Resumo: A simbiose entre as formigas cortadeiras e seu fungo originou-se a aproximadamente 50 milhões de anos. A diversidade biótica dos formigueiros, no entanto, não se restringe apenas à formiga e ao fungo simbionte. Recentemente foi descoberto um terceiro mutualista, uma bactéria filamentosa do grupo dos actinomicetos, cuja principal função seria a inibição do crescimento de parasitas do jardim de fungos, especialmente o fungo conhecido como Escovopsis sp, através da produção de antibióticos. O presente trabalho teve como objetivos verificar o potencial das linhagens de Streptomyces, que foram isoladas de Attini, como produtoras de substâncias antimicrobianas frente aos fungos Escovopsis weberi e outros microrganismos e também a caracterização dessas linhagens através de técnicas de biologia molecular. Foram selecionadas nove linhagens de Streptomyces, que foram cultivadas em meio SCN líquido, para a obtenção dos filtrados. Para os ensaios de antibiose envolvendo os fungos Escovopsis weberi, foram testadas diferentes concentrações de filtrados adicionadas ao meio A sólido e foi verificada a porcentagem de germinação dos conídios em cada concentração. Para a determinar a atividade dos filtrados frente as bactérias e leveduras, os testes foram realizados pelo método de difusão em agar. Os resultados mostraram que, mesmo variando os filtrados obtidos das linhagens de Streptomyces, a inibição da germinação dos conídios foram muito semelhantes, e todas as linhagens do fungo Escovopsis weberi apresentaram uma inibição homogênea frente a mesma concentração de filtrado. Com relação as bactérias e leveduras, os resultados mostraram que houve diferenças na intensidade da resposta. Algumas linhagens inibiram o crescimento de todas as bactérias e leveduras testadas, outras não inibiram apenas algumas culturas e teve linhagens que não inibiram nenhuma das...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The symbiotic relationship between leaf-cutting ants (Tribe Attini) and their mutualistic fungus probably arose fifty million years ago. However, these two organisms are at least, part of the biological diversity found in nests of these insects. Recently, it was discovered a third mutualist, an antibioticproducing actinomycete, which is used by the ants to control the development of garden parasites, specially within the microfungus genus Escovopsis sp. In order to determine which isolates of this actinomycete could affect the growth of Escovopsis weberi and other microorganisms; nine strains of Streptomyces sp. were grown in liquid SCN and the resultant media (extract) were filtered and used in the experiments. Also, all actinomycete strains were characterized by molecular sequencing of the 16 rDNA region. In the assays involving E. weberi, different extract amounts were added into solid medium (Meio A) and the conidial germination rate were determined after incubation. Disk-difusion method were used to verify the antimicrobial activity of these extracts over a large range of bacteria and yeasts. In spite of the concentration used in E. weberi assays, inhibiton of spore germination was achieved and this response was similiar among E. weberi isolates. On the other hand, bacteria and yeasts demostrated a high degree variability in this response. Some Streptomyces sp. strains inhibited all bacteria and yeasts tested, but other just inhibited a few of them. The molecular sequencing of the 16S rDNA region have shown that all actinomycete strains used in this work were grouped with other Streptomyces species found in GenBank. In spite of phylogenetic analyses have grouped Attini isolates in different clades, the activity of the antimicrobial compounds produced by these bacteria had a high degree of homogenicity over E. weberi... (Complete abstract, click electronic address below) / Orientador: Maurício Bacci Junior / Coorientador: Fernando Carlos Pagnocca / Banca: Lara Durães Sette / Banca: Dejanira de Franceschi de Angelis / Mestre

O objetivo deste trabalho consiste na análise teórica e experimental do desempenho térmico de dois arranjos de micro tubos de calor. Os arranjos diferem entre si pelo material base de fabricação, que são Acrilonitrila Butadieno Estireno (ABS) e latão, pelo número de canais e pelas dimensões. O fluido de trabalho utilizado foi R134a. A literatura indica micro tubos de calor como soluções proeminentes e de destaque para resfriamento de micro sistemas. Estes dispositivos podem ser adaptados a diferentes condições térmicas através da mudança de fluidos de trabalho, geometrias e materiais base do trocador. O estudo teórico foi baseado no modelo de circuitos térmicos proposto no presente trabalho, que visa calcular indicadores de desempenho térmico, sendo condutividade térmica efetiva e resistência térmica equivalente dos micro tubos de calor a partir das temperaturas obtidas experimentalmente. O estudo experimental foi baseado em obter distribuições de temperaturas dos dispositivos propostos sob diferentes condições de trabalho, variando-se a fração de enchimento de fluido de trabalho, inclinação e temperatura do condensador. Os resultados obtidos para o arranjo de micro tubos de calor em latão demonstrou uma razão de aumento de até 1482% na capacidade de transporte de calor, enquanto que o arranjo de micro tubos de calor em ABS apresentou uma razão de aumento de 247%. Os melhores desempenhos de ambos os casos foram observados para ângulos positivos com baixas frações de enchimento. / The purpose of this work is the theoretical and experimental study on the thermal performance of two micro heat pipes arrays. The differences between the arrays are the base substrate, which are Acrylonitrile Butadiene Styrene (ABS) and brass, the number of channels and their dimensions. The working fluid used was R134a. Previous works indicate micro heat pipes as prominent solutions for the cooling of micro systems. These devices can be adapted to different thermal conditions by changing the working fluids, geometries and base materials of the heat exchanger. The theoretical study was based on the thermal circuits model presented in this work, that aims on computing thermal performance indicators, such as the effective thermal conductivities and the equivalent thermal resistances of the micro heat pipes from the temperatures obtained experimentally. The experimental study was based on obtaining temperature distributions of the micro heat pipes under different working conditions, by varying the working fluid filling ratio, tilt angle and the temperature of the cooling water at the condenser. The results obtained for the brass micro heat pipe array showed a performance ratio increase up to 1482% in heat transfer capacity, while the ABS micro heat pipe array showed a performance ratio increase of 247%. The best performance for both cases were observed for positive tilt angles with low working fluid filling ratios.

Dans le cadre du projet ANR AGATCO (Advance GAz Turbine for COgeneration) qui a débuté fin 2012, la conception d’un micro-cogénérateur aux granulés de bois permettant de produire 1,5 kW électrique et 10 kW thermique a été entrepris et est présentée dans ce manuscrit. Basé sur la technologie d’une turbine à air chaud à combustion externe, ce micro-cogénérateur utilise la combustion des granulés couplés à un échangeur de chaleur et une micro-turbine. La technologie demande la conception d’un nouveau foyer (brûleur et chambre de combustion) adapté pour la production de fumées à haute température (1200°C). Le défi est grand car le débit de fumées souhaité est important (27g/s) et la puissance de combustible est faible (15kW). Deux solutions sont proposées pour répondre à la problématique, la première utilise de l’air frais à température ambiante et la deuxième utilise le recyclage des fumées chaudes. La haute température des fumées permet d’obtenir une température d’entrée turbine de 1100°C après le transfert de chaleur dans l’échangeur. La caractérisation expérimentale et par simulation numérique de l’échangeur permet de vérifier ses performances. La micro-turbine utilise une technologie nouvelle de canaux hélicoïdaux à la place d’aubes qui lui permettent d’avoir des dimensions faibles pour les performances souhaitées. Les travaux effectués ont permis de mettre en valeur plusieurs résultats : la réalisation de la combustion haute température dans des conditions fortement défavorables, les performances très intéressantes de l’échangeur de chaleur tous en proposant des améliorations pour optimiser les échanges et les améliorations à apporter à la turbine / As part of the AGATCO ANR project (Turbine Advance GAz for cogeneration), which began at the end of 2012, the design of a micro-cogeneration generating 1.5 kW of electricity and 10 kW of heat was started and presented in this manuscript. Based on the technology of an externally fired gas turbine, this micro-CHP uses the combustion of pellets coupled to a heat exchanger and a micro-turbine. This technology requires the design of a new fireplace (burner and combustion chamber) suitable to produce fumes at high temperatures (1200°C). The challenge is significant because the desired smoke flow is important (27 g/s) and the fuel power is low (15 kW). Two solutions are proposed to solve the problem, the first uses fresh air at ambient temperature and the second uses recycled hot fumes. The high temperature of the fumes makes it possible to obtain a turbine inlet temperature of 1100°C after the transfer of heat into the exchanger. Experimental and numerical simulation characterization of the exchanger makes it possible to verify its performances. The micro-turbine uses a new technology using channel instead of blades allowing it to have small dimensions for the desired performance. The work carried out made it possible to highlight several results: the realization of the high temperature combustion in very unfavorable conditions, the very interesting performances of the heat exchanger while proposing improvements to optimize the exchanges and the improvements to be brought to the turbine

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores (Major Automação). Faculdade de Engenharia. Universidade do Porto. 2009

Estágio realizado na Self Energy e orientado pelo Eng.º Pedro Manuel Pereira Fonseca Santos / Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores (Major Energia). Faculdade de Engenharia. Universidade do Porto. 2010

This thesis constitutes the documentation for a Doctoral research program undertaken at the Industrial Research Institute of Swinburne University of Technology (IRIS) between 2001 and 2005. The focus of the research was an investigation of the open- and closed-loop response of piezoelectric micro-pumps for micro-fluidic applications, particularly for chemical and biomedical environments. Specifically, in order to successfully integrate micro-devices into functional systems, it was important to address issues of real-time performance monitoring and control. The research addresses some of these problems in the context of a piezoelectric-driven micro-pump, equipped with interferometric displacement feedback, which was used to measure the dynamic displacement of the micro-pump actuator surface. During the course of the research, both a discrete component and a fully integrated (laboratory-on-a-board) test system were developed for open-loop characterization of the micro-pump. The laboratory-on-a-board system was also used for closed-loop control application. Measurements showed significant differences in actuator velocity, displacement and settling time between different pumping media. In addition, transient underdamped vibration of the actuator surface was observed during the rapid excursion and recursion phases of the pump movement while pumping air. These non-contact measurements could be used to determine the open-loop characteristics of a micropump and provide information for design improvement or failure detection/analysis. The technique could also be used to provide continuous measurement for adaptive compensation, so that the pump performance criteria are always satisfied. To this end, an automated interference fringe counting algorithm was developed, so that the steadystate parameters could be mapped into the closed-loop control elements in real time. The performance of this algorithm is discussed herein, together with the implications for optimal control of the micro-pump, and eventual integration of the interferometer and micro-pump systems. The research indicated that there were potential benefits in closed-loop control of micro-pumps, particularly where failure detection was required and for pumping of non-homogeneous media. The thesis also documents the relative performance differences between open and closed-loop control in homogenous media.

Although existing continuum models for the elasto-viscoplastic response of amorphous polymeric materials phenomenologically capture the large deformation response of these materials in a reasonably acceptable manner, they do not adequately account for the creep response of these materials at stress levels below those causing “macro-yield”, as well as the Bauschinger-type reverse yielding phenomena at strain levels less than ≈ 30% associated with the macro-yield transient. Anand [1] has recently generalized the model of Anand and Gurtin [2] to begin to capture these important aspects of the mechanical response of such materials. In this work, we summarize Anand’s constitutive model and apply it to the amorphous polymeric solid poly(methyl methacrylate) (PMMA), at ambient temperature and compressive stress states under which this material does not exhibit crazing. We describe our compression-tension and creep experiments on this material from which the material parameters in the model were determined. We have implemented the constitutive model in the finite-element computer program ABAQUS/Explicit [3], and using this finite-element program, we show numerical results for some representative problems in micro-indentation of PMMA, and compare them against corresponding results from physical experiments. The overall predictions of the details of the load, P, versus depth of indentaion, h, curves are very encouraging. / Singapore-MIT Alliance (SMA)

Holes with different sizes from microscale to nanoscale were directly fabricated by focused ion beam (FIB) milling in this paper. Maximum aspect ratio of the fabricated holes can be 5:1 for the hole with large size with pure FIB milling, 10:1 for gas assistant etching, and 1:1 for the hole with size below 100 nm. A phenomenon of volume swell at the boundary of the hole was observed. The reason maybe due to the dose dependence of the effective sputter yield in low intensity Gaussian beam tail regions and redeposition. Different materials were used to investigate variation of the aspect ratio. The results show that for some special material, such as Ni-Be, the corresponding aspect ratio can reach 13.8:1 with Cl₂ assistant etching, but only 0.09:1 for Si(100) with single scan of the FIB. / Singapore-MIT Alliance (SMA)

Thesis (M.S.M.E.)--University of Delaware, 2006. / Principal faculty advisor: Sunil K. Agrawal, Dept. of Mechanical Engineering. Includes bibliographical references.

Las instituciones microfinancieras en Bolivia están constituidas por dos grupos: bancos especializados en micro crédito, los FFP's, ONG's financieras y las Cooperativas de Ahorro y Crédito. Es importante determinar si: "El crecimiento de la Cobertura de las Instituciones Microfinancieras está determinada por las Tecnologías de Crédito de las instituciones microfinancieras y el contexto económico del país". En el presente trabajo se analiza la comparación entre los aspectos más relevantes del Sistema Financiero Tradicional de Bolivia y las Microfinanzas, tomándose cuatro elementos importantes relacionados al crédito: la accesibilidad, las tasas de interés activas, la evolución y destino de cartera. A través de una investigación inductivo y deductivo; con tipo de estudio descriptivo – explicativo; y con fuentes de información primaria como las ONG’s financieras, FADES, ANED, SARTAWI, DIACONIA, etc. Del cual se concluye que: las tecnologías de crédito para ser determinante en el crecimiento de las instituciones microfinancieras, deben tomar en cuenta el contexto y entorno que influye en la población; las diferentes tecnologías generan ventajas comparativas en nichos particulares de mercado por esta razón la adopción de la tecnología apropiada para una clientela es critica; la cartera de créditos con tecnología Individual, es la que presenta mayor impacto para la ampliación de cobertura de las instituciones microfinancieras ; la evolución de la cartera asociativa es la segunda variable más importante para el crecimiento de la cobertura de las instituciones microfinancieras; y que la cobertura del sistema microfinanciero expresado como la red de agencias y sucursales de atención al público se caracteriza por un crecimiento sostenido de la capacidad instalada de atención a los clientes .