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You searched for +publisher:"Penn State University" +contributor:("Diane Marie Henderson, Outside Member"). Showing records 1 – 2 of 2 total matches.

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Penn State University

1. Nichols, Stephen Matthew. Properties of Low Frequency Underwater Ambient Noise in the Ocean Sound Channel.

Degree: 2017, Penn State University

In the ocean sound channel, where sounds are known to propagate great distances, the ambient noise field is a dynamic mixture of many distinct noise sources. This work is focused on identifying predictable properties of the low frequency (<100 Hz) noise field and improving the capabilities of hydroacoustic systems for sensing and monitoring geophysical, biologic, and anthropogenic activity. In this dissertation, three unique analyses of the properties of ambient noise are examined. First, the composition of an ambient noise field is assessed, by identifying sets of characteristic spectra. Three proposed methods for identifying these spectrum sets are: spectrum correlation matrix sorting, manual replica selection, and Principal Component Analysis. The characteristic spectra identified by each of these techniques are then used to reconstruct an approximation of the measured noise field. The accuracy of each of these methods for reconstructing the measured noise field is assessed by comparing the frequency correlation matrices of the measured and reconstructed noise fields, which characterize the dominant frequency behavior within a dataset, helping to identify the dominant source mechanisms. Second, the wind-driven component of the acoustic spectrum below 20 Hz is compared across measurement locations in three different ocean basins. In a 1993 study by McCreery et al., the authors proposed that the spectrum of wind-driven noise below 5 Hz should follow a characteristic -23 dB/octave slope, which should be constant across all measurement locations, because of its purely geophysical driving mechanism. In testing this hypothesis, the current work identifies strong similarities between the spectra measured at various sites, though small, basin-dependent spectral features arise due to the local seafloor configuration. Lastly, the angular dependence of the apparent sound speed measured by a receiver array is examined. For an array that is small relative to the source distance, the arrival angle and propagation speed of a signal can be computed by assuming that it can be approximated as a plane wave, and comparing the acoustic arrival time differences. In general, it is expected that the sound speed in water should be isotropic, ignoring any effects of local currents and refraction. However, if the sensor coordinates used to derive the arrival angle and sound speed are incorrect, the resulting sound speeds will strongly depend on the source arrival angle. The current work identifies the form of the angular sound speed dependence for incorrect sensor locations, which is subsequently used to estimate the correct distances between sensors in the array. This procedure is further developed to attempt to identify relative motion of the moored hydrophones within local tidal currents. The data used in this study comes from three stations of the Comprehensive nuclear-Test Ban Treaty Organization’s (CTBTO) hydroacoustic monitoring system. These stations have produced multi-year recordings of low frequency ambient noise in the ocean… Advisors/Committee Members: David Bradley, Dissertation Advisor/Co-Advisor, David Bradley, Committee Chair/Co-Chair, Charles Holland, Committee Member, Thomas B Gabrielson, Committee Member, Diane Marie Henderson, Outside Member.

Subjects/Keywords: Ambient noise; CTBTO; Correlation matrices; Array shape estimation

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Nichols, S. M. (2017). Properties of Low Frequency Underwater Ambient Noise in the Ocean Sound Channel. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/13595smn5198

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Nichols, Stephen Matthew. “Properties of Low Frequency Underwater Ambient Noise in the Ocean Sound Channel.” 2017. Thesis, Penn State University. Accessed October 28, 2020. https://submit-etda.libraries.psu.edu/catalog/13595smn5198.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Nichols, Stephen Matthew. “Properties of Low Frequency Underwater Ambient Noise in the Ocean Sound Channel.” 2017. Web. 28 Oct 2020.

Vancouver:

Nichols SM. Properties of Low Frequency Underwater Ambient Noise in the Ocean Sound Channel. [Internet] [Thesis]. Penn State University; 2017. [cited 2020 Oct 28]. Available from: https://submit-etda.libraries.psu.edu/catalog/13595smn5198.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Nichols SM. Properties of Low Frequency Underwater Ambient Noise in the Ocean Sound Channel. [Thesis]. Penn State University; 2017. Available from: https://submit-etda.libraries.psu.edu/catalog/13595smn5198

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Penn State University

2. Swaminathan, Anand. Experimental Investigation of Dynamic Stabilization of the Rayleigh-Bénard Instability by Acceleration Modulation.

Degree: 2017, Penn State University

This dissertation presents the results of an experimental investigation of the parametric stabilization of Rayleigh-Bénard convection through the imposition of vibration. It has been theorized for many years that vibration could be employed to suppress natural convection, in an analogous manner to the Kapitza pendulum. The ability to dynamically stabilize Rayleigh-Bénard convection using acceleration modulation is of interest to groups who design and study thermoacoustic machines, as the introduction of parasitic convection can have deleterious effects on the desired operation and efficiency of the device. These performance issues caused by suspected convective instability have been seen both in traveling wave thermoacoustic refrigerators and in cryogenic pulse tube chillers. This dissertation reports the results of an experiment intended to determine the vibratory, fluidic, and geometric conditions under which a small, rectangular container of statically unstable fluid may be stabilized by vertical vibration, incorporating the computational methods of R. M. Carbo [J. Acoust. Soc. Am. 135(2), 654–668 (2014)]. Measurements are obtained using a large-displacement kinematic shaker of an original design with the convecting gas characterized using both thermal transport measurements and flow visualization employing tracer particles illuminated by a diode laser light sheet phase-locked to the shaker. These experiments are believed to be the first demonstrating the suppression of convection through vibration in rectangular containers of macroscopic scale. Advisors/Committee Members: Steven L. Garrett, Dissertation Advisor/Co-Advisor, Steven L. Garrett, Committee Chair/Co-Chair, Robert M. Keolian, Committee Member, Victor Ward Sparrow, Committee Member, Diane Marie Henderson, Outside Member, Robert William Smith, Special Member.

Subjects/Keywords: Thermoacoustics; Acoustics; Rayleigh-Bénard convection; Pulse tube cryocooler; Parametric stabilization

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Swaminathan, A. (2017). Experimental Investigation of Dynamic Stabilization of the Rayleigh-Bénard Instability by Acceleration Modulation. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/14553azs5363

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Swaminathan, Anand. “Experimental Investigation of Dynamic Stabilization of the Rayleigh-Bénard Instability by Acceleration Modulation.” 2017. Thesis, Penn State University. Accessed October 28, 2020. https://submit-etda.libraries.psu.edu/catalog/14553azs5363.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Swaminathan, Anand. “Experimental Investigation of Dynamic Stabilization of the Rayleigh-Bénard Instability by Acceleration Modulation.” 2017. Web. 28 Oct 2020.

Vancouver:

Swaminathan A. Experimental Investigation of Dynamic Stabilization of the Rayleigh-Bénard Instability by Acceleration Modulation. [Internet] [Thesis]. Penn State University; 2017. [cited 2020 Oct 28]. Available from: https://submit-etda.libraries.psu.edu/catalog/14553azs5363.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Swaminathan A. Experimental Investigation of Dynamic Stabilization of the Rayleigh-Bénard Instability by Acceleration Modulation. [Thesis]. Penn State University; 2017. Available from: https://submit-etda.libraries.psu.edu/catalog/14553azs5363

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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