• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.1
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• pp.131-131
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• 2003

A benzopyranyl derivative, KR32158, synthesized as a plausible KATP opener, has been shown to exert cardioprotective effect in vivo myocardial infarction model. Myocardial ischemia, induced by oxidative stress, mental stress and fever, result in artheroscleosis, myocardial infarction and hypertrophy. In this study, we investigated in vitro effect of KR32158 by determining whether KR32158 produce cardioprotective effect against oxidative stress-induced death in heart-derived H9c2 cells. (omitted)

• Korea-Australia Rheology Journal
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• 제14권1호
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• pp.17-23
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• 2002

A novel and simple method using a cylindrical penetrometer is being developed for the measurement of yield stress. The principle of this technique is based on the measurement of the static equilibrium of a falling penetrometer in a yield stress fluid. The yield stress is simply determined by a balance of forces acting on the penetrometer. The yield stress of Carbopol gels and $TiO_2$ suspensions has been measured using this method. The results are in reasonable agreement with the values from conventional methods. The effects of the dimensions and weight of the penetrometer have been examined. The long-term behaviour was also observed. No measurable creep was seen and equilibrium was found to be very quickly established. The cylindrical penetrometer technique promises to be a simple, quick and reliable static method for the measurement of yield stress.

• 한국작물학회지
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• 제51권1호
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• pp.73-80
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• 2006

Sesame (Sesamum indicum L.) seeds contain abundant oil and antioxidative lignans related to the seed quality. To evaluate the potential effects of drought stress on the chemical composition of sesame seeds, eighteen cultivars were imposed water-deficit condition by withholding irrigation during 15 days at podding and maturing stage, compared with well-watered plants as control in seed yield and chemical composition. Drought treatments showed great decrease of seed yield with not affecting seed weight. The contents of sesamin and sesamolin decreased while lignan glycosides inversely increased in response to drought stress. Oil content was not significantly changed by drought treatment in spite of its slight decrease. In case of fatty acid composition, there were significant differences in increase of oleic acid while inverse decrease of linoleic acid under drought stress condition. These results demonstrate that the chemical composition of sesame seed may be modified with drought stress. In particular, the increase of sesaminol glucosides with strong antioxidative activity was observed.

• Korea-Australia Rheology Journal
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• 제18권1호
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• pp.15-24
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• 2006

The first international inter-laboratory study, involving six laboratories, has been conducted to examine issues associated with yield stress measurements in suspensions. The initial focus of the project was to evaluate the reliability and reproducibility of several common yield stress measuring techniques employed in different laboratories and with different instruments. Aqueous suspensions of colloidal $TiO_2$ at concentrations of 40-70 wt% solids were used as the test fluids. A wide range of instruments and techniques employing both direct and indirect methods were used to determine the yield stress of the samples prepared according to a prescribed procedure. The results obtained indicated that although variations of results existed among different techniques, direct yield stress measurements using static methods produced more reliable and repeatable results than other methods. Variability of the yield stress measured using different techniques within any laboratory however was less significant than variability of the results among different laboratories. The nature and condition of the test suspensions was identified as the most likely factor responsible for the poor reproducibility of yield stress measurements from different laboratories.

• Korea-Australia Rheology Journal
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• 제13권3호
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• pp.109-123
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• 2001

A stress jump, defined as the instantaneous gain or loss of stress on startup or cessation of a deformation, has been predicted by various models and has relatively recently been experimentally observed. In 1993, Liang and Mackay measured shear stress jump data of xanthan gum solutions, and in 1996, Orr and Sridhar reported extensional stress jump data of Boger fluids. Shear stress jumps of suspensions and liquid crystal polymers have also been observed. In this contribution, experimental work as well as a variety of theoretical models, which are able to predict a stress jump, are reviewed.

• Korea-Australia Rheology Journal
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• 제15권1호
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• pp.9-17
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• 2003

The rheological behaviour of anatase $TiO_2$ with organic coating has been investigated extensively in this study. The yield stress was measured over a wide range of solids concentration and pH using stress-controlled and speed-controlled rheometers. The organic treatment leads to a shift of the isoelectric point (IEP) from around pH 5.5 to pH 2.4. A maximum yield stress occurs in the vicinity of the isoelectric point determined by electrokinetic measurements. The transition of rheological behaviour between elastic solid and viscous liquid is represented by a stress plateau in a plot of stress against strain. It is hypothesised that the slope of the stress plateau reflects the uniformity of the structure, and hence the distribution of bond strength. Altering the concentration and the surface chemistry can vary the bond strength and its distribution. therefore, resulting in different type of failure: "ductile-type" or "brittle-type". pH and volume fraction dependence of yield stress could be described quantitatively using existing models with reasonable agreement.easonable agreement.

• 폴리머
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• 제38권5호
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• pp.645-649
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• 2014

사출성형품의 잔류응력 형성의 원인은 사출성형공정 중 재료가 받는 높은 온도변화와 전단응력이다. 케미컬 크랙킹 테스트는 잔류응력을 측정하는 방법 중의 하나이며 크랙은 잔류응력의 크기에 따라 형성된다. 본 연구에서는 시편이 받고있는 응력과 케미컬 크랙킹과의 관계를 연구하였다. 변형지그를 설계하고 이를 이용하여 시편에 변형을 주어 응력을 가하였다. 시편은 폴리카보네이트를 이용하여 핫 프레스로 제작하였고 시편의 제작 중에 형성된 잔류응력을 제거하기 위해 어닐링을 하였다. 시편을 변형지그에 고정시키고 시편에 크랙을 유도하기 위해 이를 솔벤트에 담궜다. 솔벤트는 tetrahydrofuran과 methyl alcohol을 이용하여 제조하였다. 시편에서 변형에 따라 응력이 증가할수록 크랙의 빈도수와 밀도가 증가하였다. 본 연구의 결과는 케미컬 크랙킹 방법으로 폴리카보네이트 사출성형품의 잔류응력을 정량적으로 측정하는데 활용될 수 있다.

• 한국건축시공학회지
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• 제14권2호
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• pp.170-176
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• 2014

본 연구에서는 알칼리활성 황토콘크리트의 응력-변형률 관계에 대한 화학적 침식의 영향을 평가하였다. 배합의 주요변수는 물-결합재비와 공기량이다. 알칼리활성 황토콘크리트의 응력-변형률 관계는 재령 28일 이후 침지일이 0, 7, 28, 56 및 91일일 때 측정하였다. 실험결과를 기반하여, 화학적 침식하에서 감소된 알칼리활성 황토콘크리트의 압축강도 모델이 제시되었다. 또한, 화학적 침식하에서 알칼리활성 황토콘크리트의 응력-변형률 관계는 공기량과 화학용액에 침지된 일수에 현저한 영향을 받았는데, 침지일수에서 탄성계수의 저하는 동일한 압축강도 저하비율에 비해 더 컸다. 결과적으로 CEB-FIP 기준의 예측모델은 화학적 침식하에서 측정된 응력-변형률 관계와 잘 일치하지 않았다.

• 한국정밀공학회지
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• 제28권2호
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• pp.219-225
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• 2011

Silicone resin is recently used as encapsulant for high-power LED module due to its excellent thermal and optical properties. In the present investigation, finite element analysis of cure process was attempted to examine residual stress evolution behavior during silicone resin cure process which is composed of chemical curing and post-cooling. To model chemical curing of silicone, a cure kinetics equation was evaluated based on the measurement by differential scanning calorimeter. The evolutions of elastic modulus and chemical shrinkage during cure process were assumed as a function of the degree of cure to examine their effect on residual stress evolution. Finite element predictions showed how residual stress in cured silicone resin can be affected by elastic modulus and chemical shrinkage behavior. Finite element analysis is supposed to be utilized to select appropriate silicone resin or to design optimum cure process which brings about a minimum residual stress in encapsulant silicone resin.

• 반도체디스플레이기술학회지
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• 제4권4호
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• pp.1-4
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• 2005

The chemical composition and uniaxial compressive stress are varied to observe their effect on the current-voltage characteristics of ZnO based ceramics. The variation of chemical composition produces two kinds of ceramics showing ohmic and nonohmic current-voltage characteristics. The current at a fixed voltage increased with the increase of the compressive stress for both ohmic and nonohmic ceramics. Ceramics showing nonohmic behavior exhibit better reversible return of current-voltage curve when the applied compressive stress is removed from the ceramics than those showing ohmic behavior do. We found an appropriate chemical composition showing linear relation between current and stress at a fixed voltage. The ceramic materials with an appropriate chemical composition can be used as a potential sensing material in pressure sensors.