• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.347-349
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• 1997

In this study, we designed a vascular occlusion device based on the principle that slowing blood flow would induce thrombosis. Tungsten, stainless steel and platinum were tested for finding a good embolic metallic coil. The primary coil and the second coil were done with heat treatment or different time. The pitch distance and the shape retention capability of second coil were characterized by SEM. To increase thrombogenicity, we tried to treat different proteins on steel coils: thrombin, gelatin and both gelatin and thrombin. To verify protein materials treated on coils, the surface of coil treated with different proteins were characterized using Laser Raman Spectrophotometer. After observation of embolic coils, the peptides bonds on theirs' surface were found. In order to compare the thrombogenicity of different embolic agents, we measured whole blood clotting time.

• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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• pp.28-31
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• 2015

An in-flight fragment separator, which aims to produce and study rare isotopes, consists of superferric quadrupole triplets and $30^{\circ}$ dipole magnets to focus and bend the beams for achromatic focusing and momentum dispersion, respectively. The separator is divided into pre and main stages, and we plan to use superconducting magnets employing high-Tc superconductor (HTS) coils in the pre-separator area, where radiation heating is high. The HTS coils will be cooled by cold He gas in 20-50 K, and in the other area, superferric magnets using low-temperature superconductor (LTS) will be used at 4 K. A few LTS coils were wound and successfully tested in a LHe dewar, and the design of cryostat has been optimized. Development of the HTS coils is ongoing in collaboration with a group at KERI. An HTS coil of racetrack shape was wound and tested in a $LN_2$ bath and in a dewar with cryocooler. No degradation on critical current due to coil winding was found.

• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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• pp.36-39
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• 2015

Many studies are being conducted to implement wireless charging, for example, for cellular phones or electronic tooth brushes, via wireless power transmission technique. However, the magnetic induction method had a very short transmission distance. To solve this problem, the team of Professor Marin Soljacic proposed a magnetic resonance system that used two resonance coils with the same resonance frequency. It had an approximately 40% efficiency at a 2m distance. The system improved the low efficiency and short distance problems of the existing systems. So it could also widen the application range of wireless power transmission. Many studies on the subject are underway. In this paper, the superconductor coil was used to improve the efficiency of magnetic resonance wireless power transmission. The resonance wireless power transmission system had a source coil, a load coil, and resonance coils (a transmitter and a receiver). The efficiency and distance depended on the characteristics of the transmitter and receiver coils that had the same resonance frequency. Therefore, two resonance coils were fabricated by superconductors. The current density of the superconductor was higher than that of the normal conductor coil. Accordingly, it had a high quality-factor and improved efficiency.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.40-44
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• 2013

The contactless power transfer (CPT) systems have been recently gaining popularity widely since it is an available option to realize the power delivery and storage with connector-free devices across a large air gap. Especially, the CPT with electromagnetic resonance coupling method is possible to exchange energy within 2 m efficiently. However, the power transfer efficiency of CPT in commercialized products has been limited because the impedance matching of coupled coils is sensitive. As a reasonable approach, we combined the CPT system with HTS wire technology and called as, superconducting contactless power transfer (SUCPT) system. Since the superconducting coils have an enough current density, the superconducting antenna and receiver coils at CPT system have a merit to deliver and receive a mass amount of electric energy. In this paper, we present the feasibility of the SUCPT system and examine the transmission properties of SUCPT phenomenon between room temperature and very low temperature at 77 K as long as the receiver is within 1.0 m distance.

• ETRI Journal
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• v.41 no.6
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• pp.838-849
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• 2019

We present a permanent magnet-based spherical wheel motor that can be used in omnidirectional mobility applications. The proposed motor consists of a ball-shaped rotor with a magnetic dipole and a hemispherical shell with circumferential air-core coils attached to the outer surface acting as a stator. Based on the rotational symmetry of the rotor poles and stator coils, we are able to model the rotor poles and stator coils as dipoles. A simple physical model constructed based on a torque model enables fast numerical simulations of motor dynamics. Based on these numerical simulations, we test various control schemes that enable constant-speed rotation along arbitrary axes with small rotational attitude error. Torque analysis reveals that the back electromotive force induced in the coils can be used to construct a control scheme that achieves the desired results. Numerical simulations of trajectories confirm that even without explicit methods for correcting the rotational attitude error, it is possible to drive the motor with a low attitude error (<5°) using the proposed control scheme.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.6
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• pp.856-862
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• 2008

This paper propose a advanced technique for exciting and receiving the guided torsional wave to detect flaws in pipe systems. There are some difficulties in selecting and exciting of modes by using the nickel strip attached on pipe systems, such as qualification of residual magnetic field and multi-exciting of the unwanted modes etc. In order to there difficulties we propose the new sensor, so called Crossed-coils sensor. We will prove that it is possible to select the modes to be excited and to find a optimal excitation condition for torsional mode by using the proposed sensor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.623-628
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• 2015

In this paper, the shield plate was applied to the wireless power transfer (WPT) system. Then we compared transmission efficiency of WPT system between transmitter and receiver coils. The superconductor coil was applied to transmitter and receiver coils in order to increase the transmission efficiency of WPT. The superconductor coil was more effective to power transmission as its current density was higher than normal conductor coil. Efficiency of WPT between transmitter and receiver coils was changed by a quality of shielding. We used the shielding materials such as glass, iron, steels, aluminum etc. The efficiency of WPT system was depended on the shielding materials of transmitter and receiver coils. As a result, magnetic material such as aluminum, iron reduced the magnetic flux density and the efficiency of WPT. remarkably, but in non-magnetic material such as glass and plastic, the efficiency of WPT was unaffected.

• Progress in Superconductivity and Cryogenics
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• v.14 no.1
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• pp.30-33
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• 2012

A double pancake winding method is widely used to make the superconducting magnet, using high temperature superconductor (HTS) tape. In the double pancake winding method, the joints with contact resistances between double pancake coils are inevitably needed. The electrical joule heating on the contacts causes refrigerant loss during operation. And a space outside the winding, for splices and mechanical support, is more than that for its layer-wound equivalent. In this paper, a double pancake winding method in order to reduce the number of the joints was proposed. Both of the double pancake coils using the conventional winding method and the proposed winding method have been fabricated and tested to make the solution technically feasible in the double pancake winding method. Especially, critical-current tests of the fabricated double pancake coils were conducted in order to show the same performance and confirm contact resistances between double pancake coils.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.3
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• pp.282-291
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• 1998

Heat transfer performance are studied for the turbulent flow of water in 3 smooth tube coils having ratios of coil to tube diameter of 16, 21 and 27, and a corrugated-coiled tube having a ratio of coil to tube diameter of 29, for Reynolds numbers from 8000 to 60000 and is also compared with the limited results available to data. The experiments are carried out for the fully developed turbulent flow of water in tube coils under the condition of uniform heat flux. This work is limited 0 tube coils of R/a between 10 and 30. The tube having a ratio of coil to tube diameter of 27 among the 3 smooth tube coils shows the best heat transfer performance. The performance of coiled tube best transfer performance. The performance of coiled tube with a similar curvature ratio is better for a corrugated-coiled tube(R/a=17) than for a smooth coiled tube(R/a=16). An empirical relation which correlates most of the data within $\pm$25% was also developed. Test result shows that the Nusselt number is found to be affected by a secondary flow due to curvature.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.8
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• pp.1010-1013
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• 2012

This paper demonstrates the use of the convex optimization to localize the transverse magnetic $B_1^+$ field in regions of interest for recently proposed multi-sectioned alternating impedance coils and the traditional transmission line coil. An approach based on different axial slices to identical RF coils except upper stripline structure is investigated. Electromagnetic simulation results are compared for RF coils and discussed in detail at 7.0 T.