Digital Commons Network^™

Provenance And Depositional Environments Of The Upper Permian-Lowermost Triassic Fluvial And Lacustrine Sandstones, Wutonggou Low-Order Cycle, Bogda Mountains, Nw China, Dongyu Zheng

Doctoral Dissertations

"This work integrates petrographic and fieldwork studies and documents the spatial and temporal distributions of compositions and textures of the upper Permian-lowermost Triassic fluvial-lacustrine sandstones, Wutonggou low-order cycle (WTG LC), Bogda Mountains, NW China. In the first part, three petrofacies are identified on the basis of the relative abundances of quartz, feldspar, and lithics and conglomerate compositions and paleocurrent directions are documented. These data indicate that rocks of the eastern North Tianshan Suture (ENTS) and rift shoulders were the provenance lithology. Moreover, the upsection changes of petrofacies and conglomerate compositions suggest that the lithology of ENTS changed. During approximately Wuchiapingian, …

Non-Invasive Microwave And Millimeter Wave Reflectometry And Imaging For Human Skin Diagnosis And Materials Characterization, Yuan Gao

Doctoral Dissertations

"Microwave and millimeter wave reflectometry and synthetic aperture radar (SAR) imaging techniques have been successfully applied in many applications, such as nondestructive testing and evaluation (NDT&E), security inspection and medical diagnosis. In this dissertation, the feasibility of using microwave and millimeter reflectometry and SAR imaging for burn diagnosis is investigated through both simulations and measurements, with promising results. To correctly model the interaction between electromagnetic waves and skin, the proper knowledge of the complex permittivity of healthy skin is critically important. To this end, the common used measurement methods for in vivo skin complex permittivity are reviewed and analyzed in …

Nanomorphology Dependent Optical And Mechanical Properties Of Aerogels, Chandana Mandal

Doctoral Dissertations

"Aerogels are very low density, light weight open pore materials. A hypothesis that is under intense current investigation by the scientific community states that the mechanical properties of nanostructured polymers depend on their nanomorphology. Aerogels are nanostructured ultra-lightweight nanoporous materials with skeletal frameworks that can display a wide range of nanomorphologies. Thereby aerogels comprise a suitable platform for testing not only that hypothesis but also a wide range of other properties such as light scattering for applications, for example, in thermally insulating windows.

To study the mechanical properties of nanostructured matter as a function of nanomorphology, various shape-memory polyurethane aerogels …

Passive Harmonic Generation At Spring Contacts, Sen Yang

Doctoral Dissertations

"In the first paper, the RF passive harmonic generation phenomenon on the spring contact is studied. A spring contact harmonic generation measurement system is developed. The factors that may have an impact on the spring contact harmonic generation, such as contact material, contact force, and contact resistance are characterized by the measurement system. The gold-to-gold contact is found to be much superior to the stainless-steel contacts. It is also found that the passive nonlinearity at the spring contact is the semiconductor-like junction formed by the surface oxide film.

In the second paper, we show that the maximum E-field coupling occurs …

A Systems And Cost Analysis Of Human Rated Mars Entry, Descent, And Landing Vehicles, Paul Daniel Friz

Doctoral Dissertations

"Cost is one of the biggest obstacles to sending humans to Mars. However, spacecraft costs are typically not taken into consideration until after the preliminary vehicle and mission concepts have been designed. Once costs have been estimated, managers and project teams often lack confidence that the final cost of the mission will match the preliminary estimates. The present work provides a robust methodology for using cost as a valid metric early in the design phase of future human Mars Entry, Descent, and Landing (EDL) vehicles. This is done in three parts. First, state of the art parametric costing methods are …

Origin Of Periclines In The Ozark Plateau, Missouri: A Field And Numerical Modeling, Chao Liu

Doctoral Dissertations

"A series upright sub-horizontal folds in sandstones of the early Ordovician Roubidoux Formation are exposed in road cuts along US Highway 63 in the northern part of the Salem Plateau of central Missouri for over a distance of approximately 10 km. These folds are in marked contrast to the more typical horizontal to sub-horizontal Ordovician strata of the Ozark Plateau. The origin of those folds remains enigmatic. The inspection of the characteristics of these folds using stereographic analysis revealed a non-cylindrical geometrical pattern than a near cylindrical fold. Structural data of 54 folds indicate an alternating basin and dome pattern. …

Applications Of Machine Learning In Nuclear Imaging And Radiation Detection, Shaikat Mahmood Galib

Doctoral Dissertations

"The main focus of this work is to use machine learning and data mining techniques to address some challenging problems that arise from nuclear data. Specifically, two problem areas are discussed: nuclear imaging and radiation detection. The techniques to approach these problems are primarily based on a variant of Artificial Neural Network (ANN) called Convolutional Neural Network (CNN), which is one of the most popular forms of 'deep learning' technique.

The first problem is about interpreting and analyzing 3D medical radiation images automatically. A method is developed to identify and quantify deformable image registration (DIR) errors from lung CT scans …

Development And Characterization Of Nanostructured Steels And High Entropy Alloys For Nuclear Applications, Andrew Kalevi Hoffman

Doctoral Dissertations

"Nuclear reactor materials are subjected to a harsh environment including high temperatures and radiation fluences. In order to extend the lifetime of current light water reactors (LWRs) and realize the development of advanced Gen IV nuclear reactors new materials must be developed which can withstand such an environment. This thesis involves two approaches to solving this materials problem: advanced manufacturing of current commercial alloys using severe plastic deformation (SPD) and the development of new advanced high entropy alloys (HEAs).

Because SPD is effective at achieving grain refinement, this technique was used to obtain material having a high volume fraction of …

Characterization Of A Green Electric Solid Propellant For Electric Propulsion, Matthew Scott Glascock

Doctoral Dissertations

"Electric solid propellants are advanced solid chemical rocket propellants that can be controlled (ignited, throttled and extinguished) through the application and removal of an electric current. These propellants are also being considered for use in ablative pulsed plasma thruster and multimode systems. In this work, the behavior and performance of a novel green electric solid propellant operating in an electrothermal ablation-fed pulsed plasma thruster was investigated. Using an inverted pendulum micro-Newton thrust stand, the impulse bit and specific impulse of the device using the electric solid propellant were measured for short-duration and long-duration runs to end-of-life, at energy levels of …

Modeling Strategies For Estimating And Suppressing Electromagnetic Interference And Improving Power Integrity, Tamar Makharashvili

Doctoral Dissertations

"Decoupling capacitors are used to suppress high-frequency noise in power distribution networks. The inductance associated with a mounted decoupling capacitor can vary by 26% depending on characteristics of the printed circuit board. Here, simple and accurate inductance models of 2- and 8-terminal capacitors including connections to the power and return plane are developed. Circuit models of the capacitors and layout are created using the partial equivalent element circuit method which provide options for circuit-level simulations as well as analytic estimation of inductance. The circuit solution matches results from the full-wave simulation model within 9% for the 8-terminal capacitor and within …

Fault Imaging Enhancement In Taranaki Basin, New Zealand And Rock Physics And Inversion Based Reservoir Characterization In The Central Gulf Coast Region Of Texas, Tianze Zhang

Doctoral Dissertations

"Fault imaging technique and reservoir characterization based on rock physics analysis and pre-stack inversion has been widely used hydrocarbon exploration. For the fault imaging technique, the ant tracking has been widely used in fault interpretation. However, the reliability of the results is highly dependent on appropriately choosing a signal processing method and volume attributes. In our study area, which lies in the southern Taranaki Basin, we applied Graphic Equalizer as the processing tool and the Chaos attribute before running the ant tracking algorithm. Results show that the procedure provides a better result and can map both the major and minor …

Designing Novel Multinary Transition Metal Selenides As High-Efficiency Oxygen Evolution Reaction Electrocatalysts And Investigating Surface Properties, Xi Cao

Doctoral Dissertations

”Water splitting has been widely considered to be an efficient way to generate sustainable and renewable energy resources in fuel cells, metal-air batteries and other energy conversion devices. Exploring efficient electrocatalysts to expedite the anodic oxygen evolution reaction (OER) is a crucial task that needs to be addressed to boost the practical application of water splitting. This research focuses on the identification of OER electrocatalysts by systematically designing non-stochiometric mixed transition metal-based selenide OER electrocatalysts through combinatorial electrodeposition and investigation of selenide-based naturally occurring minerals as effective OER electrocatalyst. Paper I describes the study of Ni-Fe-Co selenides as OER catalysts …

Numerical Modeling Study Of A Neutron Depth Profiling (Ndp) System For The Missouri S&T Reactor, Mubarak Mohammed Albarqi

Doctoral Dissertations

”For decades, Neutron Depth Profiling has been used for the non-destructive analysis and quantification of boron in electronic materials and lithium in lithium ion batteries. NDP is one of the few non-destructive analytical techniques capable of measuring the depth profiles of light elements to depths of several microns with nanometer spatial resolution. The technique, however, is applicable only to a handful of light elements with large neutron absorption cross sections. This work discusses the possibility of coupling Particle Induced X-ray Emission spectroscopy with Neutron Depth Profiling to yield additional information about the depth profiles of other elements within a material. …

Volumetric Error Compensation For Industrial Robots And Machine Tools, Le Ma

Doctoral Dissertations

“A more efficient and increasingly popular volumetric error compensation method for machine tools is to compute compensation tables in axis space with tool tip volumetric measurements. However, machine tools have high-order geometric errors and some workspace is not reachable by measurement devices, the compensation method suffers a curve-fitting challenge, overfitting measurements in measured space and losing accuracy around and out of the measured space. Paper I presents a novel method that aims to uniformly interpolate and extrapolate the compensation tables throughout the entire workspace. By using a uniform constraint to bound the tool tip error slopes, an optimal model with …

Deep Understanding Of Degradation In Lithium Ion Batteries Through Experimental And First-Principles Study, Yufang He

Doctoral Dissertations

"The growing interests in Lithium-ion Batteries (LIBs) have significantly accelerated the development of active materials. However, the key challenge is that electrode materials suffer from degradation, which include transition metal dissolution, solid electrolyte interphase (SEI) layer formation, and mechanical fracture. To address these issues, applying an ultrathin coating onto active materials via Atomic Layer Deposition (ALD) is an efficient way. Although numerious works have been done for active material performance improvement via ALD technology, the fundamental enhancement mechanisms of ALD coating on battery performance improvement are not yet known. Therefore, this dissertation consists of four papers, which focused on the …

Structure And Function In Petioles Of Pelargonium, Dustin M. Ray

Doctoral Dissertations

As the connection between lamina and stem, petioles are essential for plant survival. Petioles serve two major functions in service to the leaf blade. First, they hold the leaf blade away from the stem to reduce self-shading and optimize light interception, a mechanical function. Second, petioles serve as the bridge between the stem and lamina allowing water to move up the plant body and photo-assimilates to move down to the plant body from the leaf blade, a physiological function. While mechanics and physiology have been studied independently, the petiole could be a space-limited structure leading to tradeoffs between the two …

Evaluating The Impact Of Local Vegetable Messaging On Elementary School Students’ Vegetable Choice And Nutrition Behaviors, Jesse Chiero

Doctoral Dissertations

Farm to school (FtS) initiatives within a school setting may include purchase of local foods, nutrition education, and school gardening. Previous FtS research has indicated a positive impact on child nutrition behaviors and body weight but less is known about how and what aspects of local foods within school meals impact child nutrition behaviors. The specific aims of this project were to: 1) Determine which benefit(s) of eating local vegetables are most salient to 3^rd-5^th grade students for a local vegetable message campaign intervention and compare if message preferences varied by age, gender and school district, and …

Fine Scale Modeling To Estimate Human Exposures To Air Pollution, Fatema Parvez

Doctoral Dissertations

Traffic related air pollution is considered one of the major challenges for a large number of urban population. The rapid growth of the world’s motor-vehicle fleet due to population growth and economic improvement causes a significant negative impact on public health. As pollutants from roadway emission sources reach background concentration levels within a few hundred meters from the source, it is very challenging to implement a model that captures this behavior. Currently available air quality modeling approaches can compute the source specific pollutant fate on either a regional or a local scale but still lack effective ways to estimate the …

Accelerating Synchronization On Futuristic 1000-Cores Multicore Processor With Moving Compute To Data Model, Halit Dogan

Doctoral Dissertations

Single chip multicore processors are now prevalent and processors with hundreds of cores are being proposed and explored by both academia and industry. Shared memory cache coherence is the state-of-the-art technology for these processors to enable synchronization and communication between cores. However, since the synchronization of cores on shared data using hardware cache coherence suffers from instruction retries and cache line ping-pong overheads, it prevents performance scaling as core counts increase on a chip.

This thesis proposes to utilize a novel moving computation to data model (MC) to overcome this synchronization bottleneck in a 1000-cores scale shared memory multicore processor. …

Dual Functional Metal Oxide Nano-Materials Enabled Sensors For Both Non-Enzymatic Glucose And Solid-State Ph Sensing, Qiuchen Dong

Doctoral Dissertations

Glucose sensing and pH sensing are of paramount importance in managing diabetes diseases and accurately monitoring acidity and alkalinity of the solution. To date, numerous reports have reported about solid-state pH sensing and metal oxide based non-enzymatic glucose sensing, however, there is an unmet challenge to realize dual functional sensing elements in a single unit for both glucose sensing and solid-state pH sensing.

As a new class of multifunctional materials, high-temperature annealing enabled iridium oxide nanofibers, rhodium oxide nanocorals, cobalt oxide hollow fiber, and gold-doped iridium oxide nanomaterials were synthesized and then they are first employed as the sensing element …

Optimal Selection Of Test Designs And Sensor Sets For Active Fault Diagnosis, Kyle Palmer

Doctoral Dissertations

Fault detection and isolation (FDI) is crucial to identifying problems that can occur in complex systems. Many industrial systems require the implementation of model-based FDI to reduce the risk of system failure and increase good performance while minimizing the use of additional hardware. Active FDI has become increasingly popular as it uses auxiliary tests to reduce the impact of uncertainty and improve fault diagnosis. A methodical approach is needed to consistently generate feasible test designs for the optimal detectability and isolability of faults in targeted systems. The focus of this dissertation is to design a general framework that improves the …

The 'Land Of Opportunity' Or The Land That Makes Us The Opportunity: An Examination Of Latinx For-Profit Choice Within The Central San Joaquin Valley, Joe A. Vasquez

Doctoral Dissertations

The San Joaquin Valley in Central California is known as an abundant agricultural epicenter with an extensive history of farming, migration, and political movements. Though this geography holds a rich representation of agricultural economy, it is also the site of major inequalities and underrepresentation, especially with regard to post-secondary education within its overrepresented Latinx population. Further amplifying the inequalities around post-secondary education and Latinx’s is the increasing occurrence of post-secondary enrollment into for-profit institutions by this population. Inequities associated with for-profit enrollment, such as high student loan debt and lack of career attainment, further stratify this geography classified as being …

Strain Path Sensitive Polycrystal Plasticity Constitutive Models Within Finite Elements For Metal Forming Simulations, Milovan Zecevic

Doctoral Dissertations

An optimal sheet metal forming process shapes a metal part to the accurate geometry, while avoiding instabilities causing localization of deformation and fracture. Understanding the underlying mechanisms responsible for deformation localization and deviation of final part geometry from the desired geometry facilitates the search for the optimal sheet metal forming process. Accurate modeling of forming processes allows prediction of the formed part shape and can provide insight into the material behavior by interpretation of experimental measurements and prediction of variables not accessible to experimental characterization. In this work, a micromechanical material model is coupled with finite elements to create a …

A Combined Model Of Statistical Downscaling And Latent Process Multivariable Spatial Modeling Of Precipitation Extremes, Meng Zhao

Doctoral Dissertations

Future projections of extreme precipitation can help engineers and scientists with infrastructure design projects and risk assessment studies. Extreme events are usually represented as return levels which are equivalent to upper percentiles of an extreme value distribution, such as the Generalized Pareto distribution, which is used for exceedances above a certain threshold.

My dissertation focus is on uncertainty quantification related to estimation of future return levels for precipitation at the local (weather station) to regional level. Variance reduction is achieved through spatial modeling and optimally combining suites of climate model outputs. The main contribution is a unified statistical model that …

Addressing The Nitrogen Challenge: Footprint Tools And On-Farm Solutions, Allison M. Leach

Doctoral Dissertations

Nitrogen management presents a unique dilemma: We must use nitrogen to grow our food and sustain life on earth, but excess reactive nitrogen that accumulates in the environment contributes to a cascade of negative impacts to human and ecosystem health. Addressing this nitrogen challenge will require a suite of solutions. This dissertation presents and explores three nitrogen management strategies: 1) The first ever integrated carbon and nitrogen footprint tool for campus sustainability management; 2) Exporting compost to improve a farm’s nitrogen efficiency; and 3) Methods for reducing gas emissions from aerated static pile heat recovery composting.

Nitrogen footprint tools connect …

Practicality And Application Of The Algebraic Side-Channel Attack, Chujiao Ma

Doctoral Dissertations

Algebraic Side-Channel Attack (ASCA) is a side-channel attack that models the cryptographic algorithm and side-channel leakage from a system as a set of equations, then solves for the secret key. Unlike pure side-channel attacks, ASCA has low data complexity and can succeed in unknown plaintext/ciphertext scenarios. However, past research on ASCA has been done on either 8-bit microcontroller data or simulated data. In this dissertation, we explore the application and feasibility of error tolerant ASCA on a field-programmable gate array (FPGA). FPGAs run faster and are more difficult for the encryption power trace to be isolated, so it presents more …

High Temperature Characterization Of Ge2sb2te5thin Films For Phase Change Memory Applications, Lhacene Adnane

Doctoral Dissertations

The recent proliferation of portable communication devices or data storage equipment is strongly related to the development of memory technology. Non-volatile semiconductor solid-state memories are needed for high-capacity storage media, high-speed operation and low power consumption, with stringent requirements of retention and endurance. Phase change memory (PCM) is currently seen as one of the most promising candidates for a future storage-class memory with the potential to be close to dynamic random-access memory (DRAM) in speed but with much longer retention times and as dense as flash memory. PCM devices utilize chalcogenide materials (most commonly Ge₂Sb₂Te_{5 …}

Modeling And Control Of Partial Differential Equations (Pde) Described Systems, Tong Ma

Doctoral Dissertations

This proposed research is aimed to develop a novel modeling and control algorithm for the PDE described systems. When dealing with time-dependent PDE problems, the partial derivatives of a function over spatial variables are obtained by approximating the function values at interpolation nodes and their corresponding neighbors as a finite summation of polynomial series. A cluster of interpolation nodes guarantees the boundedness of the residual derivatives. Substituting these approximations in the PDE and discretizing the spatial domain of variables while keeping the time domain continuous yields a system of ODEs. By using an eigenvalue-based technique, a reduced-order model is derived, …

Vulnerability Of Small Island Developing States Across Multiple Scales, Neil Oculi

Doctoral Dissertations

Abstract: Small Island Developing States (SIDS) are among the countries most vulnerable to climate change because of their isolation, geopolitical stature, and limited resources. Climate change will continue to exacerbate SIDS’ vulnerabilities. With this in mind, in this dissertation, I will investigate implications of vulnerabilities of SIDS at global, regional, and local scales.

The first chapter examines the discourse on vulnerability to climate change and its many complexities. Among these is the constant tension between policy makers and academics about vulnerability. This chapter unpacks these complexities in order to analyze how SIDS deal with the notion of vulnerability at the …

Extrusion-Based Direct Write Of Functional Materials From Electronics To Magnetics, Alan Shen

Doctoral Dissertations

New micro- and nanoscale fabrication methods are of vital importance to drive scientific and technological advances in electronics, materials science, physics and biology areas. Direct ink writing (DW) describes a group of mask-less and contactless additive manufacturing (AM), or 3D printing, processes that involve dispensing inks, typically particle suspensions, through a deposition nozzle to create 2D or 3D material patterns with desired architecture and composition on a computer-controlled movable stage. Much of the functional material printing and electronics area remains underdeveloped for this new technology. There is a need to understand and establish the advantages and shortcomings of extrusion-based DW …