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MODELING AND ANALYTICAL STUDY OF NATURAL ORGANIC MEMRISTORS FOR NEUROMORPHIC COMPUTING
Get PDFThe need for faster and more energy-efficient chips is growing in the era of artificial intelligence. However, the conventional computing architecture suffers from the Von-Neumann bottleneck caused by the lag in data transfer between memory and processors. Neuromorphic computing systems offer an alternative to overcome this bottleneck. Similar to how neurons and synapses work in the human brain, this technology carries out memory and processing functions in the same cell, reducing the time required to transfer data between memory and processor. Memristive devices are promising candidates for implementing neuromorphic computing systems. In recent years, several materials for organic-based memristors have been under investigation, showing a promise for sustainability by reducing e-waste with environmentally friendly disposal. Honey, in particular, has been a viable dielectric thin-film for resistive switching, offering the benefits of being dissolvable and eco-friendly. However, the progress in advancing this technology is limited by a lack of understanding of the switching mechanism that dictates the device functionality. In particular, no physical model exists to explain the behavior of organic memristors. This paper proposes a physics-based numerical model to explain the I-V characteristics of an organic Ag/Honey/ITO memristor. Field-dependent filament nucleation and gap formation are used to describe the SET and RESET processes. To derive the temperature and field, carrier continuity and heat equations are self-consistently solved within an FEM solver. A 3D axisymmetric structure is constructed to perform the simulation. The primary conduction mechanism used in this work is phonon-assisted hopping. During the SET and RESET state, Gibb's free energy minimization determines the filament and gap evolution. The modelaccurately accounts for the SET/RESET characteristics of the Honey memristor, providing insights into the resistive switching behavior from a thermodynamic point of view. The results will be beneficial in optimizing the device's performance and implementing it in a neuromorphic system
THE EFFECTS OF INSULATION ON MANTLE DYNAMICS AND EARTH’S THERMAL EVOLUTION
Get PDFThe Earth’s mantle is bracketed by continental lithosphere above and Large Low Velocity Provinces (LLVPs) below. Both continental lithosphere and LLVPs impact the efficiency of convective heat transfer within the mantle. For example, prior studies find continents to behave like mantle insulators by buffering the amount of heat leaving the system, increasing mantle temperatures over time. Other studies suggest that LLVPs behave as core insulators, reducing heat transport from the core to the mantle and, consequently, decreasing mantle temperatures over time. Past studies focused mainly on the investigating mantle convection with one insulator (either top or bottom), however, a gap remains that considers two insulators operating in tandem. Do these two insulating surfaces cancel each other out? Or does one outcompete the other? To answer and better understand these questions, we first model the mantle with a single insulator. Here we present results from a suite of mantle convection simulations using the finite element code ASPECT. These simulations are isoviscous and use a two-dimensional spherical shell geometry with seven levels of mesh refinement. The model continents and LLVPs were imposed as two regions of constant viscosity, density, and thickness, one at the top (continent) and one at the bottom (LLVP) of the model mantle. To quantify the impact of insulation we examined two different conditions: (1) a system with only a top insulator, (2) a system with only bottom insulator. Within each of these conditions, we examined a range of surface average coverages of the two regions, from full surface area coverage to no surface area coverage. We found that continents reduce surface heat flux and heat the mantle with increasing surface area coverage. On the other hand, LLVPs inhibit basal heat flux and decreasing internal mantle temperatures with increasing surface area coverage. We then discuss the impacts of changes to internal temperature on mantle dynamics and the thermal evolution of the Earth, Finally, we discuss implications on the origin and morphology of LLVPs as well as the impacts of core-mantle boundary heterogeneity on the geodynamo and geomagnetic reversals
Threads of Becoming
Get PDFWe are born into structures shaped by culture and society. From a young age, we are taught how to walk, talk, feel, and behave. These lessons are imparted through education, parental expectations, religion, laws, and governmental systems. Language frames these intricate rules and knowledge. But is it possible to question this conditioning and truly understand who we are beyond such structures?As an immigrant who moved from Vietnam to the United States nearly ten years ago, my experience of adapting to a new culture, language, and societal framework has profoundly shaped my identity. This journey has taught me resilience and adaptability. It has also shown me the importance of questioning my beliefs, unlearning what I have been taught, rethinking what has been coded into my mind, and unfolding the structures that have shaped my understanding of the world, and ultimately, taught me how to live.This thesis explores the process of self-reconstruction within the immigrant experience, examining how cultural displacement challenges notions of identity and belonging. Threads of Becoming includes works that reflect a personal journey of self-discovery and adaptation, but they also extend beyond the personal, gesturing toward a collective process of transformation. By engaging with these installations and performances, viewers are invited to participate in this unfolding: to move, to reflect, to become. In the space of art, we are free to construct new languages, new ways of seeing, and new ways of being. We can weave, unweave, and weave again, with each stitch becoming a step toward reimagining what is possible
An Exploration of Age Differences in Climate Policy Support Among Republicans
Get PDFOne of the primary barriers to implementing climate change policy within the United States has been a history of opposition from Republicans. Historically, this opposition was characterized by a lack of belief in climate change, but climate belief has steadily increased across all groups in the United States over the last 20 years. While belief has increased, partisan divides on climate policy remain strong. However, recent research indicates that younger Republicans are more likely to support climate policy than older Republicans, and that the relationship between age and policy support is stronger for Republicans than for Democrats. I argue that this shift remains underexplored, and that it is at least partially a result of differences among Republicans across three factors: climate anxiety, experiences with extreme weather, and more negative attitudes toward capitalism, all of which may be impacting younger Republicans to a greater extent. I apply a series of regression analyses to a large non-probability sample of Republicans (n = 1,249) to determine the significance of these three factors. Results show all three factors to be significant, although the importance of each individual factor shifts by age bracket. These results support existing data showing the shift of young Republicans towards increased climate policy support and begin to work on a basis through which researchers can determine the reasons for such a shift. I conclude with a discussion of the potential implications of potential climate policy depolarization, as well as future paths for research on climate policy and conservatism
SURGICAL TECHNOLOGY PRECEPTOR PRACTICES AN EXPLORATION OF FEEDBACK TO SURGICAL TECHNOLOGY STUDENTS
Get PDFFeedback is an integral part of the learning process. In the healthcare setting providing feedback is especially important as it is a fast-paced environment that will leave newcomers behind if they do not catch on to necessary skills quick enough. Nine surgical technology professionals who act as preceptors to surgical technology students were interviewed to better understand their feedback giving process in the clinical setting. The findings showed relationship building to be a constant activity as preceptors navigated through challenges while deciding what feedback to provide to support the student
DISABILITY AND EDUCATION A QUALITATIVE STUDY OF TEACHERS’ AND PARENTS’ PERCEPTIONS OF RESOURCES, ACCOUNTABILITY, AND RELATIONSHIPS
Get PDFNCES (2024) reports that there were 7.5 million students, aged between 3 to 21 years, receiving special education services under the Disabilities Education Act (IDEA) in the academic year 2022-23 (para. 1). Trends suggest that the number of students with disabilities will continue to increase each year and alongside this so will the number of disabled students participating in general education spaces (NCES, 2024, Table 3, para. 5). Throughout this dissertation, I explore disability in the general English Education classroom. ELA teachers and parent/guardians of disabled students within a Northwest region of the United States were invited to participate in the research study and complete an anonymous survey. After situating the study in relevant literature and describing the theoretical frameworks and methods I draw on, I share the themes that emerged across the open-ended survey responses and discuss the multiple choice and Likert scale questions answered by the participants using descriptive statistical analysis. In consideration of the findings, I offer future implications for both practicing teachers and pre-service teachers, while offering supporting materials for the inclusion of Disability Studies Pedagogy as well as share resources for including representations of disability and teaching about disability within the ELA curriculum using Young Adult Literature to facilitate learning opportunities for students
WILL A TALE OF TWO CATS BECOME A TALE OF ONE? CANADA LYNX AND BOBCAT DENSITY AND DYNAMIC OCCUPANCY IN A MOUNTAIN ECOSYSTEM
Get PDFClimate change causes divergent range shifts for cold versus warm adapted species, potentially reshuffling biotic interactions at range peripheries. Yet, outside of coarse distributional metrics, little information exists regarding the population ecology of species along range-peripheries. Here, we use camera trap data in combination with spatially-explicit capture-recapture (‘secr’; Chapter 1) and dynamic occupancy models (Chapter 2) to examine how climate influences density and abundance (Chapter 1), and colonization-extinction dynamics (Chapter 2) of two potentially interacting species – the cold-adapted Canada lynx (‘Lynx’; Lynx canadensis) and the warm-adapted bobcat (Lynx rufus) – at a range periphery in a montane ecosystem within northcentral Washington, United States.In Chapter 1, we modeled density and abundance of lynx and bobcats during the summer of 2023 as a function of temperature and environmental gradients, and used secr models to map spatial variation in density and calculate density overlap between the two species. We also predicted future patterns of density, abundance, and density overlap using three different Shared Socioeconomic Pathway (SSP) climate change scenarios. Density was influenced primarily by temperature, with lynx density declining as a function of temperature and bobcat density increasing. Future abundances declined for lynx under all SSPs, but were stable for bobcats, with both species experiencing upward elevational shifts in density. Areas of the landscape with high lynx and low bobcat densities declined in the future, but areas with low lynx and high bobcat densities increased. Our approach, which could be applied to other species inhabiting montane systems, revealed how temperature gradients shape range edge patterns of density of cold and warm adapted mammals, with implications for future population trajectories and interactions.In Chapter 2, we utilized a long-term (2016-2024) camera trap dataset to model local colonization and extinction dynamics for lynx and bobcats in relation to changing climatic and disturbance conditions. We found that maximum summer temperature and winter snow depth are important drivers of local colonization and extinction probabilities for both species. Increasing summer temperatures reduced lynx and bobcat colonization probabilities, increased lynx extinction probabilities, and reduced bobcat extinction probabilities. Decreasing winter snow depths reduced lynx colonization probabilities and increased bobcat colonization probabilities. In the short-term, our results suggest fairly stable occupancy dynamics for both species. However, in the long-term, we suggest that the interplay of climate change with our documented colonization and extinction dynamics will result in lynx range contractions and bobcat range expansions. Thus, by utilizing a long-term camera trap dataset, we provide insights into the mechanisms driving range dynamics for cold versus warm adapted species, and our framework can be extended to other montane ecosystems to gain a process based understanding of species range shifts under changing climatic conditions
SEARCHING FOR ACTIVE GALACTIC NUCLEI IN LOW-MASS GALAXIES
Get PDFIt is now understood that supermassive black holes (SMBHs, log MBH /M⊙ ≳ 5) occupy the centers of all massive galaxies (log M∗/M⊙ ≳ 10). Despite their ubiquitous nature, much about these extreme systems remains a mystery. The origin of these SMBHs is still unknown, though astronomers have narrowed their formation pathways to a few potential seeding mechanisms. These models predict observable differences in the resulting population of BHs, particularly in low-mass galaxies. Additionally, constraining these models involves finding and studying the still elusive population of intermediate mass BHs (2 ≲ log MBH /M⊙ ≲ 6).Observations of these low-mass systems remain scarce, however; the sphere of influence of a 105 M⊙ BH would only be large enough to be resolvable within the Local Group. Astronomers have then learned to detect indirect signatures of BH activity, namely through interactions with their environment. Among these are active galactic nuclei, complex structures of gas and other material accreting onto a central massive BH. Because of the extreme astrophysical processes at play, these objects radiate a tremendous amount of energy throughout the entire electromagnetic spectrum. Not only do their signals contain a myriad of unique AGN signatures, but their light has been shown to vary stochastically across time. This photometric variability can be modeled mathematically, providing a prolific tool for finding AGNs that is less likely to overlook low-mass and low-metallicity AGNs.With the advent of large time-domain surveys, recent works have been able to search for AGN activity in tens of thousands of galaxies, identifying hundreds of AGNs in dwarf galaxies. In anticipation of the next generation of surveys, this work seeks to understand the resulting population of low-mass AGN candidates and examine alternative methods to find them. We assess the results of various AGN selection methods on a small group of variability-selected AGNs, finding X-ray emission is less than half of the sample. We present the results a large scale variability search, finding over one thousand new AGN candidates in dwarf galaxies. Despite this large number of new candidates whose masses are consistent with previous relations, emission line diagnostics and broad Hα emission only detect BH activity in a small fraction of our resulting sample. Finally, we explore a variety of machine learning algorithms with a particular emphasis on the low-mass regime. Gradient Boosted Trees and a Neural Network are found to be the most capable of finding AGNs in the low-mass range without sacrificing generalizability for massive galaxies
APPLICATIONS OF MICROSCOPIC FLUID FLOW PART A: OBLIQUE DROPLET IMPACT ON MICROHOLED HYDROPHILIC SUBSTRATE PART B: DESIGN OPTIMIZATION OF A FISH-ON-CHIP DEVICE FOR NEUROLOGICAL STUDY
Get PDFMicroscopic fluid flow occurs at micrometer to millimeter scales where the flow is usually laminar, dominated by viscous forces over inertial forces and significantly influenced by surface tension, capillary action and wall effects. It plays a crucial role in various engineering and biomedical applications. This thesis explores two distinct yet interconnected aspects of micro-scale fluid interactions: (1) dynamics of oblique droplet impact on microholed hydrophilic substrate and (2) the design optimization of a microfluidic device for zebrafish larval culture to study microbiome-neurological interactions, specifically sensorineural hearing loss.In the first part, I investigated the behavior of a water droplet on an inclined hydrophilic surface with a microhole at the center of it for inclination angles ranging from 0° to 30°. The droplet exhibited asymmetric spreading due to the interplay between surface energy and tangential velocity component. I identified almost consistent normal Weber numbers (WeN) across different jetting (through the microhole) regimes (i.e., no pinch off, single pinch off, multiple pinch off) and established a power-law relationship for maximum spreading of the droplet along the tangential direction, βm ∼ WeN0.27, independent of inclination angle within the experimental range of inclination angles. The power law was found to be in good agreement with the literature models. However, deviation may be anticipated at higher angles which is out of the scope of this study. The time for maximum spreading of the droplet along the tangential direction was found to be quite independent of the inclination angle within the experimental range for a certain WeN. Additionally, jet velocity scaled linearly with impact velocity, while pinch-off time and maximum jet length showed predictable trends with capillary dynamics.In the second part, two Fish-on-Chip (FOC) devices (Design A and Design B) were developed and evaluated for their effectiveness in supporting zebrafish embryo development over a four-day culture period. Design A, while simpler to fabricate, exhibited higher flow rates and lower hatching success due to unfavorable geometry. Design B, with a more complex dual-layer PDMS structure, demonstrated improved flow control and significantly higher hatching rates. However, both designs resulted in reduced larval length compared to controls, indicating the need for further refinement to ensure optimal developmental conditions within the chip environment. Together, these investigations advance understanding of fluid behavior at the microscale and contribute toward the development of microfluidic platforms for biological studies
EFFECTS OF DISABILITY LEGITIMACY, IMPAIRMENT, AND CAUSALITY ON PERCEPTIONS OF PEOPLE WITH DISABILITIES IN ORGANIZATIONS
Get PDFResearch demonstrates the relevance of the perceived legitimacy of disability statuses, perceived degree of impairment, and causal attributions regarding disability acquisition as relevant to perceptions of people with disabilities (PWD) in organizations. However, literature does not examine such variables utilizing the same labels and definitions across studies nor does it consider that these variables may be related in informing perceptions of PWD. Additionally, research posits the relevance of an external source implying disability legitimacy or considering the effect of disability model endorsement on perceptions of PWD as potential methods of improving perceptions. Likewise, although previous research notes that PWD face worse perceptions in the form of unfavorable ratings on variables including organizational citizenship behavior, counterproductive work behavior, perceived incompetence, coworker trustworthiness, and accommodations granting likelihood, such research has not systematically studied these work-related outcomes in relation to the perceived legitimacy of disability statuses, perceived degree of impairment, or causal attributions. Therefore, across three experimental vignettestudies, we investigated these constructs using the same labels and definitions and methods of improving perceptions of PWD as they relate to such work-related outcomes. Study 1 results demonstrated the perceived degree of impairment as disproportionately impacting perceptions of PWD, study 2 results demonstrated an external source implying legitimacy result in worse perceptions of PWD, and study 3 results demonstrated higher social model endorsement as increasing participant likelihood to grant accommodations for PWD. Across studies 2 and 3, participants rated physical disabilities better on the above work-related outcome variables compared to developmental and psychological disabilities