176 results about "Wave equation" patented technology

The invention discloses a microseismic source positioning method, device and system, and a storage medium. The method comprises the following steps: dividing a microseismic data sample data set into a training set and a test set; according to the training set, constructing a microseism inversion subnet containing a Swin Transform encoder, and according to the training set, constructing a microseism inversion subnet containing a Swin Transform encoder; the micro-seismic forward modeling subnet realizes seismic wave field continuation by inputting a micro-seismic source position and a speed model and utilizing a recurrent neural network structure and a convolution operator, and establishes a forward modeling subnet based on a wave equation; constructing an inversion-forward modeling closed-loop neural network according to the micro-seismic inversion subnet and the forward modeling subnet based on the wave equation; and inputting the test set into the inversion-forward closed-loop neural network to carry out micro-seismic source positioning. By adopting the technical scheme of the invention, the limitations on physical constraint, feature modeling and anti-noise capability in the prior art are overcome.

The invention discloses a three-dimensional intelligent seismic velocity modeling method based on a two-dimensional self-attention U-shaped network and low-rank adaptation, and belongs to the technical field of seismic services of geophysical exploration. The problems that in the prior art, a traditional three-dimensional intelligent seismic velocity modeling method is low in efficiency and insufficient in model generalization ability are solved. The method comprises the following steps: generating a three-dimensional hybrid geological velocity model, obtaining multi-shot seismic record data based on a wave equation, obtaining a three-dimensional initial velocity model through Gaussian filtering, and obtaining an imaging result by adopting reverse time migration; carrying out dimension reduction processing on the three-dimensional data, and constructing a multi-dimensional pre-training sample set; carrying out pre-training by utilizing the training set to obtain an optimized LAUNet framework; and performing fine tuning by adopting a dual-stage collaborative optimization mechanism, and obtaining a fine-tuned LAUNet framework through a LoRA * method. The method effectively improves the model inversion efficiency, and can be applied to the establishment of a three-dimensional intelligent seismic velocity model.

The invention discloses a least square reverse time migration method and device for a three-dimensional anisotropic medium, and the method comprises the steps: building a forward equation of the three-dimensional anisotropic medium for a seismic block to be subjected to reverse time migration, and obtaining a background wave field under the three-dimensional anisotropic medium through regional forward modeling; determining a three-dimensional anisotropic medium adjoint wave field by using a pre-established wave equation of the adjoint wave field; according to the adjoint wave field and the background wave field, determining an initial gradient by using a pre-established least square reverse time migration cross-correlation equation, and obtaining a migration result according to the initial gradient; and updating an imaging result through a conjugate gradient method according to the offset result to obtain a reflected wave record.

The invention discloses a thermal-fluid-solid medium seismic wave simulation method, device, program and medium, and relates to the technical field of oil and gas resource geophysical exploration, and the method comprises the following steps: constructing a first-order thermal-fluid-solid coupling wave equation in an equation coupling form; constructing a coupling wave equation staggered network finite difference discrete format; analyzing numerical stability conditions; constructing a complete matching layer absorption boundary; and performing forward modeling simulation of seismic waves in the three-layer heat-fluid-solid coupling model according to the model parameters and the seismic source parameters. The method breaks through the assumption that the classical seismic wave propagation theory is completely elastic under the isothermal or adiabatic deformation condition, considers the influence of temperature change on the propagation of seismic waves in fluid and solid media, and improves the description precision of the propagation process of the seismic waves in the heat-fluid-solid media. And the capability of inverting the underground temperature field based on seismic wave data in the later period can be effectively improved.

The invention provides a frequency dispersion curve calculation method based on a decoupling type Legendre-Gauss-Labatto spectral element method, and belongs to the technical field of discrete solution of guided wave propagation in a thin plate, and the method comprises the following steps: S1, constructing a wave equation which comprises a Cartesian space coordinate system based on an orthotropic plate, and combining a constitutive equation, a geometrical relationship under the coordinate system and guided wave displacement to obtain a wave dispersion curve; substituting into a control equation when the volume force is zero to obtain an improved three-dimensional elastic wave equation; s2, a differential matrix is constructed, wherein discretization and decoupling are carried out on a wave equation on the basis of a Lagrange interpolation basis function of a Legendre-Gauss-Labatto node; s3, explicitly embedding the stress free boundary condition into the solving process through matrix line transformation, and solving to obtain a frequency dispersion curve, the derivation process is simplified, the boundary and the interior of the material are decoupled, and the physical significance is clearer. And meanwhile, the high-precision advantage of the spectrum method is maintained, and the calculation rate is remarkably improved.

The present application belongs to the technical field of oil and gas exploration and seismic data processing, and discloses a seismic data interpolation method and system based on CBAM-Res2Unet network. The method solves the problems of limited receptive field caused by fixed convolution kernel in traditional ResUNet network and non-selective transmission of low-level features in skip connection. The method comprises: generating seismic records through wave equation forward modeling and constructing a training set containing random missing data; designing CBAM-Res2Unet network, wherein the encoder and the decoder adopt Res2Net modules containing compression excitation modules, and the multi-scale feature extraction capability is enhanced through grouped convolution and hierarchical residual connection; introducing CBAM modules in the skip connection to adaptively weight the features by using channel and spatial attention mechanisms; and adding a spectral normalization layer in the deep network to stabilize the training. The system comprises data acquisition, network generation, training and interpolation modules. Through multi-scale feature fusion, attention mechanism and stability optimization, the present application realizes high-precision interpolation of complex missing seismic data.

The embodiment of the specification discloses a self-adaptive variable grid forward modeling method for middle-deep dry hot rock mass. p , a transverse wave velocity V s and a medium density p model, pre-setting forward modeling parameters; performing self-adaptive variable grid processing on the velocity model, determining a mapping relationship between coordinate systems, and determining a wave equation under variable grid based on the mapping relationship; performing self-adaptive variable grid processing on the velocity model, determining a mapping relationship between coordinate systems, obtaining the underground medium longitudinal wave velocity, transverse wave velocity and density after variable grid, determining a wave equation under variable grid based on the mapping relationship, and generating final regular grid horizontal direction longitudinal wave field, horizontal direction transverse wave field, vertical direction longitudinal wave field and vertical direction transverse wave field information by using the mapping relationship reversely according to the wave field information in each direction at a specific moment after the variable grid, so that the memory occupation is small and the calculation speed is faster.

The invention discloses a surface shallow creep detection method and system based on a time reversal technology, relates to the technical field of geological engineering, and solves the problem that the surface shallow creep detection precision is relatively low. The method comprises the following steps: acquiring multi-source physical field data of an earth surface shallow layer of a target area; establishing a simulation model of the surface shallow layer based on the multi-source physical field data; sending a first signal to the surface shallow layer through an antenna, and receiving a returned second signal; performing time reversal on the second signal to obtain a third signal; based on the simulation model, simulating a signal propagation path of a third signal sent by the antenna to the surface shallow layer to obtain target time inversion data; and comparing the target time inversion data with the historical time inversion data to obtain a creep abnormal region. Creep detection is carried out by adopting the time reversal technology, the creep abnormal area can be accurately positioned by utilizing the time reversibility of the wave equation and combining the self-consistent focusing characteristic of the time reversal signal at the real source point, and the creep detection precision is improved.

A seismic energy estimation method based on generalized spherical wave propagation, relating to the field of earthquake engineering. The method comprises: determining initial seismic total energy and seismic power on the basis of seismic source characteristics and a seismic magnitude; determining a generalized spherical wave equation, and calculating an average energy flow density of propagated waves on the basis of the wave equation of spherical waves; using an earth surface spherical crown, which is projected on the zone of a seismic source surface, as a main impact zone of seismic spherical waves on an earth surface, the main impact zone being equivalent to a square and performing grid division, and calculating the hypocentral distance between the center of each grid and the center of a seismic source so as to form a hypocentral distance matrix; and expressing the generalized spherical wave energy flow density of each grid as the sum of the energy flow density of longitudinal waves and the energy flow density of transverse waves, performing grid subdivision, estimating the average amplitude of each subdivided grid mass unit within a seismic action period, and evaluating the seismic action energy of a site. The present invention estimates the action of seismic energy on the earth surface by defining the generalized spherical wave propagation of seismic source energy, thereby more accurately evaluating the distribution condition of seismic energy on the earth surface.

The invention relates to the technical field of elastic waves, and discloses an elastic wave full-waveform inversion method, which comprises the steps of inputting observed seismic data into a preset neural network encoder, and extracting to obtain high-dimensional feature representation; inputting the high-dimensional feature representation into a preset neural network decoder to obtain a gradient update value; obtaining an elastic parameter model based on the gradient update value and the initial elastic parameter model; obtaining Lame parameters based on the longitudinal wave velocity, the transverse wave velocity and the medium density; based on a Lame parameter and an elastic wave equation, obtaining synthetic seismic data; obtaining an objective function based on the observed seismic data and the synthesized seismic data; using the target function to iteratively update the preset neural network weight until the loss function reaches a first preset threshold value or the number of iterations reaches a second preset threshold value, and obtaining a target gradient update value; and based on the target gradient update value and the target elastic parameter model, obtaining a final target elastic parameter model so as to relieve discomfort caused by simultaneous inversion of multiple elastic parameters.

The invention discloses an elastic reverse time migration imaging method based on deviatoric stress characterization, and relates to the technical field of exploration geophysics. Deviatoric stress is introduced into a conventional elastic wave equation, and a speed-deviatoric stress elastic wave equation describing stress propagation characteristics is obtained through derivation; based on Hooke's law, P wave contribution in total partial strain is removed through partial strain decomposition, decoupling of P-S wave stress components is achieved, and correctness of amplitude, phase and physical unit of a decoupling wave field is guaranteed; and then a joint imaging condition with the average stress as a seismic source wave field and the multi-stress component as a receiving wave field is constructed, PP waves are subjected to normalization superposition through the average stress and the deviatoric stress, and PS waves are subjected to shear stress imaging. According to the method, the sensitivity to heterogeneity and local stress variation of underground media can be remarkably improved, P-S wave crosstalk and imaging noise are effectively eliminated, the imaging precision and resolution of a complex geologic structure are greatly improved, and a reliable technical means is provided for high-precision seismic exploration of complex oil and gas reservoirs.

The invention relates to a meshbelt structure simulation method with heterogeneous left and right selvedges based on parameterized segmented modeling, which comprises the following steps of: deconstructing a meshbelt into three heterogeneous functional areas of left overlock, middle main body and right connection, and independently controlling by adopting a Bezier curve, a composite wave equation and a catenary fusion model respectively; the synchronous accurate expression of the closeness of the left side overlock coil, the warp and weft interweaving stability of the main body and the mechanical rationality of the right side U-shaped connection is realized, and the problem of geometric distortion caused by unified modeling in the prior art is solved. According to the method, a cross-scale coupling equation of tension (T), a friction coefficient (mu) and linear density (rho) is introduced, and a closed-loop mapping relation of technological parameters, geometrical morphology and mechanical response is established. For example, when the tension of the braid is increased, the curvature radius of the U-shaped connecting part is automatically reconstructed according to a formula, so that parameter regulation and control are upgraded from experience trial and error to intelligent optimization of physical driving.

The invention relates to a stable Q compensation reverse time migration method for seismic exploration data, a medium and equipment, and belongs to the technical field of geophysical exploration data processing. According to the method, based on a fractional order Laplace viscous acoustic wave equation, a physically guided time-varying regularization compensation operator is constructed in a wavenumber domain, the energy amplitude of a previous time step length is introduced as a reference, an energy growth monitoring mechanism is established, and the energy growth is monitored. And designing a three-level adaptive constraint system: local energy growth constraint, high-frequency adaptive attenuation and boundary region stabilization processing, and realizing adjustment of excessive compensation and adaptive suppression of noise in the wave field continuation process. According to the method, amplitude attenuation and phase frequency dispersion caused by stratum absorption are effectively recovered, meanwhile, the stability of numerical calculation can be guaranteed, the precision and resolution of deep structure imaging are remarkably improved, and good numerical stability and anti-noise capacity are achieved.

The application discloses an explicit finite element parallel computing method for seismic wave simulation, comprising the following steps: constructing a three-dimensional computing domain, generating an unstructured finite element grid based on real terrain and velocity structure data; performing domain decomposition on the computing domain, and dividing the grid into multiple sub-regions; distributing the tasks of the sub-regions to parallel computing nodes, discretely solving a three-dimensional elastic wave equation containing a damping term by using explicit time integration and a lumped mass matrix, synchronously calculating time sequences of wave fields of the sub-regions; integrating the results to obtain seismic wave field distribution, and outputting ground motion parameters of a target region. By constructing an integrated explicit finite element parallel computing framework of a seismic source-medium-terrain, efficient, stable and high-precision simulation of seismic wave propagation under complex geological conditions is realized, and the reliability of strong ground motion prediction is significantly improved.

The invention discloses a concrete ultrasonic propagation characteristic modeling method and system, and relates to the technical field of ultrasonic non-destructive testing, and the method comprises the steps: obtaining the rheological behavior data of unsolidified cement slurry, building a concrete slurry fractional order viscoelastic constitutive model by adopting a Caputo type fractional order derivative, and obtaining a complex modulus; constructing a frequency domain wave equation by using the complex modulus, and calculating ultrasonic attenuation coefficients under different frequencies; dividing the concrete medium into thin layers along the propagation direction, and setting the thickness and characteristic impedance of each layer; a Waterman-Truell model is used to calculate a corrected complex wave number, and a structure factor is combined to correct scattering space correlation; calculating the total attenuation value of the attenuation coefficient of each thin layer, and establishing a propagation path total attenuation model. According to the method, the frequency response consistency is enhanced, the modeling precision of the heterogeneity and the multi-scale scattering characteristic of the concrete is improved, and the method has higher simulation accuracy and physical interpretation.

The application provides a warning method and system for the tipping moment of a thermoacoustic system under Lévy noise, and relates to the technical field of thermoacoustic system stability analysis and early warning control, which comprises the following steps: based on the physical model of the thermoacoustic system, a non-uniform wave equation describing the pressure and velocity fluctuation of the system is constructed; the Galerkin modal expansion and Taylor expansion truncation are performed on the equation, and a random differential equation model is established by combining the time-varying control parameters and Lévy noise; the random differential equation model is solved by the Monte Carlo simulation and the random fourth-order Runge-Kutta numerical method, and the amplitude sequence of the thermoacoustic system changing with time is obtained; based on the probability distribution of the amplitude sequence, the change of the system dynamics characteristics is quantified by calculating the Shannon entropy, and the sequence of the Shannon entropy changing with time is obtained; the warning moment when the Shannon entropy sequence first passes through the preset threshold is determined, and the warning domain is generated according to the time difference between the warning moment and the actual tipping moment of the thermoacoustic system, so that the warning for the tipping moment of the thermoacoustic system is realized.

The invention discloses a seismic wave field simulation method and system in an attenuation medium. A new constant Q viscous sound wave equation is constructed to accurately meet the dispersion relation of the Kjartansson constant Q theory, and an amplitude attenuation item and a phase dispersion item are subjected to explicit separation, so that complete decoupling of attenuation and dispersion can be realized while the theoretically accurate constant Q dispersion relation is kept, and the frequency dispersion accuracy is improved. And solving a constant Q viscous acoustic wave equation through a generalized pseudo-spectral numerical simulation method based on space Fourier transform to obtain a seismic wave field with spatio-temporal variation, so that the precision of viscous acoustic wave simulation is remarkably improved.

This invention relates to the field of seismic imaging technology and discloses a method, apparatus, equipment, and medium for forward modeling of seismic acoustic waves in a viscoelastic-acoustic (VTI) medium. The method includes: obtaining a desired Q value; calculating the viscoelastic velocity of the seismic acoustic wave based on the desired Q value; fitting parameters of a generalized standard linear body model; constructing a wave equation for the seismic acoustic wave in the VTI medium based on the generalized standard linear body model; and solving the wave equation for the seismic acoustic wave in the VTI medium using the finite difference method and the viscoelastic velocity. This invention solves the problem that traditional seismic simulations cannot simultaneously consider seismic anisotropy and seismic attenuation, significantly improving the accuracy and applicability of seismic simulations, as well as the accuracy of seismic simulations in complex terrain, geology, and oil and gas reservoir areas. It provides a foundation for subsequent high-precision seismic velocity modeling and seismic migration imaging.

The invention belongs to the technical field of petroleum geophysical exploration, and relates to an overlapped meshless undulating surface seismic wave field numerical simulation method and system. The method comprises the following steps: establishing an undulating surface seismic wave speed model and an absorption attenuation Q model based on geological parameters of an exploration area; based on the undulating surface seismic wave speed model and the absorption attenuation Q model, adopting an overlapping meshless node subdivision method to obtain a node data set of an overlapping region; taking the node data set as input, expanding a radial basis function based on a Chebyshev polynomial and forming a difference matrix, and solving to obtain a node difference coefficient set; and taking the node data set and the node difference coefficient set as input, performing finite difference discretization on a Kelvin-Voigt model-based viscous-acoustic wave equation based on a radial basis function, implementing forward continuation of the wave field, and completing the seismic wave field numerical simulation of the overlapped meshless undulating surface. According to the method, the constant Q model is accurately described, amplitude-phase decoupling is realized, and the absorption attenuation effect of the medium can be effectively described.

A method and an apparatus for measuring ultrasonic viscoelasticity, a device and a medium are provided. The method includes: establishing an inhomogeneous viscoelastic wave equation; coding the inhomogeneous viscoelastic wave equation as a loss function, and constructing a physics-informed neural network, where the spatial-temporal neural network is configured to predict a stream function, the inhomogeneous viscoelastic wave equation is used to obtain vertical vibration velocity of particles based on the stream function outputted, the spatial neural network is configured to predict shear modulus and viscosity, and the loss function is used to calculate an aggregate loss; inputting the multi-frame vertical vibration velocity of particles of the object to be measured as supervisory data into the physics-informed neural network, to obtain a spatial distribution of the shear modulus and a spatial distribution of the viscosity of the object to be measured.

The invention discloses a sound field model construction method based on a mixture of a parabolic equation theory and a finite element method, and belongs to the technical field of sound field propagation. According to the method, a sound field is divided into a far-field region and a near-field region, a parabolic equation is established in the far-field region, a PINN model is constructed, an initial sound field result calculated by the parabolic equation is corrected and optimized by using the PINN model in each step of calculation by the parabolic equation, and a final sound field result is obtained. The method comprises the following steps: performing grid division in a near-field region, establishing a wave equation in each grid unit, constructing a unit stiffness matrix and a unit mass matrix, finally assembling a global stiffness matrix and a global mass matrix, and further solving detailed information of a three-dimensional sound field; and sound field information at the junction is processed through a multi-physics field coupling boundary condition at the junction. According to the method, a proper calculation method can be selected according to the physical characteristics of different areas, and the propagation rules of sound waves in different scales and environments can be better reflected.

The present application belongs to the technical field of oil and gas seismic exploration, and particularly relates to a pre-stack depth migration imaging method based on generalized diffraction stacking. The present application uses one-way wave equation to calculate the Green's function required for imaging, thereby avoiding the defects of two-way wave equation, making the imaging result not containing the wave field component useless for imaging, ensuring good imaging effect, and reducing the calculation amount, accelerating the operation speed, and improving the imaging efficiency. Moreover, the Green's function is solved in the frequency domain, and there is no sampling rate dispersion problem in the time domain, so that the calculation mode of one-way wave equation can adapt to larger spatial grid interval. Moreover, the relative positions of the imaging point, the source point and the receiver point are judged through angle calculation, so as to perform regional decomposition on the velocity model, and only the necessary region needs to be recursively calculated when solving the Green's function, without recursively calculating in the whole velocity model space. On the basis of ensuring the recursive effect, the useless calculation region is removed, and the imaging efficiency is further improved.

This disclosure pertains to the field of exploration geophysics and presents a method and system for combined active and passive source reverse time migration imaging of metallic minerals. The method includes: performing time difference correction on active and passive source seismic data from the same subsurface structure; performing wavefield separation on the time-aligned active and passive source seismic data to reconstruct the P-wave and S-wave fields of the active source and the passive source; performing active and passive source wavefield extrapolation based on the two-way wave equation; obtaining active and passive source PS-converted wave imaging results using cross-correlation imaging conditions; and performing weighted superposition and fusion to obtain the combined active and passive source imaging results. This disclosure leverages the high resolution advantage of active sources combined with the deep detection capability of passive sources, replacing the limitations of single-source detection and achieving high-precision deep reverse time migration imaging.

The embodiment of the specification discloses a geothermal rock mass elastic wave reverse time migration method based on adaptive variable grid. By inputting the migration velocity model and seismic record of the geothermal rock mass, and setting the imaging parameters, the seismic wave is generated according to the migration velocity model, the seismic record and the imaging parameters; the migration velocity model is adaptively processed by variable grid, the mapping relationship between the coordinate systems is determined, and the wave equation under the variable grid is determined based on the mapping relationship; according to the wave equation, the reverse time continuation of the wave field of the receiver point wave field is carried out in the variable grid along the time reverse propagation direction, and the reverse continuation wave field is generated; the cross-correlation imaging condition is used for the forward continuation wave field and the reverse continuation wave field, the reverse time migration profile under the variable grid is generated, and the imaging result under the variable grid is obtained by stacking; the imaging result is reversely processed by the variable grid according to the mapping relationship, and the reverse time migration imaging result in the conventional coordinate system is obtained; thereby the memory occupation is reduced, and the calculation is fast.

The invention discloses a microseism synchronous inversion method based on multi-task learning, and belongs to the field of microseism inversion, and the method comprises the steps: firstly constructing a ternary data set corresponding to seismic data, a speed model and seismic source position probability distribution; then a double-branch U-Net network model is designed, a shared encoder of the double-branch U-Net network model is integrated with a multi-scale convolution module to extract multi-scale features, and double decoders realize feature decoupling and reinforcement through a task-adaptive guided attention gate; meanwhile, based on wave equation Frechet derivative analysis, a physically-driven dynamic weight adjustment strategy is provided, and optimization of focus positioning and speed modeling tasks is adaptively balanced in the training process. According to the method, the seismic source position and the underground velocity model can be synchronously and precisely inverted from the microseismic data, the problems of parameter coupling, multiplicity, unstable training and the like in a traditional method are effectively solved, and the inversion precision and robustness are remarkably improved.

The invention provides a foundation pile low-strain reflection wave method test method, and belongs to the technical field of pile foundation detection. The method comprises the following operation steps: S1, building a column-bearing platform-pile soil system three-dimensional dynamic model under a rectangular coordinate system according to an elastic theory; s2, a pile, a bearing platform, a column, soil around the pile and soil at the bottom of the pile are regarded as isotropic linear elastomers, physical power is not considered, and system dynamic response is solved based on an elastic wave equation; s3, analyzing the influence of different excitation force positions and different vibration pickup positions on the speed response curve; s4, verifying the correctness of the theoretical model by comparing the numerical calculation curve with the actual measurement curve, and applying the theoretical model to engineering practice to assess the completeness of the foundation pile. Through three-dimensional theoretical innovation, test technology optimization and engineering verification, the accuracy, reliability and practicability of low-strain detection of the column-bearing platform-pile system are comprehensively improved; an effective technical solution is provided for foundation pile integrity evaluation under complex conditions, and the method has important theoretical value and engineering application prospects.

The invention discloses an ARM (Advanced RISC Machines) architecture-oriented CGFDM (China General Microbiological Fused Deposition Modeling) seismic wave solver for hybrid precision and vectorization collaborative optimization and a simulation method, and aims to break through the bottleneck of memory bandwidth and calculation efficiency of ARM platform seismic simulation. According to the method, firstly, an elastic wave equation is reconstructed in a dimensionless mode, key physical quantities are made to adapt to the FP16 range, the mixed precision strategy of FP16 storage and FP32 calculation is adopted, and on the premise that precision is guaranteed, about 50% of memory consumption is reduced. And secondly, for ARM scalable vector expansion (SVE), the CGFDM differential template is mapped to a vector register, SIMD parallel computing is realized, and the throughput is remarkably improved. Finally, the FP16-SVE solver realizes data rearrangement and conversion between the FP16 and the FP32, the problems of alignment and efficiency in mixed precision operation are solved, and synchronous improvement of storage and calculation efficiency is realized. Tests show that the method has the advantages that while the precision is maintained, the memory is halved, nearly three times of speed-up ratio is obtained, and an efficient scheme is provided for large-scale earthquake simulation and real-time disaster assessment of an ARM platform.

Provided is a combined de-aliasing method of one-way wave equation modeling in a frequency-wavenumber domain. 1, nonphysical signal distortion or artificial noise resulting from a folding effect of Fourier transform and undersampling of Fourier transform and improper mathematical operations of numerical truncation or singular value generation from numerical calculation is eliminated in both of a frequency-wavenumber domain and a spatio-temporal domain; and a specific technical solution includes the following steps: step 1, eliminating singular-value aliasing; step 2, eliminating an artificial boundary noise; step 3, eliminating a Fourier folding effect; and step 4, outputting a correct one-way wave equation after eliminating the aliasing. The combined de-aliasing method of one-way wave equation modeling in a frequency-wavenumber domain involves a reasonable denoising technique, is especially aimed at a one-way wave equation modeling equation in an acoustic medium, and can be extended to elastic mediums and viscoelastic mediums.

The invention discloses a sample and multi-scale fault and crack prediction method, and relates to the technical field of tight sandstone fault and crack body geophysical prediction, and the method comprises the following steps: S1, simulating a fault and a crack generated by stratum fracture or deformation after a stratum is stressed through a discrete element method, analyzing the fault and crack development positions and the crack density, and obtaining a fault and crack prediction result; establishing a fracture and fold seam body geologic model; s2, utilizing logging information of a research area to establish a fracture and fold crack body speed model, designing an observation system, and adopting wave equation forward modeling to obtain fracture and fold crack body sample seismic data; s3, using gray level co-occurrence mean value attributes to fuse gradient structure tensor attributes to describe a stratum deformation zone; s4, performing fracture detection by adopting frequency division edge detection; and S5, obtaining short-cycle characterization fracture and fold crack body seismic characteristics of the characterization crack belt by using a long-short cycle separation technology, and solving the problems that in the prior art, due to the fact that no sample fracture and fold crack body seismic data exists, whether attribute selection is reasonable or not is generally difficult to judge, and a prediction result is difficult to evaluate.

The application discloses an ultrasonic CT waveform inversion method and device based on a dynamic aperture, and belongs to the technical field of ultrasonic image processing, and comprises the following steps: acquiring an observed sound pressure signal at a position of a receiving element of an ultrasonic CT data acquisition system; inputting a current sound velocity distribution into a wave equation to obtain a synthesized sound pressure signal at the position of the receiving element; for each transmitting element, extracting the synthesized sound pressure signals at the positions of M receiving elements away from the transmitting element; calculating the difference between the synthesized sound pressure signals at the positions of the M receiving elements corresponding to all the transmitting elements and the corresponding observed sound pressure signals; calculating the gradient of the current sound velocity distribution by using an adjoint state method according to the difference, and then obtaining an updated sound velocity distribution; re-substituting the updated sound velocity distribution into the wave equation for iteration, and simultaneously increasing the value of M until the iteration is stopped, and outputting the updated sound velocity distribution. The application can improve the accuracy of a reconstructed image under the condition of missing low-frequency information.