Orientador: Maria Beatriz Felgar de Toledo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-08T13:37:39Z (GMT). No. of bitstreams: 1 Garcia_DiegoZuquimGuimaraes_M.pdf: 1006389 bytes, checksum: 8016f0659ec60b1ef54c6aaf41fba177 (MD5) Previous issue date: 2007 / Resumo: A tecnologia de serviços Web possui algumas propriedades importantes para o desenvolvimento e a execução de aplicações distribuídas. Entretanto, ela ainda não oferece apoio para tratar as características não-funcionais dos serviços. Os consumidores de serviços Web podem requerer serviços com parâmetros de qualidade específicos e esperar garantias de níveis de qualidade. O objetivo desta dissertação é estender o modelo de serviços Web para apoiar a gerência de características não-funcionais para serviços Web. O modelo proposto inclui mediadores para auxiliar na descoberta de serviços de acordo com os requisitos funcionais e não-funcionais dos consumidores e monitores para verificar os atributos de qualidade. As principais contribuições desta dissertação são: a utilização do padrão Web Services Policy Framework (WS-Policy) para complementar as descrições de serviços Web Services Description Language (WSDL) com políticas para atributos de qualidade; uma extensão para o padrão Universal Description Discovery & Integration (UDDI) para a publicação e a descoberta de serviços Web incluindo características nãofuncionais; e o monitoramento e a atualização de características não-funcionais para refletir os atributos reais dos serviços / Abstract: Although the Web service technology allows the development and execution of distributed applications, it still lacks facilities to deal with Quality of Service (QoS). Consumers may require services with particular non-functional characteristics and expect quality level guarantees. The goal of this thesis is to propose an extended Web service architecture supporting QoS management for Web services. It includes brokers to facilitate service selection according to functional and non-functional requirements and monitors to verify QoS attributes. The main contributions of this approach are: the use of the Web Services Policy Framework (WS-Policy) standard to complement Web Services Description Language (WSDL) specifications with QoS policies; an extension to the Universal Description Discovery & Integration (UDDI) standard for QoS-enriched Web service publication and discovery; and QoS updating to reflect actual service attributes / Mestrado / Mestre em Ciência da Computação

No description available.

Orientador: Marcelo El Khouri Buzato / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Estudos da Linguagem / Made available in DSpace on 2018-08-27T03:43:36Z (GMT). No. of bitstreams: 1 Sachs_RafaelSalmazi_M.pdf: 10793959 bytes, checksum: 2d0fd06b73083ec060e8de59058173ea (MD5) Previous issue date: 2015 / Resumo: Esta dissertação teve como objetivo mais amplo gerar inteligibilidades acerca da relação entre a cultura digital e a ação política na contemporaneidade, a partir da articulação, no campo da Linguística Aplicada, entre a noção de linguagem digital como processo e o conceito de política como regime de enunciação, que objetiva traduzir em um os interesses de muitos. Como contexto para o estudo, escolheram-se os eventos das Jornadas de Junho de 2013, caracterizadas tanto pela emergência repentina de massivos protestos de rua no Brasil, quanto pela publicação, em sites de redes sociais, de uma grande quantidade de remixes e mashups contendo enunciados políticos a respeito. Compõem o corpus empírico da pesquisa 88 textos verbovisuais desse tipo, publicados no Facebook entre junho e julho de 2013. Entendidos como frutos de percursos de desmontagem e remontagem, e, portanto, de desressemiotização, esses textos foram analisados com base na articulação (proposta como objetivo teórico do trabalho) entre as categorias da Semiótica Social para a multimodalidade e as da Teoria Ator-Rede para translações. Como objetivo empírico, buscou-se descrever os significados representacionais e os percursos de constituição das montagens do corpus, em relação ao regime de enunciação da política. As perguntas de pesquisa foram duas, a saber: (1) quais foram os principais actantes mobilizados nos remixes estudados, e em que tipo de processos semióticos tais actantes apareceram com maior frequência?; e (2) quais foram algumas das operações de ressemiotização empregadas nas desreestabilizações sucessivas das diferentes versões de Brasil e realidade brasileira constituídas nesses textos? Os resultados elencaram as figurativizações mais comuns e os processos representacionais mais frequentes no corpus, em que os manifestantes, a nação brasileira, os políticos e a grande mídia foram os principais actantes representados, em geral, através de processos atributivos simbólicos. Destacou-se, nesse levantamento, a figura do gigante de pedra se levantando no Rio de Janeiro, empregada por muitos como representação unificada do Brasil e dos interesses múltiplos em atuação nas Jornadas. A partir dessa figura, descreveram-se ainda os processos de negociação de affordances para constituição de alguns dos textos analisados, e sua relação com as disputas pelo significado dos acontecimentos das Jornadas de Junho, e pela definição que era "ser brasileiro" no momento dos protestos. Como conclusão, os dados refletem a necessidade de buscar caminhos para compreensões menos deterministas da relação entre política, tecnologias digitais e sociedade, e modos de formação cidadã, no âmbito das mídias digitais, que viabilizem a compreensão de enunciados políticos como fruto de enredamentos semióticos sempre articulados em disputas de interesse, mesmo quando se pretendem neutros / Abstract: The main goal of the present study is to suggest ways of understanding the relation between digital culture and contemporary political action, based on the connection, drawn in the field of Applied Linguistics, between the notion of digital language as process and the concept of politics as a regime of enunciation which aims to translate the interests of many into one. The events of the June Journeys in 2013 were taken as context for the study, since they included not only the sudden emergence of massive protests on Brazilian streets, but also the publishing, on social network sites, of large amounts of remixes and mashups containing political statements on that regard. Seen as the outcomes of disassembling and assembling trajectories, and therefore, of deresemiotization trajectories, those texts were analyzed in the light of an articulation (also presented as a theoretical objective of this work) between Social Semiotics studies on multimodality and Actor-Network Theory principles for the understanding of translations. As empirical objectives, this work aimed to describe the representational meanings and the assembling trajectories of the texts in the corpus, in relation to the political regime of enunciation. The research questions were two: (1) what were the main actants mobilized in the remixes in the corpus, and in which kind of semiotic processes those actants appeared more often?; and (2) what were some of the resemiotization operations used for the continuous derestabilizations of different versions of Brazil and Brazilian reality represented in those texts? Results enroll the most frequent figurativizations and the most usual representational processes in the corpus, in which the demonstrators, Brazilian nation, politicians and mass media were the main actants, and were depicted, in general, through symbolic attributive processes. In that enrollment, the image of a stone giant rising in Rio de Janeiro was prominent, for it was used by many as a unified depiction of Brazil as a whole and of the multiple interests acting during the Journeys. From that picture, the results described the processes of negotiation of affordances for the composition of some of the analyzed texts, and their relation to the disputes for the meaning of the June Journeys events, and for what meant "to be Brazilian" then. As a conclusion, data reflects the need of pursuing less determinist ways of understanding the relation among politics, digital technologies and society, as well as the need for ways of citizenship education, regarding digital media, that address the understanding of political statements as outcomes of semiotic entanglements which are always connected to interests in dispute, even when allegedly neutral / Mestrado / Linguagem e Sociedade / Mestre em Linguística Aplicada

<p>This thesis presents an approach for working with low level source code that enables automatic restructuring and raising the abstraction level of the programs. This makes it easier to understand the logic of the program, which in turn reduces the development time.The process in this thesis was designed to be flexible and consists of several independent tools. This makes the process easy to adapt as needed, while at the same time the developed tools can be used for other processes. There are usually two basic steps. First is the translation to WSL language, which has a great number of semantic preserving program transformations. The second step are the transformations of the translated WSL. Two tools were developed for translation: one that works with a subset of x86 assembly, and another that works with MicroJava bytecode. The result of the translation is a low level program in WSL.The primary goal of this thesis was to fully automate the selection of the transformations. This enables users with no domain&nbsp; knowledge to efficiently use this process as needed. At the same time, the flexibility of the process enables experienced users to adapt it as needed or integrate it into other processes. The automation was achieved with a <em>hill climbing </em>algorithm.Experiments that were run on several types of input programs showed that the results can be excellent. The fitness function used was a built-in metric that gives the &ldquo;weight&rdquo; of structures in a program. On input samples that had original high level source codes, the end result metrics of the translated and transformed programs were comparable. On some samples the result was even better than the originals, on some others they were somewhat more complex. When comparing with low level original source code, the end results was always significantly improved.</p> / <p>U okviru ove teze se predstavlja pristup radu sa programima niskog nivoa koji omogućava automatsko restrukturiranje i podizanje na vi&scaron;e nivoe. Samim tim postaje mnogo lak&scaron;e razumeti logiku programa &scaron;to smanjuje vreme razvoja.Proces je dizajniran tako da bude fleksibilan i sastoji se od vi&scaron;e nezavisnih alata. Samim tim je lako menjati proces po potrebi, ali i upotrebiti razvijene alate u drugim procesima. Tipično se mogu razlikovati dva glavna koraka. Prvi je prevođenje u jezik WSL,za koji postoji veliki broj transformacija programa koje očuvavaju semantiku. Drugi su transformacije u samom WSL-u. Za potrebe prevođenja su razvijena dva alata, jedan koji radi sa podskupom x86 asemblera i drugi koji radi sa MikroJava bajtk&ocirc;dom. Rezultat prevođenja je program niskog nivoa u WSL jeziku.Primarni cilj ovog istraživanja je bila potpuna automatizacija odabira transformacija, tako da i korisnici bez iskustva u radu sa sistemom mogu efikasno da primene ovaj proces za svoje potrebe. Sa druge strane zbog fleksibilnosti procesa, iskusni korisnici mogu lakoda ga pro&scaron;ire ili da ga integri&scaron;u u neki drugi već postojeći&nbsp;&nbsp; proces.Automatizacija je&nbsp; postignuta pretraživanjem usponom (eng. hill climbing).Eksperimenti vr&scaron;eni na nekoliko tipova ulaznih programa niskog nivoa su pokazali da rezultati mogu biti&nbsp; izuzetni. Za funkciju pogodnosti je kori&scaron;ćena ugrađena metrika koja daje &ldquo;težinu&rdquo; struktura u programu. Kod ulaza za koje je originalni izvorni k&ocirc;d bio dostupan, krajnje metrike najboljih varijanti prevedenih i transformisanih programa su bile na sličnom nivou. Neki primeri su bolji od originala, dok su drugi bili ne&scaron;to kompleksniji. Rezultati su uvek pokazivali značajna unapređenja u odnosu na originalni k&ocirc;d niskog nivoa.</p>

Ces dernières années, les technologies d’écran se sont considérablement améliorées. Par exemple, le contraste des écrans à plage dynamique élevée (HDR) dépasse de loin la capacité d’un écran conventionnel. De plus, un écran à gamut de couleur étendu (WCG) peut couvrir un espace colorimétrique plus grand que jamais. L'évaluation de la qualité de ces nouveaux contenus est devenue un domaine de recherche actif, les métriques de qualité SDR classiques n'étant pas adaptées. Cependant, les études les plus récentes négligent souvent une caractéristique importante: les chrominances. En effet, les bases de données existantes contiennent des images HDR avec un gamut de couleur standard, négligeant ainsi l’augmentation de l’espace colorimétrique due au WCG et les artefacts chromatiques. La plupart des mesures de qualité HDR objectives non plus ne prennent pas en compte ces artefacts. Pour surmonter cette problématique, dans cette thèse, nous proposons deux nouvelles bases de données HDR/WCG annotés avec des scores subjectifs présentant des artefacts chromatique réaliste. En utilisant ces bases de données, nous explorons trois solutions pour créer des métriques HDR/WCG: l'adaptation des métrics de qualité SDR, l’extension colorimétrique d’une métrique HDR connue appelée HDR-VDP-2 et, enfin, la fusion de diverses métriques de qualité et de features colorimétriques. Cette dernière métrique présente de très bonnes performances pour prédire la qualité tout en étant sensible aux distorsions chromatiques. / To improve their ability to display astonishing images, screen technologies have been greatly evolving. For example, the contrast of high dynamic range rendering systems far exceed the capacity of a conventional display. Moreover, a Wide Color gamut display can cover a bigger color space than ever. Assessing the quality of these new content has become an active field of research as classical SDR quality metrics are not adapted. However, state-of-the-art studies often neglect one important image characteristics: chrominances. Indeed, previous databases contain HDR images with a standard gamut thus neglecting the increase of color space due to WCG. Due to their gamut, these databases are less prone to contain chromatic artifacts than WCG content. Moreover, most existing HDR objective quality metrics only consider luminance and are not considering chromatic artifacts. To overcome this problematic, in this thesis, we have created two HDR / WCG databases with annotated subjective scores. We focus on the creation of a realistic chromatic artifacts that can arise during compression. In addition, using these databases, we explore three solutions to create HDR / WCG metrics. First, we propose a method to adapt SDR metrics to HDR / WCG content. Then, we proposed an extension of a well-known HDR metric called HDR-VDP-2. Finally, we create a new metric based on the merger of various quality metric and color features. This last metric presents very good performance to predict quality while being sensitive to chromatic distortion.

Kein roter Knopf wurde gedrückt, keine große Rede gehalten: einige Klicks, etwas Tastengeklapper und der neue Katalog der Universitätsbibliothek Leipzig war online. Was am 21. März des Jahres gegen 12 Uhr so unspektakulär und doch nicht ohne Lampenfieber über die Bühne ging, hat inzwischen einige Beachtung gefunden. Es folgten kollegiale Glückwünsche und ein starkes Interesse aus vielen Bibliotheken, von denen die entfernteste sicher die Technical University Sydney ist. Für die Beteiligten aber am wichtigsten war ein weitgehend positives, manchmal geradezu begeistertes Feedback im Chat und im Blog durch die Nutzerinnen und Nutzer der Universitätsbibliothek Leipzig. Die kritischen Hinweise kommen meist aus dem eigenen Haus: Der Katalog ist uns wichtig, wir wollen ihn noch besser machen!

Seit Jahren überzeugen die Städtischen Bibliotheken Dresden mit hervorragenden Leistungen und neuen innovativen Angeboten und Projekten im Bildungsbereich und in der Leseförderung. Sie sind eine feste Größe in der Kulturlandschaft für die Bürgerinnen und Bürger der Stadt.

Stand der Technik sind IGBTs und Freilaufdioden aus Silizium (Si). Jahrzehntelange Forschung hat zu einer nahezu perfekten Technologie geführt. Jedoch werden die Fortschritte hinsichtlich der Reduzierung von Schalt- und Durchlassverlusten mit jeder neuen Generation von Si-IGBTs immer kleiner. Die anfallende Verlustleistung kann jedoch signifikant mit Leistungshalbleiter-Bauelementen aus Siliziumkarbid (SiC) und Galliumnitrid (GaN) gesenkt werden. Ziel dieser Arbeit ist es, zu untersuchen, ob und inwieweit mit diskreten SiC-Bipolartransistoren im TO-247- und SiC-Schottky-Dioden im TO-220-Gehäuse der Wirkungsgrad eines Antriebsstromrichters gesteigert werden kann. Ein Exkurs in die Siliziumkarbid-Halbleitertechnologie am Anfang soll deren Vorteile in Hinblick auf verlustärmere Leistungselektronik aufzeigen. Die Vorteile des Halbleitermaterials Siliziumkarbid werden anhand des SiC-Bipolartransistors im Vergleich zum ersten Leistungstransistor - dem Bipolartransistor aus Silizium - herausgearbeitet. Beim SiC-Bipolartransistor muss im laststromführenden Zustand ein Steuerstrom in die Basis eingeprägt werden. Damit erhöht sich der Treiberaufwand. Deshalb wird der erste Themenschwerpunkt auf den Treiber gelegt. In dieser Arbeit wurden ein einfacher und ein komplexer Treiber aufgebaut und evaluiert. Mit leichten Modifikationen wurden mit dem komplexeren Treiber auch IGBTs und SiC-MOSFETs für Vergleichsmessungen angesteuert. Ein neuer Ansatz zur Reduzierung der Treiberverlustleistung im Wechselrichter mit SiC-Bipolar-Transistoren wird vorgestellt. Er setzt beim Kommutierungsalgorithmus des Wechselrichters an. Ein wesentlicher Teil der Arbeit widmet sich der Charakterisierung des SiC-Bipolartransistors, insbesondere dem Schaltverhalten. Ein- und Ausschaltwärmen für verschiedene Arbeitspunkte werden ermittelt. Am Ende der Arbeit werden experimentelle Untersuchungen an einem SiC-Wechselrichter durchgeführt. Abschließend werden die Potenziale, die mit dem Einsatz von SiC-Bipolartransistoren verbunden sind, bewertet aber auch die Grenzen aufgezeigt.:1 Einleitung 1 2 Aufbau des SiC-Bipolartransistors 2.1 Siliziumkarbid (SiC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1.1 Eigenschaften von monokristallinem Siliziumkarbid . . . . . . . . . . 5 2.1.2 Herstellung des SiC-Wafers . . . . . . . . . . . . . . . . . . . . . . . . 8 2.1.3 Herstellung des SiC-Bipolartransistors . . . . . . . . . . . . . . . . . . 10 2.1.4 Defekte im Siliziumkarbidkristall . . . . . . . . . . . . . . . . . . . . 11 2.2 Halbleiterphysikalische Grundlagen . . . . . . . . . . . . . . . . . . . . . . . 12 2.2.1 Gesperrter pn-Übergang . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.2.2 Stromführender pn-Übergang . . . . . . . . . . . . . . . . . . . . . . . 15 2.3 Bipolartransistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.3.1 Aufbau und Funktionsprinzip . . . . . . . . . . . . . . . . . . . . . . . 17 2.3.2 Sperrfähigkeit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.3.3 Erster und zweiter Durchbruch . . . . . . . . . . . . . . . . . . . . . . 23 2.3.4 Stromverstärkung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2.3.5 Ladungsträgermodulation . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.3.6 Eindimensionaler spezifischer Widerstand der Driftzone . . . . . . . . 30 3 Ansteuerung des SiC-Bipolartransistors 3.1 Einführung Treiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.2 Herausforderungen beim Ansteuern von SiC-Bipolartransistoren . . . . . . . . 34 3.3 Treiberkonzepte für SiC-Bipolartransistoren . . . . . . . . . . . . . . . . . . . 36 3.4 Konventioneller Treiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 3.5 3-Level-Treiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.6 Treiber für SiC-MOSFET und IGBT . . . . . . . . . . . . . . . . . . . . . . . 45 4 Reduzierung der Treiberverluste durch Einschrittkommutierung 4.1 Einschrittkommutierung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 4.2 Stromvorzeichenerkennung . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.3 Berechnung der Verlustleistungen für den eingeschalteten Zustand des SiC- Bipolartransistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 4.4 Messung der Treiberverlustleistung . . . . . . . . . . . . . . . . . . . . . . . . 52 5 Charakterisierung des SiC-Bipolartransistors 5.1 Messaufbau für Untersuchung des Ein- und Ausschaltverhaltens . . . . . . . . 55 5.2 Doppelpulsverfahren . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 5.3 Definition der Schaltzeiten und Schaltverlustleistung . . . . . . . . . . . . . . 57 5.4 Messung der Schaltwärme . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.4.1 Spannungstastköpfe . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.4.2 Stromsensoren . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 5.4.3 Zeitliche Verschiebung der Messsignale . . . . . . . . . . . . . . . . . 62 5.4.4 Vergleich von konventionellem und 3-Level-Treiber . . . . . . . . . . . 65 5.4.5 Vergleich bei unterschiedlicher Treiberspannung . . . . . . . . . . . . 66 5.4.6 Vergleich bei halb und voll bestückter Halbbrücke . . . . . . . . . . . . 68 5.4.7 Vergleich von SiC-Bipolartransistor mit SiC-MOSFET und Si-IGBT . . 69 5.4.8 Reduzierung der Spannungsspitze beim Ausschalten . . . . . . . . . . 74 5.5 Simulation des Schaltverhaltens eines SiC-Bipolartransistors . . . . . . . . . . 79 5.5.1 Schaltverhalten bei Ansteuerung mit unipolarem Treiber . . . . . . . . 79 5.5.2 Simulation des Einfluss der Emitter-Induktivität auf Schaltwärme . . . 81 5.5.3 Vergleich von Simulation und Messung . . . . . . . . . . . . . . . . . 82 5.6 Durchlassverlustleistung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 6 Einsatz von SiC-Bipolartransistoren im Wechselrichter 6.1 Aufbau der Wechselrichter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 6.2 Inbetriebnahme des Wechselrichters . . . . . . . . . . . . . . . . . . . . . . . 89 6.3 Überspannungen an den Motorklemmen der 1 kW-Asynchronmaschine . . . . 91 6.4 Umbau des SiC-Wechselrichters . . . . . . . . . . . . . . . . . . . . . . . . . 93 6.5 Spannungsspitzen in der Ansteuerspannung . . . . . . . . . . . . . . . . . . . 94 6.6 Halbbrückenverluste im Leerlauf . . . . . . . . . . . . . . . . . . . . . . . . . 98 7 Zusammenfassung und Fazit 101 Literaturverzeichnis 104 A Anhang A.1 Netzliste für SiC-Bipolartransistor FSICBH057A120 . . . . . . . . . . . . . . 113 A.2 Leiterplatten für Doppelpuls-Test und SiC-Wechselrichter . . . . . . . . . . . . 114 A.3 Herleitung des Feldverlaufs in der Driftzone des gesperrten pn-Übergangs . . . 116 A.4 Herleitung des Emitterwirkungsgrads . . . . . . . . . . . . . . . . . . . . . . . 119 A.5 Herleitung des spezifischen Widerstands der Driftzone . . . . . . . . . . . . . 121 A.6 Lebenslauf von Henry Barth . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 A.6.1 Persönliche Angaben . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 A.6.2 Wissenschaftlicher Werdegang . . . . . . . . . . . . . . . . . . . . . . 124 / State-of-the-art are IGBTs and free-wheeling diodes made of silicon (Si). Decades of research have led to an almost perfect technology. Nevertheless, progress in terms of reduction of switching and forward conducting losses becomes smaller and smaller with each new generation of Si IGBTs. The resulting power dissipation, however, can be significantly reduced with power semiconductor devices made of silicon carbide (SiC) and gallium nitride (GaN). The objective of this work is to investigate whether and to what extent discrete SiC bipolar junction transistors (BJT) in TO-247 and SiC Schottky diodes in TO-220 packages can be used to increase the efficiency of a power drive inverter. At the beginning, a digression into silicon carbide semiconductor technology is intended to show its advantages in terms of lower-loss power electronics. The advantages of the semiconductor material silicon carbide are illustrated by the SiC bipolar junction transistor in comparison with the first power transistor - the silicon bipolar junction transistor. For the on-state of SiC bipolar junction transistors, a continuous current must be injected into the base. This increases the driving effort. Therefore, the first topic focuses on the driver. In this work, a simple and a complex driver were built and evaluated. With slight modifications, the more complex driver was also used to drive IGBTs and SiC-MOSFETs for comparative measurements. A new approach to reduce driver power dissipation in the inverter when using SiC bipolar junction transistors is presented. It focuses on the commutation algorithm of the inverter. A significant part of the work is devoted to the characterization of the SiC bipolar junction transistor, especially the switching behavior. Turn-on and turn-off switching losses for different operating points are determined. At the end of the work, experimental investigations are performed on a SiC inverter. Finally, the potentials associated with the use of SiC bipolar junction transistors are evaluated but also the limitations are shown.:1 Einleitung 1 2 Aufbau des SiC-Bipolartransistors 2.1 Siliziumkarbid (SiC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1.1 Eigenschaften von monokristallinem Siliziumkarbid . . . . . . . . . . 5 2.1.2 Herstellung des SiC-Wafers . . . . . . . . . . . . . . . . . . . . . . . . 8 2.1.3 Herstellung des SiC-Bipolartransistors . . . . . . . . . . . . . . . . . . 10 2.1.4 Defekte im Siliziumkarbidkristall . . . . . . . . . . . . . . . . . . . . 11 2.2 Halbleiterphysikalische Grundlagen . . . . . . . . . . . . . . . . . . . . . . . 12 2.2.1 Gesperrter pn-Übergang . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.2.2 Stromführender pn-Übergang . . . . . . . . . . . . . . . . . . . . . . . 15 2.3 Bipolartransistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.3.1 Aufbau und Funktionsprinzip . . . . . . . . . . . . . . . . . . . . . . . 17 2.3.2 Sperrfähigkeit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.3.3 Erster und zweiter Durchbruch . . . . . . . . . . . . . . . . . . . . . . 23 2.3.4 Stromverstärkung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2.3.5 Ladungsträgermodulation . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.3.6 Eindimensionaler spezifischer Widerstand der Driftzone . . . . . . . . 30 3 Ansteuerung des SiC-Bipolartransistors 3.1 Einführung Treiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.2 Herausforderungen beim Ansteuern von SiC-Bipolartransistoren . . . . . . . . 34 3.3 Treiberkonzepte für SiC-Bipolartransistoren . . . . . . . . . . . . . . . . . . . 36 3.4 Konventioneller Treiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 3.5 3-Level-Treiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.6 Treiber für SiC-MOSFET und IGBT . . . . . . . . . . . . . . . . . . . . . . . 45 4 Reduzierung der Treiberverluste durch Einschrittkommutierung 4.1 Einschrittkommutierung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 4.2 Stromvorzeichenerkennung . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.3 Berechnung der Verlustleistungen für den eingeschalteten Zustand des SiC- Bipolartransistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 4.4 Messung der Treiberverlustleistung . . . . . . . . . . . . . . . . . . . . . . . . 52 5 Charakterisierung des SiC-Bipolartransistors 5.1 Messaufbau für Untersuchung des Ein- und Ausschaltverhaltens . . . . . . . . 55 5.2 Doppelpulsverfahren . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 5.3 Definition der Schaltzeiten und Schaltverlustleistung . . . . . . . . . . . . . . 57 5.4 Messung der Schaltwärme . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.4.1 Spannungstastköpfe . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.4.2 Stromsensoren . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 5.4.3 Zeitliche Verschiebung der Messsignale . . . . . . . . . . . . . . . . . 62 5.4.4 Vergleich von konventionellem und 3-Level-Treiber . . . . . . . . . . . 65 5.4.5 Vergleich bei unterschiedlicher Treiberspannung . . . . . . . . . . . . 66 5.4.6 Vergleich bei halb und voll bestückter Halbbrücke . . . . . . . . . . . . 68 5.4.7 Vergleich von SiC-Bipolartransistor mit SiC-MOSFET und Si-IGBT . . 69 5.4.8 Reduzierung der Spannungsspitze beim Ausschalten . . . . . . . . . . 74 5.5 Simulation des Schaltverhaltens eines SiC-Bipolartransistors . . . . . . . . . . 79 5.5.1 Schaltverhalten bei Ansteuerung mit unipolarem Treiber . . . . . . . . 79 5.5.2 Simulation des Einfluss der Emitter-Induktivität auf Schaltwärme . . . 81 5.5.3 Vergleich von Simulation und Messung . . . . . . . . . . . . . . . . . 82 5.6 Durchlassverlustleistung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 6 Einsatz von SiC-Bipolartransistoren im Wechselrichter 6.1 Aufbau der Wechselrichter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 6.2 Inbetriebnahme des Wechselrichters . . . . . . . . . . . . . . . . . . . . . . . 89 6.3 Überspannungen an den Motorklemmen der 1 kW-Asynchronmaschine . . . . 91 6.4 Umbau des SiC-Wechselrichters . . . . . . . . . . . . . . . . . . . . . . . . . 93 6.5 Spannungsspitzen in der Ansteuerspannung . . . . . . . . . . . . . . . . . . . 94 6.6 Halbbrückenverluste im Leerlauf . . . . . . . . . . . . . . . . . . . . . . . . . 98 7 Zusammenfassung und Fazit 101 Literaturverzeichnis 104 A Anhang A.1 Netzliste für SiC-Bipolartransistor FSICBH057A120 . . . . . . . . . . . . . . 113 A.2 Leiterplatten für Doppelpuls-Test und SiC-Wechselrichter . . . . . . . . . . . . 114 A.3 Herleitung des Feldverlaufs in der Driftzone des gesperrten pn-Übergangs . . . 116 A.4 Herleitung des Emitterwirkungsgrads . . . . . . . . . . . . . . . . . . . . . . . 119 A.5 Herleitung des spezifischen Widerstands der Driftzone . . . . . . . . . . . . . 121 A.6 Lebenslauf von Henry Barth . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 A.6.1 Persönliche Angaben . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 A.6.2 Wissenschaftlicher Werdegang . . . . . . . . . . . . . . . . . . . . . . 124

The purpose of this study was to examine and describe the events of the first iteration of the Media Technology and Diversity course with an in-depth analysis of its electronic discourse. In conceptualizing the viable alternatives for delivering college-level distance education via on-line technologies, Harasim (1990) cautions that the mere introduction of computer mediated communication "does not in itself improve learning; design (or method) is crucial" (p. xx). The role of instructional design as the cornerstone of all effective instruction is relevant as new technologies are used in teaching and learning. The MTD distance education course content was delivered via the World Wide Web, where the course homepage was the on-line classroom and e-mail and Webchat communication supported participants' interaction. The participants of the study were the instructors and teaching assistants, as well as the undergraduate and graduate students who took the course. The electronic archive data, student assignments, and follow-up interviews with participants provided multiple data points for analysis. The Webchat archive data was analyzed using the NUD.DIST qualitative research software to sort and produce descriptive statistics. The analysis of e-mail and Webchat discourse revealed that participant interaction differed between media types and between asynchronous and scheduled the Webchat discussions. The differences were temporal, topical, and structural. Student initiated thought-provoking Webchat dialogue yet on-line content delivery, course structure, and reliability of computer systems reduced student participation in on-line discourse and course activities. Significantly, lessons learned from the design of the MTD experience indicate that on-line course development requires advance technical skill and accessible instructional technologies. Instructional designers should develop course materials with the end-users' lowest common denominator technologies to increase participation and learning opportunities. The lessons learned from the electronic discourse analysis indicate that the WWW is a very complex instructional environment that requires carefully designed pedagogical activities and interaction. Research results indicate that where as asynchronous Webchat discussions encourage students to initiate conversation topics, the overall participation in on-line discourse is low. On the other hand, scheduled Webchat discussions promote lengthy and more thought-provoking discussions, but students generally respond to instructor-posted questions or topics. / Ph. D.

Major Depressive Disorder (MDD) is a complex and chronic disease that ranks fourth as cause of disability worldwide. Thirteen to 14 million adults in the U.S. are believed to have MDD and an estimated 75% attempt suicide making MDD a major public health problem. Recently several genome-wide association (GWA) studies of MDD have been reported; however, few GWA studies focus on the analysis for MDD related phenotypes such as neuroticism and age at onset of MDD. The purpose of this study is to determine risk factors for MDD, identify genome-wide genetic variants affecting neuroticism and age at onset as quantitative traits, and detect gender differences influencing neuroticism. Bivariate and multiple logistic regression analyses were performed on 1,738 MDD cases and 1,618 non-MDD controls to determine phenotypic risk factors for MDD. Multiple linear regression analyses in PLINK software were used for GWA analyses for neuroticism and age at onset of MDD with 437,547 Single Nucleotide Polymorphisms (SNPs). Gender (OR: 1.43; 95% CI: 1.24 - 1.64) and a family history (OR: 2.88; 95% CI: 2.48 - 3.35) were significantly associated with an increased risk of MDD, which supports the findings of prior studies. Through GWA analysis 34 SNPs were identified to be associated with neuroticism (p < 10-4). The best SNP was rs4806846 within the TMPRSS9 gene (p = 7.79 x10-6). Furthermore, 46 SNPs were found showing significant gene x gender interactions for neuroticism with p<10-4. The best SNP showing gene x gender interaction was rs2430132 (p = 5.37x10-6) in HMCN1 gene. In addition, GWA analysis showed that several SNPs within 4 genes (GPR143, ASS1P4, MXRA5 and MAGEC1/2) were significantly associated with age at onset of MDD (p < 5x10-7). This study confirmed previous findings that MDD is associated with an increased prevalence in women (about 43% more compared to men) and is highly heritable among first degree relatives. Several novel genetic loci were identified to be associated with neuroticism and age at onset. Gender differences were found in genetic influence of neuroticism. These findings offer the potential for new insights into the pathogenesis of MDD.