47 results about "Helmholtz equation" patented technology

A system and method for accurately estimating the fluctuating pressure loads on components, such as steam dryers, within a BWR steam dome using pressure time history measurements made on components of the BWR facility external to the steam dome. The method uses existing sensors to obtain the pressure time histories. An accurate determination of the fluctuating pressure loads within the steam dome may be obtained by modeling and analyzing the steam delivery system external to the steam dome, including all possible acoustic sources, using acoustic circuit methodology and pressure time histories, and then coupling these results, essentially as part of the boundary conditions, to the solutions for Helmholtz equation within the steam dome.

The invention discloses a variable-angle illumination tomography method and a device based on a deep learning generation network. The method comprises the following steps of according to the Helmholtzequation of the wave and the Fourier propagation model of the light, deriving a distribution model of a diffraction field and a refraction field when the light propagates layer by layer in a non-uniform transparent medium; generating a neural network by simulating the physical process of the deep learning during the time-domain and frequency-domain propagation process in a complex form; through an angle spectrum propagation formula, backwardly transmitting a collected output optical complex field wherein samples cannot penetrate the collected output optical complex field as the complex fielddata of the input light, and adopting the complex field of a collected and transmitted to-be-reconstructed sample as the complex field data of the output light; according to a reconstruction resolution condition, adjusting the parameters of the deep learning network, and training the deep learning network; solving the three-dimensional refractive index distribution of the sample through a weight obtained through training the deep learning network, and realizing the chromatographic reconstruction of the sample. According to the invention, the chromatographic reconstruction capability low in acquisition amount and high in resolution is achieved. The resolution precision of the sample tomography reconstruction is effectively improved.

The invention discloses a three-dimensional sound source localization method based on compressed sensing, so as to solve the technical problem of poor anti-noise performance of the existing three-dimensional sound source localization method. In the technical scheme, the measurement value of sound source signals is acquired through a microphone array, a selected three-dimensional sound source area is subjected to uniform mesh generation, and each mesh node is used as a hidden sound source position; according to a Helmholtz equation of a free field Green's function, a measurement matrix between the mesh node and the microphone array is built, and a three-dimensional narrowband sound source localization sparse representation model between the measurement value of the microphone array and unknown sound source signals is acquired; through carrying out singular value decomposition on the measurement value of the microphone array in the sparse representation model, a sound source localization sparse representation model after deformation is acquired; and finally, a compressed sensing OMP (orthogonal matching pursuit) algorithm is adopted to carry out iterative solution on the representation model after deformation, the sound source strength of each mesh node in the sound source area is acquired, and the sound source is localized. The anti-noise performance of sound source localization is improved.

A system for analyzing noise sources correlates the sound pressure level value at any field point to the acoustic energy directly flowing out of any individual panel of a vibrating structure. This acoustic energy flow or acoustic intensity depicts how sound radiates and in which direction a sound wave propagates in the field. Therefore, the result represents a true contribution of an individual panel to an acoustic field. The acoustic intensity on the surface of a vibrating object is reconstructed by the Helmholtz equation least squares (HELS) based nearfield acoustical holography (NAH). The acoustic intensity is utilized to establish correlations between user-designated panels and the SPL value at any field point. With this information users can rank the order of contributions from individual panels of any vibrating structure to an acoustic field. These order ranking and panel contribution analyses help engineers to come up the best strategy to tackle various noise issues in the most cost-effective manner. The method is applicable to both interior and exterior regions.

The invention relates to a testing method of material performance and particularly relates to a carbon dioxide adsorption isotherm precision testing method for materials. The method disclosed by the invention is based on a capacity method, a CO2 adsorption isotherm is obtained by continuously recording gas pressure and temperature of each of all parts of the material during an adsorption or release process and calculating the adsorption amount of the material corresponding to different CO2 gas pressures according to a Helmholtz equation, and the whole calculation and drawing process of CO2 real density is realized by programming through a computer. According to the method disclosed by the invention, as the influence of temperature fluctuation in a gas storage chamber on experimental results is considered during the procedure, even the part of the gas storage chamber of equipment can not realize constant temperature, the CO2 adsorption isotherm obtained by testing is still real and reliable. The method disclosed by the invention has a great practical value, the equipment becomes simple and easy to operate, and the credibility is simultaneously higher when the high-pressure CO2 adsorption isotherm of the material is tested.

The invention discloses an underwater sound field numerical simulation method and system based on a Chebyshev polynomial spectrum and a medium. The method comprises the following steps: establishing asimplified control equation of an acoustic propagation Helmholtz equation under a cylindrical coordinate system; completing independent variable transformation from a z coordinate to an x coordinateby using the simplified control equation; implementing Chebyshev forward transformation on the simplified control equation, and mapping a physical space to a spectral space to form a discretized linear equation set in the spectral space; solving the discretized linear equation set in the spectral space to obtain a solution in the spectral space; implementing Chebyshev inverse transformation on thesolution in the spectral space, and mapping the solution in the spectral space back to the physical space; completing independent variable inverse transformation from an x coordinate to a z coordinate to obtain u (r, z), and solving a sound pressure field p; calculating propagation losses. The method is suitable for obtaining higher calculation precision under the condition that few discrete gridpoints are used, the calculation performance of a hardware platform can be brought into full play, and the speed of numerical simulation is remarkably increased.

The invention discloses a time domain spectral element simulation method for a microwave ferrite component. According to the method, a curved hexahedron unit is utilized to conduct discretization to a whole electromagnetism space containing ferrite materials, ferrite magnetic conductivity which is in a tensor form and contains a damping factor is introduced into an electric field time domain Helmholtz equation, and a single-axis electrical anisotropy perfectly matched layer serves as an absorbing boundary condition, after Galerkin transformation, a central difference scheme is adopted in time discretization, and a time domain electric field iteration formula is obtained; time-domain simulation is conducted to the target ferrite component twice through the time domain electric field iteration formula, and according to the definition of a microwave network scattering parameter, insertion loss, return loss and isolation of the target ferrite component at each port within a working frequency range are determined. The time domain spectral element simulation method for the microwave ferrite component has the advantages of being high in computation accuracy, high in computation speed and broad in range of application.

Methods and systems for simulating acoustic field resulted from particular excitations by performing vibro-acoustic analysis of a structure are disclosed. According to one aspect of the present invention, vibro-acoustic analysis of a structure is performed in two stages. First, steady state dynamic (SSD) responses are obtained using a finite element analysis model of a structure subject to harmonic excitations (e.g., external nodal loads, pressures, or enforced motions (e.g., ground motions), etc.). The steady state responses are the results (e.g., nodal velocities at desired locations of the structure) obtained in a finite element analysis in frequency-domain. Second, an acoustic analysis is conducted according to Helmholtz equation using the nodal velocities obtained at desired locations on the structure as a boundary condition. The acoustic analysis can be performed in a number of procedures (e.g., boundary element method, Rayleigh approximation method, etc.).

The invention discloses a concentric annular type topological super-lens, a method for acquiring a structure thereof and a manufacturing method. The method for acquiring the structure comprises the following steps: taking the maximation of optical wave field energy density on a focal position corresponding to a preset numerical aperture as a target; and deducing a super lens main body which takes circular polarized wave or radiation polarized wave as stimulation, is arranged on an appointed base and has rotation symmetry; establishing a lossless titanium dioxide interpolation function in a symmetric plane of the super lens main body; solving a helmholtz equation of a transverse magnetic wave which takes the maximation of the optical wave field energy density on the focus as the target, thereby acquiring a surface structure of the convergent super lens main body; and rotating the surface structure of the convergent super lens main body around a symmetry axis, thereby acquiring the main body of the concentric annular type topological super-lens. By adopting a reverse deducing manner, the structure of the super lens main body is deduced, so that the numerical aperture of the super lens can be freely appointed according to the requirement, the super lens is small in volume, the process is simple, the manufacturing cost is low and the super lens is easily integrated and arrayed.

The invention discloses an anti-resonance breakwater design method. The method comprises the steps of determining an arrangement axis of a vertical wall type structure; obtaining input parameters of the computational domain; discretizing a computational domain through a finite element eight-node isoparametric element method; carrying out wave field simulation through a quasi-Helmholtz equation wave model, and determining a reflection wave field under the frequency domain change of a computational domain; and according to the grating equation, determining the design parameter wave number K and amplitude A of the sine curved surface of the vertical wall type structure. A Laplace equation is solved through an FAT theory, boundary conditions are substituted, a quasi-Helmholtz equation containing wave nonlinearity under the condition that the water depth is not changed is derived, a wave field of a harbor basin is calculated through a finite element method, the grating principle and the quasi-Helmholtz equation wave theory are combined, a breakwater vertical wall section structural form is designed, the size of a vertical wall curved surface is determined, and the wave propagation process is attenuated, and wave propagation is dissipated, so that harbor resonance caused by propagation of incident waves to a harbor basin is reduced.

The invention discloses a method and system for forecasting an ocean vector sound field and a medium. The method comprises the steps: S1, obtaining the field measurement data and sound source parameter information of a to-be-forecasted ocean region, building a cylindrical coordinate system underwater sound Helmholtz equation, and obtaining a depth equation after transformation; S2, solving a depthequation to obtain a sound pressure kernel function and a vertical vibration velocity kernel function of each dielectric layer interface; S3, calculating the sound pressure according to the sound pressure kernel function, calculating the vertical vibration velocity by using a vertical derivative based on an Hankel inverse transformation integral formula according to the vertical vibration velocity kernel function, and calculating the horizontal vibration velocity based on a horizontal derivative of the Hankel inverse transformation integral formula; and S4, according to the solved sound pressure and vibration velocity vector, calculating a water sound propagation loss and sound intensity vector of the to-be-forecasted ocean area. The method can achieve the prediction of the vibration velocity vector based on the marine environment measurement data, and can improve the prediction precision of the vibration velocity vector.

The invention discloses a parameter calculation method for an all-dielectric polarization beam splitting metamaterial device, and the method comprises the steps: determining the period of a grating, and enabling the grating to only have zero-stage diffraction and -1-stage diffraction; obtaining an intrinsic equation of terahertz wave diffraction in the grating area based on a Helmholtz equation; solving the intrinsic equation to obtain the equivalent refractive indexes of the first two Bloch modes propagated in the grating; based on the Mach-Zehnder interferometer principle, obtaining the approximate function relationship between the diffraction efficiency of the two Bloch modes and the grating depth; and giving a duty ratio to obtain the grating depth when the 0-stage or -1-stage diffraction efficiency of the grating reaches the maximum. The invention further discloses an all-dielectric polarization beam splitting metamaterial device. According to the parameter calculation method, a simplified modal method is adopted, the calculation method is simple, and the calculation amount is small. The all-dielectric polarization beam splitting metamaterial device is simple to process, incident terahertz waves of different polarizations can be diffracted to different directions, and high efficiency is achieved.

A system and method for designing photonic band gap structures. The system and method provide a user with the capability to produce a model of a two-dimensional array of conductors corresponding to a unit cell. The model involves a linear equation. Boundary conditions representative of conditions at the boundary of the unit cell are applied to a solution of the Helmholtz equation defined for the unit cell. The linear equation can be approximated by a Hermitian matrix. An eigenvalue of the Helmholtz equation is calculated. One computation approach involves calculating finite differences. The model can include a symmetry element, such as a center of inversion, a rotation axis, and a mirror plane. A graphical user interface is provided for the user's convenience. A display is provided to display to a user the calculated eigenvalue, corresponding to a photonic energy level in the Brilloin zone of the unit cell.

Method for rapidly computing updates to frequency-domain seismic wave fields by utilizing a matrix perturbation approach. The method speeds up model (e.g., velocity) parameter estimation by iterative inversion of measured seismic data. The method applies to the line search where the optimal size of the model update is estimated by testing different size updates to see which one generates the minimum objective function. By treating the model update as a perturbation, perturbation theory is used to relate the model perturbation to a corresponding wavefield perturbation. Thus, the Helmholtz equation is solved only once per iteration cycle.

The invention discloses a method and a system for improving ocean sound field forecasting precision and a medium. The method comprises the steps: S1, obtaining the field measurement data of a to-be-measured ocean underwater sound field and the parameter information of a sound source, building a cylindrical coordinate system underwater sound Helmholtz equation in a horizontal layered ocean environment, and obtaining a depth equation after transformation; S2, establishing sound vectors of upper and lower boundaries of a sound field; S3, transmitting the sound vectors from the upper boundary andthe lower boundary to a middle depth; S4, establishing a sound vector equation at the middle depth, solving the vertical vibration velocities of the upper boundary and the lower boundary, and calculating the sound pressure wave number kernel function of each layer; S5, performing horizontal wave number integration on the sound pressure wave number kernel function to obtain a sound pressure value of a receiving depth; and S6, calculating a propagation loss curve of the receiving depth, and forecasting the to-be-measured ocean sound field. According to the invention, sound field forecasting canbe realized based on marine environment measurement data, and the marine sound field forecasting precision can be improved.

The invention relates to a satellite electric propulsion system xenon filling thermodynamic characteristic numerical simulation method which includes the following steps: step S101, xenon fluid state equations are established, the xenon fluid state equations include Redlich-Kwong equation, BWR equation and Helmholtz equation for using least square method numerical interpolation fitting to establish thermodynamic properties, the three different types of empirical parameter equations are compared and analyzed; step S102, according to thermodynamic parameters of xenon in a particular state or region range, one or more of the three different types of empirical parameter equations of the RK equation, the BWR equation and the Helmholtz equation is / are selected; and step S103, xenon filling thermodynamic characteristic numerical simulation can be performed by setting of the simulation parameters. The satellite electric propulsion system xenon filling characteristic numerical simulation method can simulate satellite electric propulsion system xenon filling characteristics, test and estimate xenon filling total temperature and total pressure range numerical simulation, and has the advantages of strong adaptability, high precision and easiness in use.

The invention discloses a liquid crystal filled photonic crystal fiber analysis method based on a full-wave mixed spectral element method, and relates to photonic crystal fibers. The method includes selecting a calculation area without repeated calculation according to a solid model, performing mesh generation of limited sub-domains on the calculation area, and dividing each sub-domain unit into aquadrilateral structure; using a mode of combining a full-wave Helmholtz equation and a Gaussian law, constructing a primary function by a Gaussian-Legendre-Lobatto polynomial, and obtaining the energy band characteristic of the complex medium photonic crystal in a full-wave calculation mode of mutually coupling a TM mode and a TE mode, and the method can inhibit the generation of a zero pseudo mode. Different photonic band gaps under different parameters can be obtained by calculating the liquid crystal filled photonic crystal through a full-wave mixed spectral element method, that is, the photonic crystal fiber can flexibly control the transmission spectrum, and the problem that the transmission characteristic of a traditional photonic crystal fiber cannot be changed any more once the photonic crystal fiber is drawn is solved.

The invention discloses a topological optimization method for an interval contraction sound insulation structure, which comprises the following steps of performing acoustic modeling on the interval contraction sound insulation structure according to a Helmholtz equation, and proposing a new interpolation function for continuous material interpolation of density and volume modulus by adopting a topological optimization method based on a variable density method. A constraint condition of the volume fraction of the material in the design domain is introduced, sensitivity analysis is carried out on an objective function and the constraint function by using an adjoint method by taking the minimized quadratic sum of the transmission sound pressure of the target frequency band in the evaluation domain as the objective function, and the objective function is optimized by using a moving asymptotic line method to obtain the optimal distribution of the solid material in the design domain; and finally, broadband sound insulation of the ventilation sound barrier in a limited space is realized. The method gets rid of the traditional thought of designing sound insulation structure parameters by experience, takes sound insulation frequency band widening as a target, and reversely designs material distribution by means of a topological optimization algorithm to obtain the optimal sound barrierwith the characteristics of broadband, ventilation, light weight and the like.

A system and method for accurately estimating the fluctuating pressure loads on components, such as steam dryers, within a BWR steam dome using pressure time history measurements made on components of the BWR facility external to the steam dome. The method uses existing sensors to obtain the pressure time histories. An accurate determination of the fluctuating pressure loads within the steam dome may be obtained by modeling and analyzing the steam delivery system external to the steam dome, including all possible acoustic sources, using acoustic circuit methodology and pressure time histories, and then coupling these results, essentially as part of the boundary conditions, to the solutions for Helmholtz equation within the steam dome.

The invention aims at providing a sound field separation method based on a least square method of a Helmholtz equation. The sound field separation method comprises the following steps: acquiring a sound pressure on a measurement surface; resampling the sound pressure on the measurement surface to obtain different measuring point groups; decomposing the sound pressures generated by a sound source Aand a sound source B at each measuring point according to a sound pressure expansion formula in an HELS acoustic holography method, and establishing a transmission relationship between the sound pressures of the two sound sources on the measurement surface; establishing a transfer matrix between the measurement surface and the sound source surface; and performing singular value decomposition on the transfer matrix to obtain the sound pressure generated by the sound source A on the measurement surface or any position, thereby realizing sound field separation. According to the invention, the single measurement surface and the HELS method are used for sound field separation and reconstructionand only the sound pressure data of the single measurement surface need to be collected, so that thecollection workload and the collection cost are reduced; the number of needed measurement points is small, the calculation efficiency is high, and the implementation mode is simple.

The invention discloses an arbitrary three-dimensional graphics surface reconstruction method based on Helmholtz equation, comprising the following steps: S10, scanning a three-dimensional graphics target body to obtain data points near the surface of the target body and obtaining coordinate information of the data points; S20, acquiring the actual coordinate information of the points on the surface of the target body, and assigning a dimensionless value u to the actual coordinate information of the known points on the surface of the target body as a boundary condition for solving Helmholtz equation; S30, importing the coordinate information of all the data points obtained in the step S10 into a radial basis function interpolation formula, The dimensionless values of all data points shownin the description are solved by boundary point interpolation technique; S40, Using the dimensionless value u in step S20 as the classification criterion, the data points shown in the description areselected as three-dimensional surface points, so as to achieve the purpose of surface reconstruction. The invention applies the boundary node interpolation technology to the surface reconstruction ofthree-dimensional graphics for the first time, reconstructs the graphics surface by utilizing only the coordinate information of a part of points on the boundary surface, and accurately and efficiently obtains the surface position information of the target body.

The invention discloses a multi-phase cage type induction motor magnetic field calculation method and system, and the method comprises the steps: dividing a motor solving region according to the type of an excitation source, thereby obtaining a motor model, and obtaining a distribution function of the current density of a stator winding based on the motor model; aiming at the influence of the k current density harmonics, taking the vector magnetic potential in each sub-domain as a solving object of a control equation, respectively establishing a Laplace's equation, a Poisson equation and a Helmholtz equation, and solving a general solution of the vector magnetic potential according to boundary conditions among interfaces; based on the general solution of the vector magnetic potential of each sub-domain, solving the harmonic coefficient of each sub-domain; and based on the harmonic coefficient of each sub-domain, solving the radial and tangential components of the air gap flux density according to the vector magnetic potential expression of the air gap sub-domain, and solving the torque caused by the k space harmonics of the magnetomotive force and the total electromagnetic torque according to the radial and tangential components of the air gap flux density and the Maxwell tensor method.

A computer system and method are proposed for solving physical problems governed by Poisson or Helmholtz equations. Values of at least one unknown physical quantity at points are determined using known values of at least one second physical quantity. The points are clustered into a hierarchical skeleton structure using a clustering algorithm based on distances between the points. Interactions between distant clusters are approximated, to give a system of equations which can be solved more efficiently.

A gradient method (GM) for constructing and using absorbing boundary conditions (ABCs) for high accuracy numerical computations of various physical phenomena which are governed by partial differential equations (PDEs) is disclosed. The PDEs to which the GM is applicable are for example: the Helmholtz equation (also known as the wave equation in the frequency domain), the elastic wave equation in the frequency domain, Maxwell's equations, and Schrodinger's equation. The GM can be used to develop ABCs for the solution of PDE problems in two or more dimensions. The GM is a tool based on two principles: (1) Any directional derivatives in an ABC must be taken in the direction of the gradient of the unknown function or functions of the PDE, and (2) any ABC using such gradient derivatives may be applied to any domain of a convex shape, even if the ABC was originally developed for domains of a restricted shape.

A system extracts the sound spectrum and sound pressure level (SPL) values of a target source in a non-ideal environment. This system can be critical for in-line or end-of-line quality control (QC) testing of sound-producing products in a manufacturing environment in which background noise level is high. The underlying principle of this system is the assumption that the sound field can be described using two sets of expansion functions, one for direct sound radiation from a target source and the other for the background sounds that travel in the opposite direction as that of direct sound from the target. The coefficients associated with these expansion functions are determined in a similar manner as those in the Helmholtz Equation Least Squares (HELS) method. Once the expansion coefficients are determined, however, only the direct sound spectrum and corresponding SPL value are displayed. This allows for suppression of background noise produced by the neighboring sources and reflections from nearby surfaces.

The invention discloses a method for calculating scattering characteristics of a two-dimensional non-Gaussian rough body target. The method specifically comprises the steps that a scalar Helmholtz equation and physical optical approximation are utilized, coherent and incoherent components of a non-Gaussian distribution rough body target scattering field are obtained through strict theoretical derivation, the ratio of the incoherent components and scattering intensity are normalized, and the scattering characteristics of Gaussian and non-Gaussian distribution rough body targets are compared. Through research on random rough surface scattering characteristics, a theoretical basis is provided for calculation of theoretical modeling of a rough body target with more complex non-Gaussian distribution, laser scattering detection, statistical characteristics of identification and the like.

A gradient method (GM) for constructing and using absorbing boundary conditions (ABCs) for high accuracy numerical computations of various physical phenomena which are governed by partial differential equations (PDEs) is disclosed. The PDEs to which the GM is applicable are for example: the Helmholtz equation (also known as the wave equation in the frequency domain), the elastic wave equation in the frequency domain, Maxwell's equations, and Schrodinger's equation. The GM can be used to develop ABCs for the solution of PDE problems in two or more dimensions. The GM is a tool based on two principles: (1) Any directional derivatives in an ABC must be taken in the direction of the gradient of the unknown function or functions of the PDE, and (2) any ABC using such gradient derivatives may be applied to any domain of a convex shape, even if the ABC was originally developed for domains of a restricted shape.

The invention belongs to the technical field of underwater sound field calculation, and particularly relates to a sound field acquisition method of a three-dimensional sound field model based on global matrix coupling normal waves, which comprises the following steps of: applying Fourier transform to a pre-established three-dimensional Helmholtz equation according to acquired marine environment parameters of a target area to obtain a three-dimensional sound field model; a two-dimensional line source Helmholtz equation for the target area is obtained; dispersing the horizontal change waveguide into a plurality of sections of horizontal invariant waveguides; selecting a certain specific characteristic value, applying a corresponding boundary condition on the vertical boundary of each section of the horizontal invariant waveguide to obtain a global matrix, solving a normal wave coefficient corresponding to each section of the horizontal invariant waveguide, and obtaining a two-dimensional sound pressure solution corresponding to each section of the horizontal invariant waveguide; and repeating the above process, then obtaining two-dimensional sound pressure solutions corresponding to each characteristic value in each section of horizontal invariant waveguide, performing summation, and then adopting inverse Fourier transform to obtain a three-dimensional sound pressure solution of the target area.

The invention discloses a method, a system and a medium for predicting an ocean vector sound field. The method steps include: S1. Acquiring on-site measurement data and sound source parameter information of an ocean area to be predicted, establishing a cylindrical coordinate system hydroacoustic Helmholtz equation, and after transformation Obtain the depth equation; S2. Solve the depth equation to obtain the sound pressure kernel function and vertical vibration velocity kernel function at the interface of each medium layer; S3. Calculate the sound pressure according to the sound pressure kernel function, and use the inverse Hankel transform based on the vertical vibration velocity kernel function. The vertical vibration velocity is calculated by the integral vertical derivative, and the horizontal vibration velocity is calculated based on the integral horizontal derivative of the Hankel inverse transformation; S4. According to the calculated sound pressure and vibration velocity vector, calculate the underwater acoustic propagation loss and Sound intensity vector. The invention can realize the prediction of the vibration velocity vector based on the marine environment measurement data, and at the same time can improve the precision of the prediction of the vibration velocity vector.

The invention discloses a time-domain spectral element simulation method for microwave ferrite components. The method uses a curved hexahedron unit to discretize the entire electromagnetic space containing ferrite materials, and the The magnetic permeability of ferrite is introduced into the electric field time-domain Helmertz equation, and the uniaxial electric anisotropy perfectly matched layer is used as the absorption boundary condition. After the Galerkin transformation, the central difference scheme is adopted in the time dispersion, and the time Domain electric field iterative method; use the time domain electric field iterative method to perform two time domain simulations on the target ferrite components, and determine the insertion loss and return of each port of the target ferrite component in the working frequency band according to the definition of microwave network scattering parameters. wave loss and isolation. The invention has the advantages of high calculation precision, fast calculation speed and wide application range.