• 한국통신학회논문지
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• 제21권6호
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• pp.1425-1429
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• 1996

누락펄스가 발생할 시 PRI 분석을 위한 전형적인 sequence search 알고리즘은 harmonic 문제를 발생시킨다. 본 논문에서 이러한 harmonic 문제를 해결할 수 있는 PRI 분석 알고리즘을 제안한다. 분석해야 할 전체 PRI 범위를 harmonic이 없도록 subband 로 나눈 후, sequence search를 forward 및 backward로 행한다. 전형적인 sequence search 알고리즘에 비하여 제안한 알고리즘의 성능이 증대된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(4)
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• pp.85-88
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• 2002

In this paper, the proposed watermark algorithm is based on energy distribution of the subband coefficients in the frequency domain and edge of the original image in the spacial domain. Out of these information, the KeyMap which decides the embedded position of watermark is produced. And then the binary watermark is embedded into the wavelet coefficient of LL3 subband using KeyMap and LFSR(Linear Feedback Shift Register).

• 한국통신학회논문지
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• 제18권6호
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• pp.895-906
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• 1993

본 논문에서는 영상의 대역분할 부호화를 위한 다중비트율 트리구조 벡터양자화를 제안하였다. 영상의 대역분할은 원영상을 특정 대역과 방향성을 갖는 대역성분들로 분리하므로, 대역분할을 거친 각 대역성분을 학습영상으로 사용하여 다중비트율 트리구조 벡터양자화기를 설계하였다. 대역분할을 거친 각 대역성분에 대한 최적비트할당은 원하는 비트율과 왜곡을 갖는 다중 비트율 트리구조 벡터양자화기의 전정서브트리를 선택하는 문제로 귀착된다.

• ETRI Journal
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• 제24권4호
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• pp.270-279
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• 2002

We present a self-consistent numerical method for calculating the conduction-band profile and subband structure of AlGaN/GaN single heterojunctions. The subband calculations take into account the piezoelectric and spontaneous polarization effect and the Hartree and exchange-correlation interaction. We calculate the dependence of electron sheet concentration and subband energies on various structural parameters, such as the width and Al mole fraction of AlGaN, the density of donor impurities in AlGaN, and the density of acceptor impurities in GaN, as well as the electron temperature. The electron sheet concentration was sensitively dependent on the Al mole fraction and width of the AlGaN layer and the doping density of donor impurities in the AlGaN. The calculated results of electron sheet concentration as a function of the Al mole fraction are in excellent agreement with some experimental data available in the literature.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(4)
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• pp.7-10
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• 2000

There are many Problems such as low detection ratio, velocity and increase of false hit ratio on the detection of gradual scene changes with the previous shot transition detection algorithms. In this paper, we Propose an improved dissolve detection method using color information on low-frequency subband and edge elements on high-frequency subband. The Possible dissolve transition are found by analyzing the edge change ratio in the high-frequency subband with edge elements of each direction. Using the double chromatic difference on the lowest frequency subband, we have the improvement of the dissolve detection ratio. The simulation results show that the performance of the proposed algorithm is better than the conventional one for dissolve detection on a diverse set of uncompressed video sequences.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(4)
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• pp.230-233
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• 2000

In this paper, we proposed a wavelet-based digital watermarking algorithm using human visual system and subband-adaptive threshold. After the original image is transformed using discrete wavelet transform(DWT), the perceptually significant coefficients of the each subband excluding the lowest level subbands are utilized to embed the watermark. To select perceptually significant coefficients, we use subband-adaptive threshold. For the selected coefficients, the watermark is embedded by rising HVS. We tested the performance of the proposed algorithm compared with conventional watermarking algorithm by computer simulation. The experimental results show that the proposed algorithm is superior to the conventional algorithm.

• The Journal of the Acoustical Society of Korea
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• 제15권2E호
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• pp.24-32
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• 1996

A rigorous theory for modeling, analysis, optimum nonseparable filter bank in multidimensional M-band quantized subband codec are developed in this paper. Each pdf-optimized quantizer is modeled by a nonlinear gain-plus-additive uncorrelated noise and embedded into the subband structure. We then decompose the analysis/synthesis filter banks into their polyphase components and shift the down-and up-samplers to the right and left of the analysis/synthesis polyphase matrices respectively. Focusing on the slow clock rate signal between the samplers, we derive the exact expression for the output mean square quantization error by using spatial-invariant analysis. We show that this error can be represented by two uncorrelated components : a distortion component due to the quantizer gain, and a random noise component due to fictitious uncorrelated noise at the uantizer. This mean square error is then minimized subject to perfect reconstruction (PR) constraints and the total bit allocation for the entire filter bank. The algorithm gives filter coefficients and subband bit allocations. Numerical design example for the optimum nonseparable orthonormal filter bank is given with a quincunx subsampling lattice.

• 한국음향학회지
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• 제27권5호
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• pp.239-243
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• 2008

본 논문에서는 스펙트럼의 주파수 및 시간 방향의 특성을 결합한 오디오 인식 방법을 제안하였다. 특히 스펙트럼의 형태를 모사하기 위해 부밴드로 나누고 주파수와 시간 방향의 무게중심을 구하고 정규화하여 인식기에 사용하였다. 무게중심 값은 스펙트럼의 형태적 특징을 잘 나타내면서도 간결하여 인식기에 사용되는 특징 DB의 크기를 줄여줄 수 있는 장점이 있다. 수 천곡 규모의 오디오에 대해서, 부밴드 스펙트럼의 주파수와 시간 방향 무게중심의 인식 성능을 비교하였다. 실험 결과 주파수와 시간 방향 특징을 결합하면 상보적으로 인식 성능을 높일 수 있음을 발견하고, 선형 변환을 이용하여 주파수와 시간 방향 특징을 하나로 결합하는 방법을 제안하였다.

• 전기학회논문지
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• 제59권3호
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• pp.669-673
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• 2010

This paper proposes a new active noise control (ANC) system for canceling broadband noise. The proposed ANC system is designed based on the multiband-structured delayless subband adaptive filter (MDSAF), which has advantages of fast-convergence speed and higher noise reduction performance by eliminating the aliasing and band-edge effects caused by band-partitioning. The simulation results show that the proposed ANC system has faster convergence speed as compared to the conventional ANC systems and effectively reduces the wideband noise.

• 한국통신학회논문지
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• 제22권11호
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• pp.2375-2380
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• 1997

The need for developing effective coding techniques for various multimedia services is increasing in order to meet the demand for image data. In this paper, a zeroblock coding algorithm is proposed for progressive transmission of images. The zeroblock coding algorithm is constructed as an embedded coding so that the encoding and decoding process can be terminated at any point and allowing reasonable image quality. Some features of zeroblock coding algorithm are 1) coding of subband images by prediction of the insignificance of blocks across subband leels, 2) aset of sate transition rules for representing the significance map of blocks, and 3) block coding by vector quantization using a multiband codebook consisting of several subcodebooks dedicated for each subband at a given threshold.