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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Results of the first two seasons of underwater surveys at Episkopi Bay and Akrotiri, Cyprus

Leidwanger, Justin Ryan 14 March 2013 (has links)
During the summers of 2003 and 2004, a small team of graduate students initiated an underwater archaeological survey off the coast of Cyprus as part of the University of Cincinnati excavations at Episkopi-Bamboula. With the support of the Institute of Nautical Archaeology (INA) at Texas A&M University and RPM Nautical Foundation, the project explored the seabed south and west of the Akrotiri Peninsula at Episkopi Bay. The overall aim of this ongoing diachronic survey is to determine the extent and nature of maritime contacts at Episkopi-Bamboula and its Greco-Roman successor, Kourion, from the Bronze Age through the Byzantine period. Efforts during these first two seasons concentrated on simple visual inspection of several promising areas near dangerous cliffs, offshore rocks and shallow reefs, as well as potential harbors and anchorages. The team recorded substantial pottery and anchor assemblages at Dreamer?s Bay, Cape Zevgari, and Avdimou Bay, including at least three shipwreck sites. Throughout the area, amphoras and anchors attest to varying levels of maritime activity over the past three millennia.The underwater material record reveals a modest level of Classical trade, followed by a respectable increase during the Hellenistic era. While very little material thus far can be attributed to the earlier Imperial centuries, the greatest quantities in terms of both individual sherds and coherent assemblages speaks strongly to intense trade during the Late Roman (Early Byzantine) period, from the fourth through the seventh century. Not surprisingly, this rapid floruit in maritime trade parallels the expansion of settlement throughout the island, including its eventual collapse in the middle of the seventh century.
52

Software defined acoustic underwater modem

Lindgren, Jakob January 2011 (has links)
Today many types of communication are employed on seagoing vessels, such as radio, satellite and Wi-Fi but only one type of communication is practical for submerged vessels, the acoustic underwater modem. The "off-the-shelf" modems are sometimes difficult to update and replace, especially on a large submarine. But by separating the hardware from the signal processing and making the software modular more versatility can be achieved.   The questions that this thesis are asking are: is it possible to implement the signal processing in software? How small or large should the modules be? What kind of architecture should be used? This thesis shows that it is indeed possible to implement simple algorithms that can isolate a signal and read its content regardless of the hardware configuration. Calculations show that up to 13 kbps can be reached at a range of one kilometer. It is most practical to make the entire physical layer into one module and the size of the system could drastically change the type of architecture used.
53

Distributed Underwater Sonar

Meesangphrao, Ukrit January 2011 (has links)
This thesis is focused on possibility of constructing distributed underwater sonar which has an ability to increase or decrease number of sensor elements without any modification on its hardware. Each sonar module works individually. Its synchronization and communication between modules and the image processing unit are archived by using CAN protocol. This new design concept gives several advantages over conventional design.Only one prototype was made, but several modules must be combined in the actual application. The discussion about a complete system can be found in the future work section.The project composes of two main parts: design and building a prototype. The testing procedure and result of both parts are described and summarized with a conclusion.
54

Coherent Reflection of Acoustic Plane Wave From a Random Sea floor

Shen, Chien-Ou 09 August 2001 (has links)
The problem of coherent reflecton of an acoustic plane wave from a random seabed consisting of a randomly inhomogeneous sediment layer overlying a uniform elastic sea floor is considered in this analysis. The random perturbation in the sediment layer is attributable to the sound-speed variations, resulting in volume scattering due to medium inhomogenieties. An approach based upon perturbation theory, combining with a derived Green's function for a slab bounded above and below respectively by a fluid and an elastic half space ,is employed to obtain an analytic solution for the coherent field in the sediment layer. A linear system is then constructed to facilitate the analysis of the coherent reflection field. The results of the coherent reflection coefficient for various sediment randomness, frequency , sediment thickness, and sea floor elasticity have been numerically generated and analyzed. It was found that the higher/larger size of randomness , frequency, thickness, and shear-wave speed, the lower the coherent reflection. Physical interpretation for the characteristics of various results were provided.
55

Condition auditing and repair of marine concrete structures in Hong Kong

Lai, Tsan-kei. January 2001 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references.
56

A theoretical and experimental study on multiple scattering from bubbles, with emphasis on scattering from a bubble located close to the air-sea interface /

Kapodistrias, Georgios. January 2001 (has links)
Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 75-80).
57

Tail separation and density effects on the underwater trajectory of the JDAM

Bushnell, Jillene Marie. January 2009 (has links) (PDF)
Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Chu, Peter. Second Reader: Almquist, Brian "December 2009." Description based on title screen as viewed on February 02, 2010. Author(s) subject terms: Hydrodynamic, STRIKE35, Joint Direct Attack Munition (JDAM), Mine Countermeasure (MCM), mine, improvised explosive device (IED), numerical modeling, Stand-off Assault Breaching Weapon Fuze Improvement (SOABWFI). Includes bibliographical references (p. 69-71). Also available in print.
58

Comparison of channel equalization filtering techniquies in underwater acoustic communications /

Kuchler, Ryan J. January 2002 (has links) (PDF)
Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Charles W. Therrien, Kevin B. Smith. Includes bibliographical references (p. 147-149). Also available online.
59

Underwater acoustic backscatter from a model of Arctic ice open leads and pressure ridges

Browne, Michael Joseph. January 1987 (has links) (PDF)
Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, June 1987. / Thesis Advisor(s): Medwin, Herman. Second Reader: Bourke, Robert H. "June 1987." Description based on title screen as viewed on March 16, 2010. DTIC Identifier(s): Mode conversion. Author(s) subject terms: Underwater Acoustics, Arctic Ice, Backscatter, Mode Conversion, Diffraction. Includes bibliographical references (p. 156-157). Also available in print.
60

Construction and testing of low noise Hydrophones /

Bakas, Konstantinos. January 2004 (has links) (PDF)
Thesis (M.S. in Applied Physics)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Thomas J. Hofler, Bruce Denardo. Includes bibliographical references (p. 57). Also available online.

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