살오징어 (Todarodes pacifica)의 음향 반사강도 측정

강돈혁 ( Don Hyug Kang ),황두진 ( Doo Jin Hwang ),이경훈 ( Kyoung Hoon Lee ),( Tohru Mukai ),( Kohji IIDA ) 한국수산과학회 2004 한국수산과학회지 Vol.37 No.4

N/A Target strength (TS) of Japanese common squids (Todarodes pacificus) were measured using 38 and 120 kHz split beam scientific echosounders under the live condition. For the TS measurement of an individual, a total of 3 squids (mantle length (ML): 22.8, 25, and 27 cm) were used using small fishhook method, whereas for measurement of swimming angle, a total of 8 squids (ML: 21-27 cm) were used under live condition, confined with net cage with 2 m diameter. At the same time, two underwater video cameras enabled continuous monitoring of squid behavior. Considering normal behavior, the mean TS at 38 and 120 kHz varied from -48.6 to -45.9 dB, and from -46.5 to -44.6 dB, respectively. In both frequencies, mean TS at 120 kHz is relatively higher than that of 38 kHz, approximately 1.3-2.5 dB. From free living condition, the mean swimming angle of the squids was -24˚ The results of the measurement will be provided basic information for conducting acoustic surveys of the squid.

남극 남쉐틀란드 군도 북부 해역의 크릴 분포 및 자원량

강돈혁(Don Hyug Kang),황두진(Doo Jin Hwang),김수암(Su Am Kim) 한국수산과학회 1999 한국수산과학회지 Vol.32 No.6

To estimate biomass and distribution of the Antarctic krill (Euphausia Superba), hydroacoustic survey was conducted on board of R/V Yuzhmorgeologiya, which was chartered by Korea Antarctic Research Program (KARP) group from 18 to 21 December 1998, in the northern part of the South Shetland Islands, Antarctic Ocean. The scientific echo sounder (towing body type) used was EK-500 (SIMRAD, Norway) with echo integrator (BI-500) at 38 ㎑ frequency and recorded mean backscattering cross-section coefficient (SA) per 1 mile² of sea surface. Also, Bongo net sampling was carried out to determine the size of krill and CTD (Conductivity, Temperature and Depth) casting to understand physical structure. Water column was divided into 5 lsyers (22∼65 m, 65∼ 115 m, 115∼165 m, 165∼215 m and 215∼315 m) to know vertical distribution of krill biomass. The standard length of krill collected was between 30 ㎜ and 51 ㎜, and adult krill had single mode (41 ㎜). Maximum horizontal length of krill patch was about 35 nautical mile and vertical thickness was about 275 m. High density of krill was appeared in frontal area between Circumpolar Deep Water(>1℃) and very low temperature water mass(<-0.5℃) that originate from Weddell Sea. According to the results calculated using target strength equation, krill density was totally higher in continental slope and open water areas than in coastal area. In the study area, krill seems to distribute in depth; density was low at first layer (ρ￣=17.0 g/㎡) and higher at fourth layer (ρ￣=40.19 g/㎡). The estimated krill biomass at total survey area and water column was about 2.77 million metric ton (ρ￣=151.0 g/㎡) and coefficient of variance (CV, %) was 19.92. The proortions and biomass of krill biomass at each layer were as follows; layer 1(11.3%, 0.31 million metric ton, CV=16.24), layer 2 (13.3%, 0.37 million metric ton, CV=34.91), layer 3 (23.7%, 0.66 million metric ton, CV=41,5), layer 4 (26.6%, 0.74 million metric ton, CV=27.84) and layer 5 (25%, 0.69 million metric ton, CV= 26.83).

수산음향기법을 이용한 아산만 멸치(Engraulis japonicus)와 기타어군의 분포 및 현존량 추정

이형빈 ( Hyung Been Lee ),강돈혁 ( Don Hyug Kang ),임양재 ( Yang Jae Im ),이경훈 ( Kyoung Hoon Lee ) 한국수산과학회 2014 한국수산과학회지 Vol.47 No.5

The distribution and abundance of coastal fish species in Asan Bay, Korea, were estimated from hydroacoustic survey and net catches. Acoustic data were collected with 38 and 200 kHz from July to October of 2012, and converted to the nautical area scattering coefficient (NASC, m2/mile2) for 0.25 n·mile along ten transects. Japanese anchovy Engraulis japonicus was the dominant specie in the net catches. The virtual echogram technique was used to distinguish E. ja-ponicus from other species based on the differences in the mean volume backscattering strength (△MVBS) at 38 and 200 kHz. Engraulis japonicus and other fishes are mainly distributed in the center channel and outer part of Asan Bay. E. japonicus tends to move from inner to outer Asan Bay in summer and fall. From NASC data, the target strength and length-weight function of E. japonicus and other fishes were used to estimate the E. japonicus stock at 24.1-93.3 tons, and other fish at 40.6-88.4 tons from July to October 2012. The estimated anchovy biomass compared well with the cumulative catch weight from stow net catches. The hydroacoustic method offers an approach to understanding spatial/temporal structure and estimating the biomass of fish aggregations in coastal areas.

다중 주파수를 이용한 캐비테이션 기포의 분포량 추정

김대욱,나형술,최지웅,나정열,강돈혁,Kim, Dae-Uk,La, Hyoung-Sul,Choi, Jee-Woong,Na, Jung-Yul,Kang, Don-Hyug 한국음향학회 2009 韓國音響學會誌 Vol.28 No.3

캐비테이션 기포 (cavitation bubble)가 존재하는 유체 내에서 다중 주파수 (multi-frequency)를 송수신할 때 음파의 감쇠(attenuation)와 음속 (sound speed) 변화가 발생되었고, 이 특징을 이용하여 기포의 크기와 분포량을 추정하였다. 음향실험은 $20{\sim}300\;kHz$ 대역의 다중 주파수를 이용하여 실시하였고, 기포가 존재하는 경우와 존재하지 않는 경우의 주파수별 음속 비와 음파의 감쇠 값을 측정하였다. 캐비테이션 기포는 모터 끝에 장착된 둥근 막대형 블레이드 (blade)를 물 속에서 고속회전시켜 발생되었다. 캐비테이션 기포의 크기 및 분포량은 모터의 회전 속도, 블레이드 끝단 (tip)의 겉넓이를 변화시키며 관측하였고, 기포 생성 후 시간별 기포량 감소율을 측정하였다. 실험 결과 발생된 기포의 크기는 반경 $10{\sim}60{\mu}m$였고, $10{\sim}20{\mu}m$와 $20{\sim}30{\mu}m$ 반경의 기포가 전체의 약 45%와 25%를 차지하였다. 세부실험 결과로 모터의 회전 속도가 증가할수록 더 많은 양의 기포가 발생되지만 블레이드 끝단 면적의 증가와 기포 발생량의 변화는 상관성이 없음을 확인하였다. 또한 기포량의 감소율은 지속시간별로 일정하였고, 2분 이내에 전체량의 80%가 소멸됨을 관측하였다. 음향실험의 결과를 검증하기 위해 동일한 조건에서 광학카메라로 촬영한 기포 분포량과 비교하였다. Distribution of cavitation bubbles relative to change of the sound speed and attenuation in the water was estimated using acoustic signal from 20 to 300 kHz in two cases that cavitation bubbles exist and do not exist. To study generation and extinction property of cavitation bubble, bubble distribution was estimated in three cases: change of rotation speed (3000-4000 rpm), surface area of blade ($32-98\;mm^2$) and elapsed time (30-120 sec). As a result, the radii of the generated bubbles ranged from 10 to $60{\mu}m$, and bubble radius of $10-20{\mu}m$ and $20-30{\mu}m$ was accounted for 45 and 25% of the total number of cavitation bubbles, respectively. And generation bubble population correlated closely with the rotating speed of the blades but did not correlate with the surface area of blade. It was observed that 80% of total bubble population disappeared within 2 minutes. Finally, acoustic data of bubble distribution was compared with optical data.

2002년 하계 동중국해에 있어서 음향을 이용한 어족자원분포에 관한 연구

황두진(Doo jin HWANG),강돈혁(Don hyug KANG),김용주(Yong ju KIM),신형호(Hyeong ho SHIN),윤양호(Yang ho YOON) 전남대학교 수산과학연구소 2003 수산과학연구소논문집 Vol.12 No.-

This study adopts the marine environment research in 2002 for preservation and management of the ecosystem and fishery resources of the East China Sea. We carried out bottom trawl and acoustic survey from July 4 to 10 in 2002. During the survey, a total of 9 locations were towed along with hydroacoustic transect lines, intervals of which were about 30 ㎚ latitudinal, covering areas of 30˚ 30’ ~ 33˚ .00’ N and 123˚ 45’ ~ 120˚ E. We have been obtained giographical distribution of fisheries resources by the EK-500 echo sounder system. The high density were observed along the north-western part of the East China Sea, the volume backscattering coefficient of which were from -55㏈ to -53㏈. The serival dominant fish of which were common mackerel (Scomber japonicus), Yellowfin horse mackerel (Trachurus japonicus), and Squid.

음향조사에 의한 황해 주요어족생물의 분포특성에 관한 연구

황두진 ( Doo Jin Hwang ),신형호 ( Hyong Ho Shin ),강돈혁 ( Don Hyug Kang ) 한국어업기술학회 2002 수산해양기술연구 Vol.38 No.2

ADCP 를 이용한 남극 크릴 분포에 관한 연구

김수암,강돈혁 한국수산자원학회 1998 한국수산자원학회지 Vol.1 No.1

Current information, hsing 153.6-kHz downward looking Acoustic Doppler Current Profilers(ADCP), was collected around the South Shetland Islands and Elephant Island areas, Antarctica, onboard R/V Yuzhmorgeologiya, which was chatered by US NOAA A ntarctic Marine Living Resources Group in austral summer 1996/97. The ADCP recorded current speed and direction as well as the backscattered echo intensity caused by biological organisms which comprised mainly of zooplankton, especially Antarctic krill. Combining these echo data with the simultaneous current profiles the vertical and horizontal distribution patterns of Antarctic krill were shown over the upper 150m. By applying some parameters such as echo intensity, transmission loss, absorption coefficient, sound speed, and temperature conversion factors to sonar equation, mean volume backscattering strength(Sv) was calculated. With the prior scientific results that the scatters in Antarctic Ocean were predominately krill, the values of Sv were calculated at 3 layers of the scatterer. According to the results calculated major krill concentration appeared between 100m and 150m depth at the northern area of the Elephant Island. Also krill formed swarms at small area occasionally,e.g., south of Elephant Island and north of King George Island . Comparing ADCP data with those from scientific fish finder (SIMRAD,EK-500) collected by US NOAA scientists, both results reveal similar patterns of krill distribution at below 100m depth along 55° transect in the study area. Additionally, in general, current direction looked very complex showing eddy-like pattern and instantaneous speed was a relatively high magnitude near the Elephant Island. Between Elephant Island and South Shetland Islands, the current flew to northwest at all layers.