• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.4
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• pp.282-290
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• 2015

In this study, a latching control technology, proposed by Sheng et al.(2015), was applied in order to maximize the extraction efficiency of WEC (Wave Energy Converter), which is the heaving buoy coupled with linear electric generator. The latching control is the phase-control technique for improving the wave energy conversion with appropriate latching duration of keeping the buoy fixed. From the time-domain analysis in regular waves, the latching control technology can significantly improve the heave velocity and extracted power, even though the resonance condition is not satisfied. By using the latching control technology, the draft of buoy as well as the required PTO damping force can be significantly reduced along with increased extracted power, which is a big advantage in manufacturing the WEC.

• Journal of Biomedical Engineering Research
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• v.28 no.4
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• pp.549-555
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• 2007

In order to study cortical properties in human, it is necessary to obtain an accurate and explicit representation of the cortical surface in individual subjects. Among many approaches, surface-based method that reconstructs a 3-D model from contour lines on cross-section images is widely used. In general, however, medical brain imaging has some problems such as the complexity of the images, non-linear gain artifacts and so on. Due these limitations, therefore, extracting anatomical structures from imaging data is very a complicated and time-consuming task. In this paper, we present an improved method for extracting contour lines of cortical surface from magnetic resonance images that simplifies procedures of a conventional method. The conventional method obtains contour lines through thinning and chain code process. On the other hand, the proposed method can extract contour lines from comparison between boundary data and labeling image without supplementary processes. The usefulness of the proposed method has been verified using brain image.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.11
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• pp.1093-1101
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• 2007

This study presents the design improvement process for door module. Its objective evades the resonance generated at module plate due to the operation of window regulator motor. For this study, the design improvement process is composed of experimental methods having three steps. First step is modal analysis at door assembly status for acquisition of dynamic characteristics which are modal frequency and damping. Second step is a vibration experiment to get the test mode considered an efficiency of window regulator motor. Last step is a vibration measurement by the form of $6{\times}6$ array on module plate. A vibration measurement of $6{\times}6$ array form can be got to three analysis results which are a transfer path of vibration using cross correlation function, a vibration map using OA level and a contribution by frequency band using coherent output power spectrum on module plate. These results are applied to SDM(structural dynamic modification) for design improvement to get around the resonance on module plate by the excitation of window regulator motor.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.7-14
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• 2004

The metal halide lamps are now widely used in the application and commercial lighting due to their attracting properties such as good color rendering and high efficiency. But, they have a serious problem of acoustic resonance using high frequency operation and they need a high voltage to ignite. So, they have not been applied to indoors. Over the past few years, a considerable number of studies have been conducted on the electronic ballast with hot restarting and resonance phenomenon. But, Very few attempts have been made at adaptive ignition method according to lamp state. In this paper is proposed electronicballast for metal halide lamps with an igniter for adaptive ignition. The proposed electronic bllast can generate a different ignition voltage according to the arc tube state.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.263-266
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• 2002

In this paper, It is indicating that an issues of the conventional boost converter for high frequency induction heating. To improve those issues, it is proposed, simulated and analyzed that the current resonant circuit, simulated. As the result, we knew that the proposed circuit has a good point to improve the waveform of input current and to make high efficiency. On the other side, in the inverter for the high current power supply, it is proposed that the high frequency inverter of the half bridge topology, be done the circuit analysis to extract the optimal circuit parameter. It is making sure of the soft switching operating by the inductor to reverse parallel connected on the inverter main switch, decreasing the surge voltage when the switch is turn-off by compulsion, and repressing the switch current and bringing the high current amplitude operation by the multi resonance.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.301-308
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• 1993

Phenomenological nonlinear gain saturation effect on the modulation characteristics in a multi-electrode DBR laser, when the lasing wavelength changes, continuously is analized theoretically. FM efficiency, 3 dB bandwidth, and resonance frequency decrease with increasing bias current to the passive section, except increasing the flat FM response. It is found that the nonlinear gain saturation effect severely affects the modulation characteristics such as FM/IM response, 3 dB bandwidth, resonance frequency and CPR, but hardly affects the behavior of continuous frequency tuning.

• Journal of Power Electronics
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• v.7 no.3
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• pp.246-256
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• 2007

In this paper, a novel type auxiliary active edge resonant snubber assisted zero current soft switching pulse modulation Single-Ended Push Pull (SEPP) series load resonant inverter using IGBT power modules is proposed for cost effective consumer high-frequency induction heating (IH) appliances. Its operating principle in steady state is described by using each switching mode's equivalent operating circuits. The new multi resonant high-frequency inverter with series load resonance and edge resonance can regulate its high frequency output power under a condition of a constant frequency zero current soft switching (ZCS) commutation principle on the basis of the asymmetrical pulse width modulation (PWM) control scheme. Brand-new consumer IH products using the proposed ZCS-PWM series load resonant SEPP high-frequency inverter using IGBTs is evaluated and discussed as compared with conventional high-frequency inverters on the basis of experimental results. In order to extend ZCS operation ranges under a low power setting PWM as well as to improve efficiency, the high frequency pulse density modulation (PDM) strategy is demonstrated for high frequency multi-resonant inverters. Its practical effectiveness is substantially proved from an application point of view.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.804-808
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• 2018

Interest in wireless power transfer (WPT) has been growing recently due to the rapid increase in the use of electronic devices. Wireless charging systems are currently being applied to mobile phones and many studies are being conducted to apply wireless charging systems to various devices. The current wireless charging systems are capable of 1:1 charging. For wireless charging, when the devices with the same resonance frequency are present in the vicinity, the charging efficiency may be significantly lowered due to frequency interference or the wireless charging systems may stop operating. In this paper, variable capacitors were applied to a superconducting WPT system to solve the frequency interference among multiple devices with the same frequency. When a wireless charging system was performing 1:1 operation, the frequency of the other devices was varied using variable capacitors. As a result, it was confirmed that the highly efficient WPT is possible without frequency interference even when multiple receivers are present.

• Journal of Power Electronics
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• v.18 no.1
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• pp.160-170
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• 2018

For high power photovoltaic (PV) grid-connected converters, high order filters such as multi-tuned filters and Traps+RC filters with outstanding filtering performance have been widely researched. In this paper, the optimization of a multi-tuned filter with a low damping resistance and research on its corresponding control scheme have been combined to improve the performance of the proposed filter. Based on the characteristics of the switching harmonics produced by PWM, the proposed filter is optimized to further improve its filtering performance. When compared with the more common Traps+RC filter, the advantages of the proposed filter with low damping resistances in attenuating the major switching harmonics have been demonstrated. In addition, a simpler topology and reduced power loss can be achieved. On the other hand, to make the implementation of the proposed filter possible, on the base of the unique frequency response characteristic of the proposed filter, a digital single-loop control scheme has been proposed. This scheme is a simple and effective means to suppress the resonance peak caused by a lack of damping. Therefore, a smaller volume, better efficiency of the proposed filter, and easy implementation of the corresponding control scheme can be realized. Finally, the superiority of the proposed filter topology and control scheme is verified in experiments.

• Journal of the Korean Magnetic Resonance Society
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• v.25 no.4
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• pp.64-69
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• 2021

In the developed NMR hyperpolarization techniques, Signal amplification by reversible exchange (SABRE) technique is thought to be a promising method to overcome the low sensitivity of bio-NMR/MRI. Most experiments using SABRE have been done in methanol, which is biologically harmful solvent. Therefore, more biological friendly solvent, such as ethanol can be more appropriate solvent to be applicable in bio-NMR and MRI. As the proof of concept, successful hyperpolarization on pyridine via SABRE is carried out in ethanol and its enhancement factor is calculated to be more than 150 folds. To investigate more about its possibility of hyperpolarization in different alcohol solvents, methanol and propanol are used for SABRE in the same condition. The overall polarization trend in different external magnetic field is similar but its polarization number is decreased with higher molecular weight solvents (the order from methanol to propanol). This result indicates that the efficiency of SABRE is different from solvent system despite its same functional group and similar properties. Higher para-hydrogen concentration, higher partial pressure of para-hydrogen, and deuterated solvent can increase the hyperpolarization in any solvents. With these series of successful SABRE results, future studies on SABRE in more biofriendly environment, on more various solvent systems, and with more substrates are needed and it will be the firm basis for applying the SABRE system on the future bio-NMR/MRI.