Digital Commons Network^™

Sparse Methods For Blind Source Separation Of Frequency Hopping Rf Sources, Anushreya Ghosh

Dissertations

Blind source separation (BSS) is performed on frequency hopping (FH) sources. These radio frequency (RF) signals are observed by a uniform linear array (ULA) over a Spatial Channel Model (SCM) in four different propagation environments: (i) line-of-sight (LOS), (ii) single-cluster, (iii) multiple-cluster, and (iv) LOS with interference. The sources are spatially sparse, and their activity is intermittent and assumed to follow a hidden Markov model (HMM). BSS is achieved by utilizing direction of arrival (DOA) of the sources and clusters. A sparse detection framework is applied to obtain estimates of the sources' FH and DOA patterns. The solutions are binned …

Cu/Bnx Catalysts For Electrocatalytic Reduction Of Nitrogen And Nitrate Waste, Siming Huo

Dissertations

Ammonia (NH₃) is one of the most important chemicals to the whole human society. The invention of the Haber-Bosch process enabled the industrial production of NH₃. However, owing to the high capital costs of the centralized plant and the equipment and the negative environmental impact, it is no longer suitable for today's needs of human development. As a result, there is an urgent need to investigate sustainable approaches for ammonia production. Among those reported studies, nitrogen reduction (NRR) and nitrate reduction reaction (NO₃RR) are considered applicable in the future. However, after decades of studying …

Ai Approaches To Understand Human Deceptions, Perceptions, And Perspectives In Social Media, Chih-Yuan Li

Dissertations

Social media platforms have created virtual space for sharing user generated information, connecting, and interacting among users. However, there are research and societal challenges: 1) The users are generating and sharing the disinformation 2) It is difficult to understand citizens' perceptions or opinions expressed on wide variety of topics; and 3) There are overloaded information and echo chamber problems without overall understanding of the different perspectives taken by different people or groups.

This dissertation addresses these three research challenges with advanced AI and Machine Learning approaches. To address the fake news, as deceptions on the facts, this dissertation presents Machine …

Mapping Programs To Equations, Hessamaldin Mohammadi

Dissertations

Extracting the function of a program from a static analysis of its source code is a valuable capability in software engineering; at a time when there is increasing talk of using AI (Artificial Intelligence) to generate software from natural language specifications, it becomes increasingly important to determine the exact function of software as written, to figure out what AI has understood the natural language specification to mean. For all its criticality, the ability to derive the domain-to-range function of a program has proved to be an elusive goal, due primarily to the difficulty of deriving the function of iterative statements. …

Importance Of Vegetation In Tsunami Mitigation: Evidence From Large Eddy Simulations With Fluid-Structure Interactions, Abhishek Mukherjee

Dissertations

Communities worldwide are increasingly interested in nature-based solutions like coastal forests for the mitigation of coastal risks. Still, it remains unclear how much protective benefit vegetation provides, particularly in the limit of highly energetic flows after tsunami impact. The present thesis, using a three-dimensional incompressible computational fluid dynamics model with a fluid-structure interaction approach, aims to quantify how energy reflection and dissipation vary with different degrees of rigidity and vegetation density of a coastal forest.

In this study, tree trunks are represented as cylinders, and the elastic modulus of hardwood trees such as pine or oak is used to characterize …

Influence Of Material Properties On Granules Prepared By Dry Co-Rotating Twin Screw Extrusion And Counterrotating Batch Mixing, Afstathios Steve Pafiakis

Dissertations

Recently, the pharmaceutical industry has shown interest in continuous granulating technology because of the flexibility it offers as an option that bypasses the costly scale-up process associated with batch manufacturing. However, the granulation mechanism(s) using twin screw co-rotating hot melt extrusion (HME) has not been fully explored, and it is not yet well understood. This leads to costly experiments during development and process reliability problem in commercial manufacturing. The main objective of this dissertation is to increase the mechanistic understanding of the twin screw granulation process of systems containing an active pharmaceutical ingredient (API) and a polymer excipient. This is …

Pbm And Dem Simulations Of Large-Scale Closed-Circuit Continuous Ball Mill Of Cement Clinker, Nontawat Muanpaopong

Dissertations

Cement milling is known to be inefficient and energy-intensive. Thus, even small improvements in cement milling's performance could significantly reduce operation costs. This dissertation aims to develop a simulation tool for dry milling and generate a fundamental process understanding, which enables process optimization. To this end, a true unsteady-state simulator (TUSSIM) for continuous dry milling is developed and applied to model various processes: (a) open circuit continuous mills, (b) closed-circuit continuous mills, and (c) vertical roller mills. TUSSIM is based on the solution of the cell-based population balance model (PBM) for continuous milling, which consists of a set of differential …

Continuum Modeling Of Active Nematics Via Data-Driven Equation Discovery, Connor Robertson

Dissertations

Data-driven modeling seeks to extract a parsimonious model for a physical system directly from measurement data. One of the most interpretable of these methods is Sparse Identification of Nonlinear Dynamics (SINDy), which selects a relatively sparse linear combination of model terms from a large set of (possibly nonlinear) candidates via optimization. This technique has shown promise for synthetic data generated by numerical simulations but the application of the techniques to real data is less developed. This dissertation applies SINDy to video data from a bio-inspired system of mictrotubule-motor protein assemblies, an example of nonequilibrium dynamics that has posed a significant …

V-Shaped Temperature Dependences And Pressure Dependence Of Elementary Reactions Of Hydroxyl Radicals With Several Organophosphorus Compounds, Xiaokai Zhang

Dissertations

Organophosphorus compounds have brought increasing attention since they are widely used as flame-retardants, which can take effect in combustion via reactions with reactive radicals. These reactions are influenced by variables such as temperature and pressure, resulting in a temperature and pressure dependent rate constant. Studying this reaction kinetics has great importance in both combustion reaction and atmospheric environment.

This study is focused on kinetics of several elementary reactions of combustion importance. The kinetics of hydroxyl radicals were studied using pulsed laser photolysis coupled to transient UV-vis absorption spectroscopy over the 295 - 837 K temperature range and the 1 - …

Development Of Non-Viral Nano-Carriers For Gene Delivery And Covid-19 Vaccines, Zhongyu Li

Dissertations

Gene therapy is one of the most promising medical fields with the potential to effectively advance the treatment of difficult diseases by producing therapeutic proteins or repairing defective gene sequences. However, gene therapy presents severe challenges in delivery including renal clearance, phagocytosis, enzymatic degradation, protein absorption, and cellular internalization barriers, which have been barriers for translation into the clinic. Naked nucleic acids, with their intrinsic negative charge, electrostatically repulse the anionic cell membrane, preventing cellular uptake. Also, they are considered foreign genetic material when introduced into the body and are rapidly cleared by the reticuloendothelial system or degraded by nucleases, …

Development Of Novel Nanocarbon Based Materials And Membranes With Enhanced Biocidal Capabilities For Clean Water Generation, Indrani Gupta

Dissertations

Water scarcity is one of the major challenges facing humanity today, driven by population growth, economic development, and dietary shifts towards more water-intensive animal products. To address this issue, efficient water resource management and recycling of wastewater are essential. However, around 80% of wastewater globally is discharged into water bodies without treatment, posing a risk to ecosystems and human health. Pathogens, or harmful microorganisms, are a primary cause of water impairment and the transmission of waterborne diseases, leading to increased mortality rates. Traditional methods of treating pathogens involve the use of radiation or chemical disinfectants. Nonetheless, these methods have drawbacks, …

Large-Scale And Meso-Scale Ion Dynamics Of The Near-Earth Space Environment, Matthew Cooper

Dissertations

The mechanisms whereby low energy (order of lOs to 100s of eV) solar wind and ionosphere sourced particles are accelerated to high energy (order of 10s to 100s keV) in the Earth's magnetosphere are a trending research topic due to impacts on radiation belt populations, coupling to the high-latitude ionosphere, and energy budgets for collision-less plasma in dipole fields. Ultra-low frequency (ULF, order of 1-100 mHz) Alfven waves observed in the nightside inner magnetosphere during geomagnetic activity are one such acceleration mechanism. Several source processes for these waves, including the micro-scale drift-mirror mode, have been previously suggested but observational evidence …

Design, Synthesis, Biological And Computational Studies Of Flavonoid Acetamide Derivatives, Daniel Kasungi Isika

Dissertations

Flavonoid compounds (FC) have extensive biological applications through potent antimicrobial, anti-inflammatory, anticancer, antidiabetic, and antioxidant properties. These applications are nevertheless limited by low bioavailability, poor aqueous solubility, enzymatic degradation, rapid metabolism, and fast body clearance. FC show unique structure-activity relationships (SARs) essential in assessing and mitigating the prevalent challenges impeding their applications. These challenges can be addressed by structural modification of the FC through functionalization of the phenolic rings, modification of the ketone group, and modification of the phenolic hydroxyl groups with bioisosteres.

The objectives of this work are to (i) design and synthesize novel flavonoid acetamide derivatives (FADs) and …

Improving Recognition Of Depression Among The Adult Patients In Psychiatric Settings, Jane A. Ferraris

Dissertations

Depression rating scales may improve depressive symptom identification. At the project site, there was no consistent process for determining patients' depressive symptoms, so an evidence-based solution was sought. The purpose of this quality improvement project was to determine if the translation of Dunlop et al.'s research utilizing the Hamilton Depression Rating Scale-6 (HAMD-6) would impact the rate of identification of depressive symptoms and referrals to psychology for Cognitive Behavioral Therapy (CBT) among adult patients.

Molecular Simulations Of Mechanical Effects Of Adsorption In Gas And Liquid Phases, Alina Emelianova

Dissertations

Fluids adsorbing in nanoporous solids cause high pressures that affect the solids and the properties of the fluids themselves. This work explores the mechanical response of solids to the adsorption of gas and liquid. Chapter 1 outlines the current achievements in investigating the mechanical response of adsorbents to the adsorption process, specifically, the computational approaches to predict adsorption-induced deformation. Chapter 2 introduces the theoretical and computational methods employed in this work. Chapters 3-7 address the design and application of the computational techniques for such prediction in different systems: mesoporous silica, microporous zeolites, and metal-organic frameworks, and Chapter 8 focuses on …

Multi-Physics Numerical Simulation Of Corrosion And Service Life Evaluation Of Novel Reinforced Concrete Systems, Jin Fan

Dissertations

Durability challenges of reinforced concrete materials can shorten the service life and increase the carbon footprint of civil infrastructure systems. Novel alternative materials, such as high-performance fiber reinforced cementitious composites (HPFRCCs) and recycled aggregate concrete (RAC), offer an alternative to tradi-tional concrete materials by increasing the service life of infrastructure or reducing raw material consumption, thereby reducing the life-cycle carbon footprint. Due, in part, to a lack of robust numerical tools, predicting the durability response of these emerging cementitious materials has been insufficiently addressed. A time-dependent multi-physics modeling framework is proposed and adopted to investigate the chloride induced deterioration mechanisms …

Development Of Novel Hybrid Structures For Fast Dissolution Of Hydrophobic Drugs, Mohammad Saiful Islam

Dissertations

Nanomaterials have proven to be highly effective in the design and development of biomedicine. Complementary nanostructured hybrid particles show great promise in drug delivery applications. By improving functionalization, the physicochemical properties of the particles can be enhanced resulting in a high surface area, tunable hydrophilicity and porosity. These characteristics can provide a suitable environment for drug encapsulation, biocompatibility, high drug loading, and customizable release capabilities.

The formulation of drugs with poor water solubility faces multiple challenges, such as insufficient dissolution and inconsistent therapeutic efficacy, particularly when administered orally over an extended period. To overcome these challenges, some of the beneficial …

Oil Droplet Size In Subsea Oil Spills: The Experimental And Numerical Investigation, Ruixue Liu

Dissertations

Well blowout or oil leakage may occur during the offshore oil exploration activities. A great number of crude oils are released to the water environment in those accidents. Three sequent processes after the blowouts are commonly modelled: the droplet formation near the leakage or orifice, the transport of oil droplets in the water column, and the transport of oil slick with waves near the ocean surface. The oil droplet size distribution (DSD) serves as a vital role as it affects any further process, including chemical process such as biodegradation and physical process such as transport, which provides reference for assessing …

A Piezoelectric Gelatin Scaffold For Schwann Cell Induced Spinal Cord Repair, Scott Stratton

Dissertations

Spinal cord injury (SCI) results in axonal damage and consequently, functional loss for which there is no effective treatment at the present time. Axon growth across the injured site is needed to restore disruptive axonal circuitry, which is needed for recovery of lost function, but endogenous axon growth is poor. A Schwann cell (SC) transplant has shown promise in promoting axon growth in the injured spinal cord. Similarly, it has been shown that axons grow into biomaterial conduits especially when they are engineered to provide physical and biochemical growth-promoting cues. While both approaches are promising, their overall effect on axon …

Anxiety And Agitation In Adult Patients Admitted To An Emergency Room During The Covid-19 Pandemic, Doris L. Asombrado

Dissertations

Purpose: The purpose of this retrospective correlational study was to identify the relationship between COVID-19 status and the prevalence of anxiety-agitation with select sociodemographic and clinical characteristics in adults admitted to the ED during the pandemic (03/01/2020 through 12/31/2020).

Background: COVID-19 infections combined with the WHO and CDC recommendations to mitigate spread have had deleterious psychosocial and economic outcomes with the risk of subsequent COVID-19 related mental illness. Studies indicate one in three adults experience anxiety or depression.

Methods: This retrospective correlational study reviewed 2,572 psychiatric admissions from a Southern California ED during the pandemic from March 1, 2020 through …

Nursing Students' Intention To Work With The Elderly After Graduation: A Qualitative Study, Terri Murabito

Dissertations

America's population is aging. More than one in five Americans will be over 65 by 2030. These numbers are expected to challenge existing healthcare systems. The recruitment and retention of qualified, competent registered nurses (RNs) to care for this vulnerable population have become urgent. However, undergraduate baccalaureate nurses consistently report geriatric nursing as the least preferred clinical area to in work after graduation. To understand how graduating nurses discern their career intentions, a basic qualitative study was undertaken using Ajzen's theory of planned behavior as an underlying theoretical framework. The purpose of the study was to understand and interpret nursing …

Simulation And Improving Clinical Judgment In Prelicensure Nursing Students: A Mixed Method Approach, Lizabeth J. Reents

Dissertations

Simulation has been considered a valid pedagogy for health professionals in education and actual practice. Its proper execution is vital for proper assimilation of knowledge, skills, and attitudes within the pre-licensure students throughout their curricular journey. High fidelity and multi-patient simulation scenarios were employed for beginner fundamental and advanced senior level nursing students with significant quantitative increases in clinical judgment found between groups using an independent t test and the Lasater Clinical Judgment Rubric (LCJR). The LCJR is based upon the Tanner's clinical judgment model and has been extensively used throughout the world demonstrating solid reliability and validity. Qualitative responses …

Resistencia Indocumentada: Exploring The Lived Experiences Of Higher Education Undocumented Students In The San Diego-Tijuana Border Region, Adan Escobedo Sanchez

Dissertations

Undocumented students face myriad obstacles while attending higher education institutions that would deter them from completing their academic journeys. Furthermore, they are placed with a dual narrative that labels them as either dangerous or exceptional. This study explored the lived experiences of undocumented students in college in the San Diego-Tijuana border region to consider what factors have led to resilience and resistance in their academic journey. By understanding these factors, the research aimed to tackle the dual narrative that burdens undocumented students from the illegality as a master status they possess.

This study used narrative inquiry and a literature review …

Analysis Of One Secondary School's Support Systems For Aspiring First-Generation Latinx College Students: A Case Study, Tiffany Cunningham

Dissertations

U.S. Census Bureau Report (2020c) showed Hispanic students constituted 18.5% of the U.S. population, 36% attended higher education and only 14% completed postsecondary education. Research has shown Hispanic, specifically Latinx, students faced barriers in accessing higher education’s hidden curriculum, compounded by deficit beliefs about their language, culture, and lack of family involvement (Kiyama, 2018; C. Martinez & Mendoza, 2020). Additionally, first-generation college students require college readiness skills, including specialized knowledge about college and measurable and immeasurable skills shown to support student success in college (Chlup et al., 2018; Duncheon, 2021; Morley et al., 2021). Despite secondary school supports like college …

From Childhood Through Adulthood To Godhood: Trodding The African Ancestral Path To Become A Shining Star Of Ourstory, Salim Kenyatta

Dissertations

This autoethnographic narrative examines the importance of conceiving and sharing liberating stories, and participating in independent communal training processes that advance young African American males' psychosocial and mental development. To bring my analyses to light, I applied the foundational frameworks of African Worldview and Critical Race Theory to my research to uncover many of the influences that helped me evolve from boyhood (nescient) to manhood (laborer) and later to Godhood (master who is in union with all).

Employing the autoethnographic methodology enabled me to share key points in my educational journey, which propelled my transformation. This contemplative engagement was a …

Using Imagery Practice To Improve Airline Pilot Situational Awareness, Brian Christopher Sajdak

Dissertations

Pilot error remains the primary cause of airline airplane accidents (Federal Aviation Administration, n.d.). Airline pilots have relied on Crew Resource Management and Threat Error Management to reduce or eliminate errors (Helmreich & Foushee, 2019). Unfortunately, the worldwide accident rate continues to increase (International Air Transport Association, 2021), demonstrating the need for further research into improving aviation safety. Current regulations do not require imagery training for airline pilots to improve situational awareness (Federal Aviation Administration, 2017a). Athletes and other professionals, such as musicians and medical professionals, use imagery to improve performance (Munzert et al., 2009). Imagery practice may improve the …

Affective Commitment, Mentoring, And Anticipated Turnover Among Millennials, Keiasha Hypolite

Dissertations

ABSTRACT

Millennials comprise the largest group of individuals in the workforce, yet organizations struggle to keep millennials engaged in the workplace. Millennials move from job to job, with an average stay at one employer between 12 and 18 months (Hechl, 2017). Researchers have reported that millennials cause the majority of turnover in the workplace. Globally, human resources practitioners experience difficulties retaining millennials (Sahraee et al., 2021). Previous studies have researched millennials, affective commitment, mentoring, and turnover. However, no known research has used all four factors to solve a global problem. In their discussion of the highly competitive labor market, Ramírez …

Connecting Social And Ecological Systems In Small-Scale Fisheries In The Philippines, Sara Eisler Marriott

Dissertations

Nearly 50% of all marine fish capture in the Philippines is from artisanal fisheries, most of which is un- or under-reported. As in many emerging nations around the world, the Philippines cannot fully address overfishing by managing only half of the catch that comes from commercial fisheries. Marine reserves are a popular governance strategy for conservation and of growing interest for fisheries management. Many marine reserves in the Philippines, however, are not considered effective. In 2014, Rare, an international NGO, implemented a community-based management program to increase the effectiveness of the marine reserves, and while it found biomass increased, there …

Origin And Structure Of The First Sharp Diffraction Peak Of Amorphous Solids, Devilal Dahal

Dissertations

Several explanations have been reported in the literature about the origin of extended-range oscillations (EROs) in the atomic pair-correlation function of amorphous materials. Although the radial ordering beyond the short-range order of about 5 Å has been extensively studied in amorphous materials, the exact nature of the radial ordering beyond a nanometer is still not resolved. This dissertation address this problem and explains the nature of the EROs by using high-quality models of amorphous silicon (a-Si) obtained from Monte Carlo and Molecular Dynamics simulations. The extended-range ordering in a-Si is examined through radial oscillations on the length …

Note-Taking In College Mathematics: An Examination Of The Effectiveness Of Guided Notes And Interactive Notebooks On Student Achievement In College Algebra, Verlonda Neal

Dissertations

The purpose of this study was to investigate how the use of interactive guided notes influences the mathematical performance of college algebra students when solving univariate linear equations. The research involved 68 students enrolled in College Algebra at a community college. The participants were divided into two groups: those who took notes using an interactive guided notes method and those who did not use the interactive guided notes note-taking method to cite instructional information. The participants were administered a test on solving univariate linear equations before and after receiving instruction to answer the research questions posed by the study. An …