995 resultados para Defense Technical Information Center (U.S.)
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"Results from a search of the technical report database over a 10-year period ... references cover only unclassified, unlimited document references with abstracts."
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Caption title.
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"Sample."
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"Results from a search of the technical report database over a 10-year period ... references cover only unclassified, unlimited document references with abstracts."
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"Results from a search of the technical report database over a 10-year period ... references cover only unclassified, unlimited document references with abstracts."
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"Results from a search of the technical report database over a 10-year period ... references cover only unclassified, unlimited document references with abstracts."
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"Results from a search of the technical report database over a 10-year period ... references cover only unclassified, unlimited document references with abstracts."
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"Supersedes DLAH 4185.8, 17 May 88"--1st prelim. p.
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"January 1987."
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.
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Mid-frequency active (MFA) sonar emits pulses of sound from an underwater transmitter to help determine the size, distance, and speed of objects. The sound waves bounce off objects and reflect back to underwater acoustic receivers as an echo. MFA sonar has been used since World War II, and the Navy indicates it is the only reliable way to track submarines, especially more recently designed submarines that operate more quietly, making them more difficult to detect. Scientists have asserted that sonar may harm certain marine mammals under certain conditions, especially beaked whales. Depending on the exposure, they believe that sonar may damage the ears of the mammals, causing hemorrhaging and/or disorientation. The Navy agrees that the sonar may harm some marine mammals, but says it has taken protective measures so that animals are not harmed. (PDF contains 20 pages)