The interaction between competition and environmental policy is quite complex, particularly before state aids, whose control level reflects the emerging opportunity cost between both policies. In order to illustrate the potential efficiency losses or the imbalances on level playing field of competition, this article analyzes the legal, economic and political dimensions of the European Union Emissions Trading System (EU ETS) free allocation of allowances mechanism for the power generation sector. / La interacción entre la política de competencia y la medio ambientales bastante compleja, especialmente en el caso de las ayudas estatales, cuyo nivel de control refleja el coste de oportunidad emergente entre ambas. Con el fin de ilustrar las potenciales pérdidas de eficiencia o los desequilibrios en la equidad de condiciones de competencia, este artículo analiza las dimensiones legal, económica y política del mecanismo de asignación gratuita de permisos de emisión del Régimen Comunitario de Comercio de Derechos de Emisión (RCCDE) de la Unión Europea para el sector de la generación eléctrica.

Orientador: Furio Damiani / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-11T03:06:29Z (GMT). No. of bitstreams: 1 Werneck_NicolauLeal_M.pdf: 1556046 bytes, checksum: 677310006250588d7e6a0fb0eedfc170 (MD5) Previous issue date: 2007 / Resumo: Existem diversos problemas ligados à análise de sinais musicais que podem se beneficiar de um conhecimento mais detalhado da estrutura dos sinais gerados pelos diferentes instrumentos. Entre eles se destaca a compressão de sinais baseada em áudio estruturado, onde o codificador determina a partir de um sinal parâmetros para reproduzí-lo com um sintetizador inspirado em modelos físicos dos instrumentos. Para realizar este tipo de análise e síntese é necessário conhecermos as características físicas dos instrumentos e dos sinais produzidos. Este conhecimento é ainda útil para auxiliar no desenvolvimento de instrumentos e outros equipamentos utilizados por músicos para obter o timbre desejado. Esta dissertação apresenta experimentos realizados com uma guitarra elétrica para revelar a dinâmica não-linear de suas cordas e seu filtro linear associado, comparação de sinais gravados com resultados esperados por modelos matemáticos da forma de onda, e ainda uma proposta de uma potencial técnica para a medição de parâmetros para um modelo matemático de um circuito de distorção musical, além de uma maneira de se mapear um par destes parâmetros para um espaço de maior significado psicoacústico / Resumo: Existem diversos problemas ligados à análise de sinais musicais que podem se beneficiar de um conhecimento mais detalhado da estrutura dos sinais gerados pelos diferentes instrumentos. Entre eles se destaca a compressão de sinais baseada em áudio estruturado, onde o codificador determina a partir de um sinal parâmetros para reproduzí-lo com um sintetizador inspirado em modelos físicos dos instrumentos. Para realizar este tipo de análise e síntese é necessário conhecermos as características físicas dos instrumentos e dos sinais produzidos. Este conhecimento é ainda útil para auxiliar no desenvolvimento de instrumentos e outros equipamentos utilizados por músicos para obter o timbre desejado. Esta dissertação apresenta experimentos realizados com uma guitarra elétrica para revelar a dinâmica não-linear de suas cordas e seu filtro linear associado, comparação de sinais gravados com resultados esperados por modelos matemáticos da forma de onda, e ainda uma proposta de uma potencial técnica para a medição de parâmetros para um modelo matemático de um circuito de distorção musical, além de uma maneira de se mapear um par destes parâmetros para um espaço de maior significado psicoacústico / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Objetivos: avaliar a prevalência de alterações auditivas em recém-nascidos de muito baixo peso na Unidade de Tratamento Intensivo Neonatal do Hospital de Clínicas de Porto Alegre e estudar as variáveis que possam estar relacionadas com as alterações da acui-dade auditiva. Métodos: foi realizado um estudo transversal que incluiu todos os recém-nascidos de muito baixo peso admitidos na Unidade de Tratamento Intensivo Neonatal do Hospital de Clínicas de Porto Alegre no período de 1o de setembro de 2001 a 31 de janeiro de 2002. To-dos os pacientes foram submetidos ao exame de otoemissão acústica evocada por produto de distorção no momento da alta hospitalar. O exame foi repetido em 30 dias quando havia alte-ração no primeiro exame. Quando o paciente apresentava o exame de otoemissão acústica al-terada em duas ocasiões, era realizado o potencial auditivo evocado cerebral, considerado al-terado a partir de 35 dB NA. Resultados: foram estudados 96 recém-nascidos. Seis tiveram tanto o exame de otoemissão acústica quanto o potencial auditivo evocado cerebral alterados. A média da idade gestacional foi de 31,5 ± 2,6 semanas, o peso de nascimento variou de 640 a 1.500 g e 57,3% dos pacientes eram do sexo feminino. A idade gestacional e o índice de Apgar no 5o minuto foram inferiores no grupo otoemissão acústica e potencial auditivo evocado cerebral alterados em relação aos demais grupos, atingindo significância limítrofe. Conclusões: a prevalência de perda auditiva nos recém-nascidos de muito baixo peso da Unidade de Tratamento Intensivo Neonatal do Hospital de Clínicas de Porto Alegre foi de 6,3%, tendo sido observadas associações de significância limítrofe com idade gestacional e índice de Apgar no 5o minuto. / Objectives: to evaluate the prevalence of hearing loss in very low birth weight patients in the Neonatal Intensive Care Unit of the Hospital de Clínicas de Porto Alegre and to study the variables that can be related to hearing loss. Methods: a transversal study was carried through including all very low birth weight neonates admitted in the Neonatal Intensive Care Unit of the Hospital de Clínicas de Porto Alegre during September 1, 2000 to January 31, 2002. All patients were undergone to the distortion evoked otoacoustic emission test in the hospital discharge. When the patient presented alteration in this test, it was repeated in 30 days. However, when the patient who presented pathologic otoacoustic emission on two ocasions was undergone to the auditory evoked brain response. This test was considered abnormal from 35 dB NA. Results: we studied 96 neonates. Six children presented alteration in the distortion evoked otoacoustic emission test as well in the auditory evoked brain response. The children age average was 31.5 ± 2.6 weeks, their birth weight was between 640 g and 1,500 g, and 57.3% of the patients were female. The gestational age and the Apgar score at 5 minutes were inferior in the otoacoustic emission and auditory evoked brain response abnormal group related to the other groups, reaching bordering significance. Conclusions: the hearing loss prevalence of the very low birth weight neonates from the Neonatal Intensive Care Unit of the HCPA was 6.3%, and it was observed bordering significance associations related to gestational age and 5 minutes Apgar score.

Today, there is an essential need for lightweight, energy-efficient, environmentally benign engineering systems, and this is the driving force behind the development of a wide range of structural and functional materials for energy generation, energy storage, propulsion, and transportation. These challenges have motivated the use of magnesium alloys for lightweight structural systems. Magnesium has a density of 1.74 g/cm3, which is almost 30% less than that of aluminium, one quarter of steel, and almost identicalto polymers. The ease of recycling magnesium alloys as compared to polymers makes them environmentally attractive, but their poor mechanical performance is the primary reason for the limited adoption of these alloys for structural applications. The Mg-Al-Zn alloy AZ91D exhibits an excellent combination of strength, die-castability, and corrosion resistance. However, its mechanical performance with regard to creep strength, for example, at evaluated temperatures is poor. Moreover, very little is known about the correlation between its mechanical properties and microstructural features. This thesis aims to provide new knowledge regarding the role played by microstructure in the mechanical performance of the magnesium alloy. The properties/performance of the material in relation to process parameters became of great interest during the investigation. An exhaustive characterisation of the grain size, secondary dendrite arm spacing (SDAS) distribution, and fraction of Mg17Al12 was performed using optical and electron backscatter diffraction (EBSD). These microstructural parameters were correlated to the offset yield point (Rp0.2), fracture strength, and elongation to failure of the material. It was proposed that the intermetallic phase, Mg17Al12, plays an important role in determining the mechanical and physical properties of the alloy in a temperature range of room temperature to 190°C by forming a rigid network of intermetallic. The presence of this network was confirmed by studying the thermal expansion behaviour of samples of the alloy containing different amounts of Mg17Al12. A physically based constitutive model with a wide validity range was successfully adapted to describe the flow stress behaviour of AZ91D with various microstructures. The temperature-dependent variables of the model correlated quite well with the underlying physics of the material. The model was validated through comparison with dislocation densities obtained using EBSD. The influence of high-pressure die-cast parameters on the distortion and residual stress of the cast components was studied, as were distortion and residual stress in components after shot peening and painting. Interestingly, it was found that intensification pressure has a major effect on distortion and residual stresses, and that the temperature of the fixed half of the die had a slight influence on the component's distortion and residual stress. / Numera finns det ett väsentligt behov av lätta, energieffektiva och miljövänliga tekniksystem. Detta behov är drivkraften för utveckling av ett brett utbud av material för energigenerering, energilagring, framdrivning och transport. Dessa utmaningar motiverade användningen av magnesiumlegeringar för lättviktskonstruktioner. Magnesium har en densitet på 1,74 g/cm3, vilket är ca 30% lägre än för aluminium, en fjärdedel av densiteten för stål och nästan i nivå med många polymerer. Då magnesiumlegeringar dessutom är lätta att återvinna, jämfört med polymerer, gör det dem miljömässigt attraktiva. Låga mekaniska egenskaper är den främsta orsaken till begränsad användning av dessa legeringar för lastbärande tillämpningar. Mg-Al-Zn-legeringen AZ91D uppvisar en utmärkt kombination av styrka, gjutbarhet och korrosionsbeständighet. Dess mekaniska egenskaper vid förhöjd temperatur, som tex kryphållfasthet, är låga. Dessutom är korrelationen mellan mikrostruktur och mekaniska egenskaper oklar. Denna avhandling syftade till att ge ny kunskap om mikrostrukturens roll för magnesiumlegeringars mekaniska egenskaper. Slutligen var materialets egenskaper i förhållande till processparametrar vid tillverkningen av stort intresse. En omfattande karaktärisering av kornstorleks-, sekundära dendritarmavstånds (SDAS)-fördelning och fraktion av Mg17Al12 utfördes med hjälp av optisk mikroskopering och diffraktion av bakåtspridda elektroner (EBSD). Mikrostrukturen korrelerades till sträckgränsen (Rp0.2), brottstyrkan och brottförlängningen. Det föreslogs att den intermetalliska fasen, Mg17Al12, spelar en viktig roll vid bestämning av legeringens mekaniska och fysikaliska egenskaper vid temperaturintervall från rumstemperatur upp till 190°C genom att bilda ett styvt nätverk av intermetaller. Uppkomsten av ett sådant nätverk stöddes genom en studie av den termiska expansionen av legeringen för olika fraktioner av Mg17Al12. En fysikalisk konstitutiv modell med ett brett giltighetsområde användes framgångsrikt för att beskriva det plastiska flytbeteendet hos AZ91D för olika mikrostrukturer. De temperaturberoende variablerna i modellen korrelerade ganska väl med materialets underliggande fysik. Modellen validerades genom att jämföra dislokationstätheten som predikterades av modellen och den med EBSD uppmätta dislokationstätheten. Påverkan av pressgjutningsparametrar på geometrisk tolerans och restspänning hos de gjutna komponenterna studerades. Vidare studerades geometrisk tolerans och restspänning av komponenter efter pening och målning. Intressant nog hade eftermatningsfasen en stor effekt på geometrisk tolerans och restspänningar. Dessutom hade temperaturen på den fasta formhalvan av verktyget även ett visst inflytande på komponentens geometriska tolerans och restspänning.

2016年的英國脫歐公投，最終以51.89%比48.11%的差距，決定了英國脫歐的命運。各界紛紛揣測各種可能造成民眾投下脫歐一票的原因，包含個人經濟狀況、政黨認同、受民粹操控、反菁英、對歐洲認同等。本文針對既有研究中尚存在之空缺，聚焦「議題投票取向」對選民投票抉擇的影響，探究脫歐陣營對資訊的扭曲是否對選民的投票抉擇有顯著影響。論文就脫歐派針對國民健保、移民、脫歐後的英國對外經貿、失業率、勞工權益保障與是否能無條件持續享有歐盟單一市場好處這六項議題，透過「二分勝算對數模型」進行分析，從個體層次行為來瞭解資訊扭曲對選民在脫歐公投中投票行為的影響。 研究結果顯示，在移民潮來襲、民眾高喊反全球化與選民不安全感高漲的大環境背景下，脫歐陣營對選民所關心之議題的煽動與對資訊的操控使選民在做出投票抉擇時受到明顯誤導。此外，模型結果亦顯示，選民的個人社經背景與心理態度認知同樣對選民投票行為產生影響。總結而言，本研究透過微觀層次的分析，針對促使選民投下脫歐一票的因素做出深入探討，並以「資訊扭曲」作為重要變數，補充議題投票相關研究之不足。 / In the Brexit referendum held in June 2016, 51.89 per cent of the voter voted Leave and 48.11 per cent voted Remain. The result sealed the fate of the UK as an outsider of the European Union. While the reasons behind voter’s choice to leave the EU remain disputed, individual voter’s socio-economic status, party identification, populism, anti-elite mood, and identity toward European were among the most frequently listed factors. In order to fill the gap that existing researchs has left, this thesis focuses on the significance of “issue voting” in voting behavior. It discusses if the distortion of information by the Leave campaign had a significant impact on people’s voting choice. It uses the “logistic regression model” to analyse six issues brought about by the Leave campaign. They include the NHS, immigration, trading arrangements with other nations, unemployment, working conditions for British workers, and unconditional maintaining of all the benefits from the EU. By focusing on the individual level, I try to investigate how the distortion of information has impacted upon people’s voting behavior in the Brexit referendum. The study shows that against the background of an increased flow of immigrants and heightened anti-globalization mood, voters had a strong sense of insecurity. Under such circumstances, the Leave campaign exploited the opportunity to incite voters on issues they cared most about, manipulated information during the demagogic campaign, and misled people on their voting decision. In addition, the model also demonstrates that voters’ socioeconomic status and mental cognizance have the same effect on people’s voting behavior. In the nutshell, this thesis uses micro-level analysis to investigate voter behavior in the Brexit referendum. It brings in “information distortion” as a key variable in explaining voter behavior, a variable largely neglected in the existing literature on issue voting.

The phenomenon of spray in crossflow is of relevance in gas turbine combustor development. The current work focuses on spray in crossflow rather than liquid jet in crossflow from the standpoint of enhancing fuel dispersion and mixing. Specifically, the first part of the work involves study of spray structure, droplet sizing, and velocimetry for sprays of water and ethanol in a crossflow under ambient conditions. Laser-based diagnostic techniques such as Particle/Droplet Image Analysis (PDIA) and Particle Tracking Velocimetry (PTV) are utilized. Using spray structure images, trajectory equations are derived by multi-variable regression. It is found that the spray trajectory depends only on the two-phase momentum ratio and is independent of other flow parameters. A generalized correlation for the spray trajectory is proposed incorporating the liquid surface tension, which is found to be effective for our data, with water and ethanol, as well as data on Jet-A from the literature for a wide variety of operating conditions. An interesting phenomenon of spatial bifurcation of the spray is observed at low Gas-to-Liquid ratios (GLRs). The reason for this phenomenon is attributed to the co-existence of large and highly deformed ligaments along with much smaller droplets at low GLR conditions. The smaller droplets lose their vertical momentum rapidly leading to lower penetration, whereas the larger ligaments/droplets penetrate much more due to their larger momentum leading to a spatial separation of the two streams. The second part of the study focuses on evaporating sprays in preheated crossflow. Experiments are conducted using ethanol, decane, Jet-A1 fuel, and a two-component surrogate for Jet-A1 fuel. The crossflow air is heated up to 418 K and the effect of evaporation is studied on spray trajectory and droplet sizes. Measured droplet sizes and velocities at two successive locations are used to estimate droplet evaporation lifetimes. Evaporation constant for the d2 law derived from the droplet lifetimes represents the first-ever data for the above-mentioned liquids under forced convective conditions. This data can be used to validate multi-component droplet evaporation models. The last part of the study focuses on Large Eddy Simulations (LES) of the spray in crossflow. The near-nozzle spray structure is investigated experimentally to obtain droplet size and velocity distributions that are used as inputs to the computational model. For the spray in crossflow under ambient conditions, trajectory and droplet sizes at different locations are compared with experimental results. While the predicted trajectory is found to be in good agreement with data, the predicted droplet sizes are larger than the measured values. This is attributed to the implicit assumption in the secondary breakup model that the droplets are spherical, whereas the experimental data in the near-nozzle region clearly shows presence of mostly ligaments and non-spherical droplets, especially for the low GLR cases. A modified breakup model is found to lead to improved agreement in droplet sizes between predictions and measurements. Overall, the experiments and computations have provided significant insight into spray in crossflow phenomenon, and have yielded useful results in terms of validated spray trajectory correlations, droplet evaporation lifetimes under forced convective conditions, and a methodology for simulation of airblast sprays.

L’écoulement de jeu dans les compresseurs axiaux est étudié à l’aide de la Zonal Detached Eddy Simulation (ZDES). L’objectif consiste à évaluer la capacité de méthodes hybrides URANS/LES à simuler l’écoulement de jeu d’un compresseur axial réaliste afin de mieux comprendre la physique de cet écoulement, notamment son comportement au vannage ainsi que l’effet de sillages venant du stator amont sur le rotor aval. Après avoir choisi la méthode hybride ZDES, un banc d’essai numérique est défini afin de simuler le premier rotor du compresseur de recherche CREATE. Ce banc a la particularité de pouvoir prendre en compte les effets instationnaires venant de la roue directrice d’entrée (RDE), notamment son sillage ainsi que les tourbillons générés en pied et en tête. Basé sur des critères de maillage ZDES, il est utilisé pour évaluer cette méthode comparativement aux méthodes classiques RANS et URANS. La ZDES est validée par étape jusqu’à une analyse spectrale de l’écoulement de jeu se basant sur des données expérimentales. Elle s’est révélée capable de capturer plus précisément l’intensité et la position des phénomènes instationnaires rencontrés en tête du rotor, notamment le tourbillon de jeu. Les densités spectrales de puissance analysées montrent que cela est dû en partie à une meilleure prise en compte du transfert d’énergie des grandes vers les petites structures de l’écoulement avant leur dissipation. De plus, l’écart entre les approches s’accentue lorsque le tourbillon de jeu traverse le choc en tête. Proche pompage, les effets d’interaction entre le choc, le tourbillon de jeu, la couche limite carter et le tourbillon venant de la tête de la RDE sont amplifiés. Le décollement de la couche limite carter s’accentue et une inversion locale de l’écoulement est observée. De plus, le tourbillon de jeu s’élargit et est dévié vers la pale adjacente, ce qui intensifie le phénomène de double écoulement de jeu. L’interaction du tourbillon venant de la tête de la RDE avec le choc et le tourbillon de jeu du rotor est ensuite étudiée au point de dessin. Un battement du tourbillon de jeu est rencontré lors de l’interaction de ce tourbillon avec le tourbillon de tête de la RDE, ce qui diminue le double écoulement de jeu. / The tip-leakage flow in axial compressors is studied with the Zonal Detached Eddy Simulation (ZDES). This study aims at evaluating the capability of hybrid URANS/LES methods to simulate the tip-leakage flow within a realistic axial compressor in order to better understand the involved physics, especially the behaviour of the flow near surge and the effects of stator wakes on the downstream rotor. Once the ZDES method is chosen, a numerical test bench is defined to simulate the first rotor of the research compressor CREATE. This bench takes into account the unsteady effects of the Inlet Guide Vane (IGV), such as its wake as well as vortices generated at the IGV hub and tip. It is based upon ZDES meshing criteria and is used to evaluate this method compared to classic RANS and URANS approaches. A method validation is carried out up to a spectral analysis compared to experimental data. The ZDES is capable to capture more accurately the intensity and position of the unsteady phenomena encountered in the tip region, especially the tip-leakage vortex. The power spectral densities highlight that this partly originates from a better capture of the energy transfer from large to small structures until their dissipation. The discrepancy between the methods is accentuated as the tip-leakage vortex crosses the shock. Near the surge line, the interactions between the shock, the tip-leakage vortex, the boundary layer developing on the shroud and the vortex generated by the IGV tip are amplified. The boundary layer on the shroud separates earlier and a local flow inversion occurs. Besides, the tip-leakage vortex widens and is deflected toward the adjacent blade. This strengthens the double leakage. At the design operating point, the interaction of the IGV tip vortex with the shock and the rotor tip vortex is studied. A vortex flutter is observed as the IGV tip vortex arrives on the rotor blade and stretches the rotor tip vortex. This phenomenon decreases the double leakage.

The Clement Ader Institute of Albi and the von Karman Institute follow<p>since numerous years works about IR radiometry with the aim to do quantitative<p>thermography (true temperature measurement without contact). These works allowed<p>to explore potentiality several spectral bands :8-12µm, 3-5µm and recently the<p>0.75-1.7µm band (near IR) with the help of CCD camera (Si) or VisGaAs camera.<p>Studies done in this specific domain have underlined some perturbations emphasized<p>at high-temperature (T>800◦C). This work has to deal in details with the<p>treatment of parameters playing a role in camera measurements. The first of these<p>parameters is the emissivity, this treatment is made in another thesis. The second<p>parameter affects particularly the hot spot location and the spatial distortion. This<p>perturbation comes from convective effect present around every hot objects.The<p>purpose of this thesis is to analyze this effect and to correct it. Indeed, when a hot<p>object is in a colder surrounding media, a temperature gradient is shaped around<p>the object and thus a refractive index gradient too. This phenomena brings inevitably<p>distortions of the spatial information received by the camera. The goal of this<p>work will be to estimate and correct error made on temperature and/or distortion<p>measurement by CCD or VisGaAs camera on hot object.We chose to focus our work<p>on the convective plume created by a hot horizontal disk. This study will be done<p>with an experimental and a numerical approach. For the numerical approach, a raytracing<p>code has been developed in order to obtain numerically the displacement<p>due to the light deviation occurring in the perturbation. The input data of the code<p>is the refractive index of the hot air present around the object. This refractive index,<p>depending on the wavelength, can be found directly from the temperature thanks<p>to the Gladstone-Dale law. The temperature is given by a CFD software such as<p>FLUENT. Experimentally, we will use the Background Oriented Schlieren (BOS)<p>method in order to retrieve the displacement. We can see that the displacement can<p>reach 4 pixels in the plume (corresponding to 1mm in this case). This perturbation<p>has been studied for several spectral bands (visible, near infrared, infrared). Finally,<p>some solutions of correction are given, like using the inverse Abel Transform<p>in order to retrieve from the 2D displacement, a 3D (axisymmetric) refractive index<p>field that we will implement in the ray-tracing code and consequently predict the<p>displacement for any kind of wavelength or distance (distance between the camera<p>and the object)./L’Institut Clément Ader Albi (ICAA) et l’Institut von Karman (IVK)<p>mènent depuis un certain nombre d’années des travaux sur la radiométrie IR dans<p>le but de faire de la thermographie quantitative (mesure de température vraie sans<p>contact). Ces travaux ont permis d’explorer les potentialités de plusieurs bandes<p>spectrales :8-12µm, 3-5µm et plus récemment la bande 0,75-1,7µm (proche IR) à<p>l’aide de caméras CCD (Si) ou VisGaAs. Les travaux effectués dans ce domaine<p>spectral ont permis de mettre en évidence un certains nombre de perturbations<p>renforcées par les hautes températures (T>800◦C). Cette thèse aborde de façon détaillée<p>le traitement d’un certain nombre de grandeurs d’influence liées à la mesure<p>de différents paramètres dans le domaine du proche IR mais également étendus aux<p>domaines du visible et de l’IR. La première de ces grandeurs est l’émissivité dont le<p>traitement a déjà été abordé par d’autres études. La seconde grandeur d’influence<p>touche plus particulièrement à la localisation des points chauds sur l’objet et la distorsion<p>du champ de température apportée par les effets convectifs présents autour<p>d’un objet à haute température, elle est le coeur de cette thèse. En effet, lorsqu’une<p>pièce chaude se trouve dans un milieu ambiant beaucoup plus froid, il se crée un<p>gradient de température et donc d’indice de réfraction autour de la pièce. Or les<p>caméras travaillant dans les différentes bandes spectrales vont être plus ou moins<p>sensibles à ces variations d’indices de réfraction du fait de la dépendance de l’indice<p>optique avec la longueur d’onde et de la résolution spatiale de la caméra utilisée.<p>Ce phénomène, appelé effet mirage, entraîne inévitablement une déformation des<p>informations spatiales reçues par la caméra. Le but de cette thèse a donc été d’estimer<p>et de proposer une première approche pour corriger l’erreur faite sur la mesure<p>de température et/ou de déformation faites par caméras sur des pièces chaudes.<p>La démarche générale du travail a donc été dans un premier temps de calculer le<p>champ de température autour de l’objet considéré en se ramenant d’abord à des cas<p>simplifiés. On en a déduit alors le champ de réfraction entraînant une « déformation<p>» de l’objet, en faisant le lien entre T et n. Cette étape correspond à l’approche<p>numérique de notre étude. Cette étape numérique a été réalisé à l’aide d’un outil de<p>lancer de rayons développée à l’ICA. L’approche expérimentale a consisté à l’utilisation<p>de méthodes telle que la BOS (Background Oriented Schlieren), la PIV,<p>la srtioscopie afin de déduire le champ de déplacements provoqué par le panache<p>convectif. Ces résultats ont été comparés à la méthode numérique et ceci pour différentes<p>longueurs d’ondes. Enfin, une stratégie de correction d’images perturbées<p>a été abordé à l’aide de méthodes telles que la transformée d’Abel inverse afin de<p>remonter au champ d’indice de réfraction 2D axisymétrique à partir d’une déformation<p>plane. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

The theme of the master´s thesis is design a microphone preamplifier which uses vacuum tube as a main amplifying element. Part of the work is theoretical assumptions for the optimal design and implementation of peripheral involvement, comparing the properties of components used and the resulting parameters of modeled device. The thesis also includes a proposal of the source unit for supplying all parts of the preamplifier. The results are accompanied by circuit simulations and laboratory measurements of the main parameters of the designed device.

Massive MIMO (multiple-input–multiple-output) is a multi-antenna technology for cellular wireless communication, where the base station uses a large number of individually controllable antennas to multiplex users spatially.  This technology can provide a high spectral efficiency.  One of its main challenges is the immense hardware complexity and cost of all the radio chains in the base station.  To make massive MIMO commercially viable, inexpensive, low-complexity hardware with low linearity has to be used, which inherently leads to more signal distortion.  This thesis investigates how the degenerated linearity of some of the main components—power amplifiers, analog-to-digital converters (ADCs) and low-noise amplifiers—affects the performance of the system, with respect to data rate, power consumption and out-of-band radiation. The main results are: Spatial processing can reduce PAR (peak-to-average ratio) of the transmit signals in the downlink to as low as 0B; this, however, does not necessarily reduce power consumption.  In environments with isotropic fading, one-bit ADCs lead to a reduction in effective signal-to-interference-and-noise ratio (SINR) of 4dB in the uplink and four-bit ADCs give a performance close to that of an unquantized system.  An analytical expression for the radiation pattern of the distortion from nonlinear power amplifiers is derived.  It shows how the distortion is beamformed to some extent, that its gain never is greater than that of the desired signal, and that the gain of the distortion is reduced with a higher number of served users and a higher number of channel taps.  Nonlinear low-noise amplifiers give rise to distortion that partly combines coherently and limits the possible SINR.  It is concluded that spatial processing with a large number of antennas reduces the impact of hardware distortion in most cases.  As long as proper attention is paid to the few sources of coherent distortion, the hardware complexity can be reduced in massive MIMO base stations to overcome the hardware challenge and make massive MIMO commercial reality. / Massiv MIMO (eng: multiple-input–multiple-output) är en flerantennsteknologi för cellulär trådlös kommunikation, där basstationen använder ett stort antal individuellt styrbara antenner för att multiplexa användare i rummet.  Denna teknologi kan tillhandahålla en hög spektral effektivitet.  En av dess främsta utmaningar är den enorma hårdvarukomplexiteten och kostnaden hos basstationens alla radiokedjor.  För att massiv MIMO skall bli kommersiellt attraktivt, måste billiga, enkla hårdvarukomponenter med låg linjäritet användas, vilket oundvikligen leder till mer signaldistorsion.  Denna avhandling undersöker hur den försämrade linjäriteten hos några av huvudkomponenterna – effektförstärkare, analog-digital-omvandlare (AD-omvandlare) och lågbrusförstärkare – påverkar systemets prestanda, i termer av datatakt, effektförbrukning och utombandsstrålning.  Huvudresultaten är: Rumslig signalbehandling kan reducera sändsignalernas toppvärde i nerlänken ända ner till 0dB, vilket dock inte nödvändigtvis minskar effektförbrukningen.  I miljöer med isotrop fädning leder enbits-AD-omvandlare till 4dB lägre signal-till-interferens-och-brus-förhållande i upplänken, och fyrabits-AD-omvandlare ger en prestanda nära den ett system utan kvantisering kan uppnå.  Ett analytiskt uttryck för strålningsmönstret för distorsionen från icke-linjära effektförstärkare härleds.  Det visar hur distorsionen till viss del lobformas, att dess förstärkning aldrig är starkare än förstärkningen för den önskade signalen och att distorsionens förstärkning minskar med ett högre antal betjänade användare och ett högre antal kanaltappar.  Icke-linjära lågbrusförstärkare ger upphov distorsion som delvis kombinerar koherent och begränsar det möjliga signal-till-brus-och-interferens-förhållandet.  Slutsatsen är att rumslig signalbehandling med ett stort antal antenner reducerar hårdvarudistorsionens inverkan i de flesta fall.  Så länge som de få källorna till koherent distorsion ges tillbörlig uppmärksamhet, kan hårdvarukomplexiteten minskas i basstationer för massiv MIMO för att övervinna hårdvaruutmaningen och göra massiv MIMO kommersiell verklighet. / 蜂窩無線通訊領域中的大規模多天線技術以多個單獨可控的天線通過空間複用的方式服務多個用戶。如是可以大幅提高頻譜效率。實現此技術的主要難題在於基站所用射頻單元的極大複雜度及成本。爲使大規模多天線技術適用在商業系統中，需使用導致失真的低複雜度低成本的非線性硬件。本文探討若將一些主要部件——功放、模數轉換器、低噪聲放大器——的線性程度降低，系統性能是如何受到影響的，即系統的速率、功耗、帶外泄露等指標。主要的結果爲：空間信號處理可以降低下行信號的峯均比，直至０分貝；然而低峯均比不一定能夠降低功耗。用一比特模數轉換器使上行的信干噪比減少４分貝；用四比特模數轉換器可在各向同性衰落的環境裏實現接近無量化系統的性能。本文推導出非線性功放失真輻射方向的解析公式。該公式展示失真在某種程度上會被波束成形的；具體而言，失真的波束成形增益不大於有效信號的增益，波束成形增益會根據服務用戶數量和信道階數的增長而降低。非線性低噪聲放大器引起的失真，一部分會相干地合併，因此會限制信干噪比的增長。結論爲多天線的空間信號處理可以減少硬件失真的影響。只要適當地處理少數相干失真的來源，大規模多天線基站可以降低硬件複雜度，解決硬件難題，使大規模多天線技術成功地應用在商業系統中成爲現實。