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Zero-Emission Transport Vehicles: Detailed Multi-Domain Modeling and Real-Time Digital-Twin Hardware Emulation
No full textRapid innovation in renewable energy technologies have transitioned transport vehicles into utilizing zero-emission clean energy in recent years. The growing scale of energy conversion and storage devices, as well as the complexity of power converters, have introduced significant challenges in modeling and electromagnetic transient simulation during the initial design phase in the electric transport industry, as well as in real-time hardware-in-the-loop (HIL) emulation of large-scale of sustainable energy systems. Therefore, this thesis aims to advance multi-domain models of energy conversion and storage devices, and real-time HIL emulation technology in multi-terminal DC (MTDC) grids for zero-emission transport vehicles by proposing detailed device-level models, investigating HIL emulation architectures and implementing parallel computing algorithms. The detailed multi-domain models are necessary to validate the design and assess stability and safety by revealing insights into device behavior. The novel acceleration techniques and real-time digital-twin (RTDT) are developed for the hierarchical emulation of energy conversion, storage, and power systems
UNDERSTANDING THE INTERDEPENDENCE BETWEEN HYPER-INFLAMMATION, CROHN’S DISEASE, AND PERIODONTAL DISEASE IN MALE/FEMALE TNFΔARE MICE
No full textThis thesis provides new foundational knowledge on the interplay of chronic systemic hyperinflammation and Periodontal Disease, an aspect which has not yet been widely investigated. Using a mouse model of deregulated TNFα production, it investigates oral manifestations in chronic systemic hyperinflammatory conditions like Crohn’s Disease, and how Periodontal Disease is linked to Crohn’s Disease in males/females in the presence/absence of periodontal injury, whether females are at higher risk of developing Periodontal Disease due to estrogen in the presence/absence of periodontal injury, and how all this affects alveolar bone loss and subsequent tissue repair in males/females Crohn’s Disease patients.
In the introductory literature review presented in chapter one, I explore the significance of biological reasoning and its integration into clinical interpretation and treatment. I synthesize evidence of shared biological principles across research disciplines, specifically focusing on their application to the interlink between Crohn’s Disease and Periodontal Disease. Chapter one introduces Crohn’s Disease and explores how in Crohn’s Disease the inflammatory cytokines like TNFα take center stage and becomes mainly responsible for the damage to the host tissues/organs. Further to this, it explores how females are more prone in developing Crohn’s Disease and several oral diseases like Periodontal Disease. Chapter one also introduces Periodontal Disease and delves into the current body of knowledge on how gingivitis can subsequently lead to Periodontitis, how Crohn’s Disease is linked with Periodontal Disease, and explains the periodontal injury/ligature model. This chapter further focuses on TNFα cytokine, the regulation and pathological dysregulation of TNFα, and its interactions with estrogen hormone. Last part of chapter one focuses on TNFΔARE mouse model and explains how this is an established mouse model for Crohn’s Disease and arthritis research due to TNFα-mediated hyperinflammation. Further, various mouse models for Periodontal Disease induction, including ligature induced Periodontal Disease mouse model are discussed. The methodology used in the primary research chapters is summarized in chapter two.
The experimental studies are presented in results chapters 3-6, in which I investigate the response of periodontal tissues to TNFα-mediated hyperinflammation in the presence/absence of periodontal injury around maxillary left second molar. Chapter three outlines the characterization of TNFΔARE mouse model, together with gingival and periodontal tissue response to the hyperinflammation due to increased TNFα levels. While some changes to the oral epithelium were noted, mutant mice did not develop spontaneously periodontal disease, suggesting that increased TNFα levels in Crohn’s Disease might result in some epithelial hyperplasia, mild gingivitis, but is not sufficient to establish Periodontal Disease. The follow-up study, in chapter four, describes the effect of inducing periodontal injury on gingival and periodontal tissues using the silk ligature model. The most notable changes were observed in the gingival tissues in periodontal injury model, suggesting that increased TNFα levels in Crohn’s Disease even in the presence of an aggressive periodontal injury is not sufficient to establish Periodontal Disease. Further to this, gingival and alveolar bone changes were observed mainly in females, mainly at the lingual apex/apical root region of the maxillary left second molar, suggesting that there is not only a gender-based difference in susceptibility to Periodontal Disease, but also a difference in the way Periodontal Disease progresses between males and females. As females reveal changes in gingival tissues and alveolar bone volume, as a follow-up, in chapter five & six, I investigated TNFα-mediated hyperinflammation in ovariectomized females in the presence/absence of periodontal injury. Ovariectomized females with periodontal injury reveal signs of increased periodontal remodeling, mainly at the lingual apex/apical root region of the maxillary left second molar, though is still not enough to cause obvious periodontal disease. The bone remodeling increased in females once the periodontal injury was removed. In the final chapter, chapter 7, this thesis provides a comprehensive discussion on the interlink between Crohn’s Disease and Periodontal Disease in males/females. Understanding how chronic systemic hyperinflammation affects oral and periodontal health, leads to Periodontal Disease, compromises bone healing and subsequent tissue repair is critical for accurate health advice for Crohn’s Disease affected individuals. This thesis has direct relevance to oral hygiene instructions for Crohn’s Disease patients, as our data suggest that there is not only a difference between males and females in susceptibility to Periodontal Disease, but also a difference in the way gingivitis/Periodontal Disease progresses
Theatre for Development [TfD] as a Tool for Communicating Change and Development: Critical Reflections from Ijede Community Experience in Ikorodu, Lagos, Nigeria
No full textTheatre scholars’ attempts to connect theatre practice and theory to social development, whether
local, national or global, has a long history. Presently, there exists a passion among theatre and
literary scholars to prove that theatre, whether in the literary or performative form, has a
contribution to make to the development of the society. Examples abound on how dramatists have
linked theatre with pressing issues affecting citizens, such as political oppression, economic
deprivation, illiteracy, poor health care, and so on.
In this thesis, I will explore how theatre for development (TfD) can be used as a viable tool for the
development of the society. This research is based on a project I embarked upon as an
undergraduate student researcher in Ijede Community in Ikorodu Local Government Area, Lagos
State (Nigeria) in 2013. Every community should be able to enjoy the basics of life, such as access
to food, shelter, water, and education, but in some communities, the lack of potable water,
electricity, and medical facilities hinders their ability to lead a fulfilling life. I will demonstrate
how the citizens of the Ijede Community took advantage of TfD to bring about some social changes
and development in their own community, noting the extent communities can network and stir up
efforts through self-help, to socio-economically empower themselves
Investigating the role of extratropical cyclones in North Atlantic deep water formation
No full textThe Atlantic Meridional Overturning Circulation (AMOC) is a vital mechanism of heat transport in the climate system, but it has been suggested that its strength will change in the coming decades. This strength depends in part on water mass transformations in the North Atlantic, and understanding the factors that contribute to this variability is crucial to predicting the future behaviour of the AMOC. In the Labrador and Nordic Seas, where deep convection occurs and replenishes the deep water masses of the AMOC, atmospheric forcing is a critical factor in the priming and initiation of convection. In particular, extratropical cyclones (ETCs) provide high-frequency forcing that can influence hydrographic properties in the upper water column. These effects can be studied by forcing an ocean model with atmospheric datasets that include such storms, and then analyzing the response of the ocean to them. This thesis will first present background information on the processes of deep convection and deep water formation in the North Atlantic, as well as discussing extratropical cyclones and the air-sea interactions associated with them. Details of the ocean model and atmospheric datasets used to perform this study will be described. ETC statistics are calculated to study seasonal and interannual patterns of storm characteristics. The results indicate that stronger cyclones tend to occur in the cold season, and that the maximum strength of ETCs on a year-to-year basis may correlate with the phase of the NAO. Various properties from the ocean model output are also examined as time series associated with individual cyclones that are detected in the atmospheric datasets. These time series are also averaged to calculate the mean ocean response to various categories of ETCs. We find that individual cyclones may change sea surface temperatures by up to 2°C, though the mean change was around 0.2°C. The density and depth of the mixed layer do increase in response to ETC passage, and these changes persist for at least a week post-cyclone. The depth of
the mixed layer also tends to remain somewhat deeper than its pre-cyclone depth even after returning to equilibrium, suggesting that ETCs passing in succession may progressively deepen the mixed layer over time
Atomic Silicon Dimer Wires on The Hydrogenated Silicon Surface
No full textTechnology has been advancing toward miniaturization, with transistors now measuring just a few nanometers in size and powering our everyday electronic devices. As these devices approach their size limits due to quantum mechanical effects, studying structures on even smaller scales has become crucial for paving the way for future technologies. Motivated by this challenge, we focused on atomic-scale wires constructed on silicon (100) surface, a material foundational to semiconductor technology. This thesis examines dimer wires on hydrogenated silicon surfaces, where the hydrogen passivation enables selective atomic patterning by removal of individual hydrogen atoms.
The bare Si(100)-2×1 surface consists of a unit cell with two atoms forming rows of periodically aligned dimers. These dimers undergo buckling, a surface reconstruction that minimizes surface energy, resulting in one atom adopting sp3 hybridization and raising, while the other adopts sp2 hybridization and lowers. At low temperatures and near surface defects, this buckling can be visualized with scanning tunneling microscope (STM); however, it disappears when the surface is passivated with a hydrogen monolayer. The hydrogenated surface retains the 2×1 unit cell but exhibits symmetric dimers without buckling. Removing individual hydrogen atoms creates silicon dangling bonds (DBs), which exist in one of three charge states—positive, neutral, or negative—depending on the net electron count. DBs, with their enhanced local density of states, serve as critical building blocks for atomic-scale devices on this surface.
Using STM, we fabricated and studied dimer wires—structures two atoms wide with variable lengths. These investigations are divided into two regimes: dynamic and static. The dynamic regime involves rapid buckling switches due to high tunneling rates (tip bias exceeding ±1 V), while the static regime focuses on the stable buckled configurations observable at lower tunneling rates (tip bias between ±1 V).
In the dynamic regime, we analyzed the electronic states of dimer wires, emphasizing their evolution with increasing length. Our results revealed that each additional dimer introduced one filled state aligned with the valence band and one empty state in the bandgap. At higher biases, tip-induced band bending (TIBB) raised the empty states above the conduction band, causing ionization and forming characteristic disk-like features. To complement these experimental findings, we developed a one-dimensional numerical simulation, which successfully replicated the filled states at a reduced computational cost compared to density functional theory (DFT). Additionally, Fourier analysis of the wires revealed a hole band, enabling the effective hole mass to be extracted through parabolic fitting.
In the static regime, reduced tunneling rates allowed imaging of buckled configurations. Bias pulses enabled controlled switching of buckled orientations, opening up potential applications beyond conduction. These include memory elements (based on orientation flipping), random telegraph noise generation (at slightly elevated biases), signal routing (via combined wires), and charge detection (by monitoring buckled orientation near charged entities).
Finally, we explored nano-lithographed samples to facilitate electrical connections between atomic devices and macroscopic systems. These samples enabled precise targeting and repeated identification of specific surface areas. Using doped lines to the targeted regions, atomic devices such as dimer wires patterned on this surface could be integrated with macro-scale electronics, bridging the gap between nanoscale constructs and practical applications
Nature-inspired design and implicit modeling for additive manufacturing: Advancing lattice structures for multidisciplinary applications
No full textThis thesis presents the development and evaluation of a nature-inspired lattice structure, the development of an algorithm for the implicit modeling of various lattice architectures, and the exploration of lattice structures as a potential solution for addressing microplastic pollution. The nature-inspired lattice, termed the Dual Curved Cubic (DCC) lattice, draws from the phenomenon of inosculation—where plant branches intergrow to form interwoven load paths. The DCC lattice was designed and implicitly modeled with curved struts to mimic this interwoven behavior. The fabricated lattice, produced via stereolithography (SLA), was subjected to quasi-static compressive testing to assess its strength, energy absorption, and deformation behavior. Experimental and numerical results showed that the DCC lattice outperformed conventional Body-Centered Cubic (BCC) and Octet lattices by 98.68% and 45.08%, respectively, in compressive strength, while also offering tunable energy absorption characteristics through adjustments in curvature and relative density. Furthermore, the implicit modeling approach was extended into a coordinate-driven framework, StrutGen, using Signed Distance Functions (SDFs) to generate, export, and homogenize advanced lattice structures. This tool enhances existing open-source capabilities by enabling the modeling of curved, hollow, hybrid, and platetype lattices, as well as field-driven grading for functionally tailored properties. Lastly, this thesis explores the application of lattice structures in the design of MicroTRAP, a microfiber filtration device aimed at reducing microplastic emissions from laundry effluents. Experimental validation demonstrated a microfiber removal efficiency of 99.9%, underscoring the interdisciplinary potential of lattice-based design. Overall, this work advances the field of computational design for additive manufacturing by introducing a biomimetic lattice structure, a robust and scalable implicit modeling methodology, and a demonstrated application spanning both engineering and environmental domains
Thermal Cycle-Microstructure-Toughness Correlation in the Heat-Affected Zone of Multi-Pass Pulsed Gas-Metal Arc Welded API X70 Line Pipe
No full textThe girth welding process for heavy gauge pipeline construction follows a multi-pass sequence, involving root, hot, fill, and cap passes progressing from the inner diameter (ID) to the outer diameter (OD) of the line pipe. However, the multiple passes and corresponding thermal cycles involved in pipeline construction led to complex metallurgical characteristics and toughness behavior in the coarse-grained heat-affected zone (CGHAZ). The inter-critically reheated CGHAZ (ICCGHAZ) is particularly critical, yet less understood. This research establishes, for the first time, a comprehensive and quantitative correlation between pulsed gas metal arc welding (GMAW-P) heat input (< 1 kJ/mm), local thermal cycles, microstructural evolution, and fracture toughness in the ICCGHAZ of multi-pass girth welded X70 line pipe (19.0 mm thick).
Three multi-pass girth welds were produced by varying the heat inputs of 0.9 kJ/mm, 0.7 kJ/mm and 0.5 kJ/mm for the fill passes. This study uniquely combined pyrometer temperature measurement, thermal modeling, quantitative microstructural characterization, and crack tip opening displacement (CTOD) testing to evaluate the influence of thermal cycles (temperature and time) on ICCGHAZ microstructure features and CTOD toughness profiles. Bead surface temperatures were measured during the multi-pass girth welding using a two-color pyrometer. A three-dimensional (3D) transient (spatial and temporal) heat transfer model of the two fill-pass process was developed to simulate the thermal cycles of the ICCGHAZ. The predicted peak temperatures in the CGHAZ (~1300°C) and in the inter-critical reheating thermal cycle (~890°C), under similar preheat/inter-pass (~75°C) conditions from the middle width of the ICCGHAZ, were insensitive to the fill-pass heat input. The lowest heat input of 0.5 kJ/mm resulted in the highest heating rate (1600°C/s), the shortest time above Ac1 (2.1 s) and the fastest cooling rate (170°C/s) in the CGHAZ. The predicted bead surface thermal cycles and transverse isothermal shapes showed good consistency compared with the measured bead surface thermal cycles and optical bead shape in the transverse direction.
The effects of varying the GMAW-P heat inputs on martensite-austenite (MA) constituent morphology, prior austenite grain (PAG) size, retained austenite, density of high angle grain boundaries, and microhardness in the ICCGHAZ of X70 line pipe were studied for the first time. The PAG size and MA constituent area and aspect ratio were measured using optical microscopy. There was a minor difference in aspect ratio of MA constituents for all heat input samples. However, the total number (680) and the area fraction (2.1%) of MA constituents in the ICCGHAZ were highest for the 0.5 kJ/mm sample due to a smaller PAG size distribution and the fastest cooling rate (120°C/s). The highest input of 0.9 kJ/mm resulted in the highest fraction (0.22%) of retained austenite and the lowest area fraction (0.5%) and minimum total number (263) of MA constituents. This was because the slow cooling rate (35°C/s) promoted bainitic ferrite formation and carbon enrichment in the remaining austenite resulting in the most retained austenite in the ICCGHAZ. The ICCGHAZ had the highest hardness for the entire heat-affected zone and the microhardness increased as the heat input decreased.
CTOD values measured at -6°C ranged from a maximum of 0.42 mm for the 0.5 kJ/mm heat input weld to a minimum of 0.097 mm for the 0.9 kJ/mm heat input weld. Higher CTOD values (> 0.25 mm) for the 0.5 kJ/mm and 0.7 kJ/mm samples were observed when the notch axis was in the outer region of the ICCGHAZ, because of the high density of high angle gain boundaries. In contrast, lower CTOD values for the 0.7 kJ/mm and 0.9 kJ/mm heat inputs occurred when the notch axis was positioned in the middle region and adjacent to the fusion boundary of the ICCGHAZ, which contained a high area fraction of MA constituents, Ti- rich carbonitride particles, and low index planes ({100} and {110}). CTOD values increased as the notch axis was moved away from the fusion boundary to the outer portion of the ICCGHAZ.
This research establishes a strong quantitative correlation between thermal cycles associated with varied GMAW-P heat inputs, local microstructural evolution in the ICCGHAZ, and the CTOD fracture toughness of multi-pass welded X70 line pipe. The findings provide a practical guidance for the pipeline industry in optimizing welding processes and designing fracture toughness testing methodologies for advanced pipeline welding applications
Condylar Volume Changes in Class II Division 2 Patients Treated with Proclination of Maxillary Incisors, Overbite Reduction, and Dentoalveolar Expansion Using Clear Aligners
No full textIntroduction: To assess the possible three-dimensional changes in condylar volume in Class II Division 2 growing patients following using Invisalign® clear aligners to “unlock” the mandible.
Unlocking the mandible was done through proclining the maxillary incisors, correcting the overbite, and expanding the maxillary arch.
Methods: Cone-beam computed tomography (CBCT) data of 22 adolescent patients with Class II Division 2 (11, treatment group; 11, control group) were obtained at time points T1 (before the
start of treatment) and T2 (1.5-2 years after T1). Dolphin imaging software was used for cephalometric tracing while 3D Slicer and ITK-SNAP software were used to obtain the condylar volume at T1 and T2 for all the study participants. Using SPSS software package, repeated measures ANOVA was used to compare the change in condylar volume (mm3) for both groups.
Pearson’s Correlation Coefficient was used to correlate the percentage of condylar volume change with the ANB angle change in the treatment group.
Results: The increase in the condylar volume between T1 and T2 was significant for both groups, treatment (p < 0.001, 127.45 + 30.97) and control (p = 0.015, 98.8 + 36.31), with no significant
difference between the mean condylar volume in both groups at T1 (p = 0.289, 89.19 + 81.2) and T2 (p = 0.167, 117.9 + 81.7). The decrease in ANB angle between the two time points for the
treatment group did not show a strong linear correlation with the increase in condylar volume
(Pearson’s Correlation Coefficient = -0.15, p = 0.681).3
Conclusion: Both groups, treatment and control, of Class II Division 2 growing patients showed
comparable increase in condylar volume upon the use of Invisalign® clear aligners to unlock the mandible. We hence attributed the increase in condylar volume to the normal growth of the patients rather than the introduced aligners’ treatment. The change in condylar volume was not correlated with the clinical correction of Class II malocclusion