76 results about "A wave amplitude" patented technology

The invention discloses a textile production defect detection method and system based on image processing, and belongs to the field of textile defect detection. According to the method, the point cloud data is generated by collecting the surface deformation stripes, and the penetrability reflection signal containing the sound wave propagation time is obtained through the multi-frequency ultrasonic probe. Denoising the point cloud data and then positioning a surface deformation candidate area based on a curvature gradient and a normal vector deflection angle; and an internal abnormal region is determined by separating and extracting a reflection wave amplitude value and a time delay parameter through an ultrasonic frequency band. And matching the surface point cloud coordinates with the ultrasonic propagation time by adopting an iterative nearest point algorithm to establish feature association between the normal vector deflection angle and the reflected wave amplitude. And dynamically distributing fusion weights for the surface features and the internal features according to the curvature gradient change rate and the amplitude attenuation rate to generate a multi-modal defect distribution diagram. And geometric shape and reflection intensity parameters are extracted and matched with a preset defect template to realize type and position judgment, and the method can be suitable for production defect detection of the thick textile with a multi-layer composite material structure.

The invention relates to the technical field, in particular to a power grid overhead line traveling wave recording fusion fault positioning system, which comprises signal acquisition, traveling wave event stamp capturing, zero-sequence current data flow generation, fault triggering, zero-sequence integral comparison based on time reference to generate an activation instruction, and fault recording. The characteristic topology associates and fuses the traveling wave amplitude and the zero-sequence peak value, calculates a node attenuation rate and marks a breakpoint, and the positioning solution links a double-end timestamp and a wave velocity library according to the position of the breakpoint to output a fault coordinate. According to the invention, accurate locking of the fault moment is realized through synchronous acquisition of multi-source signals; a transient window defined by traveling wave triggering ensures complete capture of features; branch identification precision is improved through current vector fusion; parameters are automatically adjusted through dynamic wave velocity matching to improve positioning accuracy; time synchronization and wave velocity compensation eliminate the influence of line parameters.

The invention provides an aero-engine blade damage detection method based on an improved ultrasonic sparse reconstruction algorithm, and relates to the technical field of aero-engine damage detection positioning, and the method comprises the steps: S1, setting a sensor array and a detection region of a to-be-detected blade, and obtaining an actual measurement damage reflection signal dictionary through a sensor; s2, wave number distribution of a detection area is determined according to a variable thickness structure Lamb wave propagation model, signal reconstruction is carried out, and a theoretical damage reflection signal dictionary is obtained; s3, an aero-engine blade damage detection model is constructed, an improved sparse reconstruction algorithm is adopted to solve and optimize, and damage judgment is carried out; and S4, according to the pixel value distribution condition of the aero-engine blade detection area, generating an aero-engine blade damage detection image, and positioning a damage position. According to the method, the reflected wave amplitude information can be obtained from the array sensor signals, and the reflected wave amplitude information is compared with the reconstructed theoretical reflected signals, so that the damage condition of the aero-engine blade is identified and positioned.

The invention provides a three-dimensional skin waviness fitting analysis method. The method comprises the following steps: performing boundary analysis on skin point cloud data obtained by laser measurement, performing interpolation sampling from the point cloud data according to a specified area and resolution to obtain point cloud coordinates which can reflect the real condition of the skin and are regularly arranged, performing bicubic spline surface least square approximation based on a sampling point set, and calculating the skin point cloud data according to the bicubic spline surface least square approximation. The method comprises the following steps: acquiring a reference curved surface reflecting the overall distribution trend of an analysis area, calculating distance deviation from a sampling point to the reference curved surface, carrying out filtering smoothing processing, forming a smooth deviation curved surface capable of reflecting the deviation condition of a measurement curved surface, extracting information such as wave crest and wave trough positions, wave amplitude, wavelength and slope in the deviation curved surface, and carrying out skin waviness characteristic analysis. According to the method, the tiny waviness characteristics of the irregular curvature surface of the aircraft can be extracted, the skin waviness distribution condition can be visually displayed, and the method has the advantages of being wide in applicability, small in error, high in reliability, low in time cost and the like.

The invention provides an aviation nacelle part waviness automatic detection and evaluation method, and belongs to the field of product production detection, and the method comprises the steps: carrying out the protocol scanning of part surface contour features, and obtaining the undistorted coordinate point discrete point cloud data of the actual surface contour; filtering the point cloud data; obtaining a piece of flattened deviation value discrete point cloud data; obtaining a flattened deviation value continuous curve by adopting a general standard curve reduction method; extracting waviness components, and obtaining a curve center line; obtaining a crest value and a trough value participating in calculation; and calculating the maximum wave amplitude, the waviness and the slope for evaluating the waviness by using the wave peak value and the wave trough value. According to the method, the relation between the minimum cut-off wavelength of the waviness and the sampling interval is stipulated, the undistorted reduction of the surface profile curve is ensured, the influence of non-waviness profile components in the digital evaluation of the waviness is eliminated through a combined calculation method, and the evaluation accuracy of the waviness of the aviation nacelle part is improved.

The invention relates to the technical field of construction quality evaluation, in particular to a dynamic compaction construction quality evaluation and analysis system which comprises the steps of collecting compaction vibration signals, screening out abnormal segments, extracting frequent fluctuation sections, counting peak value dense areas, recognizing impact concentration sections, tracking amplitude fluctuation changes, positioning energy accumulation areas and calculating the amplitude change rate. And the position of an inflection point is calibrated, a frequency change track is compared, a compaction state area is divided, and a compaction grade distribution map is generated. According to the method, amplitude change rate mutation fragments are eliminated, stable response sections are extracted, peak aggregation areas are divided according to time, impact concentration sections are identified, the amplitude continuous fluctuation trend is tracked, energy concentration areas are delimited, state turning nodes are positioned based on amplitude change rate comparison, and frequency span and fluctuation duration characteristics are combined. Compacting state areas are classified in a layered mode, and a compacting distribution structure is constructed.

The invention discloses a metering equipment remote calibration method and device, a medium and equipment. The method comprises the following steps: calculating a loss index according to current characteristics of an extracted current signal in a monitoring period, and determining a phase offset of each harmonic based on the loss index; constructing an environment gain coefficient according to the environment temperature and the environment humidity in the environment management period; constructing a current correction coefficient according to the fundamental wave amplitude of the current signal in the monitoring period and the environment gain coefficient; and correcting each harmonic amplitude in the next monitoring period according to the current correction coefficient, and correcting each harmonic phase in the next monitoring period according to the phase offset of each harmonic to obtain a calibration current in the next monitoring period.

This invention discloses a method for calculating the vibration response of a delaminated composite laminate, belonging to the field of structural defect calculation and analysis. The method includes: dividing the composite laminate with delamination defects into delaminated and intact regions based on the damage condition; decoupling the delaminated regions dynamically; describing the vibration characteristics of each component in both the delaminated and intact regions using elastic waves based on elastic wave propagation theory, and establishing vibration state vector expressions for each region; determining the compatibility relationship based on the displacement continuity and internal force equilibrium conditions at the coupling point between the delaminated and intact regions, and establishing structural dynamic equilibrium equations in wave space based on the boundary conditions of the composite laminate; solving the structural dynamic equilibrium equations to obtain the amplitudes of elastic waves of each order; and calculating the vibration response of each region of the composite laminate based on elastic wave theory and amplitude calculation. This invention solves the problem of low computational efficiency in existing methods.

The invention discloses an intelligent research and judgment method and device for a distribution feeder fault based on traveling wave characteristics. In the operation process of the power distribution feeder line, forming time sequence original sampling data based on a unified time service reference, determining a traveling wave disturbance event and generating candidate traveling wave data; constructing a traveling wave time sequence consistency criterion based on the corresponding relationship between the traveling wave head first arrival time and the unified time service reference, and screening to obtain an effective traveling wave feature set; performing correlation analysis on the effective traveling wave feature set and historical operation feature data of the power distribution feeder to form a target traveling wave feature set; according to the time difference relation between the first arrival time of the wave head of the traveling wave in the target traveling wave feature set, the traveling wave propagation distance is calculated to determine the fault occurrence position, meanwhile, the polarity direction of the traveling wave and the amplitude variation of the traveling wave are integrated, the fault type and grounding characteristics are researched and judged, and a fault research and judgment result is output. According to the invention, the accuracy and reliability of power distribution feeder fault positioning and type identification can be effectively improved.

The invention relates to the technical field of permanent magnet synchronous motors, and discloses a permanent magnet synchronous motor turn-to-turn short circuit fault detection method and device, and the method comprises the steps: determining a discrete Fourier transform coefficient according to a carrier wave ratio; sampling the motor stator current for multiple times, and calculating a fundamental wave amplitude corresponding to the motor stator current by using discrete Fourier transform; and judging whether a turn-to-turn short circuit fault occurs or not according to the fundamental wave amplitude. According to the invention, fault detection is realized only through sampling and signal processing (for example, determining a DFT coefficient based on a carrier wave ratio and calculating a fundamental wave amplitude and an unbalance degree) on the stator current in an existing motor control system, and hardware equipment such as a resistance network and the like is not required to be additionally installed like a method based on a neutral-point voltage zero-sequence component, so that the hardware cost is prevented from being increased, and the fault detection efficiency is improved. And the system structure complexity and the subsequent maintenance difficulty are reduced, and the target of improving the reliability of the equipment is consistent.

The invention relates to the technical field of ocean resource development, in particular to a method for calculating vortex-induced vibration of a deep-sea mining riser under the action of internal waves. According to the method, velocity and acceleration distribution characteristics of a flow field are determined according to wave parameters such as amplitude and wavelength of ocean internal waves, and load input is provided for calculation of vortex-induced vibration of the deep-sea mining riser; the ocean internal wave flow field has remarkable particularity, is different from uniform flow and typical shear flow, and is unsteady non-uniform shear flow; based on the particularity of an ocean internal wave flow field, vortex-induced load distribution on a deep-sea mining riser under the action of a traditional wake flow vibrator model is obtained by improving the traditional wake flow vibrator model; according to the geometric nonlinear problem caused by the large slenderness ratio of the deep-sea mining super-long riser and the weak constraint characteristic of the deep-sea mining riser, the rigid body displacement and the elastic deformation of the riser are separately calculated by adopting a co-rotation coordinate method, so that the calculation efficiency is improved to meet the actual engineering requirements; the invention discloses a calculation method for vortex-induced vibration of a deep-sea mining riser under the action of ocean internal waves.

The invention provides a nuclear power plant thermal discharge dynamic change prediction analysis method, and relates to the technical field of data processing, and the method comprises the steps: collecting a temperature observation data set, extracting a temperature maximum value sequence and a temperature minimum value sequence in an equal-tide period, calculating a wave amplitude stable factor, extracting a plurality of trend inflection points of a temperature change first-order derivative curve, and calculating the temperature change first-order derivative curve. The method comprises the following steps: determining thermal expansion boundary candidate areas caused by thermal drainage, evaluating a time interval and amplitude difference between a lag response inflection point in each thermal expansion boundary candidate area and a previous dominant temperature rise point to obtain a thermal lag offset value, extracting a boundary sensitive area, performing multipoint communication fitting, determining a maximum space extrapolation boundary influenced by the thermal drainage effect, and performing thermal expansion on the maximum space extrapolation boundary. And carrying out trajectory tracking and change direction regression on the extrapolation boundaries at multiple different time points, and identifying a heat disturbance movement trend to obtain dynamic evolution data. The method can identify the diffusion trend of the warm discharged water and predict the temperature change.

The invention discloses a distribution network traveling wave head analysis and fault location method and system based on edge calculation. The method comprises the steps that S1, terminal parameters are configured on a power distribution terminal; s2, monitoring a traveling wave signal and a power frequency electrical quantity of the distribution line in real time, and starting wave recording when a traveling wave amplitude exceeds a threshold value; s3, wave recording data are screened through the power frequency electrical quantity change and the traveling wave starting sequence; and S4, carrying out wave head detection on the fault initial traveling wave recording data, carrying out section determination on the fault so as to carry out double-end distance measurement, and then carrying out correction processing on the distance measurement result of the power distribution terminal located in the fault section based on the line section parameters. According to the method, a marginal distribution calculation mode is adopted, and fault identification, wave recording screening and positioning calculation capabilities are integrated on a power distribution terminal side, so that the data communication traffic and the calculation pressure of a master station are greatly reduced, real faults and interference wave recording can be effectively distinguished, and distance measurement errors caused by wave velocity differences in a mixed line in a traditional method are overcome.

The invention relates to the field of non-invasive monitoring, and particularly provides a method for evaluating vascular elasticity through radial artery pulse waves. The method comprises the following steps that 1, radial artery pulse waves are obtained; step 2, preprocessing the radial artery pulse wave to obtain an average pulse period; 3, calculating a dominant wave angle based on the average pulse period; step 4, calculating pulse duration based on the average pulse period; step 5, calculating rise time based on the average pulse cycle; step 6, calculating a main wave amplitude based on the average pulse period; step 7, calculating a waveform area based on the average pulse period; and 8, establishing an evaluation model, inputting the dominant wave angle, the pulse duration, the rise time, the dominant wave amplitude and the waveform area into the evaluation model, and outputting a vascular elasticity predicted value by the evaluation model. According to the method, the accuracy of predicting the vascular elasticity is high, and the cost is low.

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.

The invention discloses a method and a device for calculating the surge amplitude of a bifurcated channel. The method comprises the following steps: acquiring a surge wave of a surge before shunting at a bifurcated opening of the bifurcated channel; the method comprises the following steps: performing simplified fitting on a surge wave in front of a bifurcated opening to form an initial surge waveform; decomposing and dispersing the initial surge waveform into independent surge waves; on the basis of the initial surge waveform and the initial height of the independent surge wave, the amplitude of the independent surge wave at the bifurcated opening position at the moment t1 before collision reflection occurs in the shunting process is calculated; according to the movement and reflection path of each independent swell wave in the bifurcated mouth, the position of the independent swell wave at the moment t2 after collision reflection of the independent swell wave occurs is obtained; overlapping the amplitudes of the independent surge waves at the same position at the t2 moment to obtain the overlapped amplitude of the independent surge waves; and determining the superposed wave amplitude meeting a preset condition as the wave amplitude of the surge in the bifurcated channel. The invention provides a bifurcated channel amplitude calculation method.

The invention discloses a mutual inductor secondary circuit defect identification method and apparatus, a terminal device and a storage medium. The method comprises the steps of obtaining a secondary voltage waveform signal of a to-be-identified mutual inductor; performing Fourier transform according to the secondary voltage waveform signal to obtain a fundamental component and a harmonic component; judging whether a harmonic amplitude condition is met or not according to the harmonic component to obtain a first judgment result; according to the secondary voltage waveform signal, determining a corresponding waveform zero point and a wave crest; according to the secondary voltage waveform signal and the waveform zero point, judging whether a waveform abnormal condition is met or not, and obtaining a second judgment result; judging whether a fundamental wave amplitude condition is met or not according to the wave crest and the fundamental wave component to obtain a third judgment result; and obtaining a secondary circuit defect identification result of the mutual inductor to be identified according to the first judgment result, the second judgment result and the third judgment result. According to the invention, the monitoring efficiency of the power system is improved.

This invention discloses a method for calculating the vibration response of a delaminated composite laminate, belonging to the field of structural defect calculation and analysis. The method includes: dividing the composite laminate with delamination defects into delaminated and intact regions based on the damage condition; decoupling the delaminated regions dynamically; describing the vibration characteristics of each component in both the delaminated and intact regions using elastic waves based on elastic wave propagation theory, and establishing vibration state vector expressions for each region; determining the compatibility relationship based on the displacement continuity and internal force equilibrium conditions at the coupling point between the delaminated and intact regions, and establishing structural dynamic equilibrium equations in wave space based on the boundary conditions of the composite laminate; solving the structural dynamic equilibrium equations to obtain the amplitudes of elastic waves of each order; and calculating the vibration response of each region of the composite laminate based on elastic wave theory and amplitude calculation. This invention solves the problem of low computational efficiency in existing methods.

The invention discloses a pulse wave matching method, device and equipment for non-invasive blood pressure measurement. The method comprises the steps that pulse wave data on each pressure step are collected to obtain a typical pulse wave waveform in a rising-first and falling-second form; performing characteristic value extraction on the pulse waveform by adopting double sliding windows, and judging whether the characteristic values of the current pulse wave and the previous pulse wave are matched or not; the characteristic values comprise a pulse wave amplitude value, a processing signal peak value, a processing signal valley value and a processing signal peak-valley interval; if not, continuing to collect the pulse wave data and continuing to perform characteristic value matching, and if yes, collecting the pulse wave data on the next pressure step. According to the method, the pulse wave features are enhanced through double-window processing, and the influence of interference factors is effectively reduced while the matching judgment precision is improved in combination with the original waveform features.

The invention provides a method and a device for acquiring a grass-shaped wave amplitude value of a rail flaw detection car, and the method comprises the following steps: acquiring each frame of echo signal in a preset detection time gate interval in a detection channel of the rail flaw detection car, and storing each frame of echo signal; determining the maximum amplitude value of each frame of echo signal as a first maximum amplitude value of each frame of echo signal; counting again when the frame number of the stored echo signals reaches the detection frame number of the preset section every time, screening out the maximum amplitude value from the first maximum amplitude values of all frames of echo signals in each section, and determining the maximum amplitude value as the second maximum amplitude value of the section where the maximum amplitude value is located; when the detection section number of the rail flaw detection car reaches a preset detection section number, screening out the minimum amplitude value from the second maximum amplitude values of all sections, and determining the minimum amplitude value as the grass-shaped wave amplitude value of the detection channel of the rail flaw detection car; according to the method, the grass-shaped wave amplitude of the detection channel of the rail flaw detection car can be accurately obtained, the influence of human factors on gain adjustment is reduced, and data support is provided for rail detection.

The invention discloses a method for detecting impact damage of a plate-shaped structure based on elastic waves. The method comprises the steps that S1, a typical part is tested; and S2, real-time monitoring. According to the method, on one hand, an impact event detection process, an impact point location determination process and a damage evaluation process with elastic waves are obtained based on a simulation test, related characteristics formed when a plate structure is impacted are obtained in real time without manual intervention, and impact occurrence time, impact occurrence position, impact occurrence energy and damage evaluation can be obtained through comparison; on the other hand, impact point location information is accurately obtained based on a triangulation method, linear attenuation characteristics of elastic waves are obtained based on wave amplitude and relative distance detected by linearly arranged sensors, and a damage evaluation criterion is formed by combining simulation impact, so that health monitoring requirements of aviation, aerospace and important industrial structures are met; meanwhile, related human factors such as human negligence, fatigue errors and dangerous environments are eliminated, the labor cost is saved, the operation period is shortened, and the purpose of reducing the operation cost is achieved.

The present invention discloses a method for determining the equivalent design wave of a ship's wave load under level 6 sea conditions, relating to the field of ship structural safety. The method comprises: treating the hull as a variable-section beam, and for a ship at a constant speed, calculating the wave load transfer function at the hull beam section under different wave conditions, wherein the wave conditions include different wave direction angles and different circular frequencies of the incident wave; based on the wave load transfer function at the hull beam section, calculating the short-term predicted extreme values ​​of the wave load under different wave direction angles and different zero-crossing periods within the significant wave height range of level 6 sea conditions; selecting a maximum value from all the short-term predicted extreme values ​​of the wave load, and determining the equivalent design wave parameters of the wave load under level 6 sea conditions based on the maximum value. The equivalent design wave is a sinusoidal regular wave, and its parameters include wave amplitude, circular frequency, and wave direction. By converting the study of the load on the hull under random waves into the study of the hull load under regular waves, this method is of great significance for subsequent research on hull load levels and structural safety.

The invention discloses an aerial cable fault detection method combining traveling wave distance measurement and an artificial intelligence algorithm, relates to the technical field of cable fault detection, and solves the problem that distance measurement errors are caused due to the fact that traveling wave arrival time selected at a single moment is prone to deviation. According to the invention, through a cross validation mechanism of multi-group moment combination in a double-end traveling wave distance measurement method, traveling wave signal moments received by monitoring nodes are subjected to full-scene non-repeated selection and verification, and through combination of dual validation logic of length difference judgment and reflected wave time matching, the risk of misjudgment possibly caused by signal interference in single moment selection is effectively avoided; in particular, the accurate fault point location is further screened out through feature comparison and dynamic movement verification of the amplitude of the reflected wave and the main traveling wave signal, the problem of positioning deviation caused by interference such as advanced arrival of the reflected wave and signal superposition in traditional traveling wave distance measurement is solved, and the accuracy and stability of fault point positioning are remarkably improved.

Provided are a heat dissipation fin construction method, a related apparatus, and a heat dissipation fin. The heat dissipation fin construction method comprises: setting a plurality of structural parameter sets according to the preset numerical ranges of the twill angle, the wave amplitude, and the wavelength of a heat dissipation fin; separately obtaining respective heat transfer coefficients and air side pressure drops of the structural parameter sets, and establishing a fitting relationship between the heat transfer coefficients and the air side pressure drops for structural parameters; generating a corresponding performance map and a corresponding contour map on the basis of performance data of the fitted structural parameter sets; and determining an optimization interval of the wave amplitude and the wavelength of the heat dissipation fin according to the contour map, and constructing the heat dissipation fin according to the optimization interval.

The invention provides an anti-interference echo signal detection method and system for an ultrasonic flowmeter, and relates to the technical field of signal processing. Comprising the following steps: identifying wave crest positions and wave trough positions of a plurality of continuous waves in an ultrasonic echo signal, and determining time and amplitudes of the wave crest positions and the wave trough positions; calculating wave amplitudes of the plurality of waves, judging whether the wave amplitudes of the plurality of waves are all greater than an amplitude threshold, and if so, meeting the amplitude requirement; calculating wave crest frequencies and wave trough frequencies of the plurality of waves, judging whether differences between the wave crest frequencies and the wave trough frequencies of the plurality of waves and the frequency of the driving signal are within a set frequency width range or not, and if so, meeting the frequency requirement; the ultrasonic echo signals meeting the amplitude requirement and the frequency requirement at the same time serve as effective echo signals. According to the method, the echo signal is identified and positioned by taking the echo frequency and the echo amplitude as judgment conditions, so that the situations of signal failure and the like caused by abnormal deformation of the signal are reduced.

The invention discloses a three-phase coupled falling type dangerous rock surge amplitude prediction method which comprises the following steps: when a dangerous rock impacts a water body to form a cavitation bubble, the cavitation bubble is subjected to three stages of development, contraction and closing, and data of the thickness a of the dangerous rock, the length Lpot of the cavitation bubble and the water depth hw are acquired; the speed v0 and the initial potential energy Ec of the dangerous rock at the moment of making contact with the water surface and the initial kinetic energy Ek0 of the dangerous rock at the moment of impacting the water surface are calculated; iteratively solving the movement speed in all subsequent movement time, and establishing a speed-time relation curve after the dangerous rock enters water; according to the speed at any moment, the corresponding cavitation bubble diameter, the change rate and the change rule of the cavitation bubble potential energy along with time are obtained, and then the potential energy maximum value of the cavitation bubble above the closed point is obtained; the surge wave energy conversion rate is solved according to the maximum cavitation bubble potential energy value, and finally the maximum surge amplitude is solved. The method has the advantages that the energy conversion mechanism of the gas-phase substance in the wave making process is quantified by introducing the cavitation kinetic model, and the wave amplitude prediction precision is remarkably improved.

This invention discloses a method for testing the amplitude and phase characteristics of plane waves in a compact field quiet zone based on scattering measurements. It primarily addresses the shortcomings of existing methods, such as the difficulty in testing the amplitude and phase characteristics of plane waves in a compact field quiet zone and the challenge in eliminating environmental clutter interference. The implementation scheme is as follows: Spatial coordinate calibration of the area to be tested determines the coordinates of sampling points. A standard scatterer is placed at each point, and its single-station scattering data is measured. The standard scatterer is moved to the next sampling point, and this measurement process is repeated until scattering data from the standard scatterer at all sampling points are obtained. Environmental clutter in the data is filtered out using a range gate filter. The radiation pattern of the compact field feed antenna is measured, and a target scattering field compensation matrix is ​​constructed. This matrix is ​​used to compensate for the scattering of the filtered results. The amplitude and phase characteristics of the plane wave in the compact field quiet zone are calculated based on the compensation results, and the range of the compact field quiet zone is determined using these characteristics. This invention can achieve relatively simple measurement of the amplitude and phase characteristics of a compact field quiet zone and can be applied to the performance testing and analysis of compact field quiet zones.

The invention provides an experimental determination method for an annular flow pattern interface shear force, and belongs to the technical field of gas well drainage and mining processes, the method comprises the following steps: carrying out a visual physical simulation experiment, observing an annular flow pattern flow state, taking a base membrane area as a liquid membrane main body bearing part, uniformly distributing ripples with micron-order wave amplitudes on the surface, and taking the ripples with micron-order wave amplitudes as a liquid membrane main body bearing part; a disturbance wave area shows three-dimensional wave structure characteristics, a liquid film structure under different flow parameters is a complex combination of disturbance waves and ripples, the disturbance wave area is divided into a base film area and the disturbance wave area, and for the base film area, a sectional roughness expression is constructed with the critical liquid film thickness as a threshold value; for a disturbance wave area, Weber number, Froude number, pipe diameter and liquid phase Reynolds number expressions are introduced, and an experimental determination method of the annular flow pattern interface shear force is provided through weighted solution. Therefore, the calculation method is high in actuarial performance, and a theoretical basis is provided for optimization design of the drainage and mining process.

The present application relates to photovoltaic power generation technical field, disclose a kind of pulse width modulation method and inverter, comprising the following steps: obtaining three-phase initial, DPWM modulation wave;First common-mode modulation wave is generated;According to the reference modulation wave of first common-mode modulation wave amplitude and three-phase initial modulation wave;Whether three-phase reference modulation wave amplitude is in the set range is compared: yes then first common-mode modulation wave amplitude is multiplied with correction coefficient and obtains second common-mode modulation wave amplitude;Otherwise first common-mode modulation wave amplitude is used as second common-mode modulation wave amplitude.Second common-mode modulation wave is generated.The superposition obtains three-phase output modulation wave.The present application combines the clamping state of the modulation wave of three-phase DPWM of three-phase inverter, the first common-mode modulation wave is smoothly handled, effectively eliminates the high-frequency harmonic component of first common-mode modulation wave, and then determines three-phase output modulation wave according to the second common-mode modulation wave and the three-phase initial modulation wave, thereby improve the system stability of three-phase inverter.

The application belongs to the technical field of marine resource development, and is a calculation method for vortex-induced vibration of a deep-sea mining riser under the action of internal waves. According to wave parameters such as the wave amplitude and wavelength of the marine internal waves, the velocity and acceleration distribution characteristics of the flow field are determined to provide load input for the calculation of vortex-induced vibration of the deep-sea mining riser. The marine internal wave flow field has significant particularity, which is different from uniform flow and typical shear flow, and is a kind of non-uniform shear flow. Based on the particularity of the marine internal wave flow field, the vortex-induced load distribution on the deep-sea mining riser under the action of the improved traditional wake oscillator model is obtained. In view of the geometric nonlinearity problem caused by the large slenderness ratio of the deep-sea mining super-long riser and the weak constraint characteristics of the deep-sea mining riser, the rigid body displacement and elastic deformation of the riser are separated and calculated by using the co-rotational coordinate method, so as to improve the calculation efficiency to meet the actual engineering requirements, and form the calculation method for vortex-induced vibration of the deep-sea mining riser under the action of the marine internal waves.