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- Conflict, Paradox, and the Role of Structure in True IntelligenceBettendorf, Isaac T. (Virginia Tech, 2024-04-04)Novel forms of brain-inspired programming models related to novel computer architecture are required to both understand the mysteries of intelligence as well as break barriers in computational complexity, and computer parallelism. Artificial Intelligence is focused on developing complex programs based on abstract, statistical prediction engines that require large datasets, vast amounts of computational power, and unbounded computation time. By contrast, the brain utilizes relatively few experiences to make decisions in unpredictable, time-constrained situations while utilizing relatively small amounts of physical computational space and power with high degrees of complexity and parallelism. We observe that intelligence requires the accommodation of ambiguity, conflict, and paradox. From a structural perspective, this means the same set of inputs leads to conflicting results that are likely produced in isolated regions of the brain that function independently until an answer must be chosen. We further observe that, unlike computer programs, brains constantly interact with the physical world where external constraints force the selection of the best available response in time-quality trade-offs ranging from fight-or-flight to deep thinking. For example, when intelligent beings are presented with a set of inputs, those inputs can be processed with different levels of thinking, utilizing heterogeneous algorithms to produce answers dependent upon the time available to process them. We introduce the Troop meta-approach, which is a novel meta computer architecture and programming. Experiments demonstrate our approach in modeling conflict when the same set of inputs are heterogeneously processed independently using maze solving and ordered search in real-world environments with unpredictable, random time constraints. Across one hundred trials, on average, the Troop solution solves mazes almost six times faster than the only other solution, which does not accommodate conflict but can always produce a result when required. Two other experiments based on ordered search show that, on average, the Troop solution returns a position that is over twice as accurate as the other solutions which do not accommodate conflict but always produce a result when required. This work lays the foundation for more research in algorithms that utilize time-accuracy trade-offs consistent with our approach.
- The Effect of Austenitization Temperature on the Microstructure, Bend Properties, and Hardness of a Chrome-Bearing White Cast IronAdelmann, Joshua Thomas (Virginia Tech, 2024-04-25)The goal of this line of research is to add to the existing body of literature on the effect of heat treatments on the microstructure of chrome-bearing white irons and add bend test data to the literature concerning chrome-bearing white irons. This project was intended to support an existing line of research into cast metal-ceramic lattices using chrome white iron as a substitute for sintered ceramic tiles used to defeat projectiles. Chrome-bearing white irons have a substantial quantity of chromium carbides, giving them high hardness and abrasion resistance. Additionally, tiles cast from white iron proved to be more durable than sintered ceramic tiles, breaking into large chunks rather than a powder following an impact. These properties make tiles cast from chrome-bearing white iron a low-cost alternative to sintered carbides. The alloy investigated contained nominally 14 chromium and 3.2 carbon by weight percent. Three-point bend test specimens were cut from cast plates. These specimens were austenitized, air cooled, then tempered prior to three-point bend and hardness testing. The microstructure of the specimens was evaluated using optical microscopy, SEM, and XRD. This line of research revealed that lower austenitization temperatures resulted in a martensitic matrix with fewer, smaller secondary carbides, resulting in higher strength and hardness. In contrast, higher austenitization temperatures produced an austenitic matrix with coarser carbides, resulting in lower strength and hardness. This research did not reveal an appreciable change in ductility over heat treatment temperature.
- Low-Power Wireless Sensor Node with Edge Computing for Pig Behavior ClassificationsXu, Yuezhong (Virginia Tech, 2024-04-25)A wireless sensor node (WSN) system, capable of sensing animal motion and transmitting motion data wirelessly, is an effective and efficient way to monitor pigs' activity. However, the raw sensor data sampling and transmission consumes lots of power such that WSNs' battery have to be frequently charged or replaced. The proposed work solves this issue through WSN edge computing solution, in which a Random Forest Classifier (RFC) is trained and implemented into WSNs. The implementation of RFC on WSNs does not save power, but the RFC predicts animal behavior such that WSNs can adaptively adjust the data sampling frequency to reduce power consumption. In addition, WSNs can transmit less data by sending RFC predictions instead of raw sensor data to save power. The proposed RFC classifies common animal activities: eating, drinking, laying, standing, and walking with a F-1 score of 93%. The WSN power consumption is reduced by 25% with edge computing intelligence, compare to WSN power that samples and transmits raw sensor data periodically at 10 Hz.
- Deadwood Dynamics: A Case Study at Prince William Forest Park, VirginiaMaslyukova, Daria Yurevna (Virginia Tech, 2024-04-25)Deadwood, characterized as both downed woody material (DWM) and standing and dead stems, i.e., snags, is a significant component of terrestrial forest ecosystems. Deadwood amount and structure may influence potential wildfire hazard by altering combustible DWM mass and creating fuel structures that increase fire intensity and spread. Deadwood is also critical to carbon storage and nutrient cycling and may vary based upon the size classes of individual deadwood pieces. Lastly, deadwood structural variability has been found to positively affect species richness in bees, salamanders, birds, and small mammals, such as shrews and woodland mice. However, in the Mid-Atlantic Piedmont, there are no accessible tools to rapidly estimate deadwood of long unmanaged second growth forests to help inform future management decisions. Management agencies within this region, such as the National Park Service, may benefit from a greater understanding of the potential factors that influence deadwood accumulation, retention, and decomposition. Therefore, a project was funded by the National Park Service to investigate deadwood dynamics at Prince William Forest Park (PRWI). From May to August 2023, a deadwood inventory was conducted using planar intercepts nested within fixed radius plots along the gradient of forest cover types, aspect, elevation, and soil orders found within PRWI. Forest cover type was significant in the generalized linear model for percent dead basal area, total DWM, fine woody material, litter, and duff mass. The Virginia pine (Pinus virginiana) forest cover type had the highest percent dead basal area and total DWM mass per hectare. Elevation, aspect, and soil order were not significantly related to percent dead basal area, total DWM, 1,000 hr, fine woody material, litter, and duff mass. Data from this study may serve as a baseline for similar second growth forests of the mid-Atlantic Piedmont.
- Optimizing Reservoir Computing Architecture for Dynamic Spectrum Sensing ApplicationsSharma, Gauri (Virginia Tech, 2024-04-25)Spectrum sensing in wireless communications serves as a crucial binary classification tool in cognitive radios, facilitating the detection of available radio spectrums for secondary users, especially in scenarios with high Signal-to-Noise Ratio (SNR). Leveraging Liquid State Machines (LSMs), which emulate spiking neural networks like the ones in the human brain, prove to be highly effective for real-time data monitoring for such temporal tasks. The inherent advantages of LSM-based recurrent neural networks, such as low complexity, high power efficiency, and accuracy, surpass those of traditional deep learning and conventional spectrum sensing methods. The architecture of the liquid state machine processor and its training methods are crucial for the performance of an LSM accelerator. This thesis presents one such LSM-based accelerator that explores novel architectural improvements for LSM hardware. Through the adoption of triplet-based Spike-Timing-Dependent Plasticity (STDP) and various spike encoding schemes on the spectrum dataset within the LSM, we investigate the advantages offered by these proposed techniques compared to traditional LSM models on the FPGA. FPGA boards, known for their power efficiency and low latency, are well-suited for time-critical machine learning applications. The thesis explores these novel onboard learning methods, shares the results of the suggested architectural changes, explains the trade-offs involved, and explores how the improved LSM model's accuracy can benefit different classification tasks. Additionally, we outline the future research directions aimed at further enhancing the accuracy of these models.
- Changing Relationship Between Temperature and Pathogen Growth on Bats with White-nose SyndromeFife, Josh (Virginia Tech, 2024-04-22)Emerging infectious diseases (EID) pose significant threats to biodiversity. Human influence over the environment has increased opportunities for the introduction of novel pathogens to naïve hosts, potentially leading to host extinction. Understanding mechanisms of host persistence is critical for effectively conserving species affected by EIDs. Our study investigated the disease dynamics of white-nose syndrome (WNS), caused by the fungal pathogen Pseudogymnoascus destructans (Pd), in little brown bats (Myotis lucifugus) across a spatiotemporal gradient. We explored the relationship between bat roosting temperatures and Pd growth rates across three phases of pathogen invasion comprising years since WNS has been present at sites: invasion (0-3), established (4-8), and endemic (9+ years). Data used by this study comes from a combination of field-based data collection in New York where WNS has been present the longest and data from a long-running project which includes from other locations in the Northeast and Midwest regions of the United States. Our results reveal a weakening interaction between temperature and fungal growth rates time with WNS progresses. We additionally observed a decrease in early hibernation fungal loads and variation in infection prevalence over time, suggesting the onset of a coevolutionary relationship between bats and Pd. This study highlights the importance of investigating changing disease dynamics when understanding the reasonings for host persistence.
- Assessment of a Fixed Media Partial Denitrification/Anammox Process Startup in a Full-Scale Treatment TrainWieczorek, Nathan Vincent (Virginia Tech, 2024-04-18)Partial denitrification anammox (PdNA) is an emerging wastewater treatment technology with the potential to increase process capacity and save on energy and carbon. PdNA circumvents potential issues with stability of the more familiar mainstream partial nitritation anammox (PNA) process. The PdNA process can be used to effectively remove ammonia, nitrate, and nitrite from mainstream municipal waste streams. To retain slow growing anammox, some sort of retention system is needed with media being a common solution to this problem. PdNA has been successfully implemented in mainstream full-scale systems in sand filters and with moving media. The goal of this study was to assess the denitrifying capabilities, anammox treatment capacity, and effective surface area to volume of two types of fixed media. A nitrifying pilot was set up to assess the effective surface area to volume. To assess the nitrifying and anammox ammonia removal capabilities of the fixed media, a fixed media PdNA system was installed in the second anoxic zone of a full-scale municipal wastewater treatment plant. The fixed media system consisted of three modules of sheets modified to mimic a plug flow system. After accounting for the estimated nitrate removal from mixed liquor, denitrification rates normalized to media surface area were 0.52 +/- 1.9 g/m2-day in the first module, 0.62 +/- 0.91 g/m2-day for the second module, and 0.56 +/- 0.90 g/m2-day for the third module. In ex situ batch testing it was found that maximum ex-situ anammox ammonia removal rates for the
- El hambre en el cine cubano del Período EspecialJaime Castillo, Joana (Virginia Tech, 2021-10-06)This thesis examines the trope of hunger in Cuban cinema produced during the socio-economic context known as the Special Period. Films selected for this discussion are Fresa y chocolate (1993) by Tomás Gutiérrez Alea and Juan Carlos Tabío, and El Rey de La Habana (2015) by Agustí Villaronga. Focused on the analysis of the trope of hunger, this study offers a summary of the Cuban cultural manifestations of the last decades that have addressed the issue of hunger as well as a brief historical context that allows us to understand the development of this trope from 1960 to the present. Focused on the aforementioned films, this study has observed the aesthetic and stylistic particularities used in filmic representations to convey the island's shortcomings. The thesis demonstrates the existence of two main famines within Cuban society: cultural hunger and physiological hunger. Cultural hunger is studied in Fresa y chocolate as a direct consequence of the cultural control of the repressive ideological apparatus implanted in the sixties. The analysis of El Rey de la Habana shows how physiological hunger builds a marginal and abject subject, unable to escape the vicious circle that society has imposed on him.
- Selective Deposition of Copper Traces onto Additively Manufactured All-Aromatic Polyimides via Laser Induced Graphene to Enable Conformal Printed ElectronicsWotton, Heather Dawn (Virginia Tech, 2024-04-03)The hybridization of direct write (DW) and additive manufacturing (AM) technologies to create additively manufactured electronics (AME) has enabled the integration of electrical functionality to form multifunctional AM components. Current work in AME has demonstrated the integration of conductive traces into and onto geometries and form factors that are not possible through traditional electronics packaging processes. This has largely been accomplished by using AM and DW technology to deposit conductive inks to form interconnects on the surface of AM substrates or within multimaterial AM geometries. However, the requisite thermal post-processing and high resistivity of the conductive inks and the limitations in thermal and dielectric performance of printable substrates commonly used in AME restrict the capabilities of these parts. This thesis proposes an alternative process for the conformal deposition of low resistivity traces on additively manufactured all-aromatic polyimides (AM-PI) without the use of conductive inks. This is accomplished through the selective patterning of laser induced graphene (LIG), a porous 3D graphene fabricated via laser irradiation, onto the AM-PI. While the resultant LIG is conductive, its resistivity is further reduced by the electrodeposition of copper (Cu-LIG). In this thesis, the synthesis of LIG on AM-PI, thermally post processed to 240℃, 300℃, and 450℃, is demonstrated and characterized through sheet resistance measurements and Raman spectroscopy. AM-PI post-processed to 300℃ demonstrated the lowest resistivity LIG formation (13.8 Ω/square). The resistivity of Cu-LIG is compared to an industry standard silver ink (Micromax CB028) used in direct write hybrid manufacturing applications. Cu-LIG was found to have a measured resistivity (1.39e-7 Ω·m), two orders of magnitude lower than the measured resistivity of the CB028 silver ink (1.62e-5 Ω·m). Additionally, the current capacity of the Cu-LIG was demonstrated and Joule heating of the material was observed via IR thermography. Cu-LIG demonstrated no failure of conductive trace or substrate under 5A of current for 2 minutes, heating to a maximum recorded temperature of 76.3℃. Several multifunctional components were fabricated as case studies to further validate the process. Several small passive electronic devices (e.g., a heater and an interdigitated capacitor) are fabricated to demonstrate selective deposition of complex copper traces. The fabrication of an Archimedes spiral on a hemispherical substrate via Cu-LIG is completed to demonstrate the ability to use the process to fabricate conformal conductive traces. An LED circuit is fabricated on a face-center cubic AM-PI lattice which demonstrates multi-planar fabrication on geometrically complex 3D printed substrates.
- Impact of Brewing Industry Byproducts Used as Feed Additives for Aquaculture-Raised Fish: Studies of the Host-Microbe RelationshipLayton, Anna Rayne (Virginia Tech, 2024-04-15)Aquaculture, the cultivation of aquatic organisms in a controlled environment, offers both economic and nutritional benefits to human society. As there is an increased demand to feed a growing human population, many wild-caught fisheries have struggled due to the overexploitation of resources. Currently, production relies heavily on wild-caught fish to produce fishmeal to feed farm-raised fish. The demand for alternative materials in fish feeds has grown rapidly as fishmeal resources have become limited. Antibiotic resistance emergence in aquaculture systems is another area of concern. Reducing antibiotic use via alternate prophylactic measures to increase host health is an essential area of research; modulation of the host intestinal bacterial community via prebiotics is one possibility. Prebiotics refer to non-digestible food ingredients that are thought to stimulate the growth of beneficial bacteria, consequently benefiting host health by indirectly reducing the possibility of bacterial pathogen proliferation. This occurs through various measures such as competition for space and resources. The intestinal bacterial community has a significant impact on a variety of host factors that include host development, physiology, immunity, and nutrient acquisition. In turn, there are multiple factors impacting the bacterial community, including the presence of pathogens and/or antibiotics, environmental conditions, host genetics, and the diet consumed. To promote environmental sustainability and improve production and animal health in aquaculture, a collaboration was created with Anheuser-Busch of the brewing industry and Maltento, a functional ingredient company. With breweries around the globe, Anheuser-Busch produces consistent, food grade byproducts that are safe for human consumption. Two of the most prevalent brewery byproducts are brewer's spent yeast (BSY) and brewer's spent grain (BSG). BSY contains a variety of beneficial nutrients such as proteins, essential amino acids, and carbohydrates. BSG is high in fiber but low in protein; however, black soldier fly larvae can be cultured on BSG to convert the low-value product into insect biomass to be used in fish feed, as insects themselves are full of beneficial lipids and proteins. The objective of the work presented in this thesis was to evaluate the efficacy of using low-value brewery waste products, converted into high-value feed additives, for aquaculture practices. Specifically, the effects of dietary feed additives on the production, health, and intestinal bacterial community of aquaculture-raised rainbow trout were examined. Inadvertently, benefits of the feed additives on fish subjected to chronic and acute thermal stress were also assessed. Overall, the results of the study found that the feed additives did not significantly change the production efficiency of the rainbow trout, though some increase in growth was observed. When subjected to chronic thermal stress conditions, fish fed the experimental diets outperformed those fed the control diet regarding growth parameters. The intestinal bacterial community of the fish was significantly altered from the beginning of the trial compared to the end of the trial, though differences were not attributed to the feed additives. Instead, the resulting intestinal dysbiosis is believed to have stemmed from the physiological response of the fish to thermal stress conditions. When the fish underwent an acute thermal stress event, causing mortality, fish fed three of the five experimental diets were found to have higher survival rates compared to the control. Ultimately, results of this project suggest that the BSY and BSG-fed insect feed additives may have increased the health and robustness of the fish during a period of thermal stress. However, further research under controlled conditions is needed to evaluate if the observed host health benefits can directly be attributed to the feed additives.
- A 3D Deep Learning Architecture for Denoising Low-Dose CT ScansKasparian, Armen Caspar (Virginia Tech, 2024-04-11)This paper introduces 3D-DDnet, a cutting-edge 3D deep learning (DL) framework designed to improve the image quality of low-dose computed tomography (LDCT) scans. Although LDCT scans are advantageous for reducing radiation exposure, they inherently suffer from reduced image quality. Our novel 3D DL architecture addresses this issue by effectively enhancing LDCT images to achieve parity with the quality of standard-dose CT scans. By exploiting the inter-slice correlation present in volumetric CT data, 3D-DDnet surpasses existing denoising benchmarks. It incorporates distributed data parallel (DDP) and transfer learning techniques to significantly accelerate the training process. The DDP approach is particularly tailored for operation across multiple Nvidia A100 GPUs, facilitating the processing of large-scale volumetric data sets that were previously unmanageable due to size constraints. Comparative analyses demonstrate that 3D-DDnet reduces the mean square error (MSE) by 10% over its 2D counterpart, 2D-DDnet. Moreover, by applying transfer learning from pre-trained 2D models, 3D-DDnet effectively 'jump starts' the learning process, cutting training times by half without compromising on model accuracy.
- Striped Bass and Summer Flounder Population Dynamics in the Chesapeake Bay: an Ecosystem Based EvaluationOakley, Josephine Marie (Virginia Tech, 2024-03-27)The Chesapeake Bay is the largest estuary in the United States and is highly productive making it a key habitat for species like striped bass and summer flounder. Striped bass and summer flounder have exhibited changes in abundance over recent years within the Chesapeake Bay. There is a lack of understanding of how environmental factors may be impacting striped bass and summer flounder abundance and how other species may be responding to these environmental drivers. To improve our understanding of striped bass, summer flounder and the aquatic community we set out to identify the environmental drives of their abundance changes from local to global scales. The fish community in the Bay has previously shifted due to environmental perturbations, so we also investigate if the community has changed more recently. We used a hurdle model to standardize interannual abundance of fish species caught in the Chesapeake Bay from two sources of fishery-independent trawl survey data. This standardization process led to relative abundance indices for 58 late juvenile to adult species from 2002-2018, and relative abundance indices for 26 juvenile species from 1995-2019. Species with similar and contrary abundance trends with striped bass and summer flounder were identified through a correlation analysis, and life history traits were assessed between species to determine mechanisms of change. We then used nonmetric multidimensional scaling (nMDS) to see if the community structure had drastically changed, the applied a principal response curve (PRC) to investigate the spatial and functional group change of the community. Among the factors examined, sea surface temperature (SST) in the Bay has increased since 2006 based on change point analysis while the mean Bay SST range and gradient have both decreased. Striped bass have had variable abundance in the Bay but exhibited a positive correlation with increasing SST. Summer flounder have declined in abundance since 2006 in the Bay and exhibited a negative correlation with increasing SST. Striped bass and summer flounder had relationships with global climate oscillations such as the winter North Atlantic Oscillation, Atlantic Multidecadal Oscillation, and the Gulf Stream North Wall oscillation. From a community perspective, our results showed that the late juvenile to adult fish community shifted after 2011, which coincided with the freshwater surge due Hurricane Irene and Tropical Storm Lee. The increase in abundance of striped bass, Bay anchovy, and Atlantic menhaden, and decrease in abundance of summer flounder, weakfish, spot, and Atlantic croaker were the main species that contributed to the difference in community structure after 2011. The change in functional group structure after 2011 was defined by a decline in opportunistic demersal fish, and this change was significantly different in the portion of the Bay north of the Potomac River. We did not identify any significant correlation between functional groups and environmental factors but did discover the important relationship that top predators like striped bass and summer flounder have with their key fish prey species, both in presence and population trends. Long term monitoring and further research in to how the community changed over smaller periods and the distribution changes of species could improve our understanding of what is impacting the Chesapeake Bay community to inform better management strategies.
- Hydro-Urbanism : Reimagining Urban Landscapes to Accommodate and Utilize StormwaterPutta, Praneetha (Virginia Tech, 2024-04-09)Urban flooding presents a significant challenge to cities worldwide, resulting in loss of life and economic damage. Factors such as urbanization, climate change, and extreme weather events compound the vulnerability of urban areas to flooding, with rapid urbanization emerging as a primary driver of increased flood risk. In response to this pressing issue, this thesis embarks on a transformative exploration, advocating for a paradigm shift in urban stormwater management through the lens of "Hydro-Urbanism." Central to this concept is recognizing stormwater as a valuable resource rather than a mere liability. By implementing targeted strategies to curb runoff, detain stormwater, and replenish groundwater, cities can mitigate the adverse impacts of urban flooding while enhancing resilience and livability. Through a comprehensive review of existing literature and analysis of case studies, this research explores the efficacy of diverse stormwater management techniques in alleviating urban flooding and fostering sustainable urban development. In addition to technical aspects, the study delves into the socioeconomic dimensions of Hydro-Urbanism, highlighting the significance of community engagement and participatory planning in creating resilient and inclusive urban environments. Focused on Hyderabad city in Telangana, India, this project lies at the intersection of cultural heritage and modernity, confronting significant challenges posed by urban flooding amidst rapid urban expansion. By reframing the narrative around water from vulnerability to resilience and opportunity, the project aims to harness the power of stormwater as a catalyst for change. A tailored typology-based approach seeks to nurture a future where cities and water coexist harmoniously, protecting urban areas from flooding and fostering a more harmonious relationship between urban communities and the natural world.
- Evaluating Alternative Inertial Measurement Unit Locations on the Body for Slip Recovery MeasuresMorris, Michelle Ann (Virginia Tech, 2024-04-03)Slips are a leading cause of injury among older adults. Specific slip recovery measures, including slip distance and peak slip speed, have been shown to increase significantly among fallers as compared to non-fallers. Often, slipping kinematics are measured using optoelectronic motion capture (OMC), requiring a laboratory setting and limiting data collection to experimentally-controlled conditions. Inertial measurement units (IMUs) show promise as a portable and wearable form of motion capture. This study had two objectives. First, we investigated whether foot and ankle IMU-derived slip recovery measures could be considered equivalent to the same OMC-derived measures. Second, we investigated if both participant-placed and researcher-placed IMU-derived slip recovery measures could be considered equivalent to the same OMC-derived measures. 30 older adults (ages 65-80) were exposed to a slip while wearing both IMUs and OMC markers. Slip distance and peak slip speed were measured by both systems and compared. Equivalence testing (α = 0.05) showed that IMUs placed on the foot and the ankle were equivalent to OMC in measuring these slip recovery measures. Furthermore, it was shown that researcher and participant-placed IMUs were equivalent (α = 0.05) to OMC in measuring these slip recovery measures. These results confirm that IMUs can be a viable substitute for OMC and have the potential to expand data capture to a real-world environment.
- Understanding the Phase Transformations of a Medium Manganese Steel as a Function of Carbon ContentKalil, Andrew Jeffrey (Virginia Tech, 2024-04-03)Medium-manganese steels (5-12 wt%) are candidates for third-generation advanced high strength steel (AHSS). Potential applications for these steels are centered around the automotive industry due to their combination of high tensile strength, high tensile ductility, and low alloying cost. Previous studies at VT have been primarily focused on the effect of chemistry on mechanical properties with only a minor emphasis on microstructure. This led to a detailed investigation into the effect of carbon content on the microstructure of Fe8Mn2AlSiC alloys. Six different chemistries with carbon contents of 0.30, 0.34, 0.39, 0.44, 0.49 and 0.52 wt% were produced at the Kroehling Advanced Materials Foundry. After a variety of heat treatments, the samples were characterized using x-ray diffraction (XRD), electron backscatter diffraction (EBSD), electron probe microanalysis (EPMA), optical microscopy, and hardness testing. This thesis will discuss how the microstructure and hardness of these medium manganese steels is influenced by the carbon content.
- Adaptive Beam Management for Secure mmWave CommunicationBaron-Hyppolite, Adrian Louis (Virginia Tech, 2024-04-09)Millimeter wave systems leverage beamforming to generate narrow, high-powered beams for overcoming the increased path loss in the millimeter wave spectrum. These beams are spa- tially confined, making millimeter wave links more resilient to eavesdropping and jamming attacks. However, the millimeter wave radios locate each other and establish communica- tion by exhaustively probing all possible angular directions, increasing their susceptibility to attacks. In this thesis, we showcase a secure beam management solution where we apply an adaptive beam management procedure that avoids probing the directions of potential attackers. We employ a reinforcement learning agent to control the probing and dynami- cally restrict sweeps to a subset of beams in the millimeter wave transmitter codebook to avoid the locations of potential attackers based on a proposed metric that quantifies the beam sweeping secrecy over a pre-defined area. We evaluate our proposed system through numerical simulations and an experimental real-life implementation on the CCI xG Testbed.
- An Investigation on Acoustic Metamaterial Physics to Inspire the Design of Novel Aircraft Engine LinersHubinger, Benjamin Evan (Virginia Tech, 2024-04-02)Attenuation of low frequency turbofan engine noise has been a challenging task in an industry that requires low weight and tightly-packed solutions. Without innovative advancements, the technology currently used will not be able to keep up with the increasingly stringent requirements on aircraft noise reduction. A need exists for novel technologies that will pave the way for the future of quiet aircraft. This thesis investigates acoustic metamaterials and their ability to achieve superior transmission loss characteristics not found in traditional honeycomb liners. The acoustic metamaterials investigated are an array of Helmholtz resonators with and without coupled cavities periodically-spaced along a duct wall. Analytical, numerical, and experimental developments of these acoustic metamaterial systems are used herein to study the effects of this technology on the transmission loss. Particularly focusing on analytical modeling will aid in understanding the underlying physics that governs their interesting transmission loss behavior. A deeper understanding of the physics will be used to aid in future acoustic metamaterial liner design. A parameter study is performed to understand the effects of the geometry, spacing, and number of resonators, as well as resonator cavity coupling on performance. Increased broadband transmission loss, particularly in low frequencies, is achieved through intelligent manipulation of these parameters. Acoustic metamaterials are shown to have appealing noise cancellation characteristics that prove to be effective for aircraft engine liner applications.
- Defining an Optimal Range of Centrifugation and Concentration Parameters for Canine Semen ProcessingSugai, Nicole J. (Virginia Tech, 2024-03-21)There is an increased demand for artificial insemination and shipping canine semen in clinical practice. However, we need to process the semen samples using centrifugation and dilution with extenders to help preserve the breeding dose and semen quality. Our objective was to determine a clinically relevant range of centrifugation and concentration parameters for processing canine semen. In the first experiment, we hypothesized that higher g force and longer treatment improves sperm recovery rates yet causes greater decline in semen parameters over a 48-hour cooling period. Our study design used the raw semen evaluations which served as each dog's own control. Sperm RR (%) was calculated post-centrifugation, and sperm viability (%, Nucleocounter® SP-100™), total and progressive motility (%, subjective and computer-assisted sperm analysis), and morphology (NM%, eosin-nigrosin staining) were assessed on initial raw semen (T0), post-centrifugation (T1), and 24 (T2) and 48 hours (T3) after cooling. Sperm losses were minimal and similar for all treatment groups (median >98%, P≥0.062). Spermatozoa viability was not different between centrifugation groups at any time point (P≥0.38) but declined significantly during cooling (T1 vs. T2/T3, P≤0.001). Similarly, total and progressive motility did not differ across treatments but declined in all groups from T1 to T3 (P≤0.02). In conclusion, our study showed that centrifugation within a range of 400g-900g for 5-10 minutes is appropriate for processing canine semen. In the second phase, we compared different sperm concentrations for cooled canine semen storage and hypothesized that lower concentrations would result in better semen quality. Individual ejaculates were divided into a control aliquot (CON) extended 1:3 vol:vol with a commercial extender. The remaining sample was centrifuged and extended to 200 x106 sperm/ml (C200), then serially diluted to 100, 50, and 25 x106 sperm/ml concentrations (C100-C25). Aliquots were cooled for 24h, then centrifuged and re-extended. Parameters were assessed in raw semen (T0), post-extension (T1), after 24h of cooling (T2), and after processing at 24h (T3). Cooling resulted in significant declines in STM and NM for all groups, and in decreased PMI for CON and C25-50. After cooling (at T2), PMI was significantly lower for C25 compared to all groups and higher for CON compared to C25-100 (p≤0.038). For the motility parameters and NM, C25 performed worse than all or most of the other groups. Comparing CON at T3 with C25-200 at T2, PMI, STM and NM for CON were significantly lower than C25-200, C200, and C100-200, respectively. In conclusion, our results show that cooling canine semen for 24h at 200 x106 sperm/ml final concentration after processing or extending 1:3 vol:vol without centrifugation is preferred based on highest PMI. If volume restrictions apply, processing raw semen and extending to the desired volume with higher sperm concentrations at the collection facility is superior to centrifugation and volume adjustment after 24h of cooled storage.
- Magnetic Field Sensing via Multi-Material Acoustic Sensing Optical Fibers with Magnetostrictive Cladding InclusionsDejneka, Zachary Bryce (Virginia Tech, 2024-03-28)In this conducted research, optical fiber sensors are used to measure low strength alternating magnetic fields. Various fiber sensor configurations are tested and investigated to demonstrate sensing capabilities at different field magnitudes and frequencies. Distributed acoustic sensing fibers (DAS) have been largely studied and documented across a variety of applications and sensing systems. This research uses the DAS technology in tandem with magnetostrictive materials to create a distributed multi-material optical fiber magnetic sensor. Magnetic sensing has high demand across different fields and often runs into challenges of extreme environments including high temperature, corrosion, and areas with poor accessibility. The robust and distributed nature of optical fiber sensors which can be cheaply produced for long lengths is an attractive option over other single point magnetic sensors. In down hole applications specifically, having a distributed sensor able to be deployed easily and over long distances for magnetic sensing would be a large improvement to bulkier traditional magnetometers. In the conducted study, different magnetostrictive materials are implemented in distributed optical fiber sensors to analyze and compare the effective sensitivity and potential commercial viability. Nickel, galfenol alloy, and MetGlas alloy inclusions are drawn into fused silica optical fibers with Bragg gratings inscribed later on for DAS capability. Each was investigated for its response to varying AC magnetic fields to determine relative sensitivity and resolution for distributed magnetic field sensing.
- Effect of Kaolin clay, Planting Dates, and Color Mulches on Summer Tomato Production in the Eastern Shore of VirginiaGandini Taveras, Ricardo Jose (Virginia Tech, 2024-04-15)As climate change exacerbates heat stress during the summer season, it becomes increasingly critical to develop effective strategies to safeguard the productivity of tomato plants (Solanum Lycopersicon L.). This research delves into the tools and techniques aimed at enhancing the cultivation of summer tomatoes in the coastal region of Virginia. The study explores the optimization of transplant dates, the implementation of reflective mulches, and the application of kaolin clay particle films. Field trials spanning two seasons were carried out, comparing different planting dates in May, June, and July, as well as the use of reflective, black, and white plastic mulches, both with and without foliar kaolin sprays. The findings of this study underscore the impact of transplanting tomatoes in May, demonstrating a substantial increase in yields when compared to transplanting in June and July. Reflective mulches enhanced plant height and fruit production relative to the conventional black plastic mulch. The combination of kaolin clay sprays with standard black mulch, resulting in yield increases of over 35%, rivaling the outcomes achieved with reflective and white mulch treatments. The application of kaolin did not significantly affect leaf-level physiological processes. These results highlight the significant potential of strategic early planting and the adoption of emerging heat mitigation technologies, such as kaolin clay films, in sustaining and enhancing the productivity of summer tomatoes. This becomes particularly relevant as growing conditions continue to evolve due to rising temperatures and the increasing extremity of weather events resulting from climate change.