Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 21 for “"effective diffusion coefficient"”.
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Mechanism of anisotropic shrinkage during sintering of metalli powders
… of classical sintering theory, to calculate an effective diffusion coefficient along the two directions, which resulted higher for direction parallel to the compaction direction than perpendicular to it. In both directions, the effective diffusion coefficient is larger than that reported in the …
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Characterization of chemical composition, milling properties and carbon dioxide diffusivity resulting from early harvest corn and corn stover
… livestock and ethanol industries. Developing an effective corn harvesting, storage and utilization system can help reduce the competition for the limited corn supply in the current period. The overall goal of this study was to examine the feasibility of early harvest of corn and corn stover and …
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Study of Plasma/flowing Liquid Metal Interactions
… with a simple transport model to estimate an effective diffusion coefficient. Measurements of trapped helium content released upon thermal annealing are presented as well, showing that the possibility of long-term helium trapping exists. For the case of hydrogen, preliminary results are …
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Analytical Modeling of Bentonite Swelling and Numerical Reactive Transport Modeling in Nuclear Waste Disposal Systems
… the changing pore volume, reaction rate, and effective diffusion coefficient as a function of porosity and temperature. (3) Develop a macroscale model by using the reactive transport properties obtained from the pore-scale modeling, and validate the results with research-purpose software, …
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Formation and transport of undesirable compounds during repeated deep frying
… deep frying were also investigated and the diffusion parameters of polar compounds were experimentally determined. The major findings for this dissertation were: (1) Introduction of food to oil overweighed the high-temperature frying as a more influential factor contributing to oil …
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Investigation of Nanopore Confinement Effects on Convective and Diffusive Multicomponent Multiphase Fluid Transport in Shale using In-House Simulation Models
… (porosity and tortuosity factor) on predicting effective diffusion coefficient are investigated. First, a previously developed compositionally extended black-oil simulation approach is modified, and extended, to include the effect of large gas-oil capillary pressure for modeling first contact …
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Molecular Dynamics Study of Microstructural Evolution in Alloys Subjected to Severe Plastic Deformation
… deformation that has been uncovered is that the effective diffusion coefficient increases, nearly linearly, with the separation distance of pairs of atoms. This superdiffusive mixing is revealed by monitoring the relative displacement of atoms as a function of the separation distance. This result …
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A Numerical Model for Flux Decline During the Crossflow Ultrafiltration of Colloidal Suspensions
… expressed using the two-dimensional convective-diffusion equation. Numerical simulations showed that mass transfer in crossflow filtration quickly reaches a steady-state for constant boundary conditions. Hence, the unsteady nature of the permeate flux decline must be caused by changes in the …
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Analysis of gas differential diffusion through porous media using prompt gamma activation analysis
Accurate estimates for the molecular transport coefficients are critical to predicting the movement of gases in geological media. Here I present a novel methodology for using prompt gamma activation analysis to measure the effective diffusivity of noble gases in a porous medium. I also present a …
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Characterizing Erythrocyte Motions in Flowing Blood
… present at normal levels, but follow convective diffusion in dilute suspensions. A critical need is to understand and characterize dispersion and diffusion as they apply to red cells in suspension flow. The dispersive motions of <br />0.5-micrometer beads and fluorescently labeled human RBC …
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A Lattice Boltzmann method model of diffusion-weighted magnetic resonance imaging in skeletal muscle
… noninvasive methods is paramount in developing effective therapeutic procedures for the elderly, such as physical exercise. Using special proton magnetic resonance imaging (MRI) protocols we can investigate non-invasively diffusion phenomena within skeletal muscle. This project focuses on the …
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Kinetics of alkali metal ion self-exchange on polystyrene sulfonate resin in dimethyl sulfoxide-water media
<p>Rates of alkali metal cation self-diffusion in a polystyrene sulfonate ion exchange resin and in the external solution have been measured over a range of dimethyl sulfoxide (DMSO)-water mixtures from 0 to 70 mole % DMSO. Interpretation of results is simplified by the choice of this system which …
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Diffusion, sub-diffusion, and escape: A study of over-damped Brownian motion
… with one-dimensional systems, we derive the diffusion coefficient for motion in a piecewise-defined potential where the barrier height of each section is taken from a probability distribution. When the distribution is exponential the usual transition between diffusion and sub-diffusion is …
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Barrier Heights and Diffusion Coefficients in Protein Folding
… twilight-zone and two-state like. The average effective diffusion coefficient to folding (D<sub>eff</sub>) is predicted to be strongly temperature dependent changing from 1/(20-25 microseconds) at 298 K to 1/(2 microseconds) at ~330-340 K. The activation term on the D<sub>eff</sub> is found to …
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Modeling temporal and spatial variations in dissolved oxygen in Amite River
… model for improved estimation of reaeration coefficient (K2) in natural streams, (2)VART-DOS model for simulation of temporal variations in DO in response to sediment resuspension, and (3)VART DO-3L model for simulation of spatial variations in DO. A major advantage of VART-DO model is the …
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Study of VOCs Transport and Storage in Porous Media and Assemblies
… for a given VOC can be characterized by its diffusion coefficient and partition coefficient, respectively, and such data are currently lacking. Besides, environmental conditions are another important factor that affects the VOCs emission. The main purposes of this dissertation are: (1) …
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The influence of prior creep damage on the fracture localisation in X20 CrMoV12-1 cross-weld creep tests
… to the numerous small grains, there is a high effective diffusion coefficient (HEDC). The multi axial stresses induced during in service/ creep testing conditions together with the HEDC causes voids to form at an accelerated rate. Significant void coalescence promotes the formation of micro …
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Experimental and theoretical examination of the chemical kinetics of a pollutant coating on porous particles
… because of the chemical reaction, the radial diffusion from the agglomerate center to the periphery and because of the evaporation of the substance from the agglomerate surface. It is considered also in the model that the concentration of the hydroxyl radicals alters with the penetration in …
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Method comparison for analysis of LNAPL natural source zone depletion using CO₂ fluxes
… risks to human health and the environment, effective remediation approaches are needed to address impacts. Natural source zone depletion (NSZD) is a remedial approach gaining wide acceptance, wherein natural mechanisms in the subsurface act to deplete LNAPL in the source zone. Recent …
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Physical performance and durability evaluation of rubberized concrete
… test were conducted namely, 1) Chloride ion diffusion test, 2) Abrasion wear resistance test, and 3) Freezing and thawing test. Up-to-date, many successful achievements were reported by researchers around the world. However, in Asian cases, very rare information on the use of wasted as a …
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