• 한국전기전자재료학회논문지
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• 제34권6호
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• pp.461-465
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• 2021

A diffusion heat treatment process for YBa₂Cu₃O_7-y bulk superconductor in a Gd₂O₃ powder was attempted. As a result of measuring the critical temperature of the superconducting bulk, there was no change in the superconducting transition temperature as the Gd particles diffused into the YBa₂Cu₃O_7-y lattice, resulting in dense microstructure. As a result of measuring the critical current, the critical current density (J_c) of the superconducting bulk having treated by the Gd thermal diffusion treatment at 0 T increased to 3×10⁴ A/cm² at 0 T, which was higher than that of the superconducting bulk without thermal diffusion treatment. The surface magnetic force of the superconducting bulk with Gd thermal diffusion treatment was observed at the center of the superconducting bulk with the maximum trapped magnetic force (Hmax) of 1.51 kG. This result means that the Gd thermal diffusion treatment contributes to improving the critical current density Jc of YBa₂Cu₃O_7-y, and it is believed that Gd particles migrating into the superconducting bulk through thermal diffusion either fill the surface pores of YBa₂Cu₃O_7-y superconductors or act as a flux pinning center.

• Journal of Magnetics
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• 제5권2호
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• pp.44-49
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• 2000

Computer simulation of sensing current effects on the magnetic and magnetoresistance properties of a crossed spin-valve head is carried out. The spin-valve head has the following layer structure: Ta (8.0 nm)/NiMn (25 nm)/NiFe (2.5 nm)/Cu (3.0 nm)/NiFe (5.5 nm)/Ta (3.0 nm), and it is 1500 nm long and 600 nm wide. Even with a high pinning field of 300 Oe and a high hard-biased field of 50 Oe, the ideal crossed spin-valve structure, which is essential to the symmetry of the output signal and hence high density recording, is not realized mainly due to large interlayer magnetostatic interactions. This problem is solved by applying a suitable magnitude of sensing currents along the length direction generating magnetic fields in the width direction. The ideal spin-valve head is expected to show good symmetry of the output signal. This has not been shown explicitly in the present simulation, however, The reason for this is possibly related to the simple assumption used in this calculation that each magnetic layer consists of a single domain.

• 한국주조공학회지
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• 제29권5호
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• pp.213-219
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• 2009

Optimum conditions for production of semi-solid Al-Zn-Mg alloy billets was carried out by the Taguchi design method. And, Al-Zn-Mg alloy billets contained Sc (free, 0.1 and 0.3 mass %) were fabricated at optimum conditions. Evolution of microstructure in semi-solid state was investigated through various liquid fractions, holding times and holding temperatures. The Al-Zn-Mg alloy billets reheated at $615^{\circ}C$ during 30min are grain growth and it was fractured due to increasing liquid fraction before quenching. And, during reheating up to $600^{\circ}C$, grain growth of Al-Zn-Mg alloy billets contained Sc (0.1 and 0.3 mass %) was not occurred in comparison with those of Al-Zn-Mg alloy without Sc. It was thought that $Al_3Sc$ phases have a pinning effect in grain boundary and Sc content of 0.1 mass% is able to inhibit grain growth effectively through reheating process.

• Composites Research
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• 제34권5호
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• pp.317-322
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• 2021

적층 복합재의 특성상 두께 방향 물성이 취약하여 비틀림, 저속충격, 피로 하중 등 복합 하중을 받게 되면 재료 내부의 미세크랙 진전을 통해 층간분리 현상이 발생하게 된다. 이를 방지하고자 Z-pinning, Stitching 등 다양한 3차원 보강 공법과 구조물의 미세균열을 실시간으로 검출하는 구조 건전성 감시 기법이 꾸준히 연구되고 있다. 본 논문에서는 I-fiber 스티칭 공법으로 보강된 Single-lap joint를 Co-curing 방법으로 제작하였으며, 제작된 시편의 강도 및 파손신호 검출 특성을 평가하였다. 균열과 파손신호 검출을 위하여 전기저항법과 AE법을 사용하였으며, 신호분석을 위한 전용회로를 제작하여 인장시험 중의 파손신호를 분석하였다. 실험결과, I-fiber 스티칭으로 보강된 Single-lap joint 시편은 보강이 없는 Co-cured single-lap joint 시편에 비해 강도가 약 44.6% 향상되었다. 또한, I-fiber로 보강된 Single-lap joint 시편은 강도 향상과 더불어 전기저항법과 AE법에 의한 파손 검출이 모두 가능하므로 파손 모니터링에도 효과적인 구조임을 확인하였다.

• Archives of Plastic Surgery
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• 제45권4호
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• pp.351-356
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• 2018

Background Mallet fracture can easily occur during sports activities or in daily life; however, the principles and methods of treatment for such fractures remain debated. Among the surgical treatments, various methods of closed reduction have been proposed. We treated patients with the extension block method (EBM) and the direct pinning method (DPM), and then compared the results. We assessed differences in range of motion and measurements of finger movement after surgery. Methods A total of 41 patients who underwent surgery from August 2013 to September 2015 were evaluated retrospectively. Among them, 21 patients were treated with the EBM and 20 patients were treated with the DPM. We then compared extensor lag, range of motion, and outcomes according to Crawford's criteria between before surgery and at 6 to 8 months postoperatively. Results The postoperative extensor lag improvement was $4.28^{\circ}$ and $10.73^{\circ}$, and the postoperative arc of motion was $55.76^{\circ}$ and $61.17^{\circ}$ in the EBM and DPM groups, respectively. The Crawford assessment showed no statistically significant difference between the groups, although the score in the DPM group was higher than that in the EBM group (3.5 vs. 3.1). Conclusions As closed reduction methods for the treatment of mallet fracture, both the EBM and DPM showed good results. However, the DPM proved to be superior to the EBM in that it produced greater improvements in extensor lag and range of motion.

• Progress in Superconductivity
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• 제10권1호
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• pp.12-16
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• 2008

In this work, nano size $BaCeO_3$, which is a possible flux pinning medium of melt processed $YBa_{2}Cu_{3}O_x$ superconductor, was synthesized by the conventional solid state reaction method using powders. $BaCeO_3$ and $CeO_2$ were mixed thoroughly using a ball milling for 24 hours and calcined at $1200^{\circ}C$ for 5 hours for the formation $BaCeO_3$ powder. The obtained $BaCeO_3$ powder was attrition milled at various milling times of 60 min, 120 min and 240 min. The $BaCeO_3$ powders of various milling times were mixed with $YBa_{2}Cu_{3}O_x$ powder. Seed melt processed $YBa_{2}Cu_{3}O_x$-$BaCeO_3$ (15wt.%) superconductors were prepared and the superconducting properties were investigated. It was found that $T_c$ of $Y_{1.5}Ba_{2}Cu_{3}O_x$ samples was not significantly affected by $BaCeO_3$ addition, but $J_c$ of samples was increased by $BaCeO_3$ addition. The $J_c$ improvement by fine $BaCeO_3$ powder (120 min attrition-milled) was effective at low magnetic fields less than 2 T.

• 한국임상수의학회지
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• 제36권1호
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• pp.82-84
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• 2019

A common kestrel (Falco tinnunculus) was presented with inability to stand and fly at Chungnam Wild Animal Rescue Center. The kestrel showed non-weight bearing ambulation on both legs and crepitation with no external wound. Radiographs revealed a fracture on mid-diaphysis of right tibiotarsus and a distal end fracture of left femur. Intramedullary pinning was chosen for reduction of both fractures. The right tibiotarsal fracture was corrected first, and left femur was repaired 5 days later. The kestrel was managed with a specially designed sling to prevent further iatrogenic damage for 2 weeks. Three weeks after the surgery, the kestrel was able to stand and found to perch in 4 weeks. On 5 weeks, The kestrel could fly free at outdoor aviary and was released through rehabilitation for 3 months finally.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권9호
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• pp.442-445
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• 2006

In order to realize the commercial application of HTSC materials, it is necessary to develop the fabrication process of high Tc oxide superconductor materials with desired shape and for practical application and high critical current density as well as good mechanical strength which can withstand high lorenz force generated at high magnetic field. Much studies have been concentrated to develop the fabrication technique for high critical current density but still there are a lot of gap which should be overcome for large scale application of HTSC materials at liquid nitrogen temperature. Recently some new fabrication techniques have been developed for YBaCuO bulk superconductor with high mechanical strength and critical current density. In this project, the establishment of fabrication condition and additive effects of second elements were examined so as to improve the related properties to the practical use of YBaCuO superconductor, and we reported the production of the YBaCuO high Tc superconductor by the pyrolysis method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1407-1409
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• 2002

BiPbSrCaCuO계 초전도 소결체에 산화은을 첨가하여 자기 부양 효과를 나타나는 시료의 제작 조건을 조사하였다. 2%의 산화은이 첨가된 시편에서 자기 부양 효과가 가장 효과적으로 관측되었다. toroidal자석에서 관측되는 자기 부양 효과는 자석의 중심부분에서만 발생하며, 자석의 ring부분에서는 관측되지 않았다. 이 결과는 본 연구의 자기 부양 효과의 발생에는 자석의 형상 및 자속의 분포 형태와 밀접한 관련성이 있음을 의미한다. 자기 부양 효과에 관한 측정 결과로부터 자속 밀도가 극소가 되는 장소에 초전도체가 놓이게 되면 초전도체는 반자성효과로 인하여 초전도체의 상하로부터 작용하는 자기력을 받게 된다. 또한 산화은을 첨가하지 않은 BiPbSrCaCuO계 초전도체와 2%의 산화은이 첨가된 시편의 자기부양 효과를 조사한 결과 pinning center의 역할이 중요함을 알 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.63-66
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• 1996

The method for calculation of $Y_2$BaCuO$_{5}$ contents was set up. It was estimated that the optimum value of 211 contents in the textured YBCO superconductor as flux pinning center was about 20wt.%. Ag contents have no influence on the critical temperature, but have large influence on the critical current density of the textured YBCO. When Ag contents over 15wt.%, which was the solubility of condensed YBCO, the critical current densities tend to a stable value.e.