Διηλεκτρικά υγρά (έλαια) χρησιμοποιούνται ευρέως για τη μόνωση κύριων τμημάτων του εξοπλισμού υψηλών τάσεων. Ειδικά τα φυτικά έλαια εμφανίζουν αυξανόμενο ενδιαφέρον έναντι των ορυκτών ελαίων, λόγω των ιδιαίτερων φυσικοχημικών χαρακτηριστικών τους (π.χ. υψηλότερη διηλεκτρική αντοχή, βιοδιάσπαση κτλ). Στην παρούσα διπλωματική εργασία, πραγματοποιήθηκε μελέτη ηλεκτρικών φαινομένων και φαινομένων οπτικής εκπομπής κατά τη διάρκεια καταπόνησης φυτικού ελαίου FR3TM σε ανομοιογενές ηλεκτρικό πεδίο. Συγκεκριμένα, χρησιμοποιήθηκε διαμόρφωση ηλεκτροδίων ακίδας-πλάκας (1 cm και 2 cm) και εφαρμόστηκε τυποποιημένη διακοπτική κρουστική υψηλή τάση. Μεταξύ άλλων, εξήχθησαν συμπεράσματα σχετικά με τη φάση προεκκένωσης εντός του ελαίου υποβαλλόμενου σε αυτό το ανομοιογενές πεδίο. Αυτά εμφανίζουν πρακτικό ενδιαφέρον αφού στον εξοπλισμό υψηλών τάσεων τα διάκενα είναι ομοιόμορφα σε λίγες μόνο περιπτώσεις. Η όλη πειραματική εργασία εκτελέσθηκε στο Εργαστήριο Υψηλών Τάσεων του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών της Πολυτεχνικής Σχολής του Πανεπιστημίου Πατρών. / Dielectric liquids (oils) are widely used for the insulation of main parts of high voltage equipment. Especially, vegetable oils have increasing interest compared to mineral oils, due to their particular physicochemical features (e.g. higher dielectric strength, biodegradability etc). In the present diploma thesis, a study of electrical and optical emission effects was realized during the stressing of vegetable oil FR3TM in an inhomogeneous electric field. More specific, point-to-plane electrode configuration was used (1 cm and 2 cm) and standard switching high voltage was applied. Among other results, conclusions related to the pre-breakdown phase in the oil subjected to this inhomogeneous field were figured out. These conclusions have interest from the practical point of view since in the high voltage equipment the gaps are uniform in a few cases only. The experimental work as a unit was carried out in the High Voltage Laboratory of the Electrical and Computer Engineering Department of the Engineer Faculty of the University of Patras.

Τα Σύνθετα Υλικά χρησιμοποιούνται από την αρχαιότητα αλλά η ουσιαστική τους ανάπτυξη άρχισε από τον 20ο αιώνα. Είναι πολυφασικά υλικά τα οποία μπορούν να οριστούν ως ένας συνδυασμός από δύο ή περισσότερα υλικά που είναι ευδιάκριτα με φυσικό τρόπο και εύκολα διαχωρίσιμα με μηχανικό τρόπο. Ο συνδυασμός αυτός οδηγεί στη δημιουργία ενός υλικού με ανώτερες ιδιότητες από αυτές των διακριτών συστατικών. Τα επιμέρους συστατικά δεν είναι διαλυτά το ένα στο άλλο και μπορούν να αναμιχθούν μεταξύ τους με ελεγχόμενο τρόπο και με καθορισμένες αναλογίες. Τα σύνθετα υλικά αποτελούνται από δυο φάσεις: τη μήτρα και τη φάση ενίσχυσης ή φάση διασποράς ή έγκλεισμα. Η μήτρα είναι αυτή που δίνει στο υλικό την ακαμψία και το σχήμα του. Μεταφέρει, επίσης, τις μηχανικές τάσεις μέσα στο σύνθετο υλικό, διατηρεί τον προσανατολισμό των συστατικών και προστατεύει τα εγκλείσματα από τις περιβαλλοντικές συνθήκες. Τα εγκλείσματα διαφέρουν σε μέγεθος, γεωμετρία και σύσταση. Βρίσκονται σφηνωμένα στη μήτρα και είναι αυτά που προσδίδουν τις ιδιαίτερες ιδιότητες στο Σύνθετο Υλικό. Στη παρούσα εργασία γίνεται μια πειραματική διερεύνηση με ηλεκτρικές μεθόδους της επίδρασης νανοενισχύσεων στη μήτρα πολυμερών ινωδών σύνθετων υλικών συνεχούς ενίσχυσης. Για το σκοπό αυτό χρησιμοποιήθηκαν πολυμερή ινώδη σύνθετα υλικά με ενίσχυση υαλονημάτων, στη μήτρα των οποίων προσμίχθηκαν σε δύο περιπτώσεις πολυφλοιικοί νανοσωλήνες άνθρακα και πολύστρωτο γραφένιο σε συγκεντρώσεις της τάξης του 1%. Και τα δύο υλικά φημίζονται για τις εξαιρετικές ηλεκτρικές τους ιδιότητες. Στη συνέχεια διενεργήθηκαν τρεις τύποι ηλεκτρικών μετρήσεων. Αρχικά διενεργήθηκαν μετρήσεις της ηλεκτρικής αγωγιμότητας των υλικών υπό συνεχές ρεύμα, έπειτα διενεργήθηκαν μετρήσεις ηλεκτρικής αγωγιμότητας υπό την επίδραση εναλλασσόμενου ρεύματος και τέλος πραγματοποιήθηκαν μετρήσεις κρουστικής υψηλής τάσης προκειμένου να ελεγχθεί η ικανότητα των πολυλειτουργικών νανοσύνθετων υλικών να φέρουν κεραυνικά ηλεκτρικά φορτία τα οποία επιφέρουν μεγάλα πλήγματα στη δομή των αεροπορικών κατασκευών. Για τις μετρήσεις της ηλεκτρικής αγωγιμότητας συνεχούς ρεύματος DC χρησιμοποιήθηκε ένα ψηφιακό πολύμετρο “Keithley DMM 2002”. Για τις μετρήσεις ηλεκτρικής αγωγιμότητας υπό εναλλασσόμενο ρεύμα χρησιμοποιήθηκε η μέθοδος της διηλεκτρικής φασματοσκοπίας. Ο ηλεκτρικός χαρακτηρισμός των δειγμάτων πραγματοποιήθηκε σε εύρος συχνοτήτων από 10-1Hz έως 107Hz, με χρήση της ηλεκτρικής γέφυρας Alpha-N Analyser (High resolution dielectric analyzer) της εταιρείας Novocontrol. Όλα τα εξετασθέντα δείγματα υποβλήθηκαν σε ισόθερμες σαρώσεις συχνοτήτων. Η κυψελίδα μετρήσεων που χρησιμοποιήθηκε ήταν η BDS 1200 της ίδιας εταιρείας. Τέλος, οι μετρήσεις κρουστικής υψηλής τάσης πραγματοποιήθηκαν στο Εργαστήριο Υψηλών Τάσεων με χρήση της διβάθμιας κρουστικής γεννήτριας HAEFELY. Από την πειραματική διαδικασία και τα αντίστοιχα αποτελέσματα, που παρουσιάζονται αναλυτικά στα κεφάλαια 8 και 9 προέκυψαν τα συμπεράσματα που περιγράφονται στο κεφάλαιο 10. Συνοπτικά σημειώνεται ότι σε τρεις διαφορετικές πειραματικές διαδικασίες και σε καθεστώς διαφορετικών συνθηκών (στατική φόρτιση, εναλλασσόμενη φόρτιση και επιβολή κρουστικών τάσεων) το υλικό 1% CNT παρουσίασε σε όλες τις περιπτώσεις αισθητά καλύτερη αγώγιμη συμπεριφορά. / The Composite materials have been used since ancient times but their actual development did not start till the 20th century. These are polyphase materials which can be identified as a combination of two or more components which are distinguishable in a natural way and easily separable in a mechanical way. This combination leads to the development of a material with superior qualifies to those of distinct components. The particular components are not dissolvable but they can mix with each other when under control and in specific proportions. The composite materials are composed by two phases. The matrix and the reinforcement phase. The matrix is the one responsible for the rigidness and the shape of the material. It also transfers the mechanical stretches within the composite material, it sustains orientation of the components and protects the reinforcement phase from environmental conditions. Particulates of the reinforcement phase differ in size, geometry and composition. They are firmly located in the matrix and they are the ones to add specific qualities to the Composite. This work aims to survey experimentally through electric methods the impact of the nano-reinforcements in the matrix of fiber polymers. For this purpose fibre polymer composites with fiberglass reinforcement were used. In the matrix of these materials multi-walled carbon nanotubes και multi-layer graphene in concentration of about 1% were blended. Both materials are known for their exceptional electrical properties. Then, three types of electric conductivity measurements were carried out. Initially measurements of electric conductivity of the material was performed under dc, then measurements of electric conductivity under ac and finally there were measurements of impulse high voltage in order to check the ability of multifunctional nano-composite material to conduct thunder electric charges which may gravely afflict aeroplanes. For the specific measurements of the electric conductivity under dc, a digital polymeter “Keithley DMM 2002” was used. For the measurements under ac the method of dielectric spectroscopy was used. The electric characterization of the materials was carried out in frequency range of 10-1Hz έως 107Hz, using the Alpha-N Analyser (high resolution dielectric analyzer) of Novocontrol company. All the materials were subjected to frequency scanning of constant temperature. For this experiment the BDS 1200 device of the same company was used. Finally, the impulse high voltage measurements were performed in High Voltage Lab using the HAEFELY two stage impulse generator. The results which occurred from the experimental procedure and the respective results and which are presented in chapters 8 & 9 are described in chapter 10. In summary, it is noted that in three different experimental procedures and different status conditions (DC, AC and impulse high voltage) the material 1% CNT showed in all cases significantly better conductive behavior.

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One of the most difficult and serious challenges facing the mental health professional is the prevention of suicide. Efficient prevention, however, depends on early detection of patients at risk for suicidal behaviour, which in turn depends on a better understanding of the predisposing factors. Over the last years, based on a large volume of data, it has become increasingly clear that subjects who commit suicide present high levels of impulsive and impulsive-aggressive behaviours. / In the first approach, we investigate whether levels of the impulsive aggressive diathesis were more important in suicide occurring at different life stages. In the second, we investigate whether levels of the diathesis predicted when during the course of major depressive disorder suicide occurs. / Family studies have consistently indicated that suicidal behaviour tends to cluster in families. However, relatives also present increased risk for psychiatric morbidity, and therefore, the critical question is whether or not the liability to suicidal behavior is given by the same predisposition to the coexistent psychiatric disorders. / Therefore, in the third study, we examined the independence of familial liability using a three group design. The relatives of deceased suicide probands who died in the context of a major depressive episode are compared to the relatives of living depressed subjects without a history of suicide and to the relatives of healthy controls screened for the absence of major depression and suicide.

Ultra-wideband (UWB) is a wireless system which transmits signals across a much wider frequency spectrum than traditional wireless systems. The impulse radio (IR) UWB technique uses ultra-short duration pulses of nanoseconds or less. The objective of this thesis is to provide the design, implementation and testing of the timing recovery between the transmitter and receiver of the recently emerging differential code-shifted reference (DCSR) Impulse radio (IR) ultra-wideband (UWB) system. A new non-coherent energy detection based technique and its algorithm are proposed for timing recovery by means of a phase-locked loop (PLL) circuit. Simulations are presented first to verify the proposed algorithm. Then, it is implemented and tested in the Lattice ECP2 field-programmable gate array (FPGA) evaluation board with VHDL codes (a VHSIC hardware description language). The simulation and implementation results show that the proposed timing recovery scheme can be effectively achieved without much error.

Problem gambling is best understood from a biopsychosocial perspective, whereby multifaceted biological, psychological, and socio-environmental factors interact in ways that may lead to individual risk. Reinforcement contingencies and operant conditioning appear to play particularly important etiological roles. Theoretically, operant conditioning approaches should therefore comprise particularly effective treatment strategies. While operant conditioning in the form of contingency management is known to be an effective treatment for alcohol and substance abuse, it has never been applied by clinical practitioners in community-based treatment for problem gambling. The present pilot study explored the utility of adding concrete reward contingencies to community outpatient treatment, from the perspectives of clinical effectiveness and client/counsellor experiences. At 3-month follow-up, clinical outcomes compared well to typical treatment outcomes, and treatment retention appeared to be superior. Participating clients perceived concrete rewards to be moderately effective in the change process, while active therapist acceptance of this technique appeared to be limited. / xi, 186 leaves ; 29 cm. --

Impulse control, an executive process that restrains inappropriate actions, is impaired in numerous psychiatric conditions. This thesis reports three experiments that utilized a novel animal model of impulse control, the response inhibition (RI) task, to examine the substrates that underlie learning this task. In the first experiment, rats were trained to withhold responding on the RI task, and then euthanized for electrophysiological testing. Training in the RI task increased the AMPA/NMDA ratio at the synapses of pyramidal neurons in the prelimbic, but not infralimbic, region of the medial prefrontal cortex. This enhancement paralleled performance as subjects underwent acquisition and extinction of the inhibitory response. AMPA/NMDA was elevated only in neurons that project to the ventral striatum. Thus, this experiment identified a synaptic correlate of impulse control. In the second experiment, a separate group of rats were trained in the RI task prior to electrophysiological testing. Training in the RI task produced a decrease in membrane excitability in prelimbic, but not infralimbic, neurons as measured by maximal spiking evoked in response to increasing current injection. Importantly, this decrease was strongly correlated with successful inhibition in the task. Fortuitously, subjects trained in an operant control condition showed elevated infralimbic, but not prelimbic, excitability, which was produced by learning an anticipatory signal that predicted imminent reward availability. These experiments revealed two cellular correlates of performance, corresponding to learning two different associations under distinct task conditions. In the final experiment, rats were trained on the RI task under three conditions: Short (4-s), long (60-s), or unpredictable (1-s to 60-s) premature phases. These conditions produced distinct errors on the RI task. Interestingly, amphetamine increased premature responding in the short and long conditions, but decreased premature responding in the unpredictable condition. This dissociation may arise from interactions between amphetamine and underlying cognitive processes, such as attention, timing, and conditioned avoidance. In summary, this thesis showed that learning to inhibit a response produces distinct synaptic, cellular, and pharmacological changes. It is hoped that these advances will provide a starting point for future therapeutic interventions of disorders of impulse control. / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2011-07-11 09:44:54.815

This thesis takes the reader on an exploratory journey into the development of impulse purchasing behaviour stemming from the increased usage of web-connected smartphones. At an unprecedented rate, consumers are able to access businesses online, twenty-four hours a day, seven days a week, at their own convenience, without restrictions other than a connection to the World Wide Web. This mobile phenomenon has effectively pushed the commercial market to new boundaries and simultaneously created new possibilities for retailers to reach out to consumers by providing seamless and innovative marketing solutions on portable devices to a fast-growing market segment. This emergent technology and the trends it brings with it, demands special attention to the analysis of consumer behaviourism. As of date, academia has put relatively little emphasis on the evolution of impulse purchasing behaviour as a product of smartphone usage. In this paper, the authors investigate the attitude of local consumers towards so-called ‘push notifications’, whose purpose is to stimulate an impulsive behaviour in the smartphone user. The results of this study show that multiple factors in relation to push notifications on smartphones play an important part in shaping the attitude of consumers and furthermore can elicit impulse buying behaviour. These factors often bridge each other and are at times mutually dependent.

Natural lightning strikes induce impulsive overvoltages on transmission lines and its terminal equipment. These overvoltages may cause failures in insulation mechanisms of electrical devices in the power system. It is important to test the insulation strength of a device against these impulsive overvoltages. Usually, Marx generators are used to generate impulse waveforms for testing purposes. A novel approach is proposed to obtain resistor settings of a Marx generator for impulse testing of power transformers. This approach enables us to overcome most of the major challenges in the commonly used trial-and-error method, including excessive time consumption and potential damage to the transformer. The proposed approach uses the frequency response of the transformer to synthesize a circuit model. Then, a genetic algorithm based optimization-enabled electromagnetic transient simulation approach is used to obtain the resistor settings. The proposed approach is validated by a real impulse test conducted on a three phase power transformer.

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