• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.12
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• pp.606-615
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• 2004

The discharge characteristics of a ramp reset waveform in the alternating current plasma display panel(ac PDP) were studied using a 2-dimensional numerical simulation. We analyzed the wall charge variation during the reset discharge, address discharge and sustain discharge adopting a ramp reset waveform. Then we investigated the principal parameters for a successful discharge. In this paper, we suggest a new parameter, printing particles' density and its effects on the stability of the ramp discharge. The maximum current flows of the three electrodes during the ramp reset period were decreased with the increase in the priming particles's density which was explained with the wall charge characteristics and the current flow characteristics obtained by a 2-D simulation.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.37-43
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• 2000

In this experimental study we proposed the double dielectric barrier discharge (DDBD) reactor to produce as high an electric field as possible. The experiment are conducted for applied voltage from 15 to 20[kV], $1~4[\ell/min]$ of gas flow rate and 120[Hz] and 240[Hz] of pulse rate. Superposition discharge(SPD) generated in DDBD which combined the surface discharge with the silence discharge was the most effective to reduce the $NO_x$. In the decomposition efficiency per watt, the low pulse rate gave better efficiency than the high pulse rate. However in DeNOx rate, the high pulse rate gave better performance than the low pulse rate. $NO_x$ removal rate and efficiency increased with increasing the applied voltage in all reactors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.248-254
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• 1998

In the present study the glow discharge characteristics of $CO_2$ in a parallel plate electrode system were investigated, and the decomposition properties of $CO_2$ concerned with the discharge characteristics were discussed. The results show that $CO_2$ concentration decreases with increase in discharge power and decrease in gas pressure. The maximum conversion of $CO_2$ by glow discharge was 52% under the conditions of gas pressure, 10m Torr and 290W of discharge power.

• Journal of Korea Water Resources Association
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• v.50 no.12
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• pp.877-887
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• 2017

The energy losses due to surcharged flow at four-way combining manhole, which is mainly installed in the downstream of urban sewer system, is the main cause of inundation in urban area. Surcharged four-way combining manholes form various flow configuration such as straight through, T-type, and four-way manholes depending on variation of inflow discharge in inlet pipes. Therefore, it is necessary to analyze change of energy loss and estimate head loss coefficients at surcharged four-way combining manhole with variation of inflow discharge ratio. The hydraulic experimental apparatus which can change inflow ratios were installed to analyze the flow characteristics at four-way combining manhole. In this study, to calculate the head loss coefficient according to change of the inflow discharge ratios at the surcharged four-way combining square manhole, the discharge conditions of 40 cases which the inflow ratios of each inlet pipe were changed by 10% interval was selected. The head loss coefficient at surcharged square manhole showed the lowest value of 0.40 at the straight manhole and the highest value of 1.58 at the $90^{\circ}$ junction manhole. In the combining manholes (T-type and four-way), the head loss coefficients were calculated more higher as the lateral flow rate was biased. The contour map of head loss coefficient range was constructed by using the estimated head loss coefficients and the empirical formula of head loss coefficients was derived to consider the variation of inflow discharge ratios at the surcharged square manhole. The empirical formula could be applied to the design and assessment of the urban drainage system.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1311-1315
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• 2009

Understanding of the hydraulics of flow is very important to support the management of river. The cross-sectional area, average velocity, flow depth and discharge can be regarded as a power function each other. In this paper the flow of Bocheong stream basin is experimentally studied. The correlation analysis was performed between observed hydraulic factors by the power type function. The constants resulted from the correlation analysis were calculated by the geomorphologic characteristics of the watershed using the power type function. The correlation coefficients between the hydraulic factors were appeared close to unit having strong correlationship. The two conditions of equality of the continuity equation were analysed, and the conditions were found to be good results. From these results the observed hydraulic data of Bocheong stream basin can be concluded as a reliable data. The correlation coefficients between the parameters of the hydraulic characteristics and geomorphologic factors were found to be close to unit.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.151-160
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• 2000

An experimental and theoretical analysis for the improvement of dynamic characteristics and design of electro-hydraulic flow control servo valve are performed. The theoretical results are compared with the experimental step responses, and the important design parameters of an electro-hydraulic flow control servo valve are derived by using the simulation program. Simulation parameters of nozzle jet coefficient and orifice and spool valve discharge coefficient are given through experiment. The theoretical and experimental step response curves show that the valve gain depends on the fixed orifice and nozzle $ratio(R_on)$ and is maximum at $R_on=1.$ And drain orifice in the flapper - nozzle return line creates a small back pressure, which improves the performance fur the valve.

• Journal of Korean Society on Water Environment
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• v.31 no.1
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• pp.35-41
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• 2015

This study focuses on whether a physical habitat model, River2D, is useful to assess and design stream restoration. To achieve the aim, the habitat suitability for Zacco Platypus was analyzed using River2D at midstream of the Anyang-Cheon through modifying the low flow channel and changing the flow discharge. The River2D simulation results show that the inhabited environment for Zacco Platypus is improved by increasing the sinuosity of the low flow channel, and vice versa. Also the inhabited environment for Zacco Platypus gets worse when there is no additional flow for maintenance water supply at the stream flowing through cities. In this respect, the physical habitat simulation study based on the River2D model is useful because it provides a practical guidance in designing stream restoration.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.28-31
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• 2002

The water level fluctuation (WLF) method is a conventional method for quantifying groundwater recharge by multiplying the specific yield to the water level rise. A 2-D unconfined flow model with a time series of the recharge rate is developed. It is used for elucidating the errors of the WLF method which is implicitly based on the tank model where the horizontal flow in the saturated zone is ignored. Simulations show that the recharge estimated by the WLF method is underestimated for the observation well near the discharge boundary. This is due to the fact that the hydraulic stress resulting from the recharge is rapidly dissipating by the horizontal flow near the discharge boundary Simulations also reveal that the recharge was significantly underestimated with increase in the hydraulic conductivity and the recharge duration, and decrease in the specific yield.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.199-210
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• 1996

The measurements of velocities of internal flow in a scaled-up nozzle were made by laser Doppler velocimetry in order to clarify the effect of internal flow on the characteristics of fuel spray. The investigated length to diameter ratio(L/d) of the orifice were 1, 3, 4, 5 and 8, and inlet radius to diameter ratio(r0/d) were 0 and 0.5. Mean and fluctuating velocities and discharge coefficients were obtained at various Reynolds number ranging between 15,000 and 28,000, and L/d ranging between 1 and 8 in sharp and round inlet nozzle. The turbulent intensity and turbulent kinetic energy at exit in a sharp inlet nozzle were higher than that in a round inlet nozzle. For sharp inlet nozzle, fluctuating velocities near exit were decreased with increasing L/d.

• Journal of Korean Society on Water Environment
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• v.29 no.4
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• pp.523-530
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• 2013

This study has been carried out to clarify the characteristics of discharge and pollutant loading according to flow conditions at jiseok stream watershed (JSW). A flow rate and pollutant load in the study watershed were estimated by equation of stage-discharge and discharge-loads rating curve. By using the methods above, I've evaluated the water quality (WQ) of the JSW if it is satisfied with the standard target. I've collected the data of BOD and T-P from the JSW every 8 days for the duration of 12 months. And then, I've schematized the data upon the load duration curve and the results showed me that the WQ of JSW was satisfied with the standard target. I've also collected the same data every each day for the duration of 12 months from JSW and have schematized the data again. And the results showed that it also was satisfied with the standard target. To be concluded, I've determined that point pollution sources of JSW gives more significant impacts to the WQ than non-point pollution sources of JSW and hence, as time goes, point pollution sources will keep depriciating the WQ of JSW. Therefore, further efforts will be required to JSW to maintain the WQ.