Digital Commons Network^™

Decentralized Resource Allocation Through Constrained Centroidal Voronoi Tessellations, Bhagyashri Telsang

Doctoral Dissertations

The advancements in the fields of microelectronics facilitate incorporating team elements like coordination into engineering systems through advanced computing power. Such incorporation is useful since many engineering systems can be characterized as a collection of interacting subsystems each having access to local information, making local decisions, interacting with neighbors, and seeking to optimize local objectives that may well conflict with other subsystems, while also trying to optimize certain global objective. In this dissertation, we take advantage of such technological advancements to explore the problem of resource allocation through different aspects of the decentralized architecture like information structure in a team. …

A Novel Approach To Orbital Debris Mitigation, Timothy S. Turk

Doctoral Dissertations

Since mankind launched the first satellite into orbit in 1957, we have been inadvertently, yet deliberately, creating an environment in space that may ultimately lead to the end of our space exploration. Space debris, more specifically, orbital debris is a growing problem that must be dealt with sooner, rather than later. Several ideas have been developed to address the complex problem of orbital debris mitigation.

This research will investigate the possibility of removing orbital debris from the Low Earth Orbit (LEO) regime by using a metaheuristic algorithm to maximize collection of debris resulting from the February 2009 on-orbit collision of …

Novel Mixed Integer Programming Approaches To Unit Commitment And Tool Switching Problems, Najmaddin Akhundov

Doctoral Dissertations

In the first two chapters, we discuss mixed integer programming formulations in Unit Commitment Problem. First, we present a new reformulation to capture the uncertainty associated with renewable energy. Then, the symmetrical property of UC is exploited to develop new methods to improve the computational time by reducing redundancy in the search space. In the third chapter, we focus on the Tool Switching and Sequencing Problem. Similar to UC, we analyze its symmetrical nature and present a new reformulation and symmetry-breaking cuts which lead to a significant improvement in the solution time. In chapter one, we use convex hull pricing …

Confinement And Interface Effects In Self Assembly Of Functional Block Copolymers, Jonathan P. Coote

Doctoral Dissertations

Functional block copolymers are of increasing interest for their ability to combine the functional properties of one polymer, such as a polymer electrolyte or semiconductor, with the mechanical properties of another polymer. Balancing properties in this way can be challenging, however, due to the complex relationship between self-assembled morphology and resulting properties. Interface effects in particular, whether due to confinement within a self-assembled domain or at macroscopic boundary, are poorly understood in such functional block copolymers. This dissertation consists of two main thrusts, each investigating confinement or interfacial effects in a different functional block copolymer system. The first thrust focuses …

Uranium Holdup Mass Quantification By Hybrid Gamma Imaging, Blake R. Montz

Masters Theses

Accurate quantification of uranium holdup is crucial in the efficient operation of many processing facilities involved with special nuclear material (SNM). The varying shapes and sizes of holdup deposits can make accurate quantification a challenge. The most common approach is the Generalized Geometry Holdup (GGH) method which simplifies the shape of the deposit to a point, line, or area source. Although the GGH method is quick and easy to implement, the oversimplifying assumptions can lead to systematic uncertainties as high as 50%. The research presented here is exploring gamma-ray imaging as a more accurate method of quantifying deposits. A PHDs …

Component Monitoring Strategies For Ipwr Plant Systems During Operational Transients, Matthew S. Scott

Masters Theses

Small modular reactors (SMRs) are currently at the forefront of the nuclear industry as potential next stage in nuclear energy production. Implementing a new reactor technology in a commercial setting contains many challenges in terms of maintaining safety and regulatory standards since all of the regulatory framework is based on the traditional PWR design. One benefit of the SMR design is the increased ability to load-follow to meet the constant changes in grid demand. This type of operational strategy introduces changes into the system that impacts the operational lifespan of system components due to increased degradation. Since there are no …

Image Based Processing For Weld Defect Detection, Shems-Eddine Belhout

Masters Theses

There is a growing need for automation in the welding industry due to a growing shortage in skilled welders. TIG [Tungsten Inert Gas] welding, a method of welding that uses an electrode shielded by gas and is fed externally by a wire, is incredibly advantageous for its precise heat control. TIG welding is considered the standard for nuclear application which requires highly precise welds to be performed. Robotic welding can address this issue, and one major problem that occurs during welding is welding defects. Typical weld defect detection requires a highly knowledgeable welder or destructive and nondestructive evaluation. Destructive evaluation …

A Study Of Readiness For Transportation Electrification And Automation Focusing On Safety And Future Adoption, Steve Lee

Doctoral Dissertations

Transportation electrification and automation are growing societal trends and considered promising pathways to enhance the safety, mobility, efficiency, and sustainability of the surface transportation system. At this early stage of transportation electrification and automation, one of the most critical issues is whether and to what extent people are willing to adopt electric vehicle (EV) and automated vehicle (AV) technologies in the future. Another critical issue, especially concerning transportation automation, is how to thoroughly ensure the safety of automated driving performance to resolve safety concerns about AVs, which is one of the key challenges to AV adoption. In this regard, the …

Towards Reduced-Order Model Accelerated Optimization For Aerodynamic Design, Andrew L. Kaminsky

Doctoral Dissertations

The adoption of mathematically formal simulation-based optimization approaches within aerodynamic design depends upon a delicate balance of affordability and accessibility. Techniques are needed to accelerate the simulation-based optimization process, but they must remain approachable enough for the implementation time to not eliminate the cost savings or act as a barrier to adoption.

This dissertation introduces a reduced-order model technique for accelerating fixed-point iterative solvers (e.g. such as those employed to solve primal equations, sensitivity equations, design equations, and their combination). The reduced-order model-based acceleration technique collects snapshots of early iteration (pre-convergent) solutions and residuals and then uses them to project …

Oscillation Analysis And Its Mitigation Using Inverter-Based Resources In Large-Scale Power Grids, Khaled Alshuaibi

Doctoral Dissertations

In today's interconnected power grids, forced oscillations and poorly damped low-frequency oscillations are major concerns that can damage equipment, limit power transfer capability, and deteriorate power system stability.

The first part of the dissertation focuses on the impact of a wide-area power oscillation damping (POD) controller via voltage source converter-based high voltage direct current (VSC-HVDC) in enhancing the power system stability and improving the damping of low-frequency oscillation. The POD controller's performance was investigated under a three-phase temporary line fault. The Great Britain (G.B.) power grid model validated the POD controller performance via active power modulation of VSC-HVDC through TSAT-RTDS …

Improving Strength And Stability In Continuum Robots, Jake A Childs

Doctoral Dissertations

Continuum robots, which are bio-inspired ’trunk-like’ robots, are characterized for their inherent compliance and range of motion. One of the key challenges in continuum robotics research is developing robots with sufficient strength and stability without adding additional weight or complexity to the design. The research conducted in this dissertation encompasses design and modeling strategies that address these challenges in strength and stability. This work improves three continuum robot actuation paradigms: (1) tendon-driven continuum robots (TDCR), (2) concentric tube robots (CTR), and (3) concentric push-pull robots (CPPR). The first chapter of contribution covers strategies for improving strength in TDCRs. The payload …

First Development And Demonstration Of Fiber Optic Bolometer, Seungsup Lee

Doctoral Dissertations

The fiber optic bolometer (FOB) was demonstrated observing a fusion plasma for the first time, and 2D fiber optic bolometer was developed and demonstrated to have high spatial resolution. The FOB is a novel type of a bolometer that is theoretically immune to EMI. A bolometer that is a sensor that measure the power of the incoming electromagnetic radiation. The most common bolometer used in fusion research is a resistive bolometer that utilize resistors in an electrical circuit. Due to high electromagnetic interferences (EMI) in fusion environment, noise can be a serious problem in determining accurate plasma radiation. The demonstration …

Encapsulation Of Antimicrobial Peptides In Bicontinuous Microemulsions For Topical Delivery To Surgical Site Infections And Chronic Wounds, Madison A. Oehler

Masters Theses

Surgical site infections and chronic wounds, especially those caused by antibiotic-resistant microorganisms, result in hospitalization and fatalities each year. Methods to prevent these infections, such as cleaning and preparing medical tools, have had minimal success in preventing infections. Further, antibiotic treatments have become less successful in treating infections and wounds because of antibiotic-resistant bacteria. Antimicrobial peptides (AMP) are a possible treatment solution for wound infections. AMPs are oligopeptides that occur in nature or can be synthesized in vitro which possess a broad spectrum of antimicrobial activity against bacteria and other harmful microorganisms. AMPs operate by disrupting the packing arrangements of …

Application Of Load Shifting For Commercial Hvac-R Systems Via Static And Dynamic Event Automated Demand Response, Justin Anthony Martinez

Masters Theses

Life in the modern era is inextricably tied to energy and the unending, ever-growing need for more. The technologies that drive society, in fields such as communication, infrastructure, and heavy industry, are dependent on that electrical energy being reliable and readily available. This places an extreme importance on the power generation sector as a function of meeting the demand required for stability. However, as seen with increased climate volatility due to misused or otherwise mismanaged resources in the heavy industry, and the uncertain and variable renewable energy generation; there must also be ecological as well as economic consideration when discussing …

Fundamental Understanding Of The Transient Melt Pool Dynamics, Solidification Kinetics And Build Texture In Spot-Melt Additive Manufacturing Of Ti-6al-4v, Rakesh Rajaram Kamath

Doctoral Dissertations

The overarching goal of this dissertation is to better understand the underlying process-structure relationships in play during the implementation of a spot melt strategy for metal additive manufacturing, which has become a popular alternative to the conventional raster melt strategy for site-specific microstructure control. In the first part of this dissertation, the effect of a spot melt strategy on the solidification texture, variant selection, phase fraction, and their variations along the build height of an E-PBF Ti-6Al-4V is investigated in comparison to a conventional linear melt strategy using high-energy synchrotron x-ray diffraction. In spite of the thermal excursions involved, the …

Aluminum-Based Material Fabrication By Friction Stir Processing: Microstructural Evolution And Mechanical Properties, Suhong Zhang

Doctoral Dissertations

Friction stir processing (FSP) is an energy efficient solid-state material processing technique for microstructure modification of commercial high-strength Al alloys. Many variant techniques were developed in recent years that enabled light-weight and high-strength structure fabrication. Identifying relationship among process conditions, microstructures, and mechanical properties is of critical importance to facilitate the practical implementation of these new techniques. The research in the dissertation focusses on developing two main techniques of the FSP: a) friction stir back extrusion (FSBE) of 6063 aluminum alloy for tube making and b) FSP of 7075 aluminum alloy from powder feedstock. FSBE fabricated Al 6063 alloy tubes …

Heat Pipes With Arbitrary Boundary Conditions, Katrina Sweetland

Doctoral Dissertations

Heat pipes passively transfer heat in numerous applications. Traditionally one side of the heat pipe is coupled to a heat source (evaporator) while the opposite side is coupled to a heat sink (condenser). This configuration has working fluid stagnation points at each end of the heat pipe. Other configurations may also prove useful, such as heat pipes with multiple evaporators or multiple condensers. In such heat pipes, additional working fluid stagnation points form at locations dependent on the configuration of the thermal boundary conditions. These stagnation points divide the heat pipe into multiple cells that each have an evaporator and …

Demonstrating The Use Of Multiple Experimental Techniques To Investigate Helium-Hydrogen Synergies In Tungsten, Wendy A. Garcia

Doctoral Dissertations

Polycrystalline W sample discs measuring 6 mm by 0.5 mm have been exposed to a low-energy (70 eV) He plasma using a low flux ( ) [1.3 times 10 to the 17 Helium per meter squared per second] ECR source located at the University of Tennessee in Dr. Donovan's laboratory. The samples were exposed to three different He fluences ( ) [5 times 10 to the 19 Helium per meter squared, 5 times 10 to the 20 Helium per meter squared, 5 times 10 to the 21 Helium per meter squared] at surface temperatures of ~300 K, 600 K and …

Remote Human Vital Sign Monitoring Using Multiple-Input Multiple-Output Radar At Millimeter-Wave Frequencies, Toan Khanh Vo Dai

Doctoral Dissertations

Non-contact respiration rate (RR) and heart rate (HR) monitoring using millimeter-wave (mmWave) radars has gained lots of attention for medical, civilian, and military applications. These mmWave radars are small, light, and portable which can be deployed to various places. To increase the accuracy of RR and HR detection, distributed multi-input multi-output (MIMO) radar can be used to acquire non-redundant information of vital sign signals from different perspectives because each MIMO channel has different fields of view with respect to the subject under test (SUT). This dissertation investigates the use of a Frequency Modulated Continuous Wave (FMCW) radar operating at 77-81 …

Functional Bottlebrush Polymer Additives For Thin Films And Coatings, Travis S. Laws

Doctoral Dissertations

Bottlebrush polymers are a class of highly branched polymers consisting of polymeric side chains that are densely grafted to a linear backbone. Their highly branched architecture results in surface enrichment across a broad range of materials. The goal of my research has been centered around the design of functional bottlebrush polymers and their use as surface active additives in blend films and coatings.

In the first chapter, we examine the segregation behavior of polystyrene bottlebrushes that are blended with linear polystyrene. We systematically vary the lengths of the bottlebrush backbone (Nb), side-chain (Nsc), and the linear matrix (Nm) in order …

Computational Investigation Of Planar Fault Structures In Ni-Based Concentrated Alloys, Liubin Xu

Doctoral Dissertations

The Nickel-based Cantor-type concentrated alloys have drawn tremendous research interest as they exhibit great potential for advanced structural materials. The origins of their mechanical performances have been largely associated with planar fault structures, such as stacking faults and deformation twins, as well as their interplay with other defects. Therefore, it is essential to investigate the energetics and the evolution of the planar faults during the deformation processes of the materials.

In the first part of this dissertation, we compute the stacking fault energies (SFEs) in the Ni-based concentrated binary and ternary alloys at both density functional theory (DFT) and atomistic …

Analysis And Development Of Multiple Phase Shift Modulation In A Sic-Based Dual Active Bridge Converter, Yu Yan

Doctoral Dissertations

Renewable energy adoption is a popular topic to release the stress of climate change caused by greenhouse gas. Electricity is ideal secondary energy for clean primary energy such as nuclear, wind, photovoltaic, and so on. To extend the application of electricity and reduce fossil energy consumption by transportation sectors, electric vehicles (EVs) become promising technology that can further inspire the development of renewable energy.

Battery as the core in an EV provides the energy to the motor and all on-board electric equipment. The battery charger is mainly composed of a power factor correction (PFC) and isolated DC-DC converter. Therefore, power …

Investigating The Blending Mechanism And Strength Development Of 100% Hot In-Place Recycled Asphalt Mixtures, Yuetan Ma

Doctoral Dissertations

The current tendency in the asphalt paving industry is to increase the utilization of recycled asphalt pavement (RAP). Hot in-place recycling (HIR) is a promising approach to consume 100% RAP from the existing pavement for pavement surface rehabilitation in the field. However, some concerns remained regarding the utilization of HIR techniques in pavement rehabilitation: 1. Whether it is cost-effective to apply the in-place recycling techniques to pavement rehabilitation compared to the conventional HMA surface milling & filling? 2. How to improve the performance of the asphalt mixtures with HIR technique? 3. How much RAP binder can be available for coating …

How Dynamic Bond Results In The Unique Viscoelastic Behavior Of The Associating Polymers, Sirui Ge

Doctoral Dissertations

Associating polymer is a special kind of polymer possessing transient reversible bonds in addition to the conventional covalent bonds. The reversible bonds provide unique dynamics and fascinating viscoelastic properties, resulting in attractive applications for these polymers, such as self-healing and shape memory materials. Despite many years of studies, the understanding of dynamics of polymers with reversible bonds, especially on molecular level, is still in the rudimentary stage, preventing the rational design of the potential novel functional materials based on associating polymers. In this dissertation, we provide a detailed and quantitative understanding of the dynamics and viscoelastic properties of associating polymers. …

Power Quality Control And Common-Mode Noise Mitigation For Inverters In Electric Vehicles, Yang Huang

Doctoral Dissertations

Inverters are widely utilized in electric vehicle (EV) applications as a major voltage/current source for onboard battery chargers (OBC) and motor drive systems. The inverter performance is critical to the efficiency of EV system energy conversion and electronics system electro-magnetic interference (EMI) design. However, for AC systems, the bandwidth requirement is usually low compared with DC systems, and the control impact on the inverter differential-mode (DM) and common-mode (CM) performance are not well investigated. With the wide-band gap (WBG) device era, the switching capability of power electronics devices drastically improved. The DM/CM impact that was brought by the WBG device-based …

Predictive Capabilities Of Laminar-Turbulent Transition Models For Aerodynamics Applications, Jared Alexander Carnes

Doctoral Dissertations

Laminar-turbulent boundary-layer transition has a demonstrable impact on the performance of aerospace vehicles. The ability to accurately predict transition is integral to properly capturing relevant flow physics. Traditionally, computational fluid dynamics simulations are performed fully turbulent, meaning that laminar flow is neglected. This, however, can result in errant predictions of vehicle performance as quantities such as skin-friction drag may be overpredicted. Resultingly, development of Reynolds-averaged Navier-Stokes transition models has seen significant attention over the last decades in order to model transition and realize the performance improvements of laminar flow.

In this work, the behaviors of several different transition-prediction methods are …

Stability Analysis And Design Of Grid-Interactive Power Electronic Converters, Le Kong

Doctoral Dissertations

The increasing penetration of power electronic converters (PECs) can provide high flexibility, full controllability, sustainability, and improved efficiency for future electric power systems. However, it also introduces new challenges since the wide-frequency-band control dynamics of PECs can interact with the power system and result in different types of instability issues. To holistically address the instability issues, several research activities are conducted in this dissertation.

The modular multilevel converter (MMC), which is one of the most common PECs in high- or medium-voltage power systems, is investigated. An improved MMC dc impedance model is developed by considering both the submodule voltage and …

Power Market Cybersecurity And Profit-Targeting Cyberattacks, Qiwei Zhang

Doctoral Dissertations

The COVID-19 pandemic has forced many companies and business to operate through remote platforms, which has made everyday life and everyone more digitally connected than ever before. The cybersecurity has become a bigger priority in all aspects of life. A few real-world cases have demonstrated the current capability of cyberattacks as in [1], [2], and [3]. These cases invalidate the traditional belief that cyberattacks are unable to penetrate real-world industrial systems. Beyond the physical damage, some attackers target financial arbitrage advantages brought by false data injection attacks (FDIAs) [4]. Malicious breaches into power market operations could induce catastrophic consequences on …

Efficient Control Approaches For Guaranteed Frequency Performance In Power Systems, Samaneh Morovati

Doctoral Dissertations

Due to high penetration of renewable energy, converter-interfaced sources are increasing in power systems and degrading the grid frequency response. Synthetic inertia emulation and guaranteed primary frequency response is a challenging task. Still, there is high potential for application of highly controllable converter-interfaced devices to help performance. Renewable energy sources and demand side smart devices also need to be equipped with innovative frequency control approaches that contribute to frequency regulation operations.

First, the wind turbine generator is chosen to represent an example of a converter- interfaced source. An augmented system frequency response model is derived, including the system frequency response …

Optimizing Strategic Planning With Long-Term Sequential Decision Making Under Uncertainty: A Decomposition Approach, Zeyu Liu

Doctoral Dissertations

The operations research literature has seen decision-making methods at both strategic and operational levels, where high-level strategic plans are first devised, followed by long-term policies that guide future day-to-day operations under uncertainties. Current literature studies such problems on a case-by-case basis, without a unified approach. In this study, we investigate the joint optimization of strategic and operational decisions from a methodological perspective, by proposing a generic two-stage long-term strategic stochastic decision-making (LSSD) framework, in which the first stage models strategic decisions with linear programming (LP), and the second stage models operational decisions with Markov decision processes (MDP). The joint optimization …