Investigou-se o efeito do \"caráter iônico\" de interfaces zwitteriônicas, formalmente neutras, representadas por micelas e vesículas obtidas de monômeros com cabeça hidrofílica dipolar, nas propriedades de acumulação e troca de espécies iônicas. Os sistemas estudados incluíram, micelas de 1-(N-hexadecil-N,N-dimetilamônio) propanossulfonato (HPS), Hexadecil fosforil colina (C16PN), 3-hexadecil glicerofostidil colina (lisoPC) e vesículas de fosfatidil colina (PC). O estudo da ligação e troca iônica nestas interfaces foi monitorado a partir de efeitos sobre reações prototrópicas de sondas como a 8-hidroxi-1,3,6-pirenotrisulfonato de sódio (piranina). Observou-se a ligação crescente da piranina na seguinte ordem lisoPC < C16PN < HPS e troca iônica com sais adicionados (função do ânion) na ordem inversa, isto é, lisoPC &gt; C16PN &gt; HPS. Estudos de reprotonação de 1 e 2 naftóis incluídos nestes agregados, via salto de pH induzido por laser, revelaram um perfil de concentração de prótons inverso àquele das cargas do dipolo, isto é, concentração nos polos negativos e exclusão nos positivos. Este resultados foram ainda reforçados por estudos de excitação de volume, via espalhamento de luz, com micelas de HPS em função de sal adicionado. A partir destes resultados propôs-se um modelo de capacitor esférico imerso em meio eletrolítico para estas interfaces, o qual se mostrou bastante versátil na análise e previsão de resultados experimentais. Em suma, estabeleceu-se no presente trabalho a visão de que interfaces dipolares são geradoras de assimetria iônica na circunvizinhança da interface, assimetria esta de polaridade invertida àquela do dipolo radialmente disposto à interface. A generalidade deste modelo pode ser extrapolado para outras interfaces e colaborar na compreensão de diversos processos que dependem da acumulação e troca iônica. / The effect of ionic domains of formally neutral zwitterionic interfaces, represented by micelles and vesicles obtained with dipolar headgroups amphiphiles, on the binding and exchange of ionic species were investigated. The systems studied included: aqueous micelles of 1-(N-hexadecyl-N,N-dimethylammonio) Propane Sulfonate (HPS), Hexadecyl Phosphoryl Choline (C16PN), and 1-hexadecylglycerophostidyl Choline (lisoPC) and vesicles of Phosphatidylcholine (PC). Binding and ion-exchange processes were assessed from the effect of these agreggates on prototropic reactions of probes such as 8-hydroxy-1,3,6-pyrenetrisulfonate pyranine). Binding of pyranine increased in the following order lisoPC < C16PN < HPS. The effectiveness of anion dependent salt displacement of the probe from the aggregates was opposite to that of affinities, i.e. lisoPC &gt; C16PN &gt; HPS. Laser pH jump studies with 1 and 2 naphtols incorporated in these aggregates revealed a proton concentration profile inverse to that of the charged dipole, that is, accumulation in the region vicinal to the negatively charged group and exclusion from the positive end of the dipole. This finding were substantiated by HPS micelle excluded volume data, obtained from light scattering studies as function of added salt. A model of a spherical capacitor immersed in an electrolyte media for these interfaces was proposed. This model accounts for satisfactorily the observed characteristics of these interfaces. The model establishes that dipolar interfaces generate ionic asymmetries in the neighborhood of the interface that opposes the radially extended monomer dipole. The generality of the model can be very helpful in the analysis and understanding of several processes occurring in/at zwitterionic interfaces.

The aim of this diploma thesis is to optimize a method of interfacial rheology for testing the interfacial behaviour of biofilms on the liquid-air interface and after that use the method for studying the biofilm formation under optimal and stress conditions. For studying the biofilm formation, Kombucha was used. It is a microbial culture forming a cellulose biofilm on the interface. As the stress conditions, reduction of sucrose concentration, change of pH and change of ionic strength was used. Next, the ability of regeneration of biofilm formed on the interface was studied. The biofilm formation was occured in all cases except of increasing ionic strength. As expected, the best biofilm biofilm growth was observed under optimal condition, which means a sucrose concentration 100 g/l.

[pt] Filmes finos líquidos desempenham um grande papel em diversas aplicações cotidianas e são de interesse indiscutível para pesquisadores científicos e industriais. Evidências de filmes finos são observadas na natureza em grandes escalas, como avalanches de neve nas montanhas, escoamento de lava em vulcões e deslizamentos de terra, e em pequenas escalas, como nas vias respiratórias pulmonares e na superfície dos olhos. Eles também são estão presentes em muitas aplicações industriais, variando de resistores de filme fino de alta resistência, atomização, métodos de litografia e várias técnicas de revestimento. Entender os mecanismos que contribuem para a estabilidade de filmes finos líquidos é um problema desafiador, pois o escoamento de filmes finos apresenta uma interface fluido-fluido livre para deformar. A instabilidade de um filme fino é geralmente impulsionada por forças intermoleculares de longo alcance, também conhecidas como atrações de van der Waals, e resultam na ruptura do filme. Investigações numéricas são frequentemente usadas para entender a dinâmica de ruptura de filmes líquidos finos, abordando a evolução da espessura do filme usando derivações assintóticas da teoria da lubrificação ou técnicas de rastreamento de interface. Neste trabalho, uma investigação computacional da dinâmica de ruptura de um filme fino líquido estacionário com uma interface viscosa é apresentada. O método Arbitrary Lagrangian-Eulerian (ALE) é usado para rastrear a posição da interface. O comportamento reológico da interface viscosa é modelado pela lei constitutiva de Boussinesq-Scriven, e a solução numérica é obtida através da aproximação de elementos finitos. Os resultados mostram que a estabilidade do filme líquido fino é influenciada tanto pela reologia da superfície quanto pela atração intermolecular e que o caráter viscoso da interface retarda a quebra da folha, levando a filmes mais estáveis. / [en] Thin liquid films play a big role in many real-life applications and are of indisputable interest to scientific and industrial researchers. Evidence of thin films are observed in nature in large scales such as snow avalanches in the mountains, lava flows on volcanoes and landslides, and in small scales such as the pulmonary airways and the eye surface. They are also widespread in many industrial applications, ranging from high-resistance thin film resistors, atomization, soft-lithography methods and several coating techniques such as dip, roll, slot, spin and curtain coating. Understanding the physical mechanisms contributing to the stability of thin liquid films is a challenging problem, as thin films flows present a fluid-fluid interface which is free to deform. The interface is bounded between two liquids or a liquid and a gas, typically having its own dynamic properties from which interfacial tension effects and complex interfacial rheological behavior arises. Instability is usually driven by long-range intermolecular forces, also known as van der Waals attractions, and may result in the rupture of the layer. Numerical investigation is often used to understand the breakup dynamics of thin liquid sheets by addressing the evolution of the film thickness using either asymptotic derivations of the lubrication theory or interface tracking techniques. In this work, a computational investigation of the breakup dynamics of a stationary thin liquid sheet bounded by a passive gas with a viscous interface is presented. The Arbitrary Lagrangian-Eulerian method (ALE) is used to track the interface position. The rheological behavior of the viscous interface is modeled by the Boussinesq-Scriven constitutive law, and the numerical solution is obtained through finite element approximation. The results show that thin liquid film stability is influenced both by surface rheology and disjoining effects and that the viscous character of the interface delays the sheet breakup, leading to more stable films.

Organic field-effect transistors (OFETs) have attracted tremendous attention due to their flexibility, transparency, easy processiblity and low cost of fabrication. High-performance OFETs are required for their potential applications in the organic electronic devices such as flexible display, integrated circuit, and radiofrequency identification tags. One of the major limiting factors in fabricating high-performance OFET is the large interfacial barrier between metal electrodes and OSC which results in low charge injection from the metal electrodes to OSC. In order to overcome the challenge of low charge injection, carbon nanotubes (CNTs) have been suggested as a promising electrode material for organic electronic devices. In this dissertation, we study the effect of carbon nanotube (CNT) density in CNT electrodes on the performance of organic field effect transistor (OFETs). The devices were fabricated by thermal evaporation of pentacene on the Pd/single walled CNT (SWCNT) electrodes where SWCNTs of different density (0-30/um) were aligned on Pd using dielectrophoresis (DEP) and cut via oxygen plasma etching to keep the length of nanotube short compared to the channel length. From the electronic transport measurements of 40 devices, we show that the average saturation mobility of the devices increased from 0.02 for zero SWCNT to 0.06, 0.13 and 0.19 cm2/Vs for low (1-5 /µm), medium (10-15 /µm) and high (25-30 /µm) SWCNT density in the electrodes, respectively. The increase is three, six and nine times for low, medium and high density SWCNTs in the electrode compared to the devices that did not contain any SWCNT. In addition, the current on-off ratio and on-current of the devices are increased up v to 40 times and 20 times with increasing SWCNT density in the electrodes. Our study shows that although a few nanotubes in the electrode can improve the OFET device performance, significant improvement can be achieved by maximizing SWCNT/OSC interfacial area. The improved OFET performance can be explained due to a reduced barrier height of SWCNT/pentacene interface compared to metal/pentacene interface which provides more efficient charge injection pathways with increased SWCNT/pentacene interfacial area.

<p>The structural and thermodynamic properties of a crystal-melt interface in</p> <p>elemental magnesium have been investigated using molecular dynamics (MD)</p> <p>simulations with an embedded atom method description of the interatomic potential.</p> <p>Three low index interfacial orientations, (0001), (1101) and (1120), have been studied.</p> <p>From fine-grained atomic density profiles, the structural interfacial widths show obvious anisotropy and the variation of interatomic planar spacing as a function of distance through the crystal-melt boundary is established. Mainly from the coarse-grained density profiles, the effective 10-90 width of the interface region, defined as the intrinsic width, in each orientation has been determined. In addition, the interfacial stresses are obtained from an integration of the interfacial stress profiles and the results show significant anisotropy, which is possibly related to the anisotropy of occupation fraction profiles. Finally, from a determination of the excess energy and interfacial stress of the solid-liquid interface and from previous published results for the interfacial free energy at the melting point, the Gibbs-Cahn integration is employed to derive an estimation of the temperature dependence of the interfacial free energy at non-equilibrium temperatures. All of the crystal-melt interfacial properties for magnesium are compared with simulation data from other elemental metals and alloys, as well as from other model systems such as Lennard- Jones and hard spheres.</p> / Master of Applied Science (MASc)

Chemical enhanced oil recovery (cEOR) aims to increase the oil recovery of mature oil fields, using aqueous solutions of surfactants and polymers, to mobilize trapped oil and maintain production. The interfacial tensions (IFTs) between the injected aqueous solution, the oil droplets in reservoirs, and other possible phases formed (e.g., a “middle phase” microemulsion) are important for designing and assessing a chemical formulation. Ultralow IFTs, less than 10^-2 mN·m^-1, are needed to increase the capillary number and help mobilize trapped oil droplets. Despite this fact, phase behavior tests have received more attention than IFTs for designing and evaluating surfactant formulations that result in high oil recovery efficiencies, because incorporating reliable IFTs into such evaluation process is avoided due to difficulties in obtaining reliable values. Hence, the main thrusts of this dissertation are to: (a) develop robust IFT measurement protocols for obtaining reliable IFTs regardless of the complexity of water and oil phase constituents and (b) improve the existing surfactant polymer formulation evaluation and screening processes by successfully incorporating the IFT as one of the critical parameters.<br>First, two robust tensiometry protocols using the known emerging bubble method (EBM) and the spinning bubble method (SBM) were demonstrated, for determining accurately equilibrium surface tensions (ESTs) and equilibrium IFTs (EIFTs). The protocols are used for measuring the dynamic surface tensions (DSTs), determining the steady state values, and establishing the stability of the steady state values by applying small surface area perturbations by monitoring the ST or IFT relaxation behavior. The perturbations were applied by abruptly expanding or compressing surface areas by changing the bubble sizes with an automated dispenser for the EBM, and by altering the rotation frequency of the spinning tube for the SBM. Such robust tension measurement protocols were applied for Triton X-100 aqueous solutions at a fixed concentration above its critical micelle concentration (CMC). The EST value of the model solution was 31.5 ± 0.1 mN·m^-1 with the EBM and 30.8 ± 0.2 mN·m^-1 with the SBM. These protocols provide robust criteria for establishing the EST values.<br>Second, the EIFTs of a commercial single chain anionic surfactant solution in a synthetic brine against a crude oil from an active reservoir were determined with the new protocol described earlier. The commercial surfactant used here has an oligopropoxy group between a hydrophobic chain and a sulfate head group. The synthetic brine has 9,700 ppm of total dissolved salts, which are a mixture of sodium chloride (NaCl), potassium chloride (KCl), manganese (II) chloride tetrahydrate (MnCl₂·4H₂O), magnesium (II) chloride hexahydrate (MgCl₂·6H₂O), barium chloride dihydrate (BaCl₂·2H₂O), sodium sulfate decahydrate (Na₂SO₄·10H₂O), sodium bicarbonate (NaHCO₃), and calcium chloride dihydrate (CaCl₂·2H₂O). The DSTs curves of the surfactant concentrations from 0.1 ppm to 10,000 ppm by weight had a simple adsorption/desorption equilibrium at air/water surface with surfactant diffusion from bulk aqueous phase. Such a mechanism was also observed from the tension relaxation behavior after area perturbations for the oil/water interfaces while DIFT measurements. The CMC of the commercial surfactant was determined to be 12 ppm in water and 1 ppm in the synthetic brine used. From the initial tension reduction curves from DST and DIFT measurements, the equilibrium timescales were shorter with brine than with water, because the adsorbed surfactant on the oil/water interfaces were partitioned into oil phases. For both DST and DIFT results suggest that the adsorbed surfactant layer at interfaces were typical adsorbed soluble monolayers.<br>Third, the phase and rheological behavior of a commercial anionic surfactant in water and in brine are important for large scale applications. A phase map of the surfactant at 25 °C at full range of surfactant concentration was obtained. The supramolecular structures of the various phases were characterized by dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), conductimetry, densitometry, and x-ray scattering. The identified phases evolved as the surfactant concentration was increased; they were a micellar solution phase, a hexagonal liquid crystalline phase, and a lamellar liquid crystalline phase. In addition, the characterization results provided detailed information about supramolecular structure parameters such as micellar sizes and their aggregation numbers, and liquid crystal spacings. The phase and rheological behavior trends identified here were of great importance because the trend was similar to that of single chain monoisomeric surfactant. Thus, this study provides a potential universality of phase behavior trends of surfactant-water systems despite of the multicomponent nature of surfactants.<br>Fourth, the EIFTs of the pre-equilibrated mixtures of surfactant, brine, and oil were determined and compared to the EIFTs prior to pre-equilibration, in order to systematically identify the most relevant IFT for oil recovery. The EIFT between surfactant solutions and oil without any pre-equilibration prior to tension measurements is defined as the un-pre-equilibrated EIFT (EIFT_up). The EIFT between oil and water phases after the pre-equilibration of surfactant, brine, and oil is defined as pre-equilibrated EIFT (EIFT_p). The EIFT_p’s were generally higher than EIFT_up’s. In addition, the effects of three mixing methods and the water-to-oil volume ratio (WOR) on the EIFT_p were evaluated. Out of three mixing methods, (A) mild mixing, (B) magnetic stirring, and (C) shaking vigorously by hand, method C produced mixtures which are the closest to the equilibrium state. The mixtures produced by method C had the largest decrease of the surfactant concentration during pre-equilibration due to the surfactant partitioning into oil phases. Moreover, the WOR affects the EIFT_p significantly due to the preferential partitioning of surfactant components into oil phases. More specifically, the WOR and the EIFT_p were found to be inversely correlated, because the amount of partitioned surfactant increased as the oil volume fraction increased. The EIFT_p’s were different from the EIFT_up’s at the same total surfactant concentrations in the aqueous layer evidently because of preferential partitioning of the various surfactant components.<br>Finally, the effect of surfactant losses due to adsorption into the rock surface on the pre-equilibrated EIFT (EIFT_p) were evaluated to improve surfactant formulation protocols. Here, five types of EIFTs were identified, along with robust protocols for determining them. These are: (I) the un-pre-equilibrated equilibrium IFT (EIFT_up); (II) the un-pre-equilibrated EIFTs in the presence of rock (EIFT_up,rock); (III) the pre-equilibrated EIFTs (EIFT_p) in the presence of oil; (IV) the pre-equilibrated EIFT in the presence of rock and oil (EIFT_p,rock); and (V) the effluent EIFT (EIFT_eff). The EIFT_up is the EIFT of the aqueous surfactant/brine solution against an oil drop without any pre-equilibration. The EIFT_up,rock is the EIFT between an oil drop and the surfactant solution after pre-equilibration with a rock sample to account for adsorption losses. The EIFT_p is the EIFT between the pre-equilibrated water and the oil phases from surfactant/brine/oil mixtures. The EIFT_p,rock is the EIFT between the pre-equilibrated water and the oil phases from surfactant/brine/oil/rock mixtures. The EIFT_eff is the EIFT from an effluent sample mixture of a laboratory-scale core flood test. Among the five types of EIFTs, the EIFT_p,rock was found to be the most important for the highest oil recovery performance in core flood tests, because it captures the most important surfactant partition processes, the partitioning to the oil phase and the partitioning by adsorption on the rock surface. Among three surfactant formulations tested with core flood experiments, the one with the lowest EIFT_p,rock (~0.01 mN·m^-1) had the highest oil recovery ratio (78%), and the one with the highest EIFT_p,rock (~0.2 mN·m^-1) had the lowest oil recovery ratio (55%). The other EIFTs correlated less with the oil recovery performance. Identifying surfactant formulations that have low or ultralow EIFTs, especially ultralow EIFT_p,rock’s, are critical for screening formulations appropriate for core flood tests and target field applications, and for predicting oil recovery performance. These works are a significant contribution for improving (a) the surfactant formulation evaluation protocols, and (b) the utilization of reliable IFTs and phase behavior test protocols for oil recovery and many other surfactant and colloid sciences applications.<br>

In the event of hypothetical accident scenarios in PWR, emergency strategies have to be mapped out, in order to guarantee the reliable removal of decay heat from the reactor core, also in case of component breakdown. One essential passive heat removal mechanism is the reflux condensation cooling mode. This mode can appear for instance during a small break loss-of-coolant-accident (LOCA) or because of loss of residual heat removal (RHR) system during mid loop operation at plant outage after the reactor shutdown. In the scenario of a loss-of-coolant-accident (LOCA), which is caused by the leakage at any location in the primary circuit, it is considered that the reactor will be depressurized and vaporization will take place, thereby creating steam in the PWR primary side. Should this lead to ¿reflux condensation¿, which may be a favorable event progression, the generated steam will flow to the steam generator through the hot leg. This steam will condense in the steam generator and the condensate will flow back through the hot leg to the reactor, resulting in counter-current steam/water flow. In some scenarios, the success of core cooling depends on the behaviour of this counter-current flow. Over several decades, a number of experimental and theoretical studies of counter-current gas¿liquid two-phase flow have been carried out to understand the fundamental aspect of the flooding mechanism and to prove practical knowledge for the safety design of nuclear reactors. Starting from the pioneering paper of Wallis (1961), extensive CCFL data have been accumulated from experimental studies dealing with a diverse array of conditions A one-dimensional two field model was developed in order to predict the counter-current steam and liquid flow that results under certain conditions in the cold leg of a PWR when a SBLOCA (small break loss of coolant accident) in the hot leg is produced. The counter-current model that has been developed can predict the pressure, temperature, velocity profiles for both phases, also by taking into account the HPI injection system in the cold leg under a counter-current flow scenario in the cold leg. This computer code predicts this scenario by solving the mass, momentum and energy conservation equations for the liquid and for the steam separately, and linking them by using the interfacial and at the steam wall condensation and heat transfer, and the interfacial friction as the closure relations. The convective terms which appear in the discretization of the mass and energy conservation equations, were evaluated using the ULTIMATE-SOU (second order upwinding) method. For the momentum equation convective terms the ULTIMATE-QUICKEST method was used. The steam-water counter-current developed code has been validated using some experimental data extracted from some previously published articles about the direct condensation phenomenon for stratified two-phase flow and experimental data from the LAOKOON experimental facility at the Technical University of Munich. / Romero Hamers, A. (2014). STUDY OF THE THERMAL STRATIFICATION IN PWR REACTORS AND THE PTS (PRESSURIZED THERMAL SHOCK) PHENOMENON [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36536

O escoamento estratificado óleo-água é bastante comum na indústria do petróleo, especialmente em poços direcionas offshore, oleodutos e gasodutos. Entretanto, existem poucos trabalhos na literatura sobre a natureza da estrutura ondulatória observada no escoamento em dutos ascendentes ou descendentes a partir da horizontal. O objetivo deste trabalho foi estudar as propriedades geométricas e cinemáticas da onda interfacial, i.e, forma média, comprimento, amplitude e celeridade, e assim contribuir para a compreensão do papel da onda interfacial na dinâmica do escoamento estratificado. Um software baseado em plataforma Labview® possibilitou a automação para obtenção dos dados das ondas interfaciais extraídas de imagens de vídeos de alta resolução. Além das propriedades das ondas, também se coletaram valores de fração volumétrica in situ e de gradiente de pressão bifásico para cinco ângulos de inclinação (-20°, -10°, 0°, 10° e 20°) em diferentes pares de vazões de óleo e água. Desenvolveu-se um modelo fenomenológico considerando os termos ondulatórios do escoamento para o cálculo da fração volumétrica in situ e do gradiente de pressão bifásico, sendo comparado com modelos disponíveis na literatura e dados experimentais. A concordância do modelo proposto com os dados coletados neste trabalho se mostrou muito boa, o que sugere um avanço em comparação ao existente na literatura. O estudo da equação da onda de perturbação interfacial para o escoamento estratificado óleo-água indicou que a natureza da onda observada é cinemática e não dinâmica; e baseado na equação da celeridade da onda cinemática pode-se confrontar a celeridade experimental com a teórica, revelando boa concordância. / The oil-water stratified flow is quite common in the oil industry, especially in offshore directional wells and pipelines. However, there are few studies on the physics of the wavy structure observed in upward and downward stratified flow. The goal of this work was to study the geometric and kinematic properties of interfacial waves, i.e., the average shape, wavelength, amplitude and celerity. A homemade Labview®-based software enabled the automatic acquisition of data extracted from frames obtained via high resolution video recording. In situ volume fraction and two-phase pressure gradient data for five inclination angles (-20°, -10°, 0°, 10° and 20°) at several pairs of oil and water flow rates were also collected. A phenomenological model that takes into account the wavy structure is proposed to calculate volume fractions and two-phase pressure gradient and it was compared with available models from the literature and experimental data. The good agreement of the proposed model with the data collected in this study is promising and suggests that it may provide better predictions in comparison with models from the literature. The study of the interfacial perturbation wave equation for stratified flow indicates that the observed waves nature is kinematic and not dynamic; and based on the kinematic wave velocity equation we could compare the experimental celerity with the theoretical one, with good agreement.

Neste trabalho, sondas solvatocrômicas foram empregadas no estudo da solvatação em solventes puros e misturas aquosas de solventes polares práticos e apráticos. A partir da polaridade de misturas aquosas de solventes orgânicos, determinou-se a concentração de água interfacial de micelas catiônicas. Finalmente, avaliou-se o efeito da polaridade e força iônica interfaciais de micelas catiônicas sobre a velocidade da reação entre p-nitrofenildifenilfosfato e o íon fluoreto. No estudo de misturas aquosas de solventes orgânicos, um novo modelo de solvatação preferencial foi elaborado, segundo o qual três espécies presentes em solução competem pela camada de solvatação da sonda: água, solvente orgânico e o \"complexo\" formado por uma molécula de água e outra de solvente orgânico (Solv-Água). Através deste modelo, analisou-se o efeito da temperatura e das propriedades das sondas e dos solventes orgânicos sobre o fenômeno da solvatação. Em soluções aquosas de micelas catiônicas, observou-se uma desidratação da interface em função do aumento do grupo hidrofílico do tensotativo e da mudança de geometria micelar de esférica para cilíndrica. Verificou-se que a velocidade da reação entre pnitrofenildifenilfosfato e fluoreto é pouco afetada pela interface micelar e pode ser reproduzida, na ausência de micelas, em soluções com mesma concentração de água e força iônica que as micelas. / Solvatochromic probes have been employed to study the polarity of pure solvents and binary mixtures of water with protic and aprotic polar solvents. From polarity data of aqueous organic mixtures, the concentration of interfacial water of cationic micelles has been determined. In aqueous solutions of cationic micelles, the dehydration of interfacial region has been observed as a result of increasing the volume of the surfactant head group and changing micellar geometry from spherical to cylindrical. Finally, the effect of interfacial polarity and ionic force on the rate of the reaction between 4-nitrophenyldiphenylphosphate and fluoride ion has been evaluated. In studying aqueous organic mixtures, a new preferential solvation model has been developed, that considers the competition between three species in solution for the probe micro-solvation shell: water, organic solvent and a 1:1 \"complex\" formed by water and organic solvent (Solv-Água). Based on this new model, the effect of temperature, as well as probe and organic solvent properties on solvation has been analyzed. It has been observed that the rate of the reaction between p-nitrophenyldiphenylphosphate and fluoride ion shows little dependence on the properties of interfacial region of cationic micelles and can be reproduced, in the absence of micelles, in solutions containing the same water concentration and ionic force as the micellar pseudo-phase.

Uma nova metodologia para a medida não intrusiva da fração volumétrica e da área interfacial é proposta neste trabalho, com base em redes neurais para processar respostas obtidas de sinais acústicos. A distribuição geométrica das fases dentro do escoamento é mapeada pela velocidade local de propagação acústica, considerada na equação diferencial que governa o problema. Esta equação é resolvida numericamente pelo método de diferenças finitas com as condições de contorno reproduzindo a estratégia de pulso/eco. Um número significativo de distribuições das velocidades de propagação foi considerado na solução da equação diferencial para construir uma base de dados, da qual os parâmetros da rede podem ser ajustados. Especificamente, o modelo neural é construído para mapear características extraídas dos sinais obtidos de quatro sensores acústicos, localizados no contorno externo do domínio de sensoriamento, estimando a fração volumétrica e a área interfacial correspondentes. Estas características correspondem às amplitudes e aos tempos de chegada dos três maiores picos da onda acústica. Os resultados numéricos mostram que o modelo neural pode ser treinado em um tempo computacional razoável e é capaz de estimar os valores da fração volumétrica e da área interfacial dos exemplos do conjunto de teste. / A new methodology for measuring the volumetric fraction and interfacial area in two-phase flows is proposed in this work, based on neural network for processing the responses obtained from an acoustic interrogation signal. The geometrical distribution of the phases within the flow is mapped by the local acoustic propagation velocity which is considered in the governing differential equation. This equation is solved numerically by the finite difference method with boundary conditions reproducing the pulse/echo strategy. A significant number of propagation velocities distributions were considered in the solution of the differential equation in order to construct a database from which the neural model parameters could be adjusted. Specifically, the neural model is constructed to map the features extracted from the signals delivered by four acoustic sensors, placed on the external boundary of the sensing domain, into the corresponding volumetric fraction and interfacial area. These features correspond to the amplitudes and the times of arrival on the three first peaks of the acoustic wave. Numerical results showed that the neural model can be trained in a reasonable computational time and it is capable of estimating the values of the volumetric fraction and the interfacial area of examples of the set of test.