• Journal of the Korean Magnetics Society
• /
• v.19 no.2
• /
• pp.43-46
• /
• 2009

The magnetic and structural properties of the (8, 0) BN nanotubes with transition metals (TM) of Fe, Co, or Ni substitution for B or N were investigated using a first-principles calculation. It was found that TM substitution makes the cross section being distorted and the bond length TM-B or TM-N being longer than that of the original B-N one. The magnetic moment is larger for the TM substitution for B than one for N, and it is mainly due to the 3d electrons of TM atoms.

• Journal of the Korean Chemical Society
• /
• v.47 no.2
• /
• pp.96-103
• /
• 2003

Density Functional Theory(DFT) calculations are performed to estimate the hydrogen bonding interaction energies in pyridine-water and amino-substituted pyridine-water complexes. Some equilibrium properties are also obtained for these complexes at B3LYP/aug-cc-pVDZ level. It is shown that the amino substitution increases the proton affinity of pyridine and stabilizes the hydrogen bond. The degree of stabilization upon formation of the complex varies with the number and the position of the amino groups.

• Magazine of the Korea Concrete Institute
• /
• v.9 no.5
• /
• pp.149-155
• /
• 1997

고로슬래그 미분말을 사용한 콘크리트\ulcorner 수화속도가 느려 어린 재령시 동해의 영향을받기 쉽다. 본 연구에서는 고로슬래그 미분말을 사용한 콘크리트의 동결융해 저항성을 알아보기 위해 고로슬래그 미분말의 치환율과 물-결합재비를 변화시켜 제조한 콘크리트에 대해 동결융해시험을 실시하였다. 또한 동일한 치환율, 물-결합재비의 콘크리트에 AE제를 첨가시켜 동결융해 저항성의 개선효과를 알아보았다. 시험결과 고로슬래그 미분말의 치환율이 증가할수록 동결융해 저항성은 작게 나왔다. 또한 non-AE 콘크리트의 경우 물-결합재비가 51%, 45%일 때 내구성지수는 각각 2.4%, 40.0%이하로 매우 나쁘게 나타났으나, AE콘크리트의 경우 물 -결합재비가 45%와 51%인 콘크리트의 내구성지수는 각각 90.2% 80.9%이상으로 동결융해 저항성이 매우 우수하게 나타났다.

• Journal of the Korea Concrete Institute
• /
• v.27 no.6
• /
• pp.687-693
• /
• 2015

The present study proposed a k-value to determine the water-to-binder ratio of concrete using fly ash (FA) or ground granulated blast-furnace slag (GGBS) as a partial replacement of ordinary portland cement (OPC) with regard to an equivalent strength of OPC concrete. From the regression analysis using an extensive database including 7076 concrete mixes, k-values were determined for various water-to-binder ratios when the replacement ratio of OPC by the addition of FA or GGBS were below 50%. For deriving an equation to identify k-value, the relationship of concrete compressive strength and water-to-binder ratio was generalized by an exponential function. In general, k-values decreased with the increases in the addition of FA or GGBS for replacement of OPC and water-to-binder ratio. The rate in decreasing k-value against water-to-binder ratio was marginally affected by the addition of FA or GGBS, although a higher k-value was commonly obtained for GGBS concrete than for FA concrete at the same water-to-binder ratio. Consequently, the determined k-values were simplified as a function of water-to-binder ratio and the addition ratio of FA or GGBS as replacement of OPC.

• Journal of the Korea Concrete Institute
• /
• v.21 no.1
• /
• pp.29-35
• /
• 2009

Recently, the press and institute recognized fly ash as it had excellent performance. Its research and applications are on the rise largely as a substitute for cement. On the contrary, it is in a situation that the regulation of high fineness fly ash remains at a low level. As for the fly ash in $3,000{\sim}4,500\;cm^2/g$ class fineness regulated in KS L 5405, it is used by substituting it around the unit weight of cement 20%. Accordingly, the regulation in upper classification is in a situation of being insufficient. Therefore, this study aimed to establish 4000, 6000, and 8000 class of fineness of fly ash and three levels of substitute like 15%, 30%, and 45% in order to analyze the substitute and effect of water-binder ratio for fly ash that affected the properties of ternary system concrete. As a result of experiment by planning water-binder ratio for two levels like 40% and 50%, the more replacement ratio and fineness of fly ash increased in the performance not hardened, the more the fluidity increased. This study has found out that the air content decreased, and that there was setting acceleration and it decreased the heat of hydration. In addition, as for the strength properties in a state of performance hardened concrete, the more the replacement ratio and the ratio of water-binding materials increased, the more it had a tendency of being decreased.

• Journal of the Korea Concrete Institute
• /
• v.23 no.2
• /
• pp.145-150
• /
• 2011

Presently, mass concrete structures are being built in federal and private projects of civil infrastructures and building structures. The hydration heat of mass concrete structures is the most important factor in the quality of concrete matrix and construction period. Moreover, internal cracks caused by hydration heat degrades durability, water tightness, and strength of concrete. To reduce hydration heat, it is necessary to blend belite cement (${\beta}-C_2S$) with industrial by-products (i.e. granulated slag and fly ash). In this experiment, 14 levels of binary binders and 4 levels of ternary binders were used to understand the effect of different replacement ratio on hydration heat, strength and microstructure (i.e. SEM and XRD) of mortar. Cumulative hydration heat at 28 days for the binary and ternary binders was affected by replacement ratio of fly ash and/or granulated slag. As fly ash content increased, hydration heat decreased. As granulated slag content increased, reduction rate of the hydration heat was lower than when fly ash was used. Especially, the hydration heat of ternary binder blended with 40% flyash and 30% granulated slag showed about 50% of hydration heat from using belite cement (P). The study results showed that the temperature rise of concrete matrix can be decreased by using blended belite binders producing low hydration heat and reasonable strength.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.39 no.4
• /
• pp.329-335
• /
• 2013

Three-dimensional quantitative structure-activity relationships (3D-QSARs) models between the substituents with changing groups ($R_1$ & $R_2$) of 4-hydroxybenzyl alcohol (4-HBA) derivatives as substrate molecule and their inhibitory activities against tyrosinase were derived and discussed quantitatively. The optimized CoMSIA FF model showed the best predictability and fitness ($r^2$ = 0.858 & $q^2$ = 0.951). The contour maps of the optimized CoMSIA FF model showed that, the inhibitory activities of the analogues against tyrosinase were expected to increase when hydrophobic (Hy) favor, negative charge (E) favor, steric (S) disfavor and hydrogen bond donor (HD) disfavor groups were substituted at the $R_2$ position. When the hydrogen bond donor (HD) favor groups were substituted at the $R_1$ position, it is predicted that the substituents will be able to increase the inhibitory activity.

• Proceeding of EDISON Challenge
• /
• 2015.03a
• /
• pp.40-47
• /
• 2015

본 연구에서는 일치환된 방향족 화합물의 $NO_2{^+}$ 치환반응에서의 반응성 (reactivity)과 지향성 (regioselectivity)에 대해 분석하였다. 기존의 연구에 따르면, 방향족 고리와 치환체 사이의 ${\sigma}$ 결합을 통한 유발효과와 ${\pi}$ 결합을 통한 공명효과로 인해 벤젠 고리의 전자 분포가 증가하게 되면 반응성이 증가하는 것으로 알려져 있다. 또한 반응중간생성물인 탄소양이온의 안정성을 통해 지향성을 확인할 수 있는 것으로 알려진 바가 있다. 이에 따라, 본 연구에서는 반응성과 지향성이 실험적으로 잘 알려진 7가지의 치환기 (OH, $OCH_3$, $CH_3$, Cl, COOH, CN, $NO_2$)를 선정하여 DFT functional인 B3LYP를 사용하여 natural bond orbital (NBO) 계산을 하였고, 각각의 일치환된 벤젠 고리가 갖는 전자 분포를 ${\sigma}$와 ${\pi}$ 전자로 나누어서 보기로 했다. 그 결과, 일치환된 방향족 고리 치환반응의 반응성과 지향성은 ${\sigma}$ 결합을 통한 유발효과에 의해서는 영향을 받지 않고, 공명 효과로 인한 반응물의 ${\pi}$ 전자 분포에 의해 결정되는 것을 확인할 수 있었다. 이외에도 반응성을 비교 하기 위해 친핵체로 작용하는 일치환된 방향족 고리의 highest occupied molecular orbital(HOMO) 에너지와 친전자체인 $NO_2{^+}$의 lowest unoccupied molecular orbital (LUMO) 에너지의 차이를 비교하였으며, 친핵체의 HOMO 에너지가 높을수록 반응성이 커짐을 알 수 있었다.

• Journal of Applied Biological Chemistry
• /
• v.54 no.1
• /
• pp.56-62
• /
• 2011

Molecular docking of polyhydroxy substituted flavone analogues (1-25) as substrate molecules to the active site of tyrosinase (PDB ID: Deoxy-form (2ZMX) & Oxy-form (1WX2)) and Free-Wilson analysis were studied to understand the roles of hydroxyl substituents ($R_1-R_9$) in substrate molecules for the tyrosinase inhibitory activation. It is founded from Free-Wilson analysis that the $R_1$=hydroxyl among $R_1-R_9$ substituents had the strongest influence on the tyrosinase inhibitory activity. H-bonds between the hydroxyl substituents of substrate molecules and amino acid residues in the active site of tyrosinase were contributed to make a stable substrate-receptor complex compound. Particularly, it is proposed from the findings that the noncompetitive inhibitory activation would take place via H-bonding between peroxide oxygen (Per404) atom in the active site of tyrosinase and the hydroxyl substituents in substrate molecule.

• Journal of the Korean Ceramic Society
• /
• v.38 no.6
• /
• pp.558-567
• /
• 2001

본 연구에서는 알콕사이드를 전구물질로 하는 졸겔공정을 이용하여 Bi 과잉 12 mol%의 조성인 B $i_4$ $Ti_3$ $O_{12}$ 박막과 B $i_4$ $Ti_{3-x}$T $a_{x}$ $O_{12}$(x=0.1, 0.2, 0.3) 박막을 제조하였다. XPS 분석에 따르면 Ta 치환 x=0.2에서 Bi 4f의 photoemission 곡선이 낮은 결합에너지로 이동하였고 피크 강도가 감소하는 현상이 관측되었다. 이는 x=0.1과 0.2 사이에서 Bi-O 결합이 길어져 인장상태 하에 있었음을 나타내었다. B $i_4$ $Ti_3$ $O_{12}$(BIT) 박막의 유전상수와 유전손실은 100 kHz에서 340, 0.05이었고, B $i_4$ $Ti_{3-x}$T $a_{x}$ $O_{12}$ 박막에서 이들 값은 x=0.1에서 가장 높았으며, 각각 480, 0.13이었다. B $i_4$ $Ti_3$ $O_{12}$ 박막의 잔류분극과 항전계는 1.24$\mu$C/$ extrm{cm}^2$, 31.4 kV/cm 이었으나, Ta 치환 x=0.2에서 이들 값은 각각 19.7$\mu$C/$\textrm{cm}^2$, 49.5 kV/cm 에 이르렀다. 또한, B $i_4$ $Ti_3$ $O_{12}$ 박막의 누설전류 밀도는 ~$10^{-6}$ A/$\textrm{cm}^2$ 정도이었으며, Ta 치환은 누설전류를 감소시켜 Ta 치환 x=0.2 이상에서 BIT 박막에 비해 한 차수 정도 낮아졌다. Ta 치환에 따른 B $i_4$ $Ti_3$ $O_{12}$ 전기 물성에서 변화는 Bi-O 결합에서 관측된 인장상태로의 전이와 연관성이 있었으며, 덧붙여 치환에서 생성된 전자에 의한 정공보상이 이에 영향을 끼쳤다. 정공보상이 이에 영향을 끼쳤다.끼쳤다.