• Title, Summary, Keyword: Air atmosphere

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A Study on the Relationship among the Concentration of Reacting Air Pollutants in Urban Atmosphere (도시 대기중에서 반응성 대기오염물질의 농도변화 상관성에 관한 연구)

  • Lee, Hwa-Woon;Kim, Yoo-Keun;Jang, Eun-Suk
    • Journal of Environmental Science International
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    • v.6 no.4
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    • pp.351-357
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    • 1997
  • In the Atmosphere under the various physical and chemical condition different chemical reactions occur and there are a number of air pollutants which are generated by photochemical reaction by absorbing solar energy. Therefor various testing simulation was done as foundation work to develop the numerical model for the prediction of concentration of air pollutants. It was shown change of msjor air pollutants concentration In according to variation of photodissociation speed constant, Kl and Initial condition of air pollutants concentration which plays major role In photochemical reaction. The photochemical reaction model which was used In this study Is found to be useful for understanding relationship among the concentration of reacting air pollutants and the prediction of concentration of air pollutants in urban atmosphere.

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Effect of Oxidation on Hot Ductility Behavior of Plain Carbon Steel (탄소강의 열간연성 거동에 미치는 산화의 영향)

  • Park, Tae Eun;Lee, Un Hae;Sohn, Kwang Suk;Lee, Sung Keun;Kim, In Soo;Yim, Chang Hee;Kim, Donggyu
    • Korean Journal of Metals and Materials
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    • v.48 no.5
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    • pp.394-400
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    • 2010
  • The effects of oxidation behavior on the hot ductility of plain carbon steels were investigated at various temperatures in order to simulate the continuous casting process more precisely, in which the process undergoes in air atmosphere rather than Ar atmosphere. The high temperature oxidation behavior and scale morphology of the carbon steels exposed to the air and Ar atmosphere at various temperatures were also investigated in order to assess the mechanism of the RA value decreasing in an air atmosphere. The RA values obtained from the air atmosphere were marked below 45% by the test temperature, except for over 1000${^{\circ}C}$, with the RA values remaining in low values in both the low and high temperature region, at which the RA values generally recovered in the Ar atmosphere. The surface roughness of the specimen was developed by external and internal oxidation when the specimen was deformed in an air atmosphere at high temperature, with the result being the stress concentrated at the roughness of the specimen surface, resulting in low RA values. The hot ductility in the air atmosphere was found to be likely controlled by the oxidation rate instead of the microstructures corresponding to test temperatures.

Tribological Behaviour of $WS_2$Solid Lubricant ($WS_2$ 고체윤활제의 마찰.마모 거동)

  • 신동우;김인섭;윤대현;김경도;김성진;정진수
    • Tribology and Lubricants
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    • v.14 no.2
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    • pp.35-41
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    • 1998
  • The $WS_2$ solid lubricant synthesized through the vapour phase transport method was coated on the commercial bearing steel (SUJ 2) substrate, and the tribological behaviour of the lubricant was investigated using a ball-on-disk type tester. The $WS_2$ powder was spray-coated at room temperature using compressed air, and the change of friction coefficient was examined in various conditions, i.e., specimen configuration, atmosphere (air and nitrogen), applied load and rotating speed. $WS_2$ coated ball and disk showed the optimum friction coefficient of 0.07 and wear life of 45,000 cycles in the nitrogen atmosphere under 0.3 kgf and 100 rpm, whereas relatively high coefficient of 0.13 and reduced wear life of 4,000 cycles were observed in air atmosphere. The effect of rotating speed on the friction coefficient was not observed both in nitrogen and in air atmospheres. This confirmed that the spray-coated $WS_2$ solid lubricant was effective in reducing the friction coefficient and improving wear life in nitrogen atmosphere, and the oxygen and moisture existing in air could seriously deteriorate the lubrication effect of $WS_2$ coating layer.

The Effect of Sintering Atmosphere on the Microwave Dielectric Properties of $(1-x)CaTiO_3-xLaAlO_3$ System (소결 분위기가 $(1-x)CaTiO_3-xLaAlO_3$계의 마이크로파 유전특성에 미치는 영향)

  • 여동훈;김현재;문종하
    • Journal of the Korean Ceramic Society
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    • v.34 no.5
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    • pp.505-511
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    • 1997
  • The effects of sintering atmospheres(air, O2, N2) on the sintering and microwave dielectric properties of (1-x)CaTiO3-xLaAlO3 system was investigated. The sintered density of (1-x)CaTiO3-xLaAlO3 under air atmosphere increased linearly with increasing x, but it decreased in the range of x>0.5 under O2 atmosphere and x>0.6 under N2 atmosphere in spite of the increament of the smaller La(1.06$\AA$) and Al(0.5 $\AA$) ion than Ca(0.99$\AA$) and Ti(0.6$\AA$). In case of the air sintering atmosphere of (1-x)CaTiO3-xLaAlO3 the two phases of orthorhombic and rhombohedral crystal system were coexisting, and the XRD peak of rhombohedral crystalsystem was to be higher with increasing x. However, the sintering atmosphere of O2 and N2 made the monophasic crystal system of orthorhombic keep up by x=0.5 and x=0.6, respectively, and it transformed to pseudo-cubic crystal system in x>0.5 and x>0.6. The XRD peak intensity of (1-x)CaTiO3-xLaAlO3 was to be gradually higher with increasing x under the air atmosphere of sintering. Whereas, its XRD peak intensity increased till x=0.6 but decreased with increasing x in the range of x>0.6 under O2 and N2 atmosphere. The relative dielectric constant of (1-x)CaTiO3-xLaAlO3 sintered under air atmosphere decreased linearly and the Q.f0 value increased according as x increased. On the other hand, the relative dielectric constant of (1-x)CaTiO3-xLaAlO3 under O2 and N2 atmosphere decreased in the range of x$\leq$0.5 with increasing x, but increased rapidly in the range of x$\geq$0.6. And the Q.f0 value increased till x=0.6 but decreased in the range of x>0.6 with increasing x. The temperature coefficient of resonant frequency had no relation to sintering atmosphere.

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Research for Carbon Dioxide Fluctuation using Drone above the Mud Flat and Reed Beds in the Suncheon Bay (드론 관측을 통한 순천만 갯벌과 갈대밭 상부 대기의 이산화탄소 농도 분포 연구)

  • Kang, Dong-hwan;Jo, Won Gi;Yun, Yeon Su;Yu, Hun Sun;Jang, Seon Woong;Kim, Dong Lib;Park, Jeong Hwan;Song, Young Chul;Choi, Yong Jae
    • Journal of Environmental Science International
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    • v.29 no.7
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    • pp.703-713
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    • 2020
  • In this study, carbon dioxide concentration and air temperature at different elevations were observed and analyzed in the upper atmosphere of mud flat and reed beds at low tide in Suncheon Bay. The carbon dioxide concentration and air temperature sensors were mounted on the drone, and the carbon dioxide concentration and air temperature by altitude (5 m, 10 m, 20 m, 40 m) at five points in the tidal flat and reed beds were observed in the morning and afternoon. The carbon dioxide concentrations in the upper atmosphere of the tidal flat ranged from 453.0 to 460.2 ppm in the morning and 441.6 to 449.7 ppm in the afternoon. The carbon dioxide concentrations in the upper atmosphere of the reed beds ranged from 448.9 to 452.4 ppm in the morning and 446.0 to 454.4 ppm in the afternoon. The carbon dioxide concentrations in the upper atmosphere of the tidal flat was higher in the morning than in the afternoon, and the carbon dioxide concentration decreased as the altitude increased. The carbon dioxide concentration in the upper atmosphere of the reed beds was similar in the morning and afternoon at all altitudes, and the carbon dioxide concentration decreased as the altitude increased. The correlation coefficient between carbon dioxide concentration and air temperature observed in the tidal flat in the morning was -0.54 ~ -0.77, and the correlation coefficient between carbon dioxide concentration and air temperature observed in the afternoon was 0.56 ~ 0.80. The correlation coefficient between carbon dioxide concentration and temperature observed in the morning in the reed field was low, below 0.3, and the correlation coefficient between carbon dioxide concentration and air temperature observed in the afternoon was 0.35 ~ 0.77. In the upper atmosphere of the tidal flats and reed beds, the linear function was suitable for the change of carbon dioxide concentration as a air temperature, and the coefficient of determination of the estimated linear function was higher in the afternoon than in the morning. Through this study, it was confirmed that the carbon dioxide concentration in the upper atmosphere of the tidal flat and the reed beds was different, and the increase rate of carbon dioxide concentration in the upper atmosphere of the tidal flat and the reed beds was higher in the afternoon than in the morning.

Effects of Chilling and Packing Methods on Physico-chemical Properties of Cold-stored Chicken Breast and Thigh Meats (냉각방법과 포장방법에 따른 냉장계육의 이화학적 특성 변화)

  • 박구부;하정기;진상근;박태선;신택순;이정일
    • Korean Journal of Poultry Science
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    • v.24 no.1
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    • pp.17-28
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    • 1997
  • This experiment was carried out to investigate the effects of different chilling and packing methods on physico-chernical properties of cold-stored chicken breast and thigh meats. Dehoned chicken breast and thigh meats were chilled either air spray or ice-water immersion method. The chilled meats were either vacuum packed or atmosphere packed, and stored at -2˚C for 1, 3, 7, 11, 15, and 20 days. The pH of both immersion chilled meats and vacuum packed meats were higher than those of their counterparts(P<0.05). The pH of atmosphere packed meats increased as the storage period extended. The moisture contents of vacuum packed meats were remarkably higher than those of atmosphere packed meats. The pH of all treatments decreased as the storage period extended. The shear values of air spray chilled and vacuum packed breast meats were significantly higher than immersion chilled and vacuum packed ones. However, immersion chilled and atmosphere packed breast meats were significantly higher than those of air spray chilled and atmosphere packed breast meats. The shear values of immersion chilled and vacuum packed thigh meats were significantly higher than those of immersion chilled and vacuum packed thigh meats. In atmosphere packed thigh meats, air spray chilling method showed higher shear values than those of immersion chilled thigh meats. In thigh muscle, tenderness values tended to decrease as the storage period extended(P<0.05). Contents of water soluble proteins of vacuum packed and air spray chilled breast and thigh meats were higher than those of their counterparts as the storage period extended(P<0.05). The contents of water soluble proteins significantly decreased as the storage period extended. Salt soluble proteins of atmosphere packed breast and thigh meats were remarkably higher than those of vacuum packed ones(P<0.05). Total lipid contents of atmosphere packed and air spray chilled breast and thigh meats were higher than those of atmosphere packed and immersion chilled meats as the storage period extended. The vacuum packed meats were significantly higher in total lipid contents than those of atmosphere packed meats. The storage period decreased the total lipid contents of cold chicken, Major fatty acids in cold-stored chicken were oleic, palmitic, linoleic and stearic acids, regardless of chilling method. Unsaturated fatty acids of all treatments decreased, but saturated fatty acids increased as the storage period extended.

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Electrochemical Properties of Carbon Composites Prepared by Using Graphite Ball-milled in Argon and Air Atmosphere

  • Lee, Kyoung-Muk;Oh, Seh-Min;Lee, Sung-Man
    • Bulletin of the Korean Chemical Society
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    • v.29 no.6
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    • pp.1121-1124
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    • 2008
  • A carbon composite was synthesized by mechanical mixing of ball-milled graphite and PVC powders, followed by pyrolysis reaction of PVC. Natural graphite ball milled under atmosphere of argon or air leads to a disordered structure. It appears that the electrochemical lithium intercalation reaction is dependent on the atmosphere in which the graphite is ball milled. The carbon composite obtained using air-milled graphite shows a high reversible capacity and high initial coulombic efficiency compared to argon-milled graphite. This is attributed to the enhanced thermal stability of a disordered structure in the air milled sample. For the one with air-milled graphite, the disordered structure is maintained during heat treatment, while argon-milled graphite is partially crystallized.

A Study of the Irradiation Environment Effects on the Electrical Properties of Ethylene Propylene Rubber (방사선 조사 환경에 의한 에칠렌 프로필렌 고무의 전기 특성에 관한 연구)

  • 이성일
    • Journal of the Korea Safety Management & Science
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    • v.2 no.2
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    • pp.187-200
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    • 2000
  • The charge and discharge current in EPR(Ethylene Propylene Rubber), which were irradiated with the radiant capacity of 0~600 [kgy/h], have been measured in order to investigate the influence of the atmosphere (oxygen, air and vacuum) on electrical properties. It has been shown that the charge and discharge current increase as the amount of radiant capacity increases in air and vacuum atmosphere. This electrical property degradation can be speculated due to that the C=O radicals or impurities, which comes from during shaping process, may act as dipoles. On the other hand, the charge and discharge current are shown to be higher in the amount of 1[kgy/h] than these in 10[kgy/h] in air atmosphere, because the charge and discharge current can be increased as the exposure time is extended with slower rate. Under the same amount of irradiation, the charge and discharge current in oxygen atmosphere are shown to be higher than those in vacuum. This is possibly due to that the main chain can be broken by oxidation when it is exposed to the $\gamma$ -rays.

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Electrical Conductivity, Flammable Gas Response and Humidity Effect of Pporous ZnO (다공질 ZnO의 전기적 특성, 환원성 가스 감응 특성 및 습도의 영향)

  • 윤당혁;최경만
    • Journal of the Korean Ceramic Society
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    • v.32 no.11
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    • pp.1283-1291
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    • 1995
  • The electrical conductivity, flammable gas response and their humidity effect of porous ZnO, added with 5wt% corn starch as the fugitive phase, were examined. Porous ZnO showed different conductivity curves during increasing and decreasing temperature, and its electrical conductivity decreased rapidly by desorption of OH- between 20$0^{\circ}C$ and 35$0^{\circ}C$ when the temperature increased in dry air. The CO gas sensitivity of starchadded ZnO samples was higher than that of ZnO without starch addition. The sensitivity of porous, starchadded ZnO to 200ppm CO gas was much less in humid atmosphere than in dry atmosphere since water vapor increased the conductivity of porous ZnO in air, but decreased the conductivity in CO. Maximum sensitivity to 200 ppm CO gas balanced by air was about 100 in dry atmosphere and about 15 in RH 23% atmosphere.

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GENERATION OF p-DINITROBENZENE ATMOSPHERE AND METHEMOGLOBIN FORMATION IN RATS

  • Kim, Young-Chul
    • Toxicological Research
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    • v.5 no.2
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    • pp.97-104
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    • 1989
  • A new exposure system was developed to generate p-dinitrobenzene (p-DNB) containing atmosphere. A glass column was filled with small glass beads coated with the chemical. The p-DNB containing medium was heated to a temperature beyond the boiling point of p-DNB. A stream of air flow was forced to pass through the column and let it mixed with fresh air before introducing into an inhalation chamber. The concentration of p-DNB in the chamber air was measured by direct assaying the air directly and by sampling the chemical using a microfilter installed in the chamber.

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