| Project/Area Number |
04554031
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
地質学一般
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| Research Institution | Shimane University |
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Principal Investigator |
TOKUOKA Takao Professor.Department of Geology.Faculity of Science.Shimane Univ., 理学部, 教授 (30025358)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIMURA Kiyokazu Senior Res.Geological Survey of Japan, 海洋調査部, 主任研究官
ANMA Kei Director Kawasaki Geological Engineering Co.Ltd., 海洋調査部, 部長
TUCHIYA Youichi Director Senbon Denki Co.Ltd., 技術部, 部長
TAKAYASU Katsumi Professor.Research Center for Coastal Lagoon Environment.Shimane Univ., 汽水域研究センター, 教授 (00127490)
三瓶 良和 島根大学, 理学部, 助手 (00226086)
大西 郁夫 島根大学, 理学部, 教授 (40032445)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥17,500,000 (Direct Cost: ¥17,500,000)
Fiscal Year 1993: ¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 1992: ¥14,500,000 (Direct Cost: ¥14,500,000)
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| Keywords | acoustic impedance / wedge-like saline layr / Lakes Nakaumi and Shinji / echo-sounding / 汽水域 / ヘドロ / 塩分躍層 / 中海 / 浚渫 |
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| Research Abstract |
In brackish lakes it is well known that sea water is overlain by fresh water. Their mutual boundary, which is recognized as the boundary of the haloline, sometimes appears on echo-sounding records. These phenomena are caused by the rapid change of acoustic impedance at the boundary of saline and fresh water, and has been termed the deep scattering layr (D.S.L.). The project to analyze this boundary using more sensitive echo-sounding equipment has been performed. This component was made by modification of a 200 kHz precision echo-sounder (Model 101, Senbon Denki Co., Ltd.). The receiving circuit was modified to use straight amplifiers to maintain the linearity and accuracy of signals. In addition, the recieving circuit was equipped with signal output for digital recording. The recorder consists of a 12 bit higt-speed A/D converter at 1MHz sampling and an EXABYTE tape drive using 8 mm tape (max.2.2GByte). Clear reflector in Lake Nakaumi could be observed in water about 6 m in depth with additinal refletors, correspoudig to changes in water quality, particularly changes in salinity. The newly developed underwater acoustic profiler equipped with a digital recorder can contribute much in understanding many phenomena of brackish lakes.
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