판상형 충전제의 함량과 배향에 따른 PP복합체의 열팽창계수 영향 연구

이기윤(Kee Yoon Lee),이용현(Yong Hyun Lee),정선경(Sun Kyoung Jeoung),황효연(Hyo Yeon Hwang),이승구(Seung Goo Lee) 한국고분자학회 2012 폴리머 Vol.36 No.3

두 가지의 종횡비(ρα=a1/a3 and ρβ=a1/a2)에 의해 특징지어진 3차원 타원체(a1 > a2 > a3)를 사용하여 polypropylene 복합체의 판상형 충전제 함량과 방향이 열팽창률에 미치는 영향에 대해 실험적인 연구를 수행하였다. 측정된 실험적인 값은 Lee와 그의 연구자들이 제안한 이론적인 모델에 의한 계산 값과 비교분석되었다. 판상형충전제로는 운모와 탈크가 사용되었다. 실험 결과로 운모의 경우 종횡비는 ρα= 13.5, ρβ= 1.8이 사용되 어, 20 wt% 함량일때 α11/αm는 약 0.56으로 감소하였으나, α33/αm는 오히려 1.018로 증가함을 보였다. 탈크의 경우의 종횡비는 ρα=3.7, ρβ= 1.4이었고 α11/αm는 0.63으로 감소하였다. 결국 운모와 탈크 모두 그 함량증가에 따라 종단방향과 횡단방향에서 열팽창률은 감소하였으나 수직방향에서는 초기 낮은 충전제 함량에서는 오히려 증가하는 경향을 보였다. Experimental study was performed regarding the effects of disc-like filler orientation and contents on the coefficient of thermal expansion (CTE) of polypropylene composites using the three dimensional ellipsoids (a1 > a2 > a3) analyzed by two aspect ratios(ρα=a1/a3 and ρβ=a1/a2). Measured data were compared with the theoretical approaches proposed by Lee et al. Mica and talc were useed as disk-like fillers in the composites. As experimental results, α11/αm decreased down to ca. 0.56 with mica content of 20 wt% and the aspect ratios, ρα=13.5, ρβ=1.8. However, α33/αm increased to more than 1. In the case of talc, α11/αm decreased to ca. 0.63 with 20 wt% and ρα=3.7, ρβ=1.4. Finally, the longitudinal CTEs (α11) of polypropylene composites decreased as filler contents increased, but normal CTE (α33) increased in the low filler contents like the theory.

Plant regeneration from callus of Iris odaesanensis Y. N. Lee native to Korea via organogenesis

Bae, Kee-Hwa,Yoo, Kyoung-Hwa,Lee, Mi-Hyun,Jeong, Jae-Hun,Choi, Yong-Eui,Yoon, Eui-Soo The Korean Society of Plant Biotechnology 2013 식물생명공학회지 Vol.40 No.3

Iris odaesanensis Y. N. Lee. is an important endangered and native plant belonging to the family Iridaceae in Korea. This study describes a method for rapid micropropagation of this species via from leaf, rhizome and root explants derived calli. Leaf, rhizome and root explants were cultured on Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxy acetic acid (2,4-D) for callus induction. Rhizome explants yielded calli at a frequency of 72% when cultured at 1.0 mg/l 2,4-D. Calli were maintained at 1.0 mg/l 2,4-D. These calli were transferred to MS medium supplemented with 0, 0.5, 1.0, and 2.0 mg/l 2,4-D in combination with 0, 0.5, 1.0, and 3.0 mg/l BA for adventitious shoot induction. The highest number of adventitious shoot (228.9 per petri-dish) were formed at 1.0 mg/l 2,4-D and 1.0 mg/l BA. WPM medium was the best to convert calli into plantlets, where up to 98.2% of calli were regenerated into plantlets. This in vitro propagation protocol should be useful for conservation of this endangered plant.

판상형 충전제의 함량과 배향에 따른 PP복합체의 영률 변화 연구

서상범(Sang Bum Seo),이용현(Yong Hyun Lee),정선경(Sun Kyoung Jeong),이승구(Seung Goo Lee),이기윤(Kee Yoon Lee) 한국고분자학회 2012 폴리머 Vol.36 No.2

이 논문은 판상형 충전제의 함량과 배향에 따라 폴리프로필렌 복합체의 영률 변화에 미치는 영향을 연구 하였다. 이론적인 예측은 Lee와 그의 연구자들에 의해 제안된 두 개의 종횡비, ρα=a1/a3과 ρβ=a1/a2 를 이용하여 3차원 타원체의 형상을 계산하였고 실험값과 비교 분석하였다. 판상형 충전제로 운모와 탈크를 사용하였다. 충전제의 형태는 SEM을 이용해 관찰하였고, 종횡비는 고분자의 흐름을 기준으로 좌표축을 설정하여 통계적 방법으로 계 산하였다. 충전제가 운모인 경우에 ρα=13.5와 ρβ=1.8이었고, 탈크의 경우는 ρα=3.8과 ρβ=1.4이었다. 또한 충전제 의 2개의 종횡비와 함량이 기계적 물성에 미치는 영향을 실험적으로 연구하였다. 운모의 경우 30 wt% 함량일 때 E11이 약 2.7배 향상되었다. 탈크의 경우는 E11이 약 2.3배 향상하였다. This paper studied the effects of the content and the orientation of the disk shape fillers on the modulus of PP composites. The experimental results were compared with the theoretical calculations which included the three dimensional ellipsoids and analyzed by two aspect ratios, ρα=a1/a3 and ρβ=a1/a2 proposed by Lee and his researchers. Mica and talc were used as disk shape fillers in the composites. The shapes of mica and talc were observed by SEM and aspect ratios were statistically calculated. For the case of mica, the average aspect ratios were ρα=13.5 and ρβ=1.8, and for the case of talc, they were ρα=3.8 and ρβ=1.4. Also, the effects of two aspect ratios and the content of filler on the mechanical properties were studied: For 30 wt% of mica, E11 increased up to about 2.7 times, and for the other case of talc, E11 increased up to about 2.3 times, respectively.

생쥐 대장 평활근 세포에서 내향 정류성 칼륨 전류의 특성 연구

이은주,김명,정명섭,조향훈,김기훈,하현철,김준수,최석,전제열 朝鮮大學校 附設 醫學硏究所 2006 The Medical Journal of Chosun University Vol.31 No.2

Objectives: K^(+) channels play an important role in regulating cellular excitability. The aim of this study was to know whether or not inward rectifier K^(+) channel exists in colonic smooth muscle cells. Methods: Mouse colonic smooth muscle cells were isolated using collagenase, and then we recorded their membrane currents using a whole-cell patch clamp technique. Results: With 90 mM K^(+) in bath, hyperpolarization-induced inward currents from -120 mV to 20 mV with 400 ms duration at a holding potential of -10 mV showed rapid activation, inactivation and inward rectification. The inactivation showed single exponential time course. Reduction of external K^(+) to 60 mM decreased the amplitudes of the currents in whole test voltage range and shifted the reversal potential to more negative potential. The inactivation process and peak currents of hyperpolarization-induced inward currents were not affected by removing external Na^(+). External Ba^(+) blocked hyperpolarization-induced inward currents by dose-dependent manner and pure Ba^(+)-sensitive currents showed strong inward rectification. Cs^(+) also suppressed hyper- polarization-induced inward currents. Ba^(+) and Cs^(+)-induced inhibitiOn of hyperpolarization-induced inward currents was voltage-dependent, and the extent of inhibition increasing with membrane hyperpolarization. Conclusions: These results suggest that inward rectifier KU channels may exist in proximal colonic smooth muscle and may play an important role in regulating membrane potential.

저열팽창성 Fe-29Ni-17Co 코바 합금의 고온균열 발생과 고온연성에 미치는 S 및 Mn의 영향

이기안,박종혁,조봉현,남궁정,김문철 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12

The effect of S & Mn on the hot ductility of Fe-29Ni-17Co Kovar alloy and the mechanism of high temperature cracking occurrence were investigated. It has been found that the brittle intergranular fracture at high temperature cracking is closely associated with the sulfide along grain boundary. Experimental results showed, especially when the S content was high and the Mn content was free, that small cavities could be nucleated easily on FeS particles along grain boundary and propagated fast at high temperature. The hot ductility of Kovar alloy was drastically increased with the addition of Mn and it was also increased with decreasing S content. SEM and FE-SEM analyses showed that the Mn addition in this alloy could cause ductile intergranular fracture appearance below 1150℃ by the precipitation of MnS. It was proposed from the results that the addition of Mn and optimum S content (below 30 ppm) in Kovar alloy was necessary in order to reduce the hot cracking susceptibility.

β-Carotene 이 혈중 효소활성도에 미치는 영향

이상한,우기민,조만희,장예진,김창세,김현철 순천향의학연구소 1997 Journal of Soonchunhyang Medical Science Vol.3 No.2

This study was carried out in order to observe the effects of ethanol and β-carotene on the cholesterol, Triglyceride, LDL-cholesterol, HDL-cholesterol, glutathione peroxidase and catalase activities. The normal white S.D rats were classified into 4 group: 0.9% NaCl administration and 20% ethanol administration were referred to as group A, 20% ethanol and 50% β-carotene mixture administration was group B and 50% β-carotene administration was group C for the 30 day-feeding experiment. The results were obtained as following: 1. The blood lipid concentration was most highly increased in group A, was almost normal in group B, but significantly decreased in goup C. 2. The blood antioxidant enzyme activities were significantly decreased in group A, but significantly increased in goup B and C. 3. The blood β-carotene concentration were significantly decreased in group A, and slightly decreased in group B. Surprisingly it was increased in group C.

치과용비귀금속합금의 파단조직에 미치는 주형온도의 영향

이기대,정현곤 慶北大學校 齒科大學 1987 慶北齒大論文集 Vol.4 No.1

The purpose of this study was to investigate the effect of mold temperature on the change in fractured microstructure of Ticonium Premium 100 (Ni-Cr alloy) and Regalloy (Co-Cr alloy). Tensile specimens were casted from the types of alloys by centrifugal casting machine in mold temperatures of 500, 600, 700, 800, 900 and 1,000℃. After testing the tensile strength of castings, the microstructure and the pattern of fracture were investigated. The grain size of Ticonium Premium 100 and Regalloy increased with the increase of mold temperature.

Fe-Ni-Co 저열팽창성 합금의 고온 변형 특성 및 열간가공에 따른 열팽창 거동 연구

이기안,박종혁,조봉현,남궁정,김문철 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.9

The high temperature deformation behavior and the effect of hot compression on the thermal expansion behavior of Fe-29Ni-17Co low thermal expansion Kovar alloy were investigated in the compressive temperature range of 900~1300℃ at the strain rate range of 25~0.01 sec.^(-1). The temperature (T) and strain rate (ε˙) dependence of the flow stress (σ_(0.7)) could be well described by hyperbolic sine law as ε˙= A [sinh(0.0084 σ)^(5.2018)] exp(-330.41/RT). Surface hot cracking and significant voids around grain boundary could be found at low temperature below 1000℃ and low strain rate (0.01 sec.^(-1)). Thermal expansion coefficient α_(30~400) generally increased with increasing compressive temperature. Moreover, α_(30~400) remarkably increased as strain rate decreased at high temperature above 1100℃. However the thermal expansion coefficient α_(30~400) of low compressive temperatures (900℃ and 1000℃) anomalously increased especially at high strain rates. Experimental results indicated that not only α phase appearance but also grain size had definite influence on the thermal expansion behavior with hot deformation. The correlation between microstructure and thermal expansion behavior of Kovar alloy were also discussed.

Phenazine Methosulfate의 Superoxide Radical 生成作用에 미치는 光線의 影響

李民化,李起榮,梁誠烈,朴昞柱,全鉉權 全南大醫大 1985 전남의대학술지 Vol.22 No.4

대학생의 개인재무관리역량

이슬기, 박현정, 김민정 충북대학교 생활과학연구소 2012 생활과학연구논총 Vol.16 No.1

The purpose of this study is to measure financial competency of students in Chung-buk national university. The financial competency included financial attitude, financial knowledge, and financial skills. The major findings are as follows: First, as the financial management competency of university students, their attitude towards financial management was 75 points, knowledge in financial management was 68.5 points, and financial management skill was 59.9 points. Second, male students showed higher scores than female students in all areas. Third, students in the fields of medicine, education, and laws showed higher levels of financial management knowledge yet their financial management skill was low. Forth, students who receive allowances from parents showed high points of attitude towards financial management yet their financial management skill was low. Those who receive allowances from people that are not parents showed lower points in the attitude towards financial management or the knowledge than those who do not receive allowances. Fifth, students who spend money they earned showed higher points in every area than other students’ points. Finally students who received financial education showed similar or lowered points in financial management attitude and financial management knowledge with students who did not receive the financial education. However, the level of their financial management function was higher. Students who have saving accounts, periodicaldeposits, fixed deposits, a check card, or debit card showed higher levels of financial management knowledge and function that those who do not have the above items.