Doctoral Dissertations

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  • Modeling Flotation from First Principles Using the Hydrophobic Force as a Kinetic Parameter
    Gupta, Mohit (Virginia Tech, 2024-03-15)
    Flotation is regarded as the best available separation method for the recovery of valuable minerals such as chalcopyrite (CuFeS2), sphalerite (ZnS), etc., from mined ores. Practically all metals humans use today are produced by flotation. The process relies on controlling the stability of the thin liquid films (TLFs) of water formed between minerals and air bubbles (wetting film), air bubbles (foam film), and mineral particles (colloid films). In flotation, a desired mineral is rendered hydrophobic by surfactant coating as a means to destabilize the TLFs, so that they can be attached to the hydrophobic air bubbles. A TLF ruptures when the disjoining pressure (or surface forces per unit area) of the film becomes negative, i.e., Π < 0. Thermodynamically, a wetting film can rupture when the contact angle (θ) of a mineral surface is larger than zero. It would, therefore, be reasonable to consider the roles of the surface forces to better understand the fundamental mechanisms involved in flotation. The surface forces considered in the present work included the electric double layer (EDL), van der Waals (vdW), and attractive hydrophobic (HP) forces. A flotation model has been developed by using the hydrophobic force as a kinetic parameter, which made it possible to track the fates of mineral particles of different of size, surface liberation, and contact angle to predict both recovery and grades for the first time. The model has been validated against the plant survey data obtained from an operating copper flotation plant. The simulation results obtained using the first principles model have been utilized to address the limitations of current flotation practices. One such limitation is the presence of slow-floating target minerals present in the cleaner-scavenger tails (CST) that are routinely recycled back to the rougher flotation bank as circulating loads (CLs) to allow longer retention times for the slow-floating particles for additional recovery. The simulation results show also that opening a flotation circuit by treating the CST streams separately in an advanced circuit can substantially improve the plant performance. One of the major limitations of flotation is that the coarse particles in a feed stream are difficult to recover due to the low hydrophobicity associated with poor surface liberation. A new flotation model developed in the present work suggests various ways to address the problem. One is to increase the hydrophobicity of the composite (poorly liberated) particles using the Super Collectors that can increase the contact angles to 150 -170o. Simulation results obtained using the model developed in the present work show significant financial benefits of using Super Collectors. Flotation is controlled by surface forces as noted above. As particle size becomes larger than 150 µm, however, the gravitational force comes into the picture and can override the surface forces. A new flotation cell has been developed to mitigate the effects of the extraneous force by decreasing the effective specific gravity (SG) by attaching air bubbles to facilitate levitation and by creating a pulsation to allow particles to move according to SGs independent of particle size, which should help increase the upper particle size limit of flotation. Surface forces in foam and oil-in-water emulsion films have been measured at different temperatures to determine the changes in thermodynamic properties of the thin liquid films (TLFs) of water confined between two bubbles and two oil drops. The results show that the films are destabilized by the attractive hydrophobic forces created during the course of building H-bonded structures in confined spaces, which entails decreases in enthalpy (H < 0) and entropy (TS < 0), the second term representing the thermodynamic cost of building the structures.
  • Supplementation Strategies for Growing and Finishing Beef Cattle on Tall Fescue Pastures in the Southeast
    Murray, Adam Riley (Virginia Tech, 2024-03-15)
    While the Southeastern U.S. does not produce cereal grains at the same output as Midwestern states, a relatively temperate climate and consistent rainfall allow for abundant forage production. Tall fescue dominated pastures in this region provide a high-quality forage source to support consistent cattle growth and production. Furthermore, the nearly year-round grazing potential serves as a cost-effective feed source. Leveraging forage resources is imperative for the U.S. beef industry to maintain consistent production of a quality human protein source at a consumer-friendly price, but energy content in purely forage diets is lacking to produce comparable growth and carcass performance to concentrate-based diets. Therefore, the objectives of this dissertation are to examine supplementation strategies for growing and finishing cattle in fescue-based systems in the Southeast to optimize value for cattle producers. The first experiment investigated whether steer performance and grazing behavior was affected by supplement feeding time and delivery method in a forage-based backgrounding program. Traditionally, producers choosing to supplement backgrounding cattle with grain or coproduct feeds do so in a single meal event in the early morning. It has been hypothesized that these morning feedings could disrupt the natural diurnal grazing pattern of cattle to negatively affect forage utilization and overall cost of gain. Additionally, while self-feeder systems using supplements containing intake limiters give producers an option to reduce feeding labor compared to daily hand-fed supplementation, alternate methods of supplement delivery also have the potential to influence grazing behavior and cost of gain within backgrounding programs. This experiment used backgrounding steers supplemented daily at 0930 (AM), steers supplemented daily at 1330 (PM), and steers provided supplement through a self-feeder (SELF) to provide cattle performance and economic data directly relevant to regional producers. Combined 2-yr results show that while AM, PM, and SELF cattle all exhibited altered grazing routines, treatments did not result in differences (P ≥ 0.18) in final body weight (BW), average daily gain (ADG), ultrasound 12th rib fat thickness (uFT), or overall forage mass disappearance. Dry matter intake (DMI) in the SELF treatment exceeded the target despite inclusion of intake limiters, resulting in increased (P < 0.01) supplement DMI, a tendency (P = 0.07) towards decreased G:F, and substantially greater (P < 0.01) cost of gain in SELF relative to the hand-fed treatments. Results support that producers have flexibility in scheduling daily supplementation routines without compromising steer performance in pasture-based backgrounding programs. Furthermore, producers should consider the tradeoff between labor efficiency and ration cost when considering utilizing self-feeders containing intake limiters. The second experiment investigated the effects of frame size and supplementation containing a rumen protected fat (RPF) on growth performance and carcass characteristics of pasture finished cattle. Market dynamics continue to favor cattle that produce heavier carcasses, which discounts smaller framed feeder calves at sale barns. At the same time, Virginia is flush with cow-calf production, high quality tall fescue pastures, and access to population dense areas with markets that incentivize pasture-finished beef through price premiums. Together, this provides an alternative marketing channel for smaller framed calves through pasture-finished beef markets, but questions remain on how to optimally produce this specialty beef. Supplemental feeds can increase cattle production on pasture, and RPF offer a feeding strategy to increase energy intake without negatively effecting ruminal fiber digestion. There is limited work investigating the application of RPF within beef cattle systems and carcass traits, and it is unclear if RPF has been utilized specifically within pasture finishing systems. Therefore, this experiment examined growth performance, carcass characteristics, and organoleptic qualities of beef from small-framed (SM) and medium-framed (MED) cattle on novel endophyte-infected fescue pasture finishing systems either offered no supplement (NON) or daily supplementation (SUP) containing RPF. Pasture treatments were compared relative to a grain-fed feedlot control (F) to show these cattle had the genetic merit to meet expectations of the U.S. fed-beef system. Results from this 2-yr experiment indicate that frame size had little impact on growth performance, with SM and MED cattle having similar (P ≥ 0.37) final BW, ADG, and forage DMI in this pasture finishing system. However, MED cattle produced more valuable carcasses compared to SM cattle as evident by greater (P ≤ 0.04) mean HCW, 12th rib fat thickness, and marbling score. Samples of M. longissimus thoracis from MED cattle also had greater (P ≤ 0.02) concentrations of 14:0, 16:0, 18:0, 18:1, and 18:2 fatty acids compared to samples from SM cattle. While NON cattle produced carcasses with a lower (P = 0.01) yield grade than SUP cattle, overall, SUP cattle were more productive by both live and carcass metrics. The SUP treatment produced greater (P ≤ 0.04) final BW, ADG, 12th rib fat thickness, HCW, marbling score, dressing percentage, and concentrations of 14:0, 16:0, 18:0, 18:1, and 18:2 fatty acids. Similarity (P = 0.55) in objective measures of meat tenderness between F and pasture treatments emphasizes the importance of harvesting cattle before 2 years of age to prevent declines in meat tenderness associated with advancement of connective tissue. There tended (P = 0.05) to be a frame by supplement interaction for marbling score driven by lower values in SM-NON in relation to other pasture treatments. Tendencies towards frame by supplement interactions for Warner-Bratzler shear force (P = 0.08) and total energy (P = 0.06) were also driven by increased values in SM-NON relative to other pasture treatments. Taken together, a lack fat deposition in SM-NON cattle appears to have a negative impact on beef tenderness relative to pasture treatments. Overall results of this experiment support low levels of supplementation in pasture-finishing systems to improve carcass value, and that medium framed cattle are more flexible in profit margins compared to smaller framed counterparts. Collectively, these investigations support that tall fescue grazing systems in the Southeast can serve as a nutritional foundation to beef cattle growing and finishing enterprises. Data from these experiments can be directly applied to help producers match cattle type to feed resources when supplementing a pasture-based system to optimize resource management and overall profitability.
  • Optimal Design and Control of Multibody Systems with Friction
    Verulkar, Adwait Dhananjay (Virginia Tech, 2024-03-15)
    In practical multibody systems, various factors such as friction, joint clearances, and external events play a significant role and can greatly influence the optimal design of the system and its controller. This research focuses on the use of gradient-based optimization methods for multibody dynamic systems with the incorporation of joint friction. The dynamic formulation has been derived in using two distinct techniques: Index-1 DAE and the tangent-space formulation in minimal coordinates. It employs a two different approaches for gradient computation: direct sensitivity approach and the adjoint sensitivity approach. After a comprehensive review of different friction models developed over time, the Brown McPhee model is selected as the most suitable due to its accuracy in dynamic simulations and its compatibility with sensitivity analysis. The proposed methodology supports the simultaneous optimization of both the system and its controller. Moreover, the sensitivities obtained using these formulations have been thoroughly validated for numerical accuracy and benchmarked against other friction models that are based on dynamic events for stiction to friction transition. The approach presented is particularly valuable in applications like robotics and servo-mechanical systems where the design and actuation are closely interconnected. To obtain numerical results, a new implementation of the MBSVT (Multi-Body Systems at Virginia Tech) software package, known as MBSVT 2.0, is reprogrammed in Julia and MATLAB to ensure ease of implementation while maintaining high computational efficiency. The research includes multiple case studies that illustrate the advantages of the concurrent optimization of design and control for specific applications. Efficient techniques for control signal parameterization are presented using linear basis functions. A special focus has been made on the computational efficiency of the formulation and various techniques like sparse-matrix algebra and Jacobian-free products have been employed in the implementation. The dissertation concludes with a summary of key results and contributions and the future scope for this research.
  • Perceptions of How Middle School Teachers Utilize Culturally Competent Pedagogy and Practice for Positive Student, Family, and Peer Relationships
    Frye, Kisha Tiala (Virginia Tech, 2024-03-15)
    The purpose of this study was to identify the strategies that middle school teachers utilize when incorporating culturally responsive pedagogy and practices to build positive relationships with students and families while building and maintaining positive student-peer relationships in the classroom. This qualitative study design, conducted in an urban public-school division in central Virginia, employed a teacher interview protocol questionnaire featuring open-ended questions. The primary objective was to investigate how middle school teachers utilize and incorporate culturally responsive pedagogical practices to build and maintain positive relationships with students, families, and peers. The resulting findings indicated teachers established cultural awareness and diversity to build and maintain relationships, communicated effectively through conferencing and discussions with their students, and communicated effectively through emails and in-person with their students' families. Teachers used multiple communication strategies for parent involvement, such as phone calls, text messages, emails, conferences, and social media. Students sharing life experiences during discussion helped them understand the material and establish classroom culture and diversity. Thus, implications indicated school divisions and building administrators should continually participate in cultural competence training, provide teachers with professional development to establish regular and consistent communication channels with students' families to build positive relationships, provide teachers with professional development to implement culturally responsive pedagogy, provide time for teachers to incorporate open-ended questions and alternative perspectives into lessons to stimulate critical thinking, and building-level administrators should foster a school culture that embraces diverse values by establishing and consistently reinforcing clear expectations of respect for all students and adults.
  • Process/Structure/Property Relationships of Semi-Crystalline Polymers in Material Extrusion Additive Manufacturing
    Lin, Yifeng (Virginia Tech, 2024-03-14)
    Material Extrusion additive manufacturing (MEX) represents the most widely implemented form of additive manufacturing due to its high performance-cost ratio and robustness. Being an extrusion process in its essence, this process enables the free form fabrication of a wide range of thermoplastic materials. However, in most typical MEX processes, only amorphous polymers are being used as feedstock material owing to their smaller dimensional shrinkage during cooling and well-stablished process/structure/property (P/S/P) relationship. Semi-crystalline polymers, with their crystalline nature, possess unique properties such as enhanced mechanical properties and improved chemical resistance. However, due to the inherent processing challenges in MEX of semi-crystalline polymers, the P/S/P relationships are much less established, thus limits the application of semi-crystalline polymers in MEX. The overall aim of this thesis is to advance the understanding of P/S/P relationship of semi-crystalline polymers in MEX. This is accomplished through both experimental and simulation-based research. With a typical commodity semi-crystalline polymer, Poly (ethylene terephthalate) (PET), selected as the benchmark material. First, we experimentally explored the MEX printing of both neat and glass fiber (GF) reinforced recycled PET (rPET). Excellent MEX printability were shown for both neat and composite materials, with GF reinforced parts showing a significant improved mechanical property. Notably, a gradient of crystallinity induced by a different toolpathing time was highlighted. In the second project, to further investigate the impact of MEX parameter on crystallinity and mechanical properties, a series of benchmark parts were printed with neat PET and analyzed. The effect of part design and MEX parameter on thermal history during printing was revealed though a comparative analysis of IR thermography. Subsequent Raman spectroscopy and mechanical test indicated that crystallinity developed during the MEX process can adversely affects the interlayer adhesion. In the third project, a 3D heat transfer model was developed to simulate and understand the thermal history of MEX feedstock material during printing, this model is then thoroughly validated against the experimental IR thermography data. While good prediction accuracy was shown for some scenarios, the research identified and discussed several unreported challenges that significantly affect the model's prediction performance in certain conditions. In the fourth project, we employed a non-isothermal crystallization model to directly predict the development of crystallinity based on given temperature profiles, whether monitored experimentally or predicted by the heat transfer model. The research documented notable discrepancies between the model's predictions and actual crystallinity measurements, and the potential source of the error was addressed. In summary, this thesis explored the MEX printing of semi-crystalline polymer and its fiber reinforced composite. The influence of MEX parameters and part designs on the printed part's thermal history, crystallinity and mechanical performance was then thoroughly investigated. A heat transfer model and a non-isothermal crystallization model were constructed and employed. With rigorous validation against experimental data, previously unreported challenges in MEX thermal and crystallization modeling was highlighted. Overall, this thesis deepens the understanding of current semi-crystalline polymer's P/S/P relationship in MEX, and offers insights for the optimization and future research in the field of both experiment and simulation of MEX.
  • Traffic Signal Phase and Timing Prediction: A Machine Learning and Controller Logic Hybrid Approach
    Eteifa, Seifeldeen Omar (Virginia Tech, 2024-03-14)
    Green light optimal speed advisory (GLOSA) systems require reliable estimates of signal switching times to improve vehicle energy/fuel efficiency. Deployment of successful infrastructure to vehicle communication requires Signal Phase and Timing (SPaT) messages to be populated with most likely estimates of switching times and confidence levels in these estimates. Obtaining these estimates is difficult for actuated signals where the length of each green indication changes to accommodate varying traffic conditions and pedestrian requests. This dissertation explores the different ways in which predictions can be made for the most likely switching times. Data are gathered from six intersections along the Gallows Road corridor in Northern Virginia. The application of long-short term memory neural networks for obtaining predictions is explored for one of the intersections. Different loss functions are tried for the purpose of prediction and a new loss function is devised. Mean absolute percentage error is found to be the best loss function in the short-term predictions. Mean squared error is the best for long-term predictions and the proposed loss function balances both well. The amount of historical data needed to make a single accurate prediction is assessed. The assessment concludes that the short-term prediction is accurate with only a 3 to 10 second time window in the past as long as the training dataset is large enough. Long term prediction, however, is better with a larger past time window. The robustness of LSTM models to different demand levels is then assessed utilizing the unique scenario created by the COVID-19 pandemic stay-at-home order. The study shows that the models are robust to the changing demands and while regularization does not really affect their robustness, L1 and L2 regularization can improve the overall prediction performance. An ensemble approach is used considering the use of transformers for SPaT prediction for the first time across the six intersections. Transformers are shown to outperform other models including LSTM. The ensemble provides a valuable metric to show the certainty level in each of the predictions through the level of consensus of the models. Finally, a hybrid approach integrating deep learning and controller logic is proposed by predicting actuations separately and using a digital twin to replicate SPaT information. The approach is proven to be the best approach with 58% less mean absolute error than other approaches. Overall, this dissertation provides a holistic methodology for predicting SPaT and the certainty level associated with it tailored to the existing technology and communication needs.
  • Exploring Immersed FEM, Material Design, and Biological Tissue Material Modeling
    Kaudur, Srivatsa Bhat (Virginia Tech, 2024-03-13)
    This thesis utilizes the Immersed Interface Finite Element Method (IIFEM) for shape optimization and material design, while also investigating the modeling and parameterization of lung tissue for Diver Underwater Explosion (UNDEX) simulations. In the first part, a shape optimization scheme utilizing a four-noded rectangular immersed-interface element is presented. This method eliminates the need for interface fitted mesh or mesh morphing, reducing computational costs while maintaining solution accuracy. Analytical design sensitivity analysis is performed to obtain gradients for the optimization formulation, and various parametrization techniques are explored. The effectiveness of the approach is demonstrated through verification and case studies. For material design, the study combines topological shape optimization with IIFEM, providing a computational approach for architecting materials with desired effective properties. Numerical homogenization evaluates effective properties, and level set-based topology optimization evolves boundaries within the unit cell to generate optimal periodic microstructures. The design space is parameterized using radial basis functions, facilitating a gradient-based optimization algorithm for optimal coefficients. The method produces geometries with smooth boundaries and distinct interfaces, demonstrated through numerical examples. The thesis then delves into modeling the mechanical response of lung tissues, particularly focusing on hyperelastic and hyperviscoelastic models. The research adopts a phased approach, emphasizing hyperelastic model parametrization while reserving hyperviscoelastic model parametrization for future studies. Alternative methods are used for parametrization, circumventing direct experimental tests on biological materials. Representative material properties are sourced from literature or refit from existing experimental data, incorporating both empirically derived data and practical values suitable for simulations. Damage parameter quantification relies on asserted quantitative relationships between injury levels and the regions or percentages of affected lung tissue.
  • Training and Preparedness of Teachers to be Evaluated on Culturally Responsive Practices in One Public School Division in Virginia
    Marbury, Kristen Renee (Virginia Tech, 2024-03-12)
    This study was designed to determine if teachers in one public school in Virginia were prepared to be evaluated based on culturally responsive practices (CRP) after completing Virginia Department of Education's (VDOE) Cultural Competency Training Module. This qualitative study sample included eight teachers from a suburban school division. The conceptual framework illustrated the connections between the evaluation of CRP and teacher preparedness after teachers completed VDOE's Cultural Competency Training Module. The research questions that directed this study were: (1) How has Virginia Department of Education's Cultural Competency Training Module prepared teachers to implement culturally responsive practices? (2) To what extent do teachers feel prepared to be evaluated based on culturally responsive practices after completing Virginia Department of Education's Cultural Competency Training Module? The research method included a basic qualitative research design that used interview protocol. Interview prompts were created based on Virginia's Cultural Competency Domains that underpin legislation approved by the 2021 Virginia General Assembly requiring that teacher evaluations include a standard for CRP. Interviews took place during the summer months of 2023 as virtual meetings using the Zoom video conferencing platform. Interview transcriptions were utilized as the data set. As categories and themes emerged, the interconnectedness of data was examined using open coding. The findings of this study revealed that teachers indicated a support for Virginia's Cultural Competency Domains. However, teachers perceived that VDOE's Cultural Competency Training Module did not achieve the desired focus of providing educators with the tools needed to implement CRP. Instead, teachers perceived that their lived experiences framed their individual approach to understand and implement CRP. The implications of the study encouraged VDOE to consider a redesign of the Cultural Competency Training Module. Another implication emphasized the need for school divisions to consider investing in professional trainers to provide deep level culturally competency training in a format that also accounts for the emotional security and comfortability of teachers.
  • A Comprehensive Analysis of Deep Learning for Interference Suppression, Sample and Model Complexity in Wireless Systems
    Oyedare, Taiwo Remilekun (Virginia Tech, 2024-03-12)
    The wireless spectrum is limited and the demand for its use is increasing due to technological advancements in wireless communication, resulting in persistent interference issues. Despite progress in addressing interference, it remains a challenge for effective spectrum usage, particularly in the use of license-free and managed shared bands and other opportunistic spectrum access solutions. Therefore, efficient and interference-resistant spectrum usage schemes are critical. In the past, most interference solutions have relied on avoidance techniques and expert system-based mitigation approaches. Recently, researchers have utilized artificial intelligence/machine learning techniques at the physical (PHY) layer, particularly deep learning, which suppress or compensate for the interfering signal rather than simply avoiding it. In addition, deep learning has been utilized by researchers in recent years to address various difficult problems in wireless communications such as, transmitter classification, interference classification and modulation recognition, amongst others. To this end, this dissertation presents a thorough analysis of deep learning techniques for interference classification and suppression, and it thoroughly examines complexity (sample and model) issues that arise from using deep learning. First, we address the knowledge gap in the literature with respect to the state-of-the-art in deep learning-based interference suppression. To account for the limitations of deep learning-based interference suppression techniques, we discuss several challenges, including lack of interpretability, the stochastic nature of the wireless channel, issues with open set recognition (OSR) and challenges with implementation. We also provide a technical discussion of the prominent deep learning algorithms proposed in the literature and also offer guidelines for their successful implementation. Next, we investigate convolutional neural network (CNN) architectures for interference and transmitter classification tasks. In particular, we utilize a CNN architecture to classify interference, investigate model complexity of CNN architectures for classifying homogeneous and heterogeneous devices and then examine their impact on test accuracy. Next, we explore the issues with sample size and sample quality with regards to the training data in deep learning. In doing this, we also propose a rule-of-thumb for transmitter classification using CNN based on the findings from our sample complexity study. Finally, in cases where interference cannot be avoided, it is important to suppress such interference. To achieve this, we build upon autoencoder work from other fields to design a convolutional neural network (CNN)-based autoencoder model to suppress interference thereby ensuring coexistence of different wireless technologies in both licensed and unlicensed bands.
  • Parkification of Disturbed Landscapes: Uncovering the Process of Transforming Post-Industrial Sites into Urban Parks at Ruseifa, Jordan
    Alrayyan, Kawthar Mazin (Virginia Tech, 2024-03-12)
    In 2020, following over 35 years of abandonment, the local authority of Jordan made a major decision to transform three post-industrial sites simultaneously within Ruseifa city into urban public parks, namely the Pepsi Pond site, the Phosphate Ore Hills site, and the Phosphate Old Mines and Administration Building site. These transformative processes, known as "Parkification," not only represent a significant shift in how post-industrial sites are treated but also reflect an unprecedented approach for these sites in Jordan. Therefore, this dissertation has traced and analyzed the parkification processes integral to this transformation as benchmarks for developing post-industrial sites. To unravel the parkification processes, key drivers behind parkification, and perception of stakeholders and decision-makers towards post-industrial sites in Ruseifa, three research questions were examined: 1) How do decision-makers and other development influences Ruseifa view and treat post-industrial sites in Ruseifa city? 2) What are the parkification processes transforming post-industrial sites into parks in Ruseifa? and 3) What are the compelling issues of post-industrial sites, and how do the parkification processes address them? The research employed a two-phase, multi-method qualitative approach, utilizing several data collection methods. It involved gathering secondary data, conducting site visits and case studies, and conducting semi-structured interviews with key players engaged in the parkification projects at the case study sites. Thematic and content analyses were employed, followed by comparative analysis to conceptualize and analyze the transformation processes. The findings highlighted the unique characteristics of each process, identifying three distinct parkification approaches transforming post-industrial sites in Ruseifa. Key driving factors were uncovered by examining the landscape pattern, mechanism of transformation, dynamic interactions among key players, and varying perceptions involved in the parkification processes. The findings also analyzed the parkification approaches within the decision-making processes, contextualizing them as a tool, strategy, or intention. The study's results contribute to a broader understanding of decision-making processes for developing post-industrial sites in Jordan and their transformation into public parks. It provides a framework to evaluate transformation processes on disturbed sites that can be utilized in improving post-industrial planning and preservation. Moreover, this study adds a valuable contribution to Ruseifa, documenting the transformation process of these parkification projects and shedding light on post-industrial sites and their development in Jordan.
  • Evaluation of Markerless Motion Capture to Assess Physical Exposures During Material Handling Tasks
    Ojelade, Aanuoluwapo Ezekiel (Virginia Tech, 2024-03-12)
    Manual material handling (MMH) tasks are associated with the development of work-related musculoskeletal disorders (WMSDs). Minimizing the frequency and intensity of handling objects is an ideal solution, yet MMH remains an integral part of many industry sectors, including manufacturing, construction, warehousing, and distribution. Physical exposure assessment can help identify high-risk tasks, guide the development and evaluation of ergonomic interventions, and contribute to understanding exposure-risk relationships. Physical exposure can be evaluated using self-assessment, observational methods, and direct measurements. Nevertheless, implementing these methods in situ can be challenging, time consuming, expensive, and infeasible or inaccurate in many cases. Thus, there is a critical need to improve physical exposure assessments to protect workers and save costs. This dissertation assessed the accuracy of a markerless motion capture system (MMC) to quantify physical exposures during MMH tasks using three studies. Specifically, the first study investigated the performance of an MMC system, together with machine learning algorithms, for classifying diverse MMH tasks during a simulated complex job. In the second study, the feasibility of predicting dynamic hand forces was determined, using alternative measures, such as kinematics from MMC and/or in-sole pressure systems, coupled with a machine learning algorithm. Finally, in the third study, we systematically evaluated MMC for assessing biomechanical demands, by comparing outputs from a full-body musculoskeletal model driven by kinematic and kinetics from gold standard input and estimates derived from the MMC and in-sole pressure measurement system. Overall, the findings of these studies demonstrated the potential of using MMC to classify several common occupational tasks and to estimate the associated biomechanical demands for a given worker (automatically and with minimal physical contact). Additionally, the methods developed here can help stakeholders rapidly assess an individual worker's exposure to physical demands during diverse tasks.
  • Differentiating more effective and less effective teachers of elementary-aged, at-risk students
    Smith, Beth Cross (Virginia Polytechnic Institute and State University, 1996)
  • Black parent perceptions of factors which facilitate or inhibit participation in education
    Porter, Miriam Hall (Virginia Polytechnic Institute and State University, 1994)
  • A comparison of staff development programs in two-year colleges with and without formalized staff development plans
    McCall, Michael Baxter (Virginia Polytechnic Institute and State University, 1976)
  • A survey of family therapists concerning the inclusion of young children in family therapy
    Greenwood, Philip Davis (Virginia Polytechnic Institute and State University, 1985)
  • Previous conformity, status and the rejection of the deviant
    Katz, Gary Martin (Virginia Polytechnic Institute and State University, 1976)