Hydraulic conductivity (K) is a key parameter required for the accurate prediction of contaminant transport in an aquifer. Traditionally, pump tests, slug tests, grain size analysis and, to a lesser extent, tracer tests have been employed to estimate the K of an aquifer. These methods have disadvantages in respect to assessing the K of a contaminated aquifer, for example, pumping tests generate large quantities of potentially contaminated water, slug tests interrogate only a small portion of aquifer to generate K values, and tracer tests are costly to perform. The recirculating well pair (RWP) system, assessed in this study, attempts to minimise these disadvantages while producing accurate estimates of K. The RWP system uses two wells, each screened in two positions; one screen injects water and the other extracts water from the aquifer. One well extracts water from the lower screen and injects it into the aquifer via the upper screen, whereas the second well extracts water from the upper screen and injects it through the lower screen. When these two wells are pumped in tandem a recirculation system is created within the aquifer. No water is lost or gained from the aquifer in this system. Hydraulic conductivity can be estimated from a RWP system by either the multi dipole or the fractional flow methods. The multi dipole method estimates K by measuring steady state hydraulic heads, whereas the fractional flow method uses a tracer test to obtain steady state concentrations at the four screens to estimate K. Both methods utilise a 3D flow model to simulate the aquifer system. Inverse modelling in conjunction with a genetic algorithm simulate the hydraulic head values obtained from the multi dipole experiments or the tracer steady state values obtained from the fractional flow method. Hydraulic ii conductivity estimates are obtained by matching the simulated and observed steady state hydraulic head, or tracer steady state values. An investigation of the accuracy of the two RWP methods, when system parameters are varied, in estimating K values was undertaken. Five multi dipole experiments were undertaken with varying dipole flow rates to assess the effect of altering dipole flow rate on estimates of K. Two experiments were also undertaken to assess the effect of altering the pumping well incidence angle as compared to the regional flow on the accuracy of K estimates. Five fractional flow experiments were conducted, four to assess the effect of changing dipole pumping rates and one to assess the influence of altering the incidence angle of the pumping wells on estimation of K. All experiments were undertaken in an artificial aquifer that allowed control of hydraulic parameters and accurate measurement of aquifer K by independent methods. Experimental results were modelled with the two RWP methods. Results indicate that both the multi dipole and fractional flow methods provide accurate estimates of the K of the artificial aquifer (5 % to 57% greater than the actual K and -14% to 17% of the actual K, respectively). Altering the ratio between the pumping well and regional aquifer flow rates had no effect on the estimated K results in both methods. Although preliminary results were positive, further work needs to be undertaken to determine if changing the orientation of the well pairs affects the estimation of K.

Our previous computational studies of two-dimensional quantum waveguide structures formed at the interface of the A1GaAs/GaAs heterostructure have focused on systems with centered attractive potential wells. From those studies we direct our attention to the quantum waveguide structures with an attractive potential well placed asymmetrically in the transverse direction. In particular, we are interested in the conductance spectrum for higher energy regimes where Fano resonances are the dominant resonance form. Of interest is the change and progression of Fano resonance peaks as a function of both the potentials' depth and offset, especially as it relates to the Breit-Wigner resonance forms observed in lower energy regimes. To accomplish this, the hard-wall models and Fortran code in our previous work have been expanded to include the asymmetrical positioning through solving the single-electron Schrodinger and associated equations used in the tight-binding Hamiltonian and recursive Green's functions. The observed Fano resonance structures are fitted to their characteristic equations through the use of zero-pole pairs. / Department of Physics and Astronomy

No description available.

No description available.

Thesis (Ph. D.)--Ohio University, November, 1991. / Title from PDF t.p.

Thesis (Ph. D.)--Ohio University, March, 1993. / Title from PDF t.p.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "December 2006." Includes bibliographical references (leaves 55-59). Online version available on the World Wide Web.

Thesis (Ph.D.)--University of Tulsa, 1990. / Bibliography: leaves 323-328.

Thesis (Ph.D.)--University of Tulsa, 1987. / Bibliography: leaves 160-163.

Thesis (Ph.D.)--University of Tulsa, 1993. / Includes bibliographical references (leaves 149-153).