• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.2
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• pp.126-138
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• 2010

To investigate seasonal variation of fisheries resources composition and their correlationships with environmental factors in the coastal ecosystem of the middle Yellow Sea of Korea, shrimp beam trawl were carried out for the fisheries survey. Fisheries resources of 81 species, 57 families, and 6 taxa totally were collected by shrimp beam trawl in the middle coastal ecosystem of Yellow Sea of Korea. Species were included 6 species in Bivalvia, 6 in Cephalopoda, 22 in Crustacea, 2 in Echinodermata, 5 in Gastropoda, and 40 in Pisces. Diversity indices (Shannon index, H') showed seasonal variation with low value of 2.14 in winter, and high value of 2.67 in spring. Main dominant species were Oratosquilla oratoria, Octopus ocellatus, Acanthogobius lactipes, Cynoglossus joyneri, Rapana venosa venosa, Loligo beka, Chaeturichthys stigmatias, Raja kenojei, Microstomus achne and Paralichthys olivaceus, that were occupied over 58% of total individuals, and 55% of wet weight. Fisheries organism made four coordinative seasonal groups by the principal component analysis (PCA), showing stronger seasonal variation than spatial variation. PC from PCA showed statistically significant cross-correlationships with seawater temperature, $NH_4$-N, TP and chlorophyll a (P < 0.05).

• ALGAE
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• v.36 no.3
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• pp.207-217
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• 2021

An increase in seawater temperature owing to global warming is expected to substantially limit the growth of marine algae, including Pyropia yezoensis, a commercially valuable red alga. To improve our knowledge of the genes involved in the acquisition of heat tolerance in P. yezoensis, transcriptomes sequences were obtained from both the wild-type SG104 P. yezoensis and heat-tolerant mutant Gy500. We selected 1,251 differentially expressed genes that were up- or downregulated in response to the heat stress condition and in the heat-tolerant mutant Gy500, based on fragment per million reads expression values. Among them, PyHRG1 was downregulated under heat stress in SG104 and expressed at a low level in Gy500. PyHRG1 encodes a secretory protein of 26.5 kDa. PyHRG1 shows no significant sequence homology with any known genes deposited in public databases to date. However, PyHRG1 homologs were found in other red algae, including other Pyropia species. When PyHRG1 was introduced into the single-cell green alga Chlamydomonas reinhardtii, transformed cells overexpressing PyHRG1 showed severely retarded growth. These results demonstrate that PyHRG1 encodes a novel red algae-specific protein and plays a role in heat tolerance in algae. The transcriptome sequences obtained in this study, which include PyHRG1, will facilitate future studies to understand the molecular mechanisms involved in heat tolerance in red algae.

• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3635-3642
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• 2021

Natural circulation systems (NCSs) are extensively applied in nuclear power plants because of their simplicity and inherent safety features. For some passive natural circulation systems in floating nuclear power plants (FNPPs), the ocean is commonly used as the heat sink. Condensation induced water hammer (CIWH) events may appear as the steam directly contacts the subcooled seawater, which seriously threatens the safe operation and integrity of the NCSs. Nevertheless, the research on the formation mechanisms of CIWH is insufficient, especially in NCSs. In this paper, the characteristics of flow rate and fluid temperature are emphatically analyzed. Then the formation types of CIWH are identified by visualization method. The experimental results reveal that due to the different size and formation periods of steam slugs, the flow rate presents continuous and irregular oscillation. The fluid in the horizontal hot pipe section near the water tank is always subcooled due to the reverse flow phenomenon. Moreover, the transition from stratified flow to slug flow can cause CIWH and enhance flow instability. Three types of formation mechanisms of CIWH, including the Kelvin-Helmholtz instability, the interaction of solitary wave and interface wave, and the pressure wave induced by CIWH, are obtained by identifying 67 CIWH events.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.172-176
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• 2019

A benthic microbial fuel cells(BMFC) is fuel cell using electricity produced by decomposing organic matter in a sea or a lake. In this study, we used a gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEMFC) as a BMFC electrode to find out the operation conditions with high performance. The performance of BMFC was increased as resistance of external resistor increased. It was possible to maintain the performance by avoiding the increase of the contact resistance with the electrode due to corrosion of the lead wire in seawater. The bubble generator was able to increase the maximum power density by more than 2 times and the optimum operating temperature was $40^{\circ}C$.

• Korean Journal of Ichthyology
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• v.31 no.1
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• pp.23-29
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• 2019

The embryonic development and hatchability of the artificially fertilized eggs of convict grouper (Hyporthodus septemfasciatus) ♀${\times}$giant grouper (Epinephelus lanceolatus) ♂ (CGGG) were compared to those of the maternal pure species (convict grouper ♀${\times}$♂, CG) to establish a novel grouper hybrid for aquaculture industry. The fertilized eggs were divided into nine 5-L beakers (3,000~5,000 eggs/beaker) filled with UV sterilized seawater and incubated at a temperature range of $23.5{\sim}24.8^{\circ}C$ (32.1~32.8 psu). The percentages of fertilization and hatching of CGGG were $69.4{\pm}1.5%$ and $59.0{\pm}5.1%$, respectively and were significantly lower than those of CG (p<0.05). The CGGG proceeded normal embryonic development similar to that of CG, but showed an irregular cleavage, immature embryonic body and spinal deformity in hatched larvae. The incubation time from fertilization to hatching of CGGG was 31 hrs, which was approximately 2 hrs slower than that of CG. Our study provided the possibility of mass production of grouper hybrid CGGG larvae.

• Korean Journal of Environmental Biology
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• v.39 no.1
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• pp.81-87
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• 2021

The monthly variability in marine algal flora and community structure was examined in the intertidal zones of Doripo, and the biomass of an edible alga, Ulva prolifera, at Gaip-ri of Hampyong Bay on the southwestern coast of Korea was investigated over one year from April 2008 to March 2009. A total of 22 seaweeds were identified including five green, four brown, and 13 red algae. Based on importance value, Ulva australis was dominant over the year and the subdominant species were Ulva linza and Caulacanthus ustulatus at the Doripo coast of Hampyong Bay. The vertical distribution in terms of importance values was in the order of Ulva linza - C. ustulatus - U. australis - Sargassum thunbergii from the upper to the lower intertidal zones. The biomass of U. prolifera ranged between 2.4-98.2 g dry wt. m^-2, with a maximum in June and a minimal in November. In the field, U. prolifera biomass could be positively related to seawater temperature. However, further research on the association between biomass and other environmental factors such as nutrients and light intensity is required.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.7
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• pp.767-776
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• 2020

Due to the recent climate change caused by global warming, weather changes in a different pattern from the past have occurred, and the increase in seawater temperature has led to an increase in the size and intensity of typhoons. Accordingly, there is an increasing need for bitts that can be used to secure mooring safety of the ship when a sudden gust occurs. Based on 12 scenarios of a mooring safety evaluation program, this study analyzed the criteria for arranging bollard and bitt, and analyzed the sensitivity of mooring safety when using storm bitts. As a result of the evaluation, it was analyzed that the mooring factor value decreased compared to the general mooring line arrangement when the fore and stern breastline were added to the bitts for gusts. The results of this study can be used as basic data for proposing storm bitts arrangements for gusts in consideration of the characteristics of berth ships and ports. From the perspective of ship operators, storm bitts at the pier will be an effective method for securing the ship's mooring safety in case of a gust of wind.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.255-259
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• 2022

Solar membrane steam generation is a very promising technology that can harvest purified water from seawater or wastewater during the current danger of running out of pure water. However, solar Membrane steam generation had direct contact with water, making it difficult to increase the efficient amount of evaporation. Here, we propose solar membrane steam generator composed of polydimethylsiloxane (PDMS) and graphene oxide (GO) and improved evaporation through wettability control in part throughout the water-absorbing membrane. Wettability control has shown significant improvements in thermal localization and temperature rise in the area of heat exchange with sunlight. The evaporator has an evaporation rate of 1.54 kg m^-2 h^-1 under 1 sun irradiation. The results showed that Solar membrane steam evaporation can effectively harvest pure water through an increase in evaporation.

• Fisheries and Aquatic Sciences
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• v.25 no.5
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• pp.298-310
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• 2022

Although giant and large fish species are highly important as a keystone species in the marine ecosystem, there have been no or few studies on their spatio-temporal variations around the Korean peninsula. For this, we analyzed daily reports made by observers at 57 fishery landing sites in Korea over 6 years, from 2011 to 2016. In total, 153 fish species were re-identified based on photos and descriptions recorded by Korean observers, of which five species were classified as a giant fish over 5 m in maximum total length (MTL) and 17 species as a large fish from 3 m to 5 m MTL according to the data presented by Froese & Pauly (2021). Among the giant and large fish species, Mola mola was the most abundant species, with 75 individuals landed as by-catch. The second most abundant species was Isurus oxyrinchus (31), followed by Mobula mobular (23), Lamna ditropis (17), Masturus lanceolatus (16), Sphyrna zygaena (14), and Prionace glauca (12). As a result of cluster analysis based on the number of individuals of giant and large fish species by year and sea, six years were separated into two clusters (2011-2013 vs. 2014-2016), with high contribution of M. mola, I. oxyrinchus, and M. lanceolatus; and three seas were separated into two clusters (eastern + southern seas vs. western sea), with high contribution of M. lanceolatus, L. ditropis, and I. oxyrinchus. The largest number of M. mola accounted for 64% of the total in 2014 and 2016, and 71% in summer (June-August). It is assumed to have a correlation between seawater temperature fluctuation and the occurrence of giant and large fish species. Our study highlights importance of longterm monitoring of giant and large fish species, and can help to understand the life cycle such as natal or nursery migration of giant and large fish species around the Korean peninsula.

• Membrane and Water Treatment
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• v.13 no.5
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• pp.235-243
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• 2022

The paper presents the effect of operating temperatures and flow rates on the distillate flux that can be obtained from a hydrophobic membrane having the characteristics: pore size of 0.15 ㎛; thickness of 130 ㎛; and 85% porosity. That membrane in the present investigation could be the direct contact (DCMD) or the air-gap membrane distillation (AGMD). To model numerically the membrane distillation processes, the two-dimensional computational fluid dynamic (CFD) is used for the DCMD and AGMD cases here. In this work, DCMD and AGMD models have been validated with the experimental data using different flows (Parallel and Counter-current flows) in non-steady-state situations. A good agreement is obtained between the present results and those of the experimental data in the literature. The new approach in the present numerical modeling has allowed examining effects of the nature of materials (Polyvinylidene fluoride (PVDF) polymers, copolymers, and blends) used on thermal properties. Moreover, the effect of the area surface of the membrane (0.021 to 3.15 ㎡) is investigated to explore both the laminar and the turbulent flow regimes. The obtained results found that copolymer P(VDF-TrFE) (80/20) is more effective than the other materials of membrane distillation (MD). The mass flux and thermal efficiency reach 193.5 (g/㎡s), and 83.29 % using turbulent flow and an effective area of 3.1 ㎡, respectively. The increase of feed inlet temperatures and its flow rate, with the reduction of cold temperatures and its flow rate are very effective for increasing distillate water flow in MD applications.