• Current Optics and Photonics
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• 제7권5호
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• pp.529-536
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• 2023

The Morlet wavelet transform method is proposed to analyze a single interferogram with spatial carrier frequency that is captured by an optical interferometer. The method can retain low frequency components that contain the phase information of a measured optical surface, and remove high frequency disturbances by wavelet decomposition and reconstruction. The key to retrieving the phases from the low-frequency wavelet components is to extract wavelet ridges by calculating the maximum value of the wavelet transform amplitude. Afterwards, the wrapped phases can be accurately solved by multiple iterative calculations on wavelet ridges. Finally, we can reconstruct the wave-front of the measured optical element by applying two-dimensional discrete cosine transform to those wrapped phases. Morlet wavelet transform does not need to remove the spatial carrier frequency components manually in the processing of interferogram analysis, but the step is necessary in the Fourier transform algorithm. So, the Morlet wavelet simplifies the process of the analysis of interference fringe patterns compared to Fourier transform. Consequently, wavelet transform is more suitable for automated programming analysis of interference fringes and avoiding the introduction of additional errors compared with Fourier transform.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2002년도 춘계학술대회논문집
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• pp.213-217
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• 2002

Recently the subject of "wavelet analysis" has be drawn by both mathematical and engineering application fields such as Signal Processing, Compression/Decomposition, Wavelet-Neural Network, Statistics and etc. Even though its similar to courier analysis, wavelet is a versatile tool with much mathematical content and great potential for applications. Especially, wavelet transform uses localizable various mother wavelet functions in time-frequency domain. Therefore, wavelet transform has good time-analysis ability for high frequency component, and has good frequency-analysis ability for low frequency component. Using the discriminative ability is more easy method than other conventional techniques. In this paper, Morlet wavelet transform was applied to discriminate the kind of line fault by acquired data from real power transformation network. The experimental result presented that Morlet wavelet transform is easier, and more useful method than the FFW (Fast courier Transform).ransform).

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.173-180
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• 2002

This paper presents a signal processing procedure to detect damage locations of frame structures by using continuous wavelet transform. Morlet wavelet is used as a mother wavelet in wavelet transform. Wavelet transform has the characteristics that allows the use of long time intervals at more precise low-frequency information, and shorter regions at high-frequency information. By this wavelet transform characteristics, Morlet wavelet may be used to identify the locations of damages in the structures. The numerical case studies show that this method can be applied to detect the damage location under a controlled sweeping load.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 춘계 학술발표회 논문집
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• pp.143-150
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• 2002

This paper presents the application of continuous wavelet transform for determination of dynamic parameters of continuous beam subjected to moving load. Morlet wavelet is used as mother wavelet in wavelet transform. Dynamic parameters are estimated from the magnitudes and arguments of the wavelet coefficients obtained by wavelet transforming the response time histories of joints on the beam. This study shows that the estimated parameters such as natural frequencies, dmping ratios and mode shapes are to be well-compared with those of the finite element analysis.

• Journal of Mechanical Science and Technology
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• 제15권5호
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• pp.535-543
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• 2001

This paper presents the ride comfort analysis of a vehicle based on wavelet transform. Traditionally, the objective evaluation of impact harshness is based on the vibration dose value (VDV) and frequency weighting method. These methods do not consider the damping effect of the suspension system of a vehicle. In this paper, the damping is estimated using wavelet transform based on Morlet mother wavelet and its effect is considered for the subjective evaluation of impact harshness of a car.

• 조명전기설비학회논문지
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• 제21권3호
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• pp.75-81
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• 2007

Wavelet 변환은 신호를 분석하고 해석하는데 효과적인 수학적 도구로 알려져 여러 응용분야에서 다양한 연구가 진행되고 있다. Wavelet 변환은 Fourier 변환과 유사한 측면도 있으나, Fourier 변환과는 달리 다양한 Wavelet 모함수를 사용함으로써 해석 속도가 빠르고, 시간-주파수 영역에서 국재화가 가능하다는 특징을 가지고 있을뿐만 아니라 고주파 성분에 대해선 시간 분해능이 높고, 저주파 성분에 대해선 주파수 분해능이 좋다는 장점을 가지고 있으므로, 전력계통의 다양한 고장 전류의 판별에 적극 이용할 수 있을 것으로 생각된다. 본 논문에서는 고장 전류의 특성을 해석하는데 용이한 복소형의 Morlet Wavelet 모함수를 사용하여 전력계통의 고장기록장치로부터 얻어지는 선로의 전류 데이터를 Wavelet 변환하였고, 이로부터 다양한 고장 모드를 판별할 수 있었다. 실험 결과 Wavelet 변환을 이용하여 선로의 고장 모드를 판별하는 것이 기존의 고속 Fourier 변환을 이용하는 것보다 특징점 고찰에 더욱 유용하다는 것을 확인할 수 있었다.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2001년도 춘계학술대회 학술발표 논문집
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• pp.109-112
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• 2001

Recently, the subject of \"wavelet analysis\" has drawn much attention from both mathematical and engineering application fields such as Signal Processing, Compression/Decomposition, Statistics and ets. Analogous to Fourier analysis, wavelets is a versatile tool with very rich mathematical content and great potential for applications. Specially, wavelet transform uses localizable various mother wavelet functions in time-frequency domain. In this paper, discrimination analyses of acquired electrical current signals for each and mixed loads were tried by using Morlet wavelet transform. Their representative loads were classified as TV, DRY(Dryer), REF(Refrigerate), and FL(Fluorescent Lamp).

• 한국구조물진단유지관리공학회 논문집
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• 제9권2호
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• pp.129-136
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• 2005

교량의 안전진단 과정에서 안전성 평가를 위해 전면교통통제 하에 차량재하시험이 일반적으로 실시된다. 교통통제의 단점을 개선시킨 최근에 제안된 의사정적재하시험에서는 계측된 시간이력 데이터 중 자유진동 부분을 퓨리에변환시켜 고유진동수를 구한다. 이렇게 구해진 고유진동수에는 분석기법에 따른 오차가 포함되며, 자유진동 데이터의 획득에도 다소 애로사항이 따른다. 이 연구에서는 Morlet wavelet를 모웨이블렛으로 하는 웨이블렛변환을 의사정적재하시험으로 계측한 데이터에 적용하여 구한 고유진동수와 감쇠율이 신뢰성을 가지며, 이 분석기법이 의사정적재하시험에 의한 차량재하시험의 자료 분석에 적용 가능하고 타당성이 있음을 보인다.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2002년도 추계학술대회 및 정기총회
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• pp.427-430
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• 2002

Recently the subject of "wavelet analysis" has be drawn by both mathematical and engineering application fields such as Signal Processing, Compression/Decomposition, Wavelet-Neural Network, Statistics and etc. Even though its similar to Fourier analysis, wavelet is a versatile tool with much mathematical content and great potential for applications. Especially, wavelet transform uses localizable various mother wavelet functions in time-frequency domain. Therefore, wavelet transform has good time-analysis ability for high frequency component, and has good frequency-analysis ability for low frequency component. Using the discriminative ability is more easy method than other conventional techniques. In this paper, Morlet wavelet transform was applied to discriminate the kind of line fault by acquired data from real power transformation network. The experimental result presented that Morlet wavelet transform is easier,and more useful method than the FFT (Fast Fourier Transform).

• Wind and Structures
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• 제20권5호
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• pp.661-682
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• 2015

This study investigates the use of time-frequency coherence analysis for detecting and evaluating coherent "structures" of surface pressures and wind turbulence components, simultaneously on the time-frequency plane. The continuous wavelet transform-based coherence is employed in this time-frequency examination since it enables multi-resolution analysis of non-stationary signals. The wavelet coherence quantity is used to identify highly coherent "events" and the "coherent structure" of both wind turbulence components and surface pressures on rectangular prisms, which are measured experimentally. The study also examines, by proposing a "modified" complex Morlet wavelet function, the influence of the time-frequency resolution and wavelet parameters (i.e., central frequency and bandwidth) on the wavelet coherence of the surface pressures. It is found that the time-frequency resolution may significantly affect the accuracy of the time-frequency coherence; the selection of the central frequency in the modified complex Morlet wavelet is the key parameter for the time-frequency resolution analysis. Furthermore, the concepts of time-averaged wavelet coherence and wavelet coherence ridge are used to better investigate the time-frequency coherence, the coherently dominant events and the time-varying coherence distribution. Experimental data derived from physical measurements of turbulent flow and surface pressures on rectangular prisms with slenderness ratios B/D=1:1 and B/D=5:1, are analyzed.