• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.178-184
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• 1996

Electrical properties such as surface flashover discharge and discharge degradations of insulating materials for superconducting cable have been investigated. It is found that the surface voltage is proportional to /$\^$0.7/(/: discharge length) in LHe(Liquid Helium). V-t characteristic LHe were a n=5.5 that was less than liquid N$_2$. After applied AC voltage, the surface condition of polymer films were observed non-eroded area and eroded area. The eroded area is depending on the applied voltage. In case of LHe, the crack was observed.

• 대한화학회지
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• 제7권2호
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• pp.115-121
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• 1963

Aliphatic hydrocarbon gases from rubber pyrolysis have been identified by gas chromatography with tetraethyleneglycol dimethylether column. Rubbers used in this work are polyisoprene, SBR, NBR, polybutadiene, buthyl rubber, polychloroprene and polyurethane rubber. The chromatogram is characteristic for each polymer. Author proposes a method of identification of synthetic rubbers by gas chromatograph of pyrolyzed gas. Sample is pyrolyzed at $450^{\circ}C$ under nitrogen or more effectively helium and gaseous portion, which eliminated liquid condensate, is passed to the column. The appearance of exclusively large peak of isoprene, isobutylene and carbon dioxide shows the presence of polyisoprene, polyisobutylene and polyurethane, respectively. Large peak of butadiene will appear in case of polybutadiene, SBR and NBR, but SBR can be identified through the styrene peak in gas chromatogram of liquid pyrolyzate and NBR can be identified by the evolution of hydrogen cyanide during pyrolysis. Polychloroprene is identified by the evolution of hydrogen chloride. This method could be applied to the identification of copolymer or polymer blend.

• Journal of Korean Vacuum Science & Technology
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• 제7권2호
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• pp.27-32
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• 2003

A large cryo-pumping system composed of 4 cryosorption pumps was designed and manufactured to satisfy the pressure requirements of the NBI test stand. The cryosorption pump consists of a thermal shield/baffle assembly and a cryopanel coated with activated carbon granules. The thermal shield is cooled by liquid nitrogen, and the cryopanel by a commercial helium refrigerator. The operation characteristics and vacuum performance of the cryosorption pump were investigated. The cooling down time of the cryopanel to 20 K was about 6 hours with a liquid nitrogen consumption rate of about 35 L/hr. The maximum pumping speed of the cryosorption pump for the hydrogen gas measured by the steady pressure method was about 90,000 L/s.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.168-175
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• 2005

액체로켓 추진시스템에서 가압시스템은 발사체 추진제 탱크의 얼리지 공간에 제어된 가스를 공급하는 것이다. 가압시스템에서 고온 가스 열교환기를 적용하는 데는 가압제의 비용적을 증가시켜 전체 발사체 시스템의 중량을 감소시키는 장점이 있다. 가압시스템 성능에 있어서 주목할 만한 개선점은 극저온 시스템에서 얻어질 수 있다. 이러한 경우 가스 공급은 극저온 탱크 내부에 저장되어 진다. 극저온 가압제의 온도 특성은 가압시스템에서 구성 단품을 개발하는데 있어서 매우 중요하다. 본 연구에서는 SINDA/FLUINT를 이용한 수치적 모델링과 PTF(Propellant-feeding Test Facility)에서 수행된 실험에 대하여 해석 및 시험이 수행되었다.

• 항공우주기술
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• 제7권2호
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• pp.170-175
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• 2008

본 연구에서는 다양한 기체를 사용한 액체로켓엔진의 시동특성 및 적합성, 그리고 호환성 등에 대해 고찰하였다. 엔진의 시동특성은 파이로 시동기 및 헬륨 기체 시동에 대해 고찰하였으며, 파이로 시동기 및 헬륨, 수소+질소 혼합기체 그리고 공기 등을 구동매질로 할 때의 시험 적합성과 호환성 등에 대해 고찰하였다. 대부분의 기체가 엔진의 시동특성과 호환성을 만족시키는 것을 알 수 있었으나, 공기의 경우 저추력의 경우에만 사용할 수 있는 것을 알 수 있었다.

• 항공우주시스템공학회지
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• 제12권2호
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• pp.15-22
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• 2018

7개의 방정식으로 구성된 DIM을 사용하여 압축성 다상 유동에 대해 연구하였다. 액체와 기체의 상세한 경계면 유동 구조를 얻기 위해 5 차의 MLP와 변형된 HLLC 근사 리만 해법을 포함하는 고차 수치기법이 구현되었다. 수치 방법의 유효성 검증을 위해 물과 공기로 구성된 다양한 1차원 충격관 문제를 해석하였고, 불연속면에 대해 뛰어난 해상도를 얻을 수 있었다. 마하수 1.22의 충격파 조건에서의 2차원 공기-헬륨 기포에 대한 충격파 상호 작용을 수치 해석하였고, 충격파 현상들을 잘 모사하였으며 실험결과와 비교 검증하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제24권4호
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• pp.59-64
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• 2022

The cryogenic system of RAON which is Korea's first heavy ion accelerator was numerically modeled and simulated. EcosimPro which is widely used off-the-shelf numerical software for a large scale cryogenic system was used for the simulation. The model of SRF TF cryogenic system, which is the testbed of cryomodule, was firstly established. The integrity of system of SRF TF was confirmed by comparison of simulation and experimental results. The cool-down strategy to minimize the thermal stress of the cavity was simulated and an optimal strategy was established. In addition, the influence of valve and pump control parameters on the cooling time was investigated, and optimal control parameters were also derived. The cryogenic system of SCL3 that is a low-energy acceleration section including 55 cryomodules, valve boxes, and helium supply lines was also modeled. The soundness of the thermal shield system and interlock system of SCL3 was investigated.

• 한국수소및신에너지학회논문집
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• 제30권6호
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• pp.490-498
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• 2019

The intermittent electric power supply of renewable energy can have extremely negative effect on power grid, so long-term and large-scale storage for energy released from renewable energy source is required for ensuring a stable supply of electric power. Power to gas which can convert and store the surplus electric power as hydrogen through water electrolysis is being actively studied in response to increasing supply of renewable energy. In this paper, we proposed the novel concept of hydrogen liquefaction process combined with pre-cooling process using the liquid air. It is that hydrogen converted from surplus electric power of renewable energy was liquefied through the hydrogen liquefaction process and vaporization heat of liquid hydrogen was conversely recovered to liquid air from ambient air. Moreover, Comparisons of specific energy consumption (kWh/kg) saved for using the liquid air pre-cooling was quantitatively conducted through the performance analysis. Consequently, about 12% of specific energy consumption of hydrogen liquefaction process was reduced with introducing liquid air for pre-cooling and optimal design point of helium Brayton cycle was identified by sensitivity analysis on change of compression/expansion ratio.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.107-110
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• 2003

High Temperature Superconductor (HTS) transmission cable can carry more than 2 to 5 times higher electricity and also obtain substantially lower transmission losses than conventional cables. Liquid nitrogen is to be used to cool the HTS power cable and its cost is much cheaper than the liquid helium used for the cooling of metal superconducting wire. In Korea the HTS power cable development project has been ongoing since July, 2001 with the basic specifications of 22.9kV, 50MVA and told dielectric type as the first 3-year stage. The cryogenic system of the HTS cable is composed of HTS cable cryostat termination and refrigeration system. Termination of HTS cable is a connecting part between copper electrical cable at room temperature and HTS cable at liquid nitrogen temperature. In order to design the termination cryostat, it is required that the conduction heat leak and Joule heating on the current lead be reduced, the cryostat be insulated electrically and good vacuum insulation be maintained during long time operation. Heat loads calculations on the copper current lead have been performed by analytical and numerical method and the feasibility study fer the other candidate materials has also been executed.

• Journal of Advanced Marine Engineering and Technology
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• 제35권6호
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• pp.802-808
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• 2011

극저온 온도 구조 재료의 중요한 기계적 성질 중 하나는 파괴 인성이다. 파괴 인성 시험 방법의 규격화에 대한 연구는 극저온 구조 요소의 개발과 함께 매우 중요한 문제가 되고 있다. 특히 용접부의 경우 극저온 환경 하에서 사용할 때 불안정파괴를 유발할 수 있기 때문에 용접부의 각 미세조직에 따른 기계적 성질 평가가 중요하다. 본 연구에서는 STS-316L 모재와 용접재를 대상으로 액체질소(77K), 액체헬륨(4K), 293K 온도에서 제하컴플라이언스법과 예민화 열처리한 소형화된 시험편 대상으로 파괴인성평가 실험을 수행하였다.