• Journal of Advanced Marine Engineering and Technology
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• 제38권10호
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• pp.1347-1353
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• 2014

It's possible for a human to breathe under water, if dissolved oxygen is effectively used. Fish can stay under water using the gill which extracts dissolved oxygen from water. Water includes small amounts of oxygen, so a human needs larger amounts of water to acquire oxygen enough for underwater breathing. The exhalation gas from a human is another method to get higher amounts of oxygen under water. It mainly composes of oxygen, nitrogen and carbon dioxide. So, if only carbon dioxide is decreased, the exhalation gas has good characteristics for breathing of a human under water. In this paper, composition of the exhalation gas from a human was analyzed using GC. Based on these results, the synthesized gas was prepared and mixed into water which was used for experimental devices to analyze separation characteristics of dissolved gases from water. Experimental devices included a water pump, a hollow fiber membrane module and a vacuum pump. The effects of pressure and water flow on separation characteristics of synthesized gas were investigated. The compositions of gases separated from water using synthesized gas were investigated using GC. These results expect to be applied to the development of underwater breathing technology for a human.

• 한국추진공학회지
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• 제18권3호
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• pp.26-33
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• 2014

기체중심 스월 인젝터는 대형 액체 로켓 엔진의 주연소기로 광범위하게 사용되고 있다. 케로신과 산소과잉 가스와 같은 기체-액체 추진제들은 임계 압력 이상의 높은 압력 조건에서 혼합, 연소되므로 대기조건에서의 비연소 분무실험은 실제적인 분무 거동을 정확히 재현할 수 없다. 기체중심 스월 인젝터에서 실제 조건과 유사한 분무 패턴을 관측하기 위해서, 고압 챔버와 제어 시스템이 구성되었고 선명한 가시화 결과를 얻기 위하여 실험 과정이 정밀하게 제어되었다.

• 한국분말재료학회지
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• 제3권1호
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• pp.49-56
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• 1996

The effect of$H_{2}/N_{2}$gas sintering atmosphere on the carbon content and mechanical properties during the metal injection molding process of carbonyl iron-nickel powder was studied. The carbon content of the specimen after debinding in the pure$N_{2}$atmosphere appeared 0.78 wt%. After showing the maximum value of 1.48 wt.% in the debinding atmosphere of 10%$H_{2}/N_{2}$gas mixture, the carbon content of the debinded specimen decreased gradually with increasing the$H_2$content in the$H_{2}/N_{2}$gas mixture. The carbon contents of the sintered specimen were 0.46~0.63wt% in Na gas atmosphere, while they appeared extremely low above 40%$H_{2}/N_{2}$gas atmosphere. The relative sintered density increased abruptly from 88~90% to 93~96% with the addition of Ni, while the density nearly unchanged above 2% Ni addition. The sintered density increased with increasing the fraction of$H_{2} in H_{2}/N_{2}$gas mixture. Tensile strength and hardness increased, and elongation decreased with increasing carbon and Ni content. In spite of high carbon content of 0.63 wt%, the superior elongation value of 10% was shown.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.285-288
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• 1996

The electronic operation of the gas discharge tube is controlled by the electrical energy as sinusoidal waveform in arbitrary frequency range, or as a sequence of pulses at a wide range of duty cycle, the gas composition, the kind of electrode and the vessel geometry. In this paper, the pulsed mode operated gas discharge tube is composed with mixed gas of IIg-Ne ( 10 Torr ), in the tube of 15.0 mm outer diameter and has variable color from red to blue with changing frequency and pulse width in high voltage. As increasing pulse width and frequency in the gas discharge tube, the phenomenons that the electron temperature in the positive column increases and the radiation from atoms of higher upper state energy levels increases, exist. The color have the locus from red (0.4972, 0.3128) to blue (0.2736, 0.2619) in CIE chromacity diagram with increasing pulse width and frequency. The changing method of pulse width and frequency has been shown to be suitable for the luminous color control.

• 동력기계공학회지
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• 제6권4호
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• pp.23-29
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• 2002

This paper is studied to investigate the effect of slits and swirl vanes on the main flow fields of a gun-type gas burner through X-Y plane and Y-Z plane respectively by using X-probe from hot-wire anemometer system. This experiment was carried out with flow rate $450{\ell}/min$ in respective burner models installed in the test section of a subsonic wind tunnel. The burner models with only slits and only swirl vanes respectively were made by modifying original gun-type gas burner. The fast jet flow spurted from slits played a role such as an air-curtain because it encircled rotational flow by swirl vanes and drives mixed main flow to axial direction. As a result, the gun-type gas burner had a wider flow range up to about Y/R=1.5 deviated from slits and maintains a comparatively large velocity in the central part of burner within the range of about X/R=2.5. Therefore, it was very desirable that swirl vanes were installed within slits in gun-type gas burner in order to control the main flow fields effectively.

• 대한안전경영과학회지
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• 제25권1호
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• pp.51-58
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• 2023

Determination of explosion reference pressure is important in designing and testing flameproof enclosures (Ex d). Although relative humidity affects to explosion pressure, its effect is not well investigated for the gas group IIB, IIA, and I. This study tested explosion pressure for Ethylene (8 vol.%), Propane (4.6 vol.%), and Methane (9.8 vol.%), which are the representative gas of the gas group IIB, IIA, and I, at ambient temperature and atmospheric pressure (1 atm) under different relative humidity (0% ~ 80%). Ethylene- and Propane-air mixed gases generally tended to decrease as the relative humidity increased; however, explosion pressure was largely dropped at 20% of relative humidity compared to 0% and 10% of relative humidity. On the other hand, Methane-air mixture gas showed similar pressures at 0% and 10% of relative humidity; but no explosion occurred at more than 20%. The results of this study can be used in setting a testing protocol of explosion reference pressure for designing and testing a flameproof enclosure.

• 한국가스학회지
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• 제27권4호
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• pp.56-61
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• 2023

플랜트는 사회기반시설로써 중요한 보호시설이고, 여기서 발생 가능한 가스 누출 및 폭발과 같은 사고에 대한 안전성 확보는 설계 시 반드시 고려해야 한다. 하지만 플랜트에서의 폭발압력에 대한 연구는 경제성 등의 이유로 거의 없으며, 이에 대한 데이터가 부족한 실정이다. 본 연구에서는 플랜트에서 발생할 수 있는 폭발 시나리오를 고려한 실험 설계안을 제시하고 폭발 실험을 통해 폭압을 확인하였다. 가연성 물질로 수소-메테인 혼합 가스가 이용되었으며, 밀폐도와 밀집도가 폭압에 주는 영향에 대해 연구하였다. 밀폐도에 따라 압력파의 중첩이 폭압에 주는 영향과 밀집도에 따른 난류 영향을 구분하여 논의한다. 본 연구에서의 결과는 다양한 안전설계 시 입력자료로 활용될 수 있다.

• 한국대기환경학회지
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• 제12권3호
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• pp.231-241
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• 1996

The effect of radiation and buoyancy on the thermophoresis phenomenon owing to the presence of highly absorbing, emitting particles (such as soot or pulverized coal) suspended in a two phase flow system was investigated numerically for a turbulent mixed convection flow. The analysis of conservation equations for a gas-particle flow system was performed on the basis of a two-fluid model from a continuum Eulerian viewpoint. The modified van Driest and Cebeci mixing length turbulence model was adopted in the anaylsis of turbulent flow. In addition, the P-1 approximation was used to evaluate the radiation heat transfer. As expected from the particle concentration and drift velocity distribution, the cumulative collection efficiency E (x) becomes larger when the buoyancy effect increases (i.e. higher Grashof number), while smaller as the radiation effect increases (i.e. higher optical thickness).

• Journal of Welding and Joining
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• 제15권2호
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• pp.72-80
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• 1997

The spatter generation rate of GMA welding with $CO_2$ gas shielding was measured with the change of welding conditions such as wire feeding rate and welding voltage and then the results were analized with the accompanying changes in metal transfer mode and in bead geometry. The spatter generation rate (SGR) was relatively low not only wit the short circuit transfer but with the truely globular transfer mode. However, the SGR resulted with the mixed mode were consistantly high. The resultant wave pattern of mixed mode was due to the coexistance of short-circuit and globular transfer and characterized by the frequent appearance of instantaneous short circuit. Considering the result of SGR and that of bead geometry, it could be concluded that when the wire feeding rate (or welding current) was either low or high, the optimum bead shape could be obtained along with the low spatter generation. However, in the middle range of wire feeding rate, the optimum bead shape was only obtained in the mixed mode condition resulting in the high spatter generation.

• 한국환경보건학회지
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• 제20권4호
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• pp.10-16
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• 1994

A Study was performed in order to measure mixed organic solvent concentrations in air of painting operations during January 5-28, 1991. The mixed organic solvent concentrations were analyzed by the gas chromatography. The results were as follows: 1. The detection of organic solvent was highest in aromatic hydrocarbon(68%), and followed by aliphatic hydrocarbon (18%), and ketone (14%). 2. The detection of organic solvent by component category was highest in the grid class solvent (79.4%), and followed by the 3rd class solvent (20.6%). 3. Number of cases exceeding TLVS of mixed solvent level in air was highest on dipping operation (44%), and followed by spray operation (40%), dry and washing operation (33%), and adhensive operation (12%).