VTechWorks
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.
Open Access Policy
Virginia Tech's open access policy enables researchers to deposit the accepted version of scholarly articles with no embargo.
Theses and Dissertations
Virginia Tech was first in the world to require ETDs in 1997, and continues to add scans of older theses and dissertations.
Open Textbooks
More than 50 freely available and openly licensed textbooks are among our most downloaded items.
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Recent Submissions
Impacts of Financial Literacy Training on Refugee Youth Outcomes
Das, Nandini; Gupta, Anubhab; Mingo, Cristobal; Zhu, Heng (Routledge, 2025-04-14)
As humanitarian assistance from international organizations transitions from in-kind- to cash- aid, and increasingly through digital payments, the importance of digital financial literacy to complement cash transfer programs has grown significantly. This paper evaluates the impact of a financial literacy training program on refugee youth outcomes in Uganda. We adopt an approach that closely emulates a natural experiment by leveraging the staggered geographic rollout of the program to identify its impacts. Using reduced-form econometric analyses, robust to various specifications, we find that participation in the training program is associated with significant positive effects on financial knowledge and financial behavior among young refugees. The findings are important because financial knowledge is essential for saving decisions, responsible borrowing, business operations, and various other life goals among refugees. Our results also suggest that the training program boosted youth’s confidence in terms of integrating with the host population.
Initializing a Public Repository for Hosting Benchmark Datasets to Facilitate Machine Learning Model Development in Food Safety
Qian, Chenhao; Yang, Huan; Acharya, Jayadev; Liao, Jingqiu; Ivanek, Renata; Wiedmann, Martin (Elsevier, 2025-02-26)
While there is clear potential for artificial intelligence (AI) and machine learning (ML) models to help improve food safety, the development and deployment of these models in the food safety domain are by and large lacking. The absence of publicly available databases that host well-curated datasets that can be used to develop and validate AI /ML models represents one likely barrier. Thus, we took three previously published datasets, which we further cleaned and annotated, and made them publicly available in a repository called Cornell Food Safety ML Repository. The selected datasets include (i) presence or absence of Listeria spp. in soil samples collected across the U.S. with paired metadata for soil properties, geolocation, climate, and surrounding land use, (ii) presence or absence of Salmonella and Campylobacter in young chicken carcasses tested in processing facilities with associated meteorological and temporal metadata, and (iii) presence or absence of fecal contamination as well as E. coli concentration in New York watersheds with associated metadata for land use, water attributes, and meteorological factors. These datasets can serve as benchmark datasets for developing ML models. To demonstrate the utility of the repository, we developed customizable scripts as well as LazyPredict (a quick screening method) scripts for training different types of ML models using the shared datasets. While this repository provides an important starting point that will allow for the development and testing of ML models to predict foodborne pathogens contamination in different sources, the inclusion of further datasets is clearly needed to advance this field. This paper thus includes a call to action for the deposit of well-curated datasets that can be used for further development of predictive models in food safety. This paper will also discuss the benefits of such public databases, including the assessment of data-sharing scenarios using existing privacy-preserving techniques.
Hotspots of bacterial pathogen abundance and exposure risk in soils of the contiguous United States
Matthews, Emily A.; Goh, Ying-Xian; Hepp, Shannon L.; Liao, Jingqiu; Calder, Ryan S. D. (American Geophysical Union, 2025-12-11)
Soils are reservoirs of pathogenic bacteria that cause human illness, particularly after mobilizing events such as extreme rain. Land-use patterns (e.g., proximity to agriculture) and soil properties (e.g., moisture) are associated with abundance of individual pathogenic bacteria. However, there are major uncertainties in (a) the importance of local/regional land-use decisions relative to overall natural variability of pathogenicity and (b) the correlations among pathogen abundance, climate-linked physical processes increasing pathogen mobility, and the vulnerability of human receptors. This impairs identification of priority areas for outbreak surveillance, which has traditionally focused on food and water distribution networks, and the development of process-based risk screening models. Here, we analyze a novel data set of 622 soil samples covering 42 of the 48 contiguous United States. We describe (a) the relationship between putative pathogenicity and natural and land-use drivers and (b) how hotspots of putative pathogen abundance intersect with climate-linked hazard of mobilization via fire, floods, wind, and fluvial transport, and the social vulnerability of local human populations. Variability in putative pathogenicity can be partially explained by known drivers, with natural variables having greater explanatory power than land-use variables. Relative abundance of putative pathogens is generally higher in forested ecoregions, notably in the eastern and southeastern United States and in proximity to surface waters. Higher relative abundance of putative pathogens, climate risks promoting pathogen mobility, and a relatively vulnerable rural population intersect in the southeastern United States. Integrated sampling and modeling are needed to monitor and forecast health risks from soilborne pathogens.
SS Precursor Imaging Reveals a Global Oceanic Asthenosphere Modulated by Sea-floor Spreading
Sun, Shuyang; Zhou, Ying (American Geophysical Union, 2025-09-17)
The asthenosphere is a weak layer in the upper mantle where geotherm may exceed mantle solidus and partial melt occurs. Although it has been suggested that an increase in seismic wavespeed at about 220 km depth represents the base of the asthenosphere, seismic studies to-date have not been able to provide evidence for the existence of such a global interface in the oceanic regions. In this study, we report observations of SS precursors reflected at this boundary throughout the global oceans. The average depth of the discontinuity is approximately 250 km, with a velocity jump of about 7% across the interface. Finite-frequency tomography of SS precursor traveltimes reveals large depth variations of the discontinuity over short spatial distances, which explains the absence of this discontinuity in previous global stacks. The depth perturbations are characterized by alternating linear bands of shallow and deep anomalies that roughly follow seafloor age contours, indicating a fundamental connection between seafloor spreading and asthenosphere convection. The base of the asthenosphere is smoother under seafloors formed at slow-spreading centers and becomes much rougher under seafloors formed at fast-spreading centers with a spreading rate greater than (Formula presented.) mm/yr. This observation suggests that different geophysical processes at slow and fast spreading centers generate lithospheric plates with different chemical compositions and physical properties, which in turn influences the convection in the oceanic asthenosphere.
Global finite-frequency tomography of the 220-km discontinuity
Sun, Shuyang; Zhou, Ying (Oxford University Press, 2026-02)
The asthenosphere is a weak layer in the upper maare available from the publicntle that supports the movement of the overriding tectonic plates and facilitates mantle convection. In this study, we compile a global data set of SS precursors reflected at the base of the asthenosphere, also known as the 220-km discontinuity. The global data set includes the oceanic SS precursors from Sun & Zhou and new measurements with bounce points in continental regions. Similar to the oceanic data set, the continental SS precursors are observed on about 45 per cent of the SS waves, with bounce points distributed across all tectonic regions—from orogeny belts to stable cratons. We image the depth of the discontinuity at a global scale using finite-frequency tomography. In oceanic regions, the depth of the 220-km discontinuity agree well with the previous study, with discontinuity depth structure characterized by alternating linear bands of shallow and deep anomalies that roughly follow seafloor age contours. In continental regions, the variations are not spatially oscillatory but are instead much broader, with prominent perturbations associated with convergent plate boundaries. The base of the asthenosphere is shallow along the southern border of the Eurasian plate, from the Mediterranean region to Southeast Asia. Shallow discontinuity anomalies are also observed in the continental interiors—in Eurasia, from the northern Tian Shan through Mongolia to eastern Siberia, and in North America east of the Rocky Mountains. These anomalies form a linear structure roughly parallel to the Pacific subduction zones. The average depth of the discontinuity, as well as the velocity contrast across the interface, is globally consistent across both oceans and continents, with an average depth of approximately 251 km and a velocity increase of about 7 per cent. Given that the continental lithosphere has been cooling for much longer than the oceanic lithosphere, the observed consistency in the average depth of the discontinuity implies that secular cooling does not significantly impact the thermal structure at the base of the asthenosphere.