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BSCCO(2212) 벌크 초전도체의 주조조건 및 SrSO<sub>4</sub> 최적함량에 대한 연구
김규태,박의철,장석헌,임준형,주진호,김찬중,김혜림,현옥배,Kim Kyu-Tae,Park Eui-Cheol,Jang Seok-Hern,Lim Jun-Hyung,Joo Jin-Ho,Kim Chan-Joong,Kim Hye-Rim,Hyun Ok-Bae 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.6
We fabricated BSCCO-2212 (2212) rod by the melt casting process (MCP) and evaluated the effect of the melt flowing on the critical current ($I_c$) by using vertical and tilt casting. It was observed that the $2212-SrSO_4$ rod processed by the tilt casting method with homogeneous pre-heating temperature of the mold had a higher $I_c$ than that processed by the vertical casting method. We also evaluated the influence of the strontium sulfates ($SrSO_4$) addition on the texture, microstructure, critical current and temperature, and mechanical hardness of the $2212-SrSO_4$ rods. It was observed that the addition of $SrSO_4$ improved the critical current ($I_c$) and mechanical hardness of the 2212. The $I_c$ of the 2212 increased as the $SrSO_4$ content increased and reached a peak value (260 A at 77 K) at an $SrSO_4$ content of 6 wt.%. In addition, the addition of $SrSO_4$ had a beneficial effect on the mechanical hardness of the 2212. We studied the possible cause of the variation in the $I_c$ with the melt flowing and the $SrSO_4$ content based on the XRD, EPMA analysis and the microstructural observation.
선천성 기관 석회화와 조롱박 구멍 협착 (Nasal Pyriform Aperture Stenosis)에 의한 호흡 곤란증 1례
김규태,김영미,박수은,박재홍,노환중,김학진,Kim, Kyu Tae,Kim, Young Mi,Park, Su Eun,Park, Jae Hong,Noh, Hawn Jung,Kim, Hak Jin 대한소아청소년과학회 2002 Clinical and Experimental Pediatrics (CEP) Vol.45 No.5
저자들은 출생 후 수 시간 뒤에 발생한 호흡 곤란을 주소로 내원한 환아에서 우연히 발견된 기관의 석회화와 양측 조롱박 구멍 협착증을 진단하고 비강 내에 스텐트를 위치시키는 수술로서 호흡 곤란 등의 증상 호전된 환아를 보고하는 바이다. Nasal obstruction is a cause of respiratory distress in newborns. The congenital nasal airway obstructive abnormalities are classified into three forms according to the location: posterior choanal atresia, nasal cavity stenosis and congenital nasal pyriform aperture stenosis(CNPAS). CNPAS is located at the anterior part of the nasal fossa. CT is the study of choice to make the diagnosis of CNPAS and rule out other causes of nasal obstruction. Though conservative management of CNPAS is recommended, in cases of severe CNPAS surgical treatment should be considered. Calcification of cartilage in the larynx, trachea and bronchi is extremely rare in children. Such calcifications are generally discovered in young children with congenital stridor. The clinical course is favorable. No case with CNPAS and tracheal calcification is reported in newborn. We report a one-day-old girl with CNPAS and tracheal calcification who presented with respiratory difficulty immediately after birth.
BSCCO-2212/$SrSO_4$ 벌크 초전도체의 제작 및 특성평가
김규태,장석헌,박의철,황수민,주진호,홍계원,김찬중,김혜림,현옥배,Kim, Kyu-Tae,Jang, Seok-Hern,Park, Eui-Cheol,Hwang, Su-Min,Joo, Jin-Ho,Hong, Gye-Won,Kim, Chan-Joong,Kim, He-Lim,Hyun, Ok-Bae 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
We fabricated Bi-2212/$SrSO_4$ bulk superconductors by the casting process and evaluated the effects of the powder mixing method and annealing temperature on the texture, microstructure, and critical current. In the process, the Bi-2212 powders were mixed with $SrSO_4$ by hand-mixing(HM) and planetary ball milling(PBM) method and then the powder mixtures were melted at $1100^{\circ}C{\sim}1200^{\circ}C$, solidified, and annealed. We observed that the rod made by the PBM had a more homogeneous microstructure and smaller $SrSO_4$ and second phases than that of the rod made by the HM, resulting in increased $I_c$. The $I_c$ of the rod also depended on the annealing temperature and the highest $I_c$ was obtained to be 200 A when prepared by HM at $1200^{\circ}C$ and annealed at $810^{\circ}C$ which is probably due to the moderate density and 2212 texture and the smaller and less second phase compared to that at higher temperature. The possible causes of the variations of $I_c$ with the powder mixing method and annealing temperature were related to the microstructural evolution based on the SEM, EPMA, and DTA analyses.
양축 정렬된 Ni 기판의 특성에 미치는 W 첨가의 효과
김규태,임준형,김정호,장석헌,김호진,주진호,김찬중,송규정,신형섭,Kim Kyu Tae,Lim Jun Hyung,Kim Jung Ho,Jang Seok Hern,Kim Ho-Jin,Joo Jinho,Kim Chan-Joong,Song Kyu Jung,Shin Hyung Sub 한국초전도학회 2004 Progress in superconductivity Vol.6 No.1
We fabricated cube-textured Ni and Ni-W alloy substrates for coated conductors and characterized the effects of W addition on microstructure, mechanical strength, and magnetic properties of the substrate. Pure Ni and Ni-(2, 3, 5at.%)W alloys were prepared by plasma arc melting, heavily cold rolled and then annealed at various temperatures of $600-1300^{\circ}C$. The texture was evaluated by pole-figure and orientation distribution function (ODF) analysis. Mechanical properties were investigated by micro Vickers hardness and tension test. Ferromagnetism of the substrate was measured by physical property measurement system (PPMS). It was observed that Ni-W substrates had sharp cube texture, and the full-width at half-maximums (FWHMs) of in-plane texture was $^{\circ}$-5.57$4.42^{\circ}$, which is better than that of pure Ni substrate. In addition cube texture of Ni-W substrates was retained at higher temperature up to $1300^{\circ}C$. Microstructural observation showed that the Ni-W substrates had fine grain size and higher mechanical properties than the pure Ni substrate. These improvements are probably due to strengthening mechanisms such as solid solution hardening and/or grain size strengthening. PPMS analysis showed that addition of W effectively reduced saturation magnetization in applied magnetic field and Curie temperature.
열처리조건이 BSCCO-2212 벌크의 특성에 미치는 영향
김규태,김찬중,임준형,박의철,박진현,주진호,현옥배,김혜림,Kim, Kyu-Tae,Kim, Chan-Joong,Lim, Jun-Hyung,Park, Eui-Cheol,Park, Jin-Hyun,Joo, Jin-Ho,Hyun, Ok-Bae,Kim, Hye-Rim 한국초전도학회 2008 Progress in superconductivity Vol.9 No.2
We fabricated BSCCO-2212(2212) bulk superconductors by using a casting process and evaluated the superconducting properties. The effects of annealing conditions on microstructure and critical properties were studied. It was found that the homogeneous and uniform microstructure improved the critical properties and the microstructures of ingot and annealed rods were different with the size of 2212 rod and tube. The critical current($I_c$) of rods increased with increasing annealing time, probably due to increased grain size of 2212. Annealing time of the highest $I_c$ for the smaller rod(diameter of 10 mm) was shorter(150 hr) than that of the larger rod(diameter of 16 mm, 400 hr). This size effect seems to be related to different grain sizes of the intermediate phases such as 2201 and secondary phases in the ingot. In addition, we fabricated 2212 tubes from the rod by removing the center region which contained inhomogeneous microstructures. The $I_c$ of 2212 tube with the outer diameter of 16 mm and the thickness of 2 mm was measured to 844 A, which corresponds to the critical current density of $1017\;A/cm^2$ at 77 K.
10의 -10승 수준에서 조셉슨 전압표준기 불확도 평가
김규태,김문석,정연욱,김완섭,송운,Kim, K.T.,Kim, M.S.,Chong, Y.,Kim, W.S.,Song, W. The Korean Superconductivity Society 2007 Progress in superconductivity Vol.9 No.1
The most recent improvement in the 10 V array system was carried out with focusing on noise reduction. We have evaluated the uncertainty of the 10 V Josephson array system after the improvement. The uncertainty evaluation of 10 V standard included a comparison with a programmable Josephson array system at 1 V. Every contribution to the measurement uncertainty was evaluated in the level of $10^{-10}$. The estimated combined uncertainty was found to be approximately $10^{-9}$ at 10 V, which was limited only by the indirect verifying method. In the near future, a direct comparison with another 10 V Josephson voltage standard is expected to be carried out to provide more accurate uncertainty evaluation for the KRISS Josephson voltage standard.
용융주조법으로 제조한 BSCCO-2212 초전도체의 공정변수 연구
김규태,장석헌,임준형,주진호,김찬중,홍계원,김혜림,현옥배,Kim, Kyu-Tne,Jang, Seok-Hern,Lim, Jun-Hyung,Joo, Jinho,Kim, Chan-Joong,Bong, Gye-Won,Kim, Rye-Lim,Hyun, Ok-Bae 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.6
We fabricated BSCCO-2212 (2212) bulk superconductor by melt casting process, and evaluated the dependence of the critical properties on the temperature and cooling .ate of mold and the pouring methods of melt. It was observed that the critical current (Ic) of 2212 was significantly dependent on the pre-heating temperature of the mold. At the pre-heating temperature of $500^{\circ}C$ followed by air cooling condition, Ic of 48 A at 77 K was obtained which was higher than others processed at different temperatures. In addition, the Ic improved to 132 A when tilt casting method was applied. The improved Ic is probably due to the fact that the tilt casting reduced a turbulent flow of the melt during casting causing less porosity and more homogeneous microsructure. Critical temperature was measured to be 87-89 K after the first heat treatment and it improved to 90-91 K when subsequently heat treated at $650^{\circ}C$ in a nitrogen atmosphere. This improvement was considered to be due to an optimization of the oxygen content in the range of 8.16-8.2.
개심술후의 Ventilator Weaning 에 관한 임상적 고찰
김규태,한승세,이종태,Kim, Kyou-Tae,Han, Sung-Sae,Lee, Chong-Tae 대한흉부심장혈관외과학회 1981 Journal of Chest Surgery (J Chest Surg) Vol.14 No.3
Cardiac surgery is generally followed by a period of routine ventilator support. When the patient seems hemodynamically stable and relatively alert following surgery, respiratory adequacy is tested by the weaning trial. In this study, physiological and clinical prediction of postoperative respiratory adequacy, including values of pulmonary function tests, were examined in an attempt to identity those few variables which predicted the outcome of the ventilator weaning trial following surgery. Our series comprised 27 patients who underwent elective open intracardiac operations at the Department of Thoracic and Cardiovascular Surgery, School of Medicine, Kyungpook National University, from October 1979 to July, 1980. The pulmonary function tests performed on all patients included the following; forced vital capacity [FVC], forced expiratory volume [FEV1.0], forced expiratory flow [FEF 25--75~], residual volume [RV], and functional residual capacity [FRC], measured with a helium dilution technique. Of our 27 patients, 8 were successfully weaned within 20 hours of operation. All patients with cyanotic heart diseases or acquired heart diseases were unsuccessfully weaned. The bypass time in the successful weaning group was shorter in the mean value [82.8 minutes]than in the unsuccessful weaning group [120.5 minutes]. There was a relatively significant difference in the mean values for the two groups in arterial pressure, bleeding amounts and FiO2 among the postoperative monitoring variables, and in forced vital capacity [FVC]. The postoperative clinical assessments appeared vague but corresponded reasonably well to appraisal of success in weaning, especially in variables of cough and self-respiration efforts.
자카스펭귄에서 발생한 Aspergillus fumigatus 감염증
김규태,조성환,손화영,류시윤,Kim, Kyoo-Tae,Jo, Sung-Whan,Son, Hwa-Young,Ryu, Si-Yun 대한수의학회 2004 大韓獸醫學會誌 Vol.44 No.4
A three years old male Jackass penguin(Spheniscus demersus) showed anorexia, depression, respiratory problem for a few days, followed by clinical treatment for 20 days resulted in death. Grossly, multiple white nodules measuring 2~3 mm in diameter were observed in the surface of and inside lung, liver, kidney, thoracic wall. Microscopically, granuloma formations were observed in the lung and liver. The margin of granuloma surrounded by connective tissue barrier and infiltrated lymphocytes, and also observed giant cell near the granuloma. By Periodic acid Schiff reaction, hyphae were detected in granuloma of lung and liver. This case was a chronic and systemic aspergillosis caused by Aspergillus fumigatus infection in a Jackass penguin at a zoo.