37 results about "Time domain algorithm" patented technology

Signals of interest in magnetic resonance imaging (MRI) systems comprise narrowband, circularly polarized (CP) radio-frequency magnetic fields from rotating atomic nuclei. Background “body noise” may comprise broadband, linearly polarized (LP) magnetic fields from thermally-activated eddy currents, and may exceed the signal in a band of interest, limiting the imaging resolution and requiring excessive averaging times. Noise may be selectively detected and substantially suppressed, while enhancing the signal of interest, using appropriate digital time-domain algorithms. At least two quadrature receiving antennas may be employed to distinguish and separate the LP noise from the CP signal. At least one broadband receiver may be used to identify and localize fast noise sources and to digitally filter the representation of their radio-frequency magnetic fields in the signal. Selective body noise reduction may allow enhanced signal-to-noise ratio of the system, leading to improved imaging resolution and shorter scan time.

The invention belongs to the field of optical communication, and is applied to the polarization demultiplexing of a polarization diversity multiplexing coherent optical communication system. According to the invention, for the problem of the polarization demultiplexing in the polarization diversity multiplexing coherent optical communication system, a special training sequence and related algorithms are designed. Through the method, a coherent receiver can fast, automatically and accurately perform the polarization demultiplexing. As the track of the training sequence, viewed from a planisphere, rotates along a unit circle after sign power is normalized, the training sequence provided by the invention is called a constant rotation sign training sequence. The invention discloses two processing algorithms for the constant rotation sign training sequence, which are a frequency-domain algorithm and a time-domain algorithm respectively, wherein the frequency-domain algorithm can be combined with frequency-domain dispersion compensation without adding a frequency spectrum calculation module. Through the method, the receiver does not need synchronizing with an initial position of the training sequence.

The invention discloses an external radiation source radar direct wave recovery method adopting blind source separation. The method comprises the following steps that: (1) a linear array receives signals x1(n), ..., xN(n), and a digital wave beam is formed; (2) wave beam signals yS(n) of a reference radio station and wave beam signals y1(n), ..., yJ(n) of J interference radio stations are input into an instant ICA (independent composition analysis) blind source separation module, then output signals p0(n), p1(n), ..., pJ(n) of the blind source separation are sent to an ambiguity-resolving processing module, and obtaining the signal q(n) of the reference radio station; (3) yl(n) is input into a plurality FIR (finite impulse response) filters of a spatial domain-fast time domain module, two-dimensional self-adaptive filtering processing is carried out through a multi-dimensional spatial domain-fast time domain algorithm, and a monitoring channel signal z(n) is output and obtained; and (4) based on the signal q(n) of the reference radio station and the monitoring channel signal z(n), a time delay Doppler plane of a target is calculated. According to the invention, the sequence ambiguity problem of output signals of the blind source separation method is solved, and the reliable reference radio station direct wave recovery is ensured.

The invention provides a pilot protection method of a VSC-HVDC (Voltage Source Converter-High Voltage Direct Current) power transmission circuit based on shunt capacitance parameter identification. According to the pilot protection method, internal and external faults are distinguished by identifying shunt capacitance values at two sides of the VSC-HVDC power transmission circuit by adopting a time domain algorithm. When the direct-current power transmission circuit generates an external fault, the capacitance values at two sides of the circuit can be accurately identified simultaneously; and when the direct-current power transmission circuit generates an external fault, the capacitance values at two ends of the circuit cannot be identified simultaneously. According to the characteristics, pilot protection criteria are constructed. The pilot protection method is simple in principle, easy to implement, not affected by transition resistance, circuit distributed capacitance and control modes and can be used for rapidly and reliably distinguishing the internal and external faults under various working conditions. The pilot protection method can be not only used for supplementing main protection of the traditional VSC-HVDC power transmission circuit, but also used for accelerating backup protection action. The pilot protection method provided by the invention is not only suitable for a two-end VSC-HVDC system, but also suitable for a multi-end VSC-HVDC system.

The invention discloses a bumpy platform SAR rapid time domain imaging method based on a mixed coordinate system. The method comprises the following steps of carrying out distance direction matching filtering processing on a baseband echo signal to obtain a distance-compressed signal; dividing a subaperture to construct a mixed coordinate system imaging grid; carrying out backward projection on each subaperture data on the mixed coordinate system imaging grid; and carrying out a rapid backward projection or rapid decomposition backward projection algorithm in the mixed coordinate system on a sub-aperture image in the mixed coordinate system to obtain an SAR image with a full spatial resolution. In the invention, a polar coordinate subaperture imaging grid in a rapid time domain algorithm is replaced with a mixed coordinate grid, a two-dimensional interpolation in the time domain imaging algorithm is optimized, execution efficiency of the time domain algorithm is improved, and a processing speed and imaging quality of the time domain algorithm are increased and improved.

Ferromagnetic material hardness prediction algorithm based on improved BP neural network algorithm. Firstly, the Barkhausen signal of ferromagnetic material is collected, the signal set is divided, and the Barkhausen noise training set and Barkhausen noise test set are obtained. Then the collected signal is analyzed by AR spectrum. The second derivative of the expanded signal is obtained by choosing five orders of expansion, which are 4, 8, 16, 32 and 64 respectively. The valley width, the valley depth and the position of the valley point of the second order derivative signal are taken as thecharacteristics. The valleys are encoded by kmeans algorithm, thus the unification of the characteristic dimensions is achieved Then the BP neural network model is optimized and trained. The simulation results show that the prediction result of the invention is very good, and the mean square error is only 80, that is, the error of each hardness prediction can be guaranteed to be 9 Vickers hardness, and the mean square error of the time domain algorithm is 229, that is, more than 15 Vickers hardness, so the algorithm is proved to be effective.

The invention belongs to the field of aeronautical material performance test, and relates to a piezoelectric crystal plate resonant frequency measurement method. According to the method, a short-term high-voltage pulse method is adopted to excite a piezoelectric crystal plate, the piezoelectric crystal plate generates response vibration, a high voltage pulse is used as wideband excitation, the piezoelectric crystal plate responds selectively to vibration, and the vibrational frequency of the piezoelectric crystal plate is the resonant frequency of the piezoelectric crystal plate. According to the method, a pure time domain algorithm is adopted, the method is direct and simple and convenient, is small in interference factor, and high in accuracy. The piezoelectric crystal plate in a certain shape corresponds to more than one resonant frequency. For example, a round crystal plate has a high-frequency thickness mold vibration resonant frequency and a low-frequency radial mold resonant frequency. The method can totally measure the resonant frequency of mold vibration in different directions.

The invention relates to a method for detecting an interference shape of a broadband spectrum based on longitudinal phase splicing. The method comprises the following steps: controlling an interference objective to longitudinally scan and move through a piezoelectric ceramic precise moving station by virtue of a Mirau-type white light interference system, and storing a series of collected broadband spectrum interference images; calculating the collected interference images by virtue of frequency domain and time domain algorithms, so as to obtain the distribution of modulation degrees and wrapped phases; setting a reasonable modulation degree threshold, and determining whether to carry out phase expansion on a pixel point according to the size of each pixel point; and carrying out longitudinal phase splicing by virtue of effective regions of the two adjacent images, and finally splicing the interference images, so as to obtain absolute phase distribution of the whole measured shape and the surface shape restoration. The method has the characteristics that the measurement precision is high, and the influences caused by the scanning moving precision are low; and particularly, aiming at the detection of a high-depth micro-nano structure, the measurement speed is high, and the practicability is strong.

The invention discloses an electromagnetic wave three-dimensional reverse time migration imaging method under a higher-order time domain algorithm, and relates to the computing electromagnetics and broadband radar detection. The method is suitable for the exploration and data collection and imaging of an underground object of a UWB (ultra wide band) radar and a hidden medium region, and is also widely suitable for the geological prospecting, road inspection and through-wall imaging. The forward direction field distribution of a time domain excitation signal received by the UWB radar and the reverse field distribution of a time domain observation signal received by the UWB radar are obtained through a three-dimensional high-order time domain finite difference method and an experiment signaldetected by the UWB radar. The method theoretically overcomes the inclination restriction under the condition that the requirements of the reverse time migration imaging are met, and can achieve theprecise imaging. The method employs the radar signal for the numerical simulation of the reverse time migration imaging simulation of a target region, and can effectively obtain the dynamic information of a to-be-detected object. Compared with a conventional electromagnetic imaging algorithm, the method is higher in imaging resolution, and layers a solid foundation for the discrimination of the to-be-detected object and the parametric inversion.

Signals of interest in magnetic resonance imaging (MRI) systems comprise narrowband, circularly polarized (CP) radio-frequency magnetic fields from rotating atomic nuclei. Background “body noise” may comprise broadband, linearly polarized (LP) magnetic fields from thermally-activated eddy currents, and may exceed the signal in a band of interest, limiting the imaging resolution and requiring excessive averaging times. Noise may be selectively detected and substantially suppressed, while enhancing the signal of interest, using appropriate digital time-domain algorithms. At least two quadrature receiving antennas may be employed to distinguish and separate the LP noise from the CP signal. At least one broadband receiver may be used to identify and localize fast noise sources and to digitally filter the representation of their radio-frequency magnetic fields in the signal. Selective body noise reduction may allow enhanced signal-to-noise ratio of the system, leading to improved imaging resolution and shorter scan time.

The present invention discloses a hypersonic flight target flow field model and electromagnetic model coupling method. The method comprises: taking an appropriate volume to contain a target and a surrounding flow field assembly model of the volume, carrying out required electromagnetic grid division on the volume, mapping each flow field grid node to the electromagnetic grids, and taking the meanvalue of flow field node data contained in the electromagnetic grid for the grid containing the flow field nodes in the electromagnetic grid to replace the flow field data at the location of the electromagnetic grid; using the existing data electromagnetic grid linear interpolation technology for the remaining electromagnetic grids to obtain flow field data at the locations of the electromagneticgrids; converting the flow field data at locations of all electromagnetic grids into electromagnetic parameters required by the electromagnetic simulation through the formula; and establishing a plasma Drude model, and converting the plasma Drude model into a time domain for simulation and calculation. The coupling method disclosed by the present invention is more reasonable, and can better show the superiority of the time domain algorithm.

The invention discloses a Turbo time domain equalization method for short-wave communication, and the method comprises the steps: firstly carrying out the equalization of a received signal through anMMSE equalizer; inputting the data into a decoder for decoding; constructing average information and variance information by utilizing soft information output by a decoder; calculating a transverse filter tap coefficient at the jth moment by utilizing the variance extrinsic information matrix; simulating a received signal in combination with known multipath channel parameters and average extrinsicinformation so as to obtain estimation of the signal; and finally, enabling the MMSE equalizer to equalize the multipath signal again by using the analog receiving signal r and the real receiving signal r. According to the method, complex matrix inversion operation in a time domain algorithm is avoided, the processing complexity of iterative equalization is effectively reduced, linear and nonlinear interference can be eliminated at the same time on the premise that the equalization performance is not reduced, and the calculation complexity can be greatly reduced.

The invention provides an acoustic wave equation reverse time migration imaging method based on a pseudospectral time-domain algorithm and relates to geophysical exploration. The method is characterized by, according to specific situations of an initial model and with existing computing resource states being combined, reasonably dividing shot aperture and shot interval, and by utilizing calculation resources, calculation time and precision, setting each shot interval, shot aperture, source position and depth of each shot to be same; carrying out processing on each shot; after all shots are processed independently, superposing imaging results of all shots in sequence according to specific division situations to form an overall imaging result; and for the imaging result, carrying out filtering on low-frequency noise through a high-pass filter, thereby improving imaging resolution. Numerical simulation is the most important component of reverse time migration imaging; in the reverse time migration imaging, a two-way wave equation needs to be subjected to wavefield continuation; and in the solving process, numerical iteration and cross correlation of a source wavefield and a detector wavefield need to be realized simultaneously, which need to be realized concretely through a certain numerical method.

The invention discloses a surface acoustic wave sensor frequency-temperature analytical time domain algorithm. The surface acoustic wave sensor frequency-temperature analytical time domain algorithm is characterized in that the surface acoustic wave sensor frequency-temperature analytical time domain algorithm comprises the following steps that: step 1, the natural frequency f0 of a surface acoustic wave sensor is determined; step 2, the reflection frequency f of the surface acoustic wave sensor is made to be equal to the natural frequency f0; step 3, a relationship between temperature and the reflection frequency is determined, and the relationship between the frequency of the surface acoustic wave sensor and the temperature can be represented by the formula that f0(T)=f0(T0)[1+a<f>(1)(T-T0)+a<f>(2)(T-T0)2+a<f>(3)(T-T0)3+...], wherein a<f>(i) w is an i-order temperature coefficient under a reference temperature T0; and step 4, a temperature value can be obtained according to the relationship between the temperature and the reflection frequency. With the surface acoustic wave sensor frequency-temperature analytical time domain algorithm adopted, temperature inside a switch cabinet can be analyzed according to the change of the frequency. The monitoring precision of the surface acoustic wave sensor frequency-temperature analytical time domain algorithm can be so high that the precision can be within 1 DEG C.

The invention discloses a high-sampling-rate vibration analysis device based on a Zynq Ultra Scale + MPSoC platform. The high-sampling-rate vibration analysis device comprises a front-section analog circuit, the Zynq Ultra Scale + MPSoC platform and peripheral equipment, the front-section analog circuit is used for conditioning signals of the acceleration sensor and the rotating speed sensor; theZynq Ultra Scale + MPSoC platform is used for processing a signal; and the peripheral equipment comprises an LCD display screen and is used for displaying processing results of the frequency domain algorithm and the time domain algorithm. The problems that in the prior art, the real-time performance is low, and real-time analysis and positioning of working states of all parts of the rotating machine by technicians are not facilitated can be solved.

The invention provides a rapid backward projection imaging method based on offline projection, and a rapid time-domain imaging idea based on an offline projection method is provided aimed at solving the problem that a time-domain algorithm is high is computational complexity and long in time consumption. Aimed at an application scene determined according to the geometric relation of imaging and known in advance, an offline calculation manner is used to calculate and store variables needed in the backward projection algorithm in advance, the flexibility and high precision of the time-domain algorithm are maintained, and in the imaging process, the calculation steps can be reduced substantially and time consumption of imaging is reduced.

The invention relates to an all-vanadium redox flow battery peak power estimation method based on a rolling time domain algorithm, and the method comprises the steps: estimating the peak power of a battery in a future period of time based on a first-order equivalent circuit model, on the basis of known model parameters and a battery charge state, the peak power of the battery in a period of time in the future is estimated by adopting a rolling time domain method, and the error between the expected output at the future moment and the predicted output at the future moment is compensated through the predicted control quantity at the future moment according to the principle of the rolling time domain method. According to the method, it is assumed that the peak current changes in the estimation period, according to the target function, the optimization variable is the battery current, and it is expected that the battery is charged or discharged as much as possible, and the peak current is optimized.

The invention relates to an implantable antenna work site performance test method and system. The method comprises the following steps: acquiring a field test signal of a tested implantable antenna byusing a free space test field, acquiring an antenna direct wave signal in the field test signal by using a time domain gate function, and according to the antenna direct wave signal and an antenna model of the implantable antenna based on an electromagnetic field time domain integral equation theory and a time recursion method, obtaining the radiation characteristic of the implantable antenna; and based on a time domain EPMCHW algorithm, obtaining the far-field radiation characteristics of the implantable antenna in the work site model according to the radiation characteristics of the implantable antenna. According to the method, the influence of the equipment where the implantable antenna is located and the application environment of the implantable antenna on the antenna radiation performance is considered, the far-field radiation characteristics of the implantable antenna in the specific application environment are obtained on the basis, targeted performance testing can be carriedout on the implantable antenna in the working site environment, and a more accurate testing result is obtained.

The invention discloses a time domain and frequency domain combined non-reciprocal medium micro-discharge threshold prediction method. The method is characterized in that a time domain method and a frequency domain method are combined, and in order to solve the problem that a non-reciprocal medium electric field and a non-reciprocal medium magnetic field cannot be accurately solved in a time domain algorithm, a finite element method is used for solving the size and distribution of the fields in a frequency domain; in order to solve the problem of low efficiency of a particle propulsion calculation method in a frequency domain algorithm, a solving frequency domain field is combined with a time domain algorithm, so that the operation efficiency is further improved. In addition, a particle motion technology, a secondary electron emission model and particle-electromagnetic boundary conditions are utilized to quickly calculate and predict the micro-discharge threshold of the non-reciprocalmedium. Particularly, when the micro-discharge threshold value is calculated, the prediction track of the equivalent macro particle motion can be obtained, so that the distribution of the equivalent macro particles and the electric quantity of the macro particles can be predicted.

The invention discloses an electromagnetic wave three-dimensional reverse time migration imaging method under a higher-order time domain algorithm, and relates to the computing electromagnetics and broadband radar detection. The method is suitable for the exploration and data collection and imaging of an underground object of a UWB (ultra wide band) radar and a hidden medium region, and is also widely suitable for the geological prospecting, road inspection and through-wall imaging. The forward direction field distribution of a time domain excitation signal received by the UWB radar and the reverse field distribution of a time domain observation signal received by the UWB radar are obtained through a three-dimensional high-order time domain finite difference method and an experiment signaldetected by the UWB radar. The method theoretically overcomes the inclination restriction under the condition that the requirements of the reverse time migration imaging are met, and can achieve theprecise imaging. The method employs the radar signal for the numerical simulation of the reverse time migration imaging simulation of a target region, and can effectively obtain the dynamic information of a to-be-detected object. Compared with a conventional electromagnetic imaging algorithm, the method is higher in imaging resolution, and layers a solid foundation for the discrimination of the to-be-detected object and the parametric inversion.

The invention relates to an infrared weak and small target detection method and device based on an image inpainting technology. The method comprises the following steps: extracting a to-be-processed current frame infrared image from an infrared video image, respectively detecting weak and small targets through a spatial domain algorithm and a time domain algorithm, merging suspected weak and small target areas obtained by the two ways into a candidate weak and small target area, digging out the candidate target area from an original infrared image, and obtaining a weak and small target area; the method comprises the following steps of: recovering and estimating a pixel where a candidate target is located by using an image inpainting technology, reconstructing a current frame of infrared background image, subtracting the current frame of infrared background image from the current frame of infrared background image to obtain a target saliency map, and segmenting the target saliency map to obtain a weak target. According to the method, the detection rate of the infrared weak and small target is effectively improved, false alarms caused by noise, clutter, edges and other factors are reduced, the algorithm complexity is low, the calculation amount is small, and the real-time requirement in actual engineering application is easily met.

The invention provides a pilot protection method of a VSC-HVDC (Voltage Source Converter-High Voltage Direct Current) power transmission circuit based on shunt capacitance parameter identification. According to the pilot protection method, internal and external faults are distinguished by identifying shunt capacitance values at two sides of the VSC-HVDC power transmission circuit by adopting a time domain algorithm. When the direct-current power transmission circuit generates an external fault, the capacitance values at two sides of the circuit can be accurately identified simultaneously; and when the direct-current power transmission circuit generates an external fault, the capacitance values at two ends of the circuit cannot be identified simultaneously. According to the characteristics, pilot protection criteria are constructed. The pilot protection method is simple in principle, easy to implement, not affected by transition resistance, circuit distributed capacitance and control modes and can be used for rapidly and reliably distinguishing the internal and external faults under various working conditions. The pilot protection method can be not only used for supplementing main protection of the traditional VSC-HVDC power transmission circuit, but also used for accelerating backup protection action. The pilot protection method provided by the invention is not only suitable for a two-end VSC-HVDC system, but also suitable for a multi-end VSC-HVDC system.

The invention discloses a method for removing vertical stripes of an infrared image in real time by utilizing improved local moment matching, which is suitable for gun sights, gun sights and hardware of an uncooled infrared detector, in infrared movement hardware of the uncooled infrared detector, the image acquisition frame frequency is 50Hz, and according to the video frequency 25Hz which can be recognized by human eyes, the image acquisition frame frequency is 20Hz. Under the condition that the final output observation video frame rate is not influenced, the time domain algorithm processing advantage is carried out in combination with the infrared image, and the frequency is determined to be 50 Hz; the infrared movement hardware has a separation blade correction function, and can correct and compensate the heterogeneity of an infrared image; the infrared focal plane detectors share one amplifier in the same column; compared with the prior art, the method has the advantages that the vertical stripe noise of the infrared detector is filtered in real time on a machine core assembly of the uncooled infrared detector, and the infrared image detection capability is improved.

The invention discloses an external radiation source radar direct wave recovery method adopting blind source separation. The method comprises the following steps that: (1) a linear array receives signals x1(n), ..., xN(n), and a digital wave beam is formed; (2) wave beam signals yS(n) of a reference radio station and wave beam signals y1(n), ..., yJ(n) of J interference radio stations are input into an instant ICA (independent composition analysis) blind source separation module, then output signals p0(n), p1(n), ..., pJ(n) of the blind source separation are sent to an ambiguity-resolving processing module, and obtaining the signal q(n) of the reference radio station; (3) yl(n) is input into a plurality FIR (finite impulse response) filters of a spatial domain-fast time domain module, two-dimensional self-adaptive filtering processing is carried out through a multi-dimensional spatial domain-fast time domain algorithm, and a monitoring channel signal z(n) is output and obtained; and (4) based on the signal q(n) of the reference radio station and the monitoring channel signal z(n), a time delay Doppler plane of a target is calculated. According to the invention, the sequence ambiguity problem of output signals of the blind source separation method is solved, and the reliable reference radio station direct wave recovery is ensured.

The invention provides a rapid backward projection imaging method based on offline projection, and a rapid time-domain imaging idea based on an offline projection method is provided aimed at solving the problem that a time-domain algorithm is high is computational complexity and long in time consumption. Aimed at an application scene determined according to the geometric relation of imaging and known in advance, an offline calculation manner is used to calculate and store variables needed in the backward projection algorithm in advance, the flexibility and high precision of the time-domain algorithm are maintained, and in the imaging process, the calculation steps can be reduced substantially and time consumption of imaging is reduced.

The invention belongs to the field of optical communication, and is applied to the polarization demultiplexing of a polarization diversity multiplexing coherent optical communication system. According to the invention, for the problem of the polarization demultiplexing in the polarization diversity multiplexing coherent optical communication system, a special training sequence and related algorithms are designed. Through the method, a coherent receiver can fast, automatically and accurately perform the polarization demultiplexing. As the track of the training sequence, viewed from a planisphere, rotates along a unit circle after sign power is normalized, the training sequence provided by the invention is called a constant rotation sign training sequence. The invention discloses two processing algorithms for the constant rotation sign training sequence, which are a frequency-domain algorithm and a time-domain algorithm respectively, wherein the frequency-domain algorithm can be combined with frequency-domain dispersion compensation without adding a frequency spectrum calculation module. Through the method, the receiver does not need synchronizing with an initial position of the training sequence.

The invention relates to the technical field of satellite navigation, in particular to a method for obtaining an anti-interference signal of a satellite navigation receiver. The method comprises steps: preprocessing the signal sent by the antenna array to obtain an intermediate frequency signal containing an interference signal which is not completely filtered; wherein the intermediate frequency signals are respectively used as inputs of a space-time domain algorithm and a power inversion algorithm to obtain corresponding output results; and multiplying the result output by the power inversionalgorithm by the result output by the space-time domain algorithm to obtain an anti-interference signal, namely a signal obtained by the satellite navigation receiver. According to the method, a space-time domain algorithm and a power inversion algorithm are combined, and when the signals sent by the antenna array to the satellite navigation receiver contain pulse interference, broadband interference and weak interference signals, the interference signals can be suppressed by the algorithm, so that the quality of the signals received by the satellite navigation receiver is improved.

The invention discloses a coal monitoring method and device based on a reverse time migration imaging algorithm and a storage medium, and the method comprises the steps: obtaining source wave field data transmitted at each moment of a target region, and receiving reflection echo data corresponding to the source wave field data; determining target receiving data based on the reflection echo data and pre-detected receiving data, and performing reverse continuation on the target receiving data based on a preset pseudo-spectrum time domain algorithm to obtain receiving wave field data at each moment in the target area; performing wave field decomposition on the source wave field data and the receiving wave field data to obtain decomposed source wave field data and decomposed receiving wave field data; performing cross-correlation imaging on the decomposed source wave field data and the decomposed receiving wave field data at the same moment to obtain each cross-correlation imaging result; and carrying out filtering processing on each cross-correlation imaging result, and determining a final reconstructed image of the target area. The technical problem of low monitoring accuracy of a complex geological structure is solved.