• Journal of Korean Society for Atmospheric Environment
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• v.19 no.5
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• pp.515-528
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• 2003

The characteristics of one year observation aerosol data in Seoul, 200 I was studied using an OPC (Optical Particle Counter). The size resolved aerosol number concentrations of 0.3 ∼ 25 11m were measured. The results were compared with PM$_{10}$ mass concentration data under various meteorological conditions including dust and precipitation events. For fine particles whose diameter is less than 2.23 ${\mu}{\textrm}{m}$, the number concentration increases in the early morning which is considered due to transportation. while the coarse mode particles increase during daytime. This increase can be explained as local sources and human activities near sampling site. Hourly averaged data show that there exists diurnal variation. Generally, PM$_{10}$ data showed a similar tendency with OPC data. The size resolved OPC data showed that the particles of 0.5 ∼ 3.67 ${\mu}{\textrm}{m}$ are positively correlated with PM$_{10}$ data. The accumulated volume fraction of size resolved aerosol concentration in 0.5 ∼ 10 ${\mu}{\textrm}{m}$ showed that 0.5 ∼ 2.23 ${\mu}{\textrm}{m}$ particles occupied 59.2% of total aerosol volume of 0.5 ∼ 10 ${\mu}{\textrm}{m}$./TEX>.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.3 s.22
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• pp.47-56
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• 2006

With the aim to develop the monitoring technology on background atmosphere and climate change over Korean Peninsula, observations and studies on chemical, physical and optical properties of the atmospheric aerosols are made. Aerosol number concentration are measured with Optical Particle Counter from 2001 to 2003 at Gosan for 8 size intervals from 0.3 to $25{\mu}m$ diameter range. For the seasonal variation, the number concentration of coarse particles in spring at Gosan was higher than other seasons due to the influence of sand storm in spring. There is no significant correlations between fine particles ($0.3{\sim}0.5{\mu}m$) and meteorological parameters, such as relative humidity, wind speed and visual range, while the correlation between the number concentration of small particles ($0.5{\sim}2.23{\mu}m$) and relative humidity showed a positive value. This trend was inversed for the case of wind speed: aerosol number concentration showed a small decreasing tendency with increasing wind speed for small particles but the high wind speed in winter season increased coarse particle concentration. Finally, Particles most efficient in light extinction were found to be at the size of about $0.5{\sim}1{\mu}m$.

• International Journal of Naval Architecture and Ocean Engineering
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• v.4 no.4
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• pp.403-411
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• 2012

This study presents the nano-sized particle emission characteristics from a small turbocharged common rail diesel engine applicable to prime and auxiliary machines on marine vessels. The experiments were conducted under dynamic engine operating conditions, such as steady-state, cold start, and transient conditions. The particle number and size distributions were analyzed with a high resolution PM analyzer. The diesel oxidation catalyst (DOC) had an insignificant effect on the reduction in particle number, but particle number emissions were drastically reduced by 3 to 4 orders of magnitude downstream of the diesel particulate filter (DPF) at various steady conditions. Under high speed and load conditions, the particle filtering efficiency was decreased by the partial combustion of trapped particles inside the DPF because of the high exhaust temperature caused by the increased particle number concentration. Retarded fuel injection timing and higher EGR rates led to increased particle number emissions. As the temperature inside the DPF increased from $25^{\circ}C$ to $300^{\circ}C$, the peak particle number level was reduced by 70% compared to cold start conditions. High levels of nucleation mode particle generation were found in the deceleration phases during the transient tests.

• 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 environmental and Sanitary engineering
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• v.17 no.2
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• pp.11-17
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• 2002

Diesel particulate matter (DPM) is known to be one of the major harmful emissions produced by diesel engines. The majority of diesel particles are in the range of smaller than $I{\mu}\textrm{m}$. Because of their tiny volume, ultrafine diesel particles contribute very little to the total mass concentration which is currently regulated for automobile emissions. Diesel particles are known to have deleterious effects upon human health because they penetrate human respiratory tract and have negative effects on the health. The measurement of the number distribution of nanometer size particles (nanoparticles) in the diesel exhaust emission is important in order to evaluate their environmental and health impact, and to develop new types of diesel particulate filters. In this study, we directly sampled particulate matters emitted from a diesel truck mounted on the chassis dynamometer by a flow separator and dilution system, and measured the nanoparticles using two types of differential mobility analyzers combined with a Faraday cup electrometer (FCE) and a condensation particle counter (CPC). The particle size distributions were analyzed by changing engine operation condition, i.e. ratio of engine loading. The total number concentration of particles were increased with the engine loading ratio and the nanoparticles (less than 50nm) were affected by hydrocarbon (HC) concentration in the diesel exhaust.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.4
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• pp.313-320
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• 2010

Carbon cloth was impregnated into PTFE emulsion. PTFE is a fluoropolymer used as a coating material in various fields due to its hydrophobicity and excellent mechanical properties. In this study, PTFE emulsion was prepared different particle size of 5~500 nm and $3{\sim}5{\mu}m$. FE-SEM and FT-IR spectroscopy were used microscopic observation and investigation of chemical structure change after PTFE coating. Mass variations, gas permeability and water contact angles were analyzed to determine a GDL performance of PTFE coated carbon cloth. PTFE coated carbon cloth show different mass increase according as PTFE concentration and the number of coating times. Water contact angle of PTFE coated carbon cloth was not effected by size of PTFE particle and the number of coating time; meanwhile, gas permeability was rapidly changed at carbon cloth coated by emulsion with size of $3{\sim}5{\mu}m$ PTFE particle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1062-1068
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• 2002

In our previous study, it was proven that the mean size and the total number concentration of carbon soot particles emitted from a $C_2$H$_4$ normal diffusion flame decreased when a DC corona was discharged to pin-pin electrodes. In this work the effect of AC corona discharge on soot emission was investigated and compared with that of DC corona discharge. For the pin-pin electrodes the size of soot particles and the number concentration decreased by the AC voltage. There were only slight changes in size distribution with frequencies, while the magnitude of applied voltage was constant. When the electric field was applied to plate-plate electrodes, the size and the number concentration also decreased with the applied AC voltages. For applied voltages above 2kV the effect of frequency increase on the soot emission was effective.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.10
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• pp.1359-1367
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• 2000

In-situ particle monitors(ISPMs) are widely used for monitoring contaminant particles in vacuum-based semiconductor manufacturing equipment. In the present research, the performance of a Particle Measuring Systems(PMS) Vaculaz-2 ISPM at low pressures has been studied. We generated the uniform sized methylene blue particle beams using three identical aerodynamic lenses in the center of the vacuum line, and measured the detection efficiency of the ISPM. The effects of particle size, particle concentration, mass flow rate, system pressure, and arrangement of aerodynamic lenses on the detection efficiency of the ISPM were examined. Results show that the detection efficiency of the ISPM greatly depends on the mass flow rate, and the particle Stokes number. We also found that the optimum Stokes number ranges from 0.4 to 1.9 for the experimental conditions.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.6
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• pp.757-765
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• 1999

Lagrangian particle dispersion model(LPDM) is an effective tool to calculate the dispersion from a point source since it dose not induce numerical diffusion errors in solving the pollutant dispersion equation. Fictitious particles are released to the atmosphere from the emission source and they are then transported by the mean velocity and diffused by the turbulent eddy motion in the LPDM. The concentration distribution from the dispersed particles in the calculation domain are finally estimated by applying a particle count method or a Gaussian kernel method. The two methods for calculating concentration profiles were compared each other and tested against the analytic solution and the tracer experiment to find the strength and weakness of each method and to choose computationally time saving method for the LPDM. The calculated concentrations from the particle count method was heavily dependent on the number of the particles released at the emission source. It requires lots fo particle emission to reach the converged concentration field. And resulting concentrations were also dependent on the size of numerical grid. The concentration field by the Gaussian kernel method, however, converged with a low particle emission rate at the source and was in good agreement with the analytic solution and the tracer experiment. The results showed that Gaussian kernel method was more effective method to calculate the concentrations in the LPDM.

• Atmosphere
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• v.15 no.3
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• pp.149-153
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• 2005

A balloon-borne Optical Particle Counter (hereafter "OPC Sonde"), which was developed by the atmospheric research group of Nagoya University, is used for getting the information of vertical profile of particle size and concentration in Anmyeon ($36^{\circ}32^{\prime}N$ $126^{\circ}19^{\prime}E$) on 18 March 2005. A range of five different particle sizes is shown in the vertical profile of aerosol number density estimated from the OPC Sonde. It was found that small size particles have vertically larger aerosol number density than relatively big ones. For all size ranges the vertical aerosol number density shows a decreased pattern as the altitude becomes higher. The aerosol number density of $0.3{\sim}0.5{\mu}m$, $0.5{\sim}0.8{\mu}m$, $0.8{\sim}1.2{\mu}m$ size ranges at the 10km height, which is the tropopause approximately, are $1,000,000ea/m^3$, $100,000ea/m^3$, $10,000ea/m^3$ respectively. The data of OPC Sonde are also compared with the data of PM10 $\beta$-ray) and Micro Pulse Lidar which are operating at Korea Global Atmosphere Watch Observatory in Anmyeon.