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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The Magnetoplasmadynamic (MPD) thruster is an electromagnetic thruster that produces a higher specific impulse than conventional chemical rockets and greater thrust densities than electrostatic thrusters, but the well-known operational limit---referred to as ``onset"---imposes a severe limitation efficiency and lifetime. This phenomenon is associated with large fluctuations in operating voltage, high

The Magnetoplasmadynamic (MPD) thruster is an electromagnetic thruster that produces a higher specific impulse than conventional chemical rockets and greater thrust densities than electrostatic thrusters, but the well-known operational limit---referred to as ``onset"---imposes a severe limitation efficiency and lifetime. This phenomenon is associated with large fluctuations in operating voltage, high rates of electrode erosion, and three-dimensional instabilities in the plasma flow-field which cannot be adequately represented by two-dimensional, axisymmetric models. Simulations of the Princeton Benchmark Thruster (PBT) were conducted using the three-dimensional version of the magnetohydrodynamic (MHD) code, MACH. Validation of the numerical model is partially achieved by comparison to equivalent simulations conducted using the well-established two-dimensional, axisymmetric version of MACH. Comparisons with available experimental data was subsequently performed to further validate the model and gain insights into the physical processes of MPD acceleration. Thrust, plasma voltage, and plasma flow-field predictions were calculated for the PBT operating with applied currents in the range $6.5kA < J < 23.25kA$ and mass-flow rates of $1g/s$, $3g/s$, and $6g/s$. Comparisons of performance characteristics between the two versions of the code show excellent agreement, indicating that MACH3 can be expected to be as predictive as MACH2 has demonstrated over multiple applications to MPD thrusters. Predicted thrust for operating conditions within the range which exhibited no symptoms of the onset phenomenon experimentally also showed agreement between MACH3 and experiment well within the experimental uncertainty. At operating conditions beyond such values , however, there is a discrepancy---up to $\sim20\%$---which implies that certain significant physical processes associated with onset are not currently being modeled. Such processes are also evident in the experimental total voltage data, as is evident by the characteristic ``voltage hash", but not present in predicted plasma voltage. Additionally, analysis of the predicted plasma flow-field shows no breakdown in azimuthal symmetry, which is expected to be associated with onset. This implies that perhaps certain physical processes are modeled by neither MACH2 nor MACH3; the latter indicating that such phenomenon may not be inherently three dimensional and related to the plasma---as suggested by other efforts---but rather a consequence of electrode material processes which have not been incorporated into the current models.
ContributorsParma, Brian (Author) / Mikellides, Pavlos G (Thesis advisor) / Squires, Kyle (Committee member) / Herrmann, Marcus (Committee member) / Arizona State University (Publisher)
Created2011
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Description
Microchannel heat sinks can possess heat transfer characteristics unavailable in conventional heat exchangers; such sinks offer compact solutions to otherwise intractable thermal management problems, notably in small-scale electronics cooling. Flow boiling in microchannels allows a very high heat transfer rate, but is bounded by the critical heat flux (CHF). This

Microchannel heat sinks can possess heat transfer characteristics unavailable in conventional heat exchangers; such sinks offer compact solutions to otherwise intractable thermal management problems, notably in small-scale electronics cooling. Flow boiling in microchannels allows a very high heat transfer rate, but is bounded by the critical heat flux (CHF). This thesis presents a theoretical-numerical study of a method to improve the heat rejection capability of a microchannel heat sink via expansion of the channel cross-section along the flow direction. The thermodynamic quality of the refrigerant increases during flow boiling, decreasing the density of the bulk coolant as it flows. This may effect pressure fluctuations in the channels, leading to nonuniform heat transfer and local dryout in regions exceeding CHF. This undesirable phenomenon is counteracted by permitting the cross-section of the microchannel to increase along the direction of flow, allowing more volume for the vapor. Governing equations are derived from a control-volume analysis of a single heated rectangular microchannel; the cross-section is allowed to expand in width and height. The resulting differential equations are solved numerically for a variety of channel expansion profiles and numbers of channels. The refrigerant is R-134a and channel parameters are based on a physical test bed in a related experiment. Significant improvement in CHF is possible with moderate area expansion. Minimal additional manufacturing costs could yield major gains in the utility of microchannel heat sinks. An optimum expansion rate occurred in certain cases, and alterations in the channel width are, in general, more effective at improving CHF than alterations in the channel height. Modest expansion in height enables small width expansions to be very effective.
ContributorsMiner, Mark (Author) / Phelan, Patrick E (Thesis advisor) / Herrmann, Marcus (Committee member) / Chen, Kangping (Committee member) / Arizona State University (Publisher)
Created2011
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Description
A numerical study of incremental spin-up and spin-up from rest of a thermally- stratified fluid enclosed within a right circular cylinder with rigid bottom and side walls and stress-free upper surface is presented. Thermally stratified spin-up is a typical example of baroclinity, which is initiated by a sudden increase in

A numerical study of incremental spin-up and spin-up from rest of a thermally- stratified fluid enclosed within a right circular cylinder with rigid bottom and side walls and stress-free upper surface is presented. Thermally stratified spin-up is a typical example of baroclinity, which is initiated by a sudden increase in rotation rate and the tilting of isotherms gives rise to baroclinic source of vorticity. Research by (Smirnov et al. [2010a]) showed the differences in evolution of instabilities when Dirichlet and Neumann thermal boundary conditions were applied at top and bottom walls. Study of parametric variations carried out in this dissertation confirmed the instability patterns observed by them for given aspect ratio and Rossby number values greater than 0.5. Also results reveal that flow maintained axisymmetry and stability for short aspect ratio containers independent of amount of rotational increment imparted. Investigation on vorticity components provides framework for baroclinic vorticity feedback mechanism which plays important role in delayed rise of instabilities when Dirichlet thermal Boundary Conditions are applied.
ContributorsKher, Aditya Deepak (Author) / Chen, Kangping (Thesis advisor) / Huang, Huei-Ping (Committee member) / Herrmann, Marcus (Committee member) / Arizona State University (Publisher)
Created2011
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Description

The Electoral College, the current electoral system in the U.S., operates on a Winner-Take-All or First Past the Post (FPTP) principle, where the candidate with the most votes wins. Despite the Electoral College being the current system, it is problematic. According to Lani Guinier in Tyranny of the Majority, “the

The Electoral College, the current electoral system in the U.S., operates on a Winner-Take-All or First Past the Post (FPTP) principle, where the candidate with the most votes wins. Despite the Electoral College being the current system, it is problematic. According to Lani Guinier in Tyranny of the Majority, “the winner-take-all principle invariably wastes some votes” (121). This means that the majority group gets all of the power in an election while the votes of the minority groups are completely wasted and hold little to no significance. Additionally, FPTP systems reinforce a two-party system in which neither candidate could satisfy the majority of the electorate’s needs and issues, yet forces them to choose between the two dominant parties. Moreover, voting for a third party candidate only hurts the voter since it takes votes away from the party they might otherwise support and gives the victory to the party they prefer the least, ensuring that the two party system is inescapable. Therefore, a winner-take-all system does not provide the electorate with fair or proportional representation and creates voter disenfranchisement: it offers them very few choices that appeal to their needs and forces them to choose a candidate they dislike. There are, however, alternative voting systems that remedy these issues, such as a Ranked voting system, in which voters can rank their candidate choices in the order they prefer them, or a Proportional voting system, in which a political party acquires a number of seats based on the proportion of votes they receive from the voter base. Given these alternatives, we will implement a software simulation of one of these systems to demonstrate how they work in contrast to FPTP systems, and therefore provide evidence of how these alternative systems could work in practice and in place of the current electoral system.

ContributorsSummers, Jack Gillespie (Co-author) / Martin, Autumn (Co-author) / Burger, Kevin (Thesis director) / Voorhees, Matthew (Committee member) / Computer Science and Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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System and software verification is a vital component in the development and reliability of cyber-physical systems - especially in critical domains where the margin of error is minimal. In the case of autonomous driving systems (ADS), the vision perception subsystem is a necessity to ensure correct maneuvering of the environment

System and software verification is a vital component in the development and reliability of cyber-physical systems - especially in critical domains where the margin of error is minimal. In the case of autonomous driving systems (ADS), the vision perception subsystem is a necessity to ensure correct maneuvering of the environment and identification of objects. The challenge posed in perception systems involves verifying the accuracy and rigidity of detections. The use of Spatio-Temporal Perception Logic (STPL) enables the user to express requirements for the perception system to verify, validate, and ensure its behavior; however, a drawback to STPL involves its accessibility. It is limited to individuals with an expert or higher-level knowledge of temporal and spatial logics, and the formal-written requirements become quite verbose with more restrictions imposed. In this thesis, I propose a domain-specific language (DSL) catered to Spatio-Temporal Perception Logic to enable non-expert users the ability to capture requirements for perception subsystems while reducing the necessity to have an experienced background in said logic. The domain-specific language for the Spatio-Temporal Perception Logic is built upon the formal language with two abstractions. The main abstraction captures simple programming statements that are translated to a lower-level STPL expression accepted by the testing monitor. The STPL DSL provides a seamless interface to writing formal expressions while maintaining the power and expressiveness of STPL. These translated equivalent expressions are capable of directing a standard for perception systems to ensure the safety and reduce the risks involved in ill-formed detections.

ContributorsAnderson, Jacob (Author) / Fainekos, Georgios (Thesis director) / Yezhou, Yang (Committee member) / Computer Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description

The market for searching for food online is exploding. According to one expert at Google, “there are over 1 billion restaurant searches on Google every month” (Kelso, 2020). To capture this market and ride the general digital trend of internet personalization (as evidenced by Google search results, ads, YouTube and

The market for searching for food online is exploding. According to one expert at Google, “there are over 1 billion restaurant searches on Google every month” (Kelso, 2020). To capture this market and ride the general digital trend of internet personalization (as evidenced by Google search results, ads, YouTube and social media algorithms, etc), we created Munch to be an algorithm meant to help people find food they’ll love. <br/><br/>Munch offers the ability to search for food by restaurant or even as specific as a menu item (ex: search for the best Pad Thai). The best part? It is customized to your preferences based on a quiz you take when you open the app and from that point continuously learns from your behavior.<br/><br/>This thesis documents the journey of the team who founded Munch, what progress we made and the reasoning behind our decisions, where this idea fits in a competitive marketplace, how much it could be worth, branding, and our recommendations for a successful app in the future.

ContributorsInocencio, Phillippe Adriane (Co-author) / Rajan, Megha (Co-author) / Krug, Hayden (Co-author) / Byrne, Jared (Thesis director) / Sebold, Brent (Committee member) / Computer Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

Before the COVID-19 pandemic, there was a great need for United States’ restaurants to “go green” due to consumers’ habits of frequently eating out. Unfortunately, COVID-19 has caused this initiative to lose traction. While the amount of customers ordering takeout has increased, there is less emphasis on sustainability.<br/>Plastic is known

Before the COVID-19 pandemic, there was a great need for United States’ restaurants to “go green” due to consumers’ habits of frequently eating out. Unfortunately, COVID-19 has caused this initiative to lose traction. While the amount of customers ordering takeout has increased, there is less emphasis on sustainability.<br/>Plastic is known for its harmful effects on the environment and the extreme length of time it takes to decompose. According to the International Union for Conservation of Nature (IUCN), almost 8 million tons of plastic end up in the oceans at an annual rate, threatening not only the safety of marine species but also human health. Modern food packaging materials have included a blend of synthetic ingredients, trickling into our daily lives and polluting the air, water, and land. Single-use plastic items slowly degrade into microplastics and can take up to hundreds of years to biodegrade.<br/>Due to COVID-19, restaurants have switched to takeout and delivery options to adapt to the new business environment and guidelines enforced by the Center of Disease Control (CDC) mandated guidelines. Some of these guidelines include: notices encouraging social distancing and mask-wearing, mandated masks for employees, and easy access to sanitary supplies. This cultural shift is motivating restaurants to search for a quick, cheap, and easy fix to adapt to the increased demand of take-out and delivery methods. This increases their plastic consumption of items such as plastic bags/paper bags, styrofoam containers, and beverage cups. Plastic is the most popular takeout material because of its price and durability as well as allowing for limited contamination and easy disposability.<br/>Almost all food products come in packaging and this, more often than not, is single-use. Food is the largest market out of all the packaging industry, maintaining roughly two-thirds of material going to food. The US Environmental Protection Agency reports that almost half of all municipal solid waste is made up of food and food packaging materials. In 2014, over 162 million tons of packaging material waste was generated in the states. This typically contains toxic inks and dyes that leach into groundwater and soil. When degrading, pieces of plastic absorb toxins like PCBs and pesticides, and then each piece will, in turn, release toxic chemicals like Bisphenol-A. Even before being thrown away, it causes negative effects for the environment. The creation of packaging materials uses many resources such as petroleum and chemicals and then releases toxic byproducts. Such byproducts include sludge containing contaminants, greenhouse gases, and heavy metal and particulate matter emissions. Unlike many other industries, plastic manufacturing has actually increased production. Demand has increased and especially in the food industry to keep things sanitary. This increase in production is reflective of the increase in waste. <br/>Although restaurants have implemented their own sustainable initiatives to combat their carbon footprint, the pandemic has unfortunately forced restaurants to digress. For example, Just Salad, a fast-food restaurant chain, incentivized customers with discounted meals to use reusable bowls which saved over 75,000 pounds of plastic per year. However, when the pandemic hit, the company halted the program to pivot towards takeout and delivery. This effect is apparent on an international scale. Singapore was in lock-down for eight weeks and during that time, 1,470 tons of takeout and food delivery plastic waste was thrown out. In addition, the Hong Kong environmental group Greeners Action surveyed 2,000 people in April and the results showed that people are ordering out twice as much as last year, doubling the use of plastic.<br/>However, is this surge of plastic usage necessary in the food industry or are there methods that can be used to reduce the amount of waste production? The COVID-19 pandemic caused a fracture in the food system’s supply chain, involving food, factory, and farm. This thesis will strive to tackle such topics by analyzing the supply chains of the food industry and identify areas for sustainable opportunities. These recommendations will help to identify areas for green improvement.

ContributorsDeng, Aretha (Co-author) / Tao, Adlar (Co-author) / Vargas, Cassandra (Co-author) / Printezis, Antonios (Thesis director) / Konopka, John (Committee member) / Department of Supply Chain Management (Contributor) / School of International Letters and Cultures (Contributor) / Department of Information Systems (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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CubeSats can encounter a myriad of difficulties in space like cosmic rays, temperature<br/>issues, and loss of control. By creating better, more reliable software, these problems can be<br/>mitigated and increase the chance of success for the mission. This research sets out to answer the<br/>question: how do we create reliable flight software

CubeSats can encounter a myriad of difficulties in space like cosmic rays, temperature<br/>issues, and loss of control. By creating better, more reliable software, these problems can be<br/>mitigated and increase the chance of success for the mission. This research sets out to answer the<br/>question: how do we create reliable flight software for CubeSats? by providing a concentrated<br/>list of the best flight software development practices. The CubeSat used in this research is the<br/>Deployable Optical Receiver Aperture (DORA) CubeSat, which is a 3U CubeSat that seeks to<br/>demonstrate optical communication data rates of 1 Gbps over long distances. We present an<br/>analysis over many of the flight software development practices currently in use in the industry,<br/>from industry leads NASA, and identify three key flight software development areas of focus:<br/>memory, concurrency, and error handling. Within each of these areas, the best practices were<br/>defined for how to approach the area. These practices were also developed using experience<br/>from the creation of flight software for the DORA CubeSat in order to drive the design and<br/>testing of the system. We analyze DORA’s effectiveness in the three areas of focus, as well as<br/>discuss how following the best practices identified helped to create a more reliable flight<br/>software system for the DORA CubeSat.

ContributorsHoffmann, Zachary Christian (Author) / Chavez-Echeagaray, Maria Elena (Thesis director) / Jacobs, Daniel (Committee member) / Computer Science and Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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"No civil discourse, no cooperation; misinformation, mistruth." These were the words of former Facebook Vice President Chamath Palihapitiya who publicly expressed his regret in a 2017 interview over his role in co-creating Facebook. Palihapitiya shared that social media is ripping apart the social fabric of society and he also sounded

"No civil discourse, no cooperation; misinformation, mistruth." These were the words of former Facebook Vice President Chamath Palihapitiya who publicly expressed his regret in a 2017 interview over his role in co-creating Facebook. Palihapitiya shared that social media is ripping apart the social fabric of society and he also sounded the alarm regarding social media’s unavoidable global impact. He is only one of social media’s countless critics. The more disturbing issue resides in the empirical evidence supporting such notions. At least 95% of adolescents own a smartphone and spend an average time of two to four hours a day on social media. Moreover, 91% of 16-24-year-olds use social media, yet youth rate Instagram, Facebook, and Twitter as the worst social media platforms. However, the social, clinical, and neurodevelopment ramifications of using social media regularly are only beginning to emerge in research. Early research findings show that social media platforms trigger anxiety, depression, low self-esteem, and other negative mental health effects. These negative mental health symptoms are commonly reported by individuals from of 18-25-years old, a unique period of human development known as emerging adulthood. Although emerging adulthood is characterized by identity exploration, unbounded optimism, and freedom from most responsibilities, it also serves as a high-risk period for the onset of most psychological disorders. Despite social media’s adverse impacts, it retains its utility as it facilitates identity exploration and virtual socialization for emerging adults. Investigating the “user-centered” design and neuroscience underlying social media platforms can help reveal, and potentially mitigate, the onset of negative mental health consequences among emerging adults. Effectively deconstructing the Facebook, Twitter, and Instagram (i.e., hereafter referred to as “The Big Three”) will require an extensive analysis into common features across platforms. A few examples of these design features include: like and reaction counters, perpetual news feeds, and omnipresent banners and notifications surrounding the user’s viewport. Such social media features are inherently designed to stimulate specific neurotransmitters and hormones such as dopamine, serotonin, and cortisol. Identifying such predacious social media features that unknowingly manipulate and highjack emerging adults’ brain chemistry will serve as a first step in mitigating the negative mental health effects of today’s social media platforms. A second concrete step will involve altering or eliminating said features by creating a social media platform that supports and even enhances mental well-being.

ContributorsGupta, Anay (Author) / Flores, Valerie (Thesis director) / Carrasquilla, Christina (Committee member) / Barnett, Jessica (Committee member) / The Sidney Poitier New American Film School (Contributor) / Computer Science and Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

Over the years, advances in research have continued to decrease the size of computers from the size of<br/>a room to a small device that could fit in one’s palm. However, if an application does not require extensive<br/>computation power nor accessories such as a screen, the corresponding machine could be microscopic,<br/>only

Over the years, advances in research have continued to decrease the size of computers from the size of<br/>a room to a small device that could fit in one’s palm. However, if an application does not require extensive<br/>computation power nor accessories such as a screen, the corresponding machine could be microscopic,<br/>only a few nanometers big. Researchers at MIT have successfully created Syncells, which are micro-<br/>scale robots with limited computation power and memory that can communicate locally to achieve<br/>complex collective tasks. In order to control these Syncells for a desired outcome, they must each run a<br/>simple distributed algorithm. As they are only capable of local communication, Syncells cannot receive<br/>commands from a control center, so their algorithms cannot be centralized. In this work, we created a<br/>distributed algorithm that each Syncell can execute so that the system of Syncells is able to find and<br/>converge to a specific target within the environment. The most direct applications of this problem are in<br/>medicine. Such a system could be used as a safer alternative to invasive surgery or could be used to treat<br/>internal bleeding or tumors. We tested and analyzed our algorithm through simulation and visualization<br/>in Python. Overall, our algorithm successfully caused the system of particles to converge on a specific<br/>target present within the environment.

ContributorsMartin, Rebecca Clare (Author) / Richa, Andréa (Thesis director) / Lee, Heewook (Committee member) / Computer Science and Engineering Program (Contributor) / School of Mathematical and Statistical Sciences (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05