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Enhancing Power System Strength and Inertia in the Saudi Electric Grid for Solar Power Integration
Get PDFAs electricity demand continues to increase and environmental challenges from conventional power generation persist, a worldwide shift toward renewable energy sources (RESs) has been initiated. Saudi Arabia, with its advantageous geographical location, presents exceptional potential for solar photovoltaic (PV) integration. This natural advantage positions the country as an ideal adopter of solar PV, facilitating its path toward reduced reliance on fossil fuels.While the shift toward renewable energy offers significant benefits, it also introduces complexities to power grid stability due to the inherent limitations of RESs in providing sufficient strength and inertia support. Successful integration requires adapting existing grid infrastructure and developing innovative solutions. This dissertation addresses the emerging challenges associated with reduced grid strength and inertia. It primarily focuses on the implications of full solar PV integration, where conventional generators are entirely replaced within the Saudi Electricity Company (SEC) grid. The research explores several solutions, including implementing synchronous condensers (SynCons) to enhance grid strength by improving short-circuit capacity and inertia, ensuring stable voltage and frequency regulation. Protection systems were adapted to address the reduced fault current associated with solar PV integration. Using the short-circuit ratio (SCR) as a strength index, findings indicate that an SCR increase of 3 with SynCons significantly improved system stability and post-disturbance recovery. These insights offer adaptable strategies and practical approaches to enhance grid resilience, supporting power systems worldwide in their transition to RESs
Mechanical behavior and thermal stability of Ti-Zr-Hf-Nb-Ta alloys
Get PDFRefractory high entropy alloys (RHEAs) are interesting from both scientific and engineering viewpoints. Using group IV, V, and VI elements, the compositional space available to RHEAs grants greater freedom to obtain material properties that are often in competition with each other such as high melting temperature and room-temperature ductility. As a model system, Ti-Zr-Hf-Nb-Ta alloys show promise with their high melting temperature and ductility that allows for cold rolling. Despite over a decade since the discovery of the equiatomic alloy TiZrHfNbTa, there is still a dearth of basic composition-property data for its derivatives. This work aims to address three issues with respect to TiZrHfNbTa alloys: relationship between composition and (i) uniaxial tensile behavior, (ii) fracture toughness behavior, and (iii) thermal stability. The equiatomic alloy TiZrHfNbTa and four other alloys were investigated that represented relatively wide compositional changes within the Ti-Zr-Hf-Nb-Ta space that could be processed. With respect to tensile properties in the single-phase state, the alloys behave similarly and their yield strengths can be predicted well by an analytical theory based on edge dislocations. During fracture toughness testing, sudden crack extension is seen in TiZrHfNbTa but not the other alloys. Finally, the thermally stable phases in the four derivative alloys showed three unique microstructures: single-phase with incidental minor phases, HCP homogenously precipitated in BCC, and lamellar BCC-HCP microstructure akin to eutectoid microstructures
Design Considerations on Insulation and Magnetics for Medium Voltage DC/DC Converters
No full textMedium voltage (MV) SiC devices have drawn considerable attention thanks to their high voltage blocking and fast switching capabilities, enabling new generations of high-power and high-density MV power conversion. However, many challenges can be found in implementing MV converters with MV SiC devices, such as insulation, efficiency, density, and parasitics. In this dissertation, several techniques have been proposed to address those issues.
First, a low-loss leakage integration technique using ferrite bridges and 2-D laminated magnetic cores is proposed for shell-type transformer structures. Then, a 2-D lamination configuration for ribbon- and sheet-based magnetic core is proposed, which further reduces the leakage-induced eddy current loss.
Second, a ferrite shielding strategy is introduced to reduce eddy current losses in laminated-core inductors and transformers by covering critical surfaces and bracketing the core sides. The mechanism of the proposed ferrite is analyzed and experimentally validated.
Third, a dry-type insulation scheme is proposed for the MV inductor and transformer windings. Insulation materials are characterized with simple test sample designs. The winding structure, shielding, and field grading methods have been introduced. A simplified vacuum encapsulation process is also proposed with fewer chambers and less tubing while the quality of the encapsulation is maintained.
A common-mode (CM) switching loss reduction method is proposed for DC/DC feeding cascaded H-bridge (CHB) converters by studying the mechanism and applying a diode-clamped grounding circuit. The operating principle of the diode-clamped circuit for the CHB is also discussed.
A compact MV power stage design strategy is also developed. The proposed heatsink field shaping is implemented to reduce the insulation clearance requirement. With the sloping air duct design, additional creepage distance can also be provided. Simplified gate drive design with commercial solution and compact power stage design are also demonstrated.
Finally, a flux balancing scheme for MV dual-active-bridge (DAB) converter transformers is proposed utilizing the magnetizing harmonic current. Ferrite gaps generate harmonics for flux unbalance detection, modeled and verified with dedicated sensing and control in DAB prototypes
Underlying Event Fluctuations and Jet Background in √sNN = 200 GeV Au+Au Collisions Using the sPHENIX Detector
Get PDFAt the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, heavy ions are collided at ultra-relativistic speeds. The motivation for these collisions is to study an extreme form of Quantum Chromodynamical matter called Quark-Gluon Plasma (QGP). The QGP can be studied using collimated sprays of particles that are products of initial hard-scatterings between colliding partons in the moments prior to the production of QGP. These collimated sprays of particles are called jets. Comparing how jets are modified in heavy ion collision systems to that of proton-proton collisions, where QGP production is not expected, provides a useful tool to probe the strongly interacting medium and test predictions of Quantum Chromodynamics.
Measurements of jets in heavy ion collisions must contend with the high entropy and the presence of a large, fluctuating background of soft particles unrelated to the hard-scattering event. This underlying event and its fluctuations must be well understood in order to correct for it in the most challenging jet kinematic regimes. Jet momentum reconstruction for low momenta jets in heavy ion collisions at the Relativistic Heavy Ion Collider is particularly difficult due to the low initial momentum transfer of the hard-scatterings, and the large fraction of gluon-initiated jets.
In this analysis, the underlying event in Au+Au collisions at a center of mass energy of 200 GeV is measured using the sPHENIX detector. The spatial and multiplicity correlations for underlying event fluctuations are presented and the sources of underlying event fluctuations are determined and quantified. The fluctuations of the underlying event are found to be primarily driven by statistical fluctuations in particle multiplicity and non-stochastic contributions to the underlying event are found to be primarily due to initial geometric anisotropies in the colliding nuclei.
Direct comparisons between jet background subtraction methods are presented based on each jet background subtraction method\u27s ability to suppress underlying event fluctuations. This is the first direct comparison between methods used by different experiments for jet background reconstruction. Machine learning applications to jet background subtraction are presented and their applicability to data is discussed. Interpretable machine learning techniques are applied to previously published jet background subtraction methods and a physics motivation is presented based on learned expressions. We apply a new jet background subtraction method, based on jet constituent multiplicity, to data for the first time. Our findings provide guidance for future jet measurements at sPHENIX
Soapstone Characterization as a Proxy for Trade in the Archaic Southeast
Get PDFSoapstone is a soft, metamorphic rock frequently created by hydrothermal flows through a parent material and containing at least 35% Talc naturally. Soapstones are only naturally located along the eastern and southern edges of the Appalachian Mountains and have been utilized for a number of artifact types with soapstone vessels being of particular interest. While much debate surrounds the temporal range and use of the material it is generally accepted to have been used during the Late Archaic through the Early Woodland. The relatively narrow period of use, the ubiquity of the soapstone vessels throughout the Southeast and, the limited geographic location of sources makes the material particularly attractive for research into trade and interaction between sites. This project uses pXRF and FORS, both relatively inexpensive and non-destructive methods, to characterize soapstone vessel fragments from Webb’s Cache (Louisiana), 1Ma26 (Alabama), Townsend (Tennessee) and Birdwell (Tennessee) to identify possible trade interactions between these sites
Of ful gret sadnes : The Presentation of Feminine Grief, Sorrow, and Mourning in John Lydgate\u27s Troy Book
Get PDFLooking to the work of the medieval poet and monk John Lydgate (1370-1451), this thesis seeks to identify the way in which various female Troy Book characters express and represent the multifaceted experience of grief. Spanning across three chapters, this thesis identifies Medea’s anticipatory grief regarding her union with Jason, Cassandra’s national and anticipatory grief in prophesying the fall of Troy, and Penthesilea’s revenge-focused, chivalric grief following the murder of Hector as critical points in analyzing medieval womanhood alongside a sorrowful war narrative. Acknowledging the overlap between Troy Book’s predecessors (the Iliad, Geoffrey Chaucer, Guido delle Colonne, etc.) and the text itself, this study shows that Lydgate’s presentation of female grief is not only indicative of the women’s roles in the text but also reflects his familiarity with discourses of femininity in the Middle Ages. Through textual analysis of select Middle English passages from Lydgate’s Troy Book, this thesis explores the foundations of these women’s grief and offers ample insight into the text itself, as well as perceptions of medieval grief as a whole
Beyond Traffic Signals: Coordinating Heterogeneous Mixed Traffic at Unsignalized Intersections
Get PDFUrban intersections are inherently complex, hosting a diverse mix of vehicles ranging from small cars to large semi-trailers, each with distinct driving behaviors and space requirements. Managing such heterogeneous traffic becomes particularly challenging at unsignalized intersections, where the absence of traffic lights demands real-time coordination. This thesis explores how robot vehicles (RVs), powered by reinforcement learning (RL), can dynamically optimize mixed traffic flow under varying degrees of automation. By gradually increasing RV penetration from 10% to 90%, our findings reveal a substantial reduction in average waiting times—up to 86% compared to signalized intersections—demonstrating the efficiency of RL-based control. Notably, we observe a rarity advantage , where less frequent vehicle types, such as trucks, experience the most significant improvements, benefiting from RV-driven coordination by as much as 87%. Additionally, space headways decrease consistently across all vehicle types, suggesting enhanced road space utilization. While RVs operate at higher speeds, leading to increased energy consumption, the overall efficiency gains surpass those of conventional traffic signals. These insights underscore the transformative potential of RL in coordinating heterogeneous mixed traffic, paving the way for more adaptive and scalable traffic management solutions in real-world urban mobility
The role of perR on Group B Streptococcus peroxide and iron regulation
Get PDFStreptococcus agalactiae, also known as Group B Streptococcus (GBS), is a Gram Positive facultative anaerobe that generally persists in the gut and reproductive tract, and can become opportunistically pathogenic in immunocompromised hosts. To better understand GBS persistence and disease morphologies, we have investigated the peroxide responsive repressor (perR) in GBS, to allow for better characterization of this organism’s response to reactive oxygen species (ROS) stress and iron regulation mechanisms. PerR is a repressive regulator that has been characterized in other Gram-Positive organisms, but not in GBS. However, in GBS it has been identified in a murine vaginal colonization transposon library experiment as impactful for the purpose of persistence in that environment. Characterizing the role of perR in GBS will increase our understanding of how this catalase negative organisms response to reactive oxygen stress, and how the ROS response and iron homeostasis may interact. Using perR deletion strains, we showed that perR does act as a regulator of the peroxide stress response, as deletion strains show increased resistance to hydrogen peroxide. In a murine model of GBS vaginal colonization, perR depletion strains also showed a modest decreased colonization persistence compared to WT strains in CD-1 mice. PerR was also shown to play a role in iron regulation and homeostasis, as a deletion strain shows both increased sensitivity to iron chelation, and increased resistance to iron toxicity. Q-PCR was also used to identify several iron homeostasis genes, fetB and VIT, that are upregulated in a perR mutant background. Due to the role of GBS as an opportunistic pathogen in systemic disease, we also investigated the virulence of the perR mutant in a murine model of systemic disease. In this model, the mutant strain showed significantly decreased virulence compared to WT strains. Overall, in GBS perR has been characterized as being a driver of regulation for both peroxide stress and iron homeostasis, as well as a regulatory of certain virulence genes and phage elements
Response of Pulmonary Artery Endothelial Cells to Altered Stress Conditions
Get PDFHealthy human hearts function with two ventricles; however, single ventricle defects (SVD), a type of congenital heart defect, results in one of these ventricles not functioning properly. A series of surgeries, culminating in the Fontan procedure, are used to correct these defects, which can vary widely. The resulting Fontan physiology of the heart can cause comorbidities as the patients grow, such as pulmonary hypertension and dysrhythmias. Because this subject is understudied, it is important to determine the connection between Fontan physiology, the comorbidities, and the potential cause of the complications. It is expected that the Fontan population is to double within the next 20 years. We hypothesize that wall shear stress plays a role in pulmonary hypertension, which may be a potential cause of Fontan failure. This work aims to determine a connection between wall shear stress and expression of various molecular markers by exposing cells to various stress conditions using an orbital shaker. We found that vascular endothelial growth factor, nitric oxide, and lipids may be a potential molecular marker in clinical settings for the detection of Fontan failure
EVALUATION OF NOVEL PROTEIN-BASED INGREDIENTS DERVIED FROM INDUSTRIAL HEMPSEED (Cannabis sativa L.)
No full textIndustrial hempseed (Cannabis sativa L.) is gaining recognition as a sustainable plant-based protein source, yet its allergenic potential remains largely unexplored. Similarly, the impact of consuming hemp ingredients long term has not been assessed. Thus, this study aimed to investigate the physicochemical properties and immunogenicity of hemp protein isolate (HPI) extracted at pH 10 and 12, with and without 30-minute enzymatic hydrolysis using bromelain, Alcalase, and trypsin. Furthermore, HPI-10, HPI-12 and hemp meal derived at pH 10 (HM-10) were used as supplementary sources of protein (in place of casein in the AIN-93G diet) in a 90-day feeding murine model to investigate the impact of prolonged hemp-protein consumption on growth parameters, blood chemistry, hematological, and histopathological changes.
Results found that enzymatic hydrolysis significantly altered the protein structure of HPI-10, redistributing the molecular weight via an increase in low molecular weight peptides (\u3c 10 kDa), significantly increasing the degree of hydrolysis for all 3 hydrolysates (p \u3c 0.05), and disrupting native folded tertiary conformations, as assessed by SDS-PAGE, degree of hydrolysis via Orthophtaldialdehyde, and fluorescence spectroscopy, respectively. Immunogenicity was evaluated through Enzyme-linked Immunosorbent Assay (ELISA) and Western blot using human allergic IgE antibodies corresponding to the Big 9 food allergens, as well as hempseed. Results demonstrated that hydrolysis for both HPI-10 and HPI-12 effectively minimized the qualitative immunogenic responses with hemp-allergic plasma while revealing potential immunogenic interactions with unhydrolyzed HPI-10 and wheat and soy allergic individuals. Results from the long-term feeding study outlined no significant differences between the control diet and the three supplementary proteins in histopathological, hematological, and growth parameters (p \u3c 0.05), outlining the safety for hemp protein supplementation in diets. These findings suggest that both enzymatically hydrolyzed HPI and HM may serve as a hypoallergenic, nutritionally safe, high protein ingredients, warranting further investigation into their application in functional food formulations