• Title, Summary, Keyword: Wavelet transformation

Search Result 207, Processing Time 0.047 seconds

Enhancing the Reconstruction of Acoustic Source Field Using Wavelet Transformation

  • Ko Byeongsik;Lee Seung-Yop
    • Journal of Mechanical Science and Technology
    • /
    • v.19 no.8
    • /
    • pp.1611-1620
    • /
    • 2005
  • This paper shows the use of wavelet transformation combined with inverse acoustics to reconstruct the surface velocity of a noise source. This approach uses the boundary element analysis based on the measured sound pressure at a set of field points, the Helmholtz integral equations and wavelet transformation for reconstructing the normal surface velocity field. The reconstructed field can be diverged due to the small measurement errors in the case of nearfield acoustic holography (NAH) using an inverse boundary element method. In order to avoid this instability in the inverse problem, the reconstruction process should include some form of regularization for enhancing the resolution of source images. The usual method of regularization has been the truncation of wave vectors associated with small singular values, although the order of an optimal truncation is difficult to determine. In this paper, a wavelet transformation is applied to reduce the computation time for inverse acoustics and to enhance the reconstructed vibration field. The computational speed-up is achieved, with solution time being reduced to $14.5\%$.

WAVELET-BASED FOREST AREAS CLASSIFICATION BY USING HIGH RESOLUTION IMAGERY

  • Yoon Bo-Yeol;Kim Choen
    • Proceedings of the KSRS Conference
    • /
    • /
    • pp.698-701
    • /
    • 2005
  • This paper examines that is extracted certain information in forest areas within high resolution imagery based on wavelet transformation. First of all, study areas are selected one more species distributed spots refer to forest type map. Next, study area is cut 256 x 256 pixels size because of image processing problem in large volume data. Prior to wavelet transformation, five texture parameters (contrast, dissimilarity, entropy, homogeneity, Angular Second Moment (ASM≫ calculated by using Gray Level Co-occurrence Matrix (GLCM). Five texture images are set that shifting window size is 3x3, distance .is 1 pixel, and angle is 45 degrees used. Wavelet function is selected Daubechies 4 wavelet basis functions. Result is summarized 3 points; First, Wavelet transformation images derived from contrast, dissimilarity (texture parameters) have on effect on edge elements detection and will have probability used forest road detection. Second, Wavelet fusion images derived from texture parameters and original image can apply to forest area classification because of clustering in Homogeneous forest type structure. Third, for grading evaluation in forest fire damaged area, if data fusion of established classification method, GLCM texture extraction concept and wavelet transformation technique effectively applied forest areas (also other areas), will obtain high accuracy result.

  • PDF

THE ADAPTIVE WAVELET FOR HIGH ORDER ACCURATE AND EFFICIENT COMPUTATIONAL FLUID DYNAMICS (고차정확도 및 효율적인 전산유체해석을 위한 Adaptive Wavelet)

  • Lee, Do-Hyung
    • 한국전산유체공학회:학술대회논문집
    • /
    • /
    • pp.261-265
    • /
    • 2011
  • An adaptive wavelet transformation method with high order accuracy is proposed to allow efficient and accurate flow computations. While maintaining the original numerical accuracy of a conventional solver, the scheme offers efficient numerical procedure by using only adapted dataset. The main algorithm includes 3rd order wavelet decomposition and thresholding procedure. After the wavelet transformation, 3rd order of spatial and temporal accurate high order interpolation schemes are executed only at the points of the adapted dataset. For the other points, high order of interpolation method is utilized for residual evaluation. This high order interpolation scheme with high order adaptive wavelet transformation was applied to unsteady Euler flow computations. Through these processes, both computational efficiency and numerical accuracy are validated even in case of high order accurate unsteady flow computations.

  • PDF

Chatter Detection for Improving Surface Quality of Hard Turning Process with Wavelet Transformation (Wavelet을 이용하여 하드터닝 공정에서 표면품위의 향상을 위한 채터 진단에 관한 연구)

  • 박영호;공정흥;양희남;김일해;장동영;한동철
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.28 no.1
    • /
    • pp.70-78
    • /
    • 2004
  • This paper presents study of efficiency of wavelet transformation for on-line chatter detection during hard fuming process. From comparison with other time series and statistical methods such as fast fourier transformation (FFT), Kurtosis and standard deviation (STD), wavelet transform is better than others in on-line chatter detection. With using wavelet function with pseudo frequency corresponding to chatter frequency, chatter could be detected more sensitively. And for both force signal from dynamometer and displacement signal from capacitance type cylindrical sensor (CCS), wavelet transform with DB2 function on level 4 could be well used for chatter detection in hard turning process.

Three-Dimensional Subband Coding of Video using Wavelet Packet Algorithm (웨이브릿 패킷 알고리즘을 이용한 3차원 비디오 서브밴드 코딩)

  • Chu, Hyung Suk;An, Chong Koo
    • The Transactions of the Korean Institute of Electrical Engineers D
    • /
    • v.54 no.11
    • /
    • pp.673-679
    • /
    • 2005
  • This Paper presents the 3D wavelet transformation based video compression system, which possesses the capability of progressive transmission by increasing resolution and increasing rate for multimedia applications. The 3D wavelet packet based video compression system removes the temporal correlation of the input sequences using the motion compensation filter and decomposes the spatio-temporal subband using the spatial wavelet packet transformation. The proposed system allocates the higher bit rate to the low frequency image of the 3D wavelet sequences and improves the 0.49dB PSNR performance of the reconstructed image in comparison with that of H.263. In addition to the limitation on the propagation of the motion compensation error by the 3D wavelet transformation, the proposed system progressively transmits the input sequence according to the resolution and rate scalability.

Quincunx Sampling Method for Performance Improvement of 2D High-Density Wavelet Transformation (2차원 고밀도 이산 웨이브렛 변환의 성능 향상을 위한 Quincunx 표본화 기법)

  • Lim, Joong-Hee;Shin, Jong-Hong;Jee, Inn-Ho
    • The Journal of The Institute of Internet, Broadcasting and Communication
    • /
    • v.13 no.4
    • /
    • pp.179-191
    • /
    • 2013
  • The quincunx lattice is a non-separable sampling method in image processing. It treats the different directions more homogeneously and good frequency property than the separable two dimensional schemes. The high density discrete wavelet transformation is one that expands an N point signal to M transform coefficients with M > N. In two dimensions, this transform outperforms the standard discrete wavelet transformation in terms of shift-invariant. Although the transformation utilizes more wavelets, sampling rates are high costs. This paper proposed the high density discrete wavelet transform using quincunx sampling, which is a discrete wavelet transformation that combines the high density discrete transformation and non-separable processing method, each of which has its own characteristics and advantages. Proposed wavelet transformation can service good performance in image processing fields.

Crack identification with parametric optimization of entropy & wavelet transformation

  • Wimarshana, Buddhi;Wu, Nan;Wu, Christine
    • Structural Monitoring and Maintenance
    • /
    • v.4 no.1
    • /
    • pp.33-52
    • /
    • 2017
  • A cantilever beam with a breathing crack is studied to improve the breathing crack identification sensitivity by the parametric optimization of sample entropy and wavelet transformation. Crack breathing is a special bi-linear phenomenon experienced by fatigue cracks which are under dynamic loadings. Entropy is a measure, which can quantify the complexity or irregularity in system dynamics, and hence employed to quantify the bi-linearity/irregularity of the vibration response, which is induced by the breathing phenomenon of a fatigue crack. To improve the sensitivity of entropy measurement for crack identification, wavelet transformation is merged with entropy. The crack identification is studied under different sinusoidal excitation frequencies of the cantilever beam. It is found that, for the excitation frequencies close to the first modal frequency of the beam structure, the method is capable of detecting only 22% of the crack depth percentage ratio with respect to the thickness of the beam. Using parametric optimization of sample entropy and wavelet transformation, this crack identification sensitivity is improved up to 8%. The experimental studies are carried out, and experimental results successfully validate the numerical parametric optimization process.

IN-CYLINDER FLOW ANALYSIS USING WAVELET ANALYSIS

  • Park, D.;Sullivan, P.E.;Wallace, J.S.
    • International Journal of Automotive Technology
    • /
    • v.7 no.3
    • /
    • pp.289-294
    • /
    • 2006
  • Better fundamental understanding of the interactions between the in-cylinder flows and combustion process is an important requirement for further improvement in the fuel economy and emissions of internal combustion(IC) engines. Flow near a spark plug at the time of ignition plays an important role for early flame kernel development(EFKD). Velocity data measurements in this study were made with a two-component laser Doppler velocimetry(LDV) near a spark plug in a single cylinder optical spark ignition(SI) engine with a heart-shaped combustion chamber. LDV velocity data were collected on an individual cycle basis under wide-open motored conditions with an engine speed of 1,000rpm. This study examines and compares the flow fields as interpreted through ensemble, cyclic and discrete wavelet transformation(DWT) analysis. The energy distributions in the non-stationary engine flows are also investigated over crank angle phase and frequency through continuous wavelet transformation(CWT) for a position near a spark plug. Wavelet analysis is appropriate for analyzing the flow fields in engines because it gives information about the transient events in a time and frequency plane. The results of CWT analysis are provided and compared with the mean flows of DWT first decomposition level for all cycles at a position. Low frequency high energy found with CWT corresponds well with the peak locations of the mean velocity. The high frequency flows caused by the intake jet gradually decay as the piston approaches the bottom dead center(BDC).

A Digital Distance Relaying Algorithm using a Wavelet Transformation (Wavelet 변환을 이용한 디지털 거리계전 알고리즘)

  • Kang, Sang-Hee;Lee, Joo-Hun;Nam, Soon-Ryul;Park, Jong-Keun
    • The Transactions of the Korean Institute of Electrical Engineers A
    • /
    • v.48 no.10
    • /
    • pp.1215-1221
    • /
    • 1999
  • A high speed digital distance relaying algorithm based on a Wavelet Transformation is proposed. To obtain stable phasor values very quickly, first, a lowpass filter which has low cutoff frequency is used. Secondly, db2(Daubechies 2) Wavelet which has the data window of 4 samples is used. A FIR filter which removes the DC-offset component in current relaying signals is applied. In accordance with a series of tests, the operation time of the relaying algorithm is less than 3/4 cycles after faults in a 80 [km], 154[kV], 60[Hz] over-head transmission line system.

  • PDF

An Approach to Fuse IKONOS Images by Wavelet Transformation

  • Zhu, Changqing;Wang, Yuhai
    • Proceedings of the KSRS Conference
    • /
    • /
    • pp.776-782
    • /
    • 2003
  • This paper develops an approach to fuse 1-meter resolution spatial panchromatic and 4-meter resolution multi-spectral IKONOS images. The approach is based on the characteristics of four-band wavelet transformation. The experiment shows that the fused images based on four-band wavelet method contain with not only high spatial resolution but also rich spectral characteristic.

  • PDF