Accurate Q parameter is hard to be obtained, but there is great difference between Q measurements from different measurement methods in seismic physical modelling. The influence factors, stability and accuracy of diff...Accurate Q parameter is hard to be obtained, but there is great difference between Q measurements from different measurement methods in seismic physical modelling. The influence factors, stability and accuracy of different methods are analyzed through standard sample experiment and the seismic physical modelling. Based on this, we proposed an improved method for improving accuracy of pulse transmission method, in which the samples with similar acoustic properties to the test sample are selected as the reference samples. We assess the stability and accuracy of the pulse transmission, pulse transmission insertion, and reflection wave methods for obtaining the quality factor Q using standard and reference samples and seismic physical modeling. The results suggest that the Q-values obtained by the pulse transmission method are strongly affected by diffraction and the error is 50% or greater, whereas the relative error of the improved pulse transmission method is about 10%. By using a theoretical diffraction correction method and the improved measurement method, the differences among the Q-measuring methods can be limited to within 10%.展开更多
Debris flows have caused serious human casualties and economic losses in the regions strongly affected by the Ms8.0 Wenchuan earthquake of 2oo8. Debris flow mitigation and risk assessment is a key issue for reconstruc...Debris flows have caused serious human casualties and economic losses in the regions strongly affected by the Ms8.0 Wenchuan earthquake of 2oo8. Debris flow mitigation and risk assessment is a key issue for reconstruction. The existing methods of inundation simulation are based on historical disasters and have no power of prediction. The rain- flood method can not yield detailed flow hydrograph and does not meet the need of inundation simulation. In this paper, the process of water flow was studied by using the Arc-SCS model combined with hydraulic method, and then the debris flow runoff process was calculated using the empirical formula combining the result from Arc-SCS. The peak discharge and runoff duration served as input of inundation simulation. Then, the dangerous area is predicted using kinematic wave method and Manning equation. Taking the debris flow in Huashiban gully in Beichuan County, Sichuan Province, China on 24 Sep. 2oo8 as example, the peak discharge of water flow and debris flow were calculated as 35.52 m3·s-1 and 215.66 m3·s-, with error of 4.15% compared to the measured values. The simulated area of debris-flow deposition was 161,500 m2, vs. the measured area of 144,097 m2, in error of 81.75%. The simulated maximum depth was 12.3 m, consistent with the real maximum depth between lO and 15 m according to the field survey. The minor error is mainly due to the flow impact on buildings and variations in cross-section configuration. The present methodology can be applied to predict debrisflow magnitude and evaluate its risk in other watersheds inthe earthquake area.展开更多
A dual transponder carrier ranging method can be used to measure inter-satellite distance with high precision by combining the reference and the to-and-fro measurements. Based on the differential techniques, the oscil...A dual transponder carrier ranging method can be used to measure inter-satellite distance with high precision by combining the reference and the to-and-fro measurements. Based on the differential techniques, the oscillator phase noise, which is the main error source for microwave ranging systems, can be significantly attenuated. Further, since the range measurements are derived on the same satellite, the dual transponder ranging system does not need a time tagging system to synchronize the two satellites. In view of the lack of oscillator noise analysis on the dual transponder ranging model, a comprehensive analysis of oscillator noise effects on ranging accuracy is provided. First, the dual transponder ranging system is described with emphasis on the detailed analysis of oscillator noise on measurement precision. Then, a high-fidelity numerical simulation approach based on the power spectrum density of an actual ultra-stable oscillator is carried out in both frequency domain and time domain to support the presented theoretical analysis. The simulation results under different conditions are consistent with the proposed concepts, which makes the results reliable. Besides, the results demonstrate that a high level of accuracy can be achieved by using this oscillator noise cancelation-oriented ranging method.展开更多
We present a study on the retrieval sensitivity of the column-averaged dry-air mole fraction of CO2(XCO2) for the Chinese carbon dioxide observation satellite(TanSat) with a full physical forward model and the optimal...We present a study on the retrieval sensitivity of the column-averaged dry-air mole fraction of CO2(XCO2) for the Chinese carbon dioxide observation satellite(TanSat) with a full physical forward model and the optimal estimation technique. The forward model is based on the vector linearized discrete ordinate radiative transfer model(VLIDORT) and considers surface reflectance, gas absorption, and the scattering of air molecules, aerosol particles, and cloud particles. XCO2 retrieval errors from synthetic TanSat measurements show solar zenith angle(SZA), albedo dependence with values varying from 0.3 to 1 ppm for bright land surface in nadir mode and 2 to 8 ppm for dark surfaces like snow. The use of glint mode over dark oceans significantly improves the CO2 information retrieved. The aerosol type and profile are more important than the aerosol optical depth, and underestimation of aerosol plume height will introduce a bias of 1.5 ppm in XCO2. The systematic errors due to radiometric calibration are also estimated using a forward model simulation approach.展开更多
An isoratio method is proposed to study the chemical potential of neutrons(protons) from the yield ratio of isotopes(isotones) differing in neutron-excess(I = N- Z). The measured fragments in the 140 A MeV ^(40),^(48)...An isoratio method is proposed to study the chemical potential of neutrons(protons) from the yield ratio of isotopes(isotones) differing in neutron-excess(I = N- Z). The measured fragments in the 140 A MeV ^(40),^(48) Ca and^(58),^(64) Ni +~9Be reactions, as well as those in the simulated^(58),^(64) Ni +~9Be reactions by using the antisymmetric molecular dynamics(AMD) model plus the secondary decay model gemini, have been adopted to perform the isoratio analysis.The results of the isoratio method verify that they are similar to that of the well known isoscaling method. The isoratio scaling phenomenon suggested by the isoratio method has also been found in the measured data and the fragments simulated by the AMD + gemini models.展开更多
基金supported by the National Nature Science Foundation of China(No.41474112)the National Science and Technology Major Project(No.2017ZX05005-004)
文摘Accurate Q parameter is hard to be obtained, but there is great difference between Q measurements from different measurement methods in seismic physical modelling. The influence factors, stability and accuracy of different methods are analyzed through standard sample experiment and the seismic physical modelling. Based on this, we proposed an improved method for improving accuracy of pulse transmission method, in which the samples with similar acoustic properties to the test sample are selected as the reference samples. We assess the stability and accuracy of the pulse transmission, pulse transmission insertion, and reflection wave methods for obtaining the quality factor Q using standard and reference samples and seismic physical modeling. The results suggest that the Q-values obtained by the pulse transmission method are strongly affected by diffraction and the error is 50% or greater, whereas the relative error of the improved pulse transmission method is about 10%. By using a theoretical diffraction correction method and the improved measurement method, the differences among the Q-measuring methods can be limited to within 10%.
基金supported by the National Basic Research Program of China(973 Program)(Grant No.2011CB409902)the National Natural Sciences Foundation of China(Grant No. 40671025)
文摘Debris flows have caused serious human casualties and economic losses in the regions strongly affected by the Ms8.0 Wenchuan earthquake of 2oo8. Debris flow mitigation and risk assessment is a key issue for reconstruction. The existing methods of inundation simulation are based on historical disasters and have no power of prediction. The rain- flood method can not yield detailed flow hydrograph and does not meet the need of inundation simulation. In this paper, the process of water flow was studied by using the Arc-SCS model combined with hydraulic method, and then the debris flow runoff process was calculated using the empirical formula combining the result from Arc-SCS. The peak discharge and runoff duration served as input of inundation simulation. Then, the dangerous area is predicted using kinematic wave method and Manning equation. Taking the debris flow in Huashiban gully in Beichuan County, Sichuan Province, China on 24 Sep. 2oo8 as example, the peak discharge of water flow and debris flow were calculated as 35.52 m3·s-1 and 215.66 m3·s-, with error of 4.15% compared to the measured values. The simulated area of debris-flow deposition was 161,500 m2, vs. the measured area of 144,097 m2, in error of 81.75%. The simulated maximum depth was 12.3 m, consistent with the real maximum depth between lO and 15 m according to the field survey. The minor error is mainly due to the flow impact on buildings and variations in cross-section configuration. The present methodology can be applied to predict debrisflow magnitude and evaluate its risk in other watersheds inthe earthquake area.
基金Project(61106113)supported by the National Natural Science Foundation of China
文摘A dual transponder carrier ranging method can be used to measure inter-satellite distance with high precision by combining the reference and the to-and-fro measurements. Based on the differential techniques, the oscillator phase noise, which is the main error source for microwave ranging systems, can be significantly attenuated. Further, since the range measurements are derived on the same satellite, the dual transponder ranging system does not need a time tagging system to synchronize the two satellites. In view of the lack of oscillator noise analysis on the dual transponder ranging model, a comprehensive analysis of oscillator noise effects on ranging accuracy is provided. First, the dual transponder ranging system is described with emphasis on the detailed analysis of oscillator noise on measurement precision. Then, a high-fidelity numerical simulation approach based on the power spectrum density of an actual ultra-stable oscillator is carried out in both frequency domain and time domain to support the presented theoretical analysis. The simulation results under different conditions are consistent with the proposed concepts, which makes the results reliable. Besides, the results demonstrate that a high level of accuracy can be achieved by using this oscillator noise cancelation-oriented ranging method.
基金supported by the Strategic Priority Research Program- Climate Change: Carbon Budget and Relevant Issues (Grant No. XDA05040200)the National High-tech Research and Development Program of China (Grant No. 2011AA12A104)
文摘We present a study on the retrieval sensitivity of the column-averaged dry-air mole fraction of CO2(XCO2) for the Chinese carbon dioxide observation satellite(TanSat) with a full physical forward model and the optimal estimation technique. The forward model is based on the vector linearized discrete ordinate radiative transfer model(VLIDORT) and considers surface reflectance, gas absorption, and the scattering of air molecules, aerosol particles, and cloud particles. XCO2 retrieval errors from synthetic TanSat measurements show solar zenith angle(SZA), albedo dependence with values varying from 0.3 to 1 ppm for bright land surface in nadir mode and 2 to 8 ppm for dark surfaces like snow. The use of glint mode over dark oceans significantly improves the CO2 information retrieved. The aerosol type and profile are more important than the aerosol optical depth, and underestimation of aerosol plume height will introduce a bias of 1.5 ppm in XCO2. The systematic errors due to radiometric calibration are also estimated using a forward model simulation approach.
基金Supported by the Program for Science and Technology Innovation Talents in Universities of Henan Province under Grant No.13HASTIT046
文摘An isoratio method is proposed to study the chemical potential of neutrons(protons) from the yield ratio of isotopes(isotones) differing in neutron-excess(I = N- Z). The measured fragments in the 140 A MeV ^(40),^(48) Ca and^(58),^(64) Ni +~9Be reactions, as well as those in the simulated^(58),^(64) Ni +~9Be reactions by using the antisymmetric molecular dynamics(AMD) model plus the secondary decay model gemini, have been adopted to perform the isoratio analysis.The results of the isoratio method verify that they are similar to that of the well known isoscaling method. The isoratio scaling phenomenon suggested by the isoratio method has also been found in the measured data and the fragments simulated by the AMD + gemini models.
