• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.438-443
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• 1998

A simple single-stage AC/DC forward converter with transformer magnetic energy feedback technique for power factor correction is proposed. The operational principle of the proposed converter is presented. The proposed converter gives the good power factor correction, low line current harmonic distortions, and tight output voltage regulation. The prototype shows high power factor with low line current harmonics.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.132-135
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• 2000

In this paper, we propose to exploit a multi-code CDMA scheme for power line communication (PLC) systems, and its performance on non-Gaussian impulse and harmonic noises is presented. The proposed multi-code CDMA scheme utilizes convolutional coding and block interleaving to combat with the non-Gaussian noises, and simulation results indicate effective alleviation of these noises, and thus significant bit error rate improvement by the proposed scheme even under strict restriction of frequency band allowed in PLC systems.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.411-411
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• 2004

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.315-316
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• 2019

This paper proposes the operation scheme and control method for a four-level hybrid half-bridge flying-capacitor inverter (4L-HHBFCI). With in-phase disposition level-shifted modulation (IPD), the flying capacitor voltage ripple is less than 1% of the reference value, while the line-to-line voltage total harmonic distortion is 23.27% at unity modulation index. The performance and effectiveness of the proposed inverter operation have been verified by simulation results.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.8
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• pp.16-25
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• 1994

The prediction of crosstalk in one of important problems in estimating the EMC of a system for high speed digital signal transmission. Crosstalk curves are shown in terms of characteristic impedance of lines spacing between lines and rise time of pulse by using general multiple coupled transmission line equation and harmonic-balance method. The coupled symmetrical two-line on dielectric material epoxy-glass FR 4(${\varepsilon}_r$), is fabricated to measure crosstalk occuring at the near end and far end of the passive line. The inter-line is inserted to reduce crosstalk between two microstrip lines. The simulation results and the measurement results are shown and found to be very close.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.151-156
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• 2019

The aim of this investigation is to detect specific waveforms in a distribution line prior to the occurrence of a fault. Conditions were introduced such that a feeder remote terminal unit (FRTU) of the distribution automation system selects and stores fault waveforms from the different waveforms detected in the distribution line. In addition, an algorithm was developed to detect specific waveforms from the fault waveforms stored using the FRTU. This algorithm exploits the duration and periodicity of harmonic changes in voltage and current. The efficacy of the algorithm was confirmed based on the measurements of fault waveforms in an actual distribution line. The results indicated that faults in a distribution line can be predicted via experimental measurements.

• Communications of the Korean Mathematical Society
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• v.9 no.2
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• pp.327-329
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• 1994

The Dirichlet problem (DP) on the upper half plane {z = x ＋ iy : y > 0} is to find a real-valued harmonic function u(x, y) satisfying u(x, 0) = g(x) almost everywhere for some reasonably nice function g defined on the real line, which is called the data on the boundary for (DP).(omitted)

• Journal of the Chungcheong Mathematical Society
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• v.23 no.2
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• pp.251-256
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• 2010

In this article, we consider a minimal graph in $R^3$ which is bounded by a Jordan curve and a straight line. Suppose that the boundary is symmetric with the reflection under a plane, then we will prove that the minimal graph is itself symmetric under the reflection through the same plane.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1877-1883
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• 2010

We examined the mechanism of generation of higher harmonics by theoretically analyzing the frequency characteristics of a narrow-band surface wave generated by a laser beam with line-arrayed slit masks. We experimentally analyzed the effects of slit opening width and laser intensity on the acoustic nonlinearity of aluminum 6061-T6 alloy by using single-slit and line-arrayed slit masks. The magnitude of the harmonic wave depended on the slit opening width. In our experiment, we generated a 1.75-MHz surface wave by using an arrayed slit with intervals of 1.67 mm. The magnitude of the second harmonic component decreased about by 80% when the slit opening width was increased from 0.5 mm to 1.0 mm. In addition, the relationship between the magnitudes of the fundamental and the second harmonic wave showed good linearity, which agreed well with the typical behavior of acoustic nonlinearity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.118-125
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• 2007

Harmonic band of bandpass filter(BPF) is suppressed using coupled mushroom structure. Between double positive (DPS) transmission line such as microstrip and double negative(DNG) transmission line such as one dimensional mushroom structure, strong coupling broadly arises in the cross range of dispersion curves of isolated microstrip and mushroom structure because of complex propagation constant in the cross range. Strong coupling inhibits wave propagation, so that this kind of structure can be utilized as bandstop filter(BSF). This BSF utilizes coupled transmission line instead of coupled resonator, resulting in broad bandwidth(>30 %), shan-rejection, and high rejection level. The strong coupling between DPS and DNG transmissionline makes it possible shorten coupling length, resulting in compact size. In this paper, parallel coupled BSF having center frequency of 4 GHz and 3 dB fractional bandwidth of 40 % is designed and utilized to suppressed spurious mode of two bandpass filters.