The formulas which are suitable to birefringent medium with symmetric plane are derived by means of phase retard integration.We have adopted this concept to the axisymmetric problems and deduced some useful formulas f...The formulas which are suitable to birefringent medium with symmetric plane are derived by means of phase retard integration.We have adopted this concept to the axisymmetric problems and deduced some useful formulas for these cases.As a practical application,the strain rate analysis of flow in a diverging or a converging vessel is illustrated at the end of this paper.展开更多
This article uses the phase space path integral method to find the propagator for a particle with a force quadratic in velocity. Two specific canonical transformations has been used for this purpose.
The epitaxial material, device structure, and corresponding equivalent large signal circuit model of GaAs planar Schottky varactor diode are successfully developed to design and fabricate a monolithic phase shifter, w...The epitaxial material, device structure, and corresponding equivalent large signal circuit model of GaAs planar Schottky varactor diode are successfully developed to design and fabricate a monolithic phase shifter, which is based on right-handed nonlinear transmission lines and consists of a coplanar waveguide transmission line and periodically distributed GaAs planar Schottky varactor diode. The distributed-Schottky transmission-line-type phase shifter at a bias voltage greater than 1.5 V presents a continuous 0°–360° differential phase shift over a frequency range from 0 to 33 GHz. It is demonstrated that the minimum insertion loss is about 0.5 dB and that the return loss is less than-10 dB over the frequency band of 0–33 GHz at a reverse bias voltage less than 4.5 V. These excellent characteristics, such as broad differential phase shift, low insertion loss, and return loss, indicate that the proposed phase shifter can entirely be integrated into a phased array radar circuit.展开更多
Active Magnetic Bearing(AMB)levitates rotor by magnetic force without friction,and it can provide active control force to suppress vibration while rotating.Most of vibration suppressing methods need angular speed sens...Active Magnetic Bearing(AMB)levitates rotor by magnetic force without friction,and it can provide active control force to suppress vibration while rotating.Most of vibration suppressing methods need angular speed sensors to obtain rotating speed,but in many occasions,angular speed sensor is difficult to install or is difficult to guarantee reliability.This paper proposed a vibration suppressing strategy without angular speed sensor based on generalized integrator and frequency locked loop(GI-FLL)and phase shift generalized integrator(PSGI).GI-FLL and high-pass filter estimate frequency from control current,PSGI is applied to generate compensating signal.Firstly,model of AMB system expressed by transfer function is established and effect of centrifugal force is analyzed.Then,principle and process of vibration suppressing strategy is introduced.Influence of parameters are analyzed by root locus and bode diagram.Simulation results display the process of frequency estimation and performance of displacement.Experiments are carried on a test rig,results of simulations and experiments demonstrate the effectiveness of proposed vibration suppressing strategy.展开更多
The invariant, propagator, and wavefunction for a variable frequency harmonic oscillator in an electromagnetic field are obtained by making a specific coordinate transformation and by using the method of phase space p...The invariant, propagator, and wavefunction for a variable frequency harmonic oscillator in an electromagnetic field are obtained by making a specific coordinate transformation and by using the method of phase space path integral method. The probability amplitudes for a dissipative harmonic oscillator in the time varying electric field are obtained.展开更多
This paper presents a three-phase integrated power electronic transformer(PET)topology with the capability of DC fault clearance based on the investigation of PET topology.The proposed PET has three ports of high-volt...This paper presents a three-phase integrated power electronic transformer(PET)topology with the capability of DC fault clearance based on the investigation of PET topology.The proposed PET has three ports of high-voltage AC,high-voltage DC and low-voltage DC,which can achieve the flexible access of distributed energy resources・The power unit of the PET adopts a three-phase integrated topology,and the single-phase fluctuating power in the DC-link capacitor is reduced by a 4-port DC/DC converter,thereby reducing the capacitance of the DC-link capacitor;Meanwhile,the power unit uses the clamp double sub-module(CDSM)to allow for self-clearing of the short-circuit fault on the high-voltage DC side.Finally,this paper verifies the proposed PET through an EMT simulation and experimental prototype.展开更多
Antiferromagnetism has become a promising candidate for the next generation electronic devices due to its thermal stability,low energy consumption,and fast switching speed.However,the canceling of the net magnetic mom...Antiferromagnetism has become a promising candidate for the next generation electronic devices due to its thermal stability,low energy consumption,and fast switching speed.However,the canceling of the net magnetic moment in antiferromagnetic order presents great challenge on quantitative characterization and modulation,hindering its investigation and application.In this work,utilizing the optical second harmonic generation(SHG)in a wide temperature range,the integrated differential phase contrast scanning transmission electron microscopy,and firstprinciples calculations,we performed a quantitative study on the evolution of non-collinear antiferromagnetic order in BiFeO_(3)films with a series of strains.We found that the antiferromagnetic coupling was significantly enhanced,featured by the increase of Néel temperature from 428 K to 646 K,and by one order of enhancement of SHG intensity contributed from the G-type antiferromagnetic order by strain manipulation from-2.4%to+0.6%.We attributed the enhancement of the antiferromagnetic coupling to the enhancement of the superexchange interaction as the Fe-O-Fe bond angle approaches 180°when the in-plane lattice constants increase,which might also result in a tendency from a non-collinear antiferromagnetic order to a collinear one.Our work not only bridges the antiferromagnetic order and the strain manipulation in epitaxial multiferroics,more importantly,also paves a way for quantitative characterization by SHG technology and the precise manipulation of antiferromagnetism.展开更多
A simple and highly-efficient method for numerically evaluating the waves created by a ship that travels at a constant speed in calm water, of large depth or of uniform depth, is given. The method, inspired by Kelvin...A simple and highly-efficient method for numerically evaluating the waves created by a ship that travels at a constant speed in calm water, of large depth or of uniform depth, is given. The method, inspired by Kelvin＇s classical stationary-phase analysis, is suited for evaluating far-field as well as near-field waves. More generally, the method can be applied to a broad class of integrals with integrands that contain a rapidly oscillatory trigonometric function with a phase function whose first derivative（and possibly also higher derivatives） vanishes at one or several points, commonly called points of stationary phase, with the range of integration.展开更多
Ferroelectric barium titanate nanoparticles(BTO NPs)may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors.While increasing experimental and theoretical understandi...Ferroelectric barium titanate nanoparticles(BTO NPs)may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors.While increasing experimental and theoretical understandings on the structure of BTO and doped BTO have been developed over the past decade,the majority of the investigation was carried out in thin-film materials;therefore,the doping effect on nanoparticles remains unclear.Especially,doping-induced local composition and structure fluctuation across single nanoparticles have yet to be unveiled.In this work,we use electron microscopy-based techniques including high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),integrated differential phase contrast(iDPC)-STEM,and energy dispersive X-ray spectroscopy(EDX)mapping to reveal atomically resolved chemical and crystal structure of BTO and strontium doped BTO nanoparticles.Powder X-ray diffraction(PXRD)results indicate that the increasing strontium doping causes a structural transition from tetragonal to cubic phase,but the microscopic data validate substantial compositional and microstructural inhomogeneities in strontium doped BTO nanoparticles.Our work provides new insights into the structure of doped BTO NPs and will facilitate the materials design for next-generation high-density nano-dielectric devices.展开更多
基金The project supported by National Natural Science foundation of China.
文摘The formulas which are suitable to birefringent medium with symmetric plane are derived by means of phase retard integration.We have adopted this concept to the axisymmetric problems and deduced some useful formulas for these cases.As a practical application,the strain rate analysis of flow in a diverging or a converging vessel is illustrated at the end of this paper.
文摘This article uses the phase space path integral method to find the propagator for a particle with a force quadratic in velocity. Two specific canonical transformations has been used for this purpose.
基金Project supported by the Fundamental Research Funds for Central Universities,China(Grant No.XDJK2013B004)the Research Fund for the Doctoral Program of Southwest University,China(Grant No.SWU111030)the State Key Laboratory for Millimeter Waves of Southeast University,China(Grant No.K201312)
文摘The epitaxial material, device structure, and corresponding equivalent large signal circuit model of GaAs planar Schottky varactor diode are successfully developed to design and fabricate a monolithic phase shifter, which is based on right-handed nonlinear transmission lines and consists of a coplanar waveguide transmission line and periodically distributed GaAs planar Schottky varactor diode. The distributed-Schottky transmission-line-type phase shifter at a bias voltage greater than 1.5 V presents a continuous 0°–360° differential phase shift over a frequency range from 0 to 33 GHz. It is demonstrated that the minimum insertion loss is about 0.5 dB and that the return loss is less than-10 dB over the frequency band of 0–33 GHz at a reverse bias voltage less than 4.5 V. These excellent characteristics, such as broad differential phase shift, low insertion loss, and return loss, indicate that the proposed phase shifter can entirely be integrated into a phased array radar circuit.
基金the National Natural Science Foundation of China(NSFC)under Grant 51877091.
文摘Active Magnetic Bearing(AMB)levitates rotor by magnetic force without friction,and it can provide active control force to suppress vibration while rotating.Most of vibration suppressing methods need angular speed sensors to obtain rotating speed,but in many occasions,angular speed sensor is difficult to install or is difficult to guarantee reliability.This paper proposed a vibration suppressing strategy without angular speed sensor based on generalized integrator and frequency locked loop(GI-FLL)and phase shift generalized integrator(PSGI).GI-FLL and high-pass filter estimate frequency from control current,PSGI is applied to generate compensating signal.Firstly,model of AMB system expressed by transfer function is established and effect of centrifugal force is analyzed.Then,principle and process of vibration suppressing strategy is introduced.Influence of parameters are analyzed by root locus and bode diagram.Simulation results display the process of frequency estimation and performance of displacement.Experiments are carried on a test rig,results of simulations and experiments demonstrate the effectiveness of proposed vibration suppressing strategy.
文摘The invariant, propagator, and wavefunction for a variable frequency harmonic oscillator in an electromagnetic field are obtained by making a specific coordinate transformation and by using the method of phase space path integral method. The probability amplitudes for a dissipative harmonic oscillator in the time varying electric field are obtained.
基金supported by National Key Research and Development Program of China(2016YFB0400505)Science and Technology Project of State Grid Corporation(SGRIGLBDTKJ[2017]676).
文摘This paper presents a three-phase integrated power electronic transformer(PET)topology with the capability of DC fault clearance based on the investigation of PET topology.The proposed PET has three ports of high-voltage AC,high-voltage DC and low-voltage DC,which can achieve the flexible access of distributed energy resources・The power unit of the PET adopts a three-phase integrated topology,and the single-phase fluctuating power in the DC-link capacitor is reduced by a 4-port DC/DC converter,thereby reducing the capacitance of the DC-link capacitor;Meanwhile,the power unit uses the clamp double sub-module(CDSM)to allow for self-clearing of the short-circuit fault on the high-voltage DC side.Finally,this paper verifies the proposed PET through an EMT simulation and experimental prototype.
基金supported by the National Key Basic Research Program of China(Grant No.2019YFA0308500,2020YFA0309100,and 2021YFA1400701)the National Natural Science Foundation of China(Grant No.12174437,No.12222414,No.12074416,and No.12104054)+4 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB33030200)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.Y2022003)the China Postdoctoral Innovative Talent Support Program(Grant No.BX20240409)the China Postdoctoral Science Foundation(Grant No.2024M763507)the Beijing Natural Science Foundation(Grant No.1222035).
文摘Antiferromagnetism has become a promising candidate for the next generation electronic devices due to its thermal stability,low energy consumption,and fast switching speed.However,the canceling of the net magnetic moment in antiferromagnetic order presents great challenge on quantitative characterization and modulation,hindering its investigation and application.In this work,utilizing the optical second harmonic generation(SHG)in a wide temperature range,the integrated differential phase contrast scanning transmission electron microscopy,and firstprinciples calculations,we performed a quantitative study on the evolution of non-collinear antiferromagnetic order in BiFeO_(3)films with a series of strains.We found that the antiferromagnetic coupling was significantly enhanced,featured by the increase of Néel temperature from 428 K to 646 K,and by one order of enhancement of SHG intensity contributed from the G-type antiferromagnetic order by strain manipulation from-2.4%to+0.6%.We attributed the enhancement of the antiferromagnetic coupling to the enhancement of the superexchange interaction as the Fe-O-Fe bond angle approaches 180°when the in-plane lattice constants increase,which might also result in a tendency from a non-collinear antiferromagnetic order to a collinear one.Our work not only bridges the antiferromagnetic order and the strain manipulation in epitaxial multiferroics,more importantly,also paves a way for quantitative characterization by SHG technology and the precise manipulation of antiferromagnetism.
文摘A simple and highly-efficient method for numerically evaluating the waves created by a ship that travels at a constant speed in calm water, of large depth or of uniform depth, is given. The method, inspired by Kelvin＇s classical stationary-phase analysis, is suited for evaluating far-field as well as near-field waves. More generally, the method can be applied to a broad class of integrals with integrands that contain a rapidly oscillatory trigonometric function with a phase function whose first derivative（and possibly also higher derivatives） vanishes at one or several points, commonly called points of stationary phase, with the range of integration.
基金This work was supported by the National Natural Science Foundation of China(Nos.21625304,21872163,21991153,22072090,21991153,and 21991150)L.C.acknowledges the support from the Ministry of Science and Technology(No.2016YFA0200703)P.L.acknowledges the financial support from the Carlsberg Foundation.
文摘Ferroelectric barium titanate nanoparticles(BTO NPs)may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors.While increasing experimental and theoretical understandings on the structure of BTO and doped BTO have been developed over the past decade,the majority of the investigation was carried out in thin-film materials;therefore,the doping effect on nanoparticles remains unclear.Especially,doping-induced local composition and structure fluctuation across single nanoparticles have yet to be unveiled.In this work,we use electron microscopy-based techniques including high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),integrated differential phase contrast(iDPC)-STEM,and energy dispersive X-ray spectroscopy(EDX)mapping to reveal atomically resolved chemical and crystal structure of BTO and strontium doped BTO nanoparticles.Powder X-ray diffraction(PXRD)results indicate that the increasing strontium doping causes a structural transition from tetragonal to cubic phase,but the microscopic data validate substantial compositional and microstructural inhomogeneities in strontium doped BTO nanoparticles.Our work provides new insights into the structure of doped BTO NPs and will facilitate the materials design for next-generation high-density nano-dielectric devices.
