Masters Theses

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Performance in Multipath & High-Mobility Leveraging Terrestrial and Satellite Networks
Ghafoori, Amirreza (Virginia Tech, 2024-12-17)
High-mobility scenarios, such as those experienced by autonomous vehicles or users in transit, demand reliable and high-performance network communication. This thesis presents a comprehensive measurement study comparing the performance of terrestrial 5G networks (ATT, Verizon, T-Mobile) and the Starlink satellite network in high-mobility scenarios. The study evaluates key performance metrics, including throughput and latency, across six globally distributed server locations: Virginia, California, Paris, Singapore, Tokyo, and Sydney. Measurements were conducted using a carefully designed testbed while driving a total of 860 km across urban, suburban, and rural terrains. The results reveal that 5G networks, particularly Verizon, excel in urban regions with higher peak throughput and lower latency, while Starlink demonstrates consistent performance in rural and remote areas. The impact of vehicle speed on network performance was also analyzed, highlighting Starlink’s resilience to high speeds compared to terrestrial networks. Heatmaps and statistical analyses underscore the complementary strengths of these networks, suggesting their integration via multipath protocols (e.g., MPTCP, MPQUIC) could enhance reliability and performance in critical applications such as autonomous vehicles, video conferencing, and AR/VR. This work provides valuable insights into the behavior of 5G and satellite networks in real-world high-mobility scenarios and lays a foundation for designing robust and efficient communication systems.
Toward Transformer-based Large Energy Models for Smart Energy Management
Gu, Yueyan (Virginia Tech, 2024-11-01)
Buildings contribute significantly to global energy demand and emissions, highlighting the need for precise energy forecasting for effective management. Existing research tends to focus on specific target problems, such as individual buildings or small groups of buildings, leading to current challenges in data-driven energy forecasting, including dependence on data quality and quantity, limited generalizability, and computational inefficiency. To address these challenges, Generalized Energy Models (GEMs) for energy forecasting can potentially be developed using large-scale datasets. Transformer architectures, known for their scalability, ability to capture long-term dependencies, and efficiency in parallel processing of large datasets, are considered good candidates for GEMs. In this study, we tested the hypothesis that GEMs can be efficiently developed to outperform in-situ models trained on individual buildings. To this end, we investigated and compared three candidate multi-variate Transformer architectures, utilizing both zero-shot and fine-tuning strategies, with data from 1,014 buildings. The results, evaluated across three prediction horizons (24, 72, and 168 hours), confirm that GEMs significantly outperform Transformer-based in-situ (i.e., building-specific) models. Fine-tuned GEMs showed performance improvements of up to 28% and reduced training time by 55%. Besides Transformer-based in-situ models, GEMs outperformed several state-of-the-art non-Transformer deep learning baseline models in efficiency and efficiency. We further explored the answer to a number of questions including the required data size for effective fine-tuning, as well as the impact of input sub-sequence length and pre-training dataset size on GEM performance. The findings show a significant performance boost by using larger pre-training datasets, highlighting the potential for larger GEMs using web-scale global data to move toward Large Energy Models (LEM).
Evolution of Preconsolidation Pressure of Normally Consolidated Clays Over Full Temperature Range
Gevorgyan, Suzanna (Virginia Tech, 2025-02-19)
While it has been established that temperature can change the preconsolidation pressure of clays, the current understanding is limited to specific ranges of temperatures, with temperatures above freezing being studied entirely independently of temperatures below freezing. However, as temperature is a continuous domain and clays may be subjected to both above- and below- freezing temperatures over the course of an engineering application, a unified view is necessary. The first goal of this thesis is to develop a single model which can be used to predict the preconsolidation pressure of a normally consolidated clay at any temperature over a wide range which includes both frozen and elevated temperatures. To do so, consolidation tests were run at various temperatures between -7 °C and 50 °C, and the yield stress at each consolidation temperature was determined. As previous studies have established that the temperature response of clays is dependent upon their mechanical stress history, the specimens were consolidated initially at a reference temperature until they reached the normally consolidated state. Subsequently, the temperature of the specimens was changed and the volume changes during the temperature change stage were recorded. Once the specimens stabilized at the new temperature, they were consolidated once again and the preconsolidation pressure determined at the new consolidation temperature. The volumetric strains and changes in preconsolidation pressure for each temperature used in this study align generally with the previous data published for each temperature domain. Heating led to a decrease in the volume of the specimens, cooling to minimal strain, and freezing to an increase in the specimen volume. Changing the consolidation temperature by either heating, cooling, or freezing the specimen led to various degrees of increase in the preconsolidation pressure. A mathematical model was developed to fit the observed preconsolidation pressures at each consolidation temperature. This model can be used to predict the yield stress of NC kaolinite at any temperature within the tested range, and captures the smaller magnitude increases in yield stress which occur upon heating and cooling as well as the large increases which occur upon freezing the clay. With the effects of unidirectional thermal paths having been treated in the previous portion, a second investigation was also undertaken to assess how much of the temperature history of the soil might influence the behavior at its final consolidation temperature. In particular, the impacts of previous freezing on the preconsolidation pressure at elevated temperatures were investigated. The same clay material was first consolidated to the NC state and then frozen to -15 °C. Subsequently, the material was thawed or heated to various final temperatures and consolidated further to determine the preconsolidation pressure. The results of these tests indicate that the preconsolidation pressure was independent of the consolidation temperature for previously-frozen soil. While increasing contractive axial strains were recorded with increasing temperature, there was no accompanying increase in the preconsolidation pressure. These results indicate the thermal history of the clay can alter its behavior at the current temperature, overriding the effects of the most recent thermal path.
Vector Based Control for Power Electronics Dominated AC Power Grid
Ashraf, Haris Bin (Virginia Tech, 2025-02-14)
The global trend towards electrifying the grid has positioned power electronics at the forefront of modern power systems. To control power electronics in grid-connected applications, Grid Forming (GFM) control has become a focal point of research. GFM control utilizes control laws derived from steady-state relationships in the phasor domain. Although these control methods have historically performed well in traditional power systems dominated by electrical machines, they exhibit unexpected control issues in power electronics-dominant power systems. The root of these unexpected behaviors lies in the foundational assumptions of these control methods (Droop control and Virtual Synchronous Machine) i.e. frequency is considered to be a steady state quantity which is constant within the fundamental line cycle. This thesis critically examines these assumptions and elucidates their potential inapplicability in power electronics-dominated power systems. This thesis also introduces vectors as an alternative representation of voltages and currents. Unlike phasors, vectors are instantaneous and time-varying representation of electrical quantities at any point in time, defined by three time-varying values: Magnitude, Polar angle, and Azimuthal angle, using the spherical coordinate system. An initial attempt to demonstrate the capability of using these vectors to control the active and reactive power in inverters connected to the grid has also been presented in this thesis. The proposed vector-based control is able to track the commanded power setpoints within a fraction of the fundamental AC voltage cycle.
Design and Testing of a Bubble Generator for Molten Salt Surrogate Fluid
Breeden, Courts Holland (Virginia Tech, 2025-02-13)
This study explores the design, testing, and modeling of a bubble injector intended for use in studying bubble dynamics in molten salt reactors using a room temperature surrogate fluid by matching the Reynolds number, Eötvös number, and Morton number defined by the properties of the helium bubbles in the pump bowl of the Molten Salt Reactor Experiment (MSRE). The injector, constructed from polydimethylsiloxane (PDMS) and acrylic, was tested to generate bubbles within a precise size range suitable for simulating conditions in molten salt reactors. Experimental data showed that the equivalent bubble diameter is directly proportional to gas flow rate and inversely proportional to liquid flow rate, with clear trends emerging when data were subdivided into constant flow rate plots. The study applied and adapted the bubble size control model proposed by Lu et al. (2014), revealing limitations in existing models under modified conditions such as an elongated two-phase channel. A novel model was developed to better predict bubble size, incorporating dependencies on both flow rate ratios and the capillary number of the microchannels. The injector's design facilitates convenient modifications in channel geometry to achieve target bubble sizes, and future improvements in pressure monitoring and imaging are recommended. This work contributes to the advancement of microfluidic bubble injection technology.
Reproductive Injustice: Abortion Restrictions and Maternal Mortality Rates
Ayala, Calinda Carolina (Virginia Tech, 2025-02-13)
This research establishes a statistically significant connection between maternal mortality rates and abortion restrictions from a reproductive injustice perspective, integrating the theory of necropolitics. Using a time-series cross-sectional analysis of all 50 U.S. states from 2009 to 2019, this study highlights the impact of restrictive abortion policies during a period of intensified legislative activity, including pre-abortion counseling requirements, TRAP laws, and trigger laws. Data from the Guttmacher Institute's hostility scale and the Institute for Health Metrics and Evaluation's maternal mortality statistics reveal that states with higher hostility toward abortion experienced increased maternal mortality. Notably, a 1% increase in state hostility is associated with a 0.45% rise in overall maternal mortality rates (p < 0.001). The analysis further demonstrates that each marginalized racial and ethnic group examined face heightened risks from higher abortion hostility, with maternal mortality rising among Hispanic women by 0.40% (p < 0.001); among non-Hispanic American Indian and Alaskan Native women increasing by 0.29% (p < 0.05); among non-Hispanic Asian, Native Hawaiian or Other Pacfic Islander women by 0.53% (p < 0.001); and non-Hispanic Black women by 0.39% (p < 0.001) per 1% increase in state hostility. However, the largest increase was found among non-Hispanic White women (p < 0.001). This study contributes to reproductive justice scholarship by incorporating a feminist and sociological perspective on the relationship between abortion restrictions and maternal mortality, particularly as moderated by race and ethnicity. The findings call for urgent policy interventions to dismantle systemic inequities in healthcare access, ensuring the protection of reproductive rights and the reduction of maternal mortality across all communities.
Urban Brownfield Integration – Site Planning and Design Implementation of the Baltimore Community Center
Scherer, Hope Anne (Virginia Tech, 2025-02-13)
Many of the mid-west and eastern cities in the United States were first formed through industrial manufacturing which relied on waterways – rivers, canals, and lakes – to ship the necessary raw materials. As industry and manufacturing declined throughout the 19th century, many cities were left with large, waterfront sites, often contaminated with chemicals and empty industrial buildings. These waterfront sites – designated "Urban Brownfields" – became important potential centerpieces to the revitalization of the cities where manufacturing facilities were slowly being replaced by buildings that would better serve the modern community for tourism, office space, and land use uses ranging from parks to centers for cultural arts. The basic premise of this thesis project is to investigate what can be done to reclaim the often-vast parcels of land that are considered Urban Brownfields – land that once held active industry, but now is left abandoned. The Allied Chemical plant site in Baltimore is a prototypical site that exemplifies many of the issues shared by these types of sites. The project is a vehicle to explore design in terms of structures and their relationship to "domesticated nature." The project development process also considers urban planning and components of growth for urban areas, as well as the importance of density. Design elements incorporate industrial imagery and considerations relative to human scale and experience – from macro to micro. Out of these goals stemmed a project that became the Baltimore Community Waterfront Park and Recreation Center.
xG-SS: Towards a Hardware and Simulation Experimentation Platform for Spectrum Sharing with 5G NR-U
Sathish, Aditya (Virginia Tech, 2025-02-13)
The advent of 6th Generation (6G) wireless systems and the increasing demand for spectrum to accommodate a growing number of users and diverse services have necessitated novel ap- proaches to spectrum sharing. Among these approaches, distributed spectrum sharing offers the most flexibility by allowing real-time spectrum use based on user demand and network con- straints. However, this approach presents significant challenges due to the probabilistic nature of system dynamics and the autonomous behavior of each incumbent, which require advanced strategies to predict and manage spectrum usage effectively. Listen-Before-Talk (LBT) is the most widely adopted method for distributed spectrum sharing in unlicensed bands. While LBT has been extensively studied in the context of Wireless Fidelity (Wi-Fi), providing key insights into its performance under various conditions, its application in synchronized, slot-scheduled sys- tems like New Radio (NR) Unlicensed (NR-U) remains underexplored. This gap exists primarily due to the lack of hardware testbeds and system-level simulation platforms that are essential for evaluating the effectiveness of LBT in NR-U and for developing improved methods for operating in shared spectrums with deterministic worst-case delays. This thesis addresses the existing gap by proposing a reference architecture for spectrum sharing based on 5th Generation (5G) NR-U to facilitate further research and experimentation in distributed spectrum sharing. The approach taken in this thesis is threefold: (i) the establishment of a system architecture for an end-to-end 5G NR-U system based on existing work in hardware and simulation models; (ii) the realization of this system model on the Network Simulator 3 (ns-3) discrete-event simulator by leveraging developments from the 5G Long-Term Evolution (LTE) Enhanced Packet Core (EPC) Network Simulator (LENA) (5G-LENA) system architecture; and (iii) the conceptual design for implement- ing the Physical (PHY) layer of a 5G NR-U system using Software-Defined Radios (SDRs) and the OpenAirInterface (OAI) 5G software platform. A key novelty of this reference architecture is the proposed mitigation of LBT latency in split architectures with SDRs and General-Purpose Processors (GPPs). The LBT block is designed for implementation within the Field Program- ming Gate Array (FPGA) of Universal Software Radio Peripheral (USRP) SDRs, thereby enabling heterogeneous coexistence experimentation with Common Off-the-Shelf (COTS) Wi-Fi Access Points (APs). The thesis presents a simulation-based experiment that optimizes traffic manage- ment to improve the ability to serve delay-critical traffic in NR-U systems operating under ho- mogeneous coexistence conditions. The thesis then outlines a reference design for exploring heterogeneous coexistence between Wi-Fi and NR-U in the sub-7 GHz spectrum. This concep- tual framework leverages a proposed hardware experimentation platform with SDRs. The in- frastructure supporting these simulations and proposed hardware experiments is envisioned as virtualized resources over the Commonwealth Cyber Initiative (CCI) xG Testbed, with potential extensions for advanced spectrum sharing use cases across indoor and outdoor testbed sites. The thesis outlines potential enhancements to this testbed, specifically toward spectrum sharing with scheduled-access systems.
Assessing the Potential of Granular Activated Carbon Filters to Limit Pathogen Growth in Drinking Water Plumbing Through Probiotic Versus Prebiotic Mechanisms
Deck, Madeline Emma (Virginia Tech, 2025-02-06)
Legionella pneumophila (Lp) and nontuberculous mycobacteria (NTM) are opportunistic pathogens that can be transmitted via drinking water, when tiny droplets containing the bacteria are aerosolized and inhaled during activities such as showering. The resulting respiratory illnesses, Legionnaires' Disease and NTM lung disease, are among the leading sources of drinking water associated disease in the United States and other parts of the world. Lp and NTM are both difficult to control, because they establish as part of natural biofilms that form within the interiors of pipes and fixtures that deliver drinking water to the point of use. These pathogens are especially problematic within premise (i.e., building) plumbing, where intermittent use throughout the day leads to long periods of stagnation, increased water age, warmer temperatures, and depleted disinfectant residuals that exacerbate bacterial growth. The recent advent of high throughput DNA sequencing has led to the discovery that drinking water microbiomes are diverse, complex, and largely comprised of non-pathogenic microbes. This has further led researchers to hypothesize that the microbial ecology of this diverse microbiome could be harnessed as a natural means to control Lp and NTM, i.e., a "probiotic" approach, but such an approach has not yet been demonstrated. The objective of this study was to assess this hypothesis by utilizing biologically active granular activated carbon (GAC) filters, which are already a widely used drinking water treatment both at the municipal and household scale, as a means to naturally shape the microbial ecology of downstream premise plumbing and inhibit Lp and NTM proliferation. GAC has an extremely high surface area that aids removal of organic carbon via adsorption but also provides an ideal habitat for establishment of biofilms, which removes organic carbon from the water via biodegradation. Convectively-mixed pipe reactors (CMPRs) were used for replicable simulation of premise plumbing distal taps. The CMPRs consisted of four-foot-long closed polyvinyl chloride (PVC) pipe segments with the sealed bottom portion resting in a ~48 °C water bath and with the top portion plugged and exposed to the cooler, ambient atmosphere (25 °C in this study), inducing convective mixing and resulting in an internal water temperature of 37 °C. PVC was chosen because it is common in premise plumbing and generally leaches the least organic carbon among the different types of plastic pipe. Four different influent water conditions were implemented in the experimental design: 1) Untreated, dechlorinated municipal tap water with high organic carbon and low biomass; 2) GAC-treated tap water with low organic carbon and elevated, viable biomass; 3) GAC-treated + 0.22-m pore size membrane-filtered tap water to remove both nutrients and biomass; 4) GAC-treated tap water pasteurized at 70 °C with low nutrients and elevated, killed biomass. The 0.22-m pore size membrane filter simulated the use of a building scale particle filter, while pasteurization simulated water passing through a hot water heater at an elevated temperature recommended for pathogen thermal disinfection. To understand the influence of these experimental conditions on older pipes containing mature biofilms versus new pipes that leach more organics and are being freshly colonized, a set of older pipes colonized with mature ~4-year-old biofilms were compared to newly purchased pipes. Each set of pipes was tested in triplicate for the four different experimental conditions with the full volume replaced three times a week for eight months, simulating infrequently used taps containing warm, continuously mixing water thought to create conditions at a very high risk for opportunistic pathogen growth. In the aged CMPR bulk water effluents, droplet-digital-polymerase-chain-reaction measurements showed a one-log reduction of Lp and NTM when receiving GAC-treated or GAC-treated + particle-filtered influent water versus receiving dechlorinated municipal tap water or GAC-treated + pasteurized water. These findings suggest that decreased biodegradable dissolved organic carbon achieved by GAC filtration acted to suppress Lp and NTM growth, while the additional step of biomass removal by particle filtration provided a more modest benefit. In the CMPRs consisting of new pipes, concentrations of Lp and NTMs in the effluent bulk water were similar among the experimental conditions, except that the CMPRs receiving the GAC-treated + particle-filtered influent water experienced a two-log reduction in NTMs. These results demonstrate that the colonization and proliferation of NTM within premise plumbing can be significantly controlled by limiting nutrients and biomass in the influent water. This work demonstrates the potential of harnessing GAC-treatment as a means to Control Lp and NTM in premise plumbing via nutrient removal. In scenarios where chemical disinfectants have been depleted, off-the-shelf GAC-treatment used as point-of-entry treatment to large buildings with recirculating plumbing could provide benefits that have previously been unrecognized. Alternatively, pasteurization in very hot water heaters could provide a short-term disinfection benefit, but eventually the nutrients embodied in the dead biomass undermine the positive influence of the nutrient removal provided by the GAC-treatment. Improved mechanistic understanding of probiotic strategies to opportunistic pathogen control would be needed to overcome inherent limitations to the approaches examined herein, if more effective control is desired in the absence of thermal or chemical disinfection.
A Choreography of Water, Light, and Space Interplay
Pourkhodagholi, Negar (Virginia Tech, 2025-02-06)
This thesis explores the interplay of water, light, and space in a choreography of architectural sequences. Through the design of a spa, it explores how these elements can evoke sensory and emotional responses, shaping human perception and interaction within spatial environments. The project unfolds as a choreography where water in its various states and qualities interacts with light and architectural space, creating an immersive sensory journey. This choreography carefully modulates centrifugal (outward-directed) and centripetal (inward-directed) experiences, crafting a dynamic interplay between the individual and the surrounding space.
Improving Precision in Forest Inventory through Small Area Estimation for Loblolly Pine Plantations in Coastal Georgia
Subedi, Bipana (Virginia Tech, 2025-01-31)
The use of small area estimation (SAE) in forest inventory has shown promise for improving the precision of estimates needed for informed decision-making when sample data are sparse. We evaluated the potential of unit-level SAE for increasing the precision of stand-level estimates of basal area, volume, and above-ground biomass estimates in loblolly pine plantations in coastal Georgia. Following the unit-level approach, field plots sampled in plantations owned by Rayonier Inc. were georeferenced to aerial lidar data using high-quality GPS field coordinates. Results focused on A) gains in precision for stand-level basal area, volume, and above-ground biomass estimates achieved by combining data from field plots with lidar-derived canopy height models in a SAE framework, B) impacts of small sample sizes on the precision of estimated stand level attributes, and C) the effects of nonrandom field plot placement in stands of interest when using unit-level SAE. Findings indicate that higher precision is achievable with greater variance stability than what is possible from very small samples of field data alone. This was true for all three attributes of interest. With careful attention to checking assumptions of the unit-level SAE approach, the use of non-random sampling does not appear to impair SAE's ability to deliver unbiased estimates for forest plantation stands. Simulating the entire population's basal area to test for the effects of non-random plot placement showed that SAE is robust to the type of sampling technique used. However, results can be affected when sampling is intentionally biased. This work can be useful to landowners and forest managers working with southern loblolly pine plantations. By leveraging simulation techniques to generate non-random sampling data from the available random sampling data, this study attempted to bridge the gap between the available empirical data and the desired sampling framework, ultimately widening the applicability of SAE in forest inventory settings.
Comparative Analysis of Machine Learning Models for ERCOT Short Term Load Forecasting
Singh, Gurkirat (Virginia Tech, 2025-01-29)
This study investigates the efficacy of various machine learning (ML) and deep learning (DL) models for short-term load forecasting (STLF) in the Electric Reliability Council of Texas (ERCOT) grid. A dual comparative approach is employed, evaluating models based on temporal features alone as well as in combination with actual and forecasted weather variables. The research emphasizes region-specific forecasting by capturing heterogeneous load patterns for ERCOT's individual weather zones and aggregating them to predict total load. Model evaluation is conducted using accuracy and bias metrics, with particular attention to high-demand months and peak load hours. The findings reveal that Generalized Additive Models (GAM) consistently outperform other models, most importantly during summer months and peak load hours.
Development of a Lung Surrogate Model for Assessing Biomechanical Responses to Underwater Explosions (UNDEX)
Anbarasu Kalpana, Pradikshan (Virginia Tech, 2025-01-29)
Underwater explosions (UNDEX) generate high-energy shock waves that pose significant risks to military personnel during training exercises and combat scenarios. The primary objective of this research is to develop a surrogate modeling framework using engineering materials to investigate the biomechanical response of lung tissue during UNDEX events. A representative lung surrogate was designed to mimic the mechanical behavior of human lungs, utilizing thermoplastic elastomers (TPE) and polyurethane foam to replicate the elastic and porous nature of lung tissue and alveolar sacs. Material characterization tests were conducted to simulate quasi-static deformation through uniaxial tensile tests and dynamic loading conditions using dynamic mechanical analysis (DMA). The viscoelastic response of the surrogate material across a wide range of temperatures and frequencies is presented. A series of UNDEX experimental tests were conducted on the surrogates using the Virginia Tech Shockwave Generator (SWG), with targeted overpressures ranging from 10 to 20 psi. The surrogates were instrumented with sensors to record changes in principal strains and internal pressures. The results were analyzed to evaluate strain and pressure trends, impulse, and potential injury mechanisms. A linear relationship was observed between shockwave impulse, peak pressure, and principal strains, while no significant differences in internal pressure dynamics were observed within the tested blast overpressure ranges.
Reevaluating Encoding-Retrieval Match and Cue Overload
Shafer, Erica S. (Virginia Tech, 2024-12-06)
The encoding specificity principle, initially proposed by Thompson and Tulving in 1973, asserts that the congruence between encoding and retrieval conditions plays a crucial role in successful memory retrieval. Although this principle has largely been supported, Nairne (2002) has challenged memory theorists to reconsider its direct causality, proposing that the diagnostic value of retrieval cues with respect to a specific memory is the primary determinant of successful retrieval. This study sought to investigate this claim. This study builds upon the work conducted by Goh and Lu (2012) by adapting the manipulations of encoding-retrieval match and cue overload in their original task design. The current study replaced the implicit category cue in the high-overload, high-match conditions with an explicit cue in an attempt to strengthen the manipulation. We hypothesized that the addition of an explicit high-overload cue to our experimental design would lead to a significant effect of encoding-retrieval match in the high-overload condition, in contrast with Goh and Lu’s (2012) findings. Our findings provide mixed support for this hypothesis. We observed weak evidence for a main effect of encoding-retrieval match, with better performance in the high-match condition than the low-match condition without evidence for a significant interaction between encoding-retrieval match and cue overload. However, planned t-tests somewhat conflicted with this finding in that encoding-retrieval match had a significant effect only when the cues were low-overload, not when match was increased with a high-overload cue. Further investigation is needed before conclusions can be drawn from this data.
Making Space for Daydreams
Finney, Trevor G. (Virginia Tech, 2025-01-28)
I describe and reflect on the creation of my exhibition Making Space for Daydreams, containing two large sculptures and a collection of conversational audio recordings. The sculptural artworks utilize interdisciplinary techniques and both digital fabrication and handcrafted approaches, including: woodworking, hand-cut paper, laser-cut illustration, motion capture, projection mapping and pencil drawings. The exhibition explores themes related to daydreaming, and the value of recognizing and building spaces that help make daydreaming possible. In addition, the work explores presence, memory, and inner child relationships as way to understand and frame my own relationship to daydreaming. By engaging in an act of imaginative play, I collaborated with my inner child and benefited from a strengthened sense of self-identity. Through acts of obscuring in the artwork I create allowances for imagination and invite the viewer to reflect on their own experiences and daydreams.
Profiles of Caregiver-Level Factors Associated with Emotion Regulation in Adolescents with and without ADHD
Pham, Stephanie Ngoc Tran (Virginia Tech, 2024-12-18)
Environmental factors, most significantly caregivers, substantially contribute to youth emotional development. Emotion regulation (ER) deficits and emotion dysregulation (ED) are a significant, pervasive concern for individuals with attention-deficit/hyperactivity disorder (ADHD), especially during adolescence. Although there has been empirical support for how caregiver factors independently contribute to youth ER abilities, there is little known about whether there are any underlying patterns or permutations of caregiver-related variables that relate to ER and ED in adolescents. This master’s thesis was a secondary analysis of a multi-site longitudinal study of 266 adolescents (54.1% male; 81.6% White; 51.1% comprehensively diagnosed with ADHD). The primary aims were to explore potential latent profiles of caregiver-level factors in this sample and investigate whether caregiver profiles that emerge vary based on whether their adolescents are diagnosed with ADHD, and whether caregiver profiles relate to adolescent ER and ED outcomes. Three distinct caregiver profiles emerged: Low Internalizing/ED and High Authoritative Parenting, Moderate Internalizing/ED and Permissive Parenting, and High Internalizing/ED and Moderate Authoritative Parenting. Results indicated that caregivers of adolescents with ADHD are more likely to fall into the High Internalizing/ED and Moderate Authoritative Parenting profile. Profiles characterized by authoritative parenting practices were generally associated with better adolescent ER outcomes, though no significant differences in self-reported adolescent ED were observed across profiles. These findings highlight the potential for caregiver psychopathology, ED, and parenting practices to serve as targets for interventions aimed at improving adolescent ER and reducing ED, particularly in neurodiverse populations.
Pairing Water Rights to Land Parcels -- Connecting the Prior Appropriations Doctrine and Croplands in the western US
Schantz, Megan Wilson (Virginia Tech, 2025-01-27)
Agricultural production in the western United States faces uncertainty with climate change leading to reduced crop yields from higher temperatures, lower precipitation rates, and shifting the growing seasons. This impacts farmers and their livelihood but more broadly, the United States's food supply and economic activity. While climatic characteristics are necessary to understand how crop production in the western United States will shift, many studies neglect the role that the water rights priority system plays in determining which croplands receive water under drought conditions. This study introduces a methodology to pair water rights, including priority dates, to land parcels and irrigated croplands. Crops were analyzed within hydrologic and state boundaries to determine which are at risk under the water rights priority system in drought conditions. Lastly, outputs from a global hydrologic model were used to assess water availability under common large-scale water allocation schemes versus the priority system in practice in the western United States, to evaluate schemas impact on water's spatial distribution. The novel pairing of land and water rights in this study increased water right boundaries from 29 to 59 percent across 10 states by implementing spatial overlays, radius, and waterway methods, with the spatial overlays achieving the highest accuracy. Median priority dates of the nine most cultivated crops in the western United States revealed a hierarchical system for water rights seniority, with oats and other hay having the most senior water rights, while junior water rights showed less of a hierarchy, although corn appeared to have the most junior water rights. This study is significant as it establishes a novel framework for linking water rights to croplands, enabling regional-scale analysis and introducing a methodology to integrate this data into a global hydrologic model to achieve insights on a field-level.
Numerical Modeling of the Energy Release of Aluminized Oxyacetylene Detonations
Walters, Iliana Rose (Virginia Tech, 2025-01-27)
This research explored the energy release of pure oxyacetylene and aluminized oxyacetylene detonations and their blast efficiency. A numerical model was developed using blastFoam to accurately capture shock wave parameters using a compressed gas balloon method. For this method, the explosive was replaced by a compressed gas balloon with calibrated initial conditions to replicate the explosive's blast characteristics. The numerical model was validated with experimental data from 0.11 m3 oxyacetylene detonations acquired by Cheney (2024) in the large-scale shock tube research facility at VA Tech (VTSTRF). A series of studies were carried out in this process of model development including: the preliminary building of the model domain with the shock tube geometry and approximation of specific energy of oxyacetylene, a symmetry study, an all-direction mesh refinement study, and an x-direction mesh refinement study. The goal of these studies was to develop a model that accurately captures the energy release from the 0.11 m3 detonation in a sufficiently quick manner. Once the numerical model was developed, it was used to determine the energy release of detonations with varying oxyacetylene volumes and H-10 aluminum concentrations as compared to data collected in the VTSTRF by Cheney (2024) and Kamide and Jacques (2024). A comparison of energy values was carried out against a traditional approach of blast scaling. Similar relationships were found between aluminum concentration and total energy of detonation and blast efficiency. The blastFoam numerical model enables a simpler method of capturing energy release from complex non-ideal detonations, requiring input dependent only on specific energy of the balloon and balloon volume.
The Effects of Curvature on Turbulent Boundary Layers Over a 3D Bump Geometry: An Experimental Study Using BeVERLI Hill
Chen, Fangzhou (Virginia Tech, 2025-01-23)
This thesis presents an experimental investigation of the effects of curvature on turbulent boundary layers using the Benchmark Validation Experiment for RANS and LES Investigations (BEVERLI) Hill setup. The study focuses on analyzing the flow behavior over a three-dimensional bump geometry that incorporates both concave and convex surfaces, with the aim of improving the understanding of the complex interactions among curvature, pressure gradients, and turbulence characteristics. The study examines the mean velocity, Reynolds shear stresses, pressure gradient, turbulence intensity, and pressure coefficient variations in relation to the bump curvature. The results are consistent with prior studies on the destabilizing influence of concave curvature with observations such as increased turbulence intensity, a decrease in mean velocity relative to the free-stream velocity U_{∞, and higher Reynolds stresses normalized by U^{2_{∞ throughout entire turbulent boundary layer, particularly in the near-wall region. Convex curvature results are consistent with prior study as well, which exhibits a stabilizing effect, shown to reduce turbulence intensity, an increase mean velocity relative to the free-stream velocity U_{∞, and lower Reynolds stresses normalized by U^{2_{∞ throughout entire boundary layer. This study also highlights the influence of pressure gradient effect, which acts with the curvature effect, impacts the boundary layer stability. This interaction is observed in amplification of turbulence with increasing of turbulence intensity and boundary layer growth. This stability particularly reflects on the embedded shear layers with inflection points which can create conditions for linear instabilities to grow, thus enhancing coherent turbulent motions.

Furthermore, the thesis discusses the challenges in separating the influence of curvature from pressure gradient effects in current model, and proposes future research directions to address this issue. By conducting experiments under controlled pressure gradient flow conditions over concave and convex curvature, researchers can analyze the contributions of curvature effect separately from pressure gradient effect. Alternatively, using a hybrid RANS-LES model, will lead to a more precise understanding of flow dynamics over curved surfaces.}}}}}}
Prototype Development and Feasibility Assessment of a Vertically Mounted Floating Element Skin Friction Balance
Raza, Muhammad (Virginia Tech, 2025-01-23)
Wall shear stress is one of the most essential scaling parameters used in fluid dynamics. It is significant because it helps us compare results in different experimental studies. The accurate measurements of wall shear stress will be instrumental in improving the existing empirical models and validating CFD models. Wall shear stress is also vital in improving fuel efficiency, heat transfer efficiency, and aerodynamic efficiency in real-world applications. This work discusses the design and implementation of a prototype floating element balance — a direct method of wall shear measurement. The direct measurement methods are robust and can significantly improve the validity of experimentation when perfected. In this work, a prototype floating element balance is designed and developed to estimate the wall shear stress in a smooth wall pilot facility to assess its feasibility for large-scale development. The floating element balance utilizes a strain gauge to estimate the wall shear stress. The preliminary tests show promising results, revealing potential design improvements. A strain measurement study is conducted to investigate the force-strain relationship and the reliability of the balance, which highlights the long-term stability and consistency in the strain measurement. However, further investigations are required into the drift response of the floating element balance. The strain measurements are also employed to calibrate the balance using a linear curve fit with a coefficient of determination of R^2 = 0.99, indicating a satisfactory linear estimation.

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