• Journal of Korean Society for Atmospheric Environment
• /
• v.10 no.1
• /
• pp.41-48
• /
• 1994

A monitoring system for atmospheric CFC-12 and CFC-11 has been established at Mt. Kwan-Ak, Seoul National University (SNU) since July, 1991. The concentrations showed quite a large variation ranging from 495 to 37600 pptv (pptv=part per trillion, 10$^{-12}$ , v/v) for CFC-12 and from 233 to 12100 pptv for CFC-11 due to many local sources. However, monthly medians show rather limited ranges ; 553~765 pptv for CFC-12 and 301~431 pptv for CFC-11. Furthermore minimum concentrations could be defined relatively well during the whole period of observation. The regional background concentrations in 1993 near SNU wer estimated as 533 pptv for CFC-12 and 293 pptv for CFC-11. These values are very comparable to global averages in Northern Hemisphere, 523 pptv for CFC-12 and 287 pptv for CFC-11, reflecting the fast atmospheric mixing processes within the hemisphere. Examinations with meteorological parameters such as wind speed and direction suggest the possible measurement-window at SNU, appropriate for regional monitoring. Studies for improving the monitoring capability of the SNU station such as automation of the analysis system along with correlation with other meteorological parameters, are in progress at the present time.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.10 no.5
• /
• pp.569-580
• /
• 1998

In this study, condensation heat transfer coefficients(HTCs) of a plain tube, low fin tube, and Turbo-C enhanced tube for CFC-11, HCFC-123, CFC-12, HFC-l34a are measured and compared against each other. All data are taken at the vapor temperature of 39$^{\circ}C$ with a wall subcooling temperature 3~8$^{\circ}C$. Test results show that HTCs of a low vapor pressure refrigerant, HFC-123, for a plain, low fin, and Turbo-C tubes are 10.5~20.5%, 8.2~12.2%, 16.5~19.2% lower than those of CFC-11, respectively. On the other hand, HTCs of a medium vapor refrigerant, HFC-l34a, for a plain, low fin, and Turbo-C tubes are 20.6~31.8%, 0.0~8.0%, 13.2~20.9% higher than those of CFC-12, respectively. For all refrigerants tested, HTCs of Turbo-C tube are the highest among the three tubes showing almost 8 times increase in HTCs as compared to those of a plain tube. Nusselt's prediction equation for a plain tube yielded 12% deviation for all plain tube data while Realty and Katz's prediction equation for a low fin tube yielded 20% deviation for all low tube data.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1997.04a
• /
• pp.12-12
• /
• 1997

CFC-222 is a novel fluoroqinolone antibacterial agent synthesized and under development by the Cheil Jedang Corporation, Korea. CFC-222 exerts the antibacterial activity by inhibition of bacterial DNA gyrase leading to bactericidal action. In in vitro and in vivo preclinical testing, CFC-222 has been shown to possess a broad spectrum of antibacterial activity. In particular CFC-222 is very potent against Gram-positive bacteria such as Staphylococcus spp., Streptocuccus spp. (in particular penicillin G-resistant and -susceptible S. pneumoniae) and Enterococcus spp. when compared to other quinolones (ciprofloxacin, ofloxacin or lomefloxacin). CFC-222 also showed potent activity against the methicillin resistant clinical isolates of S. aureus (MRSA). Against Gram-negative bacteria (E. coli, Pseudomonas and Sarcina) the activity of CFC-222 was slightly weaker than that of ciprofloxacin, but was more potent than that of ofloxacin or lomefloxacin. In urinary systemic infections caused by both Gram-positive and -negative bacteria, CFC-222 demonstrated a potent therapeutic efficacy in particular against Cram-positive bacteria S. aureus, S. pyrogen 203 and S. pneumonia TypeIII.

• Journal of the Korean Society of Safety
• /
• v.14 no.3
• /
• pp.93-100
• /
• 1999

Decomposition efficiency, power consumption, and applied voltage of CFC(Chlorofluorocatbon) were investigated by SPCP(surface induced discharge plasma chemical processing) reactor to obtain optimum process variables and maximum decomposition efficiencies. Decomposition efficiency of CFC-12 with various electric frequencies(5~50kHz). flow rates (100~1,000mL/min), initial concentrations(100~1,000ppm), electrode materials(W, Cu, Al). electrode thickness(1, 2, 3mm) and reference gases($N_2$, $O_2$, air) were measured and the products were analyzed with FT-IR. Experimental results showed that at the frequency of 10kHz, the highest decomposition efficiency of 92.7% for CFC-12 were observed at the power consumptions of 29.6W. respectively, and that decomposition efficiency decreased with increasing frequency above 20kHz and decomposition efficiency per unit power were 3.13%/W for CFC-12. Decomposition efficiency was increased with increasing residence times and with decreasing initial concentration of pollutants. Decomposition efficiency was increased with increasing thickness of discharge electrode and the highest decomposition efficiency was obtained for the electrode diameter of 3m. As the electrode material, decomposition efficiency was in order that tungsten(W), copper(Cu), aluminum (Al). Decomposition of CFC-12 in the reference gas of $N_2$ showed the highest efficiency among three reference gases, and then the effect of reference gas on the decomposition efficiency decreased in order of air and $O_2$. The optimum power for the maximum decomposition efficiency was 25.3W for CFC.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.28 no.5
• /
• pp.389-395
• /
• 1999

냉동공조설비, 발전설비, 화학플랜트설비 등에 사용되는 응축기는 주로 증기가 관의 외부에서 응축을 하고 냉각수가 관 내부로 흐르는 쉘-튜브(shell and tube)형 태를 취하고 있다. 초기투자비용 및 운전비용을 줄이기 위해서는 응축기의 열교환 성능을 향상시키는 일이 필수적이며 이를 위해 코팅 표면(coated surfaces), 거친 표면(rough surfaces), 코일 튜브(coiled tubes), 선회 흐름장치(swirl flow), 전열면적을 넓힌 낮은 핀관과 3차원 형상을 갖는 열전달 촉진관의 사용이 제시되고 있다.

• Economic and Environmental Geology
• /
• v.40 no.1 s.182
• /
• pp.129-140
• /
• 2007

CFC(CFC-12, CFC-11 and CFC-113) analytical system for air and water was constructed using a customized purge and trap extraction device and a gas chromatograph with an electron capture detector. Sampling methods of air and water for CFCs were also established. The analytical system was experimentally optimized to result in reproducibilities of triplicates less than 2% for current air samples and less than 5% for groundwater samples with CFC-12 concentration of 160 to 180 pg/kg, and verified with respect to the CFC system in USGS, which showed analytical results were in agreement within 10%. CFCs in air were monitored at three sites over 19-month period in the central part of South Korea, and the result indicates no significant local sources of CFCs in those areas. For groundwater in Jeju Island, CFCs were measured over a year with a two-month interval. The time-series data showed seasonal fluctuations which could be interpreted by the effect of recharge pulse derived from large amount of rainfall during monsoon period with a few month delay, which indicates high permeability of basaltic rocks in Jeju Island.

• Journal of Soil and Groundwater Environment
• /
• v.8 no.2
• /
• pp.1-8
• /
• 2003

Two types of ground-water sampling techniques for CFCs (chlorofluorocarbons) analysis, the cold-welded copper tube method and flame-sealed borosilicate glass ampule method, were compared and evaluated. CFCs concentrations by the copper tube method showed a poor reproducibility among triplicates whereas those by the glass ampule method showed a good agreement and relative standard deviations of triplicates were less than 5%. The poor reproducibility of the copper tube method appears to be attributed to the incomplete sealing in connection between faucets of wellhead and the sampling apparatus. The copper tube method also showed higher CFCs concentrations than the glass ampule method, which is more pronounced for CFC-11 than for CFC-12. The plastic tubings and rubber gasket of faucets in case of the copper tube method possibly contaminated the samples with CFC-11 and CFC-12. The potential of CFCs contamination for the glass ampule method was eliminated by using stainless steel and Nylon only and by connecting the sampling equipment directly to the main discharge pipe of wellhead. The validity of the glass ampule method were also verified by detecting very low level of CFCs for the ground-water sample which is old enough to have negligible CFCs.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.7 no.2
• /
• pp.249-265
• /
• 1995

The performance of a refrigerant mixture of propane(R290)/isobutane(R600a) as a substitute for CFC12 was investigated in a domestic refrigerator with single evaporator. A thermodynamic cycle simulation indicated an increase in COP of a 1.7 to 2.4% with R-290/600a in the composition range of 0.2 to 0.6 mass fraction of R290 compared to CFC12. For the tests, two units($299{\ell}$, $465{\ell}$) were used. All refrigeration components remained the same throughout the tests, except that the length of capillary tube and amount of charge were changed for the mixture. The refrigerators were fully instrumented with more than 20 thermocouples, 2 pressure transducers, and watt/watt-hour meter for each refrigerator. 'Energy consumption test' and 'no load pulldown test' were performed under the same condition. The experimental results obtained with the same compressor indicated that R-290/600a mixture at 0.6 mass fraction of R290 showed a 3 to 5% increase in energy efficiency and a faster cooling speed compared to CFC12. The R-290/600a mixture showed a shorter compressor on-time and a lower compressor dome temperature than CFC12. In conclusion, the proposed hydrocarbon mixture seems to be an appropriate candidate to replace CFC12 without causing more environmental problems.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2004.09a
• /
• pp.138-141
• /
• 2004

The environmental tracers tritium/helium-3 (3H/3He) and chlorofluorocarbons (CFCs) were investigated in ground water from Jeju Island, Korea, a basaltic volcanic island. The apparent 3H/3He and CFC-12 ages were in relatively good agreement in samples with low concentrations of terrigenic He. Ground water mixing was evaluated by comparing 3H and CFC-12 concentrations with mixing models, which distinguished old water with negligible 3H and CFC-12, young water with piston flow, and binary mixtures of the two end members. The ground water CFC-12 age is much older in water from wells completed in confined zones of the hydro-volcanic Seoguipo formation in coastal areas than in water from the basaltic aquifer. Comparison of major element concentrations in ground water with the CFC-12 age shows that nitrate contamination processes contribute more solutes in young water than are derived from water-rock interactions in non-contaminated old water. Chemical evolution of ground water resulting from silicate weathering in basaltic rocks reaches the zeolite-smectite phase boundary. The calcite saturation state of ground water increased with the CFC-12 apparent (piston flow) age. In agricultural areas, the temporal trend of nitrate concentration in ground water was consistent with the known history of chemical fertilizer use on Jeju Island, but the response of nitrate concentration in ground water to nitrogen inputs follows an approximate 10-year delay. Based on mass balance calculations, it was estimated that about 40% of the nitrogen applied by fertilizers reached the water table and contaminated ground water resources when the fertilizer use was at the highest level.

• Biomolecules & Therapeutics
• /
• v.2 no.4
• /
• pp.331-335
• /
• 1994

As a part of the safety evaluation of Pseudomonas vaccine(CFC-101), antigenicity tests were carried out in guinea pigs and mice. In active systemic anaphylaxis(ASA) test, guinea pigs showed no sign or only moderate sign(1/5) when sensitized and challenged with up to 200 $\mu\textrm{g}$/kg. In homologous passive cutaneous anaphylaxis(PCA) test using guinea pigs, inoculation of CFC-101 alone did not produce CFC-101-specific antibody. When inoculated with 200 $\mu\textrm{g}$/kg plus adjuvant, challenge of 200 $\mu\textrm{g}$/kg produced PCA titer of 32(5/5) but challenge of 20 $\mu\textrm{g}$/kg did not produce CFC-101-specific antibody. In heterologous PCA test using mice, CFC-101-specific antibody was not detected when sensitized with CFC-101 alone. Some animals(3/12) showed positive PCA response when inoculated with 200 $\mu\textrm{g}$/kg plus alum. In passive hemagglutination (PHA) test, although no antibody was detected at 20 $\mu\textrm{g}$/kg, inoculation of 200 $\mu\textrm{g}$/kg alone or with alum produced positive response in all animals. This result has already been predicted because CFC-101 is a vaccine developed for the purpose of immunization. From the above results, it can be concluded that there is no adverse antigenic potential up to 10 times clinical dose of 200 $\mu\textrm{g}$/kg.