Magnetic Coupling Model Research Articles

A Novel Model of Magnetic Eddy-current Coupling Based on the Magnetic Equivalent Circuit Method

Nowadays, magnetic eddy-current couplings have been widely used in medium and high power electric motors. During the development of initial or optimum design of magnetic eddy-current couplings, it has been more and more essential to build a model with accurate and time-saving features the magnetic equivalent circuit method (MEC) has been used in this paper to build the static magnetic circuit model while the Ampere theorem has been applied to develop the dynamic magnetic model. Finally, analytical expressions of coupling torque are obtained and validity of the novel model has been verified by three-dimension finiteelement simulation.

Research on modelling and simulation for dynamic characteristics of magnetic shaft coupling

This paper investigates the dynamic characteristics of magnetic shaft coupling by modelling and simulation. A dynamic model of magnetic shaft coupling is developed and simplified by linearisation at the equilibrium point of steady state. The simulation results indicate that magnetic shaft coupling could lessen mechanical shock during starting process. The linearisation error is computed and analysed. The dynamic block-diagram of the linearised model is simplified and arranged, and then a typical second order oscillating system is achieved. Further, the dynamic characteristics of the oscillating system are discussed.

A Flat Design and a Validated Model for an AUV Reconfigurable Magnetic Coupling Thruster

Reconfigurable Magnetic Coupling Thruster (RMCT) is an enabling technology for achieving vectorial thrust on AUVs. This allows us to dispose of dynamic, compliant, and secure propulsion to enhance their agility for demanding locomotion tasks. RMCT can generate and control a thrust vector by redirecting its propeller through the compliance of the magnetic coupling and therefore achieve thrust vectoring for AUVs. In this paper, a new design of RMCT is presented. This new prototype uses a flat geometry magnetic coupling for a better AUV full integrability. The new design provides some additional advantages with regard to its predecessor (spherical RMCT); namely, construction simplicity and better torque transmission. The first characteristic is derived from its flat shapes, which makes it easier to manufacture (cubic magnets) and to isolate (planar air gap between rotors). The second characteristic is due to the fact that now both parts of the magnetic coupling can store magnets (increasing the maximal transmitted torque). This paper proposes a thruster dynamics model, a magnetic coupling model, and shows the use of a dynamic parameter identification method based on algorithms used for robotic manipulators. The validity of the dynamic model and identified parameters is then analyzed by means of experimental tests.

A Novel Design Method of Passive Shimming for 0.7-T Biplanar Superconducting MRI Magnet

The homogeneity of magnetic field is one of the most critical parameter of magnetic resonance image (MRI) magnet. Passive shimming (PS) technique is widely used to correct the inhomogeneity of the basic field. The conventional PS methods are always based on the hypothesis of saturation magnetization and linear programming. However, due to engineering approximation, nonlinear magnetization characteristic of shimming pieces (SPs) and special field condition in 0.7-T biplanar superconducting MRI, the error of conventional method is too large. Hence, a novel PS method based on magnetic coupling (MC) model and niching genetic algorithm (NGA) is presented in this paper. MC model is proposed to calculate the magnetizations in SPs instead of statured-magnetization hypothesis. To solve this complex and large-scale optimization problem, NGA is employed, which can avoid the error caused by rounding and improve the effect of optimization. During the procedure of optimization, the magnetizations of each individual are update in each iteration. The theoretical and experimental results show that the MC model and the NGA are effective and reliable.

The effect of Co doping on the conductive properties of ferromagnetic ZnxCo1−xO films

The reduction of conductivity and the enhancement of ferromagnetic order following Co-doping in ZnO films are interpreted within a (Co–VO)-mediated model of magnetic coupling.

A First-Principles Investigation of the Carrier Doping Effect on the Magnetic Properties of Defective Graphene

The carrier doping effects on the magnetic properties of defective graphene with a hydrogen chemisorbed single-atom vacancy (H-GSV) are investigated by performing extensive spin-polarized first-principles calculations. Theoretical results show that the quasi-localized pz-derived states around the Fermi level are responsible for the weakened magnetic moment (MM) and magnetic stabilized energy (MSE) of the H-GSV under carrier doping. The mechanism of reduced MSE in the carrier doped H-GSV can be well understood by the Heisenberg magnetic coupling model due to the response of these pz-derived states to the carrier doping. Within the examined range of carrier doping concentration, the total MM of H-GSV is always larger than 1.0μB with μB representing the Bohr magneton, which is mainly contributed by the localized sp2 states of the unsaturated C atom around the vacancy. These findings of H-GSV provide fundamental insight into defective graphene and help to understand the related experimental observations.

The Design and Simulation of Circuit for Electromagnetic Force Assisted Line Heating Device

In the process of line heating, a pulsed electromagnetic force is added to steel plates as an approximately consecutive constrained force of certain frequency. It improves the condition of steel plates heated at high temperatures and the efficiency of steel deformation and be conducive to the control of process and the improvement for the accuracy of deformation. According to the actual needs of electromagnetic force assisted line heating process, the design ideas of circuit for the electromagnetic force assisted line heating device (EFALHD) and functions of the branch circuits are introduced. The distribution of the electromagnetic force and parameters’ influence rules are analyzed by building magnetic field and circuit coupling model in ANSYS. By adding thermal analysis on the electromagnetic field analysis, a new method of line heating finite element analysis is established to support the parameter determinations of EFALHD.

Intermediate-mass black holes in globular clusters: constraints on the spin of a black hole

The spin of central black holes with intermediate masses in globular clusters is determined using the well known relationship between the kinetic power of a relativistic jet and the observed radio luminosity of the region closest to a central black hole. The estimate of the magnitude of the spin is based on the known Blandford-Znajek mechanism. The magnetic field near the event horizon of a black hole is determined using a magnetic coupling mechanism that assumes equality between the densities of the magnetic and kinetic energies of the accreting gas (the Magnetic Coupling Model). The rate of accretion $$ \dot{M} $$ is derived on the basis of the Bondi-Hoyle mechanism.

Electromagnetic interaction in stacked split ring resonator arrays

We theoretically demonstrate the coupling between the unit cells and the interactionbetween constituents within each cell in metamaterials consisting of stacked split ringresonator arrays which are embedded in a homogeneous dielectric. It is found that theresonant frequency due to plasmon hybridization depends on the symmetry of resonancemodes. Both for the first and third order plasmon resonances, we show that the resonancesat lower frequency are not sensitive to the variation of lattice density, while the resonancesat higher frequency rely on the coupling between cells due to the symmetric distribution ofcurrent. The underlying physics is qualitatively interpreted according to the quasistaticelectric and magnetic dipole coupling model combined by the calculated field distributions.

Magnetic coupling of a rotating black hole with advection-dominated accretion flows

A model of magnetic coupling (MC) of a rotating black hole (BH) with advection-dominated accretion flow (MCADAF) is proposed. It turns out that MCADAF provides a natural explanation for the transition radius between ADAF and SSD, and could be used to interpret the highest luminosity of GX 339-4 in hard-state. A very steep emissivity index can be produced in the innermost part of the MCADAF, which is consistent with the recent XMM-Newton observations of the nearby bright Seyfert 1 galaxy MCG-6-30-15 and with two X-ray binaries (XRBs): XTE J1655-500 and GX 339-4. In addition, we estimate the BH spins in Seyfert 1 galaxy MCG-6-30-15 and in the two XRBs based on this model.

Phenomenological band structure model of magnetic coupling in semiconductors

A unified band structure model is proposed to explain the magnetic ordering in Mn-doped semiconductors. This model is based on the p–d and d–d level repulsions between the Mn ions and host elements and can successfully explain magnetic ordering observed in all Mn doped II–VI and III–V semiconductors such as CdTe, GaAs, ZnO, and GaN. The model can also be used to explain the interesting behavior of GaMnN, which changes from ferromagnetic ordering to antiferromagnetic ordering as the Mn concentration increases. This model, therefore, is useful to provide a simple guideline for future band structure engineering of magnetic semiconductors.

Nuclear ordering and excitations in [formula omitted

The energy splitting of Nd nuclear levels and Nd nuclear polarization in NdFeO 3 have been studied by using high resolution inelastic neutron backscattering with simultaneous neutron diffraction at temperatures between 100 mK and 15 K. Inelastic peaks are observed below 4.5 K with a corresponding energy splitting Δ E = 1.24 μ eV below 0.9 K. The Nd nuclear magnetic moments are polarized below 1 K with a maximal polarization of 17% observed at 100 mK. Both these phenomena directly observed in NdFeO 3 are described by assuming a magnetic hyperfine coupling model. It is found that the present experimental data on NdFeO 3 and the literature data concerning Nd 2 CuO 4 can be consistently described by using the same value of the magnetic hyperfine coupling constant A = 1.10 ( 5 ) μ eV / μ B .

A Toy Model for 3:2 Ratio of kHz QPO Frequency in Black Hole X-ray Binaries

Production of pairs of high frequency quasi-periodic oscillations (QPOs) in black hole X-ray binaries is discussed based on a model of non-axisymmetric magnetic coupling of a rotating black hole (BH) with its surrounding accretion disk, in which a puzzling 3:2 ratio of the upper frequency to the lower frequency is explained. In addition, the correlation of the pairs of high frequency QPOs with the jets from microquasars is discussed.

Spatially resolving the accretion shocks on the rapidly-rotating M0 T-Tauri star MN Lupi

We obtained high-resolution, high-quality VLT/UVES spectra to reconstruct the two-dimensional surface structure of the rapidly-rotating classical T-Tauri star MN Lupi on two separate nights. Both surface maps show a structured warm (5000 K) band centered around the pole at a latitude of ≈65 ◦ . Located within the band are two hot spots with temperatures of approximately or possibly even in excess of 5800 K, i.e. 2000 K above the effective photospheric temperature. Both maps appear with an adjacent equatorial band of temperature 3400 K, some 400−500 K below the effective photospheric temperature. While we interpret the two hot spots and the warm high-latitude band to be the heating points from two accretion impacts at the time of our observations and their redistributed energy trailed due to the fast stellar rotation, respectively, the cool equatorial band may not be cool after all but due to obscuration of the stellar surface by the innermost region of the disk. The fact that the hot spots appear at high stellar latitude is in agreement with the magnetospheric accretion model that proposes material funnelling onto the star along a predominantly dipolar magnetic field at roughly 50 ◦ latitude. The evidence of ongoing disk accretion, together with the very fast rotation of MN Lupi of just 3−4 times below its break-up velocity, suggests that the accretion mechanism is the cause of its rapid surface rotation. We present a model of magnetic star-disk coupling for MN Lupi that predicts a polar surface magnetic field of ≈ 3k G.

Two-dimensional molecular magnets based on [Pt(mnt)2]− ions: Structures and magnetic properties

Two compounds of composition [FBzPy][Pt(mnt) 2 ] ( 1 ) and [FBzPy][Pt(mnt) 2 ] · 0.25-MeCN ( 2 ) ([FBzPy] + = 1-(4′-fluorobenzyl)pyridinium and mnt 2− = maleonitriledithiolate) were prepared and their crystal structures were determined. The solvent molecule, MeCN, incorporated into lattice leads the anionic stacking pattern to be distinct between 1 and 2 . The regular anionic stacking columns are connected by the anionic dimers to construct into 2D anionic networks in 1 , while the anionic fourfold subunit develop into anionic layers though lateral S⋯S interactions in 2 . As for two compounds, the magnetic susceptibilities in 2–350 K were measured, and the magnetic exchange schemes were built based on the analyses both crystal structures and extended Huckel molecular orbital calculations. The magnetic coupling model of an alternating AFM Heisenberg chain with an isolated AFM coupling dimer was dealt with 1 , while a spin dimer with s = 1/2 with 2 , and the magnetic coupling parameters were further gained via simulating the temperature dependent magnetic susceptibility data of two compounds.

Analysis of a self-regulated, self-excited, brushless three-phase synchronous generator, which includes the effect of core losses

This paper presents a novel analysis of a self-regulated, self-excited, brushless three-phase synchronous generator, which includes the effect of core losses. The core losses are modeled by equivalent core loss resistances connected to additional windings on the generator's magnetic coupling model. A magnetic circuit is drawn from the magnetic coupling model, and an electrical equivalent circuit of the generator is derived by utilizing a duality between the magnetic and electric circuits. Using this equivalent circuit, the generator's steady-state performance is theoretically predicted, and the results are verified through experiment. In addition, the power losses during power generation are analyzed quantitatively. The proposed analysis takes into account the nonlinearity of the exciting impedances due to magnetic saturation. © 2000 Scripta Technica, Electr Eng Jpn, 131(2): 51–60, 2000

Analysis of a Self-Regulated, Self-Excited, Brushless Three-Phase Synchronous Generator, which Includes the Effect of Core Losses

This paper presents a novel analysis of a self-regulated, self-excited, brushless three-phase synchronous generator, which includes the effect of core losses. The core losses are modeled by equivalent core loss resistances connected to additional windings on the generator's magnetic coupling model. A magnetic circuit is drawn from the magnetic coupling model, and an electrical equivalent circuit of the generator is derived by utilizing a duality between the magnetic and electric circuits. Using this equivalent circuit, the generator's steady-state performance is theoretically predicted, and the results are verified through experiment. In addition, the power losses during power generation are analyzed quantitatively. The proposed analysis takes into account of the nonlinearity of the exciting impedances due to magnetic saturation.

Magnetic properties of nanocrystalline nickel

The ferromagnetic properties of compaction-prepared nanocrystalline Ni specimens, (crystallite size 10 nm) were investigated in order to study the correlation between the disordered interfacial structure and the macroscopic properties. The magnetic moment of the atoms in the interfaces is decreased to 0.34 μB/atom (0.6 μB/atom in bulk Ni) and the Curie temperature T ci =545 K of the interfacial components is lower than the value T cb =630 K of the Ni bulk crystal. Both results are due to open structure of the interfaces and will be discussed within a band model of itinerant ferromagnetism. The temperature variation of the coercivity H c of the nanocrystalline specimens suggest a model of weak magnetic coupling of single-domain particles with a non-spherical shape.

Comparison between electric and magnetic rf drive in long Josephson junctions

Three models of long Josephson junctions irradiated by a microwave field are compared by means of the usual perturbative approach: the magnetic coupling model, the electric coupling model and the mixed magnetic-electric one. Some possible experimental tests are suggested to find out the most relevant model according to the parameters defining the junction.