47 results about "Helmholtz equation" patented technology

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 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 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.

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.

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.