• 환경위생공학
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• 제10권3호
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• pp.105-114
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• 1995

There has been increasing awareness on the importance of not only removal of organic materials but also sterilization of microbial cell in the drinking water purification research, so there has been many researches on that area. This study has been designed to analyze the effects of $TiO_{2}$ and ZnO coated on activated carbon on Escherichia coli. In this study, the sterilization power was analyzed by (1) variation of $TiO_{2}$ and ZnO concentration coated on activated carbon (2) variation of UV intensity. In addition, the kinetics between exposure time and sterilization velocity was viewed by the method of Chick. The results are as follows. 1. Survival ratio of E. coli decreased as time goes on in application of $TiO_{2}$, ZnO and $TiO_{2}{\cdot}ZnO$. In $TiO_{2}$ and ZnO, the effect increased upto certain concentration, but decreased there-after. In $TiO_{2}{\cdot}ZnO$, the effect of sterilization was in similar way among 3 combinations. 2. Survival ratio of E. coli decreased proportionately to an increase of light intensity in ZnO and $TiO_{2}{\cdit}ZnO$. In $TiO_{2}$, the survival ratio differed over extent of irradiation but the difference over the light intensity was not significant. 3. When Chick's law of sterilization was applied, m values of three concentrations of $TiO_{2}$ were 1.57,0.98, 1.96 respectively. M values of three concentration of ZnO were 1.10, 1.18,0. 11 respectively and those of three combination of $TiO_{2}{\cdot}ZnO$ were 1.17, 1.24, 1.74 respectively.

• 한국세라믹학회지
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• 제39권9호
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• pp.835-839
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• 2002

Micro-Pulling Down(${\mu}$-PD)법을 이용하여 직경 1 mm, 길이 30∼35 mm의 $Er_2O_3$와 MgO가 첨가된 화학양론조성 $LiNbO_3$단결정을 성장하였다. 성장된 결정의 $Er_2O_3$와 MgO 첨가에 따른 up-conversion 특성의 변화 및 MgO 첨가량이 광손상에 미치는 영향을 관찰하기 위해 투과율을 측정하였다. 또한 $LiNbO_3$ 단결정 내의 결함유무를 광학현미경을 이용하여 관찰하였고, Electron Probe Micro Analysis(EPMA)를 이용하여 결정 내에 $Er_2O_3$와 MgO가 균일하게 분포되어있음을 확인하였다.

• 한국환경과학회지
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• 제22권12호
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• pp.1561-1569
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• 2013

This study carried out a laboratory scale plasma reactor about the characteristics of chemically oxidative species (${\cdot}OH$, $H_2O_2$ and $O_3$) produced in dielectric barrier discharge plasma. It was studied the influence of various parameters such as gas type, $1^{st}$ voltage, oxygen flow rate, electric conductivity and pH of solution for the generation of the oxidant. $H_2O_2$ and $O_3$.) $H_2O_2$ and $O_3$ was measured by direct assay using absorption spectrophotometry. OH radical was measured indirectly by measuring the degradation of the RNO (N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical). The experimental results showed that the effect of influent gases on RNO degradation was ranked in the following order: oxygen > air >> argon. The optimum $1^{st}$ voltage for RNO degradation were 90 V. As the increased of $1^{st}$ voltage, generated $H_2O_2$ and $O_3$ concentration were increased. The intensity of the UV light emitted from oxygen-plasma discharge was lower than that of the sun light. The generated hydrogen peroxide concentration and ozone concentration was not high. Therefore it is suggested that the main mechanism of oxidation of the oxygen-plasma process is OH radical. The conductivity of the solution did not affected the generation of oxidative species. The higher pH, the lower $H_2O_2$ and $O_3$ generation were observed. However, RNO degradation was not varied with the change of the solution pH.

• The Korean Journal of Ceramics
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• 제3권4호
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• pp.235-238
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• 1997

Basic properties of new cement pastes based on the system $CaO-Al_2O_3-P_O_5-H_2O$were studied Phosphoric acid solutions and calcium dialuminate clinkers synthesized by the hydration-burning method were used for liquid and powder components of the paste, respectively Variation in the compositions of the paste was achieved by changing the liquid/powder ratio and the concentration of phosphoric acid solution. The hardening rate of the paste was so largely affected by the amount of phosphoric acid that hardening was inhibited with the low-concentrated solution but was explosively accelerated with the high-concentrated solution. The phosphoric acid solutions of concentration of 45~50% and the liquid/powder ratio of 0.5~1.5 were favoured for the high early-strength cement paste with the reasonable hardening rate and high strength. The binding phase of hardened paste was the dense amorphous gel of the system $CaO-Al_2O_3-P_O_5-H_2O$. in which the unreacted calcium dialuminate grains were embeded.

• 한국전기전자재료학회논문지
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• 제15권8호
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• pp.664-670
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• 2002

The electrical characteristics of $ZnO-Pr_6O_{11}-CoO-Cr_2O_3-Y_2O_3$(ZPCCY)-based varistors were investigated with $Y_2O_3$ content in the range of 0.0~4.0 mol%. As $Y_2O_3$ content is increased, the average grain size was markedly decreased in the range of 18.6~3.2 $\mu m$ and the density of the ceramic was decreased in the range of 5.53 ~3.74 $g/\textrm{cm}^3$. While, the varistor voltage was increased in the range of 39.4~748.1 V/mm and the nonlinear exponent was in the range of 4.5~51.2 with increasing $Y_2O_3$ content. The addition of $Y_2O_3$ greatly enhanced the nonlinear properties of varistors, compared with the varistor without $Y_2O_3$. In particular, the varistors with $Y_2O_3$content of 0.5 mol% exhibited the highest nonlinearity, in which the nonlinear exponent is 51.2 and the leakage current is 1.3 $\mu A$. The donor concentration and the density of interface states were decreased in the range of (4.19~0.14) $\times$10$^{18}$ /㎤ and (5.38~1.15)${\times}10^{18}/\textrm{cm}^3$, respectively, with increasing $Y_2O_3$ content.

• Journal of Microbiology and Biotechnology
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• 제21권9호
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• pp.988-994
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• 2011

A significant amount of nitrous oxide ($N_2O$), which is one of the serious greenhouse gases, is emitted from nitrification and denitrification of wastewater. Batch wastewater nitrifications with enriched nitrifiers were carried out under oxygen-limited condition with synthetic (without organic carbon) and real wastewater (with organic carbon) in order to find out the effect of ammonium concentration on $N_2O$ emission. Cumulated $N_2O$-N emission reached 3.0, 5.7, 6.2, and 13.5 mg from 0.4 l of the synthetic wastewater with 50, 100, 200, and 500 mg/l ${NH_4}^+$-N, respectively, and 1.0 mg from the real wastewater with 125 mg/l ${NH_4}^+$-N. The results indicate that $N_2O$ emission increased with ammonium concentration and the load. The ammonium removal rate and nitrite concentration also increased $N_2O$ emission. Comparative analysis of $N_2O$ emission from synthetic and real wastewaters revealed that wastewater nitrification under oxygen-limited condition emitted more $N_2O$ than that of heterotrophic denitrification. Summarizing the results, it can be concluded that denitrification by autotrophic nitrifiers contributes significantly to the $N_2O$ emission from wastewater nitrification.

• Metals and materials international
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• 제24권6호
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• pp.1386-1393
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• 2018

The solubility of $TiO_2$ in $NaF-CaF_2-BaF_2$ ternary eutectic melts was investigated at the temperature range of $1025-1150^{\circ}C$. The least-squares equation was obtained from the relationship between the reciprocal temperature and the natural logarithm of the titanium concentration in the melts saturated with $TiO_2$. The corresponding partial molar enthalpy of dissolution of $TiO_2$ was found to be 188 kJ/mol. The titanium saturation concentration was 3.73 wt% at $1100^{\circ}C$. From the titanium concentration change with the added amount of $TiO_2$ at different holding time after a final stirring, it was found that not only complete dissolution of $TiO_2$ but also enough sedimentation of excessive $TiO_2$ should be guaranteed to obtain more reliable solubility data. The holding time of 10 h was found to be enough for the excessive $TiO_2$ particles to settle down in our experimental conditions. It is noteworthy that in case of adding $TiO_2$ in excess of its solubility, the $Ba_{1.12}(Ti_8O_{16})$ phase was observed at the lower and bottom of the solidified salt ingots.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.359-360
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• 2013

The effect of electrode and deposition methods on non-linear interfacial resistive switching in HfO2 based $250{\times}250$ nm2 cross-point device was studied. HfO2 based device has the interfacial resistive switching properties of non-linearity and self-compliance current switching. The operating current in HfO2 based device was increased with negatively increasing the heat of formation energy in top electrode. Also, it was investigated that the operating current in HfO2 based device was changed with deposition methods of O3 reactant ALD, H2O reactant ALD and dc reactive sputtering, resulting the magnitude of the operating current and on/off ratio in order of HfO2 films deposited by dc reactive sputtering, H2O reactant ALD, and O3 reactant ALD. To investigate the effect of electrode and deposition methods on operating current of non-linear interfacial resistive switching in the cross-point device, X-ray photoelectron spectroscopy was measured. Through the analysis of O 1s spectra, non-lattice oxygen concentration, which is closely related to oxygen vacancies, was increased in order of Pt, TiN, and Ti top electrodes and in order of O3 reactant ALD, H2O reactant ALD, and O3 reactant ALD, and dc reactive sputtering deposition method. From all results, non-lattice oxygen concentration in ultra-thin HfO2 films play a crucial role in the operating current and memory states (LRS & HRS) in the non-linear interfacial resistive switching.

• 한국응용과학기술학회지
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• 제24권3호
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• pp.246-252
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• 2007

$BaTiO_3$ powders were prepared by sol-gel method from different concentration of KOH aqueous solution and Ba/Ti molar ratio. Particle shape, size and crystal structure of prepared $BaTiO_3$ powders were analyzed by SEM, XRD, and FT-IR. As the result of KOH concentration changing, spherical particles were obtained by condition more than 3 M and particle size decreased as concentration increasing. Different appearance showed between dried and sintered powders against changing of Ba/Ti molar ratio. In case of dried powders, the crystallinity decreased as molar ratio increasing. On the other hand, increased as molar ratio increasing in case of sintered powders.

• 한국자기학회지
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• 제6권4호
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• pp.225-234
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• 1996

자기 기록용 전구체에 적합한 침상형 $\alpha-Fe_{2}O_{3}$ 입자를 수열반응법에 의해 수용액 중에서 비정질 수산화제이철로부터 직접 제조하였다. Ellipsoidal 또는 rectangular 형상의 $\alpha-Fe_{2}O_{3}$ 입자는 염기도 10.75~11.75 범위에서 생성되었다. 구연산 농도가 증가함에 따라 침상 입자의 길이와 침상비는 점차 감소하였으며, 구연산 농도 $1.5{\times}10^{-4}\;mol$ 이상 일때는 침상형 $\alpha-Fe_{2}O_{3}$ 입자로의 결정화가 저해되었다. 수열 반응 온도 $140^{\circ}C$에서 가장 침상성이 우수한 $\alpha-Fe_{2}O_{3}$ 입자가 제조되었으며, $220^{\circ}C$ 이상에서는 침상형 입자의 생성을 기대할 수 없었다.