• Particle and aerosol research
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• v.15 no.4
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• pp.149-157
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• 2019

Infiltration characteristics of airborne particulate matter had been investigated in real-life for about 90 days over 2 years in a Korean apartment building where a 3-person household had lived and the exclusive private area was 84.9 ㎡. Airtightness was measured by fan depressurization, and the ACH₅₀ was 2.41 times per hour. In and outdoor particle concentrations were measured by optical particle counters. Infiltration factors and filtration efficiencies of the house, which reflect the removal of outdoor particles penetrating building envelope and the deposition inside a building, were obtained from data screened based on an empirical evaluation process. Infiltration factor of fine particles showed a range from about 42% at 0.4 m/s of wind speed to 72% at 4.2 m/s of wind speed with closed windows and doors. Filtration efficiency was like a MERV 13 grade filter with an open window outside at a balcony at low outdoor wind speed under 1 m/s. The grade decreased to MERV 11 by opening another outside window at the other balcony. Filtration efficiencies decreased as much as 29% in average at a range of 0.3~2.5 ㎛.

• Korean Journal of Materials Research
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• v.29 no.2
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• pp.73-78
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• 2019

Lead free $(Ba_{0.7}Ca_{0.3})TiO_3$ thick films with nano-sized grains are prepared using an aerosol deposition (AD) method at room temperature. The crystallinity of the AD thick films is enhanced by a post annealing process. Contrary to the sharp phase transition of bulk ceramics that has been reported, AD films show broad phase transition behaviors due to the nano-sized grains. The polarization-electric hysteresis loop of annealed AD film shows ferroelectric behaviors. With an increase in annealing temperature, the saturation polarization increases because of an increase in crystallinity. However, the remnant polarization and cohesive field are not affected by the annealing temperature. BCT AD thick films annealed at $700^{\circ}C/2h$ have an energy density of $1.84J/cm^3$ and a charge-discharge efficiency of 69.9 %, which is much higher than those of bulk ceramic with the same composition. The higher energy storage properties are likely due to the increase in the breakdown field from a large number of grain boundaries of nano-sized grains.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.58.2-58.2
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• 2010

This paper deals with the simulation of solid particle coating technology via supersonic nozzle in vacuum environment to devote as an aerosol-deposition device. In order to improve efficiencies of nozzle and coating process, effects of shockwave, nozzle geometry, and substrate location were studied computationally under a fixed chamber pressure of 0.01316 bar which is nearly vacuous. Shockwave is the important factor affect to entire flow because shockwave in the jet flow dissipates the kinetic energy of the flow in the supersonic condition. Results show that various nozzle geometries have significant effect on the supersonic flow and we know that the supersonic nozzle should be optimized to minimize the loss of the flow. Another parameter, the distance between substrate and nozzle tip, shows little effect in this study.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.E3
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• pp.87-94
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• 2005

Wet scavenging by rain drops is a most important removal process of air pollutants. In order to study the scavenging mechanisms of aerosol particles, the characteristics of chemical components in the rain water were examined as a function of the amount of rainfall. Rain water were collected continuously and separated into the soluble and insoluble components. The elemental concentrations in both components were determined by a PIXE analysis. The physical and chemical characteristics of atmospheric aerosols during the rainfall events were measured simultaneously. The elemental concentrations in rain water decreased substantially just after rain started and then gradually declined in subsequential rain fall exceeding 1.0 mm. The large particles were scavenged more easily than the fine particles. Fe, Ti and Si in rain water were in high insoluble state. Contrarily, almost whole of S was dissolved in rain water.

• Korean Journal of Materials Research
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• v.31 no.10
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• pp.546-551
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• 2021

To improve ferroelectric properties of PZT, many studies have attempted to fabricate dense PZT films. The AD process has an advantage for forming dense ceramic films at room temperature without any additional heat treatment in low vacuum. Thick films coated by AD have a higher dielectric breakdown strength due to their higher density than those coated using conventional methods. To improve the breakdown strength, glass (SiO₂-Al₂O₃-Y₂O₃, SAY) is mixed with PZT powder at various volume ratios (PZT-xSAY, x = 0, 5, 10 vol%) and coating films are produced on silicon wafers by AD method. Depending on the ratio of PZT to glass, dielectric breakdown strength and energy storage efficiency characteristics change. Mechanical impact in the AD process makes the SAY glass more viscous and fills the film densely. Compared to pure PZT film, PZT-SAY film shows an 87.5 % increase in breakdown strength and a 35.3 % increase in energy storage efficiency.

• Progress in Superconductivity
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• v.8 no.1
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• pp.71-74
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• 2006

High $J_c$ over 1 $MA/cm^2$ YBCO film has been successfully prepared using nitrate precursors by spray pyrolysis method. Aerosol drolpets generated using a concentric spray nozzle were directly sprayed on a $LaAlO_3$(100) single crystal substrate. The cation ratio of precursor solution was Y:Ba:Cu=1:2.65:1.35. The distance between nozzle and substrate was 15 cm. Deposition temperature was ranging from $750^{\circ}C\;to\;800^{\circ}C$. Deposition pressure was 100 Torr, and oxygen partial pressure was varied from 10 Torr to 50 Torr. The microstructure, phase formation, texture development and superconducting properties of deposited films were largely changed with oxygen partial pressure. Deposited films showed a texture with(001) planes parallel to substrate plane. High quality film was obtained when film was deposited at $760^{\circ}C$ with an oxygen partial pressure of 30 Torr. The critical current density($J_c$) of the YBCO film was 1.75 $MA/cm^2$ at 77 K and self-field.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.11
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• pp.86-91
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• 2021

Recently, functional clothes that can reduce deposition and/or penetration of fine dust have been developed. However, there are no methods to quantitatively evaluate the performance of these clothes. In this study, we developed a method to contaminate a fabric using fine dust and established an approach to quantitatively assess the degree of particle contamination on the fabric surface. Silicate powder was chosen as the particle to simulate fine dust because silicate particles are fluorescent under UV light; therefore, they can be distinguished from any color of non-fluorescent fabric surface. A camera with a high-resolution lens system was used to scan the surface of the contaminated fabric surface, and the degree of particle contamination of the fabric surface was analyzed in terms of the pixels corresponding to the area of the fabric surface contaminated by silicate particles. Finished or unfinished nylon fabrics as well as cotton fabrics were contaminated with silicate particles, and their surfaces were scanned using the established camera. The proposed assessment method was found to be useful for quantitatively comparing the degree of particle contamination of the fabrics.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.22-27
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• 2017

$TiO_2$ films, thickness of $1{\sim}30{\mu}m$ were deposited on glass substrate at room temperature by room temperature granule spray in vacuum. The starting powder was calcinated at $600^{\circ}C$ for 4 h using $Al_2O_3$ crucible in the furnace. The particle size of the $TiO_2$, $1.5{\mu}m$ was measured by a particle size analyzer. The effect of different process parameters such as number of pass, gas flow rate and feeder voltage was studied. As the number of passes increased, the film thickness increased proportionally due to adequate kinetic energy conserved. The effect of three different flow rates (i.e. 15, 25, and 35 LPM) on deposited film was investigated. As gas flow rate increased, the film thickness increased up to 25 LPM and then decreased. Higher feeder voltage with low flow rate of 15 LPM resulted in unsufficient coating thickness due to insufficient kinetic energy. Microstructure of $TiO_2$ films was investigated by scanning electron microscope and high resolution tramission electron microscope.

• Tuberculosis and Respiratory Diseases
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• v.44 no.1
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• pp.124-135
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• 1997

Background : Diffuse panbronchiolitis(DPB) is a disease characterized clinically by chronic cough, expectoration and dyspnea; and histologically by chronic inflammation localized mainly in the region of the respiratory bronchiole. It is prevalent in Japanese, but is known to be rare in Americans and Europians. Only a few cases in Chinese, Italians, North Americans and Koreans have been reported. It is diagnosed by characteristic clinical, radiological and pathologic features. High-resolution CT(HRCT) is known to be valuable in the study of the disease process and response to therapy in DPB. To our knowledge, there has been no correlation of its appearance on HRCT with the severity of the disease process, and radioaerosol scan(RAS) of the lung has not previously been used for the diagnosis of DPB. Method : During recent two years we have found 12 cases of DPB in Kangnam St. Mary's Hospital, Catholic University Medical College. We analysed the clinical characteristics, compared HRCT classifications with clinical stages of DPB, and determined characteristic RAS manifestations of DPB. Results : 1. The ages ranged from 31 to 83 years old(mean 54.5 years old), and male female ratio was 4:8. 75%(9/12) of patients had paranasal sinusitis, and only one patient was a smoker. 2. The patients were assigned to one of three clinical stages of DPB on the basis of clinical findings, sputum bacterology and arterial blood gas analysis. of 12 cases, 5 were in the first stage, 4 were in the second stage, and 3 were in the third stage. In most of the patients, pulmonary function tests showed marked obstructive and slight restrictive impairments. Sputum culture yielded P.aeruginosa in 3 cases of our 12 cases, K.pneumoniae in 2 cases, H.influenzae in 2 cases, and S.aureus in 2 cases. 3. Of 12 patients, none had stage I characteristics as classified on HRCT scans, 4 had slage II findings, 5 had stage III findings, and 3 had stage IV characteristics. 4. We peformed RAS in 7 of 12 patients With DPB. In 71.4% (5/7) of the patients, RAS showed mottled aerosol deposits characteristically in the transitional and intermediary airways with peripheral airspace defects, which contrasted sharply with central aerosol deposition of COPD. 5. There were significant correlations between HRCT stages and clinical stages(r= 0.614, P < 0.05), between HRCT types and Pa02(r= -0.614, P < 0.05), and between HRCT types and ESR(r= 0.618, P < 0.01). Conclusion : The HRCT classifications correspond well to the clinical stage. Therfore in the examination of patients with DPB, HRCT is useful in the evaluation of both the location and severity of the lesions. Also, RAS apears to be a convenient, noninvasive and useful diagnostic method of DPB.