• 제목/요약/키워드: Gaseous

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A Review on Total Gaseous Mercury Concentration Levels in the East Asia

  • Kim, Ki-Hyun
    • 한국지구과학회지
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    • 제24권1호
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    • pp.1-6
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    • 2003
  • In this work, the present concentration levels of total gaseous mercury (TGM) are compared among three East Asian countries, Korea, China, and Japan. Comparison of Hg distribution patterns was made by selecting representative figures for each type of land use among those three countries. The results of the analysis indicate that Hg concentrations within a country can fall into a wide range due probably to the diversity of source processes. It is seen that the urban areas of China and Japan generally exhibit large spatial variability with notably high Hg levels (above 10 ng m$^{-3}$), compared to their Korean counterparts. Although the presence of high Hg levels in Chinese locations can be accounted for by the major man-made source processes (e.g., the use of coal), the causes of unexpectedly high Hg data in Japanese sites appear to be rather complicated. The Hg concentration levels in relatively remote locations however show much reduced values, above 3 ng m$^{-3}$, which is still higher than the typical background concentrations of 1 to 2 ng m$^{-3}$ in Europe or America. Considering that the presence of unusually high Hg levels in urban areas of Asia is the consequence of man-made activities, the prevalence of excessively high Hg values in certain regions of the Asian continent needs further research to accurately assess the fundamental picture of Hg geochemistry in the East Asia.

소나무 종별 대기 중 PCBs의 침착특성 (Deposition Characteristics of Atmospheric PCBs by Type of Leaves in Pine Needles)

  • 신은상;여현구;조기철;천만영
    • 한국환경보건학회지
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    • 제32권1호
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    • pp.46-52
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    • 2006
  • Results for the concentrations of total polychlorinated biphenyls (total PCBs) and the PCB profile with different types of leaves from four coniferous trees (pine needles) at the same sampling site are presented. Concentrations of total PCBs detected in pine needles were very similar among them regardless of their different types of leaves, which means a possibility for bio-monitoring regional contamination of PCBs. Correlation coefficients(r) of PCB congeners between pine needles were very significant (r>0.97, p<0.001), which showed that PCB congener's patterns of each pine needle were similar. Profiles of PCBs detected in pine needles showed correlation with gaseous phase PCBs in air, otherwise not with particle phase PCBs in air. Therefore, it was estimated that dry gaseous deposition was a principal pathway of PCBs accumulation in pine needles. In addition, although we analyse a different types of leaves in pine needles at the same region, they can be used to identify regional contamination patterns of PCBs for larger regions.

Test of a Multilayer Dose-Verification Gaseous Detector with Raster-Scan-Mode Proton Beams

  • Lee, Kyong Sei;Ahn, Sung Hwan;Han, Youngyih;Hong, Byungsik;Kim, Sang Yeol;Park, Sung Keun
    • IEIE Transactions on Smart Processing and Computing
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    • 제4권5호
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    • pp.297-304
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    • 2015
  • A multilayer gaseous detector has been developed for fast dose-verification measurements of raster-scan-mode therapeutic beams in particle therapy. The detector, which was constructed with eight thin parallel-plate ionization chambers (PPICs) and polymethyl methacrylate (PMMA) absorber plates, is closely tissue-equivalent in a beam's eye view. The gas-electron signals, collected on the strips and pad arrays of each PPIC, were amplified and processed with a continuous charge.integration mode. The detector was tested with 190-MeV raster-scan-mode beams that were provided by the Proton Therapy Facility at Samsung Medical Center, Seoul, South Korea. The detector responses of the PPICs for a 190-MeV raster-scan-mode proton beam agreed well with the dose data, measured using a 2D ionization chamber array (Octavius model, PTW). Furthermore, in this study it was confirmed that the detector simultaneously tracked the doses induced at the PPICs by the fast-oscillating beam, with a scanning speed of 2 m s-1. Thus, it is anticipated that the present detector, composed of thin PPICs and operating in charge.integration mode, will allow medical scientists to perform reliable fast dose-verification measurements for typical dynamic mode therapeutic beams.

강한 음향장에 구속된 고압 액적의 연소 (Unsteady Vaporization of Burning Droplet at High Pressure Environments With Linear Acoustic Mode)

  • 김성엽;신현호;윤웅섭
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 추계학술대회
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    • pp.1122-1127
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    • 2004
  • an isolated droplet combustion exposed to pressure perturbations in stagnant gaseous environment is numerically conducted. Governing equations are solved for flow parameters at gas and liquid phases separately and thermodynamic parameters at the interfacial boundary are matched for problem closure. For high-pressure effects, vapor-liquid interfacial thermodynamics is rigorously treated. A series of parametric calculations in terms of mean pressure level and wave frequencies are carried out employing a n-pentane droplet in stagnant gaseous air. Results show that the operating pressure and driving frequency have an important role in determining the amplitude and phase lag of a combustion response. Mass evaporation rate responding to pressure waves is amplified with increase in pressure due to substantial reduction in latent heat of vaporization. Phase difference between pressure and evaporation rate decreases due to the reduced thermal inertia at high pressure. In addition to this, augmentation of perturbation frequency also enhances amplification of vaporization rate because the time period for the pressure oscillation is much smaller than the liquid thermal inertia time. The phase of evaporation rate shifts backward due to the elevated thermal inertia at high acoustic frequency.

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초음파 발생 미스트를 이용한 TiO2 광촉매 시스템에서의 가스상 톨루엔 제거 (Removal of Gaseous Toluene Using a TiO2 Photocatalytic System with Mist Generated by Ultrasonic Atomization)

  • 최민석;한세현;장성찬;정용원
    • 한국대기환경학회지
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    • 제25권3호
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    • pp.211-218
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    • 2009
  • Feasibility study of using $Ti0_2$ mist generated by ultrasonic atomization for photocatalytic degradation of gaseous toluene was attempted in this study. For this, the photocatalytic reactor consisting of mist generator and photo-reactor was designed. Most of experimental results showed that steady state reached about 30 minutes after the start of experiments. The effects of $Ti0_2$ concentration, toluene concentration, and UV wavelength on toluene removal ratio were investigated. It was found that the highest removal efficiency was obtained when $Ti0_2$ concentration was 0.6 g/L in slurry. At this condition, it was found that the toluene removal efficiency increased as toluene concentration in feed decreased. In order to investigate the effect of UV wavelength, experiments were carried out using three UV lamps with different UV wavelength. The results showed that the highest removal efficiency was achieved when the lamp with the shortest wavelength were employed.

Application of Oxide Nanofibers Synthesized by Electrospinning to Chemical Sensors

  • Choi, Sun-Woo;Akash, Katoch;Jung, Sung-Hyun;Kim, Sang-Sub
    • 한국재료학회:학술대회논문집
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    • 한국재료학회 2011년도 추계학술발표대회
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    • pp.3.2-3.2
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    • 2011
  • Nanofibers, one of various one-dimensional nanomaterials such as nanorods, nanowires and nanotubes have been successfully synthesized by many groups in recent years and their applications to chemical sensors, catalytic filters and biomedicine, etc. are extensively tested. In particular, there is a possibility that chemical sensors based on oxide nanofibers can overcome the shortcomings of chemical sensors based on single nanowires. In order to prepare oxide nanofibers, the electrospinning method is most widely used. In this work, we synthesized various oxide nanofibers including ZnO, SnO2 and CuO by employing an electrospinning method and various shapes of nanofibers including core-shell nanofibers and hollow nanofibers as well. The response properties of the various nanofibers to oxidizing and reducing gaseous species have been investigated systematically. The normal oxide nanofibers showed high sensitivity and quite fast response time to many gaseous species. Furthermore, derivatives of normal nanofibers including hollow nanofibers, core-shell nanofibers and heterostructured nanofibers display much superior sensing properties. These results hold promise for the practical application of oxide nanofibers to chemical sensors. In addition, the sensing mechanisms operated in the nanofibers will be discussed in detail.

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서울시 주요 터널내 기체상 오염물질 농도 측정 (Measurements of Gaseous Pollutants in Major Tunnels in Seoul)

  • 김영성;경남호;손재익;문길주;김용표;백남준;김태오
    • 한국대기환경학회지
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    • 제9권4호
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    • pp.320-328
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    • 1993
  • Gaseous pollutants in Namsan Nos. 1, 2, and 3 tunnels and Pukak tunnel were measured along the road by an air-monitoring van from the evening of February 9 to the morning of February 12 in 1993. Average concentrations of pollutants in Namsan tunnels were 9.2-13.5 ppm CO and 0.037-0.047 ppm SO$_{2}$. Average concentrations of SO$_{2}$ in Pukak tunnel was 0.79 ppm, higher than those in Namsan tunnels, due to the traffic of heavy-duty buses and trucks. The pollutant concentrations in Namsan tunnesl could be explained by emission of passenger cars using unleaded gasolin and LPG taxies. Average concentration of NO$_{x}$ in Namsan tunnels was at least 1.1 ppm, estimated from the emission factor of pasenger cars using unleaded gasoline. Pollutant concentrations in Namsan No. 3 tunnel were higher at the exit because of the piston action of air mass in the tunnel provided by the traffic. Fans installed at Namsan and Pukak tunnes could be useful, but their flushing action of ambient air in the tunnel was not clearly observed.d.

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환경 대기중에서 Nitrate의 생성에 관한 연구(II) (A Study on the Formation of Nitrate in Atmosphere(II))

  • 천만영;이영재;김희강
    • 한국대기환경학회지
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    • 제9권3호
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    • pp.216-221
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    • 1993
  • This study was carried out to determine the concentration of gaseous nitrate$(HNO_3)$ particulate nitrate$(NO_3^-)$ and conversion rate of NOx to nitrate in atmosphere in Seoul from Oct 1991 to July 1992. The average concentration of gaseous nitrate in daytime(09:00 - 17:00) was 9.93, 3.37, 7.40 and 10.40$\mug/m^3$ and, in highttime was 6.21, 7.31, 4.79 and 3.86$\mug/m^3$ respectively. The concentratin of $HNO_3$ was greater in summer and daytime than winter and nighttime. But the concentration of $NO_3^-$ was greater in winter and nighttime than in summer and daytime. The average conversion rate of NOx to $HNO_3$(Fn) indaytime was 13.18, 3.78, 9.13 and 23.13% and, in nighttime was 3.06, 1.37, 1.70 and 8.72% during fall, winter, spring and summer respectively. But the average conversion rate of NOx to $NO_3^-$(Fn') in daytime was 5.79, 5.77, 2.63 and 3.90% and in nighttime was 5.95, 6.51, 3.25 and 4.84% respectively. The average conversion rate of NOx to total nitrate $(HNO_3 + NO_3^-)$(Fn') was 12.72, 7.81, 7.82 and 18.40% respectively. The average conversion rate of NOx to $HNO_3$(Fn) was greater than $NO_3^-$(Fn') about 1.6 times.

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에틸렌 난류확산 화염에 관한 실험적 연구 (Experimental Study on Turbulent Ethylene Diffusion Flame)

  • 양고수;김용문
    • 한국연소학회지
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    • 제4권2호
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    • pp.23-33
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    • 1999
  • A turbulent non-premixed ethylene flame, which was set up in a vertical wind tunnel, was examined to understand the effect of turbulent mixing on formations of soot and gaseous species in the flames. Temperature and velocity profiles were measured using uncoated thermocouples and LDV system. Gaseous samples were withdrawn by using a water cooled stainless iso-kinetic gas sampling probe. The samples for inorganic compounds and light hydrocarbons were collected with sampling bottles and were analyzed by a gas chromatography. The samples for aromatic hydrocarbons were collected on a sorbent tube and were analyzed on a GC/MS system. Some of main results were followed. CO and $CO_2$ were measured relatively in early part of flame and the concentration of CO was greater than that of $CO_2$ all over the early flame region due to the scavenging of the oxidizing species OH by soot particles. Aromatic hydrocarbons were measured at x/D=122 along the radial direction and main important species were benzene, xylene, toluene, styrene, indene, naphthalene. The peak points of these compounds occurred at r/D=0.8 apart from the center of flame, around in which the concentration of $C_2H_2$ decayed relatively rapidly from the maximum value.

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Atmospheric Concentrations of Semivolatile Bifunctional Carbonyl Compounds and the Contribution from Motor Vehicles

  • Ortiz, Ricardo;Shimada, Satoru;Sekiguchi, Kazuhiko;Wang, Qinyue;Sakamoto, Kazuhiko
    • Asian Journal of Atmospheric Environment
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    • 제7권3호
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    • pp.152-160
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    • 2013
  • Seven potentially harmful bifunctional carbonyls were measured in particulate and gaseous phases at a roadside site and a suburban site in an area about 30 km north-northwest from Tokyo metropolitan area in the Kanto region in Japan. For the first time, these compounds were measured in both phases with a time resolution of 2 h. We found that wind direction is an important parameter that affects the collection of these compounds near the source, and it can cover the effects of other important variables. Our results confirmed that motor vehicles and especially diesel fuelled vehicles are important sources of these compounds. Photochemical generation is also an important source of these compounds in the gaseous phase. Transportation from the urban area is also important, particularly in the aerosol phase.