• 한국세라믹학회지
• /
• 제42권5호
• /
• pp.338-345
• /
• 2005

To prepare the complex gel of flux and pseudo-boehmite used in precursor of the flaky ${\alpha}-A1_2O_3$ crystal, aqueous solution of the mixture of sodium carbonate and sodium phosphate was added with stirring in aqueous solution of the mixture of sodium sulfate, potassium sulfate and titanium sulfate. The complex gel was dried at $110^{\circ}C$ and was crystallized above $1,050^{\circ}C$, and then the effect of the amount of titanium sulfate on size, morphology, thickness and crystal size distribution of the flaky ${\alpha}-A1_2O_3$ crystal was investigated. Addition of titanium sulfate was prevented the aggregation and generation of twin crystal, and had an effect on the crystal size and the thickness during crystal growth. When the amount of titanium sulfate was more than 6 g, particle size was decreased but was free from crystal twining and aggregation. On the other hand, when the amount of titanium sulfate was lower than 6 g, crystal size was increased but crystal twinning and aggregation were noticed.

• 대한화학회지
• /
• 제57권5호
• /
• pp.554-559
• /
• 2013

본 연구에서는 ${\beta}$-D-glucopyranose 분자의 hydroxymethyl group의 두 torsion angle의 변화에 따른 포텐셜 에너지의 변화를 진공 상태와 implicit water 상태에서 연구하였으며 이를 통해 Solvation Energy가 구조에 미치는 영향에 대해서 알아보았다. 계산에 사용한 프로그램은 AMBER package였으며, force field는 GLYCAM_06을 사용하였다. Solvation model은 Hawkins, Cramer, Truhlar 등이 제안한 generalized Born model을 사용하였다. 계산 결과, methyl hydroxyl group 내의 hydroxyl group이 고리구조의 hydroxyl group과 강한 수소결합이 가능한 영역에서 많은 변화가 일어났다. 이를 통해 solvation effect로 인해서 수소 결합의 중요성이 감소했다는 결론을 내렸다.

• 한국화재소방학회논문지
• /
• 제32권3호
• /
• pp.1-7
• /
• 2018

본 연구는 ABC 분말소화약제와 제1인산암모늄의 열분해생성물이 목재표면에 미치는 영향에 대해 검토하였다. 목재표면에서 열분해 생성물을 제거하였을 때 제1인산암모늄은 점도가 높은 투명한 열분해 생성물이 눌어붙어 제거하기 힘들었으나 ABC 분말소화약제는 덩어리진 형태로 쉽게 제거되었다. 열분석 결과 각 시료의 열분해 특성은 유사하나 열분해 잔존물의 중량이 ABC 분말소화약제는 55.9%, 제1인산암모늄은 25.2%로 나타나 차이를 보였다. ABC 분말소화약제에 첨가된 첨가제가 열분해 잔존물의 중량 및 메타인산의 방신효과에도 영향을 미치는 것으로 나타났다.

• Bulletin of the Korean Chemical Society
• /
• 제35권1호
• /
• pp.117-122
• /
• 2014

As a Chinese herbal medicine used in East Asia for thousands years, Cortex Magnoliae Officinalis (CMO) was observed to possess a protective effect against OH-induced DNA damage in the study. To explore the mechanism, the antioxidant effects and chemical contents of five CMO extracts were determined by various methods. On the basis of mechanistic analysis, and correlation analysis between antioxidant effects & chemical contents, it can be concluded that CMO exhibits a protective effect against OH-induced DNA damage, and the effect can be attributed to the existence of phenolic compounds, especially magnolol and honokiol. They exert the protective effect via antioxidant mechanism which may be mediated via hydrogen atom transfer (HAT) and/or sequential electron proton transfer (SEPT). In the process, the phenolic-OH moiety in phenylpropanoids is oxidized to the stable quinine-like form and the stability of quinine-like can be ultimately responsible for the antioxidant.

• 분석과학
• /
• 제18권2호
• /
• pp.168-172
• /
• 2005

A comparison study of XRF and $^{31}P$-NMR method for the analysis of phosphorous in lubricating oil has been described. Pure oil and water were used for the observation of matrices effect variation by different analytical methods. Quantitative analysis was carried out by XRF and $^{31}P$-NMR using real samples. Significant difference is observed from the slopes on the calibration curves by the XRF due to the matrices (water: 124.0, oil: 276.6). While the result obtained from XRF showed a large matrix effect, the slopes obtained from $^{31}P$-NMR results of two different matrices, however, are in good agreement ranged of ${\pm}9%$ (water: 4.9, oil: 5.3).

• 대한화학회지
• /
• 제55권5호
• /
• pp.824-829
• /
• 2011

In Fischer-Tropsch Synthesis, because of few reactants ($H_2$, CO), scarce operating parameters affected on efficiency especially the selectivity of products. In this research, effect of operating parameters on the selectivity of Co-Mn-$TiO_2$ Fischer-Tropsch synthesis catalyst were studied by design of experimental procedure and Taguchi method. According to this research, interactions between operating factors have a crucial effect on light products selectivity. Among these interactions, (temperature${\times}$feed ratio) has the main influence on light hydrocarbons selectivity. It was concluded that temperature and feed ratio ($H_2$/CO) were the most integral operating parameters for much greater selectivity of light hydrocarbons.

• Bulletin of the Korean Chemical Society
• /
• 제29권6호
• /
• pp.1131-1136
• /
• 2008

The electrical repulsive energy between two model cylinders was calculated by solving nonlinear Poission- Boltzmann (P-B) equation under Derjaguin approximation. Effects of the surface potential, Debye screening length, and configuration of cylinders on the repulsive interaction energy were examined. Due to the anisotropy of the shape of cylinder, the interaction repulsive energy showed dependence to the configuration of particles; cylinders aligned in end-to-end configuration showed largest repulsive energy and crossed particles had lowest interaction energy. The configuration effect is originated from the curvature effect of the interacting surfaces. The curved surfaces showed less repulsive energy than flat surfaces at the same interacting surface area. The configuration dependency of interaction energy agreed with the previous analytical solution obtained under the linearized P-B equation. The approach and results present in this report would be applicable in predicting colloidal behavior of cylindrical particles.

• Korean Chemical Engineering Research
• /
• 제44권3호
• /
• pp.289-293
• /
• 2006

탄산칼슘을 제조하는 연속식 결정화 공정에서 결정의 입도분포에 대한 온도와 교반속도 영향을 연구하였다. 연속식조업에서 용액의 산도 변화는 적었다. 교반속도가 300 RPM 이하, 용액의 온도가 낮으면 탄산칼슘 결정의 부피 평균크기는 안정하였고, 전자현미경 사진 관찰에서 calcite와 aragonite가 만들어졌음을 알 수 있었다

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
• /
• pp.687-692
• /
• 2002

The chemical shrinkage and the autogenous shrinkage have been determined experimentally for cement pastes incorporating different W/C ratio and different amount of the following addition: silica fume, fly ash and sand. The measurement method of the chemical shrinkage and autogenous shrinkage both were the volumetric technique. The silica fume has a effect of increasing the autogenous shrinkage while have a minor effect on the chemical shrinkage. The addition of fly-ash and sand both decreased the amount of chemical shrinkage and autogenous shrinkage.

• Natural Product Sciences
• /
• 제8권3호
• /
• pp.108-110
• /
• 2002

A new ardimerin (1) was isolated from the herb of Ardisia japonica. Its structure was determined by the elucidation of spectroscopic data and a chemical transformation. Compound (1) showed potent radical scavenging effect on DPPH radical $(IC_{50},\;0.32\;{\m}M)$.