• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.125-132
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• 1984

A simple stratification/mixing model has been developed for shelf waters of the Yellow Sea and the East China Sea. The results are summarized in the form of maps of stratification parameter which utilized the estimates of tidal dissipation from non-linear two-dimensional tidal model of the region. Ultimate aim of this study is to evaluate the applicability of the tidal mixing criteria to the Yellow Sea especially for the offshore region near Taean Peninsula in the west coast of Korea using hydrographic data and computed stratification parameter.

• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.699-708
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• 1997

The effective unsaturated hydraulic conductivity in stratified soils is evaluated using a three-dimensional stochastic approach. Because of the disparity of the correlation scales in a stratified soil, the general stochastic equations are simplified. This allows analytical evaluation of generic expressions for the effective hydraulic conductivities. Simple asymptotic expressions, valid at particular ranges(wetting front, drying condition, wetting condition) of the mean flow characteristics, are also derived. An example of applying the derived theoretical result to a imaginaryl clay soil is presented. It reveals found that the effective unsaturated hydraulic conductivity showed large-scale hysteresis. Such large-scale hysteresis was produced by the spatial variability of hydraulic soil properties rather than hysteresis of the local parameters. In addition the results show that the effective hydraulic conductivities were larger in the case of accommodating heterogeneity of soil preperties rather than neglecting heterogeneity of soil properties.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2001.05a
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• pp.199-200
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• 2001

• Composites Research
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• v.18 no.2
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• pp.30-37
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• 2005

In this paper, geometrically non-linear finite element analyses were performed to study the mechanical behavior of the material system of the envelope of stratospheric airships. The microstructure of the load-bearing plain weave layer was identified and modeled. The Updated Lagrangian formulation was employed to consider the geometric non-linearity as well as the induced structural non-linearity for the fiber tows. The stress-strain behavior was predicted and the effective elastic modulus was calculated by numerical experiments. It was found the non-linear stress-strain curves were largely different from those by linear analysis. And non-linear elastic moduli were much higher than linear elastic moduli. The difference was more distinguishable when the tow waviness ratio was smaller.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.116-122
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• 1988

Interfacial shear stresses have been determined for countercurrent stratified flow of air and water in a nearly-horizontal rectangular channel, based upon measurements of pressure drop, gas velocity profiles and mean film thickness. A dimensionless correlation for the interfacial friction factor has been developed as a function of the gas and liquid Reynolds numbers. Equivalent surface roughnesses for the interfacial friction factor have been calculated using the Nikuradse correlation and have been compared with the intensity of the wave height fluctuation on the interface. The results show that the interfacial shear stress is mainly affected by turbulent mixing near the interface due to the wave motion rather than by the roughened surface.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.81-93
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• 2015

The comprehensive master plan in November 2010 on Saemangeum internal development has been released, and there is a need for complementary measures related to in-situ monitoring methods in order to acquire water temperature (T) and salinity (S) data. Thus, these data are monitored and analyzed by Korea Rural Community Corporation continuously. The purposes of current study are to evaluate the distributions of seasonal T and S, sigma-t, and stratification parameter and to compare annual stratification system in 2011 and 2012. To achieve these objectives, monthly vertical changes of T, S, and sigma-t, which are reproduced by a kriging technique, have been analyzed. In summer, the temperature difference between surface and bottom layers varies from 2 to $3^{\circ}C$, and the stratification of T is considerably weak. The stratification of S occurs abruptly within depth of EL. (-)5 to EL. (-)10 m. Therefore, stratification is induced by sudden increasing of water inflow amount due to a localized downpour during the rainy season, and these stratification processes are strongly influenced by inflowing a fresh water from watersheds in estuary environment.

• Nuclear Engineering and Technology
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• v.24 no.2
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• pp.130-140
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• 1992

The physical benchmark problem on the direct-contact condensation under the horizontal occurrent stratified flow was analyzed using the RELAP5/MOD2 and /MOD3 one-dimensional model. Analysis was peformed for the Northwestern experiments, which involved condensing steam/water flow in a rectangular channel. The study showed that the RELAP5 interfacial heat transfer model, under the horizontal stratified flow regime, predicted the condensation rate well though the interfacial heat transfer area was underpredicted. However, some discrepancies in water layer thickness and local heat transfer coefficient with experimental results were found especially when there is a wavy interface, and those were satisfied only within the range.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.21-27
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• 2008

Triangular structure is used as basic shape of artificial structures for generating the upwelling current in order to make rich fishing ground at sea. Artificial upwelling current could bring the deep sea water containing a lot of nutrients from the bottom up to the surface. The purpose of this study is to examine the flow characteristics around underwater triangular structure with various stratification parameter. An experimental study was carried out for the triangular structure model in the circulating water channel to investigate flow characteristics by flow visualization method. A velocity fields around the underwater structure were measured by particle image velocimetry(PIV). The experimental results showed that the upwelling effect at the back and upper region of the structure could be best when the water depth was 2 times of the structure height and the stratification parameter was approximately 3.0. These quantitative data will be useful to determine the functional efficiency cf artificial upwelling structures.

• Korean Journal of Remote Sensing
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• v.29 no.5
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• pp.581-588
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• 2013

We developed the three channel lidar system to measure stratospheric aerosols at the Gwangju Institute for Science and Technology (GIST), a suburban site in Republic of Korea. The system provides backscatter coefficient (${\beta}$) at 532 and 1064 nm as well as depolarization ratios (${\delta}$) at 532 nm ($2{\beta}+1{\delta}$) using the doubled Nd:YAG laser wavelength at 532 and 1064 nm. The lidar system is optimized to measure stratospheric aerosols such as volcanic ashes. This paper describes the details of the optical setup, data acquisition system, and analysis method. This study shows an example of measuring stratospheric aerosols emitted by the volcanic eruption which occurred in Mt. Nabro ($13.37^{\circ}$ N, $41.70^{\circ}$ E).

• Journal of Korea Water Resources Association
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• v.44 no.9
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• pp.741-751
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• 2011

In this study, a methodology was devised to overcome that difficulty for thermal stratification modeling using EFDC. For the increase of reproductability for thermal stratification analysis, the effect of parameter such as distribution of solar radiation, depth of active bed temperature layer, heat transfer coefficients were analyzed. The simulation period was from June to December in 2005 and statistical index is used to analyze the model results. The results showed that distribution of solar radiation is zero and depth of active bed temperature layer is 10 m are suitable for simulation of thermal stratification in Yongdam Dam reservoir. This study results can be used for guideline to analyze the thermal stratification of large dam reservoir in Korea.