71 results about "Target strength" patented technology

A fishfinder is provided for identifying with high precision a single fish under the ship and for measuring the length of the fish precisely. An operator of the fishfinder is assisted to grasp the depth and the length of the fish. A fishfinder transmits an ultrasound pulse having a high carrier frequency and an ultrasound pulse having a low carrier frequency by means of a pulse transmission and reception device at predetermined time intervals. A single fish echo is determined and tracked for a plurality of transmission intervals of ultrasound pulses emitted into the water. A target strength of single fish is measured based on the signal strength of a low carrier frequency echo signal from the single fish. The length of the fish is measured based on the target strength. A fish mark is displayed on the screen of an indicator, with the size of the fish mark depending on the fish length.

The invention, which belongs to the technical field of the laser radar, provides a composite-modulation-pulse-code-based 4D imaging photon counting laser radar, so that a problem that the existing photon counting laser radar loses target strength information can be solved. The composite-modulation-pulse-code-based 4D imaging photon counting laser radar comprises a signal generator, a laser, a transmitting optical system, a unidirectional reflector, a scanner, a total reflection mirror, a receiving optical system, a narrow-band filter, a Gm-APD single photon detector, and a signal processing module. An optical signal outputted by the transmitting optical system is transmitted by the unidirectional reflector and is sent into the scanner; the scanner outputs an optical detection signal to a target; an echo signal reflected by the target is transmitted into the scanner; the echo signal outputted by the scanner is reflected by the unidirectional reflector and the total reflection mirror and the is transmitted to the transmitting optical system to carry out collection and echoing; the collected echo signal is filtered by the narrow-band filter and the is detected by the Gm-APD single photon detector; and a detection result is inputted into the signal processing module. The composite-modulation-pulse-code-based 4D imaging photon counting laser radar is mainly applied to target detection.

A computer-readable software stored on a storage medium and executed on a computer to perform an integrated sonar simulation, includes a parameter definition code for defining a plurality of parameters of a sonar, target and sonar environment, and a SNR computation code for computing a SNR of the sonar as a function of range to target, based upon the parameters defined by the parameter definition code. The parameters defined by the parameter definition code include ambient noise, volume scattering strength of the sonar environment, sound velocity profile of the sonar, beam patterns of both projector and receiver of the sonar, type of sonar, range resolution of the sonar, number of eigenrays striking the surface and bottom of the sonar environment, number of eigenrays striking the target, ray trajectories to the target, and surface and bottom scattering strength as a function of angle. The software also includes a target strength model generating code for computing scattering from a selected complex target of a stored set of complex target selections, to thereby generate a target strength model for the selected complex target.

The invention discloses an air conditioner outdoor fan starting method. The air conditioner outdoor fan starting method comprises the following steps of initializing, main controlling and noise feeding back. In the initializing step, an air conditioner is powered on to be started, a main control chip gives an outdoor fan starting instruction, and an EEPROM provides a PWM voltage with the initial duty ratio value being a to an outdoor fan. In the main controlling step, the outdoor fan feeds back the actual rotation speed to the main control chip, the main control chip compares the actual rotation speed with a target rotation speed, and if the actual rotation speed is lower than the target rotation speed, the duty ratio value of the PWM is increased according to the time interval T until the actual rotation speed is equal to the target rotation speed. In the noise feeding back process, noise signals are collected regularly, the strength of the noise signals is compared with target noise strength and if the noise strength is higher than the target strength, the value of the time interval T is increased. According to the air conditioner outdoor fan starting method, the noise strength signal is collected and fed back to a control system to be used as a parameter for outdoor fan starting control, the duty ratio of the fan starting voltage is adjusted in an adaptive mode, the starting noise is effectively reduced, and the matching and debugging workload of a fan system is also reduced.

A quantitative echo sounder includes delay circuits, phase correction circuits, an incidence angle calculator and a directivity correction unit. The delay circuits adjust transmission start timing or phases of acoustic waves radiated by individual vibrating elements based on pitch and roll angles measured by a motion sensing device so that the direction of an acoustic axis of a transmitting beam matches a sounding direction. The phase correction circuits adjust phases of received echo signals based on the pitch and roll angles so that the direction of an acoustic axis of a receiving beam matches the sounding direction. The incidence angle calculator calculates echo signal incidence angle with respect to the sounding direction from phase differences among receiving beam signals obtained by four vibrating element groups. The directivity correction unit corrects a measured target strength by using the echo signal incidence angle calculated by the incidence angle calculator.

The invention discloses a multi-target tracking method in the case of loss of measurement data. The multi-target tracking method includes the following steps: initializing probability hypothetical density and potential distribution of a target state set; predicting the probability hypothetical density and potential distribution of the target state set; updating and converting a deviation matrix and a covariance matrix for measurement; introducing a scaling factor, and changing a gain matrix; using an ellipsoid threshold to remove irrelevant measurement data for the weight of a target strength function; performing trimming and merging, and extracting a target state; determining if a target exists or not, returning to the step of predicting the probability hypothetical density and potential distribution of the target state set if so, otherwise ending target tracking. According to the invention, the scaling factor is introduced during updating of a CPHD filter to regulate the filter gain matrix, and the robustness of the filter can be improved; a self-adaption threshold can simplify a measurement set, the observation number of a current observation set is reduced, all the measurement data irrelevant with a detected target is removed, and finally, the computing amount is reduced.

The invention discloses an improved Gaussian mixed potential probability hypothesis density filtering method. The method comprises the following steps: 1) forming a target state set and a target strength function; 2) initializing probability hypothesis density and potential distribution of an initial target; 3) carrying out predication on the probability hypothesis density and potential distribution of the target state set at the time of k+1 to obtain probability hypothesis density and potential distribution at the time of k+1; 4) updating the probability hypothesis density and potential distribution of the target state set at the time of k+1 to obtain probability hypothesis density and potential distribution at the time of k+1, carrying out unbiased conversion on a true covariance matrix and true deviation, and setting an ellipsoid threshold value to simplify a measurement set and reduce observation number of a current observation set; 5) carrying out trimming and combining on Gaussian items of the target strength function, and extracting target state estimation and carrying out performance evaluation; and 6) repeating the steps 3)-5), and tracking the target until the target disappears. The method facilitates direct application of radar data information, and reduces calculation amount of a filter.

The invention relates to multi-strength regeneration brick aggregate fiber concrete and a preparing method thereof. The multi-strength regeneration brick aggregate fiber concrete is prepared from cement, fine aggregate, natural coarse aggregate, regeneration brick coarse aggregate, polyolefin fiber, steel fiber and water according to the weight ratio of 1: (0.780-1.309) : (0-1.830) : (0.390-1.568) : (0-0.019) : (0-0.161) : (0.33-0.48). The regeneration brick aggregate fiber concrete with the target strength grade of CF30-CF50 can be prepared by means of the raw materials, strength grade is high, and application range is wide. The obtained regeneration brick aggregate fiber concrete has high working performance including peaceability and water-retaining property, compressive strength and splitting-tension strength are high, the preparing process is simple and environmentally friendly, and construction is easy.

The invention relates to a method and apparatus for detecting infrared dim small targets under a complex background, belonging to the technical field of infrared target detection. At first, the invention adopts a bilateral filtering algorithm to preprocess the single-frame infrared images in an image sequence successively, so as to reduce noise interference in the image and enhance the signal-to-noise ratio at the target; then, a single-frame infrared target detection algorithm based on block extremum is used to detect the potential candidate target sets in each preprocessed image frame by frame; based on the spatio-temporal continuity of small targets in multi-frame images, a pipeline filtering algorithm is used to identify the possible real targets in the candidate target set; finally the false alarm removal strategy is used to eliminate the false target and finally confirm the true target. Through the process, the invention overcomes the shortcomings of weakening target intensity, blurring edge, enlarging contour and the like brought by the prior infrared image processing technology, and can better retain and enhance the dim small target information, improve the target detectionrate, and reduce the missed detection rate and false alarm rate of the target.

A high-strength, high-toughness seamless steel pipe used for a line pipe contains 0.03 to 0.06% of C, 0.05 to 0.15% of Si, 1.6 to 2.0% of Mn, 0.010 to 0.10% of Al, 0.3 to 0.7% of Ni, 0.10 to 0.40% of Mo, 0.01 to 0.06% of V, 0.003 to 0.03% of Nb, 0.003 to 0.020% of Ti, and 0.0010 to 0.0100% of N, the relationships Mo+5V>=0.4% and 2Nb-V<=0% being satisfied, and the balance being Fe and incidental impurities. Consequently, it is possible to provide the high-strength, high-toughness seamless steel pipe used for a line pipe in which grade X80 strength and toughness are stably ensured, and the target strength can be easily attained regardless of the size.

The invention relates to a salinized soil curing agent prepared from industrial waste slag. The salinized soil curing agent prepared from the industrial waste slag consists of the following components in percentage by mass: (i) 60 to 95 percent of steel slag or composition of steel slag and one or more of other industrial waste slag, (ii) 4 to 25 percent of carbide slag and (iii) 0 to 20 percent of waste industrial gypsum. A preparation method of the salinized soil curing agent comprises the following steps of: (1) drying the component (i), the component (ii) and the component (iii), and grinding the components respectively or mixing the components and grinding the mixture until the specific surface area is 250 m<2> / kg to 600 m<2> / kg; (2) determining the mass percentage of the component (i), the component (ii) and the component (iii) according to the salt content and the physical and chemical properties of the salinized soil and the target strength of the solidified soil, and mixing and stirring the component (i), the component (ii) and the component (iii) uniformly to obtain the salinized soil curing agent.

The invention discloses an acoustic cover layer beneficial for underwater damping and sound absorbing of ships. The cover layer is composed of a surface layer, a sandwich sound absorbing layer, and anadhesive layer. The surface layer is made of glass fiber reinforced plastic, wherein the density of the glass fiber reinforced plastic is close to water density, and the impedances of the glass fiberreinforced plastic and water are matched. The sandwich sound absorbing layer is composed of polyurethane and vermiculite powder and is prepared by a layering method. The sandwich sound absorbing layer has a functional gradient structure, whose material parameters change along with the thickness direction. Hollow glass beads are distributed in the sandwich sound absorbing layer; the content of thehollow glass beads decreases from outer to inner along with the thickness direction, the density increases; the adhesive layer and the surface layer are adhered on the steel shell of a ship, and theadhesive layer is made of an visco-elastic material. The cover layer satisfies two conditions that the impedances are matched and the sound attenuation performance is good; the target strength and radiation noise of ships and underwater structures can be reduced effectively; the anti-detection performance and stealth performance of ships and underwater structures are both improved; and the cover layer has a wide application prospect in fields such as military ships, civilian ships, underwater structures, and the like.

Provided is a tungsten sintered sputtering target, wherein the phosphorus content is 1 wtppm or less and the remainder is other unavoidable impurities and tungsten. The inclusion of phosphorus heavily affects the abnormal grain growth of tungsten and the deterioration in the target strength. In particular, if phosphorus is contained in an amount exceeding 1 ppm, crystal grains subject to abnormal grain growth will exist in the tungsten target. Thus, the object is to prevent the abnormal grain growth of tungsten and improve the product yield of the target by strongly recognizing the phosphorus contained in the tungsten as a harmful impurity and controlling the inclusion thereof to be as low as possible.

The invention relates to a cage culture biomass monitoring acoustic system and method. According to the system and method, a free moving platform, an underwater sound transducer and a transceiver control device are installed in a net cage and are connected with a data processing system. Sound wave signals are transmitted to the net cage, sound scattering signals of fish in the net cage are received by the transceiver control device, sound scattering target strength of the fish is measured and processed by means of the data processing system, and the size, quality, density and total biomass of the fish in the net cage are detected by means of the system and method.

The invention discloses a PHD (probability hypothesis density) filtering algorithm based on self-adaptive new target strength. The PHD filtering algorithm is implemented through the following steps: carrying out track initiation and track confirmation; constructing a strength function of a new target random set according to confirmed track initiation position information; merging a new target strength function constructed by current frames with a known new target strength function at previous moment so as to produce an adaptive new target strength function of the current frames; starting a PHD filter by using the adaptive new target strength function so as to complete the prediction and updating of the PHD filter; and carrying out multiple target state extraction. According to the Bayesian multiple target tracking method based on the filtering algorithm, a new target strength function is constructed only according to measurement information completely without using priori information. The algorithm can be used for solving the problem that an original PHD filter lacks a new target tracking function. The algorithm has the advantages that a new target of which the position is unknown can be tracked well, so that the application range is enlarged, the robustness of the PHD filter is improved, and the like.

The invention proposes a method for obtaining the target distance and the target intensity realized on the basis of a 4D imaging photon counting laser radar system, which relates to the technical field of a laser radar. The method solves the problems that a currently available method for obtaining the target distance and the target intensity requires a large amount of computation for distance calculation and that the process is time consuming and the computation intensity is low in accuracy. According to the invention, first, a local oscillation signal is transformed so that is possesses the same form as an echo signal, then the reconstructed local oscillation signal and the Gm-APD detection result are subjected to frequency-mixing treatment to obtain a related peak spectrum. On the one hand, the distance information is worked out by searching the position of the peak maximum in the peak spectrum; on the one hand, the intensity information is worked out through processing the number M of photon counting pulses in the local oscillator signal outputted by the signal generator and the number of photon counting pulses M' in the echo signal detected by the Gm-APD single-photon detector. The invention is mainly used to detect the distance and intensity of a target.

Provided is a ruthenium alloy sputtering target as a ruthenium alloy sintered compact target obtained by sintering mixed powder of ruthenium powder and metal powder capable of creating oxides easier than ruthenium, wherein purity of the target excluding gas components is 99.95 wt % or higher, said target contains 5 at % to 60 at % of metal capable of creating oxides easier than ruthenium, relative density is 99% or higher, and oxygen content as impurities is 1000 ppm or less. This ruthenium alloy sputtering target is capable of reducing its oxygen content, reducing the generation of arcing and particles during sputtering, increasing the target strength by improving the sintered density, and improving the deposition quality by strictly restricting the amount of B and P impurities in the target in order to prevent the compositional variability of B and P added in minute amounts to the Si semiconductor.

The invention relates to a fish acoustic target strength measurement device, which is provided with a water tank. The inner side of the water tank is provided with an arc guide rail which is matched with a pulley, and the pulley is provided with a clinometer and an energy converter. A dial is flatly arranged above the water tank, and a center hole of the dial is provided with a rotating shaft the lower end of which is connected with a level rotation pole. The lower part of the level rotation pole is connected with a connector, and the emission surface of the energy converter points to the center of the arc guide rail. In measurement, a tested fish is hung below the level rotation pole to be positioned at the center of the arc guide rail. A middle sliding wheel is driven, the pulley is adjusted to a needed incident sound wave angle, and the value of the incident sound wave angle is read by the clinometer. The rotating shaft is rotated to change the horizontal angle of the tested fish, and the horizontal angle is read by the dial. By receiving the size of a fish echo rating, the device measures the target strength value of different fishes in different incident directions. The device has the advantages of easy use, good operation, easy control, simple integral structure and low manufacturing cost.

The invention discloses a probability hypothesis density based variable target number video tracking algorithm. The algorithm includes the following steps: adopting a motion detection method to realize quick effective segmentation of a motion target so as to generate target measurement; utilizing a motion detection result to design a newly generated target strength updating method so as to generate a newly generated target strength function; forecasting and updating PHD; trimming updated Gauss elements; extracting states and outputting estimated target numbers and states; adopting an auction track identification method to perform 'track-state estimation' association so as to identify a target track, and outputting the track with identity. By the algorithm, variable-number multiple targets can be effectively tracked, newly generated targets with tracking positions unknown can be tracked particularly, and the target track can be generated. By the algorithm, performance of GM-PHD filter is improved, robust estimation state can be obtained under the conditions of target number change and target crossing, and the target track can be identified.

The invention discloses a passive radar fixed target frequency domain direction-finding method based on an external radiation source. The passive radar fixed target frequency domain direction-finding method comprises the steps of establishing a direction-finding system model; deducing a slant range progress of a single-scattering-point target; deducing a demodulated single-scattering-point target echo signal model and performing variable substitution for obtaining a frequency domain expression; expanding the frequency domain expression of the single-scattering-point target echo signal to a multi-target condition, modifying a target scattering strength function, and obtaining a relationship between the frequency domain expression of a multi-target echo signal and the modified target strength function; and calculating the direction of each target by means of a polar coordinate algorithm. The passive radar fixed target frequency domain direction-finding method is realized based on a narrow-band external radiation source signal in a two-dimensional space; the polar coordinate algorithm is used; and convolution operation is performed. The convolution operation can be processed through fast Fourier transform and inverse transformation, thereby greatly reducing calculation amount of the algorithm, realizing high robustness, obtaining relatively high direction finding precision and simultaneously finding a plurality of target directions in an observing area.

A fishfinder is provided for identifying with high precision a single fish under the ship and for measuring the length of the fish precisely. An operator of the fishfinder is assisted to grasp the depth and the length of the fish. A fishfinder transmits an ultrasound pulse having a high carrier frequency and an ultrasound pulse having a low carrier frequency by means of a pulse transmission and reception device at predetermined time intervals. A single fish echo is determined and tracked for a plurality of transmission intervals of ultrasound pulses emitted into the water. A target strength of single fish is measured based on the signal strength of a low carrier frequency echo signal from the single fish. The length of the fish is measured based on the target strength. A fish mark is displayed on the screen of an indicator, with the size of the fish mark depending on the fish length.

The invention relates to a method for optimizing and selecting transmitting frequency of an ADCP (acoustic Doppler current profiler) with environmental adaptability. The method comprises the followingsteps: S1, according the mathematic relation among a transducer receiving level in an ADCP transducer receiving level as well as a sound source level, one-way propagation loss, a target intensity level and a background noise level, acquiring a sonar equation of the transducer receiving level as well as the sound source level, the one-way propagation loss, the target intensity level and the background noise level; S2, according to the mathematic relation among transmitting frequency, acoustic diameter of a transmitting transducer, the wavelength of transmitting sound wave and the sound sourcelevel, acquiring a calculation formula of the sound source level; S3, according to the mathematic relation among the measuring distance, the attenuation coefficient of water for the sound wave and theone-way propagation loss, acquiring a calculation formula of the one-way propagation loss; and performing other steps to acquire the transmitting frequency. The echo signal-to-noise ratio of the ADCPby using the method can be increased by at most 20 dB compared with that of the ADCP with fixed transmitting frequency.

The invention relates to a low-frequency active towed line array sonar shallow sea detection efficiency evaluation method based on a cloud model, which comprises the following steps: establishing a low-frequency active towed linear array sonar shallow sea detection efficiency index system; generating a detection efficiency standard sample set psi0; calculating the weight of each detection efficiency index of the psi0 by using a variation coefficient improved CRITIC method for the psi0; sequencing elements in the psi0 to generate psi1, and recombining to generate psi2; calculating the digital characteristic values of n indices and I levels multidimensional cloud model by using an MBMCT-SR algorithm for psi2 to generate I n-dimensional normal clouds; selecting sonar parameters and calculating each detection efficiency index; and substituting the sonar parameters into a target strength formula to calculate the certainty degree of the sonar parameters belonging to each detection efficiencygrade, and judging the detection efficiency grade according to a maximum certainty degree principle. The low-frequency active towed line array sonar shallow sea detection efficiency evaluation methodcan quickly and intuitively judge the detection efficiency and provide an auxiliary decision for the combat use of the low-frequency active towed linear array sonar.

The invention discloses a common underwater acoustic measurement system mainly composed of a transmitting transducer set, a transmitting extension set, a receiving extension set and a display control extension set. The display control extension set is connected with the transmitting extension set and the receiving extension set. The transmitting extension set is connected with the transmitting transducer set and used for driving the transmitting transducer set. The transmitting transducer set is used for finishing underwater launching of acoustic signals in a working frequency band. The transmitting extension set is used for finishing generation of underwater acoustic measurement signals and driving the transmitting transducer set, the receiving extension set is used for finishing receiving, conditioning, collecting and storing of the underground acoustic signals, and the display control extension set is used for finishing parameter setting, transmitting and receiving controlling, state monitoring, received waveform displaying and target strength calculating. The common underwater acoustic measurement system is high in universality and performance cost ratio and convenient to carry and use, the modular design is adopted, and subsystems can be independently used.

The invention provides an efficient prefabricated concrete shield segment steam-curing kiln and an application method thereof. The efficient prefabricated concrete shield segment steam-curing kiln comprises a kiln body, wherein a still-cured thermal insulation region, steam-cured heating region, a steam-cured constant-temperature region and a steam-cured cooling region are sequentially arranged inside the kiln body from an inlet to an outlet; and a plurality of groups of steam tubes are arranged in each of the steam-cured heating region, the steam-cured constant-temperature region and the steam-cured cooling region. A prefabricated concrete shield segment is placed on a maintenance truck, and has strength of 20 MPA after sequentially passing through the still-cured thermal insulation region, the steam-cured heating region, the steam-cured constant-temperature region and the steam-cured cooling region, wherein retention time, in the still-cured thermal insulation region, of the maintenance truck is 126-189 minutes. The prefabricated concrete shield segment can reach target strength within 6 hours, so that production efficiency is improved. About 7 million RMB needs to invest for construction and later-stage operation. About 60 millions of RMB can be saved for construction and production investment of a comprehensive field area, so that the economic effects are remarkable. Concrete still-curing time is prolonged, and early-stage strength of the shield segment can be effectively improved.

The invention aims to provide a measuring method for target echo strength. The measuring method includes that a transponder is arranged on a target, and a transceiving transducer is arranged on a measuring terminal; the measuring terminal sends broadband measuring signals to the target; the measuring terminal receives echo signals of the target and the transponder and stores the echo signals after sound waves are transmitted to the target and then returned to the measuring terminal; time reversal processing of echoes is performed to the ith transponder, and broadband signals are added at the front ends of the signals to be finally sent to the target; the received signals and the sent signals are convoluted after the echoes are received to measure a peak value Pi of the ith transponder; and the steps are respectively repeated to other transponders rather than the ith transponder, the echoes of the transponders are changed into the echoes of the target, the peak value of the target echoes is measured, and target strength is finally figured out. By the method, numerous interferences and measuring errors during measuring are reduced, and measuring accuracy of the target strength is improved.

A two-phase stainless steel pipe that has not only a corrosion resistance required for oil well pipes but at the same time has a targeted strength is produced, without excessively adding alloying components, by selecting cold drawing conditions.A method for producing a two-phase stainless steel pipe, which comprises, preparing a two-phase stainless steel material having a chemical composition that consists of, by mass %, C: 0.03% or less, Si: 1% or less, Mn: 0.1 to 2%, Cr: 20 to 35%, Ni: 3 to 10%, Mo: 0 to 4%, W: 0 to 6%, Cu: 0 to 3% and N: 0.15 to 0.35%, and the balance being Fe and impurities, forming a material pipe by subjecting to a hot working or further a solid-solution heat treatment, and performing a cold drawing, where the cold drawing is characterized in being performed under the conditions that the working ratio Rd, in terms of the reduction of area, in the final cold drawing step is within a range from 5 to 35%, and the following formula (1) is satisfied:Rd(%)≧(MYS−55) / 17.2−{1.2×Cr+3.0×(Mo+0.5×W)}  (1)wherein Rd and MYS signify the working ratio (%) in terms of the reduction of area and the targeted yield strength (MPa), respectively, and Cr, Mo and W signify the contents (mass %) of the individual elements, respectively.

A device for deflecting acoustic waves for an object in a liquid environment includes a heating grid and a cooling grid. The heating grid is positioned about the object and increases the temperature in the liquid environment. The cooling grid is positioned about the object to cool the liquid environment outside the heating grid. Jointly, these grids establish a temperature gradient in the liquid environment that is capable of bending acoustic waves in the environment. The cooling grid and heating grid can be established through mechanical, electrical or chemical methods. Alternatively, the required temperature gradient can be established by a heating grid alone in a moving vehicle wherein the heating grid is continuously in contact with undisturbed water at the ambient temperature.

The invention discloses a phosphate cement mortar matching method. The phosphate cement mortar matching method comprises the following steps of (1) determining target performance, including a target strength average value fMKPCM, m and consistency C0 of phosphate cement mortar, of the phosphate cement mortar; (2) according to the target intensity average value fMKPCM, m, which is set in advance, of the phosphate cement mortar, determining production strength fMKPCM, 0 of the phosphate cement mortar; (3) according to the consistency C0, which is set in advance, of the phosphate cement mortar, determining unit water use Mw0 of the phosphate cement mortar; (4) determining a water-binder ratio w / b, and according to the water-binder ratio w / b, calculating the dosage of phosphate cement; and (5)determining the dosage Ms0 of sand. By means of the method, a matching ratio of the phosphate cement mortar can be obtained accurately and fast on the basis of the target use performance, operation of the method is simple, convenient and reasonable, manpower and material resource waste brought by repeated tentative production and adjustment is avoided, and the method has good operability and practicability.