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Acoustics, Dynamics, and Controls Commons™

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Old Dominion University

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Articles 31 - 33 of 33

Full-Text Articles in Acoustics, Dynamics, and Controls

Underwater Acoustic Wavefront Phase Fluctuations, George L. Vojtech Jr. Jan 1984

Underwater Acoustic Wavefront Phase Fluctuations, George L. Vojtech Jr.

OES Theses and Dissertations

In conventional underwater acoustics sound propagation is generally modeled and applied as a coherent or incoherent process. This paper addresses a relatively new theory, that of a range driven increasingly incoherent ray propagation through a real ocean environment, Possible mechanisms are discussed and experimental data presented to reinforce the theory.


Sound Absorption In N2-H2O Gas Mixtures At Elevated Temperatures, Roger W. Meredith Dec 1980

Sound Absorption In N2-H2O Gas Mixtures At Elevated Temperatures, Roger W. Meredith

Physics Theses & Dissertations

Sound absorption measurements were conducted in N2 -H2O gas mixtures at 297, 343, and 387 Kelvin to determine the location of the vibrational relaxation peak of nitrogen on the frequency/pressure, (f/P), axis as a function of humidity and temperature. At low humidities the best fit of the data is to a linear relationship between (f/P)max and humidity (h) yields a slope of 1 .84 X 104 Hz/ atm mole fraction at all three temperatures. The slope is the same as that reported by Zuckerwar and Griffin (2.00 X 104 Hz/atm mole fraction) but is …


Finite Element Model Of A Timoshenko Beam With Structural Damping, Louis Ablen Roussos Jan 1980

Finite Element Model Of A Timoshenko Beam With Structural Damping, Louis Ablen Roussos

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical integration technique, a modified version of the Newmark method, is applied to transient motion problems of systems with mass, stiffness, and small nonlinear damping. The nonlinearity is cast as a pseudo-force to avoid repeated recalculation and decomposition of the effective stiffness matrix; thus, the solution technique is dubbed the "pseudo-force Newmark method." Comparisons with exact and perturbation solutions in single-degree-of-freedom problems and with a Gear-method numerical solution in a cantilevered Timoshenko beam finite element problem show the solution technique to be efficient, accurate, and, thus, feasible provided the nonlinear damping is small. As a preliminary step into the …