• Title, Summary, Keyword: CFCS

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Evaluation of Ground-Water Sampling Techniques for Analysis of Chlorofluorocarbons (지하수의 CFCs(Chlorofluorocarbons) 조사를 위한 시료 채취 방법의 평가)

  • 고동찬;이대하
    • Journal of Soil and Groundwater Environment
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    • v.8 no.2
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    • pp.1-8
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    • 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.

CFCs 조사를 위한 지하수 시료채취방법 비교 및 평가

  • 고동찬;이대하;성현정;강철희;고경석
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.21-23
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    • 2002
  • Two sampling methods for chlorofluorocarbons(CFCs) in groundwater were compared and assessed with groundwater samples in Jeju Island. CFCs concentrations from copper tube method were widely variable among triplicates and higher than those from flame-sealed glass ampule method. For the copper tube method, this is aggravated by rubber packings in the faucet of discharge line of wells, which was removed for the glass ampule method. The poor reproducibility and apparent contamination of results by copper tube method is due to the improper sealing of copper tubes and materials in water discharge line. This suggests that it is more difficult to achieve complete isolation from the atmosphere in the copper tube method and that materials that could release CFCs should be avoided along the sampling flow lines. It seems that the flame-sealed glass ampule method is more relevant for groundwater sampling for CFCs though it requires more complicated equipments and procedures.

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On the Continuous Monitoring System of CFCs in the Ambient Air (CFCs 자동연속측정시스템 구축)

  • 한진석;강창국;노혜란;이덕희;최양일
    • Proceedings of the Korea Air Pollution Research Association Conference
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    • pp.94-95
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    • 1999
  • 불소나 염소가 수소대신에 치환 되어있는 활로겐화 화합물인 염화불화탄화수소(CFCs chlorofluoro carbons)는 오존층 파괴물질 그리고 지구온난화 기체물질로 널리 알려져있다. 이러한 CFCs는 Mauna Loa, Niwot Ridge, South Pole과 같은 지구배경농도지역에서 70년대 후반부터 지속적으로 측정되어 오고 있다. 대기중 CFCs농도는 일반적으로 수백 ppt 수준으로 매우낮아 측정이 매우 어려운 것으로 알려져왔다.(중략)

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Experimental Evaluation of an Analytical Method for Chlorofluorocarbons (CFSs) in Air and Water Using Gas Chromatography (가스 크로마토그래피를 이용한 대기와 물시료의 CFCs(chlorofluorocarbons) 분석법의 실험적 평가)

  • Koh, Dong-Chan;Choi, Beom-Kyu;Kim, Yong-Je
    • Economic and Environmental Geology
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    • v.40 no.1
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    • pp.129-140
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    • 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.

On the Development of the Generic CFCS for Engineering Level Simulation of the Surface Ship (공학수준 수상함 지휘무장통제체계 범용 모델 개발방안 연구)

  • Jung, Young-Ran;Han, Woong-Gie;Kim, Cheol-Ho;Kim, Jae-Ick
    • Journal of the Korea Institute of Military Science and Technology
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    • v.14 no.3
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    • pp.380-387
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    • 2011
  • In this paper, we considered the authoritative representation of Command and Fire Control System(CFCS) for the surface ship that was the engineering level model to develop system specifications and to analyze operational concepts on the concept design phase and to analyze military requirements, effectiveness and performance for the system. The engineering level model of CFCS can be used in simulation independently of the surface ship's type, and also it takes reuse, interoperability, and extension into consideration. The detailed sub-models, internal and external data interface, data flow among each sub-model, sensor and weapon models about the engineering level model of CFCS was defined. It was verified via engineering level simulations according to the V&V process.

A Study of Performance Improvement of CFCS SW Using HPC (HPC를 활용한 지휘무장통제체계 SW 성능향상 연구)

  • Baek, Chi-Sun
    • Proceedings of the Korean Society of Computer Information Conference
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    • pp.1-2
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    • 2017
  • 본 논문에서는 지휘무장통제체계(이하 CFCS) 소프트웨어의 성능 향상 기법으로 고성능 컴퓨팅(이하 HPC) 시스템 활용 기법을 제안한다. 이 기법으로 본 논문에서는 HPC 분야인 멀티코어 프로세서를 활용하는 방법을 제안한다. 복잡한 반복연산을 하는 작업이 많은 CFCS의 특정 SW모듈에 대해 멀티코어 프로세싱 아키텍처를 이용한 병렬처리를 적용하여 기존 순차처리 대비 작업실행시간을 단축함으로써 작업 응답시간을 상당히 줄일 수 있다. 본 논문에서는 CFCS 시험 환경의 일부 특정 SW모듈 상에서 기존의 순차처리 방식으로 수행한 연산 결과와 다중 처리 프로그래밍 API인 OpenMP를 적용하여 수행한 연산 결과를 비교하여 CFCS에서의 멀티코어 프로세싱이 체계 전반의 성능 향상 면에서 효율적으로 사용될 수 있음을 보인다.

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Effect of Specific Surface Area on the Reaction of Silicon Monoxide with Porous Carbon Fiber Composites

  • Park, Min-Jin;Lee, Jae-Chun
    • The Korean Journal of Ceramics
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    • v.4 no.3
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    • pp.245-248
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    • 1998
  • Porous carbon fiber composites (CFCs) having variable specific surface area ranging 35~1150 $\m^2$/g were reacted to produce silicon carbide fiber composites with SiO vapor generated from a mixture of Si and $SiO_2$ at 1673 K for 2 h under vacuum. Part of SiO vapor generated during conversion process condensed on to the converted fiber surface as amorphous silica. Chemical analysis of the converted CFCs resulting from reaction showed that the products contained 27~90% silicon carbide, 7~18% amorphous silica and 3~63% unreacted carbon, and the composition depended on the specific carbide, 7~18% amorphous silica and 3~63% unreacted carbon, and the composition depended on the specific surface area of CFCs. CFC of higher specific surface area yielded higher degree of conversion of carbon to silicon and conversion products of lower mechanical strength due to occurrence of cracks in the converted caron fiber. As the conversion of carbon to silicon carbide proceeded, pore size of converted CFCs increased as a result of growth of silicon carbide crystallites, which is also linked to the crack formation in the converted fiber.

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