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Articles 121 - 125 of 125

Full-Text Articles in Acoustics, Dynamics, and Controls

Study Of Single-Fiber Fiber Optic Lever Microphone, Trung Duc Nguyen Jul 1993

Study Of Single-Fiber Fiber Optic Lever Microphone, Trung Duc Nguyen

Electrical & Computer Engineering Theses & Dissertations

Fiber optic sensors are widely used in today's technological applications, providing many advantages that conventional sensors lack. In particular, there is a demand in hypersonic applications to develop microphones to measure acoustic pressure that performs in high temperature and noisy surroundings. This thesis analyzes fiber optic lever microphones (FOLM), since they perform at high temperatures. An FOLM system is an intensity modulated sensor, which is simple to implement and is small in size. Two models of the FOLM have been fabricated and calibrated. The first model uses a seven-element fiber array while the second uses a single-fiber to transmit and …

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Second Coefficient Of Viscosity In Air, Robert L. Ash, Allan J. Zuckerwar, Zhonquan Zheng Jan 1991

Second Coefficient Of Viscosity In Air, Robert L. Ash, Allan J. Zuckerwar, Zhonquan Zheng

Mechanical & Aerospace Engineering Faculty Publications

Acoustic attenuation measurements in air were analyzed in order to estimate the second coefficient of viscosity. Data over a temperature range of 11 C to 50 C and at relative humidities between 6 percent and 91 percent were used. This analysis showed that the second coefficient of viscosity varied between 1900 and 20,000 times larger than the dynamic or first coefficient of viscosity over the temperature and humidity range of the data. In addition, the data showed that the molecular relaxation effects, which are responsible for the magnitude of the second coefficient of viscosity, place severe limits on the use …

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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.

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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 …

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Making Beats Visible, Carl J. Ulrich Jan 1944

Making Beats Visible, Carl J. Ulrich

Journal of the Minnesota Academy of Science

No abstract provided.

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