• Macromolecular Research
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• v.17 no.5
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• pp.296-300
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• 2009

Ethylene-1-butene copolymers were prepared with $SiO_2$-supported $TiCl_4$ catalyst by changing of 1-butene/ethylene molar ratio in feed, and the resulting copolymers were analyzed using temperature rising elution fractionation (TREF) and crystallization fractionation (Crystaf) methods to investigated the influence of $C_4/C_2$ molar ratio in feed on chemical compositional distribution and other parameters such as molecular weight and its distribution. TREF analysis showed that the copolymers had a broad and bimodal chemical compositional distribution (CCD) regardless of the content of 1-butene in the copolymer. The chemical composition was in the range of 5 to 55 branches per 1,000 carbons for all copolymers prepared in the study. Furthermore, the broader CCD was revealed for the copolymers having the higher content of 1-butene. Crystaf analysis did not showed a bimodal CCD for the copolymers having the 1-butene content of less than 5.1 wt%. The lower crytalline part having 1-butene content in Crystaf analysis was less than of TREF analysis.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.404-410
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• 1998

In Yonggwang nuclear units 3 and 4 currently under commercial operation, the cold leg temperature was very close to the technical specification limit of 298$^{\circ}C$ during initial startup testing, which was caused by the higher-than-expected reactor coolant system flow. Accordingly, the reference temperature (Tref) program needed to be revised to allow more flexibility for plant operations. In this study, the method of a specific test performed at Yonggwang nuclear unit 4 to revise the Tref program was described and the test results were discussed. In addition, the modified Tref program was evaluated on its potential impacts on system performance and safety. The methods of changing the Tref program and the associated pressurizer level setpoint program were also explained. Finally, for Ulchin nuclear unit 3 and 4 currently under initial startup testing, the effects of reactor coolant system flow rate on the coolant temperature were evaluated from the thermal hydraulic standpoint and an optimum Tref program was recommended.

• International Journal of Advanced Culture Technology
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• v.8 no.4
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• pp.137-143
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• 2020

Traffic-related environmental factors (TREF) are a major problem in developed countries, leading to increased atopic sensitivity, allergy symptoms, and diseases. This study shows an association between traffic-related pollutants, distance of road and gas station from the children's daycare center, and allergy symptoms. Data was obtained from the 2018 survey, an ongoing allergic diseases prevalence survey for children aged 4-7 (n=1175). This survey considered 36 public daycare centers, across 6 districts in Seoul. Allergic symptoms were defined as the presence of at least 1 or more allergic diseases (International Study of Asthma and Allergies in Childhood (ISAAC)). TREF was derived from the distance to the nearest main roads and gas stations. Geographic data processing and variable computation were conducted using ArcGIS version 10.2. The odds ratios for allergy symptoms increased by 1.189 (1.235-2.679) times with decreasing distance to main roads and by 1.846 (1.176-2.896) times with decreasing distance to a gas station. This study concludes that main roads and gas-stations near children's daycare centers are related to the allergy symptoms in children.