Digital Commons Network^™

Fermi-Gbm : The 10 Year Spectral Catalog And Exploring Physically-Motivated Models To Fit Gamma-Ray Burst Spectra, Suraj Poolakkil

Dissertations

Gamma-ray Bursts (GRBs) are ultra-relativistic jets of plasma and radiation formed by two known progenitors: core-collapse supernovae (a.k.a. “collapsars”) and binary mergers of compact objects, especially neutron stars. They have been studied extensively since their discovery in the 1960s, but many aspects of their prompt emission remain a mystery. In the first part of this dissertation I present the systematic spectral analyses of GRBs detected by the Fermi Gamma-ray Burst Monitor during its first ten years of operation. It consists of spectral fits from 2297 GRBs, resulting in a compendium of over 18,000 spectra. In the second part, I explore …

Design Of Secure, Low-Power Internet Of Medical Things With Precise Time Synchronization, Steven C. Puckett

Dissertations

With the emerging worldwide aging crisis, low power, secure health monitoring becomes increasingly important. Internet of Things (IoT) technology is revolutionizing many application fields, creating a new opportunity: Internet of Medical Things (IoMT). The main IoMT issues include security, energy efficiency, and time synchronization. This study evaluates the IoMT design space, security weaknesses of IoMT systems, and methods of synchronization of distributed IoT sensors. The researcher presents an analysis of the design space of IoMT controllers in Espressif ESP-32 family of microcontrollers and the development, implementation, and evaluation of the ecoSync: a time-synchronization algorithm for IoMT devices on standard Wi-Fi …

Improving Undergraduate Student Engagement In Stem Through Bioinformatics Research, Michele C. Morris

Dissertations

A novel intervention to introduce undergraduate students to bioinformatics, provide authentic research opportunities, and support student retention in science majors and careers is presented in the Characterizing Our DNA Exceptions (CODE) project. The need to increase the number of qualified STEM graduates, particularly in the fields of bioinformatics and computational research, was the impetus for this project that leads students down the path of scientific discovery as they characterize genomic variants of uncertain significance (VUS). This study sought to examine if student participation in a CODE research project would increase their bioinformatics awareness, interest, comfort, and knowledge, as well as …

Novel Approaches To The Analysis Of Gene Regulation Data, Brian S. Roberts

Dissertations

The study of gene regulation is crucial to understanding differentiation, cell specialization, and response to external stimuli observed in multicellular organisms. Genome-scale technologies enabled by high-throughput sequencing have allowed insight into many aspects of gene regulation. However, these techniques produce large, complex data that require the development of computation-based analytical techniques. I present here two analytical techniques that I have created for gene regulation data. First, I describe an approach for the analysis of sequencing-based reporter data that reveals new features of human genetic sequence that generate biased strand transcription even out of genomic context. Next, I present a package …

Spectral And Radiometric Calibration And Atmospheric Modeling For Sounding Rockets, Nicolas Gene Donders

Dissertations

Sounding rocket telescopes are demonstration test beds for novel science capabilities. These programs explore cutting-edge solar physics around the globe, leading to missions aboard satellites and orbital labs. My research with the sounding rocket team at Marshall Space Flight Center (MSFC) involved various experimental efforts in the lab alongside computer modeling of spectroscopic signals. This dissertation focuses on the Full-Sun Ultraviolet Rocket SpecTrograph (FURST), which is led by a team at Montana State University (MSU) and will deliver spectroscopic observations over a range of 120-181 nm. FURST aims to provide full-disk data at a similar spectral resolution to Hubble (R …

Modeling Freely Flying Insects Using A Strongly Coupled High Fidelity Numerical Framework, Jeremy A. Pohly

Dissertations

Flying insects, with their remarkable abilities, serve as fascinating sources of inspiration. Deciphering the complex mechanisms that enable monarch butterflies to migrate nearly 80 million times their body length, requires advanced modeling tools. These tools must capture the interplay between non-linear wing aerodynamics, dynamic body responses, and flexible wings, characteristics of the monarch. A novel framework is introduced that tightly integrates these physical phenomena through a dynamic relaxation scheme. The model’s application extends to examining the longitudinal flight of monarch butterflies and the hovering flight of fruit flies, bumblebees, and hawkmoths. A bio-inspired feedback controller ensures stable flight across all …

Bioimpedance-Based Real-Time Wearable Physiological Monitoring, Robert Joseph Mathews

Dissertations

Cardiovascular and respiratory diseases account for nearly forty percent of worldwide deaths. A critical factor in preventing these deaths is early detection, treatment, and monitoring of the diseases. Remote patient monitoring coincides with significant advances in integrated circuit technology resulting in greater performance and lower power consumption. In this work, novel monitoring configurations and frequency excitations are assessed across ten subjects to evaluate their suitability for monitoring cardiac and respiratory activity. A custom bioimpedance controller board was fabricated and integrated into the existing UAH euHy board. In the pilot experiment, the average inter-beat interval (IBI) derived from bioimpedance compared with …

Joint Sonar And Communication (Soncomm) System Using Solvable Chaos, Tamseel Mahmood Syed

Dissertations

An ever increasing number of actively interconnected wireless devices tend to exert congestion on the naturally limited resources provided by the electromagnetic spectrum. This fact imposes a significant engineering challenge on efficient utilization of communication channels. One method to lessen the stringency of the spectrum access is to combine functionality of wireless applications via jointly operational (multi-purpose) waveforms. Solvable chaos was previously shown to have inherent detection benefits when used independently in practical demonstrations of either acoustic ranging or communication. This dissertation focuses on the design of a joint sonar-communication (SonComm) system via solvable chaotic waveforms. First, individual hardware demonstrations …

Self-Powered Sensor Systems For Space Applications, Saininad Chandrakant Naik

Dissertations

Harvesting energy from ambient sources allows sensors and systems to become self-reliable and not depend on small batteries or energy sources, which is of paramount importance in space applications. In recent decades, multi-band or wideband energy harvesters have attracted much attention. The main challenge to design such energy harvesters is that they need to efficiently scavenge the electromagnetic waves at multiple bands and deliver the received multi-frequency signals to the rectifier that has a frequency dependent impedance. In this dissertation, a compact dual-band harvesting sensor is developed for space applications at the RF (900 MHz) and the ISM (2400 MHz) …

Using Materialized Views For Answering Graph Pattern Queries, Michael Lan

Dissertations

Discovering patterns in graphs by evaluating graph pattern queries involving direct (edge-to-edge mapping) and reachability (edge-to-path mapping) relationships under homomorphisms on data graphs has been extensively studied. Previous studies have aimed to reduce the evaluation time of graph pattern queries due to the potentially numerous matches on large data graphs.

In this work, the concept of the summary graph is developed to improve the evaluation of tree pattern queries and graph pattern queries. The summary graph first filters out candidate matches which violate certain reachability constraints, and then finds local matches of query edges. This reduces redundancy in the representation …

Android Security: Analysis And Applications, Raina Samuel

Dissertations

The Android mobile system is home to millions of apps that offer a wide range of functionalities. Users rely on Android apps in various facets of daily life, including critical, e.g., medical, settings. Generally, users trust that apps perform their stated purpose safely and accurately. However, despite the platform’s efforts to maintain a safe environment, apps routinely manage to evade scrutiny. This dissertation analyzes Android app behavior and has revealed several weakness: lapses in device authentication schemes, deceptive practices such as apps covering their traces, as well as behavioral and descriptive inaccuracies in medical apps. Examining a large corpus of …

Carrier Transport Engineering In Wide Bandgap Semiconductors For Photonic And Memory Device Applications, Ravi Teja Velpula

Dissertations

Wide bandgap (WBG) semiconductors play a crucial role in the current solid-state lighting technology. The AlGaN compound semiconductor is widely used for ultraviolet (UV) light-emitting diodes (LEDs), however, the efficiency of these LEDs is largely in a single-digit percentage range due to several factors. Until recently, AlInN alloy has been relatively unexplored, though it holds potential for light-emitters operating in the visible and UV regions. In this dissertation, the first axial AlInN core-shell nanowire UV LEDs operating in the UV-A and UV-B regions with an internal quantum efficiency (IQE) of 52% are demonstrated. Moreover, the light extraction efficiency of this …

Improving The Stimulation Selectivity In The Human Cochlea By Strategic Selection Of The Current Return Electrode, Ozan Cakmak

Dissertations

The hearing quality provided by cochlear implants are poorly predicted by computer simulations. A realistic cochlear anatomy is crucial for the accuracy of predictions. In this study, the standard multipolar stimulation paradigms are revisited and Rattay’s Activating Function is evaluated in a finite element model of a realistic cochlear geometry that is based on µ-CT images and a commercial lead. The stimulation thresholds across the cochlear fibers were investigated for monopolar, bipolar, tripolar, and a novel (distant) bipolar electrode configuration using an active compartmental nerve model based on Schwartz-Eikhof-Frijns membrane dynamics. The results suggest that skipping of the stimulation point …

Photonic Monitoring Of Atmospheric Fauna, Adrien P. Genoud

Dissertations

Insects play a quintessential role in the Earth’s ecosystems and their recent decline in abundance and diversity is alarming. Monitoring their population is paramount to understand the causes of their decline, as well as to guide and evaluate the efficiency of conservation policies. Monitoring populations of flying insects is generally done using physical traps, but this method requires long and expensive laboratory analysis where each insect must be identified by qualified personnel. Lack of reliable data on insect populations is now considered a significant issue in the field of entomology, often referred to as a “data crisis” in the field. …

Integrated Machine Learning And Optimization Approaches, Dogacan Yilmaz

Dissertations

This dissertation focuses on the integration of machine learning and optimization. Specifically, novel machine learning-based frameworks are proposed to help solve a broad range of well-known operations research problems to reduce the solution times. The first study presents a bidirectional Long Short-Term Memory framework to learn optimal solutions to sequential decision-making problems. Computational results show that the framework significantly reduces the solution time of benchmark capacitated lot-sizing problems without much loss in feasibility and optimality. Also, models trained using shorter planning horizons can successfully predict the optimal solution of the instances with longer planning horizons. For the hardest data set, …

Faceted Nanomaterial Synthesis, Characterizations And Applications In Reactive Electrochemical Membrane Filtration, Qingquan Ma

Dissertations

Facet engineering of nanomaterials, especially metals and metal oxides has become an important strategy for tuning catalytic properties and functions from heterogeneous catalysis to electrochemical catalysis, photocatalysis, biomedicine, fuel cells, and gas sensors. The catalytic properties are highly related to the surface electronic structures, surface electron transport characteristics, and active center structures of catalysts, which can be tailored by surface facet control. The aim of this doctoral dissertation research is to study the facet-dependent properties of metal or metal oxide nanoparticles using multiple advanced characterization techniques. Specifically, the novel atomic force microscope-scanning electrochemical microscope (AFM-SECM) and density functional theory (DFT) …

Hydrodynamic Investigation Of The Discharge Of Complex Fluids From Dispensing Bottles Using Experimental And Computational Approaches, Baran Teoman

Dissertations

The discharge of non-Newtonian, complex fluids through orifices of industrial tanks, pipes, dispensers, or packaging containers is a ubiquitous but often problematic process because of the complex rheology of such fluids and the geometry of the containers. This, in turn, reduces the discharge rate and results in residual fluid left in the container, often referred to as heel. Heel formation is undesired in general, since it causes loss of valuable material, container fouling, and cross-contamination between batches. Heel may be of significant concern not only in industrial vessels but also in consumer packaging. Despite its relevance, the research in this …

The Future Of The Urban Street In The United States: Visions Of Alternative Mobilities In The Twenty-First Century, Esther Zipori

Dissertations

This dissertation is concerned with the present and future of urban streets in the United States. The goal is to document and analyze current visions, policies, and strategies related to the form and use of American urban streets. The dissertation examines current mobility trends and offers a framework for organizing visions of the future of urban streets, evaluating them through three lenses: safety, comfort, and delight: assessing physical conditions in accordance with livability standards toward sustainable development. At the same time, it demonstrates the way 12 scenarios (NACTO Blueprint for Autonomous Urbanism, Sidewalk Labs: Quayside Project, Public Square by FXCollaborative, …

Interactions Of Amyloid Peptides With Lipid Membranes, Yanxing Yang

Dissertations

The aggregation of amyloid proteins into fibrils is a hallmark of several diseases including Alzheimer’s (AD), Parkinson’s, and Type II diabetes. This aggregation process involves the formation of small size oligomers preceding the formation of insoluble fibrils. Recent studies have shown that these oligomers are more likely to be responsible for cell toxicity than fibrils. A possible mechanism of toxicity involves the interaction of oligomers with the cell membrane compromising its integrity. In particular, oligomers may form pore-like structures in the cell membrane affecting its permeability or they may induce lipid loss via a detergent-like effect. This dissertation aims to …

Microhydrodynamic, Kinetic And Thermal Modeling Of Wet Media Milling For Process Optimization And Intensification, Gulenay Guner

Dissertations

Nanoparticle production by wet stirred media milling (WSMM) is a common method for the formulation of poorly water-soluble drugs. While most of the studies in the WSMM literature focus on the formulation aspects to overcome the stability challenges, a thorough mechanistic understanding of the process is lacking, and the process is slow, costly, and energy-intensive. This dissertation presents experimental and modeling work with the ultimate goals of (i) gaining a deeper and more mechanistic understanding of the WSMM process and breakage kinetics of the particles using a microhydrodynamic model with various improvements and advancements, (ii) examining the heat dissipation during …

Machine Learning-Based Data Analytics For Understanding Space Weather And Climate, Yasser Abduallah

Dissertations

This dissertation addresses multiple crucial problems in space weather and climate, presenting new machine learning-based data analytics algorithms and models for tackling the problems.

First, the dissertation presents two new approaches to predicting solar flares. One approach, called DeepSun, predicts solar flares by utilizing a machine-learning-as-a-service (MLaaS) platform. The DeepSun system provides a friendly interface for Web users and an application programming interface (API) for remote programming users. It adopts an ensemble learning method that employs several machine learning algorithms to perform multiclass flare prediction. The other approach, named SolarFlareNet, forecasts the occurrence of solar flares within the next 24 …

Bioremediation Of Petroleum Hydrocarbons In Coastal Sediments, Charbel Abou Khalil

Dissertations

The biodegradation of dispersed crude oil in the ocean is relatively rapid (a half-life of a few weeks). However, it is often much slower on shorelines, usually attributed to low moisture content, nutrient limitation, and higher oil concentrations in beaches than in dispersed plumes. Another factor may be the increased salinity of the upper intertidal and supratidal zones since these parts of the beach are potentially subject to prolonged evaporation and only intermittent inundation. Therefore, two laboratory experiments are conducted to investigate whether such an increase in porewater salinity results in additional inhibitory effects on oil biodegradation in seashores.

In …

Combustion Soot Nanoparticles: Mechanism Of Restructuring And Mechanical Properties, Ali Hasani

Dissertations

Soot, a product of incomplete combustion of fossil fuels, is a global warming agent. The effect of soot particles on climate depends on their morphology. Freshly released soot particles are fractal lacey aggregates, but they often appear collapsed in atmospheric samples collected away from emission sources. A body of work has concluded that the collapse is caused by liquid shells when they form by vapor condensation around soot aggregates. However, some recent studies argue that soot remains fractal even when engulfed by the shells, collapsing only when the shells evaporate. To reconcile this disagreement, the effects of the condensation and …

Monitoring Climate Change With Machine Learning And Uncertainty Quantification, Firas Gerges

Dissertations

The impact of climate change on the environment has become increasingly visible today. One important topic in climate change monitoring is to forecast future climate events, which relies on long-term prediction of climate variables at a local regional scale. This topic is crucial for disaster risk management and for resolving climate change at the local level. General Circulation Models (GCMs) allow for the simulation of several climate variables, decades into the future. GCM simulations, however, are at a global large scale and are too coarse to monitor climate change at the local small scale. This dissertation explores new machine learning …

Amphiphilic Block Copolymers And The Applications In Therapeutics Delivery, Jie Dou

Dissertations

Well-defined thermo-responsive triblock copolymers containing polyethylene oxide (PEO) and poly(N-isopropyl acrylamide) PNIPAM are synthesized by a type of living controlled polymerization, named iniferter polymerization. The polymers are amphiphilic in nature and are self-assembled into a micelle. Their properties and application are characterized and investigated in this work.

Foremost, the initiator of the polymerization (iniferter) is designed and synthesized by condensation polymerization, where PEO is incorporated into the structure to improve biocompatibility, which has great potential for biological application. Moreover, this iniferter reagent could be applied to more than 70 percent of vinyl monomers.

NIPAM, a commercial vinyl monomer, is chosen …

Biotransformation And Biodefluorination Of Fluorotelomer Carboxylic Acids, Chen Wu

Dissertations

Per- and polyfluoroalkyl substances (PFASs), a class of emerging contaminants of concern, have attacked unprecedented attention given their prevalent detection and adverse health effects. Primary regulatory attention has been focused on PFOA, PFOS, and other perfluoroalkyl acids (PFAAs). Recent investigations revealed that fluorotelomer carboxylic acid (FTCAs), particularly 5:3 FTCA and 6:2 FTCA, were dominant in landfill leachates and other environmental matrixes. FTCAs are also found as common intermediates during the biotransformation of PFAA precursors. Unfortunately, FTCAs have higher bioaccumulating potential and are at least two orders more toxic than their corresponding PFCAs. However, information regarding the potentials and mechanisms of …

A Novel Biomaterial Platform For Cardiac Tissue Engineering, Andrew House

Dissertations

Heart disease is one of the leading causes of death in the world. With a growing demand for in vitro cardiac models that can recapitulate the complex physiology of the cardiac tissue, there is a desire to create novel therapies and treatments. However, due to a lack of fundamental understanding of the heart's inflammatory response to myocardial infarction, the development of new therapies is both time consuming and costly. In this work, a novel approach to fabricating a dynamic hydrogel cardiac platform is reported. This platform better mimics the dynamic changes occurring in the native cardiac tissue microenvironment during cardiac …

Angiogenic Supports For Microvascular Engineering, Zain Siddiqui

Dissertations

Ischemic tissue disease is caused by a lack of circulation / blood supply to tissue. This can be treated by introducing a number of angiogenic (pro-blood vessel forming) factors into the tissue. This work presents strategies for ischemic tissue treatment utilizing a novel proangiogenic self-assembling peptide hydrogel platform. To demonstrate the utility of this platform, its use alone as an angiogenic therapeutic (both alone as a self-assembling hydrogel and with two-component systems), and its ability to vascularize implants is explored. Due to these angiogenic scaffolds demonstrating efficacy to regenerate microvasculature, this work evaluates diseases that can be treated by the …

Polymeric Nitrogen: Computational Catalysis And Materials Design, Safa Alzaim

Dissertations

The urgent climactic crisis currently endangering all life on earth is largely due to the combustion of fossil fuels as an energy source. This work combines physics, chemistry, mathematics and computer science to develop new ways to harvest, store and use sustainable energy. In particular, this work centers on polymeric nitrogen (PN). PN is highly desirable because the energy density is extremely high. This energy density lends PN to applications such as rocket fuel and energetic materials. Recently, the polymeric phase N₈ was shown to be highly active for oxygen reduction reactions (ORR); the material is an excellent electrocatalyst …

Nondirect Line-Of-Sight Free-Space Optical Communications And Networks, Paa Kwesi Affir Esubonteng

Dissertations

Nondirect Line-of-Sight Free-Space Optical Communications (NLoS-FSOC) uses diffuse reflected light to establish communication between two or more stations that are with or without line-of-sight (LoS) to each other. Different from free-space optical communications (FSOC), NLoS-FSOC uses a diffuse reflector (DR) between a transmitter and a receiver so that LoS is not required between them but between the station and the DR. Unlike a mirror, the DR reflects the incident light to all directions and except to itself. That multidirectional reflection broadcast the optical transmission to all receivers with LoS to the DR. The optical broadcast channel establishes a true optical …