The primary bottleneck to extracting wood defects during ultrasonic testing is the accuracy of identifying the wood defects. The wavelet energy moment was used to extract defect features of artificial wood holes drill...The primary bottleneck to extracting wood defects during ultrasonic testing is the accuracy of identifying the wood defects. The wavelet energy moment was used to extract defect features of artificial wood holes drilled into 120 elm samples that differed in the number of holes to verify the validity of the method. Wavelet energy moment can reflect the distribution of energy along the time axis and the amount of energy in each frequency band,which can effectively extract the energy distribution characteristics of signals in each frequency band; therefore,wavelet energy moment can replace the wavelet frequency band energy and constitute wood defect feature vectors. A principal component analysis was used to normalize and reduce the dimension of the feature vectors. A total of 16 principal component features were then obtained, which can effectively extract the defect features of the different number of holes in the elm samples.展开更多
The existing absorption coefficient measurement in a water tube is limited in low frequency due to the limitation of the pulse tube length.A wide-band pulse tube method based on the post-processing inverse filter is p...The existing absorption coefficient measurement in a water tube is limited in low frequency due to the limitation of the pulse tube length.A wide-band pulse tube method based on the post-processing inverse filter is proposed.After obtaining the response of the entire system,the transducer is excited with wide-band,short-duration signals.Then,the received signals are processed with inverse filters and the ＂blurred＂ reflective signals of standard reflector and test sample are recovered respectively,finally,the reflection coefficient and absorption coefficient are calculated.Simulation work is implemented to verify the advantage of postprocessing inverse filter over pre-processing inverse filter in terms of low frequency measurement.To verify the proposed method,two different wide-band pulses in the separate frequency ranges are adopted to measure the same rubber material.The experimental results indicate that the wide-band pulse method and CW（Continuous Wave） pulse method have good agreement in both low frequency range and high frequency range.Wide-band pulse method is of high efficiency,and the low frequency reaches 350 Hz,which is able to extend the low frequency range.展开更多
基金financially supported by the Fundamental Research Funds for the Central Universities(2572016CB11 and 2572014CB35)Natural Science Foundation of Heilongjiang Province(F2015036 and QC2014C010)948 Project(2014-4-78)
文摘The primary bottleneck to extracting wood defects during ultrasonic testing is the accuracy of identifying the wood defects. The wavelet energy moment was used to extract defect features of artificial wood holes drilled into 120 elm samples that differed in the number of holes to verify the validity of the method. Wavelet energy moment can reflect the distribution of energy along the time axis and the amount of energy in each frequency band,which can effectively extract the energy distribution characteristics of signals in each frequency band; therefore,wavelet energy moment can replace the wavelet frequency band energy and constitute wood defect feature vectors. A principal component analysis was used to normalize and reduce the dimension of the feature vectors. A total of 16 principal component features were then obtained, which can effectively extract the defect features of the different number of holes in the elm samples.
基金supported by the National Natural Science Foundation of China(11474230)the National Key Research and Development Program of China(2016YFF0200900)the Science and Technology Research and Development Program of Shaanxi Province(2016GY-111)
文摘The existing absorption coefficient measurement in a water tube is limited in low frequency due to the limitation of the pulse tube length.A wide-band pulse tube method based on the post-processing inverse filter is proposed.After obtaining the response of the entire system,the transducer is excited with wide-band,short-duration signals.Then,the received signals are processed with inverse filters and the ＂blurred＂ reflective signals of standard reflector and test sample are recovered respectively,finally,the reflection coefficient and absorption coefficient are calculated.Simulation work is implemented to verify the advantage of postprocessing inverse filter over pre-processing inverse filter in terms of low frequency measurement.To verify the proposed method,two different wide-band pulses in the separate frequency ranges are adopted to measure the same rubber material.The experimental results indicate that the wide-band pulse method and CW（Continuous Wave） pulse method have good agreement in both low frequency range and high frequency range.Wide-band pulse method is of high efficiency,and the low frequency reaches 350 Hz,which is able to extend the low frequency range.
