L'objectif de cette thèse est d'étudier la fiabilité et la cyclabilité des jonctions Tunnel magnétique pour mieux comprendre les mécanismes de dégradation et de claquage de la barrière. Une étude de l'endurance de la barrière MgO jusqu'au claquage électrique est présentée. Les échantillons ont été testés sous un mode impulsionnel. Par l'étude de l'effet de retard entre des impulsions successives, une durée de vie optimale des JTM est observée pour une valeur intermédiaire de retard entre les impulsions correspondant à un compromis optimal entre la densité moyenne de charge piégée dans la barrière et la modulation temporelle de charge. En outre, un modèle de piégeage / dépiégeage de charge a été développé qui appuie cette interprétation. L'étude souligne le rôle des pièges de charges dans le mécanisme de claquage de la barrière tunnel. Elle montre aussi que l'endurance extrêmement longue pourrait être obtenue en réduisant la densité des sites de piégeage d'électrons dans la barrière tunnel. Puis, une étude de l'endurance et le bruit basse fréquence a été dans les jonctionS CoFeB/MgO/CoFeB pour STT-MRAM ou TA-MRAM. Une corrélation a été observée et expliquée par la présence de sites de piégeage d'électrons dans la barrière de MgO et le rôle des phénomènes de charge/ décharge à la fois dans la fiabilité et la puissance du bruit en 1 / f électrique. Ces résultats prouvent que le test du bruit basse fréquence peut être utilisé comme une caractérisation prédictive de l'endurance. Enfin, en perspectives, des mesures complémentaires en été proposées pour développer plus le modèle de charge/décharge, une optimisation de la barrière pourrait ainsi être réaliser pour réduire le nombre des pièges de charge au sein de la barrière et par conséquent améliorer la fiabilité des jonctions Tunnel. / The thesis objective is to study the Magnetic Tunnel Junction reliability and cyclability to more understand the barrier breakdown mechanisms. An investigation of barrier endurance till electrical breakdown in MgO-based magnetic tunnel junctions (MTJs) is presented. Samples were tested under pulsed electrical stress. By studying the effect of delay between successive pulses, an optimum endurance of MTJs is observed for an intermediate value of delay between pulses corresponding to an optimum trade-off between the average density of charge trapped in the barrier and the amplitude of its time-modulation at each voltage pulse. Furthermore, a charge trapping/detrapping model was developed which support this interpretation. The study emphasizes the role of electron trapping/detrapping mechanisms on the tunnel barrier reliability. It also shows that extremely long endurance could be obtained in MTJs by reducing the density of electron trapping sites in the tunnel barrier. Then the write endurance and the 1/f noise of electrical origin were characterized in CoFeB/MgO/CoFeB MTJ for STT-MRAM or TA-MRAM. A correlation was observed and explained by the presence of electron trapping sites in the MgO barrier and the role of electron trapping/detrapping phenomena in both the MTJ reliability and its 1/f electrical noise power. These results suggest that 1/f noise could be used as a predictive characterization of the MTJ endurance. Finally, as thesis perspectives, some complement measurements were proposed to further investigate this model and an optimization of MgO barrier which could be carried out to reduce the density of these trapping sites was presented to ameliorate the MTJs reliability.

Parmi les architectures candidates pour les générations sub-22nm figurent les transistors sur silicium sur isolant (SOI). A cette échelle, les composants doivent intégrer des films isolants enterrés (BOX) et des canaux de conduction (Body) ultra-minces. A ceci s'ajoute l'utilisation d'empilements de grille avancés (diélectriques à haute permittivité / métal de grille) et une ingénierie de la contrainte mécanique avec l'utilisation d'alliages SiGe pour le canal des transistors de type P. La mise au point d'une telle technologie demande qu'on soit capable d'extraire de façon non destructive et avec précision la qualité du transport électronique et des interfaces, ainsi que les valeurs des paramètres physiques (dimensions et dopages), qui sont obtenues effectivement en fin de fabrication. Des techniques d'extraction de paramètres ont été développées au cours du temps. L'objectif de cette thèse est de reconsidérer et de faire évoluer ces techniques pour les adapter aux épaisseurs extrêmement réduites des composants étudiés. Elle combine mesures approfondies et modélisation en support. Parmi les résultats originaux obtenus au cours de cette thèse, citons notamment l'adaptation de la méthode split CV complète qui permet désormais d'extraire les paramètres caractérisant l'ensemble de l'empilement SOI, depuis le substrat et son dopage jusqu'à la grille, ainsi qu'une analyse extrêmement détaillée du transport grâce à des mesures en régime de couplage grille arrière à température variable ou l'exploitation de la magnétorésistance de canal depuis le régime linéaire jusqu'en saturation. Le mémoire se termine par une analyse détaillée du bruit basse fréquence. / Silicon on insulator (SOI) transistors are among the best candidates for sub-22nm technology nodes. At this scale, the devices integrate extremely thin buried oxide layers (BOX) and body. They also integrate advanced high-k dielectric / metal gate stacks and strain engineering is used to improve transport properties with, for instance, the use of SiGe alloys in the channel of p-type MOS transistors. The optimization of such a technology requires precise and non-destructive experimental techniques able to provide information about the quality of electron transport and interface quality, as well as about the real values of physical parameters (dimensions and doping level) at the end of the process. Techniques for parameter extraction from electrical characteristics have been developed over time. The aim of this thesis work is to reconsider these methods and to further develop them to account for the extremely small dimensions used for sub-22nm SOI generations. The work is based on extended characterization and modelling in support. Among the original results obtained during this thesis, special notice should be put on the adaptation of the complete split CV method which is now able to extract the characteristic parameters for the entire stack, from the substrate and its doping level to the gate stack, as well as an extremely detailed analysis of electron transport based on low temperature characterization in back-gate electrostatic coupling conditions or the exploitation of channel magnetoresistance from the linear regime of operation to saturation. Finally, a detailed analysis of low-frequency noise closes this study.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / A espasticidade é observada na maioria dos pacientes após Acidente Vascular Encefálico (AVE), e exercem influência na presença de deficiências e incapacidades, comprometendo a função motora. As estratégias de neuroreabilitação, o biofeedback eletromiográfico (EMG), têm sido utilizado com aceitação na comunidade médica para reajustes nas habilidades sensório-motoras como retreinamento motor, redução da espasticidade e/ou treinamento de relaxamento. A intervenção ainda apresenta evidências delimitadas quanto a sua efetividade na reabilitação, principalmente, quanto a interferência sobre a atividade cortical e na redução dos sinais espásticos que oferece características negativas na execução do movimento. O objetivo dessa pesquisa foi analisar a possível interferência do treino com biofeedback eletromiográfico sobre a conscientização do controle motor no membro espástico e a caracterização da atividade das bandas de baixa frequência em diferentes regiões corticais orientada pela técnica de treinamento. Dezesseis voluntários acometidos por AVE isquêmicos foram selecionados e divididos em dois grupos (n=8). Grupo experimental (GE) submetidos ao treino com biofeedback associado a fisioterapia, e o grupo controle (GC) submetido apenas à fisioterapia convencional. Foi realizada a avaliação do grau de espasticidade pelo limiar de reflexo do estiramento tônico (LRET) e pela Escala Modificada de Ashworth (EMA) antes e três semanas após o término do treinamento com a técnica. Os sujeitos foram submetidos ao biofeedback durante 6 semanas, com 2 sessões semanalmente. O mesmo tempo para o tratamento fisioterápico foi padronizado para o GC. Os resultados mostram variação do percentual médio de melhora do grau de espasticidade, mensuradas pelo LRET, de 38,59% (dp=13,03%) no GE comparado com 18,58% (dp=11,90%) do GC. Essa variação apresentou diferença significativa (p=0,020; t=2,776; p<5%) entre os grupos (controle e experimental), e a diferença significativa do LRET antes e após do treinamento no GE (p=0,003; t=5,338; p<5%) quando comparado ao GC (p=0,015; t=3,657; p<5%). A medida semi-quantitativa da EMA antes e após o término das sessões mostraram variações apenas no GE. Com relação a atividade cortical, houve diferença de atividade das bandas (delta, teta, alfa e beta) quando a 3ª e 12ª sessão foram comparadas para cada sujeito do GE. Essa diferença foi encontrada, principalmente, em regiões frontal, central (vértex), parietal e occipital em ambos hemisférios (ipsilateral e contralateral a lesão) tanto na fase de planejamento cognitivo motor quanto na execução do movimento. Houve predominância da diferença de atividade para a banda delta, alfa e beta em diferentes sujeitos distribuída difusamente ao longo dos canais de registro de viii EEG. A atividade diferenciada das bandas foi devido ao aumento e/ou diminuição da energia espectral entre as sessões, notado apenas em alguns voluntários do GE. Observou ainda diferença de atividade em áreas motoras secundárias. As avaliações, principalmente do LRET mostram que o treino com biofeedback EMG foi efetivo na redução do grau de espasticidade. A diferença de atividade cortical das bandas de frequência entre as sessões sugere que o biofeedback modula a cognição por meio do esforço e atenção imposta pela tarefa na tentativa do movimento no membro acometido. Além de que a diferença de energia espectral entre as sessões é dependente do ajuste e complexidade da tarefa direcionado pelos sinais do biofeedback, auxiliando na aprendizagem motora. / Spasticity is observed in most patients after cerebrovascular accident (CVA), and exerts influence in the presence of disabilities, affecting motor function. For neurorehabilitation strategies, electromyographic biofeedback (EMG) has been used with acceptance in the medical community for adjustments in the sensory-motor skills as a motor retraining, reducing spasticity and/or relaxation training. The intervention still presents limited evidence regarding their effectiveness in rehabilitation, especially as the interference of cortical activity and the reduction of spastic signs that provides negative characteristics in movement execution. The aim of this study was to analyze the workout possible interference with EMG biofeedback on the motor control awareness in spastic member in the characterization of the activity of low-frequency bands in different cortical regions targeted by the training technique. Sixteen volunteers affected by ischemic stroke were selected and divided into two groups (n = 8). Experimental group (EG) underwent biofeedback training associated with physical therapy and control group (CG) only conventional physiotherapy. The assessment of the degree of spasticity by reflex threshold of the tonic stretch (TSRT) and Modified Ashworth Scale (MAS) was performed before and three weeks after the end of treatment with the technique. The subjects underwent biofeedback for 6 weeks, with two sessions weekly. The same time for physiotherapy treatment was standardized to the GC. The results show variation of the average percent improvement in the degree of spasticity measured at TRST, 38,59% (sd=13,03%) in GE compared to 18,58% (sd=11,90%) of GC. This variation showed a significant difference (p=0.020; t=2,776; p<5%) between groups (control and experimental), and the significant difference of TRST before and after training in EG (p = 0.003; t=5,338; p <5%) when compared to the CG (p=0.015; t=0,015; p<5%). The semi-quantitative measure of the MAS before and after the end of the sessions presented variations only in GE. Regarding the cortical activity, there were band activities differences when 3rd and 12th sessions were compared for each subject of GE. This difference was found primarily in the frontal, central (vertex), parietal and occipital lobe in both hemispheres (contralateral and ipsilateral to the lesion) in both the cognitive motor planning phase and in the movement execution. It was observed the predominance of activity difference for the delta band, alpha and beta in different subjects distributed diffusely over the EEG recording channels. The different activity of the bands was due to the increase and/or decrease the spectral energy between sessions, x noticed only in some GE volunteers. It was also pointed out distinct activity in secondary motor areas. Evaluations mainly from TSRT show that training with EMG biofeedback was effective in reducing the degree of spasticity. The difference in cortical activity of the frequency bands between sessions suggested that biofeedback modulates cognition through the effort and attention required by the task of movement attempt in the affected limb. Besides that, the spectral energy difference between the sessions depends on the tuning and task complexity driven by biofeedback signals, helping motor learning. / Tese (Doutorado)

It is proved that the initial value problem for a system of two Benjamin-Bona-Mahony equations coupled through both dispersive and nonlinear terms is locally and globally well posed in the Soboloev spaces Hs ×Hs with s ≥ 0 / Dado el problema de valor inicial para un sistema de dos ecuaciones de Benjamin-Bona-Mahony (BBM) acopladas a través de los términos dispersivos y no lineales, se demuestra que está bien colocado localmente y globalmente en los espacios Hs × Hs con s≥0.

O objetivo principal deste trabalho é o estudo de transistores MuGFETs de porta tripla de Corpo de canal tipo-n com e sem a aplicação da configuração DTMOS. Este estudo será realizado através de simulações numéricas tridimensionais e por caracterizações elétricas. A corrente de dreno, a transcondutância, a resistência, a tensão de limiar, a inclinação de sublimiar e a Redução da Barreira Induzida pelo Dreno (DIBL) serão analisadas em modo DTMOS e em configuração de polarização convencional. Importantes figuras de mérito para o desempenho analógico como transcondutância-sobre-corrente de dreno, a condutância de saída, a tensão Early e o ganho de tensão intrínseco serão estudados tanto experimentalmente como através de simulações numéricas tridimensionais para diferentes concentrações de dopantes no canal. Os resultados indicam que a configuração DTMOS apresenta as características elétricas superiores (4 e 10 %) e maior eficiência dos transistores. Além disso, os dispositivos DTMOS com alta concentração de dopantes no canal apresentaram um desempenho analógico muito melhor quando comparados ao transistor de porta tripla de Corpo em modo de operação convencional. O ruído de baixa frequência (LF) é pela primeira vez experimentalmente analisado na região linear e saturação. A origem do ruído é analisada de maneira a compreender os mecanismos físicos envolvidos neste tipo de ruído. As medições mostraram que os espectros do sinal dos dispositivos de porta tripla de Corpo e DTMOS são compostos por flutuações referentes ao número de portadores devido ao ruído flicker e por ondas de ruído de geração e recombinação no dielétrico de porta que se torna maior com o aumento da tensão de porta. No entanto, o principal fato desta análise é que o dispositivo DTMOS apresentou praticamente a mesma magnitude do ruído LF na região linear e de saturação que o dispositivo de Corpo. A energia de 60 MeV na fluência de p/1012 cm-2 de radiações de prótons é também estudada experimentalmente em termos das características elétricas, desempenho do analógico e ruído LF nos dispositivos de porta tripla de Corpo e DTMOS. Os resultados indicam que combinado com as suas melhores características elétricas e um ótimo desempenho analógico do DTMOS, faz o transistor de porta tripla de Corpo um candidato muito competitivo para aplicações analógicas em ruído de baixa frequência antes e depois da irradiação. A vantagem da técnica DTMOS em transistores de porta tripla em ambientes onde os dispositivos têm de suportar alta radiação é devido à menor penetração do campo de dreno que reduz o efeito das cargas induzidas pelo óxido de isolação (STI). Finalmente, o transistor de Corpo de porta tripla de canal tipo-n é experimentalmente estudado como célula de memória, isto é, como 1T-DRAM (Memória de Acesso Aleatório Dinâmico com 1 transistor). Para escrever e ler 1 é utilizado um modo de programação que utiliza o efeito do transistor bipolar parasitário (BJT) enquanto a polarização direta da junção do corpo e do dreno é usada para escrever 0. As correntes de leitura e escrita aumentam com o aumento da tensão do corpo (VB) porque as cargas induzidas pelo efeito BJT é armazenada dentro da aleta. Quando o corpo do transistor está flutuante, o dispositivo retém mais cargas dentro da sua aleta. Além disso, transistor de Corpo pode ser utilizado como 1T-DRAM com eletrodo de porta e substrato flutuando. Neste caso, o dispositivo funciona como um biristor (sem porta). / The main goal of this work is to investigate the n-channel MuGFETs (triple-gate) Bulk transistors with and without the application of DTMOS operation. This work will be done through three-dimensional numerical simulation and by electrical characterizations. The drain current, transconductance, resistance, threshold voltage, subthreshold swing and Drain Induced Barrier Lowering (DIBL) will be analyzed in the DTMOS mode and the standard biasing configuration. Important figures of merit for the analog performance such as transconductance-over-drain current, output conductance, Early voltage and intrinsic voltage gain will be studied experimentally and through three-dimensional numerical simulations for different channel doping concentrations. The results indicate that the DTMOS configuration has superior electrical characteristics (4 e 10 %) and higher transistor efficiency. In addition, DTMOS devices with a high channel doping concentration exhibit much better analog performance compared to the normal operation mode. Low-Frequency (LF) noise is for the first time experimentally investigated in linear and saturation region. The origin of the noise will be analyzed in order to understand the physical mechanisms involved in this type of noise. Measurements showed that the signal spectra for Bulk and DTMOS are composed of number fluctuations related flicker noise with on top generation and recombination noise humps, which become more pronounced at higher gate voltage. However, the most important finding is the fact that DTMOS devices showed practically the same LF noise magnitude in linear and saturation region than standard Bulk device. Proton irradiation with energy of 60 MeV and fluence of p/1012 cm-2 is also experimentally studied in terms of electric characteristic, analog performance and the LF noise in Bulk and DTMOS triple gate devices. The results indicate that the combined of the better electrical characteristics and an excellent analog performance of DTMOS devices, makes it a very competitive candidate for low-noise RF analog applications before and after irradiation. The advantage of dynamic threshold voltage in triple gate transistors in environments where the devices have to withstand high-energy radiation is due to its lower drain electric field penetration that lowers the effect of the radiation-induced charges in the STI (shallow trench isolation) regions adjacent to the fin. Finally, the n-channel triple gate Bulk device is used for memory application, that is, 1T-DRAM (Dynamic Random Access Memory with 1 Transistor). Bipolar junction transistor (BJT) programming mode is used to write and read 1 while the forward biasing of the body-drain junction is used to write 0. The reading and writing current increases with increasing body bias (VB) because the load induced by the BJT effect is stored within the fin. When the body of the transistor is floating, the device retains more charge within its fin. In addition, transistor could also operate as 1T-DRAM with both gate and bulk contacts floating, which is similar to the biristor (gateless) behavior.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-06-10T11:59:43Z No. of bitstreams: 1 marcelopaschoaldias.pdf: 2362586 bytes, checksum: de75d2d7f7b0ebf296ee1a44eeb6874f (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-13T13:48:14Z (GMT) No. of bitstreams: 1 marcelopaschoaldias.pdf: 2362586 bytes, checksum: de75d2d7f7b0ebf296ee1a44eeb6874f (MD5) / Made available in DSpace on 2016-07-13T13:48:14Z (GMT). No. of bitstreams: 1 marcelopaschoaldias.pdf: 2362586 bytes, checksum: de75d2d7f7b0ebf296ee1a44eeb6874f (MD5) Previous issue date: 2012-08-29 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta dissertação tem como foco principal a avaliação do emprego de um conversor de baixo custo, operando em baixa frequência, para o acionamento de diodos emissores de luz (LEDs) usados em luminárias de baixa potência. A proposta considera inicialmente um conversor CA-CC conhecido como pré-regulador boost de alto fator de potência operando em baixa frequência, ou seja, um único acionamento liga-desliga para cada semiciclo da rede elétrica. Um protótipo experimental com potência de saída de 11 W foi implementado e comprova a possibilidade de emprego do conversor pretendido. Neste caso, foi observada por meio de avaliação fotométrica uma redução de 11% na eficácia luminosa do conjunto luminoso, em comparação com operação CC ideal, algo que se atribui à natureza descontínua da corrente nos LEDs. O pré-regulador apresentou um fator de potência de 0,97 e uma eficiência de 59%, em especial devido ao uso de um transformador abaixador de baixa frequência sobredimensionado. Pelo fato de impor à lâmpada uma corrente descontínua, o conversor proposto não emprega capacitores eletrolíticos, característica que contribui para uma elevada vida útil do circuito de acionamento. Um circuito similar, orientado à iluminação pública e que dispensa o uso de transformadores abaixadores, também é avaliado com apoio de simulação computacional. Neste caso, pode ser esperada uma eficiência global muito mais elevada. Outro pré-regulador baseado no mesmo princípio, porém empregando uma topologia tipo Ćuk, também é avaliado por meio de simulações, permitindo-se antever uma proposta de baixo custo, acionamento simplificado, elevada eficiência global, elevada eficácia luminosa e elevada vida útil. Finalmente, um estudo complementar desta dissertação considera a influência do posicionamento geométrico dos LEDs para a distribuição luminosa no plano de trabalho. Uma análise matemática e experimental é conduzida neste sentido e contribuiu para a alocação das unidades luminosas ao longo da barra de suporte da luminária de baixa potência implementada. / This work is mainly focused on the evaluation of the use of a low-frequency and low-cost converter intended to drive light emitting diodes employed in low power lighting fixtures. The proposal considers at first a high power factor boost pre-regulator converter featuring a low frequency switching of the main power device, which is driven twice each electric mains cycle. An experimental prototype with output power of 11 W is implemented and proves the concept feasibility. In this case, photometry studies show a reduction of 11% in the LEDs luminous efficacy, as compared to an ideal DC operation, which is due to the discontinuous nature of the output current. The boost pre-regulator presented a power factor of 0.97 and a global efficiency of 59%, something that can be imputed to the use of an underrated low frequency transformer. Despite some disadvantages, the discontinuous nature of LEDs current allows the converter to avoid using electrolytic capacitors, what confers an extended lifetime to the proposed driver. A similar circuit, which does not need transformers at all and is devised to be employed in street lighting, is also evaluated by means of numerical simulation. Moreover, another low frequency pre-regulator based on the Ćuk converter is evaluated with the aid of computer simulation, and the results show that it could be attained in practice a high global efficiency, high luminous efficacy and extended driver lifetime. Finally, a complementary study accomplished during this dissertation evaluates the influence of the geometric positioning of the LEDs for the luminous distribution over a given plane to be lit. Mathematical and experimental analysis have been developed contributing for the right allocation of lighting unities along the heatsink bar which bears the lighting fixture prototype.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This master thesis presents the analysis and design of an electronic drive system for fluorescent induction lamps. This lighting technology, despite being patented since the 60s, is not widely diffused in the market context. However, it is an extremely attractive alternative due to long lifetime and high luminous efficiency. The analysis circuit consists of a power factor correction associated with a power control stage, which provides the lamp ignition and current limitation. An integration methodology is applied in order to reduce the number of active semiconductor switches. The resulting topology, called here SEPIC half-bridge, presents a shared switch able to act, both in the pre-regulator stage, as well as for the power control stage. The number of elements reduction also occurs by magnetic integration. In this case, the pre-regulator inductors are distributed in a single core. For electronic system flexibility, it was inserted the dimming capability, where the low frequency modulation technique was evaluated. This technique is suitable for high power variation rates and provides a stable operation. The topology is controlled by a feedback system ensuring a satisfactory response of the system when subjected to disturbances, in addition to ensuring the correct power to the lamp. The electronic ballast designed behavior was evaluated experimentally. In this situation, there was obtained a low input current distortion associated with a high power factor. The lamp power variation range was 70% (30 W to 100 W), with an average efficiency around 82%. / Neste trabalho de mestrado, apresenta-se a análise e o projeto de um sistema eletrônico de acionamento para lâmpadas fluorescentes de indução. Esta tecnologia de iluminação, apesar de ser patenteada desde a década de 60, ainda é pouco difundida em âmbito comercial. Entretanto, é uma alternativa extremamente atraente devido a longa vida útil e a elevada eficiência luminosa. O circuito analisado consiste de um estágio de pré-regulação do fator de potência associado a um estágio de controle de potência, capaz de prover as necessidades de partida e limitar a corrente aplicada à lâmpada. Para estes estágios, visando a redução do número de semicondutores ativos, é aplicada a metodologia de integração de interruptores. A topologia resultante, chamada de SEPIC half-bridge, apresenta um interruptor compartilhado, capaz de atuar tanto para o pré-regulador, quanto para o controle de potência. A redução do número de elementos se dá também pela integração de magnéticos. Nesta situação, os indutores do pré-regulador são distribuídos em um único núcleo. Buscando a flexibilidade do sistema eletrônico, neste foi inserido a capacidade de variação da intensidade luminosa, onde a técnica de modulação de baixa frequência foi avaliada. Tal técnica é apropriada para elevados índices de variação de potência, além de proporcionar uma operação estável do circuito. A topologia é controlada por um sistema de retroalimentação, capaz de garantir uma resposta satisfatória do sistema quando submetido a distúrbios, além de garantir a potência processada pela lâmpada. O comportamento do reator eletrônico projetado foi avaliado experimentalmente. Nesta situação, obteve-se uma baixa distorção da corrente de entrada e elevado fator de potência. A faixa de variação de potência foi de 70% (100 W à 30 W), com um rendimento médio de 82%.

An increased share of construction with timber is one possible way of achieving more sustainable and energy-efficient life cycles of buildings. The main reason is that wood is a renewable material and buildings require a large amount of resources. Timber buildings taller than two storeys were prohibited in Europe until the 1990s due to fire regulations. In 1994, this prohibition was removed in Sweden.     Some of the early multi-storey timber buildings were associated with more complaints due to impact sound than concrete buildings with the same measured impact sound class rating. Research in later years has shown that the frequency range used for rating has not been sufficiently low in order to include all the sound characteristics that are important for subjective perception of impact sound in light weight timber buildings. The AkuLite project showed that the frequency range has to be extended down to 20 Hz in order to give a good quality of the rating. This low frequency range of interest requires a need for knowledge of the sound field distribution, how to best measure the sound, how to predict the sound transmission levels and how to correlate numerical predictions with measurements.     Here, the goal is to improve the knowledge and methodology concerning measurements and predictions of low frequency impact sound in light weight timber buildings. Impact sound fields are determined by grid measurements in rooms within timber buildings with different designs of their joist floors. The measurements are used to increase the understanding of impact sound and to benchmark different field measurement methods. By estimating transfer functions, from impact forces to vibrations and then sound pressures in receiving rooms, from vibrational test data, improved possibilities to correlate the experimental results to numerical simulations are achieved. A number of excitation devices are compared experimentally to evaluate different characteristics of the test data achieved. Further, comparisons between a timber based hybrid joist floor and a modern concrete floor are made using FE-models to evaluate how stiffness and surface mass parameters affect the impact sound transfer and the radiation.     The measurements of sound fields show that light weight timber floors in small rooms tend to have their highest sound levels in the low frequency region, where the modes are well separated, and that the highest levels even can occur below the frequency of the first room mode of the air. In rooms with excitation from the floor above, the highest levels tend to occur at the floor levels and in the floor corners, if the excitation is made in the middle of the room above. Due to nonlinearities, the excitation levels may affect the transfer function in low frequencies which was shown in an experimental study. Surface mass and bending stiffness of floor systems are shown, by simulations, to be important for the amount of sound radiated.     By applying a transfer function methodology, measuring the excitation forces as well as the responses, improvements of correlation analyses between measurements and simulations can be achieved / ProWood / Silent Timber Build / Urban Tranquility / BioInnovation FBBB

Les liquides diffèrent des solides par une réponse retardée à la sollicitation en cisaillement; c’est-à-dire une absence d’élasticité de cisaillement et un comportement d'écoulement à basses fréquences (<1 Hz). Ce postulat pourrait ne pas être vrai à toutes échelles. A l’échelle submillimétrique, les mesures viscoélastiques (VE) réalisées en améliorant l'interaction entre le liquide et le substrat, montrent qu’une élasticité basses-fréquences existe dans des liquides aussi variés que les polymères, les surfondus, les liquides à liaison H, ioniques ou van der Waals. Ce résultat implique que les molécules à l'état liquide ne seraient pas dynamiquement libres, mais élastiquement corrélées.En utilisant les propriétés biréfringentes des fluctuations prétransitionnelles qui coexistent dans la phase isotrope des cristaux liquides, nous montrons qu'il est possible de visualiser ces corrélations « cachées ». Dans des conditionssimilaires aux mesures VE, une biréfringence optique synchrone à la déformation est observée dans la phase isotrope à des fréquences aussi basses que 0.01 Hz et des températures éloignées de toute transition. Le comportement dela biréfringence basses-fréquences a des similitudes avec l'élasticité; elle est en phase avec la déformation à faibles amplitudes de déformation, puis en phase avec le taux de déformation à plus grandes amplitudes. La biréfringence basses- fréquences est forte, sans défaut et réversible. Elle indique un ordre à longue portée. La synchronisation de la réponse à la sollicitation en fréquence et l’état ordonné qu’elle produit ne sont pas compatibles avec un état liquide isotrope mais montrent qu’il s’agit d’un état élastique soumis à déformation (entropie élastique). / Liquids differ from solids by a delayed response to a shear mechanical solicitation; i.e. they have no shearelasticity and exhibit a flow behaviour at low frequency (<1 Hz). This postulate might be not verified at thesub-millimeter scale. By optimizing the measurement in particular by improving the liquid/substrate interactions (wetting), a low frequency shear elasticity has been found in liquids including molten polymers, glass-formers, H-bond polar, ionic or van der Waals liquids. This result implies that molecules in the liquid state may not be dynamically free but weaklyelastically correlated. Using the birefringent properties of the pretransitional fluctuations coexisting in the isotropic phase of liquid crystals, we show that it is possible to visualize these “hidden” shear-elastic correlations. We detect a synchronized birefringent optical response in the isotropic phase that is observable at frequencies as low as 0.01 Hz and at temperatures far away from anyphase transition. The low-frequency birefringence exhibits a strain dependence similar to the low frequency elasticity: An optical signal that is in-phase with the strain at low strain amplitudes and in-phase with the strain-rate at larger strain amplitudes. The birefringent response is strong, defect-free, reversible and points out a collective response. This long-range ordering rules out the condition of an isotropic liquid and its synchronized response supports the existenceof long-range elastic (solid-like) correlations. In the light of this, the strain dependence of the harmonic birefringent signal and the shear elasticity may correspond to an entropy-driven transition.

Over the years, RFID (radio frequency identification) technology has gained popularity in a number of applications. The decreased cost of hardware components along with the recognition and implementation of international RFID standards have led to the rise of this technology. One of the major factors associated with the implementation of RFID infrastructure is the cost of tags. Low frequency (LF) RFID tags are widely used because they are the least expensive. The drawbacks of LF RFID tags include low data rate and low range. Most studies that have been carried out focus on one frequency band only. This thesis presents an analysis of RFID tags across low frequency (LF), high frequency (HF), and ultra-high frequency (UHF) environments. Analysis was carried out using a simulation model created using OPNET Modeler 17. The simulation model is based on the Basic Frame Slotted ALOHA (BFSA) protocol for non-unique tags. As this is a theoretical study, environmental disturbances have been assumed to be null. The total census delay and the network throughput have been measure for tags ranging from 0 to 1500 for each environment. A statistical analysis has been conducted in order to compare the results obtained for the three different sets.