• Journal of Energy Engineering
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• v.27 no.4
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• pp.80-85
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• 2018

Usable capacity is one of the most important parameters for evaluating the performance of an adsorbent for $CO_2$ capture from flue gas streams. In the pressure swing adsorption (PSA) process, the usable capacity is calculated as the difference between the quantity adsorbed in flue gas at high pressure (ca. 20 bar) and the quantity adsorbed at lower purge pressure (ca. 2 bar). In this paper, two stereo-types of metal-organic framework (MOF) were evaluated as an promising adsorbent for $CO_2$ capture: flexible structured MOF (MIL-53) and MOF possessing strong binding sites (MOF-74). The results showed that a total $CO_2$ capture capacity is strongly related to the specific surface area and heat of adsorption, revealing high uptake in MOF-74. However, the usable capacity was more pronounced in MIL-53 due to a structural transition.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.2
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• pp.15-21
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• 2019

We investigated the structural, electrical and optical properties of zinc oxide (ZnO) ultra-thin films grown at $150^{\circ}C$ by atomic layer deposition (ALD). Diethylzinc and deionized water were used as metal precursors and reactants, respectively, for the deposition of ZnO thin films. The growth rate per ALD cycle was a constant 0.21 nm/cycle at $150^{\circ}C$, and samples below 50 cycles had amorphous properties due to the relatively thin thickness at the initial ALD growth stage. With the increase of the thickness from 100 cycles to 200 cycles, the crystallinity of ZnO thin films was increased and hexagonal wurtzite structure was observed. In addition, the particle size of the ZnO thin film increased with increasing number of ALD cycles. Electrical properties analysis showed that the resistivity value decreased with the increase of the thin film thickness, which is correlated with the decrease of the grain boundary concentration in the thicker ZnO thin film due to the increase of grain size and the improvement of the crystallinity. Optical characterization results showed that the band edge absorption in the near ultraviolet region (300 nm~400 nm) was increased and shifted. This phenomenon is due to the increase of the carrier concentration with the increase of the ZnO thin film thickness. This result agrees well with the decrease of the resistivity with the increase of the thin film thickness. Consequently, as the thickness of the thin film increases, the stress on the film surface is relaxed, the band gap decreases, and the crystallinity and conductivity are improved.

• Korean Journal of Heritage: History & Science
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• v.43 no.3
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• pp.102-121
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• 2010

Three bronze bells excavated from the Hoeamsa temple site were investigated for their microstructures and chemical compositions in an effort to understand the technology applied in fabrication, which may represent the related industry established in the early Joseon period. The result shows that the bells were cast from alloys of approximately 85% copper-8% tin-7% lead. The chemical analysis for ten trace elements shows that they were all kept below 0.3 weight %, suggesting that the alloys were made of relatively well-refined copper, tin and lead. The presence of sulfur and iron indicates that chalcopyrite or chalcocite may have been used in the smelting of copper. Evidence has been found that the bells were cast by pouring the liquid metal from the top of the sand molds that were set up in an upright position. No additional treatments, thermal or mechanical, other than a little grinding were applied upon the completion of casting. After the shaping process, a balancing plate was attached to the top of the bell using a steel connection ring. The connection assembly was then fixed to the main body by using molten bronze as a solder. The surface inscription was found carved using different techniques. The differences in the order of strokes and the calligraphic style indicate that the carving was carried out by more than one master. In the absence of documentary evidence on past bronze technology, the present bronze bells with known chronology, provenance and the main agent of production, prove to be a rare and valuable archaeological material for the understanding of the related technology in use in the early Joseon period.

• Composites Research
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• v.32 no.5
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• pp.284-289
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• 2019

In the present paper, the dynamic force-moment equilibrium equations, driving power and energy equations are analyzed to formulate the equation for fuel economy(km/liter) equivalent to the driving distance (km) divided by the fuel volume (liter) of the vehicle, a selected model of gasoline powered KIA K3 (1.6v). In addition, the effects of the dynamic parameters such as speed of vehicle (V), vehicle total weight(M), rolling resistance ($C_r$) between tires and road surface, inclined angle of road (${\theta}$), as well as the aerodynamic parameters such as drag coefficient ($C_d$) of vehicle, air density(${\rho}$), cross-sectional area (A) of vehicle, wind speed ($V_w$) have been analyzed. And the possibility of alternative materials such as lightweight metal alloys, fiber reinforced plastic composite materials to replace the conventional steel and casting iron materials and to reduce the weight of the vehicle has been investigated by Ashby's material index method. Through studies, the following results were obtained. The most influencing parameters on the fuel economy at high speed zone (100 km/h) were V, the aerodynamic parameters such as $C_d$, A, ${\rho}$, and $C_r$ and M. While at low speed zone (60 km/h), they are, in magnitude order, dynamic parameters such as V, M, $C_r$ and aerodynamic ones such as $C_d$, A, and ${\rho}$, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.497-502
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• 2019

Metal oxide nanostructures are promising materials for advanced applications, such as high sensitive gas sensors, and high capacitance lithium-ion batteries. In this study, tin oxide (SnO) nanostructures were grown on a Si wafer substrate using a two-zone horizontal furnace system for a various substrate temperatures. The raw material of tin dioxide ($SnO_2$) powder was vaporized at $1070^{\circ}C$ in an alumina crucible. High purity Ar gas, as a carrier gas, was flown with a flow rate of 1000 standard cubic centimeters per minute. The SnO nanostructures were grown on a Si substrate at $350{\sim}450^{\circ}C$ under 545 Pa for 30 minutes. The surface morphology of the as-grown SnO nanostructures on Si substrate was characterized by field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Raman spectroscopy was used to confirm the phase of the as-grown SnO nanostructures. As the results, the as-grown tin oxide nanostructures exhibited a pure tin monoxide phase. As the substrate temperature was increased from $350^{\circ}C$ to $424^{\circ}C$, the thickness and grain size of the SnO nanostructures were increased. The SnO nanostructures grown at $450^{\circ}C$ exhibited complex polycrystalline structures, whereas the SnO nanostructures grown at $350^{\circ}C$ to $424^{\circ}C$ exhibited simple grain structures parallel to the substrate.

• Conservation Science in Museum
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• v.25
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• pp.85-94
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• 2021

Conservation treatment of metallic artifacts contaminated with corrosion and foreign substances requires changes in the shape, characteristics, weight and thickness of the artifacts. Thus far, recording the changes after conservation treatment has mainly been performed through visual observation and photography, which lacks any quantitative description of the changes. In this study, the processes of removing foreign substances, joining cracks, and restoring an affected area were recorded using 3D scanning and then quantitatively analyzed to identify changes in form due to conservation treatment. The volume change after the conservation process was calculated based on the results of the 3D scanning, and numerical data on the changes to the form was analyzed. It was revealed that the foreign or corroded substances removed after the conservation accounted for 18.1 cm³, which is approximately 52% of the total volume of the ring pommel, and those substances were removed from about 98% of the surface of the ring pommel. This study confirmed that 3D form analysis was useful for recording the processes of conservation treatment and analyzing the results. It is therefore believed that this methodology can be applicable to not only metal artifacts, but to cultural heritage items in a range of materials.

• Korean Journal of Ecology and Environment
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• v.53 no.4
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• pp.355-364
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• 2020

This study was carried out to investigated changes in sediments in the eight weir sections of Nakdong River. Sediments were collected and analyzed for Grain Size, Ignition loss, Total Organic Carbon, Total Nitrogen, Total Phosphorus, and Meta. The upstream of the weir was found that fine-grained sediments have repeated increases and decreases. It was found that coarse-grained sediments were being maintained in the downstream part of the weir. The sediments Ignition Loss, Total Organic Carbon, Total Nitrogen, Total Phosphorus are strongly correlated with Grain Size, and these increased at the point where sediments are fine. In the case of metal, the concentration increased across the board, and the correlation with Grain Size, Ignition loss, Total Organic Carbon, Total Nitrogen, and Total Phosphorus was weak. Although there were some sections where fine-grained sediments, organic materials, nutrients, metals increased in the Nakdong River, the overall pollution level is considered weak.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.7
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• pp.858-863
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• 2020

We experimented with the particle-settling velocity and CHCl3 absorption efficiency of seven activated-carbon and analyzed seven heavy metal contents by elution for application to the field treatment of sunken HNS on the marine seabed. The mean particle-settling velocity was in the range 0.5-8 cm/s, except when the 8-20 mesh was used. The larger the HNS particle, the faster the particle-settling velocity was, and the CHCl3 absorption efficiency increased considerably owing to the larger surface area. In addition, the elution test results showed that the total Zn and As contents in >100-meshed activated carbon was higher than the contents criteria for the standard for water-treatment agents, and Cr, Zn, and As were released at higher concentrations than those released by other activated-carbon groups. Taken together, the CHCl3 absorption efficiency, settling velocity, and elution test results suggested that the 20-60, 20-40, and 2mm&down mesh activated-carbon adsorbents could be applied to the field treatment of HNSs and that the minimum required amount for field treatment were 0.82, 0.90, and 1.28 ton/㎘, respectively, as calculated based on the HNS-adsorption-capacity priority.

• Clean Technology
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• v.26 no.4
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• pp.263-269
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• 2020

Zeolite was synthesized hydrothermally using the water-treatment sludge, and the effects of various synthesis parameters like reaction temperature, reaction time, and Na2O/SiO2 molar ratio on the crystallization of zeolite were investigated. Crystal structure, physical property, and thermal stability of zeolite crystals were characterized by X-ray powder diffraction, FTIR spectroscopy, BET nitrogen adsorption, and TGA measurements. The removal efficiencies of nitrogen in ammonia, heavy metal ions, and TOC were calculated to evaluate zeolite's adsorption capacity. The primary chemical composition of water-treatment sludge was 28.79% Al2O3 and 27.06% SiO2. The zeolites were synthesized by merely employing the water-treatment sludge as silica and alumina sources without additional chemicals. Zeolite crystals synthesized through the water-treatment sludge were confirmed as an A-type zeolite structure. Zeolite A had the highest crystallinity obtained from a gel with the molar composition 2.1Na2O-Al2O3-1.6SiO2-65H2O after 5 h at a temperature of 90 ℃. The specific surface area of zeolite obtained was 55 ㎡ g-1, which was higher than commercial zeolite A. The removal efficiency of nitrogen in ammonia was 68% after 3 h of reaction time, while the removal efficiencies of Pb2+ and Cd2+ ions were 99.1% and 99.3%, respectively. These results indicate active ion exchange between Pb2+ or Cd2+ ion and Na+ ion in the zeolite framework. The adsorption experiments on the different zeolite addition conditions were performed for 3 h with 300 ppm humic acid. Based on the results, TOC's highest efficiency was 83% when 5 g of zeolite was added.

• Journal of the Korean Society of Radiology
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• v.16 no.6
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• pp.719-725
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• 2022

This study aimed to measure, quantitatively evaluate, and set the criteria for the minimum lead(Pb) shield thickness per level of clinically applied electron beam energy. The lead shield thickness per electron beam energy was measured using the primary field 95% reduction based on the open field at the depth of maximum dose (d_max) and depth from the surface as the reference depth of tissue dose(10 mm). The measured values were 1.906 mmPb and 1.992 mmPb at the d_max and 10 mm, respectively, regarding the lead shield thickness for 6 MeV electron beam; 2.746 mmPb and 3.743 mmPb for 9 MeV electron beam, 3.718 mmPb and 6.093 mmPb for 12 MeV electron beam, 7.300 mmPb and 15.270 mmPb for 16 MeV electron beam, and 16.825 mmPb and 25.090 mmPb for 20 MeV electron beam. Consequently, a thicker lead shield was required if the measurement was at 10 mm. The required lead shield thickness was also higher than that of the theoretical formula for electron beams of ≥ 16 MeV.