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.
Communities in VTechWorks
Select a community to browse its collections.
Recent Submissions
Review: "Ginseng Roots: a Memoir"
Stanley, Sarah (Art Libraries Society of North America, 2026-09-04)
A book review of Ginseng Roots: A Memoir, by Craig Thompson.
2026 GAP Report: Restarting Growth: The Role of Regenerative Agriculture in Productivity Growth and Profitability
Maples, Chellie (Virginia Tech. College of Agriculture and Life Sciences, 2026-09-29)
Global agricultural total factor productivity (TFP), the ratio of all agricultural outputs to all agricultural inputs, grew an average of 0.63 percent annually during 2015–2024. That rate is roughly 30 percent of the 2001–2010 peak and the lowest recorded since the 1970s, raising the average annual TFP growth required through 2050 to 2.10 percent. Input intensification once again accounts for roughly half of global output growth, leaving producers more exposed to volatile input costs, supply chain disruption, and climate stress.
The 2026 GAP Report™ develops a framework, built from the existing scientific literature, that connects regenerative agriculture (RA) practices to TFP growth and producer profitability through three channels: input reduction, natural capital accumulation that improves output over time, and output stabilization under climate stress. Applied across crop, livestock, and aquaculture systems, the framework shows input reduction carries the strongest near-term evidence, while natural capital and stabilization gains accrue over longer horizons than standard farm financial models capture. Outcomes vary by practice, soil, climate, tenure, and market access, and no study yet directly measures TFP growth attributable to RA adoption.
A regional spotlight on the European Union, where TFP growth is now the only remaining source of output growth, examines three decades of farm accounts across 213 regions and finds no consistent relationship between agri-environment payment intensity and TFP growth.
The report identifies three sequential bottlenecks to scaling RA: the evidence and data base, usable decision tools, and enabling policy and market environments. It sets out five priorities to drive a restart in productivity growth using regenerative practices and tools: harmonized monitoring, reporting, and verification (MRV) infrastructure; long-run, whole-system trials; localized decision tools delivered with extension; transition finance matched to risk; and target-based frameworks that include TFP growth as an outcome indicator.
Phase-change systems with self-propelled matter: Disks, droplets, and bubbles
Tapocik, Jack Thomas (Virginia Tech, 2026-09-29)
Phase-change phenomena such as boiling, condensation, and melting are ubiquitous in both natural and engineered systems. One example of a phase-change process producing motion is the Leidenfrost ratchet, where a superheated asymmetrically patterned surface rectifies the vapor flow to generate net viscous propulsion. Leidenfrost ratchets have been demonstrated for liquid–vapor and solid–vapor systems, yet solid–liquid systems remain largely uncharacterized. We first performed experiments with melting ice on a herringbone ratchet to characterize the governing physical mechanism. Two surface wettabilities were tested: hydrophilic and superhydrophobic. On the hydrophilic surface, viscous entrainment analogous to that of the Leidenfrost ratchet was observed. On the superhydrophobic surface, a distinct ``slingshot" mechanism emerged, in which a Laplace pressure mismatch across the melt puddle drives rapid re-centering of the ice disk, propelling it forward.
After characterizing the first solid–liquid ratchet, we extended the results using paraffin wax. The wax disks traveled ten times farther and twice as fast as the ice. The improved mobility of wax disks enables several practical applications for enhanced heat and mass transfer. The self-propelled motion reduces the melt thickness by sevenfold, enabling faster melting and enhanced thermal conduction. Wax disks also enable mass transfer applications, including the transport of payloads up to 16× their own weight, self-cleaning of contaminated surfaces, and deposition of embedded particles.
Another form of self-propulsion is jumping-droplet condensation, in which two quasi-spherical droplets on a superhydrophobic surface coalesce and spontaneously jump away from the surface. On superhydrophobic wheat leaves infected with pathogenic rust spores, coalescing droplets jump and carry spores away upon departure. Extending this study to infected barley leaves, a previously unreported ejection mechanism was observed, in which dry spores are launched during jumping-droplet condensation. This occurs when spores conglomerate into clusters, allowing droplets to nucleate and grow underneath the cluster of spores. Upon coalescence, the merged droplet jumps upward into the roof of the spore cluster, transferring its momentum and launching dry spores into the air. This previously unknown mode of spore dispersal carries implications for understanding disease transmission pathways in agricultural crops.
The final phase-change process addressed in this thesis is bubble departure during pool boiling. Traditionally, buoyancy governs bubble departure, and methods to reduce the departure diameter have relied on nano/micro-structured surfaces, surfactants, electric fields, or surface wettability modifications. It was discovered that the coalescence of two bubbles during pool boiling can produce departure diameters an order of magnitude smaller than conventional values. Here, we designed and fabricated a custom pool boiling chamber that can visualize the individual bubble coalescence events on micron-sized features. After preliminary testing, we discovered that the bare silicon wafers result in high surface adhesion and don't allow for the bubbles to depart the surface. Instead, we investigated the spatial control and nucleation density of bubbles on a micro-patterned silicon chip using a custom boiling chamber. This thesis primarily details the design and construction of the custom boiling chamber and the rationale for the micro-patterned feature parameters.
These collective works all leverage surface structures to impart dynamic heat and mass transfer phenomena to phase-change processes. Potential applications include: self-cleaning, accelerated energy transfer with phase-change materials, particle sensing, and enhanced heat transfer coefficients for boiling or condensation. Future work will include finishing ongoing projects related to the spatial control and coalescence-induced jumping of nucleating micro-bubbles, furthering our understanding of pathogenic spore dispersal, and extending the practicality of phase-change materials.
Integrating high-frequency data, ecosystem models, and forecasts to understand the effects of global change on carbon dynamics in freshwater reservoirs
Howard, Dexter William (Virginia Tech, 2026-09-29)
Freshwater ecosystems are increasingly threatened due to anthropogenic global change, leading to changes in water quality and ecosystem functioning. Notably, global change, through changing land use, warmer temperatures, and changing hydrology, is altering freshwater dissolved organic matter (DOM) dynamics. DOM influences many components of freshwater ecosystem functioning, including carbon cycling, microbial and plankton food webs, metals complexation, and light attenuation, among others. Given the important role of DOM in freshwater ecosystems, I leveraged field, lab, modeling, and forecasting techniques through my dissertation to answer the question: How do DOM dynamics in reservoirs vary over temporal and spatial scales? First, I explored the effect of changing winter conditions on ecosystem metabolism rates, which govern rates of DOM production and respiration in freshwaters. I analyzed six years of high-frequency oxygen data in an intermittently ice-covered reservoir in the southern Appalachian Mountains and found that shorter winters did not affect annual metabolism rates. This finding contrasts with previous work conducted in northern lakes with prolonged ice cover, suggesting that ecosystems with intermittent ice cover may have already crossed ecologically meaningful tipping points. Second, I conducted monthly spatial field surveys across a reservoir watershed over a year to understand changes in DOM concentration and composition across the lotic (stream inflow) to lentic (reservoir basin) gradient. My findings suggest that important transformations in DOM occur at the lotic-lentic boundary in backwater and shallow cove sites in reservoirs, highlighting that these understudied transitional zones may be hotspots of biogeochemical cycling. Third, I tested the importance of catchment (terrestrial) and water column (aquatic) processes in driving reservoir DOM concentrations using a suite of contrasting models to generate 1 to 30 day-ahead predictions of reservoir DOM. I found that both catchment and water column drivers can be important controls on reservoir DOM but that their relative importance may vary seasonally, suggesting that multiple modeling approaches and drivers may be needed to accurately predict and understand reservoir DOM variability. Finally, I developed the first (to our knowledge) near-term iterative forecasts of reservoir DOM across three reservoirs using multiple modeling approaches. I found that forecast accuracy was consistent across reservoirs but not among seasons over one year of evaluation. Altogether, my dissertation identified high spatial and temporal variability in DOM cycling within and across three reservoirs over minute to year time scales. My work has provided fundamental understanding and tools to understand DOM dynamics that will be needed as DOM dynamics and freshwater ecosystems are increasingly influenced by global change.
Letter From the Co-Editor: Yes, “Shit’s Got to Change.” But How? A Call for a Deep Scholarship Social Movement
McGehee, Nancy G. (SAGE Publications, 2025-04-01)
This letter from the editor is in response to Benjamin et al.'s (2024) call to action surrounding the structures and systems of the tourism academy. It recommends a social movements approach as a possible framework for taking next steps. This Deep Scholarship Movement suggests (1) identifying and assembling key leadership change agents with diverse viewpoints, (2) enhancing self-efficacy, increasing consciousness-raising, and maximizing resource mobilization, the three primary components of successful social movements, and using them to work toward (3) community consensus building. These are challenging and daunting recommendations. This letter argues, however, that this or some other systemic, organized approach is necessary for those of us in varying aspects of leadership to clear the way and establish deeper, richer, more inclusive and less oppressive environments for our early-and mid-career colleagues.