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
This paper discusses the measurement of the absorption coefficient of atmospheric aerosols and its meas- uring system based on the principle of integrating plate. Measurements in Beijing show that the absorption coeff...This paper discusses the measurement of the absorption coefficient of atmospheric aerosols and its meas- uring system based on the principle of integrating plate. Measurements in Beijing show that the absorption coefficient of atmospheric aerosols in the heating period varies in a range of 10-3 to 10-4 m-1 and in the non-heating period, its values are near 10-4m-1.展开更多
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.
文摘This paper discusses the measurement of the absorption coefficient of atmospheric aerosols and its meas- uring system based on the principle of integrating plate. Measurements in Beijing show that the absorption coefficient of atmospheric aerosols in the heating period varies in a range of 10-3 to 10-4 m-1 and in the non-heating period, its values are near 10-4m-1.
