• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.9
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• pp.822-827
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• 2010

In this study, it is experimentally investigated how bell acoustics are influenced by the internal cavity of the bell and the gap between the bell bottom and the floor. Acoustic transmission function and natural frequency of a test bell are measured and analysed. Experimental study is conducted to evaluated how the resonance effect influences the bell sound and how the bell sound is different according to the striking condition and the measurement direction. Acoustic resonance frequency of the cavity-gap system is predicted by boundary element analysis using SYSNOIS and the validity of the predicted result is verified by experiment. The result of the study could be applied to determine the optimal gap size which makes the bell sound strong and long.

• Journal of Magnetics
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• v.18 no.2
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• pp.155-158
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• 2013

FeCoB films were being prepared on a Ru underlayer by using the oblique incidence of sputtered and back-scattered particles which have a high in-plane magnetic anisotropy field $H_k$ above 400 Oe. It is suitable to attain such deposition condition when facing targets sputtering system. The in-plane X-ray diffraction analysis clarified that there is anisotropic residual stress which is the origin of the high in-plane magnetic anisotropy. The directional crystalline alignment and inclination of crystallite growth were also observed. Such anisotropic crystalline structures may affect the anisotropic residual stress in the films. The B content of 5.6 at.% was appropriate to induce such anisotropic residual stress and $H_k$ of 410 Oe in this experiment. The film with B content of 6 at.% possessed large saturation magnetization of 22 kG and high $H_k$ of 500 Oe. The film exhibited high ferromagnetic resonance frequency of 9.2 GHz.

• Journal of Magnetics
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• v.18 no.2
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• pp.178-182
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• 2013

We have developed a new non-conventional electron paramagnetic resonance (EPR) spectrometer, in which no resonant cavity was used. We previously demonstrated a wide frequency range operation of an EPR spectrometer using two loop antennas, one for a microwave transmission and the other for signal detection [1]. In contrast to Ref. [1], the utilization of a microstrip antenna as a transmitter enhanced a capability of wide-band operation. The replacement of conventional capacitors with varactor diodes makes resonance condition easily reproducible without any mechanical action during tuning and matching procedure since the capacitance of the diodes is controlled electronically. The operation of the new EPR spectrometer was tested by measuring a signal of 1,1-diphenil-2-picrylhydrazyl (DPPH) sample in the frequency range of 0.8-2.5 GHz.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.59-64
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• 2000

Especially, demands for the noise reduction of mold transformer has been becoming an common issue because it has been used mainly at the residence area such as building and ship. So, this paper investigates the noise source and countermeasure of mold transformer radiated high noise abnormally. The result of impact hammering test for core of transformer ascertains the core resonance by harmonics of line frequency and high noise can be reduced to avoid core resonance by changing torque strength of tie rod. Magnetic field analysis is performed to identify the reason that noise of V-phase is higher than U and W-phase in the normal condition. It is the cause that flux density and magnetic force of V-phase is higher than the other phase respectively.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.443-447
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• 2005

When the high-speed train running on the track, there is a speed band which track distortion is unusually increased according to the condition of track and roadbed. This speed is called critical velocity and physical parameter value increased greatly. These phenomenon happened as high-speed train were developed, studied regularly through TGV 100 running test in France. As research result until now, the main reason is soft roadbed's capacity. Wave propagation and track support capacity is varied by the site characteristics. This paper achieved theoretical examination about resonance band(speed and frequency) that occurred in roadbed on the base rock in point of geotechnical engineering. The examination of resonance divides with ground response analysis, critical band analysis by the shear wave velocity of roadbed, train critical speed through the ground stratum.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1791-1797
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• 2018

Sub-Synchronous Resonance (SSR) is a phenomenon that harms turbine generator shafts because the phenomenon induces sub-synchronous wavering in the system. In the study presented in this paper, a dynamic resistance bank is used to mitigate the occurrence of sub-synchronous phenomenon. A fuzzy logic controller using rotor speed deviation and its derivative as inputs is implemented to damp sub-synchronous oscillations more efficiently. An eigenvalue technique is used to analyse the stability of the system, and a simulation in MATLAB is conducted, based on the IEEE Second Benchmark, to validate the effectiveness of the proposed method under a 3-phase fault condition at an infinite bus. The time-domain simulation and eigenvalues are used to observe the proposed method's superior ability to damp sub-synchronous oscillation.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.299-300
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• 2015

This paper proposes current-fed bi-directional DC-DC converter using a resonance (CF-BCR) with wide output voltage range. The steady state analysis and operation principles of CF-BCR are introduced. To increase the output voltage range with satisfying soft switching condition, switching frequency, duty and number of times of the resonance are controlled. The proposed converter and its control method are verified by theoretical analysis and PSIM simulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.429-434
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• 2004

Vibration response of the tower structure of a 750kW wind turbine generator is investigated by measurement and analysis. Acceleration response of the tower under various operation condition is monitored in real time by vibration monitoring system using LabVIEW. Resonance state of the tower structure is diagnosed in the operating speed range. To predict the tower resonance frequency, tower is modeled as an equivalent beam with a lumped mass and Rayleigh energy method is applied. Calculated tower bending frequency is in good agreement with the measured value and the result shows that the simplified model can be used in the design stage of the wind turbine tower.

• Investigative Magnetic Resonance Imaging
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• v.25 no.3
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• pp.189-192
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• 2021

Anti-myelin oligodendrocyte glycoprotein (anti-MOG) syndrome is an immune-mediated inflammatory condition of the central nervous system, which usually involves spinal cord and optic nerves. Herein, we studied the case of a 57-year-old female patient who presented with acute/subacute symptoms of sphincter dysfunction, paraparesis, and ocular pain. The patient was diagnosed with anti-MOG syndrome with findings resembling snake-eye appearance (SEA), characterized by nearly symmetrical round high signal intensity lesions located at anterior horns (gray matter) on T2-weighted image.

• Investigative Magnetic Resonance Imaging
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• v.23 no.2
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• pp.175-178
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• 2019

Juvenile hypertrophy of the breast is a rare condition, leading to hyperplastic breast anomalies in adolescents. Here, we report a case involving a 15-year-old girl, presented with asymmetric enlargement of the left breast. Pronounced parenchymal thickening was found on initial ultrasonography (US). MRI and second-look US revealed a focal mass-like lesion on the left mid-lateral breast, confirmed as juvenile hypertrophy of the breast on pathology.