• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.3
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• pp.215-220
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• 2008

This study examined the stability of cross- and box-type artificial reefs used to construct seaweed beds. Theoretical and experimental studies have clarified the Froude similitude. However, basic data needed to develop a more stable design for artificial reefs must be collected from long-term studies and analyses of sliding caused by waves. Hydraulic experiments are important for solving problems in the design and construction of artificial reefs. This study examined some design parameters for artificial reefs under wave and currents. The results showed the stability of cross- and box-type artificial reefs for constructing seaweed beds using a dimensionless parameter (the surf similarity parameter), water particle velocity, and so on. The hydraulics experiment indicated that the stability of artificial reefs differed according to their method of installation. This implies that artificial reefs should be installed after considering various environmental factors, such as wave breaking, reflection, and sediments.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.21 no.6
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• pp.311-322
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• 1988

Application of the simple buoyancy adjustment model, similar to Davey's (1983), indicates that buoyancies imposed locally or from outside of the basin are the major factor of the Japan Sea circulation. Within the context of the model considered, the relatively strong SW gradient of temperature, and corresponding western boundary current, in the SW region is due to the beta-effect. Kelvin waves make the western side colder and the eastern side warmer. Buoyancy input (presumably by fresh water discharge) in the NW region, so far neglected, plays an important role in strengthening the NKCC (North Korea Cold Current) and suppressing the EKWC (East Korea Warm Current) thereby breaking the conventional branching system of the Tsushima Warm Current.

• Journal of the Korean Institute of Navigation
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• v.13 no.1
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• pp.77-106
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• 1989

Two numerical models of the shoreline change and sediment transport rates, explicit and implicit, are simulated with shore structures such as breakwaters, a jetty, groins and a seawall. The applied study area is songdo Beach, Youngil bay, Korea since it has all the shore structures mentinoed above. The two models investigate the beach line changes and sedimen transport rates for the beach before design of three groins with and without an offshore breakwater. In order to estimate the shoreline changes after three groins were built, the beach response inside the three groin compartiments and the offshore barrier are also investigated. The simulation based on the initial shoreline conditions surveyed by the Hydrographic office, Koreai 1979 and 1984. The breaking wave characteristics are introduced into the models by calculation from the empirical equations and modification from the numerical and hydraulic model test results developed for waves behind an offshore breakwater. The numerical simulation describes well the tendencies of the sand transport and shoreline changes affected by wave diffraction behind a detached breakwater and by interruption of sand transport at three groins.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.1
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• pp.15-21
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• 2013

The safety and stability of 5MW class offshore wind turbine Jack-up platform was investigated through ocean basin experiment. For simulating the environmental condition of yellow sea in the South Korea, diverse waves, winds and currents were performed based on Froude's number. Regular wave and irregular wave based on Froude's number were applied to the wind turbine structure. In experiments, the height and period of regular wave type were scaled down as the 1:50 ratio of real wave condition. Irregular wave type was simulated with TMA(Texel Storm, Marsen and Arsloe)spectrum. The vertical reaction force, resonance period and wave pressure applied to multi-supporters of wind offshore structure were measured experimentally. Finally, the results showed that the capsizing situation of the offshore structure was generated by the severe environmental condition.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.1 no.1
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• pp.45-50
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• 1997

Understanding the nonlinear flow caused by orographic effects can be valuable in siting of new businesses, industries, and transportation facilities. In spite of recent work on large-amplitude waves and wave breaking, the studies of flow around large scale mountains have just begun. The generative mechanism of lee vortices in the lee of large scale mountain is investigated by Ertel's theorem. The CSU RAMS is used as a numerical model. According to the numerical results, the isentropes are depressed behind the large scale mountains. This means the vortex lines must run upward and downward along the depression surface because vortex lines adhere to isentropic surfaces. Therefore, the vertically oriented vorticity can be formed in the lee of the large scale mountain. This vorticity plays an important role for orographic precipitation, because strong vertical velocity and cloud bands are developed along isothermal deformation surface.

• Journal of Environmental Science International
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• v.1 no.1
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• pp.45-50
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• 1992

Understanding the nonlinear flow caused by orographic effects can be valuable in siting of new businesses, industries, and transportation facilities. In spite of recent work on large-amplitude waves and wave breaking, the studies of flow around large scale mountains have just begun. The generative mechanism of lee vortices in the lee of large scale mountain Is investigated by Ertel's theorem. The CSU RAMS is used as a numerical model. According to the numerical results, the isentropes are depressed behind the large scale mountains. This means the vortex lines must run upward and downward along the depression surface because vortex lines adhere to isentropic surfaces. Therefore, the vertically oriented vorticity can be formed in the lee of the large scale mountain. This vorticity plays an important role for orographic Precipitation, because strong vertical velocity and cloud bandy are developed along isothermal deformation surface.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.2
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• pp.138-146
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• 2012

Using Shear-free Ship wake theory it was predicted the detectable submarine's turbulent wake on the sea surface was about 12km long when there was no breaking waves on the sea surface. It means that there are sufficient detectable turbulent kinetic energies on the sea surface as well as in the water. In this paper, we have proposed some concepts of non acoustic anti-submarine surveillance systems; SAR for sea surface surveillance, LIDAR for sub-surface surveillance and propelled gliders for under -water surveillance.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.4
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• pp.353-363
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• 1994

In order to give a useful guide for engineering applications on numerical models based on nonlinear stream function wave theory. collocation method and least squares method are directly compared input parameters of the revised Dean's Table (Chaplin, 1980). Two models ive both accurate and almost same results for all the cases except very long or nearly breaking waves. Overall comparison seems to favor the least squares method for general use.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.163-163
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• 2011

평활입자동역학법(SPH, Smoothed Particle Hydrodynamics)은 붕괴파(도수, 댐붕괴류, 쇄파) 등과 같이 수면 변동이 큰 유체 역학 문제를 해결하기 위한 무격자법 중의 하나이다. SPH를 이용한 붕괴파의 모의에서는 압력, 점성, 밀도(압축성), 척력 등 다양한 계산 인자가 필요하다. 이들 인자가 SPH 모의 결과에 미치는 영향을 도수와 댐붕괴류에 대해서 검토하였다. 그 결과 압력과 관련하여, 상태 방정식 계수로 표현되는 유체의 음속은 입자들의 흩어짐 현상과 밀접한 관계를 가지는 것을 밝혀내었다. 평활 거리는 수치해의 안정성과 밀접한 관련이 있으며, 너무 작거나 크게 설정하는 경우 해의 정확도가 떨어지는 것으로 나타났다. 일반적으로 2차원 문제의 경우 20~23개 정도의 입자가 해의 내삽에 사용되는 것이 바람직하다.

• Journal of Wetlands Research
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• v.14 no.4
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• pp.439-455
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• 2012

Coupled wave induced current modeling system(WIC) was developed from combining with the nearshore spectral wave model, SWAN, the wave induced force model, WIF, and the flow model, EFDC. The reasonable results were obtained from WIC modeling system. The ratio of the wave height calculated with respect to refraction and diffraction effects over submerged spherical shoal was occurred approximately 1~5 % errors compared to Goda(2000)'s result. The radiation stress suggested by Longuet-Higgins and Stewart(1960), the stresses due to rollers in breaking waves proposed by Dally and Osiecki(1994), and Kim(2004)'s new spreading approach instead of the previous lateral mixing approach were added to calculate wave induced force. The results of the WIC modeling system show good agreement with Nishimura et al.(1985)'s laboratory measurements and better than Kim(2004)'s 2 dimensional depth averaged numerical computations for a plane beach with detached breakwater. The present flow field computed agrees reasonably well with the measured flow field. The relative merit of WIF model in WIC modeling system is unconditional stable for time increment.