Engineering Commons^™

On Variants Of Sliding And Frank-Wolfe Type Methods And Their Applications In Video Co-Localization, Seyed Hamid Nazari

All Dissertations

In this dissertation, our main focus is to design and analyze first-order methods for computing approximate solutions to convex, smooth optimization problems over certain feasible sets. Specifically, our goal in this dissertation is to explore some variants of sliding and Frank-Wolfe (FW) type algorithms, analyze their convergence complexity, and examine their performance in numerical experiments. We achieve three accomplishments in our research results throughout this dissertation. First, we incorporate a linesearch technique to a well-known projection-free sliding algorithm, namely the conditional gradient sliding (CGS) method. Our proposed algorithm, called the conditional gradient sliding with linesearch (CGSls), does not require the …

Ligand-Promoted Dissolution Of Uranyl Phosphate Across Scales, Brennan Ferguson

All Dissertations

The formation of uranyl phosphate precipitate is a remediation strategy because the low solubility of uranyl phosphate minerals, like chernikovite, limits the mobility of uranium in contaminated soils. However, organic ligands can complex with aqueous metal cations to form more soluble species. For example, citrate is a commonly occurring organic ligand produced by plants and microbes that increases the solubility of uranium and therefore the dissolution of uranyl phosphate minerals in the uranyl phosphate-citrate system. This effect is an important control on the mobility of uranium in organic-rich, and near-surface vegetated environments. Nevertheless, key aspects of the citrate-uranyl phosphate system …

Elucidation Of Active Site And Mechanism Of Metal Catalysts Supported In Nu-1000, Hafeera Shabbir

All Dissertations

Advances in extraction of shale oil and gas has increased the production of geographically stranded natural gas (primarily consisting of methane (C1) and ethane (C2)) that is burned on site. A potential utilization strategy for shale gas is to convert it into fuel range hydrocarbons by catalytic dehydrogenation followed by oligomerization by direct efficient catalysts. This work focuses on understanding metal cation catalysts supported on metal-organic framework (MOF) NU-1000 that will actively and selectively do this transformation under mild reaction conditions, while remaining stable to deactivation (via metal agglomeration or sintering). I built computational models validated by experimental methods to …

Geology-Based Shear-Wave Velocity Model Of Reference Site Conditions In South Carolina For Seismic Site Response Analysis, Camilius Amevorku

All Dissertations

Assessing earthquake hazard in the State of South Carolina is important because it is one of the most seismically active regions of the eastern United States and has experienced earthquakes of damaging levels in the historical past. Examples of these damaging seismic events are the 1886 Charleston earthquake (M 6.7 to 7.5) and the 1913 Union County earthquake (M 4.5 to 5.5).

Small-strain shear-wave velocity (V_S) is an important parameter in performing site response analysis. The deep nature of the top of reference firm rock (i.e., V_S ≥ 760 m/s or B-C boundary) due to …

Development Of A Reverse Engineered, Parameterized, And Structurally Validated Computational Model To Identify Design Parameters That Influence American Football Faceguard Performance, William Ferriell

All Dissertations

Traumatic brain injury (TBI) continues to have the greatest incidence among athletes participating in American football. The headgear design research community has focused on developing accurate computational and experimental analysis techniques to better assess the ability of headgear technology to attenuate impacts and protect athletes from TBI. Despite efforts to innovate the headgear system, minimal progress has been made to innovate the faceguard. Although the faceguard is not the primary component of the headgear system that contributes to impact attenuation, faceguard performance metrics, such as weight, structural stiffness, and visual field occlusions, have been linked to athlete safety. To improve …

Controlled Manipulation Of Droplets On Fibers: Fundamentals And Printing Applications, Yueming Sun

All Dissertations

In this dissertation, the drop interactions with a single fiber is discussed under an application angle for the development on new Drop-on-Demand (DOD) printhead using a fiber-in-a-tube platform[1] to print highly viscous materials[2]. To control the drop formation and manipulation on fiber, one needs to know how the fiber wetting properties and the fiber diameter influence drop formation. And then, one needs to know the effects of fiber movement in the device on drop formation. These two questions constitute the main theme of this dissertation.

Before this study, it was accepted that the liquids could not form axisymmetric droplets if …

Subwavelength Engineering Of Silicon Photonic Waveguides, Farhan Bin Tarik

All Dissertations

The dissertation demonstrates subwavelength engineering of silicon photonic waveguides in the form of two different structures or avenues: (i) a novel ultra-low mode area v-groove waveguide to enhance light-matter interaction; and (ii) a nanoscale sidewall crystalline grating performed as physical unclonable function to achieve hardware and information security. With the advancement of modern technology and modern supply chain throughout the globe, silicon photonics is set to lead the global semiconductor foundries, thanks to its abundance in nature and a mature and well-established industry. Since, the silicon waveguide is the heart of silicon photonics, it can be considered as the core …

Quantum-Mechanical Evaluation Of Defects In Uranium-Bearing Materials, Megan Hoover

All Dissertations

Quantum-mechanical calculations using density functional theory with the generalized gradient approximation were employed to investigate the effects dopants have on the uranium dioxide (UO₂) structure. Uraninite is a common U⁴⁺ mineral in the Earth's crust and an important material used to produce energy and medical isotopes. Though the incorporation mechanism remains unclear, divalent cations are known to incorporate into the uranium dioxide system. Three charge-balancing mechanisms were evaluated to achieve a net neutral system, including the substitution of (1) a divalent cation for a tetravalent uranium atom and oxygen atom; (2) two divalent cations for a tetravalent …

Porous Silicon Photonics For Label-Free Interferometric Biosensing And Flat Optics, Tahmid Hassan Talukdar

All Dissertations

This dissertation uses porous silicon as a material platform to explore novel optical effects in three domains: (i) It studies dispersion engineering in integrated waveguides to achieve high performance group index sensing. With proper design parameters, the sensor waveguides can theoretically achieve 6 times larger group index shift compared to the actual bulk effective refractive index shift. We demonstrate the guided mode confinement factor to be a key parameter in design and implementation of these waveguides. (ii) It explores multicolor laser illumination to experimentally demonstrate perceptually enhanced colorimetric sensing, overcoming the limitations faced by many contemporary colorimetric sensors. Our technique …

Characterization Of Water Flow And Solute Transport Driven By Preferential Flow In Soil Vadose Zone, Abdullah Al Mamun

All Dissertations

The vadose zone acts as a buffer zone between the ground surface and the aquifers underneath and controls the transmission of infiltrating water and contaminants, for example, pesticides and chemical spills. Therefore, understanding the flow and transport processes that dominate the vadose zone is important. Macropores are ubiquitous and particularly found in abundance in the vadose zone. These macropores facilitate preferential flow, through which water travels rapidly deep into the soil, bypassing most of the porous matrix. Preferential flow and transport have environmental significance as their processes impact hydrology, ecology, agriculture, subsurface contamination, and waste management sectors. Thus, the overall …

Extractive Membranes For The Detection And Screening Of Waterborne Plutonium, James Foster

All Dissertations

The development of rapid screening tools for special nuclear materials remains a crucial focus for nonproliferation efforts. Traditional approaches for the analysis of trace-level Pu isotopes in water requires tedious and time-consuming sample preparation steps that do not lend well to expeditious screening. Therefore, a novel analytical method that combines both Pu concentration and source preparation into a single detection system would make for an invaluable tool for nuclear security applications. Extractive membranes absorbers can help to fulfill this role as they are capable of concentrating Pu to detectable limits while subsequently serving as alpha spectrometry sample sources. In Chapter …

Synthesis And Molecular Processes Governing Self-Healing Polymeric Materials, Siyang Wang

All Dissertations

Self-healing polymers capable of recovering from physical damages are promising materials for advanced technologies. In these studies, we developed routes to achieve self-healable properties in acrylic-based copolymers that rely on non-covalent dipolar interactions present in essentially all polymeric materials. Using a combination of spectroscopic tools, thermo-mechanical analysis, and molecular dynamic (MD) simulations, these studies have shown that dipolar interactions lead to conformational changes of macromolecular segments which, in turn, result in self-healing without external intervention. This dissertation also describes the development of novel self-healable acrylic-based covalent adaptable networks (CANs) that combine reprocessing and self-healing properties. The utilization of dipolar interactions …

Wetland Uranium Transport Via Iron-Organic Matter Flocs And Hyporheic Exchange, Connor J. Parker

All Dissertations

Uranium (U) released from the M-Area at the Department of Energy Savannah River Site into Tims Branch, a seasonal wetland and braided stream system, is estimated to be 43,500 kg between 1965 and 1984. The motivation for this work is the uranium’s persistence in the wetland for decades, where it is estimated that 80% of the U currently remains in the Tims Branch wetland. U has begun to incorporate into wetland iron (Fe) and carbon cycles, associating with local Fe mineralogy and deposits of rich wetland organic matter (OM). The objective of this work is to characterize the chemical phases …