Digital Commons Network^™

Comprehensive Investigation Of Using Tire-Derived Aggregate In Chip Seal Subjected To Various Traffic And Environmental Conditions, Alireza Pourhassan

Doctoral Dissertations

"Chip seal is one of the most cost- and performance-effective pavement preservation treatments commonly used in the United States. Using crumb rubber obtained from scrap tires as a partial or full replacement for mineral aggregate has been proposed as a sustainable solution to reduce the negative environmental impacts of scrap tire accumulation and excessive consumption of natural resources. However, there was no data available regarding the performance of rubberized chip seal under traffic loads and environmental conditions. An extensive study using laboratory specimens and conditioning as well as field implementation and assessments were conducted to bridge this gap. Different traffic …

Characterization Of The Acquisition Parameters Of A Submersible Gamma-Ray Computed Tomography System, Zhongmin Jin

Doctoral Dissertations

"The purpose of this work is to study a component of a submersible gamma-ray computed tomography (CT) system used in the non-destructive testing of irradiated nuclear fuels. The first section of this study proposes two acceleration approaches for rapidly modeling a transmission-type gamma-ray tomography system. The first relies on Monte Carlo simulations with a monodirectionally biased source sampled from a sub-volume of the whole source volume. This method estimates the real count rate using analytical correction factors. The second way of acceleration is based on deterministic calculations that use the Beer-Lambert law and detector response characteristics. It shows that both …

Novel Uses Of Distributed Optical Fiber Sensing For Geo-Mechanical Monitoring, Samuel Vincent Nowak

Doctoral Dissertations

"Rock mass monitoring in underground excavations is crucial for ensuring workplace safety and efficiency. As mines become deeper and more complex, the need to monitor larger volumes of rock during mining becomes impractical with existing instruments due to high costs. Distributed Optical Fiber Sensing (DOFS) is a powerful technology with advantages like long sensor length, real-time measurement capabilities, ease of installation, low cost, and distributed measurement. However, its application in rock mass monitoring is limited, especially in the mining industry. This study addresses a major gap in DOFS technology, specifically the inability of long-range distributed optical fiber strain sensors to …

Design, Synthesis, And Characterization Of Complex Chalcogenides For Energy Storage And Energy Conversion Applications, Srikanth Balijapelly

Doctoral Dissertations

"Through this investigation, complex chalcogenides with the combination of main group metals, transition metals, and rare earth metals have been synthesized using the building block approach and their structure-property relationships are evaluated. The main emphasis of research is on rationally designing new materials for applications in sodium and lithium ion conducting solid electrolytes, cathodes, thermoelectrics, and nonlinear optics. Along with the experimental studies, theoretical calculations are also employed to better understand the physicochemical properties of the synthesized compounds.

The first part of the research will discuss designing alkali ion containing complex chalcogenides using the building block approach. This investigation resulted …

Understanding Catalyst Design Principles In Transition Metal Mixed Anionic Chalcogenides For Electrocatalytic Energy Conversion, Ibrahim Abdullahi

Doctoral Dissertations

"This research focused on the synthetic design of transition metal mixed anionic chalcogenide catalysts containing various ligand types around the central metal atom (chalcogen anion and chalcogen-based organic ligand) generating diverse crystal structure types applied for water splitting and carbon dioxide reduction reactions (CO₂RR).

A series of catalysts were synthesized starting with isolated metal complexes (ME_n) with a central metal core (M = Co, Ni, Cu, and Cr) through molecular clusters, to bulk nanostructured solids of similar M-E coordination. Bis(dichalcogenoimidodiphosphinato) were employed as ligands in the metal complexes, and anionic chalcogen (E = S, Se, and …

Semiconductor Physics Based Signal Integrity Analysis For 3d Ic, Ze Sun

Doctoral Dissertations

"Three-dimensional integrated circuits (3DICs) are becoming increasingly popular in high-speed electrical systems. 3DICs are made by stacking multiple dies vertically and connecting them with through-silicon vias (TSVs). In this dissertation, three studies were carried out to model the performance of 3DICs in extreme working conditions and the signal integrity (SI) performance of 3DICs.

First, an in-house Monte Carlo particle simulator was developed to characterize extreme working conditions (ESD/EMP) for ICs at the microscopic level instead of the macroscopic level. The ability of the simulator was demonstrated by modeling a voltage regulator diode under forward and reverse bias. The diode simulation …

Applications Of Computational Intelligence And Data Fusion Techniques For Biomedical Images, Anand Krishnadas Nambisan

Doctoral Dissertations

"The realm of melanoma diagnosis has been significantly advanced by deep learning (DL) techniques, yet the current approaches are not without limitations, including missed diagnoses and the challenge of interpreting these "black box" models. The research is comprised of three studies, each contributing uniquely towards advancing melanoma detection accuracy and interpretability. The first study focuses on improving the detection of specific dermoscopic structures through a deep learning-based segmentation approach, while the second study builds upon this by employing a fusion technique that combines traditional image features with advanced deep learning models. This method significantly improves melanoma detection, particularly in recall …

Lithospheric Drip And Mantle Thermal Upwelling Beneath Central Asia And The Southern Great Plains Of North America: Evidence From Receiver Function Imaging, Yangyang Liao

Doctoral Dissertations

"Investigating the depth of mantle transition zone (MTZ) discontinuities provides insights into mantle dynamics, including regional-scale downwelling of mantle lithosphere (i.e., lithospheric drip) and upwelling of thermal materials (i.e., mantle plume). In our study, we employ receiver functions to image the 410 km (d410) and 660 km (d660) mantle discontinuities and to ascertain thickness of the MTZ beneath Central Asia and the Great Plains in United States. The findings unveil a significantly thickened transition zone, exhibiting an average thickness of 284 km beneath East Sayan. When considered alongside geochemical observations, our results indicate that the descent of the lithosphere is …

Exploring Seismic Anisotropy In The Crust And Mantle Of The Tibetan Plateau And Analyzing Seismic Velocity Variations In Yellowstone, Cong Shen

Doctoral Dissertations

"Seismology is a scientific discipline that utilizes seismic waves to investigate the deep structures within the Earth's interior, which are otherwise inaccessible to direct observation by humans. These seismic waves can be categorized into two types: body waves and surface waves, each with distinct propagation modes and behaviors, carrying valuable information about their travel paths. The first paper concentrates on the analysis and inversion of body waves produced by large seismic events. It employs shear wave splitting and receiver function methods to explore the geodynamic structure of the south-central Tibetan Plateau, near the plate boundary. The investigation covers the depth …

Kinetic Modeling And Simulations Of Plasma-Surface-Dust Interactions For Lunar Exploration, David Clifford Lund

Doctoral Dissertations

"Due to the recent relevance of NASA’s focus on lunar missions, a better understanding of the lunar plasma-surface-dust environment is vital for their success. The lunar surface, devoid of an atmosphere and a global magnetic field, is directly exposed to solar radiation and solar wind plasma. This exposure leads to the electrical charging of the lunar surface due to the bombardment of solar wind plasma and the emission/collection of photoelectrons. Therefore, this research developed accurate and efficient computational models of plasma-surface-dust interactions and extend a legacy simulation code, namely the Immersed-Finite-Element Particle-in-Cell (IFE-PIC), to a parallel version: Parallel Immersed-Finite-Element Particle-in-Cell …

Investigation Wettability Contact Angle Using 2d Imaging Technology, Saleh Alsayegh

Doctoral Dissertations

"Investigation wetting preference of tight carbonate reservoir rocks and several other unconventional reservoir rocks, and their relation to oil production, is becoming noticeably important for field development in Kuwait, as in many future unconventional tight carbonate reservoirs in the Middle East. The overall objective of this investigating and modeling study is to discover many fundamental relationships from totality wettability preference as a tool for reservoir recovery predictions and management. The investigation includes advancing position of water wet preference into smaller capillaries of the matrix voids and incrementally more oil-wet into larger capillaries of natural fractures (NF). Also, investigating water/ oil …

Improving Syngas Quality In A Downdraft Biomass Gasifier With Blended Feedstocks, Rania Almusafir

Doctoral Dissertations

"Biomass gasification is the greatest potential renewable energy source and will play an important role in the energy mix of the future. To achieve a high quality of produced synthesis gas (syngas) in the gasification system, the syngas cleaning and cooling processes pose challenges. The main objectives of the present work are advancing the knowledge of the gasification process and producing syngas in the studied pilot-scale downdraft biomass gasifier.

A Thermogravimetric analysis (TGA) has been developed and utilized to experimentally investigate the impact of biomass feedstock diversity on the performance of the gasification process of hardwood (HW), softwood (SW) pellets, …

Processing-Microstructure-Properties Relationships In Additively Manufactured Zrb2-Sic Ceramics, Marharyta Lakusta

Doctoral Dissertations

"The study explores the pressure less sintering (PS) and chemical compatibility of ZrB₂-30 vol.%SiC produced by additive manufacturing (AM) with CO₂. The oxidation kinetics and scale microstructures were compared for ZrB₂-SiC made by hot pressing (HP) and by AM coupled with PS. All specimens exhibited parabolic oxidation kinetics. The difference in oxidation behavior becomes evident at temperatures of 1100-1400°C (200-900h). Oxidation rates increased as grain size increased. Similar oxide scale morphologies were observed in both CO₂ and air, with an outer borosilicate layer and an inner porous ZrO₂ layer containing partially oxidized …

Effect Of Ai–Si Coating Weights On Corrosion And Weldability Of Ultra-High-Strength Steel Usiborr 1500 Used In Automotive Structures, Hilary Anayochukwu Onyishi

Doctoral Dissertations

"There has been increased demand for hot-stamped pre-coated Usibor 1500R in automotive industries due to its excellent properties (ultra-high strength, weight reduction, low spring back and excellent corrosion protection). In this research work, investigation was conducted to better understand the effect of Ai-Si Coating Weights on weldability and corrosion of Ultra-High-Strength Steel Usibor 1500R used in Automotive Structures”. The results show that weld nugget diameter increases with increasing weld current, better spot-weld nugget diameter is recorded at weld currents above 7.5 kA for both AS80 and AS150 and the weld current range decreases as the interdiffusion layer (IDL) thickness increases. …

Highly Dipole-Parallel Aligned Nonlinear Optical Organic Molecular Crystalline Materials: Rational Design, Experimental And Theoretical Studies Of Supramolecular Structures And Non-Covalent Interactions, Harmeet Singh Bhoday

Doctoral Dissertations

Highly dipole-parallel aligned donor-acceptor substituted organic molecules are attractive for a wide array of applications, including nonlinear optics. However, only a limited number of crystals are known to adopt polar non-centrosymmetric space groups. The concepts guiding the fabrication of these polar materials have been described. The study focused on unsymmetrical donor-acceptor substituted azines and butadiene's. An improved design over (MeO, Y)-azines led to the realization of three crystals perfectly aligned in dipole parallel orientation for (PhO, Y)-azines with Y = Cl, Br, I, and one nearly perfectly aligned crystal for Y = F (Paper I). The unique bonding properties associated …

Modeling Of Power Distrubition Network (Pdn) Noise Coupling Induced Clock Phase Noise, Zhekun Peng, Junyong Park, Chaofeng Li, Joey Stecher, Srinivas Venkataraman, Xu Wang, Granthana Rangaswamy, Donghyun Kim

Electrical and Computer Engineering Faculty Research & Creative Works

Phase noise analysis is important to clock design. Noise sources of spurs shown on the phase noise result are challenging to find out due to the unknown source locations and coupling mechanisms. Noise from power distribution network (PDN) is one of the most troublesome sources. A behavioral modeling methodology is proposed to simulate the clock phase noise induced by PDN noise coupling for two different mechanisms: PDN-to-clock additive coupling and PDN-to-PDN up-conversion modulation. The thermal noise and 1/f flicker noise are simplified to provide a straightforward view of spur level. The model can be applied to both single-ended clock and …

Not Just Bony Fish: All Nonmammalian And Nonavian Animals Are Neglected In Both Welfare And General Research, Jennifer A. Mather Ph.D.

Animal Sentience

The lack of research on fish welfare highlighted by Oldfield & Bonano (2024) is only part of a more general problem: a relative neglect of animals other than mammals and birds. The causes are our lack of knowledge, our negative view of what we consider to be “lower” animals and our underestimation of their intelligence and sensitivity. Our estimation will increase as our knowledge increases. As a broader view spreads to the public through the media, it should gradually increase the demand to expand both research and welfare, especially beyond mammals and birds.

Production Of Glass-To-Metal Seals Using Additive Manufacturing Techniques, Aaron Read

Masters Theses

"Glass-to-metal (GtM) seals are hermetic barriers between glass and metal components, often used in the electronic and vacuum industries. Creating the seals traditionally requires heating all the components to the glass melting temperature, where the glass will flow and bond to the metal. Due to the manufacturing constraints of the individual components and sealing conditions there are geometric and material restrictions. Additive manufacturing techniques were used to make GtM seals to reduce these restrictions.

Hermetic, single pin seals were produced using printed metal shells, by selective laser melting (SLM), and digital light processing (DLP) printed glass preforms. Glass preforms were …

Computational Fluid Dynamics Analysis Of Thermal-Hydraulic Phenomena In Nuclear Reactor Systems, Mehedi Hasan Tusar

Masters Theses

"A computational analysis of thermal-hydraulic processes in nuclear reactor systems is performed, leveraging Computational Fluid Dynamics (CFD) to advance the design and ensure the safety of nuclear reactors. Divided into two primary sections, the initial part examines thermal-hydraulic behavior in the Replacement Research Reactor (RRR) operating at 20 megawatts and evaluates potential enhancements for the Missouri University of Science and Technology Reactor (MSTR) to operate at an increased capacity of 2 megawatts from the existing 0.2 megawatts. Detailed simulations reveal insights into flow characteristics, temperature distributions, and pressure drops, highlighting the effective use of realistic and porous media modeling techniques …

Addressing The Negative Externalities Of Trade: Flanking Policies And The Role Of Package Treaties, Gregory Shaffer

Georgetown Law Faculty Publications and Other Works

This article examines the rationales for addressing sustainability and social inclusion in trade policy and the tradeoffs among imperfect institutional choices in doing so through “flanking policies.” It examines three types of negative spillovers or externalities implicated by trade: material, moral, and social/political. Part I defines terms and sets forth the argument. Part II typologizes the three categories of negative externalities and then highlights the challenges posed for flanking measures given the reciprocal nature of externalities. It respectively addresses environmental harms and labor and social inclusion concerns. Part III assesses different institutional choices for addressing negative externalities, dividing them between …

Blinded By The Light: Resolving The Conflict Between Satellite Megaconstellations And Astronomy, David A. Koplow

Georgetown Law Faculty Publications and Other Works

The sudden emergence of large constellations of small satellites in low altitude orbits represents one of the most dramatic contemporary innovations in outer space. Promising low-cost, low-latency global communications and spectacular capacities for remote sensing of the Earth, these satellites will soon number in the tens of thousands, sponsored by diverse corporations and countries around the world. But this proliferation of spacecraft comes at a steep cost in unavoidable interference with ground-based astronomy: as the satellites overfly the observatories, they block the views of remote objects and phenomena, leaving obliterating white streaks on the collected imagery, and obscuring access to …

Shades Of Service: Navigating Racial Diversity, Mental Health, And Occupational Stress Among Black Police Officers, Manina Jeudy

Theses and Dissertations

This study was conducted to learn about the unique challenges Black police officers face by exploring their lived experiences. This study looked at how these current and retired Black police officers navigate racial diversity, handle occupational stress and how their mental health is affected. The research was prompted by the lack of existing literature that focuses specifically on the lived experiences of Black police officers, as most studies of policing do not address this population in depth. Through Zoom interviews with a small group of officers, this study revealed their struggles at work and in their personal lives. By sharing …

A Descriptive Study Of The Perception Of Emerging Adults Aged 18-25 Years Toward Police Efficacy And Image In The United States, Jude Louis

Theses and Dissertations

The purpose of this study was to investigate the perceptions of emerging adults toward police efficacy and image. The study was descriptive, used quantitative methodology, and utilized a non-experimental design. Close-ended questions were used in an online format to survey emerging adults aged 18-25 years in the United States. The data was collected using the SurveyMonkey Audience, which was relatively cost-effective, able to gather information from the target audience within a short period of time, and efficient with any sample size. The study occurred over two months in 2024. Emerging adults in the United States aged 18-25 years irrespective of …

A Phenomenological Study On University Students’ Perceptions And Attitudes Of The Effectiveness Of Mobile Apps On Communicative Competence, Leveth Jackson

Theses and Dissertations

This phenomenological study is focused on understanding how university students who are learning English as a foreign language (EFL) perceive and experience using mobile application on their speaking abilities. The primary goal was to examine the perception and attitudes of EFL learners towards using mobile apps for independent English-speaking practice and creating a customized learning experience outside of the classroom.

The researcher also investigated the participants’ views on the challenges and advantages of incorporating mobile apps into university speaking courses. The findings of this investigation may inform language educators at universities on the potential benefits of using mobile apps in …

Diversidad De Enfoques Del Liderazgo Transformacional En Instituciones Educativas: Una Revisión Sistemática, Néstor Amado Cárdenas

Theses and Dissertations

El liderazgo transformacional por la amplitud en su definición ha sido hasta la fecha uno de los estilos más discutidos o investigados a nivel mundial, tanto en el ámbito académico como empresarial. Originalmente concebido como producto de la influencia que el líder ejerce sobre sus seguidores, muchos autores amplían esta idea a otra en la que este estilo de liderazgo es producto de diversos factores aledaños al de la influencia del líder como las cualidades del líder, la estructura de la organización o prácticas organizacionales, la cultura imperante tanto dentro como fuera de la misma, o hasta en la sociedad …

Percepción Sobre Los Factores Que Inciden En La Utilización De La Plataforma De Microsoft Teams En Tiempos De Pandemia, Jessica Rosa Domenech

Theses and Dissertations

El diseño de investigación fue de naturaleza exploratorio con un enfoque fenomenológico correspondiente al paradigma cualitativo. Se utilizó la entrevista en profundidad para obtener la información. Los hallazgos relevantes demostraron que Los factores internos que incidieron en el uso del Microsoft Team incluyeron la disposición y competencia tecnológica de los maestros, su nivel de familiaridad con la plataforma y su capacidad para integrarla en su metodología de enseñanza. Los factores externos, la disponibilidad de recursos tecnológicos y acceso a Internet en las escuelas y hogares de los estudiantes es un aspecto importante que puede influir en la utilización de TEAMS. …

El Impacto De La Herramienta Teams En Los Maestros Como Medio De Enseñanza Ante Un Evento Pandémico, Jessica M. Rivera Figueroa

Theses and Dissertations

La herramienta de Microsoft Teams demuestra ser una completa y efectiva en el desarrollo de clases virtuales sincrónicas y asincrónicas ante una pandemia. La accesibilidad permitió la continuidad de la educación en el Departamento de Educación de Puerto Rico. Dicho proceso trajo consigo muchas incógnitas para el uso efectivo de la herramienta a pesar de adiestramientos y asistencias.

El propósito del estudio fue identificar el impacto de la herramienta Teams en los maestros como medio de enseñanza durante la pandemia para mejorar su uso en el proceso educativo y que se logre un uso efectivo en todas las materias de …

A Post-Pandemic Measurement Of The Required Soft Employability Skills For Business School Graduates, Sean O. Stallings

Theses and Dissertations

This non-experimental descriptive quantitative applied dissertation was designed to identify and analyze the soft employability skills desired by mid-Atlantic employers of business school graduates in a post-pandemic environment. The study evaluated alignment of the competencies possessed by business school graduates and the desired skills of employers. The study explored opportunities to guide change in the development of learning outcomes for business school undergraduates that were influenced by the effects of COVID-19 to ensure adequate postgraduation placement and overall effectiveness of business school graduates.

Workplace readiness or employability also included identifying new hires who had the full package that included hard …

Black Teachers, Black Students, And Cultural Brokering: Leveraging Positionality To Strengthen Academic Identity, Shakasha L. Stevenson

Theses and Dissertations

This study utilized a phenomenological photovoice approach to understand the lived experiences of veteran Black high school teachers. Black teachers are positioned to serve as cultural brokers to support the academic identity of Black students. The prevalence of symbolic violence in the Eurocentric curriculum and other curricular practices continues to hinder successful outcomes for Black students. The study leverages the experiences of Black teachers to understand how their positionalities influence their decision-making and pedagogical practices.

The literature review explored research on the social and political implications of Black education, Black identity development, cultural brokering, and academic identity. More specifically, the …

Victim Advocates' Experiences In The Provision Of Domestic Violence Services For Jewish Women, Michael Sue Jenefsky

Theses and Dissertations

Domestic violence is a serious, dangerous global epidemic and does not discriminate. Domestic violence has no limitations happening in all communities, religions, and cultures. There are many types of abuse, and it is not always physical; however, the underlying threat of violence is perceived by victims. Abusers use manipulative and coercive tactics to gain and maintain power and control of victims. It is deliberate and a choice. Feelings of shame, guilt, blame, failure, helplessness, and being trapped with no means to escape are prevalent among victims. Jewish women have specific feelings and fears that are associated with halakha, Jewish law, …