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Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3716. Adviser: Mark Rood. Includes bibliographical references (leaves 112-125) Available on microfilm from Pro Quest Information and Learning.

<p> Smart materials, within the realm of structural engineering, are mainly used as either sensoric mechanisms or as structural damping mechanisms. For the most part, structural enhancement utilizing smart materials is not seen in main stream structural engineering practices. </p><p> Piezoelectric ceramics and shape memory alloys are two smart materials that are explored. In comparison shape memory alloys have far greater actuation strain (2% - 7%) than piezoelectric (0.08% - 0.11%) ceramics. </p><p> Piezoelectric actuators are employed as surface actuators. Shape memory alloys are also explored in this manner, but the analysis is taken a step further where shape memory alloys are explored as beam and column retrofit elements. </p><p> Because of the low mechanical range of the piezoelectric material, the potential for stress reduction is bound to lower stress applications. The general conclusion for shape memory alloys is that it would be suitable for high stress applications which include main stream steel applications. </p>

This work contains the results of studies of three fluid projects that investigated aspects of groundwater contaminant transport and remediation. The first project performed at Hill Air Force Base in Utah evaluated the performance of a vertical water flushing system for the remediation of a multi-component non-aqueous phase liquid. This project also encompassed determining contaminant distribution through soil core analysis and partitioning tracer studies. The work determined that the limited aqueous solubility of the primary contaminants led to the lack of efficient removal by the vertical water flushing system. The second remediation test evaluated the performance of the solubility enhancing agent cyclodextrin in restoring the contaminated aquifer at Air Force Plant 44 in Tucson, Arizona. The results concluded that this advanced remediation technique was efficient in removing trichloroethene. Further, the project demonstrated the ability to separate TCE from the extracted solution through treatment with an air-stripping system and re-inject it for another multiple flushing of the aquifer. Additional site assessment including determination of lithological and contaminant distribution through well-bore sampling and system optimization by conducting a series of vertical tracer studies. To evaluate the impact of groundwater chemistry and travel distances on the transport behavior of enteric virus, experiments were conducted in the unconfined aquifer at the USGS Cape Cod Research Site. Separate experiments examined the transport behavior of bromide (Br-) and the bacteriophage PRD-1 in the effluent plume and the shallower uncontaminated groundwater. Results indicated the vast majority of the bacteriophages were lost from solution upon injection. The results further showed that this initial loss occurred within the first meter for the uncontaminated zone, whereas it occurred over a 4-meter distance in the contaminated zone. The greater distance required for the contaminated zone to defect similar mass loss is attributed to anion-exchange competition by organic matter, phosphate, and other anions present in higher concentrations in the contaminated zone. The results of this study indicate that a small, but infectious fraction of viable virus particles can persist and travel significant distances in sedimentary aquifers, despite variability in water chemistry.

Thunderstorm rainfall in semi-arid areas has very high spatial and temporal variability. Knowledge of the spatial characteristics of thunderstorm rainfall is important for the increasing demands of distributed hydrological modeling. Rainfall data from the semiarid USDA-ARS Walnut Gulch Experimental Watershed (WGEW) were used to investigate the spatial characteristics of thunderstorm rainfall in southeast Arizona and to develop a daily thunderstorm rainfall generator. WGEW has a very dense rain-gage network (1 gage per 2 km²) and very comprehensive historical records (over 40 years). These data were used to identify the following physical characteristics of thunderstorm rainfall: the transition probabilities, thunderstorm cell size, orientation, maximum rainfall depth within a storm cell and storm center location. The following statistical characteristics were identified through an analysis of the WGEW data: the storm center locations on WGEW have a Poisson distribution, the maximum depth within a storm cell has a lognormal distribution, the shape of a storm cell is elliptical with an average major axis length to the minor axis length ratio of 1.55 and the orientation of a storm cell is primarily NW or NE. The storm coverage and the maximum rainfall depth within a storm cell have a linear relationship after a logarithmic transformation. Storm occurrences have higher frequencies during the last two weeks of July and the first two weeks of August than other wet periods (July ∼ September). The stochastic daily summer rainfall generator being developed based on the statistical characteristics above was tested by comparing the simulation results with long-term historical records of representative gages on WGEW.

The first part of this work demonstrates that membrane air-stripping (MAS) is an efficient method for separating volatile organic compounds from water. The introduction of a membrane barrier to separate the air and water phases provides several advantages without increasing the total mass transfer resistance. Efficient removal can be achieved at lower air/water ratios than are typically required in packed-tower. Mathematical models were developed to simulate the performances of both countercurrent-flow and cross-flow contractors. Model simulations indicate that the cross-flow contractor is more efficient than the countercurrent-flow contractor. The second part of this work demonstrates the degradation of aqueous-phase CT in a continuous-flow reactor with a porous copper electrode. Removal of CT increases with more negative cathode potentials until hydrogen evolution becomes excessive. At that point, the increase in solution potential offsets further change in cathode potential and limits further improvement in reactor performance. Removal efficiency was predicted to vary inversely with the liquid velocity. At solution conductivities less than 1.0 S/m, both experiment and simulation showed that reactor performance is seriously handicapped by solution potential. The model predictions were in reasonable agreement with experimental results for high conductivity solutions (≥1.0 S/m). At lower conductivities, the discrepancies between the predictions and experimental results are due to the loss of validity of the zero-solution-potential boundary condition at the downstream end of the cathode. The third part of this work investigates a cylindrical reactor geometry in which the anode is wrapped closely around the cathode. This arrangement eliminates the solution potential limitation encountered in the downstream-anode configuration, making it a promising tool for remediation of low-conductivity groundwater. Higher removals of CT are achieved under more negative cathode potential. Increasing the hydrodynamic residence time by increasing the cathode length is also an efficient way to improve the CT conversion even for low-conductivity solutions. An intrinsic drawback of this configuration is lowered current efficiency due to the high proton concentration at the perimeter of the cathode where most of the current is generated. However, low energy consumption due to small overall potential drop across the reactor at least partially compensates for the drawback.

Chlorinated solvents are pollutants found frequently in the environment. Whereas lower chlorinated solvents are easily degraded under aerobic conditions, degradation of higher chlorinated solvents is favored under anaerobic conditions. It is known that some compounds can act as redox mediators assisting the electron exchange required for the anaerobic dechlorination reactions to occur. Redox mediators are compounds that can assist the anaerobic dechlorination reactions either abiotically or biologically by accelerating the degradation rates. The objective of this study is to evaluate the role of different redox mediators on the anaerobic degradation of higher chlorinated solvents such as chloroform (CF), carbon tetrachloride (CT) and perchloroethylene (PCE). The redox mediators studied are vitamin B12 (cyanocobalamin CNB12-hydroxocobalamin HOB12), riboflavin (RF) and a model of humic compound anthraquinone-2,6-disulfonate (AQDS). The study includes abiotic and biological redox mediated dechlorination. The biological studies involve two varieties of unadapted methanogenic sludge. The results obtained demonstrate that redox mediators greatly enhance the degradation rates of CF and CT when utilized at substoichiometric molar ratios. At the same time, the results also highlight the importance of the role of the microorganisms during the dechlorination process. Vitamin B12 and riboflavin presented larger impact than AQDS on the degradation rates of CF and CT. Since vitamin B12 had the highest positive impact on the biodegradation rates of CF and CT, an attempt was done to stimulate its biosynthesis by the methanogenic sludge during the CT dechlorination. The approach used to promote the biosynthesis of vitamin B12 involved different vitamin B12 precursors such as porphobilinogen, and some primary substrates such as methanol and 1,2-propanediol. The results obtained show that the formation of the corrin ring may be the limiting step during vitamin B12 biosynthesis. One carbon substrates such as methanol, combined with porphobilinogen had a positive impact on the biodegradation rates of CT. The study suggests that the combination of methanol and vitamin B12 precursors could be a good alternative to stimulate the vitamin B12 biosynthesis by methanogens and therefore, the enhancement of the biodegradation rates of chlorinated solvents. This study presents the lowest molar ratio of vitamins that enhanced the dechlorination rates reported so far for biodegradation of chlorinated solvents involving methanogens. Also, this is the first report on the use of riboflavin as a redox mediator during dechlorination processes.

This research presents an integration of a stochastic space-time rainfall model and distributed hydrologic simulation with GIS. The integrated simulation system consists of three subsystems: a stochastic space-time rainfall model, a geographical information system (GIS), and a distributed physically-based hydrologic model. The developed stochastic space-time rainfall model is capable of estimating the storm movement and simulating a random rainfall field over a study area, based on the measurement from three raingauges. An optimization-based lag-k correlation method was developed to estimate the storm movement, and a stochastic model was developed to simulate the rainfall field. A GIS tool, ARC/INFO, was integrated into this simulation system. GIS has been applied to automatically extract the spatially distributed parameters for hydrologic modeling. Digital elevation modeling techniques were used to process a high resolution digital map. A distributed physically-based hydrologic model, operated in HEC-1, simulated the stochastic, distributed, interrelated hydrological processes. The Green-Ampt equation is used for modeling the infiltration process, kinematic wave approximation for infiltration-excess overland flow, and the diffusion wave model for the unsteady channel flow. Two small nested experimental watersheds in southern Arizona were chosen as the study area where three raingauges are located. Using five recorded storm events, a series of simulations were performed under a variety of conditions. The simulation results show the model performs very well, by comparing the simulated runoff peak flow and runoff depth with the measured ones, and evaluated by the model efficiency. Both model structure and model parameter uncertainties were investigated in the sensitivity analysis. The statistical tests for the simulation results show that it is important to model stochastic rainfall with storm movement, which caused a significant change in runoff peak flow and runoff depth from that where the input is only one gage data. The sensitivity of runoff to roughness factor N and hydraulic conductivity Ks were intensively investigated. The research demonstrated this integrated system presents an improved simulation environment for the distributed hydrology.

A series of chlorinated low-molecular-weight alkanes and alkenes was transformed electrolytically at metal cathodes at potentials from -0.3 to -1.4V (vs. SHE). Products included nonchlorinated hydrocarbons and less chlorinated intermediates. Product distributions are highly dependent on cathode material and applied cathode potential. Kinetics was first-order in the concentration of the halogenated targets. The specific first-order rate constants are function of cathode potential, cathode material, solution characteristics, and reactant identify. When transformation kinetics was governed by polarization resistance, rate constants were correlated with degree of halogenation and standard reduction potential for the predominant transformation reaction (as indicated by product analysis). Log-transformed reaction rate constants for reduction of chlorinated alkanes, derived via experiments at the same cathode potential (E(c) = -1.0 or -1.2V vs. SHE), were linearly related to carbon-halogen bond dissociation energies. A physical model for the observed correlation was developed from transition-state theory. The chlorinated ethenes reacted much faster than predicted from bond enthalpy calculations, suggesting that alkenes are not transformed via the same mechanism as the chlorinated alkanes. Polarographic study demonstrated that the shift of E₁/₂ of CCl₄ reduction was correlated with water concentration in solvent-predominated mixtures. Successful interpretation of these findings with a physical model suggested that solvents involved the rate-determining step of CCl₄ electrolysis both kinetically and mechanistically. The capture of trichloromethyl radicals with a spin trap (PBN) in an electrochemical system provided direct evidence supporting the free radical mechanism in electrolytic reduction of CCl₄. Gas-phase reductions of chlorinated alkanes and alkenes were studied in a modified fuel cell. Reactor performance was a function of the metal catalyst amended to the reactor cathode, the reactor potential, cathode temperature, the target compound identity, the partial pressure of O₂(g) in the cathode chamber and the condition (time in service) of the cathode. Single-pass CCl₄ conversions could achieve 90 percent with a mean residence time for gases in the porous cathode much less than a second. Reactor performance deteriorated with the presence of oxygen and time in service. Conversion efficiency was restored, however, by temporarily eliminating the halogenated target(s) from the influent stream or by briefly reversing reactor polarity.