• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.3
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• pp.71-78
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• 2011

This paper propose image steganalysis scheme based on independence between parent and child subband on the multi-layer wavelet domain. The proposed method decompose cover and stego images into 12 subbands by applying 3-level Haar UWT(Undecimated Wavelet Transform), analyze statistical independency between parent and child subband. Because this independency is appeared more difference in stego image than in cover image, we can use it as feature to differenciate between cover and stego image. Therefore we extract 72D features by calculation first 3 order statistical moments from joint characteristic function between parent and child subband. Multi-layer perceptron(MLP) is applied as classifier to discriminate between cover and stego image. We test the performance of proposed scheme over various embedding rates by the LSB, SS, BSS embedding method. The proposed scheme outperforms the previous schemes in detection rate to existence of hidden message as well as exactness of discrimination.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.2
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• pp.94-101
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• 2012

This paper proposes an improved image steganalysis scheme to raise the detection rate of stego images out of cover images. To improve the detection rate of stego image in the steganalysis, tiny variation caused by data hiding should be amplified. For this, we extract feature vectors of cover image and stego image by two steps. First, we separate image into upper 4 bit subimage and lower 4 bit subimage. As a result, stego noise is expanded more than two times. We decompose separated subimages into twelve subbands by applying 3-level Haar wavelet transform and calculate co-occurrence probabilities of two different subbands in the same scale. Since co-occurrence probability of the two wavelet subbands is affected by data hiding, it can be used as a feature to differentiate cover images and stego images. The extracted feature vectors are used as the input to the multilayer perceptron(MLP) classifier to distinguish between cover and stego images. We test the performance of the proposed scheme over various embedding rates by the LSB, S-tool, COX's SS, and F5 embedding method. The proposed scheme outperforms the previous schemes in detection rate to existence of hidden message as well as exactness of discrimination.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.07a
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• pp.110-112
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• 2015

지상파 디지털멀티미디어방송(T-DMB)을 이용하여 국지적인 재난경보 방송을 실시하고 있지만 산간오지 등과 같은 전파 음영 지역에는 시설 투자의 한계로 서비스가 제한되고 있는 실정이다. 무선 마을 방송 시스템은 ISM 밴드 주파수를 사용하고 있으며 마을 방송용으로 주파수를 제한하여 간섭영향이 상대적으로 적은 장점을 갖는다. 본 논문에서는 T-DMB 재난 방송을 기존 무선 마을 방송 시스템의 장점을 이용하여 산간오지의 댁내까지 방송 가능한 시스템을 제안하였다. 재난 발생시 T-DMB 특수 수신기의 재난 방송 출력 신호를 무선 마을 방송 송신기와 복수의 댁내 무선 수신기를 통하여 방송 가능한 구조이며 T-DMB 수신기와 무선 방송 송신기간에는 접점 인터페이스를 통하여 정확한 시퀀스 제어가 필요하다. 무선 마을 방송 시스템은 UHF 대역의 ISM 밴드 무선 주파수를 이용하여 오지산간 지역의 부락에 적합한 특성을 갖고 있다. 장애물로 인한 장거리 전송의 한계는 무선 중계기를 이용하여 커버리지를 확장 가능하다. 따라서, 본 논문에서는 T-DMB 재난 방송을 재송신하는 수단으로 ISM 밴드와 연동할 경우 방송 음영지역 해소 및 재난 방송 수신율이 개선되어 국지적 재난에 대한 대국민 인명과 재산보호에 기여할 것으로 판단된다.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.834-838
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• 2003

Vibration of turbine is concerned with array of last moving blade at lower pressure turbine. When last moving blade at lower pressure turbine was replaced, we must consider mass unbalance problems of blades. If mass unbalance happened at rotor, it is impossible to operate turbine. In this paper, we have how to minimize the mass unbalance problems of last moving blade at lower pressure turbine.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.7
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• pp.32-38
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• 2009

In this paper, we consider the overlaid system of single frequency network broadcast service and cellular-based unicast data service. In general, broadcast service and unicast data service were considered as a separate services so that different frequency resources have been allocated for each. As the frequency resource get more expensive, however, there were some efforts to provide both the broadcast and unicast service over the same frequency resource by employing the so-called superposition coding. In fact, such an service overlay system has already been accepted as a standards in 3GPP long-term evolution (LTE). In this paper, we specifically investigate such overlay system within 3GPP framework and evaluate their performance in terms of BC coverage and UC data throughput.

• Journal of Advanced Navigation Technology
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• v.20 no.1
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• pp.93-98
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• 2016

The purpose of this study is to design for MOB antenna attached on safety helmet using microstrip patch antenna. The patch antenna is fabricated in 0.2 mm FR-4 substrate with $64{\times}64mm$ size. The proposed antenna is based on a slot-ring design which cover Inmarsat (1.52 ~ 1.65 GHz) and GPS (1.575 GHz) frequency band. To obtain the optimized parameters, HFSS simulator is used, and antenna is designed by optimized parameters. After antenna was etched, SMA connector was attached to the microstrip feeding line and the result between antenna simulation and measurement was analyzed. Proposed antenna is satisfied the -10 dB bandwidth requirement while simultaneously covering the 1.53 ~ 1.65 GHz.

• Electronics and Telecommunications Trends
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• v.24 no.5
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• pp.10-19
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• 2009

본 논문에서는 통신과 방송서비스가 하나의 기기 또는 단말장치 안에서 결합되고 단말 내부에서는 디바이스의 통합에 따라 코덱의 개수를 최소화하기 위한 음성기반 오디오 융합코덱의 기술동향에 대해 기술한다. 하지만 기술적으로 완전히 태생이 다른 음성과 오디오 코덱을 진정한 의미에서 융합할 수 있는 기술적 모델과 기법은 아직 개발되지 않고 있다. 본 고에서는 이러한 시도의 일환으로 ITU-T SGl6을 중심으로 진행되고 있는 음성기반 코덱을 점진적 대역폭 확장 기술을 사용하여 광대역 음성, 슈퍼와이드 밴드 및 향후 오디오 대역까지 커버할 수 있는 임베디드 가변비트율 코덱기술을 중심으로 기술동향의 분석을 시도한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.914-923
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• 2009

Helix antennas have been widely applied to satellite TT&C, data communication and GPS receiver systems onboard military, remote sensing and communication purpose satellites. The helix antennas are known to be convenient to control impedance and radiation coverage characteristics with a maximum directivity in satellite z-axis. Waveguide horn is commonly used for radar system that needs ultra-wideband pulse for exploration ground radar and electromagnetic disability measurement etc. It has high efficiency and low reflection characteristics provided by the low-profile shape and suppressed radiation distortion. In this paper, a waveguide horn structure incorporated with helix antenna design is proposed for satellite applications that require ultra-wideband pulse radar and high rate RF data communication link to ground station over wide coverage area. The main design concern is to synthesize variable beam forming pattern based on modified horn-helix combination helicone structure such that multi-mission antenna is implemented applicable for TT&C, earth observation, high data rate transmission. Waveguide horn helps to reduce the overall antenna structure size by introduction fold type reflector connected to the tapered helix antenna. The next generation KOMPSAT satellite currently under development requires high-performance precision attitude control system. We present an initial design of a hybrid hern-helix antenna structure suitable for efficient RF communication module design of multi-purpose satellite systems.