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  • Fisheries
  • Fishery policy
  • Industrial Chemistry
  • Inorganic Chemistry
  • Seismology
  • Victoria: Seychelles Fishing Authority  (4)
  • Acoustical Society of America  (2)
  • Am. Meteor. Soc.
  • 2005-2009  (6)
  • 1950-1954  (1)
  • 1
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    Acoustical Society of America
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2007. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 122 (2007): 777-785, doi:10.1121/1.2751268.
    Description: A highly efficient frequency-controlled sound source based on a tunable high-Q underwater acoustic resonator is described. The required spectrum width was achieved by transmitting a linear frequency-modulated signal and simultaneously tuning the resonance frequency, keeping the sound source in resonance at the instantaneous frequency of the signal transmitted. Such sound sources have applications in ocean-acoustic tomography and deep-penetration seismic tomography. Mathematical analysis and numerical simulation show the Helmholtz resonator's ability for instant resonant frequency switching and quick adjustment of its resonant frequency to the instantaneous frequency signal. The concept of a quick frequency adjustment filter is considered. The discussion includes the simplest lumped resonant source as well as the complicated distributed system of a tunable organ pipe. A numerical model of the tunable organ pipe is shown to have a form similar to a transmission line segment. This provides a general form for the principal results, which can be applied to tunable resonators of a different physical nature. The numerical simulation shows that the “state-switched” concept also works in the high-Q tunable organ pipe, and the speed of frequency sweeping in a high-Q tunable organ pipe is analyzed. The simulation results were applied to a projector design for ocean-acoustic tomography.
    Description: The work was supported by ONR.
    Keywords: Acoustic generators ; Underwater sound ; Acoustic resonators ; Oceanographic equipment ; Seismology
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © Acoustical Society of America, 2008. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 123 (2008): 667-678, doi:10.1121/1.2821975.
    Description: This paper introduces a perturbative inversion algorithm for determining sea floor acoustic properties, which uses modal amplitudes as input data. Perturbative inverse methods have been used in the past to estimate bottom acoustic properties in sediments, but up to this point these methods have used only the modal eigenvalues as input data. As with previous perturbative inversion methods, the one developed in this paper solves the nonlinear inverse problem using a series of approximate, linear steps. Examples of the method applied to synthetic and experimental data are provided to demonstrate the method's feasibility. Finally, it is shown that modal eigenvalue and amplitude perturbation can be combined into a single inversion algorithm that uses all of the potentially available modal data.
    Description: Funding for the research presented here was provided by the Office of Naval Research, and the WHOI Academic Programs Office.
    Keywords: Geophysical techniques ; Inverse problems ; Sediments ; Seismology
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Victoria: Seychelles Fishing Authority
    Publication Date: 2021-05-19
    Description: Seychelles is composed of over 100 islands with a land area of approximately 455 km², centred close to 4°30'S and 55°30'E. The combined coastline is approximately 600 km long, the oceanic shelf totals about 50 000 km² and the Exclusive Economic Zone (EEZ) is over 1 370 000 km². The total population (1994 census) stands at just under 74 000. in 1994, the population registered a growth rate of 2.2%. The GDP (1994) was SR 2373.8 million, fisheries representing 4.8% of this sum. Licensing agreements for foreign fishing activities provided a yearly revenue of SR8 million. Port Victoria is seen as a prime centre for tuna fishing operations in the Indian Ocean. In the artisanal fishery just under 900 persons are working. The largest contributor to catch by vessel type are the traditional whaler vessels representing 47.8% of the total catch. Over 66.3% of the catch is by the handline method. Carangidae representing 24% and Lutjanidae 19% of total landings. There are six specific objectives to the fisheries sector policy, which aims as resource development and maximisation of potential benefits. Nearshore fishery resources are considered to be heavily exploited, however opportunities exist around the distant islands and in deeper waters off the Mahe plateau shelf. Aquaculture of molluscs and prawns is being developed and carried out. The main constraints to development are seen as the lack of skilled manpower and foreign exchange.
    Description: Published
    Keywords: Country profile ; Fisheries ; Seychelles ; Statistics ; Fisheries ; Fishery statistics
    Repository Name: AquaDocs
    Type: Report , Non-Refereed
    Format: 186058 bytes
    Format: 520444 bytes
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    Format: 19
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  • 4
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    Victoria: Seychelles Fishing Authority | Victoria
    Publication Date: 2021-08-09
    Description: Published
    Description: Industrial tuna fishing
    Keywords: Tuna ; Fisheries ; Fishery economics ; Fishery industry ; Fishery statistics ; Tuna fisheries
    Repository Name: AquaDocs
    Type: Report , Non-Refereed
    Format: 1589602 bytes
    Format: application/pdf
    Format: 28
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  • 5
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    Victoria: Seychelles Fishing Authority
    Publication Date: 2021-01-30
    Description: Published
    Keywords: Fishery statistics ; Fishery policy ; Fishing vessels statistics
    Repository Name: AquaDocs
    Type: Book , Non-Refereed
    Format: 1946882 bytes
    Format: application/pdf
    Format: 64
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  • 6
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    Victoria: Seychelles Fishing Authority
    Publication Date: 2021-05-19
    Description: Published
    Keywords: Fishery economics ; Fishery policy ; Bilateral agreements
    Repository Name: AquaDocs
    Type: Proceedings Paper , Non-Refereed
    Format: 121780 bytes
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  • 7
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    Am. Meteor. Soc.
    In:  Professional Paper, Compendium of Meteorology, Dover, 439 pp., Am. Meteor. Soc., vol. 7, no. XVI:, pp. 1303-1311, (ISBN: 3-540-23712-7)
    Publication Date: 1951
    Keywords: Micro seismicity ; Seismology ; NOISE
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