71 results about "Spectral density function" patented technology

The invention discloses a method for generating a flat-topped beam array, and the method comprises the steps: introducing a multi-Gaussian function and a hyperbolic function, carrying out the superposition of the hyperbolic function, and constructing a weighting function and a kernel function with Gaussian distribution intensity based on the superposed hyperbolic function and multi-Gaussian function; introducing a partially coherent light construction formula, and constructing a cross spectral density function of a multi-cosine multi-Gaussian correlation light field containing a multi-cosine function at a source plane by combining a weighting function and a kernel function; introducing a free space transmission formula, and constructing a light intensity expression of the multi-cosine multi-Gaussian correlation light field at any transmission distance according to a cross spectral density function of the multi-cosine multi-Gaussian correlation light field, namely, an expression of the multi-cosine multi-Gaussian correlation light field; adjusting parameters of the transmission distance and the multi-cosine multi-Gaussian correlation light field to obtain flat-topped beam arrays with different row numbers and column numbers, and realizing an array form with adjustable flat-topped sub-beams; according to the invention, the number of the sub-beams of the flat-topped beam array can be effectively regulated and controlled.

The invention discloses a method for regulating and controlling a cosine multi-Gaussian correlation structure light field, and the method comprises the steps: introducing a hyperbolic cosine function and a multi-Gaussian function, and constructing a weighting function and a kernel function based on the hyperbolic cosine function and the multi-Gaussian function; introducing a partially coherent light construction formula, and constructing a cross spectral density function of a cosine multi-Gaussian correlation structure light field at the source plane by combining a weighting function and a kernel function; introducing a free space transmission formula, and constructing a light intensity expression of a cosine multi-Gaussian correlation structure light field at any transmission distance according to a cross spectral density function, namely, an expression of the cosine multi-Gaussian correlation structure light field; adjusting the transmission distance and parameters of the cosine multi-Gaussian correlation structure light field to obtain light intensity distribution regulation and control of the cosine multi-Gaussian correlation structure light field, and further obtaining an array form in which sub-beams are flat-topped beams according to the light intensity distribution regulation and control; according to the invention, controllable transmission of the cosine multi-Gaussian correlation structure light field can be realized, and effective regulation and control of the array form in which the sub-beams are flat-topped beams can be realized.

Disclosed in the present invention are a method and apparatus for synthesizing spatially cross-correlated multi-point ground motions fitting a response spectrum. The method comprises: using an influence matrix method to obtain ground motion acceleration time histories fitting a target reaction spectrum with high precision, and calculating a Fourier amplitude spectrum and a phase spectrum thereof; and considering a calculation relationship between a power spectral density function and the Fourier amplitude spectrum, taking the power spectral density function of the obtained time histories as an initial value, using a random vibration theory and Cholesky decomposition to obtain spatially cross-correlated multi-point ground motion time histories, further taking into account a phase spectrum of the ground motion time histories fitting the target reaction spectrum with high precision, and performing correction and iteration to obtain spatially cross-correlated multi-point ground motions fitting a response spectrum. The present invention overcomes the shortcomings in current multi-point ground motion time history synthesis techniques, such as the difficulty in ensuring good fitting to a target response spectrum and the non-stationarity of synthesized ground motions, helping to improve the reliability of dynamic response analysis results for large-scale engineering structures under the action of multi-point ground motions.

The invention discloses a structural damping ratio identification method and device considering frequency spectrum leakage error compensation. The method comprises the following steps: firstly, obtaining a cut-off free attenuation signal under impact vibration, and carrying out Fourier transform on an autocorrelation function and a cross-correlation function of the signal to obtain a response power spectral density matrix influenced by a spectrum leakage error; singular value decomposition is carried out on the response power spectrum density function through a frequency domain decomposition method to obtain a damping ratio and an inherent frequency, a spectrum leakage error is calculated through the calculated inherent frequency and the damping ratio, and the error obtained through calculation is substituted into an output power spectrum. And the inherent frequency and the damping ratio are identified by using the power spectrum after the frequency spectrum leakage error is compensated, and the above process is iterated for multiple times, so that the frequency spectrum leakage error in damping ratio identification can be compensated. When the free attenuation data is used for identifying the damping ratio, spectrum leakage errors caused by data truncation can be made up, the signal-to-noise ratio of the data can be improved, the influence of noise can be reduced, and the identification precision of the damping ratio is improved.

The invention provides a sea surface oil spill GNSS reflection signal simulation system and method, and the method comprises the steps: building an oil spill sea surface dielectric constant module, determining the effective dielectric constant of an oil spill sea surface, and obtaining a Fresnel reflection coefficient; establishing an oil spill sea surface rough spectrum module, obtaining a model of a sea wave spectrum of the oil spill sea surface according to a traditional model of the sea wave spectrum and the influence of oil spill on the sea wave spectrum, and obtaining a surface spectral density function and a surface root-mean-square height; establishing a microwave scattering module of the oil spill sea surface, and determining a microwave scattering coefficient according to the Fresnel reflection coefficient, the surface spectral density function and the surface root-mean-square height; a DDM simulation module is established, and a DDM waveform is obtained through simulation according to the GNSS signal parameters and the microwave scattering coefficients; and the DDM waveform is obtained through simulation of each module. According to the simulation system and method, a unified mathematical model is established to describe the relation between the oil film and the GNSS reflection signal, and accurate simulation of the influence of the oil film on the GNSS reflection signal is achieved.

The invention discloses a stationary non-Gaussian random process simulation method, and relates to the field of random vibration numerical simulation, and the method comprises the following steps: obtaining an autocorrelation function through the conversion of a power spectrum density function of a target non-Gaussian random process, and obtaining an autocorrelation coefficient matrix of the target non-Gaussian random process through the autocorrelation function, the autocorrelation function in the step is obtained through Fourier transform calculation. According to the method, FMKL generalized lambda distribution and memory-free nonlinear transformation are combined, non-Gaussian characteristics of natural phenomena such as wind speed and seismic waves are accurately simulated, the defects of a traditional Gaussian model are overcome, and simulation precision and engineering design reliability are improved. By improving the Mehler formula and the spline interpolation method, the equivalent correlation coefficient calculation efficiency is improved, the calculation time is shortened, resource use is optimized, and the method is suitable for large-scale complex engineering structure simulation. The method has flexibility and is widely suitable for various non-Gaussian random process simulation requirements.

The invention discloses a three-degree-of-freedom real-time motion simulation method and system of a ship in sea waves based on power spectrum analysis, and belongs to the technical field of ship and ocean engineering, and the method comprises the steps: obtaining sea wave data and basic parameters of the ship; establishing a sea wave simulation model based on a frequency density spectrum to obtain a sea wave spectrum; based on the sea wave spectrum and the ship basic parameters, establishing a power spectrum density function of ship swaying motion; establishing a kinetic equation of the ship swaying motion, and solving a coefficient of the kinetic equation of the ship swaying motion and a power spectral density function of the ship swaying motion according to the sea wave data and the ship basic parameters; and solving the kinetic equation of the ship swaying motion, and obtaining time calendar data of the three-degree-of-freedom swaying motion of the ship through inverse Fourier transform. By means of the method, simulation calculation of rolling, pitching and heaving three-degree-of-freedom motion of any ship type under any sea condition can be achieved, and manpower, material resource and financial resource input of ship model tests and real ship sea tests is saved.

The invention discloses a method for generating a hollow array light source. The method comprises the following steps: selecting a vortex phase which has Gaussian intensity distribution and carries topological charges in an initial light field; introducing a Hermite-Gaussian correlation function, and constructing a cross spectral density function of the Hermite-Gaussian correlation vortex light source based on a vortex phase having Gaussian intensity distribution and carrying a topological charge and the Hermite-Gaussian correlation function; an ABCD optical system is introduced, a transmission model is constructed based on a cross spectral density function of Hermitian associated vortex and the ABCD optical system, parameters in the transmission model are adjusted, a plurality of hollow array light beams are formed, and then a hollow array light source is formed through the plurality of hollow array light beams; through combined regulation and control of the Hermitian correlation structure and the vortex topological charge, effective control of array light intensity distribution can be realized, preparation of the hollow array light beam is realized, the array light source is formed by adjusting the array light beam, and the method is simple to operate and easy to realize.

The invention provides a communication method, a communication device and a communication system, which can be used for improving spectrum efficiency through a small amount of feedback overhead. In the method, a terminal receives a first reference signal, and the first reference signal is transmitted on a reference channel and a target channel; based on the first reference signal, determining a channel measurement result of a reference channel and related parameters, the channel measurement result of the reference channel comprising: a CQI corresponding to each transmission layer in one or more transmission layers on the reference channel, the related parameters are used for indicating a relationship between a limit spectral density function of a target channel and a limit spectral density function of a reference channel, the limit spectral density function of each channel is used for indicating a singular value corresponding to each transmission layer in one or more transmission layers on each channel, and the singular value corresponding to each transmission layer is used for determining a corresponding CQI; and sending first indication information, wherein the first indication information is used for indicating the channel measurement result and related parameters of the reference channel.

The invention discloses a method for generating a hollow light array with rectangular distribution. The method comprises the following steps: constructing a kernel function based on a spiral phase and a Gaussian function; superposing hyperbolic cosine functions to construct a weighting function so as to obtain a multi-cosine correlation vortex light field; introducing a partially coherent light construction formula, and constructing a cross spectral density function of the multi-cosine correlation vortex light field at the initial plane in combination with the kernel function and the weighting function; a free space transmission formula is introduced, a light intensity expression of the multi-cosine correlation vortex light field at any transmission distance is constructed in combination with a cross spectral density function, parameters of the transmission distance and the multi-cosine correlation vortex light field are adjusted, and light intensity distribution regulation and control of the multi-cosine correlation vortex light field are obtained. According to parameter regulation and control, the array form that the sub-beams are hollow beams is obtained, and a rectangular distribution hollow light array is obtained; according to the invention, the controllable transmission of the multi-cosine Gaussian correlation vortex beam can be realized, and the effective regulation and control of the array distribution with the sub-beams being hollow beams can be realized.

The invention relates to a method and a system for generating a fractional order circular coherent correlation light beam, and relates to the technical field of partially coherent light beam design, and the method comprises the following steps: in a space-frequency domain, representing a partially coherent light beam through a cross-spectral density function, and converting the cross-spectral density function into an integral form; a fractional order is introduced into the cross-spectral density function in the integral form to serve as a regulation dimension, and a cross-spectral density function of the partially coherent light beams at the light source is obtained; normalizing the cross spectral density function at the light source to obtain a coherence degree function of the partially coherent light beams; representing the propagation process of the partially coherent light beams, and representing a cross-spectral density function in a discrete form; and substituting the representation of the partially coherent light beam in the propagation process and the cross spectral density function in the discrete form into the coherence degree function to obtain a fractional order circular coherent correlation light beam. According to the invention, a fractional order circular coherent correlation beam with beam shaping capability is constructed.

The present application provides a kind of quantitative evaluation method of the influence of wind tunnel inner surface roughness on airflow quality, belongs to the technical field of wind tunnel, the present application is collected by laser confocal scanner wall roughness multi-resolution point cloud data, high frequency, medium frequency and low frequency roughness component is extracted by wavelet decomposition, power spectral density function and fractal dimension are calculated to establish random roughness field probability distribution model, local velocity field and vorticity distribution are obtained by using lattice Boltzmann algorithm to simulate rough wall near flow field, the uniformity of airflow is calculated by generating equivalent random roughness field sample using Monte Carlo method for statistical analysis, the polynomial mapping function of roughness statistical characteristic parameter and airflow quality degradation index is established, when degradation index exceeds allowable threshold, wall roughness is over standard, solve the technical problems of low precision and insufficient calculation efficiency in quantitative evaluation of the influence of multi-scale random roughness on wind tunnel airflow quality.

The invention relates to a signal bandwidth estimation method for power spectral density function integration, which is used for realizing bandwidth estimation of a signal under a satellite communication channel, and comprises the following steps of: firstly, performing fast Fourier transform (FFT) on the signal, squaring a module value of the converted signal, and then converting a component value to obtain power spectral density; integrating the power spectrum density, and obtaining rough estimation values of the upper limit and the lower limit of the signal in the frequency spectrum according to the extreme value of the slope change of the integrated power spectrum; and performing power change estimation on the power spectral density according to the coarse estimation value to obtain a fine estimation value, and converting the real bandwidth of the signal according to the sampling rate of the signal and the FFT point number. According to the invention, high-precision bandwidth estimation under low calculation complexity can be realized.

A method of forming an illumination mode using an illumination system comprising an array of individually controllable reflective elements arranged to direct portions of a radiation beam to desired locations in a pupil plane. The method comprises allocating different reflective elements of the array to direct radiation to different locations in the illumination mode by: determining a desired power spectral density function of radiation directed by the array of reflective elements to the illumination mode, the desired power spectral density function including a cutoff frequency; applying different phases to frequency components of the power spectral density function; transforming the power spectral density function into a spatial domain signal that varies as a function of positions of the reflective elements; and using the spatial domain signal to allocate reflective elements that direct radiation to different locations in the illumination mode.

The invention relates to a method and a system for simulating internal noise of a slave clock in a master-slave synchronization network in the technical field of clock synchronization. The method comprises the following steps: establishing a first equivalent model and a second equivalent model; generating a first phase-locked loop output power spectral density function based on the first equivalent model, and generating a second phase-locked loop output power spectral density function based on the second equivalent model; calculating equivalent loop bandwidth conditions of the first equivalent model and the second equivalent model; a second phase-locked loop output power spectral density function is updated by using a loop bandwidth condition, a gain coefficient and a slave clock bandwidth of a second equivalent model are calculated by using a TDEV template and an MTIE template, and the second phase-locked loop output power spectral density function is updated for the second time to obtain a noise generation time domain function; the problem that the stability of the slave clock cannot be accurately simulated due to the fact that the MTIE corresponding to the generated time domain noise exceeds the limit of the MTIE template because only the TDEV template is considered and the MTIE template is not considered in the existing method for simulating the internal noise of the slave clock is solved.

The application discloses a method for generating a flat-top beam array, comprising the following steps: introducing a multi-Gaussian function and a hyperbolic function, superimposing the hyperbolic function, constructing a weight function and a kernel function with Gaussian distribution intensity based on the superimposed hyperbolic function and the multi-Gaussian function; introducing a partial coherent light construction formula, combining the weight function and the kernel function to obtain a cross-spectral density function of a multi-cosine multi-Gaussian correlation light field containing a multi-cosine function at a source plane; introducing a free space transmission formula, constructing an intensity expression of the multi-cosine multi-Gaussian correlation light field at an arbitrary transmission distance according to the cross-spectral density function of the multi-cosine multi-Gaussian correlation light field, that is, an expression of the multi-cosine multi-Gaussian correlation light field; adjusting the transmission distance and the parameters of the multi-cosine multi-Gaussian correlation light field to obtain a flat-top beam array with different numbers of rows and columns, and realizing an array form with adjustable flat-top sub-beams; and the application can effectively control the number of the flat-top beam array sub-beams.

The invention discloses a vehicle testing method, device and equipment and a storage medium, and relates to the technical field of vehicle testing, and the method comprises the steps: carrying out the axial splitting of a real vehicle motion curve, and obtaining an acceleration curve of each axis; performing frequency domain conversion on the acceleration curve of each axis to generate a power spectral density function corresponding to each axis; to-be-converted amplitudes are extracted from the power spectral density function, and a to-be-converted amplitude sequence corresponding to each axis is obtained; constructing a rotation axis motion curve corresponding to each axis according to the amplitude sequence to be converted; and controlling the small simulation test bench based on the rotating shaft motion curve so as to carry out vehicle motion sickness test. According to the method, the frequency domain conversion is firstly carried out, and based on the amplitude after the frequency domain conversion, on the premise of keeping the whole MSDV unchanged, the frequency domain conversion is carried out, and the rotation axis motion curve corresponding to each axis is constructed, so that the small test simulation rack can be controlled to simulate the same working condition of the real MSDV test; therefore, the motion sickness test can be carried out by using the small simulation test bench.

The invention relates to an offshore wind speed synthesis method and a wind power prediction method. The method is suitable for the technical field of offshore wind power. The technical problem to be solved by the invention is to provide an offshore wind speed synthesis method and a wind power prediction method. According to the technical scheme, the offshore wind speed synthesis method comprises the steps of generating wind speed data under a second time scale on the basis of an average wind speed under a first time scale in combination with a Weibull distribution model and wind speed time characteristics; and generating wind speed data under a third time scale based on the wind speed data under the second time scale in combination with a Vor-karman power spectral density function and an autoregressive moving average model.

The present invention relates to the field of optical technologies, and in particular to a method and device for generating high-order deterministic vortices based on coherent structure regulation. The method includes: encoding the angular and radial order characteristics of a Laguerre-Gaussian beam into a random beam through fractional Fourier transform, constructing a theoretical model for generating a deterministic vortex beam with controllable angular and radial orders at any specified propagation distance; transforming it into a manipulable random electric field distribution through mode decomposition to obtain the cross-spectral density function; introducing a completely coherent plane wave as a reference light to interfere with the random field signal light at the specified propagation distance to obtain an interference intensity spot, and using the off-axis holographic method to recover the random electric field therefrom; generating a high-order vortex beam with controllable order based on the cross-spectral density function and the random electric field, realizing the flexible generation of a high-order vortex beam at the specified propagation distance.

The application discloses a kind of based on the partial coherence light field generation method and system of multi-core optical fiber, method includes: according to the cross spectral density function of target partial coherence light field determines multiple electric field modes and generates hologram;The phase distortion between the each core of multi-core optical fiber is measured and compensation chart is generated;After the superposition of both as synthetic hologram, the wavefront modulation of incident laser is carried out;Modulated light is coupled into multi-core optical fiber and exports target light field.The corresponding system includes mode and compensation chart generation module, hologram synthesis module, wavefront modulation module and coupling transmission module.The present application realizes system miniaturization and strong environmental adaptability using multi-core optical fiber, by hologram sequence and phase compensation combination, can flexibly generate and transmit multiple partial coherence light with specific spatial coherence structure, solve the problem that prior art is not flexible, difficult to apply in tortuous narrow environment.

The application discloses a method for measuring threshold enhancement factor size by using spectral effective width, and belongs to the technical field of laser design; the method comprises the following steps: encoding a PRBS signal; based on the phase of the PRBS signal, modulating a fiber laser at a preset modulation depth to obtain a power spectral density function after phase modulation; performing denoising processing on the power spectral density function after phase modulation to obtain a spectral effective width; and measuring the threshold enhancement factor size according to the spectral effective width. The application also provides a system for measuring threshold enhancement factor size by using spectral effective width. The application provides a spectral effective width calculation method, and aims to solve the problems of large calculation error and incomplete application of the spectral effective width in the existing simulation.

A kind of underwater vehicle noise prediction correction method based on bayesian inference, calculation model (1) includes Corcos autospectrum and Corcos normalized cross power spectral density function calculation model;According to calculation model (1), construct the schematic diagram (2) of bayesian network, the key factor identification and state analysis of the key factor of the modeling of the influencing factor of turbulent fluctuation pressure in bayesian network in schematic diagram (2) of bayesian network are built-in bayesian inference;According to the schematic diagram (2) of bayesian network, model in NETICA software, construct directed acyclic bayesian network (3);Reference calculation model (1) and directed acyclic bayesian network (3) are simulated setting (4) and noise signal comparison (5).The present application has the advantages of ensuring the precision of low-frequency noise prediction in sparse grid large size, improves the problem that the grid scale of finite element model and the space related scale of turbulent boundary layer pressure do not match and the calculation amount is too large when fine grid is used.

The invention discloses a self-similar fluctuating wind speed frequency spectrum simulation method, a storage medium and electronic equipment, and the method comprises the steps: obtaining an actually-measured wind number, carrying out the data analysis, and carrying out the calculation to obtain a power spectrum density function, an average wind speed and a turbulence value in three component directions; determining Kaimal power spectrums of the three component directions according to the average wind speed and the turbulence value of the three component directions, and determining connection frequencies of the three component directions by combining a power spectrum density function; generating a low-frequency wind speed curve from the low-frequency part smaller than the connection frequency by adopting a harmonic superposition method; a Weierstrass-Mandelbrot function is adopted for the high-frequency part with the frequency larger than the connection frequency to generate a high-frequency wind speed curve; and superposing the low-frequency wind speed curve and the high-frequency wind speed curve to synthesize a pulse wind speed curve. A harmonic superposition method and a Weierstrass-Mandelbrot function simulation method are fused, the randomness and the multi-scale performance of real atmospheric wind speed fluctuation can be simulated, meanwhile, the multi-scale characteristic of the real atmospheric wind speed fluctuation is achieved, and input conditions closer to the real wind condition are provided for load calculation of a draught fan.

The invention relates to the technical field of marine rail-mounted vehicles, and discloses a marine rail-mounted vehicle operation safety analysis method, which comprises the following steps of: 1, establishing a deck-rail coupled finite element model in finite element software; 2, extracting power spectral density functions of motion in different directions under different sea conditions, and carrying out inverse derivation to form shipborne random excitation; step 3, constructing a deck-track-vehicle coupling system dynamic model; 4, inputting shipborne random excitation and track irregularity excitation into the deck-track-vehicle coupling system dynamic model to realize marine environment-oriented track vehicle dynamic behavior analysis; and 5, proposing an evaluation index of the traffic safety of the marine railway vehicle, and obtaining an operation safety evaluation index limit value suitable for the marine railway vehicle. According to the invention, ship motion excitation can be generated by adopting ship motion simulation data, model data and actually measured data, and the ship motion excitation simulation method can be suitable for any ship type.

The invention discloses an extreme wave spectrum calculation method based on a wave element co-occurrence recurrence period, and belongs to the technical field of coast and ocean engineering. Comprising the following steps: acquiring significant wave height and spectral peak period length time sequence data of a certain station, constructing an annual extreme value sample pair, and mapping the annual extreme value sample pair to a unified probability space; based on the Copula theory, quantitative characterization is carried out on a dependent structure among wave elements, and optimal selection is carried out on candidate Copula models according to an AIC information criterion; determining a joint exceeding target probability according to the co-occurrence recurrence period definition, and determining a joint design point based on a maximum probability density criterion; and based on the joint design points, inversely calculating spectral scale parameters through zero-order spectral moment energy matching and finishing effective wave height consistency checking, and further calculating an extreme wave spectral density function curve meeting the co-occurrence recurrence period constraint. According to the method, the co-occurrence recurrence period design sea condition is determined, wave spectrum calculation self-consistency is achieved, and the rationality and engineering applicability of an extreme wave spectrum calculation result are improved.

Provided are a communication method, a communication apparatus, and a system, which can improve the spectral efficiency at the cost of a small amount of feedback overhead. The method comprises: a terminal receiving a first reference signal, wherein the first reference signal is transmitted on a reference channel and a target channel; on the basis of the first reference signal, determining a channel measurement result of the reference channel and a related parameter, wherein the channel measurement result of the reference channel comprises a CQI corresponding to each transmission layer among one or more transmission layers on the reference channel, the related parameter is used for indicating a relationship between a limiting spectral density function of the target channel and a limiting spectral density function of the reference channel, the limiting spectral density function of each channel is used for indicating a singular value corresponding to each transmission layer among one or more transmission layers on the channel, and the singular value corresponding to each transmission layer is used for determining the corresponding CQI; and sending first indication information, wherein the first indication information is used for indicating the channel measurement result of the reference channel and the related parameter.

The present invention provides a method for predicting the multi-axial fatigue life of a structure under a random vibration load, comprising: decomposing the power spectrum density function of a non-Gaussian random vibration load into third-order Gaussian components through a Gaussian mixture model, loading each order component into a structural model as a load, extracting the stress component power spectrum density function for a dangerous position, calculating the maximum variance value of the equivalent stress power spectrum density function of a spatial plane based on a multi-axial fatigue criterion and a maximum variance method, and determining the position of a critical plane. Based on a critical plane frequency domain method, the multi-axial power spectrum density function of a dangerous point is processed into a uniaxial equivalent power spectrum density function, and the third-order non-Gaussian mixture probability density function of the equivalent stress power spectrum density function is calculated according to the Dirlik method to predict the fatigue damage and life of the structure. The present invention takes into account the influence of the multi-axial stress state on the fatigue life of the structure, so that the problem of predicting the fatigue life of the structure is more in line with the fatigue damage mechanism. The method is simple and has better universality.

The invention belongs to the technical field of aircraft fatigue life design, and particularly relates to a random stress amplitude vibration fatigue curve determination method and device. The method comprises the following steps: carrying out random vibration response analysis on a structural dynamic finite element model of a cantilever beam with one end clamped and supported, and obtaining a vibration stress power spectral density function and a vibration stress root-mean-square; determining a k-order moment of the power spectral density function; determining an expected value of the number of stress amplitudes in unit time; determining a coefficient value of a vibration stress amplitude probability density function formula, and determining vibration fatigue life time by using a Miner damage accumulation theory; determining a random vibration fatigue life cycle number; and determining a curve parallel to the equal stress amplitude S-N curve and passing through the random vibration fatigue life cycle number and the vibration stress root-mean-square corresponding point as a random stress amplitude vibration fatigue curve. The random stress amplitude vibration fatigue curve constructed by the invention improves the efficiency of evaluating the vibration fatigue life of the structure.

The present invention provides a sidelobe suppression method based on a dynamic array element observation angle, comprising: obtaining the position coordinates and echo signals of virtual array elements, obtaining a received signal matrix after matched filtering based on the echo signals; obtaining an array covariance matrix of the received signal matrix based on the received signal matrix after matched filtering; orthogonalizing the signal subspace and noise subspace obtained based on eigendecomposition of the array covariance matrix to obtain an orthogonalized array covariance matrix, reconstructing the orthogonalized array covariance matrix to obtain an array spectral density matrix; obtaining a spatial spectral density function of a two-dimensional multi-signal classification algorithm based on the array spectral density matrix and the received signal matrix after matched filtering; and then obtaining corresponding elevation and azimuth angles to reconstruct beam sidelobes. By improving the two-dimensional multi-signal classification algorithm and applying it to sidelobe suppression, the mainlobe and sidelobe positions are found, thereby reducing the sidelobes of the spectral density function and improving the radar imaging effect of multiple targets at close range.

The invention relates to the field of ship structure safety evaluation, and discloses a large-area distributed random ice load frequency domain identification mathematical model morbidity elimination method, which comprises the following steps: firstly, by establishing a finite element model comprising a ship hull plate, a rib and a stringer structure, converting an ice load effect into an equivalent concentrated force model; the method comprises the following steps: firstly, constructing a structure, arranging multiple strain response measuring points on the surface of the structure, then obtaining frequency response data by applying simple harmonic excitation, forming a frequency response function matrix, optimizing a high morbid frequency through a multiple expansion retrieval algorithm, screening out a submatrix with the minimum condition number, reconstructing a frequency domain identification model, and finally, identifying the high morbid frequency according to the frequency domain identification model. And based on the optimized frequency response function sub-matrix, combining a structure response spectrum and an inverse problem theory, and solving by utilizing a generalized inverse method to obtain an ice load power spectral density function. A frequency response function matrix is optimized through a multiple expansion retrieval algorithm and a generalized inverse method, the stability and recognition precision of the model are remarkably improved, and the problem of discomfort caused by high ill-conditioned frequency in an existing method is solved.