Les travaux de recherche présentés dans ce mémoire, portent sur la conception et l’étude de MOSFETs de puissance faible tension pour des applications automobiles micro-hybrides de type alterno-démarreur. Pour certaines de ces applications, en plus des modes de fonctionnement standards passant et bloqué, les composants développés doivent être capables de fonctionner en mode d’avalanche à fort courant et à des températures élevées. Pour reproduire en laboratoire ces conditions de fonctionnement, les MOSFETs sont soumis à un test UIS répétitif spécifique. Afin d’évaluer la température du silicium pendant ce test, plusieurs méthodes de mesure de température ont été développées et comparées. En parallèle, un suivi des paramètres électriques standards (BVDSS, IDSS, RDSon…) tout au long du test est effectué, dans le but de déterminer l’impact de l’avalanche répétitive sur le transistor. Seule la RDSon des MOSFETs semble évoluer avec le nombre d’impulsions d’avalanche. Ce phénomène est expliqué par la méthode de mesure de RDSon et par la variation de la résistance du métal source pendant le cyclage. En effet, différentes observations ont permis de constater un vieillissement de la métallisation de source du composant, accompagné d’une modification de sa résistivité. Divers types de métaux et de techniques d’assemblage ont alors été expérimentés pour tenter de limiter cet effet. Aussi des structures de test ont été conçues pour étudier l’évolution du métal et pour pouvoir comparer rapidement le comportement de différentes métallisations / Research work presented in this thesis concern the conception and the study of low voltage power MOSFETs for micro hybrid vehicles (starter alternator). For some of these applications, developed transistors must be able to operate in classical ON and OFF state mode and in avalanche mode at high current and high temperature. To reproduce this operating mode, MOSFETs are submitted to a specific repetitive UIS test. In order to evaluate silicon’s temperature during this test, several temperature measurement methods have been developed and compared. In parallel, in order to understand the impact of repetitive avalanche on the transistor, standard electrical parameters (BVDSS, IDSS, RDSon…) are monitored during the test. The only parameter that seems to be shifting with the number of cycles is the RDSon. This phenomenon is due to the measurement method and to a variation of source metallization resistance during cycling. Indeed several observations have shown source metallization ageing and a shift in its resistivity. Different metallization and assembly parameters have been tested to limit this phenomenon. Also various test structures have been designed to study metallization evolution and to compare different metallization behaviors

Aluminium Al-Mg-Si alloys are the most commonly used in automotive and construction industry. Hexagonal ’-phase is one of the metastable phases occured in this type of alloys. Unlike classic square -phase, this ’-phase is characterized by different crystalographic orientation to the matrix and shape. Standard method used for identification of aluminium alloys is scanning electron microscopy (SEM), because of its quickness and efficiency, but in case of very thin or damaged structures (as a result of metallographic process) it’s insufficient. Scanning low energy electron microscopy (SLEEM) can be appropriate for identification of mentioned precipitates due to its physical principles resulting in many advantages compared to SEM. So the most important benefits are interaction volume reduction (which leads to improvement of surface sensitivity), increase of material contrast (ability to change matrix / precipitates contrast) as well as crystalographic contrast.

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Desde hace más de una década el Grupo de Investigación en Sistemas Electrónicos y Electromectrónicos (GISEE) de la Universidad Nacional del Sur dise~na y ensaya circuitos integrados en sus distintas líneas de investigación. La fabricación de éstos ha sido posible a través de convenios específicos entre la Universidad y compañías que proveen el acceso a los procesos a escala de prototipado con fines educativos, de investigación o comercialización a baja escala. Durante el desarrollo de la investigación para acceder al título de doctorado se encontró que para realizar el prototipo de prueba de concepto era necesario realizar funciones digitales y trasmitir datos a la máxima frecuencia permitida por la tecnología. Detectada esta necesidad se comenzó con el dise~no de dos bloques, un transmisor de datos digitales y un generador de reloj. Entre las características técnicas más importantes del transmisor de datos se puede destacar la compatibilidad con los dispositivos FPGA disponibles en el laboratorio. Por el lado del generador de reloj, la característica más importante a destacar es la posibilidad de variar la frecuencia de salida mediante la configuración de una palabra digital. A medida que se avanzaba en las tareas de diseño de ambos bloques se propuso la idea de documentar el trabajo con dos fines sumamente importantes. El primero es la disponibilidad de los resultados obtenidos como bloques de propiedad intelectual para cualquier otro miembro del grupo pudiera utilizarlos. El segundo, detallar y documenta el proceso de diseño facilita la migración del dise~no a otro proceso de fabricación en caso de ser necesario. El objetivo de este trabajo es dise~nar y fabricar un sistema de trasmisión de datos digitales y un bloque de generación de reloj reutilizables por otros miembros del grupo de investigación. / Since more than ten years ago the Electronic and Electromechatronics Systems Research Group (GISEE) from Universidad Nacional del Sur design and measure integraded circuits IC in several diferents investigation topics. The fabrication have been posible thougth agreements between the university and different company, who provides acces to severals integration procces for low volume with educational and reserch purposes. A proof of concept prototype, for doctoral thesis, requires a high speed digital data transmitter and a clock generator working at the speed limit the best available tecnology. The transmitter main characteristics is the compatibility with the FPGA available at the lab. The clock generator must be able to change the output frequency using a digital word. This work have two main objetives. First, create common blocks for digital high speed systems and share it with other group membres who needed it. Second, the build an apropiated documentation to migrate the design to other technology if it is needed.

During recent years, new types of materials have been discovered with unique properties. One family of such materials are two-dimensional materials, which include graphene and MXene. These materials are stronger, more flexible, and have higher conductivity than other materials. As such they are highly interesting for new applications, e.g. specialized in vivo drug delivery systems, hydrogen storage, or as replacements of common materials in e.g. batteries, bulletproof clothing, and sensors. The list of potential applications is long for these new materials. As these materials are almost entirely made up of surfaces, their properties are strongly influenced by interaction between their surfaces, as well as with molecules or adatoms attached to the surfaces (surface groups). This interaction can change the materials and their properties, and it is therefore imperative to understand the underlying mechanisms. Surface groups on two-dimensional materials can be studied by Transmission Electron Microscopy (TEM), where high energy electrons are transmitted through a sample and the resulting image is recorded. However, the high energy needed to get enough resolution to observe single atoms damages the sample and limits the type of materials which can be analyzed. Lowering the electron energy decreases the damage, but the image resolution at such conditions is severely limited by inherent imperfections (aberrations) in the TEM. During the last years, new TEM models have been developed which employ a low acceleration voltage together with aberration correction, enabling imaging at the atomic scale without damaging the samples. These aberration-corrected TEMs are important tools in understanding the structure and chemistry of two-dimensional materials. In this thesis the two-dimensional materials graphene and Ti3C2Tx MXene have been investigated by low-voltage, aberration-corrected (scanning) TEM. High temperature annealing of graphene covered by residues from the synthesis is studied, as well as the structure and surface groups on single and double Ti3C2Tx MXene. These results are important contributions to the understanding of this class of materials and how their properties can be controlled.

Η ανίχνευση των δυναμικών δραστηριότητας συμβάλλει στη μείωση των δεδομένων προς αποστολή από ένα εμφυτεύσιμο σύστημα ασύρματης καταγραφής της νευρωνικής δραστηριότητας ενός ζώντα οργανισμού. Η παρούσα Mεταπτυχιακή Διπλωματική Εργασία έχει ως στόχο την σχεδίαση ενός ανιχνευτή δυναμικών δραστηριότητας σε νευρωνικές κυματομορφές ικανό να λειτουργεί σε περιβάλλον χαμηλής τάσης τροφοδοσίας για την επίτευξη μειωμένης κατανάλωσης ισχύος. Για το σκοπό αυτό, προτείνεται η σχεδίαση συστημάτων στο πεδίο του λογαρίθμου με τη χρήση MOS τρανζίστορ που είναι πολωμένα στην περιοχή υποκατωφλίου. Αρχικά, μελετώνται τα φυσικά χαρακτηριστικά των δυναμικών δραστηριότητας, δηλαδή το συχνοτικό τους περιεχόμενο και το σχήμα τους στο πεδίο του χρόνου. Επίσης, παρουσιάζεται ο μη-γραμμικός τελεστής ενέργειας και ο λόγος για τον οποίο αυτός καθίσταται σημαντικός στην επεξεργασία νευρωνικών σημάτων. Στη συνέχεια, παρουσιάζονται οι βασικές αρχές για τη σχεδίαση κυκλωμάτων στο πεδίο του λογαρίθμου. Ακόμα, κάνοντας χρήση των βασικών δομικών μονάδων του λογαριθμικού πεδίου, των μη-γραμμικών διαγωγών Ε Cells, υλοποιούνται τόσο οι συμπληρωματικοί τελεστές όσο και οι δομές επεξεργασίας σήματος που είναι απαραίτητες για την πραγματοποίηση του μη-γραμμικού τελεστή ενέργειας. Οι δομές αυτές είναι διαφοριστές και πολλαπλασιαστές τεσσάρων τεταρτημορίων τρόπου ρεύματος. Τέλος, δίνεται η ολοκλήρωση του συστήματος με την σχεδίαση ενός συγκριτή ρεύματος που επιτελεί την λειτουργία της κατωφλιοποίησης. Για την εξομοίωση του συστήματος, χρησιμοποιείται μια νευρωνική κυματομορφή, το Analog Design Environment του λογισμικού Cadence και οι παράμετροι της τεχνολογίας TSMC 130nm. / The detection of action potentials contributes to the reduction of data to be transmitted by an implantable wireless neural activity recording system. The goal of the present M.Sc. Τhesis is the design of an action potential detector capable of operating in a low-voltage environment, in order to achieve reduced power dissipation. For this purpose, the log-domain designing technique is suggested by using MOS transistors operating in the subthreshold region. Initially, the physical characteristics of action potentials are studied, i.e. the frequential content and time-domain shape. Moreover, the nonlinear energy operator is presented in addition to the reason that makes this system crucial for neural signal processing. Thereafter, the basic principles of designing log-domain circuits are presented. Furthermore, the complementary operators as well as the signal processing blocks that are necessary for the realization of NEO are implemented by using the main log-domain building units, the nonlinear transconductors E cells. The blocks required for the NEO implementation are current-mode differentiators and four-quadrant multipliers. Finally, the complete system is given after the design of a current comparator which is responsible for the operation of thresholding. The simulation of the system has been performed through the utilization of the Analog Design Environment of Cadence software and the design kit of TSMC 130nm process in addition to a neural waveform.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The slip synchronous-permanent magnet generator (SS-PMG) is a direct-driven, direct-to-grid generator for wind turbine applications. This investigation focuses on achieving automated grid connection and low voltage ride-through for a small-scale SS-PMG. To reduce cost and complexity, components such as blade pitch controllers and frequency converters are avoided. Instead, electromagnetic braking is employed to control turbine speed prior to grid synchronisation and compensation resistances are used to facilitate grid fault ride-through. The conditions under which the SS-PMG can be successfully synchronised with the grid are determined, indicating a need for speed control. An evaluation of electromagnetic braking strategies reveals that satisfactory speed control performance can be achieved when employing back-to-back thyristors to switch in the braking load. Simulations show that controlled synchronisation can be executed successfully under turbulent wind conditions. All controllable parameters are held within safe limits, but the SS-PMG terminal voltage drop is higher than desired. Compensation is developed to allow the SS-PMG to ride through the voltage dip profile specified by the Irish distribution code. It is found that a combination of series and shunt resistances is necessary to shield the SS-PMG from the voltage dip, while balancing active power transfer. The flexibility offered by thyristor switching of the shunt braking load is instrumental in coping with turbulent wind conditions and unbalanced dips. The South African voltage dip profile is also managed with conditional success. Following on from the theoretical design, the grid connection controller is implemented for practical testing purposes. Protection functions are developed to ensure safe operation under various contingencies. Before testing, problems with the operation of the thyristors are overcome. Practical testing shows that grid synchronisation can be undertaken safely by obeying the theoretically determined conditions. The speed control mechanism is also shown to achieve acceptable dynamic performance. Finally, the SS-PMG is incorporated into a functioning wind turbine system and automated grid connection is demonstrated under turbulent wind conditions. Future investigations may be focused on optimal control strategies, alternative solid-state switching schemes, and reactive power control. Low voltage ride-through should also be optimised for the South African dip profile and validated experimentally. / AFRIKAANSE OPSOMMING: Die glip-sinchroon permanente magneet generator (GS-PMG) is ‘n direkte dryf, direkte netwerkgekoppelde generator vir windturbine toepassings. Hierdie ondersoek fokus op die bereiking van ’n ge-outomatiseerde netwerkkoppeling en lae spanning deurry vir ‘n kleinskaalse GS-PMG. Om kostes en kompleksiteit te verminder, word komponente soos lemsteekbeheerders en frekwensie-omsetters vermy. In plaas daarvan word elektromagnetiese remwerking gebruik om die turbine spoed, voorgaande net-werksinchronisasie, te beheer, en word kompensasieweerstande gebruik om netwerkfoutdeurry te handhaaf. Die omstandighede waaronder die GS-PMG suksesvol met die netwerk gesinchroniseer kan word, is vasgestel en dit het die behoefte aan spoedbeheer uitgewys. ‘n Evaluering van elektromagnetiese remstrategië wys uit dat ’n bevredigende spoedbeheervermoë verkry kan word as anti-parallelle tiristors gebruik word om die remlas te skakel. Simulasies wys dat beheerde netwerksinchronisasie suksesvol uitgevoer kan word, selfs onder turbulente windtoestande. Alle beheerbare parameters is binne veilige perke gehou, maar die GS-PMG se klemspanningsval is gevind as hoë as verwag. Kompensasie is ontwikkel om die GS-PMG toe te laat om deur die spanningsvalprofiel, soos gespesifieer deur die Ierse distribusiekode, te ry. Dit is gevind dat ‘n kombinasie van serie- en parallelle weerstande nodig is om die GS-PMG teen die spanningsval te beskerm, terwyl aktiewe drywingsoordrag gebalanseer word. Die buigbaarheid wat verkry word met die tiristorskakeling van die parallele weerstand is noodsaaklik in die hanteering van turbulente windtoestande en ongebalanseerde spanningsvalle. Die Suid-Afrikaanse spanningsvalprofiel is ook met voorwaardelike sukses hanteer. In opvolg van die teoretiese ontwerp is die netwerkkoppelingsbeheerder vir praktiese toetsdoeleindes in werking gestel. Beskermingsfunksies is ontwikkel om veilige werking onder verskeie gebeurlikhede te verseker. Die probleme met die werking van die tiristors is oorkom voor die aanvang van die toetse. Die praktiese toetse bewys dat netwerksinchronisasie veilig gedoen kan word deur die teoretiese bepaalde voorwaardes te volg. Dit is ook getoon dat met die spoedbeheermeganisme aanvaarbare dinamiese gedrag verkry kan word. Ten laaste is die GS-PMG in ‘n werkende windturbinestelsel geïnkorporeer en outomatiese netwerkkoppeling is onder turbulente windtoestande gedemonstreer. Toekomstige ondersoeke kan toegespits word op optimale beheerstrategië, alternatiewe vaste toestand skakelingskemas en reaktiewe drywingsbeheer. Lae spanning deurry moet nog vir die Suid- Afrikaanse spanningsprofiel ge-optimeer en eksperimenteel bevestig word.

Im unter Ruhebedingungen abgeleiteten Elektroenzephalogramm (Ruhe-EEG) können Episoden niedergespannter EEG-Aktivität sowohl mit Schläfrigkeit, als auch mit geistiger Aktivität assoziiert sein. Aus diesem Grunde stellt niedergespannte EEG-Aktivität eine potentielle Fehlerquelle bei der Interpretation des Ruhe-EEGs dar. Wird niedergespannte EEG-Aktivität jedoch von für das Einschlafen charakteristischen, langsamen Augenbewegungen (Slow horizontal eye movements, SEM) begleitet, ist eine Assoziation mit geistiger Aktivität ausgeschlossen. Ziel dieser Dissertation ist die Untersuchung der Frage, ob niedergespannte EEG-Aktivität im Ruhe-EEG, welche von SEM begleitet wird (B1+), sich von solcher ohne begleitende SEM (B1-) hinsichtlich ihrer spektralen und räumlichen Zusammensetzung unterscheidet. Hierzu wurden 35 Ruhe-EEGs gesunder Probanden analysiert, welche jeweils mindestens 10s B1-, B1+ sowie 10s niedergespannter EEG-Aktivität während der Bearbeitung einer Kopfrechenaufgabe (calc) präsentierten. Unter Verwendung der Methode der standardized low resolution brain electromagnetic tomography (sLORETA) wurden für calc, B1- und B1+ die kortikalen Stromdichteverteilungen in vier verschiedenen, individuell angepassten Frequenzbändern berechnet. Die statistische Auswertung ergab signifikante Unterschiede zwischen B1- und B1+: Es zeigte bei B1- sowohl im Delta- als auch im Theta-Band eine geringere Aktivität im Bereich des Cingulums sowie benachbarten Teilen der Frontal-, Parietal- und Okzipiallappen. Zusätzlich zeigte sich eine erhöhte Aktivität im Frequenzbereich des Beta-Bandes in den Temporallappen für B1- verglichen mit B1+. Der Vergleich von calc mit B1+ erbrachte ähnliche Resultate. Die Befunde lassen eine Zugehörigkeit von B1- zu einem, verglichen mit B1+ höheren Vigilanzniveau vermuten und liefern Evidenz für die Einteilung niedergespannter Episoden im Ruhe-EEG in solche mit und ohne begleitende SEM.

Assessing the impact of domestic low-carbon technologies on the electricity distribution network requires a detailed insight into the operation of networks and the power demands of consumers. When used on a wide-scale, low-carbon technologies, including domestic scale micro-generation, heat pumps, electric vehicles and flexible demand, will change the nature of domestic electricity use. In providing a basis for the quantification of the impact upon distribution networks, this thesis details the construction and use of a high-resolution integrated model that simulates both existing domestic electricity use and low voltage distribution networks. Electricity demand is modelled at the level of individual household appliances and is based upon surveyed occupant time-use data. This approach results in a simulation that exhibits realistic time-variant demand characteristics, in both individual dwellings, as well as, groups of dwellings together. Validation is performed against real domestic electricity use data, measured for this purpose, from dwellings in Loughborough in the East Midlands, UK. The low voltage distribution network is modelled using real network data, and the output of its simulation is validated against measured network voltages and power demands. The integrated model provides a highly detailed insight into the operation of networks at a one-minute resolution. This integrated model is the main output of this research, alongside published articles and a freely downloadable software implementation of the demand model.

Le travail présenté dans ce mémoire concerne la réalisation d’un microsystème intégrant une centrale inertielle permettant la détection de mouvements. Le microsystème étudié est composé d’un accéléromètre capacitif associé à son électronique de traitement. L’accéléromètre capacitif a conduit à l’élaboration d’un outil logiciel afin de le pré-dimensionner. Ce pré-dimensionnement a été effectué en fonction des spécifications de l’application et de la technologie de fabrication. Cet outil intègre des modèles fluidiques et électrostatiques en vue de calculer des paramètres du modèle de l’accéléromètre pour une simulation système. L’électronique de traitement de l’accéléromètre capacitif a été conçue autour d’un convertisseur ”Sigma-Delta”. L’architecture ”Sigma-Delta” a nécessité des modifications pour pouvoir être adaptée au capteur. Nous avons alors développé, sous ”Matlab-Simulink”, une bibliothèque de composants permettant d’ajuster le fonctionnement du convertisseur. Une fois l’architecture optimisée et les caractéristiques des composants connues, la conception de l’architecture ”Sigma-Delta” est ainsi réalisable sous le logiciel CADENCE. / The aim of this thesis is the realisation of microsystem for movements detection. This microsystem is composed of capacitive accelerometers and of their electronics. The conception of capacitive accelerometers has induced developement of a software for the first dimensionnement of sensors. This software computes parameters of capacitive accelerometers thanks to electrostatic models, flow models, specifications of application and fabrication process. The electronics of capacitive accelerometer is a ”Sigma-Delta” convertor. The adaptation of convertor leads to developement of components libraries for ”Matlab-Simulink”. The simulation systems allows to fit parametres convertor for the application. After that,the conception of convertor under CADENCE software is then possible.