Dissertations / Theses on the topic 'Space charge region'

The classical capacitance voltage characteristics based on the depletion approximation, is adequate at reverse bias, but introduces errors at high forward bias. Because of its inherent simplicity and compactness this classical depletion model is well studied and widely used in circuit simulators. In this work, a new model for the semiconductor space charge region (SCR) capacitance, based on physical justification, will be derived. This new model takes three input parameters, C0 , Vbi and m, thus eliminating the fitting parameter FC currently used in SPICE. This new model is applicable for any applied voltage and will be compared with the SCR capacitance extracted from the numerical device simulator PISCES, and with the SCR capacitance models proposed by Gummel and Poon and by DeGraaff and Klaassen.

Ce travail de thèse étudie les moyens d’étendre les zones de charge d’espace des photodiodes PN d’un imageur CMOS afin d’améliorer la collection des charges photogénérées dans le silicium, en particulier dans le proche infra-rouge. Deux possibilités sont abordées : l’augmentation de la tension de polarisation des photodiodes et la diminution du dopage du silicium. Dans un premier temps, une étude théorique articulée autour de modèles analytiques et de simulations TCAD montre les difficultés technologiques pour parvenir à une augmentation de polarisation des photodiodes, ainsi que les conséquences de l’utilisation de substrats résistifs sur les éléments de l’imageur et sur ses performances. Ces simulations permettent de définir les éléments influençant l’extension de la charge d’espace d’un pixel. Sur la base de cette étude, un imageur CMOS à pixel 3T a été développé et fabriqué sur substrat float-zone très fortement résistif afin de valider les observations théoriques. La caractérisation de ce composant confirme la dépendance de la zone dépeuplée à la conception du pixel. Elle démontre également la corrélation entre l’extension des zones dépeuplées et les performances électro-optiques. Des règles de conception sont définies permettant d’optimiser les performances tout en limitant les courants de fuite entre pixels
This work investigates solutions to extend the space charge region in CMOS image sensors in order to enhance the photo-generatedcharge collection from near-infraredradiations. Photodiode bias increase and low doped silicon substrate are proposed for this study. A theoretical analysis based on analytical model and TCAD simulations shows technological difficulties for photodiode bias in crease and the consequences of using high-resistivity silicon substrates on the imager performances. Space charge region dependency on the pixel design is assessed through simulations. A 3T pixel CMOS image sensor was developed and fabricated on a high resistivity float-zone silicon. Sensor characterization confirms space charge region dependency on the pixel design and the correlation between its extension and electro-optical performances. Design rules are defined to optimize electro-optical performances while limiting punchthrough current in the pixels array

Radio frequency oscillations up to several hundreds of MHz were observed during turn-off the high-current conducting IGBTs. They are described in this work as Transient Avalanche oscillations. Other than PETT oscillations that happen in the tail current phase, this oscillation appears during the rise of collector-emitter voltage VCE and during the fall of the collectoremitter current ICE. The turn-off process of IGBTs are investigated with the help of measurements, the circuit- and device-simulations to reveal the working mechanisms of transient high-frequency oscillations. For the first time the Transient Avalanche Oscillation is successfully reproduced with computer simulation, which allows the further investigation on the influences of individual parameters. The participation of IMPATT mechanism in Transient Avalanche oscillation is demonstrated. The interaction between IMPATT mechanism und PETT mechanism during the setting up of depletion region in IGBTs was investigated. Measures to suppress such oscillation are discussed on the levels of chip design, module design and the driver concept. Supplying electron current during critical phase is found to be an effctive method to avoid the dynamic avalanche and the TA-oscillation
Radio Frequenz Oszillationen bis zu mehreren hundert MHz wurden während des Abschaltens von Hochstrom leitenden IGBTs beobachtet. Sie werden in dieser Arbeit als Transient Avalanche Oscillationen beschrieben. Anders als PETT Oszillationen, die in der Tail-Strom Phase vorkommen, erscheint diese Oszillation während des Anstiegs der Kollektor-Emitter-Spannung VCE und des Fallens des Kollektor-Emitter Stroms ICE. In dieser Arbeit werden die Abschaltvorgänge von IGBTs mit Hilfe von Messungen, Schaltungs- bzw. Device-Simulationen untersucht, um die Wirkungsmechanismen der transient erscheinenden hochfrequenten Oszillationen zu erklären. Es ist erstmals gelungen solche Transient Avalanche Oszillationen mit der Simulation zu reproduzieren und anschließend die Einflüsse einzelner Parameter zu untersuchen. Die Beteiligung des IMPATT Mechanismus an der Transient Avalanche Oszillation wurde nachgewiesen. Die Interaktion von IMPATT und PETT während Aufbau der Raumladungszone im IGBT wurde untersucht. Maßnahmen zur Unterdrückung der Oszillation werden auf den Ebenen von Chip-Design, Modulauslegung und der Treiberschaltung diskutiert. Das Zuführen des Elektrostromes während der kritischen Phase wird als ein effective Methode zur Vermeidung der TA-Oscillation nachgewiesen

This thesis investigates the adaptation to climate change that is taking place in the WaterSupply and Waste Water (WSW) sector of the Stockholm Region. The adaptation processis analyzed in terms of building adaptive capacity and implementing adaptive decisions.Theories on organizational learning and the concept of an organization’s adaptation spaceare used to understand the factors that influence the adaptation process and the capacityof the studied WSW organizations to adapt to climate change. A case study approach hasbeen used and by focusing the research on four regional WSW organizations – thatcomprise a majority of the region’s WSW activities – it is argued that conclusionsrelevant to the region’s WSW sector as a whole can be made. Semi-structured interviewswith the complete management board – in three out of four organizations – and officialdocuments and reports, are the main sources of primary data for the analysis.The results show that adaptation to climate change is occuring in the WSW sector of theStockholm Region. The adaptation is mainly taking the form of building adaptivecapacity and there is only limited evidence of implementation of adaptive decisions. Theresearch suggests that there are few technical and organizational limitations foradaptation to take place and that the main factors influencing the adaptation space of thesector is how the climate change issue and risks are interpreted and perceptions of howthe WSW organizations should function and use their limited economical resources. Twoconclusions are drawn from these results: first, factors influencing the feasibility andattractiveness of different adaptation options need to be included and analysed in order tounderstand the actual adaptation space of an organization. Second, due to the factorsidentified as influencing the adaptation space, it is unlikely, at present, that robustinfrastructure solutions – which have been suggested in the literature as a viable way todeal with the intrinsic uncertainties related to climate change – can be implemented in theWSW sector of the Stockholm Region solely due to concerns of climate change.

Radio frequency oscillations up to several hundreds of MHz were observed during turn-off the high-current conducting IGBTs. They are described in this work as Transient Avalanche oscillations. Other than PETT oscillations that happen in the tail current phase, this oscillation appears during the rise of collector-emitter voltage VCE and during the fall of the collectoremitter current ICE. The turn-off process of IGBTs are investigated with the help of measurements, the circuit- and device-simulations to reveal the working mechanisms of transient high-frequency oscillations. For the first time the Transient Avalanche Oscillation is successfully reproduced with computer simulation, which allows the further investigation on the influences of individual parameters. The participation of IMPATT mechanism in Transient Avalanche oscillation is demonstrated. The interaction between IMPATT mechanism und PETT mechanism during the setting up of depletion region in IGBTs was investigated. Measures to suppress such oscillation are discussed on the levels of chip design, module design and the driver concept. Supplying electron current during critical phase is found to be an effctive method to avoid the dynamic avalanche and the TA-oscillation.
Radio Frequenz Oszillationen bis zu mehreren hundert MHz wurden während des Abschaltens von Hochstrom leitenden IGBTs beobachtet. Sie werden in dieser Arbeit als Transient Avalanche Oscillationen beschrieben. Anders als PETT Oszillationen, die in der Tail-Strom Phase vorkommen, erscheint diese Oszillation während des Anstiegs der Kollektor-Emitter-Spannung VCE und des Fallens des Kollektor-Emitter Stroms ICE. In dieser Arbeit werden die Abschaltvorgänge von IGBTs mit Hilfe von Messungen, Schaltungs- bzw. Device-Simulationen untersucht, um die Wirkungsmechanismen der transient erscheinenden hochfrequenten Oszillationen zu erklären. Es ist erstmals gelungen solche Transient Avalanche Oszillationen mit der Simulation zu reproduzieren und anschließend die Einflüsse einzelner Parameter zu untersuchen. Die Beteiligung des IMPATT Mechanismus an der Transient Avalanche Oszillation wurde nachgewiesen. Die Interaktion von IMPATT und PETT während Aufbau der Raumladungszone im IGBT wurde untersucht. Maßnahmen zur Unterdrückung der Oszillation werden auf den Ebenen von Chip-Design, Modulauslegung und der Treiberschaltung diskutiert. Das Zuführen des Elektrostromes während der kritischen Phase wird als ein effective Methode zur Vermeidung der TA-Oscillation nachgewiesen.

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The alcohol sector has shown a remarkable process of expansion since 2000, towards the central Cerrado, admittedly favored by situation anchored in renewable energy and defense of national sovereignty. The state of Goias is one of the prime targets of this expansion, since 2004, primarily from 2006 to 2007, and has been concentrating a strong sugar industry in southern Goiás / Southwest Microregion of Quirinópolis (MRQ), where he spent about 4 000 ha more than 150 000 ha planted in the period, with great impact on the local socio-economy, according to previous studies, and subsidiaries of this thesis. This micro-region has favorable soil and climatic characteristics and economic importance of high logistics intra-and inter-regional exports, but the changes in land use and environmental impacts related to this process are still poorly studied. This thesis aims to understand the spatial pattern of expansion of sugarcane and the MRQ, with emphasis on soil and its use changes, considered by many authors as the agricultural frontier expansion of the 1970s, but more organized and capitalized technified, aiming prove the hypothesis that there has been setting a new centrality of the sugarcane industry in the Cerrado, focusing on production of ethanol and bio-energy, multi-scale consequences of which affect, among other things, the other pre-existing supply chains, especially food production. We analyzed in more detail the succession of land uses in the period since 2004, before the arrival of the cane in order to identify the substitution patterns of crops and pastures by the new culture and the potential for direct environmental impacts of sugarcane due observation of pressure on water resources for irrigation purposes and on soils associated with the management system of high technological standards, involving inputs and pesticides, and heavy machinery, among others. The research was based mainly on compiling data and maps, and thematic development of multi-scale cartographic documents, including use of satellite imagery and GIS analysis of census data and detailed study of various impacts on soil and water resources, with sampling Field and laboratory analysis. It is concluded that sugarcane has focused initially on the best land of the MRQ, where it has the best infrastructure in regional / state, where it stood, triumphant, with other uses, in particular, grains (soybeans), and secondarily pastures, in which continues with the current expansion. The process as in the past is supported by federal policy, now the PNE - 2030, and receives federal and state subsidies. It's still fast and plays the same model of previous agricultural expansion, occupation of Savannah in the 1970s, differing, however the fastest and well-planned action of large financial groups and the rapid formation of joint ventures and sugar and alcohol agribusiness complexes horizontal extension of those South-East and even multinationals. These groups previously selected areas where expansion triggered the installation of plants inducing a re-zoning, but retained the strategy of producing agricultural commodities. Finally, it was found that the main direct environmental impacts cultivated areas are the loss of soil biodiversity and water resources soil compaction and increase their resistance to penetration, indicating compression, and it is assumed that there is potential for erosion and also the subsequent contamination of their time, because crop management. It was concluded that MRQ experience, paradoxically, both positive and negative social and environmental impacts arising from a rapidly expanding sugarcane which materialized a new centrality of the space sector in the Central Cerrado, similar to that which occurred in the past the state of São Paulo, but this time relying on an industry already established in the south-southeast and which together make up what is called the polygon of the cane and a new center, as part of this arc expansion of sugar cane, as undeniable and great expression of state and national levels, and gradually reference also becoming international.
O setor sucroalcooleiro vem apresentando um processo notável de expansão desde 2000, rumo ao Cerrado central, reconhecidamente favorecido por conjuntura ancorada na defesa da energia renovável e soberania nacional. O estado de Goiás é um dos alvos preferenciais dessa expansão, desde 2004, principalmente 2006-2007, e vem concentrando uma forte agroindústria canavieira na região Sul Goiano/Sudoeste, Microrregião de Quirinópolis (MRQ), onde passou de cerca de 4 mil ha a mais de 150 mil ha plantados no período, com grande impacto na socioeconomia local, segundo estudos anteriores e subsidiários desta tese. Essa microrregião conta com características edafoclimáticas favoráveis e logísticas de grande relevância econômica intra e inter-regional para exportação, porém as mudanças de uso do solo e impactos ambientais relacionados a esse processo ainda são pouco estudados. A presente tese objetiva compreender o padrão espacial de expansão da cana para e na MRQ, com ênfase em solos e suas mudanças de uso, entendidas por vários autores como expansão da Fronteira Agrícola da década de 1970, porém mais organizada, tecnificada e capitalizada, visando comprovar a hipótese de que aí vem se configurando uma nova centralidade do setor sucroenergético no Cerrado, voltado à produção de etanol e bioenergia, cujas consequências multiescalares afetam, dentre outros aspectos, as demais cadeias produtivas pré-existentes, especialmente de produção de alimentos. Analisou-se com mais detalhe a sucessão de usos do solo no período desde 2004, anterior à chegada da cana, de modo a identificar os padrões de substituição de culturas e pastagens pela nova cultura e o potencial de impactos ambientais diretos da cana devida constatação de pressão sobre os recursos hídricos para fins de irrigação e sobre os solos associados ao sistema de manejo de elevado padrão tecnológico, envolvendo insumos e defensivos, além de maquinaria pesada, dentre outros. A pesquisa baseou-se principalmente na compilação de dados e mapas, e elaboração de documentos cartográficos temáticos multiescalares, incluindo uso de imagens de satélite e SIG, análise de dados censitários diversos e estudo detalhado de impactos através de entrevistas dos principais atores, de descrição e coleta de amostras de solos e recursos hídricos e análise laboratorial. Conclui-se que a cana se concentrou inicialmente nas melhores terras da MRQ, onde conta com a melhor infra-estrutura regional/estadual, e vem concorrendo, vitoriosa, com outros usos, em particular, grãos (soja), e secundariamente pastagens, nas quais prossegue com a expansão atual. O processo, como no passado está amparado em política federal, ora o PNE - 2030, e recebe subsídios federais e estaduais. Ainda está acelerado e reproduz o mesmo modelo de expansão da Fronteira Agrícola anterior, de ocupação do Cerrado dos anos de 1970, diferenciando-se, entretanto pela rápida e mais bem planejada atuação de grandes grupos financeiros e formação rápida de joint ventures e complexos agroindustriais sucroalcooleiros horizontais em extensão daqueles do Sul-Sudeste e mesmo multinacionais. Esses grupos selecionaram previamente as áreas de expansão onde desencadearam a instalação das usinas induzindo um novo zoneamento, mas mantiveram a estratégia de produção de commodities agrícolas. Por fim, constatou-se que os principais impactos ambientais diretos nas áreas cultivadas são a perda de biodiversidade dos solos e dos recursos hídricos a compactação dos solos e a aumento de sua resistência à penetração, indicando compactação, e supõe-se que há potencial de erosão subsequente e também de sua contaminação com o tempo, devido manejo da cultura. Conclui-se também que a MRQ vivencia, paradoxalmente, os impactos socioambientais positivos e negativos decorrentes de uma expansão sucroalcooleira que materializou rapidamente uma nova centralidade espacial do setor no Cerrado Central, similar àquela ocorrida no passado no estado de São Paulo, porém desta feita contando com um setor já consolidado no Sul-Sudeste e que juntos se configuram no que se está chamando de polígono da cana e numa nova centralidade, esta como parte do arco de expansão da cana, já de inegável e grande expressão estadual e nacional, e aos poucos se tornando referência também internacional.

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Against the backdrop of the denominational status of network Adventist education present in a remarkable way in the school space and the intense religious diversity students, this research analyzes the relationship of possible tensions between the denominational school status and religious diversity present. It takes into account the process of modernity causing significant change in education, in religion and in the form of the two institutes relate to each other. It took into account the socio-economic and religious profile of the students and how is the reception of religious education in Adventist school space, including students who declare themselves Adventists. The area chosen for this research was the Adventist schools located in the ABCD Paulista context, which offer high school. These school units are located in the cities of Diadema, Santo Andre and Sao Caetano do Sul, cities located in the same micro region, but with different socioeconomic realities.
Tendo como pano de fundo a confessionalidade da rede adventista de educação presente de maneira marcante no espaço escolar e a intensa diversidade religiosa discente, esta pesquisa analisa a relação de possíveis tensões entre a confessionalidade escolar e a diversidade religiosa presente neste espaço. Leva em consideração o processo de modernidade causadora de importantes transformações na educação, na religião e na forma dos dois institutos se relacionarem. Levou-se em consideração o perfil socioeconômico e religioso dos alunos e possíveis tensões na recepção do religioso no espaço escolar adventista por parte dos discentes, inclusive por aqueles que se declaram adventistas. O espaço escolhido para esta pesquisa foi o de colégios adventistas localizadas no contexto do ABCD Paulista, que ofertam o Ensino Médio. Estas unidades escolares estão situadas nas cidades de Diadema, Santo André e São Caetano do Sul, cidades localizadas na mesma microrregião, mas com distintas realidades socioeconômicas.

La démographie et les modes de vie ont considérablement évolué au cours des dernières décades. De tels changements sont destinés à influencer la conception de l’habitation et ils incluent notamment une série de besoins émergents: s’en suivent des besoins additionnels en espace pour répondre à l’arrivée de ces activités additionnelles au niveau du logement. La planification en vue de répondre à ces besoins émergeants constitue le principal thème de la présente thèse. Dans le cas de la maison unifamiliale détachée, le sous-sol est disponible pour offrir des espaces appropriés à ces besoins émergents. Par contre, une telle ressource n’est normalement pas présente dans le cas d’un édifice multifamilial. La thèse propose un espace additionnel spécifique en vue de répondre à ces besoins émergents : l’espace supplétif. Même si un tel espace n’est pas envisagé dans les publications du domaine, des précédents existent quant à sa présence en planification multifamiliale. Le but de la présente étude est d’offrir des lignes directrices quant à la conception et l’intégration d’un tel espace supplétif. Elle va s’appuyer sur l’approche systémique en raison de la logique de déduire la solution à partir d’une analyse de l’objectif. L’application de l’approche systémique implique donc que tous les critères correspondant à la nature spécifique de l’espace supplétif seront extrapolés à partir de l’objectif. Dans le cas la présente étude, ce sont les critères du bureau à domicile qui seront d’abord précisés car il s’agit de l’activité émergente la plus exigeante. Les critères seront traités comme vecteurs d’un modèle générique indicatif de la manière d’organiser l’espace supplétif. Ce modèle visera le bureau à domicile en vue d’offrir les solutions pertinentes et il se concentrera principalement sur les critères d’intimité visuelle et spatiale. La contribution du modèle sera de suggérer des lignes directrices en vue d’incorporer l’espace supplétif à l’intérieur des édifices résidentiels de type multifamilial, ce que la planification conventionnelle n’offre pas. C’est le concept d’adaptabilité qui est à la base de toute stratégie visant à permettre le changement en architecture et en habitation, d’autant plus lorsqu’il s’agit d’un espace supplétif. À cet effet, l’espace supplétif va recourir à l’approche Open Building afin d’appliquer le concept d’adaptabilité, en raison de ses avantages majeurs tant au niveau conceptuel que constructif. Différentes applications de l’approche Open Building, telles que le projet NEXT21 et le protocole KSI (Kikou support and Infill), offrent des exemples susceptibles de constituer d’efficaces lignes directrices pour la conception d’un espace supplétif. La faisabilité du modèle d’espace supplétif proposé est vérifiable et démontrable dans le monde réel. Les systèmes constructifs industrialisés sont en mesure de permettre le changement sans démolition car leurs joints mécaniques « à sec » rencontrent généralement les normes DfD (Design for Disassembly), non seulement en ce qui concerne l’espace supplétif mais pour l’ensemble du logement.
Demographics and lifestyles have changed considerably in the past few decades. These changes are bound to influence the design of housing and they notably include a series of emerging needs: additional spatial needs due to additional activities brought to the traditional housing premises. Planning for those emerging needs is the main theme of this thesis. In a typical single-family detached house, the basement is available to accommodate the spatial requirements for these emerging needs. However, such a provision does not typically exist in multi-family housing. This thesis proposes a specific additional space to accommodate these emerging needs: the supplementary space. Although such a space has not been explored in the literature, there are precedents for its application in multi-family floor planning. The objective of this study is to provide guidelines for the design and the integration of this supplementary space. It relies on the systems approach as the design-decision methodology due to its logic of deducting the solution from the analysis of the objective. Applying the systems approach means that all the criteria corresponding to the specific purpose of the supplementary space will be extrapolated from the objective. However, once the supplementary space is being used to deal with emerging needs, it will then introduce its own relevant criteria. This study will start with the criteria for designing a home office because this is the most demanding emerging needs activity. The criteria are organized as vectors of a generic model indicating how the supplementary space can be formulated. The model will target the workplace at home and subsequently offer solutions to them. This study focuses on the planning provisions dealing mainly with visual and spatial privacy. The overall outcome of the model is to suggest guidelines to incorporate the supplementary space within multi-family residential buildings, a feature not offered in traditional planning. The concept of adaptability is the key design strategy to accommodate change in architecture and housing, even more in the case of a supplementary space. Therefore, the supplementary space model will apply the concept of adaptability through the Open Building (OB) approach; elaborating more on the practical design and construction features. Different OB applications, such as the NEXT21 project and the KSI (Kikou Support and Infill) protocol in Japan, are examples that can be used as efficient guidelines to design a supplementary space. The feasibility of the supplementary space model can be validated and served in the real world. Industrialized building systems are capable of accommodating change without demolition as their dry mechanical joints are generally at meeting the DfD (design for disassembly) standards, not only for the supplementary space but also for the whole dwelling unit.

GeV electron bunches accelerated on a centimeter scale device exemplify the extraordinary advances of laser-plasma acceleration. The combination of high charges from optimized injection schemes and intrinsic femtosecond short bunch duration yields kiloampere peak currents. Further enhancing the current while reducing the energy spread will pave the way for future application, e.g. the driver for compact secondary radiation sources such as high-field THz, high-brightness x-ray or gamma-ray sources. One essential key for beam transport to a specific application is an electron bunch with high quality beam parameters such as low energy spread as well as small divergence and spot size. The inherent micrometer size at the plasma exit is typically sufficient for an efficient coupling into a conventional beamline. However, energy spread and beam divergence require optimization before the beam can be transported efficiently. Induced by the high peak current, the beam loading regime can be used in order to achieve optimized beam parameters for beam transport.
In this thesis, the impact of beam loading on the transverse electron dynamic is systematically studied by investigating betatron radiation and electron beam divergence. For this reason, the bubble regime with self-truncated ionization injection (STII) is applied to set up a nanocoulomb-class laser wakefield accelerator. The accelerator is driven by 150TW laser pulses from the DRACO high power laser system. A supersonic gas jet provides a 3mm long acceleration medium with electron densities from 3 × 10^18 cm^−3 to 5 × 10^18 cm^−3. The STII scheme together with the employed setup yields highly reproducible injections with bunch charges of up to 0.5 nC. The recorded betatron radius at the accelerator exit is about one micron and reveals that the beam size stays at the same value. The optimal beam loading, which is observed at around 250 pC to 300 pC, leads to the minimum energy spread of ~40MeV and a 20% smaller divergence. It is demonstrated that an incomplete betatron phase mixing due to the small energy spread can explain the experimentally observed minimum beam divergence.