• Journal of Magnetics
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• v.20 no.1
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• pp.57-61
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• 2015

In this paper wireless power transmission system based on magnetic resonance coupling circuit was carried out. With the research objectives based on the mutual coupling model, mathematical expressions of optimal coupling coefficients are examined. Equivalent circuit parameters are calculated by Maxwell software, and the equivalent circuit was solved by Matlab software. The power transfer efficiency of the system was derived by using the electrical parameters of the equivalent circuit. System efficiency was analyzed depending on the different air gap values for various characteristic impedances. Hence, magnetic resonance coupling involves creating a resonance and transferring the power without radiating electromagnetic waves. As the air gap between the coils increased the coupling between the coils were weakened. The impedance of circuit varied as the air gap changed, affecting the power transfer efficiency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.332-335
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• 2007

This paper presents a theoretical approach to describe the vibration characteristics of a piezoelectric shell transducer. Governing equations for the motion of the piezoelectric shell are classified and simplified according to the boundary conditions. Applied mechanical and electrical boundary conditions have yielded each characteristic equation for circumferential, longitudinal, and radial motions of the piezoelectric shell transducer. Theoretical calculations of the resonance frequencies have been compared with the results obtained by the experiment and have shown a good agreement.

• Journal of the Korea Society for Simulation
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• v.24 no.3
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• pp.45-54
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• 2015

This paper presents the influence of backlash can be greatly increased on the frequency response characteristic which is presented as the angular velocity of a motor to the motor input voltage, if the motor input voltage is adequately reduced. And, this paper verifies theoretically, analytically and experimentally the availability on the method of detecting the change of backlash magnitude by investigating on the change of the anti-resonance and resonance frequencies in the frequency response characteristic due to the change of backlash magnitude. The amount of change of anti-resonance frequency is more useful that of resonance frequency when detecting the change of backlash magnitude, because the change of anti-resonance frequency can be measured more stable. This paper also shows the sharp change of resonance frequency can be investigated when the motor input voltage is enough reduced. The work will be useful for the further research on the backlash estimation method of a servo system with a gear reducer.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.4
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• pp.643-650
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• 2017

This pap4er analyzes resonance characteristics of a slave motor that is not controlled by load and parameter differences between Dual motors during parallel operation in middle-low speed. Dual SPMSMs(Surface mounted Permanent Magnet Synchronous Motor) connected in parallel to a single inverter controlled by the master and slave control in this paper. Based on the stability analysis of the SPMSM for a variation of torque angle, the 6th nonlinear state equation of the torque angle variation in the SIMM(Single Inverter Multi Motor) structure is derived according to a mathematical model for the dual motors. In general, an analysis of the 6th order nonlinear state equation is complex. Therefore, a resonance frequency generated from the slave motor is found from the characteristic equation of the 2nd order system obtained by linearization and model reduction near steady state operation point. Through simulations and experiments, it is confirmed that the stability analysis of the SPMSMs and state equation models are useful for the variation of the torque angle analyzed in this paper.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.916-917
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• 2008

In this paper, Switching damage of switches that is used to proposed power conversion system is reduced by soft switching way. dissipation by part resonance and my resonance stress for resonance of resonance circuit are decreased. Is acted by conversion system high effectiveness. Have following characteristic. Design snubber circuit that is used by switch protection in existent hard work rate Topology by resonant circuit for sogt switching, circuit structure was simple and control system is easy. Also, Can generate free output voltage by multi level Tuesday of output that use individuation Power Cell's Phase Shift PWM, and Low-end switching frequency the harmonic is few.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.9
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• pp.849-855
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• 2010

Damping may change the response characteristics of nonlinear oscillations due to the parametric excitation of a thin cantilever beam. When the natural frequencies of the first bending and torsional modes are of the same order of magnitude, we can observe the one-to-one combination resonance in the perturbation analysis depending on the characteristic parameters. The nonlinear behavior about the combination resonance reveals a chaotic motion depending on the natural frequencies and damping ratio. We can analyze the chaotic dynamics by using the eigenvalue analysis of the perturbed components. In this paper, we derived the equations for autonomous system and solved them to obtain the characteristic equation. The stability analysis was carried out by examining the eigenvalues. Numerical integration gave the physical behavior of each mode for given parameters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.511-518
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• 2006

In this paper, a small RFID tag antenna in UHF band which has bandwidth-enhanced characteristic is proposed. The shape of the proposed antenna is a meander antenna to have size-reduced characteristic, and it consists of two radiators which make dual resonance in adjacent frequency to enhance bandwidth. By adjusting length and location of each radiator, the proposed antenna can make dual resonance at arbitrary location on the Smith chart, which is able to make impedance matching with RFID tag chip in wide frequency range. And it is apparent that the proposed antenna can have bandwidth-enhanced characteristic according to the simulated and measured results.

• Investigative Magnetic Resonance Imaging
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• v.21 no.4
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• pp.273-275
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• 2017

Thiemann's disease is a form of idiopathic avascular necrosis of the immature epiphyses of the phalanges of the fingers and toes. Few cases of Thiemann's disease have been reported because the disease is rare and difficult to diagnose. To the best of our knowledge, magnetic resonance imaging (MRI) findings of Thiemann's disease have not been reported. Here, we report a case of Thiemann's disease diagnosed by typical clinical symptoms and characteristic MRI findings before radiologic bony abnormalities were apparent.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.2
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• pp.174-180
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• 2011

Nondestructive surface imaging of elastic characteristic and mechanical property has been studied on nanoscale surface with ultrasonic AFM. Resonance frequency variation of cantilever is theoretically analyzed with respect to contact mechanics as well as experimentally measured. The contact resonance frequency is calculated theoretically using the spring-mass and Herzian model in accordance with the resonance frequency of UAFM cantilever measured experimentally. Consequently, the topography and amplitude images could be obtained successfully and the elastic characteristic at the nanoscale surface was evaluated qualitatively by amplitude signals.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.3
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• pp.98-103
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• 2001

This paper presents the numerical analysis of piezoelectric devices using three-dimensional finite element analysis. The characteristic of piezoelectric transducer, such as mechanical displacement and electrical are analyzed and the validity is confirmed by experiments Applying the finite element routine to a piezoelectric transformer, the resonance features electrical impedance. the ratio of step-up voltage and vibration mode of piezoelectric transformer are calculated numerically By using three-dimensional finite element method effects of width variation to resonance features, electrical input impedance and the voltage step-up ratio for a piezoelectric transformer, can be considered in design procedure.