• Journal of the Korean Geotechnical Society
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• v.22 no.5
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• pp.47-57
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• 2006

The shear wave velocity is related with the stiffness of granular skeleton and mass density. The shear stiffness of the granular skeleton remains unaffected by the presence of the fluid. Bender elements are convenient shear wave transducers for instrumenting soil cells due to optimal soil-transducer coupling. This study addresses the principles of the shear wave, the design and implementation of bender elements including electromagnetic coupling prevention, directivity, resonant frequency, detection of first arrival, and near field effects. It is shown that electromagnetic coupling effects can be minimized using parallel-type bender elements. Thus, the in-plane S-wave directivity is quasi-circular. The resonant frequency of bender element installations depends on the geometry of the bender element, the anchor efficiency and the soil stiffness. One of the most cumbersome parts in the bender element test is near field effects, which affect the selection of arrival time. The selection of the first arrival within the near field Is effectively solved by the multiple reflection technique and signal matching technique. Bender elements, which requires several considerations, may be effective tools for the subsurface characterization by using S-wave.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.7
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• pp.272-277
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• 1986

The system that follows to the resonance frequency of high frequency MOSFET inverter and varies according to the changes of load characteristics is proposed. Also we suggested a method how to select the resonant load type between series and parallel circuit for a given inverter type. It leads to the conclusion that in the case of high impedance loads, parallel resonant circuits are preferable, on the other hand, for low impedance loads, series resonant circuits are more preferable. For frequency tracking, a PLL circuit is used as main control element to detect the phase difference of current and voltage of load. The realized apparatus composed of control circuit and voltage type full-bridged MOSFET elements as main parts of inverter. A stable frequency follow-up characteristics are obtained for 1.2MHz, 1.5KW high frequency output and power is always supplied to the load with unity power factor.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.212-214
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• 2009

In this paper, we have proposed a Parallel Resonant Soft Switching Inverter based on Delta-Modulation Method. The conventional full-bridge inverter generates switching losses due to the hard switching. The proposed inverter operates soft switching using a DC-link switch and resonant circuit. So, all of the switches in the proposed inverter operates soft switching. Therefore the proposed inverter can reduce not only switching loss but also capacity and size of passive devices due to the resonant elements. The validity of the proposed inverter is verified thorough the theoretical analysis and simulation.

• Journal of Power Electronics
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• v.9 no.4
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• pp.567-574
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• 2009

A linear transfer function for the output current control of frequency-controlled resonant inverters is proposed in this paper. The circuit of resonant inverters can be transformed into two coupled circuits through the complex phasor transform. The circuits consist of cross-coupled power sources and passive elements. The circuits are used to induce the state space equation, which is transformed into the $4^{th}$ order cross-coupled transfer function. The $4^{th}$ order cross-coupled transfer function is modeled into a $2^{nd}$ order linear transfer function based on a behavior analysis of the pole and zero locations that facilitate a simple and intuitive linear transfer function. The feasibility and validity of the proposed linear transfer function were verified by simulation and experiment.

• Journal of electromagnetic engineering and science
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• v.17 no.2
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• pp.86-90
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• 2017

In this study, a novel third-order bandpass filter, which is based on a rectangular closed loop resonator, is presented. By adding a series resonator to the conventional loop resonator, the resonator's even resonant mode is split into two modes, while the odd resonant mode is not affected. Therefore, by varying the values of the series resonator elements, the resonant frequencies of two even modes can be determined independent of the odd-mode resonant frequency. In the proposed triple-mode filter design, instead of using a lumped series resonator, a T-shaped transmission line is coupled to the resonator via a small gap. To verify the design method, a filter is designed at 2.4 GHz with a bandwidth of 100 MHz. The improved performances of the proposed triple-mode filter are compared with those of the conventional dual mode filter.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.6
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• pp.432-440
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• 2010

In this paper, a LC series resonant boost converter using a single switch is proposed. The proposed topology contains additional passive elements in the conventional boost converter and performs Zero Voltage Switching(ZVS) without an additional auxiliary switch when a main switch turned on and off. The switch off time of the proposed system determined by LC series resonance, thus a on-time variable Pulse Frequency Modulation(PFM) method is adapted to control output voltage in the proposed converter. Operational modes of the proposed topology are divided with respected to the current conduction paths and then through the theoretical analysis and experimental results, operational modes and characteristics of the proposed converter are verified.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.3
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• pp.266-274
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• 1991

This paper proposed the resonant DC-DC converter with constant switching frequency. Its output is controlled by the auxiliary switch which is attached in conventional MRC circuits. The average output voltage is equal to the average voltage of the auxiliary switch. If the on time of the auxiliary switch is short, output voltage is decreased. Because of using the multi resonant method, the power loss from the parasitic elements can be decreased. Experimental performance of DF ZVS Forward MRC topology with switching frequency of 1MHz is presented.

• Journal of electromagnetic engineering and science
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• v.2 no.1
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• pp.45-49
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• 2002

This paper presents the basic characteristics of a forced resonant type EMI dipole antennas for frequencies below 80 MHz in which two reactance elements are used for the impedance matching at the fined point. The input impedance of the short dipole less than half-wavelength is controlled by the properly determined loading position and the value of loading reactance. The numerical results show that the small-sized EMI dipole antenna with loller antenna factors for frequencies below 80 MHz can be realized by the reactance loading. In case tole proposed center driven forced resonant type EMI dipole antenna with 0.3 λ length is loaded from the center, the input impedance is matched at feed line with 50 $\Omega$, and hence the antenna has lower factors in the frequency range of 30 to 80 MHz.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.3
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• pp.186-195
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• 2008

This paper studies the operating characteristics of the high voltage flyback converter including the resonant elements. The detailed mode analysis and the design procedure are presented in designing a high voltage flyback converter. To verify and to confirm the validities of the presented analysis and design procedure, the computer simulation and the experiments have been performed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1345-1348
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• 2003

The Ferrule for the Optical Communication Connector is the product to set the optical ares of an optical fiber very precisely. Therefore, it is required high expectations such as high dimensional precision and new including flaws. Up to new the optical instrument has been used for the defeat and shape inspection of the ferrule, but in the paper we examined the detectable defeat and expectation by using Resonant Ultrasound Spectroscopy(RUS). The RUS is the measurement which is to excite specimen and to inspect the difference at natural frequency pattern between acceptable specimen and specimen which has some defeats. We analyzed the difference of natural frequency pattern in the experiment using Spectrum Analyzer. And we compared the results in the experiment with those in the simulation from the explicit finite elements code, Nastran.