377 results about "Acoustical impedance" patented technology

The invention provides a PCBA circuit board defect detection method, apparatus and device, and a storage medium. The method comprises the steps of obtaining three-dimensional point cloud data of the surface of a circuit board by projecting multispectral composite structured light; performing feature fusion on the multi-modal image of the circuit board according to the three-dimensional point cloud data to generate a fused multi-channel feature map; performing non-rigid registration on the acoustic impedance distribution data and the three-dimensional point cloud data to generate an acousto-optic fusion defect probability distribution diagram; performing multi-scale edge detection on the fused multi-channel feature map to generate an optimized binary edge map; and performing scattering transformation on the optimized binary edge graph, and determining the defect type of the circuit board according to the acousto-optic fusion defect probability distribution graph. Through implementation of the scheme, non-rigid registration is performed by using the acoustic impedance distribution data and the three-dimensional point cloud data, the acousto-optic fusion defect probability distribution diagram is generated, the surface three-dimensional information and the internal acoustic impedance data are combined, internal hidden defects are effectively identified, and comprehensive detection of surface and internal defects is realized.

The invention discloses an ultrasonic enhanced tactile sensor system, a sensor and a sensing method. The tactile sensor system comprises a multi-mode sensing unit and a processing unit. The multi-mode sensing unit integrates an ultrasonic module and a visual tactile sensing module, ultrasonic acoustic impedance matching and optical imaging transmission are achieved through an acousto-optic matching structure, and ultrasonic echo signals and tactile deformation images can be synchronously collected. In the processing unit, an event triggering module detects a contact event based on a tactile image and generates a switching signal, and a self-adaptive processing module dynamically controls an ultrasonic mode, distance measurement during non-contact, and switching to object internal imaging or material property identification during contact according to the switching signal. And the three-level fusion processing module outputs a multi-modal sensing result through signal-level synchronous acquisition, feature-level cross-modal fusion and decision-level task switching. According to the system, multi-dimensional perception of proximity sense, surface texture and deep information is realized, and the pre-judgment and accurate operation capability of the robot in a complex scene is improved.

The invention discloses a B-ultrasonic auxiliary diagnosis system based on artificial intelligence. The B-ultrasonic auxiliary diagnosis system comprises a data acquisition and preprocessing module used for acquiring B-ultrasonic images and performing standardization processing; the physical characteristic extraction module is used for extracting physical characteristics of acoustic impedance, attenuation coefficients, echo intensity and scattering and reflection modes and providing embedded data for the feature fusion module; the feature fusion and representation module is used for deeply combining physical characteristics and spatial features through a multi-modal feature fusion and adaptive graph convolution method to generate high-dimensional feature representation; the deep learning diagnosis model module is used for realizing joint optimization of feature learning and diagnosis tasks on the basis of a multi-task deep neural network framework guided by physical semantics; and the visualization and auxiliary diagnosis module is used for presenting diagnosis results and providing decision support for doctors through thermodynamic diagrams, multi-modal analysis and intelligent explanation. According to the method, the limitation of a traditional deep learning model under the challenges of low contrast, noise interference, data shortage and the like can be solved.

The invention relates to the technical field of crack image analysis, in particular to a building crack width measuring method based on image analysis, which comprises the following steps of: acquiring an autofluorescence attenuation image of a building surface under ultraviolet excitation, and generating a crack response coefficient matrix according to a material aging degree; driving micro-area pulse thermal imaging based on the crack response coefficient matrix, and extracting a heat conduction abnormal boundary as a crack physical edge; surface attachment interference is eliminated through an edge acoustic impedance matching model, and the real width value of the crack is calculated under a material intrinsic coordinate system. According to the method, the normal width of the crack is measured through uniform point selection in the main axis direction, the measured value is subjected to weighted fusion in combination with the local acoustic impedance matching weight, the obtained width result can better reflect the actual structural integrity and elastic continuity of the crack, geometric quantities are provided, and the local damage degree is reflected; the method is suitable for subsequent structure analysis and safety evaluation.

The invention belongs to the technical field of acoustic devices and ultrasound, and discloses an ultrasonic transducer, a multi-layer gradient acoustic impedance matching layer and a preparation method of the multi-layer gradient acoustic impedance matching layer, and the multi-layer gradient acoustic impedance matching layer comprises a plurality of acoustic impedance layers which are arranged in sequence and have different acoustic impedances; in the direction from the first acoustic impedance layer to the last acoustic impedance layer, the acoustic impedance of the acoustic impedance layer is in a decreasing trend; the surface of the previous acoustic impedance layer is provided with a micro-columnar structure, the micro-columnar structure extends into the next acoustic impedance layer, a mechanical interlocking interface is formed between the previous acoustic impedance layer and the next acoustic impedance layer through the micro-columnar structure, and the micro-columnar structure is gradually thinned from the bottom to the tip. According to the invention, the gradient impedance design of the acoustic impedance layers significantly reduces the acoustic reflection between the acoustic impedance layers, improves the acoustic energy transmission efficiency, and widens the working bandwidth of the ultrasonic device; the micro-columnar structure not only maintains the stability of interlayer adhesion in a high vibration or thermal stress environment, but also further smooths gradient transition and reduces interface reflection.

The invention discloses a method, a system, equipment and a medium based on a multi-composite ultrasonic penetration technology, and the method comprises the steps: generating high-frequency fundamental ultrasonic waves through a piezoelectric transducer array, and adjusting the frequency range to match the acoustic impedance characteristic of target soil; first, second and third harmonics are generated through the induction of a nonlinear medium in the fundamental wave propagation process, the phases of the harmonics are adjusted to realize coherent superposition, and the fundamental wave and the first, second and third harmonics are guided into a composite waveguide device for focusing and delay compensation to form a high-energy composite wave beam; a pulse interval is adjusted by adopting an intermittent emission strategy so as to inhibit energy attenuation in the soil; reflected wave spectrum components are monitored through an embedded acoustic sensor array, and driving parameters are dynamically adjusted; and residual ultrasonic energy is captured and fed back to a driving circuit to form a closed-loop energy utilization system. By integrating multi-order harmonic resonance and a dynamic frequency tuning technology, efficient transmission and deep penetration of ultrasonic energy in a complex medium are realized.

The invention provides a textile cloth defect real-time detection method and system based on multi-modal feature fusion, and the method comprises the steps: collecting visual image data, infrared thermal imaging data and ultrasonic acoustic data of textile cloth through a multi-sensor array, and forming multi-modal input; performing time sequence alignment and noise filtering preprocessing on the multi-modal data to eliminate motion artifacts and environmental interference; a parallel feature extraction module is used for extracting texture features from the visual data, extracting temperature distribution features from the thermal imaging data and extracting acoustic impedance features from the acoustic data. By deeply fusing complementary information of three modes of vision, thermal imaging and ultrasonic wave, the detection capability is improved, the vision mode captures surface texture details, the thermal imaging mode reveals thermodynamic anomalies related to friction and materials, the ultrasonic wave mode perceives subcutaneous structure defects, hidden flaws which cannot be recognized by a single mode can be found, and the detection efficiency is improved. Therefore, the omission ratio is greatly reduced, and flaw types are distinguished more accurately.

The invention relates to an alveolar bone surface tooth root detection method and detector, and the method comprises the following steps: obtaining age data and bone density data of a testee according to CT data and imaging data of the testee, and matching corresponding ultrasonic parameters and acoustic impedance correction parameters; constructing a multi-layer medium acoustic impedance model comprising a tooth root layer of the bone surface of the alveolar bone; configuring transmitted ultrasonic waves based on the ultrasonic wave parameters; receiving an echo signal corresponding to the transmitted ultrasonic wave, and performing adaptive correction on parameters of each layer in the multilayer medium acoustic impedance model based on the acoustic impedance correction parameters by taking minimization of the difference between the echo signal and a theoretical reflection signal obtained by the multilayer medium acoustic impedance model as a target; and based on the multi-layer medium acoustic impedance model after self-adaptive correction, realizing detection of the tooth root on the bone surface of the alveolar bone. Compared with the prior art, the method has the advantages of accurate detection of the tooth root on the bone surface of the alveolar bone, high adaptability and the like.

The invention discloses a reconfigurable acoustical holography modulation method and device based on a crystalline polymer. The programmable acoustical holography device is composed of a single-layer photoresponse crystalline polymerization flat plate, is switched between two phases when the temperature irradiated by laser changes, has a crystalline state and a non-crystalline state, and reversibly changes along with the temperature. Space sound field modulation can be realized by spatially arranging the coding units, the crystalline polymer flat plate subjected to laser patterning phase change is recovered to the previous crystalline state after being cooled, the patterned coding acoustical holography disappears, and new phase acoustical holography is written in, so that a new sound field modulation function is realized. According to the programmable phase acoustical holography device based on the crystalline polymer, the incident plane wave of the probe can be modulated into any three-dimensional complex sound field, and the programmable phase acoustical holography device is of a complete plane type, is matched with underwater acoustic impedance, and is high in acoustic energy coupling efficiency, compact in structure, easy to prepare and low in price.

This invention discloses a method and apparatus for cementing quality inspection based on ultrasonic Lamb waves. The method includes: acquiring a first ultrasonic Lamb wave signal received by a first receiver and a second ultrasonic Lamb wave signal received by a second receiver; calculating the first wave energy of a zero-order symmetric Lamb wave within a first time window of the first ultrasonic Lamb wave signal, and calculating the second wave energy of a zero-order symmetric Lamb wave within a second time window of the second ultrasonic Lamb wave signal; calculating the attenuation rate of the zero-order symmetric Lamb wave based on the first wave energy, the second wave energy, a first distance, and a second distance; comparing the attenuation rate with a pre-generated attenuation rate threshold, and determining the external medium properties based on the comparison result. This approach improves the accuracy of cementing quality inspection; and it allows for independent cementing quality evaluation without the need for combined acoustic impedance information, simplifying the cementing quality inspection process and improving its efficiency.

The invention discloses a micro-scale tin soldering device and method for ultrasonic laser composite energy field coordinated regulation and control. The micro-scale tin soldering device comprises a coordinated energy output module, a multi-physical field monitoring module, a wire feeding module, an intelligent regulation and control system and a motion platform, and a workpiece to be welded is arranged on the motion platform; the collaborative energy output module comprises a laser unit, an ultrasonic vibration unit and a focusable focus lens, the ultrasonic vibration unit comprises an ultrasonic generator, and the multi-physical field monitoring module comprises an infrared thermometer, a high-speed holographic imaging system and an acoustic impedance sensor; the high-speed holographic imaging system is used for recording brazing filler metal molten pool flowing and IMC nucleation dynamic states; the acoustic impedance sensor monitors the ultrasonic energy transmission efficiency; the intelligent regulation and control system is electrically connected with the multi-physics field monitoring module, and a multi-physics field coupling prediction model based on an LSTM neural network is arranged in the intelligent regulation and control system. According to the technical scheme, the structural design is reasonable, the energy field coupling efficiency is high, the material adaptability is high, the structure performance is controllable, the defect rate is remarkably reduced, and practicability is good.

The invention discloses a rotator cuff injury impact test method based on sensor data analysis, and relates to the technical field of intelligent medical equipment, and the method comprises the steps: inputting a joint contracture data set into a generative adversarial network model, carrying out pressure propagation mode analysis through a three-dimensional convolution layer, carrying out energy hot spot aggregation through an attention mechanism layer, and carrying out pressure propagation mode analysis through a three-dimensional convolution layer; the method comprises the following steps: generating a pressure field comprehensive vector of a contracture joint, extracting gradient amplitude and energy density characteristics in the pressure field comprehensive vector, performing neighborhood smoothing through Gaussian average filtering, obtaining an acoustic impedance value matrix, synchronously performing spatial continuous mapping, obtaining an acoustic impedance distribution diagram, and obtaining an acoustic impedance value of the contracture joint according to the acoustic impedance distribution diagram. And performing dynamic compensation on the pressure field comprehensive vector through an acoustic transmission equation to obtain a corrected pressure field comprehensive vector, and converting the corrected pressure field comprehensive vector into an impact control signal through a PID (Proportion Integration Differentiation) controller. According to the invention, through the generative adversarial network model and the PID controller, the multi-physical field data of the joint contracture area can be integrated, and the frequency and pulse width of the shock wave therapeutic apparatus can be adjusted.

The invention belongs to the technical field of biomedical materials, and particularly relates to preparation of a hydrogel ultrasonic coupling patch for long-term stable continuous monitoring. According to the patch, an interpenetrating double-network structure system is formed by an alginate component and a polyacrylic acid component through intermolecular interaction, and the patch has excellent adhesion performance and mechanical performance. Compared with the prior art, by optimizing the components and the preparation process, the obtained hydrogel patch has the following advantages that the excellent acoustic impedance matching characteristic is achieved, and high-fidelity transmission of ultrasonic signals is ensured; the tissue adhesion is strong, and long-term stable attachment can be realized; good mechanical stability and durability are achieved, and the method is suitable for continuous monitoring application. The product effectively solves the technical problems that the traditional liquid coupling agent is easy to lose, the solid coupling patch is insufficient in adhesion and the like, and has important application value in the fields of medical ultrasonic diagnosis and long-term monitoring.

The invention provides a cell acoustic characteristic parameter estimation method and system based on a full-connection neural network and a computer medium, and relates to the technical field of biomedical engineering and micro-nano operation, and the method comprises the steps: constructing a three-layer spherical shell model of a target cell, defining the radius, density and sound velocity of each layer and a surrounding medium, and constructing a three-layer spherical shell model of the target cell; the acoustic impedance and the wave number of each layer are calculated; obtaining a transducer driving parameter, a displacement speed of the cell or equivalent particle solid sphere particle, and physical parameters of the cell and a medium; inputting the input feature data into a pre-trained full-connection neural network model to output acoustic characteristic parameters such as a scattering coefficient and an internal refraction coefficient; and calculating acoustic radiation force based on the acoustic characteristic parameters to realize dynamic control. Based on the full-connection neural network and the three-layer spherical shell model, the cell acoustic parameters are efficiently and accurately estimated, the problems that a traditional method is complex in calculation and insufficient in precision are solved, and accurate operation of the acoustic tweezers on the cells is achieved.

The invention discloses a pipeline detection device and method based on phased array ultrasonic waves, and relates to the technical field of pipeline detection. The pipeline detection device based on phased array ultrasonic waves comprises a shell with an opening in the lower portion and a phased array ultrasonic detector installed in the shell, an arc-shaped filter plate is fixedly connected to the upper portion of a strip-shaped discharging groove in an embedded mode, and a scraping and collecting mechanism used for scraping and collecting a coated coupling agent in time after detection is completed is arranged on the right portion of an inner cavity of the shell. According to the invention, the coupling agent is uniformly coated on the surface of the pipeline in a thickness-constant manner through the self-extrusion coating mechanism, the consistency of acoustic impedance in a welding seam or a detection area is ensured, the stability of ultrasonic echo intensity is improved, and a detection blind area caused by coating missing is avoided, so that the detection accuracy and reliability are improved; couplant can be scraped and collected in time after detection, the retention time of the couplant on the surface of the pipeline is shortened, solidification residues are effectively prevented, and the surface quality of the pipeline is protected.

The invention provides a method and system for controlling a comb for promoting hair growth based on ultrasonic waves, and the method comprises the steps: simulating vibration wave propagation and interference modes under different comb tooth geometrical shapes and arrangement modes through a finite element algorithm, and obtaining a target phase difference range between adjacent comb teeth; a laser Doppler vibration meter is adopted to obtain vibration waves of the comb tooth group in a resonance frequency parameter range, the distribution condition of a superposition area and a counteracting area of the vibration waves is analyzed, and the modulation frequency of local vibration intensity is determined; a scalp bionic acoustic model is built according to acoustic impedance characteristics of human scalp, local vibration intensity modulation frequency is input into the scalp bionic acoustic model, propagation attenuation of ultrasonic waves in the scalp is simulated, and random sampling simulation is performed on sound field distribution in the scalp.

The invention provides a shared excitation source ultrasonic and infrared thermal imaging integrated detection method and system, and the method comprises the steps: applying a shared excitation source to a to-be-detected object, synchronously collecting a multi-channel ultrasonic echo signal and an infrared thermal imaging image, dividing the to-be-detected object into a plurality of target regions, and calculating the frequency band ultrasonic attenuation coefficient and acoustic impedance of each region, further obtaining a densification value; after a heat flow response feature map is extracted from an infrared image, adaptive partitioning is carried out on multi-modal data according to the spatial gradient of a densified value and a heat flow response energy accumulation area, and a plurality of data analysis subsets are formed. For each subset, constructing a local joint dictionary according to the densification value and the heat flow feature of the subset; and performing joint sparse representation on the ultrasonic and infrared features in the subsets by using the dictionary to obtain a group of cross-modal fusion coefficients, accurately determining defect information in the object to be detected based on the fusion coefficients and a defect identification model, and generating a defect distribution diagram.

The invention provides a breast cancer molecular subtype recognition and prediction method and system based on an ultrasonic image, and the method comprises the steps: carrying out the feature fusion preprocessing of a breast ultrasonic image based on acoustic impedance difference, and obtaining a standardized ultrasonic image; dividing the image into fan-shaped regions based on the radial fiber structure of the mammary gland, and dynamically adjusting the window size according to tissue characteristics to carry out adaptive window segmentation to obtain a window set carrying anatomical structure position information; inputting the window set into a pre-trained cross window Transform model for feature extraction, and analyzing a feature association mode between the windows through a cross window attention mechanism to obtain a multi-dimensional ultrasonic feature vector; and inputting the feature vector into a classifier for molecular subtype classification prediction to obtain a breast cancer molecular subtype identification prediction result. According to the method, through adaptive window segmentation, breast anatomical structure information is utilized, local and global feature association is captured through a cross window attention mechanism, and the prediction accuracy is improved.

The invention discloses a surface acoustic wave resonator and a filter. The surface acoustic wave resonator comprises a substrate; the interdigital transducer is positioned on one side of the substrate; the reflecting grating and the interdigital transducer are arranged on the same layer, and the reflecting grating is located on the two sides of the interdigital transducer in the first direction; the plurality of reflecting gratings are arranged along a first direction and extend along a second direction; in the first direction, a reflecting grating gap is formed between any two adjacent reflecting gratings; the first direction and the second direction intersect and are parallel to the plane where the substrate is located; the orthographic projection of the acoustic impedance structure on the plane where the substrate is located is at least overlapped with the orthographic projection of the reflecting grating gap on the plane where the substrate is located; the acoustic impedance of the acoustic impedance structure is different from the acoustic impedance of the reflecting grating. By adopting the technical means, the acoustic impedance structure is arranged, and the acoustic impedance of the acoustic impedance structure is different from that of the reflecting grating, so that a stray mode in the resonator can be inhibited, and the performance of the surface acoustic wave resonator is further improved.

The invention discloses a solid ultrasonic gel patch as well as a preparation method and application thereof, and belongs to the technical field of medical chemistry. The solid ultrasonic gel patch is prepared from an acrylamide monomer, polyvinyl alcohol, sodium polyacrylate, sodium carboxymethyl cellulose, nano silicon dioxide, propylene glycol, glycerol, acrylic acid, triethanolamine, a cross-linking agent, an initiator and water according to a specific ratio. The prepared solid ultrasonic gel patch is highly matched with human soft tissue in acoustic impedance (about 1.62-1.63 * 10 < 6 > Pa.s / m), low in acoustic attenuation coefficient (less than or equal to 0.034 dB / (cm.MHz)), moderate in skin adhesion, excellent in flexibility and moisture retention, capable of solving the problems that a traditional ultrasonic coupling agent is inconvenient to use, easy to dry, poor in experience and the like, and suitable for acoustic wave conduction in ultrasonic examination and treatment.

The invention discloses a method for inverting the velocity of a cementing medium after casing based on ultrasonic Lamb waves, and relates to the field of geophysical logging. According to the method, ultrasonic Lamb wave logging and ultrasonic pulse reflection logging are carried out at all depth points through a post-casing scanning imaging logging instrument, waveform records at all the depth points are obtained, the thickness of a casing in the specified direction at all the depth points and acoustic impedance of a post-casing cementing medium are calculated in an inversion mode, and then the thickness of the casing in the specified direction at all the depth points and the acoustic impedance of the post-casing cementing medium are calculated on the basis of the ultrasonic Lamb wave logging waveform records. For each specified orientation of each depth point, Fourier transform is carried out on the full waveform of the near-bending Lamb wave and the full waveform of the far-bending Lamb wave, the phase difference of the far-bending Lamb wave and the far-bending Lamb wave is calculated, group delay processing is carried out, the working frequency band of the imaging logging instrument is scanned after combination, and the phase difference of the far-bending Lamb wave and the near-bending Lamb wave is calculated; and frequency values corresponding to the minimum values of the group delays at all the directions of all the depth points are obtained, and after a frequency set is obtained, the wave velocity and the medium type of the cementing medium after casing are determined according to the frequency values at all the directions in the frequency set, the frequency number of the minimum values and the acoustic impedance value.

An apparatus may include a display stack, an ultrasonic sensor stack and a high-impedance stack including one or more high-impedance layers. The ultrasonic sensor stack may include an ultrasonic transceiver layer and an ultrasonic transceiver circuitry (UTC) layer. Each of the high-impedance layers may have an acoustic impedance that is higher than an acoustic impedance of the UTC layer. The high-impedance stack and the ultrasonic sensor stack may form an acoustic resonator bounded by the UTC layer and the high-impedance stack. The acoustic resonator may be configured to enhance the ultrasonic waves transmitted by the ultrasonic sensor stack at a peak frequency of the ultrasonic sensor stack. The peak frequency may be a frequency used by the ultrasonic sensor stack for obtaining fingerprint images. An apparatus stack portion that includes the ultrasonic sensor stack may have a thickness corresponding to a multiple of a quarter wavelength at the peak frequency.

The invention provides an MEMS heart sound and electrocardio detection system, method and equipment, and relates to the technical field of medical instruments, the MEMS heart sound and electrocardio detection system comprises a bionic cilium heart sound sensor, an electrocardio acquisition circuit and a signal fusion model; the bionic cilia heart sound sensor comprises hollow bullet type bionic cilia and a cantilever beam microstructure; the hollow bullet type bionic cilia and the cantilever beam microstructure are mechanically coupled, and the cantilever beam microstructure comprises a Wheatstone bridge formed by arranging a plurality of piezoresistors and is used for collecting heart sound signals; the electrocardio acquisition circuit and the bionic cilium heart sound sensor are packaged in an acoustic impedance matching mode, and the electrocardio acquisition circuit comprises an electrocardio acquisition electrode plate, a power supply voltage stabilization module, an instrument amplification module, a band-pass filtering module and a notch filter and is used for acquiring and conditioning electrocardio signals; the signal fusion model comprises a Resnet18 feature extractor, an encoder and a mutual cross attention mechanism, and is used for performing feature extraction, linear transformation and feature deep fusion on the collected electrocardiosignals and electrocardiosignals and outputting a signal classification result.

The invention relates to the field of high-end ultrasonic transducer manufacturing, and particularly discloses a patch type ultrasonic transducer for deep tissue imaging and an acoustic material preparation method, and a backing preparation method comprises the following steps: weighing an adhesive, a metal filler and a non-metal additive according to a mass ratio of 15: 55-75: 2; fully and uniformly mixing the weighed raw materials, and putting the mixed sample into a molding mold capable of demolding; the pressure is maintained for 10-30 min under the conditions that the pressure is larger than 10 MPa and the plasticizing temperature of the adhesive is reached, then the heating function is turned off, when the temperature is reduced to 120 DEG C, the pressure is rapidly reduced to 0 MPa at the moment, the adhesive is taken out when the adhesive is naturally cooled to the room temperature, and the backing is obtained. The problems of high sound attenuation, low sound impedance and low sound velocity preparation of the backing are solved, the dilemma problem of low sound impedance and ultrahigh sound attenuation is effectively solved, and the problem that the ultrathin design of the wearable patch type ultrasonic transducer conflicts with the maintenance of excellent acoustic performance due to insufficient sound attenuation of the existing backing is effectively solved.

The invention discloses a forest biomass nondestructive testing device and method in forestry carbon sink measurement, and relates to the technical field of forestry resource monitoring and carbon sink evaluation, the device comprises a multi-mode sensing unit, an underground biomass monitoring module and a data processing unit, the multi-mode sensing unit collects forest stand data through cooperation of a microwave radar, a laser radar and a hyperspectral imaging assembly. The underground biomass monitoring module collects acoustic impedance data of a root system; the data processing unit comprises an environment feature recognition module, a dynamic calibration engine, an organ recognition unit, a dynamic carbon distribution unit and a carbon sink metering module, the method comprises the following steps: cooperatively acquiring data through an air base and a foundation, analyzing environment features, dynamically calibrating, segmenting organs and generating a carbon distribution coefficient, and finally calculating the carbon sink amount of a single tree according to a formula. According to the invention, non-contact multi-parameter synchronous acquisition is realized, environmental changes are adapted through dynamic calibration, accurate metering is realized by means of organ-level carbon distribution, and the precision and reliability of forestry carbon sink metering are improved.

The invention discloses a modeling method of an acoustic impedance calculation model for an ablated surface of a carbon-based composite material, and belongs to the field of aerospace. Aiming at the defects of a modeling method of an existing Fedorov acoustic impedance model on a carbon-based fiber material, heat flow resistance and heat characteristic length are introduced on the basis of a formula of an original impedance model, and a dimensionless complex dynamic compressibility coefficient is modified, so that the Fedorov acoustic impedance model is developed from a four-non-acoustic-parameter impedance model to a six-non-acoustic-parameter impedance model. An impedance model used for correction is a JCAL acoustic impedance model, the impedance model is often used in the acoustics field to predict the surface acoustic impedance of the irregular fiber material, and then the prediction precision of the original impedance model on the surface acoustic impedance of the non-uniformly distributed carbon-based fiber material is improved. And fitting the improved impedance model into a test result of an impedance tube experiment through parameter inversion to obtain non-acoustic parameter data suitable for the ablated carbon-based composite material, and obtaining an improved acoustic impedance model suitable for the carbon-based composite material.

The embodiment of the invention relates to a noise reduction device and power equipment. The noise reduction device comprises an air duct structure and a first expansion chamber. The air duct structure includes an air duct wall defining an air duct including an inlet and an outlet. The air duct wall comprises a first wall, and a first hole is formed in a first area of the first wall. The first expansion chamber is adjacent to the first wall of the air duct structure and comprises a first expansion chamber wall, the first expansion chamber wall and the first wall define a first space, and the first space communicates with the air duct through the first hole. The first aperture is configured such that acoustic impedance within the duct increases at the first region by an amount exceeding a first threshold to prevent acoustic waves of a first frequency band entering the duct through the inlet from passing through the outlet. Through the technical scheme of the embodiment of the invention, the noise emitted by the noise source can be effectively reduced, and the noise pollution of the environment is reduced.

The invention provides a method for detecting dissolved gas in transformer oil, and belongs to the technical field of dissolved gas in transformer oil, and the method comprises the following steps: firstly, transmitting a plurality of groups of ultrasonic waves with different frequencies into the transformer oil at the same time, obtaining and preprocessing a joint spectrum, and then utilizing a wavelet multi-scale decomposition technology considering a time sliding window to obtain a pre-processed joint spectrum; the signal is disassembled into a stable spectrum and three levels of fluctuation spectrums. Extracting the characteristics of interference, spectrum attenuation, waveform complexity, coupling, energy distribution and the like from each level of fluctuation spectrum, and calculating the influence characteristics of microbubbles on ultrasonic waves, including acoustic attenuation, propagation velocity, scattering, acoustic impedance change and nonlinear acoustic characteristics. By performing weight fusion on the three-level fluctuation spectrum energy ratio, comprehensive characteristics are generated and input into a gas calculation model, so that the state of gas in transformer oil is accurately evaluated and diagnosed, and the technical problem that an existing offline sampling analysis method is difficult to meet the requirement of a power system for evaluating the running state of a transformer in real time is solved.

The invention relates to the technical field of acoustic measurement, and particularly provides a method for measuring acoustic parameters of a material, which comprises the following steps of: acquiring geometric parameters and an actual sound absorption coefficient of an impedance tube and a sound pressure signal propagating in the impedance tube; a blank pipe simulation model of the impedance pipe is constructed based on the geometric parameters, the inner pipe wall flow resistance rate and the corresponding simulation sound absorption coefficient of the impedance pipe are obtained, and under the condition that the difference value of the simulation sound absorption coefficient and the actual sound absorption coefficient is smaller than or equal to a preset threshold value, the corresponding inner pipe wall flow resistance rate serves as the simulation flow resistance rate; performing simulation based on the simulation flow resistivity to obtain the acoustic impedance of the inner surface of the impedance tube so as to calculate the wavenumber loss factor of the impedance tube; calculating the actual wave number of the impedance tube based on an iterative algorithm and the wave number loss factor; based on the geometric parameters, the sound pressure signals and the actual wave number, acoustic parameters of the to-be-tested material are calculated. The problem that in the prior art, loss in an impedance tube cannot be accurately corrected, and consequently the accuracy is low when acoustic parameters of a material are measured is solved.

The invention relates to a planar active focusing air coupling ultrasonic transducer, and belongs to the technical field of piezoelectric ultrasonic transducers, and the planar active focusing air coupling ultrasonic transducer is characterized in that a piezoelectric plate and a matching layer are arranged in a shell; the rear cover plate covers the tail end of the shell; the interface is arranged on the shell; a plurality of concentric annular structure electrodes are arranged on the first surface of the piezoelectric plate; the width of each concentric ring in the plurality of concentric ring structure electrodes is gradually increased from outside to inside; a second surface of the piezoelectric plate is provided with a second electrode; and the piezoelectric plate is connected with the interface through leads led out from the plurality of concentric ring-shaped structure electrodes and the whole-surface electrode. According to the plane active focusing air coupling ultrasonic transducer provided by the invention, active focusing of a plane acoustic beam is realized by changing the electrode structure of the piezoelectric plate and arranging a plurality of concentric annular electrode structures on the single surface of the piezoelectric plate, and the plane acoustic impedance matching layer with uniform thickness is matched; and the sensitivity of the focusing air coupling transducer is improved under the condition that the transverse resolution of the transducer is not influenced.