• Journal of the Korean earth science society
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• v.23 no.8
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• pp.707-721
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• 2002

Seafloor acoustic image data using the side scan sonar system were gathered on the Sindu-ri offshore near the Taean peninsula, middle western Korea. The relationship between the back-scattering acoustic intensity and the sea-bottom sediment properties was studied. And these two data sets were compared and interpreted with the water depth, respectively. Most of sediment properties were correlated well to the acoustic intensity, however the distribution patterns of the sea-bottom sediment and the seafloor acoustic image were not similar to each other except the rocky bottom area. The water depth was not only influential on the distribution pattern of seafloor acoustic image but also showed a linear relation with the sediment properties distribution.

• Economic and Environmental Geology
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• v.41 no.5
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• pp.617-624
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• 2008

Azerbaijan, located on western part of Caspian Sea, has been developed oil and gas exploration and production business from about 200 years ago and once charged of 50% of world oil production in the early 20th century. After Azerbaijan was independent of Soviet Union in 1991, foreign oil companies, including Korean oil companies, have been investing in Azerbaijan oil business on offshore blocks. Productive capacity of downstream in the Azerbaijan is lower than productive capacity of upstream, whereas there are important pipelines, such as BTC, SCP, NREP, and WREP, provide opportunities of the oil and gas exporting to the world. Oil fields in onshore blocks in the Azerbaijan are almost mature oil fields, caused by high recovery rate. Offshore oil blocks are still high potential in oil exploration with high risk.

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.93-103
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• 2008

For conventional gravity type offshore structures constructed on the soft ground, which is located on the western and/or southern Korea, the excessive consolidation settlements are caused by the self-weight of the structures and so additional ground treatment methods are generally needed. Several types of improved foundation systems utilizing buoyancy applicable to even the soft ground were introduced for economical and efficient design of the offshore structure. In this study, a series of numerical simulations on the consolidation and lateral behaviors of breakwaters with the improved foundation systems utilizing buoyancy were carried out. From the results of numerical simulations it is found that the foundation systems utilizing buoyancy are efficient for reducing the maximum consolidation settlements without reducing lateral safety.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.2
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• pp.170-179
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• 2018

This paper introduces a new method to study the hydroelastic behavior of hinged Very Large Floating Structures (VLFSs). A hinged two-module structure is used to confirm the present approach. For each module, the hydroelasticity theory proposed by Lu et al. (2016) is adopted to consider the coupled effects of wave dynamics and structural deformation. The continuous condition at the connection position between two adjacent modules is also satisfied. Then the hydroelastic motion equation can be established and numerically solved to obtain the vertical displacement, force and bending moment of the hinged structure. The results calculated by the present new method are compared with those obtained using three-dimensional hydroelasticity theory (Fu et al., 2007), which shows rather good agreement.

• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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• pp.15-23
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• 2010

The absolute clay mineral compositions and regional distribution of the 131 bulk marine surface sediments around the Jeju Island was compared to their relative compositions and distribution using quantitative X-ray diffraction analysis. Average absolute clay mineral composition is illite 15.3% (0.5~40.5%), chlorite 2.6% (0~7.9%), and kaolinite 1% (0~5.6%). Total contents of the clay minerals are very high in the South Sea of Korea, northwestern part and southern offshore of Jeju Island. The average relative composition is illite 70.9% (16.7~89%), chlorite 21.5% (8.4~68.5%), and kaolinite 7.6% (0~29.3%). Relative illite contents are high in the northwestern and southeastern part of study area, and southern part of Jeju Island. Chlorite contents are high in the eastern part of study area and western part of Jeju Island. Kaolinite contents are high in the western and southern part of Jeju Island, and southern offshore of Jeju Isand. Absolute Distribution patterns are very similar to those of fine-grained (from clay to silt) sediment, whereas relative distribution patterns do not show any relationship with those of fine-grained sediment.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.18-25
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• 1999

Western coastal ports of Korea experience severe tidal range with up to 9.7 meter between high and low tides. The significant water level variation implicates many operational difficulties during loading and un-loading from cargo ships. To overcome problems due to tide and to secure the continuous loading operation, a new loading system for container cargo called "container pallet system" is developed and introduced in the paper. Three types of structure forms, offshore structural deck, double bottom structural form and the mixed form, are inverstigated with MSC/NASTRAN software. The results prove that the mixed type structure with truss enforcement is found to be the most appropriate for the region.

• Journal of the korean society of oceanography
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• v.32 no.4
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• pp.181-190
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• 1997

A large subtidal sand ridge (Jungang Satoe) in Asan Bay, on the west coast of Korea, was studied in order to understand the morphology and sediment transport trend in a macrotidal setting, by means of analyzing sediment samples, current data, side-scan sonographs and seismic profiles. The ridge is about 15 km long and 2-5 km wide, with a relief of about 15 m. It is elongated in the flow direction of flood (SE) and ebb (NW) tidal currents, but asymmetrical in cross section. The western and southwestern side of the ridge is characterized by relatively gentle slopes averaging 0.4$^{\circ}$, whereas on the northeastern side, relatively steep slopes were mapped with 1.6$^{\circ}$ slope angles. Tidal currents associated with the ridge are very strong; maximum surface velo-cities range from neap values of 50 cm/s to spring values of 130 cm/s. The shear velocities during flood and ebb are strong enough to erode and transport sands on the ridge. Sand waves and megaripples (dunes) are the most common bedforms produced by the tidal currents, which show regional differences in shape and size on the ridge. The distribution pattern of these bedforms in-dicates that the flood tidal currents are dominant on the offshore (northwest) side of the ridge, whereas the onsho.e (southeast) side of the ridge is ebb-dominated. The sand transport path as inferred from bedform orientations is directed toward the ridge crest on the flanks, whereas on the crest, it is near-longitudinal to the ridge axis. The convergent, upslope movement of sands on the ridge flanks appears to be important in sand ridge building and maintenance. A significant ridge migration toward the northeast can be suspected on the basis of the ridge morphology, which may cause offshore hazards for navigation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.281-294
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• 2015

In order to quantitatively estimate the nonlinear destructive interaction of wave load with wind load, which is very vital for the optimal design of offshore wind energy converter, we carried out a hydraulic model test and wind tunnel test. As a substructure of offshore wind energy converter, we would deploy the monopile, which is popular due to its easiness in construction. Based on the simulation using Monte Carlo simulation using Kaimal spectrum and cross spectrum, the instantaneous maximum wind velocity is adjusted to 10 m/s. And, considering the wave conditions of the Western Sea where a pilot wind farm is planned to be constructed, $H_s=0.1m$, 0.15 m, 0.2 m is carefully chosen. It turns out that the nonlinear destructive interaction between the wind and wave loads acting on the offshore wind energy converter is more clearly visible at rough seas rather than at mild seas, which strongly support our deduction that a Large eddy, a swirling vortex developed near the bumpy water surface in the opposite direction of the wind, is the driving mechanism underlying nonlinear destructive interaction between the wind and wave loads.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.6
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• pp.665-669
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• 2010

To confirm the distributon of finless porpoise, Neophocaena phocaenoides, in the South Sea of Korea, data on bycatch, stranding, and drifting of finless porpoises from 1999 to 2009 were used and a sighting survey was conducted from the R/V Tamgu No. 9 and 10 in June and November, 2009 and March, 2010. The total number of bycaught, stranded, and drifting finless porpoises was 607, with position being known for 186 of these. At the center of Yeosu, there were few position data on bycaught, stranded, and drifting finless porpoises, and data could not confirm the distribution of finless porpoises. Thus, there were limits on the usefulness of bycaught, stranded, and drifting data for confirming the distribution of finless porpoises. In the three sighting surveys, the sighting rate was highest at 0.231 ind./n.m. in the western South Sea in June, 2009. Sighting rate was less than 0.1 ind./n.m. in November, 2009 and March, 2010. This is likely to be due to seasonal migration in western South Sea. All sighting rates in the eastern South Sea were over 0.13 ind./n.m.. According to the results of the sighting survey, finless porpoises are distributed around the islands and inner bay along the path of the research vessel in the South Sea. There were numerous finless porpoises in the offshore areas of Mokpo, Yeosu, Tongyeong, Dadaepo, and Gaduk-do. This study will be utilized as part of a future abundance assessment of finless porpoise in the South Sea of Korea.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.3
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• pp.165-169
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• 1998

In August 1996, seawater salinity and nutrient distribution were investigated at surface waters in the South Sea of Korea. The low-salinity (< 20.00 psu) waters were observed in the western and southwestern offshore areas of Cheju Island. Relatively low saline (< 30.0 psu) waters occupied most of the survey areas only except in the eastern part. The observed minimum salinity was lower by 11.78 psu than that of the average between 1963 and 1995. The low saline waters appeared in the upper layer of generally 10-20 m deep, and were obriously distinguished from high-salinity (> 32.00 psu) waters, 30 m deep. The low saline waters may originate from the freshwater discharge of vast amount of from Yangtze River during the heavy rainfall season in China. Phosphate concentrations in the surface waters were relatively low and were less variable than those of nitrate and silicate. The maximum concentrations of nitrate and silicate occured in the western and southwestern offshore areas of Cheju Island, where the salinities were the lowest. The concentrations of nitrate and silicate were inversely correlated with salinity, whereas that of phosphate showed a considerable scatter and non-conservative behaviours. This indicates extensive desorption reactions of suspended materials releasing phosphate.