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A new approach for separating mixed model parameters:application to simultaneous inversion of earthquake source parameters
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作者 Weijian Mao 《Earthquake Science》 2014年第2期189-196,共8页
A method for simultaneous determination of mixed model parameters,which have different physical dimensions or different responses to data,is presented.Mixed parameter estimation from observed data within a single mode... A method for simultaneous determination of mixed model parameters,which have different physical dimensions or different responses to data,is presented.Mixed parameter estimation from observed data within a single model space shows instabilities and trade-offs of the solutions. We separate the model space into N-subspaces based on their physical properties or computational convenience and solve the N-subspaces systems by damped least-squares and singular-value decomposition. Since the condition number of each subsystem is smaller than that of the single global system,the approach can greatly increase the stability of the inversion. We also introduce different damping factors into the subsystems to reduce the tradeoffs between the different parameters. The damping factors depend on the conditioning of the subsystems and may be adequately chosen in a range from 0.1 % to 10 % of the largest singular value. We illustrate the method with an example of simultaneous determination of source history,source geometry,and hypocentral location from regional seismograms,although it is applicable to any geophysical inversion. 展开更多
关键词 Separation of model parameters Damped least-squares Singular value decomposition(SVD) Source inversion
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A new damping ratio identification method based on pattern search
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作者 刘彦 谭久彬 +1 位作者 谭志波 王雷 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2010年第1期141-144,共4页
In order to improve the effectiveness of traditional time domain identification methods in identifying damping ratios, a new damping ratio identification method based on pattern search is proposed by fluctuating the r... In order to improve the effectiveness of traditional time domain identification methods in identifying damping ratios, a new damping ratio identification method based on pattern search is proposed by fluctuating the reliable natural frequency obtained through traditional time domain identification methods by about 10% to build the boundary conditions, using all the initial identification results to establish the free decay response of the system, and using the pattern search method to correct the initial identification results with the residual sum of squares between the free decay response and the actually measured free-decay signal as the objective function. The proposed method deals with the actually measured free-decay signal with curve fitting and avoids enlarging the identified error caused by intermediate conversion, so it can effectively improve the identified accuracy of damping ratios. Simulations for a room-sized vibration isolation foundation show that the relative errors of analyzed three damping ratios are down to 1.05%, 1.51% and 3.7% by the proposed method from 8.42%, 5.85% and 8.5% by STD method when the noise level is 10%. 展开更多
关键词 modal parameter identification damping ratio pattern search
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Transformation between polar and rectangular coordinates of stiffness and dampness parameters in hydrodynamic journal bearings 被引量:1
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作者 Zhuxin TIAN Yu HUANG 《Friction》 SCIE EI CAS CSCD 2021年第1期201-206,共6页
The stiffness and dampness parameters of journal bearings are required in rectangular coordinates for analyzing the stability boundary and threshold speed of oil film bearings.On solving the Reynolds equation,the oil ... The stiffness and dampness parameters of journal bearings are required in rectangular coordinates for analyzing the stability boundary and threshold speed of oil film bearings.On solving the Reynolds equation,the oil film force is always obtained in polar coordinates;thus,the stiffness and dampness parameters can be easily obtained in polar coordinates.Therefore,the transformation between the polar and rectangular coordinates of journal bearing stiffness and dampness parameters is discussed in this study. 展开更多
关键词 coordinate transformation stiffness parameters dampness parameters hydrodynamic journal bearings
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