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Chemical engineering

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Articles 31 - 60 of 273

Full-Text Articles in Engineering

Synthesis And Characterization Of Nanostructured Aluminas , Weihua Deng Jan 2005

Synthesis And Characterization Of Nanostructured Aluminas , Weihua Deng

Retrospective Theses and Dissertations

In the work, mesoporous aluminas were produced by nonionic supramolecular templating and characterized to determine the stability of their physical structure during extended calcination at elevated temperatures. The effect of synthesis temperature on the physical structure of these materials and the resulting thermal evolution from synthesized aluminum hydroxide to transitional alumina was studied using thermogravimetric analysis. A high resolution multiple quantum magic angle spinning NMR spectroscopy method was used to determine quantitatively the evolution of the aluminum coordination during the thermal processing. The mesoporous alumina exhibited high stability upon prolonged heating, which is essential for their future applications in catalytic ...


Mechanistic Insight Into The Production Of Ethylene Glycol And Propylene Glycol From Biorenewable Resources , Daniel George Lahr Jan 2005

Mechanistic Insight Into The Production Of Ethylene Glycol And Propylene Glycol From Biorenewable Resources , Daniel George Lahr

Retrospective Theses and Dissertations

The production of ethylene glycol and propylene glycol from biorenewable resources, i.e. sorbitol, has been parametrically examined numerous times. However, the current selectivity is too low to be economically feasible. In order to develop improved catalyst systems, a better understanding of the reaction mechanism is required. Sorbitol, due to its many functional groups is quite complex. Thus, in order to begin understanding of this system, analysis of the products is required. The study of the degradation of the product glycols and reaction of glycerol under hydrogenolysis conditions gives foundational insight. The effects of pH, competitive adsorption, and product degradation ...


Force Computations In Automated Docking , Chandrika Mulakala Jan 2005

Force Computations In Automated Docking , Chandrika Mulakala

Retrospective Theses and Dissertations

Automated docking refers to the problem of computing the optimal complementary fit of two molecules---a macromolecular receptor such as DNA or protein and a small molecule of interest (ligand). AutoDock is a docking software that computes the receptor-ligand binding energy to rank docked ligands. In this work, AutoDock's grid-based method for energy evaluation was exploited to complement the binding energies with computed forces on docked ligand atoms. These forces and energies helped to provide insights into enzyme-substrate interaction mechanisms of three different enzymes--- Hypocrea jecorina Cel7A, a cellobiohydrolase, Fusarium oxysporum Cel7B, an endoglucanase, and Saccharomyces cerevisiae alpha-1,2-mannosidase. Cel7A ...


Continuous-Time Block-Oriented Nonlinear Modeling With Complex Input Noise Structure , Dongmei Zhai Jan 2005

Continuous-Time Block-Oriented Nonlinear Modeling With Complex Input Noise Structure , Dongmei Zhai

Retrospective Theses and Dissertations

The continuous-time closed-form algorithms to sinusoidal input changes are proposed and presented for single-input, single-output (SISO) Hammerstein and Wiener systems with the first-order, second-order, and second-order plus lead dynamics. By simulation on theoretical Hammerstein and Wiener systems, the predicted responses agree exactly with the true process values. They depend on only the most recent input change. The algorithms to SISO Hammerstein and Wiener systems can be conveniently extended to the multiple-input, multiple-output (MIMO) systems as shown by the two-input, two-output examples and demonstrated by the simulated seven-input, five-output continuous stirred tank reactor (CSTR). The predictions and the simulated theoretical responses ...


Design Of Catalytic Domains Within Organosulfonic Acid-Functionalized Mesoporous Silica , Isa Kipkoech Mbaraka Jan 2005

Design Of Catalytic Domains Within Organosulfonic Acid-Functionalized Mesoporous Silica , Isa Kipkoech Mbaraka

Retrospective Theses and Dissertations

Organic-inorganic hybrid mesoporous silicas were synthesized via nonionic supramolecular assembly using the co-condensation synthesis technique with the intention of understanding the catalytic domain as well as developing strategies to control the catalytic functionalities at the molecular level. Esterification of free fatty acids in natural oils and fats was used to probe the catalytic activity of the synthesized acid-modified mesoporous catalysts. Application of solid acid catalysts in such reaction systems can possibly simplify the manufacturing process, reducing production costs, as well as eliminate environmental hazards posed by toxic wastes generated in homogeneous catalyzed reactions;The catalytic performance of the functionalized mesoporous ...


The Role Of Reduction In The Deactivation Of Potassium-Promoted Iron Oxide Dehydrogenation Catalysts , Sipho C. Ndlela Jan 2004

The Role Of Reduction In The Deactivation Of Potassium-Promoted Iron Oxide Dehydrogenation Catalysts , Sipho C. Ndlela

Retrospective Theses and Dissertations

One of the largest commercial application for potassium promoted iron oxide catalyst (K-Fe2O3) in petrochemical industry is in the dehydrogenation of ethylbenzene (EB) to styrene (ST). It is generally accepted that the active sites on the K-Fe2O3 catalyst is potassium ferrite (KFeO2), which resides on the surface of a bulk magnetite phase and potassium polyferrite (K2Fe22O 34). This dehydrogenation reaction is typically performed in excess steam and the catalyst is known to experience short-term deactivation when the steam-to-hydrocarbon molar ratio (S/EB) is lowered. While possible causes for the deactivation phenomena are coking or reduction of the reactive site, the ...


Flux Analysis In Central Carbon Metabolism In Plants: 13c Nmr Experiments And Analysis , Ganesh Sriram Jan 2004

Flux Analysis In Central Carbon Metabolism In Plants: 13c Nmr Experiments And Analysis , Ganesh Sriram

Retrospective Theses and Dissertations

Metabolic flux analysis is crucial in metabolic engineering. This research concentrated on improvements in 13C labeling-based flux analysis, a powerful flux quantification method, particularly oriented toward application to plants. Furthermore, systemic 13C flux analyses were performed on two model plant systems: Glycine max (soybean) embryos, and Catharanthus roseus hairy roots.;The concepts 'bond integrity', 'bondomer' and the algorithm 'Boolean function mapping' were introduced, to facilitate efficient flux evaluation from carbon bond labeling experiments, and easier flux identifiability analysis.;13C labeling experiments were performed on developing soybean (Glycine max) embryos and C. roseus hairy roots. A computer program, NMR2Flux, was developed ...


Engineering Bioerodible Polymers With Tailored Micro/Nanostructure For Vaccine Delivery , Matthew J. Kipper Jan 2004

Engineering Bioerodible Polymers With Tailored Micro/Nanostructure For Vaccine Delivery , Matthew J. Kipper

Retrospective Theses and Dissertations

This work describes the investigation of bioerodible polyanhydrides as controlled drug delivery vehicles. The polymers studied are based on the 1,6-bis(p-carboxyphenoxy)hexane (CPH) and sebacic acid (SA) monomers. These two materials erode at vastly different rates and can be combined in random copolymers or blends to achieve tailored erosion kinetics. The hydrophobic nature of these materials offers the potential to stabilize proteins, and their mutual incompatibility and semicrystallinity provide an interesting phase behavior, which can be exploited to aid in tailoring the release kinetics. Theoretical and experimental description of the microstructure of polyanhydride copolymers reveals the details of ...


Combinatorial Synthesis And Screening Of Fuel Cell Catalysts , Shrisudersan Jayaraman Jan 2004

Combinatorial Synthesis And Screening Of Fuel Cell Catalysts , Shrisudersan Jayaraman

Retrospective Theses and Dissertations

Polymer electrolyte membrane fuel cells (PEMFCs) are compact power sources that can operate with high efficiencies and low emission of environmentally harmful gases. One of the major barriers impeding the development of PEMFCs as a competitive energy source is the inability of existing anode catalysts to oxidize fuels other than hydrogen at sufficient levels due to catalyst deactivation by carbon monoxide (CO) and other partial oxidation products. The focus of this research is the development and application of combinatorial strategies to construct and interrogate electrooxidation (anode) catalysts pertaining to PEMFCs to discover catalysts with enhanced performance in catalyst deactivating environments ...


Theoretical And Experimental Explorations In Atomic Force Microscopy , Anil Gannepalli Jan 2004

Theoretical And Experimental Explorations In Atomic Force Microscopy , Anil Gannepalli

Retrospective Theses and Dissertations

Nanotechnology is the capability to build by controlling the arrangement of individual atoms and molecules. Such a technology would be founded on the ability to control, manipulate and investigate matter at the atomic scale. The invention of atomic force microscope (AFM) and the advances in micro-cantilever based scanning probe technology have significantly enhanced the experimental capability to probe and modify matter at the nanoscale. However, it is still severely limited in achieving the necessary bandwidth, sensitivity and resolution. To further the advances in this field an in-depth understanding of the nature and effects of the tip-sample interactions is imperative. A ...


Particle Size Prediction In Reactive Precipitation Processes , Jesse Ted Pikturna Jan 2004

Particle Size Prediction In Reactive Precipitation Processes , Jesse Ted Pikturna

Retrospective Theses and Dissertations

The aqueous reductive precipitation of palladium metal has been studied in semibatch stirred tank reactors. Scale-up from the bench scale to the 20 gallon scale has been studied using empirical scale-up rules. Some of the well-known difficulties and benefits associated with empirical methods for scale-up have been observed in this system.;In order to accurately predict particle size distributions (PSDs) in precipitation reactions, local variations in hydrodynamics, degree of supersaturation, and particle size distributions need to be accurately tracked. Discretized Population Balance (DPB) methods can accurately model precipitation process in well-mixed, uniform shear environments, but the implementation of DPB routines ...


Tnt Phytotransformation In Native And Genetically Modified Species: Significance Of Aromatic Hydroxylamines In The Metabolic Pathway , Murali Subramanian Jan 2004

Tnt Phytotransformation In Native And Genetically Modified Species: Significance Of Aromatic Hydroxylamines In The Metabolic Pathway , Murali Subramanian

Retrospective Theses and Dissertations

The presence and role of hydroxylamines in TNT transformation were ascertained in two axenic (microbe-free) hydroponic plant systems through high TNT feeding experiments and the use of different analytical detection schemes. Hydroxylamines were formed within 10 hours of TNT addition, and usually disappeared within 20 hours, displaying a high turnover rate due to their instability and high reactivity. Hydroxylamines were shown to add biomolecules to their functional group and thereby directly form conjugates. The 4-isomer of the hydroxylamine was detected in very high levels (up to 30% of initial TNT added) in a transgenic tobacco system that had a bacterial ...


Computational Fluid Dynamics Simulation Of Precipitation Processes , Liguang Wang Jan 2004

Computational Fluid Dynamics Simulation Of Precipitation Processes , Liguang Wang

Retrospective Theses and Dissertations

First, an experimental and computational investigation of the effects of local fluid shear rate on the aggregation and breakage of ~10 mum latex spheres suspended in an aqueous solution undergoing laminar and turbulent Taylor-Couette flow was carried out, according to the following program. First, computational fluid dynamics (CFD) simulations were performed and the flow field predictions were validated with data from particle image velocimetry experiments. Subsequently, the quadrature method of moments (QMOM) was implemented into the CFD code to obtain predictions for mean particle size that account for the effects of local shear rate on the aggregation and breakage. These ...


Thermodynamic Property Prediction For Solid Organic Compounds Based On Molecular Structure, Benjamin T. Goodman Nov 2003

Thermodynamic Property Prediction For Solid Organic Compounds Based On Molecular Structure, Benjamin T. Goodman

Theses and Dissertations

A knowledge of thermophysical properties is necessary for the design of all process units. Reliable property prediction methods are essential because reliable experimental data are often not available due to concerns about measurement difficulty, cost, scarcity, safety, or environment. In particular, there is a lack of prediction methods for solid properties. Predicted property values can also be used to fill holes in property databases to understand more fully compound characteristics. This work is a comprehensive analysis of the prediction methods available for five commonly needed solid properties. Where satisfactory methods are available, recommendations are made; where methods are unsatisfactory in ...


Analysis And Design Of A Calcium-Based Sulfur Sorbent For Applications In Integrated Gasification Combined Cycle Energy Systems , David Johann Ludwig Hasler Jan 2003

Analysis And Design Of A Calcium-Based Sulfur Sorbent For Applications In Integrated Gasification Combined Cycle Energy Systems , David Johann Ludwig Hasler

Retrospective Theses and Dissertations

The reactivity of various Ca-based sorbent materials in pelletized form with H2S or CO2 was investigated at high temperatures (750--880°C). An extensive study was conducted to compare the performance of sorbent pellets derived from plaster of Paris and limestone. Multicycle absorption and regeneration tests showed that plaster-based pellets out performed the limestone-based pellets primarily due to a higher surface area and mesoporosity.;The effect of pore-modifiers on the reactivity of limestone with H 2S was investigated by incorporating additives such as cornstarch, graphite and polyvinylalcohol (PVA) in the sorbent. Multicycle sulfidation and regeneration tests of the modified sorbent showed ...


Hybrid Finite-Volume/Transported Pdf Method For The Simulation Of Turbulent Reactive Flows , Venkatramanan Raman Jan 2003

Hybrid Finite-Volume/Transported Pdf Method For The Simulation Of Turbulent Reactive Flows , Venkatramanan Raman

Retrospective Theses and Dissertations

A novel computational scheme is formulated for simulating turbulent reactive flows in complex geometries with detailed chemical kinetics. A Probability Density Function (PDF) based method that handles the scalar transport equation is coupled with an existing Finite Volume (FV) Reynolds-Averaged Navier-Stokes (RANS) flow solver. The PDF formulation leads to closed chemical source terms and facilitates the use of detailed chemical mechanisms without approximations. The particle-based PDF scheme is modified to handle complex geometries and grid structures. Grid-independent particle evolution schemes that scale linearly with the problem size are implemented in the Monte-Carlo PDF solver. A novel algorithm, in situ adaptive ...


Behavior Of Interfacial Micro-Defects In Aluminum And Its Oxide Film , Renchun Huang Jan 2003

Behavior Of Interfacial Micro-Defects In Aluminum And Its Oxide Film , Renchun Huang

Retrospective Theses and Dissertations

In this dissertation, numerical simulation was used to calculate the equilibrium solution composition of cylindrical nanopores in surface oxide films as a step to evaluate their possible roles in the breakdown of protective oxide films. The solution composition of such nanopores is of interest from a corrosion perspective, since they play prominent roles in several mechanisms for the breakdown of passive films leading to pitting corrosion. The chemical composition of the pore solution would determine whether rapid dissolution at the pore could initiate. The effects of nanoscale pore dimensions, solution pH and adsorbing ion borate concentration on the solution composition ...


Biomass Reburning For Control Of Nitrogen Oxides , Jeffrey James Sweterlitsch Jan 2002

Biomass Reburning For Control Of Nitrogen Oxides , Jeffrey James Sweterlitsch

Retrospective Theses and Dissertations

Fuel-Lean Gas Reburning(TM) (FLGR) is a method of controlling NO x emissions produced during coal combustion in utility boilers by injecting natural gas into the boiler downstream of the primary combustion zone. Whereas traditional reburning requires 10%--20% of the total energy input from the reburn fuel followed by over-fire air to complete combustion of fuel fragments, FLGR uses only 5%--10% of the total energy input from the reburn fuel. Because less fuel is used, the overall environment in the boiler remains fuel-lean, with only localized eddies that are fuel-rich, where the NOx reduction takes place. FLGR does ...


Development Of Novel Polymeric Materials For Gene Therapy And Ph-Sensitive Drug Delivery: Modeling, Synthesis, Characterization, And Analysis , Brian Curtis Anderson Jan 2002

Development Of Novel Polymeric Materials For Gene Therapy And Ph-Sensitive Drug Delivery: Modeling, Synthesis, Characterization, And Analysis , Brian Curtis Anderson

Retrospective Theses and Dissertations

The aim of this work was to obtain a fundamental understanding of drug release mechanisms from polymers that undergo thermoreversible gelation and to synthesize new polymers based on these that exhibit both pH and temperature sensitivity. Novel block and random copolymers with cationic character have been developed for drug delivery and gene therapy applications. The development of these materials began with a study of the mechanism of drug release from poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) block copolymers. This study revealed the release rates of drugs from water-soluble hydrogels composed of the PEO-PPO-PEO block copolymer PluronicRTM F127 ...


Recovery Of Recombinant Proteins From Transgenic Plants: Strategies In Implementation And Optimization , Todd J. Menkhaus Jan 2002

Recovery Of Recombinant Proteins From Transgenic Plants: Strategies In Implementation And Optimization , Todd J. Menkhaus

Retrospective Theses and Dissertations

Strategies to optimize the recovery of recombinant proteins from plant hosts have been investigated. The use of different crops, different product molecules, and different separation techniques was studied to suggest modes of operation that reduce the overall processing cost for obtaining purified recombinant proteins from plants.;Polyelectrolyte precipitation of beta-glucuronidase (GUS), an acidic model protein, with polyethyleneimine (PEI), a polycatonic polymer, from the extracts of canola, corn germ, soybean, and pea met with varying degrees of success. Precipitation from canola required the least amount of PEI and was capable of providing the highest enrichment. In contrast, soy and pea allowed ...


Mechanistic Understanding Of Miscibility Effects On Fracture Strength Of Polymer Interfaces , Russell E. Gorga Jan 2002

Mechanistic Understanding Of Miscibility Effects On Fracture Strength Of Polymer Interfaces , Russell E. Gorga

Retrospective Theses and Dissertations

This research has provided a fundamental framework based on both experiment and theory to understand the fracture behavior as a function of system miscibility for nonreinforced polymer interfaces. The system chosen for study was polystyrene (PS) and the statistically random copolymer poly (styrene-r-4-bromostyrene) (PBS), where the volume fraction of bromine in the copolymer, f, and the degree of polymerization, N, control the miscibility. The phase behavior of thin film blends of PS and PBS as a function of f and N was studied using atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). Simulations based on the Flory-Huggins theory ...


Investigation Of Napl Dissolution And Instability Using A Pore-Scale Network Model: Sensitivity Analysis Of Porous Medium Characteristics , Yanhui Hu Jan 2002

Investigation Of Napl Dissolution And Instability Using A Pore-Scale Network Model: Sensitivity Analysis Of Porous Medium Characteristics , Yanhui Hu

Retrospective Theses and Dissertations

Nonaqueous phase liquids (NAPLs) introduced into an aquifer can cause long-term contamination. While some of the NAPL may be recoverable, most will dissolve into the surrounding water over a period of years or centuries. A three-dimensional pore-scale network model was developed to investigate the NAPL dissolution process in porous media. The model explicitly investigated two dissolution mechanisms: stagnant layer diffusion and channel flow dissolution. Numerical experiments were conducted to determine the effects of ganglion size, aqueous phase flow rate, and porous medium characteristics on the NAPL dissolution rate, ganglion configuration, and ganglion instability, both initial and dissolution-induced. It was found ...


Interdiffusion Phenomena At Partially Miscible Polymer Interfaces , Erin Lynne Jablonski Jan 2002

Interdiffusion Phenomena At Partially Miscible Polymer Interfaces , Erin Lynne Jablonski

Retrospective Theses and Dissertations

This research is focused on understanding the effect of miscibility on interdiffusion phenomena in bilayers of polystyrene (PS) and the statistically random copolymer, poly (styrene-r-4-bromostyrene) (PBS). Miscibility in such systems can be quantified by N*chi, where N* is an effective degree of polymerization and chi the Flory-Huggins interaction parameter. In the PS/PBS system, miscibility decreases as N *chi increases. The extent of interdiffusion at a bilayer interface is ultimately determined by the miscibility of the system. A description of the effect of miscibility on interdiffusion phenomena, interfacial width, phase behavior, and fracture energy and a relationship between these ...


Effects Of Fly Ash On The Oxidation Of Mercury During Post-Combustion Conditions , Hongqun Yang Jan 2002

Effects Of Fly Ash On The Oxidation Of Mercury During Post-Combustion Conditions , Hongqun Yang

Retrospective Theses and Dissertations

Mercury emissions from coal-fired power plants pose impact on human health. The emissions will be regulated in the near future. Mercury speciation in flue gas has an important effect on the efficiency of mercury emission control devices. This study focuses on the role of fly ash on the oxidation of Hg 0 in bench-scale simulated flue gas environment and in laboratory-scale coal combustion flue gas environment. The effects of flue gas matrices, temperature, fly ash mineralogy and morphology on the oxidation of Hg0 are studied. Conclusions are drawn based on the testing results: (1) Mercury chemistry is very complex in ...


A Study Of Rheology, Processing And Phase Behavior Of Engineered Inorganic Glass-Organic Polymer Hybrid Materials , Peter Christopher Guschl Jan 2002

A Study Of Rheology, Processing And Phase Behavior Of Engineered Inorganic Glass-Organic Polymer Hybrid Materials , Peter Christopher Guschl

Retrospective Theses and Dissertations

Due to the consequence of expensive development costs that arise with manufacturing and synthesizing new polymers, interest in polymer blends has gained considerable attention in recent years. It is well known that the production of miscible and immiscible blends of polymers can lead to composite materials with special chemical, thermal, mechanical, and rheological properties. The morphology of immiscible polymer blends arises during mixing and is affected by the processing conditions, particular interactions, and the interfacial tension and viscosity ratio between the components. The significance of the interfacial energy between the blend components and its inherent effect on the rheology is ...


Pathway And Surface Mechanism Studies Of 1,3-Butadiene Selective Oxidation Over Vanadium-Molybdenum-Oxygen Catalysts , William David Schroeder Jan 2001

Pathway And Surface Mechanism Studies Of 1,3-Butadiene Selective Oxidation Over Vanadium-Molybdenum-Oxygen Catalysts , William David Schroeder

Retrospective Theses and Dissertations

The partial oxidation of 1,3-butadiene has been investigated over VMoO catalysts synthesized by sol-gel techniques. Surface areas were 9--14 m2/g, and compositions were within the solid solution regime, i.e. below 15.0 mol% MoO3/(MoO3 + V2O 5). Laser Raman Spectroscopy and XRD data indicated that solid solutions were formed, and pre- and post-reaction XPS data indicated that catalyst surfaces contained some V+4 and were further reduced in 1,3-butadiene oxidation. A reaction pathway for 1,3-butadiene partial oxidation to malefic anhydride was shown to involve intermediates such as 3,4-epoxy-1-butene, crotonaldehyde, furan, and 2-butene-1,4-dial. The ...


Effects Of Fluid-Induced Shear Stress On Articular Cartilage Regeneration Under Simulated Aspects Of Microgravity , David James Wendt Jan 2001

Effects Of Fluid-Induced Shear Stress On Articular Cartilage Regeneration Under Simulated Aspects Of Microgravity , David James Wendt

Retrospective Theses and Dissertations

Because a true microgravity environment results in a reduction of mechanical forces on the human body, possibly at each level of physiological organization, we have investigated the effects of applying a stimulus in the form of fluid-induced shear stress to regenerating articular cartilage cultured in an environment hypothesized to simulate aspects of microgravity. Significant alterations to the NASA-designed rotating wall vessel were made to create a unique bioreactor specifically designed for this study. This distinctive reactor not only allowed us to apply fluid-induced shear stress to tissue constructs, it allowed for control of its magnitude, and for independent control of ...


Development Of A Regenerable Calcium-Based Sorbent For Hot Gas Cleanup , Tetteh Akiti Jan 2001

Development Of A Regenerable Calcium-Based Sorbent For Hot Gas Cleanup , Tetteh Akiti

Retrospective Theses and Dissertations

Experiments were conducted to develop a regenerable calcium-based sorbent for hot coal gas desulfurization. Spherical sorbent pellets were fabricated in a novel core-in-shell configuration. All pellets were prepared using a bench-scale pelletizer. In accordance with the core-in-shell concept, a reactive calcium compound (CaO) was surrounded by a strong shell consisting of a composite material. Limestone (CaCO3) and hemihydrate (CaSO4·0.5 H2O) were used as starting materials that were eventually decomposed to produce CaO. Different types of cements and aluminas were investigated as strength enhancing shell materials.;The sorbent pellets were characterized by measuring their compressive strength, surface area, pore ...


Study Of Transport And Dissolution Of A Nonaqueous Phase Liquid In Porous Media: Effects Of Low-Frequency Pulsations And Surfactants , Mirrya Mosier Fontenot Jan 2001

Study Of Transport And Dissolution Of A Nonaqueous Phase Liquid In Porous Media: Effects Of Low-Frequency Pulsations And Surfactants , Mirrya Mosier Fontenot

Retrospective Theses and Dissertations

The transport and dissolution of residual non aqueous phase liquids (NAPLs) trapped in water saturated porous media is a problem pertinent to both environmental and petrochemical industries. In this work we have quantitatively examined the complete dissolution of residual entrapped NAPL at the pore-scale in three dimensions using refractive index matching techniques along with planar laser induced fluorescence. The results yielded pore-scale information regarding ganglia volume, surface area, and position over time at various Capillary numbers. We found that with increasing Capillary numbers, the time for total dissolution decreased. In addition, it appears that large ganglia exhibit fractal area to ...


The Roles Of The Surface Oxide Film And Metal-Oxide Interfacial Defects In Corrosion Initiation On Aluminum , Huiquan Wu Jan 2001

The Roles Of The Surface Oxide Film And Metal-Oxide Interfacial Defects In Corrosion Initiation On Aluminum , Huiquan Wu

Retrospective Theses and Dissertations

In the first part, a mathematical model was developed for oxide thickness and faradaic current, assuming high-field conduction and a uniform oxide layer thickness, and incorporating as input the measured potential. Electrochemical current and potential transients were measured during anodic oxidation of aluminum. The ratio of the experimental faradaic current density to the predicted one using high field model, p, was calculated. The measured faradaic current is about 104 times smaller than that predicted by this model initially, but the two converge after the initial period of time when p approaches 1. This discrepancy may be caused by several reasons ...