A maior parte das concessionárias de energia elétrica brasileiras normalmente não trata as falhas em transformadores de distribuição como um problema relevante sob ponto de vista financeiro, uma vez que qualquer ação preventiva para minimizar o problema dentro da realidade atual pode ser mais onerosa. Portanto, políticas adequadas para investigar as falhas de transformadores de distribuição são geralmente relegadas a segundo plano ou às vezes nem existem. Neste contexto, a informação existente em falhas de transformadores pode não conter dados importantes. No entanto, novas leis que afetam as concessionárias de energia estão mais severas e demandam por maior eficiência por parte delas. Neste novo cenário, uma metodologia forense, criada há muitos anos por várias concessionárias para analisar falhas em transformadores de distribuição, foi recentemente resgatada com a análise de 3159 equipamentos. Essa metodologia é conhecida como Metodologia Forense para Transformadores de Distribuição (MFTD) e será utilizada como ferramenta de diagnóstico para estudos de casos. Novos testes e ensaios como medição de resistência de isolamento, índice de absorção dielétrica e polarização, análise físico-química entre outros, serão agregados à metodologia forense para aprimorá-la. Além disso, os para-raios, sendo parte do sistema de proteção de transformadores de distribuição, também são estudados com o objetivo de verificar possíveis falhas de projeto e desafios a serem superados. / Most Brazilian utility companies normally do not treat failures in distribution transformers as a relevant problem in large financial point of view, since any preventive action to minimize them within the current reality can be more costly. Thus, proper policies for investigating faults in distribution transformers are usually disregarded by the power utilities and sometimes policies may not even exist. In this context, existing information on faulty distribution transformers may not contain important data. However, new laws affecting power distribution companies are becoming more severe and there are demands for greater efficiency. In this new scenario, a forensic methodology to analyse faults in distribution transformers, created some years ago by many utilities, has recently been resurrected with the analysis of 3,159 distribution transformers. This methodology is known as Forensic Analysis Applied to Distribution Transformers (FAADT). New tests and trials as measuring insulation resistance, polarization index and dielectric absorption, physical and chemical analysis among others, will be added to the forensic methodology to improve it. Moreover, the surge-arresters, being part of the system of protection of distribution transformers, are also studied in order to evaluate possible design flaws and challenges to overcome.

無論在企業組織中的任何工作情境下，當一個人的角色產生衝突、模糊、及過荷時，會使得個人產生工作壓力，連帶影響其工作滿足及工作績效。所謂角色衝突(role conflict)，係指預期的行為彼此間產生衝突與摩擦；角色模糊(role ambiguity)，係指員工不確定或不明白如何執行工作，不確定或不明自工作的期望是什麼，不確定或不明自工作績效及期望結果間的關係。而角色過荷(role overload)，係指員工承受過多的工作責任和活動績效。 　　內部稽核人員係組織內的幕僚人員，其職務之範圍，可涵蓋整個組織，所涉及的層面，包括人與事，廣泛而複雜。內部稽核人員在企業中同時對高階管理、受查核單位及自己的稽核專業負責，因此，內部稽核人員往往因為身兼多重角色，而且角色間又相互衝突，而承受角色壓力。本研究探討國內企業內部稽核人員不同構面的角色壓力、工作滿足，及內部稽核工作品質間之問題。在研究過程中，為了解我國內部稽核人員的角色壓力對工作滿足，工作滿足對內部稽核工作品質，以及角色壓力與工作滿足對內部稽核工作品質之關係，本研究發展了四個假說，分別為：假說一：內部稽核人員的角色壓力對工作滿足呈負相關。假說二：內部稽核人員的工作滿足對內部稽核工作品質呈正相關。假說三：內部稽核人員的色壓力對內部稽核工作品質呈負相關。假說四：內部稽核人員的角色壓力會透過工作滿足而對內部稽核工作品質產生間接效果。 　　根據實證分析，本研究之研究結論為，一、內部稽核人員的角色壓力對工作滿足呈負相關。當內部稽核人員受到越大的角色壓力，其工作滿足就越低；反之，當內部稽核人員受到越小的角色壓力，其工作滿足就越高。二、內部稽核人員的工作滿足對內部稽核工作品質呈正相關。當內部稽核人員獲得越高的工作滿足，則內部稽核工作品質就越佳；反之，當內部稽核人員無法獲得越高的工作滿足，則內部稽核工作品質就不佳。三、內部稽核人員的角色壓力對內部稽核工作品質呈負相關。當內部稽核人員的角色壓力大，則內部稽核工作品質就越不佳；反之，當內部稽核人員的角色壓力小，則內部稽核工作品質就越佳。四、內部稽核人員的角色壓力會透過工作滿足而對內部稽核工作品質產生間接效果。本研究以Baron and Keny(1986)之中介模式加以驗證，結果得知內部稽核人員的角色壓力對內部稽核工作品質並不直接產生效果，角色壓力會透過工作滿足，以工作滿足作為中介，而對內部稽核工作品質產生間接效果。 / Employees, under whatever working environment, are facing role conflict, role ambiguity as well as overload in a business organization, which inevitably will affect their job satisfaction and performance. "Role conflict" in this paper refers to the disagreement and friction resulting from an expected behavior. And role ambiguity means the employees are not clear or un-known as how to do the work, what is to expect from the work, nor what is the relationship between work performance and the expected results. Whereas "role overload" indicates that the employees take too much responsibility from the job and activity performance. 　　This study tries to examine the relationship among the role stress, the job satisfaction and the internal audit quality of the internal auditors in Taiwan. The research models established in Bron and Kenny's study are adopted. The four regression models explicitly incorporate efficient and effective measures, and reflect the interactive nature of outcome-generating activities for the internal auditors. Forty-one pair questionnaires are included in the sample. 　　The results of this study are as following: Firstly, a role stress is negatively related to job satisfaction, implying that higher role stress reduces job satisfaction; and vice versa. Secondly, there is an obvious positive relationship between auditor's job satisfaction and the internal audit quality; the more of job satisfaction, the better of the internal audit quality. Thirdly, the relationship between auditor's role stress and the internal audit quality is reverse; noting their role stress decreases the internal audit quality. Finally, the effect of auditor's role stress against the internal audit quality probably is indirectly generated through their job satisfaction.

<p><p><p>Allmänhetens uppfattning är att desto fler valmöjligheter det finns desto bättre är det. Men är det verkligen så i alla olika valsituationer vi ställs inför? (Iyengar & Lepper 2000)  </p><p> </p><p>Utifrån tidigare forskning testar vår uppsats om människors valmöjligheter, ett experiment där vi ser hur människor gör sina val på den svenska fondmarknaden. De fick välja mellan ett mindre (limited) urval eller ett större (extensive) urval av fonder. </p><p> </p><p>Utgångspunkten i uppsatsen är två olika forskningsartiklar från Iyengar & Lepper (2000) samt Iyengar & Jiang (2003) där de testar hur människor gör sina val när de får olika stora utbud att </p><p>välja bland. I deras forskning kommer de fram till att även om människor tycker att det är roligare att ha många valmöjligheter så blir det oftare val gjorda eller saker köpta om de har </p><p>mindre saker att välja bland. Detta fenomen kallas choice overload och innebär alltså att det finns en valtrötthet för människor när de ska göra sina val. </p><p> </p><p>Vårt huvudsyfte med denna uppsats är att testa om fenomenet choice overload kan tillämpas på den svenska fondmarknaden och därmed se om beslutet att själv välja fonder påverkas av fondutbudets storlek. Experimentet skedde genom en enkätundersökning på två stycken bankkontor där slumpvis utvalda kunder fick svara på enkäterna. Vi hade två olika enkäter där </p><p>den ena bestod av en fråga där de skulle välja bland ett mindre urval fonder (10st) och den andra bland ett större urval fonder (60st). Varje respondent fick bara en enkät och var därmed helt ovetande om att den andra existerade. Istället för att välja själva kunde de även få låta en </p><p>rådgivare välja åt dem, detta för att få ett alternativ till att välja själv. När vi samlat in alla enkäterna (98st) så jämförde vi resultaten mot varandra i statistikprogrammet SPSS. </p><p> </p><p>Delsyftet som kompletterar huvudsyftet i uppsatsen är att vi rensar för demografiska skillnader som t.ex. kön, utbildning och ålder, så att de inte har någon inverkan på beslutet att välja fonder.  </p><p> </p><p>Genom experimentet vi gjorde så visade det sig att människor valde fonder själva i större utsträckning när de fick enkäten med det mindre fondutbudet på (limited) än när de fick den enkäten med det större fondutbudet (extensive). Denna slutsats är förenlig med den forskning </p><p>vi hade som utgångspunkt till uppsatsen. Alltså att människor hellre gör sina val när de har ett mindre utbud att välja bland. Även om människor gillar att ha många valmöjligheter så kan det leda till att det blir så komplext att hantera att det leder till fenomenet choice overload. </p><p>Vårt experiment med enkäter visar även att de demografiska skillnaderna inte spelar någon signifikant roll för resultatet. </p></p></p>

Allmänhetens uppfattning är att desto fler valmöjligheter det finns desto bättre är det. Men är det verkligen så i alla olika valsituationer vi ställs inför? (Iyengar &amp; Lepper 2000)     Utifrån tidigare forskning testar vår uppsats om människors valmöjligheter, ett experiment där vi ser hur människor gör sina val på den svenska fondmarknaden. De fick välja mellan ett mindre (limited) urval eller ett större (extensive) urval av fonder.    Utgångspunkten i uppsatsen är två olika forskningsartiklar från Iyengar &amp; Lepper (2000) samt Iyengar &amp; Jiang (2003) där de testar hur människor gör sina val när de får olika stora utbud att  välja bland. I deras forskning kommer de fram till att även om människor tycker att det är roligare att ha många valmöjligheter så blir det oftare val gjorda eller saker köpta om de har  mindre saker att välja bland. Detta fenomen kallas choice overload och innebär alltså att det finns en valtrötthet för människor när de ska göra sina val.    Vårt huvudsyfte med denna uppsats är att testa om fenomenet choice overload kan tillämpas på den svenska fondmarknaden och därmed se om beslutet att själv välja fonder påverkas av fondutbudets storlek. Experimentet skedde genom en enkätundersökning på två stycken bankkontor där slumpvis utvalda kunder fick svara på enkäterna. Vi hade två olika enkäter där  den ena bestod av en fråga där de skulle välja bland ett mindre urval fonder (10st) och den andra bland ett större urval fonder (60st). Varje respondent fick bara en enkät och var därmed helt ovetande om att den andra existerade. Istället för att välja själva kunde de även få låta en  rådgivare välja åt dem, detta för att få ett alternativ till att välja själv. När vi samlat in alla enkäterna (98st) så jämförde vi resultaten mot varandra i statistikprogrammet SPSS.    Delsyftet som kompletterar huvudsyftet i uppsatsen är att vi rensar för demografiska skillnader som t.ex. kön, utbildning och ålder, så att de inte har någon inverkan på beslutet att välja fonder.     Genom experimentet vi gjorde så visade det sig att människor valde fonder själva i större utsträckning när de fick enkäten med det mindre fondutbudet på (limited) än när de fick den enkäten med det större fondutbudet (extensive). Denna slutsats är förenlig med den forskning  vi hade som utgångspunkt till uppsatsen. Alltså att människor hellre gör sina val när de har ett mindre utbud att välja bland. Även om människor gillar att ha många valmöjligheter så kan det leda till att det blir så komplext att hantera att det leder till fenomenet choice overload.  Vårt experiment med enkäter visar även att de demografiska skillnaderna inte spelar någon signifikant roll för resultatet.

The main goal of this thesis is to develop practical digital controller architectures for multi-phase dc-dc converters utilized in low power (up to few hundred watts) and cost-sensitive applications. The proposed controllers are suitable for on-chip integration while being capable of providing advanced features, such as dynamic efficiency optimization, inductor current estimation, converter component identification, as well as combined dynamic current sharing and fast transient response. The first part of this thesis addresses challenges related to the practical implementation of digital controllers for low-power multi-phase dc-dc converters. As a possible solution, a multi-use high-frequency digital PWM controller IC that can regulate up to four switching converters (either interleaved or standalone) is presented. Due to its configurability, low current consumption (90.25 μA/MHz per phase), fault-tolerant work, and ability to operate at high switching frequencies (programmable, up to 10 MHz), the IC is suitable to control various dc-dc converters. The applications range from dc-dc converters used in miniature battery-powered electronic devices consuming a fraction of watt to multi-phase dedicated supplies for communication systems, consuming hundreds of watts. A controller for multi-phase converters with unequal current sharing is introduced and an efficiency optimization method based on logarithmic current sharing is proposed in the second part. By forcing converters to operate at their peak efficiencies and dynamically adjusting the number of active converter phases based on the output load current, a significant improvement in efficiency over the full range of operation is obtained (up to 25%). The stability and inductor current transition problems related to this mode of operation are also resolved. At last, two reconfigurable digital controller architectures with multi-parameter estimation are introduced. Both controllers eliminate the need for external analog current/temperature sensing circuits by accurately estimating phase inductor currents and identifying critical phase parameters such as equivalent resistances, inductances and output capacitance. A sensorless non-linear, average current-mode controller is introduced to provide fast transient response (under 5 μs), small voltage deviation and dynamic current sharing with multi-phase converters. To equalize the thermal stress of phase components, a conduction loss-based current sharing scheme is proposed and implemented.

The organic materials used for stator winding insulation are subject to deterioration from thermal, electrical, and mechanical stresses. Stator winding insulation breakdown due to excessive thermal stress is one of the major causes of electric machine failures; therefore, prevention of such a failure is crucial for increasing machine reliability and minimizing financial loss due to motor failure. This work focuses on the development of an efficient and reliable stator winding temperature estimation scheme for small to medium size mains-fed induction machines. The motivation for the stator winding temperature estimation is to develop a sensorless temperature monitoring scheme and provide an accurate temperature estimate that is capable of responding to the changes in the motors cooling capability. A discussion on the two major types of temperature estimation techniques, thermal model-based and parameter-based temperature techniques, reveals that neither method can protect motors without sacrificing the estimation accuracy or motor performance. Based on the evaluation of the advantages and disadvantages of these two types of temperature estimation techniques, a new online stator winding temperature estimation scheme for small to medium size mains-fed induction machines is proposed in this work. The new stator winding temperature estimation scheme is based on a hybrid thermal model. By correlating the rotor temperature with the stator temperature, the hybrid thermal model unifies the thermal model-based and the parameter-based temperature estimation techniques. Experimental results validate the proposed scheme for stator winding temperature monitoring. The entire algorithm is fast, efficient and reliable, making it suitable for implementation in real time stator winding temperature monitoring.

Η πληροφοριακή υπερφόρτωση των χρηστών αποτελεί βασικό πρόβλημα ενός οργανισμού. Η συσσώρευση μεγάλου όγκου πληροφορίας στα πληροφοριακά συστήματα, προκαλεί στους χρήστες άγχος και υπερένταση, με αποτέλεσμα να δυσχεραίνει την ικανότητά τους για λήψη αποφάσεων. Λόγω αυτού, η επίδραση της πληροφοριακής υπερφόρτωσης στους οργανισμούς είναι καταστροφική και απαιτείται η αντιμετώπισή της. Υπάρχουν διάφοροι τρόποι αντιμετώπισης της πληροφοριακής υπερφόρτωσης όπως τα συστήματα υποστήριξης λήψης αποφάσεων, τα συστήματα φιλτραρίσματος πληροφορίας, οι αποθήκες δεδομένων και άλλες τεχνικές της εξόρυξης δεδομένων και της τεχνητής νοημοσύνης, όπως είναι οι ευφυείς πράκτορες. Οι ευφυείς πράκτορες αποτελούν εφαρμογές που εφάπτονται της τεχνικής νοημοσύνης, οι οποίες έχουν την ικανότητα να δρουν αυτόνομα, συλλέγοντας πληροφορίες, εκπαιδεύοντας τον εαυτό τους και επικοινωνώντας με τον χρήστη και μεταξύ τους. Συχνά, υλοποιούνται πολυπρακτορικά συστήματα προκει-μένου να επιλυθεί ένα πρόβλημα του οργανισμού. Στόχος τους είναι να διευκολύνουν τη λήψη αποφάσεων των χρηστών, προτείνοντας πληροφορίες βάσει των προτιμήσεών τους. Ο σκοπός της παρούσας διπλωματικής εργασίας είναι να αναλύσει σε βάθος τους ευφυείς πράκτορες, σαν μία αποτελεσματική μέθοδο αντιμετώπισης της πληροφοριακής υπερφόρτωσης, να προτείνει πειραματικούς πράκτορες προτά-σεων και να εξετάσει επιτυχημένες υλοποιήσεις. Συγκεκριμένα, παρουσιάζεται ένα ευφυές σύστημα διδασκαλίας για την ενίσχυση του e-Learning/e-Teaching, προτείνεται ένα σύστημα πρακτόρων για τον οργανισμό Flickr, ενώ εξετάζεται το σύστημα προτάσεων του Last.fm και ο αλγόριθμος προτάσεων του Amazon. Τέλος, αναλύεται μια πειραματική έρευνα ενός ευφυούς πράκτορα προτάσεων, ο οποίος αντιμετώπισε με επιτυχία την αντιληπτή πληροφοριακή υπερφόρτωση των χρηστών ενός θεωρητικού ηλεκτρονικού καταστήματος. Τα αποτελέσματα του πειράματος παρουσίασαν την επίδραση της αντιληπτής πληροφοριακής υπερφόρτωσης και του φορτίου πληροφορίας στην ποιότητα επιλογής, στην εμπιστοσύνη επιλογής και στην αντιληπτή αλληλεπίδραση μεταξύ ηλεκτρονικού καταστήματος και χρήστη, ενώ παρατηρήθηκε η καθοριστική συμβολή της χρήσης των ευφυών πρακτόρων στην αντιμετώπιση της πληροφοριακής υπερφόρτωσης. / -

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One of the most prominent factors affecting the performance and longevity of risers is vortex induced vibration (VIV), which can cause severe fatigue damage, especially in risers used in deep waters. The available approaches for analyzing VIV induced fatigue in risers mainly focus on the VIV aspect of the problem; indeed less attention has been paid on the effect of VIV on a riser’s fatigue life and in prediction of fatigue life using various models. This dissertation first demonstrates how one can characterize fatigue of pipes and risers using an equivalent plate specimen as opposed to using a pipe specimen, thereby simplifying the task, yet obtaining good accuracy. Actual variable amplitude loadings (VAL) are used to study the fatigue crack growth in risers’ material with a focus on the various influencing parameters. Extensive experimental investigations are performed, followed by analytical and computational nonlinear finite element analyses. It is shown that the higher harmonics do cause significant fatigue damage, thus their influence should not be ignored. The influence of load interaction effects is also investigated, focusing on the fatigue crack growth retardation effects due to tension overloads, as well as the acceleration effects due to compression underloads. The crack closure concept is then used to explore into both the fatigue retardation and acceleration effects within a VAL scenario. An effective method for calculation of the stress intensity factor is proposed, which considers only the tensile portion of the stress range, while proposing another effective approach for accounting for the influence of compressive stress cycles. Moreover, a two-parameter approach is used in this dissertation, relating the fatigue crack growth rate (FCGR) to the crack tip opening displacement (CTOD). It is shown that the CTOD provides adequate information for calculating the FCGR under VAL, and it can be effectively used to account for the influence of the compressive stress cycles. The experimental investigation also considers the retardation effect resulting from the applied peak tensile overload cycles (TOLC) and the influence of various so-called “clipping” levels, demonstrating the significant influence of the TOLC on crack growth retardation in VAL.