• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.587-601
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• 2020

The ocean circulation was simulated in the East Sea and Ulleungdo-Dokdo region using ROMS (Regional Ocean Modeling System) model. By adopting the East Sea 3 km model and the HYCOM 9 km data, Ulleungdo 1 km model and Ulleungdo-Dokdo 300 m model were constructed with one-way grid nesting method. During the model development, a correction method was proposed for the distortion of the open boundary data which may be caused by the bathymetry data difference between the mother and child models and the interpolation/extrapolation method. Using this model, a super-high resolution ocean circulation with a horizontal resolution of 300 m near the Ulleungdo and Dokdo region was simulated for year 2018. In spite of applying the same conditions except for the initial and boundary data, the numerical models result indicated significantly different characteristics in the study area. Therefore, these results were compared and verified by using the surface current data estimated by satellites altimeter data and temperature data from NIFS (National Institute of Fisheries Science). They suggest that in general, the improvement of the one-way grid nesting with the HYCOM data on RMSE, Mean Bias, Pattern correlation and Vector correlation is greater in 300 m model than in the 1 km model. However, the nesting results of using East Sea 3 km model showed that simulations of the 1 km model were better than 300 m model. The models better resolved distinct ridge/trough structures of isotherms in the vertical sections of water temperature when using the higher horizontal resolution. Furthermore, Karman vortex street was simulated in Ulleungdo-Dokdo 300 m model due to the terrain effect of th islands that was not shown in the Ulleungdo 1 km model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.165-172
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• 2016

An experimental study of the thermal-hydraulic characteristics of passive safety systems (PSSs) was conducted using a system-integrated modular advanced reactor-integral test loop (SMART-ITL). The present passive safety injection system for the SMART-ITL consists of one train with the core makeup tank (CMT), the safety injection tank, and the automatic depressurization system. The objective of this study is to investigate the injection effect of the PSS on the small-break loss-of-coolant accident (SBLOCA) scenario for a 0.4 inch line break in the safety-injection system (SIS). The steady-state condition was maintained for 746 seconds before the break. When the major parameters of the target value and test results were compared, most of the thermal-hydraulic parameters agreed closely with each other. The water level of the reactor pressure vessel (RPV) was maintained higher than that of the fuel assembly plate during the transient, for the present CMT and safety injection tank (SIT) flow rate conditions. It can be seen that the capability of an emergency core cooling system is sufficient during the transient with SMART passive SISs.

• Journal of the Mineralogical Society of Korea
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• v.28 no.3
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• pp.221-231
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• 2015

Precambrian Jirisan gneiss complex suffered retrograde metamorphism ranging from granulite facies to the amphibolite facies and/or greenschist facies. Intrusive anorthositic rocks in gneiss complex are influenced by late metamorphism. Mafic mineral in anorthositic rock composed mainly of amphiboles, which can anticipate the information about metamorphic conditions and metamorphic facies. Amphiboles from anorthositic rock show subhedral to anhedral in shape and mostly blueish green and/or green in colour in plane polarized light. Some of brownish amphiboles show zonal texture with brownish to blueish green in color from core to rim. Reaction parts in clinopyroxene which exchange with amphibole. It suggests retrograde metamorphism and/or alteration. Amphiboles composing anorthositic rocks can be classified into two types depending on the size and occurrence of amphibole. The first type is microcrystalline amphibole occurring matrix [Group I: ferrohornblende]. The second type is amphibole with 1 mm or larger in size, which is usually occurred in the boundary between opaque mineral and plagioclase [Group II: ferropargasite]. Electron microscopic analyses base on the $Al^{vi}$ composition in amphiboles suggest that the metamorphic pressure of anorthositic rock was low with 5 kbar or less. Ti compositional range in amphibole and representing hornblende+ plagioclase+garnet+biotite+chlorite mineral assemblage suggest that metamorphic facies of anorthositic rock is in amphibolite facies.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.3
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• pp.164-174
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• 2008

In this study we try to identify the three-dimensional mixing characteristics of Seomjin River discharges in Seomjin River Estuary and Gwangyang Bay using a seasonal field observation (CTD) during spring tide and a three-dimensional numerical model with EFDC (Environmental Fluid Dynamics Code). The tidal elevation conditions of the four main tidal harmonic constituents on the open boundary and river discharges and thermal effluents at the specific boundary are considered. The calculated harmonic constants of tide and tidal current agreed well with those of observations at two stations for tide and two stations for tidal current. The model successfully reproduced well known the estuarine circulation in Seomjin River Estuary where tide and river discharges are dominant forcings. In the winter mean discharges case, tidal currents move Seomjin River discharges in Seomjin River mouth and in the summer mean discharges case, river flows move Seomjin River discharges near ae Seomjin River Estuary. A three-dimensional mixing characteristics of Seomjin River Estuary show well a three-dimensional estuarine circulation and thermal effluents effect to the seasonal variation of river discharges.