189 research outputs found
On the continuity of the magnetizing current density in 3-D magnetic field analysis with edge element
The effects of the continuity of the magnetizing current density on the convergence of the incomplete Cholesky conjugate gradient method and the accuracy of the calculated flux densities are investigated by imposing different continuity conditions for both nodal and edge elements. It is shown that the continuity condition should be imposed precisely in the case of edge elements </p
Mott transition in Kagom\'e lattice Hubbard model
We investigate the Mott transition in the Kagom\'e lattice Hubbard model
using a cluster extension of dynamical mean field theory. The calculation of
the double occupancy, the density of states, the static and dynamical spin
correlation functions demonstrates that the system undergoes the first-order
Mott transition at the Hubbard interaction (:bandwidth). In
the metallic phase close to the Mott transition, we find the strong
renormalization of three distinct bands, giving rise to the formation of heavy
quasiparticles with strong frustration. It is elucidated that the quasiparticle
states exhibit anomalous behavior in the temperature-dependent spin correlation
functions.Comment: 4 pages, 6 figure
Finite temperature Mott transition in Hubbard model on anisotropic triangular lattice
We investigate the Hubbard model on the anisotropic triangular lattice by
means of the cellular dynamical mean field theory. The phase diagram determined
in the Hubbard interaction versus temperature plane shows novel reentrant
behavior in the Mott transition due to the competition between Fermi-liquid
formation and magnetic correlations under geometrical frustration. We
demonstrate that the reentrant behavior is characteristic of the Mott
transition with intermediate geometrical frustration and indeed consistent with
recent experimental results of organic materials.Comment: 5 pages, 6 figure
Practical analysis of 3-D dynamic nonlinear magnetic field using time-periodic finite element method
A practical 3-D finite element method using edge elements for analyzing stationary nonlinear magnetic fields with eddy currents in electric apparatus, in which the flux interlinking the voltage winding is given, has been proposed. The method is applied to the analysis of magnetic fields in the Epstein frame </p
Effects of residual magnetism due to minor loop on magnetic property of permanent magnet type of MRI
Summary form only given. The flux distribution of a permanent magnet type of MRI shown in Fig.1 is affected by the hysteresis (minor loop) and eddy currents in the pole piece and yoke due to the pulse current (Fig.2) of the gradient coil. In this paper, the effects of the hysteresis and the eddy current in the yoke on the residual flux density of the probe coil are investigated. It can be assumed that the eddy current does not flow in the pole piece because it is divided into pieces. The eddy current flows in the yoke. Fig.3 shows the change of residual flux density /spl Delta/B/sub z/ at the point S(0,0) in Fig.1. /spl Delta/B/sub z/ is given by /spl Delta/B/sub z/=B/sub z1/-B/sub z0/ (1), where B/sub z0/ is the flux density at the instant t=0(I=0A). B/sub z1/ is the flux density at the instant t=i(I=0A). The instant of 1,2,3,... in Fig.2 corresponds to 1,2,3,... in Fig.3. Fig.3 shows that the hysteresis in the pole piece and yoke should be taken into account. The effect of eddy current in the yoke on the residual flux density /spl Delta/B/sub z/ is not negligible. These results suggests that the reduction of the amplitudes of minor loop and eddy current is important in order to improve the operating characteristics of the permanent magnet type of MRI.</p
Effect of minor loop on magnetic characteristics of permanent magnet type of MRI
A modeling technique of the minor loop using typical hysteresis loops is shown. The effect of the minor loop and eddy current in the pole piece of a permanent magnet type of MRI on the residual flux density of the probe coil is examined. It is illustrated that the change ΔB of residual flux density occurs due to the minor loop of the pole piece. It is also pointed out that the choice of time interval Δt is important in a nonlinear analysis considering the minor loop</p
Analysis of the magnetic property of a permanent-magnet-type MRI - Behavior of residual magnetization
The minor loops of B and H of steel due to pulse excitation and eddy currents induced in steel affect the magnetic characteristics of a permanent-magnet-type MRI. In this paper, the magnetic properties of a permanent magnet assembly is examined by using the finite-element method taking into account minor loop. The distribution of residual magnetization in the yoke is illustrated, and the effect of residual magnetization on the behavior of residual flux density is examined. It is shown that the behavior of B and H in minor loops is affected by the eddy currents in the yoke and pole piece.</p
Finite-Temperature Mott Transition in Two-Dimensional Frustrated Hubbard Models
We investigate the Hubbard model on two typical frustrated lattices in two
dimensions, the kagome lattice and the anisotropic triangular lattice, by means
of the cellular dynamical mean field theory. We show that the metallic phase is
stabilized up to fairly large Hubbard interactions under strong geometrical
frustration in both cases, which results in heavy fermion behavior and several
anomalous properties around the Mott transition point. In particular, for the
anisotropic triangular lattice, we find novel reentrant behavior in the Mott
transition in the moderately frustrated parameter regime, which is caused by
the competition between Fermi-liquid formation and magnetic correlations. It is
demonstrated that the reentrant behavior is a generic feature inherent in the
Mott transition with intermediate geometrical frustration, and indeed in
accordance with recent experimental findings for organic materials.Comment: 20 pages, 19 figures, to be published in the proceedings of YKIS2007
conference as a special issue of Prog. Theor. Phys. Supp
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