94 results about "Amplitude ratio" patented technology

The invention relates to the technical field of fault detection, and discloses a diesel generating set fault detection method and system based on deep learning, and the method comprises the steps: obtaining first vibration signal data, and carrying out the time-frequency decomposition, and obtaining a dynamic change feature; de-noising processing is carried out on the dynamic change features to obtain a time-frequency feature sequence; extracting a peak energy distribution data set, and calculating each frequency band entropy value to obtain a frequency band entropy value sequence; classifying the frequency band entropy sequence, determining a random fluctuation reference mode, and separating to obtain an abnormal frequency component; calculating a spectral line spacing and amplitude ratio, obtaining a spectral line feature data set, classifying the spectral line feature data set, and determining a fault classification result; obtaining current second vibration signal data, performing similarity calculation on the current second vibration signal data and a pre-established normal mode library, and outputting a fault feature vector; and verifying the fault feature vector to obtain a final fault detection result. According to the method, closed-loop diagnosis from signal acquisition to fault classification can be realized, and the fault detection precision of the diesel generating set is improved.

The invention discloses a double-frequency anti-interference ultrasonic water meter and a metering method thereof, and relates to the technical field of fluid metering. A 500kHz sound velocity reference channel is constructed in a self-transmitting and self-receiving mode of a single transducer, the sound path length under solidified pure water is calibrated through a factory, the current water quality sound velocity is calculated in real time in a zero flow state, the zero offset of a 1MHz main channel is dynamically corrected, and a high-precision temperature sensor is omitted. Meanwhile, online water quality diagnosis is realized by utilizing a double-frequency cooperation mechanism: turbidity is quantized according to the amplitude ratio of 500kHz and 1MHz signals (based on the characteristics of high-frequency scattering sensitivity and high low-frequency penetrability), and bubbles are detected according to the time domain volatility of the 1MHz signals; and dynamically optimizing the flow metering precision of the main channel according to a diagnosis result by combining a sound velocity compensation model (the sound velocity is inversely proportional to the turbidity) and a graded bubble compensation model (the sound velocity or the flow is corrected according to the volatility). According to the method, medium interference is effectively overcome, measurement reliability is improved, and real-time monitoring and reporting of basic water quality (turbidity and bubbles) are achieved at low cost.

The invention relates to a large-span bridge flutter critical wind speed prediction method based on an L-P perturbation method. The method comprises the following steps that S1, physical characteristics and aerodynamic parameters of a bridge are obtained through a wind tunnel test to serve as basic data; s2, establishing a bridge motion control matrix equation based on modal displacement; s3, deriving an explicit solution of the modal frequency, the damping ratio and the modal characteristic of each modal branch based on an L-P perturbation method; s4, iteratively solving the modal frequency, directly solving the damping ratio, the amplitude ratio and the phase difference on the basis, observing the change of the modal damping ratio xi in each direction along with the wind speed U, and determining the flutter critical wind speed; the problems that an explicit closed solution of an existing three-degree-of-freedom flutter starting condition needs to carry out multiple times of iterative calculation on modal frequency, damping ratio and vibration mode, the influence of structural parameters and pneumatic parameters on pneumatic instability is difficult to clearly explain, and the flutter critical wind speed of a large-span bridge cannot be well predicted are solved.

The invention belongs to the technical field of flow field optical measurement, and particularly relates to a high-enthalpy plasma gas temperature measurement method, system and device based on an absorption spectrum. Generating a composite modulation signal through a high-frequency sine wave and a low-frequency sawtooth wave, and enabling incident light to pass through a flow field measurement area in parallel through laser modulation and beam shaping; the detector receives the transmission light and converts the transmission light into an electric signal containing harmonic information, the signal acquisition device is used for performing signal acquisition, the phase-locked demodulation algorithm is used for extracting second harmonic, and the temperature is inversely deduced by combining the double-spectral-line temperature measurement method and the Fourier coefficient amplitude ratio of the second harmonic with the HITRAN database. The system comprises a signal driving module, a laser emission module, a detection acquisition module and a temperature measurement module. The device is composed of a signal generator, an in-phase adder and the like, and a laser is matched with a driving power supply to guarantee stable work. According to the scheme, aiming at the problems of weak signal absorption and insufficient signal-to-noise ratio under complex working conditions, the measurement accuracy and reliability are improved by composite modulation, harmonic extraction and a bispectral line algorithm, and an effective means is provided for research on thermal characteristics of the high-enthalpy plasma.

The invention discloses an asymmetric coupling rigidity disturbance type MEMS modal localization accelerometer and a detection method. The accelerometer comprises an upper signal conversion layer and a lower glass substrate layer. The upper signal conversion layer comprises a sensitive mass block, a supporting structure and asymmetrical coupled resonator pairs which are symmetrically distributed. According to the asymmetric coupling resonator pair, a first type resonator and a second type resonator form a weak coupling system through electrostatic coupling, the first type resonator is fixed to a glass substrate layer through anchor points, the second type resonator is fixed to a sensitive mass block, and the first type resonator and the second type resonator meet the mass and rigidity asymmetric relation. When being subjected to the acceleration effect, the sensitive mass block generates micro displacement, changes the static coupling rigidity and triggers the modal localization effect, so that the amplitude ratio of the two resonators is changed, and acceleration measurement is realized by detecting the amplitude ratio change. By adopting the asymmetric structure, the sensitivity of the accelerometer is doubled compared with that of a symmetric structure, and meanwhile, the accelerometer has good linearity and anti-interference capability.

The invention provides a phase generated carrier demodulation method based on two-parameter estimation. The method comprises the following steps of: firstly, realizing estimation of a C value by extracting an amplitude ratio of a carrier frequency multiplication component in an interference signal frequency spectrum and combining a Bessel function characteristic; then, carrying out operation processing by utilizing a first frequency multiplication signal and a second frequency multiplication signal to extract carrier phase delay theta c; and finally, eliminating the influence through dynamic phase compensation. According to the demodulation method provided by the invention, the nonlinear drift of the modulation depth parameter C and the synchronous estimation and compensation of the carrier phase disturbance signal theta c can be realized, the cross interference error in the traditional demodulation system is effectively inhibited, the phase demodulation robustness is remarkably improved, and the harmonic nonlinear distortion is effectively inhibited.

The invention provides a CEEMDAN-SSA-based power distribution network fault identification method, and the method comprises the steps: receiving a traveling wave signal of a power distribution network, and carrying out the preprocessing of the traveling wave signal; decomposing the preprocessed traveling wave signal by adopting CEEMDAN to obtain an intrinsic mode function component set, and selecting a high-frequency intrinsic mode function component from the intrinsic mode function component set; performing noise reduction on the high-frequency intrinsic mode function component by using singular spectrum analysis to obtain a pure fault feature signal; analyzing and reconstructing the frequency spectrum characteristics of the pure fault characteristic signal by using fast Fourier transform, and calculating the average frequency spectrum content of the low-frequency-band signal and the amplitude ratio of the high-frequency-band signal according to the frequency spectrum characteristics; and generating a fault identification result of the power distribution network by taking the average frequency spectrum content of the low-frequency-band signal as a main criterion and taking the amplitude proportion of the high-frequency-band signal as an auxiliary criterion according to the fault traveling wave transmission characteristics. Therefore, high-precision power distribution network fault identification can be realized in a complex working condition and a high-noise environment.

The invention provides an anti-noise interference frequency parameter estimation method for high-precision optical coherence ranging, which comprises the following steps: acquiring a spectral interference signal of an optical low-coherence interference system and a reference light spectral signal output only by a reference arm, and converting the spectral interference signal into interference signals with wave number space arranged at equal intervals, carrying out spectral density amplitude normalization to obtain a standard interference signal so as to eliminate interference of light source spectrum fluctuation and non-uniform sampling on frequency estimation; hanning window modulation is applied to a standard interference signal, spectrum leakage is suppressed, spectrum analysis is performed on the modulated signal, a peak value and an adjacent secondary peak value of a spectrum main lobe are extracted, a frequency correction amount is calculated based on a peak value and secondary peak value amplitude ratio relation derived by a Hanning window spectrum mode function, and an accurate frequency of the interference signal is obtained; and calculating the displacement of the object to be measured according to the product of the accurate frequency and the spectral resolution of the optical low-coherence interference system in combination with the refractive index of the light in the measurement medium.

The invention relates to the technical field of seismic exploration, in particular to a method for determining structural parameters and sweep frequency signals of a controllable impact seismic source, which is used for carrying out an indoor physical test of a controllable impact seismic source model machine and ensuring the effectiveness of a design scheme of the controllable impact seismic source. Constructing and verifying a multi-body dynamics numerical model of single impact, performing single variable sensitivity analysis on key structure parameters, and determining an optimal structure parameter combination by taking a frequency domain of output seismic waves as an evaluation index; constructing a multi-impact model, performing a simulation test on the sweep frequency control parameter, and determining an optimal sweep frequency signal parameter based on the main lobe amplitude and the main lobe-side lobe amplitude ratio of the output signal autocorrelation function; through forward modeling and cross-correlation-scattered wave inversion imaging processing, an application method of a controllable impact seismic source is established, and validity is verified. The technical problems that a traditional trial and error method is low in efficiency, main lobe energy of seismic source output signals is dispersed due to an unknown parameter influence mechanism, side lobe interference is large, and the signal-to-noise ratio is low are solved.

This invention relates to a method for measuring the stability margin of a constant-temperature hot-wire anemometer based on in-situ open-loop frequency characteristics, belonging to the field of fluid measurement and automatic control technology. The method disclosed in this invention includes the following steps: S1. Connecting an ultra-low frequency low-pass filter to the closed-loop circuit to form an in-situ open-loop system with a DC closed loop and an AC open loop; S2. Injecting a sweep frequency excitation signal E at the bias circuit. stimu And measure the output response E of the amplifier circuit. a By comparing the amplitude ratio and phase difference of the two, the open-loop frequency response G of the system under actual operating conditions of the hot wire is obtained. open (jω); S3. According to G open (jω) Obtain the phase margin of the system and determine its stability. This invention proposes a new method for measuring the stability margin of a constant-temperature hot-wire anemometer, transforming the complex system stability problem into a measurable and analyzable open-loop frequency characteristic stability margin problem, providing a direct and reliable engineering basis for the circuit design of constant-temperature hot-wire anemometers.

This application relates to the field of electromagnetic waves, specifically providing a polarization state detection method and apparatus. The method utilizes a polarization state detection device for detection and includes: inputting the beam to be detected into the polarization state detection device to obtain orthogonal first and second Bessel beams; using a polarizer to obtain the azimuth angles corresponding to the interference weakening or enhancement regions in the interference patterns of the first and second Bessel beams, and determining the phase difference between the first and second Bessel beams based on the azimuth angles; using the polarizer to obtain the first amplitude of the first Bessel beam and the second amplitude of the second Bessel beam, respectively, and obtaining the amplitude ratio based on the first and second amplitudes; and calculating the polarization state of the wave to be detected based on the phase difference and amplitude ratio. This polarization state detection method simplifies the polarization state detection process for terahertz and millimeter waves, promoting the miniaturization and integration of detection equipment.

The invention discloses a sum and difference angle measurement method based on angle discrimination curve piecewise fitting, which belongs to the field of signal processing, and comprises the following steps: firstly, carrying out digital beam synthesis on four-quadrant signals, synthesizing a sum beam, an azimuth difference beam and a pitch difference beam, and measuring the amplitude of the sum beam, the amplitude of the azimuth difference beam and the amplitude of the pitch difference beam; thirdly, according to a fixed frequency interval, completing beam pattern scanning of M frequency points of a target frequency band, calculating a sum-difference amplitude comparison result, and generating M groups of angle measurement parameters by adopting an angle discrimination curve segmentation fitting method; and finally, measuring signal frequency, sum beam amplitude, azimuth difference beam amplitude, pitch difference beam amplitude, azimuth sum difference phase difference and pitch sum difference phase difference in real time, selecting angle measurement parameters according to a frequency proximity principle, and calculating a target azimuth angle and a pitch angle in real time. According to the invention, sum-difference angle measurement of a wide-frequency-domain signal receiving system can be realized, the angle measurement precision is improved, and the engineering realization complexity is reduced.

A method for determining the elevation angle and / or azimuth angle of a signal received by an ultrasound sensor includes: providing an ultrasound sensor with a frequency-dependent radiation pattern; transmitting a first ultrasound wave at a first frequency; transmitting a second ultrasound wave at a second frequency different from the first frequency; receiving reflections of the first and second waves, the reflections being caused by an object; and determining the elevation angle of the first and second reflected waves based on amplitudes of the reflections of the first and second waves. Determining the elevation angle (and / or azimuth angle includes calculating a ratio between the amplitudes of received reflections of the first and second waves and mapping a calculated ratio to an elevation angle and / or azimuth angle. The mapping is based on a predetermined ratio curve or ratio dataset which associates a certain amplitude ratio to an elevation angle and / or azimuth angle.

This improves the reliability and throughput of characteristic measurement of films formed on substrates. [Solution] Polarization components consisting of p-polarized and s-polarized terahertz waves with mutually orthogonal vibration planes are incident on a substrate, the time waveforms of the electric field strengths of the p-polarized and s-polarized waves are obtained from the time waveform of the electric field strength of the polarization components reflected from the substrate, the spectra of the measured amplitude ratio of the p-polarized and s-polarized waves and the spectra of the measured phase difference of the p-polarized and s-polarized waves are obtained, the spectra of the calculated amplitude ratio of the p-polarized and s-polarized waves and the spectra of the calculated phase difference of the p-polarized and s-polarized waves are obtained by simulation using an optical model of the substrate, the properties of the film formed on the substrate are measured by fitting which at least matches the spectra of the calculated amplitude ratio to the spectra of the measured amplitude ratio, and the most reliable measurement value is used from among the multiple measurement values ​​used when measuring the properties of the film.

The invention relates to a vibration sensor fault detection method, which comprises the following steps of: acquiring vibration data of vibration sensors arranged at different measuring points, and extracting the amplitude of the vibration data at a characteristic frequency point as a target characteristic amplitude; for any characteristic frequency point of any measuring point, calculating the amplitude ratio of the target characteristic amplitude between the current measuring point and the other measuring points to obtain a target amplitude ratio; and comparing the target amplitude ratio with a reference ratio parameter, and if the ratio of the target amplitude ratio and the reference ratio parameter is imbalance, determining that a sensor fault occurs. The fault of the vibration sensor can be effectively detected.

The application discloses a three-dimensional positioning method of a seismic source based on a multi-channel amplitude ratio. The method obtains waveform data of the same event on at least four sensor channels and spatial coordinates of the sensors, pre-processes the waveforms, determines an event window corresponding to the event, extracts amplitude indicators of each channel in the event window and performs channel consistency correction, constructs an amplitude logarithm ratio observation on an arbitrary channel based on an exponential decay model to eliminate a source intensity factor, and further forms a constraint related to a distance difference of the seismic source and the sensor. A redundant channel constraint set is further constructed, and an abnormal channel is down-weighted or removed. A weighted nonlinear least square is used in combination with an iterative reweighted least square or a robust loss function to solve the problem, a residual threshold is determined and is updated with iteration. A plurality of candidate solutions are obtained by solving a multi-initial value or a coarse grid initial value in a preset feasible region, and an optimal solution is output. The method reduces the dependence on the arrival time picking, and can be used for microseismic monitoring, acoustic emission positioning and underground engineering safety monitoring.

The embodiment of the invention relates to the technical field of seismic data processing, in particular to a frequency band width determination method and device, equipment, a medium and a product program. The invention provides a method for determining a frequency bandwidth. The method comprises the following steps: determining the total amplitude of target channel data in shot gather data; determining an amplitude ratio between the amplitude of each frequency in the target channel data and the total amplitude; determining a target frequency set of high-amplitude frequencies meeting a preset condition according to the amplitude ratio; constructing a kernel density curve according to the target frequency set; and determining the frequency band width of the low-frequency high-amplitude data according to the kernel density curve. According to the method, the problem that seismic traces containing low-frequency high-amplitude data in seismic trace data cannot be determined is solved, whether high-amplitude low-frequency data is needed in the seismic trace data or not is quickly determined, and if the high-amplitude low-frequency data exists, the frequency band width of the low-frequency data is quickly positioned.

The application discloses a kind of self-adapting noise reduction filtering method, system, medium and equipment, the method includes to input dynamic signal and carry out direct current offset preprocessing;Time-frequency representation matrix is generated by time-frequency transform, and amplitude spectrum is calculated accordingly;Along time axis analysis amplitude spectrum, extract short time and long time noise amplitude and fusion generate basic noise amplitude;Signal noise amplitude ratio is calculated based on basic noise amplitude, and final noise amplitude is determined;According to final noise amplitude, calculate noise reduction spectrum amplitude, retain original phase information, reconstruct as noise reduction time domain signal by inverse transform;The system includes preprocessing module, amplitude spectrum generation module, double time scale noise estimation module, denoising module, noise reduction and signal reconstruction module;The application is accurately described by double time scale noise estimation Dynamic distribution of noise, combined with the adaptive noise reduction adjustment based on signal noise amplitude ratio, effectively suppress complex, non-stationary noise, while enhancing the relative intensity of characteristic frequency band.

The invention discloses a single-stage gear parametrically-excited vibration response frequency spectrum prediction method based on modulation feedback, and the method comprises the steps: building a single-degree-of-freedom kinetic equation containing time-varying meshing stiffness based on the Newton second law, and solving a main oscillation frequency through employing a modulation feedback theory and a trigonometric series approximation method; constructing a quantitative prediction model of excitation parameters and dominant side frequency orders on the basis of a first-class Bessel function, and solving system response by applying a four-order Runge-Kutta method in combination with fast Fourier transformation to verify the prediction model; a parameter sensitivity analysis framework is established through a harmonic coefficient method, and the influence of excitation parameters on the main oscillation frequency and the side frequency amplitude ratio is quantified.

The invention discloses an adaptive integrated empirical mode decomposition method based on a quartile difference algorithm. The adaptive integrated empirical mode decomposition method comprises the following steps: inputting an initial decomposition signal; initializing a value range for adding white noise amplitude ratio coefficients and an amplitude ratio coefficient interval value, and gradually increasing the white noise amplitude ratio coefficients in the value range by taking the quartile difference of the initial decomposition signal as a reference to obtain white noise corresponding to each white noise amplitude ratio coefficient; sequentially adding white noise into the initial decomposition signal from small to large to obtain a noise-added decomposition signal; solving a local maximum value point position and a local minimum value point position of the noise-added decomposition signal to obtain a sequence formed by maximum value points and a sequence formed by minimum value points; calculating a quartile difference between the maximum value point sequence and the minimum value point sequence by adopting a quartile difference calculation method to obtain an extreme point distribution characteristic of the noise-added decomposition signal and a corresponding change relation curve between the extreme point distribution characteristic and a coefficient; obtaining the optimal value of the added white noise amplitude ratio coefficient according to the corresponding change relation curve; and performing integrated empirical mode decomposition on the initial decomposition signal by using the optimal value to obtain an n-order intrinsic mode component. By using the method, the purpose of adaptively optimizing decomposition parameters according to actual decomposition signals in integrated empirical mode decomposition can be achieved, signal extreme points are distributed more uniformly, the fluctuation degree is as small as possible, mode aliasing is reduced, and adaptive decomposition of nonlinear and non-stationary signals is achieved.

The invention discloses an electrosurgical tissue impedance measurement system and method based on frequency domain analysis. The system comprises a main energy generation module, a modulation signal generation module, an output superposition module, a signal acquisition module, an impedance calculation module and a feedback control module. The main energy generation module outputs a high-frequency main waveform for tissue cutting or blood coagulation; the modulation signal generation module is used for generating a modulation signal, and the modulation signal comprises one of a multi-cosine signal or a multi-frequency sweep-frequency signal and a pseudo-random sequence; the output superposition module is used for superposing the modulation signal into the main waveform; the signal acquisition module synchronously acquires tissue voltage and current signals after the modulation signal is loaded; the impedance calculation module is used for performing frequency domain analysis on the voltage and current signals acquired by the signal acquisition module, extracting frequency components corresponding to modulation signals by using fast Fourier transform (FFT), phase lock detection (PLL) or a time-frequency analysis algorithm, and performing frequency domain analysis on multi-cosine signals or frequency sweep signals; by comparing the amplitude ratio and the phase difference of the corresponding frequency components of the modulation signal output end and the response end, the impedance Z = RZ < Z of the measured tissue is inverted according to the known reference impedance, and Z is the impedance of the measured tissue; rZ is the amplitude of the measured impedance and reflects the magnitude of the impedance; < Z represents the phase difference between the voltage and the current; for a pseudo-random sequence signal, a matched filter is used for carrying out related detection on an input signal, and a pseudo-random sequence value is extracted so as to obtain a system signal and control data; a feedback control module adjusts the output power or the cutting / coagulation mode of the electrosurgical equipment in real time according to the tissue impedance obtained through calculation and the dynamic change of the tissue impedance; wherein the dynamic change is a group of dynamic sequence values of the impedance of the measured tissue from the time dimension. By means of the design, real-time accurate measurement can be achieved, the anti-interference capability is high, errors are small, and efficient and safe cutting / blood coagulation can be achieved.

The invention discloses a sub-pixel positioning method, system and device based on a signal amplitude ratio and a medium, and is applied to the technical field of semiconductor radiation detection and imaging, and the method comprises the steps: obtaining induction signals generated by the same energy deposition event in at least two adjacent pixel units; processing the sensing signal to obtain digital amplitude values respectively corresponding to the at least two pixel units; calculating an amplitude ratio according to the digital amplitude value; determining sub-pixel level position information of the energy deposition event relative to the at least two pixel units according to the amplitude ratio based on a preset mapping relation between the amplitude ratio and the sub-pixel position; outputting a positioning result containing the sub-pixel level position information; according to the invention, the precise function relation between the amplitude ratio of the adjacent pixel induction signals and the action position is established, so that the high-precision positioning of the sub-pixel level can be realized through simple and efficient calculation, and the spatial resolution of the detector is remarkably improved.

The invention discloses a dangerous rock mass stability evaluation method and system based on an amplitude ratio and a frequency ratio, and relates to the technical field of geological disaster risk assessment, and the method comprises the steps: collecting dangerous rock three-way vibration data and bed rock three-way vibration data in the same time interval; the dangerous rock three-dimensional vibration data and the bedrock three-dimensional vibration data are synthesized into dangerous rock one-dimensional amplitude data and bedrock one-dimensional amplitude data respectively, and the ratio of the dangerous rock amplitude standard deviation to the bedrock amplitude standard deviation is calculated to obtain an amplitude ratio; calculating the ratio of the dangerous rock peak frequency to the bedrock peak frequency to obtain a frequency ratio; and inputting the amplitude ratio and the frequency ratio as inputs into a trained dangerous rock mass stability evaluation model, and identifying the stable state of the dangerous rock mass. According to the method, the problem that the accuracy of a stability evaluation result is insufficient due to excitation and equipment temperature drift in dangerous rock mass vibration monitoring in the prior art is solved.

A correction value calculation method calculates correction values to correct the 2-phase sinusoidal signals (X, Y) output by the encoder, and includes: a polar coordinate calculation step for calculating, for N phase angles and the Lissajous radius corresponding to each phase angle in the Lissajous waveform drawn by the 2-phase sinusoidal signals, a squared radius, which is the square of the Lissajous radius corresponding to each phase angle; and a correction value calculation step for calculating, based on each phase angle and corresponding squared radius, at least a correction residual of an offset error of the signal X, a correction residual of an offset error of the signal Y, a correction residual of an amplitude ratio error of the signals X and Y, and a correction residual of a phase difference error between the signal X and the signal Y, and then calculating correction values based on the correction residuals.

The invention relates to the technical field of image processing, and discloses a coke quality stability evaluation method comprising the following steps: step S101, obtaining a normalized angle frame sequence; s102, performing weighted least square fitting on the curve of the intensity of each pixel changing along with the polarization angle; step S103, obtaining a pixel-level polarization biharmonic normalization amplitude ratio; step S104, obtaining a field-of-view polarization biharmonic normalized amplitude ratio; step S105, obtaining a stability distance; and S106, obtaining a polarization stability index. According to the method, the influence of gain drift is eliminated through angle frame space mean value normalization, a harmonic projection layer adapts to non-equiangular or unfilled corner sampling through weighted least squares and generates a reliability weight to eliminate abnormal angle frame interference, and visual indexes are output by combining effective domain screening, distribution comparison quantification batch difference and index mapping. Therefore, the anisotropy and stability characteristics of the coke can be accurately reflected.

According to the active terahertz polarization conversion and detection method based on the gap regulation metasurface, any completely polarized light can be decomposed into two orthogonal polarization components, the two components have a certain phase difference and amplitude ratio, and target polarization response can be obtained by changing the phase difference or the amplitude ratio. Therefore, in order to obtain the required polarized light, any phase retarder, namely a wave plate, is used for changing the phase difference between two orthogonal components of the incident polarized light, so that a target polarization state is obtained; the detection method is based on the reciprocity principle of an electromagnetic field, a device with a polarization conversion function can be reconfigured into a polarization detection system under time reversal symmetry, different polarization states are switched according to a time sequence through the conversion relation between a Jones matrix and a Muller matrix, and the detection accuracy is improved. And the light intensity with different polarization components is measured in sequence to realize full Stokes polarization detection of incident polarized light.

The invention discloses a step frequency imaging method based on speed matched filtering and false scattering point elimination, and the method comprises the steps: firstly, obtaining a distance unit corresponding to the maximum amplitude in a non-coherent processing channel and a speed matched filtering result, and calculating a target compensation speed range; traversing each speed value in the compensation speed range, and generating a target one-dimensional range profile corresponding to different speeds according to the sub-pulse data; taking the ratio of the kurtosis of the range profile to the envelope entropy as a cost function, and taking the range profile corresponding to the maximum cost function as a range profile after speed compensation; and finally, calculating a scattering point correlation coefficient by using the distance image after speed compensation and the scattering point sample, performing false scattering point judgment according to the scattering point correlation coefficient and an amplitude ratio, and obtaining a high-resolution one-dimensional distance image of the target through false scattering point elimination. According to the invention, accurate estimation of the target speed is realized, the imaging accuracy of the step frequency system is improved, and the measurement and calculation precision of detection target parameters is improved.

The invention discloses a trace water content detection method based on a tunable laser absorption spectrum, and relates to the technical field of gas moisture detection.The method comprises the steps that a laser generating device is adopted to generate an optical signal, the optical signal is irradiated into an integrated small gas chamber storing to-be-detected gas, and a first harmonic signal and a second harmonic signal of the optical signal passing through the to-be-detected gas are collected; performing light energy compensation by using the first harmonic signal and the second harmonic signal to obtain an inversion parameter; and performing water vapor concentration nonlinear fitting inversion by using the inversion parameters to obtain the moisture content of the gas to be detected. The extracted first harmonic signal and the extracted second harmonic signal are utilized, and a stable signal amplitude ratio is adopted as a subsequent processing signal. The signal amplitude ratio makes the detection signal no longer depend on the absolute value of the light intensity, but is determined by the relative relationship between the two harmonic components. The influence of light intensity fluctuation is compensated, periodic noise such as optical interference fringes is inhibited to a certain degree, and then rapid and high-precision detection of the gas water content is achieved.

The invention proposes a system for monitoring the vibrations, in particular the natural frequency, of a tower (1) of a wind turbine (2), comprising vibration sensors (3) associated with the tower (1) and comprising an evaluation device (4) for processing vibration sensor data. In order to be able to make reliable statements about damage to the tower (1), it is proposed that a plurality of vibration sensors (3) are arranged annularly around the tower axis (6) in three or more tower cross-sectional planes (5) along the tower axis (6), wherein the evaluation device (4) stores, in addition to the natural frequency (fi), vibration amplitudes (A) associated with the respective tower cross-sectional planes (5) at observation times (Ti) and identifies structural damage in the tower (1) by way of comparing the natural frequencies (fi) and the amplitude ratios (A) over an observation period.