Based on the variational theory, a wavelet-based numerical method is developed to calculate the defect states of acoustic waves in two-dimensional phononic crystals with point and line defects. The supercell technique...Based on the variational theory, a wavelet-based numerical method is developed to calculate the defect states of acoustic waves in two-dimensional phononic crystals with point and line defects. The supercell technique is applied. By expanding the displacement field and the material constants （mass density and elastic stiffness） in periodic wavelets, the explicit formulations of an eigenvalue problem for the plane harmonic bulk waves in such a phononic structure are derived. The point and line defect states in solid-liquid and solid-solid systems are calculated. Comparisons of the present results with those measured experimentally or those from the plane wave expansion method show that the present method can yield accurate results with faster convergence and less computing time.展开更多
The development of Web-based global 3D visual system has made progresses. However, there exist few mature and effective ways for managing, transmitting and visualizing massive spatial data. Based on the related work, ...The development of Web-based global 3D visual system has made progresses. However, there exist few mature and effective ways for managing, transmitting and visualizing massive spatial data. Based on the related work, the paper illustrates the ellipsoidal quadtree technique for rapid access multi-scale and multiple level geographical data, integrates the streaming with level-of-detail rendering method for transmitting the data on the network, and im-plements large-scale terrain surface simplification using M-band wavelet transforms and mul-tiresolution triangulations. We fulfil a web-based global terrain visual system using COM com-ponents on the basis of the above techniques. The system has a good prospect in the military simulation and city plans.展开更多
Microseismicity signals released during rock failure process are firstly recorded using microseismicity monitoring system.A wavelet transform scheme is then developed on the basis of the discrete wavelet transform and...Microseismicity signals released during rock failure process are firstly recorded using microseismicity monitoring system.A wavelet transform scheme is then developed on the basis of the discrete wavelet transform and implemented into MATLAB to study the energy distribution characteristics of the monitored microseismicity signals.The wavelet transform scheme decomposes the recorded microseismicity signals into various wavelets at seven scales and eight frequency bands.The microseismicity energy at each frequency band is then calculated by integrating the wavelets in each scale.It is found that,for the microseismicity signals recorded during the uniaxial loading of the granite,the microseismicity energies are mainly distributed between the bands 7.8125-15.625 kHz,15.625-31.250 kHz and 31.25-62.5 kHz and the percentages of the released energies at these frequency bands are 8.24%,62.72%,28.08% of the total energies,respectively.The results reveal that the microseismicity energies at these levels are directly related to the damage mechanisms of the granite although further studies are need to identify the failure modes.Then these monitored signals were processed using wavelet transformation to find out the frequency distribution rule and the frequency band energy varying rule of the acoustic emission(AE) signals during the different rock damage and failure stages.The rock failure mechanism was interpreted from the perspective of the relationship between AE signal frequency change and crack propagation.The frequency band energy distribution histograms of the microseismicity signals at different damage stages were computed and drawn by the energy calculation method of wavelet transformation implemented into MATLAB.The energy percentage of the low frequency band(d7-a7) and that of the dominated frequency band(d4-d6) and their variation rule were analyzed especially.Accordingly,the critical damage point is that the low frequency energy percentage is above a certain threshold.This index could be used as the failure precur展开更多
The theory of discrete orthogonal 2 band (or dyadic) wavelet decomposition to the M band case was generalized. Specifically, it was shown that any finite energy signal can be expanded in terms of the dilates and...The theory of discrete orthogonal 2 band (or dyadic) wavelet decomposition to the M band case was generalized. Specifically, it was shown that any finite energy signal can be expanded in terms of the dilates and translates M 1 M band wavelet. Orthogonal and linear phase M band wavelet transform was used to decompose the image into channel which corresponds to different directions and resolution levels. Final edge maps of color medical endoscope image were obtained through combination of both vertical and horizontal directional edge maps.展开更多
基金the National Natural Science Foundation of China(No.10632020)the German Research Foundation(No.ZH 15/11-1)jointly by the China Scholarship Council and the German Academic Exchange Service(No.D/08/01795).
文摘Based on the variational theory, a wavelet-based numerical method is developed to calculate the defect states of acoustic waves in two-dimensional phononic crystals with point and line defects. The supercell technique is applied. By expanding the displacement field and the material constants （mass density and elastic stiffness） in periodic wavelets, the explicit formulations of an eigenvalue problem for the plane harmonic bulk waves in such a phononic structure are derived. The point and line defect states in solid-liquid and solid-solid systems are calculated. Comparisons of the present results with those measured experimentally or those from the plane wave expansion method show that the present method can yield accurate results with faster convergence and less computing time.
基金This work was supported by“973”Program(Grant No.G2000077906)Program of Data Fusion for Flood Analysis and Decision Support(ANFAS)863 Program(Grant No.2001AA130020).
文摘The development of Web-based global 3D visual system has made progresses. However, there exist few mature and effective ways for managing, transmitting and visualizing massive spatial data. Based on the related work, the paper illustrates the ellipsoidal quadtree technique for rapid access multi-scale and multiple level geographical data, integrates the streaming with level-of-detail rendering method for transmitting the data on the network, and im-plements large-scale terrain surface simplification using M-band wavelet transforms and mul-tiresolution triangulations. We fulfil a web-based global terrain visual system using COM com-ponents on the basis of the above techniques. The system has a good prospect in the military simulation and city plans.
基金partially supported by the National Natural Science Foundation of China (Grant Nos.51204029, 51525402,51374049,51474050 and U1602232)the Science Career Public Welfare Research Foundation of Liaoning Province (No.2015003001)the Scientific Research Foundationfor the Returned Overseas Chinese Scholars,State Education Ministry (No.50-2).
文摘Microseismicity signals released during rock failure process are firstly recorded using microseismicity monitoring system.A wavelet transform scheme is then developed on the basis of the discrete wavelet transform and implemented into MATLAB to study the energy distribution characteristics of the monitored microseismicity signals.The wavelet transform scheme decomposes the recorded microseismicity signals into various wavelets at seven scales and eight frequency bands.The microseismicity energy at each frequency band is then calculated by integrating the wavelets in each scale.It is found that,for the microseismicity signals recorded during the uniaxial loading of the granite,the microseismicity energies are mainly distributed between the bands 7.8125-15.625 kHz,15.625-31.250 kHz and 31.25-62.5 kHz and the percentages of the released energies at these frequency bands are 8.24%,62.72%,28.08% of the total energies,respectively.The results reveal that the microseismicity energies at these levels are directly related to the damage mechanisms of the granite although further studies are need to identify the failure modes.Then these monitored signals were processed using wavelet transformation to find out the frequency distribution rule and the frequency band energy varying rule of the acoustic emission(AE) signals during the different rock damage and failure stages.The rock failure mechanism was interpreted from the perspective of the relationship between AE signal frequency change and crack propagation.The frequency band energy distribution histograms of the microseismicity signals at different damage stages were computed and drawn by the energy calculation method of wavelet transformation implemented into MATLAB.The energy percentage of the low frequency band(d7-a7) and that of the dominated frequency band(d4-d6) and their variation rule were analyzed especially.Accordingly,the critical damage point is that the low frequency energy percentage is above a certain threshold.This index could be used as the failure precur
文摘The theory of discrete orthogonal 2 band (or dyadic) wavelet decomposition to the M band case was generalized. Specifically, it was shown that any finite energy signal can be expanded in terms of the dilates and translates M 1 M band wavelet. Orthogonal and linear phase M band wavelet transform was used to decompose the image into channel which corresponds to different directions and resolution levels. Final edge maps of color medical endoscope image were obtained through combination of both vertical and horizontal directional edge maps.
