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Description
Due to the use of fertilizers, concentrations of harmful nitrate have increased in groundwater and surface waters globally in the last century. Water treatment plants primarily use separation techniques for nitrate treatment, but these technologies create a high nitrate concentration brine that is costly to dispose of. This dissertation focuses on catalytic hydrogenation, an emerging technology capable of reducing nitrate to nitrogen gas using hydrogen gas (H2). This technology reduces nitrate at rates >95% and is an improvement over technologies used at water treatment plants, because the nitrate is chemically transformed with harmless byproducts and no nitrate brine. The goal of this dissertation is to upgrade the maturity of catalytic nitrate hydrogenation systems by overcoming several barriers hindering the scale-up of this technology. Objective 1 is to compare different methods of attaching the bimetallic catalyst to a hollow-fiber membrane surface to find a method that results in 1) minimized catalyst loss, and 2) repeatable nitrate removal over several cycles. Results showed that the In-Situ MCfR-H2 deposition was successful in reducing nitrate at a rate of 1.1 min-1gPd-1 and lost less than 0.05% of attached Pd and In cumulatively over three nitrate treatment cycles. Objective 2 is to synthesize catalyst-films with varied In3+ precursor decorated over a Pd0 surface to show the technology can 1) reliably synthesize In-Pd catalyst-films with varied bimetallic ratios, and 2) optimize nitrate removal activity by varying In-Pd ratio. Results showed that nitrate removal activity was optimized with a rate constant of 0.190 mg*min-1L-1 using a catalyst-film with a 0.045 In-Pd ratio. Objective 3 is to perform nitrate reduction in a continuous flow reactor for two months to determine if nitrate removal activity can be sustained over extended operation and identify methods to overcome catalyst deactivation. Results showed that a combination of increased hydraulic residence time and reduced pH was successful in increasing the nitrate removal and decreasing harmful nitrite byproduct selectivity to 0%. These objectives increased the technology readiness of this technology by enabling the reuse of the catalyst, maximizing nitrate reduction activity, and achieving long-term nitrate removal.
ContributorsLevi, Juliana (Author) / Westerhoff, Paul (Thesis advisor) / Rittmann, Bruce (Thesis advisor) / Garcia-Segura, Sergi (Committee member) / Wong, Michael (Committee member) / Lind Thomas, Mary Laura (Committee member) / Emady, Heather (Committee member) / Arizona State University (Publisher)
Created2023
Description
The main objective of this work is to study novel stochastic modeling applications to cybersecurity aspects across three dimensions: Loss, attack, and detection. First, motivated by recent spatial stochastic models with cyber insurance applications, the first and second moments of the size of a typical cluster of bond percolation on finite graphs are studied. More precisely, having a finite graph where edges are independently open with the same probability $p$ and a vertex $x$ chosen uniformly at random, the goal is to find the first and second moments of the number of vertices in the cluster of open edges containing $x$. Exact expressions for the first and second moments of the size distribution of a bond percolation cluster on essential building blocks of hybrid graphs: the ring, the path, the random star, and regular graphs are derived. Upper bounds for the moments are obtained by using a coupling argument to compare the percolation model with branching processes when the graph is the random rooted tree with a given offspring distribution and a given finite radius. Second, the Petri Net modeling framework for performance analysis is well established; extensions provide enough flexibility to examine the behavior of a permissioned blockchain platform in the context of an ongoing cyberattack via simulation. The relationship between system performance and cyberattack configuration is analyzed. The simulations vary the blockchain's parameters and network structure, revealing the factors that contribute positively or negatively to a Sybil attack through the performance impact of the system. Lastly, the denoising diffusion probabilistic models (DDPM) ability for synthetic tabular data augmentation is studied. DDPMs surpass generative adversarial networks in improving computer vision classification tasks and image generation, for example, stable diffusion. Recent research and open-source implementations point to a strong quality of synthetic tabular data generation for classification and regression tasks. Unfortunately, the present state of literature concerning tabular data augmentation with DDPM for classification is lacking. Further, cyber datasets commonly have highly unbalanced distributions complicating training. Synthetic tabular data augmentation is investigated with cyber datasets and performance of well-known metrics in machine learning classification tasks improve with augmentation and balancing.
ContributorsLa Salle, Axel (Author) / Lanchier, Nicolas (Thesis advisor) / Jevtic, Petar (Thesis advisor) / Motsch, Sebastien (Committee member) / Boscovic, Dragan (Committee member) / Platte, Rodrigo (Committee member) / Arizona State University (Publisher)
Created2023
Description
Sediment transport by atmospheric flows shapes landscapes on Earth and other planets. Improving the ability to quantify and predict sand transport by windblown (aeolian) processes has important implications for managing erosion, land degradation, desertification, dust emissions, air quality, and other climate change hazards and risks. Despite progress since Bagnold's seminal works in the 1930s, the most frequently used aeolian sand transport equations show discrepancies between predicted and observed transport rates upwards of 300%. Differences of this magnitude strongly support re-examining how fundamental physical aeolian processes are expressed in predictive equations. Wind tunnel experiments using a Particle Imaging Velocimetry/Particle Tracking Velocimetry (PIV/PTV) system with a high-speed camera and high-powered laser were conducted to visualize fluid motions and sand particle trajectories to provide simultaneous measurements of wind flow and sand transport to re-examine the fundamental physical relationships between flow dynamics, sediment motions, and bedform development.
The first experiment of this dissertation focuses on the characteristics of near-surface sand transport in the saltation cloud. From PTV particle trajectories, mean particle velocities appear independent of freestream wind speed, while velocity distribution characteristics (such as modality) and particle concentration intermittency vary with increasing sand transport. Particle trajectories from rippled bed runs show evidence of local slope influence on near-bed particle vectors.
The second experiment used manual sand grain tracking to quantify particle-bed splash interactions. Results highlight that common rebound and ejecta functions do not sufficiently represent aeolian saltation splash events. Data indicate a shadowing effect of ripples, suggesting feedback between the saltation cloud, splash events, and bedform migration.
The third experiment used dual PIV/PTV analysis to quantify fluid-particle interactions and compare sand concentrations with fluid stresses and turbulence characteristics through the saltation cloud. Results show that increased saltation leads to the disappearance of the constant fluid stress region, changes in aerodynamic roughness length, and increases in turbulence intensities. Leveraging technology advancements and multiple analysis methods, these results provide new, detailed information on the relationships between flow dynamics, sediment motions, and the presence of ripple bedforms. These novel empirical data illustrate some needed corrections to the theoretical and numerical frameworks for quantifying aeolian sand transport.
ContributorsKelley, Madeline (Author) / Schmeeckle, Mark (Thesis advisor) / Walker, Ian (Thesis advisor) / Dorn, Ron (Committee member) / Swann, Christy (Committee member) / Arizona State University (Publisher)
Created2023
Description
Cyberbullying has become increasingly prevalent, difficult to detect, and harmful to its victims. Whereas correlates of cyberbullying victimization and perpetration have been studied extensively, there has been less research on the critical role that bystanders to cyberbullying instances can play. This study explored the extent to which Big Five personality traits, social dominance orientation, narcissism, moral disengagement, self-control, and cyberbullying severity level are related to bystander behavior in cyberbullying situations. Adults in the U.S. took part in an online survey in which they were presented with a series of 12 simulated social media interactions in the form of screenshots that involved exchanges between two social media users. Each screenshot depicted one of three distinct levels of cyberbullying severity: none, low severity, and high severity. For each screenshot, participants were asked to report the likelihood that they would respond in a range of ways as a bystander. Participants then completed a series of individual difference scales. The results indicated that as the severity of the cyberbullying depicted in a screenshot increased, bystanders were more likely to support the victim, flag the post, and confront the bully, and less likely to be passive observers or support the bully. Higher levels of extraversion, conscientiousness, and agreeableness were associated with a lower likelihood of remaining a passive observer, while social dominance orientation and moral disengagement were positively correlated with bystander interaction in support of the bully. Additionally, agreeableness and extraversion were positively correlated with the likelihood of supporting the victim; and agreeableness was positively correlated with the likelihood of confronting the bully. No significant relationship was discovered between self-control, narcissism, and cyberbystander behavior. This research offers experimental validation for the predictive value of both cyberbullying severity and individual differences for understanding diverse forms of cyberbystander behavior.
ContributorsLi, Haojian (Author) / Hall, Deborah (Thesis advisor) / Powell, Derek (Committee member) / Kuo, Trudy (Committee member) / Arizona State University (Publisher)
Created2023
Description
Lifestyle factors including nutrition, may play a role in the development of cognitive impairment. Previous studies based in the United States have shown that nutrient deficiencies in vitamin B-12 and folate can increase the risk of developing mild cognitive impairment in adults, while high levels of potassium increase the risk of cognitive impairment. Among the Tsimane and Moseten subsistence communities in Bolivia, there is a low prevalence of Alzheimer’s dementia and related diseases, but any impacts of micronutrients on cognitive impairment have not been assessed. Using a mixed longitudinal design to estimate nutrient intake via 855 dietary recall questionnaires (24-hour) from 370 Tsimane and Moseten aged 43-85 years (mean age 62 years, 47% male), a culturally specific dementia assessment (3MSE, KIKA, neurological exam) was conducted, and individuals were diagnosed as having normal cognition, mild cognitive impairment, or dementia. Logistic regressions with clustered standard errors (to account for multiple dietary questionnaires per individual) examined the association between dietary intake and cognitive impairment. Controlling for age, sex, body mass index, and education, those with higher daily caloric intake had a lower odds ratio of cognitive impairment, with every 100 additional calories associated with decreased risk (OR = 0.95, p=0.032). Higher B-12 intake was associated with lower cognitive impairment, while higher potassium intake was associated with greater cognitive impairment. The presented data indicate a correlation between diet and nutrition and cognitive impairment within a subsistence population. This observation underscores the potential tradeoffs individuals face in allocating resources towards survival versus the upkeep of cognitive faculties, reflecting broader considerations in life history strategies.
ContributorsBalasubramanian, Sophia (Author) / Trumble, Benjamin C (Thesis advisor) / Jenkins, Carrie L (Committee member) / Aronoff, Jacob E (Committee member) / Arizona State University (Publisher)
Created2024
Description
The world has seen a revolution in cellular communication with the advent of 5G (fifth-generation), which enables gigabits per second data speed with low latency, massive capacity, and increased availability. These modern wireless systems improve spectrum efficiency by employing advanced modulation techniques, but result in large peak-to-average power ratios (PAPR) of the transmitted signals that degrades the efficiency of the radio-frequency power amplifiers (PAs) in the power back-off (PBO) region. Envelope tracking (ET), which is a dynamic supply control technology to realize high efficiency PAs, is a promising approach for designing transmitters for the future. Conventional voltage regulators, such as linear regulators and switching regulators, fail to simultaneously offer high speed, high efficiency, and improved linearity. Hybrid supply modulators (HSM) that combine a linear and switching regulator emerge as promising solutions to achieve an optimized tradeoff between different design parameters. Over the years, considerable development and research efforts in industry and academia have been spent on maximizing HSM performance, and a majority of the most recently developed modulators are implemented in CMOS technology and mainly targeted for handset applications. In this dissertation, the main requirements for modern HSM designs are categorized and analyzed in detail. Next, techniques to improve HSM performance are discussed. The available device technologies for HSM and PA implementations are also delineated, and implementation challenges of an integrated ET-PA system are summarized. Finally, a Current-Mode with Dynamic Hysteresis HSM is proposed, designed, and implemented. With the proposed technique, the HSM is able to track LTE signals up to 100 MHz bandwidth. Switching at a peak frequency of 40 MHz, the design is able to track a 1 Vpp sinusoidal signal with high fidelity, has an output voltage ripple around 54 mV, and achieves a peak static and dynamic efficiency of 92.2% and 82.29%, respectively, at the maximum output. The HSM is capable of delivering a maximum output power of 425 mW and occupies a small die area of 1.6mm2. Overall, the proposed HSM promises competitive performance compared to state-of-the-art works.
ContributorsBHARDWAJ, SUMIT (Author) / Kitchen, Jennifer (Thesis advisor) / Ozev, Sule (Committee member) / Bakkaloglu, Bertan (Committee member) / Singh, Shrikant (Committee member) / Arizona State University (Publisher)
Created2024
Description
The organ sonatas of Hans Fährmann are some of the fullest realizations of the orchestral potential of the pipe organ. These works fill a crucial gap in the existing canonic organ repertoire; they allow the organist to engage with the late German Romantic symphonic works of Brahms, Mahler, and Strauss. There is relatively little remaining documentary evidence about Fährmann’s life. This paper provides a biography summarizing what is known about the composer and situates his work historically. Turn-of-the-century Dresden, the so-called “El Dorado on the Elbe,” provided an environment where musical conservatism and radical progressivism lived uneasily side-by-side. The evolution of the German Romantic organ and the organ sonata paved the way for Fährmann’s important contributions to the genre. Fährmann’s own musical language situates him between the organ tradition and broader trends in 19th-century German composition, especially Richard Wagner.Although there is little information on the performance practice of Fährmann’s music, it is possible to derive ideas from German Romantic conducting practices. The study compares the rhythmic interpretive decisions of conductors contemporary to Fährmann with organ-playing in the Straube tradition. The symphonic performance tradition is a better source for organists interpreting Fährmann because of the stylistic similarities between his organ sonatas and the orchestral repertoire, as opposed to the approach of the Straube school, which was at that time laying the foundation for and engaging with the Orgelbeewgung. To elucidate the registration of Fährmann’s organ sonatas, the author investigates contemporary practices and specification of the Johanneskirche instrument on which Fährmann spent most of his time. The study concludes with an analysis of his First Sonata, demonstrating the composer’s craftsmanship and creation of a narrative arch across the form.
ContributorsHalbert, Nicholas (Author) / Marshall, Kimberly (Thesis advisor) / Campbell, Andrew (Committee member) / Reymore, Lindsey (Committee member) / Arizona State University (Publisher)
Created2024
Description
This dissertation was developed in response to a long-standing imperative for teachers and scholars of writing: the need to meet students where they are (technologically) and keep up with emerging writing technologies. Said differently, when an emerging writing technology comes on the scene, teachers of writing tend to develop theoretical and pedagogical approaches for students' use of that technology in the writing classroom. While the imperative to keep up is well-meaning, the attempt can feel futile or, at the very least, pedagogically frustrating. This frustration is often fueled by permanent innovation, or when a culture’s technological innovation outpaces its ability to adapt to and for those technologies. To address the ever-evolving difficulties inherent within the relationship between writing, developing technologies, and teaching writing, this dissertation offers the field of Composition a path through the futility and frustration represented by keeping up. I call this intervention Composition’s “Technological Boneyard,” or more simply, “the boneyard.” The boneyard is first and foremost a metaphor, an imagined dumping ground that contains the obsolete, trashed, and forgotten technologies of writing that Composition has used and discarded in its move toward its raison d'être: the study and teaching of writing. Brimming with obsolete and discarded technologies of writing—like the first personal computers, floppy and hard disks, keyboards, and early mobile devices—the boneyard allows Composition to (re)investigate its technological and techno-pedagogical history, as well as its current relationships with developing technologies and writing. Through two qualitative case studies, this dissertation investigates the technologies in the boneyard and considers how abandoned, obsolete, and forgotten writing tools have shaped (and continue to shape) the teaching of writing in higher education, as well as Composition’s own history.
ContributorsBrown, Eric D. (Author) / Webb, Patricia (Thesis advisor) / Jensen, Kyle (Committee member) / Rose, Shirley K (Committee member) / Greene, Jacob (Committee member) / Arizona State University (Publisher)
Created2024
Description
The complexity of the U.S.-Mexico border is rooted in a fixation on establishing a clear separation of land that is unsafe and safe, between them and us. Chicana cultural theorist Gloria Anzaldúa states, “A border is a dividing line, a narrow string along a steep edge. A borderland is a vague and undetermined place created by the emotional residue of an unnatural boundary. It is in a constant state of transition” (Anzaldúa 1987, 3). In her 1987 semi-autobiographical work, Borderlands/La Frontera: The New Mestiza, she examines the U.S.-Mexico borderland as an in-between space that allows for physical, emotional, and creative transformation through the lens of nepantla, a Nahuatl term for the “space between, in the middle of, or in the midst of.” Recognizing that collective landscapes, specifically that of the U.S.-Mexico border, are separated through policy and physical barriers, filmmaker Alejandro González Iñárritu (b. 1963, Mexico City, Mexico) explores the permeability of the U.S.-Mexico border desert landscape through his mixed reality immersive installation, Carne y Arena (Virtualmente Presente, Fisicamente Invisible) (Flesh and Sand: Virtually Present, Physically Invisible) (2017). This thesis analyzes the use of virtual reality technologies as immersive storytelling tools in Carne y Arena through a social history of art and scholar Gloria Anzaldúa's reinterpretation of the concept of nepantla as a liminal space of transformation. González Iñárritu’s Carne y Arena makes visible the perils Latin American migrants face when crossing the Southwest desert in an experiential presentation. Through a socially conscious lens, he depicts real-life individuals and their stories with humanity and empathy. Carne y Arena draws attention to the dehumanization of Latin American migrants and transforms the U.S.-Mexico border landscape into a political theater of imagination, empathy, and memory.
ContributorsZacarias, Deliasofia (Author) / Fajardo-Hill, Cecilia (Thesis advisor) / Hoy, Meredith (Thesis advisor) / Gonzalez, Rita (Committee member) / Tompkins, Cynthia (Committee member) / Arizona State University (Publisher)
Created2024
Description
Given increasing frequency and intensity of extreme weather events and disparities in socio-economic conditions, managing flood risks has become ever more challenging. Building a community flood resilience becomes an essential strategy to reduce flood risks and achieve sustainable development. However, enhancing community flood resilience presents numerous obstacles and potential downsides. To address such a challenge, this dissertation investigates the interactions among natural, built environment, and actor systems using a case study of flooding in Jakarta, Indonesia, focusing on the Ciliwung river watershed. The study first develops a conceptual framework for community flood resilience by integrating concepts from disaster, flood, and community resilience research to represent how water, structural elements, and actors are connected and can contribute to hazards and vulnerabilities. Building on the framework, the study utilizes a mixed-methods approach, combining stakeholder interviews with network and heatmap analysis to identify the roles and interconnections of relevant actors in Jakarta’s flooding. Next, the study employs a hybrid of agent-based and system dynamics modeling to explore the complex interactions among the watershed’s physical and actor systems. The model evaluates how the level of collaboration among government agencies affects flood management interventions and community resilience under various scenarios concerning weather patterns and land-use change.
The research provides an exploratory tool and a strategic guide for enhancing community flood resilience. The stakeholder analysis reveals the complexity of stakeholder relationships and challenges such as imbalance in resource allocation, authority overlap, and low engagement. These insights highlight the need for trust-building, community involvement, and strategic alignment in flood management efforts. Systems modeling to derive policy recommendations bridges the gap between theoretical frameworks and governance challenges, offering empirical evidence of the critical role of governmental collaboration in reducing exposure to floods. The systems modeling results suggest that under conditions of uncertainties, enhancing community flood resilience requires a coordinated approach among stakeholders.
ContributorsSulistyo, Sinta Rahmawidya (Author) / Agusdinata, Datu Buyung (Thesis advisor) / Aggarwal, Rimjhim (Committee member) / Brundiers, Katja (Committee member) / Arizona State University (Publisher)
Created2024