89,753 research outputs found
An inverse approach for magnetic material characterization of an EI core electromagnetic inductor
In this paper, the complete magnetic material characteristic, hysteretic and anhysteretic, is reconstructed for an EI electromagnetic inductor. The material identification process, including air gap assessment, is carried out using a coupled experimental-numerical inverse technique, based on a set of well chosen global and local magnetic measurements. It is shown that a higher accuracy is obtained when local measurements are performed in regions with less stray fields, and the air gap assessment is strongly improved by the use of local magnetic measurements
Magnetization reversal in amorphous Fe/Dy multilayers: a Monte Carlo study
The Monte Carlo method in the canonical ensemble is used to investigate
magnetization reversal in amorphous transition metal - rare earth multilayers.
Our study is based on a model containing diluted clusters which exhibit an
effective uniaxial anisotropy in competition with random magnetic anisotropy in
the matrix. We simulate hysteresis loops for an abrupt profile and a diffuse
one obtained from atom probe tomography analyses. Our results evidence that the
atom probe tomography profile favors perpendicular magnetic anisotropy in
agreement with magnetic measurements. Moreover, the hysteresis loops calculated
at several temperatures qualitatively agree with the experimental ones
Giant magnetoimpedance: new electrochemical option to monitor surface effects?
Magnetoimpedance, MI, change due to surface modification of the sensitive
element caused by biofluids was studied with the aim of creating a robust
sensor capable of separating the chemical surface modification from the sensing
process. A MI sensor prototype with an as-quenched FeCoSiB amorphous ribbon
sensitive element was designed and calibrated for a frequency range of 0.5 to
10 MHz at an intensity of the current of 60 mA. Measurements as a function of
the exposure time were made, first, in a regime where chemical surface
modification and sensing were separated and then, in a regime where they were
not separated (in a bath for fluids). The MI variation was explained by the
change of the surface magnetic anisotropy. It was shown that the
magnetoimpedance effect can be successfully employed as a new electrochemical
option to probe the electric features of surface-modified magnetic electrodes
when the biofluid, the material of the sensitive element, and the detection
conditions are properly selected and synergetically adjusted.Comment: 22 pages, 6 figure
rDLB: A Novel Approach for Robust Dynamic Load Balancing of Scientific Applications with Parallel Independent Tasks
Scientific applications often contain large and computationally intensive
parallel loops. Dynamic loop self scheduling (DLS) is used to achieve a
balanced load execution of such applications on high performance computing
(HPC) systems. Large HPC systems are vulnerable to processors or node failures
and perturbations in the availability of resources. Most self-scheduling
approaches do not consider fault-tolerant scheduling or depend on failure or
perturbation detection and react by rescheduling failed tasks. In this work, a
robust dynamic load balancing (rDLB) approach is proposed for the robust self
scheduling of independent tasks. The proposed approach is proactive and does
not depend on failure or perturbation detection. The theoretical analysis of
the proposed approach shows that it is linearly scalable and its cost decrease
quadratically by increasing the system size. rDLB is integrated into an MPI DLS
library to evaluate its performance experimentally with two computationally
intensive scientific applications. Results show that rDLB enables the tolerance
of up to (P minus one) processor failures, where P is the number of processors
executing an application. In the presence of perturbations, rDLB boosted the
robustness of DLS techniques up to 30 times and decreased application execution
time up to 7 times compared to their counterparts without rDLB
Bayesian Coronal Seismology
In contrast to the situation in a laboratory, the study of the solar
atmosphere has to be pursued without direct access to the physical conditions
of interest. Information is therefore incomplete and uncertain and inference
methods need to be employed to diagnose the physical conditions and processes.
One of such methods, solar atmospheric seismology, makes use of observed and
theoretically predicted properties of waves to infer plasma and magnetic field
properties. A recent development in solar atmospheric seismology consists in
the use of inversion and model comparison methods based on Bayesian analysis.
In this paper, the philosophy and methodology of Bayesian analysis are first
explained. Then, we provide an account of what has been achieved so far from
the application of these techniques to solar atmospheric seismology and a
prospect of possible future extensions.Comment: 19 pages, accepted in Advances in Space Researc
Dimensional reduction of the Luttinger-Ward functional for spin-degenerate -dimensional electron gases
We consider an isotropic spin-degenerate interacting uniform -dimensional
electron gas (DDEG) with within the Luttinger-Ward (LW) formalism. We
derive the asymptotically exact semiclassical/infrared limit of the LW
functional at large distances, , and large times, , where and are the Fermi wavelength and the Fermi
energy, respectively. The LW functional is represented by skeleton diagrams,
each skeleton diagram consists of appropriately connected dressed fermion
loops. First, we prove that every -dimensional skeleton diagram consisting
of a single fermion loop is reduced to a one-dimensional (1D) fermion loop with
the same diagrammatic structure, which justifies the name dimensional
reduction. This statement, combined with the fermion loop cancellation theorem
(FLCT), agrees with results of multidimensional bosonization. Here we show that
the backscattering and the spectral curvature, both explicitly violate the FLCT
and both are irrelevant for a 1DEG, become relevant at and ,
respectively. The reason for this is a strong infrared divergence of the
skeleton diagrams containing multiple fermion loops at . These diagrams,
which are omitted within the multidimensional bosonization approaches, account
for the non-collinear scattering processes. Thus, the dimensional reduction
provides the framework to go beyond predictions of the multidimensional
bosonization. A simple diagrammatic structure of the reduced LW functional is
another advantage of our approach. The dimensional reduction technique is also
applicable to the thermodynamic potential and various approximations, from
perturbation theory to self-consistent approaches.Comment: 15 pages, 4 figure
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