• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.6
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• pp.937-942
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• 2002

The use of digital imaging technique and digital contents based on internet has grown rapidly for last several years, and the needs of digital image protection become more important. For the purpose of copyright protection on digital image, the verification of authentication techniques like content authentication, ownership authentication, illegal copy and etc are needed. Digital watermarking, the invisible encryption technique to insert digital watermark into image the sophisticated perceptual information should be used for providing transparency and robustness of images on watermarking process. In this paper, we implement the algorithm for preventing forged attack, ownership protection and authentication by transforming the wavelet algorithms in frequency domain in terms of human visual system.

• Proceedings of the KIEE Conference
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• 2004.05b
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• pp.227-230
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• 2004

The Co-Gen System which maximize energy efficiency was installed at the industrial plants at the initial stage. However Small Scale Co-Gen System was expanded even to the general end-users such as housing and building owing to ESCO business recently. For this SSC, inter-connected operation to the utility is desirable due to voltage and frequency fluctuation following to unbalance between power output and load. Then voltage unbalance with utility system, frequency, increase of short circuit capacity, reclosing, and ALTS etc. should be fully considered for the inter-connected operation. Voltage variation, protection coordination, Co-Generators single running, and short circuit capacity should also be solved. For Con-Gen users, the several protection relays are recommended to install at the user's main incoming panel by the guide lines and/or instructions of the interconnected utility Then user's main CB(Circuit Breaker) have the chance to be tripped by some of this recommended relays and users have to undergo the unexpected blackout. So the circuit breaker trip schemes targeted to trip with these protection relays are reconsidered and the study result is hereunder proposed.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.8
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• pp.426-432
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• 2004

This paper presents a systematic approach of measurement, modeling and analysis of grounding system impedance in the field of lightning protection system and intelligent power equipments. The measurement and analysis system of ground impedance is based on a computer aided technique. The magnitude and phase of ground impedance were determined by the novel measurement and analysis using the revised fall-of-potential method. The ground impedances of the ground rod of 50 m long are considerably dependent on the frequency. The ground impedance is mainly resistive in the frequency range of 3-20 kHz. At higher frequencies, the reactive components of the ground impedances are no longer negligible and the inductance of the ground rod was found to be the core factor deciding the ground impedance. Although the steady-state ground resistance of the ground rod of 50 m was less than that of the ground rod of 10 m, the ground impedances of the ground rod of 50 m over the frequency range of more than 60 kHz were much greater than those of the ground rod of 10 m. Furthermore, the equivalent circuit model based on the measured data was proposed. and the calculated results were in approximately agreement with the measured data.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.237-242
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• 2017

This paper presents development of the transponder system which provides an accurate train position, especially for supporting 400km/h high speed train. Here, we analyzed an operating frequency band of the transponder system which can be interoperable with the Eurobalise system already installed in Korea railroad as to be used for the automatic train protection (ATP). By investigating the power frequency band and its data frequency band of the transponder system, we presents the adoptable frequency band for the developed transponder system. Additionally, through the real testbed using HEMU-430X, we evaluate its performance requirement and shows interoperable operation with the Eurobalise system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.139-147
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• 2006

This paper suggests an efficient method of protection ratio calculation and shows some results applicable to frequency coordination in microwave(M/W) relay system networks, and the net filter discrimination(NFD) associated with Tx spectrum mask and overall Rx filter characteristics has been examined to obtain the adjacent channel protection ratio. The protection ratio comprises several factors such as C/N of modulation scheme, noise-to-interference ratio, multiple interference allowance, fade margins of multi-path and rain attenuation, and NFD. According to computed results for 6.7 GHz, 64-QAM, and 60 km at BER $10^{-6}$, fade margin and co-channel protection ratio are 41.1 and 75.2 dB, respectively. NFD for channel bandwidth of 40 MHz reveals 28.9 dB at the first adjacent channel, which results in adjacent channel protection ratio of 46.3 dB. In addition, NFD and protection ratio for different systems with channel bandwidth 20 and 40 MHz have been investigated to be used for actual M/W networks. The proposed method provides some merits of an easy calculation, systematic extension, and applying the same concept to frequency coordination in millimeter wave relay system networks.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.144-146
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• 2007

High frequency voltage signal injection have been widely used but they have some problems like over current protection. High frequency current signal injection and feedback control are more stable than voltage signal injection. In this paper, high frequency current controller for self-sensing and parameter estimation of induction motors is presented.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2199-2200
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• 2006

Reliable frequency estimation is important for active power control, load shedding and generator protection. Thereby, frequency estimation is researched and some algorithms is proposed. This paper analyzed strength and weakness of each algorithms through comparative analysis of frequency estimation. Used algorithms are Zero Crossing detection, Discrete Fourier Transformation, Least Error Squares.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.567-568
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• 2006

Reliable frequency estimation is important for active power control, load shedding and generator protection. Thereby, frequency estimation is researched and some algorithms is proposed. This paper analyzed strength and weakness of each algorithms through comparative analysis of frequency estimation. Used algorithms are Zero Crossing detection, Discrete Fourier Transformation, Least Error Squares.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1233-1234
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• 2006

Reliable frequency estimation is important for active power control, load shedding and generator protection. Thereby, frequency estimation is researched and some algorithms is proposed. This paper analyzed strength and weakness of each algorithms through comparative analysis of frequency estimation. Used algorithms are Zero Crossing detection, Discrete Fourier Transformation, Least Error Squares.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1693-1694
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• 2006

Reliable frequency estimation is important for active power control, load shedding and generator protection. Thereby, frequency estimation is researched and some algorithms is proposed. This paper analyzed strength and weakness of each algorithms through comparative analysis of frequency estimation. Used algorithms are Zero Crossing detection, Discrete Fourier Transformation, Least Error Squares.