Engineering Commons^™

Wind Flow Characteristics Of Multi-Vortex Tornadoes And Their Wind Effects On Residential Houses, Yi Zhao

Doctoral Dissertations

"Tornadoes strike the USA very frequently, with an average of 1200 reports per year, and the average annual tornado-induced property loss has reached $10B. The devastation from recent tornadoes have prompted a renewed interest in better understanding tornado dynamics, their interactions with the built environment, and the performance of civil structures during tornadoes. In the past, the wind effects caused by single-vortex tornadoes have been widely studied, while the multi-vortex tornadoes were rarely considered. In fact, many previous deadly, costly tornadoes involved multiple vortices. Therefore, it is important to understand the wind flow characteristics of multi-vortex tornadoes in order to …

Ecological Restoration Of Lead/Zinc/Copper Mine Tailings: Phytomanagement And Amendment Strategies To Enhance Substrate Functionality And Biomass Production, Mariam K. Al-Lami

Doctoral Dissertations

“The extreme physiochemical characteristics of mine tailings inhibit microbial processes and natural plant growth. Consequently, vast and numerous tailings sites remain barren for decades and highly susceptible to wind and water erosion. Phytostabilization is a cost-effective and ecologically productive remediation approach; however, tailings revegetation is generally challenging and must often be assisted with appropriate soil amendments. Amendments applied individually in greenhouse studies discussed herein revealed notable improvement in bioenergy crops growth only with biosolids treatments. Recalcitrant carbon amendments (biochar and humus) showed notable impact only on tailings physichochemical and hydraulic properties. Nevertheless, biosolids may not support sustained vegetation due to …

Exposure Assessment Of Emerging Contaminants: Rapid Screening And Modeling Of Plant Uptake, Majid Bagheri

Doctoral Dissertations

"With the advent of new chemicals and their increasing uses in every aspect of our life, considerable number of emerging contaminants are introduced to environment yearly. Emerging contaminants in forms of pharmaceuticals, detergents, biosolids, and reclaimed wastewater can cross plant roots and translocate to various parts of the plants. Long-term human exposure to emerging contaminants through food consumption is assumed to be a pathway of interest. Thus, uptake and translocation of emerging contaminants in plants are important for the assessment of health risks associated with human exposure to emerging contaminants. To have a better understanding over fate of emerging contaminants …

Investigation Of Urea Decomposition And Deposit Formation In Diesel Exhaust After-Treatment System, Anand Alembath

Doctoral Dissertations

“Urea-selective catalytic reduction (SCR) system has proved to be an effective solution to reduce NO_x emissions in commercial vehicle (CV) diesel engines. A significant challenge in urea injection is to comprehend its decomposition chemistry that leads to formation of undesired deposits in the exhaust system unit. Due to complex interaction of multi-phase fluid flow and transport processes, significant uncertainty is associated with the identification of interacting factors that control the deposit initiation and its growth. To meet the future ultra-low NO_x emissions and to deliver ammonia without deposit formation, there is an imminent need to develop the urea-SCR …

Physical And Biological Factors Affecting Oxygen Transfer In The Activated Sludge Wastewater Treatment Process, Kenneth A. Campbell

Doctoral Dissertations

“The activated sludge (AS) process is widely utilized for wastewater treatment due to its versatility and general resiliency, but is energy intensive, requiring aeration and mixing energy inputs to maintain the biochemical reaction and optimize treatment performance. This study is focused on determining different factors that influence oxygen transfer and consequently its energy demand.

AS morphology, as described by the d₁₀, d₂₀, d₃₂, specific filament length (SFL), 30 min settleability (SV₃₀), etc., does influence the OTE. Filamentous organisms increase the hydrodynamic radius of suspended particles, which dilates mixed liquor apparent viscosity (µ …

The Combined Toxic Effect Of Nanoparticles And Lead In The Presence Of Algae (Raphidocelis), Xuesong Liu

Doctoral Dissertations

"The elevated toxicity of toxic metals in the presence of nanoparticles (NPs) has raised significant concerns on the NP environmental safety. This research focuses on the impact of environmental conditions, specifically algae, on this type of toxicity. An indicator aquatic organism, Ceriodaphnia dubia (C. dubia), was used to examine the combined toxicity and toxicity mitigation from algae by monitoring its 24-h mortality. Four papers are included in this research, which focus on four aspects of the combined toxicity and the corresponding algae (Raphidocelis) impact. The first paper examines the algae impact on the combined toxicity of …

Designing Bifunctional Materials For In-Situ Capture And Conversion Of Volatile Organic Compounds, Anirudh Krishnamurthy

Doctoral Dissertations

”Volatile organic compounds (VOCs) are a class of organic liquid compounds with low vapor pressures, which enables them to vaporize at ambient conditions. VOCs are largely toxic, carcinogenic, and mutagenic, and have profound adverse effects on human health and the ecological environment. Many VOCs cause ruinous health effects even at very low concentrations (ppm) and therefore control of these organic compounds is essential for ensuring good air quality. A large portion of VOCs cause catastrophic health effects such as cancer or liver damage even at very low concentrations (ppm), and the control of these compounds is vital in ensuring good …

Atomic Layer Deposition Prepared Nanostructured Materials For Various Catalytic Reactions, Xiaofeng Wang

Doctoral Dissertations

"Atomic layer deposition (ALD) has been widely used for thin film coating and metal nanoparticles (NPs) preparation. In this report, the applications of ALD prepared nanostructured materials in catalysis were examined.

Highly dispersed Pt monometallic catalysts with different substrates and multi-walled carbon nanotubes (MWCNTs) supported Pt-Co bimetallic catalysts were synthesized by ALD for selective hydrogenation of α, β-unsaturated aldehydes to unsaturated alcohols (UA). Pt/MWCNTs showed the highest selectivity of UA in selective hydrogenation of citral, as compared to Pt/SiO₂, Pt/ALD-Al₂O₃, and Pt/γ-Al₂O₃. After adding Co, the highest selectivity was achieved …

Contributing Factors To Child Stunting In Guatemala: A Systems Analysis Focused On Enteric Disease Transmission And Mycotoxin Exposure, Lee Emerson Voth-Gaeddert

Doctoral Dissertations

"Child stunting -- low height-for-age -- is a United Nation's indicator for chronic malnutrition that has been linked to both acute and chronic health problems. Data from Guatemala suggests for children under five years of age, 49% are classified as stunted. This dissertation tests the following hypotheses, among children in Guatemala 1) environmental enteric dysfunction (EED) is correlated with height-for-age, 2) aflatoxin B (AFB) exposure is correlated with height-for-age, and 3) AFB exposure is correlated with EED. A network analysis was conducted on data from the US Agency for International Development (USAID) collected in 2012 to identify trends in a …

Phytoforensics: Applications In Vapor Intrusion Assessment, Jordan Lee Wilson

Doctoral Dissertations

"Vapor intrusion (VI) occurs when contaminants in the vapor phase migrate in the shallow subsurface and enter buildings through cracks, seams, and gaps and has been recognized as a serious human-health threat as occupants are exposed to potentially harmful concentrations over long periods of time. The VI pathway has recently (2017) been identified as a primary exposure pathway and implemented into the Hazard Ranking System for inclusion on the Nation Priorities List. However, assessing VI and human exposure is not simple and current methods are time-, cost-, and labor-intensive; intrusive; and temporally and spatially variability. Trees are ideal candidates for …