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Articles 2311 - 2340 of 23710
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Developing Geopolymer-Based Adsorptive Materials For Nutrient Removal From Agricultural Runoff And Drainage, Gabrielle Jacquelle Savoir
Developing Geopolymer-Based Adsorptive Materials For Nutrient Removal From Agricultural Runoff And Drainage, Gabrielle Jacquelle Savoir
Dissertations
With the rise of population placing strain on food supplies and the failure of current prevention strategies to mitigate effects of agricultural pollution, research is needed to develop new technologies for the removal and recovery of nutrients from agricultural runoff and drainage. Geopolymer, an alkali-silicate material polymerized within an acidic or alkaline medium, is promising as an adsorptive substrate due to its multifaceted customizability, cost effectiveness, and adsorptive properties. Hence, the objective of this research was to develop porous metakaolin (MK) geopolymer based adsorptive materials with high affinities for phosphate and ammonium/ammonia to act as nutrient control within agricultural runoff …
Nonlinear Dynamics Of Acoustic Fluctuations In One-Dimensional Ducts With And Without Unsteady Combustion, Swarnalatha Kathalagiri Vasantha Kumar
Nonlinear Dynamics Of Acoustic Fluctuations In One-Dimensional Ducts With And Without Unsteady Combustion, Swarnalatha Kathalagiri Vasantha Kumar
Dissertations
The overall objective of this research is to analyze the nonlinear dynamics of combustors in one dimensional Cartesian coordinate. This research was carried out in four parts, with each successive part building on the previous one. The first part begins with investigation of the coupled nonlinear evolution of acoustic modes in a quasi 1-D duct with axially inhomogeneous mean velocity and mean thermodynamic properties. A novel modification of the Krylov--Bogoliubov method of averaging (KBMA) is developed to analytically solve the modal-amplitude equations that are linearly and nonlinearly coupled with both quadratic and cubic nonlinearities. Approximate analytical solutions based on the …
The Role Of Surface Processes In Modulating Land-Sea Breeze Circulation : An Observational And Numerical Modeling Study In Java, Georgios Priftis
The Role Of Surface Processes In Modulating Land-Sea Breeze Circulation : An Observational And Numerical Modeling Study In Java, Georgios Priftis
Dissertations
In the Maritime Continent (MC), sea and land breezes (SLB), shaped by its numerous islands, are key drivers of the tropical climate. Island morphology, terrain, land cover, and orientation relative to prevailing winds affect these breezes and associated convection. While research has largely focused on larger islands, smaller islands like Java remain understudied. Java features a mountainous chain with several gaps and experienced significant land use and land cover changes (∆LULC) over the past two decades. This dissertation aims to: 1) adapt observational methods to detect mesoscale boundaries in numerical models, 2) analyze the role of Java’s topography and cloud- …
Becoming Transfer Friendly: Evaluating Four-Year Higher Education Institution Strategies To Support Community College Transfer Student Success, Aarti V. Dhupelia
Becoming Transfer Friendly: Evaluating Four-Year Higher Education Institution Strategies To Support Community College Transfer Student Success, Aarti V. Dhupelia
Dissertations
Four-year higher education institutions (HEIs) nationwide must become more transfer friendly so that more community college transfer (CCT) students persist and complete their bachelor’s degrees, as a path to more students’ economic mobility and to equity across communities. This study aims to provide learnings to support achievement of this imperative. The research question studied here is: What is the relationship between community college transfer (CCT) student support strategies at a four-year higher education institution (HEI) and the first-to-second-year retention of CCT students at their four-year HEI? Through quantitative analysis of a broad set of variables’ ability to predict student retention …
Perception Of The Elementary Education Profession And Levels Of Job Satisfaction: Is There A Correlation?, Alexis H. Redman
Perception Of The Elementary Education Profession And Levels Of Job Satisfaction: Is There A Correlation?, Alexis H. Redman
Dissertations
The purpose of this dissertation was to introduce the context and purpose of the research study. The study’s focus was on the perception of the elementary education profession and the prestige ascribed to classroom teachers working in public education by individuals outside the education system. The research questions were as follows: (1) What level of prestige is afforded to the elementary public school classroom teacher from the noneducator perspective? (2) To what extent do noneducators’ perceptions affect the level of job satisfaction among elementary public school classroom teachers? Themes found in literature supporting the research questions included the perceived devaluation …
Pauline Echoes In The Preaching And Activism Of Francis James Grimké (1850–1937): Confronting Ethnic Prejudice Through An Evangelical Emancipatory Homiletic (Eeh), Eric J. Freeman
Dissertations
Pauline Echoes in the Preaching and Activism of Francis James Grimké (1850–1937): Confronting Ethnic Prejudice through an Evangelical Emancipatory Homiletic examines how Grimké’s sermons and public discourse, rooted in the proclaimed and embodied gospel of Jesus Christ and resonant with the Apostle Paul’s hermeneutic and pastoral heart, addressed social injustices—particularly ethnic prejudice—through a distinct, socially conscious homiletic. This research defines Grimké’s unique homiletic as an Evangelical Emancipatory Homiletic (EEH), a term coined here to convey the gospel-embodied, contextually aware nature of his ministry. Framed within the practical theology of homiletics, this study illustrates how Grimké’s EEH incorporated textual and thematic …
Spiritual Grounding As An Influence On Servant Leadership Practice Among Senior Executives In U.S. Publicly Traded Companies, Nancy K. Bosire
Spiritual Grounding As An Influence On Servant Leadership Practice Among Senior Executives In U.S. Publicly Traded Companies, Nancy K. Bosire
Dissertations
This dissertation investigates the influence of spiritual grounding on the practice of servant leadership among senior executives in publicly traded companies in the United States (U.S.). The research problem centers on the potential marginalization of individuals aspiring to practice servant leadership without spiritual grounding. The study aims to investigate whether spiritual grounding is foundational for servant leadership practice and to examine the relationship between servant leadership, spiritual grounding, and reliance on authoritative sources. Through a comprehensive review and analysis of existing literature, this research identifies a gap in understanding the role of spirituality and authoritative sources in servant leadership practices. …
Lived Experiences Of Cooperating Teachers And Student Teachers In Their Clinical Year, Ashley Nolette
Lived Experiences Of Cooperating Teachers And Student Teachers In Their Clinical Year, Ashley Nolette
Dissertations
Many aspects of a student teacher’s clinical year help determine their success in the future. Understanding the lived experiences of both cooperating teachers and student teachers is essential to understanding the dynamics of that relationship and how district-university partnerships foster an environment of mentoring and support. This study aims to understand and evaluate the lived experiences of cooperating teachers and their student teachers during the clinical year. This study focuses on understanding the cooperating teacher-student-teacher relationship and how mentoring does or does not happen in that relationship. For this study, the problem is selecting cooperating teachers and the lack of …
Exploring The Leadership Competence Strategies And Assessment Procedures In Southern Baptist Churches In A Small County In The Southeastern United States: A Qualitative Research Case Study, Coleman F. Smoak Jr.
Exploring The Leadership Competence Strategies And Assessment Procedures In Southern Baptist Churches In A Small County In The Southeastern United States: A Qualitative Research Case Study, Coleman F. Smoak Jr.
Dissertations
This dissertation explores the strategies of Southern Baptist churches which contribute to the competence of their lay leadership. It examines the procedures for evaluating lay leaders’ knowledge of church doctrine and goals, as well as their motivation for pursuit of successful ministry. The research assessed Southern Baptist churches in a small county in the Southeastern United States through a qualitative case study with the primary research instrument being one-on-one, semi-structured interviews of church staff. The researcher sought an understanding of these churches’ practices to ensure that lay leaders are equipped for their ministry positions with regard to their leadership approaches, …
Emotional Intelligence And Its Influence On Burnout From Surface Acting In A Seasonal Service Industry, Jeremy Fishman
Emotional Intelligence And Its Influence On Burnout From Surface Acting In A Seasonal Service Industry, Jeremy Fishman
Dissertations
In the world of customer service, it is commonly believed that the customer is always right, even when they may not be or may be. Roles that carry immediate interaction with the consumer have certain expectations that employees must fulfill, necessitating both surface acting and deep acting; tenets of emotional labor (Diefendorff et al., 2006). Previous research has revealed that relying solely on surface acting can lead to emotional exhaustion and burnout, impacting individuals and even spreading through emotional contagion (Mawritz et al., 2012; Totterdell & Holman, 2003). Leaders turn to emotional intelligence to address these challenges, which can potentially …
Diminished Aspirations Or Something More? A Phenomenological Study To Examine How Educational Leadership Experiences Influence Career Aspirations, Chevy A. Benson
Diminished Aspirations Or Something More? A Phenomenological Study To Examine How Educational Leadership Experiences Influence Career Aspirations, Chevy A. Benson
Dissertations
This qualitative study utilized a phenomenological approach to examine the lived experiences female educational leaders’ face, which may influence their career aspirations. Phenomenology allowed the researcher to explore the commonalities across female educational leaders’ experiences. Female educational leaders from two school districts were invited to participate in the study, provided they had a minimum of one year of experience as school administrators. Participants were purposefully selected. The researcher utilized an electronic invitation inviting female educational leaders to participate in the study. The researcher then scheduled individual, semi-structured interviews with the participants to obtain data pertaining to the participants’ experiences. The …
Connectedness To Others Through Virtual Social Music Improvisation, Jody Webb
Connectedness To Others Through Virtual Social Music Improvisation, Jody Webb
Dissertations
This mixed methods action research intervention study analyzed the influence of social music improvisation (SMI) on students' behaviors and perceptions of their connectedness to others in a virtual middle school classroom setting. Nine 10-minute SMI sessions allowed for the accumulation of data, with two additional pre-sessions being informative and exploratory to describe the SMI intervention and practice its aspects with participants in the intervention group. This study acquired pretest and posttest data from the Hemingway Measure of Adolescent Connectedness (Karcher, 2005) and observational information through process coding and field notes. Results showed how the presence or absence of SMI influenced …
Developmental Pathways From Player To Coach For Volunteers In An American Football Organization In Germany, Gary Cramer
Developmental Pathways From Player To Coach For Volunteers In An American Football Organization In Germany, Gary Cramer
Dissertations
The leadership style of organizational leaders is a key factor affecting volunteer coach recruitment and retention; yet the examination of developmental pathways from player to coach is lacking in the literature, especially as viewed from the perspective of those who are followers. The study addressed the following research question: How do volunteer coaches in an American football organization in Germany, who once played for the same head coach in the organization they currently coach, describe their pathway of development from player to coach? The purpose of this phenomenological case study was to inductively investigate the developmental pathways of volunteer sport …
An Empirical Study Of The Relationship Between Automation And Aircrew Accident Performance In High Performance Aircraft Operating In The U.S. Naval Shipboard, Richard Matthew Gensley
An Empirical Study Of The Relationship Between Automation And Aircrew Accident Performance In High Performance Aircraft Operating In The U.S. Naval Shipboard, Richard Matthew Gensley
Dissertations
The research described in this dissertation was an empirical study of cockpit automation and aircrew accident performance in high performance aircraft. The data set consisted of 3,249 accident records released by the U.S. Naval Safety Center and publicly available information for high performance aircraft based aboard U.S. aircraft carriers between the years of 1980 and 2013. Five conclusions resulted from this study. The first result was a demonstration that through statistical analysis, it is possible to assess if different aircraft over a prolonged period of time have been exposed to a common operating environment. The second result was that while …
Characterization Of Size Effects In Additively Manufactured Grcop-42 And Their Influence On Mechanical Response, Gabriel Demeneghi
Characterization Of Size Effects In Additively Manufactured Grcop-42 And Their Influence On Mechanical Response, Gabriel Demeneghi
Dissertations
This study investigates size effects on microstructure, mechanical behavior, and fatigue performance of additively manufactured GRCop-42. Systematic analyses, encompassing changes on powder composition, wall thickness, and heat treatment, was conducted on specimens produced through laser powder bed fusion (L-PBF) and laser powder direct energy deposition (DED) techniques. L-PBF specimens exhibited a reduction in strength and elongation with decreasing thickness, attributed to increasing porosity as specimen’s thickness decreases. Conversely, in DED specimens, decreasing mechanical properties with thickness were associated to surface topography. Emphasizing the non-generalizability of size effects across AM methods. Size effects were also investigated on high cycle fatigue, as …
Exploring The Impact Of Ionizing Radiation On Security And Reliability In Modern Semiconductor Memories, Umeshwarnath Surendranathan
Exploring The Impact Of Ionizing Radiation On Security And Reliability In Modern Semiconductor Memories, Umeshwarnath Surendranathan
Dissertations
Radiation effects in semiconductor devices have gained great traction in recent years due to an exponential growth in space exploration. The harsh conditions of space, devoid of the atmosphere and Earth's magnetic field, pose considerable challenges to electronic systems due to ionizing radiation exposure. While radiation-hardened (rad-hard) components are continually under development, they often lag several technology generations compared to commercial off-the-shelf (COTS) parts. Notably, rad-hard memories, particularly in terms of capacity (megabytes vs. terabytes) and cost, fall short compared to regular COTS memories. This underscores the compelling need to evaluate the radiation tolerance of COTS memories. This dissertation focuses …
A Large-Sample X-Ray Absorption Line Analysis In Search Of The Missing Baryons In The Hot Whim, David Spence
A Large-Sample X-Ray Absorption Line Analysis In Search Of The Missing Baryons In The Hot Whim, David Spence
Dissertations
A well known problem in astrophysics that has seen a significant amount of investigation in recent years is the ”missing baryons problem”, in which up to 40% of baryons have been reported missing at low redshifts [62]. Predictions show that these remaining baryons are likely residing within the Warm-Hot Intergalactic Medium (WHIM). The process of finding these baryons involves searching for absorption line systems in the WHIM, and using column densities of those absorbing ions to calculate the cosmological density of the medium. Several wide scale FUV studies (e.g. [21]) have been completed to work towards solving this problem, but …
Online Learning For Adaptive Control : Stable Learning And Control For Aerospace And Robotics, Jacob G. Elkins
Online Learning For Adaptive Control : Stable Learning And Control For Aerospace And Robotics, Jacob G. Elkins
Dissertations
Aerospace and robotic systems perform various tasks in uncertain, dynamic environments. Further, the data that a system encounters in the real-world is often the most valuable. The most advanced aerospace and robotic systems of the future will be able to learn online, during operation, from this real-world data. Aerospace and robotic systems are often expensive and difficult to model, and the controllers of these systems thus require rigorous control proofs and safety guarantees. Recently, general research in artificial intelligence and machine learning (AI/ML) has made significant strides in developing learning-based systems and controllers. However, much of this research has focused …
Transition-Aged Youth Perspectives On Social Media Use Behaviors And Mental Health: A Qualitative Study, Lauren L. Niles
Transition-Aged Youth Perspectives On Social Media Use Behaviors And Mental Health: A Qualitative Study, Lauren L. Niles
Dissertations
Rates of mental health difficulties have risen drastically in recent years. Transition-aged youth (TAY) ages 18-24 years old represent a vulnerable population at risk for poor mental health outcomes, with depression and anxiety diagnoses increasing faster than any other age group. While the cause for this upsurge is multifaceted, these trends have occurred concurrently with the increasing popularity of social media (SM) platforms. Current evidence presents contradictory findings as to the impact of SM platforms on mental health, revealing a critical gap in knowledge. This study addresses this gap by exploring how TAY perceive their use of SM platforms and …
Analysis Of A Magnetically Enhanced Microwave Powered Split-Ring Resonator Plasma Source For Micropropulsion, Andrew Walsten
Analysis Of A Magnetically Enhanced Microwave Powered Split-Ring Resonator Plasma Source For Micropropulsion, Andrew Walsten
Dissertations
This work focuses on better understanding split-ring resonators (SRRs) as plasma devices and exploring their use as a plasma source in a two-stage Hall thruster. This is done by first studying the effect of a single versus a coupled SRR on plasma production. Through the use of simulations in ANSYS HFSS and Langmuir probe measurements, it is found that coupled SRRs result in a more uniform plasma at higher pressures due to the introduction of a secondary ionization point, and the electromagnetic coupling resulting in a slightly stronger electric field being produced at the primary gap. Experiments were also done …
Adaptive Discrete Time Sliding Mode Control For N-Th Order Flapping-Wing Micro Air Vehicles With Unknown Parameters, Joshua Hill
Adaptive Discrete Time Sliding Mode Control For N-Th Order Flapping-Wing Micro Air Vehicles With Unknown Parameters, Joshua Hill
Dissertations
Small aerial systems, such as nature-inspired flapping-wing micro aerial vehicles (FWMAV), operate in uncertain and dynamic environments that are subject to unknown disturbances, e.g., wind gusts. With the proliferation of inexpensive system components, extensive research has been dedicated to improving the operation of these FWMAVS, both in civilian and military applications. Given dynamic environments and variations in individual components, sliding mode control has become an increasingly applied control method for FWMAV. Its robustness proves invaluable to ensure stability in the presence of uncertain system parameters and environmental disturbances. This dissertation presents three discrete-time sliding mode control (DSMC) methods and applies …
The Zero Forcing Number Of Graphs With Prescribed Girth, Paige Gant
The Zero Forcing Number Of Graphs With Prescribed Girth, Paige Gant
Dissertations
The zero forcing number is a graph parameter that was introduced in 2008 to study the minimum rank of matrices. Since then, it has garnered attention due to its applications in search problems, control theory, and power grid monitoring as well as a subject of theoretical interest in its own right. We denote the zero forcing number of a graph Z(G). Consider a subset Z of the vertex set of a simple graph G and color the vertices in Z pink. If a pink vertex has exactly one uncolored neighbor, then that pink vertex forces its sole uncolored neighbor to …
Variability In Semidiurnal Surface And Internal Tides In Global Ocean Model Simulations, Harpreet Kaur
Variability In Semidiurnal Surface And Internal Tides In Global Ocean Model Simulations, Harpreet Kaur
Dissertations
This dissertation focuses on semidiurnal (D2) surface and internal tides. Chapter 2 investigates the transition of M2 barotropic Kelvin waves into Hybrid Kelvin-Edge (HKE) waves and the associated generation of internal tides at widening shelves using theory and a realistic global baroclinic Hybrid Coordinate Ocean Model (HYCOM) simulation. To understand the effect of complex, realistic bathymetry on the HKE wave transition, we perform quasi-realistic barotropic HYCOM simulations of the Celtic Sea/Bay of Biscay shelf areas. We conclude that the HKE wave transition is most likely masked by the effects of complex bathymetry and offshelf baroclinic fluxes cannot be exclusively …
Leading From The Middle: Arts Administrators' Beliefs About The Impact Of Arts Education On High-Needs Students, Sofia Fojas
Leading From The Middle: Arts Administrators' Beliefs About The Impact Of Arts Education On High-Needs Students, Sofia Fojas
Dissertations
Research on arts education notes the positive impact of arts education on educational outcomes for students, particularly students of color, students in poverty, and students needing additional academic support. Students living in low-income communities receive different educational opportunities than those in high-wealth districts. This disparity is especially true for highly mobile and high-needs students of color. Arts education has made positive differences in student outcomes. This qualitative study examined the beliefs of county arts leads, leaders in the middle, situated between the California Department of Education and their local school districts, and how they can be empowered to be change …
Development Of A Continuum Damage Constitutive Model And Simulation For Brittle Materials In Space Infrastructure Application, Luis Eduardo Deganis
Development Of A Continuum Damage Constitutive Model And Simulation For Brittle Materials In Space Infrastructure Application, Luis Eduardo Deganis
Dissertations
The purpose of this work is to develop a continuum damage constitutive material model and apply it to structural response characterization of brittle materials for in-situ construction of space infrastructure. This research improves and expands the utility of the physics-based dominant crack algorithm (DCA) model in order to account for very low-strain rate phenomena in plain concrete structures. The DCA model is strain-rate dependent and has been effectively utilized for highly dynamic phenomena. The model has a strong basis in micromechanics and is able to capture the strain-softening response of brittle materials. The newly developed constitutive model can be easily …
A New, Intuitive Method For The Design And Analysis Of Multi-Pass Cavities, Adam S. Mansor
A New, Intuitive Method For The Design And Analysis Of Multi-Pass Cavities, Adam S. Mansor
Dissertations
This dissertation develops a new analytical approach for designing and analyzing multi-pass cavities like the Herriott cell employing the graphical yӯ diagram approach. The new technique can be deployed in spectroscopy absorption detection, femtoseconds laser cavities, or any off -axis spherical mirror interferometers applications. Such a system can be uniquely designed and evaluated by entering a few parameters that define the required physics for the cell, the packaging size limits for the system and the probe beam size, plus two user selected parameters. The existing design method, developed by Herriott, is discussed and then the yӯ diagram method is presented …
Application Of A New Scale-Resolving Turbulence Model To Supersonic Retropropulsion Flows With Chemistry, Gabriel C. Nastac
Application Of A New Scale-Resolving Turbulence Model To Supersonic Retropropulsion Flows With Chemistry, Gabriel C. Nastac
Dissertations
Turbulent compressible flows are ubiquitous in many engineering applications of flight and propulsion. Computational fluid dynamics simulations are commonly performed to analyze these flows. Scale-resolving turbulence models inherently better capture various flow phenomena, including separation and mixing, as well as enable predictions of fluctuations, which can be critical for design compared to traditional steady-state turbulence models. In this work, new scale-resolving blended Partially-Averaged Navier-Stokes (BPANS) turbulence models are developed to account for compressibility effects and are employed to efficiently simulate turbulent compressible flows. Specifically, supersonic retropropulsion flows are investigated. Supersonic retropropulsion is a key technology for next-generation rockets. The new …
Modeling On-Demand Meal Delivery With Multi-Modal Couriers: Considering Both Certain And Uncertain Orders, Zohre Noormohamadzade
Modeling On-Demand Meal Delivery With Multi-Modal Couriers: Considering Both Certain And Uncertain Orders, Zohre Noormohamadzade
Dissertations
The on-demand meal delivery sector has experienced significant transformation, reshaping consumer dining habits and operational practices in the food delivery industry. This dissertation explores the changing landscape of on-demand meal delivery services through two interrelated topics, namely Modeling On-demand Meal Delivery in a Link-Node Based stochastic User Equilibrium with certain demand and Modeling On-demand Meal Delivery with different vehicle modes and uncertain demand, aiming to address the evolving challenges and opportunities in this dynamic industry. The rest of this dissertation is composed of two parts. The first part addresses the integration of internal restaurant couriers and third-party platform couriers to …
Thermal Processing Of Al-Zn-Cu-Mg-Zr Laser Powder Bed Fusion Material For Increased Ductility, Jeffrey S. Gaddes
Thermal Processing Of Al-Zn-Cu-Mg-Zr Laser Powder Bed Fusion Material For Increased Ductility, Jeffrey S. Gaddes
Dissertations
Although the use of wrought high strength aluminum alloys is prevalent throughout aerospace systems, they often have long lead times and become difficult to source throughout the long lifecycle of aviation systems. Laser Powder Bed Fusion (LPBF) Additive Manufacturing (AM) provides opportunity to directly manufacture wrought equivalent aluminum products without forging supply chain challenges. If these LBPF components are made with the same aluminum material system with similar strength and ductility, they can be a direct replacement for traditionally manufactured components. However, existing 7xxx aluminum alloys are prone to cracking during fusion welding and therefore are not readily produced through …
Coronal Magnetic Field Extrapolation And Topological Analysis Of Multi-Scale Magnetic Structures For Solar Eruptions, Wen He
Dissertations
Solar eruptions are manifestations of strong solar activities which occur in multiple scales and vary significantly in observations. It has also been increasingly realized that some scenarios initially proposed for relatively large-scale eruptions may persist down to much smaller/finer scales, largely owing to increasingly high-resolution observations of the Sun. However, confirming the coherent magnetic structures on the Sun remains challenging due to the lack of direct coronal magnetic field measurement. This dissertation mainly focuses on the topological analysis of multi-scale magnetic structures embodied in different solar eruptions with available observations. It is achieved by reconstructing the 3D coronal magnetic field …