• Proceedings of the Korean Environmental Sciences Society Conference
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• 2008.11a
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• pp.488-490
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• 2008

등온 및 비등온 TGA 열분석을 이용하여 TTSP를 이용하여 실험적으로 Shift factor(Acceleration factor) ${\alpha}_T$를 구하고 이로부터 마스터 커브 (master curve)를 도출할 수 있었고, 실험에 사용된 개질된 NR고무재료는 Arrhenius식을 잘 따르는 것이 확인되었으며, 이로부터 TTSP에 의한 촉진시험 결과의 신빙성을 확인할 수 있었다. 한편, 등온 TGA 실험으로부터 얻은 활성화에너지는 37.70 kJ/mol인 반면, 비등온 TGA로부터 Kissinger plot에 의해 얻은 활성화에너지는 166.20 kJ/mol이었는데, 이는 저온과 고온에서 서로 다른 분해기구에 의해 중량 감소가 일어나기 때문인 것으로 생각 되었다.

• Elastomers and Composites
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• v.52 no.4
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• pp.237-241
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• 2017

The tensile strength (TS) and elongation-at-break (EB) loss of a CR/CB rubber composite sample prepared for the automotive parts were measured after accelerated thermal ageing at temperatures of 100, 120, 140, and $150^{\circ}C$. The change in TS was observed to be linear from the master curve prepared using the time-temperature superposition-principle (TTSP). An Arrhenius type of shift factor, $a_T$ was used to predict the life time of the sample, and a plot of ln $a_T$ vs. 1/T was also shown to be linear. The activation energy ($E_a$) of the sample was calculated as 70.30 kJ/mole from the Arrhenius plot. The expected life time of the sample was predicted at the given operating conditions by applying Arrhenius analysis. Assuming the $E_a$ value was constant at lower operating condition, life time of the sample was calculated as 2.3 years when the life limit was set as time to reach the 20% decrease of the initial TS value at operating temperature of $40^{\circ}C$.

• Elastomers and Composites
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• v.48 no.2
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• pp.156-160
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• 2013

A study on compressive creep behavior of ACM rubber for automotive engine gasket was performed using TMA thermal analysis. From the results of isothermal measurements with constant load of 1 N at several different temperatures of 160, 180, 200, and $220^{\circ}C$, compressive creep data at the given temperatures were obtained, and therefrom, shift factor ($a_T$) and master curve at reference temperature of $160^{\circ}C$ were obtained using time-temperature superposition principle (TTSP). $C_1$ and $C_2$ of WLF (Williams-Landel-Ferry) equation were calculated through the WLF plot as -1.107 and 11.571, respectively. From this, life time of ACM rubber at $120^{\circ}C$ was predicted as about 24,000 hrs.

• Elastomers and Composites
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• v.44 no.3
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• pp.269-273
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• 2009

A study on the life-time expectation of a CR-modified NR rubber composite through the change of thermal degradation characteristics was performed using both isothermal thermogravimetric analysis (TGA) and thermomechanical analysis (TMA). Master curves at reference temperature of $90^{\circ}C$ could be obtained with shift factor $a_T$, which was determined empirically using Time-Temperature Superposition Principle (TTSP). Activation energies could be calculated from the slope of Arrhenius plot of shift factor and showed similar values of $E_{a,TGA}$= 41.2 and $E_{a,TMA}$= 54.5 kJ/mol, respectively. It was considered from the results that chemical degradation resulting weight loss of the sample might be closely related to a physical degradation such as the dimensional change of the sample.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.265-268
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• 1999

감쇠가 큰 고분자 복합재료에서 초음파 다중반사파를 이용한 Pulse Echo법, 공진주파수에서 내부마찰계수 측정법과 Rheometer를 이용한 동적탄성계수 측정법을 사용하여 음향감쇠계수를 측정하고 각각의 측정자료를 비교하는 연구를 수행하였다. Pulse Echo법을 이용하여 0.5, 1.0, 2.25MHz에서 음향감쇠계수를 측정하였고, 이때 폴리에틸렌기지 복합재료의 음향감쇠계수는 강화재의 부피분율에 따라 3-15dB/cm 정도로 큰 값을 나타내었다. 폴리에틸렌기지 복합재료를 600kHz 근처에서 공진주파수를 가지도록 시편을 만든 후에 내부마찰계수를 측정한 결과로 계산된 음향감쇠계수는 Pulse Echo 실험에서 구한 값과 잘 일치하는 결과를 얻을 수 있었다. Rheometer를 이용한 동적탄성계수 측정법은 0.1-100Hz의 주파수에서 측정한 자료를 TTSP 이론을 이용하여 1MHz의 결과와 비교하였는데, 단일 고분자 재료에서는 다른 측정방법과 음향감쇠계수가 일치하였지만 복합재료에서는 음향감쇠계수값이 일치하지 않는 결과를 나타내었다.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.2
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• pp.691-694
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• 2013

Purpose: By carrying out a meta-analysis of randomized controlled trials that compared sorafenib or combined chemotherapy with placebo or combined chemotherapy, the effectiveness of sorafenib in hepatocellular carcinoma was evaluated in the present study, which also provided clinical practice guidelines of evidence-based-medicine. Methods: We reviewed PubMed citations concerning sorafenib treating hepatocellular carcinoma in randomized controlled trials from Jan 2000 to July 2012. All the literature was extracted by Cochrane systematic reviews and underwent meta-analysis with RewMan 5.0 software. Results: Finally, four papers documenting randomized controlled studies were included. Compared with controls, sorafenib was shown to significantly increase overall survival (OS), time to progression (TTP), and disease control rates (DCR), but not the time to symptom progression (TTSP) in hepatocellular carcinoma patients. The incidence of grade-III/IV adverse reactions, including hand-foot-skin reactions, diarrhea, hypertension and skin rash or desquamation, in sorafenib treatment group was higher than that in controls. However, there was no significant difference in the incidence of hypodynamia between the two groups. Conclusions: Sorafenib exerts significant curative effects in hepatocellular carcinoma.

• Elastomers and Composites
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• v.47 no.3
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• pp.254-258
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• 2012

Material characteristics and the prediction of life time of polyacrylic rubber (ACM) for automotive engine gasket were studied. Two kinds of ACM rubber compounds, having chlorine cure-site and carboxyl cure-site, were made with optimum formulations and the properties of each materials were examined. As a test results for the thermal properties and compression set, which are very important in the application for the automotive engine gasket, the compound using ACM with carboxyl cure-site was evaluated as having a better characteristics than that of ACM with chlorine cure-site. Arrhenius relationship based on time-temperature superposition principle (TTSP) was obtained through the accelerated heat aging test to predict the useful life-time for the compound using ACM with carboxyl cure-site.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1661-1667
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• 2009

Post-cure characteristics of a silicone rubber material which is widely used for a LCD lamp holder were investigated using thermogravimetric analysis (TGA). Research was especially focussed on searching for the optimum post-cure conditions in relation to the practical operation environments. The results showed that incipient volatile temperature(Ti) during the process was considered as the most important factor and, thereby, post-curing for 2hrs at $250^{\circ}C$seemed to be a reasonable condition in the practical view-point. Arrhenius plot of shift factors which were empirically determined from the time-temperature-superposition-principle showed good linearity, exhibiting the post-cure mechanism might be proceeded through single mechanism with activation energy of 108.25kJ/mol.

• International Journal of Highway Engineering
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• v.16 no.3
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• pp.43-50
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• 2014

PURPOSES : The dynamic modulus can be determined by applying the various theories from the Impact Resonance Testing(IRT) Method. The objective of this paper is to determine the best theory to produce the dynamic modulus that has the lowest error as the dynamic modulus data obtained from these theories(Complex Wave equation Resonance Method related to either the transmissibility loss or not, Dynamic Stiffness Resonance Method) compared to the results for dynamic modulus determined by using the Universal Testing Machine. The ultimate object is to develop the predictive model for the dynamic modulus of a Linear Visco-Elastic specimen by using the Complex Wave equation Resonance Method(CWRM) came up for an existing study(S. O. Oyadiji; 1985) and the Optimization. METHODS : At the destructive test which uses the Universal Testing Machine, the dynamic modulus results along with the frequency can be used for determining the sigmoidal master curve function related to the reduced frequency by applying Time-Temperature Superposition Principle. RESULTS : The constant to be solved from Eq. (11) is a value of 14.13. The reduced dynamic modulus obtained from the IRT considering the loss factor related to the impact transmissibility has RMSE of 367.7MPa, MPE of 3.7%. When the predictive dynamic modulus model was applied to determine the master curve, the predictive model has RMSE of 583.5MPa, MPE of 3.5% compared to the destructive test results for the dynamic modulus. CONCLUSIONS : Because we considered that the results obtained from the destructive test had the most highest source credibility in this study, the dynamic modulus data obtained respectively from DSRM, CWRM were compared to the results obtained from the destructive test by using th IRT. At the result, the reduced dynamic modulus derived from DSRM has the most lowest error.