• Journal of the Korean Society for Precision Engineering
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• v.15 no.7
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• pp.36-43
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• 1998

Surface roughness of cold rolled steel sheet as well as the coating technique itself is quite important in obtaining high image clarity of electronic products and car outer panels. Especially, surface characteristics of steel sheet have acquired increasing attention from the steel and automotive industries. While the influence of such characteristics on paintability formability and painted surface appearance is important in defining steel surface requirements for automotive industries. Therefore this paper is dedicated primarily to the issue of paint appearance and reviews for improvement of roughness and peak count about the surface of work roll for the actual temper mill. The conclusions were obtained as follows ; 1) Roughness and peak count about the surface of steel sheet is strongly affected by surface condition of work roll. 2) The electro-discharge textured roll has more uniform roughness distribution than shot blasted roll and it's painted appearance of steel sheet has more improvement than that of the shot blasted because it has more harmonic wave roughness, and the higher peak count of surface roughness.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.6
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• pp.35-40
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• 2008

High performance light emitting diodes(LEDs) have been developed using GaN-based materials grown on sapphire substrates in recent years. Although these LEDs are already commercially available, we have to consider electrostatic discharge(ESD) damage related to both basic materials of diode and miniaturization of LEDs. ESD damage is one of the important parameters influencing reliability of the light emitting devices. We investigated mass production of GaN-based LEDs suffered from ESD during production process and present the solutions in order to improve the ESD problem. Most of EDS problems were controlled by using instruments properly and improvement of the process circumstances as well.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1769-1776
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• 2016

For on-line partial discharge (PD) monitoring of rotating machines, a novel sensor is proposed, which can be installed on the power lead inside the terminal box of the machine. The sensor has been designed to have high capacitance, and minimal reflection of measured pulses. As a sensitivity of the sensor, transfer impedance $Z_t$ has been measured and compared to conventional coupler-type sensors. A simple method is presented for measuring $Z_t$ of coupler sensors, using a vector network analyzer and a practical lead-cable of rotating machine. Through this method, it became possible to measure the $Z_t$ of coupler sensors including the installation environment of them. The $Z_t$ of the proposed sensor is higher than that of same sized other conventional couplers at frequencies between 30 and 92 MHz. Another sensitivity test has been performed using a PD calibrator as a test pulse source. The proposed sensor has higher measured peak voltage than the conventional coupler type sensors when the same charges were input.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.41-41
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• 1996

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.620-620
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• 2006

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.740-743
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• 2009

In this paper we proposed a new electrode design to get an enhanced luminous efficiency in AC PDP. The width and shape of the TTO electrode were varied, and the electro-optical properties such as luminance, power consumption, luminous efficiency were estimated with the variation of frequency, duty ratio and applied voltage. The discharge characteristics were investigated to explain the effect of the new electrode structure on the electro-optical properties.

• Journal of Powder Materials
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• v.18 no.2
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• pp.149-158
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• 2011

Electro-Discharge Sintering (EDS) employs a high-voltage/high-current-density pulse of electrical energy, discharged from a capacitor bank, to instantaneously consolidate powders. In the present study, a single pulse of 0.57-1.1 kJ/0.45 g-atomized spherical $Ti_{52}Zr_{28}Ni_{20}$ powders in size range of 10~30 and $30\sim50{\mu}m$ consisting of ${\beta}$-(Ti, Zr) and icosahedral phases were applied to examine the structural evolution of icosahedral phase during EDS. Structural investigation reveals that high electrical input energy facilitates complete decomposition of icosahedral phase into C14 laves and ${\beta}$-(Ti, Zr) phases. Moreover, critical input energy inducing decomposition of the icosahedral phase during EDS depends on the size of the powder. Porous Ti and W compacts have been fabricated by EDS using rectangular and spherical powders upon various input energy at a constant capacitance of $450{\mu}F$ in order to verify influence of powder shape on microstructure of porous compacts. Besides, generated heat (${\Delta}H$) during EDS, which is measured by an oscilloscope, is closely correlated with powder size.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.7
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• pp.167-175
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• 1996

Work roll wear in the cold rolling of steel strip is strongly affected by rolling materials, rolling conditions and lubrication. Tests were performed to find the effects of rolling materials under the same lubricating conditions. Surface roughness of cold rolled steel strip as well as the coating technique itself is quite improtant in obtaining high image clarity of electronic products and car outer panels. Therefore this paper reviews for improvement of roughness and peak count about the surface of Cr coated work roll is investigated from the actual temper mill. The conclusions were obtained as follows; 1) Work roll wear in the cold rolling of steel strip is strongly affected by carbon contents of rolling materials, but there is not a separating force and total reduction ratio. 2) The roughness of strip surface is larger in the direction of width than in roll direction. 3) The electro-discharge textured roll has more uniform roughness distribu- tion than shot blasted roll and it's life time is two times longer than shot blasted because it has more harmonic wave roughness, and the higher peak count of surface roughness. 4) The life time of Cr coated work roll is 2 times longer than that of shot blasted work roll and variation of peak count, roughness and life time of Cr coated work roll is similar to electro-discharge texturing work roll. 5) The proper Cr coating thickness is 10 .mu. m at the work roll of temper mill.

• Journal of Electrical Engineering and information Science
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• v.3 no.3
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• pp.316-321
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• 1998

In recent years, concern has been raised about the technique of controlling electrical breakdown by using laser in many fields. Especially, laser has attracted much attention in the Electro-Discharge Macining(EDM) because of its many merits. Therefore, this research has been performed to obtain fundamental data relevant to discharge processing by using a pulsed Nd:YAG laser. The experiments of laser-guided dc discharge by laser radiation have been carried out at low air pressure ranging from 0.2 to 20 torr. The minimum laser-guided dc discharge voltage V\ulcorner at the given pressures P and distances D between an anode and a cathode was measured. It is found that the minimum laser-guided dc discharge voltage is much lower than the natural discharge voltage V\ulcorner\ulcorner, and the values of V\ulcorner and V\ulcorner as a function of P.D has a similar tendency. The laser output energy Eout decreases with input pulse duration tp increasing, and the more the value of tp increases, the higher that of V\ulcorner is obtained because the number of photons during the discharge time N decreases with t\ulcorner increasing. There is the time lag frequently when the discharge by laser radiation is misguided under the condition of the applied voltage less than V_G.min.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.1-8
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• 1999

In recent years, concern has been raised about the technique of controlling electrical breakdown by using laser in many fields. Especially, laser has attracted much attention in the Electro-Discharge Machining(EDM) because of its many rrents. 1berefore, this research has been perfonred to obtain fundarrental data for the discharge guide technology by a pulsed Nd:YAG laser which can be awJied to discharge processing machining. 1be experilnnts of laser-guided de discharge have been carried out at low air pressure ranging from 0.2 to 20 torr. The minimum laser-guided de discharge voltage $V_{G.min}$ at the given pressures P and distances d between an anode and a cathode was rreasured It is found that $V_{G.min}$ is much lower than the natural discharge voltage $V_{ND}$, and the values of VGrrin and $V_{ND}$ as a function of P.d has a similar tendency. The laser output energy $E_{out}$ decreases with input pulse duration $t_p$ increasing, and the rrore the value of $t_p$ increases, the higher that of V$V_{G.min}$ is obtained because the number of photons N decreases with $t_p$ increasing. In addition, the laser-guided de discharge range and the discharge guide characteristics as laser outpIt $E_{out}$ was investigated.igated.