• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.9
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• pp.1023-1029
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• 2007

In this paper, we propose the method to solve the BLT equations using Laguerre polynomials in time domain. The solution of BLT equations is obtained by recursive, differential and integral properties of Laguerre polynomials. The verification of the proposed method is tested by applying it to the two-wired transmission line with resistors and capacitors, which is illuminated by the electromagnetic plane wave pulse. And the result is compared with the corresponding transient responses obtained from inverse fast Fourier transform(IFFT) of the frequency domain solutions of BLT equations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.9
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• pp.1047-1056
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• 2007

In this paper, we analyze the performance of the encoding and the modulation processes in the downlink and uplink of the EPCglobal Gen-2 system through the analysis and simulation. Furthermore, the synchronization issues on time and frequency domain and the preamble architecture are evaluated. By incorporating the encoding and the modulation technigue in the downlink and uplink, we assess the performance of the EPCglobal Gen-2 system. We also introduce the encoding and backscatter modulation process as well as the BER performance of FM0 code. In addition, the importance and the role of the frequency and time synchronization, such as the preamble and frame synchronization are explained. Through the simulation in the uplink on the detection probability through preamble, we find that the detection probability approaches 1 for 13 dB $E_b/N_0$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.11
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• pp.1012-1018
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• 2016

We perform a electromagnetic analysis method for indirect effects of a high-conductive structure such as an aircraft exposed by lightning, by using the finite-difference time-domain(FDTD) method. The lightning waveform used to analyze indirect effects has low frequency spectrum and high-conductive materials such as aluminum and carbon fiber composite materials have very short skin depths, and thus, it requires large memory and long computation time using conventional three dimensional FDTD analysis method. We develop an efficient electromagnetic analysis method suitable for lightning and high-conductive structures. The developed analysis method is based on two dimensional FDTD and impedance network boundary condition(INBC) algorithms and we investigate the indirect effects on the structures exposed to lightning.

• Phonetics and Speech Sciences
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• v.12 no.3
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• pp.55-63
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• 2020

Voice conversion can be applied to various voice processing applications. It can also play an important role in data augmentation for speech recognition. The conventional method uses the architecture of voice conversion with speech synthesis, with Mel filter bank as the main parameter. Mel filter bank is well-suited for quick computation of neural networks but cannot be converted into a high-quality waveform without the aid of a vocoder. Further, it is not effective in terms of obtaining data for speech recognition. In this paper, we focus on performing voice-to-voice conversion using only the raw spectrum. We propose a deep learning model based on the transformer network, which quickly learns the voice conversion properties using an attention mechanism between source and target spectral components. The experiments were performed on TIDIGITS data, a series of numbers spoken by an English speaker. The conversion voices were evaluated for naturalness and similarity using mean opinion score (MOS) obtained from 30 participants. Our final results yielded 3.52±0.22 for naturalness and 3.89±0.19 for similarity.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.2
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• pp.172-177
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• 2013

With Brain Computer Interface (BCI) system, a person with disabled limb could use this direct brain signal like electroencephalography (EEG) to control a device such as the artifact arm. The precise force control for the artifact arm is necessary for this artificial limb system. To understand the relationship between control EEG signal and the gripping force of hands, We proposed a study by measuring EEG changes of three grades (25%, 50%, 75%) of hand grip MVC (Maximal Voluntary Contract). The acquired EEG signal was filtered to obtain power of three wave bands (alpha, beta, gamma) by using fast fourier transformation (FFT) and computed power spectrum. Then the power spectrum of three bands (alpha, beta and gamma) of three classes (MVC 25%, 50%, 75%) was classified by using PCA (Principal Component Analysis) and LDA (Linear Discriminant Analysis). The result showed that the power spectrum of EEG is increased at MVC 75% more than MVC 25%, and the correct classification rate was 52.03% for left hand and 77.7% for right hand.

• Journal of IKEEE
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• v.18 no.2
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• pp.220-227
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• 2014

This paper presents a control method of Single-Inductor Dual-Output DC-DC Converter using Common mode feedback and differential feedback loops. To generate duty used for differential mode feedback loop, this paper propose relative sawtooth circuit using current divider circuit which makes ramp signal with variable dead-time. Two outputs of the Single-Inductor Dual-Output DC-DC Converter are specified for 2.8 V and 4.2 V with input voltage 2.5 V. The maximum conversion efficiency of designed SIDO DC-DC Converter is 95% at total output power of 539mW. Cross regulations of Boost1 and Boost2 are 3.57% and 4% each, when increasing twice times output current.

• Journal of IKEEE
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• v.24 no.1
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• pp.19-24
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• 2020

This paper presents a 3-level, 2-level SVPWM technique with 100 kHz switching using Verilog HDL, one of the languages of FPGA. In the case of IGBT devices mainly used in inverters, they have a switching frequency around 20kHz. Recent research and development of next-generation power semiconductor devices such as GAN has enabled switching of more than 100kHz, which can miniaturize power converters, and apply various new algorithms due to the injection of harmonics. In the existing system using the IGBT, the control using the DSP is common, but the controller configuration for 100 kHz switching requires the use of FPGA. Therefore, this paper explains the theory and implementation of SVPWM applied to two-level and three-level inverters using FPGAs and verifies the performance through the output waveform. In addition, this paper implements 3-level SVPWM by using only one carrier instead of using two carriers in the conventional method.

• Journal of the Korean Geotechnical Society
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• v.30 no.3
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• pp.17-28
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• 2014

In this study, the seepage behavior has been analyzed, which is the most important in determining the stability of the embankment. Large-scale embankment of weathered granite has been installed and TDR (time domain reflectory) sensors were used to detect the seepage lines. The TDR graphs could be separated into 3 sections, which are initial, unsaturated and saturated zones. TDR sensor can detect seepage line more easily than point sensor without analysis. Comparisons of the results of numerical analyses and the TDR sensors showed differences at water level rising condition, and then Comparisons of the results generally showed good agreement at another condition.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.3
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• pp.45-52
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• 2006

In this paper, we analyze on the effect of LCR filter to mitigate transient overvoltage on the high voltage induction motor fed by H-bridge cascaded 7-level inverter. The switching surge voltage that it was occurred in inverter appears transient overvoltage at the motor input terminal. the transient overvoltage becomes the major cause to occur the insulation failure by serious voltage stress in the stator winding of high voltage induction motor. The effect of transient overvoltage appears more serious in high voltage induction motor than low voltage induction motor. We selected LCR filter for reduction of the transient overvoltage. Consequently, we demonstrated that the LCR filter connected to the invertor output terminals greatly reduces the transient voltage stress and ringing. The results of simulation show the suppression of transient overvoltage at the motor end of a long cable. using EMTP

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.1
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• pp.132-140
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• 2008

Power system of Jeju is interconnected to the mainland using HVDC and that is also interconnected two wind farms. Control of Jeju power system will be difficult if HVDC is disconnected or HVDC is overhauled under large scale wind farms interconnected. We measured and analysed the power quality of two substation and two wind farms to assess that wind farms and HVDC overhaul have an effect on Jeju system or not during the HVDC overhaul. We found that the frequency of Jeju system is very unstable and the voltage distortion excess the limitation. Harmonic currents of wind farms flew into Jeju system in proportion to the power of wind turbine. And the voltage of nearby distribution line was distorted by power of wind turbine when the amount is more that 3,000[kW].