• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.761-768
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• 1997

A numerical model is developed to analyze the incompressible unsteady flow induced by the pump trip-out in the cooling water discharge culvert of thermal power plants. The numerical models has various features to deal concureently with the overall behavior of complicated unsteady flow due to the presence of cooling water internal system, seal well, air chamber, culvert, manholes, open channel and sea water. A leap-frog finite difference scheme is employed to solve governing equations, and the model is tested for a simple case of two tanks connected with a pipe. A fixed free surface boundary condition used earlier at the downstream end of culvert for large water body is investigated.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.6
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• pp.129-137
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• 2014

This research presents an streamflow modeling approach in a data-scarce estuary reservoir watershed which has been suffered from high salinity irrigation water problem after completion of land reclamation project in South Korea. Since limited hydrology data was available on the Iwon estuary reservoir watershed, water balance relation of the reservoir was used to estimate runoff from upstream of the reservoir. Water balance components in the reservoir consists precipitation, inflow from upstream, discharge through sluice, and evaporation. Estimated daily inflow data, which is stream discharge from upstream, shows a good consistency with the observed water level data in the reservoir in terms of EI (0.93) and $R^2$ (0.94), and were used as observed flow data for the streamflow modeling. HSPF (Hydrological Simulation Program - Fortran) was used to simulate hydrologic response of upstream of the reservoir. The model was calibrated and validated for the periods of 2006 to 2007 and 2008 to 2009, respectively, showing that values of EI and $R^2$ were 0.89 and 0.91 for calibration period, 0.71 and 0.84 for validation period.

• Macromolecular Research
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• v.10 no.3
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• pp.150-157
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• 2002

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a microbial storage polymer with biodegradable properties. In order to improve the cell compatibility of PHBV surfaces, the physicochemical treatments have been demonstrated. In this study, physical method was corona discharge treatment and chemical method was chloric acid mixture solution treatment. The physicochemically treated PHBV film surfaces were characterized by the measurement of water contact angle, electron spectroscopy for chemical analysis, and scanning electron microscopy (SEM). The water contact angle of the physicochemically treated PHBV surfaces decreased from 75 to 30～40 degree, increased hydrophilicity. due to the introduction of oxygen-based functional group onto the PHBV backbone chain. The mouse NIH/3T3 fibroblasts cultured onto the physicochemically treated PHBV film surfaces with different wettability. The effect of the PHBV surface with different wettability was determined by SEM as counts of cell number and [$^3$H]thymidine incorporation as measures of cell proliferation. As the surface wettability increased, the number of the cell adhered and proliferated on the surface was increased. The result seems closely related with the serum protein adsorption on the physicochemically treated PHBV surface. In conclusion, this study demonstrated that the surface wettabilily of biodegradable polymer as the PHBV plays an important role for cell adhesion and proliferation behavior for biomedical application.

• Proceedings of the Korea Water Resources Association Conference
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• 1992.07a
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• pp.133-141
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• 1992

A three water-intake structure designed to built along the right bank of the Missouri River near Chesterfield, Missouri was model-tested at an undistorted scale of 1:5. Although the discharge capacity of each of six pumps to be installed is only 21,000 gpm, the model indicated strong flow circuation and unstable free-surface conditions as flow entered the two-pump bay through a narrow sluice opening at an angle. Strong free-surface vartices were also observed in the model. The sump modifications developed in the study included an array of baffle bars, a perforated plate, floor splitters, and floor-corner fillets. The solutions developed in this study could be applied to other pump sumps with multiple pump units.

• Proceedings of the Korea Water Resources Association Conference
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• 2003.05a
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• pp.93-100
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• 2003

In order to use radar rainfall data for flood management, it is necessary to study and develop a method for optimum error correction to obtain radar rainfall values that agree closely with surface rainfall data. This paper proposes an optimum estimation method for calculating rainfall in a river basin by using data from surface raingauges and radar raingauge systems. This paper also reports on recent applications of radar raingauge systems for accurate simulation of flood discharge based on river basin rainfall values obtained from radar raingauge systems.

• Journal of Korean Society on Water Environment
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• v.27 no.6
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• pp.848-854
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• 2011

The objective of this research was to experimentally test the effect of rice straw mats on the reduction of runoff, sediment and discharge under a laboratory scale with different rainfall intensity and slopes. We used the small runoff plots of $1m{\times}1m{\times}0.65m$ ($L{\times}W{\times}H$) in size were filled with loamy sand. Experimental treatments were bare (control), rice straw mats + PAM(SP), rice straw mats + PAM + sawdust(SPS) and rice straw mats + PAM + rice husks(SPR); slope of 10% or 20%; and rainfall intensity of 30 or 60 mm/hr. Runoff volume and coefficient from covered plots were significantly lower than those from control plots. Under the 30 mm/hr and 10% simulations, average runoff coefficient of covered plots decreased more than 92%. Under 60 mm/hr and 20% simulations, the ratios were between 39.8~58.1%. Under the condition of 30 mm/hr rainfall and 10% slope, sediment discharge from covered plots was practically zero. And at 20% plots, sediment reduction ratio was more than 95%. Under the condition of 60 mm/hr rainfall, sediment reduction ratio of 10 and 20% plots ranged between 86.3~95.3% and between 79.8~86.5%, respectively. The differences in initial runoff time, runoff and sediment discharge among different cover materials were not significant. Rainfall intensity showed higher impact on initial runoff time, runoff, and sediment discharge than slope. It was also shown that even if runoff reduction by surface cover were low, sediment discharge reduction could be very significant and contribute to improve the water quality of streams in sloping agricultural regions. It was concluded that the use of straw mat and PAM on sloping agricultural fields could reduce soil erosion and muddy runoff significantly and help improve the water quality and aquatic ecosystem in receiving waters.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.4
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• pp.3-22
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• 2000

To know characteristics of water quality in coastal sea around the Keum river estuary in summer, we studied the water quality of surface, middle and bottom level during Jun e～september, 1998. The mean concentrations of COD, DIN, DIP & chlorophyll-a were 1.36mg/L, 28.60㎍-at/L, 0.48㎍-at/L and 4.14㎍/L, respectively, which were over eutrophication criteria in sea water. After the Keum river dyke was constructed, seasonal freshwater discharge was largely changed. About 80% of total annual freshwater discharge was concentrated in summer as rainy season from July to September. The correlation coefficient of DIN versus salinity was shown to be high, and thus the concentration of DIN was closely related to freshwater discharge. Maximum Chlorophyll-a concentration was occurred in September, due to increased DIP concentration, high water temperature and low salinity after heavy rainfall in August. The results of Principal Component Analysis showed that the first factor represented a series of eutrophication factors, the second factor w3s a valiance of seasonal fluctuation, and the third was a variance of progress of mass change.

• Journal of Korean Society of Rural Planning
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• v.8 no.1 s.15
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• pp.3-14
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• 2002

Changes of chemical properties by times of the reclaimed tidal land soils and soil surface water, underground infiltration water with precipitation-runoff on natural meteological condition in the unripened tidal reclaimed paddy fields were investigated. This study was carried out to use environment-friendly farm land in the reclaimed tidal lands. The soils used in this study were saline-alkaline soils with the high $Na^+$ and $Mg^{++}$ content. As the results of investigation outflow loading of nutriments through outflow water in the unripened tidal reclaimed paddy fields by precipitation during the survey period, nutriments equivalent to T-N $1{\sim}2\;kg\;10a^{ -1}$ and T-P $0.01{\sim}0.02\;kg\;10a^{-1}$ from in the unripened tidal lands were discharged. Besides, the results of comparison losses of cation through outflow water showed $Na^+>\;K^+>\;Mg^{++}\;>\;Ca^{++}$, and the highest appeared water discharge of $Na^+$. In case of saemangeum reclaimed tidal land soils water discharge of cations showed $Ca^{++}$ 1.3 kg $10a^{-1}$, $Mg^{++}$ 1.6 kg $10a^{-1}$, $Na^+$ 17.7 kg $10a^{-1}$, and $K^+$ 3.2 kg $10a^{-1}$ respectively. On the other hand, in case of koheung reclaimed tidal lands soils water discharge of cations showed $Ca^{++}$ 18.1 kg $10a^{-1}$, $Mg^{++}$ 31.2 kg $10a^{-1}$, $Na^+$ 320.8 kg $10a^{-1}$ and $K^+$ 51.2 kg $10a^{-1}$ respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.678-686
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• 2002

This paper presents the effects of accumulation of surface charges on hydrophobic level and the changes of surface potential decay with various artificial environment treatments on high temperature vulcanized (HTV) silicone rubber used for outdoor insulating material. For this study, the charging apparatus by corona discharge, in which grid electrode was installed between the main corona and ground electrode, was used. From this study, it was found that the accumulation of surface charges above a critical surface potential on silicone insulating materials could lead to the temporary loss of surface hydrophobicity. In addition, corona stress and water absorption stress increase the decay rate of surface charges of HTV silicone rubber, while ultraviolet (UV) stress causes longer decay time. We could conclude that the effects of surface charges on hydrophobicity level and the changes of surface state by various artificial treatments were found through a trend of surface potential decay.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.89-95
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• 2019

Mooring observations of water temperature and salinity were conducted to investigate the effects of freshwater discharge patterns on the mouth of Nakdong River from April 2017 to March 2018. More than $500-1000m^3\;s^{-1}\;d^{-1}$ of freshwater was frequently discharged into the estuary throughout the rainy season, but less than $200m^3\;s^{-1}\;d^{-1}$ was discharged through the normal season. Sluice gates of the estuarine barrage operated depending on the tide level during spring tide, but they were constantly open during neap tide. Water temperature and salinity fluctuated regularly with intermittent discharges of freshwater, whereas they were stable while freshwater discharge was continuous. Mean salinity was 29 during the study period. Salinity exceeded the mean value in the normal season and rapidly recovered after a temporary reduction. In contrast, water with salinity below the mean value prevailed in the estuary for three months over the rainy season. These results indicate that water temperature and salinity were affected by the amount of freshwater discharge, as well as the frequency of discharge on a large scale and the time over which the freshwater discharge continued.