• Journal of Korean Society for Atmospheric Environment
• /
• v.19 no.1
• /
• pp.67-76
• /
• 2003

Recently consideration of health and interest on bio aerosols have been growing steadily. In this study, inertial impactor, which can be used to collect airborne particles and bio aerosols, was newly devised for real-time observation on the particles collected on impaction plate. and named Visual Impactor. Flow field and particle trajectory in the space between nozzle and impaction plate was analyzed numerically, and the collection effciencies were calculated. Calibration and performance evaluation of the Visual Impactor was conducted with polydisperse aerosols generated from 0.1％ sodium chloride solution. Cut-off diameter from numerical simulation was in good agreement with that from experimental results. Because of particle bounce and particle deposition on nozzle tip due to short jet-to-plate distance, the collection efficiencies from numerical and experimental analyses were different slightly. Visual Impactor was used to collect airborne particles, and the features of collected particles could be seen in real-time. Airborne particles in different weather conditions (fine, cloudy, and rainy) were sampled and compared one another The features of collected airborne particles were dependent strongly upon relative humidity. In addition, with hours elapsing, shapes and colors of collected particles were changed by evaporation and surface tension, etc.

• Journal of Korean Society for Atmospheric Environment
• /
• v.16 no.5
• /
• pp.445-451
• /
• 2000

To estimate dry deposition flux of 12 elements in aerosols, aerosol particles were sampled by a low-pressure impactor(LPI) and a dust jar. The concentrations of 12 elements in aerosol particle and dry deposition were analyzed by a PIXE analysis using as a 2.0 MeV-proton beam. The mean dry deposition velocities of 12 elements were estimated by ranges of 0.74∼2.62 cm/sec. The results showed that the highest value was 3.26 cm/sec for Ca and the lowest value 0.74 cm/sec for Fe. The dry deposition flux for elements was calculated as a function of particle size by 1-step method and 12-step method. In this work, dry deposition velocities were computed with the two existing models; the coarse-particle fraction(4∼30 mm diameter) using the dry deposition velocity model of the Noll and Fang(1998) and the fine-particle fraction (0.05∼4mm diameter) using the Shemel and Hodgson(1980) model. The ratios of the mean calculated/measured fluxes were 3.59 for 1-step method and 0.60 for 12-step method respectively.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1874-1879
• /
• 2008

It is not easy to detect nano-sized airborne particles (< 100 nm in diameter) in air. Therefore, the condensation of the nanoparticles alongside of the size-classification is needed for their detection. This paper proposes a hybrid (aerodynamic+electrical) particle classification and condensation device using a micro virtual impactor (${\mu}VI$). The ${\mu}VI$ can classify the nanoparticles according to their size and condense the number concentration of nanoparticles interested. Firstly, the classification efficiency of the ${\mu}VI$ was measured for the particles, polystyrene latex (PSL), ranging from 80 to 250 nm in diameter. Secondly, the nanoparticles, NaCl of 50 nm in diameter, were condensed by 4 times higher. In consequence, the output signal was amplified by 4 times (before condensation: 4 fA, after condensation: 16 fA). It is expected that the proposed device will facilitate the detection of nanoparticles.

• Journal of Korean Society for Atmospheric Environment
• /
• v.17 no.6
• /
• pp.441-450
• /
• 2001

A three stage impactor with the cutoff diameters of 1, 2.5, and 10$\mu\textrm{m}$ in aerodynamic diameter was developed and tested. The gravimetric method and the particle counting method were utilized to evaluate the collection performance of each stage. A vibrating orifice aerosol generator was employed to generate monodisperse test aerosols larger that 2$\mu\textrm{m}$ in diameter. Polystyrene latex (PSL) particles smaller than 2$\mu\textrm{m}$ in diameter were generated by an atomizer and the particle number concentration was measured by an Aerodynamic Particle Sizer Spectrometer. The experimental cutoff diameters obtained from the particle collection efficiency curves are in good agreement with the designed values. The square roots of Stokes number at 50% collection efficiency for stage 1, 2, and 3 are 0.42, 0.48, and 0.45, respectively. Effects of the particle bounce and the impaction plate on the collection efficiency were investigated. The collection efficiency curves including effect of the particle bounce were also compared with those of the MOUDI cascade impactor.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.2
• /
• pp.64-69
• /
• 2012

Head injury is one of the most common cause of deaths in car-to-pedestrian collisions. To reduce the severity of such injuries, many international safety committees have performed headform impact test for pedestrian protection. In this paper, an adult headform impactor model is developed based on the finite element (FE) method and validated through the numerical simulation. The skin material of headform impactor is known as polyvinyl chloride skin (PVC) and its material was assumed as viscoelastic. The viscoelastic parameters of headform skin are identified by a series of trial and error methods. The new developed FE adult headform impactor is verified by the drop test and FE JARI adult headform impactor provided by Madymo program.

• Particle and aerosol research
• /
• v.15 no.3
• /
• pp.115-126
• /
• 2019

In this study, a serial methodology is presented for estimating the effective density of ambient sub-micron aerosol employing lab-made 1 stage low-pressure impactor of Hyun et al. (2015) and SMPS (Scanning Mobility Particle Sizer) together. The effective density from this methodology (Impactor+SMPS) was compared with another methodology (BAM+SMPS) for estimating the effective density employing BAM (Beta-Attenuation Monitor) and SMPS. As a result, the effective density obtained with impactor+SMPS ranged from $0.42g/cm^3$ to $2.36g/cm^3$, while the effective density obtained with BAM+SMPS ranged from $1.01g/cm^3$ to $1.72g/cm^3$. The difference between these results might be caused by the particle loss in the impactor.

• Journal of Environmental Science International
• /
• v.24 no.5
• /
• pp.679-687
• /
• 2015

Atmospheric aerosol particles were investigated at GNTECH university in Jinju city. Samples were collected using the Nanosampler period from January to December 2014. The Nanosampler is a 6 stage cascade impactor(1 stage : > $10{\mu}m$, 2 stage : $2.5{\sim}10{\mu}m$, 3 stage : $1.0{\sim}2.5{\mu}m$, 4 stage : $0.5{\sim}10{\mu}m$, 5 stage : $0.1{\sim}0.5{\mu}m$, back-up : < $0.1{\mu}m$) with the stages having 50% cut-off ranging from 0.1 to $10{\mu}m$ in aerodynamic diameter. The mass size distribution of Atmospheric aerosol particles was unimodal with peak at $1.0{\sim}2.5{\mu}m$ or $0.5{\sim}1.0{\mu}m$. The annual average concentrations of TSP, $PM_{10}$, $PM_{2.5}$, $PM_1$, $PM_{0.5}$ and $PM_{0.1}$ were $44.0{\mu}g/m^3$, $40.3{\mu}g/m^3$, $31.4{\mu}g/m^3$, $18.0{\mu}g/m^3$, $8.0{\mu}g/m^3$, $3.0{\mu}g/m^3$, respectively. On average $PM_{10}$, $PM_{2.5}$, $PM_1$, $PM_{0.5}$ and $PM_{0.1}$ make up 0.91, 0.70, 0.41, 0.19 and 0.07 of TSP, respectively. The annual average of $PM_{2.5}/PM_{10}$ ratio was 0.77.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.41 no.4
• /
• pp.221-228
• /
• 2017

We proposed a novel method to remove PM2.5 dusts without HEPA filters aiming at applications in kitchens or enclosed work spaces generating PM2.5 at high concentrations. Many workers are exposed to PM2.5 owing to lack of air purification because the high replacement costs of HEPA filters make their application impractical. A key idea is to use the condensational growth of nanoparticles. Once particles grow to the size of a few micrometers, it is much easier to remove them because of their increased inertia. We developed and tested a prototype consisting of an air saturator (equipped with water spray nozzles), a condenser in which humid air was cooled down to make the particles grow, and a multi-impactor assembly for collecting the grown particles.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.10
• /
• pp.5963-5967
• /
• 2014

Reducing the impact of collisions of cars is a major issue for reducing the injury and death of passengers. According to the statistical data of the Road Traffic Authority, the deaths from side collision accidents caused by the collision of passenger cars is greater than the deaths from head-on collision accidents. To accommodate this, vehicle designers have added a reinforcing material called the impact frame and impact beam on the inside of the door. Many experiments are needed to develop the door impact beam. These reinforcements to develop a collision experiment is essential. Collision experiments are costly and time consuming. This study used a drop Impactor to obtain the impulse and a strain experimental device was developed for this purpose. The economic costs were reduced and the ideal experiment device configuration was determined. A comparison of the experimental results with numerical value analysis revealed $3.5{\tiimes}10-3sec$ strain ranging from $3.49{\tiimes}10-3$ to $3.99{\tiimes}10-3$.

• Fire Science and Engineering
• /
• v.31 no.6
• /
• pp.8-15
• /
• 2017

Most fire victims succumb to smoke inhalation, and fire smoke toxicity from interior materials is increasing with increased use of plastics. Large amounts of hazardous effects of smoke are related to deposition of smoke particles in respiratory tracts, and deposition characteristics are influenced by size distribution of particles. Thus, it is essential to know the size distribution of smoke particles from plastics for hazard analysis of fire smoke. In a recent study, it has been shown that size distributions of smoke particles from PP are different from wood in many aspects. In order to know whether other plastics show the same characteristics as PP, size distributions of smoke particles from four plastic materials (LDPE, PA66, PMMA, and PVC) were measured in real time under each fire type with various temperature and oxygen supply. In this study, smoke particles from different plastics were generated uniformly by using steady-state tube furnace method provided in ISO/TS 19700. Their size distributions were measured by using an electrical low pressure impactor (ELPI). Results of measurements showed that size distributions of smoke particles from these four plastic materials were similar to those from PP in many aspects. However, they were distinctively different from those of wood.