• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.358-359
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• 2002

Particulate matter smaller than $10{\mu}textrm{m}$ in aerodynamic diameter (PM10) is known as thoracic particles that are capable of reaching the thoracic region of humans. PM10 is further divided into two size ranges, which are fine particles (nuclei mode plus accumulation mode) and coarse particles, based on different sources and chemical composition. Fine particles can penetrate deep into the alveolar region of the human lungs, while coarse particles be deposited in the upper respiratory system. (omitted)

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.861-866
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• 2003

While coarse geomaterials with abundant fine particles are common, comparatively little information is available to know their engineering behaviour. In this study, the effects of fine particle content of coarse geomaterials on engineering properties, such as shear strength, deformability and permeability were investigated. It was known through large triaxial compression tests that when they are compared with good rock materials, the rock materials with abundant fine particles have different compaction characteristics, low shear strength, low stiffness, and low permeability.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.2
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• pp.163-170
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• 2013

The fine-particles, moisture and variety of hazardous gases are produced during electronic manufacture process. Most of the fine-particles are 0.1~10 ${\mu}m$ in size and the hazardous gases such as HF, $SiH_4$, CO, $NH_3$, etc. seriously affect environment, human's body and manufacturing process. To remove these characterized gases and fine-particles, Water-Cyclone designed and tested for removal efficiency on fine-particles and $NH_3$ under -980Pa negative pressure condition. As a result, under 0.1~1.0 $m^3/min$ flow condition, the efficiency on 5 ${\mu}m$ particles was 80~96%, 10 ${\mu}m$ particles was 86~96%, and 20 ${\mu}m$ particles was 91~99%. Besides, the removal efficiency on soluble gas $NH_3$ was 56.5% at 0.5m3/min and 79.1% at 1.0m3/min under 500 ppm flow concentration and 70.0% at 1.0 $m^3/min$ under 1,000 ppm flow concentration. Therefore, on particles, as the flow rate and particle size increased, the collection efficiency rate was increased. On soluble gas, as the flow rate increased, the removal efficiency was increased under the same concentration.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.374-379
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• 2014

After completing deacidification process and evacuating rest of solvent, white fine particles of MgO are found on the surface of archival materials, such as books and documents. When MgO particles remain on the surface of archives, instead of being well dispersed and absorbed into cellulose fiber of archives, such white fine particles are found. These particles have raised concerns for employees' deacidification environment and their health; however, the concerns have not been addressed. To find the cause of white fine particles on the surface of archives after deacidification process and to propose the its solution, an acidic paper and wood free paper were applied with deacidifying chemicals. We analyzed the domestic and abroad deacidifying chemicals' physical properties and conducted deacidifcation processes to find effects of different contents and sizes of MgO on white fine particles. When the size of MgO particle was 847 nm, there was significantly less amount of white fine particles on the surface of archival materials. This means that the size of MgO particle plays a significant role in producing white fine particles on the surface of archives.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.846-851
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• 1998

An experimental research on the preparation of zinc oxide fine particles in w/o emulsions was conducted. Precipitation solutions were zinc nitrate aqueous solutions with hexamethylenetetramine(HMTA) as precipitant. The precipitation solutions formed stable w/o emulsions with kerosine in the presence of Span 80. Homogeneous precipitation reaction occurred in the w/o emulsion after the resultant w/o emulsion was heated above the decomposition temperature of HMTA and zinc oxide particles were precipitated. In some case, zinc oxide particles of bi-modal distribution were obtained. However, zinc oxide fine particles of narrow particle size distribution could be obtained, even when the initial zinc concentration of precipitation solution and the conversion to zinc oxide are both higher that those in bulk homogeneous precipitation.

• Journal of Magnetics
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• v.17 no.3
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• pp.185-189
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• 2012

The coercivity of near single domain size $Nd_2Fe_{14}B$-type particles prepared by ball milling of HDDR-treated $Nd_{12.5}Fe_{80.6}B_{6.4}Ga_{0.3}Nb_{0.2}$ alloy was investigated. The feasibility of a surface nitrogenation for improving the coercivity stability of the fine $Nd_2Fe_{14}B$-type particles was also studied. The near single domain size $Nd_2Fe_{14}B$-type particles had a high coercivity of over 9 kOe. However, the coercivity radically deteriorated as the temperature increased in air (< 2 kOe at $200^{\circ}C$). This coercivity reduction was attributed to the soft magnetic phases, ${\alpha}$-Fe and $Fe_3B$, which formed on the surface of the fine particle due to oxidation. Surface nitrogenation of the fine particles significantly improved the stability of their coercivity. The improvement in coercivity stability was attributed to the formation of a thin nitrogenated layer on the surface of the fine $Nd_2Fe_{14}B$-type particles, which enhanced the anisotropy field and gave improved resistance to oxidation (dissociation).

• Journal of Environmental Health Sciences
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• v.46 no.2
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• pp.192-203
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• 2020

Objectives: The concentration distributions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenlys (dl-PCBs), and polycyclic aromatic hydrocarbons (PAHs) in fine particles were investigated to provide basic data on POP behavior and composition analysis. Methods: The concentrations of PCDD/Fs, dl-PCBs, and PAHs by particle size were evaluated for TSP, PM₁₀, and PM_2.5. Also, fine dust component analysis and factor analysis were performed to identify the source of PCDD/Fs. Results: The particle size distribution was found to account for 24.3% of >10 ㎛, 14.5% of 2.5-10 ㎛, and 61.2% of <2.5 ㎛. The average contributions of coarse particles (>2.5 ㎛) and fine particles (<2.5 ㎛) were PCDD/Fs 67%, dl-PCBs 66%, benzo (a) pyrene 83% and PAHs 84%, and the contributions of fine particles (<2.5 ㎛) were higher than coarse particles (>2.5 ㎛). However, the contributions of coarse particles increased in April to September with higher temperatures, while those of fine particles increased in February to March with lower temperatures. Conclusions: Low chlorinated (4Cl-5Cl) PCDD/Fs were more adsorbed compared to coarse particles due to the influence of pollutant migration from particulate to gas phase according to temperature rise, whereas high chlorinated (6Cl-8Cl) PCDD/Fs were more adsorbed compared to fine particles. PCDD/Fs sources were assessed to be major sources of emissions, such as incineration facilities and/or open burning.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.96-96
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• 2016

Nanotechnology mostly employs nano-materials and nano-structures with distinctive properties based on their size, structure, and composition. It is quite difficult to produce nano-materials and nano-structures with identical sizes, structures, and compositions in large quantities, because of spatiotemporal fluctuation of production processes. In other words, fluctuation is the bottleneck in nanotechnology. We propose three strategies to suppress such fluctuations: employing 1) difference between linear and nonlinear phenomena, 2) difference in time constants, and 3) nucleation as a bottleneck phenomenon. We are also developing nano- and micro-scale guided assembly using plasmas as a plasma nanofabrication.1-5) We manipulate nano- and micro-objects using electrostatic, electromagnetic, ion drag, neutral drag, and optical forces. The accuracy of positioning the objects depends on fluctuation of position and energy of an object in plasmas. Here we evaluate such fluctuations and discuss the mechanism behind them. We conducted in-situ evaluation of local plasma potential fluctuation using tracking analysis of fine particles (=objects) in plasmas. Experiments were carried out with a radio frequency low-pressure plasma reactor, where we set two quartz windows at the top and bottom of the reactor. Ar plasmas were generated at 200 Pa by applying 13.56MHz, 450V peak-to-peak voltage. The injected fine particles were monodisperse methyl methacrylate-polymer spheres of $10{\mu}m$ in diameter. Fine particles were injected into the reactor and were suspended around the plasma/sheath boundary near the powered electrode. We observed binary collision of fine particles with a high-speed camera. The frame rate was 1000-10000 fps. Time evolution of their distance from the center of mass was measured by tracking analysis of the two particles. Kinetic energy during the collision was obtained from the result. Potential energy formed between the two particles was deduced by assuming the potential energy plus the kinetic energy is constant. The interaction potential is fluctuated during the collision. Maximum amplitude of the fluctuation is 25eV, and the average is 8eV. The fluctuation can be caused by neutral molecule collisions, ion collisions, and fluctuation of electrostatic force. Among theses possible causes, fluctuation of electrostatic force may be main one, because the fine particle has a large negative charge of -17000e and the corresponding electrostatic force is large compared to other forces.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.1
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• pp.13-20
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• 2010

Airborne particulate matters have two modes of size distributions of coarse mode and fine mode. The coarse mode which is formed by break down mechanism of large particles has a peak around the $100\;{\mu}m$, and the fine mode formed by condensation and build up mechanism of evaporated vapors has a peak at several ${\mu}m$. The coarse mode particles can be removed easily by conventional collecting equipments such as a cyclone, an electrostatic precipitator, and a filter, however the fine mode particles can not be collected easily. Usually the fine mode particles are generated in the high temperature conditions especially through boilers and incinerators, so the high efficient and temperature filter is essential for the filtration. In this study, a nano ceramic filter for the removal of fine particles in the high temperature is developed and tested for several characteristics. The nano ceramic filter has double layer of micro and nano structure and the pressure drop and the filtration efficiency for $0.31\;{\mu}m$ at 3 cm/s are 15.45 mmAq, and 96.75%, respectively. The thermal conductivity is $0.038\;W/m{\cdot}K$, and the coefficient of water vapor permeability is $3.63\;g/m^2{\cdot}h{\cdot}mmHg$. It is considered that the sensible heat exchange rate is very poor because the low thermal conductivity but it has high potential to exchange latent heat.

• Progress in Superconductivity and Cryogenics
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• v.22 no.2
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• pp.7-11
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• 2020

When rivers and lakes are contaminated with numerous contaminants, usually the contaminants are finally deposited on the sediments of the waterbody. Many clean up technologies have been developed for the contaminated sediments. Among several technologies dredging is one of the best methods because dredging removes all the contaminated sediments from the water and the contaminated sediments can be completely treated with physical and chemical methods. However the most worried phenomenon is suspension of fine particles during the dredging process. The suspended particle can release contaminants into water and resulted in spread of the contaminants and the increase of risk due to the resuspension of the precipitated contaminants such as heavy metals and toxic organic compounds. Therefore the success of the dredging process depends on the prevention of resuspension of fine particles. Advanced dredging processes employ pumping the sediment with water onto a ship and release the turbid water pumped with sediment into waterbody after collection of sediment solids. Before release of the turbid water into lake or river, just a few minutes allowed to precipitate the suspended particle due to the limited area on a dredging ship. However the fine particle cannot be removed by the gravitational settling over a few minutes. Environmental technology such as coagulation and precipitation could be applied for the settling of fine particles. However, the process needs coagulants and big settling tanks. For the quick settling of the fine particles suspended during dredging process magnetic separation has been tested in current study. Magnetic force increased the settling velocity and the increased settling process can reduce the volume of settling tank usually located in a ship for dredging. The magnetic assisted settling also decreased the heavy metal release through the turbid water by precipitating highly contaminated particles with magnetic force.