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VTechWorks provides global access to Virginia Tech scholarship, including journal articles, books, theses, dissertations, conference papers, slide presentations, technical reports, working papers, administrative documents, videos, images, and more by faculty, students, and staff. Faculty can deposit items to VTechWorks from Elements, including journal articles covered by the University open access policy. Email vtechworks@vt.edu for help.
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More than 50 freely available and openly licensed textbooks are among our most downloaded items.
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Recent Submissions
Rhetorical Authority in Context: A Study of Technical Accounts of Flint, Michigan's Water Crisis from 2014-2017
Hockman, Cassandra Rose (Virginia Tech, 2026-03-30)
Essays on Modeling Human Behavior During Epidemics: Simulation, Statistical, and Optimization Approaches
Babaei Shalmani, Kian (Virginia Tech, 2026-03-30)
Human behavior is at the core of epidemics. Public risk perception shapes compliance with non- pharmaceutical interventions, mobility and contact patterns, and vaccine uptake; in turn, these behaviors alter transmission dynamics and future perceptions. A central challenge in integrating behavior into epidemiological analysis is that perception and response are not instantaneous.
Information diffuses through societies with delays, and behavioral adjustment often occurs gradually and asymmetrically responding differently when risk is rising than when it is falling.
Ignoring these delay structures can bias empirical inference about behavioral responsiveness and can misstate the effects of policies evaluated using models that treat behavior as exogenous or contemporaneous.
This dissertation advances the modeling and estimation of behavioral feedback in epidemics by focusing on how delayed risk perception links epidemic indicators to behavioral change and policy outcomes. The first essay develops and validates a delay-aware empirical framework for estimating how mobility responds to epidemic risk. Using synthetic experiments, it shows that assuming immediate response (or relying on ad hoc fixed lags) can yield biased estimates of both the magnitude and timing of behavioral response. The essay introduces a structured approach to representing perception delays using distributed-lag formulations motivated by information diffusion and provides practical methods for estimating delay parameters alongside behavioral sensitivity.
The second essay extends the framework by allowing delay structures to be asymmetric across phases of the epidemic, recognizing that behavioral responses to increasing risk may differ from responses to declining risk. Through additional synthetic tests and application to U.S. state-level COVID-19 mobility data, the essay demonstrates that the assumed delay structure materially affects inference about responsiveness and can change conclusions about how quickly behavior adjusts to worsening versus improving conditions.
The third essay connects behavioral estimation to policy design by examining optimal vaccination strategies under endogenous, delayed behavioral feedback. It compares a conventional SEIRV framework with constant contact rates to a behavioral SEIRbV framework in which perceived risk reduces contacts with a perception delay. In both a homogeneous setting and an age-stratified allocation setting, the analysis shows that accounting for behavioral feedback can shift suppression thresholds and the relative performance of vaccination strategies, highlighting the marginal importance of operational levers such as earlier starts and faster rollout alongside prioritization rules.
Taken together, the three essays show that delays in risk perception are a first-order feature of epidemic systems. By providing methods to estimate delay-aware behavioral responses and demonstrating how behavioral feedback reshapes vaccination policy evaluation, this dissertation contributes tools and evidence to improve inference, forecasting, and the design of effective interventions in epidemic settings.
Advanced Grid-Interface Three-Phase Converters: Grid-Support Capabilities and Grid Impact Analysis
Wang, Biqi (Virginia Tech, 2026-03-30)
The increasing penetration of power electronic converter–interfaced resources is fundamentally transforming modern power systems by displacing conventional synchronous generators, thereby introducing new challenges to system reliability and stability. To address existing challenges and technical gaps, this dissertation develops advanced grid-interface three-phase converters with grid-support capabilities and systematically assesses their impacts on power system operation, including dynamic behavior, small-signal stability, fault current characteristics, protective relay performance, and black-start restoration.
Control frameworks are developed for both grid-forming inverters (GFIs) and newly proposed grid-supporting rectifiers (GSRs), enabling grid-regulation support and enhancing overall system stability. Impedance-based small-signal assessments incorporating the generalized Nyquist criterion (GNC) are conducted, with emphasis on (i) comparative stability analysis between conventional grid-tracking rectifiers (GTRs) and the proposed GSR under weak-grid conditions (Chapter 3), and (ii) stability of grid–GFI interconnections during black-start operations, particularly during restoration initial stages (Chapter 5). The proposed converters exhibit more benign impedance characteristics and enhanced stability performance, therefore reducing adverse dynamic interactions and enabling stable operation under weaker grid conditions. In addition, a GFI control strategy with improved fault ride-through capability is proposed. The impacts of inverter-interfaced distributed energy resources on grid fault current characteristics and protective relay performance are analytically investigated, focusing on potential issues of desensitization effect and selectivity deterioration (Chapter 4). Furthermore, a black-start-friendly GFI control is developed, and the feasibility of black-start operations supported by GFI-based renewable resources is systematically studied (Chapter 5). The effectiveness of proposed grid-support control strategies the and the accuracy of the grid-impact analyses are validated by comprehensive simulation studies and hardware experimental results. Overall, this dissertation provides a comprehensive control, modeling, and assessment framework for grid-interface converters in future converter-dominated power systems. The proposed GFI and GSR control strategies, together with impedance-based stability and protection analyses, contribute practical insights for the improving the stability, protection reliability, and restoration capability of low-carbon power grids.
Do Clinicians Have Patience? Examining Delay Discounting, Perceived Stress, and Low-Value Antibiotic Prescribing
King, Mary Jane (Virginia Tech, 2026-03-30)
Antimicrobial resistance has been deemed one of the top global threats by the World Health Organization, and the overuse of antibiotic medications contributes to antimicrobial resistance. Yet low-value antibiotic prescribing (LVAP; the prescription of antibiotics when not clinically indicated) is still widely prevalent across multiple healthcare disciplines, often for viral illnesses such as acute bronchitis. Behavioral factors such as delay discounting (DD; the extent to which someone prefers smaller, sooner rewards over larger, delayed rewards) and perceived stress may independently and interactively contribute to clinicians' high rates of LVAP. Examining how DD and perceived stress levels are related to each other and LVAP can help develop interventions to improve prescribing rates and promote high-quality patient care. In study one, we compared DD and probability discounting (PD; the extent to which someone prefers smaller, guaranteed rewards over larger, risky rewards) between cross-sectional survey samples of primary care clinicians and non-healthcare workers, finding that clinicians had lower DD and higher PD rates compared to non-healthcare workers. In study two, we analyzed data from the survey of non-healthcare workers to determine whether there was a significant relationship between DD, PD, and perceived stress levels, finding that both DD and PD were associated with perceived stress. In study three, we examined the associations between DD, perceived stress, and LVAP in a sample of clinicians from multiple departments across a large healthcare system. This included both self-reported likelihood of LVAP based on two clinical vignettes in a cross-sectional survey, as well as electronic health record-based incidence rates within 12 months prior to survey administration, and we found that DD was associated with self-reported LVAP likelihood in both clinical scenarios assessed. Ultimately, these three studies suggest that DD may be an important behavioral marker that warrants further investigation in the context of LVAP, a complex and recurring issue in healthcare. Future studies investigating the connection between LVAP and behavioral factors such as discounting and stress should seek to examine workplace-specific stress levels and further explore possibilities for interventions involving DD as a behavioral marker.
Voices of Strength: Counselor Experiences of Resilience and Wellness Among Refugee Youth
Perinchery, Saudamini Agarwal (Virginia Tech, 2026-03-30)
An estimated 117 million people worldwide are currently displaced due to war and other human rights violations, with refugee children and adolescents among the most vulnerable. Their heightened exposure to trauma, violence, and chronic instability places refugee youth at increased risk for mental health challenges such as post-traumatic stress disorder, anxiety, and depression. While resilience and wellness are increasingly recognized as protective factors that foster positive adaptation, little is known about how school and clinical mental health counselors understand and support these constructs in their work with refugee youth.
This study explored how counselors experience the resilience of refugee youth in their care, as well as uncover their lived experiences in providing wellness support to them. Using Interpretative Phenomenological Analysis (IPA), six practicing counselors were interviewed to gain in-depth insight into how they experience resilience and implement wellness-based interventions. The analysis revealed four Group Experiential Themes (GETs) describing counselor experiences of resilience and four GETs illustrating their experiences providing wellness support to refugee children and adolescents. An additional GET emerged from the data analysis of the two original research questions established for this study, reported below.
The following themes emerged for Research Question 1 pertaining to resilience: Counselors Experience the Resilience of Refugee Children by Observing their Responses to Significant Stressors; Counselors Experience the Resilience of Refugee Children by Observing their Individual Internal Strengths; Counselors Experience the Resilience of Refugee Children by Observing the Influence of Relational Support Systems; and Counselors Experience the Resilience of Refugee Children by Observing the Impact of Schools.
The following themes emerged for Research Question 2 pertaining to wellness: Supporting Wellness by Viewing Wellness Through a Holistic Lens; Supporting Wellness by Building Trust; Supporting Wellness by Empowering Clients Through Advocacy; and Supporting Wellness by Practicing Culturally Responsive Care and Using Creative Approaches.
The following theme emerged from the data analysis of Research Questions 1 and 2, pertaining to broader counselor experiences of working with refugee children: Working with Refugee Youth as a Source of Growth for the Counselor.
Findings indicated that counselors conceptualize resilience as a dynamic interplay of internal (e.g., faith, hope, self-belief, and persistence) and external factors of resilience (e.g., family, community, educational access, and resources). Counselors reported utilizing holistic, strengths-based, and evidence-based practices to support wellness, and schools were observed to play a critical role in providing stability and promoting well-being. Results demonstrated a shift away from deficit-based perspectives toward approaches that recognize and leverage the existing strengths of refugee youth, illustrating how counselors translate theoretical concepts of resilience and wellness into practice.
This study contributes a foundational framework to the literature by offering one of the first comprehensive examinations of resilience and wellness as enacted by counselors serving refugee youth. Implications for counselor education include the need for a linguistically diverse workforce, integration of resilience and wellness-oriented training in counselor curriculum, and increased emphasis on advocacy and collaboration with local agencies and schools. Recommendations for future research include longitudinal studies, greater attention to intersectionality, and exploration of effective training, supervision, and interdisciplinary collaboration models. Overall, this study reframes refugee youth experiences through a lens of strength and positive adaptation, advancing research, training, and practice within counselor education and systems of care.