• 한국지반공학회논문집
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• 제19권2호
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• pp.199-206
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• 2003

흙을 나타내는 가장 기본적인 물리적 성질중의 하나가 흙을 구성하는 입자들의 입도분포이며, 입도분포특성을 분석하기 위해 최근에 대두되고 있는 방법중의 하나가 프랙탈 이론이다. 본 연구에서는 fragmentation 프랙탈을 이용하여 흙의 입도분포곡선의 특성을 파악하였다. Fragmentation 프랙탈을 표현하는 방법에는 ‘개수-입경’프랙탈과 '중량-입경' 프랙탈이 있으며, 본 연구 결과, '중량-입경' 방법이 더 실용적이었다. 균등계수($C_{u}$)가 4이하에서는 균등계수가 증가함에 따라 프랙탈차원($D_{tot}$)이 급격히 증가하였으나, 균등계수가 6이상에서는 일정한 값에 수렴되는 결과를 나타냈다. 곡률계수($C_{c}$)가 3이상에서는 프랙탈차원은 크기가 작은 입자들의 영향을 받고, 곡률계수가 3이하에서는 큰 입자들의 영향을 받는 것으로 나타났다. 유효입경($D_{10}$)의 크기에 따른 프랙탈차원의 변화를 분석한 결과, 균등계수와 곡률계수가 같을 경우 프랙탈차원은 유효입경의 크기에 영향을 거의 받지 않는 것으로 나타났다. 전체 입자의 크기분포를 고려할 수 있는 프랙탈 개념을 입도분석에 적용하는 것이 바람직할 것으로 판단되며, 향후 프랙탈차원과 흙의 공학적 특성과의 관계정립에 대한 지속적인 연구가 필요하다.

• 한국물환경학회지
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• 제36권3호
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• pp.185-193
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• 2020

Bimodal flocculation describes the aggregation and breakage processes of the flocculi (or primary particles) and the flocs in the water environment. Bimodal flocculation causes bimodal size distribution with the two separate peaks of the flocculi and the flocs. Extracellular polymeric substances and ionic species common in the water environment increase the occurrence of bimodal flocculation and flocculi-floc size distribution, under the flocculation mechanisms of electrostatic attraction and polymeric bridging. This study investigated bimodal flocculation and flocculi-floc size distribution, with respect to the extracellular polymeric substance concentration and ionic strength in the kaolinite-containing suspension. The batch flocculation tests comprising 0.12 g/L of kaolinite showed that the highest flocculation potential occurred at the lowest xanthan gum (as extracellular polymeric substances) concentration, under all the ionic strengths of 0.001, 0.01, and 0.1 M NaCl. Also, it was important to note that the higher ionic strength resulted in the higher flocculation potential, at all the xanthan gum concentrations. The bimodal flocculation and flocculi-floc size distribution became apparent in the experimental conditions, which had low and intermediate flocculation potential. Besides the polymeric bridging flocculation, steric stabilization increased the flocculi mass fraction against the floc mass fraction, thereby developing the bimodal size distribution.

• 상하수도학회지
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• 제22권1호
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• pp.159-168
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• 2008

A special field experiment has been carried out from March 2001 to June 2001 at the Changhowon in Kyunggi to investigate a better methodology for the estimation of dry deposition of pollutions applicable in Korea. In this study, dry deposition plate was used to measure of total and water soluble acidic mass fluxes, and CPRI(Coarse Particle Rotary Impactor), CI(Cascade Impactor) were also used to measure ambient concentrations in various particle size ranges. Sehmel-Hodgson model was used to estimate dry depostion velocity and Weibull probability distribution function was applied to get generalized particle size distribution for the size fractioned concentration data sampled by CPRI and CI. Atmospheric dry deposition fluxes of mass and ionic matters estimated by the various techniques(one-step, multi-step, equi-concentration, subdivision for only the coarse particle range, applying Weibull distribution function, etc.) were compared to flux data sampled by DDP. It was found out that the deposition fluxes estimation methodology calculated by the each particle size range devided by particle size distribution characteristics and the rapidly changed points of deposition velocity using Weibull probability distribution function was the most applicable.

• 한국대기환경학회지
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• 제15권5호
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• pp.677-685
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• 1999

Aerosol mass size distributions were measured at Kosan, Cheju Island in April 1998 and their compositions were analyzed. Microorifice Uniform Deposit Impactor(MOUDI) was used to collect aerosols. Sulfate and ammonium ions were predominatly present at fine mode of the aerosols while nitrate, chloride, and metal ions were mostly at coarse mode. Based on the size distribution of nitrate, it is suggested that most nitrate were from gas to particle conversion on coarse particles. Non-sea salt(nss) fraction of sulfate accounted for more than 90% of total sulfate mass concentration. In general, ion concentrations in this study are lower than those measured at the same site from the previous studies. Ion balance and chloride ion levels indicates that there had been anthropogenic chloride emission sources near to the site during the measurements.

• 환경영향평가
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• 제8권2호
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• pp.31-44
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• 1999

Atmospheric dry deposition flux and ambient particle mass size distribution were measured to evaluate the impact of atmospheric deposition around the Nanjido landfill sites. Wind direction affects greatly on the variation of mass flux and mass size distribution and made two times higher when the wind was blown from the road side. The effect of Nanjido landfill on the mass size distribution was significant comparing to simultaneously measured mass size distribution at the other sampling site. The results showed that the particle diameter bigger than $10{\mu}m$ explained the majority of atmospheric dry deposition flux. A survey was also carried out to investigate the contamination of soils in a completed Nanjido landfill. The chemical properties of the soil analyzed in the present study include pH, oxidation-reduction potential (ORP), anion and cation concentration, total organic carbon(TOC), and some-metal elements concentrations were analyzed. Microbial activity in the soils was also evaluated by measuring dehydrogenase activities. TOC in the soil contaminated with leachate was $467.0{\mu}g/g-dry$ soil, and the TOC in the soil, where Nanjido landfill gases were emitted from, was $675{\mu}g/g-dry$ soil. The highest microbial activity of $968.0{\sim}2147{\mu}g-TPF/g-dry$ soil day was found in the soil spouting Nanjido landfill gases. Compared with those in the uncontaminated soil, the concentrations of Cr, Cu and Ph in the contaminated soil were higher.

• 한국환경보건학회지
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• 제32권6호
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• pp.543-555
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• 2006

During a twenty-day period in 2005, a nine-stage Andersen cascade impactor was used to determine the seasonal size distribution of atmospheric particles and its inorganic ion species sampled for 24hr in Iksan city, located southwest of the Korean peninsula. Samples were analyzed for major water-soluble ion species using Dionex-100 ion chromatograph. Average fine and coarse mass concentrations of atmospheric particles were, respectively, 31.4 and $82.6{\mu}g\;m^{-3}$ in spring and 35.8 and $73.4{\mu}g\;m^{-3}$ in fall-winter during the sampling period of 2005, while measurements of 69.8 and 9.9 were obtained in the sampling period of summer, The size distribution of particulate mass concentration during the non-Asian dust period was generally bimodal, whereas the size distribution of particulate mass concentration during the Asian dust period was unimodal due to the significant increase of coarse particles, which originated from long-range transport of soil dust particles from loess regions of the Asian continent. Among ionic species, $SO{_4}^{2-},\;NH{_4}^+,\;K^+$ were mainly distributed in fine particles due to their characteristics of emission sources and gas-to-particle conversion, while $Na^+,\;Mg^{2+}\;and\;Ca^{2+}$ were dominantly in coarse particles. However, $NO_3{^-}\;and\;Cl^-$ were distributed in both coarse particles and fine particles. Although $SO{_4}^{2-}$ was mainly distributed in fine particles, the size distributions of $SO{_4}^{2-}$ in coarse mode were significantly increased during the Asian dust events compared to those during the non-Asian dust period. $Ca^{2+}$ showed the most abundant species in the atmospheric particles during the Asian dust period. $NH{_4}^+$ was found to mainly exist as $(NH_4)_2SO_4$ in fine particles.

• 대기
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• 제22권3호
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• pp.367-379
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• 2012

Measurements of $PM_{10}$ mass concentration, aerosol light scattering and absorption coefficients as well as aerosol size distribution were made to characterize the aerosol physical and optical properties at the two Korean WMO/GAW regional stations, Anmyeondo and Gosan. Episodic cases of the severe Asian dust events occurred in spring of 2009-2010 were studied. Results in this study show that the aerosol size distributions and optical properties at both stations are closely associated with the dust source regions and the transport routes. According to the comparison of the $PM_{10}$ mass concentration at both stations, the aerosol concentrations at Anmyeondo are not always higher than those at Gosan although the distance from the dust source region to Anmyeondo is closer than that of Gosan. The result shows that the aerosol concentrations depend on the transport routes of the dust-containing airmass. The range of mass scattering efficiencies at Anmyeon and Gosan was 0.50~1.45 and $0.62{\sim}1.51m^2g^{-1}$, respectively. The mass scattering efficiencies are comparable to those of the previous studies by Clarke et al. (2004) and Lee (2009). It is noted that anthropogenic fine particles scatter more effectively the sunlight than coarse dust particles. Finally, we found that the aerosol size distribution and optical properties at Anmyeondo and Gosan show somewhat different properties although the samples for the same dust_episodic events are compared.

• 한국환경과학회지
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• 제12권10호
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• pp.1043-1054
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• 2003

During the period from April to September 2002, the size distributions of ambient aerosol were measured at the coastal site at Hamduk in Jeju Island. Na$\^$+/, K$\^$+/, Mg$\^$2+/, Ca$\^$2+/and Cl$\^$-/ exhibited mostly a bimodal coarse mode size distribution, while ammonium and sulfate were mainly in the fine size range, with maximum at around 0.54$\mu\textrm{m}$. The average molar concentration ratio of ammonium to sulfate for fine particles was equal to 2.0${\pm}$0.9. Nitrate was evenly found in both the coarse and fine modes. Elements like Al, Fe, Cu, Mg, Na, Ti, Sr and Mn were dominant in coarse particles, with the maximum at around 5.25$\mu\textrm{m}$. S and Pb were mainly in the submicrometer size range. Other elements with a fine and coarse modes were V, Ni, Cu, Ba and Mo. The patterns of the size distributions of trace elements measured at the downtown in Jeju City were very similar to those at the coastal site in Hamduk. However, the amplitude of size fractional concentrations at Jeju City was narrower than that at Hamduk. While the mass median diameters for the chemical species originated from the natural origin such as marine and crust were relatively large, those for ammonium, sulfate, S and Pb were very small.

• 터널과지하공간
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• 제12권3호
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• pp.198-209
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• 2002

To assess deep geological environment for the research and development of hish-level radioactive waste disposal, six boreholes of 3" in diameter were installed in two granitic areas. An areal extent of the rock block scale in the study sites was estimated by the lineament analysis from satellite images and shaded relief maps. The characterization of fracture system developed in rock block scale was carried out based on the acoustic televiewer logging in deep boreholes. In the Yuseong site, the granite rock mass was divided into the upper and lower zones at around -160m based on the probabilistic distribution characteristics of the geometric parameters such as orientation, fracture frequency, spacing and aperture size. Since the groundwater flow is dependent on the fracture system in a fractured rock mass, the correlation of the fracture frequency and cumulative aperture size to the hydraulic conductivity was also discussed.

• 천문학회보
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• 제40권2호
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• pp.48.3-49
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• 2015

Scaling relations of early-type galaxies (ETG) provide a deep insight into their formation and evolution. Interestingly enough, most relations extending into the dwarf regimes display non-linear or broken-linear features, unlike the linear relations for normal (i.e., intermediate-mass to giant) ETGs only. Here we investigate the mass-size scaling relation of ETGs using a massive database of galaxies from SDSS DR12. We divide ETGs into two groups by the indication of star formation such as colors, and examine their distinction along the mass-size relation. We find that the mass-size distribution of blue, young normal galaxies is in good agreement with that of dwarf ETGs. Our result suggests that blue, young normal ETGs may serve as links between (passive) normal ETGs and dwarfs. We discuss the possibility of blue, young ETGs being progenitors of dwarf ETGs.