• 한국가스학회:학술대회논문집
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• 한국가스학회 2005년도 추계학술발표회 논문집
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• pp.88-93
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• 2005

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권3호
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• pp.129-134
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• 2004

To analyze the performance of the gas circuit breaker(GCB), the flow field variables such as temperature, pressure and density should be evaluated accurately In the puffer chamber of puffer type GCB, the pressure rise may Exceed 20 bar and in this range of high pressure, $SF_6$ gas deviates the ideal gas property. Therefore, the real gas property of $SF_6$ should be taken into consideration for the accurate analysis of flow field. This paper presents the analysis technique of cold gas flow in GCB employing the real gas state equation of SF6. The FVFLIC method is Employed to solve the axisymmetric Euler equation. To reduce the computational effort of real gas state equation, the relationship between density and pressure is approximated by the polynomial at the temperature of 300K. The proposed method is applied to the test GCB model and simulation results show good agreement with the experimental ones.

• 한국수소및신에너지학회논문집
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• 제29권4호
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• pp.357-362
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• 2018

In this study, computer simulation and optimization works have been performed for a refrigeration cycle using ammonia as a refrigerant and also how much power was saved when the liquefied natural gas cold heat is replaced for the refrigeration cycle. PRO/II with PROVISION release 10.0 from Schneider electric company was used, and Peng-Robinson equation of the state model was selected for the modeling of the refrigeration cycle and LNG cold heat utilization process.

• 설비공학논문집
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• 제6권3호
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• pp.247-258
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• 1994

In this study, experimental investigations to find cold energy storage performance have been made for two different temperatures at condenser. Temperatures at inlet and outlet of condenser were measured to calculate global heat transfer coefficient of direct contact method in our cold energy storage system. Also storage performance by direct contact method was compared with that of Ice-On-Coil type ice storage which was calculated by analytic solution. Results show that, in the case of $-8.0^{\circ}C$ at condenser inlet, heat transfer coefficient of direct contact method is 3.25 times higher than that of conventional method and COP of system is improved by using R141b as refrigerant which produces gas hydrate and has higher phase change temperature than $0.0^{\circ}C$.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.238-239
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• 2006

Nozzle geometry influences gas dynamics making sprayed particle behavior one of the most important parameters in cold spray process. Gas flows at the entrance convergent section of the nozzle takes place at relatively high temperature and are subsonic. Thus, this region is a very suitable environment for heating spray particle. In this study, numerical simulation and experiments were conducted to investigate the effect of nozzle contour, entrance geometry of nozzle and powder injection position at nozzle on the cold spray process. The process changes were observed through numerical simulation studies and the results were used to find a correlation with coating properties.

• 한국가스학회지
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• 제18권2호
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• pp.41-47
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• 2014

본 논문에서는 유기랭킨사이클과 LNG 사이클로 구성된 복합사이클의 열역학적 성능 해석을 수행한다. 이 복합사이클에서는 현열 형태의 저등급 폐열을 사용하며 LNG 냉열은 열싱크 뿐 아니라 동력 생산에도 사용된다. 시스템의 성능에 대한 터빈입구압력, 응축온도, 열원온도 등 주 파라미터들의 영향을 상세하게 분석한다. 시뮬레이션 결과는 이 복합시스템은 LNG 냉에너지를 사용하지 않은 일반의 ORC에 비해 현저하게 성능이 개선될 수 있음을 보여준다.

• International Journal of Automotive Technology
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• 제3권1호
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• pp.41-46
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• 2002

Effect of secondary air injection (SAI) on hydrocarbon reduction has been investigated in a single cylinder Sl engine operating at cold-steady/cold-start conditions. The hydrocarbon emission and exhaust gas temperature with and without catalytic converter were compared with continuous and synchronized SAIs, which injected secondary air intermittently into exhaust port. Effects of SAI location, SAI pressure, SAI timing, and location of catalytic converter have been investigated and the results are compared for both SAls with base condition. At cold-steady condition, the rate of HC reduction increased as the location of SAI was closer to the exhaust valve for both synchronized and continuous SAls. The emission of HC decreased with increasing exhaust-A/F when it was rich, and was relatively insensitive when it was lean. The timing of SAI in synchronized SAI had significant effect on HC reduction and exhaust gas temperature and the synchronized SAI was found to be more effective in HC reduction and exhaust gas temperature compared to the continuous SAI . At cold-start condition, when the catalytic converter was located 20 cm downstream from the exhaust port exit, the catalytic converter warm-up period for both SAls decreased by about 50%, and the accumulated hydrocarbon emission during the first 120 s decreased about by 56% and 22% with the synchronized and continuous SAIs, respectively, compared to that of the base condition.

• 천문학회지
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• 제53권3호
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• pp.77-85
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• 2020

In the molecular cloud G33.92+0.11A, massive stars are forming sequentially in dense cores, probably due to interaction with accreted gas. Cold dense gas, which is likely the pristine gas of the cloud, is traced by DCN line and dust continuum emission. Clear chemical differences were observed in different source locations and for different velocity components in the same line of sight. Several distinct gas components coexist in the cloud: the pristine cold gas, the accreted dense gas, and warm turbulent gas, in addition to the star-forming dense clumps. Filaments of accreted gas occur in the northern part of the A1 and A5 clumps, and the velocity gradient along these features suggests that the gas is falling toward the cloud and may have triggered the most recent star formation. The large concentration of turbulent gas in the A2 clump seems to have formed mainly through disturbances from the outside.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.164-166
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• 1998

This paper presents the results of the measured pressure-rise and the analyzed results of the cold gas flow-field in a 72.5kV 20kA gas circuit breaker for the electrical railway system. The analysis of cold gas flow field and the calculation of electric field strength have been performed in 3 types of interrupters and the low current interruption capability has been estimated for each of the gas circuit breaker considering the opening speed, the nozzle shape and the stroke length.

• 천문학회보
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• 제46권1호
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• pp.29.1-29.1
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• 2021

There have been many studies aiming to reveal the origins of the star-gas misalignment found in galaxies, but there still is a lack of understanding of the contribution from each formation channel candidate. We explore the properties, origins, and lifetimes of the star-gas misalignment using Horizon-AGN, a large-volume cosmological simulation. First, the misalignment fraction shows a strong anti-correlation with the kinematic morphology (V/sigma) and the cold gas fraction of the galaxy. This result is consistent with the result of integral field spectroscopy observations. Second, we have identified four main formation channels of misalignment and quantified their level of contribution: mergers (35%), interaction with nearby galaxies (23%), interaction with dense environments or their central galaxies (21%), and secular evolution including smooth accretion from neighboring filaments (21%). Third, the decay timescale of the misalignment is strongly linked with the kinematic morphology of the galaxy: early-type galaxies (2.28 Gyr) tend to have a longer misalignment lifetime than LTGs (0.49 Gyr). We also found that the morphology and cold gas fraction are both and independently anti-correlated with the misalignment lifetime.