• 제목/요약/키워드: Cloud particle characteristics

검색결과 25건 처리시간 0.024초

형상 계수를 이용한 알루미나 입자구름의 열복사 예측 기법 연구 (A Study of Thermal Radiation from The Alumina Particle Cloud in The Plume Using View Factor Method)

  • 고주용;김인선
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2007년도 춘계학술대회B
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    • pp.2044-2049
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    • 2007
  • In order to predict the thermal radiation induced from alumina particle cloud in the plume of solid propellant motor, view factor method is applied to space shuttle SRB and the result is compared with that of monte carlo method. For this purpose, radiative characteristics, such as particle cloud temperature distribution, effective emissivity or emissive power of particle cloud are studied. In the case of effective emissivity, inverse wavelength method is applied and plume reduction characteristic length is used for emissive power distribution. As a result, thermal radiation using view factor method gives more conservative results than that using monte carlo method. So it can be used for preliminary design of thermal protection system.

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Measurement of Insoluble Mineral Particles in a Saturated Atmosphere

  • Ma, Chang-Jin;Choi, Sung-Boo
    • Journal of Korean Society for Atmospheric Environment
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    • 제24권E1호
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    • pp.44-53
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    • 2008
  • This study was undertaken to measure the properties of individual mineral particles in an artificially saturated atmosphere at a vertical extinct mine with 430 m height. By synchrotron radiation X-ray fluorescence (SR-XRF) microprobe analysis, it was possible to determine the elemental composition of residual insoluble particles on individual cloud droplet replicas formed on the Collodion film. The XRF visualized elemental maps enabled us not only to presume the chemical mixing state of particles retained in cloud droplet, but also to estimate their source. Details about the individual mineral particles captured by artificial cloud droplets should be helpful to understand about the removal characteristics of dust particles such as interaction with clouds. Nearly all individual particles captured in cloud droplets are strongly enriched in Fe. Mass of Fe is ranged between 41 fg and 360 fg with average 112 fg. There is a good agreement between single particle analysis by SR-XRF and bulk particle analysis by PIXE.

Cloud Generation Using a Huge Vertical Mine

  • Ma, Chang-Jin
    • Journal of Korean Society for Atmospheric Environment
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    • 제22권E2호
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    • pp.78-88
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    • 2006
  • In order to study the characteristics of cloud, a real-scale experiment for cloud generation was carried out using an extinct vertical mine (430 m height) located in the northeastern Honshu, Japan. The dry particles generated from the three-step concentrations of NaCl solutions were used for cloud generation. The number size distributions of initial dry particles and cloud droplets were monitored by Scanning Mobility Particle Sizer (SMPS) and Forward Scattering Spectrometer Probe (FSSP) at bottom and upper sites of pit, respectively. The polymeric water absorbent film (PWAF) method was employed to measure liquid water content ($W_L$) as a function of droplet size. Moreover the chemical properties of individual droplet replicas were determined by micro-PIXE. The CCN number concentration shows the lognormal form in dependence of the particle size, while the number size distributions of droplets are bimodal showing the peaks around $9{\mu}m$ and $20{\mu}m$ for every case. In comparison to background mineral particles, right shifting of size distribution line for NaCl particles was occurred. When NaCl solutions with three-step different concentrations were neulized, $W_L$ shows the strong droplet size dependence. It varied from $10.0mg\;m^{-3}$ up to $13.6mg\;m^{-3}$ with average $11.6mg\;m^{-3}$. A good relationship between $W_L$ and cloud droplet number concentration was obtained. Both chemical inhomogeneities (mixed components with mineral and C1) and homogeneities (only mineral components or C1) in individual droplet replicas were obviously observed from micro-PIXE elemental images.

미분탄의 집단점화 해석 (Analysis of Group Ignition of Pulverized Coal Particles)

  • 서경근;김호영
    • 한국연소학회지
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    • 제4권2호
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    • pp.1-10
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    • 1999
  • Pulverized coal is widely used as the source of electrical power generation and industrial processes. Numerical analysis on the transient ignition process of the cloud of pulverized coal particles in various cases is carried out. Particle radius, initial particle temperature, number density are chosen as major parameters that influence the characteristics of ignition and combustion. The result can be summarized as follow. The ignition occurs at the position that is closed to the surface of the cloud. Maximum temperature and velocity appear at ignition point, and the concentrations of gaseous fuel and oxidizer decrease rapidly near the ignition point. The chemical reaction takes place in wider zone as number density and particle radius decrease. The ignition delay is shortest when particle radius is about $50\;{\mu}m$, and tends to be shorter as number density and initial ambient temperature increase.

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1994년 6월 서울지역 시정장애의 측정 및 분석 (Measurement and Analysis of Visibility lmpairment during June, 1994 in Seoul)

  • 백남준;이종훈;김용표;문길주
    • 한국대기환경학회지
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    • 제12권4호
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    • pp.407-419
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    • 1996
  • Characteristics of visual air quality in Seoul have been investigated between June 13 and 21, 1994. Optical properties (extinction coefficient and particle scattering coefficient), meteorological parameters (relative humidity, temperature, wind speed, wind direction, and cloud cover), particle characteristics (mass size distribution, components) were measured and analyzed. During measurement periods, northwest wind with less than 2m/sec of wind speed deteriorates visibility. Effects of relative humidity are though to be not a direct factor which influence to visibility through the size change due to hygroscopic species in aerosol. During the smoggy period both the aerosol mass concentration and fine particle fraction of the size distribution are increased compared to the clear period. Sulfate, organic carbon, and elemental carbon in aerosol are the major species in determining the occurrence and severity of a smog in Seoul.

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구름물리 관측시스템 및 산출물 검정 (Cloud Physics Observation System (CPOS) and Validation of Its Products)

  • 장기호;오성남;정기덕;양하영;이명주;정진임;조요한;김효경;박균명;염성수;차주완
    • 대기
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    • 제17권1호
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    • pp.101-108
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    • 2007
  • To observe and analyze the cloud and fog characteristics, the METeorological Research Institute (METRI) has established the Cloud Physics Observation System (CPOS) by implementing the cloud observation instruments: Forward Scattering Spectrometer Probe (FSSP), PARticle SIze and VELocity (PARSIVEL), Microwave Radiometer (MWR), Micro Rain Radar (MRR), and 3D-AWS at the Daegwallyeong Enhanced Mountain Weather Observation Center. The cloud-related products of CPOS and the validation status for the size distribution of FSSP, the precipitable water of MWR, and the rainfall rate of MRR and PARSIVEL are described.

부유 및 퇴적의 분체 조건이 화재폭발 특성에 미치는 영향 (Effect of Powder Condition on the Fire and Explosion Characteristics of Suspended and Deposited Dusts)

  • 한우섭;서동현;최이락;임진호
    • Korean Chemical Engineering Research
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    • 제60권2호
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    • pp.229-236
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    • 2022
  • 동일 분체특성의 분진이 평균입경, 농도, 분진조건(부유 또는 퇴적) 변화에 따른 화재폭발 위험성을 조사하였다. 이를 위해 20L분진폭발시험장치, 열중량분석장치, 연소속도시험장치(UN시험법)를 사용하였다. 4종 분진(Sugar, Mg, Al, Zr)의 입경이 서로 다른 8개 분진 시료에 대하여 부유 분진의 폭발특성과 화염전파속도(FPV), 그리고 퇴적분진의 화염확산속도(FSV)를 조사하였다. 부유 분진 조건에서 Mg 및 Al 분진은 입경이 감소하면 폭발 위험성이 증가하였지만, Sugar는 입경 변화에 따른 폭발 위험성의 영향이 거의 나타나지 않았다. 부유 분진의 화염전파속도(FPV)는 마이크로 범위에서의 입경 변화보다 마이크로에서 나노로 입경이 감소하면 크게 증가하였다. 퇴적층의 화염확산속도(FSV)는 수평면(기울기 0°)보다 경사면(기울기 30°)에서 증가하는 경향을 나타냈으며, 경사면(기울기 30°) 퇴적층 조건에서는 상방 전파가 하방 전파보다 높게 나타났다.

대관령 구름물리관측시스템 산출물 평가 및 FSSP를 이용한 시정환산 시험연구 (Intercomparison of Daegwallyeong Cloud Physics Observation System (CPOS) Products and the Visibility Calculation by the FSSP Size Distribution during 2006-2008)

  • 양하영;정진임;장기호;차주완;정재원;김유철;이명주;배진영;강선영;김금란;최영진;최치영
    • 대한원격탐사학회지
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    • 제26권2호
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    • pp.65-73
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    • 2010
  • 구름과 강수특성을 분석하기 위해 대관령에 구름물리관측시스템(Cloud physics Observation System, 이하 CPOS)을 2003년부터 운영해 오고 있다. 주요 관측 기기는 다음과 같다: FSSP (Forward Scattering Spectrometer Probe), OPC (Optical Particle Counter), VS (Visibility Sensor), PARSIVEL disdrometer, MWR (Microwave Radiometer), MRR (Micro Rain Radar). 앞의 4개 장비는 지상구름 (안개)과 강수 특성을, 뒤의 2개 장비는 연직구름의 특성을 실시간으로 관측하고 있다. CPOS 산출물을 검증하기 위해 FSSP는 흡습성 물질 시딩 실험 중 OPC와, MWR의 가강수량은 라디오존데와, PARSIVEL과 MRR은 우량계와 비교 연구가 수행되었다. 그 결과를 보면 대부분이 0.7이상의 좋은 상관도를 보인다. 이와 같이 신뢰도를 확보한 CPOS 관측 자료는 구름과 에어로솔의 간접효과나 기상조절 실험에 유용한 자료로 활용될 수 있을 것이다. FSSP의 입자 크기 분포를 시정값으로 환산해 보았으며 FSSP 환산 시정값은 visibility sensors (SVS)와 PWD22 (Present Weather Detect 22)의 시정계 값에 비해 1.7~1.9배 과도한 경향을 보였다. 이는 FSSP에 의해 관측되는 입자 크기($2{\sim}47\;{\mu}m$)의 한계 때문으로 사료된다. 향후 다른 입자크기분포를 측정할 수 있는 장비를 도입하여 추가 분석을 추진할 계획이다.

대기 안정도에 따른 인공증설 항공실험 효과 분석: IJCO-WCE 2019 캠페인 사례 연구 (Analysis of the Effects of Airborne Snowfall Enhancement Experiments Based on Atmospheric Stability: A Case Study of the IJCO-WCE 2019 Campaign)

  • 고아름;김부요;정운선;김지형;구정모;장기호;차주완;이철규;이용희
    • 대기
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    • 제34권4호
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    • pp.445-462
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    • 2024
  • This study analyzes and compares the results of airborne snowfall enhancement experiments conducted on November 25 and 28, 2019, as part of the International Joint Cloud Observation and Weather Control Experiment (IJCO-WCE) 2019 campaign. The objective was to assess the effects of experimental interventions on cloud precipitation patterns. To address the challenges in verifying artificial snowfall enhancement, this study proposes an innovative approach, utilizing a post-experiment zigzag flight path for in-situ observations. This approach allowed for detailed comparisons between affected and unaffected cloud regions. Precipitation was observed in the target area on the leeward side on November 25, whereas no precipitation was recorded during the November 28 experiment. We concluded that airborne snowfall enhancement is more effective when the lower atmosphere is unstable at the rear of a trough, as confirmed by changes in the distribution of precipitation particles in the clouds and on the ground. Two identical flight experiments were conducted using the KMA/NIMS atmospheric research aircraft, allowing detailed observations. Data collected from onboard cloud observation instruments and six ground stations facilitated detailed analyses of changes in the concentration and size distribution of cloud particles (e.g., supercooled droplets, ice crystals, and snow particles). The method of comparing particle sizes between clouds affected and unaffected by the experiments is used to verify the effectiveness of artificial snowfall enhancement techniques. This methodology could be widely adopted in future studies to improve our understanding of weather modification strategies.

기능성 마이크로스피어의 개발 (I) - 열유도 상분리에 의한 Poly(ethylene-co-vinyl acetate) 마이크로스피어의 제조와 특성 - (Development of functional microsphere (I) - Formation and characteristics of poly(ethylene-co-vinyl acetate) microspheres via thermally induced phase separation -)

  • 이신희;김효정;박수민
    • 한국염색가공학회지
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    • 제15권4호
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    • pp.57-64
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    • 2003
  • Poly(ethylene-co-vinyl acetate)(EVA) microspheres were prepared by a thermally induced phase separation. The microsphere formation occurred by the nucleation and growth mechanism in the metastable region. The diluent used was toluene. The microsphere formation and growth was followed by the cloud point of the optical microscope measurement. The microsphere size distribution, which was obtained by SEM observation and particle size analyzer, became broader when the polymer concentration was higher, the content of vinyl acetate in EVA copolymer was higher, and the cooling rate of EVA copolymer solution was lower.