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
Pigs' BCS Estimation using Computer Vision and Deep Learning Approaches
Desai, Zeel Amitkumar (Virginia Tech, 2026-03-27)
This research presents an end-to-end automated system for Body Condition Score (BCS) assessment in pigs using multi-modal RGB-D computer vision and deep learning. Manual BCS evaluation is subjective, labor-intensive, and inconsistent across large-scale farming op erations. To address these limitations, we developed a hybrid ensemble deep learning pipeline combining ResNet-50 and DenseNet-121 architectures with integrated depth information from Intel RealSense D435 cameras. The system was trained and validated on a dataset of 268 pigs across six pens collected from Virginia State University farms, with video streams captured as .bag files and converted to PNG images for analysis.
Experimental results demonstrate that the multi-modal RGB-D approach achieves a 13.68% accuracy improvement over traditional RGB-only methods when evaluated using the en semble model. The hybrid ensemble achieves 84.18% accuracy using multi-image temporal aggregation across five architectures: ResNet-50, DenseNet-121, EfficientNetV2-S , Vision Transformer, and the proposed hybrid ensemble . Overall, the system achieves 84.18% multi-image classification accuracy.
The proposed automated pipeline demonstrates the feasibility of objective and scalable livestock health monitoring, with potential productivity gains through improved nutri tional management. Future work will focus on expanding the dataset through multi-farm validation and integrating behavioral monitoring systems to enable more comprehensive an imal welfare assessment.
New Frontiers in Seismic Imaging of the Critical Zone
Eppinger, Ben Julius (Virginia Tech, 2026-03-27)
The critical zone (CZ) is the life-supporting skin of our planet, spanning the top of vegetation to the base of weathered bedrock. This thin layer is the only place in the known universe where biota, water, atmosphere, and geologic materials interact and transform. Direct observations of the critical zone's subsurface structure typically require invasive methods such as drilling boreholes or excavating soil pits. Seismic imaging has been used for decades to circumvent direct measurements of the subsurface, but traditional approaches often rely on a limited subset of the information contained within the seismic wavefield, such as the timing of first arrival waveforms. By leveraging more of the data contained in the seismic wavefield, new facets of critical zone evolution can be revealed. This thesis develops and applies advanced geophysical techniques, specifically full-waveform inversion (FWI) and multi-component surface wave analysis, to constrain high-resolution models of p-wave velocity, s-wave velocity, and radial anisotropy.
In the first manuscript, a workflow is developed to implement 2D full waveform inversion (FWI) within the critical zone. The workflow involves inverting surface waves and body waves separately to ensure that high-amplitude surface waves do not dominate and overprint the information contained in body waves. When applied to a site near Laramie Wyoming, the resulting FWI models reveal that bedrock fracture density serves as an important bottom-up control on CZ architecture. These findings show that the transition from saprolite to intact bedrock is sharp in areas with low fracture density but more diffuse where the underlying rock exhibits higher fracture density. Additionally, the FWI models show better agreement with borehole data as compared to previously published first arrival travel time tomography models.
The second study explores the role of inherited rock fabric in the development of critical zone porosity by measuring radial anisotropy with surface waves. This novel method utilizes multi-component surface seismic data associated with Rayleigh and Love waves to quantify radial anisotropy at the hillslope scale. Field data and in situ measurements from the South Carolina Piedmont demonstrate a strong correlation between seismic anisotropy and porosity, with both properties developing concurrently as rock undergoes in situ weathering. This empirical evidence suggests that weathering processes do not act stochastically, and instead, are guided by the geologic fabric of the parent material. Moreover, this research provides further evidence that inherited rock fabric plays a major role in dictating the form and function of landscapes.
The final study investigates subsurface structure and water stores beneath giant sequoias in Yosemite National Park. By employing dense arrays for multicomponent nodal geophones, a revised time-frequency-phase FWI algorithm, and geostatistical rock physics modeling, this research estimates volumetric water content beneath giant sequoias at different landscape positions. The results indicate that giant sequoias located on ridges and hillslopes lack sufficient shallow soil moisture and must instead rely on deep rock moisture from depths exceeding 2 meters to avoid water stress during arid summers. As such, this work underscores the importance of rock moisture to valued species in arid landscapes.
These three studies present several avenues for seismic imaging to catalyze research in the critical zone. The advent and integration of multicomponent, dense nodal data sets with advanced processing methods such as FWI means that previously undiscernible subsurface characteristics can now be elucidated. By contextualizing novel images of the shallow subsurface within the vibrant field of critical zone science, we can better understand how Earth supports life.
Subverting the Script: Female Playwrights and the Fluidity of Gender and Class in 18th-Century France
Stacks, Kerrie Maria (Virginia Tech, 2026-03-27)
This thesis explores how gender and marriage are depicted in 18th-century pre-revolutionary French theaters written by women. While conventional tropes of arranged marriage and forbidden love permeate the period's theater, this study highlights a focus on gender inversion and female autonomy within the selected corpus. By analyzing the works of Barbier, Graffigny, and Benoist, the research demonstrates how Enlightenment values were interpreted through a gendered lens, resulting in fluid portrayals of behavior, emotion, and kinship systems. Furthermore, by expanding the scope beyond public stages to include private theatrical spheres, this thesis reveals how female dramatists utilized the public nature of theater to challenge social norms. Ultimately, these works facilitate a critical dialogue on the evolution of gendered identity and the subversive potential of early modern female authorship.
Methods for Improving Comparability of Propeller Acoustic Experiments Conducted at Different Facilities and Scales
Duong, ThanhLong James (Virginia Tech, 2026-03-26)
Development of urban air mobility (UAM) vehicles are on the rise, and their noisy operation near many people can cause negative health effects, so it is important to quickly understand their acoustic behaviors. This is done through many conduits, including computational fluid dynamics (CFD), outdoor field tests, and controlled indoor experiments. Outdoor field tests allow for full-scale vehicle testing, but subjects the test article to uncontrollable, unpredictable variables, whereas indoor experiments are much more controllable and predictable, but such indoor experiments are often constrained by space and are unable to test the full-scale vehicle. Research should develop methods to improve comparability between indoor and outdoor acoustic experiments. The presented work aims to provide such methods with three experiments: one investigating ground board acoustic behavior in an anechoic chamber, one investigating propeller noise in an outdoor facility, and one investigating propeller noise in an indoor facility.
Ground boards are thin rigid boards, typically in the shape of a 1m diameter circle a few millimeters thick, and are standardized for use [5] [10] [11] [13] in outdoor acoustic experiments to mount microphones and provide a consistent reflective surface. An experiment was conducted in an anechoic chamber to observe the behavior of a 1m diameter, 6mm thick plywood ground board with the noise source at various incidence angles and with the microphone lain at the center and at three-quarters the radius of the ground board. The configuration of interest is a 23° incidence angle with the microphone at the center since this is the configuration used in the outdoor field test. With this configuration, the behavior of the ground board is similar to that of a perfect reflector (6dB increase in measured sound pressure level (SPL)) within about 200Hz to 10000Hz. Below 2000Hz, the shallower source angles (20°, 23°, and 45°) have a lower SPL magnification; in the 2000Hz to 8000Hz frequency range, there appears to be little dependence of ∆P SD on the source angle; above 8000Hz, the higher source angles (65° and 80°) have a lower SPL magnification. With the microphone lain at three-quarters the radius of the ground board, a similar trend was observed, but its sensitivity to the source angle was lower.
A Techsburg Inc. propeller was tested in an outdoor facility at two scales: 0.9144m and 0.4572m diameters. The propeller was mounted with its center 1.905m above the ground, and 13 microphones were placed on top of ground boards in a 4.572m semicircle around the propeller, ranging from upstream to downstream of the propeller. Wind measurements were simultaneously collected from an anemometer a few meters away from the microphone arc. The background noise at this facility was significant up to about 800Hz, and motor noise was significant around 5000Hz to 9000Hz. Wind velocity data was collected simultaneously to acoustics, and a relationship was found between broadband noise and inflow velocity. The total propeller noise was decomposed into broadband and tonal components through phase averaging methods, and it was found that the overwhelming majority of the noise was dominated by the broadband component. Generally, when the inflow velocity was about −1m/s to 0.5m/s, the broadband noise within 2000Hz to 5000Hz was about 1dB to 2dB louder than when the inflow velocity was about 0.5m/s to 3m/s. Furthermore, the spectra calculated from when the inflow velocity was between −1m/s and 0.5m/s was much more comparable to the Gill-Lee Spectrum Model (GLSM), a trailing edge noise prediction model trained on hundreds of propeller noise datasets primarily at a hover condition. To compare the two scales, the tip Mach number was held constant, so the 0.9144m diameter propeller rotated half as fast as the 0.4572m diameter propeller, resulting in half the blade passage frequency (BPF) and twice the harmonics. The broadband noise of the larger propeller peaked around 2000Hz, whereas the smaller propeller's broadband curve peaked around 4500Hz. This relative peak behavior is reflected in the GLSM, although the GLSM generally overpredicts both scales. The expected difference in tones between the two scales was calculated from the thrust squared to be approximately 11dB, and the observed difference in tones was observed to be approximately 7dB at most. However, these thrust measurements were averaged over the entire sampling period, so the absolute magnitude of this calculation should be considered with reasonable skepticism. The reduction in pitch angle resulted in quieter broadband noise, which is expected since this would reduce thrust and therefore reduce noise. The addition of turbulence trips did not result in the expected consistent increase in broadband noise, but this may be due to the inherent difficulty of outdoor acoustic experiments: the environmental conditions in field tests are uncontrollable, and sequestration was unable to isolate period of similar wind velocities, so the two datasets were not entirely comparable.
A similar experiment was performed in an anechoic wind tunnel, the Virginia Tech Subsonic Modular Anechoic Research Tunnel (VTSMART), to observe the effects of test facility. Five microphones were mounted at the same height as the propeller 1.016m away from the propeller, evenly spaced by 10° between each, starting from 10° upstream to 30° downstream. A sixth microphone was mounted further downstream closer to the axis of rotation. Due to size constraints of the wind tunnel, only the 0.4572m diameter propeller was tested at this facility. Background noise was much quieter and more consistent than the outdoor facility, and the SNR was positive throughout 100Hz to 20000Hz. Spectrograms were generated for both background and propeller noise measurements, and both were found to be relatively constant in time, so the background noise was directly subtracted from the propeller noise measurements. Again, the total propeller noise was broken into broadband and tonal components, and the majority of the noise was still composed of the broadband component. The tunnel was operated at two conditions: one without flow and one with 4m/s flow. Between the two tunnel conditions, the broad spectral features did not change significantly, and the largest differences were observed in the tonal features. With 4m/s flow, the tones at the BPF were quieter than without flow by approximately 5dB. The GLSM generally captured the broad spectral features at the indoor facility better than at the outdoor facility, typically within about 3dB of the experimental data. The data from both experiments were compared to each other after a correction to account for the difference in distance. The outdoor broadband noise with an inflow velocity of about 0.5m/s to 3m/s was similar to the indoor broadband noise with 4m/s flow in the 2000Hz to 6000Hz range within about 2dB, and a similar result is seen when comparing the outdoor broadband noise with an inflow velocity of −1m/s and 0.5m/s to the indoor broadband noise with no flow. All configurations were again compared to each other at this facility, but much smaller differences were observed. This is likely due to the confinement of the wind tunnel facility and the inability of the wake to be convected far enough downstream of the propeller, causing these broadband noise sources to dominate over changes in pitch and turbulence trips.
In each experiment, there are many limitations and possible improvements with further research. For the ground board experiment, more source incidence angles, microphone orientations, and surrounding substrates could be tested, which would improve the understanding of ground board response. Such research has been done in the past [2] [4] [14] [22]. For the outdoor Drone Park experiment, the ground boards could have been calibrated before collecting propeller acoustics so that measurements could be properly corrected for the effects of the ground board in the field. Wind anemometer data could also be fully synchronized to the propeller acoustics such that direct correlations would be more meaningful. Similarly, synchronized performance data should be collected as well, specifically thrust and torque, which would allow for more accurate GLSM calculations, since this model takes thrust into consideration. For the indoor VTSMART experiment, particle imaging velocimetry (PIV) could be conducted to observe the physical phenomena and confirm if the confinement of the wind tunnel is indeed causing the wake to loiter near the propeller.
Prognostic Outcomes Between Conservative and Surgical Interventions in Patients with Full-Thickness Rotator Cuff Tears
Little, Jarett (Virginia Tech, 2026-03-18)
Context: Full-thickness rotator cuff tears are one of the most common musculoskeletal conditions affecting a variety of patient populations. This condition, if not treated, leads to increased pain, reduced functional abilities, and reduced efficiency with activities of daily living all culminating into decreasing the patient’s overall quality of life. Surgical repair is generally the standard of care for these patients; however, new evidence suggests that conservative treatment may be just as effective.
Objective: The aim of this systematized review was to describe measurable outcomes (pain, mobility, and strength) and how they compare surgical treatment compared to conservative treatment in full-thickness tear rotator cuff patients.
Design: A systematized review of the current literature from 2015-2025, assessing the prognostic outcomes of both conservative and surgical methods of treatment of full-thickness rotator cuff tears.
Eligibility Criteria: Adults ≥30 years old diagnosed with full-thickness rotator cuff tears confirmed by imaging; full thickness rotator cuff tear (supraspinatus, infraspinatus, teres minor, subscapularis); Interventions (Surgical repair: Mini open repair, arthroscopic repair, open repair, injections. Conservative (non-surgical): Physical Therapy Protocol and exercise interventions); Outcomes: Constant-Murley Score (CMS), ASES, Quick-DASH, MMT, ROM.
Study Selection: 16 out of 887 initial studies met all the inclusion criteria.
Results: Both interventions demonstrated effective progress in overall condition. Surgical interventions demonstrated faster improvement with significant improvement in functional scores occurring at 6-12 months followed by a plateau where both intervention groups would produce similar functional scores after one year. Tear size and level of symptoms were the most significant indicators for patient success. Tears that were not classified as “large” demonstrated consistent and non-variable progress regardless of method used.
Conclusion: Both methods of interventions provide significant clinical results with surgical groups demonstrating progress at 6-12 months while conservative groups reached the same functional scores in the long term. Overall, conservative treatment was able to produce similar outcomes for tears that were classified as small to medium demonstrating its effectiveness with this patient population. These results suggest a patient centered/stepwise approach would be most effective for patients with small to medium tears. This means incorporating patient factors with an initial conservative approach followed by surgical intervention if the conservative treatment has not improved overall patient condition. Larger tears, however, should directly receive surgical intervention due to its variability in presentation and outcomes.