The working principle of LFEC（Low frequency electromagnetic casting） process developed in Northeastern University, China was introduced and the metallurgical results of LFEC were discussed according to the casting p...The working principle of LFEC（Low frequency electromagnetic casting） process developed in Northeastern University, China was introduced and the metallurgical results of LFEC were discussed according to the casting practices. The low frequency field around the mold produces Lorenz force, which can be divided into two parts： one is the potential force which will be balanced by a pressure gradient of the liquid and results in the formation of a convex surface meniscus and improves the surface quality; the other is the rotary force which stirs the liquid in the mold to refine the microstructures and homogenize the distribution of alloying elements. LFEC can refine microstructures remarkably, improve surface quality of the ingots, depress macrosegregation and eliminate cracks. Some new technologies, such as horizontal direct chill casting under low-frequency electromagnetic field （HLEC）, DC casting of hollow billets under electromagnetic fields （HBEC）, electromagnetic modifying of hypereutectic A1-Si alloys（EMM）, air film casting under static magnetic field （AFCM）, and multi-ingots casting under low-frequency magnetic field （MLFEC） were developed based on LFEC.展开更多
A new mechanism of radiation emission in the polar gap of a pulsar is proposed. It is the curvature radiation emitted by positrons moving towards the surface of the neutron star along inclined magnetic field and refle...A new mechanism of radiation emission in the polar gap of a pulsar is proposed. It is the curvature radiation emitted by positrons moving towards the surface of the neutron star along inclined magnetic field and reflected from the surface. Such radiation interferes with transition radiation emitted from the neutron star when positrons hit the surface. Proposed mechanism explains the mystery of the interpulse shift in the Crab pulsar at high frequencies discovered by Moffett and Hankins twenty years ago. We have found also reflected energy flux and spectrum, discussed coherence and disappearance of interpulse shift with increase of frequency.展开更多
Epoxy resin laminate onto which a pair of copper foil was printed was employed as test samples.The samples were placed in an artificial atmospheric chamber, which was vacuumed by a rotary pump from 100 kPa to 5 kPa.Th...Epoxy resin laminate onto which a pair of copper foil was printed was employed as test samples.The samples were placed in an artificial atmospheric chamber, which was vacuumed by a rotary pump from 100 kPa to 5 kPa.The magnetic field was produced by permanent magnets that were assembled to make E×B drift away from, into and parallel to the sample surface, respectively.Magnetic flux density was adjusted at 120 mT, 180 mT and 240 mT respectively.By applying a negative bias voltage between the electrodes, the ...展开更多
In this paper,we report on our study of the trajectories of solar wind electrons reflected by lunar electric and magnetic fields through analysis of reflectivity and distribution under different conditions.Our calcula...In this paper,we report on our study of the trajectories of solar wind electrons reflected by lunar electric and magnetic fields through analysis of reflectivity and distribution under different conditions.Our calculations and simulations showed that the variations of both the magnetic field and surface potential play important roles in changing the directions of the traces of electrons.Furthermore,we were able to distinguish the changes resulting from these two variations through further analysis of the results.Thus,both the magnitude of the crustal field and the surface potential can be acquired from the data of satellites such as the Lunar Prospector.These findings could also contribute to the design and development of new devices in future lunar programs.展开更多
Magnetic Fe films grown on single-crystal Mg O(001) and(011) substrates were prepared by direct current magnetron sputtering. The experimental results showed that by applying an external magnetic field of about 300 Oe...Magnetic Fe films grown on single-crystal Mg O(001) and(011) substrates were prepared by direct current magnetron sputtering. The experimental results showed that by applying an external magnetic field of about 300 Oe to film during deposition, a fourfold cubic magnetic anisotropy on Mg O(001) substrate and a twofold uniaxial magnetic anisotropy on Mg O(011) substrate were generated, compared to the isotropic magnetization of Fe film grown without applying the external magnetic field.Our results suggested that external magnetic field during preparation effectively induced relatively higher surface mobility of sputtered Fe atoms and further promoted the crystallization of Fe film and the enhancement of magnetic anisotropy.展开更多
Manipulation of spin states via purely electric means forms the research branch "all-electric spintronics".In this paper,we briefly review recent progress relating to the all-electric spintronics,including e...Manipulation of spin states via purely electric means forms the research branch "all-electric spintronics".In this paper,we briefly review recent progress relating to the all-electric spintronics,including electric-field control of Rashba spin-orbit coupling,magnetic anisotropy,exchange bias,ferromagnetism,and other forms of magnetoelectric coupling.Special focus is given to surface/interface systems,including semiconductor(oxide) heterostructures,magnetic/nonmagnetic surfaces,semiconductor-metal interfaces,and other nanostructures,which can be good candidates for functional materials for spintronic.展开更多
Internal magnetic gradient plays a significant role in Nuclear Magnetic Resonance(NMR)measurements of fluid saturated porous media.The quantitative characterization and application of this physical phenomenon could ef...Internal magnetic gradient plays a significant role in Nuclear Magnetic Resonance(NMR)measurements of fluid saturated porous media.The quantitative characterization and application of this physical phenomenon could effectively improve the accuracy of NMR measurements and interpretations.In this paper,by using the equivalent magnetic dipole method,the three-dimensional distribution of internal induced magnetic field and its gradients in the randomly packed water saturated glass beads are quantitatively characterized.By simulating the diffusive motion of water molecules in porous media with random walk method,the computational dephasing effects equation related to internal gradients is deduced.Thereafter,the echo amplitudes are obtained and the corresponding T2-G spectrum is also inverted.For the sake of verifying the simulation results,an experiment is carried out using the Halbach core analyzing system(B0=0.18 T,G=2.3 T/m)to detect the induced internal field and gradients.The simulation results indicate the equivalent internal gradient is a distribution of 0.1-0.3 T/m,which matched well with the experimental results.展开更多
This work is related to the flow of a magnetohydrodynamic Burgers fluid.The flow of an incompressible conducting Burgers fluid in the presence of a uniform transverse magnetic field over a plate that is moved suddenly...This work is related to the flow of a magnetohydrodynamic Burgers fluid.The flow of an incompressible conducting Burgers fluid in the presence of a uniform transverse magnetic field over a plate that is moved suddenly is considered.By the application of the Laplace and Fourier sine transforms techniques,the exact analytical expressions for the velocity field and associated shear stress are determined in simple forms.They are written as a sum of steady-state and transient solutions.The graphical results are plotted for different values of indispensable parameters and some interesting results are concluded.The corresponding solutions for the hydrodynamic Burgers fluid appear as the limiting cases of the obtained solutions.展开更多
We show that the（2＋1）-dimensional Dirac-Moshinsky oscillator coupled to an externa/ magnetic field can be treated algebraically with the SU（1,1） group theory and its group basis.We use the su（1,1） irreducible r...We show that the（2＋1）-dimensional Dirac-Moshinsky oscillator coupled to an externa/ magnetic field can be treated algebraically with the SU（1,1） group theory and its group basis.We use the su（1,1） irreducible representation theory to find the energy spectrum and the eigenfunctions.Also,with the su（1,1） group basis we construct the relativistic coherent states in a closed form for this problem.展开更多
基金Project(2005CB623707) supported by the National Basic Research Program of China Projects(2007CB613701 and 2007CB613702) supported by the National Key Basic Research Program of China+2 种基金Projects(50974037,51004032 and 50904018) supported by the National Natural Science Foundation of ChinaProject(NCET-08-0098) supported by the New Century Excellent Talents in University,Ministry of Education,ChinaProject(20100471468) supported by China Postdoctoral Science Foundation
文摘The working principle of LFEC（Low frequency electromagnetic casting） process developed in Northeastern University, China was introduced and the metallurgical results of LFEC were discussed according to the casting practices. The low frequency field around the mold produces Lorenz force, which can be divided into two parts： one is the potential force which will be balanced by a pressure gradient of the liquid and results in the formation of a convex surface meniscus and improves the surface quality; the other is the rotary force which stirs the liquid in the mold to refine the microstructures and homogenize the distribution of alloying elements. LFEC can refine microstructures remarkably, improve surface quality of the ingots, depress macrosegregation and eliminate cracks. Some new technologies, such as horizontal direct chill casting under low-frequency electromagnetic field （HLEC）, DC casting of hollow billets under electromagnetic fields （HBEC）, electromagnetic modifying of hypereutectic A1-Si alloys（EMM）, air film casting under static magnetic field （AFCM）, and multi-ingots casting under low-frequency magnetic field （MLFEC） were developed based on LFEC.
文摘A new mechanism of radiation emission in the polar gap of a pulsar is proposed. It is the curvature radiation emitted by positrons moving towards the surface of the neutron star along inclined magnetic field and reflected from the surface. Such radiation interferes with transition radiation emitted from the neutron star when positrons hit the surface. Proposed mechanism explains the mystery of the interpulse shift in the Crab pulsar at high frequencies discovered by Moffett and Hankins twenty years ago. We have found also reflected energy flux and spectrum, discussed coherence and disappearance of interpulse shift with increase of frequency.
基金Supported by National Natural Science Foundation of China (No.50777048)
文摘Epoxy resin laminate onto which a pair of copper foil was printed was employed as test samples.The samples were placed in an artificial atmospheric chamber, which was vacuumed by a rotary pump from 100 kPa to 5 kPa.The magnetic field was produced by permanent magnets that were assembled to make E×B drift away from, into and parallel to the sample surface, respectively.Magnetic flux density was adjusted at 120 mT, 180 mT and 240 mT respectively.By applying a negative bias voltage between the electrodes, the ...
基金supported by the knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX2-yw-T13)the National Natural Science Foundation of China (Grant No. 40974108)
文摘In this paper,we report on our study of the trajectories of solar wind electrons reflected by lunar electric and magnetic fields through analysis of reflectivity and distribution under different conditions.Our calculations and simulations showed that the variations of both the magnetic field and surface potential play important roles in changing the directions of the traces of electrons.Furthermore,we were able to distinguish the changes resulting from these two variations through further analysis of the results.Thus,both the magnitude of the crustal field and the surface potential can be acquired from the data of satellites such as the Lunar Prospector.These findings could also contribute to the design and development of new devices in future lunar programs.
基金supported by the National Natural Science Foundation of China(51332001 and 51402164)Tsinghua University Initiative Scientific Research Program(2014Z21010 and 2014Z01006)
文摘Magnetic Fe films grown on single-crystal Mg O(001) and(011) substrates were prepared by direct current magnetron sputtering. The experimental results showed that by applying an external magnetic field of about 300 Oe to film during deposition, a fourfold cubic magnetic anisotropy on Mg O(001) substrate and a twofold uniaxial magnetic anisotropy on Mg O(011) substrate were generated, compared to the isotropic magnetization of Fe film grown without applying the external magnetic field.Our results suggested that external magnetic field during preparation effectively induced relatively higher surface mobility of sputtered Fe atoms and further promoted the crystallization of Fe film and the enhancement of magnetic anisotropy.
基金supported by the National Basic Research Program of China(Grant No.2013CB922300)the National Natural Science Foundation of China(Grant Nos.11004211,61125403 and 50832003)+1 种基金PCSIRT, NCET,ECNU Fostering Project for Top Doctoral DissertationsFundamental Research Funds for the central universities(ECNU)
文摘Manipulation of spin states via purely electric means forms the research branch "all-electric spintronics".In this paper,we briefly review recent progress relating to the all-electric spintronics,including electric-field control of Rashba spin-orbit coupling,magnetic anisotropy,exchange bias,ferromagnetism,and other forms of magnetoelectric coupling.Special focus is given to surface/interface systems,including semiconductor(oxide) heterostructures,magnetic/nonmagnetic surfaces,semiconductor-metal interfaces,and other nanostructures,which can be good candidates for functional materials for spintronic.
基金supported by the National Natural Science Foundation of China(Grant Nos.41074102 and 41130417)"111 Program"(Grant No.B13010)Program for Changjiang Scholars and Innovative Research Team in University
文摘Internal magnetic gradient plays a significant role in Nuclear Magnetic Resonance(NMR)measurements of fluid saturated porous media.The quantitative characterization and application of this physical phenomenon could effectively improve the accuracy of NMR measurements and interpretations.In this paper,by using the equivalent magnetic dipole method,the three-dimensional distribution of internal induced magnetic field and its gradients in the randomly packed water saturated glass beads are quantitatively characterized.By simulating the diffusive motion of water molecules in porous media with random walk method,the computational dephasing effects equation related to internal gradients is deduced.Thereafter,the echo amplitudes are obtained and the corresponding T2-G spectrum is also inverted.For the sake of verifying the simulation results,an experiment is carried out using the Halbach core analyzing system(B0=0.18 T,G=2.3 T/m)to detect the induced internal field and gradients.The simulation results indicate the equivalent internal gradient is a distribution of 0.1-0.3 T/m,which matched well with the experimental results.
文摘This work is related to the flow of a magnetohydrodynamic Burgers fluid.The flow of an incompressible conducting Burgers fluid in the presence of a uniform transverse magnetic field over a plate that is moved suddenly is considered.By the application of the Laplace and Fourier sine transforms techniques,the exact analytical expressions for the velocity field and associated shear stress are determined in simple forms.They are written as a sum of steady-state and transient solutions.The graphical results are plotted for different values of indispensable parameters and some interesting results are concluded.The corresponding solutions for the hydrodynamic Burgers fluid appear as the limiting cases of the obtained solutions.
基金Supported by SNI-Mexico,COFAA-IPN,EDI-IPN,EDD-IPN,SIP-IPN project number 20140598
文摘We show that the（2＋1）-dimensional Dirac-Moshinsky oscillator coupled to an externa/ magnetic field can be treated algebraically with the SU（1,1） group theory and its group basis.We use the su（1,1） irreducible representation theory to find the energy spectrum and the eigenfunctions.Also,with the su（1,1） group basis we construct the relativistic coherent states in a closed form for this problem.
