• 한국해양공학회지
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• 제24권1호
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• pp.99-105
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• 2010

The concentration and size analysis of in-situ suspended particulate material were measured using an optical instrument, LISST-100, in the bottom layer at the three inlets of the Seomjin River Estuary, mouth of Gwangyang bay, and Gwangyang bay-side of the Namhae Bridge. In the Seomjin river estuary and mouth of Gwangyang bay-side of the Namhae Bridge, the in-situ mean grain size of the suspended material changed from a uni-modal distribution with a dominant peak at a coarse fraction to a bi-modal distribution with a secondary peak at the finer particles. Seomjin River. The interactions between suspended particulate concentration and beam attenuation coefficient of suspended particulate matters depended on the supply of finer and coarser particles in the mouth of Gwangyang Bay and Seomjin River. So, interactions reflected difference of the concentration, mean size and sorting of suspended particulate matters. The difference of interaction showed dynamic behaviors to the resuspension and deflocculation processes increased river discharge. This showed that it may be possible to use the interactions between the suspended particle concentration and beam attenuation coefficient to monitor the temporal and spatial distributions of in-situ particles.

• 한국염색가공학회지
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• 제27권4호
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• pp.245-260
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• 2015

The effect of salt milling process on the crystal size, morphology, and color characteristics of C.I. Pigment Red 57:1 was studied. The primitive morphology and color properties of the pigment after synthesis were studied in the former series work. The size and morphology of primary particles and the second aggregation features should be considered because they are very important to determine pigment quality. We compared the primary morphology of pigment particles before drying with the secondary aggregated morphology of pigment particles after drying and salt milling process. Morphological properties were investigated by particle size analysis, X-ray diffraction, and scanning electron microscopy and color measurement was carried out. Significant reduction in particle size as well as enhanced crystallite size after salt milling process was observed. This result might give a difference in color of the pigment, turning into brighter and more blue-toned red color. It was revealed that synthesis condition affect the morphology and color of the pigment even after milling. Increase in HCl concentration in the synthesis process enhanced crystal size and quality forming bluer-red pigments but an increase in $CaCl_2$ concentration resulted in more amorphous crystals forming darker-red pigments after salt milling.

• 대한기관식도과학회지
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• 제5권1호
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• pp.42-48
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• 1999

Background： This study was undertaken to detect the patterns of ciliogenesis in newborn rats trachea. Materials and Methods： The experimental animals(Sprague-Dawley strain) were divided five groups, one day, two day, three day, five day and seven day newborns as experimental groups. To obtain differential distribution of $\alpha$-tubulins in the ciliated cells and patterns of ciliogenesis, we used immunohistochemical stain method with mouse anti $\alpha$-tubulin monoclonal antibody as the primary antibody and gold particles conjugated goat anti mouse IgG as the secondary antibody. And we observed the specimens by electron microscope (Hitach-600 Model). Results : 1) The distribution of the $\alpha$ -tubulin reactions in apical zone was slightly decreased from three day after birth. 2) From 5th day after birth, the decreasing number of gold particles in intermediate zone was remarkable. 3) On the comparison with the other zones, the number of gold particles in the Golgi zone for seven days showed no statistical difference. Conclusion : The ciliogenesis of the tracheal ciliated cells in early newborn rat were made via centriolar and acentriolar pathways, in late groups, from five day after birth, the major ciliogenesis pattern might be centriolar pathway.

• 대한기계학회논문집B
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• 제28권8호
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• pp.976-983
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• 2004

In high-density hard disk drives, the slider should be made to fly close to the magnetic recording disk to generate better signal resolution and at an increasingly high velocity to achieve better data rate. The slider disk interaction in CSS (contact-start-stop) mode is an important source of particle generation. Contamination particles in the hard disk drive can cause serious problems including slider crash and thermal asperities. We investigated the number and the sizes of particles generated in the hard disk drive, operating at increasing disk rotational speeds, in the CSS mode. CNC (condensation nucleus counter) and PSS (particle size selector) were used for this investigation. In addition, we examined the particle components by using SEM (scanning electron microscopes), AES (auger electron spectroscopy), and TOF-SIMS (time of flight-secondary ions mass spectrometry). The increasing disk rotational speed directly affected the particle generation by slider disk interaction. The number of particles that were generated increased with the disk rotational speed. The particle generation rate increased rapidly at motor speeds above 8000 rpm. This increase may be due to the increased slider disk interaction. Particle sizes ranged from 14 to 200 nm. The particles generated by slider disk interaction came from the lubricant on the disk, coating layer of the disk, and also slider surface.

• Asian Journal of Atmospheric Environment
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• 제11권3호
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• pp.165-175
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• 2017

In Japan, the primary carbonaceous particles emitted from motor vehicles and waste incinerators have been reduced due to strict regulations against exhaust gas. However, the relative contribution of carbonaceous particles derived from plants and biomass has been increasing. Accordingly, compositional analysis of carbonaceous particles has become increasingly important to determine the sources and types of particles produced. To reveal the sources of the organic particles contained in particulate matter with diameters of ${\leq}2.5{\mu}m$ ($PM_{2.5}$) and the processes involved in their generation, we analyzed molecular marker compounds (2-methyltetrols, cis-pinonic acid, and levoglucosan) derived from the plants and biomass in the $PM_{2.5}$ collected during daytime- and nighttime-sampling periods in summer (July and August) and autumn (November) in Kazo, which is in the northern area of Saitama prefecture, Japan. We also measured $^{14}C$ carbonaceous concentrations in the same $PM_{2.5}$ samples. The concentrations of 2-methyltetrols were higher in the summer than in the autumn. Because the deciduous period overlaps with this decrease in the levels of 2-methyltetrols, we considered the emission source to broad-leaved trees. In contrast, the emission source of the cis-pinonic acid precursor was considered to be conifers, because its concentration remained almost constant throughout the year. The concentration of levoglucosan was considerably increased in the autumn due to frequent biomass open burning. The ratio of plant-derived carbon to total carbon, obtained by measuring of $^{14}C$, in summer $PM_{2.5}$ sample was higher in the nighttime, and could be influenced by anthropogenic sources during the daytime.

• 대한기계학회논문집
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• 제18권8호
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• pp.2184-2193
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• 1994

A flow visualization experiment using water-table models was performed. The water-table models simulated the two-dimensional cold flow fields inside the combustion chambers of incinerators. The flow were visualized by small but neutrally bouyant particles photographed by an overhead camera. The experimentally simulated flow fields apparently showed distinct features of two combustion chamber shapes; counter and parallel flow types. The significance of the secondary air injection on the mixing of combustion gases were clearly observed. The effects of the recirculation zones, which were present in the secondary chamber, were discussed by considering the importance of them for optimal combustion.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
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• pp.139-148
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• 1999

In oder to analyze the effect of operating conditions on pulverized coal combustion, a numerical study is conducted at the pulverized coal combustor. Eulerian approach is used for the gas phase, whereas Lagrangian approach is used for the particle phase. Turbulence is modeled using standard ${\kappa}-{\varepsilon}$ model. The description of species transport and combustion chemistry is based on the mixture fraction/probability density function(PDF) approach. Radiation is modeled using P-l model. The turbulent dispersion of particles is modeled using discrete random walk model. Swirl number of secondary air affects the flame front, particle residence time and carbon conversion. Primary/Secondary air mass ratio also affects the flame front but little affects the carbon conversion and particle residence time. Air-fuel ratio only affects the flame front due to lack of oxygen. Radiation strongly affects the flame front and gas temperature distribution because pulverized coal flame of high temperature is considered.

• 대한기계학회논문집B
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• 제30권1호
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• pp.48-56
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• 2006

We investigated gas residence time and mixing characteristics due to various swirl numbers generated by normal injection of secondary air to a lab-scale cylinderical combustor. The residence time was estimated by measuring the temporal pressure difference which was caused by deposition of test particles on a filter media after the injection by a syringe. The mixing characteristics were evaluated by standard deviation value of test gas concentration at different measuring points. The test gas concentration was detected by a gas analyzer. The swirl number of $20{\sim}30$ for ${\theta}=5^{\circ}$ caused long residence time enough to improve mixing characteristics. Numerical calculations were also carried out to understand physical meanings of the experimental results.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 International Symposium on Clean Environment
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• pp.216-225
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• 2003

Fine particles with aerodynamic diameter less than 2.5 ${\mu}m$ (PM2.5) were collected from three sites in Beijing during April, August, and November 2000 and January 2001. After chemical components in samples are analyzed, a chemical mass balance (CMB) receptor model using PARs as tracers is applied to quantify the source contributions to PM2.5 in Beijing. The results show that the major sources are coal combustion, fugitive dust, vehicle exhaust, secondary sulfate and nitrate, and organic matter while biomass burning and construction dust contribute only a small fraction. In addition, source inventory in Beijing is used to determine the primary source contributions. The two methods result in comparable results. Source apportionment at three sampling sites presents similar contributions to PM2.5 although the sites are far away from each other. However, distinct seasonal pattern is presented for the source contributions from coal combustion, fugitive dust, biomass burning, secondary sulfate and nitrate.

• 전기화학회지
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• 제11권1호
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• pp.37-41
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• 2008

The effects of carbon-coated silicon anode on the electrochemical properties and structural change were investigated. The carbon-coated silicon powders have been prepared by thermal decomposition under argon/10wt% propylene mixed gas flow at $700^{\circ}C$. The surface and crystal structure of the synthesized materials were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Lithium cells with electrodes made from the uncoated and the carbon coated silicon anode were assembled and tested. The carbon-coated silicon particles merged together well after the insertion/extraction of lithium ions, and showed a relatively low irreversible capacity compared with the uncoated silicon particle.