• Bulletin of the Korean Chemical Society
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• 제20권2호
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• pp.247-249
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• 1999

• Bulletin of the Korean Chemical Society
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• 제32권8호
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• pp.2661-2665
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• 2011

We studied the effect of structural and morphological changes on the conductivity of a stretched conducting polymer film. To improve the poor processability of polyaniline, we used dodecylbenzenesulfonic acid as both a surfactant and a dopant during emulsion polymerization, followed by blending with high-impact polystyrene. UV-Vis/NIR spectra were obtained to observe conformational changes, and SEM and AFM were used to investigate morphological changes. FT-IR dichroism was applied to determine the microscopic orientation, and XRD patterns were obtained for quantitative crystallinity analysis. The electrical conductivity (${\sigma}_{\parallel}/{\sigma}_{\perp}$) was measured as a function of draw ratio. We found a clear correlation between morphological changes and (${\sigma}_{\parallel}/{\sigma}_{\perp}$), especially at the stretching limit. The conductivity of the films can be modified according to the desired application by controlling their structure and morphology.

• 농업과학연구
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• 제11권1호
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• pp.45-52
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• 1984

Changes of chemical componts and populations of total bacteria and lactic acid bacteria were examined during a month-long storage of sweet potatoes crushed and sealed up with polyethylene film at $7-8^{\circ}C$. 1. Changes of starch, total protein, volatile acid and ammonia-nitrogen contents were li 2. In a three days, pH down and increase of non-volatile acid content were notable, populations of total bacteria and lactic acid bacteria were maximum. 3. Vitamic C and soluble sugar contents tended to be reduced during the storage and the leftover were 75-85% and 41-45% respectively. 4. ${\beta}$-Amylase activity decreased gradually and vanished 15-30days. 5. Variations of chemical compontents of the samples inoculated lactic acid bacteria were larger than non- treated to some extent. 6. As above results, mainly homo lactic acid fermentation was done in this storage condition.

• 한국응용과학기술학회지
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• 제17권4호
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• pp.273-278
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• 2000

Cellulose tosylate(CT) was prepared by reaction of cellulose with p- toluenesulfonylchloride in DMAc/LiCl homogeneous system. In order to study a reversible photoisomerization of disperse red 1(DR-1) attached on natural polymer, cellulose tosylate containing DR-1(DR-1/CT adduct) was prepared at $110^{\circ}C$ in DMAc, and the changes of UV/Vis spectra of its solutions and thick film were investigated by alternate irradiation technique. Form the UV/Vis spectra of DR-1/CT adduct dissolved in cosolvents, such as DMAc, DMAc/THF, DMAc/benzene, and DMAc/chloroform and irradiated with 360 nm and 450 nm ligths, we found out changes of UV/Vis spectra were reversible in all solvents systems and we found out changes of UV/Vis spectra were reversible at thick film, also.

• Bulletin of the Korean Chemical Society
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• 제19권8호
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• pp.836-840
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• 1998

The intrinsic and equilibrium isotope effects on the 13C NMR chemical shift of the cyclooctanone-2-D were investigated. Equilibrium constants and changes in the free energies, enthalpy, entropy, which are derived from the temperature dependence of the isotope shifts, are reported for this isotopomer.

• 한국산업보건학회지
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• 제21권2호
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• pp.73-81
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• 2011

The purpose of this study was to obtain scientific information regarding classification and health hazards that may result from a 13 weeks inhalation exposure of isoprene in Sprague-Dawley (SD) rats. The testing method was conducted in accordance with OECD guidelines for the testing of chemicals No. 413. The Rats were divided into 4 groups (10 male and 10 female rats in each group) and exposed to 0, 360, 1,620, 7,300 ppm isoprene in each exposure chamber for 6 h/day, 5 days/week, for 13 weeks. As a result, there were no mortality or abnormality during the period of study and did not show any significant changes of body weight. There were no dose response changes in urinalysis, hematological and serum biochemical value examination. Relative organ weight was increased significantly the right kidney in 7,300 ppm group of male rats. In female rats, relative organ weight of the left kidney and the both lungs in 1,620 ppm group and the left lung and the both kidneys in 7,300 ppm group were increased significantly. But the histopathological findings did not reveal any exposure-related changes. According to the above results, the no observable adverse effect level (NOAEL) of isoprene was 7,300 ppm (20.3 mg/L) in both male and female rats. In conclusion, Isoprene was not classified specific target organ toxicity of the 'Standard for Classification and Labeling of Chemical Substance and Material Safety Data Sheet' (Ministry of Employment and Labor, 2009).

• Bulletin of the Korean Chemical Society
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• 제5권1호
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• pp.27-32
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• 1984

To investigate the hydration effects on the conformational changes of N-pivaloly-L-prolyl-N-methyl-N'-isopropyl-L-alanin amide (PPMIA), the conformational free energy changes have been calculated by using an empirical potential function varying all the independent degrees of freedom of PPMIA backbones. It is found that cis conformers are folded by a strong intramolecular hydrogen bond involving both terminal CO and NH groups whereas trans conformers accommodate the open conformation. Conformers in the free state are proved to be less stable than in the hydrated state. The free energy changes of cis and trans PPMIA due to the hydration are -50.5 and -39.8 kcal/mole, their conformational energy changes are -52.3 and -41.0 kcal/mole, and their conformational entropy changes are -5.9 and -4.0 e.u., respectively. The free energy changes of cis PPMIA to trans PPMIA in the free and hydrated states are 5.3 and 16.0 kcal/mole, their conformational energy changes are 7.6 and 18.8 kcal/mole, and the entropy changes due to the conformational transitions correspond to 7.5 and 9.4 e.u., respectively. From these results, it is found that the bound water molecules play an important role in stabilizing the conformation of PPMIA.

• Korean Chemical Engineering Research
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• 제44권1호
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• pp.97-105
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• 2006

본 연구에서는 대장균 내에서 L-threonine의 생합성에 영향을 미치는 저해제들에 대한 모사 연구를 위하여 L-aspartate에서 L-threonine까지의 아미노산 생합성 대사 네트워크를 문헌 및 데이터베이스를 통해 구축하였다. 또한 L-threonine 생합성에 영향을 미치는 저해제들을 수학적으로 모델링하여 효소 반응식에 적용시켰다. 모사 연구를 위해 초기 농도값을 L-aspartate 5 mM, ATP 5 mM, NADPH 2 mM으로 설정하고 저해제의 농도 변화에 따른 세포내 대사 물질들의 농도변화를 확인하였다. 그 결과 저해제 L-lysine, L-methionine, L-glutamate는 저해제 농도 변화에 따라 대사 물질들의 농도 변화가 없었다. 그러나 저해제 L-serine, L-cysteine 그리고 L-threonine의 경우 저해제의 농도 변화에 따라 세포내 대사물질들의 농도 곡선이 서로 다른 결과를 얻었다. 대장균 내에서 소비되어진 L-aspartate의 농도는 세포 내 생성되는 L-threonine과는 관련이 없었고, 생성되는 L-threonine의 농도는 세포 내에 축적된 D,L-aspartic ${\beta}$-semialdehyde에 반비례하였다.

• 한국환경보건학회지
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• 제46권2호
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• pp.159-169
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• 2020

Objectives: The purpose of this study was to investigate changes among the nine kinds of reduction chemical substances in Korea over the period of 2008-2017. We will define basic data for improving the management methods for reducing chemical substances. Methods: A survey of hazardous pollutant emissions for 2008-2017 was conducted through the pollutant Release and Transfer Register homepage. Nine kinds of designated reduction chemical substances (Benzene, Vinyl chloride, Trichloro ethylene, 1,3-butadiene, Dichloro methane, Tetrachloro ethylene, N,N-dimethylformamide, Acrylo nitrile, and Chloroform) provided the study subjects. The emission of hazardous chemicals and health effects used the National Health Statistics and Integrated Chemicals Information System (ICIS) as a reference. Results: Hazardous pollutant emissions increased by 1.2 times over the past decade, and nine types of reduction chemical substances increased by 1.6 times. By region, the emissions of reduction chemical substances over the last 10 years were in the order of Chungbuk, Gyeonggi, and Gyeongbuk. Emissions of Dichloro methane was the highest in Chungbuk and Gyeongbuk. N,N-dimethylformamide was the highest in Gyeonggi. Carcinogen pollutant emissions showed a tendency to increase continuously. In addition, group 1 carcinogen emissions showed a tendency to decrease. Conclusion: In the last decade, the amount of hazardous chemical emissions has been continuously increasing. Hazardous chemical emissions require facility improvement for continuous emissions reduction. More research on reduction of emissions is needed.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.984-990
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• 2014

Polymers are the most commonly used di-electrics because of their reliability, availability, ease of fabrication and cost. The commercial and industrial demand for advanced polymeric materials which are capable of being used in harsh environment is need of the hour. The study of the effect of electron beam irradiation on polymeric materials is an area of rapidly increasing interest. This paper discusses the resultant beneficial effects of electron beam irradiation on the SiR-EPDM blend having 50:50 composition. The changes in mechanical and electrical properties of SiR-EPDM blend which are exposed to three different doses of electron beam radiation namely 5 Mrad, 15 Mrad and 25 Mrad are presented. The irradiated blends are analyzed for their electro-mechanical and physico chemical properties. The electrical changes induced by irradiation are investigated by arc resistance, surface resistivity and volume resistivity measurements as per ASTM standards. The mechanical changes are observed by the measurement of tensile strength and elongation at break. Physico chemical investigation has been done using the FTIR, in order to investigate the irradiation induced chemical changes.