• Transactions on Electrical and Electronic Materials
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• v.12 no.4
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• pp.152-155
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• 2011

This paper presents a comparative analysis on step and the touch voltages generated by either a sine and a ring wave voltage generator; this analysis was done as a basic study in order to develop a small and lightweight ground meter. A ring wave generator using pulsed power technology was fabricated; an experimental grounding system specified in Institute of Electrical and Electronics Engineers standards 80 and 81 was installed. The step and the touch voltages, which were measured using comparable a sine and a ring waves in terms of magnitude and frequency, were equal. Using pulsed power technology, the weight of the fabricated ring wave generator could be reduced to one-fifth of that of a sine wave generator. Consequently, if a ground meter adopts the ring wave instead of a sine wave, it will be possible to reduce the weight of a ground meter and improve the efficiency of measurement.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.12
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• pp.4889-4908
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• 2020

With the advances in Information Technology (IT), users can download or stream copyrighted works, such as videos, music, and webtoons, at their convenience. Thus, the frequency of use of copyrighted works has increased. Consequently, the number of unauthorized copies and sharing of copyrighted works has also increased. Monitoring is being conducted on sites suspected of conducting copyright infringement activities to reduce copyright holders' damage due to unauthorized sharing of copyrighted works. However, suspected copyright infringement sites respond by changing their domains or blocking access requests. Although research has been conducted for improving the effectiveness of suspected copyright infringement site detection by defining suspected copyright infringement sites' response techniques as a lifecycle step, there is a paucity of studies on automation techniques for lifecycle detection. This has reduced the accuracy of lifecycle step detection on suspected copyright infringement sites, which change domains and lifecycle steps in a short period of time. Thus, in this paper, an automated detection technique for suspected copyright infringement sites is proposed for efficient detection and response to suspected copyright infringement sites. Using our proposed technique, the response to each lifecycle step can be effectively conducted by automatically detecting the lifecycle step.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.744-747
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• 1991

In this paper, the design of optimal feedforward regulators with the optimal feedforward filters for improving power frequency deviations in an interconnected system, using a polynominal LQG approach, is proposed. The performances of the regulators with the optimal feedforward filters were compared with the frequency feedback regulator only in power system by simulation. The results show that the optimal feedforward regulators reduce the power frequency standard deviation by 25%-60% in the white noise load and the peak deviation in the step load by 8%-27%.

• Journal of Korean Institute of Industrial Engineers
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• v.41 no.4
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• pp.381-388
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• 2015

The rapid growth of the World Wide Web and online information services has generated and made accessible a huge number of text documents. To analyze texts, selecting important keywords is an essential step. In this paper, we propose a feature selection method that combines a term frequency-inverse document frequency technique and symmetrical conditional probability. The proposed method can identify features with N-gram, the sequential multiword. The effectiveness of the proposed method is demonstrated through a real text data from the machine learning repository, University of California, Irvine.

• The Journal of the Acoustical Society of Korea
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• v.18 no.4
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• pp.3-10
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• 1999

Investigations of temperature differences between both cnds of thermoacoustic exchanger generated by acoustic heat transport have been carried out as a function of the position of TAC(Thermo-Acoustic Couple)[1] in a 68-cm-long duct. Fixed with the electric power at 50W, measurements were compared with the theory changing the frequency from 150Hz to 300Hz with 10Hz step. The frequency-position dependent distribution of temperature difference corresponding to the Q-values was obtained with the numerical simulation. Through this distribution, the optimum position of the thermoacoustic exchanger and the optimum driving frequency can be determined.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1578-1582
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• 1998

The ground potential rise generated by the switching surge or lightning stroke may be dangerous to personnel and cause damage to electronic control parts. For a first step to the transient performance analysis. high frequency impedances of grounding grids have been calculated and discussed. Grounding grids include 7 square grids from $10m{\times}10m$ to $80m{\times}80m$. The high frequency current was injected into the center and a corner of the grounding grid. The calculation results indicate that the impedance of the grounding grid is significantly influenced by frequency and the point of injection of the current. and the effective radius of a large grounding grid may be represented in $15{\sim}20m$.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.1
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• pp.27-32
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• 2018

In this paper, we developed an algorithm to detect arc of PV power plant through frequency analysis. For arc detection based on frequency analysis, the filter should be designed to emphasize the difference between the arc state and the normal state. Therefore, in this paper, we analyzed the arc detection performance according to various filter structures. The arc detection algorithm developed in this paper extracts the filtering signal on current by using various filters and then calculates the frequency components and total energy using the FFT. In the final step, the arc is detected using the calculated energy magnitude. In order to verify the performance of the proposed arc detection algorithm, experiments were conducted on 51 kW solar inverters connected to power line. Through various experiments, it was confirmed that the proposed method effectively detects the arc.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.249-256
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• 2004

KRISO/KORDI is currently developing a deep-sea unmanned underwater vehicle (UUV) system which is composed of a launcher, an ROV, and an AUV. Two USBL acoustic positioning systems will be used for UUV's navigation. One is for the deep sea positioning of all three vehicles and the other is for AUV's guidance to the docking device on the launcher. In order to increase the position accuracy MFSK(Multiple Frequency Shift Keying) broadband signal will be used. As the first step to the implementation of a USBL system, this paper studies USBL positioning algorithm using MFSK signals. Firstly, the characteristics of MFSK signal is described with various MFSK parameters: number of frequencies, frequency step, center frequency, and pulse length. Time and phase delays between two received signals are estimated by using cross-correlation and cross-spectrum methods. Finally an USBL positioning algorithm is derived by converting the delays to difference of distances and applying trigonometry. The simulation results show that the position accuracy is improved highly when both cross-correlation and cross-spectrum of MFSK signals are used simultaneously.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.11
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• pp.1178-1185
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• 2009

In this paper, a wideband ultra-high speed & high purity discrete frequency synthesizer having minimum 2.5 MHz step size was proposed. To achieve fast and wideband operation, discrete frequencies were synthesized by mixing of 3 different pre-synthesized 16 frequencies made from fixed PLL and frequency dividers. Frequencies with discrete 2.5 MHz step were produced in 710~1,610 MHz. The measured hopping response time was 350 nsec average, output level was 21.5 dBm average with 2.65 dB flatness, spurious and harmonics level were suppressed below -60 dBc, and phase noise was -94 dBc/Hz@100 Hz. Also, a new measurement method for synthesizer response time was described.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.4
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• pp.247-252
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• 2009

This paper presents an Integer-N phase-locked loop (PLL) frequency synthesizer using a novel prescaler based on a charge pump and clock triggering circuit. A quadrature VCO has been designed for the 900MHz UHF RFID application. In this circuit, a voltage-controlled oscillator(VCO), a novel Prescaler, phase frequency detector(PFD), charge pump(CP), and analog lock detector(ALD) have been integrated with 0.35-${\mu}m$CMOS process. The integer divider has been developed with a verilog-HDL module, and the PLL mixed mode simulation has been performed with Spectre-Verilog co-simulator. The sweep range of VCO is designed from 828 to 960 MHz and the VCO generates four phase quadrature signals. The simulation results show that the phase noise of VCO is -102dBc/Hz at 100 KHz offset frequency, and the maximum lock-in time is about 4us with 32MHz step change (from 896 to 928 MHz).