Tesi sul tema "Transport Phenomena Engineering Thermodynamics"

Past nuclear weapon production activities have left a significant legacy of uranium (U) contamination in the vadose zone (VZ) of the Department of Energy (DOE) Hanford Site. This U is a source of groundwater (GW) contamination. There is a concern that elevated U concentration would slowly infiltrate through the VZ, reach the GW water table, and then end up in nearby rivers and lakes. Remediation of U-contaminated low moisture content soil is a challenging task considering the VZ depth, where contamination is found between 70 and 100 m below the ground surface, and the formation of highly soluble and stable CaUO2CO3 complexes is influenced by Hanford’s soil rich in carbonate. Injection of reactive gasses (e.g., NH3) is a promising technology to decrease U migration in through the VZ. The NH3 injection creates alkaline conditions that would alter the pore water chemistry (e.g., dissolving some aluminosilicates). Over time as the pH neutralizes, U(VI) could precipitate as uranyl mineral (e.g., Na-boltwoodite). Also, the dissolved U(VI) could be incorporated into the structure of some mineral phases or be coated by non-U minerals. These chemical reactions could control the U(VI) mobility to the GW. However, there is a lack of knowledge on how the VZ pore water constituents (e.g., Si, Al3+, HCO3-, and Ca2+) would affect U(VI) removal/precipitation in alkaline conditions. This study quantified the role of the major pore water constituents on the U(VI) removal and evaluated the uranyl minerals that could precipitate from a variety of SPW solutions. Results showed that the percentage of U(VI) removal was controlled by Si/Al ratios and Ca2+ concentration regardless of HCO3- concentration tested. XRD revealed the presence of uranyl minerals by analyzing precipitates formed from SPW solutions, but none of them were identified as uranyl silicates as expected from speciation modeling. The SEM images displayed dense amorphous regions high in silica content, where EDS elemental analysis unveiled higher U atomic percentage in some samples. U(VI) silicate and carbonate minerals were predicted by the speciation modeling.

High-temperature, high-pressure (HTHP) conditions are exemplified in ultra-deep petroleum reservoirs and can be exhibited within diesel engines. Accurate pure component hydrocarbon data is essential in understanding the overall behavior of petroleum and diesel fuel at these conditions. The present study focuses on the HTHP properties of toluene since this hydrocarbon is frequently used to increase the octane rating of gasoline and toluene occurs naturally in crude oil. In this thesis experimental densities and viscosity are presented to 535 K and 300 MPa extending the database of toluene viscosity data to higher temperature than previous studies. The data is correlated to a Tait-like equation and a Padѐ approximate in conjunction with a single mapping of the isotherms. Free-volume theory and a superposition of the viscosity in relation to the Leonnard-Jones repulsive force are both used to model the toluene viscosity data. It was found that the data are in good agreement with the available literature data.

Avec les progrès de la technologie, il est désormais devenu possible de manipuler des faibles quantités d’objets nanométriques, voire des objets uniques. Observer une réaction chimique de quelques centaines de molécules sur des catalyseurs, étudier le travail exercé lors du déploiement d’un brin d’ADN unique ou mesurer la chaleur émise par un unique électron dans un circuit électrique constituent aujourd’hui des actes expérimentaux courants. Cependant, à cette échelle, le caractère aléatoire des processus physiques étudiés se fait plus fortement ressentir. Développer une théorie thermodynamique à ces échelles nécessite d'y inclure de manière exhaustive ces fluctuations.Ces préoccupations et les résultats expérimentaux et théoriques associés ont mené à l’émergence de ce que l’on appelle aujourd’hui la thermodynamique stochastique. Cette thèse se propose de développer une approche originale à la thermodynamique stochastique, basée sur une extension de l'hypothèse d'équilibre local aux variables fluctuantes d'un système. Cette théorie offre de nouvelles définitions des grandeurs thermodynamiques stochastiques, dont l'évolution est donnée par des équations différentielles stochastiques (EDS).Nous avons choisi d'étudier cette théorie à travers des modèles simplifiés de phénomènes physiques variés; transport (diffusif) de chaleur ou de masse, transport couplé (comme la thermodiffusion), ainsi que des modèles de réactions chimiques linéaires et non-linéaires. A travers ces exemples, nous avons proposé des versions stochastiques de plusieurs grandeurs thermodynamiques d'intérêt. Une large part de cette thèse est dévolue à l'entropie et aux différents termes apparaissant dans son bilan (flux d'entropie, production d'entropie ou dissipation). D'autres exemples incluent l'énergie libre d'Helmholtz, la production d'entropie d'excès, ou encore les efficacités thermodynamiques dans le transport couplé.A l'aide de cette théorie, nous avons étudié les propriétés statistiques de ces différentes grandeurs, et plus particulièrement l'effet des contraintes thermodynamiques ainsi que les propriétés cinétiques du modèle sur celles-là. Dans un premier temps, nous montrons comment l'état thermodynamique d'un système (à l' équilibre ou hors d'équilibre) contraint la forme de la distribution de la production d'entropie. Au-delà de la production d'entropie, cette contrainte apparaît également pour d'autres quantités, comme l'énergie libre d'Helmholtz ou la production d'entropie d'excès. Nous montrons ensuite comment des paramètres de contrôle extérieurs peuvent induire des bimodalités dans les distributions d'efficacités stochastiques.Les non-linéarités de la cinétique peuvent également se répercuter sur la thermodynamique stochastique. En utilisant un modèle non-linéaire de réaction chimique, le modèle de Schlögl, nous avons calculé la dissipation moyenne, non-nulle, engendrée par les fluctuations du système. Les non-linéarités offrent aussi la possibilité de produire des bifurcations dans le système. Les différentes propriétés statistiques (moments et distributions) de la production d'entropie ont été étudiées à différents points avant, pendant et après la bifurcation dans le modèle de Schlögl.Ces nombreuses propriétés ont été étudiées via des développements analytiques supportés par des simulations numériques des EDS du système. Nous avons ainsi pu montrer la fine connexion existant entre les équations cinétiques du système, les contraintes thermodynamiques et les propriétés statistiques des fluctuations de différentes grandeurs thermodynamiques stochastiques.
Over the last decades, nanotechnology has experienced great steps forwards, opening new ways to manipulate micro- and nanosystems. These advances motivated the development of a thermodynamic theory for such systems, taking fully into account the unavoidable fluctuations appearing at that scale. This ultimately leads to an ensemble of experimental and theoretical results forming the emergent field of stochastic thermodynamics. In this thesis, we propose an original theoretical approach to stochastic thermodynamics, based on the extension of the local equilibrium hypothesis (LEH) to fluctuating variables in small systems. The approach provides new definitions of stochastic thermodynamic quantities, whose evolution is given by stochastic differential equations (SDEs).We applied this new formalism to a diverse range of systems: heat or mass diffusive transport, coupled transport phenomena (thermodiffusion), and linear or non-linear chemical systems. In each model, we used our theory to define key stochastic thermodynamic quantities. A great emphasis has been put on entropy and the different contributions to its evolution (entropy flux and entropy production) throughout this thesis. Other examples include also the stochastic Helmholtz energy, stochastic excess entropy production and stochastic efficiencies in coupled transport. We investigated how the statistical properties of these quantities are affected by external thermodynamic constraints and by the kinetics of the system. We first studied how the thermodynamic state of the system (equilibrium \textit{vs.} non-equilibrium) strongly impacts the distribution of entropy production. We then extended those findings to other related quantities, such as the Helmholtz free energy and excess entropy production. We also analysed how some external control parameters could lead to bimodality in stochastic efficiencies distributions.In addition, non-linearities affect stochastic thermodynamics quantities in different ways. Using the example of the Schlögl chemical model, we computed the average dissipation of the fluctuations in a non-linear system. Such systems can also undergo a bifurcation, and we studied how the moments and the distribution of entropy production change while crossing the critical point.All these properties were investigated with theoretical analyses and supported by numerical simulations of the SDEs describing the system. It allows us to show that properties of the evolution equations and external constraints could strongly reflect in the statistical properties of stochastic thermodynamic quantities.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

In this thesis the factors surrounding the permeation of alkali and alkaline earth metal salts through hydrogel membranes are investigated. Although of relevance to aqueous separations in general, it was with their potential application in sensors that this work was particularly concerned. In order to study the effect that the nature of the solute has on the transport process, a single polymer matrix, poly (2-hydroxyethyl methacrylate), was initially studied. The influence of cation variation in the presence of a fixed anion was looked at, followed by the effect of the anion in the presence of a fixed cation. The anion was found to possess the dominant influence and tended to subsume any influence by the cation. This is explained in terms of the structure-making and structure-breaking characteristics of the ions in their solute-water interactions. Analogies in the transport behaviour of the salts are made with the Hofmeister series. The effect of the chemical composition of the polymer backbone on the water structuring in the hydrogel and, consequently, transport through the membrane, was investigated by preparing a series of poly (2-hydroxyethyl methacrylate) copolymer membranes and determining the permeability coefficient of salts with a fixed anion. The results were discussed in terms of the `free-volume' model of permeation and the water structuring of the polymer backbone. The ability of ionophores to selectively modulate the permeation of salts through hydrogel membranes was also examined. The results indicated that a dualsorption model was in operation. Finally, hydrogels were used as membrane overlays on coated wire ion-selective electrodes that employed conventional plasticised-PVC-valinomycin based sensing membranes. The hydrogel overlays were found to affect the access of the analyte but not the underlying electrochemistry.

A numerical study was carried out to predict three dimensional turbulent flow heat and mass transfer in RH-ladles. To model the turbulence in the system, the popular Launder and Sharma (7) version of the low Reynolds number k-$ varepsilon$ model was employed. The governing equations for fluid flow and heat transfer were solved using a control volume-based finite difference method. The buoyancy effect in the axial momentum equation was incorporated through the Boussinesq approximation. From the fluid flow and turbulence characteristics predicted by the numerical model, the mass transfer occurring from the dissolution of steel rods immersed in the liquid steel was computed using the Sherwood number correlation recently proposed by Mazumdar et al. (25). The parameters studied include: the flow rate of steel, the heat flux from the solid walls and various radial positions of the vertically immersed steel rod. The fluid flow results are presented as vector plots. The heat transfer aspects are shown through temperature contours at various vertical planes and the mass transfer results are graphically presented in plots showing variance of mass transfer coefficients with key parameters.
The flow field results were found to be in qualitative agreement with previously reported 3D numerical studies for similar systems. Due to the lack of any experimental or numerical results related to heat and/or mass transfer in RH-ladles, the heat and mass transfer results obtained in the present study could not be compared and verified.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 111-117).
Electrochemical reactions in materials and processes induce morphological instability on the cathode, which can lead to porous deposits or system failure. The growth of the protrusion is a complex phenomenon which involves chemical, electrical, and momentum driving forces in the system. Thus, it is important to understand the effect of electrochemistry in phase boundary evolution in order to optimize the performance of such processes. This thesis contributes to predicting and controlling such interface instability phenomena by developing a computational model that captures them. Successful application of the model to emerging metal extraction processes demonstrates its usefulness. A phase field model of electrochemical interface is developed for transport-limited electrolysis with rapid charge redistribution. This new Cahn-Hillard phase field formulation includes a model electrostatic free energy term, which captures the behavior of the diffuse interface under the applied electric field, in addition to transport by free energy gradient and convection. The model agrees with published stability criterion for a solid cathode. When the electrodes and electrolyte are low-viscosity fluids, flow stabilizes the interface.
(cont.) A new stability criterion for metal reduction in a liquid-liquid system is derived and agrees well with the model results. Next, the phase field model is extended for a ternary system to model titanium reduction in a supported electrolyte system. The model can simulate phase boundaries migration depending on the composition of the electrolyte and also electronically mediated reactions. Finally, Solid Oxide Membrane Electrolytic Smelting with Rotating Cathode (SOMERC), an emerging technology to electrolytically reduce titanium oxide from molten salt, is investigated. In the SOMERC process, rotational flow is introduced to create shear force that is expected to stabilize the interface. Computational fluid dynamics models of rotational flow are carried out to estimate the relationship between cathode rotational speed, shear strain rate, and boundary layer thicknesses. The phase field model presented in this thesis can be applied to any electrochemical reduction processes that are in the mass-transport controlled regime. Stability criteria and detailed morphology in two and three dimensions can be explored.
by Wanida Pongsaksawad.
Ph.D.

An estimated 85% of haemorrhagic strokes are secondary to the rupture of an intracranial aneurysm (IA), a localised, blood-filled dilation of the artery wall. The clinically observed rupture of occluded IAs has led to hypothesise that the presence of thrombus may restrict the transport of nutrients, most notably oxygen, to the aneurysmal wall, thus heightening the risk of rupture through the deleterious effects of hypoxia on cellular functionality. The limited research into O2 transport within IAs demonstrate the need for further exploration into the possible detrimental hypoxic conditions as a result of intrasaccular haemodynamics and thrombusformation in untreated, treated and evolving IAs, with the ultimate goal of further understanding disease evolution and developing prognostic decision support models for clinical intervention. Preliminary computational fluid dynamic simulations conducted on a 2Daxisymmetric model of a thrombosed artery highlighted the relative importance of wall-side versus the fluid-side mass transport of oxygen. A sensitivity analysis demonstrated that variations in thrombus thickness, and arterial wall cellular respiration rates have the greatest influence on the oxygen distribution to the portion of wall in direct contact with the thrombus. The results of the coupled flow-mass transport computational fluid dynamic simulations within patient-specific IA show that a reduction in intrasaccular flow as a consequence of stent deployment affects the rate at which oxygenated blood reaches the entirety of the dome. Nonetheless, the distribution ofO2 to the aneurysmal wall itself does not differ from the observed oxygen distribution across the wall when the same IA is left untreated. Conversely, the low velocity recirculations observed in an IA presenting with a very high aspect ratio (i.e a narrow neck and high sack height) limited the transport of oxygen to such an extent as to completely deprive the delivery of oxygen to the fundus. The presence of thrombus within the IA dome results in a dramatic reduction in oxygen delivery to the wall, the extent of which is dependent on the local thrombus thickness. Finally, a novel fluid-solid-growth-mass transport (FSGT) mathematical model is conceived to explore the biochemical role of thrombus on the evolution of an IA. The shear-regulate propagation of a thrombus layer during membrane expansion leads to the gradual decrease in oxygen tension within the wall. Moreover, as a consequence of coupling this oxygen deficiency to fibroblast functionality, the collagen fibre mass density was shown to increase at an insufficient rate to compensate for the transfer in load from the degrading elastinous consitituents to the collagenous constituents, thus resulting in the increased stretch of collagen fibres in order to maintain mechanical equilibrium. Moreover this over-expansion results in the gradual unstable evolution of the IA. The observed obstruction to oxygen delivery as a result of intrasaccular haemodynamics and thrombosis compounds the need for further development of more comprehensive chemo-mechano-biological models of IAs so as to better ascertain the level of rupture risk posed by a hypoxic environment. Refinement to the models proposed within this work would prove invaluable to creating a fully integrated multi-physics, multi-scale in silico framework in aid to patient diagnostics and individual treatment planning of IAs.

Tissue engineering has great potential as a method for replacing or repairing lost or damaged tissue. However, progress in the field to date has been limited, with only a few clinical successes despite active research covering a wide range of cell types and experimental approaches. Mathematical modelling can complement experiments and help improve understanding of the inherently complex tissue engineering systems, providing an alternative perspective in a more cost- and time-efficient manner. This thesis focusses on one particular experimental setup, a hollow fibre membrane bioreactor (HFMB). We develop a suite of mathematical models which consider the fluid flow, solute transport, and cell yield and distribution within a HFMB, each relevant to a different setup which could be implemented experimentally. In each case, the governing equations are obtained by taking the appropriate limit of a generalised multiphase model, based on porous flow mixture theory. These equations are then reduced as far as possible, through exploitation of the small aspect ratio of the bioreactor and by considering suitable parameter limits in the subsequent asymptotic analysis. The reduced systems are then either solved numerically or, if possible, analytically. In this way we not only aim to illustrate typical behaviours of each system in turn, but also highlight the dependence of results on key experimentally controllable parameter values in an analytically tractable and transparent manner. Due to the flexibility of the modelling approach, the models we present can readily be adapted to specific experimental conditions given appropriate data and, once validated, be used to inform and direct future experiments.

Maintaining the uniformity of the temperature distribution of the liquid metal before it enters the mold of Direct Chill (DC) casting processes is critical from the standpoint of defect formation. The temperature of the liquid phase depends on the flow pattern of the molten metal which is strongly inter-connected to the design characteristics of the metal distributor and the process parameters used for a particular alloy such as, casting speed, melt superheat, mold water flow rate, etc. If the melt distribution system is improperly designed and can't sufficiently reduce the turbulence of the incoming melt in the liquid pool, then it will act as a continuous source of oxide formation and contamination during the whole casting process. This will impact adversely on the cast quality and enhance the scrap rate. In order to minimize the impurities in the cast, the present research study suggests and models various new designs of melt distribution systems where the melt is filtered before entering the mold. As part of this effort, a comprehensive 3-D mathematical model of the coupled turbulent fluid flow, heat transfer with mushy region solidification was developed for the vertical DC casting process during steady state phase for an industrial scale rolling ingot. The model was specifically used for understanding the complex interactions between the melt flow and temperature evolution in the solidifying Al-1050 ingot under six different melt feeding arrangements for various casting speeds and melt superheats. The predicted results are presented in the form of temperature and velocity fields. In addition, the quantitative values of the sump depth, the mushy zone thickness, the shell thickness, and the local surface heat flux are given in both graphical and tabular forms. The results show that the temperature distributions and the velocity fields in the melt and in the mushy region are significantly different under different melt feeding schemes. The predictions of the various aspects of the ingot have provided a clear insight about the thermal variations in the entire cross-sections of the ingot. The fundamental models which have been developed in this research can be used as a powerful tool for process optimization and quality control.
Maintenir l'uniformité de la distribution de température d'un métal liquide avant qu'il soit mis dans un moule de traitement thermique Direct Chill (DC) est critique pour réduire la formation de défauts. La température de la phase liquide d'un métal en fusion dépend sur sa configuration d'écoulement, et ce dernier est fortement liée aux particularités du distributeur de métal utilisé, ainsi qu'aux paramètres choisis pour l'alliage en question, tel que la vitesse de moulage, la fusion en surchauffe, la vitesse d'écoulement de l'eau de moule, etc. Si le système de distribution de température a des défauts de conception et ne peut pas réduire suffisamment la turbulence du métal en fusion qui arrive dans le réservoir, il agira comme source continuel de formation d'oxyde et de contamination durant le processus de moulage. Ceci aura des effets négatifs sur la qualité du moulage et augmentera le taux de rebuts. Pour minimiser les impuretés durant le moulage, notre projet de recherche vise à développer plusieurs conceptions de systèmes de distributions de température où le métal en fusion est filtré avant d'arriver dans la moule. Dans ce but, un modèle mathématique 3-D représentant l'écoulement de fluide turbulent couplé, ainsi que le transfert de chaleur avec solidification de région molle, a été développé pour le processus de moulage DC durant la phase stable pour un lingot roulé de taille industrielle. Plus précisément, ce modèle a été utilisé pour comprendre les interactions complexes qui se produisent entre l'écoulement de métal en fusion et l'évolution de température du lingot solidifié Al-1050 sous différentes paramètres de fusion, pour plusieurs vitesses de moulage et de fusion en surchauffe. Ce modèle est basé sur le la méthode des volumes finis. Cet algorithme simple a été utilisé pour couplé la vélocité et les champs de pression pour que les vélocités répondent à l'équation de conservation. Une formulation de phase simple a été adoptée pour résoudre les trois régions, dont liquide, molle et solide, grâce à un ensemble d'équations gouverneurs. Le modèle 'low-Reynolds number k- ε' de Launder et Sharma a été utilisé dans la région en fusion pour justifier l'augmentation de viscosité effective et la conductivité thermique effective, et donc balancer les effets de turbulence qui se présentaient. La méthode populaire 'enthalpy-porosity' a été adopté pour couplé l'équation d'énergie avec l'équation de quantité de mouvement. La loi de Darcy a été utilisée dans les équations de quantité de mouvement pour modeler l'écoulement de fusion dans la région molle. Les termes de convections des équations ont été discrétisées en utilisant la méthode de la différence hybride. Les effets de convection naturelle dans le métal liquide ont été ajoutés grâce à l'approximation Boussinesq. Le filtre, qui a été placé sur le sommet du réservoir, a été modelé grâce à l'équation 'Brinkman-Forchheimer extended Darcy' pour matières poreuses. L'approche proposé par Pedras et de Lemos a été utilisé pour modeler le courant turbulent et le transfert de chaleur dans les matières poreuses. Avec cette approche, l'opérateur de la moyenne des volumes a été appliqué à l'équation des heures de turbulence locales. Les zones de refroidissement primaires et secondaires ont été simulées en changeant le coefficient de transfert de chaleur sur la surface du lingot. Les données de coefficient de transfert de chaleur ont été prises de la littérature sur le moulage DC. Le modèle 3-D CFD a été validé contre les résultats de phases de solidification stable obtenus par d'autres études sur le moulage, pour un lingot roulé 1320 mm x 660 mm AA3104, moulé avec un système de délivrance combo 'standard bag'. La comparaison du front de solidification prévu avec les données mesurées, récupérées avec des thermocouples sacrificiels intégrés, indiquent que le modèle donne des résultats fiables.

To simulate transport phenomena, macrosegregation and segregation defects known as "freckles" during directional solidification of Ni-base superalloys, numerical modeling can be used; hence it is essential to have reasonably accurate values of the thermodynamic and transport properties for the alloys. In this research, therefore, the equilibrium partition ratios of the solutes in the Ni-Al-Ta-Cr quaternary system, as a model alloy, were measured, and the solid- and liquid-densities in Ni-base superalloys. were estimated. Also, the importance of these properties on the sensitivity of the results of numerical simulations was studied. The partition ratios apply to equilibria between melts and gamma-phase in the range of 1615 K to 1694 K, and it was found that the equilibrium partition ratio of Ta varies from approximately 0.6 at dilute Ta to 0.85 at 17 wt.% Ta. For the same range of Ta-contents, the partition ratios of Al and Cr vary much less and range from about 0.92 to 0.96. In addition to the partition ratios, the liquidus temperatures of the liquid in equilibrium with γ in the Ni-Al-Ta-Cr system were estimated with a multidimensional regression analysis. To calculate the densities of solid Ni-base superalloys as functions of temperature and composition, lattice parameters at 20°C and coefficients of thermal expansion (CTEs) were estimated by combining available data. The CTEs calculated from the regressions result in densities that are within 0.5% error or less for seventeen alloys. To estimate the densities of liquid Ni-base superalloys, the densities and temperature coefficients of density of the liquid transition-metals, which are used as alloy elements in Ni-base superalloys, were applied to a simple correlation. By using this approach, the estimates of the liquid densities of five Ni-base superalloys agree with the measured values to ±2.5%. Finally, the importance of using reasonably accurate estimates of the transport properties was illustrated by simulations of the thermosolutal convection and macrosegregation during solidification in a directionally solidified Ni-base alloy casting. In these simulations, the sensitivities of equilibrium partition ratio, solutal expansion coefficient and viscosity on the simulation of macrosegregation were determined. It was found that the segregation and convection are sensitive to the properties, especially to the equilibrium partition ratio.

A full-scale physical model of a delta-shaped, four-strand tundish was constructed at McGill University to find optimal operating conditions for the tundish. The objective of this work was to determine how best to increase steel production rates by 14% over current tundish operating conditions, these being 12 tons/min with four 15.0 mm outlet nozzles for a 500 mm depth of liquid steel while maintaining steel quality levels. Two options were suggested: the normal head option uses 16.0 mm outlet nozzles and maintains the 500 mm tundish level, while the high head option uses 14.8 mm outlet nozzles and raises the depth of liquid steel within the tundish to 800 mm. The important effects of flow control devices on the hydrodynamic performance of the tundish were also tested, using two different types of flow modifiers: Impact Pad and Turbo-Stop. For a proper comparison between the two options, three aspects were investigated; vortex formation phenomena during tundish draining between ladle changes, Residence Time Distribution (RTD), and Inclusion Separation Ratios (ISR). Inclusion removal rates were studied experimentally with the aid of the aqueous" Liquid Metal Cleanliness Analyzer (LiMCA) system. Particle Image Velocimetry (PIV) was used to visualize the actual instantaneous, or momentary, flows, thereby providing the data needed for time averaged velocity fields and turbulent kinetic energies. A mathematical model based on METFLO was developed to simulate these tundish operations numerically. The Renormalization Group turbulence model (RNG) as well as the standard high Reynolds number k-s turbulence model (STD) was implemented in order to simulate the turbulent flows within the tundish. The validity of METFLO was confirmed by PIV measurements and the numerical predictions of the RTD, and RRI matched the results of physical modelling.

A numerical modelling study has been undertaken to analyze transport phenomena in various steel casters. During the course of this work, a general three-dimensional parabolic heat flow model was developed for casters of arbitrarily shaped mould using a body-fitted coordinate transformation technique. The heat flow model was specifically applied to a beam blank caster as well as to an industrial slab caster of regular rectangular cross section, so as to analyze solidification within casters.
Furthermore, a fully coupled turbulent flow and solidification model was developed to describe the turbulent transport processes in the upper part of a steel slab caster as well as to evaluate the process variables affecting the casting. Solidification modelling was carried out using a fixed grid enthalpy method while the mushy zone was modelled based on a Darcy-porosity approach. A modified low-Reynolds number version of the $ kappa$-$ epsilon$ model of turbulence was employed to calculate eddy viscosity within the liquid and mushy regions. A control volume based on finite difference method was used to solve the transport equations, wherein a SIMPLER algorithm was adopted to resolve the velocity-pressure coupling in the momentum equations. In order to verify the turbulent flow model, a water modelling study was performed for fluid flow in the mould region of a slab caster. Reasonable agreement was obtained between the mathematical model's predictions, and water modelling experiments.
Macrosegregation of carbon in a steel billet caster was also modelled based on a continuum formulation, in which the conservation equations are derived in terms of mixture dependent variables. The effect of turbulence on the transport of solute in the liquid and mushy regions was taken into account using the $ kappa$-$ epsilon$ model adopted in this work.
Various parametric studies have been preformed on different casting systems, and their effects on temperature distributions and velocity fields within the strand, solidification profiles, and trajectories of inclusions were predicted. Typical predicted results of the models have been compared against the experimental measurements on operating casters reported in the literature and relatively good agreement was obtained.

A permeable highly sensitive heat flux meter has enabled the first measurements of rapidly changing local heat transfer at a moving surface with and without throughflow. This sensor was tested for turbulent confined impinging single and multiple slot jets, with throughflow and impingement surface motion both separately and in combination.
Impingement surface motion, variously claimed to increase or decrease convective transfer rate, decreases Nusselt number. At industrially used conditions this decrease for slot jets is by as much as 25%.
Convective heat transfer for both single and multiple slot jets at H/w $ leq$ 8 is enhanced by throughflow according to a factor, $ Delta overline{ rm St}$/Mu$ sb{ rm s}$ = 0.17, is independent of Re$ sb{ rm j}$, Mv$ sb{ rm s}$ and extent of heat transfer surface.
In numerical prediction of impingement heat transfer with the high-Re version of the k-$ epsilon$ turbulence model, a modified Chieng-Launder nearwall model improves considerably the agreement between experiment and prediction. This model gives reasonable results for multiple and single slot jets except close to symmetry centrelines, where all such models fail, but does not eliminate the inability of numerical models to predict the effect of nozzle exit turbulence. The effect of throughflow on heat transfer under single and multiple jets is predicted for the first time, accurate to 10% for throughflow velocity up to 0.1m/s.

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007.
Includes bibliographical references (p. 245-255).
This study investigates the thermal transport behavior of nanoparticle colloids or nanofluids. The major efforts are: to determine methods to characterize a nanoparticle colloid's mass loading, chemical constituents, particle size, and pH; to determine temperature and loading dependent viscosity and thermal conductivity; to determine convective heat transfer coefficient and viscous pressure losses in an isothermal and heated horizontal tube; and finally to determine the feasibility for potential use as enhanced coolants in energy transport systems, with focus on nuclear application. The efforts result in proving that the two selected nanofluids, alumina in water and zirconia in water, have behavior that can be predicted by existing single phase convective heat transfer coefficient and viscous pressure loss correlations from the literature. The main consideration is that these models must use the measured mixture thermophysical properties. With the acquired knowledge of the experiments, investigation into the potential use or optimization of a nanofluid as an enhanced coolant is further explored. The ultimate goal of contributing to the understanding of the mechanisms of nanoparticle colloid behavior, as well as, to broaden the experimental database of these new heat transfer media is fulfilled.
by Wesley Charles Williams.
Ph.D.

Honeycomb sandwich panels offer an extremely lightweight solution for aerospace structures. As efficiency demands increase, low-cost non-autoclave manufacturing solutions are sought for honeycomb and other composite structures. Vacuum-bag-only (VBO) manufacturing is one possible solution that relies on vacuum to remove all entrapped volatiles prior to cure, and then the differential pressure between the inside and outside of the vacuum bag consolidates the layers during cure. This technique can be very effective for monolithic laminates made with out-of-autoclave (OOA) prepregs, but honeycomb structures introduce two additional manufacturing nuisances. First, the core entraps up to 98 % of its volume during lay-up, and second, non-metallic cores readily absorb ambient moisture. Entrapped air and moisture can increase the honeycomb core pressure during processing, reducing part quality. Given that the honeycomb core pressure is crucial to achieving success in VBO manufacturing of honeycomb panels, a threefold approach was used in this thesis to study the transport phenomena that influence this behaviour. First, the transport phenomena of the constituent materials were characterized. Applying an impermeable boundary condition to the tool-side skin allowed for simple air permeability characterization of honeycomb skins by considering only the bag-side skin. An instrumented test fixture was used to measure the honeycomb core pressure during the pre-processing vacuum hold. The results revealed that a transverse interconnected pore space was required in OOA prepreg skins for gas evacuation to proceed in honeycomb panels. The same test fixture was used to characterize the honeycomb skin air permeability and honeycomb core moisture diffusivity during elevated temperature processing. The evolving skin air permeability and core diffusivity were observed to cause the honeycomb core pressure to increase during the temperature ramp and decrease during the temperature hold. Second, a process model was developed to predict honeycomb core pressure throughout the manufacturing process. The process model identified that the honeycomb core pressure can exceed the vacuum bag consolidation pressure due to the high core moisture adsorption and elevated temperature diffusivity. Choosing, or creating, a honeycomb skin with high air permeability was identified as a key process parameter to avoid exceeding the consolidation pressure. Finally, the material characterization and process modelling were successfully scaled to reproduce the honeycomb core pressure behaviour in holistic honeycomb panels. The in-situ honeycomb core pressure was measured throughout the manufacturing process in dual-skin honeycomb panels using embedded pressure sensors. The embedded pressure sensor response validated the material characterization assumptions and model simplifications used to predict the honeycomb core pressure during the VBO manufacturing process. Manufacturing honeycomb panels is a complex activity with many material and processing variables. A suitable skin material and bagging configuration was selected for VBO manufacturing of honeycomb panels by coupling transport phenomena modelling and tailored material characterization. This approach could be used to reduce manufacturing trial and error before scaling these materials to larger applications.
Les panneaux sandwich en nid d'abeille offrent une solution extrêmement légère pour les structures aérospatiales. Avec l'augmentation de la demande pour les structures en matériaux composites, les solutions de fabrication de ces structures hors de l'autoclave sont recherchées afin de réduire les coûts. La méthode de fabrication avec sac sous vide requiert une pompe à vide pour enlever tous les gaz piégés après le drapage des matériaux préimprégnés et créer le différentiel de pression entre l'intérieur et l'extérieur du sac à vide afin de consolider les couches de composite. Cette technique peut être très efficace pour les laminés monolithiques, mais les structures en nid d'abeille présentent deux difficultés supplémentaires lorsque des nids d'abeilles non métalliques sont utilisés. D'abord, le nid d'abeille contient 98% du volume d'air piégé pendant le drapage, et deuxièmement, les nids d'abeilles non métalliques absorbent l'humidité pendant leur manipulation. L'air emprisonné dans le nid d'abeilles et l'humidité va augmenter la pression pendant la mise en forme, et peuvent créer des défauts. Cette thèse est divisée en trois thèmes pour étudier et pour optimiser le processus de fabrication des panneaux de composite sandwich avec nid d'abeilles. Tout d'abord, une condition imperméable a été appliquée sur le côté de l'outil, ce qui permet une caractérisation simple des matériaux utilisés pour la mise en forme combinés avec les matériaux préimprégnés de côté de sac à vide. La perméabilité à l'air pour les matériaux préimprégnés a été mesurée durant l'évacuation de l'air avant la cuisson, révélant un degré significatif de l'anisotropie de perméabilité à l'air. Pendant la cuisson à température élevée, la perméabilité à l'air a évolué avec le cycle de cuisson. En outre, le coefficient de diffusion de l'humidité du nid d'abeille non métallique a été caractérisé par une fonction de la concentration d'humidité et de la température. Deuxièmement, un modèle a été développé pour prédire la pression dans le nid d'abeille pendant le processus de fabrication. Des cartes de processus ont été créées afin d'identifier les combinaisons de conditions de traitement pouvant augmenter la pression dans le nid d'abeille au-dessus de la pression de consolidation. Finalement, des panneaux ont été fabriqués avec un laminé sur le côté de l'outil ainsi que sur le côté du sac à vide. Des capteurs de pression ont été incorporés pour mesurer la pression dans le nid d'abeilles pendant le processus de fabrication. La caractérisation des matériaux et la modélisation des processus développées à partir d'expériences simples à petite échelle ont permis de reproduire avec succès le comportement complexe de la pression dans le nid d'abeilles des pièces de grandes dimensions.

A comprehensive, transient three-dimensional model of a single-pass laser surface alloying process has been developed and used to examine the heat, momentum and species transport phenomena. A numerical study is performed in a co-ordinate system moving with the laser at a constant scanning speed. In this model a fixed grid enthalpy-porosity approach is used, which predicts the evolutionary pool development. In this model two extreme cases of alloying element and base metal combinations are considered based on their relative melting points. One extreme case is for an alloying element with its melting point much lower than that of the base metal. In this case the alloying element melts almost instantaneously. Hence it is assumed that the alloying element introduced on the melt pool surface is in the molten state. Thus, while solving the species conservation equation a species flux condition is used on the entire melt pool surface. This case is analysed for aluminium alloying element on iron base metal. The final species distribution in the melt pool as well as in the solidified alloy is predicted. The other extreme case is studied for an alloying element with its melting point relatively higher than that of the base metal. In this case all the alloying element particles on the melt pool surface will not melt. Only those particles which fall in the region on the melt pool surface where the local temperature is higher than the melting point of the alloying element will melt. The particles which fall away from this region are advected into the melt pool, due to a strong Marangoni convection on the melt pool surface. If a particle is advected into the inner region in the melt pool (where the temperature is higher than its melting point), it starts melting and thus the molten species mass gets distributed. Hence, the species flux condition at the entire surface of the melt pool is not valid. The particles are tracked in the melt pool by assuming the alloying particles to be spherical in shape and moving without any relative velocity with the surrounding fluid. Simultaneously, the temperature field inside the spherical particle is solved by assuming its surface temperature to be the local temperature in the melt pool. The amount of particle mass that fuses as it passes through a particular control volume is noted. The same procedure is repeated for a large number of particles initiated at various locations on the pool surface, and a statistical distribution of the species mass source in the entire pool is obtained. This species mass source distribution is then used to solve the species conservation equation. Nickel alloying element on aluminium base metal is used to illustrate this case. The numerical results obtained from the two cases are compared with the available experimental results. A qualitative matching is found between the numerical and experimental results.

A comprehensive, transient three-dimensional model of a single-pass laser surface alloying process has been developed and used to examine the heat, momentum and species transport phenomena. A numerical study is performed in a co-ordinate system moving with the laser at a constant scanning speed. In this model a fixed grid enthalpy-porosity approach is used, which predicts the evolutionary pool development. In this model two extreme cases of alloying element and base metal combinations are considered based on their relative melting points. One extreme case is for an alloying element with its melting point much lower than that of the base metal. In this case the alloying element melts almost instantaneously. Hence it is assumed that the alloying element introduced on the melt pool surface is in the molten state. Thus, while solving the species conservation equation a species flux condition is used on the entire melt pool surface. This case is analysed for aluminium alloying element on iron base metal. The final species distribution in the melt pool as well as in the solidified alloy is predicted. The other extreme case is studied for an alloying element with its melting point relatively higher than that of the base metal. In this case all the alloying element particles on the melt pool surface will not melt. Only those particles which fall in the region on the melt pool surface where the local temperature is higher than the melting point of the alloying element will melt. The particles which fall away from this region are advected into the melt pool, due to a strong Marangoni convection on the melt pool surface. If a particle is advected into the inner region in the melt pool (where the temperature is higher than its melting point), it starts melting and thus the molten species mass gets distributed. Hence, the species flux condition at the entire surface of the melt pool is not valid. The particles are tracked in the melt pool by assuming the alloying particles to be spherical in shape and moving without any relative velocity with the surrounding fluid. Simultaneously, the temperature field inside the spherical particle is solved by assuming its surface temperature to be the local temperature in the melt pool. The amount of particle mass that fuses as it passes through a particular control volume is noted. The same procedure is repeated for a large number of particles initiated at various locations on the pool surface, and a statistical distribution of the species mass source in the entire pool is obtained. This species mass source distribution is then used to solve the species conservation equation. Nickel alloying element on aluminium base metal is used to illustrate this case. The numerical results obtained from the two cases are compared with the available experimental results. A qualitative matching is found between the numerical and experimental results.

The global population is predicted to increase to around 11 billion by 2100. By 2050, the average age in the most populous age group will be over sixty. The ageing population (over sixty-five) is projected to exceed the number of children by 2047. These demographics imply that as the ageing population section increases, there will be a greater need for long-term care services. In order to adequately prepare against this trend, medical experts and evidence-driven policymakers are realising that personalised healthcare can help alleviate the burden related to the planning and commissioning of services allied to long-term care. Central to this picture is conditions that affect the brain - the most important organ of the human body. Dementia, stroke, and other conditions have a tremendous impact on loss of life, quality of life and healthcare cost. The challenge regarding brain disease is exacerbated further due to the difficulty regarding accessibility of this organ, but also due to the immense complexity regarding its morphology and functionality. In this context, advanced biophysical modelling is considered a promising option for studying brain pathophysiology and becomes a priority investment regarding routes for brain research. Simulations offer the promise of improved, clinically relevant, predictive information, acceleration for the pipeline of drug discovery/design and better planning of long-term care for patients. Within this paradigm, a particular model of water transport in the cerebral environment is essential. Numerous brain disorders arise from water imbalance in the cerebral environment, such as hydrocephalus (HCP), oedema and Chiari malformations to name a few. In this research, a novel multiscale model of fluid regulation and tissue displacement in the cerebral environment is developed, arising from the use of Multiple-network Poroelastic Theory (MPET). Characteristics of a four-network poroelastic model (4MPET) are first explored. Then, this model is extended to a fully dynamic (transient) six-network model (6MPET) via the addition of two new compartments, namely the glial cells compartment and the glymphatic system compartment. The introduction of these two compartments in the MPET paradigm reflects recent seminal findings in cerebral physiology, namely the extent and importance regarding transport/clearance of the perivascular spaces of the brain vasculature. We develop and present a numerical implementation of the 6MPET model, and we utilise this framework to analyse acute HCP and cerebral oedema in a variety of settings, in order to show the enhanced capability of the proposed 6MPET model compared to the classical 4MPET. Investigations of acute hydrocephalus through the fully dynamic 6MPET reveal compensatory trans-ependymal pressure behaviour in the glymphatic compartment. It was also shown that aquaporin-4 (AQP4) deficient expression exaggerates ventriculomegaly, and this too is demonstrated in acute hydrocephalus. Additionally, using the 6MPET model, one is able to witness three mitigating factors for cytotoxic oedema. Specifically, these are: reducing water mobility in the glial cells compartment, increasing the compliance of the glial cells compartment and finally AQP4-deficient expression.

Physical and mathematical modelling studies were performed, in order to analyze various transport phenomena occurring during steel making tundish operations. Their effects on liquid metal quality were reported. A full-scale water model of a twelve tonne, delta shaped, four strand, billet caster tundish was used for physical modelling. The commercial code ANSYS FLUENT 12 was used for carrying out mathematical modelling. The tundish used in the present study is a full scale replica of that operated at the RTIT/QIT plant in Sorel Tracy, Canada and is located at MMPC's water modelling laboratory at McGill University. It is a long lasting fact that the flow pattern within a tundish greatly affects the output metal quality. As such the insertion of flow modifiers in a tundish is a common practice. In the present study, eighteen different arrangements of flow modifier systems (combinations of impact pad and dams) were considered, and mathematical modelling was performed to predict the inclusion removal efficiency for each tundish configuration. A new dimensionless number (Gu) has been proposed, which is a good measure of steel cleanliness. During melt transfer from the ladle to the tundish, inert gas is injected into the ladle shroud, just below the slide gate, so as to prevent aspiration of ambient air. The effect of inert gas shrouding on the fluid flow patterns and slag movements have been numerically predicted by using a 3D mathematical model, and then validated with water model experiments. The effect of the alignment of the ladle shroud during melt transfer was also studied, using a 3D mathematical model, supported by subsequent water model experiments. It was demonstrated that a slight bias from the vertical can be very detrimental to steel quality. Remedial measures have been suggested. During typical steelmaking tundish operations, conditions are generally non-isothermal. Variable heat losses take place from the free surface and from the walls of the tundish. Similarly, during a ladle change, the steel poured in from the new ladle will tend to be at a higher temperature than the liquid steel remaining in the tundish. Flow patterns change under non-isothermal conditions and hence affect output steel quality. A thorough study has been performed to visualize the effect of thermal gradients on fluid flow patterns, and temperature distributions generated within the delta shaped tundish.
Dans la présente étude, la modélisation physique et numérique fut utilisée pour analyser l'effet sur la qualité du métal liquide de différents phénomènes de transports ayant lieu dans un panier répartiteur durant les opérations de coulée d'acier. Un modèle physique pleine échelle d'un panier répartiteur de forme triangulaire d'une capacité de douze tonnes comprenant quatre jets pour la coulée de billettes ainsi qu'un modèle mathématique utilisant le logiciel ANSYS FLUENT 12 fut utilisé. Le panier utilisant l'eau comme fluide plutôt que l'acier est une réplique de celui utilisé à l'aciérie RTIT/QIT de Sorel Tracy, Canada. Il est bien connu que les patrons d'écoulement qui se développent dans le panier affectent grandement la qualité du métal à la sortie et, en conséquence, l'insertion de modificateurs d'écoulements est pratique courante. Dans la présente étude, dix huit arrangements différents de modificateurs d'écoulements (panneaux d'impacts et digues) furent considérés et furent numériquement modélisés pour prédire l'efficacité à limiter l'entrainement d'inclusion lors de la coulée. Durant le transfert de l'acier de la poche de coulée vers le panier répartiteur, du gaz inerte est injecté dans le jet immédiatement en dessous de la valve coulissante pour prévenir l'aspiration d'air ambiant. L'effet de l'injection du gaz sur le patron d'écoulement et sur les mouvements du laitier de surface a été estimé grâce à un modèle mathématique en volume (3D) et les résultats furent validés expérimentalement en utilisant le modèle physique à l'eau contenant un laitier de microbilles de verre creuses flottantes. L'effet de l'alignement du jet provenant de la poche de coulée qui alimente le panier répartiteur fut aussi étudié par modélisation mathématique en trois dimensions et subséquemment, par des tests physiques avec l'eau. Il fut prouvé que les conséquences d'un léger désalignement vertical du jet est catastrophique et des solutions correctrices sont proposées.Durant les opérations réelles de coulées de l'acier avec panier répartiteur, les conditions ne sont pas isothermes. Il y a des pertes calorifiques provenant de la surface et des côtés du panier. Durant les opérations de changement de poche de coulée, l'acier provenant de la nouvelle poche peut aussi être plus chaud que le restant du panier provenant de la poche précédente. Les patrons d'écoulement change donc sous ces effets non isothermes et affectent aussi la qualité de l'acier sortant. Une étude poussée fut menée pour illustrer l'effet des gradients thermiques sur les patrons d'écoulements et sur la distribution de température dans le panier triangulaire.

Micromechanical approach is employed to investigate the transport and freezing within unsaturated porous media. In unsaturated porous media, water film as well as disjoining pressure are introduced in the transport and freezing problems. In the modeling, it is found that, capillary layer along with pore water dominate the transport at high saturation degree (Sr>10%). However, water film will play a significant role in transport at low saturation degree (Sr<10%), and the diffusion coefficient will be lower than 3 to 4 orders of magnitude than that at higher saturation degree. A micromechanical model of freezing in unsaturated porous media is established. Micromechanical model of freezing is more physical based in nature. That is because different from poromechanical model of freezing media in which ice crystal pressure is introduced, the disjoining pressure of unfrozen water film instead of ice crystal pressure is introduced in the micromechanical model of freezing

Thesis: Ph. D. in Environmental Fluid Mechanics, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2014.
116
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 227-235).
From the canopy scale to the blade scale, interactions between fluid motion and kelp produce a wide array of hydrodynamic and scalar transport phenomena. At the kilometer scale of the kelp forest, coastal currents transport nutrients, microorganisms and spores. But, kelp forests exert a drag force on currents, causing the flow to decelerate and divert as it encounters the canopy, affecting the fate of species transported by the current. We identify a dimensionless flow-blockage parameter, based on canopy width and density, that controls both the length of the flow deceleration region and the total flow in the canopy. We further find that shear layers at the canopy edges can interact across the canopy, providing additional exchange between the canopy and the surrounding water. At the sub-meter scale, kelp blades are the photosynthetic engines of kelp forests, but are also responsible for the majority of the fluid drag force on the plants and for acquiring nutrients directly from the surrounding water. These blades are highly flexible structures which move in response to the local fluid forcing. Recent studies documenting changes in blade flexural rigidity in response to changes in flow demonstrate a need for understanding the role blade flexural rigidity plays in setting both drag forces, and nutrient flux at the blade surface. We create a model physical system in which we investigate the role of blade rigidity in setting blade forces and rates of scalar exchange in a vortex street. Using a combination of experimental and theoretical investigations, we find that, broadly, forces are higher for more flexible blades, countering the adage that "going with the flow" is beneficial. Below a critical value of the dimensionless blade rigidity, inertial forces from the rapidly deforming blade become significant, increasing the likelihood of blade failure. Nutrient transport is also affected by blade rigidity. As blades deform, they alter the relative fluid motion at the blade surface, affecting nutrient fluxes. We develop a novel experimental method that simulates nutrient uptake to a blade using the transport of a tracer into polyethylene. Through these experiments and modeling, we demonstrate that increased blade flexibility leads to increased scalar transport. Ultimately, blade flexural rigidity affects both mass and momentum flux.
by Jeffrey Tsaros Rominger.
Ph. D. in Environmental Fluid Mechanics

Preservation of tissue structure, morphology and biomarkers is of utmost importance for pathological examination of biopsy specimens for diagnostic and therapeutic purposes. However current methods employed to evade tissue degradation and preserve biomarkers have several shortcomings that include irreproducibility, morphological artifacts and altered biomarker antigenicity. These artifacts may affect the analysis and subsequent diagnosis of the tissue pathology. This creates need for developing improved preservation methods that reproducibly maintain tissue morphology and biomarker antigenicity and are simple, rapid and inexpensive. Experiments conducted for testing the hypothesis that cryopreservation procedures yield high quality morphology and antigenicity showed that cryopreservation maintains tissue structure, morphology and antigenicity at equivalent or better levels compared to standard freezing techniques. In order to understand the mechanisms of osmotic transport in cellular systems upon exposure to multi-component solutions that are prevalent in virtification protocols, experimental studies were undertaken using microfluidics for single cell manipulation. The experimental data yielded permeability parameters in binary and ternary solutions for MC3T3-E1 murine osteoblasts for the first time. The hydraulic conductivity (L(p)) decreased with increasing concentrations but the solute permeability either increased or decreased with increasing solution concentration. The changes in hydraulic conductivity were consistent with previously published trends and conform to a functional relationship in the form of Arrhenius type relationship between L(p) and solution concentration. Further a theoretical model was developed from principles of linear irreversible thermodynamics to simulate multi--‐‑component mass transport across membrane. The model was successfully validated by comparison with experimental data for murine osteoblasts and showed good agreement between the numerical predictions and experimental observations. The modeling approach can be used to investigate the transport mechanisms, which show that in multicomponent osmotic transport response, the dynamics is dictated by slower moving solute.

In a 2D cell culture, the cells are mainly grown on flat surfaces which are usually made of polystyrene plastic. Cells are able to attach to these surfaces, forming individual cell formations or colonies. In this study, we have been looked at many different platforms to improve cell growth, adhesion, attachment and proliferation on two different promising cell lines. These cell lines are the human neural stem cells (hNSCs) and human liver hepatocellular carcinoma cells (HepG2). Researchers have been very interested in studying these cell lines in the recent years as they have very useful potentials in the long run to aid and cure many of the disorders, diseases and possibly replace infected or injured organs as well. This can be done using actual clinical applications for cell therapies and tissue transplantation. Based on the studies conducted for this thesis, we have been able to show that cells can be maintained in a 2D culture setting with increasing growth and adhesion factors. The conditions used for these studies were a way to not use the traditional materials for cell attachment and growth. This was pursued due to the fact that most stem cells for their continuity require a microenvironment that will support their physical and chemical properties of an effective extra cellular matrix (ECM). To reiterate, presently most ECM molecules are human or animal derived for effective cell culture applications but not clinical. This is a major problem as each batch varies, they are difficult to isolate and most contain biological components that have been known to limit their use in clinical applications. Hence, this study concentrated on developing synthetic polymer based ECMs as they do not have the problems of the human or animal derived ECMs, but also as they are relatively low-cost, reliable and easily fabricated. Through many experimental trials we have successfully developed synthetic polymer based ECM molecules that sustain stem cell growth for HepG2 liver hepatocellular carcinoma and hNSC human neural stem cell lines. The different substrates developed were a peptide fabricated in our lab; different concentrations and solutions of Poly 4-vinylphenol (P4VP) that were used on a flat hollow fiber membrane made using Polyacrylonitrile (PAN) doped in a solution containing PAN/N, N-dimethylformamide (DMF) having a high biocompatibility. This hollow fiber membrane study was maintained with eight different conditions over a period of 6 weeks.

Hamnefjärden är ett havsområde utanför Oskarshamns kärnkraftverk som har en förhöjd temperatur jämfört med vad som har varit naturligt innan Oskarshamnsverket togs i bruk. Sedan dess har kylvattnet från anläggningen påverkat ekologin med konstanta plymer av varmvattentillförsel med hög temperatur. I och med detta har påverkan av dessa utsläpp undersökts med hjälp av en sammanställning av litteratur gällande de fysikaliska och biologiska påverkningarna som skett på Hamnefjärden. Mätningar där Hamnefjärden jämförts med ett referensområde, visar att den lokala ekologin har påverkats av varmvattnet till en grad. Stora temperaturskillnader i mynningen för kylvattnet visar på stor fysikalisk påverkan men de biologiska verkar mindre påtagliga.
Hamnefjärden is a sea area outside of Oskarshamn nuclear powerplant which has an increased temperature compared to what was natural before the powerplant was started. Ever since the cooling water from the powerplant has been affecting the ecology with constant plumes of inflow with heated water. This discharge has thus been investigated by compiling literature about the physical and biological effects on Hamnefjärden. Surveys, in which Hamnefjärden has been compared to a reference area, shows that the local ecology has been affected by the heated water somewhat. Large differences in temperature in the estuary of the coolingwater indicates large physical effects but the biological effects seem smaller.

The corrugated board is considered as the second most used packaging material and the world’s environmentally acceptable solution for packaging, with wide range of applications. After the manufacturing process, the corrugated board is cut into sheets and stored in a stack until optimum moisture content has been reached in order to avoid undesired properties. However, due to complex and various structures, it is difficult to estimate the appropriate time so to achieve the acceptable moisture level of the corrugated board stack. So a homogenized model of the stack has to be created which will have the same average properties as the real stack. In order to achieve this goal the behavior of a smaller part of the stack, the unit cell, is investigated. In the second step a homogenized model is created with the average transport of mass and heat. At the end, the unit cell is scaled up. In this master thesis, only the first and the second steps were simulated. This was achieved by creating a 3-D mathematical model using finite element method and simulating its properties in COMSOL Multiphysics®. Four mathematical models were used in the description of the 3-D model: the heat transfer, the moisture transfer, the vapour concentration and the gas pressure. Moreover, by applying the gradient in one direction in each case, the behavior of the detailed unit cell was investigated. Finally different simplified geometries were created and investigated so to approach a homogenized model which described better the average properties of the detailed model. By comparing the results of the models, it was concluded that the homogenized models 2 and 3 approached the values of the second detailed model but only inside of the unit cell. However, the deviation was not negligible and further investigation is required in order to find a new homogenized method.

Area averaging is one of the techniques used to solve problems encountered in the transport of momentum, heat, and mass. The application of this technique simplifies the mathematical solution of the problem. However, it necessitates expressing the local value of the dependent variable and/or its derivative(s) on the system boundaries in terms of the averaged variable. In this study, these expressions are obtained by the two-point Hermite expansion and this approximate method is applied to some specific problems, such as, unsteady flow in a concentric annulus, unequal cooling of a long slab, unsteady conduction in a cylindrical rod with internal heat generation, diffusion of a solute into a slab from limited volume of a well-mixed solution, convective mass transport between two parallel plates with a wall reaction, convective mass transport in a cylindrical tube with a wall reaction, and unsteady conduction in a two -layer composite slab. Comparison of the analytical and approximate solutions is shown to be in good agreement for a wide range of dimensionless parameters characterizing each system.

ABSTRACTXIONG, MING. Investigation of Transport Phenomena in the Presence of Interfaces: Forced Convection in Composite Porous/Fluid Domains, Solidification with a Mushy Region, and Meniscus Formation in Dip Coating Processing (Under the direction of Andrey V. Kuznetsov)Transport phenomena play an important role in many practical applications. Every time a new technology is developed, analysis of transport processes is crucial for its success. Numerical and analytical investigations of transport processes in forced convection in composite porous/fluid domains, solidification of binary alloys, and meniscus formation in dip coating process are performed. These processes include mass, momentum, and energy transport across interfaces. For forced convection in composite porous/fluid domains, the validity of single-domain approach is investigated via comparisons between the numerical and exact solutions. An analytical solution for fluid flow described by the Brinkman-Forchheimer-Darcy equation is obtained by utilizing the boundary layer approximation. Solidification of binary alloys is studied by utilizing a porous medium approach for modeling transport processes in the mushy zone. A three-phase model is developed to predict microporosity formation during this process. Solute redistribution during this process is modeled by using the Scheil and lever rules to describe solute transport at the local scale. The investigations show that initial hydrogen concentration is an important factor affecting microporosity formation. Also, some effective ways of controlling microporosity formation are suggested based on these investigations. Another process studied in this dissertation is the dip coating with liquid carbon dioxide used as a solvent. This is a new deposition technique developed in recent years. A model accounting for evaporation during this process is obtained based on the classical free meniscus theory. Numerical results agree well with experimental data. These results show that the dry film thickness increases with the increase of evaporation rate and initial solute concentration.

Recently, considerable attention has been focused on the generation of nano- and micrometer scale multicomponent polymer particles with specifically tailored mechanical, electrical and optical properties. As only a few polymer-polymer pairs are miscible, the set of multicomponent polymer systems achievable by conventional methods, such as melt blending, is severely limited in property ranges. Therefore, researchers have been evaluating synthesis methods that can arbitrarily blend immiscible solvent pairs, thus expanding the range of properties that are practical. The generation of blended microparticles by evaporating a co-solvent from aerosol droplets containing two dissolved immiscible polymers in solution seems likely to exhibit a high degree of phase uniformity. A second important advantage of this technique is the formation of nano- and microscale particulates with very low impurities, which are not attainable through conventional solution techniques. When the timescale of solvent evaporation is lower than that of polymer diffusion and self-organization, phase separation is inhibited within the atto- to femto-liter volume of the droplet, and homogeneous blends of immiscible polymers can be produced. We have studied multicomponent polymer particles generated from highly monodisperse micrordroplets that were produced using a Vibrating Orifice Aerosol Generator (VOAG). The particles are characterized for both external and internal morphology along with homogeneity of the blends. Ultra-thin slices of polymer particles were characterized by a Scanning Electron Microscope (SEM), and the degree of uniformity was examined using an Electron Dispersive X-ray Analysis (EDAX). To further establish the homogeneity of the polymer blend microparticles, differential scanning calorimeter was used to measure the glass transition temperature of the microparticles obtained. A single glass transition temperature was obtained for these microparticles and hence the homogeneity of the blend was concluded. These results have its significance in the field of particulate encapsulation. Also, better control of the phase morphologies can be obtained by simply changing the solvent/solvents in the dilute solutions. Evaporation and drying of a binary droplet containing a solute and a solvent is a complicated phenomenon. Most of the present models do not consider convection in the droplet phase as solvent is usually water which is not very volatile. In considering highly volatile solvents the evaporation is very rapid. The surface of the droplet recedes inwards very fast and there is an inherent convective flow that is established inside the solution droplet. In this dissertation work, a model is developed that incorporates convection inside the droplet. The results obtained are compared to the size obtained from experimental results. The same model when used with an aqueous solution droplet predicted concentration profiles that are comparable to results obtained when convection was not taken into account. These results have significance for more rigorous modeling of binary and multicomponent droplet drying.

L'objectif de ce travail de thèse est de dégager des méthodes et des outils permettant de mieux comprendre le rôle joué par les phénomènes de transport (cellulaire, hydraulique et chimique) dans la mise au point de stratégies thérapeutiques de réparation osseuse. Pour cela, nous avons choisi d'associer deux approches : la réalisation d'études expérimentales et la mise au point de modèles numériques. Nous avons ainsi pu, lors d'une première étude présentée dans le chapitre 2 de ce document, relier la perméabilité intrinsèque d'un milieu poreux, paramètre déterminant dans l'étude du transport de fluide en son sein, à la structure géométrique de ses pores. Nous avons également mis en évidence l'importance des interactions électrochimiques lors de la progression d'une solution ionique (telle que les fluides physiologiques) à travers le tissu osseux, en raison de la structure poreuse et de la composition chimique (présence de fibres de collagènes chargées par exemple) de ce dernier. Ces outils ont ensuite permis d'analyser, en première approche, les résultats expérimentaux obtenus lors de la réalisation de tests de perméabilité sur des échantillons de périoste fémoral ovin, dans le but d'identifier les phénomènes physico-chimiques à l'origine du comportement particulier de cette membrane (chapitre 5). Nous nous sommes par ailleurs intéressés au développement d'implants osseux associant un substrat minéral biocompatible et des cellules souches mésenchymateuses, afin de favoriser une reconstruction tissulaire en volume des lésions de grande taille. Nous avons ainsi pu mettre en place, dans le chapitre 3, un dispositif expérimental permettant de réaliser de manière reproductible un test d'ensemencement cellulaire et d'évaluer le nombre, la répartition et le taux de viabilité des cellules greffées sur le biomatériau utilisé. A partir des résultats expérimentaux issus des tests d'ensemencement cellulaire, nous avons ensuite développé un modèle numérique dans le chapitre 4, pour dégager un ensemble de critères à respecter dans l'élaboration d'un substitut osseux qui favoriserait un développement tissulaire homogène contrôlé lors des premières étapes de la culture in vitro de ce type d'implants. Ce modèle constitue une première étape dans la détermination d'un cahier des charges géométrique de tels substrats
This study aims to set up methods and tools to improve our understanding of the role played by transport phenomena (transport of cells, fluid and chemical species) in the development of new therapeutic protocols for bone reconstruction, using a double approach: experimental studies and numerical simulations. Hence, in the second chapter of this document, we have been able to link the intrinsic permeability of a porous medium – a key parameter regarding fluid transport through porous media – to the geometric structure of its pores. We have also highlighted the influence of electrochemical interactions on the flow of an ionic solution (such as physiologic fluids) through cortical bone, due to its porous structure and its chemical composition (presence of electrically charged fibers). These tools have then enabled us to analyze, at first glance, the experimental results of permeability tests conducted on ovin femoral periosteum, to identify the chemical-physical phenomena responsible for the specific behavior of this membrane (chapter 5). We also focused on the development of large bone implants coupling a mineral substitute and mesenchymal stem cells to enhance a volumic reconstruction of critical-sized bone defects. We have therefore designed, in chapter 3, a custom experimental set up that allows one to perform a reproducible cell seeding test on a porous scaffold and quantify the number of seeded cells as well as their viability rate. The experimental results provided by these tests have then initiated the numerical model exposed in chapter 4, that aims to highlight criteria to meet regarding the design of new bone substitutes that would enhance a homogeneous volumic tissue growth during the first stages of the extit [in vitro} development of coupled implants

Three methods were developed to better understand and characterize the near-field dynamic processes of rotary bell atomization. The methods were developed with the goal of possible integration into industry to identify equipment changes through changes in the primary atomization of the bell. The first technique utilized high-speed imaging to capture qualitative ligament breakup and, in combination with a developed image processing technique and PIV software, was able to gain statistical size and velocity information about both ligaments and droplets in the image data. A second technique, using an Nd:YAG laser with an optical filter, was used to capture size statistics at even higher rotational speeds than the first technique, and was utilized to find differences between serrated and unserrated bell ligament and droplet data. The final technique was incorporating proper orthogonal decomposition (POD) into image data of a side-profile view of a damaged and undamaged bell during operation. This was done to capture differences between the data sets to come up with a characterization for identifying if a bell is damaged or not for future industrial integration.

Froth flotation is the most commonly used process to recover and upgrade the portion of the coal preparation plant feed that has a particle size smaller than 150 microns. Problems that occur when employing froth flotation in the coal industry include i) coal surfaces that are weakly-to-moderately hydrophobic, and ii) flotation systems that are overloaded and limited by insufficient retention time. Research was performed to evaluate techniques that could be implemented to improve flotation performance under the aforementioned scenarios. Pre-aeration of flotation feed using a cavitation system was extensively evaluated in laboratory and full-scale test programs. The benefits of adding hydrophobic, magnetic plastic particles were also investigated to improve froth stability and increase bubble surface area. Laboratory tests revealed that pre-aeration through a cavitation tube improved coal recovery by as much as 20 absolute percentage points in both conventional cells and flotation columns when treating difficult-to-float coals. Carrying capacity increased by 32% which was projected to provide a 4 t/h increase in flotation recovery for a typical 4-m diameter flotation column. Product size analyses suggest that the improved particle recovery was more pronounced for the finest coal fractions as a result of particle agglomeration, resulting from the use of the nucleated air bubbles on the coal surfaces as a bridging medium. In-plant testing of a commercial-scale cavitation system found that feed pre-aeration could reduce collector dosage by 50% when no additional air is added and by 67% when a small amount of air is added to the feed to the cavitation system. At a constant collector dosage, recovery increased by 10 absolute percentage points with cavitation without additional air and 17 absolute points when additional air is provided. The addition of hydrophobic plastic particles to the flotation feed at a 10% concentration by weight was found to substantially improve froth stability thereby elevating the recovery and enhancing carrying-capacity. Test results showed that the primary flotation improvements were directly linked to the coarsest particle size fractions in the plastic material which supports the froth stability hypothesis. Combustible recovery was increased up to 10 percentage points while producing the desired concentrate quality.

The demand for high performance electronic devices is ever increasing in today's world with advent of digital technology in every field. In order to support this fast paced growth and incursion of digital technology in society, smarter, smaller integrated circuits are required at a lower cost. This primary requirement drives semiconductor industries towards the integration of larger number of smaller transistors on a given circuit area. The past decades have seen a rapid evolution of material processing and fabrication techniques, as focus shifts from submicron to sub-nanometer length scales in device configuration. As the functional feature size of an integrated circuit decreases, the threshold of defect causing impurities rises drastically. Huge amount of resources are spent in downstream and upstream processing in order to restore system from contamination upsets and in the upkeep of Ultra-High-Purity (UHP) process streams to meet these stringent requirements. Contamination once introduced into the system also drastically reduces process yield and throughput resulting in huge losses in revenue. Regular UHP fluid distribution system maintenance as well as restorative operations involve a purging operation typically known as Steady State Purge (SSP). This purge operation involves large amount of expensive UHP gas and time. Depending on the scale of the system and type of process involved this results in significant tool, process downtimes and can have a wide range of environment, health and safety (ESH) ramifications. A novel purge process, referred to as Pressure Cyclic Purge (PCP) was studied for establishing gas phase contamination control in UHP applications. In understanding the basic mechanism of this technique and to analyze its extent of application in aiding purging operations, a coupled approach involving experimental investigation and computational process modelling was used. Representative and generic distribution sections such as main supply lines and sections with laterals were contaminated with a known amount of moisture as impurity. The dynamics of the impurity transport through the system from purging with SSP as well as PCP was captured by a highly sensitive analyzer. The surface interactions between the moisture and EPSS were characterized in terms of adsorption and desorption rate constants and surface site density. A computational process model trained using experimental data was then validated and used to study the steady and cyclic purge mechanisms and predict complex purge scenarios. Industrially relevant and applicable boundary conditions and system definitions were used to increases the utility of the computational tool. Although SSP compared closely with PCP on simple systems without laterals, a drastic difference in dry-down efficiency was noticed in systems with dead volumes in the form of capped laterals. Studies on system design parameters revealed that the disparity in performance was observed to increase with larger number and surface area of dead volumes, opening a path to critical understanding of the differences in process mechanisms. Beneficial transient pressure gradient induced convective flow in the dead volumes during cyclic purge was identified to be the main factor driving the enhanced dry down rate. Similar trends were observed on using surface concentration as the purge metric. Hybrid purge schemes involving a combination of SSP and PCP were found to yield higher benefit in terms of efficient use of purge gas. Removal of strongly interacting contaminant species showed a higher benefit from use of controlled PCP scheme. Although, parametric analysis carried out on the operating factors of cyclic purge suggested that the enhancement in dry down increased with higher pressure range, it was highly conditional towards configurational factors in design and operation such as system dimensions, holding time, cycling pattern, valve loss coefficients and the complex inter coupling between them. The robustness of the process simulator allows the development of optimal purge scenarios for a given set of system parameters in order to perform a controlled purge. The benefit of using a hybrid PCP scheme was evaluated in terms of UHP purge gas and process time as a function of purity baseline required. Apart from UHP gas distribution systems, process vessels, chambers and components along the process stream are also prone to molecular contamination and pose a threat to product integrity. The dead volumes acting as areas of contaminant accumulation represent cavities or dead spaces in flow control elements such as mass flow controllers (MFCs), gauges, valves or dead spaces in process chambers. Steady purge has very little effect in cleanup of such areas and more efficient methods are necessitated to raise purge efficiency. The analysis of application of PCP is extended to such components through the development of a robust and comprehensive process simulator. The computational model applies a three dimensional physical model to analyze purge scenarios with steady and cyclic purge. The results presented pertain to any generic gas phase contaminant and electronic grade steel surfaces. Close investigation of the purge process helped elaborate the cleaning mechanism. Critical steps driving the purge process were identified as - dilution of chamber by introduction of fresh gas during re-pressurization and chamber venting during depressurization. Surface and gas phase purging of chambers with dead spaces using steady and cyclic purge were studied and compared. Cyclic purge exhibited a higher rate of dry down. The effect of system, design and purge operating parameters on surface cleaning were studied. Although higher frequency cycles and larger operating pressure ranges optimized for a given geometry are found to deliver better pressure cyclic purge (PCP) performances, the benefit is found to be contingent to a strong interplay between system parameters. PCP is found to be advantageous than steady state purge (SSP) in terms of purge gas usage and operation time in reaching a certain purity baseline. Specialty process gases supplied to the fabrication facility are typically stored in the form of liquids in enormous tanks outside the fab. Ammonia is a widely used in UHP concentrations for a variety of process including epitaxial growth, MOCVD, etching and wet processes in the semiconductor industry. The recent development in LED research has risen the demand and supply for Ammonia based compounds. Stringent baselines are maintained for the impurities associated with the manufacturing of such gases (e.g. Moisture in Ammonia). Apart from the difference in the rates of evaporation of the individual species from the storage cylinder causing accumulation of slower evaporating species, external temperature fluctuations also generate unsteady flux of desired species. When concentrations rise above this threshold additional purification or in most cases discarding large volumes of unused gas is warranted, causing loss of resources and causing ESH issues. Bulk gases are usually delivered over long lengths of large diameter pipes which produce large density of adsorption sites for contaminants to accumulate and eventually release into the gas stream. In order to establish contamination control in the gas delivery system, the surface interactions of the multispecies system with the delivery line surface was characterized. Desired concentrations of moisture in ammonia and UHP nitrogen mixtures were produced in a gas mixing section capable of delivering controlled mass flow rates to an EPSS test bed. Transient moisture profiles during adsorption and desorption tests at various test bed temperatures, mass flow rates and moisture concentration were captured by a highly sensitive analyzer. A mathematical model for single and multi-species adsorption was used in conjunction with experimental data to determinate kinetics parameters for moisture, ammonia system in EPSS surface. The results indicate competitive site binding on EPSS between ammonia and water molecules. Also, the concentration distribution of each species between surface, gas phase is interdependent and in accordance to the kinetic parameters evaluated. Back diffusion of impurity is a major source of contaminant introduction into UHP streams. Back diffusion refers to the transport of contaminants against the flow of bulk process stream. Molecular species can back diffuse from dead volumes, during mixing operations etc., simply when there is a gradient of concentration. A steady state approach was used to analyze the mechanism and effects of various geometrical and operational parameters on back diffusion. High sensitivity moisture detectors were used to capture the dynamics of contamination in a section of a generic distribution system. Results showed that back diffusion can occur through VCR fittings, joints and valves under constant purge. General trends on the effect of design parameters on back diffusion were derived from studies on various orifice sizes, system dimensions, flow rates and test moisture concentrations. Coupled parametric studies helped identify critical variable groups to perform dimensionless analysis on back diffusion of moisture. Crucial points where back diffusion can be minimized or completely eliminated are identified to help set up guidelines for cyclic and steady purge parameters without excessive use of expensive UHP gas or installation of unnecessarily large factors of safety. Wet cleaning of micro/nano sized features is a highly frequent process step in the semiconductor industry. The operation is a huge consumer of ultra-pure water and one of the main areas where process time minimization is focused. Comprehensive process model is developed to simulate the mechanism and capture the dynamics of rinsing high aspect ratio Silicon features in the nanometer scale. Rinsing of model trench, post etch contaminated with ammonium residue is studied. Mass transport mechanisms such as convection, diffusion are coupled with surface processes like adsorption and desorption. The effect of charged species on the trench surface and in the bulk, the resultant induced electric field on the rinse dynamics and decay of surface species concentration is studied. General rinsing trends and critical points in change in mechanisms were identified with critical groups such as mass transfer coefficient and desorption coefficient. The model is useful in evaluating process efficiency in terms of rinse time and DI water consumption under varying process temperature, contaminant concentration, and rinse fluid flow rate. The generic build of the model allows extension of its functionality to other impurity-substrate material couples.

Capillarity is often exploited in self-cleaning, drag reducing and fluid absorption/storage (sanitary products) purposes just to name a few. Formulating the underlying physics of capillarity helps future design and development of optimized structures. This work reports on developing computational models to quantify the capillary pressure and capillary forces on the fibrous surfaces. To this end, the current study utilizes a novel mass-spring-damper approach to incorporate the mechanical properties of the fibers in generating virtual fibrous structures that can best represent fibrous membranes. Such virtual fibrous structures are then subjected to a pressure estimation model, developed for the first time in this work, to estimate the liquid entry pressure (LEP) for a hydrophobic fibrous membrane. As for accurate prediction (and not just estimation) of the capillary pressure, this work also presents an energy minimization method, implemented in the Surface Evolver code, for tracking the air–water interface intrusion in a hydrophobic fibrous membrane comprised of orthogonally oriented fibers. This novel interface tracking algorithm is used to investigate the effects of the membrane’s microstructure and wetting properties on its resistance to water intrusion (i.e., LEP). The simulation method developed in this work is computationally affordable and it is accurate in its predictions of the air–water interface shape and position inside the membrane as a function of pressure. Application of the simulation method in studying effects of fiber diameter or contact angle heterogeneity on water intrusion pressure is reported for demonstration purposes. Capillary forces between fibrous surfaces are also studied experimentally and numerically via the liquid bridge between two parallel plates coated with electrospun fibers. In the experiment, a droplet was placed on one of the polystyrene- or polyurethane-coated plates and then compressed, stretched, or sheared using the other plate and the force was measured using a sensitive scale. In the simulation, the liquid bridge was mathematically defined for the Surface Evolver finite element code to predict its 3-D shape and resistance to normal and shearing forces, respectively, in presence of the contact angle hysteresis effect. Despite the inherent non-uniformity of the fibrous surfaces used in the experiments and the simplifying assumptions considered for the simulations, reasonable agreement was observed between the experiments and simulations. Results reveal that both normal and shear force on the plates increase by increasing the liquid volume, or decreasing the spacing between the plates.

Selectively permeable biological membranes composed of lipophilic barriers inspire the design of biomimetic carrier-mediated membranes for aqueous solute separation. This work imparts selective permeability to lipid-filled pores of silica thin film composite membranes using carrier molecules that reside in the lipophilic self-assemblies. The lipids confined inside the pores of silica are proven to be a more effective barrier than bilayers formed on the porous surface through vesicle fusion, which is critical for quantifying the function of an immobilized carrier. The ability of a lipophilic carrier embedded in the lipid bilayer to reversibly bind the target solute and transport it through the membrane is demonstrated. Through the functionalization of the silica surface with enzymes, enzymatic catalysis and biomimetic separations can be combined on this nanostructured composite platform. The successful development of biomimetic nanocomposite membrane can provide for efficient dilute aqueous solute upgrading or separations using engineered carrier/catalyst/support systems. While the carrier-mediated biomimetic membranes hold great potential, fully understanding of the transport processes in composite synthetic membranes is essential for improve the membrane performance. Electrochemical impedance spectroscopy (EIS) technique is demonstrated to be a useful tool for characterizing the thin film pore accessibility. Furthermore, the effect of lipid bilayer preparation methods on the silica thin film (in the form of pore enveloping, pore filling) on ion transport is explored, as a lipid bilayer with high electrically insulation is essential for detecting activity of proteins or biomimetic carriers in the bilayer. This study provides insights for making better barriers on mesoporous support for carrier-mediated membrane separation process. Porous silica nanoparticles (pSNPs) with pore sizes appropriate for biomolecule loading are potential for encapsulating dsRNA within the pores to achieve effective delivery of dsRNA to insects for RNA interference (RNAi). The mobility of dsRNA in the nanopores of the pSNPs is expected to have a functional effect on delivery of dsRNA to insects. The importance of pores to a mobile dsRNA network is demonstrated by the lack of measurable mobility for both lengths of RNA on nonporous materials. In addition, when the dsRNA could not penetrate the pores, dsRNA mobility is also not measurable at the surface of the particle. Thus, the pores seem to serve as a “sink” in providing a mobile network of dsRNA on the surface of the particle. This work successfully demonstrates the loading of RNA on functionalized pSNPs and identified factors that affects RNA loading and releasing, which provides basis for the delivery of RNA-loaded silica particles in vivo.

Submitted by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-25T11:32:18Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Um modelo para dispersão de poluentes na camada limite planetária com coeficientes de difusão dependentes da distância da fonte.pdf: 1813716 bytes, checksum: 2b7788e4583766741e3b5c4e7ae8da30 (MD5)
Approved for entry into archive by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-25T11:33:16Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Um modelo para dispersão de poluentes na camada limite planetária com coeficientes de difusão dependentes da distância da fonte.pdf: 1813716 bytes, checksum: 2b7788e4583766741e3b5c4e7ae8da30 (MD5)
Made available in DSpace on 2017-01-25T11:33:16Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Um modelo para dispersão de poluentes na camada limite planetária com coeficientes de difusão dependentes da distância da fonte.pdf: 1813716 bytes, checksum: 2b7788e4583766741e3b5c4e7ae8da30 (MD5) Previous issue date: 2013-07-15
Este trabalho apresenta a solução da equação da difusão-advecção bidimensional estacionária para simular a dispersão de poluentes na Camada Limite Planetária. A solução é obtida através do método ADMM (Analytical Dispersion Multilayer Model) e da técnica de inversão numérica utilizando o algoritmo de Fixed Talbot. A validação da solução é comprovada, mediante os parâmetros estatísticos, através do confrontamento das concentrações calculadas a partir do modelo com as obtidas experimentalmente pelo experimento de Prairie Grass. Para a determinação das concentrações utiliza-se o perfil do vento segundo o modelo de similaridade de Monin-Obukhov e os parâmetros de turbulência com dependência da distância longitudinal da fonte e da altura vertical, considerando a componente vertical do espectro Euleriano e de acordo com o modelo sugerido por Hɸjstrup que divide os espectros em alta e baixa frequência. Para efeito comparativo utiliza-se um coeficiente de difusão para grandes tempos de difusão. Os melhores resultados foram alcançados com a utilização dos coeficientes de difusão considerando a distância longitudinal da fonte e a altura vertical.
This work presents the solution of two-dimensional advection-diffusion equation stationary to simulate the dispersion of pollutants in the Planetary Boundary Layer. The solution is obtained through the ADMM method (Analytical Multilayer Dispersion Model) and the numerical inversion technique using the algorithm Fixed Talbot. Validation of the solution is proven, statistical parameters, through the confrontation of the concentrations calculated from the model with those obtained experimentally by the Experiment of Prairie Grass. For the determination of the concentration profile of the wind the form of Monin-Obukhov similarity and turbulence parameters with longitudinal distance dependence of source and of vertical height, considering the vertical component of the Eulerian spectrum and according to the model proposed by Hɸjstrup that divides the high and low frequency spectra. To use the comparative effect diffusion coefficient for large diffusion times according. The best results were achieved with the use of diffusion coefficients considering the longitudinal distance from the source and the vertical height.