Process Modeling of Soil Thermal and Hydrological Dynamics

To explicitly simulate the soil thermal state effects on hydrological response, the soil thermal regime, frozen soil, and permafrost simulation capability in the Geophysical Institute Permafrost Laboratory (GIPL) model have been included into the physically based, distributed watershed model Gridded Surface Subsurface Hydrologic Analysis (GSSHA). The GIPL model is used to compute a vertical soil temperature profile in every lateral two-dimensional GSSHA computational element using the soil moisture information from hydrologic simulations in GSSHA; GSSHA, in turn, uses this temperature and phase, ice content, and information to adjust hydraulic conductivities for both the vertical unsaturated soil flow and lateral saturated groundwater flow. This two-way coupling increases computational accuracy in both models by providing additional information and processes not previously included in either. The soil moisture physical state is defined by the Richards Equation, and the soil thermal state is defined by the numerical model of phase change based on quasi-linear heat conduction equation. Results from the demonstration site, a head water sub-catchment at the peak of the Caribou-Poker Creeks Research Watershed, representing Alaskan woodland and tundra ecosystem in permafrost-active region, indicated that freezing temperatures reduce soil thermal conductivity and soil storage capacity, thereby increasing overland flow and peak discharges

Design of Pneumatic Diffuser System

During non-generation periods, leakage through the wicket gates of a hydroturbine often results in very poor quality water (low or zero dissolved oxygen) in the tailrace of the hydropower facility. Generally, the leakage rate is relatively small, usually about 5-10 cfs per turbine. A bottom-mounted diffuser system was designed based on laboratory-measured and manufacturer-supplied specifications about the gas transfer characteristics of the bubble plume generated by an 11- inch flexible head diffuser. The design criteria and the overall effectiveness of the system were evaluated in field tests at Lake Eufaula, Oklahoma. The analysis of field data is reported herein

Catchment Hydrological Modeling with Soil Thermal Dynamics during Seasonal Freeze-Thaw Cycles

To account for the seasonal changes in the soil thermal and hydrological dynamics, the soil moisture state physical process defined by the Richards Equation is integrated with the soil thermal state defined by the numerical model of phase change based on the quasi-linear heat conductive equation. The numerical model of phase change is used to compute a vertical soil temperature profile using the soil moisture information from the Richards solver; the soil moisture numerical model, in turn, uses this temperature and phase, information to update hydraulic conductivities in the vertical soil moisture profile. Long-term simulation results from the test case, a head water sub-catchment at the peak of the Caribou Poker Creek Research Watershed, representing the Alaskan permafrost active region, indicated that freezing temperatures decreases infiltration, increases overland flow and peak discharges by increasing the soil ice content and decaying the soil hydraulic conductivity exponentially. Available observed and the simulated soil temperature comparison analysis showed that the root mean square error for the daily maximum soil temperature at 10-cm depth was 4.7 °C, and that for the hourly soil temperature at 90-cm and 300-cm was 0.17 °C and 0.14 °C, respectively

Relative Importance of Impervious Area, Drainage Density, width Function, and Subsurface Storm Drainage on Flood Runoff from an Urbanized Catchment

The literature contains contradictory conclusions regarding the relative effects of urbanization on peak flood flows due to increases in impervious area, drainage density and width function, and the addition of subsurface storm drains. We used data from an urbanized catchment, the 14.3 km(2) Dead Run watershed near Baltimore, Maryland, USA, and the physics-based gridded surface/subsurface hydrologic analysis (GSSHA) model to examine the relative effect of each of these factors on flood peaks, runoff volumes, and runoff production efficiencies. GSSHA was used because the model explicitly includes the spatial variability of land-surface and hydrodynamic parameters, including subsurface storm drains. Results indicate that increases in drainage density, particularly increases in density from low values, produce significant increases in the flood peaks. For a fixed land-use and rainfall input, the flood magnitude approaches an upper limit regardless of the increase in the channel drainage density. Changes in imperviousness can have a significant effect on flood peaks for both moderately extreme and extreme storms. For an extreme rainfall event with a recurrence interval in excess of 100 years, imperviousness is relatively unimportant in terms of runoff efficiency and volume, but can affect the peak flow depending on rainfall rate. Changes to the width function affect flood peaks much more than runoff efficiency, primarily in the case of lower density drainage networks with less impermeable area. Storm drains increase flood peaks, but are overwhelmed during extreme rainfall events when they have a negligible effect. Runoff in urbanized watersheds with considerable impervious area shows a marked sensitivity to rainfall rate. This sensitivity explains some of the contradictory findings in the literature

Michael F. BeckerTime-Resolved Study of Third Harmonic Generation from Anisotropically Expanding Clusters

loved me so much and are in my heart. Acknowledgments This work was possible due to many people. Most significantly, I thank my research supervisor Dr. Michael Downer, who has supported me for my graduate work and has guided me in developing my research skills and insight of physics. When I struggled, he gave me nice suggestions (most of his suggestions turned out to be major breakthroughs), waiting patiently. When I had good results, he discussed the results with me for several hours and motivated me to do more. Without his patience, creativity and enthusiasm, this work would be absolutely impossible. I thank Dr. Todd Ditmire and his student, Gregory Hays. Dr. Ditmire gave me guidance in this research as a true pioneer of the atomic cluster science and his numerous journals about cluster-laser interaction motivated me to do third harmonic generation simulation. I enjoyed a lot working with Gregory Hays. His knowledge and experience about physics, laser science and humor are incorporated in this dissertation and were crucial to our experimental success