9 results about "Frequency dispersion" patented technology

The application discloses a component fatigue micro-damage early identification method based on a nonlinear static component, and particularly relates to the technical field of material nondestructive testing and structural health monitoring, which comprises the following steps: arranging an excitation probe and a receiving probe on the surface of a component to be measured; selecting an excitation frequency based on a frequency dispersion curve and generating a Hanning window modulated wave; collecting a propagation response signal; extracting a static component amplitude A and a fundamental wave amplitude A through time-frequency processing; calculating a nonlinear static parameter beta=A / A²; further calculating a first derivative S(N) and a second derivative ΔS(N) of beta with respect to a fatigue loading cycle N; and identifying a dislocation dominant stage, a dislocation saturation or rearrangement stage, a micro-crack initiation stage and a macro-crack formation stage according to the first derivative S(N) and the second derivative ΔS(N). The application can be used for early stage identification of the evolution process of component fatigue micro-damage.

This invention belongs to the field of applied geophysical logging technology, specifically relating to a method for identifying low-resistivity oil layers based on time-frequency joint analysis. The method comprises the following steps: constructing a frequency-varying invasion factor based on multi-frequency array induced resistivity data at different times during drilling and after completion; constructing a time-varying dynamic index based on the frequency-varying invasion factor at different times during drilling and after completion; constructing a weighted dispersion index based on the time-varying dynamic index; calculating the average value of the time-varying dynamic index and the average value of the weighted dispersion index within the layer to be identified, comparing them with preset thresholds, and identifying the fluid properties based on the comparison results. This invention establishes a dual-verification identification mechanism for low-resistivity oil layers by integrating time-series evolution information and multi-frequency dispersion characteristics, and sets dual thresholds to improve the corresponding logging interpretation accuracy.

The application discloses a polar ice layer bending wave pulse signal detection method, belongs to the polar ice layer signal detection field, and is based on the physical dispersion characteristics of the polar ice layer bending wave.The method comprises the following steps: S1, collecting an acoustic signal by using a sensor and preprocessing to obtain a preprocessed signal; S2, setting a frame length, a frame span, a frequency modulation order and a threshold; S3, performing transformation processing on the signal of each frame; S4, calculating the maximum value of the spectrum of each frame signal after transformation; and S5, judging whether the frame data has a signal or not by using a preset threshold.According to the frequency dispersion effect of the bending wave in the polar ice layer, a transformation method for signal detection is provided.The experimental results show that the method can realize the detection of the bending wave pulse signal in the polar ice layer, and the fast Fourier transformation is used to improve the calculation efficiency.

A microwave photon beam forming network architecture based on switch switching type optical adjustable true delay line and its phased array radar system. The architecture realizes delay difference adjustment of multiple optical signals by modulating microwave signals in the optical domain and utilizing the characteristics of multiple adjustable delay paths in a single channel switch switching type delay line, thereby supporting high precision, wideband beam forming without beam oblique view while greatly reducing the number of delay lines and delay units; through two or more levels of delay configuration, the network can flexibly meet the wideband delay compensation requirements of different array antenna units, has relatively low complexity and strong dynamic reconfigurable ability, is suitable for implementation of large-scale photon integrated chips, the number of delay lines of the application is reduced by about 50%, and no frequency dispersion is generated, which can significantly reduce the system complexity, cost and power consumption, and is especially suitable for wideband phased array systems such as millimeter wave, satellite communication and radar detection.

The application relates to the field of power system state monitoring, and discloses a power equipment fault diagnosis system suitable for a complex power grid environment, which comprises a propagation medium model construction unit, a transient traveling wave synchronous acquisition unit, a fault positioning unit and a fault property and equipment state analysis unit. The propagation medium model construction unit is used for dynamic correction of a benign transient wave. The transient traveling wave synchronous acquisition unit is used for high-precision synchronous acquisition of traveling wave data. The fault positioning unit is used for determining a fault position based on a time difference residual minimization principle. The fault property and equipment state analysis unit is used for deep analysis by comparing a measured reflection wave path spectrum and a theoretical reflection wave path spectrum and by comparing frequency dispersion characteristics. The method comprises the following steps: constructing and dynamically correcting a transient wave propagation medium model; synchronously acquiring transient traveling waves excited by electrical events; calculating a fault physical position; and analyzing propagation characteristics of the transient traveling waves to determine a fault property and an equipment state. The application can also identify and position electrical asymmetry hidden dangers by actively injecting a pure positive sequence traveling wave probe, and realizes the combination of passive diagnosis and active early warning.

The application provides a nuclear power plant pipe defect online detection method and system, electromagnetic ultrasonic waves are sent to the cold side pipeline of the nuclear power plant during cooling circulation, echo signals of the cold side pipeline are collected, and a frequency dispersion curve offset feature of the echo signals is determined; a dynamic stability criterion model of the critical speed of steam during gas-liquid flow type conversion is established through the steam flow rate and the frequency dispersion curve offset feature, and a gas-liquid interface instability region in the cold side pipeline is screened out according to the dynamic stability criterion model; flow damping to gas film flow in the cold side pipeline is identified according to the gradient change of the temperature data; the identification boundary of the gas-liquid interface instability region is corrected based on the flow damping, and a defect region of the cold side pipeline under the cold-heat cycle alternating working condition is determined according to the reflection signal of the electromagnetic ultrasonic wave in the corrected gas-liquid interface instability region; the above scheme can correct the oscillation region boundary of the steam in combination with the surface tension distribution, and realize accurate positioning of the pipeline defect under complex working conditions.

The application discloses a kind of SBP-SAT-based block staggered grid seismic wave simulation method, belong to the technical field of seismic numerical simulation, first establish the first-order velocity-pressure acoustic wave equation containing auxiliary differential equation, then complete space domain staggered grid SBP discrete and SAT boundary correction term is injected into physical variable equation and PML auxiliary differential equation simultaneously, subsequently construct the non-uniform grid interface SAT coupling term that meets SBP energy compatible condition, finally complete seismic wave field simulation by parameter setting and time domain integration.The whole process eliminates the long-time numerical drift problem of PML under high-order format theoretically, realizes the energy conservation and stable coupling of coarse and fine grid interface, takes into account the double advantages of staggered grid low-frequency dispersion and block grid high efficiency, significantly improves the precision and computing performance of complex medium acoustic forward.

The application relates to the field of long-distance pipeline detection, and discloses a long-distance pipeline outer anticorrosion layer damage point intelligent identification method and system based on a multi-frequency current attenuation gradient; a multi-frequency excitation signal is collected and analyzed in a complex domain by arranging measuring stations along the pipeline axis, an inherent phase difference spectrum is extracted, and a multi-frequency data set is constructed; the soil dielectric frequency dispersion characteristics are estimated based on the data set, phase synchronization compensation is implemented, and the phases of current density complex vectors of all frequencies are aligned; the complex domain attenuation gradient between adjacent stations is calculated, a fusion gradient feature sequence is obtained through coherent superposition and adaptive weighted fusion, the damage point position and boundary are identified through adaptive threshold segmentation and spatial clustering, and the accurate intelligent identification of the long-distance pipeline outer anticorrosion layer damage point is realized, so that the detection sensitivity and positioning accuracy are effectively improved.