• 전자공학회논문지B
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• 제32B권11호
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• pp.1383-1392
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• 1995

In this paper, the method to incorporate TCVQ(Trellis Copded Vector Quantizer) into the encoding of the wavelet trans formed(WT) image followed by a variable length coding(VLC) or an entropy coding(EC) is considered. By WT, an original image is separated into 10 bands with various resolutions and directional components. TCVQ used to compress these WT coefficients is a finite state machine that encodes the input source on the basis of the current input and the current state. Wavelet basis used in this paper is designed by orthogonal spline function. A modified set partitioning algorithm to Wang's is also presented. A simple modification to Wang's algorithm gives a highly time-efficient result. Proposed WT-TCVQ encoder shows a very competitive result, giving 37.46dB in PSNR at 1.002bpp when encoding 512$\times$512 LENA.

• 한국통신학회논문지
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• 제25권3B호
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• pp.557-564
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• 2000

This paper presents a watermarking algorithm for embedding visually recognizable pattern (Mark, Logo, Symbol, stamping or signature) into the image. first, the color image(RGB model)is transformed in YCbCr model and then the Y component is transformed into 3-level wavelet transform. Next, the values are assembled with pattern watermark. PN(pseudo noise) code at spread spectrum communication method and mutilevel watermark weights. This values are inserted into discrete wavelet domain. In our scheme, new calculating method is designed to calculate wavelet transform with integer value in considering the quantization error. and we used the color conversion with fixed-point arithmetic to be easy to make the hardware hereafter. Also, we made the new solution using mutilevel threshold to robust to common signal distortions and malicious attack, and to enhance quality of image in considering the human visual system. the experimental results showed that the proposed watermarking algorithm was superior to other similar water marking algorithm. We showed what it was robust to common signal processing and geometric transform such as brightness. contrast, filtering. scaling. JPEG lossy compression and geometric deformation.

• 대한전기학회논문지:전력기술부문A
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• 제50권5호
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• pp.211-217
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• 2001

This paper proposes a new fault detection criterion logic that extracts the features of magnetizing inrush and internal faults by making use of Daubechies Wavelet Transform which analyzes distinct features. To prove the effectiveness of proposed method, the paper constructs power system model including power transformer by using EMTP, and collects data through simulation using various fault inception angle and magnetizing inrush. The conclusions implemented by the C program and the Wavemenu of MATLAB Toolbos are more effective and simpler to distinguish inter-turn faults from magnetizing inrush states.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권11호
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• pp.616-621
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• 2000

This paper deals with the multiresolution analysis of wavelet transform for partial discharge(PD). Test arrangement is based on the needle-plane electrode system and applied AC high voltage. The measured PD signal was decomposed into "approximations" and "details". The approximation are the high scale, low-frequency components of the PD signal. The details are the low-scale, high frequency components. The decomposition process are iterated to 3 level, with successive approximation being decomposed in turn, so that PD signal is broken down into many lower-resolution components. Through the procedure of signal wavelet transform, signal noise extraction and signal reconstruction, the signal is analyzed to determine the magnitude of PD.

• 대한의용생체공학회:의공학회지
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• 제15권3호
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• pp.305-316
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• 1994

All physical data in the real world are nonstationary signals that have the time varying statistical characteristics. Although few algorithms suitable to process the nonstationary signals have ever been suggested, these are treated the nonstationary signals under the assumption that the nonstationary signal is a piece-wise stationary signal. Recently, statistical analysis algorithms for the nonstationary signal have concentrated so much interest. In this paper, nonstationary EMG signals are mapped onto the orthogonal wavelet transform domain so that the eigenvalue spread of its autocorrelation matrix could be more smaller than that in the time domain. Then the model in the wavelet transform domain and an algorithm to estimate the model parameters are suggested. Also, an test signal generated by a white gaussian noise and the EMG signal are identified, and the algorithm performance is considered in the sense of the mean square error and the evaluation parameters.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 춘계종합학술대회
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• pp.1017-1021
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• 2005

현대에 있어서 영상정보는 아주 큰 비중을 차지하고 있다. 따라서 이러한 영상정보를 얼마나 빨리 그리고 많이 압축 시킬 수 있는가가 핵심적인 관건이다. 본 논문에서는 공간적 압축 방식의 핵심인 DCT와 비교하여 블록킹 효과(Blocking Effect)과 없고, 우수한 압축 성능을 갖는 DWT(Discrete Wavelet Transform)알고리즘을 적용한 2차원 이산 웨이브렛 변환 필터를 설계하였다. 본 논문에서 구현한 DWT 필터는 FIR필터 방법으로 설계하였으며, Daubenchies-4 Tap을 이용하였고, 파이프라인 연산으로 승산기, 가산기를 병렬로 처리하여 고속연산을 수행하였다. 뿐만 아니라 메모리 맵핑 과정과 메모리 컨트롤 어드레스 발생기를 사용하여 메모리와 연산량을 최소화 하여 칩사이즈를 줄여 설계하였다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2000년도 가을 학술발표논문집 Vol.27 No.2 (2)
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• pp.209-211
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• 2000

SPIHT(Set Partitioning In Hierarchical Trees) 부호화 알고리즘은 EXW(Embedded Zerotree Wavelet) 부호와 알고리즘의 부호화 방법을 개선하여 압축 효율을 개선한 알고리즘이다. SPIHT 부호화 알고리즘은 웨이브렛 변환된 영상의 계수 값이 동일한 방향은 갖는 대역 사이에서 상관 관계를 갖는다는 점을 이용한다는 점에서 EZW 부호화 알고리즘과 동일하다. 그러나 zerotree의 부호화 부분에서 계수의 중요도에 따라 부분 집합으로 분할해 가는 과정과 분할된 계수들을 부호화하는 과정을 개선하였다. 이 부호화 과정에서의 significant map은 모든 threshold에 대해서 LSP(List of Insignificant Pixels), LIP(List of Insignificant), LIS(List of Insignificant Sets)의 세가지 리스트를 통하여 구하여 진다. 그리고, 전체 알고리즘은 초기화, Sorting pass, Refinement pass, 양자화 값 갱신의 네 가지 단계로 구성된다. 본 논문에서는 SPIHT 구현에 필요한 자료구조를 제안하고 SPIHT 부호화 모듈을 구현에 대하여 설명한다.

• 대한전기학회논문지:전력기술부문A
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• 제54권12호
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• pp.561-566
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• 2005

This paper introduces a compression technique for power qualify disturbance signal via discrete wavelet transform(DWT). The proposed approach is based on a previous estimation of the stationary component of power quality disturbance signal, so that it could be subtracted from the original signal in order to reduce a dynamic range of signal and generate transient events signal, which is subsequently applied to the compression technique. The compression techniques is performed through the difference signal decomposition, thresholding of wavelet coefficients, and signal reconstruction. It presents the relation between compression efficiency and threshold. It shouts that the wavelet transform leads to a power quality data compression approach with high compression efficiency, small compression error and good de-nosing effect.

• 대한전기학회논문지:전력기술부문A
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• 제50권3호
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• pp.105-111
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• 2001

The research presented in this paper focuses on a method for the detection of High Impedance Fault(HIF). The method will use the wavelet transform and neural network system. HIF on the multi-grounded three-phase four-wires primary distribution power system cannot be detected effectively by existing over current sensing devices. These paper describes the application of discrete wavelet transform to the various HIF data. These data were measured in actual 22-9kV distribution system. Wavelet transform analysis gives the frequency and time-scale information. The neural network system as a fault detector was trained to discriminate HIF from the normal status by a gradient descent method. The proposed method performed very well by proving the right state when it was applied staged fault data and normal load mimics HIF, such as arc-welder.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권1호
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• pp.25-34
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• 2003

Gas insulated switchgear(GIS) is an important equipment in a substation. It is highly desirable to measure a partial discharge(PD) in GIS which is a symptom before insulation breakdown occurs. The issue is that the PD signal is weak and sensitive to external noise. In this paper, the algorithm for detection of PD in GIS using wavelet transform is proposed. The wavelet transform provides a direct quantitative measure of spectral content, "dynamic spectrum", in the time-frequency domain. The recommended mother wavelet is 'Daubechies' wavelet. 'db4', the most commonly applied mother wavelet in the power quality analysis, can be used most properly in disturbance phenomena which occurs rapidly for a short time. Through the procedure of wavelet transform, noise extraction and reconstruction, the signal is Analyzed to determine the magnitude of PD in GIS. In experimental results, we can know that partial discharge is exactly detected in combination of Dl and D2 using wavelet transform.transform.