• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.9-16
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• 2011

The feasibility of wave energy extraction from a heaving truncated cylinder and the corresponding response of the linear electric generator (LEG) composed of spring, magnet, and coil has been investigated in the frame of three-dimensional linear potential theory. The heaving motion of a circular cylinder is calculated by means of the matched eigenfunction expansion method. Further, the analytical results are validated by numerical results using the ANSYS AQWA commercial code. By the action of a heaving circular cylinder, the magnet suspended by a spring can slide vertically inside the heaving cylinder. The mechanical power is extracted from the magnet motion relative to the coil/stator which is attached to the cylinder. The coupled ODE of a heaving cylinder and LEG system in waves is derived to obtain the magnet motion relative to a cylinder. To maximize the relative motion of the magnet, both the buoy draft and the LEG system parameters (spring stiffness, damping) should be selected properly for generating the double resonance considering the peak frequency of the target spectrum.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2158-2167
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• 2018

This paper analyzed the magnetic field produced by the cylindrical stator coils of permanent magnet spherical motor (PMSM). The elliptic equations about the vector magnetic potential were given. Given that the eddy current effects are neglected, the magnet field of the PMSM is regarded as irrotational field, which can be calculated by scalar magnetic potential. The current density of cylindrical stator coil was proposed based on the definition of current density. The expression of current density of stator coil was obtained according to the double Fourier series decomposition and spherical harmonic functions. Then the magnetic flux density for scalar magnetic potential was derived. Further, the influence of different parameters on radial flux density was also analyzed. Finally, the results by the analytical method in this paper were validated by finite element analysis (FEA).

• Structural Engineering and Mechanics
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• v.17 no.3_4
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• pp.291-302
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• 2004

In this paper, load monitoring technologies using U-shape Magnetoelastic (EM or ME) sensors have been exploited systemically for the first time. The steel rod to be tested is the Japan 7 mm piano steel rod. The load dependence of the magnetic properties of the piano steel rod was manifested. Two experimental designs of U-shape magnetoelastic sensors were introduced, one with double pick-up concentric coils wound on the rod to be tested, the other with pick-up coil on one yoke foot. The former design is used to derive the correlation of the relative permeability with elastic tension, while the latter is aimed to reflect the stress induced magnetic flux variation along the magnetic circuit. Magnetostatic simulations provide interpretations for the yoke foot sensing technology. Tests with double pick-up coils indicate that under proper working points (primary voltages), the relative permeability varies linearly with the axial load for the Japan 7 mm piano steel rod. Tests with pick-up coil on the yoke foot show that the integrated sensing voltage changes quadratically with the load, and error is more acceptable when the working point is high enough.

• Journal of Korean Neurosurgical Society
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• v.48 no.2
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• pp.115-118
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• 2010

Objective : Cerebral aneurysms which cause oculomotor nerve [cranial nerve (CN) III] palsy, are frequently found with a daughter sac of the aneurysm dome. We assumed that CN III might be compressed by the daughter sac and it would be more helpful not to fill the daughter sac with coils than vice versa during endosaccular embolization for recovering from CN III palsy, because it may give a greater chance for the daughter sac to shrink by itself later. We reviewed the initial results of our experiences of such cases. Methods : Among 9 aneurysms accompanied by CN III palsy, 7 (6 unruptured, 1 ruptured) showed a daughter sac. We tried to fill the main dome completely and spare the daughter sac from coil filling to increase the possibility of decompression. We evaluated the short-term effectiveness of this concept using medical records and angiograms. Results : After initial embolization, all of CN III palsy caused by unruptured aneurysms (6/6) resolved completely after various periods (3-90 days) of time. No adverse effects were noted during and after the procedures except for one case of harmless coil stretching during coil filling using double microcatheter. Conclusion : During the coil embolization of the cerebral aneurysm causing CN III palsy, sparing the daughter sac from coil packing while tightly packing the main dome, can be helpful in increasing the effectiveness of decompression. However, a long-term follow-up will be required.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.219-225
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• 2013

Separate and layered transmitting and receiving spiral coil arrays had been used for the optimized individual applications of magnetostrictive type long-range ultrasonic testing. In this study, it was demonstrated that when taking advantages of the spiral coils with the leg width reduced to be half of the previous one and of the empty spaces due to the decrease of leg width, the transmitting and receiving coil array can be arranged to form a single layer structure allowing more easy use and fabrication. Because of the number of turns of the receiving coils that is proportional to their leg width, the sensitivity of the single layer coil array was about half that of the corresponding double layer coil array while it allowed the receiving amplifier to get faster recovery from a saturation due to the main bang echo. It was also found that the two types of coil arrays have almost the same performances in the view points of signal-to-noise ratio and directivity control.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.9-16
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• 2020

Wireless charging has been considered an essential part of recent mobile devices. Moreover, various wireless charging systems have emerged through many studies. Among the systems, in the 2D flat coil system, the transmitter coil and receiver coil are arranged horizontally as close as possible to improve the charging efficiency. Nowadays, the 3D coil system has been proposed by adding some slope to flat 2D coils to reduce the volume. On the other hand, the 3D coil system has a lower charging efficiency than the 2D system that decreases rapidly with increasing distance. This paper proposes a new system that improves the low efficiency and charging freedom, which are the drawbacks of the existing 3D systems. The proposed system was designed in three-dimensions, and another transmitter coil was added to the transmitter coil to improve the transmission efficiency and flexibility. The measurement showed that the charging efficiency of the proposed system was 40.10% when the distance between coils was 8 mm, which is 20.5 % improvement over the existing one. The proposed method can be applied when new wireless charging systems are designed and improve charging efficiency can be improved.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.3
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• pp.578-585
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• 2009

In this paper, we present the design of an electromagnetic scanning mirror with torsional springs. The scanning mirror consisting of torsional springs and electromagnetic coils was designed for the applications of laser animation systems. We analyzed and optimized three types of torsional springs, namely, straight beam springs (SBS), classic serpentine springs (CSS), and rotated serpentine springs (RSS). The torsional springs were analyzed in terms of electrical resistance, fabrication error tolerance, and resonance mode separation of each type using analytical formula or numerical analysis. The RSS has advantages over the others as follows: 1) A low resistance of conductors, 2) wide resonance mode separation, 3) strong fabrication error tolerance, 4) a small footprint. The double-layer coils were chosen instead of single-layer coils with respect to electromagnetic forces. It resulted in lower power consumption. The geometry of the scanning mirror was optimized by calculations; RSS turn was 12 and the width of double-layer coil was $100{\mu}m$, respectively. When the static rotational angle is 5 degrees, the power consumption of the mirror plate was calculated to be 9.35 mW since the resistance of the coil part and a current is $122{\Omega}$ and 8.75 mA, respectively. The power consumption of full device including the mirror plate and torsional springs was calculated to be 9.63 mW.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.5
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• pp.558-563
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• 2008

Vibration/shock affects biggest taking a train subtraction of vehicle and durability decline. Therefore, absorber is used for vibration/shock isolation and various qualities of the material and design are applied to isolation. This paper proposes vibration/shock absorber that applies 'Disc' spring. Through comparison with 'Disc' spring that has nonlinearity and coil spring that is having linearity, see effect that nonlinearity of isolation gets in vibration/shock Isolation. Coil spring and 'Disc' spring are non-linear numerical analysis and simulation through theory for this, get and investigate comparison result through an experiment finally. Expressed and formulated shock through 'Runge-Kutta' method/impact response to nonlinear-vibration-equation of 1 degree of freedom for numerical analysis. Double half sine pulse of excitation used and analyzed result through spectrum response analysis here. Response of disc spring is compared to response of coil spring by changing $h_o/t$ ratio with computer simulation and the usage of disc spring is increased through analysis of effect of design factors. The purpose of this paper is that the shock response of disc spring is calculated through numerical simulation and to design the optimal absorber under the limited condition. And then, the isolation effect was analyzed through the shock test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.990-993
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• 2008

Vibration/shock affects biggest taking a train subtraction of vehicle and durability decline. Therefore, absorber is used for vibration/shock isolation and various qualities of the material and design are applied to isolation. This paper proposes vibration/shock absorber that applies 'Disc'spring. Through comparison with 'Disc' spring that has nonlinearity and coil spring that is having linearity, see effect that nonlinearity of isolation gets in vibration/shock isolation. Coil spring and 'Disc' spring are non-linear numerical analysis and simulation through theory for this, get and investigate comparison result through an experiment finally. Expressed and formulated shock through 'Runge-Kutta' method/impact response to nonlinear-vibration-equation of 1 degree of freedom for numerical analysis. Double half sine pulse of excitation used and analyzed result through spectrum response analysis here. Response of disc spring is compared to response of coil spring by changing ho/t ratio with computer simulation and the usage of disc spring is increased through analysis of effect of design factors. The purpose of this paper is that the shock response of disc spring is calculated through numerical simulation and to design the optimal absorber under the limited condition. And then, the isolation effect was analyzed through the shock test.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.7
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• pp.62-68
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• 2014

We proposed a series connection-type superconducting fault current limiter(SFCL) using E-I core that can prevent the internal magnetic flux generation of cores during normal operation, and prevent the saturation of cores due to a sudden magnetic flux generation at the initial stage of fault occurrence while limiting the peak current. Through a short-circuit simulation experiment, we analyzed the operating status of the two superconducting elements and limiting characteristics according to the size of the fault current peak before and after the failure. Further, the double peak current limiting characteristics according to the winding directions as well as the current and the voltage of each coil were compared and analyzed.