ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
Displaying 21 - 30 of 67
Description
In this dissertation, far UV spectroscopy is applied to investigate the optical properties of dielectric thin films grown by atomic layer deposition. The far UV (120 – 200 nm) reflectance for several dielectric oxides and fluorides, including AlF3, Al2O3, Ga2O3, HfO2, and SiO2, was measured at variable angles and thicknesses. Multiple optical calculation methods were developed for the accurate determination of the optical constants from the reflectance. The deduced optical constants were used for optical designs, such as high-reflectivity coatings, and Fabry-Perot bandpass interference filters. Three filters were designed for use at 157 nm, 212 nm, and 248 nm wavelengths, based on multilayer structures consisting of SiO2, Al2O3, HfO2, and AlF3. A thorough error analysis was made to quantify the non-idealities of the optical performance for the designed filters. Far UV spectroscopy was also applied to analyze material mixtures, such as AlF3/Al and h-BN/c-BN mixtures. Using far UV spectroscopy, different phases in the composite can be distinguished, and the volume concentration of each constituent can be determined. A middle UV reflective coating based on A2O3 and AlF3 was fabricated and characterized. The reflective coating has a smooth surface (?? < 1 nm), and a peak reflectance of 25 – 30 % at a wavelength of 196 nm. The peak reflectance deviated from the design, and an analysis of the AlF3 layer prepared by plasma-enhanced atomic layer deposition (PEALD) indicated the presence of Al-rich clusters, which were associated with the UV absorption. Complementary techniques, such as spectroscopic ellipsometry, and X-ray photoelectron spectroscopy, were used to verify the results from far UV spectroscopy. In conclusion, this Dissertation demonstrated the use of in-situ far UV spectroscopy to investigate the optical properties of thin films at short wavelengths. This work extends the application of far UV spectroscopy to ultrawide bandgap semiconductors and insulators. This work supports a path forward for far UV optical filters and devices. Various errors have been discussed with solutions proposed for future research of methods and materials for UV optics.
ContributorsHuang, Zhiyu (Author) / Nemanich, Robert (Thesis advisor) / Ponce, Fernando (Committee member) / Menéndez, Jose (Committee member) / Holman, Zachary (Committee member) / Arizona State University (Publisher)
Created2021
Description
The climate-driven volumetric response of unsaturated soils (shrink-swell and frost heave) frequently causes costly distresses in lightly loaded structures (pavements and shallow foundations) due to the sporadic climatic fluctuations and soil heterogeneity which is not captured during the geotechnical design. The complexity associated with the unsaturated soil mechanics combined with the high degree of variability in both the natural characteristics of soil and the empirical models which are commonly implemented tends to lead to engineering judgment outweighing the results of deterministic computations for the basis of design. Recent advances in the application of statistical techniques and Bayesian Inference in geotechnical modeling allows for the inclusion of both parameter and model uncertainty, providing a quantifiable representation of this invaluable engineering judgement. The overall goal achieved in this study was to develop, validate, and implement a new method to evaluate climate-driven volume change of shrink-swell soils using a framework that encompasses predominantly stochastic time-series techniques and mechanistic shrink-swell volume change computations. Four valuable objectives were accomplished during this research study while on the path to complete the overall goal: 1) development of an procedure for automating the selection of the Fourier Series form of the soil suction diffusion equations used to represent the natural seasonal variations in suction at the ground surface, 2) development of an improved framework for deterministic estimation of shrink-swell soil volume change using historical climate data and the Fourier series suction model, 3) development of a Bayesian approach to randomly generate combinations of correlated soil properties for use in stochastic simulations, and 4) development of a procedure to stochastically forecast the climatic parameters required for shrink-swell soil volume change estimations. The models presented can be easily implemented into existing foundation and pavement design procedures or used for forensic evaluations using historical data. For pavement design, the new framework for stochastically forecasting the variability of shrink-swell soil volume change provides significant improvement over the existing empirical models that have been used for more than four decades.
ContributorsOlaiz, Austin Hunter (Author) / Zapata, Claudia (Thesis advisor) / Houston, Sandra (Committee member) / Kavazanjian, Edward (Committee member) / Soltanpour, Yasser (Committee member) / Arizona State University (Publisher)
Created2022
Description
Some subterranean animals, such as mole-rats, can burrow underground, sense the environment around them, and communicate with each other. Inspired by the mole-rats, this dissertation is dedicated to developing an active wireless underground sensor network (WUSN) for active underground exploration. Special attention is paid to two key functions: wireless underground data transmission, and underground self-burrowing. In this study, a wireless underground communication system based on seismic waves was developed. The system includes a bio-inspired vibrational source, an accelerometer as the receiver, and a set of algorithms for encoding and decoding information. With the current design, a maximum transmission bit rate of 16–17 bits per second and a transmission distance of 80 cm is achieved. The transmission range is limited by the size of container used in the laboratory experiments. The bit error ratio is as low as 0.1%, demonstrating the robustness of the algorithms. The performance of the developed system shows that seismic waves produced by vibration can be used as an information carrier and can potentially be implemented in the active WUSNs. A minimalistic horizontal self-burrowing robot was designed. The robot mainly consists of a tip (flat, cone, or auger), and a pair of cylindrical parts. The robot can achieve extension-contraction with the utilization of a linear actuator and have options for tip rotation with an embedded gear motor. Using a combined numerical simulation and laboratory testing approach, symmetry-breaking is validated to be the key to underground burrowing. The resistance-displacement curves during the extension-contraction cycles of the robot can be used to quantify the overall effect of asymmetries and estimate the burrowing behavior of the robots. Findings from this research shed light on the future development of self-burrowing robots and active WUSNs.
ContributorsZhong, Yi (Author) / Tao, Junliang (Thesis advisor) / Kavazanjian, Edward (Committee member) / Martinez, Alejandro (Committee member) / Arizona State University (Publisher)
Created2023
Description
Seed awns (Erodium and Pelargonium) bury themselves into ground for germination usinghygroscopic coiling and uncoilingmovements. Similarly,wormlizards (Amphisbaenia) create
tunnels for habitation by oscillating their heads along the long axis of the trunks. Inspired by
these burrowing strategies, this research aims to understand these mechanisms from a soil
mechanics perspective, investigate the factors influencing penetration resistance, and develop
a self-burrowing technology for subterranean explorations. The rotational movements of
seed awns, specifically their coiling and uncoiling movements, were initially examined
using the Discrete Element Method (DEM) under shallow and dry conditions. The findings
suggest that rotation reduces penetration resistance by decreasing penetrator-particle contact
number and the force exerted, and by shifting the contact force away from vertical direction.
The effects of rotation were illustrated through the force chain network, displacement field,
and particle trajectories, supporting the "force chain breakage" hypothesis and challenging
the assumptions of previous analytical models. The factors reducing penetration resistance
were subsequently examined, both numerically and experimentally. The experimental results
link the reduction of horizontal penetration resistance to embedment depth and penetrator
geometry. Notably, both numerical and experimental results confirm that the reduction of
penetration resistance is determined by the relative slip velocity, not by the absolute values.
The reduction initially spikes sharply with the relative slip velocity, then increases at a slower
rate, leveling off at higher relative slip velocities. Additional findings revealed a minimal
impact of relative density, particle shape, and inertial number on penetration resistance
reduction. Conversely, interface friction angle appeared to increase the reduction, while
penetrator roundness and confining pressure decreased it. The investigation also extended
to the effect of rotational modes on the reduction of penetration resistance. Reductions
between cone-continuous rotation (CCR) and cone-oscillatory rotation (COR) cases were
i
comparable. However, whole-body-continuous rotation (WCR) yielded a higher reduction
under the same relative slip velocities. Interestingly, the amplitude of oscillation movement
demonstrated a negligible effect on the reduction. Lastly, a self-burrowing soft robot was
constructed based on these insights. Preliminary findings indicate that the robot can move
horizontally, leveraging a combination of extensioncontraction and rotational movements.
ContributorsTang, Yong (Author) / Tao, Junliang (Thesis advisor) / Kavazanjian, Edward (Committee member) / Marvi, Hamid (Committee member) / Arizona State University (Publisher)
Created2023
Characterization and Manipulation of Microbiomes From Arid Landfills for Improved Methane Production
Description
Environmentally harmful byproducts from solid waste’s decomposition, including methane (CH4) emissions, are managed through standardized landfill engineering and gas-capture mechanisms. Yet only a limited number of studies have analyzed the development and composition of Bacteria and Archaea involved in CH4 production from landfills. The objectives of this research were to compare microbiomes and bioactivity from CH4-producing communities in contrasting spatial areas of arid landfills and to tests a new technology to biostimulate CH4 production (methanogenesis) from solid waste under dynamic environmental conditions controlled in the laboratory. My hypothesis was that the diversity and abundance of methanogenic Archaea in municipal solid waste (MSW), or its leachate, play an important role on CH4 production partially attributed to the group’s wide hydrogen (H2) consumption capabilities. I tested this hypothesis by conducting complementary field observations and laboratory experiments. I describe niches of methanogenic Archaea in MSW leachate across defined areas within a single landfill, while demonstrating functional H2-dependent activity. To alleviate limited H2 bioavailability encountered in-situ, I present biostimulant feasibility and proof-of-concepts studies through the amendment of zero valent metals (ZVMs). My results demonstrate that older-aged MSW was minimally biostimulated for greater CH4 production relative to a control when exposed to iron (Fe0) or manganese (Mn0), due to highly discernable traits of soluble carbon, nitrogen, and unidentified fluorophores found in water extracts between young and old aged, starting MSW. Acetate and inhibitory H2 partial pressures accumulated in microcosms containing old-aged MSW. In a final experiment, repeated amendments of ZVMs to MSW in a 600 day mesocosm experiment mediated significantly higher CH4 concentrations and yields during the first of three ZVM injections. Fe0 and Mn0 experimental treatments at mesocosm-scale also highlighted accelerated development of seemingly important, but elusive Archaea including Methanobacteriaceae, a methane-producing family that is found in diverse environments. Also, prokaryotic classes including Candidatus Bathyarchaeota, an uncultured group commonly found in carbon-rich ecosystems, and Clostridia; All three taxa I identified as highly predictive in the time-dependent progression of MSW decomposition. Altogether, my experiments demonstrate the importance of H2 bioavailability on CH4 production and the consistent development of Methanobacteriaceae in productive MSW microbiomes.
ContributorsReynolds, Mark Christian (Author) / Cadillo-Quiroz, Hinsby (Thesis advisor) / Krajmalnik-Brown, Rosa (Thesis advisor) / Wang, Xuan (Committee member) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2022
Description
The presence of expansive soils underneath pavement structures is considered one of the most common sources of pavement distresses, due to differential settlements caused by differential moisture distribution attributed to soil heterogeneity and seasonal climatic fluctuations. The cost of the repairs to the infrastructure caused by expansive soils is estimated to exceed 10 billion dollars annually in the US, as reported by Puppala and Cerato (2009). Although many studies have been developed to better understand the volume change of unsaturated soils and incorporate the effect of swelling/shrinkage behavior into pavement design procedures, current methodologies are still based on simple correlations with index properties or other empirical methods. Such solutions lead to poor or uneconomical design practices. The objective of this study was to calibrate and implement a new mechanistic, stochastic model that predicts pavement distresses caused by the presence of expansive soils. Three major tasks were completed to fulfill the objective of this study: 1) a laboratory research program performed to estimate the volume change of compacted specimens, with different expansion potential, due to the simultaneous application of suction and net normal stresses, 2) the calibration of a new mechanistic free-swell model for expansive soils tailored to pavement structures, based on elevation information collected from the Long Term Pavement Performance (LTPP) program, and 3) the incorporation and calibration of the free-swell stochastic model results into the current Pavement Mechanistic-Empirical (ME) Design procedure using the International Roughness Index (IRI) models.
The results presented includes: 1) an empirical model to estimate volume change due to the coupled effect of suction, and net normal stresses, for soils with different soil index properties, 2) a calibrated model to adjust the free-swell results of the mechanistic-stochastic model developed by Olaiz et al. (2021), and 3) an updated IRI equation for asphalt concrete pavements to account for volume change fluctuations due to changes in suction stress conditions. The models presented can be easily implemented into currently available pavement design procedures and greatly improves over the existing empirical models that have been used for more than four decades.
ContributorsMosawi, Mohammad (Author) / Zapata, Claudia E (Thesis advisor) / Kavazanjian, Edward (Committee member) / Kaloush, Kamil E (Committee member) / Arizona State University (Publisher)
Created2022
Description
Bridge scour at piers is a major problem for design and for maintaining old infrastructure. The current methods require their own upkeep and there may be better ways to mitigate scour. I looked to the mangrove forests of coastal environments for inspiration and have developed a 2D model to test the efficacy of placing a mangrove-root inspired system to mitigate scour. My model tests the hydrodynamics of the root systems, but there are additional benefits that can be used as bioinspiration in the future (altering the surrounding chemistry and mechanical properties of the soil).Adding a mangrove inspired minipile system to bridge piers changes scour parameters within my 2D COMSOL models. For the volume of material added, the minipiles compare favorably to larger sacrificial piles as they reduce A_wcz and 〖τ'〗_max by similar (or even better) amounts. These two parameters are indicators of scour in the field. Within the minipile experiments, it is more beneficial to place them upstream of the main bridge pier as their own ‘mangrove forest.’ The value of A_wcz and 〖τ'〗_max for complex 2D models of scour is unclear and physical experiments need to be performed. The model geometry is based on the dimensions of the experimental flume to be used in future studies and the model results have not yet been verified through experiments and field trials. Scale effects may be present which cannot be accounted for in the 2D models. Therefore future work should be conducted to test ‘mangrove forest’ minipile systems in 3D space, in flume experiments, and in field trials.
ContributorsEnns, Andrew Carl (Author) / van Paassen, Leon (Thesis advisor) / Tao, Junliang (Thesis advisor) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2021
Description
It has been found that certain biological organisms, such as Erodium seeds and Scincus scincus, are capable of effectively and efficiently burying themselves in soil. Biological Organisms employ various locomotion modes, including coiling and uncoiling motions, asymmetric body twisting, and undulating movements that generate motion waves. The coiling-uncoiling motion drives a seed awn to bury itself like a corkscrew, while sandfish skinks use undulatory swimming, which can be thought of as a 2D version of helical motion. Studying burrowing behavior aims to understand how animals navigate underground, whether in their natural burrows or underground habitats, and to implement this knowledge in solving geotechnical penetration problems. Underground horizontal burrowing is challenging due to overcoming the resistance of interaction forces of granular media to move forward. Inspired by the burrowing behavior of seed-awn and sandfish skink, a horizontal self-burrowing robot is developed. The robot is driven by two augers and stabilized by a fin structure. The robot’s burrowing behavior is studied in a laboratory setting. It is found that rotation and propulsive motion along the axis of the auger’s helical shape significantly reduce granular media’s resistance against horizontal penetration by breaking kinematic symmetry or granular media boundary. Additional thrusting and dragging tests were performed to examine the propulsive and resistive forces and unify the observed burrowing behaviors. The tests revealed that the rotation of an auger not only reduces the resistive force and generates a propulsive force, which is influenced by the auger geometry, rotational speed, and direction. As a result, the burrowing behavior of the robot can be predicted using the geometry-rotation-force relations.
ContributorsShaharear, Md Ragib (Author) / Tao, Junliang (Thesis advisor) / Kavazanjian, Edward (Committee member) / Marvi, Hamidreza (Committee member) / Arizona State University (Publisher)
Created2023
Description
Rare-earth tritellurides (RTe3) are two-dimensional materials with unique quantum properties, ideal for investigating quantum phenomena and applications in supercapacitors, spintronics, and twistronics. This dissertation examines the electronic, magnetic, and phononic properties of the RTe3 family, exploring how these can be controlled using chemical pressure, cationic alloying, and external pressure.The impact of chemical pressure on RTe3 phononic properties was investigated through noninvasive micro-Raman spectroscopy, demonstrating the potential of optical measurements for determining charge density wave (CDW) transition temperatures. Cationic alloying studies showed seamless tuning of CDW transition temperatures by modifying lattice constants and revealed complex magnetism in alloyed RTe3 with multiple magnetic transitions.
A comprehensive external pressure study examined the influence of spacing between RTe3 layers on phononic and CDW properties across the RTe3 family. Comparisons between different RTe3 materials showed LaTe3, with the largest thermodynamic equilibrium interlayer spacing (smallest chemical pressure), has the most stable CDW phases at high pressures. Conversely, CDW phases in late RTe3 systems with larger internal chemical pressures were more easily suppressed by applied pressure.
The dissertation also investigated Schottky barrier realignment at RTe3/semiconductor interfaces induced by CDW transitions, revealing changes in Schottky barrier height and ideality factor around the CDW transition temperature. This indicates that chemical potential changes of RTe3 below the CDW transition temperature influence Schottky junction properties, enabling CDW state probing through interface property measurements.
A detailed experimental and theoretical analysis of the oxidation process of RTe3 compounds was performed, which revealed faster degradation in late RTe3 systems. Electronic property changes, like CDW transition temperature and chemical potential, are observed as degradation progresses. Quantum mechanical simulations suggested that degradation primarily results from strong oxidizing reactions with O2 molecules, while humidity (H2O) plays a negligible role unless Te vacancies exist.
Lastly, the dissertation establishes a large-area thin film deposition at relatively low temperatures using a soft sputtering technique. While focused on MoTe2 deposition, this technique may also apply to RTe3 thin film deposition.
Overall, this dissertation expands the understanding of the fundamental properties of RTe3 materials and lays the groundwork for potential device applications.
ContributorsYumigeta, Kentaro (Author) / Tongay, Sefaattin (Thesis advisor) / Ponce, Fernando (Committee member) / Drucker, Jeffery (Committee member) / Erten, Onur (Committee member) / Arizona State University (Publisher)
Created2023
Description
One of the most economical and viable methods of soil improvement is dynamic compaction. It is a simple process that uses the potential energy of a weight (8 tonne to 36 tonne) dropped from a height of about 1 m to 30 m, depending on the project requirement, on to the soil to be compacted hence densifying it. However, dynamic compaction can only be applied on soil deposits where the degree of saturation is low and the permeability of the soil mass is high to allow for good drainage. Using dynamic compaction on saturated soil is unsuitable because upon application of the energy, a part of the energy is transferred to the pore water. The technique also does not work very well on soils having a large content of fines because of the absence of good drainage. The current research aims to develop a new technology using biogenic gas production to desaturate saturated soils and extend the use of dynamic compaction as a ground improvement technique to saturated soils with higher fines content. To evaluate the feasibility of this technology an experimental program has been performed. Soil columns with varying soil types have been saturated with substrate solution, resulting in the formation of nitrogen gas and the change in soils volume and saturation have been recorded. Cyclic triaxial tests have been performed to evaluate the change in volume and saturation under elevated pressure conditions and evaluate the response of the desaturated soil specimens to dynamic loading. The experimental results showed that soil specimens treated with MIDP under low confinement conditions undergo substantial volume expansion. The amount of expansion is seen to be a factor of their pore size, which is directly related to their grain size. The smaller the grain size, smaller is the pore size and hence greater the volume expansion. Under higher confining pressure conditions, the expansion during gas formation is suppressed. However, no conclusive result about the effect of the desaturation of the soil using biogenic gas on its compactibility could be obtained from the cyclic triaxial tests.
ContributorsBorah, Devajani (Author) / van Paassen, Leon A. (Thesis advisor) / Kavazanjian, Edward (Committee member) / Zapata, Claudia E. (Committee member) / Arizona State University (Publisher)
Created2018