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Analysis of Tempered Fractional Operators

D'Elia, Marta; Olson, Hayley

Tempered fractional operators are useful in models for subsurface transport and diffusion due to their ability to capture anomalous diffusion: a behavior which the classical partial differential equation models cannot describe. We analyze tempered fractional operators within the nonlocal vector calculus framework in order to assimilate them to the rigorous mathematical structure developed for nonlocal models. First, we show they are special instances of generalized nonlocal operators in correspondence of a proper choice of nonlocal kernels. Then, we work towards showing tempered fractional operators are equivalent to truncated fractional operators. These truncated operators are useful because they are less computationally intensive than the tempered operators.

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TYPE Other Report YEAR 2020
DOIOSTI

Using Raman scattering to study reacting gas flow over a catalyst

Ungar, Alexander

l present a series of computational methods for analyzing and correcting Raman scattering from a reacting gas flow. My work focused on the laser diagnostic measurements of formaldehyde production over a silver catalyst, specifically the Raman spectroscopy component. This technique offers a non-intrusive, in situ way to measure the coupling between the gas phase and surface activity of a catalytic reaction at relevant industrial conditions. This report outlines the steps followed for correcting the non-idealities in the data due to both the detection optics and scattering mechanics. By implementing such refinement steps, l can generate an accurate 2D spatial map of the temperature profile, number densities for major species, and relative consumption of reactants throughout the reactor cell.

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TYPE Other Report YEAR 2020
DOIOSTI

Nanoantenna-Enhanced Resonant Detectors for Improved Infrared Detector Performance

Goldflam, Michael; Anderson, Evan M.; Fortune, Torben; Klem, John F.; Hawkins, Samuel D.; Davids, Paul; Campione, Salvatore; Pung, Aaron J.; Webster, Preston; Weiner, Phillip; Finnegan, Patrick S.; Wendt, Joel; Wood, Michael G.; Haines, Chris; Coon, Wesley; Olesberg, Jonathon T.; Shaner, Eric A.; Kadlec, Clark N.; Foulk, James W.; Sinclair, Michael B.; Tauke-Pedretti, Anna; Kim, Jin K.; Peters, David

Abstract not provided.

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TYPE Conference Poster YEAR 2020
OSTI

Propagation of a Stress Pulse in a Heterogeneous Elastic Bar

Silling, Stewart

The propagation of a wave pulse due to low-speed impact on a one-dimensional, heterogeneous bar is studied. Due to the dispersive character of the medium, the pulse attenuates as it propagates. This attenuation is studied over propagation distances that are much longer than the size of the microstructure. A homogenized peridynamic material model can be calibrated to reproduce the attenuation and spreading of the wave. The calibration consists of matching the dispersion curve for the heterogeneous material in the limit of long and moderately long wavelengths. It is demonstrated that the peridynamic method reproduces the attenuation of wave pulses predicted by an exact microstructural model over large propagation distances.

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TYPE SAND Report YEAR 2020
DOIOSTI
Results 16201–16300 of 99,299
Results 16201–16300 of 99,299