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자기압력식 측심기와 음향 측심기를 이용한 측심방법에 관한 연구
김도명(Do-Myeong Kim),박성진(Seong-Jin Park),서재민(Jae-Min Seo),황두진(Doo-Jin Hwang) 전남대학교 어업기술연구소 2013 어업기술연구소보고지 Vol.6 No.1
This study uses two types of sounders; echo sounders (PI-32) and magnetic pressure sounders (TDR-minilog), which are widely used at the moment. Comparing depth sounding methods and values of both types of machines, this study identifies effective use of each type of sounders. This study was conducted in East China Sea at 26th of June, 2010. Data that came from the total six (6) stations of depth sounding were used. To check the depth of water using both sounders simultaneously and verify that both sounders appropriately show the depth of water where objects were located, this study was carried out with FMT (Framed Midwater Trawl) that has a square shape with 2 m length and 2 m width, A magnetic pressure sounder was installed on the top of FMT while an echo sounder is attached on the bottom of FMT. It was expected that the difference was 2 m that was the same as the height of FMT. The experiment shows that a magnetic pressure sounder only displays measured data after hauling a net although it more accurately measures the depth of water than a echo sounder while extracting an object from the depth of water desired. On the other hand, an echo sounder has fluctuation of depth sounding values due to irregular signal reception although it has an automatic function to control a net with real-time information. This study finds that combination of two types of sounder can obtain more accurate depth sounding values as advantages and disadvantages of both sounders are very different, though a magnetic pressure sounder provides more accurate depth than an echo sounder.
윤은아(Eun-A Yoon),타카노 아유미(Ayumi Takano),이민우(Min-Woo Lee),최슬기(Seul-Gi Choi),황두진(Do-Jin Hwang) 전남대학교 어업기술연구소 2014 어업기술연구소보고지 Vol.7 No.1
The global warming increased the temperature on the sea surface and consequently, jellyfish numbers rapidly have been increasing. Especially toxic Nemopilema nomurai increased in our coast and gave a lot of damage. To reduce damage, we have to know of distribution the biomass of the jellyfish. In recent years, to identify biomass distribution of the jellyfish, acoustic technology has been extensively used. This acoustic assessment is required for precise estimate of target strength (TS) of a jellyfish. Among methods to estimate TS, theoretical scattering model method is generally dependent on the sound speed contrast (h) and density contrast (g) of jellyfish. So, we measured sound-speed contrast and density contrast of the large jellyfish Nemopilema nomurai. This experiment was carried out by separating umbrella and oralarm. The sound-speed contrast was measured by using the time-of-flight method and the density contrast was measured by using volume-mass method. The measured sound-speed contrast varied between 0.9977 and 1.0027 (mean 1.0005) in umbrella and between 0.9957 and 1.0014 (mean 0.9985) in oralarm. The measured density contrast varied between 0.9878 and 0.9981 (mean 0.9930) in umbrella and between 1.0029 and 1.0060 (mean 1.0044) in oralarm. There was a difference in sound speed contrast and density contrast of umbrella and oralarm of Nemopilema nomurai.