• Korean Journal of Food Science and Technology
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• v.34 no.2
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• pp.174-179
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• 2002

A simple and sensitive analysis method based on reverse phase (RP) HPCL with flourescence detector was developed for simultaneous determination of bisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE), and their degradation products, $BADGE{\cdot}H_2O$, $BADGE{\cdot}2H_2O$, $BFDGE{\cdot}H_2O$, $BFDGE{\cdot}2H_2O$, $BADGE{\cdot}HCl{\cdot}H_2O$, $BADGE{\cdot}HCl$, $BADGE{\cdot}2HCl$, $BFDGE{\cdot}HCl{\cdot}H_2O$, $BFDGE{\cdot}HCl$ and $BFDGE{\cdot}2HCl$, which were hydrolyzed and chlorinated forms of BADGE and BFDGE, in canned foods and food simulants. These compounds were identified by GC/MSD with $MSTFA-NH_4I-DTE$ derivatization. Recovery study was performed at each 100 ng/mL levels of BPA, BPF, BADGE and BFDGE added to canned foods and food simulants. This method was resulted in recovery of $90{\sim}114%$ with relative standard deviation of $4.1{\sim}7.0%$, detection limits of $6{\sim}11$ ng/mL and quantitation limits of $12{\sim}18\;ng/mL$. Calibration curves were linear with correlatin coefficients of 0.997 for BPF, 0.996 for BPA, 0.9987 for BFDGE, and 0.9989 for BADGE.

• Clean Technology
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• v.21 no.3
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• pp.200-206
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• 2015

In order to investigate the effect of cerium oxide addition, Cu-ZnO-CeO₂ catalysts were prepared using co-precipitation method for water gas shift (WGS) reaction. A series of Cu-ZnO-CeO₂ catalyst with fixed Cu Content (50 wt%, calculated as CuO) and a given ceria content (e.g., 0, 5, 10, 20, 30, 40 wt%, calculated as CeO₂) were tested for catalytic activity at a GHSV of 95,541 h^-1, and a temperature range of 200 to 400 ℃. Cu-ZnO-CeO₂ catalysts were characterized by using BET, SEM, XRD, H₂-TPR, and XPS analysis. Varying composition of Cu-ZnO-CeO₂ catlysts led the difference characteristics such as Cu dispersion, and binding energy. The optimum 10 wt% doping of cerium facilitated catalyst reduction at lower temperature and improved the catalyst performance greatly in terms of CO conversion. Cerium oxide added catalyst showed enhanced activities at higher temperature when it compared with the catalyst without cerium oxide. Consequently, ceria addition of optimal composition leads to enhanced catalytic activity which is attributed to enhanced Cu dispersion, lower binding energy, and hindered Cu metal agglomeration.

• Journal of the Korean Ceramic Society
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• v.38 no.9
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• pp.853-859
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• 2001

The dispersion stability of nano $Y_2O_3-CeO_2$ system was investigated using colloid surface chemistry. Green body of $Y_2O_3$ doped $CeO_2$ was prepared by slip casting in and aqueous system. The dispersion stability of suspension between powders and organic additive was accomplished through electrokinetic behavior of suspension, which was done by ESA apparatus. The dynamic mobility of particles was enhanced when the anionic dispersant of the amount of 1wt% was added. The dissolution of $Y^{3+}$ ion in suspension occurred in the acidic region so that pH value in slurries did not move to below 7.0. In the $CeO_2-Y_2O_3$ system, optimal preparation of suspension was made after adding the anionic dispersant as the amount of 1wt% and pH value of 11.0, and then slip-cast and sintered at 1400$^{\circ}$C, 2 hrs. It appeared relative density of >98% and homogeneous distribution of Y element in depth direction as well as in the microstructure of surface.

• Journal of the Korean Chemical Society
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• v.59 no.3
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• pp.209-214
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• 2015

The formation of complexes between SO₂ and acetic acid was studied theoretically. The ab initio and DFT calculations were performed with MP2 and B3LYP methods using 6-311++G(d,p), aug-cc-pVDZ and aug-cc-pVTZ basis sets. Six stable complexes were identified, and three stable bidentate complexes, C1, C2 and C3, were formed between SO₂ and syn-acetic acid, which is more stable form of acetic acid. Anti-acetic acid also form three complexes, C4, C5 and C6, with SO₂. C4 is bidentate and C5, C6 are monodentate complexes, which are less stable. The most stable complex, C1 has S⋯O=C and O⋯H-O interactions, and the S⋯O and O⋯H distances are less than the sum of van der Waals radii. The vibrational frequencies of complexes were calculated and were compared with those of monomers. The frequency shifts after formation of complex were found, and the overall pattern of frequency shifts relative to monomers is similar among the six complexes.

• Korean Journal of Materials Research
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• v.14 no.2
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• pp.90-93
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• 2004

Silicon dioxide thin films were deposited on p-type Si (100) substrates by atomic layer deposition (ALD) method using alternating exposures of $SiH_2$$Cl_2$ and $O_3$ at $300^{\circ}C$. $O_3$ was generated by corona discharge inside the delivery line of $O_2$. The oxide film was deposited mainly from $O_3$ not from $O_2$, because the deposited film was not observed without corona discharge under the same process conditions. The growth rate of the deposited films increased linearly with increasing the exposures of $SiH_2$$Cl_2$ and $O_3$ simultaneously, and was saturated at approximately 0.35 nm/cycle with the reactant exposures over $3.6 ${\times}$ 10^{9}$ /L. At a fixed $SiH_2$$Cl_2$ exposure of $1.2 ${\times}$ 10^{9}$L, growth rate increased with $O_3$ exposure and was saturated at approximately 0.28 nm/cycle with $O_3$ exposures over$ 2.4 ${\times}$ 10^{9}$ L. The composition of the deposited film also varied with the exposure of $O_3$. The [O]/[Si] ratio gradually increased up to 2 with increasing the exposure of $O_3$. Finally, the characteristics of ALD films were compared with those of the silicon oxide films deposited by conventional chemical vapor deposition (CVD) methods. The silicon oxide film prepared by ALD at $300^{\circ}C$ showed better stoichiometry and wet etch rate than those of the silicon oxide films deposited by low-pressure CVD (LPCVD) and atmospheric-pressure CVD (APCVD) at the deposition temperatures ranging from 400 to $800^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.24-30
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• 2003

A formation and conversion of AFm phases decisively play role in the hydration, hardening and corrosion processes of various cement. In this study, the conversion of Alumino-Ferrite Monohydrates(AFm) phases under the addition of $CaCO_3,;CaCl_2;and;CaSO_4{cdot}2H_2O$was investigated by the XRD quantitative analysis. The thypical AFm phases are $M_S(monosulfoaluminate),;M_C(monocarboaluminate);and;M_{Cl}(monochloroaluminate and also Called Friedel's salts)$in this cementitious system, The conversion reaction were not occurred in $M_C-CaCO_3,;M_{Cl}-CaCO_3$ and $M_{Cl}-CaCl_2$system. However, in $M_S-CaCO_3$ system, ettringite and $monocarboaluminate(M_C)$ were formed. In $M_S-CaCl_2;system;M_S$ was transformed to Friedel's $salts(M_{Cl})$ and ettringite was formed. In the case of $CaSO_4{cdot}2H_2O$ addition, all AFm $phases(M_S,;M_C;and;M_{Cl})$ were transformed to ettringite. The order of stabilization of AFm phases under $CaCO_3,;CaCl_2;and;CaSO_4{cdot}2H_2O$ was as follows : $M_S< M_C

• Journal of Sensor Science and Technology
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• v.6 no.3
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• pp.200-206
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• 1997

Using $SiCl_{2}H_{2}$, $NH_{3}$ and $N_{2}O$, we have fabricated silicon oxynitride ($Si_{x}O_{y}N_{z}$) layers on thermally oxidized silicon wafer by low pressure chemical vapor deposition. Three different compositions were achieved by controlling gas flow ratios($NH_{3}/N_{2}O$)) to 0.2, 0.5 and 2 with fixed gas flow of $SiCl_{2}H_{2}$. Ellipsometry and high frequency capacitance-voltage(HFCV) measurements were adapted to investigate the difference of the refractive index, dielectric constant, and composition, respectively. Regardless of nitride content, silicon oxynitrides had similar stability to silicon nitrides. The relative standing of alkali ion sensitivity in silicon oxynitride layers was influenced by nitride content. The better alkali ion-sensitivity was achieved by increasing oxide content in bulk of silicon oxynitrides.

• YAKHAK HOEJI
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• v.37 no.2
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• pp.129-135
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• 1993

Serratia sp. Y-4 was isolated from soil. Many characteristics of the strain and optimum cultivation condition for protease production were investigated.,The protease from Serratia sp. Y-4 was purified and studied for the properties of the enzyme. The isolated strain was identified to the genus Serratia. The strain was cultivated in 1%-casein, 0.5%-Na$_{3}$PO$_{4}$.7H$_{2}$O, 0.1%-NaCl, 0.05%-KCI, 0.02%-MgSO$_{4}$.7H$_{2}$O, 0.02%-CaCl$_{2}$.2H$_{2}$O, 0.02%-ZnSO$_{4}$.7H$_{2}$O, 0.02%-MnCl$_{2}$.4H$_{2}$O and 0.5%-soy bean oil at pH 7.0 for 35 hrs. The enzyme was purified about 5.89 fold from the culture broth with 31.1% recovery and 19,613 u/mg through ultrafiltration, ammonium sulfate, DEAE-sephacel and Superose-12 chromatography. The purified enzyme was identified as one band by isoelectric focusing, SDS- and native-PAGE. It has maxium activity at $37^{\circ}C$ and pH 9.0. Molecular weight of it is approx. 50 kD and pl is about 6.70. Its Km value for casein was 20 mg/ml. 5 mM-EDTA, 5mM-SDS, Ag$^{+1}$, Cu$^{+2}$, Hg$^{+2}$ and Pb$^{+2}$ inhibited the enzyme.

• Journal of Energy Engineering
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• v.15 no.3 s.47
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• pp.146-153
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• 2006

A performance test of the stainless steel based sintered metal filter was conducted on the low and intermediate level radioactive waste (LILW) vitrification process. The applicability of the metal filter was based on the test results as well. The baseline pressure drop of the metal filter was evaluated similar to the ceramic filter. During the test, when the flow rate of off-gas was $110Nm^{3}/h$, the total baseline pressure drop was shown as $92mmH_{2}O$. The total pressure drop was attributed to the filter media and the residual dust layer and the value of each was $25mmH_{2}O\;and\;67mmH_{2}O$ respectively. The SEM-EDS spectrum and micrograph of the metal filter specimen showed, no corrosion and no physical damage both at the skin membrane and at the support layer. And most of the baseline pressure drop was caused by the deposition of dust on the surface of the membrane. In conclusion, even though the filter exposure time was short at the test, the performance of the stainless steel based metal filter was acceptable for the treatment of LILW vitrification process.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.238-238
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• 2011

Ion sensitive field effect transistor (ISFET)는 용액의 이온 농도를 측정하는 반도체 센서로, 1970년 Bergveld에 의해 처음으로 제안되었다. ISFET가 제안된 이래로, 제조공정이 간단하고 감지막의 감지 특성 평가가 용이한 electrolyte-insulator-semiconductor (EIS) pH센서 또한 지속적으로 연구되었다. EIS pH센서는 작은 소자 크기, 견고한 구조, 빠른 응답속도와 CMOS공정과의 호환성이 좋다는 장점이 있다. EIS 또는 ISFET 센서를 이용하여 생물학적 요소의 신호 감지 특성을 평가함에 있어 소자의 signal to noise 비율이 우수해야 한다. EIS pH센서의 높은 signal to noise 비율을 얻기 위해, 소자의 표면적을 증가시키거나 감지막으로 유전상수가 높은 물질을 사용하여 출력 특성을 향상시켜야 한다. 본 연구에서는 trench구조와 SiO2/HfO2/Al2O3 (OHA) 적층 감지막을 갖는 EIS pH센서를 제작하여 출력 특성을 증가시키는 실험을 실시하였다. 120 nm, 380 nm, 780 nm의 다양한 깊이를 가진 trench를 형성하였으며, trench 깊이에 따른 출력특성을 비교하였다. 또한, 제작된 EIS 소자의 pH감지 특성을 분석하였다. 제작된 EIS소자의 감지막 중 SiO2는 Si와 high-k물질의 계면 상태를 보완하기 위한 완충막으로 성장되었고, HfO2는 높은 유전상수를 가지고 있어 signal to noise 비율을 향상시키는 물질로 증착되었다. 최종적으로 Al2O3는 pH용액과의 화학적 손상을 막기 위한 물질로 증착되었다. 실험 결과, trench 깊이가 깊어질수록 출력값이 증가하였고 이는 signal to noise 비율이 향상되는 것을 의미한다. 결론적으로 trench 형성을 통한 표면적 증가와 high-k물질을 적층한 감지막으로 인해 높은 출력 특성을 갖는 우수한 EIS 바이오센서를 제작할 수 있었다.