• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.200-203
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• 2005

Most of electrical fires are caused by short circuits, overheating of wires, deterioration and incomplete connection of wiring devices. The last two cases are predictable before the occurrence of fire because of its slow progress. In this paper, we have simulated the discharge signals caused by the deterioration and incomplete connection of wiring devices using an aged concent to provide information on the characteristics of discharge signals. From the experimental data, we could characterize the frequency spectrums of the discharge signals depending on the cases. The higher frequency components of the signal are attenuated by the capacitance and inductance of power lines as the measuring point is getting away from the discharges. Main frequency components of the discharge signal are existent at 600 kHz - 1.5 MHz in incomplete connections and at 210 kHz - 8 Mhz in deteriorations of the concent.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.824-829
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• 2012

Zn wires have been electrically exploded in methanol or distilled water using the pulsed power technologies. The nanopowders produced by the explosions have been observed by using SEM and TEM, and analyzed its phase by using EDS and XRD. The nanopowders produced in distilled water showed ZnO phase only. On the other hands, the nanopowder produced in methanol showed mixed phases with Zn and ZnO. The HR-TEM images of the nanopowders produced in methanol showed that the some particles have been coated with carbon like materials. It is considered that the carbon coatings could be depended on the positions of the particles during the plasma state formed by explosion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.238-239
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• 2007

The important merit of Bi-2212/Ag wire is to apply cable as round wire state. Bi-2212 high Tc superconducting wires were fabricated in order to apply Rutherford cable near the future. Various Ag ratio from 0.22 to 0.42 of Ag tubes for PID (powder-In-Tube) process were used to investigate the workability and to prevent breakage of filaments during drawing. KERI and Nexans Korea manufactured Rutherford cabling machine by ourselves. Rutherford cables with 20 - 30 strands could be fabricated by this machine. The shape of Rutherford cables were satisfied. The critical current of Bi2212/Ag round wire with 847 filaments showed 400 A at 4.2K and self field.

• Journal of Astronomy and Space Sciences
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• v.36 no.3
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• pp.181-186
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• 2019

The attitude information of spacecraft can be obtained by the sensors attached to it using a star tracker, three-axis magnetometer, three-axis gyroscope, and a global positioning signal receiver. By using these sensors, the spacecraft can be maneuvered by actuators that generate torques. In particular, electromagnetic-torque bars can be used for attitude control and as a momentum-canceling instrument. The spacecraft momentum can be created by the current through the electrical circuits and coils. Thus, the current around the electromagnetic-torque bars is a critical factor for precisely controlling the spacecraft. In connection with these concerns, a solar-cell array can be considered to prevent generation of a magnetic dipole moment because the solar-cell array can introduce a large amount of current through the electrical wires. The maximum value of a magnetic dipole moment that cannot affect precise control is $0.25A{\cdot}m^2$, which takes into account the current that flows through the reaction-wheel assembly and the magnetic-torque current. In this study, we designed a 300-W solar cell array and presented an optimal wire-routing method to minimize the magnetic dipole moment for space applications. We verified our proposed method by simulation.

• Corrosion Science and Technology
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• v.23 no.1
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• pp.33-40
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• 2024

The concentration and diffusion coefficient of oxide ion vacancies in the oxide scale formed on Fe-22Cr-0.5Mn ferritic stainless steel with and without molybdenum (Mo) was measured at 800℃ by the electrochemical polarization method. After pre-oxidation for 100 h in ambient air at 800 ℃, the oxide scale on one side was completely removed with sandpaper. A YSZ plate was placed on the side where the oxide scale remained. Platinum (Pt) meshes were attached on the top of the YSZ plate and the side where the oxide scale was removed. Changes in electrical current were measured after applying an electrical potential through Pt wires welded to the Pt meshes. The results were interpreted by solving the diffusion equation. The diffusion coefficient and concentration of oxide ion vacancy decreased by 30% and 70% in the specimen with Mo, respectively, compared to the specimen without Mo. The oxide ion vacancy concentration of chromia decreased due to the addition of Mo.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4968-4974
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• 2010

Electrical Railroads provide electric power, which can operate vehicles, via feeder wires. And the supplied current returns to the transformer substation through lines and ground net. In domestic cases, the configuration of ground net affecting such a return current mostly uses an exclusive earth method. However, along with the introduction to Gyeongbu HSL(High Speed Line), the concept of Common Earth was applied to Electrical Railroads. In this paper, based on the return currents analyzed to be measured in the electrified sections for the operation of High Speed Rails in existing lines, we analyze the relations between earth methods and return currents in electrified sections. For analysis, we utilize the measured values of return currents measured in track circuits in Gyeongbu HSL, and predictive values of those compared to the earth methods between Gyeongbu HSL and the existing electrified sections.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.2
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• pp.126-129
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• 2021

We fabricated plate typed shunt resistors composed of carbon nanotube (CNT) and metal alloy for measuring DC current. CNT plates were prepared from dispersed CNT/Urethane solution by squeezing method. Cu/Ni alloys were prepared from composition-designed alloy wires for adjusting the temperature coefficient of resistance (TCR) by pressing them. As well, we fabricated a hybrid resistor by squeezing the CNT/Urethane solution on the metal alloy plate directly. In order to confirm the composition ratio of the Cu/Ni alloy, we used an energy-dispersed X-ray spectroscopy (EDX). Cross-section and surface morphology were analyzed by using a scanning electron microscopy (SEM). Finally, we measured the initial resistance of 2.35 Ω at 25℃ for the CNT paper resistor, 7.56 mΩ for the alloy resistor, and 7.38 mΩ for the hybrid resistor. The TCR was also measured to be -778.72 ppm/℃ at the temperature range between 25℃ to 125℃ for the CNT paper resistor, 824.06 ppm/℃ for the alloy resistor, and 17.61 ppm/℃ for the hybrid resistor. Some of the hybrid resistors showed a near-zero TCR of 1.38, -2.77, 2.66, and 5.49 ppm/℃, which might be the world best-value ever reported. Consequently, we could expect an error-free measurement of the DC current using this resistor.

• Korean Journal of Acupuncture
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• v.40 no.4
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• pp.156-168
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• 2023

Objectives : This study aimed to determine the status of thermal stimulation devices approved in Korea for medical applications over the past 10 years, and based on this, to obtain insight for future thermal treatment in Korean medical institutions. Methods : We searched the item classification list entitled "Regulations on Medical Device Items and Rating by Item" from the Ministry of Food and Drug Safety Notice No. 2021-24, 2021 (Enforced March 19, 2021; www.mfds.go.kr) for individually licensed heaters using the terms "heat" and "heating". Results : We identified 17 items of thermal stimulation product group, of which 1,308 devices were licensed by February 4, 2022, and 53.2% of them (n=696) were devices with valid permits for distribution in Korea. Among the licensed devices, heating pad systems under/overlay (electric, home use) were approved the most, but combinational stimulator (for medical use, home use; Grade 2) accounted for the highest percentage among the current valid permission. Moxibustion apparatuses were licensed separately for electrical use and non-electrical use, and occupied a low percentage of the total devices. We analyzed 307 devices that were accompanied by technical documents and found that the heat sources were wires in 145 (47.2%), infrared rays in 44 (14.3%) and ultrasonic waves in 42 (13.7%) devices. Most (83.1%) devices were used for pain relief, while other applications included beauty, cancer treatment, maintenance of infant body temperature, and healing fractures. Conclusions : Thermal stimulation devices accounted for about 0.9% of all medical devices, and among them, combinational stimulators and heating pad systems under/overlay had the most valid permits. Thermal stimulation devices using heating wires and infrared rays were the most prevalent, and most were used to relieve pain. In order to develop a range of thermal stimulation devices that can be utilized in Korean medical institutions, it is imperative that they have potential applications beyond pain management, addressing various medical purposes. To achieve this, foundational research is necessary to effectively apply diverse heat sources based on medical objectives.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.7
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• pp.664-672
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• 2009

In this paper we propose an on-glass antenna which consists of conducting dual center striplines and multi-loaded striplines. Multi-loaded striplines and dual center lines were employed for achieving a broad matching bandwidth and improving a vertical radiation gain, respectively. The detail design parameters were determined using the Pareto genetic algorithm with an full wave EM simulator. The optimized design was built and installed on a commercial vehicle, and the antenna performances such as the return loss and the radiation gain were measured in a semi-anechoic chamber. The measurement results showed the matching bandwidth($S_{11}$<-3 dB) of about 49 % in the T-DMB frequency band, the vertical gain of about -3 dBi along the bore-sight direction, and the average gain of about -10 dBi along the azimuth direction.

• Progress in Superconductivity and Cryogenics
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• v.5 no.3
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• pp.34-37
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• 2003

A 1 MVA single-phase high temperature superconducting (HTS) transformer with BSCCO-2223 wire was designed in this paper. The rated voltages of each sides of the transformer are 22.9 kV and 6.6 kV respectively. Double pancake HTS windings arranged reciprocally will be used for the transformer windings, because of the advantages of insulation and distribution of surge voltage in case of a large power and high voltage transformer. Single HTS wire was used for the primary windings and four parallel wires were used for the secondary windings of the transformer with transposition. A core of the transformer was designed as a shell type core separated with the windings by a cryostat made of GFRP with a room temperature bore. The operating temperature of the HTS windings will be about 65K with sub-cooled liquid nitrogen. A cryogenic cooling system using a GM-cryocooler for this HTS transformer by natural convection of liquid nitrogen was designed. This type of cooling system can be a good option for compactness, efficiency, and reliability of the HTS transformer.