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Browsing by Author "Phillips, Jonathan"

Now showing 1 - 2 of 2
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    Hybrid Composites Based on Carbon Fiber/Carbon Nanofilament Reinforcement
    Tehrani, Mehran; Yari Boroujeni, Ayoub; Luhrs, Claudia; Phillips, Jonathan; Al-Haik, Marwan S. (MDPI, 2014-05-28)
    Carbon nanofilament and nanotubes (CNTs) have shown promise for enhancing the mechanical properties of fiber-reinforced composites (FRPs) and imparting multi-functionalities to them. While direct mixing of carbon nanofilaments with the polymer matrix in FRPs has several drawbacks, a high volume of uniform nanofilaments can be directly grown on fiber surfaces prior to composite fabrication. This study demonstrates the ability to create carbon nanofilaments on the surface of carbon fibers employing a synthesis method, graphitic structures by design (GSD), in which carbon structures are grown from fuel mixtures using nickel particles as the catalyst. The synthesis technique is proven feasible to grow nanofilament structures—from ethylene mixtures at 550 °C—on commercial polyacrylonitrile (PAN)-based carbon fibers. Raman spectroscopy and electron microscopy were employed to characterize the surface-grown carbon species. For comparison purposes, a catalytic chemical vapor deposition (CCVD) technique was also utilized to grow multiwall CNTs (MWCNTs) on carbon fiber yarns. The mechanical characterization showed that composites using the GSD-grown carbon nanofilaments outperform those using the CCVD-grown CNTs in terms of stiffness and tensile strength. The results suggest that further optimization of the GSD growth time, patterning and thermal shield coating of the carbon fibers is required to fully materialize the potential benefits of the GSD technique.
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    A Review and Prospects on the Use of Unmanned Aerial Systems (UAS) in Precision Agriculture for the Mid-Atlantic United States
    Thompson, Aaron Scott (Virginia Tech, 2024-11-14)
    This case study is a comprehensive evaluation of the level of adoption for precision agriculture Unmanned Aerial Systems, (UAS) in farming activities in the Mid-Atlantic United States. For context, the Federal Aviation Administration (FAA) defines Unmanned Aircraft Systems (UAS) as an aircraft that is operated without the possibility of direct human intervention from within or on the aircraft. The term UAS encompasses the unmanned aircraft (UA) (commonly referred to as drones), the controller on the ground, and the communication link between them. This system allows for the operation and navigation of unmanned aircraft. Since the turn of the 19th Century, industrialized agriculture has advanced globally at a rate that is hard to imagine. This advancement has been highly accelerated since the dawn of the digital era. Part of that digital technology advancement has come in the form of UAS. UAS provide a scalable technology platform to accomplish improved efficiency for individual agricultural work functions such as crop/herd monitoring and precision spraying solutions. This case study assesses the integration levels of agricultural UAS operations, specifically within smaller farms, orchards, and vineyards, across the Mid-Atlantic compared to the rest of the United States. The primary objective of the study is to evaluate the extent to which UAS integration in the Mid-Atlantic United States has been effective, as well as to identify barriers that have caused Mid-Atlantic UAS implementation rates to be lower than those of the Western United States. Using qualitative in-field interviews and quantitative data analysis, the study examines the effect of UAS technology on crop/herd management, pest management, irrigation management, and overall farm productivity. Finally, this case study examines the financial impact of incorporating agricultural UAS into the average-sized Mid-Atlantic farm versus maintaining standard practices. The analysis compares outcomes when hiring a drone service versus purchasing and implementing a drone program internally. Economic implications of drones on net-profit and expenses for a representative 200-acre soybean farm are projected utilizing a University of Tennessee enterprise budget (Appendix A) and RStudio visualizations (Appendix B). The study also examines legal and regulatory components around drones utilized in agriculture, such as airspace restrictions, data/general privacy, and Federal Aviation Administration (FAA) policy compliance. This case study revealed practical contributions of drone technology for Mid-Atlantic agriculture allowing farmers, policy makers and other stakeholders to make informed decisions about the uses and expansion of UAS in agricultural operations.