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Enhancing Photovoltaic Inverter Reliability Through Advanced Hardware Protection and Simulation Techniques
Full text linkPower electronics converter reliability is an issue in today’s grid, and it is an issue that will only become more prevalent as the nation and world move toward greater renewable energy penetration. While a significant amount of research has been conducted pertaining to power electronics converter reliability, (1) there lacks a universal way to protect the most critical component in a power electronics converter—the power device—from the two most common failure modes—short- and open-circuit faults; and (2) there does not exist a tool that considers both the component- and system-levels of a photovoltaic (PV) inverter for the purposes of lifetime prediction. In response to this gap in research, this dissertation proposes a universal solution to protect power devices from short- and open-circuit faults. It also provides significant contributions to the development of a framework for PV inverter reliability modeling and lifetime prediction. First, an introduction is given, highlighting the importance of power electronics converter reliability. Second, a universal short- and open-circuit fault detection and protection scheme is developed. Third, a failure mode and effects analysis (FMEA) is conducted for a PV inverter. Fourth, a methodology is proposed for the construction of an environmental-based component-level reliability model. Fifth, a foundation for a simulation platform capable of predicting PV inverter reliability is built. Sixth, a simulation modeling method allowing for the usage of parallel computing in power electronics simulations is proposed. Seventh, a conclusion and future works section is provided, summarizing the work done in this dissertation and the work to be done in the future. The results of this dissertation identify flaws in current converter reliability while providing solutions to improve and predict reliability moving forward, supporting the continued growth of power electronics.
The specific contributions of this dissertation are given by the construction of the following: (1) a novel, inexpensive, and universal method to protect and detect short-circuit and open-circuit faults on a sub-microsecond scale for a power converter’s power device; (2) an original failure mode and effects analysis for PV inverters encompassing component-level failures; (3) a lifetime modeling methodology for environmentally-affected components, resulting in a reliability model for PV inverter cooling fans including both electrical and mechanical subsystems; (4) a framework for a simulation platform capable of predicting power electronics system failures; and (5) a general method for simulating power electronics converters utilizing high-performance computing, allowing for the reduction of computation time while maintaining switching-level modeling accuracy
Amyloid Aggregation and Mitigation
Full text linkThe buildup of protein in tissues and organs plays a major role in unfunctional several serious diseases, including Alzheimer’s disease, Parkinson’s disease, and Type 2 diabetes, each tied to specific proteins that form harmful amyloid deposits. Amyloid aggregation typically follows a sigmoidal kinetic curve, beginning with a slow lag phase, followed by rapid fibril growth, and eventually reaching a plateau where mature, stable fibrils are formed. However, the early stage of aggregation remains particularly difficult to capture experimentally due to the highly dynamic nature and low abundance of small oligomeric species. In this dissertation, we employed discrete molecular dynamics (DMD) simulations to investigate these early aggregation events (Chapter 3-5) and provide molecular insights into the inhibition mechanisms of several amyloid aggregation inhibitors (Chapter 6-7).
Multiple studies have highlighted the connection between liquid–liquid phase separation (LLPS) and amyloid aggregation. Using a simplified coarse-grained model, we successfully captured the LLPS process and further demonstrated that the nanodroplet/oligomer morphology is influenced by the hydrophobic/hydrophilic distribution within peptide sequences. This published work offers valuable insight into how sequence features shape oligomer structures, providing a molecular foundation for understanding amyloidosis and guiding the development of peptide-based therapeutic strategies. Full details of this study are presented in Chapter 3.
Additionally, we employed all-atom simulations to investigate the early-stage assembly of two amyloidogenic Bri23 variants, ADan and ABri, which arise from mutations in the Bri2 gene. ADan and ABri are associated with amyloid deposits across the central nervous system and are linked to two rare familial dementias, familial Danish dementia and familial British dementia. Our simulations captured the formation of parallel in-register β-sheets—hallmarks of mature fibrils—within oligomeric intermediates. Notably, ADan formed longer β-sheets than ABri, suggesting a lower nucleation barrier and offering a possible explanation for the earlier onset of FDD compared to FBD. This study introduces a new criterion for evaluating amyloidogenicity: the ability to form extended parallel β-sheets during early aggregation. Full details are provided in Chapter 4.
While many amyloids such as Aβ and IAPP are associated with human diseases, the functional bacterial amyloid FapC from Pseudomonas aeruginosa also warrants attention. FapC plays a key role in bacterial biofilm formation, but growing evidence suggests it may exacerbate human conditions via the gut-brain axis following infection. Our study indicates that FapC can promote Aβ fibril formation, highlighting a potential link between bacterial infections and the progression of amyloid-related diseases. The full details of this published study are presented in Chapter 5.
Building on the above findings, a promising strategy to inhibit Pseudomonas aeruginosa bacterial activity focuses on disrupting extracellular connections between cells—specifically by preventing the aggregation of the functional bacterial amyloid FapC. One promising approach involves non-toxic silver nanoparticles and nanoclusters (AgNPs and AgNCs) capped with cationic branched polyethylenimine (bPEI), which have demonstrated antimicrobial potential by reducing FapC aggregation and disrupting biofilm formation. In this study, we employed discrete molecular dynamics (DMD) simulations to provide molecular insights into how nano silver particles prevent FapC from forming β-sheet-rich aggregates, thereby blocking fibril growth and subsequently reducing biofilm development. This published work is presented in detail in Chapter 6.
Although nano silver particles have shown effectiveness in inhibiting amyloid aggregation, their exogenous nature raises concerns about potential immune responses. As a result, the exploration of endogenous inhibitors remains an active area of research. A key example is the BRICHOS domain from the Bri2 gene, which has been experimentally demonstrated to delay Aβ and IAPP fibril formation even at low molar ratios. Our all-atom simulations revealed that the BRICHOS domain preferentially binds to the weakly populated fibril seeds rather than to amyloid monomers. When bound to a fibril seed, the BRICHOS domain tends to remain on the elongation surface, thereby preventing fibril extension by occupying unsaturated hydrogen donors and acceptors. The ability of BRICHOS to inhibit multiple amyloids highlights its potential as a therapeutic candidate. This work has been published and the details are provided in Chapter 7.
Together, these investigations provide a comprehensive view of amyloid formation and potential strategies to prevent aggregation. They span the liquid–liquid phase separation, nucleation dynamics, human amyloid interactions with bacterial amyloids, and both exogenous (nano silver particles) and endogenous (BRICHOS domain) approaches to inhibiting fibril growth. These insights contribute to a deeper understanding of amyloid-related diseases and offer promising directions for therapeutic development
The Immobile Nobility of “Life Herself ”: Silence and Stillness in “The Irish Dramatic Movement,” \u3ci\u3eThe Bounty of Sweden\u3c/i\u3e, and \u3ci\u3eNew Poems\u3c/i\u3e
Full text linkBridging the knowledge gap: professional development connecting educators and caregivers of multilingual learners
Full text linkPurpose – The purpose of this paper is to examine the professional growth of a cohort of teachers working with multilingual learners (MLs) during an MEd program and their recommendations for the development of a literacy course for ML caregivers. In addition, this study explores whether the school district capacity supports teacher growth, as reflected through district representatives’ feedback.
Design/methodology/approach – This design-based research study, informed by the culturally relevant pedagogy and dual capacity building frameworks, explores 30 in-service K-12 teachers and 11 district representatives. Data were collected through semestrial surveys and research logs over two years using mixed methods. Researchers address the following questions: How do teachers conceptualize ML caregiver support based on their professional development (PD)? and How do school district representatives’ perspectives for supporting ML caregivers align with teachers’ professional growth?
Findings – Findings revealed that teacher recommendations evolved, increasingly emphasizing studentcentered and culturally relevant approaches, indicating the PD’s positive impact. They also gained confidence in offering suggestions for an ML caregiver literacy course. District representatives offered fewer suggestions, echoing some teachers feedback, but also exhibited deficit perspectives.
Originality/value – This study addresses a gap in research by highlighting teachers’ visions for supporting ML caregivers and how their new knowledge informs their recommendations. Findings provide insights into the needs for PD design for teachers and district representatives, as well as what they perceive as successful learning experiences forML caregivers
Crusade From Afar: British Conservative Revolutionaries and the Nationalist Cause in Spain
Full text linkThe Spanish Civil War catalyzed a distinctive intellectual movement among Britain\u27s interwar right—the Conservative Revolutionaries. This thesis explores how this conflict provided ideological coherence to figures like Arnold Lunn, Arthur Bryant, and Douglas Jerrold, who occupied a unique position between conventional conservatism and fascism. Through organizations such as the Friends of Nationalist Spain, these intellectuals translated their abstract critiques of liberalism, democracy, and industrial capitalism into concrete political action. The thesis demonstrates that these figures were neither simple conservatives nor card-carrying fascists, but proponents of a third way between the two. This study challenges the conventional narrative that portrays British politics as immune to radical right-wing currents that swept continental Europe, complicates our understanding of the relationship between conservatism and fascism in Britain, and illuminates the diverse responses to the perceived crisis of liberal democracy and capitalism during the interwar period
Tsunamigenesis on a Buoyant Granular Layer as a Model of Ice Mélange in Ice-choked Fjords
No full textGlacial calving events can often create destructive tsunami waves in ice-choked fjords in the arctic region, posing a threat to local inhabitants and damaging coastlines. Here the sea is covered by a polydisperse granular material called ice mélange, whose properties can affect the wave characteristics. To investigate the role of a buoyant granular layer, as a model of ice mélange, on tsunami generation, or tsunamigenesis, a series of laboratory experiments were conducted by collapsing a column of dense granular material into a body of water with a layer of buoyant particles distributed across the liquid surface. Experiments were performed over a wide range of parameters, including the dense granular column geometry and water depth, allowing for a broad comparison with prior experimental work for systems without buoyant particles. Observed waveforms include solitary waves, bore waves, breaking waves, and non-linear transition waves. The wave morphology is significantly impacted by the buoyant particles, generally leading to higher amplitude, shorter wavelength, and suppression of wave breaking. Notably, as the particle size increases, the breaking action of the waves is further suppressed, indicating a damping mechanism by the buoyant particles. A strong correlation is observed between the maximum amplitude of the waves and the geometry of the collapsed granular material, allowing for the development of a predictive model for tsunami generation in fjords with ice mélange
Community Wastewater Treatment Resilience Assessment
Full text linkWith the rising threat of climate change and cascading impacts from infrastructure failure there is a growing need to strengthen community resilience. Theoretical and practical resilience frameworks are available, but they vary in aim and scope; there is no standard tool to assess resilience. This research expands on the resilience matrix (RM) application methods of previous research completed by the United States Army Corps of Engineers (USACE) and Clemson University. That work focused on drinking water treatment systems and developed a few dozen specific indicators, or metrics, to quantify resilience. This research adds wastewater infrastructure with the aim of identifying vulnerabilities and strengths through resilience metrics specific to the wastewater domain. The research question for this study is how do wastewater treatment systems prepare for, absorb, recover from, and adapt to disruptions to their system? A resilience assessment tool was developed and applied to several wastewater treatment systems in the upstate of South Carolina. The results of this research demonstrate traditional risk mitigation strategies are focused on more than recovery strategies. Case studies are provided to highlight the variables necessary to determine a wastewater treatment system’s resilience
TikTok Made Me do it: #75Hard
Full text linkTikTok is one of many social media platforms that distribute entertainment videos to its users based on an interactive algorithm. It has an influential impact on the information individuals are exposed to, especially when it is a trending topic. These trending TikTok videos reach millions of viewers; one popular trend on this app is #75Hard. #75Hard is a restrictive fitness program emphasizing mental toughness, self-discipline, and strict diet and exercise routines. However, popular trends like this one can perpetuate unrealistic and unattainable goals that put people at risk for negative outcomes such as body dissatisfaction and disordered eating. The present study aimed to investigate the relationship between viewing TikTok videos from the #75Hard trend and body image concerns. Participants (N=140) completed quantitative measures of body dissatisfaction before and after viewing a series of #75Hard videos. Results indicated that exposure to the videos significantly increased participants’ self-reported body dissatisfaction as measured by the Visual Analogue Scale, t(133) =1.859, p=.033, d=.161. However, no significant changes were found for thin ideal internalization, t(135)=-.20, p=.422, d=-.02, muscular ideal internalization t(136)=-.61, p=.270, d=-.05, or overall body image satisfaction scales t(140) =.54, p=.295, d=.05. These findings suggest that short-term exposure to fitness-related TikTok trends like #75Hard might lead to small increases in body dissatisfaction but does not significantly alter internalization of thin/fit ideals. Findings of the present study underscore the need for more research on how social media trends, particularly those involving fitspiration content, spread among users, and whether repeated or prolonged exposure exacerbates body dissatisfaction. Future research should also investigate these trends in other demographic groups, such as men and the LGBTQ+ population
Development of Rolipram Loaded PgP Nanoparticles for Spinal Cord Injury Repair
No full textSpinal cord injury (SCI) leads to devastating neurological deficits due to primary mechanical damage and secondary injury mechanisms, including inflammation, oxidative stress, excitotoxicity, and inhibitory scarring, which collectively impede neural regeneration. One key aspect of SCI pathology is a significant reduction in cyclic adenosine monophosphate (cAMP) levels, primarily due to increased phosphodiesterase (PDE 4) activity. As a ubiquitous second messenger, cAMP regulates key signaling pathways, including protein kinase A (PKA) / cAMP response element-binding protein (CREB) and exchange protein activated by cAMP 2 (EPAC2). Therefore, restoring/increasing cAMP level is one of the major therapeutic strategies to reduce neurotrauma and restore function. Rolipram, a selective PDE4 inhibitor, prevents cAMP degradation and enhances downstream signaling, promoting axonal regeneration and neuroprotection. However, its poor solubility, rapid clearance, and systemic side effects limit clinical application. Thus, there is a clear need for improved therapeutic strategies to safely deliver rolipram to the injured spinal cord. Our lab developed a proprietary cationic amphiphilic graft copolymer, poly (lactide-co-glycolide)-graft-polyethylenimine (PLGA-graft-PEI or PgP, US Patent 10,232,050 B1) as a nanocarrier for hydrophobic drugs. In previous studies, we successfully loaded rolipram (Rm) in PgP (Rm-PgP) and demonstrated that Rm-PgP can inhibit secondary injury in a rat severe compression SCI model.
The objective of this project was to investigate the therapeutic efficacy of Rm-PgP administered by 1) local intraspinal injection immediately after injury, 2) single and repeat intrathecal injection, a minimally invasive and clinically relevant administration route, immediately after injury, and 3) determine the treatment time window of Rm-PgP by delayed treatment (1 day and 4 weeks post injury) in a rat moderate contusion SCI model. We observed first that local intraspinal administration of Rm-PgP immediately after injury reduced secondary injury (inflammatory response, apoptosis, astrogliosis, and neuronal cell death), improved motor function, and delayed neuropathic pain induction. Second, we observed that both single and repeated treatment of Rm-PgP by intrathecal administration significantly reduced secondary injury, improved motor function recovery, and mitigated neuropathic pain compared to untreated SCI animal group. Finally, we observed that Rm-PgP delayed treatment at 1 day post injury in acute phase significantly reduced cavity volume and apoptosis and improved motor function recovery compared to untreated SCI animal group. For 4 weeks delayed treatment in chronic phase, we did not observe the improvement of motor function, but mitigation of neuropathic pain as well as reduced secondary injury were observed, although the changes were not significantly different.
In conclusion, these findings establish nanoparticle-mediated rolipram delivery as a promising therapeutic strategy for SCI, offering targeted, sustained drug release and improved functional outcomes. This work advances the development of translational neuroprotective and regenerative approaches for SCI treatment
Real-Time Active Thermal Management and Degradation Forecasting of Power Electronics Building Blocks In All-Electric Ships
Full text linkWith advancements in semiconductor technology, power electronic devices play a critical role in modern power systems, enabling efficient energy conversion in applications such as renewable energy integration, electric vehicle drives, industrial automation, and Navy ship power systems. However, the increasing use of power converters presents challenges such as harmonic reduction, cost optimization, reliability improvement, and thermal management, especially in weight- and space-constrained environments like wind turbines and shipboard systems. High-frequency switching, while reducing passive filter size, increases thermal stress on semiconductor devices, impacting efficiency and longevity. Active thermal control, which regulates junction temperature through power loss management, and degradation forecasting, which aids future maintenance decision-making, are key to enhancing semiconductor reliability and operational efficiency.
This dissertation presents a comprehensive study of thermal control and management strategies in power electronics, with a focus on their application in All-Electric Ship (AES) power systems. It begins by reviewing existing electro-thermal management techniques and identifying their limitations in mission-critical, space-constrained environments. The dissertation then introduces a novel Finite Control Set Model Predictive Control (FCS-MPC) strategy that simultaneously regulates thermal behavior and controls the electrical performance of Modular Multilevel Converter (MMC)-based Power Electronic Building Blocks (PEBBs). In addition, a data-driven framework utilizing Deep Neural Networks (DNNs) is developed to forecast PEBB degradation, supporting more accurate and informed electro-thermal management decisions. By integrating real-time thermal regulation, enhanced electrical control, and predictive maintenance planning, this work aims to improve both the reliability and operational efficiency of AES power systems