• 한국환경과학회지
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• 제7권3호
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• pp.393-400
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• 1998

A microorganism, Klebsiella gr. 47, capable of degrading BTX(benzene, toluene and xylene) was isolated from oil-contaminated soil and its characteristics of BTX degradation were investigated. When benzene and toluene were fed to Klebstella gr. 47 simulataneously, they showed competitive ingibition. The degradation rate of xylene was enhanced as much as 3 times when xylene was fed with benzene or toluene. Degradation rate of benzene and toluene was also enhanced by cocultured with Alcaligenes xylosoxidans. When benzene-adapted microorganism was used, each BTX compound was degraded efficiently within 5 hours.

• 한국초지조사료학회지
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• 제20권3호
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• pp.177-184
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• 2000

This study was conducted to examine of rice straw after chemical treatments and ensiling on its feeding value, in situ studies using a rumen fistulated Korean cow and nylon bag technique. NaOH treatment greatly improved the degradation the Dry matter and Neutral detergent fiber degradation in the rumen but the intake was not affected. Ammonia treatment did not improve the degradation rate of rice straw in the rumen, but remarkably increased the rice straw digestibility and intake by sheep. Making silage of rice straw did not affect its rumen degradation rate, but the digestibility and its take by sheep were greatly improved especially when a little molasses together with Lactobacillus were supplemented. Degradation rate of rice straw in the rumen measured by nylon bag technique was influenced by various treatments but did not appear to coincide with digestibility by sheep. This would be due to the fact that feed intake affect digestibility as well as the degradation in rumen. Therefore, it can be said that making silage with some molasses and Lactobacillus is one of the easest way of using rice straw for animal feed. (Key words : NaOH, Digestibility, Silage, Molasses )

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 2001년도 추계학술대회 및 정기총회
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• pp.88-88
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• 2001

The effects of pH and temperature on the degradation of prokidn in various buffered aqueous solutions(pH 1.32~9.66) and temperatures (35, 45 and 6$0^{\circ}C$ were investigated. The effect of ionic strength on the degradation of prokidin was also measured by varying ionic strength (0.0466~1.5) at pH 1.35 and 45$^{\circ}C$ The effect of metal ions on the degradation of prokidin at pH 7.35 and 3.98 was observed. The degradation of prokidin followed the pseudo- first- order kinetics. The degradation rate of prokidin showed pH-dependent and temperature-dependent patterns. Prokidin was very stable at the pH below 3.95, where half-lives at 35, 45 and 6$0^{\circ}C$were 294, 206 and 107 day, respectively. However, it degraded very rapidly at pH above 6.49; the half-lives at 35, 45 and 6$0^{\circ}C$were 60, 25 and 13 day, respectively. As ionic strength increased, the degradation rate of prokidin increased. Some metal ions increased the degradation rate in the rank order of Mn > Fe > Cu >Fe On the other hand. other metal ions such as Bi, Ba. Zn, Ni, Co did not show unfavorable effect.

• 한국환경과학회지
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• 제27권12호
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• pp.1205-1214
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• 2018

During the past few decades, significant increase in the consumption of coffee has led to rapid increase in the production of coffee waste in South Korea. Spent coffee waste is often treated as a general waste and is directly disposed without the necessary treatment. Spent Coffee Grounds (SCGs) can release several organic contaminants, including caffeine. In this study, leaching tests were conducted for SCGs and oxidative degradation of caffeine were also conducted. The tested SCGs contained approximately 4.4 mg caffeine per gram of coffee waste. Results from the leaching tests show that approximately 90% of the caffeine can be extracted at each step during sequential extraction. Advanced oxidation methods for the degradation of caffeine, such as $UV/H_2O_2$, photo-Fenton reaction, and $UV/O_3$, were tested. UV radiation has a limited effect on the degradation of caffeine. In particular, UV-A and UV-B radiations present in sunlight cause marginal degradation, thereby indicating that natural degradation of caffeine is minimal. However, $O_3$ can cause rapid degradation of caffeine, and the values of pseudo-first order rate constants were found to be ranging from $0.817min^{-1}$ to $1.506min^{-1}$ when the ozone generation rate was $37.1g/m^3$. Additionally, the degradation rate of caffeine is dependent on the wavelength of irradiation.

• 한국환경과학회지
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• 제13권6호
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• pp.599-603
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• 2004

In a batch reactor, the characteristics of photocatalytic degradation of brilliant blue FCF in titanium dioxide suspension was studied under the irradiation of ultra-violet ray. Photocatalytic degradation in anatase type of TiO$_2$ was more effective than in rutile type of $TiO_2$ below the dosage of 5g. The degradation rate was slightly increased with decreasing initial pH of brilliant blue FCF aqueous solution, but rapidly increased with the addition of oxidant. Potassium bromate acted as more effective oxidant than ammonium persulfate. The photocatalytic degradation rate of brilliant blue FCF was pseudo-first order with rate constants of 0.012, 0.006 and $0.003min^{-1}$ at initial pH 3.1, 5.2 and 7.1 of brilliant blue FCF solution, respectively.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권2호
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• pp.103-111
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• 2017

Purpose: Accelerated degradation tests can speed time to market and reduce the test time and costs associated with long term reliability tests to verify the required service life of a product or material. This paper proposes a service life prediction method for components or materials using an accelerated degradation tests based on the relationships between temperature and the rate of failure-causing chemical reaction. Methods: The relationship between performance degradation and the rate of a failure-causing chemical reaction is assumed and least square estimation is used to estimate model parameters from the degradation model. Results: Methods of obtaining acceleration factors and predicting service life using the degradation model are presented and a numerical example is provided. Conclusion: Service life prediction of a component or material is possible at an early stage of the degradation test by using the proposed method.

• 대한전자공학회논문지SD
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• 제40권10호
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• pp.32-38
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• 2003

SIMOX 웨이퍼를 사용하여 제작된 GAA 구조 SOI MOSFET의 열전자에 의한 소자열화를 측정·분석하였다. nMOSFET의 열화는 스트레스 게이트 전압이 문턱전압과 같을 때 최대가 되었는데 이는 낮은 게이트 전압에서 PBT 작용의 활성화로 충격이온화가 많이 되었기 때문이다. 소자의 열화는 충격이혼화로 생성된 열전자와 홀에의한 계면상태 생성이 주된 원인임을 degradation rate와 dynamic transconductance 측정으로부터 확인하였다. 그리고 pMOSFET의 열화의 원인은 DAHC 현상에서 생성된 열전자 주입에 의한 전자 트랩핑이 주된 것임을 스트레스 게이트 전압변화에 따른 드레인 전류 변화로부터 확인 할 수 있었다.

• 한국환경과학회지
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• 제18권7호
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• pp.797-802
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• 2009

To control degradation rate of biodegradable poly(lactide)s (PLA), the stereochemical PLAs with different ratios of d-lactide and l-lactide units were synthesized by the ring open polymerization and the their degradation kinetics were measured by a Langmuir film balance. The alkaline (pH=11) degradation of poly(l-lactide) (l-PLA) monolayer showed the faster rate at a surface pressure of 4 mN/m in the ranges from to 0 to 7 mN/m. However, the enzymatic degradation of l-PLA with Proteinase K did not occur until 4 mN/m. Above a constant surface pressure of 4 mN/m, the degradation rate was increased with a constant surface pressure. These behaviors might be attributed to the difference in the contacted area with degradation medium: alkaline ions need small contact area with l-PLA while enzymes require much bigger one to be activated due to different medium sizes. The stereochmical PLA monolayers showed that the alkaline degradation was increased with their optical impurities while the enzymatic one was inversed. These results could be explained by the decrease of crystallinity with the optical impurity and the inactivity of enzyme to d-LA unit.

• 한국식품과학회지
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• 제23권3호
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• pp.355-359
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• 1991

글루타민산 나트륨(MSG)의 열안정성을 조사하기 위하여 가열온도 및 pH를 변화시키면서 가열 중 MSG의 분해정도를 비교하였다. 가열온도와 pH의 범위는 각각 $100{\sim}120^{\circ},\;4{\sim}9C$로 하였고, MSG는 2% 용액으로 만들었으며 가열 중 잔류 MSG 농도를 HPLC로 측정하였다. 그 결과 pH 4와 $120^{\circ}C$의 3시간 가열로 약 73% MSG가 감소한 반면, $100^{\circ}C$에서의 3시간 가열은 12% 정도만이 감소함을 보였다. 가열온도와 pH에 따른 초기 MSG의 분해속도와 분해 속도상수{(%MSG/log(hrs)}를 비교한 결과 $110^{\circ}C$와 $120^{\circ}C$에서의 초기 분해속도는 pH 4가 가장 빨랐으며 분해 속도상수도 상당히 높은 값을 보였다. 분해가 가장 적었던 pH 범위는 $pH6{\sim}8$ 범위였다. 또한 가열온도에 영향을 가장 많이 받았던 pH 4와 pH 5의 MSG 열분해 속도상수와 1/T의 관계에서 계산된 활성화에너지는 각각 18.3 kcal/mole과 9.2 kcal/mole이었다.

• Preventive Nutrition and Food Science
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• 제12권2호
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• pp.115-118
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• 2007

Tocopherols are important lipid-phase antioxidants that are subject to heat degradation. Therefore, kinetic analyses for oxidative degradation of tocopherols as a function of temperatures and times were performed. Alpha-, gamma- and delta-tocopherols dissolved in glycerol were heated at 100${\sim}$250$^{\circ}C$ for 5～60 min. Oxidized tocopherols were analyzed by HPLC using a reversed phase ${\mu}$-Bondapak C$_{18}$-column with two kinds of elution solvent systems in a gradient mode. The degradation kinetics for tocopherols followed a first-order kinetic model. The rate of tocopherol degradation was dependent on heating temperatures. The degradation rate constants for ${\gamma}$- and ${\delta}$-tocopherols were higher than those for ${\alpha}$-tocopherol. The experimental activation energies of ${\alpha}$-, ${\gamma}$- and ${\delta}$- tocopherols were 2.51, 6.05 and 5.34 kcal/mole, respectively. The experimental activation energies for the oxidative degradation of ${\gamma}$- and ${\delta}$-tocopherols were higher than that of ${\alpha}$-tocopherol.