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You searched for subject:(Wave directionality). Showing records 1 – 3 of 3 total matches.

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NSYSU

1. Chien, Kuo-feng. Ambient Noise Analysis of Internal Wave of Sand Dune Region in North South China Sea.

Degree: Master, Institute of Undersea Technology, 2016, NSYSU

In recent years, internal wave of North South China Sea has become an important ocean research topic. The tidal energy from Luzon Ridge formed a huge nonlinear internal wave in deep ocean. This event dropped water column dramatically, the maximum isotherm downward shift can be 15.9 meters at 200 meter water depth in our observation. During the propagation of internal wave, the convergence of surface water can form a significant breaking wave strip with loud noise. Data used in this research came from Sand Dunes project of South China Sea of June 2014. Experimental site was located in sand dune region of upper continental slope of North South China Sea. When internal wave passed, strong current caused turbulence and strumming noises due to the existence of mooring structure. The correlation coefficient between breaking wave noise enhancement and amplitude of internal wave is 0.7. However, if measurement location was close to sea bed or sand dune region, the correlation would be declined. Multiple correlation shows that background noise would limit breaking wave noise contribution, and coefficient of determination among internal wave amplitude, noise enhancement and background noise level can be as high as 0.9. In the past, some researches suggested that noise notch might be related to internal wave, but acoustical mode coupling of internal wave might on the other hand diminish the notch. According to analysis of vertical directionality in this research, the energy of breaking wave noise of internal wave was not enough to form noise notch, and mode coupling may also prevent the formation of noise notch. Advisors/Committee Members: Linus Y.S. Chiu (chair), Shiuh-Kuang Yang (chair), Ruey-Chang Wei (committee member).

Subjects/Keywords: North South China Sea; Internal Wave; Sand Dune; Breaking Wave Noise; Multiple Correlation; Vertical Directionality; Noise Notch

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

APA (6th Edition):

Chien, K. (2016). Ambient Noise Analysis of Internal Wave of Sand Dune Region in North South China Sea. (Thesis). NSYSU. Retrieved from http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1010116-105312

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):

Chien, Kuo-feng. “Ambient Noise Analysis of Internal Wave of Sand Dune Region in North South China Sea.” 2016. Thesis, NSYSU. Accessed October 14, 2019. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1010116-105312.

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

MLA Handbook (7th Edition):

Chien, Kuo-feng. “Ambient Noise Analysis of Internal Wave of Sand Dune Region in North South China Sea.” 2016. Web. 14 Oct 2019.

Vancouver:

Chien K. Ambient Noise Analysis of Internal Wave of Sand Dune Region in North South China Sea. [Internet] [Thesis]. NSYSU; 2016. [cited 2019 Oct 14]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1010116-105312.

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

Council of Science Editors:

Chien K. Ambient Noise Analysis of Internal Wave of Sand Dune Region in North South China Sea. [Thesis]. NSYSU; 2016. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1010116-105312

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


Georgia Tech

2. Narisetti, Raj K. Wave propagation in nonlinear periodic structures.

Degree: PhD, Aerospace Engineering, 2010, Georgia Tech

A periodic structure consists of spatially repeating unit cells. From man-made multi-span bridges to naturally occurring atomic lattices, periodic structures are ubiquitous. The periodicity can be exploited to generate frequency bands within which elastic wave propagation is impeded. A limitation to the linear periodic structure is that the filtering properties depend only on the structural design and periodicity which implies that the dispersion characteristics are fixed unless the overall structure or the periodicity is altered. The current research focuses on wave propagation in nonlinear periodic structures to explore tunability in filtering properties such as bandgaps, cut-off frequencies and response directionality. The first part of the research documents amplitude-dependent dispersion properties of weakly nonlinear periodic media through a general perturbation approach. The perturbation approach allows closed-form estimation of the effects of weak nonlinearities on wave propagation. Variation in bandstructure and bandgaps lead to tunable filtering and directional behavior. The latter is due to anisotropy in nonlinear interaction that generates low response regions, or "dead zones," within the structure.The general perturbation approach developed has also been applied to evaluate dispersion in a complex nonlinear periodic structure which is discretized using Finite Elements. The second part of the research focuses on wave dispersion in strongly nonlinear periodic structures which includes pre-compressed granular media as an example. Plane wave dispersion is studied through the harmonic balance method and it is shown that the cut-off frequencies and bandgaps vary significantly with wave amplitude. Acoustic wave beaming phenomenon is also observed in pre-compressed two-dimensional hexagonally packed granular media. Numerical simulations of wave propagation in finite lattices also demonstrated amplitude-dependent bandstructures and directional behavior so far observed. Advisors/Committee Members: Massimo, Ruzzene (Committee Chair), Leamy, Michael (Committee Co-Chair), Bauchau, Olivier (Committee Member), Ferri, Aldo (Committee Member), Lieuwen, Timothy Charles (Committee Member).

Subjects/Keywords: Nonlinear wave propagation; Amplitude dependent dispersion; Nonlinear finite element dispersion; Nonlinear periodic structures; Strongly nonlinear chains; Granular media; Wave directionality; Amplitude dependent wave beaming; Nonlinear wave equations; Wave motion, Theory of; Nonlinear theories

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

APA (6th Edition):

Narisetti, R. K. (2010). Wave propagation in nonlinear periodic structures. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/39643

Chicago Manual of Style (16th Edition):

Narisetti, Raj K. “Wave propagation in nonlinear periodic structures.” 2010. Doctoral Dissertation, Georgia Tech. Accessed October 14, 2019. http://hdl.handle.net/1853/39643.

MLA Handbook (7th Edition):

Narisetti, Raj K. “Wave propagation in nonlinear periodic structures.” 2010. Web. 14 Oct 2019.

Vancouver:

Narisetti RK. Wave propagation in nonlinear periodic structures. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2019 Oct 14]. Available from: http://hdl.handle.net/1853/39643.

Council of Science Editors:

Narisetti RK. Wave propagation in nonlinear periodic structures. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/39643


Georgia Tech

3. Jeong, Sang Min. Analysis of Vibration of 2-D Periodic Cellular Structures.

Degree: PhD, Aerospace Engineering, 2005, Georgia Tech

The vibration of and wave propagation in periodic cellular structures are analyzed. Cellular structures exhibit a number of desirable multifunctional properties, which make them attractive in a variety of engineering applications. These include ultra-light structures, thermal and acoustic insulators, and impact amelioration systems, among others. Cellular structures with deterministic architecture can be considered as example of periodic structures. Periodic structures feature unique wave propagation characteristics, whereby elastic waves propagate only in specific frequency bands, known as "pass band", while they are attenuated in all other frequency bands, known as "stop bands". Such dynamic properties are here exploited to provide cellular structures with the capability of behaving as directional, pass-band mechanical filters, thus complementing their well documented multifunctional characteristics. This work presents a methodology for the analysis of the dynamic behavior of periodic cellular structures, which allows the evaluation of location and spectral width of propagation and attenuation regions. The filtering characteristics are tested and demonstrated for structures of various geometry and topology, including cylindrical grid-like structures, Kagom and eacute; and tetrhedral truss core lattices. Experimental investigations is done on a 2-D lattice manufactured out of aluminum. The complete wave field of the specimen at various frequencies is measured using a Scanning Laser Doppler Vibrometer (SLDV). Experimental results show good agreement with the methodology and computational tools developed in this work. The results demonstrate how wave propagation characteristics are defined by cell geometry and configuration. Numerical and experimental results show the potential of periodic cellular structures as mechanical filters and/or isolators of vibrations. Advisors/Committee Members: Ruzzene, Massimo (Committee Chair), Cunefare, Ken (Committee Member), Hanagud, Sathyanaraya (Committee Member), Hodges, Dewey (Committee Member), Jacobs, Laurence (Committee Member).

Subjects/Keywords: Grid-like structures; Periodic lattices; Directionality; Mechanical pass-band filters; Phononic band-gaps; Structural frames Vibration; Wave-motion, Theory of; Grillages (Structural engineering) Vibration; Space frame structures Vibration

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

APA (6th Edition):

Jeong, S. M. (2005). Analysis of Vibration of 2-D Periodic Cellular Structures. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/7122

Chicago Manual of Style (16th Edition):

Jeong, Sang Min. “Analysis of Vibration of 2-D Periodic Cellular Structures.” 2005. Doctoral Dissertation, Georgia Tech. Accessed October 14, 2019. http://hdl.handle.net/1853/7122.

MLA Handbook (7th Edition):

Jeong, Sang Min. “Analysis of Vibration of 2-D Periodic Cellular Structures.” 2005. Web. 14 Oct 2019.

Vancouver:

Jeong SM. Analysis of Vibration of 2-D Periodic Cellular Structures. [Internet] [Doctoral dissertation]. Georgia Tech; 2005. [cited 2019 Oct 14]. Available from: http://hdl.handle.net/1853/7122.

Council of Science Editors:

Jeong SM. Analysis of Vibration of 2-D Periodic Cellular Structures. [Doctoral Dissertation]. Georgia Tech; 2005. Available from: http://hdl.handle.net/1853/7122

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