple-source separation algorithms could also be implemented in this system). Finally the communication between both systems is performed by a packet transfer protocol that allows remote operation (e.g. a local monitoring and a remote analysis and diagnosis).This work has been supported by the Spanish National Ministry of Science and Innovation, under the R&D project No. DPI 2009-14628-C03-01 and the scholarship FPI No. BES-2010-042083

Multichannel detection of acoustic emissions and localization of the source with external and internal sensors for partial discharge monitoring of power transformers

The detection of acoustic emissions with multiple channels and different kinds of sensors (external ultrasound electronic sensors and internal optical fiber sensors) for monitoring power transformers is presented. The source localization based on the times of arrival was previously studied, comparing different strategies for solving the location equations and the most efficient strategy in terms of computational and complexity costs versus performance was selected for analyzing the error propagation. The errors of the acoustic emission source location (localization process) are evaluated from the errors of the times of arrival (detection process). A hybrid programming architecture is proposed to optimize both stages of detection and location. It is formed by a virtual instrumentation system for the acquisition, detection and noise reduction of multiple acoustic channels and an algorithms-oriented programming system for the implementation of the localization techniques (back-propagation and multiple-source separation algorithms could also be implemented in this system). The communication between both systems is performed by a packet transfer protocol that allows continuous operation (e.g., on-line monitoring) and remote operation (e.g., a local monitoring and a remote analysis and diagnosis). For the first time, delay errors are modeled and error propagation is applied with this error source and localization algorithms. The 1% mean delay error propagation gives an accuracy of 9.5 mm (dispersion) and a maximum offset of 4 mm (less than 1% in both cases) in the AE source localization process. This increases proportionally for more severe errors (up to 5% reported). In the case of a multi-channel internal fiber-optic detection system, the resulting location error with a delay error of 2% is negligible when selecting the most repeated calculated position. These aim at determining the PD area of activity with a precision of better than 1% (less than 10 mm in 110 cm).This work was supported by the Spanish National Ministry of Science and Innovation, under the R&D project No. DPI 2009-14628-C03-01 and the scholarship FPI No. BES-2010-042083

Dynamic analysis of self-oscillating H-bridge inverters with state feedback

This paper presents a comprehensive approach to analyze the dynamics of a generalized model of resonant inverters using nonsmooth dynamical system theory. The model simultaneously covers both parallel and series resonant inverters under state feedback control. The multi-parametric physical space is reduced to a plane, which is divided in several regions with different dynamical behavior. The boundaries separating these regions are located by solving their corresponding equations and it is found that they all emerge from a singular point in the parameter plane. Suitability for applications of these regions is emphasized, thus providing useful criteria for parameter selection.Postprint (author's final draft

Bifurcation patterns in homogeneous area-preserving piecewise-linear maps

The dynamical behavior of a family of planar continuous piecewise linear maps with two zones is analyzed. Assuming homogeneity and preservation of areas we obtain a canonical form with only two parameters: the traces of the two matrices defining the map. It is shown the existence of sausage-like structures made by lobes linked at the nodes of a nonuniform grid in the parameter plane. In each one of these structures, called resonance regions, the rotation number of the associated circle map is a given rational number. The boundary of the lobes and a significant inner partition line are studied with the help of some Fibonacci polynomials.Postprint (author's final draft

Optical fiber sensor of partial discharges in high voltage DC experiments

A setup simulating High Voltage DC (HVDC) transformers barriers was developed to demonstrate the effectiveness of an optical fiber (OF) sensor in detecting partial discharges (PD) under these peculiar conditions. Different PD detection techniques were compared: electrical methods, and acoustic methods. Standard piezoelectric sensors (R15i-AST) and the above mentioned OF sensors were used for acoustic detection. The OF sensor was able to detect PD acoustically with a sensitivity better than the other detection methods. The multichannel instrumentation system was tested in real HVDC conditions with the aim of analyzing the behavior of the insulation (mineral oil/pressboard).This work was supported by the Spanish Ministry of Science and Innovation under the Project DPI2009-14628-C03-01 and the scholarship FPI BES-2010-042083 and the Spanish Ministry of Economy and Competitiveness under the visiting researcher grant EEBB-I-2013-07675. C.G. Azcárraga-Ramos gratefully acknowledges the Instituto de Investigaciones Eléctricas for a study leave and the Mexican Science Council (CONACYT) for financially supporting his graduate studies. PD tests have been made in the High Voltage and Material Engineering Laboratory of the University of Bologna

Overdentures-supported with implants in totally edentulous geriatric patients

En la actualidad, la implantología oral constituye una modalidad terapéutica en el tratamiento prostodóncico de los pacientes mayores edéntulos totales. La utilización de implantes oseointegrados para rehabilitar la mandíbula o el maxilar edéntulos ha aumentado en el tratamiento de los pacientes geriátricos. La odontología clínica ha demostrado la aplicación con éxito de las técnicas implantológicas orales en los pacientes ancianos. Las sobredentaduras son una excelente modalidad terapéutica de prótesis sobre implantes con una buena respuesta funcional y estética en estos pacientes. La valoración médica y un plan de tratamiento es necesaria para optimizar los beneficios de la rehabilitación oral con sobredentaduras implantosoportadas sobre la calidad de vida de los pacientes geriátricos. Algunos implantes pueden constituir los elementos retentivos, mediante ataches de las sobredentaduras. Los resultados clínicos de muchos estudios demuestran que la rehabilitación prostodóncica mediante una sobredentadura con implantes de los pacientes edéntulos representa una terapéutica implantológica con éxito

Providing 3D video services: the challenge from 2D to 3DTV quality of experience

Recently, three-dimensional (3D) video has decisively burst onto the entertainment industry scene, and has arrived in households even before the standardization process has been completed. 3D television (3DTV) adoption and deployment can be seen as a major leap in television history, similar to previous transitions from black and white (B&W) to color, from analog to digital television (TV), and from standard definition to high definition. In this paper, we analyze current 3D video technology trends in order to define a taxonomy of the availability and possible introduction of 3D-based services. We also propose an audiovisual network services architecture which provides a smooth transition from two-dimensional (2D) to 3DTV in an Internet Protocol (IP)-based scenario. Based on subjective assessment tests, we also analyze those factors which will influence the quality of experience in those 3D video services, focusing on effects of both coding and transmission errors. In addition, examples of the application of the architecture and results of assessment tests are provided