An important source of freshwater in arid lands is found in groundwater aquifers that are recharged after storm events. However, most of the precipitation is lost due to evaporation and only small fractions actually recharge the aquifers. The construction of dams along wadi channels enables the retention of stormwater, however the reservoirs are still subject to huge evaporative losses and contamination. In this study, the hydraulic properties of a dunefield in western Saudi Arabia are evaluated in order to determine the feasibility of designing a stormwater storage aquifer storage and recovery facility using the dune sands as a natural medium and design recommendations are addressed. The accurate estimation of hydraulic conductivity of unlithified sediments such as dune sands has become very important in the design of natural filtration projects, including aquifer recharge and recovery systems. Therefore, a comparison and selection of methods for the determination of the hydraulic conductivity from grain size distribution found in the literature was done. An improvement to these equations based on measurements on dune samples was obtained.

This research had two main objectives: quantify surface-water and groundwater interactions along a stream reach, and determine the hydraulic conductivity at the site where two reservoirs are proposed. The objectives of this research aim to help maintain stream ecology and increase surface water storage for recreational and industrial purposes. The stream reach, located in the Pascagoula River Basin of southeast Mississippi, begins at Lake Okatibbee and terminates at Pascagoula into the Gulf of Mexico. Four USGS continuous gauging stations provided more than forty years of stream discharge data for a hydrograph baselow-recession analysis, which determined the baseflow component within the stream. The analysis showed that baseflow decreases along the stream reach and increases again before reaching the Gulf of Mexico. Thirteen borehole samples were collected at the sites of the proposed reservoirs in George County, Mississippi to determine the hydraulic conductivity of the sediments, which showed high a hydraulic conductivity.

A method to incorporate grain size effects into crystal plasticity is presented. The classical Hall-Petch equation inaccurately predicts the macroscopic yield strength for materials with non-equiaxed grains or materials that contain unequal grain size distributions. These deficiencies can be overcome by incorporating both grain size and orientation characteristics into crystal plasticity theory. Homogenization relationships based on a viscoplastic Taylor-like approach are introduced along with a new function, the grain size and orientation distribution function (GSODF). Estimates of the GSODF for high purity α-titanium are recovered through orientation imaging microscopy coupled with the chord length distribution. A comparison between the new method and the traditional viscoplastic Taylor approach is made by evaluating yield surface plots.

This research paper was submitted to the Department of Geography in fulfillment of the requirements of Geography 4C6. / This study reports on the relationship between the foreshore slopes, grain size characteristics and the wave height on the Hamilton-Burlington Beach. This beach is a non-tidal, low-energy beach. At five stations along the beach, profiles were taken, sediment samples were collected and the average wave heights determined. The slopes were plotted against the mean grain size, the median grain size and the wave heights. There was no clear relationship between the variables tested. It was determined, however, that there existed three areas along this beach. The first area was he one affected only by the wave energy, the second are was affected by both the wave energy and the grain size characteristics, and the third region was affected by the grain size characteristics. / Thesis / Bachelor of Arts (BA)

No description available.

No description available.

No description available.

No description available.

No description available.

Mechanical alloying, compaction by cold isostatic pressing, and pressureless sintering were used to study the potential for W â 3 wt% Ni â 1 wt% Fe to be processed into the bulk nanocrystalline form as a replacement material for depleted uranium in kinetic energy penetrators. Milling time and sintering temperature were varied from 15 to 100 hours and 1000 to 1300°C respectively. Particle size analysis and SEM showed a bimodal particle size distribution with most of the particles below 10 µm in size. XRD peak broadening analysis showed crystallite size to be reduced to below 50 nm, while peak shifting indicated a reduction in W lattice parameter due to dissolution of Ni and Fe atoms into the W BCC lattice. Post-sintering bulk characterization showed density increasing strongly with increasing sintering temperature to above 90% of theoretical density at 1200°C. Apparent activation energy for sintering decreased strongly with increasing milling time. SEM micrographs showed a bimodal grain size distribution with some areas of smaller submicron grains and others with larger grains on the order of 1 – 4 µm, likely connected to the bimodal particle size distribution from milling. XRD and SEM also showed the precipitation of two secondary phases during sintering: (Fe, Ni)6W6C incorporating carbon from the grinding media and an FCC solid solution of Ni, Fe, and W. The intermetallic carbide phase will increase strength but reduce ductility of the bulk material, which is not desirable. Micro and macrohardness testing show similar trends as density with a strong correlation with sintering temperature. / Master of Science