Based on the measurement of the arrival time of maxima magnitude from band-pass filtering signals which were determined using a new Morlet wavelet multiple-filter method, we develop a method for measuring intrinsic an...Based on the measurement of the arrival time of maxima magnitude from band-pass filtering signals which were determined using a new Morlet wavelet multiple-filter method, we develop a method for measuring intrinsic and attenuative dispersion of the first cycle direct P-wave. We determine relative group delays of spectral components of direct P-waves for 984 ray paths from SML and ALS stations of the Taiwan Central Weather Bureau Seismic Network （CWBSN）. Using continuous relaxation model, we deduce a new transfer function that relates intrinsic dispersion to attenuation. Based on the genetic algorithm （GA）, we put forward a new inversion procedure for determining which is defined the flat part of quality factor Q（ω） spectrum, τ1 and τ2 parameters. The results indicate that ① The distribution of Om values versus epicentral distance and depth show that Qm values linearly increase with increasing of epicentral distance and depth, and Qm values is clearly independent of earthquakes magnitude; ② In the different depth ranges, Qm residual show no correlation with variations in epicentral distance. Some significant changes of Qm residual with time is likely caused by pre-seismic stress accumulation, and associated with fluid-filled higher density fractures rock volume in the source area of 1999 Chi-Chi Taiwan earthquake. We confirm that Qm residual with time anomaly appears about 2.5 years before the Chi-Chi earthquake; ③ A comparison of Qm residual for different depth range between SML and ALS stations show that the level of stress has vertical and lateral difference; ④ The area near observation station with both anomalously increasing and decreasing averaged Qm residual is likely an unstable environment for future strong earthquake occurrence. This study demonstrates the capability of direct P-waves dispersion for monitoring attenuation characteristics and its state changes of anelastic medium of the Earth at short propagation distance using seismograms recorded from very small events.展开更多
The selectivity of gas sensing materials is increasingly important for their applications. The oxygenregulated SnO2 films with(110) and(101) preferred orientation were obtained through magnetron sputtering, followed b...The selectivity of gas sensing materials is increasingly important for their applications. The oxygenregulated SnO2 films with(110) and(101) preferred orientation were obtained through magnetron sputtering, followed by annealing treatment. Their micro-structure, surface morphology and gas response were investigated by advanced structural characterization and property measurement. The results showed that the as-prepared(110)-oriented SnO2 film was oxygen-rich and had more adsorption sites while the as-prepared(101)-oriented SnO2 film was oxygen-poor and more sensitive to de-oxidation.H2 gas sensitivity, response speed, selectivity between H2 and CO of the(110)-orientated SnO2 film was superior to that of the(101)-orientated SnO2 film. After treated at high temperature and high vacuum,the reduction of gas-sensing properties of the annealed(110) SnO2 film was much more than that of the annealed(101) SnO2 film. The lattice oxygen was responsible for the difference in gas-sensing response between(110) and(101)-oriented SnO2 films under oxygen regulation. This work indicated the gassensing selectivity of the different crystal planes in SnO2 film, providing a significant reference for design and extension of the related materials.展开更多
基金supported by the National Science Council of Taiwan granted NSC-94-2816-M-194-004
文摘Based on the measurement of the arrival time of maxima magnitude from band-pass filtering signals which were determined using a new Morlet wavelet multiple-filter method, we develop a method for measuring intrinsic and attenuative dispersion of the first cycle direct P-wave. We determine relative group delays of spectral components of direct P-waves for 984 ray paths from SML and ALS stations of the Taiwan Central Weather Bureau Seismic Network （CWBSN）. Using continuous relaxation model, we deduce a new transfer function that relates intrinsic dispersion to attenuation. Based on the genetic algorithm （GA）, we put forward a new inversion procedure for determining which is defined the flat part of quality factor Q（ω） spectrum, τ1 and τ2 parameters. The results indicate that ① The distribution of Om values versus epicentral distance and depth show that Qm values linearly increase with increasing of epicentral distance and depth, and Qm values is clearly independent of earthquakes magnitude; ② In the different depth ranges, Qm residual show no correlation with variations in epicentral distance. Some significant changes of Qm residual with time is likely caused by pre-seismic stress accumulation, and associated with fluid-filled higher density fractures rock volume in the source area of 1999 Chi-Chi Taiwan earthquake. We confirm that Qm residual with time anomaly appears about 2.5 years before the Chi-Chi earthquake; ③ A comparison of Qm residual for different depth range between SML and ALS stations show that the level of stress has vertical and lateral difference; ④ The area near observation station with both anomalously increasing and decreasing averaged Qm residual is likely an unstable environment for future strong earthquake occurrence. This study demonstrates the capability of direct P-waves dispersion for monitoring attenuation characteristics and its state changes of anelastic medium of the Earth at short propagation distance using seismograms recorded from very small events.
基金financially supported by the National Natural Science Foundation of China (Nos. 51502126 and 51874169)the Natural Science Foundation of Liaoning Province (No. 20180550802)
文摘The selectivity of gas sensing materials is increasingly important for their applications. The oxygenregulated SnO2 films with(110) and(101) preferred orientation were obtained through magnetron sputtering, followed by annealing treatment. Their micro-structure, surface morphology and gas response were investigated by advanced structural characterization and property measurement. The results showed that the as-prepared(110)-oriented SnO2 film was oxygen-rich and had more adsorption sites while the as-prepared(101)-oriented SnO2 film was oxygen-poor and more sensitive to de-oxidation.H2 gas sensitivity, response speed, selectivity between H2 and CO of the(110)-orientated SnO2 film was superior to that of the(101)-orientated SnO2 film. After treated at high temperature and high vacuum,the reduction of gas-sensing properties of the annealed(110) SnO2 film was much more than that of the annealed(101) SnO2 film. The lattice oxygen was responsible for the difference in gas-sensing response between(110) and(101)-oriented SnO2 films under oxygen regulation. This work indicated the gassensing selectivity of the different crystal planes in SnO2 film, providing a significant reference for design and extension of the related materials.
