• The Journal of the Acoustical Society of Korea
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• v.32 no.1
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• pp.14-21
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• 2013

The erosion, suspension, and transport of sediment frequently occur in the coastal waters and estuarine. These processes often generate the so-called fluid mud layer, which is defined as a high-concentration aqueous suspension of fine grained sediment (> 10 g/l), consisting mainly of silt and clay-size particles. Therefore the high-resolution ultrasound is mostly used to detect or monitor the fluid mud layer. Because the sound attenuation tends to increase rapidly with the suspended sediment concentration, it is necessary to consider the accurate attenuation correction to estimate the backscattering strengths from the suspended sediment layers. In this paper, the volume backscattering strengths with various suspended sediment concentrations were measured using 5-MHz ultrasound signal in a small-scale water tank. The sound attenuation due to the viscosity and scattering from suspended sediment particles was predicted by the Richard's model and applied to the sonar equation to estimate the volume backscattering strengths from the suspended sediment concentrations. For the case that the additional attenuation was not considered, the volume backscattering strengths increased to the concentration of 20 g/l, and over this point, the backscattering strengths were roughly constant. However, for the case that the attenuation due to the suspended sediment concentration was considered, the backscattering strengths increased with the concentration.

• Korean Journal of Ichthyology
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• v.11 no.1
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• pp.52-61
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• 1999

Seasonal variation in species composition of fish with depth was determined by analysis of bimonthly samples collected by a beach seine at the shallow water (St. 1 < 1.5m) and by beam trawl at the two stations (St. 2, 5~7m and St. 3 > 15 m) from October 1997 to August 1998 off Ippa-do in Asan Bay. Of forty species identified, 13 species at St. 1,28 species at the St. 2 and 30 species at the St. 3 were collected. The fish density was also increased with depth. Favonigobius gymnauchen occupied 55.7% at St. 1 and 38.9% of the number of individuals at St. 2. Almost of fish collected at these two stations were juveniles, and they were principally collected in August and in November. At St. 3, relatively large fishes were collected. Among them Pholis fangi and Chaeturichthys stigmatias predominated in the number of individuals. Abundance was low, but a large number of species were collected in winter. Principal component analysis revealed that the species composition at the shallower stations was different from that at the deeper station. The number of species and abundance of fish in Asan Bay was lower than in the other western coastal waters of Korea. Species composition in the study area of sandy bottom was different from that in the inner Asan Bay of mud bottom.

• Korean Journal of Microbiology
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• v.50 no.2
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• pp.164-168
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• 2014

The ecosystem of the Arctic region has been increasingly affected by global warming. Archaeal ammonia monooxygenase alpha subunit coding gene (amoA) which is a key enzyme for nitrification was used to investigate the effect of runoff water of ice melt on microbial community of nitrogen cycle. The archaeal amoA genes at coastal area of Svalbard, Arctic region were PCR-amplified and sequenced after clone library construction. Analysis of archaeal amoA gene clone libraries suggested that the station 188 which is in the vicinity to the area of runoff water harbor lower ammonia-oxidizing archaeal diversity than the station 176 and 184. The average amino acid sequence identity within all archaeal amoA gene clones was 94% (with 91% nucleotide sequence identity). While all the clones of the station 188 were affiliated with Nitrosoarchaeaum clade containing strains isolated from low-salinity and terrestrial environments, about 45% of total clones of the station 176 and 184 were related to marine Nitosopumilus clade. Interestingly, other typical archaeal amoA gene clones of thaumarchaeal I.1b clade frequently retrieved from terrestrial environments was identified at station 188. Microbial community of nitrogen cycle in marine sediment might be affected by input of sediments caused by runoff glacier melt waters.

• The Korean Journal of Malacology
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• v.32 no.3
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• pp.197-202
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• 2016

This research reports the intersexuality of bivalves, such as Crassostrea gigas, Mytilus galloprovincialis, Rupiditapes philippinarum, Gomphina veneriformis and Barnea davidi discovered during the process of investigating the ecological health status of coastal waters of Korea. In intersex ovaries, the opposite germ cells were observed either individually or in groups in the interfollicular space and inside the oogenic follicle. Oocytes in the intersex testis were at the previtellogenic or initial vitellogenic stage. They were either scattered individually or in groups in the interfollicular space and inside the spermatogenic follicle. The intersexuality in C. gigas was 10.4% (n = 19/183), while female (12.2%, n = 6/49) exhibited a higher proportion than male (9.7%, n = 13/134). The intersexuality in M. galloprovincialis was 31.7% (n = 19/60), while female (36.4%, n = 12/33) exhibited a higher proportion than male (25.9%, n = 7/27). The intersexuality in R. philippinarum was 11.2% (n = 11/98), while male (16.7%, n = 7/42) exhibited a higher proportion than female (7.1%, n = 4/56). The intersexuality in G. veneriformis was 28% (n=30/107), while male (31.5%, n=17/54) exhibited a higher proportion than female (24.5%, n=13/53). The intersexuality in B. davidi was 18.4% (n = 7/38), while female (35.7%, n =5 /14) exhibited a higher proportion than male (8.3%, n = 2/24).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.2
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• pp.89-95
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• 2000

Test fishing was carried out to examine the selectivity of the mesh size in trammel net for tonguefish (Cynoglossidae spp.) from May to August, 1999 and a total of 30 times of test fishing have been done in the coastal waters around Dolsando, Yosu, South Chunra province, Korea. A gill net and a trammel net which were composed of three different mesh sizes (70.5mm, 86.6mm and 101mm) were used for the experiment. The selectivity curve of mesh size was estimated by Kitahara's method for Robust tonguefish (Cynoglossus robustus). The results obtained are summarized as follows ; 1. Catching efficiency of the trammel net (70.5mm-sized-lint main net) was 39.0% and it was 2.5 times higher than 15.8% for the gill net. 2. The optimum l/m value of the trammel net was 3.51 and it was 0.13 higher than 3.38 for the gill net. 3. The selectivity of trammel net was similar to that of the gill net for low length-class. However, the selectivity of trammel net was not good compared with that of the gill net for high length-class. The 50% selectivity was 1.33 for the trammel net and 0.83 for the gill net. According to the experimental results, fishing efficiency of the trammel net was better than that of the gill net for tonguefish (Cynoglossidae spp.) and it was known that catch length for targeted species could be selected by controlling the mesh size.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.3
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• pp.239-248
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• 2003

This paper was conducted as an attempt in order to construct the data bank of target strength for acoustic estimation of fish length in the coastal waters of Korea. The fish length dependence of acoustic target strength for 13 large yellow croakers (Pseudosciaena crocea) at 75 kHz was investigated and the prediction of the target strength by using the Kirchhoff-Ray Mode model (KRM model) was compared with target strength measurements. The results obtained are summarized as follows; 1. In the averaged target strength pattern for 13 large yellow croakers the maximum target strength was -35.13 dB at $-13.35^{\circ}$ on a tilted angle. 2. The relationship between fork length(L, cm) and averaged target strength(TS, dB) was expressed as follows; TS=23. 76log (L) -73.45 (r=0.47) TS=20log(L) -67.35 From this result, the conversion coefficient was -73.45 dB and 6.1 dB lower than the coefficient -67.35 dB where the value of the slope of the regression equation is forced to be 20. 3. Averaged target strength and a length conversion coefficient derived from a target strength histogram for 13 large yellow croakers of mean length 25.59 cm were -41.23 dB, -69.72 dB, respectively. 4. In the range of $$2;{\ll} L (fish length /{\lambda}(wave length);{\ll}40$$, the prediction of the averaged target strength by the KRM model increased gradually with the increasing of $L/{\lambda}$ and was lower than the measured target strength.

• Korean Journal of Environmental Agriculture
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• v.21 no.4
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• pp.274-278
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• 2002

Nitrate removal rate in three wetland cells was examined. The acreage of each cell was 150 $m^2$. They were a part of a stream water treatment demonstration system which was composed of two ponds and six wetland cells. Earth works far the pond-wetland system were finished from April 2000 to May 2000 and reeds were planted in the three cells in May 2001. Waters of Sinyang Stream flowing into Kohung Esturiane Lake located southern coastal area of Korean Peninsula were pumped into a primary pont Effluents from a secondary pond were funneled into the three cells. Volumes and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Inflow and outflow averaged 20 $m^3/d$ and 19.3 $m^3/d$, respectively. Hydraulic retention time was 1.5 days. Average influent and effluent nitrate concentration was 2.30 mg/L, 1.75 mg/L, respectively. Nitrate removal rate in the three cells averaged 80.9 $mg/m^2/day$. Seasonal changes of nitrate retention rates were closely related to those of wetland temperatures. Full growth of reeds within a few years can develope litter-soil substrates beneficial to the denitrification of nitrate, which may lead to increases of the nitrate retention rates.

• Korean Journal of Environmental Agriculture
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• v.21 no.4
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• pp.269-273
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• 2002

A 0.19 hectare stream water purification demonstration wetland was constructed and planted with cattails from April 2001 to May 2001. Some portions of its bottom surfaces adjacent to levees have a variety of slope of 1:4 $\sim$ 1:15 and two small open water areas were installed in the wetland. These make its shape closer to a natural wetlant Nitrogen removal was a major objective of the wetlant Waters of Sinyang Stream flowing into Kohung Esturiane Lake located southern coastal region of Korean Peninsula were pumped and funneled into it. Volumes and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Average inflow and outflow were 120 $m^3/d$ and 112 $m^3/d$, respectively. Hydraulic retention time was about 3.1 days. Average nitrate and total nitrogen removal rate for the early stage of the wetlands were 85.8 $mg/m^2/day$, 171.4 $mg/m^2/day$ respectively. Full establishment of cattails within a few years can develope litter-soil substrates and supply available carbon sources beneficial to the denitrification of nitrate. These can lead to increases of the nitrate retention rate. Short circuiting and dead zone areas which might be occurred due to the close-to-nature layout of the wetland were not observed during the monitoring period.

• Journal of Korean Society of Transportation
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• v.28 no.6
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• pp.33-42
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• 2010

Recently, the reduction of greenhouse gases(GHG) for climate change is the most important international issue. In order to control efficiency GHG emission rate reduction, it is essential to establish GHG emission inventory preferentially. The emission of ships that are emitting its $CO_2$ in international waters is becoming chief among the issues which country is put under an obligation. In the IMO reports, shipping is estimate to emit 1,046million tonnes of $CO_2$, which corresponds to 3.3% of global emission during 2007. International shipping is estimated to have emitted 870 million tonnes, about 2.7% of global emission of $CO_2$ in 2007. In this study, the general information of GHG emission, based on fuel consumption statistic, Tier 1, and the emission inventory is calculated to break down in to domestic and international emission. The GHG emission from ships in Korea was total 31,646 Gg $CO_2$-eq in 2009, which is included fishing, Korea flag coastal ship, Korea flag ocean going ship and foreign flag ships. And domestic emission and international emission was 5,398Gg $CO_2$-eq, 7,630Gg $CO_2$-eq and foreign flag ship was 18,618Gg $CO_2$-eq respectively.

• The Korean Journal of Malacology
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• v.26 no.4
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• pp.291-296
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• 2010

Samples of Turbo (Batillus) cornutus Lightfoot, 1786 in Jeju Island were collected from September 2009 to May 2010. Population ecological parameters and stock assessment of the turban shell were determined, based on the length and age composition data from 2000 to 2009 and ecological parameters. Instantaneous coefficient of total mortality (Z) of turban shell was estimated to be 2.2062/year. The estimated instantaneous coefficient of natural mortality (M) was 0.874/year. The age of turban shell at its first capture ($t_c$) was 2.636 year. Yield-per-recruit were estimated under harvest strategies that based on $F_{max}$, $F_{0.1}$, $F_{35%}$, and $F_{40%}$ was 10.44 g, 1.87 g, 6.53 g and 7.46 g.