• 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.

• 한국입자에어로졸학회지
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• 제5권2호
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• pp.45-52
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• 2009

Black carbon, which is a by-product of combustion of fossil fuel and biomass burning, is the component that imposes the largest uncertainty on quantifying aerosol climate effect. The direct, indirect and semi-direct climate effects of black carbon depend on its state of the mixing with other water-soluble aerosol components. The process that transforms hydrophobic externally mixed black carbon particles into hygroscopic internally mixed ones is called "aging". In most climate models, simple parameterizations for the aging time scale are used instead of solving detailed dynamics equations on the aging process due to the computation cost. In this study, a new parameterization for the black carbon aging time scale due to condensation and coagulation is presented as a function of the concentration of hygroscopic atmospheric components and the black carbon particle size. It is shown that the black carbon aging time scale due to condensation of sulfuric acid vapors varies to a large extent depending on the sulfuric acid concentration and the black carbon particle size. This result indicates that the constant aging time scale values suggested in the literature cannot be directly applied to a global scale modeling. The aging time scale due to coagulation with internally mixed aerosol particles shows an even stronger dependency on particle size, which implies that the use of a particle-size-independent aging time scale may lead to a large error when the aging is dominated by coagulation.

• 한국세라믹학회지
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• 제21권4호
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• pp.366-372
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• 1984

Unstabilized Zirconia was added to basic composition under 44$mu extrm{m}$ of 57.80wt% Clay-22.20wt% Chamotte-20.00wt% Agalmatolite system. Here the amount and the particle size of Zirconia were 5-25wt% and -20${\mu}{\textrm}{m}$ respectively and the body of these composition was first at 135$0^{\circ}C$. The results obtained from examining the properties of sintered body were as follows. 1. Firing linear shrinkage apparent density and bulk density apparent porosity and water absorption of the samples had the tend to increase according as the particle size of zirconia became larger and the amount of zirconia increased. 2. Modulus of rupture was inversely proportional to the particle size and the additive amount of zirconia, . Especially in case that the particle size of zirconia over 5${\mu}{\textrm}{m}$ and the additive amount of zirconia was 25wt% the modulus of rupture had shrunk drastically. 3. The maximum value of KIC was obtained at 20wt% additive amount of zirconia according to the each particle size of zirconia. Especially the highest value of KIC is 2, 173 M. Pa. M1/2 when the particle size of zirconia is 5~10${\mu}{\textrm}{m}$ and the additive amount is 20wt%.

• 한국분말재료학회지
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• 제18권3호
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• pp.221-225
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• 2011

In the current study, the effects of particle size on compaction behavior of water-atomized pure iron powders are investigated. The iron powders are assorted into three groups depending on the particle size; 20-45 ${\mu}M$, 75-106 ${\mu}M$, and 150-180 ${\mu}M$ for the compaction experiments. The powder compaction procedures are processed with pressure of 200, 400, 600, and 800 MPa in a cylindrical die. After the compaction stage, the group having 150-180 ${\mu}M$ of particle size distribution shows the best densification behavior and reaches the highest green density. The reason for these results can be explained by the largest average grain size in the largest particle group, due to the low plastic deformation resistance in large grain sized materials.

• 한국축산식품학회지
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• 제42권3호
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• pp.486-503
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• 2022

This study explored the physiochemical and rheological properties of chicken breast sausages containing red ginseng marc (RGM) which contains useful components but is discarded. When compared to the control group, the use of RGM significantly increased the water holding capacity (WHC) as the particle size increased. As for the change in color value, addition of RGM resulted in an increase in a and b values; as the quantity was increased and particle size decreased, the a and b values increased significantly. The smaller the particle size of RGM, the greater was the radical scavenging activity. According to the results of the measurement of the viscoelasticity of chicken breast sausage containing RGM, the G' and G'' values increased with increasing amounts of RGM and particle size. Neither the addition of RGM nor its amount or particle size had any significant effect on gel formation temperature. The texture profile analysis (TPA) experiment examined the average TPA measurements of each sample under different measurement conditions, and no significant difference between the RGM and control groups were observed. In conclusion, when RGM is used in chicken breast sausages, the WHC, antioxidant capacity, and viscoelastic properties are affected. RGM can possibly be utilized in high value-added processed meat products if its quantity and particle size are altered based on product characteristics.

• Elastomers and Composites
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• 제43권4호
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• pp.230-240
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• 2008

분산중합법에 의해 무기물을 포함하는 고분자 미립자를 합성하기 위해 styrene과 n-butyl methacrylate가 알루미나와 함께 중합되었다. Styrene과 n-butylmethacrylate의 무게 비는 3:1이었고, 입자안정제는 poly(N-vinyl pyrrolidon), 중합 개시제로는 2,2'-azobis(isobutyronitrile)를 사용하여 개시제의 농도, 분산매의 종류, 분산매의 혼합 용해도 상수 (${\delta}_{mix}$), 커플링제의 종류와 농도에 따른 입자경을 조사하였다. 개시제의 농도가 증가함에 따라 입자경이 소폭 상승하였고 분산매의 극성이 증가할수록 입경이 증가하였고, 분산매로서, 이소프로판올과 이온교환수를 조성비에 따라 사용한 경우, $[{\delta}_{mix}]^{-4.01}\;{\propto}$ 평균 입자경과 $[{\delta]_{mix}]^{-0.83}\;{\propto}$ 입경 분포의 관계를 얻을 수 있었다. 커플링제의 종류와 농도변화에 따른 입자경 및 입자경 분포는 뚜렷한 차이가 없었다.

• 한국재료학회지
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• 제15권11호
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• pp.717-721
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• 2005

Silica powders were synthesized using emulsion solution containing water, nonionic surfactant of Triton N-57, and cyclohexane. Silica powders were prepared at low cost using inexpensive starting material of sodium silicate and ammonium sulfate. Morphology, size and size distribution were observed and determined using SEM. The powder was identified as silica by FT-IR and XRD analysis. Particle size and size distributions were affected by concentration of reactants, reaction time, and concentration of surfactant. Particle size were increased with increasing concentration of reactants and particles became dense with increasing reaction time. As R value increased, tile particle size was increased, reached a certain value and then decreased again. The silica powders synthesized under optimum condition were spherical in shape, $0.8{\mu}m$ in average particle size, narrow in particles size distribution, and well dispersed.

• 에너지공학
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• 제6권2호
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• pp.162-169
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• 1997

The particle size effect on the combustion characteristics of pulverized coal was investigated in the cylindrical-shape, horizontal furnace, fired in the range of 8.8∼10.6 kw. Three differently-sized fractions (5, 30, and 44 microns in average diameter) of high-volatile bituminous coal, were burned in the test furnace. Burnout behavior of pulverized coal flame were determined through the measurement of stable species concentrations (CO$_2$and H$_2$O). Concentrations of CO$_2$were compared with the theoretical values and the result showed good agreement. Thermal behavior of pulverized coal flame were determined as maximum flame temperatures occurred at fuel-rich conditions in every case. Flame lengths were also determined by decreasing with the particle size decrease. The flame length of the fine sized coal sample was comparable to that produced by distillate oil. The color of the coal flames ranged from orange to yellow, with the flame of the fine size fraction being brighter and yellower than the others.

• 한국분말재료학회지
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• 제27권1호
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• pp.44-51
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• 2020

Powder characteristics, such as density, size, shape, thermal properties, and surface area, are of significant importance in the powder bed fusion (PBF) process. The powder required is exclusive for an efficient PBF process. In this study, the particle size distribution suitable for the powder bed fusion process was derived by modeling the PBF product using simulation software (GeoDict). The modeling was carried out by layering sintered powder with a large particle size distribution, with 50 ㎛ being the largest particle size. The results of the simulation showed that the porosity decreased when the mean particle size of the powder was reduced or the standard deviation increased. The particle size distribution of prepared titanium powder by the atomization process was also studied. This study is expected to offer direction for studies related to powder production for additive manufacturing.

• 한국입자에어로졸학회지
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• 제13권3호
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• pp.133-139
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• 2017

In this paper, we proposed an emulsification method without using an emulsifier and investigated the effects of particle size distribution in fluids on dispersion stability. Surfactant-free oil in water emulsion was prepared with 1 % (w/w) of olive oil by using high speed agitation, high pressure and ultrasonic dispersion methods. The particle size, microscopic observation, and dispersion stability of each sample were evaluated and dispersion stability according to various dispersion methods was compared. As a result, the emulsion dispersed by the ultrasonic dispersion method showed the smallest particle size and uniform distribution of $0.07{\sim} 0.3{\mu}m$ and was the most stable in a 7 days stability evaluation. In the above experiment, four olive oil emulsions having different particle sizes were prepared using ultrasonic dispersion technology that was capable of producing stable emulsions. The dispersion stability of each samples with oil droplet sizes of (A) 0.1 to $0.5{\mu}m$, (B) 0.3 to $4{\mu}m$, (C) 1 to $10.5{\mu}m$ and (D) 2 to $120{\mu}m$, was observed for 7 days, and the relationship between the stability and performance was studied. Emulsion (A) with particle size less than $0.5{\mu}m$ displayed the dispersion stability showing below 5 % change in a 7 days stability evaluation. In the case of (B), (C), and (D) that had larger particle than $0.5{\mu}m$, the changes of dispersion stability were 10 %, 13 % and 35 % respectively. From these results, it was proved that dispersion stability of emulsion with uniform particle size of $0.5{\mu}m$ or less was confirmed to be very stable.