The on-going interest in thermoelectric (TE) materials, in the form of bulk and films, motivates investigation of materials that exhibit low thermal conductivity and good electrical conductivity. Such materials are phonon-glass electron-crystals (PGEC), and the multi-component type-I clathrate Ba8Ga16Ge30 is in this category. This work reports the first investigation of Ba8Ga16Ge30 films grown by pulsed laser deposition (PLD). This dissertation details the in-situ growth of polycrystalline type-I clathrate Ba8Ga16Ge30 thin-films by pulsed laser ablation. Films deposited using conventional laser ablation produced films that contained a high density of particulates and exhibited weak crystallinity. In order to produce high quality, polycrystalline, particulate-free films, a dual-laser ablation process was used that combines the pulses of (UV) KrF excimer and (IR) CO2 lasers that are temporally synchronized and spatially overlapped on the target surface. The effect of the laser energy on stoichiometric removal of material and morphology of the target has been investigated. In addition, in-situ time-gated emission spectroscopy and imaging techniques were used to monitor expansion of components in the ablated plumes. Through these investigations, the growth parameters were optimized not only to significantly reduce the particulate density but also to produce large area stoichiometric films. Structure and electrical transport properties of the resultant films were also evaluated. This work provides new insight toward the in-situ growth of complex multi-component structures in thin-film form for potential TE applications.

No description available.

Endocannabinoids are endogenous lipid mediators involved in various biological processes, and have immunomodulatory and anti-inflammatory activities. Anandamide (arachidonoyl ethanolamine, AEA) and 2-arachidonoyl glycerol (2-AG) are the main representatives of this group. The endocannabinoid receptors CB1 and CB2 with AEA have been found in human HaCaT keratinocytes and fibroblasts, but the metabolic pathway leading to endocannabinoid production in the skin has not been fully elucidated. This study aimed to investigate the profile of endocannabinoids and their main metabolizing enzymes in human skin cells and assess whether omega-3 polyunsaturated fatty acids (n-3 PUFA) altered these profiles. In addition, an investigation was carried out to check whether UV radiation could stimulate the production of endocannabinoids and N-acylethanolamines (NAE) in human skin cells. For this purpose HaCaT keratinocytes and 46RB.1N fibroblast cells were treated with 10 and 50µM of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) or oleic acid (OA) in the presence or absence of UVR (15mJ/cm2). Data suggest that n-3 PUFA may both directly (by up-regulating NAPE-PLD levels) and indirectly (by decreasing FAAH levels) increased endocannabinoid and NAE levels in HaCaT keratinocytes and 46BR.IN fibroblasts. DHA treatment significantly decreased COX-2 expression in the absence of UVR and inhibited UVR-induced COX-2 overexpression in 46BR.IN fibroblasts. In contrast, DHA appeared to induce COX-2 up-regulation in the absence of UVR and did not prevent UVR induced COX-2 up-regulation in HaCaT keratinocytes. EPA appeared to induce COX-2 down-regulation in the absence of UVR and did not prevent UVR induced COX-2 up-regulation in both HaCaT keratinocytes and 46BR.IN fibroblasts. UVR did not have any significant effect on endocannabinoid and NAE biosynthesis. However, UVR induced endocannabinoid production in some experiments of this study. A clinical study was carried on 16 volunteers from two different ethnic groups and two different skin types. The purpose was to assess the effect of UVR on the serum endocannabinoids and NAE, therefore, the volunteers were subjected to multiple doses (1.3, SED/ 6 min) of UVR for 6 weeks. Data showed that UVR did not have major effect on human serum NAE in both skin phototypes II and V but increased 2-AG in human serum in both skin types but the more pronounced effect was evident in skin phototypes V rather than in skin phototypes II. Human serum docosahxaenoylethanolamide levels were found to be higher in White Caucasians group (skin phototypes II). Based on these it can be concluded that n-3 PUFA and UVR alter the endocannabinoids and NAE profile in HaCaT keratinocytes and 46BR.IN fibroblasts. In addition, results of the clinical study indicated that UVR has no major effects on serum endocannabinoids or NAE therefore, further studies are required to address this question in vivo.

No description available.

In dieser Arbeit werden das Wachstum und die Charakterisierung der Heterostruktur eines FeFET auf der Grundlage von BaSnO3, LaInO3 und (K,Na)NbO3 Schichten untersucht. Für jedes Material wurden die Wachstumsbedingungen bestimmt und im Hinblick auf die strukturellen und elektrischen Eigenschaften optimiert. Epitaktische BaSnO3 Filme, die auf SrTiO3 Substraten gewachsen sind, weisen eine hohe Dichte an Versetzungen auf, die ihre elektrischen Eigenschaften beeinträchtigen. Die Verwendung von NdScO3 Substraten und Einführung einer SrSnO3 Pufferschicht verbesserten die strukturellen und elektrischen Eigenschaften der BaSnO3 Schichten. Dies ermöglichte schließlich Untersuchungen an der LaInO3/BaSnO3 Grenzfläche. Schon eine geringe La-Dotierung der BaSnO3 Schicht von 0,3 % führte zur Bildung eines 2DEG nach der Grenzflächenbildung und damit zum Einschluss von Elektronen an der Grenzfläche. Dies konnte durch C-V, Van-der-Pauw und Hall-Effekt-Messungen eindeutig nachgewiesen werden. Eine deutliche Verbesserung der strukturellen und elektrischen Eigenschaften der BaSnO3 Schichten wurde durch die Verwendung von LaInO3:Ba Substraten erreicht. Diese sind gitterangepasst an BaSnO3, sodass zum ersten Mal vollständig verspannte Schichten ohne Versetzungen gewachsen werden konnten. Strukturelle und elektrische Eigenschaften von (K,Na)NbO3 Schichten wurden auf SrRuO3/DyScO3 und SrTiO3:Nb-Substraten untersucht. Auf diese Weise wurden der Einfluss der Gitterdehnung auf die kritische Schichtdicke und die Prozesse der plastischen Relaxation des Gitters bestimmt. Die elektrische Charakterisierung ergab einen hohen Leckstrom, der durch strukturelle Defekte verursacht wird. Die gesamte FeFET Heterostruktur wurde auf LaInO3:Ba Substraten gewachsen und untersucht. BaSnO3 und LaInO3 Schichten wuchsen kohärent, während (K,Na)NbO3 Schichten eine plastische Gitterrelaxation aufwiesen. Das führte zur Bildung von Strukturdefekten und zu einer Verschlechterung der ferroelektrischen Eigenschaften. / In this thesis, the design, growth and characterisation of the heterostructure of a FeFET based on BaSnO3, LaInO3 and (K,Na)NbO3 thin films are investigated. For each material, the growth conditions were determined and optimised with respect to their structural and electrical properties. Epitaxial BaSnO3 thin films grown on SrTiO3 substrates exhibit a high density of threading dislocations, which degrade their electrical properties. The use of NdScO3 substrates and the introduction of a SrSnO3 buffer layer improved the structural and electrical properties of the BaSnO3 thin films. This finally allowed investigations on the LaInO3/BaSnO3 heterointerface. Even a low La doping of the BaSnO3 layer of 0.3 % led to the formation of a 2DEG after interface formation and thus to the confinement of electrons at the interface. This could be clearly demonstrated by C-V, Van-der-Pauw and Hall effect measurements. A significant improvement of the structural and electrical properties of the BaSnO3 thin films was achieved by using LaInO3:Ba substrates. These are lattice-matched to BaSnO3 so that, for the first time, fully strained thin films could be grown without dislocations. Structural and electrical properties of (K,Na)NbO3 thin films were investigated on SrRuO3/DyScO3 and SrTiO3:Nb substrates. In this way, the influence of lattice strain on the critical film thickness and plastic lattice relaxation were determined. Their electrical characterisation revealed a high leakage current caused by structural defects. Therefore, the entire FeFET heterostructure was grown and investigated on LaInO3:Ba substrates. The BaSnO3 and LaInO3 thin films were grown coherently, while the (K,Na)NbO3 thin films exhibited plastic lattice relaxation. This led to the formation of structural defects and consequently to a deterioration of their ferroelectric properties.

No description available.

This thesis proposes a novel approach to power electronics system design that is based on the open-architecture distributed digital controller and modular power electronics building blocks (PEBBs). The proposed distributed digital controller partitions the controller in three levels of control authority. The power stage controller, designated as hardware manager, is responsible for low-level hardware oriented tasks; the high level controller, designated as applications manager, performs higher-level application-oriented tasks; and the system level controller handles system control and monitoring functions. Communications between the hardware-oriented controller and the higher-level controller are implemented with the previously proposed 125 Mbits/sec daisy-chained fiber optic communication protocol. Real-time control and status data are communicated by means of communication protocol. The distributed controller on the power converter level makes the system open, flexible and simple to use. Furthermore, this work gives an overview and comparison of current state-of-the-art communication protocols for real-time control applications with emphasis on industrial automation and motion control. All of the studied protocols have been considered as local area networks (LAN) for system-level control in power converter systems. The most promising solution has been chosen for the system level communication protocol. This thesis also provides the details of design and implementation of the distributed controller. The design of both the hardware and software components are explained. A 100 kVA three-phase voltage source inverter (VSI) prototype was built and tested using the distributed controller approach to demonstrate the feasibility of the proposed concept. / Master of Science

Le stannate (SrSnO3) et le titanate de strontium (SrTiO3) sont des oxydes de type pérovskite, de structures orthorhombique (Pbnm) et cubique (Pm3m), respectivement. Ces matériaux ont reçu beaucoup d'attention ces dernières années en raison de leurs propriétés physiques et chimiques intéressantes conduisant à différents types d'applications technologiques. Pour ces raisons, ces deux matériaux ont été combinés pour obtenir la solution solide de SrSn1-xTixO3, sous forme de poudres et couches minces. Au niveau des poudres, la solution solide a présenté des transitions de phases successives allant d'une structure orthorhombique à tétragonale puis cubique avec l’augmentation de la quantité de Ti4+ dans le système. Ces transitions ont été observées par affinement Rietveld des spectres de diffraction des rayons X et confirmées par spectroscopie Raman. Ces différentes structures cristallines ont conduit à des propriétés différentes de photoluminescence dans le spectre visible, l’émission variant d’une région de basse énergie vers les régions de plus haute énergie avec l’augmentation de Ti4+ dans la structure (structure orthorhombique (SrSnO3), tétragonale (SrSn0,75Ti0,25O3) à cubique (SrSn0,50Ti0,50O3, SrSn0,25Ti0,75O3 et SrTiO3). Ces émissions sont probablement favorisées par différents types de défauts formés dans le gap d’énergie de ces matériaux. Par ailleurs, les couches minces ont montré différents types de croissance qui ont été fortement influencés par la nature cristalline du substrat, la composition des films ainsi que par la méthode de dépôt utilisée (dépôt par voie chimique en solution – CSD – et dépôt par ablation laser pulsé – PLD). Les films minces déposés sur silice sont polycristallins (croissance aléatoire des cristallites), les couches sur saphir-R (Al2O3-012) sont également polycristallines mais avec une orientation préférentielle (h00) quand préparées par PLD (croissance texturée), excepté SrTiO3 qui est épitaxié avec une rotation de 45º par rapport au plan du substrat de saphir-R. Tous les films déposés sur LAO (LaAlO3-100) sont épitaxiés (h00) quelque soit la méthode de dépôt. De plus, les caractéristiques morphologiques et les propriétés photocatalytiques des films ont également été fortement influencées par ces mêmes paramètres cités précédemment. Concernant les propriétés photocatalytiques, les films préparés par la méthode CSD ont été plus efficaces que ceux obtenus par PLD et les couches de compositions plus riches en Sn4+ ont été plus actives face à la photodégradation du colorant Remazol jaune or, l’efficacité maximale étant observée pour la couche polycristalline de SrSnO3 obtenue par CSD avec un pourcentage de dégradation et de décoloration d’environ 55 et 90 %, respectivement. Le type de croissance des films de SrSnO3 préparés par les deux méthodes de dépôt a aussi montré une forte influence sur la photodégradation du colorant, les couches polycristallines d’orientation aléatoire obtenues sur silice étant plus efficaces que les texturées, elles-mêmes plus efficaces que les couches épitaxiales. / Strontium stannate (SrSnO3) and titanate (SrTiO3) are perovskite type oxides that have orthorhombic (Pbnm) and cubic (Pm3m) structures, respectively. These materials have received much attention due to their interesting physical and chemical characteristics, leading to a variety of technological applications. In this sense, these two materials were combined to each other in order to obtain powders and thin films of a solid solution, SrSn1-xTixO3. In relation to the powders, this solid solution presented successive phase transitions ranging from orthorhombic and tetragonal structures to a cubic one with increasing of Ti4+ amount in the composition. These transitions were observed by XRD Rietveld refinement of the samples and confirmed by Raman spectroscopy. The different crystalline structures of the compositions within the solid solution led to different photoluminescent properties in the visible spectrum varying the range of emission, moving from a lower energy region to a higher one with increasing of Ti4+ in the structure (from orthorhombic (SrSnO3), tetragonal (SrSn0.75Ti0.25O3) to cubic (SrSn0.50Ti0.50O3 ; SrSn0.25Ti0.75O3 and SrTiO3). These emissions were probably favored by specific defects created inside the band gap of these materials. On the other hand, the thin films of this system showed different growth orientations that are associated to the crystalline nature of the substrates, the composition of the thin films and the deposition method (Chemical Solution Deposition - CSD - and Pulsed Laser Deposition - PLD). The films deposited on silica substrate were polycrystalline (random growth of the crystallites), whereas the films deposited on sapphire-R (Al2O3-012) were also polycrystalline, with a preferred orientation (h00) for the films deposited by PLD (textured growth), except SrTiO3 which was rotated 45° epitaxially in the sapphire plane. On the contrary, all of the films deposited on LAO (LaAlO3-100) had an (h00) epitaxial growth. In addition to that, the morphological characteristics and photocatalytic properties were strongly influenced also by the same parameters described above. Regarding the photocatalytic efficiency of the films, those obtained by CSD were more efficient than the ones obtained by PLD. Moreover, the films with Sn4+ richer compositions were the most active in the photodegradation of the azo dye Remazol yellow gold, reaching a maximum efficiency with the polycrystalline SrSnO3 thin film obtained by CSD whose degradation and decolorization percentage were 55 and 90 %, respectively. The type of orientation of the SrSnO3 films showed also a strong influence on the photodegradation of the dye. The polycrystalline films with a random orientation obtained on silica were more efficient than the textured films and these ones were more than the epitaxial films. / O estanato (SrSnO3) e o titanato de estrôncio (SrTiO3) são óxidos do tipo perovskita que apresentam estrutura ortorrômbica (Pbnm) e cúbica (Pm3m), respectivamente. Estes materiais têm recebido bastante atenção nos últimos anos devido às suas características físicas e químicas interessantes, levando à diferentes tipos de aplicações tecnológicas. Portanto, estes dois materiais foram combinados com intuito de obter uma solução sólida, SrSn1-xTixO3, na forma de pós e filmes finos. Em relação aos pós, esta solução sólida apresentou transições de fase sucessivas com o aumento da quantidade de Ti4+ no sistema, passando de uma estrutura ortorrômbica à tetragonal levando à cúbica. Estas transições foram observadas através de difração de raios-X e refinamento Rietveld, e confirmadas por espectroscopia vibracional Raman. Os diferentes tipos de estrutura cristalina das composições da solução sólida levaram a diferentes propriedades fotoluminescentes no espectro visível, variando a região de emissão de mais baixa à mais alta energia com o aumento de Ti4+ na estrutura, ou seja, passando da estrutura ortorrômbica (SrSnO3), tetragonal (SrSn0,75Ti0,25O3) até à cúbica (SrSn0,50Ti0,50O3, SrSn0,25Ti0,75O3 e SrTiO3). Estas emissões foram provavelmente favorecidas pelos tipos de defeitos específicos criados dentro do band gap destes materiais. Por outro lado, os filmes finos deste sistema apresentaram diferentes tipos de crescimento os quais são associados à natureza cristalina dos substratos, composição dos filmes e com o método de deposição utilizado (método de deposição química em solução - CSD - e método de deposição por laser pulsado – PLD). Os filmes depositados sobre sílica e safira-R (Al2O3-012) apresentaram como policristalinos (crescimento aleatorio dos cristalitos), enquanto os filmes depositados por PLD apresentaram orientação preferencial (h00) (crescimento texturizado), com exceção do filme de SrTiO3 que é epitaxial rotacionado em 45º no plano da safira-R. Todos os filmes depositados através dos dois métodos de deposição sobre LAO (LaAlO3-100) apresentaram um crescimento epitaxial (h00). Além disso, as características morfológicas e as propriedades fotocatalíticas também apresentaram forte influencia dos mesmos parâmetros acima citados. Em relação às propriedades fotocatalíticas, os filmes obtidos pelo método CSD apresentaram maior eficiência que os obtidos por PLD e os filmes com composições mais ricas em Sn4+ foram os mais ativos na fotodegradação do corante azo Remazol amarelo ouro, chegando a uma eficiência fotocatalítica máxima com o filme policristalino de SrSnO3 obtido por CSD com percentagem de degradação e de descoloração de 55 e 90 %, respectivamente. A orientação dos filmes de SrSnO3 também mostrou uma forte influencia na fotodegradação do corante, sendo os filmes policristalinos com orientação aleatória mais eficiente que o texturizado e estes por sua vez mais eficientes que os epitaxiais.

The digitization of classical control systems presents a number of challenges and opportunities with respect to the miniaturization, distribution, reliability verification and obsolescence of both the controller and the underlying system under control. A method for the design of proportional-integral-derivative (PID) compensators realized in the form of all-digital components is presented. All-digital refers to a system implementation that is realizable with a wide range of digital logic components including discrete digital logic elements and programmable logic devices (PLDs) such as field-programmable gate arrays. The proportional, integral and derivative components of the classical PID control law were re-envisioned in terms of frequency of occurrences or counts for adaptation to combinatorial and sequential digital logic. Modification of the control scheme around this newly formed representation of system error enables the development of a PID-like FPGA-based or PLD-based controller. Details of the design of an all-digital PID-like controller including abstract, causal block diagrams and a MATLAB® and Simulink® based implementation are presented. The compensator was simulated in a velocity tracking DC motor control application and was found to perform comparably to that of a classical PID based control. Methods for assessing the resultant stability of an all-digital PID compensated system under control are discussed.

This thesis describes the design guidelines from two medical teams, electrocardiogram and pulse oximetry using embedded logic circuitry such as FPGA and microcontrollers, digital filters used to filter the signals obtained from analog converters to digital, graphic obtaining the data is displayed in a graphic display GLCD, and has an interface to send data to a PC through a port USB 2 at full speed. The digital filters used are FIR filters, these filters are chosen to be linear and time invariant, developed with 40 coefficients FIR filters, these filters were implemented in the FPGA, use a FPGA that has implemented only 20 multipliers For the implementation we used the VHDL language and algorithmic state machines in order to control the 20 boxes and get the 40 products. Filtered data in the stage of the FPGA, are taken to a microcontroller that is responsible for managing the data, can lead to a graphic display GLCD, and so we can see the signal and obtained values or you can send the data to a PC right through USB port and software right through it can see the graphics on the PC.