• Journal of the korean Society of Automotive Engineers
• /
• v.13 no.6
• /
• pp.16-21
• /
• 1991

자동차용 가솔린 엔진유의 품질은 엔진성능의 향상과 함께 점진적으로 발전되면서 서비스 수준에 의한 분류로 SA급에서부터 SF급까지 발전되어 왔다. 그러나 지난 1980년에 SF급 오일이 설정된 이후 8년이 지나서 새로운 가솔린 엔진 오일의 규격인 SG급이 1988년에 설정되었다. 본 고에서는 왜 SG급이 필요한가, 또 SF에 비해 어떤면이 얼마나 가혹하게 되었는가에 관하여 자세히 보고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.4C
• /
• pp.283-289
• /
• 2005

In this paper, we propose two efficient symbol detection algorithms for space-frequency OFDM (SF-OFDM) transmit diversity scheme. When the number of sub-carriers in SF-OFBM scheme is small, the interference between adjacent sub-carriers may be generated. The proposed algorithms eliminate this interference in a parallel or sequential manlier and achieve a considerable performance improvement over the conventional detection algorithm. The bit error rate (BER) performance of the proposed detection algorithms is evaluated by the simulation. In the case of 2 transmit and 2 receive antennas, at $BER=10^{-4}$ the proposed algorithms achieve the gain improvement of about 3 dB. The symbol detectors with the proposed algorithms are designed in a hardware description language and synthesized to gate-level circuits with the $0.18{\mu}m$ 1.8V CMOS standard cell library. With the division-free architecture, the proposed SF-OFDM-PIC and SF-OFDM-SIC symbol detectors can be implemented using 140k and 129k logic gates, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.8
• /
• pp.1416-1422
• /
• 2010

$SF_6$ is the most commonly used insulating gas in electrical systems. But In these days $SF_6$ mixtures and alternative gas has been studied because of global warming. so although many studies have been carried out about binary gas mixtures with $SF_6$, few studies were presented about breakdown characteristics of $SF_6/N_2$ mixtures. At present study the breakdown characteristics of $SF_6/N_2$ mixtures in Non-uniform field was performed. In this paper, The simulation value are compared with experiment values. Streamer breakdown criterion was used for predicting breakdown voltage. For accurate simulation this simulation apply utilization factor using CST(computer simulation technology) EM $studio^{tm}$ program. AC breakdown experiments in non-uniform field was performed to compare with the breakdown simulation values. The pressure range of gas mixtures was 0.4 MPa to 0.7 MPa. The rod-plane was used and mixture ratio is $SF_6$ 20% : $N_2$ 80%. The gap lengths are 10mm to 70mm. As the pressure increase, this simulation value does not correspond to the experiment value. So this simulation need surface roughness factor. As a result of applying surface roughness factor this simulation decrease a relative error (|experiment value - simulation value| /simulation value).

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

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.261-261
• /
• 2011

펄스 직류 전원 $BCl_3/SF_6$ 플라즈마를 이용하여 GaAs/$Al_{0.2}Ga_{0.8}As$의 선택적 식각을 연구하였다. 식각 주요 공정 변수는 $BCl_3/SF_6$ 플라즈마에서 $SF_6$ 가스 유량(0~50%)이었다. $BCl_3/SF_6$의 총 가스 유량은 20 sccm이었다. 다른 공정 조건인 공정 압력(100 mTorr), 펄스 파워(500 V), 펄스 주파수(200 kHz), 리버스 시간 (0.7 ${\mu}s$)은 일정하게 고정시켰으며 기계적 펌프만을 이용하여 공정을 진행하였다. 오실로스코프(Oscilloscope) 데이터에 의하면 가스의 조성 변화에도 척에 걸리는 입력 전압과 전류가 거의 변화가 없었다. $BCl_3/SF_6$ 가스가 10%의 조성에서 GaAs와 $Al_{0.2}Ga_{0.8}As$의 식각 선택비가 약 48 : 1로 우수한 결과를 나타내었다. 그러나 $BCl_3/SF_6$ 가스의 증가는 GaAs의 식각율과 선택도를 감소시켰다. 그리고 $SF_6$ 가스의 조성비가 30% 이상일 경우에는 GaAs와 $Al_{0.2}Ga_{0.8}As$가 식각되지 않았다. 식각 후에 GaAs의 표면 거칠기(RMS surface roughness)는 0.7~1.3 nm로 나타났다. 위의 결과들을 종합적으로 보면 펄스 직류 전원 $BCl_3/SF_6$의 조성비가 10%일 때 가장 좋은 식각 선택비를 얻을 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.11a
• /
• pp.591-593
• /
• 2000

In this paper, we describe the results of a combined experimental theoretical study designed to understand and predict the dielectric properties of SF$_{6}$ and SF$_{6}$+Ar mixtures. The electron transport, ionization, and attachment coefficients for pure SF$_{6}$ and gas mixtures containing SF$_{6}$ has been analysed over the E/N range 30~300[Td] by a two term Boltzmann equation and by a Monte Carlo Simulation using a set of electron cross sections determined by other authors, experimentally the electron swarm parameters for 0.2[%] and 0.5[%] SF$_{6}$+Ar mixtures were measured by time- of- flight method, The results show that the deduced electron drift velocities, the electron ionization or attachment coefficients, longitudinal and transverse diffusion coefficients and mean energy agree reasonably well with the experimental and theoretical for a rang of E/N values. Electron energy distribution functions computed from numerical solutions of the electron transport and reaction coefficients as functions of E/N. We have calculated $\alpha$,η and $\alpha$-η the ionization, attachment coefficients, effective ionization coefficients, and (E/N), the limiting breakdown electric-field to gas density ratio, in SF$_{6}$ and SF$_{6}$+Ar mixtures by numerically solving the Boltzmann equation for the electron energy distribution. The results obtained from Boltzmann equation method and Monte Carlo simulation have been compared with present and previously obtained data and respective set of electron collision cross sections of theections of the

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.4
• /
• pp.381-387
• /
• 2007

The excellent dielectric properties of $SF_6$(sulfur hexafluoride) have lead to its wide range of application in the field of high voltage insulation. Because there has been some recent concern regarding the environmental impacts of $SF_6$ binary gas mixtures, with $SF_6$ as the main component, have been the subject of active research. Scientists have long been interested in the possible use of gaseous fluorocarbons, including $CF_4$ (Carton Tetrafluoride), in high voltage applications due to their inert character and high dielectric strength. This paper presents experimental results concerning the AC breakdown characteristics lot various mixtures of $SF_6/CF_4$ in a test chamber and 25.8 kV GIS (Gas Insulation Switchgear) at practical pressures (0.1-04 MPa) and gap lengths (0.5 mm, 1 mm) in a test chamber. In the result, it was observed that an increase in the dielectric strength is attained through the addition of $SF_6$ to $CF_4$. It is possible to make an environment friendly gas insulation material while maintaining the dielectric strength by combing $SF_6$ and $CF_4$ which generates a lower level of the "global warming" effect.

• Korean Journal of Culture and Social Issue
• /
• v.26 no.4
• /
• pp.501-524
• /
• 2020

This study was conducted to validate the Korean Love addiction Questionnaire-Short Form (K-LAQ-SF) applicable to Korean society. As a result of exploratory factor analysis for Love addiction 40 Questions(Peabody, 2005), the final 5 factors and 15 questions appeared, and the model fit of the final scale was confirmed through confirmatory factor analysis. The results of the equivalence test showed that the theoretical structure of the abbreviated scale works in the same way for each gender. The results of correlation analysis between K-LAQ-SF and original scale showed that the abbreviated scale represented the original scale relatively faithfully. Finally, the results of correlation analysis between this scale and relationship addiction, love type and depression showed that convergence, discrimination and criterion validity were secured. K-LAQ-SF is significant in that it can be usefully used to easily measure the characteristics of Korean adults' love addiction in a short time based on stable reliability and validity.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.20 no.2
• /
• pp.85-92
• /
• 2010

$SF_6$ gas has been widely used in many industrial fields as insulating, cleaning and covering gases due to its outstanding arc-extinguishing and insulating properties. However, global warming potential of $SF_6$ gas is 23,900 times more than that of $CO_2$ and it remains in the air during 3,200 years. For these reason, technological and economical effects could be expected for the separation of $SF_6$ from gas mixtures by hydrate forming process. In this study, we carried out morphological studies for the $SF_6$ hydrate crystal to understand its formation and growth mechanisms. $SF_6$ hydrate film was initially formed at the interfacial boundary between gas and liquid regions, and then subsequent dendrite crystals growth was observed. The dendrite crystals grew to the direction of gas region probably due to the guest gas concentration gradient. The detailed growth characteristics of $SF_6$ hydrate crystals such as nucleation, migration, growth and interference were discussed in this study.

• Korean Journal of Microbiology
• /
• v.47 no.3
• /
• pp.200-208
• /
• 2011

Most problematic antibiotic resistance mechanism for MLS (macrolide-lincosamide-streptogramn B) antibiotics encountered in clinical practice is mono- or dimethylation of specific adenine residue at 2058 (E. coli coordinate) of 23S rRNA which is performed by Erm (erythromycin ribosome resistance) protein through which bacterial ribosomes reduce the affinity to the antibiotics and become resistant to them. ErmSF is one of the four gene products produced by Streptomyces fradiae to be resistant to its own antibiotic, tylosin. Unlike other Erm proteins, ErmSF harbors idiosyncratic long N-terminal end region (NTER) 25% of which is comprised of arginine well known to interact with RNA. Furthermore, NTER was found to be important because when it was truncated, most of the enzyme activity was lost. Based on these facts, capability of NTER peptide to inhibit the enzymatic activity of ErmSF was sought. For this, expression system for two different proteins to be expressed in one cell was developed. In this system, two plasmids, pET23b and pACYC184 have unique replication origins to be compatible with each other in a cell. And expression system harboring promoter, ribosome binding site and transcription termination signal is identical but disparate amount of protein could be expressed according to the copy number of each vector, 15 for pACYC and 40 for pET23b. Expression of NTER peptide in pET23b together with ErmSF in pACYC 184 in E. coli successfully gave more amounts of NTER than ErmSF but no inhibitory effects were observed suggesting that there should be dynamicity in interaction between ErmSF and rRNA rather than simple and fixed binding to each other in methylation of 23S rRNA by ErmSF.