Al-Mg 및 Al-Zn-Mg 합금의 미시편석과 균질화 거동에 미치는 Ti 의 영향

최정철 亞洲大學校 1989 論文集 Vol.12 No.-

Microsegregation and its homogenization behavior was investigated the amount of non-equilibrium crystallized and solute concentration of perimary dendrite arm in Al-9.4%Mg and Al-4.75%Zn-1.5%Mg alloy with /without Ti. The amount of nonequilibrium crystallized phase increases and miniumm solute concentration of primary dendrite arm decreases with Ti addition; microsegregation degree increases as well. The homogenization of Ti-added alloy is slower than that of non-added alloy attthe early stage. The homogenization of Ti-added alloy is not completed although the alloy is heat-treated for over 100 hours and the microsegregation remains at the low concentration region of magnesium and zinc in Ti-rich structure, which is same as cast. According to the diffusion couple for Al-2%Mg/Al-2%Mg-0.15%Ti alloys, those results indicate that because Ti is hardly diffused at common homogenization temperature, only maegnesium and zine is diffused and the chemical potential is to be equilibrium at the condition of lower zine and magnesium concentration than of a matrix, outside of Ti-rich structure.

Ti에 의해 결정립 미세화한 Al-Cu 및 Al-Cu-Mg 합금주괴에 있어서의 미시편석

최정철 亞洲大學校 1989 論文集 Vol.12 No.-

Microsegregation of solute elements with titanium and its homogenization behavior of titanium itself are studied in Al-4.5%Cu alloys. The microsegregation and their solutionization process at 530℃ are determined by concentration analyses and structural observations. It is found that microsegregation degree increase, that minimum solute concentration decreases and that the amounts of crystallized compound increase as titanium elements increase. The findings were analysed by another examination: the diffusion of copper is examined in Al-4.5%Cu alloys with/without titanium. As the titanium element segregated markedly. Ti-rich cored structure was formed. The structure did not vanish at the solutioninzation temperature and time of copper and magnesium elements. Therefore the results can be suggested that segregated titanium affects the following treatments such as aging.

관상동맥 스텐트 시술 후의 재협착에 관한 연구

김윤철,이정우,김보영,강정아,임대승,이민수,김정희,성보영,최성준,성인환,전은석 충남대학교 의과대학 지역사회의학연구소 2000 충남의대잡지 Vol.27 No.1

Coronary stent implacement is known as an effective treatment in the intimal dissection after percutaneous transluminal coronary angioplasty and the prevention of restenosis. However, In-stent restenosis still remains a major concern in clinical stenting. The stents were placed in 103 patients from July 1996 to March 1999 and performed follow-up coronary angiograms in 59(57.3%) patients. To identify the clinical, angiographic and procedurerelated variables 'which predict late restenosis within the stented artery, 59 patients(58.3±9.9, M:F= 41:18) were studied. The clinical characteristics of the patients were stable angina in 23(39.0%), unstable angina in 14(23.7%), acute myocardial infarction in 21(35.6%) and old myocardial infarction in 1(1.7%). Coronary stenting was performed in 1 patient(1.7%) for primary lesion, 50 patients(84.7%) for suboptimal results after PTCA, 6 patients(10.2%) for bail-out procedure, and 2 patients(3.4%) for restenotic lesions. All patients were treated with aspirin and ticlopidinc. The follow-up angiograms were obtained at 7±4 months. The overall in-stent restenosis rate was 27.1%. The coronary angiographic findings were 32 single vessel(54.2%), 19 two vessel(32.2%) and 8 three vessel disease(13.6%). The angiographic morphological characteristics were type A in 33(55.9%), type B in 14(23.7%), type C in 12(20. 3%) cases. Variables of 16 patients with restenosis were compared with those of 43 patients without restenosis. Previously known predictors for in-stent restenosis were multiple stenting, stenting for restenotic lesions, residual stenosis after stenting, stenting for total occlusion lesions, reference diameter, balloon to vessel ratio, acute gain and minimal luminal diameter after procedure, design and characteristics of stents, ostial lesion of aorta, high pressure method for stenting, lesion length, diabetes mellitus, size of artheroma, saphenous vein grafts, ulcerlating lesions and calcified lesions. In this study, Reference diameter before stenting(2.43±0.54mm vs. 2.88±0.65mm, p=0.016) and balloon-to-artery ratio(1.28±0.26 vs. 1.11±0.18, p=0.006) were predictors for in-stent restenosis. 1) The overall in-stent restenosis rate was 27.1%. 2) In the analysis of predictors for in-stent restenosis, there was no significant differences in clinical, angiographic factors between group with restenosis and without restenosis. But, Only reference diameter before stenting and balloon-toartery ratio were predictors of late in-stent restenosis. In conclusion, stenting is effective revascularisation method for selected patients with ischemic heart disease, and to minimize in-stent restenosis rate, stent implanting is achieved in a large vessel on the basis of an artery-to-stnet ration of 1:1, if possible.

난포기 및 황체기에 있어서 돼지 난관 협부 평활근의 neurotransmitter들의 수축효과에 대한 estradiol-17β및 progesterone의 영향

이민기,노규진,심철수,남윤정,김주현,최상용 慶尙大學校 1991 論文集 Vol.30 No.2

The effects of estradiol-17β or progesterone on the contractility of neurotransmitters on pig oviductal isthmic smooth muscle were investigated. The motility of the isolated smooth muscle was recorded by using physiological recording system. The results were summarized as follows : 1. The contractility induced by histamine or prostaglandin F2α was depressed by the pretreatment of estradiol-17β but was not by the preteatment of progesterone in follicular or luteal stage. 2. The contractility induced by acetylcholine was depressed un follicular stage but excited in luteal stage by the pretreatment of estradiol-17β or progesterone. 3. The contractility induced by norepinephrine was depressed by the pretreatment of progesterone in follicular stage but was excited by the pretreatment estradiol-17β in luteal stage.

자동 선구조 추출 알고리즘의 개발과 적용사례

최은영 ( Choe Eun Yeong ),최동석 ( Choe Dong Seog ),최현석 ( Choe Hyeon Seog ),임태근 ( Im Tae Geun ),정래철 ( Jeong Lae Cheol ),윤왕중 ( Yun Wang Jung ) 한국지구물리탐사학회 2003 지구물리와 물리탐사 Vol.6 No.1

Rheo-Compocasting 에 의한 SiCp / 6063 Al 합금의 복합조직

최정철 ( Jeong Cheol Choe ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.4

N/A Aluminum alloy matrix composites reinforced by SiC particles were prepared by rheocompocasting, a process which consists of the incoporation and distribution of reinforcement by stirring within a semi-solid alloy. When the volume fraction of SiCp and stirring speed were fixed, the dispersion of SiCp in Al-matrix alloy depended on stirring time and solid volume fraction in slurry. The results were as follows : 1) As a dispersed SiCp during stirring at 647℃ in 6063-Al alloy, SiC was better dispersed than that other temperature, where solid volume fraction was 43% in slurry. 2) When increased solid fraction in slurry, rate of dispersing SiC increased during stirring and porosities decreased in matrix alloy after casting. 3) Inspite of stirring with 800rpm, since solid particles of matrix alloy in slurry joined each other and occured joining growth, so that SiC was not dispersed into solid particle.

Melatonin이 Cisplatin에 의한 신장 독성에 미치는 영향

최혜정 ( Choe Hye Jeong ),신영호 ( Sin Yeong Ho ),문교철 ( Mun Gyo Cheol ),송대규 ( Song Dae Gyu ),김인철 ( Kim In Cheol ),서상혁 ( Seo Sang Hyeog ),곽춘식 ( Gwag Chun Sig ),장은주 ( Jang Eun Ju ),김현철 ( Kim Hyeon Cheol ) 대한신장학회 2004 Kidney Research and Clinical Practice Vol.23 No.2

목 적 : Cisplantin은 항암제로 널리 사용되나 활성산소를 생성하여 신장 기능 손상 등의 부작용이 있는 것으로 알려져 있긴 강력한 항산화제인 melatonin은 cisplatin에 의한 산장독성을 줄일 수 있을 것이다. Cisplatin에 의한 신장 독성에 대하여 melatonin의 방어 효과를 알아보고자 하였다. 방 법 : 실험군을 대조군인 제 1군, cisplatin 투여군인 제 2군 및 cisplatin과 melatonin을 투여한 제 3군으로 나눈 후 신장 조직의 형태학적 변화와 더불어 산화적 손상에 대한 연구를 수행하였으며 과산화수소, malondialdehyde 및 항산화효소의 활성도를 측정하였다. 결 과 : 혈청 BUN (p<0.001), creatinine 농도 (p<0.001) 및 신장의 과산화수소 생성량은 제 1군에 비해 제 2군에서 증가하였고, 제 2군에 비해 제 3군에서는 감소되었으며, 활성산으로 인한 손상 표지자인 malondialdehyde 농도도 같은 경향을 나타내었다. Creatinine 청소는 제 1군에 비해 제 2군에서 감소를 보였고, 제 2군에 비해 제 3군에서는 증가되었다. 신장의 superoxide dismutase 활성도는 제 1군에서 제 2군에 비해 감소하였고 catalase 활성도는 제 1군에 비해 제 2군에서 증가되었으며, 제 1군에 비해 제 3군에서는 더욱 증가되었다. Glutathione peroxidase는 통계학적으로 의미 있는 변화가 없었다. 또한 광학 현미경 소견을 보면 제 2군의 사구체에서는 특이한 변화가 없었으나, 근위 곱슬 세관은 심한 괴사를 나타내었고, 제 3군의 근위 곱슬 세관에서 중등도의 괴사를 나타내었으며 제 2군보다 경한 변화를 보였다. 결 론 : Cisplatin은 신장에서 superoxide dismutase 활성도 증가와 catalase의 활성도를 저하시켜 과산화수노의 생성을 유도하여 신장 손상을 유발하는 것으로 생각되며, melatonin은 superoxide dismutase 활성도 증가와 catalase 활성도 증가를 유도하여 cisplatin에 의해 유발된 신장 손상을 줄이는 것으로 생각된다. Background : Cisplatin (CP), an antitumor agent widely used in the treatment of cancers, has nephrotoxicity. This side effect is closely related to oxidative stress. In the present study, we attempted to reduce CP-induced nephrotoxicity in rats by administering melatonin, an antioxidant. Methods : Male Sprague-Dawley rats were divided into different groups and were treated as follows : ⑴ saline control; ⑵ CP (16 mg/kg, i.p.); ⑶ CP plus melatonin (10 mg/kg, i.p.). The rats were sacrificed at the 6th day after CP treatment. To evaluate renal damage, BUN, serum creatinine, creatinine clearance and microscopic examination were done. Hydrogen peroxide which is one of the oxygen free radicals, and malondialdehyde which is known as a marker of the oxygen free radical mediated injury, and the activities of the antioxidant enzymes such as superoxied dismutase, catalase, and glutathione peroxidase were also measured. Results : CP-treated rats showed the increase of BUN, serum creatinine, malondialdehyde, hydrogen peroxide and superoxide dismutase (SOD) in kidney. And CP-treated rats also showed the decrease of creatinine clearance and catalase levels. CP-treated rats showed severe tubular necrosis in proximal convoluted tubules under the light microscopic examination. The light microscopic finding and all of the parameters except SOD were restored in the rats injected with CP plus melatonin than those with CP alone. SOD level was higher in the rats injected with CP plus melatonin than that with CP alone. Conclusion : These results suggest that melatonin suppresses CP-induced nephrotoxicity by suppressing the production of reactive oxygen species via the activation of SOD and catalase. (Korean J Nephrol 2004;23(2):205-212)

배산 근린공원의 산림식생 구조와 정밀식생도 작성에 관한 연구

최정호 ( Choe Jeong Ho ),정진철 ( Jeong Jin Cheol ),전경수 ( Jeon Gyeong Su ) 원광대학교 생명자원과학연구소 2004 생명자원과학연구 Vol.26 No.-

건축 마감재 종류에 따른 역학변색센서의 접착 및 변형거동

최경철(Choe, Gyeong Cheol),김홍섭(Kim, Hong Seop),전준서(Jeon, Jun Seo),이문환(Lee, Mun Hwan),남정수(Nam, Jeong Soo),편수정(Pyeon, Su Jeong) 한국콘크리트학회 2022 한국콘크리트학회 학술대회 논문집 Vol.34 No.1

Rheo - compocasting 에 의한Al - Cu / Sic 복합재료의 조직

최정철 ( Jeong Cheol Choe ),윤여창 ( Yeo Chang Yoon ),천병선 ( Byung Sun Chun ) 대한금속재료학회 1992 92년 알루미늄의 신가공기술 Vol.- No.-