• Tribology and Lubricants
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• v.16 no.4
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• pp.253-258
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• 2000

Frictional behavior of wire electric discharge machined surfaces of spheroidized annealed STDll steel was investigated. The surfaces were produced with a various series of finish cuts where pulse energy was reduced with increase in the number of finish cuts. Roughness and micro-hardness of the surfaces were also measured. It is observed that the increase in the number of finish cuts produces the surface exhibiting lower frictional resistance followed by higher resistance after considerable wear. Effects of finish cuts on the friction characteristics are discussed with the aid of roughness and micro-hardness of the surfaces.

• Journal of Environmental Science International
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• v.13 no.9
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• pp.759-765
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• 2004

HEC-RAS model is used for estimation of rating-curve of Musung in Wi stream. Discharge is computed from stage estimated by HEC-RAS model, is compared with the discharge of water surface slope method. The relative deviation of observed and computed discharge is 5.37%, and shows as a good results. A rating-curve by HEC-RAS model shows better results than by water surface slope method.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.683-689
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• 2016

Most outdoor solid insulators may suffer from surface degradations due to non-stationary currents that flow on the insulator surface. These currents may be classified as leakage, discharge and tracking currents due to their disturbing potencies respectively. The magnitude of these currents depends on the degree of the contamination of surface. The leakage signals are followed by discharge signals and tracking signals which are capable of forming carbonized tracking paths on the surface between high voltage and earth contacts (surface tracking). Surface tracking is one of the most breakdown mechanisms observed on the solid insulators, especially polymers which may cause severely reduced lifetime. In this study the degradations observed on polyester resin based insulators are investigated according to the IEC 587 Inclined Plane Test Standard. The signals are monitored and recorded during tests until surface tracking initiated. In order to prevent total breakdown of an insulator, early detection of tracking signals is vital. Continuous Wavelet Transform (CWT) is proposed for classification of signals and their energy levels observed on the surface. The application of CWT for processing and classification of the surface signals which are prone to display high frequency oscillations can facilitate real time monitoring of the system for diagnosis.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.628-631
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• 2002

$Al_2O_3$ capping layer and MgO protective layer were deposited by electron beam evaporation method using single crystal source. Thickness of the capping layer, $Al_2O_3$, was varied from 5 nm to 10 nm. Surface morphology was observed by SEM and AFM before and after hydration. And microstructure of deposited $Al_2O_3$ layer and chemical shift of electron binding energy were also observed by high resolution TEM and XPS, respectively, after hydration. From these results, it was found that Mg atoms diffused into $Al_2O_3$ layer, reacted with moisture and formed $Mg(OH)_2$ during hydration. As thickness of $Al_2O_3$ increased, extent of hydration increased. $Al_2O_3$ capped MgO thin films and uncapped MgO thin films were deposited on AC-PDP test panel to characterize discharge properties. Although $Al_2O_3$ has poor discharge properties rather than MgO, because of many hydrated species on the surface of MgO, similar discharge properties were observed.

• Journal of Korean Society on Water Environment
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• v.30 no.2
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• pp.184-198
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• 2014

For estimating discharge and pollution loads into the Yeongsan lake, a conceptual watershed model HSPF(Hydrological Simulation Program - Fortran) was applied to the Yeongsan River Basin. Various spatial data set including DEM, watershed boundaries and land uses were used to set up the model for the Yeongsan River Basin that was divided into 45 sub-basins. The model was calibrated and validated for the river discharges, SS, BOD, TN and TP concentrations against the data observed in 2011 at several monitoring stations. The simulation results show good agreement with the observed water flows($R^2$ = 0.46 - 0.97, NSE = 0.70 - 0.96). The simulated concentrations of SS, BOD, TN and TP are also in good agreement with the observed. The total freshwater discharge to the Yeongsan lake is estimated $2,406{\times}10^6m^3/year$ which the Jiseok and Hwangryoung stream contribute as much as 19%, 17% respectively. It is estimated that the total discharges to the Youngsan lake is SS 152,327 ton/year, BOD 15,721 ton/year, TN 10,071 ton/year, TP 563 ton/year. Both water and pollution loads are high in summer, particularly in July, when the monsoon season arrives at the Korean peninsula.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.537-542
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• 2000

Wire deflection, surface roughness and roundness were observed on changing discharge time for electrical discharge machining(EDM) of STD-11 in various conditions of thickness. The wire deflection was decreased as increasing discharge time and wire tension. The deflection is the smallest at the speed of wire of 10.6m/min and the water specific resistivity of 5k$\Omega$.cm. The deflection is found to be decreased as increasing dwell time. But if the water pressure is high, it is found not to be changed after the vibration of 4sec. The component of copper(Cu) and zinc(Zn), which is the main material of wire electrode, is observed for rough wire-cutting EDM of STD-11. This phenomena is found to be similar in spite of the change of EDM energy level. But it will be improved by changing the material and the shape of wire. The roundness of middle is found to be worse than that of upper and it is increased as the thickness of material is increased.

• Journal of the Korean institute of surface engineering
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• v.56 no.6
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• pp.386-392
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• 2023

In this work, we describe the reduction kinetics of gold nanoparticles synthesized by plasma discharge in aqueous solutions with varied voltages and precursor (HAuCl₄) concentrations. The reduction rate of [AuCl₄]^- was determined by introducing NaBr to the gold colloidal solution synthesized by plasma discharge, serving as a catalyst in the reduction process. We observed that [AuCl₄]^- was completely reduced when its characteristic absorption peak at 380 nm disappeared, indicating the absence of [AuCl₄]^- for ligand exchange with NaBr. The reduction rate notably increased with the rise in discharge voltage, attributable to the intensified plasma generated by ionization and excitation, which in turn accelerated the reduction kinetics. Regarding precursor concentration, a lower concentration was found to retard the reduction reaction, significantly influencing the reduction kinetics due to the presence of active H⁺ and H radicals. Therefore, the production of strong plasma with high plasma density was observed to enhance the reduction kinetics, as evidenced by optical emission spectroscopy.

• Journal of Environmental Impact Assessment
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• v.20 no.6
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• pp.833-843
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• 2011

The purpose of this study is to analysis pollutant loading of upper Nakdong River basin according to the variation of discharge. The correlation between discharge and pollutant concentration and between discharge and pollutant loading were analyzed by statistical method, respectively. Regression equation of pollutant loading and discharge was represented as $L=_aQ^b$ in which L = pollutant loading(kg/day), and b = regression coefficients, and Q = discharge($m^3/day$). The correlation coefficient of study area was in range of 0.8428 to 0.9935. The SS was the highest b value 1.2856~1.7730 among water quality parameters because the pollutant loading of SS was much affected by flow. Additionally, the applicability of the regression equations was verified by comparing predicted results with observed value. The correlation coefficient of verification was in range of 0.8983 to 0.9987 and NSEC was in range of 0.7018 to 0.9960. Therefore the pollutant loading was good correlated with discharge. The main result will be used as basic data for water quality management and design of environment fundamental facilities.

• Journal of Environmental Science International
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• v.20 no.5
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• pp.623-630
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• 2011

This study investigated the degradation of N, N-Dimethyl-4-nitrosoaniline (RNO, indicator of the generation of OH radical) by using dielectric barrier discharge (DBD) plasma. The DBD plasma reactor of this study consisted of a quartz dielectric tube, titanium discharge (inner) and ground (outer) electrode. The effect of shape (rod, spring and pipe) of ground electrode, diameter (9~30 mm) of ground electrode of spring shape and inside diameter (4~13 mm) of quartz tube, electrode diameter (1~4 mm), electrode materials (SUS, Ti, iron, Cu and W), height difference of discharge and ground electrode (1~15.5 cm) and gas flow rate (1~7 L/min) were evaluated. The experimental results showed that shape of ground electrode and materials of ground and discharge electrode were not influenced the RNO degradation. The thinner the diameter of discharge and ground electrode, the higher RNO degradation rate observed. The effect of height gap of discharge between ground electrode on RNO degradation was not high within the experimented value. Among the experimented parameters, inside diameter of quartz tube and gas flow rate were most important parameters which are influenced the decomposition of RNO. Optimum inside diameter of quartz tube and gas flow rate were 7 mm and 4 L/min, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.4
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• pp.783-787
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• 2009

A point-to-mesh type discharge system, utilizing a water-pen point as a corona discharge electrode and a mesh as an ion induction electrode, has been proposed, and the effect of the water-pen point electrode of the discharge system to the ionic wind velocity and generation yield was investigated. It was observed that the proposed discharge system with the water-pen point electrode can generate a higher ionic wind velocity as compared with that of the metal point electrode. As a result, the peak ionic wind velocities of 2.61 and 4.05 m/s for the positive and negative corona discharges of the proposed discharge system can be obtained, which are 1.39 and 1.15 times higher than those of the metal point electrode with same design. The ionic wind generation yield of 4.72 m/s/W of the discharge system with the water-pen point electrode was obtained for the positive corona, which was 3.66 times higher than that of the metal point electrode. This enhancement may be due to the effect of the water-pen point electrode.