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모비키즈: 통신전자파 노출과 어린이청소년의 뇌종양에 관한 환자 -대조군 연구 프로토콜
최경화,김동석,이정일,나영신,피지훈,안영환,권종화,이애경,최형도,하미나,Choi, Kyung-Hwa,Kim, Dong-Seok,Lee, Jung-il,Ra, Young-Shin,Phi, Ji Hoon,Ahn, Young Hwan,Kwon, Jong Hwa,Lee, Ae-Kyoung,Choi, Hyung-Do,Ha, Mina 한국환경보건학회 2015 한국환경보건학회지 Vol.41 No.3
Objectives: To introduce a protocol of Mobi-kids study which was aimed to examine an association between radiofrequency (RF) radiation exposure by mobile phone use and brain tumor risk in children and adolescents. Methods: The Mobi-kids study was a multinational matched case control study using a standardized protocol with the number of subjects targeted about 1,000 cases and 2,000 controls aged 10 to 24. In Mobi-Kids Korea, the source population was restricted to Seoul, Incheon, and Gyeonggi-do province. Eligible cases of primary brain tumor (glioma, meningioma, and others) were diagnosed from January 2012 to June 2015. Eligible controls were appendicitis patients operated during the study period. Two controls were matched on age, gender, and study region for 1 case. Information about pattern and history of mobile phone use and other covariates were obtained by face to face interview by trained interviewer. The Mobi-kids study has been involved in Mobi-expo as a validation study about mobile phone use, XGridmaster to localize tumor in the brain for RF energy calculation, and histological review for validation of diagnosis. Results: The Mobi-kids was the first and largest study in children and adolescents to estimate risk of brain tumor in association with the RF energy absorption in the brain estimated by mobile phone use. Forty-six-cases and 54 controls were collected as of September 2014 in Korea. Conclusions: The meaningful results of the study were expected because of the largest sample size, high validity of EMF exposure assessment as well as the susceptible study populationof children and adolescents.
최경화,박지희,서진호,Choi, Kyoung-Hwa,Park, Ji-Hee,Seo, Jin-Ho 국립문화재연구소 2010 保存科學硏究 Vol.31 No.-
Paper cultural heritages experience chemical and physical deterioration due to various factors including preservation environments and the property of paper materials1). Thus, it is important to develop optimal preservation and restoration methods for the damaged paper cultural heritages. Currently, lining is a popular treatment for the restoration of paper cultural heritages in Korea. Since lining paper is a layer of paper directly attached to the inside of cultural heritages for protection, understanding of the preservation properties of lining paper is primarily needed in order to devise the better preservation methods. The main material of lining paper is the paper mulberry, but additives such as chalk and white clay is sometimes used to enhance the preservation properties of lining paper. To date, the properties of the functional lining paper containing these additives have been not fully understood yet. In this study, dry heating aging at $105^{\circ}C$ and biological aging by the Aspergillus versicolor and Penicillium polonicum for the lining paper, which is made from paper mulberry and the chalk, are carried out to evaluate changes in their preservation properties by these aging factors. As a result, it is found that the functional lining paper containing 25.1% of chalk can control the growth of fungi, while the paper containing 32.7% of chalk do not show any protection effect. However, the functional lining paper added by chalk is more aged than the lining paper made from paper mulberry by dry heating accelerated aging.
위조문서 감별을 위한 현대 문서용지 특성 분석 ( I )
최경화(Kyoung-Hwa Choi),이재훈(Jae-Hoon Lee),류정용(Jeong-Yong Ryu) 한국펄프·종이공학회 2018 펄프.종이기술 Vol.50 No.3
In this study, the composition and content of filler within the 188 species of split sheets of a graduate thesis, whose publication year was verified, were analyzed to investigate the characteristics of modern document paper. Based on the results of ash-measurements and SEM-EDS analysis, it was found that major fillers, including talc, clay and calcium carbonate, are used in modern paper making. Between 1978 and 2000, talc was used as a major filler in document paper. Since around 2000, calcium carbonate was begun to be used, and calcium carbonate was mainly used in recent years. It is closely related with not only the use of calcium carbonate due to a conversion into neutral papermaking system in 1985 but also the decline of price due to a increase of domestic production of calcium carbonate in 1999. The ash content of the paper samples varied from about 10% to 30%. Several samples are assumed to contain fillers and coating pigments. To increase the reliability of analysis data, we need to continually sample and investigate more diverse documents.
최경화(Kyoung-Hwa Choi),정혜영(Hye Young Jeong),조병욱(Byoung-Uk Cho) 한국펄프·종이공학회 2015 펄프.종이기술 Vol.47 No.6
This study was conducted to investigate the effect of the strengthening treatment of methyl cellulose (MC) on properties and aging characteristics of the dewaxed papers during humid heating aging. Beeswax-treated Hanji was dewaxed by the supercritical fluid extraction method, and subsequently the strengthening treatment was performed with MCs having three different viscosities. MC was first applied by dipping a dewaxed paper into a MC solution whose concentration was controlled from 0.5% to 1.5%. After the strengthened papers were artificially aged at 80℃ and 65% RH, the changes in optical and mechanical properties of the samples were evaluated. The results show that viscosity and especially pick-up of MC influenced the strengthening efficiency and aging characteristics of dewaxed paper. Strength was increased with the MC coating weight; in addition, strengthening with MC improved preservability of the dewaxed paper. The optimum conditions for the strengthening with MC was found to be the coating ratio of 4% with 1500 cP MC.
최경화(Kyoung-Hwa Choi),이재훈(Jae-Hun Lee),조병욱(Byoung-Uk Cho) 한국펄프·종이공학회 2014 펄프.종이기술 Vol.46 No.6
Optical brightening agents (OBA) is generally used to improve the optical property of printing paper in the paper industry. However, effects of OBA addition on paper preservability has been not fully understood yet. Therefore, this study was aimed to investigate effects of a OBA on the aging characteristics of paper. The OBA treatment of three different types was performed by dipping a filter paper into each a OBA solutions of different concentrations. The filter papers applied with a OBA were artificially aged at 80℃ and 65% RH, and their optical and mechanical properties were evaluated. It was found that application of OBAs influenced the aging characteristics of paper. Especially, after aging, the optical and mechanical properties of the filter paper treated with the tetra-type OBA were more significantly decreased than those of the non-treated filter paper. The more the concentration of the tetra-type OBA increased, the more decreasing rate of optical and mechanical properties of the filter paper. While, in case of di-type OBA and hexa-type OBA, paper optical and mechanical properties were slightly decreased or not changed with a OBA treatment.
TMP의 LB 공융용매 처리 시 젖산/베타인 몰 비율이 리그닌 함량 및 수초지 특성에 미치는 영향
최경화(Kyoung-Hwa Choi),이명구(Myoung-Ku Lee),류정용(Jeong-Yong Ryu) 한국펄프·종이공학회 2016 펄프.종이技術 Vol.48 No.2
This study was conducted to investigate the effects of deep eutectic solvent (DES) treatment on properties of TMP fibers and handsheets. DES was prepared by mixing of lactic acid and betaine (L and B), and the molar ratio of these two components mixtures was controlled to 2:1 (L:B=2:1) and 5:1 (L:B=5:1). As results, lignin was partly extracted from the TMP fibers. Especially, the delignification of TMP samples was promoted according to the increase of the molar ratio of lactic acid. Except for tear index, both tensile index and burst index of handsheets were increased when higher molar ratio of lactic acid was mixed for DES preparation. However, the LB DES treatment of TMP fibers didnt give any effect on the optical properties of TMP handsheets. The plausibility of TMP fiber was to be enhanced by LB DES treatment.
상이한 몰 비율의 LB 공융용매 처리에 따른 BCTMP 섬유 및 수초지 특성의 변화
최경화(Kyoung-Hwa Choi),남윤석(Yun-Seok Nam),이명구(Myoung-Ku Lee),류정용(Jeong-Yong Ryu) 한국펄프·종이공학회 2016 펄프.종이技術 Vol.48 No.1
This study was conducted to investigate the effects of deep eutectic solvent (DES) treatment on BCTMP fibers and handsheets properties. DES was prepared using lactic acid and betaine (LB), and the molar ratio of these two components mixtures was controlled to 2:1 (LB 2:1) and 5:1 (LB 5:1). As results, 2% of BCTMP pulp (o.d. weight) was extracted when it was treated by LB 5:1 at 50℃ for 12 hours, stirring constantly at 120 rpm. In contrast, lignin was not extracted when BCTMP was mildly treated by the LB DES mixed with 50% of distilled water at the reacting condition of temperature 60℃ for 2 hours using water bath. These results indicate that conditioned water content and adequate reaction time are needed to achieve effective extraction of lignin. It was also found that stiffening of cellulose fiber due to the mild treatment of LB DES to BCTMP fiber leads to the increase of paper bulk without the loss of strength.
최경화(Kyoung-Hwa Choi),이재훈(Jae-Hun Lee),조병욱(Byoung-Uk Cho) 한국펄프·종이공학회 2017 펄프.종이技術 Vol.49 No.3
This study was conducted to investigate the effect of molecular weight and degree of substitution of carboxymethyl cellulose (CMC) on the grinding characteristics of hardwood bleached kraft pulp (HwBKP) during MFC production. CMCs having different molecular weights and degree of substitution were added into the pulp stock before grinding, and then the fibrillation and morphological properties of HwBKP during grinding were analyzed. The result showed that CMC contributed to improvement in grinding of HwBKP. Fibrillation factors including fibril area, water retention value, and pulp slurry viscosity were increased with CMC addition. It is speculated that CMC improved fibrillation of HwBKP during grinding because CMC acted as a lubricant and/or a thickener. The CMC with a high molecular weight showed improved grinding characteristics while a distinct effect of degree of substitution of CMC was not observed.