Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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- Creators: Electrical Engineering Program
Description
The ability of magnetic resonance imaging (MRI) to image any part of the human body without the effects of harmful radiation such as in CAT and PET scans established MRI as a clinical mainstay for a variety of different ailments and maladies. Short wavelengths accompany the high frequencies present in high-field MRI, and are on the same scale as the human body at a static magnetic field strength of 3 T (128 MHz). As a result of these shorter wavelengths, standing wave effects are produced in the MR bore where the patient is located. These standing waves generate bright and dark spots in the resulting MR image, which correspond to irregular regions of high and low clarity. Coil loading is also an inevitable byproduct of subject positioning inside the bore, which decreases the signal that the region of interest (ROI) receives for the same input power. Several remedies have been proposed in the literature to remedy the standing wave effect, including the placement of high permittivity dielectric pads (HPDPs) near the ROI. Despite the success of HPDPs at smoothing out image brightness, these pads are traditionally bulky and take up a large spatial volume inside the already small MR bore. In recent years, artificial periodic structures known as metamaterials have been designed to exhibit specific electromagnetic effects when placed inside the bore. Although typically thinner than HPDPs, many metamaterials in the literature are rigid and cannot conform to the shape of the patient, and some are still too bulky for practical use in clinical settings. The well-known antenna engineering concept of fractalization, or the introduction of self-similar patterns, may be introduced to the metamaterial to display a specific resonance curve as well as increase the metamaterial’s intrinsic capacitance. Proposed in this paper is a flexible fractal-inspired metamaterial for application in 3 T MR head imaging. To demonstrate the advantages of this flexibility, two different metamaterial configurations are compared to determine which produces a higher localized signal-to-noise ratio (SNR) and average signal measured in the image: in the first configuration, the metamaterial is kept rigid underneath a human head phantom to represent metamaterials in the literature (single-sided placement); and in the second, the metamaterial is wrapped around the phantom to utilize its flexibility (double-sided placement). The double-sided metamaterial setup was found to produce an increase in normalized SNR of over 5% increase in five of six chosen ROIs when compared to no metamaterial use and showed a 10.14% increase in the total average signal compared to the single-sided configuration.
ContributorsSokol, Samantha (Author) / Sohn, Sung-Min (Thesis director) / Allee, David (Committee member) / Jones, Anne (Committee member) / Barrett, The Honors College (Contributor) / Electrical Engineering Program (Contributor)
Created2022-05
Description
Precise Position, Navigation, and Timing (PNT) is necessary for the functioning of many critical infrastructure sectors relied upon by millions every day. Specifically, precise timing is primarily provided through the Global Positioning System (GPS) and its system of satellites that each house multiple atomic clocks. Without precise timing, utilities such as the internet, the power grid, navigational systems, and financial systems would cease operation. Because oscillator devices experience frequency drift during operation, many systems rely on the precise time provided by GPS to maintain synchronization across the globe. However, GPS signals are particularly susceptible to disruption – both intentional and unintentional – due to their space-based, low-power, and unencrypted nature. It is for these reasons that there is a need to develop a system that can provide an accurate timing reference – one disciplined by a GPS signal – and can also maintain its nominal frequency in scenarios of intermittent GPS availability.
This project considers an accurate timing reference deployed via Field Programmable Gate Array (FPGA) and disciplined by a GPS module. The objective is to implement a timing reference on a DE10-Lite FPGA disciplined by the 1 Pulse-Per-Second (PPS) output of an MTK3333 GPS module. When a signal lock is achieved with GPS, the MTK3333 delivers a pulse input to the FPGA on the leading edge of every second. The FPGA aligns a digital oscillator to this PPS reference, providing a disciplined output signal at a 10 MHz frequency that is maintained in events of intermittent GPS availability. The developed solution is evaluated using a frequency counter disciplined by an atomic clock in addition to an oscilloscope. The findings deem the software solution acceptable with more work needed to debug the hardware solution
ContributorsWitthus, Alexander (Author) / Allee, David (Thesis director) / Hartin, Olin (Committee member) / Barrett, The Honors College (Contributor) / Electrical Engineering Program (Contributor)
Created2022-05
Description
This study measure the effect of temperature on a neural network's ability to detect and classify solar panel faults. It's well known that temperature negatively affects the power output of solar panels. This has consequences on their output data and our ability to distinguish between conditions via machine learning.
ContributorsVerch, Skyler (Author) / Spanias, Andreas (Thesis director) / Tepedelenlioğlu, Cihan (Committee member) / Barrett, The Honors College (Contributor) / Electrical Engineering Program (Contributor)
Created2022-12
Description
This paper delves into the carbon footprint generated by AI chips during their training and operational phases. It highlights the often-overlooked environmental impact of training AI models like ChatGPT, emphasizing the significant CO2 emissions and computational demands involved. The paper also explores the paradoxical nature of AI, which, while contributing to climate change, also holds potential in combating its effects. This dual role of AI sparks ethical debates, particularly concerning strategies to minimize the carbon emissions associated with AI training. Some potential solutions, such as increased transparency among AI-utilizing companies and the adoption of analog-in-memory computing, to address these challenges while also continuing to push the boundaries of AI computing.
ContributorsMulvey, Nicole (Author) / Marinella, Matthew (Thesis director) / Short, Jesse (Committee member) / Barrett, The Honors College (Contributor) / Electrical Engineering Program (Contributor)
Created2023-12
Description
This research explores the potential use of microwave energy to detect various substances in water, with a focus on water quality assessment and pathogen detection applications. There are many non-thermal effects of microwaves on microorganisms and their resonant frequencies could be used to identify and possibly destroy harmful pathogens, such as bacteria and viruses, without heating the water. A wide range of materials, including living organisms like Daphnia and Moina, plants, sand, plastic, and salt, were subjected to microwave measurements to assess their influence on the transmission (S21) measurements. The measurements of the living organisms did not display distinctive resonant frequencies and variations in water volume may be the source of the small measurement differences. Conversely, sand and plastic pellets affected the measurements differently, with their arrangement within the test tube emerging as a significant factor. This study also explores the impact of salinity on measurements, revealing a clear pattern that can be modeled as a series RLC resonator. Although unique resonant frequencies for the tested organisms were not identified, the presented system demonstrates the potential for detecting contaminants based on variations in measurements. Future research may extend this work to include a broader array of organisms and enhance measurement precision.
ContributorsChild, Carson (Author) / Aberle, James (Thesis director) / Blain Christen, Jennifer (Committee member) / Barrett, The Honors College (Contributor) / Electrical Engineering Program (Contributor)
Created2023-12
Description
Every year, Arizona mobile home residents suffer hundreds of fatalities and severe
illnesses due to the effects of extreme heat within their homes exacerbated by high energy costs, a lack of energy-efficient infrastructure, and underlying socio-economic issues. Many of these deaths and severe illnesses can be prevented via active monitoring and reporting of temperature and humidity data from these living spaces. The team will design, build, test, and implement a Heat Warning Detection System (HWDS) to mitigate heat-related illnesses and deaths. The HWDS will detect when temperature and humidity levels have reached a dangerous threshold and will issue notifications to the emergency contacts of the resident over SMS and/or email. This will allow for timely preventative measures to be taken to ensure the safety of the resident. The team will investigate the ideal threshold to notify the mobile home residents.
HWDS will require minimal user interaction. Apart from the initial physical installation of the device, the user will have to provide a list of emergency contacts that they would like the
system to notify in the event that HWDS detects dangerous conditions in their residence. By
deploying prototypes of HWDS to volunteer participant homes, we will be able to validate the
functionality of the system as well as the usability of the physical device by homeowners.
HWDS provides homeowners and their loved ones with the opportunity to take preventative
measures before being exposed to conditions that could potentially have more severe
implications. In the spirit of promoting accessibility and prevention among the most vulnerable
communities in Greater Phoenix, our team partners with the Knowledge Exchange for Resilience at ASU (KER) to interface with organizations such as the Arizona Association of Manufactured Home, RV & Park Model Owners (AAMHO) to promote legislation and subsidies aimed towards making solutions such as ours more financially viable for the communities that need it most.
ContributorsDrake, Thomas (Author) / Yeager, William (Co-author) / Ward, Trenton (Co-author) / Schoepf, Jared (Thesis director) / Solís, Patricia (Committee member) / Barrett, The Honors College (Contributor) / Electrical Engineering Program (Contributor)
Created2024-05
ContributorsDrake, Thomas (Author) / Yeager, William (Co-author) / Ward, Trenton (Co-author) / Schoepf, Jared (Thesis director) / Solís, Patricia (Committee member) / Barrett, The Honors College (Contributor) / Electrical Engineering Program (Contributor)
Created2024-05
ContributorsDrake, Thomas (Author) / Yeager, William (Co-author) / Ward, Trenton (Co-author) / Schoepf, Jared (Thesis director) / Solís, Patricia (Committee member) / Barrett, The Honors College (Contributor) / Electrical Engineering Program (Contributor)
Created2024-05