Submitted by CAMILO CARRANZA (carranzacamilo@gmail.com) on 2017-07-25T19:58:22Z No. of bitstreams: 1 Camilo_PhD_Thesis.pdf: 11035322 bytes, checksum: efe400c07b13cabff41e927078789c59 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-07-26T18:31:30Z (GMT) No. of bitstreams: 1 carranzalopez_jc_dr_ilha.pdf: 11035322 bytes, checksum: efe400c07b13cabff41e927078789c59 (MD5) / Made available in DSpace on 2017-07-26T18:31:30Z (GMT). No. of bitstreams: 1 carranzalopez_jc_dr_ilha.pdf: 11035322 bytes, checksum: efe400c07b13cabff41e927078789c59 (MD5) Previous issue date: 2017-06-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nesta tese são investigadas, teórica e experimentalmente, a sincronização em fase e a sincronização em anti-fase de dois metrônomos oscilando sobre uma base móvel, a partir de um modelo aqui proposto. Uma descrição do funcionamento do mecanismo de escapamento dos metrônomos é feita, junto a um estudo da relação entre este e o oscilador de van der Pol. Também uma aproximação experimental do valor do amortecimento do metrônomo é fornecida. A frequência instantânea das respostas, numérica e experimental, do sistema é usada na analise. A diferença de outros trabalhos prévios, os dados experimentais têm sido adquiridos usando vídeos dos experimentos e extraídos com ajuda do software Tracker. Para investigar a relação entre as condições iniciais do sistema e seu estado final de sincronização, foram usados mapas bidimensionais chamados ‘basins of attraction’. A relação entre o modelo proposto e um modelo prévio também é mostrada. Encontrou-se que os parâmetros relevantes em relação a ambos os tipos de sincronização são a razão entre a massa do metrônomo e a massa da base, e o amortecimento do sistema. Tem-se encontrado, tanto experimental quanto teoricamente, que a frequência de oscilação dos metrônomos aumenta quando o sistema sincroniza-se em fase, e se mantém a mesma de um metrônomo isolado quando o sistema sincroniza-se em anti-fase. A partir de simulações numéricas encontrou-se que, em geral, incrementos no amortecimento do sistema levam ao sistema se sincronizar mais em fase do que em anti-fase. Adicionalmente se encontrou que, para dado valor de amortecimento, diminuir a massa da base leva a uma situação em que a sincronização em anti-fase é mais comum do que a sincronização em fase. / This thesis concerns a theoretical and experimental investigation into the synchronization of two coupled metronomes. A simplified model is proposed to study in-phase and anti-phase synchronization of two metronomes oscillating on a mobile base. A description of the escapement mechanism driving metronomes is given and its relationship with the van der Pol oscillator is discussed. Also an experimental value for the damping in the metronome is determined. The instantaneous frequency of the responses from both numerical and experimental data is used in the analysis. Unlike previous studies, measurements are made using videos and the time domain responses of the metronomes extracted by means of tracker software. Basins of attraction are used to investigate the relationship between initial conditions, parameters and both final synchronization states. The relationship between the model and a previous pendulum model is also shown. The key parameters concerning both kind of synchronization have been found to be the mass ratio between the metronome mass and the base mass, and the damping in the system. It has been shown, both theoretically and experimentally, that the frequency of oscillation of the metronomes increases when the system reaches in-phase synchronization, and is the same as an isolated metronome when the system synchronizes in anti-phase. From numerical simulations, it has been found that, in general, increasing damping leads the system to synchronize more in-phase than in anti-phase. It has also been found that, for a given damping value, decreasing the mass of the base results in the situation where anti-phase synchronization is more common than in-phase synchronization.

We study the chaotic phase synchronization (CPS) between the external periodically driving signals and the nonlinear dynamic systems. The periodical signal was applied to drive the Chua circuit system with two-scroll attractor and the four-scroll attractor circuit system. The phase synchronization between the outputs of these two circuit systems and the driving signals were investigated. Besides, the chaotic phase synchronization of the periodically pump-modulated microchip Nd:YVO4 laser and the microchip Nd:YVO4 laser with optical feedback were also examined in this study. Phase synchronization (PS) transition of these periodically driven nonlinear dynamic systems exhibited via the stroboscopic technique and recurrence probability. The recurrence probability and correlation probability of recurrence were utilized to estimate the degree of PS. In this thesis, the degree of PS was studied by taking into account the amplitude and frequency of the external driving signal. The experimental compatible numerical simulations also reflected the fact that the Arnold tongues are experimentally and numerically exhibited in the periodically driven nonlinear dynamic systems.

The thesis deals with the analysis and the reception of the freely available signals of the navigation satellites in the L1 and E1 bands of the GPS and Galileo systems. The described signal reception sections include the process of the acquisition, the carrier frequency and phase synchronization and tracking, the spreading code phase tracking, the signal demodulation and the channel decoding. The simulation of the entire receiver is performed in MATLAB. The deeply analyzed signal reception component is the one responsible for the carrier phase and frequency synchronization and tracking. In that case, more methods and their comparison are usually listed. The signal reception component, which is responsible for the carrier phase and frequency tracking and the spreading code phase tracking, is also implemented in FPGA.

No description available.

Práce se zabývá procesem návrhu digitálního přijímače pro signály družic dálkového průzkumu Země v pásmu X. V první části je uveden seznam družic které umožnují příjem vědeckých dat pomocí amatérských neautorizovaných stanic. Jsou zde vypsány základní signálové parametry některých družic, z nichž EOS-PM-1 je zvolena jako hlavní objekt pro návrh přijímače. Ve druhé části je použit software MATLAB pro simulaci družicového O-QPSK signálu v základním pásmu, mechanizmu kompenzace kmitočtového ofsetu, synchronizaci nosné, symbolové synchronizaci, rámcové synchronizaci a odstranění fázové dvojznačnosti vlivem modulace. Třetí část práce pojednává detailněji o implementaci jednotlivých bloků přijímače do FPGA při použití aritmetky s pevnou řádovou čárkou. Je zde popsána metoda pro verifikaci celého designu v reálném čase a závěrem je zde uvedeno porovnání výsledků měření touto metodou a výsledků simulace.

Approved for public release, distribution is unlimited / Synchronization of orthogonal frequency-division multiplexed (OFDM) signals is significantly more difficult than synchronization of a single-carrier system. The recently approved IEEE Standard 802.11g specifies a packet-based OFDM system that provides a basis for the discussion of OFDM synchronization in a packet-based environment. Algorithms that synchronize the receiver carrier demodulation frequency and phase, the data frame, the OFDM symbol timing, and the data symbol timing are discussed and analyzed in an AWGN channel. System View simulation is used to implement the frame and carrier frequency synchronization algorithms, where the performance of these algorithms is analyzed and they are shown to be useful detection algorithms for Standard 802.11g signal reception. / Lieutenant Commander, United States Navy

Gegenstand dieser Arbeit ist die Untersuchung generischer Synchronisierungsphänomene in interagierenden komplexen Systemen. Diese Phänomene werden u.a. in gekoppelten deterministischen chaotischen Systemen beobachtet. Bei sehr schwachen Interaktionen zwischen individuellen Systemen kann ein Übergang zum schwach kohärenten Verhalten der Systeme stattfinden. In gekoppelten zeitkontinuierlichen chaotischen Systemen manifestiert sich dieser Übergang durch den Effekt der Phasensynchronisierung, in gekoppelten chaotischen zeitdiskreten Systemen durch den Effekt eines nichtverschwindenden makroskopischen Feldes.<br /> Der Übergang zur Kohärenz in einer Kette lokal gekoppelter Oszillatoren, beschrieben durch Phasengleichungen, wird im Bezug auf die Symmetrien des Systems untersucht. Es wird gezeigt, daß die durch die Symmetrien verursachte Reversibilität des Systems nichttriviale topologische Eigenschaften der Trajektorien bedingt, so daß das als dissipativ konstruierte System in einem ganzen Parameterbereich quasi-Hamiltonische Züge aufweist, d.h. das Phasenvolumen ist im Schnitt erhalten, und die Lyapunov-Exponenten sind paarweise symmetrisch.<br /> Der Übergang zur Kohärenz in einem Ensemble global gekoppelter chaotischer Abbildungen wird durch den Verlust der Stabilität des entkoppelten Zustandes beschrieben. Die entwickelte Methode besteht darin, die Selbstkonsistenz des makroskopischen Feldes aufzuheben, und das Ensemble in Analogie mit einem Verstärkerschaltkreis mit Rückkopplung durch eine komplexe lineare Übertragungssfunktion zu charakterisieren.<br /> Diese Theorie wird anschließend für einige theoretisch interessanten Fälle verallgemeinert. / Subject of this work is the investigation of generic synchronization phenomena in interacting complex systems. These phenomena are observed, among all, in coupled deterministic chaotic systems. At very weak interactions between individual systems a transition to a weakly coherent behavior of the systems can take place. In coupled continuous time chaotic systems this transition manifests itself with the effect of phase synchronization, in coupled chaotic discrete time systems with the effect of non-vanishing macroscopic mean field.<br /> Transition to coherence in a chain of locally coupled oscillators described with phase equations is investigated with respect to the symmetries in the system. It is shown that the reversibility of the system caused by these symmetries results to non-trivial topological properties of trajectories so that the system constructed to be dissipative reveals in a whole parameter range quasi-Hamiltonian features, i.e. the phase volume is conserved on average and Lyapunov exponents come in symmetric pairs.<br /> Transition to coherence in an ensemble of globally coupled chaotic maps is described with the loss of stability of the disordered state. The method is to break the self-consistensy of the macroscopic field and to characterize the ensemble in analogy to an amplifier circuit with feedback with a complex linear transfer function.<br /> This theory is then generalized for several cases of theoretic interest.

Extraction of physiological and clinical information hidden in biosignals, such as cardiac and neural signals, is an important and fascinating field of research. Noninvasive assessment of the physiological parameters of a patient enables to study the physiology and pathophysiology of the investigated system, with minimal interference and inconvenience. This approach may also help to assess noninvasively the clinical condition of the patient. The primary focus of this study is therefore to extend the arsenal of research tools for the noninvasive investigation of the neural and cardiac systems. The approaches developed in this work concern two major directions: The first direction relies on the analysis of cardiac and neural responses during hypoxia. Hypoxia-ischemia remains a great challenge to the researchers, since it triggers complex responses at different levels in the organism. The functional recovery depends on a number of factors among which the state of autonomic nervous system (ANS) regulation plays an important role. Two different applications were considered in this framework. The first application studied the effect of global ischemic preconditioning on the heart rate variability (HRV) response to the asphyxia insult. Using linear (time and frequency domain) and nonlinear (approximate entropy and parameters of Poincare plots) measures, we evaluated the dynamic time course of the HRV response to the asphyxia insult and the effect of preconditioning on the autonomic neurocardiac control. Our results show for the first time that global ischemic preconditioning influences the HRV response to the asphyxia injury. The neuroprotective effect of preconditioning translates into a faster recovery of the basal HRV and the autonomic modulation of the heart. For the preconditioned group, at about 90 min after the asphyxic insult, the autonomic neural balance (measured by LF/HF ratio) appears fully recovered. Another application addressed the problem of phase synchronization analysis of EEG signals during monitoring of recovery process following brain injury episode. The concept of phase synchronization offers a new perspective on the understanding and quantification of the dynamical interactions established among coupled systems. In this thesis, we present a new approach for the identification of the degree of interaction between two complex dynamical systems from experimental data analysis. We use the empirical-mode-decomposition (EMD) technique to decompose the output signals into a number of elementary orthogonal modes with well defined instantaneous attributes (IMFs). The second direction addressed the problem of correlations between anticipatory pursuit eye movements and the neural response in the Supplementary Eye Fields (SEF) of the Macaque monkey. Anticipatory pursuit is a smooth movement of the eye occurring before the appearance of an expected moving target. The expectation of the subject is based on a subjective estimation of the probability that the target will move in a given direction. Recently, it has been suggested that the SEF could play a role in using past experience to guide anticipatory pursuit. This hypothesis is currently being tested at the single neuron level. In the behaving monkey, it has been shown that electrical microstimulation in the SEF can facilitate smooth pursuit initiation towards a moving target, suggesting that activation of the SEF might change the internal gain of the smooth pursuit pathway. In this study, we favored anticipatory responses in monkeys by using a cognitive cue, which produces a different anticipatory pursuit response than the one observed in previous studies, based on repetition. / H εξαγωγή φυσιολογικών και κλινικών πληροφοριών οι οποίες είναι κρυμμένες σε βιοσήματα όπως τα καρδιακά και νευροφυσιολογικά σήματα είναι ένας σημαντικός και πολύ ενδιαφέρον τομέας έρευνας. Μη επεμβατική αξιολόγηση των φυσιολογικών παραμέτρων ενός ασθενή επιτρέπει την μελέτη της φυσιολογίας και παθολογίας του μελετούμενου συστήματος με τις λιγότερες παρεμβολές και ενόχληση. Η προσέγγιση αυτή μπορεί επίσης να βοηθήσει στην μη επεμβατική αξιολόγηση της κλινικής κατάστασης του ασθενή. Η πρώτη προσέγγιση της μελέτης αυτής είναι να επεκτείνει το οπλοστάσιο των ερευνητικών εργαλείων για την μη επεμβατική αναζήτηση του νευρικού και καρδιακού συστήματος. Οι προσεγγίσεις που αναπτύσσονται σε αυτή τη δουλειά αφορούν δύο κύριες κατευθύνσεις: Η πρώτη κατεύθυνση υπόκειται στην ανάλυση των καρδιακών και νευροφυσιολογικών αποκρίσεων κατά τη διάρκεια της υποξίας. Η ισχεμία – υποξία παραμένει μια μεγάλη πρόκληση στους ερευνητές εφόσον πυροδοτεί πολύπλοκες αποκρίσεις σε διαφορετικά επίπεδα στον οργανισμό. Η λειτουργική αποκατάσταση εξαρτάται από έναν αριθμό συντελεστών μεταξύ των οποίων ο έλεγχος της κατάστασης του αυτόνομου νευρικού συστήματος παίζει έναν πολύ σημαντικό ρόλο. Δύο διαφορετικές εφαρμογές ελήφθησαν υπόψη στο πλαίσιο αυτό. Η πρώτη εφαρμογή μελέτησε το φαινόμενο της ολικής ισχαιμικής προκατάστασης στην μεταβλητότητα του καρδιακού ρυθμού (heart rate variability - HRV) σε προσβολή από ασφυξία. Χρησιμοποιώντας γραμμικές (στον τομέα του χρόνου και των συχνοτήτων) και μη γραμμικές (υπολογισμός εντροπίας και παραμέτρων των γραφημάτων Poincare) τεχνικές υπολογίσαμε την δυναμική χρονική εξέλιξη της HRV απόκρισης στην προσβολή από ασφυξία και η επίπτωση της προ-κατάστασης στο αυτόνομο νευροκαρδιολογικό έλεγχο. Τα αποτελέσματά μας έδειξαν για πρώτη φορά ότι η ολική ισχαιμική προκατάσταση επηρεάζει την HRV απόκριση στον τραυματισμό από την ασφυξία. Η νευροπροστατευτική επίπτωση της προκατάστασης μεταφράζεται σε μία γρηγορότερη αποκατάσταση του βασικού HRV και μία αυτόνομη εναρμόνιση της καρδιάς. Για την ομάδα με την προκατάσταση σε περίπου 90 λεπτά μετά την προσβολή από ασφυξία, η αυτόνομη νευρολογική ισορροπία (μετρούμενη από τον λόγο χαμηλών προς υψηλών συχνοτήτων εμφανίζεται πλήρως αποκαταστημένη. Μία άλλη εφαρμογή απευθύνεται στο πρόβλημα της ανάλυσης του συγχρονισμού φάσεων των σημάτων Ηλεκτροεγκεφαλογραφήματος κατά τη διάρκεια παρακολούθησης της διαδικασίας αποκατάστασης μετά από επεισόδιο εγκεφαλικής βλάβης. Η ιδέα του συγχρονισμού φάσεων προσφέρει μία νέα προοπτική στην κατανόηση και ποσοτικοποίηση των δυναμικών αλληλεπιδράσεων μεταξύ συστημάτων συζευγμένων ταλαντωτών. Σε αυτή τη διδακτορική διατριβή παρουσιάζουμε μια νέα προσέγγιση για την ανίχνευση του βαθμού της αλληλεπίδρασης μεταξύ δύο πολύπλοκων δυναμικών συστημάτων από την ανάλυση πειραματικών δεδομένων. Χρησιμοποιούμε την τεχνική του εμπειρικού τρόπου αποδόμησης (empirical-mode-decomposition EMD) για να διασπάσουμε τα σήματα εξόδου σε έναν αριθμό βασικών ορθογώνιων μερών με πολύ καλά καθορισμένες στιγμιαίες ιδιότητες (instantaneous attributes IMFs). Η δεύτερη κατεύθυνση είναι το πρόβλημα των συσχετίσεων μεταξύ προνοητικών κινήσεων των ματιών και των νευροφυσιολογικών αποκρίσεων στα παιδία των ματιών (Supplementary Eye Fields SEF) πιθήκων Macaque. Οι προνοητικές κινήσεις είναι απαλές κινήσεις των ματιών που συμβαίνουν πριν την εμφάνιση ενός αναμενόμενου κινούμενου στόχου. Η αναμονή από το υποκείμενο βασίζεται σε έναν υποκειμενικό υπολογισμό της πιθανότητας ότι ο στόχος θα κινηθεί σε μια δεδομένη κατεύθυνση. Πρόσφατα, έχει υποτεθεί ότι τα SEF μπορούν να παίζουν ρόλο στην χρησιμοποίηση παλαιών εμπειριών στην καθοδήγηση αναμενόμενων κινήσεων. Αυτή η υπόθεση έχει ελεγχθεί στο επίπεδο ενός μόνο νευρώνα. Στον πίθηκο έχει βρεθεί ότι ο ηλεκτρικός μικροερεθισμός στο SEF μπορεί να διευκολύνει την ομαλή έναρξη της κίνησης προς έναν κινούμενο στόχο, συνιστώντας ότι η ενεργοποίηση του SEF μπορεί να αλλάξει την εσωτερική απόδοση του δικτύου της ομαλής κίνησης. Σε αυτή τη μελέτη, ενισχύσαμε την εκκίνηση των ομαλών κινήσεων των πιθήκων προς ένα κινούμενο στόχο η οποία παράγει μία διαφορετική προνοητική κίνηση αυτής που παρατηρείται σε προηγούμενες μελέτες η οποία βασίζεται σε επανάληψη.

For most of the naturally occurring signals, especially biomedical signals, the underlying physical process generating the signal is often not fully known, making it difficult to obtain a parametric model. Therefore, signal processing techniques are used to analyze the signal for non-parametrically characterizing the underlying system from which the signals are produced. Most of the real life systems are nonlinear and time varying, which poses a challenge while characterizing them. Additionally, multiple sensors are used to extract signals from such systems, resulting in multichannel signals which are inherently coupled. In this thesis, we counter this challenge by using Recurrence Plot based techniques for characterizing biomedical systems such as heart or brain, using signals such as heart rate variability (HRV), electroencephalogram(EEG) or functional magnetic resonance imaging (fMRI), respectively, extracted from them. In time series analysis, it is well known that a system can be represented by a trajectory in an N-dimensional state space, which completely represents an instance of the system behavior. Such a system characterization has been done using dynamical invariants such as correlation dimension, Lyapunov exponent etc. Takens has shown that when the state variables of the underlying system are not known, one can obtain a trajectory in ‘phase space’ using only the signals obtained from such a system. The phase space trajectory is topologically equivalent to the state space trajectory. This enables us to characterize the system behavior from only the signals sensed from them. However, estimation of correlation dimension, Lyapunov exponent, etc, are vulnerable to non-stationarities in the signal and require large number of sample points for accurate computation, both of which are important in the case of biomedical signals. Alternatively, a technique called Recurrence Plots (RP) has been proposed, which addresses these concerns, apart from providing additional insights. Measures to characterize RPs of single and two channel data are called Recurrence Quantification Analysis (RQA) and cross RQA (CRQA), respectively. These methods have been applied with a good measure of success in diverse areas. However, they have not been studied extensively in the context of experimental biomedical signals, especially multichannel data. In this thesis, the RP technique and its associated measures are briefly reviewed. Using the computational tools developed for this thesis, RP technique has been applied on select single channel, multichannel and multimodal (i.e. multiple channels derived from different modalities) biomedical signals. Connectivity analysis is demonstrated as post-processing of RP analysis on multichannel signals such as EEG and fMRI. Finally, a novel metric, based on the modification of a CRQA measure is proposed, which shows improved results. For the case of single channel signal, we have considered a large database of HRV signals of 112 subjects recorded for both normal and abnormal (anxiety disorder and depression disorder) subjects, in both supine and standing positions. Existing RQA measures, Recurrence Rate and Determinism, were used to distinguish between normal and abnormal subjects with an accuracy of 58.93%. A new measure, MLV has been introduced, using which a classification accuracy of 98.2% is obtained. Correlation between probabilities of recurrence (CPR) is a CRQA measure used to characterize phase synchronization between two signals. In this work, we demonstrate its utility with application to multimodal and multichannel biomedical signals. First, for the multimodal case, we have computed running CPR (rCPR), a modification proposed by us, which allows dynamic estimation of CPR as a function of time, on multimodal cardiac signals (electrocardiogram and arterial blood pressure) and demonstrated that the method can clearly detect abnormalities (premature ventricular contractions); this has potential applications in cardiac care such as assisted automated diagnosis. Second, for the multichannel case, we have used 16 channel EEG signals recorded under various physiological states such as (i) global epileptic seizure and pre-seizure and (ii) focal epilepsy. CPR was computed pair-wise between the channels and a CPR matrix of all pairs was formed. Contour plot of the CPR matrix was obtained to illustrate synchronization. Statistical analysis of CPR matrix for 16 subjects of global epilepsy showed clear differences between pre-seizure and seizure conditions, and a linear discriminant classifier was used in distinguishing between the two conditions with 100% accuracy. Connectivity analysis of multichannel EEG signals was performed by post-processing of the CPR matrix to understand global network-level characterization of the brain. Brain connectivity using thresholded CPR matrix of multichannel EEG signals showed clear differences in the number and pattern of connections in brain connectivity graph between epileptic seizure and pre-seizure. Corresponding brain headmaps provide meaningful insights about synchronization in the brain in those states. K-means clustering of connectivity parameters of CPR and linear correlation obtained from global epileptic seizure and pre-seizure showed significantly larger cluster centroid distances for CPR as opposed to linear correlation, thereby demonstrating the efficacy of CPR. The headmap in the case of focal epilepsy clearly enables us to identify the focus of the epilepsy which provides certain diagnostic value. Connectivity analysis on multichannel fMRI signals was performed using CPR matrix and graph theoretic analysis. Adjacency matrix was obtained from CPR matrices after thresholding it using statistical significance tests. Graph theoretic analysis based on communicability was performed to obtain community structures for awake resting and anesthetic sedation states. Concurrent behavioral data showed memory impairment due to anesthesia. Given the fact that previous studies have implicated the hippocampus in memory function, the CPR results showing the hippocampus within the community in awake state and out of it in anesthesia state, demonstrated the biological plausibility of the CPR results. On the other hand, results from linear correlation were less biologically plausible. In biological systems, highly synchronized and desynchronized systems are of interest rather than moderately synchronized ones. However, CPR is approximately a monotonic function of synchronization and hence can assume values which indicate moderate synchronization. In order to emphasize high synchronization/ desynchronization and de-emphasize moderate synchronization, a new method of Correlation Synchronization Convergence Time (CSCT) is proposed. It is obtained using an iterative procedure involving the evaluation of CPR for successive autocorrelations until CPR converges to a chosen threshold. CSCT was evaluated for 16 channel EEG data and corresponding contour plots and histograms were obtained, which shows better discrimination between synchronized and asynchronized states compared to the conventional CPR. This thesis has demonstrated the efficacy of RP technique and associated measures in characterizing various classes of biomedical signals. The results obtained are corroborated by well known physiological facts, and they provide physiologically meaningful insights into the functioning of the underlying biological systems, with potential diagnostic value in healthcare.