Digital Commons Network^™

An Investigation Of Unsteady Thermal Exchange Processes In Geothermal Heat Exchangers, Ganesh Ravi Shanker

Doctoral Dissertations

“Geothermal heat exchangers, has become one of the highly recognized non conventional heat exchangers as they utilize renewable energy source earth to initiate the thermal energy transfer. However, these heat exchangers suffer from a expensive installation cost due to their conservative design model, thereby facilitating the need to identify and improve the design. In this dissertation, three gaps, which identifies improvement over conservative design were investigated, to assess the heat exchanger performance. In the first approach, borehole thermal and geometrical properties were investigated keeping the outlet leg of the heat exchanger as adiabatic, which neglects the thermal short-circuiting between the …

Development Of High-Performance Hydrogels, Buddhabhushan Salunkhe

Doctoral Dissertations

Here, we present a systematic approach to design robust hydrogel compositions. The goal was to achieve excellent properties to open up new opportunities in especially two challenging applications not previously well-served by hydrogels.

The first part of this research will discuss the systematic screening of polymers for their hydrothermal stability under brine, acidic, neutral, and basic pH conditions followed by novel designs of hydrogel compositions. Certain hydrogel compositions withstand temperatures of up to 150 °C for more than 24 months in high salinity brines. This novel hydrogel composition fills a technology gap between the existing polyacrylamide-based preformed particle gels (PPGs) …

Modeling For Off-Chip High-Speed Designs, Siqi Bai

Doctoral Dissertations

”Signal integrity (SI) and power integrity (PI) are essential for datacenter application. A typical datacenter rack consists of a switch on the top of the rack, servers, and storage units. Three SI/PI related problems for datacenter application are analyzed in this research.

The first topic is analysis on power via induced Quasi-quarter-wavelength resonance to reduce crosstalk. Using an analytical model and 3D full-wave simulation models, a physical explanation for the unexpected resonance in the differential signal pairs is proposed. Considering the difficulty in changing the pin map of the IC-package, several PCB layouts to eliminate the power via induced quasi-quarter-wavelength …

Designing Transition Metal Chalcogenides Electrocatalyst Surfaces For High-Efficiency Water Oxidation, Umanga De Silva

Doctoral Dissertations

”The rising demand for energy security and reducing fossil fuel dependence has prompted researchers to search for a clean, sustainable, and efficient energy generation system with low environmental impact. Water electrolysis has been identified as one of the most important processes satisfying the above needs to generate hydrogen as a clean fuel. Two half-cell reactions of oxygen evolution reaction (OER) at the anode and hydrogen evolution reaction (HER) at the cathode comprise the main process of water electrolysis. However, the oxygen evolution reaction is the most crucial step for efficient water splitting. Traditionally, metal oxides have been utilized as catalysts …

Secure Data Sharing In Cloud And Iot By Leveraging Attribute-Based Encryption And Blockchain, Md Azharul Islam

Doctoral Dissertations

“Data sharing is very important to enable different types of cloud and IoT-based services. For example, organizations migrate their data to the cloud and share it with employees and customers in order to enjoy better fault-tolerance, high-availability, and scalability offered by the cloud. Wearable devices such as smart watch share user’s activity, location, and health data (e.g., heart rate, ECG) with the service provider for smart analytic. However, data can be sensitive, and the cloud and IoT service providers cannot be fully trusted with maintaining the security, privacy, and confidentiality of the data. Hence, new schemes and protocols are required …

High Throughput Analysis To Study Emerging Pollutants And Nanoparticle Fate In Biological Systems, Xiaolong He

Doctoral Dissertations

”The increasing applications of emerging and fugitive contaminants (EFCs) and engineered nanoparticles (ENPs) attract significant research interest for their potential risks to human health and the environment. In order to assess the health risks of these emerging contaminants, rapid and reliable analytical methods to measure the concentrations and fates of these contaminants are imperative. This dissertation focuses on the developments of advanced analytical methods and their applications to study those emerging contaminants in crop plant and simulated gastric fluid (SGF). Three types of mass spectrometry based methodologies have been developed, one is freeze-thaw/centrifugation extraction followed by high performance liquid chromatography …

Prediction Of Deflection Of Helical Anchors Under Load, Andre Stephen Hawks

Doctoral Dissertations

”As the sophistication of modern structural design methods has improved over time, the ability to accurately predict and model foundation stiffness has become increasingly more important. In complicated structural systems with deep foundations, correct calculation of the distribution of load and serviceability requires proper modeling of axial load-deflection characteristics. To keep pace with advances in structural analysis, there is much need for more practical and scientific work on the load-deflection prediction of deep foundations including Helical Anchors.

The load-settlement mechanism of an axially loaded helical pile is a complex soil-structure interaction problem influenced by helical pile dimensions, installation method, and …

Development Of Intelligent Stimuli-Responsive Biomaterials And Nanodevices, Shuo Yang

Doctoral Dissertations

"Structural DNA nanotechnology utilizes DNA molecules as building blocks to fabricate ordered artificial nanostructures at the molecular level. Among all DNA-based techniques, DNA origami has been considered as one of the most powerful tools for constructing artificial nanostructures with excellent programmability and addressability. Currently, most DNA origami nanostructures are static and do not have the ability to response to environmental stimulation. The development of environmental-responsive DNA origami nanostructures is a critical step towards the realization of intelligent dynamic DNA origami-based nanodevices. This research focuses on the design and fabrication process of both static and dynamic DNA origami nanostructures and their …

Additively Manufactured Metallic Cellular Structures, Okanmisope Aziel Fashanu

Doctoral Dissertations

"Cellular structures are lightweight structures with excellent mechanical, thermal, and acoustic properties. They offer promise in a series of applications, including lightweight applications, sandwich cores, mechanical damping, acoustic absorption, strain isolation, and thermal management. The manufacturing of these complex cellular structures is expensive and time-consuming, which hinders the adoption of these structures in many industries. Advancement in manufacturing technologies, such as additive manufacturing (AM), however, have changed this. AM allows for the rapid and less expensive manufacturing of complex cellular structures. This work aimed to investigate the performance of additively manufactured cellular structures for lightweight and sandwich core applications. In …

Identification Of Neuromarkers Using Structural And Functional Neuroimaging, Sreevalsan Sanathanan Menon

Doctoral Dissertations

"One of the grand challenges in science is understanding the human brain. Recent advances in magnetic resonance imaging have opened unmatched opportunities to demystify neural circuitry. In this research, the spatially and temporally complex neuroimaging data were used to identify neuromarkers that aids in quantifying a brain’s health. In the first part, a comparison of static and dynamic functional connectivities was made to study their efficacies in identifying intrinsic individual connectivity patterns. Results show that the intrinsic individual connectivity pattern can be used as a ‘fingerprint’ to distinguish among and identify subjects and their biological sex and is more accurately …

Prediction Of Battery Health Dynamics, Damola Martins Ajiboye

Doctoral Dissertations

"The successful market penetration of lithium-ion batteries in the last 30 years has ushered in a new dawn in energy applications. Notwithstanding their widespread use, lithium-ion batteries are affected by a plethora of fundamental issues — safety, cycle life, performance, and cost. In this work, advanced modeling techniques are developed to tackle some of these issues. This dissertation is subdivided into four parts, the first is introduction while the remaining are dedicated to the development of computational techniques for predicting battery health dynamics.

In the second part of this work, we developed fast and accurate algorithms for modeling essential battery …

Assessment Of Rib Failure Mechanisms Using Discontinuum Mechanics Based Modeling Approach, Maurice Nuonituo Sunkpal

Doctoral Dissertations

"Coal mine rib failures are major safety and health challenge for coal mines worldwide. The need for clear procedures to evaluate mine rib behavior and to provide an efficient, reliable, and consistent rib control protocol is needed. Understanding coal rib geomechanics is essential for improving rib stability and eliminating fatality and injury trends due to rib failures. This knowledge is also vital to determine support requirements.

The rib control practices used in the 21st Century in most countries originated in roof control techniques. Understandably, applying roof control methods to coal rib does not yield desirable results. The geology of structures …

Studying The Effects Of New Additive Materials For The Improvement Of The Capacity And Cycle Life Performance Of The Lead-Acid Battery, Julian Kosacki

Doctoral Dissertations

"Lead-acid batteries are an established technology with nearly 99% recyclability; however, lead-acid batteries produce only 40% of their theoretical capacity due to poor active mass utilization and PbSO4 pore blockage, and the longevity of the batteries is hampered by secondary reactions during the cycle life such as corrosion and gassing.

Lead-acid batteries were investigated and improved through several different approaches: an alternative electrolyte to mitigate secondary reactions, graphite additives to improve positive active mass (PAM) utilization, and dispersant additives to help the industrial pasting process.

The thermodynamics and chemical reactions of a commercial electrolyte replacement called Tydrolyte^TM were investigated …

Sources Of Quality Uncertainty In Laser Powder Bed Fusion Metal Additive Manufacturing, Zachary Young

Doctoral Dissertations

"Powder based additive manufacturing (AM) exhibits tremendous uncertainties, where variations in build quality is present despite utilizing similar build processing parameters. First, this work reports the features and formation mechanisms of five unique types of spatter during the LPBF process by in-situ high-speed, high-energy x-ray imaging. The unique physical characteristics of spatter are determined. The effect of laser scan speed and laser power on spatter formation, ejection, and mitigation are determined. Second, this work addresses the uncertainty challenge by identifying the sources of uncertainty in SLM by in-situ characterization due to variations from the additive manufacturing processing parameters needed for …

Layer-To-Layer Feedback Control For Direct Energy Deposition Additive Manufacturing, Michelle Gegel

Doctoral Dissertations

"Additive manufacturing (AM) has garnered much attention in recent years, some calling it the fourth industrial revolution. It was first used to create rapid prototypes, although recent efforts have been made to advance the technology towards production of functional parts. This requires advancement in the materials used in AM, as well as the ability to produce quality parts repeatably. More specifically, direct energy deposition (DED) of metal powders is a process capable of producing and repairing parts with complex geometries; however, it is not widely used in industry due to challenges with quality control. In this process, metal powder is …

Novel Synthetic Methods And Applications Of Porous Materials: Aerogel Foams, Metallic Aerogels, Amorphous And Graphitic Carbon Aerogels, Rushi Soni

Doctoral Dissertations

"We report novel methods for the synthesis of porous materials such as polymeric aerogel foams, pure metallic aerogels, amorphous and graphitic carbon aerogels, and their applications. I. Polyurethane based aerogel foams were synthesized with an aliphatic triisocyanate and ethylene glycol through a pressurized (7 bar) sol-gel method. The foam-like structure is prepared without any chemical foaming agents or templates, resulting in less expensive, more efficient, readily adaptable, and environmentally friendly process. Those materials exhibited lower thermal conductivity (by 25%) and higher oil adsorption capacity (by 36% w/w) than their corresponding aerogels. II. Monolithic, pure metallic Co(0) aerogels were synthesized from …

Non-Academic Support Math Faculty Members Provide In Developmental Accelerated And Corequisite Support Courses In California Community Colleges, David Vakil '92

Doctoral Dissertations

To guide practitioners of rapidly evolving developmental math reform in community colleges, this study surveyed California community college math faculty who taught accelerated developmental courses or corequisite support courses. The survey was conducted during the early implementation phase of both course types, during spring and fall 2018 terms. This study measured faculty’s self-reported provision of forms of non-academic support, frequency of implementation, and reasons faculty believed the support would help students succeed. The literature review guided grouping non-academic support into five forms: nurturing, helping students’ motivation, providing a growth mindset theory of intelligence, helping provide social integration, and helping to …

Investigating The Self-Efficacy Awareness Of Black Female Technology Leaders, Marie Roberts De La Parra

Doctoral Dissertations

Black female technology leaders lack leadership opportunities, which affects their self-efficacy and is a crucial concern. Self-efficacy is based on the concept that an individual’s belief in what they can achieve influences their actions and how much effort they invest in the selected action. Self-persuasion can provide high or low self-satisfaction as a determinant for creating incentives for success or failure and converting thoughts and emotions to actions. Limited research has investigated the mindset, the thought patterns, and the self-belief undertaken by Black females in the world of technology. Despite limited amounts of research, data suggest that Black female leaders …

Replanting A Wild Seed: Black Women School Leaders Subverting Ideological Lynching, Whitneé Louise Garrett-Walker

Doctoral Dissertations

Much race-based educational research is focused on teachers interrupting systems ofoppression in their classrooms, through methods such as curriculum and instruction, and preparing students to engage in the world (Alston, 2012; Bertrand & Rodela, 2017; Carpenter & Diem, 2013; Gooden & Dantley, 2012; Furman, 2012). I intentionally focus my attention on school leadership because while all stakeholders are responsible for maintaining school culture, as school leaders it is our responsibility to create conditions where the work of enacting social justice is expected in our schools. There continues to be a gap in educational research that deeply examines this level of …

Equity In Language Programs: Revitalizing Indigenous Languages In Secondary School In Anchorage, Alaska, Betsy Watson (Paskvan)

Doctoral Dissertations

"Wherever there is a situation of domination and subordination between any two groups, whatever their color or religion, this will be reflected in the language relationship: one language dominating the other." —wa Thiong’o (2011, p. 244) Indigenous language and culture education efforts in Anchorage, Alaska are limited by omissions in the public school curriculum. One of the many reasons for this is that policy makers believe there is not sufficient demand for Alaska Native languages in public schools. Further there is a perceived lack of language teacher-leaders and experts to build programs for Alaska Native language instruction. This study used …

Voices Of Chinese International Students: A Critical Understanding Of Their Experiences In The United States, Shudao Zhang

Doctoral Dissertations

This qualitative study investigated the lived experiences of Chinese international students in the United States. It focused on their academic learning, sociocultural relationship, self-reflection and their identity development. This study addressed the active role of international students as participants who can manage cross-cultural difficulties as well as make new interpretations of their life in the host country. This study adopted three theoretical frameworks - transnationalism, transformative learning theory, and social identity theory - to present the intricate educational and social context in study abroad. Through in-depth interviews with eight Chinese students at a private university in California, together with the …

Pilipinx Radical Imagination: Healing And Visioning In Our Process Of Becoming, Anthony Abulencia Santa Ana

Doctoral Dissertations

There are estimated 10.4 million Filipinos living or working abroad primarily in the Middle East, Europe, Canada, and the United States searching for a better life for themselves and their families (Commission on Filipino Overseas, 2013). Due to economic motivation, assimilating to the host country's culture, values, and traditions is an act of survival. While the majority of the research has focused on the domestic workers’ experience, rarely has there been a study focusing on Filipinos in the diaspora positive contributions to the host country and their Pilipinx Radical Imagination. As a result, the purpose of this qualitative study is …

Effect Of Transcendental Meditation On The Social Emotional Well-Being Of Bilingual Teacher Leaders, Margaret Peterson

Doctoral Dissertations

Teaching is one of the most stressful professions in the human service industry (Curry & O’Brien, 2012; Fisher, 2011; Herman et al., 2018; Martin, et al., 2012; Montgomery & Rupp, 2005; Schonert-Reichl, 2017). Stress and burnout have been shown to contribute to the attrition of teachers (Darling-Hammond, 2001; Fisher, 2011; Johnson et al., 2005; Klingbeil & Renshaw, 2018; Winchester, 2020). While there are shortages across many disciplines, the bilingual teacher shortage has been documented as the most severe (Swanson & Mason, 2017). This study utilized Community Cultural Wealth as a theoretical framework to investigate how bilingual teacher leaders experience stress …

The Ignatian Pedagogical Paradigm As A Critical Theoretical Framework To Enhance Teachers' Professional Identity In Diverse Context, Lourdu Sunder Reddy Mummadi

Doctoral Dissertations

Several previous studies have revealed the need and necessity to enhance teachers’ perception of professional identity (PI) as it impacts their feeling of satisfaction and effectiveness in the classroom and their persistence in the profession (Moore & Hofman, 1988; Sanders et al., 1997; Hanushek, 2011). According to some scholars, teachers’ professional identity includes teachers’ understanding of themselves and the factors impacting their teaching (Beijaard et al., 2000; Sachs, 2005; Day, 2018). The danger is that if a teacher lacks self-knowledge, they may be influenced by unexamined beliefs, stereotypes, cultural myths, and, most importantly, fears that affect the ways they relate …

A Critical Feminist Case Study Of The Northern California Cherry Blossom Queen Program, Alison Kepola Nishiyama-Young

Doctoral Dissertations

Asian American women are chronically underrepresented in leadership positions in almost every sector including higher education, government, private, and non-profit (Youngberg et al., n.d.). Many researchers have suggested the need for more leadership development programs specifically designed to support the needs of Asian American women (Akutagawa, 2014; Canlas, 2016; Gee & Peck, 2015; Lin, 2007; Youngberg et al., n.d.). Though there are a number of leadership programs geared towards Asian Americans, there are very few that cater to Asian American women explicitly. Historically, cultural pageant programs in the Asian American community have played this role and one such program is …

Fabrication Of 304l Stainless Steel And Aluminum Parts By Laser Foil Printing And Process Automation, Chia-Hung Hung

Doctoral Dissertations

"This work presents research conducted on a novel metal additive manufacturing process, called Laser Foil Printing (LFP), to fabricate metal parts with various geometries layer by layer using metal foil as the feedstock. To investigate the processability and characteristics of LFP for fabricating metal parts, the materials included 304L stainless steel and Al-1100 aluminum alloy. The LFP process parameter windows for both 304L and Al-1100 were determined, and the optimal process parameters with stable formation of the melt pools were selected to fabricate dense metal parts. The microstructure and properties of LFP-fabricated parts were characterized and analyzed using tensile testing, …

Collaborative Planning In The Construction Industry: A Holistic Framework For Assessing Collaborative Planning Practices And Predicting Project Performance, Amr Elsayegh

Doctoral Dissertations

"The fragmentation of the construction industry prompted developing novel methods such as collaborative planning, lean construction, advancements in technology, integrated project delivery, and relational contracting. Current research focused on specific facets of collaborative planning without presenting a comprehensive analysis of its factors. As such, the goal of this research is to develop a holistic framework that studies and evaluates collaborative planning practices in construction projects. This research offers significant addition to the body of knowledge through various theoretical and practical contributions. In relation to that, this research developed a comprehensive framework by (1) identifying a comprehensive list of factors influencing …

Instrumentation, Modeling, And Sound Metamodeling Foundations For Complex Hybrid Systems, Natasha Amelia Jarus

Doctoral Dissertations

Many of our critical infrastructures, from power grids to water distribution networks, are complex hybrid systems that use software to control their non-trivial physical dynamics. These systems must be able to capably serve their purpose, while also being reliable, dependable, safe, secure, and efficient. Representation and analysis of these features requires the creation of several distinct models. These models may encode design goals or be derived from collected instrumentation data, reflecting both how a system ought to operate and how it does operate. It is essential to ensure that all of these models consistently and accurately describe the same system. …

Composition As Bodily Rhetoric: A Multimodal Understanding Of Student-Athlete Literacy Practices, Samantha Ellyn Donnelly

Doctoral Dissertations

“Composition as Bodily Rhetoric: A Multimodal Understanding of Student-Athlete Literacy Practices” examines aspects of the lives, scholarly identities, and different writing that student-athletes engage in while on the field for their sport and off the field in their academics. Utilizing embodied rhetoric in communication and forms of technical writing, I challenge the notion that academics and athletics are working toward contradictory aims. Through examining the embodied learning within the writing process and drawing connections between writing studies and sports discourse, my work illuminates the complexities of the composing processes of student-athletes and examines how they can bring these advanced composing …

Genomic And Physiological Bioremediation Characteristics Of The Actinobacteria Frankia, Erik Swanson

Doctoral Dissertations

Introduction: Frankia is a genus of symbiotic, nitrogen fixing actinobacteria found in the soil and root tissue of actinorhizal plants throughout the world. Both Frankia and actinorhizal plants are resistant to a wide range of environmental and chemical stresses including heavy metals, high salinity, and drought. This makes Frankia and the actinorhizal symbiosis an interesting candidate for bioremediation applications. However, the microbial community found in the actinorhizal rhizosphere and surrounding soil has been implicated in some of the symbiotic and resistance traits attributed to Frankia. This necessitates thorough investigation of the genomic and genetic components of any bioremediation traits possessed …