• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.439-442
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• 2007

A solid state Hg(Au)/HgO reference electrode was prepared utilizing gold amalgam solid particles. Solid fine powder of the gold amalgam was prepared by chemical reduction of Au(III) with NaBH4 followed by reduction of Hg(II) in the presence of gold fine particles. The solid content in the suspension of the gold amalgam particles and fine mercury oxide particles in DMF containing PVC was precipitated by the addition of a large amount of water to give solid Hg(Au)/HgO/PVC mixture. After drying, the mixture was pressure-molded to a physically stable Hg(Au)/HgO composite reference electrode material. The electrochemical characteristics of the electrode as a reference electrode were very similar to an ordinary Hg/HgO reference electrode. The electrode material can be molded and fabricated in any desired shape and size. The surface can be renewed by a simple polishing process whenever contaminated or deactivated. The applicability of the electrode in the electrochemical detection of carbohydrates after anion exchange separation was evaluated.

• The Korean Journal of Ceramics
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• v.1 no.4
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• pp.214-218
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• 1995

Partially stabilized zironia with magnesia (Mg-PSZ) is known as one of the toughest monolithic ceramics. However, the very large grain sizes obtained after sintering at a high solution-heat treatment temperature in the cubic region of the phase diagram limit the strength of this material rather modest. In this study fine-grained Mg-PSZ materials were fabricated by adding TiC particles as a dispersed phase. Samples were hot-pressed at $1750^{\circ}C$ and then annealed at $1420^{\circ}C$ for various times. Grain growth was retarded severely by the TiC particles resulting in grain sizes smaller by more than one order of magnitude than those of PSZ without TiC. The fine-grained microstructure lead to doubly-increased fracture strength while maintaining the same level of high fracture toughness as that of conventional Mg-PSZ without TiC particles.

• Resources Recycling
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• v.6 no.1
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• pp.17-22
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• 1997

An electromagnetic fluidized bed was proposed for the continuous separation of magnetic particles from the fine a admixtures with nonHmagnetic particles. The effects of operating variables on the magnetic fraction in the separated p particles were examined, including superficial gas velocity, mixing fraction of magnetic particles (= 100-mixing fraction of n non-magnetic particles) in the admixture, and electric current supplied to the electwmagnet. It was found that the s separation was possible when a magnetic force formed by the electromagnets works on the magnetic particles over the hydrodynamic force caused by a gas stream for fluidizing the fine admixture.

• Environmental Engineering Research
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• v.12 no.2
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• pp.72-80
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• 2007

Experiments were conducted to identify the emissions from the car air freshener and to identify the formation of ultra-fine particles and secondary gaseous compounds during the ozone-initiated oxidations with emitted VOCs. The identified primary constituents emitted from the car air freshener in this study were $\alpha$-pinene, $\beta$-pinene, $\rho$-cymene and limonene. Formation of ultra-fine particles (4.4-160 nm) was observed when ozone was injected into the chamber containing emitted monoterpenes from the air freshener. Particle number concentrations, particle mass concentrations, and surface concentrations were measured in time dependent experiments to describe the particle formation and growth within the chamber. The irritating secondary gaseous products formed during the ozone-initiated reactions include formaldehyde, acetaldehyde, acrolein, acetone, and propionaldehyde. Ozone concentration (50 and 100 ppb) and temperature (30 and $40^{\circ}C$) significantly affect the formation of particles and gaseous products during the ozone-initiated reactions. The results obtained in this study provided an insight on the potential exposure of particles and irritating secondary products formed during the ozone-initiated reaction to passengers in confined spaces.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.1 s.16
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• pp.13-21
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• 2005

Experiments on settling behaviour of fine-grained particles without destroying the large fragile aggregates were carried out in still water with a CCD (Charged Coupled Device)-Camera. The experiments dealt with the measuring of the vertical concentration profile of cohesive particles with a CCD-Camera and the physico-chemical influences (NaCl, density, temperature and pH value) on the vertical distribution of the concentration. The vertical concentration profile of fine suspended particles (alumina and quartz) was possible up to $20,000\;mg/{\ell}$ with a CCD-Camera. The vertical concentration profile of cohesive sediments was on the decrease because of the increasing initial concentration, temperature and salinity. The vertical concentration profile of alumina was on the decrease quicker than quartz with increasing salinity. Furthermore, the pH value affects the settling behaviour of alumina. At a PH value of 4.2 the settling rate of the particles was very low and on the increase until pH 8.9 because of the aggregation behaviour of particles. From the PH value of 9 the average settling velocity was on the decrease.

• Journal of Korea Foundry Society
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• v.13 no.4
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• pp.369-381
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• 1993

Aluminum alloy(AC8A) matrix composites reinforced with SiC particles(10% in vol.) were fabricated by Centrifugal Spray Deposition(CSD) process. The microstructures were investigated in order to evaluate both the mixing mode between aluminum matrix and SiC particles, and the effect of SiC particles on the cooling behaviours of droplets during flight and preforms deposited. A non-continuum mathematical calculation was performed to explain and to quantify the evolution of microstructures in the droplets and preforms deposited. Conclusions obtained are as follows; 1. The powders produced by CSD process showed, in general, ligament type, and more than 60% of the powders produced were about 300 to 850 um in size. 2. AC8A droplets solidified during flight showed fine dendritic structure, but AC8A droplets mixed with SiC particles showed fine equiaxed grain structure, and eutectic silicon were formed to crystallize granularly between fine aluminum grains. 3. SiC particles seem to act as a nucleation sites for pro-eutectic silicon during solidification of AC8A alloy. 4. The microstructure of composite powders formed by CSD process showed particle embedded type, and resulted in dispersed type microstructure in preforms deposited. 5. The pro-eutectic silicon crystallized granularly between fine aluminum grains seem to prohibit grains from growth during spray deposition process. 6. The interfacial reactions between aluminum matrix and SiC particles were not observed from the deposit performs and the solidified droplets. 7. The continuum model seem to be useful in connecting the processing parameters with the resultant microstructures. From these results, it was concluded that the fabrication of aluminum matrix composites reinforced homogeneously with SiC particles was possible.

• Journal of Microbiology
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• v.35 no.1
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• pp.1-9
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• 1997

Distribution of airborne microorganisms was determined with two different types of air samplers, the Anderson cascade sampler and the Aerobioscope sampler, in the vicinity of Taejon. The size distribution of particles carrying bacteria and fungi was concurrently measured. The concentration of detected viable airborne particles was greatly varied. It was observed that the number of microbial particles increased in April and October. The most isze o particles carrying bacteria was larger than 4.7 .mu.m in mean aerodiameter, which made up 69.8% of the total particle fraction. About 63.2% of fungi-carrying particles were smaller than 4.7 .mu.m in aerodiameter. The distribution of particles on Yellow Sand Phenomena days was also analyzed. The number of fine particles having mass median aero-diameter from 1.0 to 10.mu.m increased on Yellow Sand Phenomena days to about 6 times that on normal days and the n umber of colony forming unit (CFU/$\textrm{m}^3$) of airborne bacteria also increased by 4.3 times in April. The reuslts from the Anderson sampler showed that the concentration of bacteria increased greatly on the fraction of fine particles ranging from 0.6 $\mu$m to 4.7 $\mu$m in diameter. Unlike the increase in bacterial floraon Yellow Sand Phenomena days, the fungal concentration slightly decreased and showed a normal size distribution parttern. This study suggests that a long-range transmission of bacteria results form bacteria adsorbing onto the fine particles during the Yellow Sand Phenomena.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.234.2-234.2
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• 2003

Recently, the need for ultra-fine particles, especially nano-sized particles has increased in the fields preparing raw powders such as pharmaceutical additive and high value added products in the Nano-Technology processes. Therefore, the research in ultra-fine grinding is very important, especially, in nanometer grinding. In the previous paper, a series of wet grinding experiments using grinding aids using a stirred ball mill have been performed on grinding rate constant based on grinding kinetics. (omitted)

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.144-153
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• 2008

A numerical analysis has been carried out to examine the flow characteristics and the collection efficiency for fine particles in a cyclone using Computational Fluid Dynamics (CFD) technique. The cyclone with the cylinder diameter of 60 mm has been considered for the investigation of the particle collection in a relatively smaller cyclone with somewhat higher inlet air velocities. Fundamental air flow patterns for different inlet velocities have been calculated and then the motions of particles of different sizes have been obtained. The calculated collection efficiencies for fine particles are compared with the experimental results, which shows a good agreement. The current result can be used for the design of cyclones with high collection efficiency.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.295-298
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• 2008

In the reactor for the american standard test method (ASTM) D5757-95 with swirl injection nozzles, the attrition characteristics of sand was investigated. The change of particle size distribution and weight of fine particles were compared to identify the effect of swirl injection nozzle on attrition. The fine particles due to particle attrition increased with increasing gas velocities. The weight of fine particles due to jet attrition was changed with angle of swirl injection nozzle. The fine particles decreased with decreasing the angle of swirl injection nozzle. Also, the change of particle size distribution increased with increasing the number of swirl injection nozzles at the same flow rate.