AlGaN/GaN high electron mobility transistors (HEMTs) have appeared as attractive candidates for high power, high frequency, and high temperature operation at microwave frequencies. In particular, these devices are being considered for use in the area of high RF power for microwave and millimeter wave communications transmitter applications at frequencies greater than 100 GHz and at temperatures greater than about 150 °C. However, there are concerns regarding the reliability of AlGaN/GaN HEMTs. First of all, thermal reliability is the chief concern since high channel temperatures significantly affect the lifetime of the devices. Therefore, it is necessary to find the solutions to decrease the temperature of AlGaN/GaN HEMTs. In this study, we explored the methods to reduce the channel temperature via high thermal conductivity diamond as substrates of GaN. Experimental verification of AlGaN/GaN HEMTs on diamond substrates was performed using micro-Raman spectroscopy, and investigation of the design space for devices was conducted using finite element analysis as well. In addition to the thermal impact on reliability, environmental effects can also play a role in device degradation. Using high density and pinhole free films deposited using atomic layer deposition, we also explore the use of ultra-thin barrier films for the protection of AlGaN/GaN HEMTs in high humidity and high temperature environments. The results show that it is possible to protect the devices from the effects of moisture under high negative gate bias stress testing, whereas devices, which were unprotected, failed under the same bias stress conditions. Thus, the use of the atomic layer deposition (ALD) coatings may provide added benefits in the protection and packaging of AlGaN/GaN HEMTs.

This thesis summarizes my work at the University of Victoria to design and evaluate a proof-of-concept instrument called the Confocal Acoustic Holography Microscope (CAHM). The instrument will be able to measure small changes in temperature and composition in a fluid specimen, which can be indirectly measured via small fluctuations in the speed of sound. The CAHM combines concepts of confocal microscopy, interferometry, and ultrasonic imaging. This recent work in confocal acoustic holography has progressed from our previous research in confocal laser holography. The prototype CAHM design uses a frequency of 2.25 MHz, and can measure sound speed changes of 16 m/s, temperature changes of 5°C, with a spatial resolution of 660 μm. With future improvements to the CAHM, utilizing the latest technologies such as 2D array detectors, MEMS, and acoustic lenses, we expect resolutions of 1 m/s, 0.5°C, and 150 μm. The design of the CAHM involved the production of a 3D CAD layout of the optomechanical components and ray tracing simulations using Zemax optical design software. Simulated acoustic holograms and fringe shifts were produced and they were found to match up very well with theoretical calculations. A simplified acoustic holography instrument was built and tested. Speed of sound measurements were made for several test specimens, while keeping temperature constant. Specimens of ethanol, isopropanol, acetic acid, glycerine, and mineral oil were measured. Holograms were collected for acetic acid and mineral oil and were compared to the reference case (distilled water). The fringe spacing and phase shifts measured experimentally matched up well with the Zemax simulations and the theoretical calculations. Hence, the popular Zemax optical software can be effectively used to design acoustic instruments. To our knowledge, this is the first use of Zemax for acoustic designs. Based on the successful results of the simulations and experiments, the CAHM is expected to have many useful applications, especially in medical diagnostics where it could be used to measure density and temperature within the human body. Phase contrast images could also be used to help identify suspicious lesions, such as those found in prostate or breast tissue. Other applications include non-destructive testing of electronic and mechanical parts, measurements of fluid samples, material science experiments, and microgravity experiments, where non-invasive examination is required.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23883号 / 工博第4970号 / 新制||工||1776(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 蓮尾 昌裕, 教授 鈴木 基史, 教授 江利口 浩二 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Syngas, a gaseous mixture of H2, CO and diluents such as N2, CO2, is a clean fuel generated via gasification of coal or biomass. Syngas produced via gasification typically has low calorific values due to very high dilution levels (~60% by volume). It has been recognized as an attractive energy source for stationary power generation applications. The present work focuses on experimental and numerical investigation of syngas-air counterflow diffusion flames with varying composition of syngas. Laser-based diagnostic techniques such as Particle Imaging Velocimetry, Rayleigh thermometry and Laser-induced fluorescence have been used to obtain non-intrusive measurements of local extinction strain rates, temperature, quantitative OH and NO concentrations, respectively, for three different compositions of syngas. Complementing the experiments, numerical simulations of the counterflow diffusion flame have been performed to assess the performance of five H2/CO chemical kinetic mechanisms from the literature. The first part of the work involved determination of local extinction strain rates for six H2 /CO mixtures, with H2:CO ratio varying from 1:4 to 1:1. The extinction strain rates were observed to increase from 600 sec-1 to 2400 sec-1 with increasing H2:CO ratio owing to higher diffusivity and reactivity of the H2 molecule. Numerical simulations showed few mechanisms predicting extinction conditions within 5% of the measurements for low H2:CO ratios, however, deviations of 25% were observed for higher H2 :CO ratios. Sensitivity analyses revealed that the chain branching reactions, H+O2 <=>O+OH, O+H2 <=>H+OH and the third body reaction H+O2 +M<=>HO2 +M are the key reactions affecting extinction limits for higher H2:CO mixtures. The second phase of work involved quantitative measurement of OH species concentration in the syngas-air diffusion flames at strain rates varying from 35 sec-1 to 1180 sec-1. Non-intrusive temperature measurements using Rayleigh thermometry were made in order to provide the temperature profile necessary for full quantification of the species concentrations. The [OH] is observed to show a non-monotonous trend with increasing strain rates which is attributed to the competition between the effect of increased concentrations of H2 and O2 in the reaction zone and declining flame temperatures on the overall reaction rate. Although the kinetic mechanisms successfully captured this trend, significant deviations were observed in predictions and measurements in flames with H2:CO ratios of 1:1 and 4:1, at strain rates greater than 800 sec-1 . The key reactions affecting [OH] under these conditions were found to be the same reactions identified earlier during extinction studies, thus implying a need for the refinement of their reaction-rate parameters. Significant disagreements were observed in the predictions made using the chemical kinetic mechanisms from the literature in flames with high H2 content and high strain rate. The final phase of work focused on measurement of nitric oxide (NO) species concentrations followed by a comparison with predictions using various mechanisms. NO levels as high as ~ 48 ppm were observed for flames with moderate to high H2 content and low strain rate. Quantitative reaction pathway diagrams (QRPDs) showed thermal-NO, NNH and prompt-NO pathways to be the major contributors to NO formation at low strain rates, while the NNH pathway was the dominant route for NO formation at high strain rates. The absence of an elaborate CH chemistry in some of the mechanisms has been identified as the reason for underprediction of [NO] in the low strain rate flames. Overall, the quantitative measurements reported in this work serve as a valuable reference for validation of H2/CO chemical kinetic mechanisms, and the detailed numerical studies while providing an insight to the H2:CO kinetics and reaction pathways, have identified key reactions that need further refinement.

Les recherches consacrées aux points fixes à haute température (PFHT) ont été intensifiées depuis 1996, suite à une recommandation du Comité Consultatif de Thermométrie de développer des références au-delà de 2000 °C. Les Laboratoires Nationaux de Métrologie se sont alors engagés dans le développement de PFHT construits à partir d'alliages de métal et de carbone. Ces points fixes ont montré des transitions de phase à des températures reproductibles indépendamment de la proportion de carbone dans le métal. Les projets internationaux qui ont suivis les premiers developpements ont permis d'accroitre la robustesse et la stabilité à long terme des points fixes et ont mis en évidence l'importance des conditions thermiques de mise en œuvre. Aujourd'hui ces points fixes montrent une reproductibilité de l'ordre de 0.1 °C et sont en voie de renforcer l'exactitude des mesures pyrométriques aux plus hautes températures, jusqu'ici limitée par l'incertitude d'extrapolation dans l'Echelle Internationale de Température (EIT-90). Un projet de mesure par voie radiométrique de la température thermodynamique des PFHT les plus étudiés a été récemment mené. Les résulats de ces mesures absolues permettent aujourd'hui d'aborder la future mise-en-pratique du kelvin à haute température, par des méthodes de dissémination directe de la température thermodynamique sans recours à l'EIT-90. Ce document décrit les principales étapes depuis la conception de ces nouvelles références, jusqu'à la mesure de leur température thermodynamique. / Research dedicated to high-temperature-fixed-points (HTFPs) have been intensified since 1996, further to a recommendation of the Consultative Committee for Thermometry to develop references above 2000 °C. National Laboratories of Metrology envolved in the development of HTFPs based on metal-carbon alloys. These fixed points showed phase transitions at reproducible temperatures independently to the proportion of carbon in the metal. The international projects that followed the first developments allowed increasing the robustness and the long-term stability of the fixed points and highlighted the importance of the thermal conditions of implementation. Today these fixed points show a reproducibility of about 0.1 °C and are on the way to strengthen the accuracy of radiation thermometry measurements at high temperatures, up to now, limited by the uncertainty of the International Temperature Scale (ITS-90). A project to measure the thermodynamic temperature of the most studied HTFPs by a radiometric method was recently led. Results of this absolute measurement is a step towards the future mise en pratique of the kelvin at high temperature, by a direct dissemination of the thermodynamic temperature without any link to the ITS-90. This document describes the main steps from the conception of these new references, up to the measurement of their thermodynamic temperature.

Neste trabalho é apresentada uma proposta para o ensino de termometria e calorimetria, em nível de ensino médio, que enfatiza a habilidade de leitura e interpretação de gráficos. A motivação do trabalho é o crescente aumento da importância, no cenário nacional, do Exame Nacional do Ensino Médio (ENEM) exigindo a referida habilidade em parcela significativa das questões. A fundamentação teórica está baseada na Teoria da Aprendizagem de David Ausubel, tanto no que diz respeito à concepção e elaboração do material instrucional, quanto à sua aplicação em sala de aula. O módulo didático, perfazendo um total de 20 horas aula, é composto por um conjunto de aulas expositivo-dialogadas, aulas práticas, listas de exercícios, que partem de exercícios elementares até exercícios de concursos de vestibular, exercícios associados à visualização de vídeos, correção de atividades com a projeção de respostas erradas inspiradas no Peer Instruction e um texto produzido especialmente para o produto educacional, constituindo-se este conjunto no produto educacional do mestrado. Quanto à habilidade de leitura e interpretação de gráficos, adotou-se a classificação de Curcio em três níveis: “ler os dados, ler entre os dados e ler além dos dados”. O módulo didático foi aplicado no Colégio Concórdia de Porto Alegre em uma turma de 37 alunos do segundo ano do Ensino Médio. Para avaliar os alunos na leitura e interpretação de gráficos foi produzido um teste de conhecimentos prévios e conhecimentos adquiridos, com quinze questões que envolvem a leitura e interpretação de gráficos em diferentes níveis conforme a classificação de Curcio. O teste de opinião aplicado para avaliar a percepção dos alunos em relação ao desenvolvimento da proposta, de um modo geral, foi favorável à proposta. / This dissertation presents a proposal for teaching thermometry and calorimetry at high school level, which emphasizes graphs reading and interpreting skills. The motivation behind this study is the increasing importance, on the Brazilian national scene, of the National Secondary Education Exam (ENEM), requiring these skills in a significant portion of the questions. The theoretical foundation is the Meaningful Learning Theory by David Ausubel, regarding the design and preparation of instructional material for its use in the classroom. The teaching module, comprising a total of 20 class hours, consists of a set of expository-dialogued classes, practical classes, exercises, starting from elementary exercises to university entrance exams questions, exercises associated with video watching, tasks correction with the projection of wrong answers based on Peer Instruction and a text produced especially for the educational product, constituting this set the educational product for a master degree program. As for graphs reading and interpreting skills, Curcio´s classification has been adopted on three levels: "reading the data, reading between the data and reading beyond the data". The teaching module was applied to a class of 37 students in the second year of high school at Concordia School in the City of Porto Alegre. In order to assess students about graphs reading and interpreting, it was produced a pretest with fifteen questions at different levels according to Curcio´s classification. This test was applied before the didactic proposal for two main reasons: to detect previous knowledge of the students and to evaluate their learning improvement after the implementation of the proposal, using the same test as a posttest. At the end of the teaching module, a test was applied to assess the acquired knowledge of thermometry and calorimetry. The opinion test used to assess the students' perception concerning the proposal, in general, was favorable to the proposal.

Submitted by Rodrigo Garcia Brunini null (rgbrunini@gmail.com) on 2017-10-16T12:44:32Z No. of bitstreams: 1 ÍNDICES DE ESTRESSE HÍDRICO EM CANA-DE-AÇÚCAR NAS DIFERENTES FASES DE DESENVOLVIMENTO.pdf: 3562731 bytes, checksum: 5623f942a491de28b94f811adf7f8e01 (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-10-18T17:47:16Z (GMT) No. of bitstreams: 1 brunini_rg_dr_jabo.pdf: 3562731 bytes, checksum: 5623f942a491de28b94f811adf7f8e01 (MD5) / Made available in DSpace on 2017-10-18T17:47:16Z (GMT). No. of bitstreams: 1 brunini_rg_dr_jabo.pdf: 3562731 bytes, checksum: 5623f942a491de28b94f811adf7f8e01 (MD5) Previous issue date: 2017-09-29 / O Brasil é lider mundial na produção de açúcar e etanol, devido ao intenso cultivo da cultura de cana-de-açúcar principalmente na região Sudeste do país. No entanto sua expansão em outras áreas vem ganhando força nos últimos anos, o que tem acarretado variações significativas nas safras devido aos problemas relacionados ao clima da região e caracterísiticas topográficas do terreno. A limitação hídrica e as altas temperaturas do ar podem gerar danos irrerversíveis às plantas e impactos ao produtor final. O uso de índices de estresse hídrico nas fases de desenvolvimento da cultura pode atuar como uma ferramenta essencial no manejo da irrigação, prevenindo os efeitos negativos desencadeados pelo estresse hídrico nas plantas. Objetivou-se com este trabalho determinar índices de estresse hídrico em cana-de-açúcar nas diferentes fases de desenvolvimento. Para isso avaliaram-se os índices de estresse hídrico nas diferentes fases de desenvolvimento das plantas, o potencial de água no solo, o potencial matricial de água, a taxa fotossintética e o índice do conteudo de clorofila das folhas e a condução do sistema produtivo no período de coleta de dados. A pesquisa foi desenvolvida na área experimental do Departamento de Engenharia Rural da FCAV/UNESP, denominada “Bacia Hidrográfica Experimental”, utilizando superfícies caracterizadas como H1 (superfície horizontal na capacidade de campo) e H2 (superfície horizontal, sob déficit hídrico induzido), 20N e 40N (superfícies com 20 e 40% de declividade e exposição norte, sob déficit hídrico induzido), 20S e 40S (superfícies com 20 e 40% de declividade e exposição sul, sob déficit hídrico induzido), 20E e 40E (superfícies com 20 e 40% de declividade e exposição leste, sob déficit hídrico induzido) e 20 e 40W (superfícies com 20 e 40% de declividade e exposição oeste, sob déficit hídrico induzido). As análises foram realizadas in loco e em laboratório. Os resultados indicaram que o momento de irrigar difere para cada fase de desenvolvimento da cana-de-açúcar, em uma faixa entre 2,0°C até 5,0°C, sendo crítica a fase de perfilhamento. Verificou-se inclusive que a topografia do terreno teve influência na quantidade de radiação solar nos tratamentos. A superfície H1 mantida na capacidade de campo obteve menor índice de estresse hídrico e maior produtividade (124,0 Mg ha-1), diferindo estatisticamente dos demais tratamentos. / Brazil is the world leader in the production of sugar and ethanol, due to the intense cultivation of sugarcane cultivation mainly in the Southeast region of the country. However, its expansion in other areas has been gaining strength in the last years, which has caused significant variations in the harvests due to problems related to the climate of the region and topographic characteristics of the terrain. Water limitation and high air temperatures can generate irreversible damage to the plants and impacts the final producer. The use of water stress indices in the development stages of the crop can act as an essential tool in the management of irrigation, preventing the negative effects triggered by water stress in the plants. The objective of this work was to determine water stress indexes in sugarcane at different stages of development. For this, the water stress indexes were evaluated in the different phases of plant development, soil water potential, water matrix potential, photosynthetic rate and index of leaf chlorophyll content and the conduction of the productive system in the soil. period of data collection. The research was developed in the experimental area of the Department of Rural Engineering of the FCAV / UNESP, denominated "Experimental Hydrographic Basin", using surfaces characterized as H1 (horizontal surface in the field capacity) and H2 (horizontal surface, under induced water deficit), 20N and 40 N (surfaces with 20 and 40% slope and northern exposure, under induced water deficit), 20S and 40S (surfaces with 20 and 40% slope and south exposure, under induced water deficit), 20E and 40E (surfaces with 20 and 40% slope and east exposure, under induced water deficit) and 20 and 40W (areas with 20 and 40% slope and west exposure, under induced water deficit). The analyzes were performed in loco and in the laboratory. The results indicated that the time of irrigation differs for each phase of development of sugarcane, in a range between 2.0 ° C and 5.0 ° C, and the tillering phase is critical. It was also verified that the topography of the terrain influenced the amount of solar radiation in the treatments. The H1 surface maintained in the field capacity obtained lower index of water stress and higher productivity (124.0 Mg ha-1 ), differing statistically from the other treatments.

Resumo: O uso das Tecnologias da Informação e Comunicação tem crescido nas mais variadas atividades agrícolas. Como conseqüência, vem revolucionando a forma de pensar e agir do produtor que almeja se estabelecer em um mercado cada vez mais competitivo. Entretanto, o alto custo de aquisição e manutenção dessas tecnologias é um fator que pode inibir sua disseminação e aceitação, principalmente a um grande número de pequenos produtores de grãos. Diante desse cenário, há uma necessidade de soluções inovadoras adequadas a esse universo de produtores. Partindo-se dessa premissa, este trabalho apresenta o desenvolvimento de um protótipo de baixo custo para o monitoramento de temperatura e umidade de grãos armazenados em silos, utilizando uma tecnologia de comunicação sem fio por radiofreqüência. Para tanto, foram analisadas as implicações econômicas de custo/benefício do emprego inovador da transmissão sem fio no processo de termometria de grãos. O protótipo foi composto por duas unidades eletrônicas, uma de aquisição e outra de recepção de dados, além de um programa computacional que ofereceu ao produtor informações mais precisas para o controle da aeração. Por meio de testes realizados quanto à estabilidade, integridade e confiabilidade da transmissão de dados via rádio, utilizando componentes eletrônicos de baixo custo, pode-se considerar o sistema desenvolvido potencialmente viável. Este apresentou o diferencial da comunicação sem fio via rádio no processo de termometria de grãos, proporcionando mobilidade, minimizando custos com cabeamento, manutenção e oferecendo facilidades para sua expansão; também adequou-se ao monitoramento de temperatura eumidade de grãos em silos; e mostrou-se com viabilidade operacional, além do baixo custo de desenvolvimento quando comparado a produtos similares encontrados no mercado brasileiro. / Abstract: The use of Information and Communication Technology has grown in most agricultural activities. As a consequence, it has changed the way of thinking and acting of the farmer who wants to establish in a more and more competitive market. However, the high costs of acquisition and maintenance of those technologies may be a factor which can inhibit its spread and acceptance, mainly to a large number of small grain Brazilian farmers. In this context, there is a need for innovative solution which are proper for this universe of farmers. Starting from this premise, this paper presents the development of a low cost prototype to the monitoring process of temperature and humidity values of grains stored in silos, using communication based on wireless technology by radio frequency. Therefore, the economic implications of cost/benefit ratio of innovative application of wireless transmission in the process of thermometry of grains were analysed. The prototype was made of two electronic units, one of acquisition and another one of data reception, as well as a computational software, which offered the farmer more precise information for the control of aeration. By means of stability, integrity and reliability tests of data transmission via radio, using low cost electronic components, the development system can be considered as potentially viable. It presented the difference regarding the wireless communication via radio in the process of grains thermometry, providing mobility, reducing cabling costs and maintenance, and also offering an easy system expansion; it was also appropriate to temperature and humidity monitoring in grain silos; and revealed operational viability, besides 4 the low cost development when compared to similar products available in the Brazilian market. / Orientador: Marco Antonio Martin Biaggioni / Coorientador: Ariangelo Hauer Dias / Banca: Marcelo Giovaneti Canteri / Banca: Ivo Mario Mathias / Banca: Célia Regina Lopes Zimback / Banca: Kléber Pereira Lanças / Doutor

Neste trabalho é apresentada uma proposta para o ensino de termometria e calorimetria, em nível de ensino médio, que enfatiza a habilidade de leitura e interpretação de gráficos. A motivação do trabalho é o crescente aumento da importância, no cenário nacional, do Exame Nacional do Ensino Médio (ENEM) exigindo a referida habilidade em parcela significativa das questões. A fundamentação teórica está baseada na Teoria da Aprendizagem de David Ausubel, tanto no que diz respeito à concepção e elaboração do material instrucional, quanto à sua aplicação em sala de aula. O módulo didático, perfazendo um total de 20 horas aula, é composto por um conjunto de aulas expositivo-dialogadas, aulas práticas, listas de exercícios, que partem de exercícios elementares até exercícios de concursos de vestibular, exercícios associados à visualização de vídeos, correção de atividades com a projeção de respostas erradas inspiradas no Peer Instruction e um texto produzido especialmente para o produto educacional, constituindo-se este conjunto no produto educacional do mestrado. Quanto à habilidade de leitura e interpretação de gráficos, adotou-se a classificação de Curcio em três níveis: “ler os dados, ler entre os dados e ler além dos dados”. O módulo didático foi aplicado no Colégio Concórdia de Porto Alegre em uma turma de 37 alunos do segundo ano do Ensino Médio. Para avaliar os alunos na leitura e interpretação de gráficos foi produzido um teste de conhecimentos prévios e conhecimentos adquiridos, com quinze questões que envolvem a leitura e interpretação de gráficos em diferentes níveis conforme a classificação de Curcio. O teste de opinião aplicado para avaliar a percepção dos alunos em relação ao desenvolvimento da proposta, de um modo geral, foi favorável à proposta. / This dissertation presents a proposal for teaching thermometry and calorimetry at high school level, which emphasizes graphs reading and interpreting skills. The motivation behind this study is the increasing importance, on the Brazilian national scene, of the National Secondary Education Exam (ENEM), requiring these skills in a significant portion of the questions. The theoretical foundation is the Meaningful Learning Theory by David Ausubel, regarding the design and preparation of instructional material for its use in the classroom. The teaching module, comprising a total of 20 class hours, consists of a set of expository-dialogued classes, practical classes, exercises, starting from elementary exercises to university entrance exams questions, exercises associated with video watching, tasks correction with the projection of wrong answers based on Peer Instruction and a text produced especially for the educational product, constituting this set the educational product for a master degree program. As for graphs reading and interpreting skills, Curcio´s classification has been adopted on three levels: "reading the data, reading between the data and reading beyond the data". The teaching module was applied to a class of 37 students in the second year of high school at Concordia School in the City of Porto Alegre. In order to assess students about graphs reading and interpreting, it was produced a pretest with fifteen questions at different levels according to Curcio´s classification. This test was applied before the didactic proposal for two main reasons: to detect previous knowledge of the students and to evaluate their learning improvement after the implementation of the proposal, using the same test as a posttest. At the end of the teaching module, a test was applied to assess the acquired knowledge of thermometry and calorimetry. The opinion test used to assess the students' perception concerning the proposal, in general, was favorable to the proposal.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2017-06-23T17:02:47Z No. of bitstreams: 2 Dissertação - Patrícia Cardoso de Andrade - 2017.pdf: 2778221 bytes, checksum: 777088966ede58904a5d760acc52b11e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Erika Demachki (erikademachki@gmail.com) on 2017-06-29T18:28:28Z (GMT) No. of bitstreams: 2 Dissertação - Patrícia Cardoso de Andrade - 2017.pdf: 2778221 bytes, checksum: 777088966ede58904a5d760acc52b11e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-06-29T18:28:28Z (GMT). No. of bitstreams: 2 Dissertação - Patrícia Cardoso de Andrade - 2017.pdf: 2778221 bytes, checksum: 777088966ede58904a5d760acc52b11e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-05-05 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Measuring internal temperature and/or temperature gradient in materials is of fundamental interest in both engineering and basic sciences because the temperature is closely related to the properties of the material. The purpose of this study was to develop an ultrasound thermometry system for internal temperature gradient monitoring of materials subjected to a heat source. A low cost oscilloscope was used as a system for the acquisition of ultrasonic signals. Jointly, was developed a computational algorithm responsible for estimating the internal temperature distribution of materials. For this purpose was used a low cost oscilloscope as a system for the acquisition of ultrasonic signals. Measurements were taken during the heating and cooling regimen of an aluminum block. A thermocouple temperature measurement system was used to verify and validate the temperature distribution obtained by the ultrasound thermometry method. The development of the computational algorithm responsible for communication and data collection provided real-time temperature measurements. The comparison of the temperature measurements derived from both methods showed agreement greater than 96%, with differences lower than 0.70°C. The methodology presented was relevant within the laboratory context to estimate the internal temperature of heated materials. / Medir temperatura interna e/ou gradiente de temperatura em materiais é de fundamental interesse, tanto nas engenharias quanto nas ciências básicas, pois a temperatura está intimamente relacionada com as propriedades do material. O objetivo desse estudo foi desenvolver um sistema de termometria por ultrassom para monitoramento interno de gradiente de temperatura em materiais submetidos a fonte de calor. Conjuntamente, foi desenvolvido um algoritmo computacional responsável em estimar a distribuição de temperatura interna dos materiais. Para essa finalidade foi empregando um osciloscópio de baixo custo como sistema de aquisição de sinais ultrassônicos. Medições foram realizadas durante o regime de aquecimento e resfriamento de um bloco de alumínio. Um sistema de medição de temperatura por termopares foi utilizado para verificar e validar a distribuição de temperatura obtida pelo método de termometria por ultrassom. O desenvolvimento do algoritmo computacional responsável pela comunicação e coleta de dados propiciou medições de temperatura em tempo real. A comparação das medições de temperatura derivada de ambos os métodos apresentou concordância maior que 96%, com diferenças inferiores a 0,70°C. Portanto, conclui-se que a metodologia apresentada mostrou-se relevante dentro do contexto laboratorial para estimativa de temperatura interna de materiais aquecidos.