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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Enhancement in Degradation of Environmental Pollutants: Fenton Degradation of 2,4,6-Trinitrotoluene and Photodegradation of Deepwater Horizon Crude Oil

King, Sarah M. 18 May 2012 (has links)
Pollution poses serious threats to both the environmental and the organisms that depend on their environment for survival. Due to the toxicity of most contaminants, there is a dire need for remediation of polluted sites. Remediation studies were conducted on two high priority pollutants: 2,4,6-trinitrotoluene (TNT) and crude oil. TNT was the most common explosive used in the 20th century. Continuous contamination has resulted in an urgent need for remediation. Fenton reagent provides an advanced oxidation process that is capable of remediating recalcitrant explosives, such as TNT. One drawback of Fenton chemistry is that the reaction requires acidic pH to prevent precipitation of iron. Our studies have investigated Fenton degradation of TNT at near neutral pH with several modifiers present: β-cyclodextrin, carboxymethyl-β-cyclodextrin, alcohols, and polyethylene glycol (PEG, MW 200, 400, or 600 g/mol). Fenton degradation was also carried out on other nitroaromatics to better understand the reaction mechanism with PEG 400. Further mechanistic studies investigated the production of nitrate and ammonium with and without PEG 400. The Deepwater Horizon oil spill devastated the Gulf of Mexico and the surrounding wetlands. There are several mechanisms for degradation of oil released into aquatic environments. Bioremediation is one of the most important remediation methods; however degradation becomes stagnant in low nutrient waters. Furthermore, larger molecular weight alkanes and polycyclic aromatic hydrocarbons (PAHs) are not readily available for biodegradation. Transformation of these molecules often requires initial photodegradation. We have investigated the photochemical transformation of oil films with and without photocatalysts present. To better understand the photochemical transformations that occur to the Deepwater Horizon oil, we have conducted additional studies with dispersants present.
2

Achieving Reliable Generation \& Delivery of Energy Through Robust Optimization

Danandeh, Anna 01 January 2015 (has links)
In this dissertation, we elaborate on the inherent risks and uncertainties in power systems and associated industries, and develop practical solution methods to eliminate their adverse effects. our research agenda consists of practice-driven problems in different stages of power generation as follows. (1) Affordable fuel procurement through developing a comprehensive fuel supply chain design and operations planning system for electricity generation companies, (2) reliable electricity generation through incorporating dynamic asset rating concept in the unit commitment problem, and (3) efficient demand management through proposing a job scheduling model for effective local generation consumption. Since reliability cannot be compromised in energy sector, robust optimization has been adopted as a powerful method to model multiple sources of uncertainty, and to protect the performance of the systems against worst situations. Exact and heuristic methods are then developed and customized to solve these computationally challenging problems. In particular, inspired by the challenges in solving two-stage robust optimization problems, we developed a multi-scenario cutting plane generation algorithm, that considers all the realizations of the uncertainty set at once, and thus, alleviates the computational challenge.
3

Surface area of coal as influenced by low temperature oxidation processes

Arredondo, Salvador Leon 01 January 1980 (has links)
The possibility of increasing the amount of readily accessible surface area by enlarging the 5 A pore was examined via pretreating the PSOC-371 coal with gases such as nitrogen, nitrogen-oxygen, and ozone-oxygen and hydrogen peroxide solutions. Surface areas were obtained from nitrogen adsorption at 77 K and carbon dioxide adsorption at either 298 or 195 K for each sample before and after treatment.
4

One-step Laser-Induced Hydrogen Generation from Coal Powders in Water

Seyitliyev, Dovletgeldi 01 July 2017 (has links)
This study presents a simple way of obtaining hydrogen gas (H2) from various ranks of coal, coke, and graphite using nanosecond laser pulses. Powder samples of coal and graphite with and without water were irradiated with 1064 nm and 532 nm pulses from an Nd: YAG laser for 45 minutes under air and argon atmospheres. It was observed that 532 nm laser pulses were more effective than 1064 nm pulses in gas generation and both were nonlinearly correlated with respect to the laser energy density. Mainly hydrogen (H2) and carbon monoxide (CO) were observed. The H2 to CO ratio shows that the highest efficiency rank was the anthracite coal, with an average ratio of 1.4 due to its high fixedcarbon content and relatively high hydrocarbon amount. Coal samples were characterized by scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, Thermogravimetric analyzer (TGA), and calorimeter. Graphite was used as a pure carbon source to study the possible reactions of gas yielded during irradiation process. The amount of H2 produced was negligible when graphite powder was exposed under the air and argon atmospheres. On the other hand, H2 was obtained from irradiation of graphite powder in the presence of water due to a possible carbon-water reaction. When coal powders were irradiated under air and argon atmosphere, the amount of produced H2 increased drastically compared to graphite due to the presence of hydrocarbons in coal. In addition, theoretical simulations by a standard finite difference method supported experimental observations.
5

Transportation Electrification and Hospital Emergency Planning

Skinner, Nathaniel Winfield 01 January 2018 (has links)
Because transportation in the San Francisco Bay Area is increasingly dependent on electricity, factors such as limited electricity storage capacity and nontransferability of batteries between vehicles need to be considered by emergency response planners (ERPs). The purpose of this study was to investigate planning for providing the power to provide emergency transportation for hospital staff/administration and those injured after earthquakes. The research questions of transportation need of emergency staff and patients after an earthquake and differences between Bay Area cities and counties in considering transportation needs were addressed in this qualitative study utilizing a collective case study to assess electric vehicle use as articulated in 48 public emergency management and health agency documents that discussed post-disaster transportation planning. Norris, Stevens, Pfefferbaum, Wyche, and Pfefferbaum's community resilience theory served as the theoretical lens for analyzing the impacts of electric transportation on hospitals. Some ERPs included transportation fuel in their documents, whereas ERPs specifically focused on transportation did not. The review, coding, and analysis yielded 2 primary themes: fuel for emergency planning is focused primarily on fuel for generators, with few documents discussing fuel for transportation; many documents lack currency with 28 updated before 2015 or not having an identifiable date. Community resilience from disruption is likely to lead to a state of vulnerability as well as a disconnection between community resilience theory and ERP planning. The implication for positive social change is to help Bay Area ERPs understand how to increase community resilience by including adaptation to changes in transportation fuel sources in their plans.
6

Design of Colloidal Composite Catalysts for CO2 Photoreduction and for CO Oxidation

Mankidy, Bijith D. 01 January 2012 (has links)
In this doctoral dissertation, novel colloidal routes were used to synthesize nanomaterials with unique features. We have studied the impact of nanoparticle size of catalyst, role of high surface area of a photocatalyst, and the effect of varying elemental composition of co-catalytic nanoparticles in combination with core-shell plasmonic nanoparticles. We have demonstrated how physical and chemical characteristics of nanomaterials with these unique features play a role in catalytic reactions, specifically the oxidation of CO and the photoreduction of CO2. The first objective of this doctoral dissertation involved the preparation of CoO nanoparticles with discrete nanoparticles sizes (1-14 nm) using a colloidal thermal decomposition technique. The impact of size of CoO for CO oxidation reaction was studied using an in-situ FTIR reactor. By analyzing the reaction intermediates observed using in-situ IR, a two-step reaction mechanism was proposed. The average values of activation energies of step-1 and step-2 were ∼15 kJ/mol and ∼90 kJ/mol that showed step-2 was the rate determining step. From activation energy calculations for the catalysts of different CoO sizes, it was found that activation energy increased as nanoparticle size increased. The second objective of this doctoral research involved the development of high surface area TiO2 nanoshells using polymeric templates. The deposition of TiO2 was achieved by surface functionalization procedures. TiO2 was then deposited on colloidal SiO2 after the SiO2 surface was modified by grafting poly(NIPAAM) oligomers. TiO2 nanoshell composites possessed high surface of ∼35 m2/gm. The photocatalytic performances of TiO2 nanoshells and Pt deposited TiO2 nanoshells were evaluated for CO2 photoreduction reaction. Primary products from CO2 photoreduction reactions were carbon monoxide and methane. The product yield and product selectivity of hydrocarbons produced during CO2 photoreduction was measured using a home-built FTIR reactor. When Pt was deposited on TiO2 nanoshells, the overall yield was nearly doubled and the CH4 selectivity nearly quadrupled. The third objective pursued in this research project was to synthesize Ag, Pt and bimetallic Ag-Pt nanoparticles to demonstrate the role of elemental composition of metal co-catalysts for CO2 photoreduction reaction. The novel bimetallic nanoparticles played an important role in improving product selectivity in the photocatalytic reduction of CO2. Bimetallic Ag-Pt nanoparticles synthesized with low Pt content had 4-5 times higher CH4 selectivity compared to native TiO2. The final objective was to prepare Ag(core)/SiO2(shell) nanoparticles with specific core-shell structure to enhance photoactivity of TiO2 during catalytic reactions. Ag@SiO2 core-shell nanoparticles have plasmonic character that helped to improve product yield by increasing the number of electron-hole pair generations. When bimetallic Ag-Pt nanoparticles were used in combination with core-shell Ag@SiO2 plasmonic nanoparticles, the overall yield increased ∼8-fold compared to native TiO2.
7

Improving Methods for the Successful Establishment of Switchgrass

Monin, Whitney Marie 01 January 2014 (has links)
Our research investigated whether priming switchgrass seeds with water or ethephon would increase stand establishment in the field. ‘Alamo’ seed germinated faster and grew taller than ‘Cave-in-Rock.Seeds primed for six days in water or for one day in ethephon 10 mM had the greatest seedling densities. In growth chamber environments seed priming were tested to hasten germination velocity. Seeds primed for two, four or six days in water germinated faster than unprimed seeds. Ethephon treatments reduced overall germination and germination velocity. Accent and Accent Q herbicides containing nicosulfuron are used to control weeds. To test ‘Alamo’ sensitivity to these herbicides, greenhouse evaluations were conducted. Seedlings treated with Accent Q had lower shoot fresh and dry weights than Accent treated seedlings. Seedling atrazine tolerance was examined in a greenhouse study at various growth stages (1, 2 and 4 true leaves). One and two true leaf were more sensitive to herbicide damage than the 4 leaf seedlings. To investigate difference in atrazine tolerance due to differential atrazine metabolism, 14C atrazine metabolism was examined in 1, 2 and 4 leaf ‘Alamo’ seedlings. 24-48 hours after exposure, 4 leaf seedlings metabolized atrazine at a greater rate than 1 and 2 leaf stage seedlings.
8

Relationship of Solar Energy Installation Permits to Renewable Portfolio Standards and Insolation

Butler, Kirt Gordon 01 January 2015 (has links)
Legislated renewable portfolio standards (RPSs) may not be the key to ensure forecast energy demands are met. States without a legislated RPS and with efficient permitting procedures were found to have approved and issued 28.57% more permits on average than those with a legislated RPS. Assessment models to make informed decisions about the need and effect of legislated RPSs do not exist. Decision makers and policy creators need to use empirical data and a viable model to resolve the debate over a nationally legislated RPS. The purpose of this cross-sectional study was to determine if relationships between the independent variables of RPS and insolation levels and the dependent variable of the percentage of permits approved would prove to be a viable model. The research population was 68 cities in the United States, of which 55 were used in this study. The return on investment economic decision model provided the theoretical framework for this study and the model generated. The output of multiple regression analysis indicated a weak to medium positive relationship among the variables. None of these relationships were statistically significant at the 0.05 level. A model using site specific data might yield significant results and be useful for determining which solar energy projects to pursue and where to implement them without Federal or State mandated RPSs. A viable model would bring about efficiency gains in the permitting process and effectiveness gains in promoting installations of solar energy-based systems. Research leading to the development of a viable model would benefit society by encouraging the development of sustainable energy sources and helping to meet forecast energy demands.
9

STRATIGRAPHIC, GEOCHEMICAL, AND GEOCHRONOLOGICAL ANALYSIS OF THE WOLFCAMP-D INTERVAL, MIDLAND BASIN, TEXAS

Perlman, Zachary S. 01 January 2017 (has links)
Subsurface data derived from ~388 ft of drill core from Martin County (TX) were used to understand the depositional setting of the Wolfcamp-D, a petroleum producing interval in the Midland Basin. Elemental geochemistry collected via x-ray fluorescence revealed a highly variable depositional history marked by the deposition of diverse siliciclastic and carbonate lithofacies. Integration of multiple datasets resulted in the interpretation of nine lithofacies, whose deposition appears cyclical. Correlations between molybdenum and total organic carbon indicate slow recharge of bottom waters and anoxic/euxinicconditions within the basin. The presence of phosphatic nodules coinciding with siliceous black mudrocks suggested high levels of primary productivity driven by upwelling. High-frequency sea level variability, driven by far-field glaciation and regional paleoclimate, were key controls on both the chemostratigraphy and lithofacies. Along-strike variability is seen throughout the basin due to paleobathymetry, proximity and connections to paleochannels, and localized structures. Rhenium-osmium (Re/Os) geochronology was conducted on siliceous mudrocks with high total organic carbon. A depositional age of 300 ± 18 Ma was obtained, partially confirming previous correlations to shelf biostratigraphic data. Scatter in the Re/Os data is likely due to mixing in the basin or non-hydrogenous Os incorporated into the analysis due to the method of preparation.
10

Algae: Opportunities for Biomass Feedstock Production, Wastewater Treatment and Educational Outreach

Halfhide, Trina Cassandra 01 May 2014 (has links)
Algae are a diverse group of simple organisms that lack roots, stems or leaves and are able to use sunlight, carbon dioxide, and nutrients to produce complex compounds, such as carbohydrates, proteins and lipids. These compounds, especially lipids, are highly sought-after by agricultural, nutraceutical and energy interests. Although there is great potential for algae derived biofuels, there are technical and economic challenges associated with their cultivation. Relevant to this dissertation, the environmental impacts associated with algae cultivation can be reduced by using municipal and agricultural wastewaters as a water and nutrient source. This research was divided into three sections to address current challenges in the algal industry and science, technology, engineering and math (STEM) education. The sections were: 1) examination of the growth of indigenous algae on wastewater (centrate) produced from dewatering anaerobically digested municipal sludge, 2) examination of the effect of non-axenic conditions on the growth of three different algal cultures using wastewater from a recirculating aquaculture system (RAS), and 3) using wastewater treatment and algae to increase scientific inquiry in authentic science research with high school students. In the first section, indigenous algae were cultivated on centrate under natural light conditions in a semi-continuous photobioreactor. A non- linear bio-optical model was developed considering Michaelis-Menten photosynthesis-irradiance response. The bio-optical model was applied to fit the cumulative biomass data and had an R-squared value of 0.96. The second section examined the growth and accumulation of storage product. Higher calorific values were observed for all algae cultures when grown under non-axenic conditions, most likely due to significantly higher lipid contents. Significantly higher algal lipid contents under non-axenic conditions may be attributed to the stress of the presence of RAS microorganisms. Finally, having a university-based algal project with involvement of University of South Florida (USF) researchers, teachers and high school (HS) students facilitated increased scientific understanding and skills among HS students. Outcomes included graduate students gaining greater in-depth practical understanding as these students had to learn skills, such as designing a photobioreactor and then immediately had to teach HS students how to construct photobioreactors, design and conduct experiments, and gather scientific data. HS students gained a greater understanding of biological and chemical processes, such as photosynthesis. In addition, they learned important skills, such as calculating means and standard deviations using Excel, orally communicating scientific concepts and preparation of a PowerPoint presentation.

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