A measuring method of the echo reduction of passive materials by using the time reversal（TR） technique is presented. To measure the echo reduction of a sample with this approach, the received signals are firstly foc...A measuring method of the echo reduction of passive materials by using the time reversal（TR） technique is presented. To measure the echo reduction of a sample with this approach, the received signals are firstly focused according to the TR theory. Then, the sample is removed and the TR processing is again employed to realize the focus of the received signal.Finally, the echo reduction of the sample is evaluated with these focusing signals. Besides, to calibrate the measured echo reduction via the TR technique, a standard sample is employed to measure a constant coefficient that only depends on the measurement environment. An aluminum plate sample and a steel plate sample with the same size of 1.1 mxl.O m x0.005 m axe tested in a wave guide tank. The experimental results show that the calibrated values are well consistent with theoretical results under the free field at the measured frequency range of0.5-20 kHz. The relative errors of all the measured values are less than 10% and the values of the expanded uncertainty are less than 1.5 dB. The TR processing focuses the energy in spatial domain and temporal domain, so it can be used to measure the echo reduction of passive materials in the environments with reflections induced by boundaries and low frequency sources.展开更多
A method using the time reversal（TR） technique to measure the insertion loss（IL） of passive materials is presented.Firstly the received signals are focused according to the TR theory when there is not a sample bet...A method using the time reversal（TR） technique to measure the insertion loss（IL） of passive materials is presented.Firstly the received signals are focused according to the TR theory when there is not a sample between the source and the received array.Then,the sample is placed near the received array and the TR processing is again employed to realize the focus of the received signal.Finally,the IL of the sample is evaluated from these focusing signals.Because the TR processing can focus the energy in spatial domain and time domain,the method can be used to measure acoustic properties of passive materials in a waveguide tank with reflections induced by boundaries or with low source frequencies.Two samples with the same size of 1.1 m×1.0 m×5 mm are tested in the waveguide tank.The method is demonstrated by the comparison of the theoretical and the experimental results in the measured frequency range of 1-20 kHz.展开更多
应用Lorenz-RR散点图、1 h t-RR散点图及逆向分析技术,对5例复杂性心律失常患者进行分析,结果发现:借助心电散点图这项技术,可以快速判断与鉴别快速性心律失常合并缓慢性心律失常,也可以快速判断多源性室性早搏中室性并行心律的存在。...应用Lorenz-RR散点图、1 h t-RR散点图及逆向分析技术,对5例复杂性心律失常患者进行分析,结果发现:借助心电散点图这项技术,可以快速判断与鉴别快速性心律失常合并缓慢性心律失常,也可以快速判断多源性室性早搏中室性并行心律的存在。心电散点图既简化了动态心电图的分析过程,也强化了其诊断与鉴别诊断功能,使复杂性心律失常的诊断更为快捷准确。展开更多
文摘A measuring method of the echo reduction of passive materials by using the time reversal（TR） technique is presented. To measure the echo reduction of a sample with this approach, the received signals are firstly focused according to the TR theory. Then, the sample is removed and the TR processing is again employed to realize the focus of the received signal.Finally, the echo reduction of the sample is evaluated with these focusing signals. Besides, to calibrate the measured echo reduction via the TR technique, a standard sample is employed to measure a constant coefficient that only depends on the measurement environment. An aluminum plate sample and a steel plate sample with the same size of 1.1 mxl.O m x0.005 m axe tested in a wave guide tank. The experimental results show that the calibrated values are well consistent with theoretical results under the free field at the measured frequency range of0.5-20 kHz. The relative errors of all the measured values are less than 10% and the values of the expanded uncertainty are less than 1.5 dB. The TR processing focuses the energy in spatial domain and temporal domain, so it can be used to measure the echo reduction of passive materials in the environments with reflections induced by boundaries and low frequency sources.
文摘A method using the time reversal（TR） technique to measure the insertion loss（IL） of passive materials is presented.Firstly the received signals are focused according to the TR theory when there is not a sample between the source and the received array.Then,the sample is placed near the received array and the TR processing is again employed to realize the focus of the received signal.Finally,the IL of the sample is evaluated from these focusing signals.Because the TR processing can focus the energy in spatial domain and time domain,the method can be used to measure acoustic properties of passive materials in a waveguide tank with reflections induced by boundaries or with low source frequencies.Two samples with the same size of 1.1 m×1.0 m×5 mm are tested in the waveguide tank.The method is demonstrated by the comparison of the theoretical and the experimental results in the measured frequency range of 1-20 kHz.
文摘应用Lorenz-RR散点图、1 h t-RR散点图及逆向分析技术,对5例复杂性心律失常患者进行分析,结果发现:借助心电散点图这项技术,可以快速判断与鉴别快速性心律失常合并缓慢性心律失常,也可以快速判断多源性室性早搏中室性并行心律的存在。心电散点图既简化了动态心电图的分析过程,也强化了其诊断与鉴别诊断功能,使复杂性心律失常的诊断更为快捷准确。
