• Journal of Korean Society of Steel Construction
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• v.8 no.4 s.29
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• pp.133-133
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• 1996

Application of the relationship $da/dN=C({\Delta}K)^{m}$ is effective in the analysis of fatigue crack growth life. The values of material constant C and m have great influences on the predicted fatigue life and the relationship between fatigue crack growth rate(da/dN) and stress intensity factor range(${\Delta}K$) is effective in fatigue crack growth behavior. In this paper, fatigue crack growth behavior of the welded joints in HT60 grade TMCP(Thermo Machanical Control Process) steel have been studied. To evalute the fatigue crack growth rates of HT60 grade TMCP steel, fatigue test was performed by base metal(BM), heat affected zone(HAZ) and weld metal(WM) in TMCP steel at room temperature. We determined the relationship of $da/dN-{\Delta}K$ by correlation between C and m obtained from the Paris-Erdogan power law data supplied HT60 grade TMCP steel. The obtained results from this study indicate that fatigue crack growth rate of TMCP steel is not influenced by softening effect which occurs in the HAZ when high heat input weld is carried out. Softening effects, which affect fatigue properties. are shown that it is not affected to the fatigue growth rates significantly.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.299-303
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• 2007

Dry sliding wear behavior of ultra-fine grained(UFG) plain low carbon dual phase steel, of which microstructure consists of hard martensite in a ductile ferrite matrix, has been investigated. The wear characteristics of the UFG dual phase steel was compared with that of a coarse grained dual phase steel under various applied load conditions. Dry sliding wear test were carried out using a pin-on-disk type tester at various loads of 1N to 100N under a constant sliding speed condition of 0.20m/s against an AISI 52100 bearing steel ball at room temperature. The sliding distance was fixed as 1000m for all wear tests. The wear rate was calculated by dividing the weight loss, measured to the accuracy of 10-5g by the specific gravity and sliding distance. The worn surfaces and wear debris were analyzed by SEM, EDS and profilometer. Micro-vickers hardness of the cross section of worn surfaces were conducted to analyze strain hardening underneath the contact surfaces. The wear mechanism of the UFG dual phase steel was investigated with emphasis on the unstable nature of the grain boundaries of the UFG microstructure.

• Journal of Powder Materials
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• v.13 no.2 s.55
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• pp.129-137
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• 2006

In this study, high purity fine $BaTiO_3$ powders were prepared by SHS (Self-propagating High-temperature Synthesis). We would examinate the study of sintering properties and characteristics as a function of temperature with various additives (binder, sintering agent). In separately binder addition, the green and sintered density of specimen were increased as binder content increases. The increased porosity resulted in fine grain size due to the inhibition of grain boundary moving. The $Al_{2}O_{3},\;TiO_{2}$ and MgO playa role of increasing dielectric constants at room temperature. These values were decreased at curie temperature. In case of $SiO_2$, the Curie temperature was decreased. In this study, a high dielectric ceramic capacitor material with temperature stability was synthesized by using various additives.

• Journal of Animal Environmental Science
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• v.21 no.3
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• pp.77-82
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• 2015

This survey was conducted to collect basic data about the effect of buffering zone installation in weaned pig house. Buffering zone was installed either inside or outside of pig house to compare changes of temperature, humidity and air velocity of pig room. The body weight and mortality of weaned pigs in house with buffering zone was also measured. There was no difference in temperature, humidity and air velocity between inside and outside buffering zone. Mortality of weaned pig in house with buffering zone was drastically decreased compare to pigs in house without buffering zone that could be useful to maintain constant temperature and decrease mortality.

• Proceedings of the KAIS Fall Conference
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• 2006.05a
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• pp.203-206
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• 2006

The sensor consists of a heater, an insulating layer, a pair of contact electrodes, and CNT-sensing film on a micromachined diaphragm. The heater plays a role in the temperature change to modify sensor operation. Gas sensor responses of CNT-film to $NO_2$ at room temperature are reported. The sensor exhibits a reversible response with a time constant of a few minutes at thermal treatment temperature of $130^{\circ}C$.

• Proceedings of the KAIS Fall Conference
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• 2006.05a
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• pp.223-226
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• 2006

The micro-gas sensor based on carbon nanotubes (CNTs) was fabricated and its gas sensing characteristics on nitrogen dioxide ($NO_2$) have been investigated. The sensor consists of a heater, an insulating layer, a pair of contact electrodes, and CNT-sensing film on a micromachined diaphragm. The heater plays a role in the temperature change to modify sensor operation. Gas sensor responses of CNT-film to $NO_2$ at room temperature are reported. The sensor exhibits a reversible response with a time constant of a few minutes at thermal treatment temperature of $130^{\circ}C$.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.785-789
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• 2005

Low temperature deposition of silicon and silicon nitride films by catalytic CVD technique was studied for application to thin film transistors on plastic substrates for flexible AMOLEDs. The substrate temperature initially held at room temperature, and was controlled successfully below $150^{\circ}C$ during the entire deposition process. Amorphous silicon films having good adhesion, good surface morphology and sufficiently low content of atomic hydrogen were obtained and could be successfully crystallized using excimer laser without a prior dehydrogenation step. $SiN_x$ films showed a good refractive index, a high deposition rate, a moderate breakdown field and a dielectric constant. The Cat-CVD silicon and silicon nitride films can be good candidates for fabricating thin films transistors on plastic substrates to drive active-matrix organic light emitting display.

• Electrical & Electronic Materials
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• v.8 no.2
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• pp.151-157
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• 1995

Frequency-dependent electrical properties of $C_{22}$-Quinolinium(TCNQ) LB films were investigated in a frequency range of 10[Hz]-13[MHz] along a perpendicular direction. The films were heat-treated to understand an electrodynamic response in a temperature range of 20-240[.deg. C]. Frequencydependent dielectric constants show that there are two characteristic dispersions; one is a dispersion occuring near 1[MHz] coming from the orientational polarization of the molecules and the other one is an interfacial polarization effect below 1[kHz] or so when the annealing temperature is above 80 [.deg. C]. The overall frequency-dependent dielectric constant is higher near 80[.deg. C]. It may be due to a softness of the alkyl chains. Several other methods were employed to identify the internal structure change of the films. DSC(differential scanning calorimetry) data of the $C_{22}$-Quinolinium(TCNQ) molecules shows that there is an endothermic process near 110[.deg. C] and a weak exothermic process near 180[.deg. C]. While the endothermic process is related to a disordering of the alkyl chains, the exothermic process seems to be due to a chemical structure change of the TCNQ molecules. Thickness measurement by ellipsometry shows that there is a thickness drop near 100[.deg. C], and the thickness above 120[.deg. C] becomes around 20[%] of the room-temperature value.lue.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.152-155
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• 2006

Carbon nitride ($CN_X$) films were prepared by reactive RF magnetron sputtering system at various deposition conditions and the C-V characteristics of MIS(metal - insulator - semiconductor) capacitors that have the structures of Al/$CN_x$/p-Si/Al and Al/$CN_x$/$Si_3N_4$/p-Si/Al were investigated. The resistivity of carbon nitride was above $2.40{\times}10^8{\Omega}{\cdot}cm$ at room temperature. The C-V plot showed a typical capacitance-voltage characteristics of semiconductor insulating layers, while it showed hysterisis due to interface charges. Amorphous carbon nitride (a-$CN_x$) films, that have relatively high resistivity and low dielectric constant could be useful as interlayer insulator materials of VLSI(very large-scale integration) and ULSI(ultra large-scale integration).

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.278-282
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• 2007

In the complex insulation system that is used in extra high voltage(EHV) devices, according to the trend for electric power equipment of high capacity and reduction of its size, macro interfaces between two different bulk materials which affect the stability of insulation system exist inevitably. In this paper, the dielectric strength decrease of the macro interfaces between epoxy and ethylene propylene diene terpolymer(EPDM) was estimated by using the applied voltage to breakdown time characteristics. Firstly, the AC short time dielectric strength of specimens was measured at room temperature. Then, the breakdown time was measured under the applied constant voltage which is 70% of short time breakdown voltage. With these processes, the life exponent n was determined by inverse power law, and the long time breakdown voltage can be evaluated. The best condition of the interface was LOS(low viscosity(350 cSt) silicone oil spread specimen). When 30 years last on the specimens, the breakdown voltage was estimated 44% of the short time breakdown voltage.