• 한국결정성장학회:학술대회논문집
• /
• 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
• /
• pp.13-19
• /
• 1997

From the formation of the monodispersed silica particle which is a valuable for the industry by Sol-Gel process, the effects of the parameters participated in the process, the growth mechanism and the characteristics of silica particles for each rection conditions are investigated. To investigate about the formation of final silica particles, the suspension which performs the polymerization is reacted with molybdic acid, and the evolutions of TEOS and silica particle size are investigated in the reaction time ？ 새 the characteristics of molybdic acid with the suspension. From the results, a constant number of silica particle is formed at early reaction stage. Silica particles grow through the aggregation of smaller particles and nucleation is rate-limiting step for the growth of particles. In the conditions of this study, spherical silica particles are formed, [NH$_3$] and [$H_2O$] concentration increase the particle size but particle size decrease with [$H_2O$] concentration which is a certain above region. Average particle sizes are 187.4~483.3 nm and standard deviations in the average particle size are 1.7~2.9% with each experimental condition. From the BET results, specific surface area is 5.5~23.4 $m^2$/g and these values decrease with increase size. The average pore size is 50~70$\AA$.

• 상하수도학회지
• /
• 제22권1호
• /
• pp.159-168
• /
• 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
• /
• 제5권2호
• /
• pp.45-52
• /
• 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.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2021년도 가을 학술논문 발표대회
• /
• pp.19-20
• /
• 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.

• 한국대기환경학회지
• /
• 제27권6호
• /
• pp.663-671
• /
• 2011

Although a scooter is a convenient transportation means for a short distance traveling with a light package in the congested urban center, it might be one of the significant sources of air pollutants to which many people can easily be exposed during its passing-by. In this paper, we measured concentrations of gases and particles emitted from a scooter at roadside with no other traffic. To understand the characteristics of scooter emissions with respect to driving speed (idling, 30 km/h) at the roadside, total particle number concentration, particle size distribution, average surface area of particles deposited in the alveolar region, and concentrations of black carbon, CO, and $NO_x$ were measured. The concentrations of the particle number, surface area of deposited particles, CO, and $NO_x$ were highly fluctuated in the scooter's idling condition. The trends of particle number concentration, CO, and $NO_x$ generation were similar to one another. When the scooter started to move, all of $NO_x$, CO and particle number concentrations increased and after it passed by at the speed of 30 km/h, the concentration peaks of the particles and gases appeared at the same time. Unimodal size distribution with ~70 and ~93 nm mode diameters was observed for the idling and cruising condition, respectively. From this work, we found that emission from a passing vehicle could be characterized using a roadside monitoring technique.

• Tribology and Lubricants
• /
• 제15권3호
• /
• pp.265-271
• /
• 1999

Wherever there are rotating equipment and contact between surface, there is wear and the generation of wear particles. The particles contained in the lubricating oil carry detailed and important information about the condition monitoring of the machine. This information may be deduced from particle shape, composition, size distribution, and concentration. Therefore, This paper was undertaken to Ferrography system of wear debris generated from lubricated moving machine surface. The lubricating wear test was performed under different experimental conditions using the Falex wear test of Pin and V-Block type by Ti(C, N) coated. It was shown from the test results that wear particle concentration (WPC) and wear severity Index( $I_{S}$), size distribution in normal and abnormal wear have come out all the higher value by increases sliding friction time. Wear shape is observed on the Ferrogram it was discovered a thin leaf wear debris as well as ball and plate type wear particles. This kind of large wear shape have an important effect not only metals damage, but also seizure phenomenon.

• 한국응용과학기술학회지
• /
• 제28권4호
• /
• pp.386-392
• /
• 2011

We are crystallized to the linear low density polyethylene(LLDPE) particles by a thermally induced phase separation(TIPS). TIPS process based on the phase separation mechanism was performed for the LLDPE system which undergoes liquid-solid phase separation. The linear low density polyethylene particle formation occurred by the nucleation and growth mechanism in the metastable region. Although the growth rates depended on the experimental conditions such as the polymer concentration and temperature, the particles were larger when the polymer concentration was higher or temperature was higher. The particles were observed by SEM. The LLDPE particle size distribution became broader when the polymer concentration was higher.

• 한국전기전자재료학회논문지
• /
• 제18권10호
• /
• pp.929-935
• /
• 2005

In this paper, synthetic conditions of titania nanparticle was investigated to enhance its uniformity of the particle size as a child particle on organic mother particle of liquid powder type electronic paper. The physical properties are very important to improve the uniformity of electrical charging properties Concentration of titania raw material ($C_9H_{19}NO_4Ti$) in the ethanol solvent, pH, and concentration of the solution in the D.I. water were selected as parameters. As a result, ultrafine and well crystallized titania nanoparticle with good uniformity could be synthesized as the concentration of the $C_9H_{19}NO_4Ti$ in the ethanol solvent, pH of the solution, and the amount of the D.I. water were increased. Using the optimized conditions, the titania nanparoticle with uniformly ultrafime size of 10 nm could be synthesized.

• 한국입자에어로졸학회지
• /
• 제7권1호
• /
• pp.1-8
• /
• 2011

In this study, the formation of nanoparticles by a reaction of ozone with the volatile organic compounds(VOCs) emitted from a commercial home cleaner liquid was investigated using a $1-m^3$ reaction chamber($1{\times}1{\times}1m$). The home cleaner liquid was found to contain many VOCs, particularly terpenes. Some of these VOCs are known to readily react with ozone, forming indoor secondary pollutants. The correlation of particle concentration and reacted ozone concentration was examined with injections of three different ozone concentrations; 50, 100 and 200 ppb. The secondary nanoparticles were formed faster, with their numbers and mass concentrations becoming higher on increasing the concentration of ozone injected.

• 한국초전도ㆍ저온공학회논문지
• /
• 제23권3호
• /
• pp.26-31
• /
• 2021

Advanced classification of Cs contaminated soil by using a magnetic force-assisted selection pipe was investigated. A selection pipe is a device that sort particles depending on their particle size, based on the relationship between buoyancy, drag, and gravity force acting on the particles. Radioactive cesium is concentrated in small-particle size soil components with a large specific surface area. Hence, the volume of the Cs contaminated soil can be reduced by recycling the large-particle size soil components with low radioactive concentration. One of the problems of the selection pipe was that the radioactive concentration of the stayed soil in the selection pipe exceeds 8000 Bq/kg, which is the standard value of recycling of Cs contaminated soil, due to low classification accuracy. In this study, magnetic fields were applied to the lab-scale selection pipe from upper side to improve the classification accuracy and to reduce the radioactive concentration of the stayed soil.