A method for calculating electromagnetic scattering characteristics of dihedral angle at any angle based on BSDF

Abstract

The application discloses a kind of arbitrary angle dihedral angle electromagnetic scattering characteristic calculation method based on BSDF, steps are as follows: establish the dihedral angle model formed by two finite metal planes;Respectively calculate the single scattering contribution of two flat plates under different incident angles;The multiple scattering path of each order dihedral angle is expressed as the cascade form of physical optical scattering matrix and geometric optical reflection matrix, wherein the obtuse dihedral angle only calculates the secondary scattering path meeting the condition, and introduces the ray divergence cutoff, and the acute dihedral angle recursively obtains secondary, tertiary, quaternary and higher order paths according to the multiple reflection condition;The results of single scattering and multiple scattering matrix are superimposed to obtain the total scattering matrix, and the VV polarized radar scattering cross section and total field phase are calculated.The application realizes the explicit rewriting of BSDF multiple scattering formula for dihedral angle structure, can uniformly process arbitrary angle dihedral angle, and has good engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of numerical calculation technology of target electromagnetic scattering characteristics, and in particular, it is a method for calculating the electromagnetic scattering characteristics of an arbitrary dihedral angle based on BSDF. Background Technology

[0002] Dihedral structures are widely found at the junction of building walls and ground, ship superstructures, aircraft connections, and various target surfaces, and are among the most common strong scattering structures in radar targets. Dihedrals with different angles exhibit significantly different scattering patterns: obtuse dihedrals, under specific bistatic geometry, mainly produce strong echoes through secondary scattering, while acute dihedrals, due to internal multiple reflections, exhibit multiple scattering events exceeding secondary scattering. The number of scattering events and the final emission angle satisfy the geometric law under the image method.

[0003] Existing BSDF theory treats target scattering as consisting of point, line, and surface scatterers and their combinations. Multiple scattering can be written as the interaction between scatterers, explicitly considering polarization effects, equivalent phase, and shading functions. For dihedral structures, the BSDF multiple scattering formula provides an important foundation for establishing a unified model. However, these formulas are more general theoretical descriptions. When implementing specific dihedral targets in engineering, it is usually necessary to further provide explicit geometric parameterization, path existence determination, construction of locally illuminated regions, and numerical stabilization strategies.

[0004] When applying the general multiple scattering formula of BSDF directly to the implementation of dihedral angle programs, the existing technology still has the following problems: First, there is a lack of a unified explicit parameterization method for acute and obtuse dihedral angles; Second, the shading and illumination areas are usually expressed by general functions, lacking closed-form solutions for local illuminated subplanes; Third, the path is prone to response discontinuity near the critical angle of appearance and disappearance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the electromagnetic scattering characteristics of an arbitrary dihedral angle based on BSDF.

[0006] The technical solution to achieve the objective of this invention is: a method for calculating the electromagnetic scattering characteristics of an arbitrary dihedral angle based on BSDF, comprising the following steps:

[0007] Step 1: Establish a parameterized model of the dihedral angle consisting of metal plane one and metal plane two. Determine the rotation angle of metal plane one based on the angle of the dihedral angle, and construct the vertex coordinates, midpoint coordinates of the sides, side vectors, reference points and normal vectors of the two planes.

[0008] Step 2: Based on the incident wave direction, observation direction, and the normal relationship between the two planes, determine the illumination state, shadow area, and local effective illumination area of ​​each plane, and use them to calculate the single scattering matrix of the two plates respectively.

[0009] Step 3: Based on the idea of ​​cascaded scatterers in the BSDF multiple scattering formula, each multiple scattering path is represented as a cascade of the physical optical PO scattering matrix and the geometric optical reflection matrix. The solution framework is automatically switched to acute or obtuse dihedral angles based on the dihedral angle to obtain the multiple scattering matrices of each order. Finally, the single scattering matrix and the multiple scattering matrix are superimposed to obtain the total scattering matrix, and the radar cross section and total field phase are calculated.

[0010] Furthermore, the dihedral angle parameterization model described in step 1 is established by transforming the dihedral angle of plane 1 through a deflection matrix, while plane 2 remains fixed; the midpoints and edge vectors of the sides are constructed based on the vertex coordinates of the two planes, which are used to calculate the PO physical optics scattering matrix in single scattering and multiple scattering in subsequent physical optics boundary integral calculations.

[0011] Furthermore, in step 2, the illumination relationship between the two planes is determined based on their positional relationship; firstly, it is determined whether the equivalent grazing angle of plane one is less than 0, i.e. ,if If plane one is not directly illuminated by a plane wave, then the normal vector is flipped, the order of the vertices of plane one is flipped, and the midpoint and edge vector of each edge are recalculated; and the shadow boundary position of plane one projected onto plane two is determined. Determine and calculate how many areas of plane two can still be directly illuminated by the incident wave, calculate the actual illuminated area, and calculate the single scattering matrix based on the actual illuminated area.

[0012] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method described above.

[0013] A computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps of the above-described method.

[0014] A computer program product includes a computer program that, when executed by a processor, implements the steps of the above-described method.

[0015] Compared with the existing BSDF multiple scattering formula, the modifications and optimizations of this invention are mainly reflected in the following aspects: First, the scatterer combination relationship in the general BSDF formula is rewritten for dihedral structures as an explicit path-level expression of "multiplication of the PO scattering matrix and the GO reflection matrix", which can be directly implemented in programming; Second, the general shading function is rewritten as a closed-form solution for the length and center position of the local illuminated plane; Third, a rigorous path truncation based on the ray divergence relationship is introduced in the obtuse angle case, and a higher-order path recursion and cosine transition weight are introduced in the acute angle case; Fourth, a negative phase correction is introduced for even-numbered higher-order paths to eliminate the phase abrupt change caused by the 180° topological flip.

[0016] This invention can uniformly handle acute and obtuse dihedral angles; it can directly output the total scattering matrix, VV polarization RCS, and total field phase; it has better continuity and stability near the path cutoff; and it retains the physical meaning of the BSDF multiple scattering formula, thus having good engineering application value. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the secondary scattering path at an obtuse dihedral angle.

[0018] Figure 2 This is a schematic diagram of the secondary scattering path at an acute dihedral angle.

[0019] Figure 3 This is a schematic diagram of the triple scattering path of an acute dihedral angle.

[0020] Figure 4 This is a schematic diagram of the dimensions of the obtuse dihedral model with an angle of 105° in Example 1, which is a large metal electrode.

[0021] Figure 5 This is a comparison chart of the VV polarization RCS of an obtuse dihedral angle with an opening angle of 105° in Example 1 and the results obtained using the Feko method.

[0022] Figure 6 This is a comparison chart of the VV polarization phase of the obtuse dihedral angle with an opening angle of 105° in Example 1 and the results obtained by the Feko method.

[0023] Figure 7 This is a schematic diagram of the dimensions of the acute dihedral model with a 45° opening angle in Example 2.

[0024] Figure 8 This is a comparison chart of the VV polarization RCS of an acute dihedral angle with an opening angle of 45° in Example 2 and the results obtained using the Feko method.

[0025] Figure 9 This is a comparison chart of the VV polarization phase of an acute dihedral angle with a subtended angle of 45° in Example 2 and the results obtained using the Feko method. Detailed Implementation

[0026] This invention proposes a method for calculating the electromagnetic scattering characteristics of an arbitrary-angle dihedral angle based on BSDF (Browser-Based Dispersion Array). First, a dihedral model is established consisting of two finite metallic planes, where plane one can be rotated by any angle using a rotation matrix, while plane two remains fixed. Second, based on the incident and observation directions, the illumination state, back-side illumination relationship, shadow region, and locally effective illumination region of the two planes are determined, and the single-scattering contribution of the two plates at different incident angles is calculated. Then, combining the idea of ​​cascaded scattering in BSDF multiple scattering, the multiple scattering paths of each order of the dihedral angle are expressed as the physical optical scattering matrix and the geometric optical reflection matrix. The invention employs a cascaded approach, where obtuse dihedral angles only calculate secondary scattering paths satisfying certain conditions, and introduce ray divergence truncation. Acute dihedral angles recursively calculate secondary, tertiary, quartic, and higher-order paths based on multiple reflection conditions. Furthermore, addressing issues in engineering implementation such as the BSDF multiple scattering formula's applicability only to positive dihedral angles, discontinuous path switching, and abrupt phase changes in even-order higher-order paths, the invention proposes a method for constructing a locally illuminated subplane, a smoothing truncation function, a transition weighting function, and phase correction for higher-order paths. Finally, the results of single and multiple scattering matrices are superimposed to obtain the total scattering matrix, and the VV-polarized radar cross-section and total field phase are calculated. This invention provides an explicit rewrite of the BSDF multiple scattering formula for dihedral structures, enabling unified handling of dihedral angles at arbitrary angles, and possesses significant engineering application value. The specific steps of this method are as follows:

[0027] Step 1: Establish a parametric model of a dihedral angle consisting of two finite-sized metal planes: plane one is obtained by rotation using a rotation matrix, while plane two remains fixed. Assume the operating frequency is... , wavelength is wave number is The angle subtended by the dihedral angle is The rotation angle is Furthermore, the reference points, normal vectors, vertex coordinates, midpoint coordinates, and edge vectors of the two planes are constructed.

[0028] Step 2: Construct the incident unit vector and observation direction based on the scan angle and azimuth angle. Determine the illumination relationship between the two planes based on the scan angle and azimuth angle; if there is back illumination, reverse and correct the normal vector and vertex order; if there is local occlusion, construct the illuminated sub-plane based on the shadow origin, local illumination length, and local center position, and calculate the single scattering matrix for each. and ;

[0029] Step 3: The concept of scatterer combination in the general formula for multiple BSDF scattering is concretized into a path-level matrix expression. For any path... Let its scattering matrix be expressed as ,in The physical optical scattering matrix of the final illuminated plane. This is the geometric optical reflection matrix of all reflecting surfaces in the preceding stage. For obtuse dihedral angles, only the quadratic paths 1→2 and 2→1 that satisfy the reachability condition are retained, and the local effective illumination length is calculated; for acute dihedral angles, the second, third, fourth, and higher order paths are recursively calculated based on the multiple reflection conditions, and the propagation direction and path matrix are updated level by level.

[0030] Step 4: Modify and optimize the general multiple scattering formula for BSDF: replace the general shading function with a closed-form function for the local illuminated subplane; adopt... Smoothly truncate the effective path length; introduce cosine transition weights for higher-order paths near the cutoff boundary; introduce negative phase corrections for even-numbered higher-order paths that undergo a 180° topology flip.

[0031] Step 5: Superimpose the single scattering matrix with all effective multiple scattering path matrices to obtain the total scattering matrix, extract the VV polarization complex scattering amplitude, and further calculate the RCS and total field phase.

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] The present invention provides a method for calculating the electromagnetic scattering characteristics of acute and obtuse dihedral angles based on BSDF, comprising the following steps:

[0034] Step 1: Establish a parameterized dihedral angle model consisting of two finite-size metal planes. Let the free space permittivity be... Magnetic permeability is speed of light The operating frequency is , wavelength is wave number is Let the angle subtended by the dihedral angle be... rotation angle of the first plane Furthermore, the reference points, normal vectors, vertex coordinates, edge midpoint coordinates, and edge vectors of the two planes are constructed. The local vertex coordinates of plane one are obtained by rotation. And further construct the midpoint of the edge. and edge vector ; Plane 2 remains fixed, and we obtain , and .

[0035] Step 2: Based on the scanning incident angle Construct the incident unit vector and take Determine the illumination state of the two planes. If plane one has a back side that is illuminated, i.e. Let the effective normal vector be The vertex order is flipped to ensure that the boundary integral direction is consistent with the normal; otherwise, the calculation is performed directly using the original normal vector.

[0036] Step 3: Calculate the single scattering matrix. For each illuminated plane, first construct the polarization basis, then calculate the physical optical polarization term and the boundary integral term.

[0037] when When, the boundary integral form based on the edge midpoint and edge vector is used; when When the area approaches zero, a degenerate area expression is used. Gordon's formula:

[0038] ;

[0039] This indicates that the incident wave is Polarization, the emitted wave is Scattering coefficient under polarization , are the polarization vectors of the incident electric field and the exit electric field, respectively. Let be the polarization vector of the incident magnetic field. The polygon consists of m sides, has an area of ​​A, and the normal vector of the plane containing the polygon is . The reference point of the polygon is The vector of the midpoint of the m-th edge relative to the reference point is The length of the m-th edge is , direction is , The time is the mirror direction. Time harmonic functions are omitted from all field vectors. For the second plane, a locally illuminated sub-plane is first constructed based on the shadow initiation point, illumination initiation point, and local illumination length, and then its single scattering matrix is ​​calculated. and .

[0040] Step 4: Construct a path-level matrix expression based on the BSDF multiple scattering formula. The general second and multiple scattering formulas of BSDF emphasize the combination of scatterers, polarization effects, equivalent phase, and masking function. This invention modifies these formulas as follows: "Combination of scatterers" is specified as "multiplication of the PO scattering matrix and the GO reflection matrix"; "general masking function" is specified as the length and center position of the local illuminated plane; and "general phase term" is specified as the propagation phase in each level of the reflection matrix.

[0041] For obtuse dihedral angles, only paths 1→2 and 2→1 that satisfy the geometric reachability condition are retained, and the local effective irradiation length is calculated through the ray divergence relationship; for acute dihedral angles, the reflection propagation direction and higher-order paths are recursively calculated based on the multiple reflection conditions.

[0042] Schematic diagrams of obtuse dihedral second scattering, acute dihedral second scattering, and acute dihedral third scattering are shown below. Figures 1-3 As shown.

[0043] The condition for the number of scatterings is determined by the angle of incidence. and the angle subtended by the dihedral angle The decision is made that, for a single scattering, the following conditions must be met. The condition for secondary scattering is The condition for triple scattering is The condition for four-fold scattering is given; similarly, the condition for multiple-fold scattering can be summarized as follows: for m-fold scattering to occur, the angle must satisfy... The angle of incidence must satisfy... One angular shape is The dihedral angle will occur at most Secondary scattering This indicates rounding up to the nearest integer.

[0044] First, determine the number of paths to calculate based on the angle of incidence and the included angle of the dihedral angle. Both plane 1 and plane 2 may be illuminated first, and two paths are calculated simultaneously.

[0045] Based on the analysis of determining the number of scatterings using the included angle of the dihedral angle and the angle of incidence, when... At most, there will be two scatterings;

[0046] For each path, the remaining theoretically irradiated area on each plane must first be calculated:

[0047] ;

[0048] in It is the theoretically irradiated region. It is the equivalent glancing angle of the plane that is first illuminated.

[0049] To avoid discontinuous jumps near the critical angle, a smooth cutoff function is introduced:

[0050] ;

[0051] in It is the theoretically irradiated region; This represents the maximum allowable irradiation length, which is the upper limit of the actual size of the irradiated plane. Here, it is normalized to 1. This is the smooth truncation parameter, set to 0.05;

[0052] Therefore, its effective irradiation length is:

[0053] ;

[0054] in The center of the corresponding effective irradiation area is:

[0055] ;

[0056] Then, the reflection matrix of this path is calculated using the form of a concatenated matrix:

[0057] ;

[0058] in This is the reflection matrix of this path. It is the PO scattering matrix on the illuminated subplane of the last illuminated plane. It is the mirror reflection matrix of the first plane that the plane hits.

[0059] when At most, there are three scattering events.

[0060] when At most, there are four scattering events.

[0061] The rest of the components are the same as those for secondary scattering;

[0062] For cubic and quartic paths, cosine smoothing weights are introduced:

[0063] ;

[0064] in For cosine smoothing weights, For the corresponding equivalent glancing angle, This is the geometric critical angle of the multiple scattering path of this order. This is the width of the transition band near the critical angle. When The path is fully valid; when The contribution of the time path gradually decreases; when The time path is completely suppressed.

[0065] when When plane one enters the backlit area, only the path starting from plane two is retained.

[0066] The first The geometric parameters of the first-order reflection path are defined as follows:

[0067] ;

[0068] in It is the order of reflection. It is the equivalent included angle of a dihedral angle. It is the plane equivalent glancing angle; when If so, it means the path can be achieved.

[0069] Define path scaling factor:

[0070] ;

[0071] in It is the path length scaling factor. It is a path geometry parameter; this parameter represents the proportion of the projection length of the reflection path onto the target surface.

[0072] And define:

[0073] ;

[0074] in This indicates the maximum visible height of the path on the next reflective surface.

[0075] Let the starting point of the two-shaded section in the plane be... The upper bound of the visible region can be recursively determined as follows:

[0076] ;

[0077] in : No. Upper bound of the visible region of the path; It is the shadow boundary formed by plane one on plane two; this recursive relationship indicates that as the reflection order increases, the visible area on the target surface gradually shrinks.

[0078] No. The projection length of the path on the target surface is:

[0079] ;

[0080] The corresponding effective lighting length is:

[0081] ;

[0082] The center of the lighting area is:

[0083] ;

[0084] No. The contribution of the first-order multiple scattering path is:

[0085] ;

[0086] in It is the nth order scattering matrix; It is the path weight coefficient; It is the physical optical scattering matrix of the last illuminated surface; It is the accumulation of the reflection matrices from the first n reflections; It is the phase correction factor.

[0087] in :

[0088] ;

[0089] Step 5: Superimpose the single scattering matrix with all effective multiple scattering matrices to obtain the total scattering matrix. Extract the VV polarization complex scattering amplitude, calculate RCS_VV, and further utilize this to obtain the total field phase.

[0090] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0091] Example 1

[0092] Combination Figures 4-6 This embodiment performs electromagnetic scattering calculations for obtuse dihedral angles. The operating frequency is set to 10 GHz, and the azimuth angle is... The scanning angle θ varies within the range of 0° to 90°, and the subtended angle is 105°. Following the steps described above, a dihedral model is established, and the single scattering matrices and two secondary scattering paths of the two planes are calculated respectively. Using the method of this invention, the VV polarization RCS curve and the total field phase curve can be obtained, and the mechanism by which a strong echo is mainly formed by secondary scattering under specific geometric conditions of an obtuse dihedral angle can be reflected.

[0093] Example 2

[0094] Combination Figures 7-9 This embodiment performs high-order multiple scattering calculations for acute dihedral angles. Assuming the operating frequency is also 10 GHz, the azimuth angle... The scanning angle θ varies within the range of 0° to 90°, with a sub-angle of 45°. Secondary, tertiary, quaternary, and, if necessary, higher-order scattering paths are recursively calculated based on the reflection order condition. PO scattering calculations are then performed after constructing a local irradiation sub-plane on the irradiated plane. By introducing smooth truncation, transition weights, and phase corrections for even-numbered higher-order paths, a more continuous amplitude and phase response can be obtained.

Claims

1. A method for calculating the electromagnetic scattering characteristics of an arbitrary dihedral angle based on BSDF, characterized in that, Includes the following steps: Step 1: Establish a parameterized model of the dihedral angle consisting of metal plane one and metal plane two. Determine the rotation angle of metal plane one based on the angle of the dihedral angle, and construct the vertex coordinates, midpoint coordinates of the sides, side vectors, reference points and normal vectors of the two planes. Step 2: Based on the incident wave direction, observation direction, and the normal relationship between the two planes, determine the illumination state, shadow area, and local effective illumination area of ​​each plane, and use them to calculate the single scattering matrix of the two plates respectively. Step 3: Based on the idea of ​​cascaded scatterers in the BSDF multiple scattering formula, each multiple scattering path is represented as a cascade of the physical optical PO scattering matrix and the geometric optical reflection matrix. The solution framework is automatically switched to acute or obtuse dihedral angles based on the dihedral angle to obtain the multiple scattering matrices of each order. Finally, the single scattering matrix and the multiple scattering matrix are superimposed to obtain the total scattering matrix, and the radar cross section and total field phase are calculated.

2. The method for calculating the electromagnetic scattering characteristics of an arbitrary dihedral angle based on BSDF according to claim 1, characterized in that, The dihedral angle parameterization model described in step 1 is established by transforming the dihedral angle of plane 1 through a deflection matrix, while plane 2 remains fixed. The midpoints and edge vectors of the sides are constructed based on the vertex coordinates of the two planes, which are used to calculate the PO physical optics scattering matrix in single scattering and multiple scattering in subsequent physical optics boundary integral calculations.

3. The method for calculating the electromagnetic scattering characteristics of an arbitrary dihedral angle based on BSDF according to claim 1, characterized in that, In step 2, the illumination relationship between the two planes is determined based on their positional relationship; first, it is determined whether the equivalent grazing angle of plane one is less than 0, i.e. ,if If plane one is not directly illuminated by a plane wave, then the normal vector is flipped, the order of the vertices of plane one is flipped, and the midpoint and edge vector of each edge are recalculated; and the shadow boundary position of plane one projected onto plane two is determined. Determine and calculate how many areas of plane two can still be directly illuminated by the incident wave, calculate the actual illuminated area, and calculate the single scattering matrix based on the actual illuminated area.

4. The method for calculating the electromagnetic scattering characteristics of an arbitrary dihedral angle based on BSDF according to claim 1, characterized in that, Step 3 concretizes the scatterer combination concept in the BSDF multiple scattering formula into a path-level matrix expression. Based on the angle of the dihedral angle, the path solution structure for acute and obtuse dihedral angles can be automatically switched to obtain multiple scattering matrices of various orders, as follows: First, determine the number of paths to calculate based on the angle of incidence and the included angle of the dihedral angle. Both plane one and plane two may be illuminated first, so two paths are calculated simultaneously; among them It is the angle subtended by the dihedral angle; The number of scattering events is determined by the included angle of the dihedral angle and the angle of incidence. At most, there will be two scatterings; For each path, the theoretical irradiated area on each plane must first be calculated: ； in It is the theoretically irradiated region. It is the equivalent grazing angle of the first illuminated plane. To avoid discontinuous jumps near the critical angle, a smooth cutoff function is introduced: ； in It is the theoretically irradiated region; This represents the maximum permissible irradiation length, normalized to 1. It is a smooth truncation parameter; Therefore, its effective irradiation length is: ； in The center of the corresponding effective irradiation area is: ； Then, the reflection matrix of this path is calculated using the form of a concatenated matrix: ； in This is the reflection matrix of this path. It is the PO scattering matrix on the illuminated subplane of the last illuminated plane. It is the specular reflection matrix of the first plane that the plane hits; when At most, there are three scattering events. when At most, there are four scattering events. The rest of the components are the same as those for secondary scattering; For cubic and quartic paths, cosine smoothing weights are introduced: ； in For cosine smoothing weights, For the corresponding equivalent glancing angle, This is the geometric critical angle of the multiple scattering path of this order. The width of the transition band near the critical angle; when The path is fully valid; when The contribution of the time path gradually decreases; when The time path is completely suppressed; when When plane one enters the backlit area, only the path starting from plane two is retained; The first The geometric parameters of the first-order reflection path are defined as follows: ； in It is the order of reflection. It is a dihedral angle. It is the plane equivalent glancing angle; when If so, it means the path can be achieved; Define path scaling factor: ； in It is the path length scaling factor. It is the plane equivalent glancing angle. It is a path geometry parameter; this parameter represents the proportion of the projection length of the reflection path on the target surface; And define: ； in Indicates the maximum visible height of the path on the next reflective surface; Let the starting point of the two-shaded section in the plane be... The upper bound of the visible region can be recursively determined as follows: ； in It is the first Upper bound of the visible region of the path; It is the shadow boundary formed by plane one on plane two; this recursive relationship indicates that as the reflection order increases, the visible area on the target surface gradually shrinks; No. The projection length of the path on the target surface is: ； The corresponding effective lighting length is: ； The center of the lighting area is: ； No. The contribution of the first-order multiple scattering path is: ； in It is the first scattering matrix of order; It is the path weight coefficient; It is the physical optical scattering matrix of the last illuminated surface; It was before Accumulation of secondary reflection matrices; It is a phase correction factor; in : ； For obtuse dihedral angles, only paths 1→2 and 2→1 that satisfy the geometric reachability condition are retained, and the local effective irradiation length is calculated through the ray divergence relationship; for acute dihedral angles, the reflection propagation direction and higher-order paths are recursively calculated based on the multiple reflection conditions.

5. The method for calculating the electromagnetic scattering characteristics of an arbitrary dihedral angle based on BSDF according to claim 4, characterized in that, Set to 0.

05.

6. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the method described in any one of claims 1-5.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method described in any of claims 1-5.

8. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the steps of the method described in any one of claims 1-5.

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