• Environmental Engineering Research
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• 제25권4호
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• pp.447-461
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• 2020

In recent years, stimuli-responsive materials have garnered interest due to their ability to change properties when exposed to external stimuli, making it useful for various applications including gas separation. Light is a very attractive trigger for responsive materials due to its speedy and non-invasive nature as well as the potential to reduce energy costs significantly. Even though light is deemed as an appealing stimulus for the development of stimuli-responsive materials, this avenue has yet to be extensively researched, as evidenced by the fewer works done on the photo-responsive membranes. Of these, there are even less research done on photo-responsive materials for the purpose of gas separation, thus, we have collected the examples that answer both these criteria in this review. This review covers the utilisation of photo-responsive materials specifically for gas separation purposes. Photo-chromic units, their integration into gas separation systems, mechanism and research that have been done on the topic so far are discussed.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.112-122
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• 1995

As an alternative fuel producing less exhaust emissions, natural gas is of interest for use both in SI and CI engines. The potential of natural gas fuelled dual-fuel engine is considered high enough. However, much effort has to be made so that gaseous fuel is used efficiently with simultaneous minimum use of pilot oil. Hence, a simplified three-dimensional model, using a finite volume method in cylindrical coordinates, has been developed to facilitate an understanding of the dual-fuel combustion phenomena and to predict the complex interactions between the pilot distillate and natural gas. The computer model was calibrated by comparing it with the experimental results obtained from diesel engine like combustion bomb tests. In the pre-mixed natural gas combustion, the fuel burning was highly reliant on the injection condition and subsequent burning nature of the pilot distillate.

• 한국약용작물학회지
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• 제9권1호
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• pp.26-32
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• 2001

$10^{\circ}C\;N_2\;gas$ 3시간 처리시 무처리에 비해 총질소, 총아미노산, 비타민 C 함량이 약간 높았고, 탄닌과 엽록소 함량은 낮은 경향이었다. 기능성 성분인 GABA 함량은 무처리 (35mg/100g)에 비해 $51{\sim}205mg/100g$으로 $1.5{\sim}6$배 높았다. 제다 품질은 무처리에 비해 3시간 gas 처리시 차이가 없었다. $20^{\circ}C\;N_2$ gas 3시간 처리가 무처리에 비해 품질관련 성분 중 총질소, 총아미노산(데아닌), 카페인 함량은 많았고, 탄닌과 비타민 C 함량은 약간 낮았다. GABA함량은 무처리 (35mg/100g)에 비해 gas처리가 $85{\sim}225mg/100g$으로 $2.5{\sim}7$배 높았다. 제다 품질은 무처리 80.4점에 비해 gas 처리 $76.3{\sim}78.1$점으로 약간 저하되었다. $30^{\circ}C\;N_2$ 3시간 처리시 무처리와 기호성 관련성분이 거의 차이가 없었고 1, 5시간 처리는 무처리에 비해 품질이 약간 떨어지는 경향이었다. GABA 함량은 무처리 (30mg/100g)에 비해 gas처리가 $115{\sim}217mg/100g$으로 $3{\sim}7$배 증가하였다 제다품질도 무처리 80.4점에 비해 gas 처리가 $74.3{\sim}77.2$점으로 열악하였다. 따라서, $10^{\circ}C$에서는 5시간 gas처리, 20, $30^{\circ}C$에서는 3시간 gas 처리 후 제다를 하는 것이 기호성 및 기능성이 우수한 녹차(GABA차)를 제조할 수 있다고 생각된다.

• 천문학회보
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• 제39권1호
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• pp.37.2-37.2
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• 2014

Gas in disk galaxies interacts nonlinearly with a underlying stellar spiral potential to form galactic spiral shocks. Numerical simulations typically show that these shocks are unstable to the wiggle instability, forming non-axisymmetric structures with high vorticity. While previous studies suggested that the wiggle instability may arise from the Kelvin-Helmholtz instability or orbit crowding of gas elements near the shock, its physical nature remains uncertain. It was even argued that the wiggle instability is of numerical origin, caused by the inability of a numerical code to resolve a shock that is inclined to numerical grids. In this work, we perform a normal-mode linear stability analysis of galactic spiral shocks as a boundary-value problem. We find that the wiggle instability originates physically from the potential vorticity generation at a distorted shock front. As the gas follows galaxy rotation, it periodically passes through multiple shocks, successively increasing its potential vorticity. This sets up a normal-mode that grows exponentially, with a growth rate comparable to the orbital angular frequency. We show that the results of our linear stability analysis are in good agreement with the those of local hydrodynamic simulations of the wiggle instability.

• 한국가스학회지
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• 제18권6호
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• pp.21-26
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• 2014

연료의 사용으로 인한 이산화탄소의 발생량을 줄일 수 있는 방법으로 바이오가스 또는 매립가스와 같은 신재생 가스 연료를 사용하는 방법이 도움이 될 수 있다. 그러나 다량의 불활성가스가 포함되어 있기 때문에 저발열량 및 연료 조성의 불균일함은 신재생 가스 연료를 발전용 엔진에 적용하는 경우, 엔진 성능에 큰 영향을 미칠 수 있기 때문에 이에 대한 연구가 필요하다. 본 연구에서는 신재생가스연료에 불활성가스가 엔진 연소가 불안정한 정도로 많이 포함된 경우에 수소 연료를 첨가함으로써 연소 안정성을 개선할 수 있음을 확인하고, 엔진의 열효율 및 배기 특성과 같은 성능 변화에 대하여 살펴보았다. 또한 같은 조건에서 엔진 효율 및 배기 성능을 향상시키기 위한 방안으로 길이가 긴 전극을 갖는 스파크 플러그를 적용하여 효과가 있음을 확인하였다.

• 한국수소및신에너지학회논문집
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• 제30권2호
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• pp.111-118
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• 2019

Greenhouse gas emissions have a profound effect on global warming. Various environmental regulations have been introduced to reduce the emissions. The largest amount of greenhouse gases, including carbon dioxide, is produced in the steel industry. To decrease carbon dioxide emission, hydrogen-based iron oxide reduction, which can replace carbon-based reduction has received a great attention. Iron production generates various by-product gases, such as cokes oven gas (COG), blast furnace gas (BFG), and Linz-Donawitz gas (LDG). In particular, COG, due to its high concentrations of hydrogen and methane, can be reformed to become a major source of hydrogen for reducing iron oxide. Nevertheless, continuous COG cannot be supplied under actual operation condition of steel industry. To solve this problem, this study proposed to use two alternative COG-based fuel mixtures; one with natural gas and the other with biogas. Reforming study on two types of mixed gas were carried out to evaluate catalyst performance under a variety of operating conditions. In addition, methane conversion and product composition were investigated both theoretically and experimentally.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.21-26
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• 2005

Gas Chromatography (GC) is a wisely technique used for the separation and analysis of liquid and gas sample. Separation of the sample vapors is achieved via their differential migration through a capillary column with an insert carrier gas. The identity and quantity of each vapor in the mixer can be determined from its retention time in the column and a particular property of the gas, such as thermal conductivity, which can be related to the concentration of sample vapor in the carrier gas. Therefore, the flow characteristics in the spiral gas chromatographic column are numerically investigated in this study. Especially, different pressure drop between the front and the rear of GC column with various flow rates is estimated the governing equations are derived from making using of three-dimensional Naver-Stokes equation with incompressible and laminar model due to the nature of low Reynolds number flow. Using a commercial code, FLUENT, the pressure and flow fields in GC column are calculated with various flow rates. The characteristics of thermal cycling which is one of the most important factors affecting the column efficiency and analysis time is also estimated. Furthermore, numerical analyses are also carried out by using commercial code, ANSYS, with various values of power, which is applied to the heating element located at lower GC column.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권3호
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• pp.149-154
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• 2000

Bi-layer Mo films were deposited on soda-lime glass substrates using DC magnetron supttering. Increasing gas pressure, the resistivity varied from $1\times10^{-5}\; to\; 8.3\times10^{-3}\; \Omega.cm$. Furthermore, stress direction yielded compressive-to-tensile transition stress curves. The micro-structure of the compressively-stressed film which had poor adhesion consists of tightly packed columns, but of the tensile-stressed films had less dense structure. Under all gas pressure conditions, Mo films exhibited distinctly increasing optical reflection with decreasing gas pressure. The expansion of (110) peak width with the gas pressure meant the worse crystalline growth. The impurity levels in the Mo film exhibited highly concentrated Na, Se and O elements due to less dense micro-structure. The degree of Na diffusion depends on the type of the glass substrate used and the nature of the Mo film.

• 천문학회보
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• 제46권2호
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• pp.41.1-41.1
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• 2021

Neutral (HI) gas clouds associated with galaxies are responsible for fuelling the star-formation in the universe. In literature, the extremely strong damped Lyman-alpha absorbers (or ESDLAs) have been known to be sensitive to the effects of HI-H2 transition and star-formation in galaxies. Yet, ESDLAs are rare to probe due to the smaller cross section they subtend on the sky (similar to galaxies). In my talk, I will focus primarily on my study of the nature of ESDLAs that are observed as absorption signature along the line-of-sight (LOS) of a quasar (QSO). I will further look at the HI-H2 transition and interesting results relevant to diffuse molecular gas and the multi-phase medium (gas in different ionization states) that are associated with ESDLAs. Furthermore, I will also discuss how the ESDLA environments differ from the high star-forming and molecular environments detected in blind optical and radio surveys consecutively.

• 천문학회보
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• 제41권2호
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• pp.34.3-35
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• 2016

Ram pressure stripping of early-type galaxies has been largely neglected until now because of their gas poor nature. MUSE IFU observation vividly reveal the presence of star-forming blobs and ionised gas tails, around an early-type galaxy in Abell 2670. The galaxy was identified as a post-merger galaxy with disturbed faint features, in MOSAIC 2 deep optical images. The imaging also revealed a series of star-forming blobs, situated in the direction facing away from the cluster centre. Thanks to the revolutionary wide field-of-view of the MUSE, combined with 8.2-m VLT (UT-4) at Cerro Paranal, we could simultaneously obtain IFU spectra of the blobs, as well as the galaxy. The MUSE spectra clearly confirms that the star-forming blobs are associated with the early-type galaxy. Moreover, MUSE reveals long ionised-gas tails, emanating from the galaxy. The quantity of gas indicates a gas rich progenitor has merged with the early-type galaxy. However the direction of the tails and blobs, and the blob morphology, appears to indicate that strong ram-pressure stripping may have stripped out gas brought in by the merger. We will present kinematic structure of the whole system (the galaxy, star-forming blobs, and gas tails), as well as the star formation history of the system, supporting a scenario where a recent galaxy merger is subjected to cluster environmental mechanisms.