• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.233-234
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• 2003

부유 분진의 입경에 따른 물리, 화학적 특성은 대기질 및 인체의 건강 측면에서 중요한 변수로 작용되고 있으며, 호흡기내 침착 및 가시도의 영향에도 밀접한 관련이 있다. 거대입자는 주로 자연적 발생원에서 방출되고 호흡시 구강이나 코에서 대부분 제거된다. 미세입자는 인위적인 배출원에서 주로 방출되며 입경이 10$\mu\textrm{m}$이하인 것으로 보고되고 있다. 이들 1차 생성분진과는 달리 대기중에서 황산가스나 휘발성유기화합물 등이 응축과정을 거쳐 가스상에서 입자상으로 변환되어 생성된 입자도 환경학적으로 매우 중요한 의미를 갖는다. (중략)

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.131-137
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• 1998

A composite copper coated powder was generated by pressure hydrogen stripping copper from Kelex 100 solvent extractant in the presence of silica powder. Within the limitation of solvent extraction under constant conditions, both loading level and stripping rate were reproducible. The stripping copper kinetics are reduced from a divalent state to a metallic state and then deposited on the surface of the silica powder. Copper nucleates heterogeneously on the seed particles. They are giving an agglomerated and non - uniform powder.

• Applied Chemistry for Engineering
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• v.2 no.3
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• pp.238-245
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• 1991

Chlorination of methane was carried out over the Pt/NaY zeolite catalysts having different dispersion and location. On the finely dispersed platinum particles inside the zeolite methylchloride was the sole product, while on the large platinum ones outside surface of the zeolite all four chloromethanes were produced. Besides the role of highly dispersed platinum particles, the confined volume of the supercages in the support seems to have played another role on the exclusive production of methylchloride by restricting the further chlorination.

• Journal of the Korea Society of Computer and Information
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• v.18 no.1
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• pp.149-156
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• 2013

In this paper, Commercial program, STAR-CCM+, was used for computer simulation. And also Multi Inner Stage(MIS) cyclone which especially designed for the real experiments of particle removal efficiency. Under negative pressure condition of outlet, computer simulation was performed to predict the removal efficiency for $5{\mu}m$ and $10{\mu}m$ particles by using a turbulence model and lagrangian method. The simulation results are 55.7% and 64.1% for $5{\mu}m$ and $10{\mu}m$ particles, respectively. To compare the simulation results with the actual test of MIS cyclone, we generated the $SiO_2$ particles by heat reactor. Although removal efficiency of actual tests is 63~76% at different flow rate, the size of $SiO_2$ particles which confirmed by SEM(scanning electron microscope) and WAPS(wide range aerosol particle spectrometer) is too small(15~30nm) to compare each results. And so the alternative experiments were performed by using commercial alumina particles ($5{\mu}m$, $10{\mu}m$ and $20{\mu}m$). It was shown that the actual removal efficiency, 76~95%, from MIS cyclone is higher than simulated one.

• Clean Technology
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• v.25 no.4
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• pp.283-288
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• 2019

Monodisperse microparticles has been particularly enabling for various applications in the encapsulation and delivery of pharmaceutical agents. The microfluidic devices are attractive candidates to produce highly uniform droplets that serve as templates to form monodisperse microparticles. The microfluidic devices that have micro-scale channel allow precise control of the balance between surface tension and viscous forces in two-phase flows. One of its essential abilities is to generate highly monodisperse droplets. In this paper, a microfluidic approach for preparing monodisperse polycaprolactone (PCL) microparticles is presented. The microfluidic devices that have a flow-focusing generator are manufactured by soft-lithography using polydimethylsiloxane (PDMS). The crucial factors in the droplet generation are the controllability of size and monodispersity of the microdroplets. For this, the volumetric flow rates of the dispersed phase of oil solution and the continuous phase of water to generate monodisperse droplets are optimized. As a result, the optimal flow condition for droplet dripping region that is able to generate uniform droplet is found. Furthermore, the droplets containing PCL polymer by solvent evaporation after collection of droplet from device is solidified to generate the microparticle. The particle size can be controlled by tuning the flow rate and the size of the microchannel. The monodispersity of the PCL particles is measured by a coefficient of variation (CV) below 5%.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2009.10a
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• pp.644-645
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• 2009

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.207-212
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• 2008

This study focused on shorten the period of the struvite crystal birth and development by adding seed materials. For this purpose, three different seed materials were selected: sand, anthracite and struvite. The experiments has been conducted to evaluate the effect of the particle size of the selected seed material on the struvite crystallization, and to study the mixing effect which can be expressed by the value of $G{\cdot}t_d$(the multiple of mean velocity gradient(G) and mixing time($t_d$)). It was observed in this study that the removal efficiency of ammonia nitrogen increased by 9%, 11%, and 20% for sand, anthracite, and struvite added as the seed material, respectivley. This indicated that the struvite crystallization efficiency had a close correlation with the specific surface area of the seed particle. It was found that when struvite was selected as the seed material, the struvite crystallization proceeded at lower $G{\cdot}t_d$ value as compared with other seed materials. This observation implied that the secondary crystal birth would be dominated in this reaction. It was concluded in this study that the particle size was not significant factor on the struvite crystallization, while the $G{\cdot}t_d$ value was a considerably important factor in terms of the theory of the struvite crystal birth.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.602-609
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• 1997

The seed formation and growth of $\alpha$-ferric oxyhydroxide with aerial oxidative precipitation from aqueous solution of ferrous sulfate with KOH, NaOH, $Na_2CO_3$ and $K_2CO_3$ as precipitants have been studied by free pH drift experiment. It has been shown that all precipitants give same particle formation and growth path, and average particle length from KOH and NaOH as precipitants was about 1.5 times shorter than that of $K_2CO_3$ and $Na_2CO_3$. When initial mole ratio, $R_o=[Fe^{2+}]_o/[OH^-]_o$ of KOH was decreased the particle was grown oxyhydroxide seed growth from aqueous solution of ferrous sulfate with KOH has been studied. The influence of the air flow rate, reaction temperature and initial mole ratio, $R_o=[Fe^{2+}]_o/[OH^-]_o$, on the kinetics of seed growth are investigated by static pH experiment. The oxidation rate of seed growth increased with increase in the air low rate, reaction temperature and initial mole patio. The activation energy of seed growth is 16.16 KJ/mol and the rate equation of seed growth can be written as follows: $-\frac{d[Fe^{2+}]}{dt}=1.46{\times}10^4[P_{o2}]^{0.66}[OH^-]^{2.19}exp(-\frac{16.16}{dt})$.

• Fire Science and Engineering
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• v.28 no.6
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• pp.8-12
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• 2014

Interior finishing materials using noncombustible were regulated by the building codes to prevent the spread of fire and protect occupants. The average deed of stopping time of experimental mouse exposing combustion gas were measured by KS F 2271 gas toxicity test. At that time, The average deed of stopping time under 9 minutes were judged a inconsistence. This experiment method has limit to find out a cause of toxicity effect factor. In this study, particle size analysis were performed for investigate a major factor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.10-16
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• 2016

This work investigates the size and dispersion characteristics of silver nanoparticles synthesized by a liquid phase reduction method using PAA. The experimental variables were the molecular weight and doses of the PAA, reducing agent, dispersant, and organic solvent (ethanol-acetone). UV-visible spectrophotometer results confirm the formation of the silver particles, and SEM indicates size in the nanometer range. As the ultrasonication time increases, there is a tendency toward smaller agglomerates of nanoparticles. The agglomerates were dispersed into 1-5 agglomerates of particles by ultrasonication for 3 hours or more. Relatively spherical nanoparticles were produced with a completely homogeneous dispersion and size of 49.56-85.75 nm by ultrasonication using BYK-192, a dispersant containing copolymer with a pigment affinic group. The average size of the silver nanoparticles was increased to 36.82, 50.66, and 56.06 nm with increasing molecular weight of PAA. Also, the size of the nanoparticles increased with the capping of PAA on the surfaces of the nanoparticles when increasing the amount of PAA. The addition of hydrazine as a reducing agent produced relatively small particles because many nuclei were created by the reduction reaction. The ethanol-acetone solvent helped with the regular arrangement of the silver nanoparticles.