16 results about "Boundary integral equations" patented technology

The invention discloses a method for calculating a quantitative magnetic susceptibility image through total field inversion based on a Green function. The method is used for separating a background magnetic field and reconstructing a whole-brain quantitative magnetic susceptibility image in magnetic resonance imaging. According to the boundary element method full-field inversion method, filtering and regularization processing on tissue magnetic susceptibility are prevented from being additionally introduced when background field interference is removed, the background field can be effectively separated, a whole-brain quantitative magnetic susceptibility image can be reconstructed, the boundary erosion phenomenon cannot occur, and the boundary element method full-field inversion method particularly shows excellent performance in a cortex area. According to the method, a fast multipole method is adopted to efficiently process storage and calculation of a dense matrix generated by a boundary integral equation.

The application relates to the technical field of power detection, and discloses a power equipment medium identification method based on digital-analog driving, which comprises the following steps: constructing an equipment geometric field and arranging boundary measuring points; obtaining physical quantity and normal derivative data of the measuring points through non-invasive measurement and fitting; based on a physical control equation, unknown medium parameters are converted into equivalent source terms through standardization and an equivalent source method, and then the boundary integral equation is converted into the boundary integral equation through a boundary element method, so that the measurement data and the internal source terms are associated; a surface quadrature neural network is constructed, the field point coordinates and the boundary data are taken as inputs, the internal equivalent source term distribution is output, and a loss function is constructed based on the boundary integral equation to train the network; real-time data are calculated forwardly by using the trained network, the equivalent source terms are obtained, and the medium distribution is inversed, the application provides the power equipment medium identification method based on the digital-analog driving, which can quickly judge the cause of the internal condition of the equipment and perform tracing and positioning.

The invention discloses a three-dimensional acoustic elasticity calculation method based on combined potential, and relates to the field of ship three-dimensional acoustic elasticity calculation, and the method comprises the steps: constructing a speed potential in an outer watershed of an underwater ship structure into a linear combination form of a single-layer potential and a double-layer potential, and constructing a boundary integral equation on a wet surface of the underwater ship structure; according to fluid-solid coupling boundary conditions on the wet surface of the underwater ship structure, a boundary integral equation on the wet surface of the underwater ship structure is solved by adopting a boundary element method, and virtual source intensity distribution on the wet surface of the underwater ship structure is obtained; according to the virtual source intensity distribution of the wet surface of the underwater ship structure and the dry modal displacement of the structure, acoustic elasticity response parameters are obtained through calculation. By constructing the watershed speed potential outside the underwater ship structure in a linear combination form of single-layer potential and double-layer potential, the irregular frequency of acoustic elasticity calculation is effectively eliminated under the condition that the calculation scale and modeling workload are not additionally increased, and the efficiency of three-dimensional acoustic elasticity analysis can be remarkably improved.

The present application relates to the technical field of numerical calculation, in particular to a large-scale boundary element iteration initial value generation method based on boundary information neural network, comprising: constructing a basic data set of a small-scale example to train a pre-constructed deep neural network architecture; inputting known physical quantities of a to-be-solved domain into a physical information neural network based on boundary integral equation constraint obtained after training to predict small-scale unknown physical quantities; mapping the small-scale unknown physical quantities to actual calculation points corresponding to a large-scale fast boundary element method by using a boundary integral equation, and aligning degrees of freedom to generate a large-scale initial vector of degrees of freedom; and inputting the large-scale initial vector of degrees of freedom into a large-scale fast boundary element iteration solver to perform iteration as an initial value. Thus, the defects of the existing large-scale fast boundary element method in processing complex engineering problems, such as slow iteration convergence and large influence of initial value selection on calculation efficiency, are solved.

The invention discloses a finite element and time domain boundary element asynchronous length different node coupling calculation method for dynamic response simulation, which comprises the following steps of: establishing and solving a boundary integral equation of a boundary element sub-domain to obtain displacement and surface force distribution of the boundary element sub-domain; a motion equation of the finite element sub-domain is established and solved, and displacement, speed and acceleration of the finite element sub-domain are obtained; on the common boundary, surface force distribution of the boundary element sub-domain is converted into equivalent node force of the finite element sub-domain through a force transfer matrix, meanwhile, displacement of the finite element sub-domain is converted into boundary displacement of the boundary element sub-domain through a displacement transfer matrix, and space coupling of the boundary element sub-domain and the finite element sub-domain on the common boundary is achieved; based on a force balance condition and a displacement coordination condition, processing data obtained by the boundary element sub-domain and the finite element sub-domain under different time steps by adopting a time interpolation method to realize time coupling; and processing the space coupling and the time coupling based on iterative solution to obtain the dynamic response of the structure.

The present application belongs to the field of ship hydrodynamics and motion prediction, and in particular to a device and method for predicting the hydrodynamics and motion of a ship coupled with ice, which first derives a Green function that satisfies the boundary conditions of the ice layer and the free surface, as well as all other conditions except the surface condition of the ship, and through the Green function, the differential equation of the velocity potential is converted into a boundary integral equation on the surface of the ship only, which introduces an extended surface at the waterline of the ship body to eliminate the influence of irregular wave frequencies; an asymptotic solution formula of the Green function is analytically derived, thereby establishing an approximate and effective solution program for the coupled interaction of the ship / wave / ice layer, and numerically calculating the results of the added mass, damping coefficient and wave exciting force of the ship body; through the method, the interaction mechanism of the water wave / ship / ice layer under different parameter characteristics can be deeply understood, and theoretical support is provided for the hydrodynamic problems, motion prediction and rational design of polar ships.

The invention discloses a transverse isotropic functionally graded material crack propagation analysis method and a service life prediction system, and relates to the field of civil engineering materials and structural safety, and the transverse isotropic functionally graded material crack propagation analysis method comprises the following steps: constructing a dual boundary integral equation set based on a transverse isotropic multilayer medium basic solution; calculating a crack tip mixed mode stress intensity factor with high precision by adopting a self-adaptive grid division technology; and realizing full-automatic prediction of a fatigue crack propagation path and a structural fatigue life by combining a crack propagation law and a virtual crack propagation strategy. By only automatically discretizing the boundary and the crack surface, the huge calculation burden of a traditional finite element method in global discretization and repeated grid division is avoided, and the method is particularly suitable for processing the fatigue problem of transverse isotropic functionally graded materials (such as layered rock mass, side slope foundation and oriented fiber reinforced composite materials) in a semi-infinite domain. And the calculation efficiency, the precision and the engineering practical level of durability analysis and life prediction of the civil engineering structure under the cyclic load are remarkably improved.

The application discloses a kind of based on high-order boundary element's three-dimensional water wave band gap attenuation coefficient solving method, belong to water wave regulation field, including the following steps: S1, based on linear potential flow theory establishes three-dimensional fixed structure infinite periodic array model, fluid is divided into several identical units, and the control equation and boundary condition that fluid domain velocity potential satisfies are obtained;S2, high-order boundary element method is selected to solve three-dimensional Laplace equation, boundary condition is substituted into boundary integral equation and simple Green function is selected, by numerical dispersion into high-order grid unit, and linear homogeneous equation set is established;S3, by organizing equation set, equation set has solution problem is converted into local minimum value problem to solve complex Bloch wave number, and the attenuation coefficient of water wave band in band gap is obtained.The application adopts the above solving method, realizes the fast and accurate solution of three-dimensional fixed structure band gap structure and attenuation coefficient in band gap.

The invention discloses a high-order grid parallel generation method based on GPU acceleration and fine projection, and the method comprises the steps: firstly inputting an original volume grid and a surface grid, and carrying out the order lifting processing, and obtaining a high-order volume grid and a high-order surface grid; secondly, calculating physical offsets of all nodes on the high-order surface grid relative to the high-order surface grid through projection by utilizing an AABB tree structure, and storing the offsets as displacement potential function values; then, on the basis of a boundary integral equation, physical offset vectors of all internal nodes in the volume mesh are calculated in parallel through a GPU; and finally, traversing all grid nodes, and updating all point coordinates according to the physical offset vectors of the internal nodes to obtain a generated high-order grid. According to the method, the calculation time of the boundary offset is greatly shortened, and the method has the advantages of high efficiency, high expandability and high precision and is suitable for high-precision CFD simulation pretreatment of industrial-grade complex shapes.

The invention relates to the technical field of electromagnetic full-wave inversion, in particular to a two-dimensional cross-layered efficient electromagnetic full-wave inversion method based on a spectral element boundary integral method.During forward modeling calculation, a scatterer crossing multiple horizontal layers is surrounded by a one-dimensional smooth boundary, and two-dimensional electromagnetic field distribution is solved by adopting a spectral element method in a region; accurately truncating an SEM solving domain on the boundary by using a boundary integral equation; for a transverse electric mode and a transverse magnetic mode, equivalent current / magnetic current is solved by using BIE, and a receiver scattering field is calculated in combination with a layered two-dimensional vector Green function; in the full-wave inversion, in order to reconstruct TE mode isotropic scatterer model parameters and TM mode anisotropic scatterer model parameters respectively, first-order derivatives of a mass matrix and a stiffness matrix relative to the corresponding parameters are calculated respectively, a sensitivity matrix is constructed, and an LM optimization algorithm is adopted to iteratively call an SEBI forward solver to complete inversion; multiple groups of numerical experiments verify the accuracy and high efficiency of the SEBI-LM algorithm in forward modeling and FWI.

This invention discloses a time-domain numerical method for calculating the hydrodynamic performance of ships in the field of marine hydrodynamics. The method includes: establishing a three-dimensional numerical model of the hull and free surface; decomposing the total velocity potential based on time-domain potential flow theory; constructing boundary integral equations; introducing a time-increasing monotonically increasing function to smooth the initial transient response; simultaneously iteratively solving the free surface evolution and the ship's six-degree-of-freedom motion equations; and achieving self-consistent coupling between flow field pressure and ship motion using a closed feedback loop. This method also supports nonlinear free surface boundary conditions, suppresses numerical dissipation through high-order extrapolation, and dynamically calculates the restoring force matrix based on surface element integrals, significantly improving the calculation accuracy and stability of ship motion response in confined waters. It is suitable for engineering prediction of complex conditions such as near-shore navigation, shallow water resonance, and shoreline reflection.

The invention relates to the field of electron beam lithography, and provides an electron optical track simulation method based on a boundary element and a genetic algorithm. The method comprises the following steps: firstly, constructing a preliminary model, encoding corresponding geometric parameters and electrical parameters, performing grid division after population initialization, constructing a boundary integral equation according to an electromagnetic field theory, calculating electric field distribution in a field domain in combination with boundary conditions, and calculating a track of electrons under the action of an electric field by utilizing a self-adaptive step length method. And calculating a fitness function fi, carrying out selection, intersection and mutation to generate new individuals, carrying out calculation again, carrying out continuous circulation until a termination condition is met, and selecting the individual with the highest fitness to obtain optimal geometric parameters and electrical parameters. The method is oriented to electron beam optical system structure optimization and electron trajectory calculation, on the premise of guaranteeing precision, electron optical system structure related parameters meeting the electron trajectory requirement are rapidly calculated, and 10-100 times of acceleration is achieved compared with a standard FDM / FEM method.

The invention relates to a seismic wave forward modeling method and device based on a viscoelastic medium and electronic equipment. The method comprises the following steps: acquiring viscoelastic medium parameters of a stratum to construct a viscoelastic wave fluctuation equation; acquiring a wave equation based on a viscoelastic wave wave equation, and constructing a second-order Green displacement tensor based on the viscoelastic medium density, the angular frequency and a Green function of a scalar wave equation; the method comprises the following steps: acquiring a first coefficient expression of a second-order green displacement tensor based on a geometric model of a viscoelastic medium, introducing a frequency-dependent complex velocity, constructing a green function based on the complex velocity, and acquiring a first solving subitem based on the green function and the first coefficient expression; based on Hooke's law and the first solving subitem, obtaining a second solving subitem; obtaining a frequency domain viscoelastic medium boundary integral equation on the basis of the first solving subitem and the second solving subitem; and performing discrete solution on the frequency domain viscoelastic medium boundary integral equation to obtain the displacement and stress of the seismic wave in the propagation process. And calculation errors can be reduced.

This invention relates to the field of capacitance calculation technology and discloses a fast algorithm for extracting parasitic capacitance in large-scale integrated circuits. This method combines the method of moments (MoM), a fast multipole algorithm for layered dielectrics, and overlapping region decomposition preprocessing techniques to construct a complete parasitic capacitance extraction solution. By directly introducing the Green's function for the layered dielectric, the numerical solution strictly satisfies the electric field transport conditions at the dielectric interface, and the electrostatic problem in the layered dielectric is transformed into boundary integral equations defined on the interconnect surface. Subsequently, the MoM is used to discretize these boundary integral equations, resulting in a large-scale dense system of linear algebraic equations. To improve solution efficiency, an efficient preprocessing strategy based on overlapping region decomposition is further designed, and combined with the matrix-free minimum residual iteration method and the layered fast multipole algorithm, achieving efficient solution with low computational and storage overhead.

The invention discloses a GIL basin-type insulator surface charge inversion algorithm based on a boundary integral equation and a least square method, and the algorithm comprises the steps: enabling an experiment platform to apply a stable DC voltage to a basin-type insulator in a cavity through a DC high-voltage console, and enabling a protection resistor to be connected in series in front of an insulating sleeve; the damage to direct-current power supply equipment caused by accidental surface flashover in an experiment process is prevented; the basin-type insulator sample is driven to rotate through the rotating platform, and dynamic measurement of the surface potential is completed in cooperation with the electrostatic probe; and the electrostatic potentiometer transmits potential data acquired in real time to the computer through the data acquisition card for subsequent processing. The method is suitable for online monitoring of the insulation state of the + / -800 kV direct current GIL, economic losses and safety risks of workers caused by faults are reduced, and meanwhile high-precision and high-robustness experiment and data support is provided for equipment optimization design and safe operation.

The invention discloses a fluid saturation crack seismic wave scattering modeling method based on a virtual stress method, and belongs to the field of geophysical exploration. According to the technical scheme, a linearization fluid mechanics equation is used for describing fluid movement in a fracture, a Green function basic solution of a plane strain elastic wave problem is deduced, a boundary integral equation of fracture scattering is established in combination with a virtual stress method, numerical simulation is achieved, and a synthetic seismic map and a wave field snapshot are obtained. Compared with the prior art, the boundary element method is used for carrying out numerical simulation, so that the influence of viscous fluid saturation cracks in an infinite stratum on seismic wave dispersion and attenuation can be reflected more truly, and the limitation of finite volume numerical rock sample simulation is avoided; besides, a fluid mechanics equation is used for replacing a traditional method that a pore medium equation is used for describing the flowing behavior of fluid in the crack, the essence of physical problems is restored, and calculation errors caused by using a non-fluid equation to describe fluid dynamics behaviors are avoided. The method can be applied to the fields of geophysical exploration, petroleum logging engineering detection, underground complex environment monitoring and the like.