529 results about "Finite difference method" patented technology

A method for modeling diffraction includes constructing a theoretical model of the subject. A numerical method is then used to predict the output field that is created when an incident field is diffracted by the subject. The numerical method begins by computing the output field at the upper boundary of the substrate and then iterates upward through each of the subject's layers. Structurally simple layers are evaluated directly. More complex layers are discretized into slices. A finite difference scheme is performed for these layers using a recursive expansion of the field-current ratio that starts (or has a base case) at the lowermost slice. The combined evaluation, through all layers, creates a scattering matrix that is evaluated to determine the output field for the subject.

Method for efficient processing of controlled source electromagnetic data, whereby Maxwell's equations are solved [107] by numerical techniques [109] such as finite difference or finite element in three dimensions for each source location and frequency of interest. The Reciprocity Principle is used [103] to reduce the number of computational source positions, and a multi-grid is used [105] for the computational grid to minimize the total number of cells yet properly treat the source singularity, which is essential to satisfying the conditions required for applicability of the Reciprocity Principle. An initial global resistivity model [101] is Fourier interpolated to the computational multi grids [106]. In inversion embodiments of the invention, Fourier prolongation is used to update [120] the global resistivity model based on optimization results from the multi-grids.

The present invention relates to a method of predicting an amount of production from a fractured reservoir and a recorded medium for the method. The method of predicting an amount of production from a fractured reservoir can include: (a) generating a fracture network model, which includes discrete fractures, using fracture characteristic information; (b) generating a flow model for representing flow paths for a fluid between the discrete fractures using a 2-dimensional finite difference method; and (c) predicting the amount of production from the fractured reservoir using the flow model.

The invention relates to the technical field of optical communication and discloses an optical grating coupler and an optical signal coupling method. The optical grating coupler comprises a top silicon layer, a base silicon layer and a silicon dioxide layer, wherein the silicon dioxide layer is arranged on the upper surface of the base silicon layer, the top silicon layer is disposed on the upper surface of the silicon dioxide layer, the top silicon layer is of a structure formed by ranking at least two right triangles in the direction perpendicular to the light transmission direction, and received optical fibers face toward the rank structure of the right triangles. According to the optical grating coupler and the optical signal coupling method, through application of triangular optical gratings, work bandwidth of the optical grating coupler is increased, and applicability of the optical grating coupler is improved; besides, simulating calculation is performed through a three-dimensional time domain finite difference method so that TE and TM light coupling efficiencies are the same, optical grating structural parameters are determined, polarization insensitivity is achieved; the optical grating coupler has the advantages of being simple in structure, wide in work bandwidth, low in polarization loss and high in coupling efficiency.

The present invention provides a motion information and trajectory association-based video pedestrian detection and tracking method. Pedestrian detection comprises: detecting motion by using a frame difference method; first detecting a motion area in a video in combination with a morphological method of digital image processing; then extracting a feature from the motion area in a manner of sliding window searching; and performing classification by using a previously trained pedestrian detection classifier, to finally obtain a classification result. The tracking method comprises: using the pedestrian detection result obtained in the previous step as input of this step; in the beginning, initializing a tracker for each detected pedestrian, wherein each tracker comprises history motion information and appearance information of an object; and when a current frame is being processed, extracting location information and appearance information for each input detection result, and establishing a correlation matrix based on this to associate with a tracking object of a previous frame, and finally obtaining a tracking trajectory of a pedestrian. The present invention has good real-time performance, and also has good robustness in a relatively complex situation.

The invention discloses a moving target detecting and tracking method combining a frame difference method and a Gaussian mixture model. The method includes the following steps: acquiring a video image, and carrying out difference calculation on a current frame of input video image and a previous frame of video image to get an inter-frame difference image; using an initialized Gaussian mixture model algorithm to process the video image acquired to get a foreground region image and a background region image of the input video image; fusing the inter-frame difference image and the foreground region image to get a fused video image; binarizing and morphologically processing the fused video image to get a moving target image in the current input video image; and matching the moving target image extracted from the current input video image with a moving target image extracted from the previous frame of video image, and getting a moving target tracking result according to the matching result. By combining the advantages of two target detection algorithms, accurate and real-time detection of a moving region is realized.

The invention discloses a difference method for improving the sensitivity and the absolute precision of a CPT (Coherent Population Trapping) atom magnetometer. The method comprises the following steps: putting a low-intensity magnetic field probe in a magnetic field to be detected at a constant temperature; adjusting a laser control circuit to keep the laser wavelength stable and keep resonance of the laser wavelength and alkali metal atomic ground state level; vertically putting a half-wave plate and a polarization beam splitter prism in laser, and adjusting the polarization angle of the optical axis of the half-wave plate and the laser; enabling a quarter-wave plate to be vertical to two beams of parallel laser; adjusting the polarization angle of the optical axis of the quarter-wave plate and the laser, wherein the polarization of the parallel laser becomes left-hand circular polarization and right-hand circular polarization respectively; carrying out laser detection on the left-hand circular polarization and the right-hand circular polarization by two photovoltaic conversion devices, and subtracting obtained light intensity values by a subtracter, wherein the magnetic induction intensity B of the magnetic field to be detected is obtained through acquisition and signal processing of data acquisition and processing equipment. The difference method has the advantages of easy operation, high sensitivity and high precision.

The present invention is a method for determining a parameter of interest of a region of interest of the earth. At least one component of potential fields data is measured at a plurality of locations over a region of interest including a subterranean formation of interest. The potential fields data are selected from magnetic data and gravity data. An initial geophysical model is determined for the region including the subterranean formation of interest. For the model, geophysical tensor data is updated using a forward model at a plurality of locations using a High Order Compact Finite Difference method. A difference between the estimated model value and the measured value of the potential field measurements are determined, and the geophysical model is updated. The model is iteratively updated and compared to the measured data until the differences reach an acceptable level and the parameter of interest has been determined.

The invention discloses a student tracking and positioning method based on primary and secondary cameras. The method does not influence normal teaching of a lesson, is higher in adaptability to change of external environment such as light rays and can handle the situation that two students stand up. According to the method, two secondary cameras and one primary camera with a cradle head device are used. The secondary cameras can generate a region-of-interest automatically or manually, detect whether students enter or leave the region-of-interest or not through a background difference method and send detection results to the primary camera; the primary camera judges the number of students standing up according to the information transmitted from the secondary cameras, and selects a panoramic recording mode or a positioning recording mode according to the number of the students standing up, wherein in the positioning recording mode, profiles of all moving objects are detected through an inter-frame difference method, the object, of which, the profile central point is highest, is judged to be a student, the primary camera is driven to rotate and zoom according to the coordinates and the area of the student, so that positioning of the students is realized.

The invention provides a nonlinear optimization based time-space domain staggered grid finite difference method and device. The method includes: determining finite difference coefficients; optimizing the finite difference coefficients on the basis of time-space domain dispersion relation and a nonlinear inversion algorithm; utilizing the optimized finite difference coefficients to perform elastic wave forward modeling. By the method and device, the technical problems of high middle-high frequency dispersion and low simulation precision caused by the fact that a finite difference method of taylor series expansion and space domain dispersion relation is utilized to acquire the finite difference coefficients so as to perform elastic wave forward modeling are solved, dispersion of middle and high frequency is achieved, and technical effect of simulation precision is improved.

The invention discloses a human body motion capture and posture analysis system and a method for carrying out foreground detection and automatic extraction of joint points through the human body motion capture and posture analysis system. According to the human body motion capture and posture analysis system, a human body motion image is captured through a camera, the human body foreground and the human body joint points are extracted from the human body motion image, and then human body motions are analyzed through a tracking and recognition algorithm. Due to the fact that a human body target in a video is extracted through an algorithm combining a background difference method and a frame difference method, the defect that background noise interference easily exists in the process of foreground detection based on the background difference method is overcome; due to the fact that the method with combination of a plurality of algorithms is adopted, automatic initialization of the human body joint points is achieved, and the defects that optical marks or manual marking is needed by a traditional joint point extraction method, and an existing automatic extraction method is large in calculated amount and poor in accuracy are overcome. The human body motion capture and posture analysis system is low in complexity and high in accuracy, and the intelligence and the efficiency of the human body motion capture and posture analysis system are improved.

The invention relates to the technical field of civil engineering construction, in particular to a construction method of an ultra-deep underground diaphragm wall in a water-rich soft-soil area. The construction method comprises the following steps: making an analysis and research on the stability of trench walls of the underground diaphragm wall and doing relevant preparations, preparing wall protecting slurry, building a guide wall, performing trenching construction, wall cleaning and sediment removal, manufacturing and hoisting reinforcing cages, backfilling joints between trench sections, and pouring wall concrete. According to the construction method, through a stability analysis method that introduces strength reduction, the security coefficients of stability of the trench walls are calculated based on a finite difference method; through parameter-reduction circular calculations, not only the limit stress and large deformation state of the trench walls but also the stability coefficients of the trench walls are obtained, which has practice guiding significance in construction; and the results are simple and practical and conform to the habits in the engineering field, and the stability requirements of the trench walls are effectively guaranteed, so that the engineering construction can be completed safely and fast with high quality.

The invention discloses a finite difference design method of a magnatic resonance imaging (MRI) system gradient coil, which comprises the following steps: firstly, dividing finite difference grids in the coil space, and establishing finite difference relation between a node stream function and grid current density on each grid node; subsequently, selecting a constraint field point in the magnetic field related region of the MRI system gradient coil, and computing the magnetic induction intensity on the constraint field point according to the design requirements; then, establishing a system of linear equations between the node stream function and the magnetic induction intensity of the constraint field point according to the Biot-Savart law; simultaneously, establishing a penalty function of the system of linear equations according to the actual engineering requirements; and finally, solving the system of linear equations by a method of regularization to acquire a node stream function value, and determining the current style of the coil by a constant stream function line. The invention is simple and effective and can be suitable for designing gradient coil systems in any structure.

The invention discloses a simulation method of ultra wideband electromagnetic waves. The invention proposes a new PML method on the basis of the PML method under a stretch coordinate system and a difference scheme of a higher-order time domain finite difference method (FDTD (2, 2M)). A piecewise linearity convolutional perfectly matched layer (PCPML, Piecewise linearity CPML) under self-adapting absorption parameters absorbs a boundary condition. PML absorption factors are set to be adjustable parameters by the method so as to absorb different ultra wideband electromagnetic waves from high frequency to low frequency, and the parameters are obtained by a mixed method of an optimization method of a real coding genetic algorithm and a linear iteration method in a self-adapting manner so as to adapt to the absorption of ultra wideband electromagnetic waves. The absorption boundary condition adopted by the method can absorb and process high frequency waves and low frequency waves, and also can reduce the reflection error of a matched layer caused by grid dispersion and edge reflection and improve the absorption efficiency and the accuracy of simulation result.

The invention discloses a vehicle line-crossing detection method based on an intelligent video analysis technology. The method comprises the steps that a video monitoring image is preprocessed according to real-time light intensity; an improved three-frame difference algorithm is adopted to detect a vehicle in the video monitoring image; after the position of the vehicle is detected, a motion track of the vehicle is traced; the actual position of a target in a current frame is obtained through continuous iterative calculation, and the motion track of the vehicle is acquired; the result of thelast frame is used as an initial value of the next frame, and loop iteration is continued in this way; and multiple motion tracks of the vehicle are obtained, an appropriate motion track is selected to detect whether a warning line and the track intersect, and whether the vehicle crosses the line is determined. According to the method, the improved three-frame difference method is adopted to quickly detect the target vehicle, the motion tracks of the vehicle are traced through a mean shift algorithm based on kernel density estimation, then whether the vehicle has a line-crossing behavior is determined through the vehicle motion tracks, and the method is high in instantaneity, high in precision and wide in application range.

This invention discloses a method for judging current mutual inductor heavy saturation with a time difference method for relay protection which can distinguish heavy saturation. Since the saturated point at CT saturation separates a second current into unsaturated zone and saturated zone, relations of their differential current and stalling current are different, it can identify the heavy CT saturation when saturation time reaches to 2ms. CT saturation arisen from faults in or out of the zone can be distinguished using the time difference method.

The invention discloses a method for simulating energy flow based on a transient model of a power-gas interconnection comprehensive energy system. The method comprises the following steps of 1) by considering dynamic characteristics of a slow process of a natural gas pipe network, building a transient model of the natural gas pipe network; 2) by adopting an implicit finite difference method, dividing a time-space partial differential equation for describing dynamic characteristics of gas flow of a natural gas pipeline into algebraic equation expressions; 3) coupling a power network and the natural gas pipe network through a gas turbine and a power-to-gas technology, and building the transient model of the system; 4) solving multi-time-period transient energy flow of the power-gas interconnection comprehensive energy system; and 5) performing performance testing in the comprehensive energy system. According to the method provided by the invention, the calculation precision is effectively improved and a real-time running state of a natural gas system can be described more accurately.

The invention discloses a method for the layout optimal design of a multi-assembly structure system, which is used for solving semi-analytical sensitivity of geometric parameters in the layout optimal design of a multi-assembly structure system. The method comprises the following steps of: dividing a finite element model of the multi-assembly structure system into three parts: structure lattice, assembly lattice and transition lattice; respectively evaluating influences of different geometric parameter perturbations on the three parts of lattices as well as a rigidity matrix and a quality matrix thereof to obtain the semi-analytical sensitivity of the rigidity matrix and the quality matrix; and further obtaining the sensitivity of various design indexes by derivation. Compared with the finite differential method for the traditional layout optimal design, the semi-analytical method of the invention effectively avoids the finite element solving process after the geometric parameter perturbations are updated, saves the time for sensitivity analysis and optimal design, shortens the cycle of the layout optimal design of the multi-assembly structure system, and enhances design efficiency.

The invention provides a rotor-rotor. The nonlinear dynamics analysis method for the bearing system comprises the following steps: inputting calculation parameters; Calculating a system overall mass matrix, a rigidity matrix, a damping matrix and a gyroscopic effect matrix; Calculating unbalanced excitation of the rotor; Calculating the thickness of the bearing oil film at the t moment; And calculating the bearing oil film pressure at the t moment. Judging whether the oil film pressure meets a convergence condition or not; Calculating a bearing friction force and an end leakage flow at a t moment; Calculating the effective temperature and effective viscosity of the lubricating oil at the t moment; And calculating the oil film bearing capacity at the t moment. Newmark-based And algorithm: calculating the vibration response of the rotor system at the t + t moment. And whether the break + t moment reaches a time upper limit is determined. According to the method, the bearing nonlinear oilfilm force solving process based on the finite difference method is embedded into calculation of the rotor vibration response, and influence factors such as lubricating oil rheological properties andbearing bush surface elastic deformation are considered when the oil film force is solved, so that the response calculation is more accurate.

The invention provides a time domain analysis method for a transient response of lossy nonuinform multi-conductor transmission lines and aims to solve the problem that the coupling among the lossy nonuniform multi-conductor transmission lines interferes with the computation in the field of integrity of electronic circuit signals. The method comprises the following steps of: performing differential dispersion on space differential operators in an electric wave equation; and integrating time differential operators in the electrical wave equation by a trapezoidal integration method to ensure that the oscillation, which is caused by a central difference method, of a computed result can be eliminated effectively, voltage and current transient response waveforms of any point on the transmissionlines can be acquired; and the transient analysis of the transmission lines in a longer time period is effective, the waveforms can be analyzed in a longer duration without large errors, and the coupled transmission lines are not needed to be decoupled when a model of the transmission lines is built. By the method, the computational load is reduced, and the simulation efficiency is improved. The method can be used for analyzing the transient response of the lossy nonuinform multi-conductor transmission lines.

The present invention relates to an ultrasonic real-time nondestructive body temperature measuring device and the temperature measurement method; the present invention establishes a relationship model of the temperature increment and the echo signal in the time domain or the frequency domain based on that the thermal characteristics of the human tissues and the ultrasound beams which pass through the human tissues thereof have better correlation with the temperature increment on the beam path during the slow change, furthermore, the present invention uses the numerical calculation method (such as, finite element / finite difference method) which is based on the nonlinear medical ultrasonic field to carry out the real-time dynamic calibration of the thermal coefficient of the deep tissue by establishing a Pennes biological heat conduction equation (BHTE) in a human structural model, so as to solve the difficulties that the characteristic parameters of the tissue temperature are too changeable ; the present invention uses the combination method of the numerical calculation and the ultrasonic detection to eliminate the problem of the heat-acoustic lens and adopts the fusion imaging method of the temperature information and the tissue structure information to visually display the temperature distribution and the structure distribution in the body.

The invention discloses a method for calculating various properties of a hydrostatic oil pad by considering inclination and heat. According to the method, influences from inclination and the heat are considered, and pressure distribution and temperature distribution of the oil pad are calculated through the finite difference method. The method comprises the following steps that firstly, an N-S equation and an energy equation are simplified and a two-dimension Reynolds equation is deduced; secondly, dimensionless processing is conducted on the equations; thirdly, the bearing capacity, rigidity and damping of the oil pad are calculated; finally, on the basis of the finite difference method, a calculation program is written through Matlab so as to obtain parameters of the properties of the oil pad. The method is characterized in that the simplified N-S equation is used for deducing the Reynolds equation, and the energy equation and the Reynolds equation are coupled with each other through a viscosity-temperature equation and a density-temperature equation. The coupled equation is solved through the finite difference method, the bearing capacity of the oil pad is obtained through the bearing surface integral, and the rigidity and the damping are obtained by deriving the bearing capacity. The method can provide guidance for use and design of a rotary table.

The invention discloses a sliding bearing universe lubricant film thickness distribution detection method to realize real-time detection of the sliding bearing universe lubricant film thickness distribution under an actual working condition. The method comprises the following steps: through the finite difference method, iterating to solve the lubricant basic equation of the sliding bearing to acquire the theoretical distribution of the lubricant film thickness of the sliding bearing, then, according to the theoretical distribution of the lubricant film thickness of the sliding bearing, determining the positions of distributed measure points of the sliding bearing, at the selected positions of the measure points, mounting circular sheet ultrasonic sensors in an embedded manner, and acquiring the real-time film thickness values of all measure points by adopting the ultrasonic film thickness measurement technology, and finally, performing interpolation on the measured lubricant film thickness values at all distributed measure points to acquire the distribution of the lubricant film thicknesses of the sliding bearing under the actual working condition.

The invention provides an improved measurement method of a time difference type ultrasonic flow meter. The influences of external interference multiple ultrasonic signals can be effectively reduced by improving an existing time difference method and on the basis of ultrasonic receiving end over-zero point analysis and time difference correction, and an effective method for accurately obtaining forward and reserve time differences is provided. By correcting flow calculation, in actual measurement of the flow meter, the average flow speed of fluid is infinitely close to the true value, and the metering precision of the time difference type ultrasonic flow meter is greatly improved.

The invention discloses an oil-water distribution recognition method based on a well-ground potential method. The oil-water distribution recognition method comprises the following steps: firstly, establishing an oil-water two-phase seepage equation; based on a potential and water saturation model, coupling the seepage equation with a potential differential equation to form a well-ground potential model; adopting a finite difference method and solving the pressure of the model by adopting an implicit expression and solving the saturation degree of the model by adopting an explicit expression; establishing a difference potential differential equation by utilizing a relation between the water saturation and conductivity, and solving the potential by adopting the implicit expression; establishing a computer solving model on the basis; carrying out analog computation on a one-dimensional water displacement oil process; simulating the whole water displacement oil process through numerical solution to obtain a correlational relation between potential distribution and resistivity of an underground target layer; after solving the resistivity of the target layer, inversing the water saturation of a reservoir stratum by utilizing an Archie equation. The method can be used for quantitatively describing the water saturation and oil saturation in the reservoir stratum by utilizing the potential determined on the ground, and oil-water distribution can be more rapidly and accurately recognized.

The invention discloses a 3D TTI double-phase medium seismic wave field value simulation method based on a finite difference method. The 3D TTI double-phase medium seismic wave field value simulation method comprises steps of obtaining a solid and fluid stress tensor and a solid and flow strain tensor and transforming the tensors to a constitutive equation, obtaining a geometry equation according to the corresponding relation of stress and the displacement, obtaining a motion differential equation according to the constitutive equation, the geometry equation and the fluid motion relative to the solid and the corresponding relation between the stress and the displacement, taking the divergence on two ends of the motion differential equation to obtain a first longitudinal wave equation and a second longitudinal wave equation of the seismic wave, as for the first longitudinal wave equation and the second longitudinal equation, enabling a partial derivative to y to be zero and performing difference discrete on the space partial derivative and the time partial derivative by employing an 2N order precision expansion formula and a 2-order precision center difference form to obtain a first difference equation and a second difference equation, and performing boundary absorbing condition processing on the first difference equation and the second difference equation to obtain the corresponding seismic wave field value. The invention realizes the real-time transmission simulation of the physics seismic wave field.

The invention relates to a gravity and magnetic data processing method used in physical geography exploration, comprising the following steps that: with a wave-number domain, a gravity and magnetic data frequency spectrum is respectively multiplied by an n derivative in any direction( or an integral frequency response function), an upward continuation response function and a finite difference method downward continuation operation frequency response function to obtain a frequency spectrum after downward continuation; and the frequency spectrum after downward continuation is quickly carried out through inverse Fourier transform to obtain a three-dimensional gravity data volume after downward continuation. The three-dimensional gravity data volume after downward continuation is used to combine data about earthquake, geology and wellboring to compare and analyze next favorable zone and objective to be explored. The method has lager downward continuation depth and excellent anti-noise capability, thereby acquiring a stable lower half-space three-dimensional gravity and magnetic data distribution image.

The invention belongs to the technical field of high-quality and high-efficiency milling of complex curved surface parts, and relates to a global optimization method for a cutter-axis vector based onthe minimum angular acceleration of a machine tool rotating shaft. The method comprises the steps of generating a cutter track by using an equal residual height method according to the curved surfaceand cutter characteristics; establishing an inverse kinematics relation of a five-axis machine tool; converting the cutter-axis vector under the workpiece coordinate system into a rotation angle valueof rotary feeding shaft of the machine tool, calculating the angular speed and the angular acceleration of the rotary feeding shaft of the machine tool by using a finite difference method; calculating a feasible space of the cutter axis at the position of a cutter contact point by means of a C space method according to an interference judgment criterion, judging the concavity and convexity of a cutter path curve, and determining a key cutter-axis vector on the cutter path curve; and optimizing the cutter-axis vector by taking the minimum angular acceleration in each interval as an objective.The method can effectively reduce the angular acceleration of the rotary feeding shaft of the machine tool in the machining process, realize the stability of the machining process, improve the surfacemachining quality and reduce the machining contour error.