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Ramasamy, Devaraj. "Extension of electrochemically active sites in SOFCs and SOECs." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14813.
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Doutoramento em Nanociências e NanotecnologiaSolid oxide fuel (SOFCs) and electrolyzer (SOECs) cells have been promoted as promising technologies for the stabilization of fuel supply and usage in future green energy systems. SOFCs are devices that produce electricity by the oxidation of hydrogen or hydrocarbon fuels with high efficiency. Conversely, SOECs can offer the reverse reaction, where synthetic fuels can be generated by the input of renewable electricity. Due to this similar but inverse nature of SOFCs and SOECs, these devices have traditionally been constructed from comparable materials. Nonetheless, several limitations have hindered the entry of SOFCs and SOECs into the marketplace. One of the most debilitating is associated with chemical interreactions between cell components that can lead to poor longevities at high working temperatures and/or depleted electrochemcial performance. Normally such interreactions are countered by the introduction of thin, purely ionic conducting, buffer layers between the electrode and electrolyte interface. The objective of this thesis is to assess if possible improvements in electrode kinetics can also be obtained by modifying the transport properties of these buffer layers by the introduction of multivalent cations. The introduction of minor electronic conductivity in the surface of the electrolyte material has previously been shown to radically enhance the electrochemically active area for oxygen exchange, reducing polarization resistance losses. Hence, the current thesis aims to extend this knowledge to tailor a bi-functional buffer layer that can prevent chemical interreaction while also enhancing electrode kinetics.The thesis selects a typical scenario of an yttria stabilized zirconia electrolyte combined with a lanthanide containing oxygen electrode. Gadolinium, terbium and praseodymium doped cerium oxide materials have been investigated as potential buffer layers. The mixed ionic electronic conducting (MIEC) properties of the doped-cerium materials have been analyzed and collated. A detailed analysis is further presented of the impact of the buffer layers on the kinetics of the oxygen electrode in SOFC and SOEC devices. Special focus is made to assess for potential links between the transport properties of the buffer layer and subsequent electrode performance. The work also evaluates the electrochemical performance of different K2NiF4 structure cathodes deposited onto a peak performing Pr doped-cerium buffer layer, the influence of buffer layer thickness and the Pr content of the ceria buffer layer. It is shown that dramatic increases in electrode performance can be obtained by the introduction of MIEC buffer layers, where the best performances are shown to be offered by buffer layers of highest ambipolar conductivity. These buffer layers are also shown to continue to offer the bifunctional role to protect from unwanted chemical interactions at the electrode/electrolyte interface.
As pilhas de combustível e eletrolisadores de óxido sólido (PCOSs e EOSs) têm sido promovidas a tecnologias promissoras para estabelecer o abastecimento de combustível e sua utilização futura em sistemas de energia limpa. As PCOSs são dispositivos que produzem energia elétrica pela oxidação de combustíveis como o hidrogénio ou de hidrocarbonetos de elevada eficiência. Alternativamente, as EOSs funcionam de maneira inversa, na qual podem ser gerados combustíveis sintéticos ao fornecer energia eléctrica renovável ao sistema. É, pois, devido a esta natureza semelhante e ainda que inversa, que estes dispositivos têm sido tradicionalmente construídos a partir de materiais compatíveis. No entanto, a entrada no mercado destas tecnologias encontra-se ainda condicionada por diversos factores. Um dos mais limitantes, está associado a problemas de estabilidade química entre os constituintes da célula, que podem reduzir a longevidade a elevadas temperaturas de operação e/ou a um desempenho eletroquímico insuficiente. Normalmente, tais problemas de compatibilidade são minimizados pela introdução de uma camada de proteção muito fina constituída por um material condutor puramente iónico, na interface elétrodo/eletrólito. Deste modo, o objetivo deste trabalho é avaliar se modificando as propriedades de transporte destas camadas de proteção se pode conduzir ao aumento das propriedades de cinética do elétrodo, através da introdução de catiões polivalentes. A introdução de condutividade eletrónica menor na superfície do electrólito foi anteriormente relatada apresentando uma melhoria muito considerável das zonas eletroquimicamente activas para a permuta de oxigénio, reduzindo, desta forma, as perdas de resistência de polarização.Assim, esta dissertação tem por objetivo desenvolver este conhecimento para adaptar uma camada de proteção bifuncional que consiga evitar os problemas de interação química e ao mesmo tempo aumentar a cinética dos elétrodos. Esta dissertação apresenta um cenário típico de um eletrólito à base de zircónia estabilizada com ítrio combinado com um elétrodo de oxigénio contendo lantanídeos. Foram investigados como materiais de proteção, os sistemas de céria dopada com gadolínio, térbio e praseodímio. As propriedades inerentes à condução eletrónica e iónica mista (MIEC) dos materiais dopados foram analisadas e agrupadas. Posteriormente, foi realizada uma análise detalhada sobre o impacto das camadas de proteção na cinética do elétrodo de oxigénio em dispositivos PCOS e EOS. Foi dada especial atenção às potenciais relações entre as propriedades de transporte da camada proteção e subsequente desempenho do elétrodo. O trabalho também avalia o desempenho eletroquímico de cátodos de K2NiF4 com diferentes estruturas, depositadas sobre a camada de proteção que apresentou melhor desempenho, isto é, a céria dopada com praseodímio, assim como a influência da espessura da camada e da fração de Pr presente na céria. Demonstrou-se que a introdução de camadas de proteção à base de MIECs levou a um aumento drástico no desempenho do elétrodo, nomeadamente pelos MIECs de maior condutividade ambipolar. Estas camadas de proteção utlizadas provaram ser também eficazes em manter o papel de inibidores de interactividade química na interface elétrodo/eletrólito.
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Sharma, Vivek Inder. "Degradation mechanisms in La₀.₈Sr₀.₂CoO₃ as oxygen electrode bond layer in solid oxide electrolytic cells (SOECs)." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/57886.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 100-104).
High temperature steam electrolysis is an efficient process and a promising technology to convert electricity and steam or a mixture of steam and CO₂, into H₂ or syn-gas (H₂2 + CO) respectively. It is carried out in Solid Oxide Electrolytic Cells (SOECs). At the high temperature of operation, above 8000[degree] C, loss in the rate of hydrogen (or syn gas) production by SOECs has been observed. This loss of performance has been a scientific and technological challenge. The goal of this thesis is to identify the mechanisms for the loss in the electrochemical performance of SOECs due to the oxygen electrode and bond layer degradation. Our specific research objectives were focused on two main mechanisms: 1) Cr transport into the oxygen electrode and bond layer, and 2) Long-range segregation of cations in the bond layer. For SOECs provided by Ceramatec Inc. for this analysis, La₀.₈Sr₀.₂CoO₃ (LSC) was the bond layer and A₀.₈Sr₀.₂MnO₃ (ASM*) was the oxygen electrode, both comprised of perovskite structure. The approach in thesis integrated complementary spectroscopy and microscopy techniques in a novel manner to carry out the 'post-mortem' analysis of SOECs from a high level to a high resolution. Raman spectroscopy was employed to identify secondary phases on the top surface of LSC near the interconnect interphase. Surface chemistry and microstructure of the air electrode and the bond layer was studied using scanning Auger Electron Spectroscopy (AES) with nano-probe capability.
(cont.) High-resolution analysis of the cation distribution in the bulk of the LSC bond layer was achieved by employing Energy Dispersive X-ray Analysis (EDX) coupled with Scanning Transmission Electron Microscopy (STEM). Electrochemical treatment and characterization was performed to isolate the mechanism(s) governing the long-range segregation of cations, leading to the dissociation of the LSC bond layer. Less-conducting, secondary phases of Cr₂O₃, LaCrO₃, La₂CrO₆ and Co₃0₄ were identified on the top surface of LSC bond layer. The bond layer exhibited: 1) presence of Cr, with average Cr-fraction of approximately 0.07 at the surface of its grains, and 2) surface composition variation locally, with La/Co ranging widely from 0.67 to 16.37 compared to the stoichiometric La/Co value of 0.8. Sr and Co cations migrated from the bond layer structure to the LSC/interconnect interface, over a distance of 10-20 microns. Furthermore, STEM/EDX results showed the presence of phase separated regions at the nano-scale rich in Cr and La but lacking Co, and vice-versa. This indicates the dissociation of bond layer bulk structure at nano-scale. Cr fraction in LSC bulk varied from 10 to 33%, which is higher than the average Cr-content at the surface of LSC grains. The maximum Sr fraction observed in LSC bulk was 4.16%, confirming the migration of Sr to LSC/interconnect interface.
(cont.) We hypothesize that the long-range transport of Sr, Co, and Cr cations can be caused by two primary mechanisms: 1) Driven by Cr-related thermodynamics, where the Crcontaning species (i.e. at the vicinity of the interconnect) could thermodynamically favor the presence of select cations (i.e. Sr and Co) at the region interfacing the interconnect. 2) Driven by the electronic or oxygen ion current. To test these hypotheses and to isolate the governing mechanism, we simulated controlled electrochemical conditions on reference cells having ASM electrodes coated with LSC, on both sides of SSZ electrolyte, without any Cr-containing layers on the LSC bond layer. The reference cells degraded even in the absence of Cr. AES results showed that the microstructure and surface composition of the reference cells stayed stable and uniform upon the electrochemical treatment, in spite of the degradation. Thus, this thesis concludes that the Cr-related thermodynamics could be the dominant mechanism driving the uneven dissociation and segregation of cations in LSC as observed in the stack cells. As a mechanism for Cr-deposition in the LSC bond layer, we suggest that a thermodynamically-favored reaction between the La-enriched phase (at the surface of the LSC grains) and the volatile Cr-species (Cr0₃ and CrO₂(OH)) is responsible for the formation of poorly-conducting secondary phases. This interaction is likely to be limited by the presence of the segregated La-O-species which can serve as a nucleation agent for this reaction.
by Vivek Inder Sharma.
S.M.
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Zhang, Jinming. "Surface chemistry study on the SOEC electrodes during high-temperature H2O electrolysis." Electronic Thesis or Diss., Strasbourg, 2024. https://publication-theses.unistra.fr/public/theses_doctorat/2024/ZHANG_Jinming_2024_ED222.pdf.
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Cette thèse se concentre sur les performances électrochimiques et la chimie de surface des cellules d'électrolyse à oxyde solide avancées (SOEC), avec une attention particulière sur le comportement des électrodes Ni/YSZ lors de l'électrolyse de l'eau. Les SOEC présentent un potentiel considérable pour la production d'hydrogène par électrolyse de l'eau et le stockage d'énergie, tandis que les piles à combustible à oxyde solide (SOFC) utilisent l'hydrogène pour la production d'électricité. Compte tenu de l'efficacité économique, de la compatibilité thermique et de la haute conductivité des composites à base de nickel, largement utilisés dans les applications industrielles, cette recherche se concentre sur l'amélioration de ces matériaux grâce à la modification de surface. À l'aide de la spectroscopie de photoélectrons par rayons X à pression quasi ambiante (NAP-XPS), l'interaction entre les électrodes Ni/YSZ et la vapeur d'eau a été étudiée dans des conditions de circuit ouvert et de polarisation. Des modifications ont été apportées aux cathodes poreuses traditionnelles en Ni/YSZ afin d'observer directement les zones fonctionnelles proches de l'électrolyte YSZ. Les résultats ont révélé des changements dynamiques dans les états d'oxydation et la composition du Ni/YSZ dans des atmosphères de H2 et de H2O. En outre, cette étude met en lumière l'impact de l'oxydation des électrodes sur la dégradation pendant l'électrolyse et souligne la relation entre l'état d'oxydation de la surface du nickel et les performances électrochimiques de la cellule. Des nanoparticules (NP) à base de cérium ont été introduites pour modifier la surface des électrodes Ni/YSZ. Deux types de NP — le cérium dopé au nickel (NiCeOx) et le cérium non dopé (CeOy) — ont été synthétisés et utilisés pour imprégner des électrodes métalliques Ni/YSZ préfabriquées. L'étude comparative a montré que le NiCeOx présentait des performances supérieures en raison d'une meilleure dispersion et d'une taille de particules plus réduite. Les résultats obtenus par synchrotron ont également révélé que le dopage au nickel modifiait les propriétés rédox du cérium, conduisant à une réduction plus forte de Ni/YSZ par rapport à CeOy, ce qui a augmenté le nombre de sites actifs et amélioré l'efficacité de l'électrolyse. De plus, des essais expérimentaux impliquant des nanoparticules de cérium dopé au vanadium et au cobalt ont été présentés, bien que les améliorations de performances aient été limitées. Enfin, les surface des électrodes La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) ont été étudiés, en se concentrant sur la ségrégation du Sr. L'étude a également examiné le Pr6O11 en tant que catalyseur électrochimique alternatif pour les applications SOEC, démontrant son potentiel. En somme, cette recherche souligne l'impact significatif des modifications de surface des nanoparticules sur les performances électrochimiques des électrodes dans l'électrolyse de l'eau, révélant des améliorations notables en termes d'efficacité et de stabilité. La combinaison d'une conception innovante des matériaux et de techniques de caractérisation avancées offre des perspectives précieuses pour le développement de solutions énergétiques durablesThis thesis focuses on the electrochemical performance and surface chemistry of advanced Solid Oxide Electrolysis Cells (SOECs), with particular emphasis on the behavior of Ni/YSZ electrodes in water electrolysis. SOECs hold significant potential for hydrogen production through water electrolysis and energy storage, while Solid Oxide Fuel Cells (SOFCs) use hydrogen for power generation. Given the cost-effectiveness, thermal compatibility, and high conductivity of nickel-based composites, widely used in industrial applications, this research concentrates on improving these materials through surface modification. Using Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS), the interaction between Ni/YSZ electrodes and water vapor under both open-circuit and polarization conditions was investigated. Modifications to traditional porous Ni/YSZ cathodes were made to directly observe the functional electrode areas near the YSZ electrolyte. Results revealed dynamic changes in the oxidation states and composition of Ni/YSZ in H2 and H2O atmospheres. Additionally, the study emphasizes the impact of electrode oxidation on degradation during electrolysis and highlights the relationship between the nickel surface oxidation state and the cell’s electrochemical performance. Cerium-based nanoparticles (NPs) were introduced to modify the surface of Ni/YSZ electrodes. Two types of NPs—Ni-doped ceria (NiCeOx) and undoped ceria (CeOy)—were synthesized and used to impregnate pre-fabricated Ni/YSZ cermet electrodes. The comparative study demonstrated that NiCeOx exhibited superior performance due to enhanced dispersion and reduced particle size. Synchrotron results further showed that Ni doping altered the redox properties of ceria, leading to stronger reduction of Ni/YSZ compared to CeOy, which increased the number of active sites and improved electrolysis efficiency. Additionally, the thesis presents experimental trials involving vanadium and cobalt-doped ceria nanoparticles, although their performance enhancements were limited. Finaly the surface state of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) electrodes were explored, focusing on Sr segregation. The study also examined Pr6O11 as a potential alternative electrocatalyst for SOEC applications. Overall, the research highlights the significant impact of nanoparticle surface modifications on the electrochemical performance of electrodes in water electrolysis, revealing substantial improvements in both efficiency and stability. The combination of innovative material design and advanced characterization techniques offers valuable insights for the future of sustainable energy solutions
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Vibhu, Vaibhav. "Stabilité et vieillissement des études de nickelates base praséodyme comme cathodes pour oxyde solide piles à combustible." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0017/document.
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Ce travail de thèse est consacré à l’étude des nickelates La2-xPrxNiO4+δ, comme nouveaux matériauxde cathodes pour piles à combustible haute température, SOFC, et en particulier à la caractérisationde leur stabilité chimique et leur comportement en fonctionnement. En effet, du fait de leurpropriété de conduction mixte ionique et électronique, MIEC, les nickelates de structure typeK2NiF4, Ln2NiO4+δ (Ln = La, Pr, Nd), correspondant au terme n = 1 de la série de Ruddlesden-Popper (An+1MnO(3n+1)), sont des matériaux prometteurs pour des fonctionnements à températureintermédiaire, IT-SOFC (T < 800 °C). Compromis entre la stabilité chimique de La2NiO4+δ et lestrès bonnes performances électrochimiques de Pr2NiO4+δ, les phases La2-xPrxNiO4+δ, ont étésynthétisées et leurs propriétés physico-chimiques, de transport et électrochimiques ont étédéterminées. L’étude approfondie des caractéristiques des électrodes par spectroscopied’impédance en cellules symétriques a été réalisée à courant nul et sous polarisation anodique etcathodique sur des périodes d’un mois. De façon surprenante, même après la dissociation complètede Pr2NiO4+δ en PrNiO3-δ, Pr4Ni3O10+δ et Pr6O11, la résistance de polarisation ne montre pas dechangement significatif. L’étude de PrNiO3-δ et Pr4Ni3O10+δ, comme matériau de cathode pour pilesà combustible, démontre l’excellent comportement de la phase Pr4Ni3O10+δ et ceci en cellulesymétrique (Rp (Pr4Ni3O10+δ) = Rp (Pr2NiO4+δ) = 0.15 Ω.cm² à 600 ° C) et cellule complète (1.6W.cm-2 at 800 °C)This PhD work is dedicated to stability and ageing studies of Praseodymium based nickelates ascathodes for Solid Oxide Fuel Cells (SOFCs). With this respect Ln2NiO4+δ (Ln=La, Pr or Nd)compounds with the K2NiF4 type structure act as alternative cathode materials for IT-SOFC due totheir mixed ionic and electronic conductivity (i.e. MIEC properties). Pr2NiO4+δ shows excellentelectrochemical properties at intermediate temperature (i.e. low polarization resistance Rp value, Rp= 0.03 Ω.cm² at 700 °C), while La2NiO4+δ exhibits higher chemical stability. So, the properties ofLa2-xPrxNiO4+δ nickelates were investigated with the aim to find best compromise between chemicalstability and electrochemical performances. After synthesis, the physical and chemical properties aswell as their transport and electrochemical properties have been determined. Measurements of thepolarization resistance of symmetrical half-cells have been carried out by impedance spectroscopy.Then, the chemical stability and the electrochemical performance of the materials have been studiedfor duration up to one month. As an interesting point, even after complete dissociation of Pr2NiO4+δinto PrNiO3-δ,Pr4Ni3O10+δ and Pr6O11, the polarization resistance does not show significant change.So finally, two new materials PrNiO3-δ and Pr4Ni3O10+δ were investigated as SOFCs cathodeshowing very promising results for Pr4Ni3O10+δ in symmetrical cell (Rp (Pr4Ni3O10+δ) = Rp(Pr2NiO4+δ) = 0.15 Ω.cm² à 600 ° C) and complete cell (1.6 W.cm-2 at 800 °C)
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Frank, Nadine P. R. "Umsetzung von Kohlenwasserstoffen in SOFCs." München Dr. Hut, 2010. https://mediatum2.ub.tum.de/node?id=808645.
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Russi, Luigi. "modeling the pressure drop and thermal profile of a novel solid oxide fuel cell stack design with a homogenized approach." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Find full textAbstract:
Le celle a combustibile a ossidi solidi (SOFCs) rappresentano una tecnologia chiave in uno scenario di decarbonizzazione delle attività umane per i prossimi anni.
Gli stack attualmente disponibili presentano elevati gradienti di temperatura e grandi perdite di carico attraverso lo stack, così come distribuzioni di corrente disuniformi, problemi di perdita di contatto e di deterioramento.
Un innovativo design dello stack, detto"Chessboard", è stato ideato al DTU Energy.
La determinazione dei campi di temperatura, pressione e velocità nello stack tramite simulazione risulta fondamentale per valutare la qualità di un certo design. Infatti non sempre è possibile misurare sperimentalmente grandezze fisiche locali all'interno dello stack.
In questo lavoro un modello tridimensionale (3D) dello stack è stato costruito. L'approccio modellistico utilizzato si basa sulla tecnica di omogenizzazione. Un metodo efficiente a livello computazionale basato sull'utilizzo di una geometria semplificata, ma con proprietà termofisiche anisotropiche che rispecchino la vera geometria dello stack per reincrementare il livello di dettaglio.
Fra tutte le fisiche che descrivono i fenomeni in una SOFC, solo il moto dei fluidi e la trasmissione del calore sono effettivamente risolte dal modello nell'attuale stadio di sviluppo, mentre i fenomeni elettrochimici sono definiti come parametri in ingresso.
Una volta impostato il modello, è stato eseguito uno studio parametrico, con lo scopo di ottenere i profili di temperatura e pressione in funzione delle dimensioni dello stack, dell'eccesso d'aria, della pressione in ingresso dell'aria e della dimensione dei pori. Individuando quindi una finestra di esercizio sicura per i 4 parametri considerati.
Dai risultati si evince che è possibile trovare diverse combinazioni di parametri che soddisfino l'obiettivo di progetto dato da limiti sui materiali costituenti lo stack, tutto questo con dei tempi di risoluzione nell'ordine dei minuti.
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Fagg, Duncan Paul. "Anodes for SOFCs (solid oxide fuel cells)." Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU082955.
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The success of Solid Oxide Fuel Cells (S.O.F.C) rests heavily on material selection. The performances of several compounds were investigated as possible anode materials, starting with reduced titanates such as the magnesium titanate and zirconium titanate. These compositions, although possessing many qualities beneficial for use as an anode material, were found to be too unstable for practical use. For this reason further work concentrated on stable, zirconia based, compounds with exhibited mixed conduction under reducing atmospheres. The mobility of electronic carriers is considered to be much higher than that of ionic defects, therefore, promising mixed conductors can be formed by doping a good ionic conductor with a small concentration of transition metal ions. Zirconia based mixed conductors were studied for two reasons. Firstly, zirconia stabilised in the cubic defect fluorite structure, exhibits a high level of ionic conductivity. Secondly, it is the most common electrolyte material for an S.O.F.C. An anode based on zirconia would, therefore, be expected to offer a good physical compatibility with the electrolyte material and to exhibit a high ionic contribution to total conductivity. Large defect fluorite solid solutions in the systems Y2O3-ZrO2-Nb2O5, Yb2O3-ZrO2-Nb2O5 and CaO-ZrO2-Nb2O5 were established, which enabled the effects of composition, dopant size and charge on conduction to be investigated. These effects were shown to be linked to structure. From these results and comparisons with the Y2O3-ZrO2-TiO2 system, optimum, mixed conducting, compositions were established. The sample Y0.25Ti0.15Zr0.60O1.875 exhibited the best mixed conducting properties to date, obtained for compositions based on zirconia.
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Zianbetov, Eldar. "Horlogerie distribuée pour les SoCs synchrones." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-01053729.
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Cette thèse aborde le problème de génération d'horloge globale dans les SoCs complexes dans le contexte des technologies CMOS profondément submicroniques. Actuellement, afin de contourner les difficultés liées aux techniques classiques de distribution d'horloge (p.ex. arbre, grille) dans les systèmes synchrones, les concepteurs qui désirent de se rendre sur le paradigme Synchronisation Globale se tournent vers les techniques de synchronisation rompant avec les approches classiques (par exemple oscillateurs distribués, les ondes stationnaires , oscillateurs couplés, les retards programmables). Cette étude s'inscrit dans ce courant. Dans ce travail, nous avons étudié et mis au point un système de génération d'horloge sur puce destiné à un SoC synchrone de haute fiabilité. Cette architecture est basée sur un réseau d'oscillateurs couplés en phase et en fréquence à l'aide d'un réseaux de boucles à verrouillage de phase tout numériques (ADPLLs). Pendant cette recherche nous avons mis au point les spécifications et choisi une architecture de réseau. Un modèle théorique du système a été mis en place en collaboration avec CEA-LETI et Supélec dans le cadre du projet ANR HODISS. Nous avons analysé le comportement du système dans les simulations sur différents niveaux d'abstraction, en enquêtant des conditions de stabilité de son fonctionnement synchrone. L'ADPLL a été proposé comme un nœud élémentaire du réseau de synchronisation distribuée. L'utilisation d'ADPLL permet de contourner les difficultés d'implémentation, qui sont généralement associées à PLL analogique. Nous avons conçu les blocs principaux de l'ADPLL: un oscillateur à commande numérique (Digitally-Controlled Oscillator, DCO), un détecteur de phase/fréquence (PFD) et un bloc de traitement d'erreur. Une technique de conception basée sur les cellules a été adapté pour le développement d'oscillateur. Cette technique réduit considérablement la complexité de l'implémentation de l'oscillateur. Les autres blocs ont été conçus en utilisant un flot de conception numérique commun. Afin de réduire les risques associés à l'implémentation de silicium, le système a été validé dans une plate-forme de prototypage FPGA. Les résultats des mesures ont montré que la synchronisation de réseau se comporte comme prédit par la théorie et ainsi que les simulations. Deux circuits de prototypage ont été conçus, mis en œuvre et testés dans une technologie CMOS 65 nm de STMicroelectronics. La première puce est une preuve de concept d'un DCO conçu très linéaire et monotone. Les paramètres mesurés de l'oscillateur sont conformes aux spécifications. La performance mesurée a démontré une gigue de moins de 15 ps rms, en consommant 6.2 mW/GHz @ 1.1 V. La plage de réglage de l'oscillateur est 999-2480 MHz avec une résolution de 10 bits. La deuxième puce est un réseau d'horloge avec 4x4 nœuds qui se compose de 16 ADPLLs distribués. Chacun d'entre eux utilise les blocs conçu précédemment: DCO, PFD et bloc de traitement d'erreur. Les expérimentes ont montré que la technique proposée de génération d'horloge distribuée est réalisable sur une puce réelle CMOS. La performance mesurée démontre l'erreur de synchronisation entre les oscillateurs voisins moins de 60 ps, alors que la consommation d'énergie est 98.47 mW/GHz.
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Barry, A. C. "Regulation of TCR signalling by SOCS." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479241.
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Stanislowski, Michael. "Verdampfung von Werkstoffen beim Betrieb von Hochtemperaturbrennstoffzellen (SOFCs)." Jülich : Forschungszentrum, Zentralbibliothek, 2006. http://d-nb.info/98787103X/34.
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Hibino, Takashi, Atsuko Tomita, Mitsuru Sano, Masahiro Nagao, Kohsuke Okamoto, Takanori Kawai, and Masaya Yano. "Single-Chamber SOFCs Using Dimethyl Ether and Ethanol." The Electrochemical Society, 2007. http://hdl.handle.net/2237/18431.
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Lysunenko, Natalia, Mykola Brychevskyi, Ihor Polishko, and Valentine Mokiychuk. "Electrical efficiency of anode- and electrolyte-supported SOFCs." Thesis, Institute of Technical Sciences of SASA, 2016. http://er.nau.edu.ua/handle/NAU/28421.
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Solid oxide fuel cell is considered now as a promising technology for reliable and
environmentally safe energy generation. SOFC convert chemical energy of fuel and oxidant
directly into electrical energy through electrochemical reactions.
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BRUNETTI, Emanuela. "Caratterizzazione di generatori SOFCs tubolari a supporto anodico." Doctoral thesis, Università Politecnica delle Marche, 2013. http://hdl.handle.net/11566/242687.
Full textAbstract:
I sistemi basati sulla tecnologia delle celle a combustibile sono fra i più promettenti per
la produzione di energia elettrica per le loro elevate efficienze energetiche, le basse
emissioni ambientali e per l’ampiezza delle possibili applicazioni. La tecnologia trova
impiego nei settori della generazione distribuita, della cogenerazione residenziale e
industriale e della generazione portatile. Tra le varie tipologie di celle a combustibile
quella ad ossidi solidi (SOFC) sta riscuotendo un interesse sempre più crescente in
quanto l’alta temperatura di funzionamento rende questa tecnologia particolarmente
interessante per la micro-cogenerazione. La presente tesi mostra una analisi teorica e
sperimentale di un generatore SOFC tubolare a supporto anodico prodotto dalla
società statunitense Acumentrics Corporation. L'attività si è concentrata sullo studio
termo-fluidodinamico e della reazione elettrochimica di una singola cella a
combustibile ad ossidi solidi tubolare a supporto anodico con il principale obiettivo di
implementare la reazione elettrochimica in ANSYS-FLUENT per una analisi puntuale dei
fenomeni che intervengono nella singola cella stessa. Inoltre lo stesso approccio è
stato applicato allo studio dell'intero stack di celle a combustibile e ad un recuperatore
catodico. Tutte le caratteristiche dimensionali ed operative dei componenti considerati
sono stati forniti da Acumentrics Corporation. Si è inoltre compiuta la caratterizzazione
sperimentale delle prestazioni di un prototipo di generatore SOFC, sempre fornito da
Acumentrics Corporation. Il generatore è stato installato all'interno di un banco di
prova ed alimentato ad idrogeno. Data la correlazione lineare tra alcune variabili di
funzionamento i dati sono stati interpretati attraverso il metodo di analisi multivariata
per l'analisi delle componenti principali. Attraverso tale metodo è stato possibile
derivare regole generali che descrivono il funzionamento di un sistema e da queste
regole studiare la risposta del sistema alla variazione dei parametri di funzionamento
anche in condizioni diverse da quelle sperimentali.The systems based on the technology of fuel cells are among the most promising for the production of electrical energy for their high energy efficiency, low environmental emissions and wideness of possible applications. The technology is normally proposed for distributed generation, residential and industrial cogeneration and portable generation. Among the various types of fuel cells, the solid oxide fuel cells (SOFCs) are getting a growing interest because the high operational temperatures make this technology attractive for micro-cogeneration. This thesis shows a theoretical and experimental analysis of a tubular-anode-supported SOFCs generator produced by Acumentrics Corporation. The activity was focused on the study of the thermo-fluid dynamics and electrochemical reaction of a single tubular-anode-supported solid oxide fuel cell using ANSYS-FLUENT. The same approach has been applied to the study of the of fuel cell system and to the cathodic recuperator. All the considered dimensions and components were provided by Acumentrics Corporation. Furthermore the experimental characterization of the performance of a prototype SOFC generator was carried out. The generator was installed in a test rig and it was powered by hydrogen. The data were analyzed through a multivariate method (principal component analysis). Applying this method to the experimental data, a linear correlation among some operational variables was highlighted. Through this method it was possible to derive general rules describing the operation of the system and study the response of the system to changes in operating parameters even in conditions different from the experimented one.
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Vaiciunas, Aline. "Expressão de genes hipotalâmicos em novilhas Nelore precoces e não precoces." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/10/10135/tde-13082007-110544/.
Full textAbstract:
O mecanismo pelo qual a sinalização da leptina no hipotálamo permite o início da puberdade ainda não foi esclarecido. Um possível mecanismo para a ação molecular da leptina no eixo reprodutivo é constituído por uma alteração na sinalização do NPY. Objetivou-se neste estudo foi verificar se novilhas precoces Bos taurus indicus possuem a expressão modificada de genes hipotalâmicos relacionadas à sinalização da leptina. Dentre uma população de 500 novilhas entre 20 e 25 meses de idade, 100 novilhas foram selecionadas com base nas características da raça (Nelore), mês de nascimento e peso corpóreo (290 kg). Estas 100 novilhas foram classificadas de acordo com a presença ou não de um corpo lúteo (CL) notável. Dez novilhas sem um CL e dez novilhas com CL notável receberam uma injeção de prostaglandina, e de acordo com a observação visual de cio e palpação retal, 6 novilhas precoces e 6 novilhas não precoces foram selecionadas para o experimento. Estas 12 novilhas foram abatidas e amostras de tecido do hipotálamo foram coletadas e congeladas em nitrogênio liquido. A expressão de SOCS-3, NPY, NPY-Y1 e NPY-Y4 no hipotálamo foi quantificada por PCR em tempo real usando uma proteína ribossomal RP-L19 como um gene de referência. A expressão hipotalâmica de SOCS-3 ou NPY não foi diferente entre os grupos de novilhas (P > 0,50). Acreditava-se que as novilhas ciclando poderiam ser resistentes à leptina devido a um aumento na expressão do SOCS-3 no hipotálamo. Houve uma tendência (P = 0,10) de redução na expressão dos receptores do NPY, NPY-Y1 e NPY-Y4 em novilhas que atingiram a puberdade precocemente. A expressão do NPY-Y1 foi 8.3 vezes menor e a expressão do NPY-Y4 foi 14.3 vezes menor em novilhas precoces. Quando analisados em conjunto, houve uma redução de 11 vezes na expressão dos receptores de NPY em novilhas precoces, e este efeito foi estatisticamente significante (P = 0,03). Estes resultados sugerem que, a menor expressão dos receptores de NPY pelo hipotálamo de novilhas precoces pode torná-lo menos sensível à inibição do NPY, e permitir a obtenção da puberdade com maior peso vivo e níveis menores de leptina circulante. Em conclusão, não houve uma correlação entre a expressão do gene NPY e SOCS-3 e a precocidade sexual das novilhas Nelore, porém houve uma tendência significativa de redução da expressão dos receptores de NPY-Y1 e NPY-Y4 no hipotálamo das novilhas precoces.The molecular mechanism by which leptin signaling in the hypothalamus might permit the initiation of puberty has not been elucidated. One possible mechanism for leptin molecular action on the reproductive axis is affecting NPY signaling. It was our objective to test whether early-maturing Bos indicus heifers have altered expression of hypothalamic genes related to leptin signaling. Among a population of 500 heifers between 20 and 25 months of age, 100 heifers were selected base on breed attributes (Nelore), month of birth, and body weight (290 kg). These 100 heifers were scored as prepubertal or pubertal according to the presence or not of a noticeable corpus luteum (CL). Ten heifers without a CL and ten heifers with noticeable CL received a prostaglandin injection, and according to visual observation of heat and rectal palpation, 6 prepubertal and 6 pubertal heifers were selected for the experiment. These 12 heifers were slaughtered and samples of hypothalamus were collected and frozen in liquid nitrogen. Expression of SOCS-3, NPY, NPY-Y1 and NPY-Y4 at the hypothalamus was quantified by real-time PCR using the ribosomal protein RP-L19 as a reference gene. Hypothalamic expression of SOCS-3 or NPY was not different between groups of heifers (P > 0, 50). It was thought that late-maturing heifers could be resistant to leptin due to an increased expression of SOCS-3 at the hypothalamus. However, there was a tendency for NPY-Y1 and NPY-Y4 expression to be reduced in heifers that reached puberty earlier (P = 0,10). Expression of NPY-Y1 was 8.3-folds lower and NPY-Y4 expression was 14.3-folds lower in early-maturing heifers. When analyzed together, there was an 11-fold reduction in NPY receptors expression in early-maturing heifers, and this effect was statistically significant (P = 0,03). These results suggest that, because of the lower expression of NPY receptors, the hypothalamus of early-maturing heifers could be less sensitive to NPY inhibition, and therefore reach puberty with lower levels of circulating leptin. In conclusion, there was no effect between the expression of NPY and SOCS-3 and sexual precocity of Nelore heifers, but there was a significant tendency of reduction in NPY-Y1 e NPY-Y4 receptors expression in the hypothalamus of sexually precocious heifers.
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Contino, Anna Rita. "Modification of Anode Microstructure to Improve Redox Stability of Solid Oxide Fuel Cells (SOFCs)." Doctoral thesis, University of Trento, 2010. http://eprints-phd.biblio.unitn.it/349/1/Modification_of_Anode_Microstructure_to_Improve_Redox_Stability_of_Solid_Oxide_Fuel_Cells_(SOFCs).pdf.
Full textAbstract:
In the last decade the increase in energy demand, the awareness of limited availability of fossil fuels and the need to reduce green house gases emission impelled governments and research institutions to focus on the study of renewable energy sources such as solar, wind and biomass derived energy and on the increase in the energy production devices efficiency.
Within such scenario a relevant contribution is given by fuel cells technologies as advanced power generation system. Fuel cells are high efficiency devices and comply with the request of environmental friendly source of energy. They convert directly fuel energy into power and heat by electrochemical reactions without the need for combustion as intermediate step. The possibility to use Hydrogen makes fuel cells virtually zero-emission devices being water the only reaction product; nevertheless, also the use of hydrocarbons as fuel reduces considerable CO2 emissions.
Among the different systems, solid oxide fuel cells (SOFCs) operate at high temperatures (650-1000°C) and allow to achieve the highest electrical efficiency, from 45 to 60% for common fuels, values not attainable by traditional electrical power generation methods, and up to 70% in combination with a gas turbine for Hybrid Power System generation, with an overall electrical and thermal efficiency higher than 90%.
Moreover, such technology presents many advantages such as the possibility to be fed with different fuels, the absence of moving parts, modularity and limited emissions. These characteristics make SOFC suitable for application in the distributed generation market.
Despite all the mentioned advantages, SOFCs show problems that make these devices not suitable for the production on industrial scale yet. In particular they present low reliability and are not competitive with traditional powers sources.
SOFCs are constituted by single cells (consisting of an anode and a cathode separated by a solid electrolyte) that are collected together in a stack by interconnects in order to obtain the required power. This means that a stack is a multilayer assembly of materials with different thermal, mechanical and chemical properties that need to fulfil many prerequisites for their own function. Moreover, some of these properties must match for other connected components; for instance they have to show similar thermal expansion coefficients, to be stable at high temperatures and during thermal transients.
Due to the high working temperature, stack components are necessarily subjected to degradation phenomena, which reduce their long term reliability. Among them, poisoning of cathode by Chromium evaporation from metallic interconnects, chemical interactions between glass–ceramic sealants and ferritic steel interconnects, anode poisoning caused by carbon or sulphur deposition, reduction of electrical conductivity are worthy of mention. Furthermore, various cycling conditions such as thermal cycle, redox cycle, and load cycle affect stability of SOFCs. All these degradation phenomena must be minimized in order to increase SOFC reliability. All these issues are object of intense research.
The research work of the present thesis has been focused on the increase of redox stability of anode supported cells, which is considered one of the key point to improve stack reliability.
The state of the art materials for the anode is Ni/YSZ cermet due to its high performance. Nevertheless, this cermet is prone to severe degradation upon redox cycling.
Due to the high operating temperatures, Nickel particles tend to coalesce and coarsen. Fuel supply interruptions, over-potentials and leakages can cause the re-oxidation of Ni to NiO with a consequent volumetric expansion that can generate internal stresses and lead to cracks formation within the YSZ network and the electrolyte resulting in cell failure. Different approaches can be taken in account in order to minimize redox instability.
In order to study redox phenomena and produce redox stable cells many aspects related to the modification of anodic microstructure were analyzed. Among these, one of the most promising method is to modify the anode microstructure by increasing its porosity.
The present thesis is divided in two parts. In the first section the theoretical background of fuel cells, specifically SOFCs, is reported. A particular attention is dedicated to describe redox phenomenon and the state of the art of the research in this field.
The second experimental part concerns with the production of anodes with improved microstructure. The modification of microstructure was realized by using different powders and by adding different pore formers and doping elements. A detailed study of the effects on redox stability of the microstructure modifications induced by the addition of each of the aforesaid substances is described.
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NOVARESIO, VALERIO. "Design and modelling an innovative SOEC stack." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2604774.
Full textAbstract:
The present work is focused on the design of a solid oxide cell stack that mainly works in electrolysis mode. The framework of the activity is the energetic issue related to the renewable sources management and storage capabilities. The analysis starts observing the energetic issue from an alternative standpoint that emphasizes the ethical aspects and instills in the reader the secondary importance of the efficiency respect to the feasibility and the robustness of the devices. In order to predict the stack performance, a new numerical solver has been developed based on open source tool. This multi-physic solver can handle complete SOC stack both in fuel cell mode and in electrolysis mode. As a part of this activity an insight concerning SOC Electrochemical Impedance Spectroscopy physical simulation has been done. This part of the solver can be coupled with additional plugins and provides the basis for the impedance analysis of the low frequency part of the SOC spectrum. Basing on pragmatic approach a new stack design was proposed and technical drawings have been released. The stack is based on tubular cells considering some peculiarity of the planar configuration especially concerning charge transfer between electrodes and external current takes. Some simulations have been run in order to validate the main assumptions of the design process.
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DE, CARVALHO MAURICIO. "Innovative Techniques for Testing and Diagnosing SoCs." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2612755.
Full textAbstract:
We rely upon the continued functioning of many electronic devices for our everyday welfare,
usually embedding integrated circuits that are becoming even cheaper and smaller
with improved features. Nowadays, microelectronics can integrate a working computer
with CPU, memories, and even GPUs on a single die, namely System-On-Chip (SoC).
SoCs are also employed on automotive safety-critical applications, but need to be tested
thoroughly to comply with reliability standards, in particular the ISO26262 functional
safety for road vehicles.
The goal of this PhD. thesis is to improve SoC reliability by proposing innovative
techniques for testing and diagnosing its internal modules: CPUs, memories, peripherals,
and GPUs. The proposed approaches in the sequence appearing in this thesis are described
as follows:
1. Embedded Memory Diagnosis: Memories are dense and complex circuits which
are susceptible to design and manufacturing errors. Hence, it is important to understand
the fault occurrence in the memory array. In practice, the logical and physical
array representation differs due to an optimized design which adds enhancements to
the device, namely scrambling. This part proposes an accurate memory diagnosis
by showing the efforts of a software tool able to analyze test results, unscramble
the memory array, map failing syndromes to cell locations, elaborate cumulative
analysis, and elaborate a final fault model hypothesis. Several SRAM memory failing
syndromes were analyzed as case studies gathered on an industrial automotive
32-bit SoC developed by STMicroelectronics. The tool displayed defects virtually,
and results were confirmed by real photos taken from a microscope.
2. Functional Test Pattern Generation: The key for a successful test is the pattern applied
to the device. They can be structural or functional; the former usually benefits
from embedded test modules targeting manufacturing errors and is only effective
before shipping the component to the client. The latter, on the other hand, can be
applied during mission minimally impacting on performance but is penalized due
to high generation time. However, functional test patterns may benefit for having
different goals in functional mission mode. Part III of this PhD thesis proposes
three different functional test pattern generation methods for CPU cores embedded
in SoCs, targeting different test purposes, described as follows:
a. Functional Stress Patterns: Are suitable for optimizing functional stress during
I
Operational-life Tests and Burn-in Screening for an optimal device reliability
characterization
b. Functional Power Hungry Patterns: Are suitable for determining functional
peak power for strictly limiting the power of structural patterns during manufacturing
tests, thus reducing premature device over-kill while delivering high test
coverage
c. Software-Based Self-Test Patterns: Combines the potentiality of structural patterns
with functional ones, allowing its execution periodically during mission.
In addition, an external hardware communicating with a devised SBST was proposed.
It helps increasing in 3% the fault coverage by testing critical Hardly
Functionally Testable Faults not covered by conventional SBST patterns.
An automatic functional test pattern generation exploiting an evolutionary algorithm
maximizing metrics related to stress, power, and fault coverage was employed
in the above-mentioned approaches to quickly generate the desired patterns. The
approaches were evaluated on two industrial cases developed by STMicroelectronics;
8051-based and a 32-bit Power Architecture SoCs. Results show that generation
time was reduced upto 75% in comparison to older methodologies while
increasing significantly the desired metrics.
3. Fault Injection in GPGPU: Fault injection mechanisms in semiconductor devices
are suitable for generating structural patterns, testing and activating mitigation techniques,
and validating robust hardware and software applications. GPGPUs are
known for fast parallel computation used in high performance computing and advanced
driver assistance where reliability is the key point. Moreover, GPGPU manufacturers
do not provide design description code due to content secrecy. Therefore,
commercial fault injectors using the GPGPU model is unfeasible, making radiation
tests the only resource available, but are costly. In the last part of this thesis, we
propose a software implemented fault injector able to inject bit-flip in memory elements
of a real GPGPU. It exploits a software debugger tool and combines the
C-CUDA grammar to wisely determine fault spots and apply bit-flip operations in
program variables. The goal is to validate robust parallel algorithms by studying
fault propagation or activating redundancy mechanisms they possibly embed. The
effectiveness of the tool was evaluated on two robust applications: redundant parallel
matrix multiplication and floating point Fast Fourier Transform.
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Corre, Gaël Pierre Germain. "Studies of alternative anodes and ethanol fuel for SOFCs /." St Andrews, 2009. http://hdl.handle.net/10023/841.
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Corre, Gaël Pierre Germain. "Studies of alternatives anodes and ethanol fuel for SOFCs." Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/841.
Full textAbstract:
This thesis explores the development of efficient engineered composite alternative anodes and the use of ethanol as a fuel for Solid Oxide Fuel Cells. SOFCs can in theory operate with fuels other than hydrogen. However, this requires the design of efficient alternative anode material that do not catalyze carbon formation and that are tolerant to redox cycles. An innovative concept has been developed that relies on the impregnation of perovskites into porous YSZ structures to form the anode functional layer. Catalysts are added to provide sufficient catalytic activity. Cells with anodes containing LSCM and Ce/Pd have displayed excellent performance. At 800°C, and with a 65 μm thick electrolyte, the power outputs were above 1W/cm² in humidified hydrogen and 0.7 W/cm² in humidified methane. These electrodes have shown the ability to reduce CO₂ electrochemically with an efficiency that is similar to that which can be achieved for H₂O electrolysis and the anodes could operate on pure CO₂. The importance of incorporating an efficient catalyst was demonstrated. The use of 0.5 wt% of Pd is sufficient to dramatically improve the performance in such electrodes. The microstructure of impregnated LSCM-YSZ composites plays an important role in the high performance obtained. A layer of LSCM nanoparticles covering the YSZ is formed upon reduction, offering a great surface area for electrochemical reactions. The fabrication method presented in this thesis is a powerful tool for designing microstructures in situ. Among the various fuels under consideration for SOFCs, ethanol offers outstanding advantages. Half cell measurements have been performed to characterize the performance of different types of anodes when operated on ethanol/steam mixtures. Steady performance was achieved on LSCM-CGO anodes. Carbon deposits from gas phase reactions have been evidenced and were found to be responsible for the performance enhancement when the cell is operated in diluted ethanol as compared to hydrogen. At high steam content, polarization resistances of LSCM-CGO-YSZ anodes in ethanol/ steam mixtures were shown to be below 0.3 Ω.cm² at 950°C.
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Flack, Natasha. "Thin film components for solid oxide fuel Cells (SOFCs)." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2007271/.
Full textAbstract:
Thin film components for solid oxide fuel cells (SOFCs) have been investigated in this thesis. This work focuses on electrolyte materials such as samarium doped ceria (SDC) and cathode materials including neodymium barium cobalt oxide (NBCO) and barium calcium yttrium iron oxide. Single layer growth of NBCO or SDC is achieved on single crystal strontium titanate (001) before these materials were grown via pulsed laser deposition as a bi-layer and multilayers. Ordered NBCO required deposition at 850°C, whereas it was found that the SDC grew with a lower surface roughness at lower temperatures of around 650°C. The motivation was to investigate how the conductivity is affected by the interfaces between these layers, as motivated by previous studies of yttrium stabilised zirconia (YSZ) with strontium titanate (STO). NBCO was found to be unstable at the temperatures required for AC impedance measurements. From the transmission electron microscopy (TEM) and Energy Dispersive X-ray (EDX) data there is likely migration of Nd into the SDC layers. The interfaces are also less sharp for the multilayer films deposited at the higher temperature for the SDC growth. However, in all cases the SDC growth appears more favourable in the TEM when compared to the NBCO, with some regions even showing Co-metal and fluorite structures potentially attributed to Co-Ox where we would expect to see the perovskite block. Thin films of barium calcium yttrium iron oxide were grown on single crystal strontium titanate (001). The material is a candidate cathode for solid oxide fuel cells (SOFCs) and in the intermediate temperature (IT) region at 600°C the in-plane AC conductivity of the thin film is found to be 30.0Scm-1, significantly enhanced over 3.5Scm-1 found for the polycrystalline form. This is assigned to reduction of the grain boundary density and alignment of the planes predicted to have the highest electronic and ionic conductivities. The symmetry of the film appears to be tetragonal within the resolution of the measurements employed, as opposed to the orthorhombic symmetry of the bulk phase, which may be attributed to the in-plane structural match between the cubic STO substrate and the grown layer. Three potential geometries investigating both single and double-sided growth for measuring the area specific resistance of thin films are discussed and an experimental prototype constructed and tested.
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Toniolo, Patrícia Argenta. "STAT e SOCS na modulação funcional de células dendríticas derivadas de doadores saudáveis e pacientes com câncer." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/42/42133/tde-15122014-110253/.
Full textAbstract:
A descoberta de novos alvos terapêuticos capazes de reverter o efeito tumoral imunossupressor sobre as células dendríticas (DCs) é de grande relevância clínica. Identificamos que monócitos de pacientes com leucemia linfóide crônica (LLC) têm alterações na sinalização de STAT6 induzida por IL-4 que previne a maturação fenotípico-funcional das DCs. Embora os monócitos dos pacientes apresentem alta expressão de IL-4R, a atividade de STAT6 está inibida devido aos elevados níveis de SOCS5. IL-10 reproduz esta desregulação de STAT6/SOCS5 nos monócitos de doadores saudáveis, causando diferenciação defeituosa das DCs. Isso indica que SOCS5 está envolvida nas alterações das DCs de pacientes. Ainda, encontramos que a inibição de STAT3 com pirimetamina, um composto em ensaio clínico para LLC, não afeta a maturação das DCs, diferentemente da inibição de STAT5 por JQ1. Isso mostra que STAT5 é importante para a maturação das DCs, e sugere que a JQ1, mas não a pirimetamina, pode causar imunossupressão. Já SOCS5 pode ser um novo potencial alvo para terapia do câncer.Discovery of new targets to reverse tumor immunosuppression on dendritic cells (DCs) hold great therapeutic promise. Here, we identify that monocytes from chronic lymphocytic leukemia (CLL) patients have alteration in IL-4-induced STAT6 signaling that prevents DCs phenotypic and functional maturation. Although patients monocytes display high IL-4R expression, STAT6 activity is inhibited because of elevated SOCS5 levels. IL-10-treatment of healthy donors monocytes reproduces this altered mechanism (STAT6/SOCS5) and leads to a defective DC differentiation. These findings indicate that a high SOCS5 level is involved on CLL-DCs impaired function. Moreover, we find that pharmacologic inhibition of STAT3 by pyrimethamine, a clinical trial compound for CLL, does not affect LPS-induced DCs maturation while STAT5 inhibition by JQ1 prevents it. Our findings show that STAT5 is important for DCs maturation, and suggest that JQ1, but not pyrimetamine, can cause immunosuppression. Additionally, SOCS5 emerges as a new potential target for cancer treatment.
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Capan, Colt Dylan. "Effects of SOCS1 and SOCS3 Peptide Mimetics on MacrophagePhagocytosis of Malignant Cells." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1501263743238988.
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Sörensen, Astrid. "Auswirkungen einer Überexpression von SOCS-1 oder SOCS-3 auf die Expression der antiviralen Proteine MxA und 2',5'-OAS." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-82181.
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Sörensen, Astrid. "Auswirkungen einer Überexpression von SOCS-1 oder SOCS-3 auf die Expression der antiviralen Proteine MxA und 2',5'-OAS." kostenfrei, 2008. http://edoc.ub.uni-muenchen.de/8218/.
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Fitzsimons, Amy. "SOCS regulate macrophage polarisation : importance in cancer development." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601476.
Full textAbstract:
Macrophages (M0s) which can have a profound impact on tumour growth and are broadly classified into two subsets: 1) Inflammatory, tumoricidal "classically activated" Ml M0s or anti-inflammatory, pro-tumour "alternatively activated" M2 M0s. High M2 M0 density within tumours is associated with poor prognosis in patients. sacs proteins attenuate cytokine signalling via the JAKJSTA T pathway, and therefore regulate inflammatory responses. Our findings indicate that deletion of Socs2 and Socs3 genes in mice alter M0 subset homeostasis and polarisation towards Ml or M2 subsets, respectively. Opposing M0 subsets observed in these mice resulted in divergent tumour growth rates in both in a chemically inducible model of squamous cell carcinoma (SCC) and a syngeneic murine colorectal adenocarcinoma model Adoptive transfer FACS sorted bone SOCS2/3-null monocytes into WT tumour bearing mice resulted in similar trends in tumour growth are transferrable. Myeloid restricted deletion of SaCS3 in mice results in accelerated tumour growth accompanied by enhanced angiogenesis, and macrophage infiltration. These findings suggest that SOCS proteins have a profound influence on macrophage polarization and consequently tumour growth. Targeting SOCS proteins may be a viable therapeutic target in treatment of cancer.
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Garitselov, Oleg. "Metamodeling-based Fast Optimization of Nanoscale Ams-socs." Thesis, University of North Texas, 2012. https://digital.library.unt.edu/ark:/67531/metadc115081/.
Full textAbstract:
Modern consumer electronic systems are mostly based on analog and digital circuits and are designed as analog/mixed-signal systems on chip (AMS-SoCs). the integration of analog and digital circuits on the same die makes the system cost effective. in AMS-SoCs, analog and mixed-signal portions have not traditionally received much attention due to their complexity. As the fabrication technology advances, the simulation times for AMS-SoC circuits become more complex and take significant amounts of time. the time allocated for the circuit design and optimization creates a need to reduce the simulation time. the time constraints placed on designers are imposed by the ever-shortening time to market and non-recurrent cost of the chip. This dissertation proposes the use of a novel method, called metamodeling, and intelligent optimization algorithms to reduce the design time. Metamodel-based ultra-fast design flows are proposed and investigated. Metamodel creation is a one time process and relies on fast sampling through accurate parasitic-aware simulations. One of the targets of this dissertation is to minimize the sample size while retaining the accuracy of the model. in order to achieve this goal, different statistical sampling techniques are explored and applied to various AMS-SoC circuits. Also, different metamodel functions are explored for their accuracy and application to AMS-SoCs. Several different optimization algorithms are compared for global optimization accuracy and convergence. Three different AMS circuits, ring oscillator, inductor-capacitor voltage-controlled oscillator (LC-VCO) and phase locked loop (PLL) that are present in many AMS-SoC are used in this study for design flow application. Metamodels created in this dissertation provide accuracy with an error of less than 2% from the physical layout simulations. After optimal sampling investigation, metamodel functions and optimization algorithms are ranked in terms of speed and accuracy. Experimental results show that the proposed design flow provides roughly 5,000x speedup over conventional design flows. Thus, this dissertation greatly advances the state-of-the-art in mixed-signal design and will assist towards making consumer electronics cheaper and affordable.
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Weiss, Alexander. "Effiziente externe Beobachtung von CPU-Aktivitäten auf SoCs." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-184227.
Full textAbstract:
Die umfassende Beobachtbarkeit von System‐on‐Chips (SoCs) ist eine wichtige Voraussetzung für das effiziente Testen und Debuggen eingebetteter Systeme. Ausgehend von einer Analyse verschiedener Anwendungsfälle ergibt sich ein Katalog von Anforderungen an die Beobachtbarkeit von SoCs. Ein wichtiges Kriterium ist hier die Vollständigkeit der Beobachtung und umfasst die Aktivitäten der CPU (ausgeführte Instruktionen, gelesene und geschriebene Daten, Verhalten des Caches, Ausführungszeiten), des Bussystems und von Umgebungsbedingungen.
Weitere Kriterien sind die Echtzeitfähigkeit und die Kontinuität der Beobachtung sowie die gleichzeitige Durchführung verschiedener Beobachtungsaufgaben. Dabei soll es zu einer möglichst geringen Beeinflussung des SoCs kommen. Weitere wichtige Aspekt sind die Kosten der Lösung, die Universalität, die Skalierbarkeit sowie die Latenz der Verfügbarkeit der Beobachtungsergebnisse.
Für viele Anwendungen, besonders in sicherheitskritischen Bereichen, muss zudem nachgewiesen werden, dass das Beobachtungsverfahren kein Fehlverhalten des SoCs bewirkt bzw. ein solches maskiert. Eine besondere Herausforderung stellen Multiprozessor‐SoCs (MPSoCs) dar, da hier die Kommunikation zwischen den einzelnen CPUs im Inneren des SoC stattfindet und entsprechend schwierig für einen externen Bobachter sichtbar zu machen ist.
Der Stand der Technik zur Beobachtung von SoCs wird im Wesentlichen durch zwei Verfahren dargestellt. Bei der Software‐Instrumentierung wird zum funktionalen Programmcode zusätzlicher Code hinzugefügt, welcher zur Beobachtung des Programms dient. Diese Methode ist einfach und universell anwendbar, erfüllt aber die genannten Kriterien nur sehr eingeschränkt. Nachteilig ist hier der Ressourcenverbrauch im Falle des Verbleibs der Instrumentierung im fertigen Produkt. Wird die Instrumentierung nur temporär dem Code hinzugefügt, muss sichergestellt werden, dass das Beobachtungsergebnis auch für den finalen Code anwendbar ist – was besonders bei ressourcen‐abhängigen Integrationstests nur schwierig erfüllbar ist.
Eine alternative Lösung stellt eine spezielle Hardware‐Unterstützung in SoCs („embedded Trace“) dar. Hier werden im SoC Zustandsinformationen (z.B. Taskwechsel, ausgeführte Instruktionen, Datentransfers) gesammelt und mittels Trace‐Nachrichten an den Beobachter übermittelt. Dabei stellt die Bandbreite, die zur Ausgabe der Trace‐Nachrichten vom SoC verfügbar ist, ein entscheidendes Nadelöhr dar ‐ im SoC sind viel mehr den Beobachter interessierende Informationen verfügbar als nach außen transferiert werden können.
Damit haben beide dem gegenwärtige Stand der Technik entsprechende Beobachtungsverfahren eine Reihe von Einschränkungen, die sich besonders bei der Vollständigkeit der Beobachtung, der Flexibilität, der Kontinuität und der Unterstützung von MPSoCs zeigen.
In dieser Arbeit wird nun ein neuer Ansatz vorgestellt, welcher gegenüber dem Stand der Technik in einigen Bereichen deutliche Verbesserungen bietet. Dabei werden die Trace‐Daten nicht vom zu beobachtenden SoC direkt, sondern aus einer parallel mitlaufenden Emulation gewonnen. Die Bandbreite der für die Synchronisation der Emulation erforderlichen Daten ist in vielen Fällen deutlich geringer als bei der Ausgabe von umfassenden Trace‐Nachrichten mittels „embedded Trace“‐Lösungen. Gleichzeitig ist eine vollständige, äußerst detaillierte Beobachtung der Vorgänge innerhalb des SoC möglich. Das neue Beobachtungsverfahren wurde mittels verschiedener FPGA-basierter Implementierungen evaluiert, hier konnte auch die Anwendbarkeit für MPSoCs gezeigt werden.
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Vert, Belenguer Vicente Bernardo. "ELECTRODOS AVANZADOS PARA PILAS DE COMBUSTIBLE DE ÓXIDO SÓLIDO (SOFCs)." Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/14669.
Full textAbstract:
Las celdas de combustible de óxido sólido (cuyo acrónimo en inglés es SOFC) son dispositivos energéticos capaces de convertir la energía química de un combustible directamente en energía eléctrica. Esto las dota de unas eficiencias eléctricas muy elevadas, que pueden llegar a ser del 80% si se aprovecha su calor residual de alta calidad mediante turbinas. Además, son capaces de funcionar con una gran variedad de combustibles: hidrógeno, gas natural, gas de síntesis, etanol, metanol, etc. Sin embargo, para su inserción en la cadena de producción energética, su temperatura de funcionamiento debería disminuir al rango de 500-700 ºC sin que se redujeran las densidades de potencias eléctricas generadas.
Las SOFC convencionales se basan en la conducción de iones oxígeno de su electrolito, que separa la reacción de combustión del combustible en sus semi-reacciones electroquímicas, generando de este modo la energía eléctrica directamente. Al disminuir la temperatura de operación en este tipo de SOFC, con electrolitos (o membranas) delgados e hidrógeno como combustible, la principal limitación de funcionamiento se centra en la activación y reducción del oxígeno que tiene lugar en el electrodo denominado cátodo. Por otro lado, el empleo de otros combustibles basados en carbono no es compatible con los materiales de ánodos actualmente utilizados.
Por tanto, es necesario el desarrollo de nuevos cátodos con mejoradas propiedades electrocatalíticas para la reducción de oxígeno a menores temperaturas, cuyas propiedades termo-mecánicas sean compatibles con las del resto de componentes de la celda, y la obtención de ánodos capaces de funcionar con combustibles basados en carbono.
La combinación conjunta de varios lantánidos y bario en la estructura perovskita (LalPrpSmsBab)0.58Sr0.4Fe0.8Co0.2O3 ha permitido obtener compuestos con resistencias de polarización de electrodo significantemente menores que las mostradas por el cátodo del estado de la técnica La0.6Sr0.4Fe0.8Co0.2O3 en el rango de temperaturas 450-650 ºC.Vert Belenguer, VB. (2011). ELECTRODOS AVANZADOS PARA PILAS DE COMBUSTIBLE DE ÓXIDO SÓLIDO (SOFCs) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14669
Palancia
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Chibani, Mohamed. "Increasing the Robustness of CELP Speech Sodecs against packet losses." [S.l. : s.n.], 2006.
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Helmy, Amr. "Mise en œuvre de techniques de démonstration automatique pour la vérification formelle des NoCs." Grenoble INPG, 2010. http://www.theses.fr/2010INPG0035.
Full textAbstract:
Les technologies actuelles permettent l'intégration sur une même puce de systèmes complexes (SoCs) qui sont composés de blocs préconçus (IPs) pouvant être interconnectés grâce à un réseau sur la puce (NoCs). De manière générale, les IPs sont validés par diverses techniques (simulation, test, vérification formelle) et le problème majeur reste la validation des infrastructures des communications. Cette thèse se concentre sur la vérification formelle des réseaux sur puce à l'aide d'un outil de preuve automatique, le démonstrateur de théorèmes ACL2. Un méta-modèle pour les réseaux sur puce a été développé et implémenté dans ACL2. Il satisfait des propriétés de correction générique, conséquences logiques d'un ensemble d'obligations de preuve sur les constituants principaux du réseau (topologie, routage, technique de commutation,. . . ). La preuve de correction pour une instance spécifique de réseau sur puce est alors réduite à la vérification de ces obligations de preuve. Cette thèse poursuit les travaux entrepris dans ce domaine en étendant ce méta-modèle dans plusieurs directions : prise en compte plus fine de la modélisation temporelle, du contrôle de flux, des mécanismes de priorités,. . . Les résultats sont démontrés sur plusieurs réseaux actuels : Hermes (Université fédérale du Rio Grande do Sul, Brésil et LIRMM) et Nostrum (Royal Institute Of Technology, Suéde)The current technology allows the integration on a single die of complex systems-on-chip (SoC's) composed of manufactured blocks (IP's) that can be interconnected through specialized networks-on-chip (NoCs). IP's have usually been validated by diverse techniques (simulation, test, formal verification) and the key problem remains the validation of the communication infrastructure. This thesis addresses the formal verification of NoCs by means of a mechanized proof tool, the ACL2 theorem prover. A meta-model for NoCs has been developed and implemented in ACL2. It satisfies generic correctness statements, which are logical consequences of a set of proof obligations for each one of the NoC constituents (topology, routing, switching technique,. . . ). Thus the verification of a particular NoC instance is reduced to discharging this set of proof obligations. The purpose of this thesis is to extend this meta-model in several directions: more accurate timing modeling, flow control, priority mechanisms,. . . The methodology is demonstrated on realistic and state-of-the-art NoC designs: Spidergon (STMicroelectronics), Hermes (The Federal University of Rio Grande do Sul, Brazil, and LIRMM) , and Nostrum (Royal Institute Of Technology, Sweden)
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Akhtar, Lisa Nowoslawski. "The role of SOCS proteins in HIV immune evasion." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2010. https://www.mhsl.uab.edu/dt/2010p/akhtar.pdf.
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Coulot, Thomas. "Stratégie d'alimentation pour les SoCs RF très faible consommation." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00951423.
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Les réseaux de capteurs sans fil nécessitent des fonctions de calcul et de transmissionradio associées à chaque capteur. Les SoCs RF intégrant ces fonctions doivent avoir uneautonomie la plus grande possible et donc une très faible consommation. Aujourd'hui, leursperformances énergétiques pourraient être fortement améliorées par des systèmes d'alimentationinnovants. En effet, les circuits d'alimentation remplissent leur fonction classique de conversiond'énergie mais aussi des fonctions d'isolation des blocs RF et digitaux. Leurs performancess'évaluent donc en termes d'efficacité énergétique et de réponse transitoire mais aussi d'isolationentre blocs et de réjection de bruit.Ce travail de thèse concerne l'intégration du système de gestion et de distribution del'énergie aux différents blocs RF d'un émetteur/récepteur en élaborant une méthodologie " topdown" pour déterminer la sensibilité de chaque bloc à son alimentation et en construisant unearchitecture innovante et dynamique de gestion/distribution de l'énergie sur le SoC. Cetteméthodologie repose sur la disponibilité de régulateurs de tension présentant des performancesadaptées. Un deuxième volet du travail de thèse a donc été de réaliser un régulateur linéaire detype LDO à forte réjection sur une bande passante relativement large et bien adapté àl'alimentation de blocs RF très sensibles aux bruits de l'alimentation.
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Du, Ling. "CIS/SOCS Proteins in Growth Hormone Action: A Dissertation." eScholarship@UMMS, 2000. https://escholarship.umassmed.edu/gsbs_diss/92.
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CIS/SOCS (cytokine-inducible SH2 protein/suppressor of cytokine signaling) are a family of proteins that are thought to act as negative regulators of signaling by erythropoetin, interleukin-6 and other cytokines whose receptors are related to the growth hormone receptor (GHR), and like growth hormone (GH), signal through the JAK/STAT pathway. We examined the possibility that CIS/SOCS proteins may also be involved in GH signaling, in particular, in termination of the transient insulin-like effects of GH. mRNAs for CIS, SOCS3, and to a lesser extent SOCS1 were detectable by Northern blot analysis of rat adipocyte total RNA, and the expression of CIS and SOCS3 was markedly increased 30 min after incubation with 500 ng/ml hGH. Both CIS and SOCS3 were detected in adipocyte extracts by immunoprecipitation and immunoblotting with their corresponding antisera. GH stimulated the tyrosine phosphorylation of a 120 kDa protein (p120) that was co-precipitated from adipocyte extracts along with αCIS and detected in Western blots with phospho-tyrosine antibodies. However, no tyrosine phosphorylated proteins in these cell extracts were immunoprecipitated with antibodies to CIS3/SOCS3. p120 was later identified as the GHR based on the observations that two GHR antibodies recognized p120 in scale-up experiments and that p120 and the GHR share several characteristics, including their molecular weights, tyrosine phosphorylation upon GH stimulation, interaction with CIS, similar extent of glycosylation as judged by electrophoretic mobility shift after Endo F digestion, comparable mobility shifts upon thrombin digestion, and N-terminal histidine-tagging. The findings, however, do not rule out the possibility that there might be other tyrosine phosphorylated 120 kDa protein(s) that interact with CIS and contribute to the p120 signal, as well as the GHR.
Further studies of the association of CIS with the GHR revealed that CIS might selectively interact with multiply tyrosine phosphorylated forms of the GHR, and these tyrosines are likely located near the carboxyl end of the GHR. Overexpression of CIS partially inhibited GH-induced STAT5 phosphorylation in CHO cells. Studies in freshly isolated and GH-deprived (sensitive) adipocytes revealed that the abundance of CIS does not correlate with the termination of the insulin-like effects of GH or the emergence of refractoriness. Neither the association of CIS with the GHR nor the tyrosine phosphorylation status of the GHR, JAK2 and STAT5 appear responsible for refractoriness in adipocytes. These data imply that some negative regulators other than CIS might contribute to the termination of GH-induced insulin-like effects in adipocytes.
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Frantz, Arthur Pereira. "Designing fault tolerant NoCs to improve reliability on SoCs." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/11302.
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Com a redução das dimensões dos dispositivos nas tecnologias sub-micrônicas foi possível um grande aumento no número de IP cores integrados em um mesmo chip e consequentemente novas arquiteturas de comunicação são usadas bucando atingir os requisitos de desempenho e potência. As redes intra-chip (Networks-on-Chip) foram propostas como uma plataforma alternativa de comunicação capaz de prover interconexões e comunicação entre os cores de um mesmo chip, tratando questões como desempenho, consumo de energia e reusabilidade para grandes sistemas integrados. Por outro lado, a mesma evolução tecnológica dos processos nanométricos reduziu drasticamente a confiabilidade de circuitos integrados, tornando dispositivos e interconexões mais sensíveis a novos tipos de falhas. Erros podem ser gerados por variações no processo de fabricação ou mesmo pela susceptibilidade do projeto, quando este opera em um ambiente hostil. Na comunicação de NoCs as duas principais fontes de erros são falhas de crosstalk e soft errors. No passado, se assumia que interconexões não poderiam ser afetadas por soft errors, por não possuirem circuitos seqüenciais. Porém, quando NoCs são usadas, buffers e circuitos seqüenciais estão presentes nos roteadores e, consequentemente, podem ocorrer soft errors entre a fonte e o destino da comunicação, provocando erros. Técnicas de tolerância a falhas, que tem sido aplicadas em circuitos em geral, podem ser usadas para proteger roteadores contra bit-flips. Neste cenário, este trabalho inicia com a avaliação dos efeitos de soft errors e falhas de crosstalk em uma arquitetura de NoC, através de simulação de injeção de falhas, analisando detalhadamente o impacto de tais falhas no roteador. Os resultados mostram que os efeitos dessas falhas na comunicação do SoC podem ser desastrosos, levando a perda de pacotes e travamento ou indisponibilidade do sistema. Então é proposta e avaliada a aplicação de um conjunto de técnicas de tolerância a falhas em roteadores, possibilitando diminuir os soft errors e falhas de crosstalk no nível de hardware. Estas técnicas propostas foram baseadas em códigos de correção de erros e redundância de hardware. Resultados experimentais mostram que estas técnicas podem obter zero erros com 50% a menos de overhead de área, quando comparadas com a duplicação simples. Entretanto, algumas dessas técnicas têm um grande consumo de potência, pois toda essas técnicas são baseadas na adição de hardware redundante. Considerando que as técnicas de proteção baseadas em software também impõe um considerável overhead na comunicação devido à retransmissão, é proposto o uso de técnicas mistas de hardware e software, que podem oferecer um nível de proteção satisfatório, baseado na análise do ambiente onde o sistema irá operar (soft error rate), fatores relativos ao projeto e fabricação (variações de atraso em interconexões, pontos susceptíveis a crosstalk), a probabilidade de uma falha gerar um erro em um roteador, a carga de comunicação e os limites de potência e energia suportados.As the technology scales down into deep sub-micron domain, more IP cores are integrated in the same die and new communication architectures are used to meet performance and power constraints. Networks-on-Chip have been proposed as an alternative communication platform capable of providing interconnections and communication among onchip cores, handling performance, energy consumption and reusability issues for large integrated systems. However, the same advances to nanometric technologies have significantly reduced reliability in mass-produced integrated circuits, increasing the sensitivity of devices and interconnects to new types of failures. Variations at the fabrication process or even the susceptibility of a design under a hostile environment might generate errors. In NoC communications the two major sources of errors are crosstalk faults and soft errors. In the past, it was assumed that connections cannot be affected by soft errors because there was no sequential circuit involved. However, when NoCs are used, buffers and sequential circuits are present in the routers, consequently, soft errors can occur between the communication source and destination provoking errors. Fault tolerant techniques that once have been applied in integrated circuits in general can be used to protect routers against bit-flips. In this scenario, this work starts evaluating the effects of soft errors and crosstalk faults in a NoC architecture by performing fault injection simulations, where it has been accurate analyzed the impact of such faults over the switch service. The results show that the effect of those faults in the SoC communication can be disastrous, leading to loss of packets and system crash or unavailability. Then it proposes and evaluates a set of fault tolerant techniques applied at routers able to mitigate soft errors and crosstalk faults at the hardware level. Such proposed techniques were based on error correcting codes and hardware redundancy. Experimental results show that using the proposed techniques one can obtain zero errors with up to 50% of savings in the area overhead when compared to simple duplication. However some of these techniques are very power consuming because all the tolerance is based on adding redundant hardware. Considering that softwarebased mitigation techniques also impose a considerable communication overhead due to retransmission, we then propose the use of mixed hardware-software techniques, that can develop a suitable protection scheme driven by the analysis of the environment that the system will operate in (soft error rate), the design and fabrication factors (delay variations in interconnects, crosstalk enabling points), the probability of a fault generating an error in the router, the communication load and the allowed power or energy budget.
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Fikelepi, Ursula Nobulali. "Guiding principles on building sustainable SOEs in South Africa." Diss., University of Pretoria, 2010. http://hdl.handle.net/2263/23805.
Full textAbstract:
This paper examines the performance of SOEs in developing countries in competitive sectors such as aviation, telecommunications and energy to ascertain whether there are any common principles that determine such performance. Through a case study analysis and interviews with executive managers of South Africa’s SOEs, the paper will determine whether the common principles ascertained in the successful performance of the other developing countries’ SOEs can be applied to South Africa and whether any differences in principle exist between South African SOEs and other developing country SOEs. The paper uses the strategic management schools of organisational and institutional theory, agency theory and the resource based view to determine if there are any differences in principle between SOEs in South Africa and other developing countries. The paper also explores whether the environments and contexts of the different SOEs materially impacts their performance and ability to create a competitive advantage over a sustained period. A qualitative approach was used given that this is an explorative study, to provide better insights and in-depth discussion on the relatively new issues that have not been studied in great detail before. The main research findings are that successfully performing SOEs from developing countries exhibit certain common factors that can be applied by SOEs seeking to reform and improve their performance across developing countries. CopyrightDissertation (MBA)--University of Pretoria, 2010.
Gordon Institute of Business Science (GIBS)
unrestricted
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Balasubramanian, Sidharth. "Low-voltage and low-power libraries for Medical SoCs." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259776639.
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Vitkovskiy, Arseniy <1979>. "Memory hierarchy and data communication in heterogeneous reconfigurable SoCs." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/1127/1/Tesi_Vitkovskiy_Arseniy.pdf.
Full textAbstract:
The miniaturization race in the hardware industry aiming at continuous increasing
of transistor density on a die does not bring respective application performance
improvements any more. One of the most promising alternatives is to
exploit a heterogeneous nature of common applications in hardware. Supported by
reconfigurable computation, which has already proved its efficiency in accelerating
data intensive applications, this concept promises a breakthrough in contemporary
technology development.
Memory organization in such heterogeneous reconfigurable architectures becomes
very critical. Two primary aspects introduce a sophisticated trade-off. On
the one hand, a memory subsystem should provide well organized distributed data
structure and guarantee the required data bandwidth. On the other hand, it should
hide the heterogeneous hardware structure from the end-user, in order to support
feasible high-level programmability of the system.
This thesis work explores the heterogeneous reconfigurable hardware architectures
and presents possible solutions to cope the problem of memory organization
and data structure. By the example of the MORPHEUS heterogeneous platform,
the discussion follows the complete design cycle, starting from decision making
and justification, until hardware realization. Particular emphasis is made on the
methods to support high system performance, meet application requirements, and
provide a user-friendly programmer interface.
As a result, the research introduces a complete heterogeneous platform enhanced
with a hierarchical memory organization, which copes with its task by
means of separating computation from communication, providing reconfigurable
engines with computation and configuration data, and unification of heterogeneous
computational devices using local storage buffers. It is distinguished from the
related solutions by distributed data-flow organization, specifically engineered
mechanisms to operate with data on local domains, particular communication infrastructure
based on Network-on-Chip, and thorough methods to prevent computation
and communication stalls. In addition, a novel advanced technique to accelerate
memory access was developed and implemented.
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Vitkovskiy, Arseniy <1979>. "Memory hierarchy and data communication in heterogeneous reconfigurable SoCs." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/1127/.
Full textAbstract:
The miniaturization race in the hardware industry aiming at continuous increasing
of transistor density on a die does not bring respective application performance
improvements any more. One of the most promising alternatives is to
exploit a heterogeneous nature of common applications in hardware. Supported by
reconfigurable computation, which has already proved its efficiency in accelerating
data intensive applications, this concept promises a breakthrough in contemporary
technology development.
Memory organization in such heterogeneous reconfigurable architectures becomes
very critical. Two primary aspects introduce a sophisticated trade-off. On
the one hand, a memory subsystem should provide well organized distributed data
structure and guarantee the required data bandwidth. On the other hand, it should
hide the heterogeneous hardware structure from the end-user, in order to support
feasible high-level programmability of the system.
This thesis work explores the heterogeneous reconfigurable hardware architectures
and presents possible solutions to cope the problem of memory organization
and data structure. By the example of the MORPHEUS heterogeneous platform,
the discussion follows the complete design cycle, starting from decision making
and justification, until hardware realization. Particular emphasis is made on the
methods to support high system performance, meet application requirements, and
provide a user-friendly programmer interface.
As a result, the research introduces a complete heterogeneous platform enhanced
with a hierarchical memory organization, which copes with its task by
means of separating computation from communication, providing reconfigurable
engines with computation and configuration data, and unification of heterogeneous
computational devices using local storage buffers. It is distinguished from the
related solutions by distributed data-flow organization, specifically engineered
mechanisms to operate with data on local domains, particular communication infrastructure
based on Network-on-Chip, and thorough methods to prevent computation
and communication stalls. In addition, a novel advanced technique to accelerate
memory access was developed and implemented.
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Gontard, Pierre. "Régulations et recherche de nouveaux partenaires des protéines SOCS." Nice, 2010. http://www.theses.fr/2010NICE4019.
Full textAbstract:
Les protéines SOCS (Suppressor Of Cytokine Signaling) sont exprimées en réponse aux cytokines ou aux hormones et exercent le plus souvent un rétrocontrôle négatif sur le signal qui les a induites. Ainsi, il est connu que les SOCS inhibent la voie de signalisation de l’insuline. La dérégulation de l’expression ou de l’action des SOCS pourrait donc jouer un rôle majeur dans la résistance à l’insuline et le diabète. Au cours de ma thèse j’ai tout d’abord mis en évidence des microARNs ciblant les ARNm de SOCS-1, -2 et -3 et régulant donc potentiellement leur niveau d’expression. Dans le but de préciser le mécanisme d’action des SOCS j’ai également voulu identifier de nouveaux partenaires de ces protéines. Ainsi, j’ai mis en évidence que la phosphatase calcineurine interagit avec SOCS-3 in vitro et in vivo. Chez un modèle de souris transgénique exprimant constitutivement SOCS-3 dans le muscle squelettique, cette interaction se traduit par une délocalisation et une séquestration de la calcineurine à la périphérie des fibres. En corrélation avec une altération de l’action de la calcineurine, ces animaux présentent une activité locomotrice réduite. J’ai étudié en parallèle l’effet de SOCS-3 sur la fonction sécrétoire du muscle squelettique. J’ai alors montré que, contrairement aux souris contrôles, les souris transgéniques SOCS-3 ne présentent pas d’augmentation du taux circulant d’interleukine-6 (sécrétée en partie par le muscle) sous un régime riche en graisse. Mes travaux apportent de nouveaux éléments sur les mécanismes d’action des SOCS et suggèrent que ces protéines peuvent, indépendamment de leur rôle de répresseurs, être des molécules de signalisation à part entièreSOCS (Suppressor Of Cytokine Signaling) proteins are expressed in response to cytokines and hormones. Generally speaking SOCS exert a negative feedback on signaling pathways, which induce their expression. Thus, SOCS proteins are potent inhibitors of insulin signal and dysregulation of their expression and/or action could play a key role in insulin resistance and diabetes. During my PhD, I first identified microRNAs targeting SOCS-1, -2 and –3 mRNAs and potentially implicated in the regulation of SOCS expression. In addition, to specify the molecular mechanisms driven by SOCS proteins, I planed to define new partners of SOCS-3. Thus, I demonstrated that the phosphatase calcineurin interacts with SOCS-3 in vitro and in vivo. In transgenic mice expressing constitutively SOCS-3 in skeletal muscle, this association is illustrated by a colocalization of calcineurin and SOCS-3 leading to the delocalization and sequestration of calcineurin at the periphery of muscle fibers. In correlation with altered calcineurin function, a decreased locomotor activity is observed in transgenic animals. Since it was known that skeletal muscle is able to synthesize and secrete molecules, I wanted to determine whether constitutive expression of SOCS-3 in muscle could alter its secretive function. My analysis showed that whereas increased circulating levels of Interleukin-6 (partially produced by skeletal muscle) are detected in control animals under a high fat diet, no variation is observed in transgenic mice. My investigations brought new insights into the molecular mechanisms driven by SOCS and suggested a new role for SOCS proteins, beside their repressive function, as signaling molecule
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Sano, Mitsuru, Ushio Harada, Takashi Hibino, Atsuko Hashimoto, and Daisuke Hirabayashi. "Bi-Based Oxide Anodes for Direct Hydrocarbon SOFCs at Intermediate Temperatures." The Electrochemical Society, 2004. http://hdl.handle.net/2237/18432.
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Wu, Zhonglin. "Mixed ionic-electronic conductors for electrodes of barium cerate based SOFCs." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19979.
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Hodgeman, Darren. "New cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs)." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/18675/.
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The work presented in this thesis focuses on the synthesis of long axis A-site ordered perovskites, which have ordered oxygen vacancies. The materials discussed have also been assessed as potential cathodes for solid oxide fuel cells (SOFCs), targeting an intermediate temperature (IT) SOFC operating range of 500 800 °C. In chapter 3 of this thesis, a 16ap phase (ap = 1 perovskite unit, ABO3-δ), Y2.24Ba2.28Ca3.48Fe7.44Cu0.56O21-δ, was first observed in a powder X-ray diffraction (PXRD) pattern that resulted from the attempted Cu doping of a 10ap phase (Y0.9Ba1.7Ca2.4Fe5 xCuxO13 δ). This phase was indexed as ap √2 × 16ap × ap √2 by selective area electron diffraction (SAED). Mössbauer spectroscopy identified that Fe3+ existed in three different coordination environments and a Rietveld refinement was carried out using combined powder synchrotron (S) XRD and powder neutron diffraction (ND) data. High Angle Annular Scanning Transmission Electron Diffraction (HAADF-STEM) confirmed the A-site ordering from the refinement. The 16ap phase exhibited good thermal stability, CO2 stability and chemical compatibility with state of the art electrolytes (GDC, SDC and LSGM), as well as a close matching thermal expansion coefficient (TEC) with the same electrolytes. Although possessing low electronic conductivity, 3.5 S.cm-1 at 750 °C, a good area specific resistance (ASR) of 0.12 Ω.cm2 at 750 °C was achieved, within the IT-SOFC operating range. In chapter 4, a 10ap phase, Y0.9Ca2.4Sr1.7Fe5O13-δ (YCSFO), was discussed. The space group Imma was identified from SXRD data, while the structure was closely related to brownmillerite. A Rietveld refinement carried out with the addition of SXRD data collected at the K absorption edge for Sr determined A-site ordering. The ASR of YCSFO was three times higher than that of the 16ap phase, highlighting the ordering of oxygen vacancies. The final phases investigated in chapter 5 of this thesis belong to a family of Co doped 10ap phases (Y0.9Ba1.7Ca2.4Fe5 xCoxO13 δ). A range of compositions were synthesised by varying the cation ratios, in order to obtain high Co content phase pure samples. The highest Co content was x = 1.85 for compositions Y1.24Ba1.85Ca1.91Fe3.15Co1.85O13-δ (annealed in O2) and Y1.6Ba1.8Ca1.6Fe3.15Co1.85O13-δ. AC impedance measurements carried out showed that increased Co content reduced the ASR, with the values at 700 °C of 0.19 Ω.cm2 and 0.23 Ω.cm2 respectively.
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Schlegl, Harald. "Microstructure and electrochemical performance of fully ceramic composite anodes for SOFCs." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6361.
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Solid Oxide Fuel Cells could play a key role in energy systems of the future because they can directly convert the chemical energy of fuels into electrical energy in a reliable and energy efficient way. The choice of materials for the components of fuel cells is crucial for the achievement of the high performance and the low price necessary to establish fuel cell technology in the energy market. Current state of the art anodes consisting of nickel and yttria stabilised zirconia (Ni/YSZ) offer good electrochemical performance but suffer from limitations like carbon deposition, redox instability and sulphur poisoning. This thesis explores the properties of composite fully ceramic anodes consisting of a skeleton of yttria stabilised zirconia (YSZ) or cerium gadolinium oxide (CGO) and a perovskite phase based on B-site doped lanthanum strontium titanate. The perovskite phase was fabricated in situ inside the pores of the skeleton material by the infiltration of an aqueous precursor and subsequent firing (impregnation method). Material characterisation of the composite anodes was carried out by X-ray diffraction and the microstructure investigated by electron microscope techniques. The electrochemical performance was tested by IV-curves and impedance spectroscopy. Particularly the investigation of the connection between the microstructure of the impregnated anodes and their electrochemical performance is a main objective of this work. The electrochemical performance of cells with a CGO skeleton and an impregnated lanthanum strontium titanate phase was found to be inferior compared to cells with a YSZ skeleton, even if the ionic conductivity of CGO is known to be higher than the ionic conductivity of YSZ. The difference was assigned to mass transport problems tightly connected to the different microstructure of the composite anodes. A significant improvement of the performance could be achieved by the utilisation of A-site deficient perovskites as impregnated phase in a YSZ skeleton. Cells with composite anodes of YSZ and La₀.₄Sr₀.₄Ti₀.₉₄Mn₀.₀₆O[sub](3-δ) show power densities of 156.2 mW/cm² at a measuring temperature of 750 °C compared to 58.5 mW/cm² measured in a similar cell with A-site stoichiometric LSTM, both cells having an electrolyte thickness of around 60 μm. The superiority of the performance of anodes with A-site deficient perovskites is mainly due to a lower ohmic resistance of only 0.5 Ω*cm², indicating better conductivity of the composite with A-site deficient perovskites. The investigation of the microstructure of composite anodes with A-site deficient perovskites showed the decoration of the surface with nanoparticles after reduction. These nanoparticles originate from exsolution of ions from the B-site of the perovskite and can't be found in A-site stoichiometric perovskites. The influence of fabrication parameters like firing temperature of the skeleton, firing temperature after impregnation or vacuum impregnation on the microstructure and electrochemical performance of the composite anodes was studied. Particularly the increase of the firing temperature of the skeleton from 1400 °C to 1500 °C resulted in an impressive improvement of total cell resistance and maximal power density.
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Suh, Taeweon. "Integration and Evaluation of Cache Coherence Protocols for Multiprocessor SoCs." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14065.
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System-on-a-chip (SoC) designs is characterized by heavy reuse of IP blocks to satisfy specific computing needs for target applications, reduce overall design cost, and expedite time-to-market. To meet their performance goal and cost constraint, SoC designers integrate multiple, sometimes heterogeneous, processor IPs to perform particular functions. This design approach is called Multiprocessor SoC (MPSoC). In this thesis, I investigated generic methodologies for enabling efficient communication among heterogeneous processors and quantified the efficiency of coherence traffic. Hardware techniques for two main MPSoC architectures were studied: Integration of cache coherence protocols for shared-bus-based MPSoCs and Cache coherence support for non-shared-bus-based MPSoCs.
In the shared-bus-based MPSoCs, the integration techniques guarantee data consistency among incompatible coherence protocols. An integrated protocol will contain common states from these coherence protocols. A snoop-hit buffer and region-based cache coherence were also proposed to further enhance the coherence performance. For the non-shared-bus-based MPSoCs, bypass and bookkeeping approaches were proposed to maintain coherence in a new cache coherence-enforced memory controller. The simulations based on micro-benchmark and RTOS kernel showed the benefits of my methodologies over a generic software solution.
This thesis also evaluated and quantified the efficiency of coherence traffic based on a novel emulation platform using FPGA. The proposed technique can completely isolate the intrinsic delay of the coherence traffic to demonstrate the impact of coherence traffic on system performance. Unlike previous evaluation methods, this technique eliminated non-deterministic factors in measurements such as bus arbitration delay and stall in the pipelined bus. The experimental results showed that the cache-to-cache transfer in the Intel server system is less efficient than the main memory access.
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CAI, DAPENG, and JIE LI. "Causes, effects, and prevention of agent corruption in Chinese SOEs." 名古屋大学大学院経済学研究科附属国際経済政策研究センター, 2006. http://hdl.handle.net/2237/11918.
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Terosiet, Medhi. "Conception d'un oscillateur robuste contrôlé numériquement pour l'horlogerie des SoCs." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00836916.
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L'intégration d'un plus grand nombre de fonctions sur des circuits intégrés plus rapides à chaque nouvelle génération. Malheureusement, elles ont rendu la tâche des concepteurs plus difficile, avec notamment la montée de la puissance consommée et des temps de propagation des signaux à travers la puce. La distribution de l'horloge, assurant le synchronisme des opérations du circuit, en est l'élément le plus symptomatique. La génération distribuée de l'horloge apparaît comme une alternative aux solutions classiques. Elle repose sur la mise en place d'un réseau de N oscillateurs géographiquement distribués sur l'ensemble de la puce. Chaque oscillateur génère localement une horloge pour la zone de la puce dans laquelle il se trouve. La phase d'une horloge est accordée sur celle de ces proches voisines. Ainsi, l'horloge n'a plus à parcourir de long chemin. Toutefois, les performances du circuit d'horloge sont liées, non pas à un, mais à N oscillateurs évoluant dans un environnement hostile (variations de l'alimentation, de la température, etc.). Aussi, les travaux de cette thèse portent sur la conception d'un oscillateur contrôlé numériquement. Plus précisément, notre problématique est : " Comment concevoir un DCO (Digitally Controlled Oscillator) robuste soumis à l'environnement hostile d'un SoC en technologie CMOS submicronique ? ". Pour répondre à cette question, nous proposons, dans un premier temps, la modélisation d'une topologie d'oscillateur contrôlé numériquement ; le but étant de déterminer sa pertinence quant à notre application d'horlogerie. Comme cette dernière est émergente, il n'y a à l'heure actuelle aucune théorie la caractérisant. A travers notre analyse, nous mettons en évidence ses faiblesses et la nécessité de lui adjoindre des circuits de protection. De ce fait, les performances du circuit d'horloge ne sont plus seulement dépendantes de l'oscillateur, mais aussi des dispositifs mis en place pour le protéger des agressions des circuits environnants. Ce constat a motivé le développement d'une alternative qui ne serait pas soumise aux mêmes contraintes. Nous proposons finalement un oscillateur contrôlé numériquement robuste à la fois contre les variations de l'alimentation et de la température. Cet oscillateur est conçu à partir de blocs analogiques connus et bien décrits par la littérature. Pour limiter l'influence de la tension d'alimentation et de la température à laquelle évolue l'oscillateur, nous tirons profit des effets de canal court propres aux technologies submicroniques.
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Stevenson, N. J. "Chemoattractant induced SOCS-1 regulates LPS and G-CSF signal." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403345.
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Travagli-Gross, Julia. "Régulation transcriptionnelle du gène codant pour la protéine SOCS-1." Paris 11, 2005. http://www.theses.fr/2005PA114821.
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L'Interleukine-4 est une cytokine pléiotropique qui joue de nombreux rôles biologiques après fixation sur son récepteur. L'activation des tyrosines kinases JAK a un rôle clef dans l'activation des voies de signalisation, incluant le recrutement et la tyrosine phosphorylation du facteur de transcription STAT6. Les protéines STATs peuvent dimériser, transloquer dans le noyau et réguler de nombreux gènes en réponse à l'IL-4. Afin de contre réguler l'effet des cytokines, il existe des régulateurs négatifs. Parmi ces régulateurs, les protéines SOCS ont été décrites pour réguler négativement la voie JAK-STAT. Notre travail a consisté à caractériser le promoteur du gène Socs-1 et à étudier les régions promotrices ainsi que les voies de signalisation mises en jeu après une stimulation des cellules HaCaT (kératinocytes) par l'IL-4. Nous avons également étudié la régulation du promoteur du gène Socs-1 après une stimulation des kératinocytes par l'Interféron-γ qui est connu pour être un très bon inducteur du gène Socs-1. Nous avons mis en évidence l'implication du facteur de transcription IRF-1 dans la régulation de l'expression du gène codant pour la protéine SOCS-1 dans des kératinocytes stimulés par l'IFN-γInterleukin (IL)-4 is a pleotropic cytokine, which displays a variety of biological responses by binding to high affinity receptor complexes. The Jak-STAT pathway has been shown to be activated by IL-4. Activation of JAK, is pivotal for the activation of downstream signaling events including the recruitment and rapid tyrosine phosphorylation of STAT6. STAT6 can dimerize and translocate into the nucleus, where it regulates IL-4 target genes. Responsiveness to cytokines depends upon a balance of positive and negative regulators. Among these regulators SOCS proteins have been described to negatively regulate the JAK/STAT pathway. IL-4 upregulates Socs-1 in the keratinocyte HaCaT cell line, we investigated which sequence of the 5' Socs-1 gene are responsive to IL-4. Collectively, our data demonstrate the involvement of STAT6 and Ets, via a composite DNA element, in IL-4 regulation of Socs-1 gene expression in keratinocytes. We also studied the regulation of the promoter of the Socs-1 gene after stimulation by the IFN-g which is known to be very good inductive Socs-1 gene. We therefore examined the IFN-g activated transcription factors implicated in regulation of Socs-1 gene
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Terosiet, Mehdi. "Conception d'un oscillateur robuste contrôlé numériquement pour l'horlogerie des SoCs." Paris 6, 2012. http://www.theses.fr/2012PA066474.
Full textAbstract:
L’intégration d’un plus grand nombre de fonctions sur des circuits intégrés plus rapides à chaque nouvelle génération. Malheureusement, elles ont rendu la tâche des concepteurs plus difficile, avec notamment la montée de la puissance consommée et des temps de propagation des signaux à travers la puce. La distribution de l’horloge, assurant le synchronisme des opérations du circuit, en est l’élément le plus symptomatique. La génération distribuée de l’horloge apparaît comme une alternative aux solutions classiques. Elle repose sur la mise en place d’un réseau de N oscillateurs géographiquement distribués sur l’ensemble de la puce. Chaque oscillateur génère localement une horloge pour la zone de la puce dans laquelle il se trouve. La phase d’une horloge est accordée sur celle de ces proches voisines. Ainsi, l’horloge n’a plus à parcourir de long chemin. Toutefois, les performances du circuit d’horloge sont liées, non pas à un, mais à N oscillateurs évoluant dans un environnement hostile (variations de l’alimentation, de la température, etc. ). Aussi, les travaux de cette thèse portent sur la conception d’un oscillateur contrôlé numériquement. Plus précisément, notre problématique est : « Comment concevoir un DCO (Digitally Controlled Oscillator) robuste soumis à l’environnement hostile d’un SoC en technologie CMOS submicronique ? ». Pour répondre à cette question, nous proposons, dans un premier temps, la modélisation d’une topologie d’oscillateur contrôlé numériquement ; le but étant de déterminer sa pertinence quant à notre application d’horlogerie. Comme cette dernière est émergente, il n’y a à l’heure actuelle aucune théorie la caractérisant. A travers notre analyse, nous mettons en évidence ses faiblesses et la nécessité de lui adjoindre des circuits de protection. De ce fait, les performances du circuit d’horloge ne sont plus seulement dépendantes de l’oscillateur, mais aussi des dispositifs mis en place pour le protéger des agressions des circuits environnants. Ce constat a motivé le développement d’une alternative qui ne serait pas soumise aux mêmes contraintes. Nous proposons finalement un oscillateur contrôlé numériquement robuste à la fois contre les variations de l’alimentation et de la température. Cet oscillateur est conçu à partir de blocs analogiques connus et bien décrits par la littérature. Pour limiter l’influence de la tension d’alimentation et de la température à laquelle évolue l’oscillateur, nous tirons profit des effets de canal court propres aux technologies submicroniquesThe regular downscaling of MOS transistors dimensions allows integrating a largest number of functions on integrated circuits with an increase of their speed at each tech- nology node. Unfortunately, it has induced more difficulties for designers, notably due to the increase of the power consumption and to the propagation time of signals through the chip. The clock distribution, which insures the synchronism of circuit operations, is the most symptomatic component. The distributed generation of clock comes out as an alternative to traditional solu-tions. It relies on the set of N oscillators geographically distributed on the chip. Each oscillator locally generates the clock for its own zone. Clock phase of a generator is adjusted with respect to its close neighbourhoods. In this way, clock signal doesn’t have to cover a large distance. However, performances of the horology system are linked, not to one, but to N oscillators operating in a hostile environment (power supply and temperature variations, etc. ). Thus, this thesis aims of the design of a robust digitally controlled oscillator. More precisely, our issue is : « How To Design a robust DCO (Digitally Controlled Oscillator) subject to the hostile environment of a SoC (System-On-Chip) in a sub-micrometer CMOS technology ? » To answer this question, we propose, in a first time, the characterization of a topology of DCO; the goal is to determine its relevance with respect to our application. Since this topology is emergent, for the moment, no theory is provided by the literature. With our analysis, we highlight its weakness and the need to join protection devices. For this reason, the clock circuit performances are not only dependent on the oscillator, but also on the safety system added. This conclusion motivates the development of an alternative which doesn’t imply the same constraints. Finally, we propose a robust digitally controlled oscillator able to stand power supply and temperature variations. This one is designed from well-known analog blocks described by the literature. To limit the impacts of supply voltage and temperature variations on the oscillator, we take advantage on short channel effects exhibited by current MOSFETs
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Gatts, Timothy J. "Investigation of the heating and cooling of composite glass seals for SOFCs." Connect to resource, 2008. http://hdl.handle.net/1811/32060.
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