• 한국연소학회지
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• 제16권3호
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• pp.21-26
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• 2011

Thermal analyses are conducted to measure chemical kinetic parameters of an unknown liquid fuel with various components. Thermal Analyses are divided into two different methods such as TGA(Thermo-Gravimetric Analysis) and DSC(Differential Scanning Calorimety). Non-isothermal experimental results are analyzed by adopting TGA and they are filtered by Freeman-Carroll method. As a results of the analysis, chemical parameters of the activation temperature and the reaction order are measured to be 6128.2 K and 1.4, respectively. Furthermore, the chemical kinetic parameters are obtained by a variety of mathematical processing methods. It has been found that they show a little difference depending on the processing method.

• 설비공학논문집
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• 제13권12호
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• pp.1223-1229
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• 2001

Though conventional calorimetry methods such as differential scanning calorimetry (DSC) and differential thermal analysis (DTA) are used generally in measuring heat of fusion, T-history method has the advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermal properties of inhomogeneous phase change materials (PCMs) in sealed tubes. However, random criteria (a degree of supercooling) used in selecting the range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

• International Journal of Air-Conditioning and Refrigeration
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• 제11권1호
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• pp.32-39
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• 2003

Though conventional calorimetry methods such as differential scanning calorimetry and differential thermal analysis are used generally in measuring heat of fusion, T-history method has advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermophyical properties of in-homogeneous phase change materials in sealed tubes. However, the degree of supercooling used in selecting a range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.429-434
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• 2010

A novel T-type polyester 7 containing 1-(2,5-dioxyphenyl)-2-{5-(1,2,2-tricyanovinyl)-2-thienyl}ethenes as nonlinear optical (NLO) chromophores, which are part of the polymer backbone, was prepared and characterized. Polyester 7 is soluble in common organic solvents such as dimethylsulfoxide and N,N-dimethylformamide. It showed a thermal stability up to $300^{\circ}C$ in thermogravimetric analysis thermogram and the glass-transition temperature ($T_g$) obtained from differential scanning calorimetry thermogram was around $113^{\circ}C$. The second harmonic generation (SHG) coefficient ($d_{33}$) of poled polymer films at 1,560 nm fundamental wavelength was around 1.85 pm/V. The dipole alignment exhibits a greater thermal stability even at $10^{\circ}C$ higher than $T_g$, and there is no SHG decay below $125^{\circ}C$ due to the partial mainchain character of the polymer structure, which is acceptable for nonlinear optical device applications.

• BMB Reports
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• 제40권2호
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• pp.205-211
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• 2007

The stability curve - a plot of the Gibbs free energy of unfolding versus temperature - is calculated for bovine erythrocyte carbonic anhydrase in 150 mM sodium phosphate (pH = 7.0) from a combination of reversible differential scanning calorimetry measurements and isothermal guanidine hydrochloride titrations. The enzyme possesses two stable folded conformers with the conformational transition occurring at ~30$^{\circ}C$. The methodology yields a stability curve for the complete unfolding of the enzyme below this temperature but only the partial unfolding, to the molten globule state, above it. The transition state thermodynamics for the low- to physiological-temperature conformational change are calculated from slow-scan-rate differential scanning calorimetry measurements where it is found that the free energy barrier for the conversion is 90 kJ/mole and the transition state possesses a substantial unfolding quality. The data therefore suggest that the x-ray structure may differ considerably from the physiological structure and that the two conformers are not readily interconverted.

• 열처리공학회지
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• 제9권4호
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• pp.252-260
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• 1996

A study was conducted to examine the precipitation phenomena of Al-2.1Li-2.9Cu alloy by differential scanning calorimetry and transmission electron microscopy. DSC curves were measured over the temperature range of $25{\sim}550^{\circ}C$ at a heating rate of $2{\sim}20^{\circ}C$/min.. Three heat evolution peaks and three heat absorption peaks were observed in the DSC curve for the as-quenched specimen. From DSC results and TEM analysis, it was proved that the precipitation sequence in the as-quenched specimen is supersaturated solid solution ${\rightarrow}$ GP zone ${\rightarrow}{\delta}^{\prime}{\rightarrow}T_1{\rightarrow}T_2$ and ${\theta}^{\prime}$ was detected in the peak aged specimen at $160^{\circ}C$. The major phase formed at peak hardeness in the aging at $160^{\circ}C$ was ${\delta}^{\prime}$ phase. The activation energies for the formation of ${\delta}^{\prime}$ and $T_1$ phases were 22.3kcal/mole and 24.3kcal/mole, respectively. These lower activation energies than those for diffusion of Cu and Li in Al are ascribed to the quenched-in excess vacancies.

• 한국추진공학회지
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• 제19권5호
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• pp.15-21
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• 2015

착화기의 1차 점화장약으로 널리 사용되어지고 있는 ZPP(Zirconium/Potassium perchlorate)의 열분해 특성을 differential scanning calorimetry(DSC)를 사용하여 평가하였다. ZPP의 열분해반응에 대한 속도론적 파라미터를 결정하기 위하여, 다른 가열 속도를 갖고 수행된 DSC 결과들을 AKTS사의 Thermokinetics software를 사용하여 분석하였다. 결정된 속도론적 파라미터를 사용하여 계산된 모사값들은 실험적 결과들과 잘 일치함으로써, ZPP의 열분해과정에 대한 속도론적 모사의 유효성을 검증할 수 있었다.

• 한국식품과학회지
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• 제30권1호
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• pp.237-240
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• 1998

새로운 저열량 감미료인 tagatose를 이용한 초콜렛을 제조하여 설탕으로 제조한 초콜렛과 물성을 비교하였다. 제조한 초콜렛의 물성을 Casson 식에 적용한 결과 tagatose를 첨가하여 만든 초콜렛의 consistency index는 1,070 cp이었고 yield stress는 3.4 Pa으로 설탕을 사용한 초콜렛과 유사한 점도 특성을 보였다. Tagatose를 첨가하여 제조한 초콜렛을 DSC를 사용하여 열 특성을 살펴본 결과 설탕을 사용한 초콜렛과 유사하였다. 두 초콜렛의 점성 특성과 열 특성은 유사하였으나 강도의 경우는 tagatose를 사용한 제품의 강도가 설탕으로 만든 초콜렛의 강도보다 떨어짐을 보여주었다.

• Macromolecular Research
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• 제15권3호
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• pp.234-237
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• 2007

3,4-Bis-(3,4-dicarboxyphenylcarboxyethoxy)-4'-nitrostilbene dianhydride was prepared and reacted with 4,4'-(hexafluoroisopropylidene)dianiline to yield a novel Y-type polyimide containing the 3,4-dioxynitrostilbenyl group as an NLO-chromophore, which constituted part of the polymer backbone. The resulting polyimide was soluble in polar solvents such as acetone and N,N-dimethylformamide. The polymer exhibited good thermal stability up to $370^{\circ}C$ in the thermogravimetric analysis. The glass-transition temperature ($T_g$) obtained from the differential scanning calorimetry thermogram was near to $153^{\circ}C$. The second harmonic generation (SHG) coefficient ($d_{33}$) of the poled polymer film at the fundamental wavelength of $1064\;cm^{-1}$ was around $2.15\;{\times}\;10^{-8}\;esu$ (9.01 pm/V). The dipole alignment exhibited exceptionally high thermal stability even at a temperature $30^{\circ}C$ above the $T_g$, and there was no SHG decay below $180^{\circ}C$ because of the partial main chain character of the polymer structure.

• 한국추진공학회지
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• 제20권4호
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• pp.34-39
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• 2016

열분석기인 시차 주사 열량계를 이용하여 $BKNO_3$ 화약의 아레니우스(Arrhenius) 동역학 상수인 활성화 에너지와 Pre-Exponential Factor를 구하였다. 기존의 방법과 달리 고온 가속 노화와 DSC를 병행하여 보다 정밀한 활성화 에너지를 구하였고 열 유속의 적분값을 비교하여 저장 온도에 따른 분율을 구하였다. 이를 통하여 수명 예측을 위한 $BKNO_3$ 화약의 가속노화 시험 조건을 제시하고 열 가속노화에 관한 의미를 재고하였다.