Groundwater use is of fundamental importance to meet rapidly expanding urban, industrial, and agricultural water requirements, particularly in semiarid zones. To quantify the current rate of groundwater recharge is thus a prerequisite for efficient and sustainable groundwater resource management in these dry areas, where such resources are often the key to economic development. Increased groundwater recharge has been documented where native vegetation or forest/shrub land was converted to grassland or pasture, or where the land was cleared for agricultural purposes. The basic argument for increased recharge is that evapotranspiration, primarily interception and transpiration, is higher in shrublands than grasslands. Chloride mass balance (CMB) has been used to estimate ancient recharge, but recharge from recent land-use change has also been documented, specifically where vegetation has been altered and deep-rooted species replaced with shallow-rooted grasses. Chloride concentrations are inversely related to recharge rates: low Clconcentrations indicate high recharge rates as Cl- is leached from the system; high Cl concentrations indicate low recharge rates since Cl- accumulates as a result of evapotranspiration. The objectives were (1) to assess the hypothesis that removal of woody-shrub vegetation and replacement with grasses increases deep drainage, (2) to quantify the amount of deep drainage after land-use change, and (3) to provide science-based data for a better understanding of changing land-use impacts on deep drainage. Eight soils from five locations in the Central Rolling Red Plains near Abilene and Sweetwater were sampled. Each location consisted of a pair of similar soils with contrasting vegetative cover: shrubland and grassland. At each site three to five soil cores were taken as deep as possible and samples were taken by horizon, but horizons were split when their thickness exceeded 0.25 m. Soil Cl- profiles under shrubland at three sites showed that virtually no water escapes beyond the root zone. High Cl- concentrations and inventories reflect soil moisture fluxes that approached 0 mm yr-1 with depth. Evapotranspiration may be largely responsible for Cl- enrichment in those profiles. Surprisingly, soil moisture flux past 200 cm under juniper woodlands was the highest with 2.6 mm yr-1. Evapotranspirative Cl- enrichment in the upper 300 cm was not observed and may suggest a different water uptake mechanism for this plant community. Soil Cl- profiles showed increased recharge rates under grassland vegetation ecosystem. Estimated deep drainage past 200 cm of 0.1 to 1.3 mm yr-1 was observed. Low Cl- concentrations and inventories suggest a leaching environment that may be in response to changes in land use/land cover.

Liquefied Natural Gas (LNG) is flammable when it forms a 5 – 15 percent volumetric concentration mixture with air at atmospheric conditions. When the LNG vapor comes in contact with an ignition source, it may result in fire and/or explosion. Because of flammable characteristics and dense gas behaviors, expansion foam has been recommended as one of the safety provisions for mitigating accidental LNG releases. However, the effectiveness of foam in achieving this objective has not been sufficiently reported in outdoor field tests. Thus, this research focused on experimental determination of the effect of expansion foam application on LNG vapor dispersion and pool fire. Specifically, for evaluating the use of foam to control the vapor hazard from spilled LNG, this study aimed to obtain key parameters, such as the temperature changes of methane and foam and the extent reduction of vapor concentration. This study also focused on identifying the effectiveness of foam and thermal exclusion zone by investigating temperature changes of foam and fire, profiles of radiant heat flux, and fire height changes by foam. Additionally, a schematic model of LNG-foam system for theoretical modeling and better understanding of underlying mechanism of foam was developed. Results showed that expansion foam was effective in increasing the buoyancy of LNG vapor by raising the temperature of the vapor permeated through the foam layer and ultimately decreasing the methane concentrations in the downwind direction. It was also found that expansion foam has positive effects on reducing fire height and radiant heat fluxes by decreasing fire heat feedback to the LNG pool, thus resulting in reduction in the safe separation distance. Through the extensive data analysis, several key parameters, such as minimum effective foam depth and mass evaporation rate of LNG with foam, were identified. However, caution must be taken to ensure that foam application can result in initial adverse effects on vapor and fire control. Finally, based on these findings, several recommendations were made for improving foam delivery methods which can be used for controlling the hazard of spilled LNG.

Marine and aquatic species relying on external fertilization must have special adaptation against sperm-dilution in the water. In addition mating competition may be another important source of limitation to an individual¡¦s reproductive success. If the two above mechanisms are in direct conflict, real adaptation would reflect whichever is more critical to one¡¦s fitness. In using the same logic, the unidirectional induction of spawning, i.e., females inducing males, but not males inducing females, has been reported as an evidence for the relative importance of natural selection, that is, sperm-dilution, in limiting the fitness of brittlestars in shallow waters. If the above deduction is correct, one would predict more adaptations to offset the adverse effect of sperm-dilution in various aspects of spawning-related characteristics. Two species of brittlestars. Ophiocoma dentata, living in subtidal zone, and O. scolopendrina, living in intertidal zone, were studied at Kenting, southern Taiwan. Experimental approaches were adopted to figure out if these two species have any adaptation in space and in time that can perceivably counteract the effect of sperm dilution. Spatially, the male O. dentata has the ability to search for females, and the males living with females have higher rates of responding to female spawn than unpaired males; the males do not actively search for eggs released in the water. In O. scolopendrina, neither male nor female had the ability to distinguish the sex of other individuals, they do not form pairs in nature. Males, however, have strong ability to search released eggs and then approach and spawn near the eggs. Temporally, the males of the O. scolopendrina, are sensitive to tidal rhythms in terms of inducibility by female spawns, they only spawn at the time of low tide. The possible effect of water level and photophase were both ruled out. In contrast, no such tidal rhythms of male inducibility was found in the subtidal O. dentata. Sexual selection needs not be invoked in any of the above behaviors, whereas natural selection against sperm dilution is an acceptable explanation. Last, the male O. scolopendrina displays interference behavior by blocking other males from approaching eggs are in the water. The blocked individuals are less likely to spawn.

A phenomenological cohesive term is proposed and added to an existing cohesive constitutive law (by Roy and Dodds) to model the crack tip high inertia region proposed by Gao. The new term is attributed to fracture mechanisms that result in high energy dissipation around the crack tip and is assumed to be a function of external energy per volume input into the system. Finite element analysis is performed on PMMA with constant velocity boundary conditions and mesh discretization based on the work of Xu and Needleman. The cohesive model with the proposed dissipative term is only applied in the high inertia zone i.e., to cohesive elements very close to the crack tip and the traditional Roy and Dodds model is applied on cohesive elements in the rest of the domain. It was observed that crack propagated in three phases with a speed of 0.35cR before branching, which are in good agreement with experimental observations. Thus, modeling of high inertia zone is one of the key aspects to understanding brittle fracture.

Work zones create one of the most challenging environments for drivers. Implementing work zones on urban freeways creates many issues, especially with respect to mobility. Decisions made regarding the work zone should be informed by quantitative data, collected in work zones, to ensure that the mobility impacts of the work zone treatments implemented are mitigated. A new decision-making process, which addresses the shortcomings in the current decision-making processes, was developed through the course of this research. The new process incorporates a Performance Measure/Treatment matrix, which recommends multiple performance measures, each of which is chosen to measure the mobility impacts particular to a specific work zone implementation. Most importantly, the revised decision-making process incorporates a feedback loop. Quantitative data collected in work zones is analyzed after the work zone is complete, to determine the impacts specific decisions had on mobility in the work zone. The lessons learned in previous work zones are then incorporated into the decision-making process, lessening the mobility impacts of future work zones. This thesis develops the new decision-making process, and examines the issues with the application of the process.

Thesis (M.M.A.)--University of Washington, 2009. / Includes bibliographical references (leaves 26-28). Also available on the World Wide Web.

Thesis (M.P.A.)--Kutztown University of Pennsylvania, 2009. / Source: Masters Abstracts International, Volume: 47-05, page: 2639. Adviser: Paula A. Holoviak. Includes supplementary digital materials.

Thesis (M.M.A.)--University of Washington, 2009. / Title from Web page (viewed on Feb. 3, 2010). Includes bibliographical references (leaves 26-28).

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Haynes alloy 282 is a new gamma prime (γ’) precipitation strengthened nickel-base superalloy developed for high temperature applications in land-based and aero turbine engines. Joining is a crucial process both during the manufacturing of new components and repair of service-damaged turbine parts. Unfortunately, the new superalloy cracks during laser beam welding (LBW), which is an attractive technique for joining superalloys components due to its low heat input characteristic that preclude the geometrical distortion of welded components. This research is therefore initiated with the goal of studying and developing an effective approach for preventing or minimizing cracking during LBW of the new superalloy Haynes 282. Careful and detailed electron microscopy and spectroscopy study reveal, for the first time, the formation of sub-micron grain boundary M5B3 particles, in the material. Microstructural study of welded specimens coupled with Gleeble thermo-mechanical physical simulations shows that the primary cause of weld heat affected zone (HAZ) cracking in the alloy is the sub-solidus liquation reaction of intergranular M5B3 borides in the material. Further weldability study showed that the HAZ liquation cracking problem worsens with reduction in welding heat input, which is normally necessary to produce the desired weld geometry with minimum distortion. In order to minimize the HAZ cracking during low heat input laser welding, microstructural modification of the alloy by heat treatment at 1080 - 1100oC has been developed. The pre-weld heat treatment minimizes cracking in the alloy by reducing the volume fraction of the newly identified M5B3 borides, while also minimizing non-equilibrium grain boundary segregation of boron liberated during dissociation of the boride particles. Further improvement in resistance to cracking was produced by subjecting the material to thermo-mechanically induced grain refinement coupled with a pre-weld heat treatment at 1080oC. This approach produces, for the first time, crack-free welds in this superalloy, and the benefit of this procedure in preventing weld cracking in the new material is preserved after post-weld heat treatment (PWHT), as additional cracking was not observed in welded specimens subjected to PWHT.