• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.695-699
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• 2021

In this study, Selective Catalytic Reduction on Diesel Particulate Filter (SDPF) after-treatment system was introduced to simultaneously remove NO_x and Particulate Matters (PM) emitted from trucks and special cargo vehicles using old engine. First, in order to select an Selective Catalytic Reduction (SCR) catalyst for SDPF, the de-NO_x performance of V/TiO₂ and Cu-Zeolite catalysts were compared, and the SCR catalyst characteristics were analyzed through Brunauer Emmett Teller (BET), X-ray Diffraction (XRD) and NH3-TPD (Temperature Programmed Desorption). From the activity test results, the Cu-zeolite catalyst showed the best thermal stability. For optimal coating of SDPF, slurry was prepared according to the target particle size. From the coating stability and back pressure test results of SDPF according to the amount of SCR coating, As a result of comparing coating stability, back pressure, and de-NOx performance by producing A, B, and C samples for each loading amount of the SDPF catalyst, the best results were found in the B sample. The engine dynamometer test was conducted for the optimal SDPF after-treatment system, and the test results satisfied Eu-5 regulations.

• The Journal of the Petrological Society of Korea
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• v.27 no.4
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• pp.185-194
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• 2018

The basaltic rocks of Daljeon-ri columnar joint (Natural Monuments # 415) and Noeseongsan Noerok site (Natural Monuments # 547) were analysed in order to understand basalt types of two areas. The basaltic rocks of the Pohang Daljeon-ri columnar joint show a typical porphyritic texture containing phenocrysts (olivine and clinopyroxene) and groundmasses composed of clinopyroxene, plagioclase, and opaque minerals,. In contrast, basaltic rocks of Noeseongsan Noerok are characterized by fine-grained groundmass with large phenocrysts of plagioclase. Other analysis such as magnetic susceptibility, X-ray diffraction and X-ray fluorescence also support the petrological differences of two basalt rocks. The Daljeon-ri basaltic rocks are plotted on phonotephrite volcanic rocks of alkaline series in TAS(total alkali silica), and on within plate basalt in Zr-Ti diagram. The Noeseongsan basalts, on the other hand, are plotted on basaltic andesite to andesite of sub-alkaline series in TAS, and on volcanic arc basalt in Zr-Ti diagram. These results indicate that the original mantle materials between two basalt rocks were different each other, which probably originated from the change of a tectonic setting in the southeastern Korean peninsula during the Miocene.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.5
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• pp.192-202
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• 2019

Physicochemical properties and sintering characteristics of pottery stone (Taebaek, Haenam, Aphae, Haengnam) were evaluated as a raw material for porcelain products. Due to acid leaching procedure, the concentration of iron oxide ($Fe_2O_3$) was decreased to < 1.0 wt%, which affects the whiteness of sintered samples. Mean particle size of acid leached samples is $5.7{\sim}10{\mu}m$ with narrow particle size distribution (PSD), which is lower than that of the pristine ($8{\sim}18{\mu}m$) with broad PSD. According to phase analysis by X-ray diffraction, most of pottery stones (PS) have Quartz phase as a main phase with Pyrophyllite as a second phase, however, Haenam PS shows halloysite phase. The absorption rate was in order of Taebaek (A, B, C)~Aphae (A, B) < Taebaek (Special A) < Haengnam < Haenam, and the samples sintered in reductive atmosphere showed lower absorption rate. This result might be due to the concentration of feldspar contained in PS, working as a flux in sintering process. Comparing the color of the sintered samples, the whiteness of refined PS (Taebaek special A, Haenam, Hangnam) is higher than acid leached PS (Taebaek A/B/C, Aphae A/B). The whiteness (L*) for refined PS is 95~97 %, which is higher than acid leached (82~96 %). This might be due to lower iron oxide concentration of the refined PS (0.11~0.58 %) than those of the acid leached PS (0.41~1.91 %) even though most of iron oxide was removed by acid leaching.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.23-29
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• 2011

The oxidation slag has been widely used in civil engineering project, whereas the reduced slag from electric furnace has yet to be applied. Consequently in order to find out the recycling method in civil engineering field, the mineral compositions of the reduced slag were analyzed and some tests on water quality were performed to estimate the potential release of toxic compounds. Slag-soil mixtures of 0, 10, 20 and 30%(dry weight) soil were prepared in lysimeter columns and the effluents were collected with the period of one, two and four week options in closed system, respectively. The result from qualitative and quantitative analysis using X-ray Diffraction(XRD) and X-ray Fluorescence(XRF) indicates that the main mineral of the reduced slag is $Ca_2(SiO_4)$, a kind of calcium silicate. Also, the leaching medium analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy(ICP-OES) showed that main heavy metals such as Al, Fe and Mn are included in the reduced slag due to the effect of steel production process. It can be seen that the leachate does not violate the regulation guide line of waste material of heavy metal. Also the pH levels were increased from pH 6.9 for 0% soil to pH 10 for 30% soil. However the influence on leachate circulation period of one through four weeks was negligible.

• Bulletin of the Korean Chemical Society
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• v.22 no.2
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• pp.164-170
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• 2001

The crystal structures of fully dehydrated Ni2+- and Tl+ -exchanged zeolite X (Ni17Tl58-X, and Ni12Tl68-X; X=Si100Al92O384) have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at $21(1)^{\circ}C$ (a=24.380(4) $\AA$, 24.660(4) $\AA$, respectively). Their structures have been refined to the final error indices R1=0.037 and R2=0.043 with 485 reflections, and R1=0.039 and R2=0.040 with 306 reflections, respectively, for which I >36(I). In Ni17Tl58-X, 17 Ni2+ ions per unit cell were found at only two sites: 15 at site I at the center of the hexagonal prism (Ni-O=2.203(9) $\AA)$ and the remaining 2 at site II near single six-oxygen rings in the supercage (Ni-O=2.16(3) $\AA).$ Fifty-eight Tl+ ions were found at five crystallographic sites: 28 at site II (Tl-O=2.626(8) $\AA)$, 2 at site I' in the sodalite cavity near the hexagonal prism (Tl-O=2.85(1) $\AA)$, another 2 at site II' in the sodalite cavity (Tl-O=2.77(1) $\AA).$ The remaining 26 were found at two nonequivalent Ⅲ' sites with occupancies of 23 and 3. In Ni12Tl68-X, 12 Ni2+ ions per unit cell were found at two sites: 10 at site I (Ni-O=2.37(2) $\AA)$ and the remaining 2 at site II (Ni-O=2.13(2) $\AA).$ Sixty-eight Tl+ ions were found at five crystallographic sites: 28 at site II (Tl-O=2.63(1) $\AA)$, 12 at site I' (Tl-O=2.62(1) $\AA)$, 2 at site II' (Tl-O=3.01(2) $\AA)$, and the remaining 26 at two III' sites with occupancies of 23 and 3. It appears that Ni 2+ ions prefer to occupy site I and II, in that order. The large Tl+ ions occupy the remaining sites, I', II, II' and two different III' sites. In both crystals, only the Ni2+ ions at site II were reduced and migrated to the external surface of zeolite X when these crystals were treated with hydrogen gas.

• Journal of Korea Water Resources Association
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• v.54 no.3
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• pp.167-179
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• 2021

In order to characterize the mixing process of confluence for understanding the impacts of a river on the other river, it has been crucial to analyze the spatial mixing patterns for main streams depending on various inflow conditions of tributaries. However, most conventional studies have mostly relied upon hydraulic or water quality numerical models for understanding mixing pattern analysis of confluences, due to the difficulties to acquire a wide spatial range of in-situ data for characterizing mixing process. In this study, backscatters (or SNR) measured from ADCPs were particularly used to track sediment mixing assuming that it could be a surrogate to estimate the suspended sediment concentration. Raw backscatter data were corrected by considering the beam spreading and absorption by water. Also, an optical Laser diffraction instrument (LISST) was used to verify the method of acoustic backscatter and to collect the particle size distribution of main stream and tributary. In addition, image-based spatial distributions of sediment mixture in the confluence were monitored in various flow conditions by using an unmanned aerial vehicle (UAV), which were compared with the spatial distribution of acoustic backscatter. As results, we found that when acoustic backscatter by ADCPs were well processed, they could be proper indicators to identify the spatial patterns of the three-dimensional mixing process between two rivers. For this study, flow and sediment mixing characteristics were investigated in the confluence between Nakdong and Nam river.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.1
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• pp.47-54
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• 2021

For the bonding of smaller PCB solder bumps of less than 100 microns, an experiment was performed to make up a tin plating solution and find plating conditions in order to produce a bump pattern through tin electroplating, replacing the previous PCB solder bumps process by microballs. After SR patterning, a Cu seed layer was formed, and then, through DFR patterning, a pattern in which Sn can be selectively plated only within the SR pattern was formed on the PCB substrate. The tin plating solution was made based on methanesulfonic acid, and hydroquinone was used as an antioxidant to prevent oxidation of divalent tin ions. Triton X-100 was used as a surfactant, and gelatin was used as a grain refiner. By measuring the electrochemical polarization curve, the characteristics of organic additives in Triton X-100 and gelatin were compared. It was confirmed that the addition of Triton X-100 suppressed hydrogen generation up to -1 V vs. NHE, whereas gelatin inhibited hydrogen generation up to -0.7 V vs. NHE. As the current density increased, there was a general tendency that the grain size became finer, and it was observed that it became finer when gelatin was added.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.4
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• pp.121-127
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• 2022

β-Gallium oxide (Ga₂O₃), an ultra-wide bandgap semiconductor, has attracted great attention due to its promising applications for high voltage power devices. The most stable phase among five different polytypes, β-Ga₂O₃ has the wider bandgap of 4.9 eV and higher breakdown electric field of 8 MV/cm. Furthermore, it can be grown from melt source, implying higher growth rate and lower fabrication cost than other wide bandgap semiconductors such as SiC, GaN and diamond for the power device applications. In this study, β-Ga₂O₃ bulk crystals were grown by the edge-defined film-fed growth (EFG) process. The growth direction and the principal surface were set to be the [010] direction and the (100) plane of the β-Ga₂O₃ crystal, respectively. The spectra measured by Raman an alysis could exhibit the crystal phase an d impurity dopin g in the β-Ga₂O₃ ingot, and the crystallinity quality and crystal direction were analyzed using high-resolution X-ray diffraction (HRXRD). The crystal quality and various properties of as-grown β-Ga₂O₃ ribbon was systematically analyzed in order to investigate the spatial variation in entire crystal grown by EFG method.

• Journal of Applied Biological Chemistry
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• v.65 no.4
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• pp.457-462
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• 2022

Manganese (Mn) exists in various oxidation states and Mn(II) is the most mobile species of Mn, which is toxic to plants and limits their growth. Therefore, the purpose of this study was to reduce Mn toxicity by immobilizing Mn using various adsorbents including iron oxides and calcium compounds. Ferrihydrite, schwertmannite, goethite were synthesized, which was confirmed by X-ray diffraction. Hematite was purchased and used as Mn adsorbent. Calcium compounds such as CaNO₃, CaSO₄, and CaCO₃ were used to increase pH and oxidize Mn. For Mn adsorption, Mn(II) solution was reacted with four iron oxides, CaNO₃, CaSO₄, and CaCO₃ for 24 hours, filtered, and the remaining Mn concentrations in the solution were analyzed by inductively coupled plasma optical emission spectroscopy. The adsorption rate and adsorption isotherm were calculated. Among iron oxides, the adsorption rate was highest for hematite followed by ferrihyrite, but goethite and schwertmannite did not adsorb Mn. In the case of calcium compounds, the adsorption rate was high in the order of CaCO₃>CaNO₃>CaSO₄. In conclusion, treatment of CaCO₃ was the most effective in reducing Mn toxicity by increasing pH.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.620-629
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• 2022

By varying various experimental conditions such as heating rate, molar hourly space velocity (MHSV), and nitridation reaction temperature, vanadium oxynitride was prepared through temperature programmed reduction/nitridation reaction (TPRN) of vanadium pentoxide and ammonia, and characterization were performed. In order to investigate the physico-chemical properties of the prepared catalyst, N₂ adsorption-desorption analysis, X-ray diffraction analysis (XRD), hydrogen temperature programmed reduction (H₂-TPR), temperature programmed oxidation (TPO), ammonia temperature programmed desorption (NH₃-TPD), transmission electron microscopy (TEM) was performed. Transformation of V₂O₅ with 5 m² g^-1 low specific surface area by reduction at 340 ℃ to V₂O₃ showed a high specific surface area value of 115 m² g^-1 by micropore formation. As the nitridation temperature increased beyond that, the specific surface area continued to decrease due to sintering. The nitridation reaction variable that had the greatest influence on the specific surface area was the reaction temperature, and the x + y value of VN_xO_y of a single phase approached from 1.5 to 1.0 as the nitridation reaction temperature increased. At a high reaction temperature of 680 ℃, the cubic lattice constant a was VN. close to the value. At 680 ℃, the highest nitridation temperature among the experimental conditions, the ammonia conversion rate was 93%, and no deactivation was observed.