• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1270-1273
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• 2004

The combination of methane-chemical activation and Self-propagating High-temperature synthesis (SHS) has widened the possibilities for both methods. For YBCO systems the investigation showed that a short-term mechano-chemical activation of initial powders before SHS leads to single-phase and ultra-fine products. A new technique for preparation ultra-fine high-temperature superconductors of YBCO composition with a grain size d < $1{\mu}m$ is developed. The specific feature of the technique is formation of the $YBa_2Cu_3O_{7-x}$ crystalline lattice directly from an X-ray amorphous state arising as a result of mechanical activation of the original oxide mixture. The technique allows the stage of formation of any intermediate reaction products to be ruled out. X-ray and magnetic studies of ultra-fine high temperature superconductors (HTS) are carried out. Dimension effects associated with the microstructure peculiarities are revealed. A considerable enhancement of inter-grain critical currents is found to take place in the ultra-fine samples investigated.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.280-284
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• 2000

The prototype high-T$_c$ superconducting (HTS) power transmission cables have been designed and fabricated multi layers of spirally wound HTS tapes. The cables were made Bi-2223 based Ag-sheathed HTS tapes, and tested in LN$_2$. Critical currents of 700A dc and better were achieved. The magnetic flux density and field direction were analyzed in the cable configuration. In this paper the results of analysis and tests of HTS power transmission cables were described.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.633-634
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• 2008

본 논문에서는 안정화 층이 없는 YBCO CC(Coated Conductor)의 YBCO층을 임의의 수로 분할한 경우에 대하여 전기적인 특성을 알아보기 위해 각 소선의 임계전류 값을 측정하는 방법을 제안하였다. 안정화 층이 없음으로 통전 중 주울 열에 의한 선재의 소손을 막기 위해 전류를 펄스파 형태로 인가하여 측정하였으며, 선형적으로 전류를 인가하는 측정 방법에 의한 결과와 비교하였다. 결과적으로 안정화층이 없는 경우의 전기적 특성 측정을 위해서는 본 논문에서 제안한 방법이 우수함을 보였다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2000.11a
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• pp.155-159
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• 2000

This paper describes the self healing characteristics of metalized polypropylene film(MPPF) under ac condition. PDs were generally observed at relatively low voltage, and the PDIVs were differently varied depending on the number of pre-self healing due to void defects. Several pre-self healing events took place at lower voltage than the critical breakdown voltage of PPF. Self healing mainly occurred at pin tips, wrinkle sides, and cross points of wrinkles. The applied voltage at self healing was increased with PPF thickness. The burn out area at self healing was also increased with the applied voltage and PPF thickness. The peak currents in a grounding conductor at self healing was also increased with the applied voltage.

• 한국초전도학회:학술대회논문집
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• v.12
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• pp.69-69
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• 2002

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.213-215
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• 2003

This paper deals with the characteristics of a prototype solenoid for basic design of DC reactor type superconducting fault current limiter (SFCL). The prototype high-Tc Super-conducting (HTS) solenoid was manufactured with 4 stacked Bi-2223 tape. The critical currents were measured with respect to the number of stacks. In order to test the safety of HTS solenoid in quenched state, the transport tests of AC over-current were performed. These experimental results could be applied to the basic design of HTS DC reactor for SFCL effectively.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.3-6
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• 2003

We have developed a small-sized superconducting magnetic energy storage (SMES) device, which provides electric power with high quality to sensitive electric loads. In large magnets such as the SMES magnets the stability, which is determined by several factors, e.g. conductors cooling condition and operating current, magnets winding structure, is a crucial problem. The effect of the cooling condition, the copper ratio, and the conductor's size upon the recovery currents was investigated experimentally. The results indicate that the recovery current characteristics of the strands vary considerably according to their insulation method. In the fully insulated strands with a low copper ratio, the recovery current densities range from 10 to 20 % of their engineering critical current densities. The recovery current density of the 30-conductor with a cooling channel is about a factor of 1.8 higher than that without a cooling channel.

• ETRI Journal
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• v.37 no.3
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• pp.637-645
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• 2015

Common-mode noise (CMN) is an unresolved problem in wireless capsule endoscopy (WCE) systems. In a WCE system, CMN originates from various electric currents found within the human body or external interference sources and causes critical demodulation performance degradation. The differential operation, a typical method for the removal of CMN rejection, can remove CMN by subtracting two signals simultaneously received by two reception sensors attached to a human body. However, when there is impedance mismatching between the two reception sensors, the differential operation method cannot completely remove CMN. Therefore, to overcome this problem, we propose an enhanced CMN rejection method. The proposed method performs not only subtraction but also addition between two received signals. Then a CMN ratio can be estimated by sufficient accumulation of division operation outcomes between the subtraction and addition outputs during the guard period. Finally, we can reject the residual CMN by combining the subtraction and addition outputs.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.115-122
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• 2012

The purpose of this study is to optimize the design of the jack-up platform for 5MW offshore wind turbine system. Considering all the environmental loads such as currents, waves, winds and so on, the members of structures have been designed and optimized based on the AISC and API-RP-2A to be within the allowable stress even in the most critical and severe condition. In addition to the above strength check of structural members, the joint punching shear check and the hydrostatic collapse check are also performed where they are required for the design. The design life of the jack-up platform is 50 years for the static strength check and the fatigue design life is 100 years including to the DFF(Design Fatigue Factor) of 2.0 to have enough stability and workability for the design optimization.

• Journal of the Speleological Society of Korea
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• no.78
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• pp.1-8
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• 2007

The combination of mechano-chemical activation (MCA)and Self-propagating High-temperature Synthesis (SHS) has widened the technical possibilities for both methods. For YBCO systems the investigation showed that a short-term MCA of initial powders before SHS leads to single-phase and ultra-fine products. A new technique for preparation ultra-fine high-temperature superconductors (HTS) of YBCO composition with a grain size d <1m is developed using combination of MCA and SHS. The specific feature of the technique is formation of the $YBa_2Cu_3O_7-$ crystalline lattice directly from an X-ray amorphous state arising as a result of mechanical activation of the original oxide mixture. The technique allows the stage of formation of any intermediate reaction products to be ruled out. X-ray and magnetic studies of ultra-fine high temperature superconductors are carried out. Dimension effects associated with the microstructure peculiarities are revealed. A considerable enhancement of inter-grain critical currents is found to take place in the ultra-fine samples.