• Korean Journal of Materials Research
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• v.30 no.5
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• pp.223-230
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• 2020

As a case study on aspect ratio behavior, Kaolin, zeolite, TiO₂, pozzolan and diatomaceous earth minerals are investigated using wet milling with 0.3 mm media. The grinding process using small media of 0.3 pai is suitable for current work processing applications. Primary particles with average particle size distribution D₅₀, ~6 ㎛ are shifted to submicron size, D₅₀ ~0.6 ㎛ after grinding. Grinding of particles is characterized by various size parameters such as sphericity as geometric shape, equivalent diameter, and average particle size distribution. Herein, we systematically provide an overview of factors affecting the primary particle size reduction. Energy consumption for grinding is determined using classical grinding laws, including Rittinger's and Kick's laws. Submicron size is obtained at maximum frictional shear stress. Alterations in properties of wettability, heat resistance, thermal conductivity, and adhesion increase with increasing particle surface area. In the comparison of the aspect ratio of the submicron powder, the air heat conductivity and the total heat release amount increase 68 % and 2 times, respectively.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.471-474
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• 2006

The Mixer is apparatus that help precipitation or an inhomogeneous distribution of various phases to be mixed and that user makes necessary material mixing one or the other. Mainly the mixer which is used from chemical and food industry is very important system in engineering that mixes the material. The inside flow of the mixer under the actual states which put a basis in flow of the fluid is formed rotation of the impeller. The inside flow of impeller will be caused by various reasons change with shape of impeller, number of rotation, mixing material and flow pattern of free surface etc. Also mixer study depended in single-phase flow and experimental research. So the numerical analysis of flow mixing solid-fluid particle is simulated. It is become known, that the case where agitator inside working fluid includes the solid particle the sinkage reverse which the solid particle has decreases an agitation efficiency. From the research which it sees the hazard solid which examines the effect where the change of the sinkage territory which it follows agitation number of revolution and diameter of the particle goes mad to an agitator inside flow distribution - numerical analysis the inside flow distribution of liquid state with Eulerian Two-Phase Method.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.5
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• pp.345-353
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• 2002

A study of polydispersed aerosol dynamics by Electrostatic Precipitator (ESP) was carried out. The log-normal particle size distribution was assumed and moment method was considered. In order to apply moment method in Deutsch-Anderson equation, Cunningham slip correction factor and Cochet's charge equation were simplified for certain range of particle size. The three parameters, which explain the particle size distribution, such as total number concentration, geometric mean diameter, and geometric standard deviation were considered to derive the analytic solution. The obtained solution was compared with available numerical results (Bai et al., 1995). The comparison of the numerical and analytic results showed a good agreement.

• Journal of ILASS-Korea
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• v.6 no.2
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• pp.22-28
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• 2001

Recently, many researches have been performed to improve the combustion and emission in a D.I.Diesel engine. Especially reduction of the soot formation in the combustion chamber is the essential to acquire the improvement of the emission performance. This emission of the diesel combustion is effected by the characteristics of air-fuel mixing. Therefore, the optical measurement technique such as LII and LIS were established in order to visualize the distribution of the soot and analyze the particle including spray in the combustion chamber. In this study, we developed the algorithm for calculating relative diameter and density of particle and applied this method to measure stimultaneously the distribution of soot and spray in a D.I. diesel engine. From this experiment we found that the soot is existed in the rich region of spray and generated caused by incapable air fuel mixture.

• Analytical Science and Technology
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• v.34 no.2
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• pp.87-98
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• 2021

In this study, we developed the nanoparticle multi-generator by 3D printer fusion deposition modeling (FDM) method that can reliably generate and deliver nanoparticles at a constant concentration for inhalation risk assessment. A white ABS filament was used as the test material, and SMPS was used for concentration analysis such as particle size and particle distribution. In the case of particle size, the particle size was divided by 100 nm or less and 100 to 1,000 nm, and the number of particles concentration, mass concentration, median diameter of particles, geometric average particle diameter, etc were measured. The occurrence conditions were the extruder temperature, the extruding speed of the nozzle, and the air flow rate, and experiments were conducted according to the change of conditions including the manufacturer's standard conditions. In addition, the utility of inhalation risk assessment was reviewed through a stability maintenance experiment for 6 h. As a result of the experiment, the size of the nanoparticles increased as the discharger temperature increased, as the discharge speed of the nozzle increased, and as the air flow rate decreased. Also, a constant pattern was shown according to the conditions. Even when particles were generated for a long time (6 h), the concentration was kept constant without significant deviation. The distribution of the particles was approximately 80 % for particles of 60 nm to 260 nm, 1.7 % for 1 ㎛ or larger, 0.908 mg/㎥ for the mass concentration, 111 nm for MMAD and 2.10 for GSD. Most of the ABS particles were circular with a size of less than 10 nm, and these circular particles were aggregated to form a cluster of grape with a size of several tens to several hundred nm.

• Particle and aerosol research
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• v.18 no.4
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• pp.129-136
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• 2022

The line width of circuits in semiconductor devices continues to decrease down to a few nanometers. Since nanoparticles attached to the patterned wafer surface may cause malfunction of the devices, it is crucial to remove the contaminant nanoparticles. Physical cleaning that utilizes momentum of liquid for detaching solid nanoparticles has recently been tested in place of the conventional chemical method. Dropwise impaction has been employed to increase the removal efficiency with expectation of more efficient momentum exchange. To date, most of relevant studies have been focused on drop spreading behavior on a horizontal surface in terms of maximum spreading diameters and average spreading velocity of drop. More important is the local liquid velocity at the position of nanoparticle, very near the surface, rather than the vertical average value. In addition, there are very scarce existing studies dealing with microdroplet impaction that may be desirable for minimizing pattern demage of the wafer. In this study, we investigated the local velocity distribution in spreading liquid film under various impaction conditions through the CFD simulation. Combining the numerical results with the particle removal model, we estimated an effective cleaning diameter (ECD), which is a measure of the particle removal capacity of a single drop, and presented the predicted ECD data as a function of droplet's velocity and diameter particularly when the droplets are microns in diameter.

• Journal of the Korean Society of Safety
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• v.11 no.2
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• pp.96-101
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• 1996

The effects of coal type and mixing fraction of coal on attrition and elutriation were studied in a 15. 5cm diameter fluidized bed coal combustor. The domestic low-grade anthracite coal with heating value 2010kcal/kg and the imported bituminous coal from Australia with heating value of 6520kcal/kg were used as coal sample. It was found from the experimental that the elutriation rate inclosed with an increseing anthracite mixing fraction. The size of elutriated particle had a very wide distribution was found in this experiment. The mean size of elutriated particle increased with decreaseing anthracite mixing fraction.

• International Journal of Automotive Technology
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• v.2 no.4
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• pp.165-170
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• 2001

This study is focussed on the investigation of spray characteristics from the high pressure gasoline injector for the application of gasoline direct injection engine. For the analysis of spray structure of high pressure gasoline injector; the laser scattering method with a Nd-Yag laser and the Phase Doppler particle analyzer system were applied to observe the spray development and the measurement of the droplet size and velocity of the spray, respectively. Also spatial velocity distribution of the spray droplet was measured by use of the particle image velocity system. Experimental results show that high pressure gasoline injector shapes the hollow-cone spray, and produce the upward ring shaped vortex on the spray surface region. This upward ring shaped vortex promotes the secondary atomization of fuel droplets and contributes to a uniform distribution of fuel droplets. Most of fuel droplets are distributed under 31$\mu m$ of the mean droplet size (SMD) and the frequency distribution of the droplet size under 25$\mu m$ is over 95% at 7 MPa of injection pressure. According to the experimental results of PIV system, the flow patterns of the droplets velocity distribution in spray region are in good agreement with the spray macroscopic behaviors obtained from the visualization investigation.

• Journal of Preventive Medicine and Public Health
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• v.19 no.1 s.19
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• pp.130-136
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• 1986

The particle size of suspended particulates was measured by a Anderson air sampler from Mar. 1982 to Feb. 1984 in a part of Seoul. It was concluded as follows : 1) The arithmetic concentration of suspended particulates was $147.8{\mu}g/m^3$ in Spring, 136.9 in Summer, 131.9 in Autumn and 158.1 in Winter respectively. 2) The cumulative distribution of suspended particulates size in logarithmic diagram showed similar to normal log distribution. 3) The atmospheric particulate matters showed a bimodal size distribution on the base of unit particle concentrations, which divided at approximately $2{\mu}m$ in the diameter. 4) While the fine particulates less than $2.1{\mu}m\;was\;35.4{\sim}45.0%$, the coarse particulates was $55.0{\sim}64.5%$. 5) The higher the concentration of suspended particulates, the more increased the ratio of fine particulates. The higher the concentration of suspended particulates, the lower median size of suspended particulate as well. 6) The respirable dust particulates less than $4.7{\mu}m\;was\;52.2{\sim}62.9%$ in seasonal average through the 2 year samples. With the above result, air pollution concerned with public health could be evaluated and the control measures also are suggested.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.22 no.3
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• pp.184-190
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• 2012

Objectives: This study aimed to characterize the nanoparticles produced by welding and grinding processes. Methods: The number concentrations of particles were mapped to determine the distribution of welding fumes in a workplace atmosphere using a hand-held condensation particle counter. An electrical low-pressure impactor was used for measuring the number concentration and particle size distribution. Results: High number concentrations were found around arc cutting and welding (grinding) processes. In the worker's breathing zone, the mean number concentration was 655,000 particles/cm3 and the count median diameter (CMD) was 84 nm with several multi peak distributions (~20, 70, 300 nm). However, at a distance of 3 m from the welding position, the number concentration decreased to 153,000 particles/cm3 with a 70 nm single peak size distribution. During a grinding process, peaks with high concentrations of nanoparticles were temporarily observed. The mean number concentration was 1,520,000 particles/cm3, and the CMD was 30 nm. Nanoparticles (<100 nm) made up 58% and 92% of the aerosols produced by welding and grinding processes, respectively.