461 results about "First order derivative" patented technology

The invention relates to a lateral deviation full-bridge double-interdigital metal strain gauge capable of measuring surface strain lateral partial derivatives, which comprises a base and four sensitive grids, and is characterized in that both ends of each sensitive grid are respectively connected to an outgoing line, each sensitive grid comprises a sensitive section and a transition section, and axes of the sensitive sections are straight lines and parallelly arranged in the same plane; in the plane determined by the axes of the sensitive sections, the axis direction of the sensitive sections is an axial direction, and the direction perpendicular to the axial direction is a lateral direction; the four sensitive grids are consistent in resistance, the resistance variation amount is consistent under the same strain, the four sensitive grids are called as an upper-upper sensitive grid, an upper-lower sensitive grid, a lower-upper sensitive grid and a lower-lower sensitive grid from top to bottom along the lateral direction, the upper-upper sensitive grid and the upper-lower sensitive grid are arranged in an interdigital mode, and the lower-upper sensitive grid and the lower-lower sensitive grid are also arranged in the interdigital mode; and centers of the four sensitive grids have no deviation in the axial direction and have deviation in the lateral direction. The lateral deviation full-bridge double-interdigital metal strain gauge not only can measure the strain, but also can effectively detect a lateral first-order derivative and a lateral second-order derivative of the surface strain.

A method of driving a MEMS mirror scanner having an electrostatic actuator, comprising a step of driving the electrostatic actuator according to an input signal in accordance with a driving waveform obtained by the following equation,whenC+′(θ)≠0VV(t)=1C+′(θ)I[-C-′(θ)IVB+-(1ICL(θ)θ)(1ICR(θ)θ)VB2+C+′(θ)I(θ¨+2BIθ.+κIθ)]whenC+′(θ)=0VV(t)=θ¨+2BIθ.+κIθ2C-′(θ)IVBwhere, B / I, κ / I, (1 / I)·dCL(θ) / dθ and (1 / I)·dCR(θ) / dθ are parameters for obtaining the driving waveform, θ(t) is a desired mirror angle response, I is a moment of inertia of a moving part including a mirror, 2B is a damping factor (damping coefficient), κ is a spring constant, CL(θ) and CR(θ) are angle dependencies of an electric capacitance, VB is a constant bias voltage in differential driving, and C+′(θ) and C−′(θ) are ½ of the sum and the difference of the first order derivative of CL(θ) and CR(θ) with respect to θ, respectively, which are represented by defined equations.

The present invention is directed to a method and apparatus for testing a fiber-optic cable. An Optical Time Domain Reflectometer (OTDR) is presented. Test signals are generated from the OTDR and received by the OTDR for processing. The received test signals are sampled and analyzed. The received test signals include reflectance spikes and a slope. A first-order derivative is taken of the received signal. The first-order derivative is then filtered to remove the reflectance spikes and the slope. Discontinuities in the filtered first-order derivative denote a fault in the fiber-optic cable.

The invention provides an electric power steering system with an individually adjustable-parameter and curve-type power characteristic. The system is characterized in that: the power characteristic curve is a segmentation curve which is symmetric about the centre of a zero input moment point; an integral curve can be determined by setting 5 key parameter values on the curve, and, when one or more key parameters are regulated, the integrity of the curve and the continuity of the first-order derivative can still be guaranteed without modifying other parameters. The power characteristic of the electric power steering system provided by the invention can change the shape of the curve by adjusting 5 of the key parameter values to achieve different assisting effects, so the electric power steering system has the optimum steering performance which is expected by drivers.

Disclosed are systems and methods for detecting the QRS portion of an electrocardiogram and also for detect QRS onset / offset points. QRS complexes are identified by testing selected waveform samples to determine if they are in a high curvature region. If a region passes the high curvature test, a verification test is applied to adjacent samples to confirm that the region is within a QRS complex. The search for a QRS onset point begins at an adaptive distance from this region. The curvature of selected regions ahead in the search direction is examined. The search moves past all such high curvature regions. The onset point is then located by searching for a region that is “flat” in either of two senses. First, a region may be locally flat (i.e. small first derivative) in an absolute sense. Second, a region is flat in a relative that further movement away from the interior of the QRS (e.g. toward “earlier” samples) does not result in a significant change in the value of the first derivative. The search is performed by hopping through the waveform samples. Once an onset point is located, the search for an offset point proceeds in a similar manner from a starting point that is an adaptively determined distance from the onset point.

A rotary-table servo system neural network control method comprises (1) building a mechanical dynamic model of a permanent magnet synchronous motor rotary-table servo system, and initializing the system state, sampling time and relative control parameters; (2) according to the differential mean value theorem, enabling a non-linear input dead zone in the system to linearly approximate to a simple time-varying system, avoiding complex calculation of dead-zone inverse compensation, and finally inferring a rotary-table servo system model provided with an unknown dead zone; (3) at each sampling moment, calculating and controlling a system tracking error, a fast terminal sliding mode surface and a first-order derivative of the system; (4) based on the rotary-table servo system model provided with the unknown dead zone, selecting a neural network approaching unknown trend, designing an adaptive robust finite-time neural network controller according to the system tracking error, the fast terminal sliding mode surface and the first-order derivative of the system, and updating a neural network weight matrix; and (5) entering the next sampling moment, and repetitively executing the steps from (3) to (5).

Methods and devices are provided for determining metabolic factors using electrocardiogram measurements from a person's Wilson points. A first derivative of an electrocardiogram measurement is calculated. A ratio is calculated of the absolute value of the positive spike of the first derivative to the sum of the absolute values of the positive and negative spikes. In some embodiments, the ratio is multiplied by a constant to determine a metabolic factors. Further operations may be performed on the ratio to determine other metabolic factors. In some embodiments, a garment is provided for easily locating Wilson points. Methods and devices are provided for taking and processing EGC measurements to determine metabolic factors and for using the metabolic factors to optimize an exercise program.

The invention provides a hypersonic velocity static wind tunnel nozzle design method and a hypersonic velocity static wind tunnel nozzle transition position determining method. The hypersonic velocity static wind tunnel nozzle transition position determining method comprises the steps that a Gulet logarithm N is determined according to the design requirements of a hypersonic velocity static wind tunnel nozzle; an axle wire of the hypersonic velocity static wind tunnel nozzle serves as an X axis, and the first formula shown in the specification is utilized for determining the vertical coordinate yT of a transition point, wherein the vertical coordinate yT of a transition point conforms to a second formula shown in the specification. According to the second formula, T is the transition point, the GT is the Gulet number of the point T, deltaT is the boundary layer thickness of the point T, RdeltaT is the boundary layer thickness Reynolds number of the point T, rT is the wall curvature radius of the transition point T, y'T is the first-order derivative of the y-axis coordinate of the transition point T, and y''T is the second-order derivative of the y-axis coordinate of the transition point T; according to the vertical coordinate yT of the transition point T, the horizontal coordinate xT of the transition point T is determined. According to the hypersonic velocity static wind tunnel nozzle design method and the hypersonic velocity static wind tunnel nozzle transition position determining method, the transition position of the hypersonic velocity static wind tunnel nozzle can be easily and accurately obtained, and the repeated debugging step in the design process of the hypersonic velocity static wind tunnel nozzle is omitted.

The invention relates to a five-axis numerical control processing technique for complex curved surfaces, in particular to a tracking smoothing method suitable for a five-axis numerical control device, which belongs to the technical field of numerical control. The method comprises the following steps of: 1, continuously reading a segment of numerical control command point sequence, and identifying a program segment which satisfies a smooth curve interpolation condition; 2, estimating the positions of interpolation points between adjacent command points, and taking the positions as first-time correction command points; 3, parameterizing the first-time correction command point; 4, generating second-time correction command points, and determining first-order derivative vectors and second-order derivative vectors of the second-time correction command points; and 5, constructing a quintic spline curve for each coordinate component of adjacent second-time correction command points respectively, connecting the quintic spline curves into an integral smooth curve, and performing curve interpolation on the smooth curve. By means of the method, the processing efficiency and the processing accuracy of the five-axis numerical control device are increased, and a turning phenomenon caused by broken line tracks is eliminated.

The invention relates to a measurement system and measurement method for stress waves of Hopkinson bars by using a flexoelectric effect. The system comprises a bullet, a laser velocimeter, an input bar, an output bar, an absorbing bar, a damper, a first strain gradient sensor, a second strain gradient sensor, a speed measuring circuit and a two-way charge amplifier, wherein the first strain gradient sensor and the second strain gradient sensor are respectively attached to the input bar and the output bar, the speed measuring circuit is optically connected with the laser velocimeter, and the two-way charge amplifier is electrically connected with the first strain gradient sensor and the second strain gradient sensor; the speed measuring circuit and the output end of the two-way charge amplifier are electrically connected with signal processing, displaying and storing modules. During stress wave measurement, a test piece is fixed between the input bar and the output bar, the absorbing bar and the damper are sequentially arranged behind the output bar, and the bullet and the input bar are respectively arranged on the same horizontal plane on the two ends of the laser velocimeter. As the passive strain gradient sensors based on a flexoelectric principle are arranged, the measurement system can measure the first-order derivative of a real waveform, can directly carry out integral computation for the waveform, and can obtain the more real waveform of the stress waves, and the measurement precision is improved.

Disclosed is a sliding-mode synchronization control method of a double-permanent-magnet synchronous motor chaos system. The sliding-mode synchronization control method includes: establishing a chaos model of a permanent magnet synchronous motor system as shown in the form, and initializing system state and relevant control parameters; at each sampling instant, calculating synchronization errors, sliding model surfaces and a first-order derivative of the permanent magnetic synchronous motor chaos system; designing a robust controller by adopting an active sliding-mode control method and finally realizing quick synchronization of the chaos state of the double-permanent-magnet synchronous motor chaos system with two different initial conditions and uncertain parameters.

The invention relates to a guided wave radar level meter echo signal processing system based on first-order derivative. The system comprises a single-chip microcomputer for controlling transmitting and receiving of pulse signals, a pulse transmitting circuit, a guided wave rod, an echo signal receiving circuit and a equivalent time sampling circuit. A signal conditioning circuit, a single-chip microcomputer system for processing echo signals, a liquid crystal display and software are further provided. The echo signals processed by the equivalent time sampling circuit are sent back to the signal conditioning circuit, subjected to voltage dividing, biasing and impedance conversion and sent to the single-chip microcomputer system to be sampled. Echo signal processing includes that the echo signals are subjected to 9-point moving average filtering preprocessing, filtered signals are subjected to first-order derivative calculation to detect echo, material level echo is judged through multi-parameter organic combination, a material level location point and a reference starting point are determined to calculate time difference, then the time difference is substituted into a function relational expression of the material level determined by calibration and the time difference to calculate the material level.

The invention combines a wavelet lifting process and a difference process and provides an integratable fast algorithm for denoising electrocardiosignal and identifying QRS waves. The invention provides a method for denoising a weighted threshold value and solves the problem of signal distortion after denoising by using a global threshold value. The invention proposes to realize the lifting transformation of an electrocardiosignal by using a DB4 first-order derivative, avoid a wavelet lifting and re-decomposing process of the denoised signal and speed up the identification of QRS waves by combining the difference process in a DB4 wavelet lifting transformation process; meanwhile, an improved self-adaptive threshold updating method is adopted to improve the accuracy of QRS wave identification. In the invention, both the wavelet lifting process and a difference process, which are adopted, have the characteristics of high computing speed, low memory space occupation and capacity of realizing integer operation; therefore, the integrated application of the algorithm can be realized easily on the conventional hardware platform and can be realized easily in applications of computers and large processors.

A method based on VPF and improved SVSAN for locating the canthi and pupil in order to recognize human face, sex, expression, age, etc includes such steps as determining the horizontal coordinate of pupil center according to the maximum of VPF, determining the left and right boundaries of pupil (the diameter and radius of pupil) according to the positions of the maximal and minimal first-order derivative of VPF, matching the circle with template to obtain the circle center of pupil, and determining the positions of canthi according to improved SUSCAN operator.

A method for detecting scene changes in a video sequence in the compressed domain. DC images are extracted from the macroblocks of the video frames. Histogram differences and pixel difference of the DC images are used for scene cut detection, and the changes in the histogram differences are used for gradual scene change detection. Thus, scene cut detection is based on first order derivatives of the histogram and gradual scene change detection is based on second order derivatives of the histogram. If the macroblocks are intra-coded, they are used to compute the exact DC images. If the macroblocks are not intra-coded, motion information in the frame is partially used for scene change detection.

The invention discloses a light spot extraction and light spot mass center determination method. Firstly, an image is imported, and image components are decomposed according to three primary colors RGB; a feature image is extracted by calculating image color features; the optimal color feature is analyzed; the image is segmented through a threshold segmentation method, the colored part of the image is removed, and the image turns greyish white, wherein an optimal-threshold segmentation algorithm is adopted; finally, the laser plaque in the original image is extracted through light spot binaryzation, so that light spot extraction is completed. In the process of determining the mass center of the light spot, the light spot is positioned with a first-order derivative zero-crossing point, andthen the center coordinates of the light spot are calculated through a Gaussian fitting method with grey information of pixel center area unsaturation points, so that the mass center of the light spotis extracted.

The invention provides a curvature fairing method for a high-speed numerical control processing track. The curvature fairing method comprises the steps of: inputting tool location points of an initial processing track; interpolating the initial tool location points by utilizing B-spline curve repeatedly to obtain a tool processing track line, and representing the tool processing track line by using the B-spline curve; calculating a stiffness matrix of a track curve according to node vectors of the B-spline curve; calculating a closest point from each initial tool location point to the B-spline curve and curve parameters corresponding to the closet points, and calculating a first-order derivative of a distance (from the initial tool location points to the closest points of the B-spline curve) to control points of the B-spline curve; solving a tool processing track curvature derivative fairing model by adopting a sequence linear method to obtain a processing track after fairing optimization; and outputting tool locating points of the tool processing track after fairing optimization. The curvature fairing method solves the problem of generating the high-speed numerical control processing tool track with fair curvature, and is suitable for generating a 2.5-axis cavity high-speed processing track.

The invention belongs to the field of spectral analysis and especially relates to a near infrared spectrum analysis method based on a CC-PLS-RBFNN optimization model. According to the method, a correlation coefficient method (CC), partial least squares (PLS) and a radial basis function neural network (RBFNN) are combined for optimizing important parameters. The method comprises the following steps: utilizing three-order Savitzky-Golay convolution smooth filtering and first-order derivative correction to preprocess the original spectrum; establishing a PLS model on a whole wavelength section, and optimizing and selecting window width and PLC extracted main constituent quantity; calculating a correlation coefficient of each wavelength variable, selecting the wavelength variable with the correlation coefficient more than a preset threshold value, participating in modeling, and optimizing and selecting the threshold size; utilizing the optimized and selected window width, the main constituent quantity and the wavelength variable to acquire an optimized PLS model; and using a main constituent score and a nature matrix extracted by the optimized PLS model to train the RBF neural network, thereby acquiring the final CC-PLS-RBFNN optimization model. According to the method, the robustness and precision of near infrared spectroscopy analysis can be obviously promoted.

The invention provides a method for determining the optimal resolution of ocean surface wind field inversion based on SAR (Synthetic Aperture Radar), which comprises the steps of acquiring synthetic aperture radar images containing both co-polarization and cross-polarization, and preprocessing the acquired images; performing resampling on co-polarization and cross-polarization backward scattering coefficient images; carrying out ocean surface wind field inversion by using a co-polarization geophysical model function to obtain co-polarized wind field data with different spatial resolutions; carrying out ocean surface wind field inversion by using a cross-polarization ocean model function to obtain cross-polarization wind field data with different spatial resolutions; building a Gaussian model of a root-mean-square error, which changes along with the spatial resolution, of the co-polarization wind field data and the cross-polarization wind field data with different spatial resolutions; and performing first-order derivative derivation on the function, and when the derivative value is greater than -1*10<-4>, regarding the spatial resolution corresponding to the point is the optimal resolution. The wind speed inversed at the spatial resolution is high in accuracy.

The invention relates to a current change rate-based coal mine power grid short-circuiting fault quick judging device and method. The method includes the following four stages of judgment calculation: stage 1, current first-order derivative calculation; stage 2, current first-order derivative zero point crossing judgment; stage 3, current first-order derivative judgment; and stage 4, current second-order derivative calculation and judgment. The method specifically includes the following steps that: the current change rate of a coal mine power grid line is calculated uninterruptedly; whether a first-order derivative crosses a zero point is judged, if the first-order derivative crosses the zero point, the method enters the stage 4, current second-order calculation is started; if the first-order derivative does not cross the zero point, the method enters the stage 3, the first-order derivative is compared with a previous current change rate calculation result, if the current first-order derivative exceeds a set change range, it is judged that a short-circuiting fault occurs, otherwise, the method enters the stage 1, first-order derivative calculation is further executed; and a current second-order derivative is calculated, and is compared with a previous current change second-order derivative, if the current second-order derivative exceeds a set range, it is judged that a short-circuiting fault occurs, and corresponding operation is carried out, otherwise, the method returns to the stage 1. The current change rate-based coal mine power grid short-circuit fault quick judging device and method provided by the invention can quickly and accurately find faults at the moment when short-circuiting occurs.

The invention relates to a guided wave type radar level meter echo signal processing method based on a first-order derivative with the combination of a reference curve. The method includes the steps that firstly, the reference curve is constructed; secondly, echo signals are preprocessed; thirdly, level echo judgment is conducted; fourthly, propagation time is calculated; fifthly, a level value is calculated. Signals which comprise step parts which are not superposed with the level echo need to be stored in advance and serve as the reference curve for the subsequent level echo judgment; 9-point moving and average filtering preprocessing is conducted on the echo signals; first-order derivative calculation is conducted on the filtered echo signals, the echo is detected, multiple parameters are combined with the reference curve to judge the level echo, a level echo positioning point and a reference starting point are determined, and propagating time is calculated; three points are selected in a defined zone at will to be calibrated, and a level-propagating time model is determined; finally, the propagating time is substituted into a function relation between the level and the propagating time, and the level value is obtained.

Disclosed is a finite time synchronous control method of double permanent magnet synchronous motor chaotic systems. The method includes that a chaotic model of a permanent magnet synchronous motor system is established, and system state and relevant control parameters are initialized; at every sampling instant, synchronous errors, rapid nonsingular terminal sliding mode surfaces and first-order derivatives of principal and subordinate chaotic systems of a permanent magnet synchronous motor are calculated; according to the synchronous errors, the rapid nonsingular terminal sliding mode surfaces and the first-order derivatives, a synchronous controller of the double permanent magnet synchronous motor chaotic systems is designed, the problem of buffeting during sliding-mode control can be solved, and chaotic states of the principal and subordinate chaotic systems can be rapidly synchronized.

The invention discloses a method for determination of the polychlorotrifluoroethylene (PCTFE) content in a polymer-bonded explosive (PBX) by near infrared spectroscopy. The method includes the steps of: preparing and collecting 260 PBX samples, taking 180 samples of them as a calibration set for establishing a calibration model, taking the remaining 80 samples as a validation set for model validation, and acquiring the near infrared spectrum data of all the samples; using a standard method to determine the PCTFE content in the samples; subjecting the spectrum data of the validation set samples in the wave bands of 6102.0cm<-1>-5697.0cm<-1> and 4680.2cm<-1>-4242.9cm<-1> to a first order derivative treatment, correlating the treated spectrum data with the PCTFE content by a partial least squares method, and establishing the calibration model by cross validation; employing the calibration model to predetermine the PCTFE content of the validation set samples, and selecting an optimal model according to a minimum root mean squared error of prediction (RMSEP) of the validation set; and acquiring the near infrared spectrum data of the samples to be determined, and making use of the optimal model to obtain the PCTFE content directly. Being suitable for determination of the PCTFE content in a PBX explosive, the method has the characteristics of convenient operation, and rapid and accurate analysis.

A technique is presented for establishing a patient's BMD using a dual-energy X-ray imaging system. In the technique, the dual-energy X-ray imaging system utilizes a slit collimator to expose a series of portions of a region of interest within a patient with X-rays of two different energies. A flat-panel digital X-ray detector detects the X-rays passing through the patient's region of interest and produces data representative of the intensity of the X-rays reaching the detector. The image intensity data is corrected for scatter based on identifying the regions of the image intensity data that are produced from scatter only, and not primary X-rays. A first-order derivative of the image intensity data is used to identify these regions. A value for the intensity of the scatter at the boundary of the scatter-only region is established. The value for the intensity of the scatter at the boundary of the scatter-only region is used to estimate scatter intensity in the region of the image intensity data that is produced from primary X-rays, as well as scatter. To correct the image intensity data for scatter, the known and estimated scatter intensities are subtracted from the image intensity data.

A system and method of frequency offset compensation are disclosed for a wireless system between a fast moving radio terminal associated with a locomotive and a stationary radio terminal associated with a base station. The present invention utilizes advanced frequency offset prediction to quickly track Doppler Shift caused by a fast moving locomotive. In one embodiment according to the present invention, the frequency offset prediction is based on a first plurality of coarse frequency offsets, first-order derivatives of the first plurality of coarse frequency offsets, and second-order derivatives of the first plurality of coarse frequency offsets. In another embodiment according to the present invention, the frequency offset prediction is based on a plurality of previous frequency offsets according to a Doppler shift model.

The invention discloses a gas stove anti-dry-burning control method and device and a gas stove. The gas stove anti-dry-burning control method comprises the steps of sequentially acquiring the temperature of a pot body on the gas stove according to preset time intervals, namely delta t, and recording the temperature as TN, wherein N is a positive integer greater than zero; when TN is greater than T0, judging that the pot body reaches the dry-burning state, and controlling gas of the gas stove to stop burning; when TN is less than T', judging that the pot body does not reach the dry-burning state, and maintaining the state o the gas stove; when TN is greater than T' and less than or equal to T0, calculating a first order derivative, namely dTN / dt, and a second order derivative, namely d<2>TN / dt<2>, of the temperature TN, and judging whether dTN / dt and d<2>TN / dt<2> meet the requirements that dTN / dt is greater than delta1 and d<2>TN / dt<2> is greater than delta2 at the same time or not, wherein delta1 is greater than or equal to 0, and delta2 is greater than or equal to 0; if the requirements are met, judging that the pot body reaches the dry-burning state, and controlling the gas of the gas stove to stop burning; and if the requirements are not met, judging that the pot body does not reach the dry-burning state, and maintaining the state of the gas stove. By means of the gas stove anti-dry-burning control method, dry burning can be effectively avoided or stopped.

The invention relates to a pulse condition signal time domain feature extraction method, which belongs to the technical field of pulse condition measurement in the traditional Chinese medical science, and comprises the steps of: carrying out wavelet transformation on collected pulse condition signals, eliminating high-frequency noise, rebuilding signals, and obtaining the pulse condition signals subjected to the high-frequency noise elimination; extracting base lines, eliminating base line drift and realizing pulse condition signal preprocessing; calculating first-order derivative of the preprocessed pulse condition signals, finding the maximum value in each section of pulse condition signals and positioning the ascending branch of each estimated pulse condition period; determining the pulse condition period for each section of pulse condition signals; and finding dicrotic notches E and dicrotic waves F. The extraction method can improve the pulse condition signal time domain feature extraction efficiency and accuracy.

The invention discloses a fast aircraft attitude maneuvering method based on the fact that angular acceleration derivatives are in a sine curve. The method comprises the steps that an attitude maneuvering path undergoing the three processes of acceleration, constant speed and deceleration is designed according to the moment and angular momentum providing capacity of an actuating mechanism of a control system, in the processes of acceleration and deceleration, it is guaranteed that the derivatives of the angular acceleration are in the standard sine curve, it is guaranteed that moment output in the entire maneuvering process is continuous and first-order derivatives are continuous, so that the moment output is stably changed in the entire maneuvering process, and the trigger effect on a flexural mode in the attitude maneuvering process is small. After aircraft attitude maneuvering is in place, due to the fact that the vibration amplitude value of the flexural mode is small, the attitude of an aircraft can be stable rapidly, and therefore fast maneuvering and fast stable controlling are achieved. The fast aircraft attitude maneuvering method is particularly suitable for aircrafts which are serious in flexural mode coupling for conducting fast maneuvering control, and fast and stable control demands can be met.

The invention relates to a technique for processing petroleum geophysical prospecting seismic data, which is a method for improving the velocity spectrum resolution by using phase information. The method comprises the following steps of: stimulating and recording seismic waves to obtain a common midpoint gather; performing a first-order derivative operation along a time direction, and performing Hilbert transform to obtain a complex seismic trace; superimposing P(t) traces to obtain the optimal velocity of normal moveout correction (NMO); calculating a velocity spectrum by using a conventional velocity analysis method; and performing side lobe suppression on the selected common midpoint (CMP) for velocity analysis and each time sample vector in SPS to finally obtain the velocity spectrum. By the method, influences on the velocity analysis due to amplitude changes can be avoided, the distribution of noises is converted into the distribution with gauss distribution characteristics, so that influences on the velocity analysis due to abnormal noises can be effectively inhibited, and the resolution of the velocity spectrum and the accuracy of the velocity analysis are improved.