An adaptive transient surface wave exploration method, equipment and storage medium

Abstract

This invention proposes an adaptive transient surface wave exploration method, equipment, and storage medium. The method includes: exciting a seismic source and acquiring measurement data from the seismic source using geophones; acquiring the surface wave dispersion spectrum; the acquisition of the surface wave dispersion spectrum involves: using one geophone as the central channel and the remaining geophones within a defined range adjacent to the central channel as adjacent channels; calculating the surface wave dispersion spectrum based on the measurement data of the central channel and the measurement data of the adjacent channels; and acquiring the subsurface shear wave velocity structure of each geophone channel based on the surface wave dispersion spectrum, thereby obtaining the subsurface shear wave velocity profile across the entire measurement range to complete the exploration. Furthermore, this invention also discloses an adaptive transient surface wave exploration equipment and storage medium. This invention employs distributed cableless seismic geophones and acquires the subsurface shear wave velocity structure of each geophone channel through channel-by-channel inversion, significantly improving the resolution of the final subsurface shear wave velocity profile within the measurement range, greatly satisfying the requirements for refined exploration in complex environments.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration technology. More specifically, it relates to an adaptive transient surface wave exploration method, equipment, and storage medium. Background Technology

[0002] Active surface wave exploration (APW) is a seismic exploration method that uses artificial seismic sources such as hammering, falling weights, and explosives to generate surface waves of a certain frequency range on the Earth's surface, mainly Rayleigh-type surface waves. The shallow shear wave velocity is estimated by inverting the dispersion characteristics of the surface waves received by the geophone, thereby obtaining the subsurface shear wave velocity structure. This method has the advantages of high resolution, strong layering ability, convenient construction, and no influence from high-velocity layers. It is widely used in shallow surface exploration, especially in complex engineering geological exploration, and has a very broad application prospect.

[0003] However, conventional transient surface wave exploration methods use multiple geophones connected in series with cables to acquire seismic signals. The geophones are arranged in a straight line with fixed spacing, which places high demands on the acquisition site conditions. In complex environments, there may be obstructions from buildings or areas that are difficult to cross, making it impossible to meet the requirements of the acquisition site conditions and making it difficult to acquire seismic signals. In addition, in terms of data processing, conventional transient surface wave exploration methods only calculate one inversion result for each array, representing the velocity structure under the center of the array. Then, a two-dimensional shear wave velocity profile is obtained by lateral interpolation of the inversion results of multiple arrays. Since the inversion result of a single array represents the comprehensive reflection of the underground strata of the entire array, the lateral resolution of the final result is low, which is difficult to meet the requirements of fine exploration in complex environments. Summary of the Invention

[0004] To address at least one of the shortcomings or improvement needs of the prior art, the present invention provides an adaptive transient surface wave exploration method, device and storage medium, which can be used for exploration in complex environments, is simple and efficient to implement, and provides high resolution exploration results.

[0005] To achieve the above objectives, according to the first aspect of the present invention, the present invention adopts the following technical solution.

[0006] An adaptive transient surface wave exploration method, characterized in that the method includes:

[0007] Excite the seismic source and acquire the measurement data of the seismic source collected by the detector;

[0008] The surface wave dispersion spectrum is obtained by taking one of the detectors as the central channel and the other detectors within a set range adjacent to the central channel as adjacent channels, and calculating the surface wave dispersion spectrum based on the measurement data of the central channel and the measurement data of the adjacent channels.

[0009] Based on the surface wave dispersion spectrum, the subsurface shear wave velocity structure of each detector is obtained channel by channel, thereby obtaining the subsurface shear wave velocity profile within the measurement range to complete the exploration.

[0010] Furthermore, the detector is a distributed cableless seismic detector;

[0011] The detectors can be arranged in two ways: with equal spacing and with unequal spacing.

[0012] Furthermore, the surface wave dispersion spectrum is calculated by performing phase tilt superposition calculation on the measurement data of the center channel and the measurement data of the adjacent channels;

[0013] The measurement data includes vibration measurement data and the coordinate position of the detector.

[0014] Furthermore, the specific formula for calculating the phase tilt superposition is as follows:

[0015]

[0016] Among them, A i (f) represents the normalized amplitude spectrum of the vibration measurement data within the set range; d c d represents the offset distance of the central channel; i L represents the offset distance between adjacent channels; L represents the radius of the set range.

[0017] Furthermore, the vibration measurement data is obtained by using the detector to collect the seismic signal excited by the earthquake source, and then preprocessing the seismic signal.

[0018] The preprocessing includes noise suppression, bad sector processing, filtering, and gain compensation.

[0019] Furthermore, the underground shear wave velocity structure is obtained by inverting the dispersion curve of each detector based on the surface wave dispersion spectrum.

[0020] The inversion includes the least squares method, simulated annealing method, and genetic algorithm.

[0021] Furthermore, the underground shear wave velocity profile is obtained by performing transverse two-dimensional interpolation on the underground shear wave velocity structures of all the detectors obtained by channel-by-channel inversion to obtain a two-dimensional shear wave velocity profile, thereby obtaining the underground shear wave velocity profile within the measurement range.

[0022] Furthermore, when the central channel is located at the beginning or end of the arrangement, the surface wave dispersion spectrum is calculated after extending the arrangement by adding a detector based on the set range.

[0023] According to a second aspect of the present invention, an adaptive transient surface wave exploration device is also provided, comprising at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program that, when executed by the processing unit, causes the processing unit to perform the steps of any of the methods described above.

[0024] According to a third aspect of the invention, a storage medium is also provided, which stores a computer program executable by an access authentication device, which, when run on the access authentication device, causes the access authentication device to perform the steps of any of the methods described above.

[0025] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0026] (1) The adaptive transient surface wave exploration method, equipment and storage medium provided by the present invention uses distributed cableless seismic detectors to collect seismic signals, which allows the detectors to be flexibly deployed according to actual site conditions, breaking through the spatial limitations of traditional cables and making implementation convenient and quick; and the detectors can be arranged at equal intervals or at unequal intervals, so that the source signal can still be collected when encountering obstacles in complex environments. In particular, it has good adaptability in complex environments and has broad application prospects in engineering geological exploration.

[0027] (2) The adaptive transient surface wave exploration method, equipment, and storage medium provided by this invention perform phase tilt superposition calculation on the measurement data of the central channel and the measurement data of adjacent channels to obtain the surface wave dispersion spectrum. Based on this, the dispersion curve is obtained and inverted to obtain the underground shear wave velocity structure. In this way, the underground shear wave velocity structure of each detector is obtained by inverting each channel. Then, the underground shear wave velocity profile within the measurement range is obtained by two-dimensional lateral interpolation, thus completing the exploration. Since each detector corresponds to an underground shear wave velocity structure, the lateral resolution of the underground shear wave velocity profile within the final measurement range is greatly improved, the exploration results are more accurate, and the requirements for refined exploration in complex environments are met. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the process flow of an adaptive transient surface wave exploration method, device, and storage medium according to the present invention.

[0030] Figure 2 This is a schematic diagram of the detector arrangement and data processing of an adaptive transient surface wave exploration method, equipment, and storage medium according to the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Figure 1 This invention provides a flowchart illustrating an adaptive transient surface wave exploration method, equipment, and storage medium, which meets the requirements for refined exploration in complex environments. The method includes:

[0033] Excite the seismic source and acquire the measurement data of the seismic source collected by the detector;

[0034] Obtain the surface wave dispersion spectrum; the surface wave dispersion spectrum is obtained by taking one detector as the central channel and the other detectors within a set range adjacent to the central channel as adjacent channels. Based on the measurement data of the central channel and the measurement data of the adjacent channels, the surface wave dispersion spectrum is calculated and obtained.

[0035] The subsurface shear wave velocity structure of each detector is obtained channel by channel based on the surface wave dispersion spectrum, thereby obtaining the subsurface shear wave velocity profile within the measurement range to complete the exploration.

[0036] First, the seismic source is excited, and the measurement data of the seismic source is acquired by the detectors. Measurement data of the seismic source is acquired by each detector in a row corresponding to the same seismic source. This measurement data includes vibration measurement data and the coordinate position of the detector.

[0037] Specifically, at least one geophone is arranged linearly along the survey line. The geophones are used to collect the seismic signals excited by the earthquake source and the coordinate positions of the geophones. The seismic signals are then preprocessed to obtain vibration measurement data.

[0038] Existing technologies typically employ multiple geophones connected in series via cables to acquire seismic signals. The geophones need to be arranged in a straight line with a fixed spacing, usually 1 meter, 2 meters, or 5 meters. However, in complex environments, obstacles such as buildings, ditches, and vehicles are unavoidable, making it impossible to arrange the geophones sequentially and at equal intervals along a straight line. Therefore, the geophones in this invention preferably utilize distributed cableless seismic geophones. The geophones can be arranged arbitrarily along the survey line, with the arrangement including both equal and unequal spacing, depending on the specific conditions of the actual scenario.

[0039] This invention utilizes distributed cableless seismic detectors to acquire seismic signals from the seismic source and the coordinates of the detectors. The seismic signals are then preprocessed to obtain vibration measurement data. It is worth noting that the seismic signal is a waveform vibration signal transmitted from the seismic source, which is artificially excited to generate the waveform vibration signal using methods such as hammering or dropping. The excitation of the seismic source includes, but is not limited to, single-sided and multi-sided firing. The preprocessing includes, but is not limited to, noise suppression, bad channel processing, filtering, and gain compensation.

[0040] Then, the surface wave dispersion spectrum is obtained. The surface wave dispersion spectrum is obtained by taking one detector as the center channel and the other detectors within a set range adjacent to the center channel as adjacent channels. Based on the measurement data of the center channel and the measurement data of the adjacent channels, the surface wave dispersion spectrum is calculated.

[0041] Since the location of the seismic source and the location of the geophones both affect the calculation results of the surface wave dispersion spectrum, if the geophones are not evenly spaced, it means that the distance between the different geophones and the seismic source is also irregular. This invention uses phase tilt superposition to calculate the surface wave dispersion spectrum of the center channel by superimposing the measurement data of the adjacent channels. Regardless of whether the geophones are evenly or unequally spaced, the surface wave dispersion spectrum can be obtained by using phase tilt superposition.

[0042] It should be noted that the center channel can be any geophone used to acquire source measurement data; while adjacent channels must be other geophones within a set range adjacent to the center channel. The set range is a circle with radius L centered on the geophone of the center channel. The radius L is calculated based on multiple experiments, and the evaluation criterion is to obtain a high-quality surface wave dispersion spectrum.

[0043] Preferably, the specific formula for calculating the phase tilt superposition is as follows:

[0044]

[0045] Among them, A i (f) represents the normalized amplitude spectrum of vibration measurement data within the set range; dc Indicates the offset distance of the center track; d i The offset distance between adjacent tracks is indicated by L; L represents the radius of the set range.

[0046] When the center channel is located at the beginning or end of the array, and the beginning or end detector is the center channel, the surface wave dispersion spectrum is calculated by adding detectors to extend the array based on the set range.

[0047] Because the detectors at both ends of the array are unique, when calculating the surface wave dispersion spectrum of the center channel at both ends, there may be insufficient data channels on one side. That is, when the center channel is located at the beginning or end of the array, the beginning or end detector only has an adjacent channel on one side within the set range, which cannot accurately represent the surface wave dispersion spectrum of the beginning or end, resulting in an inaccurate underground shear wave velocity structure. Therefore, it is necessary to appropriately extend or move the array and repeat a certain number of channels. This involves setting up several additional detectors in front of the beginning detector along the survey line to obtain sufficient channel data. These newly added detectors only collect data for use by the beginning or end detectors; their surface wave dispersion spectra are not used.

[0048] Finally, the subsurface shear wave velocity structure of each detector is obtained channel by channel based on the surface wave dispersion spectrum, thereby obtaining the subsurface shear wave velocity profile within the measurement range to complete the exploration.

[0049] Specifically, the dispersion curve of the corresponding geophone is first obtained based on the surface wave dispersion spectrum of the geophone, and then the dispersion curve is inverted to obtain the subsurface shear wave velocity structure of each geophone. The inversion includes methods such as least squares, simulated annealing, and genetic algorithms. Then, the subsurface shear wave velocity structures of all geophones obtained through the inversion are subjected to lateral two-dimensional interpolation to obtain a two-dimensional shear wave velocity profile, thereby obtaining the subsurface shear wave velocity profile within the measurement range, thus enabling exploration in complex environments.

[0050] To gain a more detailed and clear understanding of the present invention, in conjunction with Figure 2 Further explanation. For example... Figure 2 The diagram shown is a schematic representation of the detector arrangement and data processing of an adaptive transient surface wave exploration method, device, and storage medium according to the present invention.

[0051] The geophones are arranged linearly along the survey line. Due to some obstructions, the spacing between the geophones is unequal. The seismic source is located to the left of the first geophone and at a certain distance from it. It is worth noting that when there are no obstructions, the geophones are preferably arranged at equal intervals; when there are obstructions, they are arranged at unequal intervals, excluding the obstructions.

[0052] First, the first detector is taken as the center channel, and the detectors within a radius of L are taken as adjacent channels; where L is the radius of a set range determined experimentally; that is, the second and third detectors are adjacent channels. The measurement data of the center channel and the measurement data of the two adjacent channels are superimposed with phase tilt to obtain the surface wave dispersion spectrum of the first detector.

[0053] Since the first geophone has an adjacent channel on only one side, a certain number of channels are repeated when the arrangement is appropriately extended or shifted. That is, several more geophones are set up to the left of the first geophone along the survey line to obtain sufficient channel data. Based on the L value, two geophones, A and B, are preferably set up. The measurement data of the first geophone, the second geophone, the third geophone, and the newly added geophones A and B are superimposed on the phase tilt data to obtain a relatively accurate surface wave dispersion spectrum for the first geophone. Then, the dispersion curve of the corresponding geophone is obtained from the surface wave dispersion spectrum, and the dispersion curve is inverted to obtain the underground shear wave velocity structure of the first geophone. Figure 2 In the data graph, the horizontal axis represents speed and the vertical axis represents depth; the greater the depth, the greater the speed.

[0054] Next, using the second detector as the central channel and detectors within a radius L as adjacent channels (i.e., the first, third, fourth, and newly added detector B are all adjacent channels), the measurement data from these five detectors (central and adjacent channels) are superimposed with phase tilt data to obtain a more accurate surface wave dispersion spectrum for the second detector. Then, based on the surface wave dispersion spectrum, the corresponding dispersion curve of the detector is obtained, and the dispersion curve is inverted to obtain the underground shear wave velocity structure of the second detector.

[0055] By analogy, the underground shear wave velocity structure of each detector is obtained in turn.

[0056] Finally, the underground shear wave velocity structure of all detectors obtained by inversion is subjected to lateral two-dimensional interpolation to obtain a two-dimensional shear wave velocity profile, thereby obtaining the underground shear wave velocity profile within the measurement range, thus completing the exploration in a complex environment.

[0057] In summary, this invention employs distributed cableless seismic detectors, which offer simpler, more flexible, faster, and more efficient deployment, exhibiting good adaptability in complex environments. Furthermore, during data processing, it combines measurement data from the central trace with data from adjacent traces within a defined range centered on the central trace to calculate the surface wave dispersion spectrum of the central trace. This process is repeated for each trace, inverting the subsurface shear wave velocity structure to obtain the values ​​for all traces. This significantly improves the resolution of the final two-dimensional velocity profile, meeting the requirements for refined exploration in complex environments.

[0058] According to a second aspect of the present invention, an adaptive transient surface wave exploration device is also provided, comprising at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program that, when executed by the processing unit, causes the processing unit to perform the steps of the above-described method.

[0059] According to a third aspect of the invention, the invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method. The computer-readable storage medium may include, but is not limited to, any type of disk, including floppy disks, optical disks, DVDs, CD-ROMs, microdrives, as well as magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic cards or optical cards, nanosystems (including molecular memory ICs), or any type of medium or device suitable for storing instructions and / or data.

[0060] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0061] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0062] In the several embodiments provided by this invention, it should be understood that the disclosed apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some service interface; the indirect coupling or communication connection between devices or units may be electrical or other forms.

[0063] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0064] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0065] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage device (CMD). Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned memory includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0066] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, which may include: a flash drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, etc.

[0067] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of other embodiments of this disclosure upon considering the specification and practicing the disclosure herein. This invention is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of adaptive transient surface wave prospecting, characterized in that, The method comprises: The method comprises: The surface wave dispersion spectrum is obtained by taking any one of the detectors as a center channel, taking the remaining detectors within a set range adjacent to the center channel as adjacent channels, and performing phase tilt stacking calculation on the measurement data of the center channel and the measurement data of the adjacent channels to obtain the surface wave dispersion spectrum. The set range is a circle with the detector of the center channel as a center point and a radius of , The offset distance of the center channel is represented by d0. The offset distance of the adjacent channel is represented by di. When the center channel is located at the head or tail end of the arrangement, the surface wave dispersion spectrum is calculated after the arrangement is extended by adding detectors based on the set range. The method comprises:

2. The method of claim 1, wherein, The method comprises: The method comprises:

3. The method of claim 1, wherein, The method comprises: wherein, represents a normalized amplitude spectrum of the vibration measurement data within the set range; represents a offset distance of the center trace; represents a offset distance of the adjacent trace; represents a radius of the set range.

4. The method of claim 1, wherein, The method comprises:

5. The method of claim 1, wherein, The method comprises:

6. An adaptive transient surface wave exploration device comprising at least one processing unit, and at least one storage unit, wherein, The method comprises:

7. A storage medium storing a computer program executable by an access authentication device, characterized by, The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method

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