Fundamentally Based Investigation And Mathematical Modeling Of The Delay Observed In The Early Stages Of E-Coat Deposition, Fardin Padash

Theses and Dissertations

The objective of this work is to enhance the understanding of the delay observed in the early stages of E-coat deposition. E-coat deposition has been widely used by industries such as the automotive industry to form the primary protective coating against corrosion. Currently, models that are used to find the best conditions under which the desired coating coverage for the entire auto body can be achieved do not accurately predict the coating coverage in recessed areas. The accuracy of large-scale models can be improved by enhancing our understanding of the mechanisms responsible for the observed delay. To accomplish this, experiments …

Durability Properties Of Concrete With 100 Percent Coarse Recycled Concrete Aggregates, Tasnia Tarannum Khan

Theses and Dissertations

The supplies of concrete aggregates from natural sources are rapidly reducing. Recycled concrete aggregates (RCA) are produced by crushing the concrete obtained from demolished concrete structures. The purpose of this study is to determine the durability properties of concrete with 100% recycled concrete coarse aggregates and relate the durability of such concrete to the physical, mechanical, and durability properties of RCA and the RCA parent concrete. The correlations of several properties are determined by developing model equations to predict RCA properties. The parent concrete is crushed and graded at two nominal maximum sizes, 1" and 0.75", to determine the RCA …

Centrifugal Assembly Of Bijel Ropes Via Helical Microfluidics, Shankar P. Kharal

Theses and Dissertations

Bicontinuous interfacially jammed emulsion gels (bijels) are soft materials that retain a liquid bicontinuous network stabilized by an interfacially jammed layer of nanoparticles. In this thesis, we investigated a microfluidic twisting method to fabricate micro-ropes of nano-structured bijel fibers. This method shows how weak microfibers with tensile strengths of a few kPa can be reinforced by 4 orders of magnitude by means of microfluidic twisting. Microfluidic twisting allows to produce continuous bijel fiber ropes of controllable architecture. Modelling the fluid flow field reveals the rope geometry dependence on a subtle force balance composed of rotational and translational shear stresses. However, …

Understanding Structure/Process-Property Relationships To Optimize Development Lifecycle In Yttria-Stabilized Zirconia Aerogels For Thermal Management, Rebecca C. Walker

Theses and Dissertations

Aerogels are mesoporous materials with unique properties, including high specific surface area, high porosity, low thermal conductivity, and low density, increasing these materials’ effectiveness in applications such as catalyst supports, sorption media, and electrodes in solid oxide fuel cells. Zirconia (ZrO₂) aerogels have special interest for high-temperature applications due to the high melting point of ZrO₂ (2715°C) and stability between 600°C and 1000°C, where other aerogel systems often begin to sinter and densify. These properties and unique pore structure make zirconia aerogels advantageous as thermal management systems, especially in aeronautics and aerospace applications. However, to be effective …

Rational Design Of Flexible And Stretchable Electronics Based On 3d Printing, Yuanhang Yang

Theses and Dissertations

Flexible and stretchable electronics have been considered as the key component for the next generation of flexible devices. There are many approaches to prepare the devices, such as dip coating, spin coating, Mayer bar coating, filtration and transfer, and printing, etc. The effectiveness of these methods has been proven, but some drawbacks cannot be ignored, such as lacking pattern control, labor consuming, requiring complex pretreatment, wasting conductive materials, etc.

In this investigation, we propose to adopt 3D printing technology to design flexible and stretchable electronics. The objective is to rationally design flexible and stretchable sensors, simplify the preparation process, form …

Therapeutic Injectable Iron-Chelating Hydrogels, Debbie Campbell-Rance

Theses and Dissertations

ABSTRACT

Therapeutic Injectable Iron-Chelating Hydrogels for Improved Central Nervous System Regeneration

By

Debbie S. Campbell-Rance

A dissertation submitted in partial fulfillment of the requirements of the degree of Doctor of Philosophy at Virginia Commonwealth University 2021.

Director: Xuejun Wen, M.D., Ph.D., AIMBE Fellow, Alice T. and William H. Goodwin Jr. Endowed Chair Professor in Regenerative Medicine, Institute for Engineering and Medicine, Department of Chemical and Life Science Engineering

Severe traumatic brain and spinal cord injuries are major global public health and socioeconomic problems in terms of mortality and morbidity. Currently there are two main lines of treatment under development for …

Changeset-Based Retrieval Of Source Code Artifacts For Bug Localization, Agnieszka Ciborowska

Theses and Dissertations

Modern software development is extremely collaborative and agile, with unprecedented speed and scale of activity. Popular trends like continuous delivery and continuous deployment aim at building, fixing, and releasing software with greater speed and frequency. Bug localization, which aims to automatically localize bug reports to relevant software artifacts, has the potential to improve software developer efficiency by reducing the time spent on debugging and examining code. To date, this problem has been primarily addressed by applying information retrieval techniques based on static code elements, which are intrinsically unable to reflect how software evolves over time. Furthermore, as prior approaches frequently …

Modeling Pa-233 Generation In Thorium-Fueled Reactors For Safeguards, Victoria Davis

Theses and Dissertations

Thorium has been researched for many decades as a possible alternative to uranium nuclear fuel. Thorium can be implemented in many different reactor designs including pressurized water reactors (PWRs), pressurized heavy water reactors (PHWRs), and molten salt reactors (MSRs). Its abundance in the earth, decreased long-lived transuranic waste, and claims that there are fewer proliferation concerns contribute to the attractiveness of using thorium as alternative nuclear fuel. However, possible proliferation pathways have been noted and must be investigated, particularly the potential diversion of ²³³Pa which can then decay to ²³³U – special fissionable material that should be under …

Molten Salt Technologies For Advanced Nuclear Fuel Cycles And Molten Salt Reactors, Dimitris Killinger

Theses and Dissertations

This dissertation provides five topics—an assessment of different monitoring and analytical techniques often cited in the literature for molten salt systems and designs for nuclear engineering applications. First, we explored commonly used materials for quasi-reference electrodes in molten chloride salts. Second, the limitations of the electrochemical analysis known as cyclic voltammetry due to the concentration of uranium(III) present were being investigated. Third, we provided an experimental assessment on the development of a spectroelectrochemical cell for interrogating various spectroelectrochemical techniques, namely chronoabsorptometry and chronofluorometry, and their limitations due to the presence of uranium(III) ions. Fourth, a study on the corrosion resistance …

The L1-Norm Regularized L1-Norm Best-Fit Line Problem And Applications, Xiao Ling

Theses and Dissertations

The best-fit subspace or low-rank approximation of a data matrix revolves
around the norm approximation technique. l²-norm criterion is probably the most
widely used norm for fitting subspaces. As the computational power increases, the
l¹-norm analogue has recently gained attention from the academic community. It is
widely agreed that the l¹ norm is insensitive to outliers, compared to its l² variant.
Because of the polyhedral structure interrelated with linear programming (LP),
the l⁰ norm is commonly relaxed into the l¹-norm problem to induce sparsity in
models. In this work, we examine …

Effects Of Additive Manufacturing Techniques On The Magnetocaloric Properties And Chemical Stability Of Lafexcoysi13-X-Y Alloys, Binyam Wodajo

Theses and Dissertations

Additive manufacturing (AM) is an emerging process to fabricate net shape, intricate, engineering components with minimal material waste; however, traditionally it has been largely applied to structural materials. AM of functional materials, such as magnetic materials, has received much less attention and the field is still in its infancy. To date, AM of magnetocaloric regenerators for magnetic refrigeration (an energy-efficient alternative to the conventional vapor-compression cooling technology), remains a challenge. There are several magnetic refrigerator device designs in existence today that are predicted to be highly energy-efficient, on condition that suitable working materials can be developed. This challenge in manufacturing …

Improving The Early Detection Of Cardiovascular Toxicity Secondary To Radiotherapy For Lung Cancer Via Patient-Specific Quantitative Magnetic Resonance Imaging, Alireza Omidi

Theses and Dissertations

Purpose: To assess the cardiopulmonary-induced dose variation on the left ventricle (LV) and evaluate the spatiotemporal evolution of cardiac/aortic function following radiotherapy (RT).

Methods: 8 lung cancer patients who were scheduled to receive RT were recruited for this study. Each patient underwent one 4D-CT at baseline. MRI scans including cine GRE, T1/T2, LGE, and 4D-flow were acquired at baseline, 3-months and 6-months post-RT to evaluate the cardiac/aortic function. Finally, image registration was used to assess the cardiopulmonary-induced dose variation on the LV.

Results: Mean RT-dose was minimum during inspiration and systole (at expiration). No significant differences were found in the …

Cadent Diffusion: Permeating The Membrane, Isabella M. Kubo

Theses and Dissertations

cadent diffusion: permeating the membrane explores and documents KUBO's journey of cultivating a sustainable and curious artistic practice during their Master’s program in Richmond, Virginia (Powhatan Land) from the Fall of 2020 to the Spring of 2022.

KUBO's practice is the affirmation between life and change in an attempt to work along the forces of singularity; to free lines, scores, concepts, and events from structures that otherwise bind them.The cadent diffusion is the rhythm in this force. Or perhaps, it is the force itself.

Machine Learning (Ml) - Assisted Tools For Enhancing Security And Privacy Of Edge Devices, Santosh Kumar Nukavarapu

Theses and Dissertations

The rapid growth of edge-based IoT devices, their use cases, and autonomous communication has created new challenges with privacy and security. Side-channel attacks are one of the examples of security and privacy vulnerabilities that can cause inference at Internet-Service Provider (ISP) and local Wi-Fi networks. Such an attack would leak user’s sensitive information such as home occupancy, medical activity, and daily routines. Another example is that these devices have weak authentication and low encryption standards, making them an easy target for malware-based attacks such as denial of service or launching other network attacks using these infected devices. This thesis dissertation …

Influence Of Annealing And Compaction On Enhancing The Temperature And Strain Sensitivities Of Multi-Walled Carbon Nanotube (Mwcnt) Films, Rufaydah Hassan

Theses and Dissertations

Carbon nanotubes (CNTs) possess superior thermal, electrical, and mechanical properties. When CNTs undergo particular fabrication procedures, they transform from a nanoscale form into macroscopic thin sheets referred to as buckypapers (BPs). The main idea behind using BP is to facilitate the handling of CNTs without losing their exceptional properties. Additionally, BPs showed potential for being the used material in strain and temperature applications thanks to their thermal stability, flexibility, high sensitivity, and the ability to conform to any complex structure.

In the current study, the multi-walled carbon nanotube (MWCNT) thin films were prepared using the vacuum filtration technique. Following the …

Therapeutic Approaches For Respiratory Distress Syndrome, Franck J. Kamga Gninzeko

Theses and Dissertations

Respiratory distress syndrome (RDS) is characterized by shortness of breath and low oxygen levels. RDS affects the neonatal and adult populations. In the neonatal population, RDS can be classified as NRDS (Neonatal respiratory distress syndrome), while in adults, it is known as ARDS (acute respiratory distress syndrome). This dissertation examines a therapeutic approach to NRDS and a mechanistic approach to ARDS with in vivo and in vitro models of lung injury. NRDS is characterized by a deficiency or lack of surfactant. Surfactant is an essential compound composed of phospholipids and proteins to prevent the lungs from collapsing. There are several …

Learning Robot Motion From Creative Human Demonstration, Charles C. Dietzel

Theses and Dissertations

This thesis presents a learning from demonstration framework that enables a robot to learn and perform creative motions from human demonstrations in real-time. In order to satisfy all of the functional requirements for the framework, the developed technique is comprised of two modular components, which integrate together to provide the desired functionality. The first component, called Dancing from Demonstration (DfD), is a kinesthetic learning from demonstration technique. This technique is capable of playing back newly learned motions in real-time, as well as combining multiple learned motions together in a configurable way, either to reduce trajectory error or to generate entirely …

Dna Condensation State Regulates Nuclear Lamina Strain And Cellular Adaptation To Physiological Forces, Brooke E. Danielsson

Theses and Dissertations

The nucleus is the largest and stiffest organelle and is exposed to mechanical forces transmitted through the cytoskeleton from outside the cell, as well as from forces generation within the cell. In recent years, the nucleus has been proposed to act as a cellular mechanosensor, with changes to nuclear shape and architecture playing an important role in how the cell responds to physiological forces. Aberrant forms of the nuclear envelope protein lamin A/C, as well as epigenetic modifications to chromatin, has been shown to modify nuclear stiffness and viscosity, therefore effecting nuclear mechanics and mechanotransduction. Altered nuclear mechanics is associated …

Rational Design Of Metal-Organic Frameworks (Mofs)-Based Functional Materials Towards Better Air Quality, Zan Zhu

Theses and Dissertations

Air pollution is a major threat to environmental safety and public health. Volatile organic compounds (VOCs), particulate matter (PM), and airborne microorganisms are three typical air pollutants. Conventional strategies to prevent and mitigate air pollution have been employed, which, however, are generally passive. For instance, VOC sensing through solid-state devices is a conventional approach, which, however, is not capable of capturing and removing VOCs. On the other hand, air filters and face masks are useful equipment to protect people from inhaling PM and airborne microorganisms. But most commercial filters can only capture them on the surfaces, which may cause secondary …

Improving Feature Learning Capability And Interpretability Of Unsupervised Neural Networks, Chathurika S. Wickramasinghe Brahmana

Theses and Dissertations

The motivation for this dissertation is two-prong. Firstly, the current state of machine learning imposes the need for unsupervised Machine Learning (ML). Secondly, once such models are developed, a deeper understanding of ML models is necessary for humans to adapt and use such models.

Real-world systems generate massive amounts of unlabeled data at rapid speed, limiting the usability of state-of-the-art supervised machine learning approaches. Further, the manual labeling process is expensive, time-consuming, and requires the expertise of the data. Therefore, the existing supervised learning algorithms are unable to take advantage of the abundance of real-world unlabeled data. Thus, relying on …

Continual Learning From Stationary And Non-Stationary Data, Lukasz Korycki

Theses and Dissertations

Continual learning aims at developing models that are capable of working on constantly evolving problems over a long-time horizon. In such environments, we can distinguish three essential aspects of training and maintaining machine learning models - incorporating new knowledge, retaining it and reacting to changes. Each of them poses its own challenges, constituting a compound problem with multiple goals.

Remembering previously incorporated concepts is the main property of a model that is required when dealing with stationary distributions. In non-stationary environments, models should be capable of selectively forgetting outdated decision boundaries and adapting to new concepts. Finally, a significant difficulty …

Novel Microfabricated Systems To Elucidate The Role Of Anisotropic Stiffness In The Tumor Microenvironment, Jiten Narang

Theses and Dissertations

Cancer is the second leading cause of death in women and late stage (metastatic) cancers have abysmal survival rates compared to early stage regional cases (27% vs 86%). As a tumor grows, the surrounding extracellular matrix (ECM) is reorganized into a dense, collagen rich matrix. The new matrix of aligned collagen fibers provides unique mechanical cues such as anisotropic stiffness and contact guidance. Matrix turnover also constricts local vasculature and restricts delivery of key nutrients and signaling molecules to malignant cells to outside the tumor creating a chemotactic gradient from outside to inside. In this work, we developed a novel …

Modeling Of Patient-Specific Periaortic Mechanics And Pulmonary Artery Hemodynamics Based On Phase-Contrast Magnetic Resonance Imaging Sequences., Johane H. Bracamonte

Theses and Dissertations

Inverse modeling in cardiovascular medicine is a collection of methodologies that can provide non-invasive patient-specific estimations of clinical risk factors using medical imaging as inputs. Its incorporation into clinical practice has the potential to improve diagnosis and treatment planning with low associated risks and costs.

Herein, three different phase contrast magnetic resonance imaging (MRI) modalities were implemented as input data, displacement encoding with stimulated echoes (DENSE MRI) applied, and time-resolved velocity encoding phase-contrast MRI, in 1D and 3D, applied to pulmonary artery (PA) hemodynamics.

A model to account for the effect of periaortic interactions due to static and dynamic structures …

Innovative Techniques Of Neuromodulation And Neuromodeling Based On Focal Non-Invasive Transcranial Magnetic Stimulation For Neurological Disorders, Ivan C. Carmona-Tortolero

Theses and Dissertations

This dissertation aims to develop alternative technology that improves the current range of application of transcranial magnetic stimulation (TMS), on a scale that would permit defining specific non-invasive treatments for Parkinson’s disease and other neurological disorders. This is accomplished through three specific objectives. 1) The design of a neurostimulation system that increases the focality in TMS to regions of narrow target areas and variable depths in the brain cortex. 2) The assessment of the feasibility of novel high-frequency neuromodulation techniques that would allow increasing the focality in deeper areas beyond the cortical surface. 3) The development of a computational model …

Towards The Systematic Evaluation Of Variable Modes Of Mechanical Conditioning On The Compositional, Microstructural And Mechanical Properties Of Engineered Tissue Vascular Grafts., Sarah Saunders

Theses and Dissertations

Coronary artery bypass surgery (CABG) remains one of the most common cardiac surgical procedures performed worldwide, frequently involving multiple bypasses, and commonly employing the patient’s internal mammary artery, radial artery, or saphenous vein. CABG is often not possible because native vessels were already employed in previous interventions or are diseased themselves. Synthetic vascular grafts are currently integral tools of vascular surgery and have had relative success in large-caliber applications providing substantial benefit to aortic or iliac grafting; however, small diameter (< 6 mm) arterial grafts have not yet translated into clinical effectiveness due to thrombosis and anastomotic intimal hyperplasia. ETVGs present an exciting potential alternative in vascular grafting by offering a blood vessel substitute that could exhibit all the functional characteristics of native vasculature. In addition to relieving supply limitations associated with coronary artery bypass surgery ETVGs are especially ideal for pediatric patients with congenital heart disease who require grafts that grow as they do, eliminating the need for reoccurring invasive surgeries.

Though the role of biomechanics in regulating cellular behavior promoting non-thrombogenicity, vasoactivity, and ECM synthesis and maintenance is well …

Branched Chain Amino Acid Strain State Monitoring With Raman Spectroscopy And Plasmonic Bowtie Nanoantenna Devices For Early Disease Detection, Caroline A. Campbell

Theses and Dissertations

This work centers on the development and the down-selection of nano-manufactured devices to be used in conjunction with Raman spectroscopy for probing a branched chain amino acid. The nano-manufactured devices integrate plasmonic nanoantennas for the purpose of amplifying molecular fingerprints, which are otherwise difficult to detect, through Surface Enhanced Raman Spectroscopy (SERS). Plasmonic nanostructures can be utilized for a variety of biomedical and biochemical applications to detect the characteristic fingerprint provided by Raman Spectroscopy. The nano-manufactured devices create an electric field that amplifies minute perturbations and raises the signal above background noise. This may provide a deeper understanding of signal …

Artificial Intelligence-Powered Chronic Wound Management System: Towards Human Digital Twins, Salih Sarp

Theses and Dissertations

Artificial Intelligence (AI) has witnessed increased application and widespread adoption over the past decade. AI applications to medical images have the potential to assist caregivers in deciding on a proper chronic wound treatment plan by helping them to understand wound and tissue classification and border segmentation, as well as visual image synthesis.

This dissertation explores chronic wound management using AI methods, such as Generative Adversarial Networks (GAN) and Explainable AI (XAI) techniques. The wound images are collected, grouped, and processed. One primary objective of this research is to develop a series of AI models, not only to present the potential …

Analysis Of Non-Conventional Radiological Terrorism, James N. Padgett

Theses and Dissertations

Nuclear terrorism has been a risk since the dawn of the first atomic bomb. Though state sponsored nuclear weapons development is of concern for countries, non-state sponsored terrorism with radiological material can be of even greater concern. This stems from the fact that the material is under less stringent or no safeguards and can readily change hands between different terrorist groups or innocent civilians may accidently come into contact with the material.

Within this paper an analysis of previous accidents using orphan radiological sources, malicious use of orphan radiological sources, and how these sources could be used by terrorists is …

Effect Of Viscoelasticity On Cellular Morphology And Activity, Thomas J. Petet Jr

Theses and Dissertations

It has been well established that there is a link between substrate stiffness and cellular activities such as proliferation, migration, and differentiation. Less characterized is the link between the time-dependent viscosity of a substrate with those cellular activities. To explore this, PDMS substrates were created with predictably tunable stiffness and viscosity parameters. A simulated model was also developed in parallel to explore the potential effects of viscosity in a computationally predictive way. It was found that the inclusion of viscosity caused a major paradigm shift to a non-zero substrate equilibrium that was sensitive to increases in the substrate stiffness. Finally, …

Theta Burst Brain Stimulation In Painful Diabetic Neuropathy Patients: Investigating Neural Mechanisms, Bhushan Thakkar

Theses and Dissertations

Chronic pain (CP) is a significant contributor to disability and disease burden globally. In 2019, approximately 50.2 million adults (20.4% of the US population) experienced chronic pain, contributing to $560-635 billion in direct medical costs. In addition, the worldwide prevalence of diabetes mellitus has reached epidemic proportions and is set to increase to 629 million by 2045. Almost 50% of patients with diabetes present with diabetic neuropathy (DN), and one in five patients with diabetes presents with painful DN (pDN) which is the most common cause of neuropathic pain (NP) in the US. Symptomatic treatment is the mainstay of management …