• Carbon letters
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• v.12 no.2
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• pp.70-80
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• 2011

Two pitches with different average molecular structures were electrospun and compared in terms of the properties of their fibers after oxidative stabilization, carbonization, and activation. The precursor with a higher molecular weight and greater content of aliphatic groups (Pitch A) resulted in better solubility and spinnability compared to that with a lower molecular weight and lower aliphatic group content (Pitch B). The electrical conductivity of the carbon fiber web from Pitch A of 67 S/cm was higher than that from Pitch B of 52 S/cm. The carbon fiber web based on Pitch A was activated more readily with lower activation energy, resulting in a higher specific surface area compared to the carbon fiber based on Pitch B (Pitch A, 2053 $m^2/g$; Pitch B, 1374 $m^2/g$).

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2581-2584
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• 2020

Boron has been considered to play a nutritionally important role in humans and animals, but its biochemical functions are not clearly understood. Though there are signs that boron affects the mineral and hormone metabolisms, there is no comprehensive epidemiological evidence establishing a relationship between a boron intake and osteoporosis due to the excretion of calcium in the bones. In this study, we investigated the influence of boron intake on the calcium excretion of old female mice in the menopause. The concentrations of calcium in backbone, thigh bone, blood, kidney, liver, and spleen were investigated by using instrumental neutron activation analysis.

• Journal of the Korean Chemical Society
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• v.64 no.3
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• pp.145-152
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• 2020

Flip-flop rate constants were measured by dithionite assay of NBD-PE fluorescence in DMPC/POPC vesicles made of various DMPC/POPC ratios. The activation energy, enthalpy, entropy, and free energy were determined based on the transition state theory. We found that the activation energy, enthalpy, and entropy increased as the amount of POPC increased, but the activation free energy was almost constant. These experimental results and other similar studies allow us to propose that the POPC molecules included in DMPC vesicles affect the flip-flop motion of NBD-PE in DMPC/POPC vesicles via increasing the packing order of the ground state of the bilayer of the vesicles. The increase in the packing order in the ground state seems to be a result of the effect of the overall molecular shape of POPC with a monounsaturated tail group, rather than the effect of the longer tail group.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.78-79
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• 2021

It is necessary to calculate Apparent Activation Energy(Ea) in order to apply the equivalent age formula to predict compressive strength using the maturity method. For carbon reduction, it is necessary to consider the change of Ea by condition of GGBFS concrete, which is widely used today. In this study, as a basic study for the design of the compressive strength model of GGBFS concrete, the apparent activation energy of the GGBFS mixed paste was calculated through a calorimeter. The experiment was carried out at a hydration temperature of 10 to 30℃ with a paste test specimen having a GGBFS content of 0 to 80%. As a result, the GGBFS replacement rate of the paste increased, and Ea tended to increase as the temperature decreased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.101-102
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• 2021

The compressive strength of concrete is greatly affected by the temperature inside the concrete at the initial age immediately after pouring. The apparent activation energy of cement and the setting time of concrete are major factors influencing the development of compressive strength of concrete. This study measured the apparent activation energy and setting time according to the change in W/B for each mixing rate of Ground Granulated Blast-Furnace Slag (GGBFS). And after calculating the compressive strength prediction model, the accuracy of the prediction model was evaluated by comparing the predicted compressive strength and the compressive strength.

• Journal of the Korean institute of surface engineering
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• v.41 no.6
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• pp.301-307
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• 2008

In this paper, nanocrystallization of CuNiTiZr bulk metallic glass (BMG) subjecting to a kinetic spraying, dependent on impact velocity, was investigated by numerical and experimental approaches. The crystallization fraction and nucleation activation energy of initial feedstock and as-deposited coating were estimated by DSC and Kissinger method, respectively. The results of numerical modeling and experiment showed that the crystalline fraction and nucleation activation energy in BMG coatings were depended on kinetic energy of incident particle. Upon impact, the conversion of particle kinetic energy leads to not only decreasing free energy barrier but also increasing the driving force for an amorphous to crystalline phase transformation. The nanocrystallization of BMGs is associated with the strain energy delivered by a plastic deformation with a high strain rate.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.356-361
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• 1996

Cure kinetics of diglycidyl ether of bisphenol A(DGEBA)/4,4'-methylene dianiline(MDA) with hydroquinone-phenyl glycidyl ether(HQ-PGE) as a reactive additive, which was preliminarily synthesized, was investigated by DSC and FT-IR analyses. Kissinger equation and Arrhenius' equation were used to calculate activation energy and pre-exponential factor. When HQ-PGE was added to DGEBA/MDA system, it reduced activation energy of system. When the 5 phr of HQ-PGE was added to DGEBA/MDA system, activation energy was 7.8 kcal/mol by FT-IR analysis and 11.3 kcal/mol by DSC, in comparison with the system without HQ-PGE, activation energy decreased about 30% and 9%, respectively. According to these results, HQ-PGE, introducing agent of this system, acted as a catalyst.

• Textile Coloration and Finishing
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• v.14 no.4
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• pp.214-222
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• 2002

In order to give a silk-like touch to PET fabrics, the PET fabrics were treated with NaOH alkaline solution in various conditions. In alkaline treatment, the liquor flow type pilot weight reduction apparatus with magnetostrictive ultrasonic transducer was used for the study. The weight loss of PET fabrics hydrolyzed in 4% and 6% NaOH solution, at $95^\circ{C}$ and $99^\circ{C}$ for 60min. with ultrasonic application showed 3.7~4.6% higher than that of treated fabric without ultrasonic application. From the difference of specific weight loss, the treatment condition of the maximum of hydrolyzation effect appeared at $95^\circ{C}$ in $4^\circ{C}$ and at $90^\circ{C}$ in 6% NaOH solution, respectively. During the alkali hydrolysis of PET fabrics, the decomposition rate constant(k) increased exponentially with the treatment temperature and were not related with ultrasonic cavitation. The activation energy$(E_a)$ in decomposition of PET fabrics were 21.06kcal/mol with ultrasonic application and 21.10kcal/mol without ultrasonic application. The ultrasonic application gave a little higher value of the activation entropy$(\Delta{S}^\neq)$ and a little lower value of Gibbs free energy$(\Delta{S}^\neq)$ compared with not used ultrasonic apparatus.

• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.120-126
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• 1997

The thermal decomposition of low density polyethylene(LDPE) and $25\%{\~}48\%$ chlorinated polyethylene(CPE) were studied using a dynamic thermogravimetry in the stream of nitrogen gas with 20ml/min. The mathematic method, differential (Friedman) and Integral (Ozawa) method were used to obtain value of activation energy of decomposition energy on the reaction. The activation energies evaluated by the above methods agree with each other very well. The maximum average activation energy calculated was 71.71kcal/mol. The thermal decomposition of LDPE and CPE were considered to be carried out by main chain scission and the thermogravimetric trace curve agree with the theoretical equation.

• Journal of the Korean Society of Combustion
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• v.15 no.4
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• pp.65-73
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• 2010

In order to provide fundamental information for developing reaction model in the practical blended coal power plants, effects of particle size and blending ratio on combustion characteristics and thermal reaction in co-firing with bituminous and sub-bituminous coals were experimentally investigated using a TGA and a laboratory-scale burner. Characteristic parameters including ignition, burnout temperature and activation energy were determined from TG and DTG combustion profiles. Distributions of flame length and mean particle temperature were investigated from the visualization of flames in slit-burner system. As coal particle size decreased and volatile matter content increased, characteristic temperatures and activation energy decreased. The ignition/burnout characteristics and activation energy are linearly influenced by a variation in particle size and blending ratio. These results indicated that the control of the coal blending ratio can improve the combustion efficiency for sub-bituminous coals and the ignition characteristics for bituminous coals.