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This work addresses the issue of transverse combustion instabilities in annular gas turbine combustor geometries. While modern low-emissions combustion strategies have made great strides in reducing the production of toxic emissions in aircraft engines and power generation gas turbines, combustion instability remains one of the foremost technical challenges in the development of next generation combustor technology. To that end, this work investigates the response of a swirling flow and swirl-stabilized flame to a transverse acoustic field is using a variety of high-speed laser techniques, especially high-speed particle image velocimetry (PIV) for detailed velocity measurements of this highly unsteady flow phenomenon. A description of the velocity-coupled transverse instability mechanism is explained with companion measurements describing each of the velocity disturbance pathways. Dependence on acoustic frequency, amplitude, and field symmetry is discussed. Significant emphasis is placed on the response of a swirling flow field to a transverse acoustic field. Details of the dynamics of the vortex breakdown bubble and the shear layers are explained using a wide variety of measurements for both non-reacting and reacting flow cases. This thesis concludes with an overview of the impact of this work and suggestions for future research in this area.

Long range stand-off Raman and Laser-Induced Breakdown Spectroscopy (LIBS) lidar signal simulations have been carried out using a modified UV-visible atmospheric transmission program and a modified lidar equation. The Hitran-PC atmospheric transmission program which normally operates over the wavelength range of 400 nm to the far-IR was modified to provide UV atmospheric attenuation (200 nm -- 400 nm) using the optical cross section data contained in the HITRAN database. The two-way lidar equation was modified in order to simulate the one-way propagation of the Raman and LIBS spectral, and thus provide calculations of the expected Raman or LIBS signal as a function of range. Estimation of the LIBS and Raman spectral intensity was then calculated for several remote sensing cases. In particular, the atmospheric attenuation spectra generated with the modified Hitran-PC program were combined with the calculated LIBS and Raman lidar emission spectra at the remote excitation site using a modified lidar equation to determine for the first time to our knowledge the power and S/N ratio versus range of the LIBS and Raman Lidar complete spectrum as a function of wavelength in the UV -- IR region. Previous simulations had only made S/N versus range calculations at a single wavelength or for the total integrated emission. These results are important as they can be used for future design of stand-off LIBS and Raman lidar systems, and for comparisons with experimental measurements. In particular, we are planning to use our simulations for comparison of 266 nm excited LIBS and Raman lidar measurements of energetic compounds at ranges of a few tens of meters.

Clear speech refers to a speaking style that is more intelligible than typical, conversational speaking styles. It is usually produced at a slower rate compared to conversational speech. Clear speech has been shown to be more intelligible than conversational speech for a large variety of populations, including both hearing impaired (Schum, 1996; Picheny, Durlach, & Braida, 1985; and Payton, Uchanski, & Braida, 1994) and normal hearing individuals (e.g. Uchanski, Choi, Braida, Reed, & Durlach, 1996) under a variety of conditions, including those in which presentation level, speaker, and environment are varied. Although clear speech is typically slower than normally produced conversational speech, recent studies have shown that it can be produced at normal rates with training (Krause & Braida, 2002). If clear speech at normal rates is shown to be as effective for individuals with hearing loss as clear speech at slow rates, it would have both clinical and research implications. The purpose of this study was to determine the effectiveness of clear speech at normal rates for older individuals with hearing loss. It examined the way in which intelligibility, measured as percent correct keyword scores on nonsense sentences, varied as a result of speaking mode (clear versus conversational speech) and speaking rate (slow versus normal) in six adults aged 55-75 years old with moderate, sloping, hearing loss. Each listener was presented with nonsense sentences in four speech conditions: clear speech at slow rates (clear/slow), clear speech at normal rates (clear/normal), conversational speech at slow rates (conv/slow), and conversational speech at normal rates (conv/normal) read by four different talkers. Sentences were presented monaurally in quiet to the listeners via headphones. Results indicated that clear/slow speech was the most intelligible condition overall. Neither conv/slow nor clear/normal provided an intelligibility benefit relative to conv/normal speech on average, suggesting that for older adults with moderate, sloping hearing loss, the combination of using clear speech and a slower speaking rate is more beneficial to intelligibility than the additive effects of altering either speaking rate or speaking mode alone. It has been suggested previously (Krause, 2001) that audiological characteristics may contribute to the lack of clear/normal benefit for certain listeners with hearing loss. Although clear/normal speech was not beneficial on average to listeners in this study, there were cases in which the clear/normal speech of a particular talker provided a benefit to a particular listener. Thus, severity and configuration of hearing loss alone cannot fully explain the degree to which listeners from hearing loss do (or do not) benefit from clear/normal speech. More studies are needed to investigate the benefits of clear/normal speech for different audiological configurations, including individuals with flat losses. In addition, the listening tasks should include more difficult conditions in order to compensate for potential ceiling effects.

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The company’s pricing is often highly impacted by the estimation of competitors’ project costs, which also is the main scope in this degree project. The purpose is to develop a pricing model dealing with uncertainties, since this is a main issue in the current pricing process. A pre-study has been performed, followed by a model implementation. An analysis of the model was then made, before conclusions were drawn. Project cost estimation foremost, but also probability distribution functions and pricing as a general concept, were investigated in the mainly literary pre-study. Two suitable methods for project cost estimation were identified; Monte Carlo simulation and Hierarchy Probability Cost Analysis. These lead to a theoretical project cost estimation model. A model was implemented in Matlab. It treats project cost estimation, but no other pricing aspects. The model was developed based on the theoretical one to the extent possible. Project costs were broken down in sub costs which were included in a Monte Carlo simulation. Competitors’ project costs were estimated using this technique. To analyse the model’s accuracy was difficult. It differs from the theoretical one in terms of how probability distribution functions and correlations are estimated. These problems depend on projects with shifting characteristics and limited data and time. A solid framework has been created though. Improvement possibilities exist, e.g. more accurate estimates and a model handling other pricing aspects. The major threat is that nobody maintains the model. Anyway, estimates are not more than just estimates. The model should therefore be viewed as a helpful tool, not an answer. / Företagets prissättning påverkas ofta till stor del av estimeringen av konkurrenters projektkostnader, vilket också är huvudområdet i detta examensarbete. Syftet är att utveckla en prissättningsmodell som hanterar osäkerheter, då detta är ett stort problem i rådande prissättningsprocess. En förstudie har utförts, följt av en modellimplementation. En analys av modellen gjordes sedan, innan slutsatser drogs. Projektkostnadsestimering främst, men även sannolikhetsfunktioner och prissättning som ett allmänt koncept, undersöktes i den i huvudsak litterära förstudien. Två lämpliga metoder för projektkostnadsestimering identifierades; Monte Carlo-simulering och Hierarchy Probability Cost Analysis. Dessa ledde till en teoretisk modell för projektkostnadsestimering. En modell implementerades i Matlab. Den behandlar projektkostnadsestimering, men inga andra prissättningsaspekter. Modellen utvecklades baserat på den teoretiska i möjlig utsträckning. Projektkostnader bröts ner i delkostnader som estimerades för konkurrenterna. Dessa ingick i en Monte Carlo-simulering. Konkurrenters projektkostnader estimerades med hjälp av denna teknik. Att analysera modellens noggrannhet var svårt. Den skiljer sig från den teoretiska beträffande hur sannolikhetsfunktioner och korrelationer estimeras. Dessa problem beror på projekt med skiftande karaktärsdrag samt begränsad data och tid. Ett solitt ramverk har dock skapats. Förbättringsmöjligheter finns, t.ex. noggrannare estimat och en modell som behandlar andra prissättningsaspekter. Det huvudsakliga hotet är att ingen underhåller modellen. Hur som helst är estimat inte mer än estimat. Modellen ska därför ses som ett hjälpverktyg, inte ett facit.

Within the Speciality Engineering Insurance Field the use of engineering opinion is the main component in risk analysis for underwriting decision making. The use of risk analysis tools to quantify the risk associated with perils such as mechanical breakdown is limited. A reliability model for the risk analysis of mechanical breakdown risk for the power generation sector, PowerRAT, has been developed and its performance evaluated against historic claim data. It has proven to closely forecast actual losses over a portfolio of power plants, and differentiate between power plant type; conventional steam, simple and combined cycle gas turbine plants. Differentiation based on the factors of equipment type and policy terms has been demonstrated. A review of existing survey report methodology has shown highly variable quality of reports with significant missing information on which to make underwriting decisions. A best practice survey report contents has been proposed in order to provide a consistent level of information for comparison with other risks. The development cycle of PowerRAT has led to a proposed framework for the development of future risk assessment tools for insurance. This is built on four main areas: risk identification, data analysis, calculation methodology and insurance factors.

The integer and fractional quantum Hall effects arise in two-dimensional electron systems subject to low temperature and high perpendicular magnetic field. The phenomenology of these two effects is rich and provides interesting insight into quantum physics. We present two experimental studies of phenomena in the fractional quantum Hall regime. The first examines the tunneling conductance of quasiparticles at filling factor 5/2. This state is of significant interest because it lies outside the traditional Jain hierarchy of fractional quantum Hall states and because it may be the first physical system found to exhibit non-abelian particle statistics. A quantum point contact is used to bring edge states on opposite sides of the system in proximity to each other, allowing quasiparticles to tunnel between the edge states. By annealing the gates forming the quantum point contact at different voltages we control the tunneling strength for fixed temperature and bias. We demonstrate a transition from strong to weak tunneling controlled in this manner. In the weak tunneling regime, the DC bias and temperature dependence of the tunneling conductance is fit to a theoretical form, resulting in values for the quasiparticle charge \(e*\) and the interaction parameter \(g\). The values of these parameters are used to help distinguish between proposed candidate states for the 5/2 wave function. Quantitative and qualitative results are most consistent with the abelian 331 state. Our second main focus is the breakdown of the fractional quantum Hall states at filling factors 4/3 and 5/3. Breakdown of integer and fractional quantum Hall states is known to occur when the Hall and longitudinal resistances deviate from their ideal values at nonzero critical currents. Although multiple studies of breakdown in the integer quantum Hall regime have been reported, corresponding results for the fractional regime are scarce. We observe breakdown over a range of integer states that is consistent with previous results. However, breakdown in the fractional regime is found to exhibit markedly different behavior. In particular, the magnitude of the critical current decreases with increased sample width. This behavior is opposite that observed for integer filling factors and does not seem to be explicable based on current theories of breakdown. / Physics

Ο εξοπλισμός και οι αγωγοί που μεταφέρουν την υψηλή τάση ακολουθούν συγκεκριμένες τιμές ασφάλειας και ελέγχου. Με τον όρο υπερτάσεις εννοούμε τις τάσεις που εμφανίζονται στα ηλεκτρικά δίκτυα και που συνήθως έχουν εύρος μεγαλύτερο από εκείνο της κανονικής τάσης λειτουργίας. Οι υπερτάσεις έχουν κατά κανόνα ανώμαλη μορφή και είναι ικανές να προκαλέσουν διηλεκτρικές καταπονήσεις μεγάλου μεγέθους στις μονώσεις ενός συστήματος. Κατά τον σχεδιασμό της μόνωσης ενός συστήματος υπάρχουν δύο εξαιρετικά σημαντικές παράμετροι που πρέπει να ληφθούν υπ’όψην από τους κατασκευαστές: 1) Ο καθορισμός της μορφής των τάσεων που καταπονούν την μόνωση 2) Ο καθορισμός της αντοχής της μόνωσης όταν υφίσταται καταπόνηση από συγκεκριμένες μορφές τάσεων. Σκοπός της παρούσας εργασίας είναι η ανάλυση της καταπόνησης που υφίσταται διάκενο ακίδα-πλάκα συνολικού μήκους 6cm στο οποίο παρεμβλήθηκε μετακινούμενο διάφραγμα. Τα συμπεράσματα που εξήχθησαν αφορούν την μελέτη της τάσης διάσπασης και τον τρόπο με τον οποίο αυτή μεταβάλλεται σε σχέση με την γεωμετρία του διακένου αλλά και τις ατμοσφαιρικές συνθηκες. Τα συμπεράσματα που προκύπτουν από την ανάλυση της καταπόνησης που υφίσταται διάκενο ακίδας-πλάκας είναι ότι καθώς απομακρύνεται το διάφραγμα από την ακίδα η τάση διάσπασης μειώνεται. Αξίζει επίσης να σημειωθεί ότι όσο πλησιάζει το διάφραγμα την ακίδα μειώνεται η τυχαιότητα του φαινομένου της διάσπασης πράγμα το οποιό σημαίνει πως ο σχεδιασμός ενός συστήματος μόνωσης δύναται να γίνει πιο ακριβής. Τέλος παρατηρείται ότι ανάμεσα σε σετ μετρήσεων με ίδια απόσταση διαφράγματος από την ακίδα υπάρχει μια απόκλιση στις τιμές της U50%. Αυτή η απόκλιση οφείλεται σε διάφορους παράγοντες. Ένας εξ’αυτών είναι η μικρή μεταβολή των ατμοσφαιρικών συνθηκών κατά την χρονική απόσταση που παρεμβλήθηκε ανάμεσα στα σετ μετρήσεων. Έναν δεύτερο παράγοντα αποτελούν οι πιθανές υπερπηδήσεις που συνέβησαν κατά την διάρκεια των επιβολών τάσης στο διάκενο. / The equipment and conductors that "carry" high voltage are taking specific values of security and control. Using the term, hyper-voltage, the researchers mean those voltages that appear in electricity networks and they usually have a width value greater than the normal operating voltage. Most of the times, hyper-voltages are typically have irregular form and they are capable of causing large dielectric stresses in the insulation of a system. When designing an insulation system there are two very important parameters that have to be taken under consideration by the manufacturers: 1) The determination of a voltage form that stresses the insulation equipment 2) The determination of the insulation resistance when there is strain from specific voltage forms. The purpose of this paper is to analyze the voltage stress that is happening in a 6cm gap of pin-plate which was inserted by removable diaphragm. The conclusions drawn are concerning the study of breakdown voltage and how it changes with respect to the geometry of the gap and the atmospheric conditions. One conclusion that arises from the stress analysis of the pin-plate gap is that when the diaphragm is moving away from the pin the breakdown voltage is decreasing. It is also worth noting that as the diaphragm is moving towards the pin, the breakdown phenomenon is becoming less random. This means that the design of an insulation system can be made more accurate. Another conclusion is related to the discrepancy in the values of U50% between different sets of measurements. The distance between the diaphragm and the spike is influencing the above observation. This discrepancy is due to several factors. The first factor is related to the small change of weather conditions during the different sets of measurements. The second factor is related to the possible jumps that occurred during the voltage imposition in the gap.

Είναι γνωστό ότι ο πιο σημαντικός παράγοντας για την προστασία και τη σωστή λειτουργία ενός εξοπλισμού υψηλής τάσης είναι η μόνωση του. Η πιο διαδεδομένη μορφή μόνωσης είναι η χρήση υγρών διηλεκτρικών, και συγκεκριμένα ελαίων. Αρχικά, χρησιμοποιούσαν μόνο ορυκτά έλαια ως μονωτικό υλικό διοτί ήταν εύκολη η διάθεση τους. Τα τελευταία όμως χρόνια, ήθισται να προτιμούνται φυτικά έλαια έναντι των ορυκτών, χάρη των ιδιοτήτων και πλεονεκτημάτων που παρουσιάζουν. Τα βασικά πλεονεκτήματα είναι η φιλικότητα τόσο προς το περιβάλλον όσο και στον άνθρωπο, η μη τοξικότητα τους, το υψηλό σημείο ανάφλεξης, η βιοδιάσπαση τους, καθώς και η βελτίωση της απόδοσης του μετασχηματιστή. Σκοπός της παρούσας διπλωματικής εργασίας είναι η διερεύνηση της συμπεριφοράς του φυτικού ελαίου FR3 κατά τη διάρκεια καταπόνησης του με εναλλασσόμενη τάση (AC) και η σύγκριση του με το ορυκτό έλαιο. Ακόμη, στόχος μας είναι να παρατηρήσουμε τη συμπεριφορά του FR3 σε συνδυασμό με μονωτικό χαρτί, αφού γνωρίζουμε ότι τα τυλίγματα μετασχηματιστών υψηλής τάσης μονώνονται και από τα 2 υλικά. Για το λόγο αυτό χρησιμοποιήθηκε η συσκευη BAUR oil tester DTA 100C που αποτελεί κομμάτι του ηλεκτρολογικού εξοπλισμού του εργαστηρίου των υψηλών τάσεων. Η παραγωγή γραμμικά αυξανόμενης εναλλασσόμενης (AC) τάσης με σταθερό ρυθμό 2kVrms/s και οι μετρήσεις της τάσης διάσπασης έγιναν από τη συσκευή αυτή. Τα διάκενα στα οποία καταπονήθηκε το φυτικό έλαιο είναι: rogowski 2mm, ακίδα-πλάκα 2mm, rogowski-πλάκα 2.5mm.Στη συνέχεια, πραγματοποιήσαμε μετρήσεις με διάταξη rogowski 2.5mm σε φυτικό λάδι χωρίς ανάδευση και σε καταπονημένο σε κρουστική τάση. Οι επόμενες μετρήσεις αφορούσαν το σύνθετο διάκενο χαρτί –λάδι και χρησιμοποιήσαμε 2 τύπους χαρτιού: DPP PAPER και KRAFT PAPER σε διάταξη rogowski 2.5mm. Τέλος, χρησιμοποιήσαμε ορυκτό έλαιο σε διάκενα rogowski 2.5mm και Ακίδα πλάκα 2,5 mm Επίσης, για να είμαστε άρτιοι στη σύγκριση των δύο τύπων ελαίων, πραγματοποιήσαμε αναλυτική στατιστική έρευνα ώστε να διαπιστώσουμε αν η κατανομή των πειραματικών αποτελεσμάτων προσεγγίζει την κανονική. Συγκεκριμένα, χρησιμοποιήσαμε το διάγραμμα διασποράς για την εκτίμηση της κατανομής. Έπειτα, με τη χρήση της συνάρτησης πυκνότητας πιθανότητας παρατηρήσαμε εποπτικά αν τα πειραματικά αποτελέσματα ακολουθούν κανονική κατανομή και υπολογίσαμε την ασσυμμετρία και την κυρτωση αυτών. Tέλος, χρησιμοποιήθηκαν τρία κριτήρια κανονικότητας, το Shapiro-Wilk, το Kolmogrov-Smirnov, και το Anderson-Darling καθώς και το διάγραμμα Normal Plot. Κρίνοντας από τα αποτελέσματα, προκύπτει ότι η τάσης διάπασης για το φυτικό έλαιο είναι μεγαλύτερη σε σχέση με το ορυκτό. Επίσης, είναι φανερό ότι η ύπαρξη σύνθετου διακένου (έλαιο – χαρτί) μειώνει την τάση διάσπασης του FR3. Τέλος, φαίνεται ότι σχεδόν για όλες τις διατάξεις, τα πειραματικά αποτελέσματα ακολουθούν την κανονική κατανομή. / It is known that the most important factor for the protection and proper operation of high voltage equipment is the insulation achievements. The most widespread form of insulation is the use of liquid dielectrics, manely dielectric oils. Initially, only mineral oil were used as an insulating material because it was easily available. However, the last decades vegetable oils are preferred to fossil thanks to the properties and advantages they present. The main advantages are the friendliness of both the environment and humans, non- toxicity, high flash point, biodegradation, as well as improving the efficiency of the transformer. The purpose of this thesis is to investigate the behavior of natural oil FR3 during stress with alternating current (AC) and compared with the mineral oil. Furthermore, our aim is to observe the behavior of this oil in combination with insulating paper, since we know that the high voltage transformer windings are insulated from the two materials. For this reason, using the device BAUR oil tester DTA 100C which is part of the electrical equipment of High Voltage laboratory. The production increased linearly alternating (ac) voltage steadily 2kVrms/s, and measurements of the breakdown voltage were made of this device.The gaps that we were measured are: rogowski 2mm, point-plane 2mm, rogowski-plane 2mm. Then, we measured the breakdown voltage for rogowski 2,5mm without stirring and for an overworked oil. Next measurments concered the combination of paper-oil, where we used two types of insulating paper:DPP and KRAFT PAPER (rogowski 2.5mm).finally we measured mineral oil in gaps: rogowski 2.5 mm and point-plane 2.5 mm Also, being correct to compare the two types of oils, we conducted a detailed survey about whether the experimental results follow the normal distribution. Specifically, we used the scatter plot to estimate the distribution of our experimental results. Then, using the probability density function we observed if the experimental results follow a normal distribution and calculated the coefficients of skewness and kurtosis. Finally, we used two hypothesis tests, the Shapiro – Wilk test,the Kolomogrov-Smirnov test and the Anderson-Darling, as well as the Normal Probability Plot. Αccording to the results, we observe that the breakdown voltage of natural ester oil is greater than mineral’s oil. Also, it is obvious that the existence of a complex gap (oil-paper) reduces the breakdown voltage. Finally, it seems that for almost all the provisions, the experimental results follow the normal distribution.