Sparse spectral analysis of atrial fibrillation electrograms

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 t��cnicas de regresi��n dispersa para la extracci��n de las se��ales cardiacas en pacientes con fibrilaci��n atrial (AF).

An��lisis de micromovilidad en v��stagos femorales mediante ensayo din��mico de oscilaciones libres

La artroplastia de cadera se considera uno de los mayores avances quir��rgicos de la Medicina. La aplicaci��n de esta t��cnica de Traumatolog��a 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 t��picas de las articulaciones y de los huesos que requieren en muchos casos la sustituci��n prot��sica total o parcial de la articulaci��n. El buen comportamiento funcional de una pr��tesis depende en gran medida de la estabilidad primaria, es decir, el correcto anclaje de la pr��tesis en el momento de su implantaci��n. Las pr��tesis no cementadas basan su ��xito a largo plazo en la osteointegraci��n que tiene lugar entre el material prot��sico y el tejido ��seo, y para lograrla es imprescindible conseguir unas buenas condiciones de estabilidad primaria. El aflojamiento as��ptico es la principal causa de fallo de artroplastia total de cadera. Este es un fen��meno en el que, debido a complejas interacciones de factores mec��nicos y biol��gicos, se producen movimientos relativos que comprometen la funcionalidad del implante. La minimizaci��n de los correspondientes danos depende en gran medida de la detecci��n precoz del aflojamiento. Para lograr la detecci��n temprana del aflojamiento as��ptico del v��stago femoral se han ensayado diferentes t��cnicas, tanto in vivo como in vitro: an��lisis num��ricos y t��cnicas 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 heterog��neos y, en muchas ocasiones, complejos y costosos, no existiendo acuerdo sobre una t��cnica simple y eficaz de aplicaci��n general. Asimismo, en la normativa vigente que regula las condiciones que debe cumplir una pr��tesis previamente a su comercializaci��n, no hay ning��n apartado referido espec��ficamente a la evaluaci��n de la bondad del dise��o del v��stago femoral con respecto a la estabilidad primaria. El objetivo de esta tesis es desarrollar una metodolog��a para el an��lisis, in vitro, de la estabilidad de un v��stago femoral implantado, a fin de poder evaluar las t��cnicas de implantaci��n y los diferentes dise��os de pr��tesis previamente a su oferta en el mercado. Adem��s se plantea como requisito fundamental que el m��todo desarrollado sea sencillo, reversible, repetible, no destructivo, con control riguroso de par��metros (condiciones de contorno de cargas y desplazamientos) y con un sistema de registro e interpretaci��n de resultados r��pido, fiable y asequible. Como paso previo, se ha realizado un an��lisis cualitativo del problema de contacto en la interfaz hueso-v��stago aplicando una t��cnica optomec��nica del campo continuo (fotoelasticidad). Para ello se han fabricado tres modelos en 2D del conjunto hueso-v��stago, 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 homog��neo. Aplicando la misma carga a cada modelo, y empleando la t��cnica de congelaci��n de tensiones, se han visualizado los correspondientes estados tensionales, siendo estos m��s severos en el modelo de uni��n sin adherencia, como cab��a esperar. En todo caso, los resultados son ilustrativos de la complejidad del problema de contacto y confirman la conveniencia y necesidad de la v��a experimental para el estudio del problema. Seguidamente se ha planteado un ensayo din��mico de oscilaciones libres con instrumentaci��n de sensores resistivos tipo galga extensom��trica. Las muestras de ensayo han sido huesos f��mur en todas sus posibles variantes: modelos simplificados, hueso sint��tico normalizado y hueso de cad��ver, seco y fresco. Se ha dise��ado un sistema de empotramiento del extremo distal de la muestra (f��mur) con control riguroso de las condiciones de anclaje. La oscilaci��n libre de la muestra se ha obtenido mediante la liberaci��n instant��nea de una carga est��tica determinada y aplicada previamente, bien con una maquina de ensayo o bien por gravedad. Cada muestra se ha instrumentado con galgas extensom��tricas convencionales cuya se��al se ha registrado con un equipo din��mico comercial. Se ha aplicado un procedimiento de tratamiento de se��al para acotar, filtrar y presentar las respuestas de los sensores en el dominio del tiempo y de la frecuencia. La interpretaci��n de resultados es de tipo comparativo: se aplica el ensayo a una muestra de f��mur Intacto que se toma de referencia, y a continuaci��n se repite el ensayo sobre la misma muestra con una pr��tesis implantada; la comparaci��n de resultados permite establecer conclusiones inmediatas sobre los efectos de la implantaci��n de la pr��tesis. La implantaci��n ha sido realizada por un cirujano traumat��logo utilizando las mismas t��cnicas e instrumental empleadas en el quir��fano durante la pr��ctica cl��nica real, y se ha trabajado con tres v��stagos 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 sint��ticas: modelos simplificados y f��mur sint��tico normalizado. ������Repetibilidad, linealidad y reversibilidad del ensayo. ������Congruencia de resultados con los valores te��ricos deducidos de la teor��a de oscilaciones libres de barras. ������Efectos de la implantaci��n de tallos femorales en la amplitud de las oscilaciones, amortiguamiento y frecuencias de oscilaci��n. ������Detecci��n de arm��nicos asociados a la micromovilidad. La metodolog��a se ha demostrado apta para ser incorporada a la normativa de pr��tesis, es de aplicaci��n universal y abre v��as para el an��lisis de la detecci��n y caracterizaci��n de la micromovilidad de una pr��tesis 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 bone���stem 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.

Learning from the living bodies: New principles and techniques for photonic sensing

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.

Estimating the modal parameters from multiple measurement setups using a joint state space model

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.

Low-resource language recognition using a fusion of phoneme posteriorgram counts, acoustic and glottal-based i-vectors

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.

Low-power vertical cavity NAND gate

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.

Nonparametric generalized belief propagation based on pseudo-junction tree for cooperative localization in wireless networks

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, NBP���s 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.

Hybrid analysis of nonlinear circuits: DAE models with indices zero and one

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.

Cooperative off-policy prediction of markov decision processes in adaptive networks

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.

A unified framework for linear function approximation of value functions in stochastic control

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.

GMM-based classifiers for the automatic detection of obstructive sleep apnea

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 coef���cients from the mel-scaled Fourier spectral envelope (Mel-Frequency Cepstral Coef���cients) or from an all-pole estimation (Linear Prediction Coding Cepstral Coef���cients) forcharacterization, and Gaussian Mixture Models for posterior classi���cation. However, the study of recently proposed GMM-based classi���ers 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, speci���cally in the automatic detection of Obstructive Sleep Apnea. The testing procedure employs an Obstructive Sleep Apnea database, in conjunction with GMM-based classi���ers looking for a better performance. The results show that an improved performance might be obtained by using such approach.

Predicci��n de la velocidad cr��tica de flameo mediante el uso de modelos aeroel��sticos extrapolados en tiempo real con datos de vuelo

La Aeroelasticidad fue definida por Arthur Collar en 1947 como "el estudio de la interacci��n mutua entre fuerzas inerciales, el��sticas y aerodin��micas actuando sobre elementos estructurales expuestos a una corriente de aire". Actualmente, esta definici��n se ha extendido hasta abarcar la influencia del control (���Aeroservoelasticidad���) e, incluso, de la temperatura (���Aerotermoelasticidad���). En el ��mbito de la Ingenier��a Aeron��utica, los fen��menos aeroel��sticos, tanto est��ticos (divergencia, inversi��n de mando) como din��micos (flameo, bataneo) son bien conocidos desde los inicios de la Aviaci��n. Las lecciones aprendidas a lo largo de la Historia Aeron��utica han permitido establecer criterios de dise��o destinados a mitigar la probabilidad de sufrir fen��menos aeroel��sticos adversos durante la vida operativa de una aeronave. Adicionalmente, el gran avance experimentado durante esta ��ltima d��cada en el campo de la Aerodin��mica Computacional y en la modelizaci��n aeroel��stica ha permitido mejorar la fiabilidad en el c��lculo de las condiciones de flameo de una aeronave en su fase de dise��o. Sin embargo, a��n hoy, los ensayos en vuelo siguen siendo necesarios para validar modelos aeroel��sticos, verificar que la aeronave est�� libre de inestabilidades aeroel��sticas y certificar sus distintas envolventes. En particular, durante el proceso de expansi��n 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 metodolog��as que predicen, en tiempo real, las condiciones de flameo en funci��n de condiciones de vuelo ya verificadas como libres de inestabilidades aeroel��sticas. De entre todas ellas, aquella que relaciona el amortiguamiento y la velocidad con un par��metro espec��fico definido como ���Margen de Flameo��� (Flutter Margin), permanece como la t��cnica m��s com��n para proceder con la expansi��n de Envolventes en altitud/velocidad. No obstante, a pesar de su popularidad y facilidad de aplicaci��n, dicha t��cnica no es adecuada cuando en la aeronave a ensayar se hallan presentes no-linealidades mec��nicas como, por ejemplo, holguras. En particular, en vuelos de ensayo dedicados espec��ficamente a expandir la envolvente en altitud/velocidad, las condiciones de ���Oscilaciones de Ciclo L��mite��� (Limit Cycle Oscillations, LCOs) no pueden ser diferenciadas de manera precisa de las condiciones de flameo, llevando a una determinaci��n excesivamente conservativa de la misma. La presente Tesis desarrolla una metodolog��a novedosa, basada en el concepto de ���Margen de Flameo���, que permite predecir en tiempo real las condiciones de ���Ciclo L��mite���, siempre que existan, distingui��ndolas de las de flameo. En una primera parte, se realiza una revisi��n bibliogr��fica de la literatura acerca de los diversos m��todos de ensayo existentes para efectuar la expansi��n de la envolvente de una aeronave en altitud/velocidad, el efecto de las no-linealidades mec��nicas en el comportamiento aeroel��stico de dicha aeronave, as�� como una revisi��n de las Normas de Certificaci��n civiles y militares respecto a este tema. En una segunda parte, se propone una metodolog��a de expansi��n 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 aeroel��stico objeto de estudio. Adicionalmente, la metodolog��a propuesta se valida contra un modelo aeroel��stico bidimensional param��trico e interactivo programado en Matlab. Para ello, se plantean las ecuaciones aeroel��sticas no-estacionarias de un perfil bidimensional en la formulaci��n espacio-estado y se incorpora la metodolog��a anterior a trav��s de un m��dulo de an��lisis de se��al y otro m��dulo de predicci��n. En una tercera parte, se comparan las conclusiones obtenidas con las expuestas en la literatura actual y se aplica la metodolog��a 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 m��todos de ensayo aplicados a la expansi��n de envolvente en altitud/velocidad y la influencia de no-linealidades mec��nicas en la determinaci��n de la misma. 2. Revisi��n de la normas de Certificaci��n Civiles y las normas Militares en relaci��n a la verificaci��n aeroel��stica de aeronaves y los l��mites permitidos en presencia de no-linealidades. 3. Desarrollo de una metodolog��a de expansi��n de envolvente basada en el Margen de Flameo. 4. Validaci��n de la metodolog��a anterior contra un modelo aeroel��stico bidimensional param��trico e interactivo programado en Matlab/Simulink. 5. An��lisis de los resultados obtenidos y comparaci��n 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.

A generalized method for flat plates impact detection and location

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.

Explointing FPGA block memories for protected cryptographic implementations

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.

Adaptive spatio-temporal filter for low-cost camera depth maps

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.