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 …

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 …

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

Doctoral Dissertations

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

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

Doctoral Dissertations

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

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

Doctoral Dissertations

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

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

Doctoral Dissertations

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

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

Doctoral Dissertations

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

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

Doctoral Dissertations

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

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

Doctoral Dissertations

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

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

Doctoral Dissertations

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