Digital Commons Network^™

Micromechanical Modeling And Evaluation Of Process-Induced Residual Stresses In 3d Woven Composites, Kostiantyn Vasylevskyi

Doctoral Dissertations

3D woven carbon/epoxy composites are high-performance materials with superior thermo-mechanical and physical properties making them an integral part of the aerospace, energy and automotive industries. However, under certain manufacturing conditions, these composites may accumulate severe intrinsic manufacturing-induced residual stresses which can even lead to microcracking. The complex reinforcement architecture makes analytical, numerical and experimental analysis of these composites challenging. This research has been focused on micromechanical analysis, computational modeling, and experimental characterization of 3D woven carbon/epoxy composites aiming to evaluate the manufacturing-induced residual stresses and enable mitigation of their negative impact on the resulting performance. A procedure to develop high-fidelity …

Investigation Of Parameter Effects On Impact Welding And Modelling Of Process, Shunyi Zhang

Doctoral Dissertations

There is a growing interest in creating light weight structures in various industries such as automobile, electronics, and aerospace in order to reduce energy consumption. One means to achieve mass reductions is to join or weld dissimilar materials to create lightweight structures. However, traditional fusion welding processes cannot be used for such dissimilar materials applications due to differences in material characteristics and the tendency to form brittle intermetallic compounds. One approach to join dissimilar materials is through high speed impact welding. With appropriate process parameters, a wavy interfacial morphology is commonly obtained at the interface of the two impact welded …

Becoming Scientists: Undergraduate Students' Literacy Activities In Laboratory Education, Allison Giannotti

Doctoral Dissertations

In laboratory courses across universities, undergraduate students are learning to act, think, and write like professional scientists. Yet, despite the centrality of language and literacy in laboratory experiments, the process of becoming scientifically literate remains ambiguous. Thus, my dissertation examines how university laboratory courses foster undergraduate students’ emergence as literate professionals and competent communicators in science, technology, engineering, and math (STEM) fields. In particular, it examines undergraduate students’ literate practices, how they change over time, and how they are affected by material and experimental processes in three sequenced, chemistry laboratory courses. Through laboratory observations and interviews with undergraduate students, faculty, …

Mechanistic Insights Into Relationship Between Network Architecture, Polymerization Kinetics, And Macromolecular Properties, Chang Liu

Doctoral Dissertations

Given the rising of environmental concern, the market of waterborne coating and adhesives has been constantly growing. Polymer latex particles produced by emulsion polymerization are one type of important components in their formulations. Thus, to tune mechanical properties of waterborne coatings and adhesives, one of the common ways is to utilize crosslinkers to form a macromolecular network structure, as known as “gel”, inside of the polymer latex. A major challenge to obtain desired properties of the material is how to control macromolecular architecture, such as sol-gel ratio and crosslinking density. Hence, this dissertation focuses on the study of predicting and …

The Ideal International Student: Intersections Of Race, Gender, And Accent In International Multilingual Student Identity, Kristin Raymond

Doctoral Dissertations

Perceptions of international multilingual students from the university community have a significant impact on those students’ identities and status on campus. These perceptions construct narratives of the ideal international multilingual student, which is defined by an optimal set of student characteristics that appear to be divorced from factors of race, gender, and accent. This dissertation examines the concept of the ideal international multilingual student in intersection with factors of race, gender, and accent. This qualitative, IRB-approved study draws from the model of investment (Norton 2000, 2013; Darvin & Norton, 2015; De Costa & Norton, 2017) and the concept of racialization …

Carbon Emissions From Streams And Rivers: Integrating Methane Emission Pathways And Storm Carbon Dioxide Emissions Into Stream And River Carbon Balances, Andrew Robison

Doctoral Dissertations

River networks play an important role in elemental cycling at watershed, regional, and global scales. They not only serve as pipes that transport elements from land to sea, but also as complex processers that can significantly modify the timing, form, and magnitude of these elemental fluxes. For example, recent studies have shown that river networks contribute significantly to the global carbon cycle by emitting greenhouse gases like carbon dioxide (CO¬2) and methane (CH4) to the atmosphere. However, we currently do not fully understand the controls on GHG emissions from river networks, particularly what drives the variability of emissions across space …

Experimental Characterization And Crystal Plasticity Modeling Of Mechanical Properties And Microstructure Evolution Of Additively Manufactured Inconel 718 Superalloy, Saeede Ghorbanpour

Doctoral Dissertations

In this thesis, the mechanical behavior of the additively manufactured (AM) IN718 nickel-based superalloy and their correlations with the evolution of microstructure are studied comprehensively. The effects of manufacturing parameters, build orientations, and post processing procedures, i.e. standard heat treatment and hot isostatic pressing (HIP), on various mechanical properties including monotonic compression and tension strength, low cyclic fatigue performance, high cyclic fatigue behaviour, and fatigue crack growth behavior are investigated. Due to the high temperature applications of the IN718 alloy, elevated temperature properties are examined as well. Electron Backscattered Diffraction (EBSD) technique is employed to measure the initial and deformed …

A High-Performance Full-Field Crystal Plasticity Solver Within Finite Elements For Micromechanical Simulation Of Metallic Components Under Large Deformations, Adnan Eghtesad

Doctoral Dissertations

It is undeniable that metals and metallic alloys are of great significance in automotive and aerospace industry. Metallic materials are aggregates of grains (i.e., crystals) in orders of microns. Understanding the behavior of multi-phase metallic structures plays a vital role in automotive and aerospace design and manufacturing industries. Work presented in this dissertation presents a high-performance crystal plasticity solver, capable of performing simulations of massively large data sets in order of few hours instead of months of run. The developed accelerated solver is capable of performing simulations of massively large data sets representing very high-resolution microstructures with tens of millions …

Metareasoning For Heuristic Search Using Uncertainty, Tianyi Gu

Doctoral Dissertations

Heuristic search methods are widely used in many real-world autonomous systems. Yet, people always want to solve search problems that are larger than time allows. To address these challenging problems, even suboptimally, a planning agent should be smart enough to intelligently allocate its computational resources, to think carefully about where in the state space it should spend time searching. For finding optimal solutions, we must examine every node that is not provably too expensive. In contrast, to find suboptimal solutions when under time pressure, we need to be very selective about which nodes to examine. In this dissertation, we will …

Synthesis Of Thioacids And Dicarboxylic Acids Derived From Open Β-Lactams For Inhibition Of Metallo-Β-Lactamases, Junfu Chen

Doctoral Dissertations

Antibiotics are important substances that have been used in clinical treatment for over 70 years. Because of overuse and misuse of antibiotics, bacteria developed resistance. However, bacterial resistance towards antibiotics, especially the β-lactam antibiotics, is becoming increasingly threat. Currently, the β-lactam antibiotics are seriously threatened by β-lactamases. Metallo-β-lactamases (MBLs), a sub-class of β-lactamases, have been found in several bacteria since they confer resistance to many different β-lactams, and as a result, the bacteria survive in their presence. A potential treatment is to synthesize inhibitors of MBLs, however, there are no inhibitors synthesized in clinical use. The goal of this project …

High Level Learning Using The Temporal Features Of Human Demonstrated Sequential Tasks, Madison Brandywine Clark-Turner

Doctoral Dissertations

Modelling human-led demonstrations of high-level sequential tasks is fundamental to a number of practical inference applications including vision-based policy learning and activity recognition. Demonstrations of these tasks are captured as videos with long durations and similar spatial contents. Learning from this data is challenging since inference cannot be conducted solely on spatial feature presence and must instead consider how spatial features play out across time. To be successful these temporal representations must generalize to variations in the duration of activities and be able to capture relationships between events expressed across the scale of an entire video.

Contemporary deep learning architectures …

Molecular Architecture Of Rod Photoreceptor Phosphodiesterase In Its Nonactivated And G-Protein Activated States, Michael Irwin

Doctoral Dissertations

The photoreceptor phosphodiesterase (PDE6) plays an important role in the G-protein coupled visual signaling pathway which uses cGMP as a second messenger to convert light stimuli into electrical signals. PDE6 is a tetrameric peripheral membrane protein consisting of two catalytic subunits and two inhibitory subunits and is localized to the outer segment membranes of rod and cone photoreceptors. Mutations in this enzyme are one cause of retinitis pigmentosa and other retinal degenerative diseases resulting in blindness or visual dysfunction that lack adequate therapeutic intervention due to inadequate knowledge of PDE6 structure and regulation PDE6 is tightly regulated in the nonactivated …

Cognitive Buffer-Aided Cooperative Networks: Scheduling, Resource Allocation, And Performance Analysis, Omid Moghimi Kandelusy

Doctoral Dissertations

Electromagnetic spectrum, as a limited resource, is prone to scarcity due to the astronomical growth in demands for ubiquitous wireless connectivity in the past few decades. Meeting such an ever-growing demand is contingent upon optimizing the spectrum utilization. In this context, dynamic spectrum access policies, such as spectrum sharing, are promising solutions to mitigate the spectrum gridlock. Spectrum sharing networks are allowed to operate on the licensed frequency bands as the secondary users of the spectrum provided that the licensed primary network is protected from any disruptive interference due to the coexistence. The stringent constraints on the secondary network for …

Multiscale Dynamics Of Energy Transfer Within The Electron Diffusion Region Of Magnetic Reconnection, Dominic Payne

Doctoral Dissertations

During the process of magnetic reconnection, anti-parallel magnetic fields with embedded plasma particles converge and undergo a dramatic topological reconfiguration in the electron diffusion region (EDR) while releasing some of the stored magnetic energy directly into the particles. This process is ubiquitous in natural plasmas, and is responsible for many of the explosive phenomena observed in the Earth's magnetosphere and on the sun. While it has long been established that magnetic reconnection is a plasma energization process, it is still unclear what mechanisms underlie the energy conversion from fields to particles, particularly in the EDR where magnetohydrodynamic (MHD) approximations are …

The Application Of Iron-Based Materials In Aqueous Energy Storage, Fenghua Guo

Doctoral Dissertations

Aqueous energy storage has been an important part of battery research for its cost-effective, environmentally benign, and robust nature. Iron-based materials, including iron hydroxides and iron oxides, are widely investigated as electrode materials for their extremely low cost and sufficient discharge capacity. Iron-based electrode materials were often operated in strong alkaline electrolytes, experiencing either slow reaction kinetics, severe side reactions, or significant capacity loss over cycling. This research focused on the application of iron-based materials in aqueous electrolytes with low alkalinity. This research showed that the synthesized γ-FeOOH measured with a cocktail electrolyte of sodium sulfate and sodium hydroxide demonstrated …

Ligand Design In C-Functionalized Cobalt Cyclams For Hybrid Photocatalytic Co2 Reduction, Ethan Edward Jarvis

Doctoral Dissertations

Global climate change is one of the most significant risks to both the planet and all life on it. The largest contributor to this ever-growing threat is CO2 and its continued emission into the atmosphere. As a result, many scientists are researching CO2 reduction processes to help slow and potentially reverse the climate change by reducing the atmospheric levels of CO2. Ideally, these reduction processes convert CO2 into useful materials such as hydrocarbon-based fuels such as methanol or ethanol, which could also help remove our dependence on finite natural energy resources. CO2 reduction is challenging to do efficiently however, due …

Preventing Violence Among Adolescents: The Many Roles Of School Personnel, Andrew Rizzo

Doctoral Dissertations

Youth violence can encompass a range of types of harmful behaviors that each have their own definitions, high prevalence rates, and litany of negative consequences for both adolescent victims and perpetrators. It includes behaviors that can be labeled based on the nature of the act itself such as physical assault, verbal harassment, relational violence, sexual violence, or cyber violence (Basile et al., 2020; Hasbrouck, 2020). One of the primary avenues of youth violence prevention is through school-based programs that often involve school personnel (Butchart et al., 2019). This dissertation contributes to the extant knowledge about school personnel’s impact on preventing …

Three Essays In Applied Microeconomics: Spillover Effects Of Anti Discrimination And Anti Violence Policies, Gokhan Kumpas

Doctoral Dissertations

In this research, I examine the intended and unintended consequences of three highly debated policies at the state and federal level: enactment of Title IX, state anti-bullying laws, and warrantless arrest laws aimed at curbing domestic violence. My first essay examines the causal relationship between athletic participation and means-tested program participation. I use the variation in the implementation of Title IX and find that a 30 percentage-point increase in female athletic participation induced by Title IX increased program participation among 25 to 40-year-old females by 2.8 percentage-points. This effect persists across SNAP, TANF, and Medicaid recipiency. Event study analysis and …

The Effect Of Deep-Water Multibeam Mapping Activity On The Foraging Behavior Of Cuvier’S Beaked Whales And The Marine Acoustic Environment, Hilary Suzanne Curran Kates Varghese

Doctoral Dissertations

Sound can propagate great distances underwater and is an important mode for marine life to obtain information. Human activities in the ocean such as global shipping, coastal construction, gas and oil exploration, and mapping navigation routes intentionally and unintentionally emit sound into the ocean, potentially interacting with marine life. Therefore, it is essential that the effects of anthropogenic noise on marine life and the ambient marine acoustic environment be understood. Most of the work, to date, has focused on the impact of low-frequency (<1 kHz) sources such as shipping noise, which is ubiquitous in the ocean, and mid-frequency (1-10 kHz) sources such as naval sonar, to which many marine mammals have shown to be sensitive. The effect of these sources can be as salient as a mass stranding event or as benign as an animal swimming away from a source of noise with no other effect. Less work has focused on higher frequency sources (>10 kHz), including ocean-mapping sonar systems. However, most marine mammals, namely toothed whales (odontocetes), are capable …

Investigation Of Anomalous Data Trends During Coal Dust Explosibilty Testing, Jacob Lee Miller

Doctoral Dissertations

Coal dust explosibility is a health and safety concern that has been a recognized hazard for over 100 years. Initial testing by the Author using a Siwek 20L apparatus recorded a secondary maximum pressure at higher dust concentrations (1,000-7,000g/m³) with Pulverized Pittsburgh Coal (PCC). Higher dust concentrations are beyond the typical ASTM E1226 testing procedure but are possible in mining and processing scenarios. No reference documents have been discovered that show a secondary maximum pressure at higher dust concentrations. Literature reviewed identified that once a coal dust concertation generates a peak pressure, the pressure remains constant or decreases …

Fabrication, Characterization Of High-Entropy Alloys And Deep Learning-Based Inspection In Metal Additive Manufacturing, Wenyuan Cui

Doctoral Dissertations

"Alloying has been used to confer desirable properties to materials. It typically involves the addition of small amounts of secondary elements to a primary element. In the past decade, however, a new alloying strategy that involves the combination of multiple principal elements in high concentrations to create new materials called high- entropy alloys (HEAs) has been in vogue. In the first part, the investigation focused on the fabrication process and property assessment of the additive manufactured HEA to broaden its engineering applications. Additive manufacturing (AM) is based on manufacturing philosophy through the layer-by-layer method and accomplish the near net-shaped components …

Integrating Snp Data And Imputation Methods Into The Dna Methylation Analysis Framework, Yuqing Su

Doctoral Dissertations

"DNA methylation is a widely studied epigenetic modification that can influence the expression and regulation of functional genes, especially those related to aging, cancer and other diseases. The common goal of methylation studies is to find differences in methylation levels between samples collected under different conditions. Differences can be detected at the site level, but regulated methylation targets are most commonly clustered into short regions. Thus, identifying differentially methylated regions (DMRs) between different groups is of prime interest. Despite advanced technology that enables measuring methylation genome-wide, misinterpretations in the readings can arise due to the existence of single nucleotide polymorphisms …

Advanced Battery Modeling For Interfacial Phenomena And Optimal Charging, Yaqi Zhu

Doctoral Dissertations

"Lithium-ion batteries are one of the most promising energy storage systems for portable devices, transportation, and renewable grids. To meet the increasing requirements of these applications, higher energy density and areal capacity, long cycle life, fast charging rate and enhanced safety for lithium-ion battery (LIBs) are urgently needed. To solve these challenges, the relevant physics at different length scale need to be understood. However, experimental study is time consuming and limited in small scale’s study. Modeling techniques provide us powerful tools to get a deep understanding of the relevant physics and find optimal solutions. This work focuses on studying the …

Infrastructure Systems Modeling Using Data Visualization And Trend Extraction, Jacob Marshal Hale

Doctoral Dissertations

“Current infrastructure systems modeling literature lacks frameworks that integrate data visualization and trend extraction needed for complex systems decision making and planning. Critical infrastructures such as transportation and energy systems contain interdependencies that cannot be properly characterized without considering data visualization and trend extraction.

This dissertation presents two case analyses to showcase the effectiveness and improvements that can be made using these techniques. Case one examines flood management and mitigation of disruption impacts using geospatial characteristics as part of data visualization. Case two incorporates trend analysis and sustainability assessment into energy portfolio transitions.

Four distinct contributions are made in this …

Analysis Of The Primary Volatile Compositions In The Oort Cloud And Jupiter-Family Comets Towards The Goal Of Understanding Their Origin And Diversity, Mohammad Saki

Doctoral Dissertations

“Knowledge of the initial conditions present in the early solar nebula is required to understand the evolution and its current volatile content. Comets were some of the first objects to accrete in the solar nebula. They are among the most pristine (primitive) remnants of the solar system formation, and their present-day volatile composition likely reflects the composition and conditions where (and when) they formed. Therefore, they are fossils of the solar system formation. High-resolution near-infrared spectroscopy is a valuable tool for sampling the parent volatile (i.e., ices subliming directly from the nucleus) composition of comets via analysis of fluorescence emission …

Scaling, Experiments, And Simulations Of Condensation Heat Transfer For Advanced Nuclear Reactors Safety, Palash Kumar Bhowmik

Doctoral Dissertations

“The purpose of this research was to perform scaled experiments and simulations to validate computational fluid dynamics (CFD) and empirical models of condensation heat transfer (CHT) for the passive containment cooling system (PCCS) of Small Modular Reactors (SMRs). SMRs are the futuristic candidates for clean, economic, and safe energy generation; however, reactor licensing requires safety system evaluations, such as PCCS. The knowledge in the reviewed relevant literature showed a gap in experimental data for scaling SMR’s safety systems and validating computational models. The previously available test data were inconsistent due to unscaled geometric and varying physics conditions. These inconsistencies lead …

Employment Discrimination: An Efficacy Study Of African American Inequities In The California Utility Sector, Victor Baker

Doctoral Dissertations

Employment Discrimination: An Efficacy Study of African American Inequities in the California Utility SectorThe economic legislation of Title VII of the Civil Rights Act of 1964 was designed a vigorous tool of law to address employment discrimination of African Americans and remedy economic disparity that unfavored African Americans. The energy utility industry served as the first Supreme Court defendant and loser of a Title VII employment discrimination challenge by a Black workforce. As a result, energy utility companies have served as the face of resistance to fair employment for African Americans despite the liberal popularity of diversity management programs. Prior …

Dysconscious Racism And Racial Microaggressions In The Public School System, Ryan Lee

Doctoral Dissertations

Dysconscious racism and racial microaggressions are two forms of racism that exist in public schools today. Dysconscious racism is a form of racism that “tacitly accepts the dominant White norms and privileges” in a given environment while racial microaggressions are brief and commonplace indignations to the target person or group whether it was intentional or unintentional (Sue et al., 2009). Teachers of color face these subtllte forms of racism within their own workplaces. The researcher conducted a qualitative study by interviewing six public school K-6 teachers of color of different ethnicities who teach in various school districts across the South …

Teaching Critical Thinking Skills In A Chinese Immersion School, Pui Hung Helen Wong

Doctoral Dissertations

As a frontline teacher and administrator, I received feedback consistently from parents and students asking for a fun and effective method of instruction for Chinese language development in the US. This study explored the micro-level of how teachers in Chinese immersion schools create an environment to support development of students’ critical thinking skills while learning Chinese. I applied a qualitative approach to the research and designed a case study focused on answering the following research questions: How do teachers help their students to develop critical thinking skills when teaching in a Chinese immersion program? What are the challenges teachers have …

The Significance Of Jesuit Educational Institution In The Reconstruction Of Postcolonial And Post-Conflict East Timor, Plinio Do Rosario Gusmao Dosreis Martins

Doctoral Dissertations

East Timor, as a postcolonial and post-conflict country, has striven to develop its educational system for almost two decades after its independence in 2002. The current educational system with the Portuguese language as the medium of instruction has been a challenge for teachers and students in the teaching and learning process. The fact that teachers and students are still using Tétum as a supplementary language to explain and express ideas shows that the educators and learners are still struggling with Portuguese despite the efforts of East Timor government to bridge the language gap.

Teachers and students, conversely, acknowledge that the …