• 한국대기환경학회지
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• 제20권6호
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• pp.823-832
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• 2004

Atmospheric aerosol particles collected in Seoul on four single days, each in every seasons of 2001, were characterized and classified on the basis of their chemical species using low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA). Low-Z particle EPMA technique can analyze both the size and the chemical species of individual aerosol particles of micrometer size and provide detailed information on the size distribution of each chemical species. The major chemical species observed in Seoul aerosol were aluminosilicate, silicon dioxide, calcium carbonate, organic, carbon-rich, marine originated, and ammonium sulfate particles, etc. The soil originated species, such as aluminosilicate, silicon dioxide, and calcium carbonate were the most popular in the coarse fraction, meanwhile, carbonaceous and ammonium sulfate were the dominant species found in the fine fraction. Marine originated species such as sodium nitrate was frequently encountered, up to 30% of the analyzed aerosol particles.

• Composites Research
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• 제26권4호
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• pp.218-222
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• 2013

본 연구에서는 제강 과정의 부산물로 발생하는 슬래그의 구조용 충전제로써의 사용 가능성을 검토하였다. 고분자 기지 슬래그 복합재료를 제작하여 슬래그 입자의 크기(8~12 ${\mu}m$ and 12~16 ${\mu}m$), 체적 비(0-30 vol.%)에 따른 슬래그 복합재료의 기계적 특성에 대한 실험적 연구를 수행하였다. 복합재료 물성에 영향을 주는 요인인 입자 분산 도와 계면상태를 고찰하기 위해 각각 시편에 대하여 조직사진을 촬영하였다. 인장 시험 결과 슬래그 복합재료의 재료강성은 슬래그 체적비가 증가할수록 증가하였고 인장 강도는 체적비가 증가할수록 감소하였다. 슬래그 복합재료의 재료강성은 슬래그 입자의 크기의 변화에 따른 뚜렷한 경향성을 띄지 않았고 인장강도는 입자의 크기가 작을수록 높은 값을 가졌다. 조직 사진 촬영 결과 슬래그 복합재료가 양호한 계면상태를 보였고, 낮은 체적 비에서는 좋은 분산 도를 나타냈지만 체적비가 높아지면 입자들의 뭉침 현상이 발생하는 것을 알 수 있었다.

• 지질공학
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• 제32권2호
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• pp.241-255
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• 2022

본 연구에서는 예천지역의 화강풍화토에 대하여 KS F 2302의 체 분석 방법과 규정에 준하여 체분석 시험을 수행하고, 물 세척시 발생되는 흙의 입자분리와 입도분포 변화의 특성을 비교 분석하였다. 광학현미경에 의한 영상이미지 분석결과 흙입자가 물에 의해 더 작은 입자로 분리됨을 확인하였고 입도분포곡선의 변화를 5가지 지표값으로 산출한 결과 세립분(0.075 mm)의 증가량은 13.67%, 임의 입경(0.25 mm)의 증가량은 19.44%, 입도분포곡선의 최대통과율폭(B_M)은 #30 체에서 21.08%가 증가되었고 입도분포곡선의 이동면적(A)은 69.28%·mm로 분석되었으며 평균입경(D₅₀)은 0.663 mm가 감소되었다. 이러한 결과는 물 세척을 수행하는 것이 세립토의 함량이 실제보다 과소평가 되는 것을 막을 수 있는 효과적인 방법임을 의미한다.

• 한국대기환경학회지
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• 제23권2호
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• pp.242-249
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• 2007

Deposition fluxes of polycyclic aromatic hydrocarbons (PAHs) were measured at the Chonbuk National University located in Jeonju between June and November 2002. Fluxes of gaseous and particulate PAHs were separately obtained using a water surface sampler (WSS) and a dry deposition plate (DDP). Most of PAHs were deposited in the gaseous form since the low molecular weight PAHs dominates in the atmosphere. The deposition velocity of particulate PAHs was higher than that of gaseous PAHs when the molecular weight was low, but substantially decreased as the fine particle fraction increased with molecular weight. The deposition velocity was generally higher at high wind speeds. However, increase in the deposition velocity in unstable atmospheric conditions was also observed for gaseous PAHs of intermediate molecular weight.

• 한국안전학회지
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• 제34권3호
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• pp.28-35
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• 2019

Dry water is a core-shell structured powder which comprises a very fine water core covered with hydrophobic silica particles. Recently, the dry water has attracted attention as a new type of fire extinguishing agents. However, characteristics of the dry water as a fire extinguishing agent have not been revealed until now. To our best knowledge, this is the first work to uncover effects of particle size of the dry water on the fire extinguishing performance. Pristine dry water, which has heterogeneous particle size distribution, was carefully separated by sieving method into three fractions which were a small size (ca. $110{\mu}m$) fraction, a medium size (ca. $220{\mu}m$) fraction and a large size (ca. $400{\mu}m$) fraction. Microscopic observations confirmed the effective separation of dry water's particle size. In extinguishing tests of wood cribs fire, the medium size dry water showed most excellent fire extinguishing performance, as compared to other dry waters having small (ca. $110{\mu}m$) and large (ca. $400{\mu}m$) particle size. The good performance of the medium size (ca. $220{\mu}m$) dry water may be attributed to the balance between cooling effect of the water core and smothering effect of the silica particles. It is also revealed that small size dry water has poor flowability than large size dry water.

• 공업화학
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• 제24권3호
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• pp.260-265
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• 2013

본 연구에서는 비타민나무 잎 추출물의 에틸아세테이트 분획 0.01, 0.03, 0.05, 0.10% 함유한 나노에멀젼을 제조하였고, 5주 동안 이들 나노에멀젼의 입자 크기, 입도분포 및 피부 투과능을 평가하였다. 나노에멀젼은 균질기(homogenizer) 처리 후 고압유화기(micro-fluidizer)를 이용하여 제조하였다. 비타민나무 잎 추출물의 에틸아세테이트 분획을 함유한 나노에멀젼은 단분산 형태를 나타내었다. 5주 동안 실험에서, 0.03% 에틸아세테이트 분획을 함유한 나노에멀젼이 가장 안정하였다. 0.03% 에틸아세테이트 분획 함유 나노에멀젼의 in vitro 피부 투과 실험을 Franz diffusion cell을 이용하여 수행하였다. Oil-in-water (O/W) 에멀젼과 비교할 때 나노에멀젼이 피부 흡수가 더 잘되는 것으로 나타났다. 이러한 결과들은 비타민나무 잎 추출물을 함유한 나노에멀젼이 O/W 에멀젼보다 안정성과 피부 투과능이 우수함을 나타낸다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.36-37
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• 2006

This study aims to investigate the usage of nano-scale particles in a micro metal injection molding ($\mu$-MIM) process. Nanoscale particle is effective to improve transcription and surface roughness in small structure. Moreover, the effects of hybrid micro/nano particles, Cu/Cu and SUS/Cu were investigated. Small dumbbell specimens were produced using various feedstocks prepared by changing binder content and fraction of nano-scale Cu particle (0.3 and $0.13{\mu}m$ in particle size). The effects of adding the fraction of nano-scale Cu powder on the melt viscosity of the feedstock, microstructure, density and tensile strength of sintered parts were discussed.

• 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.

• 한국지하수토양환경학회지:지하수토양환경
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• 제22권5호
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• pp.89-97
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• 2017

In this study, we evaluated effect of particle size on arsenic solid-state speciation and bioaccessibility in soils highly contaminated with arsenic from smelting and mining. Soils were partitioned into six particle size fractions ($2000-500{\mu}m$, $500-250{\mu}m$, $250-150{\mu}m$, $150-75{\mu}m$, $75-38{\mu}m$, <$38{\mu}m$), and arsenic solid-state speciation and bioaccessibility were characterized in each particle size fraction. Arsenic solid-state speciation was characterized via sequential extraction and XRD analysis, and arsenic bioaccessibility was evaluated by SBRC (Solubility Bioaccessibility Research Consortium) method. In smelter site soil, arsenic was mainly present as arsenic bound to amorphous iron oxides. Fine particle size fractions showed higher arsenic concentration, but lower arsenic bioaccessibility. On the other hand, arsenic in mine site soil showed highest concentration in largest particle size fraction ($2000-500{\mu}m$), while higher bioaccessibility was observed in smaller particle size fractions. Arsenic in mine site soil was mainly present as arsenolite ($As_2O_3$) phase, which seemed to affect the distribution of arsenic and arsenic bioaccessibility in different particle size fractions of the mine soil.

• Journal of Preventive Medicine and Public Health
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• 제23권1호
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• pp.43-56
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• 1990

To evaluate the difference of concentration and mutagenicity of organic pollutants between residential and traffic area of Seoul, air samples were collected in Bulkwang (residential) and Shinchon (traffic) area. Samples were analyzed to measure the concentration of extractable organic matters (EOM) and their subfractions and mutagenicities were tested using Salmonella typhimurium TA 98. The concentrations of polycyclic aromatic hydrocarbons (PAHs) were also measured by gas-chromatography and compared between two areas. The results were as follows ; 1. While the concentration of total suspended particulate (TSP) in residential area was below the environmental standard in annual average, the concentration in traffic area was above the standard and was up to its maximum $256{\mu}g/m^3$ in November. The difference of TSP concentrations in both areas of each month was statistically significant (P<0.05). 2. The concentration of fine particle in traffic area was significantly higher compare to that in residential area and showed statistically significant monthly difference in both areas (P<0.05). The proportion of concentration of fine particle to TSP was 55-68%. 3. Mean concentrations of EOM in residential and traffic areas were $4.3{\mu}g/m^3\;and\;5.3{\mu}g/m^3$ respectively. The proportion of amount of EOM from fine particle to EOM from TSP was 70-88%. 4. While the percentage of polar neutral organic compounds (POCN) of fine particle in Bulkwang's sample was higher compare to Shinchon's sample, the percentage of aliphatic compounds of fine particle in Shinchon's sample was higher compare to Bulkwang's sample. The percentages of PAH fraction were as low as 6-10% in both areas. 5. The mutagenic activity of nit concentration of organic matters extracted from fine particle was higher compare to that of coarse particle and was increased when metabolically activated with S9. Mutagenicities with metabolic activation calculated by unit air volume were significantly different between residential and traffic area, $17\;revertants/m^3$\;and\;22\;revertants/m^3$ respectively. 6. The concentrations of benzo(a)pyrene in fine particle of traffic and residential areas were $3.10ng/m^3\;and\;2.02ng/m^3$ respectively. Sixteen PAHs were higher in samples of traffic area compare to residential area and also concentrations of PAHs in fine particle were higher compare to coarse particle.