Method and system for constructing three-dimensional model in drill hole based on point cloud ring constraint

Abstract

The invention provides a borehole internal three-dimensional model construction method and system based on point cloud ring constraint, and relates to the technical field of borehole three-dimensional modeling, and the method comprises the steps: controlling a laser probe to rotate and advance, and obtaining a borehole contour information sequence at each section; drill hole contour coordinate sequences at different sections in the drill hole are obtained based on the drill hole contour information sequences of all the sections; generating a standardized three-dimensional point cloud sequence based on the drilling contour coordinate sequence; and a continuous surface model is generated based on the standardized three-dimensional point cloud sequence, constrained Delaunay triangulation and forced closed loop constraint are performed on each layer of annular point cloud of the continuous surface model, a longitudinal triangular belt grid is generated, and construction of a drilling three-dimensional model is completed. According to the method disclosed by the invention, pores or fractures in the drill hole can be intuitively displayed.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of borehole three-dimensional modeling, in particular to a borehole internal three-dimensional model construction method and system based on point cloud ring constraint. BACKGROUND

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute the prior art.

[0003] In underground engineering such as tunnels and mining, the integrity of the surrounding rock can be understood through boreholes. According to the number and location of cracks, pores and fracture zones in the borehole, potential safety hazards during construction can be detected in time, so that appropriate preventive and disposal measures can be taken in time. This helps to avoid engineering accidents, protect personnel and equipment safety, and improve construction efficiency.

[0004] Traditionally, the internal situation of the borehole is observed by using the technology of borehole peeping, a high-definition camera is pushed to the deep part of the borehole by using a splicable long rod, and a video is recorded. Personnel need to understand the integrity of the internal surrounding rock through the borehole video. This method has limitations and inconvenience. The light in the borehole is dim, and a camera light needs to be used for exploration. At this time, the reflection of the rock surface will affect the judgment of the technician. When observing a long borehole, the video time is too long, and the technician may miss important geological information during a long observation.

[0005] At present, most three-dimensional modeling methods based on digital twinning rely on high-precision equipment. These devices have high use cost, large volume and poor environmental adaptability, and are not convenient to deploy in the complex and variable construction site of the tunnel. Moreover, the traditional three-dimensional modeling technology needs to process a large amount of data, and involves a series of operations such as denoising, splicing and enhancement, which leads to a long model reconstruction period in the post-processing scheme, thereby requiring a high performance of the computing device. SUMMARY

[0006] In order to solve the above problems, the present disclosure provides a borehole internal three-dimensional model construction method and system based on point cloud ring constraint. The internal shape information of the borehole is obtained by laser ranging, the contour distance information of each section in the borehole is obtained, the standardized three-dimensional point cloud sequence is generated according to the borehole information sequence at each distance, the discrete point cloud is converted into a continuous surface model, the constraint Delaunay triangulation is performed on each layer of annular point cloud, the ring constraint is forced to be closed, the longitudinal triangular strip grid is generated, and the borehole three-dimensional model is constructed.

[0007] According to some embodiments, the present disclosure adopts the following technical solutions: The borehole internal three-dimensional model construction method based on point cloud ring constraint comprises: acquire a starting position, a starting angle and a distance corresponding to the starting angle of the laser probe in the borehole, and generate an initial borehole profile information sequence; control the laser probe to rotate, acquire an angle of rotation of the laser probe and a measured distance at the angle, generate a current borehole profile information sequence based on the initial borehole profile information sequence, the angle of current rotation and the measured distance at the angle, and control the laser probe to rotate deeper into the borehole, so as to generate a borehole profile information sequence at each position; acquire borehole profile coordinate sequences at different cross sections in the borehole based on the borehole profile information sequences at each position, and generate a standardized three-dimensional point cloud sequence based on the borehole profile coordinate sequences; generate a continuous surface model based on the standardized three-dimensional point cloud sequence, perform constrained Delaunay triangulation on each layer of annular point cloud of the continuous surface model, generate a longitudinal triangular strip grid by forcing a closed ring constraint, and complete construction of a three-dimensional model of the borehole.

[0008] According to some embodiments, the present disclosure adopts the technical solutions as follows: A borehole internal three-dimensional model construction system based on point cloud ring constraint comprises: An initialization module is configured to acquire a starting position, a starting angle and a distance corresponding to the starting angle of the laser probe in the borehole, and generate an initial borehole profile information sequence; A sequence acquisition module is configured to control the laser probe to rotate, acquire an angle of rotation of the laser probe and a measured distance at the angle, generate a current borehole profile information sequence based on the initial borehole profile information sequence, the angle of current rotation and the measured distance at the angle, and control the laser probe to rotate deeper into the borehole, so as to generate a borehole profile information sequence at each position; A point cloud processing module is configured to acquire borehole profile coordinate sequences at different cross sections in the borehole based on the borehole profile information sequences at each position, and generate a standardized three-dimensional point cloud sequence based on the borehole profile coordinate sequences; A model generation module is configured to generate a continuous surface model based on the standardized three-dimensional point cloud sequence, perform constrained Delaunay triangulation on each layer of annular point cloud of the continuous surface model, generate a longitudinal triangular strip grid by forcing a closed ring constraint, and complete construction of a three-dimensional model of the borehole.

[0009] According to some embodiments, the present disclosure adopts the technical solutions as follows: A computer program product comprises a computer program, which, when executed by a processor, implements the borehole internal three-dimensional model construction method based on point cloud ring constraint.

[0010] According to some embodiments, the present disclosure adopts the technical solutions as follows: A non-transitory computer readable storage medium for storing computer instructions, which, when executed by a processor, implement the point cloud ring constraint based three-dimensional model construction method for a borehole interior.

[0011] According to some embodiments, the present disclosure adopts the technical solution as follows: An electronic device, comprising a processor, a memory and a computer program; wherein the processor is connected with the memory, and the computer program is stored in the memory; when the electronic device is running, the processor executes the computer program stored in the memory, so that the electronic device implements the point cloud ring constraint based three-dimensional model construction method for a borehole interior.

[0012] Compared with the prior art, the present disclosure has the beneficial effects that: The point cloud ring constraint based three-dimensional model construction method for a borehole interior of the present disclosure acquires point cloud data in the borehole interior through laser ranging technology, reduces the volume of the detection instrument, and simplifies the borehole detection and data processing process.

[0013] The point cloud ring constraint based three-dimensional model construction method for a borehole interior of the present disclosure can accurately collect point cloud data in a narrow borehole, and quickly construct a three-dimensional model of the borehole through a Delaunay triangulation algorithm without relying on a large amount of computing resources. The model can accurately and intuitively show the surrounding rock conditions in the borehole, which is helpful for technicians to analyze the distribution of cracks and fractured zones in the borehole.

[0014] The point cloud ring constraint based three-dimensional model construction method for a borehole interior of the present disclosure is suitable for three-dimensional form reconstruction of small-diameter (Φ50-150mm) boreholes such as coal mine gas extraction holes, roadway and tunnel support quality detection holes, and can be compatible with various borehole types such as vertical holes and inclined holes. BRIEF DESCRIPTION OF DRAWINGS

[0015] The drawings accompanying the specification of the present disclosure serve to provide a further understanding of the present disclosure, and the illustrative embodiments of the present disclosure and their descriptions serve to explain the present disclosure, and do not constitute an improper limitation on the present disclosure.

[0016] Figure 1 A single-layer cross-section scanning result of an embodiment of the present disclosure; Figure 2 A three-dimensional model of a borehole of an embodiment of the present disclosure; Figure 3 A schematic diagram of a laser probe scanning a borehole of an embodiment of the present disclosure; Figure 4 A flowchart of the point cloud ring constraint based three-dimensional model construction method for a borehole interior of an embodiment of the present disclosure.

[0017] Wherein, 1, the long rod can be spliced; 2, the sliding support frame; 3, the borehole surrounding rock; 4, the laser ranging probe; 5, the rotating device. DETAILED DESCRIPTION

[0018] The present disclosure is further described below in conjunction with the accompanying drawings and examples.

[0019] It should be noted that the following detailed description is illustrative only, and is intended to provide further description of the present disclosure. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0020] It should be noted that the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the specification, there is a presence of the features, steps, operations, devices, components and / or combinations thereof.

[0021] Example 1 The point cloud ring constraint-based borehole internal three-dimensional model construction method of the present disclosure obtains borehole internal morphology information by laser ranging, constructs a borehole three-dimensional model, and can intuitively display the pore or fissure inside the borehole. The method steps include: Step 1: Obtain the starting position, starting angle, and distance corresponding to the starting angle of the laser probe in the borehole, and generate an initial borehole profile information sequence; Step 2: Control the laser probe to rotate and obtain the angle of rotation of the laser probe and the measured distance at that angle; based on the initial borehole profile information sequence, the current rotation angle, and the measured distance at that angle, generate a borehole profile information sequence under the rotation of 360 degrees of the current section; control the laser probe to rotate continuously into the borehole, thereby generating a borehole profile information sequence under the rotation of 360 degrees of each section; Step 3: Obtain borehole profile coordinate sequences at different sections inside the borehole based on the borehole profile information sequences of each section; generate a standardized three-dimensional point cloud sequence based on the borehole profile coordinate sequence; Step 4: Generate a continuous surface model based on the standardized three-dimensional point cloud sequence, perform constrained Delaunay triangulation on each layer of ring point cloud of the continuous surface model, and generate a longitudinal triangular strip grid by forcing the closed ring constraint, thereby completing the construction of the borehole three-dimensional model.

[0022] As an embodiment, the specific implementation process of the point cloud ring constraint-based borehole internal three-dimensional model construction method of the present disclosure includes: Step 1: Obtain the starting position, starting angle, and corresponding distance of the laser probe in the borehole, and generate a sequence of borehole contour information for the initial cross-section; Specifically, such as Figure 3 As shown, the laser probe 4 is fixed on the splicable long rod 1. The splicable long rod 1 with the laser probe 4 is extended into the surrounding rock 3 of the borehole. The laser probe 4 is fixed at the center position of the surrounding rock 3 of the borehole by the sliding support frame 2, and the initial cross-section is recorded as... x 0. Turn on the laser rangefinder module to start measuring distance and record the starting angle. θ 00 and the distance corresponding to that angle r 00, then rotate the laser probe and record the angle of rotation. θ 0 i and the distance measured by the laser probe at this angle r 0 i .

[0023] The rotating device 5 controls the rotation of the laser probe 4, and acquires the rotation angle of the laser probe 4 and the measurement distance at that angle; based on the initial borehole profile information sequence, the current rotation angle, and the measurement distance at that angle, a current borehole profile information sequence is generated, including: Subsequently, as the probe rotates, distance information is recorded every 1° of rotation, and the distance for each cross-section is recorded after a 360° rotation. x Drilling profile information sequence at section 0 [ x 0, θ 0 i , r 0 i The borehole profile information sequence of the initial cross-section is [ x 0, θ 00, r 00]-[ x 0, θ 0359, r 0359].

[0024] As one embodiment, the aforementioned laser probe employs a pulsed laser sensor to acquire spatial distance information of the borehole inner wall, performing a 360° rotation scan at 1° intervals to generate a polar coordinate data sequence. r , θ The probe completes a full circumference scan every 1cm of depth. The axial rotation drive unit has a built-in stepper motor (±0.5° accuracy) that drives the probe to rotate at a constant speed.

[0025] Step 2: Control the laser probe to rotate continuously and drill deeper into the hole, thereby generating a sequence of borehole contour information for each cross-section; Specifically, the probe is pushed into the borehole at a constant speed using a modular, long rod. The pushing speed should not be too fast to ensure the laser rangefinder probe can rotate 360° at the same position and acquire distance information. In the direction of probe advancement, the borehole profile distance information at that cross-section is measured every 1cm of advance. This allows for the acquisition of a sequence of borehole profile information at different cross-sections; for example, after advancing 1cm... x 1 is: [ x 1, θ 1 i , r 1 i [It has advanced another 1cm] x The two locations are: [ x 2, θ 2 i , r 2 i ], advancing multiple times x n The location is: [ x n , θ n i , r n i ].

[0026] Step 3: Obtain the borehole contour coordinate sequence at different cross-sections inside the borehole based on the borehole contour information sequence of each cross-section; generate a standardized 3D point cloud sequence based on the borehole contour coordinate sequence; Specifically, based on the borehole information sequence at each cross-section, the rectangular coordinates of a ring of ranging points around each location are obtained, in order to... x Drilling profile information sequence at point 0 [ x 0, θ 0 i , r 0 i For example:

[0027] in, y 0 i for x Section 0 i The horizontal axis coordinates of the contact point between the laser ranging line and the borehole wall; z 0 i for x Section 0 i The vertical axis coordinates of the contact point between the laser ranging line and the borehole wall; θ 0 i for x Section 0 i The angle between the laser ranging line and the horizontal axis; iThe number is the sequence number of the laser ranging line, ranging from 0 to 359, and the angle between each pair of measuring lines is 1 degree.

[0028] Finally, we can get x The borehole profile coordinate sequence at point 0 can be used to obtain different cross-sections inside the borehole using the same processing method. x 0- x The borehole profile coordinate sequence at point N.

[0029] Furthermore, according to axial position xn Layering is performed to generate point cloud data in a Cartesian coordinate system inside the borehole, which is then combined with the current position. xn Generate a standardized 3D point cloud sequence, with the point cloud data for each layer as follows:

[0030] in, L n For the point cloud data of each layer, y n i for x n The first section i The horizontal axis coordinates of the contact point between the laser ranging line and the borehole wall. z n i for x n The first section i The vertical axis coordinates of the contact point between the laser ranging line and the borehole wall.

[0031] This allows for the generation of point cloud data in a Cartesian coordinate system inside the borehole:

[0032] in, x n The number of layers at the axial position. y n i for x n The first section i The horizontal axis coordinates of the contact point between the laser ranging line and the borehole wall. z n i for x n The first section i The vertical axis coordinates of the contact point between the laser ranging line and the borehole wall. i These are the serial numbers of the laser ranging lines. n For a certain cross section, N This represents the total number of cross sections.

[0033] Further, the discretized normalized three-dimensional point cloud sequence is converted into a continuous surface model, a Delaunay triangulation algorithm is used to construct a three-dimensional surface model, a single-layer cross-section constraint Delaunay triangulation adds a mandatory edge constraint to ensure closed ends, the point set is projected onto a rectangular coordinate plane to generate two-dimensional scattered points, and a single-layer cross-section model is formed after connection.

[0034] Specifically, the distance between adjacent layers is:

[0035] wherein, x n is the number of axial position divisions, x n+1 is x n the next 1cm cross-section position of the cross-section.

[0036] A Delaunay triangulation algorithm is used to construct a three-dimensional surface model, a single-layer cross-section constraint Delaunay triangulation adds a mandatory edge constraint to ensure closed ends:

[0037] wherein, pi is a two-dimensional scattered point.

[0038] The point set L n is projected onto y - z a plane to generate two-dimensional scattered points, and a single-layer cross-section model is formed after connection, as shown in Figure 1 .

[0039] The corresponding relationship of the points with the same angle between the adjacent layer point clouds L n and L n+1 is defined: θ

[0040] for each pair of adjacent points p n i , p n ( i +1), p (n+1) i , p (n+1) (​i +1) generates a quadrilateral and splits it into two triangles:

[0041] For all adjacent layers of point clouds L n With L n+1 Repeat the above operation to build a three-dimensional model of the borehole, as shown in Figure 2 .

[0042] Finally, a human-computer interaction interface is provided for the three-dimensional model, supporting cross-section cutting, transparency adjustment, fissure highlighting display, and measurement tools, and real-time labeling of the distance between any two points, cross-sectional area, and other parameter comparison and analysis.

[0043] Embodiment 2 In an embodiment of the present disclosure, a point cloud ring constraint-based three-dimensional model construction system for the interior of a borehole is provided, comprising: An initialization module is configured to obtain a starting position, a starting angle, and a distance corresponding to the starting angle of a laser probe in a borehole, and generate an initial borehole contour information sequence; A sequence acquisition module is configured to control the rotation of the laser probe, and obtain an angle of rotation of the laser probe and a measured distance at the angle; generate a borehole contour information sequence under 360-degree rotation of the current cross-section based on the initial borehole contour information sequence, the current rotation angle, and the measured distance at the angle; control the laser probe to continuously rotate and penetrate into the borehole, thereby generating borehole contour information sequences under 360-degree rotation of each cross-section; A point cloud processing module is configured to obtain borehole contour coordinate sequences at different cross-sections in the borehole based on borehole contour information sequences at each position; and generate a standardized three-dimensional point cloud sequence based on the borehole contour coordinate sequences; A model generation module is configured to generate a continuous surface model based on the standardized three-dimensional point cloud sequence, perform constrained Delaunay triangulation on each layer of annular point clouds of the continuous surface model, enforce a closed ring constraint, generate a longitudinal triangular strip grid, and complete the construction of a three-dimensional model of the borehole.

[0044] Embodiment 3 In an embodiment of the present disclosure, a computer program product is provided, comprising a computer program which, when executed by a processor, implements the point cloud ring constraint-based three-dimensional model construction method for the interior of a borehole.

[0045] Embodiment 4 In an embodiment of the present disclosure, a non-transitory computer-readable storage medium is provided for storing computer instructions, which, when executed by a processor, implement the point cloud ring constraint-based three-dimensional model construction method for the interior of a borehole.

[0046] Embodiment 5 In one embodiment of the present disclosure, an electronic device is provided, comprising: a processor, a memory, and a computer program; wherein the processor is connected with the memory, and the computer program is stored in the memory; when the electronic device is running, the processor executes the computer program stored in the memory, so that the electronic device executes the method for constructing a three-dimensional model inside a borehole based on a point cloud ring constraint.

[0047] The present disclosure is described with reference to the flowcharts and / or block diagrams of the method, device (system), and computer program product according to the embodiments of the present disclosure. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the computer or other programmable data processing devices generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus for performing the functions specified in one or more flows and / or blocks.

[0048] These computer program instructions can also be loaded onto a computer or other programmable data processing device to cause a series of operational steps to be executed on the computer or other programmable data processing device to produce a computer-implemented process, so that the instructions executed by the computer or other programmable data processing device provide a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 a step for performing the functions specified in one or more flows and / or blocks.

[0049] Although the specific embodiments of the present disclosure are described above with reference to the accompanying drawings, the present disclosure is not limited to the above-described embodiments, and various modifications or changes can be made by those skilled in the art without departing from the technical solutions of the present disclosure.

Claims

1. A method for constructing a 3D model of borehole interior based on point cloud ring constraints, characterized in that, The method comprises the following steps: obtaining the starting position, starting angle and distance corresponding to the starting angle of the laser probe in the borehole, and generating an initial borehole profile information sequence; controlling the rotation of the laser probe, and obtaining the angle of rotation of the laser probe and the measured distance at the angle; based on the initial borehole profile information sequence, the current rotating angle and the measured distance at the angle, a borehole profile information sequence under the current cross section rotating 360 degrees is generated; the laser probe is continuously rotated and deepened into the borehole, and thus a borehole profile information sequence under the rotation of 360 degrees of each cross section is generated; based on the borehole profile information sequence of each cross section, a borehole profile coordinate sequence at different cross sections in the borehole is obtained; based on the borehole profile coordinate sequence, a standardized three-dimensional point cloud sequence is generated; based on the standardized three-dimensional point cloud sequence, a continuous surface model is generated, constrained Delaunay triangulation is performed on each layer of annular point cloud of the continuous surface model, a forced closed loop constraint is generated, a longitudinal triangular strip grid is generated, and the construction of the three-dimensional model of the borehole is completed. 2.The method of claim 1, wherein, The starting position, starting angle and distance corresponding to the starting angle of the laser probe in the borehole are acquired, and initial borehole profile information sequence is generated, including: placing the laser probe into the borehole, fixing the probe at the center position of the borehole, and recording the starting position x 0, recording the starting angle at this time θ 00 and the distance corresponding to the angle r 00, forming x 0 borehole profile information sequence at the cross section x 0, θ 0 i , r 0 i ]. 3.The method of claim 1, wherein, The laser probe is rotated, and an angle of rotation of the laser probe and a measured distance at the angle are obtained; a current borehole profile information sequence is generated based on an initial borehole profile information sequence, the angle of rotation and the measured distance at the angle, including: rotating the laser probe, recording the angle of rotation of the probe θ 0 i and the distance measured by the laser probe at the angle r 0 i At the time of rotation of the probe, the distance information is recorded once every 1° of rotation, and the current borehole profile information sequence is generated. 4.The method of claim 1, wherein, based on the borehole profile information sequence of each position, a borehole profile coordinate sequence at different cross sections in the borehole is obtained; based on the borehole profile coordinate sequence, a standardized three-dimensional point cloud sequence is generated, comprising: according to the borehole profile information sequence of each position, the rectangular coordinates of a circle of ranging points around each position are obtained, comprising: Obtained x 0drilling profile coordinate sequence at the position of the hole x 0, y 0i, z 0i), the drilling profile coordinate sequence of different sections inside the hole is obtained according to the calculation method, the point cloud data of the rectangular coordinate system inside the hole is generated according to the axial position layering, and the current position x The standardized three-dimensional point cloud sequence is generated.

5. The method of claim 1, wherein, the discretized standardized three-dimensional point cloud sequence is converted into a continuous surface model, a three-dimensional surface model is constructed by using a Delaunay triangulation algorithm, a single layer cross section constrained Delaunay triangulation adds a forced edge constraint, ensures the closed loop, projects the point set to the rectangular coordinate plane, generates a two-dimensional scattered point, and connects to form a single layer cross section model.

6. The method of claim 5, wherein the method further comprises: the corresponding relationship of the points with the same angle between the adjacent layer point cloud and the point cloud is defined, a quadrilateral is generated for each pair of adjacent points and is split into two triangles, the above operation is repeated between all adjacent layer point clouds and point clouds, and the three-dimensional model of the borehole is constructed.

7. A borehole internal three-dimensional model construction system based on point cloud ring constraint, characterized in that, The method comprises the following steps: an initialization module is used to obtain the starting position, starting angle and distance corresponding to the starting angle of the laser probe in the borehole, and generate an initial borehole profile information sequence; a sequence acquisition module is used to control the rotation of the laser probe, and obtain the angle of rotation of the laser probe and the measured distance at the angle; based on the initial borehole profile information sequence, the current rotating angle and the measured distance at the angle, a borehole profile information sequence under the current cross section rotating 360 degrees is generated; the laser probe is continuously rotated and deepened into the borehole, and thus a borehole profile information sequence under the rotation of 360 degrees of each cross section is generated; a point cloud processing module is used to obtain the borehole profile coordinate sequence at different cross sections in the borehole based on the borehole profile information sequence of each position; based on the borehole profile coordinate sequence, a standardized three-dimensional point cloud sequence is generated; a model generation module is used to generate a continuous surface model based on the standardized three-dimensional point cloud sequence, perform constrained Delaunay triangulation on each layer of annular point cloud of the continuous surface model, generate a forced closed loop constraint, generate a longitudinal triangular strip grid, and complete the construction of the three-dimensional model of the borehole.

8. A computer program product comprising a computer program, characterized in that, The computer program is executed by a processor to implement the point cloud ring constraint based borehole internal three-dimensional model construction method in any one of claims 1-6.

9. A non-transitory computer-readable storage medium, comprising: The non-transitory computer readable storage medium is configured to store computer instructions, and the computer instructions are executed by a processor to implement the point cloud ring constraint based borehole internal three-dimensional model construction method in any one of claims 1-6.

10. An electronic device, comprising: Comprise: A processor, a memory and a computer program; wherein the processor is connected with the memory, and the computer program is stored in the memory; when the electronic device is running, the processor executes the computer program stored in the memory, so that the electronic device executes the point cloud ring constraint based borehole internal three-dimensional model construction method in any one of claims 1-6.

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