• 제목/요약/키워드: Ambient gas

검색결과 735건 처리시간 0.023초

신너사용 작업장의 유기용제 노출 및 $TiO_2$ 광촉매를 이용한 BTX처리에 관한 연구 (Organic Solvent Exposure of Thinner-Using Occupation and Its Treatment by Means of $TiO_2$ Photocatalyst)

  • 양원호;김현용;손부순;박종안
    • 환경위생공학
    • /
    • 제17권2호
    • /
    • pp.26-33
    • /
    • 2002
  • Ultimate objective of industrial hygiene is the prevention of health impairment that may result from exposure to chemicals at workplace. Workers in solvent thinner-using occupation environment may be highly exposed to VOCs (volatile organic compounds) because solvent thinner has been used extensively such as painting, spraying, degreasing, coating and so on in Korea. The purpose of this study was to recognize, evaluate, and propose the control methods of VOCs from solvent thinner-using workplace. Five target volatile organic compounds (benzene, toluene, ethylbenzene, o-xylene, and m-xylene) were monitored in H company of Shiwa Industrial Complex and analyzed in perosnal, occupational indoor and outdoor during working hours simultaneously. Engineering control such as local ventilation should be made in considering the long-term exposure, though measured VOCs concentration did not exceed the workplace exposure standards. In addition, air cleaning device should be installed in local ventilation because Shiwa Industrial Complex has had the serious ambient air pollution. Currently, environmental purification using $TiO_2$ photocatalyst have attracted a great deal of attention with increasing number of recent environmental problems. In this study, $TiO_2$ sol coated on the ceramic bead was prepared by sol-gel method and the photodegradation of target compounds was investigated in gas phase by the exposure to UV-A lamp(365nm) in a batch system.

비정상 증발디젤분무의 측정과 그 응용해석 (Advanced Analysis and Measurement of the Unsteady Evaporative Diesel Spray)

  • 염정국;박종상;김시범;정성식;하종률
    • 대한기계학회논문집B
    • /
    • 제32권7호
    • /
    • pp.529-535
    • /
    • 2008
  • The characteristics of combustion process in an internal combustion engine are affected by the mixing process between injected fuel and ambient gas. Therefore, it is necessary to understand the mixture formation process of diesel spray. In this study, the spray structure was visualized by the exciplex fluorescence method, which can provide the simultaneous 2-D images of vapor and liquid phase in inner spray. For accurate investigation, the liquid-phase images were recorded with a 35mm still camera and CCD camera. Consequentially, it could be confirmed that the high-concentration vapor phase is formed in the region of spray tip and the edge of the liquid phase where droplets exist in the evaporating diesel spray, and the formed vapor is spread by diffusion. Also, the distribution of vapor is determined by the motion of droplets that exist in the edge of the liquid phase and the spray-tip region.

CVD Graphene Synthesis on Copper Foils and Doping Effect by Nitric Acid

  • Oh, Teresa
    • Transactions on Electrical and Electronic Materials
    • /
    • 제14권5호
    • /
    • pp.246-249
    • /
    • 2013
  • Graphene was obtained on Cu foil by thermal decomposition method. A gas mixture of $H_2$ and $CH_4$ and an ambient annealing temperature of $1,000^{\circ}C$ were used during the deposition for 30 Min., and for the transfer onto $SiO_2/Si$ and Si substrates. The physical properties of graphene were investigated with regard to the effect ofnitrogen atom doping and the various substrates used. The G/2D ratio decreased when the graphene became monolayer graphene. The graphene grown on $SiO_2/Si$ substrate showed a low intensity of the G/2D ratio, because the polarity of the $SiO_2$ layer improved the quality of graphene. The intensity of the G/2D ratio of graphene doped with nitrogen atoms increased with the doping time. The quality of graphene depended on the concentration of the nitrogen doping and chemical properties of substrates. High-quality monolayer graphene was obtained with a low G/2D ratio. The increase in the intensity of the G/2D ratios corresponded to a blue shift in the 2D peaks.

$N_2O$ 가스에서 열산화한 $SiO_2$ 막의 특성 (Properties of $SiO_2$ film oxidized in $N_2O$ gas)

  • 김동석;최현식;서용진;김태형;김창일;장의구
    • 대한전기학회:학술대회논문집
    • /
    • 대한전기학회 1992년도 하계학술대회 논문집 B
    • /
    • pp.829-831
    • /
    • 1992
  • Ultrathin metal-oxide-semiconductor(MOS) gate dielectrics have been fabricated by conventional thermal oxidation in $N_2O$ ambient. Compared to oxides grown in $O_2$, $N_2O$ oxides exhibit significantly low flatband voltage and small shift in flatband voltage. $N_2O$ oxidation induces a slight decrease in mobile ionic charge density($N_m$), fixed charge density($N_f$) and surface state charge density($N_{ss}$). This study establishes that $N_2O$ oxides may have a great impact on future MOS ULSI technology in which ultrathin gate dielectrics are required.

  • PDF

Visualization of Diesel and GTL Spray Combustion and Soot Formation in a Rapid Charging Combustion Vessel with Shadowgraph Method

  • Kim, Ki-Seong;Azimov, Ulugbek;Lee, Yong-Ho
    • Journal of Advanced Marine Engineering and Technology
    • /
    • 제32권7호
    • /
    • pp.1019-1029
    • /
    • 2008
  • In this study, visual investigation of sprays and flames has been performed and soot formation in Diesel and GTL fuels has been compared in a specially designed Rapid Charging Combustion Vessel (RCCV) under various ambient gas $O_2$ concentrations and two injection pressures. It has been concluded that soot in the mixing-controlled combustion of Diesel and GTL fuels has similar tendency to be formed in the leading portion of the jet boundaries. Auto-ignition delay for GTL fuel is shorter than that for diesel fuel. The temporal and special variation of soot concentration in the diesel flame jets at various $O_2$ concentrations was correlated with the heat release rate. Soot concentration appears in the regions when diffusion combustion starts, and its concentration reaches maximum at the peak of heat release curve and then decreases due to oxidation. Visualization by shadowgraph method showed that soot decreases with lower $O_2$ concentration, and higher injection pressure.

좁은 채널 내의 대향분류 메탄-공기 비예혼합 화염의 거동 특성 (Behavioral Characteristics of the Non-Premixed Methane-Air Flame Oppositely Injected in a Narrow Channel)

  • 윤영민;이민정;조상문;김남일
    • 대한기계학회논문집B
    • /
    • 제33권4호
    • /
    • pp.264-271
    • /
    • 2009
  • Characteristics of a counter flowing diffusion flame, which is formulated by an oppositely-injected methane-jet flow in a narrow channel of a uniform air flow. The location of the flame fronts and the flame lengths were compared by changing the flow rates of fuel. To distinguish the effects of the narrow channel on the diffusion flame, a numerical simulation for an ideal two-dimensional flame was conducted. Overall trends of the flame behavior were similar in both numerical and experimental results. With the increase of the ratio of jet velocity to air velocity flame front moved farther upstream. It is thought that the flow re-direction in the channel suppresses fuel momentum more significantly due to the higher temperature and increased viscosity of burned gas. Actual flames in a narrow channel suffer heat loss to the ambient and it has finite length of diffusion flame in contrast to the numerical results of infinite flame length. Thus a convective heat loss was additionally employed in numerical simulation and closer results were obtained. These results can be used as basic data in development of a small combustor of a nonpremixed flame.

교외지역에서 대기 중 Hexachlorocyclohexane의 농도분포 및 온도 의존성 (The Concentration Distribution and Temperature Dependence of Hexachlorocyclohexane in Rural Atmosphere)

  • 최민규;여현구;김태욱;천만영;선우영
    • 한국대기환경학회지
    • /
    • 제18권3호
    • /
    • pp.183-192
    • /
    • 2002
  • Concentrations of $\alpha$- and ${\gamma}$-hexachlorocyclohexane (HCH) were measured in ambient air samples at a two week intervals between July 1999 and February 2000 at Ansung, Kyonggi province. Their concentration levels averaged at 78 ($\alpha$-HCH) and 18 pg/m$^3$(${\gamma}$-HCH). Although the use of HCHs was ceased in South Korea since 1979, their residues are still present in air even after nearly 20 years. Given the composition of the two main HCH pesticide formulation (technical HCH antral lindane), the $\alpha$/${\gamma}$-HCH ratio in air is a useful indicator on the regional scale. The moderately low $\alpha$/${\gamma}$-HCH ration in this study indicates previous usage of both technical HCH and lindane. The relationship of temperature with gas-phase partial pressures was also examined using the Clausius-Clapeyron equation. Slopes generated by linear regression analysis between partial pressure (In P) and 1/T were considerably steep thor HCHs. It is thus suggested that their concentrations are controlled by re-volatilization processes from surfaces in the local surroundings of the sampling site.

엔진 및 차량냉각계의 냉각수유량 측정실험 및 계산방법에 관한 연구 (A Study of the Experiment and the Calculation Method on the Coolant Flow Rate of Engine and Vehicle Cooling System)

  • 오창석;유택용;이은현;최재권
    • 한국자동차공학회논문집
    • /
    • 제7권6호
    • /
    • pp.1-7
    • /
    • 1999
  • In this study, the prediction method of coolant flow rates has been developed and applied to an engine and vehicle cooling system. The flow rate passing through each component of the system is very important parameter to evaluate the heat transfer process form the combustion gas to the coolant and the heat rejection process form the radiator /heater to the ambient air. However, the present study reveals that the measurement using the flowmeter fails to give practical flow rates due to its additive resistance. In contrast, the present method which uses the parallel and serial relationship of flow resistance proved to be a good tool to predict the real flow rates. It can be also used to design the cooling system in the incipient stage of engine/vehicle development . The procedure was coded to the computer program so as to use it flexibly and, in the future, to expand it into an independent design tool of the whole cooling system including the heat release and rejection.

  • PDF

구상 페놀수지 분말과 푸르프릴 알코올로부터 주형성형에 의한 매크로 다공성 카본 폼의 제조 (Fabrication of Macro-porous Carbon Foams from Spherical Phenolic Resin Powder and Furfuryl Alcohol by Casting Molding)

  • 정현덕;김세기
    • 한국분말재료학회지
    • /
    • 제26권6호
    • /
    • pp.502-507
    • /
    • 2019
  • Macro-porous carbon foams are fabricated using cured spherical phenolic resin particles as a matrix and furfuryl alcohol as a binder through a simple casting molding. Different sizes of the phenolic resin particles from 100-450 ㎛ are used to control the pore size and structure. Ethylene glycol is additionally added as a pore-forming agent and oxalic acid is used as an initiator for polymerization of furfuryl alcohol. The polymerization is performed in two steps; at 80℃ and 200℃ in an ambient atmosphere. The carbonization of the cured body is performed under Nitrogen gas flow (0.8 L/min) at 800℃ for 1 h. Shrinkage rate and residual carbon content are measured by size and weight change after carbonization. The pore structures are observed by both electron and optical microscope and compared with the porosity results achieved by the Archimedes method. The porosity is similar regardless of the size of the phenolic resin particles. On the other hand, the pore size increases in proportion to the phenol resin size, which indicates that the pore structure can be controlled by changing the raw material particle size.

Optimal Conditions for the Post-Harvest Storage of Rhizoids of the Brown Seaweed Undaria pinnatifida (Phaeophyta) for Arachidonic Acid Production

  • Khan, Mohammed Nurul Absar;Kang, Ji-Young;Park, Nam-Gyu;Choi, Jae-Suk;Cho, In-Soon;Hong, Yong-Ki
    • Fisheries and Aquatic Sciences
    • /
    • 제15권2호
    • /
    • pp.163-168
    • /
    • 2012
  • The non-utilized biomass of the aquacultured seaweed Undaria pinnatifida, particularly the rhizoid, is an alternative source of arachidonic acid (AA). Of the five aquacultured kelps that were tested, U. pinnatifida yielded the highest amount of AA, which was isolated from the rhizoids. Its identity (C20:4 n-6) was confirmed from gas chromatography-mass spectrometry spectral data. The optimal conditions for post-harvest storage or pretreatment of the rhizoids in Provasoli's enriched seawater for AA extraction were determined to be pH 7.8, 2% $CO_2$-enriched air, 20 ${\mu}mol\;m^{-2}\;s^{-1}$ light, and $10^{\circ}C$. Under these conditions, the AA content after 1 day of storage was enhanced by up to 127%. In the absence of light under ambient aeration, the AA content after 1 day of storage diminished to 90%. Rhizoids collected late in the season (April and May) contained the highest amounts of AA (approximately 2.5 mg/g tissue).