• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.594-599
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• 2022

In the study, NH₃-SCO (selective catalytic oxidation) reaction activity accodrding to vanadium loading amount were compared when preparing Pt/V/TiO₂. Considering both NH₃ conversion rate and N₂ selectivity, V 2 wt% loading of the catalyst showed the best activity. When the correlation between physical/chemical characteristics and reaction activity was confirmed, it was confirmed that the increase in lattice oxygen and (V³⁺ + V⁴⁺) ratios were active factor. In addition, when the SO₂ durability experiment was conducted using the best catalyst, it was confirmed that the influence was insignificant even if the high concentration of SO₂ was injected.

• Analytical Science and Technology
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• v.20 no.5
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• pp.383-392
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• 2007

The water soluble components were analyzed in the $PM_{2.5}$ fine particles collected at the 1100 site of Mt. Halla for the spring seasons between 1998 and 2004. The $PM_{2.5}$ mass concentrations were within $13.4{\pm}9.6{\sim}21.7{\pm}20.0{\mu}g/m^3$, and the concentrations of ionic components were in the order of nss-$SO{_4}^{2-}$ > $NH{_4}{^+}$ > $NO{_3}{^-}$ > $Ca^{2+}$ > $K^+$ > $Na^+$ > $Cl^-$ > $Mg^{2+}$, in which the concentration of nss-$SO{_4}^{2-}$($3.41{\pm}2.42{\mu}g/m^3$) was the highest. The concentrations of $NH{_4}{^+}$, $SO{_4}^{2-}$, and $NO{_3}{^-}$, the secondary pollutants, were respectively 0.60~1.50, 2.86~4.42, and $0.24{\sim}1.57{\mu}g/m^3$, which had occupied 88 % of the total ionic components, on the other hand, the concentrations of marine species were less than 5 %. The nss-$SO{_4}^{2-}$ showed the high correlation with $NH{_4}{^+}$, $K^+$, so that $NH{_4}{^+}$ and nss-$SO{_4}^{2-}$ might exist in the form of $(NH_4)_3H(SO_4)_2$ and $(NH_4)_2SO_4$ in fine particles. From the backward trajectory analysis, in case of high concentrations of $NH{_4}{^+}$ and nss-$SO{_4}^{2-}$ simultaneously, the air masses were originated and stagnated at the east region of China for a while, then moved into the atmosphere of Jeju. However, in case of $NO{_3}{^-}$ and nss-$Ca^{2+}$, the air masses originated at China and Siberia were moved into Jeju via the eastern China.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.8
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• pp.479-483
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• 2017

The effect of $NH_3$ plasma treatment on device characteristics was confirmed for an optimized thin film transistor of poly-Si formed by ELA. When C-V curve was checked for MIS (metal-insulator-silicon), Dit of $NH_3$ plasma treated and MIS was $2.7{\times}10^{10}cm^{-2}eV^{-1}$. Also in the TFT device case, it was decreased to the sub-threshold slope of 0.5 V/decade, 1.9 V of threshold voltage and improved in $26cm^2V^{-1}S^{-1}$ of mobility. Si-N and Si-H bonding reduced dangling bonding to each interface. When gate bias stress was applied, the threshold voltage's shift value of $NH_3$ plasma treated device was 0.58 V for 1,000s, 1.14 V for 3,600s, 1.12 V for 7,200s. As we observe from this quality, electrical stability was also improved and $NH_3$ plasma treatment was considered effective for passivation.

• Journal of the Korean Chemical Society
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• v.60 no.3
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• pp.187-193
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• 2016

In this study, preparation of positively and negatively charged carbon nanotube (CNT)-collagen (CG) hydrogels with pH sensitive characteristic was reported. The positive and negative characteristics of the prepared hydrogels were created by introduction of positively functionalized CNT-NH₂ and negatively functionalized CNT-COOH, respectively, into the collagen hydrogel. The surface charge of CNTs (CNT-NH₂ and CNT-COOH), CG and CNTs/CG hydrogels was measured by Zetasizer. The swelling ratios of CNT-NH₂/CG and CNT-COOH/CG hydrogels in aqueous solution were checked by measuring of weight changes of the hydrogels in the range of pH 2~10. In detail, the positively charged CNT-NH₂/CG hydrogel swelled up to 5% at pH 4 in comparison to the weight at pH 7, while the negatively charged CNT-COOH/CG hydrogel swelled up to 10% at pH 10. The prepared CNT-NH₂/CG and CNT-COOH/CG hydrogels will be very useful as pH sensitive oral drug-delivering systems for gastrointestine (pH ~2) and small intestine (pH ~9), respectively.

• Journal of the Korean Chemical Society
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• v.16 no.3
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• pp.157-165
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• 1972

Thermal decomposition of ammonium metavanadate has been investigated by using the quartz spring balance and differential thermal analysis. It showed that the decomposition of ammonium metavanadate is proceeded at two stages which correspond to $180^{\circ}C-220^{\circ}C$ and $310^{\circ}C-330^{\circ}C$ decomposition temperatures, respectively. Evolved ammonia gas in thermal decomposition has been analyzed quantitatively by titration. And the constituents of gases evolved have been evaluated by gas chromatography and omegatron spectrometer. From these results, it was concluded that the gases evolved in the first step decomposition were $NH_3$ and $H_2O$ with 2:1 ratio and the second step decomposition corresponded to the formation of $NH_3$, $H_2O$ and $N_2O$ which was produced in oxidation of $NH_3$ by $V_2O_5$. The decomposition products were identified by means of X-ray diffraction method. The decomposition product in air was V_2O_5 and the product in vacuum $V_3O_7.$ The kinetics of the thermal decomposition was studied, giving the values of the activation energy of 41.4 kcal/mole and 64.4 (kcal/mole) respectively.

• Journal of the Mineralogical Society of Korea
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• v.31 no.2
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• pp.67-73
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• 2018

The objective of this study was to investigate the application of sulfate solvents for the economic and eco-friendly leaching of valuable metals from Au concentrate using an acid bake-water leaching system (AWS). AWS experiments were performed using an electric furnace with various baking temperatures ($100-500^{\circ}C$) and sulfate solvents ($H_2SO_4$, $K_2SO_4$, $(NH_4)_2SO_4$, $MgSO_4$, and $CaSO_4$). The efficiency of the valuable metal leaching increased as the baking temperature was increased to $400^{\circ}C$. Based on the AWS leaching time experiments, the maximum leaching rate occurred with the aqueous $(NH_4)_2SO_4$ solvent. This study demonstrates that aqueous $(NH_4)_2SO_4$ could be used as an effective solvent for valuable metal leaching using an AWS.

• Journal of Environmental Science International
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• v.11 no.4
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• pp.347-353
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• 2002

This study was conducted to investigate the characteristics of chloramination as a secondary disinfection in a drinking water distribution system. At the range from pH 6 to pH 8, monochloramine was predominant with a trace of dichloramine, and the free chlorine was detected after breakpoint. At $25^{\circ}C$, the breakpoints of pH 6, 7 and 8 appeared when the weight ratios of chlorine to ammonia nitrogen were 11:1, 9:1 and 10:1 respectively, and the peak points on the breakpoint curves at pH 6, 7 and 8 were in the Cl$_2$ / NH$_3$-N ratio of 9:1, 6:1 and 5:1 respectively. As pH increased from 6 to 8, maximum point of monochloramine on the breakpoint curve was moved from 7:1 to 5:1 in the weight ratio of chlorine to ammonia nitrogen. The maximum concentration of monochloramine was formed at the pH values of 7~8 and in the Cl$_2$ / NH$_3$-N ratio below 5:1. As the Cl$_2$/NH$_3$-N ratio increased and the pH lowered, chloramines decay proceeded at an increased rate, and residual chloramines lasted longer than the residual free chlorine. The monochloramine and the dichloramine were formed at pH 6, and then the dichloramine continued increasing with contact time.

• Journal of Bio-Environment Control
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• v.19 no.4
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• pp.229-233
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• 2010

This experiment was carried out to find optimum ratio of $NO_3^-$ to $NH_4^+$ in nutrient solution for the growth of Phalaenopsis hybrid and find the effect of the ratio of $NO_3^-$ to $NH_4^+$ on the flower stem (inflorescence) quality. The ratio of $NO_3^-$ to $NH_4^+$ of nutrient solution used in this experiment was 100% : 0%, 90% : 10%, 80% : 20% and 70% : 30%. Phalaenopsis showed better growth when $NH_4^+$ was supplied concurrently with $NO_3^-$ as nitrogen source than supplied with only $NO_3^-$. Especially, increasing the ratio of $NH_4^+$ from 0% to 10% the fresh weight and dry weight of Phalaenopsis hybrid was highest. But, the growth of shoot and root was diminished when the proportion of $NH_4^+$ in nutrient solution was increased from 10% to 30%. Inflorescence length, the number of inflorescence and flower per plant all increased as $NH_4^+$ increased from 0% to 10% but, decreased from 10% to 30%. These results suggest that the optimal ratio of $NO_3^-$ and $NH_4^+$ in nutrient solution for the growth of Phalaenopsis including inflorescence was founded to be 90%:10%.

• Journal of Bio-Environment Control
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• v.4 no.2
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• pp.181-187
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• 1995

This study was conducted to investigate the effect of NH$_4$H$_2$PO$_4$ on pH of the nutrient solution using municipal tap water during hydroponic culture of crisp lettuce (Lactuca sativa var. capitata) seedlings. The composition of starter solution was different from that of supplementary solution. The pH in the nutrient solution was suddenly declined and recovered as the supplementary solution was supplied. The pH of nutrient solution was increased with high temperature and, on the contrary, the EC of nutrient solution was decreased. It shows that plant absorbed nutrients more than water in given solution when the temperature and light was high. After supplying supplementary solution in 1st and End experiment, pH was slowly increased to 7 in NH$_4$H$_2$PO$_4$ 0.25me/$\ell$, but maintained 6.4-6.5 in NH$_4$H$_2$PO$_4$ 3me/$\ell$ and 6me/$\ell$. In 3rd experiment, pH was slowly increased from 6.7 to 7.4 in NH$_4$H$_2$PO$_4$ 0.25me/$\ell$, but decreased from 6-6.5 to 5-5.5 in NH$_4$H$_2$PO$_4$ 3me/$\ell$ and 6me/$\ell$. So it is suggested that the concentration between 0.25 me/$\ell$ and 3 me/$\ell$ by concentration base or the amount of NH$_4$H$_2$PO$_4$ between 1me/6 $\ell$ and 7me/6 $\ell$ by total quantity in solution is appropriate for stabilizing pH in the nutrient solution. Also this experiment suggests that hand operated measurements must be cautious due to the change of pH and EC within a 24-hour cycle.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.83-90
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• 2015

In this study, we investigated optimum conditions for the introduction of a lot of free radical polymerizable methacrylate groups on the multi-walled carbon nanotube (MWCNT) surface. Carboxyl groups were introduced first on MWCNT surfaces by treating with a mixture of sulfuric acid and nitric acid with ultrasonic bath for 2 hours, and oxidized MWCNTs were reacted further with thionyl chloride followed by triethylenetetramine (TETA) to introduce amino groups on the oxidized MWCNT surface, to make MWCNT-$NH_2$. To introduce free radical polymerizable methacrylate groups on the MWCNT-$NH_2$, MWCNT-$NH_2$ was reacted with 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM) by Michael addition reaction. We investigated progress of modification reactions for MWCNT by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and elemental analysis (EA). We found maximum degree of Michael addition reactions between AHM and TETA grafted on MWCNT-$NH_2$ for 10:1 mol ratio and 8 hour reaction time in our reaction conditions.