• Journal of the Korean Society of Visualization
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• v.9 no.1
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• pp.49-54
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• 2011

An investigation has been made of a viscous incompressible flow in a circular cylindrical tank. The flow is driven by the spinning bottom disk of tank together with/without central injection and radial uniform-ejection through the sidewall. Numerical solutions of steady and unsteady flows to 3-dimensional Navier-Stokes equation were obtained for several cases of injection strength. In a moderate flow rate of injection, the mass transfer occurs through the boundary layers but, as the flow rate increases, the inner region far from the container walls takes part in mass transfer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.81-91
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• 2019

Although the number of users of urban railways is greatly influenced by the land use plan around the railway station, Korea has been studying this problem in a small scale, so that the entrance width is uniformly calculated irrespective of the land use plan, And there is little deviation. Therefore, this study aims to establish a demand estimation model for the entrance and exit of urban railway stations. For this purpose, the demand, land use area, and socioeconomic indicators for each of the 20 urban railway stations were surveyed at 200m and 500m Regression model. The model is based on the assumption that the dependent variable (response variable) of the model is set to 1 day, peak 1 hour, peak time 5 minutes, Education, and park) and socioeconomic indicators (population, employer, employee, and student) as independent variables (explanatory variables). As a result, it was analyzed that the fit of the model is more statistically significant when the use area of the land use by 500 meters of the center radius of the city rail is used as an independent variable and the demand for the daily use of the railway station is used as a dependent variable. The purpose of this study is to estimate the optimal size of urban railway entrance in order to improve the mobility of the user and the transportation weak in urban railway station.

• Fire Science and Engineering
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• v.34 no.4
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• pp.96-100
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• 2020

The leakage of hazardous materials due to the defect in storage tank foundations is likely to cause tremendous fire disasters in the industry cluster area. Thus, adequate design and construction of the tank foundation is required for preventing tank leakage. In this study, four types of typical tank foundations were classified and modeled for 3D FEM analysis to perform stability evaluation on tank foundations. Furthermore, numerical analysis indicated that stress concentration just below the tank shells is 40 times that at the tank center. The settlement influence zone is about the tank radius and tank diameter in the horizontal and vertical directions, respectively. Thus, the appropriate guidelines for the design and construction of tank foundations were suggested via a comparison assessment of the numerical analysis results on the stress distribution and displacement of the tank foundations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.555-565
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• 2018

Nowadays, the artificial ground freezing (AGF) method has been used in many geotechnical engineering applications such as temporary excavation support, underpinning, and groundwater cutoff. The AGF method conducts the freezing process by employing a refrigerant circulating through a set of embedded freezing pipes to form frozen walls serving as an excavation support and cutoff wall. Two refrigerants of brine with the freezing temperature of $-20{\sim}-40^{\circ}C$ and liquid nitrogen with the freezing (evaporating) temperature of $-196^{\circ}C$ are commonly being used in geotechnical applications. This paper performed a series of field experiments to evaluate the freezing rate of marine clay in application of the AGF method. The field experiments consisted of the single freezing-pipe test and the frozen-wall formation test by circulating liquid nitrogen, which is a cryogenic refrigerant, into freezing pipes constructed at a depth of 3.2 m in the ground. The temperature of discharged liquid nitrogen was maintained through the automatic valve, and the temperature change induced by AGF method was measured at the freezing pipes and in the ground with time. According to the experimental results, the single freezing-pipe test consumed about 11.9 tons of liquid nitrogen for 3.5 days to form a cylindrical frozen body with the volume of about $2.12m^3$. In addition, the frozen-wall formation test used about 18 tons of liquid nitrogen for 4.1 days to form a frozen wall with the volume of about $7.04m^3$. The radial freezing rate decreased with increasing the radius of frozen body because the frozen area at a certain depth is proportional to the square of the radius. The radial freezing rate was formulated as a simple equation.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.479-491
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• 2013

Products of the eruption of Mt. Baekdusan are identified as volcanic materials at the estuaries of the Songhuagang river to north, the Dumangang river to east and the Amnokgang river to west. More speficially, pyroclastic flows, lahars and volcanic floods can affect an area of 400km in radius, centering around Lake Cheonji caldera. However, unlike the millenium eruption, the flow situation has been changed. Because multi-purpose dams and reserviors with a combined pondage of mora than 2 billion tons of water have been built in the rivers of which sources are originated from Lake Cheonji caldera. In addition, the flow of fluids expected to take place when the volcano has erupted is thought to be affected by artificial constructions in both direct and indirect ways. This study calculates the direction of fluids flow by using numerical analyses of pyroclastic flows, lahars and volcanic floods that can occur when the volcano of Mt. Baekdusan has erupted. We also estimate the scope of damages by pyroclastic flows, lahars, volcanic flooding caused by the pondage of the dams and water storages in and around Mt. Baekdusan. Pyroclastic flows transported over the steep slopes at the early times of eruptions move over the mountain slopes, affecting airplanes, and lahars due to leaks of Lake Cheonji could reach as far as major rivers and streams near Mt. Baekdusan. Unlike historical accounts, volcanic flood is expected to be limited in its scope of influence to reservoirs bigger than Lake Cheonji in pondage.