• Journal of the Korean earth science society
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• v.42 no.6
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• pp.677-687
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• 2021

In this study, we analyzed diatoms from core RS15-GC41 collected in Iselin Bank, Ross Sea. A total of 24 genera and 35 species of diatoms are identified, and the having valve abundance of diatoms varies from 0.2 to 28.6×10⁶/g. Four diatom assemblage zones are established by the vertical distribution of diatoms, and changed with a cycle of 100 kyrs. RS15-GC41 were deposited over the last 400 kyrs (corresponding to Marine Isotope Stages 1-11). The open-water species Fragilariopsis kerguelensis, Rhizosolenia styliformis, and Thalassionema nitzschioides abundantly occurred in interglacial periods. Whereas, Actinocyclus actinochilus abundantly dominant during the glacial periods. The distribution of these diatoms indicated, it can be seen that the sea-ice extent was larger and lasted longer during MIS 7, 9, and 11 than that of MIS 1, 3, and 5. Moreover, Paralia sulcata was abundantly predominant in MIS 7, 9, and 11; this finding suggests likely indicating that P. sulcata was transported from the coastal/inner shelf area to the study site, during accumulated in the sediments, reworked with the influx of ice-rafted debris by the currents

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.632-638
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• 2022

As Korean coastal activity is high, the incidence of accidents caused by marine waste is extensive. An accident in which marine floating waste ropes and fishing nets are wound around the propeller of a sailing ship is termed "Rope wrapped accident." To prevent such accidents, this study applied the Finite Element Method (F.E.M.) for performance evaluation of the shaver type cutter, commercialized in Korea, through a structural safety review and water tank test. The results demonstrate that all parts constituting the rope cutter were damaged before reaching 0.5s, and the safety factor of each part was found to be at least 2 based on the maximum stress generated compared to the tensile strength. In the basin test, the cutting process of the shaver type rope cutter was reviewed, and the installation angle was set for each case considering that the rope floating in the sea actually enters at various angles. Consequently, as it was successful at cutting in all the cases, it can be concluded that there will be no problem in cutting the rope regardless of the mounted angle of the cutting blade.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.4
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• pp.179-184
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• 2021

Along with the development of the fourth industry, the public sector has increasingly paid more attention to search using drones and real-time monitoring, for various goals. The drones are used and researched to complete a variety of searching and monitoring missions, including search for missing persons, security, coastal patrol and monitoring, speed enforcement, highway and urban traffic monitoring, fire and wildfire monitoring, monitoring of illegal fishing in reservoirs and protest rally monitoring. Police stations, fire departments and military authorities, however, concentrate on the hardware part, so there are little research on efficient communication systems for the real-time monitoring of data collected from high-performance resolution and infrared thermal imagining cameras, and analysis programs suitable for special missions. In order to increase the efficiency of drones with the searching mission, this paper, therefore, attempts to propose an image analysis technique to increase the precision of search by producing image data suitable for searching missions, based on images obtained from drones and provide the foundation for improving relevant policies and establishing proper platforms, based on actual field cases and experiments.

• Korean Journal of Ichthyology
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• v.33 no.1
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• pp.22-30
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• 2021

This study aimed to determine the monthly fish species composition in the eelgrass bed of Yeocha on Hansando Island, Korea, and to obtain fish species data by comparison with the nearby Bongam. The species composition was determined from monthly samples collected by a surf net from August 2009 to July 2010. During the survey, total 2,394 individuals of 29 species and 10,378 g of fish were collected. The dominant species were Gymnogobius heptacanthus, followed by Takifugu niphobles, Rudarius ercodes, Chaenogobius annularis, and Ditrema temminckii, accounting for 89% of the total individuals sampled and 83% of the fish biomass collected. The fish assemblages in the eelgrass bed varied seasonally; the number of individual fishes increased in May and was highest in July, whereas the biomass attained its highest level in April and subsequently decreased. This study confirms that the seagrass bed plays an important role as a fish nursery ground, and it is necessary to investigate changes in the coastal fishes of the southern coast via periodic surveys.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1238-1243
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• 2022

The International Maritime Organization is at the forefront of strengthening gas emission regulations for ships globally. The Korean government needs to apply measures to reduce emissions, such as setting a basic roadmap for greenhouse gas reduction. In addition, there is an urgent need to introduce a new efficient propulsion system that can reduce gas emissions. This includes applications to fishing vessels, which account for 90.6% of the greenhouse gas emissions from ships sailing along domestic coasts. In this study, an electric-combined propulsion system applicable to domestic coastal fishing vessels was developed. The target ship to which the electric-combined propulsion system could be applied was selected. A simulation system was constructed using MATLAB/Simulink to compare the expected fuel consumption when applying the developed complex electric propulsion system to the propulsion system mounted on the selected target fishing vessel. Through simulations, the differences in fuel consumption between the mechanical propulsion system and the electric hybrid propulsion system (both when charging and not charging the battery on land) were confirmed. The results show that fuel consumption can be decreased by approximately 13% and 16% when applying the electric-combined propulsion system.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.3
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• pp.95-120
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• 2023

Methane (CH₄) is a key greenhouse gas in the atmosphere with 85 times greater greenhouse potent relative to carbon dioxide (CO₂). The atmospheric concentration of CH₄ is rapidly increasing due to the intensive usage of CH₄ and the thawing of the cryosphere. Additionally, with the current warming of ocean water, the dissociation of gas hydrates, an ice-like compound and the largest reservoir of CH₄ on Earth, is expected to occur, resulting in the release of CH₄ from the seafloor into the overlying water and atmosphere. Moreover, bottom water hypoxia is another concern that potentially introduces greenhouse gases into the atmosphere. With ongoing global warming and eutrophication, the size and duration of bottom water hypoxia are rapidly increasing. These low-oxygen conditions would relocate the redox zone shallower in sediment or in the water column, causing the release of CH₄ into the atmosphere and thereby intensifying global warming. However, there exists a gap in the understanding of CH₄ dynamics including its generation in relation to bottom water hypoxia. Therefore, this review article aims to understand the relationship between CH₄ and bottom water hypoxia and to draw attention to CH₄ investigation in Korea.

• Journal of Navigation and Port Research
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• v.47 no.1
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• pp.18-24
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• 2023

After the Great East Japan Earthquake, many reports and books that compiled testimonies of adult victims were published. Thus, refugee situations are well known, but information on the refugee situations of Japanese students is not. This is because what actions the students took and how they sought refuge from an earthquake or tsunami have not been fully recognized. The purpose of this study was to examine and analyze students' refuge behavior in the Great East Japan Earthquake and to predict the refuge behavior of students affected by future disasters. The results of the study showed that students passively acquired information about earthquakes and tsunamis and that their refuge behavior was highly dependent on adults. Immediately after an earthquake, people tended to protect themselves and stay in place until the shaking stopped. However, they tended to move to another place after the shaking occurred frequently. Students living on ria coastlines were likely to move to high places to escape the threat of earthquakes and tsunamis, whereas students living in plain regions were likely to move vertically to tall buildings, such as schools. As for the mode of movement to refugee shelters, the students arrived at the final refugee shelters in one move, and it is assumed that the refugee shelters should be decided in advance and the students should move there.

• Korean Journal of Ichthyology
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• v.34 no.3
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• pp.201-207
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• 2022

Total 418 Yellow Croaker Larimichthys polyactis were examined and the range of total length (TL) was 12.0~27.5 cm and average total length was 19.6 cm. The most important prey component in the diets of L. polyactis was Pisces that constituted 46.5% in %IRI (Index of relative importance). Euphausiacea was the second largest prey component. The result of analysis in ontogenetic and seasonal changes significantly exhibited. The proportion of Pisces increased as increasing body size, whereas the consumption of Macrura decreased gradually. The diets also were different among seasons, with the difference particularly being evident between warm (summer and autumn) and cold (winter and spring) seasons. Permutational multivariate analysis of variance (PERMANOVA) revealed significant dietary differences by seasons (P=0.001).

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.11 no.1
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• pp.1-10
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• 2006

Previous studies on zooplankton in Asan Bay were mostly based on samples collected seasonally with three months intervals. Present study was aimed to know the temporal variation of meso-zooplankton distribution using the data collected monthly. Relationships between zooplankton abundances and environmental factors such as seawater temperatures, salinities and chlorophyll-a contents were also studied. Seawater temperature showed typical pattern of seasonal variation found in temperate waters. The fluctuations of environmental factors ranged relatively wider In the inner part of the bay than those in outer part of the bay. Salinity was very low right after the summer rainy period due to the sporadic outflow of freshwater from the adjacent artificial lakes. Sudden changes in salinity seemed to have significant impact on zooplankton assemblages. Chlorophyll-a contents were increased in general when compared with previous reports probably due to the recent human exploitations in the coastal zone, which might enhance the nutrients level . The timing and duration of spring bloom showed geographical differences. In the inner part of the bay it began earlier (February) and last longer (three months) while in the outer part of the bay it began late (April) and last just one month. Zooplankton abundance, especially most abundant taxon Acartia hongi, showed weak but significant positive correlation with chlorophyll-a contents. The difference in temporal variation found with two different sampling intervals indicated the necessity of shorter time interval samplings.

• Korean Journal of Ichthyology
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• v.36 no.1
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• pp.20-29
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• 2024

Hemitripterus villosus, a promising aquaculture fish species, is facing declining stocks. This study aims to provide normative standards for skeletal development to address persistent skeletal deformities in farmed fish. Specimens utilized in the study underwent artificial insemination with captured fish, and the resulting larvae and fry were preserved in a formalin solution. The skeletal ossification process commenced immediately after hatching, affecting the parasphenoid, premaxillary, maxillary, and dentary structures at an average total length of 13.65±0.71 mm (n=5). By sixty-five days post-hatching, ossification extended to the ethmoid and supraorbital, completing the head's development at an average total length of 21.24±0.50 mm (n=5). Clavicle ossification occurred at seven days post-hatching, corresponding to an average total length of 14.61±0.52 mm (n=5). At forty-four days post-hatching, the ossification of 4 actinosts took place, completing the shoulder girdle, with an average total length of 18.15±0.61 mm (n=5). Vertebral ossification initiated at ten days post-hatching, with an average total length of 14.80±0.65 mm (n=5). By fifty-four days post-hatching, 39 vertebral columns were ossified, reaching an average total length of 18.67±0.54 mm (n=5). Vertebral development was complete at sixty days post-hatching, with an average total length of 20.25±0.45 mm (n=5). This study sheds light on the skeletal development of H. villosus, providing valuable standards and fundamental data for understanding skeletal deformities in this species.