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Browsing by Author "Hill, Cary"

Now showing 1 - 2 of 2
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    Microwave Processing of Polymeric Coatings for Guitar Woods
    Hammond, Chase; Hill, Cary; Sprinkle, Charles; Sorenson, Andrew; Vera, Stalin (Virginia Tech Department of Materials Science and Engineering, 2010-03-20)
    Microwave energy was used to cure polymer coatings on instrument-grade wood. A processing method was developed that included spray coating the polymer onto raw wood panels and pulling the coated panels through a 2.45GHz multi-mode microwave cavity by means of a low-power motor. Materials characterization and testing used to analyze the feasibility of using microwave processing as a coating method for guitar woods included dielectric property measurements, moisture content measurements, density measurements, and scanning electron microscopy (SEM). Also, vibrational analysis was used to compare the damping characteristics of each coating method, providing further basis for analyzing the feasibility. A comparison was conducted between samples created using the ultraviolet curing method currently used by Taylor Guitar Co. and the microwave samples generated in this study. The results demonstrate that the microwave processing of polymeric coatings for guitar woods is feasible and produces beneficial results. SEM imaging shows enhanced interaction between the polymer and wood in the microwaved samples, which may create a stronger and more durable coating. Vibration testing shows microwave processing produced comparable damping results at half the coating thickness. This decreased coating thickness may lead to a more completely cured polymer, cost savings, and reduce emission during curing.
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    Single Mode Air-Clad Single Crystal Sapphire Optical Fiber
    Hill, Cary; Homa, Daniel S.; Yu, Zhihao; Cheng, Yujie; Liu, Bo; Wang, Anbo; Pickrell, Gary R. (MDPI, 2017-05-03)
    The observation of single mode propagation in an air-clad single crystal sapphire optical fiber at wavelengths at and above 783 nm is presented for the first time. A high-temperature wet acid etching method was used to reduce the diameter of a 10 cm length of commercially-sourced sapphire fiber from 125 micrometers to 6.5 micrometers, and far-field imaging provided modal information at intervals as the fiber diameter decreased. Modal volume was shown to decrease with decreasing diameter, and single mode behavior was observed at the minimum diameter achieved. While weakly-guiding approximations are generally inaccurate for low modal volume optical fiber with high core-cladding refractive index disparity, consistency between these approximations and experimental results was observed when the effective numerical aperture was measured and substituted for the theoretical numerical aperture in weakly-guiding approximation calculations. With the demonstration of very low modal volume in sapphire at fiber diameters much larger than anticipated by legacy calculations, the resolution of sapphire fiber distributed sensors may be increased and other sensing schemes requiring very low modal volume, such as fiber Bragg gratings, may be realized in extreme environment applications.