• 동굴
• /
• 제78호
• /
• pp.17-22
• /
• 2007

The melting temperature and critical temperature (Tc) of $YBa_2Cu_3O_x$ with deferent content impurities of PbO and $BaPbO_3$ were studied. When the PbO was used as addition in $YBa_2Cu_3O_x$, although the melting point could be reduced, the superconductivity (the transition wide, ${\Delta}T_c$) became poor. From the XRD pattern of the sintered mixture of $YBa_2Cu_3O_x$ and PbO it was known that there is a reaction between $YBa_2Cu_3O_x$ and PbO, and the product is $BaPbO_3$. In the process of the reaction the superconducting phase of $YBa_2Cu_3O_x$ was decreased and in the sample $BaPbO_3$ became the main phase. Therefore the superconductivity was reduced. $BaPbO_3$ was chosen as the impurity for the comparative study. The single phase $BaPbO_3$ was synthesized by the simple way from both mixtures of $BaCO_3$ and PbO, $BaCO_3$ and $PbO_2$. Deferent contents of $BaPbO_3$ (10%, 20%, 30%) were added in the $YBa_2Cu_3O_x$. By the phase analysis in the XRD patterns it was proved that there were not reactions between $YBa_2Cu_3O_x$ and $BaPbO_3$. When $BaPbO_3$ was used as impurity in $YBa_2Cu_3O_x$ the superconductivity was much better than PbO as impurity in $YBa_2Cu_3O_x$. But the melting point of $YBa_2Cu_3O_x$ with $BaPbO_3$ could not be found when the temperature was lower than $1000^{\circ}C$ in the DTA measurement.

• 한국환경과학회지
• /
• 제28권11호
• /
• pp.971-981
• /
• 2019

This study evaluated the photocatalytic oxidation efficiency of volatile organic compounds by $Cu_2O-TiO_2$ under visible-light irradiation. $Cu_2O-TiO_2$ was synthesized by an ultrasonic-assisted method. The XRD result indicated successful p-n type photocatalysts. However, no diffraction peaks belonging to $TiO_2$ were observed for the $Cu_2O-TiO_2$. The Uv-vis spectra result revealed that the synthesized $Cu_2O-TiO_2$ can be activated under visible-light irradiation. The FE-TEM/EDS result showed the formation of synthesized nanocomposites in the commercial P25 $TiO_2$, the undoped $TiO_2$, and $Cu_2O-TiO_2$ and componential analysis in the undoped $TiO_2$ and $Cu_2O-TiO_2$. The photocatalytic oxidation efficiencies of benzene, toluene, ethylbenzene, and o-xylene with $Cu_2O-TiO_2$ were higher than those of P25 $TiO_2$ and undoped $TiO_2$. These results indicate that the prepared $Cu_2O-TiO_2$ photocatalyst can be applied effectively to control gaseous BTEX.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제18권1호
• /
• pp.102-111
• /
• 2013

A novel MgO-based binder was developed and applied to treat the anoxic sediment that was collected from Seonakdong river, Korea and was contaminated with heavy metals. The treated sediment was evaluated by measuring compressive strength, expansion, leaching of heavy metals and storage characteristics for $CO_2$. Initially, an optimal blending ratio of lime (L)/fly ash (FA)/blast furnace slag (BFS) that was to be mixed with MgO was screened to be $L_{0.3}-FA_{0.1}-BFS_{0.6}$. Long-term strengths of the sediments that were treated by various mixtures of MgO and $L_{0.3}-FA_{0.1}-BFS_{0.6}$ were then evaluated and the blending ratios between 4 : 6 and 6 : 4 were found optimal, which yielded a compressive strength of 4.09 MPa. On this basis, the optimal MgO-based binder was selected to be a 5 : 5 mixture of MgO and $L_{0.3}-FA_{0.1}-BFS_{0.6}$. The good performance of the MgO-based binder was believed to be due to the formation of Mg $(OH)_2$, which filled the micropores and also increased the density of the solidified matrices. The MgO-based binder exhibited an average stabilizing capacities for heavy metals of 92.9%, which was similar to or higher than that of Portland cement. It was found that 69.1 kg of carbon dioxide could be sequestrated after 365 days of curing when treating a ton of anoxic sediments.

• 대한불안의학회:학술대회논문집
• /
• 대한불안의학회 2005년도 추계학술대회 및 대한정신약물학회 추계연수교육
• /
• pp.80-91
• /
• 2005

o Benzodiazepines can be effective in treating Anxiety Disorders o Efficacy of Benzodiazepines varies across Anxiety Disorders o Proper diagnosis is important before prescribing o Consider Side effects and withdrawal symptoms o Periodic Evalustion of Risk/Benefit of BZ o Advised gto use proper dose, duration for indicated Anxiety Disorders

• 한국세라믹학회지
• /
• 제30권9호
• /
• pp.740-746
• /
• 1993

TiO2-SnO2 fine powders prepared by coprecipitation from TiCl4-SnCl4 aqueous solution, and their crystal structures were studied. All the TiO2-SnO2 fine powders calcined at 180~$700^{\circ}C$ showed the complete solid solution between TiO2(rutile structure) and SnO2(rutile structure). This crystal structure of TiO2-SnO2 powders is thought to be originated mainly from the heterogeneous nucleation of Ti-hydroxde on the Sn-hydroxide with coherent structure.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
• /
• pp.953-956
• /
• 2008

Using the theoretical model of Auger electron emission, effects of MgO properties which include band gap energy, escape probability, gas ion, and doping elements on the yield of secondary electron emission were examined. The results indicated that the band gap of MgO must be decreased and escape probability must be enhanced in order to increase the yield of secondary electrons from Xe ions and that may proved to be a critical for achieving high luminance efficacy in ac-PDPs.

• 한국세라믹학회지
• /
• 제22권3호
• /
• pp.35-40
• /
• 1985

The composition of the base glass was determined to be $Na_2O$ 15, $Fe_2O_3$ 35, $B_2O_3$ 0~20, $P_2O_5$ 30~50 by mole percent. The heating temperature for nucleation was determined by means of thermal expansion curve. Crystalline phases were investigated by X-ray diffraction method and I.R Spectra. Electrical conductivities of glass spec-imens were observed in the temperature range 25~20$0^{\circ}C$ The activation energies of these specimens were caculated. The results obtained were as follows : 1) The limit composition of the melts 15mol% $Na_2O$ 35mole% $Fe_2O_5$ 20mole% $B_2O_3$ 30mole% $P_2O_5$ was able to be formed into desired shapes during cooling, . 2) In the measurement of d. c conductivity($\delta$) on the glasses in the system $15Na_2O-35Fe_2O_3$-$B_2O_3$-(50-x) $P_2O_5$ the values decreased by replacing 5 mole% $P_2O_5$ with $B_2O_3$ 3) The d. c conducties of heat treated samples were increased by replacing $P_2O_5$ with $B_2O_3$ 4) $B_2O_3$ contributed to precipitate crystals such as${\gamma}$-$Fe_2O_3$ $Fe_3O_4$ which had the advantage of electronic conduction in heat treated samples. 5) The slope plotted Log($\delta$) versus 1/T in this glass system was linear in the measured temperature range.

• The Korean Journal of Ceramics
• /
• 제6권2호
• /
• pp.134-137
• /
• 2000

Zirconia films stabilized b $Y_2O_3$, YSZ, films were deposition by metal organic chemical vapor deposition (MOCVD) onto various kind of substrates. $Y_2O_3$, $ZrO_2$and the mixtures of these two were deposited and characterized. The deposition rate, the film composition and the structure could be systematically varied through the $Y(C_{11}H_{19}O_2)_3$, Zr(O.t-$C_H_9)_4$source gas ratios and the deposition temperature. The Y/Zr ratio in YSZ film could be adjusted by controlling the ratio of $Y(C_{11}H_{19}O_2)_3$, Zr(O.t-$C_4H_9)_4$partial pressures. This is because the ratios of the deposition rates of Y and Zr atoms in $Y_2O_3$and $ZrO_2$films to those in YSZ films, Ф, are constant irrespective of the input gas concentration. However, the Y/Zr ratio was found to be smaller than that estimated based on the deposition rates of un-mixed $Y_2O_3$and $ZrO_2$films. This is because the Фs of Y and Zr atoms are not equal. The activation energy of $Y_2O_3$component in YSZ films was similar to that of $ZrO_2$component in YSZ films. These YSZ values were more than 4 times larger than those of un-mixed $Y_2O_3$or $ZrO_2$films.

• 멤브레인
• /
• 제27권4호
• /
• pp.313-318
• /
• 2017

올레핀/파라핀 분리를 위해 $Poly(ethylene oxide)(PEO)/AgBF_4/Al(NO_3)_3/Ag_2O$ 복합막이 제조되었으며, $Ag_2O$가 도입되었을 때, 복합체 분리막의 초기성능은 선택도 13.7과 투과도 21.7 GPU로 관찰되었다. $PEO/AgBF_4/Al(NO_3)_3$ 분리막의 성능(선택도 13와 투과도 7.5 GPU)에 비해서 초기성능이 증가한 이유는 $Ag_2O$의 첨가로 인한 Ag ion의 활성도 증가로 생각되었다. 하지만 시간에 따른 성능저하 현상이 관찰되었는데 이는 고분자 matrix인 PEO 때문인 것으로 생각되었다. PEO 고분자는 $Ag_2O$ 입자를 안정화 시킬 수 없기 때문에 용매가 증발하면서 $Ag_2O$ 입자끼리 뭉치게 되고, $Ag_2O$가 barrier 역할을 하게 돼서 시간이 지나면 투과도가 감소하는 것으로 분석되었다.

• 한국지형학회지
• /
• 제23권2호
• /
• pp.29-45
• /
• 2016

Chemical composition of fine sediments from Jeongdongjin area are analyzed with XRF method. The results are compared with previously reported results of sandstones of the nearest Simgok port. The weight percentage of $SiO_2$ of the samples are far lower than those of sandstones of Simgok. It is supposed to be happened by the selective elution of $SiO_2$ from the sediment layer of coastal terrace, as there's no evidence of selective input or precipitation of other elements from outside. As a result of chemical alteration or weathering of sediment at coastal terrace, weight percentage of $Al_2O_3$ and $Fe_2O_3$ of samples show far higher values than those of Simgok sandstone. In addition, the relative portion of $Al_2O_3$ and $Fe_2O_3$ are decreased to upward within outcrop of terrace sediment layers. It could be caused by the chemical weathering progress with time. However Chemical Index of alteration(CIA) of sediment samples are no larger than 90 and it could be interpreted that it would take over 100ka for total weathering of sediment in this area. Meanwhile the ratio of $SiO_2/Al2O_3$ of terrace sediment showed as 3.48~6.0 and it is far smaller than those of Simgok sandstones(23.9~49.0). The ratio of $SiO_2/Fe_2O_3$ of terrace sediment(19.19~55.85) showed similar pattern with $SiO_2/Al2O_3$ (Simgok sanstone: 119.6~601.8). The ratios have a weak trend of decreasing upwards within the outcrop, there also a huge difference in value among the samples. Chemical composition of reddish brown and gray layers which suspected as the result of psudogleization reveals that reddish brown parts have higher concentration of $Fe_2O_3$ than other parts, while there was no significant difference in concentration of $Al_2O_3$ and CaO.