航空瞬变电磁法是一种快速普查良导电金属矿的航空物探方法,由于其具有速度快、成本低、探测范围大等优点,已经在国内外获得了较为广泛的应用。由于二次场与源无关且反映地下介质的特性,所以主要针对二次场进行处理和解释。但二次场的...航空瞬变电磁法是一种快速普查良导电金属矿的航空物探方法,由于其具有速度快、成本低、探测范围大等优点,已经在国内外获得了较为广泛的应用。由于二次场与源无关且反映地下介质的特性,所以主要针对二次场进行处理和解释。但二次场的有效能量较弱,因此常常受到各种干扰的影响,以至降低了后期的处理和解释精度。为此,寻求合适的滤波或去噪方法抑制其噪声成为亟待解决的问题。本文应用短时傅里叶变换STFT(Short Time Fourier Transform)分析去噪前后二次场信号的时频特性,为航空瞬变电磁信号去噪选择合适的滤波方法提供依据,并及时评价滤波效果。实验结果表明利用STFT对航空电磁数据处理是有效的可行的。展开更多
对分层介质半空间瑞利波的频散特性,用一种时频分析方法——重排的平滑伪魏格纳维尔分布(RSPWVD,Reassign- ment of Smooth Pseudo-Wigner Ville Distribution)进行了分析和研究。对均匀半空间和两层介质半空间的理论和实验研究表明,由...对分层介质半空间瑞利波的频散特性,用一种时频分析方法——重排的平滑伪魏格纳维尔分布(RSPWVD,Reassign- ment of Smooth Pseudo-Wigner Ville Distribution)进行了分析和研究。对均匀半空间和两层介质半空间的理论和实验研究表明,由于层状介质中瑞利波的频散曲线存在多个模式,所获得的群速度频散曲线在不同的频段显示出来的模式是对应表面位移幅度占主导作用的模式。频散曲线的这种模式判定对利用层状半空间的瑞利波反演介质参数是必须预先了解的。展开更多
Adaptive data analysis provides an important tool in extracting hidden physical information from multiscale data that arise from various applications. In this paper, we review two data-driven time-frequency analysis m...Adaptive data analysis provides an important tool in extracting hidden physical information from multiscale data that arise from various applications. In this paper, we review two data-driven time-frequency analysis methods that we introduced recently to study trend and instantaneous frequency of nonlinear and nonstationary data. These methods are inspired by the empirical mode decomposition method （EMD） and the recently developed compressed （compressive） sensing theory. The main idea is to look for the sparsest representation of multiscale data within the largest possible dictionary consisting of intrinsic mode functions of the form {a（t） cos（0（t））}, where a is assumed to be less oscillatory than cos（θ（t）） and θ ＇≥ 0. This problem can be formulated as a nonlinear ι0 optimization problem. We have proposed two methods to solve this nonlinear optimization problem. The first one is based on nonlinear basis pursuit and the second one is based on nonlinear matching pursuit. Convergence analysis has been carried out for the nonlinear matching pursuit method. Some numerical experiments are given to demonstrate the effectiveness of the proposed methods.展开更多
文摘航空瞬变电磁法是一种快速普查良导电金属矿的航空物探方法,由于其具有速度快、成本低、探测范围大等优点,已经在国内外获得了较为广泛的应用。由于二次场与源无关且反映地下介质的特性,所以主要针对二次场进行处理和解释。但二次场的有效能量较弱,因此常常受到各种干扰的影响,以至降低了后期的处理和解释精度。为此,寻求合适的滤波或去噪方法抑制其噪声成为亟待解决的问题。本文应用短时傅里叶变换STFT(Short Time Fourier Transform)分析去噪前后二次场信号的时频特性,为航空瞬变电磁信号去噪选择合适的滤波方法提供依据,并及时评价滤波效果。实验结果表明利用STFT对航空电磁数据处理是有效的可行的。
文摘对分层介质半空间瑞利波的频散特性,用一种时频分析方法——重排的平滑伪魏格纳维尔分布(RSPWVD,Reassign- ment of Smooth Pseudo-Wigner Ville Distribution)进行了分析和研究。对均匀半空间和两层介质半空间的理论和实验研究表明,由于层状介质中瑞利波的频散曲线存在多个模式,所获得的群速度频散曲线在不同的频段显示出来的模式是对应表面位移幅度占主导作用的模式。频散曲线的这种模式判定对利用层状半空间的瑞利波反演介质参数是必须预先了解的。
基金supported by Air Force Ofce of Scientifc ResearchMultidisciplinary University Research Initiative+3 种基金USA(Grant No.FA9550-09-1-0613)Department of Energy of USA(Grant No.DE-FG02-06ER25727)Natural Science Foundation of USA(Grant No.DMS-0908546)National Natural Science Foundation of China(Grant No.11201257)
文摘Adaptive data analysis provides an important tool in extracting hidden physical information from multiscale data that arise from various applications. In this paper, we review two data-driven time-frequency analysis methods that we introduced recently to study trend and instantaneous frequency of nonlinear and nonstationary data. These methods are inspired by the empirical mode decomposition method （EMD） and the recently developed compressed （compressive） sensing theory. The main idea is to look for the sparsest representation of multiscale data within the largest possible dictionary consisting of intrinsic mode functions of the form {a（t） cos（0（t））}, where a is assumed to be less oscillatory than cos（θ（t）） and θ ＇≥ 0. This problem can be formulated as a nonlinear ι0 optimization problem. We have proposed two methods to solve this nonlinear optimization problem. The first one is based on nonlinear basis pursuit and the second one is based on nonlinear matching pursuit. Convergence analysis has been carried out for the nonlinear matching pursuit method. Some numerical experiments are given to demonstrate the effectiveness of the proposed methods.
