• Particle and aerosol research
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• v.19 no.4
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• pp.155-164
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• 2023

APS (Aerodynamic Particle Sizer) and OPC (Optical Particle Counter) have been widely used to real-time measurement of indoor and outdoor aerosols. The APS measures the size distribution based on an aerodynamic diameter, while the OPC uses optical diameter to measure the size distribution of aerosols. Since obtaining a size distribution based on aerodynamic diameter is important to understand aerosol characteristics, lots of researcher had been developed experimental equations which can convert optical diameter into aerodynamic diameter. However, previous studies have conducted repeated experiments on particles having a single diameter. In this study, an experimental method of converting optical diameter into aerodynamic diameter through a single experiment was presented. The collection efficiencies of an axial cyclone were measured using APS and OPC at the same time, and the correlation equation between aerodynamic diameter and optical diameter was driven through a theoretical model. Using the proposed method, the size distribution of NaCl particles measured by OPC showed a high correlation with the size distribution obtained by APS (0.93 of R-squared value). In the tests conducted on ISO A1, A2, and A4 test particles, the converted OPC size distribution tended to be similar to the APS size distribution, and for each of test particles (ISO A1, A2, and A4), the R-squared values for the APS particle size distribution were 0.75, 0.86, and 0.89, respectively.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.600-604
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• 2001

The relation between the aerodynamic diameter and some morphological parameters was studied for flame-generated aggregates. $SiO_{2}$ aggregates were generated from $SiCl_{4}$ in premixed methane/air flames. These aggregates were sampled and classified according to their aerodynamic diameter by a cascade impactor; moreover, computer program was developed and tested to find the equivalent area diameter and the fractal dimension of the aggregates. We calculated the parameters from the digitized images of the aggregate TEM micrographs. The aerodynamic diameters of the sampled aggregates were larger than $0.4{\mu}m$ in this experiment. In most cases, fractal dimension of their projection image was very close to 2.0 for these large aggregates. It was found that the equivalent area diameter of these aggregates was approximately three times larger than the Stokes' diameter of them.

• Journal of the Korean Society of Safety
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• v.11 no.2
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• pp.79-88
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• 1996

A hypothetical accident in the containment vessel of liquid metal reactor could cause a pressure, temperature rise, and a strong aerosol release. The computer codes relating to the modelization of these accident make it necessary to use various input parameter, among which is the dynamic shape factor of aerosols produced. Combustion experiments of sodium spray fire carried out in a closed vessel, which was vertical cylinder made of 1.2m in diameter and 1.8m hight with a volume of 1.7$m^3$. The results of theoretical analysis presented here was compared to data obtained from experiments. The experimental results were summarized as follows. 1) The aerodynamic diameter and geometric diameter of aerosols are decreasing with increasing of injection pressure and injection temperature of sodium 2) The dynamic shape factor of aerosol is proportional to the aerodynamic diameter for a given particle. 3) The correspondence between the aerodynamic diameter and geometric diameter can be as $D_{ae}=0.70 D_{ge}$. 4) Peak pressure rose with increase in pressure and temperature of injection sodium, being more sensitive to the injection pressure than the injection temperature.

• Particle and aerosol research
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• v.13 no.2
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• pp.53-63
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• 2017

As semiconductor process was highly integrated, particle contamination became a major issue. Because particle contamination is related with process yields directly, particles with a diameter larger than half pitch of gate should be controlled. PBMS (Particle beam mass spectrometry) is one of powerful nano particle measurement device. It can measure 5~500 nm particles at ~ 100 mtorr condition in real time by in-situ method. However its usage is restricted to research filed only, due to its big device volume and high price. Therefore aperture changeable aerodynamic lenses (ACALs) which can control particle focusing characteristics by changing its aperture diameter was proposed in this study. Unlike conventional aerodynamic lenses which changes particle focusing efficiency when operating condition is changed, ACALs can maintain particle focusing efficiency. Therefore, it can be used for a multi-monitoring system that connects one PBMS and several process chambers, which greatly improves the commercialization possibility of the PBMS. ACALs was designed based on Stokes number and evaluated by numerical method. Numerical analysis results showed aperture diameter changeable aerodynamic lenses can focus 5 to 100 nm standard particles at 0.1 to 10 torr upstream pressure.

• Journal of the Korean Society for Railway
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• v.13 no.1
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• pp.51-57
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• 2010

The aerodynamic drag of ultra high-speed train in evacuated tube have been calculated using computational fluid dynamics and the variation of aerodynamic drag for the change of major system parameter of tube-vehicle system such as the train speed, air density, and the tunnel diameter. The aerodynamic drag in the tube increases with increasing train speed, however, the ratio of drag increase in tube is larger than that on the open field, the V square rule. The aerodynamic drag decreases with increasing tunnel diameter and increasing air density, and the drag increasing for air density is almost linear just like that on open field. For some combination of the parameters, the trend of aerodynamic drag of train showed irregularity.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.7
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• pp.63-70
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• 2019

An electro-aerodynamic lens for improving the performance of virtual impactor has been proposed in this study. ANSYS FLUENT Release 16.1 was used for numerical analysis of virtual impactor with and without the electro-aerodynamic lens, used to collimate the incoming aerosol particles into a particle beam before injecting the particles into the virtual impactor. Particles supplied to the electro-aerodynamic lens were assumed to be highly charged. By using an aerodynamic lens before the virtual impactor, without any electrostatic effect, it was found that the cut-off diameter of the virtual impactor was reduced from $4.2{\mu}m$ to $0.68{\mu}m$ and that the fine particle contamination problem became more serious. However, by employing the combined electrostatic and aerodynamic effects, that is, by applying electric voltage potential to the electro-aerodynamic lens, the cut-off diameter was found to be further reduced to $0.45{\mu}m$ and the fine particle contamination was eliminated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1255-1266
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• 1998

Effects of a length-to-diameter ratio, L/D, on the three-dimensional flow and aerodynamic loss within an injection hole, which is normally oriented to the mainflow, have been investigated by using a straight five-hole probe. The length-to-diameter ratio of the injection hole is varied to be 0.5 and 2.0 for blowing ratios of 0.5, 1.0 and 2.0. Regardless of the blowing ratio, flows within the hole and at the jet exit are strongly affected by the length-to-diameter ratio. In the case of L/D=0.5, the inside flow is considerably influenced by the mainflow, and the exit flow variation is found to be the greatest. The aerodynamic loss in this case is usually attributed to jet -mainflow interactions. In the case of L/D=2.0, the flow separation and reattachment in the inlet region are completely separated from the complicated exit flow, and the aerodynamic-loss production is mainly due to the inlet flow separation.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.387-390
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• 2007

Recently the diameter of the 5MW wind turbine reaches 126m, and the tower height is nearly the same with the wind turbine diameter. The blade will experience periodic inflow oscillation due to blade rotation inside the ground shear flow region, that is, the inflow velocity is maximum at uppermost position and minimum at lowermost position. In this study we compare the aerodynamic data between two inflow conditions, i.e, uniform flow and normal wind profile. From the computed results all of the relative errors for oscillating amplitudes increased due to the ground shear flow effect. Especially My at hub and $F_x$, $M_y$, $M_z$ at LSS increased enormously. It turns out that the aerodynamic analysis including the ground shear flow effect must be considered for fatigue load analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.3
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• pp.346-359
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• 1998

The aerodynamic forces and wake structure of the non-rotating downstream circular cylinder, of which the uniform freestream flow is interfered with another spinning upstream cylinder having the same diameter that is located upstream in a line have been investigated experimentally. When the spin rate of the downstream cylinder defined as the ratio of tangential surface velocity of the spinning cylinder to the freestream velocity increases gradually from zero to 1.4, the change of surface pressure distribution, aerodynamic forces of the non-rotating downstream cylinder were measured in case of several distance ratios of 1.5, 3.0, and 4.5 defined as the ratio of distance between the centers of two cylinders to the diameter. The wake flow patterns behind the cylinder were also investigated in each case. From the present experiments, it has been found that the spin rate significantly influences the aerodynamic forces and near-wake flow phenomena of the downstream cylinder in such a way that the drag increases as the spin rate and distance ratio increase and the wake width increases as the distance ratio increases.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2277-2288
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• 2021

To regulate the safety protocols in nuclear facilities, radioactive aerosols have been extensively researched to understand their health impacts. However, most measured particle-size distributions remain at low resolutions, with the particle sizes ranging from nanometer to micrometer. This study combines the high-resolution detection of 500 size classes, ranging from 6 nm to 10 ㎛, for aerodynamic diameter distributions, with a regional lung deposition calculation. We applied the new approach to characterize particle-size distributions of aerosols generated during the plasma arc cutting of simulated non-radioactive steel alloy wastes. The high-resolution measured data were used to calculate the deposition ratios of the aerosols in different lung regions. The deposition ratios in the alveolar sacs contained the dominant particle sizes ranging from 0.01 to 0.1 ㎛. We determined the distribution of various metals using different vapor pressures of the alloying components and analyzed the uncertainties of lung deposition calculations using the low-resolution aerodynamic diameter data simultaneously. In high-resolution data, the changes in aerosols that can penetrate the blood system were better captured, correcting their potential risks by a maximum of 42%. The combined calculations can aid the enhancement of high-resolution measuring equipment to effectively manage radiation safety in nuclear facilities.