• Journal of ILASS-Korea
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• v.13 no.4
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• pp.193-199
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• 2008

Spray coating is a versatile surface modification technology in which coating is built-up based on the successive deposition of micron-scaled particles. Depending on the coating materials, the coatings can meet the required mechanical properties, corrosion resistance, and other properties of base materials. Spraying processes are mainly classified into thermal and kinetic spraying according to their bonding mechanism and deposition characteristics. Specifically, thermal spraying process can be further classified into many categories based on the design and mechanism of the process, such as frame spraying, arc spraying, atmospheric plasma spraying (APS), and high velocity oxygen-fuel (HVOF) spraying, etc. Kinetic spraying or cold gas dynamic spraying is a newly emerging coating technique which is low-temperature and high-pressure coating process. In this paper, overall view of thermal and kinetic spray coating technologies is discussed in terms of fundamentals and industrial applications. The technological characteristics and bonding mechanism of each process are introduced. Deposition behavior and properties of technologically remarkable materials are reviewed. Furthermore, industrial applications of spray coating technology and its potentials are prospected.

• Journal of Technologic Dentistry
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• v.29 no.1
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• pp.133-138
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• 2007

In this study, the castability and of commercially pure titanium(c.p.Ti) grade according to the casting condition which are the vacuum condition in casting machine and mold temperature of investment, was investigated. Argon-arc melt/centrifugal casting machine was used for casting the specimens. The microstructure and mechanical properties were evaluated by using optical microscope. The results were as follows; 1. It could make a sure that there's relatively not much defect of casting body of c.p.Ti according to the deference of air pressure. 2. It could make sure that it formed porosity on the surface inside of the casting body of c.p.Ti according to deferent temperature. and on excellent castability was below $200^{\circ}C$ 3. As the mold temperature of investment was increased, the lamellar structure of phase and coarse grains were shown, especially under 42MPa.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.415-424
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• 2004

This paper presents the effect of groundwater on tunneling performance. The interaction between the tunneling and groundwater was examined using a 3D stress-pore pressure coupled finite-element analysis, The results of the 3D coupled analysis were then compared with those of a total stress analysis. Examined items included pore pressures around lining and lining forces. Also examined include face displacements and ground surface movements, The results indicated that the interaction between the tunneling and ground water significantly increases the lining forces and ground deformations, and that the effect of ground water on tunneling can only be captured through a fully coupled analysis, Implementations of the findings from this study arc discussed in great detail.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.289-290
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• 2008

The purpose of this paper is to analyze AC Breakdown of solid/air composite insulation depending on the thickness and the pressure of dry air for eco-friendly insulation. SF6 gas has been widely used in electric equipment as gas insulation because of high dielectric strength and arc extinguishing performance. However, because SF6 gas is one of the green house effect gases, alternative insulation such as SF6 mixture, extremely low temperature gas, vacuum, liquid and solid insulating are being investigated.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.335-338
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• 2006

A Numerical study of the cavitation within a centrifugal pump is carried out using CFD commercial code, FLUENT. The objective of this study is to predict the onset of cavitation within the pump blade and the degradation in the pressure rise due to the generation and transport of vapor. A pump designed for the study is a six bladed, one-circular arc impeller design suggested by A.J. Stepanoff et al. The Steady-state calculations are performed for a wide range of flow rate without the cavitation to investigate the pump performance. The design head and efficiency show a very good agreement with the numerical results at the design flow rate. After the validation with the numerical results, the pump performance and the onset of cavitation within the blade is predicted by changing NPSH at the design flow rate.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.3
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• pp.68-77
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• 1994

TIG welding process is applied for the active metal such as aluminum and titanium, also sometimes for overlay welding of superalloy. However the welding speed to be applied is very low because of the unstable bead formed in the region of high current and high welding speed. The present study was carried out to examine the basic phenomena of high speed TIG melt run welding by the 2% Th - W electrode(dia.3.2mm) of various tip shapes.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.76-84
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• 1994

Droplet transfer modes due to welding conditions and the effect of Ca in welding wire on droplet transfer were investigated. Droplet transfer mode in CO$_{2}$ welding was classified into 2 modes, that is, short circuit and globular transfer, with increasing welding current and voltage. With increasing Ca content in wire, repulsive pressure due to vaporization of Ca was considerably increased. In short circuit transfer region, arcing time was increased and droplet transfer cycle was decreased, with increasing Ca content. In globular transfer region, welding condition for globular transfer was lower current region, with increasing Ca content.

• Journal of Welding and Joining
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• v.15 no.3
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• pp.36-46
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• 1997

Dynamics of molten drop detachment in the Gas Metal Arc (GMA) welding is investigated using the Volume of Fluid(VOF) method. The electromagnetic effects are included in the formulation of the VOF method which has been widely used to analyze the dynamics of the fluid having a free surface. The molten drop geometry, pressure and velocity profiles within the drop are calculated numerically in the cases of globular and spray transfer modes. It appears that the velocity and current distribution affect metal detachment. It is found that the taper is formed and maintained during the spray transfer by the electromagnetic force. Predicted results show reasonably good agreement with the available experimental data which validates the application of the VOF method to metal transfer analysis.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.683-687
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• 1997

The purpose of this work is to develop a highly reliable solar cell based on the diamond-like carbon(DLC)/silicon heterojunction. Thin films of DLC have been deposited by employing both filtered cathodic vacuum arc(FCVA) and magnetron plasma-enhanced chemical vapor deposition(m-PECVD) systems. Structural, electrical, and optical properties of DLC films deposited are systematically analyzed as a function of deposition conditions, such as magnetic field, substrate bias voltage, gas pressure, and nitrogen content. The I-V measurement has been used to elucidate the mechanism responsible for the conduction process in the DLC/Si junction. Photoresponse characteristics of the junction are measured and its reliability against temperature and light stresses is also analyzed.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1330-1331
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• 2008

MCCB와 같은 저압차단기는 접점사이에서 발생한 아크를 금속의 소호그리드로 유입하여 아크를 소호하게 된다. 일반적으로 고장 전류 차단시에 저압차단기에서 발생한 아크는 고압.고열이므로 아크에너지에 의해 소호부의 압력이 크게 상승하게 되며 압력에 의해 아크의 거동은 큰 영향을 받게 되므로 아크 구동력의 증가를 위해서는 압력에 의해 아크거동이 어떠한 영향을 받는지에 대한 정보가 필요하다. 본 연구에서는 압력파의 영향을 명확하게 하고 다른 요소에 의한 영향을 배제하여 압력파와 아크거동간의 상호작용만을 실험하기 위해 시험용 소호부를 고안하여 시험용 소호부에서 아크의 압력과 거동을 측정.분석하여 아크거동과 압력파의 관계를 연구하였다.