To solve the chattering problem caused by discontinuous switching function in traditional sliding mode observer,a piecewise square root switching function with continuously varying characteristics is designed,and its ...To solve the chattering problem caused by discontinuous switching function in traditional sliding mode observer,a piecewise square root switching function with continuously varying characteristics is designed,and its stability is analyzed by using Lyapunov stability criterion.Secondly,according to the relationship among bus current,switching state and phase current,a single bus resistance sampling current reconstruction scheme without current sensors is adopted,which effectively reduces the cost of motor system.Finally,the feasibility and effectiveness of the proposed scheme are verified by simulation.展开更多
High-temperature superconducting(HTS)rare-earth barium copper oxide(REBCO)-coated conductors(CCs)are widely used in large-scale applications owing to their high critical performance and excellent mechanical stability....High-temperature superconducting(HTS)rare-earth barium copper oxide(REBCO)-coated conductors(CCs)are widely used in large-scale applications owing to their high critical performance and excellent mechanical stability.However,defects can significantly degrade their performance by distorting current distributions.Conventional nondestructive evaluation techniques typically involve stepwise inversion from magnetic field measurements to current distributions,and then to defect morphology.However,these approaches suffer from intrinsic ill-posedness and limited ability to identify complex or multiple defects.To address these challenges,we propose an integrated inverse-forward framework that combines deep learning with physical modeling to directly map surface magnetic field measurements to internal defect morphology and current density distributions.The core of this method is a specially designed conditional generative adversarial network(cGAN)as the primary learner.It undergoes adversarial training on a dataset containing complex multi-defect configurations and their corresponding magnetic field distributions,enabling robust inverse prediction of defect morphology.The reconstructed defect geometry is then incorporated as a boundary constraint into the forward solution of Maxwell’s equations coupled with superconducting nonlinear constitutive relations,enabling high-fidelity reconstruction of the current density distribution.Validation was performed using finite element simulations of REBCO-CCs with various defect types under current-carrying conditions.The adversarial training was performed using the generated finite element dataset.The trained model accurately identified multiple complex defect morphologies across different operating conditions and demonstrated strong generalization capability.Furthermore,the reconstructed current density accurately reproduced the original magnetic field distribution,confirming the reliability of the proposed method.This work integrates data-driven inference with physics-based modeling to establish a unified“magnetic field-defect morphology-current density”inversion paradigm,providing an efficient and reliable approach for nondestructive evaluation and performance assessment of REBCO-CCs.展开更多
This paper constructs a concentric ellipsoid torso-heart model by boundary element method and investigates the impacts of model structures on the cardiac magnetic fields generated by both equivalent primary source--a ...This paper constructs a concentric ellipsoid torso-heart model by boundary element method and investigates the impacts of model structures on the cardiac magnetic fields generated by both equivalent primary source--a current dipole and volume currents. Then by using the simulated magnetic fields based on torso-heart model as input, the cardiac current sources--an array of current dipoles by optimal constrained linear inverse method are constructed. Next, the current dipole array reconstruction considering boundaries is compared with that in an unbounded homogeneous medium. Furthermore, the influence of random noise on reconstruction is also considered and the reconstructing effect is judged by several reconstructing parameters.展开更多
Cardiac current source reconstruction is investigated by a fast greedy sparse(FGS) method applied to simulated and real magnetocardiography(MCG) data measured using 61-channel superconducting quantum interference devi...Cardiac current source reconstruction is investigated by a fast greedy sparse(FGS) method applied to simulated and real magnetocardiography(MCG) data measured using 61-channel superconducting quantum interference device. The approach reduces the size of the lead field matrix based on a priori knowledge of dipolar magnetic field map. Consequently, the computational demands and the accuracy of sparse source reconstruction are improved simultaneously. The simulation results demonstrate that the FGS method is capable of reconstructing sparse equivalent current sources using the magnetic field data generated by a single current source with varying orientation or multiple current sources generated randomly. In addition, we analyze the cardiac current source reconstructed with real MCG data at typical instants and discuss the electrical excitation conduction during the QRS complex based on moving sparse source imaging.展开更多
A new method for the imaging of cardiac electrical activity in patients with complete right bundle branch block （CRBBB） or complete left bundle branch block （CLBBB） is investigated using magnetocardiographic recor...A new method for the imaging of cardiac electrical activity in patients with complete right bundle branch block （CRBBB） or complete left bundle branch block （CLBBB） is investigated using magnetocardiographic recordings of the surface of the body. This is based on the assumption that an equivalent single-current dipole moves along the unblocked bundle branch, whose position in the measurement plane is expressed in terms of the maximum and minimum, as well as the maximum gradient value of the measured magnetic field. The trajectory of the moving dipole on the measurement plane is indicative of theexcitation conduction of the CRBBB or CLBBB subject during ventricular depolarization and repolarization, which is deduced by comparing each change between the dipole moment and the maximum current density in a corresponding pseudo-current density map. In summary, this method can distinguish CRBBB from CLBBB subjects by means of the dipole depth and two dipole moment components. The possibility of visualizing the excitation conduction in a CRBBB or CLBBB subject during ventricular depolarization and repolarization is then discussed.展开更多
文摘To solve the chattering problem caused by discontinuous switching function in traditional sliding mode observer,a piecewise square root switching function with continuously varying characteristics is designed,and its stability is analyzed by using Lyapunov stability criterion.Secondly,according to the relationship among bus current,switching state and phase current,a single bus resistance sampling current reconstruction scheme without current sensors is adopted,which effectively reduces the cost of motor system.Finally,the feasibility and effectiveness of the proposed scheme are verified by simulation.
基金supported by the National Natural Science Foundation of China(12272156 and 12327901)National Key R&D program of China(2023YFA1609500).
文摘High-temperature superconducting(HTS)rare-earth barium copper oxide(REBCO)-coated conductors(CCs)are widely used in large-scale applications owing to their high critical performance and excellent mechanical stability.However,defects can significantly degrade their performance by distorting current distributions.Conventional nondestructive evaluation techniques typically involve stepwise inversion from magnetic field measurements to current distributions,and then to defect morphology.However,these approaches suffer from intrinsic ill-posedness and limited ability to identify complex or multiple defects.To address these challenges,we propose an integrated inverse-forward framework that combines deep learning with physical modeling to directly map surface magnetic field measurements to internal defect morphology and current density distributions.The core of this method is a specially designed conditional generative adversarial network(cGAN)as the primary learner.It undergoes adversarial training on a dataset containing complex multi-defect configurations and their corresponding magnetic field distributions,enabling robust inverse prediction of defect morphology.The reconstructed defect geometry is then incorporated as a boundary constraint into the forward solution of Maxwell’s equations coupled with superconducting nonlinear constitutive relations,enabling high-fidelity reconstruction of the current density distribution.Validation was performed using finite element simulations of REBCO-CCs with various defect types under current-carrying conditions.The adversarial training was performed using the generated finite element dataset.The trained model accurately identified multiple complex defect morphologies across different operating conditions and demonstrated strong generalization capability.Furthermore,the reconstructed current density accurately reproduced the original magnetic field distribution,confirming the reliability of the proposed method.This work integrates data-driven inference with physics-based modeling to establish a unified“magnetic field-defect morphology-current density”inversion paradigm,providing an efficient and reliable approach for nondestructive evaluation and performance assessment of REBCO-CCs.
基金Project supported by the State Key Development Program for Basic Research of China(Grant No.2006CB601007)the National Natural Science Foundation of China(Grant No.10674006)the National High Technology Research and Development Program of China(Grant No.2007AA03Z238)
文摘This paper constructs a concentric ellipsoid torso-heart model by boundary element method and investigates the impacts of model structures on the cardiac magnetic fields generated by both equivalent primary source--a current dipole and volume currents. Then by using the simulated magnetic fields based on torso-heart model as input, the cardiac current sources--an array of current dipoles by optimal constrained linear inverse method are constructed. Next, the current dipole array reconstruction considering boundaries is compared with that in an unbounded homogeneous medium. Furthermore, the influence of random noise on reconstruction is also considered and the reconstructing effect is judged by several reconstructing parameters.
基金supported by the National Natural Science Foundation of China(60771030)the National HighTechnology Research and Development Program of China(2008AA02Z308)+2 种基金the Shanghai Science and Technology Development Foundation(08JC1421800)Shanghai Leading Academic Discipline Project(B004)the Open Project of State Key Laboratory of Function Materials for Information(Shanghai Institute of Microsystem and Information Technology,Chinese Academy of Sciences)
文摘Cardiac current source reconstruction is investigated by a fast greedy sparse(FGS) method applied to simulated and real magnetocardiography(MCG) data measured using 61-channel superconducting quantum interference device. The approach reduces the size of the lead field matrix based on a priori knowledge of dipolar magnetic field map. Consequently, the computational demands and the accuracy of sparse source reconstruction are improved simultaneously. The simulation results demonstrate that the FGS method is capable of reconstructing sparse equivalent current sources using the magnetic field data generated by a single current source with varying orientation or multiple current sources generated randomly. In addition, we analyze the cardiac current source reconstructed with real MCG data at typical instants and discuss the electrical excitation conduction during the QRS complex based on moving sparse source imaging.
基金Project supported in part by the National Natural Science Foundation of China(Grant No.60771030)the National High-Technology Research and DevelopmentProgram of China(Grant No.2008AA02Z308)+3 种基金the Shanghai Science and Technology Development Foundation(Grant No.08JC1421800)the Shanghai Leading Academic Discipline Project(Grant No.B004)the Open Project of State Key Laboratory of Function Materials for Information(Shanghai Instituteof Microsystem and Information Technology,Chinese Academy of Sciences)the Key Laboratory of Medical Imaging Computing and Computer Assisted Intervention of Shanghai(Grant No.13DZ2272200-2)
文摘A new method for the imaging of cardiac electrical activity in patients with complete right bundle branch block （CRBBB） or complete left bundle branch block （CLBBB） is investigated using magnetocardiographic recordings of the surface of the body. This is based on the assumption that an equivalent single-current dipole moves along the unblocked bundle branch, whose position in the measurement plane is expressed in terms of the maximum and minimum, as well as the maximum gradient value of the measured magnetic field. The trajectory of the moving dipole on the measurement plane is indicative of theexcitation conduction of the CRBBB or CLBBB subject during ventricular depolarization and repolarization, which is deduced by comparing each change between the dipole moment and the maximum current density in a corresponding pseudo-current density map. In summary, this method can distinguish CRBBB from CLBBB subjects by means of the dipole depth and two dipole moment components. The possibility of visualizing the excitation conduction in a CRBBB or CLBBB subject during ventricular depolarization and repolarization is then discussed.
