951 resultados para Signal processing


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Atrial fibrillation (AF) is a common heart disorder. One of the most prominent hypothesis about its initiation and maintenance considers multiple uncoordinated activation foci inside the atrium. However, the implicit assumption behind all the signal processing techniques used for AF, such as dominant frequency and organization analysis, is the existence of a single regular component in the observed signals. In this paper we take into account the existence of multiple foci, performing a spectral analysis to detect their number and frequencies. In order to obtain a cleaner signal on which the spectral analysis can be performed, we introduce sparsity-aware learning techniques to infer the spike trains corresponding to the activations. The good performance of the proposed algorithm is demonstrated both on synthetic and real data. RESUMEN. Algoritmo basado en tcnicas de regresin dispersa para la extraccin de las seales cardiacas en pacientes con fibrilacin atrial (AF).

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La artroplastia de cadera se considera uno de los mayores avances quirrgicos de la Medicina. La aplicacin de esta tcnica de Traumatologa se ha incrementado notablemente en los ltimos anos, a causa principalmente del progresivo incremento de la esperanza de vida. En efecto, con la edad aumentan los problemas de artrosis y osteoporosis, enfermedades tpicas de las articulaciones y de los huesos que requieren en muchos casos la sustitucin protsica total o parcial de la articulacin. El buen comportamiento funcional de una prtesis depende en gran medida de la estabilidad primaria, es decir, el correcto anclaje de la prtesis en el momento de su implantacin. Las prtesis no cementadas basan su xito a largo plazo en la osteointegracin que tiene lugar entre el material protsico y el tejido seo, y para lograrla es imprescindible conseguir unas buenas condiciones de estabilidad primaria. El aflojamiento asptico es la principal causa de fallo de artroplastia total de cadera. Este es un fenmeno en el que, debido a complejas interacciones de factores mecnicos y biolgicos, se producen movimientos relativos que comprometen la funcionalidad del implante. La minimizacin de los correspondientes danos depende en gran medida de la deteccin precoz del aflojamiento. Para lograr la deteccin temprana del aflojamiento asptico del vstago femoral se han ensayado diferentes tcnicas, tanto in vivo como in vitro: anlisis numricos y tcnicas experimentales basadas en sensores de movimientos provocados por cargas transmitidas natural o artificialmente, tales como impactos o vibraciones de distintas frecuencias. Los montajes y procedimientos aplicados son heterogneos y, en muchas ocasiones, complejos y costosos, no existiendo acuerdo sobre una tcnica simple y eficaz de aplicacin general. Asimismo, en la normativa vigente que regula las condiciones que debe cumplir una prtesis previamente a su comercializacin, no hay ningn apartado referido especficamente a la evaluacin de la bondad del diseo del vstago femoral con respecto a la estabilidad primaria. El objetivo de esta tesis es desarrollar una metodologa para el anlisis, in vitro, de la estabilidad de un vstago femoral implantado, a fin de poder evaluar las tcnicas de implantacin y los diferentes diseos de prtesis previamente a su oferta en el mercado. Adems se plantea como requisito fundamental que el mtodo desarrollado sea sencillo, reversible, repetible, no destructivo, con control riguroso de parmetros (condiciones de contorno de cargas y desplazamientos) y con un sistema de registro e interpretacin de resultados rpido, fiable y asequible. Como paso previo, se ha realizado un anlisis cualitativo del problema de contacto en la interfaz hueso-vstago aplicando una tcnica optomecnica del campo continuo (fotoelasticidad). Para ello se han fabricado tres modelos en 2D del conjunto hueso-vstago, simulando tres tipos de contactos en la interfaz: contacto sin adherencia y con holgura, contacto sin adherencia y sin holgura, y contacto con adherencia y homogneo. Aplicando la misma carga a cada modelo, y empleando la tcnica de congelacin de tensiones, se han visualizado los correspondientes estados tensionales, siendo estos ms severos en el modelo de unin sin adherencia, como caba esperar. En todo caso, los resultados son ilustrativos de la complejidad del problema de contacto y confirman la conveniencia y necesidad de la va experimental para el estudio del problema. Seguidamente se ha planteado un ensayo dinmico de oscilaciones libres con instrumentacin de sensores resistivos tipo galga extensomtrica. Las muestras de ensayo han sido huesos fmur en todas sus posibles variantes: modelos simplificados, hueso sinttico normalizado y hueso de cadver, seco y fresco. Se ha diseado un sistema de empotramiento del extremo distal de la muestra (fmur) con control riguroso de las condiciones de anclaje. La oscilacin libre de la muestra se ha obtenido mediante la liberacin instantnea de una carga esttica determinada y aplicada previamente, bien con una maquina de ensayo o bien por gravedad. Cada muestra se ha instrumentado con galgas extensomtricas convencionales cuya seal se ha registrado con un equipo dinmico comercial. Se ha aplicado un procedimiento de tratamiento de seal para acotar, filtrar y presentar las respuestas de los sensores en el dominio del tiempo y de la frecuencia. La interpretacin de resultados es de tipo comparativo: se aplica el ensayo a una muestra de fmur Intacto que se toma de referencia, y a continuacin se repite el ensayo sobre la misma muestra con una prtesis implantada; la comparacin de resultados permite establecer conclusiones inmediatas sobre los efectos de la implantacin de la prtesis. La implantacin ha sido realizada por un cirujano traumatlogo utilizando las mismas tcnicas e instrumental empleadas en el quirfano durante la prctica clnica real, y se ha trabajado con tres vstagos femorales comerciales. Con los resultados en el dominio del tiempo y de la frecuencia de las distintas aplicaciones se han establecido conclusiones sobre los siguientes aspectos: Viabilidad de los distintos tipos de muestras sintticas: modelos simplificados y fmur sinttico normalizado. Repetibilidad, linealidad y reversibilidad del ensayo. Congruencia de resultados con los valores tericos deducidos de la teora de oscilaciones libres de barras. Efectos de la implantacin de tallos femorales en la amplitud de las oscilaciones, amortiguamiento y frecuencias de oscilacin. Deteccin de armnicos asociados a la micromovilidad. La metodologa se ha demostrado apta para ser incorporada a la normativa de prtesis, es de aplicacin universal y abre vas para el anlisis de la deteccin y caracterizacin de la micromovilidad de una prtesis frente a las cargas de servicio. ABSTRACT Total hip arthroplasty is considered as one of the greatest surgical advances in medicine. The application of this technique on Traumatology has increased significantly in recent years, mainly due to the progressive increase in life expectancy. In fact, advanced age increases osteoarthritis and osteoporosis problems, which are typical diseases of joints and bones, and in many cases require full or partial prosthetic replacement on the joint. Right functional behavior of prosthesis is highly dependent on the primary stability; this means it depends on the correct anchoring of the prosthesis at the time of implantation. Uncemented prosthesis base their long-term success on the quality of osseointegration that takes place between the prosthetic material and bone tissue, and to achieve this good primary stability conditions is mandatory. Aseptic loosening is the main cause of failure in total hip arthroplasty. This is a phenomenon in which relative movements occur, due to complex interactions of mechanical and biological factors, and these micromovements put the implant functionality at risk. To minimize possible damage, it greatly depends on the early detection of loosening. For this purpose, various techniques have been tested both in vivo and in vitro: numerical analysis and experimental techniques based on sensors for movements caused by naturally or artificially transmitted loads, such as impacts or vibrations at different frequencies. The assemblies and methods applied are heterogeneous and, in many cases, they are complex and expensive, with no agreement on the use of a simple and effective technique for general purposes. Likewise, in current regulations for governing the conditions to be fulfilled by the prosthesis before going to market, there is no specific section related to the evaluation of the femoral stem design in relation to primary stability. The aim of this thesis is to develop a in vitro methodology for analyzing the stability of an implanted femoral stem, in order to assess the implantation techniques and the different prosthesis designs prior to its offer in the market. We also propose as a fundamental requirement that the developed testing method should be simple, reversible, repeatable, non-destructive, with close monitoring of parameters (boundary conditions of loads and displacements) and with the availability of a register system to record and interpret results in a fast, reliable and affordable manner. As a preliminary step, we have performed a qualitative analysis of the contact problems in the bone-stem interface, through the application of a continuous field optomechanical technique (photoelasticity). For this proposal three 2D models of bonestem set, has been built simulating three interface contact types: loosened an unbounded contact, unbounded and fixed contact, and bounded homogeneous contact. By means of applying the same load to each model, and using the stress freezing technique, it has displayed the corresponding stress states, being more severe as expected, in the unbounded union model. In any case, the results clearly show the complexity of the interface contact problem, and they confirm the need for experimental studies about this problem. Afterward a free oscillation dynamic test has been done using resistive strain gauge sensors. Test samples have been femur bones in all possible variants: simplified models, standardized synthetic bone, and dry and cool cadaveric bones. An embedding system at the distal end of the sample with strong control of the anchoring conditions has been designed. The free oscillation of the sample has been obtained by the instantaneous release of a static load, which was previously determined and applied to the sample through a testing machine or using the gravity force. Each sample was equipped with conventional strain gauges whose signal is registered with a marketed dynamic equipment. Then, it has applied a signal processing procedure to delimit, filter and present the time and frequency response signals from the sensors. Results are interpreted by comparing different trials: the test is applied to an intact femur sample which is taken as a reference, and then this test is repeated over the same sample with an implanted prosthesis. From comparison between results, immediate conclusions about the effects of the implantation of the prosthesis can be obtained. It must be said that the implementation has been made by an expert orthopedic surgeon using the same techniques and instruments as those used in clinical surgery. He has worked with three commercial femoral stems. From the results obtained in the time and frequency domains for the different applications the following conclusions have been established: Feasibility of the different types of synthetic samples: simplified models and standardized synthetic femur. Repeatability, linearity and reversibility of the testing method. Consistency of results with theoretical values deduced from the bars free oscillations theory. Effects of introduction of femoral stems in the amplitude, damping and frequencies of oscillations Detection of micromobility associated harmonics. This methodology has been proved suitable to be included in the standardization process of arthroplasty prosthesis, it is universally applicable and it allows establishing new methods for the analysis, detection and characterization of prosthesis micromobility due to functional loads.

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Signal processing in any living being is much more complex than the one performed in artificial systems. Cortex architecture, although only partly known, gives some useful ideas to be employed in sensing technology. To analyze some of these structures is the objective of this paper. Among the points to be analyzed are the parallel transfer of information, the similarity of the different systems and the massive amount of data analyzed by physical techniques. As an example of these concepts, the possibility to transmit images in a parallel way will be reported.

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Computing the modal parameters of structural systems often requires processing data from multiple non-simultaneously recorded setups of sensors. These setups share some sensors in common, the so-called reference sensors, which are fixed for all measurements, while the other sensors change their position from one setup to the next. One possibility is to process the setups separately resulting in different modal parameter estimates for each setup. Then, the reference sensors are used to merge or glue the different parts of the mode shapes to obtain global mode shapes, while the natural frequencies and damping ratios are usually averaged. In this paper we present a new state space model that processes all setups at once. The result is that the global mode shapes are obtained automatically, and only a value for the natural frequency and damping ratio of each mode is estimated. We also investigate the estimation of this model using maximum likelihood and the Expectation Maximization algorithm, and apply this technique to simulated and measured data corresponding to different structures.

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This paper presents a description of our system for the Albayzin 2012 LRE competition. One of the main characteristics of this evaluation was the reduced number of available files for training the system, especially for the empty condition where no training data set was provided but only a development set. In addition, the whole database was created from online videos and around one third of the training data was labeled as noisy files. Our primary system was the fusion of three different i-vector based systems: one acoustic system based on MFCCs, a phonotactic system using trigrams of phone-posteriorgram counts, and another acoustic system based on RPLPs that improved robustness against noise. A contrastive system that included new features based on the glottal source was also presented. Official and postevaluation results for all the conditions using the proposed metrics for the evaluation and the Cavg metric are presented in the paper.

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The study of the Vertical-Cavity Semiconductor Optical Amplifiers (VCSOAs) for optical signal processing applications is increasing his interest. Due to their particular structure, the VCSOAs present some advantages when compared to their edge-emitting counterparts including low manufacturing costs, high coupling efficiency to optical fibers and the ease to fabricate 2-D arrays of this kind of devices. As a consequence, all-optical logic gates based on VCSOAs may be very promising devices for their use in optical computing and optical switching in communications. Moreover, since all the boolean logic functions can be implemented by combining NAND logic gates, the development of a Vertical-Cavity NAND gate would be of particular interest. In this paper, the characteristics of the dispersive optical bistability appearing on a VCSOA operated in reflection are studied. A progressive increment of the number of layers compounding the top Distributed Bragg Reflector (DBR) of the VCSOA results on a change on the shape of the appearing bistability from an S-shape to a clockwise bistable loop. This resulting clockwise bistability has high on-off contrast ratio and input power requirements one order of magnitude lower than those needed for edge-emitting devices. Based on these results, an all-optical vertical-cavity NAND gate with high on-off contrast ratio and an input power for operation of only 10|i\V will be reported in this paper.

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Non-parametric belief propagation (NBP) is a well-known message passing method for cooperative localization in wireless networks. However, due to the over-counting problem in the networks with loops, NBPs convergence is not guaranteed, and its estimates are typically less accurate. One solution for this problem is non-parametric generalized belief propagation based on junction tree. However, this method is intractable in large-scale networks due to the high-complexity of the junction tree formation, and the high-dimensionality of the particles. Therefore, in this article, we propose the non-parametric generalized belief propagation based on pseudo-junction tree (NGBP-PJT). The main difference comparing with the standard method is the formation of pseudo-junction tree, which represents the approximated junction tree based on thin graph. In addition, in order to decrease the number of high-dimensional particles, we use more informative importance density function, and reduce the dimensionality of the messages. As by-product, we also propose NBP based on thin graph (NBP-TG), a cheaper variant of NBP, which runs on the same graph as NGBP-PJT. According to our simulation and experimental results, NGBP-PJT method outperforms NBP and NBP-TG in terms of accuracy, computational, and communication cost in reasonably sized networks.

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We extend in this paper some previous results concerning the differential-algebraic index of hybrid models of electrical and electronic circuits. Specifically, we present a comprehensive index characterization which holds without passivity requirements, in contrast to previous approaches, and which applies to nonlinear circuits composed of uncoupled, one-port devices. The index conditions, which are stated in terms of the forest structure of certain digraph minors, do not depend on the specific tree chosen in the formulation of the hybrid equations. Additionally, we show how to include memristors in hybrid circuit models; in this direction, we extend the index analysis to circuits including active memristors, which have been recently used in the design of nonlinear oscillators and chaotic circuits. We also discuss the extension of these results to circuits with controlled sources, making our framework of interest in the analysis of circuits with transistors, amplifiers, and other multiterminal devices.

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We apply diffusion strategies to propose a cooperative reinforcement learning algorithm, in which agents in a network communicate with their neighbors to improve predictions about their environment. The algorithm is suitable to learn off-policy even in large state spaces. We provide a mean-square-error performance analysis under constant step-sizes. The gain of cooperation in the form of more stability and less bias and variance in the prediction error, is illustrated in the context of a classical model. We show that the improvement in performance is especially significant when the behavior policy of the agents is different from the target policy under evaluation.

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This paper contributes with a unified formulation that merges previ- ous analysis on the prediction of the performance ( value function ) of certain sequence of actions ( policy ) when an agent operates a Markov decision process with large state-space. When the states are represented by features and the value function is linearly approxi- mated, our analysis reveals a new relationship between two common cost functions used to obtain the optimal approximation. In addition, this analysis allows us to propose an efficient adaptive algorithm that provides an unbiased linear estimate. The performance of the pro- posed algorithm is illustrated by simulation, showing competitive results when compared with the state-of-the-art solutions.

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The aim of automatic pathological voice detection systems is to serve as tools, to medical specialists, for a more objective, less invasive and improved diagnosis of diseases. In this respect, the gold standard for those system include the usage of a optimized representation of the spectral envelope, either based on cepstral coefcients from the mel-scaled Fourier spectral envelope (Mel-Frequency Cepstral Coefcients) or from an all-pole estimation (Linear Prediction Coding Cepstral Coefcients) forcharacterization, and Gaussian Mixture Models for posterior classication. However, the study of recently proposed GMM-based classiers as well as Nuisance mitigation techniques, such as those employed in speaker recognition, has not been widely considered inpathology detection labours. The present work aims at testing whether or not the employment of such speaker recognition tools might contribute to improve system performance in pathology detection systems, specically in the automatic detection of Obstructive Sleep Apnea. The testing procedure employs an Obstructive Sleep Apnea database, in conjunction with GMM-based classiers looking for a better performance. The results show that an improved performance might be obtained by using such approach.

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La Aeroelasticidad fue definida por Arthur Collar en 1947 como "el estudio de la interaccin mutua entre fuerzas inerciales, elsticas y aerodinmicas actuando sobre elementos estructurales expuestos a una corriente de aire". Actualmente, esta definicin se ha extendido hasta abarcar la influencia del control (Aeroservoelasticidad) e, incluso, de la temperatura (Aerotermoelasticidad). En el mbito de la Ingeniera Aeronutica, los fenmenos aeroelsticos, tanto estticos (divergencia, inversin de mando) como dinmicos (flameo, bataneo) son bien conocidos desde los inicios de la Aviacin. Las lecciones aprendidas a lo largo de la Historia Aeronutica han permitido establecer criterios de diseo destinados a mitigar la probabilidad de sufrir fenmenos aeroelsticos adversos durante la vida operativa de una aeronave. Adicionalmente, el gran avance experimentado durante esta ltima dcada en el campo de la Aerodinmica Computacional y en la modelizacin aeroelstica ha permitido mejorar la fiabilidad en el clculo de las condiciones de flameo de una aeronave en su fase de diseo. Sin embargo, an hoy, los ensayos en vuelo siguen siendo necesarios para validar modelos aeroelsticos, verificar que la aeronave est libre de inestabilidades aeroelsticas y certificar sus distintas envolventes. En particular, durante el proceso de expansin de la envolvente de una aeronave en altitud/velocidad, se requiere predecir en tiempo real las condiciones de flameo y, en consecuencia, evitarlas. A tal efecto, en el mbito de los ensayos en vuelo, se han desarrollado diversas metodologas que predicen, en tiempo real, las condiciones de flameo en funcin de condiciones de vuelo ya verificadas como libres de inestabilidades aeroelsticas. De entre todas ellas, aquella que relaciona el amortiguamiento y la velocidad con un parmetro especfico definido como Margen de Flameo (Flutter Margin), permanece como la tcnica ms comn para proceder con la expansin de Envolventes en altitud/velocidad. No obstante, a pesar de su popularidad y facilidad de aplicacin, dicha tcnica no es adecuada cuando en la aeronave a ensayar se hallan presentes no-linealidades mecnicas como, por ejemplo, holguras. En particular, en vuelos de ensayo dedicados especficamente a expandir la envolvente en altitud/velocidad, las condiciones de Oscilaciones de Ciclo Lmite (Limit Cycle Oscillations, LCOs) no pueden ser diferenciadas de manera precisa de las condiciones de flameo, llevando a una determinacin excesivamente conservativa de la misma. La presente Tesis desarrolla una metodologa novedosa, basada en el concepto de Margen de Flameo, que permite predecir en tiempo real las condiciones de Ciclo Lmite, siempre que existan, distinguindolas de las de flameo. En una primera parte, se realiza una revisin bibliogrfica de la literatura acerca de los diversos mtodos de ensayo existentes para efectuar la expansin de la envolvente de una aeronave en altitud/velocidad, el efecto de las no-linealidades mecnicas en el comportamiento aeroelstico de dicha aeronave, as como una revisin de las Normas de Certificacin civiles y militares respecto a este tema. En una segunda parte, se propone una metodologa de expansin de envolvente en tiempo real, basada en el concepto de Margen de Flameo, que tiene en cuenta la presencia de no-linealidades del tipo holgura en el sistema aeroelstico objeto de estudio. Adicionalmente, la metodologa propuesta se valida contra un modelo aeroelstico bidimensional paramtrico e interactivo programado en Matlab. Para ello, se plantean las ecuaciones aeroelsticas no-estacionarias de un perfil bidimensional en la formulacin espacio-estado y se incorpora la metodologa anterior a travs de un mdulo de anlisis de seal y otro mdulo de prediccin. En una tercera parte, se comparan las conclusiones obtenidas con las expuestas en la literatura actual y se aplica la metodologa propuesta a resultados experimentales de ensayos en vuelo reales. En resumen, los principales resultados de esta Tesis son: 1. Resumen del estado del arte en los mtodos de ensayo aplicados a la expansin de envolvente en altitud/velocidad y la influencia de no-linealidades mecnicas en la determinacin de la misma. 2. Revisin de la normas de Certificacin Civiles y las normas Militares en relacin a la verificacin aeroelstica de aeronaves y los lmites permitidos en presencia de no-linealidades. 3. Desarrollo de una metodologa de expansin de envolvente basada en el Margen de Flameo. 4. Validacin de la metodologa anterior contra un modelo aeroelstico bidimensional paramtrico e interactivo programado en Matlab/Simulink. 5. Anlisis de los resultados obtenidos y comparacin con resultados experimentales. ABSTRACT Aeroelasticity was defined by Arthur Collar in 1947 as the study of the mutual interaction among inertia, elastic and aerodynamic forces when acting on structural elements surrounded by airflow. Today, this definition has been updated to take into account the Controls (Aeroservoelasticity) and even the temperature (Aerothermoelasticity). Within the Aeronautical Engineering, aeroelastic phenomena, either static (divergence, aileron reversal) or dynamic (flutter, buzz), are well known since the early beginning of the Aviation. Lessons learned along the History of the Aeronautics have provided several design criteria in order to mitigate the probability of encountering adverse aeroelastic phenomena along the operational life of an aircraft. Additionally, last decade improvements experienced by the Computational Aerodynamics and aeroelastic modelization have refined the flutter onset speed calculations during the design phase of an aircraft. However, still today, flight test remains as a key tool to validate aeroelastic models, to verify flutter-free conditions and to certify the different envelopes of an aircraft. Specifically, during the envelope expansion in altitude/speed, real time prediction of flutter conditions is required in order to avoid them in flight. In that sense, within the flight test community, several methodologies have been developed to predict in real time flutter conditions based on free-flutter flight conditions. Among them, the damping versus velocity technique combined with a Flutter Margin implementation remains as the most common technique used to proceed with the envelope expansion in altitude/airspeed. However, although its popularity and easy to implement characteristics, several shortcomings can adversely affect to the identification of unstable conditions when mechanical non-linearties, as freeplay, are present. Specially, during test flights devoted to envelope expansion in altitude/airspeed, Limits Cycle Oscillations (LCOs) conditions can not be accurately distinguished from those of flutter and, in consequence, it leads to an excessively conservative envelope determination. The present Thesis develops a new methodology, based on the Flutter Margin concept, that enables in real time the prediction of the Limit Cycle conditions, whenever they exist, without degrading the capability of predicting the flutter onset speed. The first part of this Thesis presents a review of the state of the art regarding the test methods available to proceed with the envelope expansion of an aircraft in altitude/airspeed and the effect of mechanical non-linearities on the aeroelastic behavior. Also, both civil and military regulations are reviewed with respect aeroelastic investigation of air vehicles. The second part of this Thesis proposes a new methodology to perform envelope expansion in real time based on the Flutter Margin concept when non-linearities, as freeplay, are present. Additionally, this methodology is validated against a Matlab/Slimulink bidimensional aeroelastic model. This model, parametric and interactive, is formulated within the state-space field and it implements the proposed methodology through two main real time modules: A signal processing module and a prediction module. The third part of this Thesis compares the final conclusions derived from the proposed methodology with those stated by the flight test community and experimental results. In summary, the main results provided by this Thesis are: 1. State of the Art review of the test methods applied to envelope expansion in altitude/airspeed and the influence of mechanical non-linearities in its identification. 2. Review of the main civil and military regulations regarding the aeroelastic verification of air vehicles and the limits set when non-linearities are present. 3. Development of a methodology for envelope expansion based on the Flutter Margin concept. 4. A Matlab/Simulink 2D-[aeroelastic model], parametric and interactive, used as a tool to validate the proposed methodology. 5. Conclusions driven from the present Thesis and comparison with experimental results.

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In the last years, many analyses from acoustic signal processing have been used for different applications. In most cases, these sensor systems are based on the determination of times of flight for signals from every transducer. This paper presents a flat plate generalization method for impact detection and location over linear links or bars-based structures. The use of three piezoelectric sensors allow to achieve the position and impact time while the use of additional sensors lets cover a larger area of detection and avoid wrong timing difference measurements. An experimental setup and some experimental results are briefly presented.

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Modern Field Programmable Gate Arrays (FPGAs) are power packed with features to facilitate designers. Availability of features like huge block memory (BRAM), Digital Signal Processing (DSP) cores, embedded CPU makes the design strategy of FPGAs quite different from ASICs. FPGA are also widely used in security-critical application where protection against known attacks is of prime importance. We focus ourselves on physical attacks which target physical implementations. To design countermeasures against such attacks, the strategy for FPGA designers should also be different from that in ASIC. The available features should be exploited to design compact and strong countermeasures. In this paper, we propose methods to exploit the BRAMs in FPGAs for designing compact countermeasures. BRAM can be used to optimize intrinsic countermeasures like masking and dual-rail logic, which otherwise have significant overhead (at least 2X). The optimizations are applied on a real AES-128 co-processor and tested for area overhead and resistance on Xilinx Virtex-5 chips. The presented masking countermeasure has an overhead of only 16% when applied on AES. Moreover Dual-rail Precharge Logic (DPL) countermeasure has been optimized to pack the whole sequential part in the BRAM, hence enhancing the security. Proper robustness evaluations are conducted to analyze the optimization for area and security.

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In this paper we present an adaptive spatio-temporal filter that aims to improve low-cost depth camera accuracy and stability over time. The proposed system is composed by three blocks that are used to build a reliable depth map of static scenes. An adaptive joint-bilateral filter is used to obtain consistent depth maps by jointly considering depth and video information and by adapting its parameters to different levels of estimated noise. Kalman filters are used to reduce the temporal random fluctuations of the measurements. Finally an interpolation algorithm is used to obtain consistent depth maps in the regions where the depth information is not available. Results show that this approach allows to considerably improve the depth maps quality by considering spatio-temporal information and by adapting its parameters to different levels of noise.