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다양한 산소분압에서 소결한 NdBCO 초전도체의 열적 안정성
정준기,김원정,박성창,강성구,임영진,김철진,Chung, J.K.,Kim, W.J.,Park, S.C.,Kang, S.G.,Lim, Y.J.,Kim, C.J. 한국초전도학회 2009 Progress in superconductivity Vol.10 No.2
The $Nd_{1+x}Ba_{2-x}Cu_3O_{7-{\delta}}$(Nd123) superconductor exhibits high performance in high magnetic field and high temperature. We have studied phase stability for Nd123 under reduced oxygen partial pressure and various heat-treatment conditions. The main phase is Nd123 and some samples contain small amounts of Nd422 depending on the temperature and oxygen partial pressure. The decomposition temperature decreases with decreasing oxygen partial pressure from $1052^{\circ}C(P(O_2)$=150 Torr) to about $845^{\circ}C(P(O_2)$=0.1 Torr). The liquidus line was steeper temperature with decreasing oxygen partial pressure. In same condition of oxygen partial pressure, the region of stable Nd123 phase was formed at slightly higher temperature than the region of stable YBCO phase.
$YBa_2CU_3O_{7-\delta}$ coated Conductor 완충층으로의 응용을 위한 $SrTiO_3 $ 박막의 성장 조건
정준기,고락길,송규정,박찬,김철진,Chung, J.K.,Ko, R.K.,Song, K.J.,Park, C.,Kim, C.J. 한국결정학회 2003 韓國結晶學會誌 Vol.14 No.2
YBa₂CU₃O/sub 7-8/(YBCO) coated conductor의 완충층 구조를 개선하기 위하여 2축배향된 Ni-3 wt%W 합금 기판위에 단일 완충층으로 SrTiO₃(STO) 박막을 증착하였다. YBCO와 STO 박막은 펄스레이저 증착법으로 성장시켰다. STO 박막의 표면은 증착온도에 따라 다른 미세조직을 보여 주었고, XRD 분석에서는 STO와 YBCO 박막이 금속기판의 배향성을 가지면서 성장되었음을 알 수 있었다. 액체질소 온도에서 1.2 MA/㎠의 임계전류밀도와 86 K의 임계온도를 가지는 짧은 길이의 coated conductor를 STO 단일완충층을 이용하여 제조하였다. SrTiO₃ (STO) thin fims were deposited on the biaxially textured Ni-3 wt%W alloy substrates to be used as a single buffer layer for YBa₂CU₃O/sub 7-8/(YBCO) coated conductor. Thin films of YBCO and STO were deposited using pulsed laser. The deposition condition for epitaxial growth of STO on the textured metal was identified, and YBCO coated conductor with a single STO buffer layer with critical current density of 1.2 MA㎠ at 77 K under zero magnetic field and critical temperature of 86 K, was fabricated.
재활용 APT를 이용한 WO<sub>3</sub> 제조와 WC-Co 의 용사코팅
정준기,김성진,온진호,문흥수,피재환,하태권,박상엽,Chung, J. K.,Kim, S. J.,On, J. H.,Moon, H. S.,Pee, J. H.,Ha, T. K.,Park, S. Y. 한국소성가공학회 2015 소성가공 : 한국소성가공학회지 Vol.24 No.4
The possibility of chemical precipitation for recycled ammonium paratungstate (APT) was studied. WO<sub>3</sub> particles were synthesized by chemical precipitation method using a 1:2 weight ratio of APT:DI-water. At the 500℃ sintering temperature, the X-ray diffraction results showed that APT completely decomposed to WO<sub>3</sub>. For the granulated powder WC-Co, vacuum heat treatment at proper temperatures increases tap density and flow-ability. Hardness of the WC-Co thermal spray coating layer was measured in the range HV 831~1266. Spray conditions for the best characteristic values were an oxygen flow rate=1500 scfh, a fuel flow rate = 5.25gph and a gun distance = 320mm.
박성창,임영진,강성구,정준기,김찬중,김철진,Park, S.C.,Lim, Y.J.,Kang, S.G.,Chung, J.K.,Kim, C.J.,Kim, C.J. 한국초전도저온학회 2008 한국초전도저온공학회논문지 Vol.10 No.1
Spherical $MgB_2$ powders was synthesized with the ultrasonic spray pyrolysis(USP) process using aqueous solutions of boron and magnesium ion. The properties of synthesized $MgB_2$ powder were characterized by XRD, SEM and EDS. A small amount of MgO was detected as the secondary phase out of the synthesized powder and the ratios of $MgB_2$ to MgO increased with increasing furnace temperature. The particle size and morphology of $MgB_2$ powder were investigated with varying molar concentration of the boron and magnesium solution and furnace temperature between $600^{\circ}C$ and $1000^{\circ}C$ in $Ar/H_2$. The average particle size of $MgB_2$ showed narrow distribution ranging from 300nm to 400nm. The morphology of particles exhibited mostly spherical shapes and uniform distribution.
신동맥분지협착에 의한 신혈관성고혈압 예에서 캅토프릴투여후 99mTc - DMSA 신 스캔
양원석(W . S . Yang),김연수(Y . S . Kim),엄재호(J . H . Earm),김상은(S . E . Kim),이동수(D . S . Lee),한진석(J . S . Han),정준기(J . K . Chung),김성권(S . K . Kim),이명철(M . C . Lee),이정상(J . S . Lee),고창순(C . S . Koh) 대한핵의학회 1990 핵의학 분자영상 Vol.24 No.2
N/A Radionuclide renal scintigraphies were performed in a 24-year-old man with right renal artery branch stenosis. Captopril enhanced Tc-99m-DTPA renal scintigraphy revealed no abnormal finding in the right kidney But, Tc-99m-DMSA renal scintigraphy showed regional cortical photon deficient area corresponding to the area supplied by the stenotic branch artery. The defect size increased in captopril enhanced Tc-99m-DMSA renal scintigrphy and nearly disappeared after successful transluminal renal angioplasty. This case suggests that the captopril enhanced Tc-99m- DMSA renal scintigraphy may be a useful method in the evaluation of renovascular hypertension, especially due to branch renal srtery stenosis.
어린이 모야모야병에서 휴식 / 아세타졸아미드 Tc-99m-HMPAO SPECT 를 이용한 수술결과 평가
이동수,현인영,왕규창,조병규,정준기,이명철 ( D. S. Lee,I. Y. Hyun,K. C. Wang,B. K. Cho,J. K. Chung,M. C. Lee ) 대한핵의학회 1998 핵의학 분자영상 Vol.32 No.4
Purpose: This study was performed to evaluate the outcome of encephalo-duro-arterio- synangiosis (EDAS) surgery with rest/acetazolamide Tc-99m HMPAO SPECT in moyamoya disease. Materials and Methods: Rest/acetazolamide subtraction SPECT with consecutive acquisition were done before and 2 months after 21 EDAS surgeries in 18 patients. Perfusion decrease was graded visually for 14 areas of each hemisphere as 0 (normal) to 3 (defectj using 4 point scoring system. Postoperative rest perfusion or perfusion reserve was compared with preoperative ones. Results: Among 294 areas of 21 hemispheres, rest perfusion abnormality was found in 97 areas of 15 hemispheres. Decrease of perfusion reserve was found in 146 areas of 18 hemispheres. Six hemispheres having normal rest perfusion and 12 of 15 hemispheres having rest perfusion abnormality showed reserve decrease. Three having rest perfusion defect did not change after acetazolamide in preoperative SPECT. After operation, 16 patients (89%) demonstrated clinical improvement. Fifteen among 18 hemispheres (83%) with decreased reserve improved. Rest perfusion abnormality improved in 6 among the 1.' hemispheres (40%). The areas having rest perfusion and/or reserve decrease improved in 8 : among 146 areas (60%). Decrease of reserve improved in 85% (68/80). However, areas without reserve decrease also improved in 29%(19/#66). The better was peoperative resi perfusion in involved areas or the more decreased vascular reserve, the rnore improved perfusion and reserve after operation. Conclusion: We conclude that assessment of perfusion and perfusion reserve using rest/acetazolamide brain perfusion SPECT predict the surgical outcome in patients with moyamoya disease. (Korean J Nucl Med 1998;32:314-24)