A numerical model for the unsteady flow under a pulsed magnetic field of a solenoid is developed, in which magnetohydrodynamic flow equations decouple into a transient magnetic diffusion equation and unsteady Navier–...A numerical model for the unsteady flow under a pulsed magnetic field of a solenoid is developed, in which magnetohydrodynamic flow equations decouple into a transient magnetic diffusion equation and unsteady Navier–Stokes equations in conjunction with two equations of the k–ε turbulent model. A Fourier series method is used to implement the boundary condition of magnetic flux density under multiple periods of a pulsed magnetic field （PMF）. The numerical results are compared with the theoretical or experimental results to validate the model under a time-harmonic magnetic field; it is found that the toroidal vortex pair is the dominating structure within the melt flow under a PMF. The velocity field of a molten melt is in a quasi-steady state after several periods; changing the direction of the electromagnetic force causes the vibration of the melt surface under a PMF.展开更多
We investigate properties of perpendicular anisotropy magnetic tunnel junctions(pMTJs) with a stack structure MgO/CoFeB/Ta/CoFeB/MgO as the free layer(or recording layer),and obtain the necessary device parameters fro...We investigate properties of perpendicular anisotropy magnetic tunnel junctions(pMTJs) with a stack structure MgO/CoFeB/Ta/CoFeB/MgO as the free layer(or recording layer),and obtain the necessary device parameters from the tunneling magnetoresistance(TMR) vs.field loops and current-driven magnetization switching experiments.Based on the experimental results and device parameters,we further estimate current-driven switching performance of pMTJ including switching time and power,and their dependence on perpendicular magnetic anisotropy and damping constant of the free layer by SPICE-based circuit simulations.Our results show that the pMTJ cells exhibit a less than 1 ns switching time and write energies <1.4 pJ;meanwhile the lower perpendicular magnetic anisotropy(PMA) and damping constant can further reduce the switching time at the studied range of damping constant α <0.1.Additionally,our results demonstrate that the pMTJs with the thermal stability factor■73 can be easily transformed into spin-torque nano-oscillators from magnetic memory as microwave sources or detectors for telecommunication devices.展开更多
The deconfinement phase transition with external magnetic field is investigated in the Friedberg-Lee model. We expand the potentiM around the two locM minima of the first-order deconfinement phase transition and extra...The deconfinement phase transition with external magnetic field is investigated in the Friedberg-Lee model. We expand the potentiM around the two locM minima of the first-order deconfinement phase transition and extract the ground state of the system in the frame of functional renormalization group. By solving the flow equations we find that the magnetic field displays a catalysis effect and it becomes more difficult to break through the confinement.展开更多
We investigate the effects of the directions of Dzyaloshinskii Moriya （DM） interaction and magnetic field on the thermal entanglement in the pure DM model. It is found that when the Hamiltonian is H1 = D. （σ1 ＋σ...We investigate the effects of the directions of Dzyaloshinskii Moriya （DM） interaction and magnetic field on the thermal entanglement in the pure DM model. It is found that when the Hamiltonian is H1 = D. （σ1 ＋σ2） ＋B.σ1, the entanglement can reach its maximum if the directions of the magnetic field and the DM vector are parallel. In addition, when the Hamiltonian is H2 = D @ （σ1 σ2） ＋ B. （σ1 ＋ σ2）, if the directions of the magnetic field and the DM vector are perpendicular in a high magnetic field, or their directions are parMlel in a weak magnetic field, the entanglement can also reach its maximum. Thus the entanglement can be enhanced by adjusting the direction of the external magnetic field, and this is feasible within the current experimental technology.展开更多
The control strategy is presented using passive and active hybrid magnetically suspended flywheels（P＆A MSFWs）,which can help meet the requirements of high precision and high stability for earth-observation satellit...The control strategy is presented using passive and active hybrid magnetically suspended flywheels（P＆A MSFWs）,which can help meet the requirements of high precision and high stability for earth-observation satellites.Compared with the conventional flywheel,P＆A MSFW has more rotation degrees of freedom（DOFs）since the rotor is suspended by magnetic bearings,and thus requires more efficient controllers.A modified sliding mode control law（SMC）to our novel nonlinear and coupled system is presented,which is interrupted by inertia matrix uncertainties and external disturbances.SMC law via Lyapunov method is improved,and a fuzzy control scheme is used to attenuate the chatting and control attitude accuracy and maintain the robustness of SMC.Simulation results are provided to illustrate the efficiency of our model by using our control law.展开更多
The CSES(China Seismo-Electromagnetic Satellite)is the electromagnetism satellite of China’s Zhangheng mission which is planned to launch a series of microsatellites within next 10 years in order to monitor the elect...The CSES(China Seismo-Electromagnetic Satellite)is the electromagnetism satellite of China’s Zhangheng mission which is planned to launch a series of microsatellites within next 10 years in order to monitor the electromagnetic environment,gravitational field.The CSES 01 probe(also called ZH-1)was launched successfully on 2 February 2018,from the Jiuquan Satellite Launch Centre(China)and is expected to operate for 5 years in orbit.The second probe CSES 02 is going to be launched in 2022.The scientific objectives of CSES are to detect the electromagnetic field and waves,plasma and particles,for studying the seismic-associated disturbances.To meet the requirements of scientific objective,the satellite is designed to be in a sun-synchronous orbit with a high inclination of 97.4°at an altitude around 507 km.CSES carries nine scientific payloads including Search-coil magnetometer,Electric Field Detector,High precision Magnetometer,GNSS occultation Receiver,Plasma Analyzer,Langmuir Probe,two Energetic Particle Detectors(including an Italian one),and Tri-Band Transmitter.Up to now,CSES has been operating in orbit for 2 years with stable and reliable performance.By using all kinds of data acquired by CSES,we have undertaken a series of scientific researches in the field of global geomagnetic field re-building,the ionospheric variation environment,waves,and particle precipitations under disturbed space weather and earthquake activities,the Lithosphere-Atmosphere-Ionosphere coupling mechanism research and so on.展开更多
The spin-transfer-torque(STT)magnetic tunneling junction(MTJ)device is one of the prominent candidates for spintronic logic circuit and neuromorphic computing.Therefore,building a simulation framework of hybrid STT-MT...The spin-transfer-torque(STT)magnetic tunneling junction(MTJ)device is one of the prominent candidates for spintronic logic circuit and neuromorphic computing.Therefore,building a simulation framework of hybrid STT-MTJ/CMOS(complementary metal-oxide-semiconductor)circuits is of great value for designing a new kind of computing paradigm based on the spintronic devices.In this work,we develop a simulation framework of hybrid STT-MTJ/CMOS circuits based on MATLAB/Simulink,which is mainly composed of a physics-based STT-MTJ model,a controlled resistor,and a current sensor.In the proposed framework,the STT-MTJ model,based on the Landau-Lifshitz-Gilbert-Slonczewsk(LLGS)equation,is implemented using the MATLAB script.The proposed simulation framework is modularized design,with the advantage of simple-to-use and easy-to-expand.To prove the effectiveness of the proposed framework,the STT-MTJ model is benchmarked with experimental results.Furthermore,the pre-charge sense amplifier(PCSA)circuit consisting of two STT-MTJ devices is validated and the electrical coupling of two spin-torque oscillators is simulated.The results demonstrate the effectiveness of our simulation framework.展开更多
The inner surface modification process by plasma-based low-energy ion implantation（PBLEII）with an electron cyclotron resonance（ECR）microwave plasma source located at the central axis of a cylindrical tube is model...The inner surface modification process by plasma-based low-energy ion implantation（PBLEII）with an electron cyclotron resonance（ECR）microwave plasma source located at the central axis of a cylindrical tube is modeled to optimize the low-energy ion implantation parameters for industrial applications.In this paper,a magnetized plasma diffusion fluid model has been established to describe the plasma nonuniformity caused by plasma diffusion under an axial magnetic field during the pulse-off time of low pulsed negative bias.Using this plasma density distribution as the initial condition,a sheath collisional fluid model is built up to describe the sheath evolution and ion implantation during the pulse-on time.The plasma nonuniformity at the end of the pulse-off time is more apparent along the radial direction compared with that in the axial direction due to the geometry of the linear plasma source in the center and the difference between perpendicular and parallel plasma diffusion coefficients with respect to the magnetic field.The normalized nitrogen plasma densities on the inner and outer surfaces of the tube are observed to be about 0.39 and 0.24,respectively,of which the value is 1 at the central plasma source.After a 5μs pulse-on time,in the area less than 2 cm from the end of the tube,the nitrogen ion implantation energy decreases from 1.5 keV to 1.3 keV and the ion implantation angle increases from several degrees to more than 40°;both variations reduce the nitrogen ion implantation depth.However,the nitrogen ion implantation dose peaks of about 2×10^（10）-7×10^（10）ions/cm^2 in this area are 2-4 times higher than that of 1.18×10^（10）ions/cm^2 and 1.63×10^（10）ions/cm^2 on the inner and outer surfaces of the tube.The sufficient ion implantation dose ensures an acceptable modification effect near the end of the tube under the low energy and large angle conditions for nitrogen ion implantation,because the modification effect is mainly determined by the ion implantation dose,just as the mass transfer process in PBLEII is dominated by low-energy ion implantation and thermal diffusion.Therefore,a comparatively uniform surface modification by the low-energy nitrogen ion implantation is achieved along the cylindrical tube on both the inner and outer surfaces.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51034012)
文摘A numerical model for the unsteady flow under a pulsed magnetic field of a solenoid is developed, in which magnetohydrodynamic flow equations decouple into a transient magnetic diffusion equation and unsteady Navier–Stokes equations in conjunction with two equations of the k–ε turbulent model. A Fourier series method is used to implement the boundary condition of magnetic flux density under multiple periods of a pulsed magnetic field （PMF）. The numerical results are compared with the theoretical or experimental results to validate the model under a time-harmonic magnetic field; it is found that the toroidal vortex pair is the dominating structure within the melt flow under a PMF. The velocity field of a molten melt is in a quasi-steady state after several periods; changing the direction of the electromagnetic force causes the vibration of the melt surface under a PMF.
基金Project supported by State Grid Corporation of China under the 2018 Science and Technology Project of State Grid Corporation:Research on electromagnetic measurement technology based on EIT and TMR(Grant No.JL71-18-007)。
文摘We investigate properties of perpendicular anisotropy magnetic tunnel junctions(pMTJs) with a stack structure MgO/CoFeB/Ta/CoFeB/MgO as the free layer(or recording layer),and obtain the necessary device parameters from the tunneling magnetoresistance(TMR) vs.field loops and current-driven magnetization switching experiments.Based on the experimental results and device parameters,we further estimate current-driven switching performance of pMTJ including switching time and power,and their dependence on perpendicular magnetic anisotropy and damping constant of the free layer by SPICE-based circuit simulations.Our results show that the pMTJ cells exhibit a less than 1 ns switching time and write energies <1.4 pJ;meanwhile the lower perpendicular magnetic anisotropy(PMA) and damping constant can further reduce the switching time at the studied range of damping constant α <0.1.Additionally,our results demonstrate that the pMTJs with the thermal stability factor■73 can be easily transformed into spin-torque nano-oscillators from magnetic memory as microwave sources or detectors for telecommunication devices.
基金Supported by the National Natural Science Foundation of China under Grant No 11405122the China Postdoctoral Science Foundation under Grant No 2014M550483
文摘The deconfinement phase transition with external magnetic field is investigated in the Friedberg-Lee model. We expand the potentiM around the two locM minima of the first-order deconfinement phase transition and extract the ground state of the system in the frame of functional renormalization group. By solving the flow equations we find that the magnetic field displays a catalysis effect and it becomes more difficult to break through the confinement.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11204061,11374085,11274010 and 11204002the Anhui Provincial Natural Science Foundation under Grant No 1408085MA16+4 种基金the China Postdoctoral Science Foundation under Grant No 20110490825the Key Project of the Ministry of Education of China under Grant No 211080the Key Program of the Education Department of Anhui Province under Grant Nos KJ2012A244 and KJ2012A020the Program of Hefei Normal University under Grant Nos 2012jd17,2013jd03 and 2014136KJC02the Excellent Young Talents Support Plan of Anhui Provincial Universities
文摘We investigate the effects of the directions of Dzyaloshinskii Moriya （DM） interaction and magnetic field on the thermal entanglement in the pure DM model. It is found that when the Hamiltonian is H1 = D. （σ1 ＋σ2） ＋B.σ1, the entanglement can reach its maximum if the directions of the magnetic field and the DM vector are parallel. In addition, when the Hamiltonian is H2 = D @ （σ1 σ2） ＋ B. （σ1 ＋ σ2）, if the directions of the magnetic field and the DM vector are perpendicular in a high magnetic field, or their directions are parMlel in a weak magnetic field, the entanglement can also reach its maximum. Thus the entanglement can be enhanced by adjusting the direction of the external magnetic field, and this is feasible within the current experimental technology.
文摘The control strategy is presented using passive and active hybrid magnetically suspended flywheels（P＆A MSFWs）,which can help meet the requirements of high precision and high stability for earth-observation satellites.Compared with the conventional flywheel,P＆A MSFW has more rotation degrees of freedom（DOFs）since the rotor is suspended by magnetic bearings,and thus requires more efficient controllers.A modified sliding mode control law（SMC）to our novel nonlinear and coupled system is presented,which is interrupted by inertia matrix uncertainties and external disturbances.SMC law via Lyapunov method is improved,and a fuzzy control scheme is used to attenuate the chatting and control attitude accuracy and maintain the robustness of SMC.Simulation results are provided to illustrate the efficiency of our model by using our control law.
基金Supported by National Key R&D Program of China(2018YFC1503501)Research Grant from Institute of Crustal Dynamics,China Earthquake Administration(ZDJ2019-22 and ZDJ2020-06)the APSCO Earthquake Research Project PhaseⅡ。
文摘The CSES(China Seismo-Electromagnetic Satellite)is the electromagnetism satellite of China’s Zhangheng mission which is planned to launch a series of microsatellites within next 10 years in order to monitor the electromagnetic environment,gravitational field.The CSES 01 probe(also called ZH-1)was launched successfully on 2 February 2018,from the Jiuquan Satellite Launch Centre(China)and is expected to operate for 5 years in orbit.The second probe CSES 02 is going to be launched in 2022.The scientific objectives of CSES are to detect the electromagnetic field and waves,plasma and particles,for studying the seismic-associated disturbances.To meet the requirements of scientific objective,the satellite is designed to be in a sun-synchronous orbit with a high inclination of 97.4°at an altitude around 507 km.CSES carries nine scientific payloads including Search-coil magnetometer,Electric Field Detector,High precision Magnetometer,GNSS occultation Receiver,Plasma Analyzer,Langmuir Probe,two Energetic Particle Detectors(including an Italian one),and Tri-Band Transmitter.Up to now,CSES has been operating in orbit for 2 years with stable and reliable performance.By using all kinds of data acquired by CSES,we have undertaken a series of scientific researches in the field of global geomagnetic field re-building,the ionospheric variation environment,waves,and particle precipitations under disturbed space weather and earthquake activities,the Lithosphere-Atmosphere-Ionosphere coupling mechanism research and so on.
基金Project supported by the National Natural Science Foundation of China(Grant No.62004223)the Science and Technology Innovation Program of Hunan Province,China(Grant No.2022RC1094)+1 种基金the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics,China(Grant No.KF202012)the Hunan Provincial Science Innovation Project for Postgraduate,China(Grant No.CX20210086).
文摘The spin-transfer-torque(STT)magnetic tunneling junction(MTJ)device is one of the prominent candidates for spintronic logic circuit and neuromorphic computing.Therefore,building a simulation framework of hybrid STT-MTJ/CMOS(complementary metal-oxide-semiconductor)circuits is of great value for designing a new kind of computing paradigm based on the spintronic devices.In this work,we develop a simulation framework of hybrid STT-MTJ/CMOS circuits based on MATLAB/Simulink,which is mainly composed of a physics-based STT-MTJ model,a controlled resistor,and a current sensor.In the proposed framework,the STT-MTJ model,based on the Landau-Lifshitz-Gilbert-Slonczewsk(LLGS)equation,is implemented using the MATLAB script.The proposed simulation framework is modularized design,with the advantage of simple-to-use and easy-to-expand.To prove the effectiveness of the proposed framework,the STT-MTJ model is benchmarked with experimental results.Furthermore,the pre-charge sense amplifier(PCSA)circuit consisting of two STT-MTJ devices is validated and the electrical coupling of two spin-torque oscillators is simulated.The results demonstrate the effectiveness of our simulation framework.
基金supported by National Natural Science Foundation of China(Nos.50725519,51271048,51321004)
文摘The inner surface modification process by plasma-based low-energy ion implantation（PBLEII）with an electron cyclotron resonance（ECR）microwave plasma source located at the central axis of a cylindrical tube is modeled to optimize the low-energy ion implantation parameters for industrial applications.In this paper,a magnetized plasma diffusion fluid model has been established to describe the plasma nonuniformity caused by plasma diffusion under an axial magnetic field during the pulse-off time of low pulsed negative bias.Using this plasma density distribution as the initial condition,a sheath collisional fluid model is built up to describe the sheath evolution and ion implantation during the pulse-on time.The plasma nonuniformity at the end of the pulse-off time is more apparent along the radial direction compared with that in the axial direction due to the geometry of the linear plasma source in the center and the difference between perpendicular and parallel plasma diffusion coefficients with respect to the magnetic field.The normalized nitrogen plasma densities on the inner and outer surfaces of the tube are observed to be about 0.39 and 0.24,respectively,of which the value is 1 at the central plasma source.After a 5μs pulse-on time,in the area less than 2 cm from the end of the tube,the nitrogen ion implantation energy decreases from 1.5 keV to 1.3 keV and the ion implantation angle increases from several degrees to more than 40°;both variations reduce the nitrogen ion implantation depth.However,the nitrogen ion implantation dose peaks of about 2×10^（10）-7×10^（10）ions/cm^2 in this area are 2-4 times higher than that of 1.18×10^（10）ions/cm^2 and 1.63×10^（10）ions/cm^2 on the inner and outer surfaces of the tube.The sufficient ion implantation dose ensures an acceptable modification effect near the end of the tube under the low energy and large angle conditions for nitrogen ion implantation,because the modification effect is mainly determined by the ion implantation dose,just as the mass transfer process in PBLEII is dominated by low-energy ion implantation and thermal diffusion.Therefore,a comparatively uniform surface modification by the low-energy nitrogen ion implantation is achieved along the cylindrical tube on both the inner and outer surfaces.
