As Vibrações Induzidas por Escoamentos (VIEs) são dos problemas dinâmicos mais importantes no projeto de trocadores de calor de tipo carcaça e tubos. Esta interação fluido - estrutura pode gerar vibrações de grande amplitude dos tubos ou partes internas do equipamento, o que pode provocar o impacto entre componentes e até falha por fadiga. Várias bancadas experimentais têm sido construídas para o estudo desta interação fluido - estrutura, no entanto, alguns mecanismos de vibração, principalmente aqueles relacionados com escoamentos bifásicos, não são completamente compreendidos. Portanto, neste trabalho, o projeto de uma estrutura dinâmica para o estudo das vibrações induzidas por escoamento bifásico é apresentado. Esta estrutura é composta por um sistema de fios de aço tensionados que permitem que a primeira frequência de ressonância do tubo seja sintonizada. O tubo instrumentado foi instalado numa seção de testes de tubos rígidos em configuração triangular normal com uma razão de passo transversal e diâmetro de 1,26. Os resultados experimentais foram contrastados com uma modelagem teórica desenvolvida para esta estrutura dinâmica. Pôde-se verificar que a primeira frequência de ressonância e seu fator de amortecimento coincidem com os valores estimados pelo modelo, enquanto que a segunda frequência de ressonância apresenta valor teórico 6,6% maior do que o experimental. A seguir, um estudo experimental no ar foi desenvolvido para o reconhecimento dos modos de vibração e as frequências de ressonância da estrutura dinâmica. O fator de amortecimento no ar também foi estimado, o método de Kennedy - Pancu combinado com o algoritmo ERA foi usado para este fim. Assim que a primeira frequência de ressonância foi reconhecida e sintonizada, testes em escoamentos de água foram realizados. A influência da velocidade do escoamento monofásico de água na amplitude de vibração e nas características da Densidade Espectral (PSD) de aceleração foi analisada. Finalmente, testes em escoamento bifásico foram feitos, a sensibilidade do tubo ao escoamento bifásico fica evidente quando analisadas as amplitudes nas PSDs. Além disso, a influência da fração de vazio na amplitude de vibração e no fator de amortecimento foi revisada, no entanto, resultados de estudos anteriores não foram conferidos pelo alto amortecimento concentrado introduzido por alguns elementos construtivos utilizados. / Flow - Induced Vibration (FIV) is the most critical dynamic issue in the design of heat exchangers. This fluid - structure phenomenon may generate high amplitude vibration of tubes or structural parts, which may lead to impacts between internal components or even failure due to fatigue. Many test benches have been constructed to study this fluid - structure interactions, however, some vibration mechanisms, mostly those related to multiphase flow, are not yet fully understood. Therefore, in this work, the design of a dynamic structure for the study of multiphase flow induced vibration is presented. This structure is composed by a system of tensioned piano wires that allow the first natural frequency of the instrumented tube to be calibrated. The tube was installed in a rigid bundle configured in a normal triangular pattern with pitch-todiameter ratio of 1.26. Then, an experimental study in air environment was performed aiming at addressing the mode shapes and resonance frequencies of the dynamic structure. The damping ratio in air environment was also estimated, the Kennedy - Pancu method in combination with the Eigensystem Realization Algorithm have been used to that purpose. Experimental results in air were compared with a theoretical model. The first resonance frequency and its damping factor presented a good agreement with the model, while the second resonance frequency deviated some 6,6% from the predicted value. Tests in water and multiphase flow were also performed. The influence of water flow velocity on vibration amplitudes and on the Power Spectrum Densities (PSDs) has been analyzed. Finally, tests for two - phase water/air flow were carried out; the tube sensitivity to multiphase flow is evident when the vibration level in acceleration PSDs is by analyzed. Also, the influence of void fraction on vibration amplitude and damping ratio have been addressed, however, previous studies could not be validated due to the high damping introduced by some constructive elements of the structure.

O sucesso das cirurgias de implantes depende de diversos fatores como a saúde sistêmica dos pacientes, qualidade e quantidades ósseas disponíveis e, o tipo de macro e microarquitetura dos implantes osseointegráveis. Este estudo propõe avaliar o tecido ósseo em radiografias panorâmicas antes e após cirurgias de implantes correlacionando com análises das Dimensões Fractais (DF), Intensidade de pixel (IP), Índice mentual (IM) e análises de estabilidade primária de implantes (AFR e TI). Foram analisadas 138 regiões de interesse de 50 pacientes, homens e mulheres com idade entre 22 e 77 anos cujas imagens pertencem ao banco de dados do curso de pós-graduação em Implantodontia da Universidade de Santos (Unimes). Foram obtidos dados cirúrgicos do ato da instalação dos implantes, análises de Frequência de Ressonância (AFR) e Torque de Inserção dos implantes (TI) e, com os dados quantitativos obtidos das radiografias panorâmicas antes e após a instalação dos implantes, DF, IP e IM foram realizados testes estatísticos de Correlação de Spearmam, Teste Kruskal Wallis e Wilcoxon para amostras relacionadas com auxílio do software IBM SPSS Advanced Statistics ® (IBM, USA) com nível de significância de 95% (p<0,05). Os resultados obtidos para as Correlações significantes foram entre a Idade e DF (r=-.647) e TI e DF (r=0.434). O teste de Wilcoxon identificou diferença significante (p>0,05) para as amostras relacionadas IP antes e IP depois (p=0,020 e 0,000) entre os grupos 1 e 2. Foram analisadas as possíveis diferenças entre as variáveis independentes para os grupos 1 e 2 em relação a Idade, com diferenças entre IP (p=0,046), TI (p=0,044), AFR_MD (p=0,040) e AFR_VL (p=0,010), em relação ao gênero encontrados diferenças entre as variáveis DF (p=0,039), IP_antes (p=0,001) e IP_depois (p=0,033). O estudo concluiu que a IP pode detectar alterações de mineralização óssea antes e após a instalação de implantes; DF é correlacionada com TI para pacientes jovens (até 45 anos) e, a análise da Idade e Gênero devem ser considerados na avaliação de exames por imagem para planejamento com implantes. / The success of dental implants depends on several factors as patient´s systemic health, bone quality and quantity, geometry of dental implants and their microarquitecture relationship to the alveolar bone. The aim of this study is to assess changes of alveolar bone of panoramic radiographs correlating with Fractal Dimension (FD), Pixel Intensity (PI), Mentual Index (MI) and Implant Stability Quocient (ISQ) measured with Insertion Torque (IT) and Resonance Frequency (RF). 138 regions of interest (ROI) of 50 participants (22 to 77 years old) have been analyzed, all data belonged to the Implantology graduate course of the Universidade de Santos (Unimes). Retrospective surgical data from dental implant surgeries were obtained (RF and IT) and statistically tested with ROI values achieved from DF, PI and MI of panoramic radiographs taken before and after all dental implants placement. Spearman correlation, Kruskal Wallis and Wilcoxon tests were done with the IBM SPSS Advanced Statistics ® software (IBM, USA), level of significance of 95% (p<0,05). Significant correlation was obtained between Age and DF (r=-.647) and TI and DF (r=0.434). Wilcoxon test identified significant difference (p>0,05) for related samples PI before and PI after implant (p=0,020 e 0,000) between groups 1 and 2. Possible differences were analyzed among the independent variables for groups 1 and 2 related to Age, the results showed differences between PI (p=0,046), IT (p=0,044), RF_MD (p=0,040) e RF_VL (p=0,010), between Gender the results showed differences between the variables FD (p=0,039), PI_before (p=0,001) e PI_after (p=0,033). The study concluded that PI can detect bone mineralization changes before and after dental implant placement. FD correlates with the variable IT for younger participants (22 to 45 years old). Age and Gender should be considered regarding imaging exams tests (FD and PI) for dental implant planning.

Avaliou-se o comportamento biomecânico, quanto à área de estabilidade protética, extensão de cantilever e estabilidade por análise freqüência de ressonância (AFR); parâmetros clínicos: índice de placa (IP), índice de sangramento (IS), supuração, distância da plataforma do implante-margem da mucosa (DPM), profundidade de sondagem (PS), nível de inserção (NI), sangramento à sondagem (SS), largura (LM), espessura (EM) da mucosa e análise radiográfica, em dois sistemas de reabilitações implanto-suportadas. Foram instalados 104 implantes, submetidos à ativação imediata, em 26 pacientes, divididos em dois grupos: A (n= 16, All-on-4®-Nobel Biocare) e B (n=10, Neopronto®-Neodent). As próteses foram instaladas em tempo médio de 32h. (T0), e controles realizados em seis (T6), doze (T12) e 24 meses (T24). Como resultado, a taxa de sucesso foi de 100% para o grupo A e 90% para o grupo B para implantes e próteses. Diferenças significantes (p<0,05) foram apresentadas entre o cantilever posterior 10,96mm e 18,81mm e o braço de resistência (BR) 13,87mm e 5,50mm, respectivamente para os grupos A e B. A área de estabilidade, no grupo A foi de 373,5mm2 e no B de 112,8mm2; a média da AFR (em ISQ) do grupo A T0= 68,62; T6=64,40; T12=67,07; T24=66,53 e do grupo B T0= 68,37; T6=66,29; T12=67,09; T24=67,10, com diferenças (p<0,05) entre os tempos (grupo A) e posição dos implantes (grupo B). O IP no grupo A=1,0 e 0,7; grupo B=0,6 e 0,9, o IS (0,7), supuração (ausente) e SS (presença) no grupo A=50% e 37,9%; grupo B=70,1 e 52,1%, no controle de 12 e 24 meses, não mostraram diferenças estatísticas entre os grupos. As médias (em mm) da LM para o grupo A (2,05 e 2,21) e B (2,29 e 2,40) e EM grupo A (1,53 e 1,56) e B (1,31 e 1,43), DPM do grupo A (2,54e 2,52) e B (0,18mm e -0,12mm), PS grupo A (3,52 e 3,52) e B (3,52 e 4,0), NI grupo A (0,98 e 0,99) e B (3,05 e 3,57) e perda óssea grupo A (0,45mm e 0,23mm ) grupo B(0,66mm e 0,22mm), respectivamente para 12 e 24 meses, apresentaram diferenças estatísticas entre os controles. Concluindo-se que 1- O grupo A apresentou área de estabilidade e extensão de cantilever anterior e posterior, com comportamento biomecânico mais favorável do que no grupo B; 2- A estabilidade primária e secundária (AFR) foi diferente entre os tempos (grupo A) e posição dos implantes (grupo B), mas semelhantes entre os grupos; 3- Os parâmetros clínicos de índice de placa, sangramento marginal, supuração, profundidade de sondagem (exceto para os períodos de controle no grupo B), sangramento a sondagem, largura e espessura de mucosa ceratinizada foram semelhantes entre os grupos; 4- A distância da plataforma do implante-margem da mucosa foi maior no grupo A e o nível de inserção foi maior no grupo B; 5- A perda na altura da crista óssea foi semelhante entre os grupos; 6- A perda óssea foi menor nos implantes anteriores do que nos posteriores, nos grupos. / Two implant-supported rehabilitation systems were evaluated considering their biomechanical behavior, the area of prosthetic stability, cantilever extensions, stability using resonance frequency analysis (RFA) and clinical parameters, such as: modified plaque index (PI), modified bleeding index (BI), suppuration, distance between the implant shoulder and the mucosal margin (DIM), probing pocket depth (PD), probing attachment level (PAL), bleeding on probing (BP), thickness (TM) width (WM) of keratinized mucosa and radiographic analysis. One hundred and four implants had been installed in twenty six patients, submitted to immediate loading and divided into two groups: A (n=16, All-on-4®-Nobel Biocare) e B (n=10, Neopronto®-Neodent). The prosthesis had been installed in average time of 32h (T0), and controls made in (T6), 12 (T12) and 24 months (T24). As result, the success rate was 100% for the group A and 90% for the group B for both implants and prosthesis. Significant differences (p<0,05) 10,96mm and 18,81mm had been presented between posterior cantilever and the resistance arm (RA) 13,87mm and 5,50mm, respectively for the groups A and B. The stability area, in the group A was of 373,5mm2 and in B of 112,8mm2; the average of RFA (in ISQ) of the group A T0= 68,62; T6=64,40; T12=67,07; T24=66,53 and of the group B T0= 68,37; T6=66,29; T12=67,09; T24=67,10, with differences (p<0,05) between the periods (Group A) and implant position (Group B). The PI in group A was of 1,0 and 0,7 and 0,6 and 0,9 for group B, o BI (0,7), suppuration (absent), DP (presence) in group A=50% and 37,9%; group B=70,1 and 52,1%, in the control of 12 and 24 months, did not present statistical differences between the groups. The average (in mm) of WM for the group A (2,05 and 2,21) and B (2,29 and 2,40) and TM group A (1,53 and 1,56) and B (1,31 and 1,43), DIM of group A (2,54 and 2,52) and B (0,18mm and -0,12mm), DP group.

<div>Roll-to-roll processes provide a low-cost and high-throughput scheme for scalable flexible devices manufacturing. Multiple processes are used in roll-to-roll manufacturing, such as functional printing, evaporation/drying, UV curing, hot embossing, laser/heat annealing, laser ablation, plasma/ chemical growth, and sputtering. These processes change the web temperature field and/ or local properties. In addition, residual stresses by the process and web tension can destabilize the process and lead to wrinkling or undesirable performance of the products.</div><div>This dissertation investigates three different multi-physics problems relevant to the roll-to-roll processes, which are web thermomechanics, air-coupled web vibrations, and the measuring of nonuniform web tension. First, a mathematical model for predicting the in-plane temperature and heat induced stress distributions in a flexible, axially moving web under arbitrary shape of heat flux is presented. The computational approach is validated on experiments performed on moving paper and PET webs with infrared laser heating source. Second, a closed-form, semi-analytical, universal hydrodynamic functions is developed to accurately predict the lowest symmetric and anti-symmetric transverse frequency responses for any uniaxially tensioned web of arbitrary material and aspect ratio used in roll-to-roll processes with the surrounding air acting as distributed added mass. Experimental validation is carried out by using pointwise laser measurements of acoustically excited webs with different pre-tensions, web materials, and aspect ratios. Finally, we develop and test a non-contact resonance method and a gentle contact stiffness mapping method based on the first principles mechanical models of a tensioned plate to accurately measure the average web tension and its linear variation for a wide range of web properties, web path, web tension, measurement configurations, and environmental conditions. The two methods are cross-validated on a stationary test stand and the non-contact resonance method is used to study the web tension distribution within a commercial roll-to-roll system.</div><div><br></div>

The purpose of this project was to investigate a cylindrical cavity resonator and use microwaves to heat up a material in the cavity. This was done by measuring the Q-factor and the resonance frequency of the cavity, both with and without material inside. The chosen material was graphite, and more accurate measurements were done with that specific material. A program called QZero was used to export the Q-factor and the resonance frequency from the measurement data received from a VNA and the program also gave error estimations. Then electromagnetic simulations were done using Comsol. Both an empty cavity and a cavity where graphite has been inserted were simulated and the results were compared to the actual measurements. To measure temperatures inside the cavity, a pyrometer was to be used. The cavity resonator has small circular holes through the side, and a frame was designed and produced using a 3D-printer in order to lock the pyrometer in place in front of one of the holes. A power supply was also installed to the pyrometer. In order to send microwaves into the cavity, a signal generator was used. It was connected to an amplifier and the amplification as well as the efficiency was noted. The pyrometer could only measure temperatures above 490 $\degree$C. This was not achieved, so a handheld electrical thermometer was used. The temperature of the graphite was measured and then compared to how hot the graphite would be without heat loss. For the empty cavity, a Q-factor of 3200 for the resonance frequency of around 2.4 GHz was measured, which matched the simulated measurements in Comsol. When graphite was inserted to the cavity, the Q-factor lowered to 300 in the real experiment. A discrepancy was found between the actual measurements, and the Comsol simulations in which the graphite only lowered the Q-factor to 2570. The reason for this is believed to be either with an error to how the material was chosen in Comsol, since there were many types of graphite to select with many settings to change. Another reason could be an error with the setup itself due to the sheer complexity of the program. / Syftet med detta projekt är att undersöka en cylindrisk kavitet samt att använda mikrovågor för att värma upp ett material i kaviteten. Detta gjordes genom att mäta kavitetens Q-faktor och resonansfrekvens med och utan material. Sedan valdes grafit ut som det materialet som skulle testas och mer noggranna mätningar gjordes på just det materialet, och programmet QZero användes för att få ut mer noggrann data samt gav en felmarginal på Q-faktorn. Efter det gjordes simuleringar i programmet Comsol av kaviteten med och utan grafit och jämfördes med de faktiska värdena. För att mäta temperatur av materialet i kaviteten designades en hållare som en pyrometer skulle fästas vid och riktas mot materialet i kaviteten. Även en strömförsörjning till pyrometern installerades. För att skicka in mikrovågor i kaviteten användes en signalgenerator som var kopplad till en förstärkare. Förstärkningen mättes och förstärkarens effekt noterades. I slutändan nåddes inte de temperaturer som krävdes för pyrometern, så en elektrisk termometer användes för att mäta temperaturen på grafiten och detta jämfördes sedan mot den energin som absorberades av grafiten, då energin tillförd till grafiten och grafitens specifika värmekapacitet var känt. Prestandan av experimentuppställningen undersöktes också. For den tomma kaviteten mättes en Q-faktor på 3200 och resonansfrekvensen var 2.4 GHz. Detta stämde bra överens med simuleringarna i Comsol. När grafit fördes in i kaviteten sänktes Q-faktorn till 300. En avvikelse upptäcktes mellan de faktiska mätningarna och simuleringarna. I simuleringen sänktes Q-faktorn bara till 2570, en andledning till detta tros vara antingen vara hur materialet valdes, då det fanns olika typer av grafit med olika inställningar att välja mellan i Comsol. En annan felkälla kan vara något fel med uppställningen på grund af hur avancerat Comsol var. I värmeexperimentet hade förstärkaren en låg verkningsgrad vilket ledde till överhettning om för stor effekt användes. Experimentet begränsades därför till att använda upp till två watt. Vid exponerig under 30 sekunder värmdes grafiten upp till 100-150$\degree$C, vilket var avsevärt lägre än den teoretiska uppvärmingen till 1700$\degree$ beräknad från energin tillförd till grafiten. Antagandet är att temperaturen hamnade i ett jämnviktsläge kring 100-200$\degree$C eller att resonansfrekvensen ändrades vilket ledde till en minskning av energi tillförd till grafiten.

Energy security, global warming, and climate change have been a major source of global discussions and development. Likewise, the rising cost of electricity for consumers and exponential demand for energy are major factors driving the incremental growth and integration of sustainable forms of energy generation into power the system cycle. Distributed generation resources are majorly integrated into the electricity distribution system at the medium voltage (MV) and low voltage (LV) level of the utility grid system. Unexpected power outages on an electricity distribution network can lead to an islanding situation, in which a distributed generation system continues to supply power to the electricity grid. It is highly recommended by operational standards that, under such conditions, a distributed generation system is disconnected from the grid within a short period to prevent damage to power equipment and ensure personnel safety. The decoupling process requires an islanding detection method (IDM). Such detection methods are implemented in grid-tied power electronic converters (PEC) to detect and prevent islanding conditions.  The thesis investigates and describes an active islanding detection method, the active frequency drift with positive feedback. It also covers the parameter design and the analysis of the non–detection zone. The effectiveness of the method was verified through MATLAB/SIMULINK simulation

No description available.

L’hyperthermie guidée par IRM permet l’ablation thermique des tumeurs, l’activation de l’expression d’un transgène sous contrôle d’un promoteur thermo-sensible ainsi que le dépôt local de médicaments à l’aide de nanovéhicules sensibles à la température ou à la pression locale. L’imagerie de température par IRM, basée sur la technique du décalage de la fréquence de résonance du proton permet le monitorage des interventions d’hyperthermie. Les procèdes interventionnels guides par IRM sur cible mobile requièrent des séquences d’imagerie rapides afin d’obtenir des images de phases ayant une résolution spatio-temporelle élevée. Nous avons démontré l’efficacité de l’association des méthodes adaptatives d’imagerie parallèle telles que TSENSE et TGRAPPA et de la méthode multi-référence de l’atlas de mouvement afin de compenser les variations du champ magnétique induites par les organes en mouvement. Les procédés interventionnels guides par IRM sont basés sur des séquences d’imagerie rapides capables de fournir des images en temps-réel ayant une relation précise entre la position de la cible représentée dans l’image et sa vraie position spatiale. Les séquences écho-planar sont très rapides mais possèdent des distorsions géométriques. Nous avons proposé une méthode de correction des distorsions des images EPI. Cette technique est basée sur des approches existantes utilisant l’acquisition de deux images EPI ayant deux temps d’écho différents. L’efficacité de la méthode proposée a été démontrée pour une expérience de thermométrie par IRM. La rapidité du traitement des données, associée à une faible diminution de la rapidité d’acquisition, rend cette méthode particulièrement adaptée pour les procédés interventionnels guides par IRM. La perfusion sanguine, la diffusion thermique ainsi que le coefficient d’absorption des ondes acoustiques ou électromagnétiques déterminent la distribution de la température durant les procédés interventionnels. Certaines tumeurs ont des taux de perfusion élevés conduisant à une évacuation importante de la chaleur et par conséquent, un refroidissement rapide de la cible. Cet effet réduit la température maximale atteinte pour une puissance donne et peut conduire à des zones d’ablation plus petites réduisant ainsi l’efficacité de l’intervention. La connaissance précise des paramètres thermiques du tissu peut aider à la planification des procédés interventionnels. Dans ce but, nous avons proposé une méthode permettant la détermination précise des paramètres cités précédemment. / MR-guided HIFU-induced hyperthermia allows for thermal ablation of tumors, for gene therapy by thermal induction of transgenic expression (based on a thermo-sensitive promoter) and for local drug delivery using thermo-sensitive liposomes. These applications require accurate temperature measurement during the therapeutic intervention. Dynamic MR-temperature imaging based on the proton resonance frequency shift technique allows monitoring the local temperature evolution during hyperthermia. MR-guided thermotherapy on moving organs requires imaging sequences providing phase images with high temporal and spatial resolution. We demonstrated the feasibility of combining adaptive parallel imaging techniques such as TSENSE or TGRAPPA with the atlas-based multi-baseline method for compensating the magnetic field variations produced by moving organs during the respiratory cycle. Many MR-guided interventional procedures rely on real-time imaging sequences for providing precise relations between the target position in the image and the true position in the scanner. Although echo-planar imaging (EPI) sequences are very fast, they are prone to geometric distortions. For correcting these distortions, we proposed a real-time correction method by applying existing approaches based on a dual EPI acquisition with varying echo times. It is demonstrated that this method works well in combination with MR-thermometry for guiding thermal therapies. Short data-processing times as well as a small penalty in acquisition speed make this method well-adapted for MR-guided interventions. Local blood perfusion, thermal conductivity and the absorption coefficient of acoustic or electro-magnetic waves determine the temperature distribution in living tissue. Some tumors have high perfusion rates resulting in considerable heat evacuation. This effect reduces the maximal temperature increase achievable for a given deposited energy and produces smaller ablation zones, which can impair the efficiency of the therapeutic procedure. A method for accurately estimating the above mentioned tissue parameters, was presented. This method could thus be useful in quantifying the influence of perfusion during thermal interventions.

O presente estudo teve por objetivo avaliar por meio da análise de freqüência de ressonância (AFR) o efeito da irradiação com laser de GaAlAs na estabilidade de implantes de titânio, como cociente de estabilidade do implante (ISQ) instalados em pacientes parcialmente edentados na região posterior da mandíbula; assim como avaliar a evolução da estabilidade dos implantes, durante o período de osseointegração. Foram selecionados 8 pacientes adultos, com boa saúde para a instalação cirúrgica de 30 implantes Xive S® (Dentsply). Portanto, foram instalados de 2 a 5 implantes por paciente, distribuídos bilateralmente. Cada paciente atuou como seu próprio controle. Os implantes do lado controle não foram irradiados, e os do lado experimental foram submetidos a terapia com laser de diodo GaAlAs com ?= 830 nm, densidade de energia de 8 j/cm2, potência de 100 mW, modo contínuo, de forma pontual em 20 pontos, durante 3 segundos por ponto. A primeira sessão de irradiação foi no pós-operatório imediato, sendo repetida a cada 48 horas nos primeiros 14 dias, totalizando 7 irradiações. Após a instalação dos implantes foi medida a estabilidade primária destes com o aparelho Osstell?. Novas medidas de ISQ foram realizadas após 10 dias, e 3, 6, 9 e 12 semanas. No momento da instalação, os valores de ISQ na região posterior da mandíbula oscilaram de 65-84 com média de 76, sofrendo queda significativa da estabilidade do 100 dia para a 6a semana no grupo irradiado e apresentando um aumento gradual a partir da 6a semana até a 12a semana. Os valores mais altos de ISQ foram observados no 100 dia no grupo irradiado, embora sem significância estatística, e os mais baixos foram observados na 6a semana em ambos os grupos. Não foi evidenciado o efeito do laser de GaAlAs na estabilidade dos implantes com o aparelho OsstellTM, porém não se pode afirmar que os padrões de reparação óssea e a taxa de osseointegração entre os implantes irradiados e não irradiados tenham sido similares. / JThe present study was carried out to evaluate the effect of irradiation with the GaALAs laser in the stability of titanium implants (ISQ), inserted in partially edentulous patients, by means of resonance frequency analysis (RFA); as well as to evaluate the evolution of the stability during the osseointegration processs. A group of 8 patients were seleted for the insertion of 30 implants (Xive S® - Dentsply). The implants in the control site were not irradiated, and the implants in the experimentall site were submitted to laser therapy with a GaAlAs with ?= 830 nm, energy density of 8 j/cm2, power of 100 mW, continuing mode, in 20 points, for 3 seconds per point. The first irradiation was immediately after the surgery, and it was repeated every 48 hours in the first 14 days, totalizing 7 irradiations. After the implants insertion, the primary stability was measured using Osstell?. New measurements were carried out after 10 days, 3, 6, 9, 12 weeks. The incial ISQ values ranged from 65-84, with a mean of 76, showing a significative decrease in the stability from the 10th day to the 6th weeks in the irradiated group, and showing a gradual increase from 6th to 12th week. The highest ISQ values were observed in the 10th day in the irradiated group, and the lower ISQ values were observed in the 6th week in both groups. The effect of the irradiation with GaAlAs laser in implant stability was not evicenced; however, it can not be affirmed that irradiated and not irradiated implants have similar bone repair patterns and osseointegration rates.

Voltage source inverter (VSI) fed induction motors are increasingly used in industrial and transportation applications as variable speed drives. However, VSIs generate non-sinusoidal voltages and hence result in harmonic distortion in motor current, motor heating, torque pulsations and increased acoustic noise. Most of these undesirable effects can be reduced by increasing the switching frequency of the inverter. This is not necessarily true for acoustic noise. Acoustic noise does not decrease monotonically with increase in switching frequency since the noise emitted depends on the proximity of harmonic frequencies to the motor resonant frequencies. Also there are practical limitations on the inverter switching frequency on account of device rating and losses. The switching frequency of many inverters often falls in the range 2 kHz - 6 kHz where the human ear is highly sensitive. Hence, the acoustic noise emission from the motor drive is of utmost important. Further, the acoustic noise emitted by the motor drive is known to depend on the waveform quality of the voltage applied. Hence, the acoustic performance varies with the pulse width modulation (PWM) technique used to modulate the inverter, even at the same modulation index. Therefore a comprehensive study on the acoustic noise aspects of induction motor drive is required. The acoustic noise study of the motor drive poses multifaceted challenges. A simple motor model is sufficient for calculation of total harmonic distortion (THD). A more detailed model is required for torque pulsation studies. But the motor acoustic noise is affected by many other factors such as stator winding distribution, space harmonics, geometry of stator and rotor slots, motor irregularities, structural issues controlling the resonant frequency and environmental factors. Hence an accurate model for acoustic noise would have to be very detailed and would span different domains such as electromagnetic fields, structural engineering, vibration and acoustics. Motor designers employ such detailed models along with details of the materials used and geometry to predict the acoustic noise that would be emitted by a motor and also to design a low-noise motor. However such detailed motor model for acoustic noise purposes and the necessary material and constructional details of the motor are usually not available to the user. Also, certain factors influencing the acoustic noise change due to wear and tear during the operational life of the motor. Hence this thesis takes up an experimental approach to study the acoustic noise performance of an inverter-fed induction motor at any stage of its operating life. A 10 kVA insulated gate bipolar transistor (IGBT) based inverter is built to feed the induction motor; a 6 kW and 2.3 kW induction motors are used as experimental motors. A low-cost acoustic noise measurement system is also developed as per relevant standards for measurement and spectral analysis of the acoustic noise emitted. For each PWM scheme, the current and acoustic noise measurements are carried out extensively at different carrier frequencies over a range of fundamental frequencies. The main cause of acoustic noise of electromagnetic origin is the stator core vibration, which is caused by the interaction of air-gap fluxes produced by fundamental current and harmonic currents. In this thesis, an experimental procedure is suggested for the acoustic noise characterization of an induction motor inclusive of determination of resonant frequencies. Further, based on current and acoustic noise measurements, a vibration model is proposed for the stator structure. This model is used to predict the acoustic noise pertaining to time harmonic currents with reasonable accuracy. Literature on motor acoustic noise mainly focuses on sinusoidal PWM (SPWM), conventional space vector PWM (CSVPWM) and random PWM (RPWM). In this thesis, acoustic noise pertaining to two bus-clamping PWM (BCPWM) schemes and an advanced bus-clamping PWM (ABCPWM) scheme is investigated. BCPWM schemes are mainly used to reduce the switching loss of the inverter by clamping any of the three phases to DC rail for 120◦ duration of the fundamental cycle. Experimental results show that these BCPWM schemes reduce the amplitude of the tonal component of noise at the carrier frequency, compared to CSVPWM. Experimental results with ABCPWM show that the overall acoustic noise produced by the motor drive is reduced at low and medium speeds if the switching frequency is above 3 kHz. Certain spread in the frequency spectrum of noise is also seen with both BCPWM and ABCPWM. To spread the acoustic noise spectrum further, many variable-frequency PWM schemes have been suggested by researchers. But these schemes, by and large, increase the current total harmonic distortion (THD) compared to CSVPWM. Thus, a novel variable-frequency PWM (VFPWM) method is proposed, which offers reduced current THD in addition to uniformly spread noise spectrum. Experimental results also show spread in the acoustic noise spectrum and reduction in the dominant noise components with the proposed VFPWM. Also, the current THD is reduced at high speeds of the motor drive with the proposed method.