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MEASURING INTERFACE EFFECTS IN SOLID-STATE BATTERIES
No full textSolid-state batteries with solid metal anodes would be a promising solution for improved energy storage. However, the unstable behaviors of solid-solid interfaces impedes implementation. Further study of these interfaces, both at the planar solid metal anode | electrolyte interface and the grain | grain interface in solid electrolytes is necessary to elucidate practical engineering techniques to improve cycling stability. We assemble three-electrode symmetric cells of Sodium | Sodium β″-Alumina | Sodium to assess the voiding and dendritic behaviors of the sodium metal electrode at varying cycling parameters and operating conditions. By modifying the applied current density and fixing areal capacities at 0.5, 1.0, and 3 mAh cm-2 and utilizing a sodium reference electrode we demonstrate polarization on plate at high current densities. Modeling comparisons with exhaustion strips, unidirectional current application to oxidize the sodium metal electrode until a cutoff potential of 1 V, indicate extensive delamination of the sodium electrode from the solid electrolyte. There is less observed delamination at lower current densities as the cutoff voltage is reached at lower areal capacities. Further study of electrode thickness and operating pressure on critical current densities, the highest achieved current density before failure to 1 V or shorting observed, and achievable capacities show limited benefit to increasing operating pressure beyond 2.0 MPa. We continue our investigation into interfacial behaviors through the assessment of hot pressing effects on argyrodite sulfide electrolytes with respect to morphology, ionic conductivity, and mechanical properties. We find that hot pressing at 150 °C improves ionic conduction without any reliance on external operating pressure with copper electrodes. Hot pressing resulted in smooth fused morphology distinct from the cold pressed (20 °C) samples with an higher modulus. Finally, our efforts in the development of an all solid-state battery database for laboratory scale single set of layer devices is discussed. We identified from the literature the core characteristics and performance metrics for a solid-state batteries and defined the ontology to capture the data for analysis. The ontology was tested and refined through the collection of fifty cells with the target of assessing the state of research, current achievements, gaps, and trends in the literature. The database now contains over 250 cells with plans for further uploads and refinements to the ontology
Collective Dynamics of Atoms Coupled to an Optical Nanofiber: From Disordered Ensembles to Tunable Arrays
No full textQuantum emitters coupled to a nanophotonic waveguide have revolutionized quantum science and technology by enabling engineered light-matter interactions. In particular, a system of neutral atoms coupled to an optical nanofiber (ONF) offers a unique platform for quantum optics and quantum computation, as it integrates two well-established technologies: neutral atoms with high-fidelity control and optical fibers with low-loss light propagation. This thesis presents a study of the collective dynamics of Rb85 atoms coupled to an ONF, with a focus on the atomic spatial distribution.
We first present the collective dynamics of V-type multilevel quantum emitters, emphasizing the interaction between multiple excited states and multiple atoms mediated by a common electromagnetic (EM) field mode. Remarkably, we observe quantum beats even in the absence of an initial superposition in the excited states, which arises from vacuum-induced coupling between the excited levels. Although such second-order processes are typically weak, they can become observable through collective enhancement. We theoretically investigate these collective quantum beats in an extended system of V-type atoms coupled to a waveguide and identify a characteristic length scale that governs the interference in the multi-atom, multi-level emission.
Then, we describe our efforts to observe long-range interaction between macroscopically separated atomic clouds via an optical fiber. We develop a theoretical framework for modeling resonant scattering of an atomic ensemble placed in front of a mirror in the waveguide quantum electrodynamics (QED) setup. We identify the competition of two parameters that govern the scattering process: the drive strength and the strength of time-delayed feedback. Our intensity correlation measurement shows that an atomic cloud coupled to an ONF operates in the independent emission regime, where time-delayed feedback is negligible. This work highlights the need for an ordered atomic array with a lattice constant commensurate with the transition wavelength to collectively enhance cooperativity.
In the final chapter, we present a novel method for creating a tunable-spacing atomic array interfaced with an ONF using a set of binary phase transmission gratings. The optical setup and preliminary results on atom trapping within the lattice are described.
Our approach opens the door to high-cooperativity neutral-atom-nanofiber interfaces, paving the way for advances in quantum optics and quantum technology
EXPLORING BELONGING: LATINA IMMIGRANT GIRLS CREATING JOY AND BELONGING ACROSS SCHOOL, HOME, AND COMMUNITY
No full textAt a time of rising anti-immigrant sentiment, gender-based oppression, and educational rollbacks, first- and second-generation Latina immigrant youth are navigating complex conditions of exclusion and resistance. This dissertation examines how four high school-aged Latina immigrant girls experience, navigate, and create belonging across school, home, and community settings.
Grounded in Chicana feminist theory and Latina/o Critical Race Theory, the study uses a comparative multi-case study design with an embedded Youth Participatory Action Research (YPAR) project. Over five months, participants engaged in bi-weekly sessions using testimonios, pláticas, photovoice, and mapping. In the final phase, they co-led a YPAR project exploring community safety for Latina girls.
The study explores three central questions: (1) What socio-cultural discourses and identities shape Latina immigrant girls’ experiences of belonging? (2) What systemic and interpersonal factors influence how they navigate and create belonging across contexts? (3) How do they use YPAR to imagine and build more affirming spaces?
Findings show that belonging is not a fixed condition but a fluid, power-laden process. The girls moved between moments of inclusion and exclusion, revealing how belonging is shaped by institutional dynamics, cultural discourses, and youth agency. Three key insights emerge: (1) belonging is relational and context-dependent; (2) community-based institutions play a critical role in sustaining belonging; and (3) youth-driven, culturally affirming spaces can support emotional safety and connection.
This study introduces the concept of Borderlands of Belonging to describe how Latina immigrant youth negotiate belonging across shifting personal, institutional, and systemic terrains. It also presents a visual model rooted in Chicana feminist thought to map how belonging is co-constructed through care, resistance, and imagination.
Methodologically, the project demonstrates how YPAR can be integrated into case study research to both document and create spaces of youth-led transformation. Practically, it offers guidance for educators, policymakers, and community leaders seeking to build systems of care that affirm culture, language, and youth voice. Ultimately, the study calls for a shift in perspective—from asking whether young people belong to examining how systems must transform to be worthy of their belonging
CINEMATIC TIME: BETWEEN CHRONOS AND AION
No full textSince the industrial revolution, people have predominantly experienced time in itschronometric form, i.e., as discrete units of time, or as a time divided into uniform spatial
intervals that can be measured by movement. In this chronometric universe, cinema emerged
toward the end of the 19th century as an industrial art, often used not merely for entertainment
but as a medium for motion analysis and for improving the efficiency of workers in factories.
Consequently, cinema as a mass entertainment machine continues to carry and spread an
essentially chronometric and chronological sense of time (time as Chronos) into everyday life,
molding people into chrono-subjects by structuring their routines, their leisure, their perceptions
and desires. Against this historical background, “Cinematic Time: Between Chronos and Aion”
aims to show that cinema is not only a tool of quantitatively measured time, but that it has
introduced into modern experience also a different sense of time. This other time, which may in
opposition to Chronos be referred to as Aion, has historically been conceived as qualitative
duration, or pure empty time, or Event. Cinema has access to this qualitative experience of
temporality because it not only records and analyses time, but also synthesizes and projects it,
thus unbinding temporal realities that give rise to different forms of perception. In this sense, the
dissertation argues that cinema is not just a chronometric entertainment machine, but also a
spiritual machine that has generated multiple artistic experiments and expanded our notions of
time, narrative, and thought. This argument is developed following Gilles Deleuze’s
philosophical work (especially Cinema I and II, and The Fold) and through close analysis of
several important contemporary filmmakers (David Lynch, Chantal Akerman, Yorgos
Lanthimos, Pedro Almodovar, Laura Citarella, and the great Chilean director Raul Ruiz).
The last chapter of this dissertation is a creative experiment that concludes andaccompanies the previous ones. The type of layout, the still images from videos, and drawings
that constitute it are therefore meant to play with an idea of non-reference, i.e., words and images
talk to each other in a free manner, or in a manner that compels the reader/viewer to be part of
the deciphering and poetic process
Modeling the impact of nutrient redutions and climate change on vibrio vulnificus using Chesapeake Bay Program model scenarios
No full textVibrio vulnificus poses significant health risks in coastal and estuarine environments, with important implications for public health and the regional economy. Building upon the empirical modeling framework established by Jacobs et al. (2014), our study employs four different empirical models to predict: the probability of encountering V. vulnificus; its abundance in colony forming units per milliliter (CFU ml⁻¹); the probability that its abundance exceeds a critical threshold (>90 CFU ml⁻¹); and the likelihood of detecting a virulence‐correlated gene indicative of toxicity. In contrast to traditional models that focus primarily on temperature and salinity, our approach incorporates an expanded suite of water quality variables (including computed Secchi depth as a proxy for water clarity, dissolved oxygen, chlorophyll‐a, and phosphate concentrations) to provide a more comprehensive assessment of V. vulnificus dynamics in the Chesapeake Bay.The models were forced using output from Chesapeake Bay Program restoration and climate change model scenarios over a ten-year period (1991–2000), spanning conditions from business as usual to full compliance with Total Maximum Daily Load (TMDL) nutrient reduction goals. Analysis of the scenarios indicate TMDL implementation, which improves water clarity by reducing nutrient loads, and increases oxygen concentration while decreasing phosphorus and chlorophyll-a concentrations can substantially lower the probability of occurrence, abundance, probability of elevated abundance and the virulence of V. vulnificus. In contrast, climate projections alone suggest that increasing water temperatures will exacerbate Vibrio risk, extending the seasonal window of exposure. TMDL compliance reduces the risk of V. vulnificus presence and human exposure in the model climate change scenarios, however it does not fully mitigate the effects of thermal increases. The results underscore the potential for integrated management strategies that combine effective nutrient reduction with climate adaptation measures to mitigate the risk of V. vulnificus and support the long-term economic and environmental sustainability of the Chesapeake Bay region
DESIGNING SANCTUARY: THE IMPACT OF TRAUMA-INFORMED DESIGN ON POST-TRAFFICKING REHABILITATION
No full textHuman Trafficking, encompassing both labor and sex exploitation, is a global crime withsevere long-term impacts on victims. This thesis explores how the built environment can provide
a nurturing experience for the rehabilitation, resilience, and empowerment of trafficking
survivors, focusing on emergency, transitional, and permanent supportive housing. Washington
D.C. ranks fourth among U.S. cities in trafficking cases according to the National Human
Trafficking Hotline, making it a critical area for study. Survivors of trafficking face significant
challenges in accessing affordable and safe housing during their recovery. Grounded in
trauma-informed care theory, the study informs the design of therapeutic living environments that aim to prevent re-traumatization. Addressing post-trafficking housing is crucial for improving recovery outcomes, increasing survivors’ cooperation with law enforcement, and
empowering victims to become agents of change. By focusing on the intersection of architecture and trauma recovery, this research aims to develop effective strategies for supporting survivors, potentially leading to higher prosecution rates and helping to break the cycle of human trafficking. The project explores innovative planning and design principles that promote community connection, safety, and survivor empowerment, working toward a framework for survivor-centered architectural solutions in Washington D.C., and beyond
MEASURING THE LIMITS: WHEN DOES LONGITUDINAL TEACHER ATTRITION BECOME PROBLEMATIC?
No full textResearchers have long examined the magnitude and causes of teacher turnover, emphasizing its variability across settings, and observed potential effects on schools and students (Gershenson et al., 2018; Goldhaber & Theobald, 2021; Holme et al., 2017; Ingersoll, 2001). While teacher attrition is often framed as excessively high and problematic (Dias-Lacy & Guirguis, 2017; Neason, 2014; Seidel, 2014) and past scholars have documented harm to students based on exposure to attrition (Henry & Redding, 2020; Ronfeldt et al., 2013), attrition is not fully avoidable. As scholars have begun to attend to the longitudinal nature of attrition within schools including episodic (temporary high attrition), chronic (sustained high attrition across multiple years), and cumulative attrition (accumulation of loss over time), it is often assumed that elevated patterns over the long term will necessarily be even more harmful to students. Yet, existing research offers little insight into when turnover shifts from typical and manageable to atypical and harmful. This study builds on the existing literature (Holmes et al., 2019) by conducting descriptive and inferential analyses to identify policy-relevant measures for episodic, chronic, and cumulative attrition.
Using 12 years of statewide data from Maryland public schools, this dissertation confirms that schools experience a wide range of attrition patterns over time, with the average school experiencing a 1-year episodic attrition rate of 14.5%, a chronic 3-year average attrition rate of just under 15%, and a cumulative 3-year attrition rate of 37%. While some schools do experience 1-year attrition rates above 60% and 3-year average attrition rates above 50%, these schools represent outliers, and only a small subset of schools lose more than 30% repeatedly.
Further, while chronic and cumulative attrition have been theorized as distinct (Holme et al., 2017), this study demonstrates that schools with above-average rates of 3- to 5-year average attrition also tend to be schools experiencing above-average rates of 3- to 5-year cumulative attrition. This finding suggests these patterns reinforce each other rather than occur independently and challenges the utility of analyzing them separately for policy and practice.
Moreover, nonlinear regression analyses reveal minimal association between 1- to 3-year average attrition and student achievement when attrition is below 30%, but there are significant declines in ELA and math performance when rates exceed 30%. Thus, while high chronic attrition rates (3-year average attrition rates) are highly uncommon, they are associated with severe consequences for students and may be driving the effects previously observed in past studies using linear models robust. These patterns are robust to alternative model specifications, including differing functional forms and the inclusion of school year fixed effects.
This study refined the measurement of chronic attrition and supports the use of nonlinear models to examine their effects. It also offers key policy insights by highlighting both the potential severity and relative rarity of the most harmful attrition environments as findings support shifting policy focus from generalized turnover concerns to monitoring persistent, high-level attrition driven by deeper organizational challenges
Floating wetlands and their potential for nitrogen removal in estuarine waters
No full textNutrient enrichment of estuarine waters remains a problem globally. New efforts have sought to apply principles of ecological engineering to promote nutrient removal within degraded aquatic systems by constructing habitats that may support enhanced nitrogen removal. Several technologies and approaches are certified as best management practices (BMPs) by the Environmental Protection Agency (EPA). These include the restoration of oyster reefs, stream and estuarine wetlands, and riparian buffers, as well as the implementation of wet retention ponds. Each of these habitats has been suggested to be a “hotspot” for nitrogen removal, but they are also biologically and chemically complex environments. Thus, the quantification of their impact on nutrient removal is difficult due to interactions with other processes that influence nitrogen transformation and loss within tidal estuarine waters. Floating wetlands have traditionally been implemented to increase the nutrient removal efficiency in freshwater retention ponds, where nutrient removal is presumed to be accomplished by plant assimilation and sediment deposition. Similar installations of floating wetlands in tidal waters have recently been implemented to achieve the same ecosystem services as in retention ponds, but little is known about their efficacy. In this dissertation, I quantified floating wetland nitrogen removal and cycling through a series of mesocosm experiments and numerical modeling. The mesocosm experiments were carried out for 90 days at the Chesapeake Biological Laboratory in both spring and summer periods during the years 2019, 2021, and 2022. My results indicate that denitrification was the major nitrogen removal process, removing ~4 times as much nitrogen as plant uptake. Denitrification rates were comparable between mesocosms with wetland plants and control mesocosm with only the media, suggesting that denitrification was occurring in microzones within the high-surface area media. Thus, a new formulation to incorporate this high surface area media was necessary to reproduce these high denitrification rates in model representations of the experiments. This dissertation research thus clearly demonstrates that floating treatment wetlands can remove nitrogen at rates that are often higher than subtidal sediments, but future work on their durability and efficacy under a wider range of conditions is needed to better assess their potential to become a certified best management practice tool for nutrient management
Master equation formulations for continuous feedback in quantum systems
No full textIn recent years, quantum experiments have become increasingly precise, fast, and capable of high resolution. Particular interest has been given to quantum control, which aims to prepare, manipulate, and steer quantum states toward desired outcomes. Common applications of quantum control include state preparation for quantum computing algorithms, protocols to implement nanoscale machines, and feedback to guide a system's evolution. Feedback involves collecting information from quantum measurements, then acting on the system based on measurement outcomes.The standard measurement model in quantum mechanics is the projective measurement, which destroys quantum coherence by causing the wave function to collapse to a subspace spanned by the eigenstates of the measured operator.
This thesis explores the theory of weak measurement processes, a class of measurement protocols that extract information from a quantum system while (partially) preserving coherence. The weak measurement protocol has a tunable parameter that controls the information obtained per measurement cycle and the disturbance (decoherence) introduced into the quantum system. Using this nondestructive form of measurement, one can extract information during the system's evolution and apply real-time feedback to drive the system's evolution to specific target states. A general master equation is derived to describe continuous feedback using weak measurements with general filtering processing. Particular cases of low-pass and band-pass filters are studied in detail and applied to a harmonic oscillator cooling protocol. Results show that ground-state cooling of the quantum harmonic oscillator can be achieved.
Finally, this dissertation discusses an experimental and computational project that uses machine learning to estimate the temperature and the number of atoms of a cold atomic cloud. The goal is to use non-destructive measurements to infer hidden properties of the atomic ensemble without disturbing the atomic trap. Results show that reasonable accuracy can be achieved using various neural network architectures, depending on the complexity of the input data. The accuracy and responsiveness of the trained models make them suitable for real-time estimators that can be used in closed-loop feedback
HYPERSONIC TURBULENT BOUNDARY LAYERS WITH INTERACTIONS
No full textThe Mach 10 Hollow-Cylinder Flare (HCF) and the Mach 6 BoLT-II hypersonic configurations were simulated and studied. Wall-Resolved Large Eddy Simulations (WRLES) with a high-bandwidth resolving WENO method and explicit third order Runge-Kutta time advancement was used to obtain detailed solutions of the flowfields, to include mean data, first and second order turbulent statistics and spectral content. The two configurations each presented a different set of flow physics which were interrogated using a variety of processing techniques. Investigation of the low frequency dynamics in the corner shock-separation of the HCF revealed pairs of Görtler-type centrifugal instabilities across the span generated by the concavity of the separation streamline. This study provided strong qualitative and statistical evidence that the low frequency pulsations of the separation bubble and shockwave are driven by the Görtler-type centrifugal instabilities, which are in turn generated by streamline distortion caused by the separation bubble, thus creating a low-frequency feedback loop. That is, the unsteady shock-separation dynamics, which are also responsible for the large pressure and heat flux fluctuations, are driven by instabilities intrinsic to the corner interaction itself.
This study provided new and important insight into the behavior of the turbulent velocity and thermodynamic correlations in the separation zone and post-shock nonequilibrium flow of the HCF. The nonequilibrium flowfield exhibits significant compression and mean strain with strong amplification of the Reynolds stresses, turbulent kinetic energy and their transport budgets, viz, production, viscous diffusion, turbulent diffusion, pressure diffusion, viscous dissipation, pressure strain and turbulent mass flux. The amplifications far exceeded that of supersonic and lower speed shock-boundary layer interaction flows, and often departed from canonical trends. Classical single-point closures used in lower-order RANS modeling of the Reynolds stress transport budgets, the turbulent kinetic energy transport budgets and turbulent heat flux were also evaluated a priori by comparing to the WRLES solution. While the models performed very well in the upstream equilibrium boundary layer, many performed poorly in the downstream post-shock nonequilibrium region, with few exceptions. The results herein have important implications in wall-bounded turbulence modeling which has typically been based on canonical non-hypersonic equilibrium flows, and to a lesser extent simple nonequilibrium flows.
A single flight condition during the descent phase of the BoLT-II hypersonic research vehicle was simulated using WRLES. For the unperturbed adiabatic wall case, flowfield solutions of the turbulent environment over the vehicle show multiple and distinct large-scale vortical instabilities on top of what is typically seen in broad-frequency turbulence. The downstream boundary layer was marked by high vorticity, temperature and skin friction. Wall normal extractions in key regions of the downstream boundary layer revealed broad-frequency turbulence as well as low frequency content in the energy spectra. An examination of the boundary layer velocity profile showed a significant departure of the transformed velocity from classical turbulence similarity scaling. For the isothermal wall case, the inlet was perturbed according to acoustic wave theory to simulate turbulence in the freestream environment. The simulations predicted precipitous rises in the downstream wall shear stress and wall heat flux mainly in the central and outboard regions, indicative of transition-to-turbulence with a two-dimensional transition front. Except for some locations across the span, the predictions of wall shear stress and wall heat flux were generally lower than that reported from the inflight sensors. However, it was noted that the particular flight condition simulated in this study fell within a very unstable flight regime where the flow flip-flops multiple times between laminar and turbulent states producing inordinately large fluctuations in the wall heat flux as indicated by flight sensor data