Digital Commons Network^™

Quantum Phase Transitions In Impurity Models And Percolating Lattices, Manal M. Al-Ali

Doctoral Dissertations

"This thesis investigates the influence of random disorder and dissipation on zero-temperature quantum phase transitions. Both phenomena can fundamentally change the character of the phases of a quantum many-particle system and of the transitions between them. If dissipation and disorder occur simultaneously in a system undergoing a quantum phase transition, particularly strong effects can be expected. In the first paper reproduced in this thesis, we study a single quantum rotor coupled to a sub-Ohmic dissipative bath. We find that this system undergoes a quantum phase transition from a delocalized phase to a localized phase as the dissipation strength is increased. …

Social-Context Based Routing And Security In Delay Tolerant Networks, Roy A. Cabaniss

Doctoral Dissertations

"Delay Tolerant Networks (DTNs) were originally intended for interplanetary communications and have been applied to a series of difficult environments: wireless sensor networks, unmanned aerial vehicles, and short-range personal communications. There is a class of such environments in which nodes follow semi-predictable social patterns, such as wildlife tracking or personal devices. This work introduces a series of algorithms designed to identify the social patterns present in these environments and apply this data to difficult problems, such as efficient message routing and content distribution. Security is also difficult in a mobile environment. This is especially the case in the event that …

Manual Modification And Plasma Exposure Of Boron Nitride Ceramic To Study Hall Effect Thruster Plasma Channel Material Erosion, Alexander J. Satonik

Masters Theses

"Worn Hall effect thrusters (HET) show a variety of unique microstructures and elemental compositions in the boron nitride thruster channel walls. Worn thruster channels are typically created by running test thrusters in vacuum chambers for hundreds of hours. Studies were undertaken to manually modify samples of boron nitride without the use of a hall effect thruster. Samples were manually abraded with an abrasive blaster and sandpaper, in addition to a vacuum heater. Some of these samples were further exposed to a xenon plasma in a magnetron sputter device. Sandpaper and abrasive blaster tests were used to modify surface roughness values …

Paste Development And Co-Sintering Test Of Zirconium Carbide And Tungsten In Freeze-Form Extrusion Fabrication, Ang Li

Masters Theses

"Ultra-high temperature ceramics are being investigated for future use in aerospace applications due to their superior thermo-mechanical properties, as well as oxidation resistance, at temperatures above 2000°C. However, their brittle properties make them susceptible to thermal shock failure. Components fabricated as functionally graded materials (FGMs) can combine the superior properties of ceramics with the toughness of an underlying refractory metal by fabricating graded composites. This paper discusses the grading of two materials through the use of a Freeze-form Extrusion Fabrication (FEF) system to build FGMs parts consisting of zirconium carbide (ZrC) and tungsten (W). Aqueous-based colloidal suspensions of ZrC and …

Parallel-Connected Solar Arrays, Majed Meshal Alabbass

Masters Theses

"The purpose of this thesis is to investigate the advantages of having various series-parallel configurations of solar arrays and make a comparison between them. The objective is to determine the best PV system configuration and thus improve the overall efficiency of a solar array. The primary focus of this thesis is to study the parallel connection of PV panels for achieving maximum efficiency while extracting maximum energy from the solar radiation. A comparison between a series connected and a parallel connected solar PV array justifies the need for installing a parallel configured solar PV array to achieve optimum performance. The …

Parameter Optimization For Controlling Aluminum Loss When Laser Depositing Ti-6al-4v, Richard Charles Barclay

Masters Theses

"The ability to predict the mechanical properties of engineering materials is crucial to the manufacturing of advanced products. In the aerospace industry, Ti-6Al-4V is commonly used to build structures. Any deviation from the alloy's standard properties can prove detrimental. Thus, the compositional integrity of the material must be controlled. The ability to directly build and repair large, complicated structures directly from CAD files is highly sought after. Laser Metal Deposition (LMD) technology has the potential to deliver that ability. Before this process can gain widespread acceptance, however, a set of process parameters must be established that yield finished parts of …

Assessment Of An Enterprise Employee Portal Using Dashboard Monitoring System: A Case Study, Aditi Mishra

Masters Theses

"A portal is a browser-based application that provides a web platform for users to improve inter-department collaboration and customer service. Portals are classified either as internal facing portals or external public facing portals. This study addresses the problems facing an internal portal related to its contents, functions and usability and provides a list of essential contents and functions that it should include through integrating theories and industry best practices. The theory framework is based on literature review and the industry best practices are based on the analysis of a number of internal portals of companies used as case studies. These …

A Modification Of Freeze-Core Technology For Collecting Granular Fluvial Sediment Samples, David Charles Smith

Masters Theses

"The presence of coarse grained sediment can potentially reduce the effectiveness of conventional sampling methods in recovering fluvial sediments. A modification to freeze-core technology was used to collect fine grained sediments for the purpose of characterizing the extent of heavy metal contamination in fluvial deposits that contain significant amounts of coarse-grained material such as cobbles and boulders. This material greatly reduces the effectiveness of conventional sampling methods. This method uses 2.5-cm and 2.9-cm diameter by 30-cm long finned samplers that were mechanically- and hand-driven into the ground. The sediment is frozen to the outside of the sampler by injecting liquid …

Water Management Capabilities Of Bio-Inspired Flow Field Configurations For Polymer Electrolyte Membrane Fuel Cells, Nicholas Warren Freer

Masters Theses

"Fuel cells have received an increasing amount of attention over the past decade for their power production capabilities. Polymer electrolyte membrane (PEM) fuel cells in particular are researched because of their high power density, large range of operating conditions, green products, and ease of scalability. PEM fuel cells do have a number of issues that reduce their overall performance. These issues include variations in reactant distribution, materials issues for the bipolar plate, and flooding caused by poor water management. Variations in the reactant distribution causes lower overall power output due to regions of low reactant density. This means that optimizing …

Green Roof Water Quality Impacts And Physicochemical Stability, Grace Ella Harper

Masters Theses

"Green roofs can provide environmental benefits and conserve energy; this research evaluated green roof stormwater management, nutrient loading, and erosion prevention for two green roof media. During a pilot study, the runoff quantity and composition from green roof material was evaluated continuously under field conditions for two different media, both tested under planted and unplanted conditions. Water quantity results show over a 40% reduction in runoff from just the growing media and over 60% reduction in runoff with established plants in green roof media over the eight month study. Previous studies have reported a "first flush" of excess nutrients but …

A New Approach To Nuclear Safeguard Enhancement Through Radionuclide Profiling, Aaron Dawon Peterson

Masters Theses

"The United States has led the effort to promote peaceful use of nuclear power amongst states actively utilizing it as well as those looking to deploy the technology in the near future. With the attraction being demonstrated by various countries towards nuclear power comes the concern that a nation may have military aspirations for the use of nuclear energy. The International Atomic Energy Agency (IAEA) has established nuclear safeguard protocols and procedures to mitigate nuclear proliferation. The work herein proposed a strategy to further enhance existing safeguard protocols by considering safeguard in nuclear fuel design. The strategy involved the use …

Lexis In Chemical Engineering Discourse: Analyzing Style In Chemical Engineering Research Articles Through A Rhetorical Lens, David Lamar Young

Masters Theses

"This study examines the style of chemical engineering research articles to discover stylistic trends that may be applicable to authors looking to publish their own research. Rhetorical stylistic analysis was used as a research method to allow for thorough analysis of all articles in the sample. Ten research articles from the two prominent chemical engineering journals were chosen using specific criteria to constitute a sample of articles that could most accurately represent the population of chemical engineering research articles. Each article was then analyzed line by line to identify markers of chemical engineering research article style, including the following: ▬Use …

Part Height Control Of Laser Metal Additive Manufacturing Process, Yu-Herng Pan

Masters Theses

"Laser Metal Deposition (LMD) has been used to not only make but also repair damaged parts in a layer-by-layer fashion. Parts made in this manner may produce less waste than those made through conventional machining processes. However, a common issue of LMD involves controlling the deposition's layer thickness. Accuracy is important, and as it increases, both the time required to produce the part and the material wasted during the material removal process (e.g., milling, lathe) decrease. The deposition rate is affected by multiple parameters, such as the powder feed rate, laser input power, axis feed rate, material type, and part …

Production Of 1,3-Propanediol From Glycerol Under Haloalkaline Conditions By Halanaerobium Hydrogeniformans, Daniel William Roush

Masters Theses

"With increased demands around the world to make modern lifestyles more environmentally friendly, the chemical commodity market has rapidly shifted. Through new technologies in chemical production, certain high value products have oversaturated the market and have become high-volume, low value waste products. The expansion of biodiesel production offers a prime example; high volumes of glycerol byproduct from this process have shifted glycerol from a high priced commodity to a common waste product. A number of microorganisms are known to synthesize the polymeric precursor 1,3-propanediol from glycerol; however, crude glycerol from biodiesel production creates a harsh environment for most microbes, and …

Role Of Nicotine In Oxidative Stress, Rakesh Kacham

Masters Theses

"Nicotine, a major alkaloid, is present in tobacco products as well as in smaller amounts in potatoes, tomatoes, and eggplants. Although it is the addictive compound in cigarettes, nicotine is believed to play a protective role in neurodegenerative disorders such as Parkinson's disease. Researchers have found that the short-term administration of nicotine may help improve the memory process by reducing oxidative stress in the brain. Our studies have shown that, by blocking Fenton's reaction, nicotine is able to inhibit free radical generation, so this research has focused on the antioxidant properties of nicotine. The cell lines of the alveoli, blood …

Trough-Silicon-Via Inductor: Is It Real Or Just A Fantasy?, Rongbo Yang

Masters Theses

"Through-silicon-vias (TSVs) can potentially be used to implement inductors in three-dimensional (3D) integrated system for minimal footprint and large inductance. However, different from conventional 2D spiral inductor, TSV inductors are buried in lossy substrate, thus suffering from low quality factors. This thesis presents how various process and design parameters affect their performance. A few interesting phenomena that are unique to TSV inductors are observed. We then proposed a novel shield mechanism utilizing the micro-channel, a technique conventionally used for heat removal, to reduce the substrate loss. The technique increases the quality factor and inductance of the TSV inductor by up …

Data Fusion Techniques For Nondestructive Evaluation And Medical Image Analysis, Soumya De

Doctoral Dissertations

"Data fusion is a technique for combining data obtained from multiple sources for an enhanced detection or decision. Fusion of data can be done at the raw-data level, feature level or decision level. Applications of data fusion include defense (such as battlefield surveillance and autonomous vehicle control), medical diagnosis and structural health monitoring. Techniques for data fusion have been drawn from areas such as statistics, image processing, pattern recognition and computational intelligence. This dissertation includes investigation and development of methods to perform data fusion for nondestructive evaluation (NDE) and medical imaging applications. The general framework for these applications includes region-of-interest …

Study Of Artificially Disordered Optical Fibers, Herath Mudiyanselage Sumudu Rasika Kumari Herath

Doctoral Dissertations

"Light transmission through photo-sensitive multi-mode fibers (MMF) with controlled volume disorder is investigated. Experiment shows that a segment of disordered MMF as short as 10 cm is sufficient to distribute power uniformly over all co-propagating modes and the intensity at the output surface of the fiber follows the Rayleigh negative exponential function. To explain the experimental findings, a comprehensive theoretical model is developed with three main results. First, statistical properties of all components of the dielectric tensor are obtained and analyzed in the framework a microscopical model of photo-sensitivity in a germano-silicate glasses. Secondly, it is shown that induced birefringence …

Finite-Horizon Optimal Control Of Linear And A Class Of Nonlinear Systems, Qiming Zhao

Doctoral Dissertations

"Traditionally, optimal control of dynamical systems with known system dynamics is obtained in a backward-in-time and offline manner either by using Riccati or Hamilton-Jacobi-Bellman (HJB) equation. In contrast, in this dissertation, finite-horizon optimal regulation has been investigated for both linear and nonlinear systems in a forward-in-time manner when system dynamics are uncertain. Value and policy iterations are not used while the value function (or Q-function for linear systems) and control input are updated once a sampling interval consistent with standard adaptive control. First, the optimal adaptive control of linear discrete-time systems with unknown system dynamics is presented in Paper I …

Fundamental Properties Of Colloidal Unimolecular Polymer Particles, Minghang Chen

Doctoral Dissertations

"Colloidal Unimolecular Polymer (CUP) particles are a new genre of material formed by self-assembly into spheroidal particles due to the effect of hydrophilic/hydrophobic interactions of the polymer with a change in the solvent. The particle sizes were characterized by means of Dynamic Light Scattering with corrected viscosities instead of water's viscosity. The distribution of particle size agreed well with the distribution of molecular weight proving that the polymer had undergone unimolecular collapse. The rheology study shows the presence of surface water and its significant effect on the rheology. The primary and secondary electroviscous effects were also found to play roles …

Geochemical And Isotopic Characterization Of Lead In Fugitive Dust From Unsurfaced Roads In Missouri, Emitt C. Witt

Doctoral Dissertations

"Eighteen unsurfaced roadways in Missouri's rural Ozark region were sampled to characterize the differences in trace element and isotopic chemistry to determine if there is a human health concern with inhaling and/or ingestion of fugitive dust generated by a moving vehicle. Road reaches were selected to represent those in similar rural areas with and without the presence of mining activity--13 roads were selected in the Viburnum Trend (VT) resource mining area and five were located to the southwest of the mining areas. Samples were collected using a novel cyclonic fugitive dust sampler (patent pending) that collects a composite sample from …

Numerical Modeling Of Heat Transfer And Fluid Flow In Laser Metal Deposition By Powder Injection, Zhiqiang Fan

Doctoral Dissertations

"Laser metal deposition is an additive manufacturing technique which allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. A self-consistent three-dimensional model was developed for the laser metal deposition process by powder injection, which simulates heat transfer, phase changes, and fluid flow in the melt pool, The governing equations for solid, liquid and gas phases in the calculation domain have been formulated using the continuum model. The free surface in the melt pool has been tracked by the Volume of Fluid (VOF) method, while the VOF transport equation was solved using the Piecewise Linear …

Phase Transitions In Disordered Systems, Fawaz Y. Hrahsheh

Doctoral Dissertations

"Disorder can have a wide variety of consequences for the physics of phase transitions. Some transitions remain unchanged in the presence of disorder while others are completely destroyed. In this thesis we study the effects of disorder on several classical and quantum phase transitions in condensed matter systems. After a brief introduction, we study the ferromagnetic phase transition in a randomly layered Heisenberg magnet using large-scale Monte-Carlo simulations. Our results provide numerical evidence for the exotic infinite-randomness scenario. We study classical and quantum smeared phase transitions in substitutional alloys A₁₋ₓBₓ. Our results show that the disorder completely destroys the phase …

Modeling And Analysis Of Dynamic Behavior Of Adsorption Stratified Column Beds Packed With Partially Fractal Porous Adsorbent Particles, Min Li

Doctoral Dissertations

"In this work novel porous adsorbent media having partially fractal structures and stratified packed-beds are constructed and their dynamic performance with respect to their adsorptive capacity through the construction and solution of rigorous models is studied. The results show that conventional columns packed with partially fractal porous adsorbent particles provide larger breakthrough times and dynamic utilization of the adsorptive capacity of the column when compared with those of conventional columns employing conventional adsorbent particles which do not possess a partially fractal structure. Furthermore, stratified column beds exhibit superior species separation performance than conventional columns when they are packed with either …

On Checkbox Diversity, Philip Lee

Journal of Civil Rights and Economic Development

No abstract provided.

Compositional Diversity In The Atmospheres Of Hot Neptunes, With Application To Gj 436b, J. I. Moses, M. R. Line, Channon Visscher, M. R. Richardson, N. Nettleman, J. J. Fortney, T. S. Barman, K. B. Stevenson, N. Madhusudhan

Faculty Work Comprehensive List

Neptune-sized extrasolar planets that orbit relatively close to their host stars—often called "hot Neptunes"—are common within the known population of exoplanets and planetary candidates. Similar to our own Uranus and Neptune, inefficient accretion of nebular gas is expected produce hot Neptunes whose masses are dominated by elements heavier than hydrogen and helium. At high atmospheric metallicities of 10-10,000 times solar, hot Neptunes will exhibit an interesting continuum of atmospheric compositions, ranging from more Neptune-like, H₂-dominated atmospheres to more Venus-like, CO₂-dominated atmospheres. We explore the predicted equilibrium and disequilibrium chemistry of generic hot Neptunes and find that …

Chemistry Of Impact-Generated Silicate Melt-Vapor Debris Disks, Channon Visscher, Bruce Fegley Jr.

Faculty Work Comprehensive List

In the giant impact theory for lunar origin, the Moon forms from material ejected by the impact into an Earth-orbiting disk. Here we report the initial results from a silicate melt-vapor equilibrium chemistry model for such impact-generated planetary debris disks. In order to simulate the chemical behavior of a two-phase (melt+vapor) disk, we calculate the temperature-dependent pressure and chemical composition of vapor in equilibrium with molten silicate from 2000 to 4000 K. We consider the elements O, Na, K, Fe, Si, Mg, Ca, Al, Ti, and Zn for a range of bulk silicate compositions (Earth, Moon, Mars, eucrite parent body, …

Usft 2013 Usf Libraries Annual Report, Usf Libraries

Library Annual Reports

No abstract provided.

Functional Near Infrared Detection Of Real And Imagined Finger Taps Using Support Vector Machine, Linear Discriminant Analysis, And Decision Tree Classification Methods, Eugene A. Stoudenmire

Computational Modeling & Simulation Engineering Theses & Dissertations

This study investigates the thesis that given cerebral response samples of an individual's left, right, both, and imagined finger tapping, continuous wave (CW) functional Near Infrared (fNIR), unregistered with fMRI, can differentiate between any two of the four categories.

Fifty subjects were outfitted with a single source/detector attached to a single, square pad, affixed to their heads using devices such as elastic bands and caps for light shielding. Slides depicting arrows pointing left, right, both directions, or made of dashed lines were presented to each subject, with a slide of text interspersed between each. Subjects tapped with their left finger, …

Connecting Inwardly To Beethoven: Ted Hughes And The Role Of The Artist As Quest Hero, David Charles Heldsinger

Theses

Ted Hughes served as English Poet Laureate from 1984 until his death in 1998. In an insightful interview in 1970, Hughes said he connected ‘inwardly’¹ to William Blake and Ludwig van Beethoven and that if he ‘could dig to the bottom’ of his ‘strata, maybe their names and works would be the deepest traces’.² Blake and Beethoven lived and worked at a pivotal moment in history as the Romantic Movement emerged in the late 18th century. This Movement has had a significant and long lasting effect on art, culture, philosophy and politics. Shortly before his death, Hughes reiterated …