Digital Commons Network^™

Modified Sodium Diuranate Process For The Recovery Of Uranium From Uranium Hexafluoride Transport Cylinder Wash Solution, Austin Dean Meredith

Theses and Dissertations

Uranium hexafluoride (UF₆) containment cylinders must be emptied and washed every five years in order to undergo recertification, according to ANSI standards. During the emptying of the UF₆ from the cylinders, a thin residue, or heel, of UF₆ is left behind. This heel must be removed in order for recertification to take place.

To remove it, the inside of the containment cylinder is washed with acid and the resulting solution generally contains three or four kilograms of uranium. Thus, before the liquid solution can be disposed of, the uranium must be separated. A modified sodium diuranate …

Fundamental Experimental Studies In Scaling, Blast Mitigation And Material Processing, Xing Zhao

Theses and Dissertations

In this work, two separate research efforts are discussed. They include experimental studies in (1) Scaling and Blast Mitigation and (2) Scaling in Friction Stir Extrusion. In both studies, the primary experimental measurement method is three-dimensional digital image correlation (3D-DIC), a non-contacting full-field measurement method that is applicable for both high-rate loading and quasi-static loading conditions.

Scaling and Blast Mitigation Studies:

A series of properly scaled structures was subjected to buried blast loading conditions via detonation of a small explosive buried in saturated sand. Using high speed stereo-vision systems to record the deformations of selected regions on the upper surface …

The Effect Of Αct-1 Peptide On Bone Marrow Stromal Cells Following Injury, Adam Clay Vandergriff

Theses and Dissertations

Connexin43 (Cx43) is a component of gap junctions and is involved in intercel- lular signaling following injury to tissues. The carboxyl terminus of Cx43 binds to the PDZ2 domain of ZO-1 in order to form gap junction plaques and connect to the cytoskeleton. A biomimetic peptide known as αCT-1, replicating the last 9 amino acids found in the carboxyl terminus of CX43, has been shown to improve wound healing by preferentially binding to the PDZ2 domain of ZO-1. A possible mecha- nism for its action is through the Epithelial-Mesenchymal Transformation (EMT). Scratch assays were performed on rat bone marrow stromal …

Fabrication And Characterization Of Surrogate Fuel Particles Using The Spark Erosion Method, Kathryn Elizabeth Metzger

Theses and Dissertations

In light of the disaster at the Fukushima Daiichi Nuclear Plant, the Department of Energy's Advanced Fuels Program has shifted its interest from enhanced performance fuels to enhanced accident tolerance fuels. Dispersion fuels possess higher thermal conductivities than traditional light water reactor fuel and as a result, offer improved safety margins. The benefits of a dispersion fuel are due to the presence of the secondary non-fissile phase (matrix), which serves as a barrier to fission products and improves the overall thermal performance of the fuel. However, the presence of a matrix material reduces the fuel volume, which lowers the fissile …

High Resistivity Amorphous Selenium Alloy Semiconductors For Radiation Detection Applications, Abhinav Mehta

Theses and Dissertations

High resolution noninvasive tools of diagnosis has always derived and enabled scientific and medical research to probe and better understand subtleties of matter, intangible to the human eye. Radiation detection systems are highly dependent on advancements in materials and devices with front-end electronics. There are various discrete applications of these radiation detectors and each application imposes certain requirements so there is no single optimum radiation detector.

Flat panel x-ray imagers have gained high demand in the past decade because of exponential improvement in readout electronics. We have synthesized and investigated stabilized amorphous selenium (a-Se) alloys suitable for high resolution flat …

Parsing The Effects Of Physical Microenvironmental Cues On Stem Cell Adhesion And Lineage Specification, Greg M. Harris

Theses and Dissertations

Tissue engineering is a broad field geared toward improving or replacing biological material and comprises an immense collection of biological nuances to consider before strategies for clinical applications can be fully realized. Physical and biochemical signals are responsible for making up a cell's microenvironment to guide morphology and function through cell-extracellular matrix signaling, cell-cell signaling, and soluble signaling. In particular, a deeper understanding of these cell-extra cellular matrix factors guiding stem cell adhesion, spreading, and differentiation is crucial to harnessing the potential to develop tissue for regenerative purposes. Mounting evidence suggests that physical cues are a key to understanding the …

Boiling And Evaporation On Micro/Nanoengineered Surfaces, Xianming Dai

Theses and Dissertations

Two-phase transport is widely used in energy conversion and storage, energy efficiency and thermal management. Surface roughness and interfacial wettability are two major impact factors for two-phase transport. Micro/nanostructures play important roles in varying the surface roughness and improving interfacial wettability. In this doctoral study, five types of micro/nanoengineered surfaces were developed to systematically study the impacts of interfacial wettability and flow structures on nucleate boiling and capillary evaporation. These surfaces include: 1) superhydrophilic atomic layer deposition (ALD) coatings; 2) partially hydrophobic and partially hydrophilic composite interfaces; 3) micromembrane-enhanced hybrid wicks; 4) superhydrophilic micromembrane-enhnaced hybrid wicks, and 5) functionalized carbon …

Dislocation Reduction In Silicon Doped High Aluminum Content Algan Layers For Deep Uv Optoelectronic Devices, Hung-Chi Chen

Theses and Dissertations

III-Nitride based deep ultraviolet (UV) light emitting diodes (LEDs) are prospective candidates to replace the conventional bulky, expensive and environmentally harmful mercury lamp as new UV light sources, used in the applications of water and air purification, germicidal and biomedical instrumentation systems, etc. Due to the lack of native substrates and poor carrier injection, AlGaN-based deep UV LED is suffering from low optical power and low overall efficiency, which prevents the availability of low cost, high efficiency deep UV LED on the market.

This dissertation is focused on improving the efficiency of deep UV LEDs, by improving the base template …

Effects Of N-Type Doping On Algan Material Quality, Devendra Diwan

Theses and Dissertations

The field of group III-nitride semiconductors has seen incredible developments during last couple of decades. They are recognized as the most promising materials for a wide field of optoelectronics and electronic devices. Their bandgap ranges from 6.2 eV for AlN to 0.7 eV for InN, covering a wide spectral range from infrared (1.77 mm) to deep ultraviolet (200 nm). Their direct bandgap makes them useful for fabricating optoelectronic devices such as light emitting diodes (LEDs), laser diodes (LDs), and photodetectors. III-nitride semiconductor materials also possess strong bond strengths and exhibit good structural, chemical and thermal stability. These properties make it …

Ultrawideband (Uwb) And Reconfigurable Antennas - New Concepts For Conformal Load Bearing Antenna Structures (Clas), Nicholas Bishop

Theses and Dissertations

Conformal antennas have been increasingly playing an important role in a vast number wireless of communication applications. More specifically, Conformal Load Bearing Antenna Structures (CLAS) have drawn a great deal of interest among researchers and engineers because of their advantages of multiple functionality, e.g. antenna and structure both. The objectives of this thesis are to investigate and design innovative conformal Ultrawideband (UWB) endfire antenna arrays and reconfigurable aperture coupled pixel patch antennas both of which are good candidates for CLAS. First, a broadband VHF-UHF end-fire Yagi-Uda array is proposed for possible air vehicle integration and operation within the 240-465 MHz …

Fault Aware Soft Restart Of An Islanded Microgrid Using An Inverter Coupled Energy Storage System, Asif Anwar

Theses and Dissertations

This research developed a method for autonomous operation of an inverter-coupled energy storage system for safe islanding- re-energization - and reconnection of the facility-island or microgrid to the utility / distribution circuit in a seamless manner in the event of a fault. This enables the energy storage system to function as an autonomous source within the utility power distribution system without the need to re-engineer the existing protection coordination in the distribution system. Fault detection based on voltage measurements from the inverter terminals are used to detect a fault and isolate the energy storage-powered facility with negligible power feed into …

Crystal Growth, Characterization And Fabrication Of Cdznte-Based Nuclear Detectors, Ramesh Madhu Krishna

Theses and Dissertations

In today's world, nuclear radiation is seeing more and more use by humanity as time goes on. Nuclear power plants are being built to supply humanity's energy needs, nuclear medical imaging is becoming more popular for diagnosing cancer and other diseases, and control of weapons-grade nuclear materials is becoming more and more important for national security. All of these needs require high-performance nuclear radiation detectors which can accurately measure the type and amount of radiation being used. However, most current radiation detection materials available commercially require extensive cooling, or simply do not function adequately for high-energy gamma-ray emitting nuclear materials …

Liquefaction Potential Of South Carolina Coastal Plain Soils Using Dilatometer Data, Joseph Ronald Williamson

Theses and Dissertations

In recent years much research has been focused on developing the flat plate dilatometer (DMT) as a tool to estimate the liquefaction potential of soils. Currently the DMT is over shadowed by the more accepted methods of estimating liquefaction potential which utilize test data from either the standard penetration test (SPT), cone penetration test (CPT), or shear wave velocity test (Vs). The SPT, CPT, and V_s tests are all well-developed methods of estimating liquefaction potential and are supported by extensive databases; however, the DMT is believed by many researchers to be the superior alternative. Due to the DMT's minimal …

Accuracy, Cost And Performance Trade-Offs For Streaming Set-Wise Floating Point Accumulation On Fpgas, Krishna Kumar Nagar

Theses and Dissertations

The set-wise summation operation is perhaps one of the most fundamental and widely used operations in scientific applications. In these applications, maintaining the accuracy of the summation is also important as floating point operations have inherent errors associated with them. Designing floating-point accumulators presents a unique set of challenges: double-precision addition is usually deeply pipelined and without special micro-architectural or data scheduling techniques, the data hazard that exists. There have been several efforts to design floating point accumulators and accurate summation architecture using different algorithms on FPGAs but these problems have been dealt with separately. In this dissertation, we present …

Walkcompass: Finding Walking Direction Leveraging Smartphone's Inertial Sensors, Nirupam Roy

Theses and Dissertations

Determining moving direction with smartphone's inertial sensors is a well known problem in the field of location service. Compass alone cannot solve this problem because smartphone's compass cannot achieve high accuracy. Moreover GPS is not suitable in indoor scenario. Another well known approach is dead-reckoning but dead-reckoning needs to know phones initial orientation and over time it keeps accumulating errors and after some time the estimation becomes to noisy to use. To overcome these limitations, we propose a solution called WalkCompass which is specially designed for pedestrians keeping in mind the variation of force during normal human walk. Therefore the …

Impact Of Curing Time And Curing Stress On The Mechanical Behavior Of Cement-Improved And Cement-Fiber-Improved Soft Soil, Ryan Daniel Starcher

Theses and Dissertations

In order to improve the engineering properties of soft soils, materials, such as cement and fiber, can be introduced to the soil mass. Currently, design criterion for a cement-soil mixture requires only the measurement of unconfined compressive strength. This simple measurement may not be adequate to describe the behavior that results from differing field loading conditions. A series of consolidation tests and unconfined compression tests were conducted with special attention being paid to the effects of curing time and vertical curing stress. It is shown that the introduction of cement into soft soils results in decreased compressibility and increased unconfined …

Experimental And Simulation Predicted Crack Paths For Al-2024-T351 Under Mixed-Mode I/Ii Fatigue Loading Using An Arcan Fixture, Eileen Miller

Theses and Dissertations

Mixed mode I/II fatigue experiments and simulations are performed for an Arcan fixture and a 6.35mm thick Al-2024-T351 specimen. Experiments were performed for Arcan loading angles that gave rise to a range of Mode I/II crack tip conditions from 0 ¡Ü ¦¤KII/¦¤KI ¡Ü ¡Þ. Measurements include the crack paths, loading cycles and maximum and minimum loads for each loading angle. Simulations were performed using three-dimensional finite element analysis (3D-FEA) with 10-noded tetrahedral elements via CRACK3D. While modeling the entire fixture-specimen geometry, a modified version of VCCT with automatic crack tip re-meshing and a maximum normal stress criterion were used to …

Mass Spectrometry And Tandem Mass Spectrometry Characterization Of Protein Patterns, Protein Markers And Whole Proteomes For Pathogenic Bacteria, Jennifer Intelicato-Young

Theses and Dissertations

There have been many recent reviews published on MALDI-TOF MS (matrix assisted laser desorption/ionization time-of-flight) MS (mass spectrometry) for identification of bacteria particularly with relevance to clinical microbiology. MALDI-TOF MS is now a mature technique for bacterial identification with great promise. The purpose of this review is to put into perspective MALDI-TOF MS and other widely used mass spectrometry methods for characterization of proteins. MALDI-TOF MS is used for rapid determination of a mass pattern of proteins for bacterial characterization; these proteins

are generally not identified. Alternatively, after gel separation, MALDI TOF-TOF MSMS (tandem mass spectrometry) or on-line LC-ESI MS-MS …

Plc Code Vulnerabilities Through Scada Systems, Sidney E. Valentine, Jr.

Theses and Dissertations

Supervisory Control and Data Acquisition (SCADA) systems are widely used in automated manufacturing and in all areas of our nation's infrastructure. Applications range from chemical processes and water treatment facilities to oil and gas production and electric power generation and distribution. Current research on SCADA system security focuses on the primary SCADA components and targets network centric attacks. Security risks via attacks against the peripheral devices such as the Programmable Logic Controllers (PLCs) have not been sufficiently addressed.

Our research results address the need to develop PLC applications that are correct, safe and secure. This research provides an analysis of …

Numerical Study Of Stable Tearing Crack Growth Events Using The Cohesive Zone Model Approach, Xin Chen

Theses and Dissertations

Numerical analysis of stable tearing crack growth events plays an important role in assessing the structural integrity and residual strength of critical engineering structures. The cohesive zone model (CZM) has been widely applied to simulate fracture processes in a variety of material systems. However, its application to the study of elastic-plastic stable tearing crack growth events in ductile materials, especially under mixed-mode loading conditions, has been limited. The current study is aimed at investigating the applicability of the CZM based approach in simulating mixed-mode stable tearing crack growth events in aluminum alloys. In the simulations, which are carried out using …

Synthesis And Characterization Of New Ionic And Mixed Ionic/Electronic Conductors, Kevin Gregory Romito

Theses and Dissertations

In a constantly growing and developing world, there is a great need to develop new forms of clean energy generation. Many solutions have been proposed to ameliorate these global concerns, which include fuel cell technology and new processes for reducing polluting chemicals in the atmosphere. These technologies are still in their infancy and require further development before becoming viable options.

In the case of fuel cells, particularly solid oxide fuel cells, and CO2 separation membranes, there is a need to develop ion conducting materials that are highly efficient, less costly to synthesize, and can perform strongly under many real-world conditions. …

A New Class Of Solid Oxide Metal-Air Redox Batteries For Advanced Stationary Energy Storage, Xuan Zhao

Theses and Dissertations

Cost-effective and large-scale energy storage technologies are a key enabler of grid modernization. Among energy storage technologies currently being researched, developed and deployed, rechargeable batteries are unique and important that can offer a myriad of advantages over the conventional large scale siting- and geography- constrained pumped-hydro and compressed-air energy storage systems. However, current rechargeable batteries still need many breakthroughs in material optimization and system design to become commercially viable for stationary energy storage.

This PhD research project investigates the energy storage characteristics of a new class of rechargeable solid oxide metal-air redox batteries (SOMARBs) that combines a regenerative solid oxide …

Comparison Of A Particle Filter And Other State Estimation Methods For Prognostics Of Lithium-Ion Batteries, Eric Alan Walker

Theses and Dissertations

A particle filter (PF) is shown to be more accurate than non-linear least squares (NLLS) and an unscented Kalman filter (UKF) for predicting the remaining useful life (RUL) and time until end of discharge voltage (EODV) of a Lithium-ion battery. The three algorithms track four states with correct initial guesses and 5% variation on the initial guesses. The more accurate prediction performance of PF over NLLS and UKF is reported for three Lithium-ion battery models: a data-driven empirical model, an equivalent circuit model, and a physics-based single particle (SP) model.

Asymmetric Hydrogenation Of Α, Β-Unsaturated Carboxylic Acid Over Chiral-Modified Palladium Catalyst, Shuai Tan

Theses and Dissertations

The production of optically pure chemicals through enantioselective catalytic reaction plays a key role a variety of industrials (e.g., pharmaceutical, agrochemical). Among several established methods, chiral-modified supported transition metal catalyst has been addressed attentions since past decades due to an environmental concern. Asymmetric hydrogenation of α, β-unsaturated carboxylic acid over Pd catalyst is of particular interest in this area. Nevertheless, the spectroscopic aspect, as well as the kinetic mechanism of such reaction system are still not clearly understood and require further study. In this work, a model catalytic reaction has been investigated from both spectroscopic and kinetic view. To be …

Fault Location In Power Networks Using Synchronized Phasor Measurements, Cuong Nguyen

Theses and Dissertations

Faults in electric power systems can lead to cascading power outages which cause tremendous loss to the economy and affect people’s lives. Technical reports of recent blackout events in the United States pointed out the lack of situational awareness as one of the main causes of widespread outages. Time synchronized phasor measurement is recommended as a technology that can improve the monitoring of power system condition. By knowing exactly where a fault occurs, necessary actions can be taken in a timely manner and thus, damage caused by that fault can be limited. In this thesis, first, a method for precise …

Impact Of Physical Activity In The Prevention Of Colorectal Cancer, Sarah Ashley Barnes

Theses and Dissertations

This review evaluates the current understanding of research on the impact of physical activity in the prevention of colorectal cancer. Current biological mechanisms implicated in physical activity and colorectal cancer risk reduction are blood glucose regulation, insulin sensitivity, leptin and adiponectin profiles, inflammation as well as secreted protein acidic and rich in cysteine (SPARC), an exercise induced myokine. Recent literature indicates that 30-60 minutes of moderate to vigorous activity a day is effective against colorectal cancer development, and there is convincing evidence of aerobic exercise as differently beneficial in recruiting mechanisms identified as preventative against colorectal cancer. This article provides …

Emulation Of An Aeroderivative Twin-Shaft Gas Turbine Engine Using An Ac Electric Motor Drive, Blanca A. Correa

Theses and Dissertations

This dissertation presents a method to use an electric motor to emulate the steady-state and transient shaft power characteristics of an aeroderivative twin-shaft turbine engine. Model-based control provides the framework for developing an aeroderivative twin-shaft engine emulation system. Criteria are developed to appropriately specify the motor and variable-speed drive, based on torque, power, and inertia. This method accounts for the difference in inertia between the engine and the emulating motor; it establishes for the first time the nominal and peak torque requirements of the machine and the peak power and current requirements of the electronic motor drive (inverter).

Our results …

Modeling And Simulation Study Of A Dynamic Gas Turbine System In A Virtual Test Bed Environment, Eshwarprasad Thirunavukarasu

Theses and Dissertations

Gas Turbine is a complex system and highly non linear in its overall performance. For power generation applications, it is essential to develop a reliable gas turbine model for simulating the impact on electric power generated under various load conditions. This research focuses on development of a dynamic gas turbine model to simulate both single shaft and twin shaft engines. The model is developed on a virtual test bed platform which is an advanced dynamic multidisciplinary simulation environment. The modeling approach starts by developing mathematical models for individual components of gas turbines based on the thermodynamic laws and is coupled …

Microstructural-Based Modeling Of Electrical Percolation In Polymer Nanocomposites, Neelima Yellepeddi

Theses and Dissertations

Polymer nanocomposites (PNCs) represent a radical alternative to conventional filled polymers or polymer blends. In contrast to conventional composites, where the included phase is on the order of micrometers, PNCs are defined as those that have discrete constituents on the order of a few hundred nanometers. The value of PNCs is not solely based on tailoring mechanical properties, as in traditional composite design and manufacture, but rather on the potential for the design and optimization of multi-functional properties. There is major interest in these polymeric materials embedded with a conductive nanoscale filler. This is due to the possibility of designing …

Welding Parameters, Distortion And Mechanical Properties Of Aa7075 Lap Joints In Ssfsw, Hejun Yu

Theses and Dissertations

Friction Stir Welding (FSW), first invented by The Welding Institute of UK (TWI) in 1991, is a solid state welding process which was initially applied to welding Aluminum Alloy. FSW has wide application in industrial sectors. Stationary shoulder friction stir welding (SSFSW) was first developed to weld low thermal conductivity Ti-based alloys, which are hard to weld using conventional friction stir welding. Previous literatures showed SSFSW can produce uniform temperature distribution through thickness during the welding process. Since SSFSW is still under study phase, its advantages and disadvantages are not yet well defined. It is important to study the characteristics …