Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Bioremediation in the vadose zone is unpredictable because of poor understanding of factors influencing microbial growth in this environment. A lab-scale experimental system was developed to examine, noninvasively, interactions between microbial growth, water flow, and solute transport in unsaturated porous media. Measurements of microbial colonization, and its impact on hydrology, were facilitated by using the luxCDABE-containing reporter bacterium Pseudomonas fluorescens HK44 and digital CCD imaging. Experiments were conducted in glass-walled two-dimensional flow cells (45 x 50 x 1 cm) packed with silica sand. Several bioengineering problems associated with chamber design and function required solution before microbial experiments were successful. These included: choice of materials for chamber components; development of sterilization, packing, and inoculation protocols; and development of procedures for data collection and chamber maintenance during experiments lasting several days. Bacterial growth was mapped daily by quantifying development of salicylate-induced bioluminescence. A model relating the rate of increase in light emission after induction successfully predicted microbial densities over four orders of magnitude (R��=0.95) provided that sufficient oxygen for the bioluminescence reaction was available. Total model-predicted growth during a one-week experiment agreed with potential growth calculated from the mass-balance of the system and previously established kinetic parameters (predicted, 1.2x10���� cells; calculated, 1.7x10���� cells). Although the rate of expansion of the colonized zone (and predicted populations in newly colonized regions) remained relatively constant, the proportion of the daily potential growth remaining within the chamber declined over time. Monitoring of bioluminescence revealed the development of an (hypothesized) anaerobic zone associated with microbial growth in the unsaturated porous media. Water content and flow streams were measured using light transmission. Accumulation of microbial growth modified the hydrologic properties of the sand causing up to 50% decrease in saturation within the colonized zone, diversion of flow around the colonized zone, and lowering (5 cm) of the capillary fringe height. Apparent solute velocity through the colonized region was reduced from 0.39 cm min����� (R��=0.99) to 0.25 cm min����� (R��=0.99). These experiments provide proof-of-concept for combining light transmission and bioluminescence technologies to study interactions between microbial growth and hydrology in unsaturated porous media. / Graduation date: 2002

The growth of vehicle travel in the United States has accelerated wear on the interstate highway system leading to frequent pavement repair and rehabilitation projects. The presence of work zones not only causes traffic congestion and backup but also increases the crash risk. Therefore, the FHWA (Federal Highway Administration) has allotted a significant amount of funds to improve work zone traffic safety and operations. This thesis compares truck and automobile crash characteristics in work zones with those of non-work zones and thus identifies engineering countermeasures to improve work zone truck safety. The researcher used a contingency analysis approach in this study. First, he categorized the North Carolina crash data using different variables. Once categorized, the Breslow-Day test is used to compare the odds of truck and automobile crashes between work zones and non-work zones. Overall, the researcher did not find a significant difference between odds of truck and automobile crashes compared to previous studies. The researcher believes that the difference in results between the present study and the previous studies could either be due to differences in the approach used or better truck management techniques employed by the North Carolina DOT (Department of Transportation). The researcher also identified that the maintenance projects performed during the day had a significantly higher odds of truck crashes relative to that of automobiles in work zones compared to control sections when workers were present, either with a lane closure or without a lane closure. The researcher believes that the results from the day maintenance projects and its subcategories are the key findings of this study. Therefore, these key findings are used to identify the possible reasons and countermeasures for any disproportionate change in truck to automobile crashes. The identified list of countermeasures includes the use of law enforcement, a smart work zone system, a dynamic late merge system, CMS (Changeable Message Signs), speed display signs, and a CB (Citizen Band) Wizard. These countermeasures were checked for cost effectiveness using a benefit cost (B/C) analysis. The researcher found that law enforcement, smart work zones with costs lower than or equal to half a million dollars, CMS, speed display signs, and the CB Wizard have B/C ratios greater than one and seem to be worthwhile for deployment in work zones. Smart work zones with significantly higher costs of 2.5 million dollars, for example, could be deployed using a more detailed analysis of work zone characteristics. Finally, dynamic late merge system could be used if the site conditions indicate a crash reduction potential of at least 10 – 15 percent.

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The growth of vehicle travel in the United States has accelerated wear on the interstate highway system leading to frequent pavement repair and rehabilitation projects. The presence of work zones not only causes traffic congestion and backup but also increases the crash risk. Therefore, the FHWA (Federal Highway Administration) has allotted a significant amount of funds to improve work zone traffic safety and operations. This thesis compares truck and automobile crash characteristics in work zones with those of non-work zones and thus identifies engineering countermeasures to improve work zone truck safety. The researcher used a contingency analysis approach in this study. First, he categorized the North Carolina crash data using different variables. Once categorized, the Breslow-Day test is used to compare the odds of truck and automobile crashes between work zones and non-work zones. Overall, the researcher did not find a significant difference between odds of truck and automobile crashes compared to previous studies. The researcher believes that the difference in results between the present study and the previous studies could either be due to differences in the approach used or better truck management techniques employed by the North Carolina DOT (Department of Transportation). The researcher also identified that the maintenance projects performed during the day had a significantly higher odds of truck crashes relative to that of automobiles in work zones compared to control sections when workers were present, either with a lane closure or without a lane closure. The researcher believes that the results from the day maintenance projects and its subcategories are the key findings of this study. Therefore, these key findings are used to identify the possible reasons and countermeasures for any disproportionate change in truck to automobile crashes. The identified list of countermeasures includes the use of law enforcement, a smart work zone system, a dynamic late merge system, CMS (Changeable Message Signs), speed display signs, and a CB (Citizen Band) Wizard. These countermeasures were checked for cost effectiveness using a benefit cost (B/C) analysis. The researcher found that law enforcement, smart work zones with costs lower than or equal to half a million dollars, CMS, speed display signs, and the CB Wizard have B/C ratios greater than one and seem to be worthwhile for deployment in work zones. Smart work zones with significantly higher costs of 2.5 million dollars, for example, could be deployed using a more detailed analysis of work zone characteristics. Finally, dynamic late merge system could be used if the site conditions indicate a crash reduction potential of at least 10 - 15 percent.

Thesis (Ph. D.)--University of Rhode Island, 2003. / Typescript. Includes bibliographical references (leaves 182-191).

Thesis (M.A.)--York University, 1998. Graduate Programme in Geography. / Typescript. Includes bibliographical references (leaves 181-186). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ27379.

Thesis (M.A.)--University of California, San Diego, 2009. / Title from first page of PDF file (viewed January 19, 2010). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 82-86).

Hyporheic flow influences both biogeochemical cycling in streambeds as well as streambed ecology. Some biogeochemical processes may be temperature dependent; therefore, heat transport associated with hyporheic flow may be an important influence on such cycles. I separately and experimentally assessed the effects of hyporheic flow due to bed topography on thermal dynamics in the sediment using a custom, tilting flume with temperature controls. Diel temperature cycles of 6° C were imposed in the flume and propagation of temperature signals into the sediment was examined for different bed morphologies (plane bed, pool-riffle-pool, and rippled bed), channel flow rates, and sediment grain sizes. Temperature fields in the sediment were monitored using an array of embedded thermistors, and this data was used to identify zones of upwelling and downwelling within the hyporheic zone. Results suggest that bedforms do induce substantially deeper downwelling upstream and downstream of the bedforms, with upwelling near the crest. This in turn leads to substantial advective heat transport and distinct thermal patterns in the sediment. Variation in permeability and channel flow rates further affects the magnitude of this advective transport. These results corroborate existing theoretical models of coupled hyporheic exchange and heat transport under bedforms. Hyporheic flow therefore affects thermal patchiness in sediment, which may in turn exert a control on biogeochemical reaction rates, and form thermal refugia for fauna. / text

Arc-continent collision is associated with vigorous mountain building and terrane accretion on relatively short (<10 Ma) geologic timescales. It is believed to be an important mechanism for the growth of continents. Taiwan represents one of the few active examples of this process. As such, is the perfect natural laboratory to investigate the nature of the continent ocean boundary and the uncertain behavior of the accretionary prism and extended, transitional rifted margin crust during the collision process. Taiwan also provides a unique opportunity to investigate structures in the backarc, yielding key insights into the still controversial tectonic conditions that were responsible for the unique subduction-collision system observed today. The obliquity of the collision between the North Luzon Arc and the Chinese rifted margin allows for examination of different temporal stages of collision at different locations. Recently acquired seismic reflection and wide-angle seismic refraction data, offshore Taiwan, document the crustal structure of the incipient mountain belt and of the Philippine Sea Plate in the backarc domain to the east. Geophysical profiles offshore southern Taiwan show evidence for a transition from the subduction of ocean crust to highly extended, transitional continental crust of the northern South China Sea distal margin. During oceanic subduction, accretion and underplating of thick sedimentary cover sequences create a large 13-15 km thick accretionary prism. Prior to the encroachment of the continental shelf, there is evidence for further underplating of transitional distal margin crust to the base of the prism. These findings support a multi-phase collisional model in which early growth of the mountain belt is driven by structural underplating of the previously sedimentary-only accretionary prism with blocks of transitional crust from the distal rifted margin. Geophysical profiles offshore eastern Taiwan show evidence for asymmetric crustal thickening, from 12-18 km, along the entire length of the Gagua Ridge suggesting the West Philippine Basin oceanic crust is underthust beneath that of the Huatung Basin. In this interpretation, the Gagua Ridge was the result of a failed subduction initiation event during the early Miocene that may have existed simultaneously and, for a short time, competed with the Manila subduction zone in accommodating convergence between the Eurasia and Philippine Sea plates. / text