Physics

Turbulent flow over homogeneous canopies with gaps of various lengths - The fluid flow within a canopy of uniform, densely packed elements containing a gap of various lengths was measured using planar particle image velocimetry. The model was submerged within a water channel in an open channel configuration with a flow depth three times the height of the canopy. The canopy included a gap which measured 0.5, 1, 2, 3, or 4 times the canopy height. The Reynolds number based on the submergence depth of the flow was found to be 12,600. Based on mean flow quantifications and turbulence statistics, the flow within the gap was found to fall into two regimes based on the ratio of the gap length to gap height. For the short gap regime, the shear layer at the top of the gap does not experience vertical growth and therefore the turbulence does not penetrate into the gap; however, for the long gap regime, the shear layer experiences significant vertical growth and enhances mixing within the gap. When compared to a solid cavity, significant differences are found in the behavior of the shear layer that develops at the top of the gap. Finally, a fluctuating velocity cross-correlation was performed to analyze the structure of vortices across the top of the canopy and over the canopy gap and additional differences were noted in the development of vortical structures over the gap when compared to the solid cavity.; Isothermal Crystallization of Poly(Vinyl Alcohol-co Ethylene) - Isothermal crystallization of the copolymer Poly(Vinyl Alcohol-co-Ethylene) was studied, with an ethylene content of 27%. Using a differential scanning calorimeter (DSC), the copolymer was crystallized between 160 and 180 degrees C. The crystallization kinetics were analyzed using the Avrami and Hoffman-Weeks methods. The overall morphology and crystal growth were determined from fitting parameters.; Rutherford Backscattering Spectrometry of Lead-Iron Diffusion - Accurate constraints of the diffusion closure temperature in radioisotope thermal-chronometers of early Solar System allow for greater accuracy in the dating of rocky bodies. These closure temperatures can be estimated based on the composition and geometry of the body, along with information about the diffusion coefficient and activation energy of the specific radioisotopes inside the body. Thin film diffusion experiments were performed on nine samples of pure iron pellets coated with 100nm of lead. These samples were subjected to heating at either 600°C for up to ten days, or 750°C for up to twenty-three hours, allowing for sufficient diffusion of the coating into the medium. The diffused samples were analysed at the University of Albany Ion Beam Laboratory using Rutherford Backscattering spectrometry (RBS). RBS spectra were processed using SIMNRA, an ion beam analysis program for Windows, to generate concentration profiles of the diffused lead. These profiles were fit to the thin-film solution to Fick's Second Law linear diffusion equation, returning diffusion coefficients for Pb in Fe 600°C and 750°C. Our results give an activation energy of 364±53 kJ/mol, within reason of expected values for diffusion in metals. This information can be used in tandem with other work in this ongoing project.