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Investigation Of Wide Bandgap Semiconductors For Room Temperature Spintronic, And Photovoltaic Applications, Vishal Saravade

Doctoral Dissertations

"Suitability of wide bandgap semiconductors for room temperature (RT) spintronic, and photovoltaic applications is investigated.

Spin properties of metal-organic chemical vapor deposition (MOCVD) – grown gadolinium-doped gallium nitride (GaGdN) are studied and underlying mechanism is identified. GaGdN exhibits Anomalous Hall Effect at room temperature if it contains oxygen or carbon atoms but shows Ordinary Hall Effect in their absence. The mechanism for spin and ferromagnetism in GaGdN is a combination of intrinsic, metallic conduction, and carrier-hopping mechanisms, and is activated by oxygen or carbon centers at interstitial or similar sites. A carrier-related mechanism in MOCVD-grown GaGdN at room temperature makes …

Development Of Horizontal Axis Hydrokinetic Turbine Using Experimental And Numerical Approaches, Abdulaziz Abutunis

Doctoral Dissertations

“Hydrokinetic energy conversion systems (HECSs) are emerging as viable solutions for harnessing the kinetic energy in river streams and tidal currents due to their low operating head and flexible mobility. This study is focused on the experimental and numerical aspects of developing an axial HECS for applications with low head ranges and limited operational space. In Part I, blade element momentum (BEM) and neural network (NN) models were developed and coupled to overcome the BEM’s inherent convergence issues which hinder the blade design process. The NNs were also used as a multivariate interpolation tool to estimate the blade hydrodynamic characteristics …

Novel Approaches For Constructing Persistent Delaunay Triangulations By Applying Different Equations And Different Methods, Esraa Habeeb Khaleel Al-Juhaishi

Doctoral Dissertations

“Delaunay triangulation and data structures are an essential field of study and research in computer science, for this reason, the correct choices, and an adequate design are essential for the development of algorithms for the efficient storage and/or retrieval of information. However, most structures are usually ephemeral, which means keeping all versions, in different copies, of the same data structure is expensive. The problem arises of developing data structures that are capable of maintaining different versions of themselves, minimizing the cost of memory, and keeping the performance of operations as close as possible to the original structure. Therefore, this research …

System Efficient Esd Design Concept For Soft Failures, Giorgi Maghlakelidze

Doctoral Dissertations

"This research covers the topic of developing a systematic methodology of studying electrostatic discharge (ESD)-induced soft failures. ESD-induced soft failures (SF) are non-destructive disruptions of the functionality of an electronic system. The soft failure robustness of a USB3 Gen 1 interface is investigated, modeled, and improved. The injection is performed directly using transmission line pulser (TLP) with varying: pulse width, amplitude, polarity. Characterization provides data for failure thresholds and a SPICE circuit model that describes the transient voltage and current at the victim. Using the injected current, the likelihood of a SF is predicted. ESD protection by transient voltage suppressor …

Pattern Selection Models: From Normal To Anomalous Diffusion, Hatim K. Khudhair

Doctoral Dissertations

“Pattern formation and selection is an important topic in many physical, chemical, and biological fields. In 1952, Alan Turing showed that a system of chemical substances could produce spatially stable patterns by the interplay of diffusion and reactions. Since then, pattern formations have been widely studied via the reaction-diffusion models. So far, patterns in the single-component system with normal diffusion have been well understood. Motivated by the experimental observations, more recent attention has been focused on the reaction-diffusion systems with anomalous diffusion as well as coupled multi-component systems. The objectives of this dissertation are to study the effects of superdiffusion …

Investigation Of Urea Decomposition And Deposit Formation In Diesel Exhaust After-Treatment System, Anand Alembath

Doctoral Dissertations

“Urea-selective catalytic reduction (SCR) system has proved to be an effective solution to reduce NO_x emissions in commercial vehicle (CV) diesel engines. A significant challenge in urea injection is to comprehend its decomposition chemistry that leads to formation of undesired deposits in the exhaust system unit. Due to complex interaction of multi-phase fluid flow and transport processes, significant uncertainty is associated with the identification of interacting factors that control the deposit initiation and its growth. To meet the future ultra-low NO_x emissions and to deliver ammonia without deposit formation, there is an imminent need to develop the urea-SCR …

Thermodynamic Investigations Of Pure And Blended Cement Mixtures, Jonathan Lapeyre

Doctoral Dissertations

” This research is made up of several studies. The first study focused on understanding the reaction kinetics of Ca₃SiO₅ and metakaolin (MK) mixtures compared to Ca₃SiO₅ and silica fume (SF) mixtures. It was shown that MK was a more effective additive than SF at small replacement levels (i.e. ≥ 10% by mass) while higher replacement levels of MK became a detriment due to excess (Al(OH)₄¯) ions preventing the nucleation and growth of C-S-H. In a follow-up study where the MK particle size distribution (PSD) was modified, similar effects were observed but …

Observer-Based Event-Triggered And Set-Theoretic Neuro-Adaptive Controls For Constrained Uncertain Systems, Abdul Ghafoor

Doctoral Dissertations

"In this study, several new observer-based event-triggered and set-theoretic control schemes are presented to advance the state of the art in neuro-adaptive controls. In the first part, six new event-triggered neuro-adaptive control (ETNAC) schemes are presented for uncertain linear systems. These comprehensive designs offer flexibility to choose a design depending upon system performance requirements. Stability proofs for each scheme are presented and their performance is analyzed using benchmark examples. In the second part, the scope of the ETNAC is extended to uncertain nonlinear systems. It is applied to a case of precision formation flight of the microsatellites at the Sun-Earth/Moon …

Fully Differential Study Of Higher-Order Contributions To The Few-Body Dynamics Of Simple Atomic Systems, Madhav Dhital

Doctoral Dissertations

”Advancing our understanding of the few-body dynamics in simple atomic systems is one of the most important goals of atomic scattering research. In perturbation theory, this goal entails accurately describing the relative contributions from first versus higher-order mechanisms. One higher-order mechanism that is particularly important for target ionization by a charged-particle impact is known as post-collision interaction (PCI). There, the projectile and the ejected electron interact with each other at least twice. In the first interaction, the projectile transfers sufficient energy for the electron to be lifted to the continuum. The second interaction occurs in the outgoing part of the …

Decolonizing Education: Using Mother Tongue And English Side By Side In Nigeria, Omobola Wusu

Doctoral Dissertations

Nigerians lack access to effective mother tongue education (MTE) at all levels of their schooling. It is well established that cognitive and educational benefits are achieved if one’s mother tongue (MT) is used as the medium of education. This study aimed to determine how adult Nigerians around the world who had been deprived of using their mother tongues (MTs) in their education reflect on their past experiences with negative messages or colonial language ideologies received in school. Also, it explored how these past experiences have shaped their positive MT identities, their MT experiences, and their perspectives on MTE. In this …

The Effectiveness Of The Preventive System Approach Through The Lens Of Character Education: An Exploratory Case Study Of A Youth Delinquency Camp In South Korea, Mankeun Yoon

Doctoral Dissertations

Juvenile delinquency is deemed a worldwide issue. Despite efforts to remediate, it persists. This study employs a case study methodology to examine the principles, implementation, and perceived impact of a Salesian youth development approach, the Preventive System, on youth delinquency in a Salesian youth Center in South Korea. The study yields three main findings regarding the practice and the effects of the Preventive System. First, this study found that structural elements revealed in the facility, such as reason, religion, and loving-kindness, implemented through assistance and familiarity, were core to the practice. Second, the study revealed that more than through training, …

A Convergence Of Conceptual Frameworks: Neurocognitive, Metacognitive And Social Cultural Techniques In Vocabulary Teaching And Learning, Malihe Eshghavi

Doctoral Dissertations

This mixed methods study investigated the effectiveness of neurocognitive, metacognitive and sociocultural techniques in vocabulary instruction at the high-intermediate level of English as a second language learners’ vocabulary learning and recall at a community college in Northern California. While previous studies offered and demonstrated different methods, those studies emphasized only one particular vocabulary learning modality. As a result, most ESL learners learn vocabulary passively but not actively. No study has proposed to explore the inclusion of the neurocognitive, metacognitive and sociocultural techniques on vocabulary learning and recall, in order to analyze the resulting effects of these proposed instruction techniques among …

An Investigation Of California Classroom Teachers' Beliefs And Ratings Of Creativity In Dance, Patricia R. Reedy

Doctoral Dissertations

Creativity is a fundamental aim of art education. Because classroom teachers are responsible for teaching the arts at the elementary-school level, how they perceive and recognize creativity effects the quality of art education their students receive. This study investigated California teachers' beliefs about creativity in dance and the relationship of their beliefs to their ratings of student dance compositions. It also investigated the extent of agreement in creativity ratings across teachers and between teachers and dance experts. Classroom teachers’ beliefs were collected through a research-constructed questionnaire, and classroom teachers (n=74) and dance experts (n=35) rated students’ creative-dance products using a …

Exploring The Experiences Of Teachers In A Bilingual Immersion Environment, Paloma Cordova

Doctoral Dissertations

The following qualitative study provides a theoretical analysis of teachers’ experiences and interactions at a progressive Mandarin immersion school. Missing from the current literature based on immersion education are the narratives of teachers, specifically international teachers from diverse teaching backgrounds in foreign language settings. An integration of Mandarin and a progressive framework is unique and therefore illuminating their voices is vital to the field of education specifically as they contribute to the growth of prospective mandarin immersion schools in the US. This study included fifteen participants who identified the ways in which their own personal reflections as pedagogues changed over …

Counter-Narratives: Haitians In Economic Transition, Patricia Barthaud

Doctoral Dissertations

The stories of Haiti and the Haitian people have often been filtered through the sensibilities of those who are not of that nation nor of African ancestry. Haitian people deserve the opportunity to tell their authentic stories of their lived realities. This study presents the stories of a small group of Haitian young people under the age of 40 who incorporated their passions into viable work to improve economic circumstances for themselves, their communities, and their country. Based upon narrative inquiry, data collection included interviews, observations, and documents gathered in Haiti. The results produced a complex portrait of participants who …

Teachers' Perceptions Of The Nine Defining Characteristics Of Catholic Identity In Ursuline Secondary Schools Of The Usa, Barbara Ann Middendorf

Doctoral Dissertations

Catholic schools are integral to the Catholic Church’s mission of evangelization. A Catholic educational institution is a place to encounter the living God who is Jesus Christ. Education is the concern and task of the Church, called to serve humankind from the heart of God. This study examined the perceptions of teachers working in Roman Union, Ursuline secondary schools of the Central Province of the United States regarding the extent to which the nine defining characteristics of Catholic identity were present in their respective schools and classrooms. For this research, Catholic identity was operationally defined using the seminal Catholic education …

An Integrated Flow-Curing Model For Predicting Residual Stresses In Textile Composites, Weijia Chen

Doctoral Dissertations

Fiber-reinforced composites have been widely employed in structural applications due to their high stiffness-to-weight ratio and easily-tailored mechanical properties. However, manufacturing of these lightweight materials involves an infusion and curing process, and flow-induced defects and residual stresses can easily occur, which can compromise the mechanical performance of the composite structures. The purpose of this work is to develop an integrated flow-curing processing model to accurately predict the resin flow front and the residual stresses in the Liquid Composite Molding (LCM) process. In the infusion model, the fiber fabrics are treated as a homogeneous and porous material, and the resin flow …

Human Dimensions Of Roadside Forest Management To Reduce Utility Infrastructure Vulnerability, Danielle Kloster

Doctoral Dissertations

During major storm events in 2011 and 2012 (Tropical Storm Irene, Storm Alfred, Hurricane Sandy), approximately 90% of power outages in Connecticut were caused by falling trees or limbs. The storms brought attention to the vulnerability of utility infrastructure and, in response, more focus was placed on vegetation management. People play a role in each step of the vegetation management process: government and utility officials planning for infrastructure resilience, tree crews conducting the management, and property owners mediating management by consenting or objecting to proposed tree pruning and removal. My research explored the human dimensions of roadside vegetation management. Media …

Exploiting Memristors For Compressive Sensing Applications, Fengyu Qian

Doctoral Dissertations

The amount of sensory signal is increasing dramatically as we’re stepping into the era of Internet of Things (IoT). Compressive Sensing (CS), feature as Sub-Nyquist sampling rate and low complexity sensing architectures, is very promising for these kinds of applications where resources are restricted. Through applying this novel compression technology, data size of sensory signals are largely compressed such that it is very efficient within the signal processing, data transmitting and storage processes. Compared to conventional codec method, CS technique requires less hardware resources and achieve lower power consumption within sensor nodes.

However, there are several bottle-necks of existing compressive …

Fabrication, Characterization And Application Of Zinc Oxide And Zinc Magnesium Oxide Nanostructures, Abdiel Rivera

Doctoral Dissertations

Zinc oxide is a wide bandgap semiconductor with relatively large exciton energy of 60 meV, and longitudinal optical phonon energy of 72 meV. ZnO can be grown in any nanostructure (nanoribbons, nanowires, nanorods, films, core-shell, among others), under any growth condition (metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxial (MBE), hydrothermal, radio-frequency sputtering, sonochemical, etc) to be implemented in a variety of applications. For instance, by adding Mg to ZnO, the energy band separation increases and shift to a lower wavelength. Using ZnMgO, in the form of vertical nanowires, can improve the resolution of solar-blind UV-detectors. Nevertheless, the sol-solubility of …

Inequity And Resistance: Latinx Students And The College Readiness Process, Israel Velez

Doctoral Dissertations

This qualitative study used Youth Participatory Action Research and Community Cultural Wealth Framework (Yosso, 2005) to understand how Vamos a La Universidad (VALU), a high school bilingual college preparation program, impacts first-generation Latinx ninth grade students’ community cultural wealth and understanding about college. This study expands our understanding of how Latinx students interpret the college preparation process after participating in a college preparation program and emphasizes the importance of students’ cultural background and social contacts in their college readiness process. This study proposes new initiatives to add to Latinx students’ college learning process and increase the students’ interest in continuing …

Impact Of Mixer Design On Lean Direct Injection Combustion, Xiao Ren

Doctoral Dissertations

To reduce the environmental impact of aviation, lean direct injection (LDI) combustion is being pursued to achieve very low emissions. LDI utilizes multi-point mixers to achieve low NOx emissions and satisfactory combustion stability. Since the performance of LDI directly depends on design parameters of each single LDI mixer, a series of fundamental investigations into lean-dome-relevant pilot combustor devices are conducted herein. A single LDI mixer typically uses swirlers with converging venturi and diverging flare to generate swirling flows, which facilitate mixing in the combustor dome. This dissertation aims to investigate the impact of LDI mixer design parameters, including swirler vane …

Cybersecurity Games: Mathematical Approaches For Cyber Attack And Defense Modeling, Mohammad Hadi Valizadeh

Doctoral Dissertations

Cyber-attacks targeting individuals and enterprises have become a predominant part of the computer/information age. Such attacks are becoming more sophisticated and prevalent on a day-to-day basis. The exponential growth of cyber plays and cyber players necessitate the inauguration of new methods and research for better understanding the "cyber kill chain," particularly with the rise of advanced and novel malware and the extraordinary growth in the population of Internet residents, especially connected Internet of Things (IoT) devices.

Mathematical modeling could be used to represent real-world cyber-attack situations. Such models play a beneficial role when it comes to the secure design and …

Three Essays On Fisheries Economics, David T. Suh

Doctoral Dissertations

Archival abstract submitted

Investigation Of Antimicrobial Secondary Metabolites From Bacterial Isolates Associated With The Hawaiian Bobtail Squid (Euprymna Scolopes), Samantha Gromek

Doctoral Dissertations

A beneficial host-microbe symbiosis that has been extensively studied is the association of the Hawaiian bobtail squid, Euprymna scolopes, with the bioluminescent bacterium Vibrio fischeri in the squid light organ. Our research used the Hawaiian bobtail squid as a model system to begin investigating the functional role of secondary metabolites associated with the accessory nidamental gland (ANG), a reproductive organ present in sexually mature female cephalopods, and jelly coat (JC) bacteria. Using this model organism, prior research supports that bacteria from the ANG are deposited into the egg JC. Subsequently, the JC bacteria produce compounds as a chemical defense …

Novel Cryptographic Authentication Mechanisms For Supply Chains And Openstack, Reza Rahaeimehr

Doctoral Dissertations

In this dissertation, first, we studied the Radio-Frequency Identification (RFID) tag authentication problem in supply chains. RFID tags have been widely used as a low-cost wireless method for detecting counterfeit product injection in supply chains. We open a new direction toward solving this problem by using the Non-Volatile Memory (NVM) of recent RFID tags. We propose a method based on this direction that significantly improves the availability of the system and costs less. In our method, we introduce the notion of Software Unclonability, which is a kind of one-time MAC for authenticating random inputs. Also, we introduce three lightweight constructions …

Sense Of Belonging And Racial Diversity At The U.S. Service Academies, Leah Pound

Doctoral Dissertations

On college campuses, access does not equal inclusion as students of color have to navigate through a predominately White space as they struggle to feel like they belong (Jack, 2019). This dissertation focuses on racial experiences and belonging within a total institution (Goffman, 1961): the U.S. service academies, colleges that are part university and part military. Across three separate papers, I explore the institutional factors that impact the disparity between Black and White students’ belonging. In Chapter 1, I apply Allport’s contact theory (1954) alongside the concept of relative deprivation (Stouffer, 1949) to systematically compare the experiences of Black and …

Application Of Machine Learning To Enhance The Diagnostic Utility Of Interictal High Frequency Oscillations In Drug-Resistant Epilepsy, Stefan Sumsky

Doctoral Dissertations

There is a need for novel biomarkers to aid in the clinical treatment of epilepsy and improve the understanding of seizure generation and the seizure onset zone (SOZ). High frequency oscillations (HFO) are a promising biomarker with the potential to fill this role, but early efforts to apply them have fallen short of clinical quality tools and validity and application of their association with seizure have not been fully explored. This study will advance the understanding and application of HFO to the clinical setting in three ways. First, the relevance of HFO to SOZ and their utility for SOZ localization …

Perceptions Of Physics Teachers In Singapore About Curriculum Sequencing, Lay Lean Fong

Doctoral Dissertations

Curricular sequencing is central to instruction design and enactment. If carefully planned for, the order of topics to be taught would determine how the fundamentals of the discipline can be presented and introduced to learners, in a sequence that eases them into more complex ways of reasoning and thinking about the domain. These sequences or learning progressions often reflect the experts’ conceptual schemas of the discipline and are conceived as strategic models for instruction (Duschl et al., 2011).

The varied findings from current research on learning progressions underscore the complexity of teaching and learning, and imply that even ‘well-crafted’, standards-based, …

A Descriptive Study Of Religious Engagement And The Internalization Of Religious Beliefs Of 12th-Grade High-School Students Who Attended Kairos Retreats And Fourth-Day Follow-Up Activities As Juniors In Five U.S. Jesuit All-Male High Schools, Chris Miller

Doctoral Dissertations

The Kairos retreat is popular among upperclassmen at Jesuit high schools across the nation. Kairos, or “God’s Time,” is a religious retreat grounded in Christian incarnational theology and the overall theology of the retreat is love in action, and its participants are challenged to “live the fourth” day, which becomes the never-ending day. Even though there has been a trend across the nation in the first decade of the 21st century within Jesuit high schools to move the retreat to the junior level, there is no empirical research examining the spiritual effects on the individual student of moving the Kairos …