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A Noise Filtering Method for Full-Wave NMR Signals Based on Independent Component Analysis

An independent component analysis, nuclear magnetic resonance technology, applied in the direction of electronic magnetic resonance / nuclear magnetic resonance detection, electric / magnetic exploration, sound wave re-radiation, etc. and other problems, to achieve the effect of saving manpower and material resources, reducing information loss, and fast computing

Inactive Publication Date: 2017-04-12
JILIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

It can be seen that independent component analysis has been successfully applied to various fields of signal processing, but it has not been applied to noise filtering of MRS signals
[0009] At present, when applying traditional independent component analysis to signal separation, the main problems are: underdetermined blind source separation, uncertain amplitude of separated signals
The so-called underdetermined blind source separation problem refers to the fact that among the noise sources contained in the MRS signal, the noise interference is complex, resulting in an unknown number of independent sources, and considering the limitations of instruments and equipment, the number of observed signals collected is less than the number of source signals Number of cases
Such problems will undoubtedly limit the application of ICA in noise filtering of NMR sounding signals
In addition, if the amplitude of the separated MRS signal cannot be accurately estimated after the noisy MRS signal is subjected to ICA, it will lead to an increase in the error rate of formation water content estimation in the subsequent inversion interpretation, which will affect the progress of the project

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Embodiment 1

[0102] This embodiment is a simulation experiment of the method of the present invention carried out under the MATLAB 7.0 programming environment.

[0103] The simulation algorithm of the full-wave NMR signal noise filtering method based on independent component analysis, refer to figure 1 , including the following steps:

[0104] Step (1): Use formula (10) to construct the Larmor frequency is 2325Hz, amplitude e 0 is 150nV, the relaxation time T 2 * is an ideal MRS signal of 0.15s, as shown in Figure 4(a), and Figure 4(b) is its corresponding spectrum. Add 2350Hz and 2300Hz power frequency interference near the Larmor frequency of the signal, and form an observed MRS signal X with a signal-to-noise ratio of -6.7471dB through a certain linear combination 1 (t) (for a row vector), as shown in Figure 5(a);

[0105] Step (2): Observing the MRS signal X 1 (t) Perform Fourier transform to obtain its frequency spectrum, as shown in Fig. 5(b). Determine the frequency of the po...

Embodiment 2

[0112] In this embodiment, the MRS signals collected in Shaoguo Town, Changchun City (the Larmor frequency is 2326 Hz) are used as the processing object of the method of the present invention. Such as figure 1 As shown, the full-wave NMR signal noise filtering method based on independent component analysis includes the following steps:

[0113] Step (1): Collect a set of observed MRS signals X using the nuclear magnetic resonance sounding (MRS) water detector 1 (t) (be a row vector), as shown in Figure 8 (a), calculate its signal-to-noise ratio as SNR=-4.9186dB;

[0114] Step (2): For the collected observed MRS signal X 1 (t) Perform Fourier transform to obtain its spectrum, as shown in Figure 8(b), it can be seen that the signal is at f 0 =2300Hz, f1 =2350Hz, f 2 = 2450Hz has strong power frequency harmonic interference, in addition, at f 3 = Strong single-frequency interference at 2383.5Hz;

[0115] Step (3): According to the noise frequency determined in step (2), use...

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Abstract

The invention discloses a full-wave nuclear magnetic resonance signal denoising method based on independent component analysis. The full-wave nuclear magnetic resonance signal denoising method is mainly used for power frequency harmonic interference or certain single-frequency interference in full-wave nuclear magnetic resonance signals. The method comprises the steps that firstly, utilizing a nuclear magnetic resonance sounding water detecting instrument for collecting MRS signals, obtaining the frequency of power frequency harmonic interference or certain single-frequency interference contained in the collected signals through spectral analysis, and adopting a digital orthogonal method for constructing input channel signals to solve the underdetermined blind source separation problem; then, using the constructed input channel signals and the collected MRS signals as input signals for conducting independent component analysis to obtain separated MRS signals; finally, adopting the spectrum correcting method for solving the problem that the separated MRS signals have uncertain amplitude, and then extracting denoised MRS signals. According to the full-wave nuclear magnetic resonance signal denoising method, the problem of the underdetermined blind source and the problem of the uncertain amplitude usually existing in independent component analysis are solved, the power frequency harmonic interference or the certain single-frequency interference in the noised MRS signals is effectively filtered out, and compared with a traditional MRS signal denoising method, the full-wave nuclear magnetic resonance signal denoising method has the advantages of being high in arithmetic speed, high in signal to noise ratio, high in practicability and the like.

Description

technical field [0001] The invention relates to a method for filtering out magnetic resonance sounding (Magnetic Resonance Sounding, MRS) signal noise, in particular to a filtering method for full-wave nuclear magnetic resonance signal noise based on the principle of independent component analysis. Background technique [0002] Magnetic resonance sounding (Magnetic Resonance Sounding, MRS) technology is a high-tech, non-destructive, high-resolution direct groundwater detection method developed in recent years. It is a weak signal detection technology, and its basic principle is to detect groundwater The NMR signal generated by the resonant transition of the hydrogen proton is used to detect groundwater. The general expression for a full-wave NMR signal is: [0003] [0004] Equation (10) contains four key parameters of the MRS signal: E 0 (q), T 2 * , ω 0 , respectively represent the initial amplitude of the signal related to the water content of the formation, the...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01V3/38G01V3/14
Inventor 田宝凤周媛媛王悦李振宇谢燕妮
Owner JILIN UNIV
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