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- Creators: Barrett, The Honors College
By means of optimized geometry analysis, pure Ge and Sn were found to adopt the alpha and beta structures, respectively, as observed experimentally. For all theoretical alloys, the corresponding αphase structure was found to have the lowest energy, for Sn percent compositions up to 90%. However at 50% Sn, the correspondingβ alloy energies are predicted to be only ~70 meV higher. The formation energy of α-phase alloys was found to be positive for all compositions, whereas only two beta formation energies were negative. Bond length distributions were analyzed and dependence on Sn incorporation was found, perhaps surprisingly, not to be directly correlated with cell volume. It is anticipated that the data collected in this project may help to elucidate observed complex vibrational properties in these systems.
The two general categories of structural health monitoring (SHM) systems include passive and active monitoring. Active SHM systems utilize an input of energy to monitor the health of a structure (such as sound waves in ultrasonics), while passive systems do not. As such, passive SHM tends to be more desirable. A system could be permanently fixed to a critical location, passively accepting signals until it records a damage event, then localize and characterize the damage. This is the goal of acoustic emissions testing.
When certain types of damage occur, such as matrix cracking or delamination in composites, the corresponding release of energy creates sound waves, or acoustic emissions, that propagate through the material. Audio sensors fixed to the surface can pick up data from both the time and frequency domains of the wave. With proper data analysis, a time of arrival (TOA) can be calculated for each sensor allowing for localization of the damage event. The frequency data can be used to characterize the damage.
In traditional acoustic emissions testing, the TOA combined with wave velocity and information about signal attenuation in the material is used to localize events. However, in instances of complex geometries or anisotropic materials (such as carbon fibre composites), velocity and attenuation can vary wildly based on the direction of interest. In these cases, localization can be based off of the time of arrival distances for each sensor pair. This technique is called Delta T mapping, and is the main focus of this study.
Anatase exists often in its reduced form (TiO2-x), enabling it to perform redox reactions through the absorption and release of oxygen into/from the crystal lattice. These processes result in structural changes, induced by defects in the material, which can theoretically be observed using advanced characterization methods. In situ electron microscopy is one of such methods, and can provide a window into these structural changes. However, in order to interpret the structural evolution caused by defects in materials, it is often necessary and pertinent to use atomistic simulations to compare the experimental images with models.
In this thesis project, we modeled the defect structures in anatase, around oxygen vacancies and at surfaces, using molecular dynamics, benchmarked with density functional theory. Using a “reactive” forcefield designed for the simulation of interactions between anatase and water that can model and treat bonding through the use of bond orders, different vacancy structures were analyzed and simulated. To compare these theoretical, generated models with experimental data, the “multislice approach” to TEM image simulation was used. We investigated a series of different vacancy configurations and surfaces and generated fingerprints for comparison with TEM experiments. This comparison demonstrated a proof of concept for a technique suggesting the possibility for the identification of oxygen vacancy structures directly from TEM images. This research aims to improve our atomic-level understanding of oxide materials, by providing a methodology for the analysis of vacancy formation from very subtle phenomena in TEM images.
“The Garden and Her Secrets” is a young adult novella focused on creating a fantastical world using ASU buildings as inspiration for the key landmarks in this magical landscape. The story centers around a giftless woman, Fiona, striving to make herself extraordinary by breaking hundreds of years of rules and wielding the musical talent of Belle, the unmagical woman who plays at the local piano bar. Fiona’s quest for both love and unlove means finding where the Secret Garden is hiding within her university, the Philomathian, and exploring her newfound feelings for Belle. Should the Secret Garden choose to remove her hood, there are certainly gifts to be had and secrets to rebury.
The aim of my thesis is to expand the placemaking analysis strategies that I learned in my previous thesis pathway course, HON 493: Placemaking in Middle Earth and Earthsea to my favorite fantasy setting, the land of Skyrim in the Elder Scrolls Universe. During the course, the class was encouraged to consider how historical texts, archaeological findings, and anthropological research served as the inspiration behind the worlds that J.R.R. Tolkien and Ursula Le Guin created along with the relationships that their fictional cultures had within those worlds. As the course drew to a close, I couldn’t help but start wondering what inspired the developers of Skyrim, the video game. One of Skyrim’s strongest features is its atmosphere and landscape. An analysis of the creation of place in Skyrim can teach future game developers how to create a land with stories rich enough to lose yourself in for years. I specifically wanted to focus on the burial practices and culture of the Nordic people, since most of the game is spent interacting with them and admittedly raiding the tombs of their ancestors in search of shiny trinkets and powerful artifacts. By delving into the inspirations behind Nordic burials, I hope to gain appreciation for the art of placemaking, and to broaden my knowledge of Nordic history, both fantasy and real. My research initially entailed finding stories about typical Norse burials, but since Skyrim’s burial grounds tend to be filled with the Nordic undead, known as the Draugr, I homed in on how the Norse believed that improper or disturbed burials could result in the rise of the dead. I also shifted attention to the importance of dragons in Norse culture, since they play a vital part in the existence of the Draugr in Skyrim, and I was curious if dragons perhaps played a similar role for the Norse people in the Viking Age. I found academic and historical studies about Viking myths about the origins of dragons and the undead and also studies on how these myths relate to the creation of place in Northern Europe. Lastly, I considered how the dragons and draugr in Skyrim depart from Norse mythology and how the inspirations and departures from Norse mythology deepen our sense of place in the land of Skyrim. This analysis made me realize how essential the Poetic Edda was to Norse mythology, since it’s one of the only written collections of Old Norse poems. The Norse people relied mostly on oral storytelling, which makes it extremely difficult to find any first-hand texts about their culture and lifestyles. After this project, or if I had more time, I think a read-through of the Poetic Edda would be an excellent way of educating myself on the breadth of Norse culture, as opposed to trying to find stories related to what I’ve experienced in Skyrim. I think there’s a limitless way of approaching an analysis of Old Norse culture in modern media and creative works, to the point that I felt I had to narrow my analysis to something simple, but fun, which was homing in on the dragons and draugr that I’ve had to battle thousands of with little previous thought as to their creative origins. The Norse people of the Viking Age may not have had access to our current understanding of the universe, but their speculations led to many fascinating beliefs about the unknown, like tales of dragons and draugar. Their mythology provided them with a unified sense of place and morals in a mercenary culture with loose collective cohesion. When their sense of place is brought into Skyrim and the dragons and draugar are brought to life, it’s easy to lose yourself in a depiction of their world. Skyrim was, and still is, a prime example of the importance of environmental storytelling in open-world games. Long after the graphics and gameplay become outdated, if the environment provides a living, breathing sense of place, then any fantasy game can stand the test of time. For those who aren’t convinced, I encourage them to try out Skyrim and experience their escape into another world with the iconic line, “Hey you, you’re finally awake”.