• Proceedings of the Korean Radioactive Waste Society Conference
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• 2007.11a
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• pp.305-306
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• 2007

ACP(Advanced Spent Fuel Conditioning Process)의 금속전환로에 $U_3O_8$을 공급하기 위하여 20 kgHM/batch의 $UO_2$ 펠릿(pellets)을 처리할 수 있는 건식분말화 장치가 개발되고있다. 건식분말화 장치는 500 $^{\circ}C$온도에서 공기를 공급하여 일정한 입도범위의 균질한 $U_3O_8$을 만든다. 이런 건식 분말화 장치의 효율을 높이기 위해서는 반웅로에 불어 넣어주는 공기의 유량을 증가시킬 필요가 있다. 하지만 공기와 반응하여 생성되는 $U_3O_8$ 입자는 그 크기가 최소 3 ${\mu}$m 정도로 매우 미세하여，반응로 출구를 통해 외부로 빠져나갈 가능성 이있다. 이를 방지하기 위해 분말화 장치 출구 바깥에는 필터가 설치되어 있으나 공기와 함께 $U_3O_8$ 입자가 계속해서 빠져 나갈 경우 입자로 인해 필터가 막혀 제 기능을 할 수 없게 된다. 따라서 건식 분말화 장치는 미세한 $U_3O_8$ 입자가 반응로 밖으로 빠져나가지 않도록 입구에서의 공기 유량을 일정 수준 이하로 조절해주는 것이 필요하다. 이 연구의 목적은 초기 유량으로부터 유량을 점점 증가시키면서 시간변화에 따른 입자 거동 특성을 해석하며， 결과로부터 주어진 크기의 타원입자에 대해 최대 허용 공기 유량을 결정하고자한다. 이 해석을 위해 유동과 입자를 동시에 해석할 수 있는 ANSYS-CFX 5.7.1과 ANSYS-CFX 10.0 두 가지의 소프트웨어가 사용되었다. 해석 결과를 바탕으로 좀더 정확한 유량 한계치 계산을 위해 추가로 수행되어야 할 해석에 대해 제안하였다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.1 no.1
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• pp.39-46
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• 1998

This study presents a numerical model that can simulate changes of particle size distribution (PSD) of PCB-contaminated coastal sediments. The developed model has one spatial dimension including sedimentation and vortical dispersion as well as coagulation. The reason for considering the vortical transport mechanisms is to calculate residence time of the particles. Using the model and Initial PSD data based on actual coastal sediments contaminated with PCBs, this study shows results of model simulations. Within 48 hours of the simulation time, the PSD changed significantly and the particles were removed from water in different rates between different particle sizes. It also shows that coagulation can act an important role in this process. The model may be useful in assessing the range of resuspended sediments that can pollute neighboring areas during environmental remediation projects such as dredging.

• Particle and aerosol research
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• v.13 no.3
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• pp.105-110
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• 2017

Real-time measurements of fine particles from stack emission gases are necessary due to the needs of continuous environmental monitoring of PM10 and PM2.5. The porous tube dilutor using hot and cold dilutions was developed to measure fine particles without condensable particles from highly humid emission gases and compared to the commercialized ejector-type dilutor. Particle size distributions were measured at the emission gases from a diesel engine and a coal-fired boiler. The porous tube dilutor could successfully measure the accumulation mode particles including relatively large particles more than $3{\mu}m$ without nuclei particles, while the ejector dilutor detected some condensable particles and could not detect large particles. The porous tube dilutor could successfully remove the already condensed water droplet particles generated by a humidifier in a $30m^3$ chamber.

• Journal of the Korean Vacuum Society
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• v.10 no.2
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• pp.275-281
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• 2001

We used the discrete-sectional model to analyze the particle growth by coagulation of particles in silane plasma reactor, considering the Gaussian distribution function for particle charges. The effects of process conditions such as monomer size and mass generation rate of monomers on particle growth in plasma reactor were analyzed theoretically/ Based on the Gaussian distribution function of particle charges, the large particles of more than 40 nm in size are almost found to be charged negatively, but some fractions of small, tiny particles are in neutral state or even charged positively. As the particle size and surface area increase with time by particle coagulation, the number of charges per particle increases with time. As the large particles are generated by particle coagulation, the particle size distribution become bimodal. The results of discrete-sectional model for the particle growth in silane plasma reactor were in close agreement with the experimental results by Shiratani et al. [3] for the same plasma conditions. We believe the model equations for the particle charge distribution and coagulation between particles can be applied to understand the nano-sized particle growth in plasma reactor.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.9-19
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• 2015

Experimental research on characteristics of particle-laden jet by using a coaxial injector was conducted in order to design fuel and oxidizer injectors of the supercavitation underwater vehicle. $1{\mu}m$ and $42{\mu}m$ particles was simultaneously injected to obtain particle and fluid velocity. Small particles($1{\mu}m$) and large particles represent fluid and fuel characteristics respectively. Small particles, which was processed using PIV algorithms, and one for the large particles processed using PTV algorithms. Fluid phase axial velocity increases according to particle loading ratio increases, and particles are located at the outside of the high vorticity region in a mixing layer of a coaxial injector.

• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.261-266
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• 1998

Since the particles are highly charged in process plasmas, the dynamics of the particles are concerned principally with the effect of the charging amount and polarity. In order to investigate the charging effect of the particles in the plasmas, the known sizes of the mono-dispersed particles with 0.05$\mu\textrm{m}$, 0.07$\mu\textrm{m}$, 0.1$\mu\textrm{m}$and 0.2$\mu\textrm{m}$ diameter are introduced into the DC air-plasmas. The characteristics of the charged particles are measured with a Faraday cup. Results show that the particle charging polarity depends on the concentrations and sizes of the particles and the condition of plasma generation, operating pressure, and power. It is also found that the number of charges per a particle is in the ranges of $10^3$~$ 10^5$.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.109-110
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• 2014

주사전자현미경(Scanning Electron Microscopy: SEM)은 고체상태에서 미세조직과 형상을 관찰하는 데에 가장 다양하게 쓰이는 분석기기로서 최근에 판매되고 있는 고분해능 SEM은 수 나노미터의 분해능을 가지고 있다. 그리고 SEM의 초점심도가 크기 때문에 3차원적인 영상의 관찰이 용이해서 곡면 혹은 울퉁불퉁한 표면의 영상을 육안으로 관찰하는 것처럼 보여준다. 활용도도 매우 다양해서 금속파면, 광물과 화석, 반도체 소자와 회로망의 품질검사, 고분자 및 유기물, 생체시료 nnnnnnnnn와 유가공 제품 등 모든 산업영역에 걸쳐 있다(Fig. 1). 입사된 전자빔이 시료의 원자와 탄성, 비탄성 충돌을 할 때 2차 전자(secondary electron)외에 후방산란전자(back scattered electron), X선, 음극형광 등이 발생하게 되는 이것을 통하여 topography (시료의 표면 형상), morphology(시료의 구성입자의 형상), composition(시료의 구성원소), crystallography (시료의 원자배열상태)등의 정보를 얻을 수 있다. SEM은 2차 전자를 이용하여 시료의 표면형상을 측정하고 그 외에는 SEM을 플랫폼으로 하여 EDS (Energy Dispersive X-ray Spectroscopy), WDS (Wave Dispersive X-ray Spectroscope), EPMA (Electron Probe X-ray Micro Analyzer), FIB (Focus Ion Beam), EBIC (Electron Beam Induced Current), EBSD (Electron Backscatter Diffraction), PBMS (Particle Beam Mass Spectrometer) 등의 많은 분석장치들이 SEM에 부가적으로 장착되어 다양한 시료의 측정이 이루어진다. 이 중 결정구조, 조성분석을 쉽고 효과적으로 할 수 있게 하는 X선 분석장치인 EDS를 SEM에 일체화시킨 장비와 EDS 및 PBMS를 SEM에 장착하여 반도체 공정 중 발생하는 나노입자의 형상, 성분, 크기분포를 측정하는 PCDS(Particle Characteristic Diagnosis System)에 대해 소개하고자 한다. - EDS와 통합된 SEM 시스템 기본적으로 SEM과 EDS는 상호보완적인 기능을 통하여 매우 밀접하게 사용되고 있으나 제조사와 기술적 근간의 차이로 인해 전혀 다른 방식으로 운영되고 있다. 일반적으로 SEM과 EDS는 별개의 시스템으로 스캔회로와 이미지 프로세싱 회로가 개별적으로 구현되어 있지만 로렌츠힘에 의해 발생하는 전자빔의 왜곡을 보정을 위해 EDS 시스템은 SEM 시스템과 연동되어 운영될 수 밖에 없다. 따라서, 각각의 시스템에서는 필요하지만 전체 시스템에서 보면 중복된 기능을 가지는 전자회로들이 존재하게 되고 이로 인해 SEM과 EDS에서 보는 시료의 이미지의 차이로 인한 측정오차가 발생한다(Fig. 2). EDS와 통합된 SEM 시스템은 중복된 기능인 스캔을 담당하는 scanning generation circuit과 이미지 프로세싱을 담당하는 FPGA circuit 및 응용프로그램을 SEM의 회로와 프로그램을 사용하게 함으로 SEM과 EDS가 보는 시료의 이미지가 정확히 일치함으로 이미지 캘리브레이션이 필요없고 측정오차가 제거된 EDS 측정이 가능하다. - PCDS 공정 중 발생하는 입자는 반도체 생산 수율에 가장 큰 영향을 끼치는 원인으로 파악되고 있으며, 생산수율을 저하시키는 원인 중 70% 가량이 이와 관련된 것으로 알려져 있다. 현재 반도체 공정 중이나 반도체 공정 장비에서 발생하는 입자는 제어가 되고 있지 않은 실정이며 대부분의 반도체 공정은 저압환경에서 이루어지기에 이 때 발생하는 입자를 제어하기 위해서는 저압환경에서 측정할 수 있는 측정시스템이 필요하다. 최근 국내에서는 CVD (Chemical Vapor Deposition) 시스템 내 파이프내벽에서의 오염입자 침착은 심각한 문제점으로 인식되고 있다(Fig. 3). PCDS (Particle Characteristic Diagnosis System)는 오염입자의 형상을 측정할 수 있는 SEM, 오염입자의 성분을 측정할 수 있는 EDS, 저압환경에서 기체에 포함된 입자를 빔 형태로 집속, 가속, 포화상태에 이르게 대전시켜 오염입자의 크기분포를 측정할 수 있는 PBMS가 일체화 되어 반도체 공정 중 발생하는 나노입자 대해 실시간으로 대처와 조치가 가능하게 한다.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.514-521
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• 2010

A new one-shot process was employed to fabricate proton exchange membranes (PEMs) over conventional solvent-casting process. Here, PEMs containing nano-dispersed silica nanoparticles were fabricated using one-shot process similar to the bulk-molding compounds (BMC). Different components such as reactive dispersant, urethane acrylate nonionmer (UAN), styrene, styrene sulfuric acid and silica nano particles were dissolved in a single solvent dimethyl sulfoxide (DMSO) followed by copolymerization within a mold in the presence of radical initiator. We have successfully studied the water-swelling and proton conductivity of obtained nanocomposite membranes which are strongly depended on the surface property of dispersed silica nano particles. In case of dispersion of hydrophilic silica nanoparticles, the nanocomposite membranes exhibited an increase in water-swelling and a decrease in methanol permeability with almost unchanged proton conductivity compared to neat polymeric membrane. The reverse observations were achieved for hydrophobic silica nanoparticles. Hence, hydrophilic and hydrophobic silica nanoparticles were effectively dispersed in hydrophilic and hydrophobic medium respectively. Hydrophobic silica nanoparticles dispersed in hydrophobic domains of PEMs largely suppressed swelling of hydrophilic domains by absorbing water without interrupting proton conduction occurred in hydrophilic membrane. Consequently, proton conductivity and water-swelling could be freely controlled by simply dispersing silica nanopartilces within the membrane.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.6
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• pp.706-712
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• 1999

PSD (particle size distribution) for 2,000 mg/$\ell$ natural loess in seawater showed normal distribution cure at 0 minute settling time, accompanying with very large particle distribution range with its mean particle diameter of 31.6 $\mu$m and coencient of variance of $72.6\%$, With elapsed time it showed that the PSD was rapidly changed from normal distribution cure to abnormal distribution curve, steepened the right-hand side of it and its coefficient of variance was getting increased because of rapid settling of large size particles, Cumulative weight distribution showed that 2,000 mg/$\ell$ natural loess in seawater was almost $100\%$ constituted of particles bigger than 20 $\mu$m in diameter. Ratio of $V_s/(D_{bm})^{1/2}$ for loess particles in seawater was increased with increase of particle size in geometrical progression. Almost all loess particles in seawater had Stokes settling velocity not less than 2,255 times of Brownian diffusion coefficient, There was almost to EDL (about 0.4 nm) around natural loess particles in seawater, Thus, there was always LVDW attractive force between loess particles approaching each other in seawater, and almost no EDL repulsive force. Loess particles were not always in the condition of easy floe formation. Concentration of natural loess in seawater increasing from 400 mg/$\ell$ to 10,000 mg/$\ell$, characteristics of the settling was changed from Type I settling (discrete settling) to Type II settling (flocculation settling). PVD (particle volume distribution) showed that natural loess particles in seawater were largely constituted of two types of particles, such as rapidly settling particles and suspended and dispersed particles for a long time. Amount of the latter was much less than that of the former.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.1
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• pp.119-125
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• 2018

The particle based computational fluid dynamics (CFD) method, which follow Lagrangian approach for fluid dynamics, fluid particle behavior by tracking all particle calculation physical quantities of each particle. According to basic concept of particle based CFD method, it is difficult to satisfy continuum theory and measure influences from neighboring particle. Article number density and weight function were used to solve aforementioned issue. Difficulties continuum mean simulate non-continuum particles such as solid including granular and sand. In this regard, the particle based CFD method modified solid particle problems by replacing viscous and surface tension forces friction and drag forces. In this paper, particle interaction model for solid particle friction model implemented to simulate solid particle problems. The broken dam problem, which is common to verify particle based CFD method, used fluid or solid particles. The angle of repose was observed in the simulation results the solid particle not fluid particle.