• 한국지구과학회:학술대회논문집
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• 2004.02a
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• pp.2-12
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• 2004

The purpose for this study is to inquire into the effects of teaching methods in the class on the conceptual change of atmospheric pressure for middle school students. After analyzing the concept of atmospheric pressure in the middle school science textbooks on the present 7th Curriculum, classes were performed adopting classified Method A and Method B. For Method A, the textbook used that explains the concept in the view of weight. For Method B, the textbook used approaching to the concept in the views of molecular movement as well as of weight. This study consists of four classes in the third grade students of middle school in Busan, which were divided into the Method A group and the Method B group. The result of the study carried out pre-post each of these classes on the learning achievement and on the conceptual change of atmospheric pressure. The result of this study were as follows: First, the effect on the learning achievement was displayed the average score of the Method B was showing meaningful difference comparing to the Method A. Second, the effect on the conceptual change measured by verifying the score for the difference among the averages for each sub-scale three out of four conceptual factors, 'the direction of atmospheric influence and the reason', 'the principle of atmospheric action' and 'the atmospheric changes by the temperature rise on the surface of the earth and the reason', showed meaningful improvement. But, the one left factor, 'the distribution of atmospheric pressure by altitudes and the reason', displayed no meaningful difference. Third, The concept of atmospheric pressure is better defined as the pressure created by the movement of air particles, in the view of kinetic theory of gas, rather than explained by the notion of the weight of air.

• Particle and aerosol research
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• v.15 no.4
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• pp.191-202
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• 2019

In this study, performance (particle removal efficiency and breathing resistance) of several commercially available face masks (electrostatic filter masks (KF80 certified), a nanofiber filter mask (KF80 certified), and an uncertified mask) with their filter structure and composition were evaluated. Also, effects of relative humidity (RH) of incoming air, water and alcohol exposure, and reusability on performance of face masks were examined. Monodisperse and polydisperse sodium chloride particles were used as test aerosols. Except the uncertified mask filter, PM_2.5 removal efficiency was found to be higher than 90%, and the nanofiber filter mask had the highest quality factor due to the low pressure drop and high removal efficiency (nanofibers were arranged in a densely packed pore structure and contained a significant amount of fluorine in addition to carbon and oxygen). In the case of the KF80 certified mask, the removal efficiency was little affected when the RH of incoming air increased. When the mask filters were soaked in water, the removal efficiency of mask filters was degraded. In particular, the uncertified mask filter showed the highest removal efficiency degradation (26%). When the mask was soaked in alcohol, the removal efficiency also decreased with the greater degree than the water soaking case. The nanofiber mask filter showed the strongest resistance to alcohol exposure among tested mask filters. During evaluation of reusability of masks in real life, the removal efficiency of certified mask filter was less than 4% for 5 consecutive days (2 hours per day), while the removal efficiency of uncertified mask filter significantly decreased by 30% after 5 days.

• Progress in Medical Physics
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• v.13 no.2
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• pp.98-103
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• 2002

The purpose of this study was to evaluate the absorbed dose to the coronary artery segment from various sized balloon angio catheters. The liquid form of Ho-166 was produced at the KAERI by (n, ${\gamma}$ ) reaction. We used GafChromic film for the estimation of the absorbed dose by beta particles. The exposed films were read using a videodensitometer. Several film exposures were made with varying irradiation times and activities. A modified micrometer was used for the measurement of the absorbed dose distribution near the balloon surface. Four balloons of coronary catheters evaluated were 30 m long and 2.5, 3.0, 3.5 and 4.0 mm in diameter. All doses are plotted in units of Gy/min/GBq/ml as a function of radial distance in mm from the surface of balloon. The absorbed dose rate was 0.86, 1.01, 1.11 and 1.24 Gy/min/GBq/ml at a balloon surface for various balloon diameter 2.5, 3.0, 3.5 and 4.0 mm respectively. Using a vacuum pump, the air in the balloon was evacuated prior to instillation of the Ho-166 source. By removing air bubbles in the balloon, the absorbed dose distribution was more uniform.

• Journal of Environmental Science International
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• v.26 no.1
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• pp.23-28
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• 2017

This study was aimed at determining the changes in heavy metal removal efficiency at different acid concentrations in a micro-nanobubble soil washing system and pickling process that is used to dispose of heavy metals. For this purpose, the initial and final heavy metal concentrations were measured to calculate the heavy metal removal efficiency 5, 10, 20, 30, 60, and 120 min into the experiment. Soil contaminated by heavy metals and extracted from 0~15 cm below the surface of a vehicle junkyard in the city of U was used in the experiment. The extracted soil was air-dried for 24 h, after which a No. 10 (2 mm) was used as a filter to remove large particles and other substances from the soil as well as to even out the samples. As for the operating conditions, the air inflow rate in the micro-nano bubble soil washing system was fixed at 2 L/min,; with the concentration of hydrogen peroxide being adjusted to 5%, 10%, or 15%. The treatment lasted 120 min. The results showed that when the concentration of hydrogen peroxide was 5%, the efficiency of Zn removal was 27.4%, whereas those of Ni and Pb were 28.7% and 22.8%, respectively. When the concentration of hydrogen peroxide was 10%, the efficiency of Zn removal was 38.7%, whereas those of Ni and Pb were 42.6% and 28.6%, respectively. When the concentration of hydrogen peroxide was 15%, the efficiency of Zn removal was 49.7%, whereas those of Ni and Pb were 57.1% and 42.6%, respectively. Therefore, the efficiency of removal of all three heavy metals was the highest when the hydrogen peroxide concentration was 15%.

• Journal of the Korea Institute of Building Construction
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• v.20 no.4
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• pp.331-338
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• 2020

The aim of the research is to evaluate the possibility of using coal gasification slag (CGS) as a combined aggregate for concrete mixture. To achieve this goal, the fundamental properties and the durability of concrete were analyzed depending on various combining ratio of CGS into both fine aggregate with favorable gradation and relatively coarse particles. According to the results of the experiment, slump and slump flow were increased with content of CGS regardless of crushed fine aggregate with good and poor gradations while the air content was decreased. For the compressive strength of the concrete, in the case of using the crushed aggregate with good gradation, increasing CGS content decreased compressive strength of the concrete, while when the concrete used crushed aggregate with poor gradation, the compressive strength was the maximum at 50% of CGS content. As a durability assessment, drying shrinkage was decreased and carbonation resistance was improved by increasing CGS content. On the other hand, for freeze-thawing resistance, CGS influenced adverse effect on freeze-thawing resistance. Therefore, it is known that an additional air entrainer is needed to increase the freeze-thawing resistance when CGS was used as a combined aggregate for concrete.

• Journal of the Korean Electrochemical Society
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• v.19 no.2
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• pp.50-56
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• 2016

Spherical lithium manganese oxide spinel, $Li_{1.10}Mn_{1.86}Al_{0.02}Mg_{0.02}O_4$ was prepared by wet-milling, spray-drying, and sintering process. In the spray-drying process, solid content in slurry was varied from 20 to 30 wt%. In the sintering process, the precursors have been sintered under air or $O_2$ atmosphere. While the as-prepared samples exhibit excellent electrochemical properties at room temperature, the discharge voltage profiles at 5.0C are very different one from another. The origin for the difference especially at initial state of discharge is oxygen defect. The sample prepared in air has larger capacity related to the plateau at 3.3 V (vs. $Li/Li^+$) which is caused by the oxygen defects than the one prepared in $O_2$. The difference of discharge voltage profiles especially at the final state of discharge comes from different diffusion rate of $Li^+$ ions. The sample prepared from 30 wt% solid content of slurry shows twice higher diffusion rate than the samples prepared from 20 wt% solid content, which is attributed to better compactness between primary particles for the sample prepared from 30wt % solid content than the one prepared by 20 wt%.

• Journal of Navigation and Port Research
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• v.40 no.1
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• pp.1-6
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• 2016

This study was conducted on a circulation system which can recycle waste water from EGCS(Exhaust Gas Cleaning System) using a wet scrubber that is used to treat air pollutants from ships. Though we developed a water treatment system that could remove effectively particulate matters and dispersed oil included in cleaning water for Ship Exhaust Gas Recycle System(DePM & DeSOx), we found that it is difficult to treat minutely dispersed oil only by means of centrifugal-typed purifier. Therefore, to this system, we applied a coalescer that coalesces emulsified minute oil particles in the 2nd phase of dispersion state after being filtered through the centrifugal-typed purifier. After we treated cleaning water drained out of Ship Exhaust Gas Recycle System(DePM & DeSOx) by using both purifier and coalescer, we found that particulate matters and dispersed oil were removed more than 55% and 99%, respectively, in comparison with those contained in cleaning water influent. Putting the results together, we conclude that the treated cleaning water can be recycled as normal cleaning water if this cleaning water treatment system is employed by the wet cleaning tower system for the reduction of air pollutants from ships.

• Resources Recycling
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• v.22 no.3
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• pp.28-35
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• 2013

The recycling of the Si/SiC mixture sludge obtained from solar cell industry is very significant, environmentally and economically. The sintering characteristics of Si/SiC mixture sludge was studied for the purpose of recycling. In this study, to understand sintering behavior, SiC content in the Si/SiC mixture was controlled using an air separator. Various Si/SiC mixtures having different SiC contents were sintered using carbon black, clay and aluminum hydroxide as sintering aids. Physical properties of Si/SiC mixture and sintered bodies have been characterized using SEM, XRD, particle size analyzer and apparent density measurement. SEM and particle size analysis result confirmed that the fine particles less than 1 ${\mu}m$ decreased or removed more effectively through the air separator in the case of 95% SiC sample compared than the case of 75% SiC sample or original SiC sample. Further, with addition of the Aluminum Hydroxide, ${\beta}$-cristobalite phase gradually decreased while mullite phase gradually increased. The addition of the carbon black improved the sintering characteristics.

• Resources Recycling
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• v.22 no.6
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• pp.64-72
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• 2013

The purpose of this study is to confirm the possibility of obtaining high grade coal from 57.39% of fixed carbon fine coal. Also, the mineralogical, physical/chemical and liberation characteristics are to be identified to decrease in ash amount, during the pre-processing of clean coal technology. In this study, batch flotation and CPT column flotation proper for the processing of fine particles were used with the variation in kinds and quantity of frother, collector and depressant. Also air flow rate and feeding rates were examined. As a result of batch flotation using 20% of pulp density DMU 101 collector(100 mL/ton), AF65 frother(300 mL/ton), sodium metaphosphate depressant (1 kg/ton), 67.57% of ash rejection and 70.90% of combustible recovery were obtained. The result of CPT column flotation was 85.59% of ash rejection and 88.97% of combustible recovery under the conditions of 5% of pulp density, DMU-101 collector (100 mL/ton), AF65 frother(10 L/ton), SMP depressant(1 kg/ton), wash water(100 mL/min.) and air flow rate(1,200 mL/min.).

• Journal of Korean Society of Disaster and Security
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• v.11 no.2
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• pp.69-74
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• 2018

Fog to which environmental impacts are sensitive has a danger to the safety of citizens due to the difficulty in predicting the specific area/time zone. Therefore, we propose a white smoke fog reduction technique using a fog removal device that can remove fog particles directly through dry air and anionic condensation nucleus instead of conventional passive countermeasures. In this study, to verify the effect of reducing fog and the effect of temperature on the white smoke fog which is frequently occurred in the detention basin. As a result, the visible distance of 100m or more was secured within 30 seconds, and it was confirmed that the fog reduction effect is more effective. Also, the lower the temperature, the larger the amount of white smoke fog was. However, the effect of reducing the white smoke fog by temperature was insignificant. Through this experiment, it was possible to verify the reduction effect of the white smoke fog generated in the detention basin through fog removal device.