• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.269-275
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• 2003

In this paper, We examined auditory threshold and critical ratio of amberjack seriola dumerili, in the Jeju Island coastal waters, to find out hearing ability of the fish. The auditory threshold level, critical ratio and hearing index of amberjack were determinded by conditioning method using a sound coupled with electric shock in the condition of ambient noise or white noise in an experimental water tank. The audio-signals of pure tone and electric shock were from 80 HZ to 800 Hz and DC 7 V, respectively. Values for the critical ratios were calculated in terms of the masked thresholds using the noise projected to stable spectrum levels at all measurement frequencies of background noise. Masking noises were in the spectrum level range of 65 dB∼75 dB $(re 1{\mu}Pa\sqrt{Hz})$. The auditory thresholds of amberjack within the test the frequencies were most sensitive at 300HZ as 94.5 dB. The critical ratios of fishes ranged from 36.4 to 52.8 dB. The noise spectrum level that started masking was about 58∼72 dB within frequencies.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.46-66
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• 2002

High-resolution multichannel seismic data were collected in the coastal area near the Gori nuclear power plant to investigate Quaternary fault pattern and timing. A 12 channel streamer, a sparker, and a portable recorder were used for data acquisition. Because the group interval of the streamer was 6.25 m and the sparker can generate acoustic waves with the frequency content of up to 500 Hz, the data show a significant improvement both in horizontal and vertical resolution. The area surveyed is covered with 30-40 m thick Holocene sediments that constitute the mud belt along the southeastern coast of Korea. The survey area is characterized by the well discriminated Pleistocene and Holocene boundary and shallow gas-charged zones. A number of Quaternary faults were found in the sediment column, that are nearly vertical and extend north-south. The Quaternary faults, arranged at a spacing of a few hundred meters, suggest that they were formed in response to compression, although some of them reveal extensional characteristics. Locally, faults disrupt Incised-channel fills that are interpreted to have formed in the early stage of transgression after the beginning of the Holocene. Seismic sections suggest that shallow gas in the mud belt sediments made its way upward through the fractured fault planes. The tectonism responsible for the opening of the East Sea has not persisted since the late Miocene, but vigorous Quaternary faulting activity in the vicinity of the southeastern Korean Peninsula indicates that tectonic stability has yet to be achieved in this region underlain by the hotter than normal mantle.

• Korean Journal of Ichthyology
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• v.34 no.2
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• pp.96-101
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• 2022

The egg, larvae, and juvenile development of Platycephalus indicus sampled from Yeosu estuary were conducted. The egg shape of P. indicus is spherical and transparent on the outside, with two perivitelline cavities inside and one oil globule. The diameter of the fertilized eggs were 1.03~1.12 mm (mean =1.08 mm, n =50). The embryos hatched in about 50 hrs 30 mins after fertilization at the water temperature of 20℃. The newly hatched larvae showed a total length of 2.72~3.04 mm (mean=2.93±0.21 mm, n=50). At 5 days after hatching, they were 3.88~4.42 mm (mean=4.11±0.31 mm, n=15) in TL and their yolk was completely absorbed, developing the teeth. They became juvenile 39 days after hatching and reached 10.23~11.95 mm (mean=11.09±0.86 mm, n=5) in TL. At 45 days after hatching, they were 12.01~13.25 mm (mean=12.63±0.62 mm, n=5) in TL, and their body shape and color were similar to those of adult fish.

• The Journal of Engineering Geology
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• v.33 no.1
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• pp.105-119
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• 2023

Water supply is decreasing due to climate change, and coastal and island regions are highly dependent on groundwater, reducing the amount of available water. For sustainable water supply in coastal and island regions, it is necessary to accurately diagnose the current condition and efficiently distribute and manage water. For a precise analysis of the groundwater flow in the coastal island region, submarine fresh groundwater discharge was calculated for the Seongsan basin in the eastern part of Jeju Island. Two methods were used to estimate the thickness of the fresh groundwater. One method employed vertical interpolation of measured electrical conductivity in a multi depth monitoring well; the other used theoretical Ghyben-Herzberg ratio. The value using the Ghyben-Herzberg ratio makes it impossible to accurately estimate the changing salt-saltwater interface, and the value analyzed by electrical conductivity can represent the current state of the freshwater-saltwater interface. Observed parameter was distributed on a virtual grid. The average of submarine fresh groundwater discharge fluxes for the virtual grid was determined as the watershed's representative flux. The submarine fresh groundwater discharge and flux distribution by year were also calculated at the basin scale. The method using electrical conductivity estimated the submarine fresh groundwater discharge from 2018 to 2020 to be 6.27 × 10⁶ m³/year; the method using the Ghyben-Herzberg ratio estimated a discharge of 10.87 × 10⁶ m³/year. The results presented in this study can be used as basis data for policies that determine sustainable water supply by using precise water budget analysis in coastal and island areas.

• Journal of Fisheries and Marine Sciences Education
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• v.12 no.2
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• pp.191-198
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• 2000

An experiment was carried out to obtain the fundamental data on the auditory thresholds of fishes for catching method using audible frequency sound, the auditory thresholds of dusky spinefoot Siganus fuscescens(Houttuyn) were measured in the presence of masking noise in the spectrum level range of 74 - 83dB re $1{\mu}Pa/{\sqrt{Hz}}$ by heartbeat conditioning technique using pure tones coupled with a delayed electric shock. The auditory critical ratios were about 23 - 34dB at measurement frequency range. The ratio increased almost linearly with increasing frequency from 200 to 500Hz. The noise spectrum level at the start of masking was about 61 - 73dB within the measurement frequency range. This suggests that hearing of dusky spinefoot is masked in the natural environment with the noise spectrum level above 70dB. The sound pressure level of which the signal sound of 100Hz is recognized by dusky spinefoot under the white noise of 70dB is above 98dB and the critical ratio of them is above 23dB.

• 한국해양학회지
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• v.27 no.1
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• pp.1-10
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• 1992

The sea surface winds are computed over the adjacent seas of Korea from the twice-dayily weather maps for the ten-year period 1978-1987 by using the Cardone model. Monthly mean wind-stress and wind0stress curl are also calculated and given as maps. the computed surface winds are compared with observed one at the JMA (Japan Meteorological Agency) Buoy. and the results show a good consistency in speed and direction. In particular, the magnitude of mean wind-stress is turned out to be twice bigger than the previous results over the sea of Japan. Monthly distributions of wind-stress curl reveal that over the yellow sea by the longitudinal boundary of $120^{\circ}{\;}~{\;}125^{\circ}{\;}E$, the area of negative cur exists over the western part of the sea except summer season, while the positive sign of the curl prevails over the eastern part of the Yellow Sea. However, over the Sea of Japan, with two positive maxima at the northern part and near the Wonsan Bay, the positive curl in the northern half and the negative curl in the southern of the sea characterize the monthly mean distribution of the wind-stress curl.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.3
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• pp.100-107
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• 2002

The sea-surface winds during the passage of 64 typhoons for 1979-1999 were simulated using two different typhoon wind models, ie, typhoon parametric model(TPM) and primitive vortex model(PVM). The model hindcast winds were compared with the winds observed at JMA ocean buoys(22001 and 21002) and Kyushu ocean observation tower. The analysis of ms and relative errors between hindcast and observed winds was made to find the accuracy and sensitivity of the typhoon wind prediction models. Both hindcast winds of TPM and PVM underestimate the observed typhoon winds, but PVM winds are more closer to the observations with less rms and relative errors. Relative errors of two model winds were small within 200km from typhoon center, but TPM's relative errors increase up to 70% as the radial distance from typhoon center increases beyond > 200km although PVM's relative errors remain in 20% with less sensitive to the distance from typhoon centers.

• Journal of Food Hygiene and Safety
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• v.13 no.1
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• pp.6-13
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• 1998

This study was carried out to investigate the antioxidative activity on oxidaton of human low density lipoprotein from marine microorganisms. Bacillus sp. RH-5 producing antioxidative activity have been isolated and identified from coast sea in Pusan. Bacillus sp. RH-5 produced at highest level of antioxidative activity in the medium of 1.0% glucose, 0.25% polypepton, 0.25% yeast extract, 0.01% $FeSO_4{\cdot}7H_2O$ and 50% sea water. The optimal medium pH, cultural temperature and shaking time for the highest production as the antioxidant were 7.0, $30^{\circ}C$ and 48 hr, respectively. The culture broth inhibited the copper catalyzed oxidation of human low density lipoprotein (LDL) at the concentration of 500 and $1,000\;\mu\textrm{g}/ml$ ethylacetate extracts in the presence of $5\;\mu\textrm{M}\;CuSo_4$. The electrophoretic mobility of the LDL oxidized in the presense of $5\;\mu\textrm{M}\;CuSo_4$ was higher than that of native LDL.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.6
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• pp.581-584
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• 2000

In order to obtain the fundamental data about method of luring fish schools by underwater audible sound, the auditory threshold of black rockfish Sebastes inermis on the coast of Cheju Island was investigated by heartbeat conditioning technique using pure tones coupled with a delayed electric shock, The audible range of black rockfish extended from 80 Hz to 800 Hz with a peak sensitivity at 300 Hz. The mean auditory thresholds of black rockfish at the frequencies of 80 Hz, 100 Hz, 200 Hz, 300 Hz, 500 Hz and 800 Hz were 102 dB, 103 dB, 99 dB, 96 dB, 116 dB and 122 dB, respectively, As the frequency became higher than 300 Hz, the auditory threshold increased rapidly.

• 한국해양학회지
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• v.17 no.2
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• pp.33-40
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• 1982

The oceanographical condition of the southeastern area off Korea is inverestigated in the point of view of the fluctuation of the thermal front. although the fearure of the front is somewhat complicate, it can be classified intl three types. the first type is elongated toward north with the narrow cold water belt inside the front. The second type is almost parallel with the latitude of 36 N and the third type is the irregular one in which the cyclonic cold water mass and the anticyclonic warm water mass develop equally. The north-south directed fronts are strengthened either by the supply of the warm Daema Current (Tsushima Current in Japanese) of by the appearance of the cold North Korean Water along the coast. In the first type the thermocline inclines up toward the coast when the southward component of the wind is weakened. On the other hand, in the second typr the homogeneous and medium warm water spreads up to the coast and the latitude of 36 N, the second type front is formed.