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
Workshop Report: Diaproportionate Collapse Resilience of Mass Timber Buildings
Raharja, Reuben; Jacques, Eric; Phillips, Adam (2026-03-22)
Virginia Tech convened a workshop on October 24, 2025 to identify state-of-the-art challenges and research needs for mitigating disproportionate collapse in multi-story mass timber and timber-hybrid buildings. The workshop included an overview presentation by Professors Phillips and Jacques followed by a facilitated discussion structured around open-ended questions on current practice, common building configurations, connection data gaps, modeling challenges, and research priorities.
Key findings:
• In practice, disproportionate-collapse evaluation is most commonly pursued for tall Risk Category III/IV projects; federal facilities may also require it, but mass timber is less frequently selected for those buildings.
• At-risk mass timber buildings typically use reinforced concrete core walls or steel braced frames for the lateral system, with post-and-plate (often residential) or post-and-beam (often commercial) gravity framing. Diaphragms are often cantilevers off a central core.
• Connection and diaphragm detailing is dominated by nailed splines, coil straps/surface-mounted plates for ties, and proprietary concealed beam-to-column connectors. Standardized strength–rotation–stiffness properties are largely unavailable, leading to highly variable modeling practices.
• Applying ASCE/SEI 76 to mass timber is limited by lack of validated connection/subassembly data; reliance on ASCE/SEI 41 does not resolve this because timber-specific parameters remain insufficient—creating a circular gap in guidance.
• Dynamic/high strain-rate effects in column-loss scenarios are poorly characterized for mass timber.
Recommended research priorities:
• Large-scale connection tests with sustained axial load to quantify rotational capacity under combined demands.
• New connection systems with high rotation capacity and reliable post-yield axial capacity (with concealed/fire-compatible detailing).
• Dynamic and high strain-rate effects in progressive-collapse response (connection- and system-level).
• Diaphragm panel/joint layout studies to better mobilize two-way cross-laminated timber (CLT) action and improve load redistribution.
• Standardize connection performance data and expand ASCE/SEI 76 with a mass timber section comparable in specificity to steel.
"Where Does the Blood Go?": Constructing an Electronic Medical Records System in the United States, 1960-1990
Parrish, Roan Gabriella (Virginia Tech, 2026-03-20)
Electronic medical record systems are complex technologies that reflect the decisions of both its developers and its users. The construction of a new electronic record system in 1960-1990 Massachusetts and Vermont is an opportunity to explore these decisions and the specific ways in which technologies have values, priorities, and demands embedded within the artifacts. The two cases examined in this analysis act as contrasting foils to each other, demonstrating how the same type of technology can be constructed in distinctly different ways that shape the artifact's place within the workplace. One case is the Laboratory of Computer Science at the Massachusetts General Hospital, developing the Hospital Computer Project in the 1960s, the programming language MUMPS in the 1960s-1970s, and the publicly available system COSTAR in the 1970s-1980s. The second case is the problem-oriented medical record and its computerized version, PROMIS, from Lawrence Weed at the University of Vermont, 1964-1990. The cases are analyzed through the lens of Andrew Abbott's The System of Professions in order to explore the social, professional, and work components of these technical artifacts. The dissertation falls into the science and technology studies traditions of studying sociotechnical systems, boundary objects, controversies, and histories of technology.
Exploring The Realm of Legionella in Water Heaters: Hormetic Copper, Antagonistic Neochlamydia, Holistic Insulation and Protective Sediment
Roman Jr, Fernando Adali (Virginia Tech, 2026-03-20)
Opportunistic premise plumbing pathogens (OPPPs), including Legionella pneumophila and Mycobacterium avium, are increasingly associated with waterborne disease outbreaks in the United States. Despite their rising prominence, several factors influencing the growth and mitigation of Legionella and other OPPPs, such as pipe materials, microbial ecology, temperature gradients, water heater configuration, and the role of sediment are poorly understood. This dissertation sheds light on the role of these factors using complementary microcosm and pilot-scale experiments to examine effects of various control strategies on OPPP growth.
Chapter 2 investigates how copper (0–2000 µg/L) impacted L. pneumophila and M. avium over an 11-month period using microcosms to simulate warm premise plumbing conditions. Copper was confirmed to have a hormetic effect, acting as a nutrient at low levels and an antimicrobial at high levels. At an intermediate copper dose of 250 μg/L, M. avium and total cell counts peaked in concentration, whereas the impact of copper on L. pneumophila at this dosage was stochastic amongst replicates. Comparatively, 2000 μg/L of copper suppressed M. avium, L. pneumophila, and total cell counts, though total cell counts steadily rebounded at this dosage throughout the entire experiment Chapter 3 closely examined the stochastic behavior of L. pneumophila in microcosms. A retrospective analysis on the copper-dosed microcosms described above and an earlier study of conditions leading to the Flint Water Crisis Legionnaires' Disease outbreak reveals a potential antagonistic relationship between Neochlamydia and L. pneumophila. This is consistent with prior evidence from pure culture studies that amoebae harboring Neochlamydia are resistant to L. pneumophila infection. The background water chemistry and pipe materials can influence the outcome of the competition between Neochlamydia and Legionella, suggesting probiotic approaches for OPPP control are already naturally occurring in some buildings.
Two chapters of the dissertation focus on full scale experiments in residential water heaters. In chapter 4 recirculating, standard, and on-demand (tankless) water heater configurations were operated and evaluated for delivered hot-water temperatures, internal thermal profiles, energy efficiency, and volumes of water within temperature ranges at risk for Legionella growth. At a setpoint of 48°C, the recirculating configuration had the lowest energy efficiency and the highest volume of water at risk for Legionella growth, whereas at 66° C the standard tank had highest growth risk. Adding extra insulation to standard electric water heaters could eliminate Legionella growth habitat while reducing heat loss--a holistic approach to improving environmental sustainability and public health.
Although thermal control is widely recommended for Legionella mitigation, chapter 5 reveals important limitations to the approach. Experiments using a typical 40-gallon residential water heater demonstrated that sediment, which can naturally accumulate at the bottom of water heater tanks, created dead space with temperatures that cooled with sediment depth. Even when the bulk water in the tank was completely mixed and the bulk water temperatures were ≥55–60 °C, portions of the sediment were cooler and permissive for Legionella growth. Two distinct mechanisms were responsible for cooling the sediment and its associated dead space: contact of the bottom of the tank with a relatively cold floor and settling of cold influent water. The sediment also increased the available surface area by several orders of magnitude compared to the internal surface area of the water heater. The cooler temperatures and high surface area could create extraordinary pathogen growth potential that causes culturable and molecularly detectable L. pneumophila to persist indefinitely. Use of external insulation between the tank and the floor can sometimes heat the sediment to a point that could eliminate Legionella growth.
Chapter 6 is a Viewpoint that examines the interplay of truth, trust, and utility practices in pre-venting waterborne disease outbreaks by shaping water quality before it enters buildings to re-duce Legionnaires' Disease risk. For instance, infrastructure upgrades and improved treatment can increase disinfectant residuals and reduce sediment in supply waters, honoring a utilities to the social contract with their customers. We argue that continued denial and deception associated with this responsibility will lead to distrust and disinvestment, similar to that which arose from past failures to deal with health treats from lead contamination due to corrosive water.
The overall dissertation illustrates how OPPP and L. pneumophila control in premise plumbing is influenced by ecological and engineering factors, including water chemistry, microbial inter-actions, temperature gradients, sediment and water heater design. These novel findings help explain why previously recommended mitigation strategies may not always suppress L. pneumophila in buildings and highlight the need for holistic control approaches targeting worst case niches in which Legionella can thrive.
Design and Assessment of an Embedded Die PCB-Based Traction Inverter
Spieler, Matthias (Virginia Tech, 2026-03-20)
Modular Microanalytical Systems for Trace-level Chemical Analysis
Thamatam, Nipun (Virginia Tech, 2026-03-20)
Airborne organic compounds, such as volatile organic compounds (VOCs) and organic aerosols (OAs), carry rich information about various ecological, environmental, physiological, and manufacturing processes. Growing concerns about environmental conditions and public health have driven the rapid development of analytical tools capable of characterizing trace levels of VOCs and OAs. Among other technologies, gas chromatography (GC) is considered the gold standard for analyzing organic compounds. However, conventional GC systems are expensive, bulky, and power-hungry, and require trained technicians to operate the system, limiting their adoption to a lab setting. Consequently, there is a growing demand for portable analytical systems capable of performing in situ, trace-level chemical analysis.
To address this need, microelectromechanical systems (MEMS)-based microanalytical tools and micro gas chromatography (μGC) systems have emerged as powerful, miniaturized platforms for (bio)chemical analysis. They miniaturize the key components of a bench-top GC by implementing microfluidic devices, including a micropreconcentrator (μPC), a microseparation column (μSC), and photoionization detectors (PIDs). These developments drastically reduce sample-reagent volume requirements, accelerate processing times, and enable automation, making them ideal for in-situ applications. Although μGC miniaturizes the functionality of a bench-top GC, effective collection of trace samples and seamless integration of microfluidic components remain challenging. These challenges arise from design constraints, manufacturing complexities, diverse functional requirements, demanding operating conditions, and incompatible maintenance procedures, collectively limit system scalability and widespread adoption.
This dissertation addresses these challenges by developing highly modular microanalytical tools for trace-level analysis of gas- and particle-phase organic compounds. Central to this work is a standardized Fluidic and Electrical Modular Interfacing (FEMI) architecture that provides removable, gas-tight, high-temperature-resistant fluidic connections for implementing complex microfluidic systems. Through the development of FEMI and a high-throughput μPC, this work demonstrates a portable μPC-based sample injection system compatible with bench-top GC, detecting VOCs down to 100 parts per trillion (ppt). This work also demonstrates FEMI-GC, a highly modular μGC that integrates μPC, μSC, and PID within a 3.75 L, 2 kg footprint, achieving a 700 ppt detection limit and a dynamic range over 50,000x. This work extends the functionality by developing a CNC-machined impactor and a μGC that successfully collected particles as small as 100 nm, enabling the detection of compounds with boiling points up to 450 ˚C, a first for μGC platforms.
Finally, this work introduces the next-generation μGC called SPOCK (Size-filtered Particle Odor Chromatographic Kernel), which combines a CNC-machined cyclone, a CNC-machined impactor, μPC, μSC, and PID to simultaneously analyze VOCs and OAs. This lays the groundwork for a near real-time, highly configurable, fabrication-agnostic μGC platform for trace-level chemical analysis.