44 results about "Virtual source" patented technology

The invention provides a medical linear accelerator virtual source model optimization method which is characterized by comprising the following steps: constructing a virtual source model and inputting initial configuration parameters; obtaining simulated dose distribution data of a typical irradiation regular field based on the model; vertically irradiating on the standard water model through a medical linear accelerator to obtain corresponding measurement dose distribution data; performing priority evaluation and sorting on part of parameters of the virtual source model, and performing iterative adjustment according to the priority until the simulation and measurement dose distribution difference is within a preset range; and inputting the parameters after iteration is completed into the virtual source model to obtain an optimized model. According to the method, full-process automatic optimization of the virtual source model can be achieved, manual intervention is remarkably reduced, the labor cost is saved, the modeling precision and efficiency are greatly improved, and the method is suitable for an efficient and high-precision source modeling process under a complex structure.

The invention relates to a biological tissue full-waveform inversion ultrasonic tomography method which comprises the following steps: placing ultrasonic transducers in a pure water medium with known sound velocity, and recording ultrasonic signal data of each transducer array element; setting a virtual source array in each transducer array element, constructing an optimization problem of sound source directivity and receiver response, and performing iterative optimization to obtain a final response coefficient and a virtual source signal of each transducer array element; the method comprises the following steps: fixing a biological tissue to be detected in an ultrasonic transducer, and collecting experimental observation signals received by each transducer array element; setting a sound velocity model to carry out forward simulation, taking the obtained virtual source signal as a sound source output, interacting with the sound velocity model, and multiplying by a response coefficient to obtain a forward simulation signal; and performing iterative updating on the sound velocity model according to the experimental observation signal and the forward simulation signal to obtain an ultrasonic tomography result. Compared with the prior art, the method has good flexibility and anti-noise capability, and the quality of the reconstructed image is remarkably improved.

The application relates to a deep-sea shadow zone target distance and azimuth fast high-precision estimation method. First, a large-aperture horizontal array is divided into two sub-arrays with a certain horizontal interval, and target azimuth estimation is performed on array receiving signals of the two sub-arrays; second, based on target azimuth estimation results of the two sub-arrays and geometric relation with the target, the sound line propagation distance of the target is estimated, and the sound line propagation distance is converted into the horizontal distance between the target and the receiving array through a virtual source model; finally, the horizontal distance obtained is utilized to correct the horizontal array system direction-finding error in combination with geometric knowledge. Compared with a traditional two-station direction-finding cross positioning method, the positioning precision of the method is higher. The basic principle and implementation scheme of the method are verified through computer numerical simulation, and the result shows that in a typical deep-sea environment, the method can effectively estimate the distance and azimuth of a near-sea surface target.

This invention provides a proton imaging method and imaging device, applicable to the fields of proton imaging technology and signal processing technology, particularly in the field of particle radiation imaging technology. The method includes: determining a virtual source position based on an initial two-dimensional dose distribution of a proton beam acquired without an imaging object; obtaining multiple sub-beam propagation paths from the virtual source position to the multiple predetermined sub-beam center positions based on the virtual source position and multiple predetermined sub-beam center positions on a predetermined plane; obtaining sub-beam data pairs corresponding to the sub-beam propagation paths and the two-dimensional dose distribution based on the two-dimensional dose distribution and the lateral distribution components determined along the sub-beam propagation paths; obtaining multiple water equivalent path lengths corresponding to at least one projection angle through an iterative algorithm based on the multiple sub-beam data pairs corresponding to at least one projection angle; and performing image reconstruction based on the multiple water equivalent path lengths corresponding to at least one projection angle to obtain a target image of the imaging object.

The application discloses a multi-sound source direction-finding positioning method based on a vector microphone in a strong reverberation environment, which comprises the following steps: converting mixed voice signals collected by the vector microphone from a waveform domain to a time-frequency domain to obtain a spectrogram of an observation signal; removing virtual source single time-frequency points by using a frequency smoothing method and iteratively generating low-reverberation self-term source time-frequency point sets; constructing a steering vector dictionary; finding a steering vector most likely to appear in any time-frequency point in the self-term source time-frequency point sets from the steering vector dictionary, and then calculating the STFT coefficient value of the video point corresponding to the source according to the steering vector, determining whether the time-frequency point is a single source time-frequency point not interfered by reverberation according to the STFT coefficient value, and generating a single source time-frequency point set not interfered by reverberation; estimating the number of sources by using a smoothing histogram method; and obtaining multi-source direction-finding results by using MUSIC. The application can accurately extract single source time-frequency points not interfered by reverberation in the time-frequency domain, and then realize accurate multi-source positioning.

This invention relates to the field of micro-motion surface wave exploration methods, and discloses an automatic extraction method for dispersion curves of micro-motion surface waves based on connected component analysis. The method includes cross-correlation extraction of virtual source surface wave shot gathers, frequency-wavenumber domain amplitude spectrum calculation, adaptive threshold binarization, connected component analysis, frequency-wavenumber domain surface wave mask generation, mask-amplitude matrix element multiplication, phase velocity picking, Hampel filtering, and automatic generation of dispersion curves. This invention utilizes image connected component analysis and other operations to process the amplitude spectrum of micro-motion surface waves, separating the surface wave signal region from the frequency-wavenumber domain amplitude spectrum image. It automatically identifies discrete phase velocity points from images containing only surface wave dispersion energy stripes and uses Hampel filtering to remove distortion points, ultimately achieving high-precision automated measurement of the dispersion curve.

In order to solve the problem of low prediction precision in the existing underwater acoustic prediction model, the invention provides the method for constructing the underwater acoustic prediction model of the steel ball, firstly, a time domain signal of underwater entry of the steel ball is collected through a near-field virtual source method and a reverberation method, and through EMD denoising processing, the time domain signal of underwater entry of the steel ball is obtained; and respectively calculating sound power levels and drawing power spectrums, then carrying out filtering fusion to obtain the whole section of radiation sound power when the steel ball enters water, simultaneously extracting an initial impact sound power level, and obtaining bubble pulsation sound power through a difference value. And repeating the multi-working-condition experiment, drawing the change rule of the sound power level along with the particle size and the water falling height, further constructing a three-layer perceptron neural network model, performing training by combining a mean square error loss function, a Dropout strategy and 5-fold cross validation, and finally obtaining a model capable of accurately predicting the water entering acoustic characteristics of the steel ball. The method is suitable for hydroacoustics research and other technical fields.

The invention discloses a three-dimensional acoustic elasticity calculation method based on combined potential, and relates to the field of ship three-dimensional acoustic elasticity calculation, and the method comprises the steps: constructing a speed potential in an outer watershed of an underwater ship structure into a linear combination form of a single-layer potential and a double-layer potential, and constructing a boundary integral equation on a wet surface of the underwater ship structure; according to fluid-solid coupling boundary conditions on the wet surface of the underwater ship structure, a boundary integral equation on the wet surface of the underwater ship structure is solved by adopting a boundary element method, and virtual source intensity distribution on the wet surface of the underwater ship structure is obtained; according to the virtual source intensity distribution of the wet surface of the underwater ship structure and the dry modal displacement of the structure, acoustic elasticity response parameters are obtained through calculation. By constructing the watershed speed potential outside the underwater ship structure in a linear combination form of single-layer potential and double-layer potential, the irregular frequency of acoustic elasticity calculation is effectively eliminated under the condition that the calculation scale and modeling workload are not additionally increased, and the efficiency of three-dimensional acoustic elasticity analysis can be remarkably improved.

The present disclosure relates to ultrasound-based strategies and techniques that are specially designed for time-resolved simultaneous cardiac tissue visualization and intracardiac flow instability mapping. First, to achieve high-resolution tissues images while also acquiring flow data, we devised an acquisition scheme which consists of two batches. The first batch is dedicated to tissue imaging, where we transmit a series of diverging waves emitted from different virtual source locations. These pulses have a single pulse-cycle to optimize axial resolution and are coherently compounded for improving lateral resolution. This paradigm generates tissue images with an improved resolution, allowing for real-time guidance at frame rates up to 50 fps. The second batch is dedicated for flow imaging where all diverging waves are transmitted from the same virtual source location. These flow pulses have a 5-cycle pulse length for improved flow signal. The length of this batch can be adjusted, but our experiments use a length of 64. The final transmission scheme alternates between the tissue batch and flow batch.

The invention provides a method for positioning a ship vibration noise source in a ship pool, and the method comprises the steps: constructing a double-layer envelope surface sound pressure measurement array in the ship pool, and building a ship radiation and pool wall reflection sound field model; establishing a sound field analysis model for inward and outward radiation of a semi-free space cylindrical surface, and constructing a semi-space double-cylindrical surface sound pressure-sound pressure transfer matrix; according to the amplitude and phase of sound pressure measured by double envelope surfaces, ship radiation and reflection sound in a ship pool is separated, and ship vibration noise source positioning in an open half-space water area is realized based on the ship radiation sound in the ship pool and based on a three-dimensional noise source positioning method formed by half-space virtual source wave beams. According to the half-space virtual source beam forming method, the actual acoustic propagation condition and the boundary effect of the ocean can be fully considered, and the spatial distribution and radiation characteristics of a ship noise source in a free sea area are directly obtained through mathematical mapping of a ship pool measurement field and an open water area target field.

An LED luminaire comprising an LED array of LED elements and an optical element. The optical element comprises one or more partially reflective or partially transmissive elements positioned normal to the plane of the LED array. In this way, the partially reflective elements create virtual sources or virtual LED elements by reflecting a portion of the light emitted by the LED elements, while allowing the original or "real" LED elements to remain visible by partially transmitting the light.

The application particularly relates to a message transmission method combining a priori routing and a DTN and a storage medium. The method comprises the following steps: establishing and maintaining a routing table in each node of the network based on a priori MANET routing protocol mechanism; when a message source node transmits a message to a message destination node: firstly, the message is transmitted by using the priori MANET routing mechanism; otherwise, a message copy distribution algorithm based on location information is used, and a DTN mechanism is used to distribute the message copy to a relay node at the topological boundary of the message source node end, so that the relay node becomes a virtual source node; if the message transmission is unsuccessful, the message copy is stored in the relay node at the interruption, so that the relay node becomes a virtual source node; the virtual source node broadcasts routing query information to its neighbor nodes, and the routing table of the neighbor nodes is inquired; when an opportunity to establish a connection with the message destination node is found, the above steps are repeated. The application can improve the reliability of message transmission by using the DTN routing mechanism, and can fully explore the connectable sub-topology in the MANET network.

The invention discloses a cylindrical lithium battery internal temperature field real-time estimation method and system, and the method comprises the steps: building a temperature space distribution model based on a heat conduction equation, normalizing the space-time quantity through scaling transformation, and converting a non-homogeneous boundary condition into a homogeneous boundary condition through variable replacement; decoupling a space-time relationship between the temperature distribution quantity and a heat production item by adopting a double decomposition technology, and regarding a heat production time variable as a virtual source; and establishing a finite-dimensional ordinary differential equation model by using a Galerkin method. Designing a self-adaptive observer, and estimating a low-order state variable and a virtual source time sequence on line by combining a self-adaptive learning algorithm so as to measure and estimate a temperature error driving update rate; and reconstructing a temperature distribution quantity and a virtual source estimation value through space-time synthesis of the estimation sequence and a preset space basis function. Real-time estimation of the internal temperature field and the heat production amount of the cylindrical lithium battery can be effectively realized by means of a small number of thermocouples only through temperature measurement data without voltage and current sensors.

The invention discloses an interference resource scheduling decision-making method based on ray tracing. The method comprises the following steps: step 1, constructing a ray tracing radio wave propagation calculation model based on a virtual source tree; and 2, an interference resource scheduling decision method. According to the method disclosed by the invention, the electromagnetic shielding instrument can be remotely controlled to send the specified signal waveform, the method is suitable for major security electromagnetic management and control working scenes, and different instructions can be effectively and quickly generated according to actual target points, so that signals with different intensities and frequencies are sent out, and a fixed-point accurate interference suppression effect is achieved; and help is provided for subsequent realization of man-machine automatic interaction.

Decoding of Ambisonics representations for a stereo loudspeaker setup is known for first-order Ambisonics audio signals. But such first-order Ambisonics approaches have either high negative side lobes or poor localisation in the frontal region. The invention deals with the processing for stereo decoders for higher-order Ambisonics HOA. The desired panning functions can be derived from a panning law for placement of virtual sources between the loudspeakers. For each loudspeaker a desired panning function for all possible input directions at sampling points is defined. The panning functions are approximated by circular harmonic functions, and with increasing Ambisonics order the desired panning functions are matched with decreasing error. For the frontal region between the loudspeakers, a panning law like the tangent law or vector base amplitude panning (VBAP) are used. For the rear directions panning functions with a slight attenuation of sounds from these directions are defined.

A system for providing spatialized audio in a vehicle, including a vehicle orientation sensor outputting a vehicle orientation signal and being disposed on the vehicle and a controller configured to receive a user orientation signal output from a user orientation sensor being on a wearable that, during use, moves with a first user's head, wherein the controller is further configured to determine an orientation of the user's head relative to the vehicle based, at least, on a difference between the vehicle orientation signal and the user orientation signal, the controller being further configured to output to a first binaural device, according to the orientation of the user's head relative to the vehicle, a first spatial audio signal, such that the first binaural device produces a first spatial acoustic signal perceived by the user as originating from a first virtual source location within a cabin of the vehicle.

The invention relates to the technical field of underground engineering geological exploration and safety monitoring, and discloses an underground hidden engineering geological defect radar detection and analysis system based on optical fiber sensing, which comprises a distributed sensing network for sensing environment vibration, a data acquisition module for acquiring original wave field data, a data preprocessing module for processing the data after the data is purified, and a data processing module for processing the data; the virtual source reconstruction module generates a broadband virtual source response, the wave field frequency modulation module decomposes the broadband virtual source response into a plurality of narrow-band responses, and the reverse time focusing imaging module images each narrow-band response to obtain a group of single-frequency energy focusing images. The resonance characteristic analysis module identifies the physical attribute of the target by analyzing the frequency difference of the focus image, and the three-dimensional visualization module generates a visual three-dimensional attribute label image. The technical problems that a traditional method depends on an artificial seismic source, the cost is high, and defect properties are difficult to distinguish are solved, and the remarkable advantages of being environmentally friendly in detection mode, low in cost, high in efficiency and wide in analysis dimension are achieved.

This invention discloses a method for predicting the impact of sonar baffles on sonar array elements based on the virtual source method. The method includes: establishing an equivalent theoretical model; simplifying the scattering problem of the equivalent theoretical model into a multiple scattering problem between two infinitely long rigid cylinders; deriving an analytical expression for the scattered sound pressure on the surface of the infinitely long rigid cylinders; calculating the theoretical analytical solution for the scattered sound pressure on the cylinder surface; establishing a finite element model of the two infinitely long rigid cylinders and using the model to solve for the scattered sound pressure on the cylinder surface; comparing the model solution with the theoretical analytical solution to verify the correctness and effectiveness of the analytical expression; changing the cylinder size and the distance between the cylinder and the baffle, comparing the calculation results with the case without a baffle, and analyzing the effect of the baffle on the scattered sound pressure on the cylinder surface. This invention ensures computational accuracy while possessing a clear physical mechanism and high computational efficiency, thus providing a reliable research basis and theoretical support for evaluating the impact of sonar baffles on sonar array elements in practical engineering.

The application discloses a seismic wave forward simulation method, device and equipment and a storage medium. The method comprises the following steps: constructing a marine geology model, setting a seismic wave field to be excited from a set depth of a shot point position, generating an upgoing wave and a downgoing wave, loading a last round of a geophone wave field as a secondary virtual field source at a position above the shot point during propagation of the downgoing wave, and simultaneously propagating a real field source and the secondary virtual field source at a position below the shot point; during propagation of the upgoing wave, only the secondary virtual source propagates below the shot point, and the upgoing wave above the shot point contains a real shot point signal and a secondary virtual field source signal; after iterative calculation, multiple wave and ghost wave information of marine seismic data are simulated and separated, and accurate seismic wave data are obtained, so that the marine seismic data can be used for marine seismic analysis, and the accuracy of marine seismic situation analysis is improved.

The application discloses a kind of deep sea direct sound zone near seabed very low frequency line spectrum target ranging method, belong to deep sea signal processing and underwater target positioning field.The method steps include: based on target sea area environmental parameter establishment sound propagation model, through near seabed vertical direct receiving array obtains depth-intensity interference fringe;Copy sound field calculation model is constructed using virtual source method, and three main propagation paths are retained to generate copy interference fringe;To measured and copy stripe are standardized, with cross-correlation coefficient as matching index, realize target distance estimation by peak search.The application realizes the estimation of target sound source distance by matching the depth-intensity interference fringe formed by the near seabed vertical array at a single frequency, with the depth-intensity one-dimensional interference fringe as the matching object, the array aperture is small, the feature dimension is lower, the calculation amount of copy field generated by virtual source method is smaller, and due to the equivalent assumption of virtual source method, the method is not sensitive to environmental mismatch, and has good robustness.

An ultrasound image processing method according to an embodiment of the present disclosure includes transmitting and receiving an ultrasound signal to and from an object through an array in which a plurality of apertures are arranged along one direction, calculating at least one of a transmission delay and a reception delay of the ultrasound signal, and forming a multi-beam through synthetic focusing by reflecting the calculated delay on the ultrasound signal received by the array, wherein the calculating of the delay is calculated through a propagation shape model in which the ultrasound signal transmitted or received through the array is centered on virtual sources parallel to the array.

This invention discloses a noise separation method and system based on spatial sound suppression and equivalent field transformation. The method includes: constructing mutually independent target space, observation space, and virtual sound insulation space; constructing the sound pressure transmission relationship between the target space, observation space, and virtual sound insulation space based on analytical Green's function; establishing a mathematical model using the virtual source point location in the target space, and introducing weighting coefficients to construct a weighted calculation model for the sound pressure at the point to be measured in the observation space; constructing a regularized optimization problem with physical constraints, using the zero sound field amplitude in the virtual sound insulation space as a constraint, and solving for the weighting coefficients of the observation array; using the weighting coefficients to perform spatial domain weighting processing on the signals acquired by the observation array, and extracting the target sound field signal. This invention solves the technical problems of low separation accuracy, numerical instability, and high sampling requirements of existing equivalent source methods under strong noise interference environments, and has many advantages such as strong noise suppression capability, low engineering cost, and high flexibility.

The present disclosure relates to a method and apparatus for fast Monte Carlo (MC) dose calculation using a virtual source model (VSM). The method includes: receiving three-dimensional (3D) CT images obtained by a CT system; receiving 3D planned dose images, 3D organ segmentation contour images, and radiotherapy plans generated by a treatment planning system (TPS); processing 3D CT images, 3D planned dose images, 3D organ segmentation contour images to have the same spatial resolution and matrix size; further processing 3D CT images to convert image intensity to 3D density maps; processing the radiotherapy plans to generate instructions on how to simulate plan delivery; building VSM using inverse cumulative density function (CDF) tables for the simulation of radiotherapy plans, wherein the step of building VSM comprises: receiving output data files containing phase-space information for the radiation output of a specific medical linear accelerator treatment head; calculating the probability of the inplane and crossplane positions of the radiation particles reverse transported from the phase-space surface back to the treatment head; calculating the Gaussian means and standard deviations of the radiation particles' positions at the treatment head; calculating the probabilities for the source of each radiation particle; calculating the probabilities for the medical linear accelerator treatment head to produce different radiation particle species; binning the inplane position probability information of radiation particles into a single histogram for each source and radiation particle species; binning the crossplane position probability information of radiation particles into histograms for each bin of the inplane position histogram for each source and radiation particle species; binning the inplane direction cosine probability information of radiation particles into histograms for each bin of the inplane position histogram for each source and radiation particle species; binning the crossplane direction cosine probability information of radiation particles into histograms for each bin of the crossplane position histogram for each source and radiation particle species; binning the kinetic energy probability information of radiation particles into radially binned histograms for each source and radiation particle species; converting probability densities for inplane and crossplane positions, inplane and crossplane direction cosines, and kinetic energies histograms into cumulative probability densities for each source and radiation particle species; and inverting cumulative probability densities and converting into probability binned inverse CDF tables; simulating and transporting external beams using VSM through virtual treatment machines to the 3D density maps according to radiotherapy plans to produce 3D simulated dose images; and post-processing the 3D planned dose images, 3D organ segmentation contour images, and the 3D simulated dose images to obtain a final report comparing planned versus simulated dose images.

The application provides an ice cover thickness detection method and system based on borehole noise imaging, and relates to the technical field of ice cover geological detection. The method comprises the following steps: arranging a two-dimensional linear survey line composed of multiple geophones around a borehole in an ice cover, collecting continuous noise data composed of mechanical noise generated by borehole operation and auxiliary equipment and environmental background noise; pre-processing the continuous noise data, which comprises the following steps: sequentially performing the following processing on the record of each geophone: removing mean value, removing linear trend, removing strong amplitude events in the time domain, and removing strong amplitude components in the frequency domain, so as to eliminate instrument drift and local strong noise interference, and obtaining pre-processed noise data; selecting one geophone in the two-dimensional linear survey line as a virtual source position, performing mutual coherence calculation on the noise data, and recovering a pseudo-shot gather reflection response corresponding to the virtual source. The application realizes high-resolution imaging of the ice-rock interface.

The present application belongs to the technical field of intelligent seismic exploration, and relates to a kind of passive source seismic data joint intelligent waveform inversion method based on physical guidance, original active and passive source seismic data is preprocessed and then seismic interference reconstruction is carried out, the passive virtual source data obtained is normalized, and passive source data close to active source amplitude is obtained. By building a mapping neural network, and cascading a completely differentiable wave equation forward operator at the network output end to build a physical constraint layer, it can adaptively focus on effective wave field characteristics and strictly follow the dynamics of seismic wave propagation, so as to achieve the purpose of intelligent high-fidelity modeling of complex subsurface velocity structure. By using joint data driving end-to-end to quickly establish a low wave number background velocity model and using a normalized cross-correlation objective function to calculate wave field residuals for physical guidance refinement, high-resolution velocity intelligent inversion is realized under sparse acquisition conditions, and the physical consistency and computational efficiency of the inversion result are greatly improved.

The application discloses a far-field wavelet acquisition method and device, electronic equipment and a storage medium, and relates to the field of geophysical exploration. The method comprises the following steps: acquiring corresponding frequency domain detection data according to near-field detection data of a near-field detector; acquiring an imaginary wavelet of each frequency sampling point according to distances between a sub-source and each near-field detector, distances between a virtual source and each near-field detector, and the frequency domain detection data of the near-field detector; and acquiring a far-field wavelet of a target far-field point at each frequency sampling point according to distances between the sub-source and the target far-field point, distances between the virtual source and the target far-field point, and the imaginary wavelet of each frequency sampling point. The technical scheme of the embodiment of the application not only realizes the calculation and acquisition of the far-field wavelet, improves the accuracy of the calculation result, but also reduces the time consumption of the calculation of the far-field wavelet and improves the calculation efficiency of the far-field wavelet.

Various implementations disclosed herein include devices, systems, and methods that provide realistic acoustic simulation for sound from a virtual source based on a site specific 3D acoustic model of a physical environment. Some implementations obtain first sensor data representing at least a portion of a first boundary of a physical environment while second sensor data corresponding to a second boundary of the physical environment is absent from the first sensor data. In some implementations, the second boundary of the physical environment is estimated based on the first sensor data. Then, a 3D acoustic model representing the physical environment is determined, where the 3D acoustic model includes a 3D shape formed of at least the first boundary and the second boundary. In some implementations, acoustics are provided for sound from a virtual source corresponding to a position within the physical environment, where the acoustics are provided based the 3D acoustic model.

The invention provides a method and a device for measuring the bubble pulsation radiation sound power when a steel ball enters water, aims to solve the problems that sound pressure measurement is greatly influenced by the environment and the bubble pulsation radiation sound power is difficult to accurately obtain in the prior art, and provides the method for measuring the bubble pulsation radiation sound power when the steel ball enters water. The method comprises the following steps: acquiring time domain signals of steel ball water entry through a near-field virtual source method and a reverberation method, performing background noise reduction processing on the two signals by using an EMD method, respectively performing sound power level calculation to obtain respective power spectral densities, and fusing the two power spectral densities to obtain a final signal; therefore, the radiation sound power of the whole section, the initial impact sound and the bubble pulsation sound when the steel ball enters water can be accurately obtained. The method is suitable for underwater acoustic measurement, and is applied to the technical fields of ocean engineering, underwater target identification, fluid mechanics, underwater acoustic physics and the like.

The application discloses a high-precision cross-hole geological radar detection method, comprising the following steps: acquiring radar single-hole self-sending and self-receiving data of a single excitation source of two detection holes respectively, and acquiring radar double-hole transmission data of the two detection holes; generating an initial geological model by using the radar single-hole self-sending and self-receiving data; converting the radar double-hole transmission data into radar single-hole reflection wave data by virtual source mapping; carrying out forward modeling on the radar double-hole transmission data based on the initial geological model to obtain a forward wave field; carrying out wave field reverse continuation on the radar single-hole reflection wave data based on the initial geological model to obtain a reverse-time wave field; imaging the forward wave field and the reverse-time wave field at the same time to obtain imaging results, and then superimposing the imaging results of the excitation sources at different depths of the same detection hole to obtain wave field migration imaging. Compared with the prior art, the method improves the imaging precision.

Provided is an electron gun using a virtual source method that may have a high angular current density, a narrow energy distribution, and stable electron emission characteristics by forming a virtual source inside a thermal electron source (LaB6, CeB6)-based emitter emitting an electron beam.