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37 results about "Scalar potential" patented technology

Scalar potential, simply stated, describes the situation where the difference in the potential energies of an object in two different positions depends only on the positions, not upon the path taken by the object in traveling from one position to the other. It is a scalar field in three-space: a directionless value (scalar) that depends only on its location. A familiar example is potential energy due to gravity.

Magnetic field generator suitable for unilateral nuclear magnetic resonance and method for making same

A unilateral NMR sensor comprising a ferromagnetic yoke; a permanent magnet arranged on the yoke; a pole piece on the magnet; the pole piece including an air-pole piece interface surface whose shape corresponds to an equipotential contour of magnetic scalar potential. An approach for designing single-sided magnets suitable for unilateral magnetic resonance (UMR) measurements is presented. The method uses metal pole pieces to shape the field from permanent magnets in a target region. The pole pieces are shaped according to solutions to Laplace's equation, and can be designed using a combination of analytical methods and numerical optimization. The design leads to analytical expressions for the pole piece shape and magnetic field. The method is developed in Cartesian, polar, and spherical coordinates, and the merits of each system are discussed. The effects of finite magnet size on the field quality are explored through simulation, and are found to have a substantial effect in many cases. A magnet is designed using our method to produce a static field with a constant gradient over a region 2 cm in diameter and 2 mm thick. This leads to a compact cylindrical magnet just over 11 cm in diameter, topped with a single metal pole piece. The design is validated through simulation. The simulated field is found to agree closely with that specified analytically through the design procedure.
Owner:UNIVERSITY OF NEW BRUNSWICK

Marine controlled source electromagnetic method finite element forward method of anisotropic media

The present invention is a marine controlled source electromagnetic method finite element forward method of anisotropic media. The method comprises: firstly, setting a reference electrical conductivity, wherein three non-zero diagonal elements of the reference electrical conductivity are electrical conductivities in the direction of three main axes: x, y, z; next, setting three Euler rotation angles, and after three times of Euler rotation, obtaining an electrical conductivity tensor model in any direction; then starting from Maxwell equations, obtaining a finite element equation that is satisfied by magnetic vector potential and scalar potential under Coulomb regulations on a condition that the electrical conductivity presents anisotropy; then, performing discrete segmentation on a research region by using a non-structural grid, so that a complicated geoelectric model can be constructed; combining an incomplete LU discomposition pre-condition factor with an IDR(s) algorithm, so as to realize efficient and precise solution of a large sparse linear equation; and finally, deriving vector potential and scalar potential of a secondary field by using weighted moving least squares solution, to obtain each component of an electromagnetic field. The method provided by the present invention has excellent universality and can be promoted for electromagnetic method numerical value simulation with complicated electrical conductivity distribution and high precision.
Owner:JILIN UNIV

Method for calculating plane wave reflection coefficients in elastic multi-layered medium

The invention discloses a method for calculating plane wave reflection coefficients in an elastic multi-layered medium. The method comprises the following steps: (1) if plane harmonic waves enter into a target layer series from a medium n+1, generating reflected longitudinal waves and reflected transverse waves in the n+1 medium, generating transmitted longitudinal waves and transmitted transverse waves in a medium 1, and writing each medium layer in a scalar potential form and a vector potential form; (2) determining relation among the displacement, stress and bit shift; (3) loading the scalar potential and vector potential of the step (1) into the step (2) to obtain a displacement and stress relation expression between the (n+1)th layer and the first layer; and (4) obtaining a displacement and stress transfer matrix containing elasticity coefficients of each layer according to the displacement and stress relation expression, which is obtained in the steps (3), between the (n+1)th layer and the first layer, solving, and obtaining reflection and transmission coefficients. According to the method, the influence of multiple waves and transformed waves of the elastic layer series as well as thickness and frequency on the reflection coefficient is considered fully, so that the method is applicable to thin-layer AVO (Amplitude Variation with Offset) analytical simulation and is high in calculation efficiency.
Owner:HOHAI UNIV

Electric conductivity rebuilding method for magnetocaloric acoustical imaging

The invention relates to an electric conductivity rebuilding method for magnetocaloric acoustical imaging. The electric conductivity rebuilding method is based on a magnetocaloric acoustical imaging principle. An exciting coil is used for exerting MHz current excitation on a conducting object, joule heat is generated in the conducting object, and further, ultrasonic signals are generated. An ultrasonic transducer is used for receiving the ultrasonic signals, the received ultrasonic signals are processed and collected, and then, an electric conductivity image of the conducting object is obtained by adopting an electric conductivity image rebuilding algorithm. The electric conductivity rebuilding method comprises the concrete steps that 1, firstly, high-signal-to-noise-ratio magnetocaloric acoustical signals are obtained; 2, the obtained magnetocaloric acoustical signals are used for rebuilding to obtain thermal sound source distribution of the conducting object; 3, the thermal sound source distribution and a one-order magnetic vector space component are used, and a non-linear finite element solution method is adopted for rebuilding a scalar potential space component; 4, the rebuilt scalar potential space component is used for rebuilding the electric conductivity.
Owner:INST OF ELECTRICAL ENG CHINESE ACAD OF SCI

Magnetic thermal sound imaging resistivity rebuilding method based on optimization iterative algorithm

The invention provides a magnetic thermal sound imaging resistivity rebuilding method based on an optimization iterative algorithm. An exciting coil generates electromagnetic thermal sound signals on a conducting object, an ultrasonic transducer receives the electromagnetic thermal sound signals, the signals are processed through an ultrasonic signal processing and collecting sub system, and a control circuit controls the synchronization of a current excitation source, the ultrasonic transducer and the ultrasonic signal processing and collecting sub system. The ultrasonic transducer carries out fault circumference scanning on the electromagnetic thermal sound signals, electromagnetic ultrasonic signals on each fault circumference are obtained, and finally, the rebuilding of a resistivity image is realized through being combined with an image rebuilding algorithm. The resistivity image rebuilding method has the advantages that an objective function satisfying a thermal sound source, the resistivity, a primary magnetism loss position space component and a scalar potential space component is firstly defined, under the condition that the thermal sound source distribution is known, the scalar potential space component is solved according to the current continuity theorem, then, the scalar potential space component and the magnetism loss position space component are substituted into the objective function, and the resistivity distribution is rebuilt.
Owner:INST OF ELECTRICAL ENG CHINESE ACAD OF SCI

Conductivity image reconstructing method for magneto-thermoacoustic coupled tomography

A conductivity image reconstructing method for magneto-thermoacoustic coupled tomography includes: acquiring a thermoacoustic source distribution of a conductive object by means of time inversion according to an electromagnetic ultrasonic signal received, and performing reconstruction according to the thermoacoustic source distribution to obtain a conductivity distribution of the conductive object. Specially, the method includes: acquiring a thermoacoustic source on a certain level by means of time inversion, acquiring a thermoacoustic source of the conductive object by means of interpolation, performing calculation by means of Biot-Savart's law according to excitation current to obtain a spatial component A1 of primary magnetic vector potential, subjecting the conductive object to spatial discretization, giving an initial value [Sigma]<0> of conductivity, according to the theorem of current continuity, solving a spatial component [Phi] <1> of scalar potential with the initial value [Sigma]<0> and the spatial component A1, substituting the spatial component [Phi]<1> of the scalar potential to a relation which the thermoacoustic source and conductivity meet so as to obtain updated conductivity [Sigma]<1>, replacing the initial value [Sigma]<0> with the updated conductivity [Sigma]<1>, repeating the process above, and stopping iteration until a relative error of the conductivity meets an equation: Sigma=||([Sigma]1-[Sigma]0)/[Sigma]0||2<=Sigma0.
Owner:INST OF ELECTRICAL ENG CHINESE ACAD OF SCI

Model verification method for prediction model of underwater ship corrosion-related static magnetic field

The invention provides a model verification method for a prediction model of an underwater ship corrosion-related static magnetic field. The method comprises the following steps: firstly, simulating seawater and ocean environments in a lab, constructing a ship model and an impressed current cathodic protection system of the ship model according to a certain scale ratio, measuring electric scalar potential distribution below the ship model, and constructing the horizontal current line prediction model of the underwater ship corrosion-related static magnetic field; secondly, loading a horizontal current line in the same experimental environment to replace the ship model, repeatedly measuring electric scalar potential in the same position below the ship model, and synchronously measuring magnetic field distribution in water; thirdly, comparing the measured electric scalar potential of the current line with a measurement result of the ship model to prove the feasibility of field source equivalency; comparing the measured magnetic field with a prediction result of the prediction model to prove the correctness of a prediction process of the prediction model. According to the method, the feasibility of field source equivalency is proved by comparing the electric field distribution, and the correctness of the prediction process is proved by comparing the magnetic field distribution, so that a model verification problem of the prediction model of the underwater ship corrosion-related static magnetic field is solved.
Owner:NAVAL UNIV OF ENG PLA

Magnetic thermoacoustic imaging conductivity reconstruction method based on linear Poisson's equation

The invention discloses a magnetic thermoacoustic imaging conductivity reconstruction method based on a linear Poisson's equation. An exciting coil generates an electromagnetic thermoacoustic signal on a conductive object; an ultrasonic transducer receives the electromagnetic thermoacoustic signal; an ultrasonic signal processing and acquiring subsystem acquires and processes the signal; and a control circuit controls the synchronization of a current excitation source, the ultrasonic transducer and the ultrasonic signal processing and acquiring subsystem. The method comprises the following steps: performing circular fault scanning on the electromagnetic thermoacoustic signal by virtue of the ultrasonic transducer, acquiring an electromagnetic ultrasonic signal on the circumference of each fault, and finally combining an image reconstruction algorithm to realize the conductivity image reconstruction. The conductivity image reconstruction method comprises the following steps: firstly defining an objective function meeting a thermoacoustic source, the conductivity, a primary magnetic dislocation spatial component and an electric scalar potential spatial component, giving the initial value of the conductivity, solving the electric scalar potential spatial component according to a current continuity theorem under the condition that the thermoacoustic source distribution is known, substituting the electric scalar potential spatial component and magnetic dislocation spatial component into the objective function, and reconstructing the conductivity distribution.
Owner:INST OF ELECTRICAL ENG CHINESE ACAD OF SCI

Magnetic field generator suitable for unilateral nuclear magnetic resonance and method for making same

A unilateral NMR sensor comprising a ferromagnetic yoke; a permanent magnet arranged on the yoke; a pole piece on the magnet; the pole piece including an air-pole piece interface surface whose shape corresponds to an equipotential contour of magnetic scalar potential. An approach for designing single-sided magnets suitable for unilateral magnetic resonance (UMR) measurements is presented. The method uses metal pole pieces to shape the field from permanent magnets in a target region. The pole pieces are shaped according to solutions to Laplace's equation, and can be designed using a combination of analytical methods and numerical optimization. The design leads to analytical expressions for the pole piece shape and magnetic field. The method is developed in Cartesian, polar, and spherical coordinates, and the merits of each system are discussed. The effects of finite magnet size on the field quality are explored through simulation, and are found to have a substantial effect in many cases. A magnet is designed using our method to produce a static field with a constant gradient over a region 2 cm in diameter and 2 mm thick. This leads to a compact cylindrical magnet just over 11 cm in diameter, topped with a single metal pole piece. The design is validated through simulation. The simulated field is found to agree closely with that specified analytically through the design procedure.
Owner:UNIVERSITY OF NEW BRUNSWICK

Transformer vortex field finite element solving method based on sinc function

The invention discloses a transformer vortex field finite element solving method based on a sinc function. According to the method, first, a model is established for a transformer, and then meshing isperformed on the established model according to a finite element method; the finite element method is adopted to calculate a stiffness matrix and a damping matrix of the model according to unit nodeinformation obtained through meshing; and a magnetic vector potential and a scalar potential are selected to serve as an unknown function of a vortex field mathematical model, a discretization formatis exported through a Galerkin finite element method, a discretization equation set is established, solutions of the discretization equation set are solved through a sinc interpolation method, electric field distribution and magnetic field distribution in a transformer solving domain can be obtained according to the solutions of the equation set, and therefore vortex distribution and loss of the transformer can be calculated. The method is simple in design, easy to implement and easy to popularize, provides more precise analysis for vortex field and loss calculation of large and ultra-large power transformers, provides a basis for transformer design and manufacturing and improves the security and stability of transformer operation.
Owner:XI AN JIAOTONG UNIV

A Conductivity Image Reconstruction Method Based on Magnetic-Thermal-Acoustic Coupling Imaging

ActiveCN104434094BConductivity reconstructionDiagnostic recording/measuringSensorsSound sourcesScalar potential
A conductivity image reconstructing method for magneto-thermoacoustic coupled tomography includes: acquiring a thermoacoustic source distribution of a conductive object by means of time inversion according to an electromagnetic ultrasonic signal received, and performing reconstruction according to the thermoacoustic source distribution to obtain a conductivity distribution of the conductive object. Specially, the method includes: acquiring a thermoacoustic source on a certain level by means of time inversion, acquiring a thermoacoustic source of the conductive object by means of interpolation, performing calculation by means of Biot-Savart's law according to excitation current to obtain a spatial component A1 of primary magnetic vector potential, subjecting the conductive object to spatial discretization, giving an initial value [Sigma]<0> of conductivity, according to the theorem of current continuity, solving a spatial component [Phi] <1> of scalar potential with the initial value [Sigma]<0> and the spatial component A1, substituting the spatial component [Phi]<1> of the scalar potential to a relation which the thermoacoustic source and conductivity meet so as to obtain updated conductivity [Sigma]<1>, replacing the initial value [Sigma]<0> with the updated conductivity [Sigma]<1>, repeating the process above, and stopping iteration until a relative error of the conductivity meets an equation: Sigma=||([Sigma]1-[Sigma]0) / [Sigma]0||2<=Sigma0.
Owner:INST OF ELECTRICAL ENG CHINESE ACAD OF SCI

A Conductivity Reconstruction Method for Magnetothermoacoustic Imaging

The invention relates to an electric conductivity rebuilding method for magnetocaloric acoustical imaging. The electric conductivity rebuilding method is based on a magnetocaloric acoustical imaging principle. An exciting coil is used for exerting MHz current excitation on a conducting object, joule heat is generated in the conducting object, and further, ultrasonic signals are generated. An ultrasonic transducer is used for receiving the ultrasonic signals, the received ultrasonic signals are processed and collected, and then, an electric conductivity image of the conducting object is obtained by adopting an electric conductivity image rebuilding algorithm. The electric conductivity rebuilding method comprises the concrete steps that 1, firstly, high-signal-to-noise-ratio magnetocaloric acoustical signals are obtained; 2, the obtained magnetocaloric acoustical signals are used for rebuilding to obtain thermal sound source distribution of the conducting object; 3, the thermal sound source distribution and a one-order magnetic vector space component are used, and a non-linear finite element solution method is adopted for rebuilding a scalar potential space component; 4, the rebuilt scalar potential space component is used for rebuilding the electric conductivity.
Owner:INST OF ELECTRICAL ENG CHINESE ACAD OF SCI

Imaging reconstruction method based on injected current thermoacoustic conductivity

A drect iteration-based injection current type thermoacoustic conductivity image reconstruction method is disclosed and comprises the following steps: in a first step, injection current type thermoacoustic signals of an object body are obtained; in a second step, a time reversal method is used for obtaining a thermoacoustic source of the object body according to the thermoacoustic signals; in a third step, an initial value of conductivity is given, and an electric scalar potential is solved; in a fourth step, new conductivity is solved; in a fifth step, the conductivity is solved via iteration. The method comprises the following specific processes: the time reversal method is used for obtaining thermoacoustic source distribution on a certain fault plane, an interpolation method is used for obtaining an overall thermoacoustic source of the object body, the initial value [sigma]0 is given, the electric scalar potential [phi]1 is solved via the known [sigma]0 based on a current continuity theorem, the electric scalar potential [phi]1 is substituted into a relational expression for the thermoacoustic source and the conductivity, updated conductivity [sigma]1 is obtained, [sigma]0 is replaced with [sigma]1, and the above processes are repeated till relative error of the conductivity satisfies epsilon=||([sigma]i-[sigma]i-1) / [sigma]i-1||2<=epsilon0.
Owner:INST OF ELECTRICAL ENG CHINESE ACAD OF SCI

A finite element solution method for transformer eddy current field based on sinc function

The invention discloses a transformer vortex field finite element solving method based on a sinc function. According to the method, first, a model is established for a transformer, and then meshing isperformed on the established model according to a finite element method; the finite element method is adopted to calculate a stiffness matrix and a damping matrix of the model according to unit nodeinformation obtained through meshing; and a magnetic vector potential and a scalar potential are selected to serve as an unknown function of a vortex field mathematical model, a discretization formatis exported through a Galerkin finite element method, a discretization equation set is established, solutions of the discretization equation set are solved through a sinc interpolation method, electric field distribution and magnetic field distribution in a transformer solving domain can be obtained according to the solutions of the equation set, and therefore vortex distribution and loss of the transformer can be calculated. The method is simple in design, easy to implement and easy to popularize, provides more precise analysis for vortex field and loss calculation of large and ultra-large power transformers, provides a basis for transformer design and manufacturing and improves the security and stability of transformer operation.
Owner:XI AN JIAOTONG UNIV
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