• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.3
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• pp.439-447
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• 2019

Some dynamical issues about the Tsushima Warm Current (TWC) are reviewed and checked for the remaining unresolved problems, focusing on the formation of the TWC, seasonal variation of its volume transport and its branching in the East Sea. The TWC is a part of the North Pacific (NP) subtropical gyre driven by the NP global wind system. However, the quantitative amount of volume transport is sensitive to friction, basin geometry, barrier effect and so on. Among many causes suggested by many scientists, subpolar winds are found to be most closely related with the seasonal variation of TWC volume transport. However, more studies relating the latter not only to the subpolar winds but also to those including the subtropical winds seem to be required. The branching of the TWC has been known to be due to the western intensification for the East Korean Warm Current (EKWC) and to the bottom trapping for the Nearshore Branch. Since the former hypothesis is problematic in explaining the seasonal variation of the EKWC, other candidate mechanisms may need to be considered.

• Ocean and Polar Research
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• v.41 no.2
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• pp.47-61
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• 2019

The Dokdo coast is known for its high biodiversity. However, few studies have examined the biodiversity and macrobenthic community on the subtidal soft-bottom. Therefore, we collected macrobenthos (> 1 mm) using a Smith-McIntyre grab ($0.1m^2$) at 15 stations along the Dokdo coast in September 2016. The sediments consisted of badly sorted (1.7) coarse sand with gravel and the mean sediment grain size was $-0.4{\phi}$. In total, 177 macrobenthic species were collected; their mean density was $1,566ind./m^2$. The number of species and density of macrobenthic fauna decreased significantly with the mean grain size. The dominant species were the amphipods Melita denticulata (16.5%) and Melita shimizui (5.5%), polychaete Salvatoria clavata (5.4%), bivalve Glycymeris aspersa (4.4%), and ophiuroid Ophionereis dubia (4.3%). The dominant macrobenthos species on the subtidal soft-bottom differed from the coastal areas of the East Sea, suggesting that the difference in the sediment grain size affected the macrobenthos. Cluster analysis was performed to divide the study area into four groups, and environmental factors which correlated with species composition and distribution in the study area were the combination of the four parameters of salinity, dissolved oxygen, total organic carbon and depth. A future seasonal investigation is needed to understand the species composition and characteristics of the Dokdo macrobenthos.

• Journal of Environmental Science International
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• v.27 no.12
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• pp.1279-1290
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• 2018

Sea gulls are high trophic level consumers in the coastal environment, and thus, which have been widely used to monitor contamination biomagnified through a food web. However, such monitoring studies using sea gulls have been rare in the Korean literature. The National Environmental Specimen Bank chose eggs of a black-tailed gulls (Larus crassirostris) to serve as an environmental specimen for the long-term monitoring of the coastal ecosystem affected by terrestrial pollutants. Black-tailed gull eggs were collected from Baengnyeongdo, Hongdo and Uleungdo, and their DDTs and total mercury content were determined. The highest concentration of ${\Sigma}DDTs$ was $231.6{\pm}106.1{\mu}g/kg$ wet in Baengnyeongdo, followed by $230.0{\pm}123.8{\mu}g/kg$ wet in Ulleungdo, and $117.7{\pm}18.3{\mu}g/kg$ wet in Hongdo. In addition, total mercury was detected at $414.5{\pm}97.6{\mu}g/kg$ wet in Ulleungdo, $363.9{\pm}123.6{\mu}g/kg$ wet in Hongdo, and $237.5{\pm}42.3{\mu}g/kg$ wet in Baengnyeongdo. Relatively high concentrations of the target pollutants were recorded in specimens from Ulleungdo. Additional comprehensive and prolonged studies are required to elucidate spatial and temporal patterns of contamination in black-tailed gull eggs with regard to monitoring contaminant trends in eggs and prey.

• Ocean and Polar Research
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• v.40 no.4
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• pp.223-235
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• 2018

This study was carried out to investigate benthic sedimentary environments and benthic polychaetous communities on the coast of Ulsan, located on the southern East Sea of Korea. This survey was conducted at 15 stations, four times seasonally in January, April, July and October 2016. From the coast to the outer sea, surface sediments turned into fine grained sediments. There were complex coarse-grained sedimentary facies in various forms in the coastal zones while those with mud facies were found in the offshore zone. Organic matter content (LOI) and sulfide amount (AVS) recorded extremely high values, and increased from the coast to the outer sea, showing a similar trend to mud content with depth. The benthic polychaetous community revealed a mean density of $525ind./m^2$, and the total species number of species was 84. The major dominant polychaetous species were Magelona japonica, Lumbrineris longifolia and Heteromastus filiformis throughout the four seasons. Magelona japonica was concentrated predominantly in shallow coastal areas, but was present in all the regions of the survey area. Lumbrineris longifolia showed higher density in offshore regions more than 30 m deep, whereas H. filiformis showed higher density in coastal areas less than 30 m in depth. As a result of cluster analysis, the study area was divided into three ecological areas according to species composition, such as the northern coastal area between Ulsan PortOnsan Port, the southern area around Hoeya River and the outer sea area. Benthic environments in the study area, as determined by AMBI and BPI index, maintained a healthy condition in all four seasons with the AMBI at a level above GOOD and BPI at a level above FAIR. As organic matter accumulation continues to take place in the Ulsan coastal area, it is essential that detailed research activities continue to be carried out and ongoing monitoring be maintained.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.470-475
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• 2019

This paper deals with a 30kW grid-connected PCS (Power Conversion System) for an Oscillating Water Column (OWC) wave-power generation system. Wave power generation in marine energy is suitable for Korea with the characteristics of a peninsula with three sides facing the sea. In the case of coastal disasters, wave generators can act as a breakwater to reduce damage, and can be integrated with other marine power generation systems to increase efficiency. Wave power generation systems are classified into various types, such as oscillating bodies, OWC, and overtopping according to the operation principle, and they can also be classified into two types according to the installation method: a fixed structure and floating structure. This paper proposes a 30kW grid-connected PCS topology and model for OWC wave power generation that is structurally stable with a turbine and generator that are relatively easy to maintain, and then provide a control method required for grid connection, including DC link voltage control. Simulation verification was performed to verify the proposed PCS.

• International Area Studies Review
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• v.14 no.1
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• pp.77-97
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• 2010

Recently, countries on the Caspian Sea were had heavily interested due to instability of international resource market. These countries having been developed basing on energy exports, especially Kazakhstan have drastically grown during a decades. However economy, heavily relied on the exports of energy, is influenced on fluctuation in the international energy price as well as sometimes exposed at Dutch disease. These days, Kazakhstan, increased trade and investment with Korea, has been on the rise as new supplier for energy. Therefore, economic change in Kazakhstan can be an important issue. In this paper, we analyze relations among oil price, interest rate, and real exchange rate during sample period from January 1999 to December 2008 expanding Balasa-Samuelson model. Empirical results present that oil price, interest rate, and real exchange rate mutually keep their balance. Eventually, we find out Kazakhstan has exposed at Dutch disease since oil price and interest rate have negative impacts on real exchange rate respectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.4
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• pp.296-305
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• 2018

Maturity and spawning of the pointhead flounder, Hippoglossoides pinetorum were investigated on the basis of samples collected in the coastal waters off Gangwon-do, East Sea from January 2012 to December 2013. The average total length of H. pinetorum was 25.0 cm and 21.9 cm for females and males, respectively. The spawning period was from May to July according to monthly changes gonadosomatic index (GSI) and maturity stages. The spawning period in Gangwon-do was delayed relatively to that in Gyeongbuk-do. The mature egg diameter ranged between $300-700{\mu}m$. The relationship between TL and fecundity (F) was F = 63.574 TL - 1471.3 ($R^2=0.7603$), that is, the larger total length, the more fecundity H. pinetorum had. We estimated that the TLs at 50% group maturity were 25.6 cm for females and 19.9 cm for males. The spawning ecology by sea area should be considered efficient resource management for H. pinetorum. Furthermore, it is necessary to study more on the relationships among growth, maturity and water temperature variations in the East Sea.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.4
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• pp.306-314
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• 2018

Species composition and seasonal variation of aquatic organism at Baekryeong-do, Korea were investigated using pots in 2016. A total of 42 species, 90,050 individuals and 2,351,666 g of aquatic organism were collected. Among them, there were 12 species and 3,826 individuals of fish, 15 species and 51,237 individuals of crustaceans, 2 species and 54 individuals of cephalopods, 7 species and 33,981 individuals of gastropods, 2 species and 757 individuals of echinodea, 2 species and 187 individuals of shellfish, and 1 species and 8 individuals of holothuroidea. The dominant species in number of individuals were Pagurus ochotensis, Neptunea cuming, Cancer gibbosulus, and Buccinum yokomaruae, which accounted for 70.0% of the total number individuals collected. The dominant species in biomass were Neptunea cuming, Portunus trituberculatus, Cancer gibbosulus, and Pagurus ochotensis, which accounted for 65.3% of the total biomass collected.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.775-782
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• 2017

The position of existing patrol ships has been decided according to subjective judgments, not purely by any reasonable or scientific criteria, because of a lack of access to marine accident positions. In this study, the optimal location of patrol ships is quantitatively determined based on historical marine accident data. The study area used included the coastal sea of Pohang in South Korea. In this study, a k-means clustering algorithm was used to derive the location of patrol ships, and then a Voronoi diagram was used to divide the region around each patrol ship. As a result, the average navigation distance for patrol ships was improved by 4.4 nautical miles, and the average arrival time was improved by 13.2 minutes per marine accident. Moreover, if the locations of patrol ships need to be changed flexibly, it will be possible to optimally arrange limited resources using the technique developed in this study to ensure a fast rescue.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.965-971
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• 2017

The primary objective of this study was to assess the energy efficiency performance of an optimized hull form capable of saving energy based on existing vessels. The bow shape of existing vessels was investigated, giving consideration to design draft and speed. Resistance performances were also assessed for existing vessels according to operating conditions. Commercial CFD codes and model test materials were used to assess effective power. An optimized hull form with minimum resistance was selected given real operating conditions. The effective horsepower of existing and optimized vessels was estimated at three speeds. Resistance performance for an optimized vessel showed a 6 % improvement in effective horsepower at design speed (12 knots) compared to existing vessels. Quasi-propulsive efficiency employed experimental data, while energy efficiency performance was analyzed based on operating days, bunker fuel oil C cost, daily fuel oil consumption and specific fuel oil consumption. Energy efficiency performance for an optimized vessel showed a gain of 30 million won per year in reduced costs at design speed (12 knots) compared to existing vessels.