3,857 research outputs found
Investigation of effectiveness of various methods with different unknown variables for 3-D eddy current analysis
Computer codes using the A-φ, A-φ-Ω, A*-0Ω-E, T-Ω, and E-Ω methods were developed. The effects of the volume ratio of the conductor region to the whole region, the shape of the conductor, and the ratio of the hole region to the conductor region on the computer storage, the CPU time, and the accuracy of the methods are investigated systematically using a few simple models. The effect of the conductivity of the conductor is also examined. The computer storage, the CPU time, and the error are found to increase with increase of the volume ratio of the conductor region to the whole region. The computer storage and the CPU time are affected by the shape of the conductor in some methods of analysis. The error of the A*-Ω(E-Ω) method is larger than that of the other methods</p
Method for determining relaxation factor for modified Newton-Raphson method
In order to reduce the CPU time for the modified Newton-Raphson method which introduces a relaxation factor, the effect of the relaxation factor on the residual of the Galerkin method is examined in detail. It is shown that a relaxation factor which always provides convergent solutions can be easily searched. Various methods of searching for the relaxation factor to be used are compared </p
Alternative formalism to the slave particle mean field theory of the t-J model without deconfinement
An alternative formalism that does not require the assumption of the
deconfinement phase of a U(1) gauge field is proposed for the slave particle
mean field theory. Starting form the spin-fermion model, a spinon field, which
is either fermion or boson, is introduced to represent the localized spin
moment. We find a d-wave superconductive state in the mean field theory in the
case of the fermion representation of the localized spin moment that
corresponds to the slave boson mean field theory of the t-J model, whereas the
d-wave superconductive state is absent in case of the Schwinger boson
representation of the localized spin moments.Comment: 8 page
Comparison of various methods of analysis and finite elements in 3-D magnetic field analysis
In order to evaluate the most suitable method of analysis (A- phi or T- Omega method) and finite element (nodal or edge element) for a given problem, the features of each method and element have been investigated. The accuracy, computer storage, and CPU time of each method and element are compared for a 3-D nonlinear magnetostatic model and a 3-D eddy current model. The flux and eddy current densities calculated are compared with those measured. It is shown that the accuracy and the CPU time of the edge element are better than those of the nodal element. The A- phi method is better than T- Omega method for nonlinear problems from the viewpoint of convergence characteristics of nonlinear iterations.</p
New Superconducting and Magnetic Phases Emerge on the Verge of Antiferromagnetism in CeIn
We report the discovery of new superconducting and novel magnetic phases in
CeIn on the verge of antiferromagnetism (AFM) under pressure () through
the In-nuclear quadrupole resonance (NQR) measurements. We have found a
-induced phase separation of AFM and paramagnetism (PM) without any trace
for a quantum phase transition in CeIn. A new type of superconductivity
(SC) was found in GPa to coexist with AFM that is magnetically
separated from PM where the heavy fermion SC takes place. We propose that the
magnetic excitations such as spin-density fluctuations induced by the
first-order magnetic phase transition might mediate attractive interaction to
form Cooper pairs.Comment: 4 pages, 4 EPS figures, submitted to J. Phys. Soc. Jp
Strong-Coupling Superconductivity of CeIrSi with the Non-centrosymmetric Crystal Structure
We studied the pressure-induced superconductor CeIrSi with the
non-centrosymmetric tetragonal structure under high pressure. The electrical
resistivity and ac heat capacity were measured in the same run for the same
sample. The critical pressure was determined to be = 2.25 GPa,
where the antiferromagnetic state disappears. The heat capacity
shows both antiferromagnetic and superconducting transitions at pressures close
to . On the other hand, the superconducting region is extended to
high pressures of up to about 3.5 GPa, with the maximum transition temperature
= 1.6 K around GPa. At 2.58 GPa, a large heat capacity
anomaly was observed at = 1.59 K. The jump of the heat capacity in
the form of is 5.7 0.1.
This is the largest observed value among previously reported superconductors,
indicating the strong-coupling superconductivity. The electronic specific heat
coefficient at is, however, approximately unchanged as a function
of pressure, even at .Comment: This paper will be published in J. Phys. Soc. Jpn. on the August
issue of 200
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