전류인입선 응용을 위한 BSCCO 초전도 튜브의 제조

최정숙,전병혁,현옥배,김찬중,Choi, Jung-Suk,Jun, Byung-Hyuk,Hyun, Ok-Bae,Kim, Chan-Joong 한국초전도학회 2009 Progress in superconductivity Vol.10 No.2

$Bi_2Sr_2Ca_1Cu_2O_x$(BSCCO 2212) superconductors for current lead were fabricated by centrifugal melting process(CMP). BSCCO 2212 powder was melted at $1200^{\circ}\C$ in a resistance furnace using a Pt crucible and poured in a rotating cylindrical mold preheated at $550^{\circ}\C$ for 2 hour. The solidified BSCCO-2212 samples were heat-treated by partial melting process in oxygen atmosphere. The current-voltage curves at 77 K of the samples were obtained by transport measurement, and the microstructure was investigated by scanning electron microscope. The $J_c$ values at 77 K of the tubes partially melted at $840^{\circ}C,\;860^{\circ}C\;and\;880^{\circ}C$ were 492, 430 and 398 $A/cm^2$, respectively. It was observed that the plate-like grains in BSCCO 2212 tube was more developed in the sample heat-treated at $840^{\circ}C$. It was found that the critical current of the BSCCO 2212 samples was dependent on the partial melting schedule regarding the grain shape and size of the BSCCO 2212.

프랙탈의 고등학교 수학교육과정에서의 도입가능성에 관한 연구

최정숙,신인선 ( Jung Suk Choi,In Sun Shin ) 한국수학교육학회 1998 수학교육 Vol.37 No.1

We seek the possibility of introduction of Fractals to the high school math. curriculum through identifying Fractals teaching programs appropriate for the scopes and sequences in math. education for the high school students. We presented the contents of Fractal theory suitable for the high school students. The following subjects were chosen to be introduced; self-similarity, Fractal dimension, Cantor set, Sierpinsky triangle, Sierpinsky carpet, Koch curve, Koch island, perimeter estimate of rugged profiles drawn on paper, and chaos game. We developed the working papers and the criteria for appraisal. Each working paper focuses on the activities in which students can solve the given problems, understanding the characteristics and ideas of Fractals. The working papers were given to the second year students who take science course, and the degree of achievements were analyzed based on the appraisal criteria. The results show that it is possible to introduce Fractals to the high school students

CMP 방법으로 제조한 BSCCO 2212 튜브의 임계전류특성에 미치는 열처리 온도의 영향

최정숙,오성룡,전병혁,김형섭,김혜림,현옥배,김찬중,Choi, Jung-Suk,Oh, Sung-Young,Jun, Byung-Hyuk,Kim, Hyoung-Seop,Kim, He-Lim,Hyun, Ok-Bae,Kim, Chan-Joong 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1

[$Bi_2Sr_2Ca_1Cu_2O_x$](BSCCO 2212) tubes were fabricated by centrifugal melting process(CMP). BSCCO 2212 powder was melted in a Pt crucible and solidified in a rotating steel mold. The BSCCO 2212 tube samples separated from steel mold were heat-treated at $800^{\circ}C\;and\;810^{\circ}C$ in oxygen flow. The critical current($I_c$) of the samples was measured by transport measurement at 77K, and the microstructure was investigated by scanning electron microscope. The $J_c$ at 77K of the tubes heated treated at $800^{\circ}C\;and\;810^{\circ}C$ were 197 and 240 $A/cm^2$, respectively. It was observed that the plate like grains in BSCCO 2212 tube was more developed in the sample heat treated at $810^{\circ}C\;and\;800^{\circ}C$ heated tube. It is found that the critical current($I_c$) of the BSCCO 2212 sample was dependent on the heating schedule regarding the growth of the BSCCO 2212 grains.

정보 과학 기술 : 교육용 프로그래밍 언어와 일반 프로그래밍 언어 비교- 두리틀을 중심으로

최정숙 ( Jung Suk Choi ),김정아 ( Jeong Ah Kim ) 한국컴퓨터교육학회 2010 한국컴퓨터교육학회 학술발표대회논문집 Vol.14 No.1

프로그래밍 학습에 있어서 학습자는 알고리즘적 사고를 위한 도구로써 프로그래밍을 접한다. 그런데 일반적인 프로그래밍 언어는 기본 문법과 구조를 이해하고 프로그램을 사용하는 방법을 익히는데 너무 많은 노력을 요구한다. 그래서 학습자가 학습 초기에 가지고 있던 의욕이나 동기는 상실되고 프로그래밍에 대한 부정적인 인식만 남게 되어 원리 교육을 받을 수 있는 차후 학습으로의 연계성이 결여된 채 프로그래밍 학습자체를 포기하게 된다. 이러한 문제점을 해결하기 위해 교육용 프로그래밍 언어인 두리틀과 기존의 프로그래밍 언어들을 비교하고 두리틀이 프로그래밍 학습을 하는데 효과적이고, 교육용 프로그래밍 언어로 적합한 언어임을 증명하고자 한다.

종양괴사인자에 의하여 유도된 혈관내피세포의 Cell Adhesion Molecules 발현을 억제시키는 플라보노이드 선별

최정숙(Jung-Suk Choi),최연정(Yean-Jung Choi),박성희(Sung-Hee Park),이용진(Yong-Jin Lee),강영희(Young-Hee Kang) 한국식품영양과학회 2002 한국식품영양과학회지 Vol.31 No.6

염증성 cytokines의 분비 또는 혈관손상으로 인한 백혈구의 adhesion과 transmigration을 통하여 죽상경화과정이 시발되는데, 본 연구에서는 이러한 죽상경화의 초기과정에서 플라보노이드가 억제작용을 발휘하는 지를 규명하고자 하였다. 본 연구에서는 화학적인 구조가 서로 다른 플라보노이드를 사용하여 화학적인 구조와 항동맥경화작용과의 상관성을 확인하였다. TNF-α는 혈관내피세포를 활성화시켜 THP-1 단핵구의 adhesion을 유의적으로 증가시켰다. 여러 형태의 플라보노이드를 전처리하고 TNF-α를 가하여 혈관내피세포를 활성화 시켰을 때, flavonols인 quercetin과 flavones의 luteolin과 apigenin은 THP-1 단핵구의 adhesion 억제효과를 보여주었다. 그러나, catechins과 flavanones의 플라보노이드는 이러한 억제효과를 전혀 보여주지 못하였다. 이러한 adhesion 억제작용을 가지는 플라보노이드는 CAMs 단백질의 발현도 차단시킨다는 것을 확인할 수 있었다. Quercetin, luteolin과 apigenin은 TNF-α에 의하여 증가된 VCAM-1, ICAM-1 및 Eselectin의 단백질 발현을 일률적으로 감소 또는 차단시켰다. 그 대신, 단핵구의 adhesion을 차단시키지 못한 (-)epigallocatechin gallate와 (+)catechin은 TNF-α에 의한 이러한 CAMs의 발현을 전혀 억제시키지 못하였다. 또한 quercetin, luteolin과 apigenin의 CAMs 단백질 발현 억제작용은 유전자 전사단계에서 mRNA의 down-regulation으로 인하여 나타난다는 사실을 알 수 있었다. 결론적으로 quercetin, luteolin, apigenin과 같은 플라보노이드는 TNF-α와 같은 염증성 cytokines에 의한 단핵구의 adhesion을 혈관내피세포의 CAMs단백질 발현을 억제하므로서 차단시킨다는 것이 확인되었다. 여기서 모든 플라보노이드가 이러한 활성을 다 지니고 있지 않아서 화학적인 구조와 초기 항동맥경화작용에는 서로 연관성이 있다는 것이 제시되었다. 또한, 선별된 플라보노이드의 초기 항동맥경화작용은 활성산소를 소거하는 플라보노이드의 항산화능과는 무관한 것 같다고 할 수 있다. Adhesion of leukocytes to the activated vascular endothelium and their subsequent recruitment/migration into the artery wall are key features in the pathogenesis of atherosclerosis and inflammatory diseases. These features have been mediated by cell adhesion molecules including vascular cell adhesion molecule-1 (VCAM-1) and in- tracellular cell adhesion molecule-1 (ICAM-1). This study examined whether flavonoids inhibit the pro-inflam- matory cytokine TNF-α-induced monocyte adhesion via a modulation of the protein expression of VCAM-1 and ICAM-1 of human umbilical vein endothelial cells (HUVECs). TNF-α markedly increased the adhesion of THP-1 monocytes to endothelial cells and induced the expression of VCAM-1, ICAM-1 and E-selectin proteins in HUVECs. Micromolar concentrations of the flavones luteolin and apigenin and the flavonol quercetin near- completely blocked the monocyte adhesion to the activated endothelial cells and the induction of these adhesion molecules. However, equimicromolar catechins of (-)epigallocatechin gallate and (+)catechin, the flavonol myr- icetin and the flavanones of naringin and hesperidin had no effect on TNF-α-activated monocyte adhesion. (-)Epigallocatechin gallate, (+) catechin, and naringin did not attenuate the TNF-α induction of these adhesion molecules. Furthermore, culture with luteolin and apigenin strongly blocked the expression of TNF-α-induced VCAM-1 mRNA and modestly attenuated ICAM-1 mRNA. Quercetin modestly decreased the TNF-α-activated VCAM-1 and ICAM-1 mRNAs. These results demonstrate that flavonoids classified as flavones and flavonols may inhibit monocyte adhesion to the TNF-α-activated endothelium, most likely due to a blockade of expression of functional adhesion molecules down-regulated at the transcriptional level, indicating a definite linkage between the chemical structure of flavonoids and the expression of cell adhesion molecules. Furthermore, the antiathero- genic feature of flavonoids appears to be independent of their antioxidant activity.

혈관내피세포의 세포사멸작용에 대한 (-)Epigallocatechin Gallate의 억제효과

최연정(Yean-Jung Choi),최정숙(Jung-Suk Choi),이세희(Se-Hee Lee),이용진(Yong-Jin Lee),강정숙(Jung-Sook Kang),강영희(Young-Hee Kang) 한국식품영양과학회 2002 한국식품영양과학회지 Vol.31 No.4

본 연구에서는 free radicals의 산화적인 손상에 의한 세포사멸에 있어서 녹차성분의 하나인 (-)epigallocatechin gallate의 억제효과를 규명하였다. 우선 radicals 소거작용에 있어서 (-)epigallocatechin gallate는 탁월한 항산화력을 발휘하였다. 혈관손상과 직결되는 혈관내피세포를 이용하여 hydroxyl radical의 H₂O₂에 의한 산화적인 손상을 유발시켜 세포생존율을 조사하였는데, (-)epigallocatechin gallate는 100 μM 이하의 농도에서는 그 자체 독성이 없었고 H₂O₂의 산화적 독성효과를 경감시키는 것으로 나타났다. 그러나 flavone인 apigenin은 고농도에서 독성을 가지며 radical 소거활성이 미약하고 H₂O₂의 산화독성은 경감시키지 못하였다. 다양한 세포사멸 검출법을 이용하여 세포 및 세포핵의 형태학적 양상을 조사한 결과, 0.25mM H₂O₂에 의한 24시간 이내의 세포죽음은 세포사멸현상에 의하여 초래되었다. 그러나 이러한 세포사멸과정을 겪고 있는 혈관내피세포에 50 μM (-)epigallocatechin gallate를 처리한 경우에 세포핵의 응축이나 DNA fragmentation은 사라지고 세포사멸작용을 억제시키는 효과를 보여주었다. 예상한 바와 같이 apigenin의 flavone은 세포사멸 억제효과를 나타내지 못하였다. (-)Epigallocatechin gallate는 녹차에 함유된 catechins의 하나로서 free radicals의 산화적 손상에 의한 세포사멸에 있어서 탁월한 방어적인 세포생리학적인 기능을 지니고 있으며, 혈관노화 및 혈관손상과 함께 유발되는 세포사멸성 심혈관 질환의 예방과 치료에 기능성 식품 신소재로서 활용될 수 있으리라 본다. Oxidative stress contributes to cellular injury following clinical and experimental ischemia/reperfusion scenarios. Oxidative injury can induce cellular and nuclear damages that result in apoptotic cell death. We tested the hypothesis that the catechin flavonoid of (-)epigallocatechin gallate, a green tea polyphenol, inhibits hydrogen peroxide (H₂O₂)-induced apoptosis in human umbilical vein endothelial cells. The effect of apigenin, a flavone found in citrus fruits, on apoptosis parameters was also examined. A 30 min pulse treatment with 0.25 mM H₂O₂ decreased endothelial cell viability within 24 hrs by>30%; this was associated with nuclear condensation and biochemical DNA damage consistent with programmed cell death. In the 0.25 mM H₂O₂ apoptosis model, 50 μM (-)epigallocatechin gallate markedly increased cell viability with a reduction in the nuclear condensation and DNA fragmentation. In contrast, equimicromolar apigenin increased cell loss with intense DNA laddering, positive nick-end labeling and Hoechst 33258 staining. Thus, polyphenolic (-)epigallocatechin gallate, but not apigenin flavone, qualify as an antioxidant in apoptosis models caused by oxidative stress. Further work is necessary for elucidating the antiapoptotic mechanisms of polyphenolic catechins.

연구논문 : 미용실 종사자 특성이 고객만족에 미치는 영향

이정경 ( Jung Kyung Lee ),최정숙 ( Jeung Suk Choi ) 한국미용학회 2003 한국미용학회지 Vol.9 No.3

보문 : 음나무(Kalopanax pictus) 수피 추출물의 항산화 활성에 관한 연구

황중덕 ( Jung Deog Hwang ),최정숙 ( Jeung Sook Choi ),김종봉 ( Jong Bong Kim ),이양숙 ( Yang Suk Lee ) 대한미용학회(구 대한미용과학회) 2011 대한미용학회지 Vol.7 No.4

This study was carried out to compare the antioxidant activities of Kalopanax pictus bark extract. The flavonoid and polyphenol contents of KBW (K. pictus bark water extract) were 17.13 mg/g and 27.14 mg/g, and KBE (K. pictus bark ethanol extract) were 15.80 mg/g and 21.36 mg/g, respectively. The tyrosinase inhibition of KBE was 16.08% and KBW was 13.15% at 2,000 μg/mL. In the results of xanthine oxidase inhibition, the half maximal inhibitory concentration (IC50) of KBW (142.59 μg/mL) represents an excellent activity compared to the ascorbic acid (192.50 μg/mL). The 1,1-diphenyl- 2-picryl hydrazyl (DPPH) radical scavenging activity, IC50 of KBW and KBE were 13.62 μg/mL, respectively, and 15.70 μg/mL, it was significantly 2.2~2.5 higher compared to the ascorbic acid (34.97 μg/mL). The superoxide dismutase (SOD)-like activity of KBW was 63.63% (IC50 1,554.90 μg/mL). The nitrite scavenging ability of KBW was 74.77% (IC50 1,000.00 μg/mL) at pH 1.2 and 61.62% (1,264.56 μg/mL) at pH 3.0. This suggest that K. pictus bark can be useful physiological source for the development of cosmetic materials.

원심 용융 성형법을 이용한 BSCCO 튜브 제조

김기익,최정숙,오성룡,전병혁,김혜림,현옥배,김형섭,김찬중,Kim Ki-Ik,Choi Jung Suk,Oh Sung Young,Jun Byung-Hyuk,Kim H.-R.,Hyun Ok-Bae,Kim Hyoung-Seop,Kim Chan-Joong 한국초전도학회 2005 Progress in superconductivity Vol.7 No.1

Bi-22l2 tubes for fault current limiter (FCL) were fabricated by centrifugal melting process. $SrSO_4$ ($10\;wt.\;\%$) was added to Bi-2212 powder to lower the melting point of Bi-22l2 and to improve the mechanical properties. The BSCCO powder was completely melted at $1300\;^{\circ}C$ using the RF furnace and then poured into rotating steel mold. The steel mold, preheated at $450\;{\circ}C{\sim}550^{\circ}C$ for 2 hour was rotated at $1020{\sim}2520\;RPM$. The solidified BSCCO tube was cooled down to room temperature in the furnace for 48 hours and separated from the mold between Bi-2212 and the mold. $ZrO_2$ solution was used to separate it easily from the mold and Ag tape was attached in the mold inner wall of the mold to analysis electrical property. Bi-22l2 tube was often cracked when the cooling rate was high. BSCCO tubes with $70{\Phi}{\times}100\;mm,\;50{\Phi}{\times}100\;mm$ and $30{\Phi}{\times}150\;mm$ size were fabricated by centrifugal melting process. The $J_{c}s$ of tubes with $50{\Phi}{\times}100\;mm{\times}4.0\;t$ and $50{\Phi}{\times}100\;mm{\times}4.l\;t$ were 178 and $74.2\;A/cm^2$ at 77K, respectively. The processing condition for Bi-2212 tube fabrication was investigated using XRD and SEM analyses.

저 순도 BaCO₃ 분말을 사용한 Yba₂Cu₃O_7-y 초전도체의 합성

김찬중,박순동,최정숙,전병혁,문종백,이상헌,성태현,Kim, Chan-Joong,Park, Soon-Dong,Choi, Jung-Suk,Jun, Byung-Hyuk,Moon, Jong-Baik,Lee, Sang-Heon,Sung, Tae-Hyun 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.1

[ $YBa_2Cu_3O_{7-y}$ ](123) powders were synthesized by the solid state reaction method using two different purity $BaCO_3$ powders (99.75% and 99.7% purity) and $Y_2O_3$ (99.9%) and CuO (99.9%) powders. The effect of $BaCO_3$ purity on the formation of a 123 phase and the superconducting properties were investigated. The mixtures of raw powders were calcined at temperature ranges of $800^{\circ}C-880^{\circ}C$ in air and finally made into a single grain samples by a melt processing with top seeding. It was found that a 123 phase was well formed at temperature above $870^{\circ}C$, but the purity effect on the 123 formation was negligible. The single-grain 123 samples prepared from the different $BaCO_3$ powders showed the same $T_c$ value of 90.5 K and similar $J_c$ values about $10^4\;A/cm^2$ at 0 T and 77 K, and $10^3\;A/cm^2$ at 2 T and 77 K. This result indicates that the low purity, cheap price $BaCO_3$ powder can be used as a raw material for the fabrication of single-grain, high-$J_c$ superconducting levitator.