31 results about "Non linear wave" patented technology

The invention provides a metal plate micro-defect detection method based on nonlinear Lamb waves. The metal plate micro-defect detection method comprises the following steps of: S1, acquiring a phasevelocity frequency dispersion curve and a group velocity frequency dispersion curve of a metal plate; S2, acquiring an excitation frequency, Lamb waves of a specific mode and an incident angle of theLamb waves of the specific mode as model parameters according to the phase velocity frequency dispersion curve and the group velocity frequency dispersion curve; S3, deriving a relative nonlinear coefficient beta' according to the Lamb waves of the specific mode in the S2, wherein the relative nonlinear coefficient beta' is used for representing the depth of a defect; S4, establishing a nonlinearultrasonic test system according to the model parameters; and S5, testing the metal plate according to the nonlinear ultrasonic test system established in the step S4, judging whether the relative nonlinear coefficient beta' is reliable or not, and if so, representing the defects of the tested metal plate by utilizing the relative nonlinear coefficient beta'. According to the metal plate micro-defect detection method, the relative nonlinear coefficient beta' represents the defects of the tested metal plate, the defects of the metal plate can be effectively represented, and the detection precision is improved.

The invention discloses a nonlinear detection method for high-cycle fatigue damage of a metal sheet. The method is suitable for detection and characterization of fatigue early-stage micro-defects and micro-damages in the metal sheet, and belongs to the field of nondestructive testing. The method comprises the steps: firstly, determining the excitation frequency of a fundamental frequency wave according to a measured object and a nonlinear Lamb wave resonance condition; arranging a pair of detection probes, namely an ultrasonic transmitting probe and an ultrasonic receiving probe, in the same side direction of a test piece, and carrying out nonlinear detection on the metal sheet structure; scanning different positions of the test piece by changing the excitation time delay of an excitation signal, and extracting a fundamental wave amplitude and a second harmonic amplitude; and finally, according to the change rule of the ultrasonic nonlinear coefficient along with the detection position, achieving detection of the fatigue damage of the metal plate and characterization of the damage degree. According to the invention, a band-pass filter at a certain frequency is introduced, and an original high-pass filter is replaced by the band-pass filter, so that the received signal is purer, and meanwhile, the data processing difficulty is greatly reduced.

A putter type golf club head having a unique ball striking face configuration to eliminate the dimple effect of grooved putters formed with a series of grooves and intermediate land areas between the grooves extending in a longitudinal direction across the striking face. Each of the grooves is characterized by a plurality of repeating, non-linear wave forms located at the center of the striking face and extending outwardly therefrom.

The invention belongs to the technical field of wave numerical water tanks, and provides a fluent UDF-based wave generation method for a numerical wave water tank. According to the method, a basic thought of a push plate type wave maker model established by a boundary element method is adopted; a new wave generation function and a new wave elimination algorithm are established, in secondary development of FLUENT software based on a Navier-stokes equation, a dynamic grid technology of FLUENT is adopted for the boundary of a wave generation plate, only speed boundary conditions are established,pressure and speed items are not coupled, and therefore the stability is higher. Similarly, wave damping layers are additionally arranged at the far ends of the wave making plate and the wave numerical water tank, and only speed items are absorbed. In research, a VOF method is applied to track free surface motion of waves. By applying the wave generation method of the wave numerical water tank, the problem of interaction between complex nonlinear waves and structures can be studied.

The invention discloses a water quality index multi-step prediction method integrating wavelet decomposition and a deep neural network. The method comprises the following steps: 1) filling missing values of monitoring historical data of original water quality indexes by using a linear interpolation method; (2) carrying out discrete wavelet transform on the data after the missing values are filled up; 3) constructing an encoder based on the bidirectional gating circulation unit, constructing a decoder based on the unidirectional gating circulation unit and the full connection layer, extracting the correlation between the hidden layer state of each step of the decoder and the states of all the hidden layers of the encoder in combination with an attention mechanism, constructing a neural network model in combination with the encoder and the decoder, and taking a plurality of decomposition sequences obtained after wavelet decomposition as input. The method has the advantages that the characteristics of nonlinearity and complex fluctuation of water quality data are fully considered, the noise influence is weakened, the influence degree of historical data in each step is adaptively extracted, the water quality indexes of multiple weeks in the future are predicted in a one-step and end-to-end mode, and the method has practical application value for water resource management and ecological guarantee.

The invention discloses a nonlinear waveform synchronous and asynchronous NOMA system design method, which comprises the following steps: step 1, establishing a synchronous and asynchronous NOMA system model of a nonlinear waveform MSK-type signal to obtain a received signal, the received signal comprising normalized time delay, transmitting power and response length; step 2, sampling the received signal by adopting an oversampling technology to obtain a received signal sampling value and a matrix form thereof; step 3, according to the Shannon theorem, obtaining the index throughput for measuring the performance of the synchronous and asynchronous systems; step 4, establishing an optimal system design problem taking the maximum throughput as a target according to the throughput expression; and step 5, analyzing the normalized time delay, the transmitting power and the relationship between the response length and the throughput. According to the nonlinear waveform synchronous and asynchronous NOMA system design method provided by the invention, the system can reach the maximum throughput by setting the normalized time delay and the transmitting power of the two users, and the optimal design of the system is completed.

The invention belongs to the field of plate wave early-stage damage nondestructive testing, and particularly relates to a damage positioning imaging method and system based on a nonlinear Lamb wave zero-frequency component, and the method specifically comprises the steps: 1, preparing a model to be detected; 2, transmitting a fundamental wave at a signal excitation point of the model, receiving a zero-frequency signal at the damaged position of the model by a signal receiving point, and obtaining a boundary point at the damaged position of the model; 3, signal excitation and signal receiving are carried out at multiple positions on the model, and a boundary dot matrix is obtained; and 4, performing model damage position positioning imaging according to the boundary dot matrix. The boundary of the material damage is determined by utilizing the high reflection characteristic of zero frequency to the early local damage of the material, so that the position of the material damage is positioned and imaged, the positioning method is simple and efficient, the detection of the early local damage can be as simple as the detection of the macroscopic damage (such as local 1cm cracks) of the material by utilizing linear fundamental waves, and the detection accuracy is high. And related bottlenecks of mixed wave and second harmonic technologies are overcome.

The present invention relates to a device and a method for pulse modulation of laser pulses of tunable laser sources. The invention relates specifically to an arrangement for spectral and/or temporal laser beam manipulation of tunable lasers using nonlinear wave interaction. By using a variable, lens based beam forming section it is possible to manipulate a laser pulse provided by a tunable laser source (i.e. tunable in pulse energy, temporal pulse length and/or wavelength) or different laser sources (i.e. different with respect to pulse energy, temporal pulse width and/or wavelength) in such a manner, that nonlinear wave interaction can occur in the most efficient way. The beam forming section according to the invention allows for adjusting the waist of the laser beam and the focal position of the laser beam inside a cell comprising a nonlinear medium.

The present invention is directed to a nonlinear controller for nonlinear wave energy converters (WECs). As an example of the invention, a nonlinear dynamic model is developed for a geometrically right-circular cylinder WEC design for the heave-only motion, or a single degree-of-freedom (DOF). The linear stiffness term is replaced by a nonlinear cubic hardening spring term to demonstrate the performance of a nonlinear WEC as compared to an optimized linear WEC. By exploiting the nonlinear physics in the nonlinear controller, equivalent power and energy capture, as well as simplified operational performance is observed for the nonlinear cubic hardening spring controller when compared to an optimized linear controller.

The invention discloses a wedge plunger wave making device suitable for making high-order nonlinear waves, the wedge plunger wave making device comprises a servo system, a motion module, a wave absorbing device and a water tank, the servo system is composed of a servo motor, a driver, a controller and a man-machine interaction interface, one side of the servo motor is provided with a transmission device through a fixing support, and the other side of the servo motor is provided with a driving device; the bottom end of the transmission device is in transmission connection with a movement module, mounting grooves are oppositely formed in the two sides of the water tank, water baffles are slidably connected into the mounting grooves in a sleeved mode and located behind the movement module, and a wave absorbing device is installed at the tail end, away from the water baffles, of the water tank. Wedge body movement rules corresponding to different waveforms are embedded into the servo controller, the servo motor is controlled to drive the wedge body to accurately do vertical movement through the driver, and the movement speed and position of the movement module and the torque change of the motor can be clearly displayed on a human-computer interaction interface. The device is used for monitoring the working condition of wave making equipment in real time.

The invention provides a method for estimating a sea surface scattering coefficient of a space-based high-frequency radar. The method comprises the following steps that a Fourier series of linear andnon-linear sea surface wave heights is constructed, a relation model between linear and non-linear wave height coefficients is further constructed through a perturbation method, and a relation model between a directed sea wave spectrum and a linear wave height coefficients is established; an incident field electric field intensity is constructed, the incident field electric field intensity is combined to construct components of a sea surface near scattering field electric field in an X-axis direction and a Z-axis direction through the perturbation method according to the Fourier series, and avertical polarization field intensity component model of a sea surface far scattering field magnetic field is further constructed; and a time autocorrelation model of a vertical polarization field intensity component of the sea surface far scattering field magnetic field is constructed, and Fourier transform is used to further construct a sea surface scattering coefficient model. Estimation of thesea surface scattering coefficient provides a reliable basis for parameter design of the space-based high-frequency radar for ocean remote sensing, and is also a theoretical basis for inversion workof ocean echo signals of the space-based high-frequency radar.

The invention discloses a method, a device and equipment for evolving non-linear waves of an incompressible fluid model. The method comprises the following steps: acquiring a non-linear model for describing an incompressible fluid; according to potential function transformation and the nonlinear model describing the incompressible fluid, a bilinear form of the nonlinear model describing the incompressible fluid is constructed, and the bilinear form comprises an auxiliary function; constructing an auxiliary function in a bilinear form of the nonlinear model describing the incompressible fluid; and obtaining a series of non-linear waves of the incompressible fluid model according to the constructed auxiliary function, potential function transformation and a bilinear form. The invention aims to obtain different types of nonlinear wave solutions of a nonlinear model by using an efficient method with small calculation amount, enrich the types of existing nonlinear waves in the field, apply the method to an incompressible fluid model, and visualize the evolution process of the nonlinear waves of the fluid model.