• Progress in Superconductivity and Cryogenics
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• v.10 no.3
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• pp.23-26
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• 2008

Constructions of coated conductor which is differently from Bi-2223 is comprised multiple coatings on a base material or substrate and designed to achieve the highest degree of alignment possibility of the atoms in the superconductor material. In this study, we are measured and analyzed degradations of critical current according to diameter. In addition to study the effects of bending strain, we observed the AC loss of coated conductor and carried out analytical study for relation between Ic degradation and AC loss as well. The measurement of AC loss and numerical calculation was carried out based on Norris theory to compare with experimental results. The relationship between critical current and AC loss of HTS tapes with partial deformation by mechanical stress was studied. These results will amount the most important basis data in the of HTS cable, magnet, etc that winding work is required.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.438-441
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• 2021

The electrical characteristics of single-crystal composite superconductors produced by a melting process were studied by neutron irradiation. In order to improve the current characteristics of the YBa₂Cu₃O_7-y superconductor, it is necessary to form an effective flux pinning center inside the superconductor. In this study, an increase in flux pinning was attempted through neutron irradiation onto YBa₂Cu₃O_7-y superconductors. The neutron irradiation was performed at 30 MeV for 500 sec, The electrical properties of the superconductors were measured in a magnetic field of 5 Tesla at 50 K using a magnetic properties measurement system (MPMS). After neutron irradiation, the critical current density of the YBa₂Cu₃O_7-y superconductor in a 1 Tesla magnetic field was 1×10⁵ A/cm². Once neutrons were irradiated at 30 MeV and 10 μA for 500 sec, the critical current density was observed to increase significantly. When neutrons are irradiated to a superconductor, micro-defects are created in the superconductor, and they act as flux pinning centers that hold the magnetic field generated when an electric current flows.

• Progress in Superconductivity and Cryogenics
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• v.16 no.2
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• pp.29-32
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• 2014

The critical current, $I_c$ of HTS superconducting tapes can be measured by transport or contactless method. Practically, the transport method using the four-probe method is the most common. In this study, a simple test procedure by clipping the voltage lead taps have been introduced instead of soldering which reduces time and effort and thereby achieving a much faster measurement of $I_c$. When using a pair of iron clips, $I_c$ value decreased as compared with the measured one by standard method using soldered voltage taps and varies with the width of the clipped specimen part. However, when using a pure Cu clip, both by clipping and by soldering voltage taps give a comparable result and $I_c$ measured are equal and close to the samples specification. As a result, material to be used as voltage clip should be considered and should not influence the potential voltage between the leads during $I_c$ measurement. Furthermore, the simulation result of magnetic flux during $I_c$ measurement test showed that the decrease of $I_c$ observed in the experiment is due to the magnetic flux density, $B_y$ produced at the clipped part of the sample by the operating current with iron clips attached to the sample.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.761-768
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• 2000

In order to investigate how the fatigue damage effects on the critical properties of superconductor, a fatigue test at room temperature and an Ic measurement test at 4.2K were carried out in this study, respectively, using a 9 strand Cu-Ni/NbTi/Cu composite cable. Through the fatigue test of a 9 strand Cu-NUNbTi/Cu composite cable, a conventional S-N curve was plotted even though there was a possibility of fretting among strands. It was found that the maximum stress corresponding to the inflection point on the S-N curve obtained was nearly the same value as the yielding strength of cable obtained from the static tensile test. However, the effect of cabling in multi-strands superconducting cable on the fatigue strength was not noticeable. The critical current(Ic) measurement was carried out at 4.2K in a NbTi strand out of the fatigued cable. It showed a degradation of lc at high stress amplitude regions over 380NTa, and the degradation became significant as the applied stress amplitude increased.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.8
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• pp.1216-1220
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• 2012

The current collection between pantograph and contact wire is a more critical component for need to train speed up in electric railway. The basic purpose of this paper is to establish a measure of determining arc by developing an arc detector assessment system. The system was designed under conditions of EN 50317 and simulations were conducted using the developed device. According to the results, it was possible to conduct certification tests following regulations of international standards. To check the validity of our approach for the intended application, we analysis contact loss of catenary system using developed arcing measurement system in Korea. The proposed arcing measurement system is expected to enhance precision of current collection quality performance assessment methods at high-speed lines and conventional lines.

• Journal of the Korean Society of Systems Engineering
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• v.14 no.2
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• pp.49-57
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• 2018

The main objective of this paper is come up with methodology approach for FPGA-based system in verification and validation lifecycle regarding software reliability using system engineering approach. The steps of both reverse engineering and re-engineering are carried out to implement an FPGA-based of safety critical system in Nuclear Power Plant. The reverse engineering methodology is applied to elicit the requirements of the system as well as gain understanding of the current life cycle and V&V activities of FPGA based-system. The re-engineering method is carried out to get a new methodology approach of software reliability, particularly Software Reliability Growth Model. For measure the software reliability of a given FPGA-based system, the following steps are executed as; requirements definition and measurement, evaluation of candidate reliability model, and the validation of the selected system. As conclusion, a new methodology approach for software reliability measurement using software reliability growth model is developed.

• Transactions of Materials Processing
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• v.24 no.1
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• pp.28-36
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• 2015

After a short review of the iterative optimal blank method, a new method of measuring the shape error for stamped parts with 3D contour lines, which is an essential component of the optimal blank design, is proposed. When the contour line of the target shape does not exist in a plane, but exists in 3D space, especially when the shape of the target contour line is very complicated as in the real automotive parts, then the measurement of the shape error is critical. In the current study, a method of shape error measurement based on the minimum distance is suggested as an evolution of the radius vector method. With the proposed method, the optimal blank shapes of real automotive parts were found and compared to the results of the radius vector method. From the current investigation the new method is found to resolve the issues with the radius vector method.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.227-230
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• 2006

The method of mass flow rate measurement using a critical nozzle is well established in the flow satisfying ideal gas law. However, in the case of measuring high-pressure gas flow, the current method shows invalid discharge coefficient because the flow does not follow ideal gas law. Therefore an appropriate equation of state considering real gas effects should be applied into the method. The present computational study has been performed to give an understanding of the physics of a critical nozzle flow for high-pressure hydrogen gas and find a way for the exact mass flow prediction. The two-dimensional, axisymmetric, compressible Navier-Stokes equations are computed using a fully implicit finite volume method. The real gas effects are considered in the calculation of discharge coefficient as well as in the computation. The computational results are compared with the previous experimental data and predict well the measured mass flow rates. It has been found that the discharge coefficient for high-pressure hydrogen gas can be corrected properly adopting the real gas effects.

• Transactions on Electrical and Electronic Materials
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• v.9 no.6
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• pp.265-272
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• 2008

In this paper, AC losses of long wire Bi-2223 tapes with different twist pitch of superconducting core were fabricated, measured and analyzed. These samples produced by a powder-in-tube method are multi-filamentary tape with Ag matrix. Also, it's produced by non-twist. The critical current measurement was carried out under the environment in Liquid nitrogen and in zero field by 4-prob method. And the Magnetic measurement was carried out under the environment of applied time-varying transport current by transport method. From experiment, the susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation. Neutron-diffraction measurements have been carried out investigate the crystal structure, magnetic structures, and magnetic phase transitions in Bi-2223([Bi, Pb]:Sr:Ca:Cu:O).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.7
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• pp.47-56
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• 2010

Faults due to salt damage prevent the provision of stable power supply because they affect large areas and require much time and man power for recovery. Korea, three sides of which are surrounded by sea, is especially exposed to the impact of sea winds and typhoons. Therefore, salt damage to power facilities is one of the greatest problems of Korea's power system. To prevent salt damage pollution of insulators, the salt damage deposit on the insulators is regularly measured, and the insulators are washed when their salt damage deposits are expected to reach a critical level. When salt is detected on the insulators, however, errors are likely to occur according to different workers and environments. Therefore, a leakage current measurement method was proposed in this study to check the salt damage pollution level and reduce these errors.