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Superconductivity of Ce$O_2$-added Y-Ba-Cu-0 Superconductors Prepared by Partial Melt Process
김찬중,김기백,이규원,원동연,Kim, Chan-Joong,Kim, Ki-Baik,Lee, Kyu-Won,Won, Dong-Yeon Materials Research Society of Korea 1992 한국재료학회지 Vol.2 No.3
$CeO_2$를 첨가한 Y-Ba-Cu-0 초전도체를 포정반응을 포함한 준용용법으로 제조하여 미세조직과 초전도성을 관찰하였다. 첨가한 $CeO_2$는 포정반응중에 $BaCeO_3$로 변화하였으며, 이 $BaCeO_3$는 방향성 성장한 1-2-3 초전도상의 기지에 미세하게 분산된다. 초전도체의 $T_{c}$는 첨가된 $CeO_2$함량에 관계없이 90K 이상으로 매우 높았다. 이는 준용융공정을 적용함으로서 제2상물질을 초전도상으로부터 분리할 수 있었기 때문으로 사료된다. The $CeO_2$-added Y-Ba-Cu-O oxides were prepared by the partial melt process involving the peritectic reaction, liquid + 2-1-1 phase ${\rightarrow}$ 1-2-3 phase, to investigate the effect of the dopant on microstructure and superconductivity. During the peritec reaction, all the added $CeO_2$ was converted to $BaCeO_3$ particles which were finely dispersed in large 1-2-3 grains. Superconducting transition temperature($T_{c}R=0$ point) of the partial-melted samples was as high as 90K regardless of $CeO_2$ content up to 5wt%, which is owing to the separation of the second phase from the 1-2-3 superconducting phase.
이호진(Lee Ho Jin),김기백(Kim Ki Baik),이봉상(Lee Bong Sang),이병섭(Lee Byung Sup) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
The true stress-true strain relation of SA508 steel was evaluated with analytical and experimental equations on the base of the indentation load-depth curve obtained from the modeling of ball indentation test. The evaluated relation between true stress and true strain is agreed well with that of SA508 steel defined in the modeling. The distribution of effective stress along the center axis of indentation depth was calculated with Tresca criteria in the modeling. The representative strains, which are defined in this study as the corresponding strains obtained from the maximum effective stresses, have a linear relation with the true strain. The true stress-true strain relation of austenitic stainless steel was evaluated by the modeling of ball indentation test to verify the case of SA508 steel.
NF-κB 활성화의 억제 및 mitochondrial permiability transition에 의하여 유발되는 인체 간암세포주에서의 TRAIL 유도성 세포사멸
김영수 ( Young Soo Kim ),함기백 ( Ki Baik Hahm ),김진흥 ( Jin Hong Kim ),조성원 ( Sung Won Cho ) 대한소화기학회 2002 대한소화기학회 춘계학술대회 Vol.2002 No.-
<Aims> TNF-related apoptosis-inducing ligand (TRAIL) is a new member of the TNF family which induces apoptosis in a wide range of malignant cells. However, some cancer cell lines including human hepatoma cells are resistant toward TRAIL-indued apoptosis.
식도정맥류 출혈에서 Histoacryl의 치료효과; 식도정맥류 결찰요법과의 비교
김영수,조성원,김호동,이광재,김진홍,유병무,함기백,고영윤,고준호,이규현,신용준 대한간학회 1999 Clinical and Molecular Hepatology(대한간학회지) Vol.5 No.4
Background/Aim: Endoscopic sclerotherapy and band ligation have been well documented beneficial therapeutic options of esophageal variceal bleeding. But acute variceal bleeding is refractory to sclerotherapy in upto one-third of patients, and rebleeding occurs in 30% to 50%. Recently alternative endoscopic modality, N-butyl-2-cyanoacrylate (Histoacryl) injection is performed in intravariceal sclerotherapy but its efficacy and safty are not clearly established. We evaluated the efficacy of Histoacryl on esophageal variceal bleeding and compared with that of endoscopic band ligation in the present study. Materials/Methods: From March 1994 to March 1998, ninety seven patients with endoscopically documented esophageal variceal bleeding were enrolled. Histoacryl injection (Histoacryl group, n=33) or endoscopic band ligation (EVL group, n=64) was done for esophageal variceal bleeding. We evaluated the rebleeding rate and in-hospital mortality in both groups. Results: Baseline characteristics were similar but active bleeding on first endoscopic session was significantly higher in Histoacryl group (Histoacryl group; 90.7%, EVL group; 26.6%, p=0.002). Successful hemostasis was done at 87.9% in Histoacryl group, 95.3% in EVL group (not significant). There were no significant differences on early rebleeding rate (18.2% vs 23.4%), late rebleeding rate (39.4% vs 37.5%) and in-hospital mortality (24.2% vs 15.6%) between Histoacryl group and EVL group. There were no technique-related fatal complications at Histoacryl injection group. Conclusion: Therapeutic efficacy of Histoacryl injection was similar to the endoscopic band ligation in patients with esophageal varix bleeding in terms of hemostasis and rebleeding. Histoacryl is effective therapeutic option for esophageal variceal bleeding as well as gastric variceal bleeding. (Korean J Hepatol 1999;5:306-313)
김호동,김진홍,조성원,함기백,고준호,유병무,김영준,고영윤,이규헌 대한소화기내시경학회 2000 Clinical Endoscopy Vol.20 No.3
Background/Aims: Common bile duct stones are the most common among bile duct diseases. In the past, common bile duct stones were considered a surgically operable disease, but is now considered a medical disease due to the advancement of endoscopy and endoscopic techniques. The aim of this study was to determine the results of endoscopic treatment of common bile duct stones. Methods: Removal of primary or secondary common bile duct stones were attempted by peroral or percutaneous endoscopy. The common bile duct stones were diagnosed by ultrasonography or cholangiography. As a primary approach route, the peroral transpapillary endoscopic approach was tried. On the other hand, percutaneous common bile duct stone removal was attempted if the patient already had a percutaneous route, peroral transpapillary approaches failed, or if conditions for endoscopy were unfavorable. Results: The study subjects consisted of 196 patients; 96 males and 100 females. The mean age was 61.8 years. A total of 272 endoscopic stone removal were attempted in 196 patients. Of the 272, peroral approaches were conducted 241 times for 183 patients, and percutaneous approaches were performed 31 times for 12 patients. The success rate of the first treatment modality to remove the common bile duct stones was 90.3% (176/195). The overall success rate of endoscopic common bile duct stones removal was 100%. Conclusions: In all patients, the common bile duct stones were removed successfully by endoscopy, and thus supporting the shift of recognizing common bile duct stones as a medical rather than surgical discase.
식도정맥류의 조기 재출혈 예방에 결찰요법과 Octreotide의 병용치료와 결찰요법 단독치료의 효과비교
조성원,김호동,이광재,김진홍,함기백,김헌종,고광현,고영윤,고준호,이규현 대한간학회 1999 Clinical and Molecular Hepatology(대한간학회지) Vol.5 No.4
Background/Aims: Endoscopic variceal ligation (EVL) has been effective modality for esophageal variceal bleeding, but recurrent bleeding occurs 20 to 40% of patients. So there has been an increased interest in the use of vasoactive drugs to lower portal hypertension and help control variceal bleeding before and after endoscopy. We investigated the efficacy of octreotide (OCT) infusion as an adjunct to EVL for preventing early rebleeding from varices. Methods: From Jan. 1997 to Feb. 1999, fifty four patients with endoscopically documented esophageal variceal bleeding were included. The patients were randomly treated by EVL alone (EVL group, n=30) or EVL plus octreotide (EVL+OCT group, n=24). We evaluated the 5-day and 6-week rebleeding rate and 6-week mortality. Results: Baseline characteristics were similar in two group but hospital stay (p=0.028) and units of transfused blood (p=0.043) were significantly less in EVL+OCT group. There were no significant differences on 5-day rebleeding rate (EVL group; 7%, EVL+OCT group; 0%) and 6-week rebleeding rate (EVL group; 20%, EVL+OCT group; 4%). Conclusions: The combined therapy did not decrease early rebleeding and mortality, but it was superior to EVL alone in hospital course such as requirement of transfusion and duration of hospitalization. (Korean J Hepatol 1999;5:299-305)
YBa (Cu, Fe) O 계에서 철 첨가에 의한 사방정-정방정 저온 상전이
원동연,김찬중,김택남,김기백,권양철,이희균 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.1
The low temperature phase transition of high-Tc superconducting phase has been investigated in Fe-doped YBaCuO systems by X-ray diffraction analysis, optical microscopy, transmission electron microscopy and electrical resistivity measurement. The phase transition from orthorhombic to tetragonal in YBa₂(Cu_(1-x) Fe_x)₃O_(7-y) superconductor is induced by replacing Cu with Fe. A mixture of the orthorhombic and tetragonal phases exists in specimens containing Fe of about x=0.03. In orthorhombic platelike grains are observed striations which are related to the formation of twins in the grains. The phase transition can be easily identified by the disappearance of the striations in platelike grains under polarized light. As Fe content increases, the twin spacing in orthorhombic phase becomes narrow. In the tetragonal phase at x$gt;0.03, the fine tweed structure is observed instead of the twin structure of the orthorhombic phase. The c parameter does not change even though the phase change occurs, implying that the tetragonal phase in Fe-doped specimen contains more oxygen than that in undoped specimen. The zero resistance temperature(Tc) and oxygen content decrease with Fe content. Nevertheless, the specimen containing Fe up to 2 at% shows high Tc of 84K, suggesting that the super conductivity in YBa₂(Cu_(1-x), Fe_x)₃O_(7-y) is more related to the oxygen content than the crystal structure.