• Journal of Korean Society on Water Environment
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• v.29 no.3
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• pp.409-419
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• 2013

In this study, the analytical method for 27 residual pharmaceuticals in raw water was developed. Online sample preconcentration/extraction and analysis with high resolution Orbitrap mass spectrometry (LC-ESI/Orbitrap MS) were performed. The calibration curves showed good linearities (above $r^2$ = 0.998) in the range of 5 ~ 1,000 ng/L. The method detection limit and the limit of quantification were 1.1 ~ 10.0 ng/L and 3.4 ~ 31.7 ng/L, respectively. Recoveries of the target compounds were between 70.1% and 115.8% (except cefadroxil, cefradine, vancomycin, and iopromide (50.2 ~ 67.0%)). The optimized analytical method can be useful to determine the residual pharmaceuticals in raw water.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1452-1456
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• 2009

Water related disasters frequently occur in these days due to global warming and climatic change. This give us that the trend of mal-distribution of available water resources would be increased and the environment of water resources management getting much worse. Therefore the establishment of the effective strategy should be required for water resources management urgently. In this paper the hydrological characteristics and corresponding social phenomena of the drought events in Geum river basin are inspected in depth. The word, social phenomena, means not the quantitative damage but the qualitative social influences and its main characters are analyzed by the collections of the mass media articles. This study will be helpful in prognosticating the future drought occurrence and the establishment of counterplan to them.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.6
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• pp.446-454
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• 2008

The purpose of this paper is to analyze two-phase flows of the hydrogen recirculation system. Two-phase flow modeling is one of the great challenges in the classical sciences. As with most problems in engineering, the interest in two-phase flow is due to its extreme importance in various industrial applications. In hydrogen recirculation systems of fuel cell, the changes in pressure and temperature affect the phase change of mixture. Therefore, two-phase flow analysis of the hydrogen recirculation system is very important. Two-phase computation fluid dynamics (CFD) calculations, using a commercial CFD package FLUENT 6.2, were employed to calculate the gas-liquid flow. A two-phase flow calculation was conducted to solve continuity, momentum, energy equation for each phase. Then, the mass transfer between water vapor and liquid water was calculated. Through an experiment to measure production of liquid water with change of pressure, the analysis model was verified. The predictions of rate of condensed liquid water with change of pressure were within an average error of about 5%. A comparison of experimental and computed data was found to be in good agreement. The variations of performance, properties, mass fraction and two-phase flow characteristic of mixture with resepct to the fuel cell power were investigated.

• Journal of Ocean Engineering and Technology
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• v.27 no.6
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• pp.32-42
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• 2013

In this paper, a wave-induced swirl water chamber (SWC) for breakwater and wave power generation is introduced and its applicability to wave power generation in the coastal waters of Korea is investigated. The SWC type of wave power generation is a way to drive a turbine using the unidirectional swirl flow that is induced in the back of a curtain wall of a breakwater due to incident waves. The typical wave characteristics are obtained by analyzing the annual statistical wave data from KHOA (Korea Hydrographic and Oceanographic Administration). A numerical analysis is carried out on the variations in the SWC entrance height, wave height, and different installation conditions. For the numerical analysis, a commercial code, Fluent based on FVM, is used. As the entrance height decreases, the mass flow rate through the entrance is rarely changed, whereas the magnitude of the flow velocity of the smaller entrance height is greater than the other ones, which is better for the formation of an SWC swirl flow inside and the flow kinetic energy at the entrance. In cases of installation conditions where a wall is place behind and under SWC, it has been shown that the mass flow rate through the entrance is greater than that in the open condition, and sufficient flow kinetic energy is generated in the entrance for wave power generation. However, the swirl flow kinetic energy is relatively small. Thus, in the future, it is necessary to study the swirl flow generation, which is affected by the SWC shape.

• Environmental Analysis Health and Toxicology
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• v.15 no.3
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• pp.99-106
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• 2000

Ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) are various applied as chelating agents for metal ions, then they are widely used in many industrial processes and domestic products. A method is described for the determination of EDTA and NTA in water samples by GC/MS . The reaction temperature, reaction time and pH for esterification of EDTA and NTA were investigated using 10% sulfuric acid-methanol, ethanol and propanol. Optimum conditions were obtained by the esterification in 80$\^{C}$ for 1hr with ethanol. Method detection limits of ethylated EDTA and NTA in the 200 ml of water samples were 0.05 ng/ml, respectively, EDTA and NTA could be determined in the range of 0.05∼23.6 and 0.05∼7.0 ng/ml in treated water, and in the range of 0.06∼25.0 and 0.05∼6.40 ng/ml in raw water respectively. Risk assessments with EDTA and NTA exposure by drinking water ingestion were carried out. Based on the results of analysis, chronic daily intakes of EDTA and NTA would be less than the value of acceptable daily intake or tolerable daily intake.

• Tunnel and Underground Space
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• v.13 no.5
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• pp.353-361
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• 2003

For RMR and Q rock mass classification at the design and construction stage, evaluation of groundwater condition is usually based upon the experience due to the restriction of available methods. Based on the results of Taejon LNG Pilot Cavern which acquire joint water pressure, inflow rate of ground water and hydraulic conductivity model, estimates from numerical analysis and analytical solutions were compared to verify each evaluation method. As the result, the Raymer(2001) approach was found to be efficient for estimating inflow rate and corresponding value.

• The Korean Journal of Food And Nutrition
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• v.12 no.2
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• pp.191-191
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• 1999

A Purge & Trap Concentrator was used to analyze various volatile organic compounds(VOCs) in wat-er. The object of this study was to observe the purge efficiency of 40 VOCs in water according to the change of parameters (purge time drypurge time sample temperature) and to determine the optimum condition for VOCs using the purge & Trap concentrator interfaced with a narrow capillary connected to a gas chromatography/mass spectrometry. The optimum condition of purge and trap is as follows: purge time at 11min drypurge time at 5min sample temperature at 6$0^{\circ}C$ at constant purge flow (40mol/min) constant desorption flow(20ml/min) desorption temperature(2$25^{\circ}C$) and desorption time (1min) At this analytical condition the detection limits of VOCs was in the range of 0.1~0.5$\mu$g/ml and the purge efficiency of each compound was over 70%.

• Journal of Ocean Engineering and Technology
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• v.21 no.5
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• pp.18-24
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• 2007

The environmental value of coastal vegetation has been widely recognized. Coastal vegetation such as reed forests and seaweed performs several useful functions, including maintaining water quality, supporting fish (and, thus, fisheries), protecting beaches and land from wave attack, stabilizing sea beds and providing scenic value. However, studies on the physical and numerical process of wave propagation, sediment transport and bathymetric change are few and far between compared to those on the hydrodynamic roles of coastal vegetation. In general, vegetation flourishing along the coastal areas attenuates the incident waves through momentum exchange between stagnated water mass in the vegetated area and rapid mass in the un-vegetated area. This study develops a numerical model for describing the wave attenuation and sediment transport in a wave channel in a vegetation area. By comparing these results, the effects of vegetation properties, wave properties and model parameters are clarified.

• Analytical Science and Technology
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• v.8 no.4
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• pp.771-778
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• 1995

The authors have developed an analytical method for determining trace amounts of 285 kinds of chemicals in natural waters by GC-ion trap MS. The results of overall recovery tests at $0.1{\mu}g/l$ showed that the mean recovery was 92.1% and the mean relative standard deviation was 10.8%. The mean of the method detection limits was $0.036{\mu}g/l$. From the results of analysis of real samples, it was confirmed that this method is useful to elucidate the concentration levels and the fate of chemicals in the aquatic environment.

• Earthquakes and Structures
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• v.18 no.2
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• pp.171-184
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• 2020

The potential of using the roof water tanks as a mitigation measure to minimize the required separation gap and induced pounding forces due to collisions is investigated. The investigation is carried out using nonlinear dynamic analysis for two adjacent 3-story buildings with different dynamic characteristics under two real earthquake motions. For such analysis, nonlinear viscoelastic model is used to simulate forces due to impact. The sloshing force due to water movement is modelled in terms of width of the water tank and the instantaneous wave heights at the end wall. The effect of roof water tanks on the story's responses, separation gap, and magnitude and number of induced pounding forces are investigated. The influence of structural stiffness and storey mass are investigated as well. It is found that pounding causes instantaneous acceleration pulses in the colliding buildings, but the existence of roof water tanks eliminates such acceleration pulses. At the same time the water tanks effectively reduce the number of collisions as well as the magnitude of the induced impact forces. Moreover, buildings without constructed water tanks require wider separation gap to prevent pounding as compared to those with water tanks attached to top floor under seismic excitations.