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Method for extracting surface nuclear magnetic resonance signals

A ground nuclear magnetic resonance and signal extraction technology, which is applied in geophysical surveying, electric/magnetic exploration, and re-radiation, to achieve the effect of small fitting error and saving manpower and material resources

Active Publication Date: 2017-05-31
JILIN UNIV
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  • Abstract
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Problems solved by technology

[0005] The technical problem to be solved by the present invention is to provide a ground nuclear magnetic resonance signal extraction method, which solves the problem of effective extraction of MRS signals caused by strong power frequency harmonic interference and random noise in the magnetic resonance sounding water search work

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  • Method for extracting surface nuclear magnetic resonance signals
  • Method for extracting surface nuclear magnetic resonance signals
  • Method for extracting surface nuclear magnetic resonance signals

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Embodiment 1

[0082] Based on power frequency harmonic modeling and autocorrelation ground nuclear magnetic resonance signal extraction method, the present invention simulates a group of measurement data sets that include 16 independent acquisitions, refer to figure 1 , including the following steps:

[0083] Step (1): Use formula (3) to construct the noisy MRS signal as Figure 5 As shown in (a), its parameter is e 0 =100nV, f = 2326Hz and The fundamental frequency of the harmonic noise collected each time is randomly generated at 49.9-50.1Hz, the number of harmonics is 100, and the harmonic amplitude is randomly distributed within 200nV; the random noise collected each time is Gaussian white noise of 200nV; Spike noise is added, assuming all spike noise has been removed by existing methods.

[0084] Step (2): Use the harmonic modeling method to obtain the power frequency harmonic model where f 0 =50.018125Hz, subtract the power frequency harmonic model from the noisy MRS signal t...

Embodiment 2

[0088] In this example, the ground NMR groundwater detection instrument independently developed was used for field data collection near the Taipingchi Reservoir in Shaoguo Town, Nong'an County, Changchun City (the geomagnetic field is 54720nT, the corresponding Larmor frequency is 2330Hz, and the variation range is less than 2Hz). Experiment with data processing. In order to detect the aquifer from shallow to deep, 20 sets of transmission pulse moments were set according to the logarithmic distribution in the range of 0.2-8.5As, and each set of pulse moments was repeated 16 times, and the sampling rate was 50kHz. The acquisition time is 1s. The MRS signals collected at the 10th, 16th and 20th pulse moments are taken as the processing objects of the method of the present invention. Such as figure 1 Shown, based on power frequency harmonic modeling and autocorrelation ground NMR signal extraction method, comprises the following steps:

[0089] Step (1): Utilize the ground nuc...

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Abstract

The invention particularly discloses a method for extracting surface nuclear magnetic resonance signals on the basis of power-frequency harmonic modeling and self-correlation. The method includes steps of (1), acquiring a group of MRS (magnetic resonance sounding) noised data by the aid of surface nuclear magnetic resonance groundwater detecting instruments; (2), judging whether spike noise exists or not by the aid of a statistic process, removing the spike noise if the spike noise exists, substituting an interpolation result for the spike noise, and keeping the measurement data unchanged if the spike noise does not exist; (3), using a harmonic modeling process to remove power-frequency harmonic noise from the data after the spike noise is removed from the data; (4), carrying out self-correlation and superposition processing on the result obtained in the step (3) to reduce random noise; (5), extracting MRS signal parameters from the result obtained in the step (4). The method has the advantages that the problem of difficulty in effectively extracting MRS signals due to strong power-frequency harmonic interference and random noise in magnetic resonance depth measuring water exploration work can be solved by the aid of the method, and the fitting errors of the key feature parameters of the acquired MRS signals are small.

Description

technical field [0001] The invention relates to the technical field of noise filtering and parameter extraction of surface nuclear magnetic resonance groundwater detection signals, and specifically utilizes a ground nuclear magnetic resonance signal extraction method based on power frequency harmonic modeling and autocorrelation. Background technique [0002] Surface NMR (Magnetic Resonance Sounding, MRS), as a new geophysical technology, has been widely used in groundwater detection in recent years. Compared with the traditional geophysical indirect water finding method, the surface nuclear magnetic resonance method has the characteristics of high resolution, high efficiency, rich information and unique interpretation of hydrological parameters. The basic principle of the surface NMR method is to detect the MRS signal generated by the hydrogen-proton resonance transition in the groundwater, extract its characteristic parameters, and then obtain the water quality information...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01V3/38
CPCG01V3/38Y02A90/30
Inventor 蒋川东朱慧田宝凤杜官峰张健任华刘健楠
Owner JILIN UNIV
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