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 40 freely available and openly licensed textbooks are among our most downloaded items.
Communities in VTechWorks
Select a community to browse its collections.
Recent Submissions
Realizing a dream: linking sustainable enterprise development with sound forest management – the case for Black Walnut Syrup
Hammett, A. L. (Tom) (New River Symposium, 2024-04-12)
Virginia Tech and Future Generations University have been collaborating on projects in the region that foster sustainable nature-based enterprises. For several years, the focus has been on maple syrup, a product with a deep heritage in the New River Valley and surrounding areas. Recently, we have built on the experience with sugar maple, and have conducted research and outreach with another tree syrup – black walnut. Black walnut is plentiful and well suited to many sites in the region. The tapping process ensures that the tree is not harmed and will continue to provide ecological benefits. Well known in other regions for its timber quality, the species is not well known for producing tree syrup. But black walnut syrup is not well-known but is fetching higher prices than maple syrup and is popular among bakers, especially in the New York City area. The author won first prize for his black walnut syrup at the 2022 New River Valley Fair! Our outreach and research projects have focused on tree syrup and non-timber forest products. Many in the area request assistance to assess the potential for tree saps. Our team has developed demonstration sites and conducted outreach activities with landowners at several sites including Tazewell, Montgomery, and Giles Counties. Research is needed to gather input from landowners, evaluate the potential for sustainable economic development, and incorporate black walnut in forest management plans. We will discuss black walnut syrup’ potential to foster sustainable development, build community resilience, and ensure sustainable land management.
Ambiguous citizenship policies: Examining implementation gaps across levels of legislation in Jordan
Frost, Lillian (2024-04-10)
Despite the prevalence of ambiguous citizenship policies that say one thing in law and another in implementing regulations, few studies have focused on systematically studying this type of implementation gap, particularly in contexts beyond North America and Europe. This largely has remained the case despite research on discursive policy gaps, which occur between a policy’s stated objectives and its laws, efficacy gaps, which describe when a policy’s outcomes fail to meet its goals, and compliance gaps, which reflect disparities between a state’s commitments to international law and its corresponding domestic policies. How can we advance conceptualizations of law-regulation implementation gaps? This paper proposes one approach by focusing on the content of domestic laws, on the one hand, and the content of related implementing regulations, on the other. When law-regulation discrepancies occur, they illustrate the agency of senior officials in writing this intentional ambiguity into different levels of legislation, challenging assumptions about institutional weakness and lower-level bureaucratic discretion as chief drivers of implementation gaps. The paper illustrates this concept by analyzing discrepancies between Jordan’s nationality and passports laws and their related implementing regulations, particularly regarding Gaza refugees’ access to passports, investors’ access to nationality, and Palestinian-Jordanians’ subjection to nationality withdrawals. These diverse cases of intentional ambiguity demonstrate that such gaps can serve to partially exclude or include a group and can occur with noncitizen and citizen as well as more or less vulnerable groups.
NeTrainSim: a network-level simulator for modeling freight train longitudinal motion and energy consumption
Aredah, Ahmed S.; Fadhloun, Karim; Rakha, Hesham A. (2024-04-09)
Although train modeling research is vast, most available simulation tools are confined to city- or trip-scale analysis, primarily offering micro-level simulations of network segments. This paper addresses this void by developing the NeTrainSim simulator for heavy long-haul freight trains on a network of multiple intersecting tracks. The main objective of this simulator is to enable a comprehensive analysis of energy consumption and the associated carbon footprint for the entire train system. Four case studies were conducted to demonstrate the simulator’s performance. The first case study validates the model by comparing NeTrainSim output to empirical trajectory data. The results demonstrate that the simulated trajectory is precise enough to estimate the train energy consumption and carbon dioxide emissions. The second application demonstrates the train-following model considering six trains following each other. The results showcase the model ability to maintain safe-following distances between successive trains. The next study highlights the simulator’s ability to resolve train conflicts for different scenarios. Finally, the suitability of the NeTrainSim for modeling realistic railroad networks is verified through the modeling of the entire US network and comparing alternative powertrains on the fleet energy consumption.
Niche partitioning and the storage effect facilitate coexistence in an amphibian community
Brooks, George C.; Caruso, Nicholas M.; Chandler, Houston C.; Haas, Carola A. (Wiley, 2023-10-18)
Virtually all natural community assemblages are dominated by a handful of common species. Dominant species can exert negative impacts on biodiversity through competitive exclusion, and thus there is a strong incentive to understand imbalances in community composition, changes in dominance hierarchies through time, and mechanisms of coexistence. Pond-breeding amphibians that utilize ephemeral wetlands provide an excellent opportunity to evaluate theoretical predictions of community composition in stochastic environments. One of the most striking features of pond-breeding amphibians is the marked stochastic fluctuations in abundance across years. Given strong theoretical and empirical links between evenness and biomass, one would expect community evenness to change from year to year. Moreover, if different species exhibit different boom-and-bust reproductive cycles, then a storage effect may help to explain why one species does not outcompete all others. Here, we explore the interplay between biotic and abiotic conditions in shaping amphibian communities at two ephemeral wetlands on Eglin Air Force Base, Florida. We document consistent community composition over 6 years of monitoring, resulting from a lack of species turnover and similar responses of all community members to environmental conditions. The similar dynamics of species argues against a storage effect as the sole mechanism for coexistence and instead points to niche partitioning as a more important factor. In support of this conclusion, we show that the degree of synchrony in breeding migrations only correlates with environmental conditions within species, not between species. The lack of pattern seen between species implies that individuals are somewhat constrained in the timing of breeding migrations, perhaps owing in part to competition with other community members. We hope that our work reinvigorates interest in amphibian communities and highlights ephemeral wetlands as model systems to study community dynamics in stochastic environments.
Forecasting the flooding dynamics of flatwoods salamander breeding wetlands under future climate change scenarios
Chandler, Houston C.; Caruso, Nicholas M.; McLaughlin, Daniel L.; Jiao, Yan; Brooks, George C.; Haas, Carola A. (PeerJ, 2023-09-19)
Ephemeral wetlands are globally important systems that are regulated by regular cycles of wetting and drying, which are primarily controlled by responses to relatively short-term weather events (e.g., precipitation and evapotranspiration). Climate change is predicted to have significant effects on many ephemeral wetland systems and the organisms that depend on them through altered filling or drying dates that impact hydroperiod. To examine the potential effects of climate change on pine flatwoods wetlands in the southeastern United States, we created statistical models describing wetland hydrologic regime using an approximately 8-year history of water level monitoring and a variety of climate data inputs. We then assessed how hydrology may change in the future by projecting models forward (2025–2100) under six future climate scenarios (three climate models each with two emission scenarios). We used the model results to assess future breeding conditions for the imperiled Reticulated Flatwoods Salamander (Ambystoma bishopi), which breeds in many of the study wetlands. We found that models generally fit the data well and had good predictability across both training and testing data. Across all models and climate scenarios, there was substantial variation in the predicted suitability for flatwoods salamander reproduction. However, wetlands with longer hydroperiods tended to have fewer model iterations that predicted at least five consecutive years of reproductive failure (an important metric for population persistence). Understanding potential future risk to flatwoods salamander populations can be used to guide conservation and management actions for this imperiled species.