• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.1
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• pp.1-6
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• 1998

Our studies diagnose insulation degradation using the method of PD system. In analysis method of degradation, we make use of degradation information that analyzed the phase angle - PD pulse amplitude - degradation time( $\Phi$- PDA - t) pattern and phase angle- PD pulse number - degradation time( $\Phi$- PDN - t) pattern using statistical operators such as skewness(S), kurtosis(K). Secondly using statically operator such as the center of gravity (G), the gradient of the discharge distribution(C), we have analyzed for the prediction of life which we can be obtained the time, occurred of many pulse of small discharge amplitude.

• Transactions on Electrical and Electronic Materials
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• v.12 no.5
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• pp.189-192
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• 2011

A flexible back-light unit (FBLU) is fabricated by embedding plasma discharge clusters in a flexible polymer matrix. The brightness uniformity of an FBLU was measured for various combinations of optical sheets and compared with the simulated results for various bending angles. A gap between light sources causes distinctive integrated brightness curves which have two inflection points depending on bending angle. The brightness distribution of a simulated BLU was in good agreement with that of an actual plasma BLU except for a dark area that appeared at the center of the simulated BLU. The real and simulated BLUs both clearly showed an angle dependency caused by mirror images located between point light sources. On the basis of these results, it is suggested that these mirror-like images could be a major factor in determining the characteristics of FBLUs.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.1-7
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• 2015

A cavitation venturi is a device that allows a liquid flow rate to be fixed or locked independent of a downstream pressure and has been successfully used in a liquid rocket engine system which requires a stable propellant flow rate. In the present research, four cavitation venturis which have same dimensions except for converging inlet angle and diverging outlet angle, were designed and manufactured. Flow rates through each venturi and upstream/downstream pressures were measured by changing the pressures. From the experimental data, the discharge coefficients and critical pressure ratios were calculated for each venturi. It was found that the inlet and outlet angles of the cavitation venturi affected the discharge coefficient, and the outlet angle influenced on the critical pressure ratio.

• Applied Science and Convergence Technology
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• v.26 no.1
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• pp.1-5
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• 2017

The spurt vacuum pump is widely used to transfer sludge and slurry, and to control flow rate in a variety of processing fields, such as the oil, chemical, and fiber industries. The efficiency of the pump depends on the design parameters of the impeller, such as the number of blades, and the blade angle. In this study, the effect of the configuration of the impeller discharge angle of a spurt vacuum pump, which influences total head, shaft power, and efficiency, was numerically investigated using the commercial code, ANSYS CFX ver. 16.1. In addition, the performance of the pump was evaluated on the basis of the correlations between the total head, pump efficiency, and pressure distribution.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.320-326
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• 2019

Recently, the application of atmospheric plasma technology in air filtration is increasing. Sterilization by an atmospheric plasma device is very effective. However, ozone gas, which is generated during atmospheric plasma formation, poses a hazard to human health. To reduce the ozone gas during plasma discharge, we fabricated a one-plate hybrid plasma discharge device with a heating element, which can decompose ozone gas effectively by a simple heating action. In this study, we evaluated the plasma discharge characteristics and ozone concentrations with various Ar flow rates and temperatures. With increasing Ar gas flow rate, the ozone concentration and spectrum intensity increased till an Ar gas flow rate of 60 sccm, and decreased thereafter. When discharged in high temperature, the ozone concentration and spectrum intensity decreased. Further, to evaluate the state of the treated surface under various plasma discharge and heating conditions, we measured the variation in the contact angles on the surface. Regardless of the temperature, the contact angle increased with increasing discharge voltage. However, the contact angle increased when discharged at high temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.59-62
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• 1999

Inception and propagation of electrical tree and properties of Partial discharge(PD) pulses accompanying with tree as a function of needle tip radius in low density polyethylene were discussed. To study on these characteristics in different tip radius, we used specimens with needle-plane electrode system made of LDPE, observed inception and propagation of electrical tree by optical microscope with computer and investigated the characteristics of the phase resolved PD pulses accompanying with propagation of electrical tree. The PD quantities detected and analysed were PD magnitude, mean phase angle, average discharge, and the statistical characteristics of the PD pulses. As the tip radius ${\gamma}$ increases, tree inception stress E$\sub$i/ converges to constance value. This result suggests that tree inception stress E$\sub$i/ increases due to stress relaxation when the tip radius is small. Branch-type electrical tree was formed When E$\sub$i/ is 640-750[kV/mm]. bush-type electrical tree when E$\sub$i/ is 370∼400[kV/mm], branch-like electrical tree when E$\sub$i/ is 370-400[kV/mm].

• Journal of computational fluids engineering
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• v.21 no.1
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• pp.50-57
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• 2016

In various industries related with construction and military machinery, a large amount of power is normally required because such machinery operations, such as digging or breaking, take place under difficult working conditions in a rough environment. Thus, a hydraulic system needs to be applied as the major power transfer system. To produce and supply hydraulic power depending on the various load conditions, a hydraulic piston pump is utilized as a typical power source for a hydraulic system. In the present study, numerical simulations were conducted using the commercial program, Ansys CFX 14.5. To lubricate the moving parts as the pump starts to operate, a small amount of oil leaks out through the clearance between the orifice in the piston-shoe and the recess at the swash-plate. Taking this into consideration, a cylindrically shaped computational domain was modeled to maintain the same equivalent leakage area. To validate the numerical method applied herein, the numerical results of the flow rate at the discharge port were compared with the experimental data, and a good agreement between them was shown. Using the verified method, the effects of the discharge pressure and the angle of the swash-plate were also evaluated under several load conditions. The results of the present study can be useful information for a hydraulic piston pump used in many different manufacturing industries.

• Journal of the Korean institute of surface engineering
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• v.44 no.2
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• pp.50-54
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• 2011

Hydrophobic a-C:F film was coated on polycarbonate film with $CF_4$, $C_2F_6$ and HFC ($C_2F_4H_2$) gas in helium discharge generated by 5~100 kHz AC power supply at atmospheric pressure and room temperature. The highest water contact angle of the a-C:F film formed with $He/C_2F_6$ mixed gas is $155^{\circ}$. X-ray photoelectron spectrum showed that there was 40% of C-$CF_3$ bond at the surface of the super hydrophobic film. The contact angle and deposition rate were decreased with increasing substrate temperature. The contact angle was generally increased with the surface roughness of the film. The contact angle was high when the surface microstructure of the film was fine and sharp at the similar roughness and chemical composition of the surface.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2308-2310
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• 1999

The effect of magnetic field on NOx removal characteristics from a combustion flue gas has been experimentally investigated for a DC corona discharge reactor with a multipoint plate geometry in our Lab. Combustion flue gas removal efficiency of this type was much higher than that of the other types. In this paper, needle-plate geometry discharge system with applied magnetic field at a right angle to the electric field was made. Input power source was used negative DC. The corona discharge characteristics for this system was investigated and compared with the corona characteristics for the corona discharge system without magnetic field.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.584-587
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• 1993

Mica, which have a good thermal and electrical characteristics, while will cleave easily at these layers. In order to bond mica materials soldily, mica/epoxy composite insulation materials were developed for generator stator winding. There are lots of problems such as delamination and partial discharge of these insulation materials caused by mechanical, electrical and thermal aging. Several experiments have been conducted in order to find the useful diagnostic parameters from the partial discharge phenomena by applying a new measurement techniques. this paper deals with the partial discharge pulse characteristics, which may be a useful diagnostic concept in predicting insulation condition of generator stator insulation materials. Long term insulation aging test shows that partial discharge phase angle an magnitude are identified as one of the main key techniques for insulation diagnosis on generator stator winding.