• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.12
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• pp.568-572
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• 2003

A longitudinal discharge heated copper vapor laser with internal diameter 28 mm and discharge length 1.3 m has been constructed and tested. At the discharging voltage 15.2 kV, pulse repetition rate 10 kHz, buffer gas pressure 40 mbar, and internal temperature of the laser plasma tube $1520^{\circ}C$, it delivers more than 30 W average laser outputs.

• Journal of Surface Science and Engineering
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• v.34 no.5
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• pp.367-377
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• 2001

Plasma is generated by electrical discharge. Most plasma generation has been carried out at low-pressure gas typically less than one millionth of atmospheric pressure. Plasmas are in general generated from impact ionization of neutral gas molecules by accelerated electrons. The energy gain of electrons accelerated in an electrical field is proportional to the mean free path. Electrons gain more energy at low-pressure gas and generate plasma easily by ionization of neutrals, because the mean free path is longer. For this reason conventional plasma generation is carried out at low pressures. However, many practical applications require plasmas at high-pressure. In order to avoid the requirement for vacuum pumps, researchers in Korea start to develop plasmas in high-pressure chambers where the pressure is 1 atmosphere or greater. Material processing, environmental protection/restoration and improved energy production efficiency using plasmas are only possible for inexpensive bulk plasmas. We thus generate plasmas by new methods and plan to set foundations for new plasma technologies for $21^{st}$ / century industries. This technological research will play a central role in material processing, environmental and energy production industries.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.12
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• pp.1077-1082
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• 2005

In this paper, it is proposed that the method for constituting pressure control system controlled by Direct Drive Valve (DDV). The DDV has a pressure-feedback-loop itself. It can eliminate non-linearity and uncertainty oi hydraulic system such as uncertain discharge coefficient and change of bulk-modulus. However, the internal feedback-loop can not compensate them perfectly. And fixed gain of the DDV's internal feedback-loop is not proper to apply it through wide pressure range. The steady state error and nonlinear characteristic of transient behaviour is observed in the experiment. So another controller is needed for the desirable performance of the system. To compose the controller, the pressure control system controlled by DDV is modeled mathematically and the parameters of the model are identified using signal-compression method. Then sliding mode controller is designed based on mathematical model. Desirable performance of the pressure control system controlled by DDV is obtained.

• Journal of Mechanical Science and Technology
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• v.20 no.10
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• pp.1716-1721
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• 2006

The Lubrication Mode of line contacts between the vane and the camring in an oil hydraulic vane pump has been investigated. First, the variations of the radial force of a vane were calculated from previous measurements of dynamic internal pressure in four chambers surrounding a vane. Next, the lubrication modes were distinguished with Hooke's chart, which is an improvement over Johnson's chart. Finally, the influence of the boundary conditions in the lubrication region on the fluid film lubrication was examined by calculating the film pressure distributions. The results showed that the lubrication mode of the vane tip exists in the rigid-variable-viscosity region, and that discharge pressure higher than 7 MPa greatly affects the oil film pressure in the small and the large arc section because of the Piezo-viscous effect.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.221-227
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• 2000

The design of the valve plate is most important to increase efficiency in the oil hydraulic axial piston pump. A theoretical study was carried out to clarify the pressure characteristics at the land of the valve plate in the oil hydraulic axial piston pump. Dynamic pressure acts on the land of the valve plate was computed numerically with discharge pressure, rotational speed and swash plate angle. Pressure distribution between the valve plate and the cylinder block also was obtained with dynamic pressure. The results are applicable to improve the design technique of the valve plate in the oil hydraulic axial piston pump.

• The Korean Journal of Pesticide Science
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• v.16 no.1
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• pp.11-20
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• 2012

As increasing the use of pesticides both in number and amount to boost crop production, consumer concerns over food quality and safety with respect to residual pesticides are also continuously increasing. However, there is still lacking of information that can effectively help to remove residual pesticides in foods. In recent years, contaminant removal by gas (or) glow discharge plasma (GDP) attracts great interests on environmental scientists because of its high removal efficiency and environmental compatibility. It was shown to be effective for the removal of some organophosphorus pesticides, phenols, benzoic acid, dyes, and nitrobenzene on solid substrate or in aqueous solution. This work mainly focuses on the removal of wide range of residual pesticides from fresh fruits and vegetables. As for preliminary study, the experiments were carried out to investigate whether GDP can be used as an effective tool for degrading target pesticides or not. With this objective, 60 selected pesticides drop wised onto glass slides were exposed to two types of GDP, dielectric barrier discharge plasma (DBDP) and low pressure discharge plasma (LPDP), for 5 min. Then, they were washed with 2 mL MeCN which were collected and used for determination of remaining concentration of pesticides using LC-MS/MS. Among selected pesticides, degradation of 18 pesticides (endosulfan-total was counted as one pesticide) by GDP could not be examined because control treatments, which were left in ambient environment, of those pesticides recovered less than 70% or even did not recover. However, majority of tested pesticides (42) were degraded by both types of GDP with satisfactory recovery (>80%) of control sample. Pesticides degradation ranged from 66.88% to 100% were achieved by both types of plasma except clothianidin which degradation in LPDP was 26.9%. The results clearly indicate that both types of gas discharge plasma are promising tools for degrading wide range of pesticides on glass substrate.

• Proceedings of the KIEE Conference
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• 1985.07a
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• pp.219-219
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• 1985

• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.207-207
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• 1999

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.1
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• pp.85-91
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• 2013

This paper studied surface discharge characteristics by a dielectric constant and diameter of solid dielectrics in $N_2/O_2$ mixture gas. Applied electric field strength at $N_2/O_2$ mixture gas was changed from the dielectric constant and diameter of the solid dielectrics, and insulation performance of the $N_2/O_2$ mixture gas determined surface discharge voltage. In each of the diameter at the solid dielectrics, the surface discharge voltage was increased by lengthening surface distance, whereas increasing rate of the surface discharge voltage was different from gas pressure. Thus, In this paper, main factors of surface discharge are as follows. 1) Insulation performance of $N_2/O_2$ mixture gas, 2) Dielectric constant of solid dielectrics, 3) Surface discharge path. It was clear that the surface discharge voltage depend on the main factors. These results will be applied to useful data for an eco-friendly composite insulation design.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2392-2401
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• 2018

Creepage discharge faults in air on solid insulating material play a vital role in degradation and ageing of material which ultimately leads to breakdown of power equipment. And electric discharge decompose air in to its by-products such as Ozone and $NO_x$ gases. By analyzing air decomposition gases is a potential method for fault diagnostic in air. In this paper, experimental research has been conducted to study the effect of creepage discharge on rate of generation of air decomposition by-products using different insulating materials such as RTV, epoxy and fiberglass laminated sheet. Moreover XRF analysis has been done to analyze creepage discharge effect on these insulating materials. All experiments have been done in an open air test cell under constant temperature and pressure conditions. While analysis has been made for low and high humidity conditions. The results show that the overall concentration of air decomposition by-products under creepage discharge in low humidity is 4% higher than concentration measured in high humidity. Based on this study a mathematical relationship is also proposed for the rate of generation of air decomposition by-products under creepage discharge fault. This study leads to indirect way for diagnostic of creepage discharge propagation in air.