• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.304-306
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• 2003

Oceanic pycnocline depth is usually obtained from in situ measurements. As ocean internal waves occur on and propagate along oceanic pycnocline, it is possible to estimate the depth remotely. This paper presents a method for retrieving pycnocline depth from synthetic aperture radar (SAR) imagery where internal waves are visible. This model is constructed by combining a two-layer ocean model and a nonlinear internal wave model. It is also assumed that the observed groups of internal wave packets on SAR imagery are generated by local semidiurnal tides. Case study in East China Sea shows a good agreement with in situ CTD data.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.445-449
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• 2005

Various methods to detect the phytoplankton/red tide blooms in the oceanic waters have been developed and tested on satellite ocean color imagery since the last two and half decades, but accurate detection of blooms with these methods remains challenging in optically complex turbid waters, mainly because of the eventual interference of absorbing and scattering properties of dissolved organic and particulate inorganic matters with these methods. The present study introduces a new method called Red tide Index (Rl), providing indices which behave as a good measure of detecting red tide algal blooms in high scattering and absorbing waters of the Korean South Sea and Yellow Sea. The effectiveness of this method in identifying and locating red tides is compared with the standard Ocean Chlorophyll 4 (OC4) bio-optical algorithm applied to SeaWiFS ocean imagery, acquired during two bloom episodes on 27 March 2002 and 28 September 2003. The result revealed that OC4 bio-optical algorithm falsely identifies red tide blooms in areas abundance in colored dissolved organic and particulate inorganic matter constituents associated with coastal areas, estuaries and river mouths, whereas red tide index provides improved capability of detecting, predicting and monitoring of these blooms in both clear and turbid waters.

• Journal of Ocean Engineering and Technology
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• v.24 no.4
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• pp.8-12
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• 2010

The use of a tidal-current power system is one source of renewable energy that can minimize the environmental impact of power production and offer many other advantages compared to conventional energy sources. Unlike other energy production approaches, rate of energy production can be precisely predicted and the operational rate is very high. The performance of the rotor, which has a vital role in energy production using tidal currents, is determined by various design factors, and it should be optimized for the specific ocean environment in the field. The horizontal-axis turbine is very sensitive to the direction of flow, and flow direction changes due to rise and fall of the tides. To investigate the performance of the rotor considering the interaction problems with incidence angle of flow, a series of experiments were conducted, and a 3D CFD model was designed and analyzed by ANSYS CFX. The results and findings are summarized in the paper.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.134-137
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• 2006

Tidal power can use conventional technology to extract energy from the tides. It is usually best deployed in areas where there i s a high tical range which includes Western and Southern coastal areas in Korea. However, to extract tical energy, a barrage across an estuary or a bay is to be constructed that is now very hard due to severe environmental impact on local estuary. The recent technology of application of tidal stream provides a new window to extract power minimizing the adverse environmental impact Tidal stream technology which directly exploits these currents is relatively new but is presently generating considerable interest Turbine rotors can be used to extract energy from the flows. Prototype devices currently on test in the UK include the 300kW SeaFlow turbine. In this paper, the recent technology and research on ocean tical stream power are addressed

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.74-79
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• 2006

General formula are presented for the maximum power available from the tidal head in a closed basin and from the tidal currents in a channel connecting two large bodies of water. In the latter case, the available energy cannot be estimated from the kinetic energy flux in the undisturbed state, but can be obtained from knowledge of the tidal head between the ends of the channel and the maximum volume flux in the undisturbed state. The results are supported by detailed calculations for Johnstone Strait, British Columbia, using a two-dimensional finite element model. The model also allows an extension to the case of multiple channels. More work is needed to allow for partial tidal fences which do not occupy the whole cross-section of a channel.

• Journal of Ocean Engineering and Technology
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• v.27 no.3
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• pp.29-35
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• 2013

The exploration areas for maritime resources such as oil and natural gas have gradually moved to deep sea areas. It has become difficult to use existing fixed marine structures, which are very costly to build, because that have reached the uppermost economic limit. Therefore, floating marine structures and flexible marine structures are preferred. In particular, slender bodies such as risers and pipes are important parts of ocean depth marine structures. These slender bodies have more flexible structural characteristics in deep water areas because their overall length becomes longer and thediameter/length slenderness ratio gets smaller. In addition, the dynamic behavior of slender bodies becomes complicated as external forces such as tides and waves act on it directly. In this study, in order to solve these problems, we performed model tests in a 2-D wave basin using flexible slender bodies with different modulus of elasticity values. As a result, we compiled statistics and compared the behaviors of flexible slender bodies with respect to the effect of the modulus of elasticity. We expect that the results could be used as reference data for the design of structures with flexible elements.

• Proceedings of the KSRS Conference
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• v.2
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• pp.856-859
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• 2006

In river with bar, the characteristics of its physical conditions have a close relationship with bar morphology. In this paper, a monitoring approach of bar transformation in the Han River Estuary is presented using RADARSAT/SAR Images. The estuary is divided into North and South Korea and its area is blocked by CCL(Civil Control Line). Satellite remote sensing, therefore, is uniquely suited to monitoring bar transformation. Based on SAR signatures for bars, bar transformation is investigated from 2000 to 2005, and monitoring of suspended-silt transportations from terrestrial runoff is tried to understand the morphology during the events of severe rain storm. SAR data did not reveal clearly the bar locations because of most of data acquisitions during high tides from 6.8 m to 9.0 m. Even though the problem, it could be said that in the estuary vegetated area and natural levees are developed well, but bars and shifted after an event like a flood. It is also showed that suspended solids such as silt transported through the estuary could contribute highly to a sedimentation environment around Incheon.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.4
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• pp.257-266
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• 2000

A vertically-averaged, two-dimensional version of the Princeton Ocean Model has been applied to the South Sea to simulate the circulation driven by tides and inflows/outflows across open boundaries. To incorporate both forcing properly, a two-step modeling approach is adopted, in which the tidal circulation is first simulated by specifying the tides along the open boundaries, and then both the calculated tidal currents and the observed steady mean currents are prescribed across the open boundaries. Model results show that the steady, subtidal circulation of the South Sea is different from the residual circulation due to tidal rectification, and subtidal currents become locally as strong as tidal currents. The Cheju Current entering the model domain across the Cheju Strait flows eastward in general while shifting onshore or offshore areas following local isobaths. The Tsushima Current entering across the southern boundary reaches farther to the north in the eastern vicinity of Cheju-Do as compared to that entering across other parts of the southern boundary. The Tsushima Current turns to the east, merges with the Cheju Current, and both the Cheju and Tsushima Current exit to the East Sea through the western channel of the Korea Strait. An intensification of the outflow occurs over the deep trough adjacent to the Tsushima Island, which appears to be due to the formation of the frictional boundary layer in order to remove excess positive relative vorticity generated by an increase in the layer thickness. The circulation driven by both the tidal and inflows/outflows is different from that driven by each forcing separately in coastal areas, which implies that both forcings should be considered simultaneously in the simulation of more realistic coastal circulation.

• 한국해양학회지
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• v.15 no.2
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• pp.112-122
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• 1980

A two-dimensional non-linear tidal model has been established to calculate the M$\_$2/ tide of Inchon Bay in the west coast of Korea. Cartesian coordinates are used for the derivation of the governing equations and account is taken of extensive drying boundaries (tidal flats) which are exposed at low tides. The tidal amplitudes and phases computed from the model agree well with those known from observation lying within bounds 5cm in amplitude and 5 in phase relative to the observed results. The work represents a further stage in the development including extensive sea measurements capable of application in various coastal engineering problems encountered in Inchon Bay area.

• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.95-100
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• 2006

Measurements of ocean color from space since 1970s provided vital information with reference to physical and biogeochemical properties of the oceanic waters. The utility of these data has been explored in order to map and monitor highly toxic/or harmful algal blooms (HABs) that affected most of coastal waters throughout the world due to accelerated eutrophication from human activities and certain oceanic processes. However, the global atmospheric correction and bio-optical algorithms developed for oceanic waters were found to yield false information about the HABs in coastal waters. The present study aimed to evaluate the potential use of red tide index (RI) method, which has been developed by Ahn and Shanmugam (2005), for mapping of HABs in Korean and neighboring waters. Here we employed the SSMM to remove the atmospheric effect in the SeaWiFS image data and the achieved indices by RI method were found more appropriate in correctly identifying potential areas of the encountered HABs in Korean South Sea (KSS) and Chinese coastal waters during 1999-2004. But the existence of high absorbing and scattering materials greatly interfered with the standard OC4 algorithm which falsely identified red tides in these waters. In comparison with other methods, the RI approach for the early detection of HABs can provide state managers with accurate identification of the extent and location of these blooms as a management tool.