• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.101-102
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• 2008

SF6 widely used as insulating gas is rising as the environment problem. For decreasing this greenhouse gas, electrical breakdown characteristics of vacuum with air are studied in non-uniform field. The gap of needle to plane was 0.5mm. The pressure of vacuum the range of 10^-4${\sim}$10^-5torr. The diameter of a plane made of the stainless steel is 150mm. As a result of the experiment, the breakdown voltage is increased about degree of vacuum increased. The electrode material influenced breakdown voltage in vacuum.

• Journal of Information Display
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• v.9 no.4
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• pp.15-20
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• 2008

A DC-magnetron inline sputter was established, and the influence of the base pressure on the structural characteristics of the ITO thin films was studied. When the inline sputter system was established and operated for ITO sputtering, its initial vacuum level did not go below $5\times10^{-6}$ torr. The vacuum leak test was conducted by measuring t he elapsed time until the vacuum level reached $1\times10^{-6}$ torr. The base pressure was successfully maintained at $1\times10^{-6}$ torr for 900 min, and the uniformity of the ITO film that had been deposited at this pressure significantly improved.

• KSTLE International Journal
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• v.1 no.2
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• pp.91-94
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• 2000

The friction and wear behavior of MoS$_2$coatings was investigated using a pin and disk type tester. The experiment was conducted with silicon nitride as the pin material and MoS$_2$-on-bearing steel as the disk material under different operating conditions that included linear sliding velocities within a range of 2266 mm/sec, normal loads varying from 9.829.4 N, corresponding to maximum contact pressures of 1.782.83 Gpa, and high vacuum, medium vacuum, and ambient air atmospheric conditions. The results showed a low friction coefficient far the coating in a high vacuum, plus the friction coefficient and wear volume increased with an increased normal load. Furthermore, under high load conditions, the friction coefficient and wear volume also increased with an increased sliding velocity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.366-367
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• 2008

SF6 widely used as insulating gas is rising as the environment problem. For decreasing this greenhouse gas, electrical breakdown characteristics of vacuum with air are studied in non-uniform field. The gap of needle to plane was 0.5mm, 0.8mm. The pressure of vacuum the range of 10^-4-10^-5torr. The diameter of a plane made of the stainless steel is150mm. As a result of the experiment, the breakdown voltage is increased about electrode gap distance increased. The electrode material influenced breakdown voltage in vacuum.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2303-2304
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• 2008

It is believed that the pre-flashover phenomena would play a very important role in the procedure of the flashover in the interface between the insulators and vacuum. This paper is mainly concerned on the pre-flashover phenomena of Alumina insulators in vacuum. There are 24 different types of alumina insulators were tested with a 0.7/4 ${\mu}s$ pulsed voltage under a $1{\times}10^{-4}Pa$ vacuum. The observed pre-flashover phenomena were classified and the pre-flashover characteristics were concluded. It is useful to study further on the flashover mechanism in vacuum.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.94-100
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• 1999

The friction and wear behavior of MoS$_2$Coatings were investigated using a pin and disk type tester. The experiment was conducted using silicon nitride as pin material and MoS$_2$-on-bearing steel as disk material under different operating conditions that include linear sliding speeds in the range of 22~66mm/sec, normal loads varying from 9.8~29.4N, corresponding to maximum contact pressure of 1.78~2.830GPa and atmospheric conditions of high vacuum, medium vacuum, ambient air. The results showed that low friction coefficient of the coating has been identified when running in high vacuum and that friction coefficient and wear volume increased with increasing normal load. Also at high load conditions, the friction coefficient and wear volume increased with increasing sliding velocity.

• Journal of Welding and Joining
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• v.17 no.4
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• pp.32-38
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• 1999

PAL(Pohang Accelerator Laboratory) designed and manufactured a 5m-long straight vacuum chamber to adopt U7 undulator that is the first insertion device. Top and bottom plates of the vacuum chamber were made of Al alloy A5083-H321, and welded together by the GTAW welding. The leak rate is less than 1×{TEX}$10^{-10}${/TEX} torr·ℓ/s with negligible welding deformation. The pressure has been maintained below {TEX}$10^{-10}${/TEX} torr after installation. This paper reports the welding process and the method applied to achieve ultimate vacuum performance and t satisfy integrity of welds.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.5 s.98
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• pp.98-103
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• 1999

The application field of porous mold is more and more expended. A mixture of alumina and cast iron is used for making porous mold using slip and vacuum casting method in this study. Slip casting is a process that slurry is poured into silicon rubber mold, dried in vacuum oven, debinded and sintered in furnace, In this procedure, slurry is composed of powder, binder, dispersion agent, and water. Vacuum casting is a technique for removing air bubbles existed in the slurry under vacuum condition. Since ceramics has a tendency of over-shrinkage after sintering, cast iron is used to compensate dimensional change. The results shows that sintering temperature has a great effect on characteristics of alumina-cast iron composite sintered parts. Finally ceramic-metal composite sintered mold can be used for aluminum alloy casting of shoe mold using this process.

• Journal of the Korean institute of surface engineering
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• v.43 no.5
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• pp.211-216
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• 2010

Vacuum carburizing process is well known process for its environment-friendly, low-cost, high-quality characteristics, compared with gas carburizing. In this study, a research was carried out to develop a process of vacuum carburizing for essential components of automotive transmission that is difficult to control its distortion. As a result, vacuum carburizing process is superior to gas carburizing in terms of cost, environment and quality.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.1
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• pp.26-30
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• 2010

The present paper studies the thermally-induced vibration phenomenon of the flexible space boom structure. In order to simulate the thermally-induced vibration phenomenon of the flexible thin boom structure of the spacecraft with the attached tip mass in space, the thermally-induced vibration including thermal flutter is experimentally investigated at various thermal environments using a heating lamp in vacuum chamber. In this experimental study, fluctuating characteristics, natural frequency and thermal strains of the thermally-induced vibration are parametrically investigated at various thermal environment conditions. Finally the thermally-induced vibration of the flexible boom structure of the orbiting earth satellite in solar radiation environment from the earth eclipse region including umbra and penumbra is simulated using the power control of the heating lamp in the vacuum chamber.