Digital Commons Network^™

Seismic Anisotropy And The Mantle Dynamics Beneath The Arabian Plate, Saleh Ismail Hassan Qaysi

Doctoral Dissertations

"We investigate mantle seismic azimuthal anisotropy and deformation beneath the Arabian Plate and adjacent areas using data from 182 broadband seismic stations which include 157 stations managed by the Saudi Geological Survey. A total of about 4000 pairs of shear wave splitting parameters are obtained using the transverse minimization technique. The individual XKS (including PKS, SKS, and SKKS) splitting measurements were manually checked to ensure the quality. The well-defined parameters show dominantly N-S fast orientations at the majority of the stations, and NW-SE fast orientations along the Zagras Mountain front. No clear systematic variations of the splitting parameters as a …

Phenolic Resin Aerogels: The Significance Of Inserting An Oxidative Ring-Fusion Aromatization Step At The Early Stages Of Pyrolytic Carbonization, And The Application Of These Materials In Co₂ Storage And Separation, Hojat Majedi Far

Doctoral Dissertations

"Phenolic aerogels, prepared via polycondensation of phenolic monomers and formaldehyde, were converted to carbon aerogels at 800 ⁰C/Ar followed by reactive etching under flowing CO₂. Previously, it was found that a lower-temperature air-oxidation of polybenzoxazine aerogels was necessary in order to obtain highly porous, isomorphic carbon aerogels with high carbonization yields. Using those findings as the point of departure, phenolic aerogels were oxidized at 240 ⁰C/air prior to carbonization. During that air-oxidation step, phenolic aerogels based on phloroglucinol (1,3,5- trihydroxybenzene) undergo fusion of their aromatic rings, yielding 6-membered heteroaromatic pyryliums with pendant phenoxide ions. The resulting carbon aerogels …

Multitarget Tracking And Terrain-Aided Navigation Using Square-Root Consider Filters, James Samuel Mccabe

Doctoral Dissertations

"Filtering is a term used to describe methods that estimate the values of partially observed states, such as the position, velocity, and attitude of a vehicle, using current observations that are corrupted due to various sources, such as measurement noise, transmission dropouts, and spurious information. The study of filtering has been an active focus of research for decades, and the resulting filters have been the cornerstone of many of humankind's greatest technological achievements. However, these achievements are enabled principally by the use of specialized techniques that seek to, in some way, combat the negative impacts that processor roundoff and truncation …

Characterization Of The Cylinderical Split Internal-Loop Photobioreactor With Scenedesmus Microalgae: Advanced Culturing, Modeling, And Hydrodynamics, Laith S. Sabri

Doctoral Dissertations

"Microalgae are fast growing photoynthetic microorganisms and it have very wide range of industrial applications such as biofuels and wastewater treatment. These cells can be grown in a wide variety of systems ranging from open culture systems (e.g., ponds) to closed culture systems of photobioreactor (e.g., airlift). The open culture systems exist in the external environment, and hence, are not intrinsically controllable. However, the microalgae production in enclosed photobioreactors faces prohibitively high production costs with special difficulty in reactor design and scale-up. The light availability and utilization efficiency in the photobioreactor in terms of design and scale-up consider as the …

Correlation Between Delay Time And Measured Concentration And Concentration Uncertainty By Neutron Activation Analysis, James Thomas Seman

Doctoral Dissertations

"For the last several decades, it has been apparent that new methods of identifying explosives can help investigators trace their origins. One way to identify an explosive is through the use of taggants: materials added to a product that encodes information about the product such as when it was manufactured.

This research investigates the survivability of a new identification taggant called the Nuclear Barcode that overcomes some of the downfalls that have been identified in prior taggants. The Nuclear Barcode encodes information as a unique combination of concentrations of rare earths (Ho, Eu, Sm, Lu, and Dy) and precious metals …

Dragline Excavation Simulation, Real-Time Terrain Recognition And Object Detection, Godfred Somua-Gyimah

Doctoral Dissertations

"The contribution of coal to global energy is expected to remain above 30% through 2030. Draglines are the preferred excavation equipment in most surface coal mines. Recently, studies toward dragline excavation efficiency have focused on two specific areas. The first area is dragline bucket studies, where the goal is to develop new designs which perform better than conventional buckets. Drawbacks in the current approach include operator inconsistencies and the inability to physically test every proposed design. Previous simulation models used Distinct Element Methods (DEM) but they over-predict excavation forces by 300% to 500%. In this study, a DEM-based simulation model …

Discrete Element And Artificial Intelligence Modeling Of Rock Properties And Formation Failure In Advance Of Shovel Excavation, Muhammad Waqas

Doctoral Dissertations

"Rock tests are performed before the start of every mining or civil engineering project as part of a detailed feasibility study. The feasibility study is costly and it comprises drilling, sample collection, sample handling and laboratory testing. Numerical modeling techniques, such as Particle Flow Code (PFC), can be used to provide reliable estimates of rock strength values. The numerical models for unconfined compressive strength (UCS), direct tension, and Brazilian tests were developed in PFC, and validated using data from literature. A particle size range of 3-5 mm with D_max/D_min = 1.67 gave the best results. The numerical …

Modeling And Characterization Of Thermo-Oxidative Behavior Of Bismaleimide Composites, Rafid Muhammad Hussein

Doctoral Dissertations

"High-temperature polymer matrix composites (HTPMCs) are susceptible to thermo-oxidation, which accelerates the composites' degradation and reduces the service life. Mechanical properties of HTPMCs deteriorate due to coupled thermo-oxidation and cross-linking mechanisms. Bismaleimides (BMIs) are commonly used high-temperature resins for aerospace applications. This work presents the viability of using experimental weight loss to model the spatial distribution of oxidation when the oxidized polymer matrix is not discernible. Three tasks are introduced: (1) Anisotropic oxidation prediction using optimized weight loss behavior of bismaleimide composites, (2) A multi-scale modeling of thermo-oxidative effects on the flexural behavior of cross-ply bismaleimide composites, and (3) Thermo-oxidative …

Modeling And Simulation Of Viscoplasticity, Recrystallization, And Softening Of Alloyed Steel During Hot Rolling Process, Xin Wang

Doctoral Dissertations

"Hot rolling is one of the most important and complex deformation processes in steel manufacturing and is essential to final product quality. The objective of this study is to investigate viscoplasticity, dynamic recrystallization, and static softening of alloyed metal during hot rolling process. Gleeble hot compression tests were performed to provide experimental stress-strain curves at different temperatures and strain rates. An inverse finite element analysis was performed to calibrate the experimental curves. Viscoplastic models including a Johnson-Cook (JC) model, a Zerilli-Armstrong (ZA) model, and a combined JC and ZA model were developed. Dynamic recrystallization behavior was investigated and modeled based …

Adaptive Data Analysis For Damage Detection And System Identification In Civil Infrastructure, Hongya Qu

Doctoral Dissertations

"Time-varying structural systems are often encountered in civil engineering. As extreme events occur more frequently and severely in recent years, more structures are loaded beyond their elastic conditions and may thus experience damage in the years to come. Even if structures remain elastic, energy dissipation devices installed on structures often reveal hysteretic behaviors under earthquake loads. Therefore, it is imperative to develop and implement novel technologies that enable the identification and damage detection of time-varying systems. In this dissertation, adaptive wavelet transform (AWT) and multiple analytical mode decomposition (M-AMD) are proposed and applied to identify system properties and detect damage …

Crustal Structure Beneath The Eastern Margin Of The Tibetan Plateau And Adjacent Areas From Receiver Function Stacking And Gravity Modeling, Yunxin Peng

Doctoral Dissertations

"To provide constraints on the mechanisms responsible for the uplift and crustal thickening of the eastern Tibetan Plateau, the thickness and Vp/Vs values of the Moho beneath 153 seismic stations are obtained by stacking P-to-S converted phases from the Moho and gravity modeling. The resulting crustal thickness generally decreases from the northwest to the south-east, from about 60 km in the Bayan Har Block to 30 km in the Sichuan Basin. The crustal Vp/Vs measurements in the Qinling Orogenic Belt, Bayan Har Block, Chuxiong Basin, and Yangtze Platform indicate an overall intermediate to felsic crustal composition. With a relatively thick …

Security Risk Assessment In Cloud Computing Domains, Amartya Sen

Doctoral Dissertations

"Cyber security is one of the primary concerns persistent across any computing platform. While addressing the apprehensions about security risks, an infinite amount of resources cannot be invested in mitigation measures since organizations operate under budgetary constraints. Therefore the task of performing security risk assessment is imperative to designing optimal mitigation measures, as it provides insight about the strengths and weaknesses of different assets affiliated to a computing platform.

The objective of the research presented in this dissertation is to improve upon existing risk assessment frameworks and guidelines associated to different key assets of Cloud computing domains - infrastructure, applications, …

Modeling And Control Of Probe-On-Probe Dynamics In Dual-Probe Atomic Force Microscopy, Ayad Al-Ogaidi

Doctoral Dissertations

“The atomic force microscope (AFM) is a widely used instrument for imaging and direct manipulation of materials and particles at the nanoscale. The AFM uses a probe, which is a microcantilever with a sharp point at the end. Typically, the AFM is constructed with a single probe. The disadvantage of this construction is that it can only be used either for imaging or manipulation in one implementation. An AFM was constructed using two probes, permitting simultaneous imaging and manipulation. A dual-probe AFM (DP-AFM) provides a foundation for feedback controlled manipulation.

Paper I investigates probe-on-probe contact stability and examines the dynamics …

Design For Optical Metamaterial Design For Optical Metamaterial Absorber, Huixu Deng

Doctoral Dissertations

“Optical metamaterlal (MM) absorbers in the visible or near-infrared range have been widely investigated in these years since they are crucial in many promising applications, such as solar energy harvesting systems, thermo-photovoltaic energy conversion devices, thermal imaging and emissivity control. This dissertation aims to design and investigate various optical metamaterial absorbers based on different mechanisms and theories, such as cavity resonance, impedance match, equivalent circuit model and waveguide stop light mode. First, via utilizing the cavity resonance, a tunable narrowband MM absorber/emitter for thermophotovoltaic (TPV) is designed and analyzed based on gold nanowire cavities to improve the overall efficiency of …

Experiences Of Women Stem Professors Who Are Considering Leadership Positions At Research Universities, Cheri Liebow

Doctoral Dissertations

Empirical evidence is needed to discern the reasons for inequities among those with doctorates hired in science, technology, engineering, and mathematics (STEM) fields. It is necessary to create a successful and motivational atmosphere for various types of female leaders who are seeking opportunities to become leaders, especially in STEM fields. This qualitative-method study used an exploratory design. The study first sought to gather information about female STEM professors’ experiences through open-ended qualitative interviews to explain gaps in details of women’s experiences as professors in STEM departments of universities. Second, the researcher sought to discern common themes in interview responses for …

Using Multiliteracies To Engage And Empower Students With Complex Support Needs, Sudha Vaghul Krishnan

Doctoral Dissertations

Using Multiliteracies to Engage and Empower Students with Complex Support Needs This dissertation is comprised of two studies:

• Creating New Learning Spaces Using Multiliteracies with Students with Complex Support Needs

• Transforming Narrative Identity through Multiliteracies

Students with complex support needs (SCSN) are frequently denied access to meaningful and challenging literacy instruction. These studies explore how student- authored narratives in the individualized education plan (IEP), implemented during a multiliteracies curriculum, can simultaneously engage and empower SCSN. These studies are based on the qualitative research that I conducted from November 15, 2018 to February 11, 2018 at a special day …

Use Of Multimedia Games For Biology Vocabulary Instruction, Ian Murray

Doctoral Dissertations

Vocabulary knowledge is considered fundamental to learning. However, students typically find learning scientific vocabulary quite difficult, and that is especially true for biology vocabulary. Games are well established as effective tools for vocabulary instruction. Multimedia instruction is likewise recognized as aiding vocabulary learning. To date, however, there seems have been little examination of the use of multimedia games in biology vocabulary instruction. This study, therefore, compared the effectiveness of digital multimedia games and traditional instruction in teaching biology vocabulary.

A two-group, quasi-experimental study was carried out over the course of 61 days. Participants were a convenience sample of 10 high …

Land-Atmosphere Interactions And Regional Climate In West Africa And South America, Amir Erfanian Javadian Entezar Yazd

Doctoral Dissertations

Land, atmosphere, and oceans interact with each other through energy, mass, and momentum exchanges. These interactions regulate climate variability and influence climate changes at the regional scale. One notable example of highly influential land-atmosphere-ocean interactions on regional climates is monsoonal systems that influence a substantial portion of the world’s population. In this dissertation, the present and future climates of West Africa (WA) and South America (SA), two important monsoon regions, were studied utilizing Regional and Global Climate Models (RCMs and GCMs), mathematical techniques and data mining tools, and observational data (in-situ, remote-sensing, and reanalysis). The objective is to advance our …

Conquering Visual Challenges While Hunting Across The Air-Water Interface; A Study Of Foraging Day Herons, Holly Brown

Doctoral Dissertations

Among several visual challenges of hunting across the air-water interface are glare, which obscures prey below the water surface; and refraction, which causes submerged prey to appear where they are not. These challenges are exacerbated by the fact that prey have visual (and other) adaptations for detecting predators. To forage successfully on underwater prey, predators must compensate. Herons are good model animals for studying how predators compensate for visual challenges at the air-water interface; they are visually-hunting, fish-eating birds. Herons also regularly tilt their long necks (“head-tilt”) while hunting, which I hypothesized could aid in compensating for glare, refraction, and …

Design And Fabrication Of Micro-Pillar Based Piezoresistive Flow Sensors, Adimali Piyadasa

Doctoral Dissertations

This study is focused on developing a new type of micro-scale gas flow sensors to be used in critical environments such as combustion engines with high pressure high temperature gas flow and integrated micro electro mechanical applications such as lab-on-chip devices. Proposed flow sensor is based on piezoresistivity of Silicon micro column cantilever. Change in resistivity tensor due to gas flow induced stress in the piezoresistive layer results in generating of an output voltage proportional to the gas flow rate in the channel. Current results show that the anisotropic properties of the Silicon can be successfully used in the gas …

Applications Of Computability Theory To Partial And Linear Orders, Marie Nicholson

Doctoral Dissertations

Applications of computability theory to partial and linear orders.

Weaponized Citizenship: A Critical Race Theory Analysis Of U.S. Citizenship Legislation In The Pacific Unincorporated Territories, Ross Dardani

Doctoral Dissertations

This dissertation examines U.S. citizenship legislation in the U.S. Pacific unincorporated territories through Critical Race Theory’s interest-convergence thesis. I employ Derrick Bell’s theory of interest-convergence to argue that it is only when economic, cultural, political, and social interests converge to benefit the United States that U.S. lawmakers have enacted legislation to extend citizenship to the Pacific unincorporated territories (Guam, American Samoa and the Commonwealth of the Northern Mariana Islands). I also rely on Mary Dudziak’s use of interest-convergence, which she used to explain the implementation of key social reforms of the Civil Rights Movement, such as desegregation, as a model …

A Qualitative Examination Of The Listening Effort Experience Of Adults With Hearing Loss, Alison Marinelli

Doctoral Dissertations

Increased effort and fatigue are common complaints of individuals with hearing loss, however the listening effort (LE) experience from the patient perspective is not well understood. Current models note the importance of cognitive factors in LE. Research, that is largely quantitative in nature, has shown equivocal findings regarding auditory signals that may cause increased LE, technologies that may ameliorate the LE experience, and the effects of LE on sensory systems. Very limited work has explored the personal aspects of LE. As a whole, however, investigations of LE fail to define the experience from the patient’s view or offer suggestions for …

Resilient Microgrids Through Software-Defined Networking, Lingyu Ren

Doctoral Dissertations

Multiple major blackouts had occurred in the U.S. power distribution system highlighting the importance of enhancing electricity resiliency. Microgrid is the new paradigm incorporating high flexibility and reliability in power supply. It allows various distributed energy resources and loads to be integrated and coordinated as an intelligent entity through control and communication infrastructure. Microgrid control technologies have been continuously developed over 20 years. However, there is still a lack of communication architecture that is able to provide fast, reliable and elastic services for multi-level data transmission and adaptable network management. This dissertation solves this intractable problem by integrating programmable networks …

Improving The Social Behavior Of High School Students With Behavioral Challenges Through Self-Management Technology, Kathryn Dooley

Doctoral Dissertations

Students with Emotional and Behavioral Disorders (EBD) struggle with social behaviors (Bradley, Henderson, & Monfore, 2004) such as distractibility and impulsivity (Wagner et al., 2004). Self-management strategies have been used effectively to increase on-task behavior and decrease off-task or inappropriate behavior of students with EBD (Briesch & Chafouleas, 2009a). Additionally, self-management applications for the Apple iPad have led to improvements in the social behavior of students with challenging behavior (Bruhn, Vogelgesang, Fernando., & Lugo, 2016; Bruhn, Vogelgesang, Schabilion, Waller, & Fernando, 2015b; Vogelgesang, Bruhn, Coghill-Behrends, Kern, & Thoughton, 2016). However, a gap in the literature in the use of self-management …

Optimizing Fabrication And Modeling Of Quantum Dot Superlattice For Fets And Nonvolatile Memories, Pial Mirdha

Doctoral Dissertations

Quantum Dot Superlattice (QDSL) are novel structures which can be applied to transistors and memory devices to produce unique current voltage characteristics. QDSL are made of Silicon and Germanium with an inner intrinsic layer surrounded by their respective oxides and in the single digit nanometer range. When used in transistors they have shown to induce 3 to 4 states for Multi-Valued Logic (MVL). When applied to memory they have been demonstrated to retain 2 bits of charge which instantly double the memory density. For commercial application they must produce consistent and repeatable current voltage characteristics, the current QDSL structures consist …

Gender And Domain Differences In College Students’ Responses To Success And Failure, Elizabeth K. Lawner

Doctoral Dissertations

Four studies examined perceptions of STEM and non-STEM college courses, gender and domain differences in responses to success and failure, and whether interventions to make failure seem normative could ameliorate negative responses to failure, particularly among women. Study 1 found that college students perceive STEM courses as more difficult than non-STEM courses, and believe that introductory STEM courses are used to remove students from those fields. Moreover, the difference in perceptions of STEM and non-STEM courses was larger for women. Study 2 piloted a novel task that was used in Studies 3 and 4. These studies did not support the …

Spatiotemporal Subspace Feature Tracking By Mining Discriminatory Characteristics, Richard D. Appiah

Doctoral Dissertations

Recent advancements in data collection technologies have made it possible to collect heterogeneous data at complex levels of abstraction, and at an alarming pace and volume. Data mining, and most recently data science seek to discover hidden patterns and insights from these data by employing a variety of knowledge discovery techniques. At the core of these techniques is the selection and use of features, variables or properties upon which the data were acquired to facilitate effective data modeling. Selecting relevant features in data modeling is critical to ensure an overall model accuracy and optimal predictive performance of future effects. The …

Structure Learning And Break Detection In High-Frequency Data, Yaohua Zhang

Doctoral Dissertations

The accurate learning of the underlying structure in high-frequency data has become critical in the analysis of time series for capturing valuable information that facilitates decision-making. The time series data in finance often is large, dynamic, heterogeneous and even structural unstable. Each aspect of these characteristics will add a degree of difficulty in efficient analysis. The goal of this dissertation is to discover the latent structure of dynamic high-frequency data that may have structural breaks, from both univariate and network perspective. We focus our analysis on durations between user-defined events in transaction-by-transaction stock prices from the Trade and Quotes (TAQ) …

Electrosprayed Polymerization: A Green, Additive Approach For Making Highly Tunable Polyamide Films For Desalination, Md Maqsudur Rahman Chowdhury

Doctoral Dissertations

In membrane based desalination processes, the thin film composite (TFC) membrane is an industry standard which uses interfacial polymerization technique to form an ultra-thin polyamide layer on the surface of polymeric substrates. Remarkably, in 30 years of using this approach, the RO industry has yet to create a polyamide film onto a supporting membrane with controllable thickness, roughness and properties that are independent from the substrate properties. While the film formation essentially is “self-controlled”, the reaction itself is simply allowed to proceed uncontrolled. Thickness and roughness impact membrane permeance and fouling propensity, respectively, and controlling these parameters could greatly benefit …