CN109100813A - A method of it is filtered based on collaboration and eliminates spike noise in ground nuclear magnetic resonance data - Google Patents
A method of it is filtered based on collaboration and eliminates spike noise in ground nuclear magnetic resonance data Download PDFInfo
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Abstract
The present invention relates to a kind of methods for being filtered based on collaboration and eliminating spike noise in ground nuclear magnetic resonance data.Judge to be divided into the presence or absence of spike noise, and by measurement data comprising spike noise and not comprising two groups of spike noise in all measurement data under a pulse square by 3 σ rules first.Secondly other that discrete cosine and Hadamard transformation are carried out to it, obtain two groups of coefficient in transform domain.Filter factor is calculated using the transformation coefficient of no spike noise data, the coefficient comprising spike noise data is filtered.Finally, carrying out Hadamard and inverse discrete cosine transform to the filtered coefficient comprising spike noise data, the elimination of spike noise is realized.The present invention does not delete or replaces the data comprising the spike noise period, unchanged the relaxation decay feature of face NMR signal.Through testing, this method is high to the elimination accuracy of spike noise in the nuclear magnetic resonance data of ground, the extraction accuracy of the number of improving characteristic parameter.
Description
Technical field
The invention belongs to ground nuclear magnetic resonance data processing fields, are particularly a kind of elimination ground nuclear magnetic resonance number
According to the method for middle spike noise.
Background technique
Ground nuclear magnetic resonance is a kind of geophysical method of non-intrusive direct detection groundwater occurrence attribute, has and differentiates
The advantages that rate height and quantitative interpretation, is widely used in the fields such as water resource exploration and the early warning of underground engineering water damage.But ground
Interference of the signal that magnetic nuclear resonance method obtains vulnerable to spike noise, industrial frequency noise and random noise causes to acquire data letter
It makes an uproar than low.
Spike noise is random instantaneous big caused by electrical equipment sparking mainly by magnetic storm in ground nuclear magnetic resonance data
Amplitude interference, it is characterised in that the duration is short (several milliseconds), and amplitude is much larger than ground nuclear magnetic resonance signal and other noises.
The presence of spike noise seriously affects the processing of industrial frequency noise and random noise, and then influences the standard that subsequent parameter extracts result
Really.
Patent CN103823244A discloses a kind of magnetic resonance three-component noise cancellation apparatus and method.Place is detected using unified
X and the correlation of y-component signal and z-component signal eliminate spike noise in z-component receiving coil, and after being filtered,
Obtain reliable ground magnetic resonance signal.But big receiving coil (100m*100m), x-component and y-component coil are laid with and are stranded
Difficulty considerably increases the complexity of field trial.
Patent CN106772646A discloses a kind of ground nuclear magnetic resonance method for extracting signal.For spike noise, propose
Statistic analysis method.Spike noise if it exists then replaces spike noise section measurement data with difference result, to realize removal point
Peak noise.But due in the MR data of ground simultaneously include industrial frequency harmonic noise, using adjacent data difference result into
Row substitution can introduce additional noise.
Patent CN107045149A discloses a kind of all-wave NMR signal noise filtering method of double singular value decompositions.
This method subtracts first time singular value decomposition first with the ground nuclear magnetic resonance data of measurement and reconstructs noise data, secondly right
It carries out second of singular value decomposition, finally reconstructs ground nuclear magnetic resonance signal.But this method is made an uproar only for industrial frequency harmonic
Sound and random noise not can be removed the interference of spike noise.
Summary of the invention
Technical problem to be solved by the present invention lies in provide spike noise in a kind of elimination ground nuclear magnetic resonance data
Method, solve in ground nuclear magnetic resonance detection it is random, substantially NMR signal characteristic parameter extraction caused by spike noise is asked
Topic.
The invention is realized in this way
A method of it is filtered based on collaboration and eliminates spike noise in ground nuclear magnetic resonance data, this method comprises:
Emit same pulse pulse square K times, acquires corresponding K group ground nuclear magnetic resonance data；
According to 3 σ rules, spike detection is carried out to K group measurement data respectively, and be grouped to data, be divided into including point
Peak noise data vS' and do not include spike noise data v 'f；
To comprising spike noise data and not including that spike noise data carry out one-dimensional discrete cosine transform respectively and obtain
One-dimensional transform domain coefficient VS' (u) and Vf' (u) obtains two-dimensional transform domain coefficient H after then carrying out one-dimensional hadamard transformation
(Vs') and H (Vf′)；
To the energy balane Wiener filtering coefficient of the coefficient in transform domain without spike noise data；
Collaboration Wiener filtering is carried out to the coefficient in transform domain containing spike noise data using Wiener filtering coefficient；
Hadamard inverse transformation and one-dimensional discrete cosine inverse transformation, realization pair are carried out to the data by collaboration Wiener filtering
The compacting of spike noise in ground nuclear magnetic resonance data.
Further, wherein the specific implementation of 3 σ rules includes:
Calculate the mean μ and standard deviation sigma of kth group (k=1 ..., K) measurement data；
Judge measurement data whether within section [+3 σ of μ -3 σ, μ]；
If there is data then think that there are spike noises beyond this section；
K group ground nuclear magnetic resonance data are divided into two classes according to spike noise whether is contained in data, include spike noise
A kind of data be denoted as vS', a kind of data not comprising spike noise are denoted as v 'f。
Further, one-dimensional discrete cosine transform obtains one-dimensional transform domain coefficient VS' (u) and Vf' (u), wherein carrying out one-dimensional
Formula used by discrete cosine transform are as follows:
Wherein t is the sampling time, and u is that generalized frequency becomes
Amount, N is sampling number.
Further, to one-dimensional transform domain coefficient VS' (u) and Vf' (u) carries out hadamard respectively and converts to obtain two-dimentional change
Change domain coefficient H (Vs') and H (Vf') used by calculation formula are as follows:
Wherein WHFor hadamard matrix.
Further, Wiener filtering coefficient w is
σ ' is v 'fVariance.
Further, to the coefficient in transform domain H (V containing spike noises') collaboration Wiener filtering is carried out, it obtains
Using following formula:
Compared with prior art, the present invention beneficial effect is: the present invention does not need out of office without changing measuring device
Increase other extra measuring process in outer experiment.Meanwhile being made using the same data bought under pulse square not comprising spike noise
For reference, it is filtered in transform domain, additional noise will not be introduced.It is total to can effectively improve ground magnetic for the implementation of this technology
The vibration quality of data, and then improve inversion result accuracy.
Detailed description of the invention
Fig. 1 is a kind of method for filtering spike noise in elimination ground nuclear magnetic resonance data based on collaboration of the present invention
Flow chart；
The time domain waveform for first group of ground nuclear magnetic resonance data that Fig. 2 is collected；
The time domain waveform for the tenth group of ground nuclear magnetic resonance data that Fig. 3 is collected；
Fig. 4 ground nuclear magnetic resonance is free of the two-dimensional transform domain coefficient of spike noise group data；
The two-dimensional transform domain coefficient of Fig. 5 ground nuclear magnetic resonance data of group containing spike noise；
Fig. 6 removes nuclear magnetic resonance data stack result figure after spike noise.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to embodiments, to the present invention
It is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, it is not used to
Limit the present invention.
To emit same pulse square 32 times, obtains corresponding 32 groups of ground nuclear magnetic resonance data instances and be illustrated.Referring to
Shown in Fig. 1,
Step 1, emit same pulse square 32 times, acquire corresponding 32 groups of ground nuclear magnetic resonances data v=[v1,v2,…,
v32]T, wherein first group and the tenth group of time domain waveform difference is as shown in Figures 2 and 3.
Step 2, using 3 σ rules, spike detection is carried out to 32 groups of measurement data respectively.Calculate separately 32 groups of measurement data
Mean μ and standard deviation sigma, 32 groups of measurement data are judged first, judge that each group is whether beyond the area [+3 σ of μ -3 σ, μ]
Between, if this group of data are denoted as a kind of v ' not comprising spike noise all without departing from the section by all dataf；It counts if it exists
According to being more than the section [+3 σ of μ -3 σ, μ], this group of data are denoted as to a kind of v comprising spike noiseS′
Step 3, firstly, according to formula (1), (2) and formula (3), (4), each group of data in two class data are carried out respectively
One-dimensional discrete cosine transform obtains one-dimensional transform domain coefficient VS' (u) and Vf′(u)。
Wherein, t is the sampling time, and u is generalized frequency variable, and N is sampling number.
Secondly, according to formula (5) and formula (6) respectively to VS' (u) and Vf' (u) carries out hadamard transformation, obtains two-dimensional transform
Domain coefficient H (Vs') and H (Vf'), it is as shown in Figure 4, Figure 5 respectively.
Wherein WHFor hadamard matrix.
Step 4, with the coefficient in transform domain H (V without spike noise dataf') energy balane Wiener filtering coefficient w,
σ ' is v 'fVariance, σ ' is equal to 10 in the present embodiment.
To the coefficient in transform domain H (V containing spike noises') collaboration Wiener filtering is carried out, see formula (7), obtains
Step 5, right using formula (8) and formula (9)Hadamard inverse transformation and one-dimensional discrete cosine inverse transformation are carried out,
It obtainsRealize the compacting of spike noise in ground nuclear magnetic resonance data.
Fig. 6 gives, and the comparison of stack result, the result are aobvious before 32 groups of data deglitch noises and after removal spike noise
Show, the method for the present invention can effectively remove the interference of the spike noise in the nuclear magnetic resonance data of ground, and will not lose signal.
The foregoing is merely illustrative of the preferred embodiments of the present invention, is not intended to limit the invention, all in essence of the invention
Made any modifications, equivalent replacements, and improvements etc., should all be included in the protection scope of the present invention within mind and principle.
Claims (6)
1. a kind of filter the method for eliminating spike noise in ground nuclear magnetic resonance data based on collaboration, which is characterized in that this method
Include:
Emit same pulse pulse square K times, acquires corresponding K group ground nuclear magnetic resonance data；
According to 3 σ rules, spike detection is carried out to K group measurement data respectively, and be grouped to data, be divided into and making an uproar including spike
Sound data vS' and do not include spike noise data v 'f；
To comprising spike noise data and not do not include spike noise data carry out respectively one-dimensional discrete cosine transform obtain it is one-dimensional
Coefficient in transform domain V 'S(u) and V 'f(u), two-dimensional transform domain coefficient H (V ' is obtained after then carrying out one-dimensional hadamard transformations) and H
(V′f)；
Utilize the energy balane Wiener filtering coefficient of the coefficient in transform domain without spike noise data；
Collaboration Wiener filtering is carried out to the coefficient in transform domain containing spike noise data using Wiener filtering coefficient；
Hadamard inverse transformation and one-dimensional discrete cosine inverse transformation are carried out to the data by collaboration Wiener filtering, realized to ground
The compacting of spike noise in nuclear magnetic resonance data.
2. according to the method for claim 1, which is characterized in that wherein the specific implementation of 3 σ rules includes:
Calculate the mean μ and standard deviation sigma of kth (k=1 ..., K) group measurement data；
Judge measurement data whether within section [+3 σ of μ -3 σ, μ]；
If there is data then think that there are spike noises in this group of data beyond this section；
K group ground nuclear magnetic resonance data are divided into two classes according to spike noise whether is contained in data, one comprising spike noise
Class data are denoted as vS', a kind of data not comprising spike noise are denoted as v 'f。
3. according to the method for claim 1, which is characterized in that one-dimensional discrete cosine transform obtains one-dimensional transform domain coefficient V 'S
(u) and V 'f(u), wherein carrying out formula used by one-dimensional discrete cosine transform are as follows:
Wherein t is the sampling time, and u is generalized frequency variable, and N is
Sampling number.
4. according to the method for claim 1, which is characterized in that one-dimensional transform domain coefficient V 'S(u) and V 'f(u) respectively into
Row hadamard converts to obtain two-dimensional transform domain coefficient H (V 's) and H (V 'f) used by calculation formula are as follows:
Wherein WHFor hadamard matrix.
5. according to the method for claim 1, which is characterized in that Wiener filtering coefficient w is
σ ' is v 'fVariance.
6. according to the method for claim 5, which is characterized in that the coefficient in transform domain H (V ' containing spike noises) carry out
Wiener filtering is cooperateed with, is obtainedUsing following formula:
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| CN110159262B (en) * | 2019-05-29 | 2020-10-13 | 中国石油大学(北京) | Noise reduction processing method and device for nuclear magnetic resonance logging echo data |
| CN113536233A (en) * | 2021-07-12 | 2021-10-22 | 中国科学院海洋研究所 | Ocean buoy data quality control system |
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