• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.3
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• pp.380-391
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• 1997

A numerical study has been done on the evolution of particle size distribution in particle laden high temperature jet flows undergoing convection, diffusion, thermophoresis and coagulation. The dynamic behavior of these particles have been modelled by approximating the particle size distribution by a lognormal function throughout the process and the moments of the particle size distribution have been used to solve the general dynamic equation. The size distributions of spherical particles in the radial and axial direction have been obtained including the effect of buoyancy. Of particular interests are the variations of geometric mean diameter, number concentration and polydispersity. Results show that buoyancy significantly alters the size distribution in both axial and radial direction. One dimensional analysis for non-spherical particles has also been done and the results have been compared with the existing experimental data.

• Journal of Korea Foundry Society
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• v.5 no.2
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• pp.85-96
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• 1985

In order to investigate the effect of particle size and distribution of silica sand on the characteristics of investment, W/P ratio, setting time, temperature change during setting, setting expansion, thermal expansion and compressive strength of the investments were measured. In this experiment, magnesia clinker and mono ammonium phosphate were used as binder, and particle size and distribution of silica sand were classified for convinence into 10 categories. The main results obtained from this investigation were summerized as follows. 1. W/P ratio decreased with increase of particle size and evenness in distribution of sand grain. 2. Setting time decreased with increase of evenness in distribution of sand grain, and temperature during setting increased with evenness in distribution of sand grain. 3. Setting expansion decreased with increase of particle size, while it increased with evenness in distribution of sand grain. 4. Thermal expansion decreased with increase of particle size. 5. Compressive strength increased with increase of particle size and evenness in distribution of sand grain. From above results, G.F.N. 250 sand which contains 30% of 50-100 mesh could be recommended for investment casting.

• Journal of Environmental Science International
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• v.32 no.3
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• pp.181-189
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• 2023

In this study, sediment cores from unvegetated tidal flats in the Hampyeong Bay (west coastal wetland) and Dongdae Bay (south coastal wetland) were sampled, the blue carbon stock in the sediments was calculated, and the characteristics of the blue carbon stock were analyzed based on particle size of the sediments. The sediments in the Hampyeong Bay tidal flat had large particle size and low mud content, and the Dongdae bay tidal flat had small particle size and high mud content. The organic carbon content and blue carbon stock in the sediments were higher in the Dongdae tidal flat than in the Hampyeong Bay tidal flat. As a result of the regression function, in both the Hampyeong Bay and Dongdae Bay tidal flats, the sediments had the smaller particle size and higher mud contents the higher the organic carbon content and blue carbon stock. The sediments with smaller particle size had the larger specific surface area, so were feasible to adsorb and store more organic matters.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.19-20
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• 2021

In order to reduce the emission of harmful substances that degrade indoor air quality, the Ministry of Environment strengthened the standards for the content of VOCs in paints to supply and sell eco-friendly paints. In this related study, an eco-friendly paint mixed with a powder-type absorbent material was prepared and its characteristics were reviewed. As the amount of powder-type absorbent material increased, the workability (viscosity, peeling, etc) decreased. Accordingly, this study aims to examine which particle size is suitable according to the particle size of the granular adsorbent while improving the problem of the powdery adsorbent by using the granular adsorbent. As an experimental plan, the particle size of granular activated clay is selected to be 0.250, 0.425, 0.710(mm), and the decrease rate of VOCs concentration and impact resistance are reviewed. As a result of the experiment, as the particle size of the granular activated clay increased, the decrease rate of the VOCs concentration increased and the impact resistance improved. Therefore, considering the problems that occur after actual painting, the particle size of granular activated clay of 0.425mm is suitable.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.147-148
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• 2022

Due to recent climate abnormalities, the form of rainfall is changing to localized torrential rains. Localized torrential rains cause flooding in urban areas. In addition, in various industrial fields, there are cases where materials necessary for the process are kept outdoors, and damage from material loss and flooding of stockyards occurs during heavy rain. Accordingly, it is necessary to introduce a drainage layer where flooding is expected. This drainage layer places the aggregate inside and allows rainwater to penetrate and drain into the voids between the aggregates. However, the amount of voids differs according to the particle size distribution and particle size of the aggregate, and the drainage performance varies according to the compositional location of the aggregate. Therefore, in this study, the drainage characteristics according to the particle size, particle size, and compositional location of aggregates are analyzed using a fluid analysis program.

• Journal of Powder Materials
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• v.21 no.4
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• pp.307-312
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• 2014

This study is focused on investigating the relation between the particle size of silver flake powder and mechanical milling parameters. Mechanical milling parameters such as ball size, impeller rotation speed and milling time of the attrition ball-mill were controlled to produce silver flake powder. The particle size of the silver flake powder increased with increasing ball size and impeller rotation speed. The change of the particle size of the silver flake powder with mechanical milling parameters was analyzed based on balls motion in the mill container of the attrition ball-mill. The silver flake particles were formed at the elastic deformation area of the ball due to the collision between balls. The change of the particle size of the silver flake powder with mechanical milling parameters well consists with the change of the collision energy of ball with parameters mentioned above.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.5
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• pp.634-641
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• 2013

Condensing species behaviour downstream of a combustor was discussed with particle size distribution in this study. The effects of operating conditions in a biomass combustion facility, i.e. concentration of condensing species, temperature gradient, residence time and injection of adsorbents, on particle size distribution were investigated. Pyroligneous liquid which was completely vaporized at the temperature higher than $350^{\circ}C$ was used as a representative of condensing gaseous species. We found that particle size downstream of a combustor increased with increasing heating temperature (i.e. concentration of condensing species) and residence time. However, temperature gradient was not an important factor to control the particle size. The addition of $SiO_2$ precursor as an adsorbent could effectively prevent the particle formation by adsorbing condensing gaseous species on $SiO_2$ particles, and increased the particle size up to 300 nm, resulting in increasing particle removal efficiency in a conventional air pollution control device.

• Korean Journal of Materials Research
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• v.12 no.1
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• pp.58-67
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• 2002

In this study copper chloride(CuCl$_2$) solution was used as raw material to produce the fine copper oxide powder which has less than 1 $\mu\textrm{m}$ average particle size and has uniform particle size distribution by spray pyrolysis process. In the present study, the effects of reaction temperature, the injection speed of solution and air, the nozzle tip size and the concentration of raw material solution on the properties of produced powder were studied. The structure of the powder became much more compact with increasing the reaction temperature regardless of copper concentration of the raw material solution. The particle size of the powder increased accordingly with increasing the reaction temperature in case of 30 g/$\ell$ copper concentration of the solution. The particle size of the powder increased accordingly, and the surface structure of the powder became more porous with increasing the copper concentration of the raw material solution. When copper concentration in raw material solution was more than 100 g/$\ell$, all produced powder was CuCl regardless of reaction temperatures. When copper concentration in solution was below 30 g/$\ell$ and reaction temperature was higher than 90$0^{\circ}C$, CuO was the main phase. The surface of the powder tended to become porous with increasing the injection speed of solution. Particle size was increased and the surface of the powder showed severely disrupted state with increasing the nozzle tip size. The particle size was decreased and the particle size distribution was more uniform with increasing the air pressure through the nozzle.

• Journal of the Korean Ceramic Society
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• v.29 no.7
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• pp.525-532
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• 1992

TiO2 fine powder was synthesized in the gas phase by chemical vapor deposition using hydrolysis of TiCl4. Content of rutile phase in the powder was investigated. Powder characteristics such as size, crystallinity and morphology were also studied by means of TEM, SEM and XRD. Rutile phase in TiO2 powder started to be formed from 100$0^{\circ}C$ and the content increased with the reaction temperature and TiCl4 concentration. As the temperature increased from 80$0^{\circ}C$ to 140$0^{\circ}C$, the primary particle size increased while secondary particle size decreased. Spherical secondary particle with fine primary crystals agglomerated was produced at low temperature of 80$0^{\circ}C$ whereas the grown primary particle being final particle size was produced at higher temperature of 140$0^{\circ}C$. Other effects of TiCl4 and H2O partial pressures on particle size were also reported in this study.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.545-551
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• 2000

Sintering behaviors of the glass-alumina composites for low firing temperature were investigated as a function of the particle size of glass frit. The system of glass frit was Pb-B-Si-Al-O. The median particle sizes of the glass frits were 2.72$\mu\textrm{m}$, 2.67$\mu\textrm{m}$ and 1.33$\mu\textrm{m}$, which were prepared with changing ball-milling times as 24 h, 48 h and 96 h. The glass-alumina composites showed maximum density at certain temperature, and further heating led to dedensification behaviors, so called over-firing. The sintering temperature, which showed maximum density, raised from 425$^{\circ}C$ to 475$^{\circ}C$ with increase of particle size of glass frit from 1.33$\mu\textrm{m}$ to 2.72$\mu\textrm{m}$. Especially, the over firing behaviors, which were occurred at high sintering temperatures, were greatly increased with decrease of particle size of glass frit.