O presente trabalho reúne elementos para projeto de precipitadores eletrostáticos, com dados levantados de cinzas volantes provenientes da combustão de gases em caldeiras de carvão mineral. Os objetivos desta pesquisa são construir um dispositivo padronizado para medição da resistividade ôhmica de materiais, levantar dados de resistividade ôhmica das cinza volantes de carvão mineral utilizado no Brasil e, com estes dados, listar recomendações sobre cuidados no dimensionamento de precipitadores (cálculo da área de captação), quando este equipamento é posicionado após uma caldeira que queima o carvão mineral nacional. A metodologia utilizada foi baseada em norma americana ASME, em que o pó (material a ser testado) é colocado sobre eletrodos de descarga e de coleta, uma alta tensão elétrica é aplicada até atingir a tensão de ruptura elétrica e neste instante é medida a resistividade. A construção do experimento e procedimento de execução foram seguidos conforme esta norma. O material de teste foi coletado de precipitadores eletrostáticos existentes na região Sul do Brasil, onde o carvão mineral tem seu uso freqüente. Os resultados apresentaram baixos valores para resistividade da cinza volante nacional, se comparados com resultados de carvões de outros países. Sua variação em função da temperatura segue a tendência de cinza volantes de outros países, ou seja, aumento da resistividade ôhmica com o aumento da temperatura. Foram realizados também experimentos com material retirado de precipitadores eletrostáticos acoplados a caldeiras de biomassa, que forneceram valores de resistividade ainda menores do que os do carvão mineral nacional. O material de teste, composição química e processo de coleta foram totalmente caracterizados, disponibilizados e uma análise completa pôde ser realizada, fato inédito no Brasil. Esses resultados permitiram listar recomendações visando o projeto de precipitadores eletrostáticos acoplados a caldeiras que queimam carvão mineral nacional. / This report is a collection of elements to be used in the design of Electrostatic Precipitators, with experimental data of fly ashes from combustion gases of Mineral Coal Fired Boilers. The aims of this research are to construct a standard device to measure the ohmic resistivity of materials, to get data of ohmic resistivity of fly ashes from mineral coals used in Brazil and with this data, to list recommendations about the key points to size electrostatic precipitators (calculation of specific collection area), when this equipment is arranged after one boiler that burns Brazilian mineral coals. The method used was based on the ASME Standard, in which the fly ash (material to be tested) is put between the discharge and the collecting electrodes, a high electrical tension is applied until the electrical break down tension to be reached; at this moment, the resistivity is measured. The construction of this device and the experimental procedure were conducted according to this standard. The tested materials were collected from existing Electrostatic Precipitator of South of Brazil, where the mineral coal is commonly used. The results indicated low values of ohmic resistivity of the Brazilian fly ashes, if compared to results of coals from other countries. Its variation with the temperature has the same behavior of fly ashes from other countries, i.e., the ohmic resistivity increases when the temperature increases. It was also executed tests with particulate materials from electrostatic precipitator of biomass boiler whose ohmic resistivity is lower than the Brazilian mineral coal. The tested material, chemical composition, and collecting process were totally described, available and a full analysis can be executed; these data are inedita in Brazil. These results allow to list the recommendations to design Electrostatic Precipitators for Brazil Mineral Coal Fired Boilers.

Orientador: Carlos Raimundo Ferreira Grosso / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-24T21:13:36Z (GMT). No. of bitstreams: 1 TelloCelis_Fernando_D.pdf: 4202305 bytes, checksum: d181431b673bfa76df0560500eb7767b (MD5) Previous issue date: 2014 / Resumo: A encapsulação permite a formação de estruturas que apresentam propriedades como a proteção e liberação controlada do material encapsulado. As características do material encapsulado determinam a escolha do material de parede da matriz encapsulante e da técnica de encapsulação. Proteínas e polissacarídeos têm sido investigados para a formação destas matrizes. Diferentes técnicas produzem partículas com diferentes propriedades. A associação de técnicas de encapsulação permite a obtenção de matrizes com melhores propriedades tecnológicas. A gelificação iônica é uma técnica de encapsulação branda, simples e rápida onde polissacarídeos aniônicos interagem com íons divalentes como o Ca2+ para a encapsulação de diversos tipos de compostos incluindo lipídicos. Neste estudo, pectina e alginato foram utilizados para produção de partículas por gelificação iônica. Na primeira parte do estudo, partículas produzidas por gelificação iônica com alginato ou pectina foram revestidas com proteínas da clara de ovo, de soro do leite e da mistura (1:1) das referidas proteínas utilizando-se diferentes concentrações de proteínas em solução a pH 4,0. Partículas de alginato aumentaram de tamanho após revestimento proteico enquanto partículas de pectina diminuíram de tamanho. Aumento da concentração desta na solução produziu aumento na quantidade de proteína adsorvida e de matéria seca nas partículas. Para o maior nível de adsorção proteica, um óleo modelo contendo alto teor de ácidos graxos insaturados foi utilizado como material de recheio e as partículas avaliadas quanto a estabilidade oxidativa. Partículas sem recobrimento proteico foram menos protetivas e quando recobertas com proteínas, apresentaram menor formação de peróxidos quando clara de ovo foi utilizada. Na segunda parte do estudo as partículas obtidas por gelificação iônica foram recobertas com diferentes quantidades de gelatina tipo A, proteínas do soro do leite e mistura das proteínas (1:1). A complexação eletrostática foi estimada pelo potencial zeta e pela quantidade de proteína adsorvida, avaliando-se o efeito do pH e das diferentes relações estequiométricas proteína : polissacarídeo. Partículas que apresentaram maior adsorção proteica foram adicionalmente avaliadas quanto à resistência física e solubilidade proteica quando submetidas a condições gastrointestinais in vitro. O aumento da quantidade de proteína em solução produziu aumento da proteína adsorvida produzindo também aumento de tamanho da partícula quando alginato foi utilizado. Morfologicamente as partículas sem revestimento proteico foram resistentes às condições gastrointestinais in vitro. Independente da proteína utilizada partículas com alginato revestidas com proteína mantiveram integridade física após ensaio intestinal enquanto partículas com pectina e revestidas com gelatina foram destruídas após ensaio intestinal e muito danificadas quando proteínas do soro do leite e mistura gelatina : proteínas do soro do leite foram utilizadas. Quando a solubilidade proteica foi utilizada como parâmetro no ensaio gastrointestinal in vitro, partículas de pectina revestidas com gelatina, a mistura proteica e a proteína do soro do leite apresentaram solubilidades no ambiente gástrico de ~ 56, 38 e 37 % enquanto as partículas de alginato recobertas liberaram ~ 32, 12 e 11 %, respectivamente. Após passagem pelo sistema intestinal, partículas de pectina liberaram praticamente todo o conteúdo proteico adsorvido (> 96 %) enquanto partículas de alginato liberaram quantidades superiores a 82 % / Abstract: Encapsulation allows the formation of structures with properties such as protection and controlled release of the encapsulated material. The characteristics of the core material determine the choice of the wall material and encapsulation technique. Proteins and polysaccharides have been investigated for the formation of these matrices. Different techniques yield particles with different properties. The association of encapsulation techniques allows obtaining matrices with better technological properties. The ionic gelation is a gentle, simple and rapid encapsulation technique in which anionic polysaccharides interact with divalent ions such as Ca2+ for the encapsulation of various types of materials including lipid compounds. In this study, alginate and pectin have been used to produce particles of ionic gelation. In the first part of the study, gelling ionic particles produced with alginate or pectin were coated with proteins from egg white, whey protein and mixture (1:1) of these proteins using different concentrations of proteins in solution at pH 4.0. Particle size increased after coating alginate particles with protein and coated pectin particles had the size reduced. Increasing the protein concentration of the solution produced an increase in the amount of adsorbed protein and dry matter in the particles. For the highest level of protein adsorbed, a model oil containing high content of unsaturated fatty acids was used as core material and the particles evaluated with respect to oxidative stability. Particles without protein coating were less protective and when coated with proteins, showed lower peroxide formation when egg white was used. In the second part of the study the particles obtained by ionic gelation were coated with different amounts of gelatin type A, protein, whey protein and a mixture of both (1:1). The electrostatic complexation was estimated by zeta potential and the amount of adsorbed protein, assessing the effect of pH and the stoichiometry of the various proteins: polysaccharide ratios. Particles showed higher protein adsorption were further evaluated for physical resistance and protein solubility when subjected to in vitro gastrointestinal conditions. The increased amount of protein in solution produced also increases the adsorbed protein causing an increase in particle size when alginate was used. Morphologically, the protein particles without coating were resistant to gastrointestinal conditions in vitro. Independent of protein used, alginate particles coated with protein maintained physical integrity after intestinal assay, while pectin particles coated with gelatin were destroyed after intestinal assay and damaged when the whey protein or and gelatin : whey proteins mixture were used. When protein solubility was used as a parameter in the gastrointestinal in vitro assay, pectin particles coated with gelatin, whey protein and gelatin : whey proteins mixture showed solubility in the gastric environment of 56, 38 and 37% while the coated alginate particle released 32, 12 and 11 %, respectively. After passage through the intestinal tract, coated pectin particles released substantially all adsorbed protein content (> 96%). Coated alginate particles released quantities above 82% / Doutorado / Consumo e Qualidade de Alimentos / Doutor em Alimentos e Nutrição

Orientador: Flavia Maria Netto / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-25T15:30:20Z (GMT). No. of bitstreams: 1 Sadahira_MitieSonia_D.pdf: 5351794 bytes, checksum: 3b4bdc18fc4978c11662cb3791bc6fe6 (MD5) Previous issue date: 2014 / Resumo: Nos confeitos aerados (marshmallow e nougat), a espuma é produzida pela aeração de xaropes de açúcares, estabilizada por proteínas tais como proteínas da clara de ovo (PCO). A pectina, polissacarídeo aniônico, pode formar complexos eletrostáticos com proteína em pH abaixo do ponto isoelétrico da proteína. A hidroxipropilmetilcelulose (HPMC) é um polissacarídeo neutro com propriedades emulsificantes. O trabalho visou estudar as propriedades espumantes (capacidade de aeração e estabilidade da espuma) da PCO na presença destes polissacarídeos em solução aquosa e sistema modelo de açúcares. Na primeira etapa, foram avaliados os efeitos das interações PCO/polissacarídeo nas propriedades espumantes em solução aquosa. Os efeitos da concentração de biopolímeros (2,0-4,0% p/p), proporção PCO:pectina (15:1-55:1) e temperatura (70-80 °C) nas propriedades espumantes no pH 3,0 foram avaliados, utilizando delineamento composto central. Na proporção PCO:pectina 15:1, os complexos eram próximos da eletroneutralidade e com tamanho médio de 95,91+ ou - 8,19 µm, conduzindo para maior estabilidade da espuma quanto à desproporção. Na proporção 55:1, os complexos não eram eletricamente neutros e com tamanho médio de 45,92+ ou - 3,47 µm, resultando em espumas com menor drenagem de líquido e coalescência. Foram avaliados os efeitos de concentração de biopolímeros (2,0-5,0% p/p), proporção PCO:HPMC (2:1-18:1) e pH (3,0-6,0) a 75 °C utilizando delineamento composto central rotacional (DCCR) e do comportamento dos biopolímeros na solução aquosa em diferentes pH nas propriedades espumantes. No pH 3,0, os biopolímeros eram compatíveis, conduzindo a melhores propriedades espumantes enquanto nos pH 4,5 e 6,0, os biopolímeros eram incompatíveis, resultando em menor estabilidade com relação a desproporção. Na segunda etapa do trabalho, foram avaliados os efeitos das interações PCO/polissacarídeo em sistema modelo de açúcares com características de marshmallow (densidade<0,50 g/mL; atividade de água<0,75). A composição da solução de açúcares (42,5% sacarose, 42,5% xarope de glicose e 15% de açúcar invertido) foi definida utilizando delineamento experimental de mistura. Os efeitos da concentração de biopolímeros (1,40¿5,60% p/p) e proporção PCO:pectina (7:1¿63:1) nas respostas foram avaliadas utilizando um DCCR, no pH 3,0. As respostas foram viscosidade aparente da mistura açúcares/PCO/pectina antes do batimento e densidade, overrun, parâmetros reológicos da amostra aerada recém-processada e após 24 horas (módulo elástico G¿, módulo viscoso G" e 'delta'). Na proporção PCO:pectina 7:1, a mistura apresentou baixa capacidade de aeração e uma espuma com característica menos sólida e baixa estabilidade. Na proporção 49:1, a mistura apresentou maior capacidade de aeração e comportamento elástico da espuma. Os efeitos da concentração de biopolímeros (1,4-5,6% p/p) e proporção clara de ovo:HPMC (2:1-18:1) nas respostas das misturas açúcar/PCO/HPMC foram avaliados, utilizando um DCCR no pH 3,0 e as mesmas respostas avaliadas no estudo com misturas açúcar/PCO/pectina. Na concentração de biopolímeros 5,0% p/p e proporção PCO:HPMC 14:1 foram realizados experimentos em diferentes pH. No pH 3,0, foram obtidos maior capacidade de aeração e comportamento elástico. No pH 4,5, a espuma apresentou melhor estabilidade comparada a espuma no pH 3,0. No pH 6,0, a espuma apresentou propriedades espumantes ruins e comportamento viscoso. Portanto, o controle das interações proteína/polissacarídeo é um fator chave para o desenvolvimento de produtos aerados com maior estabilidade física / Abstract: In aerated confectionery (marshmallow and nougat), foam is produced by aeration of sugar syrups and stabilized by proteins such as egg white protein (EW). Pectin, an anionic polysaccharide, may form electrostatic complexes with protein at pH values bellow the isoeletric point (pI) of the protein. Hydroxypropylmethylcellulose (HPMC) is a neutral polysaccharide with emulsifying properties. The study aimed at studying the foaming properties (foaming capacity and foam stability) of EW in the presence of these polysaccharides in aqueous solution and high sugar system. Firstly, the effects of EW/polysaccharide interaction on the foaming properties in aqueous solution were evaluated. The effects of biopolymer concentration (2.0-4.0% w/w), EW:pectin ratio (15:1-55:1) and temperature (70-80 °C) were evaluated at pH 3.0, using a central composite design. At EW:pectin ratio 15:1, the complexes were close to electroneutrality and with an average size of 95.91+ or - 8.19 µm, leading to greater stability related to disproportionatin. At ratio 55:1, the complexes were not electrically neutral and with an average size of 45.92+ or - 3.47 µm, resulting in a low drainage of liquid and coalescence. The effects of biopolymer concentration (2.0-5.0% w/w), EW:HPMC ratio (2:1-18:1) and pH (3.0-6.0) at 75 °C were evaluated using central composite rotatable design (CCRD) and the behavior of biopolymer in aqueous solution on the foaming properties at different pH. At pH 3.0, EW and HPMC were compatible leading to better foaming properties whereas at pH 4.5 and 6.0, EW and HPMC were incompatible resulting in lower stability related to disproportionation. In the second part of the study, the effects of EW/polysaccharide interactions on a model system of sugar with characteristics of marshmallow (density<0.50 g/mL; water activity<0.75) were evaluated. For that, a sugar solution composition (42.5% of sucrose, 42.5% of glucose syrup and 15.0% of invert sugar) was defined by a mixture experimental design. The effects of biopolymer concentration (1.40-5.60% w/w) and EW:pectin ratio (7:1-63:1) on the reponses were evaluated using CCRD, at pH 3.0. The responses were apparent viscosity of sugar/EW/pectin mixture before whipping, overrun, foam density and, rheological parameters of fresh foam and foam aged for 24 h (elastic modulus G¿, viscous modulus G" and phase angle 'delta'). At EW:pectin ratio 7:1, the mixture showed low foaming capacity and a foam with less solid character and low stability. At ratio 49:1, the mixture presented greater foaming capacity and elastic behavior of foam. The effects of biopolymer concentration (1.4-5.6% w/w) and EW:HPMC ratio (2:1-18:1) on the responses of sugar/EW/HPMC mixtures were evaluated using CCRD at pH 3.0 and the same responses evaluated in the study of sugar/EW/pectin mixtures. At biopolymer concentration 5.0% w/w and EW:HPMC ratio 14:1, experiments were carried out at different pH. At pH 3.0, the higher foaming capacity and elastic behavior were obtained. At pH 4.5, foam showed better stability than foam at pH 3.0. At pH 6.0, foam presented the poorest foaming properties and viscous behavior. Thus, the control of protein/polysaccharide interactions is a key factor for the aerated products developing with higher stability / Doutorado / Consumo e Qualidade de Alimentos / Doutora em Alimentos e Nutrição

Orientadores: Rosiane Lopes da Cunha, Ângelo Luiz Fazani Cavallieri / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-20T01:10:51Z (GMT). No. of bitstreams: 1 Mantovani_RaphaeladeAraujo_M.pdf: 4371985 bytes, checksum: 490b60583a49fed7d2421e32dcf9160e (MD5) Previous issue date: 2012 / Resumo: As proteínas do soro do leite (WPI) e lecitina de soja são amplamente utilizadas em alimentos devido às suas excelentes propriedades emulsificantes. Este trabalho visou avaliar as propriedades emulsificantes da mistura de WPI e lecitina em diferentes condições de pH e concentração dos ingredientes. A primeira etapa consistiu no estudo das interações entre os emulsificantes em meio aquoso em diferentes razões WPI:lecitina e condições de pH. Os resultados mostraram que na razão 1:1 e em pH abaixo do pI da proteína, no qual os emulsificantes encontravam-se opostamente carregados, foi favorecida a formação de complexos eletrostáticos. Na segunda etapa, emulsões O/A contendo proteínas do soro e/ou lecitina foram avaliadas através da estabilidade à cremeação, microestrutura, distribuição do tamanho de gota, densidade de carga superficial, reologia, eletroforese em gel de poliacrilamida e digestão in vitro, verificando-se a influência do pH e da pressão de homogeneização. As emulsões estabilizadas somente por proteínas apresentaram separação de fases e comportamento não-Newtoniano somente em pH próximo ao pI. As emulsões contendo somente lecitina não separaram de fases e apresentaram comportamento Newtoniano. Os sistemas em pH abaixo do pI, contendo a mistura de emulsificantes apresentaram elevada instabilidade cinética devido à forte interação eletrostática entre os componentes. No entanto, em pH próximo ao pI da prote, a interação foi favorável e levou ao aumento da estabilidade das emulsões e a menores tamanhos de gota, resultando em fluidos pouco viscosos. O aumento da pressão de homogeneização, em emulsões com pH próximo e acima do pI favoreceu a formação de agregados de alta massa molecular, o que não foi observado em pH mais ácido. Também não foi notada a formação de agregados na presença de lecitina em nenhuma das condições de pH. Os ensaios de eletroforese deram indícios de que a interação entre os emulsificantes levou a modificações na estrutura das proteínas e revelaram maior afinidade da lecitina com a ?-lactoalbumina (?-la). Finalmente, na etapa de simulação do processo de digestão as proteínas mostraram-se mais resistentes, uma vez que a presença de lecitina promoveu a liberação do óleo da emulsão logo no início da etapa gástrica. De maneira geral, a utilização das proteínas do soro juntamente com a lecitina como emulsificante levou a resultados satisfatórios pois permitiu o desenvolvimento de sistemas estáveis à cremeação em diferentes valores de pH, inclusive em pH próximo ao pI, e consideravelmente resistentes às condições adversas do trato gastrointestinal / Abstract: Whey proteins (WPI) and soybean lecithin are widely used in food due to its excellent emulsifying properties. This study aimed to evaluate the emulsifying properties of the mixture of whey protein and lecithin at different conditions of pH and concentration of ingredients. Firstly, the interactions between emulsifiers in an aqueous medium at different ratios (WPI:lecithin) and pH conditions were studied. The results showed that at mixing ratio of 1:1 and at pH below the isoelectric point of the protein (pI) in which the emulsifiers were oppositely charged, was favored the formation of electrostatic complexes. Afterwards, O/W emulsions containing WPI and/or lecithin were prepared and the influence of pH and pressure homogenization were studied. Stability, microstructure, droplet size distribution, surface charge density, rheology, electrophoresis in polyacrylamide gel (SDS-PAGE) and digestion in vitro were evaluated. The emulsions stabilized by proteins showed phase separation and non-Newtonian behavior only in pH close to the pI. The emulsions containing only lecithin were stable and showed Newtonian behavior. Systems containing the mixture of emulsifiers at pH below the pI showed high kinetic instability due to the strong electrostatic interactions between the components. However, at pH close to the pI the interaction was favorable and led to an increase of the emulsion stability and to smaller droplet sizes, resulting in lower viscosities. When the pressure homogenization was increased, emulsions at a pH close to and above the pI favored the formation of high molecular weight protein aggregates which was not observed in emulsions at lower pH. In the presence of lecithin, protein aggregates were not formed in any of the pH conditions. The SDS-PAGE analysis showed that the interaction between emulsifiers led to modifications in the structure of proteins and indicated a higher affinity of lecithin to ?-lactalbumin (?-la). Finally, proteins were more resistant to digestion, since the presence of lecithin promoted release of oil emulsion at the beginning of gastric step. In general, the use of whey protein with lecithin as emulsifier led to satisfactory results because it allowed the development of stable emulsions to creaming at different pH values, even at pH close to the pI, and substantially resistant to the adverse conditions of the gastrointestinal tract / Mestrado / Engenharia de Alimentos / Mestre em Engenharia de Alimentos

A MEMS-based micro-electro-discharge machining technique that is enabled by the actuation of micromachined planar electrodes defined on the surfaces of the workpiece is developed that eliminates the need of numerical control machines. First, the planar electrodes actuated by hydrodynamic force is developed. The electrode structures are defined by patterning l8-µm-thick copper foil laminated on the stainless steel workpiece through an intermediate photoresist layer and released by sacrificial etching of the resist layer. The planer electrodes are constructed to be single layer structures without particular features underneath. All the patterning and sacrificial etching steps are performed using dry-film photoresists towards achieving high scalability of the machining technique to large-area applications. A DC voltage of 80-140 V is applied between the electrode and the workpiece through a resistance-capacitance circuit that controls the pulse energy and timing of spark discharges. The parasitic capacitance of the electrode structure is used to form a resistance capacitance circuit for the generation of pulsed spark discharge between the electrode and the workpiece. The suspended electrodes are actuated towards the workpiece using the downflow of dielectric machining fluid, initiating and sustaining the machining process. Micromachining of stainless steel is experimentally demonstrated with the machining voltage of 90V and continuous flow of the fluid at the velocity of 3.4-3.9 m/s, providing removal depth of 20 µm. The experimental results of the electrode actuation match well with the theoretical estimations. Second, the planar electrodes are electrostatically actuated towards workpiece for machining. In addition to the single-layer, this effort uses double-layer structures defined on the bottom surface of the electrode to create custom designed patterns on the workpiece material. The suspended electrode is electrostatically actuated towards the wafer based on the pull-in, resulting in a breakdown, or spark discharge. This instantly lowers the gap voltage, releasing the electrode, and the gap value recovers as the capacitor is charged up through the resistor. Sequential pulses are produced through the self-regulated discharging-charging cycle. Micromachining of the stainless-steel wafer is demonstrated using the electrodes with single-layer and double-layer structures. The experimental results of the dynamic built-capacitance and mechanical behavior of the electrode devices are also analyzed. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

La présence de surfaces solides peut modifier l'organisation et le comportement dynamique d'espèces chargées en solution. Dans ce cadre, nous étudions des systèmes chargés de complexité croissante au voisinage d'une surface d'argile par des méthodes numériques. Il convient de choisir une échelle de description appropriée selon les propriétés que l'on cherche à obtenir, tout en limitant le temps de calcul. Modéliser le transport d'ions dans un échantillon d'argile demande de décrire sa structure complexe mais également les interactions entre les particules mobiles considérées comme ponctuelles et les parois solides. Nous proposons un modèle mésoscopique composé d'un système à deux milieux dans lequel le déplacement des ions obtenu par dynamique brownienne est conditionné par la localisation de l'espèce diffusante, les coefficients de diffusion étant extraits de simulations atomiques de dynamique moléculaire. Pour des espèces chargées non ponctuelles comme un polyélectrolyte, le système peut être simplifié en construisant un modèle à gros grains qui permet d'avoir accès aux échelles de temps adaptées à la diffusion par dynamique de Langevin. Deux cas sont envisagés, avec une description explicite ou non des contre-ions, et les paramètres sont calibrés sur des simulations atomiques. En revanche, pour des molécules chargées complexes comme les nucléotides, une description tout atome est nécessaire pour tenir compte des interactions spécifiques qui émergent de la structure locale de la molécule. Les simulations de métadynamique permettent alors d'accéder aux grandeurs liées aux phénomènes « rares » comme l'adsorption des molécules sur la surface d'argile. / The presence of solid surfaces can modify the organization and the dynamics of charged species in solution with potential applications from the transport of polluants to formation of the firt biopolymers. We study charged systems with increasing complexity in the vicinity of a clay surface by numerical methods. The level of description should be adapted according to the relevant properties while limiting calculation times. Modeling the transport of ions in a clay sample requires to describe its complex structure but also the interactions between the mobile particles considered as punctual and the solid walls. We propose a mesoscopic model composed of a two-media system in which the displacement of the ions obtained by Brownian dynamics is conditioned by the localization of the diffusing species whith the diffusion coefficients being extracted from atomic simulations of molecular dynamics. For non-punctual species such as polyelectrolytes, the system can be simplified by constructing a coarse-grained model that allows to gain access to time scales adapted to diffusion phenomenon thanks to Langevin dynamics simulations. Two cases are considered, with an explicit or non-explicit description of the counter-ions, and the parameters are calibrated on atomic simulations. However, for complex charged molecules such as nucleotides, an atomic description is necessary to take into account the specific interactions emerging from the local structure of the molecule. Then, metadynamics simulations give quantities related to "rare" phenomena such as the adsorption of molecules on the surface of clay.

This dissertation presents a free-space, long-range, passive optical communication system that uses electrostatically modulated microelectromechanical systems (MEMS) structures coupled with a glass total internal reflection (TIR)-type corner cube retroreflector (CCR) as a non-emitting data transmitter. A CCR consists of three mirrors orthogonal to each other, so that the incident beam is reflected back to the incident beam, source. The operational concept is to have a MEMS modulator fusion with TIR CCR, such that the modulators are working periodically to disrupt the evanescent waves at the air interface of one of the three back glass faces of a TIR CCR. The MEMS chip has two primary components: (1) an array of movable light scattering silicon structures with nano roughness and (2) a glass lid with a transparent conductive indium tin oxide (ITO) film. The MEMS structures are bonded to a glass lid using flip-chip bonding. Once bonded, the MEMS structures can be modulated either toward or away from the glass lid, thus disrupting evanescent energy delivered from a probing laser beam. The MEMS structure is precisely bonded to the TIR CCR with an accuracy of 10-30 arc-seconds using a Michelson interferometry feedback system. This is a novel step by which an existing passive commercial CCR can be converted into a modulating active CCR. This CCR-MEMS unit acts as the key element of the transmitter. To illustrate the concept of a low-power, unattended, sensor-monitoring system, we developed a sensor board containing temperature, humidity, and magnetic sensors along with a microprocessor and other electronics. The sensor board and CCR board are packed together and act as the transmitter unit. We developed a benchtop system and an improved portable receiver system. The receiver system contains the laser (as source), a collimating lens (to collect retroreflected signal), an optical, narrow band pass filter, and a detector. The detector signal was amplified and filtered and sent either to the oscilloscope, a lock-in-amplifier, or a laptop to display the sensor data. Using the receiver system, a sensor-CCR-based transmitter unit, and receiver with 635 nm as source, we achieved retroreflective communication over a distance of 300 m.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16400号 / 工博第3481号 / 新制||工||1526(附属図書館) / 29031 / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 引原 隆士, 教授 田畑 修, 准教授 山田 啓文 / 学位規則第4条第1項該当

Resonante Mikrobauelemente mit elektrostatischem Antrieb finden seit einigen Jahren vermehrt Anwendung in vielen Bereichen der Technik. So beruhen beispielsweise Drehraten- oder Beschleunigungssensoren, die im Automobilbau eingesetzt werden auf diesem Prinzip. Neue Anwendungsfelder ergeben sich vor allem für Aktoren, beispielsweise für die am Fraunhofer IPMS entwickelten Mikroscannerspiegel mit Out-of-plane-comb-Antrieb. Sie dienen zur geometrischen Ablenkung von Licht und können zur Realisierung von hochintegrierten Systemen zur Ausgabe (Laser-Projektor) oder Aufnahme (Laser-Imager) von Daten genutzt werden. Zum Entwurf von Mikroaktoren gibt es eine Reihe von Arbeiten, die sich meist auf ein konkretes Antriebsprinzip beziehen oder den Entwurf im Allgemeinen behandeln. Die vorliegende Arbeit verfolgt daher das Ziel, speziell die Randbedingungen beim Entwurf resonanter Mikroaktoren mit Out-of-plane-comb-Antrieb zu identifizieren bzw. zu systematisieren sowie die gewonnenen Erkenntnisse in einem effizienten Entwurfsprozess umzusetzen. Dabei sollen möglichst auch relevante nichtlineare Effekte berücksichtigt werden, sodass sich neue Möglichkeiten zur Optimierung der Bauelemente und damit zur Erweiterung des Entwurfsraums ergeben. / Electrostatically driven microsystems are utilized in technical systems for several years. For instance, they are used in automotive applications as acceleration sensors or angular rate sensors. New fields of applications appear especially for actuators. The scanning micromirror of the Fraunhofer Institute for Photonic Microsystems is such an actuator. It is a micro-­optical-­electrical microsystem (MOEMS) which is driven resonantly by an electrostatic comb drive and can be used in scanning laser imaging systems or laser projectors. Several technical and scientific publications occupy with the design and the simulation of microactuators, which refer usually to a concrete drive principle or to the issues of design in general. The intention of this thesis is to identify and systematize particularly the boundary conditions of design regarding to resonant micro actuators with out-­of-­plane­comb drive. The findings are implemented in efficient design tools and design processes. One emphasis thereby is the investigation of nonlinear properties and effects. This includes geometrically non-­linearities of suspensions as well as non-linearities caused by fluid damping and the electrostatic comb drive. The findings are utilized in an analytical, nonlinear stability analysis of the device's equation of motion as well as in an object oriented software library for the MATLAB environment, which can be used to create nonlinear reduced order models of scanning micromirrors. With the developed techniques for design and optimization the available parameter range of scanning micromirrors can be extended. By that means, it is possible to improve the properties of existing devices as well as create new devices with outreaching performance.

Granular gas bed filters have been used in industry for a considerable period and mathematical descriptions of dust capture have allowed rigorous design of static beds. Provision for bed movement and electrostatic augmentation, which allows much thinner continuous beds to be used, requires adaptation of design methods for these phenomena. Design methods that allow for this are developed for a cross-flow bed with vertical bed movement and a number of granule and dust types. Direct current charging is applied to the bed itself and to the particles before they enter the bed. In the case of electrostatic augmentation, it is shown that simple models of spherical particles describe the mechanism adequately. The advantages of pre-charging dust particles before they enter the bed are indicated by calculation and proved experimentally. Parameters to describe the enhancement of filtration efficiency by the collected dust are obtained experimentally. It is shown that the factors controlling re-entrainment vary with particle size. For the dust particles less than 1,5 micrometers in size, re-entrainment is linked closely to the electrostatic capture mechanism which is dominant in that size range. For particles approaching 10 micrometer, re-entrainment can be neglected as the impaction efficiency, which is dominant for particles of this size and larger, approaches unity. A complex situation exists between these particle sizes as the magnitude and predominance of capture mechanisms in this region are determined by a number of operational parameters. It did not prove possible to develop predictive equations for re-entrainment efficiency using the results of this study. A number of heuristics are however developed that allow rational design by the use of the empirical parameters found, and that will be valid for the range of parameters used in this work. / Thesis (PhD(Chemical Engineering))--University of Pretoria, 2006. / Chemical Engineering / unrestricted