• Journal of Korean Society for Atmospheric Environment
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• v.27 no.1
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• pp.1-15
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• 2011

Korea Global Atmosphere Watch Center (KGAWC), which is located in Anmyeondo and, belongs to the Korea Meteorological Administration (KMA), measures sulfur hexafluoride ($SF_6$) in every hour since 2007. In this study, $SF_6$ observed in 2007 are discussed. A gas chromatograph-electron capture detector (GC-ECD) with pre-cooled device is applied during the observation, and produced data are qualified by means of periodic calibration with $SF_6$ standard gas made by Korea Research Institute of Standard and Science (KRISS). $SF_6$ has been greatly paid attention since Kyoto protocol because of its high global warming potential(GWP) with 22,200 times of $CO_2$ in the period of 100 years. It is a man-made compound and has been usually used for gas insulation since 1970s and for etching process in the information technology-based industry since 1990. Average mixing ratio of $SF_6$ in 2007 was 6.65 pmol/mol at Anmyeondo. According to the GAW report published in 2008, average mixing ratio of $SF_6$ in the atmosphere is continuously growing. At present, the average mixing ratio of $SF_6$ in the atmosphere is known to be approximately 6.25 pmol/mol at global observatory. $SF_6$ value in Anmyeondo shows 0.40 pmol/mol greater than that of the Mauna Loa observatory in 2007.

• Journal of the Korean Society of Food Culture
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• v.20 no.4
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• pp.468-475
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• 2005

To determine the effect of different fermentation level on the quality of Nabak Kimchi during storage, this study was carried by analysing the result of physico-chemical properties, microbiological characteristics and sensory evaluation of Nabak Kimchi stored up to 24 days. For the physico-chemical properties, pH, total acidity, reducing sugar, carbon dioxide contents, color values were investigated while for the microbiological characteristics, total microbial counts and lactic acid bacteria were studied. Nabak Kimchi products were fermented at six different level of temperature and time and stored in Kimchi refrigerator at $4^{\circ}C$ for 24 days. As the storage period increased, the pH values of LF15, SF25 and LF25 decreased rapidly after initial fermentation and the pH values of SF4, LF4 and SF15 increased slightly in the beginning and then decreased. total acidity increased as storage period proceeded. the amount of reducing sugar was 4.92mg/ml before fermentation and increased significantly and reached its maximum values then decreased. lightness and redness of Nabak Kimchi decreased as storage period became longer, but yellow of Nabak Kimchi increased during storage. Total microbial counts of SF25 and LF25 reached to the highest at the 6th day and total microbial counts of LF15 reached to the highest at the 12th day and then significantly decreased. However, total microbial counts of SF4, LF4 and SF15 continuously increased up to the 24th day. The number of lactic acid bacteria was similar to the phase of the change of total microbial counts.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.253-254
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• 2005

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.209-210
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• 2005

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.30-32
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• 1995

The model interrupters of $SF_6$ gas electromagnetic contactor whose ratings are the voltage of 7.2kV and the short circuit current of 4.0kA have been designed and manufactured on the basis of theoretical and computational analysis for its development. The eddy current analysis, the magnetic field analysis and the calculation of the rotational force on arcs have been conducted using FLUX2D package. The short circuit current interrupting tests have been conducted to the model interrupters using the simplified capacitive synthetic test circuit in KERI. The results show that the model interrupters have a sufficient interrupting capability and the new design concept is proper for a good interrupting performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.6
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• pp.490-494
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• 2020

Sulphur hexafluoride (SF₆) is mostly used as a current-insulating medium in gas-insulated switchgears (GIS), owing to its excellent dielectric strength and arc-extinguishing performance. The global warming potential (GWP) of SF₆, however, is 23,900 times that of CO₂, and its life time in the atmosphere is 3,200 years. For these reasons, new eco-friendly gases to replace SF₆ are required. In this study, the partial discharge (PD) characteristics of green gas for grid (g³) and dry air (N₂/O₂) were analyzed to compare with those of SF₆. A PD electrode system was designed to simulate the protrusion defect in GISs and fabricated for experimentation. To compare the PD characteristics of each gas, the discharge inception voltage (DIV), discharge extinction voltage (DEV), discharge magnitude, discharge pulse number, and phase pattern were analyzed. Results from this study are expected to provide fundamental materials for the design of eco-friendly GISs.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.236-239
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• 2004

We studied the specular spin valve (SSV) having the spin filter layer (SFL) in contact with the ultrathin free layer composed of Ta3/NiFe2/IrMn7/CoFel/(NOLl)/CoFe2/Cu1.8/CoFe( $t_{F}$)/Cu( $t_{SF}$ )/(NOL2)/Ta3.5 (in nm) by the magnetron sputtering system. For this antiferromagnetic I $r_{22}$M $n_{78}$-pinned spin filter specular spin valve (SFSSV) films, an optimal magnetoresistance (MR) ratio of 11.9% was obtained when both the free layer thickness ( $t_{F}$) and the SFL thickness ( $t_{SF}$ ) were 1.5 nm, and the MR ratio higher than 11% was maintained even when the $t_{F}$ was reduced to 1.0 nm. It was due to increase of specular electron by the nano-oxide layer (NOL) and of current shunting through the SFL. Moreover, the interlayer coupling field ( $H_{int}$) between free layer and pinned layer could be explained by considering the RKKY and magnetostatic coupling. The coercivity of the free layer ( $H_{cf}$ ) was significantly reduced as compared to the traditional spin valve (TSV), and was remained as low as 4 Oe when the $t_{F}$ varied from 1 nm to 4 urn. It was found that the SFL made it possible to reduce the free layer thickness and enhance the MR ratio without degrading the soft magnetic property of the free layer.

• Journal of the Korean Applied Science and Technology
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• v.12 no.2
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• pp.13-19
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• 1995

Spin finish(SF) for nylon filament was prepared. The influence on the properties of filament obtained by treating the prepared spin finish in this study(SF-2) and foreign-made spin finish(Spinnar N-100) was compared. SF-2 prepared by blending of spindle oil 70g, paraffin wax 10g, glyceryl mono-oleate 5g, POE(6) nonylphenyl ether 4g, POE(10) nonylphenyl ether 4g, POE(10) octylphenyl ether 2g, POE(14) mono-oleate 4g and water 1g was excellent in its characteristics. Some of the properties of Nylon filament treated with SF-2 were better than those treated with Spinnar N-100. Also, optimal physical conditions of nylon filament according to the number of revolution of oil roller were obtained at conditions of 5rpm of number of revolution oil roller, 1.25% of SF-2 oil pick up, and denier 69D.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.355-356
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• 2008

현재 초고압 송변전기기에 적용되고 있는 $SF_6$ 가스는 절연 및 소호성능이 우수하며 회복특성이 뛰어나기 때문에 초고압 기기의 절연매체로서 일반적으로 사용하고 있다. 그렇지만 $SF_6$ 가스의 온난화 계수는 $CO_2$의 약 23,900배로 매우 높고, 대기 중으로 방출될 경우에는 온실효과 가스로 문제가 되고 있다. 따라서, $SF_6$ 가스의 대기 중에의 방출을 최대로 피하기 위해 단계별 연구가 필요하다. 본 논문에서는 초고압 전력기기의 DS/ES부에 Dry Air Gas와 절연코팅소재를 적용하여 절연특성에 대한 연구를 하였다.

• Clean Technology
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• v.19 no.4
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• pp.476-480
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• 2013

The growth behavior of $CH_4$ and $SF_6$ mixture gas hydrate has been investigated by a combined approach of Raman spectroscopy and molecular modeling. Raman spectroscopy results presented that when $CH_4$ is used only, $CH_4$ guest molecule is inserted first into the large cavity of the host structure built by $H_2O$ molecules and then into the small cavity to stabilize the whole gas hydrate structure. In the other hand, when $SF_6$ is mixed together, $SF_6$ is favored over (or competing with) $CH_4$ in being inserted into the large cavity and the small cavity still prefers $CH_4$ insertion. The calculations of binding energies clearly supported this. While $SF_6$ has a binding energy of -26.9 kcal/mol a little lower than -24.2 kcal/mol of $CH_4$ in the large cavity, $SF_6$ and $CH_4$ has 1.2 kcal/mol and -22.0 kcal/mol, respectively, in the small cavity. It indicates that the sizable $SF_6$ is not preferred in the small cavity but has a relative energetic advantage over $CH_4$ in the large cavity.