• 대한기계학회논문집B
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• 제33권3호
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• pp.207-214
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• 2009

Crossover of nitrogen from cathode to anode is inevitable in typical membranes used in PEM fuel cells. This crossovered nitrogen normally accumulates in the hydrogen recirculation system at anode side channels. Excessive buildup of nitrogen in the anode side lowers the relative hydrogen concentration and finally affects the performance of fuel cell stack. So it is very important to analysis the nitrogen gas crossover at various operating conditions. In this study, characterization of nitrogen gas crossover in PEM fuel cell stack was investigated. The mass spectroscopy (MS) has been applied to measure the amount of the crossovered nitrogen gas at the anode exit. Results show that nitrogen gas crossover rate was affected by current density, anode and cathode stoichiometric ratio and operating pressure. Current density, anode stoichiometric ratio and anode operating pressure do not affect nitrogen crossover rate but anode exit concentration of nitrogen. Cathode pressure and stoichiometric ratio largely affect the nitrogen crossover rate.

• 한국초전도ㆍ저온공학회논문지
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• 제8권2호
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• pp.37-42
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• 2006

A research on several characteristics such as volume breakdown and surface discharge of insulators for a termination of power transmission class HTS cable was performed. We investigated the surface discharge of glass fiber reinforced plastic (GFRP) under air, cryogenic nitrogen gas and nitrogen gas media. The breakdown characteristics of these media were studied. Experimental results revealed that flashover voltage greatly depends on pressure, temperature, the kinds of insulating media and voltages, but it is slightly affected by shape and material of electrode. The breakdown voltage of liquid nitrogen, cryogenic nitrogen gas and nitrogen gas deeply depends on the shape and dimension of electrode, kinds of voltages and pressure. Moreover, the breakdown voltage of cryogenic nitrogen gas and flashover voltage of GFRP in the cryogenic nitrogen gas is also influenced by temperature and vapour-mist density of the gas.

• 조명전기설비학회논문지
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• 제27권2호
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• pp.77-83
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• 2013

In this study, we aimed to determine the optical properties of the plasma used for the dry cleaning method. The optical properties of the atmospheric pressure plasma device were measured through the degree of ionization of hydrogen or nitrogen gas by ionized atmospheric gas. The degree of ionization of hydrogen or nitrogen is closely associated with surface modification. We observed through our experiments that argon gas, an atmospheric gas, caused an increase in the ionization of nitrogen gas, which has similar ionization energy. This type of increase in nitrogen gas ions is believed to affect surface modification. The results of our study show that the pressure of argon gas and the partial pressure of argon and nitrogen gases lead to different results. This important result shows that argon ions can affect the ionization of nitrogen gas.

• Journal of Welding and Joining
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• 제5권4호
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• pp.12-21
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• 1987

To investigate the suitability of nitrogen gas as an internal purging gas, various properties of GTA welded joints of duplex, 316L stainless steel, Cu-Ni alloy pipe using nitrogen purging gas were evaluated with reference to onew purged with argon gas. Mechanical properties evaluated by the tensile, bending test, and hardness value of welded joints with nitrogen gas purging did not show any difference those with argon gas. General and local corrosion rates of each welded joint prepared by nitrogen gas purging also showed no difference with those prepared by argon gas. Based on the present test results it is confirmed that nitrogen is a suitable purging gas for GTA welding of stainless steels and nonferrous piping systems, which can be used at lower cost instead of argon.

• 열처리공학회지
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• 제10권1호
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• pp.30-39
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• 1997

After changing the heat treating atmosphere of nitrogen gas, argon gas and vacuum, the nitrogen contents, microstructural changes, hardness and corrosion resistance of 0.25wt.%N alloyed super duplex stainless steel have been investigated in the temperature range from $1050^{\circ}C$ to $1350^{\circ}C$. The nitrogen content showed to be increased up to 0.36wt.% after heat treating the specimen in nitrogen gas at $1200^{\circ}C$, while the decrement of nitrogen content in vacuum atmosphere was shown down to 0.03wt.% at $1350^{\circ}C$. After heat treating in the mixed gas atmosphere of argon and nitrogen at $1250^{\circ}C$, the surface ${\gamma}$ phase existed as ${\alpha}+{\gamma}$ phase increased with increasing nitrogen gas content. The ${\gamma}$ single phase appeared at the surface above $80%N_2$ gas, while the surface ${\alpha}$ single phase was shown below $20%N_2$ gas. When heat treating the specimen in nitrogen gas at $1050^{\circ}C$, the hardness of austenite phases increased above Hv 40 at the surface layer compared to the hardness of the core parts, while decrement of denitriding effect caused to the hardness nearly unchanged between surface and the core parts after heat treating in vacuum atmosphere. The surface ${\gamma}$ single phase specimen showed superior corrosion resistance than the surface ${\alpha}$ single phase specimen. The surface ${\alpha}$ phase existed in the ${\alpha}+{\gamma}$ microstructure showed higher corrosion resistance after heat treating in the nitrogen gas atmosphere than the ${\alpha}$ phase heat treated in the argon gas and vacuum atmosphere.

• 대한임상독성학회지
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• 제15권1호
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• pp.47-50
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• 2017

Nitrogen is an inert gas that is harmless to humans under normal conditions. While it is not inherently toxic, nitrogen gas becomes dangerous when it displaces oxygen, resulting in suffocation. Herein, we report a case of a 34-year-old man who attempted suicide by nitrogen asphyxiation who presenting with decreased mental function and agitation. Lactic acidosis and hyperammonemia were observed on presentation at the emergency department, but these improved after a few hours. After 2 days, the patient regained full consciousness, and was discharged without any complications. Survival after asphyxiation due to nitrogen gas is very rare, and these patients are more likely to have poorer outcomes. There is a potential for the increasing use of nitrogen gas as a method of committing suicide because of the ease of access to this gas.

• 동력기계공학회지
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• 제20권5호
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• pp.14-19
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• 2016

This study is about the effect of nitrogen gas pressures during manufacturing process on the mechanical properties of composite materials. $TiO_2$/epoxy resin nanocomposites and carbon fiber reinforced epoxy resin(CFRP) composites were fabricated under various nitrogen gas pressures. Tensile strength test, vicker's hardness test and fracture surface observation were carried out to investigate the effect of nitrogen gas pressure. As a result, the tensile strength of nanocomposite and CFRP composites showed clearly increasing tendency by a change in the nitrogen gas pressure up to 3.0 atm and then the tensile strength decreased a little. However, the vicker's hardness of $TiO_2$/epoxy nanocomposites showed same hardness values regardless of the nitrogen gas pressures.

• 한국연초학회지
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• 제19권1호
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• pp.70-75
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• 1997

The expansive properties of leaf tobacco by nitrogen gas was investigated with cut tobacco AB3O-1, CD3L-1(NC82). Major factors for the best expansion of the tobacco by the gas were an impregnated pressure and expansion temperature. The expansion rate for AB3O-1 and CD3L-1 at 250℃, 750kg/cm2 was 96.6%, 99.4% respectively. The shred size and fineness index at 96.6% of expansion rate for AB3O-1 was almost the same as at 58.3% for CD3L-1. The time reaching at equilibrium moisture under of RH 57% was 36hr in non-treated leaf tobacco, but it was 20hr in expanded tobacco. We confirmed that total sugar contents of leaf tobacco by the expansion was decreased with 9.3∼10.9%. Total alkaloid was decreased with 17.5∼21.1% and ether extracts was declined with 4.9∼9.3%. These results suggest that the expansion method of leaf tobacco by nitrogen gas is a useful method without any serious environmental troubles. Key words : expansion, nitrogen gas, heat treatment, tobacco.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.173.2-173.2
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• 2014

Thin nitride thin films were synthesized by reactive radio-frequency magnetron sputtering in the ultra high vacuum (UHV) chamber. To control the characteristics of thin films, tin nitride thin films were obtained various argon and nitrogen gas mixtures, especially low nitrogen gas ratios. Tin nitride thin films were analyzed with alpha step, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and 4 point probe measurement. The result of alpha step and SEM showed that the thickness of thin nitride thin films were decreased with increasing nitrogen gas ratios. The metallic tin structure was decreased and the amorphous tin nitride structure were observed by XRD with higher nitrogen gas ratios. The oxidation state of tin and nitride were studied with high resolution Sn 3d and N 1s XP spectra.

• 한국정밀공학회지
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• 제25권7호
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• pp.124-130
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• 2008

The effect of nitrogen gas pressure in arc ion plating on surface properties of the TiN-coated high speed steel(SKH51) is presented in this paper. The surface roughness, micro-particle, micro-hardness, coated thickness, atomic distribution of TiN, and adhesion strength are measured fur various nitrogen gas pressures. It has been shown that the nitrogen gas pressure has a considerable effect on the surface roughness, adhesion strength, atomic distribution of TiN, and surface deposition of TiN of the high speed steels but that it has little influence on the micro-hardness and coated thickness.