• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1481-1486
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• 2013

Bifunctional Fe-SBA-15-$SO_3H$ mesoporous materials with different Si/Fe molar ratios (3, 5, and 7) have been synthesized via a simple direct hydrothermal method and characterized by XRD, $N_2$-adsorption/desorption, TG/DTG and FT-IR techniques, and used as solid acid catalysts in the esterification of lactic acid with methanol. XRD and $N_2$ sorption characterizations show successful iron doping within the mesoporous channels of SBA-15-$SO_3H$. The FT-IR and TG/DTG characterizations also reveal the presence of iron. With the incorporation of Fe ions into the SBA-15-$SO_3H$, the acid sites substantially increased because of the self-separated acidity of the hydrolysis of $Fe^{3+}$ solutions. However, in the Si/Fe = 3 molar ratio, the catalytic conversion decreased which is caused by the reduced cooperation effect between the acid pairs due to the weakened hydrogen bonds and collapse of the pore structure. This further suggests that the mesoporous structure decreases with the decrease in Si/Fe ratio.

• Journal of Korean Dental Science
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• 제10권2호
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• pp.53-59
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• 2017

Purpose: The objective of the present article is to determine whether there are differences in vertical enlargement ratio among various sites within both jaws in a panoramic radiograph. Materials and Methods: Two hundred and seventy-threeimplant sites in panoramic radiographs were evaluated by two observers. Magnification ratios at various sites in both jaws were calculated and compared with each other. Result: The average vertical enlargement ratio in the panoramic radiograph was 1.264 and this value was larger than original ratio 1.250. Although vertical magnification ratio of maxillary molar area was higher than that of mandibular molar area, every group showed similar magnification ratio in clinical respect. Conclusion: Vertical magnification ratio of the maxillary molar area is statistically higher than that of the mandibular molar area in the panoramic radiograph, but it is clinically negligible.

• 한국자기공명학회논문지
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• 제21권3호
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• pp.85-89
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• 2017

Pyrazinamidase (PncA) from Mycobacterium tuberculosis is the hydrolytic enzyme (hydrolase) that can hydrolyze substrate PZA to active form pyrazoic acid (POA). To investigate hydrolytic reaction of M. tuberculosis PncA, 1D NMR spectra were monitored at various molar ratios of PncA and PZA. The line-width of PZA was changed as PncA was added into PZA with different molar ratios. These results suggested that determination of PncA enzymatic activity could potentially serve as an indirect measure of PZA susceptibility.

• 한국결정학회지
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• 제14권2호
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• pp.73-78
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• 2003

(Ba/sub 1-x/Sr/sub x/)TiO₃ (BST, 0.4< x <0.65) single crystals were successfully grown by the TSSG (Top-Seeded Solution Growth) method, using a commercial [100] SrTiO₃ or as-grown [100] BST single crystals as seed crystals. To obtain the BST single crystals with various compositions x, the Ba/sr molar ratios in the solutions were systematically controlled while the Ti ion content among all cations was fixed at 67 mol%. A linear regression curve between their x values and the molar ratios of Sr/(Ba + Sr) in the solutions could be obtained, which in turn could used to select the initial composition to produce BST crystal with an aimed x value. In addition, the isothermal growth was found more effective for obtaining a compositional uniformity than a slow cooling process.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2542-2548
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• 2009

Direct methylation behaviors of 20 amino acids with tetramethylammonium hydroxide (TMAH) were studied under diluted conditions with silica. Amino acid concentration was controlled by dilution with silica ($SiO_2$) and the molar ratios of amino acid/silica were 0.20, 0.50, and 2.0. The molar ratios of amino acid/TMAH (0.51 - 4.64) also varied. It was found that arginine, asparagine, aspartic acid, cysteine, glutamic acid, and glutamine did not generate any directly methylated pyrolysis products, whereas alanine, glycine, isoleucine, leucine, methionine, phenylanaline, valine, and proline generated all the directly methylated pyrolysis products. Tri- and tetra methylated products of lysine consisted of two types. Histidine and threonine hardly generated the partly methylated products. Mono- and dimethylated products of serine, tryptophan, and tyrosine were not observed. Relative intensities of the methylated products varied with the amino acid concentration, TMAH concentration, and pyrolysis temperature. Direct methylation behaviors of amino acids were explained by the structural characteristics of amino acids.

• 대한지역사회영양학회:학술대회논문집
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• 대한지역사회영양학회 1998년도 추계학술대회 및 제3차 정기총회
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• pp.120-120
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• 1998

• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.397-400
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• 2014

Size- and shape-controlled monodisperse wurtzite structured CdS nanorods have been successfully synthesized using a facile solution-based colloidal method. Depending on the control of injection/growth temperatures and the variation of Cd-to-S molar ratios, the morphology of the CdS nanocrystals (NCs) can be adjusted into bullet-like, rod-like, and dot-like shapes. X-ray diffraction (XRD), transition electron microscopy (TEM), and absorption spectroscopy were used to characterize the structure, morphology, and optical properties of as-synthesized CdS NCs. It was found that uniform CdS nanorods could be successfully synthesized when the injection and growth temperatures were very high (> $360^{\circ}C$). The aspect ratios of different shaped (bullet-like or rod-like) CdS NCs could be controlled by simply adjusting the molar ratios between Cd and S.

• Korean Chemical Engineering Research
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• 제57권1호
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• pp.124-132
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• 2019

출발물질로서 TEOS (tetraethoxysilane)와 CTMS (chlorotrimethylsilane)를 사용하여 물과의 가수분해 및 중축합 반응에 의해 발수 코팅 용액을 합성하였다. 또한 이 용액을 PMMA 시트 위에 도포하고 열처리하여 비불소계 발수 코팅 도막을 제조하였다. 코팅 도막은 수접촉각, UV-Vis 투과율 및 미세구조 관찰에 의해 분석되었다. CTMS/TEOS의 몰비를 0.6~1.0으로 변화시켜 제조 된 코팅 도막은 CTMS/TEOS의 몰 비가 0.8일 때 $107^{\circ}$의 최대 접촉각을 나타내었다. 또한 코팅 도막은 CTMS/TEOS의 몰 비가 0.6~0.8일 때 90%의 높은 가시광선 투과율을 보였다. 그러나 CTMS/TEOS의 몰 비가 0.9~1.0인 경우에는 거친 표면의 불균일한 형상으로 인해 코팅 도막은 70% 이하의 낮은 투과율을 보였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.220-221
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• 2018

Test results showed that foaming ratio of autoclaved aerated concrete significantly affected by the CaO/Si₂O (C/S) molar ratio of the component materials, indicating the greatest foaming ratio of 202% when the C/S ratio was 0.9.

• 한국재료학회지
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• 제21권4호
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• pp.225-231
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• 2011

The effect of ferrous/ferric molar ratio on the formation of nano-sized magnetite particles was investigated by a co-precipitation method. Ferrous sulfate and ferric sulfate were used as iron sources and sodium hydroxide was used as a precipitant. In this experiment, the variables were the ferrous/ferric molar ratio (1.0, 1.25, 2.5 and 5.0) and the equivalent ratio (0.10, 0.25, 0.50, 0.75, 1.0, 2.0 and 3.0), while the reaction temperature ($25^{\circ}C$) and reaction time (30 min.) were fixed. Argon gas was flowed during the reactions to prevent the $Fe^{2+}$ from oxidizing in the air. Single-phase magnetite was synthesized when the equivalent ratio was above 2.0 with the ferrous/ferric molar ratios. However, goethite and magnetite were synthesized when the equivalent ratio was 1.0. The crystallinity of magnetite increased as the equivalent ratio increased up to 3.0. The crystallite size (5.6 to 11.6 nm), median particle size (15.4 to 19.5 nm), and saturation magnetization (43 to 71 $emu.g^{-1}$) changed depending on the ferrous/ferric molar ratio. The highest saturation magnetization (71 $emu.g^{-1}$) was obtained when the equivalent ratio was 3.0 and the ferrous/ferric molar ratio was 2.5.