163 results about "Diffusion equation" patented technology

An inverse analysis method for characterizing diffusion of vapor from an underground source of volatile contaminant using data taken by an in-situ sensor. The method uses one-dimensional solutions to the diffusion equation in Cartesian, cylindrical, or spherical coordinates for isotropic and homogenous media. If the effective vapor diffusion coefficient is known, then the distance from the source to the in-situ sensor can be estimated by comparing the shape of the predicted time-dependent vapor concentration response curve to the measured response curve. Alternatively, if the source distance is known, then the effective vapor diffusion coefficient can be estimated using the same inverse analysis method. A triangulation technique can be used with multiple sensors to locate the source in two or three dimensions. The in-situ sensor can contain one or more chemiresistor elements housed in a waterproof enclosure with a gas permeable membrane.

A battery model unit includes an electrode reaction model unit based on the Butler_Volmer equation, an electrolyte lithium concentration distribution model unit analyzing a lithium ion concentration distribution in an electrolyte solution by a diffusion equation, an active material lithium concentration distribution model unit analyzing an ion concentration distribution in a solid state of an active material by a diffusion equation, a current/potential distribution model unit for obtaining a potential distribution according to the charge conservation law, a thermal diffusion model unit and a boundary condition setting unit. The boundary condition setting unit (66) sets a boundary condition at an electrode interface such that a reacting weight at the electrode interface is not determined by a difference in material concentration between positions but a deviation from an electrochemically balanced state causes a change with time in lithium concentration at the interface and thus a (time-based) drive power for material transportation. Thereby, an appropriate charge/discharge control can be performed based on the battery model having the appropriately set battery condition.

A method for imaging objects in a highly scattering turbid medium comprises: using a group of sources and detectors to generate a plurality of emergent energy waves from the medium, determining the intensity data of the emergent energy waves and processing the intensity data by using an image reconstruction algorithm. Arrangement of sources-detectors may be in parallel (transmission and/or backscattering) geometry or in cylinder geometry. The reconstruction algorithm is a novel hybrid dual Fourier tomographic algorithm for a fast 3D image reconstruction. The forward models are the radiative transfer model based on the cumulant solution of the radiative transfer equation or the diffusion model based on the approximate diffusion equation.

An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.

Optical changes of tissue during wound healing measured by Near Infrared and Diffuse Reflectance Spectroscopy are shown to correlate with histologic changes. Near Infrared absorption coefficient correlated with blood vessel in-growth over time, while Diffuse Reflectance Spectroscopy (DRS) data correlated with collagen concentration. Changes of optical properties of wound tissue at greater depths are also quantified by Diffuse Photon Density Wave (DPDW) methodology at near infrared wavelengths. The diffusion equation for semi-infinite media is used to calculate the absorption and scattering coefficients based on measurements of phase and amplitude with a frequency domain or time domain device. An increase in the absorption and scattering coefficients and a decrease in blood saturation of the wounds compared to the non wounded sites was observed. The changes correlated with the healing stage of the wound. The methodologies used to collect information regarding the healing state of a wound may be used to clinically assess the efficacy of wound healing agents in a patient (e.g., a diabetic) and as a non-invasive method

The invention relates to a method for determining (30) the volumetric power distribution of the core of a nuclear reactor using a set of detectors for measuring a neutronic flow provided outside the reactor vessel, and a set of probes for measuring the temperature of the coolant at the outlet of the fuel assemblies. The method (30) comprises the step of determining a first volumetric power distribution using a neutronic calculation code (40) instantaneously solving the diffusion equation and updating the isotopic balance of the core during the fuel depletion based on values of the core operation parameters, and the step of determining a new volumetric power distribution by adjusting (60 and 90) the first volumetric power distribution using the measures provided by the sensors for measuringthe neutronic flow and provided outside the reactor vessel (80) and by the temperature measuring probes (100).

Method is provided for simulating a physical process such as fluid flow in porous media by performing a fine-grid calculation of the process in a medium and re-using the fine grid solution in subsequent coarse-grid calculations. For fluid flow in subsurface formations, the method may be applied to optimize upscaled calculation grids formed from geologic models. The method decreases the cost of optimizing a grid to simulate a physical process that is mathematically described by the diffusion equation.

The invention provides a detection method and a test device for catalytic properties of a heatproof material based on an emission spectrum. The test device comprises a plasma power supply, an air inlet valve, an infrared temperature measurement window, a double-colorimetric thermodetector, an emission piston, an induction heating power supply, a reaction cavity, a resistance vacuum gauge, a vacuum flange, an induction coil, a zirconium oxide support frame, a single-shaft electric stepping machine, a long-focus focusing lens and a short-focus focusing lens. According to an 'atom-dissipation' laboratory representation method based on emission spectrum diagnosis disclosed by the invention, the disturbance of the surface of the material to gas-phase atoms is quantitatively analyzed by an actinic ray strength method, and the recombination coefficient of the gas-phase atoms at the surface of the material is calculated according to mathematic models of gas-phase diffusion and object surface atomic mass conservation conditions. The test device has the advantages that the operation is simple; based on a catalytic mechanism and by virtue of an emission spectrum diagnosis technique, the surface catalysis coefficients of conductive heatproof materials in a temperature range of 600-3000 DEG C can be obtained through measuring the concentration change of oxygen atoms at the surfaces of the materials to represent the surface catalytic properties of the materials based on catalysis principles and diffusion equations.

The invention discloses an auto-fluorescence tomography re-establishing method based on a multiplier method. The auto-fluorescence tomography re-establishing method based on the multiplier method comprises the following steps of: carrying out discretization by using a finite element method diffusion equation, and establishing an optimization problem model without constraint conditions based on a penalty term of an L1 norm; obtaining a dual model of the optimization problem model without constraint conditions; establishing an augmentation lagrange function of the dual model; simplifying the maximum function of the augmentation lagrange function; solving the maximum value of the augmentation lagrange function by using a truncated-Newton algorithm; upgrading the target vector by using the gradient of the augmentation lagrange function as the steepest descent direction of a target vector; upgrading a penalty vector; and calculating an objective function value J(w), calculating k=k+1 if the ratio of the norm of J(w)k-J(w)(k-1) to the norm of Pai m being not smaller than t0l is real, and jumping to the step S4, otherwise, ending the calculation, wherein t0l is the convergence efficiency threshold value of the target function. The auto-fluorescence tomography re-establishing method provided by the invention can quickly obtain accurate and reliable light source distribution information within a large image-forming region, so that other parameters except from the regularization parameter can realize self-adaptive adjustment for improving the image-forming robustness.

The invention discloses a fractal derivative simulation method of the anomalous diffusion dynamic data reconstruction of data in concreate. The method comprises the following steps that: (1) determining an initial boundary condition; (2) determining the parameter of a diffusion equation; (3) adopting a difference method to enable a control equation to be discrete, adopting implicit scheme dispersing on an aspect of space, and determining a mesh point number according to a distribution scale of substances which need to be subjected to numerical simulation, and tidying the discrete control equation to obtain an equation set AC=b of a matrix form, wherein a time point number is Nt+1, and a space point number is Nx+1; (4) solving a linear equation set C=A/b to obtain the diffusion data of chloride ion concentration of any point x at a moment t; and (5) analyzing the diffusion data of chloride, and guiding engineering practice. By use of the method, the anomalous diffusion process and the time evolution characteristics of the condition in the concrete can be accurately simulated, peak value arrival time and advance speed in a chloride diffusion process are predicted, and a reliable guidance is provided for engineering structure design and prevention

The invention discloses a human body thoracic and abdominal cavity CT image aorta segmentation method based on a GVF Snake model. The method overcomes the shortcomings of the heavy workload and long time consuming of the traditional manual and semi-automatic segmentation, the repeatability of the method is good, and the uncertainty caused by artificial segmentation is prevented. The method includes (1) reading a CT image and performing image preprocessing; (2) performing the initial profile setting of the GVF Snake model on the image obtained after the preprocessing; (3) obtaining the edge image of the image after the preprocessing; (4) obtaining gradient vector flow GVF as the external energy field by the diffusion equation based on the obtained edge image; (5) establishing an internal energy model to maintain the smoothness of the profile; and (6) constructing an energy function E by means of internal energy and external energy, obtaining the minimum value of energy E by means of iteration operation, and the target boundary of the profile can be obtained at the end. The method has important application values in the field of human body thoracic and abdominal cavity aorta interlayer segmentation diagnosis treatment.

The invention discloses an anisotropy diffusion image noise reduction method based on a McIlhagga edge detection operator and belongs to the field of digital image noise reduction. The anisotropy diffusion image noise reduction method based on the McIlhagga edge detection operator is used for restraining speckle noise in an ultrasound image. The anisotropy diffusion image noise reduction method based on the McIlhagga edge detection operator comprises the steps that the McIlhagga edge detection operator with high robustness to noise is used for conducting edge detection on the ultrasound image so that a two-value edge image can be obtained; the two-value edge image is converted into a gradually-varied gray-level edge image through a distance mapping function; the gradually-varied edge image serves as the edge detection operator in an anisotropy diffusion equation, and noise reduction of the ultrasound image is achieved through a numerical solution method with a finite difference in an iterative mode. The method is capable of effectively reducing noise and maintaining the edge and high in robustness under the condition of large noise.

The invention discloses a method for simulating deposition on the basis of deposition process control of reference planes. The method includes analyzing deposition environments of deposition zones by the aid of well logging, mud logging and rock core information and determining change conditions of the reference planes and ancient landform conditions by the aid of burial history information; inputting ancient landforms into hydrodynamic models as initial landforms according to ancient landform analysis, simulating and reconstructing hydrodynamic characteristics of research zones, simulating and reconstructing transportation and deposition of sediment on the basis of hydrodynamic research according to sediment transport and diffusion equations, constraining deposition and denudation of deposits by the aid of the reference planes on the basis of transportation and deposition of the sediment, superposing deposition and denudation of the deposits on the initial landforms to be used as landforms for next simulation so as to carry out cyclic processes for simulating and reconstructing deposition. The method has the advantages that conditions of conditions of the reference planes are considered in simulation processes, and accordingly deposition at basin level can be simulated; the method is short in simulation time, and correction can be repeatedly carried out until requirements of geological characteristics are met.

The invention discloses an anomalous diffusion simulation method based on a discrete fraction order difference. The anomalous diffusion simulation method based on the discrete fraction order difference includes: using a one dimension classical diffusion equation for describing a diffusion phenomenon; defining the discrete fraction order difference, using the discrete fraction order difference to discretize the one dimension classical diffusion equation, and performing numerical simulation according to initial boundary conditions. Compared with a diffusion model built by using a classical fraction order diffusion equation, a diffusion model built by using the anomalous diffusion simulation method based on the discrete fraction order difference is concise in expression, and convenient and fast in numerical simulation on the premise of maintaining discrete memory effects.

The invention discloses a rapid sparse reconstruction method for exciting tomography fluorescence imaging (TFI), which comprises the following steps of: representing a diffusion equation into a linear equation by using a finite element theory; establishing a linear relation between unknown fluorescent light source distribution and boundary measuring data; calculating a surplus correlation vector to obtain the most relevant element set; merging the most relevant element set and a current support set to generate a new support set; dividing the discrete imaging space into an allowed area and a prohibited area by using the support set, and establishing a linear relation between surface fluorescence data and the allowed area; and substituting 0 for a negative element in a finally obtained solution vector. Heterogeneous characteristics of biological tissues are fully considered on the basis of a diffusion approximation model. In the process of reconstructing a light source, on the basis of sparse constraint of L1 norm, by regarding a TFI problem as a compressed sensing problem and positioning the light source by using a support set-based reconstruction method, the over-smooth phenomenonof a reconstruction result is effectively avoided, and the accuracy of TFI imaging is improved.

An adaptive TFI reconstructing method includes converting a diffusion equation into a linear equation through a finite element method; constructing a linear relation between unknown fluorescent light source distribution and a surface fluorescence measurement value; calculating a current regularization parameter and selecting an element with the largest absolute value in a difference correlation coefficient into a support set I; extracting all the current elements in the updated support set from corresponding lines in a matrix A, constituting a matrix, and obtaining a next-step searching direction; calculating the length of the next step and updating the support set; obtaining a next-step result according to the solved searching direction and step length iteration, and updating the regularization parameter; and determining whether stopping requirements are satisfied, if yes, finishing the reconstructing process, or otherwise, turning to the fourth step. According to the method, the regularization parameter is not needed to predict but determined adaptively during the reconstructing method, the reconstructing robustness is improved through adaptive regularization parameter selection, and the reconstructing efficiency is improved greatly.

A stable and accurate reactor physics thermotechnical coupling calculating method can simultaneously obtain statuses of a neutronics field, a fluid field and a heat transfer field; all variables are simultaneously updated in an iteration process, so the method has better value stability when compared with a conventional coupling method; the method uses a simultaneous time-space neutron diffusion equation and a thermotechnical equation discrete equation to obtain a novel nonlinear equation group with larger scale; using a Newton iterative method to resolve values of the novel nonlinear equation group, wherein the Newton iterative method needs to calculate a Jacobian matrix of the equation group in each iteration step, so physics thermotechnical coupling calculation is difficult. The novel method builds a value relation between the diffusion equation and thermotechnical equation, and explicit calculation can provide the Jacobian matrix, so problems caused by approximation calculation f the Jacobian matrix can be prevented; in addition, the novel method inherits Newton method characteristics, and hopes to provide faster convergence speed.

The invention discloses an image de-noising method based on bidirectional enhanced diffusion filtering, which simplifies a diffusion equation. The method comprises the steps of establishing a bidirectional diffusion coefficient so that a model can implement a bidirectional process of smoothing and sharpening in the diffusion process, enhancing an image in order to further improve the smoothing and sharpening strength, performing wavelet transform to enhance the overall outline of the image and weaken texture details of the image, then adaptively designing and improving a gradient threshold to automatically control the gradient threshold according to the maximum gray value and the iterative times of the image and further retain edge and detail features of the image, finally, simulating the purposed model, and performing simulation verification on the method by using MATLAB software. The method can be used for removing image noise and protecting detail information of edge, texture and the like, greatly improves the peak signal to noise ratio, has more excellent de-noising performance, and has a good application prospect.

The present invention relates to an electric vehicle lithium ion battery lithium precipitation diagnostic method with data drive, belonging to the technical field of battery management. The method comprises the steps of: S1: establishing an electrochemical model of a lithium ion battery; S2: in an offline phase, constructing ANN to simulate a response relation of input and output of the lithium ion battery in different conditions, and employing a Kriging model to establish a mapping relation between the ANN weight and a solid phase diffusion coefficient; S3: in an online phase, measuring datain the battery charging process through an experiment, and predicting the actual solid phase diffusion coefficients of positive and negative poles of the battery; and S4: substituting the solid phasediffusion coefficients into a solid phase diffusion equation to calculate and obtain the solid phase lithium ion concentrations of the positive and negative poles in the charging process, establish the criterion of the lithium precipitation based on the concentrations and determine whether a lithium precipitation phenomenon is generated or not in the charging process through adoption of the calculated and obtained concentrations of the positive and negative poles. In a condition of ensuring the integration of the lithium ion battery, the dependence degree of the lithium precipitation phenomenon detection process on the mechanism model is reduced.

The invention discloses a discrete fractional order differencing method in anomalous diffusion and based on step-by-step calculation. The method includes following steps: acquiring related parameters and initial-boundary conditions; adopting the discrete fractional order differencing method to discretize a control equation, and simulating distribution size of substance according to needed numerical value to determine grid point number; determining a time-space fractional order anomalous diffusion equation of anomalous diffusion, and acquiring a discrete format of the time-space anomalous diffusion equation; taking a specific value of two gamma functions in the time-space anomalous diffusion equation as a parameter, utilizing recursive relation of the gamma functions, combining concept of distributed calculation and idea of overall consideration in numerical value simulation, converting a problem of the specific value of the gamma functions into a form of product of multiple decimals, and substituting into a discrete control equation to acquire a numerical value result of diffusion concentration. The discrete fractional order differencing method has the advantages that limitation on calculation of the gamma functions is reduced, point number of simulation is expanded, and simulation efficiency is improved.

The invention relates to a biological autofluorescence tomography method and a device based on iteration reweighting. The method adopts the scheme that by capturing photon signals emitted by tumor cells of a fluorescent protein gene, a size of a tumor focal zone in an organism can be reconstructed three-dimensionally, and positioning analysis can be performed on the focal zone by fusing organism anatomical structure information provided by Micro-CT (Micro-Computed Tomography). According to the method and the device, a non-homogeneous organism model and a photon transmission model based on a diffusion equation are established by combining function information provided by autofluorescence imaging and the structure information provided by Micro-CT imaging, and three-dimensional reconstruction of an illuminant in the organism is achieved by using a norm regularization and iteration reweighting combined optimization strategy. With the adoption of the scheme, a result closer to an actual solution can be reconstructed by less observation quantity; the computational efficiency of solving can be improved effectively; the robustness of a reconstruction algorithm can be improved; and the method and the device are suitable for practical three-dimensional detection and quantitative analysis of a tumor in the practical organism.