• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.58-62
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• 2002

The purpose of this study is to analyze the charging gas effect on the resonance and performance characteristics of the linear compressor for small scale FPFD Stirling refrigerator. To ensure high performance of FPFD type Stirling refrigerator, the operating frequency of the refrigerator should be around the natural frequency of compressor. The gas spring effect which is induced from Pressure change in cylinder due to motion of pistons has significant effect on the natural frequency of the compressor. The numerical results show the linear compressor has high natural frequency when the charging pressure of working fluid is high and the stroke of compressor, current, input power and efficiency of compressor were shown with different operating conditions.

• Progress in Superconductivity and Cryogenics
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• v.1 no.1
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• pp.48-55
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• 1999

thermodynamic cycle analysis has been performed for the power generation systems to utilize the cold energy of liquefied natural gas (LNG). The power cycle used the air or water at room temperature as a heat source and the LNG at cryogenic temperature as a heat sink. Among manypossible configurations of the cycle. the open Rankine cycle. and the closed Brayton cycle, and the closed Rankine cycle are selected for the basic analysis because of their practical importance. The power output per unit mass of LNG has been analytically calculated for various design parameters such as the pressure ratio. the mass flow rate. the adiabatic efficiency. the heat exchanger effectiveness. or the working fluid. The optimal conditions for the parameters are presented to maximize the power output and the design considerations are discussed. It is concluded that the open Rankine cycle is the most recormmendable both in thermodynamic efficency and in practice.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.103-104
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• 2000

Voltage transfer curves have been used for analyzing the micro-discharge characteristics of cells in ac-PDP. This paper deals with the effect of working gas species, pressure and frequency of applied voltage on the micro-discharge characteristics. Using the mixture gases of He+Xe or He+Ne+Xe, wall voltage steeply varied compared with only He gas, and also voltage margin increased. Discharge voltage and voltage margin increased with increasing Xe percentage, and also wall voltage more steeply varied. In addition, the variation of effective wall capacitance which is significantly dependent on the discharge strength is discussed.

• Journal of the Korean institute of surface engineering
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• v.37 no.3
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• pp.164-168
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• 2004

Polycrystalline silicon thin films were deposited by inductively coupled plasma (ICP) assisted magnetron sputtering using a gas mixture of Ar and $H_2$ on a glass substrate at $250^{\circ}C$. At constant Ar mass flow rate of 10 sccm, the working pressure was changed between 10mTorr and 70mTorr with changing $H_2$ flow rate. The effects of RF power applied to ICP coil and $Ar/H_2$ gas mixing ratio on the properties of the deposited Si films were investigated. The crystallinity was evaluated by both X-ray diffraction and Raman spectroscopy. From the results of Raman spectroscopy, the crystallinity was improved as hydrogen mixing ratio was increased up to$ Ar/H_2$=10/16 sccm; the maximum crystalline fraction was 74% at this condition. When RF power applied to ICP coil was increased, the crystallinity was also increased around 78%. In order to investigate the surface roughness of the deposited films, Atomic Force Microscopy was used.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.578-581
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• 1999

The Co-Cr-Ta films are one of the most suitable candidates for perpendicular magnetic recording media. The facing targets sputtering(FTS) system has a advantage of preparing films over a wide range of working gas pressure on plasma-free substrates. In this study, we investigated the effect underlayers on the growths layers of Co-Cr-Ta recording layers. The Co-Cr-Ta/Ti(CoCr) double layers were deposited with sputter gas pressure$(P_N, 0.3-1mTorr)$ by using FTS apparatus at temperature of$40^{\circ}C~-300^{\circ}C$, respectively. Crystallographic and magnetic characteristics were evaluated by x-ray diffractometry(XRD) and vibrating sample magnetometer(VSM), respectively.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.64-69
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• 2007

This study is to develop heat recovery system using high performance heat pipe heat exchanger for Middle-high temperature range industrial exhaust gas. The naphthalene is used as working fluid of heat pipe in this study. Single naphthalene heat pipe could transport over 2,000 watts with $0.05^{\circ}C/W$. The heat pipe heat exchanger consist of 50 naphthalene heat pipes recovered 62 kW when over $400^{\circ}C$ gas exhausted and the maximum recovered heat rate was 173 kW in this study.

• Journal of the Korean institute of surface engineering
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• v.31 no.4
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• pp.217-222
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• 1998

The Facing Targets Sputtering(FTS) system has several advantages for preparing films over a wide range of working gas pressure on plasma-free substrates. Co-Cr thin films seem to be one of the most promising media for perpendicular magnetic recording system. In this study, the capabillities of the system fordepositing C0-Cr films have been investigated. Under various Ar gas pressure, films with morphologically dense microstructure and good c-axis orientation were deposited, even when the incident angle $\psi_x$ of sputtered part icles to the film plane was below abount $50^{\circ}C$. this may imply that the shadowing effect by obique incidence of particle can be compensated by rapid surface diffusion owing to the high kinetic energy of particles arriving at the growing film. It has been confirmed that the FTS system is very useful for perparing Co-Cr thin films recorging media.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.131-135
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• 2003

Zinc Oxide(ZnO) thin films on Si (100) substrate were deposited by RF magnetron sputter with changing sputtering conditions such as argon/oxygen gas ratios, RF power, and substrate temperature, chamber pressure and target-substrate distance. To analyze a crystallographic properties of the films, $\theta/2\theta$ mode X-ray diffraction, SEM, and AFM analyses. C-axis preferred orientation, resistivity, and surface roughness highly depended on $Ar/O_2$ gas ratios. The resistivity of ZnO thin films rapidly increased with increasing oxygen ratio and the resistivity value of $9{\times}10^7{\Omega}cm$ was obtained at a working pressure of 10 mTorr with $Ar/O_2$=50/50. The surface roughness was also improved with increasing oxygen ratio and the ZnO films deposited with $Ar/O_2$=50/50 showed the excellent roughness value of $28.7{\AA}$.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.376-379
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• 1993

GoldStar Industrial Systems Co. R & D center successfully developed the inverter for welding under the support of GoldStar Electric Machinery Co. Now, we are currently working on the mechanical part of articulated robot and a high-performance general purpose motion controller. By combining the above three items, we will be able to constitute the complete welding robot system on our own. In this article. the welding robot system currently under developing is introduced. The main focus will be placed on the development of general purpose motion controller with welding control module. Therefore, the architecture of welding robot controller where the general purpose motion controller is combined with the welding controller module will be explained. Here, the software system will be explained with regard to the hardware system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.434-435
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• 2005

In this work, the ITO thin films were prepared by FTS (Facing Targets Sputtering) system under different sputtering conditions which were varying $O_2$ gas flow, input current and working gas pressure. As a function of sputtering conditions, electrical and optical properties of prepared ITO thin films were measured. The electrical characteristics, surface roughness and transmittance of the ITO thin films were evaluated by Hall Effect Measurement, AFM, and UV-VIS spectrometer respectively. In addition, I-V properties of OLED cells were measured by 4156A(HP).