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High-entropy alloys possessing mechanical, chemical, and electrical properties that far exceed those of conventional alloys have the potential to make a significant impact on many areas of engineering. Identifying element combinations and configurations to form these alloys, however, is a difficult, time-consuming, computationally intensive task. Machine learning has revolutionized many

High-entropy alloys possessing mechanical, chemical, and electrical properties that far exceed those of conventional alloys have the potential to make a significant impact on many areas of engineering. Identifying element combinations and configurations to form these alloys, however, is a difficult, time-consuming, computationally intensive task. Machine learning has revolutionized many different fields due to its ability to generalize well to different problems and produce computationally efficient, accurate predictions regarding the system of interest. In this thesis, we demonstrate the effectiveness of machine learning models applied to toy cases representative of simplified physics that are relevant to high-entropy alloy simulation. We show these models are effective at learning nonlinear dynamics for single and multi-particle cases and that more work is needed to accurately represent complex cases in which the system dynamics are chaotic. This thesis serves as a demonstration of the potential benefits of machine learning applied to high-entropy alloy simulations to generate fast, accurate predictions of nonlinear dynamics.

ContributorsDaly, John H (Author) / Ren, Yi (Thesis director) / Zhuang, Houlong (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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The partially-depleted (PD) silicon Metal Semiconductor Field Effect Transistor (MESFET) is becoming more and more attractive for analog and RF applications due to its high breakdown voltage. Compared to conventional CMOS high voltage transistors, the silicon MESFET can be fabricated in commercial standard Silicon-on-Insulator (SOI) CMOS foundries without any change

The partially-depleted (PD) silicon Metal Semiconductor Field Effect Transistor (MESFET) is becoming more and more attractive for analog and RF applications due to its high breakdown voltage. Compared to conventional CMOS high voltage transistors, the silicon MESFET can be fabricated in commercial standard Silicon-on-Insulator (SOI) CMOS foundries without any change to the process. The transition frequency of the device is demonstrated to be 45GHz, which makes the MESFET suitable for applications in high power RF power amplifier designs. Also, high breakdown voltage and low turn-on resistance make it the ideal choice for switches in the switching regulator designs. One of the anticipated applications of the MESFET is for the pass device for a low dropout linear regulator. Conventional NMOS and PMOS linear regulators suffer from high dropout voltage, low bandwidth and poor stability issues. In contrast, the N-MESFET pass transistor can provide an ultra-low dropout voltage and high bandwidth without the need for an external compensation capacitor to ensure stability. In this thesis, the design theory and problems of the conventional linear regulators are discussed. N-MESFET low dropout regulators are evaluated and characterized. The error amplifier used a folded cascode architecture with gain boosting. The source follower topology is utilized as the buffer to sink the gate leakage current from the MESFET. A shunt-feedback transistor is added to reduce the output impedance and provide the current adaptively. Measurement results show that the dropout voltage is less than 150 mV for a 1A load current at 1.8V output. Radiation measurements were done for discrete MESFET and fully integrated LDO regulators, which demonstrate their radiation tolerance ability for aerospace applications.
ContributorsChen, Bo (Author) / Thornton, Trevor (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2013
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The constant scaling of supply voltages in state-of-the-art CMOS processes has led to severe limitations for many analog circuit applications. Some CMOS processes have addressed this issue by adding high voltage MOSFETs to their process. Although it can be a completely viable solution, it usually requires a changing of the

The constant scaling of supply voltages in state-of-the-art CMOS processes has led to severe limitations for many analog circuit applications. Some CMOS processes have addressed this issue by adding high voltage MOSFETs to their process. Although it can be a completely viable solution, it usually requires a changing of the process flow or adding additional steps, which in turn, leads to an increase in fabrication costs. Si-MESFETs (silicon-metal-semiconductor-field-effect-transistors) from Arizona State University (ASU) on the other hand, have an inherent high voltage capability and can be added to any silicon-on-insulator (SOI) or silicon-on-sapphire (SOS) CMOS process free of cost. This has been proved at five different commercial foundries on technologies ranging from 0.5 to 0.15 μm. Another critical issue facing CMOS processes on insulated substrates is the scaling of the thin silicon channel. Consequently, the future direction of SOI/SOS CMOS transistors may trend away from partially depleted (PD) transistors and towards fully depleted (FD) devices. FD-CMOS are already being implemented in multiple applications due to their very low power capability. Since the FD-CMOS market only figures to grow, it is appropriate that MESFETs also be developed for these processes. The beginning of this thesis will focus on the device aspects of both PD and FD-MESFETs including their layout structure, DC and RF characteristics, and breakdown voltage. The second half will then shift the focus towards implementing both types of MESFETs in an analog circuit application. Aside from their high breakdown ability, MESFETs also feature depletion mode operation, easy to adjust but well controlled threshold voltages, and fT's up to 45 GHz. Those unique characteristics can allow certain designs that were previously difficult to implement or prohibitively expensive using conventional technologies to now be achieved. One such application which benefits is low dropout regulators (LDO). By utilizing an n-channel MESFET as the pass transistor, a LDO featuring very low dropout voltage, fast transient response, and stable operation can be achieved without an external capacitance. With the focus of this thesis being MESFET based LDOs, the device discussion will be mostly tailored towards optimally designing MESFETs for this particular application.
ContributorsLepkowski, William (Author) / Thornton, Trevor (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Goryll, Michael (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2010
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The goal of this research was to identify why the federal government should invest in solar research and development, and which areas of solar improvement should be focused on. Motivation for this can be found in the pressing need to prevent and reverse the effects of climate change, the inevitability

The goal of this research was to identify why the federal government should invest in solar research and development, and which areas of solar improvement should be focused on. Motivation for this can be found in the pressing need to prevent and reverse the effects of climate change, the inevitability of fossil fuel resources eventually running out, and the economic and job creation potential which solar energy holds. Additionally, it is important to note that the best course of action will involve a split of funding between current solar rollout and energy grid updating, and the R&D listed in this research. Upon examination, it can be seen that an energy revolution, led by a federal solar jobs program and a Green New Deal, would be both an ethically and economically beneficial solution. A transition from existing fossil fuel infrastructure to renewable, solar-powered infrastructure would not only be possible but highly beneficial in many aspects, including massive job creation, a more affordable, renewable energy solution to replace coal-fired plants, and no fuel spending or negotiation required.<br/>When examining which areas of solar improvement to focus on for R&D funding, four primary areas were identified, with solutions presented for each. These areas for improvement are EM capture, EM conversion efficiency, energy storage capacity, and the prevention of overheating. For each of these areas of improvement, affordable solutions that would greatly improve the efficiency and viability of solar as a primary energy source were identified. The most notable area that should be examined is solar storage, which would allow solar PV panels to overcome their greatest real and perceived obstacle, which is the inconsistent power generation. Solar storage is easily attainable, and with enough storage capacity, excess solar energy which would otherwise be wasted during the day can be stored and used during the night or cloudy weather as necessary. Furthermore, the implementation of highly innovative solutions, such as agrivoltaics, would allow for a solar revolution to occur.

ContributorsWhitlow, Hunter Marshall (Author) / Fong, Benjamin (Thesis director) / Andino, Jean (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Engineering is a multidisciplinary field with a variety of applications. However, since there are so many disciplines of engineering, it is often challenging to find the discipline that best suits an individual interested in engineering. Not knowing which area of engineering most aligns to one’s interests is challenging when deciding

Engineering is a multidisciplinary field with a variety of applications. However, since there are so many disciplines of engineering, it is often challenging to find the discipline that best suits an individual interested in engineering. Not knowing which area of engineering most aligns to one’s interests is challenging when deciding on a major and a career. With the development of the Engineering Interest Quiz (EIQ), the goal was to help individuals find the field of engineering that is most similar to their interests. Initially, an Engineering Faculty Survey (EFS) was created to gather information from engineering faculty at Arizona State University (ASU) and to determine keywords that describe each field of engineering. With this list of keywords, the EIQ was developed. Data from the EIQ compared the engineering students’ top three results for the best engineering discipline for them with their current engineering major of study. The data analysis showed that 70% of the respondents had their major listed as one of the top three results they were given and 30% of the respondents did not have their major listed. Of that 70%, 64% had their current major listed as the highest or tied for the highest percentage and 36% had their major listed as the second or third highest percentage. Furthermore, the EIQ data was compared between genders. Only 33% of the male students had their current major listed as their highest percentage, but 55% had their major as one of their top three results. Women had higher percentages with 63% listing their current major as their highest percentage and 81% listing it in the top three of their final results.
ContributorsWagner, Avery Rose (Co-author) / Lucca, Claudia (Co-author) / Taylor, David (Thesis director) / Miller, Cindy (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
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Engineering has historically been dominated by White men. However, in modern history, engineering is becoming more diverse as the opportunity to pursue engineering has become accessible to people of all races and genders. Yet, college ready high school students from nontraditional backgrounds—women, ethnic minorities, first-generation-to-college students, and those with financial

Engineering has historically been dominated by White men. However, in modern history, engineering is becoming more diverse as the opportunity to pursue engineering has become accessible to people of all races and genders. Yet, college ready high school students from nontraditional backgrounds—women, ethnic minorities, first-generation-to-college students, and those with financial need—often lack exposure to engineering, thus reducing their likelihood to pursue a career in this field. To create engineering learning experiences that can be expanded to a traditional high school science classroom, the Young Engineers Shape the World program at Arizona State University was consulted. The Young Engineers Shape the World program encourages women, notably the most underrepresented group in the engineering field, as well as other students of diverse backgrounds, to pursue engineering. The goal of this effort was to create a 3-contact hour chemical engineering based learning experience to help students in grades 10-11 learn about an application of chemical engineering. Using knowledge of chemical engineering, a soil pH testing activity was created, simulating a typical high school chemistry science experiment. In addition to measuring pH, students were asked to build a modern garden that contained a physical barrier that could protect the garden from acid rain while still allowing sunlight to reach the plant. Student feedback was collected in the form of an experience evaluation survey after each experience. Students found that the soil-moisture quality testing and design of a protective barrier was engaging. However, an iterative curriculum redesign-implement-evaluate effort is needed to arrive at a robust chemical engineering based design learning experience.
ContributorsOtis, Timothy Kevin (Author) / Ganesh, Tirupalavanam (Thesis director) / Schoepf, Jared (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
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This thesis aims to incorporate exosomes into an electrospun scaffold for tissue engineering applications. The motivation for this work is to develop an implant to regenerate tissue for patients with laryngeal defects. It was determined that it is feasible to incorporate exosomes into an electrospun scaffold. This addition of exosomes

This thesis aims to incorporate exosomes into an electrospun scaffold for tissue engineering applications. The motivation for this work is to develop an implant to regenerate tissue for patients with laryngeal defects. It was determined that it is feasible to incorporate exosomes into an electrospun scaffold. This addition of exosomes does alter the scaffold properties, by decreasing the average fiber diameter by roughly a factor of three and increasing the average modulus by roughly a factor of two. Cells were cultured on a scaffold with exosomes incorporated and were found to proliferate more than on a scaffold alone. This research lays the groundwork for further developing and optimizing an electrospun scaffold with exosomes incorporated to elicit a tissue regenerative response.
ContributorsKennedy, Maeve (Author) / Pizziconi, Vincent (Thesis director) / McPhail, Michael (Committee member) / School of International Letters and Cultures (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
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Current methods measuring the consumption of prescription and illicit drugs are often hampered by innate limitations, the data is slow and often restricted, which can impact the relevance and robustness of the associated data. Here, wastewater-based epidemiology (WBE) was applied as an alternative metric to measure trends in the consumption

Current methods measuring the consumption of prescription and illicit drugs are often hampered by innate limitations, the data is slow and often restricted, which can impact the relevance and robustness of the associated data. Here, wastewater-based epidemiology (WBE) was applied as an alternative metric to measure trends in the consumption of twelve narcotics within a collegiate setting from January 2018 to May 2018 at a Southwestern U.S. university. The present follow-up study was designed to identify potential changes in the consumption patterns of prescription and illicit drugs as the academic year progressed. Samples were collected from two sites that capture nearly 100% of campus-generated wastewater. Seven consecutive 24-hour composite raw wastewater samples were collected each month (n = 68) from both locations. The study identified the average consumption of select narcotics, in units of mg/day/1000 persons in the following order: cocaine (528 ± 266), heroin (404 ± 315), methylphenidate (343 ± 396), amphetamine (308 ±105), ecstasy (MDMA; 114 ± 198), oxycodone (57 ± 28), methadone (58 ± 73), and codeine (84 ± 40). The consumption of oxycodone, methadone, heroin, and cocaine were identified as statistically lower in the Spring 2018 semester compared to the Fall 2017. Universities may need to increase drug education for the fall semester to lower the consumption of drugs in that semester. Data from this research encompasses both human health and the built environment by evaluating public health through collection of municipal wastewater, allowing public health officials rapid and robust narcotic consumption data while maintaining the anonymity of the students, faculty, and staff.
ContributorsCarlson, Alyssa Rose (Author) / Halden, Rolf (Thesis director) / Gushgari, Adam (Committee member) / School of Human Evolution & Social Change (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
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The goal of this study was to understand elementary school children’s perceptions of engineering. A total of 949 elementary school students were surveyed, individually or as a whole group, to examine gender and age differences in achievement-related beliefs (i.e., competency, interest, and importance) pertaining to engineering-related skills and activities. The

The goal of this study was to understand elementary school children’s perceptions of engineering. A total of 949 elementary school students were surveyed, individually or as a whole group, to examine gender and age differences in achievement-related beliefs (i.e., competency, interest, and importance) pertaining to engineering-related skills and activities. The results of this study found that specific skills and activities showed significant gender and age differences for each of the three measures. Significant findings showed that younger students (kindergarten through second grade) found many of the engineering-related skills and activities more interesting than the older students (third through fifth grade); however, the older students rated more of the skills and activities as being important. Gender differences showed that girls typically rated themselves as being more competent, more interested in, and valuing the skills and activities that pertained more to mindset ideas, such as learning from your mistakes and failures or not giving up, whereas boys rated themselves higher in more of the hands-on activities, such as building with things like legos, blocks, and k’nex.
ContributorsHandlos, Jamie Lynn Harte (Author) / Miller, Cindy (Thesis director) / Reisslein, Martin (Committee member) / School of Life Sciences (Contributor) / Chemical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
This honors thesis is focused on two separate catalysis projects conducted under the mentorship of Dr. Javier Pérez-Ramírez at ETH Zürich. The first project explored ethylene oxychlorination over supported europium oxychloride catalysts. The second project investigated alkyne semihydrogenation over nickel phosphide catalysts. This work is the subject of a publication

This honors thesis is focused on two separate catalysis projects conducted under the mentorship of Dr. Javier Pérez-Ramírez at ETH Zürich. The first project explored ethylene oxychlorination over supported europium oxychloride catalysts. The second project investigated alkyne semihydrogenation over nickel phosphide catalysts. This work is the subject of a publication of which I am a co-author, as cited below.

Project 1 Abstract: Ethylene Oxychlorination
The current two-step process for the industrial process of vinyl chloride production involves CuCl2 catalyzed ethylene oxychlorination to ethylene dichloride followed by thermal cracking of the latter to vinyl chloride. To date, no industrial application of a one-step process is available. To close this gap, this work evaluates a wide range of self-prepared supported CeO2 and EuOCl catalysts for one-step production of vinyl chloride from ethylene in a fixed-bed reactor at 623 773 K and 1 bar using feed ratios of C2H4:HCl:O2:Ar:He = 3:3 6:1.5 6:3:82 89.5. Among all studied systems, CeO2/ZrO2 and CeO2/Zeolite MS show the highest activity but suffer from severe combustion of ethylene, forming COx, while 20 wt.% EuOCl/γ-Al2O3 leads to the best vinyl chloride selectivity of 87% at 15.6% C2H4 conversion with complete suppression of CO2 formation and only 4% selectivity to CO conversion for over 100 h on stream. Characterization by XRD and EDX mapping reveals that much of the Eu is present in non-active phases such as Al2Eu or EuAl4, indicating that alternative synthesis methods could be employed to better utilize the metal. A linear relationship between conversion and metal loading is found for this catalyst, indicating that always part of the used Eu is available as EuOCl, while the rest forms inactive europium aluminate species. Zeolite-supported EuOCl slightly outperforms EuOCl/γ Al2O3 in terms of total yield, but is prone to significant coking and is unstable. Even though a lot of Eu seems locked in inactive species on EuOCl/γ Al2O3, these results indicate possible savings of nearly 16,000 USD per kg of catalyst compared to a bulk EuOCl catalyst. These very promising findings constitute a crucial step for process intensification of polyvinyl chloride production and exploring the potential of supported EuOCl catalysts in industrially-relevant reactions.

Project 2 Abstract: Alkyne Semihydrogenation
Despite strongly suffering from poor noble metal utilization and a highly toxic selectivity modifier (Pb), the archetypal catalyst applied for the three-phase alkyne semihydrogenation, the Pb-doped Pd/CaCO3 (Lindlar catalyst), is still being utilized at industrial level. Inspired by the very recent strategies involving the modification of Pd with p-block elements (i.e., S), this work extrapolates the concept by preparing crystalline metal phosphides with controlled stoichiometry. To develop an affordable and environmentally-friendly alternative to traditional hydrogenation catalysts, nickel, a metal belonging to the same group as Pd and capable of splitting molecular hydrogen has been selected. Herein, a simple two-step synthesis procedure involving nontoxic precursors was used to synthesize bulk nickel phosphides with different stoichiometries (Ni2P, Ni5P4, and Ni12P5) by controlling the P:Ni ratios. To uncover structural and surface features, this catalyst family is characterized with an array of methods including X-ray diffraction (XRD), 31P magic-angle nuclear magnetic resonance (MAS-NMR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Bulk-sensitive techniques prove the successful preparation of pure phases while XPS analysis unravels the facile passivation occurring at the NixPy surface that persists even after reductive treatment. To assess the characteristic surface fingerprints of these materials, Ar sputtering was carried out at different penetration depths, reveling the presence of Ni+ and P-species. Continuous-flow three-phase hydrogenations of short-chain acetylenic compounds display that the oxidized layer covering the surface is reduced under reaction conditions, as evidenced by the induction period before reaching the steady state performance. To assess the impact of the phosphidation treatment on catalytic performance, the catalysts were benchmarked against a commercial Ni/SiO2-Al2O3 sample. While Ni/SiO2-Al2O3 presents very low selectivity to the alkene (the selectivity is about 10% at full conversion) attributed to the well-known tendency of naked nickel nanoparticles to form hydrides, the performance of nickel phosphides is highly selective and independent of P:Ni ratio. In line with previous findings on PdxS, kinetic tests indicate the occurrence of a dual-site mechanism where the alkyne and hydrogen do not compete for the same site.

This work is the subject of a publication of which I am a co-author, as cited below.

D. Albani; K. Karajovic; B. Tata; Q. Li; S. Mitchell; N. López; J. Pérez-Ramírez. Ensemble Design in Nickel Phosphide Catalysts for Alkyne Semi-Hydrogenation. ChemCatChem 2019. doi.org/10.1002/cctc.201801430
ContributorsTata, Bharath (Author) / Deng, Shuguang (Thesis director) / Muhich, Christopher (Committee member) / Chemical Engineering Program (Contributor, Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05