• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.223-228
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• 2003

In end milling processes, characterized by use of rotating tools, the underformed chip thickness varies periodically with the phase change of tool. In current study, as a new approach to analyse shear behaviors In the shear plane and chip-tool friction behavior chip-tool contact region during an end milling process. In this approach, an up-end milling process is transformed into an equivalent oblique cutting process. Experimental investigations for two sets of cutting tests i.e.. up-end milling and the equivalent oblique cutting test were performed to verify the presented model.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.3
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• pp.270-275
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• 2013

In this study, focusing of ultrasonic Lamb wave by negative refraction with mode conversion from antisymmetric to symmetric mode was investigated. When a wave propagates backward by negative refraction, the energy flux is antiparallel to the phase velocity. Backward propagation of Lamb wave is quite well known, but the behavior of backward Lamb wave at an interface has rarely been investigated. A pin-type transducer is used to detect Lamb wave propagating on a steel plate with a step change in thickness. Conversion from forward to backward propagating mode leads to negative refraction and thus wave focusing. By comparing the amplitudes of received Lamb waves at a specific frequency measured at different distance between transmitter and interface, the focusing of Lamb wave due to negative refraction was confirmed.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.172-174
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• 2003

In this paper, a 2D axisymmetric model of thermoelectric Finite Element Method (FEM) is developed to analyze the transient thermal behavior of Resistance Spot Welding (RSW) process using commercial software, called ANSYS. The determination of the contact resistance at the faying surface is moderately simplified to reduce the calculating time, while the temperature dependent material properties, phase change and convectional boundary conditions are taken account fur the improvement of the calculated accuracy. The thermal history of the whole process (including cooling) and temperature distributions for any position in the weldment is obtained through the analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.84-89
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• 1996

The nucleation and growth of microporosities was observed during the course of annealing treatment of sputter-deposited AgInSbTe thin films. There was a close correlation between the density of microporosity and the sputtering gas pressure in annealed thin films. The void density for a given composition decreased with sputtering gas pressure. It was shown from the present study that the number of porosities decreased while the average porosity size increased as the annealing temperature and holding time increased. The mechanism of porosity formation in the sputter-deposited AgInSbTe thin flus containing Ar-impurity trapped from the Ar-plasma is discussed in the present article.

• Journal of the Korean institute of surface engineering
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• v.35 no.5
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• pp.312-318
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• 2002

A study on the change of mechanical properties and oxidation behavior of Zircaloy-4 fuel cladding after exposing at 90$0^{\circ}C$ and $1000^{\circ}C$ for various periods of exposure time under the steam atmosphere was carried out. The growth of the $ZrO_2$ layer combined with an oxygen-rich-phase layer into the Zircaloy tube material can be described by an expression, E = 1.1√Dt + $2 $\times$ 10^{-4}$ . The tensile strength of Zircaloy tubes increased for a short period of exposure time and decreased rapidly with further exposure while the hoop strength was not decreased greatly. In the meantime, the axial and circumferential elongations of oxidized Zircaloy tubes were decreased drastically with increasing exposure time as a result of embrittlement phenomena.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.841-844
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• 2003

In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. These systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the vibration behavior of flexural beam in the ultrasonic transport system is verified using Laser Scanning Vibrometer. The experiments for verifying vibration are performed in three conditions such as in the maximum transport speed, in the zero speed, and in the change of transport direction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.9
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• pp.863-871
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• 2004

The use of fossil fuels like coal, oil and natural gases around the world causes an increase of the carbon dioxide content in the atmosphere. In order to reduce the concentration of the greenhouse gas, the idea of carbon dioxide sequestration in the ocean is proposed to be an effective mitigation strategy to counteract potential global warming due to the greenhouse effect. Therefore, in the present study, calculations of the dissolution behavior of carbon dioxide when liquid carbon dioxide is released at 1,000m and 1,500m in depth by fixed pipeline are performed. The results show that carbon dioxide droplets change to carbon dioxide bubbles in gas phase around 500m in depth, and the droplets are completely dissolved below 500 m in depth if the liquide carbon dioxide is released both at 1,000 m in depth with the initial diameter of 0.007m or less and at 1,500m in depth with the diameter of 0.011m or less.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.812-813
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• 2006

Dimensional change of compact made from (Fe-Cu) prealloyed powder and copper powder compared to that of compact made from iron-copper elemental powder. The compact made from the prealloyed powder with a copper content of 7.18mass% which is nearly equal to its solution limit and copper powder showed only the large contraction in spite of penetration of liquid copper into grain boundary of the prealloyed powder. But the compact made from iron-copper elemental powder showed the large expansion in spite of same chemical composition with former case.

• Journal of the Korean Electrochemical Society
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• v.5 no.4
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• pp.216-220
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• 2002

The effects of electrolytes on electrochemical behavior from an oil thin layer interposed between a graphite electrode and an aqueous solution phase were examined. A hydrophobic electroactive species, tetrachloro-1,4-benzoquinone (TCQ), in a benzonitrile (EN) layer was employed to study ion transfer properties across the BN-water interface. Experimental results showed that hydrophobic cations as well as anions could be successfully used as ionic charge carriers. The addition of various salts into either the oil layers or the aqueous solutions offers deeper insight for the electrochemistry of the liquid thin layer system. When aqueous perchloric acid is interfaced with the BN films, the perchlorate ion of tetrahexylammonium perchlorate (THAP) substantially suppresses the dissociated proton concentration in the layer by the common ion effect while there is only a little change in the total acid concentration. Further approach by theoretical calculation makes it possible to quantitatively understand the effect of the electrolytes to the electrochemical responses of TCQ, which were previously reported (Anal. Chem. 73, 337 (2001)).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.472-475
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• 2010

Theoretical consideration on the combustion behavior of nano-aluminum and water mixture was conducted. The regions are divided into; 1)water+aluminum 2)steam+aluminum 3)reaction zone. Latent heat of vaporization was considered as a function of pressure in case of phase change of water. Also, pressure exponent was studied of various sized nano particles within the range of 0.1MPa ~ 10MPa.