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1
Lu, Zhengmao. "Evaporation from nanopores : probing interfacial transport." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118723.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 82-87).
Evaporation, a commonly found phenomenon in nature, is widely used in thermal management, water purification, and steam generation as it takes advantage of the enthalpy of vaporization. Despite being extensively studied for decades, the fundamental understanding of evaporation, which is necessary for making full use of evaporation, remains limited up to date. It is in general difficult to experimentally characterize the interfacial heat and mass transfer during evaporation. In this thesis, we designed and microfabricated an ultrathin nanoporous membrane as an experimental platform to overcome some critical challenges including: (1) realizing accurate and yet non-invasive interface temperature measurement; (2) decoupling the interfacial transport resistance from the thermofluidic resistance in the liquid phase and the diffusion resistance in the vapor phase; and (3) mitigating the blockage risk of the liquid-vapor interface due to nonevaporative contaminants. Our nano device consisted of an ultrathin free-standing membrane (~200 nm thick) containing an array of nanopores (pore diameter ~100 nm). A gold layer deposited on the membrane served as an electric heater to induce evaporation as well as a resistive temperature detector to closely monitor the interface temperature. This configuration minimizes the thermofluidic resistance in the liquid and mitigates the contamination risk. We characterized evaporation from this nano device in air as well as pure vapor. We demonstrated interfacial heat fluxes of ~~500 W/cm² for evaporation in air, where we elucidated that the Maxwell- Stefan equation governed the overall transport instead of Fick's law, especially in the high flux regime. In vapor, we achieved kinetically limited evaporation with an interfacial heat transfer coefficient up to 54 kW/cm² K. We utilized the kinetic theory with the Boltzmann transport equation to model the evaporative transport. With both experiments and modeling, we demonstrated that the kinetic limit of evaporation is determined by the pressure ratio between the vapor in the far field and that generated by the interface. The improved fundamental understanding of evaporation that we gained indicates the significant promise of utilizing an ultrathin nanoporous design to achieve high heat fluxes for evaporation in thermal management, desalination, steam generation, and beyond.
by Zhengmao Lu.
Ph. D.
2
Levitz, Pierre, Patrick Bonnaud, Pierre-Andre Cazade, Roland J. M. Pellenq, and Benoit Coasne. "Molecular intermittent dynamics in interfacial confinement." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184681.
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Levitz, Pierre, Patrick Bonnaud, Pierre-Andre Cazade, Roland J. M. Pellenq, and Benoit Coasne. "Molecular intermittent dynamics in interfacial confinement." Diffusion fundamentals 16 (2011) 16, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13745.
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Fang, Chao. "Pore-scale Interfacial and Transport Phenomena in Hydrocarbon Reservoirs." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/89911.
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Exploring unconventional hydrocarbon reservoirs and enhancing the recovery of hydrocarbon from conventional reservoirs are necessary for meeting the society's ever-increasing energy demand and requires a thorough understanding of the multiphase interfacial and transport phenomena in these reservoirs. This dissertation performs pore-scale studies of interfacial thermodynamics and multiphase hydrodynamics in shale reservoirs and conventional oil-brine-rock (OBR) systems.
In shale gas reservoirs, the imbibition of water through surface hydration into gas-filled mica pores was found to follow the diffusive scaling law, but with an effective diffusivity much larger than the self-diffusivity of water molecules. The invasion of gas into water-filled pores with width down to 2nm occurs at a critical invasion pressure similar to that predicted by the classical capillary theories if effects of disjoining pressure and diffusiveness of water-gas interfaces are considered. The invasion of oil droplets into water-filled pores can face a free energy barrier if the pressure difference along pore is small. The computed free energy profiles are quantitatively captured by continuum theories if capillary and disjoining pressure effects are considered. Small droplets can invade a pore through thermal activation even if an energy barrier exists for its invasion.
In conventional oil reservoirs, low-salinity waterflooding is an enhanced oil recovery method that relies on the modification of thin brine films in OBR systems by salinity change. A systematic study of the structure, disjoining pressure, and dynamic properties of these thin brine films was performed. As brine films are squeezed down to sub-nanometer scale, the structure of water-rock and water-oil interfaces changes marginally, but that of the electrical double layers in the films changes greatly. The disjoining pressure in the film and its response to salinity change follow the trend predicted by the DLVO theory, although the hydration and double layer forces are not simple additive as commonly assumed. A notable slip between the brine film and the oil phase can occur.
The role of thin liquid films in multiphase transport in hydrocarbon reservoirs revealed here helps lay foundation for manipulating and leveraging these films to enhance hydrocarbon production and to minimize environmental damage during such extraction.Doctor of Philosophy
Meeting the ever-increasing energy demand requires efficient extraction of hydrocarbons from unconventional reservoirs and enhanced recovery from conventional reservoirs, which necessitate a thorough understanding of the interfacial and transport phenomena involved in the extraction process. Abundant water is found in both conventional oil reservoirs and emerging hydrocarbon reservoirs such as shales. The interfacial behavior and transport of water and hydrocarbon in these systems can largely affect the oil and gas recovery process, but are not well understood, especially at pore scale. To fill in the knowledge gap on these important problems, this dissertation focuses on the pore-scale multiphase interfacial and transport phenomena in hydrocarbon reservoirs. In shales, water is found to imbibe into strongly hydrophilic nanopores even though the pore is filled with highly pressurized methane. Methane gas can invade into water-filled nanopores if its pressure exceeds a threshold value, and the thin residual water films on the pore walls significantly affect the threshold pressure. Oil droplet can invade pores narrower than their diameter, and the energy cost for their invasion can only be computed accurately if the surface forces in the thin film formed between the droplet and pore surface are considered. In conventional reservoirs, thin brine films between oil droplet and rock greatly affect the wettability of oil droplets on the rock surface and thus the effectiveness of low-salinity waterflooding. In brine films with sub-nanometer thickness, the ion distribution differs from that near isolated rock surfaces but the structure of water-brine/rock interfaces is similar to their unconfined counterparts. The disjoining pressure in thin brine films and its response to the salinity change follow the trend predicted by classical theories, but new features are also found. A notable slip between the brine film and the oil phase can occur, which can facilitate the recovery of oil from reservoirs.
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Wang, Xia. "Simulations of Two-phase Flows Using Interfacial Area Transport Equation." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1282066341.
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Liu, Ying. "Nanoscale Thermal Transport at Graphene-Soft Material Interfaces." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71715.
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Nanocomposites consist of graphene dispersed in matrices of soft materials are promising thermal management materials. A fundamental understanding of the thermal transport at graphene-soft material interfaces is essential for developing these nanocomposites. In this dissertation, thermal transport at graphene-octane interfaces was investigated using molecular dynamics simulations, and the results revealed several important characteristics of such thermal transport.
The interfacial thermal conductance of graphene-octane interfaces were studied first. It was found that the interfacial thermal conductance exhibits a distinct duality: if heat enters graphene from one side of its basal plane and leaves it through the other side, the corresponding interfacial thermal conductance, Gacross, is large; if heat enters graphene from both sides of its basal plane and leaves it at a position far away on its basal plane, the corresponding interfacial thermal conductance, Gnon-across, is small. Gacross is ~30 times larger than Gnon-across for a single-layer graphene immersed in liquid octane. Additional analysis showed that this duality originates partially from the strong, positive correlations between the heat fluxes at the two surfaces of a graphene layer.
The interfacial thermal conductance of the graphene-soft material interfaces in presence of defects in the graphene was then studied. The results showed that the heat transfer at the interfaces is enhanced by defects. Estimations based on effective medium theories showed that the effective thermal conductivity of the graphene-based composites could even be enhanced with defects in graphene when heat transfer at the graphene-soft material interface is the bottleneck for the thermal transport in these composites.
To describe the interfacial thermal transport at graphene interfaces uniformly, a nonlocal constitutive model was proposed and validated to replace the classical Kapitza model. By characterizing the thermal transport properties of graphene interfaces using a pair of thermal conductance, the model affords a uniform description of the thermal transport at graphene interfaces for different thermal transport modes. Using this model, the data interpretation in time domain thermalreflectance (TDTR) measurements was investigated, and the results showed that the interfacial thermal conductance measured in typical TDTR tests is that of the across mode for thin-layered materials.Ph. D.
7
Greco, Pierpaolo <1977>. "Microfluidic device and interfacial transport: application to biomolecules and nanostructures." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1663/.
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The aim of my dissertation is to provide new knowledge and applications of microfluidics in a variety of problems, from materials science, devices, and biomedicine, where the control on the fluid dynamics and the local concentration of the solutions containing the relevant molecules (either materials, precursors, or biomolecules) is crucial. The control of interfacial phenomena occurring in solutions at dierent length scales is compelling in nanotechnology for devising new sensors, molecular electronics devices, memories.
Microfluidic devices were fabricated and integrated with organic electronics devices. The transduction involves the species in the solution which infills the transistor channel and confined by the microfluidic device. This device measures what happens on the surface, at few nanometers from the semiconductor channel. Soft-lithography was adopted to fabricate platinum electrodes, starting from platinum carbonyl precursor. I proposed a simple method to assemble these nanostructures in periodic arrays of microstripes, and form conductive electrodes with characteristic dimension of 600 nm. The conductivity of these sub-microwires is compared with the values reported in literature and bulk platinum. The process is suitable for fabricating thin conductive patterns for electronic devices or electrochemical cells, where the periodicity of the conductive pattern is comparable with the diusion length of the molecules in solution.
The ordering induced among artificial nanostructures is of particular interest in science. I show that large building blocks, like carbon nanotubes or core-shell nanoparticles, can be ordered and self-organised on a surface in patterns due to capillary forces. The eective probability of inducing order with microfluidic flow is modeled with finite element calculation on the real geometry of the microcapillaries, in soft-lithographic process.
The oligomerization of A40 peptide in microconfined environment represents a new investigation of the extensively studied peptide aggregation. The added value of the approach I devised is the precise control on the local concentration of peptides together with the possibility
to mimick cellular crowding. Four populations of oligomers where distinguished, with diameters ranging from 15 to 200 nm. These aggregates could not be addresses separately in fluorescence. The statistical analysis on the atomic force microscopy images together with a model of growth reveal new insights on the kinetics of amyloidogenesis as well as allows me to identify the minimum stable nucleus size. This is an important result owing to its implications in the understanding and early diagnosis and therapy of the Alzheimer’s disease
8
Sharma, Prabhakar. "Effect of centrifugal and interfacial forces on colloid transport and mobilization." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Fall2007/P_Sharma_112907.pdf.
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Manzanares-Papayanopoulos, Emilio. "Bulk and interfacial molecular structure near liquid-liquid critical points." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327623.
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Atay, N. Z. "Transport and interfacial exchange kinetics in one- and two-phase disperse systems." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374831.
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Kyndiah, Adrica <1987>. "Interfacial interactions, charge transport and growth phenomena in Organic Field Effect Transistors." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7100/.
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Organic electronics is an emerging field with a vast number of applications having high potential for commercial success. Although an enormous progress has been made in this research area, many organic electronic applications such as organic opto-electronic devices, organic field effect transistors and organic bioelectronic devices still require further optimization to fulfill the requirements for successful commercialization. The main bottle neck that hinders large scale production of these devices is their performances and stability. The performance of the organic devices largely depends on the charge transport processes occurring at the interfaces of various material that it is composed of. As a result, the key ingredient needed for a successful improvement in the performance and stability of organic electronic devices is an in-depth knowledge of the interfacial interactions and the charge transport phenomena taking place at different interfaces. The aim of this thesis is to address the role of the various interfaces between different material in determining the charge transport properties of organic devices. In this framework, I chose an Organic Field Effect Transistor (OFET) as a model system to carry out this study as it An OFET offers various interfaces that can be investigated as it is made up of stacked layers of various material. In order to probe the intrinsic properties that governs the charge transport, we have to be able to carry out thorough investigation of the interactions taking place down at the accumulation layer thickness. However, since organic materials are highly instable in ambient conditions, it becomes quite impossible to investigate the intrinsic properties of the material without the influence of extrinsic factors like air, moisture and light. For this reason, I have employed a technique called the in situ real-time electrical characterization technique which enables electrical characterization of the OFET during the growth of the semiconductor.
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Liu, Hua. "Investigation on Transport Mechanisms and Interfacial Properties of Solar Cells By Simulation." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1365873270.
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Inyang, Oto-Obong Andrew. "Magnetic proximity effect and interfacial spin dependent transport in ferromagnet/heavy metal thin films." Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12795/.
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Platinum (Pt) has widely been used for interface driven spintronics applications due to its strong spin-orbit interaction. Pt has been reported to experience spin polarisation when placed in close proximity to a ferromagnetic (FM) material thereby influencing many spintronic phenomena. Consequently, the effect of proximity induced magnetization (PIM) in Pt is studied in this thesis with a detailed investigation of the mechanism and the implications of PIM on magnetoresistance measurements. In this work, CoFeTaB (CFTB) is the FM material investigated. Structural and magnetic characterisation of CFTB/Pt, Pt/CFTB and Pt/CFTB/Pt samples were made in order to investigate PIM at the interface. X-ray reflectivity (XRR) and x-ray diffraction (XRD) were performed on these samples, where asymmetry in the Pt density and the crystalline texture were observed at the top and bottom interfaces. XRD measurements show the Pt crystalline texture depends on the CFTB thickness for the CFTB/Pt interface, but no significant thickness dependence was observed for the Pt/CFTB interface. The magnetic depth profile of the CFTB layer was obtained with polarised neutron reflectivity (PNR), which shows magnetisation grading. An asymmetry in Pt magnetisation was found between the two interfaces using x-ray resonant magnetic reflectivity (XRMR) with a higher moment at the top interface and lower at the buffer interface, giving a similar CFTB thickness dependence as the XRD results. This indicated that the Pt magnetisation depends slightly on Pt texture at the interface. No PIM was found in a YIG/Pt bilayer and the Pt XRD texture was poor, supporting a possible link of Pt polarisation to crystalline the morphology at the interface. Magnetoresistance investigations in three geometries performed on Pt/CFTB and CFTB/Pt bilayers were used to decouple the magnetoresistance contributions as a result of the anisotropy of the sample, spin Hall effect and other processes. The spin Hall MR ratio obtained was ~0.2 %, with an additional contribution with a cos θ dependence of ~0.1 %, which is a result of the impact of PIM generated spin current. No evidence of the Rashba effect was found in the symmetric CFTB/Pt/CFTB sample. Also, residual plots indicated the presence of higher harmonics that are dependent on the magnetisation direction. Temperature dependent proximity induced magnetism in Pt in contact with CFTB was presented, with PNR providing the magnetic sensitivity to the FM layer while the XRMR provide sensitivity to Pt magnetisation. PIM scales linearly with CFTB magnetisation which is inconsistent with the Pauli susceptibility. Significantly, a threshold CFTB magnetization is required for PIM to occur. Therefore the asymmetry in PIM at Pt/CFTB and CFTB/Pt interface is attributed to different magnetic susceptibilities at these interfaces.
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Bradley, Colin. "Understanding Charge Transport and Selectivitiy in Ionically Functionalized Fullerenes for Electron-Selective Interfacial Layers." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23171.
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Significant improvements in power conversion efficiency (>10%) of emerging thin-film photovoltaics have been achieved in the last 5 years. High efficiencies would not be possible without the development of new selective interfacial layers. However, a complete understanding of how interfacial layers function to improve the selectivity of charge extracting contacts in thin-film photovoltaics is still being sought. The goal of this work is to contribute to the understanding of the operation of selective interfacial layers based on the study of ionically functionalized fullerenes. Just as other ionically functionalized materials have shown promise as electron-selective interfacial layers in organic photovoltaics and mixed organic-inorganic halide perovskites, Chapter II demonstrates the utility of ionically functionalized fullerenes. High performing solar cells necessitate the use of conductive interfacial layers; anomalously high conductivity in ionically functionalized materials, which have been used as interfacial layers, has been ascribed to self-doping. This work demonstrates that less than 1% of an ionically functionalized fullerene is reduced in its highly conductive pristine state and is concurrent with the presence of distinct chemical species. These studies describe how the chemical origin of the high conductivity of ionically functionalized fullerenes does not require the invocation of direct anion reduction or significant chemical transformations such as Hofmann-like elimination reactions occurring to a stoichiometric degree. This work also addresses the question of how the selectivity of a charge extracting contact is improved by the presence of an interfacial layer. The quantification of energy barrier reduction, which is often discussed in terms of work function modification or energy-level alignment, is demonstrated using metal|semiconductor junctions modified with an ionically functionalized fullerene. The barrier height of high work function electrodes was reduced significantly, by as much as 0.45 V, and was correlated to thin (2–5 nm) portions of the film rather than fullerene aggregates. The studies that comprise this work form a coherent model for understanding the key factors that have resulted in the continued use of ionically functionalized interfacial layers, their high conductivity, and energy barrier modification of the charge extracting electrodes. This dissertation contains coauthored, previously published, and unpublished work.10000-01-01
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Bahukudumbi, Pradipkumar. "Energy landscape and electric field mediated interfacial colloidal assembly." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5883.
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Chemically and physically patterned surfaces can be used as templates to guide
nano- and micro- scale particle assembly, but the design is often limited by an inability
to sufficiently characterize how pattern features influence local particle-surface
interactions on the order of thermal energy, kT. The research outlined in this dissertation
describes comprehensive optical microscopy (i.e. evanescent wave, video)
measurements and analyses of many-body and multi-dimensional interactions, dynamics
and structure in inhomogeneous colloidal fluid systems. In particular, I demonstrate
how non-intrusive observation of an ensemble of particles diffusing past each other and
over a physically patterned surface topography can be used to obtain sensitive images of
energy landscape features. I also link diffusing colloidal probe dynamics to energy
landscape features, which is important for understanding the temporal imaging process
and self-assembly kinetics. A complementary effort in this dissertation investigated the
use of external AC electric fields to reversibly tune colloidal interactions to produce
metastable ordered configurations. In addition, the electrical impedance spectra associated with colloidal assemblies formed between interfacial microelectrode gaps was
measured and consistently modelled using representative equivalent circuits.
Significant results from this dissertation include the synergistic use of the very
same colloids as both imaging probes and building blocks in feedback controlled selfassembly
on patterns. Cycling the AC field frequencies was found to be an effective
way to anneal equilibrium colloidal configurations. Quantitative predictions of
dominant transport mechanisms as a function of AC electric field amplitude and
frequency were able to consistently explain the steady-state colloidal microstructures
formed within electrode gaps observed using video microscopy. A functional electrical
switch using gold nanoparticles was realized by reversibly forming and breaking
colloidal wires between electrode gaps. Extension of the concepts developed in this
dissertation suggest a general strategy to engineer the assembly of colloidal particles into
ordered materials and controllable devices that provide the basis for numerous
emerging technologies (e.g. photonic crystals, nanowires, reconfigurable antennas,
biomimetic materials).
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Gonçalves, Bruno Batista. "Detalhando a solução unidimensional do método OQA com função coeficiente de redução constante aplicado ao transporte escalar interfacial turbulento." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-01092014-091040/.
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A adequada quantificação do transporte interfacial de escalares em escoamentos turbulentos é de interesse prático para os processos industriais e para a gestão dos problemas ambientais. O fenômeno é matematicamente complexo devido ao uso de equações governantes estatísticas não lineares e não fechadas. Neste estudo, analisam-se detalhes do método de Ondas Quadradas Aleatórias (OQA), o qual fornece uma quantificação estatística que permite fechar as equações e obter um perfil normalizado da grandeza de interesse para a transferência unidimensional turbulenta de escalares, que, num caso idealizado, depende de apenas dois parâmetros adimensionais, A e k (neste caso, k representa um coeficiente de transferência e A depende da interação entre os fenômenos de transporte molecular e turbulento). Simulações numéricas foram realizadas no intuito de se verificar a influência das derivadas de ordem superior para a função normalizada de concentração. A sensibilidade do modelo e a análise de aspectos intrínsecos ao mesmo foram também realizadas. Importante análise das condições de contorno empregadas foi desenvolvida com a inserção de um contorno adicional, com base física, no seio líquido. Como os estudos iniciais tinham se concentrado em exemplos de transferência de massa, uma extensão para o caso de transporte de calor foi considerada. Os resultados obtidos reproduzem o comportamento dos dados experimentais observados na literatura.The adequate quantification of interfacial scalar transport in turbulent flows is of practical interest for industrial processes and in environmental problems. The phenomenon is mathematically complex due to the use of unclosed nonlinear statistical equations. In this study, we analyze details of the method of Random Square Waves (RSW), which provides a statistical quantification that allows closing the set of equations and getting the normalized scalar profile of the one-dimensional turbulent scalar variable, which, in an idealized case, depends on only two nondimensional parameters, k and A (in this case, k represents a transfer coefficient and A depends on the interaction between the molecular and turbulent transports). Numerical simulations were performed in order to verify the influence of the higher order of derivatives over the normalized concentration function. The sensitivity of the model to the relevant parameters and the analysis of its intrinsic parameters were also performed. An important aspect is the analysis of the boundary conditions, for which an additional condition was proposed and employed in the bulk liquid (with based on physical grounds). Because the initial studies have focused on examples of mass transfer, an extension to the case of heat transport was here considered. The results reproduce the behavior of experimental data reported in the literature.
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Maya, Visuet Enrique. "Electrolyte Transport And Interfacial Initiation Mechanisms Of Zinc Rich Epoxy Nanocoating/Substrate System Under Corrosive Environment." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1430762942.
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Ripollés, Sanchis Teresa. "Interfacial and Bulk Operation of Polymeric Solar Cells by Optoelectronics and Structural Techniques." Doctoral thesis, Universitat Jaume I, 2014. http://hdl.handle.net/10803/277095.
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This Ph.D. Thesis focuses on the investigation of organic photovoltaic (OPV) technology, especially in aspects of experimental device processing, and optoelectronic and electrical characterization on OPV devices to be readily marketable. More specifically, the topics addressed are the following: origin of recombination current,open-circuit voltage and crystallinity, transport driving force, contact selectivity and interface states, alternative hole transporting layers and oxygen and degradation routes.
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Cristian, Alina. "Systèmes moléculaires et matériaux structurés pour la conduction ionique et le transport d’eau." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS114/document.
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L'objectif de ce travail de recherche est l'étude du transport des ions et des molécules d'eau à travers de membranes bicouche lipidique et des membranes polymériques. Dans une première partie, ce transport a été réalisé à travers des systèmes synthétiques auto-organisés, dont la sélectivité est en étroite relation avec le type d'architecture supramoléculaire formée grâce à des liaisons faibles. Le but est d'obtenir des systèmes qui peuvent imiter les fonctions de transport des protéines membranaires. Ce mimétisme fonctionnel est obtenu par l'auto-assemblage de molécules organiques contenant le cycle imidazole et la fonction urée, qui peuvent s'auto-assembler et créer des voies sélectives de transport des ions. Pour créer l'équivalent de la membrane cellulaire, nous avons utilisé des vésicules lipidiques unilamellaires. Ensuite, nous avons déterminé une relation entre l'activité des composés et leur structure. Pour ce faire, le transport des ions est étudié à l'aide d'une méthode de spectroscopie de fluorescence, et le transport d'eau par diffusion dynamique de la lumière utilisant la technique de « stopped flow ». Le but de la deuxième partie est la fabrication et la caractérisation des nouvelles membranes composites sous forme de couches minces, qui permettraient un bon compromis entre le flux d'eau et le rejet de sel. Dans ce cadre, la synthèse d'une série d'hydrazides en tant que précurseurs moléculaires a été réalisée, pour remplacer la métaphenylène diamine (MPD) classiquement utilisée. Ici aussi les liaisons hydrogène jouent un rôle important, car le principe de la séparation repose sur la création d'une organisation interne hautement réticulée. Les polymères synthétisés par polymérisation interfaciale ont été caractérisés par des méthodes de spectroscopie infrarouge, analyses thermogravimétriques et diffraction des rayons X. Les membranes composites ont été caractérisées par microscopie électronique à balayage, microscopie à force atomique et mesures d'angle de contact. Les performances membranaires ont été testées en filtration frontale d'eau et de solutions salinesThe aim of this work is the study of ion and water transport either across bilayer membranes or polymeric membranes used for reverse osmosis. In the first part, this transport through self-assembled synthetic systems was studied; the transport selectivity is in strong relation with the supramolecular structure, formed by weak intra and intermolecular bonds. Ion transport is studied by fluorescence spectroscopy and water transport is studied by light scattering using “stopped flow” technique. The objective is to obtain systems that could imitate transport functions of biomolecules as transmembrane proteins. This functional mimicry is achieved through self-assembly of organic molecules containing imidazole cycle and urea function that can self-assembly and form selective pathways for ion transport. To create the equivalent of the cell membrane, we used unilamellar lipid vesicles. Then, we determined a structure - transport activity relationship for a series of synthesized compounds. For the second part of this work we described the fabrication and the characterization of new thin film composite membranes for water desalination that can present a good balance between permeability and salt rejection. A series of hydrazides as molecular precursors was synthesized in order to replace the metaphenylene diamine (MPD), classically used. Again, hydrogen bonds play an important role, because the rejection is due to a high cross-linking. The polymers synthesized by interfacial polymerization were characterized by infrared spectroscopy, thermogravimetric analysis, and X-Ray diffraction. The membrane films were characterized by scanning electron microscopy, atomic force microscopy and contact angle measurements. Membrane performances were then tested in cross-flow filtration of water and saline solutions
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Rouhnia, Mohamad. "Vertical Transport of Sediment from Muddy Buoyant River Plumes in the Presence of Different Modes of Interfacial Instabilities." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/82506.
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This study focuses on deposition processes from sediment laden buoyant river plumes in deltaic regions. The goal is to experimentally examine the effects of various physical phenomena influencing the rate at which sediment is removed from the plume. Previous laboratory and field measurements have suggested that, at times, sedimentation can take place at rates higher than that expected from individual particle settling (i.e., C{W}_{s}). Two potential drivers of enhanced sedimentation are flocculation and interfacial instabilities. We experimentally measured the sediment fluxes from each of these processes using two sets of laboratory experiments that investigate two different modes of instability, one driven by sediment settling and one driven by fluid shear. The settling-driven and shear-driven instability sets of experiments were carried out in a stagnant stratification tank and a stratification flume respectively. In both sets, continuous interface monitoring and concentration measurement were made to observe developments of instabilities and their effects on the removal of sediment. Floc size was measured during the experiments using a separate floc camera setup and image analysis routines. Results from the stratification tank experiments suggest that the settling-driven gravitational instabilities do occur in the presence of flocs, and that they can produce sedimentation rates higher than those predicted from floc settling. A simple cylinder based force balance approach adopting the concept of critical Grashof number was used to develop a model for the effective settling velocity under settling-driven instabilities that is a function of sediment concentration in the plume only. Results from the stratification flume experiments show that under shear instabilities, the effective settling velocity is greater than the floc settling velocity, and increases with plume velocity and interface mixing. The difference between effective and floc settling velocity was denoted as the shear-induced settling velocity. This settling rate was found to be a strong function of the Richardson number, and was attributed to mixing processes at the interface. Conceptual and empirical analysis shows that the shear-induced settling velocity is proportional to U{Ri}^{-2}.
Following the experiments, analyses were made among contributions of different mechanisms on the total deposition rate, and the locations that the various mechanisms may be active in the length of a plume. This analysis leads to a conceptual discretization of a plume into three zones of sedimentation behavior and Richardson number. The first zone is the supercritical near-field plume with intense interface mixing. Zone two represents the subcritical region where interface mixing still occurs, and zone three is the high Richardson number zone where mixing at the interface is effectively nonexistent. In zones one and two, individual floc settling and shear-induced settling mechanisms play the major roles in removing sediment from the plume. While, shear-induced settling rate was found to be maximum near the river mouth, its share of the total settling rate increases in the crossshore direction, since sand and large particulates deposit near the inlet and only small particles (with relatively low settling velocity) remain as the plume propagates. The third zone, starts when the interfacial mixing diminishes and leaking commences.Ph. D.
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Gao, Xiao. "Elucidation of Ionomer/Electrode Interfacial Phenomena in Polymer Electrolyte Fuel Cells." Kyoto University, 2020. http://hdl.handle.net/2433/254528.
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Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第22708号
人博第958号
新制||人||227(附属図書館)
2020||人博||958(吉田南総合図書館)
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授 内本 喜晴, 教授 高木 紀明, 教授 中村 敏浩
学位規則第4条第1項該当
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Crozier, Paul S. "Slab-geometry molecular dynamics simulations : development and application to calculation of activity coefficients, interfacial electrochemistry, and ion channel transport /." Diss., CLICK HERE for online access:, 2001. http://contentdm.lib.byu.edu/ETD/image/etd15.pdf.
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Crozier, Paul S. "Slab-Geometry Molecular Dynamics Simulations: Development and Application to Calculation of Activity Coefficients, Interfacial Electrochemistry, and Ion Channel Transport." BYU ScholarsArchive, 2002. https://scholarsarchive.byu.edu/etd/2.
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Methods of slab-geometry molecular dynamics computer simulation were tested, compared, and applied to the prediction of activity coefficients, interfacial electrochemistry characterization, and ion transport through a model biological channel-membrane structure. The charged-sheets, 2-D Ewald, corrected 3-D Ewald, and corrected particle-particle-particle-mesh (P3M) methods were compared for efficiency and applicability to slab-geometry electrolyte systems with discrete water molecules. The P3M method was preferred for long-range force calculation in the problems of interest and was used throughout.
The osmotic molecular dynamics method (OMD) was applied to the prediction of liquid mixture activity coefficients for six binary systems: methanol/n-hexane, n-hexane/n-pentane, methanol/water, chloroform/acetone, n-hexane/chloroform, methanol/ chloroform. OMD requires the establishment of chemical potential equilibrium across a semi-permeable membrane that divides the simulation cell between a pure solvent chamber and a chamber containing a mixture of solvent and solute molecules in order to predict the permeable component activity coefficient at the mixture side composition according to a thermodynamic identity. Chemical potential equilibrium is expedited by periodic adjustment of the mixture side chamber volume in response to the observed solvent flux. The method was validated and shown to be able to predict activity coefficients within the limitations of the simple models used.
The electrochemical double layer characteristics for a simple electrolyte with discrete water molecules near a charged electrode were examined as a function of ion concentration, electrode charge, and ion size. The fluid structure and charge buildup near the electrode, the voltage drop across the double layer, and the double layer capacitance were studied and were found to be in reasonable agreement with experimental findings.
Applied voltage non-equilibrium molecular dynamics was used to calculate the current-voltage relationship for a model biological pore. Ten 10-nanosecond trajectories were computed in each of 10 different conditions of concentration and applied voltage. The channel-membrane structure was bathed in electrolyte including discrete water molecules so that solvation, entry, and exit effects could be studied. Fluid structure, ion dynamics, channel selectivity, and potential gradients were examined. This work represents the first such channel study that does not neglect the vital contributions of discrete water molecules.
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AL-AZMI, BADER SHABEEB. "ANALYSIS OF TRANSPORT MODELS AND COMPUTATION ALGORITHMS FOR FLOW THROUGH POROUS MEDIA." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1051059625.
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MBANGANGOYE, BERNARD. "Modelisation des ecoulements multiphasiques dans les lignes de transport petrolier - contribution a l'etude du frottement interfacial en regime stratifie liquide-gaz." Paris, ENSAM, 2001. http://www.theses.fr/2001ENAM0003.
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Ce travail concerne la modelisation des ecoulements multiphasiques dans les conduites horizontales et faiblement inclinees. Il s'agit plus particulierement d'etudier le frottement interfacial en regime stratifie liquide-gaz. Pour ce faire, une methode de comparaison des correlations du coefficient de frottement interfacial est presentee. Cette methode est basee sur le calcul du gradient de pression et le taux de presence des phases en utilisant chacune des correlations. Les resultats obtenus sont compares a des donnees experimentales, et montrent qu'aucune des correlations presentees ne predit, a la fois de facon satisfaisante, le gradient de pression et le taux de presence des phases. Par la suite, une voie de modelisation pouvant substituer l'usage des correlations est exploree. Il s'agit d'estimer les contraintes interfaciale et parietale en s'appuyant sur la loi de distribution universelle des vitesses obtenue a l'aide de la theorie de la couche limite et, appliquee a chacune des phases. On resout ensuite les equations de base du regime stratifie, pour determiner le gradient de pression et le taux de presence des phases. Les resultats obtenus presentent un bon accord, comparativement a des donnees experimentales. Enfin, une etude de stabilite du regime stratifie est abordee. Le modele utilise fait appel a une linearisation des equations de base dudit regime, on developpe ensuite une solution harmonique donnant l'evolution de la perturbation ainsi que la condition critique definissant le debut de l'instabilite.
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Delvert, Alexandre. "Étude de la formation, du transport et de la destruction par vidange de bulles interfaciales." Thesis, Rennes 1, 2020. https://ged.univ-rennes1.fr/nuxeo/site/esupversions/62340f16-03da-4a74-a405-afba30b16427.
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Les bulles sont des objets du quotidien qui nous ont amusés étant enfant. Elles sont aussi une source d’inspiration pour les artistes et un outil pédagogique important pour introduire diverses notions de physique. Il n’est pas étonnant que ces objets soient à l’origine de recherches scientifiques depuis des siècles. Dans ce manuscrit, nous nous intéressons à la formation, au transport et à la destruction de bulles interfaciales c’est à dire des bulles en contact avec un solide ou une interface air-liquide. D’abord, nous présentons une expérience sur la formation de bulles interfaciales par impact, à vitesse constante, de films liquides sur la surface d’un bain du même liquide. L’air piégé entre la surface libre du bain et le film liquide conduit à la formation une bulle dont la taille augmente avec la vitesse d’impact. Nous montrons l’existence de deux régimes d’écoulements d’air qui contrôlent la formation de ces bulles : l’un régi par un mécanisme visco-capillaire à basse vitesse d’impact, l’autre, à haute vitesse d’impact, par une compétition entre inertie et capillarité. Nous présentons par la suite une étude sur la vidange d’une bulle interfaciale. Nous revisitons le problème classique de la vidange d’un réservoir en étudiant le cas d’un réservoir déformable, c’est à dire une bulle interfaciale posée sur une plaque percée d’un trou. La vidange est étudiée en fonction des paramètres clefs géométriques et physico-chimiques du problème. Nous montrons que le temps de vidange peut être compris en modélisant l’écoulement d’air qui s’échappe d’une bulle à l’aide du théorème de Bernoulli, et que le déplacement d’une bulle pendant la vidange est piloté par la capillarité et est limité par la friction agissant au pied de la bulle. Nous développons dans le dernier chapitre une méthode éducative pour mesurer la viscosité de l’air avec un matériel expérimental simple de nos vies quotidiennes : un smartphone, un entonnoir, un tube et de l’eau savonneuse. L’expérience consiste à étudier le déplacement spontané d’un film liquide mince dans un entonnoir. Nous montrons que cette expérience peut servir de viscosimètre à air dans des conditions pour lesquelles l’écoulement de l’air peut être décrit par l’équation de Poiseuille et le film liquide se déplace de façon quasi-statiqueBubbles are everyday-life fluid objects that amused us when we were children. Also, they are a source of the inspiration for artists and an important educational tool to introduce several notions of physics. Not surprisingly, these objects are at the origin of many scientific studies for centuries. In this manuscript, we are interested in the formation, travel and destruction of interfacial bubbles, i.e., bubbles in contact with a solid or an air-liquid interface. First, we present an experiment about the formation of interfacial bubbles by the impact, at constant velocity, of liquid films on the free surface of a liquid bath. The air trapped between the bath and the liquid film drives the formation of an interfacial bubble and its size increases with the impact velocity. We show the existence of two distinct regimes of the air flow : one of them is governed by a visco-capillary mechanism at low impact velocity, the other, at high impact velocity, is driven by a competition between inertia and capillarity. Thereafter, we present a study about shrinking surface soap bubbles. We revisit the classical problem of the draining of a tank studying the case of a deformable tank, i.e. , an interfacial bubble sitting on a plate drilled with a circular orifice. Shrinking is studied as functions of key setting geometric and physicochemical parameters of the problem. We show the shrinking time can be understood with a model for the air flow based on Bernoulli’s principle, and a motion of a bubble during the shrinking that is driven by capillarity and is limited by the friction acting on its foot. We develop in the last chapter an educative method to measure the air viscosity with simple experimental equipment regularly used in our everyday life : a smartphone, a funnel, a pipe and soap solution. The experiment consists of studying the spontaneous motion of a thin liquid film in a funnel. We show this experiment can be used as a viscosimeter for gases (air in our experiments) with the conditions make the air flow describable by the Poiseuille’s equation and the liquid film moves quasi-statically
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Doup, Benjamin. "Methodology Development of a Gas-Liquid Dynamic Flow Regime Transition Model." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1409031809.
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Akbar, Muhammad Khalid. "Transport Phenomena in Complex Two and Three-Phase Flow Systems." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4897.
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Two and three-phase flow processes involving gas, liquid and solid, are common in nature and industry, and include some of the most complex and poorly-understood transport problems. In this research hydrodynamics, heat and mass transfer processes in complex two and three-phase flows were investigated. The interfacial surface area concentration in a short vertical column subject to the through flow of fiber-liquid-gas slurry was experimentally measured using the gas absorption technique. The experimental data were statistically analyzed for parametric effects, and were empirically correlated. The absorption of a gaseous species by a slurry droplet with internal circulation and containing reactive micro-particles was simulated, and parametrically studied. The micro-particles were found to enhance the absorption rate. The absorption rate was sensitive to droplet recirculation, and shrinkage of particles with time resulted in declining absorption rates. The transport of soot particles, suspended in laminar hot gas flowing in a tube, was modeled and parametrically studied. Due to coupled thermal radiation and thermophoresis, a radially-nonuniform temperature profile develops, leading to sharp, non-uniform radial soot-concentration profiles. The assumption of monodisperse particles leads to over-prediction of thermophoresis. The transport and removal of particles suspended in bubbles rising in a stagnant liquid pool were modeled based on a Eulerian – Monte Carlo method. The bubble hydrodynamics were treated in Eulerian frame, using the Volume-of-Fluid (VOF) technique, while particle equations of motion were numerically solved in Lagrangian frame. The bubbles undergo shape change, and have complex internal circulation, all of which influence the particle removal. Model predictions were also compared with experimental data. Using a resemblance between two-phase flow in microchannels, and in large channels at microgravity, a simple Weber number-based two-phase flow regime map was developed for microchannels. Based on the available air-water experimental data, a criterion for the prediction of conditions that lead to flow regime transition out of the stratified-wavy flow pattern in horizontal annular channels was proposed. The thermocapillary effects on liquid-vapor interface shape during heterogeneous bubble ebullition in microchannels were analytically studied.
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Pellacani, Filippo [Verfasser], Rafael [Akademischer Betreuer] Macián-Juan, and Vicent Sergio [Akademischer Betreuer] Chiva. "Development and Validation of Bubble Breakup and Coalescence Constitutive Models for the One-Group Interfacial Area Transport Equation / Filippo Pellacani. Gutachter: Sergio Chiva Vicent ; Rafael Macián-Juan. Betreuer: Rafael Macián-Juan." München : Universitätsbibliothek der TU München, 2012. http://d-nb.info/104199480X/34.
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Croeser, Sophia Louw. "Interfacing Marabastad." Diss., Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-05182005-112742.
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Kuidjo, Kuidjo Emmanuel Vianney. "Towards a predictive model to reproduce flow regime transitions in gas-liquid flows with Neptune CFD : from a dispersed to a separated regime." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0456.
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Dans les réacteurs nucléaires, divers régimes d’écoulement gaz-liquide peuvent apparaître avec des transitions entre eux. La modélisation de ces transitions dans les codes CFD 3D requière le traitement d’interfaces déformables de différentes tailles, la prise en compte d’interactions par coalescence et fragmentation ainsi que le développement de lois de fermeture indépendantes du régime. Ce travail vise la modélisation et la simulation de l’hydrodynamique des écoulements gaz-liquide adiabatiques grâce à un modèle bi-fluide à trois champs dans Neptune CFD. Dans une première étape, un modèle avec un champ liquide continu et deux champs de gaz dispersés représentant petites et grandes bulles est utilisé pour simuler des écoulements cap et churn avec un taux de vide jusqu’à 0.5 et une emphase est mise sur la prédiction de l’aire interfaciale. Dans une seconde étape, le deuxième champ dispersé est remplacé par un champ hybride continu/dispersé représentant les grandes bulles et les régions continues de gaz. Le modèle est validé sur plusieurs régimes d’écoulements en tuyaux de large diamètre et dans des canaux rectangulaires confinésIn nuclear reactors, several regimes of gas-liquid flows may occur with some transitions between them. The main challenges associated with simulating these transitions in 3D CFD codes are associated with deformable interfaces of different sizes, accounting for coalescence and breakup interactions between gas structures and developing flow regime independent closure relations. This work aims at modelling and simulating the hydrodynamics of adiabatic gas-liquid flows thanks to a three-field two-fluid model in Neptune CFD. In a first step, a model with one continuous liquid field and two dispersed gas fields for small and large bubbles is used to simulate cap and churn flows with a void fraction up to 0.5 and a focus is put on the interfacial area prediction. In a second step, the second dispersed field is replaced by a hybrid continuous/dispersed field representing both large bubbles and continuous gas regions. The model is validated on several flow regimes in large diameter pipes and in confined rectangular channels
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Alali, Abdullah [Verfasser], Rafael [Akademischer Betreuer] Macián-Juan, and Vicent Sergio [Akademischer Betreuer] Chiva. "Development and validation of new solver based on the interfacial area transport equation for the numerical simulation of sub-cooled boiling with OpenFOAM CFD code for nuclear safety applications / Abdullah Alali. Gutachter: Sergio Chiva Vicent ; Rafael Macián-Juan. Betreuer: Rafael Macián-Juan." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1048677257/34.
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Penny, Melissa. "Mathematical modelling of dye-sensitised solar cells." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16270/.
Full textAbstract:
This thesis presents a mathematical model of the nanoporous anode within a dyesensitised solar cell (DSC). The main purpose of this work is to investigate interfacial charge transfer and charge transport within the porous anode of the DSC under both illuminated and non-illuminated conditions. Within the porous anode we consider many of the charge transfer reactions associated with the electrolyte species, adsorbed dye molecules and semiconductor electrons at the semiconductor-dye- electrolyte interface. Each reaction at this interface is modelled explicitly via an electrochemical equation, resulting in an interfacial model that consists of a coupled system of non-linear algebraic equations. We develop a general model framework for charge transfer at the semiconductor-dye-electrolyte interface and simplify this framework to produce a model based on the available interfacial kinetic data. We account for the charge transport mechanisms within the porous semiconductor and the electrolyte filled pores that constitute the anode of the DSC, through a one- dimensional model developed under steady-state conditions. The governing transport equations account for the diffusion and migration of charge species within the porous anode. The transport model consists of a coupled system of non-linear differential equations, and is coupled to the interfacial model via reaction terms within the mass-flux balance equations. An equivalent circuit model is developed to account for those components of the DSC not explicitly included in the mathematical model of the anode. To obtain solutions for our DSC mathematical model we develop code in FORTRAN for the numerical simulation of the governing equations. We additionally employ regular perturbation analysis to obtain analytic approximations to the solutions of the interfacial charge transfer model. These approximations facilitate a reduction in computation time for the coupled mathematical model with no significant loss of accuracy. To obtain predictions of the current generated by the cell we source kinetic and transport parameter values from the literature and from experimental measurements associated with the DSC commissioned for this study. The model solutions we obtain with these values correspond very favourably with experimental data measured from standard DSC configurations consisting of titanium dioxide porous films with iodide/triiodide redox couples within the electrolyte. The mathematical model within this thesis enables thorough investigation of the interfacial reactions and charge transport within the DSC.We investigate the effects of modified cell configurations on the efficiency of the cell by varying associated parameter values in our model. We find, given our model and the DSC configuration investigated, that the efficiency of the DSC is improved with increasing electron diffusion, decreasing internal resistances and with decreasing dark current. We conclude that transport within the electrolyte, as described by the model, appears to have no limiting effect on the current predicted by the model until large positive voltages. Additionally, we observe that the ultrafast injection from the excited dye molecules limits the interfacial reactions that affect the DSC current.
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Richardson, Jerry Christopher. "Transport, vaporization, and ionization in particle beam liquid chromatography/mass spectrometry interfacing." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/30974.
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Karcher, Viviane. "Determinação da energia interfacial de emulsões de agua em oleo pesado." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265665.
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Orientador: Antonio Carlos BannwartDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica e Instituto de Geociencias
Made available in DSpace on 2018-08-12T08:12:48Z (GMT). No. of bitstreams: 1 Karcher_Viviane_M.pdf: 1731022 bytes, checksum: 355de3e34591ff15d14ab367330328f8 (MD5) Previous issue date: 2008
Resumo: Durante a produção de petróleo, é comum o aparecimento de água sob a forma de gotas finamente dispersas no óleo. A água pode ser oriunda de métodos de recuperação avançada e/ou do próprio reservatório (água conata). O cisalhamento turbulento produzido durante o escoamento destes fluidos através de dutos ou dispositivos, como bombas, ou até mesmo no reservatório, pode causar a formação de emulsões de água em óleo (A/O). Para os óleos pesados,estas emulsões permanecem estáveis por um período longo devido à presença de agentes emulsificantes naturais no petróleo cru. Por essa razão, a separação dessas emulsões necessita de equipamentos específicos, o que contribui para o aumento do custo do processo. O objetivo deste estudo é investigar as propriedades interfaciais de emulsões A/O compostas por água e petróleo pesado brasileiro. Para tanto, um aparato experimental foi construído com o objetivo de calcular a energia interfacial dessas emulsões. As emulsões A/O foram geradas através de um aparelho homogeneizador rotativo imerso em um vaso calorimétrico. Dois métodos foram empregados: o método calorimétrico, baseado no balanço de energia da emulsificação, e o método padrão, baseado na medida do tamanho e distribuição das gotas através da técnica de microscopia óptica. As incertezas nas medidas experimentais, em ambos os métodos, foram estudadas a fim de avaliar a viabilidade de cada um. Como principais resultados deste estudo, as magnitudes relativas dos termos do balanço de energia durante a emulsificação foram obtidas. O comportamento reológico destas emulsões também foi estudado.
Abstract: In petroleum production operations, water is commonly present within the oil phase as a finely dispersed phase. This situation originates from enhanced oil recovery methods and/or the presence of connate water inside the own reservoir. The turbulent shear associated with fluid flow during of heavy crude transportation through pipelines may cause the formation of water-in-oil emulsions (W/O). These remain stable for a long time, due the presence of naturally emulsifying agents in the crude oil phase. Therefore, emulsion separation requires specific equipments which contribute to increase the processes costs. The main purpose of this study is to investigate the interfacial properties of W/O emulsions composed by water and a Brazilian heavy crude oil. For that purpose an experimental set-up was built in order to measure the interfacial energy of the emulsions. The W/O emulsions were prepared in a calorimeter vessel by using a rotating impeller. Two methods were used, namely, the calorimetric method based on the energy balance for the emulsification and the standard method of the droplet size and distribution by means of a digital microscope. The uncertainty in experimental measurements was determined for both methods, in order to evaluate their feasibility. The main result of this research is the determination of the relative magnitudes of the different terms in the energy balance during emulsification. Results for the rheological behavior of W/O emulsions are also reported.
Mestrado
Explotação
Mestre em Ciências e Engenharia de Petróleo
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Castro, Pollyana Souza. "Desenvolvimento de microssensores eletroquímicos e aplicações no estudo de processos dinâmicos interfaciais utilizando microscopia eletroquímica de varredura." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-06042016-145742/.
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O trabalho descrito nesta tese mostra de forma detalhada a fabricação e caracterização de diferentes microssensores eletroquímicos os quais têm sido recentemente utilizados como sondas em grupo de técnicas conhecida como Scanning Electrochemical Probe Microscopy (SEPM). Desta forma, a caracterização de superfícies pode ser feita explorando diferentes fenômenos interfaciais relevantes à Ciência. Neste sentido, as interfaces de materiais cristalinos como hidroxiapatita (materiais dentários) e calcita foram o foco de estudo neste trabalho. Assim, diferentes técnicas SEPM foram exploradas no sentido de se obter informações relevantes relacionadas aos processos dentários, como a erosão ácida e hipersensibilidade. Inicialmente, microeletrodos de platina foram desenvolvidos empregando uma metodologia convencional na qual são utilizados microfibras encapsuladas em capilares de vidro. Scanning Electrochemical Microscopy (SECM) no modo amperométrico foi utilizada para obtenção de informações com relação às alterações de topografia do esmalte dentário causadas pelo contato com substâncias ácidas. Adicionalmente, SECM foi empregada no estudo do transporte de espécies eletroativas em amostras de dentina e investigações relacionadas ao bloqueio dos túbulos empregando-se cremes dentais comerciais foram realizadas. A permeação de peróxido de hidrogênio pela dentina também foi estudada. Os resultados de SECM foram comparados com imagens SEM obtidas nas mesmas condições experimentais. Microeletrodos de membrana ionófora íon-seletiva (Ion Selective Microelectrodes-ISMEs) sensíveis a íons cálcio também foram desenvolvidos e caracterizados, com subsequente aplicação em SECM no modo potenciométrico. A dissolução ácida de esmalte bovino (erosão dentária) foi investigada em diferentes valores de pH (2,5; 4,5; 6,8). Além disso, o transporte de íons cálcio através de membranas porosas sintéticas foi avaliado a uma distância tip/substrato de 300µm. Alterações no fluxo de íons cálcio foram correlacionadas em experimentos realizados na presença e ausência de campos magnéticos gerados por nanopartículas de magnetita incorporadas à membrana porosa. Microcristais de calcita facilmente sintetizados pelo método de precipitação foram utilizados como superfície modelo para investigações interfaciais, cujos resultados podem ser correlacionados aos materiais dentários. Desta forma, nanopipetas de vidro preenchidas com eletrólito suporte foram fabricadas e utilizadas como sonda em Scanning Ion Conductance Microscopy (SICM). O mapeamento topográfico de alta resolução espacial da superfície de um microcristal de calcita foi obtido utilizando o modo de varredura hopping mode. Adicionalmente, sondas multifuncionais ISME-SICM também foram desenvolvidas e caracterizadas para investigações simultâneas com relação às alterações topográficas e quantificação de íons cálcio sobre a superfície de um microcristal de calcita. A adição de reagentes ácidos no canal SICM promoveu a dissolução da superfície do microcristal, sendo obtidos dados cinéticos de dissolução. Investigações em meio neutro também foram realizadas utilizando a sonda ISME-SICM. Os resultados experimentais obtidos também foram comparados com aqueles oriundos de simulação computacional.The study reported in this thesis shows in details the fabrication and characterization of different electrochemical microsensors which have been employed as probes in SEPM. Thus, the characterization of surfaces can be performed by exploiting different interfacial phenomena that are relevant to life sciences. In this sense, the interfaces of crystalline materials such as hydroxyapatite (dental materials) and calcite were the focus of this study. Thus, different SEPM techniques were explored in order to obtain relevant information related to dental materials processes such as acid erosion and hypersensitivity. Initially, platinum microelectrodes were developed employing conventional methodology that utilizes microfibers encapsulated in glass capillaries. Amperometric SECM mode was used to obtain information regarding the topography changes of tooth enamel caused by contact with acid chemicals. In addition, SECM was used to study the transport of electroactive species in dentin samples. Investigations related to the treatment of dental hypersensitivity and dental whitening were also evaluated. SECM results were compared with SEM images obtained under the same experimental conditions. Ion-selective microelectrode (ISME) based on the ionophore membrane sensitive to calcium ions were also developed and characterized followed by application in SECM potentiometric mode. The acid dissolution of bovine enamel (dental erosion) was investigated at different pH values (2.5; 4.5; 6.8). In addition, the transport of calcium ions through synthetic porous membranes was evaluated at a tip/substrate distance of 300µm. Changes in calcium ion flux were studied in the presence and absence of magnetic fields generated by magnetite nanoparticles incorporated into the porous membrane. Calcite microcrystals easily synthesized by precipitation method were used as a model of an interfacial surface for investigations which can be correlated to the dental materials. Thus, glass nanopipette filled with supporting electrolyte was fabricated and used as SICM probe. The high resolution topographic mapping of the calcite microcrystal was obtained using hopping mode. Additionally, ISME-SICM multifunction probes were developed and characterized for simultaneous investigations related to the topographical changes and quantification of local calcium ions on the surface of a calcite microcrystal. The addition of acidic reagents in the SICM channel promoted the dissolution of the microcrystal surface and dissolution kinetic data were obtained. Investigations in neutral medium were also studied using the ISME-SICM multifunctional probe. The experimental results were also compared with those obtained by computer simulation.
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Penny, Melissa. "Mathematical modelling of dye-sensitised solar cells." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16270/1/Melissa_Penny_Thesis.pdf.
Full textAbstract:
This thesis presents a mathematical model of the nanoporous anode within a dyesensitised solar cell (DSC). The main purpose of this work is to investigate interfacial charge transfer and charge transport within the porous anode of the DSC under both illuminated and non-illuminated conditions. Within the porous anode we consider many of the charge transfer reactions associated with the electrolyte species, adsorbed dye molecules and semiconductor electrons at the semiconductor-dye- electrolyte interface. Each reaction at this interface is modelled explicitly via an electrochemical equation, resulting in an interfacial model that consists of a coupled system of non-linear algebraic equations. We develop a general model framework for charge transfer at the semiconductor-dye-electrolyte interface and simplify this framework to produce a model based on the available interfacial kinetic data. We account for the charge transport mechanisms within the porous semiconductor and the electrolyte filled pores that constitute the anode of the DSC, through a one- dimensional model developed under steady-state conditions. The governing transport equations account for the diffusion and migration of charge species within the porous anode. The transport model consists of a coupled system of non-linear differential equations, and is coupled to the interfacial model via reaction terms within the mass-flux balance equations. An equivalent circuit model is developed to account for those components of the DSC not explicitly included in the mathematical
model of the anode. To obtain solutions for our DSC mathematical model we develop code in FORTRAN for the numerical simulation of the governing equations. We additionally employ regular perturbation analysis to obtain analytic approximations to the solutions of the interfacial charge transfer model. These approximations facilitate a reduction in computation time for the coupled mathematical model with no significant loss of accuracy. To obtain predictions of the current generated by the cell we source kinetic and transport parameter values from the literature and from experimental measurements associated with the DSC commissioned for this study. The model solutions we obtain with these values correspond very favourably with experimental data measured from standard DSC configurations consisting of titanium dioxide porous films with iodide/triiodide redox couples within the electrolyte. The mathematical model within this thesis enables thorough investigation of the interfacial reactions and charge transport within the DSC.We investigate the effects of modified cell configurations on the efficiency of the cell by varying associated parameter values in our model. We find, given our model and the DSC configuration investigated, that the efficiency of the DSC is improved with increasing electron diffusion, decreasing internal resistances and with decreasing dark current. We conclude that transport within the electrolyte, as described by the model, appears to have no limiting effect on the current predicted by the model until large positive voltages. Additionally, we observe that the ultrafast injection from the excited dye molecules limits the interfacial reactions that affect the DSC current.
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Seo, Youngmi. "Structure and Dynamic Properties of Interfacially Modified Block Copolymers from Molecular Dynamics Simulations." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492628195548591.
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Jha, Neha [Verfasser], Peter [Akademischer Betreuer] Oppeneer, Markus [Gutachter] Münzenberg, and Peter [Gutachter] Oppeneer. "Interfacially Tuned Spin Transport Towards Molecular Spintronics / Neha Jha ; Gutachter: Markus Münzenberg, Peter Oppeneer ; Betreuer: Peter Oppeneer." Greifswald : Universität Greifswald, 2021. http://d-nb.info/1237413400/34.
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White, Joey. "USING DATAFLOW ARCHITECTURE TO SOLVE THE TRANSPORT LAG PROBLEM WHEN INTERFACING WITH AN ENGINEERING MODEL FLIGHT COMPUTER IN A TELEMETRY SIMULATION." International Foundation for Telemetering, 1991. http://hdl.handle.net/10150/613183.
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International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, NevadaOne of the most challenging technical problems in the development of a spacecraft telemetry simulation is the interface with a flight computer running real-world flight software. The ability of the simulation to satisfy flight software requests for telemetry data, and to load, mode, and control the flight software along with the simulation, can be constrained or degraded using conventional interface solutions. Telemetry dataflow architecture systems can be utilized to solve the interface problems with less constraints. This is an especially attractive solution in a telemetry simulation where the telemetry system can also be used to format and serialize spacecraft telemetry, and receive and preprocess commands. This paper discusses the concepts developed for such a system for a training simulation of the Orbital Maneuvering Vehicle for NASA at Johnson Space Center.
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Ahmad, Ahmad. "Caractérisation globale et locale de l'écoulement à surface libre et en charge de systèmes liquide-liquide : application au procédé d’injection pariétale pour le transport des pétroles bruts." Brest, 2010. http://www.theses.fr/2010BRES2013.
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Le travail de recherche décrit dans la présente thèse, considère l’écoulement à surface libre et en charge de systèmes liquide/liquide. La première partie du mémoire est consacrée à l’étude de la propagation d’un courant gravitaire à la surface d’un liquide ambiant plus dense et miscible, au repos. Nous avons relâché à la surface d’un bassin d’eau salée, un débit contrôlé d’eau douce, puis de solutions polymères afin de caractériser à l’aide d’une méthode basée sur l’analyse des images et l’exploitation des diagrammes spatio-temporels, l’effet de la rhéofluidification sur l’avancée, l’étalement et l’enfoncement du courant gravitaire dans le liquide ambiant. Une caractérisation locale consistant en la mise au point d’une PIV grande échelle, visant à décrire les champs hydrodynamiques dans l’un et l’autre fluides a complété l’étude globale précédente. La seconde partie présente quant à elle, considère un écoulement en-courant eau/huile dans une conduite, afin de simuler le procédé d’injection pariétale de transport de pétrole brut par pipeline, ce dernier étant représenté par une huile dôtée d’une très forte viscosité et d’un comportement viscoplastique. Nous avons notamment caractérisé l’effet de la pente et du rapport des débits sur les pertes de charge globales, afin de définir les conditions de fonctionnement de plus grande efficacité du procédé. Une caractérisation locale des instabilités interfaciales a complété l’étude globale précédenteThe present dissertation reports on investigations on open-channel flows and Poiseuille flows of liquid/liquid systems. The first part of the dissertation considers the propagation of a gravity current over a denser ambient miscible liquid. A controlled flow rate of fresh water and of polymer solutions were released upon the free surface of an ambient salty water at rest in a basin, in order to characterize with te help of a method based on image analysis and the exploitation of spatio-temporal diagrams, the effect of polymer shear-thinning property on the temporal evolution of front progress and spreading of gravity current in ambient liquid and of mixing layer depth as well. A local study consisting in the development of a large scale PIV, aiming at describe to hydrodynamic fields existing in both fluids completed the previous global study. The second part of the dissertation considers a co-current water/oil flow in a duct, in order to simulate the lubricated pipelining of heavy crude oils which were being represented by oils gifted with high viscosity and a viscoplastic rheological behaviour. The effect of bed slope and flow rates ratio on global pressure drop were characterized in order to define the conditions of process optimal efficiency. A local characterization of the interfacial instabilities completed the previous global investigation
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Morel, Floriane. "Compréhension des phénomènes interfaciaux dans les composites à base de charges carbonate de calcium précipité : influence du traitement de surface et du procédé de mise en œuvre." Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00733711.
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Ce travail a eu pour objectif la création de matériaux composites à base de nanocharges de carbonate de calcium. L'étude des phénomènes interfaciaux qui régissent ces systèmes, ainsi que leurs impacts sur les propriétés fonctionnelles du matériau et plus particulièrement des propriétés de transport, ont été réalisées. Pour ce faire, nous avons considéré deux matrices polymères de nature chimique différente : le polylactide et le polyfluore de vinylidène. Les nanocomposites ont été élaborés par deux voies de mise en œuvre : la voie fondu et la voix solvant. Une analyse fine des relations structure/morphologie/propriétés des composites a été réalisée. Nous avons mis en évidence, quelle que soit la matrice polymère choisie, l'importance du traitement de surface des charges afin d'améliorer leurs états de dispersion dans le matériau et d'augmenter la qualité de l'interface charge/polymère. Ces paramètres ont été corrélés aux propriétés de transport de ces matériaux composites.
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Bai, Guiyu. "Interfacial transport driven by redox active surfactants." 2005. http://catalog.hathitrust.org/api/volumes/oclc/64280381.html.
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"Microscale transport phenomena and interfacial reactions in diverse applications." Tulane University, 2021.
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archives@tulane.eduInterfacial phenomena and reactions commonly occur in our daily life. A wide range of applications from industrial products to medical technology involve interfacial phenomena such as water-repellent fabrics, non-stick Teflon and motor oils. Motor oils contain different additives such as overbased detergents and dispersants. These additives are well suspended in oil phase by surfactants. Various reactions take place between these additives and contaminant particles, and different behaviors of particle dispersion also play an important role on affecting the reactions. To obtain deep understanding of the phenomena, a cost effective and time saving method is developed to study the behavior of microscale transport phenomena and interfacial reactions kinetics. The first part of the thesis investigates designing and developing a microdevice, heating capillary video microscopy system. The technique provides direct visual observation and quantification, and can be operated at high temperatures. The developing process involves fabrication and characterization of transparent and conductive ITO (Indium Tin Oxide) thin film. Sol-gel dip coating process was used to coat the thin film. Factors that affect film performance was discussed. Immersing time and heat treatment temperature had significant effects on film conductivity. The optimal coating conditions was determined with immersing time 30 seconds, heat treatment temperature 500℃, coating times: 3 , and dipping rate 7 cm/min. The second part of the work is one of the applications with the low-cost method, “Time-dependence of Asphaltene Dispersion by MCL Surfactants”. With combining grayscale image analysis, HFO (Heavy Fuel Oil) dispersion kinetics is quantified and discussed. Effects on HFO dispersion included those of surfactants’ type, over-basing level and temperature, while also discussing what Carbon chain lengths can be expected to perform better. For same-chain-length surfactants, samples with higher concentration of base showed lower ability of dispersing HFO. The third part of the thesis is to study Ethanol’s Effects on Acid Neutralization by Motor Oils. Sulfuric-acid neutralization kinetics by motor oils in the presence of ethanol was investigated for the first time in literatures by quantitatively visualizing the fate of acid drops in commercial motor oils via capillary video-microscopy. A very different behavior was exhibited at 100 ℃, with rate of acid neutralization being much faster in the presence of ethanol than in absence. With 1% ethanol and temperature of 100 ℃, acid droplets were neutralized in 2 minutes, whereas at room temperature droplets expanded ~35% in diameter after 60 minutes with little neutralization. This phenomenon is a valuable information for discussing the impact of ethanol blended gasoline on engines and for further, especially for low temperature environments. The last part is to study temperature and salting out effects on nicotine. Nicotine dissolution rates and diffusion coefficients in different NaCl concentration solutions are quantified and calculated with Epstein- Plesset Model. The results will be used for future research to design a continuous separation process to reach environmentally and economical goal.
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Chia-yu Chen
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Lin, Chu Loong, and 林志隆. "qelected Problems on Interfacial Transport Phenomena in Two- phase Systems." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/37038924283335861438.
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博士國立成功大學
航空太空工程學系
84
The present study constitutes an integral part of fundamentaland applied research on the mechanics and combustion of two-phase flow systems, in particular liquid-bubble anddroplet-gas flow in modern spray combustion and relatedtechnological applications. The study focuses attentionon the theoretical and numerical analysis of three selected topics, including transient group combustion of premixed clusters, the dynamic and thermochemical response of an air bubble under a sudden compression of the surrounding liquid fuel and finally, the spray combustion analysisand optimal design of the combustion efficiency of hybrid rockets
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Chang, Yu-Cheng, and 張羽成. "Interfacial Charge Transport Kinetics in Dye-Sensitized and Perovskite Solar Cell." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/nzaekk.
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博士國立交通大學
應用化學系碩博士班
102
This study has investigated the electron transfer behaviour of dye sensitized solar cells (DSSC) and perovskite solar cell (PSC) using a range of time-resolved and steady state techniques. The enhanced understanding of these processes was then utilized to develop unique strategies to circumvent performance limitations associated with injection or recombination, thereby improving the power conversion efficiencies of the devices. In this study, four characterization techniques have been reported, transient photocurrent and photovoltage decay measurements, charge extraction measurement, photoinduced absorption spectroscopy and transient absorption spectroscopy. This thesis provide an account of each technique about its operating principle, experimental setup and data analysis. The transient photoelectric measurements, are obtained under short-circuit and open-circuit conditions, respectively, and the electron diffusion coefficients and electron lifetimes are extracted from fitting the decay curves accordingly. For the photoinduced absorption spectroscopy, which is useful in the characterization of long-lived (> μs) non-radiative excited states and used as the first step for transient absorption measurement. As case studies for each technique, examples are given to rationalize the observed potential shift, decay coefficients of electron transport and of charge recombination in relation to the corresponding photovoltaic performance of the device. For porphyrin dyes and organic dyes, by using the transient photoelectric measurements to understand the charge recombination process and TiO2 potential shift; for TiO2 nanostructure, we measured the charge transport kinetics with different morphology TiO2. For perovskite solar cell, we used these techniques to study the charge transport kinetics of the devices.
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Li, Xueliang. "Transport phenomena in foam fractionation." Thesis, 2012. http://hdl.handle.net/1959.13/932169.
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Research Doctorate - Doctor of Philosophy (PhD)This dissertation consists of experimental and theoretical approaches towards a better understanding of some principal aspects of the foam fractionation process: (i) interfacial adsorption, (ii) foam stability, (iii) foam hydrodynamics and (iv) process intensification and device design. Studies on interfacial adsorption include a flexible and robust numerical solution to the Ward-Tordai equation that can be used with any adsorption isotherm. The scheme makes use of the trapezium rule of numerical integration, coupled with the bisection method of root-finding to guarantee local consistency. The scheme is found to be robust and efficient. However, it is made clear that Ward-Tordai equation is only applicable for the adsorption of non-ionic surfactants onto quiescent planar or convex interfaces. For the adsorption of ionic surfactants onto the surface of a rising bubble in a foam fractionation column, experiments are carried out to study the rate and extent of adsorption. It is found that adsorption equilibrium of SDS (sodium dodecyl sulphate) in both the liquid pool and the foam layer can be achieved within 0.2 m of column depth. However, the equilibrium surface excess on a rising bubble is lower than that on a quiescent interface. Studies of foam stability include direct observation of inter-bubble gas diffusion in foams with different liquid fractions and the effect of environmental humidity on foam stability. Inter-bubble gas diffusion is found to be slow and only becomes significant in long term foam stability tests. However, inter-bubble gas diffusion itself does not lead to the collapse of a foam layer. Instead, it is shown conclusively that the bursting of bubbles at the free surface of a foam and the collapse of a foam layer are affected by the humidity gradient in the freeboard of a foam column. A mechanism based on the Marangoni instability is proposed to explain the dependency of foam stability on humidity. The mechanism is supported by experimental observations of the bursting of an isolated bubble under conditions of non-uniform evaporation via high speed video recording. The behaviour of pneumatic foams flowing vertically through an expansion or a contraction is theoretically and experimentally studied. It is demonstrated that although a sudden contraction of flow area decreases the in situ liquid fraction, it does not affect the volumetric liquid over-flow rate. Conversely, a sudden expansion of flow area decreases both the liquid fraction and the volumetric liquid over-flow rate. Implications of this analysis for foam fractionation device design, optimisation and process intensification are discussed. Finally, based on the theoretical analysis, a mechanistic explanation is proposed for a process intensification device. The device consists of a plate with a tube (foam riser) mounted in the centre. The plate has the same diameter of the foam column whilst the tube is narrower. When a foam riser-plate assembly is inserted into a conventional foam column, the foam is forced through a contraction of flow area followed by an expansion. A significant reduction in liquid flux is observed, without diminishing the surface area. However, due to the adsorption isotherm of SDS, the enrichment enhancement measured in the experiments herein is modest. It is believed that if the device is applied to other systems such as proteins where the adsorption isotherm favours high enrichment, the enhancement of enrichment will be more significant. The device is not optimised for any specific system in the current study. Several major aspects of foam fractionation technology that have only been addressed separately by different researchers previously are investigated on a systematic basis here. It is hoped that the work has not only provided enhanced mechanistic understanding of the foam fractionation process, but that it will also promote industrial adoption of the technology.
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Lin, Chun-Ta, and 林均達. "Miniemulsion/miniemulsion polymerization dealing with interfacial behavior, thermodynamics, transport phenomena, and polymerization." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/47130425225365904220.
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博士國立臺灣科技大學
化學工程系
103
The modified Kabal’nov equation developed by a thermodynamic approach dealing with a regular solution of monomer and conventional low molecular weight costabilizer as the two-component disperse phase adequately described the Ostwald ripening rate data in a wide range of the volume fraction of costabilizer for styrene miniemulsions stabilized by a homolog of n-alkane costabilizers (CnH2n+2; n=10, 12, 16, 18, 20, 24, 32) upon aging at 25 ℃. The results showed that the costabilizer with the shortest chain length (C10H22) is not hydrophobic enough to effectively retard the Ostwald ripening process. The effectiveness of n-alkanes as costabilizer in suppressing the Ostwald ripening process increases with increasing n-alkane molecular weight. Nevertheless, further increasing the n-alkane chain length from C24H50 to C32H66 does not lead to significant improvement in the effectiveness of n-alkane as costabilizer. Another mechanistic model that describes the Ostwald ripening behavior with a regular solution of monomer (styrene (ST) herein) and different polymeric costabilizers as the disperse phase of miniemulsion in such a colloidal system was developed. The validity of this model was verified by the Ostwald ripening rate data obtained from ST miniemulsions stabilized by living polystyrene costabilizer (PSlc) or polystyrene costabilizer (PSc) upon aging at 25 ℃. PSlc is more effective in retarding the Ostwald ripening process than PSc, though PSlc and PSc have comparable number-average molecular weights. The model can be also used to study the mutual interaction between monomer and polymeric costabilizer. Satisfactory modeling results achieved for ST miniemulsions using polymethyl methacrylate as the costabilizer (PMMAc) further verify the general validity of the present model. The values of heat of mixing and interaction parameter between ST and different polymeric costabilizers were also determined. We then investigated the effects of the molecular weight of PSc and PMMAc on the Ostwald ripening behavior at 25 ℃ of ST miniemulsions and the polymerization of these miniemulsions. The effectiveness of PSc and PMMAc in retarding the diffusional degradation of ST miniemulsions decreases with increasing the molecular weight of PSc or PMMAc. The Ostwald ripening rate data were used to determine the critical chain length of polymeric costabilizers to induce chain entanglements. The resultant critical chain length to induce chain entanglements is 363871475 and 7668521 g mol-1 for PSc and PMMAc, respectively, which are comparable to those reported in the literature. The polymerization of the ST miniemulsions stabilized by PMMAc with different molecular weights at 70 ℃ were then carried out. The polymerization rate decreases with increasing the polymeric costabilizer molecular weight. This was attributed to the reduced number of latex particles (i.e., reaction loci) with the polymeric costabilizer molecular weight. The miniemulsion polymerization kinetics is primarily controlled by the particle nucleation process (the competition between the monomer droplet nucleation and homogeneous nucleation), which is closely related to the effectiveness of these costabilizers in retarding the Ostwald ripening process. Finally, RAFT miniemulsion polymerizations of styrene with living polystyrene (PSlc) serving as both RAFT reagent and polymer costabilizer were discussed. The miniemulsion upon aging at 25 oC showed satisfactory stability against the Ostwald Ripening process. The rate of polymerization for RAFT miniemulsion polymerization initiated by oil-soluble AIBN is much slower than that for the water-soluble SPS counterpart. In addition to the predominant monomer droplet nucleation, much stronger particle nucleation taking place in the continuous aqueous phase (homogeneous nucleation) for the run with AIBN was observed. It is the different extents of homogeneous nucleation that is responsible for the quite different kinetic behaviors between the RAFT miniemulsion polymerizations initiated by different types of initiator (AIBN versus SPS). Furthermore, increasing initial molar ratio of RAFT reagent to AIBN greatly enhances the characteristics of RAFT polymerization (i.e., better control over polymer chain growth with the progress of polymerization).
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Hahn, Thomas. "Interfacial electrokinetic transport phenomena and their impact on DNA electrophoresis in microfluidics." Phd thesis, 2011. http://tuprints.ulb.tu-darmstadt.de/2433/1/PhDthesis_Hahn.pdf.
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The dissertation examines two different options to separate DNA based on differences in size by utilising electric fields. Each of the techniques is based on a new approach and faces several fundamental problems concerning electrokinetics. A microfluidic environment is chosen to experimentally investigate DNA electrophoresis at a small scale. A sophisticated setup is employed that on the one hand enables a multiphase flow, while at the same time it stabilises two immiscible polymer phases in a microfluidic compartment. An aqueous two-phase system consisting of poly(ethylene glycol) and dextran provides a stable liquid-liquid interface under quiescent conditions. Such a setup allows the application of an electric field perpendicular to the liquid-liquid interface. In doing so, DNA accumulates at the interface. The parameters influencing the electrophoretic adsorption process are examined in detail. A highlight of the experimental investigations is desorption of DNA from the interface that is triggered by increasing the electric field strength. The latter phenomenon affords a separation of different sized DNA fragments across the liquid-liquid interface. Smaller DNA fragments desorb at lower field amplitudes while larger ones desorb at larger field strengths. Although liquid-liquid interfacial phenomena in aqueous two-phase systems are complex, a preliminary understanding is achieved addressing basic theoretical issues. In the following the reader is introduced into a second and alternative setup to yield a size separation of DNA. The approach is based on traditional capillary electrophoresis. The novelty is examined by combining several preconcentration techniques with a gel-based size separation of DNA in a preparative manner. The DNA migrates due to the application of an electric field. The preconcentration is accomplished by electrokinetic trapping at a charged membrane embedded into a poly(methyl methacrylate) microchip. It has been found that a fluidic counter flow supports DNA trapping at a membrane. A subsequent DNA size separation is exploited to separate free fetal DNA from maternal DNA in blood of pregnant women providing preliminary results to afford a basis for non-invasive prenatal diagnosis.
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Reeser, Dorea Irma. "Effects of Aqueous Organic Coatings on the Interfacial Transport of Atmospheric Species." Thesis, 2013. http://hdl.handle.net/1807/43714.
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Species must interact with air—aqueous interfaces in order to transport between either phase, however organic coated water surfaces are ubiquitous in the environment, and the physical and chemical processes that occur at organic coated aqueous surfaces are often different than those at pure air—water interfaces. Three studies were performed investigating the transport of species across air—aqueous interfaces with organic coatings in an effort to gain further insight into these processes. Gas and solution phase absorption spectroscopy were used to study the effect of octanol coatings on the formation of molecular iodine (I2) by the heterogeneous ozonation of iodide and its partitioning between phases. Compared to uncoated solutions, the presence of octanol monolayers had a minor effect on the total amount of I2 produced, however, it did significantly enhance the gas to solution partitioning of I2. Incoherent broadband cavity-enhanced absorption spectroscopy (IBBC-EAS) was used to measure the gas-phase nitrogen dioxide (NO2) evolved via photolysis of aqueous nitrate solutions either uncoated or containing octanol, octanoic acid and stearic acid monolayers. Both octanol and stearic acid reduced the rate of gaseous NO2 evolution, and octanol also decreased the steady-state amount of gaseous NO2. Alternatively, octanoic acid enhanced the rate of gaseous NO2 evolution. Finally, the loss of aqueous carbon dioxide (CO2) from aqueous solutions saturated with CO2 was measured using a CO2 electrode in the absence and presence of stearic acid monolayers and octanol coatings, and a greenhouse gas analyzer was used to measure the evolution of gaseous CO2 from solutios with octanol monolayers. Enhanced losses of aqueous and evolved gaseous CO2 were observed with organic coated solutions compared to those uncoated. The results of these studies suggest that organic coatings influence the transport of I2, NO2 and CO2 via one, or a combination of: barrier effects, surface tension effects, chemistry effects and aqueous – surface – gas partitioning effects. These results, particularly the enhanced partitioning of these species to octanol coated aqueous surfaces, have important implications for species transport at air—aqueous interfaces, and may provide useful insight for future studies and parameters for atmospheric models of these species.