O crescente avanço nas mais diversas áreas da eletrônica, desde instrumentação em baixa freqüência até telecomunicações operando em freqüências muito elevadas, e a necessidade de soluções baratas em curto espaço de tempo que acompanhem a demanda de mercado, torna a procura por circuitos programáveis, tanto digitais como analógicos, um ponto comum em diversas pesquisas. Os dispositivos digitais programáveis, que têm como grande representante os Field Programmable Gate Arrays (FPGAs), vêm apresentando um elevado e contínuo crescimento em termos de complexidade, desempenho e número de transistores integrados, já há várias décadas. O desenvolvimento de dispositivos analógicos programáveis (Field Programmable Analog Arrays – FPAAs), entretanto, esbarra em dois pontos fundamentais que tornam sua evolução um tanto latente: a estreita largura de banda alcançada, conseqüência da necessidade de um grande número de chaves de programação e reconfiguração, e a elevada área consumida por componentes analógicos como resistores e capacitores, quando integrados em processos VLSI Este trabalho apresenta uma proposta para aumentar a faixa de freqüências das aplicações passíveis de serem utilizadas tanto em FPAAs comerciais quanto em outros FPAAs, através da utilização de uma interface de translação e seleção de sinais, mantendo características de programabilidade do FPAA em questão, sem aumentar em muito sua potência consumida. A proposta, a simulação e a implementação da interface são apresentadas ao longo desta dissertação. Resultados de simulação e resultados práticos obtidos comprovam a eficácia da proposta. / The increasing advance in several areas of electronics, from low frequency instrumentation to telecommunications operating in very high frequencies, and the necessity of low cost solutions in a short space of time, following the demand of the market, makes the search for digital and analog programmable circuits a common point in many researches. Digital programmable devices, which have as a great representant Field Programmable Gate Arrays (FPGAs) devices, have shown a high and continuous increase in terms of complexity, performance and number of integrated transistors for many decades. The development of analog programmable devices (Field Programmable Analog Arrays – FPAAs), however, stops in two fundamental points that make their evolution slow: the narrow bandwidth reached, consequence of the necessity of a great number of programming and configuration switches, and the huge area occupied for analog components as resistors and capacitors, when integrated in a VLSI process. This work presents a proposal to increase the frequency range of the applications that can be used also with commercials FPAAs and others FPAAs, through the use of an interface to translate and select signals, keeping the programmability characteristics of the FPAA, without increasing so much the dissipated power. The proposal, simulation and implementation of the interface are presented in this dissertation. The simulations and practical results obtained show the proposal efficiency.

A crescente utilização do concreto, que é o produto mais fabricado no mundo em termos de volume, somada à pressão do mercado por redução de custos com manutenção das exigências mínimas para segurança do projeto, tem impacto direto na importância e necessidade do controle de qualidade do material. Para concretos usinados, predominantes em grandes centros urbanos, as normas do país preconizam a não utilização dos 15% iniciais e finais do volume total de concreto do caminhão betoneira para fins de ensaio. No entanto, devido a maior facilidade e agilidade, é constatada como prática comum nos canteiros de obra da região a coleta de amostras logo da primeira porção de concreto descarregado. Considerando tal procedimento, fora do padrão preconizado por norma, somado à ausência de normatização para aferição da qualidade do misturador e uniformidade da mistura do concreto e a importância dos ensaios de controle de qualidade dos concretos perante a segurança das estruturas, a presente pesquisa tem como objetivo analisar as variações de resistência à compressão e de propriedades físicas do concreto ao longo da descarga da mistura em caminhão betoneira. A fim de atingir a meta proposta, realizaram-se coletas de amostras em cinco pontos distintos, ao longo da descarga do concreto do caminhão betoneira, para cada um dos 65 lotes (amassadas) avaliados, considerando três diferentes traços de concreto. Para cada ponto de coleta foram avaliados a resistência à compressão, o abatimento de tronco de cone e o teor de agregado graúdo. Estatisticamente, foi constatado que há amassadas em que a variação do ponto de coleta influencia na resistência à compressão, no entanto não se pode afirmar o mesmo considerando critérios da ABECE, adotados como parâmetro de análise na falta de normatização específica para o tema. Não houve a formação de um perfil representativo das variações de resistência conforme o ponto de coleta, diferentemente do teor de agregado graúdo, em que se pode visualizar claramente um perfil em que há concentração de brita nos pontos extremos, início e final da coleta. Em relação à consistência, de modo geral, houve uma redução do ponto inicial ao final, dentro dos limites de indicados por norma. / The crescent utilization of concrete which in terms of volume, is the most produced product in the world, added to the pressure of the market to reduce the costs and maintenance of the safety minimum requirements of a project, make a direct impact on the material quality control’s importance and necessity. For ready-mixed concrete, mostly seen in large urban centers, the initial and final 15% usage of its total volume is not recommended by the country standards for test purposes. However, due to the ease, it is a common practice in construction sites of the region to collect samples once the first portion of the concrete is unloaded. Taking into account such procedure, which does not meet the standards recommended, added to the lack of standardization to assess the quality of the concrete mixer, the uniformity of the concrete mixture and the importance of the quality control tests of concrete under the safety of structures, the purpose of this research is to analyze the variations of the concrete strength when compressed and its physical properties along the discharge of the mixture made in a mixer truck. In order to achieve the proposed goal, there were sampling carried out at five different points along the discharge from the concrete mixer truck, for each of the 65 lots (batches) analyzed, considering three different types of concrete. Each sampling collected was analyzed by going through a slump test, compression strength and granulometry analysis. Statistically, it was proven that the sample point collection variation of some of the batches influences the compression strength, on the other hand the same cannot be found considering the ABECE criteria, used as analysis parameter in the absence of specific regulations for the subject. No representative profile of resistance variations based on the sample collection point was formed, in contrast to the coarse aggregate content, in which profile can be clearly seen a concentration of gravels at the extreme points, at the commencement and the end of the sample collection. Regarding its consistency, on the whole, there was a reduction from the initial and to the end point, respecting the regulations standards.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The computational fluid dynamics is a technique used for the analysis of fluid flow systems By this technique, it is possible to simulate new geometries of equipments as well as optimize one in use. In this research, we propose the development of new configurations for static mixers. Is proposed 27 simulations were conducted in a 24 factorial planning with 3 central points and 8 axial points, varying the thickness and the depth of the groove and the distance between the grooves, in order to obtain the velocity gradient as response. One could obtain two optimal settings were obtained. Once the machining of the optimal geometry was difficult, modifications were proposed to facilitate the construction of the mixer. So 16 configurations were obtained and the simplest one was built to be coupled to an experimental test system. The simulated and the experimental values of the velocity gradient were compared. One set up two tubular reactor systems with and without the static mixer were built for the experiments to obtain biodiesel. In these experiments, a 23 factorial planning was done, varying alcohol:oil ratio, catalyst concentration and temperature. The static mixer presented the value of the velocity gradients of 2288.93s-1, being 4,01% lower than the value found in the (2384.61s-1). A comparison of the experiments showed that the utilization of the mixer increased the ester conversion. The equation obtained from the empirical model of conversion to ester (Y) had an adjustment coefficient of 0.97 for the smooth tube reactor and 0.94 for the reactor with mixer. / A fluidodinâmica computacional é uma técnica que permite a análise de sistemas envolvendo o escoamento de fluidos. Através desta técnica é possível simular novas geometrias de equipamentos, bem como otimizar os já utilizados. Neste trabalho, propõe-se o desenvolvimento de novas configurações para misturadores estáticos. Foram realizadas 27 simulações de um planejamento fatorial 24 com 3 pontos centrais e 8 pontos axiais variando o comprimento equivalente, a espessura, a altura das saliências e a distância entre cada saliência para obtenção do gradiente de velocidade como resposta. Foram obtidas duas configurações ótimas. Com a dificuldade de usinagem da configuração ótima, foram propostas modificações para facilitar a construção do misturador; assim, 14 configurações foram obtidas e a mais simples foi construída, para ser acoplada a um sistema de testes experimentais. Foram comparados os valores do gradiente de velocidade simulado e experimental. Foram construídos dois sistemas de reatores tubulares com e sem o misturador estático construído para a realização dos experimentos de obtenção de biodiesel. Para estes experimentos foi realizado um planejamento fatorial 23, variando os seguintes parâmetros: razão álcool:óleo; concentração de catalisador e temperatura. O misturador construído apresentou o valor do gradiente de velocidade de 2288,93s-1, sendo 4,01% inferior ao valor encontrado na simulação (2384,61s-1). Após os experimentos foi constatado que com a utilização do misturador a conversão em ésteres é maior. A equação obtida para o modelo empírico da conversão em éster (Y) teve um coeficiente de ajuste de 0,97 para o reator com tubo liso e 0,94 para o reator com misturador.

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Orientadore: Jose Roberto Nunhez, Efraim Cekinski / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-11T21:24:27Z (GMT). No. of bitstreams: 1 JoaquimJunior_CelsoFernandes_M.pdf: 1822240 bytes, checksum: 1c74330095d87b01b823d7d17fbc50c9 (MD5) Previous issue date: 2008 / Resumo: Nos processos convencionais de agitação e mistura um acionamento, através de um eixo-árvore, rotaciona um ou mais impelidores no interior de um fluido, normalmente contido em um vaso de processo. Os processos de mistura que usam dispositivos estáticos no interior de dutos de escoamento são uma opção aos processos convencionais, tendo crescente aplicação e interesse, visto utilizar-se de parte da energia cedida para o bombeamento dos fluidos, permitindo a mistura em um processo contínuo, minimizando o uso de equipamentos e instalações industriais. Contudo, sua aplicação ainda é restrita a alguns processos específicos por questões tecnológicas e, principalmente, pelo pouco conhecimento de técnicos e engenheiros dos fenômenos físicos que regem sua aplicabilidade. A inexistência de tecnologia e conhecimento nacional nesta área impõe a dependência frente a empresas estrangeiras, encarecendo e dificultando sua aplicação. Na última década, técnicas computacionais tem sido utilizadas para o projeto e otimização desses dispositivos, conhecidos como misturadores estáticos, com destaque para a fluidodinâmica computacional ¿ CFD (Computational Fluid Dynamics). Este trabalho tem como objetivo, através da aplicação de técnicas de CFD, permitir um melhor entendimento dos fenômenos que regem o escoamento de fluidos no interior de misturadores estáticos, especificamente desenhados para esta análise, permitindo sugerir e estudar seus desenhos, propondo soluções e modificações a fim de melhorar a mistura e minimizar o gasto de energia no processo. A ferramenta de CFD utilizada foi o pacote computacional CFX. Os resultados obtidos permitiram uma boa compreensão dos fenômenos envolvidos e foram coerentes com os dados experimentais disponíveis na literatura. Foram criados dois novos conceitos geométricos de misturadores estáticos, denominados de EDA e ALETAS, cujas performances permitem seu emprego em condições reais de aplicação na indústria. / Abstract: On conventional mixing processes, a shaft rotates one or more impellers in a fluid generally inside a process vessel. The mixing processes that use static mixers on tube fluid flow are an option to conventional processes which application and interest is continuously growing, minimizing the use of equipment industrial devices. However its application is restricted to some specific processes because of technological reasons and mainly due to the lack or absence of acknowledgement of technicians and engineers about the physical phenomena involved on static mixing application. The absence of national technology on this field, demands foreign companies¿ technological dependence, making more difficult more and turning expensive the applications. On the last decade, computational techniques have been used for the design and optimization of these equipments, known as static mixers, specially the computational fluid dynamics ¿ CFD. This research has the goal, by using CFD techniques, to allow a better understanding of the phenomena that determine the fluid flow in static mixers specifically designed for this analysis, permitting to study and suggest modifications and solutions to increase mixing and minimize power consumption on the process. The CFD tool used was the CFX package. The results obtained permitted a good comprehension of the phenomena involved and were in accordance with experimental data available on literature review. Two new geometric concepts of static mixers were created, named EDA and ALETAS, whose performances allow their use on industrial applications. / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Radar warning systems are life saving equipment in modern fighter aircraft. It is therefore vital that the system can tell the difference between a threat genuine frequency) and a false signal (spurious frequency). This thesis presents a model aimed at predicting the frequencies and other parameters in the RF converter of the radar warning system. The components of the RF converter have been studied, measured, and modelled. The modelling tool has been the Simulink toolbox for Matlab. Extreme accuracy has been sacrificed in order to make the model easy to use for the working engineer. Instead, this model presents a rough estimate of some of the most important properties of the radar warning system with just a few data sheet figures as input. The simulation results are satisfactory as a whole. Simulink is the limiting factor in the implementation of the model. Significantly improved results can probably be obtained by working in another software environment.

Le domaine térahertz est une région du spectre électromagnétique comprise entre 300 GHz et 30 THz. Elle représente un fort intérêt pour la communauté scientifique pour plusieurs raisons : la radiation térahertz possède en effet un potentiel de télécommunication à très haut débit important, elle constitue un moyen d'investigation efficace et non destructif pour différents types d'éléments et composés, minéraux ou organiques et elle représente une importance cruciale pour les astronomes qui estime que 98 % des photons émis par le Big Bang se trouvent dans ce domaine de fréquences. Malheureusement, à l'heure actuelle, le manque de sources et détecteurs facilement exploitables, intégrables et fonctionnant à température ambiante ne permet pas l'utilisation du domaine térahertz à grande échelle. Un nouveau phénomène physique exploitable tel que les oscillations d'ondes de plasma dans les nanotransistors représente une piste prometteuse pour combler ce manque. Ce phénomène étudié de manière analytique dans le milieu des années 1990, a donné lieu à un modèle qui reste très loin de la réalité physique et des conditions expérimentales. Des expériences récentes effectuées à température ambiante ont permis de montrer la possibilité d'exciter des oscillations d'ondes de plasma à l'intérieur d'un canal de HEMT par une radiation THz directe. Ce travail se propose de réaliser une étude systématique des transistors sous excitation effectuée par battement optique térahertz. Ceci afin de mieux comprendre et exploiter les ondes de plasma dans les nanotransistors à effet de champ. Cela nous a conduit à étudier l'effet des paramètres géométriques et physiques du transistor comme les longueurs de grille, les longueurs des cap-layers, la tension de drain et la tension de grille. En parallèle à ce travail expérimental un modèle hydrodynamique pseudo-2D était utilisé pour confronter l'ensemble des résultats pour une meilleure compréhension des phénomènes physiques. Ce travail a permis d'accéder à une compréhension et une description fines du phénomène d'excitation des ondes de plasma. ceci a permis d'initier l'étude de nouveaux dispositifs tel que un émetteur à base d'un transistor HEMT assisté par battement optique et la réalisation d'un mélangeur hétérodyne d'une radiation térahertz transposé par un battement optique en une fréquence intermédiaire plus basse et facilement exploitable. / The terahertz range covers the electromagnetic spectrum for frequencies between 300 GHz and 30 THz. It presents a strong interest in the scientific community for several reasons: Terahertz carriers allow for high-speed free-space telecommunications; Terahertz radiations can be used for efficient and non-destructive characterization of various components and materials (minerals or organic); Terahertz detection is of major interest for astronomers as 98 % of photons emitted since the Big Bang are in this frequency domain. Unfortunately, the lack of adequate sources and detectors, i.e. room-temperature-operating, low-cost and integrated, strongly limits the use of terahertz radiations for the above-mentioned applications. A new physical phenomenon called plasma waves in nanotransistors is very promising for the realization of terahertz sources and detectors. This new phenomenon was proposed in the mid-1990s on the basis of analytical calculations, although the model was rather simplified and it did not take into account the actual experimental conditions. Recent experiments performed at low and room temperature demonstrated the feasibility to excite plasma waves in the channel of a high-electron-mobility transistor (HEMT), using a THz-radiation excitation.This work presents a different way to excite this plasma wave by using an optical beating excitation. A systematic study of nanometric transistors under optical excitation to better understand and exploit plasma waves is carried on. The effects of geometrical parameters such as transistor gate length or cap-layer length are investigated. The dependence of the plasma waves on different electrical parameters such as drain voltage and gate voltage is also presented. Along with this experimental work, a pseudo-two-dimensional hydrodynamic simulator was developed to analyze the physical processes in the transistors on a more rigorous theoretical basis than the simplified analytical model. As a result of this joint experimental and theoretical investigation, we achieved a better understanding and an accurate description of the complex mechanism of plasma waves excited in field-effect transistors. Finally, we propose new structures to be used, from one hand, as a monochromatic terahertz source based on a HEMT excited by an optical beating, and,from the other hand, a spectrally-resolved heterodyne detector based on the mixing between the terahertz radiation to be analyzed and an optical beating used as a tunable local oscillator.

This dissertation focuses on developing 3D printing as a fabrication method for microfluidic devices. Specifically, I concentrate on the 3D printing approach known as Digital Light Processing stereolithography (DLP-SLA) in which serially projected images are used to sequentially photopolymerize layers to build a microfluidic device. The motivation for this work is to explore a much faster alternative to cleanroom-based microfabrication that additionally offers the opportunity to densely integrate microfluidic elements in compact 3D layouts for dramatic device volume reduction. In the course of my research, an optical approach was used to guide custom resin formulation to help create the interconnected hollow regions that form a microfluidic device. This was based on a new a mathematical model to calculate the optical dose delivered throughout a 3D printed part, which also explains the effect of voids. The model was verified by a series of 3D printed chips fabricated with a commercial 3D printer and a custom resin. Channels as small as 108 µm x 60 µm were repeatably fabricated. Next, highly compact active fluidic components, including valves, pumps, and multiplexers, were fabricated with the same 3D printer and resin. The valves achieved a 10x size reduction compared with previous results, and were the smallest 3D printed valves at the time. Moreover, by adding thermal initiator to thermally cure devices after 3D printing, the durability of 3D printed valves was improved and up to 1 million actuations were demonstrated.To further decrease the 3D printed feature size, I built a custom 3D printer with a 385 nm LED light source and a 7.56 µm pixel pitch in the plane of the projected image. A custom resin was also developed to take advantage of the new 3D printer's features, which necessitated developing a UV absorber screening process which I applied to 20 candidate absorbers. In addition, a new mathematical model was developed to use only the absorber's molar absorptivity measurement to predict the resin optical penetration depth, which is important for determining the z-resolution that can be achieved with a given resin. The final resin formulation uses 2-nitrophenyl phenyl sulfide (NPS) as the UV absorber. With this resin, along with a new channel narrowing technique, I successfully created flow channel cross sections as small as 18 µm x 20 µm.With the custom 3D printer, smaller valves and pumps become possible, which led to the invention of a new method of creating large numbers of high density chip-to-chip microfluidic interconnects based on either simple integrated microgaskets (SIMs) or controlled-compression integrated microgaskets (CCIMs). Since these structures are directly 3D printed as part of a device, they require no additional materials or fabrication steps. As a demonstration of the efficacy of this approach, 121 chip-to-chip interconnects in an 11 x 11 array for both SIMs and CCIMs with an areal density of 53 interconnects per square mm were demonstrated, and tested up to 50 psi without leaking. Finally, these interconnects were used in the development of 3D printed chips with valves having 30x smaller volume than the valves we previously demonstrated. These valves served as a building block for demonstrating the miniaturization potential of an active fluid mixer using our 3D printing tools, materials, and methods. The mixer provided a set of selectable mixing ratios, and was designed in 2 configurations, a linear dilution mixer-pump (LDMP) and a parallelized dilution mixer-pump (PDMP), which occupy volumes of only 1.5 cubic mm and 2.6 cubic mm, respectively.

Au cours de ce travail de thèse, sur l'hydrodynamique de l'écoulement dans le un réacteur continu, où les propriétés des nanomatériaux élaborés dépendent des caractéristiques morphologiques et structurales de la solution colloïdale issue du réacteur, nous avons d'abord optimisé les conditions d'utilisation (Re ≈ 6000), ainsi que la géométrie du T-mélange dans le but d'améliorer la qualité du micro-mélange. Ensuite, des mesures expérimentales ont permis de vérifier que la condition de Damköhler est respectée (Da ≤ 1). Enfin, ce résultat a été validé numériquement. Au delà de cette valeur de Re critique (Re* ≈ 8000), nous avons mis en évidence le phénomène de cavitation dans le T-mélange. Ce phénomène à été étudié expérimentalement, par des mesures SLS, et numériquement par des simulations CFD. Les résultats obtenus par ces deux approches concordent. Enfin, des mesures DLS ont été effectuées pour étudier et caractériser les bulles de cavitation. Ces dernières ont permis d'évaluer la taille des bulles ainsi que leur trajectoire le long de l'axe Z à la sortie du T-mélange. Cette étude a été suivie par des simulations numériques de la cavitation et du modèle multiphasique dans notre écoulement. Les deux études, expérimentale et numérique, ont confirmé que la diminution de l'intensité de la lumière diffusée mesurée par SLS le long de l'axe Z est due à l'évolution du nombre et de la taille des bulles / During this Phd work, on the hydrodynamics of flow in a continuous reactor, where the properties of the elaborated nanomaterials depend on the morphological and structural characteristics of the colloidal solution out coming from the reactor, we first optimized the conditions of use of the latter (Re ≈ 6000), as well as the geometry of the T-mixer in order to improve the quality of the micro-mixing. Then, experimental measurements allowed us to verify that the condition of Damköhler is respected (Da ≤ 1). Finally, this result has been validated numerically. Beyond this Re critical value (Re * ≈ 8000), we have highlighted the phenomenon of cavitations in the T-mixer. This phenomenon has been studied experimentally, by SLS measurements, and numerically by CFD simulation. The results obtained by these two approaches are in agreement. Finally, DLS measurements were made to study and characterize cavitations bubbles. These measurements allowed us to evaluate the size of the bubbles as well as their trajectory along the Z axis 121 at the outlet of the T-mixer. This study was followed by numerical simulations of the cavitations and the multiphase model in our flow. Both experimental and numerical studies confirmed that the decrease in the intensity of scattered light measured by SLS along the Z axis is result to the changes of the number and the size of bubbles.