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    Reinforcement learning for multi-agent and robust control systems

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    Recent years have witnessed phenomenal accomplishments of reinforcement learning (RL) in many prominent sequential decision-making problems, such as playing the game of Go, playing real-time strategy games, robotic control, and autonomous driving. Motivated by these empirical successes, research toward theoretical understandings of RL algorithms has also re-gained great attention in recent years. In this dissertation, our goal is to contribute to these efforts through new approaches and tools, by developing RL algorithms for multi-agent and robust control systems, which find broad applications in the aforementioned examples and other diverse areas. In this dissertation, we consider specifically two different and fundamental settings that in general fall into the realm of RL for multi-agent and robust control systems: (i) decentralized multi-agent RL (MARL) with networked agents; (ii) H2/H∞-robust control synthesis. We develop new RL algorithms for these settings, supported by theoretical convergence guarantees. In setting i, a team of collaborative MARL agents is connected via a communication network, without the coordination of any central controller. With only neighbor-to-neighbor communications, we introduce decentralized actor-critic algorithms for each agent, and establish their convergence guarantees when linear function approximation is used. Setting ii corresponds to a classical robust control problem, with linear dynamics and robustness concerns in the H∞-norm sense. In contrast to existing solvers, we introduce policy-gradient methods to solve the robust control problem, with global convergence guarantees, despite its nonconvexity. More interestingly, we show that two of these methods enjoy the implicit regularization property: the iterates of the controller automatically preserve a certain level of robustness stability, by following such policy search directions. This robustness-on-the-fly property is crucial for learning in safety-critical robust control systems. We then study the model-free regime, where we develop derivative-free policy gradient methods to solve the finite-horizon version of the problem, with sampled trajectories from the system and sample complexity guarantees. Interestingly, this robust control problem also unifies several other fundamental settings in control theory and game theory, including risk-sensitive linear control, i.e., linear exponential quadratic Gaussian (LEQG) control, and linear quadratic zero-sum dynamic games. The latter can be viewed as a benchmark setting for competitive multi-agent RL. Hence, our results provide policy-search methods for solving these problems unifiedly. Finally, we provide numerical results to demonstrate the computational efficiency of our policy search algorithms, compared to several existing robust control solvers.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste

    New perspectives on fractional quantum Hall physics

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    Despite having been discovered nearly four decades ago, fractional quantum Hall (FQH) states continue to provide platforms for the discovery of novel physical phenomena. In this thesis, I present a study of these remarkable phases of matter from three perspectives: (1) the role of an underlying lattice and its symmetries in engendering novel FQH states, (2) the description of non-Abelian FQH states using recently developed field theory dualities, and (3) the use of entanglement entropy in characterizing interfaces of FQH states. In the first part, we examine phases of matter known as fractional Chern insulators (FCIs), lattice analogues of FQH states. We begin in Chapter 2 by formulating a composite fermion theory for FCI states in a kagome lattice model, making use of a recently developed lattice Chern-Simons theory to effect the flux attachment. We identify sequences of Abelian states, including states for which the Hall conductance does not match the filling fraction, which we characterize as realizing distinct translational symmetry fractionalization classes. Next, we apply this formalism in Chapter 3 to identify paired states of composite fermions in a square-lattice Hofstadter model. Magnetic translation symmetry is found to enforce finite-momentum pairing of the composite fermions, yielding pair-density wave (PDW) states with daughter charge-density wave order, analogous to the PDWs conjectured to describe the high-T c cuprate superconductors. This constitutes a novel example of intertwined orders, in which topological order and broken symmetry order arise from a common microscopic origin. In the second part, we apply a recently proposed web of Chern-Simons-matter theory dualities to develop effective field theories for a large class of non-Abelian FQH states. First, in Chapter 4, we demonstrate how these dualities can be used to construct bosonic Landau-Ginzburg theories of the Read-Rezayi and generalized non-Abelian spin singlet states by introducing interlayer interactions in a multilayer Abelian FQH system. Next, we extend this construction in Chapter 5 to develop a field theory and motivate a trial wave function for the elusive Fibonacci FQH state, which is the minimal model for realizing a universal topological quantum computer. We subsequently examine in Chapter 6 dual fermionic non-Abelian Chern-Simons-matter theories, allowing us to develop composite fermion descriptions of the Blok-Wen FQH states and a series of states which may be understood as arising from pairing in a dual Abelian composite fermion theory. Our analysis reveals that dual fermionic theories can predict distinct ground states in a magnetic field, demonstrating the utility of dualities in mapping out regions of the phase diagram of electrons at fractional filling. In the final part of this thesis, which comprises Chapter 7, we characterize interfaces of non-Abelian Moore-Read FQH states using entanglement entropy. We first employ a cut-and-glue approach to obtain the expected topological entanglement entropy (TEE) for a uniform Moore-Read state on the torus in each topological sector. This involves approximating the entanglement as arising purely from the coupled 1D chiral edge degrees of freedom at the entanglement cut. We next consider interfaces of distinct generalized Moore-Read states, identify when the interfaces can be gapped using an anyon condensation picture, construct explicit gapping interactions, and then compute the TEE for an entanglement cut along the interface. It is found that the value of the TEE is related to the total quantum dimension of a “parent” topological phase of the two generalized Moore-Read states between which the interface is formed.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste

    Leading for diversity, equity, and improvement at the district level of a K-12 Florida school district

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    What do school districts mean when they claim to value the concepts of diversity and equity in education, and how do district stakeholders truly feel about the value of such efforts within their district? The demographic nature of the United States continues to shift to reflect a more racially diverse nation than ever before, particularly with those individuals under sixteen years of age. In response, school districts are routinely seeking ways to embody and support the concepts of diversity and equity within their school campuses, for the benefit of all students. This dissertation examines how teachers, principals, and district administrators in a large Florida school district interpret, define, and feel about the concepts of diversity and equity in education. The school district, termed Sunshine Public School District, is one of the largest districts in both the state of Florida and nation. By interviewing district stakeholders in a one-on-one fashion, their opinions and definitions of diversity and equity as concepts are revealed, as is their input on the district’s 2025 Strategic Plan, of which diversity and equity are prominently featured. This qualitative research takes the form of a case study and seeks to provide Sunshine Public School District a current snapshot of stakeholder inclination towards diversity and equity, as well as offering potential insight into what can be done to make the lofty and socially-just goals of their 2025 Strategic Plan a reality.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste

    Non-noble metal nanocatalysts for the purification and reduction of carbon dioxide

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    The transition from fossil fuels to more sustainable energy sources is expected to take several decades. A major challenge in the interim is efficient capture, purification, and upgrading of carbon dioxide (CO2). The development of novel heterogeneous catalytic systems is essential to address many of the technological and economic challenges at hand. Nanostructures based on non-noble metals have been traditionally understudied due to their high chemical instability in both synthesis and application. The unique sensitivity and chemical reactivity of their nanostructures, however, offer the possibility for designing new catalytic systems with inherent benefits (e.g., product selectivity, mass activity, and cost). This thesis contains two parts: first on the development of nanomaterial systems for the purification of CO2 from flue gas by the catalytic reduction of oxygen (O2) and second on the design of novel catalysts for the thermal and electrochemical reduction of CO2. This research aims at combining the fundamentals of nanostructures and catalysis with practical applications such to provide new processes for the sequestration and utilization of CO2.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste

    Development of systems for isolation of high-valent nickel complexes and their reactivity

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    Inspired by work published in our group utilizing macrocyclic nitrogen based pyridinophane (N4) and triazacyclononane (tacn) ligands for the isolation and study of high-valent nickel and palladium compounds, chiral variants of these ligands were synthesized in attempts to isolate high-valent organometallic nickel complexes that could play a role in enantioselective crosscoupling reactions. Utilizing readily available chiral pool primary amines, the synthesis of N4 type ligands can be amended to install chirality on the tertiary amines of the ligand, which commonly bind through dative interactions with the metal center in high-valent oxidation states. Furthermore, the synthesis can be expanded to N3 type pyridinophane compounds like N3CBr type ligands, allowing for on-ligand reactivity studies to be conducted. With these ligands in hand, a secondary organometallic nucleophile was synthesized which could allow for the synthesis of organometallic nickel complexes. The reactivity of these complexes was then examined, with hopes that insight into the role of high-valent complexes and the method for stereoinduction in enantioselective cross-coupling reactions could then be better understood. Furthermore, a synthetic route to novel chiral variants of triazacyclononane ligands was developed based on a ‘crab-like’ synthesis published by the Scarborough group in 2018. This synthesis relies on commercially available alpha-hydroxy acids, and the substituents on the ligand can be varied in a multitude of locations. This ligand synthesis allows for installation of chirality on the methylene backbone of the ligand, which will hopefully result in good chiral projection into the open binding sites of the metal complex. Further efforts to develop reactivity with this system are currently underway.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste

    Worlding through popular culture: Sport as a race/ethno making project in Korean America

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    This dissertation explores the social formation of Korean immigrants and Korean Americans in immigrant America. I attempted to articulate how sport works as a public pedagogy that specifies Asian racialization. My argument in this dissertation is straightforward: Sport is what I term a race/ethno-making project that has narrowed the scope of citizenship overdetermined by race. I hold that sport is a sorting apparatus that categorizes people based on biological difference, phenotype, and cultural difference to sort out “unwanted people.” I politicize sport to theorize Asian racialization in sport and physical culture. This means two things: (1) understanding sport provokes historical understanding of U.S. identity politics and (2) identity formation is a consistently moving force, and therefore sport—along with U.S. multicultural discourses—reinforces white ascendency. My dissertation, therefore, is a process of calling the hypocrisy of the epistemological purity of sport into question. I interpret sport as a powerful transmitter of white supremacist logics of raciality and sociality that contribute to white reconstruction. Considering the ontological and epistemological complexity beneath the surface of sport and its culture, I attempted to avoid lineal understandings of “culture.” What I attempted to do was to look at how minoritarian subjects learn, accept, normalize, and reproduce “racially” coded physical culture. I endeavored to understand Asian racialization “through” physical culture to unpack Asian racialization in a particular context. I drew on Physical Cultural Studies (PCS) as a method that allowed me to: (1) use theories to cut into taken-for-granted everyday experiences in physical culture; (2) contextualize how sport centers on whiteness and how sport becomes a metaphor for the success of Americanness; and (3) unpack power and its operations. Particularly, I focused on historical conjunctures that contribute to Asian racialization. Through adherence to Stuart Hall’s conjunctural analysis, I focused on connecting the neglected dimensions that specify Asian racialization. Overall, my argument in the dissertation considers sport in three ways: (1) as a cultural- pedagogical production that inculcates white reconstruction. Through my dissertation, I attempt to interpret white reconstruction as racial and cultural politics that continuously centers on white supremacist logics of sociality, raciality, and/or white national identity; (2) sport’s assimilation in the U.S. is associated with white supremacist logics of sociality. For example, as Chapter 5 explores, a Korean immigrant family became alienated from other Asian groups and simultaneously internalized a conservative political worldview deeply rooted in white supremacy. This assimilation into whiteness resulted in becoming Trump sympathizers; and (3) sport as a colorblind identity politics that solidifies the racial ascendency of whites. Multiculturalism is a common refrain in sport. However, sport is by no means a multicultural site. Rather, it is about a white reconstruction that redefines cultural citizenship. My work looks at, on the one hand, how Korean immigrants and Korean Americans attempt to find entry into predominately white physical culture and, on the other, how sport works as an epistemological practice that specifies Asian racialization, sustaining racially structured epistemologies that cast Asian bodies as others.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste

    How Escherichia coli uses environmental cysteine

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    Sulfur is an essential element for all forms of life. Bacteria have dedicated importers for a range of sulfur containing molecules (cystine, sulfate, taurine, glutathione). These importers are induced when bacteria are sulfur limited. Once imported, these sulfur compounds are first converted into usable cysteine and then are incorporated into biomolecules; thus, one would expect that cysteine import would be the most economical route for cells to acquire sulfur. However, uniquely among the amino acid transporters, cysteine importers are poorly characterized in the microbial world. We have demonstrated that wild-type E. coli cannot assimilate cysteine as sulfur source in the presence of other amino acids. Four transporters have adventitious cysteine import activity, but they do not import cysteine when their natural substrates are around. If these four transporters are deleted, E. coli can no longer scavenge trace cysteine. The surprising lack of an effective route to assimilate sulfur from cysteine may be due to the problems that rapid cysteine import can cause. Does this mean that cysteine is of no use for E. coli? The story doesn’t end like this. E. coli possesses a cysteine-specific importer, called YhaO, that is induced only when external cysteine is abundant. Downstream of yhaO sits yhaM, encoding a cysteine desulfidase that degrades cysteine to pyruvate, ammonia, and hydrogen sulfide. We found that this process is fast enough to allow cells to use cysteine as sole carbon or nitrogen source. YhaM is the primary sulfide producer when cells are exposed to abundant cysteine. Expression data showed that yhaO was most strongly induced when E. coli grows on poor carbon sources. The strong induction did not occur when Crp was deleted, indicating that Crp may regulate YhaOM. Indeed, Crp null mutants could not grow on cysteine as sole carbon source. We conclude that extracellular cysteine is utilized as a carbon or nitrogen source rather than as a cysteine source for protein biosynthesis.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste

    Development of a modular and submersible soft robotic arm system and corresponding learned kinematics models

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    Most soft-body organisms found in nature exist in underwater environments. It is helpful to study the motion and control of soft robots underwater as well. However, a readily available underwater soft robotic system is not available for researchers to use because they are difficult to design, fabricate, and waterproof. Furthermore, submersible robots usually do not have configurable components because of the need for sealed electronics packages. This thesis presents the development of a submersible soft robotic arm which consists of mostly off-the-shelf components and 3D printable parts which can be assembled in a short amount of time. Also, its modular design enables multiple shape configurations and easy swapping of soft actuators. As a first step to exploring machine learning control algorithms on this platform, two deep neural network models were developed, trained, and evaluated to estimate the robot's forward and inverse kinematics. The techniques developed for controlling this underwater soft robotic arm can help advance understanding on how to control soft robotic systems in general.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste

    The development of Pd(II)sulfoxide-oxazoline catalyzed allylic C—H functionalizations

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    Pd-catalyzed allylic C—H functionalization is a powerful platform to stereoselectively and regioselectively convert terminal olefins (typically considered inert under most reaction conditions) into higher value chemical commodities. At the outset of this research program, several challenges with allylic C—H functionalization included: poor to moderate enantioselectivities in stereoselective transformations, and limited scope of functionalization partners. This thesis describes effort towards the development and application of Pd(II)/sulfoxide-oxazoline (Pd(II)/SOX) catalysis towards addressing these challenges. The first chapter outlines the development and application of Pd(II)/SOX catalysis towards the difficult challenge of asymmetric allylic C—H alkylation. Critical to this strategy was investigations into the cis-SOX ligand framework—a diastereomer of the SOX ligand which was theorized to have greater enantiocontrol around the intermediate π-allyl. This chapter describes the development and application of this system to α-nitrotetralones, a versatile precursor to amino ketones and amino alcohols. The chapter also details efforts into addressing challenging β-ketoester nucleophiles, and the elucidation of a key ligand structural feature important for enantioselectivity. The second chapter outlines the development and application of Pd(II)/SOX catalysis towards allylic C—H aminations with basic secondary amines. Intermolecular C—H amination is typically limited to doubly or singly protected nitrogen species, allowing only for protected ammonia or primary amine installation. Typically, basic amines are liable to bind tightly to the electrophilic metal catalysts for C—H cleavage and can inhibit useful reactivity. An amine quaternization strategy was applied to basic secondary amines, which allowed for a slow release of the free amine. This slow release allowed for functionalization to occur with no detrimental inhibition of the electrophilic Pd(II) center. This strategy was applied to a variety of secondary amines cores, forging pharmaceutically relevant tertiary amine products. In addition, the mild selective allylic functionalization was tolerant of numerous functionalities considered traditional electrophiles for amino functionalization. Finally, several tertiary amine drugs and drug derivatives were synthesized, demonstrating the synthetic utility of this transformation.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste

    Longitudinal muscle creatine concentrations and efficacy of dietary guanidinoacetic acid supplementation in pigs

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    With the world population growing and land resources limited, there is increasing demand for the agricultural sector to not only increase output, but also to improve production efficiencies. As production agriculture continues to drive for innovation in animal nutrition specifically, the use of feed additives offers a promising opportunity to reduce the cost of production and improve production efficiencies. Guanidinoacetic acid (GAA) has been evaluated as a feed additive in pigs. However, in order to further advance research around GAA supplementation, it is important to not only understand baseline levels of muscle creatine in pigs over time, but also how GAA supplementation impacts muscle creatine levels and muscle energetics. Two studies were conducted to further understand this area of research. Experiment 1 was a 15-week farrow-to-finish feeding experiment conducted with 5 feeding phases, in which an equal number of barrows and gilts were fed the same series of diets. Sixteen pigs were randomly selected for collection at 6 different time-points (0, 7, 21, 35, 63, and 104 days of age) throughout the experiment and muscle, kidney, liver, and blood samples were collected and analyzed for creatine-related metabolites. A clear baseline of muscle creatine levels over time was established which indicated that muscle creatine decreases shortly after birth, after which it increases (P < 0.001) through the finishing phases. Relative to creatine concentrations at birth, creatine in the liver, kidney, and blood plasma increased (P < 0.05) through 21 days of age. For Exp. 2, an arginine-adequate diet (0.92% digestible Arg) based on corn, soybean meal, whey protein concentrate, and lactose was supplemented with 0, 0.12, or 0.36% GAA to produce 3 experimental diets. Starting at 21 days of age, these 3 diets were then fed to 16 replicate pens with 4 pigs per pen (2 barrows and 2 gilts; 6.65 ± 1.19 kg). Individual pig and pen feeder weights were recorded upon the initiation of the experiment and at each phase change to calculate growth performance. At 42 and 63 days of age, 1 pig per pen was randomly chosen for blood and tissue collection. While supplementing GAA had no effect on nursery pig growth performance (P < 0.05), both 0.12% and 0.36% levels of GAA increased (P < 0.001) the phosphocreatine to adenosine triphosphate (PCr:ATP) ratio at 42 days of age relative to the negative control (NC) PCr:ATP ratio values. Guanidinoacetic acid supplementation also increased (P < 0.05) muscle, liver, kidney, and blood plasma creatine levels relative to the NC at both 42 and 63 days of age. These data suggest that GAA supplementation is effective in increasing the concentration of creatine in the muscle by increasing PCr concentrations and provides additional energy by increasing the PCr:ATP ratio. This research not only sets a foundation for future work through a proven muscle biopsy collection method, but also provides a baseline of muscle creatine levels. Finally, it opens the door for future research in the area of GAA supplementation by successfully demonstrating that GAA supplementation influences muscle creatine concentrations and provides an increased potential for energy expenditure within the pig by increasing PCr:ATP ratios.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste

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