• 한국결정성장학회지
• /
• 제9권1호
• /
• pp.64-69
• /
• 1999

PANrP 탄소섬유의 고온연신에서의 변형 거동을 검토하기 위해서, 일정 하중하에서 내부저항 가열법에 의해 $1200^{\circ}C$부터 $2200^{\circ}C$까지 열처리 온도를 변화시키며 섬유의 strain 변화를 측정하였다. 부하된 응력이 증가함에 따라서 strain 변화가 크게 발생하며 또한 열처리 온도 약 $1700^{\circ}C$를 경계로 해서 그 온도 이상과 이하 사이에는 큰 차이를 보였다. 각 응력에 있어서의 strain 속도 변화로부터 얻어진 활성화 에너지는 70 MPa 및 322 MPa에 대하여 각각 67.46 및 52.27 kJ/mol로써, 큰 응력의 경우가 작은 응력을 부하하는 것 보다 섬유구조 발달에 있어서 더욱 효과적이라는 것을 알았다.

• 약학회지
• /
• 제35권5호
• /
• pp.372-378
• /
• 1991

To increase the stability and bioavailability of Omeprazole(OMP), which is used newly as a proton-pump inhibitor, inclusion complex of OMP with $\beta$-cyclodextrin($\beta$-CD) was prepared by coprecipitation method and its characteristics were ascertained by means of solubility test, DSC, IR, and the accelerated stability analysis. The type of OMP inclusion complex is classified as Bs-type on phase solubility diagram, and the stoichiometric ratio of OMP: $\beta$-CD complex is 1:2 and formation constant is 80.82/mole. The solubility of the complex could be increased remarkably by complexation compare with OMP. Degradation process of both OMP and OMP complex followed apparent first-order kinetics, of which degradation rate constants and activation energies are k$_{25}$=8.1$\times$10$^{-4}$/day, E$_{a}$=22 Kcal/mole (OMP), and k$_{25}$=4.65$\times$10$^{-6}$/day, E$_{a}$=35 Kcal/mole (complex), respectively. These results show the increase of the stability and solubility of OMP markedly, therefore it is believed that the improvement of stabilization for OMP by inclusion complexation might be practically available.

• 한국안전학회지
• /
• 제14권2호
• /
• pp.90-96
• /
• 1999

The characteristics of spontaneous ignition of painting waste was investigated at constant ambient temperature in oven. As the results of experiments, the spontaneous ignition temperature decreased as the sample vessel became large, and the spontaneous ignition temperature of the sample in small, intermediate and large vessels was $165.5^{\circ}C$, $144.5^{\circ}C$ and $134.5^{\circ}C$ respectively. The apparent activation energy calculated by the Frank-Kamentskii's thermal ignition theory was 34.73 kcal/mol.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
• /
• pp.173-178
• /
• 2000

New prediction model is investigated estimating splitting tensile strength and modulus of elasticity with curing temperature and aging. New prediction model is based on the model which was proposed to predict compressive strength, and splitting tensile strength and modulus of elasticity calculated by this model are compared with experimental values. New prediction model well estimated splittinge tensile strength and elastic modulus as well as compressive strength.

• 한국응용과학기술학회지
• /
• 제27권1호
• /
• pp.6-13
• /
• 2010

Esterification reaction between succinic acid and 1,4-butanediol was kinetically investigated in the presence of nontoxic organometallic compound catalyst(ESCAT-100E) at $150-190^{\circ}C$. The reaction rates measured by the amount of distilled water from the reaction vessel. The Esterification reaction was carried out under the first order conditions respect to the concentration of reactants, respectively. The overall reaction order was 2nd. The linear relationship was shown between apparent reaction rate constant and reciprocal absolute temperature. By the Arrhenius plot the activation energy have been calculated as 376.13 kJ/mol under nontoxic organometallic compound catalyst and also apparent reaction rate constant, k' was found to obey first kinetics with respect to the concentration of catalyst.

• 한국식품과학회지
• /
• 제20권5호
• /
• pp.711-717
• /
• 1988

배추의 염절임중 배추 조직으로의 소금흡수 속도를 측정하고 확산에 관한 수학적인 모델과 computer simulation을 통해서 확산계수를 구하였다. 배추 줄기로의 소금의 침투 및 탈염 될 때의 확산계수는 각각 $1.7{\times}10^{-11}m^2/s$와 $11.6{\times}10^{-11}m^2/s$이었다. Apparent diffusivity는 소금의 농도와 배추의 종류에 커다란 영향을 받지 않으며, 온도의존성은 Arrhenius식으로 나타낼 수 있고 이때의 활성화 에너지는 66 KJ/mol 이었다.

• 한국건축시공학회지
• /
• 제14권1호
• /
• pp.110-117
• /
• 2014

본 연구에서는 양생온도변화에 따른 자기수축의 예측을 위하여 FA 및 SF를 치환한 시멘트모르타르를 대상으로 자기수축변화를 측정하고 이를 등가재령방법으로 해석하고자 하였다. 이를 위해 수화반응의 온도민감도를 고려하는 Ea의 변화에 따라 지수함수모델을 이용하여 자기수축 해석을 실시하였는데, 경화단계의 $E_a$를 이용할 경우 응결단계의 $E_a$를 사용한 경우보다 정확한 해석이 가능한 것으로 나타났는데, 이는 경화의 전단계에 걸친 수화의 온도민감도 영향을 반영한 $E_a$값에 기인된 결과로 사료된다.

• 한국의류학회지
• /
• 제13권1호
• /
• pp.89-97
• /
• 1989

Graft polymerization of MMA onto cotton fiber was carried out in two ways, two step graft polymerization and one step emulsion graft polymerization, using tetravalent cerium ion as an initiator. At two step graft polymerization, the first step was the pretreatment of cotton fiber with an aqueous initiator solution and the second was the grafting pretreated cotton fiber in the monomer solution. In case of one step emulsion graft polymerization, MMA was emulsified with SLS in initiator solution. Under the various graft polymerization conditions, graft yield, graft efficiency and from the Arrhenius plot the apparent activation energy were compared. The results of this study were as follows: 1. Graft yield and graft efficiency of emulsion graft polymerization were higher than those of two step graft polymerization. 2. In case of two step graft polymerization, graft yield was affected by the pretreatment time of cotton fiber with an aqueous initiator solution. And graft yield of emulsion graft polymerization was increased with the concentration of emulsifier below cmc of SLS and was decreased thereafter. 3. Elevation of temperature resulted increase in graft yield for both grafting methods. The apparent activation energy of emulsion graft pelymerzation was lower than that of two step graft polymerization. 4. Increased reaction time increased in graft yield, but decreased in graft efficiency. 5. Moisture regain of grafted cotton was decreased with graft yield.

• 한국세라믹학회지
• /
• 제31권11호
• /
• pp.1249-1258
• /
• 1994

Titanium carbide was synthesized by reacting the prepared titanium powder and carbon black using SHS method sustains the reaction spontaneously, utilizing heat generated by the exothermic reaction itself. In this process, the effect of the particle size of titanium powder on combustion temperature and combustion wave velocity was investigated. By controlling combustion temperature and combustion wave velocity via mixing Ti and C powder with TiC, the reaction kinetics of TiC formation by SHS method was considered. Without reference to the change of combustion temperature and combustion wave velocity, TiC was easily synthesized by combustion reaction. As the particle size of titanium powder was bigger, or, as the amount of added diluent(TiC) increased, combustion temperature and combustion wave velocity were found to be decreased. The formation of TiC by combustion reaction in the Ti-C system seems to occur via two different mechanisms. At the beginning of the reaction, when the combustion temperatures were higher than 2551 K, the reaction was considered to be controlled by the rate of dissolution of carbon into a titanium melt with an apparent activation energy of 148 kJ/mol. For combustion temperatures less than 2551 K, it was considered to be controlled by the atomic diffusion rate of carbon through a TiC layer with an apparent activation energy of 355 kJ/mol. The average particle size of the synthesized titanium carbide was smaller than that of the starting material(Ti).

• 한국건축시공학회지
• /
• 제20권5호
• /
• pp.409-416
• /
• 2020

본 연구는 W/C 50%의 일반강도 조건에서 OPC, FA 및 BS 시멘트의 종류를 변화시켜 콘크리트의 강도 증진 성상을 한랭기 온도의 4~17℃의 평균 양생온도에서 검토하고, 등가재령에 의한 강도 해석모델을 이용하여 강도 증진 해석을 수행하고, 기온저하에 따른 기온보정강도를 제안하고자 하였다. 본 실험의 결과 등가재령을 이용하여 Plowman 모델식으로 강도증진을 해석하였고, 대체로 양생온도가 낮을수록 강도증진이 지연되는 경향을 나타내었다. 이에 양생온도 저하에 따른 강도보정을 3MPa 단위로 실시하였고, 이를 토대로 배합강도 결정시 결합재 종류 및 관리재령별 기온보정강도(T_n)을 제안하였다.