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
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Recent Submissions
High-Dimensional Functional Graphs and Inference for Unknown Heterogeneous Populations
Chen, Han (Virginia Tech, 2024-11-21)
In this dissertation, we develop innovative methods for analyzing high-dimensional, heterogeneous functional data, focusing specifically on uncovering hidden patterns and network structures within such complex data. We utilize functional graphical models (FGMs) to explore the conditional dependence structure among random elements. We mainly focus on the following three research projects.
The first project combines the strengths of FGMs with finite mixture of regression models (FMR) to overcome the challenges of estimating conditional dependence structures from heterogeneous functional data. This novel approach facilitates the discovery of latent patterns, proving particularly advantageous for analyzing complex datasets, such as brain imaging studies of autism spectrum disorder (ASD). Through numerical analysis of both simulated data and real-world ASD brain imaging, we demonstrate the effectiveness of our methodology in uncovering complex dependencies that traditional methods may miss due to their homogeneous data assumptions.
Secondly, we address the challenge of variable selection within FMR in high-dimensional settings by proposing a joint variable selection technique. This technique employs a penalized expectation-maximization (EM) algorithm that leverages shared structures across regression components, thereby enhancing the efficiency of identifying relevant predictors and improving the predictive ability. We further expand this concept to mixtures of functional regressions, employing a group lasso penalty for variable selection in heterogeneous functional data.
Lastly, we recognize the limitations of existing methods in testing the equality of multiple functional graphs and develop a novel, permutation-based testing procedure. This method provides a robust, distribution-free approach to comparing network structures across different functional variables, as illustrated through simulation studies and functional magnetic resonance imaging (fMRI) analysis for ASD.
Hence, these research works provide a comprehensive framework for functional data analysis, significantly advancing the estimation of network structures, functional variable selection, and testing of functional graph equality. This methodology holds great promise for enhancing our understanding of heterogeneous functional data and its practical applications.
Exploring Technology Integration in School-Based Agricultural Education (SBAE) Teacher Education: A Study of Preservice Teachers' Experience
Layne, Logan Joshua (Virginia Tech, 2024-11-21)
Teacher education programs have been known to omit critical aspects of technology preparation among undergraduates. Teaching practices are constantly evolving to accommodate the latest innovations in society; therefore, change is required in how we prepare educators to integrate technology into the classroom.
As technology continues to change, teachers' practices need to reflect on how teachers are prepared to integrate technology into teaching and learning. Researchers have often found various ways to help prepare teachers to incorporate technology, including field experiences and various program design models. There has been a lack of research within School-Based Agricultural Education (SBAE) of preservice teachers integrating technology into the classroom. A qualitative phenomenology was conducted among nine preservice SBAE teachers regarding their experiences integrating technology during their time in their teacher education program. The Unified Theory of Acceptance and Usage of Technology (UTAUT) served as the theoretical framework to aid in conceptualizing the experiences of preservice SBAE teachers. The thematic findings from this study address the lack of preparation from their teacher education programs, support and expectations, challenges integrating technology into the classroom, succession of technology integration, and technology strategies for teaching and learning.
How the Climate Change Threat is Shifting Australia's National Counter-Terrorism Strategy
Mortazavigazar, Amir (2023-03-08)
In this paper, we analyse how extremism and acts of terror will manifest themselves in Australia over the upcoming decades. Australia maintains a robust counter-terrorism strategy along with a comprehensive security apparatus to support that strategy. However, it is becoming apparent to the Australian intelligence community and the Australian government that the national security challenges that Australia will be facing due to climate change have been neglected over the past few years. COVID-19 restrictions demonstrated that issue-motivated extremism can fuel acts of terror and assist violent extremist organisations in their recruitment and radicalisations. In this paper, we demonstrate how climate change mitigation policies can result in issue-motivated extremism and empower violent extremist organisations which can result in acts of terror that would jeopardise Australia’s national security, therefore, we recommend that Australia’s National Intelligence apparatus broaden the issue-motivated extremism purview of terrorism by including climate change related grievances. Furthermore, we recommend amending Australia’s social cohesion and value statements to alleviate climate change related grievances and raise awareness about the threats of climate change related extremism.
Canadian hydroelectricity imports to the U.S.; Modeling of hourly carbon emissions reduction in New England
Mortazavigazar, Amir; Calder, Ryan S. D.; Howarth, Rich B.; Jackson, Chloe A.; Mavrommati, Georgia (2024-04-05)
United States’ hydroelectricity imports from Canada have increased by > 1 TWh per year between 2007 and 2021. This occurs as policymakers in the U.S. try to ramp up the deployment of new carbon free electricity generation and transmission infrastructure. Furthermore, recent modeling in the northeast U.S. demonstrates that Canadian hydroelectricity will play a significant role in New England’s least-cost decarbonization scenario. Additionally, decarbonization targets are well- defined in all states within the New England region, making it a priority. Consequently, it is anticipated that more hydroelectricity will flow from Canada into New England, resulting in the expansion of transborder electricity interconnections. To characterize the costs and benefits of such projects as compared to alternatives, a high-resolution simulation (i.e., hourly) of the electric grid is needed. In this study, we utilize the U.S. Environmental Protection Agency's dataset on hourly electricity generation and carbon emissions. Using pre-established decarbonization scenarios, we can calculate the precise reduction in greenhouse gas and air pollutant emissions for each scenario. Our preliminary results demonstrate that the scenario projection for 2026–2027 by New England ISO, which involves a combination of Canadian hydroelectric imports (2100 MW summer, 826 MW winter), new wind (308 MW summer and 682 MW), and solar (92 MW summer, 28 MW winter) generation commitments, can effectively offset carbon emissions in New England. These results further support the current decarbonization policy, which relies on a diversified mix of carbon free electricity sources.
Integrating health, economic, and environmental trade-offs into decarbonization decision-making in New England
Mortazavigazar, Amir (2024-05-15)