노니 뿌리 추출물의 pH 조건별 실크 염색성 고찰

최중환,홍엄지,최란,홍선표,고준석,Choi, Joong Hwan,Hong, Umji,Choi, Ran,Hong, Sunpyo,Koh, Joonseok 한국섬유공학회 2014 한국섬유공학회지 Vol.51 No.4

Morinda citrifolia, commercially known as Noni, is a tree that grows widely throughout the Pacific, and is recognized as one of the most significant sources of traditional medicines among Pacific Island societies. The bark and the roots of the tree contain red and yellow pigments respectively, which are both used in the manufacture of dyes. Dyes from Noni are being used traditionally, to color clothing and fabrics. In this study, dyeing properties of Noni root extracts on silk fabrics at various pH conditions were investigated.

신생아 저산소성-허혈성 뇌병증

최중환 주식회사 녹십자 2002 녹십자의보 Vol.30 No.4

7050 Al 합금의 RRA 처리에 관한 연구

최중환,김장량,이상래,김인배,Choi, Joong-Whoan,Kim, Jang-Ryang,Lee, Sang-Lae,Kim, In-Bae 한국재료학회 2000 한국재료학회지 Vol.10 No.7

The effects of RRA treatment on the microstructures and mechanical properties of 7050 Al alloy were investigated by differential scanning calolimetry, transmission electron microscopy, microhardness measurement and electrical conductivity. The hardness of 2nd-step aged specimen at $175^{\circ}C$ was decreased to mimimum value and increased to a peak hardness, and then re-decreased with retrogression treatment. It was found that the hardness of 2nd-step aged specimen was further increased by 3rd step aging treatment($120^{\circ}C$x24h). The initial decrease in hardness during 2nd-step aging was due to the partial dissolution of pre-existing GP zone, the major precipitation hardening phase at T6 condition. It was confirmed that the major precipitation hardening phase at 3rd-step aging was GP zone and η' phase. The electrical conductivity increased continually through 2nd-step and 3rd-step aging treatment. It was conclude that the optium 2nd-step aging condition was at $175^{\circ}C$ for 50min by considering the hardness and electrical conductivity. 7050 AI합금을 RRA 처리하였을 때 경도, 전기전도도 및 미세조직의 변화를 조사하였다. 120도씨에서 24시간 동안 1차 시효처리한 후 175도씨에서 2차 퇴화처리하였을 때 경도값의 변화는 초기에 감소하다가 피크 경도를 보인 다음 다시 감소하였으며, 3차 재시효처리재가 2차 시효처리재 보다 큰 경도값을 나타내었다. 2차 퇴화처리시 초기 경도 감소는 T6의 주 강화상인 GP zone의 부분적인 분해에 의한 것이며, 3차 재시효 처리하였을 때 강화상은 GP zone과 파이상이었다. 120도씨에서 24시간 동안 1차 시효처리한 후 175도씨에서 2차 퇴화처리하였을 때 전기전도도 변화는 퇴화 쵤부터 연속적으로 증가혀였으며, 3차 재시효처리에 의해 2차 퇴화처리시 보다 %IACS가 0.5 ~ 2.7 증가하였다. 3단시효에 의해 T6정도의 강도를 유지하면서 38%IACS값 이상의 전기전도도를 얻을 수 있는 최적 퇴화처리 조건은 $175^{\circ}C$ 50분이었다. 이는 퇴화처리 경도곡선의 극소점 또는 극대점과 무관하며 오히려 약간 과시효 조건이다.

INCONEL 718 초내열 합금의 열처리에 따른 미세조직 변화

최중환,이기룡,조창용,김인배 ( J . H . Choi,K . R . Lee,C . Y . Jo,I . B . Kim ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.2

Microstructural evolution of wrought Inconel 718 superalloy with different heat treatment conditions was studied. Heat treatment was performed via conventional(CHT), modified(MHT), Merrick(MeHT) and modified Merrick(MMeHT) methods. The size of γ` and γ precipitates which are principal strengthening phases in Inconel 718 superalloy increase in order of CHT, MHT, MeHT. For the case of MMeHT, a coexistence of fine γ` precipitate and very coarse particles due to exess growth of γ which is called bimodal distribution, was observed. CHT gave the finest grain size. (Ti, Nb)C carbide and needle-like δ phase were formed together at grain boundaries for CHT, and were formed both inside and at boundaries of grains for MHT, MeHT and MMeHT. Morphology of partially serrated grain boundaries was developed in all heat treatment conditions except CHT.

단분산성 고분자 용융체의 완화시간분포의 해석적인 근사계산법

최중환,Choi, Joong Hwan 한국섬유공학회 2014 한국섬유공학회지 Vol.51 No.4

The relaxation time spectrum is a versatile parameter to calculate various polymer viscoelastic properties, such as the relaxation modulus (G(t)), dynamic modulus (G'(${\omega}$)) and loss modulus (G"(${\omega}$)). However, it cannot be measured experimentally. This study calculated the relaxation time spectrum using a calculation method based on Fusso-Kirkwood's theoretical research and using the empirical loss modulus formula. The calculated relaxation time spectrum and Rouse's model could describe the viscoelastic behavior of monodisperse polystyrene successfully. This analytical approximation of the relaxation time spectrum differed from experimental data in the intermediate region between the reputation and Rouse region. This may have resulted from a limitation of the molecular theory in the Rouse region.

동적 크리프 컴플라이언스를 이용한 완화시간분포의 근사계산법

최중환,Choi, Joong Hwan 한국섬유공학회 2014 한국섬유공학회지 Vol.51 No.5

The relaxation time spectrum is a very effective parameter for transforming material functions even with a limited amount of data. The spectrum also helps in understanding the relaxation behavior of polymers at the molecular scale. In this study, a relaxation time spectrum based on Marin-Graessley's dynamic compliance model was calculated using Fuosso-Kirkwood's complex analysis. The resulting model could successfully describe the viscoelastic behavior of mono-disperse polystyrene. However, it was clear that a more effective numerical analysis method was needed to obtain more accurate parameter values.

모유 황달

崔仲煥 대한의학협회 1994 대한의학협회지 Vol.37 No.7

조산아의 집중치료

崔仲煥 中央醫學社 1995 中央醫學 Vol.60 No.4

7050 Al합금의 응력부식저항성에 미치는 2단 시효처리의 영향

최중환,김종기,김헌규,이상래,김인배,Choe, Jung-Hwan,Kim, Jong-Gi,Kim, Heon-Gyu,Lee, Sang-Rae,Kim, In-Bae 한국재료학회 1999 한국재료학회지 Vol.9 No.7

7050 Al합금의 응력부식저항성에 미치는 2단 시효처리의 영향을 미세조직관찰, 전기전도도시험 및 SCF값을 평가함으로써 조사하였다. 최대 경도 이상 과시효에 의해 주 강화상인 η'상이 η상으로 변태되었고, 입내 및 입계에 존재하는 η상의 크기와 간격이 커졌으며 그 결과 응력부식저항성이 증대되었다. 2차 시효시간의 증가에 따라 전기전도도값은 증가되었으나 항복강도의 감소로 인하여 SCF값은 감소되었는데, 이러한 결과는 응력부식저항성의 증가를 의미한다. AMS 4107규격을 기준으로 하였을 때 7050 Al합금 단조재의 적정시효조건은 1차시효가 12$0^{\circ}C$에서 6시간, 2차시효는 $175^{\circ}C$에서 12시간이었다. Effects of two-step aging treatment on the stress corrosion cracking(SCC) resistance of 7050 Al alloy were investigated by transmission electron microscopy, electrical conductivity measurement and stress corrosion facter(SCF) evaluation. It was found that η', principal hardening phase, transformed to η during over aging above maximum hardness, and SCC resistance was improved by increasing of the size and interspacing of η particles in matrix and grain boundary. The electrical conductivity increased with aging time, but SCF decreased due to the decrease of yield strength. This results mean increase of SCC resistance The optimum two-step aging condition in forged 7050 Al alloy was to be first aged at $120^{\circ}C$ for 6h and then finally aged at $175^{\circ}C$ for 12h.

Comparison of Paraquat Actions on Oxygen Radical Generation and Lipid Peroxidation between Submitochondrial Particle and Microsome of Mouse Liver

최중환,김용식,박종완,정명희,윤종구,Choi, Jung-Hwan,Kim, Yong-Sik,Park, Jong-Hwan,Chung, Myung-Hee,Yunn, Chong-Ku The Korean Society of Pharmacology 1991 대한약리학잡지 Vol.27 No.2

Paraquat 독성작용에 있어서 mitochondria의 잠재적인 역할을 평가하기 위하여, 이 약물의 산소 radical 생성과 지질과산화 반응에 미치는 영향을 mouse간의 submitochondrial particle 과 microsome에서 비교하여 보았다. Submitochondrial particle 사용시 NADH를, microsome 사용시 NADPH를 전자공여체로 이용한 경우 paraquat는 두 분획에서 superoxide anion과 hydrogen peroxide의 생성을 증가시켰다. 동일한 조건하에서 paraquat는 hydroxyl radical의 생성을 시사하는 methional로 부터 ethylene의 생성을 증가시켰다. 그러나, paraquat에 의한 이들 각각의 효과는 microsome에서 보다 submitochondrial particle에서 약간 낮았다. 한편, 두 분획 모두에서 paraquat는 지질과산화 반응을 촉진시켰다. Submitochondrial particle과 microsome에서의 Paraquat에 의한 지질과산화반응은 i) 두 분회에서 지질과산화는 SOD에 의해서 부분적으로 억제됨을 보였고, DETAPAC(iron chelator)에 의해서는 완전히 억제되었고, catalase와 hydroxyl radical scavenger에 의해서는 억제되지 아니하였으며, ii) 반응내 $ADP-Fe^{3+}$ 첨가로 paraquat에 의한 지질과산화는 더욱 증가되었지만 methional로 부터 ethylene 생성은 감소하여 hydroxyl radical 생성과 지질과산화 사이에는 상관성이 없음으로 보아 같은 기전을 통해 촉진됨을 알 수 있었고 이러한 촉진작용은 perferryl ion을 통하여 일어나리라 추측되었다. Submitochondrial particle에서 paraquat에 의해 촉진된 산소라디칼 생성과 지질과산화 반응은 p-hydroxymercuribenzoate(NADH dehydrogenase 억제제)에 의하여 억제되었으나 다른 respiratory chain 차단제들에 의해서는 거의 영향을 받지 않음으로 보아 mitochondria에서의 paraquat의 redox-cycling은 CoQ 보다는 NADH dehyrogenase와 관련이 있음을 시사하였다. 이상의 결과로 보아 산소 radical의 생성과 지질과산화를 유도하는 paraquat의 redox-cycling은 microsome에서와 마찬가지로 mitochondria에서도 일어나며, 이결과 생체내에서의 paraquat의 독작용에 관여함을 짐작할 수 있다. In order to evaluate a potential role of mitochondria in the mediation of toxicity of paraquat (PQ), submitochondrial particle and microsome of mouse liver were compared by oxygen radical generation and lipid peroxidation. With NADH in submitochondrial particle and NADPH in microsome as electron donors, PQ stimulated production of superoxide anion and $H_2O_2$ in both fractions. Under the same conditions, PQ enhanced the generation of ethylene from methional suggestiong stimulation of OH production by PQ. But these effects by PQ were somewhat lower in submitochondrial particle than in microsome. In addition, lipid peroxidation(measured as MDA production) was stimulated by PQ in both fractions. The stimulation of lipid peroxidation in both fractions seemed to occur by the same mechanism probably through perferryl ion. This was supported by the following findings: i) The lipid peroxidation in both fractions was partially inhibited by SOD and completely inhibited by DETAPAC(an iron chelator) but not by catalase or OH scavenger. ii) Addition of $ADP-Fe^{3+}$ further increased PQ-induced lipid peroxidation but decreased ethylene production from methional suggesting no correlation between OH production and lipid peroxidation. The redox-cycling of PQ in mitochondria appeared to be linked to NADH dehydrogenase, not to CoQ since all of the observed stimulations by PQ in submitochondrial particle were inhibited by p-hydroxymercuribenzoate(a NADH dehydrogenase inhibitor) but not affected by other respiratory chain blockers. The above results demonstrate that redox-cycling properties of PQ leading to oxygen radical generation and lipid peroxidation can also occur in mitochondria in the same manner as in microsome. Therefore, the observed actions of PQ in mitochondria suggest that mitochondria may also contribute to toxicity of this drug in vivo.