• Journal of the Korean Chemical Society
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• v.68 no.2
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• pp.87-92
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• 2024

The commercialization of rechargeable metal-air batteries is extremely desirable but designing stable oxygen reduction reaction (ORR) catalysts with non-noble metal still has faced challenges to replace platinum-based catalysts. The nonnoble metal catalysts for ORR were prepared to improve the catalytic performance and stability by the thermal decomposition of ZIF-8 with optimum cobalt loading. The porous carbon was obtained by the calcination of ZIF-8 and different loading amounts of Co nanoparticles were anchored onto porous carbon forming a Co/PC catalyst. Co/PC composite shows a significant increase in the ORR value of current and stability (500 h) due to the good electronic conductive PCN support and optimum cobalt metal loading. The significantly improved catalytic performance is ascribed to the chemical structure, synergistic effects, porous carbon networks, and rich active sites. This method develops a new pathway for a highly active and advantageous catalyst for electrochemical devices.

• Journal of the Korean Applied Science and Technology
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• v.34 no.3
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• pp.487-494
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• 2017

Since nitrate nitrogen is quite stable in aqueous solution, considerable skill is required to remove it. Low concentrations of nitrate nitrogen are easily removed, while high concentrations of nitrate nitrogen are difficult to remove. This study is to show that nitrate nitrogen in the form of gaseous nitrogen can be removed by using zinc ball with a diameter of about 3mm and to test the removal characteristics of nitrate nitrogen under various reaction conditions. As a result of this study, the treatment efficiency of nitrate nitrogen by continuous treatment with zinc ball was about 80%. However, there is a problem that the wastewater must be maintained in an acidic atmosphere of about pH 2, and the treated wastewater must be neutralized and discharged.

• Environmental Analysis Health and Toxicology
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• v.21 no.2 s.53
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• pp.115-126
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• 2006

This study was conducted to find out survival rate, activity, growth and change of the organ structure of bivalves exposed to heavy metal. The results of the study confirmed that zinc (Zn) induces reduction of survival rate and activity, abnormality of organ structure of the equilateral venus, Gomphina veneriformis. Experimental groups were composed of one control condition and three Zn exposure conditions ($0.64mg\;Zn{\iota}^{1},\;1.07mg\;Zn{\iota}^{-1},\;1.79mg\;Zn{\iota}^{-1}$). As the concentration of zinc increased the accumulation of lipofucin increased in the digestive gland. Survival rate was the lowest in the lowest Zn exposure group at $0.64mg;Zn{\iota}^{-1}$. Growth was not significantly different between the control and exposure group. Activity. with the exception of the lowest Zn exposure group at $0.64mg\;Zn{\iota}^{-1}$, was similar between the control and exposure group. Histological analysis of organ system illustrated expansion of hemolymph sinus, loss of striated border of inner epidermis, increase in the number of mucous cell in the mantle. Also, histological degenerations as epithelial necrosis and hyperplasia of mucous cells are recognized in the gill and foot.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.6
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• pp.240-246
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• 2021

In the ceramic industry, a drastic decrease in crystalline formation was found even among the glazes well known for their high crystalline productivity when the ceramic glaze was stored in wet conditions over a period. This study aimed to investigate the reason for decreasing willemite crystals during storage. As the starting materials ZnO, calcined ZnO and frit 3110 are selected; the composition for zinc crystalline glazes was set through a three-component system with the materials. The firing condition was used from previous studies. The study was observed how wet conditions affected the crystallization of zinc crystalline glazes from a day to 24 weeks. The results were obtained by particle size analysis, XRD, Raman spectroscopy and SEM analysis. The results indicated that ZnO is advantageous in terms of willemite crystalline development and growth; however, Zn(OH)₂ cluster, formed by the reaction with water during the storage, caused the decrease in ZnO level in the glaze. The reduction of ZnO in the glaze eventually interfered the willemite development and growth.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.439-443
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• 2019

To improve the noise characteristics, software-based noise reduction algorithms are widely used in cadmium zinc telluride (CZT) pixelated semiconductor gamma camera system. The purpose of this study was to develop an improved median filtering algorithm using a thresholding method for noise reduction in a CZT pixelated semiconductor gamma camera system. The gamma camera system simulated is a CZT pixelated semiconductor detector with a pixel-matched parallel-hole collimator and the spatial resolution phatnom was designed with the Geant4 Application for Tomography Emission (GATE). In addition, a noise reduction algorithm with a median filter using an improved thresholding method is developed and we applied our proposed algorithm to an acquired spatial resolution phantom image. According to the results, the proposed median filter improved the noise characteristics compared to a conventional median filter. In particular, the average for normalized noise power spectrum, contrast to noise ratio, and coefficient of variation results using the proposed median filter were 10, 1.11, and 1.19 times better than results using conventional median filter, respectively. In conclusion, our results show that the proposed median filter using improved the thresholding method results in high imaging performance when applied in a CZT semiconductor gamma camera system.

• Journal of the Korean Chemical Society
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• v.19 no.6
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• pp.468-470
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• 1975

• Journal of the Korean Chemical Society
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• v.32 no.6
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• pp.607-608
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• 1988

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.726-729
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• 2000

The entitled report revealed that ZnO phosphor samples treated at different temperatures under a given reduction atmosphere show the radiation brightness increase with increase of temperature up to about 900$^{\circ}C$ but become decreasing beyond the temperature. The brightness deterioration with curing temperature at higher temperatures was explained by the decrease of excess zinc ions resulted from their evaporation. The comments will open possibility for different discussions on the experimental result by introducing numerical relationships between the concentration of the native defects and the curing condition.

• Journal of the Korean institute of surface engineering
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• v.33 no.5
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• pp.381-386
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• 2000

It was found that colloidal silica sprayed to the galvanized steel sheet apparently made the molten zinc layer solidified to be the randomly oriented fine grains. Its spraying effect was also little affected by steel temperature that had been considered as one of the major operating factors in this process. From the results of surface analysis, it is considered that aluminum dissolved in coating layer reduces silica to silicon by the oxidation-reduction reaction, and that the reduced silicon acts as a more effective nucleus in solidification reaction than phosphate salt, siica and alumina.

• YAKHAK HOEJI
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• v.41 no.4
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• pp.480-483
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• 1997

The efficient synthesis of p-(acetylamino)phenylacetic acid(7), a antirheumatic agent, is reported. Methyl phenylacetate(3) was prepared from Friedel- Crafts reaction of benzene with methyl ${\alpha}$-chloro-${\alpha}$-(methylthio)acetate(1) followed by reductive desulfurization with zinc dust in acetic acid. Compound(7) was obtained from 3 by a sequence of nitration, reduction, N-acylation, and hydrolysis.