Um amplificador de transimpedância de ganho variável para aplicação em osciladores baseados em MEMS

Orientador: José Alexandre DinizDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Um amplificador de transimpedância (TIA) de ganho variável é apresentado. Implementado em tecnologia 0,18 'mi'm, o projeto relatado possui a finalidade de prover um amplificador de sustentação para osciladores baseados em ressonadores do tipo MEMS (Micro-Electro-Mechanical System). Entre outros, as peculiaridades de projeto envolvem um desafiante compromisso entre Ganho, Largura de Banda, Ruído e Consumo de potência. Sendo assim, o amplificador foi implementado através do cascateamento de quatro estágios de ganho similares, lançando-se mão de realimentação do tipo shunt-shunt para diminuir as impedâncias de entrada e saída. Através do emprego de um estágio de ganho variável, uma alta faixa dinâmica de ganho é alcançada (53 dB), com um ganho máximo de transimpedância de 118 dB'ômega'...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digitalAbstract: A variable gain Transimpedance Amplifier (TIA) is presented. Realized in 0.18 'mi'm technology, this amplifier was conceived with the purpose of providing oscillation sustaining for Micro-Electro-Mechanical System (MEMS) based oscillators. Facing a quite challenging trade-off between Gain, Bandwidth, Noise and Power consumption, the TIA was implemented through the cascade of four similar gain stages, with the application of shunt-shunt feedback to lower both input and output resistances. With the employment of a variable-gain stage, this TIA presents a large gain tunability of 53 dB, with a also large maximum transimpedance gain of 118 dB'omega'...Note: The complete abstract is available with the full electronic documentMestradoEletrônica, Microeletrônica e OptoeletrônicaMestre em Engenharia Elétric

Mathematical Modelling and Design for the Scale-up of an AACVD Process

The manufacturing process of photovoltaic devices, such as solar cells, relies on the production of Transparent and Conductive Oxide (TCO) films. One of the techniques for creating these films is based on Aerosol-Assisted Chemical Vapour Deposition (AACVD). The AACVD process comprises the atomisation of a precursor solution into aerosol droplets, which are transported to a heated chamber for the synthesis of films such as the TCOs, as well as coatings, powders, composites and nanotubes. At present, AACVD has not been used as an industrial deposition technique. However, it has the potential to be scaled-up due to its versatility and the ease through which effective functional coatings can be deposited at a laboratory-scale. Computational simulations are pivotal to study the feasibility of such a scale-up. This thesis presents, therefore, an integrated model to support the AACVD process scale-up. The model is comprised of four stages: aerosol generation, transport, delivery and chemical deposition. The generation of aerosol is described by a distribution of droplet sizes, which is the input to a transport model that incorporates the impact of aerosol losses. The output distribution provides sufficient information to predict the amount and sizing of aerosol reaching the deposition site. Experimental validation has shown the model to be effective at predicting transport losses and droplet sizes. The delivery stage includes the solvent evaporation, accounting for uncertainties in the temperature profile of the deposition site. This is a key factor for the solvent evaporation, setting the precursors free to react and form the desired products. For the chemical deposition stage, reactions in the solid and gas phases were studied. The model presented is suitable for application on the scale of industrial processes and is also suitable for processes that rely on atomisation and transport of particles, for example, spray drying or cooling and fuel combustion. Lessons learned in modelling uncertainties and their impact on process scale-up motivated the research into formulation, modelling and solution methods for such applications. Therefore, as an additional contribution, this thesis introduces Uncertainty.jl, a modelling framework focused on the treatment of uncertainty

Sentidos sobre ciências e tecnologias no ensino fundamental

Neste artigo são apresentados e discutidos resultados de uma pesquisa1 envolvendo aspectos do funcionamento da leitura em sala de aula de ciências, a partir de textos do campo da ciência e da tecnologia, veiculados pelo Programa Internacional de Avaliação de Estudantes (PISA). Objetivando compreender que sentidos sobre Ciências e Tecnologias são produzidos pelos estudantes, analisamos as condições de produção da leitura e dos discursos envolvendo esses textos, em situações de sala de aula de ciências, no ensino fundamental. Para tanto, realizamos uma pesquisa de cunho qualitativo, adotando como suporte teórico-metodológico a Análise de Discurso de linha francesa e Educação CTS, com destaque para as questões que envolvem leituras do PISA, em particular, suas paráfrases e polissemias

Multiple emulsions containing amazon oil: açaí oil (Euterpe oleracea)

The aim of this work was to formulate O/W/O multiple emulsions containing açaí oil as a model system and to evaluate their physical stability and in vivo Sun Protection Factor (SPF). Multiple emulsions are complex dispersion systems, known also as, "emulsions of emulsions". These emulsion systems, have significant potential in the cosmetic industry. Euterpe oleracea Mart., Arecaceae, popularly known in Brazil as "açaí", is an economically important plant. Açaí oil has been used as antioxidant and as anti-inflammatory activities. The multiple emulsions were prepared using a two-step procedure. The investigated formulations were characterized and their stability over time was evaluated by preliminary and accelerated stability. O/W/O multiple emulsions containing the same concentration of sunscreens with and without açaí oil were evaluated by the International Sun Protection Factor Test Method. The samples containing 70% (w/w) of primary emulsion, 5% (w/w) PEG-30-dipolyhydroxystearate, 10% (w/w) of açaí oil and 5% (w/w) of sucrose polybehenate have been found to be stable. The rheological measurements revealed that the samples exhibited non-Newtonian pseudoplastic flow behavior and thixotropy. To conclude, no statistical difference could be observed on the in vivo SPF to both multiple systems with or without açaí oil.UNICFundação de Amparo a Pesquisa do Estado de Mato Grosso (FAPEMAT

Desafios das Universidades Empreendedoras: Universidade Tradicional X Universidade Corporativa

Este artigo tem como objetivo analisar e fazer um paralelo entre a Universidade tradicional e a Universidade corporativa. Pretende ainda, colaborar na discussão do tema,Universidade empreendedora, apresentando novos desafios para as universidades brasileiras, com o intuito de estas instituições alcancem seus objetivos, diante de cenários cada vez mais instáveis. O estado da arte remete para constatações de que as universidades tradicionais necessitam de estratégias gerenciais empreendedoras e voltadas para atender as necessidades da sociedade. Que as diversas recessões políticas e financeiras, por que passam estas instituições, contribuem para que os gerentes públicos usem ferramentas gerenciais inovadores e necessárias, visando estratégias principalmente de parcerias entre universidades e empresas, interagindo para alavancar e desenvolver o mercado que as envolve, através da troca de experiências, de conhecimento e de tecnologias específicas

Business Cycle Accounting: what have we learned so far?

What drives recessions and expansions? Since it was introduced in 2007, there have been hundreds of business cycle accounting (BCA) exercises, a procedure aimed at identifying classes of models that hold quantitative promise to explain a certain period of economic fluctuations. First, we exemplify the procedure by studying the U.S. recessions in 1973 and 1990 using and reflect upon the critiques BCA has been subject to. Second, we look into the many equivalence theorems that the literature has produced and that allow BCA practitioners to identify the theories that are quantitatively relevant for the economic period under study. Third, we describe the methodological extensions that have been brought forth since BCA’s original inception. We end by providing some broad conclusions regarding the relative contribution of each wedge: GDP and aggregate investment are usually driven by an efficiency wedge, hours of work are closely related to the labor wedge and, in an open economy, the investment wedge helps to explain country risk spreads on international bonds. Larger changes in interest rates and currency crises are usually associated with the investment and/or the labor wedge. Finally, we contribute with a graphical user interface that allows practitioners to perform business cycle accounting exercises with minimal effort

Business Cycle Accounting: what have we learned so far?

What drives recessions and expansions? Since it was introduced in 2007, there have been hundreds of business cycle accounting (BCA) exercises, a procedure aimed at identifying classes of models that hold quantitative promise to explain a certain period of economic fluctuations. First, we exemplify the procedure by studying the U.S. recessions in 1973 and 1990 using and reflect upon the critiques BCA has been subject to. Second, we look into the many equivalence theorems that the literature has produced and that allow BCA practitioners to identify the theories that are quantitatively relevant for the economic period under study. Third, we describe the methodological extensions that have been brought forth since BCA’s original inception. We end by providing some broad conclusions regarding the relative contribution of each wedge: GDP and aggregate investment are usually driven by an efficiency wedge, hours of work are closely related to the labor wedge and, in an open economy, the investment wedge helps to explain country risk spreads on international bonds. Larger changes in interest rates and currency crises are usually associated with the investment and/or the labor wedge. Finally, we contribute with a graphical user interface that allows practitioners to perform business cycle accounting exercises with minimal effort