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More efficient methods are needed for the in-situ evaluation of mass transfer parameters which describe the movement of solutes through aquifer material. The objective of this study was to develop a method for estimating diffusion rate and capacity coefficients using a single-well, "push-pull" tracer test. The method consists of the pulse-type injection of a test solution into the saturated zone of an aquifer through the screen of an existing monitoring well. This is followed by a resting (diffusion) period, after which the test solution is extracted from the same well. During the extraction phase a concentration breakthrough curve is obtained. The method uses numerical simulations of the extraction phase breakthrough curve to estimate mass transfer parameters. The methodology was evaluated using a series of laboratory-scale experiments which were performed in a Physical Aquifer Model (PAM). The sediment pack contained in the PAM was modified to create an immobile region governed by diffusive processes. Results from four laboratory-scale experiments are inconclusive in determining the ability of the method to determine mass transfer parameters. Experimental difficulties contributed a significant source of error during the method evaluation. The resting period between the injection and extraction phase was to allow diffusion into the initially solute-free immobile region. Evidence suggests solute was introduced into the immobile region by advective processes during the injection phase of the experiments. Additional experimental work is required to evaluate the methodology. This may include either laboratory or field-scale evaluation of the test method. / Graduation date: 1999

Responses of biological indicators of soil quality to winter cover cropping were measured on soil samples collected from 6 commercial growers' fields and two experiment research stations in the Willamette Valley of Oregon. The research stations were the North Willamette Research and Extension Center (Aurora, OR), and the Oregon State University Vegetable Farm (Corvallis, OR). The research stations and five on-farm sites compared winter cover crops or winter fallow in rotation with a summer vegetable crop. In one on-farm site, minimum tillage or conventional till following winter cover crops was compared. The objectives of this study were to: 1) monitor changes in soil biological properties under field managed with cover crops; 2) test potential of buried cotton strip as indicator of soil biological activity and as a soil quality index; and 3) assess the degree of correlation between tensile strength and cotton strip weight loss. The major findings were: 1) microbial biomass carbon and ��-glucosidase activity were the most sensitive to cover crop management; 2) cotton strip decomposition was correlated to soil biological properties but was not very sensitive to management changes; and 3) that measuring weight loss was nearly as effective as tensile strength in assessing cotton strip decomposition in soils. / Graduation date: 1999

The Lagrangian formalism utilized by Ilinskii, Hamilton and Zabolotskaya [J. Acoust. Soc. Am. 121, 786-795 (2007)] to derive equations for the radial and translational motion of interacting bubbles is extended here to obtain a model for the dynamics of interacting bubbles and elastic particles. The bubbles and particles are assumed to be spherical but are otherwise free to pulsate and translate. The model is accurate to fifth order in terms of a nondimensional expansion parameter R/d, where R is a characteristic radius and d is a characteristic distance between neighboring bubbles or particles. The bubbles and particles may be of nonuniform size, the particles elastic or rigid, and external acoustic sources are included to an order consistent with the accuracy of the model. Although the liquid is assumed initially to be incompressible, corrections accounting for finite liquid compressibility are developed to first order in the acoustic Mach number for a cluster of bubbles and particles, and to second order in the acoustic Mach number for a single bubble. For a bubble-particle pair consideration is also given to truncation of the model at fifth order in R/d via automated derivation of the model equations to arbitrary order. Numerical simulation results are presented to demonstrate the effects of key parameters such as particle density and size, liquid compressibility, particle elasticity and model order on the dynamics of single bubbles, pairs of bubbles, bubble-particle pairs and clusters of bubbles and particles under both free response conditions and sinusoidal or shock wave excitation. / text

In addition, the vanishing viscousity limit of the solutions for viscous lake equations with the Navier type boundary conditions is obtained for both the smooth and non-smooth initial data. / The aim of the thesis is to understand the dynamics and interactions between the Ekman layer and thermal layer which are very important issues in the studies of geophysical flows. We obtain some new results on the primitive equations of the atmosphere and the incompressible Navier-Stokes equations with rotating terms. We study the asymptotic limits of the solutions to the initial boundary value problem for the three dimensional primitive equations. We have constructed the asymptotic ansatz which is uniformly valid up to the boundary to derive the quasi-geostrophic equations and the corresponding boundary layer systems. These equations are also important and widely studied in the geophysical flows. The uniform convergence to the solutions for quasi-geostrophic equations is obtained rigorously. / Niu Dongjuan. / "June 2006." / Adviser: Zhouping Xin. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1675. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 96-106). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Graduation date: 1994

A model is developed for the dynamics of an acoustically driven bubble in a channel. The bubble is assumed to be smaller than the transverse dimension of the channel and spherical in shape. The channels considered are infinite in length and formed by either parallel planes or tubes with triangular, rectangular, or hexagonal cross sections. For surfaces that are rigid or pressure release, the boundary conditions on the channel walls in each of these geometries can be satisfied using the method of images. Effects due to confinement by the channel walls are thus determined by an analysis of coupled bubble interactions in line and plane arrays. An existing model for the coupled dynamics of spherical bubbles provides the basis for the model. Liquid compressibility is an essential feature of the model, both in terms of radiation damping and the finite propagation speed of acoustic waves radiated by the bubble. Solutions for the frequency response are obtained analytically by perturbation for low drive amplitudes and weak nonlinearity, and by numerical solution for high drive amplitudes and strong nonlinearity. The perturbation solutions for the radial motion at the drive frequency and its second harmonic are obtained in closed form for a bubble between parallel planes. The response of a bubble between rigid parallel planes is found to be mass controlled, whereas for a rigid tube it is found to be radiation damping controlled. The dynamics of a bubble located near the center of a tube are found to depend on the area but not the specific geometry of the cross section. At drive amplitudes below which subharmonic generation occurs, the numerical solutions for high drive amplitudes reveal the same general properties as the perturbation solutions for low drive amplitudes. All of the solutions can be extended to tubes with arbitrary wall impedance if the radiation impedance on the bubble is known, for example calculated by normal mode expansion. / text

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published_or_final_version / Civil and Structural Engineering / Doctoral / Doctor of Philosophy