Signal processing within the neurophysiological field is challenging and requires short processing time and reliable results. In this thesis, three main problems are considered. First, a modified line source model for simulation of muscle action potentials (APs) is presented. It is formulated in continuous-time as a convolution of a muscle-fiber dependent transmembrane current and an electrode dependent weighting (impedance) function. In the discretization of the model, the Nyquist criterion is addressed. By applying anti-aliasing filtering, it is possible to decrease the discretization frequency while retaining the accuracy. Finite length muscle fibers are incorporated in the model through a simple transformation of the weighting function. The presented model is suitable for modeling large motor units. Second, the possibility of discerning the individual AP components of the concentric needle electromyogram (EMG) is explored. Simulated motor unit APs (MUAPs) are prefiltered using Wiener filtering. The mean fiber concentration (MFC) and jitter are estimated from the prefiltered MUAPs. The results indicate that the assessment of the MFC may well benefit from the presented approach and that the jitter may be estimated from the concentric needle EMG with an accuracy comparable with traditional single fiber EMG. Third, automatic, rather than manual, detection and discrimination of recorded C-fiber APs is addressed. The algorithm, detects the Aps reliably using a matched filter. Then, the detected APs are discriminated using multiple hypothesis tracking combined with Kalman filtering which identifies the APs originating from the same C-fiber. To improve the performance, an amplitude estimate is incorporated into the tracking algorithm. Several years of use show that the performance of the algorithm is excellent with minimal need for audit.

One of the most powerful and important applications that the brain accomplishes is solving the sensory "cocktail party problem:" to adaptively suppress extraneous signals in an environment. Theoretical studies suggest that the solution to the problem involves an adaptive filter, which learns to remove the redundant noise. However, neural learning is also in its infancy and there are still many questions about the stability and application of synaptic learning rules for neural computation. In this thesis, the implementation of an adaptive filter in the brain of a weakly electric fish, A. Leptorhynchus, was studied. It was found to require a cerebellar architecture that could supply independent frequency channels of delayed feedback and multiple burst learning rules that could shape this feedback. This unifies two ideas about the function of the cerebellum that were previously separate: the cerebellum as an adaptive filter and as a generator of precise temporal inputs.

One of the most powerful and important applications that the brain accomplishes is solving the sensory "cocktail party problem:" to adaptively suppress extraneous signals in an environment. Theoretical studies suggest that the solution to the problem involves an adaptive filter, which learns to remove the redundant noise. However, neural learning is also in its infancy and there are still many questions about the stability and application of synaptic learning rules for neural computation. In this thesis, the implementation of an adaptive filter in the brain of a weakly electric fish, A. Leptorhynchus, was studied. It was found to require a cerebellar architecture that could supply independent frequency channels of delayed feedback and multiple burst learning rules that could shape this feedback. This unifies two ideas about the function of the cerebellum that were previously separate: the cerebellum as an adaptive filter and as a generator of precise temporal inputs.

Αντικείμενο της παρούσας Διατριβής Διπλώματος Ειδίκευσης αποτελεί η πειραματική διερεύνηση της αποτελεσματικότητας της περίσφιγξης υποστυλωμάτων οπλισμένου σκυροδέματος με μεγάλο λόγο πλευρών με μανδύες ινοπλισμένων πολυμερών και με μανδύες ινοπλεγμάτων σε ανόργανη μήτρα. Για το σκοπό αυτό διενεργήθηκε εκτενές πειραματικό πρόγραμμα στο Εργαστήριο Μηχανικής και Τεχνολογίας Υλικών του Τμήματος Πολιτικών Μηχανικών του Πανεπιστημίου Πατρών. Το πειραματικό πρόγραμμα περιελάμβανε 18 υποστυλώματα υπό κλίμακα 3/5 ύψους 770 mm τα οποία χωρίστηκαν σε δύο ομάδες, ανάλογα με το λόγο των πλευρών τους (1η ομάδα: με λόγο πλευρών 1:3, 150×450mm, 2η ομάδα: με λόγο πλευρών 1:4, 150×600mm). Δύο από τα υποστυλώματα παρέμειναν χωρίς ενίσχυση και αποτέλεσαν τα δοκίμια αναφοράς για τα ενισχυμένα δοκίμια, τα οποία περισφίχθηκαν με μανδύες ΙΟΠ και ΙΑΜ. Τα συστήματα ενίσχυσης που χρησιμοποιήθηκαν περιελάμβαναν μανδύες ΙΟΠ ινών άνθρακα με μια, δύο ή τρεις στρώσεις, χωρίς ή με αγκύρια ινών άνθρακα μορφής θυσάνου καθώς και μανδύα με δύο στρώσεις περιμετρικά του δοκιμίου και μανδύα μορφής U και αγκύρια ινών. Επιπλέον, εξετάστηκαν και μανδύες με τέσσερεις στρώσεις ινοπλέγματος με ίνες άνθρακα σε ανόργανη μήτρα με και χωρίς αγκύρια ινών άνθρακα μορφής θυσάνου εμποτισμένων σε εποξειδική ρητίνη. Η παρούσα διατριβή αποτελείται από οχτώ κεφάλαια, κάθε ένα από τα οποία διαχωρίζεται σε κατάλληλες ενότητες, υποενότητες και παραγράφους. Στο πρώτο και δεύτερο Κεφάλαιο γίνεται μια εισαγωγή στα σύνθετα υλικά με περιγραφή των επιμέρους συστατικών τους, των χαρακτηριστικών ιδιοτήτων τους καθώς και των παραγόντων που επηρεάζουν τη συμπεριφορά τους. Στο τρίτο Κεφάλαιο πραγματοποιείται βιβλιογραφική ανασκόπηση για την περίσφιγξη υποστυλωμάτων, όπου αρχικά περιγράφονται συμβατικές τεχνικές ενίσχυσης που περιλαμβάνουν νέους μανδύες οπλισμένου σκυροδέματος, μεταλλικά ελάσματα, μεταλλικούς μανδύες κλπ και στη συνέχεια περιγράφονται τεχνικές ενίσχυσης με σύνθετα υλικά. Περιγράφεται ο καταστατικός νόμος που διέπει τη συμπεριφορά του περισφιγμένου με μανδύες σύνθετων υλικών σκυροδέματος και παρουσιάζονται συνοπτικά πειραματικές μελέτες από τη διεθνή βιβλιογραφία που αφορούν τη διερεύνηση της αποτελεσματικότητας της μεθόδου ενίσχυσης µε ΙΟΠ σε υποστυλώματα με μικρό και μεγάλο λόγο πλευρών. Τέλος, το κεφάλαιο ολοκληρώνεται με συνοπτική αναφορά πειραματικών μελετών σε δοκίμια περισφιγμένα με μανδύες σε ανόργανη μήτρα. Στο τέταρτο Κεφάλαιο παρουσιάζεται η πειραματική διαδικασία που ακολουθήθηκε για την κατασκευή των δοκιμίων καθώς και οι παράμετροι που διερευνήθηκαν. Συγκεκριμένα, περιγράφονται όλα τα υλικά που χρησιμοποιήθηκαν, τα διάφορα συστήματα ενίσχυσης που εφαρμόστηκαν καθώς και οι διαδικασίες που ακολουθήθηκαν από την προετοιμασία των δοκιμίων μέχρι την ενίσχυσής τους. Στο τέλος του κεφαλαίου γίνεται μια σύντομη περιγραφή της πειραματικής διάταξης και του επιμέρους μηχανικού εξοπλισμού που χρησιμοποιήθηκε για την υλοποίηση των δοκιμών μονοαξονικής θλίψης. Στο πέμπτο Κεφάλαιο παρουσιάζονται διεξοδικά τα αποτελέσματα όλων των δοκιμίων που συμμετείχαν στο πειραματικό πρόγραμμα. Πιο συγκεκριμένα, περιγράφονται οι τρόποι αστοχίας των δοκιμίων συνοδεία φωτογραφικού υλικού και παρατίθενται οι καμπύλες τάσης – παραμόρφωσης τόσο για κάθε ένα ξεχωριστά όσο και συγκεντρωτικά για κάθε ομάδα. Στο έκτο Κεφάλαιο γίνεται σύγκριση των αποτελεσμάτων όλων των πειραμάτων που διεξήχθησαν στο Εργαστήριο Μηχανικής και Τεχνολογίας Υλικών σε υποστυλώματα με λόγους πλευρών 1:3 και 1:4 περισφιγμένα με μανδύες ΙΟΠ και ΙΑΜ προκειμένου να εξαχθούν γενικότερα συμπεράσματα πάνω στην επίδραση του υλικού της μήτρας, του αριθμού των στρώσεων και της ύπαρξης αγκυρίων στην αποτελεσματικότητα της περίσφιγξης. Στο έβδομο Κεφάλαιο παρουσιάζονται τα αποτελέσματα από ένα αναλυτικό προσομοίωμα που χρησιμοποιήθηκε για την πρόβλεψη του μέγιστου θλιπτικού φορτίου και της οριακής παραμόρφωσης αστοχίας των περισφιγμένων με μανδύες ΙΟΠ και ΙΑΜ. Επιπλέον, γίνεται σύγκριση των αποτελεσμάτων του αναλυτικού προσομοιώματος με τα πειραματικά δεδομένα και εξετάζεται κατά πόσο αυτό το προσομοίωμα μπορεί να χρησιμοποιείται για υποστυλώματα με μεγάλο λόγο πλευρών, μετά από αλλαγή κάποιων παραμέτρων του. Στο όγδοο και τελευταίο Κεφάλαιο, παρουσιάζονται συνοπτικά τα τελικά συμπεράσματα που προέκυψαν αρχικά από την πειραματική διαδικασία και στη συνέχεια από τη χρήση του αναλυτικού προσομοιώματος. Τέλος, γίνονται και μερικές προτάσεις για περαιτέρω έρευνα πάνω σε υποστυλώματα με μεγάλο λόγο πλευρών. / The present study investigates experimentally the effectiveness of the confinement of reinforced concrete (RC) columns with high aspect ratio (wall-like RC columns) retrofitted either with fiber-reinforced polymer (FRP) or with textile-reinforced mortars (TRM) jackets. For this purpose an extensive experimental program was conducted at the Structural Materials Laboratory of the Civil Engineering Department at the University of Patras. A total of 18 identical rectangular reinforced concrete columns were constructed in a scale of 3/5 and 770 mm height so that the slenderness effects could be eliminated and tested in uniaxial compression. The columns were separated in two groups according to their aspect ratio; the first group consisted of seven RC column specimens with cross section dimensions 150mm by 450mm and an aspect ratio equal to 3, and the second group consisted of eleven RC column specimens with cross section dimensions 150mm by 600mm and an aspect ratio equal to 4. To facilitate FRP and TRM wrapping, the four corners were chamfered with a radius equal to 20mm. A number of parameters were investigated such as the kind of the matrix material (organic and inorganic), the number of layers of the jackets (1, 2, 3 and 4), the role of different cross section aspect ratios (3 and 4), the effectiveness of spike anchors (resin-impregnated fiber rovings) and local strengthening with U shape jacketing placed at the smaller sides of the columns. The first chapter provides general information on FRP materials describing their individual components, their characteristic properties, the factors affecting their behavior as well as the basic techniques for their application. The second chapter describes the composite materials in inorganic matrix (TRM) and presents a comparison between the two composite material strengthening systems. In the third chapter a brief literature review is provided about the confinement of columns with conventional techniques (e.g. steel plating, steel jacketing, RC jacketing) as well as with composite materials. The constitutional law of confined concrete with jackets of composite materials is described. Furthermore some experimental studies from the international literature are presented concerning the effectiveness of the confinement with FRP jackets of columns with small and high aspect ratio. Finally, the chapter concludes with a brief reference to experimental studies on specimens confined with jackets in inorganic matrix (TRM jackets). The fourth chapter presents the procedure for constructing and retrofitting the specimens including the materials used (carbon fiber fabric and textile, carbon fiber spike anchors, epoxy resin, inorganic matrix) as well as the equipment used for uniaxial compression tests. In the fifth chapter the results for each specimen are given presenting their failure mode and the corresponding load - displacement curve. In the following chapter the results for each group are compared in order to establish general conclusions on the effect of the kind of the matrix material, the number of layers and the existence of FRP anchors in confinement of wall-like RC columns. The seventh chapter presents the results of an analytical model used to predict the maximum compressive load and the ultimate deformation of specimens confined with FRP or TRM jackets. A comparison between the experimental and the analytical results is made and it is examined whether this model can be used for columns with high aspect ratio after modifying some of the parameters. The eighth chapter summarises the most important conclusions of all investigations carried out by the present project for both the experimental procedure and the analytical model. Finally, some suggestions for further research on columns with high aspect ratio are listed.

Le mécanisme menant à des déformations structurales suivant le bombardement d'échantillons de a-Si d'un faisceau d'ions lourds et rapides est sujet de controverses. Nous nous sommes penchés sur l'hypothèse de la formation d'une zone liquide causée par la déposition d'énergie des ions incidents dans le contexte de la théorie du pic thermique. Des échantillons de silicium amorphe furent préparés dans le but d'observer les indices d'une transition de phase l-Si/a-Si suivant la déposition locale d'énergie sur le parcours d'un ion lourd énergétique dans le a-Si. Les échantillons furent implantés d'impuretés de Cu ou d'Ag avant d'être exposés à un faisceau d'ions Ag12+ de 70 MeV. L'utilisation de l'analyse GISAXS est projetée afin d'observer une concentration locale d'impuretés suivant leur ségrégation sur la trace de l'ion. Des masques d'implantation nanométriques d'oxide d'aluminium ont été fabriqués afin d'augmenter la sensibilité de l'analyse GISAXS et une méthode d'alignement de ces masques selon la direction du faisceau fut développée. Le bombardement d'échantillons au travers de ces masques a donné lieu à un réseau de sites d'impacts isolés presque équidistants. / The machanisms underlying structural deformations following swift heavy ion beam a-Si irradiation are subject of debate. We investigated the hypothesis of the presence of a liquid phase in the wake of the energetic ions in the thermal spike framework. a-Si samples were prepared in order to track a transient liquid phase by implanting Cu or Ag on the a-Si surface and exposing the sample to a 70 MeV Ag12+ beam. Cu and Ag are both very sensitive to segregation in Si and are therefore thought to be capable of keeping track of a molten transient state by concentrating on the ion track. Samples are to be investigated with GISAXS. Nanoscale implantation masks were developed from nanoporous alumina membranes in order to impose a pattern on the ion impact sites and thus improve GISAXS sensitivitity. An alignment method is also developed for the positioning of pores parallel to the ion beam direction. A nearly equidistant impact sites pattern was achieved by irradiating fused silica through these implantation masks.

L'interaction entre la biologie et l électronique est une discipline en pleine essort. De nombreux systèmes électroniques tentent de s interconnecter avec des tissus ou des cellules vivantes afin de décoder l information biologique. Le Potentiel d action (PA) est au cœur de codage biologique et par conséquent il est nécessaire de pouvoir les repérer sur tout type de signal bio-logique. Par conséquent, nous étudions dans ce manuscrit la possibilité de concevoir un circuit électronique couplé à un système de microélectrodes capable d'effectuer une acquisition, une détection des PAs et un enregistrement des signaux biologiques. Que ce soit en milieu bruité ou non, nous considérons le taux de détection de PA et la contrainte de temps réel comme des notions primordiales et la consommation en silicium comme un prix à payer. Initialement développés pour l étude de signaux neuronaux et pancréatiques, ces systèmes conviennent parfaitement pour d autres type de cellules.

One of the most powerful and important applications that the brain accomplishes is solving the sensory "cocktail party problem:" to adaptively suppress extraneous signals in an environment. Theoretical studies suggest that the solution to the problem involves an adaptive filter, which learns to remove the redundant noise. However, neural learning is also in its infancy and there are still many questions about the stability and application of synaptic learning rules for neural computation. In this thesis, the implementation of an adaptive filter in the brain of a weakly electric fish, A. Leptorhynchus, was studied. It was found to require a cerebellar architecture that could supply independent frequency channels of delayed feedback and multiple burst learning rules that could shape this feedback. This unifies two ideas about the function of the cerebellum that were previously separate: the cerebellum as an adaptive filter and as a generator of precise temporal inputs.

Dysfunction in the central nervous system of the neonate is often first identified through seizures. The diffculty in detecting clinical seizures, which involves the observation of physical manifestations characteristic to newborn seizure, has placed greater emphasis on the detection of newborn electroencephalographic (EEG) seizure. The high incidence of newborn seizure has resulted in considerable mortality and morbidity rates in the neonate. Accurate and rapid diagnosis of neonatal seizure is essential for proper treatment and therapy. This has impelled researchers to investigate possible methods for the automatic detection of newborn EEG seizure. This thesis is focused on the development of algorithms for the automatic detection of newborn EEG seizure using adaptive time-frequency signal processing. The assessment of newborn EEG seizure detection algorithms requires large datasets of nonseizure and seizure EEG which are not always readily available and often hard to acquire. This has led to the proposition of realistic models of newborn EEG which can be used to create large datasets for the evaluation and comparison of newborn EEG seizure detection algorithms. In this thesis, we develop two simulation methods which produce synthetic newborn EEG background and seizure. The simulation methods use nonlinear and time-frequency signal processing techniques to allow for the demonstrated nonlinear and nonstationary characteristics of the newborn EEG. Atomic decomposition techniques incorporating redundant time-frequency dictionaries are exciting new signal processing methods which deliver adaptive signal representations or approximations. In this thesis we have investigated two prominent atomic decomposition techniques, matching pursuit and basis pursuit, for their possible use in an automatic seizure detection algorithm. In our investigation, it was shown that matching pursuit generally provided the sparsest (i.e. most compact) approximation for various real and synthetic signals over a wide range of signal approximation levels. For this reason, we chose MP as our preferred atomic decomposition technique for this thesis. A new measure, referred to as structural complexity, which quantifes the level or degree of correlation between signal structures and the decomposition dictionary was proposed. Using the change in structural complexity, a generic method of detecting changes in signal structure was proposed. This detection methodology was then applied to the newborn EEG for the detection of state transition (i.e. nonseizure to seizure state) in the EEG signal. To optimize the seizure detection process, we developed a time-frequency dictionary that is coherent with the newborn EEG seizure state based on the time-frequency analysis of the newborn EEG seizure. It was shown that using the new coherent time-frequency dictionary and the change in structural complexity, we can detect the transition from nonseizure to seizure states in synthetic and real newborn EEG. Repetitive spiking in the EEG is a classic feature of newborn EEG seizure. Therefore, the automatic detection of spikes can be fundamental in the detection of newborn EEG seizure. The capacity of two adaptive time-frequency signal processing techniques to detect spikes was investigated. It was shown that a relationship between the EEG epoch length and the number of repetitive spikes governs the ability of both matching pursuit and adaptive spectrogram in detecting repetitive spikes. However, it was demonstrated that the law was less restrictive forth eadaptive spectrogram and it was shown to outperform matching pursuit in detecting repetitive spikes. The method of adapting the window length associated with the adaptive spectrogram used in this thesis was the maximum correlation criterion. It was observed that for the time instants where signal spikes occurred, the optimal window lengths selected by the maximum correlation criterion were small. Therefore, spike detection directly from the adaptive window optimization method was demonstrated and also shown to outperform matching pursuit. An automatic newborn EEG seizure detection algorithm was proposed based on the detection of repetitive spikes using the adaptive window optimization method. The algorithm shows excellent performance with real EEG data. A comparison of the proposed algorithm with four well documented newborn EEG seizure detection algorithms is provided. The results of the comparison show that the proposed algorithm has significantly better performance than the existing algorithms (i.e. Our proposed algorithm achieved a good detection rate (GDR) of 94% and false detection rate (FDR) of 2.3% compared with the leading algorithm which only produced a GDR of 62% and FDR of 16%). In summary, the novel contribution of this thesis to the fields of time-frequency signal processing and biomedical engineering is the successful development and application of sophisticated algorithms based on adaptive time-frequency signal processing techniques to the solution of automatic newborn EEG seizure detection.

No description available.

The aim of my thesis is to assess the basic yield factors in the studied varieties of spring wheat. In the year 2013, there were in the framework of the test sown eight varieties (Brawura, Corso, Epos, Granny, Scirocco, Septima, Tercie and Vánek) at the land of the Faculty of Agriculture, University of South Bohemia in Ceske Budejovice. During the vegetation the number of plants, the number of sprouts and the number of spikes was recorded using a quarter tape. The data are in the results section and are converted to 1 m2. Additionally, the infestation by diseases, pests and overrunning with weeds was monitored. Before harvesting, the samples were taken for an evaluation of the number of grains per spike and HTZ. In the results section the main factors of the yield are statistically evaluated. These include the number of spikes, the number of grains per spike and HTZ. The study also evaluates the theoretical and the actual yield and the bulk density. The average number of ears in the varieties of spring wheat ranged from 411 (Corso) to 564 (Epos) ears per 1 m2. The number of grains per spike of individual varieties reached higher values, from 39,6 (Scirocco) to 57,8 (Corso). The average HTZ for the individual varieties was between 34,9 and 43,5 g. At finding of the real yield there were observed values from 3,4 t.ha-1 (Septima) to 4,5 t.ha-1 (Scirocco). The difference between the yield elements of were statistically significant all varieties.