• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.191-197
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• 2002

The prediction of the dynamic behaviors of buoyant water discharges into a large volume of water bodies, the flows of water accompanying the density differences due to temperature differences and sometimes also to salinity differences, have attracted great concern over several decades. Heated water surface discharges from power plants and freshwater discharges in estuaries are typical examples of the buoyant flows. (omitted)

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1882-1884
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• 2004

In this paper, the waveform parameters of electromagnetic pulses radiated from intracloud discharges were presented. The zero-crossing times and the full pulse widths of the large bipolar electromagnetic pulses due to intracloud discharges are gradually decreased as the stroke proceeds. Also, the electromagnetic pulses tend to be bipolar, with narrow and fast leader pulses superimposed on the initial half cycle. The mean numbers of leader pulses superimposed on the initial half cycle were 1.61${\pm}$0.74 and 1.75${\pm}$0.73 for the positive and negative polarities, respectively.

• Journal of Korea Water Resources Association
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• v.43 no.12
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• pp.1039-1050
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• 2010

Relative accuracy of six discharge measurement methods-velocity-area method, rod-float method, ADCP moving-vessel method, ADCP fixed-vessel method, electromagnetic wave surface velocimeter (EWSV), LSPIV- is evaluated by comparing discharges measured by them with dam released discharges. Data from 39 times of concurrent discharge measurement campaigns are analyzed. Except the rod-float method, measured discharges show absolute errors less than 6.2% with dam discharges. When the four methods is evaluated by being compared with discharges measured with the conventional velocity-area method, discharges with electromagnetic wave surface velocimetry shows 7.35% of absolute errors and other three methods shows absolute errors less than 6%. The rod-float method, which shows large discrepancy compared with dam and velocity-area method, need complementary verification.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.112-117
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• 2004

In this paper, in order to obtain the detailed information about lightning electromagnetic pulses, the electromagnetic pulses radiated from intracloud discharges were measured, and their characteristics and waveform parameters were analyzed statistically. The electromagnetic pulses produced by intracloud discharges are distinctly different with those by lightning return strokes. The zero-crossing times and the full pulse widths of the large bipolar electromagnetic pulses are gradually decreased as the stroke proceeds. Also, the electromagnetic pulses tend to be bipolar, with narrow and fast leader pulses superimposed on the initial half cycle. The mean numbers of leader pulses superimposed on the initial half cycle were 1.61$\pm$0.74 and 1.75$\pm$0.73 for the positive and negative polarities, respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.8
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• pp.981-994
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• 2014

Density currents formed by buoyancy discharges from rivers are numerically studied using non-dimensional two layer model including Coriolis acceleration, bottom stress, interfacial friction. Some typical numbers such as Froude number, densimetric Froude number and Kelvin number are obtained and some characteristic scales are defined as a result of non-dimensionalization of the governing equations. Besides the Coriolis effect, the configurations of bottom topography, bottom friction coefficient and interfacial friction are found to significantly affect the propagation of the warm water plume. Frontal position can fastly propagate in the case of large density difference between the two layers and small interfacial friction. Left side boundary current is easily formed under the small interfacial friction. With large Kelvin number, both right and left side boundary currents are formed. Wave-like disturbances and eddies are easily formed under the high Froude number.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.3
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• pp.3-10
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• 2007

In general method to estimate the water supplies in the large-scale basin, indirect estimation method such as unit loading factor method has been used. However, the estimated water supplies are much different to the real water supplies used in the any basin because these general methods estimate them considering water supply demands only. Especially, water supplies for irrigation are big different to the real water supplies in which the water supplies for irrigation are depend on the weather conditions such as evaporation, basin conditions such as infiltration, the reservoir operation rule for irrigation water, and distribution methods. Thus, a new estimation method is developed to estimate the real water demands which is essential factors for the effective water resources operation in the basin. This method is for estimating the water supplies and return rates based on the survey of the irrigation reservoirs and the analysis of effects to the stream flows, return flows, and water supplies for irrigation which water supplies and return rates are used in the basin water management model. The water supply usages in each subbasin are validated by comparisons between the simulated discharges from the basin water management model and the discharges measured in the control points.

• Journal of Korea Water Resources Association
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• v.39 no.6 s.167
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• pp.487-494
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• 2006

The flood discharge on the rising limb of a hydrograph at Hwawon station greatly differs from the flood discharge on the falling limb for the same stage. When there is such a big hysteresis, there can be a significant amount of errors in the rated discharge obtained from a simple rating curve. To reduce errors in rated discharges, a looped rating curve was established for Hwawon station in the Nakdong River. In order to compute the deviation between real discharges and simply rated discharges, a simple rating curve was established using the stage and discharge data from the results of a hydraulic channel routing. The relationship between the discharge deviation ${\Delta}Q$ and a product of B and ${\Delta}h/{\Delta}t$ was analysed, where B is the channel topwidth; ${\Delta}h$ is the stage increment; At is the time increment. Strong relation between ${\Delta}Q$ and $B{\Delta}h/{\Delta}t$ was found. The discharges calculated from the relationship show differences by 10 % or less for the 7 observations out of 11 observations in 1997 whose stages exceeds 7 m. The observed discharges for the stages over 9 m in 1998 also show small difference with the discharges estimated from the loop rating curve. Looped rating curve is recommended, instead of the simple rating curve to reduce the errors of rated discharges for gauging stations like Hwawon, which has relatively large loop width.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.12
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• pp.673-678
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• 2000

The dielectric barrier discharge(DBD) is a common method to create a nonthermal plasma in which electrical energy is used to create electrons with a high average kinetic energy. The unique aspect of dielectric barrier discharges is the large array of short lifetime(10ns) silent discharges created over the surface of the dielectric. A silent discharge is generated when the applied voltage exceeds the breakdown voltage of the carrier gas creating a conduction path between the applied electrode and grounded electrode. As charge accumulates on the dielectric, the electric field is reduced below the breakdown field of the carrier gas and the silent discharge self terminates preventing the DBD cell from producing a thermal arc. In fact, the most significant application of dielectric barrier discharges is to generate ozone for contaminated water treatment. Therefore, experiments were perfomed at 1∼2[bar] pressure using a coaxial geometry single dielectric barrier discharge for ozone concentrations and energy densities. The main result show that the concentration and efficiency of ozone are influenced by gas nature, gas quantity, gas pressure, supplied voltage and frequency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.2
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• pp.169-175
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• 2006

This study investigated variation leakage current maximum value and waveform considering applied voltage phase angel by simulating three environmental conditions, such as fog, salt fog, and kaolin contamination .As the result of applied voltage phase angel characteristics, leakage currents presented almost in phases in the early stage regardless of environmental conditions just after applying the voltage, and the phase of leakage currents certain phase lags for the discharge of the applied voltage when surface discharges occurred due to the continuous environmental contamination. In addition, the difference in phase significantly increased according to the intensity of discharges. The change in distortion rates according to the environmental contamination presented a nearly same level just after applying the voltage. The distortion rate of third harmonic for the fundamental wave presented by the order of fog>salt fog>kaolin when surface discharges occurred due to the applied voltage for certain continued periods. In the case of the fog and salt fog, the scale of spectrums decreased according to the increase in frequencies from the results of the analysis of high frequencies. In addition, the even number frequency presented a relatively large level compared to the odd number frequency under the kaolin contamination.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.2
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• pp.1-9
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• 2014

A modeling system is constructed by integrating an one-dimensional unsteady flow simulation model and a hydrologic model to simulate flood flows in drainage channel networks of paddy field districts. The modeling system's applicability is validated by simulating flood discharges from a paddy field district, which consists of nine paddy fields and one drainage channel. The simulation results are in good agreement with the observed. Particularly, in the verification stage, the relative errors of peak flows and peak depths between the observed and simulated hydrographs range 8.96 to 10.26 % and -10.26 to 2.97 %, respectively. The modeling system's capability is compared with that of a water balance equation-based model; it is revealed that the modeling system's accuracy is superior to the other model. In addition, the simulations of flood discharges from large-sized paddy fields through drainage channels show that the flood discharge patterns are affected by drainage outlet management for paddy fields and physical characteristics of the drainage channels. Finally, it is concluded that to efficiently design drainage channel networks, it is necessary to analyze the results from simulating flood discharges of the drainage channel networks according to their physical characteristics and connectivities.