17 results about "Critical frequency" patented technology

The invention discloses an order noise evaluation method and device, and relates to the technical field of noise analysis. The method comprises the following steps: acquiring a noise time-domain signal and a rotating speed time-domain signal, and obtaining a three-dimensional noise spectrum signal; determining all to-be-selected frequency points corresponding to the target rotating speed based on the three-dimensional noise spectrum signal; determining the frequency points of which the intermediate critical frequency bands of the to-be-selected frequency points meet preset requirements, and obtaining a plurality of target frequency points; based on the three-dimensional noise spectrum signal, calculating protrusion ratios corresponding to the plurality of target frequency points, and determining the maximum protrusion ratio as a target protrusion ratio; and evaluating the to-be-evaluated order noise based on the target outburst ratio. According to the method and the device, the frequency points of the intermediate critical frequency band including the order noise frequency band in the to-be-selected frequency points are determined, so that the evaluation of the whole frequency band range covering the order noise is ensured, the full-band evaluation of the influence range of the order noise is realized, the comprehensiveness of order noise rating is improved, and the accuracy of the evaluation result of the order noise is improved.

The application discloses a kind of acquisition methods for the acoustic transfer characteristics of a through-hull piping system, which comprises the following steps: obtaining the acoustic transfer characteristics of the piping system in the frequency range of 5Hz-1st critical frequency, drawing the relationship curve, and taking the 1st peak point on the curve; determining each high-order critical frequency, calculating and obtaining the relationship between the amplitude A of the peak point in the acoustic transfer characteristics relationship curve of the piping system and the frequency f; drawing the relationship curve between the amplitude of the peak point and the frequency, and determining the peak point of each frequency band on the curve, and calculating the acoustic transfer characteristics relationship of the corresponding peak point frequency band. The beneficial effects of the present application are: based on the traditional method, the peak point-frequency relationship of the acoustic transfer characteristics curve of the through-hull piping system is given, and an acquisition method for the acoustic transfer characteristics of the through-hull piping system is proposed, which can be used for the evaluation of the acoustic transfer characteristics of the system piping in the frequency band of 5Hz-1000Hz in the preliminary design stage of the through-hull system.

The application discloses an ionospheric parameter inversion method and system based on short-wave time difference information. A plurality of near-distance receiving stations are used to form a receiving station cluster, so that the reflection area of the short-wave propagation path corresponding to each receiving station in the ionosphere is approximately a common ionospheric reflection area, and a same set of F2 layer parameters is used to describe the ionospheric state of the area. The application obtains the observation time difference of each receiving station relative to a reference receiving station, performs ray tracing forward in a candidate parameter space to obtain the theoretical group path of each receiving station and calculate the theoretical time difference, searches for optimal ionospheric parameters by taking the error minimization of the observation time difference and the theoretical time difference as a criterion, and realizes the inversion of the F2 layer critical frequency, the peak height and the half thickness of the common ionospheric reflection area. The application uses the relative time difference between the receiving stations to replace the absolute propagation time delay for inversion, eliminates the influence of non-ionospheric factors such as the unknown transmission time, system delay and receiver clock difference, and improves the inversion precision and reliability.

The application discloses an F2 layer critical frequency continuous field reconstruction method and device, equipment and medium, and relates to the ionosphere space parameter prediction field, and comprises the following steps: adding a to-be-predicted space position as a node to an initial heterogeneous graph to obtain a target heterogeneous graph; processing the target heterogeneous graph through a preset graph attention network to obtain an F2 layer critical frequency prediction value corresponding to the to-be-predicted space position; the F2 layer critical frequency prediction value is a prediction value generated based on a scaling relationship between the F2 layer critical frequency and electron density; and performing a continuous field reconstruction operation based on a plurality of F2 layer critical frequency prediction values. Thus, the correlation of different discrete ionosphere sonde stations is utilized by the graph attention network, the F2 layer critical frequency is predicted in combination with the scaling relationship between the F2 layer critical frequency and electron density, the F2 layer critical frequency accuracy and the robustness under disturbance conditions can be improved, and the F2 layer critical frequency of any space position can be predicted, so that the reconstruction of the continuous space field is realized.

This invention discloses an automatic frequency-elevation map measurement method and system based on residual networks, enabling rapid and automatic extraction of key ionospheric parameters from frequency-elevation maps acquired by digital altimeters. The method first parses the header information and echo intensity data from the original binary file of the altimeter to generate a frequency-elevation map image. Then, a small number of samples are manually labeled to establish a training set with critical frequencies such as foF2 and h'F2 as ground truth. Based on this, an end-to-end model including a backbone residual network, pooling layers, and a feature extraction head is built. This model is trained to convergence through backpropagation and further fine-tuned using expanded sample data to obtain an engineering-deployable model. Finally, the frequency-elevation map to be processed is input into the model, and the predicted values ​​of the target parameters are output and written to the results file. This method reduces the workload of manual interpretation and verification and improves the measurement accuracy of irregular and disturbed frequency-elevation maps.

The present invention relates to a method for operating a motor (4) by means of pulse width modulation, wherein during the period duration (T) Periode During the period, with a pulse duration (T) on At least one pulse width modulation signal pulse (70) is generated at the pulse position (T0) of the pulse, wherein the resulting amplitude spectrum (64) is at the critical frequency ( kritisch The amplitude value (A) is located at a position where at least one time parameter (T) of the pulse width modulation is present. Periode T0, T on ) by time parameter (T) Periode T0, T on ) and correction factor (T) korr The sum of ) is replaced by the correction factor (T) korr The amplitude spectrum (64') is altered so that the calculated amplitude spectrum is at the critical frequency ( kritisch The amplitude value (I) is reduced at point ) Amp ), and among them, the time parameter (T) is used. Periode T0, T on ) and the changed correction factor (T) korr ) to perform pulse width modulation.

The invention discloses a short-wave communication highest available frequency prediction method based on long-term and short-term prediction data fusion processing. The method comprises the following steps: collecting F2 layer critical frequency in vertical detection data as long-term prediction data; identifying and marking an abnormal value in the original data, replacing the abnormal value by using long-term prediction data at the same moment in the current month, and taking data of an adjacent day after the abnormal value is replaced as short-term prediction data; performing data fusion on the long-term prediction data and the short-term prediction data to obtain continuous time sequence data; and inputting continuous time sequence data into the trained LSTM neural network model to obtain the highest available frequency of the short wave in the future time. According to the method, real-time fusion observation is estimated through Kalman filtering recursion, outliers are dynamically inhibited, and the optimal steady state of a linear system is kept; the data fusion technology is adopted to predict the highest available frequency, the characteristics of short-term prediction and long-term prediction are combined, and the highest available frequency of short-wave communication can be predicted more accurately in a long time.

The invention discloses a thermal power generating unit control method and device, a storage medium and electronic equipment. The method comprises the following steps: acquiring a frequency characteristic value of a main frequency conversion drainage pump and liquid level information of a low-pressure heater, wherein the frequency characteristic value is a key frequency boundary value; dividing the operating frequency range of the main variable-frequency drainage pump into a plurality of frequency intervals according to the frequency characteristic value, and setting a corresponding opening calculation rule according to the operating characteristic of each frequency interval so as to form an opening frequency curve; determining the target frequency of the main variable-frequency drainage pump according to the liquid level information of the low-pressure heater so as to control the main variable-frequency drainage pump to operate according to the target frequency; the initial opening degree of the recirculation regulating valve is determined according to the opening degree frequency curve and the target frequency; and the initial opening degree is corrected according to the outlet flow of the main variable-frequency drainage pump, the opening degree of the recirculation regulating valve is controlled to be the corrected opening degree, and therefore stable control over the liquid level of the low-pressure heater and safe operation of the main variable-frequency drainage pump are achieved.

This invention proposes a frequency selection method and system for massive MIMO skywave communication based on ionospheric maps, addressing the problems of limited channel capacity, low signal-to-noise ratio, and the strong frequency selectivity of the ionosphere, which makes it difficult to support multi-user access in skywave communication. The method includes: acquiring historical ionospheric observation data to construct an ionospheric map; calculating the azimuth and elevation angles between the base station and each user based on the geographical location information of the base station and each user; determining the location of the ionospheric reflection point based on the elevation angle and obtaining the critical frequency by querying the ionospheric map, thereby determining the carrier frequency range corresponding to the user's elevation angle; within the carrier frequency range, establishing a joint optimization model of the carrier frequency and precoding vector, and solving for the optimal carrier frequency and the corresponding precoding scheme. This invention can effectively improve the multi-user transmission rate and spectrum utilization efficiency of massive MIMO skywave communication systems and is suitable for high-reliability long-distance communication scenarios in complex ionospheric environments.

The invention discloses an Es layer propagation loss calculation method based on key thickness inversion. The method comprises the following steps: step 1, performing ionogram Es full-shielding and half-shielding identification; step 2, acquiring shielding frequency and critical frequency of the ionogram Es; 3, inverting the key thickness d of the ionized layer Es; 4, calculating the oblique propagation reflectivity of the ionized layer Es; and step 5, calculating ionosphere Es propagation loss. According to the method disclosed by the invention, the key thickness of the Es layer is reconstructed by utilizing the shielding frequency and the critical frequency of the ionogram, so that the propagation loss of various Es layers is given. Meanwhile, the critical frequency and the shielding frequency of the Es layer are considered, the key structure information of the Es layer can be complemented, and the accuracy of calculating the reflection loss of the Es layer is improved.

The invention discloses a direct-current micro-grid low-frequency oscillation analysis method and system under VSM control. The method comprises the following steps: determining a transfer function relationship between a small semaphore of a duty ratio of a current oscillation period and an acceleration of a virtual voltage of the current oscillation period and a transfer function relationship between an acceleration of a virtual voltage of a next oscillation period and the small semaphore of the duty ratio of the current oscillation period, calculating an iterative transfer function Mfg (s) from the current oscillation period to the next oscillation period, substituting a critical frequency point into the Mfg (s) to calculate an amplitude hFIF, if the hFIF is greater than 1, enabling the direct current voltage to generate a positive feedback effect and divergence, if the hFIF is less than 1, enabling the direct current voltage to generate a negative feedback effect and converge, and if hFIF1 is equal to 1, enabling the system to be in a critical stable state; the method has the advantages that the calculation burden is small, the internal relation and the dynamic interaction between the state variables are considered, and the physical characteristics of the system are visually revealed.

This invention discloses a method for determining the frequency stirring bandwidth of electrically large metal cavities based on small samples, belonging to the field of electromagnetic compatibility testing technology. The method includes the following steps: S1, configuring the test system and determining the test parameters; S2, calibrating the vector network analyzer and saving the real and imaginary parts respectively; S3, calculating candidate stirring bandwidths based on the frequencies within the test band; S4, selecting a bandwidth value from S3, using a non-parametric bootstrapping algorithm to self-sample it into M×N dimensional samples, and organizing them into magnitude values; S5, performing an A / D test on the magnitude values ​​to determine the critical frequency; S6, obtaining the critical frequency cluster corresponding to the candidate stirring bandwidths from S3, calculating the standard deviation, and selecting the candidate stirring bandwidth with the smallest standard deviation as the frequency stirring bandwidth. This method solves the technical problem of lacking an accurate method for determining the frequency stirring bandwidth of electrically large metal cavities under small sample conditions.

The invention relates to a method for generating a modulation signal (68) for a chopper using a delta-sigma modulation for damping critical frequencies, the method comprising at least the following steps: determining a transfer function, wherein a transfer function comprises a noise transfer function (56), generating an output sequence (69) by way of a delta-sigma modulator (55) by processing an input signal (63) by way of a quantizer (60) and a feedback path (61) of the delta-sigma modulator (55), using the generated output sequence (69) as a chopper sequence (53), integrating (34) a pseudo noise sequence (59) and the transfer function by way of an adding process in order to modify the input signal (63) before it is quantized, wherein a modified sequence (66) is generated, quantizing the modified sequence (66), wherein a modulation signal (68) is generated, feeding back the modulation signal (68) and repeating the determination (31) and quantizing to form the delta-sigma modulation and controlling the chopper based on the modulation signal (68).

The invention relates to a sky wave communication F2 layer critical frequency prediction (foF2) method and system. Firstly, ionosphere foF2 historical observation data and multi-source environment parameters in the global range are obtained, and the most representative input characteristics are obtained through screening by comprehensively analyzing the correlation between foF2 and multi-source space environment driving factors under the conditions of different latitudes and different local time. Then, a space-time cross gating mechanism is introduced, feature enhancement and dynamic weight adjustment are carried out on space position embedding, a driving parameter sequence and a historical foF2 sequence, and self-adaptive extraction of key change factors of the ionized layer is achieved. And then, by constructing a Transform network structure based on a multi-head self-attention mechanism, carrying out long-time dependence modeling on ionosphere spatio-temporal evolution in a global range so as to obtain a global foF2 distribution prediction result at a future moment. According to the method, the foF2 prediction precision of low-weft, middle-weft and high-weft regions can be remarkably improved, and available frequency planning and reliability evaluation of a sky wave communication link are improved.

The invention discloses an electrically large metal cavity frequency stirring bandwidth determination method based on a small sample, and belongs to the technical field of electromagnetic compatibility test, and the method comprises the following steps: S1, configuring a test system and determining test parameters; s2, calibrating the vector network analyzer, and respectively storing the vector network analyzer as a real part and an imaginary part; s3, calculating to obtain an alternative stirring bandwidth in combination with the frequency in the test frequency band; s4, selecting one broadband value in the step S3, adopting a nonparametric bootstrapping algorithm, carrying out self-sampling on the broadband value to obtain M * N-dimensional samples, and arranging the M * N-dimensional samples to form module values; s5, carrying out AD test on the modulus value, and determining a critical frequency; and S6, obtaining a critical frequency cluster corresponding to the alternative stirring bandwidth in the S3, calculating a standard deviation, and selecting the alternative stirring bandwidth with the minimum standard deviation as a frequency stirring bandwidth. With the adoption of the method, the technical problem that the frequency stirring bandwidth of the electrically large metal cavity is not accurately determined under the small sample condition is solved.

In some embodiments, a method and system for controlling distortion of the output of a miniature speaker by attenuating at least one critical frequency band of the input signal to be reproduced, using tuning parameters that have been predetermined where the critical frequency band is a frequency range of the speaker's frequency response in which Total Harmonic Distortion (THD) peaks. The distortion control is performed in a manner which allows an increase in the average loudness of the speaker's output without significantly increasing distortion. The tuning parameters include a center frequency and a bandwidth of the critical frequency band, and a power threshold value. In some embodiments, the system is a loudness maximizer configured to limit distortion of a speaker's output by limiting distortion in a critical frequency band using predetermined control parameters, and limit the dynamic range of the output signal and increase its perceived overall average loudness level.

The invention discloses an in-vehicle rough sound evaluation method and device, electronic equipment and a storage medium, and relates to the technical field of noise evaluation.The method comprises the steps that in-vehicle noise signals of a vehicle are collected, filtering processing is conducted on the in-vehicle noise signals, and noise sub-signals corresponding to a plurality of continuous critical frequency bands are obtained; performing signal processing on the noise sub-signals based on a preset masking effect model to obtain a roughness contribution value of each critical frequency band; and determining an in-vehicle coarse noise evaluation result according to the roughness contribution value of each critical frequency band. Therefore, according to the method, the masking effect model in psychoacoustics is introduced, so that the actual working principle of a human auditory system during complex sound processing is simulated, roughness analysis is carried out on the collected in-vehicle noise signals, the accuracy and credibility of an in-vehicle noise evaluation result are improved, meanwhile, a large amount of time and labor cost are saved, and the accuracy and reliability of in-vehicle noise evaluation are improved. And the test efficiency is improved.