• Bulletin of the Korean Chemical Society
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• 제18권11호
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• pp.1175-1179
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• 1997

The adsorption of oxygen on ZnO was monitored by measuring the capacitance of two contacting crystals which have depletion layers originated from the interaction between oxygen and ZnO at 298 K-473 K. An admission of oxygen to the sample induced an irreversible increase in the depth and the amount of adsorbed oxygen was less than 0.001 monolayer in the experimental condition. The relation between pressure of oxygen and variation of the depth was tested from the view point of Langmuir or Freundlich isotherm. Using Hall effect measurement and kinetic experiment, a model equation on the adsorption process was proposed. From the results, it was suggested that oxygen adsorption depended on the rate of electron transfer from ZnO to oxygen while the amount of adsorbed oxygen was kinetically restricted by the height of surface potential barrier.

• Safety and Health at Work
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• 제6권1호
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• pp.18-24
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• 2015

Background: In 2006, three farmers died at the bottom of an agricultural shallow well where the atmosphere contained only 6% oxygen. This study aimed to document the variability of levels of oxygen and selected hazardous gases in the atmosphere of wells, and to identify ambient conditions associated with the low-oxygen situation. Methods: A cross-sectional survey, conducted in June 2007 and July 2007, measured the levels of oxygen, carbon monoxide, hydrogen sulfide, and explosive gas (percentage of lower explosive limit) at different depths of the atmosphere inside 253 wells in Kamphaengphet and Phitsanulok provinces. Ambient conditions and well use by farmers were recorded. Carbon dioxide was measured in a subset of wells. Variables independently associated with low-oxygen condition (<19.5%) were identified using multivariate logistic regression. Results: One in five agricultural shallow wells had a low-oxygen status, with oxygen concentration decreasing with increasing depth within the well. The deepest-depth oxygen reading ranged from 0.0% to 20.9%. Low levels of other hazardous gases were detected in a small number of wells. The low-oxygen status was independently associated with the depth of the atmosphere column to the water surface [odds ratio (OR) = 13.5 for 8-11 m vs. <6 m], depth of water (OR = 0.17 for 3-<8 m vs. 0-1 m), well cover (OR = 3.95), time elapsed since the last rainfall (OR = 7.44 for >2 days vs. <1 day), and location of well in sandy soil (OR = 3.72). Among 11 wells tested, carbon dioxide was detected in high concentration (>25,000 ppm) in seven wells with a low oxygen level. Conclusion: Oxygen concentrations in the wells vary widely even within a small area and decrease with increasing depth.

• KEPCO Journal on Electric Power and Energy
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• 제2권2호
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• pp.285-291
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• 2016

In chemical-looping combustion, pure oxygen is transferred to fuel by solid particles called as oxygen carrier. Chemical-looping combustion process usually utilizes a circulating fluidized-bed process for fuel combustion and regeneration of the reduced oxygen carrier. The performance of an oxygen carrier varies with the active metal oxide and the raw support materials used. In this work, spraydried Mn-based oxygen carriers were prepared with different raw support materials and their physical properties and oxygen transfer performance were investigated to determine that the raw support materials used are suitable for spray-dried manganese oxide oxygen carrier. Oxygen carriers composed of 70 wt% $Mn_3O_4$ and 30 wt% support were produced using spray dryer. Two different types of $Al_2O_3$, ${\gamma}-Al_2O_3$ and ${\alpha}-Al_2O_3$, and $MgAl_2O_4$ were applied as starting raw support materials. The oxygen carrier prepared from ${\gamma}-Al_2O_3$ showed high mechanical strength stronger than commercial fluidization catalytic cracking catalyst at calcination temperatures below $1100^{\circ}C$, while the ones prepared from ${\alpha}-Al_2O_3$ and $MgAl_2O_4$ required higher calcination temperatures. Oxygen transfer capacity of the oxygen carrier prepared from ${\gamma}-Al_2O_3$ was less than 3 wt%. In comparison, oxygen carriers prepared from ${\alpha}-Al_2O_3$ and $MgAl_2O_4$ showed higher oxygen transfer capacity, around 3.4 and 4.4 wt%, respectively. Among the prepared Mn-based oxygen carriers, the one made from $MgAl_2O_4$ showed superior oxygen transfer performance in the chemical-looping combustion of $CH_4$, $H_2$, and CO. However, it required a high calcination temperature of $1400^{\circ}C$ to obtain strong mechnical strength. Therefore, further study to develop new support compositions is required to lower the calcination temperature without decline in the oxygen transfer performance.

• 한국항공운항학회지
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• 제30권2호
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• pp.55-60
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• 2022

A PSU (passenger service unit) is mounted on passenger seats in a cabin on an aircraft and consists of a crew call lamp, a reading lights, an information display lamp, an emergency oxygen generator, and an emergency oxygen mask. It is a safety device for providing convenience to passengers and providing oxygen to passengers in an emergency. This paper is a study on emergency oxygen supply systems and light systems of aircraft PSUs and a control device was developed to operate the system by analyzing the B767-300 aircraft's PSU circuit diagram. And the temperature generated by the B777-200ER aircraft's emergency oxygen generator was also measured by operating it directly. Through this, precautions for explaining the operation of an oxygen mask in an emergency were described and improvements were presented. Data acquired in these research processes can be used in the future to develop aircraft PSU (passenger service unit) and emergency oxygen generators.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1996년도 The 9th KACG Technical Annual Meeting and the 3rd Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.508-508
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• 1996

;The growth of films have considerable interest in the field of superlattice structured multi-layer epitaxy led to realization of new devices concepts. Molecular beam epitaxy (MBE) with in situ observation by reflection high-energy electron diffraction (RHEED) is a key technology for controlled layered growth on the atomic scale in oxide crystal thin films. Also, the combination of radical oxygen source and MBE will certainly accelerate the progress of applications of oxides. In this study, the growth process of single crystal films using by MBE method is discussed taking the oxide materials of Bi-Sr-Ca-Cu family. Oxidation was provided by a flux density of activated oxygen (oxygen radicals) from an rf-excited discharge. Generation of oxygen radicals is obtained in a specially designed radical sources with different types (coil and electrode types). Molecular oxygen was introduced into a quartz tube through a variable leak valve with mass flowmeter. Corresponding to the oxygen flow rate, the pressure of the system ranged from $1{\;}{\times}{\;}10^{-6}{\;}Torr{\;}to{\;}5{\;}{\times}{\;}10^{-5}$ Torr. The base pressure was $1{\;}{\times}{\;}10^{-10}$ Torr. The growth of Bi-oxides was achieved by coevaporation of metal elements and oxygen. In this way a Bi-oxide multilayer structure was prepared on a basal-plane MgO or $SrTiO_3$ substrate. The grown films compiled using RHEED patterns during and after the growth. Futher, the exact observation of oxygen radicals with MBE is an important technology for a approach of growth conditions on stoichiometry and perfection on the atomic scale in oxide. The oxidization degree, which is determined and controlled by the number of activated oxygen when using radical sources of two types, are utilized by voltage locked loop (VLL) method. Coil type is suitable for oxygen radical source than electrode type. The relationship between the flux of oxygen radical and the rf power or oxygen partial pressure estimated. The flux of radicals increases as the rf power increases, and indicates to the frequency change having the the value of about $2{\times}10^{14}{\;}atoms{\;}{\cdots}{\;}cm^{-2}{\;}{\cdots}{\;}S^{-I}$ when the oxygen flow rate of 2.0 seem and rf power 150 W.150 W.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.180-185
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• 2004

Our previous study showed that although the hybrid rocket engine with swirling gaseous oxygen had high performance, a direct injection of LOX with swirl into the combustion chamber of the hybrid rocket engine lowered the performance of the engine, compared to that with gaseous oxygen. In order to clarify this reason, combustion tests of a small PMMA combustor with an inner port diameter of 2 mm were conducted in liquid oxygen flow by comparison with gaseous oxygen flow. Although the oxygen mass fluxes of LOX were about two orders of magnitude larger than those of gaseous oxygen, the fuel regression rate of LOX were remarkably smaller than those of gaseous oxygen. For both liquid and gaseous oxygen, diffusion flames in the port of the grain controlled the combustion process of PMMA in oxygen flow. These results may be explained by the fact that only small amount of LOX vaporized and consumed in the combustion with PMMA while flowing through the port due to relatively larger latent heat of injected liquid oxygen compared to the heat of release by combustion which depended on the burning surface area of PMMA.

• 한국전기전자재료학회논문지
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• 제14권12호
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• pp.1008-1015
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• 2001

Thin films of vanadium oxide(VO$\_$x/) have been deposited by r.f. magnetron sputtering from V$_2$O$\_$5/ target in gas mixture of argon and oxygen. The oxygen/(oxygen+argon) partial pressure ratio is changed from 0% to 8%. Crystal structure, chemical composition, bonding, optical and electrical properties of films sputter-deposited under different oxygen gas pressures are characterized through XPS, AES, RBS, FTIR, optical absorption and electrical conductivity measurements. V$_2$O$\_$5/ and lower oxides co-exist in sputter-deposited films and as the oxygen partial pressure is increased the films become more stoichiometric V$_2$O$\_$5/. The increase of O/V ratio with increasing oxygen gas pressure is attributed to the partial filling of oxygen vacancies through diffusion. It is observed that the oxygen atoms located on the V-O plane of V$_2$O$\_$5/ layer participate more readily in the oxidation process. With increasing oxygen gas pressure indirect and direct optical band gaps are increased, but thermal activation energies are decreased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.435-438
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• 2001

Thin films of vanadium oxide(VO$\sub$x/) have been deposited by r.f. magnetron sputtering from V$_2$O$\sub$5/ target in gas mixture of argon and oxygen. The oxygen/(oxygen+argon) partial pressure ratio is changed from 0% to 8%. Crystal structure, chemical composition and bonding properties of films sputter-deposited under different oxygen gas pressures are characterized through XRO, XPS, RBS and FTIR measurements. All the films prepared below 8% O$_2$ are amorphous, and those prepared without oxygen are gray indicating the presence of V$_2$O$\sub$$_4$/ phase in the films. V$_2$O$\sub$5/ and lower oxides co-exist in sputter-deposited films and as the oxygen partial pressure is increased the films become more stoichiometric V$_2$O$\sub$5/. The increase of O/V ratio with increasing oxygen gas pressure is attributed to the partial filling of oxygen vacancies through diffusion. It is observed that the oxygen atoms. located on the V-O plane of V$_2$O$\sub$5/ layer participate more readily in the oxidation process.

• 센서학회지
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• 제17권5호
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• pp.329-337
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• 2008

Simple, small and portable oxygen sensors were fabricated by tape casting technique. Yttria stabilized zirconia containing cordierite ceramics (YSZC) were used as a porous diffused layer of oxygen in pumping cell. Yttria stabilized zirconia (YSZ) solid electrolyte, YSZC porous diffusion layer and heater-patterned ceramic sheets were prepared by co- firing method. Limit current characteristics and the linear relationship of current to oxygen concentration were observed. Viscosity variation of the slurries both YSZ and YSZC showed a similar behavior, but micro pores in the fired sheet were increased with increasing of the cordierite amount. Molecular diffusion was dominated due to the formation of large pores in porous diffusion layer. The plateau range of limit current in porous-type oxygen sensor was narrow than the one of aperture-type oxygen sensor. However limit current curve was appeared in porous-type oxygen sensor even at the lower applied voltage. The plateau range of limit-current was widen as increasing the thickness of porous diffusion layer of the YSZ containing cordierite. Measuring temperature of $600{\sim}650^{\circ}C$ was recommended for limit-current oxygen sensor. Porous diffusion layer-type oxygen sensor showed faster response than the aperture-type one and was stable up to 30 days running without any crack at interface between the layers.

• Journal of Preventive Medicine and Public Health
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• 제17권1호
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• pp.289-294
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• 1984

The energy expended while playing tennis was determined from the players heart rate and from the amount of oxygen they consumed. This study was made using eight healthy but unathletic male college students. Expired air was collected for 2 minute periods during each game by the Douglas bag method. Samples were collected when serving and receiving. The air collected was measured using a wet test gas meter. The amount of air collected was expressed in STPD. Oxygen consumption was determined by measuring the oxygen content of the expired air with a Orzat gas analyzer. The energy expended during the tennis games was calculated indirectly. The caloric coefficient of oxygen was multiplied by the volume of oxygen consumed. The caloric coefficient of oxygen varied from 4.6 to 5.1 kcal/liter of oxygen. In this study the value of 5 kcal/liter of oxygen was used in the calculations. The accuracy of the measurements of energy expended was tested using regression analysis of the measured volume of oxygen. The mean values of heart rate, oxygen consumed and energy expended did not vary when the activity of serving and receiving was compared. The mean value of oxygen consumed during play was $1.4329{\pm}282ml/min$ or $21.6{\pm}4.0ml/kg/min$. The energy expended was $7.15{\pm}1.46kcal/min$ or $6.45{\pm}1.23kcal/kg/min$. The values were equivalent to 5.5 mets. When the levels of oxygen consumed were estimated using the formulas, they were found to be higher than the measured levels. The estimated amounts, however, were within 25% of the measured amounts.