Based on the data synthesis simulation and the actual processing of the airgun seismic source signal,three quantitative indicators of signal-to-noise ratio,waveform correlation coefficient and phase offset,are superim...Based on the data synthesis simulation and the actual processing of the airgun seismic source signal,three quantitative indicators of signal-to-noise ratio,waveform correlation coefficient and phase offset,are superimposed. We systematically evaluate the functions of the following three stack methods including linearity,phase weighting and S-transform in the extraction of weak signals under strong background noise and quantitatively estimate the reliability of the stack results. Through the comprehensive discussion of the above three methods of stack results,the preliminary comparative analysis believes that the linear stack signal-to-noise ratio is low,but the waveform distortion is minimal; the phase-weighted superimposed signal-to-noise ratio is high and the phase offset is small,but the results of the waveform quality and linear stack are larger than the deviation; the S-transform stack has a relatively higher signal-to-noise ratio and a small loss of waveform amplitude,but there is a certain phase shift phenomenon. It is therefore suggested that linear stack technology should be used when the requirements of both waveform quality and time precision are high. However,the selection of the stack method when the airgun source excitation is limited should be emphasized. If high fidelity is required, the S-transform stack method should be selected; if the required time is high,accuracy can be selected by phase-weighted stack method to achieve reasonable extraction of weak signals.展开更多
By means of X-ray diffraction profile analysis of three different composition Fe-Mn-Si alloys, the relationship between stacking fault probability P<sub>sf</sub> with the concentrations of constituents in ...By means of X-ray diffraction profile analysis of three different composition Fe-Mn-Si alloys, the relationship between stacking fault probability P<sub>sf</sub> with the concentrations of constituents in alloys, 1/P<sub>sf</sub>=540.05+23.70×Mn wt％-138.74×Si wt％, was determined. According to the nucleation mechanism by stacking fault in this alloy,the equation between critical driving force ΔG<sub>c</sub> and P<sub>sf</sub>, ΔG<sub>c</sub>=67.487+0.1775/P<sub>sf</sub>（J/mol）, was made. Therefore,the relationship between critical driving force and compositions was established. Associated with the thermodynamic calculation, the M<sub>s</sub> of fcc（γ）→hcp（ε） martensitic transformation in any suitable composition Fe-Mn-Si shape memory alloys can be predicted and results seem reasonable as compared with some experimental data.展开更多
基金sponsored by the Spark Program of Earthquake Science and Technology,CEA(XH16003)the National Natural Science Foundation(NNSF) of China under Grant No.41474087
文摘Based on the data synthesis simulation and the actual processing of the airgun seismic source signal,three quantitative indicators of signal-to-noise ratio,waveform correlation coefficient and phase offset,are superimposed. We systematically evaluate the functions of the following three stack methods including linearity,phase weighting and S-transform in the extraction of weak signals under strong background noise and quantitatively estimate the reliability of the stack results. Through the comprehensive discussion of the above three methods of stack results,the preliminary comparative analysis believes that the linear stack signal-to-noise ratio is low,but the waveform distortion is minimal; the phase-weighted superimposed signal-to-noise ratio is high and the phase offset is small,but the results of the waveform quality and linear stack are larger than the deviation; the S-transform stack has a relatively higher signal-to-noise ratio and a small loss of waveform amplitude,but there is a certain phase shift phenomenon. It is therefore suggested that linear stack technology should be used when the requirements of both waveform quality and time precision are high. However,the selection of the stack method when the airgun source excitation is limited should be emphasized. If high fidelity is required, the S-transform stack method should be selected; if the required time is high,accuracy can be selected by phase-weighted stack method to achieve reasonable extraction of weak signals.
基金Project supported by the National Natural Science Foundation of China (Grant No. 59671023).
文摘By means of X-ray diffraction profile analysis of three different composition Fe-Mn-Si alloys, the relationship between stacking fault probability P<sub>sf</sub> with the concentrations of constituents in alloys, 1/P<sub>sf</sub>=540.05+23.70×Mn wt％-138.74×Si wt％, was determined. According to the nucleation mechanism by stacking fault in this alloy,the equation between critical driving force ΔG<sub>c</sub> and P<sub>sf</sub>, ΔG<sub>c</sub>=67.487+0.1775/P<sub>sf</sub>（J/mol）, was made. Therefore,the relationship between critical driving force and compositions was established. Associated with the thermodynamic calculation, the M<sub>s</sub> of fcc（γ）→hcp（ε） martensitic transformation in any suitable composition Fe-Mn-Si shape memory alloys can be predicted and results seem reasonable as compared with some experimental data.
