• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.12
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• pp.83-89
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• 1996

The electrochemical spike oscillations at the nickel (Ni) electrode/(0.05M KHC$_{8}$H$_{4}$O$_{4}$) buffer solution (pH 9) interface have been studied using voltammetric and chronoamperometric methods. The nature of the periodic cathodic current spikes is the activation controlled currents due to the hydrogen evolution reaction and depends onthe fractioanl surface coverage of the adsorbed hydrogen intermediate or the cathodic potential. There is two kinds of the waveforms corresponding to two kinds of the cathodic current spike oscillations. The widths, periods, and amplitudes of the cathodic current spikes are 4 ms or 5ms, 151 ms or 302 ms, and < 30 mA or < 275 mA, respectively. The fast discharge and recombination reaction steps are 1.5 times and twice and faster than the slow discharge and recombination reaction steps. The fast and slow discharge and recombination reaction steps are 1.5 times and twice faster than the slow discharge and recombination reaction steps. The fast and slow discharge and recombination reactions corresponding to the fast and slow adsorption sites at the Ni cathode.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.1
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• pp.56-59
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• 2008

We have designed 4 types(void in insulation paper, protrusion electrode, floating electrode, surface discharge) of partial discharge(PD) defect to simulate typical faults found in oil filled power transformers. Ultra-high frequency(UHF) radiation due to PD was measured using a UHF measuring system and a conventional PD measuring system, simultaneously. Electromagnetic radiation spectra of these defects show UHF radiation up to about 1.5-2 GHz range. The phase resolved partial discharge(PRPD) patterns of UHF radiation from the PD defects were also measured and the pattern reveals distinct feature for each defect types. The UHF measuring could be used to detect PDs in oil filled transformers and analysis of the PRPD pattern should provide useful information on origin of PD signal.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.104-107
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• 2009

In order to improve discharge characteristics in AC PDP, we suggest FDFA (Facing Discharge Front plate Address Electrode) structure. By adopting both long facing discharge electrodes and address electrodes in front plate, the FDFA structure make it possible to gain a high luminance, low power consumption, and a high luminous efficiency.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.5
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• pp.732-738
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• 2015

In ac discharge, emission efficiency shows an time-varying characteristics during discharge. The phenomenon is caused by the potential distribution changes during the discharge, which indicates that a specific potential distribution can contribute to a high improvement of the emission efficiency. To create an artificial environment for a potential distribution favorable to emission efficiency, we used the asymmetric electrode structure and proved the capability. Our results showed that the ratio of the area of anode to cathode became larger, the emission efficacy was greatly improved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.158-161
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• 2005

In this paper, the precision electric discharge machining technology, the powder electric discharge machining technology, is applied to making a cold forging die for making the helical type of clutch gear. Various working conditions are investigated with emphasis on reduction of the electrode wear and enhancement of the surface roughness. Through the research work, the key technology of making the helical gear forging dies is achieved.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.7
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• pp.32-39
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• 1998

This paper presents the experimental results on the 3-electrode DC-PDP which has a common electrode to improve the PDP life cycle. The measured DC characteristic proves the effectiveness of common electrode absorbing about half of discharge currents. The waveforms for pulse memory operation of3-electrode PDP without crosstalk could also be determined from the I-V characteristics. The pulse memory drives of 8*8 cell array show the frequency response fo memory margin and the luminance efficiency of 3-electrode PDP are quite different from genrally known characteristics of 2-electrode DC-PDP.

• Transactions of Materials Processing
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• v.14 no.3 s.75
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• pp.251-256
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• 2005

3-D micro structures and micro tools were fabricated using Micro Electrical Discharge Machining (MEDM). To make micro structures, micro electrical discharge milling process was applied. During micro electrical discharge milling, electrode (tool) worn in the both axial and radial direction. To compensate tool wear which has significant influence on machining accuracy, machining path overlapping was proposed. Machining characteristics of micro electrical discharge milling was investigated in considering of depth of cut and capacitance of discharge circuit. Micro complex shaped tools were also fabricated using REDM (reverse electrical discharge machining). Sacrificial electrodes were machined through electrical discharge milling process and were used as electrode to make micro tools. Using this process several micro tools shape of 'ㄷ', 'ㅁ' and 'o' were fabricated. With these complex shaped tools, micro machining was successfully applied repeatedly.

• Journal of Korean Institute of Industrial Engineers
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• v.38 no.3
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• pp.220-226
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• 2012

The Electric discharge machining (EDM) process is used to minimize the difference between designed feature and machined feature while the most workpiece is removed through the cutting processes. The tiny-deep hole machining and perpendicular wall machining in mold and die are good applications of EDM. Among EDM equipment, the super drill uses the hollowed electrode to eliminate the debris which causes the second discharge with the electrode and degrades the machining quality. Through the hollow, the high pressured discharge oil is supplied to remove the debris together with the spindle rotation. The thin-hollow electrode tends to easily wear out compared to the sold die-sinking electrode and its wear rate is might not allowed to monitor in real time during discharging. Up to now, the wear amount is measured by off line method, which leads machining time to increase because the hole pass-through moment can be check by visual (manually) with the extra tool path. Therefore, this study suggests the attractive method to evaluate the hole pass-through moment in which the gap voltage and z-axis encoder pulse are monitored to predict the moment. The commercial super drill is used to validate the proposed method and the experiment is carried out.

• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.9-12
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• 2000

A new type electrolyzing cell with slits on parallel plate electrodes and wire-to-cylinder type electrode system has been proposed instead of the conventional parallel plate type. An investigation was carried out on the effect of the number and size of slits on ion precipitation and oxidant generation characteristics, evidenced by eliminated space charge limiting action and by elevated electric fields in active interelectrode spacing. And it is also studied on the effect of the diameter of wire electrode to ion precipitation and oxidant generation characteristics. With electrode with 48 slits, very oxidants generation water of 3.1 [ppmm] and 19.0 [ppmm] in positive electrode side were obtained with tap water and 0.1 [wt%] NaCl dissolved tap waterfed. In addition, with wire-to-cylinder type electrode system, it is found that oxidant contained water of 0.48 [ppmm] and 5.46 [ppmm] in positive electrode side were obtained with tap water and 0.1 [wt%] NaCl dissolved tap water fed for the case of discharge electrode diameter of 0.5 [$mm{\phi}$]. Consequently, very high ion precipitation and dense oxidant generation characteristics can be realized by having slits on the electrodes of conventional cell as these slits increase the electric fields and decrease the space charge limiting actions in interelectrode spacing.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.268-274
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• 2013

Electric discharge machining drill (EDM-drill) is an efficient process for the fabrication of micro-diameter deep metal hole. As there is non-physical contact between tool (electrode) and workpiece, EDM-drill is widely used to machine the hard machining materials such as high strength steel, cemented carbide, titanium alloys. The electro-thermal energy forces the electrode to wear out together with the workpiece to be machined. The electrode wear occurs inside of a machining hole. and It causes hard to monitor the machining state, which leads the productivity and the quality to decrease. Thus, this study presents a methodology to estimated the electrode wear amount while two coefficients (scale factor and shape factor) of the logarithmic regression model are evaluated from the experiment result. To increase the accuracy of estimation model, the linear transformation method is adopted using the differences of initial electrode wear differences. The estimation model is verified through experiment. The experimental result shows that within minute error, the estimation model is able to predict accurately.