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전열처리 조건에 따른 Bi-2223 초전도 선재에서의 특성 변화
하동우,하홍수,오상수,이동훈,윤진국,양주생,최정규,권영길 한국초전도학회 2003 Progress in superconductivity Vol.4 No.2
A lot of efforts have been focused on the optimization of PIT parameters for Bi-2223/Ag wire. Bi-2223 superconducting wires with 55 filaments were fabricated by stacking, drawing process. Before rolling process, round wires were pre -annealed at 760 - 820 $^{\circ}C$ and low oxygen partial pressure. We confirmed that pre-annealing step was to transform Bi-2212 orthorhombic structure from Bi-2212 tetragonal structure and to reduce the formation of second phases. However Bi-2223 phases also were formed at higher than 76$0^{\circ}C$ of pre-annealing temperature. The engineering critical current densities (Je) of Bi-22231Ag tapes were sintered at low oxygen partial pressure were higher than t hat of the wires sintered at air. We could achieve 6500 A/${cm}^2$ of Je for the tape that was initially kept at slightly higher temperature than that of normal heat treatment.
Present and Future Developments of Ports in Asia and the Pacific
하동우 한국항만경제학회 2002 韓國港灣經濟學會誌 Vol.18 No.2
The continuing pace of technological change and the trend toward larger and faster ships is evident as shipping lines compete in seeking economies of scale in the global market and ports become increasingly reliant on sophisticated equipment. Across the Asia and Pacific region some of the worlds most modern container ships are calling at an extensive network of mainline and feeder ports. This paper shows that during the period from 1999 to 2011, Asian container trade is expected to continue to increase more rapidly than the world average, i.e., 7.2 per cent per annum compared with the world average of 6.3 per cent. It is forecast that the total volumes of international containers handled at the ports in Asia and the Pacific will increase at an average growth rate of 7.2 per cent per annum. In order to handle the anticipated port container traffic in 2011, new container berths are required in nearly every country in the Asia and the Pacific region. This will entail very significant capital investment requirements. If countries in the UNESCAP region are to position their ports to meet the challenges of the next decade, there is an urgent need to implement more robust strategies to address important issues including prioritisation of port development projects, promotion of private sector participation in ports, emphasis on productivity and preparation for intermodal integration and logistics growth.
내부 확산법에 의한 Nb$_3Sn$ 초전도 선재에서 부분 가열이 초전도 특성에 미치는 영향
하동우,오상수,하홍수,이남진,권영길,류강식,Ha, Dong-Woo,Oh, Sang-Soo,Ha, Hong-Soo,Lee, Nam-Jin,Kwon, Young-Kil,Ryu, Kang-Sik 한국초전도저온공학회 2000 한국초전도저온공학회논문지 Vol.2 No.2
There is the possibility that internal tin processed Nb$_3Sn$ wires are locally heated during the drawing process and the jacketing process. It is important to know the variations in J$_c$ of internal tin processed Nb$_3Sn$ wires caused by local heating. Internal tin processed Nb$_3Sn$ rods were cold worked to 2.28 mm, using the appropriate reduction ratio, and then cut into several pieces. At this stage, wires were locally 50 mm heat zone heated up to 360$^{\circ}C$. The locally heated Nb$_3Sn$ wires were drawn to a final diameter size of 0.81 mm. Others were cold worked successively to 0.81 mm and locally heated with the same conditions. 2 types of locally heat treated wires were wound on Ti-6Al-4V barrels and heat treated for the Nb$_3Sn$ reaction. Local heating of internal tin processed Nb$_3Sn$ wires after the J$_c$ of these wires. However, local heating at an intermediate stage of the drawing process caused a decrease in J$_c$. When the local heating temperatures were higher than melting point of Sn, non-Cu J$_c$'s decreased significantly. A Sn-Cu alloyed boundary appeared after local heating over the melting point of Sn, and caused work hardening and a decrease in the workability.